Fused α-β alumina bricks are high-performance cast refractory materials, produced by melting high-purity raw materials in an electric arc furnace and then casting them. The "α-β" in their name refers to their two main crystalline phases: α-Al₂O₃ (corundum) and β-Al₂O₃. By precisely controlling the composition and process, and adjusting the ratio of these two phases, they possess both high refractoriness and excellent resistance to alkaline vapor attack.
Core Characteristics and Advantages
High Purity and Density: Made primarily from high-purity alumina (such as industrial alumina), the Al₂O₃ content is typically between 93% and 97%.
Formed directly from molten state through cooling and crystallization, they have an extremely dense structure and very low porosity (close to zero), thus exhibiting exceptional resistance to glass melt, slag, and gas permeation.
Unique Two-Phase Structure:
α-Al₂O₃ phase (corundum): Extremely high hardness (Mohs hardness 9), high refractoriness, and strong corrosion resistance; it forms the framework providing high-temperature strength and chemical stability.
β-Al₂O₃ phase (chemical formula approximately Na₂O·11Al₂O₃): An alumina compound containing an alkali metal (usually sodium). While slightly lower in hardness, it exhibits excellent resistance to alkaline vapor attack and can toughen microcracks, improving the material's thermal shock resistance.
Synergistic Combination of the Two Phases: By controlling the ratio of the two phases (e.g., the common α:β = 50:50 or 60:40), an optimal balance is achieved between corrosion resistance and a certain degree of thermal shock resistance.
Excellent High-Temperature Performance:
Refractory temperature > 1850℃.
Very high load softening temperature; almost no creep occurs at high temperatures; good structural stability.
Excellent resistance to chemical attack:
It exhibits outstanding resistance to molten sodium-calcium-silica glass and alkaline vapors (especially Na₂O and K₂O), which is one of its most prominent advantages.
Preparation Process:
Ingredients: Primarily high-purity alumina powder, with the addition of a small amount of soda ash (Na₂CO₃) or other additives to regulate β-phase formation.
Melting: Completely melted in an electric arc furnace at temperatures exceeding 2000°C.
Casting and Crystallization: The molten metal is poured into pre-made sand or metal molds and solidified at a strictly controlled cooling rate, forming a coarse, interlocking columnar crystal structure composed of α and β phases.
Annealing and Machining: The ingots are slowly annealed in a tunnel kiln to eliminate internal stress. Finally, they are machined into bricks of precise dimensions through cutting, grinding, and other mechanical processes.
Main Application Areas
Its applications are highly concentrated in areas with the most stringent requirements for resisting alkali and molten glass corrosion:
Glass Industry (Core Applications):
The upper structure of melting furnaces for float glass, bottle glass, and fiberglass: such as the main arch (furnace arch), breast wall, burner nozzle, and upper grid of the regenerator. These parts are mainly subjected to corrosion from high-temperature alkali vapors, which is where α-β bricks excel.
Working pool or feed channel sidewalls: Used in areas in contact with molten glass but where corrosion is relatively minor.
Chemical and Metallurgical Industries:
High-temperature environments with strong alkali corrosion, such as alkali recovery furnaces, carbon black reactors, and dioxin treatment furnaces.
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