Simulation On The Keyhole Moving Process Of Electron Beam Welding Based On Vof Algorithm

The keyhole shape of electron beam welding was one of the main influencing factors for welding quality. In order to obtain more accurate computation and analysis in welding thermal process, should be carried out more thorough research on hydrodynamics condition of liquid metal in molten bath. In this paper, based on stress balance on the keyhole wall surface, ANSYS software is used to simulate the temperature field, molten bath flow field and keyhole shape in electron beam welding process, The research of molten bath temperature field and flow field distributed condition in welding process, has the vital significance for further study on electron beam deep fusion mechanism and welding quality control.The driving forces distribution on the keyhole wall was confirmed through investigating of the dynamic equilibrium equation. It was indicated that the keyhole was mainly driven by metal vapor recoil pressure, surface tension pressure, hydrostatic pressure, centripetal force in the normal direction. On tangential, the keyhole wall was drove by the shearing force caused by tangential velocity and the tangential force caused by surface tension gradient. When the welding process was stable, these forces were balanced. Through analysis of the strength distributed rule, it indicated that metal vapor recoil pressure and surface tension play important part in the stabilization of keyhole.Based on the mechanical equilibrium condition, a coupled mathematical model was developed to simulate keyhole shape in longitudinal thorough process and level migration process. In this model, the volume of fluid method was used to trace the process of the keyhole formation. The results showed that there were three driving mechanisms for the weld pool flow. One was related to the metal evaporation and liquid metal was drove by the metal vapor recoil pressure; one was the effects of surface tension such as additional pressure due to surface tension and Marangoni shear stress; another was due to the relative motion between weld pool and work piece. Three kind of actuation mechanism's combined action has caused the molten bath interior complex mobile characteristic. In confirmatory test, carry on the contrast to the molten bath section size and the analogue result by use of tack-welding and linear tack-welding. it can achieve the anticipated effect.