The refractory material normally used as a neutral lining is a high-alumina refractory material. It is an aluminum silicate refractory material with an Al2O3 content of more than 46%. The equilibrium phase composition of the mass fraction of Al2O3 greater than 71.8% is mullite and corundum, and the liquid phase appears at 1810 °C. Therefore, it is suitable for use as a lining.
The mass fraction of the corundum refractory Al2O3 is greater than 95%, and its crystalline form is. α-Al2O3, which is a hexagonal system, has high chemical stability, is stable in volume at high temperatures, and has a high softening point. Can be used as a lining of more than 10t.
When melting aluminum and aluminum alloy, the main cause of damage to the lining is the penetration of aluminum; the strong reduction reaction of the elements in the melt on the oxide in the lining. Common lining damage is blackening, nodules and cracking, and this reaction will increase the silicon liquid and affect the composition of the melt. Refractory materials suitable for melting aluminum and aluminum alloys must have good sintering strength, small pore diameter, low content of SiO2, Na2O, K2O, and surface and melt wetting. In addition, the lining should have good sintering properties at a temperature of 800 °C.
The aluminum-magnesium dry material is made of fused corundum as the main raw material, and an appropriate amount of MgO and an admixture are added. During the oven and operation, due to the formation of Ai-Mg·S and the structure of the admixture, it can resist the erosion of high temperature molten steel. Compared with MgO, its low thermal expansion rate, coupled with the formation of secondary spinel, can effectively prevent the occurrence of cracks.
Alumina spinel ramming material is made of high-purity electrolyzed alumina as the main raw material and blended with appropriate amount of high-purity magnesium oxide. It has excellent corrosion resistance and has a specific crystal than magnesium oxide and magnesium aluminum. Stone has a lower coefficient of thermal expansion and good thermal stability. Therefore, it is recommended for medium-frequency induction furnaces for large-scale cast steel of about 6t, and its service life can reach more than 200 heats.
