600MW超临界机组汽轮机中调门门杆断裂原因分析

Fracture Analysis on Turbine Intermediate Regulating Valve Stem of 600MW Supercritical Unit

某电厂600MW超临界机组汽轮机中调门门杆发生断裂,采用断口分析、金相组织分析及力学性能分析等方法对该门杆的断裂原因进行了分析。结果表明:门杆断裂部位存在原始缺陷,缺陷处为应力集中部位;在机组启停及甩负荷时,门杆承受较大拉应力及气流变化引起的交变冲击载荷,原始缺陷部位在交变冲击载荷及应力集中效应的共同作用下形成微裂纹,裂纹以疲劳方式扩展至临界尺寸时发生疲劳断裂。

The turbine intermediate regulating valve stem of 600MW supercritical unit fractured in a power plant. The reasons for the fracture were analyzed by using crack analysis,metallographic analysis and property analysis. The results show that the original defect exists in the fracture location, and the stress concentration exists in the original defect, in the unit commitment and load rejection, the tensile stress and alternating impact load exists the intermediate regulating valve stem. The forming of crack source was affected together by alternating impact load and stress concentration effect. The fatigue fracture happens when the crack extends to its critical size.