From a chemical point of view, all elemental and compound compounds with high melting point can be used as raw materials for the production of refractory bricks at high temperatures; From a mineralogical point of view, all minerals with high refractory degree can also be used as raw materials. Therefore, the finished product is called refractory bricks, common refractory bricks have different shapes, and strange shapes can be molded through raw material deployment and mold making, but the refractory degree and shape size of the product are indicators that must be understood and valued.
1. The refractory degree of refractory bricks is a technical indicator.
For refractory bricks, the meaning of refractory is different from the melting point. The melting point is the temperature at which the crystalline phase of a pure substance is in equilibrium with its liquid phase, such as the melting point of alumina (Al2O3) is 2050, the melting point of silicon oxide (SiO2 is 1713, and the melting point of chlorite (MGO) is 2800, etc., but the general refractory material is a multiphase solid mixture composed of various minerals, not a single-phase pure substance, so there is no certain melting point, and the melting is carried out within a certain temperature range, that is, there is only a fixed starting melting temperature and a fixed melting end temperature. In this temperature range, both the liquid phase and the solid phase exist.
Refractory brick The load deformation temperature of refractory brick is an important quality index of refractory brick, because it indicates the structural strength of the product under similar conditions to its use to a certain extent. When refractory bricks are used on the supporting roof of high-temperature kilns or as pressure furnace linings, especially when all sides of the furnace are heated, if the material is heated to the degree of softening and deformation, it will cause the deformation of the kiln body, and even sinking damage, so the load softening temperature is the deformation temperature.
Second: the correctness of the shape of the refractory brick and the accuracy of the size.
The accuracy of the shape and size of the refractory bricks has a direct impact on the tightness of the kiln masonry, and the tightness of the masonry determines the service life of the masonry to a large extent. Brick joints are the weakest and most fragile parts of the masonry weight, and the density and strength of the brick joints are much smaller than those of bricks, so they are more likely to dissolve in the slag. In the thick brick joint, the adhesive material can be separated from the refractory brick it is bonded by shrinkage in the process of using the heating process, and it itself is broken into pieces and falls down, which leads to the expansion of the contact area between the slag and the gas with the same product, thereby weakening the slag removal and thermal shock stability of the whole lining, so the correct shape and accurate size of the refractory brick is also regarded as an important indicator of the quality of the product.
Generally, according to the different types of refractory bricks and different conditions of use, there are maximum limits for dimensional tolerance, twisted deformation, missing edges and corners, and cracked copper melting. The manufacture of refractory bricks with the correct shape and size, especially large shaped products, is a complex task in production. The instability of the properties of the raw materials, as well as the violation of the determined process system, such as the proportion of raw materials, particle composition, billet moisture, molding pressure, brick mold shape and size, and drying and firing system, etc., will make the shape and size of the product incorrect.
The improvement of the shape correctness and dimensional accuracy of refractory bricks is related to the following factors, such as the improvement of the process, the mechanization and automation of all parts of the process and the necessary production experience, etc., and the appearance inspection items and specifications of various refractory brick products are also clearly stipulated in the current standards.