某火电机组三连杆恒力弹簧支吊架弹簧拉杆断裂原因

Fracture Cause of Spring Pull Rod of Constant Spring Support with Three Connecting Rods of a Thermal Power Unit

某火电机组三连杆恒力弹簧支吊架弹簧拉杆发生断裂,通过宏/微观形貌观察、化学成分分析、显微组织观察、力学性能测试及受力仿真计算等方法分析了弹簧拉杆断裂原因。结果表明:断裂弹簧拉杆材料为疲劳性能较差的非调质态45钢;弹簧拉杆螺纹加工长度不足及表面加工缺陷使其在第一个螺纹牙根部产生应力集中,形成裂纹源;三连杆恒力弹簧支吊架在运行过程中,其内部弹簧拉杆发生偏斜,承受附加弯矩,在轴向拉力、弯曲载荷及管道振动产生的附加交变应力的共同作用下,弹簧拉杆发生低应力高周疲劳断裂。

A spring pull rod of constant spring support with three connecting rods of a thermal power unit was broken.The fracture cause of spring pull rod was analyzed by means of macro and micro morphology observation,chemical composition analysis,microstructure observation,mechanical property testing and force simulation.The results show that the material of fractured spring pull rod was non-quenched and tempered 45steel with poor fatigue performance.Stress concentration at the root of the first thread was caused by the insufficient thread processing length and surface processing defects of the spring pull rod,which formed the crack source.During the operation of constant spring support with three connecting rods,the internal spring pull rod was deflected and subjected to additional bending moment.Under the joint action of axial tension,bending load,and additional alternating stress produced by pipe vibration,low stress high cycle fatigue fracture of the spring pull rod occurred.