针对管线钢存在的应变时效问题,对国产X80管线钢及其直缝埋弧焊管管体进行了不同时效后的拉伸试验,对其应变时效行为及预防措施进行了研究.结果表明:当时效温度达到210 ℃时,存在1%预应变的X80管线钢和经水压、冷扩径后的直缝埋弧焊管均出现明显的应变时效,前者屈服强度和屈强比均上升6%,后者的分别上升9.5%和6.9%,且应力-应变曲线均出现明显的屈服平台;测定拉伸性能时要尽可能降低拉伸试样的温升,降低防腐前加热温度和缩短加热时间以及降低管线钢中的碳、氮含量,采用双相显微组织并在轧制工艺中用加速冷却后立即在线热处理等方法均是降低管线钢应变时效的有效措施.

Aiming at the problems during strain aging of linepipe steel,the tensile properties of domestic X80 plate and longitudinal submerged-arc welded pipe body were tested after aging at different temperatures.The behavior and preventive measures of strain aging of domestic X80 linepipe steel were investigated.The results show that the strain aging effect of both X80 linepipe steel with 1% pre-strain and SAWL pipes after hydrostatic test and cold expansion was significant after aging at 210 ℃.The yield strength and yield-to-tensile ratio of specimens made from X80 linepipe steel were increased by 6% and the ones from the pipe body were increased by 9.5% and 6.9% respectively.In addition,the stress-strain curves exhibited significant yield plat form.To minimize the strain aging effect of high strength linepipe steel,some measures are suggested to be taken,such as reducing the temperature rise of the specimen as much as possible during tensile properties testing,decreasing heating temperature before anticorrosion treatment and shortening heating time delicately during coating,lowering C and N contents in linepipe steel and developing two-phase steel as well as applying on-line heating treatment just after accelerated cooling.