Numerical and experimental investigation of keyholing process in ultrasonic vibration assisted plasma arc welding

Abstract

To improve the keyholing capability and welding efficiency, ultrasonic vibration assisted plasma arc welding (U-PAW) is developed by connecting the specially manufactured ultrasonic horn with the tungsten electrode. The ultrasound pressure in the plasma arc is considered to derive a formula for calculating the plasma arc pressure on anode in U-PAW. A transient model of U-PAW process is developed with accounting for the dynamic variation of both heat flux and arc pressure distribution on the curved keyhole wall. The weld pool and keyhole behaviors are numerically simulated to predict the fluid flow and heat transfer as well as the dynamic keyhole evolution in U-PAW. It is found that the exerted ultrasonic vibration increases the plasma arc pressure so that open keyhole can be established at lower welding current and higher welding speed in U-PAW. The experimental observation validates the numerical simulation results.