During the use of refractory materials, they are easily melted and softened by physical, chemical, mechanical and other effects at high temperature (generally 1000~1800 °C), or are eroded by erosion, or cracked and damaged, which interrupts the operation. Contaminated material. Therefore, it is required that the refractory material must have properties that can adapt to various operating conditions. The following are 4 indicators that determine the high temperature performance of refractory materials: (1) Refractoriness Refractoriness refers to the temperature at which a material reaches a specific degree of softening under the action of high temperature, and characterizes the performance of the material against high temperature action. Refractoriness is the basis for judging whether a material can be used as a refractory. The International Organization for Standardization stipulates that inorganic non-metallic materials with refractoriness above 1500 ℃ are refractory materials. It is different from the melting point of the material and is the comprehensive expression of the mixture of multiphase solids composed of various minerals. The most fundamental factor that determines the refractoriness is the chemical mineral composition and distribution of the material. Various impurity components, especially those with strong solvent effects, will seriously reduce the refractoriness of the material. Therefore, appropriate measures should be considered in the production process to ensure and improve the purity of the raw materials. Refractoriness is not an absolute physical quantity specific to a substance, but a relative technical indicator when a material reaches a specific softening degree measured under specific test conditions. The test material is made into a truncated triangular cone (referred to as a test cone) according to the prescribed method, and a standard truncated triangular cone (referred to as a standard cone) with a fixed bending temperature at a specific heating rate. Heating, and the refractoriness is determined by comparing the degree of bending of the test cone with the degree of bending of the standard cone. The lower bottom of the truncated triangular cone is 8mm long on each side, the upper bottom is 2mm on each side, and the height is 30mm. During the measurement, a liquid phase may appear in the pyramid at high temperature. As the temperature increases, the amount of liquid phase increases, the viscosity of the liquid phase decreases, and the cone softens. When the softening reaches a certain level, the cone gradually bends due to its own weight. When the test cone and the standard cone are bent at the same time until their apex is in contact with the chassis, the determined bending temperature of the standard cone shall prevail as the refractoriness of the test cone. Also known as the softening point of refractory under load or the deformation temperature of refractory under load, it indicates the resistance of refractory to the combined action of high temperature and load under constant load or the temperature range in which refractory exhibits obvious plastic deformation. The maximum service temperature of the refractory can be inferred from the softening temperature under load. The softening temperature under load represents the structural strength of the refractory under similar conditions of use, and can be used as the basis for determining the maximum service temperature of the refractory. The main factor that determines the softening temperature under load is the chemical mineral composition of the material, which is also directly related to the production process of the material. The sintering temperature of the material has a great influence on the softening deformation temperature under load. If the sintering temperature is appropriately increased, the starting deformation temperature will be increased due to the decrease of porosity, the growth of crystals, and the good bonding. Improving the purity of raw materials and reducing the content of low melt or solvent will increase the softening deformation temperature under load. For example, sodium oxide in clay bricks and alumina in silica bricks are all harmful oxides. (3) High temperature volume stability of refractory materials Under the action of high temperature for a long time, the refractory material produces volume expansion, which is called residual expansion. The size of the residual expansion (deformation) of the refractory material reflects the quality of the high temperature volume stability. The smaller the residual deformation, the better the volume stability; on the contrary, the worse the volume stability, the easier it is to cause deformation or damage of the masonry. The change of the reburning line is often used to judge the high temperature volume stability of the material, which is an important indicator for evaluating the quality of the material. Most refractory materials will shrink under the action of high temperature. During refiring, most refractory materials will shrink, mainly because the liquid phase generated by the material at high temperature will fill the pores, so that the particles are further tightened and pulled More recently, recrystallization occurred, leading to further densification of the material. There are also a few materials that expand during refiring. For example, silica brick expands due to polycrystalline transformation during use. This is because the unconverted quartz of silica brick will continue to be transformed into tridymite or square at high temperature. Quartz, which expands in volume, is about 10% unconverted in silica bricks. In order to reduce the re-firing shrinkage and expansion of the material, it is effective to appropriately increase the firing temperature and prolong the holding time, but it should not be too high, otherwise it will cause the vitrification of the material structure and reduce the thermal shock stability. Due to the expansion of quartz particles in the material during firing and use, which offsets the shrinkage of clay, the volume change of semi-silica bricks is small, and some of them are slightly expanded. (4) Thermal shock stability The ability of refractories to resist rapid changes in temperature without destruction is called thermal shock stability. This property is also known as thermal shock resistance or thermal shock resistance. The main factor affecting the thermal shock stability index of the material is the physical properties of the material, such as thermal expansion, thermal conductivity and so on. Generally speaking, the higher the linear expansion rate of the material, the worse the thermal shock stability; the higher the thermal conductivity of the material, the better the thermal shock stability. In addition, the microstructure, particle composition and shape of the refractory material all have an impact on the thermal shock stability.