Steel in Translation

, Volume 48, Issue 1, pp 17–24 | Cite as

Composition and Mobility of Ionic Ensembles in Slags for Steel Refining in the Ladle–Furnace Unit

Article

Abstract

High-lime synthetic slags for refining steels in the ladle–furnace unit are investigated. The content of the slag mixtures is as follows: 60 wt % CaO, 7 and 8 wt % MgO, 7–23 wt % Al2O3, and 9–18 wt % SiO2, with additions of 8 wt % CaF3 and 5–15 wt % Na2O. Polymer theory is used to calculate the composition of the anionic subsystem in the slag melts. The log-mean polymerization constants K p * for multicomponent melts are calculated from the known polymerization constants in binary systems. It is found that K p * ≈ 10–3–10–2 in the range 1500–1600°C. In that range, the melt’s degree of polymerization is 3 × 10–4–8 × 10–3. In the most polymerized melt, the ionic content of the dimers Si2O 7 6- and Al2O 7 8- is no more than 0.1 and 1.5% of the values for the corresponding monomers. Therefore, we assume, with an error of about 2%, that the structural units of the anionic subsystem are monomers AlO 4 5- and SiO 4 4- simple O2– and F ions (slag 7). The cationic subsystem consists of Ca2+, Mg2+, Na+, and Al3+ ions in octahedral coordination with oxygen (less than 3% of all the Al atoms). In all the melts, the concentrations of free oxygen ions O2– and Ca2+ ions are similar. In half the cases, the content of O2– ions is greater than the content of Ca2+ ions. The mean mobility U and self-diffusion coefficient D for all the cations are calculated from data for the electrical conductivity and the density. With increase in temperature from 1500 to 1600°C, U and D increase by 50 and 60%, respectively, in all the slags. With increase in the mutual substitution of the components in the slag mixtures M = n(Na2O, CaF2)/n(Al2O3 + SiO2), mol/mol, at 1600°C, U increases from 1.14 × 10–8 to 1.46 × 10–8 m2/(V s) for slags 1–6 (0 ≤ M ≤ 1.1) and from 1.01 × 10–8 to 1.66 × 10–8 m2/(V s) for slags 7–10 (0.25 ≤ M ≤ 0.65). Correspondingly, D increases from 9.2 × 10–10 to 12.8 × 10–10 m2/s for slags 1–6 and from 8.2 × 10–10 to 14.3 × 10–10 m2/s for slags 7–10. The temperature dependence of U and D may be approximated by an Arrhenius equation with activation energies E U and E D . With increase in M in the given ranges, E U declines from 146 to 100 kJ/mol (slags 1–6) and from 124.5 to 109 kJ/mol (slags 7–10). Likewise, E D declines from 159 to 116.5 kJ/mol (slags 1–6) and from 139.5 to 124 kJ/mol (slags 7–10). The mean values of E U and E D correlate with the mean distance between the cations in the melts. On the basis of the proposed alternative model of the conductivity, the O2– ions may also transfer electric charge. Preliminary estimates show that the oxygen transport number at 1600°C may exceed 0.1 in some slags.

