MIG Welding

Inert Gas Welding. It is a process developed in the 1940’s, and is considered semi-automated. This means that the welder still requires skill, but that the MIG welding machine will continuously keep filling the joint being welded.

MIG welders consist of a handle with a trigger controlling a wire feed, feeding the wire from a spool to the weld joint. The wire is similar to an endless bicycle brake cable. The wire runs through the liner, which also has a gas feeding through the same cable to the point of arc, which protects the weld from the air.

MIG welding is most commonly used in fabrication shops where production is high, and the possibility of wind blowing away your gas shielding is unlikely.

Those seeking a job as a welder would be advised to know all of the names by which this process is known. Employers may use other names in the classifieds or on a written test.

When it was first developed it was called (GMA) Gas Metal Arc. It is also known as; GMAW or Gas Metal Arc Welding. Technically the differences in the names are the type of gas used, Inert gas versus non-inert gas.

How MIG Welding Works

MIG weld welding requires three things, electricity to produce heat, an electrode to fill the joint, and shielding gas to protect the weld from the air. MIG welding is done using a very small electrode that is fed continuously, while the operator controls the amount of weld being done. In some cases when a robot takes over this process, it becomes automatic welding.

MIG Voltage Type and Welding Polarity

MIG welding unlike most other welding processes has one standard voltage type and polarity type. The voltage used is D/C direct current, much like the current in a car battery. Direct current flows in one direction, from the negative (-) to the positive (+).

The polarity used is also standard and that is D/C electrode (+) positive. This means that the handle is the positive side of the circuit, or it may be said, the electricity flows from the metal in to the welding handle.

The power source used for MIG welding is called a “constant voltage power supply”. In MIG welding the voltage is what is controlled and adjusted. When comparing MIG welding to Arc or TIG welding, MIG welding machines use voltage settings to set the machine. TIG and Arc welding machines use amperage to set the machine or a “constant amperage power supply”.