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GMAW is a process that melts and joins metals by heating them with an arc established between a continuously fed filler wire electrode and the metals, as shown in Figure 1.18. Shielding of the arc and the molten weld pool is often obtained by using inert gases such as argon and helium, and this is why GMAW is also called the metal–inert gas (MIG) welding process. Since noninert gases such as CO₂ are also used, GMAW seems a more appropriate name. This is the most widely used arc welding process for aluminum alloys. Figure 1.19 shows gas–metal arc welds of 5083 aluminum, one made with Ar shielding and the other with 75% He–25% Ar shielding [9]. Unlike in GTAW, DCEP is used in GMAW. A stable arc, smooth metal transfer with low spatter loss and good weld penetration can be obtained. With DCEN or AC, however, metal transfer can be erratic.

Figure 1.18 Gas–metal arc welding: (a) overall process; (b) welding area enlarged.

Figure 1.19 Gas–metal arc welds in 6.4‐mm‐thick 5083 aluminum made with argon (left) and 75% He–25% Ar (right).

Source: Gibbs [9]. Welding Journal, December 1980, © American Welding Society.