The deformation of ceramic products is a common defect at present. Therefore, it is an important link in ceramic production to find out the causes of deformation and take corresponding technical and management measures to overcome the deformation defects. These defects are not only related to raw material formulation, molding, high temperature sintering and other processes, but also related to human operation and management. In short, the causes of deformation are complex.
1. Whether the formula design is appropriate or not is directly related to the influence of each production process on the product deformation: if too much clay material is added to the ingredients, the shrinkage is too large and uneven, causing deformation; The amount of clay material decreases and the plasticity decreases; When the flux raw material melts too much, more glass phase will be produced, with large loss on ignition and severe shrinkage, so the reduction deformation tendency is large; Increasing the content of silicon and aluminum in the reduction products can reduce the deformation of the products during baking, because the timely melting in alkaline silicate glass can increase the viscosity of the liquid phase, strengthen the ability to resist deformation during baking, and thus prevent high-temperature deformation. The increase of aluminum content in the green body provides a favorable factor for the increase of mullite content. Mullite is conducive to improving the high temperature structural strength of the reductant and reducing the deformation of the products.
2. Deformation caused by process treatment: the particle fineness of raw materials directly affects the high temperature viscosity of billets. Coarse feldspar particles are required to slow down their melting speed to avoid excessive increase of liquid phase. For kaolin, fine particles are needed to accelerate dissolution, maintain high viscosity of liquid phase and reduce deformation tendency.
3 Factors affecting the deformation during raw material grinding: the friction of the broken wall nozzle of the slurry mill makes the slurry directionally arranged. The surface layer of the slurry section has the highest degree of directional arrangement, and the order of cracking from the surface layer to the center gradually decreases. Because the directional arrangement is uneven, the density is uneven, resulting in deformation. The vacuum degree and aging time of the refined mud stick have a great influence on the strength and technological