Welding Fundamentals and Processes
What you must know
A Level 2 inspector is expected to explain how heat, filler metal, and shielding interact in each common arc process. Know the differences between SMAW, GMAW (including short-circuiting, globular, spray, and pulsed transfer), FCAW (self-shielded versus gas-shielded), GTAW, SAW, and the resistance and solid-state processes. Understand arc characteristics: current type and polarity, duty cycle, arc length, and travel speed, and how each affects penetration, bead shape, dilution, and spatter. Know typical welding positions (flat, horizontal, vertical, overhead) and what makes a procedure suitable for each.
Traps in questions
- Confusing electrode negative (straight polarity) with electrode positive (reverse polarity) and the resulting heat balance in GTAW versus GMAW.
- Assuming higher current always improves quality; excess current can cause undercut, burn-through, and cracking.
- Mixing deposition rate with deposition efficiency.
- Forgetting that shielding gas composition changes transfer mode and toughness.
- Treating duty cycle as a continuous rating rather than a percentage over a 10-minute period at a stated current.
Worked example
A power source is rated 250 A at 60% duty cycle. At 300 A the allowable duty cycle scales inversely with current squared: (250/300)² × 60% ≈ 42%. So a welder running 300 A continuously for 10 minutes exceeds the rating and risks overheating. Rule of thumb: when current rises, duty cycle falls by the square of the ratio.
Inspection link
Process knowledge lets you predict defect types before you look: lack of fusion in short-circuit transfer, slag inclusions in multi-pass FCAW, and porosity from poor gas coverage.