Effects of Fluorides on NaF Vaporization during Mold Powder Melting by Thermodynamic Equilibrium Calculation

Abstract

Low‐basicity fluorine‐containing mold powder, which forms a porous slag film with NaF pores, is expected to solve the contradiction between heat transfer and lubrication during the continuous casting of peritectic steel. Herein, to study the influences of different fluorine raw materials (NaF, CaF2, and Na3AlF6) on NaF vaporization, thermodynamic calculations are carried out by FactSage 8.1 during mold powder melting from 600 to 1600 °C. The results show that CaF2 is the first producing NaF gas, followed by Na3AlF6 and then NaF as the temperature increases. With the same mass of fluorine addition, NaF produces the highest amount of NaF(g), followed by Na3AlF6 and CaF2. Furthermore, the effects of basicity (%CaO/%SiO2) and Al2O3 contents on NaF vaporization are investigated. Additionally, different fluorine raw materials and Al2O3 components that can form porous slag films at low basicity (from 0.7 to 1.1) are also obtained. Therefore, this work can be used to guide mold powder design for peritectic steel.