Investigation of rheological behavior for commercial mold slags

Rheological behaviors of several commercial mold slags, which were designed for continuous casting of high-carbon steel, peritectic steel, and high-Al steel were studied using rotational viscometer with various rotating speeds. The crystallization rates, which were correlated with rheological behaviors, were detected by in-situ observation. The effect of steel-slag interface reaction between high-Al steel and CaO–Al2O3-based slag on the non-Newtonian fluid behaviors was also discussed. The main results demonstrated that these mold slags all belonged to pseudoplastic fluid and exhibited shear thinning characteristics. The index of flow characteristics in high temperature zone was less than 1 and fluctuated around 0.9, while in low temperature zone, n rapidly decreased from 0.9 to 0.3. The results show that the low temperature zone is more obvious than the high temperature zone for the shear thinning characteristics of the mold fluxes below the break temperature. The shear thinning was closely related to the crystallization rate and grain size of crystals precipitated within melts. Steel-slag interface reaction decreased the content of glass formers, such as SiO2 and B2O3. The crystallization capacity was enhanced, followed by a reduction of lubrication ability. It is found non-Newtonian behaviors of commercial mold slag are closely associated with their crystallization capacity, and the discussion range of viscosity temperature is more in line with the actual temperature drop range of molten flux during continuous casting, which is of great significance to understand the mechanism of shear thinning and optimize the comprehensive performances of commercial mold slags.