The main factors affect the thermal shock resistance of refractory brick is material in the heating or cooling process due to thermal stress generated by thermal expansion and contraction. In general, the greater the coefficient of thermal expansion of the material, the worse the thermal shock resistance, such as silica brick, magnesia brick and so on; the greater the thermal conductivity of the material, the better the thermal shock resistance, such as silicon carbide products, etc.
From the thermoelastic theory, the small elastic modulus of the material is, the large intensity is, the greater the thermal conductivity is, the better thermal shock resistance is. The energy theory is that when the products have a higher fracture surface energy, can improve thermal shock resistance. That is, when the article having fine pores, such products have a greater stress when the temperature changes, the more stored energy inherent, it is possible to generate fine cracks by the article, and these may lead to damage of the article energy released, can greatly improve the thermal shock resistance of products, namely intentional introduction of micro-cracks in the products, so the extent of crack propagation is minimized, it is one of the ways to improve the thermal shock resistance.
For example, Antistripping alumina bricks used for cement kiln , because add a small amount of ZrO2 in the ingredients, the changable of ZrO2 phase causes the formation of many tiny cracks within the article, when the temperature changes produce thermal stresses, these tiny cracks may cause damage to the refractory energy to be released, thereby improving the thermal shock resistance of high alumina bricks.
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