Electric silicon carbide heating elements are a popular choice of many furnace and kiln. They come in a variety of shapes, sizes and materials. One of the most common types is silicon carbide heater, known by several trade names including sic heater and sic heating elements. They are used extensively throughout the heat-treating industry when high temperatures, maximum power and heavy-duty cycles are required. For more details, please contact with STA Universe Group.
Silicon carbide heating elements is typically an extruded tubular rod or cylinder made from high-purity grains of silicon carbide that are fused together by either a reaction-bonding process or a recrystallization process at temperatures in excess of 2200°C. The result is a chemically stable material with a low thermal-expansion coefficient and little tendency to deform.
Recrystallization forms fine grains of silicon carbide that act as “bridges” or connection points between larger grains, thus forming conductive pathways. The number of bridges formed dictates the material’s resistance – the greater the number, the lower the resistance. The secret to the creation of a good silicon carbide heating elements is controlling this formation process within the material so as to develop a consistent electrical resistance.
The factors that influence the life of a silicon carbide heating elements include the type of furnace atmosphere, watt density, operating temperature, type of service, continuous or intermittent and maintenance. Furnace type, design and loading play an important role as well. Silicon carbide heating elements are extremely versatile, operating, for example, in air up to 1650°C, max temperature of surface of silicon carbide heater.
Transformers used for silicon carbide heating elements have multiple secondary taps in anticipation of a change in resistance of the elements over time. SiC heating elements, being 20–30% porous, oxidize or otherwise react with the furnace atmosphere and increase in resistance during their operational life. Oxidation causes a reduction in the cross-sectional area of the bridges, resulting in greater resistance to electrical flow. The oxygen in the air reacts with the silicon carbide grain, reducing it to silica (SiO2) as shown by the equation: SiC + 2O2 = SiO2+ CO2
It is estimated that new silicon carbide heater will increase in resistance 10–15% on startup, which should be taken into consideration when considering replacing the bars. In most cases, silicon carbide heating elements fail mechanically long before they fail due to aging.
The silicon carbide sic heating elements is widely used in following area:
GLASS: Melting, holding, refining, forming, display glass technologies, optical fiber production.
CERAMICS: Firing of ferrites, steatites, titanates, tiles, refractories, dinnerware, electrical porcelain, alumina, zirconia, calcining ores, and powders
SEMICONDUCTOR: Diffusion and LPCVD furnaces for silicon wafers
METALLURGICAL: Heat treating, forging, annealing, hardening and deoxidizing, brazing, sintering powdered metal parts, and melting
DIECASTING: Non-ferrous metals and alloys.
SOLAR ENERGY
LABORATORY, RESEARCH AND DEVELOPMENT
HEATING INDUSTRIES: With application temperatures over 540ºC.
