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Section 3
from the electrode. Too much AC positive
concentrates the heat on the electrode and
not on the work, overheating the electrode.
This can result in erratic arc characteris-
tics and several other problems. Symp-
toms of too much electrode positive (EP),
include needing a higher amp setting to
obtain a satisfactory weld, wide balling (or
fast consumption) of the electrode, wide
cleaning lines over 3/32" wide and uncon-
trollable weld puddles with poor penetra-
tion.
The negative portion of the AC cycle pro-
vides an equally important function. It pro-
vides the needed penetration for proper
fusing. Less AC positive output automati-
cally provides more AC negative output as
the balance is shifted toward negative po-
larity. AC negative in turn, reduces the
amount of heat concentrated on the tung-
sten and focuses it on the work. The elec-
trons are spending more time flowing to
the work piece rather than the electrode.
However, if too much electrode negative is
used, a whole set of unique problems can
result that result in weak welds. Symptoms
of too much DCEN include, dirty looking
welds, with black sooty residue, little or no
cleaning lines beside weld, dull weld pud-
dle, and even a blow out of molten metal on
the backside of the weld without a noticea-
ble puddle developing.
Keep in mind, a good starting point for ad-
justment is to set the unit at about 20-40%
EP. This will optimize cleaning action (also
called cathode etching) with minimal clean-
ing lines along side of the weld while offer-
ing excellent penetration. Higher DCEP is
possible and required at times with heavily
oxidized aluminum alloys or specially treat-
ed aluminum, but larger tungsten elec-
trodes and higher amp settings will be re-
quired to complete the welds.
No amount of Electrode Positive can sub-
stitute for thoroughly cleaning aluminum
with a stainless steel wire brush that is not
used for anything else but cleaning Alumi-
num. Do not use plain steel brushes.
Do not use special solvents to clean metal,
especially brake cleaner or other chlorinat-
ed solvents. Even small amounts of it if it
comes in contact with the welding arc and
hot surfaces will kill you. A small wisp of
vapor inhaled will result in a slow and pain-
ful death. Don't even try it. The basic com-
pound created is Phosgene gas, a deadly
nerve gas. There are approved cleaners
that can be bought for aluminum. Acetone
is a frequently used cleaner that is ac-
ceptable for use, but has its own set of
health risks. Much safer aluminum clean-
ers can be bought at welding supply stores
that reduce the health risks.
AC Frequency. As stated earlier, AC pow-
er is composed of rapidly cycling positive
and negative current. Hertz is the term
used refer to electrical frequency as it
measures cycles per second or specifically
the number of times per second that the
alternating current output of the welder
fully switches polarity from positive to neg-
ative. Older transformers were dependent
upon the input frequency of 60 Hz in North
America, (50 Hz in most other countries of
the world) and could not vary the frequen-
cy. It was quite simple, input frequency
was the same as the output frequency. You
welded with it or you didn't. Just as with
AC balance control, inverter based weld-
ers have helped revolutionize the industry
by providing a wide range of frequency
control for greater arc tuning ability. At
the old standard 60 Hz level, the arc is rela-
tively wide and unfocused compared to
what is possible with the PowerTig 185 Mi-
cro. Increasing the frequency narrows the
arc, forcing it into a tightly focused area.
This assists in several important areas. It
helps control the arc in tight corners where
it is subject to wandering and erratic be-
havior. The narrowed, high hertz arc cone
will not be as prone to instability. It also
increases the ability of the arc to penetrate
by pinpointing the heat in a narrow defined
band. This provides excellent results with
lower amp settings. The result is a narrow,
well defined weld. Conversely, a lower
Hertz may also have benefit while welding
aluminum by reducing the amount of pud-
dle agitation, preventing contamination
from mixing in the puddle.
So, what is the ideal setting? Undoubtedly,
50 or 60 hz will work and do an excellent
20
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