Although it can produce
outstanding results, GTA welding can be expensive. The equipment, electrodes, and
shielding gas are costly and the material you weld is usually much more expensive than the
material welded by other welding processes. To avoid costly mistakes, you should take the
time to prepare for each welding operation fully. Preparation is the key to producing
quality weldments.
Specific information on the
different manufacturers of GTA welding equipment is not provided in this course. You
should read the manufacturer’s instruc-tional pamphlets for specific information on
your machine. The following suggestions are considered general and you can apply them to
any GTA welding operation:
Prepare the joint according
to the welding procedure you are performing.
Clean the metal of all
oxidation, scale, oil, dirt, or other foreign matter. Regardless of the type of joint
used, proper cleaning of the metal is essential. For best results, use a stainless steel
wire brush.
Check all electrical
circuit connections to make sure they are properly connected and all fittings are tight.
Be sure the torch is the
right type and capacity for the current at which most of the welding will be done. Some
manufacturers offer different torches for different ranges of welding current.
Check the size, appearance,
and position of the tungsten electrode in the torch. Ensure that the electrode diameter
and nozzle size meet the manufacturer’s recommendations. The tip should be properly
shaped as discussed earlier (refer to figure 8-9). The electrode should extend beyond the
end of the gas cup a distance ranging from 1/8 to 3/16 of an inch for butt welding and 1/4
to 3/8 of an inch for fillet welding. Check the electrode for positioning and good
electrical contact. The electrode should be clean and silvery. A dirty tungsten electrode
can usually be cleaned satisfactorily with a fine emery cloth. If severely contaminated,
the electrode should be replaced or the tip broken off and dressed on a grinding wheel. A
contaminated tungsten electrode and a good tungsten electrode are shown in figure 8-12.
Check the ground cable
connections to the work-piece. The connections should be periodically checked after
welding begins because they tend to work loose. When this happens, the welding current
varies.
Set the machine for the
correct welding amperage. (Follow manufacturer’s recommendations.)
Open the cylinder valve and
adjust the gas flow. Before welding, check the connections on the gas supply for leaks
with soapy water.
If using a water-cooled
torch, turn on the water. Be sure the water pressure is not higher than recommended by the
torch manufacturer.
Published
by SweetHaven Publishing Services
Based upon a text provided by the U.S. Navy
