Page 95 - Module DMV20173

5. 0 JOINING PROCESSES

5.2.4 GAS METAL-ARC WELDING (GMAW)

1. Gas Metal-Arc Welding (GMAW) also known as metal inert gas (MIG). Figure 5.5
shows the illustration of GMAW process and basic equipment used in gas metal-arc-
welding operations.
2. The Metal Inert Gas Process uses a consumable electrode of wire form and an inert

gas shield of carbon dioxide when welding carbon steel.
3. The wire electrode provides a continuous feed of filler metal allowing welds of any
length without stopping. This consumable electrode is in the form of continuous filler
metal, which is fed through special gun.
4. This process is an electric arc welding process in which is an arc is struck between a

consumable wire electrode and the workpiece to be welded.
5. The inert gas shield eliminates slag and allows cleaner and stronger weld, an inert
gas surrounds the arc and shields it from the ambient to prevent oxidation.
6. The following gases are used: Argon (Ar), helium (He) and carbon dioxide. CO2 is

used extensively to weld steel, as it is the cheapest gas. Ar and He are mainly used
in the welding of aluminium, magnesium and stainless steel.
7. Carbon steels, low alloy steels, stainless steels, most aluminium alloys, zinc based
copper alloys can be welded using this process.
8. MIG welding causes a lot of spatter that needs to be sanded or filed, if cosmetically

objectionable. Thus, it is best to avoid MIG welding on exterior surfaces if cosmetics
are important.
9. The industries served include shipbuilding, general engineering (pressure vessel
tanks, pipes) and automotive industries.

10. This process is used widely for automated welding using robots.

BPLK 127 DMV 20173