Abstract
The effect of Na2O on the crystallization kinetics of mold fluxes for casting medium carbon steel was studied in this article. The Continuous-Cooling-Transformation (CCT) diagrams and Time-Temperature-Transformation (TTT) diagrams of mold fluxes with different Na2O concentrations were constructed by using single and double hot thermocouple technique (SHTT an DHTT). The results indicated that the crystallization temperature was increased with increasing Na2O content, and the incubation time of isothermal crystallization was decreased correspondingly. X-ray diffraction analysis results suggested that cuspidine was the base crystal for all the mold fluxes, and other Na bearing crystals like Na4Al2Si2O9 (2Na2O·Al2O3·2SiO2) and Ca2Si2Na2O7 (2CaO·2SiO2·Na2O) were formed with the increase of Na2O content. It was concluded that the addition of Na2O would significantly change the crystallization behaviors of medium carbon mold fluxes.
