What is MIG Welding?

MIG Welding, also known as Gas Metal Arc Welding (GMAW), is a process that utilizes a continuously fed solid electrode, shielding gas from an externally supplied source, and electrical power to melt the electrode and deposit this molten material in the weld joint. The equipment used automatically regulates the electrical characteristics of the arc. The only manual controls required of the welder for semi-automatic operation are travel speed, travel direction and gun (torch) positioning. Given proper equipment settings, the power supply will provide the necessary amperage to melt the electrode at the rate required to maintain the pre-selected arc length (voltage). For example, an increased stick-out, produced by drawing the torch back from the work piece, results in a reduction in current from the power supply. This maintains the same heating of the electrode and returns the arc length to its preset condition. Filler metal selection should be closely matched to the base material being welded. In MIG Welding, the filler metal not only conducts current to the arc zone (resulting in melting the base metal and electrode), but adds reinforcement to the completed weld joint.

MIG Welding can be used on a wide variety of metals and in a number of different base metal thicknesses. Its successful application depends on proper selection of:

  • Electrode – composition, diameter and packaging
  • Shielding Gas – type (composition), purity and flow rate
  • Process Variables – current, voltage, mode of metal transfer and travel speed
  • Equipment – power source, welding gun and wire feeder