Cold metal transfer joining aluminum alloys-to-galvanized mild steel

Abstract

The cold metal transfer (CMT) welding–brazing process provides a potential method to join dissimilar metals. In this research, various 1mm thick aluminum alloys were joined to 1mm thick mild steel (Q235) by the CMT welding technology. It was found that it is feasible to join aluminum alloys-to-galvanized mild steel using the cold metal transfer method. The optimum process variables for weldability of aluminum-galvanized steel of dimension 200mm×50mm×1mm could be obtained with a wire of Al4043, 100% argon shielding gas, a welding voltage range of 12–14V, a deviation distance range of 2–3.5mm, a welding speed range of 6–8mm/s and a wire-feed speed range of 4–6m/min. The joint strength depended primarily on the thickness of the intermetallics and softening of the Al heat-affected-zone. By properly controlling the heat input (100–200J/mm), the degradation of the HAZ property and thickness of the intermetallic reaction layer can be minimized, and consequently produced a hybrid aluminum-to-steel joint which had comparable strength to that of CMT weld-brazed Al-to-Al joint.