The Comparative Research On Laser Lap Welding And Resistance Spot Welding Of Automotive Steels

In contrast to resistance spot welding (RSW) which is a traditional welding process, laser welding (LB) is an advanced one with the advantages of high welding speed, high efficiency and good flexibility in term of application to assembly line and so on. In recent years, with the rapid development of laser welding technology, laser welding has been favored and highvalued by the automotive industry. In this paper, research on laser lap welding and resistance spot welding of automotive steels has been conducted in terms of comparative experiments.Firstly, the welding mechanisms, characteristices, advantages and disadvantages of LB and RSW were introduced respectively.Secondly, through designing the orthogonal table, a large number of welding experiments were carried out on urtal-low carbon high strength galvanized steel (H220YD+ZF) and cold rolling low carbon galvanized steel (DC56D+Z) both mostly used for automotive applications. And then research on laser lap welding was carried out in terms of the main processing parameters, such as laser power, defocusing value, welding speed, gap between two plates and shieding gas. Meaningwhile, research on resistance spot welding was carried out in terms of welding current, welding time and electrode pressure. The optimized processing parameters of laser lap welding and resistance spot welding with different combinations of two kinds of materials were obtained from a series of experiments.Finally, an analysis and comparison of properties between laser lap welding welds and resistance spot welding welds were carried out by tensile tests. Consequently, the relationship between laser seam weld length and a resistance spot welding weld was established in different situations. The principle and the influencing factors of formulating the laser seam weld length was studied during laser lap welding of dissimilar plates. Followly, the comparative analysis of the microhardness, metallographic structure and corrosion resistance of laser lap welding welds and resistance spot welding welds were conducted. The conclusion showed that the microhardness of laser lap welding welds is higher than that of resistance spot welding welds and the corrosion resistance of laser lap welding welds is prefer to that of resistance spot welding welds. Last but not least, a better way of welds arrangement was obtained through the tensile-shear tests of seven different arranged welds.