EFFECT OF RAW-MATERIAL COMPOSITION ON THE MINERAL PHASES IN LIME-FLUXED IRON-ORE SINTER

In this study small tablet specimens of powdered commercial iron ores mixed with fluxes and kaolin were heated in a reducing atmosphere and then cooled slowly in air to simulate industrial sintering. The effect of different ore and flux compositions on the phases found in the sin ter bond was studied. An increase in basicity (CaO/SiO2) favoured the formation of calcium ferrite and densification of the bond at a low si ntering temperature. The amount of calcium ferrite decreased as the Al 2O3 content decreased and the amount of reoxidized hematite produced o n cooling decreased. A decrease in Al2O3 content promoted a densificat ion of the bond. An increase in MgO content, introduced by addition of dolomite, decreased the amount of calcium ferrite slightly. When MgO was added in the form of serpentine the calcium ferrite content increa sed considerably. Increase in MgO markedly reduced the amount of reoxi dized hematite but produced a less dense bond. Generally the same comp osition and sintering temperature produced similar mineral composition s in the bond independent of the iron ore used. The only exception was when an ore with coarse dense hematite was used, in which case the bo nd contained some unreacted hematite. The porosity of the bond did var y with the type of ore used. Limonitic ore produced a bond with closed pores and less reoxidized hematite at lower temperature and basicity than did hematite ores.