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The process of laser butt welding of zinc-coated steel (SGCD3 and WLZn) blanks was presented, whose edges were prepared by laser cutting. The properties of the butt joints, such as tensile strength, bending, stamping, weld shape, and corrosion-resistant were tested. The experiments of laser cutting and welding were carried out on a custom-made system designed, which is a set of equipment for wide sheet butt welding based on a laser cutting-welding combination process. The experiments proved the technological feasibility of laser butt welding for thin zinc coated steel sheets whose edges were prepared by laser cutting on the same equipment.

In order to understand the change regulation of residual stress during multi-repaired welding to provide theoretical guidance for correct repaired welding procedure and improvement of joint properties, and to simulate the magnitude and distribution of residual stress using the finite element method (FEM). A model of temperature field of weld-repaired using FEM, which was simplified, was established. The weld stress consists of thermal stress and organization stress. Models of the thermal stress and organization stress were described. ANSYS, a software of finite element, was applied to calculate the stress, BHW35 steel was taken as an example, the simulated and experimental results for the 1st, 3rd and 5th weld-repaired were analyzed, the simulated results are in good agreement with experimental results. It can be concluded that the residual stress in the weld center changes little, and the high residual stress exists in HAZ. And in the same place, the more repaired weld, the higher residual stress, and the area of residual stress becomes wider.

Many studies have shown that type and flow rate of shielding gas are important to weld depth and weld quality during laser welding. These results are attributed that different shielding gas can change the laser radiation into the workpiece. In this paper, high- speed camera and optical emissions monitoring and spectroscopic analysis were used to study the processes of laser welding of 304 stainless steel taking He and Ar as shielding gas. The research results show that shielding gas type has more effects on welding process features. First of all, shielding gases have great effect on the spectrum of optical emission. With Ar as a shielding gas, intense spectrum lines locate the range of 450nm ~ 850nm, mainly Ar lines and Fe lines. However, with He gas, intense spectrum lines are mainly ultraviolet. Next, the shielding gas types have obviously influence on size and fluctuation frequency of plasma/vapour. The use of He gas, maximum width of the plasma/vapour is about 36 percent of that with Ar, and the dominant fluctuation frequency band of 1000Hz ~ 1500Hz is much lower than the band of 1500Hz ~ 3500Hz with Ar shielding gas. Finally, the shielding gases influence apparently on geometry of melt pool. At the same heat input, the pool volume with Ar gas is larger than that with He, and this differences increase with larger input heat. And the length of surface pool with Ar gas is much longer than with He, and the differences increase with heat input. For the length of back pool these differences are quite little. Moreover, there is a more narrow surface with He gas than with Ar. All of these results can be from its different ionization potential and resistance to breakdown for He and Ar gas. And these differences bring great effects on laser radiation into workpiece.