Abstract: Oxidization mechanism in CaO-FeO_x-SiO₂ slag with high iron content was investigated by blowing oxygen into molten slag so as to oxidize Fe(Ⅱ). The relationship between Fe(Ⅱ) content and oxidizing time at different temperatures was obtained by chemical analysis. Microstructure of slag was observed by metallographic microscope and SEM. Phases compositions were ascertained by EDXS and XRD. Grain size and crystallizing quantity of magnetite(Fe₃O₄) were determined by image analyzer. The oxidizing kinetic equations were deduced. Confirmed by graphical construction method, Fe(Ⅱ) oxidizing reaction in CaO-FeO_x-SiO₂ slag system is of first order, and the reaction apparent energy Ea is 296.67kJ/mol in the pure oxygen and 340.30kJ/mol in air. The enrichment and crystal growth mechanism of magnetite(Fe₃O₄) phases were investigated. In oxidizing process, content of fayalite declines, while that of magnetite(Fe₃O₄) increases, and iron resources enrich into magnetite(Fe₃O₄) phase. All these provide a theoretical base for compressive utilizing of those slags.

Key words: oxidizing; magnetite; kinetics; phase transformation; CaO-FeO_x-SiO₂ slag