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T
ube &
P
ipe
W
elding:
T
rends &
P
rogress
M
ay
2008
www.read-tpt.com108
›
in the aerospace industry, the motor sport
industry and latterly in the petrochemical
industry. The primary requirement then is to
provide a protective gas atmosphere to the
joint area during welding and subsequent
cooling.
The weld purge gas must be used correctly.
It should be 99.999 per cent pure – even
99.995 per cent gas can lead to some
yellow-straw discoloration. If the colour of the
welded metal begins to mottle, or if it exhibits
any hint of blue, then the gas is not pure
enough, or has not been applied correctly.
The gas flow should be started several
seconds before welding. If there is enough
essential if repeatable, high quality joints
are to be made.
For many years it was believed that
welding titanium could only be performed
satisfactorily in sealed chambers equipped
with glove ports and viewing ports, and
filled with high purity inert gas such
as argon.
A better understanding of the
mechanism of metal/gas interaction
has shown that for some applications,
as long as adequate local shielding
is provided and maintained during
welding, the use of sealed chambers
with or without vacuum pumping
systems may not be absolutely
necessary.
This understanding has afforded
possibilities for welding large
titanium fabrications and significantly
extended the application areas
for the metal and its alloys into
major structural forms, especially
It will come as no surprise to fabricators
with experience in handling titanium that
special consideration needs to be taken
during preparation and welding. Titanium
and its alloys are reactive and can become
contaminated by atmosphere gases.
Adequate shielding using inert gas is
Achieving successful welding of
titanium and its alloys
Typical flexible titanium welding enclosure
Weld purge monitor