Metal inert-gas welding

In the MIG welding process, an electric arc is established between the work piece and a wire electrode. The electrode is continuously fed by a wire feeder through a torch. The arc continuously melts to form the weld puddle. An appropriate gas or gas mixture shields the weld area from atmospheric contamination. The MIG process has advantages of high deposition rates, faster speed, and excellent weld quality. A drawback of MIG is that base metal dilution is more than other processes. As a result, a second layer of weld may have to be applied to achieve the desired hardness. 

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An engineer using a metal inert gas welding torch in the manufacture of an exhaust for a racing car. 

Arc Joins or cuts metal parts by heat generated from an electric arc that extends between the welding electrode and the electrode placed on the equipment being welded. Includes gas-metal arc welding (also called metal inert gas welding) and flux-core arc welding (mistakenly called core wire welding). 

Finally, asphyxiation, due to a lack of oxygen, is a problem In confined spaces particularly when MIG (metal Inert gas) welding Is taking place. 

Figure 11.7 Effect of the heat of welding on micro-structure, hardness, and corrosion potential of welded assemblies of two aluminum alloys. (Top) Alloy 5456-H321 base metal with Alloy 5556 filler, three-pass metal inert gas weld. (Bottom) Alloy 22I9-T87 base metal with Alloy 2319 filler, two-pass tungsten inert gas weld. The differences in corrosion potential between the HAZ and the base metal can lead to selective corrosion. (Reproduced with permission from Daubert Cromwell.)...

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