Numerical simulation of heat transfer and fluid flow during vacuum electron beam welding of 2219 aluminium girth joints

In this paper, a three-dimensional model, which is combined with the volume of fluid (VOF) model, is established to study the dynamic behaviour and keyhole stability of circumferential weld pools in vacuum electron beam welding (EBW). The influences of gravity, the Marangoni effect and recoil pressure are taken into account during the simulation process. For partial penetration welding, the humps on the keyhole wall cause a redistribution of the surface tension; furthermore, there is little difference in the keyhole evolution during flat welding and girth welding due to the supporting effect of the base metal. After entering the full penetration stage, a tail forms at the circumferential weld pool surface under the action of the Marangoni effect and the recoil pressure. Remarkably, the fluctuations in the temperature and flow velocity are more intense at the lower weld pool surface than that at the upper surface due to the interaction between the electron beam and the keyhole wall. In addition, the flow field on a three-dimensional scale is analysed. Moreover, corresponding experiments are carried out to verify the accuracy of the models adopted in this study. The simulation results are consistent with the experimental data.