The effect of quenching temperature and cooling conditions on the microstructure and mechanical properties of a 0.2%Nb medium chromium wear-resistant cast steel was investigated. The microstructure, carbides and volume fraction of retained austenite were characterized using the optical microscope, scanning electron microscope, transmission electron microscope and X-ray diffraction. The influence of heat treatment on hardness, impact toughness and tensile properties of test steel was studied. It can be observed that lath martensite can be obtained under the condition of air cooling and oil cooling upon austenitizing in the range of 900–1020 °C. Total carbide content of 0.2–1.1 wt.% under air cooling is more than that under oil cooling due to the lower cooling rate. Nb₆C₅, M₂₃C₆ and M₇C₃ were found at lower austenitizing temperature, of which niobium carbide mostly located at grain boundaries, while chromium carbides were uniformly distributed in the matrix with the size of 20–50 nm. The chromium carbides are basically dissolved into the matrix in test steel austenitized at 1020 °C. Meanwhile, the negligible growth of prior austenite grain size is achieved. Specimen austenitized at 1020 °C and cooled in air + tempered at 200 °C has a best combination of hardness, plasticity and tensile strength due to fine grain size and more amount of retained austenite. Under this condition, the hardness is 58 HRC, the impact toughness is 22.92 J/cm², and the tensile strength is 1136.9 MPa.

研究了淬火温度和冷却条件对0.2％Nb中铬耐磨铸钢组织和力学性能的影响。利用光学显微镜，扫描电子显微镜，透射电子显微镜和X射线衍射对残余奥氏体的显微组织，碳化物和体积分数进行了表征。研究了热处理对试验钢硬度，冲击韧性和拉伸性能的影响。可以观察到，在奥氏体化温度为900–1020°C的条件下，在空冷和油冷条件下可以获得板条马氏体。在空气冷却下，总碳化物含量为0.2-1.1 wt。％，比在油冷却下要高，这是因为冷却速率较低。铌₆ C ₅，M在较低的奥氏体化温度下发现了₂₃ C ₆和M ₇ C ₃，其中碳化铌主要位于晶界，而碳化铬均匀分布在基体中，尺寸为20-50 nm。碳化铬基本上溶解在1020°C奥氏体化的测试钢中的基体中。同时，基本奥氏体晶粒度的增长可以忽略不计。在1020°C下奥氏体化并在空气中冷却+在200°C下回火的试样由于晶粒细小和残留的奥氏体数量更多，因此具有硬度，可塑性和拉伸强度的最佳组合。在该条件下，硬度为58HRC，冲击韧性为22.92J / cm ²，抗拉强度为1136.9MPa。