CA6-containing main channel castable and preparation method thereof

Abstract

The invention belongs to the technical field of refractory materials, and discloses a CA6-containing main channel castable and a preparation method thereof, the castable is composed of corundum, modified calcium hexaluminate, silicon carbide, spherical asphalt, alumina micro powder, silicon oxide micro powder, pure calcium aluminate cement and an additive; according to the invention, pores of calcium hexaluminate are filled with graphene oxide to form a modified calcium hexaluminate composite material, and the modified calcium hexaluminate composite material is used in the main channel castable, so that the porosity of calcium hexaluminate is reduced, the carbon content of the castable is increased, the loss of carbon is slowed down, the sintering of the material is promoted, the structure of the material is densified, and the service life of the material is prolonged. By adding the modified calcium hexaluminate and optimizing the components and proportion of the raw materials, the main runner castable has good high-temperature strength, volume stability, erosion resistance, scouring resistance, oxidation resistance and other use performance, and the service life of the blast furnace tapping runner is remarkably prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of refractory materials, and particularly relates to a main groove castable containing CA6 and a preparation method thereof. Background Art

[0002] The damage of the blast furnace taphole often starts with the oxidation of the carbon source therein. The easy oxidation of carbon not only consumes the carbon source and releases greenhouse gases, but also reduces the performance of the refractory materials and shortens their service life. Therefore, improving the oxidation resistance of carbon-containing refractories and protecting the environment are of great practical significance. However, the refractory materials of the taphole are complex in composition and structure. During use, the properties of the respective raw materials restrict each other. While improving the oxidation resistance, it often leads to a decline in other properties of the material. Therefore, the current main research directions include two aspects: one is the optimization and adjustment of antioxidants, and the other is the continuous experimentation and improvement of the evolution of the microstructure of the material, so that the material can improve its oxidation resistance while taking into account its slag erosion resistance and mechanical properties.

[0003] As a high-quality carbon source, spherical pitch exhibits excellent hydrophilicity. This is primarily due to its ability to penetrate the pores during heating and to volatilize at high temperatures, condensing as a gas in the pores and at the contact points between particles, thus achieving uniform distribution of carbon throughout the castable. However, pitch has a low softening point; above 110°C, it will clog pores, making it difficult to remove moisture from the castable, exacerbating the cracking problem.

[0004] Calcium hexaaluminate (CaO·6Al2O3, abbreviated as CA6) is highly stable in reducing atmospheres. Its solubility in slag is low, resulting in poor wettability. Its coefficient of thermal expansion is similar to that of Al2O3, and it exhibits lamellar crystals and a large number of micropores, most of which are between 1 and 3 μm in diameter. This structure gives calcium hexaaluminate excellent thermal shock resistance and good mechanical strength in refractory materials. However, due to the difficulty in densifying calcium hexaaluminate during synthesis, its high porosity makes it susceptible to slag penetration during high-temperature use, resulting in reduced slag resistance.

[0005] Therefore, how to solve the high porosity of calcium hexaaluminate, make full use of its high temperature advantage, apply calcium hexaaluminate to the iron trough castable, and optimize the raw material ratio to improve the performance and life of the iron trough castable is currently a major problem. Summary of the Invention

[0006] In order to solve the above technical problems, the present invention provides a main groove castable containing CA6 and a preparation method thereof, wherein graphene oxide is filled in the pores of calcium hexaaluminate to form a modified calcium hexaaluminate composite material, which not only solves the problem that the high porosity of calcium hexaaluminate cannot be used, but also increases the carbon content of the castable. The pores therein also reserve a part of the channel for the softening and overflow of spherical asphalt, alleviates the bursting problem that occurs when the iron groove is baked after casting, gives full play to the high temperature advantage of calcium hexaaluminate, and greatly improves the service life of the iron groove by adding modified calcium hexaaluminate and optimizing the raw material ratio.

