Shear mechanical property and microstructure of spot welded joint of a new dual-phase high strength steel

The effect of various factors on the resistance spot welding quality of a new dual-phase high strength steel was analyzed by orthogonal test and shear test．The microstructure and mechanical properties of the spot welded joints were investigated by metallographic microstructure test．The failure mode and the metallographic microstructures of the joints were analyzed．The results show that the maximum shear stress of the spot welded joint reaches the maximum at the welding current of 8 kA，the welding time of 15 cyc and the electrode force of 2 kN．In the tensile test of high-quality welded joints，the crack initiates from the nugget near the border，then spreads to the base metal，until the spot welded joints fractures．