WLD 216 Miscellaneous SMAW Electrodes and Advanced Positions

Transcription

1 WLD 216 Miscellaneous SMAW Electrodes and Advanced Positions

2 Index Course Information 3 Welding Work Sheets 4-7 Science on Steel 8-19 Math on Metal Craftsmanship Expectations for Welding Projects Welding Projects Final Exam Information Assessment Breakdown for the Course 58 Supplemental Videos See Welding Resource Room This project was supported, in part, by the National Science Foundation Opinions expressed are those of the authors And not necessarily those of the Foundation WLD 216 5/16/12 2

3 Reading Welding Principles and Applications Writing Work Sheets Video Training Cutting Projects Complete Bill of Materials Welding Projects Snipe Pipe to Plate Pad Eye I-Beam T-Joint Down hand Advanced Corner Thick to Thin Down Hand Final Exam Written Practical Course Assignments Required Texts Welding Principles and Applications by Larry Jeffus Timeline Open-entry, open-exit instructional format allows the students to work their own pace. It is the student s responsibility for completing all assignments in a timely manner. See your instructor for assistance. Outcome Assessment Policy The student will be assessed on his/her ability to demonstrate the development of course outcomes. The methods of assessment may include one or more of the following: oral or written examinations, quizzes, written assignments, visual inspection techniques, welding tests, safe work habits, task performance and work relations. Grading criteria: The student's assessment will be based on the following criteria: 15% of grade is based on Safe work habits and shop practices 20% of grade is based on Completion of written and reading assignments 15% of grade is based on demonstrating professional work ethics 40% of grade is based on completion of welding exercises 10% of grade is based upon the final exam/project WLD 216 5/16/12 3

4 SMAW Worksheet Name: WLD 216 Date: Directions: Use Welding Principles and Applications text to complete the questions on this work sheet. Answer the questions using complete sentences, and do not hesitate to reference other sections in the packet to find answers. 1. Describe two methods of striking an arc with an electrode. 2. Why is it important to strike the arc only in the weld joint? 3. What problems may result by using an electrode at too high a current setting? 4. What problems may result by using an electrode at too high a current setting? 5. According to the text,what would the amperage range be for the following electrodes? a. 1/8 in. (3.2 mm). E6010 b. 5/32 in. (4 mm), E7018 c. 3/32 in. (2.4 mm). E7016 d. 1/8 in. (3.2 mm). E What makes some spatter Hard?. WLD 216 5/16/12 4

5 7. Why should you never change the current setting during a weld? 8. What factors should be considered when selecting an electrode size?. 9. What can a welder do to control overheating of the metal pieces being welded? 10. What effect does changing the arc length have on the weld? 11. What arc problems can occur in deep or narrow weld joints? 12. Describe the difference between using a leading and a trailing electrode angle. 13. Can all electrodes be used with a leading angle? WLD 216 5/16/12 5

6 14. What characteristics of the weld bead does the weaving of the electrode have? 15. What are some of the applications for the circular pattern in the flat position? 16. Using a pencil, draw two complete lines of the weave patterns you are most comfortable making. 17. Why is it important to find a good welding position? 18. Which electrodes would be grouped in the following F Numbers: F3, F2, F4? 19. Give one advantage of using electrodes with cellulose-based fluxes? 20. What are stringer beads? WLD 216 5/16/12 6

7 21. Describe an ideal tack weld. 22. What effect does the root opening or root cap have on a butt joint? 23. What can happen if the fillet weld on a lap joint does not have a smooth transition? 24. Which plate heats up faster on a tee joint? Why? 25. Can a tee weld be strong if the welds on both sides do not have deep penetration? Why or shy not? WLD 216 5/16/12 7

8 Science on Steel The Welding Fabrication Industry needs qualified welder fabricators who can deal with a variety of situations on the job. This portion of the training packet explores science as it relates to industry requirements. WLD 216 5/16/12 8

9 Miscellaneous Electrodes & Advanced Positions With Shielded Metal Arc Welding Contents of this Packet A. E7018 Low-Hydrogen Electrode and E6011 Cellulosic Electrode a. Benefits and Limitations of E7018 vs. E6011 b. Significance of Constant Current for SMAW c. Use of Iron Powder B. Austenitic Stainless Steel Welding a. Stainless Steel Welding with 308 and 308L Electrodes b. Electrode Overheating c. Types of 308 Covered Electrodes d. Solidification Cracking in Austenitic Stainless Steel Welds e. Example of the use of the WRC-1992 Diagram f. Welding with 309 and 309L Electrodes C. Cast Iron Welding with Nickel-Based Electrodes a. Cast Iron Welding with Cast Iron Electrodes b. Use of Nickel Based Electrodes (ENi-CI and ENiFe-CI) E7018 (Low Hydrogen) and E6011 (Cellulosic) Electrodes Benefits and Limitations of E7018 vs E6011 E6011 cellulosic electrode is discussed in detail in the science packet for WLD 114 and 115. The E7018 low hydrogen electrode is covered in the science packet for WLD 112 and 113. However, it is important to clarify several advantages and limitations between these electrodes. Both electrodes can be used in all-position with either AC or DC. The E6011 electrode has many of the benefits of E6010 except the flux coating for E6011 contains potassium which allows this electrode to be used in both AC and DCep modes. Using E6011 in the AC mode decreases its penetrating power slightly compared to E6010, but provides control of arc blow problems. Still, the penetrating power of E6011 far exceeds that for E7018. From Table 1, the cellulose-based (C 6 H 10 O 6 ) flux produces a majority of CO 2 and H gas shielding. So the E6011 weld pool is deep penetrating, fast freezing and easily visible because of the small amount of slag cover. Compared to E6011, the E7018 electrode produces only a small volume of CO 2 from the decomposition of limestone (calcium carbonate or CaCO 3 ) from the reaction: CaCO 3 CaO + CO 2 Unlike E6011, the flux coating on the E7018 electrode produces a heavy and hard slag coating containing lime (CaO) and fluorspar (CaF 2 ) as shown in Table 1. As a result, one major difference is that E7018 can not be used for root passes due to the slag build-up at the root, but, E6011 is ideal for root passes because of the penetrating power of the H + CO 2 gas and very light slag cover. WLD 216 5/16/12 9

