Abstract: The definition of area energy is introduced and its effect is investigated on weld penetration depth, weld width, forming coefficient and droplet transfer through laser power, arc parameters and welding speed. The best matching is intended to establish between laser energy and arc energy and the quantitative relationship between area energy and penetration depth. Camera high-speed video system is used to observe the droplet transfer model and the morphological changes of plasma, and acquire the image of welding arc and droplet image. Confocal scanning laser microscope is used to observe the weld morphology and measure the weld width and penetration depth. The study shows that optimal match range between laser energy and arc energy exists. The relationship between arc voltage and welding current can be described as . The relationship between welding speed and weld melt depth is nonlinear, and the welding speed selected should be a interval, in which the optimal welding speed lies corresponding to an optimal area energy. Therefore, in specific laser-arc hybrid welding, the appropriate area energy must be selected with respect to the parameters of laser and arc energy according to the thickness of steels welded, forms of joint, and so on.

Key words: Area energy, Droplet transfer, High strength steels, Hybrid laser-arc welding, Laser welding, Metal active gas welding, Weld penetration