In China’s high-temperature industries (such as glass, metallurgy, ceramics, etc.), fused cast refractory materials are widely used due to their dense structure, high temperature resistance and strong corrosion resistance.
Fused Cast Corundum Bricks (Most Widely Used High-End Fused Cast Refractories)
Fused cast corundum bricks are made from high-purity alumina (with Al2O3 content ≥ 90%, and over 99% for high-end products) as raw material. They undergo melting in an electric arc furnace at 1900~2200℃ followed by casting and shaping. With α- Al2O3 as the main crystalline phase, they serve as core “corrosion-resistant refractory materials” in high-temperature industries.
Core Characteristics of Fused Cast Corundum Brick
- Extreme Density and Corrosion Resistance: They have a bulk density of 2.9~3.8 g/cm3 and an apparent porosity of ≤ 2%, leaving almost no penetration channels. They can resist erosion by strong acid/alkaline slags (e.g., alkaline slags in the iron and steel industry, Na2O-containing glass melts in the glass industry) and molten metals (e.g., molten aluminum, molten copper).
- Ultra-High High-Temp Strength: Their compressive strength remains ≥ 80 MPa at 1600℃. They are less prone to creep (deformation) at high temperatures and maintain good dimensional stability during long-term use.
- Strong Chemical Stability: Except for hydrofluoric acid (HF), they hardly react with other industrial media, making them suitable for highly corrosive environments.
- Domestic Technological Advantages: Domestic manufacturers have achieved mass production of high-purity fused cast corundum bricks (with 99.5% Al₂O₃ content). These bricks are more cost-effective than imported ones and can be customized into large-sized products (with a single brick weight exceeding 500 kg).
Main Applications of Fused Cast Corundum Brick
Metallurgical Industry:
- Used as the hearth and wall lining of electric steelmaking furnaces (to resist erosion by molten steel and alkaline slags).
- Used as the side lining of aluminum electrolysis cells (to resist corrosion by molten aluminum and electrolytes).
- Used as the lining of copper smelting converters (to withstand scouring by molten copper).
Glass Industry:
- Used in the runners and feeders of melting furnaces for specialty glasses (e.g., photovoltaic glass, electronic glass) to prevent contamination of glass melts and ensure glass purity.
Other Fields:
- Used in the high-temperature section of ceramic roller kilns (to support roller bars and resist erosion by ceramic glazes).
- Used in the secondary combustion chamber of waste incinerators (to withstand high-temperature flue gases and acidic corrosion).
Zirconia-Corundum Bricks (Fused AZS Brick, Specialized Fused Cast Bricks for the Glass Industry, Core Consumables in Glass Kilns)
Zirconia-corundum bricks are formed by the composite melting of alumina (Al2O3) and zirconia (ZrO2, with a content of 10%~40%). Their main crystalline phases are α-Al2O3 and zircon (ZrSiO4), making them the “standard material” for parts of domestic glass melting furnaces that are in direct contact with glass melts.
Core Characteristics of Fused AZS Brick
- Targeted Resistance to Glass Melt Erosion: ZrO2 can react with SiO2 in glass melts to form a stable zircon protective layer, which prevents glass melts from penetrating into the brick. Particularly for alkali-containing glasses (e.g., daily-use glass, photovoltaic glass), their erosion resistance is far superior to that of other fused cast bricks.
- Excellent Thermal Shock Resistance: During heating and cooling, ZrO2 undergoes “crystalline phase transformation” (with slight volume expansion), which offsets the thermal stress of the brick. It can withstand 15~20 cycles of water cooling at 1000℃ without spalling, making it suitable for glass kiln scenarios with “frequent start-stop operations or temperature fluctuations”.
- Strong Adaptability to Domestic Needs: Domestic manufacturers can adjust the ZrO2 content according to the type of glass (e.g., photovoltaic glass, pharmaceutical glass). For example, 25% ZrO2 is used in ordinary glass kilns, and 40% ZrO2 in special glass kilns, to meet the needs of different glass factories.
- Good Structural Uniformity: Domestic production adopts the “gradient cooling process”, which reduces internal stress during casting and avoids subsequent cracking of the brick.
Main Applications of Fused AZS Brick
Glass Industry (Core Scenarios):
- Used as the wall and bottom lining of the melting tank in glass melting furnaces (in direct contact with glass melts, preventing kiln leakage caused by glass melt penetration).
- Used for the “arch foot” of glass kilns (the junction between the kiln roof and tank wall, withstanding high temperatures and erosion from glass melt vapor).
- Used in the “finishing tank” of photovoltaic glass melting furnaces (ensuring no bubbles in the glass melt, which requires high erosion resistance).
