| History:
Tig welding originated in USA, probably before 1939
where it was used mainly to facilitate the then rather
difficult process of welding aluminum. As less dense
than air inert gas helium occurred naturally in USA
and was readily and cheaply available, it was used as
an inert shield to prevent oxidation of the aluminum
during melt down . It was known as the Heliarc process.
Tig welding appears to have become commercially available
in UK and Europe after development around 1948. However
(and still is) very expensive in Europe so developers
turned to argon which was produced as a by-product of
air liquefaction for oxygen production. Using Argon
as shielding gas TIG welding process known as Argonarc.
Argon has certain advantages over helium, other than
cost. In passing it should be mentioned that both the
Heliarc and Argonarc methods operated on AC at that
time.
DEFINITION: It is an arc welding process where in coalescence
is produced by heating the job with an electric arc
struck between a tungsten electrode and the job. A shielding
gas (argon helium, nitrogen, etc.) is used to avoid
atmospheric contamination of molten weld pool. A filler
metal may be added, if required.
Principle: The machine work on the principle of square
wave electric arc generated between tungsten electrode
and work, it heats both electrode and work, only work
fuses due to it's lower fusion temperature than tungsten
electrode, square wave current helps in damaging oxide
layer on work, hence straight arc produced, a inert
shielding gas protects both electrode and work from
oxidation by atmospheric gases.
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