With the development of iron and steel industry, iron and steel enterprises are also increasing the requirements of refractory company: the requirements of a longer service life and cleaner liquid steel.
In recent years, some domestic refractories suppliers to take refractory contracting system, the refractory supply, construction and maintenance to the contractor responsible for the price per tonne of steel to settle. This can mobilize the enthusiasm of refractory suppliers, to reduce consumption and its economic benefits linked to, but also effectively improve the user's economic environment, will help accelerate the reduction of China's metallurgical refractories consumption. To complete the consumption from the previous more the more the more profitable consumption to the less profitable transformation of the contracting model is not only a change in management mode, more importantly, technical upgrading, especially the application of technology to enhance the use of refractory The material is adapted to the operating conditions as far as possible. The use of refractory brick for sale technology in China is relatively backward, at the same time, the lack of refractory material suppliers use experience.
Recently, an iron and steel enterprises through a series of measures to make it 60 tons of LF ladle service life from the original 40 times to 50 times extended to 88 times, refractory unit consumption from 9.3 kg per ton steel down 5.6 kg per tonne, with remarkable results . We summarize their experience as follows. The EAF tapping temperature is generally 1620 ℃ ~ 1650 ℃. Normal ladle temperature of 1590 ℃ ~ 1620 ℃, ladle capacity of about 59 tons. Ladle refining time of 40 minutes to 50 minutes, a total of about 110 minutes of steel time. Argon pressure 0.2 MPa ~ 0.4 MPa, LF refining ratio of 100%, generally each furnace plus deoxidizer SiC 40 kg to 50 kg. The chemical composition of the ladle slag is: Fe2O31.44%, Al2O35.6%, CaO40.42%, CaF29%, MgO9.97%, SiO229.84%. This indicates that the ladle slag is a low basicity slag containing fluorite. The amount of slag in the electric furnace is large, and the oxidization of the slag is strong at the end of the electric furnace, and the content of FeO is always 45%.
Before the improvement, the iron and steel enterprises 60 tons of LF ladle slag line was used MT-14A magnesium carbon brick, pool with AMC brick. It is possible to use the physical and chemical properties of such bricks. In particular, the slag line, the use of magnesia carbon brick has a good density. The use of slag magnesia carbon brick is: the first slag line brick to use 15 to 19 times, the slag has been eroded to 50 mm below. In this case, the ladle will be off the assembly line, replace the ladle slag line brick. The second slag line of magnesium carbon brick service life of only about 15 times, and then again replace the third slag line of magnesium carbon brick, its service life can only reach 12 to 14 times, the total life of three slag only 40 times ~ 50 times, or even only to about 40 furnace times. The researchers observed the surface morphology of the ladle after use, found that the brick erosion uniformity, no increase in the phenomenon of brick, bricks did not appear like buns, guns, peeling and fracture anomalies, slag erosion rate of 7 mm ~ 10 mm, wall erosion rate also reached each 2.5 mm ~ 3.5 mm. Therefore, the main reason for the service life of the ladle is the rapid erosion of the slag line.
The main reason for this ladle erosion is that the basicity of slag is low, the lower the ratio of CaO and SiO2 is, the more the slag dissolves MgO, that is, the stronger the dissolving ability of slag to MgO. The low basicity slag on the corrosion of magnesium carbon brick is more serious. According to the analysis, they have taken the method of increasing the content of CaO in the brick so as to increase the ratio of CaO and SiO2 in the system after contact with slag and improve the melting point and viscosity of the system after slag reaction, so as to reduce the erosion speed. .
Because the amount of slag during the electric furnace tapping large, and the final oxidation of the furnace slag strong, which led to the early ladle slag has a high FeO content, resulting in magnesium carbon brick in the carbon easily oxidized, thus speeding up the slag line magnesium carbon Brick damage rate. According to this situation, the oxidation resistance of slag MgO-C brick needs more attention. After the modified slag MgO-C bricks at 1000 ℃ after 3 hours of oxidation resistance test, the oxidation decarburization layer is only 1 mm, while the improved MT-14A slag MgO-C brick oxidized decarburization layer thickness of 5 mm to 7 mm . Therefore, the modified slag MgO-C brick has good oxidation resistance.
