Shear Thinning Behavior of Calcium Silicate-Based Mold Fluxes at 1623 K

Abstract

There have been consistent efforts on understanding rheological behavior of molten mold flux, used in continuous casting of steels. It is prevalent view that molten mold flux shows non-Newtonian behavior, meaning that the viscosity varies with shear rate history. Hence, the present study attempts to evaluate shear thinning, which is one of the characteristic non-Newtonian behaviors, by measuring its viscosity with a rotating type viscometer at 1623K. Furthermore, Raman spectroscopy analysis is used to appreciate the structure of molten mold flux and shear thinning. Mold fluxes tested reveal definite shear thinning characteristic of decreasing viscosity with increasing shear rate. The degree of shear thinning has been well quantified by Oswald-De Waele power law model. Lastly, the degree of polymerization, obtained from Raman spectroscopic data has proportional relationship with degree of shear thinning in the range of 1-5s(-1) shear rate. Also, it has a downward parabolic relationship with degree of shear thinning at entire shear rate ranges up to 100s(-1). This study also verifies possibility to use shear thinning behavior on actual continuous casting process.