The Temperature and Structure Dependence of Surface Tension of CaO-SiO 2 -Na 2 O-CaF 2 Mold Fluxes
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old of steel continuous casting, with the vibration of mold and the downward movement of solidified shell, the liquid mold flux flows and fills into the gap between the mold wall and the solidified shell to form a slag film, which helps the lubrication to prevent the bonding between the solidified shell and the copper plate.[1] The flowing behavior of the liquid mold flux is controlled directly by the physical properties of itself. One of the most important properties is surface tension, which influences the shape of the meniscus and the adhesion between the liquid mold flux and the solidified shell, and further influences the flowing rate and the thickness of the slag film.[2] The surface tension mainly depends on the temperature on the condition of fixed composition of the mold flux. In the mold, the temperature of the mold flux
QIANG GAO, YI MIN, and MAOFA JIANG are with the Key Laboratory for Ecological Metallurgy of Multimetallic Ores (Ministry of Education), Shenyang 110819, China and also with the School of Metallurgy, Northeastern University, Wenhua Road, Heping District, Shenyang, 110819, Liaoning, China. Contact e-mail: [email protected] Manuscript submitted 31 May 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS B
would vary with the solidification of the shell from the top location of meniscus to the bottom of the mold, thus affecting the adhesion between the liquid mold flux and solidified shell. Many studies on the effect of temperature on the surface tension of non-continuous casting mold fluxes have been reported.[3–12] For example, Dudek et al.[6] found that the surface tension of CaO-Al2O3-MgO-SiO2 melt decreased with temperature increasing. In addition, Nowok et al.[10] proposed that the surface tension of coal-ash slags increased with increasing temperature in the temperature range 1693 K to 1773 K. Sukenaga et al.[11]thought that the surface tension of CaO-SiO2-Al2O3-R2O (R = Li, Na, K) changed only slightly with temperature. King[12] found that the temperature dependence of surface tension of CaO-SiO2 melts was related with the content of SiO2. Nevertheless, the research on the temperature dependence of surface tension of the liquid mold flux is seldom concerned in the temperature range between the melting temperature of mold flux and solidification temperature of the molten steel. On the other hand, although some of them proposed that the surface tension is closely related to the structure of melt, there is still no clear explanation about the relationship between the surface tension and the melt structure. In the study, the CaO-SiO2-Na2O-CaF2 slag was chosen according to the compositions of mold fluxes for industrial production. And the effect of temperature on
the surface tension of CaO-SiO2-Na2O-CaF2 melts with different CaO/SiO2 mass ratios was investigated. Additionally, the variations of surface tension were further discussed from the viewpoint of the melt structure.
II.
EXPERIMENTAL
A. Sample Preparation On the basis of the compositions and content range of mold fluxes for industrial production, the CaO-SiO2Na
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