Effect of laser beam oscillation parameters on weld geometry and mechanical properties of dissimilar dual-phase steel welds

Abstract In this study, dissimilar butt welding of 0.8 mm thick DP600 and 1 mm thick DP1180 advanced high-strength steels was performed using fiber laser beam welding with beam oscillation. The effects of oscillation type (linear and circular), oscillation amplitude (0.5, 1, 1.5 mm), and welding speed (50–80 mm s −1 ) on weld bead geometry, microhardness, and tensile load were investigated. A total of 12 experimental sets were conducted by keeping the laser power and frequency constant at 1.2 kW and 100 Hz, respectively. Metallographic evaluations, Vickers microhardness tests, and tensile tests were carried out in accordance with standard procedures. The results revealed that welding speed had a significant influence on weld penetration and width, with optimal parameters determined as 60 mm s −1 speed and 1 mm amplitude in both oscillation types. Circular oscillation generally led to higher microhardness values, whereas linear oscillation produced wider weld seams. While amplitude increase decreased penetration depth, it improved weld width. The tensile load of all joints was largely influenced by the DP600 base metal, where fractures were consistently observed. However, the joint at 1.5 mm amplitude in circular mode fractured in the weld zone, indicating insufficient penetration. The findings suggest that proper selection of oscillation parameters can enhance weld quality and mechanical performance when joining dissimilar high-strength steels for lightweight automotive applications.