Blast furnace tapping main channel castable and preparation method thereof

Abstract

The present application relates to a kind of blast furnace iron tapping main ditch castable, including the following mass parts of raw materials: dense corundum 45~55 parts, white corundum 12~25 parts, silicon carbide 12~20 parts, alpha-Al2O3 powder 3~6 parts, rho-Al2O3 powder 2~6 parts, composite graphite particle 5~10 parts, aluminum nitride powder 0.5~0.8 parts, antioxidant 1~5 parts, anti-explosion fiber 0.1~0.3 parts, water reducing agent 0.1~0.5 parts;The composite graphite particle is graphite, magnesium sol, aluminum sol, silica sol is formed C@Mg (OH) 2@Al (OH) 3@SiO2Microspheres precursor by wet granulation under inert atmosphere Calcination is formed C@MgO@Al2O3@SiO2Microspheres particle;The antioxidant is the compound of magnesium carbide, boron carbide, aluminum powder.The iron channel main ditch castable prepared by the present application has excellent erosion resistance, thermal shock resistance and oxidation resistance.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials technology, specifically relating to a blast furnace tapping main channel castable and its preparation method. Background Technology

[0002] The blast furnace tapping trough is the channel through which molten iron and slag flow in the blast furnace. It is divided into the main trough, branch troughs, and slag trough. The main trough is the common channel for the high-temperature slag-iron mixture flowing out of the blast furnace. A slag skimmer is designed at the rear of the main trough. Molten iron in the main trough enters the branch trough from the bottom of the slag skimmer, while slag in the main trough enters the slag trough from the top of the slag skimmer's overpass. The main trough is the most important and operates in the harshest environment, not only withstanding the scouring of high-temperature molten iron but also the erosion of high-temperature slag and thermal shock damage caused by sudden temperature changes. With the development of iron and steel smelting technology, the requirements for the materials of the blast furnace tapping main trough are becoming increasingly stringent. The material laid in the tapping trough is called castable refractory, which belongs to refractory materials.

[0003] To resist the erosion of molten iron and slag, carbon materials need to be added to the castable. Carbon has the characteristics of not being easily wetted by molten iron and slag, having a small coefficient of thermal expansion and high thermal conductivity. Introducing carbon materials can improve the erosion resistance and thermal shock stability of the tapping trough. However, the addition of carbon materials also brings new problems, mainly: (1) Due to the poor water wettability of carbon, it is easy to float in the castable and difficult to disperse evenly. Therefore, the amount of carbon materials added in the existing technology is relatively low, generally not exceeding 4%; (2) After the carbon materials are introduced into the castable, more water needs to be added in order to achieve suitable fluidity and improve the construction performance. Generally, the amount of water added is more than 5% of the total mass of the castable. However, after adding more water, the time required for the castable to dry will be greatly increased; (3) Carbon materials are prone to oxidation and loss in high-temperature use environment, which leads to a reduction in the castable's resistance to erosion, thermal shock and high temperature resistance. In order to effectively play the role of carbon materials, antioxidants need to be added to the castable. However, the antioxidants in the existing technology generally have a narrow anti-oxidation temperature range, which results in the carbon materials not being able to play their effective role.

[0004] Chinese patent CN117247272A discloses an antioxidant blast furnace iron trough castable and its preparation method. The raw material composition by mass percentage is as follows: 10.5-12% brown fused alumina (15-8mm), 14.5-16% brown fused alumina (8-5mm), 10-12% brown fused alumina (5-3mm), 10-11% brown fused alumina (3-1mm), 9-10% dense fused alumina (3-1mm), 4-5% dense fused alumina (1-0mm), 11-13% silicon carbide (1-0mm), and 325-mesh carbon... The composition of this invention is as follows: silicon dioxide 9-10%, alumina micropowder 4-6%, silica micropowder 1.5-2.5%, high-alumina cement 1-1.5%, p-Al2O3 1-1.5%, andalusite 0.5-1%, spherical asphalt 2-2.5%, carbon black 0.5-1%, boron carbide 0.2-0.4%, molybdenum-strontium powder 0.05-0.1%, metallic silicon powder 1.5-2.5%, metallic aluminum powder 0.02-0.04%, organic fiber 0.04-0.07%, and water-reducing agent 0.1-0.3%. In this invention, a compound of spherical asphalt and modified carbon black is used as the carbon material, and molybdenum-strontium powder, metallic silicon powder, and metallic aluminum powder are used as antioxidants. The modified carbon black is obtained by impregnating the surface of carbon black with trimethylaluminum, causing the trimethylaluminum to react with the hydroxyl or carbonyl groups on the carbon black surface to form chemical bonds. The blast furnace iron trough castable prepared by this invention improves its oxidation resistance, thereby improving the performance and service life of the castable. However, the maximum amount of carbon material added to this castable can only reach 3.5%, and the range of oxidation resistance temperature is narrow, with better oxidation resistance only above 1000℃. Summary of the Invention

