What is MIG Welding?

MIG (Metal Inert Gas) welding, also sometimes called GMAW (gas metal arc welding), is a welding process that was originally developed back in the 1940's for welding aluminum and other non-ferrous metals. MIG welding is an automatic or semi automatic process in which a wire connected to a source of direct current acts as an electrode joins two pieces of metal, as it is continuously passed through a welding gun. A flow of an inert gas (originally Argon) is also passed through the welding gun at the same time as the wire electrode. This inert gas acts as a shield, keeping air borne contaminants away from the weld zone.

The primary advantage of MIG welding is that it allows metal to be welded much quicker than traditional welding "stick welding" techniques. This makes it ideal for welding softer metals such as aluminum. When MIG welding was first developed, the cost of the inert gas (i.e., argon) made the process too expensive for welding steel. However, over the years, the MIG welding process has evolved and semi inert gases such as carbon dioxide can now be used to provide the shielding function which makes MIG welding cost effective for welding steel.

Besides providing the capability to weld non-ferrous metals, MIG welding has other advantages:

• It produces long continuous welds much faster than tradition welding methods.
• Since the shielding gas protects the welding arc, MIG welding produces a clean weld with very little splatter.
• The versatility of MIG welding means it can be used with a wide variety of metals and alloys.

The primary disadvantages of MIG welding are:

• The welding equipment is quite complex (MIG welding requires a source of direct current, a constant source and flow of gas as well as the continuously moving wire electrode). Plus, electrodes are available in a wide range of sizes and made from a number of metal types to match the welding application.
• The actual welding technique used for MIG welding is different from traditional welding practices, so there is learning curve associated with MIG welding even for experienced welders. For example, MIG welders need to push the welding puddle away from them and along the seam.
• The necessity for the inert gas shield means that MIG welding cannot be used in an open area where the wind would blow away the gas shield.

Since it's development in the middle of last century, MIG welding has become commonplace in many manufacturing operations. For example MIG welding is commonly used in the automobile industry because of its ability to produce clean welds, and the fact that it welds metals quickly.

Written by Murray Anderson