汽轮机组阀盖紧固螺栓断裂失效分析  

Failure analysis of fastening bolts of one steam turbine valve cover

作　　者：郑建军 樊子铭 刘孝[1] 乔欣 高云鹏[1] Zheng Jianjun;Fan Ziming;Liu Xiao;Qiao Xin;Gao Yunpeng(Inner Mongolia Electric Power Science&Research Institute,Hohhot Inner Mongolia 010020,China)

机构地区：[1]内蒙古电力科学研究院,内蒙古呼和浩特010020

出　　处：《金属热处理》2021年第10期262-266,共5页Heat Treatment of Metals

基　　金：内蒙古电力科学研究院2020年自筹科技项目(510241200003)。

摘　　要：采用宏观形貌和显微组织观察、化学成分分析、力学性能测试和冲击断口微观形貌观察等方法,对某电厂4号汽轮机组中压调节阀阀盖用20Cr1Mo1VTiB钢紧固螺栓的断裂原因进行了研究。结果表明,螺栓断裂的原因主要与长时高温运行引起的蠕变损伤有关。螺栓的许用工作温度(570℃)仅略高于汽轮机组的设计温度(566℃),裕度存在不足,且螺母端第一扣螺纹牙底处的应力集中程度较高,在长期高温和低速率应力集中的共同作用下形成蠕变孔洞,冲击性能逐渐下降,并最终引发蠕变损伤断裂。据此,建议对中压调节阀紧固螺栓及相应的垫圈材料配套进行等级升级。Fracture cause of the 20Cr1Mo1VTiB steel fastening bolts used for medium pressure control valve of No.4 steam turbine of a power plant was studied by means of macroscopic morphology and microstructure observation,chemical composition analysis,mechanical properties test and impact fracture morphology observation.The results show that the fracture of the fastening bolts is mainly related to the creep damage caused by long time running at high temperature.The allowable working temperature(570℃)of the bolt is only slightly higher than the design temperature(566℃)of the steam turbine,which causes an insufficient margin.Besides,the stress concentration at the nut bottom end of the first thread is always relatively high where forms creep holes under the combined action of long-term high temperature and lowspeed stress concentration,and decreases the impact property,then finally causes creep damage and fracture.Accordingly,it is suggested to upgrade the material grade of the medium pressure control valve fastening bolt and the corresponding gasket.

关 键 词：20Cr1Mo1VTiB钢 紧固螺栓 断裂 蠕变损伤 冲击性能 

分 类 号：TG146[一般工业技术—材料科学与工程]