Influence of welding parameters on morphology and mechanical properties of laser scanner welded joints

In order to obtain high quality welded joints of galvanized sheets, laser scanner welding method was used for lap welding of 1.5 mm thick DP 780 galvanized sheets, and effects of laser power and welding speed on weld formation, microstructure and mechanical properties of welded joints were studied. The results showed that full penetration welds were obtained when laser power and welding speed were in the range of 2. 5 \sim 3.0 \mathrm~kW and 25 \sim 55 \mathrm~mm / \mathrms, respectively. Increasing welding power was beneficial to eliminate the undercut on the weld surface, while it caused serious recession on the back of the weld. In full penetration welding, increasing the welding speed reduced the degree of weld recession. The center of the weld was mainly composed of coarse lath martensite and the heat-affected zone was mainly made up of martensite and ferrite. Reducing welding power or increasing welding speed reduced the martensite content and size, and made ferrite content increased. The microhardness test showed that welded joints appeared a softened zone, it was explained that the tensile properties of joints increased in the range of 55 75 \mathrm~mm / \mathrms welding speed. The combination of welding parameters, 3 kW welding power and 35 \mathrm~mm / \mathrms welding speed, was the most suitable.