Changes of Mineral Phases during the Sintering of Iron Ore-Lime Stone Systems

In order to elucidate the fundamental aspects of the sintering processes of self-fluxing sinters, the mineral formation processes of mixtures of iron ore and lime stone with or without coke were studied. After heating between 1200° and 1350°C the sinters were examined by microscopy, X-ray diffraction and EPMA.The results indicated that the mineral formation processes of the systems were fundamentally the same as those of 80%Fe2O3 CaO-SiO2 system reported earlier. They were as follows:(1) Molten calcium ferrite was formed at the beginning.(2) Gangue minerals dissolved into the melt.(3) Iron oxides were precipitated. They were either or both of hematite and magnetite, depending on the oxygen potential or the SiO2 content of the melt.(4) At higher temperatures, solid iron oxides and a melt coexisted, and characteristic microstructure was formed during solidification depending on the basicity.On the basis of the above results, the microstructures and the formation processes of self-fluxing sinters with various basicities were discussed.