The deoxidation thermodynamics of cerium and lanthanum in liquid iron

The deoxidation thermodynamics of the Fe?Ce?O and Fe?La?O systems are estimated by combining the free energies of solution of cerium and lanthanum in iron, obtained from the respective phase diagrams, with the standard free energies of formation of cerium and lanthanum oxides given in the literature. Values for the deoxidation constants (w/o Ce)²·(w/o O)³ and (w/o La)²·(w/o O)³ of about 1×10^?20 are predicted at steelmaking temperatures. These predicted values are much lower than those obtained experimentally. It is suggested that refractory interactions, and sampling and analytical difficulties, in both laboratory and industrial determinations of these deoxidation constants, lead to erroneously high results.