Welding processes and equipment
This domain tests whether you can classify a welding process by ISO 4063, state its power-source and consumable characteristics, and derive the parameters that appear on a WPS.
Process numbering and characteristics
- 111 MMA, 121 SAW (wire), 131 MIG, 135 MAG, 136 flux-cored, 138 metal-cored, 141 TIG, 15 plasma, 311 oxy-acetylene, 21 resistance spot, 42 laser, 78 stud.
- MMA and TIG use drooping (constant-current) sources; MIG/MAG and SAW use flat (constant-voltage) characteristics.
- Polarity: MAG normally uses DCEP for penetration; TIG on carbon steel uses DCEN so the tungsten survives.
- Duty cycle: a 300 A/60 % set delivers 300 × √0.6 ≈ 232 A at 100 %.
Heat input, the calculation examiners like
Q = k · (60 · U · I) / (1000 · v), with v in mm/min and Q in kJ/mm. k = 1.0 for 111, 141 and 121; k ≈ 0.8 for 131/135/136.
Worked example
Process 135, U = 26 V, I = 280 A, travel speed 350 mm/min. Q = 0.8 × 60 × 26 × 280 / (1000 × 350) = 349 440 / 350 000 ≈ 1.0 kJ/mm. The WPS permits 0.8–1.2 kJ/mm, so the run is acceptable. At 500 mm/min the value drops to 0.70 kJ/mm and falls outside the qualified range - the same weld, a different result, because travel speed was not controlled.
Traps
Putting mm/s into the formula (a factor-of-60 error), dropping k, quoting duty cycle as a current rather than a percentage, and confusing 136 (flux-cored) with 138 (metal-cored).