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Sunrise Refractory teaches you how to solve the insufficient bulk density of non-shrinkage fused bricks

The fused α-β corundum brick is made of high-purity alumina above alumina) and a small amount of admixtures. After mixing, it is poured into a three-phase electric arc furnace. After high temperature melting above 2300 ° C, it is cast into a special mold and then carried out. After the heat-annealing, it is taken out, and the rough bricks that have been taken out have been precisely cold-processed, pre-assembled, and inspected to become fused bricks that meet customer needs. The following describes how to solve the problem of insufficient bulk density of non-shrinkage fused bricks.
Non-shrinkage products are one of the varieties of fused α-β corundum bricks, which have large brick shapes and are mostly used in key parts such as pool walls. Bulk density is an important quality indicator. Insufficient bulk density means that the product is unqualified. In the initial stage of production, the rejection rate due to insufficient bulk density is almost less than 50% of similar products. In order to solve this problem, we take a holistic view and start with the details. We have carried out a lot of experiments in mold design, electric furnace melting, heat preservation, chemical composition, etc., and finally solved the problem.
1.Improvement of mold design method
It is found through experiments that there are imperfections in the mold design method. The main manifestation is that the fused corundum brick does not form a reasonable temperature gradient when cooling, which causes the product to not have dense internal crystals. Therefore, a new mold design method is adopted. The focus is on forming a reasonable temperature gradient so that the product is layer by layer in order during rapid cooling. cool down.
2. Improvement of electric furnace melting
Melting is the key to fused refractory materials. Improving the quality of melting has a very important role in improving the intrinsic quality of the product. By referring to the melting of AZS brick products, the melting method has been improved, which has greatly improved the melting quality of electric furnaces. The intrinsic quality of the product has been significantly improved. According to statistics, the bulk density of the product after the electric furnace melting is improved by more than 10%.
3. Selection of insulation materials
Due to the natural annealing method in the insulation box, the insulation material has an important effect on the cooling rate of the product. The purity of the insulation materials used at the beginning is not enough, and the thermal conductivity is too high, which causes a large temperature difference during the insulation process. This is fatal to the cooling of the product, not only will it cause cracks in the product, but it will also loose the internal tissues, which will cause a bad bulk density Impact. In order to solve this problem, a new type of excellent thermal insulation material imported from Japan was selected, which not only greatly reduced the cracks of the product, but also greatly improved the density of the internal tissue.
4.Control of chemical composition
Because the chemical composition of fused α-β corundum bricks is relatively single, aluminum oxide and sodium oxide, the content of sodium oxide has a significant influence on the ratio of α-Al2O3 and β-Al2O3 content in the product, while α-Al2O3 and β-Al2O3 The specific gravity is different. Therefore, controlling the content of sodium oxide can increase the ratio of α-Al2O3 from several phases in the product and increase the bulk density of the product.
Through the improvement of the above 4 aspects, the problem of insufficient bulk density was finally solved, and the waste rate caused by insufficient bulk density was reduced to less than 5%.

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