The Investigation Of Phase Consititution And Reaction Between Titanium Dioxide And Calcium Ferrite

As being an important iron ore resource in China,Vanadium titanium magnetite（VTM）possesses huge reserves and contains a great number of strategic elements.Therefore,development and utilization of VTM has profound meaning.Beneficiation-agglomeration-Blast furnace-Converter process is the main utilization method of VTM in China.Poor strength and high energy consumption are major technical problems in the production of VTM sinters.SiO₂-Fe₂O₃-CaO-Al₂O₃ calcium ferrite system is the superior bonding phase in VTM sinter processing,however,TiO₂ extremely inhibits the generation of calcium ferrite but promotes the formation of perovskite which is accompanied with high melting point.Although previous work have identified the effect of TiO₂ on reaction mechanism in the VTM sinter process,reaction routes of calcium ferrite system with different addition content of TiO₂ and the distribution of TiO₂ in the phases of sintering products were rarely investigated.This study is aimed at samples of VTM in Panxi.The paper fully discussed the reaction mechanism of calcium ferrite with TiO₂,the form of TiO₂ existing in different phases,and phases transformation in sintering process.The experiments adopted micro-sintering method,the powder samples were uniformly mixed and then pressed into cylinder shape,then got roasted at 1240 oC to obtain the final tested samples for XRD and SEM analysis.The main conclusions revealed from this study were summarized: there are no intermediate products generating in the reaction process of CF and TiO₂.Perovskite and CF is formed in the low temperature roasting for mixtures of Fe₂O₃,CaO,and TiO₂.When temperature was raised to 1100 oC,CF and TiO₂ begins to generate perovskite,and this reaction process reaches to the highest rate at 1200 oC.In the CF-SiO₂-TiO₂ system,when the Si O₂ content is high（> 6%）,a new phase called titanium garnet（Ca3Fe2Si1.52Ti1.48O12）generates at 1240 oC.The experimental results further showed that titanium garnet is the precipitation of silicate phase in high temperature liquid system,existing with low melting point,weaken strength,and poor reducibility compared with CF.In the CF-Al₂O₃-TiO₂ system,perovskite can generate through substitution reaction with addition of TiO₂.In the roasting process of VTM,ferrite system is difficult to generate whereas hematite,perovskite and titanium garnet mainly produce.TiO₂ largely exists in the perovskite and titanium garnet,and was fewobserved in hematite.