Preparation method of electric arc furnace cover with gradient structure, low thermal conductivity and high erosion resistance

Abstract

This invention discloses a method for preparing a gradient structure electric arc furnace cover with low thermal conductivity and high corrosion resistance. Carbon fibers are ultrasonically dispersed in an aluminosilicate sol, then 0.1-0.5% (by mass) of fine powder is added. After ultrasonic dispersion and vacuum drying, the mixture is sintered in a vacuum furnace to obtain sol-coated carbon fibers. High-purity fused white corundum particles, activated alumina fine powder, calcium aluminate cement, and sol-coated carbon fibers are added, along with a water-reducing agent. The mixture is stirred evenly, cast into shape, and dried to obtain a furnace cover green. The sides and bottom of the furnace cover green are coated with clay slurry. The green cover is then placed in alumina powder, except for the top surface which is in contact with air, and kept at 1600-1750℃ for 4-8 hours. The clay layer is then scraped off to obtain the finished product. The refractory material for the electric arc furnace cover prepared in this invention has advantages such as wide applicability, high strength, excellent thermal shock resistance and corrosion resistance, long-term non-peeling, and good heat insulation, meeting the requirements of energy saving, consumption reduction, and long service life.

Description

Technical Field

[0001] This invention relates to the field of shaped refractory materials, and more particularly to a method for preparing an electric arc furnace cover with a gradient structure, low thermal conductivity, and high corrosion resistance. Background Technology

[0002] The electric arc furnace is one of the key pieces of equipment in the production of refractory materials such as fused zirconia-corundum bricks, fused mullite, fused white corundum, and fused magnesia. The structure of an electric arc furnace mainly consists of the furnace bottom, furnace walls, and furnace cover. The furnace cover has a curved, irregularly shaped structure with electrode holes and charging holes, requiring excellent high-temperature strength. During use, the furnace cover is susceptible to molten / slag splashing and volatilization erosion, requiring superior erosion resistance. With the development of related technologies and changes in smelting conditions such as increased melting temperatures and shorter melting cycles, the refractory material of the furnace cover needs to possess superior thermal shock resistance, spalling resistance, and a longer service life. Furthermore, since heat in the furnace is mainly transferred upwards, the insulation effect of the furnace cover directly affects the energy consumption of the electric arc furnace.

[0003] Chinese invention patent (CN113121248B) proposes a composite lining for a VD furnace cover and its preparation method. This invention combines silicon carbide powder, silicon carbide particles, and a small amount of glass powder, improving the oxidation resistance of silicon carbide and achieving moderate sintering between different raw materials, resulting in high thermal shock stability. The design of the two-layer lining exhibits a gradient distribution in structure, thermal, and mechanical properties, leading to excellent mechanical properties in the resulting VD furnace cover composite lining. However, its silicon carbide composite process is relatively complex, and the vibration required during both casting stages could potentially damage the structural integrity of the base layer. Chinese invention patent (CN106431436B) proposes an electric furnace cover castable with aluminum-chromium slag as the main material and its preparation method. However, the added aluminum-vanadium slag has a high impurity content, easily forming a liquid phase at high temperatures, which is detrimental to the high-temperature strength of the furnace cover.

[0004] Chinese invention patent (CN119080483B) proposes a high-performance rare-earth composite calcium carbide furnace cover refractory castable and its preparation method. However, the added chromium oxide green readily produces toxic hexavalent chromium under high temperature and volatile organic compound conditions. Chinese invention patent (CN106007738B) proposes an electric arc furnace cover castable, an electric arc furnace cover, and its production method. However, the addition of a large amount of sintered mullite is unsuitable for the current melting temperatures, which are generally above 1600℃. Chinese invention patent (CN120398554B) proposes a VD furnace cover castable lining and its preparation method, which requires separate pretreatment of two raw materials, making the process complex. The preparation temperature of composite coated graphite exceeds 1350℃, and the sintering process is carried out under an inert atmosphere, resulting in high production costs. (Chinese Invention Patent)

[0005] (CN120117910B) discloses a furnace cover brick for an electrofused zirconia-corundum brick furnace and its preparation method. The brick has low porosity, inevitably leading to low thermal shock resistance and high thermal conductivity. This results in large-scale spalling, severely affecting melt cleanliness, and poor insulation, leading to increased energy consumption in the electric furnace. Furthermore, while some patents incorporate organic additives such as explosion-proof fibers to improve thermal shock resistance and reduce thermal conductivity, their continuous pores become important pathways and channels for melt / slag erosion of the furnace cover, reducing its erosion resistance. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing an electric arc furnace cover with a gradient structure, low thermal conductivity, and high corrosion resistance.

