Viscosity, Flow Characteristics and Microstructural Characterization of Industrial Blast Furnace Slags

Abstract

Twenty five numbers of Blast furnace slag samples are collected from different operating Indian Blast furnaces. The viscosity, flow characteristics and microstructural characterization of these slag samples are investigated in the present study. Viscosities of these slags are estimated using various models developed by several researchers followed by experimental determination of viscosities of some selected slag samples (using a high temperature viscometer) to predict the best possible model that can be used for the present investigation. The flow behavior of these slag samples is estimated by a heating microscope and is characterized by ST (Softening Temperature), HT (Hemispherical Temperature) and FT (Flow Temperature). Finally, microstructural characterization is performed using XRD (X-Ray Diffraction) and microscopic analysis. On the basis of the viscosity results a comparison is made between the various models bringing about the shortcomings of these mathematical models. It is observed that the estimated viscosities by Iida model are best fitted with the viscosities of slags measured by high temperature viscometer and hence, the viscosity data obtained by Iida model are analysed at length to ascertain the compositional dependence of slag viscosity. It is observed that the industrial blast furnace slag viscosity is greatly influenced by its CaO/SiO2 ratio, MgO and Al2O3 contents. The characteristic temperatures also show a compositional dependence in the slag samples albeit no clear trend is observed when combined effect of all the oxides is considered. XRD and microscopic results show important phases like melilite, akermanite-gehlenite, spinel and merwinite in the slag samples investigated in the present study.