Dissimilar robotic cold metal transfer (CMT) welding of an aluminum alloy to galvanized steel

Abstract

Abstract Weight reduction and improved fuel efficiency have been attained in automobiles by means of the introduction of aluminum alloys into the steel structural parts of vehicles. The difference in the physical, mechanical and metallurgical properties of Al and steel pose a great challenge to obtaining good weld quality. In this study, a 2.0 mm thick EN-5005-H24 aluminum alloy was welded to zinc coated 0.65 mm thick BH 20/34 +Z galvanized steel by cold metal transfer (CMT) with the aim of optimizing and obtaining a sound weld. Taguchi's L16 orthogonal array was employed for the experimental plan/run while the welding parameters included wire feeding speed, pre-setting gap and post-treatment duration. The mechanical properties of the dissimilar joint was determined using a scanning electron microscope (SEM) integrated to an energy dispersive spectroscopy (EDS) and the three zones of the joints, galvanized steel side, intermetallic compound (IMC) layer and aluminum alloy side were investigated. The optimum parameters for the dissimilar robotic CMT welded BH 20/34+Z galvanized steel and EN-5005-H24 aluminum alloy investigated in this study were determined to be as follows: a wire speed of 5.5 m/min; 0.3 mm pre-setting gap and no post weld. Experimental results indicated that the intermetallic layer thickness in the CMT welds plays a critical role in achieving relatively high weld strength. Increasing the pre-setting gap also has a positive effect on increasing weld strength due to decreasing welding porosity.