Mig Welding (Metal Inert Gas Welding) or Mag Welding (Metal Active Gas Welding) welding is the most popular of the arc welding processes, this is mainly because Mig Welding is fairly easy and versatile. Mig Welding strikes an arc between a continuously fed Mig Welding filler wire and the workpiece, whilst protecting the welding arc from oxidisation by pouring a shielding gas over the weld pool. The choice of weld shielding gas will depend on the material being used and the quality required.
Pure Co2 Welding Gas is the cheapest gas to use when Mig Welding, but produces a fairly fierce welding arc with more spatter and a harder weld. The Welders Warehouse recommends using pure Co2 for Mig Welding on welding jobs where quality is not important.
Argon/Co2 welding gas mix is the most versatile welding gas to use with a Mig Welder as it can be used for Mig Welding Steel and Stainless Steel. Additionally, using Argon/Co2 mix welding gas with your Mig Welder will produce a softer more controllable arc and less hard finished weld, ideal for thin material.
Pure Argon welding gas is only used with a Mig Welder for welding Aluminium. Welding Aluminium with a Mig Welder is very difficult and is only recommended for the experienced Mig Welder operator.
Where welding gas is either unavailable or impractical (such as outside in windy conditions) flux cored wires can be used. Welding with flux cored wire is like MMA welding but with a continuous electrode.
Two methods of metal transfer from the welding filler wire to the workpiece are used:
Dip transfer - This is achieved at lower voltage settings. The wire is fed into the weld pool creating a "short circuit" the resulting heat burns the wire off. This happens many times per second and is responsible for the characteristic crackling sound of Mig/Mag welding and the associated spatter. Dip transfer offers the advantage of being able to weld in position, ie vertical.
Spray Transfer - This is achieved at higher voltage settings and is where the filler wire is melted and transfers in globules to the weld pool. Spray transfer offers smoother welds with little welding spatter but cannot be used in position.
The Mig Welders power is usually adjusted in steps and it is the welding arc Voltage that is adjusted NOT the welding Current (amps). The welding arc current will be determined by the combination of welding Voltage that has been set and the welding wire diameter. The greater the Mig welding wire, the more welding current will flow and, therefore, the greater the heat input. Larger diameter welding wire will also allow larger welds to be produced.