Magnetic material furnaces require high quality of the refractory materials used. Therefore, for a long time, the refractory materials used in domestic magnetic material production plants mainly depend on imports from Japan and Germany. The price is very high. In this experiment, high-quality raw materials were selected as aggregates, and through tests of formulations and production processes, a bearing block with excellent thermal shock resistance and erosion resistance, high strength, good effect, and long service life was developed.
Selection of raw materials Taking into account the harsh conditions of the use of the bearing seats, the selection of materials in addition to the characteristics of high strength, good thermal shock resistance, strong erosion resistance, but also no pollution to the bearing core of the deflection. After repeated comparisons, the final choice of mullite) corundum is an ideal material for the development of a bearing block.
Natural mullite is rare and artificial synthesis is generally used. As mullite has good high-temperature mechanics and high-temperature thermal properties, synthetic mullite and its products have higher density and purity, lower thermal conductivity and coefficient of thermal expansion, high temperature structural strength, and high temperature creep rate. Thermal shock resistance and strong chemical corrosion, high melting point advantages. Corundum has good elasticity, high melting point, good abrasion resistance, chemical resistance and volume stability at high temperatures, high hardness and high refractoriness. In addition, the mullite crystals are generally columnar or prismatic, and the corundum crystals are generally granular. The mullite and corundum are combined in a certain proportion to form a mullite-corundum composite material. The mullite and corundum have the above-mentioned excellent properties. , And mullite) and corundum base can meet the requirements of the use of magnetic material furnace 1.
The experimentally developed refractories have mullite as the main crystalline phase, and as much as possible to generate more mullite phase in the material when designing the formulation. In addition, the selection of a reasonable particle size distribution is a crucial step.
The high-temperature mechanical properties of mullite series have been studied, and the proportions of the two crystals combined with the best mechanical properties are 75B25 and 25B75, and it is pointed out that this is due to the interweaving of the crystals with the two crystal phases at this ratio. . Therefore, in this test, the mass ratio of synthetic mullite to electrofused corundum 3B1 was used as a green body aggregate for the test. A four-level particle size grading was used to conduct a large number of experimental studies on the size and grading of aggregate particles. For comparison, the aggregates were all selected to be tested in mullite or corundum. The results show that when the mass ratio of mullite to corundum in the granular material is 3B1, the thermal shock resistance of the sample is the best. After several tests, several groups of reasonable particle gradings were obtained.
Selection of Additives and Their Additions This test uses A-Al2O3 fine powder, Suzhou earth, andalusite concentrate powder and zirconite powder as additives. Their role is as follows: Al2O3 powder can react with free SiO2 in the pedestal to form secondary mullite, thus increasing the service life of the product. This is because Mn, Zn, Fe, etc. in the ferrite will volatilize at high temperatures and react with the free SiO2 in the susceptor holder, causing the susceptor to be corroded and cracked, thus seriously affecting the service life of the product. When formulating formulations, consideration must be given to reducing the free SiO2 content to a level that is not easily reacted with the above substances. In addition, the addition of A-Al2O3 fine powder and Suzhou clay can increase the activity of the matrix raw materials, improve the forming properties of the green body, and improve the sintering reaction ability of the products.
The test shows that the residual strength retention rate of the sample after the thermal shock gradually increases with the increase of zircon powder, and decreases after exceeding 5%. Studies have shown that after adding 5% of zircon powder, after high-temperature firing, ZrSiO4 has decomposed, and reacts with alumina to form ZrO2 agglomerates and mullite, ZrO2 aggregates are evenly distributed in the matrix, interwoven in columnar Mo To the stone network structure. In this way, the dispersed distribution of ZrO2 is formed macroscopically, and a strengthening structure of the ZrO2 agglomerates is formed on the microscopic level, thereby improving the thermal shock resistance of the material.
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