Improve the strength of corundum mullite bricks and improve the quality of ground brick pre-laying

At present, corundum mullite bricks are one of the main products of blast furnace ceramic cups, At present, this product still has some quality defects in terms of performance. The main performance is that the phenomenon of missing edges and corners in the grinding process of the product is more serious, which affects the product. Masonry quality. This article introduces a method to change this phenomenon. Through the improvement of the project, the product quality qualification rate can be increased by 2%, the quality acceptance rate of the customer can be passed smoothly, and the quality reputation can be improved, and the market share of the product can be further increased. .

1.Analyze the reasons

Corundum and mullite products have serious missing edges and corners during the grinding process. The analysis reasons are as follows:

1). Hardness. It is generally believed that hardness is an important indicator of the wear resistance of materials. The harder the material, the better the wear resistance, but in the case of large impact and wear, the impact of hardness is not necessarily very large. Refractory bricks are heterogeneous, and the hardness of each part may be different. For refractory bricks containing corundum and silicon carbide, if the bonding strength is sufficient, these high-hardness materials can still resist the abrasion of the refractory bricks after the wear-resistant materials with low hardness are worn.

2). The mutual solubility of crystal structure and crystal. Materials with a specific crystal structure have better wear resistance. For example, cobalt with a close-packed hexagonal structure has a small friction coefficient and is resistant to wear. The wear resistance between metals with poor mutual solubility in metallurgy is also good.

3). Strength. Refractory bricks will encounter a lot of impact wear during the use process, therefore, high-strength refractory bricks have strong abrasion resistance.

4). Bulk density. Refractory bricks with large bulk density and low apparent porosity have high abrasion resistance.

5). Temperature. Temperature has an impact on the hardness, mutual solubility and reactivity of the material, and thus indirectly affects the wear resistance of refractory bricks. Generally, as the temperature increases, the mutual solubility and reactivity increase. Refractory bricks are used at high temperatures, and the abrasion resistance at high temperatures is very important.

6). Atmosphere. Similar to the effect of temperature, the atmosphere affects the mutual solubility and reactivity between materials, thereby affecting their wear resistance.

2. Key technology and project implementation content

According to the above factors, the product formula system is modified in a targeted manner: in the production process of the product, through the selection and use of reasonable particle gradation and high-quality aggregates, the density of the bricks is increased; the firing temperature is optimized to improve the product The physical and chemical properties and abrasion resistance of the product ensure the quality of the later grinding process of the product, thereby ensuring the improvement of the quality of the product's pre-masonry.

1) Use high-quality raw materials: bauxite-grade raw materials of better quality and brown corundum raw materials are used as aggregates to ensure the high hardness of the material, increase the toughness of the refractory material without increasing the cost.

2) Increase the proportion of brown corundum fine powder in the matrix fine powder, while increasing the aluminum oxide fine powder, reduce the porosity of the product after firing, and increase the density of the product.

3) Change the traditional product stacking method and increase the air intake holes of the kiln car stacking to make the firing temperature more uniform.

4) Increase the sintering temperature of the product to make the product fully sintered, and the internal materials are fully combined and mutually soluble.

3. Project implementation plan

⑴ In combination with the performance requirements of the product, select raw materials with high body density and hardness, and finally determine that the raw material combination of brown corundum and bauxite is still selected. Brown corundum is used as the skeleton in terms of hardness to provide high strength for the product. In terms of hardness, it is slightly inferior to brown corundum, but it has toughness. It can be wrapped with brown corundum at a slightly lower firing temperature, and it can meet product performance and economic indicators when used together.

⑵Combined with the original formula structure, combined with a small amount of bauxite and brown corundum, supplemented by mullite raw materials and alumina powder, the bricks are formed under high pressure (increasing the body density of the bricks) to form a highly polymerized body. The traditional code kiln method increases the width of the hand seam, improves the temperature homogenization performance of the kiln car, determines the appropriate firing temperature, and achieves the effect of mutual dissolution of the raw materials in the product, tight bonding, and small pores.

4.Technical Summary

The first stage: Optimizing the incoming raw materials: After investigating a number of brown corundum and bauxite raw materials, and after research and discussion by the project team’s technicians, it is finally determined to use Dengfeng brown corundum and Shanxi bauxite. The indicators are as follows :

The second stage: further optimize the formula ratio of corundum and mullite products, and conduct multiple experiments to determine the stacking method and firing temperature. Using the principle of close packing of particles, adjust the ratio of aggregate and powder; at the same time, adjust the ratio of brown corundum particles and alumina particles in various proportions, and finally determine that the ratio of 2:1 achieves the effect of tight packing and can also serve as a package. The role of mutual solubility. In the matrix fine powder, 2a% alumina powder is added to increase the aluminum content while reducing pores. The 630-ton press is used for heavy pressure forming to increase the body density of the bricks (from 3.1 to 3.15), relax the hand-sewing of the brick kilns (increasing the width by 5mm) and increase the fire path of the kiln car to increase the firing temperature of the product (increase 40℃), so that the product is fully melted, and the internal structure is dense. The third stage: trial production of the multi-batch deployment plan, and finally a stable production plan.

5. Conclusions and recommendations

The current physical and chemical indicators of corundum mullite products:

Corundum and mullite products using brown corundum combined with bauxite can enhance the anti-wear performance of the product, but have a certain impact on the softening temperature of the product under high-temperature load, and the proportion of bauxite is not easy to increase. The amount of alumina powder added is sufficient to control 2a%. Too much alumina powder affects the firing temperature and also reduces the compactness of the brick body. In the matrix fine powder, it is beneficial to reduce the addition of bauxite raw materials, and the addition ratio can be reduced to 1a% to enhance the hardness of the matrix.