10 Table 1 Comparing the flux ingredients for E6011 cellulosic electrodes with E7018 low hydrogen electrodes. (Olson et al, ASM International Handbook, 1993, Vol. 6, pp ) Ingredient Purpose E6011 E7018 Cellulose Calcium carbonate Fluorspar Rutile Asbestos Iron powder Ferroslicon Ferromanganese Sodium silicate Potassium silicate Gas shielding Gas shielding & fluxing agent Slag former & fluxing agent Slag former & arc stabilizer Slag former & extrusion Deposition rate Deoxidizer Alloying & deoxidizer Binder & fluxing agent Arc stabilizer and binder 25-40% % Significance of Constant Current for SMAW All electrodes for SMAW applications must be used with a constant current power source. In many power sources, the slope of the volt-ampere curve is adjustable to various degrees of constant current. For example, for flat or horizontal fillet welding with the E7024 electrode, a substantially constant current setting would be desirable in order to achieve the maximum welding speed and highest quality welds for application that involve large diameter electrodes and high welding currents. Conversely, all-position electrodes such as E6010, E6011, and E7018 need a less slope in the volt-ampere curve to enable the welder to change the current within a specific range simply by changing the arc length. This is particularly useful in out-of-position welding and in root passes of joints with poor fit-up. For successful SMAW, it is important that any change in arc length (or voltage) be accompanied by a very small change in welding current so the welder can maintain control over the weld pool. Thus, the power source for SMAW must always be a constant current type. Using a constant current power source, any increase arc length is accompanied by an increase in voltage but only a small decrease in welding current. This occasional change in voltage (due to the welder s change in arc length), must not produce a substantial change in welding current and deposition rate. Thus, for manual welding processes such as SMAW and GTAW, the power source must be a constant current type to provide the welder with control. WLD 216 5/16/12 10

11 Use of Iron Powder About 25-40% of the coating weight is iron powder in E7018 electrodes while no iron powder is used with E6011. When the covering of any electrode contains more than 40% iron powder, it produces a molten pool with such excessive fluidity and mass that the electrode can only be used in the flat or near-flat positions. With E7018 electrodes, surface tension and fast freeze aspects of the flux exert more control over the molten weld pool than gravity. As a result, E7018 is still an effective all-position electrode despite its iron powder content. Austenitic Stainless Steel Welding Stainless Steel Welding with 308 and 308L Electrodes Compared to steel, austenitic stainless steels (like 308 and 308L) have much lower thermal conductivity and much higher thermal expansion characteristics, causing stainless steel weld metal to remain hotter longer and to distort more. In addition, the electrical conductivity of austenitic stainless steel is much lower than steel, so it is difficult to deliver high current through the stick electrode without overheating the electrode (discussed in the next section). Type E308 and E308L covered electrodes for SMAW are designed to join the following base metals: 201, 202, 301, 302, 304, 304L, 305, 308, 321, 347 wrought stainless steels as well as CF-3, CF-8, CF-20 and CF-8C austenitic stainless steel casting alloys. Type E308 and E308L are not produced as plate or sheet metal, but are produced only as filler metal for welding. There are two possible cost-effective techniques for manufacturing stainless steel electrodes: (1) Metal wire core may be steel. Cr & Ni are added to the flux coating, or (2) Metal wire core may be a base stainless steel composition, and little (or no) Cr and Ni alloying is provided in the flux to meet E308 specifications. This means that the covered electrode must be used in a normal manner. Because the flux coating contains Cr and Ni alloying, the composition of the as-deposited weld metal can vary depending on the use of the E308 electrode. For example, the coating should never be scrapped off. Often a welder will erroneously use a stripped E308 electrode for GTAW. This is dangerous because the wire core composition rarely ever meets the E308 specified composition. E308 specified composition for weld metal can only be achieved when the electrode is used in a manner recommended by the manufacturer. Cleaning of the joint prior to welding is extremely important because the oxide layer on stainless steel is Cr 2 O 3 which is strong insulator. In addition, unlike welding steel, the thick Cr 2 O 3 layer is much more tenacious and more chemically stable than iron oxide. As a result, oxide layer on stainless steel will tend to produce lack of fusion and slag entrapment. The root of unbacked or double V-groove welds must be thoroughly cleaned before welding the second side. WLD 216 5/16/12 11

