Analysis of phase equilibria in the system “iron oxide - carbon - CO - CO2”

At calculations of the equilibrium parameters realized at reduction of iron oxides in an atmosphere «CO - CO 2» in presence of carbon, thermodynamic characteristics of reactions of reduction of oxides, reaction of gasification of carbon and phase diagrams of “iron - oxygen” and “iron - carbon” systems were used. Were determined not only compositions of the gas phase, but also compositions of the condensed phases (wustite and carbon-saturated iron). Temperature of full reduction of iron is 955 K. Equilibrium temperature of occurrence of liquid iron at indirect reduction of iron oxides is near 1427 K. The iron obtained by reduction is saturated by carbon, and its equilibrium concentration at temperatures above 955 K corresponds to the phase diagram of “iron - carbon” system. Thermodynamic parameters of processes of carburization of iron and decarburization of steels and cast irons correspond to the equilibrium phase diagram of the “FeO 1+x - Fe - CO - CO 2 - carbon” system.