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中文摘要：
通过详细的热力学计算和推导,对高铁CaO-FeOx-SiO2（CFS）体系（铁含量50%-60%,x=1-1.5）氧化过程中铁氧化物的价态和组分相赋存状态变化规律进行了分析.结合SEM、EDX及XRD确定物相组成,图像分析仪对相分布进行定量测量,化学法分析铁组分变化情况.研究了氧化过程中,体系中相变的热力学规律以及磁铁矿相的析出特性,对不同温度条件下磁铁矿相析出情况进行了详细讨论,并简要推算了CaO的含量变化对体系相变的影响.结果表明,随熔体氧位的增加,磁铁矿相逐渐形成并饱和以晶体析出,铁组分会不断向磁铁矿相转移和富集.体系冷却后主要由磁铁矿、铁橄榄石和钙铁硅酸盐固溶体组成,氧化过程中,铁橄榄石相减少,磁铁矿相增加.在1423K以上温度,控制氧平衡分压lg（pO2/p0）〉-7.89时,体系中的铁组分主要以磁铁矿形式存在,并在冷却过程析出;冷却过程中,磁铁矿是初晶相,体系中铁离子的摩尔比n（Fe^3＋）/n（Fe^2＋）为1/4时,磁铁矿初始析出的温度约为1640K,随n（Fe^3＋）/n（Fe^2＋）比值的增加,磁铁矿析出温度升高,在n（Fe^3＋）/n（Fe^2＋）为1.8/1时,磁铁矿初始析出的温度约为1720K;体系中氧化钙含量的增加,可提高铁在磁铁矿相的富集程度.
英文摘要：
Composition and phase transformation mechanism in the oxidization process of CaO-FeOx-SiO2 （CFS） system with high iron content were investigated by comprehensive thermodynamic calculation and deduction. Variation of the iron valence states with oxygen equilibrium fractional pressure at different temperatures was calculated and phase microstructure was observed and confired by metallographic microscope, SEM, EDX, and XRD. Grain size and crystallizing quantity of magnetite were determined by imagine analyzer, and contents of iron in different valence states were obtained by chemical analysis. Thermodynamic regularity of oxidation process and magnetite （Fe3O4） precipitation were studied by calculation and confirmed by experiment data. Effects of CaO addition on enrichment of magnetite were also discussed. The results showed that, with increasing the oxygen partial pressure, content of magnetite grew up rapidly, became saturation and precipitate, iron was enriched into the magnetite phase. Main phases in the cooling down system were magnetite, fayalite （Fe2SiO4）, and glass state silicate （（Fe, Ca）SiO4）. In oxidizing process, contents of fayalite declined while those of magnetite increased. Above 1423 K, while keeping oxygen partial pressure lg（pO2/p0）〉-7.89, most iron was enriched into the magnetite phase and precipitated after cooling down, magnetite was always the first precipitated crystal phase. When molecule ratio n（Fe^3＋）/n（Fe^2＋） in the system was 1/4, initial magnetite precipitate temperature was about 1640 K. As n（Fe^3＋）/n（Fe^2＋） ratio increased, crystal precipitated temperature became higher, and it was about 1720 K while n（Fe^3＋）/n（Fe^2＋）=1.8/1. Increasing the content of CaO in the system promoted the enrichment of iron into magnetite phase during oxidizing process.
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