12 Weaving of the electrode is not recommended; and, for best quality, the weld width should not exceed 4-times the electrode core wire diameter. To further avoid discontinuities, each layer of weld metal in a deep groove should not exceed a thickness of 1/8 inch. The presence of the Cr 2 O 3 oxide layer requires these precautions when welding stainless steel. To break through the tenacious Cr 2 O 3 layer, the flux coating in E308 electrodes contains substantial fluorides to provide vigorous fluxing, which break up the oxide layer and permits free fluid flow of the molten weld metal. These fluorides (like CaF2 and MgF) are strong halides and react with the Cr 2 O 3 layer. After welding is complete, the slag must be completely cleaned because the fluorides in the slag rapidly accelerate crevice and pitting corrosion as well as stress corrosion cracking of the stainless steel weld joint. All E308 type electrodes should be treated and stored as low hydrogen electrodes in holding ovens at 200ºF - 300ºF. Electrode Overheating As mentioned earlier, austenitic stainless steel electrodes (like 308, 308L, 309 and 309L) all have substantially higher electrical resistance than mild steel electrodes. As a result, the welder will notice that the E electrode tends to heat up much faster than the same size steel E7018 electrode. At sufficiently high current settings, a 308 electrode will actually become red-hot. The electrode overheats by resistance heating because I 2 R or resistance heating, where I is the current and R is the electrical resistance during welding. The value for R for stainless steel is much higher than R for steel. So, the value of I 2 R heating for E308 electrodes is much higher than for a steel electrode like E6010 or E7018. For example, a weld is made at 150 amps, 16 volts. The electrical resistance (R) can be calculated by Ohm s Law: R = E/I where E is the voltage and I is the amperage R = 16/150 R = 0.11 ohms The resistance heating (H) of the electrode is calculated by: H = I 2 R H = (150 amps) 2 (0.11 ohms) H = 2,500 J An electric toaster in the kitchen uses a maximum of about 1,000J to energize metallic heating elements to about 760º (1400ºF). Overheating the electrode is dangerous because overheating (a) reduces the available energy that is needed to provide a stable arc, and (b) tends to deteriorate and crack the flux coating. To avoid overheating, the current should be set at the recommended range. If high current is needed, always used a larger diameter electrode. Since current density (defined as current divided by cross sectional area of the electrode) decreases with increasing diameter of electrode, the resistance heating of the electrode will also decrease. Types of E308 Covered Electrodes The E308 and E308L filler metal chemistries are adjusted produce weld metal having the desired metallurgical microstructure that is free of solidification cracks (discussed in the next section) and unacceptable discontinuities. There are three commonly used types of E308 coatings as designated by the suffixes: -15, -16 and 17. The -15 suffix to E indicates that the flux WLD 216 5/16/12 12

13 is lime-fluorspar-based (calcium oxide calcium fluoride) and only capable of delivering weld metal if DC electrode positive is used. These fluxes are basic in nature and produce the cleanest weld metal, which contains the lowest in oxygen and inclusions and most resistant to moisture and porosity. E weld metal is more ductile, more corrosion resistant, and tougher than other E308 designations. E is suited for all-position applications. The calcium carbonate slag produces gas shielding and a very light slag layer, making E desirable for pipe welding and for root passes on heavy plate. The -16 suffix indicates that the flux is rutile-limestone based (rutile is titania or titanium oxide and limestone is calcium carbonate, CaCO 3 ). E is often referred to as a basic-rutile electrode. E also contains potassium, which is easily ionized and remains ionized for a short period of time after the arc is extinguished as in AC welding. E electrode can be used with AC power or with DC electrode positive. Although E is recommended for flat position welding, some manufacturers do produce E with out-of-position capability. The -17 suffix to E electrode indicates that the flux is silica-rutile based and recommended for AC or DC welding in the flat and horizontal position with minimum clean-up required. E is designed to produce a smooth bead which blends well into the sidewall to avoid creating any crevices. Stainless steel is susceptible to crevice corrosion. Unlike E and 16, the bead profile of E is concave for maximum corrosion resistance. Solidification Cracking in Austenitic Stainless Steel Welds Austenitic stainless steel weld metal is susceptible to solidification cracking just like aluminum alloys. In fact, there is only a narrow range of weld metal compositions that are crack-resistant as shown in Figure 1. This is why the proper choice of filler metal is so important in welding stainless steels. When welding 304 stainless steel, the proper filler metal is 308 or 308L because these fillers have a sufficiently high ratio of CrEq/NiEq to promote ferrite solidification and crack-free weld metal. The theory why austenitic stainless steel weld metal is so sensitive to solidification cracking is that low-melting-point liquid films (containing impurity elements such as S and P) have very low solubility in the solidifying austenite. As a result, the liquid film between ferrite grains and dendrites rupture due to solidification shrinkage and a solidification crack is produced. Fortunately, when solidification is such that ferrite solidifies first, cracking susceptibility is virtually eliminated. Sound welds are produced because S and P have a high solubility in ferrite during solidification. The potentially low-melting liquid film is immediately absorbed in the solidifying ferrite and a sound weld is produced. Ferrite content in a weld can be predicted by the WRC-92 diagram in Figure 2, and measured by the ferrite gage at room temperature. So, to prevent solidification cracking, austenitic stainless steel weld metal must: a) Solidify as either pure ferrite (F) or Ferrite first, followed by austenite (FA) and b) Contain from 3 to 12% ferrite at room temperature WLD 216 5/16/12 13

