Long-service-life air brick for bottom blowing of steelmaking electric arc furnace and preparation method of long-service-life air brick

Abstract

The invention discloses a long-service-life air brick for bottom blowing of a steelmaking electric arc furnace and a preparation method of the long-service-life air brick. The long-service-life air brick for bottom blowing of the steel-making electric arc furnace comprises an air brick body and an air blowing pipe arranged in the air brick body. The air brick body comprises the following raw materials in parts by weight: 60-75 parts of fused magnesite particles, 5-20 parts of fused magnesite fine powder, 8-18 parts of crystalline flake graphite, 2-5 parts of an antioxidant, 2-5 parts of phenolic resin and 0.3-1 part of oriented long fibers. The preparation method comprises the following steps: uniformly mixing and grinding the fused magnesia particles, the fused magnesia fine powder, the crystalline flake graphite, the antioxidant and the phenolic resin to obtain pug; an air blowing pipe is directionally fixed in the mold, and meanwhile directional long fibers are evenly arranged in the direction parallel to the air blowing pipe; and uniformly adding the pug into a mold in which an air blowing pipe and directional long fibers are arranged, sealing the mold, and molding and baking in an isostatic pressing machine to obtain the long-service-life air brick for bottom blowing of the steel-making electric arc furnace.

Description

Technical Field

[0001] The present invention relates to the technical field of refractory materials for steelmaking, and particularly relates to a high-life permeable brick for bottom blowing of a steelmaking electric arc furnace and a preparation method thereof. Background Art

[0002] There are two types of steelmaking electric arc furnaces: direct current electric furnaces and alternating current electric furnaces. Currently, alternating current electric furnaces are used more and more. In its steelmaking process, scrap steel is used as the main raw material, alternating current is used as the power source, and graphite electrodes are used as current carriers. The high-temperature arc generated by the current passing through the graphite electrodes and the metal charge is used to heat and melt the lump materials.

[0003] With the acceleration of the smelting rhythm of electric furnaces and the continuous improvement of the requirements for molten steel quality, the temperature and composition uniformity of molten steel in large electric furnaces are becoming increasingly important. Therefore, the electric furnace bottom blowing technology has been more and more widely applied worldwide. It is an important smelting control means in the electric furnace steelmaking system, enabling the electric furnace to achieve higher smelting efficiency, reduce steelmaking costs, increase the smelting speed, uniform the temperature, composition in the furnace and shorten the melting cycle, thereby effectively reducing the production cost of the electric arc furnace.

[0004] At present, the permeable bricks for bottom blowing of electric arc furnaces mainly adopt a capillary structure, that is, generally 8 - 20 hollow steel pipes with an outer diameter of 3 - 5 mm and an inner diameter of 1 - 3 mm are arranged inside the refractory body for air permeability. The following problems mainly exist in the use process of this type of permeable brick:

[0005] 1) The length of the permeable brick for the electric arc furnace is large. Coupled with the frequent temperature fluctuations during the smelting process of the electric arc furnace, and at the same time, the blowing process of the air pipe has a certain cooling effect on the material of the permeable brick body, the temperature gradient from the inside to the hot end to the cold end of the bottom blowing permeable brick is large, and the permeable brick is prone to spalling and fracture problems.

[0006] 2) The air pipe is generally made of stainless steel, and there are great differences in materials between it and the main body magnesia-carbon material, and the bonding property is not strong. There are gaps between the two, and oxidation and burning loss are likely to occur during use, thereby affecting the service life.

[0007] For traditional refractory materials, the introduction method of fibers is generally mainly short fibers, and their lengths are short. The main reason is that it is difficult for the fibers to be evenly dispersed during the mixing process of the mud. The fiber distribution in traditional refractory materials is random. If the dispersion is uneven, it is difficult to play the role of the fibers and cannot form a good strengthening and toughening effect on the material. For long fibers with a length of more than 20 mm, their lengths generally exceed the critical particle size of the raw materials used in the refractory materials, and they cannot be effectively dispersed, so they cannot be directly introduced into the refractory material body.

