Study On Hot Forming Process Of Car B-pillar Reinforcement Plate

The hot forming of high-strength-steel sheet is a new manufacturing process that combines traditional hot forging and cold stamping.In the paper,high strength boron steel was used as the object of study,and the hot forming of B-pillar reinforced plate was studied by numerical simulation and experiment.The B-pillar finite element model was simplified and the numerical simulation of hot forming was carried out.The pressing way was optimized.The use of pressure core solved the problem that the unreasonable design of the pressure surface made the sheet metal temperature dropped so fast that the formability of the part was poor.At the same time,the variation of temperature field,strain field and stress field during the hot forming process were investigated.The influence of heating temperature,friction coefficient and stamping speed on the hot forming process was studied.The results showed that the higher heating temperature and stamping speed,the higher the temperature of the workpiece after forming,the more favorable the martensite transformation,but the maximum thickening rate of workpiece was also greater so that the surface quality of parts was seriously affected.According to the simulation results,the heating temperature was selected from 900~950℃ and the stamping speed was selected from 100~125mm/s.The mold face of B-pillar hot forming die,the sheet positioning device,the cooling system and so on were designed,on this basis,the overall structure of the B-pillar hot forming die is designed.By means of adding the surface design of the suction table in addendum on both sides of the mold,the problem of parts flange wrinkling was solved.Using the above theoretical analysis of the parameters,the B-pillar hot forming test was carried out in the development of the mold,then the parts were tested for mechanical property and microstructure observation.The results showed that the tensile strength of the four tensile specimens were all above 1400 MPa.The average hardness of the four hardness test specimens were all above 490 HV.Metallographic sample of the organization are fine martensite.The hot forming parts sufficed for the actual production requirements.The reliability of the hot forming numerical simulation and the design of the mold were verified.It will provide important technical reference for practical application of hot forming process in the automotive industry.