Everlast POWER MTS 221STi, Руководство оператора

Страница: 59 / 72

59
AC TIG Operation
reduced and over - cleaning results in wide
etch lines running parallel to the side of the
weld. Not all welds conditions will be alike
so more cleaning is required at times than
others. Similarly, more penetration will be
required at times than others. Ordinarily,
about 30
- 35% electrode positive is consid-
ered an ideal amount (65 - 70% electrode neg-
ative). This means that more heat is put into
the work than placed on the tungsten and a
sharper point can be used. Cleaning is still
sufficient at that level. Good results can be
achieved with about 30% EP or less. The
cleaning action is still significant even at
these levels. Ideally, the cleaning action
should be adjusted until a small amount of
frosting can be seen no more than
1/8” dis-
tance from the edge of the weld. If a piece
of metal is particularly heavily oxidized or
dirty, more cleaning action will be required.
If too much cleaning action is used, the tung-
sten will begin to ball and even may start to
burn away. If this much cleaning action is
truly needed, then switch to a larger sized
tungsten that can handle the increased
heating level. Signs of too little cleaning ac-
tion while welding aluminum are sooty, black
or dull looking welds. (In MIG some soot is
normal while welding aluminum.) A dedicat-
ed stainless brush and suitable aluminum
cleaner such as acetone should still be used
before welding any type of aluminum to help
break up the heaviest oxide layer so less EP is
needed and better penetration can be
achieved. Even if the aluminum has a mirror
like shine, it is still oxidized.
nating polarity between electrode negative
and electrode positive, creating something
that resembles a wave when viewed on an
oscilloscope. Normally, with standard trans-
former welders, both standard sine wave
and even square wave welders have little or
no way to change the ratio of EN to EP,
which results in welding with a molten ball
at the tip of the tungsten and a less stable
arc. Electrode negative (EN) provides pene-
tration in the TIG welding process. Electrode
positive (EP) creates a strong reverse flow of
electricity that breaks up the weld
- resistant
oxidation that covers aluminum and magne-
sium components.
AC Balance. The AC output is formed by
rapidly alternating polarity between elec-
trode negative and electrode positive, cre-
ating something that resembles a wave
when viewed on an oscilloscope. Normally,
with standard transformer welders, both
standard sine wave and even square wave
welders have little or no way to change the
ratio of EN to EP, which results in welding
with a molten ball at the tip of the tungsten
and a less stable arc. Electrode negative (EN)
provides penetration in the TIG welding pro-
cess. Electrode positive (EP) creates a strong
reverse flow of electricity that breaks up the
weld
- resistant oxidation that covers alumi-
num and magnesium components also plac-
es a lot of heat on the tungsten. In a
“ balanced ” wave where both EP and EN are
equal in time length (50%), penetration is
200 Hz 60 Hz
Basic Theory and Function
Section 3