塔河油田某站外输油管线弯管出现开裂现象。利用金相显微镜、扫描电镜对失效位置形貌进行观察，通过X衍射分析仪对腐蚀产物进行分析，并对管材力学性能进行测试，明确输油管线弯管的开裂原因。结果表明：管材组织中存在上贝氏体、贝氏体及马氏体等非正常组织，材料强度、硬度偏高，韧塑性偏低；材料中含有少量夹杂，且残余应力较高，使弯管开裂敏感性升高；管道在内应力及腐蚀介质的作用下发生应力腐蚀开裂，随着应力的持续作用，管道发生破裂，出现刺漏。

An elbow of external oil pipeline in a station in Tahe oilfield cracked. In order to determine the cracking reason of the oil pipeline elbow, the morphology of failure position were observed by metallographic microscope and scanning electron microscope, the pipeline corrosion products were analyzed by X-ray diffraction, and the mechanical properties of the pipe were tested. The results showed that there were abnormal structures such as upper bainite, bainite and martensite in the microstructure of pipeline, so the material had high strength and hardness, and low plasticity and toughness. A small amount of inclusions and high residual stress in the material caused the improvement of cracking sensitivity of the elbow. Stress corrosion cracking occurred in the pipelines under the action of internal stress and corrosive medium. With the continuous action of stress, the pipeline cracked and leaked.