Weld quality improvement and porosity reduction mechanism of zinc coated steel using tandem gas metal arc welding (GMAW)

Abstract

In this study, we present results showing the improved quality of galvannealed steel welds formed under zero-gap lap fillet configuration, using tandem gas metal arc welding (GMAW). Superior external and internal weldment characteristics are found for the optimized tandem GMAW process compared to that of single DC, single CMT, and single DC pulse processes. Geometrical parameters such as leg sizes, penetration depths, throat lengths, and toe angles are also compared and analyzed. High-speed images reveal that as the distance between the leading and the trailing arc is reduced, agitation of the weld pool is promoted, leading to a more effective Zn vapor release process. The mechanism of Zn vapor bubble formation, growth, and release process is scrutinized and compared at the various arc distances. Finally, tensile shear strength test results show that comparable strength to the base material is expected for a total wire feed rate between 7 and 10 m/min suggesting high weld quality in the previously problematic Zn coated steel weldments.