Argon / Helium Mix
Overview
Regardless of the percentage, argon-helium mixtures are used for non-ferrous materials such as aluminum, copper, nickel alloys and reactive metals. These gases used in various combinations increase the voltage and heat of GTAW and GMAW arcs while maintaining the favorable characteristics of argon. Generally, the heavier the material the higher the percentage of helium. Small percentages of helium, as low as 10%, will affect the arc and the mechanical properties of the weld. As helium percentages increase, the arc voltage, spatter and penetration will increase while minimizing porosity. A pure helium gas will broaden the penetration and bead but depth of penetration could suffer. However, arc stability also increases. The argon percentage must be at least 20% when mixed with helium to produce and maintain a stable spray arc.
Gas Blends
Argon with 25% Helium
This little used mixture is sometimes recommended for welding aluminum where an increase in penetration is sought and bead appearance is of primary importance.
Argon with 75% Helium
This commonly used mixture is widely employed for mechanized welding of aluminum greater than one inch thick in the flat position. HE-75 also increases the heat input and reduces porosity of welds in 1/4 and 1/2 in. thick conductivity copper.
Argon with 90% Helium
This mixture is used for welding copper over 1/2 in. thick and aluminum over 3-in. thick. It has an increased heat input which improves weld coalescence and provides good X-ray quality. It is also used for short circuiting transfer with high nickel filler metals.