Alternating current has the effect of removing oxides f […]
Alternating current has the effect of removing oxides from a material such as aluminum.
Aluminum oxide has a much higher melting temperature than aluminum and so it is effectively impossible to weld without removing the oxide first.
AC ionizes the shielding gas flow which then scrubs off the oxides enabling a clean, oxide free weld.
Alternating current, in the context of Tig welding, is made up of an electrode positive portion and an electrode negative portion, this can be represented by a sine wave. The electrode positive portion of the cycle provides the oxide removal, or “cleaning”, and the electrode negative portion provides the heat input into the material. Aluminum has a high thermal conductivity so it is helpful to maximize the heat input into the material. Electrode positive will put more heat into the torch and tungsten. We can use a balance control to have the maximum heat available to melt the material, reduce the negative impact of EP, while still maintaining sufficient cleaning.