Silica-molybdenum electric heating element is a stable heat-forming element, made mainly of high-purity molybdenum disilicide. It is used at high temperatures in oxidizing environments and, due to high-temperature oxidation, a thin protective film of glassy silicon dioxide is formed on the surface of the heating element, which helps protect the element from further oxidation. Thus, this type of element at high temperatures is uniquely resistant to oxidation and is used in high-temperature electric resistance furnaces with different atmospheres at temperatures from 1300 ° C to 1700 ° C. Electric heaters reliably work in the following environments: in air, oxidizing and inert gases up to 1700 ° С, and also in reducing environments up to 1500 ° С. Here is a steady report for the Development and application of molybdenum disilicide heating element
Disilicide molybdenum electric heaters are widely used in sintering and roasting special ceramics and metal ceramics, heat treating ferrites, growing crystals, cooking special glass, that is, in the metallurgical, glass, ceramic, refractory industries, as well as in producing crystals for electronic devices, manufacturing furnaces, etc. d. It is an ideal heat-forming element in industries where products agglomerate at high temperatures. In accordance with your requirements, our company can produce heating elements in the form of U, W, I, U-rectangular shapes and others.
Compared to silicon carbide, molybdenum disilicide based heaters have several advantages:
Higher operating temperature on the active part of heaters (1650-1700 ° C) due to the formation of a protective oxide film of glassy and molybdenum oxides; the ability to quickly heat up due to the growth of electrical resistance with increasing temperature; stability of electrical resistance during the entire service life of the heaters, which allows connecting them in series and replacing failed heaters without taking into account their initial electrical resistance.
A distinctive feature of molybdenum disilicide based heaters is the ability to withstand high energy load at high temperatures, which allows concentrating a large amount of energy in a small furnace volume. The disadvantages of molybdenum disilicide heaters include low mechanical strength; low heat resistance; low initial electrical resistance, necessitating the use of powerful power equipment; high initial ductility in the temperature range of 1400-1650 ° C.
Flint-molybdenum heating elements are used at high temperatures in an oxygen-containing medium. The protective oxide film of SiO 2 formed on the surface of the working part of the heater when it is heated above 1000 ° C, especially at temperatures above 1400 ° C, due to the high density prevents the heater from further oxidation. The film is maintained at a temperature of 1650 ° C, and at a higher temperature, above 1700 ° C, it begins to melt, gathering in drops, which leads to accelerated oxidation and failure of the heater.
Dense and durable oxide film, obtained as a result of the preliminary oxidation of the cores of the working part in the manufacture of heaters, is retained on the heaters. It prevents the heater from intense oxidation when it is heated from room temperature to operating temperature. In the absence of a protective film, when such a heater is heated, its intensive oxidation and destruction take place after several hours of exposure, especially in the temperature range of 400-700 ° C.