SLAG FOAMING IN REACTION BETWEEN MOLTEN SLAG CONTAINING IRON-OXIDE AND IRON OF HIGH-CARBON CONCENTRATION

Slag foaming was directly observed in a CaO-SiO2-Al2O3-FeO slag and Fe-C alloy (C=4.5mass%) system using a high temperature X-ray radiographic technique at 1 773 K. The foaming behavior was characterized by measuring the index of foaming power [k1], the foam life [tau], the bubble diameter of CO gas [d(B)], the CO gas evolution rates during the observations and the wettability between the slag and metal. The results obtained in the present study were as follows : The index [k1] and the foam life [tau] were found to be almost constant during the observations, then the slag foaming behaviour in the system was described by Ito-Fruehan's equation. A small amount of sulphur addition to the system remarkably reduces the CO gas evolution rates. The sulphur addition increases bubble diameter [d(B)], which results in the reduction of [k1] and [tau]. Then the sulphur addition drastically reduces the slag foaming in this system. Therefore, the adjustment of sulfer concentration in the system is one of the most important points for controlling the slag foaming. Main cause for the increase in the bubble diameter [d(B)] can be explained from the increase in the contact angle [theta] between slag and metal by the sulphur addition.