Table 8-5.Suggested Inert Gas Flow Rates for Various Metals
To obtain an accurate reading, you must mount the
meter in a vertical position. Any slant will create an
off-center gas flow and result in an inaccurate reading.
Also, because gas densities vary, you should use differ-
ent flowmeters for different gases.
The flow of gas necessary for good GTA welding
depends primarily on the thickness of the material.
Other factors include the following: welding current,
size of nozzle, joint design, speed of welding, and a
draft-free area in the location the welding is done. This
last factor can affect gas coverage and use considerably.
Table 8-5 shows the approximate gas flow rates for
various types of metals.
Normally you do not require filler metal when GTA
welding light-gauge materials since they tend to flow
together easily. Thick material and thin material that
needs reinforcing should be welded using a filler metal.
Special filler rods are available for GTA welding;
therefore, you should not use welding rods designed for
oxyfuel welding because they can contaminate the tung-
sten electrode. You should use filler rods that have the
same composition as the base metal; for example, use
mild steel rods to weld low-carbon steel and aluminum
rods for welding aluminum. Additionally, there are
many different compositions of the same metal; there-
fore, you should select a filler metal of the same com-
position as the metal you are welding.
Personal Protective Equipment
A welding hood like the one used in shielded
metal-arc welding should be used for gas tungsten-arc
welding. The correct shade of lens depends on the
intensity of the arc. Chapter 3 provides a chart of rec-
ommended lens shades based on the current setting of
the machine. For normal GTA welding at current ranges
of 76 to 200 amperes, a shade No. 10 lens is satisfactory.
Eye fatigue indicates you should use a different shade
of lens or there is leakage around the protective filter
In addition to the welding hood, protective clothing,
such as gloves and an apron, should be worn. Bare skin
should never be exposed to the rays of the welding arc
because painful burns may result.
GTA WELDING PREPARATION
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 pro-
ducing quality weldments.
Specific information on the different manufacturers
of GTA welding equipment is not provided in this train-
ing manual. You should read the manufacturers instruc-
tional pamphlets for specific information on your
machine. The following suggestions are considered
general and you can apply them to any GTA welding
l Prepare the joint according to the welding proce-
dure you are performing. Refer to chapter 3 of
this training manual for specific information
about joint preparation.