By A Nirala Galgotias University MIG Welding By A Nirala Galgotias University

(GMAW) MIG Welding MIG stands for metal inert gas. This type of welding refers to the use of electricity to melt and fuse pieces of metal together. Out of the various welding styles MIG is probably the most basic of all. With this technique, a wire electrode is used to create a flaming arc that generates heat and creates filler material. While this is happening, an inert gas is released around the area of the weld to keep out external contamination. Gas Metal Arc Welding (GMAW) is frequently referred to as MIG welding.  MIG welding is a commonly used high deposition rate welding process.  MIG welding is therefore referred to as a semi-automatic welding process. 

The primary shielding gasses used are: Argon  Argon – 95% to 5% Oxygen  Argon – 75% to 25% CO2  Argon/Helium CO2 is also used in its pure form in some MIG welding processes.  However, in some applications the presence of CO2 in the shielding gas may adversely affect the mechanical properties of the weld. 

Welding Parameters Which affect MIG Welding current Wire electrode extension Welding voltage Arc travel speed

WELDING CURRENT The welding current is the electrical amperage in the power system as the weld is being made. welding current is directly related to wire- feed speed (if the wire extension beyond the guide tip is constant). As the wire-feed speed is varied, the welding current will vary in the same direction. In other words, an increase (or decrease) in the wire-feed speed will cause an increase (or decrease) of the current.

WIRE ELECTRODE EXTENSION Wire extension or ”stick-out” is the distance between the last point of electrical contact, usually the end of the contact tip, and the end of the wire electrode.

WIRE ELECTRODE EXTENSION Controlling tip-to-work distance is important. Long extensions result in excess weld metal being deposited with low arc heat. This can cause poor bead shape and low penetration. In addition, as the tip-to-work distance increases, the arc becomes less stable.

WELDING VOLTAGE voltage setting directly controls the arc length. In addition, a certain range is required to maintain arc stability at any given welding current level.

ARC TRAVEL SPEED As the material thickness increases, the travel speed must be lowered. For a given material thickness and joint design, as the welding current is increased, so is the arc travel speed. The converse is also true. Higher welding speeds are attainable by using the forehand welding technique.

MIG Welding advantages Higher productivity due to time saved by not having to constantly change rods or chip plus not having to brush the weld repeatedly. Not difficult to learn and master Makes a great appearing weld Little clean up Can weld on a variety of metals (stainless, mild steel, and aluminum) Can weld in any position Simple techniques Continuously fed wire Operator has a better ability to concentrate on arc control. Can weld quicker and with more efficiency Minimal weld defects Produces little to no slag

MIG Welding disadvantages The bottle of shielding gas can be bothersome. The cost of replacing tips and nozzles. Material has to be free of rust or dirt to get a good weld. Does not deliver proper penetration for thicker steel to deliver a solid weld.

The applications for MIG welding The applications for MIG welding are as:- For the home or hobby welder MIG welding can be used for common household projects such as repairing a metal fence, swing set, or automobile. MIG welding requires a low skill level, produces a relatively clean weld, and offers versatility. For these reasons, MIG welding is one of the most popular welding processes.