The Effect Of Temperature On The Springback Of High Strength Steels After Hot Stamping

With the aggravation of the world energy crisis and the increasingly strict automobile safety regulations,weight reduction is one of the most important trends in the automobile design.The hot forming technology can effectively realize the automobile lightweight,which is favored by more and more automobile manufacturers.The obtained parts have the advantages of high formability,high strength and small springback.However,springback is still an unavoidable problem in the hot stamping.The reason of springback is the uneven stress distribution and the recovery of elastic deformation.Generally,by adjusting process parameters and die compensation,the springback of sheet can be reduced.The paper takes the u-shaped parts as the research object to explore the law of springback of 22MnB5 high-strength steel under the influence of temperature factor in the process of hot forming.The main tasks are as follows:Establish an u-shaped part model,and use Fluent and Lsdyna finite element software to simulate the heat fluid-solid coupling process involved in the hot stamping process of high strength steel.Through numerical simulation,the temperature change process and springback data of sheet and die are obtained.This paper explores the influence of temperature factors on springback of sheet metal from four aspects: initial temperature of sheet,cooling rate of mould,temperature difference between upper and lower mould and surface temperature inequality of mould.Taking the middle stringer of automobile as the research object,the hot stamping experiment was carried out,and the forming temperature and blue ray scanning data of the formed parts were obtained.The same simulation process was used to obtain the temperature cloud chart and springback data of the middle stringer.By comparing the experiment with the simulation,it is found that the simulation results are in good agreement with the experiment,which verifies the feasibility of the simulation method.Based on the analysis of the structural characteristics of the stringer and the distribution characteristics of the temperature field and displacement field of the sheet,the reasons for the springback of the formed parts are analyzed.According to the influence of temperature on the springback of sheet,the optimum scheme of the cooling system of the middle stringer is put forward to reduce the springback of the formed parts.