FCAW (Flux-Cored Arc Welding) Fundamentals
This domain tests FCAW fundamentals: flux-cored wire design, gas-shielded versus self-shielded operation, polarity, slag, deposition and outdoor use. The exam often asks you to select the right variant and explain its limitations.
Core rules
- Gas-shielded FCAW uses an external shielding gas, commonly CO2 or an Ar/CO2 mix, and usually runs DCEP.
- Self-shielded FCAW creates its own shielding from the flux core; it commonly runs DCEN and is more tolerant of outdoor drafts.
- The flux provides slag, arc stabilisers and sometimes alloying elements; slag must be removed between passes.
- FCAW generally gives high deposition and good penetration, but fume and spatter still need control.
Worked example
A contractor must weld a structural fillet outdoors where wind is likely. Reasoning: choose self-shielded FCAW with DCEN, follow the wire manufacturer’s current and voltage, and use a drag angle. No external gas cylinder is needed, but the slag must still be chipped and brushed. If the specification requires gas-shielded FCAW for toughness or low hydrogen, then wind protection and preheat/drying controls become essential.
Traps
Do not run self-shielded wire on DCEP just because it is the common solid-wire polarity. Do not leave slag between passes. Do not store flux-cored wire in damp conditions. Do not assume self-shielded means no fume control is needed.