2CaO·SiO₂と鉄鉱石間の反応に及ぼすAl₂O₃添加の影響

Abstract

The effect of Al2O3 addition on the reaction between 2CaO•SiO2 (C2S) and iron ore has been elucidated from the perspective of silico-ferrite of calcium and aluminum (SFCA) formation.Hematite iron ore, synthesized C2S, and reagent grade CaO, Al2O3, and SiO2 were mixed so that the Fe2O3/SiO2 (mass%) ratio was 14.43. The mixed powders were uniaxially pressed into the shape of a tablet, which was sintered in air at 1250 o C for 5 min. The constituent phases were investigated using XRD and EPMA for the samples where CaO/SiO2 (mass%) ratio was varied from 0.22 to 2.60 and for the samples where Al2O3 concentration was varied from 1.44 mass% (T1) to 3.98 mass% (T2). (i) The constituent phases are mainly Fe2O3 and SiO2 for the samples with a CaO/SiO2 (mass%) ratio of 0.22, and Fe2O3, SiO2, and SFCA for the samples with ratios above 1.97. (ii) The compositions of the SFCA phases are all on the plane connecting CaFe6O10, CaAl6O10 and Ca4Si3O10. The Al2O3 concentrations of SFCA in the T1 and T2 samples are in the range of 1-5 mass% and 2-8 mass%, respectively, and the Fe2O3 concentration tends to decrease with increasing Al2O3 concentration. (iii) The Rietveld analyses of XRD profiles have revealed that adding CaO and Al2O3 increases the fraction of the SFCA phase in the sintered sample. Hence, it is suggested that the placement of CaO and Al2O3 near C2S would promote SFCA formation, which leads to mitigating the decrease in strength relevant to C2S-added iron ore sinters.