Specific Welding Process: SMAW, GMAW, FCAW, and GTAW Fundamentals
Why process identity drives every other answer
A candidate must be able to separate the four common arc processes by their consumable, shielding method, and typical current type. SMAW (stick) uses a flux-coated electrode that melts to form both filler and slag; the flux provides shielding gas as it burns, so no external gas cylinder is needed. GMAW (MIG) uses a continuously fed solid wire and an external shielding gas, usually a mix of argon and carbon dioxide for steel. FCAW uses a tubular wire filled with flux; some wires are self-shielded and need no gas, while others require gas shielding. GTAW (TIG) uses a non-consumable tungsten electrode and a separate filler rod, with argon or helium shielding.
Concepts to master
Know which processes tolerate wind and outdoor work (SMAW and self-shielded FCAW), which produce slag that must be chipped (SMAW, FCAW), and which are suited to thin sheet and root passes (GTAW). Understand polarity: SMAW with a cellulosic electrode typically runs electrode-negative (DCEN) for deep penetration, while GMAW runs electrode-positive (DCEP) to carry heat into the work. Recognize that process selection is limited by position, thickness, and code requirements, not personal preference.
Traps in questions
Watch for a process described by its shielding gas rather than its electrode. A question saying "a solid wire with CO2 shielding" is GMAW, not FCAW. Another trap swaps polarity: DCEP is not the same as DCEN, and the two give opposite penetration profiles. Also beware of questions implying GTAW uses a flux; it does not.
Rule of thumb
If the stem mentions a coated electrode and slag, answer SMAW. If it mentions a wire feeder plus a gas bottle, answer GMAW. If it mentions a tubular wire that may run without gas, answer FCAW. If it mentions tungsten and a separate rod, answer GTAW.