Effect of ultrasonic vibration on current density and keyholing capability of plasma arc

Ultrasonic-assisted plasma arc welding (U-PAW) process was developed to improve the penetrability. The current density of plasma arc on the anode surface was measured in plasma arc welding (PAW) and U-PAW processes. It was found that ultrasonic vibration can increase the peak value of the current density of plasma arc on anode surface. Both PAW and U-PAW experiments were conducted to examine the effect of ultrasonic vibration on the keyholing/penetrating capability of plasma arc. The weld macrographs at transverse cross-sections in PAW and U-PAW were also compared. The results show that the integration of ultrasonic vibration and the controlled pulse current waveform can ensure the open keyhole establishment and complete penetration at lower peak current or higher welding speed.