14 In order to predict whether your weld metal will solidify as in the crack-free region of the WRC 92 diagram, you must calculate the Cr Equivalent (Cr eq ) and the Ni Equivalent (Ni eq ) of the weld admixture. Cr eq = Cr + Mo + 0.7Nb Ni eq = Ni + 30C + 20N Cu Insert the values of Cr eq and Ni eq into the WRC-1992 diagram. If the value defined by Cr eq and Cr eq falls in the FA or F region and the value of ferrite is between 3 and 12%, sound crack-free welds will be deposited. The Ferrite Gage can be used to determine the ferrite number of the weld metal. c) Ferrite content at room temperature must be between ~3 and 12% ferrite, and d) In the FA or F region of the WRC-92 diagram In the WRC-92 diagram, the F means that solidification was entirely ferritic, FA means that solidification was ferrite first followed by austenite. AF is undesirable because austenite solidifies first (followed by ferrite) and produces cracks. A is the most undesirable composition because pure austenitic solidification is extremely crack sensitive. Thus, the weld metal composition should fall in the F or FA regions while maintaining from 3 to 12 ferrite number. Example of the use of the WRC-1992 Diagram The root pass of 304 Stainless steel butt joint is welded with 308L filler metal. The weld metal admixture contains 50% 308L filler metal and 50% 304 base metal dilution. Calculate the amount of ferrite in the weld metal after it has cooled to room temperature. 308L Filler Metal 304 Base Metal Weld Admixture C Cr Ni Mn Si N Cr eq Ni eq Cr eq / Ni eq Ferrite No From the table above, the calculation for CrEq and NiEq shows that 308L would produce a high ferrite content of 12 at room temperature. This is plenty of ferrite to prevent cracking. On the other hand, the calculations for 304 stainless steel show that weld metal that is entirely 304 base metal would be susceptible to solidification cracking because the ferrite content would be only 1 WLD 216 5/16/12 14

15 ferrite number and solidifies in the undesirable AF field. By using a 308L filler metal deposited on 304 base metal, the weld admixture will produce a crack-free weld containing a ferrite number of 6 and desirable solidification mode which is ferritic followed by austenitic (FA). This procedure is not necessary for the welding of each stainless steel alloy. By following the manufacturer s recommendations and charts developed by the American Welding Society, the austenitic stainless steels alloys that are safe to weld with 308 and 308L are provided. However, all stainless steel wrought products and filler metals are sold with a chemical analysis certification, so that the student can do his/her WRC-1992 calculations. Figure 1 Solidification cracking susceptibility of austenitic stainless steel weld metal as a function solidification mode and composition. WLD 216 5/16/12 15

16 Figure 2 WRC-1992 Diagram for predicting ferrite content and solidification mode of stainless steel weld metal. Welding with 309 and 309L Electrodes Types 308 and 309 electrodes are both austenitic stainless steels, except 309 electrode contains more Cr and more Ni than conventional 308 electrodes. The L grades like 308L and 309L indicate extra low carbon. The major differences in composition between 308 and 309 is presented below: Type Typical Composition C 20Cr 9.6Ni 308L 0.03C 20Cr 9.8Ni C 24Cr 13Ni 309L 0.03C 24Cr 13Ni Type 309 electrode is used to weld 302B, 303, 309, 316 wrought metals, and CH-20, CF-8M, CF-12M and CF-3M casting alloys. Although the Cr and Ni contents for 309 are higher than those for 308 electrodes, the as-deposited ferrite content is still between 3-12% and the 309 electrode solidifies in a crack-free ferrite mode of solidification (in the F or FA area of the WRC diagram in Figure 2. Thus, both 308 and 309 electrodes provide superior resistance to solidification cracking. Because 309 has higher Cr and Ni contents, E309 and E309L are the electrodes of choice for dissimilar metal welding. A typical example is the welding of 304 austenitic stainless steel to a A36 mild steel using E309L filler metal. The E309L electrode provides the extra Ni and Cr that WLD 216 5/16/12 16

