14
Argon-Helium-Carbon Dioxide
Helium and CO2
addition to argon increase the heat input to the weld and improve arc stability.
Better wetting
and bead profile is achieved. When welding on carbon and low alloy steels, helium
additions are used
to increase the heat input and improve the puddle fluidity in much the same way
that oxygen is used except
that helium is inert and oxidation of the weld metal and alloy loss are not a
problem. When welding low
alloy material, mechanical properties can be achieved and maintained more easily.
Argon - 10-30% He - 5-15% CO2
– Mixtures in this range have been developed and
marketed for pulse spray
arc welding of both carbon and low alloy steel. Best performance is on heavy section,
out-of-position applications
where welding is desired at maximum deposition rates. Good mechnical properties
and puddle control
are characteristic of this mixture. Pulse spray arc welding with low average currents
is acceptable but mixtures
with low CO, and/or 0, percentages will improve arc stability.
60-70% He - 20-35% Ar - 4-5% CO2
– This mixture is used for short circuiting transfer
welding of high strength
steels, especially for out-of- position applications. The CO2
content is kept low to insure good weld metal
toughness. The helium provides the heat necessary for puddle fluidity. High helium
contents are not necessary,
as the weld puddle may become too fluid for easy control.
90% He - 7.5% Ar - 2.5% CO2
– This mixture is widely used for short arc welding
of stainless steel in all positions.
The CO2 content is kept low to minimize carbon
pickup and assure good corrosion resistance, especially
in multipass welds. The CO2 + argon addition
provides good arc stability and penetration. The high
helium content provides heat input to overcome the sluggish nature of the stainless
steel weld puddle. Argon-Helium-Oxygen
Just as a helium addition to argon
increases the arc energy when welding non-ferrous materials, so does a
helium addition to argon-oxygen affect
the arc with the GMAW process on ferrous materials. Ar-He-O2
mixtures have been used occasionally
for spray arc welding and surfacing low alloy and stainless steels to
improve puddle fluidity and bead shape
and reduce porosity.
