What are the Requirements for Refractory Materials for Induction Electric Furnaces?

In any case, the selection of furnace lining materials for induction furnaces is based on the utilization and economy of the furnace.

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

Sufficient Refractoriness

The operating 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 1650℃ higher.

Good 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.

Good Chemical Stability

The chemical stability of the material is closely related to the life of the furnace lining. Furnace lining materials should not be hydrolyzed and decomposed at low temperatures, should not be easily decomposed and reduced at high temperatures, and should not easily form low melting point substances with slag during the smelting process. The furnace lining should also not easily react chemically with the molten metal and additives, and should not pollute the molten metal.

Small Thermal Expansion Coefficient

As the temperature changes, the volume of the furnace lining should be relatively stable without severe expansion and contraction.

High Mechanical Properties

Furnace lining refractory materials should be able to withstand the impact of the charge when in a low temperature state, and 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. Furnace lining refractory materials should be wear-resistant and corrosion-resistant under the long-term erosion of molten metal.

Good Insulation Performance

The furnace lining must not conduct electricity at high temperatures, otherwise it will cause leakage and short circuit, resulting in serious accidents.

Good Construction Performance

It should be easy to repair and has good sintering performance, and it is convenient to build and maintain the furnace.

Induction electric furnaces have very strict requirements for refractory materials. Almost no natural refractory materials can meet the above requirements. This requires the selection of appropriate refractory materials according to different usage conditions. At the same time, necessary synthesis and reprocessing of natural mineral resources should be carried out to make their performance meet the requirements of induction electric furnaces.