MIG welding of Mg–6%Al–1%Zn–2%Ca alloys

Abstract

Effect of metal inert gas (MIG) welding parameters on tensile strength of weld joints in a Mg–6%Al–1%Zn–2%Ca (AZX612) flame retardant magnesium alloy was examined. Proper welding conditions were found by examining welding current from 70 to 140 A and welding speed from 45 to 70 cm/min. The ultimate tensile strength of weld beads was more than 70% of the strength of the base metal in all the conditions examined. The fracture origin was not Al₂Ca second phase or Al–Mn particles, which was the fracture origin of the base metal, but blowhole or oxide inclusion. High weld strength was obtained in low heat input conditions, in which blowhole formation was suppressed. In case that an oxidized MIG welding wire was used for welding, the weld strength decreased and the large oxide fracture origin with the size of 2 mm was found. To obtain high weld strength, it is important to choose proper welding conditions in which blowhole formation was suppressed and to suppress the oxidation of MIG welding wire.