[0005] In view of the problems in the prior art, such as the inability of carbon materials in blast furnace iron trough castables to effectively play their role, the low addition amount, the high water content, and the narrow range of oxidation resistance temperature in the castables, this invention provides a blast furnace tapping main trough castable to solve the above problems, thereby improving the erosion resistance, thermal shock stability, and oxidation resistance of the tapping main trough castable, and also exhibiting excellent pressure resistance.

[0006] The present invention achieves the above objectives through the following technical solutions:

[0007] This invention provides a blast furnace tapping main channel castable, comprising the following raw materials in parts by weight: 45-55 parts dense corundum, 12-25 parts white corundum, 12-20 parts silicon carbide, 3-6 parts α-Al2O3 powder, 2-6 parts ρ-Al2O3 powder, 5-10 parts composite graphite particles, 0.5-0.8 parts aluminum nitride powder, 1-5 parts antioxidant, 0.1-0.3 parts explosion-proof fiber, and 0.1-0.5 parts water-reducing agent; wherein the composite graphite particles are formed by wet granulation of graphite, magnesium sol, aluminum sol, and silica sol to form C@Mg(OH)2@Al(OH)3@SiO2 microsphere precursors, followed by calcination in an inert atmosphere; wherein the antioxidant is a compound of magnesium carbide, boron carbide, and aluminum powder.

[0008] Carbon materials enhance resistance to slag erosion and are indispensable raw materials for castable refractory troughs. However, conventional carbon materials have poor water wettability, resulting in uneven dispersion in the matrix, leading to insufficient addition and excessive water addition. This invention, through wet granulation and calcination, forms C@MgO@Al2O3@SiO2 microspheres, i.e., composite graphite particles. This significantly improves the dispersibility and water wettability of graphite, thereby increasing the amount of carbon added and further enhancing the castable's resistance to slag erosion. On the other hand, during the subsequent production of the main trough castable, under high-temperature conditions, Al2O3 in the C@MgO@Al2O3@SiO2 microspheres reacts in situ with MgO and SiO2 to generate magnesium aluminum spinel and mullite. Magnesium aluminum spinel and mullite improve the high-temperature strength and thermal shock resistance of the castable. Simultaneously, the in-situ generated magnesium aluminum spinel and mullite particles are smaller in size, which is more beneficial to improving the castable's resistance to slag erosion than "pre-synthesized" magnesium aluminum spinel and mullite. Furthermore, the in-situ generation of magnesium aluminum spinel and mullite involves a micro-expansion effect, which helps improve the density of the castable, thereby further enhancing its erosion resistance and high-temperature strength.

[0009] Carbon materials are easily oxidized, and antioxidants are generally added to castable refractory for tapping troughs to inhibit carbon oxidation. This invention uses a compound of magnesium carbide, boron carbide, and aluminum powder as an oxidant. The antioxidant reacts preferentially with oxygen over carbon at high temperatures. Magnesium carbide exhibits good antioxidant effects at 600–800℃, boron carbide at 800–1000℃, and aluminum powder at 1000℃. The antioxidant formed by this compound exhibits good antioxidant effects throughout the entire high-temperature range.

[0010] Further, the mass ratio of graphite, Mg(OH)2, Al(OH)3, and SiO2 in the C@Mg(OH)2@Al(OH)3@SiO2 microsphere precursor is 1:(0.1~0.2):(0.3~0.5):(0.15~0.25); preferably 1:(0.1~0.2):(0.4~0.5):(0.2~0.25).

[0011] Furthermore, the composite graphite particles are prepared by a method comprising the following steps:

[0012] (P1) Mix graphite, magnesium sol, aluminum sol and silica sol to form a mixed slurry;

[0013] (P2) The mixed slurry was granulated by wet process to obtain C@Mg(OH)2@Al(OH)3@SiO2 microsphere precursor;

[0014] (P3) The C@Mg(OH)2@Al(OH)3@SiO2 microsphere precursor was calcined in an inert atmosphere to obtain C@MgO@Al2O3@SiO2 microsphere particles, i.e., composite graphite particles.

