Effects of welding positions on droplet transfer in CO2 laser–MAG hybrid welding

In this paper, with constant welding parameters, the droplet transfers at different positions have been studied by high speed video during CO2 laser–MAG hybrid welding of E36 steel. The results indicated that the impact location of droplet was mainly affected by the electromagnetic force and gravity. At flat position, the droplet impacted into the weld pool near the keyhole. While at horizontal position, the impact locations of the droplet could be divided into three types: drop down, impact under the seam and impact into the weld pool. For vertical position, the large droplet impacted on the hump of weld pool. The results also showed that the droplet frequency depended on its growing speed and diameter. At flat, horizontal and vertical positions the mean droplet diameters were 2.2, 2.0 and 3.1 mm and the mean transfer frequencies were 27.0, 44.2 and 10.7 Hz, respectively. Furthermore, the optimisation of welding process has also been investigated.