What is MIG Welding?
The acronym MIG stands for Metal Inert Gas welding. It is also referred to as GMAW (Gas Metal Arc Welding).
MIG welders are usually referred to as wire-feed welders. The word "Metal" in the process name refers to the consumable wire electrode used in the process. The wire and the weld joint are shielded by an inert gas and the wire electrode which is continuously fed into the arc and weld joint acts as the filler rod. MIG is most typically used to best effect in commercial fabrication settings where continuous welding is desired, and where environmental conditions, joint preparation, and materials can be controlled.
Unlike TIG and stick welding, weld quality results are affected by more machine controlled variables: the current generating capacity of the welder, the thickness of the material to be welded, the thickness of the wire electrode, speed of travel, type of shielding gas used, flow rate of shielding gas, and (of course) the preparation of the joint (i.e., clean, properly beveled, etc.).
About 1 amp of welding current is required for each .001" of material thickness. For example, assuming welding 1/8" plate in a single "pass" requires approximately 125A of welding current. Thicker material requires even more power. A powerful professional grade MIG welder can make beautiful welds of very high quality. However, many of the low cost, low power units sold for consumer use can produce less than acceptable results. Common problems with MIG welds, derives from the fact that many of the low cost MIG units which are sold simply do not have enough power to make proper welds on thicker stock. Usually, poor penetration and or internal cracking (invisible cracks which form under the surface of the bead) are seen.
MIG welders with flux cored wire are also popular in applications where gas shielding can not be accomplished (outside, drafty, or windy conditions), and where a somewhat lower quality weld joint may be acceptable.
What is TIG Welding?
The acronym TIG stands for Tungsten Inert Gas welding. It is also referred to as GTAW (Gas Tungsten Arc Welding) and by the term Heliarc® which was the Linde Company's trade name for the TIG process when it was originally introduced. The arc is started with a sharply pointed tungsten electrode shielded by inert gas. A separate filler rod is fed manually into the weld puddle in much the same way as is done when gas welding.
TIG is a slower process than MIG welding, but it produces a more precise weld and can be used at lower amperages (for welding thin metal) and it can be used on a variety of metals (including aluminum, chrome moly, etc.) and is excellent for highly intricate work.
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