MetFab - Air Products Welder's Handbook - Flipbook - Page 16
TIG welding
Principles
Operation
Tungsten inert gas welding is usually
called TIG welding.
In manual welding the operator points
the electrode in the direction of welding
and uses the arc to melt the metal at the
joint. If filler metal is required, when
making a fillet weld for example, it is
added to the leading edge of the weld
pool. Filler is supplied as cut lengths of
wire, usually 1 meter in length.
An electric arc between a non-consumable
tungsten electrode and the workpiece
provides the heat needed for the welding
operation. The tungsten electrode is
not melted and any filler metal needed
to build up the weld profile is added
separately. The molten metal in the weld
pool, the tip of the filler wire and the hot
electrode are protected from atmospheric
contamination by a shield of inert gas.
Usually the gas is argon, but helium by
itself, or mixed with argon, may be used
for special applications. Argon-hydrogen
mixtures can be used for austenitic
stainless steel.
Arc length is controlled by the welder and
is usually between 2mm and 5mm.
Travel speed is adjusted to match the
time needed to melt the joint and keep a
constant weld pool size.
TIG welding allows independent control
of the heat from the arc and the input of
the filler material. This enables excellent
control of the weld pool making TIG
welding the optimum choice when
welding root passes, thinner materials
and when a superior weld surface finish
is required.
Tungsten
electrode
2-5mm
12
