ESAB BASIC WELDING FILLER METAL TECHNOLOGY LESSON I THE BASICS OF ARC WELDING. A Correspondence Course

Transcription

1 Arc for for Low BASIC WELDING FILLER METAL TECHNOLOGY A Correspondence Course Carbon LESSON I THE BASICS OF ARC WELDING An Introduction to Metals Electricity for ESAB ESAB & Cutting Products Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

2 Arc TABLE OF CONTENTS LESSON I THE BASICS OF ARC WELDING for for Low Carbon PART A. AN INTRODUCTION TO METALS Section Nr. Section Title Page 1.1 Source and Manufacturing Rimmed Steel Capped Steel Killed Steel Semi-Killed Steel Vacuum Deoxidized Steel Classification of Steels Carbon Steel Low Alloy Steel High Alloy Steel Specifications Crystalline Structure of Metals Grains and Grain Boundaries Heat Treatment Preheat Stress Relieving Hardening Tempering Annealing Normalizing Heat Treatment Trade-Off Properties of Metals Tensile Strength Yield Strength Ultimate Tensile Strength Percentage of Elongation Reliability of COPYRIGHT 1998 THE ESAB GROUP, INC

3 Arc for for Low Carbon Reliability of TABLE OF CONTENTS LESSON I - Con't. Section Nr. Section Title Page Reduction of Area Charpy Impacts Fatigue Strength Creep Strength Oxidation Resistance Hardness Test Coefficient of Expansion Thermal Conductivity Effects of Alloying Elements Carbon Sulphur Manganese Chromium Nickel Molybdenum Silicon Phosphorus Aluminum Copper Columbium Tungsten Vanadium Nitrogen Alloying Elements summary PART B. ELECTRICITY FOR WELDING Section Nr. Section Title Page 1.8 Electricity for Principles of Electricity Ohm s Law Electrical Power Power Generation COPYRIGHT 1998 THE ESAB GROUP, INC

4 ` Lesson 1 Arc TABLE OF CONTENTS LESSON I - Con't. Section Nr. Section Title Page for for Low Transformers Power Requirements Rectifying AC to DC Constant Current or Constant Voltage Constant Current Characteristics Constant Voltage Characteristics Types of Power Sources Power Source Controls Appendix A Glossary of Terms Carbon Reliability of COPYRIGHT 1998 THE ESAB GROUP, INC

5 Arc for for Low Carbon Reliability of AN INTRODUCTION TO METALS 1.1 SOURCE AND MANUFACTURING LESSON I, PART A Metals come from natural deposits of ore in the earth s crust. Most ores are contaminated with impurities that must be removed by mechanical and chemical means. Metal extracted from the purified ore is known as primary or virgin metal, and metal that comes from scrap is called secondary metal. Most mining of metal bearing ores is done by either open pit or underground methods. The two methods of mining employed are known as selective in which small veins or beds of high grade ore are worked, and bulk in which large quantities of low grade ore are mined to extract a high grade portion There are two types of ores, ferrous and nonferrous. The term ferrous comes from the Latin word ferrum meaning iron, and a ferrous metal is one that has a high iron content. Nonferrous metals, such as copper and aluminum, are those that contain little or no iron. There is approximately 20 times the tonnage of iron in the earth s crust compared to all other nonferrous products combined; therefore, it is the most important and widely used metal Aluminum, because of its attractive appearance, light weight and strength, is the next most widely used metal. Commercial aluminum ore, known as bauxite, is a residual deposit formed at or near the earth s surface Some of the chemical processes that occur during steel making are repeated during the welding operation and an understanding of welding metallurgy can be gained by imagining the welding arc as a miniature steel mill The largest percentage of commercially produced iron comes from the blast furnace process. A typical blast furnace is a circular shaft approximately 90 to 100 feet in height with an internal diameter of approximately 28 feet. The steel shell of the furnace is lined with a refractory material, usually a hard, dense clay firebrick The iron blast furnace utilizes the chemical reaction between a solid fuel charge and the resulting rising column of gas in the furnace. The three different materials used for the charge are ore, flux and coke. The ore consists of iron oxide about four inches in diameter. The flux is limestone that decomposes into calcium oxide and carbon dioxide. The lime reacts with impurities in the ore and floats them to the surface in the form of a slag. Coke, which is primarily carbon, is the ideal fuel for blast furnaces because it produces carbon monoxide gas, the main agent for reducing iron ore into iron metal. COPYRIGHT 1999 THE ESAB GROUP, INC

6 Arc for for Low Carbon Reliability of LESSON I, PART A The basic operation of the blast furnace is to reduce iron oxide to iron metal and to remove impurities from the metal. Reduced elements pass into the iron and oxidized elements dissolve into the slag. The metal that comes from the blast furnace is called pig iron and is used as a starting material for further purification processes Pig iron contains excessive amounts of elements that must be reduced before steel can be produced. Different types of furnaces, most notably the open hearth, electric and basic oxygen, are used to continue this refining process. Each furnace performs the task of removing or reducing elements such as carbon, silicon, phosphorus, sulfur and nitrogen by saturating the molten metal with oxygen and slag forming ingredients. The oxygen reduces elements by forming gases that are blown away and the slag attracts impurities as it separates from the molten metal Depending upon the type of slag that is used, refining furnaces are classed as either acid or basic. Large amounts of lime are contained in basic slags and high quantities of silica are present in acid slags. This differential between acid and basic slags is also present in welding electrodes for much of the same refining process occurs in the welding operation After passing through the refining furnace, the metal is poured into cast iron ingot molds. The ingot produced is a rather large square column of steel. At this point, the metal is saturated with oxygen. To avoid the formation of large gas pockets in the cast metal, a substantial portion of the oxygen must be removed. This process is known as deoxidation, and it is accomplished through additives that tie up the oxygen either through gases or in slag. There are various degrees of oxidation, and the common ingots resulting from each are as follows: Rimmed Steel - The making of rimmed steels involves the least deoxidation. As the ingots solidify, a layer of nearly pure iron is formed on the walls and bottom of the mold, and practically all the carbon, phosphorus, and sulfur segregate to the central core. The oxygen forms carbon monoxide gas and it is trapped in the solidifying metal as blow holes that disappear in the hot rolling process. The chief advantage of rimmed steel is the excellent defect-free surface that can be produced with the aide of the pure iron skin. Most rimmed steels are low carbon steels containing less than.1% carbon Capped Steel - Capped steel regulates the amount of oxygen in the molten metal through the use of a heavy cap that is locked on top of the mold after the metal is allowed to reach a slight level of rimming. Capped steels contain a more uniform core composition than the rimmed steels. Capped steels are, therefore, used in applications COPYRIGHT 1999 THE ESAB GROUP, INC

7 Arc for for Low LESSON I, PART A that require excellent surfaces, a more homogenous composition, and better mechanical properties than rimmed steel Killed Steel - Unlike rimmed or capped steel, killed steel is made by completely removing or tying up the oxygen before the ingot solidifies to prevent the rimming action. This removal is accomplished by adding a ferro-silicon alloy that combines with oxygen to form a slag, leaving a dense and homogenous metal Semi-killed Steel - Semi-killed steel is a compromise between rimmed and killed steel. A small amount of deoxidizing agent, generally ferro-silicon or aluminum, is added. The amount is just sufficient to kill any rimming action, leaving some dissolved oxygen Vacuum Deoxidized Steel - The object of vacuum deoxidation is to remove oxygen from the molten steel without adding an element that forms nonmetallic inclusions. This is done by increasing the carbon content of the steel and then subjecting the molten metal to vacuum pouring or steam degassing. The carbon reacts with the oxygen to form carbon monoxide, and as a result, the carbon and oxygen levels fall within specified limits. Because no deoxidizing elements that form solid oxides are used, the steel produced by this process is quite clean. Carbon 1.2 CLASSIFICATIONS OF STEEL The three commonly used classifications for steel are: carbon, low alloy, and high alloy. These are referred to as the type of steel Carbon Steel - Steel is basically an alloy of iron and carbon, and it attains its strength and hardness levels primarily through the addition of carbon. Carbon steels are classed into four groups, depending on their carbon levels. Low Carbon Up to 0.15% carbon Mild Carbon Steels.15% to 0.29% carbon Medium Carbon Steels.30% to 0.59% carbon High Carbon Steels.60% to 1.70% carbon The largest tonnage of steel produced falls into the low and mild carbon steel groups. They are popular because of their relative strength and ease with which they can be welded Low Alloy Steel - Low alloy steel, as the name implies, contains small amounts Reliability of of alloying elements that produce remarkable improvements in their properties. Alloying COPYRIGHT 1999 THE ESAB GROUP, INC

8 Arc LESSON I, PART A elements are added to improve strength and toughness, to decrease or increase the response to heat treatment, and to retard rusting and corrosion. Low alloy steel is generally defined as having a 1.5% to 5% total alloy content. Common alloying elements are manganese, silicon, chromium, nickel, molybdenum, and vanadium. Low alloy steels may contain as many as four or five of these alloys in varying amounts. for for Low Carbon Low alloy steels have higher tensile and yield strengths than mild steel or carbon structural steel. Since they have high strength-to-weight ratios, they reduce dead weight in railroad cars, truck frames, heavy equipment, etc Ordinary carbon steels, that exhibit brittleness at low temperatures, are unreliable in critical applications. Therefore, low alloy steels with nickel additions are often used for low temperature situations Steels lose much of their strength at high temperatures. To provide for this loss of strength at elevated temperatures, small amounts of chromium or molybdenum are added High Alloy Steel - This group of expensive and specialized steels contain alloy levels in excess of 10%, giving them outstanding properties Austenitic manganese steel contains high carbon and manganese levels, that give it two exceptional qualities, the ability to harden while undergoing cold work and great toughness. The term austenitic refers to the crystalline structure of these steels Stainless steels are high alloy steels that have the ability to resist corrosion. This characteristic is mainly due to the high chromium content, i.e., 10% or greater. Nickel is also used in substantial quantities in some stainless steels Tool steels are used for cutting and forming operations. They are high quality steels used in making tools, punches, forming dies, extruding dies, forgings and so forth. Depending upon their properties and usage, they are sometimes referred to as water hardening, shock resisting, oil hardening, air hardening, and hot work tool steel Because of the high levels of alloying elements, special care and practices are required when welding high alloy steels. Reliability of COPYRIGHT 1999 THE ESAB GROUP, INC

9 1.3 SPECIFICATIONS LESSON I, PART A Arc for for Low Carbon Reliability of Many steel producers have developed steels that they market under a trade name such as Cor-Ten, HY-80, T-1, NA-XTRA, or SS-100, but usually a type of steel is referred to by its specification. A variety of technical, governmental and industrial associations issue specifications for the purpose of classifying materials by their chemical composition, properties or usage. The specification agencies most closely related to the steel industry are the American Iron and Steel Institute (AISI), Society of Automotive Engineers (SAE), American Society for Testing and Materials (ASTM), and the American Society of Mechanical Engineers (ASME) The American Iron and Steel Institute (AISI) and the Society of Automobile Engineers (SAE) have collaborated in providing identical numerical designations for their specifications. The first two digits of a four digit index number refer to a series of steels classified by their composition or alloy combination. While the last two digits, which can change within the same series, give an approximate average of the carbon range. For example, the first two digits of a type 1010 or 1020 steel indicate a 10 series that has carbon as its main alloy. The last two digits indicate an approximate average content of.10% or.20% carbon, respectively. Likewise, the 41 of a 4130 type steel refers to a group that has chromium and molybdenum as their main alloy combination with approximately.30% carbon content The AISI classifications for certain alloys, such as stainless steel, are somewhat different. They follow a three digit classification with the first digit designating the main alloy composition or series. The last two digits will change within a series, but are of an arbitrary nature being agreed upon by industry as a designation for certain compositions within the series. For example, the 3 in a 300 series of stainless steel indicates chromium and nickel as the main alloys, but a 308 stainless has a different overall composition than a 347 type. The 4 of a 400 series indicates the main alloy as chromium, but there are different types such as 410, 420, 430, and so forth within the series The American Society for Testing and Materials (ASTM) is the largest organization of its kind in the world. It has compiled some 48 volumes of standards for materials, specifications, testing methods and recommended practices for a variety of materials ranging from textiles and plastics to concrete and metals Two ASTM designated steels commonly specified for construction are A36-77 and A The prefix letter indicates the class of a material. In this case, the letter A indicates a ferrous metal, the class of widest interest in welding. The numbers 36 and 242 COPYRIGHT 1999 THE ESAB GROUP, INC

10 Arc for LESSON I, PART A are index numbers. The 77 and 79 refer to the year that the standards for these steels were originally adopted or the date of their latest revision The ASTM designation may be further subdivided into Grades or Classes. Since many standards for ferrous metals are written to cover forms of steel (i.e., sheet, bar, plate, etc.) or particular products fabricated from steel (i.e., steel rail, pipe, chain, etc.), the user may select from a number of different types of steel under the same classification. The different types are than placed under grades or classes as a way of indicating the differences in such things as chemistries, properties, heat treatment, etc. An example of a full designation is A Grade A or A Class 70. for Low Carbon The American Society of Mechanical Engineers (ASME) maintains a widely used ASME Boiler and Pressure Vessel Code. The material specification as adopted by the ASME is identified with a prefix letter S, while the remainder is identical with ASTM with the exception that the date of adoption or revision by ASTM is not shown. Therefore, a common example of an ASME classification is SA 387 Grade 11, Class CRYSTALLINE STRUCTURE OF METALS When a liquid metal is cooled, its atoms will assemble into a regular crystal pattern and we say the liquid has solidified or crystallized. All metals solidify as a crystalline material. In a crystal the atoms or molecules are held in a fixed position and are not free to move about as are the molecules of a liquid or gas. This fixed position is called a crystal lattice. As the temperature of a crystal is raised, more thermal energy is absorbed by the atoms or molecules and their movement increases. As the distance 4000 LIQUID F 2000 between the atoms increases, the lattice breaks down and the crystal melts. If a lattice contains only one type of atom, as in pure iron, the conditions are the same at all points throughout the lattice, and the crystal melts at a single temperature (see Figure 1). Reliability of 1000 SOLID TIME SOLID-LIQUID TRANSFORMATION, PURE IRON FIGURE 1 COPYRIGHT 1999 THE ESAB GROUP

11 Arc for for Low Carbon Reliability of LESSON I, PART A However, if the lattice contains two Liquid or more types of atoms, as in any alloy-steel, it may start to melt at one temperature but not be completely molten until it has been heated Liquid and Solid to a higher temperature (See Figure 2). This creates a situation where there is a combination of liquids and solids within a range of temperatures. Solid Each metal has a characteristic crystal structure that forms during solidification and often remains the permanent TIME form of the material as long as it remains at Solid-Liquid Transformation, Alloy Metal room temperature. However, some metals FIGURE 2 may undergo an alteration in the crystalline form as the temperature is changed. This is known as phase transformation. For example, pure iron solidifies at 2795 F, the delta structure transforms into a structure referred to as gamma iron. Gamma iron is commonly known as austenite and is a nonmagnetic structure. At a temperature of 1670 F., the pure iron structure transforms back to the delta iron form, but at this temperature, the metal is known as alpha iron. These two phases are given different names to differentiate between the high temperature phase (delta) and the low temperature phase (alpha). The capability of the atoms of a material to transform into two or more crystalline structures at different temperatures is defined as allotropic. Steels and iron are allotropic metals Grains and Grain Boundaries - As the metal is cooled to its freezing point, a small group of atoms begin to assemble into crystalline form (refer to Figure 3). These small crystals scattered throughout the body of the liquid are oriented in all directions and as solidification continues, more crystals are formed from the surrounding liquid. Often, they take the form of dendrites, or a treelike structure. As crystallization continues, the crystals begin to touch one another, their free growth hampered, and the remaining liquid freezes to the adjacent crystals until solidification is complete. The solid is now composed of individual crystals that usually meet at different orientations. Where these crystals meet is called a grain boundary A number of conditions influence the initial grain size. It is important to know that cooling rate and temperature has an important influence on the newly solidified grain structure and grain size. To illustrate differences in grain formation, let's look at the cooling phases in a weld. COPYRIGHT 1999 THE ESAB GROUP, INC

12 Arc for for Low Carbon Reliability of BASE METAL LESSON I, PART A Initial crystal formation begins at the coolest spot in the weld. That spot is at the point where the molten metal and the unmelted base metal meet. As the metal continues to solidify, you will note that the grains in the center are smaller and finer in texture than the grains at the outer boundaries of the weld deposit. This is explained by the fact that as the weld metal cools, the heat from the center of the weld deposit will dissipate into the base metal through the outer grains that solidified first. Consequently, the grains that solidified first were at high temperatures for a longer time while in the solid state and this is a situation that encourages grain growth. Grain size can have an effect on the soundness of the weld. The smaller grains are stronger and more ductile than the larger grains. If a crack occurs, the tendency is for it to start in the area where the grains are largest To summarize this section, it should be understood that all metals are composed of crystals of grains. The shape and characteristics of crystals are determined by the arrangement of their atoms. The atomic pattern of a single element can change its arrangement at different temperatures, and that this atomic pattern or microstructure determines the properties of the metals. 1.5 HEAT TREATMENT FIGURE 3 GRAIN BOUNDARIES DENDRITE INITIAL COMPLETE FORMATION CRYSTAL FORMATION SOLIDIFICATION The temperature that metal is heated, the length of time it is held at that temperature, and the rate that it is cooled, all have an effect on a metal's crystalline structure. This crystalline structure, commonly referred to as "microstructure," determines the specific properties of metals. There are various ways of manipulating the microstructure, either at the steel mill or in the welding procedure. Some of the more common ways are as follows: Preheat - Most metals are rather good conductors of heat. As a result, the heat in the weld area is rapidly dispersed through the whole weldment to all surfaces where it is radiated to the atmosphere causing comparatively rapid cooling. In some metals, this rapid cooling may contribute to the formation of microstructures in the weld zone that are detrimental. Preheating the weldment before it is welded is a method of slowing the cooling COPYRIGHT 1999 THE ESAB GROUP, INC

13 Arc for for Low Carbon LESSON I, PART A rate of the metal. The preheat temperature may vary from 150 F to 1000 F, but more commonly it is held in the 300 F to 400 F range. The thicker the weld metal, the more likely will it be necessary to preheat, because the heat will be conducted away from the weld zone more rapidly as the mass increases Stress Relieving - Metals expand when heated and contract when cooled. The amount of expansion is directly proportional to the amount of heat applied. In a weldment, the metal closest to the weld is subjected to the highest temperature, and as the distance from the weld zone increases, the maximum temperature reached decreases. This nonuniform heating causes nonuniform expansion and contraction and can cause distortion and internal stresses within the weldment. Depending on its composition and usage, the metal may not be able to resist these stresses and cracking or early failure of the part may occur. One way to minimize these stresses or to relieve them is by uniformly heating the structure after it has been welded. The metal is heated to temperatures just below the point where a microstructure change would occur and then it is cooled at a slow rate Hardening - The hardness of steel may be increased by heating it to 50 F to 100 F above the temperature that a microstructure change occurs, and then placing the metal in a liquid solution that rapidly cools it. This rapid cooling, known as "quenching," locks in place microstructures known as "martensite" that contribute to a metal's hardness characteristic. The quenching solutions used in this process are rated according to the speed that they cool the metal, i.e., Oil (fast), Water (faster), Salt Brine (fastest) Tempering - After a metal is quenches, it is then usually tempered. Tempering is a process where the metal is reheated to somewhere below 1335 F, held at that temperature for a length of time, and then cooled to room temperature. Tempering reduces the brittleness that is characteristic in hardened steels, thereby producing a good balance between high strength and toughness. The term toughness, as it applies to metals, usually refers to resistance to brittle fracture or notch toughness under certain environmental conditions. More information on these properties will be covered later in this lesson and in subsequent lessons. Steels that respond to this type of treatment are known as "quenched and tempered steels." Annealing - A metal that is annealed is heated to a temperature 50 to 100 Reliability of above where a microstructure change occurs, held at that temperature for a sufficient time for a uniform change to take place, and then cooled at a very slow rate, usually in a furnace. The principal reason for annealing is to soften steel and create a uniform fine grain structure. Welded parts are seldom annealed for the high temperatures would cause distortion. COPYRIGHT 1999 THE ESAB GROUP, INC

14 Arc for LESSON I, PART A Normalizing - The main difference between normalizing and annealing is the method of cooling. Normalized steel is heated to a temperature approximately 100 above where the microstructure transforms and then cooled in still air rather than in a furnace Heat Treatment Trade-Off - It must be noted that these various ways of controlling the heating and cooling of metals can produce a desired property, but sometimes at the expense of another desirable property. An example of this trade-off is evident in the fact that certain heat treatments can increase the strength or hardness of metal, but the same treatments will also make the metal less ductile or more brittle, and therefore, susceptible to welding problems. for Low Carbon Reliability of 1.6 PROPERTIES OF METALS The usefulness of a particular metal is determined by the climate and conditions in which it will be used. A metal that is stamped into an automobile fender must be softer and more pliable than armor plate that must withstand an explosive force, or the material used for an oil rig on the Alaska North Slope must perform in a quite different climate than a steam boiler. It becomes obvious that before a material is recommended for a specific use, the physical and mechanical properties of that metal and the weld metal designed to join it must be evaluated. Some of the more important properties of metals and the means of evaluation are as follows: Tensile Strength - Tensile strength is one of the most important determining factors in selecting a metal, especially if it is to be a structural member, part of a machine, or part of a pressure vessel The tensile test is performed as shown in Figure 4. The test specimen is machined to exact standard dimensions and clamped into the testing apparatus at both ends. The specimen is then pulled to the point of fracture TEST and the data recorded. SPECIMEN The tensile strength test gives us 4 primary pieces of information: (1) Yield Strength, (2) Ultimate Tensile Strength, (3) Elongation, and (4) Reduction in Area. FORCE TENSILE TESTING APPARATUS FIGURE 4 RECORDING DIAL COPYRIGHT 1999 THE ESAB GROUP, INC

15 Arc for for Low Carbon Reliability of LESSON I, PART A Yield Strength - When a metal is placed in tension, it acts somewhat like a rubberband. When a load of limited magnitude is applied, the metal stretches, and when the load is released, the metal returns to its original shape. This is the elastic characteristic of metal and is represented by letter A in Figure 5. As a greater load is applied, the metal will reach a point where it will no longer return to its original shape but will continue to stretch. Yield strength is the point where the metal reaches the limit of its elastic characteristic and will no longer return to its original shape Ultimate Tensile Strength - Once a metal has exceeded its yield point, it will continue to stretch or deform, and if the load is suddenly released, the metal will not return to its original shape, but will remain in its elongated form. This is called the plastic region of the metal and is represented by the letter B in Figure 5. As this plastic deformation increases, the metal strains against further elongation, and Ultimate Strength an increased load must be Elong- Reduction applied to stretch the metal. As ation of Area Yield Strength Fracture the load is increased, the metal will finally reach a point where it A B C STRAIN - INCHES no longer resists and any further load applied will rapidly NOMINAL STRESS - STRAIN CURVE FIGURE 5 cause the metal to break. That point at which the metal has withstood or resisted the maximum applied load is its ultimate tensile strength. This information is usually recorded in pounds per square inch (psi) Percentage of Elongation - Before a tensile specimen is placed in the tensile tester, two marks at a measured distance are placed on the opposing ends of the circular shaft. After the specimen is fractured, the distance between the marks is measured and recorded as a percentage of the original distance. See Figure 5. This is the percentage of elongation and it gives an indication of the ductility of the metal at room temperature Reduction of Area - A tensile specimen is machined to exact dimensions. The area of its midpoint cross-section is a known figure. As the specimen is loaded to the point of fracture, the area where it breaks is reduced in size. See Figure 5. This reduced area is calculated and recorded as a percentage of the original cross-sectional area. This information reflects the relative ductility or brittleness of the metal Charpy Impacts - Metal that is normally strong and ductile at room temperature may become very brittle at much lower temperatures, and thus, is susceptible to fracture if COPYRIGHT 1999 THE ESAB GROUP, INC

16 Arc for LESSON I, PART A a sharp abrupt load is applied to it. An impact tester measures the degree of susceptibility to what is called brittle fracture The impact specimen is machined to exact dimensions (Figure 6) and then notched on one side. Quite often, the notch is in the form of a "V" and the test in this case is referred to as a Charpy V-Notch Impact Test. The specimen is cooled to a predetermined temperature and then placed in a stationary clamp at the base of the testing machine. The specimen is in the direct path of a weighted hammer attached to a pendulum (Figure 6). for Low ENERGY IN FT/LBS FRACTURES CRACKS DEFORMS CHARPY V-NOTCH SPECIMEN CHARPY IMPACT TEST MACHINE CHARPY V-NOTCH IMPACT TEST Carbon Reliability of FIGURE The hammer is released from a fixed height and the energy required to fracture the specimen is recorded in ft-lbs. A specimen that is cooled to -60 F and absorbs 40 ft-lbs of energy is more ductile, and therefore, more suitable for low temperature service than a specimen that withstands only 10 ft-lbs at the same temperature. The specimen that withstood 40 ft-lbs energy is said to have better toughness or notch toughness Fatigue Strength - A metal will withstand a load less than its ultimate tensile strength but may break if that load is removed and then reapplied several times. For example, if a thin wire is bent once, but if it is bent back and forth repeatedly, it will eventually fracture and it is said to have exceeded its fatigue strength. A common test for this strength is to place a specimen in a machine that repeatedly applies the same load first in tension and then in compression. The fatigue strength is calculated from the number of cycles the metal withstands before the point of failure is reached. COPYRIGHT 1999 THE ESAB GROUP, INC

17 Arc for for Low LESSON I, PART A Creep Strength - If a load below a metal's tensile strength is applied at room temperature (72 F), it will cause some initial elongation, but there will be no further measurable elongation if the load is kept at a constant level. If that same load were applied to a metal heated to a high temperature, the situation would change. Although the load is held at a constant level, the metal will gradually continue to elongate. This characteristic is called creep. Eventually, the material may rupture depending on the temperature of the metal, the degree of load applied and the length of time that it is applied. All three of these factors determine a metal's ability to resist creep, and therefore, its creep strength Oxidation Resistance - The atoms of metal have a tendency to unite with oxygen in the air to form oxide compounds, the most visible being rust and scale. In some metals, these oxides will adhere very tightly to the skin of the metal and effectively seal it from further oxidation as is evident in stainless steel. These materials have high oxidation resistance. In other metals, the bond is very loose, creating a situation where the oxides will flake off, and the metal gradually deteriorates as the time of exposure is extended Hardness Test - The resistance of a metal to indentation is a measure of its hardness and an indication of the materials's strength. To test for hardness, a fixed load forces an indenter into the test material (Figure 7). The depth of the penetration or the size of the impression is measured. The measurement is converted into a hardness number through the use of a variety of established tables. The most common tables are the Brinell, Vickers, Knoop and Rockwell. The Rockwell is further divided into different scales, and HARDNESS TEST SHAPE OF INDENTER INDENTER DESCRIPTION Carbon ROCKWELL A C D B F G E BRINNELL } } Diamond Cone 1/16 in. Diameter Steel Sphere 1/8 in. Diameter Steel Sphere 10 mm Sphere of Steel or Tungsten Carbide VICKERS KNOOP Diamond Pyramid Diamond Pyramid Reliability of Types of Indenters - Hardness Tests FIGURE 7 COPYRIGHT 1999 THE ESAB GROUP, INC

18 Arc for for Low LESSON I, PART A depending on the material being tested, the shape of the indenter and the load applied, the conversion tables may differ. For example, a material listed as having a hardness of Rb or Rc means its hardness has been determined from the Rockwell "B" scale or the Rockwell "C" scale Coefficient of Expansion - All metals expand when heated and contract when cooled. This dimensional change is related to the crystalline structure and will vary with different materials. The different expansion and contraction rates are expressed numerically by a coefficient of thermal expansion. When two different metals are heated to the same temperature and cooled at the same rate, the one with the higher numerical coefficient will expand and contract more than the one with the lesser coefficient Thermal Conductivity - Some metals will absorb and transmit heat more readily than others. They are categorized as having high thermal conductivity. This characteristic contributes to the fact that some metals will melt or undergo transformations at much lower temperatures than others. 1.7 EFFECTS OF THE ALLOYING ELEMENTS Carbon Reliability of Alloying is the process of adding a metal or a nonmetal to pure metals such as copper, aluminum or iron. From the time it was discovered that the properties of pure metals could be improved by adding other elements, alloy steel has increased by popularity. In fact, metals that are welded are rarely in their pure state. The major properties that can be improved by adding small amounts of alloying elements are hardness, tensile strength, ductility and corrosion resistance. Common alloying elements and their effect on the properties of metals are as follows: Carbon - Carbon is the most effective, most widely used and lowest in cost alloying element available for increasing the hardness and strength of metal. An alloy containing up to 1.7% carbon in combination with iron is known as steel, whereas the combination above 1.7% carbon is known as cast iron. Although carbon is a desirable alloying element, high levels of it can cause problems; therefore, special care is required when welding high carbon steels and cast iron Sulphur - Sulphur is normally an undesirable element in steel because it causes brittleness. It may be deliberately added to improve the machinability of the steel. The sulphur causes the machine chips to break rather than form long curls and clog the machine. Normally, every effort is made to reduce the sulphur content to the lowest possible level because it can COPYRIGHT 1999 THE ESAB GROUP, INC

19 create welding difficulties. LESSON I, PART A Arc for for Low Carbon Manganese - Manganese in contents up to 1% is usually present in all low alloy steels as a deoxidizer and desulphurizer. That is to say, it readily combines with oxygen and sulphur to help negate the undesirable effect these elements have when in their natural state. Manganese also increases the tensile strength and hardenability of steel Chromium - Chromium, in combination with carbon, is a powerful hardening alloying element. In addition to its hardening properties, chromium increases corrosion resistance and the strength of steel at high temperatures. Chromium is the primary alloying element in stainless steel Nickel - The greatest single property of steel that is improved by the presence of nickel is its ductility or notch toughness. In this respect, it is the most effective of all alloying elements in improving a steel's resistance to impact at low temperatures. with high nickel content are used to weld cast iron materials. Nickel is also used in combination with chromium to form a group known as austenitic stainless steel Molybdenum - Molybdenum strongly increases the depth of the hardening characteristic of steel. It is quite often used in combination with chromium to improve the strength of the steel at high temperatures. This group of steels is usually referred to as chrome-moly steels Silicon - Silicon is usually contained in steel as a deoxidizer. Silicon will add strength to steel but excessive amounts can reduce the ductility. Additional amounts of silicon are sometimes added to welding electrodes to increase the fluid flow of weld metal Phosphorus - Phosphorus is considered a harmful residual element in steel because it greatly reduces ductility and toughness. Efforts are made to reduce it to its very lowest levels; however, phosphorus is added in very small amounts to some steels to increase strength Aluminum - Aluminum is primarily used as a deoxidizer in steel. It may also be used in very small amounts to control the size of the grains Copper - Copper contributes greatly to the corrosion resistance of carbon steel by retarding the rate of rusting at room temperature, but high levels of copper can cause welding difficulties. Reliability of COPYRIGHT 1999 THE ESAB GROUP, INC

20 Arc for for Low Carbon LESSON I, PART A Columbium - Columbium is used in austenitic stainless steel to act as a stabilizer. Since the carbon in the stainless steel decreases the corrosion resistance, a means of making carbon ineffective must be found. Columbium has a greater affinity for carbon than chromium, leaving the chromium free for corrosion protection Tungsten - Tungsten is used in steel to given strength at high temperatures. Tungsten also joins with carbon to form carbides that are exceptionally hard, and therefore have exceptional resistance to wear Vanadium - Vanadium helps keep steel in the desirable fine grain condition after heat treatment. It also helps increase the depth of hardening and resists softening of the steel during tempering treatments Nitrogen - Usually, efforts are made to eliminate hydrogen, oxygen and nitrogen from steel because their presence can cause brittleness. Nitrogen has the ability to form austenitic structures; therefore, it is sometimes added to austenitic stainless steel to reduce the amount of nickel needed, and therefore, the production costs of that steel Alloying Elements Summary - It should be understood that the addition of elements to a pure metal may influence the crystalline form of the resultant alloy. If a pure metal has allotropic characteristics (the ability of a metal to change its crystal structure) at a specific temperature, then that characteristic will occur over a range of temperatures with the alloyed metal. The range in which the change takes place may be wide or narrow, depending on the alloys and the quantities in which they are added. The alloying element may also effect the crystalline changes by either suppressing the appearance of certain crystalline forms or even by creating entirely new forms. All these transformations induced by alloying elements are dependent on heat input and cooling rates. These factors are closely controlled at the steel mill, but since the welding operation involves a nonuniform heating and cooling of metal, special care is often needed in the welding of low and high alloy steel. Reliability of COPYRIGHT 1999 THE ESAB GROUP, INC

21 1.8 ELECTRICITY FOR WELDING LESSON I, PART B Arc for for Low Principles of Electricity - Arc welding is a method of joining metals accomplished by applying sufficient electrical pressure to an electrode to maintain a current path (arc) between the electrode and the work piece. In this process, electrical energy is changed into heat energy, bringing the metals to a molten state; whereby they are joined. The electrode (conductor) is either melted and added to the base metal or remains in its solid state. All arc welding utilizes the transfer of electrical energy to heat energy, and to understand this principle, a basic knowledge of electricity and welding power sources is necessary The three basis principles of static electricity are as follows: 1. There are two kinds of electrical charges in existence - negative and positive. 2. Unlike charges attract and like charges repel. 3. Charges can be transferred from one place to another. Carbon Reliability of Science has established that all matter is made up of atoms and each atom contains fundamental particles. One of these particles is the electron, which has the ability to move from one place to another. The electron is classified as a negative electrical charge. Another particle, about 1800 times as heavy as the electron, is the proton and under normal conditions the proton will remain stationary Material is said to be in an electrically uncharged state when its atoms contain an equal number of positive charges (protons) and negative charges (electrons). This balance is upset when pressure forces the electrons to move from atom to atom. This pressure, sometimes referred to as electromotive force, is commonly known as voltage. It should be noted that voltage that does not move through a conductor, but without voltage, there would be no current flow. For our purposes, it is easiest to think of voltage as the electrical pressure that forces the electrons to move Since we know that like charges repel and unlike charges attract, the tendency is for the electrons to move from a position of over-supply (negative charge) to an atom that lacks electrons (positive charge). This tendency becomes reality when a suitable path is provided for the movement of the electrons. The transfer of electrons from a negative to a positive charge throughout the length of a conductor constitutes an electrical current. The rate that current flows through a conductor is measured in amperes and the word ampere is often used synonymously with the term current. To give an idea of the quantities of electrons that flow through a circuit, it has been theoretically established that one ampere equals 6.3 quintillion (6,300,000,000,000,000,000) electrons flowing past a fixed point in a conductor every second. COPYRIGHT 1999 THE ESAB GROUP, INC

22 Arc LESSON I, PART B Different materials vary in their ability to transfer electrons. Substances, such as wood and rubber, have what is called a tight electron bond and their atoms greatly resist the free movement of electrons. Such materials are considered poor electrical conductors. Metals, on the other hand, have large amounts of electrons that transfer freely. Their comparatively low electrical resistance classifies them as good electrical conductors. for for Low Electrical resistance is primarily due to the reluctance of atoms to give up their electron particles. It may also be thought of as the resistance to current flow To better understand the electrical terms discussed above, we might compare the closed water system with the electrical diagram shown in Figure 8. You can see that as the pump is running, the water will move in the direction of the arrows. It moves because pressure has been produced and that pressure can be likened to voltage in an electrical circuit. The pump can be compared to a battery or a DC generator. The water flows VALVE LARGE PIPE PUMP CLOSED WATER SYSTEM SMALL PIPE FIGURE 8 SWITCH BATTERY 12 VOLT ELECTRICAL DIAGRAM RESISTOR 10 OHM Carbon Reliability of through the system at a certain rate. This flow rate in an electrical circuit is a unit of measure known as the ampere. The small pipe in the fluid circuit restricts the flow rate and can be likened to a resistor. This unit resistance is known as the ohm. If we close the valve in the fluid circuit, we stop the flow, and this can be compared to opening a switch in an electrical circuit Ohm's Law - Resistance is basic to electrical theory and to understand this principle, we must know the Ohm's Law, which is stated as follows: In any electrical circuit, the current flow in amperes is directly proportional to the circuit voltage applied and inversely proportional to the circuit resistance. Directly proportional means that even though the voltage and amperage may change, the ratio of their relationship will not. For example, if we have a circuit of one volt and three amps, we say the ratio is one to three. Now if we increase the volts to three, our amperage will increase proportionately to nine amps. As can be seen, even though the voltage and amperage changed in numerical value, their ratio did not. The term "inversely proportional" simply means that if the resistance is COPYRIGHT 1999 THE ESAB GROUP, INC

23 Arc for for Low Carbon LESSON I, PART B doubled, the current will be reduced to one-half. Ohm's Law can be stated mathematically with this equation: I = E R or E = I R or R = E I (E = Volts, I = Amperes, R = Resistance (Ohms)) The equation is easy to use as seen in the following problems: 1) A 12 volt battery has a built-in resistance of 10 ohms. What is the amperage? = 1.2 amps 2) What voltage is required to pass 15 amps through a resistor of 5 ohms? 15 5 = 75 volts 3) When the voltage is 80 and the circuit is limited to 250 amps, what is the value of the resistor? =.32 ohms The theory of electrical resistance is of great importance in the arc welding process for it is this resistance in the air space between the electrode and the base metal that contributes to the transfer of electrical energy to heat energy. As voltage forces the electrons to move faster, the energy they generate is partially used to overcome the resistance created by the arc gap. This energy becomes evident as heat. In the welding process, the temperature increases to the point where it brings metals to a molten state Electrical Power - The word "watt" is another term frequently encountered in electrical terminology. When we pay our electrical bills, we are actually paying for the power to run our electrical appliances, and the watt is a unit of power. It is defined as the amount of power required to maintain a current of one ampere at a pressure of one volt. The circuit voltage that comes into your home is a constant factor, but the amperage drawn from the utility company depends on the number of watts required to run the electrical appliance. The watt is figured as a product of volts times amperes and is stated mathematically with the following equation: W =E I E = W I I = W E (W = Watts, E = Volts, I = Amperes) The amperage used by an electrical device can be calculated by dividing the watts rating of the device by the primary voltage for which it is designed. Reliability of COPYRIGHT 1999 THE ESAB GROUP, INC

24 Arc for for Low Carbon For example, if an appliance is designed for the common household primary voltage of 115 and the wattage stamped on the appliance faceplate is 5, then the amperage drawn by the appliance when in operation is determined as shown: =.04 amperes Kilowatt is another term common in electrical usage. The preface "kilo" is a metric designation that means 1,000 units of something; therefore, one kilowatt is 1,000 watts of power. LESSON I, PART B Power Generation - Electrical energy is supplied either as direct current (DC) or alternating current (AC). With direct current, the electron movement within the conductor is in one direction only. With alternating current, the electron flow reverses periodically. Although some types of electrical generators will produce current directly (such as batteries, dry cells, or DC generators), most direct current is developed from alternating current Through experimentation, it was discovered that when a wire is moved through a magnetic field, an electrical current is induced into the wire, and the current is at its maximum when the motion of the conductor is at right angles to the magnetic lines of force. The sketch GALVANOMETER in Figure 9 will help to illustrate this principle If the conductor is moved upwards in the magnetic field between the N and S poles, the galvanometer needle will deflect plus (+). Likewise, if the conductor is moved downwards the needle will deflect minus (-). With this principle of converting mechanical energy into electrical energy understood, we can apply it to the workings of an AC generator Figure 10 is a simplified sketch of an AC FIGURE 9 generator. Starting at 0 rotation, the coil wire is moving parallel to the magnetic lines of force and cutting none of them. Therefore, no current is being induced into the winding. ELECTRO-MAGNETIC INDUCTION From 0 to 90 rotation, the coil wire cuts an increasing number of magnetic lines of force and reaches the maximum number at 90 rotation. The current increases to the maximum because the wire is now at right angles to the lines of force. Reliability of COPYRIGHT 1999 THE ESAB GROUP, INC

25 ROTATING COIL OR ARMATURE LESSON I, PART B 0 90 Arc N N 180 S N 270 S for CONTACTS S PERMANENT MAGNETS OR FIELD COILS N S N S for Low BASIC AC POWER GENERATION FIGURE From 90 to 180 rotation, the coil wire cuts a diminishing number of lines of force and at 180 again reaches zero From 180 to 270, the current begins to rise again but in the opposite direction because now the wire is in closer proximity to the opposite pole. Carbon Reliability of One cycle is completed as the coil wire moves from 270 to 0 and the current again drops to zero With the aid of a graph, we can visualize the rate at which the lines of force are cut throughout the cycle. If we plot the current versus degree of rotation, we get the familiar sine wave as seen in Figure With this sine wave, we can see that one complete cycle of alternating current comprises one positive and one negative wave (negative and positive meaning electron flow in opposing directions). The frequency of alternating current is the number of such complete cycles per second. For most power applications, 60 cycles per second (60 Hertz) is the standard frequency in North America. (+) MAXIMUM (+) MAXIMUM ( ) ( ) START 1/4 TURN 1/2 TURN 3/4 TURN FULL TURN ONE CYCLE - ALTERNATING CURRENT FIGURE 11 COPYRIGHT 1999 THE ESAB GROUP, INC

26 Arc for for Low Carbon LESSON I, PART B Some welders use a three-phase AC supply. Three-phase is simply three sources of AC power as identical voltages brought in by three wires, the three voltages or phases being separated by 120 electrical degrees. If the sine wave for the three phases are plotted on one line, they will appear as shown in Figure This illustrates that three-phase power is smoother than single-phase because the overlapping three phases prevent the current and voltage from falling to zero 120 times a second, thereby producing a smoother welding arc CYCLE THREE PHASE AC FIGURE Since all shops do not have three-phase power, welding machines for both single-phase and three-phase power are available Transformers - The function of a transformer is to increase or decrease voltage to a safe value as the conditions demand. Common household voltage is usually 115 or 230 volts, whereas industrial power requirements may be 208, 230, 380, or 460 volts. Transmitting such relatively low voltages over long distances would require a conductor of enormous and impractical size. Therefore, power transmitted from a power plant must be stepped up for long distance transmission and then stepped down for final use As can be seen in Figure 13, the voltage is generated at the power plant at 13,800 volts. It is increased, transmitted over long distances, and then reduced in steps for the end user. If power supplied to a transformer circuit is held steady, then secondary current (amperes) decreases as the primary voltage increases, and conversely, secondary current increases as primary voltage decreases. Since the current flow (amperes) determines the wire or conductor size, the high voltage line may be of a relatively small diameter. 13,800 V POWER PLANT 287,000 V STEP UP HIGH VOLTAGE 300 MILES POWER TRANSMISSION 34,000 V 132,000 V STEP DOWN 4,600 V 208V 230V 460V FINAL USE FIGURE 13 Reliability of COPYRIGHT 1999 THE ESAB GROUP, INC

27 Arc for for Low Carbon LESSON I, PART B The transformer in a welding machine performs much the same as a large power plant transformer. The primary voltage coming into the machine is too high for safe welding. Therefore, it is stepped down to a useable voltage. This is best illustrated with an explanation of how a single transformer works In the preceding paragraphs, we have found than an electrical current can be induced into a conductor when that conductor is moved through a magnetic field to produce alternating current. If this alternating current is passed through a conductor, a pulsating magnetic field will surround the exterior of that conductor, that is the magnetic field will build in intensity through the first 90 electrical degrees, or the first cycle. From that point, the magnetic field will decay during the next quarter cycle until the voltage or current reaches zero at 180 electrical degrees. Immediately, the current direction reverses and the magnetic field will begin to build again until it reaches a maximum at 270 electrical degrees in the cycle. From that point the current and the magnetic field again begin to decay until they reach zero at 360 electrical degrees, where the cycle begins again If that conductor is wound around a material with high magnetic permeability (magnetic permeability is the ability to accept large amounts of magnetic lines of force) such as steel, the magnetic field permeates that core. See Figure 14. This conductor is called the primary coil, and if PRIMARY voltage is applied to one of its terminals and the circuit is COIL completed, current will flow. When a second coil is wound 460 V around that same steel core, the energy that is stored in 460 this fluctuating magnetic field in the core is induced into TURNS this secondary coil. STEEL CORE BASIC TRANSFORMER It is the build-up and collapse of this magnetic FIGURE 14 field that excite the electrons in the secondary coil of the transformer. This causes an electrical current of the same frequency as the primary coil to flow when the secondary circuit is completed by striking the welding arc. Remember that all transformers operate only on alternating current A simplified version of a welding transformer is schematically shown in Figure 15. This welder would operate on 230 volts input power and the primary winding has 230 turns of wire on the core. We need 80 volts for initiating the arc in the secondary or welding circuit, thus we have 80 turns of wire in the secondary winding of the core. Before the arc is struck, the voltage between the electrode and the work piece is 80 volts. Remember that no current (amperage) flows until the welding circuit is completed by striking the arc. SECONDARY COIL 80 V 80 TURNS Reliability of COPYRIGHT 1999 THE ESAB GROUP, INC

28 Arc for for Low Carbon LESSON I, PART B Since the 80 volts 9600 WATTS 9600 WATTS necessary for initiating the arc is too high for practical TURNS 80 TURNS AMPS welding, some means must be VOLTS PRIMARY SECONDARY OCV used to lower this voltage to a suitable level. Theoretically, a variable resistor of the proper value could be used as an output control since voltage is OUTPUT CONTROL SIMPLIFIED WELDING TRANSFORMER FIGURE 15 inversely proportional to resistance as we saw when studying Ohm's Law. Ohm's Law also stated that the amperage is directly proportional to the voltage. This being so, you can see that adjusting the output control will also adjust the amperage or welding current After the arc is initiated and current begins to flow through the secondary or welding circuit, the voltage in that circuit will be 32 volts because it is then being controlled by the output control Power Requirements - We can make another calculation by looking back at Figure 15, and that is power consumption. Earlier, we explained that the watt was the unit of electrical power and can be calculated by the formula: Watts = Volts Amperes From Figure 15, we can see that the instantaneous power in the secondary circuit is: Watts = Watts = 9600 Watts The primary side of our transformer must be capable of supplying 9600 watts also (disregarding losses due to heating, power factor, etc.), so by rearranging the formula, we can calculate the required supply line current or amperage: Amperage = Watts Volts A = = Amps This information establishes the approximate power requirements for the welder, and helps to determine the input cable and fuse size necessary. 32 VOLTS 300 AMPS Reliability of COPYRIGHT 1999 THE ESAB GROUP, INC

29 Arc for for Low LESSON I, PART B Rectifying AC to DC - Although much welding is accomplished with AC welding power sources, the majority of industrial welding is done with machines that produce a direct current arc. The commercially produced AC power that operates the welding machine must then be changed (rectified) to direct current for the DC arc. This is accomplished with a device called a rectifier. Two types of rectifiers have been used extensively in welding machines, the old selenium rectifiers and the more modern silicon rectifiers, often referred to as diodes. See Figure 16. SILICON RECTIFIER SELENIUM RECTIFIER FIGURE The function of a rectifier in the circuit can best be shown by the use of the AC sine wave. With one diode in the circuit, half-wave rectification takes place as shown in Figure 17. SINGLE PHASE HALF WAVE RECTIFICATION FIGURE The negative half-wave is simply cut off and a pulsating DC is produced. During the positive half-cycle, current is allowed to flow through the rectifier. During the negative half-cycle, the current is blocked. This produces a DC composed of 60 positive pulses per second. Carbon By using four rectifiers connected in a certain manner, a bridge rectifier is created, producing full wave rectification. The bridge rectifier results in 120 positive half-cycles per second, producing a considerably smoother direct current than half-wave rectification. See Figure Three-phase AC can be rectified to produce an even smoother DC than single-phase AC. Since three-phase AC power produces three times as many half-cycles per second as singlephase power, a relatively smooth DC voltage results as shown in Figure 19. SINGLE PHASE FULL WAVE RECTIFICATION FIGURE 18 1 CYCLE 3 PHASE FULL WAVE RECTIFICATION FIGURE 19 Reliability of COPYRIGHT 1999 THE ESAB GROUP, INC

30 1.9 CONSTANT CURRENT OR CONSTANT VOLTAGE LESSON I, PART B Arc for for Low Carbon Reliability of power sources are designed in many sizes and shapes. They may supply either AC or DC, or both, and they may have various means of controlling their voltage and amperage output. The reasons for this is that the power source must be capable of producing the proper arc characteristics for the welding process being used. A power source that produces a satisfactory arc when welding with coated electrodes will be less than satisfactory for welding with solid and flux cored wires Constant Current Characteristics - Constant current power sources are used primarily with coated electrodes. This type of power source has a relatively small change in amperage and arc power for a corresponding relatively large change in arc voltage or arc length, thus the name constant current. The characteristics of this power source are best illustrated by observing a graph that plots the voltampere curve. As can be seen in Figure 20, the 80 curve of a constant current machine drops downward rather sharply and for this reason, this type of machine is often called a "drooper." In welding with coated electrodes, the output current or amperage is set by the operator while the voltage is designed into the unit. The operator can vary the arc voltage somewhat by increasing or decreasing the arc length. A slight increase in arc length will cause an increase in arc voltage and a slight decrease in amperage. A slight decrease in arc length will cause a decrease in arc voltage and a slight increase in amperage Constant Voltage Characteristics - Constant voltage power sources, also VOLT / AMPERE CURVE CONSTANT CURRENT known as constant potential, are used in welding with solid and flux cored electrodes, and as the name implies, the voltage output remains relatively constant. On this type of power source, the voltage is set at the machine and amperage is determined by the speed that the wire is fed to the welding gun. Increasing the wire feed speed increases the amperage. Decreasing the wire feed speed decreases the amperage Arc length plays an important part in welding with solid and flux cored electrodes, just as it does in welding with a coated electrode. However, when using a constant voltage power source and a wire feeder that delivers the wire at a constant speed, arc length caused by operator error, plate irregularities, and puddle movement are automatically V O L T S V A AMPERES CONSTANT CURRENT VOLT / AMPERE CURVE FIGURE 20 32V A 30V A COPYRIGHT 1999 THE ESAB GROUP, INC

31 Arc for for Low Carbon Reliability of LESSON I, PART B compensated for by the characteristics of this process. To understand this, keep in mind that with the proper voltage setting, amperage setting, and arc length, the rate that the wire melts is dependent upon the amperage. If the amperage decreases, this melt-off rate decreases and if the amperage increases, so does the melt-off rate In Figure 21, we see that condition #2 produces the desired arc length, voltage, and amperage. If the arc length is increased as in #1, the voltage increases slightly; the amperage decreases considerably, and therefore, the melt-off rate of the wire decreases. The wire is now feeding faster than it is melting off. This condition will advance the end of the wire towards the work piece until the proper arc length is reached where again, the melt-off rate 40 equals the feeding rate. If the arc length is decreased as in #3, the voltage drops off 30 V slightly, the amperage is increased O L considerably, and the melt-off rate of the wire increases. Since the wire is now melting off faster than it is being fed, it melts back to the proper arc length where the melt-off rate T S equals the feeding rate. This is often referred to as a self-adjusting arc. These automatic corrections take place in fractions of a second, AMPERES VOLT / AMPERE CURVE - CONSTANT VOLTAGE FIGURE 21 and usually without the operator being aware of them There are a variety of different welding machines, each with its own unique internal design. Our purpose is not to detail the function of each part of the machine, but to emphasize that their main difference is in the way they control the voltage and amperage output Types of Power Sources - A great variety of welding power sources are being built today for electric arc welding and we shall mention some of the major types briefly. power sources can be divided into two main categories: static types and rotating types Static Types - Static type power sources are all of those that use commercially generated electrical power to energize a transformer that, in turn, steps the line voltage down to useable welding voltages. The two major categories of static power sources are the transformer type and the rectifier type. COPYRIGHT 1999 THE ESAB GROUP, INC

32 Arc for for Low Carbon LESSON I, PART B The transformer type produce only alternating current. They are commonly called " Transformers." All AC types utilize single-phase primary power and are of the constant current type The rectifier types are commonly called " Rectifiers" and produce DC or, AC and DC welding current. They may utilize either single phase or three phase input power. They contain a transformer, but rectify the AC or DC by the use of selenium rectifiers, silicon diodes or silicon controlled rectifiers. Available in either the constant current or the constant voltage type, some manufacturers offer units that are a combination of both and can be used for coated electrode welding, non-consumable electrode welding and for welding with solid or flux cored wires Rotating Types - Rotating type power sources may be divided into two classifications: 1. Motor-Generators 2. Engine Driven Motor-generator types consist of an electric motor coupled to a generator or alternator that produces the desired welding power. These machines produced excellent welds, but due to the moving parts, required considerable maintenance. Few, if any, are being built today Engine driven types consist of a gasoline or diesel engine coupled to a generator or alternator that produces the desired welding power. They are used extensively on jobs beyond commercial power lines and also as mobile repair units. Both rotating types can deliver either AC or DC welding power, or a combination of both. Both types are available as constant current or constant voltage models Power Source Controls - power sources differ also in the method of controlling the output current or voltage. Output may be controlled mechanically as in machines having a tapped reactor, a moveable shunt or diverter, or a moveable coil. Electrical types of controls, such as magnetic amplifiers or saturable reactors, are also utilized and the most modern types, containing silicon controlled rectifiers, give precise electronic control A detailed discussion of the many types of welding power sources on the market today is much too lengthy a subject for this course, although additional information on the type of power sources for the various welding processes will be covered in Lesson II. Reliability of Excellent literature is available from power source manufacturers, however, and should be consulted for further reference. COPYRIGHT 1999 THE ESAB GROUP, INC

33 Arc for for Low APPENDIX A LESSON I - GLOSSARY OF TERMS LESSON I, GLOSSARY AISI American Iron and Steel Institute Allotropic A material in which the atoms are capable of transforming into two or more crystalline structures at different temperatures. Alternating An electrical current which alternately travels in either direction in a Current conductor. In 60 cycles per second (60 Hz) AC, the frequency used in the U.S.A., the current direction reverses 120 times every second. Ampere Unit of electrical rate of flow. Amperage is commonly referred to as the current in an electrical circuit. ASME American Society of Mechanical Engineers Carbon ASTM American Society for Testing and Materials Atom The smallest particle of an element that posses all of the characteristics of that element. It consists of protons, neutrons, and electrons. Carbon Steel (Sometimes referred to as mild steel.) An alloy of iron and carbon. Carbon content is usually below 0.3%. Conductor A material which has a relatively large number of loosely bonded electrons which may move freely when voltage (electrical pressure) is applied. Metals are good conductors. Reliability of Constant Current (As applied to welding machines.) A welding power source which will produce a relatively small change in amperage despite changes in voltage caused by a varying arc length. Used mostly for welding with coated electrodes. COPYRIGHT 1999 THE ESAB GROUP, INC

34 Arc for LESSON I, GLOSSARY Constant Voltage (As applied to welding machines.) A welding power source which will produce a relatively small change in voltage when the amperage is changed substantially. Used mostly for welding with solid or flux cored electrodes. Direct Current An electrical current which flows in only one direction in a conductor. Direction of current is dependent upon the electrical connections to the battery or other DC power source. Terminals on all DC devices are usually marked (+) or (-). Reversing the leads will reverse the direction of current flow. for Low Carbon Electron Negatively charged particles that revolve around the positively charged nucleus in an atom. Ferrous Containing iron. Example: carbon steel, low alloy steels, stainless steel. Hertz Hertz (Hz) is the symbol which has replaced the term cycles per second. Today, rather than saying 60 cycles per second or simply 60 cycles, we say 60 Hertz or 60 Hz. High Steels containing in excess of 10% alloy content. Stainless steel is considered a high alloy because it contains in excess of 10% chromium. Induced Current or Induction The phenomena of causing an electrical current to flow through a conductor when that conductor is subjected to a varying magnetic field. Ingot Casting of steel (weighing up to 200 tons) formed at mill from melt of ore, scrap limestone, coke, etc. Insulator A material which has a tight electron bond, that is, relatively few electrons which will move when voltage (electrical pressure) is applied. Wood, glass, ceramics and most plastics are good insulators. Reliability of COPYRIGHT 1999 THE ESAB GROUP, INC

35 Kilowatt 1,000 watts LESSON I, GLOSSARY Arc Steels containing small amounts of alloying elements (usually 1½% to 5% total alloy content) which drastically improves their properties. for for Low Non-Ferrous Containing no iron. Example: Aluminum, copper, copper alloys. Ohm Unit of electrical resistance to current flow. Phase Transformation The changes in the crystalline structure of metals caused by temperature and time. Carbon Proton Positively charged particles which are part of the nucleus of atoms. Rectifier An electrical device used to change alternating current to direct current. SAE Society of Automotive Engineers Transformer An electrical device used to raise or lower the voltage and inversely change the amperage. Volt Unit of electromotive force, or electrical pressure which causes current to flow in an electrical circuit. Watt A unit of electrical power. Watts = Volts x Amperes Reliability of COPYRIGHT 1999 THE ESAB GROUP, INC

36 Arc for for Low BASIC WELDING FILLER METAL TECHNOLOGY A Correspondence Course Carbon LESSON II COMMON ELECTRIC ARC WELDING PROCESSES ESAB ESAB & Cutting Products Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

37 Arc TABLE OF CONTENTS LESSON II COMMON ELECTRIC ARC WELDING PROCESSES for for Low Carbon Section Nr. Section Title Page 2.1 INTRODUCTION SHIELDED METAL ARC WELDING Equipment & Operation Power Sources Electrode Holder Ground Clamp Cables Coated GAS-TUNGSTEN ARC WELDING Equipment & Operation Power Sources Torches Shielding Gases Summary GAS METAL ARC WELDING Current Density Metal Transfer Modes Equipment and Operation Power Source Wire Feeder Gun Shielding Gases Short Circuiting Transfer Spray Arc Transfer Reliability of

38 Arc TABLE OF CONTENTS LESSON II - Con't. Section Nr. Section Title Page for for Low Carbon Pulse Spray Transfer FLUX CORED ARC WELDING Self-Shielded Process Gas Shielded Process Current Density Equipment Power Source Wire Feeder Guns Shielding Gases SUBMERGED ARC WELDING Submerged Arc Flux The Gun Power Sources Equipment Summary ELECTROSLAG AND ELECTROGAS WELDING Electroslag Flux Process Equipment Summary Appendix A - GLOSSARY OF TERMS Reliability of

39 Arc for for Low Carbon COMMON ELECTRIC ARC WELDING PROCESSES 2.1 INTRODUCTION After much experimentation by others in the early 1800's, an Englishman named Wilde obtained the first electric welding patent in He successfully joined two small pieces of iron by passing an electric current through both pieces producing a fusion weld. Approximately twenty years later, Bernado, a Russian, was granted a patent for an electric arc welding process in which he maintained an arc between a carbon electrode and the pieces to be joined, fusing the metals together as the arc was manually passed over the joint to be welded During the 1890's, arc welding was accomplished with bare metal electrodes that were consumed in the molten puddle and became part of the weld metal. The welds were of poor quality due to the nitrogen and oxygen in the atmosphere forming harmful oxides and nitrides in the weld metal. Early in the Twentieth Century, the importance of shielding the arc from the atmosphere was realized. Covering the electrode with a material that decomposed in the heat of the arc to form a gaseous shield appeared to be the best method to accomplish this end. As a result, various methods of covering electrodes, such as wrapping and dipping, were tried. These efforts culminated in the extruded coated electrode in the mid-1920's, greatly improving the quality of the weld metal and providing what many consider the most significant advance in electric arc welding Since welding with coated electrodes is a rather slow procedure, more rapid welding processes were developed. This lesson will cover the more commonly used electric arc welding processes in use today. LESSON II Reliability of 2.2 SHIELDED METAL ARC WELDING Shielded Metal Arc *, also known as manual metal arc welding, stick welding, or electric arc welding, is the most widely used of the various arc welding processes. is performed with the heat of an electric arc that is maintained between the end of a coated metal electrode and the work piece (See Figure 1). The heat produced by the arc melts the base metal, the electrode core rod, and the coating. As the molten metal droplets are transferred across the arc and into the molten weld puddle, they are shielded from the atmosphere by the gases produced from the decomposition of the flux coating. The molten slag floats to the top of the weld puddle where it protects the weld metal from the atmosphere during solidification. COPYRIGHT 1998 THE ESAB GROUP, INC

40 Arc for for Low Carbon Other functions of the coating are to provide arc stability and control bead shape. More information on coating functions will be covered in subsequent lessons. * Shielded Metal Arc (SMAW) is the terminology approved by the American Society Equipment & Operation - One reason for the wide acceptance of the SMAW process is the simplicity of the necessary equipment. The equipment consists of the following items. (See Figure 2) 1. power source 2. Electrode holder 3. Ground clamp 4. cables and connectors 5. Accessory equipment (chipping hammer, wire brush) MOLTEN POOL 6. Protective equipment (helmet, gloves, etc.) COATING CORE ROD SHIELDING GASES WORK PIECE FIGURE 1 WELD METAL SHIELDED METAL ARC WELDING Power Sources - Shielded metal arc welding may utilize either alternating current (AC) or direct current (DC), but in either case, the power source selected must be of the constant current type. This type of power source will deliver a relatively constant amperage or welding current regardless of arc length variations by the operator (See Lesson I, Section 1.9). The amperage determines the amount of heat at the arc and since it will remain relatively constant, the weld beads produced will be uniform in size and shape Whether to use an AC, DC, or AC/DC power source depends on the type of welding to be done and the electrodes used. The following factors should be considered: LESSON II SOLIDIFIED SLAG AC OR DC POWER SOURCE ELECTRODE CABLE ELECTRODE HOLDER ELECTRODE GROUND WORK CABLE SHIELDED METAL ARC WELDING CIRCUIT FIGURE 2 Reliability of 1. Electrode Selection - Using a DC power source allows the use of a greater range of electrode types. While most of the electrodes are designed to be used on AC or DC, some will work properly only on DC. 2. Metal Thickness - DC power sources may be used for welding both heavy sections and light gauge work. Sheet metal is more easily welded with DC because it is easier to strike and maintain the DC arc at low currents. COPYRIGHT 1998 THE ESAB GROUP, INC

41 Arc LESSON II 3. Distance from Work - If the distance from the work to the power source is great, AC is the best choice since the voltage drop through the cables is lower than with DC. Even though welding cables are made of copper or aluminum (both good conductors), the resistance in the cables becomes greater as the cable length increases. In other words, a voltage reading taken between the electrode and the work will be somewhat lower than a reading taken at the output terminals of the for for Low power source. This is known as voltage drop. 4. Position (See Appendix A - Glossary of Terms) - Because DC may be operated at lower welding currents, it is more suitable for overhead and vertical welding than AC. AC can successfully be used for out-of-position work if proper electrodes are selected. 5. Arc Blow - When welding with DC, magnetic fields are set up throughout the weldment. In weldments that have varying thickness and protrusions, this magnetic field can affect the arc by making it stray or fluctuate in direction. This condition is especially troublesome when welding in corners. AC seldom causes this problem because of the rapidly reversing magnetic field produced Combination power sources that produce both AC and DC are available and provide the versatility necessary to select the proper welding current for the application. Carbon When using a DC power source, the question of whether to use electrode negative or positive polarity arises. Some electrodes operate on both DC straight and reverse polarity, and others on DC negative or DC positive polarity only. Direct current flows in one direction in an electrical circuit and the direction of current flow and the composition of the electrode coating will have a definite effect on the welding arc and weld bead. Figure 3 shows the connections and effects of straight and reverse polarity Electrode negative (-) produces welds with shallow penetration; however, the electrode melt-off rate is high. The weld bead is rather wide and shallow as shown at "A" in Figure 3. Electrode positive (+) produces welds with deep penetration DC POWER SOURCE HIGHER BURN-OFF RATE, LESS PENETRATION A B DEEP PENETRATION, LOW BURN-OFF RATE DC POWER SOURCE and a narrower weld bead as shown at "B" in Figure 3. ELECTRODE WORK PIECE STRAIGHT POLARITY ELECTRODE WORK PIECE REVERSE POLARITY Reliability of FIGURE 3 COPYRIGHT 1998 THE ESAB GROUP, INC.

