Clearview National December 2019 - Issue 217 | Page 35

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Gas tungsten arc welding (GTAW),
commonly known as TIG (or tungsten inert
gas) welding, is a versatile welding process
for joining metal. Both AC and DC power
sources can be used in TIG welding; which is
chosen will depend on the type and thickness
of the metal to be welded.
A TIG torch is an electrode holder that
supplies welding current to the tungsten
electrode and an inert shield gas to the arc
zone. A collet-like clamping device allows
adjustment so that the right length of
electrode extends beyond the shielding gas
cup.
‘TIG welding uses a non-
consumable tungsten
electrode and has an
extremely high melting point’
TIG welding uses a non-consumable
tungsten electrode and has an extremely
high melting point which means that TIG
electrodes can heat other metals to their
melting points without themselves melting.
Argon and helium are the main shielding
gases used in TIG welding. In some
applications, however, a mixture of the two
gases can prove advantageous. On occasion,
hydrogen is mixed with argon or helium for
special applications.
• Length of arc: the distance between the
electrode and workpiece should be the
length of the diameter of the electrode’s
core wire.
• Angle of electrode: the angle of the
electrode affects weld penetration. Too
much penetration can make the weld
brittle and lead to stress cracking and
create holes in the metal; too little
penetration can result in a weak weld.
• Manipulation of weld pool: as stick
welding is performed, gas pockets can
form which can compromise weld
integrity. These can be eliminated
with a slight side-to-side motion when
welding.
• Speed of travel: A weld speed that is too
slow leads to a weld bead that is too large
while a fast weld can lead to a weld bead
that is too narrow.
SMAW WELDING TIPS
1. Take care when handling stick welding
electrodes. Rough handling can cause the
flux coating to break loose from the core
wire, rendering the electrode unusable.
2. Don’t use an electrode if the core wire
is exposed because the missing flux will
cause welding defects and result in a poor
weld.
3. Keep electrodes dry; wet electrodes can
result in porous, weak finished welds.
4. During set up, set the amperage on
the welding machine to match what is
required by the electrode being used. If
stick welding for the first time, set the
amperage exactly in the middle of the
range suggested for the electrode.
5. If using DC machine, set the polarity
according to the requirements of the
electrode being used.
TIG WELDING TIPS
1. A foot pedal allows the user to adjust the
amperage of the machine without having
to manually turn the amperage knob and
is highly recommended.
2. Torch position is important in TIG
welding. The ideal position is 90°.
However, the weld pool will be blocked
from view by the torch. Angle the
torch 15° to see the weld pool while
maintaining great results.
3. Some TIG welding requires the use of
a filler metal in the form of a filler rod
when there is insufficient metal present to
complete a strong joint.
4. Torches may be air- or water-cooled.
5. GTAW is most commonly used to
weld thin sections of stainless steel and
non-ferrous metals such as aluminium,
magnesium, and copper alloys.
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