2CaO·SiO₂と鉄鉱石間の反応に及ぼすAl₂O₃添加の影響

抄録

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^oC 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.