Investigation of forming of structural components of iron ore sinter of different basicity under heating

Abstract

A high-quality iron ore sinter must have sufficient mechanical strength both in the cold and hot state. Structural components such as the binding phases of calcium and aluminum silicoferrites SFCA and modifications of dicalcium silicate directly affect the strength characteristics of the sinter. During phase transitions, the volume of phases changes, which leads to the occurrence of stresses at the phase boundaries. Then stabilized phases of SFCA are key bundles in the iron ore sinter. Understanding the mechanisms of SFCA formation can lead to an increase in the efficiency of sintering process. The phase transformations occurring in sinter with a basicity of 1.2‒2.0 under controlled heating in an inert atmosphere and an air atmosphere are investigated. The temperatures of phase transitions during heating are shown. The study of the phase composition of sinter samples with different basicities showed that the ore phase consists of magnetite Fe3O4, hematite Fe2O3, calcium and aluminum silicoferrite SFCA and dicalcium silicate modifications α-2CaO•SiO2 and β-2CaO•SiO2. With an increase in the basicity of the sinter, the amount of magnetite and SFCA increases, the amount of hematite decreases, the content of α- and β-2CaO•SiO2 increases slightly. Heating of the sinter in the air atmosphere leads to the oxidation of magnetite to hematite, a decrease in the amount of SFCA, an increase in bicalcium and the appearance of tricalcium silicate. Heating in an inert atmosphere contributes to an increase in the amount of magnetite due to the reduction of hematite and the decomposition of the SFCA phase and an increase in the amount of dicalcium silicate.