过滤器连接螺栓断裂失效分析

某防喷器油路过滤器SCM435连接螺栓在使用过程中发生断裂,造成过滤器无法正常工作。为查找连接螺栓失效原因,采用金相显微镜、拉伸试验机、冲击试验机、显微硬度计、扫描电子显微镜和能谱仪等测试手段,研究了断裂和未断裂螺栓的显微组织、化学成分、硬度、力学性能和断口形貌。结果表明：断裂和未断裂螺栓的组织均为回火索氏体和铁素体,断裂螺栓夹杂物较多,碳含量偏高,断裂螺栓的硬度和力学性能均低于未断裂螺栓。断裂螺栓断口在平行和斜45°角的两个断面,表现为韧性断裂和脆性断裂的混合断裂形式,断裂源起源于内部。可见断裂螺栓是由于内部的碳化物等脆性相的不均匀分布,在持续外力作用下,优先形成裂纹源,随着裂纹的扩展而导致螺栓最终断裂。

Fracture failure analysis of filter connecting bolt

The connecting bolt of a blowout preventer oil circuit filter SCM435 broke during use, causing the filter to fail to work normally. In order to find out the failure causes of connecting bolts, the microstructure, chemical composition, hardness, mechanical properties and fracture morphology of fractured and unfractured bolts were studied by means of metallographic microscope, tensile testing machine, impact testing machine, microhardness tester, scanning electron microscope and energy dispersive spectrometer. The results show that the microstructure of fractured and unbroken bolts are tempered cordite and ferrite, the fractured bolts have more inclusions, high carbon content, and the hardness and mechanical properties of the fractured bolts are lower than those of unbroken bolts. The fracture bolt fracture is in the two sections of parallel and oblique 45° angle, manifested as a mixed fracture form of ductile fracture and brittle fracture, the fracture source originates from the inside. It can be seen that the fracture bolt is due to the uneven distribution of brittle phases such as internal carbides. Under the action of continuous external force, the crack source is preferentially formed, and the bolt finally breaks with the expansion of the crack.