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设计了一种新型1500 MPa级Si-Mn-Cr-Ni-Mo多组元系低合金超高强度结构钢,对比研究了控轧+控冷(TMCP)、控轧+空冷、控轧+直接淬火、控轧+直接淬火+250℃回火4种不同工艺对其微观组织和力学性能的影响.结果表明:直接淬火态钢板抗拉强度最高,可达1890 MPa,屈服强度为1280 MPa,延伸率为13%;250℃回火30 min后抗拉强度降低为1820 MPa,而屈服强度升高为1350 MPa,分析认为这归因于位错亚结构的回复软化过程与残余奥氏体分解为马氏体、析出ε-碳化物强化机制的综合作用;空冷与TMCP工艺获得板条贝氏体+马氏体+少量残余奥氏体的复相组织,贝氏体分割马氏体板条束,使实验钢具有良好的强塑性.低碳马氏体相变过程存在C扩散现象.研究发现,回火过程不仅包含残余奥氏体分解,也包含C从马氏体或贝氏体向奥氏体的分配过程.证明了立方结构的析出粒子在奥氏体中形核,在整个冷却过程长大、粗化,而相变后的马氏体或贝氏体未出现大量第二相析出核心.
A new 1500 MPa grade Si-Mn-Cr-Ni-Mo multi-component ultra-high strength low-alloy structural steel was designed. The effects of controlled rolling + controlled cooling (TMCP), controlled rolling + air cooling, controlled rolling + direct Quenching, controlled rolling + direct quenching + tempering at 250 ℃ were studied.The results show that the direct quenched steel has the highest tensile strength of 1890 MPa, the yield strength of 1280 MPa and the elongation of Rate was 13%. After tempering at 250 ℃ for 30 min, the tensile strength was reduced to 1820 MPa and the yield strength was increased to 1350 MPa. It was considered that this was attributed to the reaction softening process of the dislocation sub-structure and the decomposition of residual austenite into Martensite, precipitated ε-carbide strengthening mechanism of the combined effect of air-cooled and TMCP process lath bainite + martensite + a small amount of retained austenite complex phase, bainite martensite lath , So that the experimental steel has good ductility.The carbon diffusion phenomenon exists in the low-carbon martensitic transformation.The study found that the tempering process not only includes residual austenite decomposition, but also contains C from martensite or bainite to Austria The distribution of the body of the body proved that the cubic structure of the precipitated particles in the nucleation of austenite throughout the cooling process Large, rough, or bainite and martensite phase transition after a large number of second phase precipitation nuclei does not occur.