Investigation On Resistance Heating Process Of High Strength Steel For Hot Stamping

With the increase in consumer weight,car fuel performance and safety concerns,car manufacturers began to focus more on automotive materials,and high-strength steel as an excellent material to solve these problems has become more and more extensive application.However,there are some problems with the strength of high strength steel,such as poor forming performance,serious rebound after forming,easy cracking and other defects,seriously restricting its application in the automotive structural parts.At the same time,hot stamping molding as a high-strength steel commonly used forming method,the traditional heating method using furnace heat,there is low production efficiency,high cost and energy loss and other issues.Resistance heating can effectively improve the shortcomings in the process of furnace heat.In this paper,the performance of high-strength steel plate is improved by studying the resistance heating process.In this paper,the heating platform,which can control the heating rate,the end point temperature and the holding time,has been set up.Then,the resistance heating test of the high strength steel 22MnB5 is carried out on this platform,and the process limits corresponding to different heating parameters are preliminarily determined.Then,based on the concept of experimental optimization design,the complete experimental scheme is designed according to the selected factor level within the process limit.Then,a prediction model of strength-ductility mapping is established by analyzing the experimental data,also its accuracy is verified.According to the analysis of the response surface of the prediction model,the process parameters are optimized.Under the combination of the heating rate of 59 ? / s,the ending temperature of 915 ? and the holding time of 20 s,the strength-ductility can reach the maximum value of 15.5GPa%.The effect of different heating parameters on the mechanical properties of the molded parts is studied in depth.The strong plasticity of the materials will increase with the increase of the heating rate.The suitable end point will make the strong plasticity reach the optimum and deviate from this temperature The increase of the holding time and the increase of the holding time will lead to the decrease of the strong plasticity.At the same time,the influence of the heating parameters on the macroscopic mechanical properties is explained from the view of the grain size.On the other hand,the effect of the current on the crack morphology during the resistance heating process is studied.,A detailed analysis of the two processes of fracture and healing.Finally,the finite element simulation test was used to simulate the rectangular parts,the temperature change and the temperature distribution in the heating process were further studied.The results show that the uniformity of the temperature distribution has a significant effect on the quality of the final molded parts,and the effects of different heating strategies on the temperature distribution uniformity are further studied.In this paper,And got a more optimized strategy of heating.The application of resistance heating technology in the pre-treatment of hot stamping process has been the biggest innovation point of this topic,which shows obvious advantages compared with the traditional radiant heating method.In addition,this paper uses the response surface method to find the process window of the new technology quickly and accurately,and demonstrates the effectiveness of the method in the optimization of the new process.