Viscoelastic properties of calcium silicate based mold fluxes at 1623K

Abstract

CaO-SiO2-CaF2 based flux in a continuous steel caster has to show dual viscous functions to minimize slab defects - high viscosity enough to avoid flux entrainment at mold top surface and low viscosity enough to maximize lubrication capability at oscillated mold wall region. Liquid flux could show a shear thinning behavior when its viscosity decreases with increasing shear rates. Flux viscosity was measured by a rotational type viscometer as a function of shear rates. Raman and XPS analysis were employed to understand structural changes of flux for correlating with shear thinning behavior. The present work has focused on developing an optimum mold flux system with strong shear thinning behavior. The strong shear thinning behavior appropriate for dual viscous functions could be achieved by incorporating borate or silicon nitride into the flux. The flux compositions with a strong shear thinning behavior will be presented from the viewpoint of clean slab production. ? 2016 by The Minerals, Metals & Materials Society.