[0015] Furthermore, in step (P1), the magnesium sol has a particle size D50 of 10-60 nm and a solid content of 20%-40%, the aluminum sol has a D50 of 10-60 nm and a solid content of 20%-40%, and the silica sol has a D50 of 10-60 nm and a solid content of 20%-40%.

[0016] Furthermore, the conditions for wet granulation in step (P2) are as follows: granulation is carried out by a wet granulator with an inlet temperature of 150-250°C, an outlet temperature of 70-120°C, and a rotation speed of 1500-3000 rpm; the inert atmosphere is at least one of nitrogen, argon, and helium.

[0017] Furthermore, the calcination described in step (P3) is calcination at 300–500°C for 3–6 hours.

[0018] Furthermore, in the antioxidant, the mass ratio of magnesium carbide, boron carbide and aluminum powder is 1:(1-3):(1-2); preferably 1:(2-3):(1-2).

[0019] Furthermore, the dense corundum has a particle size of 1–8 mm; the white corundum has a particle size of 0.1–3 mm; and the silicon carbide has a particle size of 100–400 mesh.

[0020] Furthermore, the dense corundum gradation satisfies: 15-25 wt% of particles with a size of 8-5 mm, 40-60 wt% of particles with a size of 5-3 mm, and 20-40 wt% of particles with a size of 3-1 mm; the white corundum gradation satisfies: 60-80 wt% of particles with a size of 3-1 mm, and 20-40 wt% of fine powder with a size of 1-0.1 mm; the silicon carbide gradation satisfies: 60-75 wt% of fine powder with a size of 100-200 mesh, and 25-40 wt% of micro powder with a size of 200-400 mesh.

[0021] Furthermore, in the dense corundum and white corundum, Al2O3 ≥ 99 wt%, Fe2O3 ≤ 0.1 wt%, and SiO2 ≤ 0.1 wt%; in the silicon carbide, SiC ≥ 97 wt%, SiO2 ≤ 0.4 wt%, and Fe2O3 ≤ 0.3 wt%.

[0022] Furthermore, the particle size D50 of the α-Al2O3 powder is 1-6 μm, and the Al2O3 content in the α-Al2O3 powder is ≥99.0 wt%.

[0023] Furthermore, the particle size D50 of the ρ-Al2O3 powder is 1-6 μm, and the Al2O3 content in the ρ-Al2O3 powder is ≥98.0 wt%.

[0024] Furthermore, the particle size D50 of the composite graphite particles is 15-60 μm; the particle size D50 of the graphite is 1-6 μm; and the graphite is at least one of artificial graphite, natural graphite, and graphitized mesophase carbon microspheres.

[0025] Furthermore, the particle size D50 of the aluminum nitride powder is 200-400 mesh. The aluminum nitride powder decomposes upon contact with water, producing hydrogen and aluminum oxide, consuming excess moisture in the raw materials to achieve rapid drying. Simultaneously, the released ammonia gas forms micropores in the matrix, and another portion of water vapor is discharged along these pore channels, further promoting rapid drying.

[0026] Furthermore, in the antioxidant, the particle size of magnesium carbide is 200-400 mesh, the particle size of boron carbide is 200-400 mesh, and the particle size of aluminum powder is 200-400 mesh.

[0027] Furthermore, the explosion-proof fiber is made of organic fibers, such as nylon, polyethylene fiber, and polypropylene fiber, with a melting point of 90-160°C, a diameter of 4-8 μm, and a length of 8-15 mm.

[0028] Based on the maximum packing density theory, the component raw materials with different particle sizes can be packed in the best proportion to form the densest packing. That is, the gaps between the millimeter-sized particles (dense corundum, white corundum) are filled by micron-sized particles (silicon carbide, composite graphite particles, aluminum nitride powder), and the gaps between the micron-sized particles are filled by ultrafine powders (α-Al2O3 powder, ρ-Al2O3 powder). In this way, the entire system is tightly wrapped to form a complete and dense matrix structure, thereby improving the structural strength of the castable.

[0029] Furthermore, the water-reducing agent is a polycarboxylate water-reducing agent and / or sodium hexametaphosphate.

[0030] Secondly, the present invention also provides a method for preparing the above-mentioned blast furnace tapping main trench castable, comprising the following steps:

[0031] (S1) Add silicon carbide, α-Al2O3 powder, ρ-Al2O3 powder, composite graphite particles, aluminum nitride powder, and antioxidant to a container and mix them to obtain a fine mixture.

