Metal Inert Gas (MIG) Welding (also known as Gas Metal Arc Welding [GMAW]) is an arc welding technique in which a consumable electrode is used to weld two or more workpieces. A diagrammatic representation of metal inert gas welding is shown below:
Components used in Metal Inert Gas Welding (MIG Welding):
Metal Inert Gas Welding (MIG Welding) makes use of the following components:
- Consumable Electrode
- Inert Gas Supply
- Welding Head
- A.C or D.C Power Supply
- Electrode Feeding Mechanism
The workpiece to be welded and the consumable electrode (in the form of wire) are connected to the Power Supply (D.C or A.C). Whenever the consumable electrode is brought near the workpiece (with a small air gap), an arc is produced. This arc melts the electrode. The melted electrode fills uniformly over the required regions of the workpiece.
An inert gas supply is provided around the electrode (hence the name ‘Metal Inert Gas Welding’) during the welding process. It forms a gas shield around the arc and the weld (See the diagram above). This is intended to protect the weld from the external atmosphere.
The type of electrode used and the shielding gas used primary depends on the material to be welded. In many cases the shielding gas used is a mixture of many gases.
If many workpieces are to be welded continuously an electrode spool (in the form of coil) is used. Consumable electrode is continuously supplied from this spool by a suitable feeding mechanism. Commonly, servo mechanisms are used for feeding long electrodes.
In MIG Welding, consumable electrode itself acts as filler metal. So, no seperate filler rod or filler wire is needed.
Advantages of Metal Inert Gas Welding (MIG Welding):
- Consumable electrodes are easy to feed.
- No filler rod is needed.
- Welding is simple.
- Inert gas shield protects the weld automatically.
Disadvantages of Metal Inert Gas Welding (MIG Welding):
- Improper welding may lead to the floating of solid impurities over the liquid weld.
- If not handled properly, weld may become porous.
- MIG Welding exposes welders to hazardous gases.
- Care must be taken to avoid the formation of less ductile welds.
- Workpieces and Electrodes should be kept clean before welding.