Thermodynamics of the Oxygen Solutions in Niobium-Containing Fe-Ni Melts

A thermodynamic analysis is performed for the oxygen solutions in niobium-containing Fe-Ni melts. The deoxidizing capacity of niobium in iron-nickel melts is shown to be low. It decreases slightly as the nickel content in a melt increases to 40% and then increases insignificantly as the nickel content increases to 60%; a further increase in the nickel content leads to a marked increase in the deoxidizing capacity. The solubility curves of oxygen in iron-nickel melts passes through a minimum, whose position shifts toward higher niobium concentrations with increasing nickel content. Subsequent niobium additions increase the oxygen concentration in the melt. The equilibrium constants of the reactions of niobium deoxidizing of ironnickel melts, the activity coefficients, and the interaction parameters characterizing Fe-Ni-Nb-O melts are determined.