Keywords

high-lime synthetic slags anion subsystem cation subsystem polymeric theory polymerization constant degree of polymerization cation mobility self-diffusion coefficient activation energy partial substitution oxygen transport number 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1.
    Lepinskikh, B.M., Belousov, A.A., Bakhvalov, S.G., et al., Transportnye svoistva metallicheskikh i shlakovykh rasplavov. Spravochnik (Transport Properties of Metal and Slag Melts: Handbook), Vatolin N.A. ed. Moscow: Metallurgiya, 1995.Google Scholar
  2. 2.
    Panov, S.P., Shalimov, M.P., Lazutkina, O.R., et al., Determination of thermodynamic and kinetic constants for calculation of rates of interaction between steel and slag, in Fiziko-khimicheskie issledovaniya metallurgicheskikh protsessov (Physical and Chemical Researches of Metallurgical Processes), Sverdlovsk: Ural. Politekh. Inst., 1989, pp. 141–155.Google Scholar
  3. 3.
    Niwa, K., Investigation of Ca diffusion in CaO–SiO2–Al2O3 melts by the radioactive isotope method, J. Jpn. Inst. Met., 1957, vol. 21, no. 4, pp. 304–308.CrossRefGoogle Scholar
  4. 4.
    Suito, T. and Maruya, K., Diffusion of Ca in liquid slags, J. Jpn. Inst. Met., 1957, vol. 21, no. 12, pp. 728–732.CrossRefGoogle Scholar
  5. 5.
    Byalo, V.D. and Gladkii, V.N., Methodical measurement errors of electrical conductivity of slag melts and methods for their decrease, Zavod. Lab., 1993, vol. 59, no. 1, pp. 22–27.Google Scholar
  6. 6.
    Baes, C.F., A polymer model for BeF2 and SiO2 melts, J. Solid State Chem., 1970, vol. 1, no. 2, pp. 159–169.CrossRefGoogle Scholar
  7. 7.
    Masson, C.R., Anionic constitution of glass forming melts, J. Non-Cryst. Solids, 1977, vol. 25, no. 1, pp. 3–41.Google Scholar
  8. 8.
    Novikov, V.K., Development of polymeric model of silicate melts, Rasplavy, 1987, vol. 1, no. 6, pp. 21–33.Google Scholar
  9. 9.
    Esin, O.A., On complex anions in the molten slags, in Stroenie i svoistva metallurgicheskikh rasplavov (Structure and Properties of Metallurgical Melts), Sverdlovsk: Ural. Nauch. Tsentr, Akad. Nauk SSSR, 1974, pp. 76–88.Google Scholar
  10. 10.
    Yakushev, A.M. and Popravko, V.V., Viscosity of refining slags with diluting additives, Izv. Vyssh. Uchebn. Zaved., Chern. Metall., 1976, no. 3, pp. 59–62.Google Scholar
  11. 11.
    Magidson, I.A., Voldaeva, N.G., and Smirnov, N.A., On polymerization constants in CaO–Al2O3 and CaO–SiO2 melts, Izv. Vyssh. Uchebn. Zaved., Chern. Metall., 2004, no. 1, pp. 6–9.Google Scholar
  12. 12.
    Novikov, V.K. and Nevidimov, V.N., Prediction of the refining properties of multicomponent slag melts, Izv. Vyssh. Uchebn. Zaved., Chern. Metall., 1997, no. 1, pp. 5–10.Google Scholar
  13. 13.
    Esin, O.A., On equilibrium constants of reactions of the melted silicates formation, in Fiziko-khimicheskie osnovy protsessov tsvetnoi metallurgii (Physical and Chemical Bases of Nonferrous Metallurgy Processes), Sverdlovsk: Ural. Politekh. Inst., 1972, no. 204, pp. 66–71.Google Scholar
  14. 14.
    Veryatin, U.D., Mashirev, V.P., Ryabtsev, N.G., et al., Termodinamicheskie svoistva neorganicheskikh veshchestv. Spravochnik (Thermodynamic Properties of Inorganic Substances: Handbook), Moscow: Atomizdat, 1965.Google Scholar
  15. 15.
    Efimov, A.I., Belorukova, L.P., Vasil’kova, I.V., et al., Svoistva neorganicheskikh soedinenii. Spravochnik (Properties of Inorganic Compounds: Handbook), Leningrad: Khimiya, 1983.Google Scholar
  16. 16.
    Magidson, I.A., Spiryugova, M.S., and Basov, A.V., Ionic composition of high-lime polymerizing melts of CaO–Al2O3–SiO2 system, Izv. Vyssh. Uchebn. Zaved., Chern. Metall., 2010, no. 5, pp. 18–26.Google Scholar
  17. 17.
    Belashchenko, D.K. and Skvortsov, L.V., Molecular dynamics study of CaO–Al2O3 melts, Inorg. Mater., 2001, vol. 37, no. 5, pp. 476–481.CrossRefGoogle Scholar
  18. 18.
    Popel’, S.I., Sotnikov, A.I., and Boronenkov, V.N., Teoriya metallurgicheskikh protsessov (Theory of Metallurgical Processes), Moscow: Metallurgiya, 1986.Google Scholar
  19. 19.
    Damaskin, B.B. and Petrii, O.A., Osnovy teoreticheskoi elektrokhimii (Fundamentals of Theoretical Electrochemistry), Moscow: Vysshaya Shkola, 1978.Google Scholar
  20. 20.
    Esin, O.A. and Gel’d, P.V., Fizicheskaya khimiya pirometallurgicheskikh protsessov (Physical Chemistry of Pyrometallurgical Processes), Moscow: Metallurgiya, 1966.Google Scholar
  21. 21.
    Belashchenko, D.K., Computer simulation of the electrical conductivity of CaO–SiO2 melts, Inorg. Mater., 1996, vol. 32, no. 2, pp. 160–164.Google Scholar
  22. 22.
    Basov, A.V., Magidson, I.A., and Smirnov, N.A., Density and electrical conductivity of synthetic slags added to the ladle–furnace unit, Steel Transl., 2015, vol. 45, no. 11, pp. 819–824.CrossRefGoogle Scholar
  23. 23.
    Schlackenatlas, Düsseldorf: Stahl und Eisen, 1981.Google Scholar

Copyright information

© Allerton Press, Inc. 2018

Authors and Affiliations

  1. 1.Moscow State Manufacturing UniversityMoscowRussia

Personalised recommendations