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Fe-0.25C-1.5Mn-1.2Si-1.5Ni-0.05Nb(质量分数,%)钢通过淬火-碳分配-回火(Q-P-T)工艺抗拉强度可达1250 MPa以上兼具良好塑性(大于17%),显微组织为位错型板条马氏体、微合金碳化物和薄片状残留奥氏体。通过低温拉伸试验分析了Q-P-T钢在-85～25℃下的力学性能并采用透射电镜观察了试样在25℃和-85℃时拉伸前后的显微组织。结果表明,Q-P-T钢在-70～25℃时显示了良好的低温力学性能,仅当拉伸温度低于-70℃时试样塑性开始出现大幅下降;残留奥氏体在未变形前具有良好的低温稳定性,但在变形过程中会发生马氏体相变,产生相变诱发塑性(TRIP)效应,这是Q-P-T钢具有高强度和良好塑性的主要原因。
Fe-0.25C-1.5Mn-1.2Si-1.5Ni-0.05Nb (mass fraction,%) Steel Passing Quenched-Carbon Assignment-Tempering (QPT) Process Tensile Strength Up to 1250 MPa Both Good Plasticity %), The microstructure of dislocation lath martensite, micro-alloyed carbide and flaky retained austenite. The mechanical properties of Q-P-T steel at -85 ~ 25 ℃ were analyzed by low temperature tensile test and the microstructure of Q-P-T steel was observed by transmission electron microscope before and after stretching at 25 ℃ and -85 ℃. The results show that the QPT steel exhibits good low temperature mechanical properties at -70 ~ 25 ℃. The plasticity of the QPT steel begins to decrease sharply only when the drawing temperature is lower than -70 ℃. The retained austenite has good Low temperature stability, but martensitic transformation occurs during deformation, resulting in phase transition induced plasticity (TRIP) effect, which is the main reason for the high strength and good ductility of QPT steel.