Basis Research On Variable Gradient Characteristics Hot Forming Technology

Hot forming technology for HSS plays an important role in achieving lightweight vehicles, improving the safety of vehicles. The traditional hot forming products have high strength, but the plasticity of them is usually low and comprehensive mechanical performance is not high. Recently, in order to achieve both high strength with high plasticity of the hot forming parts, Variable gradient characteristics hot forming technology becomes the research hotspot. Variable gradient characteristics hot forming technology plays an important role in precision forming, lightweight, high performance, short process, low cost and environment friendly. It is an important direction for the development of hot forming technology.The process control of material gradient properties hot forming technology were summarized through the analysis of strengthening mechanism of variable gradient characteristics hot forming technology. The main direction and corresponding scientific problems of variable gradient characteristics hot forming technology, including the theoretical basis, the heating technology, mold design for variable gradient characteristics were discussed.The foundation of heat transfer, mechanics, phase transformation kinetics of the metal in the process of the variable gradient characteristics hot forming technology are introduced. Based on heat transfer theory, plastic mechanics and transformation kinetics, the incremental relationship of the stress-strain in the elastic and plastic modes were obtained.HSS for the variable gradient characteristics hot forming technology are simulated. Using thermal-mechanical coupled finite element model to studying the characteristics of different process conditions on the variable gradient characteristics hot forming technology. The main parameters of the research are: stamping speed, die temperature, and time of holding pressure. Through the result of finite element simulation, it can be used to optimize the process of the variable gradient characteristics hot forming technology, and provide reference for the industrial application.The macro morphology, tensile properties, micro hardness, microstructure of the B1500 HS heat treated steel sheet under the action of non-uniform temperature field were analyzed. Obtain basic mechanical properties of the material gradient performance data. Yield point and elongation of the material were obtained by tensile test and hardness test, the tensile strength. Comparing with the uniform temperature field, the mechanical properties of the steel under the action of the non-uniform temperature field are verified.