内衬316L双金属复合管环焊焊缝失效原因分析

针对双金属机械复合管对接环焊缝的刺漏问题，对某油田现场服役的内衬316L双金属复合管问题管段进行取样，并从焊缝横截面各区域微观组织、化学成分、抗晶间腐蚀性能等方面进行了研究。研究结果表明，对接环焊缝打底焊道的热影响区晶粒粗大，对接环焊缝打底焊道熔合线附近区域主要耐腐蚀合金元素被稀释是双金属机械复合管对接环焊缝发生刺漏的主要原因。最后给出了预防刺漏发生的措施，即通过降低打底焊热输入量，提高管端尺寸精度，增加过渡层厚度且减小第一层填充焊热输入量的方法可有效预防刺漏问题的发生。

Failure Reason Analysis on Butt Welds of Lined with 316L Bimetal Composite Pipe Butt Weld

In allusion to the butt circumferential weld perforation problem of mechanical bimetal composite pipe，the pipe section of an oil field lined with 316L bimetal composite pipe was sampled，the weld cross section was analyzed from several aspects, such as microstructure，chemical composition，intergranular corrosion properties and so on. According to analysis results the perforation reason was speculated , the HAZ grain of butt circumferential weld backing weld bead was coarse，the main reason of the butt circumferential weld perforation of mechanical bimetal composite pipe was that the main corrosion resistance alloy element near the fusion line of butt circumferential weld backing weld bead was diluted. Finally the preventive measures for perforation were given:reducing the heat input of backing weld, increasing pipe end dimension accuracy，and increasing the thickness of the transition layer with reducing the heat input of the first filled layer. All the above measures can effectively prevent the occurrence of perforation.