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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。
According to the macroscopic and microscopic analysis of the fracture surface and the physical and chemical properties of the base material and the analysis of the structure, the fracture reason of a buried bend in a oil production plant was analyzed. The results show that elbow cracking is a low stress brittle fracture. Elbow with the mother pipe for the seam resistance welded steel pipe, weld heat affected zone of the pearlite ball and along the grain boundary aggregation, reducing the grain boundary bonding strength. At the same time, the weld location is located in the outer arc area of the failed elbow and suffers the maximum circumferential tensile stress during the manufacturing and service of the elbow, thus causing cracks in the weld and heat affected zone.