Numerical Simulation On The Keyhole Form Of Deep Penetration In Electron Beam Welding For Aluminum Alloy

The key of quality control are the flow shape of welding pool and the keyhole shape in electron beam welding.It is difficult to choose and calculate the characteristic area which can indicate the welding quality. In this paper, based on the force balance study of keyhole wall. ANSYS was used to build a coupled mathematical model to investigate the heat transfer, weld pool fluid flow and keyhole formation during electron beam welding. Investigation of keyhole behavior, metal evaporation and fluid flow played important part in the quality control of electron beam welding.The driving forces distribution on the keyhole wall was confirmed through investigating of the mechanical equilibrium condition. It was indicated that the keyhole was mainly drove by metal vapor recoil pressure, surface tension pressure, hydrostatic pressure, centripetal force in the normal direction. When the welding process was stable, these forces were balanced. During electron beam welding, metal vapor recoil pressure and surface tension paid important part in the stabilization of keyhole. Based on theories of hydromechanics,hydrokinetics and heat transfer,a two dimensional transient numerical model of flow and temperature field of the electron beam welding molten pool is established. In the model,both convection heat transfer of the melted metal inside the pool and heat conduction of solid metal outside the pool,the variation of the rmophysical parameters of material with temperature,the effect of the loss of heat,including convection and radiation, and latent heat of Phase transformation on the temperature field are cansidered.In use of ANSYS,calculating software of finite element technology,the welding pool'two dimensional flow and temperature fields and their transient variation processes are calculated,the flow style and velocity of molten metal are researched,and the welding variables'infection of temperature field is alsoanalyzedBased 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. it can achieve the anticipated effect.