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Audited Supplier | SiC heating element is a type of non-metal high temperature resistances heating elements. The elements are made from fine quality a-SiC as its main raw material. The raw material is first made first in to a blank, followed by high temperature silication and recrystallization, and becomes high quality tube shaped heating elements. Compared with metal electric heating material, this type of non-metal elements is featured of high operation temperature, anti-oxidization, long service life, little deformation, easy installation and maintenance. Because of these advantages, SiC heating elements is widely used in various industries that require high temperature electric furnaces and heating devices. These typical applications include electronics, magnetic materials, powder metallurgy, ceramics, glass, metallurgy and machinery. SiC heating elements have excellent specific rate of heat zone resistance and cold end resistance, saving energy, long life, avoiding over-temperature of cold ends damaging furnace body. |
| Density: 2.5 +/-0.1 g/cm3 Bending strength: 50 +/-10 Mpa at 20C Porosity rate: 23 +/-2 % Specific heat: 1.0 kj/kg.C at 20C~1300C Heat conductivity: 14~19 W/m.C at 1000C Linear expansion coefficient: 4.5 x 10^-6/C |
| 1. Antioxidant property of elements The element start to being oxidized when heat to 800? in air; a SiO2 protect film will be generated in surface of hot zone when temperature get to 1000~1300?; cristobalite will be crystallized at 1300?; the protect film get to a certain thickness when the temperature get to 1500? which make the oxidation speed being very slowly to stable. If continue to heat to over 1627?, the protect film will be damaged and oxidation speed will be more rapid evidently and make the element damaged earlier. Thought the element will be oxidized very slowly in course of application, it also will make the resistance increased following long time application, this phenomenon calls ?ageing?. In order to lower the ageing speed, we use special technology to spread a protect film on the surface of hot zone in the course of production, which enhance the Antioxidant property of element evidently and lengthen the service life. 2. The effects of alkali and alkaline metal oxide to elements The alkali & alkaline metal oxide will react with SiC at about 1300? and generate silicate, which calls alkali-chemical corrosion, and can influence the glowing of element. 3. Some metals, such as cobalt, nickel, chrome and so on, can corrade the element in high temperature melting state and affect the service life of element. |
| Related Keywords: SiC heating elements , SiC heater |
| SiC heating element has rather large specific resistance. When it is heated in air and the surface temperature of the heat-generating part reaches 1050C, Its resistance rate is 600~ 1400?m2/m. Its resistance value changes as the temperature rises. Room-temperature below 800C is negative value, over 800C is positive value nature curve. |
| Related Keywords: SiC heating elements |
| It is the key factor to the optimum service life of the element that correctly select from the surface load of the element according to the furnace construction, atmosphere and temperature. Left figure shows the relation between furnace temperatures, element temperature and element surface load under the condition that the element radiation isn't obstructed. Recommend surface load: Furnace Temp 1100?: Surface load <17 W/cm2;** Furnace Temp 1200?: Surface load <13 W/cm2;** Furnace Temp 1300?: Surface load <9 W/cm2;** Furnace Temp 1350?: Surface load <7 W/cm2;** Furnace Temp 1400?: Surface load <5 W/cm2;** Furnace Temp 1450?: Surface load <4 W/cm2.*** |
| Reference data for the design of batch-type SiC heating element electric furnace. ***** 1. Heating power (KW) =weight of the object to be heated (kg) specific heat of the object to be heated temperature-raising speed max furnace temp. [total heating time (hour) 860] (860 kcal=1KW). Suppose: unit heat-loss is 740 kcal/M2ohour.*** 2. Heat-loss (KW) = surface area of furnace chamber (M2) 740 860. Suppose: furnace wall thickness 10cm and furnace temperature 100 is a unit constant, then the heat accumulation quantity on the furnace chamber is 635 kcal per M2.*** 3. Heat accumulation power (KW)={[(furnace wall thickness cm 10cm) ? (max. furnace temperature 100)] 635} furnace chamber area M2( total heating time (hr) 860).*** 4. 10.4 The total power needed (KW) is the sum of the above three terms. Owning to the fact that the SiC heating element protractedly operates under high temperature, it gradually ages and its resistance value increases, power decreases. In order to adjust it to the power needed, the power of transformer should be larger than 30~50% of the total power needed.*** 5. Select SiC heating element dimensions according to furnace sizes.*** 6. After determining the max furnace temperature, calculate the power (Kw) of a single SiC rod using the way of multiplying the stipulated surface load of the Sic heating element under said furnace temperature (find it out from the above table) by the surface area of the heating part of the SiC heating element (Find it out from the product dimension.)*** 7. Total power (Kw) needed single SiC heating element power=the quantity of SiC heating element that should be installed.*** 8. Design the circuit diagram and determine the resistance of the single SiC heating element.*** 9. The distance between the heating part and the furnace wall and the object to be heated: Elements Dia 8mm - Min distance 25mm; Elements Dia 12mm - Min distance 38mm; Elements Dia 14mm - Min distance 44mm; Elements Dia 16mm - Min distance 57mm; Elements Dia 20mm - Min distance 68mm; Elements Dia 25mm - Min distance 79mm; Elements Dia 30mm - Min distance 94mm.*** 10. The diameter of the hole for heating element- inserting on the furnace wall should be 1.5 times of that of the heating element end to be installed. The space there is filled with asbestos cord or aluminum silicate fibre felt.*** 11. The central distance between two heating element- inserting holes should be 3-4 times of the diameter of the heat-generating part of the heating element. 12. In order to keep the SiC heating element and the lead wire well contacting, better wrap the Al-sprayed heating element end with 2 to 3 layers of pure Al leaf. Then mount the lead wire clamp.*** In order to save energy resources, for the thermal insulation material applied to building furnace, better select well insulated high quality light aluminum bricks and proper quantity of aluminium silicate fibre felt or bricks.***** |
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