High-Speed Tensile Properties of Spot Welded Joints of Cold-rolled Hot Dip Galvanized Steel of DP780

The quasi-static tensile test and high-speed tensile test by a tensile testing machine were conducted on the spot welded joints of a cold-rolled hot dip galvanized steel plate of DP780 with thickness of 1.2 mm. The high-speed tensile properties of the spot welded joints were analyzed and compared to those of the base material. The results show that during the quasi-static and high-speed tensile testing, the specimens of the spot welded joint fractured in base material of one side and at the transition arc position, respectively. The maximum tensile stress was 9.90 kN in the quasi-static tensile testing, which increased with the increase of strain rate and reached 11.50 kN at strain rate of 500 s^-1. A fracture failure of the spot welded joint occurred when the strain was between 0.20-0.25, while the base material was still in the safe and effective range.