42 Arc for for Low LESSON II While polarity affects the penetration and burn-off rate, the electrode coating also has a strong influence on arc characteristics. Performance of individual electrodes will be discussed in succeeding lessons Electrode Holder - The electrode holder connects to the welding cable and conducts the welding current to the electrode. The insulated handle is used to guide the electrode over the weld joint and feed the electrode over the weld joint and feed the electrode into the weld puddle as it is consumed. Electrode holders are available in different sizes and are rated on their current carrying capacity Ground Clamp - The ground clamp is used to connect the ground cable to the work piece. It may be connected directly to the work or to the table or fixture upon which the work is positioned. Being a part of the welding circuit, the ground clamp must be capable of carrying the welding current without overheating due to electrical resistance Cables - The electrode cable and the ground cable are important parts of the welding circuit. They must be very flexible and have a tough heat-resistant insulation. Connections at the electrode holder, the ground clamp, and at the power source lugs must be soldered or well crimped to assure low electrical resistance. The cross-sectional area of the cable must be sufficient size to carry the welding current with a minimum of voltage drop. Increasing the cable length necessitates increasing the cable diameter to lessen resistance and voltage drop. The table in Figure 4 lists the suggested American Wire Gauge (AWG) cable size to be used for various welding currents and cable lengths. Carbon Service Range (Amperes) Total Cable Length (Ground Lead Plus Electrode Lead) Up to 50 ft. Up to 100 ft. Up to 250 ft. Up to 500 ft. Cable Voltage Cable Voltage Cable Voltage Cable Voltage Size Drop Size Drop Size Drop Size Drop 20 to 180 #3 1.8 #2 2.9 #1 5.7 # Amps 30 to 250 #2 1.8 #1 2.5 #0 5.0 # Amps 60 to 375 #0 1.7 #0 3.0 # # Amps 80 to 500 # # # # Amps 100 to 600 # # Amps Voltage drops indicated do not include any drop caused by poor connection, electrode holder, or work metal Voltage Drop Figured At FIGURE Coated - Various types of coated electrodes are used in shielded metal arc welding. used for welding mild or carbon steels are quite different than those used for welding the low alloys and stainless steels. Details on the specific types will be covered in subsequent lessons. Reliability of COPYRIGHT 1998 THE ESAB GROUP, INC

43 2.3 GAS TUNGSTEN ARC WELDING LESSON II Arc for for Low Carbon Gas Tungsten Arc * is a welding process performed using the heat of an arc established between a nonconsumable tungsten electrode and the work piece. See Figure 5. The electrode, the arc, and the area surrounding the molten weld puddle are protected from the atmosphere by an inert gas shield. The electrode is not consumed in the weld puddle as in shielded metal arc welding. If a filler metal is necessary, it is added to the leading the molten puddle as shown in Gas tungsten arc welding produces exceptionally clean welds no slag is produced, the chance inclusions in the weld metal is and the finished weld requires virtually no cleaning. Argon and Helium, the primary shielding gases employed, are inert gases. Inert gases do not chemically combine FILLER METAL with other elements and therefore, are used to exclude the reactive gases, such as oxygen and nitrogen, from forming compounds that could be detrimental to the weld metal. TRAVEL DIRECTION TUNGSTEN ELECTRODE FIGURE 5 WORK PIECE Gas tungsten arc welding may be used for welding almost all metals mild steel, low alloys, stainless steel, copper and copper alloys, aluminum and aluminum alloys, nickel and nickel alloys, magnesium and magnesium alloys, titanium, and others. This process is most extensively used for welding aluminum and stainless steel alloys where weld integrity is of the utmost importance. Another use is for the root pass (initial pass) in pipe welding, which requires a weld of the highest quality. Full penetration without an excessively high inside bead is important in the root pass, and due to the ease of current control of this process, it lends itself to control of back-bead size. For high quality welds, it is usually necessary to provide an inert shielding gas inside the pipe to prevent oxidation of the inside weld bead. ARC GAS TUNGSTEN ARC WELDING TORCH SHIELDING GAS NOZZLE INERT GAS SHIELD Reliability of * Gas Tungsten Arc (GTAW) is the current terminology approved by the American Society, formerly known as "TIG" (Tungsten Inert Gas) welding. COPYRIGHT 1998 THE ESAB GROUP, INC

44 Arc for for Low Carbon Reliability of Gas tungsten arc welding lends itself to both manual and automatic operation. In manual operation, the welder holds the torch in one hand and directs the arc into the weld joint. The filler metal is fed manually into the leading edge of the puddle. In automatic applications, the torch may be automatically moved over a stationary work piece or the torch may be stationary with the work moved or rotated in relation to the torch. Filler metal, if required, is also fed automatically EQUIPMENT AND OPERATION - Gas tungsten arc welding may be accomplished with relatively simple equipment, or it may require some highly sophisticated components. Choice of equipment depends upon the type of metal being joined, the position of the weld being made, and the quality of the weld metal necessary for the application. The basic equipment consists of the following: 1. The power source 2. Electrode holder (torch) 3. Shielding gas 4. Tungsten electrode 5. Water supply when necessary 6. Ground cable 7. Protective equipment Figure 6 shows a basic gas tungsten arc welding schematic. SHIELDING GAS SUPPLY REGULATOR FLOW METER GAS HOSE (WATER COOLED ONLY) GAS COOLED ONLY WELDING CABLE POWER SOURCE WATER FROM TORCH * COMPOSITE CABLE WATER COOLER WATER TO TORCH GROUND CABLE GAS TUNGSTEN ARC WELDING CONNECTION SCHEMATIC FIGURE 6 TORCH WORK LESSON II * COMPOSITE CABLE GAS COOLED TORCH. CURRENT IN & GAS IN. WATER COOLED TORCH. CURRENT IN & WATER OUT COPYRIGHT 1998 THE ESAB GROUP, INC.

45 2.3.2 Power Sources - Both AC and DC power sources are used in gas tungsten arc LESSON II Arc for for Low Carbon welding. They are the constant current type with a drooping volt-ampere curve. This type of power source produces very slight changes in the arc current when the arc length (voltage) is varied. Refer to Lesson I, Section The choice between an AC or DC welder depends on the type and thickness of the metal to be welded. Distinct differences exist between AC and DC arc characteristics, and if DC is chosen, the polarity also becomes an important factor. The effects of polarity in GTAW are directly opposite the effects of polarity in SMAW as described in paragraphs through In SMAW, the distribution of heat between the electrode and work, which determines the penetration and weld bead width, is controlled mainly by the ingredients in the flux coating on the electrode. In GTAW where no flux coating exists, heat distribution between the electrode and the work is controlled solely by the polarity. The choice of the proper welding current will be better understood by analyzing each type separately. The chart in Figure 7 lists current recommendations. Material & Thickness DCEN DCEP Aluminum Under 1/8" Over 1/8" Magnesium Under 1/16" Over 1/16" Carbon Steel Under 1/8" Over 1/8" Stainless Steel Under 1/8" Over 1/8" Copper Under 1/8" Over 1/8" Nickel Alloys Under 1/8" Over 1/8" Titanium Under 1/8" Over 1/8" 2 2 & AC High Freq. Argon Helium Ar/He WELDING CURRENT SHIELDING GAS Preferred Choice - Manual 2. Preferred Choice - Automatic 3. Second Choice - Automatic CURRENT/SHIELDING GAS SELECTION, TUNGSTEN GAS ARC WELDING FIGURE 7 Reliability of COPYRIGHT 1998 THE ESAB GROUP, INC.

46 Arc for for Low Direct current electrode negative (DCEN) is produced when the electrode is connected to the negative terminal of the power source. Since the electrons flow from the electrode to the plate, approximately 70% of the heat of the arc is concentrated at the work, and approximately 30% at the electrode end. This allows the use of smaller tungsten electrodes that produce a relatively narrow concentrated arc. The weld shape has deep penetration and is quite narrow. See Figure 8. Direct current electrode negative is suitable for welding most metals. Magnesium and aluminum have a refractory oxide coating on the surface that must be physically removed immediately prior to welding if DCSP is to be used Direct current electrode positive (DCEP) is produced when the electrode is connected to the positive terminal of the welding power source. In this condition, the electrons flow from the work to the electrode tip, concentrating approximately 70% of the heat of the arc at the electrode and 30% at the work. This higher heat at the electrode necessitates using larger diameter tungsten to prevent it from melting and contaminating the weld metal. Since the electrode diameter is larger and the heat is less concentrated at the work, the resultant weld bead is relatively wide and shallow. See Figure 8. LESSON II Electrode Oxide Heat Polarity Penetration Cleaning Concentration Carbon + + _ + GAS IONS ELECTRON FLOW Direct Current Straight Polarity Electrode Negative Alternating Current Direct Current Reverse Polarity Electrode Positive Deep Penetration Narrow Bead Medium Penetration Medium Width Bead Shallow Penetration Wide Bead None Good Cleans Oxide on Each Half Maximum At Work Cycle Alternates Between Electrode and Work At Electrode Reliability of EFFECTS OF CURRENT TYPE - GAS TUNGSTEN ARC WELDING FIGURE Aluminum and magnesium are two metals that have a heavy oxide coating that acts as an insulator and must be removed before successful welding can take place. with electrode positive provides a good oxide cleaning action in the arc. If we were to study the physics of the welding arc, we find that the electric current causes the shielding gas atoms to lose some of their electrons. Since electrons are negatively charged, these gas atoms now are unbalanced and have an excessive positive charge. As we learned in Lesson I, unlike charges attract. These positively charged atoms (or positive ions as they are known in COPYRIGHT 1998 THE ESAB GROUP, INC.

47 Arc for for Low Carbon Reliability of LESSON II chemical terminology) are attracted to the negative pole, in this case the work, at high velocity. Upon striking the work surface, they dislodge the oxide coating permitting good electrical conductivity for the maintenance of the arc, and eliminate the impurities in the weld metal that could be caused by these oxides Direct current electrode positive is rarely used in gas-tungsten arc welding. Despite the excellent oxide cleaning action, the lower heat input in the weld area makes it a slow process, and in metals having higher thermal conductivity, the heat is rapidly conducted away from the weld zone. When used, DCEP is restricted to welding thin sections (under 1/8") of magnesium and aluminum Alternating current is actually a combination of DCEN and DCEP and is widely used for welding aluminum. In a sense, the advantages of both DC processes are combined, and the weld bead produced is a compromise of the two. Remember that when welding with 60 Hz current, the electron flow from the electrode tip to the work reverses direction 120 times every second. Thereby, the intense heat alternates from electrode to work piece, allowing the use of an intermediate size electrode. The weld bead is a compromise having medium penetration and bead width. The gas ions blast the oxides from the surface of aluminum and magnesium during the positive half cycle. Figure 8 illustrates the effects of the different types of current used in gas-tungsten arc welding DC constant current power sources - Constant current power sources, used for shielded metal arc welding, may also be used for gas-tungsten arc welding. In applications where weld integrity is not of utmost importance, these power sources will suffice. With machines of this type, the arc must be initiated by touching the tungsten electrode to the work and quickly withdrawing it to maintain the proper arc length. This starting method contaminates the electrode and blunts the point which has been grounded on the electrode end. These conditions can cause weld metal inclusions and poor arc direction. Using a power source designed for gas tungsten arc welding with a high frequency stabilizer will eliminate this problem. The electrode need not be touched to the work for arc initiation. Instead, the high frequency voltage, at very low current, is superimposed onto the welding current. When the electrode is brought to within approximately 1/8 inch of the base metal, the high frequency ionizes the gas path, making it conductive and a welding arc is established. The high frequency is automatically turned off immediately after arc initiation when using direct current AC Constant Current Power Source - Designed for gas tungsten arc welding, always incorporates high frequency, and it is turned on throughout the weld cycle to maintain a stable arc. When welding with AC, the current passes through 0 twice in every cycle and the COPYRIGHT 1998 THE ESAB GROUP, INC

48 Arc for for Low Carbon Reliability of LESSON II arc must be reestablished each time it does so. The oxide coating on metals, such as aluminum and magnesium, can act much like a rectifier as discussed in Lesson I. The positive half-cycle will be eliminated if the arc does not reignite, causing an unstable condition. Continuous high frequency maintains an ionized path for the welding arc, and assures arc reignition each time the current changes direction. AC is extensively used for welding aluminum and magnesium AC/DC Constant Current Power Sources - Designed for gas tungsten arc welding, are available, and can be used for welding practically all metals. The gas tungsten arc welding process is usually chosen because of the high quality welds it can produce. The metals that are commonly welded with this process, such as stainless steel, aluminum and some of the more exotic metals, cost many times the price of mild steel; and therefore, the power sources designed for this process have many desirable features to insure high quality welds. Among these are: 1. Remote current control, which allows the operator to control welding amperage with a hand control on the torch, or a foot control at the welding station. 2. Automatic soft-start, which prevents a high current surge when the arc is initiated. 3. Shielding gas and cooling water solenoid valves, which automatically control flow before, during and for an adjustable length of time after the weld is completed. 4. Spot-weld timers, which automatically control all elements during each spot-weld cycle. Other options and accessories are also available Power sources for automatic welding with complete programmable output are also available. Such units are used extensively for the automatic welding of pipe in position. The welding current is automatically varied as the torch travels around the pipe. Some units provide a pulsed welding current where the amperage is automatically varied between a low and high several times per second. This produces welds with good penetration and improved weld bead shape Torches - The torch is actually an electrode holder that supplies welding current to the tungsten electrode, and an inert gas shield to the arc zone. The electrode is held in a collet-like clamping device that allows adjustment so that the proper length of electrode protrudes beyond the shielding gas cup. Manual torches are designed to accept electrodes of 3 COPYRIGHT 1998 THE ESAB GROUP, INC

49 Arc for for Low Carbon Reliability of LESSON II inch or 7 inch lengths. Torches may be either air or water-cooled. The air-cooled types actually are cooled to a degree by the shielding gas that is fed to the torch head through a composite cable. The gas actually surrounds the copper welding cable, affording some degree of cooling. Water-cooled torches are usually used for applications where the welding current exceeds 200 amperes. The water inlet hose is connected to the torch head. Circulating around the torch head, the water leaves the torch via the current-in hose and cable assembly. Cooling the welding cable in this manner allows the use of a smaller diameter cable that is more flexible and lighter in weight The gas nozzles are made of ceramic materials and are available in various sizes and shapes. In some heavy duty, high current applications, metal water-cooled nozzles are used A switch on the torch is used to energize the electrode with welding current and start the shielding gas flow. High frequency current and water flow are also initiated by this switch if the power source is so equipped. In many installations, these functions are initiated by a foot control that also is capable of controlling the welding current. This method gives the operator full control of the arc. The usual welding method is to start the arc at a low current, gradually increase the current until a molten pool is achieved, and welding begins. At the end of the weld, current is slowly decreases and the arc extinguished, preventing the crater that forms at the end of the weld when the arc is broken abruptly Shielding Gases - Argon and helium are the major shielding gases used in gas tungsten arc welding. In some applications, mixtures of the two gases prove advantageous. To a lesser extent, hydrogen is mixed with argon or helium for special applications Argon and helium are colorless, odorless, tasteless and nontoxic gases. Both are inert gases, which means that they do not readily combine with other elements. They will not burn nor support combustion. Commercial grades used for welding are 99.99% pure. Argon is.38% heavier than air and about 10 times heavier than helium. Both gases ionize when present in an electric arc. This means that the gas atoms lose some of their electrons that have a negative charge. These unbalanced gas atoms, properly called positive ions, now have a positive charge and are attracted to the negative pole in the arc. When the arc is positive and the work is negative, these positive ions impinge upon the work and remove surface oxides or scale in the weld area Argon is most commonly used of the shielding gases. Excellent arc starting and ease of use make it most desirable for manual welding. Argon produces a better cleaning action when welding aluminum and magnesium with alternating current. The arc produced is COPYRIGHT 1998 THE ESAB GROUP, INC

50 Arc LESSON II relatively narrow. Argon is more suitable for welding thinner material. At equal amperage, helium produces a higher arc voltage than argon. Since welding heat is the product of volts times amperes, helium produces more available heat at the arc. This makes it more suitable for welding heavy sections of metal that have high heat conductivity, or for automatic welding operations where higher welding speeds are required. for for Low Carbon Argon-helium gas mixtures are used in applications where higher heat input and the desirable characteristics of argon are required. Argon, being a relatively heavy gas, blankets the weld area at lower flow rates. Argon is preferred for many applications because it costs less than helium Helium, being approximately 10 times lighter than argon, requires flow rates of 2 to 3 times that of argon to satisfactorily shield the arc for gas tungsten arc welding are available in diameters from.010" to 1/4" in diameter and standard lengths range from 3" to 24". The most commonly used sizes, however, are the.040", 1/16", 3/32", and 1/8" diameters The shape of the tip of the electrode is an important factor in gas tungsten arc welding. When welding with DCEN, the tip must be ground to a point. The included angle at which the tip is ground varies with the application, the electrode diameter, and the welding current. Narrow joints require a relatively small included angle. When welding very thin material at low currents, a needlelike point ground onto the smallest available electrode may be necessary to stabilize the arc. Properly ground electrodes will assure easy arc starting, good arc stability, and proper bead width When welding with AC, grinding the electrode tip is not necessary. When proper welding current is used, the electrode will form a hemispherical end. If the proper welding current is exceeded, the end will become bulbous in shape and possibly melt off to contaminate the weld metal The American Society has published Specification AWS A for tungsten arc welding electrodes that classifies the electrodes on the basis of their chemical composition, size and finish. Briefly, the types specified are listed below: 1) Pure Tungsten (AWS EWP) Color Code: Green Used for less critical applications. The cost is low and they give good results at relatively low currents on a variety of metals. Most stable arc when used on AC, either balanced wave or continuous high frequency. Reliability of COPYRIGHT 1998 THE ESAB GROUP, INC

51 Arc for for Low 2) 1% Thoriated Tungsten (AWS EWTh-1) Color Code: Yellow Good current carrying capacity, easy arc starting and provide a stable arc. Less susceptible to contamination. Designed for DC applications of nonferrous materials. 3) 2% Thoriated Tungsten (AWS EWTh-2) Color Code: Red Longer life than 1% Thoriated electrodes. Maintain the pointed end longer, used for light gauge critical welds in aircraft work. Like 1%, designed for DC applications for nonferrous materials. 4).5% Thoriated Tungsten (AWS EWTh-3) Color Code: Blue Sometimes called "striped" electrode because it has % Thoria inserted in a wedge-shaped groove throughout its length. Combines the good properties of pure and thoriated electrodes. Can be used on either AC or DC applications. 5) Zirconia Tungsten (AWS EWZr) Color Code: Brown LESSON II Longer life than pure tungsten. Better performance when welding with AC. Melts more easily than thoriam-tungsten when forming rounded or tapered tungsten end. Ideal for applications where tungsten contamination must be minimized. Carbon Summary - Gas Tungsten Arc is one of the major welding processes today. The quality of the welds produced and the ability to weld very thin metals are the major features. The weld metal quality is high since no flux is used, eliminating the problem of slag inclusions in the weld metal. It is used extensively in the aircraft and aerospace industry, where high quality welds are necessary and also for welding the more expensive metals where the weld defects become very costly. Metals as thin as.005" can be welded due to the ease of controlling the current The major disadvantages of the process are that it is slower than welding with consumable electrodes and is little used on thicknesses over 1/4" for this reason. Shielding gas and tungsten electrode costs make the process relatively expensive. 2.4 GAS METAL ARC WELDING Gas Metal Arc * is an arc welding process that uses the heat of an electric arc established between a consumable metal electrode and the work to be welded. The electrode is a bare metal wire that is transferred across the arc and into the molten weld puddle. The Reliability of * Gas Metal Arc (GMAW) is the current technology approved by the American Society. Formerly known as "MIG" (Metal Inert Gas). COPYRIGHT 1998 THE ESAB GROUP, INC

52 Arc for wire, the weld puddle, and the area in the arc zone are protected from the atmosphere by a gaseous shield. Inert gases, reactive gases, and gas mixtures are used for shielding. The metal transfer mode is dependent on shielding gas choice and welding current level. Figure 9 is a sketch of the process showing the basic features. SOLID WIRE ELECTRODE TRAVEL DIRECTION GAS NOZZLE WELDING WIRE WELDING CABLE SHIELDING GAS LESSON II for Low GAS SHIELD ARC WELD METAL MOLTEN POOL CONTACT TIP WORK PIECE GAS METAL ARC WELDING FIGURE 9 Carbon Reliability of Gas metal arc welding is a versatile process that may be used to weld a wide variety of metals including carbon steels, low alloy steels, stainless steels, aluminum alloys, magnesium, copper and copper alloys, and nickel alloys. It can be used to weld sheet metal or relatively heavy sections. Welds may be made in all positions, and the process may be used for semiautomatic welding or automatic welding. In semiautomatic welding, the wire feed speed, voltage, amperage, and gas flow are all preset on the control equipment. The operator needs merely to guide the welding gun along the joint at a uniform speed and hold a relatively constant arc length. In automatic welding, the gun is mounted on a travel carriage that moves along the joint, or the gun may be stationary with the work moving or revolving beneath it Practically all GMAW is done using DCEP (Electrode positive). This polarity provides deep penetration, a stable arc and low spatter levels. A small amount of GMAW welding is done with DCEN and although the melting rate of the electrode is high, the arc is erratic. Alternating current is not used for gas metal arc welding Current Density - To understand why gas metal arc welding can deposit weld metal at a rapid rate, it is necessary that the term "current density" be understood. Figure 10 shows a 1/4" coated electrode and a 1/16" solid wire drawn to scale. Both are capable of carrying 400 amperes. Notice that the area of the 1/16" wire is only 1/16 that of the core wire of the coated electrode. We can say that the current density of the 1/16" wire is 16 times COPYRIGHT 1998 THE ESAB GROUP, INC.

53 Arc for for Low LESSON II greater than the current density AREA =.049 SQ. IN. of the 1/4" wire at equal welding currents. The resultant melt-off rate of the solid wire is very high. CORE WIRE AREA =.0031 SQ. IN. A If we were to increase the current A 16 through the 1/4" coated 1/16" FLUX electrode to increase the current density, the resistance heating COATING SOLID WIRE 1/4" through the 14" electrode length would be excessive, and the rod would become so COATED ELECTRODE = 16 hot that the coating would crack, rendering RELATIVE SIZE OF ELECTRODES FOR WELDING AT 400 AMPS it useless. The 1/16" wire carries the high current a distance of less than 3/4", the FIGURE 10 approximate distance from the end of the contact tip to the arc Metal Transfer Modes Spray transfer is a high current density process that rapidly deposits weld metal in droplets smaller than the electrode diameter. They are propelled in a straight line from the center of the electrode. A shielding gas mixture of Argon with 1% to 2% Oxygen is used for welding mild and low alloy steel, and pure Argon or Argon-Helium mixtures are used for welding aluminum, magnesium, copper, and nickel alloys. current at which spray transfer Carbon SPRAY TRANSFER GLOBULAR TRANSFER PULSE TRANSFER MODES OF METAL TRANSFER SHORT CIRCUITING ARC METAL TRANSFER FIGURE 11 takes place is relatively high and will vary with the metal being welded, electrode diameter, and the shielding gas being used. Deposition rates are high and welding is usually limited to the flat or horizontal fillet position. See Figure 11. Reliability of COPYRIGHT 1998 THE ESAB GROUP, INC

54 Arc for for Low Carbon Reliability of Globular transfer takes place at lower welding currents than spray transfer. There is a transition current where the transfer changes to globular even when shielding gases using a high percentage of argon are used. When carbon dioxide (CO 2 ) is used as a shielding gas, the transfer is always globular. In globular transfer, a molten drop larger than the electrode diameter forms on the end of the electrode, moves to the outer edge of the electrode and falls into the molten puddle. Occasionally, a large drop will "short circuit" across the arc, causing the arc to extinguish momentarily, and then instantaneously reignite. As a result, the arc is somewhat erratic, spatter level is high, and penetration shallow. Globular transfer is not suitable for out-of-position welding. See Figure Short circuiting transfer is a much used method in gas metal arc welding. It is produced by using the lowest current-voltage settings and the smaller wires, usually.030",.035", and.045" diameters. The low heat input makes this process ideal for sheet metal, outof-position work, and poor fit-up applications. Often called "short arc welding" because metal transfer is achieved each time the wire actually short circuits (makes contact) with the weld puddle. This happens very rapidly. It is feasible for the short circuit frequency to be times a second, but in practice, it occurs from times a second. Each time the electrode touches the puddle, the arc is extinguished. It happens so rapidly that it is visible only on high speed films Pulse transfer is a mode of metal transfer somewhat between spray and short circuiting. The specific power source has built into it two output levels: a steady background level, and a high output (peak) level. The later permits the transfer of metal across the arc. This peak output is controllable between high and low values up to several hundred cycles per second. The result of such a peak output produces a spray arc below the typical transition current Figure 11 shows the transfer method. The arc is initiated by touching the wire to the work. Upon initial contact, a bit of the wire melts off to form a molten puddle. The wire feeds forward until it actually contacts the work again, as at 1 in Figure 11, and the arc is extinguished. The short circuiting current causes the wire to neck down, as shown in 1, until it melts off, as shown at 2. As soon as the wire is free of the puddle, the arc is reignited and a molten ball forms at the end of the electrode, as at 3. The wire continues to move forward until it makes contact with the puddle, and the cycle is repeated Gas metal arc spot welding is a variation of the process that allows spot welding of thinner gauge metals, or of a thin gauge metal to a heavier section. The gun is placed directly against the work and is equipped with a special nozzle to allow escape of the shielding gas. When the trigger switch is actuated, the following sequence takes place. The shielding LESSON II COPYRIGHT 1998 THE ESAB GROUP, INC

55 Arc for for Low LESSON II gas flows for a short interval before wire feeding starts; wire feeding starts; the arc is initiated and continues for a preset time (usually a few seconds). The welding current and wire feeding stops, and the shielding gas flows for a short interval before it automatically stops. The process is also useful for tacking welding pieces in position prior to running the final weld bead EQUIPMENT AND OPERATION - The equipment used for gas metal arc welding is more complicated than that required for shielded metal arc welding. Initial cost is relatively high, but the cost is rapidly amortized due to the savings in labor and overhead achieved by the rapid weld metal deposition The equipment necessary for gas metal arc welding is listed below: 1) Power source 2) Wire feeder 3) gun 4) Shielding gas supply 5) Solid electrode wire 6) Protective equipment Carbon The basic equipment necessary for semiautomatic gas metal arc welding is shown in Figure 12. TRIGGER CONTROL LEAD FEED ROLLS GAS HOSE WIRE SPOOL WIRE FEEDER FLOWMETER REGULATOR VALVE WELD CABLE WELDING GUN 115V GROUND CABLE WORK MAGNETIC CONTACTOR + _ SHIELDING GAS POWER SOURCE SCHEMATIC DIAGRAM SEMI-AUTOMATIC GMAW EQUIPMENT Reliability of FIGURE 12 COPYRIGHT 1998 THE ESAB GROUP, INC

56 Arc for for Low Carbon Power Source - A direct current, constant voltage power source is recommended for gas metal arc welding. It may be a transformer-rectifier or a rotary type unit. The lower open circuit voltage and self-correcting arc length feature, as described in Lesson I, makes it most suitable. Constant voltage power sources used for spray transfer welding and for flux cored electrode welding (to be covered later) are the same. However, if the unit is to be used for short-circuiting arc welding, it must have "slope" or slope control. 25 Slope control is a means of limiting the high short-circuit current that is characteristic of this type welder. Figure 13 shows the effect of slope on the shortcircuiting current. V O L T S OPERATING POINT CONSTANT VOLTAGE V/A CURVE SHORT CIRCUITING CURRENT WITH SLOPE If we were EFFECT OF SLOPE ON SHORT CIRCUITING CURRENT short-arc welding at FIGURE 13 approximately 150 amperes and 18 volts, as shown in Figure 13, and had no slope components in the power source, the current at short-circuit or when the wire touches the work, would be over 1400 amperes. At this high current, a good length of the wire would literally explode off the end, cause much spatter, and the arc would be erratic. With the slope components in the circuit, the short-circuiting current is in the neighborhood of 400 amperes, and the molten ball is sort of pinched off the end of the wire more gently. For those with an electrical background, it might be added that in some machines, slope is achieved by adding a reactor in the AC secondary of the power source. In others, a slope resistor is added in the DC output portion of the circuit. Slope may be adjustable for varying wire diameters or it may be fixed, giving a good average value for.035" and.045" diameter wires, the two most popular sizes. LESSON II SHORT CIRCUITING CURRENT NO SLOPE Another factor influencing the arc in short-circuiting welding is the rate that the amperage reaches the short-circuiting current level. Using the example in Figure 13, we know that the current goes from 150 amperes to 400 amperes during each shorting period. If we were to plot the current rise on a graph, as in Figure 14, we would see that the current rise if very rapid, as shown by the broken line. Reliability of COPYRIGHT 1998 THE ESAB GROUP, INC

57 Arc for for Low Carbon Reliability of LESSON II This rapid current rise can be by using a device called an (sometimes called a stabilizer) output circuit of the welder. An 400 AMPS merely an iron core wound WITHOUT INDUCTANCE turns of heavy wire. It does current flow, but it acts somewhat like a fly wheel or WITH INDUCTANCE damper by retarding the rate of rise as shown by the solid line. By preventing the 150 AMPS rapid current rise, the arc TIME - MILLISECONDS becomes smoother, EFFECT OF INDUCTANCE ON CURRENT RISE spatter is reduced, and FIGURE 14 bead shape and appearance are improved. Because the inductor influences the time function, its design determines arc on-off time, and short-circuit frequency. Some power sources have a selector that can switch in several different inductance values to finely tune the arc power sources designed for gas metal arc welding have a 115 volt outlet to provide power to operate the wire feeder. They also have a receptacle to receive the electrical power required to close the main contactor in the power source, which turns on the welding power to the welding gun when the gun trigger is actuated Additional advancements in equipment technology have introduced many new models. Inverters, as well as microprocessor controls, have created the greatest attention. In addition, multipurpose machines have provided the user with greater flexibility with a variety of capabilities Global competition will continue to have a profound influence on future advancements in arc welding equipment. As energy prices rise, greater demands for more efficient equipment will follow Wire Feeder - When welding with a constant voltage power source, as is the case in most gas metal arc welding applications, the prime function of the wire feeder is to deliver the welding wire to the arc at a very constant speed. Since the wire feed speed determines the amperage, and the amperage determines the amount of heat at the arc, inconsistent wire feed speed will produce welds of varying penetration and bead width. Advanced electronics COPYRIGHT 1998 THE ESAB GROUP, INC.

58 Arc for for Low Carbon LESSON II technology makes it possible to design motor speed controls that will produce the same speed, even though the load on the motor varies or the input voltage to the motor may fluctuate A limited amount of gas metal arc welding is performed with constant current type power sources. In this case, the motor speed automatically varies to increase or decrease the wire feed speed as the arc length varies to maintain a constant voltage The wire feeder also controls the main contactor in the power source for safety reasons. This assures that the welding wire will only be energized when the switch on the welding gun is depressed The flow of shielding gas is controlled by a solenoid valve (magnetic valve) in the wire feeder to turn the shielding gas on and off when the gun switch is actuated. Most feeders utilize a dynamic breaking circuit to quickly stop the motor at the end of a weld to prevent a long length of wire protruding from the gun when the weld is terminated. Most feeders have a burn-back circuit that allows the welding current to stay on for a short period of time after wire feeding has stopped, to allow the wire to burn back exactly the right amount for the next arc initiation The feed rolls, sometimes called drive rolls, pull the wire off the spool or reel, and push it through a feed cable or conduit to the welding gun. These rolls must usually be changed to accommodate each different wire diameter, although some rolls are designed to feed a combination of sizes Gun - The function of the welding gun, sometimes referred to as a torch, is to deliver the welding wire, welding current, and shielding gas to the welding arc. Guns are available for semi-automatic operation and for automatic operation, where they are fixed in the automatic welding head Guns for GMAW have several characteristics in common. All have a copper alloy shielding gas nozzle, that delivers the gas to the arc area in a nonturbulent, angular pattern to prevent aspiration of air. The nozzle may be water cooled for semiautomatic welding at high amperage and for automatic welding where the arc time is of long duration. current is transferred to the welding wire as the wire travels through the contact tip or contact tube located inside the gas nozzle (Refer to Figure 9). The hole in the contact tip through which the wire passes is only a few thousandths of an inch larger than the wire diameter. A worn contact tip will result in an erratic arc due to poor current transfer. Figure 15 shows a few different semiautomatic gun configurations that are commonly used for GMAW. Reliability of COPYRIGHT 1998 THE ESAB GROUP, INC

59 LESSON II Arc CURVED NECK PISTOL TYPE for SELF CONTAINED PULL TYPE for Low SEMI-AUTOMATIC GMAW GUN TYPES FIGURE The curved neck or "goose neck" type is probably the most commonly used. It allows the best access to a variety of weld joints. The wire is pushed to this type of gun by the feed rolls in the wire feeder through a feed cable or conduit that usually is 10 or 12 feet in length. The shielding gas hose, welding current cable, and trigger switch leads are supplied with the welding gun. Carbon The pistol type gun is similar to the curved neck type, but is less adaptable for difficult to reach joints. The pistol type is also a "push" type gun and is more suitable for gas metal arc spot welding applications The self contained type has an electric motor in the handle and feed rolls that pull the wire from a 1 or 2 pound spool mounted on the gun. The need for a long wire feed cable is eliminated, and wire feed speed may be controlled by the gun. Guns of this type are often used for aluminum wire up to.045" diameter, although they may also be used for feeding steel or other hard wires. Reliability of The pull type gun has either an electric motor or an air motor mounted in the handle that is coupled to a feeding mechanism in the gun. The spool of wire is located in the control cabinet that may be located as far as fifty feet from the gun. When feeding such long distances, a set of "push" rolls located in the control cabinet assist in feeding the wire. This then becomes known as a push-pull feed system and is especially useful in feeding the softer wires such as aluminum SHIELDING GASES - In gas metal arc welding, there are a variety of shielding gases that can be used, either alone or in combinations of varying degrees. The choice is dependent on the type of metal transfer employed, the type and thickness of metal, the bead COPYRIGHT 1998 THE ESAB GROUP, INC.

60 Arc LESSON II profile (See Figure 16), penetration, and speed of welding. In our discussion, we will deal with the more common choices used for the various transfer processes. FERROUS METALS NON-FERROUS METALS for for Low Carbon CO2 ARGON + CO2 ARGON + O2 ARGON HELIUM BEAD PROFILE FIGURE Short Circuiting Transfer - Straight carbon dioxide (CO 2 ) is often used for short circuiting arc welding because of its low cost. The deep penetration usually associated with CO 2 is minimized because of the low amperage and voltage settings used with this process. Compared to other gas mixes, CO 2 will produce a harsher arc and therefore, greater spatter levels. Usually, this is minimized by maintaining a short arc length and by careful adjustment of the power supply inductance. The temperatures reached in welding will cause carbon dioxide to decompose into carbon monoxide and oxygen. To reduce the possibility of porosity caused by entrapped oxygen in the weld metal, it is wise to use electrodes that contain deoxidizing elements, such as silicon and manganese. If the current is increased above the short circuiting range, the use of carbon dioxide tends to produce a globular transfer Mixing argon in proportions of 50-75% with carbon dioxide will produce a smoother arc and reduce spatter levels. It will also widen the bead profile, reduce penetration, and encourage "wetting". Wetting, i.e., a uniform fusion, along with joining edges of the base metal and the weld metal, minimizes the weld imperfection known as undercutting (See Figure 17). UNDERCUT FIGURE 17 WETTING Reliability of The 75% Argon/25 CO 2 mixture is often chosen for short circuit welding of thin sections, whereas the combination works well on thicker sections It should be noted that shielding gases can affect the metallurgy of the weld metal. As an example, a combination of argon and carbon dioxide may be used for welding stainless steel, but as the carbon dioxide breaks down, excessive carbon may be transferred into the COPYRIGHT 1998 THE ESAB GROUP, INC

61 Arc for for Low weld metal. Corrosion resistance in stainless steel is reduced as the carbon content increases. To counteract this possibility, a less reactive mixture of 90% helium - 7-1/2% argon - 2-1/2% CO 2 is sometimes chosen. This combination, known as a trimix, provides good arc stability and wetting Spray Arc Transfer - Pure argon produces a deep constricted penetration at the center of the bead with much shallower penetration at the edges (Figure 16). Argon performs well on nonferrous metals, but when used on ferrous metals, the transfer is somewhat erratic with the tendency for the weld metal to move away from the center line. To make argon suitable for spray transfer on ferrous metals, small additions of 1 to 5% oxygen have proven to provide remarkable improvements. The arc stabilizes, becomes less spattery, and the weld metal wets out nicely. If the percentage of argon falls below 80%, it is impossible to achieve true spray transfer Pure helium or combinations of helium and argon are used for welding nonferrous metals. The bead profile will broaden as the concentration of helium increases Pulse Spray Transfer - The selection of shielding gas must be adequate enough to support a spray transfer. Material type, thickness, and welding position are essential variables in selecting a particular shielding gas. The following is a list of recommended gases: Carbon Steel Argon/CO 2 /O 2 /He (He less than 50%) Alloy Steel Argon/CO 2 /O 2 /He (He less than 50%) LESSON II Stainless Argon/O 2 /CO 2 (CO 2 max. 2%) Carbon Reliability of Copper, Nickel, & Cu-Ni Alloys Argon/Helium Aluminum Argon/Helium The solid electrodes used in GMAW are of high purity when they come from the mill. Their chemistry must be closely controlled and some types purposely contain high levels of deoxidizers for use with CO 2 shielding The electrode manufacturer draws down the electrode to a finished diameter that, with GMAW, is usually quite small. Diameters from.030" thru 1/16" are common Most steel GMAW electrodes are copper plated as a means of protecting the surface. The copper inhibits rusting, provides smooth feeding, and helps electrical conductivity Information on types and classifications will be covered in a future lesson. COPYRIGHT 1998 THE ESAB GROUP, INC

62 2.5 FLUX CORED ARC WELDING LESSON II Arc for for Low (FCAW) is quite similar to GMAW as far as operation and equipment are concerned. The major difference is that FCAW utilizes an electrode that is very different from the solid electrode used in GMAW. The flux cored electrode is a fabricated electrode and as the name implies, flux material is deposited into its core. The flux cored electrode begins as a flat metal strip that is formed first into a "U" shape. Flux and alloying elements are deposited into the "U" and then the shape is closed into a tubular configuration by a series of forming rolls The flux cored electrode is a continuous electrode that is fed into the arc where it is melted and transferred into the molten puddle. As in GMAW, the flux cored process depends on a gas shield to protect the weld zone from detrimental atmospheric contamination. With FCAW, there are two primary ways this is accomplished (See Figure 18). The gas is either applied externally, in which case the electrode is referred to as a gas shielded flux cored electrode, or it is generated from the decomposition of gas forming ingredients contained in the electrode's core. In this instance, the electrode is known as a self-shielding flux cored electrode. In addition to the gas shield, the flux cored electrode produces a slag covering for CONTACT TIP GAS CUP GAS SHIELD CONTACT TIP INSULATED GUIDE TUBE Carbon FLUX CORE FLUX CORE GAS SHIELDED FLUX-CORED ARC WELDING SELF SHIELDED FIGURE 18 further protection of the weld metal as it cools. The slag is manually removed with a wire brush or chipping hammer Self Shielded Process - The main advantage of the self shielding method is that Reliability of its operation is somewhat simplified because of the absence of external shielding equipment. COPYRIGHT 1998 THE ESAB GROUP, IN

63 Arc for for Low Carbon LESSON II Although self shielding electrodes have been developed for welding low alloy and stainless steels, they are most widely used on mild steels. The self shielding method generally uses a long electrical stick-out (distance between the contact tube and the end of the unmelted electrode) commonly from one to four inches. Electrical resistance is increased with the long extension, preheating the electrode before it is fed into the arc. This enables the electrode to burn off at a faster rate and increases deposition. The preheating also decreases the heat available for melting the base metal, resulting in a more shallow penetration than the gas shielded process A major drawback of the self shielded process is the metallurgical quality of the deposited weld metal. In addition to gaining its shielding ability from gas forming ingredients in the core, the self shielded electrode contains a high level of deoxidizing and denitrifying alloys, primarily aluminum, in its core. Although the aluminum performs well in neutralizing the affects of oxygen and nitrogen in the arc zone, its presence in the weld metal will reduce ductility and impact strength at low temperatures. For this reason, the self shielding method is usually restricted to less critical applications The self shielding electrodes are more suitable for welding in drafty locations than the gas shielded types. Since the molten filler metal is on the outside of the flux, the gases formed by the decomposing flux are not totally relied upon to shield the arc from the atmosphere. The deoxidizing and denitrifying elements in the flux further help to neutralize the affects of nitrogen and oxygen present in the weld zone The Gas Shielded Process - A major advantage with the shielded flux cored electrode is the protective envelope formed by the auxiliary gas shield around the molten puddle. This envelope effectively excludes the natural gases in the atmosphere without the need for core ingredients such as aluminum. Because of this more thorough shielding, the weld metallurgy is cleaner which makes this process suitable for welding not only mild steels, but also low alloy steels in a wide range of strength and impact levels The gas shielded method uses a shorter electrical stickout than the self shielded process. Extensions from 1/2" to 3/4" are common on all diameters, and 3/4" to 1-1/2" on larger diameters. Higher welding currents are also used with this process, enabling high deposition rates to be reached. The auxiliary shielding helps to reduce the arc energy into a columnar pattern. The combination of high currents and the action of the shielding gas contributes to the deep penetration inherent with this process. Both spray and globular transfer are utilized with the gas shielded process. Reliability of COPYRIGHT 1998 THE ESAB GROUP, INC

64 Arc for for Low Carbon Reliability of Current Density - Flux cored arc welding utilizes the same principles of current density, as explained in section 2.4.1, but there is one significant difference between the flux cored electrode and the solid electrode. With the flux cored electrode, the granular core ingredients are poor electrical conductors and therefore, the current is carried primarily through the outer metal sheathing. When an equal diameter cross section of the two are compared (See Figure CURRENT PATH 19), it is seen that the flux cored electrode has a smaller current carrying area than the solid electrode. This greater concentration of current in a smaller area increases the burnoff rate When all other factors are equal, the deposition rate of the flux cored electrode is somewhat higher than the solid electrode. 1/16" FLUX-CORED ELECTRODE FIGURE EQUIPMENT - The equipment used for flux cored arc welding is the same as shown previously in Section , Figure 12, with the exception that the self shielded method does not need the external gas apparatus Flux cored arc welding is done with direct current. All of the gas shielded electrodes are designed for DCEP operation. The self shielded electrodes are either designed specifically for DCEN or DCEP Power Source - The recommended power source is the direct current constant voltage type. The constant current type can be used but with less satisfactory results Wire Feeder - The function of the wire feeder in FCAW is the same as discussed in the section on GMAW. Since the flux cored electrode is tubular in construction, precautions must be taken not to flatten the electrode. To facilitate feeding by means other than pressure alone, specially designed feed rolls with knurled or grooved surfaces are used. Some feeders use four feed rolls rather than two to minimize unit pressure on the electrode The Gun - As compared to GMAW, the main difference in FCAW welding guns is in those used with the self shielding process. The gun is somewhat more compact due to the absence of an external gas shielding nozzle. Since the self shielding process normally requires a longer electrode extension, the self shielding gun may have an insulated guide tube (Refer back to Figure 18) to give stability to the electrode. Water cooled guns are available for high duty semi-automatic welding and for automatic welding. LESSON II 1/16" SOLID ELECTRODE COPYRIGHT 1998 THE ESAB GROUP, INC.

65 Arc for for Low Flux cored welding generates fumes, that for environmental reasons, must be removed from the welding area. This is usually done with an external exhaust system, but welding guns with internal fume extractors have been developed. They are heavier than the regular gun and must be properly maintained so that the extracting mechanism does not disturb the shielding gas SHIELDING GASES - Carbon dioxide is the most widely used gas for auxiliary shielding of the flux cored electrode. The other commonly used gas is a mixture of 75% Argon and 25% CO A carbon dioxide shield produces deep penetration and the transfer is globular. As previously discussed, CO 2 will dissociate in the heat of the arc. To counteract this characteristic, deoxidizing elements are added to the core ingredients of the electrode. The deoxidizers react to form solid oxide compounds that float to the surface as part of the slag covering. LESSON II The addition of Argon to CO 2 will increase the wetting action, produce a smooth arc arc, and reduce spatter. The transfer is spray-like, and the penetration is somewhat less than with the straight carbon dioxide. Carbon Reliability of While some flux cored electrodes are designed to operate well on both the 100% CO 2 or the 75/25 mixture, others are formulated specifically for the CO 2 shield or the Argon/ CO 2 mixture. If the recommended gas is not used with these electrodes, the weld chemistry may be affected. The reason for this is that inert gas, such as Argon, does not react with the other elements; therefore, allowing them to be transferred across the arc into the weld metal. An electrode designed for CO 2 shielding contains deoxidizing elements, such as silicon and manganese. If a high percentage of Argon is used in the shielding medium, a large portion of these elements may pass into the weld metal causing the weld metallurgy to be less ductile than intended The opposite happens with electrodes formulated for a 75/25 mixture. These electrodes are usually designed for high yield and tensile strength. If a high percentage of CO 2 is used with them, the CO 2 may react with the elements needed to attain these strength levels, thereby preventing them from passing into the weld metal. 2.6 SUBMERGED ARC WELDING Submerged Arc (SAW) is different from the previously explained arc welding processes in that the arc is not visible. The arc is submerged beneath loose granular flux. A continuous electrode is fed by automatic drive rolls through an electrode holder where current COPYRIGHT 1998 THE ESAB GROUP, INC

66 Arc for for Low LESSON II is picked up at the contact tube. The electrode moves into the loose flux and the arc is initiated. The flux is deposited from a separate container that moves at the same pace as the electrode assuring complete coverage (See Figure 20) Submerged Arc Flux - The flux helps form the molten puddle, slows the cooling rate, and acts as a protective shield. The flux, which is in close contact with the arc, is fused into a slag cover and that which is not fused is collected for reuse. The flux can contain alloying elements that, when molten, will pass into the weld metal affecting the metallurgy. Some fluxes are specifically prepared for their alloy altering capabilities while others, known as neutral fluxes, are chosen when a minimal alloy change is desired. Although these latter fluxes are called "neutral", they still have the ability to slightly alter the weld chemistry. FLUX HOPPER ELECTRODE LOOSE GRANULAR FLUX BASE METAL MOLTEN PUDDLE FUSED SLAG COVER SOLIDIFIED WELD METAL Carbon Reliability of SUBMERGED ARC WELDING FIGURE The Gun - Although there are hand-held welding guns for the submerged arc process, the majority of SAW is done with fully automatic equipment. The basic components include a wire feeder, a power source, a flux delivery system, and in some instances, an automatic flux recovery system Power Sources - The power source can be a constant current AC transformer, or it may be a DC rectifier or generator of either the constant current or constant voltage variety. The power source must be rated for high current output. When current requirements exceed the value of a single machine, two or more of the same type may be connected in parallel Equipment - Most submerged arc welding is done with DCEP because it provides easy arc starting, deep penetration and excellent bead shape. DCEN provides the highest COPYRIGHT 1998 THE ESAB GROUP, INC

67 Arc for for Low Carbon LESSON II deposition rates but minimum penetration. Alternating current is often used as a trailing arc in tandem arc applications. In this type of application, the leading DCEP arc provides deep penetration, and the closely trailing AC arc provides high deposition with a minimum of arc blow A variety of ferrous and nonferrous electrodes are used in submerged arc welding. They are usually solid electrodes refined with the appropriate alloys at the steel mill, and then shipped to electrode manufacturers where they are drawn down to a specific diameter and packaged. There is another type of sub arc electrode known as a composite electrode, that is fabricated in the same manner as a flux cored electrode. A chief advantage of this type is that the alloying elements can be added to the core of the electrode more cheaply than a steel mill can produce those same alloys in a solid form. The electrodes for SAW vary in diameter from 1/16 inch to 1/4 inch with the larger diameters being the most widely used Summary - Submerged arc welding has some advantages over other welding processes. Since the radiance of the arc is blanketed by the loose flux, there is no need for a protective welding hood (although safety glasses are recommended), there is no spatter and only a very minimal amount of fumes escape from under the blanket. High welding currents, quite commonly in the 300 to 1600 ampere range, are used. These high currents, combined with fast travel speeds, make SAW a high deposition process that is especially suitable for applications that require a series of repetitious welds. Some setups allow two or more electrodes to be fed simultaneously into the joint, further increasing the deposition rate and speed Although SAW has these advantages, it does have some limitations. The flux must be deposited and collected for every welding pass. This requires additional equipment and handling. Also because of the loose flux, the process is limited to the flat and horizontal positions. The equipment for SAW is commonly quite bulky which limits its mobility, and although the process works well on thick materials, it usually is not satisfactory for thin gauge material. The process requires care in the operation. The amperages commonly used may cause excessive heat buildup in the base metal, that may result in distortion or brittleness. Reliability of COPYRIGHT 1998 THE ESAB GROUP, INC

68 Arc 2.7 ELECTROSLAG AND ELECTROGAS WELDING Electroslag (ESW) and Electrogas (EGW) comprise only a minor portion of all welding done in the country, but they are uniquely adapted to certain applications, primarily the joining of very thick materials. The joining of a 12 inch material along a 40 foot line is not an uncommon application for the Electroslag process. LESSON II for for Low Electroslag (See Figure 21) is technically not an arc welding process, although it utilizes a current carrying consumable electrode. The only time there is an arc between the electrode and the work piece is when current is initially charged through the electrode. This initial charge heats a layer of loose flux that becomes molten and extinguishes the arc. GUIDE TUBE (CONSUMABLE GUIDE METHOD) ELECTRODE WATER INLET/OUTLET COPPER SHOE BASE METAL MOLTEN FLUX WELD POOL SOLIDIFIED METAL Carbon Reliability of ELECTROSLAG WELDING FIGURE Flux - The flux used in ESW is high in electrical resistance. As current is applied, enough heat is generated from this resistance to keep the flux, base metal, and electrode in a molten state. This axis of the weld joint is on a vertical plane. The two pieces of metal, usually of the same thickness, are positioned so that there is an opening between them. One or more electrodes are fed into the opening through a welding bead that travels vertically as the joint is filled. To contain the molten puddle, water cooled copper shoes or dams are placed on the sides of the vertical cavity. As the weld joint solidifies, the dams move vertically so as to always remain in contact with the molten puddle Process - A variation of ESW is the consumable guide method. The process is the same with this method except that the guide tube that feeds the electrode to the molten pool is COPYRIGHT 1998 THE ESAB GROUP, INC.

