天然气输送管道用L360钢HFW焊管失效分析

摘要

In the process of pressure test for a natural gas pipeline project, when the pressure rose to 3.6 MPa, the L360 HFW pipe with diameter of Φ406.4 mm×7.1 mm of pressure test section leaked. According to this phenomenon,the cracking reason for Φ406.4 mm×7.1 mm L360 HFW pipe was analyzed by chemical composition analysis, mechanical property testing , macro and scanning electron microscopy(SEM) analysis. Test results showed that the pipe body was repair welded, and thick widmans-tatten and martensite exist in the welding microstructure. Dense inclusions exist between metal welding and pipe body. The results showed that the mainly leak reason for L360 HFW pipe is the higher heat input during the repair welding and poor quality of pipe surface repair welding process.%某天然气输送管道工程项目现场试压作业过程中, 当管道内压上升至3.6 MPa时, 发现试压段L360钢Φ406.4 mm×7.1 mm 规格HFW管道存在泄漏现象. 针对这一现象, 利用化学分析、 力学性能检测、 宏观及扫描电镜显微分析等试验方法, 对现场输送管道用HFW钢管焊缝处开裂的原因进行了分析. 试验结果显示, 该管体曾经过补焊, 补焊组织中存在粗大的魏氏组织和马氏体组织, 补焊金属与管体母材之间存在密集夹杂物. 结果表明, 管体补焊过程热输入较大、 管体表面补焊工艺质量欠佳是导致管道打压泄漏的主要原因.