Abstract
Calcium is soluble in halide salts which can be used to remove phosphorus from steel as a phosphide ion. The activity and activity coefficient of calcium phosphide, and the equilibrium phosphorus distribution ratio between Ca-CaF2 and Ca-CaCl2 fluxes and pure solid iron were measured as a function of the Ca composition in the flux at 1350 °, 1400 °, and 1450 °. The Ca-Ca halide fluxes were equilibrated with pure solid iron and a Ag-Ca alloy in an iron crucible under an Ar atmosphere. The Ag-Ca alloy was used to maintain a constant chemical potential of calcium. Phosphorus distribution between between these fluxes and solid pure iron increased with increasing calcium activity and decreasing temperature. The activity coefficient of γCa 1.5 P was calculated to be 36.6 at 1350 ° and 11.0 at 1450 ° for a calcium activity of 0.2 (wt pct Ca = 2.5) in the Ca-CaF2; the activity coefficient increases with increasing Ca in the flux. In addition, the activity of Ca in the Ca-Ca halide fluxes was determined. The equilibrium phosphorus distribution ratio between Ca-Ca halide systems and molten chromium steel was calculated as functions of Cr and C contents of the metal and calcium activity in the flux at 1600 °C by using γCa 1.5 P obtained in the present work. This ratio was found to be about 20 for 18 pct Cr stainless steel at 1600 °.
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K. Kowaka and H. Fujikawa:Trans. Jap. Inst. Met., 1970, vol. 34, pp. 1047–54.
S. Suzuki: Kawasaki Steel Technical Report, 1982, No. 6, p. 31.
Y. Nakamura and S. Abe: Nippon Steel Technical Report Overseas, 1977, No. 10, pp. 114–19.
T. Matsuo, T. Ikeda, K. Kamekawa, and T. Sakane:Tetsu-to-Hagané, 1986, vol. 72, p. A-33.
S. Maruhashi, T. Yamauchi, M. Kinugasa, K. Yamada, H. Azuma, T. Hiyama, and N. Nishimae:Trans. ISIJ, 1985, vol. 25, pp. 963–69.
K. Kaneko, N. Sano, H. Onoda, and Y. Matsushita:Tetsu-to-Hagané, 1980, vol. 660, pp. 2095–99.
Y. Nakamura, N. Tokumitsu, K. Harashima, and K. Segawa:Trans. ISU, 1976, vol. 16, pp. 623–27.
N. Tokumitsu, K. Harashima, and Y. Nakamura:Tetsu-to-Hagané, 1977, vol. 63, pp. 230–38.
Y. Nakamura, K. Harashima, and M. Ito:Tetsu-to-Hagané, 1974, vol. 63, pp. 2287–91.
K. Kitamura, M. Funazaki, Y. Iwanami, and T. Tekenouchi:Trans. ISU, 1984, vol. 24, pp. 631–38.
H.J. Engell, M. Köhler, H.J. Fleischer, R. Thielmann, and E. Schurmann:Stahl und Eisen, 1984, vol. 104, pp. 443–49.
S. Tabuchi and N. Sano:Metall. Trans. B, 1984, vol. 15B, pp. 351–56.
M. Köhler and H.J. Engell:2nd Int. Symp. on Metallurgical Slags and Fluxes, The Metall. Soc. AIME, Lake Tahoe, NV, 1984, pp. 483–96.
H. Fishbach:J. Less-Common Metals, 1985, vol. 108, pp. 151–62.
H. Fishbach:Steel Research, 1985, vol. 56, pp. 365–68.
E.T. Turkdogan:Physical Chemistry of High Temperature Technology, Academic Press, New York, NY, 1980, p. 81.
P. Spencer and O. Kubaschewski:Arch. Eisenhüttenwes., 1978, vol. 49, pp. 225–28.
Metals Handbook, vol. 8,Metallography, Structures and Phase Diagram, 8th ed., ASM, Metals Park, OH, 1973, p. 304.
S. Ban-ya and M. Suzuki:Tetsu-to-Hagané, 1975, vol. 61,
I. Barin, O. Knacke, and O. Kubaschewski:Thermochemical Properties of Inorganic Substances, Supplement, Springer-Verlag, Berlin and New York, 1977.
D. J. Min and N. Sano: private communication, University of Tokyo, Japan.
H.G. Hardys, M.G. Frohberg, and J. F. Elliott:Metall. Trans., 1970, vol. 1, pp. 1867–73(with appendix by C.H.P. Lupis).
G. K. Sigworth and J. F. Elliott:Metal Science, 1974, vol. 8, pp. 298–310.
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Formerly a Graduate Student at Carnegie Mellon University
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Masumitsu, N., Ito, K. & Fruehan, R.J. Thermodynamics of Ca-CaF2 and Ca-CaCI2 systems for the dephosphorization of steel. Metall Trans B 19, 643–648 (1988). https://doi.org/10.1007/BF02659156
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DOI: https://doi.org/10.1007/BF02659156