某电厂空冷岛U型螺栓失效断裂机理分析与研究
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摘要
对某电厂空冷岛U型螺栓失效的原因进行研究。采用高分辨SEM和金相显微镜观察了断面表面形貌和金相组织;利用EDS对表面元素进行能谱分析;利用显微硬度计对失效螺栓进行硬度检测;进行了室温力学性能实验。结果表明,断口有明显的疲劳断裂特征;断面处的金相组织呈现出芯部比表面粗大的现象;表面硬度与心部硬度差超过了相关标准规定的上限值;运行情况调查结果表明该螺栓存在过载情况。因此,该螺栓失效的原因为在机组运行过程中,螺栓应力集中部位产生疲劳源,在过载情况下疲劳扩展加速,直至出现断裂失效。
The failure reasons of U-bolts in air-cooled island of a power plant were studied. High resolution SEM and metallographic microscope were used to study the surface morphology and metallographic microstructure of the section; the surface elements were analyzed by EDS. The microhardness meter was used to analyze the failure bolt hardness. The room temperature mechanical properties tests were carried out. The results show that the fracture has obvious characteristics of fatigue fracture. The core metallographical microstructure of the fracture is more coarse than that of the surface. The difference of the surface hardness and core hardness value is more than the upper limit of relevant standards. The results of the operationan investigation show that the bolts are overloaded. Therefore, the failure reasons of the bolt is due to that in the unit running process the stress concentration of the bolt generates fatigue source, and the fatigue propagation accelerates in the case of overload until the fracture failure appears.
The failure reasons of U-bolts in air-cooled island of a power plant were studied. High resolution SEM and metallographic microscope were used to study the surface morphology and metallographic microstructure of the section; the surface elements were analyzed by EDS. The microhardness meter was used to analyze the failure bolt hardness. The room temperature mechanical properties tests were carried out. The results show that the fracture has obvious characteristics of fatigue fracture. The core metallographical microstructure of the fracture is more coarse than that of the surface. The difference of the surface hardness and core hardness value is more than the upper limit of relevant standards. The results of the operationan investigation show that the bolts are overloaded. Therefore, the failure reasons of the bolt is due to that in the unit running process the stress concentration of the bolt generates fatigue source, and the fatigue propagation accelerates in the case of overload until the fracture failure appears.
引文
[1]Lei Honggang, Dong Chao, Pei Yan.The testing research on equal-amplitude fatigue behavior of large-span grid structures[C]//Proceedings of the 6th Pacific Structural Steel Conference,Beijing:Seismological Press,2001:962-966.
[2]欧阳卿.高强螺栓受力及疲劳性能研究[D].长沙:湖南大学,2013.
[3]张栋,钟培道,陶春虎,等.失效分析[M].北京:国防工业出版社,2005.
[4]合金结构钢:GB/T 3077-2015[S].
[5]1-2010紧固件机械性能螺栓、螺钉和螺柱:GB/T 3098[S].
[6]火电厂金相检验与评定技术导则:DL/T884-2004[S].
[7]王明娣.SWRCH22A自攻螺钉断裂原因分析[J].热加工工艺,2011,40(12):197-198.
[8]罗家华.40Mn2V石油套管外折裂纹分析[J].湖南冶金,2006,34(6):18-20.
[2]欧阳卿.高强螺栓受力及疲劳性能研究[D].长沙:湖南大学,2013.
[3]张栋,钟培道,陶春虎,等.失效分析[M].北京:国防工业出版社,2005.
[4]合金结构钢:GB/T 3077-2015[S].
[5]1-2010紧固件机械性能螺栓、螺钉和螺柱:GB/T 3098[S].
[6]火电厂金相检验与评定技术导则:DL/T884-2004[S].
[7]王明娣.SWRCH22A自攻螺钉断裂原因分析[J].热加工工艺,2011,40(12):197-198.
[8]罗家华.40Mn2V石油套管外折裂纹分析[J].湖南冶金,2006,34(6):18-20.