大口径JCOE工艺生产X90管线钢组织与性能的研究

Research on Structure-properties of Large Diameter X90 Pipeline Steel Produced by JCOE Technological Parameters

介绍了直缝埋弧焊管的JCOE成型工艺流程,研究了X90管线钢板和制管后的基材和焊接接头的显微组织和性能,分析了成型工艺对X90管线钢组织与性能的影响。结果表明:板材、管体及焊接接头的DWTT和夏比冲击性能均能满足《天然气输送管道用X90钢级直缝埋弧焊管技术条件》要求;管体的屈服强度有所增高,抗拉强度变化不大,从而屈强比增大,验证了针状铁素体钢具有高的形变强化能力;据试验结果,计算焊缝热影响区的硬度平均值比母材低28 HV10;制管的外焊缝热影响区出现了明显的软化现象。粗晶区由于较大的热输入导致冷却速度降低,高温停留时间长,因而晶粒相对粗大,原奥氏体晶粒的晶界清晰。外焊缝组织以极细的针状铁素体为主,并混有少量的先共析铁素体,在保证焊缝强度的同时也保持了较好的韧性。

The JCOE forming process of straight seam submerged arc welding pipe was introduced. The microstructure and properties of plate and pipe of base material of X90 pipeline steel were researched. The molding process on the microstructure and properties of X90 pipeline steel was analyzed. The hardness of the welded joint and the pipe body changed. The results show that the plate, the pipe body and welded joint of DWTT and charpy impact test results meet the natural gas pipeline with X90 steel grade straight seam submerged arc welding pipe technical conditions requirement. Increasing the yield strength of pipe body, the tensile strength changes little, so Y/T ratio increases, which can verify the acicular ferrite steel has high ability of deformation strengthening. According to the test results of calculation in table 5, the hardness of weld heat affected zone average 28 HV 10 is lower than the matrix metal. According to the pipe before and after the performance analysis, there is an obvious softening of outside weld heat affected zone. The large heat input due to coarse grain zone results in the decrease of cooling speed, high temperature and retention time is long, thus relatively bulky grains, the grain boundaries of original austenite grain is clarity. The outside microstructure of welding is given priority to with extremely fine acicular ferrite, and mixed with a small amount ofproeutectoid ferrite, which guarantees weld strength as well as keeping a good toughness.