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The Relationship Between Magnetism and Microstructure of Ethylene Pyrolysis Furnace Tubes after a Long-term Service

  • Jingfeng Guo (a1), Tieshan Cao (a1), Congqian Cheng (a1), Xianming Meng (a2) and Jie Zhao (a1)...


The magnetism and microstructure of Cr25Ni35Nb and Cr35Ni45Nb alloy tubes after 5 years of service were investigated in this paper. The saturation magnetization of the Cr25Ni35Nb alloy tube in the thickness direction is more than 20 emu/g, and the tube becomes ferromagnetic. The inner and outer walls of Cr35Ni45Nb alloy tubes also become ferromagnetic. But the saturation magnetization of the Cr35Ni45Nb alloy tubes approaches to zero in the center zone. The primary carbides M7C3 and NbC are changed into M23C6 and G phase at the outer region of the furnace tube. However, the M23C6-type carbides were replaced by carbon-rich carbides M7C3 at the carburization zone. Cr-depleted zones are formed at the inner and outer walls of the furnace tubes owing to oxidation. Carburization and oxidation reduce the Cr content of the matrix. Accordingly, the saturation magnetization is very high at the carburization zone and Cr-depleted zone. The magnetism of Cr25Ni35Nb and Cr35Ni45Nb alloy tubes has a high correlation with the Cr content of the matrix. Carburization and oxidation are the main reasons that make the paramagnetic ethylene pyrolysis furnace tube change to ferromagnetic.


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*Author for correspondence: Jie Zhao, E-mail:


