AC TIG welding with single-component oxide activating flux for AZ31B magnesium alloys

Magnesium-based alloys are finding extensive applications foreground in aerospace and automotive applications. Weldability of magnesium alloys has recently been investigated with a variety of processes. In this article, the activating flux TIG (ATIG) welding of magnesium alloys with three single-component fluxes (TiO 2 , Cr 2 O 3 and SiO 2 ) under alternating current (AC) mode was studied. The effects of welding speed, weld current and electrode gap on the weld shape and the weld arc voltage in AC TIG welding with oxide fluxes were investigated on an AZ31B magnesium alloy substrate. The mechanisms of oxide fluxes on the arc shape and the arc voltage on the weld shape are discussed. The result showed that the TiO 2 and Cr 2 O 3 increase the weld penetration of AC TIG welding of magnesium with good bead cosmetics. The SiO 2 increased the weld penetration with very poor formation of the weld surface. However, the arc voltage decreased with the used of TiO 2 flux, and increased with the used of Cr 2 O 3 flux. The mechanism of TiO 2 and Cr 2 O 3 fluxes increasing penetration should not accord with the “arc constriction”. It would comply with some potential effects of the flux interacting with the liquid metal of fusion zone.