Chapter 3 Shielded. Metal Arc Welding

Size: px

Start display at page:

Download "Chapter 3 Shielded. Metal Arc Welding"

Lee Calvin Poole
6 years ago
Views:

1 Chapter 3 Shielded Metal Arc

2 1. SMAW Electrode 2

3 Filler metals for shielded metal arc welding are composed of a metal alloy core, covered by a flux coating. The core wire carries the current for welding sufficiently enough to melt the base metal and mixes with melted base metal to form the weld 3

4 SMAW electrodes are manufactured in accordance with AWS Filler Metal Specifications that establish procedures and criteria for the manufacture of electrodes. AWS Filler Metal Specification Electrode Alloy Type AWS A5.1 Carbon Steels AWS A5.3 Aluminum and Aluminum Alloys AWS A5.4 Corrosion Resistant Steel (Stainless Steels) AWS A5.5 Low Alloy Steels AWS A5.6 Copper and Copper Alloys AWS A5.11 Nickel and Nickel Alloys AWS A5.15 Cast Irons 4

5 Electrode classifications are influenced greatly by the chemical composition of the electrode coatings. The American Society has established filler metal groupings F-1 through F-4 for low carbon steel electrodes. AWS A5.1 Filler Metal Groupings for Shielded Metal Arc Grouping Characteristic Coating Type Electrodes F-1 High Deposition, Shallow to Medium Penetration High Iron Oxide Iron Powder E7024, E7027, E7028, E 6020, E6022, E6027 F-2 Shallow Penetration High Titania E6012, E6013, E6019, E7014 F-3 Deep Penetration Cellulose E6010, E6011 F-4 Low Hydrogen, Medium Penetration Low Hydrogen E7015, E7016, E7018, E7048 5

6 Electrode coatings have these purposes: Provide shielding gas Help to control the cooling rate of the weld Influence weld bead shape Help to hold molten metal in place for vertical and overhead welding Help to initiate and stabilize the arc Add alloying elements to influence weld mechanical properties. 6

7 What do the numbers for each electrode mean? Electrodes are classified and identified by a filler metal classification number painted onto the electrode. 7

8 E7018 E = Electrode 70 = Minimum Tensile Strength X 10,000 (psi) 1 = Weld Position All 8 = Characteristics, Low Hydrogen, Iron Powder, Current Type 8

9 After the letter E the first two digits indicate the approximate minimum tensile strength of the filler metal (x1000 psi) in the as welded condition. The next to last digit indicates the welding position capabilities for electrode use ext To Last Digit Indicates Position AWS Class. Flat Horizontal Vertical Overhead EXX1X Yes Yes Yes Yes EXX2X Yes Fillet No No EXX3X Yes No No No EXX4X Yes Yes Down Yes 9

10 The final digit represents the chemical composition of the electrode coating, which greatly influences electrode characteristics and usability. AWS A5.1 Filler Metal Groupings for Shielded Metal Arc Grouping Characteristic Coating Type Electrodes F-1 High Deposition, Shallow to Medium Penetration High Iron Oxide Iron Powder E7024,E7027, E7028, E 6020, E6022, E6027 F-2 Shallow Penetration High Titania E6012,E6013, E6019, E7014 F-3 Deep Penetration Cellulose E6010, E6011 F-4 Low Hydrogen, Medium Penetration Low Hydrogen E7015,E7016, E7018, E

11 What are the correct current settings for SMAW electrodes? 11

12 Current settings vary with electrode diameters and with changes in flux coating composition. Carbon Steel All Position Capable Electrodes Electrode diameters and current ranges Current Type 3/32 1/8 5/32 EXX10 DCEP EXX11 AC/DCEP EXX12 AC/DCEN EXX13 AC/DC EXX14 AC/DC EXX15 DCEP EXX16 AC/DCEP EXX18 AC/DCEP EXX18M DCEP

13 Current settings vary with electrode diameters and with changes in flux coating composition. Carbon Steel High Deposition Electrodes Current 3/32 1/8 5/32 3/16 1/4 Type EXX22 AC/DC EXX24 AC/DC EXX27 AC/DCEN EXX28 AC/DCEP

14 Stainless Steel Electrodes Current Type Stainless Steel Electrodes 3/32 1/8 5/32 3/16 E308L Lime ( E309 suffix) E E E E coatings use DCEP and Titania (15suffix) coatings use DCEP or AC 14

4 Shielded Metal Arc Welding*

4 Shielded Metal Arc Welding* * Abbreviated MMA (Manual metal arc welding). American designation: shielded metal arc welding (SMAW). Shielded metal arc welding (SMAW) is an AW process that uses a consumable