抄録
As an action to an environmental problem, car companies attempt to reduce the weight of a car body maintaining strength by adopting a tailored blank which joins different thick metal plates. Keyhole welding with the plasma arc is generally used for the tailored blank, because this process enables high speed welding suppressing thermal distortions. A weld defect such as an undercut occurs if a welding current is higher in order to increase the welding speed, since the arc pressure is enhanced due to increase in plasma jet velocity. The numerical analysis of the plasma arc is able to assist to overcome such a phenomenon. The analyses have been conducted by many researchers in order to understand the mechanism of keyhole welding with the plasma arc and design the suitable plasma torch. In this study, we have built a unified model considering the convection flow in the weld pool and examine phenomenon in the plasma and the weld pool. A keyhole diameter determined by the pressure balance on the keyhole surface was estimated and compared with an experiment result. As a result, the keyhole diameter obtained from the simulation approximately agreed with that of the experiment and the reliability of the simulation result was confirmed.
