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在商用热成形钢B1500HS成分基础上,通过提高Si含量获得一种可适用于淬火-配分(Q&P)处理的新钢种,研究了其Q&P处理后的微观组织与力学性能。采用光学电镜(OM)、透射电子显微镜(TEM)对材料的微观组织进行观察分析,采用磁性法(PPMS)测定残留奥氏体含量。结果表明,Si含量高的钢经Q&P处理后得到板条马氏体+残留奥氏体组织,而低Si含量钢为全马氏体组织。不同Si含量材料的力学性能差别明显,Si含量由0.25wt%提高至0.89wt%时,屈服强度和抗拉强度提高约80~150 MPa,且Si含量高的钢对Q&P处理的温度和时间条件比低Si含量钢更敏感。结果显示Si含量较低的钢进行不同条件的Q&P处理后,材料的强塑积基本不变,而Si含量的提高使热成形钢适于进行Q&P处理,260℃×300 s条件下获得强塑积高于20 GPa·%的综合力学性能,比水淬试样强塑积高约71%。
Based on the composition of commercial thermoformed steel B1500HS, a new type of steel suitable for quenching - partitioning (Q & P) treatment was obtained by increasing the Si content. The microstructure and mechanical properties of the product were studied after Q & P treatment. The microstructure of the material was observed by optical microscope (OM) and transmission electron microscopy (TEM). The content of retained austenite was determined by magnetic method (PPMS). The results show that the slab martensite + retained austenite structure is obtained after Q & P treatment for steel with high Si content, while the low Si content steel is all-martensite structure. The mechanical properties of the materials with different contents of Si are obviously different. When the content of Si is increased from 0.25wt% to 0.89wt%, the yield strength and tensile strength increase about 80 ~ 150MPa, and the temperature and time condition of Q & P for steel with high Si content More sensitive than low Si steel. The results show that the Q & P treatment of the steel with lower Si content under the different conditions basically does not change, while the increase of the Si content makes the hot-formed steel suitable for Q & P treatment and the strong plasticization under 260 ℃ × 300 s The comprehensive mechanical properties with a product above 20 GPa ·% are approximately 71% more potent than water quenched specimens.