Viscous Behavior of Alumina Rich Calcium-Silicate Based Mold Fluxes and Its Correlation to the Melt Structure

Abstract

The substitutional effect of SiO2 with Al2O3 content on the viscosity in the calcium-silicate melt-based system containing 12 mass% Na2O and 5 mass% Li2O was studied. Additions of Al2O3 increased the viscosity and higher Al2O3 concentrations modified the dominant silicate network into complex alumino-silicates with the aluminate structure becoming particularly prevalent at an Al2O3 content of 20 mass% and higher. FTIR (Fourier transform infra red) and Raman analysis showed increased amounts of symmetric Al-O 0 and Si-O-Al stretching vibrations with higher Al2O3. Compared to the effect of Al2O3, structural changes and the viscosity with higher CaO/(SiO2+Al2O3) were not as significant. However, the symmetric Al-O 0 stretching and the Si-O-Al in the [AlO4] 5--tetrahedral units seems to decrease with increased apparent basicity. The apparent activation energy for viscous flow increased with higher Al2O3 due to the increased polymerization of the melt and varied from 129 to 156 kJ/mol. KEY WORDS: Al2O3; CaO/(SiO2+Al2O3); viscosity; FTIR; Raman; alumino-silicate structures.

Control of Crystal Morphology for Mold Flux During High-Aluminum AHSS Continuous Casting Process

“…In addition, it was confirmed by Kim et al measurement that the melt viscosity decreased by adding a small amount of Li 2 O into mold flux. [12] Also, experimental results of Liu et al [38] demonstrated that more faceted crystal precipitated by increasing Li 2 O content in mold fluxes within a reasonable amount, which is in accordance with our present findings.…”

“…As a result, to develop an optimized unreactive CaO-Al 2 O 3 -based mold flux, the second strategy, is increasingly investigated by many researchers. [3,4,[8][9][10][11][12] Blazek et al [3] worked on lime-alumina-based mold flux for casting high-Al AHSS steel and showed that the interaction was markedly reduced and the as-cast slab quality was improved compared to that of lime-silica-based mold flux. Cho et al [8] carried out casting trials of high-Al TRIP steel by using the newly developed lime-alumina-based mold fluxes, and their results suggested that mold heat transfer in casting process and surface quality of slab were improved, compared to that of lime-silica-based mold fluxes as well.…”

Effect of MnO on High-Alumina Slag Viscosity and Corrosion Behavior of Refractory in Slags

“…Therefore, the addition of MnO as a network modifier could increase the amount of O − and depolymerize the complex network structures of the molten slag, then decreasing the viscosity. On the other hand, the high Al 2 O 3 content of the present slag system may increase the quantity of complex aluminate or alumino-silicate structural units, 20) and a dynamic balanced reaction as shown in Eq. (2) may exist in the slag.…”

Effect of Alumina and Extended Basicity on the Viscosity and Structure in the TiO2-MnO-Al2O3-8.64ZrO2-2.77Na2O Welding Flux System

“…Al 2 O 3 , which is known to be an amphoteric oxide, can generally be considered to behave as a network forming oxide in the absence of significant acidic components such as SiO 2 similar to the present TiO 2 -MnO-Al 2 O 3 -8.64ZrO 2 -2.77Na 2 O flux system. 19,20) The general trend shows the viscosity decreases with increasing (TiO 2 +1.13MnO)/Al 2 O 3 and again seems to be more pronounced at lower temperatures, where complex network structures are prevalent in the absence of significant thermal energy, which can then be modified with compositional changes in the flux. With increased extended basicity and assuming full depolymerization is nearly reached, where complex network structures no longer exist, the viscosity seems to converge to approximately 0.03 Pa·s.…”