Phase Equilibria in the System “FeO”–CaO–SiO2–Al2O3–MgO with CaO/SiO2 1.3

A series of “FeO”-containing slags are present in iron blast furnace. Phase equilibria play an important role in optimum operation of blast furnace which involves complex chemical reactions. Phase equilibria studies have been carried out in the system “FeO”–CaO–SiO2–Al2O3–MgO in equilibrium with metallic iron. The technique used includes high temperature equilibration followed by quenching and electron probe X-ray microanalysis. Pseudo-ternary sections of the phase diagrams are presented in the form of (CaO+SiO2)–Al2O3–MgO at fixed CaO/SiO2 ratio of 1.3 and “FeO” concentrations of 5 and 10 wt%. This is the first systematic study in the system “FeO”–CaO–SiO2–Al2O3–MgO important to the blast furnace operations. It was found that melilite, Ca2SiO4, merwinite, spinel and (Mg,Fe2+)O are the primary phase fields in the composition range investigated. Liquidus temperatures increase in the melilite and spinel primary phase fields and decrease in the merwinite and Ca2SiO4 primary phase fields with increasing Al2O3 concentration. The liquidus temperature is not sensitive with Al2O3 in the spinel primary phase field. Effects of MgO and “FeO” on liquidus temperature are also discussed. Extensive solid solutions can be formed in this system that have significant influence on the liquidus temperatures and the data will be used for optimisation of the thermodynamic models.