The composition and properties of greatly affect the furnace productivity and
the quality of hot metal produced. is an important physical property of slags, strongly
influenced by the chemical composition, structure and the temperature. Experimental measurement
of slag viscosity requires temperature equipment and is time consuming. Therefore, chemical
parameters are used to identify trends in viscosity as function of chemical composition. Limited
information is available for High Blast Furnace Slags, since much of the open literature
deals with Low Alumina Slags, with alumina content less than 15 weight percentage. High Alumina
slags (alumina content in the range of 15% to 30%) are predominantly encountered in Indian Blast
Furnaces. It appears that these slags have higher viscosity and lower sulphide capacity than the low
alumina slags. The effect of chemical composition / ionic structure on viscosity has been interpreted
in this work, using the chemical parameter of optical . Data reported in the literature have
been used, along with the values of liquidus temperature, for high alumina slags. Three slag systems,
i.e., CaO–Al2O3–SiO2, CaO–Al2O3–SiO2–MgO and CaO–Al2O3–SiO2–MgO–TiO2 have been
considered in this work. The trends observed are discussed in the paper.