17 are lacking in the A36 steel in order to have a weld metal admixture that contains between 3 and 12% ferrite. Welding Cast Iron Cast Iron Welding with Cast Iron Electrodes Welding of cast iron is very difficult because their carbon (C), sulfur (S) and phosphorus (P) contents are so high. They are comprised of several groups of castings as shown below in Table 2. Table 2 Composition limits for different types of cast iron 1. White cast iron C, Si, Mn, S, P 2. Gray cast iron C, 1-3Si, Mn, S, P 3. Ductile cast iron C, Si, Mn, S, P 4. Malleable cast iron C, Si, Mn, S, P 5. A36 steel (reference).026c*, 0.4Si* Mn, 0.05S*, 0.04P* * maximum amount permitted In casting of these alloys, the high silicon (Si) content and a very slow cooling rate promote graphitization of the carbon instead of the formation of brittle carbides. So, ferritic gray iron, ferritic ductile iron and malleable iron can all be very soft materials, because the C, S and P have been utilized through the Si catalyst and very slow cooling rates (in casting) to replace the hard carbide phases with a soft graphite and iron mixture. However, when these cast irons are welded, this soft microstructure is completely destroyed during melting of the base metal and resulting microstructures in the weld is a mixture of brittle martensite and brittle iron carbide. The heat-affected zone is also cooled rapidly and can contain brittle martensite. How then is it possible to weld cast iron? The inexpensive solution is to use cheap cast iron electrodes (ECI) and an extremely high preheating temperature to produce a very slow weld cooling rate. The cast iron electrode contains a combination of high carbon equivalent and Si graphitizer. If the weld and heat affected zone experience very slow weld cooling rates, then the brittle martensite and carbides are minimized. SMAW is used to weld cast iron using ECI electrodes and a high preheating temperature. Also, oxy-acetylene is often used to weld cast iron with a slightly carburizing flame because oxy-acetylene is naturally a slow heating and slow cooling process. Use of Nickel Based Electrodes (ENi-CI and ENiFe-CI) The reason why nickel-containing (Ni) electrodes are so effective in welding cast iron is because Ni produces ductile weld metal with a microstructure consisting of a matrix of face-centeredcubic austenite and small islands of graphite. Since the formation of graphite cause the weld to expand, graphite helps to reduce the shrinkage stress that occurs during welding. Pure Ni electrodes (ENi-CI) produce the most ductile weld metal. In fact, it is rare that weld metal deposited with pure Ni electrodes ever crack. This electrode can be used with all types of cast iron. Although a pure Ni electrode (ENi-CI) prevents weld metal cracking, the cost of nickel is very expensive and the Ni electrode can not prevent cracking in the heat-affected zone. WLD 216 5/16/12 17

18 A cheaper electrode is ENiFe-CI which contains about 55% Ni and 45% Iron. This electrode produces stronger weld metal than pure Ni electrodes but it is more crack-sensitive if too much dilution from the cast iron base metal enters the admixture. As long as the weld metal contains more than about 70% ENiFe-CI filler metal, the weld metal will be crack-free. In addition, the ENiFe-CI filler metal produces weld metal that has minimal shrinkage characteristics so it is preferred to weld thick section castings. The less the weld metal shrinks, the less will be the tendency for fusion line cracking. So, ENi-CI and ENiFe-CI electrodes completely prevent cracking in the weld metal regardless of whether preheat is used or not; but, the danger of cracking in the heat-affected zone is still a problem. Since the Ni electrode has no metallurgical effect on the base metal composition, the heat-affected zone will still develop brittle microstructures at normal fast cooling rate weld. The heat-affected zone is part of the cast iron base metal. When the heat-affected zone is heated to near the melting temperature of the cast iron, several problems can develop. If a very high preheat temperature is used, the graphite and iron in the heat-affected can form low melting eutectic liquid that produces liquation cracks during cooling. On the other hand, if no preheat is used, then brittle carbides and martensite will form. Thus, preheating is considered beneficial because of the reduced brittle phases in the heat-affected zone and reduced residual stress. However, large castings are often welded by a quench welding method. In this case, the combination of thick section and small (low heat input) intermittent stringer beads produce welds with a fast cooling rate. Cracking is prevented because the liquation cracking is avoided and the brittle heat-affected zone is so narrow (due to low heat input stringers), that crack-free welds are possible. In fact, some very large castings are welded with Ni or NiFe electrodes and forcibly cooled down to about 80C between passes. Once the stringer beads are completed without cracking, subsequent passes over previously deposited Ni or NiFe weld metal can take place with relatively little danger of cracking. WLD 216 5/16/12 18

19 Science on Steel WLD 216 Name: Date: 1. What are the benefits and limitations of E7018 vs. E Why is Iron Powder used in flux? 3. What is the difference between the Stainless Steel Welding electrodes 308 and 308L Electrodes 4. When welding cast iron why is a Nickel-Based Electrode(s) used? 5. Why do you have to preheat when welding Cast Iron? WLD 216 5/16/12 19

20 Math on Metal The Welding Fabrication Industry needs qualified welder fabricators who can deal with a variety of situations on the job. This portion of the training packet explores math as it relates to industry requirements. WLD 216 5/16/12 20

