| In recent years,with the intense competition among iron and steel enterprises,some low-cost iron ore is widely utilized,which promotes reducing costs and increasing benefits for enterprises.It brings some influence on the stability of sinter metallurgical quality and the smooth operation of blast furnace.Metallurgical quality is affected by mineral composition and structure of the sinter.As the main binder phase of high basicity sinter,silico-ferrite of calcium and aluminum is less researched by studying on the formation characteristic and regulation of composition and microstructure under different conditions.Also,the related research on the slag formation behavior during reducing process needs to be supplied.Based on in-situ sinter composition,this paper investigated effects of sintering temperature,binary basicity and Al2O3 content on the structure and formation of silico-ferrite of calcium and aluminum using X-ray diffraction(XRD),optical microscope and scanning electron microscope,which the different ratio of sintered materials was configured under laboratory conditions by adopting dry powder briquetting and roasting method.Comprehensively analyzing the reducing property of different proportion sinters,and the formation behavior of primary slag and preliminary separation mechanism of slag and iron during reducing process is also studied in reduction experiment of iron ore.Finally,obtaining a suitable sintering ratio so as to provide certain theory basis for sinter proportioning.The results of regulation of composition and microstructure of silico-ferrite of calcium and aluminum show that the structure of silico-ferrite of calcium and aluminum transforms from plate-like state to acicular state gradually over the increase of temperature.At 1260°C,the content of SFCA-I and total SFCA reach the maximum value,and the mineral phase structure is obviously corroded.Binary basicity mainly determines the formation of SFCA-I,and its content increases with basicity increasing.The silicate phase increases in the condition of high basicity.The content of Al2O3 in the sample mainly affects the accumulation of columnar SFCA.With the proper increase of the ratio of Al2O3 content,it is beneficial for the formation of SFCA-I.The silico-ferrite of calcium and aluminum is plate-like state under high Al conditions which is of 3% and 4% Al2O3.The optimum sintering temperature,content and binary basicity are 1260°C,2.0 and 2% respectively.The study on the reducing property shows that this property can be improved by increasing the basicity of sinter.Owning to the formation of brownmillerite and hercynite,reduction degree fluctuates during intermediate stage.At the early stage,the reduction of high alumina ore is weak.With the free state appearance of large granular Al2O3 and Si O2 crystals during the medium stage,the viscosity of liquid phase increases,which precludes the reduction of iron oxides and the aggregation of iron,and causing reduction stagnation phenomenon.Reduction degree increases with the obvious powdering appearance.The sinter which contains 2.0 binary basicity and2% Al2O3 presents the best reduction property,slag and iron are well separated,where there is a clear interface between them,and the ultimate reduction degree can reach95.1%.The study on the formation behavior of primary slag during reduction process shows that with the decomposition of silico-ferrite of calcium and aluminum,slagging elements which contain Ca,Si and Al gradually separate and participate in the formation of slag.Ca easily combines with Si to form calcium silicate.Due to the isomorphism phenomenon,Al,Fe,Ca firstly unite to form solid solution,which gradually combine Si to form calcium aluminosilicate phase. |
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