[0007] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a main groove castable containing CA6, comprising the following raw material components in mass percentage: 12-52% corundum, 10-50% modified calcium hexaaluminate, 18-23% silicon carbide, 1.5-4% spherical asphalt, 5-8% alumina fine powder, 0.5-2.5% silica fine powder, 1.5-3% pure calcium aluminate cement, 1-3% elemental silicon, 0.06-0.3% metallic aluminum, 0.08-0.12% organic fiber, and 0.1-0.15% water reducer.

[0008] Among them, the particle size of corundum is 25-0.44mm, the particle size of modified calcium hexaaluminate is 5-0.2mm, and the particle size of silicon carbide is 2.5-0.044mm.

[0009] Among them, the particle size of spherical asphalt is 1-0.2mm, the particle size of alumina micropowder is 5-0.5μm, the particle size of silica micropowder is less than 1μm, and the particle size of pure calcium aluminate cement is less than 25μm.

[0010] Among them, the particle size of elemental silicon is 0.12-0.044 mm, and the particle size of metallic aluminum is 0.088-0.044 mm.

[0011] Among them, the preparation of modified calcium hexaaluminate is to place calcium hexaaluminate in a container with a vacuum degree of less than -0.5MPa, maintain the pressure for 20 minutes, inject graphene oxide solution, maintain the pressure again for 1 hour, release the pressure and dry it at 150°C, repeat the above operation 3-5 times, so that the mass percentage content of graphene oxide in calcium hexaaluminate is ≥1.0%, which is the required modified calcium hexaaluminate composite raw material.

[0012] The graphene oxide solution is prepared by mixing graphene oxide and water in a weight ratio of 1:2 and can be used after ultrasonic treatment, wherein the ultrasonic treatment power is 200-500W, the ultrasonic temperature is 50-70°C, and the time is 0.2-5h.

[0013] The preparation method of this main ditch castable containing CA6 is as follows: corundum, modified calcium hexaaluminate, silicon carbide and spherical asphalt are used as aggregates of the iron ditch castable, and corundum fine powder, alumina micropowder, silicon oxide micropowder, pure aluminate cement, elemental silicon, metallic aluminum, organic fiber and water reducer are used as the matrix, and the raw materials are mixed according to the mass percentage components, mixed evenly in a mixer and packaged for pouring on the main ditch construction site; before pouring, water is directly added and stirred for 3-5 minutes according to demand, and the amount of water added accounts for 3.5-6% of the total weight of the raw materials; the mixed material with water is poured into a mold supported by the main ditch for vibration molding, and demoulded after natural drying and hardening, and then dried at 90-500℃ to eliminate free water and part of structural water in the castable, so as to prepare the castable for the blast furnace main ditch and use it for passing molten iron.

[0014] The present invention proposes a main channel castable containing CA6. In the low-temperature range, calcium hexaaluminate reacts with silicon carbide and carbon monoxide to form anorthite (CAS2) and carbon. The reaction is CA6 + SiC + CO → CAS2 + C. At high temperatures, the anorthite remains stable and resists reduction, allowing the material to sinter and densify, achieving resistance to erosion and wear from molten iron. At high temperatures, carbon oxidizes to form CO, which diffuses throughout the material. At low temperatures, the presence of CA6 and SiC reduces the carbon monoxide and deposits it on the CAS2 to form carbon. The carbon present in the calcium hexaaluminate, along with the generated carbon, remains, mitigating erosion and penetration by iron slag and providing excellent protection for the tap channel lining. This significantly increases the service life of the main channel castable.

[0015] Calcium hexaaluminate belongs to the hexagonal system and has a high melting point (1875°C) and a low thermal expansion coefficient (8.0×10 -6 ℃ -1 ), the thermal expansion coefficient is similar to that of Al2O3, and its unit cell is composed of spinel matrix and Ca 2+ The mirror layer is stacked along the c-axis and has plate-like crystals and a large number of microporous structures. The pore diameters of most of the micropores are between 1 and 3 μm. The flake or plate-like microstructure gives it excellent thermal shock resistance and good mechanical strength. CA6 itself is a refractory material with high stability in a reducing atmosphere. It has low solubility in slag and poor wettability with slag. Calcium hexaaluminate has excellent thermal shock resistance and good mechanical strength among refractory materials.

