Thermodynamic behaviour of Cu in molten Fe-C-S alloys at high temperatures

Abstract

The activity of Cu in molten Fe-C-S alloys at high temperatures was measured by a thermochemical equilibration technique. The effects of the contents of Cu, C, and S in the molten alloy as well as temperature on the activity coefficient of Cu in pure and carbon-saturated iron were determined by measuring the distribution ratio of Cu between molten silver and Fe-C-S alloy melts. In molten pure iron and carbon-saturated iron, the activity coefficient of Cu under infinite dilution, γCuo was measured as 11.0 and 28.5, respectively, at 1823 K. The interaction parameters between Cu and Cu, S, C in the molten iron at 1823 K were estimated: εCuCu = -4.80, εCuS = -2.54, εCuC = -4.60. The dependence of γCuo in molten Fe-C alloy on temperature was determined as follows: pure iron: lnγCuo(Fe) = 4370/T, Fe-2%C alloy: lnγCuo(Fe-2%C) = 0.72+3840/T, carbon-saturated iron: lnγCuo(Fe-C(Satd.)) = 1.11+4100/T. Combining the effects of temperature and those of alloying components, the activity coefficient of Cu in the molten Fe-C-S alloy could be estimated as follows: lnγCu(Fe-C-S) = 4370/T·(1-XCu)2 +(2.15+4600/T) ·XC+2.54XS.