Other Fields:
- Used as the lining of special ceramic sintering kilns (resisting erosion from volatile oxides in ceramic green bodies).
Fused Cast Mullite Bricks (Cost-Effective Choice for Medium-High Temperature Applications)
Fused cast mullite bricks are produced using bauxite (or kaolin) as the raw material, which undergoes melting at 1800~2000℃. With mullite (3Al2O3·2SiO2, content ≥ 70%) as the main crystalline phase, they are the mainstream fused cast bricks for “medium-high temperature and moderate erosion scenarios” in China, balancing performance and cost.
Core Characteristics of Fused Cast Mullite Brick
- Balanced Performance: With an Al2O3 content of 55%~75%, they achieve a balance between high-temperature resistance (refractoriness: 1790~1850℃) and thermal shock resistance (withstanding ≥ 12 water-cooling cycles at 1400℃). They are denser than sintered mullite bricks (bulk density: 2.6~2.8 g/cm³) and 30%~50% lower in cost than fused cast corundum bricks.
- Better Thermal Shock Resistance Than Fused Cast Corundum: The thermal expansion coefficient of the mullite crystalline phase (5.0×10–⁶/℃) is lower than that of corundum (8.0×10–⁶/℃), resulting in less thermal stress at high temperatures. This makes them suitable for scenarios with large temperature fluctuations.
- Advantages of Domestic Raw Materials: The raw material (bauxite) has abundant reserves in China (e.g., Shanxi, Henan provinces). The production cycle is short (the annealing period after casting is approximately 7~10 days), ensuring stable supply and extremely high cost-effectiveness.
Main Applications of Fused Cast Mullite Brick
- Glass Industry: Used as the “upper tank wall” of ordinary float glass melting furnaces (not in direct contact with glass melts, but withstanding erosion from high-temperature flue gas and dust) and as the lining of flue ducts.
- Ceramic Industry: Used as the lining of the high-temperature section (1200~1400℃) of ceramic roller kilns and as support bricks for roller bars (resisting erosion from volatile substances in ceramic green bodies).
- Metallurgical Industry: Used in the high-temperature regenerator of hot blast stoves (1300~1500℃, requiring resistance to high temperatures and gas corrosion).
Other Fields: Used in the high-temperature flue ducts of industrial boilers (resisting flue gas scouring and acidic corrosion).
Fused Cast Magnesia Bricks (Specialized Bricks for Alkaline High-Temp Scenarios)
Fused cast magnesia bricks are manufactured using high-purity magnesite (or sea-water magnesia, with MgO content ≥ 90%) as the raw material. The raw material is melted in an electric arc furnace at 2500~2800℃ (a high-temp melting technology mastered by only a few domestic enterprises). With periclase (MgO) as the main crystalline phase, these bricks serve as core refractories for domestic alkaline high-temperature environments (such as steelmaking converters and cement kilns).
Core Characteristics of Fused Cast Magnesia Brick
- Strong Resistance to Alkaline Erosion: Periclase (MgO) is a typical alkaline mineral. It can react with alkaline slags in the iron and steel industry (containing CaO and MgO) to form stable MgO-CaO solid solutions. Instead of being eroded by alkaline slags, it even forms a “protective layer”.
- Ultra-High Refractoriness: With a refractoriness of ≥ 2800℃, they are among the fused cast bricks with the highest temperature resistance in China and can withstand short-term “ultra-high temperature shocks” (e.g., the arc high temperature of electric steelmaking furnaces).
- Domestic Technological Breakthroughs: In the past, China relied on imports for such bricks. Currently, domestic enterprises have achieved mass production of fused cast magnesia bricks with “low porosity” (≤ 3%), solving the problem of “poor thermal shock resistance” of traditional magnesia bricks. Through modification by adding Cr₂O₃, their thermal shock cycle can reach 8~12 times.
- Strong Slag Penetration Resistance: Their dense structure prevents alkaline slags from penetrating into the interior of the bricks, avoiding the shortening of kiln lining service life caused by the falling off of the “slag-eroded layer”.
Main Applications of Fused Cast Magnesia Brick
Metallurgical Industry (Core Scenarios):
- Used as the lining of alkaline steelmaking converters (to resist the scouring of high-CaO alkaline slags and molten steel. 90% of converters in large domestic steel plants adopt these bricks).
- Used in the burning zone of cement rotary kilns (to resist the alkaline erosion of cement clinker. they replace traditional sintered magnesia bricks and extend the service life of kiln linings by more than 30%).
- Used in non-ferrous metal smelting furnaces (e.g., ferronickel smelting furnaces, to withstand the erosion of high-temperature nickel slags).
