The difference between Tig Welding & Mig Welding

When I tell people I’m in the welding business they seem to ask these question often;
1) What is Mig Welding?
2) What is Tig Welding?
3) What is the difference between them?

Lets start with what the initials mean.
MIG = Metal – Inert – Gas
TIG = Tungsten -Inert- Gas

First > What’s the same about them?
IG = Inert – Gas
In both cases a gas is fed thru a tube, “whip” to the welding zone. A gun at the end of the whip will have a copper cone that will concentrate the gas into an area that will cover the weld zone. This gas is a pure gas, or combination of gases that protect the weld from undesirable elements. In welding, undesirable elements would be oxygen, and moisture. It’s important to remember that if your gas cone is not close enough to the weld zone or you are in a windy environment that prevents the gas from completely covering the weld, that you will end up with poor quality welds.

What’s the difference?
MIG Welding is a more automated process. The “M” in MIG is the element that transfers the electric arc, and is also the filler material that adds molten metal to the weld zone. The metal is a wire fed thru the same whip as the gas is being delivered to vthe weld zone. This wire is pushed from a wire spool with a wire feeder that is activated when the welder pulls the trigger on the gun at the end of the whip. This trigger activates the flow of gas, wire, and electricity at the same time. The electric arc that melts the base material, (materials that are being welded), and the filler metal, (wire in the whip), is created when the grounded base metal comes in contact with the wire in the gun. Important: the electric arc needs to complete a circular circuit between the welding equipment and the material being welded. This is achieved by connecting a ground clamp from the welder to any conductive metal object in contact with the object being welded.
The MIG welding process is very fast, and very long continuous welds can be accomplished easily by this method.

TIG welding is a much less automated form of the same process. The “T” in TIG is the element that transfers the electric arc, but in this case is not the filler material that is added to the weld zone. The “T” stands for “Tungsten”. The tungsten is a thin rod that is clamped inside the gun, and the guns gas cone. When the weld gun trigger is depressed, electricity flows, and so does the inert gas. In this case the tungsten tip establishes the arc between the base metal, and the tungsten tip which melts the base metal. The tungsten is not consumed and adds nothing to the weld puddle. If filler metal is needed, it must be introduced in a rod form by the operator as required, with another hand.
TIG welding requires a higher degree of talent and training than MIG welding. It is also a much slower process.
So you might ask, why bother using the TIG method.
The TIG method is a much cleaner method of welding when a very high purity of materials is required in the weld zone, ie: pharmaceutical, food service, nuclear, and a whole slew of other applications.
The TIG method is also much more precise, which makes it a better choice for welding very thin metals.

Hope this answers the questions!

Further information about welding processes can be found thru Lincoln Electric, and Miller, the 2 major players in the welding equipment manufacturing.