Why does rapid cooling create tensile stress in a refractory lining?

Rapid cooling creates tensile stress in a refractory lining because of the differential contraction between the material's layers. When a refractory object is subjected to rapid cooling from a high temperature, the surface layers cool and contract more quickly than the interior layers.1

Because the interior remains at a higher temperature and resists this contraction, the surface layers are effectively stretched, leading to the development of tensile stress. This phenomenon is a primary cause of thermal shock, which can result in the propagation of cracks throughout the material. To mitigate this, manufacturers often adjust the microstructure of ceramic refractories—such as by incorporating specific grain sizes or porosity—to help blunt cracks and improve resistance to these thermal stresses.1