[0016] As a derivative of graphene, graphene oxide has better mechanical properties and a larger specific surface area. The oxygen-containing functional groups (carboxyl, hydroxyl, carbonyl and epoxy groups) on its surface weaken the van der Waals forces between its sheets and increase the electrostatic repulsion between them, making graphene oxide more hydrophilic than graphene, which is beneficial to the dispersion of graphene oxide and makes it easier to disperse in aqueous solution. The preparation of graphene oxide-modified calcium hexaaluminate adopts the ultrasonic dispersion method, which can effectively improve the agglomeration phenomenon of graphene oxide in the system.

[0017] Graphene oxide is added to calcium hexaaluminate to form a modified calcium hexaaluminate composite. The addition of graphene oxide is intended to increase carbon content. Since calcium hexaaluminate has small pore sizes, reaching the micron level, graphene oxide makes it difficult for oxygen to enter and oxidize it, resulting in excellent oxidation resistance and reduced porosity. The addition of graphene oxide also enhances the material's mechanical properties and permeability resistance. This graphene oxide-modified calcium hexaaluminate composite combines the structural properties of CA6 with the functional design of graphene oxide, achieving synergistic performance improvements through process optimization.

[0018] As a high-quality carbon source, spherical pitch exhibits excellent hydrophilicity. This is primarily demonstrated by its ability to penetrate the pores of the material during heating. At high temperatures, it volatilizes and condenses as a gas within the pores and at contact points between particles, achieving uniform distribution of carbon throughout the castable. The amount of spherical pitch added as a carbon source influences the castable's slag resistance. This is because the residual carbon in the asphalt has high thermal conductivity, a low coefficient of expansion, and low wettability by slag and molten metal. Therefore, the addition of spherical pitch improves the castable's erosion and permeation resistance, thereby increasing the service life of the castable used in the tap channel. However, excessive spherical pitch addition, due to its hydrophobic nature, increases the water requirement for molding the castable, reducing fluidity and bulk density. Furthermore, oxidation of the volatiles and residual carbon in the asphalt increases porosity, which in turn reduces the castable's erosion resistance. The presence of CAS2 enhances the reaction between the carbon and aluminum powder to form aluminum carbide whiskers, further enhancing the castable's structural properties.

[0019] SiC is a material with high thermal conductivity and low thermal expansion coefficient, excellent performance, and relatively small stress generated after heating. During firing and use, the surface of silicon carbide will oxidize to form a SiO2 film. This SiO2 and Al2O3 and CaO in the castable easily form an Al2O3-CaO-SiO2 glass phase on the surface of silicon carbide, forming a strong bond; calcium hexaaluminate absorbs alkaline substances such as CaO in the slag at high temperatures to form other calcium aluminate mineral phases with a higher melting point, which increases the viscosity of the slag that penetrates into the castable matrix and is beneficial to resisting slag erosion.

[0020] The beneficial effects of the present invention are as follows: a main groove castable containing CA6 proposed by the present invention creatively utilizes graphene oxide to fill the pores of calcium hexaaluminate to form a modified calcium hexaaluminate composite material, which is applied to the castable of the main iron tapping groove, fully utilizing the high-temperature advantage of calcium hexaaluminate, and solving the problem that the high porosity of calcium hexaaluminate is difficult to apply. It not only reduces the porosity of calcium hexaaluminate, but also increases the carbon content of the castable and slows down the loss of carbon, promotes the sintering of the material, densifies its structure, and improves the scouring and wear of the iron tapping groove by molten iron. By adding modified calcium hexaaluminate and optimizing the raw material ratio, the main groove castable has excellent high-temperature strength, volume stability, and anti-erosion, anti-scouring, anti-oxidation and other performance properties, significantly improving the service life of the main iron tapping groove of the blast furnace, reducing ironmaking costs and improving production efficiency. DETAILED DESCRIPTION

[0021] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below with reference to specific embodiments, but the embodiments are not intended to limit the present invention.

