Laser butt welding of thin stainless steel 316L sheets in asymmetric configurations: A numerical study

Laser butt welding of thin metal sheets is a widely used fusion-based joining technique in industrial manufacturing. A comprehensive understanding of the complex transport phenomena during the welding process is essential for achieving high-quality welds. In the present work, high-fidelity numerical simulations are employed to investigate the influence of various symmetric and asymmetric welding configurations on the melt-pool behaviour in conduction-mode laser butt welding of stainless steel sheets. The analysis focuses on the effects of laser power density, heat source misplacement and different welding scenarios, including plates with a root gap, high-low mismatches, and dissimilar thicknesses, on the molten metal flow and heat transfer. The results show that advection is the dominant mechanism for energy transfer in the melt pool, and its contribution increases with higher laser power. The non-uniform temperature distribution over the melt-pool surface induces Marangoni shear forces, driving the flow of molten metal and leading to the formation of vortices and periodic flow oscillations within the pool. The effects of various types of asymmetries on the thermal and molten metal flow fields, as well as the process stability, are thoroughly examined and compared with symmetrical welding configurations. These comprehensive simulations provide valuable insights into the fluid flow dynamics and thermal field evolution during laser butt welding of thin metal sheets. The knowledge gained from this study can facilitate process optimisation and guide the improvement of weld quality in practical applications.