Intermediate frequency furnace because of its convenient use, wide casting range, high heat rate, short melting time, favored by users, intermediate frequency furnace to use a long time, the main consideration is the lining, and intermediate frequency furnace lining in the use process, there will be some damage, once found these damage, need to repair in time, but how to repair the intermediate frequency furnace lining? In addition, after repair, how to maintain the intermediate frequency furnace lining?

First, intermediate frequency furnace lining repair method

1. Repair of cracking or damage at the joint between iron outlet refractory and furnace wall. It can be repaired by pushing amorphous refractory materials. When the repair range is large, it should be dried with charcoal.

2. Repair of side wall cracking. Cracks below 1mm can continue to be used without repair; Cracks above 1mm, especially in the horizontal direction, must be repaired. Can be added boric acid and mixed evenly after the furnace refractory sieve, long medium frequency furnace with wire and other tools to fill. The surface after filling is smoothed with a wet sand mixture of water glass.

3. Repair of side wall damage or small erosion. After removing slag and residual iron, apply water glass. Then patching with mixed refractories adding 5%-6% water glass, or patching with amorphous refractories. When the erosion area is slightly larger, put the human mold repair.

4, bottom, side wall tilt part of the burn or damage repair. The repair of the bottom of the furnace can be tamped by adding the same amount of boric acid and mixed evenly with the intermediate frequency furnace refractory. The repair of the inclined part of the side wall needs to install a mold with an outer diameter 5060mm smaller than the furnace diameter and a height about 100mm higher than the damaged part. Tamping with a vibrator, each layer of ramming thickness is 2030mm, and then ramming the upper layer after shaving, until it is 10mm higher than the mold, and then trim the upper plane to a fixed slope.

Second, intermediate frequency furnace lining repair points

1, first clean the slag of the damaged part, expand the crack into a 60° gap, brush with concentrated boric acid, and then sprinkle a little dry boric acid powder; Then add the mixed lining material (plus chemical material) to the place, tighten with a mallet, and smooth the surface.

2, if there is a pit at the bottom of the furnace, the repair should first remove the slag in the pit, the furnace lining material added to the pit, its thickness is 20-30mm higher than the surrounding furnace lining, use a flat hammer to knot and tighten, and then scrape off the excess furnace lining material. Then the relatively flat charge is pressed on, and other charges are added, and the voltage is 220V.

3. When repairing the furnace lining thinned by erosion, the sintered layer that has been infiltrated by liquid steel or slag should be peeled off first, and then put into the metal mold, and then fill the surrounding space into the furnace lining material, and then power baking and sintering after tying.

Third, intermediate frequency furnace liner use maintenance skills

Good operation and maintenance of intermediate frequency furnace have a great influence on the lining life of intermediate frequency furnace. This paper introduces the following points by taking melting cast iron as an example.

1, for dry furnace, the steel mold in the furnace is not taken out. When the oven must use the principle of adding small materials and filling, to avoid local ignition and melting the inner liner, so that the dry materials collapse. Therefore, it is required to accumulate small ingredients as much as possible before the oven. At the same time, during the heating process, the steel mold should be strictly observed, and the current should be reduced when the arc is serious, if the current is too large, the steel mold will be arc breakdown and lead to the collapse of the refractory.

2, usually add metal charge, the size of the block should be appropriate, generally not more than 1/2 of the furnace diameter, while the charge should be added in small batches many times; When increasing the material, it is necessary to add the small material bottom first, which not only avoids the material, but also reduces the impact of the charge on the furnace wall and the furnace bottom.

3, when the intermediate frequency furnace encounters an unexpected event and stops the furnace, the iron liquid in the furnace solidifies and restarts the furnace, attention should be paid to:

(1) When the medium frequency furnace cannot be restarted in a short period of time, 3 to 5 steel pipes (about 20 mm in diameter) should be inserted in the furnace to facilitate the emission of gas during the remelting process.

