Use and Care Manual

14
www.lincolnelectric.com
GMAW
C
ommon Short-Circuiting Transfer Shielding Gas Blends
7
5% Argon + 25% CO
2
—
reduces spatter and improves weld
bead appearance on carbon steel applications.
80% Argon + 20% CO
2
— another popular blend, which further
r
educes spatter and enhances weld bead appearance on carbon
steel applications.
C
ommon Axial Spray Transfer shielding gas blends
98% Argon + 2% CO
2
— for axial or pulsed spray with stainless
steel electrodes and carbon steel electrodes. This blend has
seen repeated success on high-speed sheet metal applications.
T
here is excellent puddle fluidity and fast travel speeds associated
with this shielding gas blend.
95% Argon + 5% CO
2
— for pulsed spray with carbon steel
electrodes. The addition of 5% CO
2
provides for additional
puddle fluidity, and it lends itself to heavier fabrication than
blends with 2% CO
2
.
92% Argon + 8% CO
2
— for both axial and pulsed spray
applications on carbon steel. Higher energy in axial spray
transfer increases puddle fluidity.
90% Argon + 10% CO
2
— for either axial spray or GMAW-P
applications on carbon steel. The penetration is broader and it
reduces the depth of the finger-like penetration exhibited by
argon + oxygen mixes.
85% Argon + 15% CO
2
— the higher CO
2
level in axial or
pulsed spray transfer increases sidewall fusion on sheet metal or
plate thickness material. Generally produces improved toe
wetting on carbon steel with low levels of millscale. In GMAW-S,
short circuiting transfer, the lower CO
2
level translates to less
heat for welding parts with less risk of burnthrough.
82% Argon + 18% CO
2
— the effective limit for axial spray with
CO
2
. Popular European blend used for a wide range of welding
thicknesses. Broad arc enhances penetration profile along the
weld interface. Also lends itself well for use in short-circuiting
transfer or STT applications.
Argon + Oxygen
Argon/oxygen blends attain axial spray transfer at lower currents
than argon/CO
2
blends. The droplet sizes are smaller, and the
weld pool is more fluid. The use of argon + oxygen has
historically been associated with high travel speed welding on
thin materials. Both stainless steel and carbon steel benefit from
the use of argon/oxygen blends.
99% Argon + 1% Oxygen
— used for stainless steel applications.
The use of oxygen as an arc stabilizer enhances the fine droplet
transfer and maintains the puddle fluidity for this gas blend.
Stainless steel welds will appear gray because of the oxidizing
effect on the weld pool.
98% Argon + 2% Oxygen
— used as a shielding gas for either
carbon or stainless steel applications. The earliest use of
argon/oxygen blends for axial spray transfer on carbon steel
employed 2% oxygen level. It is typically applied to applications
that require high travel speed on sheet metal. Applied with
either axial spray or pulsed spray transfer modes. Stainless
deposits are dull gray in appearance. This blend is often used
when superior mechanical properties are required from low alloy
carbon steel electrodes.
9
5% Argon + 5% Oxygen
—
general purpose axial spray or
p
ulsed spray transfer shielding gas applied to heavier sections of
carbon steel. The base material is usually required to be free of
contaminants with a low level of millscale.
Ternary Gas Shielding Blends
Three-part shielding gas blends continue to be popular for
carbon steel, stainless steel, and, in restricted cases, nickel
alloys. For short-circuiting transfer on carbon steel the addition
o
f 40% helium, to argon and CO
2
,
as a third component to the
shielding gas blend, provides a broader penetration profile.
Helium provides greater thermal conductivity for short-circuiting
transfer applications on carbon steel and stainless steel base
m
aterials. The broader penetration profile and increased
sidewall fusion reduces the tendency for incomplete fusion.
For stainless steel applications, three-part mixes are quite
common. Helium additions of 55% to 90% are added to argon
and 2.5% CO
2
for short-circuiting transfer. They are favored for
reducing spatter, improving puddle fluidity, and for providing a
flatter weld bead shape.
Common Ternary Gas Shielding Blends
90% Helium + 7.5% Argon + 2.5% CO
2
— is the most popular
of the short-circuiting blends for stainless steel applications. The
high thermal conductivity of helium provides a flat bead shape
and excellent fusion. This blend has also been adapted for use
in pulsed spray transfer applications, but it is limited to stainless
or nickel base materials greater than .062" (1.6 mm) thick. It is
associated with high travel speeds on stainless steel applications.
55% Helium + 42.5% Argon + 2.5% CO
2
— although less
popular than the 90% helium mix discussed above, this blend
features a cooler arc for pulsed spray transfer. It also lends itself
very well to the short-circuiting mode of metal transfer for
stainless and nickel alloy applications. The lower helium
concentration permits its use with axial spray transfer.
38% Helium + 65% Argon + 7% CO
2
— this ternary blend is for
use with short-circuiting transfer on mild and low alloy steel
applications. It can also be used on pipe for open root welding.
The high thermal conductivity broadens the penetration profile
and reduces the tendency to cold lap.
90% Argon + 8% CO
2
+ 2% Oxygen
— this ternary mix is
applied to short-circuiting, pulsed spray, and axial spray modes
of metal transfer on carbon steel applications. The high inert
gas component reduces spatter.