P110套管特殊扣密封面细小裂纹分析

Analysis of Fine Crack on Special Thread Sealing Surface of P110 Casing

在P110套管螺纹加工时发现特殊扣套管密封面存在细小裂纹,通过外观和金相分析、宏观和微观断口形貌观察、能谱分析,发现裂纹缺陷处存在非金属夹杂物。结果表明,组织中存在非金属夹杂物是造成该套管有细小裂纹的主要原因,冬天轧制过程中前端冷却速度过快,使非金属夹杂物拉长、破碎,最终产生细小裂纹。指出,螺纹加工后能够对端部缺陷部分进行切除;对特殊性能要求的油套管可适当控制金属夹杂物的级别;在冬天轧制的过程中,在轧机的前端装加热器,可缓解管坯前端过多的温度降低,减少变形抗力和裂纹出现。

Fine crack was found on the sealing surface of special thread in the processing of P110 casing thread. Through the analysis of appearance and microstructure, the observation of macroscopic and microscopic fracture morphology and energy spectrum analysis, it is found that there is non-metallic inclusion at the crack defect. It is held that the non-metallic inclusion is the main cause of the fine crack. The fast cooling speed at the front end in the rolling process of casing steel in winter makes non-metallic inclusion elongated and broken to result in fine crack. It is pointed out that the thread processing can cut a part of the fine crack; the tubing and casing steel with special performance requirements can properly control its non-metallic inclusion level; in the rolling process of casing steel in the winter, a heater should be installed in the front of rolling mill, which can decrease the probability of crack generating due to the excessive decreasing of the temperature at the front end of tube blank.