某井口无磁钢测井电缆滚筒在测井过程中发生断裂。采用宏观观察、化学成分分析、扫描电镜分析、金相检验、力学性能测试等方法分析了该滚筒断裂的原因。结果表明:滚筒发生了疲劳断裂,疲劳起源于滚筒轴内壁的凹槽处;该滚筒的力学性能和化学成分不合格,滚筒壁厚不均匀,断口处存在大量铸造缺陷,导致滚筒的耐疲劳性能变差,滚筒轴径处存在应力集中,在交变应力的作用下,裂纹萌生并扩展,最终导致滚筒发生疲劳断裂。

A non-magnetic steel logging cable drum broke during the logging process at a certain wellhead. The frature reasons for the drum were analyzed by macroscopic observation, chemical composition analysis, scanning electron microscopy analysis, metallographic examination, and mechanical property testing. The results show that the drum experienced fatigue fracture, which originated at the groove on the inner wall of the drum shaft. The mechanical properties and chemical composition of the drum were unqualified, the drum wall thickness was uneven, there were a large number of casting defects at the fracture, resulting in poor fatigue resistance of the drum. There was stress concentration at the drum shaft diameter, under the action of alternating stress, cracks initiated and expanded, ultimately led to fatigue fracture of the drum.