[0008] After retrieval, the following prior arts exist:

[0009] The patent specification with the publication number CN101492297A discloses an electric furnace bottom-blowing directional porous permeable brick body and its preparation method. The permeable brick body is made of the following raw materials in parts by weight: 1 part of fused magnesia with a particle size of ≤5.0 mm, 0.8 - 1 part of fused magnesia with a particle size of ≤3.0 mm, 0.8 - 1 part of fused magnesia with a particle size of ≤1.0 mm, 0.3 - 0.5 part of fine fused magnesia powder with a mesh size of 200, 0.8 part of high-purity graphite, 0.1 - 0.2 part of additive, and 0.15 part of binder. The binder is phenolic resin, and the additive is made of 40% - 60% aluminum powder, 20% - 40% aluminum-magnesium alloy powder, 5% - 15% silicon powder, and 5% - 15% silicon carbide powder by weight percentage. Summary of the Invention

[0010] The present invention provides a high-life permeable brick for bottom blowing of a steelmaking electric arc furnace and its preparation method. By introducing directional long fibers into the material of the permeable brick body, the directional long fibers play a role in heat conduction, strengthening, and toughening in the length direction of the permeable brick, which is beneficial to reducing the temperature gradient from the working surface to the non-working surface of the permeable brick, improving the strengthening and toughening effect of the material at the same time, and reducing problems such as spalling and fracture during the use of the permeable brick.

[0011] [1] A high-life permeable brick for bottom blowing of a steelmaking electric arc furnace, comprising a permeable brick body and a blowing gas pipe arranged inside the permeable brick body. In parts by weight, the raw material composition of the permeable brick body includes:

[0012]

[0013] The length direction of the directional long fibers is the same as the length direction of the blowing gas pipe.

[0014] In some embodiments, the chemical composition and mass percentage content of the fused magnesia particles include: MgO ≥ 97.5 wt%, CaO ≤ 1.8 wt%, SiO2 ≤ 0.9 wt%.

[0015] In some embodiments, in parts by mass, the particle size distribution of the fused magnesia particles is:

[0016] 3 - 1 mm, excluding 1 mm, 30 - 40 parts,

[0017] 1 - 0.088 mm, excluding 0.088 mm, 25 - 35 parts.

[0018] In some embodiments, the chemical composition and mass percentage content of the fine fused magnesia powder include: MgO ≥ 97.5 wt%, CaO ≤ 1.8 wt%, SiO2 ≤ 0.9 wt%.

[0019] In some embodiments, the particle size of the fine fused magnesia powder is <0.088 mm.

[0020] In some embodiments, C≥97.0 wt% in the flake graphite.

[0021] In some embodiments, the particle size of the flake graphite is <0.15 mm.

[0022] In some embodiments, the antioxidant includes at least one of metallic Al powder, elemental Si powder, and B4C powder.

[0023] In some embodiments, Al≥98.0 wt% in the metallic Al powder.

[0024] In some embodiments, the particle size of the metallic Al powder is <0.045 mm.

[0025] In some embodiments, Si≥97.0 wt% in the elemental Si powder.

[0026] In some embodiments, the particle size of the elemental Si powder is D50 <0.5 μm.

[0027] In some embodiments, B4C≥97.0 wt% in the B4C powder.

[0028] In some embodiments, the particle size of the B4C powder is <0.045 mm.

[0029] In some embodiments, the phenolic resin is a thermosetting phenolic resin.

[0030] In some embodiments, the oriented long fibers include at least one of carbon fibers, Al fibers, and Si fibers.

[0031] In some preferred examples, the oriented long fibers include carbon fibers, Al fibers, and Si fibers.

[0032] In some embodiments, the length of the oriented long fibers is 600 - 1000 mm.

[0033] In some embodiments, C≥97.0 wt% in the carbon fibers.

[0034] In some embodiments, the diameter of the carbon fibers is 10 - 100 μm and the length is 600 - 1000 mm.

[0035] In some embodiments, Al≥97.0 wt% in the Al fibers.

[0036] In some embodiments, the diameter of the Al fibers is 20 - 200 μm and the length is 600 - 1000 mm.

[0037] In some embodiments, Si≥97.0 wt% in the Si fibers.

[0038] In some embodiments, the diameter of the Si fibers is 20 - 200 μm, and the length is 600 - 1000 mm.

[0039] In some embodiments, in terms of parts by weight, the raw material composition of the breathable brick body is as follows:

[0040] Carbon fiber: 0.1 - 0.4 parts,

[0041] Al fiber: 0.1 - 0.3 parts,

[0042] Si fiber: 0.1 - 0.3 parts.

