Development of Thermal Integrated Clinching Methodology and Process Windows for Joining of Advanced High Strength Steels

摘要

Next generation of Advanced High Strength Steels (AHSS) with higher strength and ductility in base metal are extensively considered for usage in Body-in-White (BIW) structures with lower thickness to reduce the vehicle weight, and increase fuel efficiency and occupant safety. There have been various technologies under development for mixed materials joining as an alternative joining technology to Resistance Spot Welding (RSW) for BIW assembly. However, limited research has been explored for alternative joining methodology of steel to steel with AHSS. On the other hand, a sustainable Eco-Friendly manufacturing process capable of joining complex sheet metal assemblies requires more initiatives for development of new joining solutions as a possible replacement of RSW. Traditional clinching is an accepted method of mechanical cold forming joining process which has been used in BIW for light weight metals and steels with low strength. However, this process was unable to join AHSS with ultimate tensile strength above 1180MPa. In the present study, a modified clinching process has been developed with in-situ integration of thermal treatment using light-safe laser technology to soften Usibor 1500 locally to make the clinching of Usibor 1500 to Usibor 1500 sheets feasible. Process has been studied for optimization of temperature control to increase cross-tension and tension-shear strength. The new thermal integrated clinch joining process increases joint strength significantly, this can even reach or exceed the cross-tension strength produced by conventional spot-welding process.