Effect of brazing current and speed on the bead characteristics, microstructure, and mechanical properties of the arc brazed galvanized steel sheets

Gas metal arc (GMA) brazing was employed to join hot-dip galvanized steel sheets (GI) in lap joint configuration using CuSi₃ filler. The effects of brazing current and speed on the joint characteristics such as bead geometry, microstructure, weldability, microhardness and tensile shear strength were studied. The bead geometry was assessed by examining the bead shape, width, contact angle, penetration width and depth of the fused zone. The microstructural investigations were performed using scanning electron microscopy (SEM), and composition was determined using energy dispersive spectroscopy (EDS). The formation of Fe-Si phases was noticed in the bead which was found to increase with brazing current and brazing speed. The pores were nucleated in GI lap joint at highest current 80 A and lower brazing speeds 60–70 cm/min. The bead shape and size, joint strength, weldability were found best at a combination of 70 A and 80 cm/min which could be attributed to a uniform distribution of Fe₅Si₃(Cu) in the bead. It is suggested that for a pore-free bead structure, the heat input should lie in the range of 58.5–93.6 J/mm for the arc brazing of GI sheets.