At present, corundum mullite brick is one of the main products of ceramic cup of blast furnace. At present, there are some quality defects in the performance of this product, which is mainly reflected in the serious phenomenon that the edge and Angle of the product are missing in the grinding process, which affects the quality of the product. Through the improvement of the project, the quality of the product can be guaranteed to increase by 2%, can successfully pass the quality acceptance of customers, improve the quality reputation, and further increase the market share of the product.
1. Analyze the reasons
The phenomenon of missing edges and falling corners in the grinding process of corundum mullite brick is relatively serious. The reasons are as follows:
1. Hardness. Hardness is generally regarded as an important index to measure the wear resistance of materials. The harder the material is, the better its wear resistance will be. However, in the case of great impact wear, the influence of hardness is not necessarily very great. Refractory bricks are heterogeneous, and the hardness of each part may be different. For the refractory brick containing corundum and silicon carbide, if the binding strength is enough, when the hardness of the easy to wear materials wear, these high hardness materials can still resist the wear of the refractory brick.
2, crystal structure and crystal miscibility. Materials with a certain crystal structure have better wear resistance, such as cobalt with a dense hexagonal structure of small friction coefficient, wear resistance. The wear resistance between metals with poor miscibility in metallurgy is good.
3. Intensity. The use of firebrick will encounter a lot of impact wear, therefore, high strength firebrick wear resistance ability is strong.
4. Volume density. The refractory brick with high volume density and low apparent porosity has high abrasion resistance.
5. Temperature. Temperature has an effect on hardness, miscibility and reactivity of the material, so it indirectly affects the wear resistance of firebrick. Generally, miscibility and reactivity increase with increasing temperature. Firebricks are used at high temperatures, where wear resistance is important.
6. Atmosphere. Similar to the effect of temperature, atmosphere affects the miscibility and reactivity between materials, and thus their wear resistance.
2. Technical key and project implementation content
In view of the above factors, the product formulation system is reformed: in the production process of the product, through reasonable particle gradation and high-quality aggregate selection and use, improve the density of the brick; Optimize and improve the firing temperature, improve the physical and chemical properties and wear strength of the product, and ensure the quality of the product’s later grinding processing, so as to ensure the improvement of the quality of the product’s premasonry.
1) The use of high-quality raw materials: good quality bauxite grade raw materials and brown corundum raw materials composite as aggregate use, to ensure the high hardness of materials, increase the toughness of refractory materials, and will not increase the cost.
2) Increase the proportion of brown corundum fine powder in the matrix fine powder, and increase the alumina fine powder to reduce the porosity of the product after firing and increase the density of the product.
3) Change the traditional product coding method, increase the intake hole of kiln car palletizing, so that the firing temperature is more uniform.
4) Increase the sintering temperature of the product, so that the product is fully sintered and the internal material is fully miscible.
3. Project implementation plan
(1) Combined with the performance requirements of the product, raw materials with high body density and hardness are selected, and finally the raw material combination of brown corundum and bauxite is selected. Brown corundum is used as the skeleton in terms of hardness, providing high strength for the product. Bauxite is slightly inferior to brown corundum in terms of hardness, but it has toughness and can be wrapped in brown corundum at slightly lower firing temperature. Combined use can meet the product performance and economic indicators.
(2) Combined with the original formula structure, a small amount of bauxite combined with brown corundum, coupled with mullite raw materials and alumina micro-powder, to form high pressure brick billet (improve the body density of the brick billet), forming a highly polymerization billet body, changing the traditional way of yard kiln, increasing the width of the hand seam, improving the temperature homogenization performance of the kiln car, determining the appropriate firing temperature, so that the product internal raw material miscibility, The effect of tight binding and small porosity.
4. Technical summary
The first stage: the selection of raw materials into the factory: through the investigation of many brown corundum raw materials and bauxite raw materials, the project team’s technical staff research and discussion, finally decided to use Dengfeng brown corundum and Shanxi bauxite, the indicators are as follows:
The second stage: further optimize the proportion of corundum mullite product formula, and carry out several experiments to determine the palletizing method and firing temperature. The ratio of aggregate and powder was adjusted by using the principle of compact packing of particles. At the same time, the ratio of brown corundum particles and bauxite particles is adjusted in a variety of proportions, and the ratio of 2:1 is finally determined to achieve the effect of compact packing, and can play the role of miscible encapsulation. Adding alumina powder 2a% to the matrix fine powder can reduce the porosity while increasing the content of aluminum. A 630-ton press is used to press molding under heavy pressure to improve the body density of the brick (from 3.1 to 3.15), widen the manual seam of the brick in yard kiln (increase the width by 5mm) and increase the kiln car fire channel, and improve the firing temperature of the product (increase by 40℃), so that the product can be fully fused and the internal structure is dense.
The third stage: trial production of multiple batches of deployment scheme, and finally obtain a stable production scheme