Argon / Helium / Carbon Dioxide Mix
Overview
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.
Gas Blends
Argon-10-30%, Helium-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 mechanical 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.
Helium-60-70%, Argon-20-35%, 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.
Helium-90%, Argon-7.5%, CO2-2.5%
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 multi-pass 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.