When the electric furnace is working, not only the temperature in the furnace is high, the change is large, but also suffers from the strong electromagnetic stirring effect and the impact of the charge, which will lead to the furnace lining of the electric furnace is very easy to be damaged.
Therefore, the knotting quality of induction furnace lining directly determines the life of electric furnace, and ultimately affects the production capacity of the whole production line.
We have a previous article "intermediate frequency furnace knotting material construction method", once introduced to you about the knotting knowledge of furnace linings, today we will expand, to share some knowledge about furnace linings sintering.
After the furnace lining is finished, the oven and sintering process can be carried out. The purpose is to fully exclude the water in the furnace lining, so that the silica sand is fully uniform phase transition, and finally the dense ceramic surface with high strength is fired at high temperature.
In the oven and sintering, we need to pay attention to the following:
The water cooling system, tilt system, control loop and various marks should be checked in detail before the oven.
Oven must add a certain amount of charge, about 70% of the height of the furnace, to ensure the uniformity of temperature rise and fall.
Oven to take low power, slow heating, in the power supply at the same time to pass cooling water. At the early stage of the oven, the heating rate is 100℃/h and rises evenly until 800-900℃.
Clean and rust-free return material is selected to reduce slag, of which large material should be installed around the wall of the crucible, and small material should be added in the center of the furnace bottom.
The temperature of liquid iron should be about 50℃ higher than the working temperature, and keep 1-2h, so that the furnace lining is uniformly sintered. The whole melting time of the first furnace is about 2-3 times of the normal melting time.
After melting the first furnace, the sintering layer of the crucible is still very thin, and the sintering process can be completed only after continuous melting of 2-3 furnaces.
If the sintering temperature is too low and the time is not enough, the furnace lining will break after cooling. A very common way to do this is to preheat.
The first is the warm-up process.
1. the use of induction furnace, in the absence of feeding, with 30 minutes to preheat the crucible to about 200℃, and dry for 60 minutes. This is done in order to let the surface of the crucible moisture volatilize, prevent the use of the initial burst.
2. After preheating, the crucible should be heated to 900℃-1000℃ as soon as possible (about 2 hours), keep the temperature for 20-30 minutes, and then restore to the temperature when the metal needs to be melted. This is done so that the crucible can pass quickly through temperature regions where oxidation is easy.
3. after each preheating, only need to let the electric furnace to keep running, unless there is a furnace stop or crucible again damp situation, otherwise do not need to preheat.
There are also some precautions for checking.
1. carefully check the bottom and inner wall of the crucible, if found depression and cracks, to repair in time.
2, check the furnace top, nozzle and cover plate, if found sand and loose, pay attention to dressing and fastening.
3. Check the induction coil. If there are iron filings and other debris found on it, it should be removed immediately.
4. Check the connection bolts between induction coil and insulated column. When loose and falling off are found, they should be fully filled and fastened in time.
5. check the whole water cooling circulation system, focusing on the water cooling cable, to ensure that the water supply is smooth, no leakage.
6. Check the mechanical operation of furnace body turnover, which is very important for safety production. If any fault is found, remove it in time.
This is the knowledge about induction furnace preheating. Many enterprises do not pay attention to these details when producing electric furnaces, so it will cause some production accidents. I hope our summary today will help you.
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