Full Product Manual

83
Special Notes Concerning Operation.
1. Shielding Gas Selection for MIG and TIG. While
welding aluminum with the Spool gun or MIG
gun you must use 100% Argon. You cannot use
a mix as you would with steel or stainless. For
Steel or Stainless, there are a variety of gases
that are used. The type of gas used with Steel or
Stainless depends upon whether you are using
short-circuit transfer, or spray transfer. In gen-
eral, the best general gases mixes for welding
with Steel are gas mixes that are less than 80%
Argon with the balance CO2, or CO2 and O2. A
Common mix, usually referred to as a C25 mix,
(75% Argon, and 25% CO2 ) is typically the
most economical of the steel gas mixes. 100%
CO2 is permissible as well, and is the most eco-
nomical option for steel welding. However, more
spatter and less aesthetic welds will result, re-
quiring more labor during cleanup. For Spray-
Transfer, or, gas mixes with greater than 80%
Argon content is recommended. Common spray
transfer gases for steel are 90/10 Ar/CO2, 95/5
Ar/CO2, 98/2, Ar/CO2 or 98/2 Ar/CO2. Some
welding suppliers also suggest Trimixes of Ar/
CO2/O2 for spray transfer or pulse spray transfer
welding of Steel. For Stainless, there are sever-
al recommendations for welding with stainless
whether in Short-circuit transfer. But there is
mixed consensus on the best gas for use for
short-circuit, Pulsed-spray transfer and Axial-
Spray transfer. Stainless develops a more slug-
gish puddle and wet is not as smooth and easy
flowing as steel or aluminum. 98/2 Ar/CO2, or
98/2 Ar O2 is often recommended for spray-
transfer welding when economy is needed. In
fact other less Argon rich blends are sometimes
recommended, and it is possible. But when
more CO2 is added, the rust resistance of stain-
less goes down due to the added carbon con-
tent. Ideally, there are several Tri-gas mixes out
there that are well suited to welding stainless.
These include the addition of Helium to the mix
as either the primary or secondary component of
the mix. The Helium tends to help improve wet-
in and fluidity of the puddle, but a higher voltage
may be needed to weld if the Helium content is
too high. It is also much more expensive.
Welds made with Tri-gas mixes tend to hold
their rust resistance better. But to reduce the
heat that is put into the weld , and reduce warp-
ing, there are stainless tri– gas mixes on the
market that have a content of approximately 35%
or lower Helium. These still are great for pre-
serving rust resistance of the stainless alloys.
Wet-in is still excellent and cost is much lower
than higher Helium content blends. While weld-
ing in any of the TIG modes you must also weld
use 100% Argon for any metal type. In some
cases, blends of Ar/He may be used for TIG for
welding thicker metal thicknesses, but the cost to
do so is quite high as He/Argon mixes are ex-
pensive by comparison. Do not use more than
25% He in any mix or starting the arc and main-
taining a stable arc will be difcult.
2. MIG Welding Aluminum. While welding alumi-
num with the Spool gun or MIG gun you must
use the next size up tip or a special oversize tip
for the wire because the heat will cause the alu-
minum wire to swell and it will either drag or
seize in the tip, due to the dissimilar expansion
rates of the copper tip and aluminum wire. If
you are suffering burn backs while welding Alu-
minum (and in some cases stainless), change to
a larger tip, and reduce burn back time. While
welding aluminum with the MIG process, best
results are achieved by using a dedicated stain-
less steel brush to remove the oxide layer and
using acetone or aluminum cleaner before weld-
ing to remove any residues. Even though alumi-
num may appear shiny and clean, it still has an
oxide layer and a thin layer of oil left over from
the manufacturing process. Some soot will ap-
pear in most Aluminum MIG welds but if a lot is
noticed, you have either contaminated metal, or
insufcient gas flow. You can also induce turbu-
lence by having too much of a torch angle. Start
with a 90 degree angle and then lean the gun
slightly (about 15 degrees) to the “push” posi-
tion. Welding aluminum is not typically a short
circuit process. It is a spray transfer process or a
Pulsed-Spray process. Spray and Pulsed-Spray
transfer are processes that are used to weld
many metals, but in Aluminum it must be used
to obtain the most sound quality welds.
MIG OPERATION AND THEORY
Section 3 Basic Theory and Function