Influnce Of Rasistance Spot Welding Parameters On Welding Quality Of Hot-Stamped Steel

Automotive lightweight is one of the important measures to realize energy conservation and emissions reduction,which is the important direction for the sustainable development of automobile industry in the future.With excellent applicability,good quality assurance and high efficiency,resistance spot welding is favored in the automotive industry.With the advantages of high strength and hardness,the hot-stamped steel can satisfy the body weight and enhance the safety of the car body collision at the same time.So the FAW Group i s substantially increasing the proportion of hot stamping steel in the developing models.But the particularity of the surface state of the hot formed steel plate not only makes the welding parameter window different from common steel plate,but also makes it difficult to guarantee the quality of spot welding.So it is very important to grasp the properties and microstructure of the hot stamped steel in welding,and to form effective quality control measures and to explore better welding parameters.In this article,resistance spot welding of the hot-stamped steel USIBOR1500 with 0.9mm and ordinary low carbon steel HC260LAD+Z with 1.6mm is researched.Firstly,the influence of welding current,electrify time and electrode force on mechanical property of the welded joint is studied through orthogonal experiment.The results shows welding current contributed great influence,electrify time is less critical and electrode force is the least critical.The optimal welding parameters also are found in this paper.Secondly,this thesis focuses on the influence of welding current and electrifies time on nugget diameter,indentation depth,microstructure and mechanical property.The results shows that with the increase of welding current and electrify time,both the nugget diameter and the bearing capacity of the welded joint firstly increase and then decrease,the indentation depth increases.However the increase of electrode force,the nugget diameter still firstly increases and then decrease,but the bearing capacity of the welded joint changes little.The failure mode of the joint is mainly the welding core.The thermally affected areas of the hot-stamped steel have a softening region,which is organized as the tempering martensite.With the increase of heat input,the area of the thermal affected area is enlarged and the martensitic grain is unusually large,and the joint fracture is transformed by the fusion zone into the fuse line.Spot welding joints have a large number of cracks,shrink Age and splash defects.At the same time,this paper explores the influence of alumina-silicon plating on the forming of spot welding joints and mechanical properties.The research shows that the presence of aluminum-silica coating affects the joint forming of the solder points,and the welding joints are more prone to defects.Mechanical properties are also influenced by a certain: The optimum bearing capacity of the welded joint with the coating is reduced by about 10 percent,reducing a nuclear froming current 1k A,reducing the optimum welding current 0.7k A and reducing the splash current 3.2k A.