某弯头断裂原因分析

Fracture Cause Analysis of an Elbow

通过断口宏观、微观分析和母材的理化性能、组织分析,对某采油厂一埋地弯头的断裂原因进行了分析。结果表明,弯头开裂为低应力脆断。弯头用母管为直缝电阻焊钢管,焊缝热影响区的珠光体球化且沿晶界聚集,降低了晶界结合强度。同时,焊缝位置位于该失效弯头的外弧区,在弯管制造及服役过程中承受了最大的环向拉应力,因此在焊缝及热影响区产生裂纹。

The failure reason of a buried elbow in an oil-extracting factory was studied by macro, micro analysis of fracture, physical, chemical properties and microstructure analysis of base metal. The results show that the crack of the elbow is low stress brittle fracture. The parent pipe of the elbow is electric resistance welding steel pipe. The pearlite in heat affected zone of the weld spheroidizes and aggregates along the grain boundaries, which decreases the bonding strength of grain boundary. Meanwhile, the weld is located in outer arc zone of the failure elbow, which is under the maximum circumferential tensile stress in the elbow＇s manufacture and service. Therefore, the crack is generated in the weld and heat affected zone.