Equilibrium between dissolved chromium and oxygen in liquid high chromium alloyed steel saturated with pure Cr₂O₃

Equilibrium between Cr and O in the high Cr steel melt is one of the most important information to control Cr content in the stainless steel. In spite of such importance, there are some uncertainties in the literature values including the recommended values of the Japan Society for the Promotion of Science (JSPS) on deoxidation equilibrium constant and interaction parameters. The main reason of such uncertainties of the previous works is referred to the insufficient consideration on the thermodynamic properties of oxide phase in equilibrium with liquid Fe-Cr alloy. The present work deals with the equilibrium relation between dissolved Cr and O in liquid high Cr steel saturated with pure solid Cr₂O₃. The equilibrium constant of reaction and the interaction parameter between Cr and O in liquid iron saturated with pure solid Cr₂O₃ is given by the following equations in the present work. Cr₂O₃ (s) = 2Cr+3O log K = -36 200/T+16.1 (1 823 K<T<1923 K) e_o^Cr = -123/T+O.034 (mass% Cr<46, 1 823 K<T<1 923 K). The activity of O can be expressed by above thermodynamic function without the second order interaction paramer up to 46 mass%Cr.