Figure 8-23. - GMA welding process.

Figure 8-24. - Diagram of GMA welding equipment.

position as possible. The electrode is advanced along the line of weld, using the forehand technique.

CAUTION

Always be sure there is good ventilation when welding. The fumes from some of these metals are highly toxic; therefore, a good ventilating system is essential.

GAS METAL-ARC WELDING-GMAW

The gas metal-arc welding process (GMAW), often called MIG, has revolutionized arc welding. In this process, a consumable electrode (in the form of wire) is fed from a spool through the torch (welding gun) at a preset controlled speed. As the wire passes through the contact tube of the gun, it picks up the welding current. The consumable wire electrode serves two functions: it maintains the arc and provides filler metal to the joint. The method of delivery of the filler metal allows GMAW welding to be basically a one-handed operation which does not require the same degree of skill as GTAW. Figure 8-23 shows the basic principle of gas metal-arc welding.

An important factor in the GMA welding process is the high rate at which metal can be deposited. This high rate of metal deposition and high speed of welding results in minimum distortion and a narrow heat-affected zone. When you are deciding whether to use GTA or GMA welding, the thickness of the material should