Jun 06 , 2025
When it comes to industrial furnace insulation, both high-density calcium silicate boards and high-density ceramic fiber boards are excellent choices, offering distinct advantages and disadvantages depending on the specific application and operating conditions.
Here's a comparison:
Composition: Primarily composed of calcium silicate hydrates, often reinforced with fibers (such as glass fibers or carbon fibers) and other additives to enhance specific properties. The "high-density" aspect refers to a denser, more rigid structure compared to low-density calcium silicate.
· High Compressive Strength: This is a major strong point. High-density calcium silicate boards offer excellent mechanical strength, making them suitable for load-bearing applications or areas subjected to mechanical stress, impacts, or abrasion.
· Dimensional Stability: They exhibit very low shrinkage at high temperatures, maintaining their shape and structural integrity even after prolonged exposure to heat.
· Rigidity and Structural Integrity: They provide a rigid, self-supporting structure, which can simplify furnace construction and reduce the need for extensive external support.
· Non-Wetting to Molten Aluminium: Specific grades (especially carbon-fiber reinforced ones) are engineered to be non-wetting with molten non-ferrous metals like aluminium, preventing metal adhesion and contamination. This makes them ideal for direct contact applications in aluminium holding furnaces, launders, and casting components.
· Good Thermal Insulation: While typically higher in thermal conductivity than ceramic fiber boards at equivalent thicknesses, they still provide effective insulation.
· Resistance to Chemicals: Generally resistant to various chemicals, though some formulations may react in highly acidic environments.
· Easy to Machine: Can be precisely machined into complex shapes and components, offering design flexibility.
· Non-combustible and Asbestos-Free: Safe for use in high-temperature environments.
· Lower Thermal Shock Resistance: Compared to ceramic fiber boards, they are more susceptible to cracking or spalling when subjected to rapid heating and cooling cycles.
· Brittle Nature: Can be brittle and prone to chipping or breaking if handled roughly or subjected to significant impact, particularly during transportation and installation.
· Higher Density/Weight: Generally heavier than ceramic fiber boards, which can be a consideration for certain furnace designs or installation logistics.
· Moisture Absorption: Some grades can absorb moisture, requiring careful storage and gradual drying before initial firing to prevent cracking.
· Back-up insulation behind dense refractories (bricks, castables).
· Hot-face lining in aluminium holding furnaces, launders, and distribution systems (especially carbon-fiber reinforced grades).
· Furnace door insulation and other applications requiring structural support.
· Core plates, platen press insulation.
· Electrical insulation in high-temperature settings.
Composition: Manufactured from high-purity alumina-silica fibers, often vacuum-formed and treated with binders to create a rigid board. High density indicates a greater compaction of fibers, leading to improved properties.
· Excellent Thermal Shock Resistance: This is a key advantage. Ceramic fiber boards can withstand rapid and repeated heating and cooling cycles without cracking or degrading, making them suitable for batch furnaces or applications with frequent temperature fluctuations.
· Very Low Thermal Conductivity: Generally offer superior insulating properties (lower thermal conductivity) compared to calcium silicate at similar thicknesses, leading to better energy efficiency and lower heat loss.
· Lightweight: Significantly lighter than calcium silicate boards, which can reduce the overall weight of the furnace structure, simplify installation, and lower transportation costs.
· Good Chemical Resistance: Resistant to most chemical attacks, with specific grades available for different chemical environments.
· Flexible (to a degree): While rigid, they have a slight degree of flexibility compared to calcium silicate, which can be beneficial in certain applications.
· Low Heat Storage: Their low thermal mass allows for faster heating and cooling cycles, improving furnace productivity.
· Good Machinability: Can be cut and machined relatively easily.
· Lower Compressive Strength: Generally have lower mechanical strength and are less suitable for load-bearing applications or areas subjected to high mechanical stress or abrasion unless specifically engineered for high strength.
· Not Non-Wetting to Molten Metals: Standard ceramic fiber boards will be wetted by and react with molten aluminium, making them unsuitable for direct contact applications with non-ferrous metals unless specially coated or protected.
· Fiber Shedding: Some ceramic fiber products can shed fibers, which may require precautions for worker safety and air quality, especially during installation or maintenance. (Bio-soluble fiber boards are an alternative to address this concern).
· Higher Cost: Often more expensive than calcium silicate boards.
· Hot-face lining in various industrial furnaces (e.g., heat treatment furnaces, kilns) where direct molten metal contact is not an issue.
· Back-up insulation behind dense refractories.
· Furnace door linings, expansion joints, and other areas requiring thermal shock resistance.
· High-temperature gaskets and seals.
· Insulation for boiler ducts, stacks, and other hot gas handling systems.
Feature | High-Density Calcium Silicate Board | High-Density Ceramic Fiber Board |
Primary Advantage | High compressive strength, dimensional stability, non-wetting (for specific grades) | Excellent thermal shock resistance, very low thermal conductivity |
Typical Max Temp. | Up to 1000-1100°C (specific grades up to 1200°C) | Up to 1260-1600°C (depending on fiber chemistry) |
Thermal Conductivity | Good, but generally higher than ceramic fiber | Excellent, very low |
Mechanical Strength | High compressive strength, rigid | Lower compressive strength, less rigid |
Thermal Shock Resist. | Lower | Very high |
Molten Al Contact | Yes (carbon-fiber reinforced grades) | No (unless specially coated/protected) |
Weight | Heavier | Lighter |
Brittleness | More brittle, prone to chipping | Less brittle, more resilient |
Cost | Generally moderate | Generally higher |
Export to Sheets
In conclusion, the choice between high-density calcium silicate boards and high-density ceramic fiber boards for industrial furnace insulation depends heavily on the specific requirements of the application, including operating temperature, mechanical stresses, exposure to molten metals, and thermal cycling. Often, a combination of both materials is used in different layers of the furnace lining to leverage their respective strengths.
