The development of medium frequency electric furnaces is closely related to the progress of refractory material technology. Design of a large power frequency crucible type electric furnace. Often, starting with the selection of refractory materials and simulation testing of furnace lining. The increase in the capacity of trench induction furnaces, the expansion of their application range (from non-ferrous metal melting to ferrous metal melting, from cast iron insulation to cast steel insulation), and the increase in the power of a single induction body were all achieved after the development of refractory materials for melting trenches and the improvement of furnace construction processes.

In any case, the selection of electric furnace materials for medium frequency electric furnaces is mainly based on the utilization rate and economy of the furnace. Whether for the crucible furnace lining or the groove furnace lining of the crucible furnace, for the sake of close electrical coupling, the thickness of the furnace lining should strive to be as thin as possible without affecting its service life. The working conditions of such a thin furnace wall, which is directly in contact with high-temperature metal liquid on the inside and surrounded by water-cooled sensors on the outside, are quite harsh. For crucible furnaces, there is also repeated heating and cooling, which makes their working conditions worse.

In order to ensure the normal operation of the medium frequency electric furnace, the charging material manufacturer has put forward the following requirements for the refractory material of the furnace lining:

1. Adequate fire resistance

Materials with a fire resistance higher than 1580 ℃ 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 service life of the furnace lining, it is also necessary to consider occasional or frequent overtemperature of the molten pool and the melting part. The use of refractory materials in cast iron induction furnaces and materials with low softening temperatures are often unstable. As an electric furnace material for steel casting induction furnaces,

Its fire resistance should be between 1650 and 1700 ℃, and its softening temperature should be higher than 1650 ℃.

2. Good thermal stability

The medium frequency electric furnace transfers energy through electromagnetic induction exchange, in order to ensure high electrical efficiency of the furnace, which makes the furnace lining work under a large radial temperature gradient. In addition, during the working process of the furnace, the temperature of the furnace lining is constantly changing due to factors such as feeding, tapping, and even furnace shutdown. The furnace lining often cracks due to uneven heating, which reduces its service life. Therefore, as a refractory material for electric furnaces, it should have excellent thermal stability.

3. Good chemical stability

The chemical stability of materials is closely related to the life of furnace lining. The lining material should not hydrolyze and differentiate at low temperatures, and should not be easily decomposed and reduced at high temperatures. During the melting process, it should not easily form low melting point substances with slag, and it should not react chemically with metal solutions and additives, and will not pollute the metal solution.

4. Low coefficient of thermal expansion

The volume should be relatively stable with temperature changes, without rapid expansion and contraction.

5. It has high mechanical properties

Be able to withstand the impact of the furnace material at low temperatures; When the metal is in a high-temperature molten state, it should be able to withstand the static pressure of the metal liquid and strong electromagnetic stirring effect; Wear resistance and corrosion resistance under long-term erosion of molten metal.

6. Good insulation performance

The furnace lining must not conduct electricity under high temperature conditions, otherwise it may cause leakage and torque, causing serious accidents.

7. The construction performance of the material is good, easy to repair and sintering performance is good, and the furnace construction and maintenance are convenient.

8. Rich resources and low prices.

It is not difficult to see that the requirements for refractory materials in induction furnaces are quite strict, and almost no natural refractory material can meet the above requirements. This requires selecting suitable refractory materials based on different usage conditions. At the same time, necessary purification, synthesis, and reprocessing should be carried out on natural mineral resources to ensure that their performance meets the various requirements of induction furnaces