MIG (Metal Inert Gas): Pure argon or argon/helium shielding. For aluminum, copper, titanium. MAG (Metal Active Gas): CO₂ or O₂ in shielding gas. For carbon steel and low-alloy steel.
Three challenges: 1) Al₂O₃ oxide layer melts at 2050°C (aluminum at 660°C) — needs AC or pulse to disrupt. 2) Hot cracking sensitivity. 3) Porosity from hydrogen absorption. Wire selection: ER4043 (5% Si, good fluidity) or ER5356 (5% Mg, higher strength).
Current switches between high (spray transfer) and low (background) at 50-400Hz. Benefits: controlled heat input, minimal spatter, all-position capability. Rapidly replacing conventional MAG in automotive and precision manufacturing.