Analysis of the causes of damage to the high-strength castables on the top of the aluminum melting furnace
1. Influence of thermal stress:
When the aluminum melting furnace is working, the temperature inside the furnace can reach 700-900℃. During the frequent heating and cooling process, the expansion and contraction of the various parts of the top castables are different, resulting in thermal stress. When the thermal stress exceeds the bearing limit of the castable, it will cause the castable to crack and peel off. For example, when the furnace is heated, the surface expands rapidly due to heat, while the internal temperature rises slowly and expands less. This internal and external expansion difference is easy to cause cracks.
2. Chemical erosion:
During the smelting process, aluminum liquid will produce some volatile substances, such as alkali metal oxides, which will react chemically with the top castable. After certain components in the castable react with alkali metal oxides, low-melting-point substances will be generated, which will reduce the high-temperature performance of the castable and accelerate its damage.
3. Mechanical impact:
When feeding into the aluminum melting furnace, the impact of the material may directly act on the furnace top castable. Especially when feeding by pneumatic conveying and other methods, the material is ejected at high speed, which has a certain impact force on the furnace top. Under long-term action, the surface of the castable will gradually wear and fall off.
4. Construction quality problems:
If the mixing is uneven during the construction of the castable, the internal distribution of the castable will be inconsistent and the performance will be unstable. In addition, loose vibration will cause more pores inside the castable, reducing its strength and corrosion resistance, and it is easy to be damaged during use. 2. Improvement measures for high-strength castables on the top of aluminum melting furnace
5. Optimize thermal system:
Develop reasonable heating and cooling curves to slow down the heating and cooling rates. For example, the heating rate is controlled at 50-80℃ per hour, and the cooling rate is controlled at 30-50℃ per hour to reduce the generation of thermal stress. At the same time, try to keep the temperature in the furnace stable and avoid large temperature fluctuations.
6. Choose anti-corrosion castables:
Choose castables containing high aluminum, corundum and other ingredients. Such castables have better resistance to chemical corrosion. High aluminum castables have a high content of alumina, which can effectively resist the erosion of aluminum liquid volatiles and increase the service life of furnace top castables.
7. Improve the feeding method: Change the pneumatic conveying to the bottom feeding or side feeding method to avoid the material directly impacting the furnace top. At the same time, set a buffer device above the feeding port, such as installing a buffer baffle, so that the material is buffered before impacting the furnace top, reducing the impact force on the furnace top castable.
8. Strictly control the construction quality:
Before construction, professional training is provided for construction personnel to ensure that they master the correct construction methods. During the construction process, the mixing is strictly carried out according to the ratio, and the mixing time is not less than the specified time to ensure uniform mixing. Use appropriate vibration equipment to ensure that the vibration is dense. The sufficient vibration can be judged by observing that there are no bubbles on the surface of the castable.
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