Introduction:

This lecture discusses the physico-chemical properties of slag which are relevant in steelmaking. Slag is a multi-component system and in steelmaking it consists of acidic oxides such as  and, and basic oxides such as FeO, CaO, MgO etc. In some slags  is also present. In the last lecture we noted that acidic oxides are network formers, whereas basic oxides are network breakers.

Viscosity:

Viscosity controls the fluidity of slag. The slag should be fluid so that it can be removed easily during tapping of steel. In fact fluidity is inversely proportional to viscosity of slag. In general viscosity of a slag is a function of temperature, composition and percent solid present in slag.

Viscosity of any slag composition decreases with the increase in temperature as given by the following expression:

(1)