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Effect of Chemical Composition and Temperature on Viscosity and Structure of Molten CaO-Al2O3-SiO2 System

Řeháčková L., Rosypalová S., Dudek R., Ritz M., Matýsek D., Smetana B., Dobrovská J., Zlá S., Kawuloková M.

Archives of Metallurgy and Materials

2015

Vol. 60, iss. 4

2873--2878

The effects of the change of chemical composition and temperature on the viscosity of CaO-Al2O3-SiO2 oxide system with basicity from 0.78 to 1.63 were investigated in this paper. Experimental measurements of viscosity were performed with use of the high-temperature viscometer Anton Paar FRS 1600. Viscosity was measured in a rotational mode during heating at the rate of 2.2 K/min in the temperature interval from 1673 to 1873 K. Viscosity is often sensitive to the structural changes in molten oxide systems, which implies that the analysis of viscosity is an effective way to understand the structure of molten oxide systems. Exact clarification of the change of structure of the oxide system caused by increased content of CaO was performed by Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray diffraction (XRD).

W artykule badano wpływ zmian składu chemicznego i temperatury na lepkość układu tlenków CaO-Al2O3- SiO2 o zasadowości od 0.78 do 1.63. Pomiary doświadczalne lepkości przeprowadzono z użyciem wiskozymetru wysokotemperaturowego Anton Paar FRS 1600. Lepkość mierzono w układzie obrotowym w czasie ogrzewania z szybkością 2.2 K/min w zakresie temperatur 1673-1873 K. Lepkość jest często wrażliwa na zmiany strukturalne w ciekłych układach tlenkowych, co oznacza, że analiza lepkości jest skutecznym sposobem, aby zrozumieć strukturę układu ciekłych tlenków. Przeprowadzono dokładne wyjaśnienie zmiany struktury systemu tlenków spowodowane zwiększeniem zawartości CaO przy użyciu metody FTI R (Fourier transform infrared spectroscopy), spektroskopii Ramana i XRD (X-ray diffraction).

Influence of CaO content on viscosity of molten CaO-Al2O3-SiO2 system

Řeháčková L., Rosypalová S., Dudek R., Dobrovská J.

Archives of Materials Science and Engineering

2013

Vol. 59, nr 2

61--68

Purpose: The objective of this work is experimental determination of temperature dependences of viscosity of the molten CaO-Al2O3-SiO2 system and assessment of impact of CaO on the viscosity of this system. Design/methodology/approach: The ternary oxide system CaO-Al2O3-SiO2, which represents a simplified basis of the casting powder, was chosen for the experiment. Dependencies of viscosity on the concentration of CaO and on the temperature were determined experimentally. For this purpose were prepared a concentration series with additions of 3, 6, 9, 12 and 15 wt.% of calcium oxide. Experimental measurements of viscosity was performed with use of the high-temperature viscometer Anton Paar FRS 1600. Findings: Viscosity of the studied systems decreases exponentially with the increasing temperature. Viscosity decreases with the increasing addition of CaO. Viscosity reaches its minimum value of 0.447 Pa.s (at T = 1723 K) at the basicity of CaO/SiO2 = 1.13. Viscosity increases with the further addition of CaO (CaO/SiO2 > 1.2). Influence of addition of CaO is more pronounced at higher temperatures. Research limitations/implications: Viscosity in molten oxide system is determined by the internal structure. Exact clarification of the change of structure of the oxide system caused by the increased content of CaO requires additional analyses, such as Fourier transformation infrared spectra and Raman spectra. Practical implications: The choice of an optimum slag mode influences not only the main metallurgical processes, but also the values of technical-economic indicators of the whole steelmaking process. Viscosity is an important factor affecting the service properties of slags, as it plays an important role in the area of mass transfer at chemical reactions in metallurgical processes. Originality/value: The viscosities of CaO-Al2O3-SiO2 system were measured under conditions of CaO/SiO2 = 0.78-1.44, 47.20-35.98 wt.% SiO2, 36.90-51.90 wt.% CaO and 15.90-12.12 wt.% Al2O3.