Characteristic Study on Crystallization Behaviors of Extreme High Basicity Mold Fluxes

Abstract

In recent years, automobile steels have been developed to hypo-peritectic and high alloyed steels matched to specific customer needs of low weight and high strength, which leads to severe surface cracks on the slabs. The problem can be improved by reducing the heat transfer as solidification initiates in the continuous casting process. One approach is to utilize a high basicity mold flux which shows low heat transfer rate due to larger amount of crystalline phases. As a result, basicity of the commercial mold fluxes for crack- sensitive steels has been increased gradually. Nevertheless, the studies on extreme high basicity mold fluxes are scarce.

Here crystallization characteristics of the extreme high basicity mold fluxes were investigated using Differential Scanning Calorimetry (DSC). In order to prevent evaporation of F-containing species, flux samples were sealed in a platinum crucible by welding. The morphology and composition of crystals in mold fluxes were also verified by Field Emission Scanning Electron Microscope (FE-SEM) equipped with Energy Dispersive X-ray Spectroscopy (EDS). Finally, the non-isothermal melt crystallization kinetics of cuspidine formation were studied to more fully comprehend crystallization behaviors.

The results obtained should be useful to comprehend the features of commercial mold fluxes and develop new mold fluxes from now on.