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SiC Heating Elements
General description
The Sic electric heating element is made of high quality green silicon carbide as main material, tubular and
formed by processing of billet, high temperature, silicon re-crystallization non-metallic high temperature
electric heating element. Compared to the Sic electric heating element and the metal electric heating element,
has the characteristics of high temperature, anti-oxidation, corrosion resistance, long service life,small
deformation, convenient installation and repair. A variety of high temperature furnace so Sic electric heating
element is widely used in magnetic materials, powder metallurgy, ceramics, glass, metallurgy and machinery
industry and other electric heating equipment.We Sic heating element uses the cold end of the latest
production technology, has the quality of hot, cold end resistance ratio, energy saving, long service life, at
the same time, avoid the cold end temperature is too high to damage the furnace body.
Sic Heating Elements Product number
GD(rod) type elements
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Sic Heating Elements Key
Sic Heating Elements Physical properties
The linear expansion coefficient, heat conduction and specific heat of element will change along with temperature
change .And the relational data the follows:
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Chemical properties
High temperature oxidation resistance: Under high temperature oxidation atmosphere, a dense Shi Ying
( SiO 2 ) protective layer is formed on the surface of the element to prevent MoSi 2 from further oxidation. When
the element temperature is greater than 1700 ℃ and the SiO 2 protective layer with melting point of 1710 ℃
melts, SiO 2 melts into droplets and loses its protective effect due to surface tension. When the element is
used again in an oxidizing atmosphere, the SiO 2 protective layer is regenerated.
It must be pointed out that the components should not be used for a long time in the range of 400 -
900 ℃. Otherwise, the element will be pulverized due to the strong row oxidation at low temperature.
Sic Heating Elements Oxidation resistance
When using silicon carbide heating element to 800 ℃ begins to oxidize in air , the temperature reached 100-1200 ℃ , the
heat generated on the surface portion of the protective film layer of silicon dioxide , crystallized cristobalite 1200 ℃ when ,
in 1400 ℃ , the protection film reaches a certain thickness , so that the rate of oxidation element becomes extremely slow ,
steady.If you continue to heat up to 1527 ℃ or more, destroy the protective film received a significant increase in the rate of
oxidation , resulting in premature failure of components .Silicon carbide heating elements in the course of oxidation ,
although very slow,but still long run lead to increased resistance , a phenomenon called aging.
Resistance properties
The resistivity of MoSi2 heating elements increases rapidly with the increase of temperature. Under
normal operation, the resistance of the element generally does not change with the length of time. Therefore,
new and old components can be mixed.
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Temperature and surface load under different
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Installation of elements
1、Vertically hanging
MoSi2 heating elements is brittle at normal temperature and plastic at high temperature. Therefore, the
best installation method for U - shaped components is vertical suspension. The components are suspended
vertically on the roof by fixing clamps ( porcelain clamps ). The purpose of this installation is to avoid adding
mechanical stress to the heating end of the element, otherwise it will easily cause the element to break.
2、Element holder
The weight of the whole component is borne by the fixing clip, and the position of the component is also determined
by it. Therefore, it must be carefully installed to ensure the vertical suspension of thecomponents. In order to avoid
local overheating, the conical part at the lower end of the element must extend into the furnace.
3、 Connection strap
The connecting wires of the contact elements are made of aluminum woven tape or multi-layer aluminum foil.
Outside the clip only plays a tightening role, not to conduct electricity. The end of the wire is connected to the bus
bar. In order to prevent stress from spreading to the component, the length of the wire should be slightly larger
than the linear distance between the component and the bus bar.
The screw on the chuck should not be screwed too tightly at one time when installing the component,but tightened
again when the component rises to high temperature because the component has a certain plasticity and is not easy to
break.The temperature of the chuck part should not be higher than 200 ℃.Therefore, the contact voltage between the chuck
wire and the component should be less than 0.1V . In order to prevent radiant heat from reaching the chuck, the distance
between the lower end of the chuck and the upper end of the brick should not be less than 50 mm. In order to avoid damage,
Φ 6 / 12 mm components cannot use 170A current for a long time. φ 9 / 18 mm components cannot be used for 300 a for a
long time.
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Reference data for design of Batch-type electric furnace
1、 Heating power ( kw ) = weight of heated object ( kg ) x specific heat x heating rate of
heated object ( maximum furnace temperature / total heating time h ) / 860 ( 860 kcal =
1kw ) is set: unit heat loss is 740 kcal / m2 h.
2、Heat loss ( kw ) = furnace surface area ( ㎡ ) * 740 / 860 ( 860 kcal = 1kw )
Set: The furnace wall thickness is 10 cm, and the furnace temperature is 100 ℃ as the unit
constant. At this time, the heat storage per square meter area of the furnace is 635
kilocalories.
3、 Regenerative power ( kw ) = ( furnace wall thickness cm ÷ 10 cm ) x ( maximum furnace
temperature ÷ 100 ℃ ) x 635 x furnace surface area ÷ total heating time HR× 860 ).
The total power required ( kW ) is the sum of the first three items. As the the Silicon carbide heating element works at high
temperature for a long time, it gradually ages and increases its resistance and decreases its power. In order to adjust the
required power in time, it is advisable that the transformer power should be greater than 60 - 100 % of the
total required power.
4、After determining the maximum furnace temperature, multiply the surface area of the heating part of the selected
element ( found from the product specification table ) according to the surface load specified by the element at this furnace
temperature to obtain the power ( kW ) of the single element.
5、Total Power Required ( KW ) ÷ Single Component Power = Number of Components to
be Installed.
6、Design the circuit diagram to determine the resistance of a single component.
7、The distance between the element and the furnace wall and the object to be heated.
8、The diameter of the element insertion hole on the furnace wall shall be 1.5 times the diameter of the installed element,
and the gap shall be blocked with asbestos rope or silica fiber felt.
9、The center distance between the two component insertion holes is preferably 3 - 5 times
the component diameter.
9、In order to ensure good contact between the component and the wire clamp, it is best to coat 2 - 3 layers of pure
aluminum foil at the end of the component and then install the wire clamp.
10、In order to save energy, it is best to choose lightweight high-alumina brick and aluminum silicate fiber brick with good
thermal insulation performance as thermal insulation materials for furnace construction
Reference data for the design of Continuous type electrical furnace (practice)
1、furnace load: transformer power 230 kw / m ( furnace volume ) and maximum
production power 193 kw / m ( furnace volume ); Push board: transformer power 194
kw / m ( furnace volume ) and maximum power 160 kw / m ( furnace volume ).
2、For every m furnace volume, the surface area of the heating part where components can
be installed is 19620.7c ㎡.
3、The number of components to be installed in the electric furnace = 19620.7 ㎡. The
surface area of the single heating part of the selected component is c ㎡.
4、 Refer to batch furnace for other data and requirements.
Several power Calculation ways for wire connection common use
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Dimensions of SONG AO heating elements
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SHENZHEN SUPERB HEATER TECHNOLOGY CO.,LTD
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SHENZHEN SUPERB HEATER TECHNOLOGY CO.,LTD
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SHENZHEN SUPERB HEATER TECHNOLOGY CO.,LTD
www.superbheater.com
SHENZHEN SUPERB HEATER TECHNOLOGY CO.,LTD
www.superbheater.com
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