Shielded Metal Arc Welding (SMAW)
This domain tests electrode classification, current and polarity selection, arc control, low-hydrogen storage, and the relationship between welding variables and weld soundness.
Classification
Read E7018 from left to right: E is electrode; 70 is minimum tensile strength in ksi (70,000 psi); 1 means all positions; 8 is a low-hydrogen iron-powder coating that runs on AC or DCEP. E6010 is 60 ksi, all-position, cellulosic sodium, DCEP. E6011 is similar but AC/DCEP. Position digit 2 means flat and horizontal only.
Technique and storage
Set current by electrode diameter and position; a 1/8 in E7018 commonly runs 110–150 A, while 1/8 in E6010 runs about 90–130 A. Hold a short arc, about one electrode diameter, and use a 10–15° drag angle. Clean slag between passes. Low-hydrogen electrodes absorb moisture: keep E7018 in a holding oven at 250–300°F and recondition exposed electrodes per the manufacturer before use.
Heat input
Heat input in J/in = (volts × amps × 60) ÷ travel speed in in/min. It affects cooling rate, hardness, and cracking.
Worked example: A procedure limits heat input to 35 kJ/in. The welder uses 25 V, 120 A, and 6 in/min. Heat input = (25 × 120 × 60) ÷ 6 = 30,000 J/in = 30 kJ/in, so the pass is acceptable. At 4 in/min the same settings give 45 kJ/in, which exceeds the limit and requires a travel-speed change or procedure review.
Traps: E7018 is not a DCEN electrode; “70” is 70 ksi, not 70 amps; a damp 7018 can deposit hydrogen and crack; a long arc increases spatter and loses shielding.