The quality improvement of high alumina bricks is nothing more than high-pressure forming and high-temperature sintering. However, in the production process, we must start from the source in order to better ensure the stable quality of the product.
High-alumina bricks are divided into one, two and three grades, and the quality classification of the bricks is determined by chemical and physical indicators. Except for the first-grade high alumina bricks currently used in the market, they are basically made with a small amount of waste bricks and raw materials. Regardless of the ratio, it must start with the raw material matrix.
In the production process, the selection of materials and ingredients is also very important. The selection of raw materials is the primary link. The impurities must be selected to avoid molten holes and black spots in the refractory bricks. Next is the forming of high-alumina bricks. Generally, 90% of high-alumina bricks are press-formed, and only a small number of bricks for special use parts are manually or hydraulically formed.
The amount of water added during the mixing of the machine compression molding is less than that of the manual water addition. Generally, the raw materials with a good ratio are first dry mixed, and then water is added. The raw materials of the machine compression molding are added with 6-8% water. The amount of water added for molding is 9-10%. The raw materials for manual or machine compression molding must be stirred for no less than 8 minutes. In principle, it is dry blended for 2 minutes, and stirred for about 10 minutes after adding water.
During the molding process, it is necessary to lighten the product first and then to discharge the gas of the product, so that no delamination occurs and the compactness is stronger. If it is a hand-made brick, you must hit more vertical hammers and pressurize on both sides. Fully exhaust the air in the raw material. If the gas is not fully discharged, spallation will occur, which will affect the quality.
Next is the sintered product. In the sintering process, the kiln must be carefully operated first. The semi-finished billets for the kiln must be properly installed in the kiln and a reasonable fire channel can be set aside so as to fully sinter and burn evenly to ensure the product strength. During the sintering process of the products that have passed through the dryer, the sintering temperature should be determined according to the level of the raw material matrix, and the sintering should be carried out in an oxidizing atmosphere. The reducing atmosphere cannot be sintered. The color of the high alumina brick sintered in the reducing atmosphere is dark, red and white. Different.
If it is to sinter the first-class high-alumina bricks, because the particle distribution and matrix are good, high-temperature sintering is necessary, and the kiln exit speed will be longer than the second or third-class high-alumina bricks. The time to leave the kiln is also a technology that must be mastered in the sintering process. It is not possible to burn all the products in the same sintering time. The sintering and kiln exit times are determined according to the grade of the raw materials.
During the sintering process, it is necessary to adjust the distribution of fire holes in the kiln, and adjust the temperature difference between the upper and lower kiln carts. Of course, the kiln can also be densely packed and the sintering method can be adjusted.
In short, to improve the quality of high alumina bricks, it is necessary to start with the raw materials and go through a series of fine operations such as mixing, forming and firing to ensure the various indicators of high alumina bricks.
