Characteristics of droplet transfer, molten pool formation, and weld bead formation of oscillating laser hot-wire tungsten inert gas hybrid welding

Oscillating laser hot-wire tungsten inert gas (TIG) hybrid welding of 10mm thick 316LN austenitic stainless steel in the vertical position was performed. The characteristics of droplet transfer, molten pool formation, and forming mechanism of different oscillating parameters were investigated by the experimental method. A high-speed camera was employed to observe the arc, droplet transfer, and molten pool formation. Results showed that the larger molten pool area, more intense fluid flow, and better weld bead formation were achieved when the oscillating laser joined to TIG as compared to TIG or normal laser-TIG hybrid welding. Due to the dynamic wire feed, the form of droplet transfer was mainly contact transfer, and the frequency of droplet transfer was equal to the frequency of wire feed and was independent of the parameters of the heat source. The electrical signals in the TIG and oscillating laser-TIG weld processes were collected, respectively, and the results showed that the change of conductivity might be the reason why the laser can compress the arc. The addition of laser increased the arc voltage and active power and improved the efficiency of hybrid welding.