GAS SHIELDED-ARC WELDING
The primary goal of any welding operation is to
you use a gas as a covering shield around the arc to
make a weld that has the same properties as the base
prevent the atmosphere from contaminating the weld.
metal. The only way to produce such-a weld is to protect
Gas shielding makes it possible to weld metals that are
the molten puddle from the atmosphere. In gas
otherwise impractical or difficult to weld by eliminating
shielded-arc welding, briefly discussed in chapter 3,
atmospheric contamination from the molten puddle.
Figure 8-1 shows the basic principle of gas shielded-arc
The two general types of gas shielded-arc welding
processes are gas tungsten-arc welding (GTA) and gas
metal-arc welding (GMA). GTA is often tilled TIG
(tungsten inert gas) and GMA is referred to as MIG
(metal inert gas). The term inert refers to a gas that will
not combine chemically with other elements.
Gas tungsten-arc welding is basically a form of arc
welding; however, in gas tungsten-arc welding, the elec-
trode is used only to create the arc. The electrode is not
consumed in the weld as in the shielded metal-arc
process. The gas tungsten-arc welding process generally
produces welds that are far superior to those produced
by metallic arc welding electrodes. Especially useful for
welding aluminum, it also may be used for welding
many other types of metals. The GTA process is most
effective for joining metals up to 1/8 inch thick, although
you can use it to weld thicker material.
As shown in figure 8-2, the basic GTA process
Figure 8-1.Gas shielded-arc welding principle.
involves an intense arc between the base metal and a
Figure 8-2.GTA welding process.