Mixed Alkali Effect in Viscosity of CaO-SiO 2 -Al 2 O 3 -R 2 O melts
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INTRODUCTION
MOLD fluxes play an important role in continuous casting process, such as ensuring the smooth operation of continuous casting process and improving the surface quality of slab.[1,2] The common physical and chemical properties of mold fluxes include melting point, viscosity, solidification temperature, crystallization temperature, etc. Among them, viscosity plays a significant role on the lubrication of the mold fluxes.[3,4] Alkali oxides such as Li2O, Na2O, and K2O are always added to adjust the physicochemical properties (viscosity, melting point, etc.) of mold flux. It is necessary to investigate the viscosity variation of mold fluxes resulting from the additions of different alkali oxides. In addition, viscosity measurement is a helpful tool for understanding the melt structure. In the literature, many investigations have been carried out on the viscosity of slag systems containing alkali oxides. Sukenage et al.[5] studied the influence of R2O (Li2O, Na2O, and K2O) addition on the viscosity of CaO-SiO2-20 mass pct Al2O3 slag. It was found that the viscosity decreased with the addition of Li2O or Na2O but increased with the addition of K2O. Chang et al.[6] investigated the effects of Na2O and K2O YONG HOU, GUO-HUA ZHANG, and KUO-CHIH CHOU are with the State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, Beijing 100083, China. Contact e-mail: [email protected] DEQIU FAN is with the Science and Technology Center, Guardian Industries LLC, Auburn Hills, MI 48117, USA. Manuscript submitted November 11, 2019.
METALLURGICAL AND MATERIALS TRANSACTIONS B
additions on the viscosity of CaO-SiO2-8 mass pct MgO-9 mass pct Al2O3 blast furnace-type slag with a basicity of 1.05, and concluded that viscosity decreased with the increase of Na2O, while there was a continuous increase of viscosity with the addition of K2O. Park et al.[7] investigated the effect of Li2O on the viscous behavior of CaO-SiO2-12 mass pct Na2O slag with a CaO/SiO2 mass ratio of 0.8. The results indicated that 2 mass pct addition of Li2O was effective in reducing the viscosity of slag system. A similar conclusion was also obtained by Wen et al.[8] that the addition of Li2O or Na2O would reduce the viscosity. In our previous work,[9] the effect of K2O addition on the viscosity of CaO-SiO2-Al2O3 melt was measured. The results indicated that the viscosity first increased and then decreased with the increase of K2O content. In addition, the viscosity variations of CaO-Al2O3-SiO2-Na2O melts were investigated, and viscosity first increased and then decreased as gradually increasing Na2O/CaO ratio.[10] As mentioned above, for silicate melts containing Al2O3, the R2O/Al2O3 molar ratio has a significant effect on the viscosity. Although many studies have been carried out to investigate the effect of alkali oxides (Li2O, Na2O or K2O) on the viscous behavior of silicate or aluminosilicate melt, it is still insufficient to illustrate the variation behavior of viscosity in alkali oxide bearing aluminosilicate melts. In both the w
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