Viscosity and structure of CaO–BaO–SiO 2 –Al 2 O 3 -based mold slags for continuous casting of high titanium steel with different TiO 2 absorption

The effect of TiO 2 absorption into two different CaO–BaO–SiO 2 –Al 2 O 3 -based mold slags from the steel plant on the viscosity, melting performance and microstructure of slags was investigated through the measurement of the viscosity–temperature relationship, melting temperature and Raman spectroscopy. The parameter of the number of non-bridging oxygen per tetrahedrally-coordinated atom (NBO/T) was also calculated to explain the microstructure variation of molten slags with different TiO 2 absorption. The variation of the actual slag consumption and the depth of the liquid slag in mold was explained through the comparison of the viscosity and the melting temperature of two different slags. The viscosity of mold slags (basicity = 0.6) decreased from 1.1 to 0.68 Pa s with the increase in the TiO 2 absorption from 0 to 10%, while that of slags (basicity = 0.7) decreased from 0.76 to 0.56 Pa s with the TiO 2 absorption from 0 to 6%. The activation energy of both two groups of slags had the tendency to decrease with the increasing TiO 2 absorption. The network structure of both two groups of slags measured by the Raman spectra showed that the fraction of complex structure units (Q 1 , Q 2 , Q 3 and Al–O–Al) decreased and simple structure units (Al–O − and Q 0 ) increased with the increase in TiO 2 absorption. NBO/T also increased with the increase in the TiO 2 absorption, indicating that the absorption of TiO 2 into slags resulted in the destruction of silicate/aluminate structure. Hence, the absorption of TiO 2 into the current CaO–BaO–SiO 2 –Al 2 O 3 mold slags decreased the degree of polymerization of these slags and then led to the decrease of viscosity.