[0043] In some embodiments, in the raw material composition of the breathable brick body, the total weight of the fused magnesia particles, the fused magnesia fine powder, the flake graphite, and the antioxidant is 100 parts.

[0044] In some preferred examples, in the raw material composition of the breathable brick body, based on the total weight of the fused magnesia particles, the fused magnesia fine powder, the flake graphite, and the antioxidant being 100%, the weight percentage of the carbon fiber is 0.1% - 0.4%, the weight percentage of the Al fiber is 0.1% - 0.3%, and the weight percentage of the Si fiber is 0.1% - 0.3%.

[0045] In some embodiments, the blowing pipe is made of stainless steel, such as stainless steel materials like 304, 310, 316, etc.

[0046] In some preferred examples, the outer surface of the blowing pipe is coated with (specifically, it can be one or a combination of spraying, dipping, etc.) a mixed coating of one or two of metallic Al and elemental Si. By coating the Al layer and / or Si layer on the surface of the blowing pipe, during the use of the breathable brick, the Al layer and the Si layer can react with the magnesia - carbon material of the breathable brick body to form transition layers such as Al4C3, SiC, and spinel, avoiding the occurrence of gaps between the blowing pipe and the magnesia - carbon material body, effectively protecting the blowing pipe, and reducing problems such as oxidation and burning loss of the blowing pipe at high temperatures. Thus, the service life can be greatly improved. In this preferred solution, the present invention arranges oriented long fibers in the material of the breathable brick body and coats the outer surface of the blowing pipe with Al and Si coatings to jointly improve the service life of the bottom - blowing breathable brick.

[0047] [2] The preparation method of the high - service - life breathable brick for bottom - blowing in a steel - making electric arc furnace according to [1] includes:

[0048] Mix the fused magnesia particles, the fused magnesia fine powder, the flake graphite, the antioxidant, and the phenolic resin evenly to obtain a mud material;

[0049] Orient and fix the blowing pipe in the mold, and at the same time, arrange the oriented long fibers evenly in the direction parallel to the blowing pipe;

[0050] Uniformly add the said mud material into the mold where the blowing pipe and the oriented long fibers are arranged. After the mold is sealed, it enters an isostatic press for forming. The semi-finished product of the breathable brick after forming enters a drying kiln and is baked at 180 - 260 °C for more than 24 hours. The baked breathable brick undergoes grinding, and the processes of welding the air chamber and the blowing pipe to obtain the high-life breathable brick for bottom blowing of the steelmaking electric arc furnace.

[0051] Before the semi-finished product of the breathable brick body is formed, before the mud material is added into the mold, during the process of fixing the blowing pipe in the mold, at the same time, the oriented long fibers are fixed, so that the oriented long fibers are in the same direction as the length direction of the blowing pipe in the length direction, presenting an oriented distribution mode.

[0052] In addition, before the mud material is formed and loaded into the mold, the outer surface of the blowing pipe can be coated with coatings such as metallic Al and elemental Si, and then fixed in the mold in an oriented manner.

[0053] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0054] 1. Aiming at the production and use characteristics of the breathable brick for the electric furnace, the present invention first introduces oriented long fibers (preferably carbon fiber, Al fiber, and Si fiber) into the material of the breathable brick body. Before the semi-finished product of the breathable brick body is formed, before the mud material is added into the mold, the long fibers are arranged in an oriented manner in the length direction of the breathable brick. On the one hand, it solves the problem that long fibers are not easily dispersed in the material body and avoids the problem of agglomeration and segregation during the mixing process of the mud material. On the other hand, the oriented arrangement of the long fibers in the length direction of the breathable brick is also beneficial to exert the heat conduction, strengthening, and toughening effects of the oriented long fibers in the length direction of the breathable brick, which is beneficial to reducing the temperature gradient from the working surface to the non-working surface of the breathable brick, while improving the strengthening and toughening effects of the material and reducing problems such as spalling and fracture during the use of the breathable brick. For traditional refractory materials, by introducing short fibers during the mixing process of the mud material, the fibers are randomly distributed inside the material, and it is difficult to fully exert the heat conduction, strengthening, and toughening effects of the fibers, so the improvement effect is very limited.

