制氢转化炉管服役过程中组织性能研究
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摘要
研究了制氢转化炉用25Cr35NiNb+微合金炉管服役过程中组织演变及其对性能的影响。采用场发射电子显微镜(FE-SEM)对炉管微观组织进行表征,并通过室温拉伸试验机和高温持久试验机对炉管的力学性能进行测试。结果表明,初期服役过程中,晶界骨架状碳化物粗化,向链状转变,NbC向G相(Ni_(16)Nb_6Si_7)转变,晶内析出二次碳化物。随着服役时间延长,二次碳化物在晶界聚集,晶界碳化物继续粗化至块状;炉管服役过程中抗拉强度和屈服强度逐渐降低,断后伸长率显著下降;服役8年的炉管,高温持久断裂时间较未服役炉管下降了约90%。
The microstructure evolution and its influence on mechanical properties of hydrogen reformer tubes made of 25Cr35NiNb+ MA in service process were investigated. The microstructure of the tubes was characterized by field emission gun scanning electron microscopy( FE-SEM),and mechanical properties of the tubes were tested on the tensile testing machine and creep testing machine. The results show that during the early stage of service,the skeleton carbides at grain boundaries were coarsened and transformed to a chain shape,the Nb C was changed to G phase( Ni_(16)Nb_6Si_7),whereas secondary carbides were precipitated at within the crystal. As the service time was extended,the secondary carbides gathered at grain boundaries,the carbides at grain boundaries continued to be coarsened to a blocky shape. The tensile strength and yield strength of the tubes were gradually reduced during service,and its elongation after fracture was significantly reduced. The tubes having been in service for 8 years showed a decrease of about 90% in the fracture time of high-temperature creep rupture test compared with new tubes.
The microstructure evolution and its influence on mechanical properties of hydrogen reformer tubes made of 25Cr35NiNb+ MA in service process were investigated. The microstructure of the tubes was characterized by field emission gun scanning electron microscopy( FE-SEM),and mechanical properties of the tubes were tested on the tensile testing machine and creep testing machine. The results show that during the early stage of service,the skeleton carbides at grain boundaries were coarsened and transformed to a chain shape,the Nb C was changed to G phase( Ni_(16)Nb_6Si_7),whereas secondary carbides were precipitated at within the crystal. As the service time was extended,the secondary carbides gathered at grain boundaries,the carbides at grain boundaries continued to be coarsened to a blocky shape. The tensile strength and yield strength of the tubes were gradually reduced during service,and its elongation after fracture was significantly reduced. The tubes having been in service for 8 years showed a decrease of about 90% in the fracture time of high-temperature creep rupture test compared with new tubes.
引文
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[3]沈红杰.制氢转化炉管结构与质量控制[J].高桥石化,2007,22(2):23-26.
[4]连晓明,钱兵,刘春娇,等.服役5年后乙烯裂解炉管的组织与性能研究[J].压力容器,2016,33(8):1-6.
[5] Laigo J,Christien F,Le Gall R,et al. SEM,EDS,EPMA-WDS and EBSD characterization of carbides in HP type heat resistant alloys[J]. Materials Characterization,2008,59(11):1580-1586.
[6] Gloria Dulce Barbabela,Luiz Henrique de Almeida,Tito Luiz da Silveira,et al. Role of Nb in modifying the microstructure of heat-resistant cast HP steel[J].Materials Characterization,1991,26(3):193-197.
[7] Shi S,Lippold J C. Microstructure evolution during service exposure of two cast,heat-resisting stainless steels—HP-Nb modified and 20-32Nb[J]. Materials Characterization,2008,59(8):1029-1040.
[8] Voicu R,Andrieu E,Poquillon D,et al. Microstructure evolution of HP40-Nb alloys during aging under air at1000℃[J]. Materials Characterization,2009,60(9):1020-1027.
[9]李毅,何永光,刘望平,等.制氢转化炉管损伤状况分析与剩余寿命预测[J].压力容器,2016,33(4):46-51.
[10] Swaminathan J,Guguloth K,Gunjan M,et al. Failure analysis and remaining life assessment of service exposed primary reformer heater tubes[J]. Engineering Failure Analysis,2008,15(4):311-331.