铁镍基合金HT700P焊接接头力学性能和微观组织研究

Mechanical Properties and Microstructure of Iron-nickel Based Alloy HT700P Welded Joint

采用机械TIG焊方法对铁镍基合金HT700P大口径管的环缝焊接,焊后进行稳定化热处理(980℃/3 h/AC)和无损检测(100%PT+100%RT+100%PAUT),合格后对焊接接头进行拉伸强度、弯曲、硬度性能、冲击、高温持久性能和微观金相组织试验。试验结果表明:焊接接头室温抗拉强度、屈服强度高于HT700P母材的下限值,弯曲试验合格。焊接接头中母材和热影响区的硬度明显大于焊缝,母材和热影响区硬度无明显差别。焊缝的室温冲击平均值为160.7 J,热影响区的室温冲击平均值为102.3 J,均高于HT700P母材的下限值。焊接接头105小时持久断裂强度为138.3 MPa。焊接接头宏观和微观金相组织检验合格,焊缝金相组织均为奥氏体,不存在TCP等有害相的析出。

The mechanical TIG was used to weld the large diameter pipe ring seam of iron-nickel based alloy HT700P.After the welding and stabilization heat treatment(980℃/3 h/AC)was qualified by non-destructive testing(100%PT+100%RT+100%PAUT),the welded joint was subjected to tensile strength,bending,hardness performance,impact,high temperature endurance performance,and microstructure tests.The test results showed that the tensile strength and yield strength of the welded joint at room temperature were higher than the lower limit of the HT700P alloy,and the bending test was qualified.The hardness of the BM and HAZ in the welded joint is significantly higher than weld seam,while there is no significant difference in hardness between the base metal and heat affected zone.The average room temperature impact at the weld seam is 160.7 J,and at the HAZ is 102.3 J,both of which are higher than the lower limit of the HT700P alloy.The persistent strength of the welded joint for 105 hours isσ=138.3 MPa.The macro and micro metallographic structure of the welded joint is qualified,and the microstructure of the weld is austenite without the precipitation of harmful phases such as TCP.