Mig welding

From GAWDAwiki

Metal Inert Gas (MIG) welding, also known as Gas Metal Arc (GMAW) welding, joins metals by heating them to their melting points via an electric arc. The arc, shielded from atmospheric contaminants by a shielding gas, exists between a continuous, consumable electrode wire and the metal.^[1] The power for MIG welding is most typically direct current (DC), which provides a constant voltage throughout the welding process. Some MIG welders use the varying voltage of alternating current (AC) power.

MIG welding is a "semi-automated" process developed in the 1940s. MIG welding machines provide a continuous feed of a consumable metal electrode that can be either a solid wire or flux cored wire. Welders strike an electric arc and then feed the wire from a spool through the torch after pulling the trigger to initiate the wire. The heat of the arc melts the wire into the weld joint and a shielding gas protects the weld from contamination.

Some flux cored wires emit their own shielding gas as they melt and leave a layer of flux on top of the weld that protect it from contamination and do not require the addition of a shielding gas.

Advantages

MIG welding is quicker than stick welding techniques. This makes it well suited for softer metals like aluminum.
MIG welding produces a clean weld with very little spatter, due to protective shielding gases around the welding arc.
MIG welding is suitable for a wide variety of metals and alloys.
The use of semi-inert shielding gases like carbon dioxide makes MIG welding both effective and economical. Gases can be purchased pre-mixed in cylinders or can be generated on-site using a gas mixer.^[2]^[3]
The continuous wire feed makes MIG welding a very fast welding technique.
The point and shoot nature of MIG welding makes it simple to learn.
MIG operators have greater control of the arc and can weld in a wide variety of positions effectively.

Disadvantages of MIG Welding

The ongoing cost of refilling shielding gas and replacing tips and nozzles.
Metals must be clean in order to produce a solid weld that is free from defects such as porosity.
MIG welding is not as effective for welding thicker steel.

MIG Welding Techniques

The wire should stick out of the MIG gun about one quarter of an inch. Some welders recommend more or less than that.
While welding the wire should be pointed at the leading edge of the weld pool.
Use both hands on the weld gun in order to achieve maximum control.
Weld in a series of tight, cursive "e's" for slightly wider joints that are not appropriate for straight stringer beads.
The smallest diameter wire will provide the best control when welding in difficult positions.
When welding uphill, push the torch forward in a side to side motion that moves up and down in a series of "v's" and briefly pauses on the edges of the weld joint without stopping in the middle.
A cleaner weld will be produced by keeping the torch liner and nozzle clean of spatter.