| Type: | Sic Rod |
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| Material: | Silicon Carbide |
| Form: | Tube |
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Shipping Cost:
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| Currency: | US$ |
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| Return&refunds: | You can apply for a refund up to 30 days after receipt of the products. |
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Physical
| Project | Unit | Numeric value |
| Density |
g/cm3 |
≥2.6 |
| Porosity |
% |
18-20 |
| Flexural strength |
Mpa |
≥50 |
| Hardness | Mohs |
9.8 |
| Coefficient of thermal expansion |
×10-6K-1 |
4.8 |
| Specific heat |
Cal/g•ºC |
0.183 |
| Thermal conductivity |
Calories/cm•s•ºC |
0.0365 |
|
Heat resistivity (1050ºC) |
Ω•mm2/m |
700-1500 |
|
Cold junction resistivity (20ºC) |
Ω•mm2/m |
18-24 |
| Radiance |
|
0.9 |
Chemical properties
1. Chemical composition: silicon carbon rod is a high-temperature recrystallization product of silicon carbide, which is a non-metallic high-temperature electric heating element.
The main chemical component of the heating part of silicon carbon rod
| Ingredient |
SiC |
Fe2O3 |
Al2O3 |
Si+SiO2 |
C |
| Content(%) |
≥98.5 |
≤0.5 |
≤0.2 |
≤0.4 |
≤0.3 |
2. Aging characteristics: With the increase of use time, the resistance value of silicon carbon rod gradually increases, this phenomenon is called the "normal aging" of silicon carbon rod. In the case of a voltage regulator, the resistance value of the silicon carbon rod is increased to four times the original resistance value, that is, the service life of the silicon carbon rod is considered to be end-of-life. In addition to the difference in the intrinsic quality of the electric heating element, the service life of the silicon carbide electric heating element is also affected by the use temperature of the electric heating element, the surface load density of the heating part, the surface coating, the power supply mode (intermittent and continuous use), the control mode (whether there is voltage regulation, dynamotic device), the wiring mode (series, parallel, etc.) and the atmosphere in the furnace.
3. The effect of the atmosphere in the furnace on the silicon carbon rod: the effect of dry air: the silicon carbon rod can be used for a long time in high temperature (1600 °C) and dry air, and the resistance slowly increases. Oxygen (O2) reacts with SiC at high temperatures to form silica (SiO2). Since a protective film of SiO2 is formed on the surface of the silicon carbon rod, the silicon carbon rod has strong oxidation resistance.
(2) The influence of water vapor: water vapor (H2O) undergoes a strong chemical reaction with SiC at 1100 °C to generate Si, SiO2 and C. Cracks appear on the surface of silicon carbon rods, and the resistance increases rapidly.
(3) The influence of nitrogen (N2): When the surface temperature of the silicon carbon rod reaches 1400 °C, N2 reacts with SiC to generate silicon nitride, which significantly increases the resistance value of the silicon carbon rod.
(4) The effect of hydrogen (H2): At 1250 °C, H2 reacts with SiC to form methane (CH4) and destroy SiC heating elements.
(5) The effect of ammonia (NH3): NH3 can be decomposed into N2 and H2 at high temperatures. Therefore, the use temperature should be controlled below 1250 °C.
(6) The effect of sulfur dioxide (SO2): SO2 reacts with SiC at 1300 °C, so the use temperature should be controlled below 1300 °C.
(7) The effect of chlorine (Cl2): Cl2 will react with SiC at 600 °C, and Cl2 will completely decompose the silicon carbon rod at 1200 °C.
4. SiC does not react with hydrochloric acid (HCL) and sulfuric acid (H2SO4) at high temperatures. Concentrated phosphoric acid (H3PO4) reacts with SiC at 250°C to produce oxygen (O2), methane (CH4), carbon dioxide (CO2) and silicon dioxide (SiO2). A mixture of concentrated nitric acid (HNO3) and can dissolve SiC at room temperature.
5. At 1000 °C, silicon carbon rod can chemically react with alkaline oxides, alkalis and alkaline earth metals, so the use temperature should be controlled below 1000 °C.
