Measurement of the Activity Coefficients of P and Mn in Carbon-Saturated Fe-P-Mn-C Alloy

The thermodynamic properties of the Fe-P-Mn-C(sat.) alloy, which is obtained following the reduction of steelmaking slag or manganese ore, are not adequately clarified. Thus, the current study involved measuring the activity coefficients of both Mn and P in the alloy system. The Fe-P-Mn-C (sat.) alloy (2.5 to 15.2 mass pct of P and 2.9 to 12.8 mass pct of Mn) was equilibrated with Ag in a graphite crucible at 1673 K, and thus several thermodynamic data were obtained as follows: Interaction parameters: εMn(C sat.)P=-4.72±0.27,(XMn<0.06,XP<0.25,1673K), εC(C sat.)P=6.09±0.15,(XMn<0.06,XP<0.25,1673K). C solubility: XC[in Fe-P-Mn-C(sat.)]=0.19e-(6.09XP-0.47XMn). Activity coefficient: lnγMn[in Fe-P-Mn-C(sat.)]=-4.72XP-0.47XC-0.87, lnγP[in Fe-P-Mn-C(sat.)]H-lnγP[in Fe-P-C]H=εPMnXMn=-4.72XMn, and lnγP[in Fe-P-Mn-C(sat.)]H=-4.72XMn+4.26XP+6.09XC. In addition, a comparison with the results obtained by previous studies on the selective reduction of steelmaking slag indicated that the activity coefficients of P and Mn obtained in the study were applicable.