Other Fields:
- Used in fly ash melting furnaces of waste incinerators (to resist the erosion of alkaline fly ash and high temperatures).
Fused Cast silica bricks (Low-cost Adaptable Material for Glass Industry)
Fused cast silica bricks are produced using natural silica sand (with SiO2 content ≥ 99.5%) as raw material, which is melted in an electric arc furnace at 1700~1900℃ (silica sand becomes glassy after melting) and then cast into shape. With amorphous silica glass as the main phase, they are the mainstream choice for “non-glass-contact parts” of domestic glass kilns.
Core Characteristics of Fused Cast silica bricks
- High SiO2 Purity: With SiO2 content ≥ 99.8%, they possess strong chemical stability and only react with strong alkalis (such as NaOH) at high temperatures, making them suitable for weakly corrosive environments like “flue gas channels” in glass kilns.
- Low Thermal Conductivity: The thermal conductivity at room temperature is only 0.6~1.0 W/(m·K), over 60% lower than that of fused cast corundum bricks. They integrate heat preservation and high-temperature resistance, which can reduce heat loss of kilns (domestic glass factories use them as flue linings, enabling 5%~8% energy consumption reduction).
- Domestic Cost Advantage: The raw material (silica sand) has abundant reserves in China (e.g., Jiangsu, Anhui provinces). The production process is simple, and the cost is only 1/5~1/3 of that of fused cast zirconia-corundum bricks.
- Good Machinability: Their glassy structure allows them to be cut into thin bricks (thickness ≤ 50mm) or special-shaped parts, adapting to the complex flue structure of glass kilns.
Main Applications of Fused Cast silica bricks
Glass Industry:
- Used as linings for flues and chimneys of glass melting furnaces (providing heat preservation and resisting flue gas corrosion).
- Used as “regenerator checker work” in glass kilns (for medium and low temperature sections, replacing sintered clay bricks to extend service life).
Other Fields:
- Used as linings for high-temperature pipelines in the chemical industry (resisting acidic flue gas corrosion).
- Used as linings for the preheating zone of ceramic kilns (providing both heat preservation and high-temperature resistance).
Summary Table of “Category-Characteristics-Applications” for Mainstream Fused Cast Refractory Bricks
| Product | Core Ingredients | Core Features | Main Applications | Industry |
| Fused Cast Corundum Brick | Al2O3≥90% | Dense strong corrosion resistance high temperature strength | Steelmaking electric furnace lining aluminum electrolytic cell photovoltaic glass flow channel | Metallurgy, Glass |
| Zircon Corundum Brick ( Fused AZS Brick) | Al2O3+ZrO2(10%~40%) | Good resistance to glass liquid corrosion and thermal shock | melting tank wall of glass melting furnace arch foot of glass kiln finishing tank of glass melting furnace | Glass (Core) |
| Fused Cast Mullite Brick | Al2O3 55%~75% | Balanced performance high cost performance better thermal shock resistance than corundum | upper tank wall of glass kiln ceramic roller kiln regenerator of hot blast stove | Glass, Ceramics, Metallurgy |
| Fused Magnesia Brick | MgO≥90% | Alkaline slag resistance extremely high refractoriness | lining of steelmaking converter burning zone of cement rotary kiln ferronickel smelting furnace | Metallurgy, Cement |
| Fused silica Brick | SiO2≥99.5% | High purity low thermal conductivity low cost | flue of glass kiln high-temp pipeline in chemical industry preheating zone of ceramic kiln | Glass, Chemical Industry, Ceramics |
Summary: Recommendations for Selection of Fused Cast Refractory Bricks
The core logic for selecting fused cast refractory materials is “scenario matching + cost optimization”:
- For strong corrosion + high-temperature scenarios (e.g., parts of glass melting furnaces in contact with glass melts) → select zirconia-corundum bricks.
- For alkaline environments (e.g., steelmaking converters, cement kilns) → select fused cast magnesia bricks.
- For high-purity + strong corrosion resistance requirements (e.g., parts in contact with molten metals in metallurgy) → select fused cast corundum bricks.
- For medium-temperature + cost-effectiveness needs (e.g., upper sections of glass kilns, ceramic kilns) → select fused cast mullite bricks.
- For heat preservation + weak corrosion scenarios (e.g., flues, preheating zones) → select fused cast silica bricks.
At present, China has achieved independent mass production of most fused cast refractory bricks. The performance of some categories (such as zirconia-corundum bricks and fused cast magnesia bricks) has reached the international advanced level, completely breaking free from dependence on imports. This provides key material support for the development of domestic high-temperature industries, especially photovoltaic glass and high-end steel industries.
