Gas metal arc welding, in which a solid wire fed from a spool through a gun is both electrode and filler, shielded by argon, CO2 or blends. It is fast, easy to learn and suits robots, so it dominates fabrication and manufacturing. Metal transfer mode, set mostly by voltage, wire feed speed and gas, ranges from short circuit through globular to spray and pulse. Wind strips the shielding, which limits outdoor use.
Fab shop runs GMAW on everything under half inch, 0.035 wire and 75/25 gas.
Most MIG trouble lives in the gun, not the machine: a worn contact tip, wrong liner or spatter-packed nozzle causes erratic feed and porosity.
Also heard as
- MIG
- MAG
- wire welding
- hard wire
Do not mix it up with
- FCAW: GMAW uses solid wire and relies entirely on gas shielding, while FCAW uses tubular wire with flux inside.
Related terms
Short-circuit transfer
GMAW mode in which the wire touches the pool and shorts many times a second, giving a cool, controllable arc.
Spray transfer
GMAW mode in which a stream of fine droplets sprays across the arc, giving high deposition and deep fusion.
Shielding gas
Gas that protects the arc and molten weld from the surrounding air in GMAW, GTAW and gas-shielded FCAW.
Stickout
The length of wire or electrode extending past the contact tip or cup, which changes current and heat.
Suitcase
Shop name for a portable, enclosed wire feeder carried out to the work on a long lead.