Assessment of Equilibrium between Yttrium and Oxygen in Liquid Iron

Abstract

Rare earth elements (REEs) are crucial additives in the iron and steel industry. The accurate determination of thermodynamic data is fundamental for applying REEs in steel production; however, this has proven challenging due to their strong reactivity with refractory materials. This study assessed the thermodynamic data for the yttrium–oxygen equilibrium in liquid iron, using high-temperature experiments with high-purity Y₂O₃ crucibles as the smelting container. More reliable equilibrium constants and first-order interaction coefficients are obtained by minimizing the reactions between yttrium and the crucible while ensuring favorable kinetic conditions. The results confirm that the deoxidation product of yttrium in liquid iron is Y₂O₃, and the equilibrium constant for the reaction Y₂O₃(s) = 2[Y] + 3[O] can be expressed as follows: $\log K_Y(K_Y^O=a_Y^2{a}_O^3/a_{Y_2{O}_3})=-63585/T+20.18, 1600-1700 °C$. $K{\prime }_Y=\left({[\%Y]}^2{[\%O]}^3\right)$ can be expressed as: $\log K{\prime }_Y=\log K_Y-(-31028/T+8.06)\left(3\right[\%Y]+11.1[\%O\left]\right), 0.003 \text{wt\%}<\left[Y\right]<0.23 \text{wt\%}$. The first-order interaction coefficient can be presented as: $e_O^Y=-31028/T+8.06$.