MIG welding was developed in the 1940's and 60 years later the general principle is still very much the same. MIG welding uses an arc of electricity to create a short circuit between a continuously fed anode (+ the wire-fed welding gun) and a cathode ( - the metal being welded).
The heat produced by the short circuit, along with a non-reactive (hence inert) gas locally melts the metal and allows them to mix together. Once the heat is removed, the metal begins to cool and solidify, and forms a new piece of fused metal.
A few years ago the full name - Metal Inert Gas (MIG) welding was changed to Gas Metal Arc Welding (GMAW) but if you call it that most people won't know what the heck your talking about - the name MIG welding has certainly stuck.
MIG welding is useful because you can use it to weld many different types of metals: carbon steel, stainless steel, aluminum, magnesium, copper, nickel, silicon bronze and other alloys.
Here are some advantages to MIG welding:
The ability to join a wide range of metals and thicknesses
· All-position welding capability
· A good weld bead
· A minimum of weld splatter
· Easy to learn
Here are some disadvantages of MIG welding:
MIG welding can only be used on thin to medium thick metals
· The use of an inert gas makes this type of welding less portable than arc welding which requires no external source of shielding gas
· Produces a somewhat sloppier and less controlled weld as compared to TIG (Tungsten Inert Gas Welding)