闸板防喷器活塞杆的断裂失效分析

Analysis on Fracture Failure of Piston Rod of Ram Blowout Preventer

针对某油田闸板防喷器活塞杆在使用过程中发生的断裂失效,采用金相显微镜、扫描电镜(SEM)、MTS液压万能伺服试验机、夏比摆锤冲击试验机等方法对活塞杆的化学成分、金相组织、拉伸力学性能、冲击性能以及断口宏微观形貌进行了研究,确定了裂纹源的位置及形成机理,并对断裂失效的原因进行了分析。结果表明:活塞杆的拉伸力学性能未达到石油行业标准要求,材料的热处理工艺也未达到国家标准要求,致使材料内部产生裂纹,裂纹在交变载荷的作用下扩展,最终导致活塞杆在抗应力比较薄弱的连接槽处产生解理疲劳断裂。

Metallographic microscope,scanning electron microscope(SEM),MTS hydraulic universal servo machine and charpy pendulum impact testing machine were used to study the chemical composition,metallographic structure,tensile mechanical properties,impact properties and macro and micro fracture morphology of piston rod which had fracture failure.Then,the location and the formation mechanism of crack source were determined and the cause of fracture failure was analyzed.Results indicated that the tensile mechanical properties of piston rod failed to meet the requirements of petroleum industry standards,and the heat treatment process of the material did not meet the national standard yet.These caused the formation of cracks inside the material,and then the fatigue crack extended under the alternating loads.Ultimately the cleavage fatigue fracture of piston rod occurred at the connection slot which resistance to stress was relatively weak.