SP2215/T92异种钢焊接接头微观组织与力学性能研究

Study on Microstructure and Mechanical Properties of Dissimilar Welded Joint of SP2215/T92

摘要:

采用手工钨极氩弧焊和ERNiCr-3焊丝制备了SP2215/T92异种钢钢管焊接接头，研究了热处理前后接头的微观组织，力学性能及拉伸断裂机理。结果表明:焊缝金属以完全奥氏体组织凝固成柱状枝晶，Nb元素在枝晶间偏析并形成富Nb第二相粒子，焊后热处理对焊缝组织无显著影响；T92与焊缝金属界面以及SP2215与焊缝金属界面均形成岛状或半岛状宏观偏析，跨T92与焊缝金属界面存在一定程度的碳迁移，而跨SP2215与焊缝金属界面碳迁移现象不明显，焊后热处理对宏观偏析和碳迁移无显著影响；T92侧粗晶热影响区硬度最高，细晶热影响区硬度次之，临界热影响区硬度最低，焊后热处理显著降低了粗晶热影响区和细晶热影响区的硬度，改善了T92 热影响区的微观组织和力学性能；T92侧熔合线附近形成了δ铁素体，是整个接头硬度最低区域，焊后热处理对δ铁素体的硬度无明显影响；焊态和热处理态接头室温拉伸均在焊缝处以韧性方式断裂，而650℃高温拉伸时均在T92侧以韧性方式断裂。

Abstract:

Dissimilar welded joints (DWJ) of SP2215 and T92 tube were prepared by manual-gas tungsten arc welding (M-GTAW) and ERNiCr-3 filler. The microstructure, mechanical properties and tensile fracture mechanism of DWJ before and after heat treatment were studied. The results show that the weld metal (WM) is solidified into columnar dendrites with complete austenite structure, and Nb element is segregated between dendrites to form Nb-rich secondary phase particles, post welded heat treatment (PWHT) has no significant effect on the microstructure of welded seam. Island or peninsula macro-segregation is formed at both T92/WM and SP2215/WM interface, and a certain degree of carbon migration occurs across the T92/WM interface while the carbon migration across the SP2215/WM interface is not obvious, PWHT has no significant effect on macro-segregation and carbon migration; The hardness of coarse grain heat affected zone (CGHAZ) at T92 side is the highest, followed by fine grain heat affected zone (FGHAZ), while inter-critical heat affected zone (ICHAZ) has the lowest hardness, PWHT reduces the hardness of CGHAZ and FGHAZ significantly and modified the microstructure and mechanical properties of T92 HAZ; δ ferrite is formed near the fusion line in the T92 side, which is the lowest hardness area of the DWJ, PWHT has no significant effect on the hardness of δ ferrite. Both the as-welded and heat-treated DWJs are fractured at the welded seam in a ductile manner at room temperature, while fractured at the T92 side in a ductile manner at 650℃.