The TIG (Tungsten Inert Gas) welding process (also known as gas tungsten arc
welding, GTAW, or HELIARC, a trade name of Linde) generates heat from an
electric arc maintained between a non consumable tungsten electrode and the part
TIG welding is a manual welding process that uses a non-consumable
electrode made of tungsten, an inert or semi-inert gas mixture, and a separate
Especially useful for welding thin materials, TIG welding is characterized
by a stable arc and high quality welds. It requires good operator skill and is
relatively low-speed. It's useful on many weldable materials, but is often
applied to stainless steel and light metals.
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The history of Tig welding machines
This process was developed for the aircraft industry back in the early '40s.
TIG may be used without the addition of a filler metal or a separate wire filler
metal can be added into the puddle when additional material is required, much
like the process in oxy-acetylene welding.
The puddle, the tungsten electrode
and the filler rod are protected from atmosphere by a shield of inert gas to
prevent rapid oxidation of the weld and surrounding metal. Argon is the most
widely utilized gas. Because the gas shield does not produce the slag that
normally is created by flux, the danger of slag inclusion in the weld metal is
eliminated. Also, due to the slow speed of the TIG process, gases and other
impurities escape to the surface of the puddle before solidification occurs,
eliminating pockets called "Porosity" common in weld processes that employ gas
shielding but have greater travel speeds than the TIG process.
Process and heat
TIG also produces
a welding heat is that is confined between the weld and base metal at the point
of fusion and produces a narrow heat affected zone. This reduces stress,
cracking and distortion in the finished weld. Spatter is not produced by this
process, leaving the weld and surrounding metal clean. Because of the lack of
spatter and flux smoke, the TIG process allows the operator a clear view of the
weld puddle. The torch body in most cases is small enough that the operator can
hold it in the same manner as he would hold a pencil allowing easier
The TIG welding power source is constant current, either AC, DC, or
combination AC/DC. Type of metal determines which type is used. DC (direct
current) is most normally used for TIG welding of stainless steels and mild and
low alloy steels. AC (Alternating current) is used for TIG welding of aluminum.
Surface oxidation is automatically removed by the action of the arc each time
the electrode becomes positive, (60 times per. second). Because AC crosses over
the zero volt point 120 times per second (once going positive and once going
negative each cycle), the arc shuts off 120 times per second. To keep the arc
going when using AC, a high frequency "arc stabilizer" is used. The high
frequency also allows the start of an arc in DC mode without having to "strike"
an arc, thereby reducing the possibility of tungsten contamination. If the
electrode accidentally touches the weld pool, it becomes contaminated and must
be cleaned immediately to prevent weld contamination. TIG requires an extremely
clean surface to weld successfully and is a fairly slow operation.
On the plus
side, TIG produces high quality work and does not generate slag or spatter. The
welder can adjust the heat input while welding by using foot or hand amperage