Numerical investigation of pore defect formation in the weld during high speed laser welding

The pores existing in the weld bead seriously weaken the mechanical properties and other related performances of welded joints. Therefore, to reduce the formation of defects in the weld bead and further improve the welding quality, a 3D numerical simulation model is developed in this paper to investigate pore formation during high speed laser welding. In this model, driving forces including surface tension, recoil pressure, hydrostatic pressure and hydrodynamic pressure are coupling taken into consideration. The volume of fluid method is adopted to track the boundary between the keyhole and the molten pool. The pore formation process in high speed laser welding is described in details after solving the established numerical simulation model. The calculated results demonstrate that the bottom part of the rear of the keyhole is elongated as the keyhole moves forward in high speed and then separated from the keyhole. Sequentially, the separated part is mixed with the metal flowing in the molten pool and finally formed as the pore defect in the weld bead as the molten pool cools down and solidifies. These results indicate that the proposed method is efficient for reducing the defects in the weld bead during high speed laser welding and may be used to improve the welded joints in production.