[0032] (S2) Add dense corundum and white corundum to another container and mix them to obtain mixed granules;

[0033] (S3) Under stirring conditions, the fine mixed material obtained in (S1) is added to the granular mixed material obtained in (S2), and then explosion-proof fiber and water-reducing agent are added and mixed to obtain the blast furnace tapping main channel castable.

[0034] Further, the stirring in step (S1) is carried out at a speed of 500-1000 r / min for 30-60 min; the stirring in step (S2) is carried out at a speed of 200-400 r / min for 10-30 min; and the stirring in step (S3) is carried out at a speed of 200-400 r / min for 10-30 min.

[0035] Thirdly, the present invention also provides a water-addition pouring construction method for the castable refractory of the main trough for iron tapping, wherein the amount of water added is 2 to 3.5% of the total mass of the castable refractory of the main trough for iron tapping.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1) To improve the resistance of castables to molten iron and slag erosion, carbon materials such as graphite and coke need to be added. However, conventional carbon materials such as graphite and coke have poor water wettability, resulting in low addition amounts and uneven dispersion in the matrix. This invention uses composite graphite microspheres as the carbon material, specifically C@MgO@Al2O3@SiO2 microspheres, which greatly improves the dispersibility of graphite and its water wettability, thereby increasing the amount of carbon added and reducing the amount of water added. In this invention, the addition amount of composite graphite particles reaches 5-10%, which is more conducive to improving the castable's resistance to slag erosion; at the same time, the amount of water required during the casting construction stage is small, only 2-3.5% of the total mass of the castable for the main tapping trench.

[0038] 2) During the subsequent production of the main trough castable, under high-temperature conditions, the Al2O3 in the composite graphite particles C@MgO@Al2O3@SiO2 microspheres reacts in situ with MgO and SiO2 to generate magnesium aluminum spinel and mullite. Magnesium aluminum spinel and mullite improve the high-temperature strength and thermal shock resistance of the castable. Simultaneously, the in-situ generated magnesium aluminum spinel and mullite particles are smaller in size, which is more beneficial to improving the castable's resistance to slag erosion than "pre-synthesized" magnesium aluminum spinel and mullite. Furthermore, the in-situ generation of magnesium aluminum spinel and mullite involves a slight volume expansion effect, which helps improve the density of the castable, further enhancing its resistance to slag erosion and high-temperature strength. In other words, using C@MgO@Al2O3@SiO2 microspheres as the carbon material not only leverages the role of carbon materials, improving the castable's erosion resistance, but also enhances its high-temperature strength and thermal shock resistance.

[0039] 3) This invention uses a compound of magnesium carbide, boron carbide, and aluminum powder as an antioxidant, leveraging the advantages of each component at different temperature stages. The antioxidant reacts preferentially with oxygen before carbon at high temperatures. Among them, magnesium carbide has a good antioxidant effect at 600-800℃, boron carbide has a good antioxidant effect at 800-1000℃, and aluminum powder has a good antioxidant effect above 1000℃. The composite antioxidant formed by the three compounds ensures that the castable has a good antioxidant effect throughout the high-temperature range.

[0040] 4) Aluminum nitride powder decomposes when it comes into contact with water, generating hydrogen and aluminum oxide, which consumes the excess moisture in the raw materials to achieve the purpose of quick drying; at the same time, the released ammonia gas forms micropores in the matrix, and another part of the water vapor will be discharged along these pore channels.

[0041] 5) The main components of the castable refractory for the main trough of the present invention are alumina and silicon carbide. Dense corundum, white corundum, α-Al2O3 powder, and p-Al2O3 are the main sources of alumina; among them, dense corundum and white corundum have low porosity and high hardness, which can improve the castable's resistance to slag penetration; α-Al2O3 powder and p-Al2O3 can improve the fluidity of the castable, thereby improving its construction performance. At the same time, p-Al2O3 has spontaneous hydration ability at room temperature, acting as a binder, and in the subsequent production process of the main trough castable, no low-melting-point phase is generated at high temperature, thus giving the castable better slag resistance. Silicon carbide has the characteristics of high hardness, high strength, low coefficient of thermal expansion, and high thermal conductivity, which can improve the sintering strength and slag resistance of the castable. In addition, based on the bulk density theory, the particle size and ratio of raw materials are optimized so that the entire system of the prepared castable is tightly wrapped, forming a complete and dense matrix structure.

