Effect of ultrasonic pattern on weld appearance and droplet transfer in ultrasonic assisted MIG welding process

The effect of continuous ultrasonic and pulsed ultrasonic on weld appearance and droplet transfer in ultrasonic assisted MIG welding was investigated by exploiting optical microscope and high-speed imaging. Meanwhile, the influence of eight different frequencies on welding quality of the pulsed ultrasonic assisted MIG welding (PU-MIG) was studied. The results showed that the ultrasonic assisted MIG welding process was more stable than conventional MIG welding process. Compared with the conventional MIG, the U-MIG weld penetrations increased obviously under the same welding parameters and the largest weld penetration obtained by PU-MIG with a frequency of 120 Hz. The high speed camera images showed that the droplet transfer cycle and arc length of U-MIG were remarkably improved. The arc compression was the main reason for the increasing of the weld penetration and the droplet transfer cycle. Finally, porosity formation mechanism of aluminum alloy in ultrasonic assisted MIG welding was discussed.