21 Converting Decimal Inches to the Nearest Sixteenth of an Inch Sometimes you need to convert decimal inch measurement to inches and sixteenths of an inch: For example: Suppose you want to convert a measurement of 2.25 in a dimension manual to a measurement of inches and sixteenths of an inch. To do that you (1) Write 2 down on your paper as the number of whole inches; (2) then you enter the rest of the number.25 into your calculator. Remember to put in the decimal point!.25 (3) Multiply this number by 16; this is the number of 16 th s of an inch that you have..25 x 16 = 4 or 4/16. Reduce to ¼. Put it together with the 2 to get 2 ¼! Try the following problems, converting the measurement to the nearest 1/16 of an inch: inches = inches = inches = inches = The following is an example of a number that isn t quite so neat as the ones above. It will not come out evenly to a whole number of sixteenths, so you will have to do one more step... Convert : (1) Write 4 down on your paper as the number of whole inches; then (2) Enter the rest of the number in your calculator as.395 (without the 4! BUT WITH THE DECIMAL POINT!) Notice that this number is not quite so predictable and neat as.25 (3) Multiply this number by 16* and round your answer off to the nearest whole number; this is the number of 16 th s of an inch that you have..395 x 16 = 6.32 = approx. 6 or 6/16 (4) If possible, reduce this fraction to eighths or fourths, etc. and include the whole number of inches with the answer: 4 3/8 inches inches = inches = inches = inches = *Note that if you wanted to convert to the nearest 1/8 instead of 1/16, you would multiply by 8 instead of 16, and if you wanted a finer measurement of 32nds, you would multiply by 32 instead of 16. It s that easy! WLD 216 5/16/12 21

22 On Metric to Metric Conversions Converting to larger and smaller metric units As many welding blueprints have measurements and tolerances printed in both English and metric, and since some prints you come across may only have metric measurements, it is always a good idea to have some knowledge of the metric system. The first thing to understand about conversions within the metric system is that this process is far easier than conversions from metric to standard (inch-foot-pound) units of measure. We just have to learn the language. Once you know the names of the base units and can match the prefixes (milli-, centi-, kilo-, etc.) with their relative sizes, there is no easier system than the metric system. Once you learn how to convert one type of metric unit, say meters (along with centimeters, millimeters, etc), you can convert almost any type of metric unit. Converting from millimeters to meters is exactly the same as converting from milligrams to grams! In this lesson, we are going to stick to meters and the units which are directly built on meters, such as millimeters, centimeters, and so on. To get a handle on this mini-metric lesson, let s first talk about what sizes these meters, centimeters, and millimeters actually look like. A meter (39 3/8 ) is a little over three inches longer than a yard, about one full stride in walking. A meter is the base unit of length and so needs only one letter -- m as an abbreviation. 1 yard = 36 1 meter stride 1 m one meter 39 3/8 A centimeter is just a little longer than the width of the tip of your cutting torch. For some it might also be the width of their pinkie or of the nail of their pinkie. The abbreviation for centimeter is cm, c for centi- and m for meter. 1 cm A millimeter is the thickness of a dime. The abbreviation for millimeter is mm, m for milli- and m again for meter. Keep these visual sizes in your mind s eye while you go through this lesson on metrics. THICKNESS = 1 mm WLD 216 5/16/12 22

23 It s also important to relate meters, centimeters and millimeters to each other in size. A millimeter is one-thousandth of a meter (not one millionth!). A centi-meter is one-hundredth of a meter and is also the thickness of ten millimeters (ten thousandths = 10/1000 = 1/100 reduced). What unit would probably be the best one to measure the following objects/dimensions: Use the linear units: mm, cm, m, km. Some may have two good answers. Remember that meters are similar to yards, while centimeters are similar to inches. Millimeters are used to measure fairly small dimensions, things you might just use sixteenths of an inch for. 1. length of a barbecue grill 2. the distance from your home to school 3. your own height 4. the diameter of a boiler pipe 5. the diameter of most sheet metal screws 6. the length of a plate of steel 7. the length of a pipe 8. the length of the fab bay 9. the length of a pencil 10. the diameter of hard (GMAW) wire Converting within the metric system The first thing you should do when you are deciding how to go about converting one metric unit to a larger or smaller unit is the following: determine whether you are going from a larger unit to a smaller unit OR from a smaller unit to a larger unit. Which of these is smallest? mm cm m Largest?: mm cm m Then use a little common sense. If you were using inches to measure the length of a sheet of mild steel, you would measure a lot of inches probably. If you measured how many little sixteenths of an inch, you would have even more. But if you measured that same sheet of steel in yards or in feet, it would take much fewer of these to cover its length. The same is true of all measuring units. If you convert to a smaller unit, you will need more of them to cover the length or width, and if you convert to a larger unit, you will need fewer of these larger units than you did of the small ones. So... if you convert from meters to centimeters (from a larger to a smaller unit), you will find that the amount increases (100 times as many). You need more of those little centimeters. If you convert from millimeters to meters (from a smaller unit to a much larger unit), the amount of measuring units will decrease substantially (to one-thousandth as many). You need less of those big meters than of those little millimeters to cover the length of a sheet of steel. WLD 216 5/16/12 23