69 Arc for for Low LESSON II also consumed. The chief advantage with this method is the elimination of the electrode holder which must move vertically with the weld pool. Also since the guide tube is consumed, the deposition rate is slightly increased with this method Equipment - The equipment used in ESW is all automatic and of special design. The power source may use either AC or DC current. The electrode may be either solid or flux cored, although if the flux cored is used, it must be specially formulated so as not to contain its normal amount of slag forming ingredients Summary - Electrogas is similar to ESW as far as the mechanical aspects are concerned. The equipment is automatic, the welding head travels vertically, and the molten puddle is retained by shoes on the sides of the joint. The difference is that Electrogas utilizes an arc and it is externally gas shielded. The power source is also limited to DC operation. The electrodes used in EGW can be either solid or flux cored. Carbon Reliability of COPYRIGHT 1998 THE ESAB GROUP, INC

70 APPENDIX A LESSON II Arc LESSON II - GLOSSARY OF TERMS for for Low Carbon Arc Blow Straight Polarity Reverse Polarity Slag Manual Arc Semi-Automatic Slag Inclusion Root Pass - Deviation of the direction of the welding arc caused by magnetic fields in the work piece when welding with direct current. - condition when the electrode is connected to the negative terminal and the work is connected to the positive terminal of the welding power source. - condition when the electrode is connected to the positive terminal and the work is connected to the negative terminal of the welding power source. - The brittle mass that forms over the weld bead on welds made with coated electrodes, flux cored electrodes, submerged arc welding and other slag producing welding processes. Welds made with the gas metal arc and the gas tungsten arc welding processes are slag free. - with a coated electrode where the operator's hand controls travel speed and the rate the electrode is fed into the arc. - with a continuous solid wire or flux cored electrode where the wire feed speed, shielding gas flow rate, and voltage are preset on the equipment, and the operator guides the hand held welding gun along the joint to be welded. - A weld defect where slag is entrapped in the weld metal before it can float to the surface. - The initial pass in a multi-pass weld, usually requiring 100% penetration. Reliability of COPYRIGHT 1998 THE ESAB GROUP, INC

71 Arc for for Low Gas Ions High Frequency Inert Gases LESSON II - Shielding gas atoms that, in the presence of an electrical current, lose one or more electrons and therefore, carry a positive electrical charge. The provide a more electrically conductive path for the arc between the electrode and the work piece. - (as applied to gas-tungsten arc welding) An alternating current consisting of over 50,000 cycles per second at high voltage, low amperage that is superimposed on the welding circuit in GTAW power sources. It ionizes a path for non-touch arc starting and stabilizes the arc when welding with alternating current. - Gases that are chemically inactive. They do not readily combine with other elements. Carbon Flux Current Density Slope or Slope Control - In arc welding, fluxes are formulations that, when subjected to the arc, act as a cleaning agent by dissolving oxides, releasing trapped gases and slag and generally cleaning the weld metal by floating the impurities to the surface where they solidify in the slag covering. The flux also serves to reduce spatter and contributes to weld bead shape. The flux may be the coating on the electrode, inside the electrode as in flux cored types, or in a granular form as used in submerged arc welding. - The amperes per square inch of cross-sectional area of an electrode. High current density results in high electrode melt-off rate and a concentrated, deep penetrating arc. - A necessary feature in welding power sources used for short circuiting arc welding. Slope Control reduces the short circuiting current each time the electrode touches the weld puddle (See Section 2.5.3). Inductance - (as applies to short circuiting arc welding) A feature in welding power sources designed for short circuiting arc welding to retard the rate of current rise each time the electrode touches the weld puddle. Reliability of COPYRIGHT 1998 THE ESAB GROUP, INC

72 Arc for Contact Tip Spray Transfer LESSON II - That part of a gas metal arc welding gun or flux cored arc welding gun that transfers the welding current to the welding wire immediately before the wire enters the arc. - Mode of metal transfer across the arc where the molten metal droplets are smaller than the electrode diameter and are axially directed to the weld puddle. Requires high voltage and amperage settings and a shielding gas of at least 80% argon. for Low Globular Transfer - Mode of metal transfer across the arc where a molten ball larger than the electrode diameter forms at the tip of the electrode. On detachment, it takes on an irregular shape and tumbles towards the weld puddle sometimes shorting between the electrode and work at irregular intervals. Occurs when using shielding gases other than those consisting of at least 80% argon and at medium current settings. Carbon Pulse Transfer Shortcircuiting Transfer - Mode of metal transfer somewhat between spray and short circuiting. The specific power source has built into it two output levels: a steady background level, and a high output (peak) level. The later permits the transfer of metal across the arc. This peak output is controllable between high and low values up to several hundred cycles per second. The result of such a peak output produces a spray arc below the typical transition current. - Mode of metal transfer in gas metal arc welding at low voltage and amperage. Transfer takes place each time the electrode touches or short-circuits to the weld puddle, extinguishing the arc. The short-circuiting current causes the electrode to neck down, melt off, and then repeats the cycle. Trimix or Triple Mix - A shielding gas consisting of approximately 90% helium, 7-1/2% argon, and 2-1/2% carbon dioxide used primarily for short-circuiting arc welding of stainless steels. Maintains corrosion resistance of the stainless steel and produces good wetting and excellent weld bead shape. Reliability of COPYRIGHT 1998 THE ESAB GROUP, INC

73 LESSON II Arc Electrical Stick-Out - In any welding process using a solid or flux cored wire, the electrical stick-out is the distance from the contact tip to the unmelted electrode end. Sometimes called the "amount of wire in resistance". This distance influences melt-off rate, penetration, and weld bead shape. for Out-of-Position Welds - Welds made in positions other than flat or horizontal fillets. for Low Weld Positions - FLAT HORIZONTAL FILLET VERTICAL OVERHEAD Carbon HORIZONTAL BUTT POSITIONED FILLET (FLAT) Reliability of COPYRIGHT 1998 THE ESAB GROUP, INC

74 Arc for for Low BASIC WELDING FILLER METAL TECHNOLOGY A Correspondence Course Carbon LESSON III COVERED ELECTRODES FOR WELDING MILD STEELS An Introduction to Mild Steel ESAB ESAB & Cutting Products Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

75 Arc TABLE OF CONTENTS LESSON III COVERED ELECTRODES FOR WELDING MILD STEELS for for Low Section Nr. Section Title Page 3.1 DEVELOPMENT OF COVERED ELECTRODES MANUFACTURING COVERED EELCTRODES Functions of Electrode Coatings Classification of Coating Ingredients... 4 Carbon 3.3 AWS SPECIFICATION A Chemical Composition of Weld Metal Mechanical Properties (AWS A5.1-91) Individual Electrode Characteristics SELECTING THE PROPER MILD STEEL ELECTRODE Typical Electrode Use by Classification Electrode Deposition ACID AND BASIC SLAG SYSTEMS ADVANTAGES AND DISADVANTAGES OF MILD STEEL COVERED ELECTRODES ESAB SUREWELD MILD STEEL COVERED ELECTRODES FEATURES & DATA SUREWELD 10P (AWS E6010) SUREWELD 710P (AWS E7010-P1) SUREWELD 810P (AWS E8010-P1) SUREWELD SW14 (AWS E6011) SUREWELD SW612 (AWS E6012) SUREWELD SW15 (AWS E6013) Reliability of

76 Arc TABLE OF CONTENTS LESSON III - Con't for Section Nr. Section Title Page for Low LV (AWS E6013) SUREWELD SW15-IP (AWS E7014) SUREWELD 70LA-2 (AWS E7016) ATOM ARC 7018 (AWS E7018) ATOM ARC 7018AC (AWS E7018) SUREWELD 7024 (AWS E7024) Conforms to Appendix A GLOSSARY OF TERMS Carbon Reliability of

77 LESSON III Arc for for Low 3.1 Development of During the 1890's, arc welding was accomplished with bare metal electrodes. The welds produced were porous and brittle because the molten weld puddle absorbed larg quantities of oxygen and nitrogen from the atmosphere. Operators noticed that a rusty rod produced a better weld than a shiny clean rod. Observations also showed than an improved weld could be made by wrapping the rod in newspaper or by welding adjacent to a pine board placed close to and parallel with the weld being made. In these cases, some degree of shielding the arc form the atmosphere was being accomplished. These early observations led to the development of the coated electrode Around 1920, the A.O. Smith Corporation developed an electrode spirally wrapped with paper, soaked in sodium silicate, and then baked. This was the first of the cellulosic type electrodes. It produced an effective gas shield in the area and greatly improved the ductility of the weld metal Because of the method used to manufacture these paper covered electrodes, it was difficult to effectively add other ingredients to the coating. In 1924, the A.O. Smith Corporation began work on coatings that could be extruded over the core wire. This method allowed the addition of other flux ingredients to furhter improve or modify the weld metal and by 1927, these electrodes were being produced commercially Since 1927, many improvements have been made and many different types of electrodes have been developed and produced. Through variations in the formulations of the covering and the amount of covering on the mild steel core wire, many different classifications of electrodes are produced today. 3.2 Manufacturing Mild steel covered electrodes, also commonly called coated electrodes, consist of only two major elements; the core wire or rod and the flux covering. The core wire is usually low carbon steel. It must contain only small amounts of aluminum and copper, and the sulfur and phosphorous levels must be kept very low since they can cause undesirable brittleness in the weld metal. The raw material for the core wire is hot-rolled rod (commonly called "hot rod"). It is Carbon Reliability of COPYRIGHT 2000 THE ESAB GROUP, IN

78 Arc for for Low LESSON III received in large coils, cleaned, drawn down to the proper electrode diameter, straightened, and cut to the proper electrode length The coating ingredients, from which there are literally hundreds to choose, are carefully weighed, blended in a dry state, wet mixed, and compacted into a large cylinder that fits into the extrusion press. The coating is extruded over the cut core wires which are fed through the extrusion press at a rapid rate. The coating material is removed from the end of the electrode that is clamped into the electrode holder to assure electrical contact, and also from the welding end of the electrode to assure easy arc initiation The electrodes are then stamped with the type number for easy identification before entering the ovens, where they go through a controlled bake cycle to insure the proper moisture content before packaging Of the many quality control checks made during the manufacturing process, one of the most important is the procedure that insures that the coating thickness is uniform. In shielded metal arc welding, the coating crater, or the cup-like formation of the coating, that extends beyond the melting core wire, performs the function of concentrating and directing the arc. See Figure 1. A B Carbon CONCENTRIC COATING NON-CONCENTRIC COATING GOOD ARC DIRECTION POOR ARC DIRECTION CONCENTRATED ARCEFFECT OF COATING CONCENTRICITY FIGURE 1 Reliability of Concentration and direction of the arc stream is attained by having a coating crater, somewhat similar to the nozzle on a water hoze, directing the flow of weld metal. When the coating is not concentric to the core wire, it can cause the condition shown at B in Figure 1. The poor arc direction causes inconsistent weld beads, poor shielding, and lack of penetration. The electrode burns off unevenly, leaving a projection on the side where the coating is the heaviest. This condition is often referred to as "fingernailing." COPYRIGHT 2000 THE ESAB GROUP, IN

79 3.2.1 Functions of Electrode Coatings - The ingredients that are commonly used in LESSON III Arc for for Low Carbon Reliability of coatings can be classified physically in a broad manner as liquids and solids. The liquids are generally sodium silicate or potassium silicate. The solids are powdered or granulated materials that may be found free in nature, and need only concentration and grinding to the proper particle size. Other solid materials used are produced as a result of chemical reactions, such as alloys or other complex synthetic compounds The particle size of the solid material is an important factor. Particle size may be as coarse as fine sand, or as minute as sub-sieve size The physical structure of the coating ingredients may be classified as crystalline, fibrous or amorphous (non-crystalline). Crystalline materials such as rutile, quartz and mica are commonly used. Rutile is the naturally occurring form of the mineral titanium dioxide and is widely used in electrode coatings. Fibrous materials such as wood fibers, and non-crystalline materials such as glasses and other organic compounds are also common coating ingredients The functions of the coating on covered electrodes are as follows: a) Shielding of the Weld Metal - The most important function of a coating is to shield the weld metal from the oxygen and nitrogen of the air as it is being transferred across the arc, and while it is in the molten state. This shielding is necessary to ensure the weld metal will be sound, free of gas pockets, and have the right strength and ductility. At the high temperatures of the arc, nitrogen and oxygen combine readily with iron to form iron nitrides and iron oxides that, if present in the weld metal above certain minimum amounts, will cause brittleness and porosity. Nitrogen is the primary concern since it is difficult to control its effect once it has entered the deposit. Oxygen can be counteracted by the use of suitable deoxidizers. In order to avoid contamination from the air, the stream of molten metal must be protected or shielded by gases that exclude the surrounding atmosphere from the arc and the molten weld metal. This is accomplished by using gas-forming materials in the coating that break down during the welding operation and produce the gaseous shield. b) Stabilization of the Arc - A stabilized arc is one that starts easily, burns smoothly even at low amperages, and can be maintained using either a long or a short arc length. c) Alloying Additions to Weld Metal - A variety of elements such as chromium, nickel, molybdenum, vanadium and copper can be added to the weld metal by including them in the coating composition. It is often necessary to add alloys to the coating to balance the expected loss of alloys of the core wire during the welding operation, due to volatization and

80 Arc for for Low Carbon LESSON III chemical reaction. Mild steel electrodes require small amounts of carbon, manganese and silicon in the deposit to give sound welds of the desired strength level. A portion of the carbon and manganese is derived from the core wire, but it is necessary to supplement it with ferromanganese and in some cases ferrosilicon additions in the coating. d) Concentration of the Arc Stream - Concentration or direction of the arc stream is attained by having a coating crater form at the tip of the electrodes as discussed earlier. Use of the proper binders assures a good hard coating that will maintain a crater and give added penetration and better direction to the arc stream. e) Furnish Slag for Fluxing - The function of the slag is (1) to provide additional protection against atmospheric contamination, (2) to act as a cleaner and absorb impurities that are floated off and trapped by the slag, (3) to slow the cooling rate of the molten metal to allow the escape of gases. The slag also controls the contour, uniformity and general appearance of the weld. This is particularly true in fillet welds. f) Characteristics for Position - It is the addition of certain ingredients, primarily titanium compounds, in the coating that makes it possible to weld out-of-position, vertically, and overhead. Slag characteristics, primarily surface tension and freezing point, determine to a large degree the ability of an electrode to be used for out-of-position work. g) Control of Weld Metal Soundness - Porosity or gas pockets in weld metal can be controlled to a large extent by the coating composition. It is the balance of certain ingredients in the coating that have a marked effect on the presence of gas pockets in the weld metal. The proper balance of these is critical to the soundness that can be produced. Ferromanganese is probably the most common ingredient used to attain the correctly balanced formula. h) Specific Mechanical Properties to the Weld Metal - Specific mechanical properties can be incorporated into the weld metal by means of the coating. High impact values at low temperature, high ductility, and increases in yield and tensile properties can be attained by alloy additions to the coating. i) Insulation of the Core Wire - The coating acts as an insulator so that the core wire will not short-circuit when welding in deep grooves or narrow openings; coatings also serve as a protection to the operator when changing electrodes Classification of Coating Ingredients - Coating materials can be classified into the following 6 major groups: Reliability of

81 Arc for for Low BASIC WELDING FILLER METAL TECHNOLOGY A Correspondence Course LESSON IV COVERED ELECTRODES FOR WELDING LOW ALLOY STEELS Carbon AN INTRODUCTION TO LOW ALLOY COVERED ELECTRODES ESAB ESAB & Cutting Products Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

82 Arc for for Low Carbon TABLE OF CONTENTS LESSON IV COVERED ELECTRODES FOR WELDING LOW ALLOY STEELS Section Nr. Section Title Page 4.1 LOW ALLOY STEELS Consequence of Hydrogen in Low Alloy Steel Preheat MANUFACTURING LOW HYDROGEN ELECTRODES Storage and Reconditioning Moisture Resistant Coating AWS SPECIFICATION FOR LOW ALLOY ELECTRODES Effect of Alloying Elements Mechanical Properties (AWS A5.5-96) Impact Properties SELECTING THE PROPER LOW ALLOY ELECTRODE Service Conditions Joint Design Equipment LOW HYDROGEN IRON POWDER ELECTRODES Atom Arc 7018 (AWS E7018) Atom Arc 7018 Mo (AWS E7018-A1) Atom Arc 8018N (AWS E8018-C2) Atom Arc 8018CM (AWS E8018-B2) Atom Arc 8018W (AWS E8018-G) Atom Arc 9018CM (AWS E9018-B3) Atom Arc 9018-B3L (AWS E9018-B3L) Atom Arc (AWS E10018-M) Atom Arc 10018MM (AWS E10018-D2) Atom Arc (AWS E12018-M) Reliability of COPYRIGHT 1998 THE ESAB GROUP, INC

83 Arc TABLE OF CONTENTS LESSON IV- Con't Section Nr. Section Title Page for Atom Arc "T" (AWS E11018-M) Atom Arc 9018HT (AWS E9018G) Atom Arc 4130 (No AWS Classification) Atom Arc 4130 LN (No AWS Classification) for Low Appendix A Stick Electrode Data Charts - Atom Arc Appendix B Glossary of Terms Carbon Reliability of

84 Arc COVERED ELECTRODES FOR WELDING 4.1 LOW ALLOY STEELS LOW ALLOY STEELS LESSON IV for for Low Low alloy steels, as discussed in Lesson I, are those steels to that have small amounts of alloying elements added for specific purposes; i.e., to increase strength, toughness, corrosion and rust resistance, or to alter the response to heat treatment. Nearly every steel manufacturer makes a family of low alloy steels that are usually sold under trade names such as Maynari R, Cor-ten, Man-ten, and many others. Many of the steels are designed to develop their specific properties such as high strength or toughness in the hot rolled and controlled cooling condition, rather than by subsequent heat treatment. Other compositions of low alloy steels are designed to develop specific properties following heat treatments. Examples of these types are U.S. Steel T-1, Armco Steel SS-100, Great Lakes Steel NA XTRA 100, all of which are quenched and tempered to reach high strength with good toughness. Covered low alloy welding electrodes are designed, in most cases, to match the properties of the low alloy steels rather than to match the exact chemical composition of the steel. Exceptions to this are the chromium molybdenum electrodes that need to contain about the same amounts of the alloy ingredients as the steel in order to match the properties of the steel. 4.2 CONSEQUENCE OF HYDROGEN IN LOW ALLOY STEEL Carbon Reliability of One of the reasons that low alloy steels are becoming more popular is because of the extensive research that was conducted in the development of electrodes for welding them. Although special precautions and care are required in welding the low alloy steels, they can now be joined with a high degree of reliability. But that was not always so. During World War II when there was a dramatic increase in the use of high strength low alloy steel, there was also a corresponding increase in weld defects. It was quickly realized that hardenable steels could not be welded in the same manner and with the same electrodes as were then commonly used for welding the lower strength mild steels. Through extensive research, it was found that entrapped hydrogen was the culprit in causing weld defects, and the term "hydrogen embrittlement" became synonymous with red flags warning of impending disaster When hydrogen bearing compounds such as water, minerals, or chemicals are present in the electrode coating, as is common with mild steel electrodes, the chemically combined hydrogen is dissociated into atomic hydrogen by the heat of the welding arc. The molten weld metal has the capacity to dissolve the atomic hydrogen. However, as soon as the

85 Arc for for Low Carbon LESSON IV weld metal solidifies, it loses the ability to hold the hydrogen in solution and the hydrogen is either expelled into the atmosphere or moves throughout the weld zone. Steel and weld metal are not as solid as they appear to the naked eye, being filled with tiny submicroscopic pores. The hydrogen atoms are smaller than the crystalline structure of the steel or the weld metal, and the hydrogen can move about somewhat freely in the steel, just as air can move through a filter. The hydrogen atoms move out of the weld metal into the heat affected zone. The heat affected zone (HAZ) is an area of critical importance in welding, especially in welding high strength steels The heat affected zone (See Figure 1) is that area of the weld joint that did not become molten in the welding process, but underwent a microstructure change as a result of the heat induced by the arc. This zone can become a weak link in the normally very strong joint. First of all, the grain structure of the HAZ is less SOLIDIFIED WELD METAL HEAT AFFECTED ZONE refined and therefore, weaker than the surrounding unaffected UNAFFECTED BASE METAL base metal or the once molten weld metal. And secondly, if the HAZ is permitted to cool too rapidly in certain steels, a hard brittle crystalline structure, known as Marsenite, is locked HEAT AFFECTED ZONE in place. The relatively large pores of FIGURE 1 the heat affected zone are a natural collecting place for atomic hydrogen. When two hydrogen atoms meet, they immediately unite to form molecular hydrogen. The resulting molecules are larger than the crystalline structure of the metal and can no longer move about freely. As more and more hydrogen atoms come into the pores, form molecules, and are trapped, tremendous pressure can develop. Mild steel and lower strength steels are sufficiently plastic to move a little with the hydrogen pressure and not cause the steel to crack. Steels that have high hardness and high strength do not have sufficient plasticity to move with the pressure, and if enough hydrogen is present, cracking of the steel occurs. Reliability of.

86 Arc for for Low Carbon Reliability of LESSON IV This hydrogen caused defect, known as underbead cracking (See Figure 2), begins in the HAZ making it particularly sinister since the crack is not immediately apparent to the eye. It occurs after the metal has cooled from about 400 F to room temperature, and it is sometimes referred to as "cold cracking". The defect may occur immediately after cooling, or it may take hours, days, or even months before it happens. BASE METAL WELD METAL HEAT AFFECTED ZONE Preheat - Steels that are highly hardenable by HYDROGEN INDUCED CRACKS a rapid cooling in the heat affected zone require preheat and interpass temperature control. UNDERBEAD CRACKING FIGURE 2 As preheat is applied to the steel, the cooling rate of the steel from higher temperatures is slowed. Maintaining a constant temperature between each welding pass also helps to control this cooling. Slower cooling rates prevent the steel from being excessively hardened and thus, minimizes the chance of underbead cracking. When this technique is combined with the use of low hydrogen electrodes, a high degree of reliability can be expected from the welds. 4.3 MANUFACTURING LOW HYDROGEN ELECTRODES The discovery of hydrogen related weld defects initiated the development of low hydrogen electrodes. The functions of the coating with low hydrogen electrodes (i.e., shielding, arc stabilizers, alloy additions, etc.) are much the same as those listed in Lesson III for Mild Steel, but the coating is formulated with ingredients that lack hydrogen in their chemical composition. This is primarily accomplished by eliminating organic and chemical compounds high in moisture content. In fact, control of the moisture levels in the coating is critical in the manufacture and use of low hydrogen electrodes In addition to eliminating hydrogen in the coating formula, the manufacturing process entails a high temperature bake cycle. After the coating is extruded onto the core in the same manner as a mild steel coated electrode, the low hydrogen electrodes are given an initial low temperature bake ( F), and then rebaked in a separate high temperature oven ( F) for a specified period of time. This procedure practically eliminates all moisture, and to guard against the reabsorbing of moisture that is naturally present in the atmosphere, the.

87 Arc for for Low LESSON IV electrodes are immediately packaged in hermetically sealed metal containers following the high temperature bake Storage and Reconditioning - All low hydrogen electrodes will absorb some moisture from the air after the electrode container is opened. Therefore, those electrodes that are not intended for use within a given period of time must be stored in a vented oven and maintained at a constant temperature Various structural and military codes allow only specified times of exposure. These may be anywhere from 30 minutes to 8 hours depending on the electrode alloy, the relative humidity in the work area, and the critical nature of the application. If the low hydrogen electrodes are exposed to the atmosphere beyond these time limits, they must be scrapped or reconditioned by rebaking in a vented oven for a specified time at a specific temperature The recommended storage and rebake temperatures for Atom Arc low hydrogen electrodes are follows: STORAGE RECONDITIONED F 1 F Carbon Reliability of Moisture Resistant Coating - Moisture absorption is of special concern to endusers such as shipbuilders and oil rig fabricators who are situated in areas of the world that have a high level of relative humidity. As the temperature and relative humidity increase, the chance of absorbing moisture in the low hydrogen coating is greatly increased. To combat this possibility, major electrode manufacturers have in recent years developed low hydrogen electrodes with moisture resistant coatings. These coatings low the rate of moisture absorption in electrodes that have been exposed to the air for extended periods, thus adding an extra degree of reliability to low hydrogen electrodes The following graphs (figure 3) give an idea of the effectiveness of a moisture resistant coating. The tests were conducted on Atom Arc 7018 electrodes. The method of moisture testing chosen by ESAB is that described in Section 25 of the AWS A Specification. This method was chosen because it satisfies the AWS specifications and is sensitive only to water, making it one of the most accurate and reliable methods of moisture determination currently in use The AWS structural code and military specifications allow a maximum of 0.40% and 0.20% moisture content, respectively, for E70XX low hydrogen electrodes. As shown on the preceding graphs, the Atom Arc 7018 electrode satisfied this low moisture requirement for exposure times beyond those normally allowed in field use.

88 LESSON IV Arc for Moisture at Exposure Time (hours) Zero Hours F - 70% Relative Humidity for Low 80 F - 80% Relative Humidity Moisture at Exposure Time (hours) Zero Hours.08 Carbon Reliability of Exposure Time (hours) Moisture at Zero Hours.10 EFFECTIVENESS OF MOISTURE RESISTANT COATING - ATOM ARC 7018 ELECTRODES FIGURE AWS SPECIFICATION FOR LOW ALLOY ELECTRODES A F - 90% Relative Humidity With very few exceptions, low alloy electrodes are made by adding the appropriate alloying elements to the electrode coating rather than having a core wire that matches the low alloy steel. Low alloy covered electrodes are classified according to the American Society filler metal specification A This specification contains the mechanical property require-

89 Arc for for Low LESSON IV ments and stress relieved condition, the chemical requirements, and the weld metal soundness requirements. are classified under this specification according to the mechanical properties and chemical composition of the weld metal, the type of covering, and the welding position of the electrode. The classification of the electrode is designated by the manufacturer according to the results of his own tests. The manufacturer, thereby, guarantees his electrode to meet the requirements of the AWS specification The letter-number designations for low alloy electrode classifications mean much the same as with mild steel electrodes, except that the major alloy composition is indicated by a letter-number suffix. For example, E7018-A1 indicates an electrode (letter E); with a minimum of 70,000 psi tensile strength (70); is weldable in all positions (1); is iron powder low hydrogen (8); and contains nominally 1/2% molybdenum (A1). The full list of nominal alloy compositions for this specification is contained in Table 1. TABLE 1. Nominal Alloy Designations for AWS A5.5 Specification Carbon A1 B1 B2 B2L B3 B3L B4L B5 C3 C1 C2 D1 D2 M G 1/2% Molybdenum 1/2% Chromium, 1/2% Molybdenum 1-1/4% Chromium, 1/2% Molybdenum Low Carbon version of B2 type. Carbon content is 0.05% or less 2-1/4% Chromium, 1% Molybdenum Low Carbon version of B3 type. Carbon content is 0.05% or less 2% Chromium, 1/2% Molybdenum, low carbon (0.05% or less) 1/2% Chromium, 1.1% Molybdenum 1% Nickel 2% Nickel 3% Nickel 1-1/2% Manganese, 1/3% Molybdenum 1-3/4% Manganese, 1/3% Molybdenum Conforms to compositions covered by Military specifications. Needs only a minimum of one of the elements listed in the AWS A5.5 Table for Chemical Requirements. Reliability of Effect of Alloying Elements Molybdenum - When mild steel weld metal is stress relieved, the yield point is lowered 3,000 psi or more and the tensile strength is also lowered 3,000 psi or more. When 1/2% of molybdenum is added to the weld, both the yield point and the tensile strength remain constant from the as-welded to the stress relieved condition. The presence of molybdenum also increases the tensile strength of the weld metal.

90 Arc for for Low LESSON IV Chromium - When chromium is added to the weld metal, the corrosion and high temperature scaling resistance are increased. The combination of chromium and molybdenum allows the weld metal to retain high strength levels at medium high temperatures Nickel - Mild steel weld metal usually becomes brittle at temperatures below -20 F. The addition of 1-3% nickel to the weld metal enables the weld metal to remain tough at considerably lower temperatures. The presence of the nickel also makes the weld metal more resistant to cracking at room temperature Manganese - The presence of 1-1/2% to 2% manganese in weld metal increases the tensile strength and when 1/3% molybdenum is added in combination, the high strength weld metal is crack resistant It should be noted that the A specification covers not only the low alloy low hydrogen electrodes, but also low alloy versions of the cellulosic, titania, and iron oxide type electrodes. A full list of all the electrodes covered by this specification is presented in Table 2. TABLE 2. Electrode Classifications of AWS A5.5 Specification E7010-A1 E8018-B2 E9015-B3L E11018-M Carbon E7011-A1 E8018-B2L E9016-B3 E12018-M E7015-A1 E8015-B4L E9018-B3 E7016-A1 E8016-B5 E9018-B3L EXX10-G E7018-A1 E8016-C1 E9015-D1 EXX11-G E7020-A1 E8018-C1 E9018-D1 EXX13-G E7027-A1 E8016-C2 E9018-M EXX15-G E8018-C2 EXX16-G E8016-B1 E8016-C3 E10015-D2 EXX18-G E8018-B1 E8018-C3 E10016-D2 E7020-G E8015-B2L E10018-D2 E8016-B2 E9015-B3 E10018-M Reliability of Mechanical Properties (AWS A5.5-96) - Since many low alloy steels require some post-weld heat treatment to relieve the internal stresses generated from the welding process, physical testing on the weld metal of most low alloy electrodes is required to be performed after the specimen has been stress-relieved. Only the E8016-C3, E8018-C3, E9018-M, E11018-M, and E12018-M types are permitted to be tested in the as-welded condition for classification purposes.

91 Arc for LESSON IV Impact Properties - Since many low alloy steels are developed for low temperatures service, impact properties of the weld metal designed to join these steels are very important. Except for those types already mentioned, all impact testing is performed on specimens after they have been stress-relieved. Table 3 lists the minimum charpy v-notch impacts required in the A5.5 specification. TABLE 3. Impact Requirements for AWS A5.5 Specification AS WELDED MINIMUM REQUIREMENT STRESS-RELIEVED E8016-C3 ) F. for Low Carbon E8018-C3 ) E9018-M ) ( E9015-D1 E10018-M ) ( E9018-D1 E11018-M ) F ( E10015-D2 E12018-M ) ( E10016-D2 ( E10018-D2 ( E8016-C1 20 F ( E8018-C1 ( E8016-C2 20 F ( E8018-C2 Impact values for all other classifications are not required. 4.5 SELECTING THE PROPER LOW ALLOY ELECTRODE As stated earlier, low alloy electrodes are often selected to match the properties of the steel to be welded rather than matching the exact chemical composition of the steel. These properties (i.e., strength, toughness, creep, and corrosion resistance) reflect the type of service for which the steel is intended. The letter-number suffix of the electrode classification gives an indication of that service. Whenever possible, the electrode should be selected on the basis of the appropriate strength levels and the intended service of the weldment Service Conditions - The large family of "proprietary" steels that are sold in the as rolled, controlled, cooled condition have a 50,000 psi minimum yield point and 70,000 psi minimum tensile strength. that deposit low hydrogen weld metal of those strength levels are used to weld them. Reliability of

92 Arc for for Low Carbon LESSON IV Some of the low alloy high strength steels are intended for use at subzero temperatures. Nickel bearing low hydrogen electrodes (C1, C2, C3 types) are available for such low temperature applications Chromium molybdenum low alloy steels are used for moderately high temperature service. Piping, tubing, boilers, etc., that are used extensively in power generating plants, are fabricated from these steels. Chrome-moly low hydrogen electrodes (B1, B2, B3, etc.) are produced to weld these steels Many bridges and outdoor structures are constructed from "weathering" grade steels. These are low alloy steels that, on exposure to the atmosphere, develop a thin, tightly adhering layer of rust that prevents further rusting and eliminates the need for painting. Low alloy electrodes with additions of chromium and copper are available for welding these steels Quenched and tempered low alloy steels usually develop high strength with good toughness. These types are used where substantial savings in the weight of the structure is important. Quite often, but not exclusively, these steels are used by the military. One of the more exotic applications for quenched and tempered low alloy steels is in the fabrication of the pressure hulls for nuclear submarines. The "M" series of high tensile low hydrogen electrodes is intended to weld these steels High tensile line pipe for the transmission of oil and gas is being used with greater frequency today. Low alloy cellulosic electrodes of the 7010 and 8010 variety are used for field welding Joint Design - In fillet welding of high strength quenched and tempered steels, toe cracking alongside the welds (see Figure 4) is frequently a problem. The toe cracking is caused by the high strength weld metal having a higher yield point and tensile strength than the steel When the weld area shrinks on cooling from the welding temperature, something must give, and because the yield and strength levels of the steel are lower than those of the weld metal, cracking occurs in the heat affected zone of the steel. The solution to this problem is to use a lower strength weld metal and increase the fillet size to meet the weld joint strength requirements. BASE METAL HEAT AFFECTED ZONE CRACK AT TOE OF WELD WELD METAL TOE CRACKING Reliability of FIGURE 4 COPYRIGHT 2000 THE ESAB GROUP, IN

93 Arc for for Low LESSON IV With a somewhat lower strength weld metal as the filler, the yield point of the weld metal is reached during the shrinkage on cooling. The weld metal stretches without overloading in the heat affected zone of the steel and there is no cracking Equipment - The electrode selected will operate only on the appropriate power source. Table 4 lists the type of current for which each class of electrode is designed. TABLE 4. Current Requirements for AWS Electrode Classes Electrode Class Current EXX10-X* DCRP EXX11-X AC or DCEP EXX13-X AC or DC either polarity EXX15-X DCEP EXX16-X AC or DCEP EXX18-X AC or DCEP EXX20-X AC or DCEN (horizontal fillet) AC or DC either polarity (flat) EXX27-X AC or DCEN (horizontal fillet) AC or DC either polarity (flat) * "X" indicates a variable in the classification. Carbon Reliability of

94 Arc for for Low Carbon 4.6 ESAB ATOM ARC LOW HYDROGEN IRON POWDER ELECTRODES - FEATURES AND DATA LESSON IV Atom Arc 7018 (AWS E7018) - Although this electrodes is really of the mild steel category and classification, the mechanical properties of the weld metal are sufficient to meet the similar properties of the 50,000 psi yield and 70,000 psi tensile strength steels. Usually, preheat and interpass temperature control of those steels is not necessary when welding with Atom Arc 7018, although heavier thicknesses of steel may require some preheat. Common applications include: welding carbon steels, high sulfur steels, enameling steels, and some low alloy, high tensile steels. Typical Mechanical Properties of Weld Metal As Welded Stress-Relieved Yield Point, psi 68,500 62,000 Tensile Strength, psi 75,000 72,000 % Elongation (2") % Reduction Charpy V-Notch F. 125 ft.-lbs. 130 F. 70 ft.-lbs. 75 ft.-lbs. Typical Chemical Composition of Weld Metal C Mn Silicon 0.06% 1.10% 0.50% Atom Arc 7018 Mo (AWS E7018-A1) - This electrode, which deposits 1/2% molybdenum weld metal, is useful in welding power piping and pressure vessels of molybdenum bearing steels designed for use at elevated temperatures. Typical applications include: welding of low carbon and carbon-moly tubes and piping, forged alloy steel pipe flanges, fittings and valves for high temperature service, carbon-moly steel boiler and superheater tubes, manganese-moly and manganese-moly-nickel pressure vessel plates, high strength structural steel and steel castings for highway service. Reliability of

95 Arc for for Low LESSON IV Typical Mechanical Properties of Weld Metal As Welded* Stress-Relieved* Yield Point, psi 73,500 71,000 Tensile Strength, psi 84,000 81,000 % Elongation (2") Charpy V-Notch F. 95 ft.-lbs. 95 F. 85 ft.-lbs. 85 F. 70 ft.-lbs. 70 ft.-lbs. Typical Chemical Composition of Weld Metal C Mn Ni 0.04% 1.06% 2.37% Carbon Atom Arc 8018N (AWS E8018-C2) N electrodes with 3% nickel are usually used to weld 3% nickel steels for low temperature service. It has solved many weld cracking problems by its weld crack resistance, as well as remaining tough at temperatures as low as F. Typical applications include: welding of piping for low temperature service, carbon and low alloy steel forgings and ferritic steel castings for high pressures at low temperatures, high strength steel castings for structural purposes, carbon steel forgings for railroad use and concrete reinforcement bars. Typical Mechanical Properties of Weld Metal As Welded Stress-Relieved Yield Point, psi 83,000 80,500 Tensile Strength, psi 94,000 90,500 % Elongation (2") % Reduction of Area Charpy V-Notch F. 110 ft.-lbs. 112 F. 91 ft.-lbs. 93 F. 73 ft.-lbs. 63 F. 35 ft-lbs. 30 ft.-lbs. Typical Chemical Composition of Weld Metal C Mn Si Ni 0.5% 0.84% 0.37% 3.30% Reliability of

96 Arc LESSON IV Atom Arc 8018CM (AWS E8018-B2) - This 1-1/4% chrome, 1/2% moly electrode deposits weld metal that retains high strength at temperatures up to 600 F. The 8018CM electrodes are used to weld the 1/2% chrome-1/2% moly, 1% chrome-1/2% moly steels, as well as the 1-1/4% chrome-1/2% moly power piping, boiler tubing, plates and castings. Many of the fossil fired steam boilers in electric generating plants in the United States have been welded with this electrode and its relative 9018CM. for Typical Mechanical Properties of Weld Metal Stress-Relieved Stress-Relieved 8 F. 8 F. for Low Carbon Reliability of Yield Point, psi 82,400 63,800 Tensile Strength, psi 100,000 78,300 % Elongation (2") % Reduction of Area Charpy V-Notch F. 64 ft.-lbs. 127 ft-lbs. Typical Chemical Composition of Weld Metal C Mn Si Ni Mo 0.06% 1.10% 0.40% 1.00% 0.50% Atom Arc 8018W (AWS E8018-G) - The balanced alloy combination of chromium, nickel and copper of this electrode causes the weld metal to "weather" similarly to the weathering grade steels when exposed to the atmosphere. The inform color blend of this weld metal with the weathered steel makes these electrodes the ideal choice when architectural appearance and weld integrity is important. Typical Mechanical Properties of Weld Metal Stress-Relieved As Welded 1 F. Yield Point, psi 84,600 79,100 Tensile Strength, psi 94,400 90,100 % Elongation (2") % Reduction of Area Charpy V-Notch F. 63 ft-lbs. 44 ft.-lbs. Typical Chemical Composition of Weld Metal C Mn Si Ni Mo 0.05% 1.11% 0.32% 1.70% 0.28%

97 Arc for for Low LESSON IV Atom Arc 9018CM (AWS E9018-B3) - These 2-1/4% chrome - 1% moly electrodes are used to weld and match the composition of the 2-1/4% chrome - 1% moly steels in pressure piping and power boilers. The chromium-molybdenum content of the weld metal helps retain appreciable strength at temperatures up to 800 F. Typical Mechanical Properties of Weld Metal Stress-Relieved Stress-Relieved 1 F. 2 F. Yield Point, psi 87,000 75,000 Tensile Strength, psi 102,000 91,000 % Elongation (2") % Reduction of Area Typical Chemical Composition of Weld Metal C Mn Si Ni Mo 0.05% 0.75% 0.60% 2.20% 1.05% Carbon Atom Arc 9018-B3L (AWS E9018-B3L) - The low carbon content of this 2-1/4% chrome - 1% moly electrode makes the weld metal more crack resistant in heavy sections and allows lower preheat and interpass temperatures to be used. Typical applications include: high temperature power piping, boilers, heat-exchanger and condenser tubes, pressure vessel plates and steel castings for high temperature pressure service. Typical Mechanical Properties of Weld Metal Stress-Relieved Stress-Relieved 8 F. 8 F. Yield Point, psi 86,900 69,800 Tensile Strength, psi 103,800 86,400 % Elongation (2") % Reduction of Area Charpy V-Notch F. 60 ft.-lbs. 79 ft.-lbs. Typical Chemical Composition of Weld Metal C Mn Si Ni Mo 0.02% 0.74% 0.61% 2.47% 1.10% Reliability of

98 Arc LESSON IV Atom Arc (AWS E10018-M) - The manganese-nickel-molybdenum composition of Atom Arc is used mostly on thinner sections of quenched and tempered low alloy steels where 100,000 psi tensile strength, along with good ductility and toughness at temperatures as low as -60 F, are required. This product is used primarily for military applications. for for Low Typical Mechanical Properties of Weld Metal Stress-Relieved As Welded 1 F. Yield Point, psi 96,000 96,000 Tensile Strength, psi 103, ,000 % Elongation (2") % Reduction of Area Charpy V-Notch F. 33 ft.-lbs. 22 ft.-lbs. Typical Chemical Composition of Weld Metal C Mn Si Ni Mo 0.05% 1.58% 0.40% 1.50% 0.30% Atom Arc 10018MM (AWS E10018-D2) - This electrode, with its combination of manganese and molybdenum, was originally developed during World War II to repair and fabricate manganese-molybdenum castings and armor plate. It is used to weld similar composition low alloy steels, as well as heat treatable steels comparable to hardenable steels. Carbon Typical Mechanical Properties of Weld Metal As Welded Stress-Relieved 2 F. Reliability of Yield Point, psi 101,000 91,500 Tensile Strength, psi 106, ,000 % Elongation (2") % Reduction of Area Charpy V-Notch F. 83 ft.-lbs. 73 F. 55 ft.-lbs. 50 F. 38 ft.-lbs. 34 ft.-lbs. Typical Chemical Composition of Weld Metal C Mn Si Mo 0.09% 1.77% 0.68% 0.35%

99 Arc for for Low Carbon Reliability of LESSON IV Atom Arc (AWS E12018-M) - This electrode deposits high strength weld metal in both the as welded and stress-relieved conditions, which is required for welding many of the high strength quenched and tempered steels. It is used to weld steels with 120,000 psi tensile strength in applications, such as welding carbon and high strength alloy steel forgings for railroad equipment, high strength steel castings for structural work, and steel castings for highway bridges. Typical Mechanical Properties of Weld Metal Stress-Relieved As Welded 1 F. Yield Point, psi 120, ,000 Tensile Strength, psi 132, ,000 % Elongation (2") % Reduction of Area Charpy V-Notch F. 52 ft.-lbs. 54 F. 32 ft.-lbs. 31 ft.-lbs. Typical Chemical Composition of Weld Metal C Mn Si Cr Ni Mo 0.05% 1.90% 0.25% 0.85% 2.00% 0.50% Atom Arc "T" (AWS E11018-M) - Atom Arc "T" electrodes were developed for welding U.S. Steels T-1 steel, which is quenched and tempered to high strength and ductility. It has since been used to weld all of the quenched and tempered steels, including HY-80, the steel used for the pressure hulls of nuclear submarines. Typical Mechanical Properties of Weld Metal Stress-Relieved As Welded 1 F. Yield Point, psi 103, ,000 Tensile Strength, psi 115, ,000 % Elongation (2") % Reduction of Area Charpy V-Notch F. 80 ft.-lbs. 73 F. 55 ft.-lbs. 50 F. 48 ft.-lbs. 42 F. 41 ft.-lbs. 26 ft.-lbs.

100 Typical Chemical Composition of Weld Metal LESSON IV Arc for for Low C Mn Si Cr Ni Mo 0.06% 1.53% 0.27% 0.31% 1.88% 0.43% Atom Arc 9018HT (AWS E9018G) - As the HT indicates, this electrode is intended for heat treated applications. It deposits weld metal with properties that match chromiummolybdenum steel castings and is also useful in the repair and rebuilding of hot forging dies. Typical Mechanical Properties of Weld Metal F. F. F. F. Yield Point, psi 78, ,000 Tensile Strength, psi 98, ,000 % Elongation (2") % Reduction of Area Typical Chemical Composition of Weld Metal C Mn Si Cr Mo Carbon 0.14% 0.80% 0.65% 2.30% 1.00% Atom Arc 4130 (No AWS Classification) - This composition was developed to weld heat treatable steels such as SAE4130, providing a weld metal that responds similarly to the heat treatment. Typical Mechanical Properties of Weld Metal F. F. F. F. Yield Point, psi 121, ,000 Tensile Strength, psi 138, ,000 % Elongation (2") % Reduction of Area Typical Chemical Composition of Weld Metal C Mn Si Cr Ni Mo 0.18% 1.25% 0.40% 2.50% 1.28% 0.20% Reliability of

101 Arc Atom Arc 4130 LN (No AWS Classification) - This alloy combination has less than 1% nickel so that it may be used safely to weld oil field equipment that handles "sour" (high sulfur) crude oil. The weld metal is hardenable by quenching and tempering similar to SAE4130 steel. Typical Mechanical Properties of Weld Metal LESSON IV for for Low F. F. F. F. Yield Point, psi 109, ,500 Tensile Strength, psi 125, ,000 % Elongation (2") % Reduction of Area Typical Chemical Composition of Weld Metal C Mn Si Cr Ni Mo 0.26% 1.25% 0.47% 0.49% 0.80% 0.16% Additional information on Atom Arc Low Hydrogen, Low Alloy electrodes is contained in the Atom Arc product catalog and the Atom Arc handbook for welding low alloy high tensile steels, published by ESAB. Carbon Reliability of

102 Arc APPENDIX A STICK ELECTRODE DATA CHARTS ATOM ARC ELECTRODES LESSON IV for for Low DEPOSITION EFFICIENCY DATA-LOW ALLOY, IRON POWDER ELECTRODES TYPES E7018, E8018, E9018, E10018, E11018, AND E12018 ELECTRODE DEPOSITION EFFICIENCYELECTRODE DEPOSITION EFFICIENCY DIAMETER AMPS RATE lbs/hr % DIAMETER AMPS RATE lbs/hr % 3/ / / / / / Carbon STUB"LOSS CORRECTION TABLE FOR COATED ELECTRODE EFFICIENCY INCLUDING STUB LOSS ELEC. DEPOSITION 2" 3" 4" 5" LENGTH EFFICIENCY STUB STUB STUB STUB 60% 50.0% 45.0% 40.0% 35.0% 65% 54.2% 48.7% 43.3% 37.9% 12" 70% 58.3% 52.5% 46.6% 40.8% 75% 62.5% 56.2% 50.0% 43.7% 80% 66.6% 60.0% 53.3% 46.6% 60% 51.4% 47.1% 42.8% 38.5% 65% 55.7% 51.1% 46.4% 41.8% 14" 70% 60.0% 55.0% 50.0% 45.0% 75% 64.3% 58.9% 53.6% 48.2% 80% 68.5% 62.8% 57.1% 51.4% 60% 53.3% 50.0% 46.6% 43.3% 65% 57.7% 54.2% 50.5% 46.9% 18" 70% 62.2% 58.3% 54.4% 50.5% 75% 66.6% 62.5% 58.3% 54.2% 80% 71.1% 66.6% 62.2% 57.7% CHART TO CONVERT ENGLISH ELECTRODE DIMENSIONS TO METRIC EQUIVALENTS DIAMETER LENGTH Inches mm Inches mm 3/ / / / /18 350/450 7/ / / Reliability of

103 APPENDIX B LESSON IV Arc for LESSON IV - GLOSSARY OF TERMS Quench - The rapid cooling of steel from a temperature above the transformation temperature. This results in hardening of the steel. Temper - Reheating of steel to a temperature below the transformation temperature following the quenching of steel. This usually lowers the hardness and strength and increases the toughness of the steel. for Low Stress Relieved - The reheating of a weldment to a temperature below the transformation temperature and holding it for a specified period of time. A frequently used temperature and time is 1150 F. for 1 hr. per inch of thickness. This reheating removes most of the residual stresses put in the weldment by the heating and cooling during welding. Transformation Temperature - The temperature at which the crystal structure of the steel changes, usually about 1600 F. Heat Affected Zone - The area of the base metal that did not become molten in the welding process, but did undergo a microstructure change as a result of the heat induced into that area. If the HAZ in hardenable steels is cooled rapidly, the area becomes excessively brittle. Carbon Reliability of Underbead Cracking Low Hydrogen Weathering Steel Toe Cracking - A weld defect that starts in the heat affected zone and is caused by excessive molecular hydrogen trapped in that region. It is sometimes referred to as cold cracking, since it occurs after the weld metal has cooled. - Stick electrodes that have coating ingredients that are very low in hydrogen content. The low hydrogen level is achieved primarily by keeping the moisture content of the coating to a bare minimum. - Low alloy steel that is specially formulated to form a thin tightly adhering layer of rust. This initial layer prevents further rusting and thus, the need to paint the steel is eliminated. The main alloys in this steel are copper and chromium. - A weld defect that occurs at the toe of the weld metal. The cracking occurs when the weld metal does not stretch with the base metal because the yield and tensile strength of the weld metal is greater than the steel.

104 Arc for for Low BASIC WELDING FILLER METAL TECHNOLOGY A Correspondence Course Carbon LESSON V WELDING FILLER METALS FOR STAINLESS STEELS ESAB ESAB & Cutting Products Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

105 Arc for for Low Carbon Reliability of TABLE OF CONTENTS LESSON V WELDING FILLER METALS FOR STAINLESS STEELS LESSON V Section Nr. Section Title Page 5.1 INTRODUCTION TO STAINLESS STEEL DIFFERENCES IN STAINLESS AND CARBON STEELS STAINLESS STEEL TYPES AUSTENITIC STAINLESS STEELS Carbide Precipitation Ferrite in Austenitic Stainless Steels CALCULATION OF FERRITE CONTENT IN STAINLESS STEEL SPECIAL FERRITE REQUIREMENT IN STAINLESS STEEL ELECTRODES MARTENSITIC STAINLESS STEELS FERRITIC STAINLESS STEELS DUPLEX STAINLESS STEELS ELECTRODE SELECTION WELDING DISSIMILAR STEELS STAINLESS STEEL ELECTRODES AND FILLER METALS Covered Stainless Arcaloy Lime Coated Arcaloy AC-DC Titania Coated Arcaloy Plus ARCALOY COVERED ELECTRODE PROPERTIES AND APPLICATIONS Arcaloy 308L and 308L Plus Arcaloy 309L and 309L Plus Arcaloy 309 Cb... 18

106 Arc for for Low Carbon Reliability of TABLE OF CONTENTS LESSON V - Con't. LESSON V Section Nr. Section Title Page Arcaloy 309MoL Arcaloy Arcaloy 310 Cb Arcaloy 310Mo Arcaloy Arcaloy 316L and 316L Plus Arcaloy 316LF Arcaloy 317L and 317L Plus Arcaloy Arcaloy 320 and 320LR Arcaloy 347 and 347 Plus Arcaloy ARCALOY BARE STAINLESS STEEL ELECTRODES APPLICATIONS AND COMPOSITIONS OF ARCALOY BARE STAINLESS ELECTRODES Arcaloy ER308L Arcaloy ER308LSi Arcaloy ER309L Arcaloy ER Arcaloy ER Arcaloy ER316L Arcaloy ER316LSi Arcaloy ER CORE-BRIGHT STAINLESS STEEL FLUX CORED ELECTRODES CORE-BRIGHT STAINLESS STEEL FLUX CORED ELECTRODE APPLICATIONS AND PROPERTIES Core-Bright Core-Bright 308 Mo Core-Bright 308LTo Core-Bright 309L Core-Bright 316L... 25

107 Arc for for Low TABLE OF CONTENTS LESSON V - Con't. LESSON V Section Nr. Section Title Page Core-Bright FERRITE CONTENT OF CORE-BRIGHT WELD METALS SHIELD-BRIGHT & SHIELD-BRIGHT X-TRA STAINLESS STEEL FLUX CORED ELECTRODES SHIELD-BRIGHT & SHIELD-BRIGHT X-TRA STAINLESS STEEL FLUX CORED ELECTRODE APPLICATIONS & PROPERTIES Shield-Bright 308L Shield-Bright 309L Shield-Bright 309LMo Shield-Bright 316L Shield-Bright 317L Shield-Bright Carbon 5.21 ARCALOY NICKEL ALLOY COVERED WELDING ELECTRODES - FEATURES AND DATA Arcaloy 9N10 Nickel-Copper Arcaloy 8N12 Nickel-Chromium-Iron Arcaloy Ni Arcaloy Ni ELECTRODES FOR WELDING CAST IRON Nickel-Arc Nickel-Arc Nickel-Arc Nicore Cupro Nickel Appendix A - GLOSSARY OF TERMS Reliability of

108 Arc WELDING FILLER METALS FOR STAINLESS STEELS 5.1 INTRODUCTION TO STAINLESS STEEL LESSON V for for Low Stainless steel, introduced commercially during the early 1930's, presented industry with a new "wonder metal" with its shiny surface and ability to resist rust and corrosion. This new steel alloy also presented welding problems that had not been previously encountered. It took many years of research and experimentation to develop successful welding filler metals and welding procedures for this "rustless iron" as it was then called Most of us think of stainless as an attractive metal used for trim on our stoves and automobiles, or as bright, easy-to-clean cooking utensils and cutlery. Besides being used for its corrosion resisting properties, however, stainless steel is used for low temperature applications, and for applications where its resistance to scaling at high temperatures is important Stainless steel is basically an alloy of iron and chromium. As the amount of chromium added to a steel alloy is increased, the corrosion resistance increases until the amount of chromium reaches 11% to 12%, at which point it is considered a stainless steel. The graph in Figure 1 shows how the amount of chromium affects the rate of corrosion in a semi-rural, outdoor air environment. Corrosion rate will vary with the corrosive media to which the stainless steel is exposed and with the type of stainless employed. Carbon MILD STEEL STAINLESS STEEL PERCENT CHROMIUM CORROSION RATE VERSUS PERCENT CHROMIUM OUTDOOR ATMOSPHERE, SEMI-RURAL ENVIRONMENT Reliability of FIGURE 1.

109 Arc for for Low Carbon LESSON V The mechanism by which chromium imparts corrosion resistance to steel has been well established. Essentially, the chromium combines with oxygen of the atmosphere to form a stable non-metallic oxide film on the surface of the steel. This film protects the steel by acting as a protective coating. As the chromium content of the steel increases, the tenacity, impermeability and strength of this film increases, imparting greater and greater corrosion resistance. This film is too thin to be seen. What we do see is the shiny, unoxidized steel just below this film In Lesson I we learned that the application of heat to metals can change the microstructure and thereby, the properties of that metal. The fabricator of ordinary carbon steel understands that successful welds depend upon how that material behaves under the heat of the arc. With that information as a guide, welds can be produced that satisfy the mechanical requirements of the welded joint. With stainless steel, however, other aspects such as preservation of corrosion resistance and heat resistance must also be considered Stainless steel may be welded by most of the common arc welding processes. Shielded metal-arc welding with coated electrodes is still probably the most widely used process. Other commonly used processes are flux cored arc welding, gas metal-arc welding, gas tungsten-arc welding and submerged arc welding as discussed in Lesson II The cost of stainless steel is approximately six times that of mild steel. For this reason, it is important that the proper electrodes or filler metals are selected and the proper welding procedures are followed to minimize rework or scrap losses due to faulty welds. An understanding of the peculiarities of the four types of stainless steel, and how they compare to mild or carbon steels, will help to avoid costly mistakes There are four primary grades of stainless steel: austenitic, martensitic, ferritic, and duplex. The names are metallurgical terms derived from the crystal structure of the steel at room temperature and will be covered in more detail later in this lesson. Figure 2 shows the basic differences and the composition of the four types. TYPE RANGE OF ALLOYING ELEMENTS CHROMIUM NICKEL Reliability of AUSTENITIC 16-30% 8-40% MARTENSITIC 11-18% 0-5% FERRITIC 11-30% 0-4% DUPLEX 18-28% 4-8% MAJOR STAINLESS STEEL ALLOYING ELEMENTS FIGURE 2 COPYRIGHT 2000 THE ESAB GROUP,

110 Arc for LESSON V That group of stainless steels that contain both chromium and nickel (austenitic grade) is more readily and satisfactorily welded than those that contain less than 5% nickel (martensitic and ferritic grades). Weld joints produced in austenitic stainless steels are strong, ductile and tough in their as-welded condition. They do not normally require preheat or post weld heat treatment. On the other hand, the martensitic and ferritic stainless steels are characterized by hardness or brittleness after welding, and preheat and post-heating is necessary to improve their properties Austenitic stainless is commonly referred to as the "chrome-nickel" type and the martensitic and ferritic steels are commonly called the "straight chrome" types. for Low 5.2 DIFFERENCES IN STAINLESS AND CARBON STEELS The behavior of stainless steel in the heat of the arc differs from that of mild steel. Figure 3 shows that the rate of expansion of the chromium-nickel types is about 50% greater than that of carbon steel. This means that distortion from warping must be compensated for to a greater extent. Carbon CARBON STEEL CHROMIUM- NICKEL TYPES STRAIGHT CHROMIUM TYPES INCHES EXPANSION PER FOOT 1000 F TEMPERATURE RISE RATE OF EXPANSION FIGURE When welding an austenitic stainless steel to a carbon steel, the different rates of expansion can cause cracking due to internal stresses unless the proper electrode and welding procedure is used. The expansion of the straight chromium types is about the same as or slightly less than that of carbon steels. Reliability of.

111 Arc for LESSON V The melting temperature of all stainless steels are lower than that of carbon steel as shown in Figure 5, and both chrome-nickel and straight chrome types are much more fluid in the melted state. Therefore, less heat (welding current) is required to weld stainless steels compared to carbon steels. for Low STRAIGHT CHROMIUM TYPES DEGREES FAHRENHEIT MELTING TEMPERATURES FIGURE The electrical resistance of both the chrome-nickel and the straight chrome types is considerably higher than that of the plain carbon steels as shown in Figure 5. This higher resistance creates more resistance heating in the stainless steel electrode and in the base plate. Lower welding current or amperage is required to avoid overheating the electrode. The Carbon Reliability of CARBON STEEL CARBON STEEL CHROMIUM- NICKEL TYPES CHROMIUM- NICKEL TYPES STRAIGHT CHROMIUM TYPES MICROHMS/SQ CM/CM AT 20 C. ELECTRICAL RESISTANCE FIGURE 5 electrical resistance of the chrome-nickel alloys is about six times that of carbon steel and may be substantially higher if the stainless is cold-worked. The straight chrome types have electrical resistances varying from three to six times that of carbon steel..

112 Arc for for Low The chrome-nickel stainless alloys conduct heat only 40% to 50% as fast as carbon steel and in the straight chrome types, heat conductivity is 50% to 65% that of carbon steel as shown in Figure 6. This means that the heat remains in the vicinity of the arc for a longer period of time instead of being dispersed throughout the weldment rapidly, as it does when welding materials of high thermal conductivity. This is another reason that lower amperages are required to weld these steels. CARBON STEEL CHROMIUM- NICKEL TYPES STRAIGHT CHROMIUM TYPES AT C CAL/SEC/SQ CM LESSON V THERMAL CONDUCTIVITY 5.3 STAINLESS STEEL TYPES FIGURE 6 Carbon As already mentioned, there are three principal categories of stainless steels: austenitic, martensitic, and ferritic. The names are derived from the crystalline structure of the steel normally found at room temperature. When low carbon steel is heated above 1550 F, the atoms of the steel are rearranged from the structure called ferrite at room temperatures to the crystal structure called austenite. On cooling, the low carbon steel atoms return to their original structure ferrite. The high temperature structure, austenite, is non-magnetic, plastic and has lower strength and greater ductility than the room temperature form of ferrite When more than 17% chromium and 7% nickel are added to the steel, the high temperature crystalline structure of the steel austenite, is stabilized so that it persists at all temperatures from the very lowest to almost melting. This alloy combination is the basis for the austenitic category of stainless steels. Many alloy additions are made to that base as modifications for different service requirements. Reliability of.

113 Arc for for Low LESSON V When certain alloy steels are cooled rapidly from above the transformation temperature, a very hard brittle phase occurs. This phase is called martensite. Steels that contain 5-15% chromium have this special characteristic. Unless special care is used in welding such steels, they become crack sensitive. These are the martensitic stainless steel alloys When more than 16% chromium is added to the steel, the room temperature crystalline structure, ferrite, is stabilized and the steel remains in the ferritic condition at all temperatures. Hence the name, ferritic stainless steel is applied to this alloy base. 5.4 AUSTENITIC STAINLESS STEELS Austenitic Stainless Steels are designated by a series of 300 numbers according to the American Iron & Steel Institute (AISI). Nominal compositions of some of the more important types are shown in Figure 7. About 80% of the stainless steel welded is of the austenitic type. Carbon Reliability of AISI No. Chromium % Nickel % Molybdenum % Columbium % MOST COMMON TYPES OF AUSTENITIC STAINLESS STEELS FIGURE Carbide Precipitation - Many of the austenitic stainless steels are subject to the phenomenon of carbide precipitation. At elevated temperatures in the range of F, the carbon content in excess of 0.02% migrates to the grain boundaries of the austenitic structure where it reacts with chromium to form chromium carbide. If the chromium is tied up with the carbon, it is not available for corrosion resistance. Thus, when the steel with carbide precipitation is exposed to a corrosive environment, intergranular corrosion results, allowing the grain boundaries to be eaten away. Figure 8 shows how intergranular corrosion may take place in a tank holding a corrosive liquid. Notice that the corrosion takes place only in the heat affected zone on the inside where the corrosive media is located, and there is no evidence of failure on the outside Carbide precipitation has no other effect on the steel, however, other than loss of corrosion resistance in the heat affected zone. During welding, the heat-affected zones along the sides of the weld in austenitic stainless steel are exposed to the temperatures that cause carbide precipitation.

114 Arc for for Low Carbon Reliability of WELD METAL INSIDE OF TANK HEAT AFFECTED ZONES INTERGRANULAR CORROSION FIGURE If the weldment is to be used in corrosive service, the carbide precipitation and resultant intergranular corrosion must be eliminated. Three dependable methods of controlling this problem are defined below: a. Carbide precipitation is a function of the carbon content. Keeping the carbon content as low as possible in the steel (0.04% maximum) and welding it with low carbon electrodes is one solution. b. If the carbon of the steel and weld metal are tied up by an element that has a stronger affinity for carbon than does chromium, carbide precipitation cannot occur. Columbium and titanium are alloys that have a stronger affinity for carbon. Steels with columbium or titanium, and covered electrodes with columbium present, are made for this purpose. c. Another method, although not as practical, is to heat the finished weldment to at least 1850 F allowing all of the precipitated carbides to go back into solution. The weldment is then rapidly cooled and quenched so that it passes through the critical temperature (1200 F) very quickly, allowing little or no carbides to reform. However, stainless steel weldments heated to such high temperatures would be subject to warping, sagging and other loss of dimension as well as being covered with heavy scale Ferrite in Austenitic Stainless Steel - Stainless weld metal that is fully austenitic is non-magnetic and has a relatively large grain structure. This results in the weld being cracksensitive. By controlling the balance of the alloying elements in the electrode, small amounts of another phase, ferrite, can be introduced in the weld metal. The ferrite phase causes the austenitic grains to be much finer and the weld becomes more crack-resistant Certain alloying elements used in stainless steels and weld metals behave as austenite stabilizers and others as ferrite stabilizers. Among the austenite stabilizers are nickel, carbon, manganese and nitrogen. The ferrite stabilizers are chromium, silicon, molybdenum and columbium. It is the balance between the two types of alloying elements that controls the quantity of ferrite in the weld metal. LESSON V.

115 Arc for for Low Carbon Reliability of The amount of ferrite in austenitic stainless steel weld metal may be measured by magnetic devices because the ferrite is magnetic. A small amount of ferrite in austenitic stainless weld metal is good, because it prevents weld cracking. If the weldment is to be in very low temperature service, however, large amounts of ferrite should be avoided because ferrite is not tough at low temperatures. Also, if the weldment is to be used in high temperature (higher than 1000 F) service, the ferrite should be maintained at low levels because the ferrite becomes brittle at those temperatures. 5.5 CALCULATION OF FERRITE CONTENT IN STAINLESS STEEL Several simple, yet accurate, methods have been developed for determining the balance between the austenite and ferrite forming elements in iron. When the chemical composition of the weld metal is known, the Schaeffler or WRC-1992 diagrams can be used. See Figures 9 and The purpose of these diagrams is to calculate the nickel and chromium equivalent of the weld metal in question and plot the point on the appropriate diagram. The nickel equivalent is the sum of the nickel content and all other austenite formers, multiplied by coefficients representing their austenite forming effect as compared to that of nickel. The chromium equivalent is calculated in the same manner. In both diagrams, the nickel equivalent is the vertical axis, and the chromium equivalent is the horizontal axis. The WRC-1992 diagram has an advantage since it also takes the nitrogen content into consideration. Nitrogen is a powerful austenite forming element. If the nitrogen content is not known, we assume 0.06% for GTAW and SMAW electrodes and, 0.08% for GMAW and FCAW filler metals When chemical composition is not available, two common instruments can also be used to determine ferrite content. Since ferrite at room temperature is magnetic and austenite is not, a relationship between magnetic response and ferrite content can be established. The more magnetic response to the instrument, the more ferrite present in the metal. The two commercially available instruments that use this principal to measure ferrite content are the Magne gage and the Severn gage. The Magne gage is a laboratory instrument, while the Severn gage is a pocket-size instrument designed for on-site readings In the past, ferrite was expressed as a volume percent of the metal. However, because of non-standard calibration, conflicting and inaccurate results often occurred. To eliminate this problem, the ferrite volume percent was changed to a standardized expression known as the ferrite number (FN) and has been adopted by the Research Council (WRC), the American Society (AWS), and other agencies. Ferrite numbers (FN) are LESSON V

116 LESSON V Arc for for Low SHAEFFLER CONSTITUTION DIAGRAM FOR STAINLESS STEEL WELD METAL FIGURE 9 Carbon WRC-1992 DIAGRAM FOR STAINLESS STEEL WELD DATA FIGURE 10 the same as the volume percent numbers in the range of 0-7%. At higher contents, FN values become increasingly higher than the previous percent ferrite values. The DeLong diagram shows this comparison. Reliability of.

