Originally posted by modela
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with the metal to be welded. As the tungsten is lifted off the
part, the arc is established. This is sometimes referred to as
touch start. Little if any chance of contamination is possible
due to special power source circuitry. When the Lift-Arc switch
is activated, lower power level is supplied to the tungsten
electrode. This low power allows some preheating of the
tungsten when it is in initial contact with the part. Remember
hot tungsten is a good emitter of electrons. This power level
is low enough not to overheat the tungsten or melt the work
thus eliminating the possibility of contamination. Once the
arc is established the power source circuitry switches from
the Lift-Arc mode to the weld power mode and welding can
commence. Figure 2.34 illustrates the proper techniques to
use with the Lift-Arc starting method.
Figure"
http://www.millerwelds.com/education/TIGhandbook/
Chapter II
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