The medium frequency furnace has the advantages of small size, light weight and high efficiency. It is a new generation of metal heating equipment. The medium frequency furnace needs refractory materials to protect the equipment during operation.
Refractory materials for medium frequency furnace lining: Acidic, neutral and alkaline refractory materials are widely used in coreless medium frequency furnaces. In cored induction furnaces, as refractory materials for medium frequency furnaces, they are used to melt gray cast iron, ductile iron, malleable cast iron, vermicular cast iron and cast iron alloys, melt carbon steel, alloy steel and high manganese steel.
What are the refractory materials for medium frequency furnace lining?
1. Acid lining, acid lining is mainly made of quartz sand, which is cheap, widely distributed, has good insulation, low construction requirements, few application defects, and relatively stable production, but quartz sand has low refractoriness and cannot meet the requirements of casting large medium frequency furnaces. Moreover, there are secondary phase changes during the heating process, poor dimensional stability, unsatisfactory chemical stability, and easy to react with slag to cause corrosion. To avoid these shortcomings, the fused quartz content is high, the silica content is greater than 99%, the refractoriness is significantly improved, close to the melting point, there is no secondary phase change when heated, the heating size does not change, and the thermal shock stability is greatly improved.
2. Neutral lining uses fused corundum as the medium frequency furnace lining. Because the melting point of white corundum is as high as 2050℃, the hardness is as high as 8 levels, it is wear-resistant, high temperature resistant, and the chemical stability is better than quartz. It is suitable for high-temperature cast steel or large furnace linings. It is characterized by large phase change and thermal expansion coefficient. In practice, adding spinel micropowder can significantly improve corrosion resistance and dimensional stability.
3. Alkaline furnace lining. The traditional alkaline furnace lining is formed by dry ramming of magnesia sand. Its advantages are high refractoriness, close to 2800℃. The disadvantages are large expansion coefficient and easy cracking. Magnesia sand furnace lining is corrosion-resistant, has a long service life, low price, and is widely used. Adding white corundum micropowder or spinel micropowder significantly improves service life.
4. Spinel lining, spinel lining is a new type of lining material, using alumina and magnesia, high temperature combustion or electric melting to pre-synthesize spinel, and then produce various particle specifications as required, as medium frequency lining, still using borax or boric acid, with white corundum lining. The advantages of magnesia lining, avoiding its disadvantages, is the development direction of large medium frequency lining and high temperature lining. Many imported lining materials belong to this type.
5. Adding ultrafine powder (mostly several microns) to traditional lining materials can improve the corrosion resistance and thermal shock stability of lining refractory materials, such as silicon micropowder, alumina micropowder, white corundum micropowder, spinel micropowder, etc.