Chapter 3 Shielded Metal Arc
1. SMAW Electrode 2
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
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
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
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
What do the numbers for each electrode mean? Electrodes are classified and identified by a filler metal classification number painted onto the electrode. 7
E7018 E = Electrode 70 = Minimum Tensile Strength X 10,000 (psi) 1 = Weld Position All 8 = Characteristics, Low Hydrogen, Iron Powder, Current Type 8
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
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, E7048 10
What are the correct current settings for SMAW electrodes? 11
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 40-80 65-130 90-165 EXX11 AC/DCEP 50-90 75-125 110-160 EXX12 AC/DCEN 50-95 70-130 125-200 EXX13 AC/DC 50-95 75-125 120-165 EXX14 AC/DC 65-95 110-140 130-200 EXX15 DCEP 75-110 90-145 120-210 EXX16 AC/DCEP 70-100 80-130 120-170 EXX18 AC/DCEP 75-110 90-145 120-210 EXX18M DCEP 75-110 90-145 120-210 12
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 110-150 150-170 EXX24 AC/DC 60-120 110-150 170-220 220-300 320-420 EXX27 AC/DCEN 170-230 230-300 310-440 EXX28 AC/DCEP 170-250 220-310 270-400 13
Stainless Steel Electrodes Current Type Stainless Steel Electrodes 3/32 1/8 5/32 3/16 E308L Lime (15 45-85 55-120 65-170 160-205 E309 suffix) 45-85 55-120 65-170 160-205 E310 50-75 70-100 100-145 E312 50-75 70-125 65-170 E316 45-85 55-120 65-170 160-205 E347 60-90 80-130 140-170 coatings use DCEP and Titania (15suffix) coatings use DCEP or AC 14