Simulating effects of welding speed on melt flow and porosity formation during double-sided laser beam welding of AA6056-T4/AA6156-T6 aluminum alloy T-joint

Abstract A three dimensional mathematic model is proposed to investigate the correlations of melt flow and keyhole behavior with the porosity defects formation at different welding speed. The effects of welding speed on the keyhole behavior and melt flow have been simulated, and the mechanisms influencing the porosity formation and evolution have been discussed. The results indicate that the porosity defects number not only heavily depends on the convective flow above the keyhole, but also relies on the flow direction in the trail of weld pool. Increasing welding speed is benefit for bubbles to escape from weld pool and reducing the porosity defects number. In addition, the porosity defects mainly exist in the upper and lower weld seam when adopting lower and higher welding speed, respectively. The distribution characteristics of the porosity defects at different welding speed have an excellent agreement with the simulated results under the experimental conditions examined.