Viscosity and structure of CaO–Al2O3–TiO2-based mold fluxes with various CaO/Al2O3 mass ratios

The effects of CaO/Al2O3 mass ratio on the viscosity and structure of new CaO–Al2O3–TiO2-based fluorine-free mold fluxes for high titanium steel are investigated by viscometer, molecular dynamics (MD) simulations and Raman spectroscopy. When the CaO/Al2O3 mass ratio increased from 0.6 to 1.4, the viscosities and activation energies reduced from 0.43 to 0.10 Pa·s and 127.8–74.2 kJ·mol−1, respectively. While the break temperatures raised from 1385 to 1507 K. Moreover, according to MD simulation results, the concentration of high coordination of Al–O and Ti–O bonds decreased, and the complex structure units of Q3, Q4 and Q5 turned to the simple structure units of Q0, Q1 and Q2. Raman spectra suggested that the concentrations of Ti–O–Ti(Al) linkage and Q2(Si-O−) decreased significantly, but the concentration of Q1(Si–O−) increased. Therefore, CaO/Al2O3 could simplify the network structure and decrease the viscosity of new CaO–Al2O3–TiO2-based fluorine-free mold fluxes for high titanium steel.