Modeling of keyhole dynamics and analysis of energy absorption efficiency based on Fresnel law during deep-penetration laser spot welding

Abstract Deep-penetration laser spot welding can effectively improve the utilization rate of the laser beam through forming the keyhole. In this paper, a model based on Fresnel law was developed with the computational fluid dynamics (CFD) software FLUENT. By considering the recoil pressure, surface tension, buoyancy and evaporation, a ray tracing technique was proposed to describe the absorption efficiency of the laser beam during the process of keyhole forming. It was found that there was large temperature gradient in the keyhole, recoil pressure and Marangoni flow forced the molten metal liquid to flow from bottom to top. At last it formed a nail head at the bottom and crowned at the top. The energy absorption efficiency rose from 42% to 59% during the keyhole forming, which was approximately linear with the depth of the keyhole.

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