Gas metal arc welding

Gas metal arc welding (GMAW), commonly called metal inert gas welding (MIG welding), is a type of welding which utilises a welding gun through which a continuous wire electrode and an inert shielding gas is fed. The wires used in the electrodes are typically 0.7, 1.0, 1.2 or 1.6 mm diameter, and usually solid. A related wire-welding process called flux-cored arc welding (FCAW) uses a hollow wire filled with a flux, eliminating the need for a shielding gas. Typically a constant voltage welding power supply is used for GMAW but it is possible to use a voltage sensing wire feeder with a constant current power source.

When welding steel, to prevent nitrogen and oxygen contaminating the weld, an inert shielding gas is fed around the arc, usually 75% argon and 25% carbon dioxide. The gas is fed in sufficient quantity to completely blanket the arc and the liquid metal near it. When welding aluminium the same principle is used; however, the gas is pure argon.

In metal active gas (MAG) welding, a mixture of gases is used that reacts with the metal to improve the weld quality. Usually a varying mixture of argon and carbon dioxide and traces of hydrogen.

MIG/MAG welding is typically used in the automobile industry as relatively thin sheet metal can be welded. It is best used in flat welds as it is difficult, but not impossible, to perform vertical and overhead welding using MIG.

Using MAG welding it is possible to weld aluminium, copper and stainless steel.

See also

• Gas tungsten arc welding or TIG welding
• Shielded metal arc welding or stick welding

External links

• Miller MIG welding
• ESAB.com