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为了改善超高强钢的塑韧性,采用轧后直接淬火到马氏体区等温配分的工艺,研究配分时间对中碳低合金超高强钢组织和力学性能的影响规律。结果表明:在260℃等温配分处理,钢的组织包括初生马氏体、新生马氏体和残留奥氏体,在等温过程中还有碳化物析出和等温马氏体形成。在等温配分过程中,碳由马氏体向奥氏体扩散处于主导地位,残留奥氏体含量不断增加,新生马氏体量减少,塑性和韧性提高。等温配分后期,由于碳化物不断析出消耗碳原子,导致扩散到奥氏体中的碳原子减少,残留奥氏体体积分数增加缓慢。析出相粒子在等温过程中没有明显长大,起到了抵抗马氏体软化的作用。等温60 min具有良好的强度和塑韧性能,抗拉强度1546 MPa、伸长率为15.3%,-20℃冲击功为27.5 J。
In order to improve the plasticity and toughness of ultra-high strength steel, the process of direct quenching to martensitic zone after rolling was used to study the influence of the blending time on the microstructure and mechanical properties of medium-carbon low alloy ultra-high strength steel. The results show that the microstructure of the steel includes isothermal martensite, fresh martensite and retained austenite at the isothermal temperature of 260 ℃. In the isothermal process, carbides and isothermal martensite are formed. In isothermal partitioning process, carbon is dominated by the diffusion of martensite to austenite, the content of retained austenite increases, the amount of fresh martensite decreases, and the plasticity and toughness increase. In the later phase of isothermal partitioning, the carbon atoms diffused into the austenite decreased due to the continuous precipitation of carbon atoms, and the retained austenite volume fraction increased slowly. Precipitated phase particles in the isothermal process did not significantly grow, played a role in resistance to martensite softening. Isothermal 60 min has good strength and plastic toughness, tensile strength of 1546 MPa, elongation of 15.3%, - 20 ℃ impact energy of 27.5 J.