Microscopical Investigation of the High Temperature Reduction Properties of Processed Iron Ores

Abstract

The high temperature reduction properties of processed iron ores in packed beds were investigated as a function of applied load and reduction transition. The microstructures of cohesive packed beds quenched during the reduction test were also studied quantitatively by the use of an electron microprobe.
The results obtained are summarized as follows;
(1) At a given temperature, the softening viscosity of dolomite-fluxed pellets was found to have minimum value at a certain reduction degree, which tends to increase as the temperature decreases. This behavior may be explained due to the competition of the increase of porosity and the sintering of metallic iron formed by reduction.
(2) The permeability resistance of the packed bed during reduction under load was found to be estimated accurately based on Uchida's model even after the irrigation by liquid flowed-out from wustite core.
(3) The melting-down of cohesive bed was found to start from the formation of Fe-C liquid at the surface of iron largely grown during reduction of molten wustite with solid carbon. The fact that the surface carbon concentration of the coagulated iron increases with the reduction of the FeO content in the coexisting silicate melts shows the possibility that melting-down phenomena would be controlled by the reaction equilibrium among them.