Calculation of heating current of silicon carbide rod

Calculation of heating current of silicon carbide rod

The surface load density of the silicon carbon rod refers to the electric power that the unit surface area of the heat-generating part of the rod bears in use, that is, the surface load

Under the same conditions of the furnace temperature, the unit surface load density of the rod is large, and the service life of the rod is short, so avoid overloading. The load density has the following relationship with the furnace temperature and the surface temperature of the rod:

Correct selection of surface load density is an important way to rationally use silicon carbon rods to extend the life of the rod. The following is a reference value of the maximum surface load density allowed for the rod at different furnace temperatures for the silicon carbide rod at the nominal surface temperature.

2. Selection of silicon carbon rod specifications and calculation of required counts:

The selection of silicon carbon rod specifications should mainly meet the requirements of electric furnace structure size, furnace power, furnace temperature and temperature field distribution, etc., paying attention to external wiring and power regulation. The required number of silicon carbon rods can be calculated by the following calculations: After the specifications are determined, the load power per rod is:

P1=F*W (Watts)

F-surface area per rod heat (Cm2)

W-The allowable load density (W/Cm2) of the heating part under the calculation of the furnace temperature

Need count:

P --- furnace power

U --- series branch terminal voltage (volts) u --- voltage per volt (volts)

The voltage that each rod is subjected to:

R-single rod nominal resistance value.

3. Selection of power supply equipment and connection method of silicon carbon rod:

The power supply equipment is preferably a device with a large voltage regulation range that can be smoothly and continuously regulated, such as a magnetic regulator, a thyristor AC/DC voltage regulator, and the like. If a step-regulating transformer is selected, a transformer with a small voltage difference and a large number of voltage-regulating blocks should also be used. The connection mode of the silicon carbon rod components can be combined and used in parallel. When used in series, the number of branches in series should not exceed 3.

5, silicon carbon rod use maintenance precautions

1. Before installing the silicon carbon rod, check the resistance (Ω) value marked on the cold end. If the writing is unclear, it must be retested. The test method is to measure the voltage when the silicon carbon rod is heated and heated to a high temperature of 1050 °C. , current, the resistance obtained by Ohm's law, the test principle is shown in the figure below.

2. When using silicon carbide rods, each set of rods should be subjected to high temperature resistance resistance. The allowable difference of resistance values is: ≥ φ12mm rod resistance, resistance value tolerance is ≤ 0.2Ω, ≤ φ8mm rod resistance, resistance value The tolerance is ≤0.5Ω.

3. When the rod passes through the rod holes on both sides (or up and down) of the furnace wall, it should be freely rotated 360 degrees to prevent forced installation and knocking. The rod can be tested with the rod diameter before loading.

4, the use of silicon carbon rods must be equipped with voltage regulators or thyristor regulators and voltage, ammeter and temperature automatic control instruments. In the process of use, due to rod oxidation, the resistance is gradually increased. In order to keep the furnace temperature normal, the use voltage should be increased. When the voltage is raised to the highest limit of the voltage used, the wiring can be changed. .

5. When the new furnace starts to send power, in order to prevent the broken rod, it should be used for 1/2 of the rated power of the electric furnace for a period of time. After all the normal, the voltage is gradually increased, and the temperature should be raised according to the heating method of the electric furnace to avoid the explosion due to excessive power. Broken silicon carbon rod.

6. New furnaces or long-used electric furnaces (kiln) must be oven (kiln) before use, and old rods or other heat sources should be used as much as possible in the oven (kiln).

7. It is strictly forbidden to use the silicon carbon rods for overload. If the rods are broken or the rods are unevenly heated, and the parts are incandescent or dark red for a period of time, this indicates that the rods are inconsistent in aging, and the resistance difference between the sections is too large. For repair and replacement, it is best to replace all new rods. For example, when replacing some new rods or single rods, the new rod resistance and the resistance of the used rods are not suitable, resulting in unbalanced load and uneven furnace temperature. Because of the large difference in resistance, the high and low temperature of the bar is also related, which will seriously affect the service life.

8. If the device or material factory is fired, the water is discharged during the heating process. The resistance furnace (kiln) should have a vent hole to eliminate the moisture or other exhaust gas in the furnace (kiln) to avoid affecting the rod. Service life.

9, the rod storage process, pay attention to moisture. If it is found that the aluminum spray at the end of the rod is metamorphosed, the aluminum can be re-sprayed after surface treatment. If there is no aluminum spray condition, you can wrap several layers of aluminum foil in the aluminum spray section.

10, silicon carbon rod is hard and brittle, be careful when transporting, unpacking, installation and replacement. Take it lightly, gently, and guard against mechanical knocking to avoid breaking the stick.

 

Superbheater specializing in the production of silicon carbide heating for many years.The silicon carbide is use for Electronics, magnetic materials, tantalum smelting, porcelain, glass, porcelain, semiconductor, dissection test.