
SERVICE MANUAL
TRANSTIG 300 AC/DC
June 30, 2008
7-1
SECTION 7:
BASIC TIG WELDING GUIDE
7.01 Explanation of “Fluttery Arc”
when AC TIG Welding on
Aluminum
The following will assist in understanding the
phenomenon of Arc Flutter, also referred to as Arc
Rectification.
The basic thesis is that the fluttering is caused by
lack of oxide in the weld pool.
The oxide layer on the plate reduced the energy for
electron emission. Electron emission from the weld
pool (DC+) causes the oxide layers to be disrupted,
the so-called “cleaning action”. However once the
cleaning action has produced a mirror like surface on
the weld pool, the effect of the oxide layer is limited
because the oxide layer has dissipated. This makes
electron emission from the weld pool more difficult
and increases the chance of arc instability.
This idea is supported by the observation that once
fluttering starts it can be made to stop by working
the arc away from the mirror like weld pool to an area
of oxide coated material. As soon as this is done the
arc settles back to a stable condition. So while the
arc is “consuming” oxide coated plate the instability
does not occur. But once the arc is stationary, the
pool becomes thoroughly “cleaned” by election
emission, the fluttering begins.
Tests conducted on various types of AC TIG power
sources, Fluttery Arc is not confined to one type of
power source or its' design, both conventional and
inverter types suffer from the same problem.
AC TIG on aluminum
1. The Problem:
Arc appears unstable and pulses or flutters. ie. appears to rapidly change welding current
.
Conditions that accentuate arc flutter:
Conditions that minimizes arc flutter:
•
Cold work piece
•
Preheat the work piece
•
Very short arc length
•
Increase the arc length
•
Weld pool crater about 0.39” to 0.47”
(10 to 12mm) diameter
•
Introduce filler rod material to the weld
pool, which introduces oxides
•
Arc field in one spot to produce
“mirror” clean weld pool
•
Move the weld pool around to introduce
oxides to the weld pool
•
Increased cleaning action
i.e. Prolonged oxide emission from a
stationary weld pool increases the
likelihood of arc flutter
•
Decrease the cleaning action by turning
the
WAVE BALANCE
to below 50% or
move the weld pool around
•
Accentuated when tungsten running
near its current capacity, i.e. Molten ball
on end
•
Use a larger diameter tungsten electrode
Table 7-1: Reduction of Arc Flutter
2. Conclusion:
Fluttery Arc in AC TIG is a physical phenomenon independent of machine design.
Summary of Contents for TRANSTIG 300 AC/DC
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