| In the field of automobile manufacturing,the lightweight parts,high impact performance and security protection concept is constantly advancing.A quenching hot stamping of Boron steel has been standed out and as a new technology,which realized the auto lightweight,broke the difficulty of the ultra-high strength steel plate in traditional cold stamping.In the processing of hot stamping,the final parts performance of high strength,high hardness mainly depends on martensite content.The hot forming process of phase change happened mainly in sheet metal parts quenching heat treatment process after the hot stamping process.In the production of high strength steel plate hot forming processing,not only the quenching temperature field changing affect the final parts martensite phase transformation,but also the stress field could be changed by the the difference in temperature and organizational change.Consequently,the final performance of parts is reflected with thermal-stess-phase comprehensive effect.For easy deformation,easily to produce the most car hot stamping parts which within thick,complex constructure,study thermal-mechanical-phase coupling rules of the ultra-high strength steel blank quenching has a practical significance.The hot stamping steel plate BR1500 HS was chosen as the research object,based on the hot forming theory and the finite element method analysis,the quenching heat-force-coupled mathematical model and finite element model was established;Combined with the research purpose,flat die structure was designed to the quenching process of BR15 OOHS.The microstrucre of BR1500 HS hot forming steel and physical performance related at room temperature was carried out to explore and analyze through experiment,at the same time,under different heating temperature and cooling time,direct water quench experiment was designed.After the water quenching,with the sheet of metallographic analysis to study heating temperature and cooling rate how to influence on law of sheet microstructure.Meanwhle,by using Deform on the sheet metal in direct water quenching heat treatment under the same parameters condition to have numerical simulation investigation on the martensite phase transformation simulation results were compared with experimental results by water quenching analysis,demonstrates the the correctness phase change of BR1500 HS in water quench through the Deform simulation method.Secondly,by using Deform and experiments to study the ultra high strength steel plate stamping forming process,to find out the quenching hot-force-phase coupling change rulesand the quenching stress influence parameters optimization.Firstly from the relatively simple direct water quenching heat-force-phase transition,simulation on BR1500 HS steel direct water quench under different heating temperature,to take direct water quench process numerical simulation analysis to find out temperature of phase transformation and phase transformation field influences on the stress field changes.To study of the quenching of BR1500 HS sheet,built simplified finite element model of sheet metal in the slab tool to take quenching under different initial temperature,different initial temperature of the die and different heat transfer coefficient between cooling channel and tool.Obtained sheet metal mold heat-force-phase coupling rules under three kinds of the three influence parameters.To find out the suitable quenching process parameters the Influence parameters on sheet stress are optimized in the die quenching,through which the ultimately forming parts can be ensured with high strength performance and low stress.Flat die quenching experiment and the results of simulation indicates,for further research of ultra high strength steel plate hot stamping technology,finite element numerical study can provides significant reference. |
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