24 If you convert from millimeters to centimeters, it is still a conversion to a larger unit, and the amount of units will decrease, just not by so much. It will only decrease by a tenth. What do you think will happen when you convert from centimeters to millimeters? Will you have more or less? More, because you are converting to a smaller unit. How many times more? Ten times more, because each centimeter is the same size as ten mm. Now let s learn how to use the number line on the next page and do some of these easy conversions. Keep in mind that this number line is constructed to make these conversions easy; smaller units are on the right to match the logic we covered in the last paragraph... focusing on how many we need of them, rather than on how big they are. Another way of looking at it is that centimeters are two spaces to the right of the base unit meter, just like cents (pennies) are two spaces to the right of our base unit of money -- the dollar. The metric system is based on the number ten and the decimal system. Every lined notch on the line is worth a multiple of ten. For each line you move to the right on the line, you are going to multiply by ten. This is the same as moving your decimal point one place to the right. So if you need to move one line to the right, you move your decimal one space to the right. If you need to move one line to the left, move your decimal point one space to the left. This is the same as dividing by ten. What if you need to move three lines to the left? That s a multiple of one thousandth, as when you convert millimeters to meters. Then you move your decimal point three spaces to the left. Let s do some examples. Be sure you have the metric line in front of you as you go over these. Relax and know that it s easier to do these than to read about how to do them! Example 1 Let s convert 22.5 mm (millimeters) to cm (centimeters). Start with your finger on the millimeter line and then find the centimeter (cm) line with your eyes. Count over how many lines you have to travel and remember in which direction. You should have to travel one line to the left. Therefore, you need to move your decimal point one space to the left changing 22.5 mm to 2.25 cm. Example 2 What about converting 1580 centimeters (cm) to meters? You might ask, Where is the decimal point?! If you cannot see a decimal point, it is ALWAYS at the end, the far right, of the number, just invisible. So, that would make 1580 = or Now let s convert cm to meters (m). Look on the chart and see that you need to move two lines to the left. This means you move your decimal point 2 places to the left, changing cm to or 15.8 m (meters). Now try this problem: How many mm are in 26 cm? 26 = 26. cm mm is just one line to the right of cm Move your decimal one space to the right Add a zero or zeros as you need them. 26. cm = 260. mm = 260 mm WLD 216 5/16/12 24

25 Conversions within the Metric System Mega- kilo- Base Unit centi- milli- micro- 1,000,000 1, (M-) (k-) -meter (m) (c-) (m-) (µ-) -gram (g) -liter (L) -watt (W) -volt (V) -amp(ampere) (A) -ohm (Ω) -second (s) -Newton (N) -hertz (Hz) -Pascal (Pa) etc.... WLD 216 5/16/12 32 NSF-ATE Project - Advanced Materials Joining for Tomorrow s Manufacturing Workforce

26 Metric to Metric Conversions - Practice Name: Date: Use your metric conversion line to convert these measurements to larger or smaller metric units as required: Note: l represents liters, and g represents grams m = mm l = ml mm = m 250 mg = g mm = cm cm = m m = km 7125 watts = kilowatts mm = cm mm = m Note that when you change your base metric unit, like from meters to grams, there is no difference in how you do the m = mm actual math. No new skills to learn! cm = mm mm = m WLD 216 5/16/12 33

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28 ALL WELDING PROCJECTS ARE TO BE COMPLETED IN THE SHACK WLD 216 5/16/12 35

29 Craftsmanship Expectations for Welding Projects The student should complete the following tasks prior to welding. 1. Thoroughly read each drawing. 2. Make a cutting list for each project. Cut at least two project assemblies of metal at a time. This will save a great amount of time. 3. Assemble the welding projects per drawing specifications. 4. Review the Welding Procedure portion of the prints to review welding parameter information. 5. See the instructor for the evaluation. Factors for grading welding projects are based on the following criteria: Metal Preparation Project Layout Post Weld Clean-up Oxyacetylene Cut quality Accurate (+/- 1/16 ) Remove Slag/Spatter Grind all cut surfaces clean Limit waste Remove sharp edges An example of a High Quality weld. Weld Quality per AWS D1.1 VT Criteria Cover Pass Reinforcement (groove welds) Flush to 1/8 Fillet Weld Size See specification on drawing Undercut 1/32 max depth Weld Contour Smooth Transition Penetration N/A Cracks None Allowed Arc Strikes None Allowed Fusion Complete Fusion Required Porosity None Allowed WLD 216 5/16/12 36

30 Snipe E7018 (All Positions) Project #1 VT Criteria Student Assessment Instructor Assessment Reinforcement (0 1/8 ) Undercut (1/32 ) Weld Bead Contour (Smooth) Penetration Cracks (none) Arc Strikes (none) Fusion (complete) Porosity (none) Grade Date WLD 216 5/16/12 37

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32 Pipe to Plate (Inverted 6F) Project #2 VT Criteria Student Assessment Instructor Assessment Reinforcement (0 1/8 ) Undercut (1/32 ) Weld Bead Contour (Smooth) Penetration Cracks (none) Arc Strikes (none) Fusion (complete) Porosity (none) Grade Date WLD 216 5/16/12 39

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34 Pad Eye - E6013 (4FT) Project #3 VT Criteria Student Assessment Instructor Assessment Reinforcement (0 1/8 ) Undercut (1/32 ) Weld Bead Contour (Smooth) Penetration Cracks (none) Arc Strikes (none) Fusion (complete) Porosity (none) Grade Date WLD 216 5/16/12 41

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36 I-Beam (7018) Project #4 VT Criteria Student Assessment Instructor Assessment Reinforcement (0 1/8 ) Undercut (1/32 ) Weld Bead Contour (Smooth) Penetration Cracks (none) Arc Strikes (none) Fusion (complete) Porosity (none) Grade Date WLD 216 5/16/12 43

