Study of the Formation of CaO-3FeO-Fe2O3 in Iron Oxide Systems / Untersuchungen zur CaO-3FeO-Fe2O3-Bildung in Eisenoxid-Systemen

The conditions for the formation of CaO•3FeO•Fe 2 O 3 in a blast furnace charge prepared from a mixture of powders of iron oxide and lime have been studied using microscopical methods. After being exposed to a temperature of 1220 o C, the microstructure of a typical compact consists of recrystallized hematite and molten calcium di-ferrite. A rise in temperature up to 1320 o C led to the development of a third phase which appeared as needle-like crystals, and these have been identified by etching as CaO•2Fe 2 O 3 . Upon subsequent reduction in a 60% CO and 40% CO 2 gas mixture at a temperature of 900 o C, the needle-like crystals transformed to rod-like crystals of CaO•3FeO•Fe 2 O 3