Experiment Research on Tensile-Shear Behavior of Spot-Welded Lap Joints of Ultra-High Strength Steel with Common Steel

The welding spot of Ultra-high strength steel of 22MnB5 and common steel of St16 were the investigative objects, the intermediate frequency inverter & electric servo welding system was used to weld the sheets. Electrical measuring test method was used on spot-welded joint under tensile-shear load to determinate the strain of different positions, including the strain of weld nugget, the stain around the nugget and the base metals strain near the weld nugget. The deformation regularity of spot welding joints surrounding and base metal were analysed according to the data. The test provided a reference for the numerical simulation of spot welding model. Test results show that the strain distribution on spot welding joint is not uniform, the strain of the weld nugget center is relatively small, large deformation exists mainly in the heat affected zone. That is to say, the area near the spot-welding joint heat affected zone is prone to yield. The base metal area near the weld nugget is mainly affected by tensile strain, and the strain increases with the increasing of the load. The force condition of the specimen is complicated around the nugget, the relationship between the load and the strain is erratic. The strain of the weld nugget will gradually change from axial compressive strain to axial tensile strain. The strain of spot welding specimen made of dissimilar materials (22MnB5& ST16) is negative, and almost linearly.