[0042] 6) In summary, the castable refractory for the main channel of the iron outlet of the present invention has excellent flexural strength, compressive strength and low linear change rate, whether at low temperature or high temperature. Its flexural strength after firing at 1400℃ for 3h in the cold state is above 12 MPa, its compressive strength is above 64 MPa and its linear change rate is below +0.3%. Its flexural strength after firing at 1400℃ for 0.5h in the hot state is above 4.2 MPa. Detailed Implementation

[0043] The present invention will be further described below with reference to specific embodiments.

[0044] Unless otherwise specified, the reagents and materials described in the following examples are commercially available.

[0045] Unless otherwise specified, the "parts" mentioned in the embodiments of the present invention refer to parts by mass, and the "%" refers to percentages by mass.

[0046] The magnesium sol was selected from Hebei Magnesium Biotechnology Co., Ltd., with a particle size D50 of 40nm and a solid content of 30%.

[0047] The aluminum sol was selected from LJ-030 produced by Yangzhou Zhongtianli New Material Co., Ltd., with a particle size D50 of 30nm and a solid content of 30%.

[0048] The silica sol was selected from SW15-30 / 1 of Zhejiang Delixin Micro-Nano Technology Co., Ltd., with a particle size D50 of 15nm and a solid content of 30%.

[0049] The graphite was selected from Qingdao Yucheng Graphite Co., Ltd., with a particle size D50 of 4.6μm.

[0050] The particle size D50 of α-Al2O3 powder is 5.1 μm, the particle size D50 of ρ-Al2O3 powder is 4.7 μm, the particle size of aluminum nitride powder is 300 mesh, the particle size of magnesium carbide is 325 mesh, the particle size of boron carbide is 325 mesh, and the particle size of aluminum powder is 325 mesh.

[0051] The explosion-proof fiber is selected from polyethylene fiber from Shandong Oude Chemical Fiber Products Co., Ltd., with a melting point of 105℃, a diameter of 5-6μm, and a length of 10mm.

[0052] Preparation of composite graphite particles

[0053] Preparation Example 1

[0054] (P1) Mix 1000g of graphite, 333g of magnesium sol with a solid content of 30%, 1000g of aluminum sol with a solid content of 30%, and 500g of silica sol with a solid content of 30% (i.e., the mass ratio of graphite, Mg(OH)2, Al(OH)3, and SiO2 is 1:0.1:0.3:0.15), and then stir and disperse in a high-speed disperser for 5 hours to form a mixed slurry;

[0055] (P2) The mixed slurry was granulated by a wet granulator to obtain C@Mg(OH)2@Al(OH)3@SiO2 microsphere precursors with a particle size D50 of 31.2μm; the inlet temperature of the wet granulator was 200℃, the outlet temperature was 90℃, and the rotation speed was 2100r.pm;

[0056] (P3) The C@Mg(OH)2@Al(OH)3@SiO2 microsphere precursor was calcined at 350℃ for 4h under a nitrogen atmosphere to obtain C@MgO@Al2O3@SiO2 microsphere particles, i.e. composite graphite particles a1, with a particle size D50 of 31.2μm.

[0057] Preparation Example 2

[0058] The rest is the same as in preparation example a1, except that the amounts of graphite, magnesium sol, aluminum sol, and silica sol in step (P1) are: 1000g graphite, 500g magnesium sol with a solid content of 30%, 1333g aluminum sol with a solid content of 30%, and 667g silica sol with a solid content of 30% (i.e., the mass ratio of graphite, Mg(OH)2, Al(OH)3, and SiO2 is 1:0.15:0.4:0.2). The particle size D50 of the composite graphite particles a2 obtained is 30.5μm.

[0059] Preparation Example 3

[0060] The rest is the same as in preparation example a1, except that the amounts of graphite, magnesium sol, aluminum sol, and silica sol used in step (P1) are: 1000g graphite, 667g magnesium sol with a solid content of 30%, 1667g aluminum sol with a solid content of 30%, and 833g silica sol with a solid content of 30% (i.e., the mass ratio of graphite, Mg(OH)2, Al(OH)3, and SiO2 is 1:0.2:0.5:0.25). The particle size D50 of the resulting composite graphite particles a3 is 31.6μm.

