Interaction Coefficients of Mo, B, Ni, Ti and Nb with Sn in Molten Fe–18mass%Cr Alloy

Increasing the utilization of steel scrap is strongly required for reducing CO₂ emission in iron- and steelmaking processes. In steel scrap recycling, the content of tramp elements in steel (such as copper and tin) inevitably increases. Accordingly, it is important to understand the thermodynamic characteristics of relevance to the accumulation of tramp elements in molten steel. The values of the interaction coefficients of Mo, B, Ni, Ti, and Nb with Sn in molten iron were reported previously. However, little is known about the interaction coefficients of alloying elements with tramp elements in molten high-chromium steel. In this work, the interaction coefficients of Mo, B, Ni, Ti, and Nb with Sn in the molten Fe–18mass%Cr alloy were measured at 1 873 K by a chemical equilibration technique that uses the liquid immiscibility of the Fe–18mass%Cr alloy and Ag, yielding the following results: Mo ε_{Sn(in Fe−18Cr)} = −2.9(±3.2), e_Sn(in^Mo_Fe−18Cr) = −0.0054(±0.0099) B ε_{Sn(in Fe−18Cr)} = 9.6(±1.9), e_Sn(in^B_Fe−18Cr) = 0.19(±0.02) Ni ε_{Sn(in Fe−18Cr)} = −8.9(±2.6), e_Sn(in^Ni_Fe−18Cr) = −0.036(±0.011) Ti ε_{Sn(in Fe−18Cr)} = 10.4(±5.7), e_Sn(in^Ti_Fe−18Cr) = 0.051(±0.028) Nb ε_{Sn(in Fe−18Cr)} = 20.5(±8.0), e_Sn(in^Nb_Fe−18Cr) = 0.055(±0.022) The results show that the values of the interaction coefficients of M with Sn in the Fe-18mass%Cr alloy are smaller than those for molten iron, which were measured in the previous work, except for titanium. The interaction coefficients of M with Sn in Fe and Fe–18mass%Cr alloy were estimated based on a regular solution model. The estimated interaction coefficients of B, Ni, and Ti with Sn in molten iron and Ni and Ti with Sn in the molten Fe–18mass%Cr alloy reasonably agree with the measured values.