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38 T-Joint (3F) Vertical Down Hand E-6013 Project #6 Starting from top of plate working your way to bottom of plate wrapping corner. Down Hand welding refers to a welding position. Which is Vertical Down. VT Criteria Student Assessment Instructor Assessment Reinforcement (0 1/8 ) Undercut (1/32 ) Weld Bead Contour (Smooth) Penetration Cracks (none) Arc Strikes (none) Fusion (complete) Porosity (none) Grade Date WLD 216 5/16/12 45

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40 Advanced Corner E6011 (2F and3f) Project #7 VT Criteria Student Assessment Instructor Assessment Reinforcement (0 1/8 ) Undercut (1/32 ) Weld Bead Contour (Smooth) Penetration Cracks (none) Arc Strikes (none) Fusion (complete) Porosity (none) Grade Date WLD 216 5/16/12 47

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42 Thick to Thin E6013 (2F-4F) Project #8 VT Criteria Student Assessment Instructor Assessment Reinforcement (0 1/8 ) Undercut (1/32 ) Weld Bead Contour (Smooth) Penetration Cracks (none) Arc Strikes (none) Fusion (complete) Porosity (none) Grade Date WLD 216 5/16/12 49

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44 FCAW Dual Shield Rat Hole Project #9 Using the picture below fabricate and weld out 3 pieces of steel that are the following dimensions: 1 piece of ½ x 8 x 8 2 pieces of ½ x 4 x 8 with a rat hole cut in the center of the plate that s 1 ½ radius VT Criteria Reinforcement (0 1/8 ) Undercut (1/32 ) Weld Bead Contour (Smooth) Penetration Cracks (none) Arc Strikes (none) Fusion (complete) Porosity (none) Student Assessment Instructor Assessment Grade WLD 216 5/16/12 Date 51

45 Final Exam Part One The final exam is a closed book test. Consult your instructor to determine items that you may need to review. Once you determine that you are ready for this exam, see your instructor. Complete the exam and write all answers on the answer sheet. Once completed, return the exam to your instructor Safety Oxyacetylene safety SMMAW safety Hand Tool Safety FCAW and OAC Processes Power source specifics o Polarity o Current out put AWS electrode classification OAC o Theory of cutting o Flame types o Safety Welding Symbols and Blueprints Orthographic views Isometric views Welding symbol o Weld symbols o Reference line o Tail Math and Math conversions Adding and subtracting fractions Reading a tape measure Metric conversions Study Guide WLD 216 5/16/12 52

46 WLD 216 Answer Sheet Name: Date: WLD 216 5/16/12 53

47 Part Two This portion of the exam is a practical test where you will fabricate and weld a weldment from a blueprint. The evaluation of this portion of the exam will be based on the Traveler. WLD 216 5/16/12 54

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49 Grading Traveler for the WLD 216 Practical Exam Name: Date Hold Points are mandatory points in the fabrication process, which require the inspector to check your work. You will have the following hold points that you instructor will check Points Possible Hold Points Instructor s Evaluation 5 points Blueprint Interpretation and Material Cut List 5 points = 0 errors, all parts labeled and sized correctly 3 points = 1 error in part sizing and/or identification 2 points = 2 errors or more rework required (max points) 10 Points Using the orthographic drawing convert it to an isometric sketch 10 points Material Layout and Cutting (Tolerances +/- 1/16 ) 10 points Layout and cutting to +/-1/16 Smoothness of cut edge to 1/32 7 points Layout and cutting to +/- 1/8 Smoothness of cut edge to 1/16 5 points (Rework required max points) Layout and cutting to +/-3/16 Smoothness of cut edge to 3/32 10 points Fit-up and Tack weld (Tolerances +/- 1/16 ) 10 points Tolerances +/- 1/16 Straight and square to +/-1/16 7 Points Tolerances +/- 1/8 Straight and square to +/-1/8 5 Points (Rework required - Max points) Tolerances +/- 3/16 Straight and square to +/-3/16 15 points Weld Quality Subtract 1 point for each weld discontinuity, incorrect weld size and incorrect spacing sequence. 35 points Minimum points acceptable. This equates to the minimum AWS D1.1 Code requirements. Total Points /50 WLD 216 5/16/12 56

50 WLD 216 Isometric Drawing Name: Date: WLD 216 5/16/12 57

51 Final Grades - WLD 216 Name: Instructor: Date: Welding Projects = 40% Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of A Total Project pts. / Total pts. Possible X 40 = % Written Work = 20% Out of Out of Out of Out of Out of Out of Out of Out of Out of B Total Project pts. / Total pts. Possible X 20 = % Safety = 15% Each day of attendance is worth 3 points earned. Any safety violation will result in 0 points for the day. Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of C Total pts. earned / Total pts. Possible X 15 = % Employability Skills = 15% The following attributes will be assessed - attendance, attitude, time management, team work, interpersonal skills, etc.. Daily points (there are no excused absences, hence no points earned for days missed ) 3 pts = present and working for the entire shift; 2 pts = late; 1 pt = late and left early; 0 pts = no show. Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of Out of D Total pts. earned / Total pts. Possible X 15 = % Final Exam 10% Written Exam Practical Exam Out of Out of E Total Project pts. / Total pts. Possible X 10 = % Add Lines A + B + C + D + E. This will give you your Final Grade TOTAL % FINAL GRADE WLD 216 5/16/12 58