1. Porosity: refers to the percentage of pore volume in the material in the total volume of the material. The pores of SKF Bearing high temperature resistant materials can be divided into three types according to their existing forms: closed pores, one pore - pores connected with the outside atmosphere, and the proportion of connected pores - the whole pores. SKF Bearing High Temperature brick is 7L. Small SKF Bearing high temperature resistant material has the ability of corrosion resistance and structural strength; The higher the porosity, especially the more interconnected pores, the lower the thermal conductivity of the material. Lightweight adobe bricks, lightweight high alumina bricks and other insulation materials use a method to increase porosity and reduce their thermal conductivity. 2. Water absorption: the mass percentage of water absorbed by pores in the material accounts for the dry mass of the material. 3. Permeability: the permeability of SKF Bearing high temperature resistant material can be expressed by permeability coefficient, that is, the air volume of SKF in LM2 area bearing high temperature resistant material with a thickness of 1m under 1m. The differential pressure is 10 PA. For SKF Bearing high temperature resistant materials, the air permeability of the product should be as small as possible, but in special cases, a certain air permeability is required. If molten steel is purified through permeable bricks, the permeability of the product is considered to be one of the main performance indicators.