Research On Formation And Mineralogical Characteristics Of The Calcium Ferrite In Sinter

Calcium ferrite is an important binder mineral in sinter.Its content,morphology and chemical composition directly affect the quality of sinter.At present,the formation mechanism of calcium ferrite is not clear,and the influence mechanism of chemical composition differences in sintering raw materials on different forms of calcium ferrite is still controversial.Starting from the perspective of process mineralogy,the micro sintering was carried out with chemical pure reagent.By means of polarizing microscope and electron probe,the influence laws of different temperatures,Ca O/Fe₂O₃ molar ratio,Mg O/Al₂O₃ mass ratio and constant temperature time on the formation and mineralogical properties of calcium ferrite were found out.At the same time,the influence mechanism of calcium ferrite with different contents and forms on the quality of sinter was revealed.The results show that with the increase of temperature（1100℃,1150℃,1200℃,1250℃）,the content of calcium ferrite first increases and then decreases,and the content is the highest at 1150℃and 1200℃.Therefore,it can be seen that the best formation temperature of calcium ferrite is 1150～1200℃.In the samples with Ca O/Fe₂O₃ molar ratio of 1:2,1:1 and 2:1,the content of calcium ferrite is the highest when the ratio is 1:1,which is more than 60%;With the increase of Mg O/Al₂O₃ mass ratio（0.5,0.75,1.0,1.25and 1.5）,the proportion of calcium ferrite in sinter decreased significantly,the content of acicular and heteromorphic calcium ferrite decreased,and the change of columnar calcium ferrite was not obvious;According to the composition analysis of electron probe,the internal chemical composition of different forms of calcium ferrite has little difference,and the general chemical formula is Ca_2.03Mg_0.54Si_1.27Al_1.25Fe_8.68O₂₀.With the increase of Mg O/Al₂O₃ mass ratio,the RDI_+3.15mm of sinter becomes better and the reducibility decreases;With the extension of constant temperature time（2min,5min,15min,30min and 60min）,the content of calcium ferrite in sinter increases significantly,and its shape changes from needle shape to other shape.Acicular calcium ferrite decreased from 16.34%to 6.37%.The content of columnar calcium ferrite is about 10%.According to the analysis of electron probe composition,different constant temperature time has little effect on the chemical composition of calcium ferrite,and the general chemical formula of calcium ferrite is Ca_1.97Mg_0.70Si_1.32Al_1.40Fe_8.38O_20。With the extension of constant temperature time,RDI_+3.15mm of sinter decreases and the reducibility becomes better.In general,the mass ratio of Mg O/Al₂O₃ is 1.25,and the constant temperature time at 1150℃is 2min,which is conducive to the formation of calcium ferrite.The research has certain guiding significance for further enriching the theory of calcium ferrite and improving the quality of sinter.Figure 41;Table 19;Reference 73...