Microstructure and fractography of intermediate frequency spot welding of precision ultra-high strength quenching steel

Precision ultra-high strength quenching steel EN 10 292 TL4225 was selected for the study.The intermediate frequency (IF) spot welding process,one kind of advanced jointing technologies,was used,and the perfect welded joints were obtained by using the optimum welding parameters.The mechanical properties of the joints,such as the tension strength,the hardness distribution,were tested,and the microstructure of the fracture was analyzed by scanning electron microscope.The test results show that the joints welded by using IF spot welding process has good mechanical properties,the microstructure of the joints is similar with that of the base metal,the fracture of the joints has the characteristics of plastic,and the mechanical properties completely meet the actual need of car product crash test and road testing.