摘要
应用扫描电子显微镜、光学显微镜、直读光谱仪、硬度计和冲击试验机,对铁路用20MnTiB钢高强螺栓断裂件的断口微观形貌、显微组织、化学成分、硬度和冲击性能进行了检验分析。结果表明,高强度螺栓的螺纹齿底存在折叠缺陷,产生较大应力集中。在裂纹尖端形成的应力集中和露天工作环境的共同作用下,螺栓发生应力腐蚀开裂。同时,螺栓的热处理工艺不当,在螺纹表面产生增碳现象,促进了初始裂纹的萌生。建议螺栓生产企业改进热处理工艺和螺纹滚丝工艺,避免产生增碳现象和齿底折叠缺陷。
The micrograph of fracture surface,microstructure,chemical composition,hardness and impact property of a failed 20MnTiB steel high strength bolt used for rail was analyzed by means of SEM,optical microscopy,direct reading spectrometer,hardness tester and impact testing machines. The results show that the lap defects exist on the bottom of the thread which generates large stress concentration. Both stress concentration of crack tip and corrosion condition in the open air cause the stress corrosion cracking of bolt. In addition the bolt is not properly heat treated,and carburization is observed on the surface of the thread which promots the crack initiation. It is recommended that the bolt manufacturer enterprise should improve the heat treatment process and the thread rolling technology to avoid carburization and lap defect on the surface of the bolt.
出处
《金属热处理》
CAS
CSCD
北大核心
2017年第7期185-188,共4页
Heat Treatment of Metals
关键词
高强度螺栓
断裂
折叠
应力腐蚀
增碳
high strength bolt
fracture
lap
stress corrosion
carburization
