Induction Furnace Lining

1. What Material Is Used for the Induction Furnace Lining?

The induction furnace lining is made of refractory bricks. Due to the different working conditions of each part of the lining, the material and performance of the refractory bricks used are also different.

For example, wear resistance is mainly considered for the middle and upper lining of the furnace body, thermal shock resistance and alkali metal erosion are mainly considered for the lower part of the furnace body and the furnace waist, the initial slag erosion of high FeO is mainly considered for the furnace belly, and the mechanical erosion resistance of molten iron and differential thermal expansion of refractory bricks are mainly considered for the hearth and furnace bottom.

The working frequency of the medium-frequency induction furnace (hereinafter referred to as the medium-frequency furnace) is between 50 and 10 Hz, and is widely used for smelting non-ferrous metals and ferrous metals. Compared with other casting equipment, the medium-frequency induction furnace has the advantages of high thermal efficiency, short melting time, less burning loss of alloy elements, wide melting materials, small environmental pollution, and accurate control of the temperature and composition of molten metal.

2. What Is the Function of the Lining of the Induction Furnace?

(1) Containing metal liquid.

(2) Protect the sensing ring.

(3) Accept induction heating to melt metal.

3. How Much Can the Lining of the Three-ton Medium-frequency Electric Furnace Not Be Opened?

Any furnace with cracks in its lining can no longer be used. If it continues to be used, molten iron may seep into the furnace lining through the cracks, further expand the cracks, and finally lead to a furnace-piercing accident. The accident of furnace explosion may also occur due to molten iron melting induction coil.

4. In the Lining Material Construction of the Medium Frequency Induction Furnace, What Is the Reason That the Lining Loss Is Even and the Surface Is Glassy?

(1) The working temperature in the exposed hall is higher than the maximum service temperature of the furnace lining itself.

(2) The slag has good fluidity and strong corrosivity.

(3) The smelting atmosphere of the furnace is not consistent with the type selection of furnace lining (acid, medium, and alkali).

5. How Can the Electric Pen Measure the Power of the Newly Built Induction Furnace Lining?

(1) The inductor of the medium frequency induction furnace, also known as the furnace head, is a spiral coil made of rectangular copper tubes. It is designed according to the length, diameter, heating temperature, and heating beat of the heated workpiece, and can ensure the heating temperature of the workpiece and the core surface temperature difference.

(2) In order to protect the induction coil, the inductor of medium frequency induction furnace needs to be equipped with furnace lining. At present, there are basically two types of furnace lining assembly, one is knotted furnace lining, and the other is fabricated furnace lining.

(3) When the medium frequency induction furnace inductor is in use, it is necessary to timely clean up the oxide scale that falls off due to the heating of the workpiece. If the furnace lining is damaged or has cracks or cracks, if it is not cleaned in time, it is easy to ignite and cause overcurrent protection of medium frequency power supply, and it is easy to break down the inductor coil and cause inter-turn short circuit of the inductor. In principle, the oxide scale in the inductor furnace shall be cleaned at least once every shift (8 hours).

(4) Frequently observe and maintain the lining cracks of the medium-frequency induction furnace. If the crack is not more than 2mm, the lining must be filled with knotted material in time. If the crack is more than 2mm, the lining must be re-bonded; If it is a fabricated furnace lining, it must be replaced. To avoid burning the inductor due to inter-turn short circuit caused by oxide skin falling into the gap.

(5) The coil of medium frequency induction furnace inductor is cooled by water, and there must be sufficient water flow and water pressure to ensure the normal cooling of the copper pipe of the inductor. Therefore, the working pressure of cooling water should not be less than 0.2~0.3Mpa, the inlet temperature should be less than 35 ℃, and the outlet temperature should be less than 55 ℃. If the water pressure is not enough, the inductor coil will be vaporized and heated. If not found in time, the copper pipe will break and water will overflow. The inductor is working at high temperatures. At this time, it is likely to explode. Therefore, the water cooling of medium frequency induction furnace inductor is extremely important.

(6) The newly made inductor just put into production in the medium frequency induction furnace must go through low-power baking (generally about 30KW), and the heating workpiece must be placed in the induction furnace for about 2 hours. Remove the residual water in the furnace lining to ensure the service life of the furnace lining.

(7) Once the dry guide rail (without water) of the medium frequency induction furnace is worn and deformed, it must be replaced. It is forbidden to use the furnace lining as the guide rail for heating the workpiece.

(8) The water-cooled guide rail of a medium-frequency induction furnace is worn during use, and the wall thickness of the water-cooled guide rail is generally 2mm. Therefore, the use of water-cooled guide rail has a certain period of time. If there is too much wear, it must be replaced. Otherwise, once water leakage occurs, it will cause rapid cooling of the furnace lining and directly affect the use effect of the induction furnace lining.

(9) The water-cooled guide rail in the medium frequency induction furnace inductor is actually the movement track of the heating workpiece, which has been working under high temperatures. If the water supply is insufficient or the water pressure is insufficient, gasification, redness, and deformation will occur, and the heated workpiece cannot pass through the inductor. Therefore, water cooling of the water-cooled guide rail is also extremely important.

To sum up, the medium-frequency induction furnace must be observed and inspected during use. If any problem is found, it shall be handled in time. Only in this way can the normal use of the medium-frequency induction furnace be guaranteed without affecting production.

6. To What Extent Does the Induction Furnace Lining Need to Be Rebuilt?

In order to be safe, the remaining one-third of the furnace needs to be reopened.

7. How to Improve the Lining Life of Induction Furnace?

Don’t worry, boric acid should be used better, and all kinds of sand should be prepared better than usual. But it depends on what casting you drive.

8. What Materials Are Needed for Induction Furnace Lining?

Quartz sand is used for acid furnace lining and magnesia is used for alkaline furnace lining.