Electrical properties
1. The resistance value of silicon carbon rod is greatly affected by temperature, and the temperature coefficient of silicon carbon rod resistance is negative at 0-850 °C, and the temperature coefficient of silicon carbon rod resistance value above 850 °C is positive. The resistance of silicon-carbon rod calibration is the thermal resistance value measured at 1050°C ±50°C.
2. Resistance temperature characteristic curve of silicon carbon rod, and the resistance of silicon carbon rod shows a nonlinear change law with the increase of the surface temperature of the rod.
3. The wiring method of silicon carbon rod
Triangular (Δ) connection; star (Y) connection; Concatenation; Parallel connection; and tandem; Series and parallel.
4. The relationship between the surface temperature of silicon carbon rod and the increase rate of resistance:
5. The relationship between the surface temperature, furnace temperature and surface load density of silicon carbon rod δ=W/cm2.
6. The relationship between the maximum surface load density of the heating part of the electric heating element and the furnace temperature.
Notes
(1) The texture of silicon carbon rod is hard and brittle, and it is easy to break when subjected to severe vibration and impact. Therefore, extra care should be taken when transporting, and handle it with care when handling.
(2) The length of the heating part of the silicon carbon rod should be equal to the width of the furnace. If the heating part protrudes into the furnace wall, it is easy to burn the furnace wall.
(3) The length of the cold end of the silicon carbon rod should be equal to the thickness of the furnace wall plus the length of the cold end protruding from the furnace wall. Generally, the extension length of the cold end is 50~150 mm to cool the cold end and connect the fixture.
(4) The inner diameter of the furnace hole through the silicon carbon rod should be 1.4~1.6 times the outer diameter of the cold end, the furnace hole is too small or the filling in the hole is too tight, and the high temperature will hinder the free expansion and expansion of the silicon carbon rod and cause the rod to break. When installed, the silicon carbon rod should be able to rotate 360 degrees freely.
(5) The distance between the silicon carbon rod and the heated object and the furnace wall should be greater than or equal to 3 times the diameter of the heating part. The center distance between the silicon carbon rod and the silicon carbon rod should not be less than 4 times the diameter of its heating part.
(6) The cold end of the silicon carbon rod is connected with the main circuit with aluminum braid or aluminum foil. The clamp at the cold end should be clamped tightly.
(7) New furnaces or electric furnaces that have not been used for a long time should be baked before use, and 1-day rods or other heat source ovens should be used.
(8) Silicon carbon rod should be stored to prevent moisture. Because it is easy to decompose and fall off the aluminum layer of the cold end after moisture, the contact resistance between the cold end and the fixture increases, and the silicon carbon rod is easy to crack after being energized.
(9) Silicon carbon rod should be matched before use. Silicon carbon rods with the same or close resistance value are connected in a group.
(10) Equipped with a voltage regulating device for silicon carbon rods. The initial voltage of power transmission is half of its normal working voltage, and the voltage is gradually increased after a period of stability. In this way, the silicon carbon rod will not break due to a sharp temperature rise.
(11) Silicon carbon rod has a long continuous service life; Short service life without interruption.
(12) When using silicon carbon rod, choose a reasonable surface load density and use temperature. The use temperature should not be greater than 1650 °C; When used in a harmful gas environment, it is necessary to prevent the silicon carbon rod from chemically reacting with harmful gases.
(13) When replacing the silicon carbon rod, the silicon carbon rod should be selected with a silicon carbon rod close to the resistance of the silicon carbon rod running in the furnace, and replace the whole furnace silicon carbon rod if necessary, which is conducive to improving the service life of the silicon carbon rod, and the removed silicon carbon rod, if the resistance value is appropriate, can also be replaced in the middle and late stage of the electric furnace operation.
(14) Prevent silicon carbon rod from splashing on molten metal, splashing on molten metal can easily lead to broken rod.
(15) Prevent alkali, alkaline earth metals and alkaline oxides from corroding silicon carbon rods.
(16) Frequently observe whether the readings of ammeters, voltmeters and temperature gauges are normal; whether the cold end fixture is loose, oxidized and blackened, or ignited; whether the silicon-carbon rod is broken; Whether the red heat of the heating part of the silicon carbon rod is uniform.
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