Study on the influence of different heat source leading modes in laser-arc hybrid welding on the formation mechanism of bottom hump

Zhang, F. and Lei, P. and Zhang, P. and Song, L. and Li, J. and Huang, Y. and Fang, C. (2026) Study on the influence of different heat source leading modes in laser-arc hybrid welding on the formation mechanism of bottom hump. Physica Scripta, 101 (11): 115915. ISSN 0031-8949

Abstract

This study used laser-arc hybrid welding (LAHW) technology to weld 10 mm thick AH36 steel plates, focusing on the influence mechanism of different heat source leading modes on the formation of bottom hump. Under the optimal process conditions obtained, the weld formation, droplet transition behavior, and welding current and voltage signal waveforms were compared and analyzed by constructing a high-speed camera-electric signal synchronous acquisition system and combining the dynamic evolution of keyhole and flow behavior of the molten pool in MIG-leading mode (ML) and laser-leading mode (LL). The research results show that the fundamental cause of the formation of the bottom hump is the instability of the molten pool caused by the periodic closure and opening of the keyhole, which is essentially due to the discontinuous dynamic balance of the molten pool caused by insufficient thermal input, and the direct cause is the continuous stability of the molten pool flow control, and different heat source leading modes directly affect the stability of the droplet transition behavior and the welding process. Ultimately, weld joints without hump defects were obtained in ML and LL modes, but different heat source leading modes led to differences in forming effects. Under the ML mode, stable droplet transfer and smooth melt pool dynamics were established, resulting in a broadened processing window for weld formation. In contrast, the processing window under the LL mode was notably restricted; consequently, precise synchronization of laser power and welding speed was required to ensure sound weld integrity. This study can provide theoretical guidance for the practical operation of LAHW for single-sided forming in medium-thick plate welding.