Crack Resistance of Far-infrared Honeycomb Ceramic Combustion Plates
A brief introduction to the crack resistance of far-infrared honeycomb ceramic combustion plates.
Crack Resistance of Far-infrared Honeycomb Ceramic Combustion Plates
The coefficient of thermal expansion is a key parameter determining crack resistance. A lower coefficient of thermal expansion results in smaller dimensional changes with temperature variations, lower thermal stress, and better crack resistance.
Coefficient of Thermal Expansion and Crack Resistance of Various Materials
Material | Coefficient of Thermal Expansion (×10⁻⁶/℃) | Thermal Conductivity (W/m•K) | Crack Resistance |
Cordierite | 1.5-2.5 | 1.5-2.5 | Best |
Silicon Carbide | 4.0-5.0 | 15-30 | Good |
Corundum-Mullite | 5.0-7.0 | 2.0-3.0 | Good |
Alumina (95% Ceramic) | 7.0-8.0 | 2.0-3.0 | Average |
Cordierite has the lowest thermal expansion and the best crack resistance, making it suitable for frequent start-ups and shutdowns; silicon carbide has extremely high thermal conductivity (15-30°C), allowing for rapid temperature balance and making it suitable for continuous high-temperature operations.
Cracking Mechanism and Prevention
Cracking Types | Causes | Prevention Measures |
Heating Cracking | Tensile stress caused by internal and external temperature difference | Heating rate ≤ 20℃/min |
Cooling Cracking | Surface shrinkage, internal thermal expansion | Cooling rate 50-100℃/h |
Thermal Cycling Fatigue | Alternating stress accumulation | Frequent start-stop cycles. (Selection: Cordierite) |
Rapid heating (>20℃/min) is the main cause of temperature-induced cracking; rapid cooling is more dangerous than rapid heating, and cooling should be gradual; for frequent start-stop cycles (>5 times/day), cordierite should be the preferred choice.
Structural Fit
Cordierite is preferred for large-sized slabs; leave 1-2mm expansion joints between slabs; rounded corners eliminate stress concentration.
Selection Recommendations
Working conditions | Recommended materials |
Frequent start and stop (>5 times/day) | Cordierite |
Continuous high temperature, few starts and stops | Silicon carbide |
Ultra-high temperature (>1500℃) | Alumina (temperature control required) |
Summary
Crack resistance can be categorized as follows: Cordierite (1.5-2.5) exhibits the best crack resistance and is suitable for frequent start-stop operations; silicon carbide (4.0-5.0) is suitable for high-temperature stable conditions; alumina (7.0-8.0) has poor crack resistance and requires strict temperature control.
Material selection should consider start-stop frequency, operating temperature rise rate (≤20℃/min), and expansion joints in the structure. The synergy of these three factors is key to extending the life of the combustion plate.