[0055] 2. The present invention coats the outer surface of the blowing pipe with Al and Si coatings. During the high-temperature use of the breathable brick, reactions between Al, Si and the magnesium-carbon body material form transition layers such as Al4C3, SiC, and spinel, generating micro-expansion, improving the bonding property between the blowing pipe and the magnesium-carbon body material, forming an effective protective effect on the blowing pipe, avoiding the appearance of gaps between the blowing pipe and the magnesium-carbon body material, and reducing problems such as oxidation and burning loss of the blowing pipe at high temperatures. Specific Embodiments

[0056] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. The operating methods without specific conditions noted in the following embodiments are generally carried out under conventional conditions or according to the conditions recommended by the manufacturer.

[0057] The descriptions of some raw materials used in each example and comparative example are as follows:

[0058] The particle size of fused magnesia particles is 3 to >0.088 mm, the MgO content is ≥97.5 wt%, CaO ≤1.8 wt%, and SiO2 ≤0.9 wt%;

[0059] The particle size of fused magnesia fine powder is <0.088 to 0 mm, the MgO content is ≥97.5 wt%, CaO ≤1.8 wt%, and SiO2 ≤0.9 wt%;

[0060] The chemical composition of flake graphite is C ≥97.0 wt%, and the particle size is <0.15 mm;

[0061] The phenolic resin is a thermosetting phenolic resin;

[0062] The chemical composition of metallic Al powder is Al ≥98.0 wt%, and the particle size is <0.045 mm;

[0063] The chemical composition of elemental Si powder is Si ≥97.0 wt%, and the particle size is D50 <0.5 μm;

[0064] The chemical composition of B4C powder is B4C ≥97.0 wt%, and the particle size is <0.045 mm;

[0065] In the carbon fiber, C ≥97.0 wt%, the fiber diameter is 10 to 100 μm, and the length is 600 to 1000 mm;

[0066] In the Al fiber, Al ≥97.0 wt%, the fiber diameter is 20 to 200 μm, and the length is 600 to 1000 mm;

[0067] In the Si fiber, Si ≥97.0 wt%, the fiber diameter is 20 to 200 μm, and the length is 600 to 1000 mm.

[0068] The raw material compositions of the porous plug bodies in each example and comparative example are listed in Table 1, in parts by unit mass.

[0069] Table 1

[0070]

[0071] The preparation method of the arc furnace air bricks of each embodiment and comparative example is as follows: first, put the fused magnesia particles, fused magnesia fine powder, flake graphite, antioxidant and phenolic resin binder into a high-speed mixer and stir for 40 to 60 minutes, and then discharge the material for standby use after stirring evenly. Fix 8 to 20 air-permeable steel pipes in a special mold for air-permeable bricks, and evenly arrange carbon fiber, Al fiber and Si fiber in parallel with the air-permeable steel pipes. The above-mentioned mixed mud is evenly added to the mold arranged with the air-permeable steel pipe and the oriented fiber. After the mold is sealed, it enters the isostatic press for molding. The molded air bricks enter the drying kiln and are baked at 180 to 260 ° C for more than 24 hours. The baked air bricks are ground, and the air chamber and ventilation pipe welding process is carried out to obtain air bricks for bottom blowing of steelmaking arc furnaces.

[0072] Except for Comparative Example 2, the outer surfaces of the air-permeable steel pipes used in the preparation of the electric arc furnace air-permeable bricks in the other embodiments and comparative examples are coated with the same Al and Si mixed coating.

[0073] Table 2 shows the performance test results of the air-permeable brick bodies removed from the air-permeable bricks for bottom blowing of steel-making electric arc furnaces in each embodiment and comparative example 1.

[0074] Table 2

[0075]

[0076] It can be seen from Table 2 that the long-life breathable bricks prepared by the present invention have significantly improved pressure resistance and flexural strength, high-temperature flexural strength, thermal shock stability and thermal conductivity of the breathable brick body at room temperature and after medium- and high-temperature reduction treatment, compared with traditional breathable bricks. At the same time, the elastic modulus is relatively significantly lower, indicating that the high-life breathable bricks of the present invention have better toughness. During use, the long-life breathable bricks of the present invention can effectively avoid the problem of peeling and breaking during use due to the temperature gradient problem in the length direction. In addition, by coating the surface of the breathable steel pipe of the present invention with Al and Si coatings, the bonding between the breathable steel pipe and the magnesium-carbon body material can be improved, the gap can be reduced, and effective protection can be formed, thereby reducing problems such as oxidation and burning, and improving the service life.

