高温条件下NiCrMoV转子钢焊接接头的高周疲劳性能研究

摘要

The fatigue crack initiation and propagation of the simulated rotor (30Cr2Ni4MoV) used in steam turbine was investigated by the repeated high-cycle tensile and compressive test with stress ratio R =-1.The fatigue fracture morphology was observed by the scanning electron microscope (SEM),and the composition of the selected zone was analyzed by the energy dispersive spectroscopy (EDS).For the welded rotor steel of 30Cr2Ni4MoV,the inclusions basically consisted of oxides,such as Al2O3,CaO,MgO and SiO2,etc.The results revealed that the fatigue crack generally occurred at the inclusions and pores,leading to fish-eye propagation around the defects.In addition,the effective projected area parameter model was applied to calculate the critical size of the defect causing crack initiation.Based on the present results,in order to improve the fatigue property of rotor steel,some effective measures should be adopted to control the size,shape and distribution of the defects.%通过应力比R=-1的拉压高周疲劳实验,研究了在370℃条件下汽轮机转子模拟件焊接接头的高周疲劳裂纹的萌生和扩展过程.通过扫描电子显微镜(SEM)和能谱(EDS)分析了疲劳断口的形貌特征和微区成分.研究结果表明:对于30Cr2Ni4MoV转子钢焊接接头而言,夹杂物主要成分为氧化物(Al2O3、CaO、MgO和SiO2等),疲劳裂纹往往萌生于夹杂物和气孔等内部缺陷.采用有效投影面积模型计算出母材和焊缝区域组织对应的临界缺陷尺寸,建立了夹杂物尺寸和疲劳裂纹萌生区域之间的关系.基于该研究结果,采取适当措施减少其内部的缺陷尺寸,并优化其形态和分布,以提高转子钢材料的抗疲劳性能.