A Simulation Of Keyhole Plasma Arc Welding In Aluminium Alloy

Keyhole Plasma Arc Welding(PAW) is a promising process for the high temperature, concentrated energy and complete penetration of plasma arc, and it can fulfil one-side welding of thick plates without grooving. Therefor, simulating the welding process can provide theoretic guidance for its application.Firstly, based on a theory of an approximate two-zone arc model, studied the properties of plasma arc generated for the transferred PAW process at the nozzle exit, discussed the effect of operating parameters on the arc of the welding plasma, and compared the calculated results with experiments. The results showed that arc obtained from calculation is in good agreement with the measured values.Based on theories of hydromechanics and heat transfer, established a three dimensional transient numerical model of flow and temperature field of the keyhole PAW weld pool with a moving arc, and discretized the model with the finite element method. In the model, considered three followings, both convection heat transfer of the melted metal inside the pool and heat conduction of solid metal outside the pool, the variation of thermophysical parameters of material with temperature, the effect of the loss of heat, including convection and radiation, and latent heat of phase change on the temperature field. Wlding heat source is presumed to be gaussian distribution. Also, the boundary conditions are dealed in the calculation.Consideing of featues of the model, elements are divided according to a non-uniform grid and time steps are defined to a non-uniform step in different subareas. Relative successful calculating software of finite element technology , ANSYS, is adopted. The results of comparison show that the calculated results approximately agree with the experimentally measured geometric sizes and shape of the fusion boundaries, and that the model is basically correct and credible.Finally, by the comparison with experiments and further analyzing the phenomenon of keyhole PAW, presented the modified means to the model established in this thesis, which can provide some foundation and use for reference for subsequent research efforts.