SMAW, GMAW, GTAW, FCAW, SAW — arc physics, transfer modes, electrode classification, heat input formula, and process selection criteria for structural applications.
Arc Welding Process Fundamentals
The AWS CWI Part A exam tests knowledge of all major arc welding processes: SMAW (covered electrode), GMAW (wire + shielding gas), GTAW (non-consumable tungsten), FCAW (flux-cored wire), and SAW (submerged arc). Each process has distinct shielding mechanisms, polarity requirements, and position limitations.
Heat Input Formula: HI (J/in) = (Voltage × Amperage × 60) / Travel Speed (in/min)
Key Process Limits:
- SAW: Flat (1G) and horizontal (2G) only — granular flux cannot be retained vertically
- GMAW spray transfer: Requires >80% Ar shielding gas + current above transition threshold
- GTAW: AC preferred for aluminum (cathodic cleaning); DCEN for steel
- E6010: DCEP only; deep penetrating, fast-freezing slag — the pipe root electrode
- E7018: Low hydrogen, requires baking at 700–800°F; maximum 4-hour exposure after removal from oven
Confusing DCEP (electrode positive, more heat at electrode) vs DCEN (electrode negative, more heat at work). Arc blow affects DC welding of ferromagnetic materials — switch to AC or reposition work lead to correct.
AWS A5.1 (SMAW electrodes); AWS A5.18 (GMAW solid wire); AWS A5.20 (FCAW); AWS A5.9 (GTAW filler metals); AWS A5.17 (SAW).