How to prolong the lining life of magnesia intermediate frequency induction furnace?
Author：admin Time：2018-10-23 10:34
The lining life of intermediate frequency furnace directly affects the output, quality, energy consumption and cost of production. I plant 0.5T medium frequency furnace. Magnesia medium frequency furnace lining has been used for many years. But the magnesia we use is the waste magnesia bricks and used magnesia alumina bricks that large enterprises are dumping. We knocked out the slag adhered to the bricks, cleaned it up and crushed the waste magnesite brick into magnesia with a crusher. This magnesia has high magnesia content, high refractoriness, good thermal stability, and is the cheapest and best quality material for medium frequency furnace lining. The maximum granularity of magnesia should not exceed 15mm, and the content of magnesia powder should be 20% to 25%. After crushing the magnesia, we need to use electromagnet sucker to suck out magnetic debris from magnesia. 0.5T medium frequency furnace, we generally add 5~6 boric acid powder, adding sodium hydroxide solution. The ramming material must be evenly stirred. Holding materials with hands can be chunks. When the soil falls naturally, the moisture content of the material is just right.
In order to overcome the cracking problem in the lining of medium frequency magnesia furnace, 8% ~ l2% bauxite clinker or A12 > 78% waste high alumina silicon are allowed to be added into the lining magnesia of medium frequency furnace, and 4 ~ 8mm coarse silica sand is allowed to be added in about l0%.
Ramming materials must be evenly mixed in any case, strictly controlling moisture content (dry rather wet). Especially when lining the bottom of the intermediate frequency furnace, more attention should be paid to dry rather than wet.
A tool for lining up intermediate frequency furnace lining. We use D9 type tamping machine produced by Shenyang pneumatic tool factory. Compressed air of 0.6 MPa pressure must be guaranteed when tamping intermediate frequency furnace lining. Because the hammer head of tamping machine is too big, we make hammer head of ~50mm and lengthen the piston rod properly.
The bottom material is tamped to the first induction coil, and the bottom of the hearth furnace is tamped. A heavy load is placed inside the cylinder core to stabilize the dead core. Lay a layer of 3O-50mm material, ram a layer, ram the more solid the better, medium frequency furnace lining rammed out of the simple core with a crane, medium frequency furnace lining sprinkled with liquid water glass, in order to facilitate the formation of the first furnace steel sintering layer, furnace collar material with silica sand + water glass, can be manually patted.
The increase of furnace life is not only the serious batching and pounding, but also the serious maintenance. In the production and use process to carefully maintain the oven village; oven village after tamping the best natural drying more than 7 days, during this period to open the induction coil circulating water valve, let hot water circulation so that oven village slow drying. When baking the lining of medium frequency furnace, the furnace is filled with thick-skinned scrap and pig iron, and the scrap length should not be higher than the furnace mouth. Cover the furnace mouth with a steel plate cover to help accumulate heat to raise the temperature in the furnace, save electricity power with 3 Okw can be used, do not need to use a high-power power electric oven. After the furnace is red, the electricity will be cut off and 0.5h will be sent again. Repeated times, shutdown and feeding in 30 kW power to maintain 5-6 hours, to ensure that the intermediate frequency furnace lining can increase power melting smelting after basic drying. The oven time is actually related to the moisture content of ramming material. The higher the moisture content is, the lower the oven power should be. Otherwise, it is easy to short-circuit the inductor and ask for an automatic trip. Furnace village material moisture content is high, easy to occur between the induction coil up and down short circuit, resulting in normal closing, can not start.
Furnace village must be carefully protected during its use. When filling the scrap into the furnace, we should pay attention not to bump the intermediate frequency furnace lining, especially the large scrap steel. We should try our best to lightly handle and lightly place the scrap, and not allow the intermediate frequency furnace lining to collide and vibrate. After the furnace has molten steel, it is necessary to clean the acidic slag on the surface of the steel in time. Because the chemical erosion of alkaline intermediate frequency furnace lining is mainly the acidic low melting point slag with high ferric oxide content, the higher the temperature of molten steel, the greater the erosion of these slags on magnesia intermediate frequency furnace lining. From magnesia intermediate frequency furnace lining mouth distance of 200 ram is the most serious part of erosion depression, so it can be considered that magnesia in the furnace. The service life of the frequency furnace lining is mainly caused by the destruction of the slag line. In the smelting process, we should pay attention to: 1. The quality of scrap steel is good and the life of furnace village is high; the quality of scrap steel is not good. Rust is serious. Life in furnace village is low. (2) the time for adding ferrosilicon alloy should be 3 to 5min before the tapping. Because the oxides of silicon are acidic, the early addition not only accelerates the consumption of silicon, but also accelerates the erosion of intermediate frequency furnace lining, so ferrosilicon alloy should be added after the molten steel temperature has reached the tapping requirements, chemical composition and other tapping conditions have reached. Do not produce high temperature molten steel. In general, the tapping temperature of No. 1 steel is below 1700 C. Although the refractoriness of magnesia intermediate frequency furnace lining is above 1900 C, in order to improve the service life of intermediate frequency furnace lining, it should be carried out according to the tapping temperature requirements, not high temperature steel.
In addition to protecting the lining of the intermediate frequency furnace in the smelting process, there is another important measure. That is to seriously subsidize furnace village. When the magnesia furnace is used for more than 30 furnaces, the inner surface of the lining of the medium frequency furnace will crack. If the furnace continues to use without repairing, the crack will continue to expand, the crack will deepen and widen, resulting in uneven thickness of the sintering layer of the medium frequency furnace lining, which will greatly affect the life of the furnace. In order to make the magnesia furnace have a blast furnace age, it must It is necessary to repair the furnace Village, especially the slag line. Our specific approach is: after the oven village cooled, with a small pimple and cymbal head to the oven village surface 20 ram sintering layer removed. Especially slag line location and serious damage parts. The fine magnesia of 0-2.5 ram in magnesia is sifted out with a sieve, and the magnesia powder with particle size (> 180) of 2O% is added. The magnesia powder is stirred evenly, the aqueous solution of sodium hydroxide is added, and a sticky and soft block is formed. The block is patched in circles and patched by hand. After the 6O furnace is smelted, the furnace has been subsidized once again. The lining of the MF furnace is no longer cracked. It can be directly steel-making without baking oven. We have been doing this for several years. Our tapping temperature is generally at 1650~1670 C, and the furnace life is above 8O furnace. The biggest disadvantage of using sodium hydroxide solution in magnesia furnace village is that it is difficult to disassemble the furnace. The permanent magnesia layer is lumpy and hard. Therefore, it is our experience to control the addition of caustic soda properly.