深水钢悬链立管焊接工艺及焊缝性能试验研究

Welding Process Development and Mechanical Tests for Deepwater Steel Catenary Riser

深水钢悬链立管(Steel Catenary Riser,SCR)是浮式平台的主要部件,在服役条件下由于受到海洋特殊的海浪、潮汐、台风等各种环境因素的影响,极其容易发生疲劳破坏。为解决钢悬链立管在深水服役环境中受循环载荷的作用容易产生疲劳失效的问题,采用冷金属过渡(Cold Metal Transition,CMT)打底、脉冲模式填充盖面的熔化极气体保护焊(Gas Metal Arc Welding,GMAW),开发了钢悬链立管S型铺设全自动焊工艺并进行了焊缝性能试验研究。结果表明,横向拉伸、全焊缝拉伸、侧弯、缺口断裂、冲击、宏观硬度及全尺寸疲劳等试验结果均满足SCR焊接规格书要求;SCR环焊缝通过全尺寸疲劳试验测试,所有焊缝疲劳性能满足BS7608(1993)的外径D曲线和内径E曲线的95%置信水平要求;由于CMT冷金属过渡封底为无衬垫单面焊双面成型技术,具有焊接热输入量小、无飞溅等优点,可确保焊缝根部成形与母材圆滑过渡,减小SCR焊缝应力集中,从而提高其抗疲劳性能。

Steel catenary riser(SCR) is the main component of floating platform. It is extremely prone to fatigue damage under service conditions due to the influence of various environmental factors such as ocean waves, tides and typhoons. In order to solve the problem about fatigue failure of steel catenary riser(SCR)affected by cyclic load in deep water environment,full-automatic GMAW welding process and mechanical tests were developed by using cold metal transition(CMT)for root pass and pulse mode for fill and cap pass for SCR S-lay. The test results of mechanical properties meet the requirements of SCR welding specification. The fatigue properties of all test welds meet or exceed the 95% level of confidence based on BS7608(1993) D mean curve as OD and E mean curve as ID.Because cold metal transition for root pass without backing is the technology of single side welding and double side forming, it has the advantages of smaller welding heat input and no spatter, ensuring the smooth transition between weld root forming and base metal, so as to reduce stress concentration and improve the fatigue resistance of SCR welds.