某电厂汽轮机中压转子动叶片开裂的原因

Causes of Medium-Pressure Rotor Moving Blade Cracking of Steam Turbine in a Power Plant

某电厂汽轮机中压转子动叶片在使用过程中发生开裂,通过宏观观察、化学成分分析、力学性能试验、显微组织观察及断口分析等方法,分析了动叶片开裂的原因。结果表明:动叶片裂纹呈沿晶扩展,裂纹两侧的显微组织存在明显的全脱碳现象,说明裂纹形成于热加工阶段,为典型的原始锻造裂纹;材料中磷含量超标,使晶界处易形成低熔点脆性共晶产物,在锻造加工过程中材料晶界处易形成沿晶裂纹;裂纹在工作载荷作用下逐渐扩展,最后造成叶片开裂。

The medium-pressure rotor moving blade of steam turbine in a power plant was cracked during use.The reasans for moving blade cracking were analyzed by means of macro morphology analysis,chemical composition analysis,mechanical property analysis,microstructure observation and fracture micro area analysis.The results showed that cracks of moving blade were distributed along the grain and there was obvious full decarburization in microstructure on both sides of cracks,indicating that the cracks formed in hot working stage,which was typical original forging cracks.The phosphorus content in the material exceeded the standard.It was easy to form low melting point brittle eutectic products,and intergranular cracks were easy to form at grain boundaries of material during forging process.Under the action of working load,the cracks gradually spread and finally caused the frature of moving blade.