Gas metal-arc (GMA) welding is a process that produces fusion by heating with an electric arc between a consumable wire electrode and the work. The arc and

weld puddle are shielded from the atmosphere by a gas, or a gas and a flux. The shielding gas protects the molten weld metal from oxidation or contamination by the surrounding atmosphere.

The consumable-wire electrode for GMA welding is fed through the torch to the welding arc at the same rate as the heat of the arc melts off the end of the electrode. The shielding gas flows through the torch to the arc area. The melting rate of the tiller wire depends on the level of the welding current, but must be the same as the feeding rate to maintain a constant arc length. This means that a constant balance must be maintained between the welding current and wire feeding rate.