Research On Hot Stamping Heat Transfer Coefifcient And Optimization Of Process Parameters Of Ultra-high Strength Thick Steel Sheet

The application of ultra-high strength steel on automobile manufacturing has beenwidely used in order to reduce automobile weight and improve safety and collision.High-precision and small-springback forming parts can be easily obtained as high strengthsteel sheet has better liquidity when heated to high temperature. The microstructuretransformation from austenite to martensite can greatly improve the forming strength. Thedomestic and overseas institution of scientific research and the automobile enterprisesstudy1-2mm of ultra-high strength steels in the majority, but study4mm ultra-highstrength steel less.In view of the above reasons, we took ultra-high strength steel of4mm thickness asthe research object in this study, conducted in-depth study of heat transfer performance andhot stamping process technology of heat-formed parts, and the process parameters wereoptimized by means of numerical simulation. Finally, the simulation results were verifiedby experiments. The main contents and results of this study are as follows:(1) The traditional Newton’s law of cooling and results from hot stamping test werecombined to estimate the heat transfer coefficients of quenching process. Temperature fieldwas obtained under different pressure through the finite element simulation softwarePam-Stamp compared with experimental results, which verified the accuracy of the testsolution of heat transfer coefficient.(2) The resulting heat transfer coefficient was combined with the FEM simulationsoftware Pam-Stamp. The impact of the main process parameters on the hot stampingprocess was studied taking a typical U-shape part for example. Combined with the actualindustrial demand, the optimal process parameters are: initial forming temperature800℃,pressure holding time10s.(3) Hot forming tool of thick boron steel was designed and experiment on hot formingprocess was carried on. Then the U-shape part was tested under optimized process parameters:800℃of initial forming temperature,10s of pressure holding time.Afterwards, microstructure and microhardness of different locations on U-shape part werestudied. Microstructure was mainly composed of martensite, hardness of bottom and flangecould reach to470HV. On the whole, U-shape part had good performance and could meetthe requirements of the production process.