热处理对X90管线钢组织性能的影响

将焊接的与未焊接的X90管线钢固溶后保温不同时间,对其显微组织和拉伸性能进行了分析.结果表明,X90管线钢在不同保温时间下的组织均由多边形铁素体和粒状贝氏体组成.随着保温时间的延长,粒状贝氏体由弥散状变为团状,M-A岛的含量增多,铁素体平均晶粒尺寸增大.焊接的与未焊接的实验钢保温时间为30 min,抗拉强度分别达最高660 MPa和725 MPa;保温60 min时抗拉强度分别最低为603 MPa和647 MPa.析出强化和细晶强化对钢的力学性能都有贡献,在保温30 min时,析出强化占主导地位.热处理对X90管线钢的性能影响对于经过焊接的与未焊接的实验钢,表现出了同样的趋势.

Effect of heat treatment on microstructure and mechanical properties of X 90 pipeline steel

Welded and not welded X 90 pipeline steels were heated at a certain temperature and then kept the temperature for different time. Microstructure and mechanical properties were analyzed. The results showed that all X 90 pipeline steel specimens consist of polygonal ferrite and granular bainite. Granular bainite becomes agglomerates from a dispersed state, volume fraction of M-A islands increases, and average grain size of the ferrite increases with the increasing temperature preserving time. Tensile strengths reach highest values (660 MPa and 725 MPa, respectively) when the preserving time is 30 min for welded and not welded steels. The strengths become the lowest (603 MPa and 647 MPa, respectively) when the preserving time is 60 min. The contribution comes from the precipitation and grain refinement strengthenings. When the preserving time is 30 min, the main contribution is the precipitation strengthening. There is a same trend through heat treatment of X 90 pipeline steels for welded and not welded specimens.