低硬度F91钢高压导汽管法兰组织与力学性能的研究

Study on Microstructure and Mechanical Properties of F91 Steel for High Pressure Steam Guide Pipe Flange with Low Hardness

采用光谱分析、力学性能检验、金相组织与扫描电镜等方法,分析了低硬度的F91钢高压导汽管法兰的组织和性能。结果表明,高压导汽管的合金成分符合标准要求,抗拉强度、屈服强度、冲击吸收功均不符合标准,金相组织为块状等轴铁素体和沿晶界偏聚的碳化物,拉伸断口有许多短而弯曲的撕裂棱线条,及点状裂纹源向四周放射的河流花样等。机组运行时间不长出现组织与性能异常的主要原因是制造过程中回火时温度控制不当造成的。

The microstructure and properties of F91 steel high pressure steam guide pipe flange with low hardness were analyzed by means of spectral analysis,mechanical properties test,metallographic structure and scanning electron microscope.The results show that,the alloy composition of the high pressure steam guide pipe meets the requirements of the standard.The tensile strength,yield strength and impact absorption work are not in accordance with the standard.The metallographic structure is bulk equiaxed ferrite and carbide segregated along grain boundary.The tensile fracture has a number of short and curved tear-edge lines,river pattern radiated from dotted-type crack source to the surrounding.The main reason for the abnormal structure and performance of the unit in short running time is improper temperature control during tempering in the manufacturing process.