(2) Before the top of the solidified liquid iron in the furnace is not melted, the furnace body should be shaken up, tilted 15° ~ 30°, and the insulation power is lower than that of the intermediate frequency furnace.

(3) The solidified metal in the furnace must not increase the power before it is softened, if the temperature rises too fast, the expansion of the metal exceeds the expansion of the lining, the lining can be pulled apart, and in serious cases it can lead to furnace penetration; After the solidified metal is softened, the power can be raised to about the insulation power, until the metal shell above the condensed metal is melted by the liquid metal below, the furnace body can be levelled, and it can be melted according to the normal power.

4, when the liquid iron is released, the remaining liquid iron in the furnace can be appropriately more without affecting the material and the charging without splashing, which can not only speed up the melting speed of the metal charge, but also avoid the charge directly impacting the bottom of the furnace. After the liquid iron is released, the furnace body should be shaken back to reduce the baking of the liquid iron in the furnace on the back wall of the medium frequency furnace.

5, in order to reduce the cracking of the lining due to repeated quenching and quenching, continuous opening is very important to the extension of the life of the lining, which has attracted enough attention from many users.

If the intermediate frequency furnace can not be used continuously, after the second use, the metal charge should be added to the furnace and the furnace cover should be covered, which can not only preheat the metal charge, but also prevent the crack of the furnace lining caused by rapid cooling.

6, the intermediate frequency furnace is opened to about 20 furnace to remove the furnace mouth, the purpose is to check whether the furnace lining drill iron, check whether the dry material of the furnace lining is loose and there is a gap. When repairing the furnace, try to use metal furnace rings of different heights, and do not pay attention to the old and new interfaces should be cleaned. For the next recharging operation, the bottom of the previous recharging interface should be removed, and so on. The nozzles and stoves are often slagged, eroded and impacted by the charge, and require frequent maintenance and repair to ensure the normal maintenance and use of the medium frequency furnace.

7, the furnace in the process of feeding and slagging to be often bumped, easy to damage, to protect it is very important, in the furnace along the edge of a steel plate to do with the shape of the protective ring is a better measure. The thickness of the steel plate is 5 ~ 10mm, and the diameter of the inner ring is 10 ~ 20mm smaller than the diameter of the furnace, which can be cut into the whole steel plate or welded. In order to avoid the displacement of the protective ring during feeding, the position of the protective ring can be fixed by welding three steel plates along the outer edge of the furnace brick.

8, the melting personnel must pay attention to the erosion and cracking of the lining, in the middle and late life of the lining, or observe the melting condition regularly, watch the high melting power, current and liquid iron of the electric furnace, if necessary, the liquid iron should be emptied to stop the furnace for inspection.

9, the use of the furnace cover is very important for the medium frequency furnace, some manufacturers do not pay attention to the use of the furnace cover, and even the furnace cover is not used, this practice is wrong. When opening the furnace, cover the furnace well, not only can prevent the heat loss, speed up the melting of the charge, but also can avoid the splash of iron liquid during the charging; When the furnace is shut down, the furnace cover can keep the furnace lining material slow to cool down, so as to avoid cracks.

Fourth, the use of intermediate frequency furnace lining precautions

1, the lining material should have high thermal strength, low permeability and low porosity.

2. The initial failure of the lining is caused by the pre-corrosion loss caused by the dissolution of the sintered layer of the lining refractory in the slag, and the crack caused by the cyclic change of temperature. Another factor that causes crack propagation in the integral lining is the stress caused by the different expansion coefficients between the "three bands" caused by heating to too high a temperature.

3, the life of the lining depends on the correct operation, including the detection of the lining body, and the application of "filler" to repair the cracks in time to avoid the infiltration of molten steel and slag into the lining matrix.

Reasonable use and maintenance of intermediate frequency furnace is of great benefit to improving the service life of furnace lining and reducing production cost. Anaijie is a manufacturer of installation, maintenance and debugging team, engaged in intermediate frequency furnace, intermediate frequency electric furnace production and sales, cooperation with a number of foundry manufacturers, energy saving, specific results can pay attention to our case video.