[0061] Comparative Preparation Example 1

[0062] The rest is the same as in preparation example a1, except that aluminum sol is not used in step (P1), only graphite, magnesium sol, and silica sol are used; the amounts of graphite, magnesium sol, and silica sol are: 1000g graphite, 833g magnesium sol with a solid content of 30%, and 1000g silica sol with a solid content of 30%; the particle size D50 of the obtained composite graphite particles b is 31.3μm (the C content in composite graphite particles b is the same as the C content in composite graphite particles a1).

[0063] Example 1

[0064] A blast furnace tapping main channel castable refractory comprises the following raw materials in parts by weight:

[0065] 50 parts of dense corundum, with a grain size of 3-5 mm;

[0066] 18 parts of white fused alumina, with a particle size of 1-3 mm;

[0067] 16 parts of silicon carbide with a particle size of 200 mesh;

[0068] 4.5 parts of α-Al₂O₃ powder;

[0069] 4 parts of ρ-Al2O3 powder;

[0070] The composite graphite particles a1 consist of 8 parts;

[0071] 0.6 parts aluminum nitride powder;

[0072] Three parts antioxidant, including one part magnesium carbide, one part boron carbide, and one part aluminum powder (i.e., 1:1:1);

[0073] 0.2 parts explosion-proof fiber;

[0074] 0.3 parts of water-reducing agent sodium hexametaphosphate.

[0075] Its preparation method includes the following steps:

[0076] (S1) Add silicon carbide, α-Al2O3 powder, ρ-Al2O3 powder, composite graphite particles, aluminum nitride powder, and antioxidant into a container and stir at 600 r / min for 30 min to obtain a mixed fine material;

[0077] (S2) Add dense corundum and white corundum to another container and stir at 200 r / min for 20 min to obtain mixed granules;

[0078] (S3) Maintain a stirring speed of 200 r / min, add the fine mixed material obtained in (S1) to the granular mixed material obtained in (S2), then add explosion-proof fiber and water-reducing agent, and mix and stir at a speed of 200 r / min for 20 min to obtain the main ditch castable for the iron outlet.

[0079] Example 2

[0080] The rest is the same as in Example 1, except that the composite graphite particles a2 prepared in Preparation Example 2 are used instead of the composite graphite particles a1 prepared in Preparation Example 1 in the raw material composition.

[0081] Example 3

[0082] The rest is the same as in Example 1, except that the composite graphite particles a3 prepared in Preparation Example 3 are used instead of the composite graphite particles a1 prepared in Preparation Example 1 in the raw material composition.

[0083] Example 4

[0084] The rest is the same as in Example 2, except that the raw material composition includes 3 parts antioxidant, of which 0.6 parts are magnesium carbide, 1.2 parts are boron carbide, and 1.2 parts are aluminum powder (i.e., 1:2:2).

[0085] Example 5

[0086] The rest is the same as in Example 2, except that the raw material composition includes 3 parts antioxidant, of which 0.5 parts magnesium carbide, 1.5 parts boron carbide, and 1 part aluminum powder (i.e., 1:3:2).

[0087] Example 6

[0088] The rest of Example 1 is the same, except that the raw material composition is as follows:

[0089] 50 parts of dense corundum, of which 10 parts are particles with a particle size of 8-5 mm, 25 parts are particles with a particle size of 5-3 mm, and 15 parts are particles with a particle size of 3-1 mm.

[0090] 18 parts of white fused alumina, of which 12 parts are particles with a particle size of 3 to 1 mm and 6 parts are fine powder with a particle size of 1 to 0.1 mm.

[0091] 16 parts of silicon carbide, of which 11 parts are fine powder with a particle size of 200 mesh and 5 parts are micro powder with a particle size of 400 mesh;

[0092] The remaining components are the same as in Example 1.

[0093] Example 7

[0094] Everything else is the same as in Example 1, except for the composition of the raw materials:

[0095] 45 parts of dense corundum, with a grain size of 3-5 mm;

[0096] 12 parts of white fused alumina, with a particle size of 1-3 mm;

[0097] 12 parts of silicon carbide, with a particle size of 0.1–1 mm;

[0098] 3 parts α-Al₂O₃ powder;

[0099] 2 parts of ρ-Al2O3 powder;

[0100] The composite graphite particles a1 consist of 5 parts;

[0101] 0.5 parts aluminum nitride powder;

[0102] One part antioxidant, comprising 0.33 parts magnesium carbide, 0.33 parts boron carbide, and 0.33 parts aluminum powder;

[0103] 0.1 part explosion-proof fiber;

[0104] 0.1 parts of water-reducing agent sodium hexametaphosphate.

