某电厂调节阀杆断裂事故分析

某电厂3根调节阀杆在运行过程中发生断裂，活塞杆的材料牌号为1Cr11MoV，由于活塞杆淬火冷却速度慢，调质后形成淬火冷却不足组织。阀杆的断口分析表明阀杆的断裂性质是疲劳断裂，阀杆端部及螺纹局部被氯化，在氮化组织中形成显微裂纹，增加了螺纹的脆性，导致螺纹在运行中出现局部剥落现象，形成偏载，进一步加剧了螺纹处的应力集中，最终导致阀杆疲劳断裂。

Fracture Analysis for Piston Rod of Oil Actuator of Intermediate Pressure(IP)Control Valve

Three regulating valve rods of a power plant fractured during running, the material trade mark of cylinder rod was 1Crl 1MoV. Because the quenching cooling velocity of cylinder rod is slow, it formed quenching cooling insufficient structure after hardening and tempering. Analysing the fracture of valve rod, it indicated that the property of valve rod fracture was fatigue fracture, the end of valve rod and whorl part were nitrided, and it formed microcracks in the nitration strueture. The microcracks increased the whorl fragility, so that it happened part peeling during the whorl running, and it formed bias load. Furthermore, it aggravated the stress concentration of whorl,so it led to the fatigue fracture of valve rod finally.