MetFab - Air Products Welder's Handbook - Flipbook - Page 23
Pulsed TIG
When TIG welding thin section materials
control of the weld pool and penetration
become more difficult with a continuous
weld current. Pulsing the current improves
control at the lower heat input levels
required for thin section materials. The
pulsed TIG arc switches from a low (base)
current, just sufficient to maintain the
arc and allow the weld pool to cool, and a
higher peak current selected to achieve the
required fusion and weld pool geometry.
Pulsed TIG can be used to weld cylindrical
components. This avoids the need to
increase travel speed to keep the weld
width uniform which is a great advantage
in mechanised welding.
TIG spot welding
TIG spot welding provides an alternative
to resistance spot welding where access
is from one side only or where it is not
possible to fit the component between the
arms of the spot welder.
In this technique, the electrode is held
at a fixed distance above the surface of
a lap joint using a special gas nozzle. A
combination of weld current and time is
selected to create a spot weld. After the
weld has formed the current is reduced
progressively to allow the weld to solidify
without a crater.
Low pulse frequencies are used when
a cosmetically-appealing weld finish
(commonly referred to as ‘fish scales’) is
required.
High pulse frequencies are commonly used
when a higher welding speed and a deeper
and narrower fusion profile is required.
Current
Peak
current
Mean
average
current
0
Base
current
Time
19