[0022] It should be noted that the methods described in the following embodiments are all conventional methods unless otherwise specified; the raw materials used are all commercially available unless otherwise specified.

[0023] The preparation of modified calcium hexaaluminate is to place calcium hexaaluminate in a container with a vacuum degree of less than -0.5MPa, maintain the pressure for 20 minutes, inject graphene oxide solution, maintain the pressure again for 1 hour, release the pressure and dry it at 150°C, repeat the above operation 3-5 times, so that the mass percentage of graphene oxide in calcium hexaaluminate is ≥1.0%, which is the required modified calcium hexaaluminate composite raw material.

[0024] The graphene oxide solution is prepared by mixing graphene oxide powder and water in a weight ratio of 1:2 and then subjected to ultrasonic treatment. The solution can be used, wherein the ultrasonic treatment power is 200-500W, the ultrasonic temperature is 50-70°C, and the time is 0.2-5h.

[0025] The preparation method of this CA6-containing main ditch castable is as follows: corundum, modified calcium hexaaluminate, silicon carbide and spherical asphalt are used as aggregates of the iron ditch castable, corundum fine powder, alumina micropowder, silicon oxide micropowder, pure aluminate cement, elemental silicon, metallic aluminum, organic fiber and water reducer are used as matrices, and the ingredients are respectively prepared according to the mass percentage components of each raw material in Examples 1-4, and the materials are mixed in a mixer and packaged for pouring on the main ditch construction site; before pouring, water is directly added and stirred for 3-5 minutes according to demand, and the amount of water added accounts for 3.5-6% of the total weight of the raw materials; the mixed material with water is poured into a mold supported by the main ditch for vibration molding, and demoulded after natural drying and hardening, and then dried at 90-500°C to eliminate free water and part of structural water in the castable, so as to prepare the castable for the blast furnace main ditch and use it for passing molten iron. Example 1

[0026] A main groove castable containing CA6, the raw material components, particle size and mass percentage used are as follows:

[0027] Example 2 A main groove castable containing CA6, the raw material components, particle size and mass percentage used are as follows:

[0028] Example 3 A main groove castable containing CA6, the raw material components, particle size and mass percentage used are as follows:

[0029] Example 4 A main groove castable containing CA6, the raw material components, particle size and mass percentage used are as follows:

[0030] Comparative Example 1 The raw material components, particle sizes and mass percentages of the main tapping channel castable without modified calcium hexaaluminate are as follows:

[0031] Comparative Example 2 The raw material components, particle sizes and mass percentages of the main tapping channel castable without modified calcium hexaaluminate are as follows:

[0032] The main trench castables prepared in Examples 1, 2, 3, 4 and Comparative Examples 1 and 2 were respectively sampled for physical and chemical performance testing and analysis, and the obtained performance indicators are as follows: Performance indicators of main groove castables in embodiments and comparative examples

[0033] Note: "A" in the table represents the sample baking temperature of 200℃×24h; “B” represents the sample treated in an oxidizing atmosphere at 1500°C for 3 h; "C" means the sample was baked at 200℃×24h and the strength was tested at 1450℃×1h in a reducing atmosphere; “D” means the sample was pre-heated at 1500℃ for 3h and tested 30 times at 1100℃ for 0.5h; “E” means the sample was pre-treated at 1450°C for 3 h and then at 1100°C for 5 h.

[0034] It can be seen from the performance test results in the above table that compared with the comparative example, the bulk density of the embodiment castable is slightly reduced, the line change rate after burning is slightly increased, the high-temperature flexural strength and the flexural strength retention rate after thermal shock are greatly enhanced, and the oxidation resistance is significantly improved. The performance indicators of the main groove castable containing CA6 represented by the embodiment have been optimized. The blast furnace tapping ditch is a circulation channel that molten iron and slag must pass through after melting. It is an intermittent operation. Extending the service life of the blast furnace tapping ditch castable can effectively reduce ironmaking costs and improve production efficiency. The introduction of modified calcium hexaaluminate can significantly improve the thermal shock stability of the tapping ditch, and retains the presence of carbon to the maximum extent, so that the slag iron erosion of the tapping ditch is improved. Therefore, the main groove castable containing CA6 described in the present invention has a good application prospect.

