Do you know the requirements for induction furnace lining refractory materials?

The design of large power frequency crucible induction furnaces often starts with the selection of refractory materials and simulation tests of the furnace lining.

In any case, the selection of furnace lining materials for induction furnaces is based on the utilization and economy of the furnace. Regardless of the crucible lining of the crucible furnace or the trench lining of the trench furnace, for the sake of tight electrical coupling, the thickness of the furnace lining should be as thin as possible without affecting the service life. With such a thin furnace wall, the inner side is in direct contact with high-temperature molten metal, and the outer side is surrounded by water-cooled sensors. Its working conditions are quite harsh. For crucible-type electric furnaces, there are repeated heating and cooling, which makes the working conditions even worse.

In order to ensure the normal operation of induction electric furnaces, the following requirements are put forward for furnace lining refractory materials.

① Sufficient refractoriness. Materials with a refractoriness higher than 1580°C are called refractory materials. The working temperature of the induction furnace lining is generally lower than the temperature of the molten metal. However, based on the requirements for the life of the furnace lining, accidental or frequent overtemperature of the molten pool and molten trench must also be considered. It is often unsafe to use materials with low refractoriness and softening temperature in cast iron induction furnaces. As the lining material of cast iron induction furnace, its refractoriness should be greater than 1650~1700℃, and its softening temperature should be higher than 1650℃.

②Good thermal stability. Induction electric furnaces transfer energy by electromagnetic induction exchange. In order to ensure high electrical efficiency of the electric furnace, the thickness of the lining of the induction coil part is limited, which causes the furnace lining to work under a large radial temperature gradient. In addition, during the operation of the furnace, the temperature of the furnace lining is always changing due to the effects of feeding, tapping and even stopping the furnace. The furnace lining often cracks due to uneven heating, which reduces the service life of the furnace lining. Therefore, as a refractory material for induction furnaces, it should have excellent thermal stability.

③Good chemical stability. The chemical stability of the material is closely related to the life of the furnace lining. Furnace lining materials must not hydrolyze and decompose at low temperatures, and should not be easily decomposed and reduced at high temperatures. During the smelting process, they should not easily form low-melting-point substances with slag, and should not easily react chemically with molten metal and additives. They should not pollute molten metal and The additives produce chemical reactions and will not contaminate the molten metal.

④The thermal expansion coefficient is small. As the temperature changes, the volume should be relatively stable without violent expansion and contraction.

⑤Has high mechanical properties. It should be able to withstand the impact of the charge at low temperatures; it should be able to withstand the net pressure of molten metal and strong electromagnetic stirring when the metal is in a high-temperature molten state; it should be wear-resistant and corrosion-resistant under the long-term erosion of molten metal.

⑥Good insulation performance. The furnace lining must not conduct electricity under high temperature, otherwise it will cause leakage and short circuit, causing serious accidents.

⑦The construction performance of the material is good. It is easy to repair and has good sintering performance, and it is convenient to build and maintain the furnace.

It is not difficult to see that induction furnaces have very strict requirements for refractory materials, and almost no natural refractory materials can meet all the above requirements. This requires the selection of appropriate refractory materials according to different usage requirements. At the same time, necessary purification, synthesis and reprocessing of natural mineral resources should be carried out to make their performance meet the requirements of induction electric furnaces.