117 Arc for for Low 5.6 SPECIAL FERRITE REQUIREMENT IN STAINLESS STEEL ELECTRODE In order to meet the AWS classification of a stainless steel electrode, a specific chemical range must be followed by the electrode manufacturers. Since ferrite content is mainly controlled by chemical composition, the ferrite content will also fall into certain ranges depending on the particular electrode in question. However, some users of stainless steel require the ferrite content be above or below the normal ranges as found in typical chemical analyses. An example of this is the SMAW 316 electrode. Normally, a 316 stick electrode has a FN in the 0-2 range, but a specially formulated 316 stick electrode could have a minimum of 5 FN, if needed. Since these electrodes require special chemical formulations, they must be ordered on a special request basis from most manufacturers. 5.7 MARTENSITIC STAINLESS STEEL LESSON V Carbon Reliability of Martensitic stainless steels fall into the 400 number series according to the American Iron and Steel Institute. They are magnetic and contain from 11.5% to 18% chromium. As previously noted, they get the name martensite because of the crystalline structure of the steel at room temperature. With a lower alloy content than the austenitic steels, they are lower in cost than the austenitic types. They have adequate corrosion resistance in many environments because they form the characteristic chromium oxide surface film. They also have a high hardenability characteristic Other chromium bearing heat resistant steels that have only 4% to 10% chromium (not a true stainless steel by the 11.5% minimum chrome requirement) have similar hardenability characteristics. These steels are designated by the 500 series numbers according to the American Iron and Steel Institute and from a welding standpoint, may be considered in the same grouping as the martensitic stainless steels. Nominal compositions of these types are shown in Figure These steels are frequently in a hardened AISI No. Carbon Chromium Molybdenum %* %* %* state meaning they have low ductility. If heat is applied suddenly, as in arc welding, to a min localized area and it then is allowed to cool suddenly, cracking may occur. The heated area contracts on cooling and the lack of ductility in the parent metal prevents it from following along. * Maximum unless otherwise noted. NOMINAL COMPOSITION-MARTENSITIC STAINLESS STEELS AND CHROMIUM HEAT RESISTANT STEELS FIGURE 11 This type of cracking can be prevented by preheating the steel, since preheating lowers the thermal difference between the weld area and COPYRIGHT 2000 THE ESAB GROUP

118 Arc for for Low Carbon Reliability of the base metal. This allows the weld area to cool more slowly and as a result, the steel in the heat affected zone will not be hardened as severely The preheating temperature used is in the range of 350 F to 500 F and should be maintained during the entire welding operation. Upon completion of welding, the weldment should be cooled slowly, preferably furnace cooled, allowing gradual temperature change The mechanical properties of martensitic stainless steels are affected by welding since they harden intensely, even on relatively slow cooling from high temperatures. The weld deposit and the steel that surrounds the weld deposit is hard and brittle. Heat treatment of the weldment is necessary to improve these physical properties If preheating or postweld heat treatment is not practical, it may be necessary to use a higher alloy austenitic stainless steel electrode (such as 309) that deposits tough, ductile weld metal without cracking. This solution would depend on the required properties of the weldment and is not recommended in all cases. Martensitic stainless steels make up about 15% of the stainless steels that are welded. 5.8 FERRITIC STAINLESS STEELS Ferritic stainless steels are straight chrome alloys in the AISI 400 series. They are magnetic and have varying ranges of chromium content as shown in Figure All ferritic stainless steels have the room temperature crystal structure of ferrite stabilized to all temperatures. The higher chromium content provides good resistance to high temperature scaling. For this reason, the ferritic stainless steels are used to make heat treating containers, jigs, and fixtures. LESSON V the ferritic high chromium stainless steels, however, is difficult. The steels AISI No. Carbon %* Chromium %* Other %* have rapid rates of grain growth at temperatures Aluminum over 1700 F. The large grains absorb the smaller grains and grow larger. The resultant Nitrogen 0.25 * Maximum unless otherwise noted. coarse grain structures are very crack sensitive. NOMINAL COMPOSITION-FERRITIC STAINLESS STEELS Grain growth is a time and temperature function. To keep the time of high welding temperature as FIGURE 12 short as possible, these steels should be mildly preheated to about 300 F, welded with small diameter electrodes and with the lowest possible welding current, thereby limiting the heat input. About 5% of the stainless steels welded are of the ferritic category. COPYRIGHT 2000 THE ESAB GROUP

119 5.9 DUPLEX STAINLESS STEELS LESSON V Arc for for Low Carbon Reliability of Duplex means "two". Duplex stainless steels consist of the two "building stones" (microstructure phases) ferrite and austenite and are often termed ferritic-austenitic stainless steels. Typically, duplex stainless steels have a microstructure consisting of approximately 50% ferrite and 50% austenite In simple terms, the ferrite could be said to give high strength and some resistance to stress corrosion cracking, the austenite provides good toughness, and the two phases in combination give the duplex steels their attractive corrosion resistance The most important alloying elements of duplex stainless steels are Cr, Ni, Mo and N. These elements largely govern the properties of the steels. Some grades also contain additions of copper (Cu) or tungsten (W) A wide range of different versions of duplex stainless steel is currently available on the market. At present, the 22% chromium (Cr), 5% nickel (Ni), 3% molybdenum (Mo), 0.15% nitrogen (N) grade (commonly called 2205) is the most common type of duplex stainless steel and is used in a wide range of applications. Higher alloyed duplex steels, the socalled super duplex stainless steels, have also been introduced into the market. The 25% chromium (Cr), 7% nickel (Ni), 4% molybdenum (Mo), 0.25% nitrogen (N) grade (commonly called 2507) is one example of a modern high alloy super duplex stainless steel. These steels are designed for use in demanding applications where even greater corrosion resistance or higher strength is required ELECTRODE SELECTION There are a great many AISI grades of stainless steel, and in many cases there is a matching electrode for the AISI type. For instance, if both members of a weldment are AISI type 316, the electrode to be used would be 316 also. It is not necessary to have a matching electrode for every type of stainless steel, however, because some electrodes produce satisfactory welds even though the chemical analysis of the steel may be slightly different Type 308 stainless steel electrodes may be used for welding AISI 201 and 202 that have a lower nickel content and a high manganese content. Type 308 electrodes may also be used to weld types 301, 302, 304, 305 and of course, 308 itself. Even though their chromiumnickel contents vary slightly, all of these steel types may be considered as one family of alloys. The chart in Figure 13 shows the proper Arcaloy electrode to be used for the various types of AISI steels.

120 LESSON V Arc for for Low Carbon Reliability of Arcaloy to Weld AISI Steels Chemical Analyses of Stainless Steels, percent* AISI** Other Weld with Type Number Carbon Manganese Silicon Chromium Nickel Elements Arcaloy Type Austenitic / / /5.50 N 0.25 Max. 308/308 ELC / / /5.50 N 0.25 Max. 308/308 ELC / / /308 ELC / / /308 ELC 302B / / / /308 ELC / /10.00 S 0.15 Min.*** Se / /10.00 Se 0.15 Min / / /308 ELC 304L / / ELC / / /308 ELC / / /308 ELC / / S / / / / S / / / / / / / /14.00 Mo 2.00/ /316 ELC 316L / /14.00 Mo 2.00/ ELC / /15.00 Mo 3.00/ /317 ELC / /12.00 Ti 5 x C Min. 308 ELC/ / /13.00 Cb + Ta 10 x C Min. 308 ELC/ / /13.00 Cb + Ta 10 x C Min. 308 ELC/347 Ta 0.10 Max. 20Cb / /35.00 Cb + Ta 8 x C min. 1.00% Max. 320LR Martensitic / / / / / / S 0.15 Min.*** 312/ Se / Se 0.15 Min. 312/ Over / / / / /430 CA6NM / /4.5 Mo NiMo Ferritic / Al 0.10/ / / / F / S 0.15 Min.*** 312/ Se / Se 0.15 Min. 312/ / / / N 0.25 Max. 309/310 * Single Values are Maximums Except as Noted. If service allows ** According to AISI Steel Products Manual, Stainless and Heat Resisting Steels. Not regarded as weldable *** Molybdenum Content of up to 0.60% Permissible and is optional with the Producer. STAINLESS STEEL SELECTION CHART FIGURE 13

121 5.11 WELDING DISSIMILAR STEELS LESSON V Arc for Stainless steels are expensive and the higher the alloy content of the steel, the higher the cost. The most efficient design of a structure calls for the use of the higher alloy steels only where they are needed. Such a design may call for several different steels to be used. As mentioned above, there is no problem of electrode selection when welding stainless steels or any steel to a steel of the same type. Simply match the electrode to the steels. When a change from one type of steel to another (called a transition weld) is made, care must be given to the selection of the electrode used. for Low Carbon There are two general conditions and rules for electrode selection to weld dissimilar steels. a. When the steels are similar metallurgically but dissimilar chemically, match the electrode to the lower chemical composition or less expensive steel. For example, type 310 steel (25% chromium, 20% nickel) is sometimes welded to type 304 steel (19% chromium, 10% nickel). Both types are austenitic. Type 304 steel, which is welded with 308 electrodes, is less expensive, so that weld would be made with type 308 electrodes rather than type 310 electrodes. b. When the steels to be jointed are different metallurgically and chemically, the electrode is selected to provide a tough, crack resistant weld between the two steels. For example, 304 stainless steel is frequently welded to mild structural steel. Corrosion resistance cannot be part of the problem because mild steel is on one side of the joint with practically no corrosion resistance compared to the stainless steel. If this weld is made with mild steel electrodes to match the mild steel side of joint, the weld metal would be enriched by the washin of chromium and nickel from the stainless side. This intermediate chrome-nickel is usually hard and crack sensitive. If the weld is made with type 308 electrodes to match the stainless steel side of the joint, the chromium and nickel contents of the weldment are diluted by the mild steel side of the joint to an intermediate level that would again probably be hard and crack sensitive. When welding mild steel to stainless steel, a proportion of 18% chromium and 8% nickel is desirable in the weld deposit to produce sound welds, with 17% chromium and 7% nickel being the minimum allowable amounts. Reliability of The following examples in Figure 14 show the results of making a transition weld of mild steel to 304 stainless steel with three different electrodes.

122 LESSON V Arc 60% 20% ELECTRODE 20% for for Low Carbon 304 MILD STEEL 308 ELECTRODE ELECTRODE X 60% 304 X 20% MILD WELD STEEL X 20% METAL CHROMIUM NICKEL The composition of 15.3% chromium and 7.3% nickel does not meet the minimum 17-7% proportion. The weld metal will be mostly martensitic with a very small amount of ferrite. This structure is quite brittle. 310 ELECTRODE ELECTRODE X 60% 304 X 20% MILD WELD STEEL X 20% METAL CHROMIUM NICKEL The composition of 19.2% chromium and 14.2% nickel is not near the 18/8 proportion. The weld metal would be fully austenitic and crack sensitive. 309 ELECTRODE ELECTRODE X 60% 304 X 20% MILD WELD STEEL X 20% METAL CHROMIUM NICKEL The composition of 17.4% chromium and 9.4% nickel is close to the 18/8 proportion. The weld metal will be austenitic with some ferrite and a small amount of martensite to keep the weld metal from being tough and crack resistant. 309 is the best choice. ELECTRODE SELECTION STAINLESS TO MILD STEEL Reliability of FIGURE Normally the most severe dilution of the weld metal by the base metal is 40%. Thus, the weld metal in the joint is comprised of 60% from the electrode and 40% from the base metal as shown in Figure 14. In the case of butt joints between dissimilar steels, half of the dilution comes from each side of the joint, or 20% from each base metal Many times, type 310 and 312 electrodes are used erroneously for welding stainless to mild or low alloy steel. In many cases, not only can more dependable welds be made with 309 electrodes, but appreciable savings can be achieved because of their lower cost. COPYRIGHT 2000 THE ESAB GROUP

123 Arc for for Low LESSON V Another common use of stainless steel filler metals is the overlaying or cladding of less expensive steels with a layer of stainless. Mild steel tanks designed to hold corrosive liquids may be lined with stainless steel in this manner. Usually, continuous bare or flux cored electrodes are used with an automated welding setup. Current and penetration must be controlled closely to limit dilution with the base metal. Sometimes it is necessary to deposit more than one layer to assure the correct analysis of the deposit The welding of stainless clad plate (produced by some steel mills) should also be mentioned. Thicker sections may be welded with both mild steel and stainless electrodes, and thinner sections may be welded only with stainless electrodes. Joint preparation, welding procedure and electrode selection will vary with the thickness and type of clad plate being welded. of clad plate is a specialized area of dissimilar metal welding and beyond the scope of this course STAINLESS STEEL ELECTRODES AND FILLER METALS There are several different forms of stainless steel electrodes: covered, continuous solid bare, continuous flux cored and cut length bare welding rods. Carbon Covered Stainless - Arcaloy covered stainless steel electrodes are classified according to the American Society Filler Metal Specification A As defined by that specification, the electrodes are classified by weld metal composition and type of welding current. For example, the AWS designation E means electrode (E), AISI type 308 steel (20% chrome, 10% nickel) and direct current electrode positive (-15). If the classification reference were E308-16, it would indicate an electrode (E), AISI type 308 steel (308) and AC-DC electrode positive operation (-16 & -17). Arcaloy lime coated electrodes have the DC suffix -15, Arcaloy AC-DC electrodes have the suffix -16, and Arcaloy Plus electrodes use the -17 suffix Arcaloy high alloy stainless steel covered electrodes are produced by extruding carefully formulated and mixed coating material on a stainless steel core wire, thus ensuring constant weld metal properties and composition Arcaloy stainless steel electrodes have been among the leaders in the stainless electrode industry for many years. The strict purchase specifications for the core wire and the covering materials, and the rigid quality control under which the Arcaloy electrodes are manufactured, have resulted in this position of leadership. Reliability of

124 Arc LESSON V Arcaloy lime coated electrodes were among the earliest stainless steel electrodes developed in the United States. Designed for welding with direct current, reverse polarity only, the coating contains considerable amounts of limestone and fluorspar producing a fast freezing slag that facilitates welding in the vertical and overhead positions. The weld bead is slightly convex and moderately rippled. (See Figure 15). for for Low Carbon Characterized by a strong globular arc, a moderate amount of spatter and slag removal that is somewhat difficult, the lime type is not the most popular with the welding operators. However, it is the easiest to use stainless electrode for out-of-position welding. Also, the convex bead can provide the necessary margin of safety in highly stressed joints in many cases Arcaloy AC-DC Titania coated electrodes were the first such electrodes to receive wide acceptance in this country. Designed to operate on alternating current as well as direct current, the coating contains dominant amounts of rutile (titania), medium amounts of limestone, and limited amounts of fluorspar. By far, the AC/DC type is the most popular of the coated stainless electrodes. Welders like to use it because of the smoother arc action, low amount of fine spatter and easy slag removal. Also, the bead is relatively flat, finely rippled and has good side-wall fusion (See Figure 15). Although used in all positions, vertical and overhead welding requires slightly more operator skill than with the lime types because the slag does not freeze as quickly Arcaloy "Plus" electrodes display characteristics not found in the conventional lime and AC-DC Titania coatings. Designed to operate on DCEP or AC, this coating is specially formulated to operate on a broad range of current settings, and most significantly, these electrodes perform their best at high heat inputs where conventional AC-DC electrodes tend to break down When operating at high currents, Arcaloy Plus electrodes deposit weld metal at exceptional speeds with a smooth spray transfer. The bead profile is finely rippled, concave, and evenly feathered (See Figure 15). Spatter is minimal. The molten slag does not edge into the weld puddle, thereby assuring easy visibility of the arc transfer Arcaloy Plus electrodes were developed for applications on dairy and food processing equipment and chemical containers, to name a few, where the weld radius must be smooth and concave to prevent particle entrapment. When welding in the flat and horizontal fillet positions, the concave deposit and absence of surface irregularities make it ideal for applications where cosmetic appearance, speed, and final finishing are factors. Reliability of

125 LESSON V Arc for (-15) (-16) (-17) LIME AC-DC PLUS CONVEX FLAT CONCAVE MODERATE RIPPLE LOW RIPPLE MININUM RIPPLE WELD BEAD SHAPE ARCALOY COATED ELECTRODES FIGURE 15 for Low The weld metal properties are similar for each of the three coating types: lime, AC- DC and AC-DC Plus ARCALOY COVERED ELECTRODE PROPERTIES AND APPLICATIONS Carbon Arcaloy 308L (AWS E308/308L-15 & -16), Arcaloy 308L Plus (AWS E308/308L- 17) - This extra low carbon composition is intended to weld Type 304L steels to prevent carbide participation. It can also be used to weld Types 321 and 347 steels. Typical chemical composition of weld metal is: Carbon 0.03% Chromium 19.1% Nickel 9.7% Manganese 1.6% Silicon 0.4% Ferrite No Arcaloy 309L (AWS E309L-15 & -16), Arcaloy 309L Plus (AWS E309/309L-17) - The low carbon content of Arcaloy 309 L weld metal makes it useful to weld low carbon overlay on carbon or low alloy steel to control carbide precipitation in the overlay. The chemical composition of the weld metal is the same as that of Arcaloy 309 except that the carbon content is 0.04% and the typical ferrite no. is Arcaloy 309 Cb (AWS 309Cb-15 & -16) - The addition of columbium to Type 309 weld metal improves its high temperature performance. It is also useful in welding Types 321 and 347 clad steels. The weld metal composition is the same as Type 309, except that 0.80% columbium is added and the ferrite no. is 8. Reliability of.

126 Arc for for Low Carbon BASIC WELDING FILLER METAL TECHNOLOGY A Correspondence Course LESSON VI CARBON AND LOW ALLOY STEEL FILLER METALS FOR THE GMAW, GTAW AND SAW WELDING PROCESSES ESAB ESAB & Cutting Products Reliability of COPYRIGHT 2000 ESAB WELDING & CUTTING PRODUCTS

127 Arc for TABLE OF CONTENTS LESSON VI CARBON & LOW ALLOY STEEL FILLER METALS FOR THE GMAW, GTAW, AND SAW WELDING PROCESSES LESSON VI Section Nr. Section Title Page for Low Carbon 6.1 Introduction Manufacturing Wire Selection for Gas Shielded Arc AWS Specification A Carbon Steel for Gas Shielded Arc Individual Filler Metal Characteristics ER70S ER70S ER70S ER70S ER70S ER70S ER70S-G ESAB Bare Solid Carbon Steel Wires SPOOLARC Reliability of SPOOLARC 29S SPOOLARC SPOOLARC SPOOLARC 87HP AWS Specification AWS A Low Alloy Steel for Gas Shielded Arc The Chromium-Molybdenum Types The Nickel Alloy Types... 13

128 Arc for for Low Carbon LESSON VI Section Nr. Section Title Page The Manganese-Molybdenum Types SPOOLARC SPOOLARC Hi All Other Low Alloy Types SPOOLARC 95 and Wires and Fluxes for Submerged Arc of Carbon Steels Equipment Fluxes for Carbon Steel AWS Specification A TABLE OF CONTENTS LESSON VI - Con't. Carbon Steel and Fluxes for Submerged Arc ESAB Wires and Fluxes for Carbon Steel Submerged Arc SPOOLARC SPOOLARC 29S SPOOLARC UNIONMELT UNIONMELT UNIONMELT UNIONMELT Reliability of UNIONMELT and Fluxes for Submerged Arc of the and Fluxes for the Alloys AWS Specification A Low Alloy Steel and Fluxes for Submerged Arc Composition Requirements for Solid Low Alloy Spoolarc Low Alloy Wires for Submerged Arc... 31

129 Arc for for Low Carbon TABLE OF CONTENTS LESSON VI - Con't. LESSON VI Section Nr. Section Title Page Manganese-Molybdenum Wires Chromium-Molybdenum Wires Nickel Wire High Strength Wires Special Purpose Wires Unionmelt Fluxes for Unionmelt Unionmelt Unionmelt Alloy Shield Composite for Submerged Arc of the Alloy Shield B1S Alloy Shield B2S Alloy Shield B3S Alloy Shield Ni1S Alloy Shield Ni2S Alloy Shield M2S Alloy Shield M3S Alloy Shield WS Alloy Shield F2S Alloy Shield 420SB Appendix A Glossary of Terms Reliability of

130 Arc for for Low Carbon Reliability of CARBON AND LOW ALLOY STEEL FILLER METALS FOR THE GMAW, GTAW AND SAW 6.1 INTRODUCTION WELDING PROCESSES During the early part of the 20th century, some welding was done using bare steel wires or rods. The weld quality was poor because of the oxides and nitrides found in the weld metal. Even after the advent of the extruded coated electrode in 1927, automated welding using bare wires (or lightly coated wires) continued to be used, despite the poor qualities of the welds, because this method allowed more rapid deposition of the weld metal. Critical welds, however, were made with coated electrodes The advantages of using an inert gas to shield the arc were known during the 20 s and 30 s, but the inert gases, such as helium and argon, were too expensive to produce In 1935, submerged arc welding (then known as submerged melt welding) was introduced and provided a method of producing quality welds at greater welding speeds than were obtainable with coated electrodes During World War II, the aircraft industry needed a reliable process for welding magnesium engine parts and as a result, gas tungsten arc welding (GTAW), using a bare filler wire and a helium gas shield, was developed Economical methods of producing the inert gases were ultimately developed, leading to the use of solid wire with a helium or argon gas shield in the 1940 s. This process became known as metal inert gas (MIG) welding In the early 1950 s, it was realized that a more economical shielding gas, such as carbon dioxide, could be used if the wire chemistry was adjusted to neutralize the oxidizing effect of this gas. Since carbon dioxide (CO 2 ) is not an inert gas, the name MIG welding actually did not apply to this process since CO 2 is a reactive gas. As a result, the American Society has standardized on the term GMAW (Gas Metal Arc ) to include the inert gases, active gases, and gas mixtures as covered in Lesson II. In Europe, the term MIG (Metal Inert Gas) welding still applies to the process if an inert gas or mixtures of inert and active gases are used, and the term MAG (Metal Active Gas) is used if straight CO 2 is employed as the shielding gas. LESSON VI COPYRIGHT 2000 THE ESAB GROUP, INC.

131 Arc for for Low Carbon LESSON VI Although carbon steel, low alloy steels, stainless steels, magnesium, copper, copper alloys, titanium and other metals may be welded by one or all of the processes described above, this Lesson will be confined to the filler metals for welding mild or carbon steels, and low alloy high strength steels with the GMAW and GTAW processes. 6.2 MANUFACTURING The manufacture of solid welding wires for GMAW or GTAW differs from the manufacture of coated or flux cored electrodes in that the deoxidizers and alloying elements that contribute to the purity and mechanical properties of the weld metal, must be included in the wire chemistry rather than in the flux. Therefore, the raw material must be ordered from the supplier to exact specifications. When received, a sample from both ends of each coil of the hot rolled rod is analyzed by the manufacturer to ensure that the hot rod, as it is called, meets these specifications The hot rod is cleaned to remove mill scale or rust and drawn to an intermediate diameter. At this stage, the wire has work hardened which necessitates that it be annealed before it is copper plated, drawn down to final size, spooled and packaged Close quality checks must be made throughout the manufacturing process to insure that the end product is a smooth finished, uniform diameter wire, that will feed easily through the end user s wire feeding equipment and welding gun. The wire is copper plated and/or otherwise coated to retard oxidation or rusting of the wire, to decrease contact tip wear, and to assure good electrical conductivity. The plating or coating must not flake off or leave a residue that will clog the wire feed cable or the welding gun. If copper coated, the layer of copper must be kept to a low level to minimize copper welding fumes and flaking. Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

132 Arc 6.3 WIRE SELECTION FOR GAS SHIELDED ARC WELDING When selecting the wire or filler metal for either the GMAW or GTAW process, several things must be considered. LESSON VI for for Low 1. Mechanical Properties - The wire chosen must produce weld metal having approximately the same mechanical properties as the base metal whether it is carbon steel or low alloy high tensile steel. 2. Shielding Gas - In Lesson II, we learned that the shielding gases used in GTAW of carbon steel are pure argon or argon helium mixtures. In GMAW, shielding gases may be pure CO 2, or mixtures of argon, helium, CO 2 and oxygen. The gas mixtures containing oxygen or CO 2 will exhibit oxidizing characteristics which, if they combine with carbon, will form carbon monoxide gas porosity in the weld metal. a. The most common shielding gases used for welding mild and low alloy steels may be classified in terms of their oxidizing effect as shown in Figure 1. Pure Argon or 98% Argon 75% Argon Argon - Helium 2% O 2 25% CO 2 Pure CO 2 Mixtures Process GTAW GMAW GMAW GMAW Carbon Reliability of Degree of Non- Slightly More Most Oxidation Oxidizing Oxidizing Oxidizing Oxidizing OXIDATION POTENTIAL OF COMMONLY USED SHIELDING GASES FIGURE 1 b. Each of the following variables should be considered when selecting the proper gas for a specific job: MATERIAL TYPES WELD METAL MECHANICAL - Carbon, Stainless, Aluminum, etc. PROPERTIES MATERIAL CONDITION JOB REQUIREMENT - Rusty, Oily, Primed, etc. - Fit-Up TYPES OF METAL TRANSFER - Penetration - Short Circuit, Spray, Pulse, etc. - Spatter Levels COPYRIGHT 2000 THE ESAB GROUP, INC.

133 Arc LESSON VI 3. Wire Chemistry - In order to provide specific characteristics, it may be necessary to have a filler metal that matches the base plate chemistry. The most common examples are requirements to weld 1-1/4 Cr - 1/2 Mo steel with ER80S-B2(L) or 2-1/4 Cr - 1 Mo steel with ER90S-B3(L) providing matching high temperature strength and scaling resistance. for for Low Carbon a. To minimize the oxidizing effect of the various shielding gases, elements that are called deoxidizers are included in the wire in varying amounts. These deoxidizers, usually silicon and manganese, and to a lesser extent titanium, aluminum, and zirconium, will combine with the oxygen in preference to reacting with the carbon and will form very small amounts of harmless glass-like slag islands on the weld surface. b. In the case of GTAW of steels where inert gases such as argon or argon-helium mixtures are used, there will be little or no loss of the deoxidizers. c. In GMAW, where shielding gases of different mixtures are used and welds of the highest quality are required, the filler wire must be selected to allow for the degree of oxidation of the shielding gas. When welding carbon or low alloy steels with a 98% argon - 2% oxygen mixture, wires containing low amounts of manganese and silicon may be used. If welding carbon or low alloy steels with a 75% argon - 25% CO 2 shielding gas, wires with a higher amount of deoxidizers may be necessary to maintain the proper manganese and silicon content in the weld metal. When welding with straight CO 2 as a shielding gas, wires with an even greater amount of deoxidizers may be necessary. 4. Base Metal - The type of steel in the base metal will influence the type of wire selected. Rimmed steel (see Lesson I), which involve the least oxidation during manufacture, will require that the filler wire contain a higher level of deoxidizers than semi-killed steel that is partially deoxidized. Killed steels that are fully deoxidized when manufactured may be welded with wires with a lower deoxidizer content. 5. Rust and Mill Scale - which are actually iron oxide (FeO) are a further source of oxygen that is detrimental to the weld metal unless a wire containing sufficient deoxidizers is selected. Cold rolled steel, that is devoid of mill scale and is reasonably rust free, may be welded with a wire having lower amounts of silicon and manganese. Hot rolled steel, that is characterized by having some amount of mill scale on the surface, requires a wire containing greater amounts of deoxidizers to produce sound welds. Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

134 Arc for for Low Carbon 6. Bead Geometry - Bead geometry (or bead shape) is influenced by both the amount of deoxidizers in the wire and by the specific selection of shielding gas. Increasing the silicon and manganese content of the wire will produce flatter beads and better side wall fusion (wetability) because the puddle is more fluid. See Figure 2. a. The choice of shielding gas likewise influences bead shape. CO 2 produces more spatter and a higher crown or more convex bead. Argon-CO 2 and argon-o 2 gas mixtures provide smoother metal transfer, less spatter, and better bead appearance. 7. Current - When welding at high current for greater weld metal deposition, the weld puddle becomes larger, meaning that more of the base metal has been melted and will stay molten for a longer period, allowing more time for oxidation and resultant porosity to take place. Also, high currents produce a greater amount of heat in the arc area and will cause greater amounts of an oxidizing shielding gas to be dissociated, thereby releasing more oxygen in the area of the molten pool. For these reasons, a wire with higher levels of deoxidizing elements should be selected for high current operation To summarize, the above 7 factors must be properly considered in order to produce top quality welds. The economics of your decision should never compromise the need to deposit the highest weld metal integrity possible. The result of your decision will only lead to most cost effective choice of welding materials. The following are economic considerations: 1. The cost of the wire increases with the percentage of deoxidizers and alloying elements such as silicon, manganese, chromium, molybdenum, nickel, etc. in the welding wire. 2. The cost of pure carbon dioxide is approximately one-fourth that of argon and argon-co 2 or argon-o 2 mixtures. LOW SILICON- MANGANESE CONTENT 3. The deposition efficiency of solid wires is very high, but it varies with the shielding gas and welding current being used. Figure 3 shows the average efficiency when using the more common shielding gases. The differences in efficiency are due to spatter loss, and are proportional to the amount of argon in the gas mixture. CO 2 produces more weld spatter and therefore a lower deposition efficiency. LESSON VI HIGH SILICON- MANGANESE CONTENT SILICON-MANGANESE EFFECT ON BEAD SHAPE Figure 2 Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

135 LESSON VI Shielding Gas Efficiency Range Average Efficiency Arc Pure CO 2 88% - 95% 93% 75% Ar - 94% - 98% 96% 25% CO 2 for 98% Ar - 2% O 2 97% % 98% DEPOSITION EFFICIENCIES - GAS METAL ARC WELDING CARBON AND LOW ALLOY STEEL WIRES FIGURE 3 for Low Carbon Reliability of 4. The deposition rate of solid wires is very high when compared to that of coated electrodes, but is somewhat lower than the deposition rate of flux cored electrodes. 6.4 AWS SPECIFICATION A This AWS specification is entitled Specification for Carbon Steel for Gas Shielded Arc. It covers bare carbon steel solid wires for use with the GMAW and GTAW processes. It differs from the AWS specifications in the previous lessons in that it classifies the chemical composition of the wire rather than that of the weld metal. It does, however, classify the mechanical properties of the weld metal in the as-welded condition using the gas metal arc welding process The chemical composition requirements are based on the chemical analysis of the as-manufactured wire or filler metal and include the elements in the coating or copper plating applied by the manufacturer. ELECTRODE OR WELDING ROD The letter-number designations MIN. TENSILE STRENGTH X 1000 psi in this specification are shown in Figure 4. E R X X S - X For example, ER70S-3 indicates an electrode or welding rod (ER) that will produce weld metal of a minimum 70,000 psi tensile strength (70); is a solid bare wire or welding rod (S); of a specific chemical composition (3) as shown in CHEMICAL COMPOSITION BARE SOLID ELECTRODE OR ROD LETTER - NUMBER DESIGNATIONS CARBON AND LOW ALLOY STEEL WIRES FIGURE 4 Figure 5. For a complete chemical composition of these wires, see AWS A COPYRIGHT 2000 THE ESAB GROUP, INC.

136 Arc for MAJOR ALLOYING ELEMENTS - % BY WEIGHT LESSON VI AWS CLASS CARBON MANGANESE SILICON TITANIUM ZIRCONIUM ALUMINUM ER70S ER70S ER70S ER70S ER70S ER70S ER70S-G NO CHEMICAL REQUIREMENTS CHEMICAL COMPOSITION - CARBON STEEL BARE WIRES FIGURE 5 for Low Tensile strength requirements of the weld metal produced by the filler metals in this classification are shown in Figure 6. Tensile Yield Shielding Strength Strength Elongation AWS Class Gas PSI PSI in 2" - % Min. } ER70S-2 ER70S-3 ER70S-4 ER70S-5 CO 2 72,000 60, ER70S-6 ER70S-7 ER70S-G * 72,000 60, * As agreed upon between supplier and purchaser Carbon Reliability of WELD METAL TENSILE REQUIREMENTS FIGURE Although Figure 6 shows CO 2 as the shielding gas, the specification does not restrict the use of argon-co 2 or argon-mixtures. It states that a filler metal Minimum AWS Class Impact Properties classified with CO 2 will also meet ER70S F specification requirements when used with ER70S F the above gas mixtures. ER70S-4 Not Required ER70S-5 Not Required Impact properties, according to ER70S F the Charpy V-notch test as listed in the ER70S F specification, are shown in Figure 7. ER70S-G As agreed between supplier & purchaser WELD METAL IMPACT PROPERTIES FIGURE 7 COPYRIGHT 2000 THE ESAB GROUP, INC.

137 6.5 INDIVIDUAL FILLER METAL CHARACTERISTICS LESSON VI Arc for for Low ER70S-2 - This classification covers filler metals that contain small amounts of titanium, zirconium, and aluminum, in addition to the normal deoxidizing elements of manganese and silicon. These wires are commonly referred to as triple deoxidized wires. They will produce sound welds in all types of carbon or mild steels. They are especially suited for welding carbon steels that are rusty or have mill scale on the surface. Weld integrity will vary with the amount of oxides on the surface of the steel. They may be used with CO 2, argon-co 2, or argon-o 2 shielding gas mixtures. They work well in the short-circuiting mode for out-of-position welding ER-70S-3 - Filler metals of this classification contain a relatively low percentage of deoxidizing elements; however, they are one of the most widely used GMAW wires. They produce welds of fair quality when used to weld rimmed steels (steels with high oxygen content) using argon-o 2 or argon-co 2 as a shielding gas. The use of straight CO 2 is not recommended when welding rimmed steels. Sound welds may be made when welding semi-killed (low oxygen) and killed (fully deoxidized) steels using argon-o 2, argon-co 2, or straight CO Wires of this classification may be used for out-of-position welding in the Carbon short-circuiting transfer mode using argon-co 2 or CO 2 shielding gas When CO 2 shielding gas is used, high welding currents should be avoided because welds produced may not meet the minimum tensile and yield strengths of this specification ER70S-4 - Containing slightly higher silicon and manganese contents than the ER70S-3 type, these filler metals will produce weld metal of higher tensile strength. Primarily used for CO 2 shielding gas applications where a higher degree of deoxidization is necessary ER70S-5 - The filler metals in this classification contain aluminum as well as silicon Reliability of and manganese as deoxidizers. The addition of aluminum allows these wires to be used at higher welding currents with CO 2 as the shielding gas. Not used for out-of-position short-circuiting type transfer because of high puddle fluidity. Can be used for welding rusty or dirty steels with a slight loss of weld quality ER70S-6 - Wires in this classification contain the highest combination of deoxidizers in the form of silicon and manganese. This allows them to be used for welding all types of carbon steel, even rimmed steels, using CO 2 as a shielding gas. They produce smooth, well shaped beads, and are particularly well suited for welding sheet metal. This filler metal is also useable for out-of-position welding with short-circuiting transfer. Moderately rusted or scaled COPYRIGHT 2000 THE ESAB GROUP, INC.

138 Arc for for Low LESSON VI steels may be welded successfully with this wire. The weld quality depends on the degree of surface impurities. This wire may be used for high current, high deposition welding using argon mixed with 5-10% oxygen or carbon dioxide ER70S-7 - This wire is similar to the ER70S-3 classification, but it has a higher manganese content which provides better wetting action and bead appearance. The tensile and yield strengths are slightly higher, and welding speed may be increased compared to the ER70S-3 type. This filler metal is usually recommended for use with argon-o 2 shielding gas mixtures, although argon-co 2 and straight CO 2 may be used. The weld metal will be slightly harder than that of the ER70S-3 types, but not as hard as an ER70S-6 deposit ER70S-G - This classification may be applied to solid filler metals that do not fall into any of the preceding classes. It has no specific chemical composition or shielding gas requirements, but must meet all other requirements of the AWS A specification. 6.6 ESAB BARE SOLID CARBON STEEL WIRES Spoolarc 65 (AWS Class ER70S-2) - Spoolarc 65 is a cut length electrode available for a variety of tig and oxy-fuel gas welding applications. In addition to the standard deoxidizers, ER70S-2 also contains additional cleaners such as aluminum, titanium, and zirconium. This electrode is often used on out-of-position welding of pipe joints. The ends of the 36" electrode can be flag tagged for identification purposes. Carbon A. Typical Chemical Analysis of the Wire Carbon 0.08% Phosphorus 0.011% Manganese 1.00% Sulfur 0.009% Silicon 0.40% B. Typical Mechanical Properties of the Weld Metal As Welded Stress Relieved* Yield Point, psi 67,500 62,500 Tensile Strength, psi 77,500 72,500 % Elongation (2") % Reduction of Area Charpy V-Notch Impacts F * 8 hrs. at 1150 F Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

139 Arc for for Low LESSON VI Spoolarc 29S (AWS Class ER70S-3) - Spoolarc 29S is a copper coated wire for general purpose welding with the gas-metal arc process. It contains sufficient deoxidizers to produce sound welds on killed and semi-killed steels and adequate welds on rimmed steels. Carbon dioxide or argon-co 2 shielding gas mixtures may be used. The smaller diameters (up to.045") are especially useful for welding light gauge mild steel in all positions. Among the many applications for which Spoolarc 29S may be used are farm equipment, metal furniture, iron work, trailers, truck bodies, metal fixtures, light vessels, and hoppers. A. Typical Chemical Analysis of the Wire Carbon 0.08% Phosphorus 0.007% Manganese 0.62% Sulfur 0.009% Silicon 0.27% B. Typical Mechanical Properties of the Weld Metal Using CO 2 Shielding Gas Yield Point, psi 60,100 Tensile Strength, psi 75,000 % Elongation (2") 32 Charpy V-Notch Impacts 95 F Carbon Spoolarc 85 (AWS Class ER70S-4) - Spoolarc 85 is a copper plated gas-metal arc welding wire. This wire contains more manganese and silicon for greater deoxidation than ER70S-3 wire. The additional levels of deoxidizers provides more improved rust and mill scale tolerance, while improving bead cosmetics. A. Typical Chemical Analysis of the Wire Carbon 0.07% Phosphorus 0.004% Manganese 0.75% Sulfur 0.012% Silicon 0.39% Copper 0.16% B. Typical Mechanical Properties of the Weld Metal Using CO 2 Shielding Gas Yield Point, psi 65,300 Tensile Strength, psi 78,900 % Elongation (2") 26 Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

140 Arc for for Low LESSON VI Spoolarc 86 (AWS Class ER70S-6) - Spoolarc 86 is a copper plated gas-metal arc welding wire. Containing a high level of deoxidizers, it produces sound welds in all carbon steels using CO 2 shielding gas, argon/co 2 and argon/o 2 mixtures. The arc is quiet and very stable. High speed, high deposition welds can be made with argon-oxygen gas mixtures. Ideal for welding sheet metal where smooth weld beads with good wetting action are desirable. It may be used to weld carbon steels that have a moderate amount of rust or mill scale. Spoolarc 86 can also be used for out-of-position welding with the short-circuit transfer method, making it ideal for pipe welding. Other applications are for bridges, building construction, boiler and pressure vessels, storage tanks, auto parts, and construction equipment. A. Typical Chemical Analysis of the Wire Carbon 0.09% Phosphorus 0.012% Manganese 1.18% Sulfur 0.011% Silicon 0.57% Carbon B. Typical Mechanical Properties of the Weld Metal Using CO 2 Shielding Gas Yield Point, psi 68,000 Tensile Strength, psi 81,600 % Elongation (2") 30 Charpy V-Notch Impacts 31 F Spoolarc 87HP (AWS Class ER70S-7) - Spoolarc 87HP is a high manganese carbon steel wire. It features an optimized manganese to silicon ratio to produce excellent appearing welds over a wide range of welding parameters. It also produces excellent weld metal mechanical properties and welds over moderate amounts of rust and scale. A. Typical Chemical Analysis of the Wire Carbon 0.11% Phosphorus 0.015% Manganese 1.75% Sulfur 0.014% Silicon 0.65% B. Typical Mechanical Properties of the Weld Metal Using 75% Ar/25% CO 2 Yield Point, psi 66,800 Tensile Strength, psi 79,100 % Elongation (2") 29 Charpy V-Notch Impacts 62 F Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

141 6.7 AWS SPECIFICATION A LESSON VI Arc for for Low This specification is entitled Specification for Low Alloy Steel Filler Metal for Gas Shielded Arc. It covers the solid bare wires for welding those steels commonly referred to as the chromium-molybdenum (chrome-molys), manganese-molybdenum (manganese-molys), nickel alloy and other low alloy steels. The wires referred to in this lesson are for use with the gas-metal arc welding process and also may be used as filler metals for the GTAW process The letter-number designations have the same significance as those used in the carbon steel specification shown in Figure 4. Using ER80S-B2 as an example, the letters ER indicate that it is an electrode or a welding rod; will produce weld metal of 80,000 psi tensile strength (80); is a solid bare wire (S) of a specific chemical composition (B2) as described in Figure 8. Major Alloying Elements - % By Weight AWS Class Carbon Chromium Molybdenum ER80S-B2L * ER80S-B ER80S-B3L ER80S-B * Single figure denotes maximum CHEMICAL COMPOSITION CHROMIUM-MOLYBDENUM SOLID BARE WIRES FIGURE 8 Carbon The Chromium-Molybdenum Types (Cr-Mo) - The letter B designates a Cr-Mo wire to be used for welding the Cr-Mo pressure vessel steels, and the number that follows designates the chemical composition of the filler metal. If the last number is followed by an L, it indicates that the wire has a low carbon content Figure 8 shows only the major chemical composition requirements for these filler metals. For complete requirements, see AWS A Filler Metal Specification Figure 9 shows the mechanical property requirements for the Cr-Mo weld metal Filler metals of the preceding classifications are used to weld the 1/2 Cr-1/2 Mo, 1 Cr-1/2 Mo, 1-1/4 Cr-1/2 Mo, and 2-1/4 Cr-1 Mo steels that are used in welding high temperature piping and pressure vessels. They provide a degree of corrosion resistance and are used for welding dissimilar grades of Cr-Mo steels and carbon steels. Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

142 Arc for for Low Tensile Yield Strength Strength Elongation Impact AWS Class psi psi in 2", % Properties ER80S-B2 80,000 68, Not Required ER80S-B2L 80,000 68, Not Required ER90S-B3 90,000 78, Not Required ER90S-B3L 90,000 78, Not Required All values are mininums MECHANICAL PROPERTIES OF Cr - Mo WELD METAL FIGURE These filler metals may be used with all GMAW metal transfer modes. The AWS mechanical properties and impact properties are established using argon plus 1-5% oxygen as a shielding gas. Straight CO 2 and argon-co 2 mixtures may be used. These mixtures will produce welds with deeper penetration, although impact properties will be somewhat lower low alloy high strength steels with the GMAW process requires that preheat, interpass, and post-weld temperatures be closely controlled to prevent cracking. The low carbon filler metals designated by the letter L will provide greater resistance to cracking, and are more suitable when post-weld heat treatment is not practical or possible. LESSON VI Carbon The Nickel Alloy Types (Ni) - The letters Ni designate that the filler metal is a nickel alloy wire for welding the nickel alloy steels. The number following the letters designates the chemical composition of the wire. Figure 10 shows only the amount of nickel required in the wire under this specification. For complete chemical requirements, see AWS A Filler Metal Specification. Nickel AWS Class % by Weight ER80S-Ni ER80S-Ni ER80S-Ni NICKEL REQUIREMENTS NICKEL ALLOY SOLID BARE WIRES FIGURE 10 Reliability of Figure 11 shows the mechanical property requirements for nickel alloy weld metals. Tensile Yield Strength Strength Elongation Impact AWS Class psi psi in 2", Min. Properties } ER80S-Ni F ER80S-Ni2 80,000 68, F ER90S-Ni F All values are mininums MECHANICAL PROPERTIES OF NICKEL ALLOY WELD METALS FIGURE 11 COPYRIGHT 2000 THE ESAB GROUP, INC.

143 Arc for for Low Nickel alloy wires are used for welding the nickel alloy steels that are employed in applications requiring 80,000 psi tensile strength and good toughness at low temperatures. The ER80S-Ni1 wire deposits weld metal containing a nominal 1% nickel, similar to an E8018C3 coated electrode. The ER80S-Ni2 deposits weld metal containing a nominal 2-1/ 2% nickel, similar to an E8018C1 coated electrode and the ER80S-Ni3 deposits weld metal containing a nominal 3-1/2% nickel, similar to an E8018C2 coated electrode The weld metal deposit will have a chemical composition similar to the chemical composition of the wire when argon-o 2 shielding gas is used. If CO 2 is used as a shielding gas, the deoxidizing elements, such as manganese and silicon, will be considerably reduced in the weld metal. The recommended shielding gas is argon plus 1.0 to 5.0% oxygen. the nickel alloy steels usually requires that the weldment be preheated before welding, and the interpass temperature controlled. It may also be necessary to subject the weldment to post weld heat treatment, depending on the alloy and thickness of the material. LESSON VI Carbon The Manganese-Molybdenum Types Mn-Mo - The suffix letter D designates a manganese-molybdenum wire to be used for welding the manganese-molybdenum steels. The number that follows designates the chemical composition of the wire There is only one manganese-moly wire in this classification. It is designated as ER80S-D2 and was formerly classified as E70S-1B in AWS Specification A (since updated to A ). A. Chemical Composition Requirements for ER80S-D2 Bare Solid Wire Carbon % Nickel 0.15% max. Manganese % Copper 0.50% max. Silicon % Phosphorus0.025% max. Molybdenum % Sulfur 0.025% max. B. Mechanical Property Requirements ER80S-D2 Weld Metal Yield Strength, psi 60,000 Tensile Strength, psi 80,000 % Elongation (2") 17 Charpy V-Notch Impacts 20 F Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

144 This wire is suitable for welding a large variety of low alloy and carbon steels. It is LESSON VI Arc for for Low Carbon excellent for out-of-position work and contains molybdenum for increased strength. Argon-O 2 and argon-co 2 gas mixtures are recommended for maximum mechanical properties, but welds made with CO 2 shielding gas will still deliver mechanical properties within the specification limits due to the high level of manganese and silicon in the wire. The high level of deoxidizers allows this wire to be used over moderate amounts of rust and mill scale Spoolarc 83 (AWS Class ER80S-D2) - Spoolarc 83 is a small diameter copper coated solid wire for gas metal arc welding. Because of the additional alloys, manganese, and molybdenum, the deposit is adequate for high strength low alloy steels. In addition, the higher levels of deoxidizers provide improved rust and mill scale tolerance, as well as out-of-position capabilities. This wire is most commonly used on pressure vessel and gas transmission line applications. A. Typical Chemical Analysis of the Wire Carbon 0.10% Phosphorus 0.005% Manganese 1.07% Sulfur 0.012% Silicon 0.27% Molybdenum 0.38% B. Typical Mechanical Properties of the Weld MetalUsing CO 2 Shielding Gas Yield Strength, psi 77,000 Tensile Strength, psi 92,000 % Elongation (2") 23 % Reduction of Area 66.8 Charpy V-Notch Impacts 44 F Spoolarc Hi-84 (AWS Class ER80S-D2) - Spoolarc Hi-84 is a 1/2% Mo wire that has been microalloyed to produce exceptional impact toughness at temperatures as low as -50 F. The weld metal deposit produces a high strength weld with good tolerance of rust and mill scale. A. Typical Chemical Analysis of the Wire Carbon 0.11% Nickel 0.15% Manganese 1.90% Chromium 0.08% Silicon 0.60% Ti and Zr 0.017% Molybdenum 0.50% Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

145 LESSON VI B. Typical Mechanical Properties of the Weld MetalUsing 98% Ar/2% O 2 Arc for for Low Carbon Shielding Gas Yield Strength, psi 99,000 Tensile Strength, psi 111,500 % Elongation (2") 20 Charpy V-Notch Impacts 65 F 51 F All Other Low Alloy Types Solid wires for welding the low alloy high tensile steels that do not fit into the common Cr-Mo, Ni alloys and Mn-Mo types, fall into the all other category. They produce welds with very high strength and very good notch toughness. These alloys are designated by the numbers 1, 2, or "G" as shown in Figure Only the major alloying elements for these wires are shown above. For complete chemical composition requirements, see AWS Filler Metal Specification A Major Alloying Elements - % By Weight AWS Class Carbon Manganese Nickel Chromium Molybdenum ER100S * ER100S ER110S ER120S ERXXS-G As agreed between supplier and purchaser *Single values are maximums. CHEMICAL COMPOSITION - OTHER LOW ALLOYS - SOLID BARE WIRE FIGURE The mechanical requirements for the weld metal deposited in this classification are shown in Figure 13. Tensile Yield Strength Strength Elongation Impact AWS Class psi psi in 2", Min. Properties ER100S-1 100,000 88, , ER100S-2 100,000 88, , } F ER110S-1 110,000 95, , ER120S-1 120, , , ERXXS-G * As agreed between supplier and purchaser * Ultimate tensile strength must meet value placed after "ER" Reliability of WELD METAL MECHANICAL PROPERTIES REQUIREMENTS - OTHER LOW ALLOYS FIGURE 13 COPYRIGHT 2000 THE ESAB GROUP, INC.

146 Arc for for Low LESSON VI The wires in this category were originally developed for the high strength steels in military applications. Today, they are used in structural and other applications requiring tensile strengths in excess of 100,000 psi and toughness at low temperatures. Common types of steels welded with these wires are the T-1, HY-80, HY-100, NAXtra100 and others Spoolarc 95 and 120 (AWS Class ER100S-1 and ER120S-1) - Spoolarc 95 and 120 are Military grade high strength wires designed for welding HY-80 and HY-100 steels. Both wires produce excellent mechanical properties and low temperature toughness. They can be used for nonmilitary applications requiring high strength and low temperature toughness. A. Typical Chemical Analysis of the Wire Spoolarc 95 Spoolarc 120 Carbon 0.07% 0.07% Manganese 1.40% 1.30% Silicon 0.35% 0.35% Molybdenum 0.35% 0.45% Chromium 0.20% 0.40% Nickel 1.80% 2.60% Carbon B. Typical Mechanical Properties of the Weld Metal Using 98% Ar/ 2% O 2 Shielding Gas Spoolarc 95 Spoolarc 120 Yield Strength, psi 95, ,000 Tensile Strength, psi 105, ,000 % Elongation (2") Charpy V-Notch Impacts F F The suffix letter G applies to solid wire electrodes and welding rods that do not fall into any of the other classes in this specification. They must have at least one of the following: 0.50% nickel, 0.30% chromium, or 0.20% molybdenum. They must pass the radiographic soundness test for porosity or inclusions, and also the weld metal tensile tests that are spelled out in detail in this specification. Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

147 6.8 WIRES AND FLUXES FOR SUBMERGED ARC LESSON VI Arc for for Low Carbon WELDING OF CARBON STEELS In submerged arc welding (SAW), the weld metal quality, mechanical properties and bead shape are the result of the electrode* (or wire) and flux combination used in a particular application. Unlike coated electrodes, where the core wire and flux coating are inseparable, various fluxes may be used with a given wire to produce the desired results. The weld area is shielded by this blanket of flux. When molten, the flux forms a protective layer above the molten weld metal that not only provides for specific mechanical properties, but also gives the bead some shape. Note - * The American Society has standardized on the term electrode when referring to the wires used in SAW since these wires always carry the welding current. In this Lesson, the terms wire and electrode will be used interchangeably and will have the same meaning The advantages for using SAW are numerous. They include: a. High rates of travel. b. High deposition rates. c. Superior weld metal integrity. d. Reduce edge preparations. e. Improved operator comfort and safety Equipment - The SAW process can utilize either an AC or DC power supply. DC is most often chosen because it provides the following advantages: a. Good control over bead shape and penetration. b. Best arc starting characteristics on either electrode positive (+) or electrode negative (-). c. DCEN offers 10-15% higher deposition rates than AC. d. DCEP offers better bead shape control and deeper penetration. e. Lowest cost to purchase AC, on the other hand, provides features as well. They include: a. Reduced arc blow (especially when amperage exceeds 800 amps or when welding on heavy sections). b. Increased flexibility when used in combination with multiple wires (DC-AC, AC-AC, or AC-AC-AC). Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

148 Arc for for Low Carbon Reliability of A continuous bare electrode is fed into a blanket of granular flux that covers the weld joint. Once current is applied to the electrode, usually ranging in size from 1/16" to 1/4" diameter, an arc is established and the base metal, the electrode, and the flux melt to form a molten puddle. The solid electrode is usually copper coated, except for certain nuclear applications, to minimize contact tip wear and assure good current transfer to the wire. The molten flux flows to the surface to form a slag while the metallic components create a weld Since high currents are usually applied to the electrode, extremely high deposition rates are possible with SAW. The current and voltage ranges reflected in Figure 14 will provide information on the deposition capability of SAW. Deposition Rate* Wire Diameter Current Ranges Volts lbs./hr. 1/16" (1.6 mm) ( Kg) 5/64" (2.0 mm) ( Kg) 3/32" (2.4 mm) ( Kg) 1/8" (3.2 mm) ( Kg) 5/32" (4.0 mm) ( Kg) 3/16" (4.8 mm) ( Kg) 7/32" (5.6 mm) ( Kg) 1/4" (6.4 mm) ( Kg) OPERATING RANGES AND DEPOSITION RATES (DCEP - ESO AVERAGE 8 X WIRE DIAMETER) FIGURE Composite submerged electrodes, as described in Lesson II, are not normally used for welding carbon steel. They are, however, used in welding low alloy high strength materials. Current and voltage ranges will differ, along with their respective deposition rates. These electrodes will be discussed late in this lesson Fluxes for Carbon Steel - The granular powder, referred to as flux, under which the welding takes place, shields the molten puddle from the atmosphere, cleans the weld metal, and influences the mechanical properties and shape of the weld bead. The flux also acts as a barrier preventing the heat from escaping, permitting the desired depth of penetration (this can vary with current and polarity). Fluxes differ as a result of the method used to manufacture them. LESSON VI COPYRIGHT 2000 THE ESAB GROUP, INC.

149 Arc LESSON VI Fluxes are classified as either bonded or fused based on the manufacturing methods. When manufacturing a bonded flux, fine particles of various ingredients are dry mixed and bonded together with a sodium silicate or other similar compound. The wet bonded mix is pelletized and baked at relatively low temperatures. The pellets are then broken into smaller pieces and screened into proper sizes and packaged for shipment. for for Low Carbon Reliability of The advantages of bonded fluxes are that additional deoxidizers and alloying elements can be added. Secondly, this type of flux generally has a lower consumption rate. The major disadvantage of a bonded flux is their inherent moisture pick-up, especially when opened, bags are allowed to remain exposed to the atmosphere Fused fluxes are manufactured under different conditions. The raw materials are mixed together and then melted at very high temperatures in a furnace. The molten mixture is cooled either by pouring it onto a chill table and allowed to cool, or shooting the molten mixture with a stream of water. The glass-like material is crushed, then screened to a particular particle size and packaged for shipment Fused fluxes offer several advantages to the user, including much less moisture pick-up than bonded fluxes. Secondly, the user has better control of weld metal properties after recycling used flux. The major disadvantage with fused fluxes is the inability to add additional deoxidizers and alloys during manufacturing Fluxes are also described as active or neutral, depending on the amount of alloying elements or deoxidizers (especially manganese or silicon) that are transferred to the weld metal. a. Active Fluxes - contain manganese and silicon. Active fluxes are readily transferred to the weld metal. The amount transferred depends on the amount of flux consumed per unit of wire. Excessively high manganese and silicon transferred to the weld can cause weld metal cracking. Active fluxes are recommended for single pass or limited multipass welding applications. Changes in arc voltage can greatly effect the flux consumption per unit of wire and the weld metal properties. It is, therefore, crucial to adhere to the manufacturer s suggested welding parameters. b. Neutral Fluxes - produce little significant change in weld metal properties as a result of arc voltage. The primary purpose for neutral fluxes is that they can be used on multipass weldments, especially those that exceed one inch thickness. The disadvantage for neutral fluxes is their low tolerance to rust and mill scale. Generally speaking, active fluxes are used with carbon steel electrodes, while neutral fluxes are recommended for both carbon and low alloy steels. COPYRIGHT 2000 THE ESAB GROUP, INC.

150 6.9 AWS SPECIFICATION A LESSON VI Arc for for Low This AWS specification is entitled Specification for Carbon Steel and Fluxes for Submerged Arc. It classifies the electrodes on the basis of their chemical composition as shown in Figure 15A. The fluxes are classified on the basis of the mechanical properties of the weld metal they deposit with a particular classification of electrode as shown in Figure 15B. Electrode Percent Manganese By Weight L = M = H = E X X X K When Used, Indicates Electrode Made From Silicon-Killed (Deoxidized) Steel. Percent Carbon By Weight 8 = 0.10 Max. 12 = = = 15 =} ELECTRODE DESIGNATIONS FOR SUBMERGED ARC WELDING CARBON STEEL FIGURE 15A Carbon Flux F X X X A = As Welded P = Postweld Heat Treatment 1150 for 1 Hour Costs F6XX F7XX Tensile 60,000 70,000 Strength to to psi 80,000 95,000 Yield Strength 48,000 58,000 psi Min. Min. Elongation % in 2" Min. Min. Impact Requirements Charpy V-Notch Z No Requirement 0 0 F 2-20 F 4} F 5-50 F 6-60 F 8-80 F Reliability of FLUX DESIGNATIONS FOR SUBMERGED ARC WELDING CARBON STEEL FIGURE 15B COPYRIGHT 2000 THE ESAB GROUP, INC.

151 Arc for for Low Carbon LESSON VI For example, when a manufacturer assigns the AWS classification EM12K to a given wire or electrode, he certifies that his product is an electrode (E); containing a medium manganese content of 0.80 to 1.40% (M); containing a carbon content of 0.05 to 0.15% (12); and is made from a heat of silicon-killed steel (K) When classifying a flux as to mechanical properties, it is necessary to also specify the electrode or wire with which these properties are obtained. As an example, the classification F7P6-EM12K certifies that the product is a submerged arc flux (F); will provide weld metal of 70,000 to 95,000 psi tensile strength, a minimum of 58,000 psi yield strength and a minimum of 22% elongation in two inches after the weldment has been subjected to a postweld heat treatment of 1150 F for one hour (P); and will have a minimum charpy V-notch impact of 20 ft.-lbs. at -60 F when used with an EM12K wire The eleven types of carbon steel electrodes listed in AWS A are as follows: A. Low Manganese Steel 1) EL8 2) EL8K 3) EL12 B. Medium Manganese Steel 1) EM12 2) EM12K 3) EM13K 4) EM14K 5) EM15K C. High Manganese Steel 1) EH11K 2) EH12K 3) EH The carbon and manganese content of these wires are shown in Figure 15. For complete chemical composition of these wires, see AWS Filler Metal Specification A Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

152 6.10 ESAB WIRES AND FLUXES FOR CARBON STEEL LESSON VI Arc for for Low Carbon SUBMERGED ARC WELDING Spoolarc 81 (AWS Class EM12K) - Spoolarc 81 is a general purpose submerged arc wire for moderately clean material. Applications include low and medium structural carbon steel, longitudinal and circumferential welds on low to medium strength pressure vessel steels and some offshore and ship fabrication. A. Typical Chemical Analysis of the Wire Carbon 0.11% Phosphorus 0.006% Manganese 0.956% Sulfur 0.008% Silicon 0.22% Copper 0.34% B. Typical Mechanical Properties (* See note following Unionmelt 80) Weld UTS YS % CVN (ft-lbs) AWS/ASME Flux Cond. (ksi) (ksi) F SFA 5.17 Class 231 AW F7A2-EM12K 429 AW F7A2-EM12K SR(a) F F7P4-EM12K 80 AW F6A2, F7A2-EM12K (a) F - 1 hr Spoolarc 29S (AWS Class EM13K) - Spoolarc 29S has increased amounts of silicon for both improved puddle fluidity and rust and mill scale tolerance. This wire is not recommended for material greater than 1" thickness. Applications include single pass high speed fillets on both low and medium carbon steels. A. Typical Chemical Analysis of the Wire Carbon 0.09% Phosphorus 0.008% Manganese 0.98% Sulfur 0.012% Silicon 0.52% Copper 0.28% Reliability of B. Typical Mechanical Properties (* See note following Unionmelt 80) Weld UTS YS % CVN (ft-lbs) AWS/ASME Flux Cond. (ksi) (ksi) F SFA 5.17 Class 231(a) AW F. F7A0-EM13K 429 AW F. F7A2-EM13K (a) This combination of flux and wire is only recommended for single pass welding. COPYRIGHT 2000 THE ESAB GROUP, INC.

