The viscosities of CaO-SiO 2 -7MgO-TiO 2 -12Al 2 O 3 (wt-%) slags (CaO/SiO 2 50?5-0?9, wt-% TiO 2 515-30) were investigated to promote understanding of the effect of TiO 2 and basicity (CaO/SiO 2 ) on the viscous behaviour of slags containing TiO 2 . In practice, these experimental results are significant for the blast furnace (BF) processing of vanadium-titanium magnetite ore and for controlling the selective crystallisation of Ti bearing BF slags. The slag viscosity was found to decrease with increasing TiO 2 content at a fixed basicity. The degree of viscosity decrease with increasing TiO 2 content diminishes in the slag with higher basicity or higher TiO 2 content. An increase in the basicity lowers the viscosity of slags. The apparent activation energy of viscous flow of slags decreased with additions of TiO 2 and increasing basicity. The Urbain model was empirically modified based on the present experimental data, which can be used to predict not only quinary Ti bearing slags but also quaternary and low Ti bearing slags.
The present paper investigates how the mass ratio between Al2O3 and SiO2 (mAl 2 O 3 /mSiO 2 ) in slag compositions influences the structure, viscosity and crystallization of the slag melts. The objective is to study the variations in viscosity and structure of slags with increasing mAl 2 O 3 /mSiO 2 ratio. In practice the results of the study are relevant to the significant changes in slag property caused by the changes in chemical composition during continuous casting of steels containing high amounts of dissolved aluminum.The viscosity was found to decrease slightly with increasing mAl 2 O 3 /mSiO 2 ratio up to 0.56. The degree of polymerization for [SiO4]-tetrahedra was found to decrease with increasing mAl 2 O 3 /mSiO 2 ratio based on the Fourier Transformation-Infrared Spectra (FT-IR) and Raman spectra, which could explain the observed decrease in viscosity. AtmAl 2 O 3 /mSiO 2 ratios above 0.56, the viscosity was found to abruptly increase which could be caused by the presence of spinel crystals. The activity coefficient was computed and it was found that the activity coefficient of alumina presents negative deviation when mAl 2 O 3 /mSiO 2 ratio is less than 0.35, while it shows a positive deviation when mAl 2 O 3 /mSiO 2 ratio exceeds 0.35. This phenomenon may be related to the change of the primary phase region correlating to the phase diagram to the slag composition.
The present paper is an investigation into how the Al 2 O 3 /SiO 2 ratio in the compositions of mold slags influences the crystallization behavior of molten slags. The experimental work is based upon observing the crystallization events through a Confocal Scanning Laser Microscope equipped with a hot-stage. The study is motivated by the variation in crystallization that might occur in mold slags due to the pickup of alumina during continuous casting of high Al containing TRIP steels. The crystallization temperature was found to increase with increasing Al 2 O 3 /SiO 2 ratio, and the crystal morphology was dependent upon the chemical composition and isothermal temperature. The crystallization path was complex, with CaF 2 found to precipitate first, and followed by a second precipitation event. In this second event, the precipitated phase depended on the chemical composition of mold slag and changed from cuspidine to gehlenite as the mass ratio of Al 2 O 3 /SiO 2 was increased beyond 0.65, and finally Al 2 O 3 was observed when the alumina content was 30wt.% (corresponding to a mass ratio of m Al 2 O 3 =m SiO 2 ¼ 1.42).
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