Gas Metal Arc Welding (GMAW)

Gas Metal Arc Welding (GMAW) uses a consumable filler wire as the electrode. The wire is fed continuously by a wire feeder, and an electric arc is struck between the wire and the workpiece. Shielding gas is ejected through the torch nozzle to isolate the arc and molten pool from ambient air. The arc heat melts both the wire and base material to form a weld joint.Commonly known as gas-shielded welding, it is divided into MIG (inert gas) and MAG (active gas) according to different shielding gases. The so-called CO₂ welding widely used in domestic factories belongs to MAG welding (pure CO₂ or Ar+CO₂ mixture).

Classification

MIG Welding (GMAW-I):Inert shielding gas (Ar, Ar+He); applied to non-ferrous metals such as aluminum, stainless steel and copper alloys.

MAG Welding (GMAW-A):Active shielding gas (Ar+CO₂/O₂ or pure CO₂); widely used for carbon steel and low-alloy structural steel.

Advantages

High efficiency: Continuous wire feeding eliminates frequent electrode replacement, with a higher deposition rate than manual welding.

Strong adaptability: Adjustable parameters and shielding gas enable all-position welding (flat, horizontal, vertical and overhead).

Reliable weld quality: Gas shielding effectively prevents porosity and nitriding, superior to manual welding.

Good visibility: Open arc allows easy observation of the molten pool.

Low distortion: Relatively narrow heat-affected zone, suitable for thin to medium-thick plates.

Limitations

Poor wind resistance: Porosity easily occurs outdoors without wind shielding (wind shelter required).

Sensitive to grease and rust; thorough pre-weld cleaning is necessary.

Heavy spatter in pure CO₂ welding (low spatter for argon-rich MAG and MIG processes).

Requires gas cylinders, regulators, wire feeders and other accessories, less mobile than manual welding.