153 Arc for for Low Spoolarc 80 (AWS Class EL12) - Spoolarc 80 has the least amount of manganese and silicon and is therefore intended for clean material. The major advantage of this wire is the improved ductility, ease of machining and improved crack resistance. Applications include high speed fillets on axle housings and wheel rims and thick heavy sections on highly restrained multipass weldments. A. Typical Chemical Analysis of the Wire Carbon 0.10% Phosphorus 0.003% Manganese 0.44% Sulfur 0.014% Silicon 0.04% Copper 0.16% B. Typical Mechanical Properties LESSON VI Weld UTS YS % CVN (ft-lbs) AWS/ASME Flux Cond. (ksi) (ksi) F SFA 5.17 Class 231(a) AW F. F7AZ-EL AW F. F6A2-EL12 (a) This combination of flux and wire is only recommended for single pass welding. Carbon Reliability of Unionmelt Unionmelt Flux 231 is an active flux that is limited to a maximum plate thickness of one inch or less and operated at less than 36 volts. Applications include single and multipass flat and horizontal fillets over rust and mill scale. This flux can be used with Spoolarc 81, 29S and 80. A. Typical Deposit Chemistry Wire Material C Mn Si Cu AWS/ASME SFA A F7A2-EM12K 29S(a) A F7A0-EM13K 80 A F7AZ-EL12 B. Typical Mechanical Properties (* See note following Unionmelt 80) Spoolarc Weld UTS YS % CVN Material Wire Condition (ksi) (ksi) Elong. (ft.-lbs.) A AW F A285 29S(a) AW F A36 80 AW F (a) Unionmelt Flux 231 and Spoolarc 29S are recommended for single pass welding only. COPYRIGHT 2000 THE ESAB GROUP, INC.

154 Arc for for Low Unionmelt Unionmelt Flux 429 is a neutral bonded flux designed for multipass welding. Weld metal chemistries are excellent both as-welded and stress-relieved. Applications include deep groove multipass welds found on pressure vessels and offshore oil fabrication. Commonly used with hand-held semi-automatic equipment. This flux can be used with Spoolarc 81 and 29S. A. Typical Deposit Chemistry AWS/ASME Wire Material C Mn Si Cu SFA A F7A2-EM12K 29S A F7A2-EM13K B. Typical Mechanical Properties (* See note following Unionmelt 80) Spoolarc Weld UTS YS % CVN Material Wire Condition (ksi) (ksi) Elong. (ft.-lbs.) LESSON VI A36 81 AW F SR(a) F A285 29S AW F (a) F - 1 hr. Carbon Unionmelt Unionmelt Flux 282 is an active bonded flux designed for high speed single pass welding on thin gauge material. The weld metal fluidity and high travel speeds make this flux extremely versatile. Applications include longitudinal welds on structural steel, as well as circumferential seams on spiral pipe. This flux is best used with Spoolarc 81 and 29S. A. Typical Mechanical Properties (* See note following Unionmelt 80) Spoolarc Wire Tested Per AWS A Spoolarc 81 Conforms to F7A0-EM12K (20 0 F) Spoolarc 29SConforms to F7A0-EM13K (20 0 F) Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

155 Arc for for Low Carbon LESSON VI Unionmelt 50 - Unionmelt Flux 50 is a neutral fused flux developed for high speed welding of thin gauge material (usable on relatively clean steel only). In addition, this flux works equally well for surfacing and build-up applications. Because this flux is a fused type, it is particularly resistant to moisture pick-up. Applications include propane cylinders and hot water tanks. This flux can be used with Spoolarc 81 and 80. A. Typical Deposit Chemistry Spoolarc AWS/ASME Material Wire C Mn Si SFA 5.17 A F7A2-EM12K Stress-Relieved F6P4-EM12K A F6A2-EL12 B. Typical Mechanical Properties (* See note following Unionmelt 80) Spoolarc Weld UTS YS % CVN Material Wire Condition (ksi) (ksi) Elong. (ft.-lbs.) A36 81 AW F SR(a) F A36 80 AW F (a) F - 8 hrs Unionmelt 80 - Unionmelt Flux 80 is a neutral fused flux for multipass, heavy plate welding applications. Superior mechanical properties on clean material is available in both as-welded and stress-relieved conditions. The low moisture pick-up of this flux helps reduce the handling and storage casts. Applications include carbon and low alloy steels used to fabricate pressure vessels. This flux can be used with Spoolarc 81 and 80. A. Typical Deposit Chemistry Spoolarc AWS/ASME Material Wire C Mn Si SFA 5.17 A F6A2, F7A2-EM12K A F6A2-EL12 B. Typical Mechanical Properties * Spoolarc Weld UTS YS % CVN Material Wire Condition (ksi) (ksi) Elong. (ft.-lbs.) A36 81 AW F A36 80 AW F * NOTE: The data listed for both the deposit chemistry and mechanical properties are based on laboratory tests. Results may vary according to your specific welding parameters or base metal conditions. It is, therefore, important that the user run tests that closely duplicate their actual production conditions. Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

156 Arc for for Low Carbon LESSON VI 6.11 ELECTRODES AND FLUXES FOR SUBMERGED ARC WELDING OF THE LOW ALLOY STEELS In an earlier lesson, we learned that most low alloy coated electrodes have a mild or carbon steel core wire, and the alloying elements, that produce the higher tensile strengths or improved impact properties, are in the electrode coating. In the case of stainless steel coated electrodes, a stainless steel core wire is used, and the elements that determine the specific analysis of the weld metal are included in the coating. In submerged arc welding, the choice exists as to the wire-flux combination that will produce the required end result and Fluxes for the Alloys - for welding the low alloy steels are available as low alloy solid wires or composite electrodes. Composite electrodes are similar to flux cored electrodes, but since they are used with a granular flux, the core contains mostly the necessary alloying elements. The outer sheath may be a carbon or alloy steel. Submerged arc wires are available in diameters ranging from 1/16" to 1/4" diameter the low alloy steels with the submerged arc process may be accomplished in several different manners. They are: a. A solid wire that has a sufficient amount of alloying elements included in the chemistry of the wire as manufactured, and a neutral flux that shields the weld and influences bead shape, but has a minimal affect on weld metal chemistry. b. A composite wire that contains the necessary alloying elements in the core and/or the steel sheath, used in conjunction with a neutral flux. c. A solid carbon steel wire may be used, such as an EM12K type, in combination with a flux that contains the necessary alloying elements to produce the desired low alloy weld metal. Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

157 6.12 AWS SPECIFICATION A LESSON VI Arc for for Low This AWS specification is entitled Specification for Low Alloy Steel and Fluxes for Submerged Arc. Since there are two types of welding wires, solid and composite, each must be considered in a different manner. Solid wires are classified by their as manufactured chemical analysis, but this is not possible with composite wires because the outer steel sheath and the core ingredients combine to produce the resultant weld metal. Therefore, composite wires are classified as to the weld metal chemical composition as are coated electrodes The fluxes for welding low alloys with the submerged arc process are classified by the weld metal mechanical properties they produce with a given wire or electrode. Figure 16 shows the classification of fluxes and electrodes under this specification. Tensile Yield Strength Strength Elongation psi psi % in 2" F7XX 70,000-95,000 58, F8XX 80, ,000 68, F9XX 90, ,000 78, F10XX 100, ,000 88, F11XX 110, ,000 98, F12XX 120, , , or 2 Digits Impact Requirements Charpy V-Notch Z No Requirement 0 0 F 2-20 F 4-40 F 5-50 F 6} F 8-80 F F F Carbon Flux F X X X A = As Welded P = Postweld Heat Treatment Time & Temp. per AWS A FLUX DESIGNATIONS Indicates Composite Electrode. Omission Indicates Solid Wire Electrode Used Only for Some Nuclear Requirements E C X X X N - X N H X ELECTRODE DESIGNATIONS Classification of Electrode - 2, 3, or 4 Numbers or Letters. Chemical Composition of Weld Metal - 1, 2, or 3 Numbers or Letters Optional Diffusable Hydrogen Designator Reliability of FLUX AND ELECTRODE DESIGNATIONS FOR SUBMERGED ARC WELDING - LOW ALLOY STEELS FIGURE 16 COPYRIGHT 2000 THE ESAB GROUP, IN

158 Arc Composition Requirements for Solid Low Alloy - The listing in Figure 17 indicates only the major alloying elements of each electrode type. For complete chemical composition requirements, see AWS A C = Carbon Ni = Nickel Mn = Manganese Mo = Molybdenum LESSON VI for for Low Carbon Reliability of Cr = Chromium ELECTRODE CLASSIFICATION C Mn Cr Ni Mo Si Carbon Steel EL EM12K Carbon-Molybdenum EA EA EA EA3K EA Chromium Molybdenum EB EB EB2H EB EB EB EB6H EB Nickel Steel ENi ENi ENi ENi ENi1K Other Low Alloy Steel EF EF EF EF EF EF EM EM EM EW EG No Requirements Single Figures are Maximums MAJOR CHEMICAL COMPOSITION REQUIREMENTS SOLID WIRE SUBMERGED ARC WELDING ELECTRODES. AWS A FIGURE 17 COPYRIGHT 2000 THE ESAB GROUP, INC.

159 Arc for for Low Carbon LESSON VI Figure 17 lists two carbon steel wires (EL12 and EM12K) that are the same as those listed in AWS A , the specification for mild and carbon steels. They appear here only because they can be used with fluxes that contain sufficient alloying elements to deposit a low alloy weld metal Although all of the low alloy electrodes in AWS Specification A are listed here, a complete knowledge of their uses and applications are beyond the scope of this course. They are presented here so that you will be familiar with the various AWS designations As an example, a manufacturer of a solid wire electrode may assign the AWS classification EB3. Under this specification, he certifies that this wire is an electrode (E), the chemical composition is a chrome-moly type (B) containing a nominal 2-1/2% chromium and 1% molybdenum, and it meets the other chemical requirements (3) The specification also lists the chemical composition of the weld metal which differs slightly from the chemical requirements for the wire. The same designations are used for the weld metal as for the electrode classification in Figure 17 except that the letter E is deleted. For example, the weld metal is designated as A2, B3, Ni2, F2, N3, etc. Since classification of the composite electrodes is based on the weld metal composition, the letters EC are placed before the weld metal classification and the electrode designation for composite electrodes would be ECA2, ECB3, ECNi2, etc An example of a complete flux electrode designation would be as follows: F8P10-ECNi2-Ni2. This designation refers to a flux (F) that will produce weld metal of a minimum 80,000 psi tensile strength (8), when postweld heat treated (P), and satisfies a charpy V-notch impact strength test of at least 20 ft.-lbs. at -100 F (10) when used with a composite electrode (EC) of a nickel type (Ni) containing a nominal 2-1/2% nickel (2) and will produce weld metal of the chemical composition specified under Ni2 in AWS Specification A (Ni2). Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

160 6.13 SPOOLARC LOW ALLOY WIRES FOR SUBMERGED ARC WELDING LESSON VI Arc for for Low Carbon Manganese-Molybdenum Wires Spoolarc 40A, 40B, and 40 (AWS Class EA1, EA2, and EA3) - These (Mn-Mo) wires are designed for pressure vessel fabrication requiring postweld heat treatment and weld metal tensile strength of 60 ksi, 70 ksi, and 80 ksi. They are generally used with Unionmelt 80, 124, and 429 fluxes Chromium-Molybdenum Wires Spoolarc U515 and U521 (AWS Class EB2 and EB3) - Spoolarc U515 and U521 wires are designed for welding 1-1/4% Cr - 1/2% Mo and 2-1/2% Cr - 1% Mo pressure vessels. They can be used with Unionmelt 80, 124, and fluxes Nickel Wire Spoolarc ENi4 (AWS Class ENi4) - Spoolarc ENi4 is designed for single or multipass welding on high strength steels and produces good low temperature toughness. It is usable with Unionmelt 429, 439, 709-5, and 656 flux High Strength Wires Spoolarc 44 (AWS Class EF2) - Spoolarc 44 is designed for single or multipass welding on high strength steels of 80 ksi. The addition of nickel helps it produce good low temperature toughness. It is usable with Unionmelt and 656 fluxes Spoolarc 95, 100, and 120 wires (AWS Class EM2, EM5, and EF4) - Spoolarc 95, 100, and 120 are military grade, high strength, low temperature impact wires designed for welding HY-80 and HY-100 steels. They are usable with Unionmelt and 656 fluxes Special Purpose Wires Spoolarc WS (AWS Class EW) - Spoolarc WS is designed for single and multipass welding on weathering grade steels such as A588 and Cor-Ten. The weld chemistry produces good color match, weathering resistance, and meets fracture critical code requirements. It is usable with Unionmelt 429, 439, 709-5, and 656 fluxes. Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

161 6.14 UNIONMELT FLUXES FOR WELDING LOW LESSON VI Arc for for Low ALLOY STEELS Unionmelt 429 Flux - Unionmelt 429 flux is a bonded flux developed for single or multipass butt and fillet welding on pressure vessel and structural steel fabrication. It operates on either AC or DC, single or multiple wire operation. It has good performance in the as welded or stress relieved condition on carbon and low alloy steels Unionmelt 439 Flux - Unionmelt 439 flux has similar performance to 429 flux but will give higher toughness properties Unionmelt 656 Flux - Unionmelt 656 operates similar to 439 flux, but has less tolerance for rust. It should be used on clean material. It will produce excellent low temperature toughness, better than 439 flux ALLOY SHIELD COMPOSITE ELECTRODES FOR SUBMERGED ARC WELDING OF THE LOW ALLOY STEELS Carbon ESAB produces a line of composite electrodes for welding several varieties of the low alloy steels. These electrodes carry the brand name Alloy Shield and are used with a neutral flux since the alloying elements are in the electrode core Alloy Shield electrodes are available in 3/32" - 5/32" diameters. Each size is available on 60 lb. coils and for maximum productivity, 500 lb. pay-off packs Alloy Shield B1S (No AWS Class) - Alloy Shield B1S is an electrode for welding the 1/2% Chrome - 1/2% Molybdenum steels. These steels are used principally in power piping, boiler work and other moderately high temperature applications. Recommended flux is Unionmelt Flux 80. If other fluxes are used, the weld deposit analysis may vary. Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

162 A. Typical Chemical Analysis of the Weld Metal LESSON VI Arc for for Low Carbon 0.05% Phosphorus 0.018% Manganese 1.03% Chromium 0.50% Silicon 0.39% Molybdenum 0.53% Sulfur 0.025% B. Typical Mechanical Properties of the Weld Metal Stress Relieved 1 F Yield Point, psi 70,000 Tensile Strength, psi 83,000 % Elongation (2") 24 Charpy V-Notch Impacts 30 F 20 F Carbon Alloy Shield B2S (AWS A5.23 F8PZ-ECB2-B2) - Alloy Shield B2S is an electrode for welding the 1% chromium - 1/2% molybdenum and the 1-1/4% chromium - 1/2% molybdenum steels for high temperature applications such as power piping, boiler work and tubes, plate forgings and castings covering a wide variety of ASTM steels. Recommended flux is Unionmelt Flux 80. If other fluxes are used, weld deposit analysis may vary. A. Typical Chemical Analysis of the Weld Metal Carbon 0.04% Phosphorus 0.017% Manganese 0.96% Chromium 1.25% Silicon 0.37% Molybdenum 0.55% Sulfur 0.024% B. Typical Mechanical Properties of the Weld Metal Stress Relieved 1 F Yield Point, psi 75,000 Tensile Strength, psi 90,000 % Elongation (2") 22 Charpy V-Notch Impacts 22 F 16 F Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

163 Arc for for Low LESSON VI Alloy Shield B3S (AWS A5.23 F9PZ-ECB3-B3) - Alloy Shield B3S is an electrode for welding 1% chromium - 1% molybdenum and the 2-1/4% chromium - 1% molybdenum steels. Used for welding in high strength, high temperature applications, such as power piping, boiler, and turbine work. Recommended flux is Unionmelt Flux 80. If other fluxes are used, weld deposit analysis may vary. A. Typical Chemical Analysis of the Weld Metal Carbon 0.10% Phosphorus 0.014% Manganese 1.03% Chromium 2.28% Silicon 0.50% Molybdenum 1.08% Sulfur 0.023% B. Typical Mechanical Properties of the Weld Metal Stress Relieved 1 F Yield Point, psi 88,000 Tensile Strength, psi 101,000 % Elongation (2") 20 Charpy V-Notch Impacts 30 F 20 F Carbon Reliability of Alloy Shield Ni1S (AWS Class A5.23 F7A6-ECNi1-Ni1) - Alloy Shield Ni1S is an electrode for nominal 1% Ni weld metal where notch toughness is required in the weld deposit. Recommended flux is Unionmelt Flux 651VF. If other fluxes are used, weld deposit analysis may vary. A. Typical Chemical Analysis of the Weld Metal Carbon 0.06% Sulfur 0.019% Manganese 1.18% Phosphorus 0.024% Silicon 0.34% Nickel 0.86% B. Typical Mechanical Properties of the Weld Metal As Welded Yield Point, psi 68,000 Tensile Strength, psi 80,000 % Elongation (2") 30 Charpy V-Notch Impacts 90 F 60 F 57 F COPYRIGHT 2000 THE ESAB GROUP, INC.

164 Arc for for Low LESSON VI Alloy Shield Ni2S (AWS 5.23 F8A6, F8P10-ECNi2-Ni2) - Alloy Shield Ni2S is a nickel alloy electrode for applications where good impact properties are necessary at temperatures as low as -100 F. The weld deposit contains 2-1/2% nickel. Recommended flux is Unionmelt Flux 651VF. If other fluxes are used, weld metal analysis may vary. A. Typical Chemical Analysis of the Weld Metal Carbon 0.07% Sulfur 0.021% Manganese 0.96% Phosphorus 0.025% Silicon 0.28% Nickel 2.65% B. Typical Mechanical Properties of the Weld Metal As Welded Yield Point, psi 68,000 74,000 Tensile Strength, psi 80,000 83,500 % Elongation (2") Charpy V-Notch Impacts F F F F 35 F 50 F Carbon Alloy Shield M2S (AWS A5.23 F11A6-ECM2-M2) - Alloy Shield M2S is an electrode for welding the T-1 and other similar high strength steels. Despite its high strength, the weld metal has good impact properties. Recommended flux is Unionmelt Flux 651VF. If other fluxes are used, the weld metal analysis may vary. A. Typical Chemical Analysis of the Weld Metal Carbon 0.06% Phosphorus 0.016% Manganese 1.6% Nickel 1.83% Silicon 0.64% Molybdenum 0.49% Sulfur 0.014% B. Typical Mechanical Properties of the Weld Metal As Welded Yield Point, psi 103,000 Tensile Strength, psi 115,000 % Elongation (2") 23 Charpy V-Notch Impacts 62 0 F 27 F Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

165 Arc for for Low LESSON VI Alloy Shield M3S (AWS A5.23 F11A4-ECM3-M3) - Alloy Shield M3S is an electrode for welding T-1 and other similar high strength steels requiring tensile strengths of 110,000 to 120,000 psi. It produces good low temperature impacts and is approved by the American Bureau of Shipping. Recommended flux is Unionmelt Flux 651VF. If other fluxes are used, the weld metal analysis may vary. A. Typical Chemical Analysis of the Weld Metal Carbon 0.06% Phosphorus 0.020% Manganese 1.10% Chromium 0.40% Silicon 0.39% Nickel 2.63% Sulfur 0.017% Molybdenum 0.61% B. Typical Mechanical Properties of the Weld Metal As Welded Yield Point, psi 104,000 Tensile Strength, psi 116,000 % Elongation (2") 22 Charpy V-Notch Impacts 44 F 37 F Carbon Reliability of Alloy Shield WS (AWS Class A5.23 F7A2-ECW-W) - Alloy Shield WS is for welding weathering grade steels. Weld deposit will color match to the weathering steel after exposure to the atmosphere. Recommended flux is Unionmelt Flux 651VF. If other fluxes are used, the weld metal analysis may vary. A. Typical Chemical Analysis of the Weld Metal Carbon 0.06% Phosphorus 0.017% Manganese 0.76% Chromium 0.54% Silicon 0.31% Nickel 0.68% Sulfur 0.013% Copper 0.49% B. Typical Mechanical Properties of the Weld Metal As Welded Yield Point, psi 65,000 Tensile Strength, psi 77,000 % Elongation (2") 28 Charpy V-Notch Impacts F 32 F COPYRIGHT 2000 THE ESAB GROUP, INC.

166 Arc for for Low LESSON VI Alloy Shield F2S (AWS A5.23 F10P2-ECF2-F2) - Alloy Shield F2S wire developed for welding SAE 4130 and similar hardenable steels. Retains excellent properties after stress relieving or quench and tempering. Good choice for oil field equipment requiring less than 1% nickel. Recommended flux is Unionmelt Flux If other fluxes are used, the weld metal analysis may vary. A. Typical Chemical Analysis of the Weld Metal Carbon 0.11% Phosphorus 0.016% Manganese 1.63% Nickel 0.69% Silicon 0.52% Molybdenum 0.55% Sulfur 0.012% B. Typical Mechanical Properties of the Weld Metal Stress-Relieved 12 F. Yield Point, psi 89,000 Tensile Strength, psi 101,000 % Elongation (2") 24 Charpy V-Notch Impacts F 35 F Carbon Alloy Shield 420SB (No AWS Class) - Alloy Shield 420SB was specially developed to match the analysis for continuous caster roll found in the steel making industry. Recommended flux is Unionmelt Flux S-420SB. If other fluxes are used, the weld metal analysis may vary. A. Typical Chemical Analysis of the Weld Metal Carbon 0.28% Sulfur 0.010% Manganese 1.20% Phosphorus 0.006% Silicon 0.20% Chromium 11.70% B. Hardness of Deposited Weld Metal 1 Layer on 1045 Steel - 54 Rockwell C 2 Layers on 1045 Steel - 51 Rockwell C Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

167 Arc APPENDIX A LESSON VI - GLOSSARY OF TERMS LESSON VI for for Low Carbon Composite Electrode Work Harden Anneal Deoxidizers Flux Bonded Fluxes - A filler metal electrode used in arc welding, consisting of more than one metal component combined mechanically. It may or may not include materials which protect the molten metal from the atmosphere, improve the properties of the weld metal or stabilize the arc. - The development of hardness in metals as a result of cold working such as forming, bending, or drawing. - The process of heating a metal to a temperature below the critical range, followed by a relatively slow cooling cycle to induce softness and remove stresses. - Elements, such as manganese, silicon, aluminum, titanium, and zirconium, used in welding electrodes and wires to prevent oxygen from forming harmful oxides and porosity in weld metal. - Material used to prevent, dissolve, or facilitate removal of oxides and other undesirable substances in welding, soldering, or brazing. In submerged arc welding, the flux shields the molten puddle from the atmosphere which helps to influence the mechanical weld metal deposit. - Bonded fluxes are manufactured by binding an assortment of powder together and then baking at a low temperature. The major advantage is that additional alloying ingredients can be added to the mixture. Fused Fluxes - Fused fluxes are melted ingredients which have been chilled and ground to a particular particle size. The advantage of this type flux is the low moisture pick-up and improved recycling capabilities. Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

168 LESSON VI Arc for Active Fluxes Neutral Fluxes - Active fluxes produce changes in weld metal chemistry when welding is changed. Active fluxes are restricted to single or minimal multipass welding. - Neutral fluxes produce little change to mechanical properties when adjusting the voltage. Best utilized when welding on plate thickness of one inch or more. for Low Carbon Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

169 Arc for for Low BASIC WELDING FILLER METAL TECHNOLOGY A Correspondence Course Carbon LESSON VII FLUX CORED ARC WELDING ELECTRODES FOR CARBON & LOW ALLOY STEELS ESAB ESAB & Cutting Products Reliability of COPYRIGHT 2000 ESAB WELDING & CUTTING PRODUCTS

170 Arc TABLE OF CONTENTS LESSON VII FLUX CORED ARC WELDING ELECTRODES FOR CARBON & LOW ALLOY STEELS LESSON VII Section Nr. Section Title Page for for Low Carbon Part I - for Carbon and INTRODUCTION MANUFACTURING FLUX CORED ELECTRODES FEATURES OF FLUX CORED ELECTRODES Functions of the Flux Ingredients Slag Systems GAS SHIELDED TYPES Joint Design Shielding Gas Electrode Extension All-Position Mild Steel Low Alloy SELF-SHIELDED ELECTRODES Electrode Extension All-Position High Deposition Types AWS SPECIFICATION A Tensile Strength and Elongation Usability and Performance Chemical Composition Requirements INDIVIDUAL ELECTRODE CHARACTERISTICS EXXT-1 & EXXT-1M EXXT Reliability of

171 Arc TABLE OF CONTENTS LESSON VII - Con't. LESSON VII Section Nr. Section Title Page for for Low EXXT EXXT EXXT EXXT EXXT EXXT EXXT-9 & EXXT-9M EXXT EXXT EXXT-12 & EXXT-12M EXXT-G EXXT-GS Carbon Part II - Individual Dual Shield Flux Cored Wires For Carbon Steels ELECTRODE SELECTION AWS E70T-1 ELECTRODES DUAL SHIELD ARC DUAL SHIELD 111A-C DUAL SHIELD 111HD DUAL SHIELD R-70 ULTRA COREWELD METAL CORED WIRES COREWELD COREWELD ULTRA AWS E70T-2 ELECTRODES DUAL SHIELD DUAL SHIELD SP Reliability of

172 Arc for for Low Carbon Reliability of TABLE OF CONTENTS LESSON VII - Con't. LESSON VII Section Nr. Section Title Page 7.12 AWS E70T-5 ELECTRODES DUAL SHIELD T-5 & T ALL-POSITION ELECTRODES DUAL SHIELD DUAL SHIELD 7100 ULTRA DUAL SHIELD FC DUAL SHIELD II 70 ULTRA & DUAL SHIELD II 71 ULTRA CORESHIELD SELF-SHIELDED FLUX CORED WIRES AWS E70T-4 ELECTRODES CORESHIELD AWS E70T-7 ELECTRODES CORESHIELD AWS E70T-10 ELECTRODES CORESHIELD AWS E70T-11 ELECTRODES CORESHIELD AWS E71T-GS ELECTRODES CORESHIELD AWS SPECIFICATION A AWS DESIGNATIONS USABILITY AND PERFORMANCE MECHANICAL PROPERTIES REQUIREMENTS WELD METAL CHEMICAL COMPOSITION REQUIREMENTS Carbon-Molybdenum Chromium-Molybdenum Nickel Steel... 28

173 Arc for for Low TABLE OF CONTENTS LESSON VII - Con't. LESSON VII Section Nr. Section Title Page Manganese-Molybdenum All Other Low Alloy Steel IMPACT PROPERTIES SELECTING THE PROPER LOW ALLOY ELECTRODE Dissimilar Steels Procedures ADVANCED DEVELOPMENTS IN FLUX CORED ELECTRODES DUAL SHIELD SELECTOR GUIDE APPENDIX A - GLOSSARY OF TERMS Carbon Reliability of

174 Arc for for Low Carbon Reliability of FLUX CORED ARC WELDING ELECTRODES FOR CARBON AND LOW ALLOY STEELS 7.1 INTRODUCTION Gas shielded flux cored electrodes for welding carbon steels were developed in the early 1950 s and were made commercially available in This process was developed to combine the best features of submerged arc welding and CO 2 welding. The combination of the fluxing ingredients in the core and the external CO 2 gas shield produce high quality welds and a stable arc with a low spatter level. Initially, these electrodes were available only in the larger diameters (5/64"-5/32") and were for use in the flat or horizontal positions on heavy weldments. In 1972, small diameter gas shielded flux cored electrodes for welding in all positions were developed, and this greatly expanded the flux cored arc welding field Self shielded flux cored electrodes were made available shortly after the gas shielded types were introduced and both have gained industry wide acceptance for specific applications. The major differences of the two types were covered in Lesson II and should be reviewed at this time. 7.2 MANUFACTURING FLUX CORED ELECTRODES Manufacturing flux cored electrodes requires close controls. Since the weld metal is a combination of the metal sheath and the flux ingredients, both must be closely checked for size and chemical composition before fabrication begins Since the space within the wire is limited, particle size of the ingredients becomes very important, so that the particles will nest together. Flux ingredients must be totally mixed or blended and measures taken to prevent segregation of the elements before fabrication Most flux cored electrodes are manufactured from a flat metal strip that is passed through a mill where forming rolls progressively shape it into a U-shaped section. A metered amount of granular flux is fed into the formed strip. It then passes through the closing rolls, forming the strip into a tube and tightly compressing the core material. See Figure The tube is then pulled through a series of drawing dies that reduce it to its final size, and further compress the flux to lock it in place within the tube. LESSON VII

175 LESSON VII Arc FLUX HOPPER STRIP STEEL for for Low TO DRAWING OPERATION FLUX FILL CLOSING ROLLS FLUX CORED ELECTRODE FORMING OPERATION FIGURE 1 "U" FORMING ROLLS During manufacture, close control to assure that flux voids do not occur throughout the entire length of the wire is necessary. Also, the surface of the wire must be smooth and free of contaminants that may be detrimental to feeding and welding current transfer to the wire. The wire must be carefully wound on spools, coils, or into drums, so that kinks or bends do not occur. Spools and coils are usually packaged in plastic with some sort of desiccant material to absorb moisture within the package, and are then placed in a cardboard carton for protection. Carbon Flux cored electrodes are manufactured in several different configurations. The most common are shown in Figure 2. The butt type is used for electrodes where a relatively heavy steel strip is used, and the core ingredients can be lower in volume. Most of the carbon steel and low alloy steel electrodes of 7/64" diameter and smaller are of this configuration. Some of the larger diameters and electrodes for the high alloys, such as stainless steel where it is necessary to include more alloying elements in the core, are of the lap or heart-shaped configuration. BUTT LAP HEART SHAPED Reliability of FLUX CORED ELECTRODE CONFIGURATIONS FIGURE 2

176 7.3 FEATURES OF FLUX CORED ELECTRODES LESSON VII Arc for for Low Flux cored electrodes combine the advantages of several of the welding processes we have discussed earlier. As with coated electrodes, the flux improves the weld metal chemical composition and mechanical properties. As in gas metal arc welding and submerged arc welding, productivity is increased because the electrode is continuous Flux cored electrodes may be used for welding carbon steels, low alloy high strength steels, and the high strength quenched and tempered steels. They are also used for welding stainless steels and abrasion resistant steels. These will be covered in subsequent lessons Functions of the Flux Ingredients - As with coated ingredients, each manufacturer has his own formulas for the flux ingredients. The composition of the flux core can be varied to provide electrodes for specific applications. Carbon The basic functions of the flux ingredients are: a) Deoxidizers and Denitrifiers - Since nitrogen and oxygen can cause porosity or brittleness, deoxidizers such as manganese and silicon are added. In the case of self-shielded electrodes, denitrifiers such as aluminum are added. Both help to purify the weld metal. b) Slag Formers - Slag formers such as oxides of calcium, potassium, silicon or sodium are added to protect the molten weld puddle from the atmosphere. The slag aids in improving the weld bead shape and fast freezing slags help hold the weld puddle for out-of-position welding. The slag also retards the cooling rate, especially important when welding the low alloy steels. c) Arc Stabilizers - Elements, such as potassium and sodium, help produce a smooth arc and reduce spatter. d) Alloying Elements - Alloying elements, such as molybdenum, chromium, carbon, manganese, nickel, and vanadium, are used to increase strength, ductility, hardness and toughness. e) Gasifiers - Minerals, such as fluorspar and limestone, are usually used to form a shielding gas in the self-shielded type wires. Reliability of

177 7.3.2 Slag Systems - The ingredients in the core determine the weldability of the LESSON VII Arc electrode and the mechanical properties of the weld metal. that have a preponderance of flux components of an acidic nature produce an acid type slag. Those electrodes that are composed of larger amounts of components of a basic nature are said to produce a basic type slag. produced with an acid slag system have excellent weldability. This means that the arc is smooth and spray-like with very little spatter, and for these electrodes have high operator appeal. The mechanical properties are good and meet or exceed AWS specifications having a basic slag system produce weld metal with excellent ductility and notch toughness. The weldability is not as good as that of the acid slag types. Metal for Low transfer is more globular, resulting in a bit more spatter. Figure 3 shows the characteristics of the two slag systems Some low alloy electrodes are now being produced utilizing a recent development in slag systems, that combines the excellent weldability of the acid slag types with the excellent mechanical properties of the basic slag types. SLAG MECHANICAL SYSTEMS WELDABILITY PROPERTIES Acid Excellent Good Basic Fair Excellent Rutile Basic Excellent Excellent Carbon 7.4 GAS SHIELDED TYPES SLAG SYSTEM CHARACTERISTICS FIGURE 3 Reliability of Gas shielded flux cored electrodes are available in diameters of.035" to 1/8" and utilize reverse polarity (electrode positive) welding current, resulting in high deposition rates, deep penetration, and a relatively smooth arc. High deposition rates mean that the weld metal can be deposited more quickly, saving labor and overhead costs, the largest part of the total welding cost Joint Design - Another factor that influences the cost of deposited weld metal is the joint design. Figure 4 shows the single-vee joints suggested by the American Society for producing sound welds with the least amount of weld metal for the SMAW and

178 LESSON VII Arc lbs./ft lbs./ft lbs./ft. 1" 1" 1" for for Low Carbon 1/4" 3/8" 3/16" SHIELDED SELF SHIELDED GAS SHIELDED METAL ARC FLUX CORED FLUX CORED FLUX CORED ARC WELDING VERSUS SHIELDED METAL ARC WELDING WEIGHT OF WELD METAL PER FOOT OF JOINT FIGURE 4 the FCAW processes. SMAW requires a larger included angle and a considerable root opening on vee joints, so that the larger diameter of the coated electrode can reach down into the joint to assure a good root pass. Because of the smaller diameter of the flux cored electrodes, the included angle may be smaller, and in the case of the CO 2 gas shielded types that have very deep penetration, the required root opening may be very small or in some cases eliminated. Figure 4 shows the calculated weight of the weld metal per foot of weld for each joint. The self-shielded flux cored joint requires.337 lbs (13%) less weld metal than the shielded metal arc joint. The gas shielded flux cored joint requires.970 lbs (36%) less than the shielded metal arc joint Comparable savings in the quantity of filler metal can be achieved in fillet welds made with the gas shielded flux cored process. Conventionally, fillet welds are specified and measured by the leg length of the largest triangle that can be inscribed in the cross-section of the weld. The load carrying dimension, the one that determines the strength of the weld, is the throat dimension. Figure 5A shows a sketch of a typical fillet weld made with E7018 electrodes. The 1/2" leg weld that results in a throat dimension of 0.35", has a cross-sectional area of square inches. This weld requires pounds.35 THROAT.35 THROAT A E7018 1/2 LEG B GAS SHIELDED FLUX CORED 3/8 LEG Reliability of FILLET WELD SIZE COMPARISON - SMAW vs. GAS SHIELDED FCAW FIGURE 5 COPYRIGHT 2000 THE ESAB GROUP

179 Arc for of filler metal per foot of weld. Figure 5B shows a sketch of a typical fillet weld made with the flux cored CO 2 shielded process. The leg length of this weld measures only 3/8". The deep penetration of the process results in a throat dimension equal to that in Figure 5A, 0.35". The cross-sectional area of this fillet weld is square inches and requires pounds of weld metal per foot of weld. This results in a savings of pounds per foot of weld, or a savings of 44% in weld metal volume. It should be remembered that not only is the cost of the weld metal saved, but also the cost of the labor and overhead that would be WELD METAL FILLET SIZE CU. IN/IN % INCREASE LESSON VII for Low 1/ / / / % 43% 78.5% COST OF OVERWELDING FIGURE 6 Carbon spent in depositing the extra metal. The chart in Figure 6 shows the increase in volume of weld metal required as the fillet size increases. It shows that if a 5/16" fillet weld is made where a 1/4" fillet would suffice, more than half (58%) of the amount of weld metal is wasted Shielding Gas - Gas shielded flux cored electrodes require that an adequate Reliability of gas shield be present at all times. Gusty or high velocity winds cannot be tolerated and in such instances, it may be necessary to place a curtain or other wind screen around the operator. Light breezes will not affect the gas shield. Inadequate gas shielding will be evidenced by porosity on the surface of the weld metal CO 2 is the most common shielding gas used; however, Argon-CO 2 mixtures may be recommended for some types. The gas shield effectively protects the arc from atmospheric oxygen and nitrogen but some oxygen will be present from the dissociation of the shielding gas. The deoxidizers in the core materials allow the electrodes to tolerate these small amounts of oxygen. The need to denitrify the weld metal is of less importance be-

180 Arc for for Low LESSON VII cause the shielding gas keeps atmospheric nitrogen from the weld zone. The manufacturer s shielding gas recommendation should be followed. Shielding gas flow rates of 30 to 45 cubic feet per hour are used depending on the electrode size, electrode extension, and other welding conditions Electrode Extension - Electrode extension is the length of an electrode protruding beyond the end of the contact tip during welding. This dimension is commonly referred to as electrical stickout and is relatively short when using gas shielded flux cored electrodes (3/4" to 1-1/2"). This short electrical stickout with a relatively high welding current produces narrow, deep penetrating welds All-Position - Gas shielded, all-position flux cored electrodes contain ingredients in the core that produce a fast freezing slag, and the proper puddle fluidity for vertical, overhead, or other out-of-position welding. They are available in.045",.052", and 1/16" diameters. Since the slag helps hold the puddle, the welding voltage and current may be relatively high, resulting in high deposition rates. The deep penetration of these electrodes limits the minimum material thickness to 1/8" in the vertical position, and 3/16" in the flat or horizontal position Mild Steel - Gas shielded mild steel electrodes are available for Carbon Reliability of general purpose welding, welding through rust and mill scale of varying degrees, out-of-position welding, and for applications when high mechanical properties or high impact values are necessary. designed for high deposition rates and high deposition efficiency are also available. Most of the mild steel electrodes utilize CO 2 as the shielding gas; however, some may use Argon/CO 2 mixtures Low Alloy - Gas shielded flux cored electrodes are widely used for welding the low alloy, high strength steels. They are available for welding the carbon-molybdenum, chromium-molybdenum, nickel, manganese-molybdenum and the high strength quenched and tempered steels. The combination of an external gas shield and the fluxing elements in the core produce high purity weld metal. 7.5 SELF-SHIELDED ELECTRODES Self-shielded electrodes rely solely on the materials in the core of the wire for shielding the arc from the atmosphere, purifying the weld metal and providing the slag formers necessary to protect the molten weld puddle. These electrodes do not rely on gas shielding as the gas shielded types do; therefore, they can operate more effectively in outdoor environments without a windscreen.

181 Arc for for Low Carbon LESSON VII Self-shielded electrodes are extensively used in mild steel welding applications. A few electrodes are available containing 1% nickel for improved strength and impact properties Being a continuous welding process, self-shielded electrodes are capable of higher deposition rates than coated electrodes, and are designed for specific applications such as general purpose welding, assembly and repair welding, out-of-position welding, and high deposition welding. Some electrodes are specifically designed for welding lighter gauge materials (.047" to 3/16" thickness) at high speeds. Self-shielded electrodes are available in diameters ranging from.030" to 5/32" Electrode Extension - Self-shielded flux cored electrodes utilize a longer electrode extension than the gas shielded types. The electrode extension ranges from 1/2" to 3-3/4" depending on the electrode type, and the application. The longer length of wire beyond the contact tip decreases the arc voltage, since the additional wire acts as a resistance. It causes the wire to heat and is accompanied by a lower welding current (amperage). This lower voltage and amperage results in a narrow, shallow weld bead that does not melt as much of the base metal, allowing the process to be used on welding thinner material and for poor fit-up applications. If the welding current and voltage are increased, the deposition rate will increase, and to a lesser degree, so will the penetration. It is important that the manufacturer s recommendations for each type and size of electrode are followed All-Position - The self-shielded all-position electrodes utilize direct current, straight polarity (electrode negative). Penetration is low, making them suitable for bridging gaps in poor fit-up applications. Optimum welding current and amperage settings are lower than those with the gas shielded types. The.068" and 5/64" diameters are most commonly used for out-of-position work, although the 3/32" may be used in some cases. Electrical stickout between 1/2" to 1" is recommended for these wires High Deposition Types - The high deposition types of self-shielded wires utilize long electrical stickout (1-1/2" to 3-3/4") and most use reverse polarity (electrode positive). Designed for use in the flat or horizontal positions only, they are commonly available in the 5/64", 3/32", 7/64", and.120" diameters. Reliability of

182 7.6 AWS SPECIFICATION A LESSON VII Arc for for Low This American Society (AWS) Specification is entitled Specification For Carbon Steel For. It prescribes the requirements for classifying flux cored electrodes for welding carbon steels or low alloy steels The following requirements will be covered in this text: 1. Whether gas shielded or self-shielded 2. Single pass or multiple pass 3. Type of welding current 4. position 5. As-welded mechanical properties of the weld metal 6. Chemical composition of the weld metal The letter-number designations in this specification are shown in Figure 7. Electrode Min. Tensile Strength X 10,000 psi 0: Flat and Horizontal 1: All Position EX X T - X Usability, Performance & Impacts Tubular or Flux Cored Carbon CARBON STEEL FLUX CORED ELECTRODE DESIGNATIONS FIGURE As an example, the designation E71T-1 indicates an electrode (E) that will produce weld metal of a minimum 72,000 psi ultimate tensile strength (7), may be used for welding in all positions (1), is a flux cored electrode (T), is a multipass gas shielded type for operation on direct current, reverse polarity (electrode positive), and must have a minimum Charpy V-notch value of 20 ft.-lbs at 0 F (Figure 9) Tensile Strength and Elongation - The specification has only two tensile strength classifications. They are shown in Figure 8. Reliability of

183 Arc for for Low Carbon TENSILE YIELD* ELONGATION* AWS STRENGTH STRENGTH PERCENT IN CLASSIFICATION psi. psi. 2 INCHES E6XT-X 62,000 50, E7XT-X 72,000 60, * E6XT-GS, E7XT-2, E7XT-3, E7XT-10 and E7XT-GS have no yield strength or elongation requirements. WELD METAL MECHANICAL PROPERTIES OF CARBON STEEL FLUX CORED ELECTRODES FIGURE Usability and Performance - The number of passes, shielding gas requirements, type of welding current and the impact requirements, are all specified by the last digit or letter in the electrode designation. The significance of the last digit or letter is shown in Figure 9. AWS Classification Shielding Gas Current and Polarity V-notch impact LESSON VII EXXT-1 Multiple Pass CO 2 DCEP 20 F* EXXT-1M Multiple Pass 75-80%Ar/bal CO 2 DCEP 20 F* EXXT-2 Single Pass CO 2 DCEP Not Specified EXXT-2M Single Pass 75-80%Ar/bal CO 2 DCEP Not Specified EXXT-3 Single Pass None DCEP Not Specified EXXT-4 Multiple Pass None DCEP Not Specified EXXT-5 Multiple Pass CO 2 DCEP or DCEN 20 F* EXXT-5M Multiple Pass 75-80%Ar/bal CO 2 DCEP or DCEN 20 F* EXXT-6 Multiple Pass None DCEP 20 F* EXXT-7 Multiple Pass None DCEN Not Specified EXXT-8 Multiple Pass None DCEN Not Specified EXXT-9 Multiple Pass CO 2 DCEP 20 F* EXXT-9M Multiple Pass 75-80%Ar/bal CO 2 DCEP 20 F* EXXT-10 Single Pass None DCEN Not Specified EXXT-11 Multiple Pass None DCEN Not Specified EXXT-12 Multiple Pass CO 2 DCEP 20 F* EXXT-12M Multiple Pass 75-80%Ar/bal CO 2 DCEP 20 F* EXXT-G Multiple Pass Not Specified Not Specified Not Specified EXXT-GS Single Pass Not Specified Not Specified Not Specified * "J" Designation indicates V-notch impact values of 20 F USABILITY, PERFORMANCE AND IMPACT VALUES FLUX CORED ELECTRODE DESIGNATIONS FIGURE Chemical Composition Requirements - The chemical requirements of the weld metal are specified only for the multipass electrodes, since the single pass types would show high dilution from the base metal and would be meaningless. Weld metal chemical composition requirements for the multipass types are: Reliability of.

184 Arc LESSON VII Maximum Percent by Weight (as determined) E7XT-1; E7XT-1M E7XT-4; E7XT-6 E7XT-5; E7XT-5M E7XT-7; E7XT-8 Element E7XT-9; E7XT-9M E7XT-11 E7XT-12; E7XT-12M for for Low Carbon Carbon 0.18 Reported 0.15 Manganese Silicon Sulfur Phosphorus Chromium 0.20* 0.20* 0.20* Nickel 0.50* 0.50* 0.50* Molybdenum 0.30* 0.30* 0.30* Vanadium 0.08* 0.08* 0.08* Aluminum Copper * The amounts of these elements shall be reported only if intentionally added. Single pass types EXXT-2, EXXT-3, EXXT-10 and EXXT-GS have no chemical requirements. 7.7 INDIVIDUAL ELECTRODE CHARACTERISTICS The electrodes in this specification may be grouped by their suffix i.e., T-1, T-2, T-3, etc., as having similar flux components that give them similar usability characteristics and are briefly described here EXXT-1 & EXXT-1M - of the T-1 classification are gas shielded types, Reliability of and the properties required in this specification are listed using CO 2 as the shielding gas. Argon-CO 2 gas mixtures may be used for the electrodes specified for all-position welding. These are usually the smaller wires of.045",.052", and 1/16" diameter. Using an Argon-CO 2 gas mixture will diminish the amount of oxygen present and cause the weld metal to have a higher manganese and silicon content. This will increase the tensile strength and may improve the impact properties. The manufacturer s recommendation for the type of shielding gas should be followed. Those electrodes specified for flat and horizontal fillet welding usually use a CO 2 gas shield and will range from 1/16" to 1/8" in diameter.

185 Arc for for Low Carbon Reliability of These electrodes may be used for single or multiple pass welding. The electrodes in this group have a rutile (acid) slag that is characterized by a spray-like transfer, little spatter and good weld bead contour that is flat to slightly convex EXXT-2 - These electrodes are classified as single pass electrodes because they contain higher amounts of deoxidizers (manganese and silicon) for welding through rust or mill scale. Since the rust or mill scale is iron oxide (FeO), the manganese and silicon will combine with the oxygen in the FeO and float to the slag surface as harmless manganese oxide or silicon dioxide. If no rust or mill scale is present, or if multiple passes are made over the preceding passes, the manganese and silicon will become alloying elements in the weld metal. This can change the mechanical properties drastically, and possibly cause cracking. These electrodes are for welding in the flat and horizontal positions, and the arc characteristics and deposition rates are similar to those of the T-1 types. Running one pass on each side of butt welds can be considered a single pass. There are no chemical composition requirements for the weld metal produced by these electrodes since it would be severely diluted with the base metal on single pass welds. They are, however, required to meet the minimum tensile strength specified in a transverse tensile test as specified in AWS A These electrodes can be used for welding plate with heavy rust and mill scale, and still produce X-ray quality welds EXXT-3 - These electrodes require no external shielding gas and are for making high speed, automatic single pass welds on thin material up to 3/16" thickness. current is DC electrode positive (+). They are for use in the flat and horizontal positions, and up to 20 downhill welding. These electrodes are limited to 3/16" metal thickness and single pass welding; otherwise, the welds may become hard and crack sensitive. They have a spray-like metal transfer EXXT-4 - These are self-shielded electrodes designed for high deposition rates, and they operate on DC electrode positive (+). The metal transfer is globular and the slag system desulfurizes the weld metal, making it resistant to cracking. Penetration is low, allowing the weld metal to bridge gaps caused by poor fit-up. These electrodes are for single or multipass welding in the flat and horizontal positions EXXT-5 - These are gas shielded electrodes for flat and horizontal fillet welds. They have a basic slag system that provides excellent impact properties when compared to the T-1 and T-2 acid slag types. Spatter level is slightly higher than the T-1 and T-2 electrodes. Argon-CO 2 gas mixtures are recommended by some manufacturers for the 1/16" diameter sizes, for a spray-like metal transfer and high deposition rates. CO 2 shielding gas is usually recommended for 5/64" diameters and up, and the metal transfer is more globular. They may be used for single and multipass welds. LESSON VII

186 Arc for for Low Carbon LESSON VII EXXT-6 - These self-shielded electrodes operate on direct current, electrode positive (+). Penetration is relatively good, and the metal transfer is spray-like. Deposition rate is high, and the weld metal has good low temperature impact properties. They are used for single and multiple pass welds in the flat and horizontal positions EXXT-7 - These are self-shielded electrodes for welding with direct current, electrode negative (-). The smaller diameters may be used for all-position welding. The larger diameters, 3/32" and up, produce high deposition rates in the flat and horizontal positions. The weld metal is relatively crack resistant. These electrodes may be used for single and multiple pass welding EXXT-8 - These are self-shielded electrodes for welding with direct current, electrode negative (-). They are intended for all-position welding where good impact properties are necessary. The slag system is such that it desulfurizes the weld metal that helps to resist cracking. They may be used for single or multiple pass welds EXXT-9 & EXXT-9M - in the T-9 classification are gas shielded types, and the properties required in this specification are listed using CO 2 as the shielding gas for EXXT-9 and argon-co 2 gas mixtures for EXXT-9M electrodes. The arc transfer, welding characteristics, deposition rates and welding parameters will be similar to those electrodes classified under EXXT-1 and EXXT-1M. classified as EXXT-9 and EXXT-9M are essentially EXXT-1 and EXXT-1M electrodes that deposit weld metal with improved impact properties, meeting 20 ft.-lbs at -20 F EXXT-10 - of this classification are self-shielded and operate on direct current, electrode negative (-). They are single pass electrodes for welding at high travel speeds in the flat, horizontal, and downhill (up to 20 ) position EXXT-11 - These electrodes are self-shielded and operate on direct current, electrode negative (-). They are general purpose electrodes for single and multiple pass welding in all-positions. The arc is relatively smooth and spray-like EXXT-12 & EXXT-12M - These electrodes are essentially EXXT-1 and EXXT-1M electrodes that have been modified to meet lower manganese requirements of the A-1 Analysis Group in the ASME Boiler & Pressure Vessel Code, Section IX. Therefore, EXXT- 12 and EXXT-12M electrodes will have a decrease in tensile strength and hardness, and impact properties meeting 20 ft.-lbs at -20 F. The arc transfer, welding characteristics, deposition rates, and welding parameters will be similar to EXXT-1 and EXXT-1M electrodes. Reliability of

187 Arc for LESSON VII EXXT-G - This classification is for new multipass electrodes that do not fit into any of the above categories. They may or may not require a gas shield, and their properties may be any combination of those covered by these specifications EXXT-GS - This classification is for new single pass electrodes that do not fit into any of the above categories. They may or may not require a gas shield, and their properties may be any combination of those covered by this specification. for Low Carbon Reliability of

188 Arc for for Low Carbon INDIVIDUAL DUAL SHIELD FLUX CORED WIRES FOR WELDING CARBON STEELS 7.8 ELECTRODE SELECTION ESAB has a wide variety of flux cored electrodes for welding the mild or medium carbon steels. For example, there are six electrodes that meet the E70T-1 AWS classification. Slight formula variations may make one of them more suitable for particular applications than another. Features such as tensile strength, impact properties, deposition rate, bead shape and arc characteristics can vary within this group. Another factor in electrode selection is whether or not the electrode meets the required code or specification for the particular job The following is a brief description of each of ESAB s E70T-1 electrodes currently available. Only the distinguishing points of each type are covered here to help in selecting the proper electrode. See the Dual Shield catalog for more complete details and code or specification approvals. 7.9 AWS E70T-1 ELECTRODES These electrodes are all multiple pass, CO 2 shielded types for DC electrode positive operation. They are for use in the flat and horizontal positions only DUAL SHIELD ARC 70 - The very smooth metal transfer produces minimum spatter and has a very good bead appearance. Slag is easily removed. The plate material should be reasonably clean. A. Typical Weld Metal Properties and Chemical Composition Yield Point 76,700 psi Tensile Strength 90,200 psi Elongation in 2" 26% Charpy V-notch Impact 30 F Carbon 0.07% Manganese 1.36% Silicon 0.65% LESSON VII Reliability of

189 Arc for for Low Carbon LESSON VII DUAL SHIELD 111A-C - is one of the most widely used E70T-1 types. The plate should be reasonably clean, although the relatively high level of deoxidizers will tolerate some amount of rust or scale. Good spray-like metal transfer with very little spatter. This electrode has been widely used in fabricating earth moving equipment, bridges, pressure vessels, construction, shipbuilding and in welds governed by structural, shipbuilding and nuclear codes and applications. Weld beads are flat to slightly convex. A. Typical Weld Metal Properties and Chemical Composition Yield Point 77,400 psi Tensile Strength 88,900 psi Elongation in 2" 26% Reduction of Area 59% Charpy V-notch Impact 25 F Carbon 0.07% Manganese 1.45% Silicon 0.48% DUAL SHIELD 111HD - This electrode retains good mechanical properties and operating characteristics of the 111A-C with the added advantage of high deposition rates. The 3/32" diameter will deposit weld metal at the rate of 18 lbs per hour, at the optimum parameters of 475 amps, 31 volts. The deposition efficiency is 88-90%. The steel should be reasonably clean; however, small amounts of rust or scale are tolerable. A. Typical Weld Metal Properties and Chemical Composition Yield Point 72,000 psi Tensile Strength 85,000 psi Elongation in 2" 26% Reduction of Area 59% Charpy V-notch Impact 24 F Carbon 0.07% Manganese 1.33% Silicon 0.58% Reliability of DUAL SHIELD R-70 Ultra - A newly reformulated electrode allows for greater tolerance of mill scale and surface oxides while generating lower welding fumes than other similar electrodes in the E70T-1 class. The as-welded tensile strength and notch toughness are the highest in this group. The weld bead is smooth and flat. This electrode has found extensive use in railcar, heavy equipment, and general fabrication.

