Mitigating spatters in keyhole-mode laser welding by superimposing additional ring-shaped beam

Spatters are frequently occurred defects in laser welding, which affect the weld aesthetics, deteriorate the mechanical performances and even lead to the weld joint rejection for products with strict requirement of surface finish. In this work, a novel beam shaping technology was used to mitigate spatter defects in laser welding of aluminium alloys by superimposing additional ring-shaped beam. An experimental and numerical combined research program was implemented to reveal the characterises of welding performances and mechanism of spatters mitigation in superimposed core and ring-shaped laser beam welding. The experimental results showed that a proper addition of a certain power of ring-shaped beam could significantly improve the surface finish of weld joints and mitigate the spatters. A comprehensive three-dimensional, transient, multi-physics thermal-fluid coupled model of laser welding was also established to study the changes in physical process owing to the addition of ring-shaped beam. The simulated results indicated that the additional ring-shaped beam could result in an enlarged keyhole entrance and a stabilized keyhole, which are the main factors that are attributed to the sound weld surface finish and mitigated spatters.