Crystallization features of solid slag films of ultrahigh- basicity mold fluxes for continuous casting

The ultrahigh- basicity mold flux for industrial application(binary basicity of 1. 74) was selected and solidified by an improved water- cooled copper probe. Different probe immersion times were adopted to analyze the solidification process of films. The growth speeds and closed porosities of solid films were measured. The crystallization processes by solidification and devitrification were also analyzed, respectively. The results indicate that the growth speed of the solid slag film during the initial solidification period (0-15s) is 79. 9??m/s. 2CaO??SiO2??NaF with small spherical shapes is the primary crystal which leads to devitrification. The average devitrification speed of the glassy film is 65??m/s, and the primary crystal in the outer layer of solid films is lathlike cuspidine(3CaO??2SiO2??CaF2). The growth of the lathlike cuspidine in the outer layer of films increases the closed porosity and decreases the effective thermal conductivity of solid slag films.