190 Arc for A. Typical Weld Metal Properties and Chemical Composition Yield Point 79,800 psi Tensile Strength 92,700 psi Elongation in 2" 25% Reduction of Area 52% Charpy V-notch Impact 31 F Carbon 0.06% Manganese 1.60% Silicon 0.79% LESSON VII for Low Carbon 7.10 COREWELD METAL CORED WIRES Metal cored electrodes are fabricated tubular wires having a metallic sheath with the core ingredients predominantly iron powder. Iron powder serves to increase the electrodes deposition efficiency, while improving the speed of travel. Because the slagging ingredients have been replaced with iron powder, the slag residue makes up less than 5% of the deposit. This feature provides the user the capability to multipass without deslagging. These wires are now classified to AWS A COREWELD 70 - E70C-6M (.035" - 3/32" diameters). The spray-like transfer produces deposition rates over 20 lbs/hr. at 90-97% efficiency. It is usable on a variety of low and carbon steels in a variety of positions. This electrode is ideally suitable for automatic and robotic equipment. A. Typical Weld Metal Properties and Chemical Composition 75 Ar/25 CO 2 90 Ar/10 CO 2 Shielding Shielding Yield Point 75,500 psi 72,800 psi Tensile Strength 83,300 psi 86,000 psi Elongation in 2" Charpy V-notch Impacts 40 F 42 F Carbon 0.034% 0.038% Manganese 1.250% 1.350% Silicon 0.750% 0.800% Reliability of

191 Arc for for Low Carbon COREWELD ULTRA - E70C-6M (.045" - 1/16" diameters) provides the latest in technology in production of metal cored wires. Coreweld Ultra provides excellent mechanical properties, smooth spray transfer, low spatter, and extremely low fumes. A. Typical Weld Metal Properties and Chemical Composition 75 Ar/25 CO 2 92 Ar/8 CO 2 Shielding Shielding LESSON VII Yield Point 63,700 psi 65,000 psi Tensile Strength 77,000 psi 79,000 psi Elongation in 2" % Reduction of Area Charpy V-notch Impacts 37 F 31 F 32 F 28 F Carbon 0.030% 0.031% Manganese 1.65% 1.75% Silicon 0.62% 0.69% 7.11 AWS E70T-2 ELECTRODES of this classification are all gas shielded for single pass welding, and operate on direct current reverse polarity (electrode positive). They are considered as single pass electrodes because the flux contains higher levels of deoxidizers than the T-1 types for welding on carbon steels with mill scale and rust on the surface. This deoxidation may be shown by the following reactions: Mn + FeO MnO + Fe Si + 2FeO SiO 2 + Fe The manganese combines with the oxygen to form manganese-oxide that floats to the surface of the puddle and is harmlessly trapped in the slag. The iron becomes part of the weld metal. The silicon reaction shows that the silicon reacts with the oxygen in the rust to form silicon dioxide, which floats to the surface of the puddle and again is trapped in the slag. The iron becomes part of the weld metal If used on clean plate, or if used for multiple pass welding where there is no oxide coating for the manganese and silicon to combine with, these elements become part of the weld metal. As a result, the tensile strength may increase to over 100,000 psi and cracking may occur. These electrodes may also be used for welding the rimmed steels (steels that are not deoxidized). Reliability of

192 Arc for for Low Carbon LESSON VII Since these are considered single pass electrodes, the AWS Specification does not require an all-weld metal tensile test because single pass welds would be highly diluted with the base metal. Instead, the specification only requires a transverse tension test. This is a 1/4" thick by 1-1/2" wide bar of a minimum 72,000 psi tensile strength material. It is welded with a single pass on each side of a square butt joint. The welds are ground flush with the bar, and the specimen is pulled until failure in a tensile testing machine. A specimen that breaks in the base plate is considered satisfactory to meet the 72,000 psi minimum There are no requirements in AWS A for weld metal chemical composition for the E70T-2 types, since a single pass weld would be highly diluted from the base plate. We publish the carbon, manganese and silicon content of the undiluted welding metal for information purposes to indicate the relative amount of the deoxidizers in each electrode. All of the E70T-2 types require CO 2 shielding gas and have no AWS impact requirements DUAL SHIELD This electrode contains the highest amount of deoxidizers in the group and is for use on carbon steel plate, that is heavily scaled or rusted. Bead shape is flat to convex, and the thin slag is easily removed. Meets the 72,000 psi minimum tensile strength requirements for this classification. A. Undiluted Weld Metal Analysis (For Information Only) Carbon 0.07% Manganese 2.30% Silicon 1.50% DUAL SHIELD SP - This electrode contains a lesser amount of deoxidizers than Dual Shield 110 and is for use on carbon steel plate, that has a considerable amount of mill scale and rust. The bead contour is very good, and the slag is almost self-removing. Meets the AWS minimum tensile strength of 72,000 psi. A. Undiluted Weld Metal Analysis (For Information Only) Carbon 0.06% Manganese 1.70% Silicon 1.25% Reliability of

193 7.12 AWS E70T-5 LESSON VII Arc for for Low Carbon DUAL SHIELD T-5 & T-75 - A high quality electrode of the basic slag type. It produces weld metal of excellent impact properties. The weld metal is resistant to cracking and the deposition efficiency and deposition rates are high. This electrode has the approval for use on structural work, heavy equipment, shipbuilding, and military work under many codes and specifications CO 2 shielding gas is recommended for the 3/32" and 7/64" diameters. Argon-25% CO 2 is recommended for.045" and 1/16" diameters, producing a spray-like smooth metal transfer. May be used for high current, high deposition welding ALL-POSITION ELECTRODES ESAB was the originator of gas shielded, all-position flux cored wires. These electrodes have gained wide usage because they provide the most rapid method of depositing deep penetrating, sound welds in all positions, thus eliminating costly setup time and expensive fixturing. Available in.035",.045",.052", and 1/16" diameters, they may be used on plate thicknesses as thin as 3/16" in the vertical position, and 1/8" in the flat or horizontal. They have been used for multipass welding on 3" thick material in many nuclear power plant applications. The shielding gas may be straight CO 2 or Argon-25% CO 2 as indicated below DUAL SHIELD 7000 (E71T-1/E71T-1M & E71T-9/E71T-9M) - This is the original all-position electrode and was designed to be used with either straight CO 2 or Argon-25% CO 2 shielding gas. Using the Argon-CO 2 mixture will improve the arc characteristics, increase the wetting action, and decrease penetration slightly. The fast freezing slag is easily removed and holds the weld puddle for rapid vertical-up and overhead welding. Performs well over normal mill scale and rust. A. Typical Weld Metal Mechanical Properties (As Welded) Yield Point 76,000 psi Tensile Strength 86,000 psi Elongation in 2" 27% Reduction of Area 67% Charpy V-notch Impact 32 F Reliability of

194 B. Typical Weld Metal Analysis LESSON VII Arc for for Low Carbon Carbon 0.06% Manganese 1.47% Silicon 0.60% DUAL SHIELD 7100 ULTRA (E71T-1/E71T-1M & E71T-9/E71T-9M) - This newly developed electrode is designed for optimum performance with straight CO 2 shielding while generating lower welding fumes. Ar/CO 2 mixes up to 75% Ar may be used for better arc characteristics. Fillet weld beads are flat to slightly convex and have uniform side wall fusion or wetting. Welds produced are of X-ray quality. This electrode produces a lower cost per pound of deposited weld metal than any other welding consumable, especially in the vertical-up and overhead positions. A. Typical Weld Metal Mechanical Properties (As Welded) Yield Point 78,500 psi Tensile Strength 90,000 psi Elongation in 2" 27% Reduction of Area 66% Charpy V-notch Impact 32 F B. Typical Weld Metal Analysis Carbon 0.06% Manganese 1.40% Silicon 0.70% DUAL SHIELD FC-717 (E71T-1/E71T-1M & E71T-9/E71T-9M) - This all-position flux cored wire is a lower cost alternative that produces low spatter, smooth stable arc and a flat to slightly convex bead shape. Shielding gas can be CO 2 or Argon/CO 2 mixtures up to 75% Argon. A. Typical Weld Metal Mechanical Properties (As Welded) Reliability of CO 2 75%Ar/25%CO 2 Shielding Shielding Yield Point 73,000 psi 76,500 psi Tensile Strength 82,900 psi 87,500 psi Elongation in 2" 27% 27% Charpy V-notch Impact 50 F 70 F 30 F 50 F

195 B. Typical Weld Metal Analysis LESSON VII Arc for for Low CO 2 75%Ar/25%CO 2 Shielding Shielding Carbon 0.050% 0.055% Manganese 1.10% 1.10% Silicon 0.44% 0.55% DUAL SHIELD II 70 ULTRA (E71T-1 & E71T-12M) and DUAL SHIELD II 71 ULTRA (E71T-1 & E71T-12) Dual Shield II 70 Ultra and Dual Shield II 71 Ultra provide all-position welding with excellent impact toughness and low hydrogen deposits. Arc characteristics are some of the best found in a flux cored wire with fume generation rates being extremely low. Available in 0.035" to 1/16" diameters, Dual Shield II 70 Ultra and Dual Shield II 71 Ultra are excellent choices for critical applications. A. Typical Weld Metal Mechanical Properties (As Welded) II 70 Ultra II 71 Ultra Carbon Yield Point 72,300 psi 71,500 psi Tensile Strength 81,100 psi 79,500 psi Elongation in 2" 29% 28% % Reduction in Area 75% 77% Charpy V-notch Impact 117 F 96 F 70 F 40 F B. Typical Weld Metal Analysis II 70 Ultra II 71 Ultra Carbon 0.028% 0.019% Manganese 1.30% 1.15% Silicon 0.30% 0.30% Reliability of

196 Arc for for Low 7.14 CORESHIELD SELF-SHIELDED FLUX CORED WIRES Self-shielded flux cored wires contain the necessary ingredients within the core to protect the molten weld metal from atmospheric contaminates. Typically, these products are used in windy or outdoor environments. Dependent on their specific AWS designation, they are classed as either single or multipass electrodes. Mechanical properties, especially impact toughness, is restrictive with the self-shielded electrodes AWS E70T CORESHIELD 40 - This electrode is a self-shielded, horizontal and flat position weld wire, designed for high deposition welding. The penetration is not as deep as that of the gas shielded types, making it more suitable for weld joints with poor fit-up. A. Typical Weld Metal Mechanical Properties Yield Point 64,000 psi Tensile Strength 84,000 psi Elongation in 2" 26% LESSON VII Carbon B. Typical Weld Metal Chemical Composition Carbon 0.22% Manganese 0.35% Silicon 0.35% Aluminum 1.10% 7.16 AWS E70T CORESHIELD 7 - is a multipass wire for flat and horizontal position welding. This specially developed formulation permits faster travel speeds as compared to Coreshield 40. A. Typical Mechanical Properties Tensile Strength Yield Strength 90,700 psi 67,000 psi Reliability of

197 Arc A. Typical Chemical Properties Carbon 0.26% Manganese 0.45% Silicon 0.10% Aluminum 1.55% LESSON VII for for Low 7.17 AWS E70T CORESHIELD 10 - Ideally suited for thin gauge and galvanized steels. This electrode performs well on high speed, single pass robotic applications. A. Typical Weld Metal Mechanical Properties Transverse Tensile Strength 95,900 psi Longitudinal Guided Bend Test (Aged 210 F for 48 hrs., bent 180 over 3/4" radius) 7.18 AWS E71T-11 Carbon CORESHIELD 11 - is an all-position single or multipass electrode for use in mild steel applications. The versatility of this electrode makes it an ideal choice for structural steel applications. A. Typical Mechanical Properties Yield Strength 62,500-65,000 psi Tensile Strength 88,500-91,200 psi Elongation in 2" A. Typical Weld Metal Composition Carbon 0.25% Manganese 0.65% Silicon 0.40% Aluminum 1.65% Reliability of

198 7.19 AWS E71T-GS LESSON VII Arc CORESHIELD 15 - is an all-position single pass electrode for thin gauge galvanized or mild steel application. This electrode is available in.030" - 5/64" diameters. A. Typical Mechanical Properties for Tensile Strength Longitudinal Guided Bend A. Typical Chemical Properties 76,000 psi Passed for Low Carbon 0.25% Manganese 0.70% Silicon 0.40% Aluminum 2.40% Carbon 7.20 AWS SPECIFICATION A This American Society (AWS) Specification is entitled "Specification for Low Alloy Steel for ". It prescribes the classification requirements for low alloy steel flux cored electrodes for welding carbon and low alloy steels. Among the requirements prescribed in the specification are test procedures, winding requirements, spool and coil standards, packaging standards, and the items listed below that will be covered in this text. 1. Whether gas shielded or self-shielded 2. Type of welding current 3. position 4. Chemical composition of the weld metal 5. Mechanical properties of the weld metal 7.21 AWS DESIGNATIONS The letter-number designations used in this specification are shown in Figure As an example, the designation E81T1-Ni2 indicates an electrode (E) that will produce weld metal of a minimum 80,000 psi tensile strength (8), may be used in welding Reliability of

199 Arc for for Low LESSON VII in all positions (1), is a flux cored electrode (T), is a multipass, gas shielded type for operation on direct current, electrode positive (1), and will produce weld metal containing approximately 2% nickel (Ni2). EXX T X - X Electrode Min. Tensile Strength x 10,000 psi 0: Flat and Horizontal 1: All Position Chemical Composition Usability and Performance Tubular or Flux Cored LOW ALLOY STEEL FLUX CORED ELECTRODE DESIGNATIONS FIGURE USABILITY AND PERFORMANCE Carbon The low alloy types have five classifications based on usability and performance. They are T1, T4, T5, T8, and TX-G. There are two classifications for the gas shielded electrodes, two classifications for the self-shielded electrodes, and one general classification for new electrodes that do not fit into any of the categories defined in the A specification. All of the electrodes in this specification may be used for single or multipass welds. Briefly, the usability characteristics are: EXXT1-X CO 2 Shielded DC, Electrode Positive EXXT4-X Self-Shielded DC, Electrode Positive EXXT5-X CO 2 Shielded DC, Electrode Positive EXXT8-X Self Shielded DC, Electrode Negative EXXTX-G Not Specified Not Specified A more complete description of the usability and performance may be found in Section 7.7, INDIVIDUAL ELECTRODE CHARACTERISTICS. They are the same as those specified for the carbon steel electrodes in Specification A Reliability of

200 7.23 MECHANICAL PROPERTIES REQUIREMENTS LESSON VII Arc for for Low Carbon Reliability of Figure 11 lists the mechanical property requirements for this specification. TENSILE MIN. YIELD MIN. PERCENT AWS STRENGTH STRENGTH ELONGATION CLASSIFICATION psi. psi. IN 2 INCHES E6XTX-X 60,000-80,000 50, E7XTX-X 70,000-90,000 58, E8XTX-X 80, ,000 68, E9XTX-X 90, ,000 78, E10XTX-X 100, ,000 88, E11XTX-X 110, ,000 98, E12XTX-X 120, , , EXXXTX-G As agreed by Manufacturer and Purchaser For those electrodes using a shielding gas, properties must be attained using CO2. WELD METAL MECHANICAL PROPERTY REQUIREMENTS LOW ALLOY FLUX CORED ELECTRODES FIGURE WELD METAL CHEMICAL COMPOSITION REQUIREMENTS In this section, we will be referring to the elements by their chemical symbols. The Glossary of Terms at the end of this lesson defines these symbols Carbon-Molybdenum Steel - The carbon-moly electrodes are used for moderately high tensile and moderately high temperature applications. of this classification have the suffix A1 (EXXTX-A1). Chemical composition requirements of the weld metal are listed below and the single figures indicate maximum allowable amounts. Element % by Weight Element % by Weight C 0.12 Mo Mn 1.25 P 0.03 Si 0.80 S Chromium-Molybdenum Steel - The chrome-moly types, as they are commonly referred to, are used in applications requiring strength and resistance to oxidation (scaling) at elevated temperatures. Their chemical composition requirements are shown in Figure 12.

201 Arc for for Low AWS Chemical Composition % Class. C Mn Si Cr Mo EXXTX-B EXXTX-B2L EXXTX-B EXXTX-B2H EXXTX-B3L EXXTX-B EXXTX-B3H All Classifications: P %, S % WELD METAL CHEMICAL COMPOSITION REQUIREMENTS CHROMIUM - MOLYBDENUM FLUX CORED ELECTRODES FIGURE Nickel Steel - The nickel steel electrodes are used for low temperature applications where good impacts are necessary. As the amount of nickel is increased, the low temperature impact properties increase. Figure 13 shows the chemical composition requirements for these electrodes. LESSON VII AWS Chemical Composition % Class. C Mn Si P S Ni Cr Al* Carbon EXXTX-Ni EXXTX-Ni EXXTX-Ni *Self shielding types only WELD METAL CHEMICAL COMPOSITION REQUIREMENTS NICKEL-STEEL FLUX CORED ELECTRODES FIGURE Manganese-Molybdenum Steel - The manganese-moly steels are used in high strength applications in the 90,000 to 100,000 psi tensile strength range. Figure 14 shows the chemical composition requirements for these electrodes. AWS Chemical Composition % Class. C Mn Si Mo P S Reliability of EXXT1-D EXXT1-D EXXT1-D WELD METAL CHEMICAL COMPOSITION REQUIREMENTS MANGANESE - MOLYBDENUM STEEL FLUX CORED ELECTRODES FIGURE 14.

202 LESSON VII Arc for for Low Carbon Reliability of 3.1 Development of All Other Low Alloy Steel - Low alloy steels that do not fit into any of the previous categories are in this category, with the suffix letter K, G, or W. Notice that in the weld metal chemical composition of the carbon-molybdenum, chromium molybdenum, nickel and manganese-molybdenum steels, only one or two alloyi were added or changed. In this group, the carbon content is slightly higher, and all of the classifications have varying amounts of manganese, nickel, chromium and molybdenum. Also, vanadium has been added to all but two of the elect The EXXXTX-K category includes electrodes for welding many of the trade name high strength steels, such as USS T1, HY-80, HY-90, HY-100 and many others. for welding the ASTM high strength steels, and the AISIheat treatable steels are in this group The W suffix indicates an electrode for welding the weathering grades of steel. These are steels that corrode o point where te oxide coating becomes impervious to further corrosion Figure 15 shows the weld metal composition for these electrodes. AWS Class. EXXTX-K EXXTX-K EXXTX-K EXXTX-K EXXTX-K5 Chemical Composition % a C Mn Si Ni Cr Mo V Al b Cu EXXTX-K EXXTX-K (a) single values are maximum only (b) Self-shielded electrodes only (c) Minimum values. The weld metal need have the minimum of only one of the elements listed Figure 15 Weld Metal Chemical Composition Requirements All Other Alloy Steel /4 3/ / /4 3/ /4 3/ /4 3/ /4 3/4 3/4 3/4 3/4 3/4 EXXTX-KG 3/4 1.0 c c 0.30 c 0.20 c 0.10 c 1.8 3/4 EXXTX-W /4 3/4 3/4 3/ COPYRIGHT 2000 THE ESAB GROUP, IN

203 7.25 IMPACT PROPERTIES LESSON VII Arc The impact properties of the low alloy electrodes are listed in Figure 16. AWS Impact AWS Impact Class Strength Class Strength for for Low Carbon E80T1-A1 Not Required* E90T5-Ni F* E81T1-A1 Not Required* E91T1-D F* E70T5-A F* E90T5-D F* E81T1-B1 Not Required* E100T5-D F* E81T1-B2 Not Required* E90T1-D F* E80T1-B2 Not Required* E80T5-K F* E80T5-B2 Not Required* E70T4-K F* E80T1-B2H Not Required* E71T8-K F* E80T5-B2L Not Required* E80T1-K F* E90T1-B3 Not Required* E90T1-K F* E91T1-B3 Not Required* E91T1-K F* E90T5-B3 Not Required* E80T5-K F* E100T1-B3 Not Required* E90T5-K F* E90T1-B3L Not Required* E100T1-K F* E90T1-B3H Not Required* E110T1K F* E71T8-Ni F E100T5-K F* E80T1-Ni F E110T5-K F* E81T1-Ni F E110T5-K F* E80T5-Ni F E111T1-K F* R71T8-Ni F E120T5-K F* E80T1-Ni F E120T1-K5 Not Required E81T1-Ni F E61T8-K F* E80T5-Ni F E71T8-K F* E90T1-Ni F E101T1-K F* E91T1-Ni F E80T1-W F* E80T5-Ni F EXXXTX-G ** * Require post weld heat treatment. All others are as welded. ** As agreed between manufacturer and purchaser. IMPACT REQUIREMENTS LOW ALLOY STEEL FLUX CORED ELECTRODES FIGURE 16. Notice that the impact requirement for the E80T5-Ni1 is 20 ft-lbs at -60 F., while the impact requirement for the E80T1-Ni1 is 20 ft-lbs at -20 F. The T-5 electrode has a basic slag system, and the T-1 electrode has an acid slag system. As pointed out earlier, electrodes with basic slag systems provide improved impact properties; however, they are limited to flat and horizontal fillet welding only. Reliability of

204 Arc for for Low Carbon 7.26 SELECTING THE PROPER LOW ALLOY ELECTRODE When welding low alloy steels, the tensile strength, yield strength, elongation, and impact properties of the weld metal should match those of the material being welded as closely as possible. The chemical composition of the weld metal should match that of the steel also, although this may not always be possible. The mechanical properties and chemical compositions published in the electrode manufacturer s literature are based on undiluted weld metal. Welds made on the job will be diluted with the base metal, and composition and strength level may be somewhat different than the published data. In most cases, however, matching strength and composition as closely as possible works out well Choosing an electrode that produces weld metal of slightly greater strength than the base material is allowable as long as ductility and service requirements are compatible. In some cases, it may be necessary to use an electrode that produces weld metal of lower strength than the base metal. This can be beneficial, as long as the strength is sufficient for the application, since lower strength steels are usually more ductile and less likely to cause toe-cracking in the base metal. Conversely, gross overmatching of the electrode to the base material can increase the cracking potential The wide variety of low alloy steels available today can make electrode selection a complex problem. In some cases, low alloy steels of the same chemical composition will have different mechanical properties depending on whether they have been rolled, hot or cold worked, cast or forged. For this reason, the American Society for Testing Materials (ASTM) has published several volumes of standards and classifications for the various forms of ferrous metal products (See Lesson I, "Specifications"). Steel manufacturers and fabricators assign these classification numbers to their products such as steel sheet, plate, bar, pipe, castings, forgings, and others. Electrode manufacturers usually provide a list of some of the more common ASTM specifications for which their electrodes are suited. See your Atom Arc and Dual Shield catalogs for suggested applications Dissimilar Steels - Dissimilar steels with similar metallurgical structure can be satisfactorily welded with electrodes matching the composition or behavior of the lower alloys or lower cost electrode. Nothing is gained by using electrodes that match the higher alloy or higher cost material because the lower composition steel is on one side of the joint immediately adjacent to the weld metal. As an example, 2-1/4% Cr-1% Mo steel is best welded to 1-1/4% Cr-1/2 Mo steel with an electrode producing weld metal of 1-1/4% Cr-1/2 Mo composition. LESSON VII Reliability of

205 Arc for for Low LESSON VII steels of dissimilar metallurgical structure requires a knowledge of welding metallurgy, and when in doubt, the Technical Service Department of the electrode or steel manufacturer should be consulted Procedures - Procedures for welding the low alloy high strength steels are more stringent than those used for welding the carbon steels. Preheat, interpass temperature control and post weld treating are necessary in many cases and will vary depending on the material thickness. In some cases, hammer peening between passes may be necessary to relieve stresses and prevent subsequent cracking, or to reduce distortion. Proper joint design and qualified welding procedures for the various alloys must be adhered to ADVANCED DEVELOPMENTS IN CORED WIRES Leading the industry in cored wire technology advancements has long been a tradition with ESAB & Cutting Products. Since they first introduced flux cored wires to the market in 1957, ESAB has continued to bring innovation to the industry. Consider some of the advancements in cored wire technology ESAB is proud of introducing: Carbon 1957 First flux cored wire introduced 1965 First basic slag flux cored wire introduced for improved mechanical properties 1972 First small diameter, all-position flux cored wire 1984 Dual Shield II Series of Second Generation flux cored wires with good impact properties and low hydrogen 1985 First.030" diameter flux cored wire introduced 1988 First "Ultra Series" low fume and low spatter flux cored wire introduced 1997 New technology metal cored wire combining excellent weldability with low fume and exceptional mechanical properties 1998 "H4" Technology flux cored wires The newest technology innovation is the introduction of the "H4 Technology" flux cored wires. These wires have the lowest diffusible hydrogen level of any acid slag flux cored wire, exhibiting less than 4 ml/100 gm weld metal of diffusible hydrogen. "H4 Technology" cored wires are the Third Generation of a long series of flux cored wire technology advancements. Reliability of

206 Arc 7.28 DUAL SHIELD SELECTOR GUIDE The following is a listing of the standard available types of Dual Shield flux cored low alloy electrodes. For more extensive information, see the ESAB Cored Wire Products catalog. DUAL SHIELD LOW ALLOY FLUX CORED ELECTRODES SELECTOR GUIDE LESSON VII for for Low Carbon Dual Shield Typical Properties Weld Metal Shielding Typical Type Gas Category As Stress Weld Metal AWS Class Welded Relieved Analysis % 7000-A1 CO 2 Tensile Strength, psi 91,000 90,500 C or Yield Strength, psi 80,500 78,500 Mn AWS Argon-25% Elongation %-2" Si E81T1-A1 CO 2 Reduction of Area % Mo CM Tensile Strength, psi 106,000 88,000 C Yield Strength, psi 94,000 75,000 Mn AWS Elongation %-2" Si E80T1-B2 Reduction of Area % Cr Mo B1 Argon-25% Tensile Strength, psi 103,700 99,700 C CO 2 Yield Strength, psi 91,700 86,800 Mn AWS or CO 2 Elongation %-2" Si E81T1-B1 Reduction of Area % Cr Mo B2 Argon-25% Tensile Strength, psi 104,500 98,000 C CO 2 Yield Strength, psi 93,000 87,000 Mn AWS or CO 2 Elongation %-2" Si E81T1-B2 Reduction of Area % Cr Mo T-85-B2 Argon- Tensile Strength, psi 103,000 92,000 C % CO 2 Yield Strength, psi 87,000 77,000 Mn AWS Elongation %-2" Si E80T5-B2 Reduction of Area % P Charpy V-Notch 0 F 38 ft-lb 54 ft-lb S Cr Mo CM CO 2 Tensile Strength, psi 128,000 96,000 C Yield Strength, psi 109,500 82,500 Mn AWS Elongation %-2" Si E90T1-B3 Reduction of Area % Cr Mo B3 CO 2 Tensile Strength, psi 120,000 96,000 C Yield Strength, psi 104,000 82,500 Mn AWS Elongation %-2" Si E91T1-B3 Reduction of Area % Cr Mo Description-Applications For all-position welding of 50,000 psi minimum yield steels and.5% Mo steels. For boilers, pressure vessels, pressure piping and other applications. For flat and horizontal position welding of the Cr-Mo steels. For welding plates, tubes, castings and forgings. All-position chrome-moly designed to weld 1/2% chrome - 1/2% moly steels. An all-position Cr-Mo electrode for welding low alloy steels up to 1 Cr- Mo. Similar to E8018-B2 manual electrodes. For welding plate, pipe, tubes, castings or forgings to many ASTM specifications. A basic slag electrode for the flat & horizontal positions. Optimum weld quality and resistance to cracking. For welding the low alloy steels up to 1 Cr- Mo. Made in.045" & 1/16" diameters. For high current, high deposition welding. For flat & horizontal position welding of the 2 Cr-1 Mo steels. Weld metal is similar to E9018-B3 manual electrodes. An all-position electrode for welding the 2 Cr-1 Mo steels. Suitable for many ASTM specifications such as castings, boiler tubes, forgings and plate for high temperature, high pressure container parts. Reliability of

207 LESSON VII Arc for for Low Carbon DUAL SHIELD LOW ALLOY FLUX CORED ELECTRODES SELECTOR GUIDE (Con't.) Dual Shield Shielding Typical Properties Weld Metal Typical Type Gas As Stress Weld Metal AWS Class Category Welded Relieved Analysis % Description-Applications T-95-B3 Argon- Tensile Strength, psi 124,000 98,000 C A basic slag electrode for the 2 Cr-1 Mo 25% CO 2 Yield Strength, psi 106,000 82,000 Mn steels. For flat & horizontal position welding only. Optimum weld quality and AWS Elongation %-2" Si resistance to cracking. Made in.045" and E90T5-B3 Reduction of Area % Cr /16" diameters for high current, high Charpy V-Notch 0 F 16 ft-lb 31 ft-lb Mo deposition welding. Coreweld 70 Argon-25% Tensile Strength, psi (75/25) C Ni1 CO 2 or Yield Strength, psi 76,400 Mn Argon-8% Elongation %-2" 64,200 Si AWS CO 2 Reduction of Area % 31 Cr E80C-Ni1 2% O 2 Charpy Impacts 72 Ni (75/25) (90/10) Cu F F C3 CO 2 Tensile Strength, psi 81,000 78,000 C Yield Strength, psi 70,000 67,000 Mn AWS Elongation %-2" Si E80T1-Ni1 Reduction of Area % Ni Charpy Impact 0 F 50 ft-lb 53 ft-lb -40 F 25 ft-lb 22 ft-lb Dual Shield II Argon- Tensile Strength, psi 97,000 93,000 C Ni-1 25% CO 2 Yield Strength, psi 87,000 82,000 Mn Elongation %-2" Si AWS Reduction of Area % P E81T1-Ni1 Charpy Impact -40 F 61 ft-lb 38 ft-lb S Ni (A-25% CO 2 (CO 2 ) (A-25% CO 2 ) 8000-Ni2 Argon- Tensile Strength, psi 86,000 84,000 C % CO 2 Yield Strength, psi 74,000 72,000 Mn AWS or CO 2 Elongation %-2" Si E81T1-Ni2 Reduction of Area % Ni Charpy Impact 0 F 51 ft-lb 50 ft-lb -20 F 43 ft-lb 43 ft-lb -40 F 30 ft-lb 30 ft-lb 85-C1 CO 2 Tensile Strength, psi 85,000 86,500 C Yield Strength, psi 71,000 77,000 Mn AWS Elongation %-2" Si E80T5-Ni2 Reduction of Area % Ni Charpy Impact 72 F 59 ft-lb 84 ft-lb -75 F 41 ft-lb 38 ft-lb Metal cored wire with 1% addition of nickel alloy. Improved impacts are possible. For flat and horizontal position welding of the 1% nickel steels. Good impacts at -40 F. Weld metal properties similar to E8018-C3 low hydrogen electrodes. Superior mechanical properties and impacts. A 1% Nickel electrode which exceeds the impacts of most 2% Nickel types. all-position capabilities. Smooth spray transfer. Low nickel analysis well suited for petrochemical applications. Ship building and heavy equipment. Widely used all-position electrode producing 2 % nickel weld metal. 75% Argon/25% CO2 produces improved weldability. Excellent electrode for ship building and heavy equipment. For flat & horizontal fillet positions. A basic slag electrode which produces a 2 % nickel deposit with excellent low temperature toughness and x-ray quality welds. Reliability of

208 LESSON VII Arc for for Low Carbon Reliability of DUAL SHIELD LOW ALLOY FLUX CORED ELECTRODES SELECTOR GUIDE (Con't.) Dual Shield Shielding Typical Properties Weld Metal Typical Type Gas As Stress Weld Metal AWS Class Category Welded Relieved Analysis % T-90C1 CO 2 Tensile Strength, psi 97,500 97,000 C Yield Strength, psi 82,000 84,000 Mn AWS Elongation %-2" Si E90T1-Ni2 Reduction of Area % Ni Charpy Impact 0 F 35 ft-lb -20 F 27 ft-lb -50 F 23 ft-lb 9000-C1 CO 2 Tensile Strength, psi 106, ,000 C Yield Strength, psi 101,000 93,000 Mn AWS Elongation %-2" Si E91T1-Ni2 Reduction of Area % Ni Charpy Impact -20 F 37 ft-lb 25 ft-lb -40 F 20 ft-lb 9000-D1 CO 2 Tensile Strength, psi 100, ,500 C Yield Strength, psi 92,000 90,500 Mn AWS Elongation %-2" Si E91T1-D1 Reduction of Area % Mo Charpy Impact -20 F 27 ft-lb 150 CO 2 Tensile Strength, psi 108, ,750 C Yield Strength, psi 97,000 96,500 Mn AWS Elongation %-2" Si E90T1-D3 Reduction of Area % Mo Charpy Impact 0 F 37 ft-lb -25 F 30 ft-lb -50 F 24 ft-lb 85NM CO 2 Tensile Strength, psi 98,500 85,000 C Yield Strength, psi 89,750 73,500 Mn AWS Elongation %-2" Si E80T5-K1 Charpy Impact -10 F 60 ft-lb Mo F 34 ft-lb Ni CO 2 Tensile Strength, psi 94,000 95,800 C Yield Strength, psi 85,000 84,500 Mn AWS Elongation %-2" Si E90T1-K2 Reduction of Area % Mo Charpy Impact 72 F 50 ft-lb 41 ft-lb Ni F 38 ft-lb 35 ft-lb 9000M CO 2 Tensile Strength, psi 103, ,000 C Yield Strength, psi 94,000 91,000 Mn AWS Elongation %-2" Si E91T1-K2 Reduction of Area % Ni Charpy Impact 72 F 43 ft-lb 32 ft-lb Mo F 30 ft-lb 20 ft-lb Description-Applications For flat & horizontal position welding of 2 %-3 % nickel steels and castings. Good sub-zero toughness. All-position electrode deposits nominal 2% nickel weld metal similar to T-90C1. For welding 2-3% nickel steels and castings requiring good toughness at subzero temperatures. All-position electrode for nominal 1 % Mn- % Mo steels. For pressure vessel plates and Mn-Mo steel castings. For flat & horizontal position welding of Mn- Mo steels of 100,000 psi tensile strength. For flat & horizontal position welding Mn-Mo- Ni steels. Used largely for welding ASTM A533 (grade B) steel for nuclear pressure vessels. For flat & horizontal position welds 90,000 psi tensile steels. Also for ductile attachment welds on T-1, HY-80, HY-90 & other high strength quenched & tempered steels. For all-position welds on 90, ,000 psi tensile strength steels. Properties similar to Dual Shield 98..

209 LESSON VII Arc for for Low Carbon DUAL SHIELD LOW ALLOY FLUX CORED ELECTRODES SELECTOR GUIDE (Con't.) Dual Shield Shielding Typical Properties Weld Metal Typical Type Gas As Stress Weld Metal AWS Class Category Welded Relieved Analysis % T-100 CO 2 Tensile Strength, psi 104, ,000 C Yield Strength, psi 91,000 91,000 Mn AWS Elongation %-2" Si E100T1-K3 Reduction of Area % Mo Charpy Impact 72 F 45 ft-lb 40 ft-lb Ni F 25 ft-lb 24 ft-lb -60 F 22 ft-lb 20 ft-lb (HY-80) (Mild Steel) Dual Shield Argon- Tensile Strength, psi 97,200 94,700 C II 101TM 25% CO 2 Yield Strength, psi 87,600 86,500 Mn Elongation %-2" Si AWS Reduction of Area % Ni E91T1-K2 Charpy Impacts 0 F F Dual Shield Argon- Tensile Strength, psi 109, ,250 C II % CO 2 Yield Strength, psi 101,750 99,300 Mn Elongation %-2" Si AWS Reduction of Area % Cr E100T1-K3 Charpy Impact 0 F 48 ft-lb 33 ft-lb Ni F 40 ft-lb 30 ft-lb Mo F 25 ft-lb 18 ft-lb T-8 CO 2 Tensile Strength, psi 117, ,000 C Yield Strength, psi 106, ,000 Mn AWS Elongation %-2" Si E110T1-K3 Reduction of Area % Cr Charpy Impact 72 F 42 ft-lb 35 ft-lb Ni Mo Dual Shield Argon- Tensile Strength, psi 120, ,000 C II % CO 2 Yield Strength, psi 110, ,000 Mn Elongation %-2" Si AWS Reduction of Area % Cr E110T1-K3 Charpy Impact 0 F 40 ft-lb 25 ft-lb Ni F 30 ft-lb 20 ft-lb Mo F 24 ft-lb T-115 CO 2 Tensile Strength, psi 113, ,000 C (3/32") Argon- Yield Strength, psi 107,000 96,000 Mn (.045", 1/16") 25% CO 2 Elongation %-2" Si Reduction of Area % Ni AWS Charpy Impact -20 F 50 ft-lb 48 ft-lb Mo F 36 ft-lb 32 ft-lb Description-Applications For flat & horizontal welds on 100,000 psi tensile strength steels. All-position flux cored electrode with excellent low temperature impact toughness. Developed specifically for military applications. A significant new electrode with high strength and excellent ductility. An allposition electrode for welding the T-1 and HY-80 steels. Excellent low temperature impacts. For flat & horizontal welds on 110,000 psi steels. For trade name steels such as SSS 100, N-A-XTRA 110, JALLOY S110, USS T1 Type A and others. Another Dual Shield II electrode with high strength and excellent impact properties. For all-position welding of 110,000 psi steels such as HY-100, T1 and others. For flat & horizontal welds. A basic slag electrode with excellent properties. Small diameters require Argon-CO 2 mixture for high current, high deposition welding. For welding T1, HY-80, HY-90, N-A-XTRA 90, 100 & 110 and the SSS 100 steels. Reliability of.

210 LESSON VII Arc for for Low DUAL SHIELD LOW ALLOY FLUX CORED ELECTRODES SELECTOR GUIDE (Con't.) Dual Shield Shielding Typical Properties Weld Metal Typical Type Gas As Stress Weld Metal AWS Class Category Welded Relieved Analysis % T-4130 CO 2 SEE CATALOG C FOR COMPLETE Mn AWS PROPERTIES Si No Spec. Cr Ni Mo LN Argon- SEE CATALOG C % CO 2 FOR COMPLETE Mn AWS PROPERTIES Si No Spec. Cr Ni Mo Description-Applications For flat and horizontal position welding of alloys such as A1S1 4130, 8630 and comparable types. The heat treated properties will match those of the base metal. A basic slag electrode for flat and horizontal welding positions. Resists cracking and welds are of highest quality. For welding SAE 8630 and 4130 heat treatable steels. Low nickel content meets the standards of the National Association of Corrosion Engin Carbon 88W CO 2 Tensile Strength, psi 82,000 84,000 C Yield Strength, psi 68,000 70,000 Mn AWS Elongation %-2" Si E80T1-W Reduction of Area % Cr Charpy Impact 30 F 66 ft-lb 47 ft-lb Ni F 42 ft-lb 35 ft-lb Cu F 32 ft-lb 23 ft-lb -44 F 20 ft-lb 20 ft-lb Coreweld W Argon- Tensile Strength, psi 92,500 C % CO 2 Yield Strength, psi 81,500 Mn AWS Elongation %-2" 26 Si E80C-G Charpy Impacts -20 F 38 Ni F W CO 2 Tensile Strength, psi 96,500 C Yield Strength, psi 89,500 Mn AWS Elongation %-2" 25 Si E80T1-W Reduction of Area % 61 Charpy Impacts 0 F F 31 For flat and horizontal position welding of the weathering grade steels such as Cor- Ten or Mayari R. Metal cored electrode for weathering grade steels such as A588, A242, U.S.S. Cor- Tenfi, and Mayari Rfi. All-position flux cored electrode to provide color match for weathering grade steels. Reliability of.

211 Arc for for Low Carbon Reliability of APPENDIX A LESSON VII - GLOSSARY OF TERMS Chemical symbols for the alloying elements commonly used in welding metallurgy: Flux Voids Mill Scale Preheat Temperature Interpass Temperature Peening Post Weld Heat Treatment C - Carbon S - Sulfur Mn - Manganese B - Boron Si - Silicon Al - Aluminum Cr - Chromium Cb - Columbium (Niobium) Ni - Nickel Ti - Titanium Mo - Molybdenum W - Tungsten V - Vanadium Co - Cobalt Cu - Copper Pb - Lead P - Phosphorus N - Nitrogen - Section of a flux cored electrode which contains no flux. Voids can cause serious problems, especially in low alloy types. - The iron oxide (FeO) coating normally found on the surface of hot rolled steels. - The temperature to which many of the low alloy steels must be heated before welding. Preheating retards the cooling rate, allowing more time for the hydrogen to escape, which minimizes underbead cracking. Preheat temperatures can vary from 10 F to 500 F on ½ sections to 300 F to 600 F on heavy sections, depending upon the alloy. - The minimum temperature of the weldment between passes. It is usually about the same as the preheat temperature. - The mechanical working of metal by means of hammer blows to relieve stresses and reduce distortion. Peening is recommended for thicker sections (over 1 or 2 ) of some alloys on each successive pass. Experience has shown that peening helps to reduce cracking. Peening may decrease the ductility and impact properties; however, the next pass will nullify this condition. For this reason, the last surface layers should not be peened. - Reheating the weldment to 1100 F to 1350 F after welding and holding at that temperature for a specified length of time. Heat treating allows additional hydrogen to escape, lowers the residual stresses due to welding, and restores toughness in the heat affected zone. LESSON VII

212 Arc for for Low BASIC WELDING FILLER METAL TECHNOLOGY A Correspondence Course Carbon LESSON VIII HARDSURFACING ELECTRODES ESAB ESAB & Cutting Products Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

213 Arc for for Low TABLE OF CONTENTS LESSON VIII HARDSURFACING ELECTRODES Section Nr. Section Title Page 8.1 Introduction to Hardfacing Definition and Purpose Buildup Alloys Hardfacing Alloys Wear Factors Base Metals Classification of Hardfacing Alloys... 9 Carbon Iron Base Alloys Nickel Base Alloys Cobalt Base Alloys Tungsten Base Alloys Methods of Hardfacing Oxyacetylene Surfacing Shielded Metal Arc Surfacing Gas Tungsten Arc Surfacing Surfacing Submerged Arc surfacing Gas Metal Arc surfacing Surfacing With Powders Flame Spray Process Manual Torch Process Plasma Arc Spray and Plasma Arc Process General Rules of Hardfacing Economics of Hardfacing Reliability of

214 Arc for for Low TABLE OF CONTENTS LESSON VIII HARDSURFACING ELECTRODES Section Nr. Section Title Page 8.7 ESAB Hardfacing Wear-Arc Coated Wear-O-Matic Open Arc Wear-O-Matic BR Wires Hardfacing Alloy Selection Factors Hardness Abrasion and Impact Wear-Arc and Wear-O-Matic Wires for Hardfacing Wear-Arc Wear-O-Matic Semiautomatic Cored Wires Appendix A Glossary of Terms Carbon Reliability of

215 HARDSURFACING ELECTRODES LESSON VIII Arc 8.1 INTRODUCTION for for Low Carbon Hardfacing, or hard surfacing*, has been used as a method of reclaiming industrial parts and equipment since the early 1920 s. At that time, it was found that a hard alloy deposit, properly applied to the surface of oil drilling bits, extended the life of those bits by more than ten times. Since then, hardfacing has become universally accepted as an economical and practical means of restoring plant and field equipment subjected to destructive wear Definition and Purpose - Hardfacing may be defined as the application of a hard, wear resistant alloy to the surface of a softer metal to restore it dimensionally and reduce wear caused by abrasion, impact, erosion, corrosion and heat Lubrication of machine parts is an effective method of preventing abrasive wear; however, in applications such as the external parts of farm and earth moving equipment, oil drilling tools, engine valves, etc., lubrication is not possible. In these applications, hardfacing has proven to be an effective means of extending part life by three to eight times In many cases, new parts which are destined for destructive wear, are hardfaced before being put into service initially. Savings are effected by reclaiming worn parts, reducing maintenance and replacement costs, and permitting the use of relatively inexpensive base metals Shops specializing in hardfacing are set up for automatic operation in many cases. Jigs, fixtures, and rotating devices are often used for economical surfacing of large numbers of parts. Parts which are large and costly to disassemble, such as power shovel buckets, can be hardsurfaced on site without dismantling the equipment, using semiautomatic or manual arc welding. Reliability of Various hardfacing and build-up alloys have been designed to perform specific functions with predictable results. The selection of the proper hardfacing alloys requires a knowledge of: 1. The wear factors under which it must operate. 2. The function of the part or equipment. 3. The base metal to which it must be applied. (Note: Hardfacing and hard surfacing are synonymous terms.)

216 Arc for for Low Carbon LESSON VIII Buildup Alloys - Buildup alloys are used for two purposes. They may serve as a supporting base for a more wear resistant overlay, or they may serve as a moderately wear resistant alloy surface when it is necessary to machine the part to size. In some cases, the buildup alloys may also be used for high strength attachment welds. The selection of the proper buildup alloy for parts worn beyond practical limits of hardfacing deposits is most important, since the success of the hardfacing overlay depends upon the rigidity and deformation resistance of the base metal. Experience has proven that in many cases where hardsurfacing overlays have failed, deformation of the base metal or buildup alloy took place, causing spalling of the overlay alloy Badly worn parts should be restored to within 3/16 to ¼ of their original size with a buildup alloy, which is compatible for welding to the base material and the hardfacing alloy Hardfacing Alloys - Hardfacing alloys are designed to provide maximum wear resistance to a specific wear factor or a combination of wear factors. Performance of the overlay is in direct relationship to the amount of carbide forming elements - chromium, molybdenum, tungsten, vanadium, and iron - in combination with carbon. Wear resisting carbides are formed when one of these elements is allowed to react with carbon, and as a result, is completely saturated forming a carbide consisting only of carbon and the element. The balance of the carbon remains in solution to form a semi-austenitic matrix (bonding metal) in which the hard, wear resistant carbides are evenly distributed. As the ratio of wear resistant carbides to alloy matrix increases, abrasion resistance increases. This same increase reduces the toughness of the overlay, thereby lowering its impact value. Figure 1 illustrates the effects of the carbide-to-matrix ratio. VERY HARD CARBIDES MATRIX Reliability of BETTER IMPACT RESISTANCE CARBIDES - MATRIX RATIO FIGURE 1 BETTER ABRASION RESISTANCE

217 LESSON VIII Arc The pure carbides most commonly used in hardfacing alloys are listed below in order of descending wear resistance. 1. Tungsten Carbide 2. Molybdenum Carbide for for Low 3. Chromium Carbide 4. Iron Carbide Tungsten carbide is the hardest of the commercially available carbides within the price structure feasible for hardfacing applications. It provides the maximum resistance to wear, although most hardfacing alloy deposits contain mixtures of two or more of the carbide forming elements. This balanced combination of carbides provides a tougher structure, resulting in a more wear resistant deposit Wear Factors Impact and Corrosion - These two wear factors can be discussed jointly because the requirements of a hardfacing alloy to combat them are similar Impact occurs when an object is struck by another object. Compression occurs in the form of weight or pressure. The material is said to have good resistance to impact or compressive loads when the yield strength of the material exceeds that of the opposing force Weld metals for hardsurfacing or buildup applications must have the following characteristics to successfully combat wear being caused by impact or compression Buildup Alloys - When the force of a blow is less than the yield strength of the deposit weld metal, the weld metal absorbs the force with no deformation. When the force of the blow exceeds the yield strength of the deposited weld metal, the weld metal deforms, resulting in roll over or upset. Carbon Reliability of COPYRIGHT 2000 THE ESAB GROUP, IN

218 Arc Hardfacing Alloys - Hardfacing alloys are designed to have very high compression resistance which usually results in low ductility and low shear strength. See Figure 3. LESSON VIII for HIGH COMPRESSION RESISTANCE LOW DUCTILITY LOW SHEAR STRENGTH for Low PROPERTIES OF HARDFACING DEPOSIT FIGURE Because of these characteristics, hardfacing materials should always be applied in the manner that allows impact to be absorbed as a compressive force. The term good impact resistance when applied to a hardfacing deposit, means that the deposit will not fail when impact is born as a compressive force as shown in Figure 4. Hardfacing alloys should not be applied where only shear forces exist. Carbon PULVERIZING HAMMER POWER SHOVEL TOOTH These sketches illustrate good examples of hardfacing applied so that impact is absorbed as a compressive force. ROLL CRUSHER IMPACT AS A COMPRESSIVE FORCE Reliability of FIGURE The base metal over which a hardfacing deposit is to be made must have a high yield strength to resist deformation. If the base metal has a low yield strength, it upsets under impact and the hardsurfacing alloy is stressed in tension. As a result, the hardfacing overlay breaks and spalling occurs as in Figure 5.

219 LESSON VIII HARDFACING Arc BASE METAL for MECHANICAL FAILURE DUE TO LOW YIELD BASE METAL FIGURE 5 for Low Carbon Abrasion - Abrasive wear occurs when hard particles or objects, such as sand, stone, or metallic particles, slide or roll over a surface under some amount of pressure. To scratch, scrape or gouge a surface, the abrasive particles must be harder than the surface they are in contact with. To prevent this surface damage, hardfacing supplies the logical harder wear surface, although other factors such as toughness must also be considered. Abrasion may be considered three general types: scratching, grinding, and gouging Scratching abrasion, or low stress abrasion, is the type of wear caused when the abrasive particles slide over a surface, such as sand or gravel sliding down the chute, or a plowshare working in sandy soil. The abrasive particles are not crushed. There are no large pieces impacting the surface Grinding abrasion, or high stress abrasion, is the wear caused when the abrasive particles are under a compressive stress sufficient to cause them to be crushed. Cement plant pulverizer parts and exposed drive sprockets on traced vehicles are examples of high stress abrasion Gouging abrasion is caused by relatively large sized abrasive pieces which cause grooves or visible gouges in a surface. Gouging abrasion is usually characterized by high impact forces. Rock crushing mill hammers and shovel teeth are examples of parts which are subject to gouging abrasion. In some instances, it may be necessary to sacrifice some amount of abrasion resistance for better impact properties Hardness - Although hardness is a desirable factor in combatting wear, it is not a true criteria of abrasion resistance. As mentioned earlier, those alloys containing a greater percentage of carbide forming elements will have better abrasion resistance. Hardness, in relation to abrasion resistance, is illustrated in the deposits of three alloys having equal matrix hardness, but unequal alloy composition in Figure 6. Reliability of

220 LESSON VIII 50 Rc 50 Rc 50 Rc Arc for for Low Carbon HIGH CARBIDE TO MATRIX RATIO. MOST ABRASION RESISTANT. LOW CARBIDE TO MATRIX RATIO. LESS ABRASION RESISTANT. HARDNESS IN RELATION TO ABRASION RESISTANCE FIGURE 6 NO CARBIDES. LEAST ABRASION RESISTANT The three examples shown are equal in hardness (Rockwell 50 on the C scale) but offer increased abrasion resistance as the carbide-to-matrix ratio is increased. As mentioned in Lesson I, hardness of the metal is tested by measuring its resistance to indentation. A Rockwell hardness tester produces a relatively large indentation or impression compared to the microscopic carbides suspended in the matrix, and the penetration may simply displace the carbide particles. Measurement is more of an indication of the hardness of the matrix than of the hard particles Heat - High temperature causes a reduction of wear resistance in metals by softening, reducing the strength and causing oxidation and scaling. An oxide scale can actually protect a surface from further oxidation in some cases, although in high temperature wear applications, the scale is constantly worn away, permitting further rapid oxidation. Alloys are available which retain their hardness at high temperatures and resist scaling and oxidation Corrosion - The corrosion caused by moisture is detrimental to hardfacing alloys Reliability of and if salts or acids are present in the water, corrosion will proceed at an accelerated rate. Many alloys derive some degree of corrosion resistance from a rapidly formed oxide coating on the surface. However, in an abrasive application, this coating is constantly being worn away, allowing corrosion to proceed at a rapid rate. By choosing the proper alloy, the corrosion rate can be minimized Many hardfacing applications will be subjected to a combination of the wear factors discussed above. Selecting the proper alloy requires that the wear factors be analyzed, and the alloy which most closely meets the needs is selected. As a simplified example, we might consider a back-hoe bucket which is used for digging trenches for

221 Arc for for Low Carbon Reliability of LESSON VIII burying gas lines to homes in an area where the topsoil is a sandy loam, and the sub-soil is a soft gumbo-like clay. For this application, only abrasion need be considered. If this back-hoe is moved to work in a new area where the soil contains shale and quartz rock in small and large pieces, impact and abrasion must be considered Base Metals - Basically, there are three types of steel used in the manufacture of equipment and parts subjected to heavy impact, compressive loads, and abrasive wear. These are the straight carbon steels, the low alloy high strength steels, and the austenitic manganese steels. All of these steels possess good deformation resistance and lend themselves well to the application of hardfacing alloys if the proper welding procedures are followed Carbon Steels - If the base metal is a mild carbon steel with a carbon content of.20% to.30%, preheat temperatures from 200 F to 300 F are recommended. If the carbon content of the base metal ranges from.30% to.45%, preheating to 300 F for thin sections, to 500 F for heavy sections, is necessary. For base metals to.45% to.80% carbon content, preheat temperatures of 500 F for thin sections, to 800 F for heavy sections, are necessary. High carbon tool steels containing carbon up to 1.7% are difficult to hardface because they are prone to cracking. After hardfacing, parts should be allowed to cool slowly Low Alloy High Strength Steels - Low alloy steels may be hardfaced as long as the proper welding procedure is followed. Preheat and postheat temperatures must be maintained. In some alloys, stress relieving may be necessary. As a rule of thumb, the welding procedure becomes more critical as the alloy and carbon content increases. Preheat temperatures of 100 F to 600 F are used for most alloys, although some low alloys with carbon content over.35% require preheat temperatures in the 800 F to 1100 F range Austenitic Manganese Steel - Austenitic manganese steel (known as Hadfield steel) is a high alloy containing 11-14% manganese and approximately 1.2% carbon. It is non-magnetic, unless it has been work-hardened. It is characterized by high strength, high ductility, and good wear resistance. It has no equal in its ability to work harden. It is widely used in equipment and parts that are subjected to heavy impact and compressive loads. These loads actually harden the new surface as the old is slowly worn away. It may actually have a shorter service life when used in sand where there are no impact loads to work harden the surface Unlike carbon and low alloy steels, preheating of high manganese steels is not recommended. Temperatures above 500 F to 600 F will induce embrittlement if sustained

222 Up to 200 Lesson 1 Arc for LESSON VIII for long periods of time. The lowest welding current, which produces good fusion with the base metal, should be used to minimize heat input. in one area for long periods of time should be avoided. A skip-welding technique should be used. This means that each succeeding pass should be made as far as possible from the preceding pass Preheating should only be used when the weldment has been exposed to temperatures below 50 F or when the weldment is massive. Then preheat temperatures of 100 F should not be exceeded. for Low Carbon Reliability of Type of Steel % Carbon Preheat Temp. F Type of Steel % Carbon Preheat Temp. F PLAIN CARBON STEELS NICKEL-CHROMIUM STEELS Below 0.20 SAE SAE SAE SAE CARBON-MOLYBDENUM STEELS SAE SAE SAE SAE MANGANESE STEELS SAE Silicon Structural SAE Medium Manganese SAE SAE SAE SAE SAE SAE LOW CHROMIUM-MOLYBDENUM STEELS 12% Manganese (Hadfield)* 1.25 Not Required 2.0% Cr, 0.5% Mo Up to HIGH STRENGTH STEELS 2.0% Cr, 0.5% Mo Manganese-Molybdenum % Cr, 1.0% Mo Up to Chromium-Copper-Nickel 0.12 max % Cr, 1.0% Mo Chromium-Manganese MEDIUM CHROMIUM-MOLYBDENUM STEELS NICKEL STEELS 5.0% Cr, 0.5% Mo Up to SAE Up to % Cr, 0.5% Mo SAE % Cr, 1.0% Mo 0.15 max Nickel Steel STAINLESS CHROMIUM STEELS SAE Type SAE Type SAE Type SAE STAINLESS CHROMIUM-NICKEL STEELS MOLYBDENUM STEELS 18-8 Type SAE Type Usually do SAE Type not require SAE Columbium preheat but SAE Type 347* 0.07 it may be SAE Molybdenum desirable to SAE Type 316* 0.07 heat to 32 F 18-8 Molybdenum Type * When ambient temperature is below 50 F, preheat to 100 F. Interpass temperatures over 500 F should be avoided. RECOMMENDED PREHEAT TEMPERATURES FIGURE 7.

223 Arc for for Low Carbon LESSON VIII The chart in Figure 7 lists the recommended preheat temperatures for welding the various grades of steel with the proper welding electrode. In hardfacing, the deposit is quite different from the base metal and variations dictated by experience may be necessary. 8.2 CLASSIFICATION OF HARDFACING ALLOYS Unlike the various electrodes, wires and filler metals in the previous lessons, hardfacing electrodes and filler metals are frequently proprietary alloys made to each manufacturer s specifications from formulas proven over the years. Very few of them are classified according to an AWS specification. Hardfacing systems may be divided into four basic categories: iron base, nickel base, cobalt base, and tungsten Iron Base Alloys - The iron base alloys as a group are the most widely used of all the hardfacing systems, and include a wide range of alloy types. These range from low alloy steels containing 2-12% alloying elements to high alloys containing 12-50% of these elements. This group includes a number of buildup alloys, as well as excellent hardfacing alloys. The iron based alloys are characterized by excellent resistance to abrasion in varying degrees or excellent resistance to impact, depending on alloy content. The higher alloy versions afford good wear resistant properties up to 1,000 F. Filler metal is available as coated electrodes, bare electrodes for oxyacetylene welding or gas tungsten-arc welding, solid or cored wires for submerged arc welding, and cored wires for open arc welding When surfacing with the high chromium-iron base alloys or other brittle alloys, a number of small cracks across the weld will appear. These cracks (known as checking or check cracks) are not detrimental because they do not penetrate into the tougher base metal or buildup alloy. They are, in fact, helpful in relieving stress buildup which would cause eventual longitudinal cracking in the fusion zone, leading to spalling of the hardfacing material. On heavy weldments where heat buildup is great, check cracks may not appear. They should be induced by a light water spray or by an occasional hammer blow on the weld surface The iron base alloys are the lowest in cost of the various hardfacing systems Nickel Base Alloys - The nickel base alloys contain 70-80% nickel, 11-17% chromium, % boron, and % silicon. The forming of various carbides and borides in the nickel matrix results in a deposit with excellent resistance to low temperature abrasion, and makes these the best alloys for metal-to-metal wear. These alloys also have Reliability of

224 Arc for for Low Carbon LESSON VIII good heat and corrosion resistance. They retain their hardness and temperatures up to 1200 F. The nickel base alloys lend themselves to flame spray and plasma arc applications, and are available largely in powder form. The cost of nickel base alloys is approximately five to six times that of the iron base alloys Cobalt Base Alloys - The cobalt base alloys consist of 45-63% cobalt, 24-29% chromium, % tungsten and % carbon. They are probably the most versatile of the hardfacing alloys because they resist heat, corrosion, abrasion, moderate impacts, galling, and metal-to-metal wear. Some alloys in this group remain substantially hard at temperatures up to 1500 F. Applications would include hot work equipment such as hot punches, valve parts, shear blades, etc In recent years, the price of cobalt has risen sharply since there are few sources in the world. The price of cobalt alloys per pound exceed that of the iron base alloys by approximately eighteen times Tungsten Base Alloys - The tungsten base alloys produce the most wear resistant deposits of the hard surfacing materials. They consist of hard granules of tungsten carbide distributed in a matrix of iron, carbon steel, cobalt alloy, or nickel alloy. The matrix, being somewhat softer than the carbides, wears away to a degree, leaving the hard carbides protruding. This roughness of the deposit renders these alloys useless for metal-to-metal applications, but ideal for applications such as rock drill bits and other mining, quarrying and digging applications These rods or electrodes are usually supplied as carbon steel tubes filled with tungsten carbide granules by weight. The steel matrix produced is not soft by any means, because when the tube melts, it dissolves enough of the tungsten and carbon to form a hard matrix and is capable of supporting the carbide granules Despite their excellent abrasion resistance, tungsten carbide alloys can only withstand impacts that do not produce compressive stress above their yield strength. Tungsten carbide alloys have low resistance to oxidation and low resistance to corrosion, unless deposited in a nickel or cobalt matrix. Hardness at high temperatures is approximately equal to the higher alloy iron base alloys if the tungsten carbide granules are in an iron or steel matrix. If in a nickel or cobalt matrix, better hot hardness can be achieved The cost of rods or electrodes consisting of tungsten carbide granules in a carbon steel matrix is approximately nine times that of the iron base alloys. If the matrix is a nickel or cobalt base alloy, costs will be higher. Reliability of

225 8.3 METHODS OF HARDFACING LESSON VIII Arc for for Low Hardfacing may be applied by a variety of methods and processes. The method chosen depends on a number of factors: a. Size and configuration of the part. b. End use of the hardfaced part. c. Depth of overlay required. d. Quality or smoothness of the overlay. e. Properties of the deposited overlay. f. Composition of the base metal. g. Available forms of the filler metal. h. Availability of the equipment necessary. i. Operator skill. Carbon Oxyacetylene Surfacing - The oxyacetylene process, an early method of applying surfacing alloys, is still in use today. The equipment is low in cost and consists of a torch, hoses, oxygen cylinder, acetylene cylinder, and two pressure regulators. Unlike oxyacetylene welding, a thin surface layer of the part in the immediate area being hardfaced, is brought to melting temperature. The hardfacing alloy is simultaneously melted into the molten area where it flows and spreads, and is fused to the surface in a thin smooth layer, with little dilution from the base metal. This method is commonly referred to as sweating The oxyacetylene process lends itself to servicing small parts, and fills grooves and recesses well. Other advantages are low dilution and low temperature gradients which minimize stresses and subsequent cracking. The operator requires much skill, and the deposition rate is very low. The process does not lend itself to automation, although some automatic set-ups have been developed Shielded Metal Arc Surfacing - SMAW, as described in Lesson II, is a versatile method of depositing hardfacing materials. The electrode has a flux coating to assure weld cleanliness. The equipment is the same as for SMAW and consists of a power source, Reliability of

226 Arc for for Low Carbon LESSON VIII weld cables, and an electrode holder. Surfacing may be performed in all positions and although the deposition rate is low, this process is especially useful where many short welds are to be made. This method is used extensively for field repair and rebuilding of equipment. The arc power may be either direct or alternating current. Dilution level is higher than in the oxyacetylene method, but can be kept to a minimum by using the proper welding current, using a weaving bead instead of a stringer bead and keeping the electrode in the puddle rather than on the base metal Gas Tungsten Arc Surfacing - This process utilizes the same equipment and procedures as GTAW as discussed in Lesson II. Deposition rate is low, but deposits are of high quality as long as efforts are made to keep dilution to a minimum. Normal dilution is somewhat greater than in oxyacetylene surfacing. Although argon, helium or mixtures of these gases may be used, dilution is the lowest when using pure argon. Gas Tungsten Arc Surfacing is used for many of the same type of applications as the oxyacetylene process. These are usually small wear surfaces which require a smooth high quality deposit Surfacing - Two types of continuous tubular electrodes are available for hardsurfacing; self-shielded and those which require a gas shield The self shielded type are by far the more popular, and in the hardfacing field, are known as open arc wires, indicating that they do not require externally applied granular flux or shielding gas. Deposits are comparable to those made with coated electrodes, but there is no stub loss. Since no shielding gas or flux handling equipment are necessary and the deposition rate is high, it is the most economical process for depositing hardfacing materials. Portability of the equipment allows this process to be used for hardfacing heavy equipment in the field, as well as in the shop. Dilution is higher than that of coated electrodes, but lower than that of submerged arc welding The gas shielded cored wires are used to a lesser extent. The shielding gases are used to reduce oxidation and minimize alloy loss. The use of CO 2 as a shielding gas has a tendency to increase penetration and thereby, increase dilution. Shielding gas and gas handling equipment also add to the deposition cost Submerged Arc Surfacing - Submerged arc welding utilizes both solid and Reliability of tubular wires, and a granular flux. It lends itself to automatic operation and is used for production surfacing of large numbers of parts in shops. The deposition rate and travel speeds are high, and the penetration is deep. Weld beads are smooth and of good quality. Heat input is high and for this reason, this process is not recommended for use on austenitic manganese steels. The deep penetration causes the highest dilution (up to 50%) of all

227 Arc for for Low LESSON VIII of the processes, which makes it necessary to deposit three or more layers to attain the full properties of the surfacing material Gas Metal Arc Surfacing - Gas metal arc surfacing is not widely used for hardfacing since most of the iron based alloys can be deposited more economically by other methods. It is used somewhat for out-of-position surfacing where the low penetration of the short circuiting transfer mode produces low dilution. It is also used for depositing non-ferrous alloys, such as aluminum-bronze, which cannot be applied by other methods. 8.4 SURFACING WITH POWDERS The processes previously discussed utilized hardfacing alloys in the form of solid or tubular rods and wires. Hardfacing alloys are also available in powdered form, and their method of application is quite different from the standard welding methods. powders are used for restoring worn surfaces and are widely used by original equipment manufacturers on new parts which require small hardened surfaces. The four major methods for applying powder metal hardfacing alloys are: flame spray, manual torch, plasma spray, and plasma arc welding Flame Spray Process - The flame spray process is accomplished with a special Carbon Reliability of gun-like apparatus which utilizes an oxyacetylene or oxyhydrogen flame. An air orifice aspirates the powder into the flame and deposits it on the surface. As the molten particles strike the surface, they flatten out and cool instantaneously. The bond is mechanical since there is no fusion with the base metal. If desired, fusion can be accomplished in a subsequent fusing operation with an oxyacetylene burner The process is very effective for shafts or small cylindrical parts which are rotated on a lathe while being surfaced. The surface must be cleaned and grit-blasted before applying the powder for a good initial bond. Deposition thickness can range from 1/32 to 3/ 32 inches Manual Torch Process - The manual torch process utilizes a special oxyacetylene torch which has a small hopper from which the surfacing powder is aspirated into the fuel gas stream. Application of the surfacing powder and fusion to the base metal take place in one operation. Single pass deposit thickness can range from to inches Plasma Arc Spray and Plasma Arc - These are two processes used to deposit powdered metal surfacing alloys utilizing a plasma arc torch. The plasma arc

228 Arc for for Low Carbon LESSON VIII torch has a non-consumable tungsten electrode, the end of which is behind a small constricting orifice. The electrode is surrounded by an inert gas such as argon. When the arc is established, either between the electrode and the constricting nozzle (non-transferred arc) or between the electrode and the work (transferred arc), the gas becomes ionized in the arc, forms a plasma, which is forced through the orifice by the plasma gas and impinges on the work piece. In plasma arc spraying, the non-transferred arc torch is used and the metal powder is introduced into the plasma gas. It is projected at high velocity against the object being surfaced. Because the metal particles are fully molten and travel at high velocity, the mechanical bond at the surface is very good and does not require subsequent fusing in most cases In plasma arc welding, the transferred arc method is used, which is a higher energy process. The base metal is actually melted, resulting in a fully fused surface. Both plasma arc methods lend themselves to high production, automatic surfacing applications requiring a thin overlay. 8.5 GENERAL RULES FOR HARDFACING Some general rules and precautions which will help to assure sound hardfacing deposits are listed below: a. Base Metal Identification - The base metal must be properly identified so that the proper buildup and/or hardfacing alloy can be selected. Also, base metal type will help determine the proper preheat and interpass temperature. A magnet will help to identify austenitic manganese steel since it is non-magnetic. The magnet should be tried at several locations on the part because work hardened areas will be slightly magnetic. b. Base Metal Preparation - The base metal must be cleaned with a grinding wheel and be free of rust, oil, grease, or other foreign matter. Cracks, tears, or gouges must be repaired using the proper filler metal or buildup alloy. c. Metal Removal - Rolled over and fatigued metal must removed. Work hardened surfaces of austenitic manganese steel should be ground away before buildup or surfacing. d. Buildup - Buildup of badly worn parts to within approximately ¼ of their final size with an appropriate buildup alloy prior to hardfacing is necessary. Reliability of

229 Arc for for Low e. Preheat and Interpass Temperature - The importance of observing preheat and interpass temperatures cannot be overstressed. Problems, such as spalling, cracking, and distortion can be minimized by proper preheating, interpass temperature, and slow or retarded cooling. f. Dilution - Dilution of the hardfacing deposits is expected in all cases where the hardfacing alloy is fused to the base metal and should be kept to a minimum. Excessive dilution with the base metal will alter the hardness of the deposit and in part, is a result of the heat input. Heat input is a function of the heat (amperage and voltage) and deposition rate (travel speed). LESSON VIII Note: As an example, a coated electrode, which operates at 225 amps and has a low deposition rate, may put more heat into the workpiece than an open arc continuous electrode, which operates at 400 amps but has a deposition rate three times higher than the coated electrode. The electrode manufacturer s recommended welding current should be used. Dilution will be greater in stringer beads (straight) than in a weaving bead. A weaving bead is recommended wherever possible. Electrical stickout (the amount of wire between the contact tip and the arc) must be kept relatively constant to control penetration in open arc welding. Long stickout decreases penetration and thereby, the amount of dilution. Short stickout can drastically increase penetration and dilution. g. Hardfacing Thickness - Too much hardfacing can cause more problems than too little. The hardfacing deposit should consist of no more than two layers and the total thickness should not exceed ¼ in most cases. Carbon 8.6 ECONOMICS OF HARDFACING Hardfacing filler metals are quite costly as noted earlier. The iron based alloys are the lowest in cost with the cobalt based alloys being the highest Consider a steel mill application requiring hardfacing on the guide blocks which will be subjected to abrasion and intermittent contact with hot billets at temperatures of approximately F. Logically, one might choose a cobalt base surfacing alloy, which will withstand continuously applied higher temperatures than the iron base types for this application. However, since the guide blocks are in contact with the billets intermittently for short periods of time, the constant operating temperature is well below 800 F. Iron base hardfacing alloys, which retain hardness at a constant 1000 F, are used in this application quite successfully at a considerable savings over the cobalt base types. Reliability of

230 Arc for for Low Carbon Reliability of LESSON VIII At today s high labor and overhead rates, the process chosen to apply hardfacing becomes of more importance. As an example, open arc cored electrodes can deposit metal three to five times faster than manual electrodes and should be used wherever possible. The deposition efficiency of the open arc cored electrodes range from 87-95%, while the deposition efficiency of stick electrodes is only 55-70%, depending on stub loss. If the cost of the coated hardfacing electrode is $1.00/lb., and the efficiency of that electrode is 60%, the cost of the amount of electrode necessary to deposit 1 lb. of weld metal is $ = $1.67. If the cost of an open arc electrode is $1.47/lb., and the deposition efficiency is 92%, the cost of the amount of electrode necessary to deposit 1 lb. of weld metal is $ = $ The more expensive open arc wire results in a savings of 7 for each pound of deposited weld metal. When all other factors, such as labor and overhead costs, deposition rate, and operating factor, are also taken into consideration, savings as high as 60% can be realized by using open arc continuous electrodes instead of coated electrodes. 8.7 ESAB HARDFACING ELECTRODES ESAB hardfacing electrodes are all of the iron based alloy type, which is the most widely used in the industry. They are available as Wear-Arc coated electrodes and as Wear-O-Matic continuous open arc electrodes Wear-Arc Coated - Wear-Arc electrodes have a lower hydrogen iron powder coating. The majority of the materials which are hard surfaced are steels which are hardened by the heat of welding, and are susceptible to under bead cracking due to hydrogen, as covered in Lesson IV. The use of low hydrogen electrodes minimizes this problem. Proper preheating must still be maintained however; especially on massive parts or highly restrained joints As with all low hydrogen types, Wear-Arc electrodes require that they be stored in a dry rod oven at F after the hermetically sealed can is opened Properly balanced amounts of iron powder are added to these electrodes which allow higher currents to be used without increasing the penetration and dilution. The higher welding current results in greater deposition rates. Wear-Arc electrodes allow welding in all positions Wear-O-Matic Open Arc Wires - Wear-O-Matic continuous tubular electrodes are internally stabilized, fluxed, and deoxidized. They require no shielding gas and represent the most economical means of reclaiming worn equipment and parts.

