Failure analysis of fastening bolts of one steam turbine valve cover

doi:10.13251/j.issn.0254-6051.2021.10.048

Abstract

Abstract: 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 low-speed 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.

Key words: 20Cr1Mo1VTiB steel, fastening bolt, fracture, creep damage, impact property

CLC Number:

TG146

Zheng Jianjun, Fan Ziming, Liu Xiao, Qiao Xin, Gao Yunpeng. Failure analysis of fastening bolts of one steam turbine valve cover[J]. Heat Treatment of Metals, 2021, 46(10): 262-266.

References

[1]刘发, 纪繁祥, 彭建强. 汽轮机用高温螺栓材料的发展动向[J]. 机械工程师, 2012(7): 169-170.
[2]邱康永, 张杰, 吴继全. 主汽门阀盖螺栓断裂失效分析[J]. 理化检测-物理分册, 2018, 54(4): 304-307.
Qiu Kangyong, Zhang Jie, Wu Jiquan. Failure analysis on frature of a main steam valve cover bolt[J]. Physical Testing and Chemical Analysis(Part A: Physical Testing), 2018, 54(4): 304-307.
[3]黄廷杰, 江国栋, 洪茂林. 汽轮机调速汽门螺栓断裂分析[J]. 热处理, 2007(2): 49-50.
[4]梁红芳, 郑相锋, 冀彦昭, 等. 300 MW汽轮机中压内缸螺栓断裂原因分析[J]. 河北电力技术, 2016, 35(3): 42-43.
Liang Hongfang, Zheng Xiangfeng, Ji Yanzhao, et al. Failure analysis on intermediate pressure inner cylinder of steam-turbine for 300 MW power plant[J]. Hebei Electric Power, 2016, 35(3): 42-43.
[5]陈浩, 乔欣, 郑建军, 等. 25Cr2MoV高温紧固螺栓断裂原因分析[J]. 内蒙古电力技术, 2018, 36(4): 50-56.
Chen Hao, Qiao Xin, Zheng Jianjun, et al. Fracture analysis of high temperature bolt used for 25Cr2MoV steel[J]. Inner Mongolia Electric Power, 2018, 36(4): 50-56.
[6]DL/T 439—2018, 火力发电厂高温紧固件技术导则[S].
[7]欧蓉. 浅析高温螺栓钢20Cr1Mo1VNbTiB粗晶现象及其控制[J]. 特钢技术, 2005(2): 17-19.
Ou Rong. Analysis and controlling about heavy grain of high-temp bolting steel 20Cr1Mo1VnbTiB[J]. Special Steel Technology, 2005(2): 17-19.
[8]吴红辉, 王韦. 20Cr1Mo1VNbTiB高温螺栓断裂失效分析[J]. 华电技术, 2018, 40(10): 27-29.
Wu Honghui, Wang Wei. Failure analysis of 20Cr1Mo1VNbTiB high-temperature bolt[J]. Huadian Technology, 2018, 40(10): 27-29.
[9]贾若飞, 李梁, 秦承鹏. 某1000 MW超超临界机组汽轮机IN783螺栓断裂失效分析[J]. 汽轮机技术, 2019, 61(1): 78-80.
Jia Ruofei, Li Liang, Qin Chengpeng, et al. Failure analysis of IN783 alloy bolt used on 1000 MW ultra supercritical steam turbine[J]. Turbine Technology, 2019, 61(1): 78-80.
[10]张涛, 田峰, 陈浩, 等. 超临界汽轮机中压调速汽阀2Cr12NiMo1W1V钢阀杆断裂原因分析[J]. 理化检测-物理分册, 2015, 51(4): 278-289.
Zhang Tao, Tian Feng, Chen Hao, et al. Causes analysis on rupture of 2Cr12NiMo1W1V steel reheat interceptor valve stem of a ultra-supercritical turbine[J]. Physical Testing and Chemical Analysis(Part A: Physical Testing), 2015, 51(4): 278-289.
[11]吴鸿遥. 损伤力学[M]. 北京: 国防工业出版社, 1990.
[12]Lemaitre J. 损伤力学教程[M]. 北京: 科学出版社, 1996.
[13]徐鸿, 郑善合, Maile Karl. 超(超)临界汽轮机汽缸紧固螺栓高温蠕变断裂研究[J]. 中国电机工程学报, 2007, 27(29): 80-83.
Xu Hong, Zheng Shanhe, Maile Karl. Research on creep rupture of fastening bolts of ultra-supercritical steam turbine cylinder case at high temperature[J]. Proceedings of the CSEE, 2007, 27(29): 80-83.

