| Hot stamping process for ultra high strength steel has been regardedas one of the main feasible methods to produce lightweight automobileparts, which has the high comprehensive properties with energy saving，environmental protection and good safety. The hot stamping process hasbeen widely used in advanced nations, it is laggard for China, butdeveloping very fast. Nowadays, some impact resistance part such as Bpillar for C-class car has been produce by hot stamping process. Baosteelis the only producer in China to supply hot stamping steel with cold-rolledboron steel B1500HS and boron steel BR1500HS. But the basic researchon thermodynamic characteristics for such material is not sufficient.In this thesis, the boron steel B1500HS produced by Baosteel isinvestigated. The hot stamping processes is simulated at Gleeble3500thermodynamic system to represent the real heat treatment course,numerical simulation of typical hot stamped parts are carried out byLS_Dyna software. The main purpose of this thesis is to provide referencefor selection of hot stamping process parameter, flow properties under hightemperature, prediction of hot stamping production property, and otherrelated work by using boron steel B1500HS. The following contents arediscussed:Firstly, the hot stamping processes of B1500HS are simulated atGleeble3500thermodynamic system. By testing the mechanical propertiesof B1500HS in dependency of different process parameters including heating temperature, holding time, cooling rate etc,900℃and5min arefound as the most reasonable process parameter combination. The criticalcooling rate of Martensitic transformation is about25～27℃/s.Secondly, a series of stress-strain curves of B1500HS are tested by theuniaxial hot drawing test, which show the high dependency between theflow behavior of B1500HS and the temperature, as well as the strain rate.Moreover, comparison between B1500HS and the widely used22MnB5for some typical features are carried out and lots of similarities are found.Besides, using least squre method, the material models of B1500HS underhigh temperature are fitted out.Thirdly, the finite element analysis model is established to simulatethe hot stamping process by using the commercial FEA code LS_Dyna.The profiles of temperate and other variable during the process can beobtained. In addition, since the relationship between the final mechanicalproperty and temperature history during the process has been investigatedin the above section, then a rough numerical perdition model of hotstamping production property is presented. |