In the steelmaking process, 50 to 60 kg of fluorite is added to each steel, which reduces the slag viscosity because the depth of penetration of the slag is inversely proportional to the square root of the viscosity. At the same time, it also accelerated the slag penetration of refractory materials, and lead to the slag line of magnesia carbon brick oxidation and erosion significantly improved. Therefore, the design of the production of magnesium carbon bricks, should be selected to improve the viscosity of fluorite-containing slag additives, which is conducive to improving the anti-slag erosion, but also conducive to extend the life of ladle.
As the common technology of MgO-C brick, it can improve the density of the product, the crystallinity and the purity of the raw material can significantly improve the corrosion resistance of MgO-C brick. For increased performance, large crystalline high purity fused magnesia, high purity natural graphite, and appropriate antioxidants and enhancers should be used. However, taking into account the economic efficiency of enterprises in the selection of materials should pay special attention to price. The enterprise to meet the basic requirements of the life of the case, the use of a certain amount of post-use magnesium-carbon brick renewable materials, and the use of some low-cost MP binding agent. For the regeneration of magnesium carbon materials, fewer fake particles and impurities, the more can improve the use of recycled magnesium carbon brick effect. Therefore, as far as possible the regeneration of magnesium carbon brick material removal, removal of fake particles, in order to improve the quality of recycled magnesium carbon bricks. MP binder is an asphalt modified resin binder, its residual carbon has a certain graphitization structure, with high oxidation resistance, thermal bonding properties and thermal shock resistance. Therefore, the choice of both antioxidant and enhance the role of composite additives, will help improve the performance of magnesium-carbon brick.
Based on the principle of optimal cost performance, the enterprise adopts the high quality recycled magnesium carbon material as the main raw material, with the appropriate content of 97% MgO fused magnesia, a small amount of -195 grades of graphite, composite Additives and modified resin binder, the ingredients, in the 630 tons of friction press molding, after curing system in the regeneration of magnesium carbon brick. Recycled Mg-C brick has good physical and chemical indexes, which fully meets the requirements of the national MT-12A and MT-14A quality products.
The improved MgO-C brick was applied to 60 tons of LF ladle, showing excellent corrosion resistance, oxidation resistance and thermal shock resistance. Ladle slag life from the use of MT-14A before the improvement of the Mg-C brick 15 to 19 times increased to 24 to 28 times, the erosion rate from 7 mm to 10 mm each time to 4.5 mm to 6.8 mm; From 40 to 50 times to 45 to 55 times, the erosion rate from 2.5 mm to 3.5 mm each time to reduce to 1.2 mm to 2.4 mm each. The application of this product, reducing the maintenance of ladle, get a good user evaluation.
Slag leaving slag operation: Because the final slag FeO content, not only affect the raw material yield, increased steelmaking costs, but also led to the refinement of ladle lining shorten the service life. By adjusting the oxygen gun, the angle and depth of the carbon gun, and strengthen the latter part of the electric furnace carbon spray, improve the foam slag and other methods to reduce the slag FeO content and reduce the slag in the oxygen activity, so that slag separation to reduce the amount of slag. Practice has proved that by controlling the amount of slag and slag in the FeO content, the life of refined ladle extended from 50 to 60 times, the life of refined ladle extended by 20%.
Add slag modifier: steel with SiC deoxidizer, with the electric furnace slag and slag FeO content increased, according to the deoxidation reaction: SiC +4 FeO = 4Fe + SiO2 + CO2 need more SiC deoxidizer, not only lead to refining The cost of steel increases, and the ratio of CaO and SiO2 in ladle slag is reduced, which greatly accelerates the erosion of lining. In order to reduce the ladle slag erosion of the lining, deoxidizer without SiC quality, and carbon content of 15% of the calcium and magnesium carbon steel ladle modifier, the addition of silicon carbide deoxidizing agent is basically the same, that is, per ton of steel by adding 1 kilogram. CaO in the modifier improves the basicity of the ladle slag, so that the MgO carbon brick in the erosion of MgO weakened low, MgO in the modifier MgO can increase the concentration of slag, magnesium and carbon brick to reduce MgO Of the dissolution rate. Through the trial of Mg-Ca carbonaceous modifier, the one-time service life of slag line MgO-C brick was extended from 26 times to 30 times, 15% longer.
Improve the maintenance system: slag erosion fast, the beginning of the two slag line corresponds to a molten pool. Later, with the two high aluminum brick on the pool were subsidized, that is, with the thickness of 40 mm of the two high aluminum brick attached to the molten pool, paste between the brick and the original lining with plastic binder and packing. The service life of molten pool from 60 to 88, extended by more than 45%.
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