汽轮机高压主汽门螺栓断裂失效分析

Analysis on fracture failure of bolt in high-pressure main stop valve of steam turbine

某电厂汽轮机高压主汽门螺栓发生断裂失效,对材质为20Cr1Mo1VNbTiB的断裂螺栓进行了理化试验和失效分析。结果表明:主汽门螺栓在加工制造过程中热处理工艺控制不当,导致金相组织存在粗晶,机组运行过程中,螺栓高应力的粗晶区发生沿晶开裂并不断扩展,最终发生主汽门泄漏和螺栓断裂失效。给出了防止由于粗晶问题造成螺栓失效的措施。

The bolt of high-pressure main stop valve of a power plant steam turbine was fractured.The physical and chemical test and the failure analysis for the fractured bolt,the material of which is 20Cr1Mo1VNbTiB,were carried out.The results show that during manufacturing process of the bolt of the main stop valve,the control of the heating processing was improper,and there was coarse grain in metallographic structure;in unit operation process,the inter-granular crack occurred in coarse grain zone with high stress of the bolt,and the crack continuously extended.Finally,the leakage of the main stop valve and the bolt fracture failure were occurred.The measures to prevent the bolt failure caused by coarse grain were given.