Role of Ceria in Enhancing the Resistance of Aluminosilicate Refractories to Attack by Molten Aluminum Alloy

Abstract

Rare-earth doping of aluminosilicate refractory compositions has been shown to impart improved resistance to attack by molten aluminum alloys. The basis for this improved alloy attack resistance was investigated. The addition of rare-earth oxide to bauxite was found to alter the microstructure to form large, uniformly shaped corundum crystals interlinked with cerium-containing strands. It was concluded that this unique microstructure was responsible for the enhanced attack resistance of the refractories. Other possible causes for improved alloy attack resistance, such as enhanced sintering, excess oxygen provided by the Ce02 dopant, or higher thermodynamic stability of the phases formed in the doped refractory compositions, were not consistent with the experimental findings. [

Synthesis of Al6Si2O13-BaAl2Si2O8-ZrO2-based composites and their wettability by molten Al and an Al-Si alloy

“…However, the addition of 7 wt% of this reagent improves corrosion resistance at a temperature within the range of 900 to 1100 1C [9]. The beneficial effect of CeO 2 (added to bauxite based refractories) is attributed to the enhanced grain growth in the corundum, higher matrix crystallinity and a weblike morphology of the cerium-rich regions, constituting an impediment to aluminum diffusion [17].…”

“…The most common solution is the use of additives to reduce wettability of aluminosilicate refractories by molten aluminum alloys enhancing the corrosion resistance [4]. Additives that have been used are: Na 3 AlFe 6 [5,6], Al 2 TiO 5 [7], SiC [8], CaF 2 [4,[9][10][11][12], BaSO 4 [4,9,10,[13][14][15][16], AlF 3 [4,9], CeO 2 [17] or a combination of them [4].…”

Effects of Different Calcium Compounds on the Corrosion Resistance of Andalusite-Based Low-Cement Castables in Contact with Molten Al-Alloy

“…[1] Several additives have been used in the past to improve the resistance of the refractory to corrosion by molten aluminum, such as zircon, barium sulfate, calcium fluoride, glass frits, [1] wollastonite, [2][3][4] aluminum fluoride, aluminum borate, [5] chromium oxide, aluminum titanate, cryolite, [6,7] barium celsian, [8][9][10] and ceria. [11] The additives work by decreasing the wettability of the molten aluminum alloys with the refractory, thereby decreasing the extent of corrosion and associated molten metal penetration. [12] Although these additives have been used for several decades, ambiguity exists in regard to the mechanisms responsible for the improvement in the corrosion resistance.…”

Interacción química entre sustratos mullita-SrSO₄ y SiO₂-SrSO₄ con aluminio líquido

“…Patrones de DRX mostraron la presencia de mullita y SrAl 2 Si 2 O 8 en la mezcla de mullita-SrSO 4 . En la mezcla de sílice-SrSO 4 , se detectó la presencia de sílice y SrSiO 3 . Para las muestras de mullita sin adición de SrSO 4 se encontró una capa de corrosión compuesta de alúmina con un espesor de 2 mm para una temperatura de 900 o C por 10 h. Las muestras que contienen estroncio presentaron una capa de corrosión de aproximadamente 100 μm bajo las mismas condiciones.…”

“…Mientras que el aluminio y los elementos aleantes tales como el Mg difunden dentro del refractario, el silicio de la reacción de reducción difunde hacia el aluminio y el oxígeno reacciona con el aluminio formando una capa de alúmina, la cual tiene una expansión térmica más grande que la del refractario original. Al desprenderse esta capa genera una penetración adicional del aluminio fundido dentro del refractario y por ende, mayor deterioro del mismo (3,7).…”