The thermal shock resistance of refractory materials, also known as thermal shock stability, is a key indicator to measure whether it can maintain the integrity of its structure and performance when subjected to rapid temperature changes.
1. Influencing factors
1. Thermal expansion coefficient of materials: Refractory materials with low thermal expansion coefficients produce less thermal stress when the temperature changes suddenly. For example, cordierite refractory materials have a small thermal expansion coefficient, and the internal stress caused by volume change during thermal shock is weak, so the thermal shock resistance is excellent.
2. Elastic modulus of materials: The elastic modulus reflects the ability of materials to resist deformation. Refractory materials with small elastic modulus can buffer stress through their own deformation under the action of thermal stress. For example, after introducing an appropriate amount of additives into high-aluminum refractory materials to reduce their elastic modulus, the thermal shock resistance can be improved.
3. Thermal conductivity of materials: High thermal conductivity is conducive to rapid heat transfer, reducing temperature gradients, and thus reducing thermal stress. For example, silicon carbide refractory materials have good thermal conductivity, can quickly balance temperature differences, and show strong thermal shock resistance.
4. Microstructure of the material: The dense and uniform microstructure can disperse thermal stress, making it difficult to concentrate cracks. Magnesium refractory materials with fine pores and uniform distribution have better thermal shock resistance than similar materials with ordinary structures.
2. Test methods
1. Water quenching method: Heat the sample to a specific high temperature and keep it warm for a certain period of time, then quickly put it into cold water for cooling, and repeat the cycle until the sample shows cracking, peeling and other damage phenomena, and record the number of cycles at this time. The more cycles, the stronger the thermal shock resistance.
2. Air quenching method: Similar to the water quenching method, except that the cooling medium is replaced by air. This method is relatively mild and suitable for testing refractory materials that are sensitive to water or prone to hydration reactions in water.
3. Improvement methods
1. Optimize the raw material formula: Rationally match different raw materials and adjust the proportion of ingredients, such as adding an appropriate amount of mullite in the production of chrome corundum bricks, using the characteristics of mullite to improve the overall performance of the material and enhance thermal shock resistance.
2. Improve the preparation process: Use advanced molding processes, such as isostatic pressing, to make the internal structure of the material more dense and uniform; accurately control the sintering process parameters to avoid defects and improve thermal shock resistance.
3. Surface coating treatment: Coat a layer of low thermal expansion coefficient and high toughness coating on the surface of the refractory material. During the thermal shock process, the coating is the first to bear the thermal stress and protect the base material. For example, coating the surface of magnesium carbon bricks with ceramic coatings can effectively improve their thermal shock resistance.
The thermal shock resistance of refractory materials is crucial for their reliable application in many high-temperature industrial fields such as metallurgy, building materials, and chemical industry. Continuous in-depth research on its related characteristics and optimization methods will promote the high-quality development of the refractory industry.
HOME