Hot Stamping Process Research And FEA Of High Strength Steel

With the improvement of people's living conditions, more and more people pay much attention to the safety of vehicles. Therefore, the application of high strength steel (HSS) and ultra high strength steel (UHSS) in automobile body become more and more widely. But because of the high stress and deformation resistance of high strength steel and ultra high strength steel at room temperature, it is very hard to be formed by the method of cold punch, so the hot stamping technology emerged for demands. For the time being, hot stamping parts have been widely used on the important parts of automobile body. Especially in many foreign countries, most of all important automobile body parts are made from hot stamping process. In high-end car of many famous vehicle companies in domestic country, most structure and safety parts are also made from hot stamping process. Using this technology can not only save material, lighten the weight of car, decrease automobile emission, but also can significantly enhance the body bending rigidity and torsion rigidity. Thus it can improve the strength of parts and crash safety of cars. The hot stamping of HSS and UHSS is a new forming process which heats the metal beyond the re-crystal temperature, then forming and quenching the part in mould to obtain high strength part. Because of high temperature, the material microstructure transferred into austenite, the deformation resistance decreased and easy to be formed. For quenching after forming, the microstructure switch to martensite, thus the mechanical strength has been improved greatly.This paper takes the high strength steel B400VK as research object, using combining method of numerical simulation and test to study the mechanical properties in hot stamping and to explore the influences of forming parameters on the mechanical properties. Frist, it uses the experiment to get the curve of deformation resistance in high temperature. Namely, the ture stress-stain curves are obtained after the materials becoming fully austenitic phase and carrying out the tensile tests under different temperatures and different stain rates. Then put it into the model of material in FEM. Coupled thermal-mechanical simulation of hot stamping for the U-section of A pillar reinforcer by the software Dynaform, meanwhile, it combined the process of hot stamping. It explains the distribution and variety of temperature and stress at each time in hot stamping, summarizes the influence of velocity, blank original temperature, mould original temperature, force and holding time on temperature and stress in hot stamping; it gets the mould ability of cooling in different temperature by tracking the node temperature variety. In the end,it does experimentation on U-section by hot stamping, then discovers the microstructure of part is martensite after carring out microanalysis by taking portion of the U-section . Contrasting the hot stamping and cold stamping, the experiment and result of FEA, it can prove that precision of hot stamping is better than cold stamping, and the feasibility and advantage of hot stamping. The results do significant guidance for this material and part in hot stamping of industrialization.