Increase in low-temperature reduction degradation of iron ore sinter due to hematite-alumina solid solution and columnar calcium ferrite.

Abstract

Direct observation of lattice images by TEM of magnetite reduced from hematite made clear ultramicroscopic partial distortion due to solid solution of Al2O3. Furthermore, the effect of solid solution of Al2O3 with hematite on strain of magnetite, which had reduced grains of the hematite with a mixture gas of CO-CO2, was estimated by line-broadenings of peaks of X-ray diffraction. It revealed that increasing amounts of Al2O3 increased the strain of magnetite.Fracture strength of the minerals in sintered ore was estimated quantitatively by Vickers indentation, indicating crack propagation-arrest characteristics. Fracture toughness of both glassy silicate and calcium ferrite resulted in values of the same order with a little effect of Al2O3. Calcium ferrite, however, had the lowest value for “critical load”, indicating crack initiation characteristic among all the minerals tested.An experimental study of the crystallization mechanism of skeletal hematite indicated that magnetite coexisting with liquid silicate decomposed, melted and was oxidized at the falling stage of sintering.