Analysis on Several Refractories of Medium Frequency Furnace
Refractory materials with a melting point higher than 1700°C for medium frequency furnaces are roughly classified into six categories: oxides, carbides, nitrides, sulfides, borides and chemical elements according to their chemical composition.
In the medium frequency electric furnace, the chemical elements and carbides work under high temperature and oxidizing atmosphere, which are easily oxidized or dissolved in molten iron.
Silicon carbide can be used to repair the tapping trough or feeding trough of the furnace, but it cannot be used as the lining material for induction furnaces due to its electrical conductivity. Sulfides, borides, etc. can be dissolved in or chemically react with molten iron, and are reduced by iron and carbon. They are not suitable for furnace lining materials. Among nitrides, silicon nitride (Si-3N4) and aluminum nitride, although they have good oxidation resistance, peeling resistance, and are not easily corroded by molten metal, they are expensive and cannot be used in industry.
At present, the refractory materials used for medium frequency smelting furnace lining are mainly oxides. Among the 17056 kinds of oxides in nature, there are only more than 50 kinds of oxide materials with a melting point higher than 1700°C. Some of these oxides have poor chemical stability and low decomposition pressure at high temperatures, which are often reduced by the components in the molten metal. . In addition, some oxides are easy to hydrate at low temperatures, so they cannot be used as refractory materials for medium frequency furnace linings. Some medium frequency furnaces have scarce oxide resources and are expensive, such as Y3O4, HFO2, CeO2, etc., which are rarely used as furnace lining materials. Some oxides are radioactive (ThO2) or toxic (BeO) and cannot be used as furnace lining materials. Three oxides are widely used in actual production, namely silicon oxide, aluminum oxide, magnesium oxide and mixtures of these three.