X70管线钢在役焊接局部脆化区的组织及精细结构

采用焊接热模拟试验研究了X70管线钢在役焊接粗晶区和临界粗晶区的显微组织及其精细结构,并和常规焊接进行了对比.结果表明,X70管线钢在役焊接粗晶区和临界粗晶区的组织在类别上与常规焊接相差不大,主要都是粒状贝氏体和贝氏体铁素体,不同的只是数量的多少和尺寸的大小.透射电镜下,在役焊接和常规焊接的粗晶区与临界粗晶区的主要形貌都是铁素体板条和分布在板条之间或板条基体上的岛状物,铁素体板条的亚结构都是高密度位错.在役焊接粗晶区和临界粗晶区的铁素体板条宽度都比常规焊接的要小,位错密度都比常规焊接的要高.

Metallurgical microstructure and fine structure in local brittle zone of in-service welding of X70 pipeline steel

Metallurgical microstructure and fine structure in coarse-grained heat-affected zone(CGHAZ) and intercritically reheated coarse-grained heat-affected zone(IRCGHAZ) of in-service welding of X70 pipeline steel were investigated and compared with routine welding by means of welding thermal simulation experiment.The results show that the types of metallurgical microstructure in CGHAZ and IRCGHAZ of in-service welding are almost the same with routine welding,and the main microstructure is all granular bainite and lath bainite,the difference is the amount and size of each microstructure.Observation of transmission electron microscope reveals that the fine structure of CGHAZ and IRCGHAZ of both in-service welding and routine is ferrite laths and the second phase particles that distribute on or between ferrite laths.The substructure of ferrite laths is high-density dislocations.The width of ferrite lath of in-service welding is smaller but the density of dislocations is bigger than that of routine welding.