231 Arc for for Low LESSON VIII Wear-O-Matic BR Wires - This is a gas shielded tubular, continuous electrode designed for the repair and reclamation of railroad freight car bolster bowls. It requires a 98% argon, 2% oxygen shielding gas (the full description appears in section ). 8.8 HARDFACING ALLOY SELECTION FACTORS In order to select the proper Wear-Arc or Wear-O-Matic alloy, the controlling wear factors must be determined. Hardness of an overlay deposit is frequently considered as the prime objective in the selection of a hard surfacing alloy. This might be true if all wear problems involved only straight abrasive wear. However, most wear conditions are complicated by the addition of other wear factors which demand more than just hardness of a wear resistant alloy deposit, and the role of alloy content and balance becomes a prime factor. The importance of alloy content and balance to wear resistance is illustrated in the graphs that follow. Figure 8 shows the hardness for each Wear-Arc and Wear-O-Matic alloy. HARDNESS - ROCKWELL "C" SCALE Carbon WEAR-ARC 3IP WEAR-O-MATIC 3 WEAR-ARC NICKEL MANGANESE WEAR-O-MATIC NICKEL MANGANESE WEAR-ARC WH WEAR-O-MATIC WH WEAR-ARC 41P WEAR-ARC 51P WEAR-ARC 61P WEAR-O-MATIC 6 WEAR-ARC 12IP WEAR-O-MATIC 12 WEAR-O-MATIC SUPER WH WEAR-ARC 40 WEAR-O-MATIC 40 WEAR-O-MATIC 15 WEAR-O-MATIC BR WEAR-O-MATIC RAIL ARC AS WELDED WORK HARDENED Reliability of HARDNESS COMPARISON FIGURE 8

232 Arc for for Low WEAR-ARC 3IP WEAR-O-MATIC 3 WEAR-ARC NICKEL MANGANESE WEAR-O-MATIC NICKEL MANGANESE WEAR-ARC WH WEAR-O-MATIC WH WEAR-ARC 41P } WEAR-ARC 51P WEAR-ARC 61P WEAR-O-MATIC 6 WEAR-ARC 12IP WEAR-O-MATIC 12 WEAR-O-MATIC SUPER WH WEAR-ARC 40 WEAR-O-MATIC 40 WEAR-O-MATIC 15 } } } } LESSON VIII Carbon RELATIVE RESISTANCE TO IMPACT AND COMPRESSION FIGURE Hardness - While constant hardness for various hard surfacing alloys is maintained, the particular hardness of any one alloy is a property resulting from the amount of alloying elements, including carbon, used to create the carbide formations necessary to attain a desired amount of wear resistance. Succeeding graphs illustrate the importance of alloy content in relation to hardness in the selection of overlay alloys for resistance to wear caused by abrasion, impact, compression, and heat Figure 9 illustrates the relative resistance to impact and compressive force for each alloy. Note that Wear-O-Matic 15, the hardest of the alloys in Figure 8, shows the least impact resistance. This is due to the high ratio of carbides to matrix of this alloy which provide little resistance to shock. Therefore, it is concluded that hardness alone is not a reliable deciding factor in the choice of hard surfacing alloys. Reliability of Impact and compression are usually accompanied by other wear factors. In continuing this comparison of relative wear resistance of the various alloys to different wear factor combinations, the charts show only those alloys which are practical from an economic and application standpoint for the combination of wear factors involved.

233 LESSON VIII Arc for for Low WEAR-ARC 3IP WEAR-O-MATIC 3 WEAR-ARC NICKEL MANGANESE WEAR-O-MATIC NICKEL MANGANESE WEAR-ARC WH WEAR-O-MATIC WH WEAR-ARC 6IP WEAR-O-MATIC 6 WEAR-O-MATIC SUPER WH WEAR-ARC 12IP WEAR-O-MATIC 12 WEAR-ARC 40 WEAR-O-MATIC 40 Buildup Carbon Steel Buildup Manganese Steel Only Best for Overall Buildup - All Conditions Wear-Arc 6IP Best for Out-of-position Work Hardening Alloy - Severe Impact, Moderate Abrasion Best for Overall Service - Heavy Impacts and Severe Abrasion Best for Medium Impact - Extreme Abrasion RELATIVE RESISTANCE TO ABRASION AND MEDIUM TO HEAVY IMPACT FIGURE Abrasion & Impact - When abrasion is combined with heavy impact, the alloy Carbon Reliability of best suited to render the ultimate in wear resistance must have the proper balance of carbide forming elements in relation to matrix. The alloys shown in Figure 10 have this structure and are the most suitable buildup and hard surfacing alloys for varying degrees of impact and abrasion Although Wear-O-Matic Super WH, Wear-Arc 12 IP, and Wear-O-Matic 12 show equal resistance to abrasion and impact in Figure 10, Wear-O-Matic Super WH would be the better choice if more severe impacts are expected. Wear-Arc 12 IP electrodes or Wear-O-Matic 12 wires for semi-automatic open arc deposition should be used as a wear resistant overlay in the majority of cases where heavy impact and severe abrasion are in combination. Wear-Arc 12 IP and Wear-O-Matic 12 provide an abrasion resistant chromium carbide structure, in balance with a highly impact resistant matrix structure, providing maximum wear resistance throughout the deposited overlay Wear-Arc WH and Wear-O-Matic WH semi-automatic open arc wire are work hardening buildup alloys. Their high alloy nickel-chromium-manganese deposit is austenitic in structure and can be applied to carbon and austenitic manganese steel in any thickness. Deposits, when subjected to impact, work harden on the skin surface to 48 Rockwell C and provide wear resistance throughout the buildup deposit equal to that of Wear-Arc 12 and Wear-O-Matic 12.

234 Arc for for Low Overlaying a buildup deposit of WH alloy with the #12 alloy protects the WH deposit until it has work hardened Wear-Arc 6 IP and Wear-O-Matic 6 are illustrated as having good abrasion resistance under heavy impact loading. Wear-Arc 6 IP electrodes are designed especially to be used for all-position applications Figure 11 illustrates the relative wear resistant values of the alloys with the best abrasion resistance. Wear-O-Matic 15 provides the best resistance to straight abrasion; however, its impact resistance is low as can be seen in Figure 8. For this reason, Wear-Arc 40 or Wear-O-Matic 40 would be a better choice if medium impacts are involved. Both take on a high polish and have a low coefficient of friction. WEAR-ARC 40 WEAR-O-MATIC 40 LESSON VIII WEAR-O-MATIC 15 RELATIVE RESISTANCE TO STRAIGHT ABRASION FIGURE Figure 12 illustrates the ability of Wear-Arc 40 and Wear-O-Matic 40 hardfacing alloys to retain their abrasion resistant properties at constant temperatures up to 1000 F. Intermittently, temperatures up to 1800 F may be tolerated. Carbon 60Rc 50Rc 40Rc Reliability of 30Rc 20Rc DEGREES FARENHEIT HARDNESS IN RELATION TO TEMPERATURE RISE FIGURE 12

235 Arc Figure 12 also shows that the Wear-Arc WH and Wear-O-Matic WH buildup alloys will retain their hardness at elevated temperatures. The high chromium and nickel combination of this alloy imparts excellent high temperature properties and produces an austenitic work hardening structure. LESSON VIII for for Low 8.9 WEAR-ARC COVERED ELECTRODES AND WEAR-O-MATIC WIRES FOR HARDFACING The following pages contain complete information on each of the individual buildup and hardfacing alloys supplied by ESAB as they appear in the hardfacing catalog. Each of them should be studied since several of the test questions will be based on the information contained on these pages. Carbon Reliability of

236 8.9.1 Wear-Arc LESSON VIII Arc for for Low Introduction Surfacing is the application of wear-resistant alloys to metal parts subject to destructive wear caused by abrasion, impact, compression, heat, or corrosion. The Wear-Arc electrodes are designed for manual arc welding for surfacing parts. Two types of overlay alloys are recommended to correct destructive wear patterns: Buildup Alloys Because hardsurfacing alloys are limited by maximum thickness of deposit, badly worn parts must be built up prior to depositing the wear-resistant material. Wear-Arc 3 IP, Nickel Manganese, and WH are designed for buildup applications. These alloys possess good deformation resistance and provide a strong bond with the base metal. This helps to prevent roll-over or spalling and provides a sound base for hardsurfacing. Alloys alloys are designed to provide maximum resistance to specific wear factors or combination of wear factors. The performance of these alloys is in direct relation to the amount of carbide forming elements present in combination with carbon. The carbon reacts with the carbide forming elements chromium, tungsten, molybdenum, etc. creating hard carbides from which the overlay material derives its wear resistance. These carbides are evenly distributed in a matrix and as the ratio of carbides to matrix increases, abrasion resistance increases and toughness or ductility decreases. The chart below shows the relative impact resistance or ductility and the abrasion or wear resistance of the Wear-Arc line. Carbon Relative Resistance to Impact and Abrasion Buildup Alloys Wear-Arc 3IP Wear-Arc Nickel Manganese Wear-Arc WH Impact Resistance Abrasion Resistance Currents for Wear-Arc Alloys Wear-Arc 4 IP Wear-Arc 5 IP Wear-Arc 6 IP Wear-Arc 12 IP Wear-Arc 40 Electrode 3 IP - 4 IP - 5 IP - 6 IP Nickel Diameter Flat Vertical Overhead 12 IP Manganese WH 40 1/8" (3.2 mm) /32" (4.0 mm) /16" (4.8 mm) /4" (6.4 mm) Reliability of

237 Wear-Arc 3 IP LESSON VIII Wear-Arc Nickel Manganese Arc for for Low Carbon No AWS Classification AC/DCEP (Electrode Positive) Electrode Imprint Marking: 3 IP Buildup Alloy Carbon Steels Abrasion-Resistant Steels Description: Wear-Arc 3 IP weld metal provides excellent resistance to wear caused by heavy impact and compressive loads, and is most suitable as a base alloy for hardsurfacing overlays. Wear-Arc 3 IP should be used where maximum machinability of a surface deposit is desired and as the final overlay. The ductility and compressive strength of Wear- Arc 3 IP weld metal is adequate for the wear problem of many applications. Typical applications are: steel mill wobblers and coupling boxes, bearing journals, steel mill roll necks and ends, forging hammer dies, and all carbon steel parts requiring buildup prior to hardsurfacing. Procedure: Wear-Arc 3 IP electrodes have superior welding characteristics in all positions. Because of the iron powder in the coating, higher current settings may be used than with conventional electrodes. Area Covered per Pound, 1/8" (3.2 mm) Depth in. ( cm ) 2 2 Typical Mechanical Properties As Welded Yield Strength, psi (MPa) 91,500 (631) Tensile Strength, psi (MPa) 101,750 (702) % Elongation in 2" (51 mm) 24 % Reduction in Area 64 Hardness 29 Rc* *Two Layers weaving on 1020 Steel Weld deposits can be cut with oxy-acetylene torch or by air carbon-arc cutting. Typical Undiluted Weld Metal Analysis (%) C Mn Si Cr Mo 0.20 Max Properties of Deposited Weld Metal: The chromium and molybdenum alloy balance imparts impact and compression resistance, as well as considerable wear resistance to the weld metal in all thicknesses of buildup. Deposits are machinable, forgeable, and respond to heat treatment. Standard Diameters and Packages 1/8" (3.2 mm) x 10# (4.5 kg) HSC 5/32" (4.0 mm) x 10# (4.5 kg) HSC 3/16" (4.8 mm) x 10# (4.5 kg) HSC 1/4" (6.4 mm) x 10# (4.5 kg) HSC AWS Class EFeMn-A AC/DCEP (Electrode Positive) Electrode Imprint Marking: Ni Mn Buildup Alloy Attachment Manganese Steel Severe Impact Code and Specification Data: AWS A5.13 Description: Wear-Arc Nickel Manganese weld deposit is crack resistant and forms a ductile, high-strength fusion bond on manganese steel. The austenitic structure of the weld provides excellent resistance to wear caused by heavy impact and compressive loads. Under conditions of continuous impact, the deposit surface work hardens to a BHN of 510. Wear-Arc Nickel Manganese is best suited for applications where severe impact and compressive forces are encountered continuously. Because of the sound, highstrength welds from this electrode, it should also be used for the attachment welding of wear plates, teeth, rounds, and shapes of manganese steel. Procedure: Wear-Arc Nickel Manganese electrodes require no special technique of application. When welding manganese steel, these general recommendations should be followed: 1. Weld only on sound, clean, unhardened base metal. 2. The use of preheat on manganese steel is not recommended. Avoid overheating the base metal by using the lowest current which produces good metal transfer and arc characteristics. Keep austenitic manganese steel below 600 F (316 C), interpass temperature. Typical Mechanical Properties As Welded Yield Strength, psi (MPa) 62,000 (427) Tensile Strength, psi (MPa) 116,000 (800) % Elongation in 2" (51 mm) 45 Hardness 90 Rb* Work-Hardened Hardness 48 Rc* *Two Layers on Manganese Steel Weld deposits can be cut with oxy-acetylene torch or by air carbon-arc cutting. Typical Undiluted Weld Metal Analysis (%) C Mn Si Ni Standard Diameters and Packages 5/32" (4.0 mm) x 10# (4.5 kg) HSC 3/16" (4.8 mm) x 10# (4.5 kg) HSC 1/4" (6.4 mm) x 10# (4.5 kg) HSC Reliability of

238 Arc for for Low Carbon Wear-Arc WH No AWS Classification AC/DCEP (Electrode Positive) Electrode Imprint Marking: WH Buildup Alloy High Strength Manganese & Carbon Steels Attachment Severe Impact Description: The weld deposit of Wear-Arc WH is high in alloy content, extremely deformation resistant, and has 2-4 times greater wear resistance than work-hardened austenitic manganese steel. WH contains approximately 34% alloy, properly balanced to perform the dual purpose of a work-hardening, wear-resistant buildup alloy, and also a high strength welding alloy. The alloy is austenitic and produces tough, crack-resistant welds. Wear-Arc WH produces a dependable bond to manganese steel. Users of type 308, 309, 310, or 312 stainless steel electrodes for rebuilding and repair of equipment constructed of manganese steel find Wear-Arc WH to be a superior electrode for the job. Deposits of Wear-Arc WH, when subjected to high impact and compressive loads, develop a surface hardness of Rockwell C and still retain a tough, resilient, deformation-resistant mass under the workhardened surface. Procedure: Wear-Arc WH electrodes are designed for welding with AC/DCEP (Electrode Positive) in all positions. When welding high-carbon steel, preheat to F ( C). Do not preheat manganese steel. Hold the electrode at an angle of 15 in the direction of travel with as short an arc as possible without allowing the coating to touch the weld pool. Stringer beads are preferable. Weaving should be limited to 2-1/2 times the electrode diameter. Slag should be checked thoroughly between passes. For vertical welding, the electrode should be held perpendicular to the plate using a very slight oscillation from side to side on the root bead. When welding in the overhead position, hold a short arc with no oscillation of the electrode. Area Covered per Pound, 1/8" (3.2 mm) Depth in. ( cm ) 2 2 Typical Mechanical Properties LESSON VIII Wear-Arc 14% WH Manganese Weld Metal Steel Plate As Welded Heat Treated Yield Strength, psi (MPa) 77,000 (551) 50,000 (345) Tensile Strength, psi (MPa) 97,500 (672) 86,000 (593) 120,000 (827) % Elongation in 2" (51 mm) 36 35/45 Hardness 23 Rc* 16 Rc Work-Hardened Hardness 48.5 Rc* 48 Rc *Two Layers on 1020 Steel Weld deposits cannot be cut with oxy-acetylene torch or by air carbon-arc cutting. Typical Undiluted Weld Metal Analysis (%) C Mn Si Cr Ni This chart illustrates a hardness probe of deposited Wear-Arc WH weld metal after work-hardening by peening. Notice that although the outer skin of the deposit shows a hardness of 48 Rc, the metal underneath retains the ductility necessary to resist impact or compressive loads. This toughness prevents spalling and overroll and provides an excellent base for harsurfacing overlays. Reliability of

239 Arc for for Low Carbon Wear-Arc 4 IP No AWS Classification AC/DC Electrode Imprint Marking: 4 IP Alloy Metal-to-Metal Wear Impact & Abrasion Carbon Steels & Description: Wear-Arc 4 IP is an all position, iron powder, low hydrogen hardsurfacing electrode providing sound overlays on carbon and low alloy steels, as well as many abrasion-resistant steels. The low hydrogen coating of this electrode promotes excellent fusion with the above steels and on buildup alloys without underbead cracking. Wear-Arc 4 IP electrodes are designed to provide hard, deformation-resistant, crack-free weld metal for resistance to metal-to-metal wear involving impact, compression, and abrasion. Typical applications are: Dragline bucket pins & links Shovel rollers Dredge bucket lips Shovel latch pins Dredge driving tumblers and keepers Dredge spud points Tractor idlers Can brake drums Tractor rollers Mill brake drums Wheels (Mine car, Shovel idlers skip car, etc.) Cable sheaves Ditcher drive segments Cable sheave shafts Ditcher rollers Elevator bucket lips Shovel boom heels Procedure: The iron powder, low hydrogen coating of Wear-Arc 4 IP electrodes provides excellent arc characteristics and high deposition rates. A slight weaving technique may be used. Deposit thickness should be limited to 3/8" (9.5 mm) maximum. Area Covered per Pound, 1/8" (3.2 mm) Depth in. ( cm. ) 2 2 Typical Mechanical Properties: Wear-Arc 4 IP weld metal is characterized by its smooth appearance, high hardness, and high compressive strength. The deposit is not machinable but may be forged or heat treated. Weld deposits can be cut with oxy-acetylene torch or by air carbon-arc cutting. Hardness of Deposited Metal: Two layers, weave bead on 1020 steel Rockwell C. Typical Undiluted Weld Metal Analysis (%) C Mn Si Cr Mo Wear-Arc 5 IP No AWS Classification AC/DCEP (Electrode Positive) Coded Electrode Marking: 5 IP LESSON VIII Alloy High impact and moderate abrasion Carbon steels and low alloy steels Description: Wear-Arc 5 IP is an all-position, low hydrogen hardsurfacing composite electrode providing sound overlays on carbon and low alloy steels, as well as many abrasion-resistant steels. Wear-Arc 5 IP is recommended for the reclamation of parts subject to wear caused by moderate to high impact and moderate abrasion. Typical applications are: Dipper Shovels Dipper Lips Bulldozer Trunnions Drag Line Bucket Lips Classifier Screens Bucket Pins Mud Pumps Buckets and Impellers Procedure: Wear-Arc 5 IP electrodes are designed for welding with AC or DCEP. When welding out of position, DCEP is preferred. A slight weaving technique may be used. Typical Mechanical Properties: Deposits are non-machinable, but may be forged at red temperatures. The deposit is heat treatable and magnetic. Weld deposits can be cut with oxy-acetylene torch or by air carbon-arc cutting. Hardness of Deposited Metal: One layer on 1020 mild steel Rockwell C Two layers on 1020 mild steel Rockwell C Typical Chemical Analysis of Weld Deposit (%) C Mn Si Cr Mo Reliability of

240 Arc for for Low Carbon Wear-Arc 6 IP No AWS Classification AC/DC Electrode Imprint Marking: 6 IP Alloy High Abrasion & Light Impact Carbon Steels and Manganese Steels Description: The iron powder low hydrogen coating of Wear-Arc 6 IP electrodes promotes good bonds with manganese and carbon steels. Wear-Arc 6 IP is recommended for the reclamation of parts subject to wear caused by abrasion and light impact. This electrode is ideal for field work where parts cannot be positioned for downhand welding. Typical applications are: Shovel buckets and teeth Dragline buckets and teeth Pug mill paddles Tamping tools Screens Asphalt mixer paddles Crushing equipment Granulators Trunnions Truck bodies Procedure: The iron powder, low hydrogen coating of Wear-Arc 6 IP electrodes provides excellent arc characteristics and high deposition rates in all positions using AC or DC, either polarity. A weaving technique is recommended. Deposit thickness should be limited to two passes or 1/ 4" (6.4 mm) maximum. Area Covered per Pound, 1/8" (3.2 mm) Depth in. ( cm. ) 2 2 Typical Mechanical Properties: Deposits are not machinable and are smooth, requiring a minimum amount of grinding to bring them to shape. Deposits are not affected by heat treatment and can be forged at red heat. Weld deposits cannot be cut with oxy-acetylene torch or by air carbon-arc cutting. Hardness of Deposited Metal: Two layers, weave bead on 1020 mild steel Rockwell C Typical Undiluted Weld Metal Analysis (%) C Mn Si Cr Wear-Arc 12 IP LESSON VIII No AWS Classification AC/DC Electrode Imprint Marking: 12 IP Alloy High Impact & Good Abrasion Resistance Carbon Steels and Manganese Steels Description: In addition to heavy impact and good abrasion resistance, the high alloy content of Wear-Arc 12 IP also provides good resistance to erosion and corrosion. Wear-Arc 12 IP is recommended to prolong the service life of new and worn parts subject to wear caused by abrasion and impact. Typical applications are: Dipper teeth and lips Dragline bucket lips Conveyor bucket lips Roll crushers Gyratory crusher parts Muller tires Impactors Hammer mill parts Procedure: The iron powder, low hydrogen coating of Wear-Arc 12 IP electrodes provides excellent arc characteristics and high deposition rates in all positions using AC or DC, either polarity. Weaving technique or stringer beads may be used. Deposit thickness should be limited to two passes or 1/4" (6.4 mm). Area Covered per Pound, 1/8" (3.2 mm) Depth in. ( cm. ) 2 2 Typical Mechanical Properties: Check cracks may appear as the deposit stress relieves itself. These cracks do not impair the wear resistance of the deposit, but do prevent warpage or distortion of the base metal. Deposits are non-machinable and do not respond to heat treatment. Weld deposits cannot be cut with oxy-acetylene torch or by air carbon-arc cutting. Hardness of Deposited Metal: Two layers, weave bead on 1020 mild steel Rockwell C Typical Undiluted Weld Metal Analysis (%) C Mn Si Cr Mo Reliability of

241 Arc for for Low Carbon Wear-Arc 40 No AWS Classification AC/DCEP (Electrode Positive) Electrode Imprint Marking: 40 Alloy Extreme Abrasion & Medium Impact Description: Wear-Arc 40 is a coated electrode with a special core wire and the proper amount of alloys in the coating to produce a deposit of highly abrasive resistant chrome carbides in a matrix of iron and chromium. The use of a special core wire gives much better arc action and also allows the electrode to operate at higher current settings. Deposits resist galling and seizing, and take a high polish when subject to sliding abrasive action. The hardness and wear-resistant properties of this alloy are retained at temperatures up to 1000 F (538 C) which makes it suitable for many applications where intermittent high temperature service is involved. Wear-Arc 40 is designed for use on steel mill twist guides, steel mill entry guides, wire guides, conveyor chain, and agricultural tools. This electrode also gives excellent service on certain crushing and quarrying equipment where high abrasive wear is the primary wear factor. On many applications where heat and abrasion are the prime wear factors, Wear-Arc 40 alloy may be the most economical alloy. As illustrated in the temperature hardness chart, this alloy has excellent hardness at constant temperatures up to about 1000 F (538 C). In considering this alloy for a heat and abrasion application, a constant operating temperature must be estimated. For example, a steel mill guide block surface with Wear-Arc 40 withstands exposure to intermittent contact with hot billets of bars at temperatures of F ( C). This is possible because sufficient time elapses between contacts to prevent a high temperature build-up. In this example, the constant operating temperature is only about 500 F (260 C). Temperature Hardness 58 Rc 50 Rc 40 Rc 30 Rc 100 Rb 60 Rb Temperature ( C) Temperature ( F) LESSON VIII Procedure: Wear-Arc 40 electrodes have good welding characteristics in flat and vertical-up positions. These electrodes operate on either AC or DCEP (Electrode Positive) welding current. Weaving technique or stringer beads may be used. Limit deposit thickness to two passes. Area Covered per Pound, 1/8" (3.2 mm) Depth in. ( cm. ) 2 2 Typical Mechanical Properties: The weld metal deposit of Wear-Arc 40 cannot be forged at any temperature and does not respond to heat treatment. Weld deposits cannot be cut with oxyacetylene torch or by air carbon-arc cutting. Hardness of Deposited Metal: Two layers on mild steel 57 Rockwell C Typical Undiluted Weld Metal Analysis (%) C Mn Si Cr Reliability of

242 LESSON VIII Arc for for Low Carbon Wear-O-Matic Semiautomatic Cored Wires Introduction The Wear-O-Matic cored wires for welding, buildup, and hardsurfacing are designed to provide maximum versatility, economy, and welder efficiency in their use. These 7/64" (2.8 mm) diameter wires may be used with either a constant current power source and voltage sensing variable speed wire drive or a constant potential power source and a constant speed wire feeder. These wires combine the skill of the welder and the speed of automatically fed, continuous wire welding. The variety of electrodes available plus the speed, efficiency, and economy of the Wear-O-Matic process make it the most economical means of reclaiming worn equipment parts. When hard-surfacing with stick electrodes, a minimum of two inches (50 mm) of every 14-inch (350 mm) electrode are thrown away as a stub end. This is a loss of nearly 15% of the total weight of the electrodes purchased by the user. This waste is a major contributing factor toward the low deposition efficiency (55 to 70%) normally obtained with stick electrodes. The deposition efficiency of the open arc process is usually 87 to 95%. No flux dams are required. Expensive, time consuming flux handling is eliminated, as well as the cost of the submerged arc flux. There are no shielding gases that have to be purchased, except for the Wear-O-Matic BR wires. Wires are internally stabilized, fluxed, and deoxidized. High current density and fast travel speed result in low heat input to the work, concentrated in a small area, when used with the 7/64" (2.8 mm) alloy wires. There is little slag and no flux blanket to hold heat in the weld area and cause overheating of the base metal. The total result is low penetration and less dilution of the weld metal. The higher alloy deposits provide increased wear resistance, often superior to deposits of manual electrodes of similar analysis. Most semiautomatic processes (submerged arc, inert gas) have limited use. The simplicity of open arc wire feed equipment makes it extremely portable for field or shop use. All of the visibility and advantages of manual metal arc welding are preserved. The operator can visually control the deposited metal and irregular contours can be followed easily. Wear-O-Matic 7/64" (2.8 mm) cored wires for semiautomatic application are fabricated tubular electrodes, internally stabilized for good arc characteristics without the use of shielding gas or submerged arc granular flux. Each of the grades available has a carefully balanced alloy content to produce specific properties in the deposited weld metal, providing the required wear resistance intended for each grade. Relative Resistance to Impact and Abrasion Buildup Alloys Alloys Wear-O-Matic 3 Wear-O-Matic 6 Wear-O-Matic Wear-O-Matic 12 Nickel Manganese Wear-O-Matic WH Wear-O-Matic Super WH Wear-O-Matic Bolster Repair Wear-O-Matic 40 Wear-O-Matic 15 Impact Resistance Abrasion Resistance Reliability of

243 Arc for for Low Carbon Wear-O-Matic 3 No AWS Classification DCEP or DCEN (Electrode Positive or Negative) Open Arc Buildup Alloy High Impact Resistance Carbon Steels; Description: Wear-O-Matic 3, a 7/64" (2.8 mm) diameter open-arc wire, is a buildup alloy for multiple layer application on all weldable carbon and low alloy steels. The weld deposit is sound and machinable. Wear-O-Matic 3 is recommended for the rebuilding of carbon and low alloy steel parts prior to hardsurfacing or for use where a machinable resurfacing alloy is required. Procedure: The Wear-O-Matic 3 wire should be deposited with the open arc only, using direct current, straight or reverse polarity. The recommended amperage range is amperes at arc volts. A weaving technique is recommended when a machinable deposit or multiple layer buildup is desired. Stringer beads may be used; however, this produces a harder deposit and should be limited to three passes. Preheat is not required for weld metal. A 200 F (98 C) preheat is recommended to prevent excessive deposit hardness when a small deposit is to be applied to a heavy section and the deposit is to be machined. The requirement for preheat usually depends on the properties of the base metal. The higher alloy steels generally require some preheat. Typical Mechanical Properties: The tough deposits of Wear-O-Matic 3, through the addition of manganese and molybdenum in balance with other alloying elements, produce a buildup structure for carbon and low-alloy steels which is highly resistant to deformation and impact. Although this alloy has high compressive strength and excellent ductility, Wear-O- Matic 3 is not appropriate for use as a high strength joining alloy. Hardness of Deposited Metal: Two layer deposit on 1045 steel weaving technique 30 Rockwell C Stringer bead 36 Rockwell C Abrasion Resistance: Moderate Impact Resistance: High Compressive Strength: High Machinability: Excellent Relief Checking: None Typical Undiluted Weld Metal Analysis (%) C Mn Si Cr Mo LESSON VIII Wear-O-Matic Nickel Manganese No AWS Classification DCEP (Electrode Positive) Open Arc Buildup Alloy Attachment Manganese Steel Description: Wear-O-Matic Nickel Manganese 7/64" (2.8 mm) diameter alloy wire for open arc, semiautomatic application provides the necessary high tensile and yield strength to permit this alloy to be used for both attachment welding and buildup applications on austenitic manganese steel. The weld metal has excellent ductility and provides an ideal base for subsequent hardsurfacing overlays. Wear-O-Matic Nickel Manganese open arc wires are recommended for the rebuilding and high strength welding of austenitic manganese steel parts and equipment. Procedure: Wear-O-Matic Nickel Manganese 7/64" (2.8 mm) diameter wire should be deposited with the open arc only, using DCEP (Electrode Positive). The recommended amperage range is amperes at arc volts. Austenitic manganese steel should not be overheated because loss of ductility may result. Use a skip-welding technique to keep the manganese base metal below 600 F (300 C). Typical Mechanical Properties: Wear-O-Matic Nickel Manganese wire deposits high strength, ductile weld metal having excellent resistance to impact with moderate abrasion resistance. The weld deposit improves with work-hardening, and is not machinable. It can be cut with an oxy-acetylene flame and by air carbon-arc cutting. Hardness of Deposited Metal: Two layer deposit on austenitic manganese steel: As Welded 90 Rockwell C Work-Hardened 48 Rockwell C Abrasion Resistance: Moderate improves with cold working Impact Resistance: Excellent Machinability: Non-machinable. Finish by grinding. Relief Checking: None Deposit Thickness: Multiple layers may be applied. Typical Undiluted Weld Metal Analysis (%) C Mn Si Ni Reliability of

244 Arc for for Low Carbon Wear-O-Matic BR No AWS Classification Composite Metal Cored Wire DCEP (Electrode Positive) Gas Shielded-Buildup Alloy Bolster Repair Description: The bolster wire is a gas shielded fabricated wire designed for the repair and reclamation of railroad freight car bolster bowls. This wire was designed to be used with the Gas Metal Arc process with a 98% argon/2% oxygen shielding gas mixture. With the metal cored process and the argon/oxygen shielding, a 98% deposition efficiency is possible. In addition, the wire deposits a spatter-free, slag-free weld having a Rockwell C undiluted weld hardness. It offers excellent abrasion resistance, but does not unduly impair machinability. Wear-O-Matic BR is recommended for the 40 through 100 ton bolsters of either grade B or C type castings. Another application is the rebuilding of railroad couplers. The excellent combination between hardness and ductility provides use where an unlimited layer buildup wire is needed. Depending on the carbon content and material thickness, preheat may be necessary to prevent cracking. Procedure: Wear-O-Matic BR is recommended to be used either in the semiautomatic or full automatic welding mode using a variable speed weld fixture to rotate the bolster. When welding in the automatic mode, there are only two adjustments the operator must be concerned with; they are electrode stick-out and the horizontal adjustment for overlapping of each weld. The first step in bolster repair is to chamfer the worn area of the female lip by air carbon-arc cutting, preferably with a 5/8" x 3/16" x 12" (15.9 mm x 4.8 mm x 12.7 mm) flat electrode. The female lip of the center of the bolster should be beveled approximately 1/8" (3.2 mm) from the O.D. of the top of the raised area of the female, to approximately a 45 bevel to the bottom seat of the center female section of the bolster. This will serve to open up this area into a 45 square butt to the widest point of wear across the top of the raised casting. The large amount of wear resistant weld metal from the top of the buildup joint down to the root will serve to give much longer life to this very important part of the total bolster. It will especially counteract the upsetting or flow of metal common to the impacting of any force to an edge of this kind. LESSON VIII 1. Chamfer the total circumference of the female flange at a 45 angle-1/8" (3.2 mm) from the O.D. of the female flange to the bottom seat of the flange. 2. Clean all excess or loose slag residue left from the carbon-arc or flame cutting operation. If bolster is machined as above, cleaning is unnecessary. 3. Place proper size bolster ring of either the 14" x 1-1/ 8" (356 mm x 28.6 mm) or 14" x 1-3/8" (356 mm x 34.9 mm) size, using centering device from 2" (50.8 mm) holding pin hole of the bolster; tack weld ring in place using a 3 IP or E7018 electrode to the female bottom of the bolster casting. Reliability of

245 Arc for for Low Carbon Wear-O-Matic BR (cont d. from previous page) 4. Use approximately six (6) tack welds equally spaced. Remove centering device used. The bolster ring now serves as the inner wall or square portion of the groove to be built up with the wear material. 5. Preheat casting in the heavy center portion of the bolster to be built up to 150 F (66 C) if a Grade B, 250 (121 C) if Grade C. This will minimize the possibility of cracking. 6. It is necessary to use only water-cooled equipment, guns, water-circulating equipment, etc. Put in the first pass at the root of the square butt joint using either the 1/16" (1.6 mm) or 5/64" (2.0 mm) Wear-O-Matic BR electrode with a lagging gun angle to assure proper gas coverage. A 98% argon/2% oxygen, or 95% argon/5% oxygen gas mix is recommended for use with this electrode. Be sure to put in a shallow first pass if necessary with the same size wire. 7. All consecutive buildup passes necessary should be made using the 3/32" (2.4 mm) Wear-O-Matic BR electrode with a lagging gun angle. This will speed completion of building up this section of the bolster. The last pass can be made to the inside edge of the bolster ring to the outside edge of the female lip of the casting, making a finish pass over this entire surface. 8. A single 3/16" (4.8 mm) fillet weld should be made around the I.D. of the tack welded preplaced bolster ring, using the 3IP or the Wear-O-Matic BR alloy. This will tend to give added wear in this area. We recommend 25 to 40 cubic feet of gas per hour and a water-cooled torch. The following amperes and volts for the three (3) size wires can be used as a guide: 3/32" (2.4 mm) Wear-O-Matic BR 325/375 Ampere DCEP 29/31 Volts 5/64" (2.0 mm) Wear-O-Matic BR 275/300 Ampere DCEP 28/29 Volts 1/16" (1.6 mm) Wear-O-Matic BR 225/250 Ampere DCEP 23/25 Volts Typical Properties and Features: LESSON VIII 1. The use of a fabricated wire permits precise control of the weld metal composition. 2. The use of the inert shielding gas permits a spraytype transfer having minimum penetration and spatter. In addition, slag removal is completely eliminated. 3. Costs of reclamation are reduced 60% over Shielded Metal Arc and covered wires through labor saved with the metal cored process. 4. A bolster bowl repaired with the Wear-O-Matic BR wire has % more longevity than the original casting. 5. The wire produces a weld that is more resistant to metal roll-overs and metal upset caused by severe impacting at the high speed the railroad industry operates today. 6. The same wire can be used for building up pads on bolster castings, along with a variety of other wear resistant applications in railroad maintenance shops. 7. Weld deposits can be cut with oxy-acetylene torch or by air carbon-arc cutting. Hardness Typical Range, Hardness Deposit Condition (Undiluted) Rc(1) Rc 3 layers on C1020, as welded 35 to layers on C1020, stress relieved (2) 25 to 30 Undiluted, as welded 35 to Undiluted, stress relieved (2) 28 to (1) Welded using 98% Argon/2% Oxygen Shielding Gas (2) Stress relieved for one (1) hour at 1150 F ± 25 F (621 C ± 14 C) Typical Undiluted Weld Metal Analysis (%) C Mn Si Cr Mo Reliability of

246 Arc for for Low Carbon Wear-O-Matic WH No AWS Classification DCEP (Electrode Positive) Open Arc Buildup Alloy Wear Resistant Attachment Manganese and Description: Wear-O-Matic WH alloy is a dual purpose wire for use of the economic, semiautomatic open arc process when welding manganese to carbon steel and for buildup applications involving severe impact or compressive loads. The high alloy content of this fabricated wire is balanced to perform a dual function, retaining the high strength properties of a good attachment welding material while also serving as an excellent workhardening, wear-resistant buildup material. The weld metal is austenitic at room temperature. Procedure: Wear-O-Matic WH is manufactured in 7/64" (2.8 mm) diameter, designed for semiautomatic, open arc application. Operation: Open Arc only DCEP (Electrode Positive) Amperage: 225 to 300 amps, at volts Attachment : Wear-O-Matic WH is suitable for production fabrication of manganese steel and alloy steel parts which formerly required the use of a wire such as 308 stainless. Wear- O-Matic WH gives the user the added advantage of semiautomatic welding. The outstanding physical properties of Wear-O-Matic WH weld metal are valuable in the field maintenance attachment welding of dipper teeth, tractor grousers, blade replacements, rounds and flats used as wear plates. Typical Mechanical Properties: Wear-O-Matc WH weld metal is tough and resilient, and provides strong, crack-resistant welds. The surface of the deposit is work-hardenable, especially by impact. However, the mass of material under this work-hardened surface remains strong and tough, resisting upset, overroll, and spalling. For this reason, Wear-O-Matic WH is an excellent underlay for hardsurfacing alloys on parts subject to heavy impact and compressive loads. As Welded Yield Strength, psi (MPa) 70,100 (483) Tensile Strength, psi (MPa) 102,900 (709) % Elongation in 2" (51 mm) 36 Fracture Test Sound Fissures None LESSON VIII Hardness of Deposited Metal: Two layer deposit on 1045 steel: As Welded 18 Rockwell C Work-Hardened 41 Rockwell C Typical Undiluted Weld Metal Analysis (%) C Mn Si Cr Ni Wear-O-Matic Super WH No AWS Classification DCEP (Electrode Positive) Open Arc- Alloy Severe Impact Resistance with some Abrasion Description: Wear-O-Matic Super WH deposits a tough, workhardenable alloy weld metal. Wear-O-Matc Super WH is intended for the buildup or overlay of objects subjected to severe impact or impact with some abrasion. It may be used for multiple layer surfacing without cracking or spalling. Procedure: Wear-O-Matic Super WH - 7/64" (2.8 mm) size should be welded by the open arc process only, using direct current, reverse polarity. An electrode extension stickout of about two inches from the contact tip to the work should be used with amperes. Either weaving or stringer bead technique may be used satisfactorily. Typical Mechanical Properties: The tough alloy combination of the weld metal deposited by Wear-O-Matic Super WH gives it outstanding resistance to impact in service. The impacted surface of the weld metal work-hardens to the extent that it resists wear from combined impact and abrasive service. Hardness of Deposited Metal: Two layer deposit on 1045 steel: As Welded 30 Rockwell C Work-Hardened 46 Rockwell C Six layer deposit on 1045 steel: As Welded 30 Rockwell C Work-Hardened Rockwell C Typical Undiluted Weld Metal Analysis (%) C Mn Si Cr Ni Reliability of

247 Arc for for Low Carbon Wear-O-Matic 6 No AWS Classification DCEP or DCEN (Electrode Positive or Negative) Open Arc- Alloy Severe Impact with Abrasion Carbon Steel, Low Alloy Steel, Manganese Steel Description: Wear-O-Matic 6, a 7/64" (2.8 mm) diameter open-arc wire, is a hardsurfacing alloy wire designed to provide impact and abrasion resistance. It may be applied to carbon, low alloy and manganese steel parts. Wear-O-Matic 6 is recommended for applications involving impact and abrasion on such parts as conveyor buckets, dragline and power shovel bucket lips and sides, scraper blades, and dredge bucket parts. Procedure: Wear-O-Matic 6-7/64" (2.8 mm) diameter wire should be deposited with the open arc only, using direct current, straight or reverse polarity. The recommended amperage range is amperes at arc volts. Weaving beads are recommended to develop maximum wear resistance in this alloy. Preheat is not required for sound weld metal on twolayer deposits. Where deposits over 1/4" (6.4 mm) in thickness are desired, a preheat and interpass temperature of at least 400 F (204 C) is recommended in order to achieve maximum impact and compressive wear resistance. Typical Mechanical Properties: Wear-O-Matic 6 open-arc wire is a chromium molybdenum alloy combining exceptionally good compressive strength with high hardness. Deposits may be heat treated and are forgeable. Weld deposits can be cut with oxy-acetylene torch or by air carbon-arc cutting. Hardness of Deposited Metal: Two layer deposit on 1045 steel weaving technique 48 Rockwell C Abrasion Resistance: Moderate Impact Resistance: Very High Compressive Strength: High Machinability: Machinable with carbide tools Relief Checking: None Typical Undiluted Weld Metal Analysis (%) C Mn Si Cr Mo LESSON VIII Wear-O-Matic 12 No AWS Classification DCEP (Electrode Positive) Open Arc- Alloy Heavy Impact and Severe Abrasion Description: Wear-O-Matic 12-7/64" (2.8 mm) diameter wire is a hardsurfacing alloy combining good compressive strength and hardness to provide excellent resistance to wear caused by heavy impact and abrasion. Wear-O-Matic 12 is also recommended for power shovel and dragline bucket parts, dredge buckets, and hammermill parts. Procedure: Wear-O-Matic 12-7/64" (2.8 mm) diameter wire should be deposited with the open arc only, using direct current, reverse polarity. The recommended amperage range is amperes at arc volts. A weaving technique is recommended to develop maximum abrasion and impact resistance. Application thickness should be limited to two passes or 1/4" (6.4 mm). Typical Mechanical Properties: The deposit of Wear-O-Matic 12 open-arc wire has good compressive strength. It is not machinable and cannot be forged. Relief checks may occur with this alloy but do not impair its performance. Weld deposits cannot be cut with oxy-acetylene torch or by air carbon-arc cutting. Hardness of Deposited Metal: Two layer deposit on 1045 steel weaving technique 50 Rockwell C Abrasion Resistance: High Impact Resistance: Excellent Compressive Strength: Excellent Typical Undiluted Weld Metal Analysis (%) C Mn Si Cr Mo Reliability of

248 Arc for for Low Carbon Wear-O-Matic 15 No AWS Classification DCEP or DCEN (Electrode Positive or Negative) Open Arc- Alloy Severe Abrasion Resistance Description: Wear-O-Matic 15-7/64" (2.8 mm) diameter open arc wire is a hardsurfacing alloy with outstanding resistance to wear caused by severe abrasion. Wear-O-Matic 15 produces extremely high abrasionresistant qualities that make it an outstanding surface material for pug mill knives and augers, dry cement pump screws, conveyor screws, and asphalt mixer paddles and shanks. Procedure: Wear-O-Matic 15-7/64" (2.8 mm) diameter wire should be deposited with the open arc only, using direct current, straight or reverse polarity. Recommended amperage range, amperes at arc volts. Weaving bead of 1-1/2" (38 mm) in width is recommended in order to develop maximum abrasion-resistant qualities in the deposit. Deposit thickness should be limited to two passes or 1/4" (6.4 mm). Typical Mechanical Properties: The deposit of Wear-O-Matic 15 open-arc wire attains maximum hardness as deposited and is unaffected by heat treatment. In most cases, stress relief check cracks appear in the deposit but do not impair the abrasion resistance or the ability of the deposit to take a high polish. Weld deposits cannot be cut with oxy-acetylene torch or by air carbon-arc cutting. Hardness of Deposited Metal: Two layer deposit on 1045 steel weaving technique 60 Rockwell C Abrasion Resistance: Outstanding Impact Resistance: Light Compressive Strength: High Machinability: Non-machinable. Finish by grinding. Typical Undiluted Weld Metal Analysis (%) C Mn Si Cr Mo LESSON VIII Wear-O-Matic 40 No AWS Classification DCEP (Electrode Positive) Open Arc- Alloy Severe Abrasion and Compression Description: Wear-O-Matic 40-7/64" (2.8 mm) diameter wire is a hardsurfacing alloy with high chromium and carbon content. It is designed to provide outstanding resistance to wear caused by abrasion in combination with compression. These wear-resistant properties are retained at temperatures up to 1000 F (538 C). Deposits take a high polish and do not gall or seize when subjected to metal-to-metal wear. The unique wear-resistant properties of Wear-O-Matic 40 allow a wide variety of applications: Crusher parts Hammermill parts Steel mill parts Mill guides Procedure: Wear-O-Matic 40-7/64" (2.8 mm) diameter wire should be deposited with the open arc only, using direct current, reverse polarity. The recommended amperage range is amperes at arc volts. A weaving bead of 1-1/2" (38 mm) in width is recommended. Deposit thickness should be limited to two passes or 1/4" (6.4 mm). Typical Mechanical Properties: Wear-O-Matic 40 open-arc wire is a high alloy material combining chromium and carbon with other alloying elements to provide extremely high abrasion resistance and good compressive strength. The deposit is not heat treatable and cannot be forged. Weld deposits cannot be cut with oxy-acetylene torch or by air carbon-arc cutting. Hardness of Deposited Metal: Two layer deposit on 1045 steel weaving technique 58 Rockwell C Abrasion Resistance: Excellent Heat Resistance: Excellent up to 1000 F (538 C) Impact Resistance: Light Compressive Strength: Good Machinability: Non-machinable. Finish by grinding. Relief Checking: A uniform pattern of check cracks appears in the deposit as it cools, indicating the excellent stress-relief characteristics of this alloy. This check crack pattern is necessary to prevent distortion in large parts when an alloy of this hardness and alloy content is applied. Typical Undiluted Weld Metal Analysis (%) C Mn Si Cr Mo Reliability of

249 Arc Spalling APPENDIX A LESSON VIII - GLOSSARY OF TERMS - The loss of particles or pieces from a surface due to cracking. LESSON VIII for Galling - The condition between rubbing surfaces where high spots or protrusions on a surface become friction welded to the mating surface, resulting in spalling and further deterioration. for Low Matrix Shear Hadfield Steel - A crystalline phase of an alloy in which other phases are imbedded. - A force which causes deformation or fracture of a member by sliding one section against another in a plane or planes which are substantially parallel to the direction of the force. - The name sometimes used for austenitic manganese steel derived from its inventor. Carbon Coefficient of Friction Stringer Bead - A value used in engineering calculations which is an indicator of the ability of one material to slide on another. A low coefficient of friction indicates a low rate of wear between sliding surfaces. - A straight weld bead opposed to a weaving bead. In surfacing, the weaving bead produces less dilution because the weld puddle is always in contact with the part of the bead produced on the previous oscillation rather than the base metal. Reliability of

250 Arc for for Low Carbon BASIC WELDING FILLER METAL TECHNOLOGY A Correspondence Course LESSON IX ESTIMATING AND COMPARING WELD METAL COSTS ESAB ESAB & Cutting Products Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

251 Arc TABLE OF CONTENTS LESSON IX ESTIMATING AND COMPARING WELD METAL COSTS for for Low Carbon Reliability of Section Nr. Section Title Page 9.1 Introduction Factors For Cost Formulas Labor & Overhead Deposition Rate Operating Factor Deposition Efficiency Deposition Efficiency of Coated Efficiency of Flux Cored Wires Efficiency of Solid Wires for GMAW Efficiency of Solid Wires for SAW Cost of, Wires, Gases and Flux Cost of Power Deposition Data Tables Cost Calculations Calculating the Cost Per Pound of Deposited Weld Metal Calculating the Cost Per Foot Of Deposited Weld Metal Cost Calculations - Example Example Other Useful Formulas Amortization of Equipment Costs Appendix A Lesson IX Test Questions Appendix B Problem 1 Worksheet Appendix C Problem 2 Worksheet... 27

252 Arc for for Low Carbon LESSON IX ESTIMATING AND COMPARING WELD METAL COSTS 9.1 INTRODUCTION Estimating the costs of depositing weld metal can be a difficult task because of the many variables involved. Design engineers must specify the type and size of weld joint to withstand the loads that the weldment must bear. The welding engineer must select the welding process, and type of filler metal that will provide the required welds at the least possible cost. With wages and the cost of operations rising, selection of the process that deposits weld metal most expediently must be carefully considered. Labor and overhead account for approximately 85% of the total welding cost costs may be divided into two categories; the fixed costs involved regardless of the filler metal or welding process selected, and those related to a specific welding process. Fixed costs entail material handling, joint preparation, fixturing, tacking, preheating, weld clean-up and inspection. Although some of these items will be affected by the process and filler metal chosen, they are a necessary part of practically all welding operations. Calculating these costs is best left to the manufacturer since they will depend upon his capabilities and equipment. The cost of actually depositing the weld metal however, will vary considerably with the filler metal and welding process selected. This cost element is influenced by the user s labor and overhead rates, deposition rate and efficiency of the filler metal, operating factor, and cost of materials and power This lesson will cover cost estimating for steel weldments produced by the four most common arc welding processes in use today: shielded metal-arc welding, gas metal-arc welding, flux cored arc welding and submerged arc welding. Gas tungsten arc welding will not be considered here because the variables, such as deposition rate and efficiency, are dependent on operator technique, stub use, etc. The GTAW process is a relatively costly method of depositing weld metal, and is usually chosen for weld quality or material thickness and composition limitations, rather than economy. Reliability of Large firms will frequently conduct their own deposition tests and time studies to determine welding costs, but many smaller shops do not know the actual cost of depositing weld metal In estimating welding costs, all attempts should be made to work with accurate data, which in some cases is difficult to secure. For this reason, this lesson contains charts, graphs

253 Arc LESSON IX and tables that provide average values that you may use. Electrode manufacturers will usually supply the deposition data you need through their Technical Services Department, if it is not already published in their literature. for 9.2 FACTORS FOR COST FORMULAS Labor and Overhead - Labor and overhead may be considered jointly in your calculations. Labor is the welder s hourly rate of pay including wages and benefits. Overhead for Low includes allocated portions of plant operating and maintenance costs. Weld shops in manufacturing plants normally have established labor and overhead rates for each department. Labor and overhead rates can vary greatly from plant to plant, and also with location. Figure 1 shows how labor and overhead may vary and suggests an average value to use in your calculations when the actual value is unknown. HOURLY WELDING LABOR & OVERHEAD RATES Small Shops $10.00 to $25.00/hr. Large Shops $25.00 to $50.00/hr Average $30.00/hr. APPROXIMATE LABOR AND OVERHEAD RATES FIGURE 1 Carbon Deposition Rate - The deposition rate is the rate that weld metal can be deposited by a given electrode or welding wire, expressed in pounds per hour. It is based on continuous operation, not allowing time for stops and starts caused by inserting a new electrode, cleaning slag, termination of the weld or other reasons. The deposition rate will increase as the welding current is increased When using solid or flux cored wires, deposition rate will increase as the electrical stick-out is increased, and the same amperage is maintained. True deposition rates for each welding filler metal, whether it is a coated electrode or a solid or flux cored wire, can only be established by an actual test in which the weldment is weighed before welding and then again after welding, at the end of a measured period of time. The tables in Figures 8-11 contain average values for the deposition rate of various types of welding filler metals. These are based on welding laboratory tests and published data. Reliability of

254 Arc for for Low LESSON IX Operating Factor - Operating factor is the percentage of a welder s working day that is actually spent welding. It is the arc time in hours divided by the total hours worked. A 45% (.45) operating factor means that only 45% of the welder s day is actually spent welding. The balance of time is spent installing a new electrode or wire, cleaning slag, positioning the weldment, cleaning spatter from the welding gun, etc When using coated electrodes, (SMAW) the operating factor can range from 15%-40% depending upon material handling, fixturing and operator dexterity. If the actual operating factor is not known, an average of 30% may be used for cost estimates when welding with the shielded metal arc welding process When welding with solid wires (GMAW) or metal cored welding (MCAW) using the semi-automatic method, operating factors ranging from 45%-55% are easily attainable. Use 50% for cost estimating purposes For welds produced by flux cored arc welding (FCAW) semi-automatic- ally, the operating factor usually lies between 40%-50%. For cost estimating purposes, use a 45% operating factor. The estimated operating factor for FCAW is about 5% lower than that of GMAW to allow for slag removal time. Carbon In semi-automatic submerged arc welding, slag removal and loose flux handling must be considered. A 40% operating factor is typical for this process Automatic welding using the GMAW, FCAW, and SAW processes, requires that each application be studied individually. Operating factors ranging from 50% to values approaching 100% may be obtained depending on the degree of automation The chart in Figure 2 shows average operating factor values for the various welding processes that may be used for cost estimating when the actual operating factor is not known. Reliability of WELDING PROCESS + SMAW * GMAW *FCAW *SAW 30% 50% 45% 40% *Semi-Automatic Only + Metal Cored Wires are Included APPROXIMATE OPERATING FACTOR FIGURE 2

255 Arc LESSON IX Deposition Efficiency - Deposition efficiency is the relationship of the weight of the weld metal deposited to the weight of the electrode (or wire) consumed in making a weld. It can be accurately determined only by making a timed test weld, and carefully weighing the weldment and the electrode or wire, before and after welding. The efficiency can then be calculated by the formula: for Deposition efficiency = Weight of Weld Metal Weight of Electrode Used (or) Deposition Rate (lbs/hr) Burn-off Rate (lbs/hr) for Low The deposition efficiency tells us how many pounds of weld metal can be expected from a given weight of the electrode or welding wire purchased. As an example, 100 pounds of a flux cored electrode with an efficiency of 85%, will produce approximately 85 pounds of weld metal, while 100 pounds of coated electrode with an efficiency of 65%, will produce approximately 65 pounds of weld metal, less the weight of the stubs discarded, as described below Coated - The deposition efficiency of coated electrodes by AWS definition, and in published data, does not consider the loss of the unused electrode stub that is discarded. This is understandable since the stub length can vary with the operator and the application. Long continuous welds are usually conducive to short stubs while on short intermittent welds, stub length tends to be longer. Figure 3 illustrates how the stub loss influences the electrode efficiency when using coated electrodes. Carbon In Figure 3, a 14 long by 5/32 diameter E7018 electrode at 140 amperes is considered. It is 75% efficient, and a two inch stub loss is assumed. The 75% efficiency applies 12" LENGTH OF ELECTRODE CONSUMED AMOUNT THAT BECOMES WELD METAL (LENGTH CONSUMED X EFFICIENCY) 2" STUB LENGTH 9" 14" LOST TO SLAG,SPATTER & FUMES DEPOSITION EFFICIENCY = 75% actual efficiency, including stub loss = 9 14 = 64.3% Reliability of FIGURE 3-4-.