[0105] Example 8

[0106] Everything else is the same as in Example 1, except for the composition of the raw materials:

[0107] 55 parts of dense corundum, with a grain size of 3-5 mm;

[0108] 25 parts of white fused alumina, with a particle size of 1-3 mm;

[0109] 20 parts of silicon carbide with a particle size of 0.1–1 mm;

[0110] 6 parts of α-Al₂O₃ powder;

[0111] 6 parts of ρ-Al2O3 powder;

[0112] The composite graphite particles a1 consist of 10 parts;

[0113] 0.8 parts aluminum nitride powder;

[0114] Five parts antioxidant, including 1.67 parts magnesium carbide, 1.67 parts boron carbide, and 1.67 parts aluminum powder;

[0115] 0.3 parts explosion-proof fiber;

[0116] 0.5 parts of water-reducing agent sodium hexametaphosphate.

[0117] Comparative Example 1

[0118] The rest is the same as in Example 1, except that 5.2 parts of graphite are used instead of 8 parts of composite graphite particles a1; the graphite content in 5.2 parts of graphite is equivalent to that in 8 parts of composite graphite particles a1.

[0119] Comparative Example 2

[0120] The rest is the same as in Example 1, except that composite graphite particles b prepared in Comparative Preparation Example 1 are used instead of composite graphite particles a1.

[0121] Comparative Example 3

[0122] The rest is the same as in Example 1, except that the antioxidant does not contain magnesium carbide, that is, the antioxidant is 3 parts, of which 1.5 parts are boron carbide and 1.5 parts are aluminum powder.

[0123] Performance testing

[0124] Add 3% water by mass to the main trough castable refractory prepared in the above embodiments and comparative examples, stir at 200 r / min for 10 min, and then vibrate and mold on a vibrating table to obtain a strip with dimensions of 40 mm × 40 mm × 160 mm. After curing in a mold at room temperature for 24 h, demold, dry in an oven at 110 °C for 24 h, and hold at 1400 °C for 3 h in an air atmosphere. Then, perform hot flexural strength testing at 1400 °C for 0.5 h. The performance test results are shown in Table 1.

[0125] Table 1 Performance Test Data

[0126]

[0127] As shown in Table 1, while the bulk density, flexural strength, and compressive strength of the castable refractory materials prepared in Comparative Examples 1-3 are generally sufficient for use at a low temperature of 110℃, their flexural strength and compressive strength are significantly lower when the temperature rises to 1400℃. In contrast, the castable refractory material prepared in this embodiment of the invention exhibits significantly better bulk density, flexural strength, compressive strength, and linear change rate than the comparative examples, both at low and high temperatures. Its flexural strength after 3 hours of firing at 1400℃ in the cold state is above 12 MPa, its compressive strength is above 64 MPa, and its linear change rate is below +0.3%. Its flexural strength after 0.5 hours of hot firing at 1400℃ is above 4.2 MPa. In summary, the castable refractory material prepared in this invention possesses excellent heat resistance, high strength, and hardness, resulting in good erosion resistance, thermal shock resistance, and oxidation resistance, thus extending its service life.

[0128] The above description is only a preferred embodiment of the present invention and does not limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A type of castable refractory for the main tapping channel of a blast furnace, characterized in that, The raw materials include the following parts by weight: 45-55 parts dense corundum, 12-25 parts white corundum, 12-20 parts silicon carbide, 3-6 parts α-Al2O3 powder, 2-6 parts ρ-Al2O3 powder, 5-10 parts composite graphite particles, 0.5-0.8 parts aluminum nitride powder, 1-5 parts antioxidant, 0.1-0.3 parts explosion-proof fiber, and 0.1-0.5 parts water-reducing agent; the composite graphite particles are formed by wet granulation of graphite, magnesium sol, aluminum sol, and silica sol to form C@Mg(OH)2@Al(OH)3@SiO2 microsphere precursors, followed by calcination in an inert atmosphere; the antioxidant is a compound of magnesium carbide, boron carbide, and aluminum powder.

2. The blast furnace tapping main channel castable according to claim 1, characterized in that, The mass ratio of graphite, Mg(OH)2, Al(OH)3, and SiO2 in the C@Mg(OH)2@Al(OH)3@SiO2 microsphere precursor is 1: (0.1~0.2): (0.3~0.5): (0.15~0.25).

