A new heat source model for keyhole plasma arc welding in FEM analysis of the temperature profile

It is a key issue to establish an appropriate model of the heat source in the simulation of keyhole plasma arc welding (PAW). It requires that the model account for the keyhole effect and have the characteristic of volumetric distribution along the direction of the plate thickness. For available heat source models, neither Gaussian nor double ellipsoidal modes of heat source is applicable to the keyhole PAW process. Considering the force of the high-speed plasma jet and the associated strong momentum, a modified three-dimensional conical heat source model is proposed as the basis for the numerical analysis of temperature fields in the keyhole PAW process. Further, a new heat source model for quasi-steady state temperature field in keyhole PAW is developed to consider the "bugle-like" configuration of the keyhole and the decay of heat intensity distribution of the plasma arc along the direction of the workpiece thickness. Based on this heat source model, finite-element analysis of the temperature profile in keyhole PAW was conducted and the weld geometry was determined. The results showed that the predicted location and locus of the melt-line in the PAW weld cross section are in good agreement with experimental measurements.