Activities of Sn and Sb in Liquid Fe-S Alloy Saturated with Carbon

Abstract

The activities of tin and antimony in liquid Fe-S alloy saturated with carbon were determined at 1673 K to 1873 K by the distribution method using liquid silver. The concentration range of tin and antimony measured in the iron melt was less than 2 mass% and that of sulfur was up to FeS saturation (about 1.9 mass% at 1673 K).
The activity coefficients of tin and antimony, γ^(Fe-Csat.)_Sn and γ^(Fe-Csat.) _Sb, and the solubility of carbon, [C]_sat., in iron melt measured could be empirically expressed as the function of tin, antimony and sulfur contents in liquid iron saturated with carbon and temperature as follows;
log γ^(Fe-Csat.)_Sn=485/T+0.777-28.33 X_Sn-4.20 X_S,
log γ^(Fe-Csat.)_Sb=-1000/T+0.314-18.34 X_Sb-2.17X_S,
[C]_sat.=2.54×10^-3T+0.65-0.33[mass%S]+β^M [mass%M] (mass%)
β^Sn=-0.11, β^Sb=-0.12
(1673K1873 K, Sn≤1.5 mass%, Sb≤1.9mass%, S<1.9 mass% (FeS_sat.))
The activity coefficients of SnS and SbS_1.5 in FeS-Na₂S flux were estimated to explain the distribution behavior of tin and antimony between the flux and liquid Fe-C_sat. by combining the results of the present work with the distribution ratios of tin and antimony between FeS-Na₂S flux and Fe-C_sat. melt determined in our previous work.
Equilibrium partial pressure of SnS in Fe-C-S-Sn melt was also estimated by using the activities of tin and sulfur and free energy of formation of SnS, and the possibility of tin removal from iron melt as SnS gas was quantitatively evaluated.