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Allahkaram, SR, Borjali, S Khosravi, H (2012) Investigation of weldability and property changes of high pressure heat-resistant cast stainless steel tubes used in pyrolysis furnaces after a five-year service. Mater Des 33, 476484.
Chikazumi, S, Ohta, K, Adachi, K, Tsuya, N Ishikawa, Y (1975) Handbook of Magnetic Materials. Tokyo: Asakawa-shoten.
Chun, CM, Desai, S, Hershkowitz, F Ramanarayanan, TA (2014) Materials challenges in cyclic carburizing and oxidizing environments for petrochemical applications. Mater Corro [Werkstoffe Und Korrosion] 65(3), 282295.
da Silva, IC, da Silva, RS, Rebello, JMA, Bruno, AC Silveira, TF (2006) Characterization of carburization of HP steels by non destructive magnetic testing. Ndt & E Int 39(7), 569577.
de Almeida, LH, Ribeiro, AF Le May, I (2002) Microstructural characterization of modified 25Cr-35Ni centrifugally cast steel furnace tubes. Mater Charact 49(3), 219229.
Grabke, HJ (2000) Corrosion by carbonaceous gases, carburization and metal dusting, and methods of prevention. Mater High Temp 17(4), 483487.
Guan, KS, Xu, H Wang, ZW (2005) Analysis of failed ethylene cracking tubes. Eng Failure Anal 12(3), 420431.
Guo, JF, Cheng, CQ, Li, HF, Zhao, J Min, XH (2017) Microstructural analysis of Cr35Ni45Nb heat-resistant steel after a five-year service in pyrolysis furnace. Eng Failure Anal 79, 625633.
Jakobi, D Gommans, R (2003) Typical failures in pyrolysis coils for ethylene cracking. Mater Corro—Werkstoffe Und Korrosion 54(11), 881886.
Kasai, N, Ogawa, S, Oikawa, T, Sekine, K Hasegawa, K (2010) Detection of carburization in ethylene pyrolysis furnace tubes by a C core probe with magnetization. J Nondestruct Eval 29(3), 175180.
Kaya, AA, Krauklis, P Young, DJ (2002) Microstructure of HK40 alloy after high temperature service in oxidizing/carburizing environment-I. Oxidation phenomena and propagation of a crack. Mater Charact 49(1), 1121.
Khodamorad, SH Haghshenas, DF (2012) Inspection of carburization and ovalness in ethylene cracking tubes by using a semi-robot. Eng Failure Anal 25, 8188.
Kondrat’ev, SY, Anastasiadi, GP, Petrov, SN Ptashnik, AV (2017) Kinetics of the formation of intermetallic phases in HP-type heat-resistant alloys at long-term high-temperature exposure. Metall Mater Trans A – Phys Metall Mater Sci 48A(1), 482492.
Kondrat’ev, SY, Kraposhin, VS, Anastasiadi, GP Talis, AL (2015) Experimental observation and crystallographic description of M7C3 carbide transformation in Fe–Cr–Ni–C HP type alloy. Acta Mater 100, 275281.
Konosu, S, Koshimizu, T, Iijima, T Maeda, K (1993) Evaluation of creep-fatigue damage interaction in HK40 alloy. J Mech Des 115(1), 4146.
Lanz, C, Brizuela, G Simonetti, S (2013) Internal carburisation of an industrial alloy: a quantum chemical study of microstructure’s changes. Mol Simul 39(1), 5963.
Li, TF (2003) High Temperature Oxidation and Hot Corrosion of Metals. Beijing: Chemical Industry Press.
Luis Otegui, J, De Bona, J Fazzini, PG (2015) Effect of coking in massive failure of tubes in an ethylene cracking furnace. Eng Failure Anal 48, 201209.
Majumbar, AK (1984) Magnetic phase diagram of Fe80-xNixCr20 (10≤x≤30) alloys. Phys Rev B 29, 40794085.
Mamiya, H, Rabajczyk, J, Watanabe, N, Kowalska, A Kitazawa, H (2016) Aging-treatment-induced soft magnetism in nickel-chromium-based superalloy X-750. J Alloys Compd 681, 367373.
McLeod, AC, Bishop, CM, Stevens, KJ Kral, MV (2015) Microstructure and carburization detection in HP alloy pyrolysis tubes. Metallogr Microstruct Anal 4(4), 273285.
Miodownik, AP (1982) The effect of magnetic transformations on phase diagrams. Bull Alloy Phase Diagr 2(4), 406412.
Peng, YC, Zhang, MC, Xiao, JC, Dong, JX Du, CY (2015) Investigations on carburizing mechanisms of Cr35Ni45Nb subjected to different service conditions in a high-temperature vacuum environment. J Mater Res 30(6), 841851.
Petkovicluton, R Ramanarayanan, TA (1990) Mixed-oxidant attack of high-temperature alloys in carbon-and oxygen-containing environments. Oxid Met 34(5-6), 381400.
Reihani, A Haghighi, RD (2015) Failure analysis and weld ability improvement of 35%Cr-45%Ni heat resistant alloy. Eng Failure Anal 52, 97108.
Rodriguez, J, Haro, S, Velasco, A Colas, R (2000) A metallographic study of aging in a cast heat-resisting alloy. Mater Charact 45(1), 2532.
Sadegh Borjali, SRA Hamed, Khosravi. (2012) Effects of working temperature and carbon diffusion on the microstructure of high pressure heat-resistant stainless steel tubes used in pyrolysis furnaces during service condition. Mater Des 34, 6573.
Shen, LM, Gong, JM, Jiang, Y Geng, LY (2011) Effects of aging treatment on microstructure and mechanical properties of Cr25Ni35Nb and Cr35Ni45Nb furnace tube steel. Acta Metall Sinica – Eng Lett 24(3), 235242.
Shen, LM, Gong, JM Liu, HS (2014) Carburisation layer evolution of Fe-Cr-Ni alloy in furnace after long term service: experimental study and numerical prediction. Mater High Temp 31(2), 148154.
Silva, IC, Rebello, JMA, Bruno, AC, Jacques, PJ, Nysten, B Dille, J (2008) Structural and magnetic characterization of a carburized cast austenitic steel. Scripta Mater 59(9), 10101013.
Silva, IC, Silva, LL, Silva, RS, Rebello, JMA Bruno, AC (2007) Carburization of ethylene pyrolysis tubes determined by magnetic measurements and genetic algorithm. Scripta Mater 56(4), 317320.
Stevens, KJ, Parbhu, A, Soltis, J Stewart, D (2003) Magnetic force microscopy of a carburized ethylene pyrolysis tube. J Phys D Appl Phys 36(2), 164168.
Sustaita-Torres, IA, Haro-Rodríguez, S, Guerrero-Mata, MP, de la Garza, M, Valdés, E, Deschaux-Beaume, F Colás, R (2012) Aging of a cast 35Cr-45Ni heat resistant alloy. Mater Chem Phys 133(2-3), 10181023.
Takahashi, S, Sato, Y, Kamada, Y Abe, T (2004) Study of chromium depletion by magnetic method in Ni-based alloys. J Magn Magn Mater 269(2), 139149.
Τawancy, ΗΜ (2009) Degradation of mechanical strength of pyrolysis furnace tubes by high-temperature carburization in a petrochemical plant. Eng Failure Anal 16(7), 21712178.
Ul-Hamid, A, Tawancy, HM, Mohammed, A-RI Abbas, NM (2006) Failure analysis of furnace radiant tubes exposed to excessive temperature. Eng Failure Anal 13(6), 10051021.
Wieczerzak, K, Zywczak, A, Kanak, J Bala, P (2017) Magnetic detection of chromium depleted regions in metastable Fe-Cr-C alloy. Mater Character 132, 293302.
Wu, XQ, Jing, HM, Zheng, YG, Yao, ZM Ke, W (2001) Coking of HP tubes in ethylene steam cracking plant and its mitigation. Br Corro J 36(2), 121126.
Wu, XQ, Yang, YS, Zhan, Q Hu, ZQ (1998) Structure degradation of 25Cr35Ni heat-resistant tube associated with surface coking and internal carburization. J Mater Eng Perform 7(5), 667672.
Xiao, J Zhang, M (2016) Investigations on servicing damage mechanisms of Cr35Ni45Nb alloy under complex conditions. J Mater Res 31(14), 21562163.
Young, DJ Zhang, J (2013) Carbon corrosion of alloys at high temperature. J Southern African Inst Min Metall 113(2), 153158.


The Relationship Between Magnetism and Microstructure of Ethylene Pyrolysis Furnace Tubes after a Long-term Service

  • Jingfeng Guo (a1), Tieshan Cao (a1), Congqian Cheng (a1), Xianming Meng (a2) and Jie Zhao (a1)...


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