新型热成形汽车用钢的合金化设计与力学性能分析

Alloying Design and Mechanical Performance Analysis of New Hot-formed Automobile Steel

针对传统22MnB5热冲压成形钢塑性不足导致其强塑积偏低的问题,模拟分析Mn,Cr,Co,Ni等合金元素对热成形钢显微组织临界冷却速度的影响,综合考虑淬透性、合金成本及热冲压成形钢实际生产工艺要求,设计新型汽车热冲压成形用钢,研究热冲压加热温度对其力学性能的影响。结果表明:在碳质量分数为0.20%、锰质量分数为1.70%~2.00%、铬质量分数为1.50%时,设计的热冲压成形用钢20Mn2Cr具有优良的淬透性,且在达到热冲压要求的临界冷却速度条件下成本较低;添加合金元素Cr可有效提高热成形钢的抗氧化性能,在890℃模拟热成形时,20Mn_(2)Cr钢具有优异的力学性能,抗拉强度达1600 MPa、延伸率为12%、强塑积为19 GPa·%,强塑积优于22MnB5钢。

Aiming at the problem of low strong plastic product caused by insufficient plasticity of traditional 22MnB5 hot stamping steel,the influence of alloying elements such as Mn,Cr,CO and Ni on the critical cooling rate of microstructure of hot-formed steel was simulated and analyzed.Considering the hardenability,alloy cost and the actual production process requirements of hot-formed steel,a new type of automobile hot-formed steel was designed,and the effect of heating temperature on mechanical properties of hot-formed steel was studied.The results show that when the mass fraction of carbon is 0.20%,the mass fraction of manganese is 1.70%-2.00%,and the mass fraction of chromium is 1.50%,the designed steel 20Mn2 Cr has excellent hardenability and low cost under the condition of reaching the critical cooling rate required by hot forming.The addition of alloying element Cr can effectively improve the oxidation resistance of hot-formed steel.When simulating hot forming at 890℃,20Mn_(2) Cr steel has excellent mechanical properties with tensile strength of 1600 MPa,elongation of 12%and strength-ductility product of 19 GPa·%,and its strength-ductility product better than that of 22MnB5 steel.