Melting behavior in ultrasonic-assisted narrow-gap laser welding with filler wire

The performance of ultrasonic-assisted laser welding with filler wire was investigated using high-speed imaging and a mechanical analysis of the droplet. The present study demonstrated that the droplet transition was influenced by the distance between the ultrasonic-assisted position and the weld. Due to ultrasonic assistance and plasma and metal vapor injection, the droplet was blown away and not directly above the keyhole such that the shielding and the absorption of the laser were minimal. The weld pool received direct laser irradiation for a long period. The weld depth increased by 27.2%, while the width difference was not significant when the distance between the ultrasonic-assisted position and the weld center (DUL) was 10 mm. As the DUL increased to 20 mm, the weld was formed well, and the pores were significantly reduced. With increasing the DUL, the effect of ultrasound on the weld pool became weak. Also, the droplet transition did not significantly differ from that without ultrasound, when the distance was 30 mm.