How to improve the quality of high aluminum bricks during the production process?
The quality improvement of high aluminum bricks is nothing more than high-pressure molding and high-temperature sintering. However, in the production process, we must start from the source to better ensure the stable quality of the product.
1. High alumina bricks are divided into first, second and third levels
high aluminum bricks are divided into grades one, two and three. The quality classification of bricks is determined based on chemical and physical indicators. The high alumina refractory bricks currently used on the market, except for the first-grade ones, are basically made with a small amount of waste bricks and raw materials. No matter what the ratio is, you must start with the raw material matrix.
In the production process, material selection and ingredients are also very important. The selection of raw materials is the first step. Impurities must be sorted out to avoid melting holes and black spots in the refractory bricks. The next step is the forming of high alumina bricks. Generally, 90% of high alumina refractory bricks are machine-formed. Only a small number of bricks for special use parts are formed by hand or hydraulically.
2. High alumina brick forming process
The amount of water added when mixing the machine-formed high aluminum bricks is less than that of manual mixing. Generally, the raw materials with good proportions are dry-mixed first, and then water is added. The water added to the machine-formed raw materials is 6-8 %, the amount of water added for manual molding is 9-10%. Whether it is hand-formed or machine-pressed, the raw materials of high-alumina bricks must be stirred for no less than 8 minutes. In principle, it is dry mixing for 2 minutes, and then stir for about 10 minutes after adding water.
During the molding process of high aluminum bricks, they must be lightened first and then heavy to discharge the gas from the product, so that the high alumina bricks will not crack and become denser. If it is a handmade brick, you must use more vertical hammers and pressurize both sides. Allow the air in the raw materials to be fully exhausted. If the gas is not fully discharged, spalling will occur, affecting the quality of the high-alumina bricks.
3. Fired products
The next step is to bake the products. During the sintering process, careful operation is required starting from the kiln installation. The semi-finished products must be installed properly in the kiln and leave a reasonable fire path, so that the high aluminum bricks can be fully and evenly sintered. Ensure the strength of the product. During the sintering process of the products that have passed through the dryer, the sintering temperature must be determined according to the level of the raw material matrix, and the sintering must be carried out in an oxidizing atmosphere and not in a reducing atmosphere. The color of high alumina bricks sintered in a reducing atmosphere will be dark, red and white. Not the same.
4. Adjust the distribution of fire holes in the kiln during the sintering process
If the first-level high-temperature bricks are sintered, because the particle distribution and matrix are good, they need to be sintered at high temperature, and the discharge speed from the kiln will be longer than that of second-level or third-level high aluminum bricks. The kiln exit time is also a technology that must be mastered in the sintering process. All products cannot be fired at the same sintering time. The sintering and kiln exit times are determined based on the grade of raw materials.
During the sintering process, it is necessary to adjust the distribution of the fire holes in the kiln and adjust the temperature difference between the upper and lower parts of the kiln car. Of course, the kiln can also be installed densely at the top and sparsely at the bottom, which is also a method to adjust the sintering.
In short, to improve the quality of high aluminum bricks, we must start with raw materials, and then go through a series of precise operations of mixing, shaping, and firing to ensure the various indicators of high alumina bricks.
