某X65钢级输气管道环焊缝泄漏失效分析

Leakage Failure Analysis of Girth Weld of X65 Steel Pipeline

针对某X65输气管道环焊缝泄漏失效问题,通过无损探伤、硬度试验、金相组织分析、扫描电镜分析等方法,对钢管环焊缝进行了分析研究。分析结果显示,焊接接头组织未见明显异常,但裂纹附近存在疏松组织,该疏松组织主要元素为铁和氧,以及少量铝、硅、钙、硫元素。研究表明,该疏松组织为焊接时未清理干净的焊渣,在外力和内压作用下,夹渣处裂纹相互贯穿形成穿透性裂纹,裂纹由内表面向外表面扩展,导致焊缝产生开裂而发生泄漏。

In order to find out the leakage failure of the girth weld of X65 gas transmission pipeline,the girth weld of the steel pipe was analyzed and studied by nondestructive testing,hardness test,metallographic structure analysis and SEM analysis.The results show that there is no obvious abnormality in the structure of the welded joint,but there is a loose structure near the crack.The main elements of the loose structure are iron and oxygen,as well as a small amount of aluminum,silicon,calcium and sulfur.The research shows that the loose structure is the welding slag which is not cleaned up during the welding.Under the external force and internal pressure,the cracks in the slag inclusion penetrate into each other and form the penetrating cracks.The cracks expand from the inner surface to the outer surface,resulting in cracks in the weld and leakage.