Influence of the laser thermal effect on the droplet transfer behavior in laser-CMT welding

In this study, the droplet transfer process of laser-cold metal transfer (CMT) hybrid welding was evaluated. The difference between laser-Metal Active Gas Welding (MAG) and laser-CMT has been shown in previous studies; however, systematic research on the droplet transfer behavior in the laser-CMT welding process is minimal. The characteristics of the droplet transfer process were observed by a high-speed camera system and analyzed by brightness curves. The short circuit time and transfer frequency changed with the droplet volume owing to the effect of the laser plasma. The molten pool was spread out after adding the laser; however, concurrently, the melting amount of the welding wire increased due to the thermal effect of the laser plasma. The main factor was the laser-wire distance, which influenced the coupling between the laser and arc. In addition, the increasing laser power accelerated the melting of the welding wire and expanded the pool, which improved the transfer frequency. The shielding gas flux affected the transfer behavior by changing the thermal effect of the laser. In high speed welding, the transfer frequency, weld formation, and adaptability were improved by the laser guide because the laser could stabilize the arc and avoid wire conglutination.