Why the sic heating element is broken when it is used in the high temperature furnace ?
Consider of the operation problems, usually if it is not the reason of quality and the installation of the line of sic heating element, the main reason is during the operation, the aluminum liquid splashes on the sic heater rod lead to the resistance on sic heater rod surface is uneven, which results sic heater rod is broken. In the case of the quality of sic heater rod, the main resistance is uniform, after all it is something of heating, the local resistance is low, the amperage is large, it is easy to understand wht it’s broken. In addition, we should pay attention to it and refer the following:
1. sic heater rod is hard and fragile , subject to severe vibration and impact fracture easily. Therefore, during the transportation, unpacking, installation and replacement require light take, put, to prevent mechanical beating, so as not to break the stick.
2. the length of sic heater rod should be equal to the width of the furnace. If the heat Department deep into the furnace wall, easy to burn furnace wall.
3.the length of the cold end of the silicon carbide rod should be equal to the width of the furnace wall plus the extended length of the cold end of 50 ~ 150mm, in order to cool the cold end and the connection fixture.
4. the diameter of the furnace through the sic heater rod should be 1.4 to 1.6 times the outer diameter of the cold end, the furnace hole is too small or too tight stuffing plug hole, high temperature hinders the free expansion of sic heater rod resulting in broken Baton. Installation, when the rod through the furnace wall on both sides (or up and down) after the hole, should be free to rotate 360 degrees to prevent the mandatory installation and beat, pre-installed rod diameter and can be used to test the iron pipe.
5. the distance between the sic heater rod and the object to be heated 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 carbide rod and the silicon carbide rod should not be less than 4 times the diameter of the heating part
6.the cold end of sic heater rod with the main circuit with aluminum braid or aluminum foil and cold end of the fixture to be tight.
7.Before the installation, check the resistance (Ω) value of the cold end mark. If the writing is unclear, test again. The test method is to measure the voltage when the silicon carbide rod is energized and heated to a high temperature of 1050 ℃ , Current, ohm's law for the resistance.
8. when using sic heater rod, each group of rods should be high temperature resistance with resistance. The first resistance of the same or close to the silicon carbide rods connected together with the impedance of the allowable difference is: ≥ φ12mm rod with resistance, resistance tolerance ≤ 0.2Ω, ≤ φ8mm Rod with resistance, resistance tolerance ≤ 0.5Ω.
9.the new furnace or long time not to use the furnace before use to be oven, should be used old bar or other heat source oven.
10. equipped with silicon carbon rod voltage regulator. New furnace began to send electricity, the initial transmission voltage should be half of its normal operating voltage, and then gradually increase the voltage after a period of stability. This silicon carbide rod will not be broken due to the rapid warming
11.sic heater rod continuously use is long life and intermittent service is short life
12.sic heater rod to should prevent the damp when it is storage. Because after the damp easily cold end aluminum layer decomposition, off, resulting in cold end and fixture contact resistance increases, and the silicon carbide rod is easy to crack after power; such as rod end spray aluminum metamorphosis deliquescence, after surface treatment Spray aluminum again. If no spray aluminum conditions, can be sprayed in the aluminum bar wrapped several layers of foil can be wrapped. Modification of delirium serious renewal of the bar in time to ensure the normal use.
13.when using sic heater rod to choose a reasonable surface load density and temperature. Use temperature should not exceed 1650 degrees Celsius; In the use of harmful gas environment to prevent silicon carbide rods and harmful gases chemical reaction.
14.prevent sic heater rod splashes on the molten metal, splashed on the molten metal easily lead to broken rods.
15. prevent alkali, alkaline oxide corrosion silicon carbide rod.
16.the use of sic heater rod must be configured regulator or thyristor and voltage, ammeter and automatic temperature control instrumentation. In the course of the process due to stick oxidation, the resistance value is gradually increasing, in order to maintain the normal furnace temperature, should increase the use of voltage, when the voltage to the maximum voltage can not meet the requirements, can stop the furnace to change the wiring of the rod continue use.
17. often observe the ammeter, voltmeter and thermometer readings are normal; cold end fixture is loose, oxidation black or sparking; silicon carbide rod is broken; silicon carbide heating section is uniform red fever.
18.non-use of sic heater rod overload, such as rods broken rod or found uneven fever, local was incandescent or dark red phenomenon for a period of time, indicating that the bar body is not the same aging, a segment of the resistance is too much difference, should be shut down repair change sticks, it is best to replace all the new rods, such as replacement of some new rods or single rods will be used because of resistance of the new rods and rods used to match the resistance, leading to load imbalance, uneven temperature. Due to large differences in resistance, so the bar temperature level is also related to large, will seriously affect the service life.
19. the furnace in the long run, individual sic heater rod damaged due to some reasons need to be replaced, according to the growth of resistance at that time sic heater rod, select the appropriate resistance of silicon carbon rod, can not arbitrarily take a new silicon carbon Rod replacement. If the silicon carbide rod damaged more or resistance growth is too large, can not reach the desired temperature when all the best replaced with a new silicon carbide rod. Replaced silicon carbide rod re-(with pressure gauge, ammeter) measured the resistance value, with the resistance used in the low temperature zone.
20. when fire the device or material, the water is discharged during the heating process, the furnace should have vents to exclude the furnace moisture or other harmful emissions, so as not to affect the service life of sic heater rod.