Optimizing welding angle for enhancing hybrid welding seam quality

Abstract

In this research, the effects of the welding angle on the behavior of the molten pool, keyhole, and welding defects in the laser-MAG hybrid welding process of 14-mm-thick AH36 high-strength shipbuilding steel are thoroughly analyzed. High-speed photography was used to observe the behavior of the molten pool and keyhole, while synchronized oscilloscope measurements revealed a strong correlation between arc voltage fluctuations and keyhole oscillation frequencies, demonstrating the dynamic interplay between arc plasma and keyhole stability. The results reveal that the welding angle significantly affects the quality of weld formation, molten pool flow, keyhole behavior, collapse, and bottom hump, as well as spatter phenomena. When the welding angle is 82.5°, optimal weld formation quality is achieved, characterized by a stable molten pool shape and regular keyhole behavior. At a 75° welding angle, the molten pool shape and keyhole behavior exhibit significant instability, leading to poor weld formation. This results in the periodic formation of the narrowest throat on the surface of the molten pool, presenting a wide-narrow-wide serrated characteristic, which triggers surface collapse and hump defects. Furthermore, at a 97.5° welding angle, intense unstable fluctuations occur within the molten pool, causing the molten metal to overcome surface tension and bulge beyond the surface of the molten pool, forming violent fluctuations and a raised liquid column that progressively detaches from the molten pool to form spatter. The research findings indicate that an appropriate welding angle can optimize the behavior of the molten pool and reduce welding defects.