Modeling the transient heat transfer for the controlled pulse key-holing process in plasma arc welding

It is essential to model the transient heat transfer phenomena during the controlled pulse key-holing plasma arc welding (PAW) for practical application of this novel process. In this paper, a three-dimensional transient model is developed to analyze the periodic changes of the temperature field, weld pool and keyhole shape and dimensions during the controlled pulse key-holing process. An adaptive, combined, and volumetric heat source is proposed for the numerical analysis of the temperature fields in PAW process. The force action at the weld pool surface is considered to calculate the keyhole shape inside the weld pool. The dynamic variation features of weld pool and keyhole shape in a pulse cycle are numerically simulated. The phenomena of "one keyhole in each pulse" and periodic partial-open keyhole transformation are quantitatively simulated. Experiments are conducted to validate the numerical simulation results. The calculated weld cross-section is consistent with the measured ones. The predicted information on the dynamic evolution of the temperature profiles, weld pool and keyhole geometry is useful for optimizing the multi process parameters in the controlled pulse key-holing PAW process. (C) 2011 Elsevier Masson SAS. All rights reserved.