OPERATING & MAINTENANCE INSTRUCTION MANUAL
MODELS 427A (R-1), 428A (R-2), AND 429A (R-3) WELD HEADS
REV. AB
MODEL 514 TUBEMASTER OR 515/516 PIPEMASTER POWER SUPPLY
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OTHERS FOR MANUFACTURE OR FOR ANY OTHER PURPOSE, EXCEPT AS SPECIFICALLY AUTHORIZED, IN WRITING, BY MAGNATECH, LLC
With the use of Helium, arc voltage may be raised while keeping the tungsten close to the work, which
keeps the arc spot small. A hot tight arc is not always desired. Pure Argon is more suitable for some welds
because a hot concentrated arc would result in excessive heating of the workpiece. In some cases a
mixture of 75% helium to 25% Argon is used, particularly when welding titanium. Argon tends to stabilize
weld current flow through the GTA arc and is frequently used in conjunction with helium for this reason.
Helium is used when welding aluminum alloys. Aluminum is very thermally conductive and consequently
requires a hot arc to weld it. Pure Argon gas has a negative effect on weld puddle fluidity when welding
aluminum.
A small percentage of hydrogen in the weld gas is advantageous when welding the 300 Series stainless
steels or oxygen free copper. This 2% to 5% hydrogen addition to Argon gas causes oxides in these metals
to be reduced back to base metal. The net effect is to provide a very oxide free weld pool which wets out
and flows consistently and more rapidly than by use of pure Argon.
The gases used in gas tungsten arc welding must be pure and dry. Any air or moisture in the weld gas will
cause the resultant weld to appear sooty or oxidized. Very small amounts of moisture will cause erratic and
troublesome arc wander. If any of these symptoms occur, suspect a leak somewhere in the gas system or
suspect a defective bottle of weld gas. Weld gas contamination is one of the most significant sources of
problems in TIG welding.
Proper selection of weld gas and awareness of the need for gas purity are essential for optimum results.
