稀土对20MnCrNi2Mo耐磨铸钢组织及力学性能的影响

Effect of Rare Earth on Microstructure and Mechanical Properties of 20Mn Cr Ni2Mo Wear-Resistant Cast Steel

针对未添加及添加镧、铈混合稀土的20Mn Cr Ni2Mo低合金耐磨铸钢,分别采用洛氏硬度计、电子万能试验机和电子式摆锤冲击试验机测定其力学性能,采用扫描电镜、透射电镜观察显微组织和断口形貌,并分析稀土对其铸态显微组织和力学性能的影响。结果表明,添加稀土使20Mn Cr Ni2Mo耐磨铸钢的硬度、抗拉强度和冲击吸收功(-40℃)分别提高了10.44%、5.95%和36.87%,伸长率和断面收缩率分别提高了40.49%和39.42%。添加稀土改变了20Mn Cr Ni2Mo耐磨铸钢的铸态组织,由粒状贝氏体变为粒状贝氏体+少量下贝氏体,且稀土使粒状贝氏体组织中岛状物尺寸有所减小;添加稀土也改善了20Mn Cr Ni2Mo耐磨铸钢的断口形貌,使断口处有韧窝出现。

The mechanical properties of 20MnCrNi2Mo wear-resistant cast steel without and with the mixed rare earth of La and Ce were respectively tested by Rockwell apparatus, electronic universal testing machine and electronic pendulum impact testing machine. The microstructure and the fracture morphologies of the testing steel were observed by scanning electron microscope and transmission electron microscope. The effect of the rare earth on microstructure and mechanical properties of the testing steel is analyzed. The results show that adding the mixed rare earth of La and Ce increases the hardness, the tensile strength and the impact absorbing energy （-40℃） of 20MnCrNi2Mo wear-resistant cast steel respectively by 10.44%, 5.95% and 36.87%. It also increases the elongation and the reduction in cross-section by 40.49% and 39.42%. Adding the mixed rare earth influences the microstructure of 20MnCrNi2Mo wear-resistant cast steel. It changes from granular bainite to granular bainite and a small amount of lower bainite, and the size of islands in granular bainite decreases. The mixed rare earth also affects the fracture morphology of the testing steel and results in the dimples appearing.