256 Arc for for Low LESSON IX only to the 12 of the electrode consumed in making the weld, and not to the two inch stub. When the two inch stub loss and the 25% that is lost to slag, spatter and fumes are considered, the efficiency minus stub loss is lowered to 64.3%. This means that for each 100 pounds of electrodes purchased, you can expect an actual deposit of approximately 64.3 pounds of weld metal if all electrodes are used to a two inch stub length The formula for the efficiency including stub loss is important, and must always be used when estimating the cost of depositing weld metal by the SMAW method. Figure 4 shows the formula used to establish the efficiency of coated electrodes including stub loss. It is based on the electrode length, and is slightly inaccurate, i.e. it does not take into consideration that the electrode weight is not evenly distributed, due to the flux being removed from the electrode holder end. (Indicated by the dotted lines in Figure 3.) Use of the formula will result in a % error that will vary with electrode size, coating thickness and stub length. The formula however, is acceptable for estimating purposes For the values given in Figure 3 the formula is: EFFICIENCY MINUS STUB LOSS = (ELECTRODE LENGTH STUB LENGTH) X DEPOSITION EFFICIENCY ELECTRODE LENGTH Carbon EFFICIENCY MINUS STUB LOSS FIGURE 4 Efficiency - Stub Loss = (14-2) x = 12 x = 9 14 =.6429 or 64.3% In the above example, the electrode length is known, the stub loss must be estimated, and the efficiency taken from the tables in Figures 8 and 9. Use an average stub loss of three inches for coated electrodes if the actual shop practices concerning stub loss are not known The following stub loss correction table will assist in your determination of coated electrode efficiencies. Figure 5 lists various efficiencies at a given stub loss. Reliability of

257 Arc for for Low STUB LOSS CORRECTION TABLE FOR COATED ELECTRODES EFFICIENCY INCLUDING STUB LOSS FIGURE 5 LESSON IX ELEC. DEPOSITION 2" 3" 4" 5" LENGTH EFFICIENCY STUB STUB STUB STUB 60% 50.0% 45.0% 40.0% 35.0% 65% 54.2% 48.7% 43.3% 37.9% 12" 70% 58.3% 52.5% 46.6% 40.8% 75% 62.5% 56.2% 50.0% 43.7% 80% 66.6% 60.0% 53.3% 46.6% 60% 51.4% 47.1% 42.8% 38.5% 65% 55.7% 51.1% 46.4% 41.8% 14" 70% 60.0% 55.0% 50.0% 45.0% 75% 64.3% 58.9% 53.6% 48.2% 80% 68.5% 62.8% 57.1% 51.4% 60% 53.3% 50.0% 46.6% 43.3% 65% 57.7% 54.2% 50.5% 46.9% 18" 70% 62.2% 58.3% 54.4% 50.5% 75% 66.6% 62.5% 58.3% 54.2% 80% 71.1% 66.6% 62.2% 57.7% Carbon Efficiency of Flux Cored Wires - Flux cored wires have a lower flux-to-metal ratio than coated electrodes, and thereby, a higher deposition efficiency. Stub loss need not be considered since the wire is continuous. The gas shielded wires of the E70T-1 and E70T-2 types have efficiencies of 83%-88%. The gas shielded basic slag type (E70T-5) is 85%-90% efficient with CO2 as the shielding gas, and the efficiency can reach 92% when a 75% argon, 25% CO2 gas mixture is used. Use the efficiency figures in Figure 9 for your calculations if the actual values are not known The efficiency of the self-shielded types of flux cored wires has more variation because of the large variety of available types that have been designed for specific applications. The high deposition general purpose type, such as E70T-4, is 81%-86%, depending on wire size and electrical stick-out. The chart in Figure 9 shows the optimum conditions for each wire size and may be used in your calculations Efficiency of Solid Wires for GMAW - The efficiency of solid wires in GMAW is very high and will vary with the shielding gas or gas mixture used. Using CO2 will produce the most spatter and the average efficiency will be about 93%. Using a 75% argon-25% CO2 gas mixture will result in somewhat less spatter, and an efficiency of approximately 96% can be expected. A 98% argon-2% oxygen mixture will produce even less spatter, and the average efficiency will be about 98%. Stub loss need not be considered since the wire is continuous. Figure 6 shows the average efficiencies you may use in your calculations if the actual efficiency is not known. Reliability of

258 .045" - 1/16" GMAW Lesson 1 Arc LESSON IX Efficiency of Solid Wires for SAW - In submerged arc welding there is no spatter loss and an efficiency of 99% may be assumed. The only loss during welding is the short piece the operator must clip off the end of the wire to remove the fused flux that forms at the termination of each weld. This is done to assure a good start on the succeeding weld. for Shielding Gas Efficiency Range Average Efficiency Pure CO % 93% 94-98% 96% for Low 98% Ar - 2% O % 98% DEPOSITION EFFICIENCIES - GAS METAL ARC WELDING CARBON AND LOW ALLOY STEELS FIGURE 6 Carbon Cost of, Wires, Gases and Flux - You must secure the current cost per pound of the electrode or welding wire, plus the cost of the shielding gas or flux if applicable, from the supplier. The shielding gas flow rate varies slightly with the type of gas used. The flow rates in Figure 7 are average values whether the shielding gas is an argon mixture or pure CO2. Use these in your calculations if the actual flow rate is not available. In the submerged arc process (SAW) the ratio of flux to wire consumed in the weld is approximately 1 to 1 by weight. When the losses due to flux handling and flux recovery systems are considered, the average ratio of flux to wire is approximately 1.4 pounds of flux for each pound of wire consumed. If the actual flux-to-wire ratio is unknown, use the 1.4 for cost estimating. FCAW/MCAW Wire Diameter.035".045" 1/16" 5/64" - 1/8" CFH APPROXIMATE SHIELDING GAS FLOW RATE - CUBIC FEET PER HOUR FIGURE 7 Reliability of Cost of Power - Cost of electrical power is a very small part of the cost of depositing weld metal and in most cases is less than 1% of the total. It will be necessary for you to know the power cost expressed in dollars per kilowatt- hour ($/kwh) if required for a total cost estimate.

259 LESSON IX Arc 9.3 DEPOSITION DATA CHARTS SHIELDED METAL ARC WELDING - Coated. for for Low Carbon E6010 ELECTRODE DEPOSITION EFFICIENCY DIAMETER AMPS RATE lbs/hr % 3/ % 1/ % % 5/ % % 3/ % % 7/ % % E6011 ELECTRODE DEPOSITION EFFICIENCY DIAMETER AMPS RATE lbs/hr % 3/ % 1/ % 5/ % 3/ % 7/ % 1/ % E6012 ELECTRODE DEPOSITION EFFICIENCY DIAMETER AMPS RATE lbs/hr % 1/ % 5/ % % 3/ % % 7/ % DEPOSITION DATA - SMAW - COATED ELECTRODES FIGURE ELECTRODE DEPOSITION EFFICIENCY DIAMETER AMPS RATE lbs/hr % 3/ % 1/ % 5/ % % % 3/ % % % 7/ % % % E7014 ELECTRODE DEPOSITION EFFICIENCY DIAMETER AMPS RATE lbs/hr % 1/ % % 5/ % % 3/ % % 7/ % % 1/ % % Reliability of NOTE: EFFICIENCY RATES DO NOT INCLUDE STUB LOSS

260 LESSON IX Arc for for Low Carbon E7016 ELECTRODE DEPOSITION EFFICIENCY DIAMETER AMPS RATE lbs/hr % 1/ % % 5/ % % % 3/ % % % % 1/ % % % % E7024 ELECTRODE DEPOSITION EFFICIENCY DIAMETER AMPS RATE lbs/hr % 1/ % % 5/ % % % 3/ % % % 7/ % % 1/ % LOW ALLOY, IRON POWDER ELECTRODES TYPES E7018, E8018, E9018, E10018, E11018, AND E12018 ELECTRODE DEPOSITION EFFICIENCY DIAMETER AMPS RATE lbs/hr % 3/ % % % 1/ % % % 5/ % % % 3/ % % % 7/ % % % 1/ % % % DEPOSITION DATA - SMAW - COATED ELECTRODES (Con't.) FIGURE 9 Reliability of NOTE: EFFICIENCY RATES DO NOT INCLUDE STUB LOSS

261 0.045 Lesson 1 LESSON IX Arc for for Low Carbon FLUX CORED ARC WELDING/METAL CORED ARC WELDING - Deposition data for gas shielded FCAW on all low alloy wire types and MCAW on all alloy types. FLUX CORED ARC WELDING (FCAW) GAS SHIELDED TYPES E70T-1, E71T-1, E70T-2, E70T-5, & ALL LOW ALLOY TYPES ELECTRODE DEPOSITION EFFICIENCY DIAMETER AMPS RATE lbs/hr % % % % % % % % % % % % % % % % % % % 1/ % % % % % % % 5/ % % % 3/ % % % DEPOSITION DATA - FCAW/MCAW METAL CORED ARC WELDING (MCAW) E70T-1, E71T-1, AND ALL ALLOY TYPES ELECTRODE DEPOSITION EFFICIENCY DIAMETER AMPS RATE lbs/hr % % % % % % % % % % 1/ % % % % 5/ % % % % 3/ % % % % NOTE: DATA REFLECTS USE OF 75% ARGON 25% CO2 GAS SHIELDING. DEPOSITION RATES AND EFFICIENCIES WILL INCREASE WITH THE USE OF HIGHER ARGON MIXTURES. FIGURE 10 Reliability of

262 Arc for for Low Carbon Reliability of FLUX CORED ARC WELDING, GAS METAL ARC WELDING, AND SUBfor self-shielded FCAW, and solid wires using MERGED ARC WELDING - Deposition data GMAW and SubArc. FLUX CORED ARC WELDING (FCAW) SELF-SHIELDED ELECTRODE DEPOSITION EFFICIENCY DIAMETER AMPS RATE lbs/hr % E70T-3 3/ % E70T-4 3/ % % E70T-6 5/ % 3/ % E70T-6 3/ % 7/ % E71T % 5/ % E71T-8 5/ % 3/ % E61T8-K6 5/ % E70T % 1/ % 5/ % E71T % 1/ % 5/ % 3/ % E70T4-K2 3/ % E71T-GS % % % 1/ % 5/ % DEPOSITION DATA FIGURE 11 SUBMERGED ARC WIRES (1" STICKOUT) LESSON IX GAS METAL ARC WELDING SOLID WIRES DEPOSITION RATE lbs/hr ELECTRODE 98%A/2%O275%A/25%CO2Straight CO2 DIAMETER AMPS *98% *96% *93% / * USE THIS FIGURE AS THE DEPOSITION EFFICIENCY IN THE COST CALCULATIONS ON SHEET ONE. ELECTRODE MELT-OFF EFFICIENCY DIAMETER AMPS RATE lbs/hr % 5/ / Assume / % Efficiency 5/ / NOTE: Values for 1" Stickout

263 9.4 COST CALCULATIONS - EXAMPLE 1 LESSON IX Arc Calculating the Cost Per Pound of Deposited Weld Metal Example 1 - Calculate the cost of welding 1,280 ft. of a single bevel butt joint as shown in Figure 14 using the following data. for for Low Carbon a. Electrode - 3/16 diameter, 14 long, E7018, operated at 25 volts, 250 amps. b. Stub Loss - 2 inches c. Labor and Overhead - $30.00/hr d. Electrode Cost - $.57/lb e. Power Cost - $.045/kWh The formulas for the calculations are shown on the Weld Metal Cost Worksheet in Figure 12. The following explains each step in the calculations. Line 1- Labor and Overhead - $30.00/hr (given) Deposition Rate - From shielded metal arc welding deposition data chart in Figure 9 = 5.36 lbs/hr. Operating Factor - Since it is not stated above, use an average value of 30% (.30) shown in Figure 2. The cost of labor and overhead per pound of deposited weld metal can now be calculated as $18.66/lb. Line 2 - Electrode Cost Per Pound - $.57 (given) Deposition Efficiency - From the shielded metal arc welding deposition table in Figure 9 = 74.6%. Since this is a coated electrode, the efficiency must be adjusted for stub loss by the formula following Figure 3. We know that the electrode length is 14" and the stub loss is 2" (given). The formula becomes: Efficiency - Stub Loss = (14-2) x =.639 or 63.9% 63.9% is the adjusted efficiency to be used in Line 2. The cost of the electrode per pound of deposited weld metal can now be calculated as $.89/lb. Line 3 - Not applicable for coated electrodes. Line 4 - Not applicable for coated electrodes. Reliability of

264 LESSON IX Arc EXAMPLE 1 WELD METAL COST WORKSHEET COST PER POUND OF DEPOSITED WELD METAL for for Low LABOR & OVERHEAD ELECTRODE GAS LABOR & OVERHEAD COST/HR DEPOSITION OPERATING RATE (LBS/HR) x FACTOR ELECTRODE COST/LB DEPOSITION EFFICIENCY GAS FLOW RATE (CU FT/HR) x GAS COST/CU FT DEPOSITION RATE (LBS/HR) = = = x.30 = = = = = N A FLUX POWER FLUX COST/LB x 1.4 DEPOSITION EFFICIENCY COST/kWh x VOLTS x AMPS 1000 x DEPOSITION RATE = = X x 25 x x 5.36 = = = = 5,360 N A TOTAL COST PER LB. OF DEPOSITED WELD METAL SUM OF 1 THROUGH 5 ABOVE $ Carbon 7. COST PER POUND OF DEPOSITED WELD METAL COST PER FOOT OF DEPOSITED WELD METAL X POUNDS PER FOOT OF WELD JOINT = 19.60x.814 = $ TOTAL FEET OF WELD X COST PER FOOT COST OF WELD METAL - TOTAL JOB = 1,280x = $20,422 FIGURE 12 Reliability of

265 Arc for LESSON IX Line 5 - Cost of Power - $.045/kWh (given). Volts & Amperes - 25V and 250A (given). Constant - The 1,000 already entered, is a constant necessary to convert to watt-hours. Deposition Rate lbs/hr as used in Line 1. The cost of electrical power to deposit one pound of weld metal can now be calculated as $.052. Line 6 - Total Lines 1, 2, and 5 to find the total cost of depositing one pound weld metal. The total of $ for Low Carbon Reliability of Calculating The Cost Per Foot of Deposited Weld Metal Calculating the weight of weld metal requires that we consider the following items. a. Area of the cross-section of the weld. b. Length of the weld. c. Volume of the weld in cubic inches. d. Weight of the weld metal per cubic inch In the fillet weld show in Figure 13, we know that the area of the cross-section (the triangle) is equal to one-half the base times the height, the volume of the weld is equal to the area times the length, and the weight of the weld then, is the volume times the weight of the material (steel) per cubic inch We can then write the formula: Weight of Weld Metal = ½ x Base x Height x Length x Weight of Material Substituting the values from Figure 13, we have: Wt/Ft =.5 x.5 x.5 x 12 x.283 =.4245 lbs Weights may vary depending on the density of the particular material you are attempting to calculate. The chart in Figure 14 will eliminate the need for these calculations for steel fillet and butt joints, since it lists the weight per foot directly Estimating the weight per foot of a weld using the chart, requires that you make a drawing of the weld joint to exact scale, and dimension the leg lengths, root gap, thickness, angles and other pertinent measurements as shown in Figure 15. Divide the cross-section of the weld into right triangles and rectangles as shown. Sketch in the reinforcement, i.e., the

266 LESSON IX Arc for for Low (A) HEIGHT 1/2" 1/2" (B) BASE Volume of Weld = 1/2 B x A x 12 Weight of Steel =.283 lb per cu. in. Weight of Weld = 1/2 (1/2) x 1/2 x 12 x.283 =.424 lbs. CALCULATING THE WEIGHT PER FOOT OF A FILLET WELD FIGURE 13 Carbon Reliability of domed portion above or below the surface of the plate, where required. The reinforcement should extend slightly beyond the edges of the joint. Measure the length and height of the reinforcement and note them on your drawing. The reinforcement is only an approximation because the contour cannot be exactly controlled in welding. Refer to the weight tables in Figure 14 for the weights per foot of each of the component parts of the weld, as sketched. The sum of the weights of all the components is the total weight of the weld, per foot as shown in Figure 15A. Line 7 - The total cost per pound as determined in Line 6 is entered, and multiplied by the weight per foot as determined in Figure Calculating the Cost of Weld Metal - Total Job Line 8 - The cost of the weld for the total job is determined by multiplying the total feet of weld (given) by the cost per foot as determined in Line COST CALCULATIONS - EXAMPLE 2 Calculate the total cost of depositing 1,280 ft of weld metal using the CO2 shielded, flux cored welding process in the double V-groove joint shown in Figure 14 using the following data. 1. Electrode - 3/32, 31 volts, 450 amps. 2. Labor and Overhead - $30.00/hr. 3. Deposition Rate - 15 lbs/hr. From Table in Figure Operating Factor - 45% (.45). Average from Figure 2.

267 V-GROOVE Lesson 1 Arc for for Low Carbon Reliability of T S G DOUBLE C B B A B B C S T WEIGHT PER FOOT OF WELD METAL FOR FILLET WELDS AND ELEMENTS OF COMMON BUTT JOINTS (lbs/ft) STEEL B EQUAL LEG FILLETS (USE 45 COLUMN) T T S DOUBLE BEVEL G A T T A T T C B B SINGLE BEVEL A C C T S FIGURE 14 S S C C B B B SINGLE V-GROOVE B SINGLE V NO GAP C B S T C S G LESSON IX lbs./ft. of Rectangle A lbs./ft. of Triangle B lbs./ft. Reinforcement C T G S H Inches 1/16" 1/8" 3/16" 1/4" 3/8" 1/2" / /16" 1/8" 3/16" 1/4" 1/ / / G 5/ / / / / / / / / / / / / / / / / T REINFORCEMENT H.

268 LESSON IX 45 Arc 1/ 16" 7/8" C 5/8" 1/2" A B 1" B C 1/2" for for Low A 1/8" lbs./ft. A =.265 B =.425 C =.124 TOTAL WEIGHT/FT..814 lbs B ESTIMATING WELD METAL WEIGHT FIGURE 15 C B 1/2" lbs./ft. B =.176 x 4 =.704 C =.071 x 2 =.142 TOTAL WEIGHT/FT..846 lbs 1/16" Carbon 5. Electrode Cost - $.80/lb (from supplier). 6. Deposition Efficiency - 86% (.86) From Table in Figure Gas Flow Rate - 45 cubic feet per hour. From Figure Gas Cost - $.03/cubic foot (from supplier). 9. Cost of Power - $.045/kWh. 10. Wt/Ft of Weld - From Figure 15B =.846 lbs/ft. These values are shown inserted into the formulas on the Weld Metal Cost Worksheet in Figure COMPARING WELD METAL COSTS It is interesting to note that the amount of weld metal deposited in Example 1 and Example 2 is almost the same, while the total cost of depositing the weld metal is three times higher in Example 1 as shown below. This is because the flux cored process has a higher deposition rate, efficiency and operating factor and also allows a tighter joint due to the deep penetrating characteristics of the process. Reliability of Example 1-1,280 ft x.814 lbs/ft = 1,041.9 lbs at $13,939 Example 2-1,280 ft x.846 lbs/ft = 1,082.9 lbs at $ 4, When comparing welding processes, all efforts should be made to assure that you use the proper welding current for the electrode or wire in the position in which the weld must be made. As an example, consider depositing a given size fillet weld in the vertical-up posi-

269 LESSON IX Arc EXAMPLE 2 WELD METAL COST WORKSHEET COST PER POUND OF DEPOSITED WELD METAL for for Low LABOR & OVERHEAD ELECTRODE GAS LABOR & OVERHEAD COST/HR DEPOSITION OPERATING RATE (LBS/HR) x FACTOR ELECTRODE COST/LB DEPOSITION EFFICIENCY GAS FLOW RATE (CU FT/HR) x GAS COST/CU FT DEPOSITION RATE (LBS/HR) = = = x x = = =.93 = 1.35 = FLUX POWER FLUX COST/LB x 1.4 DEPOSITION EFFICIENCY COST/kWh x VOLTS x AMPS 1000 x DEPOSITION RATE = = x x 31 x x 15 = = = = 15,000 N A TOTAL COST PER LB. OF DEPOSITED WELD METAL SUM OF 1 THROUGH 5 ABOVE $ 5.51 Carbon 7. COST PER POUND OF DEPOSITED WELD METAL COST PER FOOT OF DEPOSITED WELD METAL X POUNDS PER FOOT OF WELD JOINT = 5.51 x.846 = $ TOTAL FEET OF WELD X COST PER FOOT COST OF WELD METAL - TOTAL JOB = 1,280x 4.66 = $5,965 FIGURE 16 Reliability of

270 Arc LESSON IX tion by the GMAW process and FCAW process semi-automatically. In both processes the welding current and voltage must be lowered to weld out-of-position, and in GMAW, the short circuiting arc transfer must be used. Example 3 compares the weld metal cost per pound deposited by these processes, using the proper current and voltage for depositing a ¼ fillet weld on ¼ plate, vertically up. for for Low Carbon Note: The cost of electrical power is comparable in all processes and therefore, can be eliminated as a factor Example 3 FCAW GMAW Electrode Type dia. E71T dia. ER70S-3 Labor & Overhead - $30.00/hr $30.00/hr Current amperes 125 amperes Deposition Rate lbs/hr (Fig. 9) 2.8 lbs/hr (Fig. 10) Operating Factor - 45% (Fig. 2) 50% (Fig. 2) Electrode Cost - $1.44/lb $.66/lb Deposition Efficiency - 85% (Fig. 9) 96% (Fig. 6) Gas Flow Rate - 35 cfh (Fig. 7) 35 cfh (Fig. 7) Gas Cost Per Cu. Ft. - $.03 CO 2 $.11 75% Ar/25% CO 2 This data is tabulated in the chart in Figure As you can see, the cost of depositing the weld metal is about 33% less using the process. Since there is no slag to help hold the vertical weld puddle in the GMAW process, the welding current with solid wire must be lowered considerably. This, of course, lowers the deposition rate, and since labor and overhead is the largest factor involved, it substantially raises deposition costs. In the flat or horizontal position, where the welding current on the solid wire would be much higher, the cost difference would be considerably less pronounced. Reliability of

271 Arc for for Low LESSON IX The following information/variables must be determined prior to completing calculations: (1) Proposed Method Cost Calculation (2) Present Method Cost Calculation Gas Metal Arc E71T Dia. at 180 Amps (3) ER70S Dia. at 125 Amps (4) Actual Labor & O/H Rate for your Customer $ Actual Labor & O/H Rate for your Customer $ Deposition Rate in Pounds per Hour 4.9 Deposition Rate in Pounds per Hour 2.8 Operating Factor 45% Operating Factor 50% Electrode Cost per Pound $ 1.44 Electrode Cost per Pound $ 0.66 Deposition Efficiency 85% Deposition Efficiency 96% Gas Type CO2 Gas Type 75% Ar/25% CO2 Gas Flow Rate 35 Gas Flow Rate 30 Gas Cost per Cubic Foot $ 0.03 Gas Cost per Cubic Foot $ 0.11 Equipment Cost $ - Prepared For: NAME INFO Customer Name: NAME INFO Date: Result (1) Proposed Method Cost Calculation (2) Present Method Cost Calculation (Cost Reduction ) Formulas for Calculating Gas Metal Arc Cost Cost per Pound Deposited Weld Metal E71T Dia. at 180 Amps ER70S Dia. at 125 Amps Increase Labor& = Labor & Overhead Cost /Hr = $30.00 = $30.00 = $ $30.00 = $30.00 = $ ($7.823 ) Overhead Deposition X Operating 4.9 X 0.45 = X 0.5 = 1.4 Rate (lbs / hr) Factor Electrode Electrode Cost/lb = 1.44 = = $1.007 Deposition Efficiency Gas Type = CO2 Gas Type = 75% Ar/25% CO2 Gas Gas Flow Rate (Cuft/hr) X Gas Cost/Cu ft. = 35 X 0.03 = 1.05 = X 0.11 = 3.3 = ($0.964 ) Deposition Rate (lbs&/hr) Sum of the Above Total Variable Cost/lb Deposited Weld Metal = $ Total Variable Cost/lb Deposited Weld Metal = $ ( $7.781) T otal Carbon 9.7 OTHER USEFUL FORMULAS The information discussed below will assist you in making other useful calculations: TOTAL POUNDS OF ELECTRODES REQUIRED (REF. EXAMPLE 1) Total Pounds = Wt/Ft of Weld x No. of Ft of Weld Deposition Efficiency.814 x 1,280 Substituting the values from Example 1: = 1,631 lbs.630 WELDING TIME REQUIRED (REF. EXAMPLE 1) Reliability of Time = Wt/Ft of Weld x Ft of Weld Deposition Rate x Operating Factor Substituting the values in Example 1:.814 x 1, x.30 = 1, = 648 Hrs.

272 Arc for for Low Carbon 9.7 OTHER USEFUL FORMULAS LESSON IX The following information/variables must be determined prior to completing calculations: (1) Proposed Method Cost Calculation (2) Present Method Cost Calculation Gas Metal Arc E71T Dia. at 180 Amps (3) ER70S Dia. at 125 Amps (4) Actual Labor & O/H Rate for your Customer $ Actual Labor & O/H Rate for your Customer $ Deposition Rate in Pounds per Hour 4.9 Deposition Rate in Pounds per Hour 2.8 Operating Factor 45% Operating Factor 50% Electrode Cost per Pound $ 1.44 Electrode Cost per Pound $ 0.66 Deposition Efficiency 85% Deposition Efficiency 96% Gas Type CO2 Gas Type 75% Ar/25% CO2 Gas Flow Rate 35 Gas Flow Rate 30 Gas Cost per Cubic Foot $ 0.03 Gas Cost per Cubic Foot $ 0.11 Equipment Cost $ - Prepared For: NAME INFO Customer Name: NAME INFO Date: Result (1) Proposed Method Cost Calculation (2) Present Method Cost Calculation (Cost Reduction ) Formulas for Calculating Gas Metal Arc Cost Cost per Pound Deposited Weld Metal E71T Dia. at 180 Amps ER70S Dia. at 125 Amps Increase Labor& = Labor & Overhead Cost /Hr = $30.00 = $30.00 = $ $30.00 = $30.00 = $ ($7.823 ) Overhead Deposition X Operating 4.9 X 0.45 = X 0.5 = 1.4 Rate (lbs / hr) Factor Electrode Electrode Cost/lb = 1.44 = = $1.007 Deposition Efficiency Gas Type = CO2 Gas Type = 75% Ar/25% CO2 Gas Gas Flow Rate (Cuft/hr) X Gas Cost/Cu ft. = 35 X 0.03 = 1.05 = X 0.11 = 3.3 = ($0.964 ) Deposition Rate (lbs&/hr) Sum of the Above Total Variable Cost/lb Deposited Weld Metal = $ Total Variable Cost/lb Deposited Weld Metal The information discussed below will assist you in making other useful calculations: = $ ( $7.781) T otal TOTAL POUNDS OF ELECTRODES REQUIRED (REF. EXAMPLE 1) Total Pounds = Substituting the values from Example 1: Wt/Ft of Weld x No. of Ft of Weld Deposition Efficiency.814 x 1, WELDING TIME REQUIRED (REF EXAMPLE 1) = 1,631 lbs Current Chapter Table of Contents Go To Test Print Glossary Turn Pages Search Chapter (Faster Download) Search Document (Slower Download)

273 WELDING TIME REQUIRED (REF. EXAMPLE 1) Reliability of Time = Wt/Ft of Weld x Ft of Weld Deposition Rate x Operating Factor Substituting the values in Example 1:.814 x 1, x.30 = 1, = 648 Hrs..

274 9.8 AMORTIZATION OF EQUIPMENT COSTS LESSON IX Arc for Calculations show that you can save $7.00 per pound of deposited weld metal by switching from E7018 electrodes and the SMAW process to an ER70S0-3 solid wire using the GMAW process. However, the cost of the necessary equipment (power source, wire feeder and gun) is $2,800. How long will it take to amortize or regain the cost of the equipment knowing that the deposition rate of the ER70S-3 is 7.4 lbs/hr and the operating factor of the GMAW process is 50%? The formula is: Equipment Cost $ Savings/Lb (Deposition Rate x Operating Factor) = Man Hrs for Low Substituting the values in the formula: 2, (7.4 x.50) = Man Hrs = Man Hrs If we divide 108 into eight hour days (108 8 = 13.5) the deposited weld metal savings of one man working an eight hour day for 13-1/2 days will pay for the cost of the equipment. Carbon Reliability of

275 Arc for for Low BASIC WELDING FILLER METAL TECHNOLOGY A Correspondence Course Carbon LESSON X RELIABILITY OF WELDING FILLER METALS ESAB ESAB & Cutting Products Reliability of COPYRIGHT 2000 THE ESAB GROUP, INC.

276 Arc for for Low Carbon TABLE OF CONTENTS LESSON X RELIABILITY OF WELDING FILLER METALS Section Nr. Section Title Page 10.1 INTRODUCTION CODES, SPECIFICATIONS, AND STANDARDS THE AMERICAN WELDING SOCIETY AWS Filler Metal Specifications AWS Structural Code - Steel THE AMERICAN SOCIETY FOR TESTING AND MATERIALS AMERICAN SOCIETY OF MECHANICAL ENGINEERS SHIP CLASSIFICATION SOCIETIES The American Bureau of Shipping Lloyd s Register of Shipping Det Norske Veritas MILITARY SPECIFICATIONS STATE HIGHWAY ELECTRODE CERTIFICATION TESTING PROCEDURES Chemical Composition Analysis Test Soundness Test, All-Weld-Metal Tension Test and Impact Test Coating Moisture Test Guided Bend Tests Ferrite Test Fillet Weld Test CERTIFICATION OF ELECTRODES Typical Properties Certification Actual Certifications QUALITY ASSURANCE Reliability of Appendix A - TEST QUESTIONS... 26

277 RELIABILITY OF WELDING FILLER METALS LESSON X Arc 10.1 INTRODUCTION for for Low Producing a weld by the arc welding process has often been compared to steelmaking on a very small scale. The weld puddle is molten for a very short time and during that time, a number of reactions must take place between the base plate, the filler metal, and the electrode coating or shielding gas ingredients. These reactions must result in predictable mechanical properties and chemical composition of the weld metal produced by each of the great number of filler materials available. Reliable welding filler metals are the result of the proper formulation, adherence to certain codes and specifications, and the result of a good quality assurance program. Carbon 10.2 CODES, SPECIFICATIONS AND STANDARDS The wide use of welding as a fabricating method requires that certain controls be exercised to assure the safety and protection of persons and property exposed to structures and equipment utilizing welded joints. As a result, various codes, specifications and standards have been established by technical societies and professional organizations to assure safe, sound welds. Among other things, these groups specify or recommend the base metal requirements, joint design, filler metal, welding procedures, operator qualifications, required weld tests, testing methods, and inspection of welds The professional technical societies or organizations have no way of enforcing the codes, specifications or standards that they prepare. However, in many instances, governing bodies of municipalities, counties, states or federal agencies may adopt all or part of these documents as law. Private industry may require that work performed under contract will conform to one or more of these codes or specifications, and therefore, they become part of a legal document. Lastly, purchase orders issued for welding materials may state that the terms are to meet a particular code or specification, and as such, these purchase orders have legal implications The following is a description of the major societies and organizations whose specifications and codes are widely used in the welding filler metals industry. Reliability of

278 10.3 THE AMERICAN WELDING SOCIETY (AWS) LESSON X Arc for for Low The AWS publishes a number of specifications, standards and codes that have been adopted by many governing bodies and industries. The AWS may be considered to be the basic source of welding and welding engineering information in the USA. Many other codes and specifications will include or refer to various AWS Filler Metal Specifications. Electrode and welding filler metal manufacturers assign the appropriate AWS Classification to their products wherever possible, as a means of standardization, according to the AWS Filler Metal Specifications. The specifications prescribe the classification requirements including such items such as chemical composition of the weld metal, radiographic (X-ray) soundness tests, weld metal tension tests, impact tests, bend tests, and fillet weld tests where applicable. The following is a complete list of the AWS Filler Metal Specifications for ferrous and non-ferrous materials AWS Filler Metal Specifications Carbon Reliability of Specification No. A A A A A A A A A A A A A A A A Description Carbon Steel Covered Arc Iron & Steel Oxy Fuel Gas Rods Aluminum & Aluminum Alloy Corrosion Resisting Chromium & Chromium-Nickel Steel Low Alloy Steel Covered Arc Copper & Copper-Alloy Copper & Copper-Alloy Bare Rods & Brazing Corrosion-Resisting Chromium & Chromium-Nickel Steel Bare & Composite Metal Cored & Stranded & Rods Aluminum & Aluminum Alloy Bare Rods & Nickel & Nickel Alloy Covered Tungsten Arc Solid Surfacing Rods & Nickel & Nickel-Alloy Bare Rods & Rods & for Cast Iron Titanium & Titanium Bare Rods &

279 Specification No. Description LESSON X Arc for A A A A A A Carbon Steel & Fluxes for Submerged Arc Carbon Steel for Shielded Arc Magnesium Alloy Rods & Bare Carbon Steel for Composite Surfacing Rods & Flux Cored Corrosion Resistant Chromium & Chromium-Nickel Steel A Low Alloy Steel & Fluxes for Submerged Arc for Low A A A A Zirconium & Zirconium Alloy Bare Rods & Consumables for Electroslag of Carbon & High Strength Consumables for Electrogas of Carbon & High Strength Copper and Copper Alloy Rods for Oxyfuel Gas A A A A Low Alloy Steel for Gas Shielded Arc Low Alloy Steel for Consumable Inserts Fluxes for Brazing and Braze Carbon Reliability of These filler metal specifications also describe the classification requirements concerning standardization such as electrode size and length, packaging, spooling, marking, labeling, and others AWS Structural Code - Steel - The AWS Structural Code - Steel (AWS D1.1-96) covers the welding requirements applicable to welded steel structures including buildings, bridges, and structures consisting of tubular shaped members. Factors such as the design of welded connections, workmanship, welding procedure, welding operator qualification, and inspection requirements are covered in this code. Previous to the 1994 issue of this code, it also specified the tensile strength, yield strength, elongation, and impact requirements for the low alloy flux cored electrodes, since no AWS Filler Metal Specification existed for these electrodes. It is required that the user (contractor or fabricator) conduct tests to show that the low alloy weld metal would meet the mechanical properties mentioned above per the code.

280 Arc for for Low Carbon Reliability of With the issuance of AWS A , Specification for Low Alloy Steel for, the user now need only furnish the electrode manufacturer s certification that his product will meet the classification requirements of the latest edition of AWS A The AWS Structural Code (AWS D1.1-96) does not prescribe such design details as the location of parts or stress calculations to determine the size of load-carrying members in a structure. These details will be covered in a general Building Code that might state, This structure is to conform to the American Institute of Steel Construction (AISC) Specification for the Design, Fabrication and Erection of Structural Steel For Buildings, and the AWS Structural Code, AWS D1.1. In this case, the AWS Structural Code becomes a part of a general building code that may be adopted by a governing body The AWS publishes other specifications, standards and recommended practices covering the welding of automotive parts, construction equipment, machinery, ships, and water storage reservoirs. These, however, are less concerned with filler metal specification and selection than they are with welding techniques, procedures, and operator qualification AMERICAN SOCIETY FOR TESTING AND MATERIALS (ASTM) The main objectives of the American Society For Testing & Materials are (1) to further the knowledge of many types of materials, and (2) establish standardized specifications of and standardized test methods for these materials The chemical and mechanical tests that apply to welding filler metals, as described by the AWS and other professional organizations, are often based on the ASTM standard testing methods AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME) The ASME is instrumental in establishing many codes and specifications. The ASME Boiler & Pressure Vessel Code is of primary importance for welding materials and applications. This code is extensive, and is published in several different sections. Those parts that refer to welding filler metals and welding requirements are: LESSON X

281 Arc Section I. Power Boilers Section II. Material Specifications Section III. Nuclear Vessels Section IV. Low Pressure Boilers Section VIII. Unfired Pressure Boilers LESSON X for for Low Section II of the code, in which welding filler metals are specified, states that the ASME has adopted the AWS Filler Metal Specifications verbatim (word for word). However, they do have their own specification designation. For example, AMSE SFA Specification for Low Alloy Steel Covered Arc is the same as AWS A Under Section III of the code, the ASME issues a Quality System Certificate to manufacturers of materials (including welding electrodes and wire) to be used under the code. This certificate is issued only after an ASME plant audit and the manufacturer s entire quality assurance program is approved. Its issuance allows the manufacturer s products to be used in boiler and pressure vessel work, as well as on nuclear applications as specified in the code. Details of the Quality System Certificate will be covered under the Quality Assurance Section of this lesson. Carbon Reliability of 10.6 SHIP CLASSIFICATION SOCIETIES The American Bureau of Shipping (ABS) - The ABS is a non-profit, international ship classification society. It certifies the structural integrity and mechanical fitness of merchant ships, offshore drilling rigs, and other marine structures Annually, the Bureau publishes a listing entitled Approved, Wire-Flux and Wire-Gas Combinations. The approvals of the filler metals are based upon tests conducted to standards established by the Bureau or by other recognized agencies. As requested by the manufacturer, filler metals may be approved to an AWS Filler Metal Specification, and so listed, or approved to an ABS Grade as shown in Figure 1. In either case, the approval testing must be made in the manufacturer s facility in the presence of an ABS representative. The extent of testing will vary, depending on the type of weld for which the product is being qualified (fillet or butt), whether the filler material is being initially tested as a new product, being tested annually, or whether the product is being upgraded at the manufacturer s request At the time of annual testing, the manufacturing facilities and quality control procedures are subject to inspection also.

282 68 Lesson 1 ABS FILLER METAL MECHANICAL PROPERTY REQUIREMENTS LESSON X Arc for for Low TENSILE STRENGTH YIELD STRENGTH ELONGATION 2" ABS GRADE IMPACT F FT/LBS. MANUAL SEMI-AUTO FT/LBS. AUTOMATIC ORDINARY STRENGTH ABS FILLER METAL ,300 TO 95,100 psi 44,100 psi MIN. 22% MIN. HIGHER-STRENGTH ABS FILLER METAL 71,000 TO 95,000 psi 54,000 psi MIN. 20% MIN. 3 1Y 2Y 3Y Note: Where more than one test temperature is indicated for a specific grade, satisfactory testing according to any indicated temperature isacceptable. GRADE NOTATIONS 1,2,3 (see above) T Two pass automatic Y Higher strength & impacts S Semi-automatic only H Low hydrogen electrode A Automatic only M Multi-pass automatic SA Semi-auto or automatic ABS FILLER METAL GRADING SYSTEM Carbon FIGURE Following are the various grade designations as assigned by the ABS. MANUAL ELECTRODES FILLER METAL GRADES (SMAW) Ordinary Strength Higher Strength 1 1Y 2 2Y 3 3Y 2H (Low Hydrogen) 3H (Low Hydrogen) WIRE AND WIRE-GAS COMBINATION FILLER METAL GRADES (GMAW FCAW) Ordinary Strength 1SA, 1A, 1T 2SA, 1A, 1T 3SA, 1A, 1T Higher Strength 1YSA, 1YA, 1YT 2YSA, 2YA, 2YT 3YSA, 3YA, 3YT Reliability of

283 LESSON X Arc for for Low WIRE-FLUX COMBINATION FILLER METAL GRADES (SAW) Ordinary Strength Higher Strength 1TM, 1T, 1M 1YTM, 1YT, 1YM 2TM, 2T, 2M 2YTM, 2YT, 3YM 3TM, 3T, 3M 3YTM, 3YT, 3YM By using the table and grade notations in Figure 1, you can see that the grade ABS 2YSA signifies: (2Y) a tensile strength in the 71,000-95,000 psi range, a minimum yield strength of 54,000 psi, and a minimum elongation of 20% in 2 inches, meets the impact requirements of 20 ft.-lbs. at -4 F when welded semi-automatically, and 20 ft.-lbs. at 14 F when welded automatically: (SA) the wire-gas combination has been approved for semi-automatic and automatic welding In the annual ABS Listing, the approved electrode or wire diameter, welding position, shielding gas (if applicable) and type of welding current (AC or DC) are also listed. Each electrode or filler metal must be re-approved annually Lloyd s Register of Shipping (LRS) - Lloyd s Register of Shipping is a British Carbon ship classification society similar to the ABS. They also publish an annual approved filler metal listing with test procedures very similar to the ABS Det Norske Veritas (DNV) - Det Norske Veritas is a Norwegian ship classification society that operates very similarly to the American Bureau of Shipping and Lloyd s Register ESAB has a number of filler metals on the approved list of each of the three ship classification societies. Since the listings change annually, they do not appear in this instructional material. Information on the listings of any specific product may be secured by contacting the Technical Services Department. Reliability of

284 10.7 MILITARY SPECIFICATIONS LESSON X Arc for for Low Carbon Reliability of Military specifications are issued by the Department of Defense and it is mandatory that all work performed for that department be covered by the applicable military specification. Military specifications are identified by a letter-number designation and the title. An example is: MIL-E-22200/1E -,, Mineral Covered, Iron Powder, Low Hydrogen, Medium and High Tensile Strength, As-Welded or Stress Relieved Applications In the example, MIL designates that it is a Military specification. The first letter E stands for Electrode which is the significant word in the title. The number 22200/1 is the serial number of the specification; the letter E at the end designates the revision letter and will change as further revisions are made. The underlined portion is the title of the specification A Military specification may cover only one or a number of electrodes or wires. When the specification includes more than one item, a type designation is necessary. As an example, an E8018-C3 low alloy electrode would be designated as MIL-E-22200/1E, MIL 8018-C The following is a partial list, along with a brief description, of the more common military electrode specifications currently in use. Specification No. Description QQ-E-450a Covered Mild Steel MIL-E Covered Austenitic Steel for Armor Application MIL-E-16053L Bare Aluminum Alloy Wires MIL-E Covered Chrome-Molybdenum and Corrosion Resisting Steel MIL-E Bare Chrome-Nickel Stainless Steel Wire MIL-E Bare Nickel-Alloy Wires MIL-E-22200/1F Covered, Iron Powder, Low Hydrogen, Medium and High Tensile Steel MIL-E-22200/2C Covered Electrode, Austenitic Stainless Steel for Corrosion and High Temperature Service MIL-E-22200/3F Covered Electrode, Nickel-Base and Cobalt-Base Alloy MIL-E-22200/4C Covered Electrode, Copper-Nickel Alloy MIL-E-22200/5B Covered, Iron Powder, Low Hydrogen, Low Alloy Steel for Hardening & Tempering MIL-E-22200/6C Covered Electrode, Low Hydrogen, Medium and High Tensile Steel

285 Arc for for Low LESSON X MIL-E-22200/7B Covered Electrode, Molybdenum Alloy MIL-E-22200/8B Covered Electrode, Low Hydrogen, and Low Hydrogen Iron Powder and Corrosion Resisting Steels MIL-E-22200/10B Covered, Iron Powder, Low Hydrogen, Medium and High Tensile Steel MIL-E-23765/B (SH) Bare Solid Mild Steel Wires MIL-E-24403/A (SH) Flux Cored MIL-E-19933E (SH) Bare Solid Chromium and Chromium-Nickel Steels Some military specifications require varying degrees of testing by the manufacturer before a filler metal is submitted for use. These tests and testing procedures are spelled out in the specification, and when successfully completed, the electrode or wire is placed upon a Qualified Products List (QPL). Other specifications require the manufacturer to submit an affidavit indicating the success of the testing of each specific shipment STATE HIGHWAY ELECTRODE CERTIFICATION and filler metals are approved for bridge and highway construction according to the Federal Highway Administration Requirements. are tested, and certification is renewed annually to those states that maintain an approved list meeting Federal requirements. These listings vary annually, and the manufacturer should be consulted for verification. Carbon Reliability of 10.9 TESTING PROCEDURES Test of welding filler metals per the specifications of the various societies, professional organizations and governing bodies is time-consuming and expensive. However, accurate testing is an important factor in producing quality welding filler metals. Test plates must be welded according to the procedure stated in the specification, which in many instances requires controlled preheat and interpass temperatures. The specimens must be carefully machined from the proper portion of the test plate and held to very close dimensional tolerances so that test results will be accurate. The test equipment must be kept in accurate calibration The following are brief, partial descriptions of the more common types of tests required by various specifications and codes. They are shown here to familiarize you with the methods by which tests are conducted and are not to be construed as complete test procedures.

286 Arc for LESSON X Chemical Composition Analysis Test - A weld pad for determining the chemical composition of a filler metal must be prepared as shown in Figure The base metal size and material is specified, and the weld metal is built up in layers to the required height or number of passes to assure that the top surface has no dilution with the base metal. The welds are deposited in the flat position. After welding, the top surface is machined or ground smooth to remove all foreign matter. A sample is taken from this surface for chemical analysis by a suitable method agreed upon between the supplier and the purchaser. for Low CHEMICAL COMPOSITION SAMPLE TAKEN FROM THIS SURFACE TYPICAL WELDPAD FOR CHEMICAL COMPOSITION ANALYSIS SPECIFIED BY NUMBER OF LAYERS IN SOME SPECIFICATIONS Carbon Reliability of Figure Soundness (X-Ray) Test, All-Weld-Metal Tension Test and Impact Test - A test plate is prepared according to the specification with a sufficient number of passes to fill the groove, a sample of which is shown in Figure Some specifications require at least one stop and one start in the area of the weld that is to be radiographed (X-rayed). The specification may also call for the test plate to be preheated to a certain temperature before the first pass, and also specify an interpass temperature. This means that the test plate must be allowed to cool to a certain temperature range before the next pass is applied After the plate is completely welded, the test plate is prepared for radiographic examination by machining off the backing strip from the root (bottom) of the weld, and also

287 LESSON X Arc for for Low Carbon ALL WELD METAL TENSION SPECIMEN V-NOTCH IMPACT TEST SPECIMEN DETAILS OF TEST ASSEMBLY FOR SOUNDNESS, TENSILE AND IMPACT TESTS Figure 3 the reinforcement or excess weld metal from the top (face) of the weld. The plate is then radiographed to check for porosity or inclusions in the weld metal. The specification will show several degrees and grades of acceptable porosity or inclusions Porosity and inclusion diagrams, as shown in Figure 4, are usually labeled as fine, medium, assorted, and large. A representation of fine and large porosity is shown in Figure 4. The allowable amount of porosity may vary for different filler metal specifications. Reliability of

288 LESSON X Arc LARGE POROSITY OR INCLUSIONS 3/64" to 1/16" DIAMETER OR LENGTH MAXIMUM NUMBER IN ANY 6" OF WELD = 8 for for Low Carbon Reliability of FINE POROSITY OR INCLUSIONS 1/64" to 1/32" DIAMETER OR LENGTH MAXIMUM NUMBER IN ANY 6" OF WELD = 30 SOUNDNESS TEST POROSITY AND INCLUSION STANDARDS Figure After the test plate has been radiographed, the all-weld-metal tension specimen, and the charpy V-notch impact specimen are machined from the center of the plate as shown in Figure 3. Only the critical dimensions are shown in the sketches, and as you can see, they must be held to rather close tolerances to obtain accurate test results The.500±.010" diameter of the tension specimen is all weld metal since it is machined from the center of the weld. The area of the impact specimens in which the notch is machined is all weld metal also The tensile specimen is placed in a tensile testing machine and pulled until it fractures. (Refer to Lesson I, "Yield Strength".) The yield strength and ultimate tensile strength are recorded on the tensile tester. After fracture, the two halves of the broken specimen are fitted back together in a jig, and the distance between the two center punch marks is accurately measured. If this distance is now 2.500", it tells us that the specimen has stretched.500" or 25% of its original length before breaking. This figure is recorded as the elongation in a 2" length of the weld metal specimen The five impact specimens are broken in a Charpy Impact Tester, as described in Lesson I, "Charpy Impacts", and the energy absorbed in breaking each of them is recorded. In calculating the average impact value, the specimens with the highest and lowest values are discarded. The average value of the three remaining specimens is recorded as the impact value.

289 Arc for for Low LESSON X Coating Moisture Test - The coating moisture test is conducted by removing a small amount of the coating from the middle portions of three electrodes, all from the same can or package. A small measured amount (4 grams) of this coating sample is tested in sophisticated laboratory apparatus. The method of moisture testing satisfies AWS A and AWS D1.1 Specifications and is sensitive only to water. It is the most accurate and reliable method of moisture determination currently in use Guided Bend Tests Transverse Face Bend, Root Bend and Side Bend Tests. The specifications for some filler metals require that guided bend tests be made to evaluate the ductility and soundness of a welded joint. The test plate is welded in the flat position and is made long enough to produce the necessary number of specimens. See Figure The specimens are cut from the test plate, and the backing strip and weld reinforcement machined flush with the face and root surfaces. If the test plate is greater than 3/8" thick, it must be machined to 3/8" thickness, removing the metal from the root surface for face bends, and from the face surface for root bends. In face bends, the face of the weld is on the outside or convex surface of the specimen, and in root bends, the root of the weld is on the outside or convex surface of the bend. The specimen is bent in a guided bend test jig, the design of which is described in the specification, over a justified radius (usually a 3/4" radius) through an angle of 180. When removed from the jig, the Carbon FACE OR ROOT BEND TEST SIDE BEND TEST PLATE Reliability of FACE BEND ROOT BEND SIDE BEND TRANSVERSE GUIDED BEND TESTS FIGURE 5

290 Arc for for Low LESSON X specimen will spring back to about the angle shown in Figure 5. In face and root bends, defects in the surface of the weld are exposed as cracks, tears, or porosity Side bend tests are similar to face and root bend tests, except they are bent so the side of the weld is on the outside or convex surface of the specimen. Side bends expose defects in the interior and fusion zone of the weld Transverse Tension and Longitudinal Guided Bend Test. The transverse tension test and longitudinal guided bend test may appear separately in some specifications; however, it is shown here (Figure 6) as they appear in AWS A (applicable only to the single-pass electrodes of the E70T-2, E70T-3, E70T-10, and E70T-GS classifications.) Carbon DETAILS OF TRANSVERSE TENSION AND GUIDED BEND TESTS FIGURE An all-weld-metal tensile test, as shown in Figure 3, would not be meaningful for single-pass electrodes because in single-pass welds, the weld metal is always substantially diluted with the base metal. The bend test is prescribed for these electrodes because they contain relatively high amounts of manganese and silicon that can reduce ductility somewhat, and can cause cracking in the weld area when present in excessive amounts. Reliability of

291 Arc for for Low Carbon LESSON X The test plate must be a material having a minimum tensile strength equal to that of the electrode being tested. The test plate is welded with one weld bead on each side of the plate. This is considered a single-pass weld since each weld will be diluted with the base material. The tensile specimen is cut from the plate, machined to the shape shown in Figure 6, and pulled until fractured. A specimen that breaks in the base plate shall be considered satisfactory The weld beads on the bend specimens are ground or machined smooth and flush with the surface. The specimen is then uniformly bent over a 3/4" radius through an angle of 180 in a suitable jig. The specimen, after bending, may show no crack exceeding 1/8" in length in any direction in the weld metal or the base metal Ferrite Test - In austenitic stainless steels, ferrite (as discussed in Lesson V) can be beneficial in reducing cracking in some stainless steel weld metals, while in other environments, it can reduce corrosion resistance. It can cause brittleness in high temperature service, and can reduce toughness in cryogenic service. For these reasons, the amount of ferrite in austenitic stainless steel weld metal must be established as accurately as possible. Ferrite content can be calculated by using the Schaeffler diagram or the WRC diagram as shown in Lesson V, when the chemical analysis of the weld metal is known. It can also be determined by the use of various magnetic sensing instruments To determine the ferrite level by instrument, a weld pad, as shown in Figure 7, must be made The copper bars are used as a mold or form to build up the weld metal to the proper height as shown. The welding procedure used in preparing test pad is carefully spelled out in the specification as to welding direction, stops and starts, cleaning and WELD DEPOSIT 1/2" TO 5/8" MINIMUM HEIGHT Reliability of WELD PAD PREPARATION FOR FERRITE TEST Figure 7

292 Arc for LESSON X interpass temperature. The top surface of the completed pad is carefully filed by hand in the direction of the weld. Six readings are taken along the top of the weld pad with a properly calibrated magnetic instrument. The six readings are averaged to a single value. This average becomes the ferrite number Fillet Weld Test - Some specifications require the fillet weld test be prepared as shown in Figure 8. for Low LEG CONVEXITY FILLET WELD TEST SPECIMEN Figure 8 LEG Carbon Reliability of The weld specimen is made using the specified electrode size and plate thickness. After welding, the plate is cut on the lines indicated, and one side of the 1" wide section is polished and etched so that the weld bead is clearly visible. The largest possible right triangle with equal leg lengths is carefully scribed within the fillet weld on this surface, so that the fillet size, leg lengths, and convexity of the weld can be measured and compared to the allowable deviations in the specification The welds in the two longer sections are broken by applying a force in the direction shown in the diagram. The broken surfaces are visually examined for evidence of inclusions, gas pockets, or incomplete root fusion Fillet weld tests are especially required for all-position electrodes or wires, and the specification will require that the test plates be welded in the vertical-up and overhead positions.

293 10.10 CERTIFICATION OF ELECTRODES LESSON X Arc for for Low Carbon Reliability of The certification of electrodes and welding wires has become more critical today, and the number of test certifications requested has increased more than ten-fold in the last several years. Conducting certification tests is a costly process, and all efforts must be made to provide accurate information to the manufacturer, so that the end-user gets the material tested to the necessary degree; no more, no less filler metals may be certified by one of two methods: typical properties certification or actual properties certification Typical Properties Certification - Certifications showing typical chemistry and mechanical properties are provided with customer orders when so requested. These typical properties are based on the results of many tests on similar materials and on a very comprehensive, carefully controlled Quality Assurance System. An ESAB Typical Properties Certificate assures that the products are tested in compliance with AWS and ASME Filler Metal Specifications. A copy of a Typical Properties Certificate for Atom Arc electrodes is shown in Figure 9. Typical certifications are supplied by the manufacturer, on a no-charge basis, by request Actual Certifications - Actual certification that each lot of a particular product shipment will meet a desired specification is normally supplied by the manufacturer for a fee. In this case, packages of each lot number of the product to be shipped will be opened and tested according to the customer s request. TYPICAL PROPERTIES CERTIFICATE FIGURE 9

294 Arc for for Low In order to have the proper tests performed correctly and as inexpensively as possible, the information that accompanies the order must contain all pertinent information such as: a. To what specification must the material conform and to what revision of that specification? b. Must all the tests as required by the specification be performed? c. Are there any actual tests required in addition to those covered by the specification? d. Do special marking and packing requirements apply? e. Is the material for a government contract? f. Where is inspection to be performed and by whom? g. What number of copies and distribution method is required for the certificates? LESSON X Carbon The American Society publishes a document (AWS A ) entitled Filler Metal Procurement Guidelines. This document (together with an AWS Filler Metal Specification) is intended to assist the buyer in designating those testing requirements that are applicable to his order. It consists of the following: a. The AWS Filler Metal Classification. b. Definition of lot classification (AWS A Section 2). c. The intensity of testing schedule (i.e., number of tests to be conducted) (AWS A Section 3) A portion of Table 1, Intensity of Testing that applies to actual testing reads as follows: Intensity of Testing Schedule Requirements H Chemical analysis only for each lot shipped. Reliability of I J K Tests called for in Table 2 Required Tests for each lot shipped. All tests that the classification called for in the pertinent AWS filler metal specifications for each lot shipped. All tests specified by the purchaser, for each lot shipped.

295 Arc Table 2, referred to in Schedule I above, lists the Required Tests necessary for actual certification, and in all cases, does not include all tests included in the applicable AWS Filler Metal Specification. When the intensity of testing is not specified on an order, the product will be tested to ESAB standard testing intensity which equals or exceeds those tests required under Schedule I above. LESSON X for for Low As an example, stainless steel covered electrodes will only be tested for (1) chemical analysis and (2) calculated ferrite content as required by the AWS Filler Metal Procurement Guidelines A Any additional testing must be specified QUALITY ASSURANCE ESAB has based its Quality Assurance Program around NCA 3800 of the ASME Boiler and Pressure Vessel Code, Section III. This means that the program assures accurate documentation, close control of the raw materials including the steel and flux ingredients, in-process controls and checks, and complete traceability of each lot of product produced. It also includes close control of the inspection and measuring equipment which assures accurate testing and certification of test results. Carbon Both the Hanover, Pennsylvania and Ashtabula, Ohio Quality System Programs have been accepted by the ASME as material manufacturers. This means that customers using our products for nuclear and other applications to ASME requirements need not audit our Quality Program. Copies of the ASME Quality System Certificates for both plants are shown in figures 10 and 11. These certificates are issued only after an in-plant audit by an ASME representative, and are valid for a three year period In addition, facilities in Hanover, PA; Ashtabula, OH; Niagara Falls, NY; and Monterrey, Mexico have been certified to ISO This quality standard was first established in 1987 by the International Organization for Standardization in Geneva, Switzerland. Certification to this standard covers all areas of product manufacturing, including general management, production, research, purchasing, engineering, human resources, and quality assurance. Receipt of this certificate eliminates the costly time consuming audits normally required by our customers. Copies of these certificates are shown in figures 12 through 15. Reliability of

296 LESSON X Arc for for Low Carbon Reliability of QUALITY SYSTEM CERTIFICATE, ESAB HANOVER FIGURE 10

297 Arc for for Low Carbon Reliability of QUALITY SYSTEM CERTIFICATE, ESAB ASHTABULA FIGURE 11

298 LESSON X Arc for for Low Carbon Reliability of ISO 9000 CERTIFICATION - ESAB HANOVER FIGURE 12

299 LESSON X Arc for for Low Carbon Reliability of ISO 9000 CERTIFICATION - ESAB ASHTABULA FIGURE 13

300 LESSON X Arc for for Low Carbon ISO 9000 CERTIFICATION - ESAB Niagara Falls FIGURE 14 Reliability of