3. The blast furnace tapping main channel castable according to claim 2, characterized in that, The mass ratio of graphite, Mg(OH)2, Al(OH)3, and SiO2 in the C@Mg(OH)2@Al(OH)3@SiO2 microsphere precursor is 1: (0.1~0.2): (0.4~0.5): (0.2~0.25).

4. The blast furnace tapping main channel castable according to claim 1, characterized in that, The composite graphite particles are prepared by a method comprising the following steps: (P1) Mix graphite, magnesium sol, aluminum sol and silica sol to form a mixed slurry; (P2) The mixed slurry was granulated by wet process to obtain C@Mg(OH)2@Al(OH)3@SiO2 microsphere precursor; (P3) The C@Mg(OH)2@Al(OH)3@SiO2 microsphere precursor was calcined in an inert atmosphere to obtain C@MgO@Al2O3@SiO2 microsphere particles, i.e., composite graphite particles.

5. The blast furnace tapping main channel castable according to claim 1, characterized in that, In the antioxidant, the mass ratio of magnesium carbide, boron carbide and aluminum powder is 1:(1~3):(1~2).

6. The blast furnace tapping main channel castable according to claim 5, characterized in that, In the antioxidant, the mass ratio of magnesium carbide, boron carbide and aluminum powder is 1:(2~3):(1~2).

7. The blast furnace tapping main channel castable according to claim 1, characterized in that, The dense corundum has a particle size of 1-8 mm; the white corundum has a particle size of 0.1-3 mm; and the silicon carbide has a particle size of 100-400 mesh.

8. The blast furnace tapping main channel castable according to claim 7, characterized in that, The dense corundum gradation satisfies: 15-25 wt% of particles with a size of 8-5 mm, 40-60 wt% of particles with a size of 5-3 mm, and 20-40 wt% of particles with a size of 3-1 mm; the white corundum gradation satisfies: 60-80 wt% of particles with a size of 3-1 mm, and 20-40 wt% of fine powder with a size of 1-0.1 mm; the silicon carbide gradation satisfies: 60-75 wt% of fine powder with a size of 100-200 mesh, and 25-40 wt% of micro powder with a size of 200-400 mesh.

9. The blast furnace tapping main channel castable according to claim 1, characterized in that, In the dense corundum and white corundum, Al2O3 ≥ 99 wt%, Fe2O3 ≤ 0.1 wt%, and SiO2 ≤ 0.1 wt%; in the silicon carbide, SiC ≥ 97 wt%, SiO2 ≤ 0.4 wt%, and Fe2O3 ≤ 0.3 wt%. The particle size D50 of the α-Al2O3 powder is 1~6µm, and the Al2O3 content in the α-Al2O3 powder is ≥99.0wt%; The particle size D50 of the ρ-Al2O3 powder is 1~6µm, and the Al2O3 content in the ρ-Al2O3 powder is ≥98.0wt%; The composite graphite particles have a particle size D50 of 15~60µm; the graphite has a particle size D50 of 1~6µm; and the graphite is at least one of artificial graphite, natural graphite, and graphitized mesophase carbon microspheres. The aluminum nitride powder has a particle size D50 of 200~400 mesh; In the antioxidant, the particle size of magnesium carbide is 200-400 mesh, the particle size of boron carbide is 200-400 mesh, and the particle size of aluminum powder is 200-400 mesh.

10. The blast furnace tapping main channel castable according to claim 1, characterized in that, The explosion-proof fiber is an organic fiber with a melting point of 90~160℃, a diameter of 4~8µm, and a length of 8~15mm; the water-reducing agent is a polycarboxylate water-reducing agent and / or sodium hexametaphosphate.

11. The method for preparing the blast furnace tapping main trough castable according to any one of claims 1-10, characterized in that, Includes the following steps: (S1) Add silicon carbide, α-Al2O3 powder, ρ-Al2O3 powder, composite graphite particles, aluminum nitride powder, and antioxidant to a container and mix them to obtain a fine mixture. (S2) Add dense corundum and white corundum to another container and mix them to obtain mixed granules; (S3) Under stirring conditions, the fine mixed material obtained in (S1) is added to the granular mixed material obtained in (S2), and then explosion-proof fiber and water-reducing agent are added and mixed to obtain the blast furnace tapping main channel castable.

12. The water-addition casting construction method for the blast furnace tapping main channel castable according to any one of claims 1-10, wherein the amount of water added is 2-3.5% of the total mass of the tapping main channel castable.

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