Effect of Gas Atmosphere on the Phase Chemistry in the CaO-FeO-Fe2O3-SiO2 System Related to Iron Ore Sinter-making

Experimental phase equilibria studies have been carried out to investigate the phase chemistry in the CaO "Fe2O3"-SiO2 system related to the iron ore sinter making in 1 atm CO2 at 1 200-1 230 degrees C. The measurements have been performed using a modified experimental technique involving high temperature equilibration and rapid quenching followed by electron probe X-ray microanalysis (EPMA). In contrast to the equilibria in air, the experimental results show that no silico-ferrite of calcium (SFC solid solution) is formed in 1 atm CO2 within the temperature range investigated; that is, the SFC phase is not stable at liquidus temperatures. The liquidus for the iron -rich corner of the CaO "Fe2O3"-SiO2 system in CO2 atmosphere for the spinel (magnetite Fe3O4) and dicalcium silicate (C2S = Ca2SiO4) primary phase fields has been proposed