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Description
TIG welding
is a gas-tungsten arc welding process that uses an inert gas to protect the
weld zone from the
atmosphere.
The necessary heat for welding is provided by a very intense electric arc, which
is struck
between a virtually
non-consumable tungsten electrode and the metal workpiece (see preceding page).
TIG
welding differs
from metal inert gas (MIG) arc welding in that the electrode is not melted and
used as a filler
metal. On joints
where filler metal is required, a welding rod is fed into the weld zone and
melted with the
base metal
as in oxy-acetylene welding.
In any type
of welding, the best obtainable weld is one which has the same chemical, metallurgical,
and
physical properties
as the base metal itself. To obtain such conditions, the molten weld puddle
must be
protected
from the atmosphere during the welding operation; otherwise, atmospheric oxygen
and nitrogen
will combine
readily with the molten weld metal and result in a weak, porous weld. In TIG
welding, the weld
zone is shielded
from the atmosphere by an inert gas which is fed through the welding torch.
Either argon or
helium may
be used. Argon is widely used because of its general suitability for a wide
variety of metals, and
for the lower
flow rates required. Helium provides a hotter arc, allowing
50-60% higher arc voltage for a
given arc
length. This extra heat is especially useful when welding heavy sections. Gas
mixtures of argon
and helium
are used to provide the benefits of both gases. The selection of the proper
gas or gas mixture
will depend
on materials being welded. Your ESAB distributor has the selection information
you’ll need.
Advantages
TIG welds,
because of this 100% protection from the atmosphere and finite control over
heat input, are
stronger,
more ductile, and more corrosion-resistant than welds made with ordinary metal
arc welding
processes.
In addition, the fact that no flux is required makes welding applicable to a
wider variety of joint
types. Corrosion
due to flux entrapment cannot occur, and expensive post-welding cleaning operations
are
eliminated.
The entire welding action takes place without spatter or sparks. Fusion welds
can be made in
nearly all
metals used industrially. These include aluminum alloys, stainless steel, magnesium
alloys, nickel
and nickel-based
alloys, copper, silicon-copper, copper-nickel, brasses, silver, phosphor bronze,
plain
carbon and
low-alloy steels, cast iron, and others. The process is also widely used for
welding various
combinations
of dissimilar metals, and for applying hard-facing and surfacing materials to
steel.
