Aluminothermic Reduction Process Under Nitrogen Gas Pressure for Preparing High Nitrogen Austenitic Steels
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The aluminothermic reduction casting process under nitrogen gas pressure to make austenitic Cr-Mn-N (Ni-free) and Cr-N (Ni/Mn-free) high nitrogen stainless steels was investigated. Thermodynamic simulation of the redox reaction depending on process parameters was performed. As a result, the optimal ratio of aluminum to oxygen in the initial powder mixture to obtain the highest yield of metal product with minimal aluminum nitride contamination was predicted to be slightly greater than the stoichiometric ratio of 1.125. Microstructures of aluminothermic 26Cr1N and 23Cr9Mn1N steels, prepared taking into account the results of thermodynamic simulation, were investigated by X-ray diffraction, metallography, and transmission electron microscopy. The as-cast microstructure was a pseudo-pearlite (layered ferrite-nitride mixture) in 26Cr1N steel and a ferrite-austenite with signs of discontinuous austenite decomposition in 23Cr9Mn1N steel. After hot forging and subsequent water quenching from 1200 °C, the microstructure was fully austenitic in both steels. Tensile tests of quenched 23Cr9Mn1N steel showed a combination of high strength (ultimate strength of 1324 MPa) and ductility (elongation of 27 pct). The results illustrate that the aluminothermic casting process for producing high nitrogen steel is competitive with the commonly used methods, such as pressure electroslag remelting, both in terms of cost and mechanical properties of manufactured steel.
This work was funded by the Russian Federal Agency for Scientific Organizations (Project No. AAAA-A17-117022250039-4) and partially supported by the Presidium of the Ural Branch of the Russian Academy of Sciences (Project No. 18-10-2-41). The authors thank B.E. Pushkarev for performing scanning electron microscopy investigations.
- 15.T. Rashev: High Nitrogen Steels: Metallurgy under Pressure, Academic Publishing House of Bulgarian Academy of Science, Sofia, 1995.Google Scholar
- 17.A.D. Patel, J. Reitz, J.H. Magee, R. Smith, G. Maurer, and B. Friedrich: Int. Symp. Liq. Met. Process. Cast., TMS, Warrendale, PA, 2009.Google Scholar
- 18.V.I. Yukhvid: Adv. Mater. Technol., 2016, vol. 4, pp. 23–34.Google Scholar
- 19.G. Liu, J. Li, and K. Chen: in Handbook of Combustion, Vol. 1, M. Lackner, F. Winter, and A.K. Agarwal, eds., Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, 2010.Google Scholar
- 23.G.A. Dorofeev, V.I. Lad’janov, A.N. Lubnin, V.A. Karev, B.E. Pushkarev, and M.I. Mokrushina: Himich. Fiz. Mezosk., 2010, vol. 12, pp. 5–12 (in Russian).Google Scholar
- 24.Nitride Ceramics: Combustion Synthesis, Properties and Applications, A.A. Gromov and L.N. Chukhlomina, eds., Wiley, Weinheim, 2014.Google Scholar
- 29.N.A. Vatolin, G.K. Moiseev, and B.G. Trusov: Thermodynamic Modeling in High Temperature Inorganic Systems, Metallurgy, Moscow, 1994 (in Russian).Google Scholar
- 31.O.Y. Goncharov and O.M. Kanunnikova: Industr. Lab.: Diag. Mater., 2012, vol. 78, pp. 36–41 (in Russian).Google Scholar
- 32.V.P. Glushko: in Termicheskie Konstanty Veshchestv (“Thermal Constants of Substances”), Handbook in 10 Issues, VINITI, Moscow, 1965–1981 (in Russian).Google Scholar
- 33.C. Wagner: Thermodynamics of Alloys, Addison-Wesley Press, Cambridge, MA, 1952.Google Scholar
- 34.M. Temkin: Acta Phys. Chim. U.R.S.S., 1945, vol. 20, pp. 411–20.Google Scholar
- 40.Georgsmarienhütte Holding GmbH, Germany, http://www.energietechnik-essen.de/de/produkte/stickstoffstaehle/druckaufgestickte-austenite.html, accessed May 2018.