Figure 8-3.Power supply unit specifically designed for gas tungsten-arc welding.
tungsten electrode. The arc, the electrode, and the weld
zone are surrounded by an inert gas (usually either
helium or argon or a mixture of the two) that displaces
the air and eliminates the possibility of weld contami-
nation by the oxygen and nitrogen present in the
atmosphere. The tungsten electrode has a high melting
point that makes it virtually nonconsumable.
Specific advantages of gas tungsten-arc welding
include the following:
Welding can be done in all positions.
The weld is usually equal to the base metal in
Flux is not used; therefore, finished welds do not
require cleaning of corrosive residue.
Smoke or fumes are not present to obscure vi-
sion; therefore, you can easily see the welding
Distortion of the base metal is minimal because
the heat is concentrated in a small area.
No splatter is produced because metal is not
transferred across the arc.
GTA WELDING EQUIPMENT
The equipment and supplies required for gas tung-
sten-arc welding consist of an electric power unit,
shielding gas, a pressure-reducing regulator and flow-
meter, an electrode holder (commonly called a torch),
nonconsumable tungsten electrodes, filler rods, a supply
of cooling water (when required), and personal protec-
Electric Power Unit
Most welding power sources can provide the cur-
rent needed for GTA welding. The common welding
machines, whether alternating current (at) or direct
current (de), have their advantages in certain welding
applications; however, they can be cumbersome and
their hose and cable connections can create difficulties.
Because of this, specially designed machines with all
the necessary controls are available for gas tungsten-arc
welding (fig. 8-3).
GTA power units are equipped with solenoid valves
that turn the flow of shielding gas and cooling water on
and off. They are also equipped with a hand- or foot-
operated remote-control switch that turns the water and
gas on and off. Some of these remote-control devices