Refractory bricks are some raw materials fired through a certain production process, mainly through five steps.
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1. Preparation of clay clinker: Clay clinker is a barren raw material, which acts as a skeleton in refractory bricks. Clay clinker is made by calcining hard clay in a rotary kiln: or soft clay is pre-made into pellets and blocks, and then calcined.
2. Selection of binding clay and other binders: The basic requirements for binding clay should be high plasticity, low sinterability, and good fire resistance. According to the characteristics and technological process of raw materials in our country, semi-soft clay is usually mixed with soft clay, and semi-soft clay is the main compound ingredient.
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3. Preparation of mud: The ratio of clinker and bonded clay should be determined by many factors such as the quality requirements of refractory bricks, the shape and size and the molding method of the green body. For some large-scale refractory brick products, in order to reduce the accumulation of firing shrinkage and maintain good external dimensions, the amount of clinker is appropriately increased in the ingredients. The particle composition of clay refractory bricks generally has more coarse and fine particles and less medium particles, which not only ensures the density and strength of the refractory brick, but also improves the thermal shock stability of the refractory brick. At the same time, the particle size of the refractory bricks should be adjusted and corrected according to the size and surface quality requirements of the refractory bricks. When the materials are mixed, the coarse particles of clinker are generally added first, then the raw material slurry is added, and then the fine clinker powder and combined clay are added.
4. Forming and drying: Clay refractory bricks are generally pressed and formed by semi-dry molding method. Therefore, the billet has low water content. If the firing kiln has a drying section, it can be directly fired into the kiln without pre-drying.
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5. Firing: During the firing process of clay refractory bricks, the bricks are sintered by a series of physical-chemical changes under high temperature and suitable atmosphere conditions. The heating characteristics of the combined clay directly affect the determination of the firing system of the product. When the combined clay is heated, a physical-chemical reaction occurs, which promotes the sintering of bricks. The greater the use of the combined clay, the lower the Al2O3 content in the clay and the higher the impurity content, the more violent the reaction, the uneven volume shrinkage and heating, and the greater the internal stress. , it is easy to cause the brick to crack during the firing stage.
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