Now refractory bricks have been widely used in our lives, and its production process is also very cumbersome. The most important thing is that every step of production is very strict.
Introduction to the production process of refractory bricks: material selection, high temperature calcination, selection and classification, crushing and grinding, scientific batching, mixing, material trapping, strong restriction molding, static drying, high temperature firing, kiln inspection and packaging, loading and leaving factory.
The production and process of high alumina refractory bricks mainly depend on the properties of raw materials or the quality requirements of products. There are roughly three kinds of technological processes.
The production process of general high-alumina bricks, such as primary, secondary, and tertiary high-alumina bricks, and casting bricks, etc., and processes (II) and (III) are the processes for making high-quality high-alumina products. The difference between the two processes is that in the latter, part of the soft spot soil is added to the mud guessing in the form of mud. Multi-clinker high-alumina products are produced by this process, which can significantly improve the molding properties of the mud and the physical and high-temperature properties of the products.
1) Material preparation
Mainly the preparation of high-alumina clinker and the preparation of combined high-alumina. During the preparation of clinker, refractory high-alumina raw materials are calcined at high temperature into granular materials and fine powders of various levels, combined with the preparation of high-alumina, the high-alumina is coarsely crushed, dried, finely ground into powder and slurried.
2) Ingredients, mixing and molding
Using calcined refractory high-alumina clinker as barren material, with a certain proportion of combined high-alumina, the mixture is made. The proportion of mixed clinker is large, which is called multi-clinker product. This kind of crystal has high volume stability and good other properties, but requires strong molding. Multi-clinker bricks are the most widely produced and used high-alumina products.
The mixture is formed after kneading or kneading again. There are many ways of forming, but now semi-dry pressing is mostly used for multi-clinker products. The molding method and molding pressure have an effect on the fine density, structural strength and slag resistance of the brick.
3) Drying
The moisture content of high-alumina brick blanks varies according to the molding method. The semi-dry-pressed blanks have low moisture content and almost no shortening when the water evaporates. They can be quickly dried or directly loaded into the kiln. The bricks with more water can be dried by natural air drying or hot air heating in advance, and then sent to the tunnel kiln. The key factor in the drying process control is the drying speed, which should be based on the principle of ensuring that the bricks are not deformed, cracked and have a certain strength. After all, the moisture content of the bricks entering the kiln should be below 2%.
4) Firing
The purpose of sintering is to sinter the brick so that it has a certain strength in size, fineness and porosity, high mechanical strength, good volume stability and good fire resistance.
During the sintering process, a series of physical and chemical changes will occur in the matrix part of the brick, that is, the combined high alumina and clinker fine powder will undergo various reactions during the sintering process. When heated to 200-900 ℃, the brick is decomposed and dehydrated with high alumina, the volume is shortened by about 2% to 2.5%, and the impurity minerals and other organic substances are also decomposed and oxidized. When the temperature reaches above 900 °C, liquid phase and mullite crystallization begin to occur, and the volume continues to decrease. Above 1000-1100 ℃, mullite grains grow. After firing at 1350-1450 ℃, the total volume shortening rate can reach 4% to 5%. In order to complete the recrystallization and aggregate recrystallization of mullite, the firing speed should not be too fast. After sintering, proper heat preservation is required, so that the sintering process of the brick and various physical and chemical changes tend to be the same. Finally slow cooling out.
