technology

technology
Use note (click it to read more)

1.Check the resistance of silicon carbide heating element in the same batch before open the packing,put the closest resistance in the same phase,that will make the furnace temperature more uniform,the resistance we will write in the cold zone.

2.Because silicon carbide is a hard and brittle material,do not try to fixed when you installing it,make it can movable as possible,it means making it movable and can easy get out after you installing. The silicon carbide heating element can install with dangle or flat.

3.The silicon carbide heating element controller uses thyristor control,so the power is adjustable,the rated power of the controller should be 2-3 times higher than then rated power of the furnace,thus prolonging the silicon carbide heating element life,using it in better way.

4.Choose the reasonable wiring way depend the size and resistance of the silicon carbide heating element.

5.The new silicon carbide heating element should increase the power slowly in the heating process,make the difference between silicon carbide heating element temperature and furnace temperature is minimum,thus prolonging the silicon carbide heating element life.after install the silicon carbide heating element,the power transmission in the following manner:First put the power to 30%-40% of the design power to preheat 20 minutes -40 minutes,then increased to 60%-70% of the design power to incubation20 minutes -30 minutes,after the temperature of the silicon carbide heating element and furnace is balanced,then increase the power slowly, recorded voltage and current until the temperature reaches the desired temperature,this is the normal using voltage and current of the silicon carbide heating element,Within this current range can be set to automatic temperature control,when the resistance became large increase the voltage appropriate,to make the silicon carbide heating element to maintain stable power

6. After the furnace get ready,when the silicon carbide heating element heating us set the table as follow:When the transmission power is set to start use 40% power of normal power,heat 20 minutes,then increase the temperature to the desired temperature for 10 minutes to 30 minutes,and then set the holding time.

7.Do no just check the voltage or current in the course of using silicon carbide heating element,because when you using the resistance will became larger slowly(the voltage will be bigger and current will be smaller),when the input power is constant ,then the temperature is constant.

8.If the silicon carbide heating element is damaged after using months,do not change for new one single,change for the used silicon carbide heating element,that is because the resistance will be larger when it used,the resistance of the new one will be too small,if you use the new one the temperature will be different with the used silicon carbide heating element,so you can change the used one,that will make the resistance of the heating elements closer.if you do not have the used heating elements,please change all the heating elements to new ones,then the used one you can change when you need it.

9.The resistance will be larger when using the heating element,if the temperature can not be satisfied when the voltage reached the highest,please change the connection,such like connection in series can change to parallel,star connection change to delta connection,you should change the connection depend your controller.

10.The metal oxide and slag and other things in furnace should be cleared in time,do not store them up in furnace,in case them connect the heating element to make it damaged.

11.Continuous using will have longer life than intermittent using.

12.What you want to be heated should not have too high moisture content,in order to prevent the heating element burn-in,try to avoid direct contact with alkaline substances.

13.The temperature of silicon carbide heating element surface should not exceed 1550℃.

Coating (click it to read more)

SICTECH Silicon carbide heating element coating is a kind of synthetic film,which is coating the surface of hot zone after production silicon carbide heating element,it can extend the life of silicon carbide heating element in the special using environment,Can be separated from the gas to accelerate the aging of silicon carbide heating element,to protect the silicon carbide heating element,for more details of coating please see the following introduction:

1. T coating: this coating is using for lower oxidation rate in normal use,make the silicon carbide heating element extend working life of 30-60%.

2. D coating: this coating is using in the case of nitrogen

3. S coating: this coating is using in three phase rods(W type silicon carbide heating element) float glass

4. Q coating: this coating is using in the case of steam or hydrogen

 

Atmosphere Effect Countermeasure Recommended coat
Vapor Heater's lifespan is sometimes cut to less than one fifth of the expected lifespan under dry open-air conditions. It is important to raise the temperature after purging moisture sufficiently at a low temperature when initiating a new furnace or starting to use one after a long suspension. Q coat
Hydrogen gas the resistance increases rapidly and its mechanical strength deteriorates quickly if the temperature exceeds 1350°C in a hydrogen gas atmosphere. The service life, however, depends very much on the intensity of moisture of the gas. It is recommended that it shall be used at a temperature of less than 1300°C in the furnace chamber. It is recommended that the surface load shall be decreased as much as possible.(5W/cm2)
Nitrogen gas Nitrogen gas reacts with silicon carbide, forming silicon nitride when the temperature exceeds 1400°C, and this shortens the service life. With regard to moisture, it is the same as in the case of hydrogen. It is recommended that it shall be used at a temperature of less than 1300°C in the furnace chamber. It is recommended that the surface load shall be decreased as much as possible.(5W/cm2)。 D coat
Ammonia converted gas(H275%)、(N225%) This is the same as in the cases of hydrogen gas and nitrogen gas. It is recommended that it shall be used at a temperature of less than 1300°C in the furnace chamber. It is recommended that the surface load shall be decreased as much as possible. D coat
Decomposition reaction gas(N2、CO、CO2、H2、CH2etc.) Decomposed hydrocarbon attaches on the surface of  heating elements and may cause short-circuiting in an atmosphere including hydrocarbon. It is necessary to burn off carbon by occasionally introducing air into the furnace. The electric furnace should be designed with wide spacing between EREMA heating elements to prevent short-circuiting. D coat
Sulfur gas(S、SO2) The surface of heating elements will be damaged and resistance rapidly increases if the temperature of EREMA exceeds 1300°C. Use the  heating elements under 1300°C. D coat
Others Various substances, emitted from processed materials during calcination, including such halides as lead, antimony, alkali and alkaline earth, as well as oxides, chemical compounds thereof may occasionally stick to heating elements and corrode them. It is important to remove these beforehand from processed materials or exhaust them by installing an exhaust port. S coat
S coat
Electrical properties, chemical properties (click it to read more)

SICTECH Silicon carbide heating elements are generally subject to gradual oxidation, the formation of Silica and an increase in electric resistance, so called deterioration while in use.This oxidation reaction is shown in the following formula.

SiC  +  2O2 →  SiO2 +  CO2

Silicon carbide (SiC) reacts with oxygen (O2) in the atmosphere and the surface of the heating elements gradually oxides, forming Silica (SiO2), which is an insulator, while its amount increases. This raises electrical resistance. Oxidation occurs when the temperature reaches 800°C and is accelerated as the temperature increases. Rapid oxidation will occur in the early stage of use, but the rate of oxidation will gradually diminish. the service life limit is suggested to be when its resistance increases to about 3 times the initial resistance. (The life of LD and LS lasts until resistance reaches 2 times the original value). The reason is that, reaching an approximate threefold increase, the variation in each element's resistance becomes greater and heat distribution per one element worsens, causing inefficient temperature distribution in the furnace chamber.Also, silicon carbide heating elements, when coming to the end of their life, cause not only resistance increase but changes in apparent porosity and fracture damage by deterioration in strength, so caution must be exercised.