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30Cr2Ni4MoV 钢是一种汽轮机低压转子用钢.在工作过程中,因汽轮机反复停机,低压转子内的裂纹将会发生缓慢扩展,因此有必要对疲劳裂纹的低频扩展特性进行研究.通过对试验钢的组织结构分析及低频疲劳试验,得出了如下结果:(1)正常热处理状态下,钢的组织是回火马氏体,第二相碳化物都是渗碳体,无高钼碳化物存在;(2)在本试验条件下,低频疲劳裂纹的扩展特性与频率升高至 f=15时的疲劳试验结果并无区别;(3)随着ΔK 增大,疲劳条纹间距变大.二次裂纹的方向和最大切应力方向有关,而二次裂纹的间膈和钢的组织有关.
30Cr2Ni4MoV steel is a kind of low-pressure rotor steel for steam turbine.During the working process, the cracks in the low-pressure rotor will slowly expand due to the repeated shut-down of the steam turbine, so it is necessary to study the low-frequency expansion characteristics of fatigue crack. Microstructure analysis and low-frequency fatigue test, the following results were obtained: (1) Under normal heat treatment, the microstructure of the steel is tempered martensite and the second phase carbides are cementite without molybdenum carbide; (2) Under the conditions of this test, there is no difference between the fatigue crack propagation characteristics at low frequency and the fatigue test at f = 15; (3) As the ΔK increases, the fatigue crack spacing becomes larger. Direction and the direction of the maximum shear stress, while the secondary crack between the diaphragm and the organization of the steel.