[0077] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A high-life porous plug for bottom blowing of a steelmaking electric arc furnace, comprising a porous plug body and a blowing gas pipe arranged inside the porous plug body, characterized in that, In parts by weight, the raw material composition of the porous brick body includes: The length direction of the directional long fiber is the same as that of the blowing pipe.

2. The high-life permeable brick for bottom blowing of a steelmaking electric arc furnace according to claim 1, characterized in that, The chemical composition and mass percentage content of the fused magnesia particles include: MgO≥97.5wt%, CaO≤1.8wt%, SiO2≤0.9wt%; In parts by mass, the particle size distribution of the fused magnesia particles is: 3 - 1mm, excluding 1mm, 30 - 40 parts, 1 - 0.088mm, excluding 0.088mm, 25 - 35 parts.

3. The high-life permeable brick for bottom blowing of a steelmaking electric arc furnace according to claim 1, characterized in that, The chemical composition and mass percentage content of the fused magnesia fine powder include: MgO≥97.5wt%, CaO≤1.8wt%, SiO2≤0.9wt%; The particle size of the fused magnesia fine powder is <0.088mm.

4. The high-lifetime porous plug for bottom blowing in a steelmaking electric arc furnace according to claim 1, wherein In the flake graphite, C≥97.0wt%, and the particle size of the flake graphite is <0.15mm.

5. The high-life permeable brick for bottom blowing of a steelmaking electric arc furnace according to claim 1, characterized in that, The antioxidant includes at least one of metallic Al powder, elemental Si powder, and B4C powder; In the metallic Al powder, Al≥98.0wt%, and the particle size of the metallic Al powder is <0.045mm; In the elemental Si powder, Si≥97.0wt%, and the particle size of the elemental Si powder is D50<0.5μm; In the B4C powder, B4C≥97.0wt%, and the particle size of the B4C powder is <0.045mm.

6. The high-life permeable brick for bottom blowing of a steelmaking electric arc furnace according to claim 1, characterized in that, The phenolic resin is a thermosetting phenolic resin.

7. The high-life permeable brick for bottom blowing of a steelmaking electric arc furnace according to claim 1, characterized in that, The directional long fiber includes carbon fiber, Al fiber, and Si fiber; In the carbon fiber, C≥97.0wt%, the diameter of the carbon fiber is 10 - 100μm, and the length is 600 - 1000mm; In the Al fiber, Al≥97.0wt%, the diameter of the Al fiber is 20 - 200μm, and the length is 600 - 1000mm; In the Si fiber, Si≥97.0wt%, the diameter of the Si fiber is 20 - 200μm, and the length is 600 - 1000mm; In parts by weight, in the raw material composition of the porous brick body: Carbon fiber 0.1 - 0.4 parts, Al fiber 0.1 - 0.3 parts, Si fiber 0.1 - 0.3 parts.

8. The high-life permeable brick for bottom blowing of a steelmaking electric arc furnace according to claim 1, characterized in that, In the raw material composition of the porous brick body, the total weight of the fused magnesia particles, the fused magnesia fine powder, the flake graphite, and the antioxidant is 100 parts.

9. The high-life permeable brick for bottom blowing of a steelmaking electric arc furnace according to claim 1, characterized in that, The blowing pipe is made of stainless steel; The outer surface of the blowing pipe is coated with one or a mixture of two coatings of metallic Al and elemental Si.

10. The preparation method of the high-life porous plug for bottom blowing of the steelmaking electric arc furnace according to any one of claims 1 to 9, characterized in that, Includes: Mix and roll the fused magnesia particles, fused magnesia fine powder, flake graphite, antioxidant, and phenolic resin evenly to obtain a mud material; Orient and fix the blowing pipe in the mold, and at the same time, arrange the directional long fibers evenly in the direction parallel to the blowing pipe; Uniformly add the mud material into the mold where the blowing pipe and the directional long fibers are arranged. After the mold is sealed, it enters an isostatic press for molding. The molded semi-finished porous brick enters a drying kiln and is baked at 180 - 260°C for more than 24 hours. After baking, the porous brick undergoes grinding, welding of the air chamber and the blowing pipe processes to obtain the high - life porous brick for bottom blowing of the steel - making electric arc furnace.

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