Optimization Of Procedure Parameters And Quality Evaluation Of Projection Welding Of Hot-stamped Steel And Low-carbon Steel

With the advantage of high strength and hardness, the hot-stamped steelwhich is composed of martensite plays a more and more important role tomeet the demand of lightweight and safety in auto motive industry.Resistance projection welding is typically employed to join structural steelcomponents in large-scale automatic production of vehicle. Compared withordinary steel, the weldability of hot-stamped steel is greatly different, andthere are many other problems during the welding process, such as softeningof heat affected zone, embrittlement of nugget, splashing, and the weldingnugget migration in the resistance projection welding on different steels. Soit is significant to research the mechanical and microscopic properties of theresistance projection welding joints of hot-stamped steel, optimize weldingparameters, correct and replenish the evaluation standard of the jointsquality. This paper examines the resistance projection of B1500HS hot-stampedsteel and H220PD+Z100MB ordinary low-carbon steel with a thickness of1.5mm, the Q235A steel nut with the type of M6. The tension strength,hardness distribution, the size of nugget, microstructure and the torsion ofthe joints have been analyzed. The test results show the hot-stamped steelhas good weldability, the size of nugget and tensile shear strength and thetorsion of joints between nut and steel plate meet production requirements.There is welding nugget migration on different steels, and the softened zonenear affected zone.The existing evaluation standards of quality can measure the jointsbetween hot-stamped steel and low-carbon steel partly. The qualitystandards of tensile shear strength of joint betweent hot-stamped steel andlow-carbon steel, joint between nut and low-carbon steel, joint between nutand hot-stamped steel needs to be added according to the specific materialchanges.A coupled axisymmetric finite element model is built to simulate theresistance projection welding process of B1500HS hot-stamped steel andH220PD+Z100MB ordinary low-carbon steel with a thickness of1.5mm bythe finite element analysis software, SORPAS. Via simulation, the dynamicdata including temperature field, stress and stain distribution arequantitatively calculated. The information of the welding nugget size issimulated and compared with the one from the experiments.