Argon-helium shielding gas mixture
An inert gas combination that provides deeper penetration and increased arc voltage during the welding of non-ferrous metals due to helium's high thermal conductivity.
You use argon-helium mixtures mainly when you want to put more heat into the arc than is possible with pure argon. The helium makes the arc hotter and wider, which pays off especially with thick plates or with aluminum and copper. You get a more stable arc and better penetration, especially when welding by hand. The catch is: the mixture is more expensive, and you need more gas volume than with pure argon. Also, the arc becomes more aggressive, and you have to adjust your technique, otherwise you'll burn the material. For normal steel welding, you don't need the mixture; pure argon or a CO₂ mixture is sufficient.