- Time:Dec 14, 2022
refractory materials in the process of use, subject to high temperature (generally 1000-1800 ℃) under the physical, chemical, mechanical and other effects, easy to melt and soften, or be melt abrasion, or produce crumbling damage and other phenomena. Therefore, refractory materials are required to have the ability to adapt to the nature of various operating conditions.
1. Refractoriness
Fire resistance refers to the temperature at which a material reaches a specific degree of softening under the action of high temperature, characterizing the performance of the material against the action of high temperature. Fire resistance is the basis for determining whether a material can be used as a refractory material. It is different from the melting point of the material, and is a comprehensive performance of the mixture of various minerals composed of multiphase solids.
The most fundamental factor that determines the refractoriness is the chemical mineral composition of the material and its distribution. Various impurity components, especially those with strong solvent effects, can seriously reduce the refractoriness of the material. Therefore, appropriate measures should be considered in the production process to ensure and improve the purity of raw materials.
2. High temperature load deformation temperature
The high temperature load deformation temperature, also known as the refractory load softening point or refractory load deformation temperature, indicates the resistance of a refractory to the combined action of high temperature and load under a constant load or the temperature range at which a refractory exhibits significant plastic deformation. The load softening temperature of a refractory material can be inferred from its maximum use temperature. The load softening temperature indicates to some extent the structural strength of the refractory material under similar conditions of its use and can be used as a basis for determining the maximum use temperature of the refractory material.
The main factor that determines the load softening temperature is the chemical mineral composition of the material, but also directly related to the production process of the material. The firing temperature of the material has a great influence on the load softening and deformation temperature. If the firing temperature is increased appropriately, the starting deformation temperature will be increased due to the reduction of porosity, crystal growth and good bonding. Improve the purity of raw materials, reduce the content of low-melting substances or solvents, will improve the load softening deformation temperature.
3. High temperature volume stability
Refractory materials for a long time in the role of high temperature, volume expansion, called residual expansion. The size of the residual expansion (deformation) of refractory materials reflects the high temperature volume stability, the smaller the residual deformation, the better the volume stability; conversely, the worse the volume stability, the more likely to cause masonry deformation or damage. Commonly used to judge the high temperature volume stability of the material by the change of re-burning line.
Most refractory materials will shrink under the action of high temperature, mainly because the liquid phase produced by the material at high temperature will fill the pores in it, making the particles further tighten and draw closer, and recrystallization occurs, which leads to further densification of the material. There are also a few materials that swell when refired, such as silica bricks that swell due to the polycrystalline transformation that accompanies them in use. In order to reduce the shrinkage and expansion of the material refired, it is effective to appropriately increase the firing temperature and extend the holding time, but it should not be too high, otherwise it will cause the material tissue vitrification and reduce the thermal shock stability.
4. Thermal shock stability
Refractory material resistance to rapid changes in temperature without damage to the performance is called thermal shock stability. This performance is also known as thermal shock resistance or rapid temperature change resistance.
The main factors affecting the index of thermal shock stability of materials are the physical properties of materials, such as thermal expansion, thermal conductivity, etc. Generally speaking, the greater the linear expansion 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 organization of the refractory material, particle composition and the shape of the material have an impact on the thermal shock stability.
ZHENJIN REFRACTORIES is a manufacturing enterprise integrating R&D, production, sales, international trade and technical service, which is dedicated to providing refractory products, construction and installation and other personalized services in cement, lime, non-ferrous smelting, steel, glass and chemical industries. The series of refractory materials produced have created a number of safety use records in the cement industry and have been widely recognized by well-known cement groups in China, and the products have won the trust and praise of users for their stable performance, excellent quality and exquisite workmanship.
