Microstructure and Mechanical Properties of Girth Joint for X80 Pipeline SteelPipe Welded with Self-shielded Flux Cored Wire
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摘要: 采用自制自保护药芯焊丝对X80管线钢管进行环焊缝焊接，分析不同焊接位置接头的焊缝成形、显微组织与力学性能。结果表明：不同焊接位置的焊缝成形良好，该焊丝具有良好的全位置焊接适应性；不同焊接位置焊缝组织基本相同，盖面层由板条贝氏体和针状铁素体组成，填充层为细小的粒状贝氏体和准多边形铁素体；不同焊接位置热影响区细晶区组织基本相同，由细晶铁素体和针状铁素体组成；热影响区粗晶区由粗大的板条贝氏体和粒状贝氏体组成，且立焊位置的晶粒尺寸小于平焊和仰焊位置的；焊缝和热影响区的平均硬度分别为226，227 HV，略低于母材的（233 HV）；立焊位置焊缝和热影响区的-10 ℃平均冲击吸收功高于平焊位置的；不同焊接位置接头的抗拉强度相当，拉伸断口呈韧性断裂特征。Abstract: X80 pipeline steel was girth welded with self-made self-shielded flux cored wire. The weld formation, microstructure and mechanical properties of the joint at different welding positions were analyzed. The results show that the weld at different welding positions had good formation, indicating that the wire had good all position welding adaptability. The microstructures of the weld at different welding positions were almost the same. The cap layer consisted of lath bainite and acicular ferrite; the fine granular bainite and quasi-polygonal ferrite were in the filling layer. The fine-grained heat-affected zone had almost the same microstructure of fine-grained ferrite and acicular ferrite. The coarse lath bainite and granular bainite were in the coarse-grained heat-affected zone, and the grain size of this area at vertical position was smaller than that at flat and overhead positions. The average hardnesses of weld and heat-affected zone were 226, 227 HV, respectively, which were slightly lower than that of the base metal (233 HV). The average impact absorbing energies at -10 ℃ of weld and heat-affected zone at vertical position were higher than that at flat position. The tensile strength of joints at different welding positions was similiar, and the tensile fracture of the joints showed ductile fracture characteristics.
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