[1]	Chen Dongjun, Li Guangyang, Liu Gang. Effect of aging treatment on microstructure and mechanical properties of AlSi9Cu3 HPDC aluminum alloy [J]. Heat Treatment of Metals, 2022, 47(4): 53-56.
[2]	Chen Sijun , Chen Songyi, Chen Geng, Yuan Dingling, Chen Kanghua. Effect of Mg content on microstructure and mechanical properties of 2A14 aluminum alloy [J]. Heat Treatment of Metals, 2022, 47(4): 86-92.
[3]	Bai Qingqing, Zhang Zhihong, Zheng Huaibei, Wang Yinghu. Precipitation behavior of σ phase in 2507 super duplex stainless steel [J]. Heat Treatment of Metals, 2022, 47(4): 108-115.
[4]	Chen Gang, Luo Xiaobing, Chai Feng, Yang Caifu, Zhang Zhengyan, Yang Li. Influence of rolling heating temperature on microstructure and impact property of a high strength low alloy steel [J]. Heat Treatment of Metals, 2022, 47(4): 116-121.
[5]	Li Li, Zeng Yan, Wu Xiaochun. Heat treatment process optimization for 4Cr5Mo2VCo steel [J]. Heat Treatment of Metals, 2022, 47(4): 133-140.
[6]	Luo Diqiang, Yu Yinhong, Zhang Zhenming, Feng Xiaoming, Liu Min, Lai Chaobin. Effect of yttrium-based rare earth on inclusions and cryogenic temperature impact property of high strength shipbuilding steel [J]. Heat Treatment of Metals, 2022, 47(3): 142-146.
[7]	Li Mingxiang, Yang Ping, He Wei, Zhang Meng, Wang Wenbo. Failure analysis of hydrogen induced delayed fracture of 50CrVA steel spring [J]. Heat Treatment of Metals, 2022, 47(3): 257-260.
[8]	Yang Yuchuan, Li Wei, Xiong Yong. Analysis of fracture cause of 1Cr17Ni2 steel small shaft of control box [J]. Heat Treatment of Metals, 2022, 47(3): 261-265.
[9]	Wu Yingfei, Sun Zhonghua, Wang Yufei, Wang Chengming, Zhang Yunfei, Peng Huifen. Effect of homogenizing on microstructure and properties of Invar alloy ingot [J]. Heat Treatment of Metals, 2022, 47(2): 130-136.
[10]	Li Dejun, Gao Hua, Kong Xianglu, Yang Xiaoping, Li Ta, Dong Zhaoyuan, Zhang Xiaojia. Failure analysis of 20 steel equal-diameter tee [J]. Heat Treatment of Metals, 2022, 47(2): 262-266.
[11]	Zhao Xiaojun, Liang Xiao, Cai Zhenyang, Xiao Lairong. Effect of aluminizing and oxidation treatment on microstructure and mechanical properties of CLAM steel [J]. Heat Treatment of Metals, 2022, 47(1): 192-196.
[12]	Wu Hao, Deng Xiangtao, Li Chengru, Sui Yi, Zhang Tao, Ji Wenbo, Wang Zhaodong. Analysis on cold bending fracture of wear-resistant steel NM400 [J]. Heat Treatment of Metals, 2021, 46(9): 262-267.
[13]	Xu Qihao,Yang Lilin, Xia Ming, Qin Chen, Geng Zhenyue, Jiang Yajun, Zhao Liping. Failure analysis of 38CrMoAlA steel driveshaft [J]. Heat Treatment of Metals, 2021, 46(9): 268-272.
[14]	Yu Hongjun, Song Chuansongxin, Cheng Fuchao, Gao Zhizhe, Chen Xiaoyan, Wang Yongjin, Zhang Yingchao. Microstructure and properties of a hypoeutectic high-Cr cast iron under different heat treatment conditions [J]. Heat Treatment of Metals, 2021, 46(8): 56-60.
[15]	Nie Xiaolong, Gao Jiaqiang, Meng Kairen, Wang Junyi, Liu Xinkuan. Fracture failure analysis of 60Si2Mn spring steel [J]. Heat Treatment of Metals, 2021, 46(8): 246-249.