Characteristics analysis of droplet transfer in laser-MAG hybrid welding process

The droplet transfer, plasma morphology and droplet morphology of laser arc hybrid welding process are collected and analyzed using high speed camera. The force magnitude and acceleration of motion droplets in the arc space are calculated by the image processing and mathematical calculations. The value and distribution of the recoil force from the metal vapor on droplets are calculated. The results show that the globular transfer mode corresponds to the welding current is approximate 180 A; the streaming transfer mode corresponds to the welding current is approximate 200 A. The laser has a compress effect on the arc, and the compression on the surface of the weld pool is stronger. The acceleration of the droplet detachment from wire is 70 m/s2 and 50 m/s2 for arc welding and laser arc hybrid welding separately. In the actual welding process, the reaction force of metal vapor on molten droplets is very small, when the distance between droplet and keyhole in the surface of the weld pool is 3 mm. The pressure difference on the surface between upper and lower of the droplet is great, which results the droplet coalescence and the transfer frequency slows down.