The influences of temperature, CaO/SiO2 and Al2O3 content on the melt formation behavior of slag in FeO-CaO-SiO2-Al2O3 system were investigated by a thermodynamic calculation. In-site observations of artificial iron ore agglomerates on the melt formation behavior of slag in FeO-CaO-SiO2-Al2O3 system were carried out by a scanning laser microscope mounted with a heating device. It is evaluated from the thermodynamic calculation that CaO/SiO2 and Al2O3 content greatly influence the amount of molten slag with high FeO. The initial melt formation shifts toward high temperature with increasing CaO/SiO2 and with decreasing Al2O3 content, and the amount of melt also decreases. The melt formation behavior by the in-site observations was in reasonable agreement with the thermodynamic calculations, and therefore the thermodynamic calculation is useful to evaluate the melt formation behavior of iron ore agglomerates.
