Aluminum melting furnaces are key smelting equipment in the aluminum industry. Their working linings directly contact the high-temperature molten aluminum, slag, and gaseous environment, thus placing extremely stringent requirements on the performance of refractory materials. Refractory materials must possess excellent corrosion resistance, non-wetting properties, thermal shock stability, and mechanical strength to ensure furnace life, energy efficiency, and production safety. This review focuses on the differences between refractory bricks used for working linings and high-performance low cement refractory castables.
Application and Characteristics of Refractory Bricks in the Working Liners of Aluminum Melting Reverberating Furnaces
Refractory bricks are traditional pre-formed refractory materials, mainly made from high-purity raw materials (such as alumina, silicates, or silicon carbide) through high-pressure molding and high-temperature sintering. Commonly used types in aluminum melting furnaces include high-alumina bricks (Al₂O₃ content 70-90%), silica bricks (SiO₂ dominant), and silicate bricks. These bricks are suitable for furnace walls, furnace bottoms, and furnace tops.
Advantages:
1:High mechanical strength and volumetric stability: Maintains structural integrity at high temperatures (typical molten aluminum temperature 700-900°C), resisting mechanical shock and thermal stress. For example, high-alumina bricks can achieve a compressive strength of 50-100 MPa, suitable for areas subjected to molten aluminum flow.
2:Strong corrosion resistance: Silica bricks offer good resistance to molten aluminum and alkaline slag, reducing aluminum penetration and corrosion. According to literature, aluminum furnaces using silica bricks can significantly reduce maintenance costs.
3:Moderate thermal conductivity:Contributes to uniform heat distribution within the furnace, optimizing energy utilization.
Disadvantages:
1:Complex installation:Requires brick-by-brick construction, and joints are prone to becoming weak points, leading to aluminum leakage and accelerated corrosion. High sensitivity to thermal shock, prone to cracking, especially in environments with large furnace temperature fluctuations.
2:Limited flexibility:The brick formula is fixed and cannot be adjusted on-site to suit specific slag compositions (e.g., high-sodium or high-calcium slag).
In international markets, refractory bricks are commonly used in the non-contact areas of large furnaces, but working linings are gradually being replaced to improve efficiency.
Application and Characteristics of Low-Cement Castables in the Working Lining of Aluminum Melting Reverberating Furnaces
Low Cement refractory Castables (LCCs) are high-performance monolithic refractory materials with a cement content typically below 3%, primarily composed of high-purity aggregates (such as corundum or aluminosilicate), micro-powders, and additives. They are formed through on-site casting to create a seamless lining. In aluminum melting reverberating furnaces, LCCs are commonly used in the working layer of the molten pool, with typical formulations including 75% high-alumina, low-cement castables.
Advantages:
1:Excellent thermal shock resistance and low porosity: The low cement content reduces hydration products, allowing porosity to be controlled below 15%, improving impermeability. According to reports, LCCs exhibit 30-50% higher thermal shock resistance than traditional castables, making them suitable for environments with rapid temperature changes.
2:Non-wetting and corrosion resistance: Non-wetting agents (such as BaSO₄ or AlF₃) can be added to effectively resist erosion by molten aluminum and slag. Literature emphasizes that non-wetting additives can significantly reduce aluminum adhesion and extend furnace lining life to 12-24 months.
Highly efficient construction: Strong fluidity and self-flowability allow for pumping and casting, forming a monolithic lining and reducing joint leakage. Low thermal conductivity (approximately 1-2 W/m·K) contributes to energy savings.
3:High flexibility: With correct user feedback, LCC formulations can be customized based on smelting scenarios (e.g., high-impurity slag in secondary aluminum smelting) or slag composition (e.g., high-silica slag), such as adjusting the micron powder ratio or adding anti-slag agents to improve compatibility.
Disadvantages:
Initial strength development depends on the drying and sintering process: Improper operation may lead to cracking or insufficient strength.
Higher cost: Raw material and additive prices are higher than ordinary bricks, but long-term maintenance costs are reduced.
In international applications, European aluminum plants widely use LCC for reverberatory furnace working linings, combining innovation to reduce carbon emissions and energy consumption.
Differences and Comparisons Between Refractory Bricks and Low-Cement Refractories (LCCs)
The core differences between refractory bricks and LCCs in the working lining of aluminum melting furnaces lie in their molding methods, performance adaptability, and application scenarios. The following comparisons are made from multiple dimensions:
Molding and Construction:
Refractory Bricks: Pre-formed blocks, requiring manual installation, resulting in a long construction period (several days) and a tendency to develop joints.
LCCs: Cast in-situ, seamless monolithic structure, rapid construction (several hours), suitable for complex furnace types.
Performance Parameters:
- Mechanical Strength: Bricks have higher strength (compressive strength > 50 MPa), but LCCs retain strength better after thermal shock.
- Corrosion Resistance and Non-Wetting Properties: LCCs are superior through additive optimization, reducing aluminum penetration; bricks rely on the base material and are prone to failure at joints.
- Thermal Shock Stability: LCCs offer better resistance due to their low porosity and micro-powder structure, while bricks are more prone to cracking.
- Thermal Conductivity and Energy Saving: LCCs have lower thermal conductivity, resulting in significant energy savings.
Economy and Lifespan:
- Initial Cost: Bricks have lower initial costs but require frequent maintenance; LCC has higher initial costs but longer lifespan and lower overall costs (LCC shows energy savings of 20-30%).
In aluminum melting furnace linings, low cement refractory castables exhibit superior overall performance compared to refractory bricks, particularly in thermal shock resistance, corrosion resistance, and construction efficiency. User observations are accurate: The flexibility of LCC allows for formulation optimization based on smelting scenarios (e.g., temperature gradients) and slag composition (e.g., alkali metal content), achieving greater adaptability. However, selection requires consideration of furnace size, budget, and operating conditions; for small furnaces or cost-sensitive scenarios, refractory bricks still hold advantages. Aluminum industry companies are advised to prioritize LCC for improved efficiency and validate specific formulations through laboratory testing. In the future, with the development of nano-additives, LCC will dominate the global aluminum smelting industry.