[0035] The above embodiments are merely examples of the explanation, specific embodiments, and implementation effects of the present invention, and are not intended to limit the present invention. Based on the present disclosure, some modifications or improvements without creative contributions may be made thereto, which will be apparent to those skilled in the art. Therefore, these modifications or improvements made without departing from the spirit of the present disclosure are intended to fall within the scope of protection claimed in the present disclosure.

Claims

1. A main groove castable containing CA6, characterized in that: The invention comprises the following raw material components in percentage by mass: 12-52% of corundum, 10-50% of modified calcium hexaaluminate, 18-23% of silicon carbide, 1.5-4% of spherical asphalt, 5-8% of alumina micropowder, 0.5-2.5% of silicon oxide micropowder, 1.5-3% of pure calcium aluminate cement, 1-3% of elemental silicon, 0.06-0.3% of metallic aluminum, 0.08-0.12% of organic fiber and 0.1-0.15% of water reducing agent.

2. A main groove castable containing CA6 according to claim 1, characterized in that: The particle size of corundum is 25-0.44 mm, the particle size of modified calcium hexaaluminate is 5-0.2 mm, and the particle size of silicon carbide is 2.5-0.044 mm.

3. A main groove castable containing CA6 according to claim 1, characterized in that: The particle size of spherical asphalt is 1-0.2 mm, the particle size of alumina micropowder is 5-0.5 μm, the particle size of silica micropowder is less than 1 μm, and the particle size of pure calcium aluminate cement is less than 25 μm.

4. The main groove castable containing CA6 according to claim 1, characterized in that: The particle size of elemental silicon is 0.12-0.044 mm, and the particle size of metallic aluminum is 0.088-0.044 mm.

5. The main groove castable containing CA6 according to claim 1, characterized in that: The preparation of modified calcium hexaaluminate is to place calcium hexaaluminate in a container with a vacuum degree of less than -0.5MPa, maintain the pressure for 20 minutes, inject graphene oxide solution, maintain the pressure again for 1 hour, release the pressure and dry it at 150°C, repeat the above operation 3-5 times, so that the mass percentage of graphene oxide in calcium hexaaluminate is ≥1.0%, which is the required modified calcium hexaaluminate composite raw material.

6. A main groove castable containing CA6 according to claim 5, characterized in that: The graphene oxide solution is prepared by mixing graphene oxide and water in a weight ratio of 1:2 and then subjected to ultrasonic treatment before use.

7. A main groove castable containing CA6 according to claim 6, characterized in that: The power of ultrasonic treatment is 200-500W, the ultrasonic temperature is 50-70°C, and the time is 0.2-5h.

8. A method for preparing a main groove castable containing CA6 according to claim 1, characterized in that: Corundum, modified calcium hexaaluminate, silicon carbide and spherical asphalt are used as aggregates of the iron trench castable, and corundum fine powder, alumina micropowder, silicon oxide micropowder, pure aluminate cement, elemental silicon, metallic aluminum, organic fiber and water reducer are used as the matrix. The raw materials are mixed according to the mass percentage components, mixed evenly in a mixer and packaged for casting on the main trench construction site; before pouring, water is directly added and stirred for 3-5 minutes according to demand, and the amount of water added accounts for 3.5-6% of the total weight of the raw materials. The mixed material with water is poured into a mold supported by the main trench and vibrated to form. After natural drying and hardening, it is demoulded and then dried at 90-500℃ to eliminate free water and part of structural water in the castable. The castable is prepared into a castable for the blast furnace main trench and can be used for passing molten iron.

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