正火处理对X70管道钢焊接头组织与性能的影响

Effect of Normalizing Treatment on Microstructure and Properties of Welded Joint of X70 Pipeline Steel

采用E6010焊条对X70管道钢进行焊接,焊接头经920℃加热保温30 min正火处理。应用金相显微镜、显微维氏硬度计、拉伸试验机等对焊接接头的组织和力学性能进行检测与分析。结果表明:X70管道钢焊接头的焊缝区由大块状的铁素体+少量珠光体+少量贝氏体以及第二相颗粒组成,过热区出现了少量的魏氏体。焊接头熔合区硬度值最高,达到了261HV0.2。经正火处理后,消除了大部分的贝氏体、魏氏体,同时第二相颗粒减少、细化,显微组织分布均匀合理。正火处理后,焊接头的强度值略有下降,伸长率提高,力学性能满足结构件要求。

E6010 welding rod was used to weld X70 pipeline steel, and normalizing treatment(920℃ ×30 min) was carried out for the welded joint. The microstructure and mechanical properties of the welded joint was tested and analyzed by optical microscopy, microhardness tester and tensile testing machine. The results reveal that the microstructure of weld zone of the welded joint of X70 pipeline steel is block ferrite, small amount of pearlite, a small amount of bainite and second phase particles, and Widmanstatten structure appears in the overheated zone. The hardness of fusion zone is the highest, reaching261 HV0.2. After normalizing treatment, the majority of bainite and widmanstatten structure are eliminated, the second particle phases are reduced and refined, and the microstructure distribution is more uniform. Meanwhile, the strength value of the welded joint slightly decreases, the elongation increases, and the mechanical properties can meet structural requirements.