[0007] The innovation of this invention lies in the fact that the refractory material for the electric arc furnace cover prepared in this invention has the advantages of wide applicability, high strength, excellent thermal shock resistance and erosion resistance, no peeling after long-term use, and good heat preservation effect, thus meeting the requirements of energy saving, consumption reduction and long service life.

[0008] To achieve the above-mentioned objectives, the technical solution of this invention is: a method for preparing a gradient structure electric arc furnace cover with low thermal conductivity and high corrosion resistance, comprising the following steps:

[0009] (1) Disperse the carbon fibers in the aluminosilicate sol ultrasonically for 1-2 hours, then add 0.1-0.5% of the mass of the aluminosilicate sol. Fine powder is ultrasonically dispersed for 30-60 minutes, then vacuumed for 30-60 minutes and dried at 50-80℃ for 4-8 hours. Finally, it is sintered in a vacuum furnace at 300-800℃ for 2-3 hours to obtain sol-coated carbon fiber.

[0010] (2) Take the following raw materials in the following mass percentages: 65~80wt% high-purity fused white corundum particles, 10~25wt% activated alumina fine powder, 5~10wt% calcium aluminate cement, 2~5wt% sol-coated carbon fiber, then take 1~2% of the raw material mass of water-reducing agent and mix them together evenly, then add 2~5% of the raw material mass of water and mix evenly, cast into shape and dry to obtain furnace cover green blank;

[0011] (3) Coat the sides and bottom of the furnace cover blank with 5-10 mm of clay slurry, then place the furnace cover blank in 70-150 mesh alumina powder. Except for the upper surface which is in contact with air, the sides and bottom of the furnace cover blank are buried in 70-150 mesh alumina powder and kept at 1600-1750℃ for 4-8 hours. Then scrape off the clay layer to obtain the finished product.

[0012] Furthermore, the carbon fiber has a diameter of 5–10 μm, a length of 5–10 mm, and a C content of ≥95 wt%.

[0013] Furthermore, the aluminosilicate sol has a pH value of less than or equal to 2.0, a solid content of ≥30wt%, and a silicon-to-aluminum ratio of ≥1 / 3.

[0014] Furthermore, the aforementioned The fine powder is of analytical grade and has a particle size ≤1μm.

[0015] Furthermore, the high-purity electrofused white corundum particles Content ≥99.6wt%.

[0016] Furthermore, the activated alumina fine powder Content ≥99.8wt%, crystal form is α phase.

[0017] Furthermore, the impurity content of the calcium aluminate cement is ≤0.5wt%.

[0018] Furthermore, the clay slurry is made by uniformly mixing clay and water at a material-to-water ratio of 1:3~7, wherein the clay impurity content is ≤5wt% and the specific surface area is 42~54m2 / g.

[0019] Furthermore, the impurity content of the 70-150 mesh alumina powder is less than 0.05 wt%, which is... .

[0020] The beneficial effects of this invention are:

[0021] 1. In this invention, carbon fibers are first ultrasonically dispersed in an aluminosilicate sol with a pH value of less than or equal to 2.0, thereby achieving surface modification of carbon fibers by the acidic solution, which enhances the adhesion of aluminum and silicon ions in the aluminosilicate sol to the carbon fibers. The solid content of the aluminosilicate sol is strictly controlled, and aluminum and silicon ions are evenly distributed on the carbon fibers during the ultrasonic process. Through process control, ultrasonication and vacuuming are used to achieve uniform distribution of V2O5 fine powder between aluminum and silicon ions while it adheres to the surface of the carbon fibers.

[0022] 2. The pretreatment of carbon fiber in this invention plays a crucial role in the overall performance of the furnace lid. Sintering in a vacuum furnace achieves the initial reaction of the sol, ensuring that aluminum and silicon ions are tightly bound while preventing complete reaction to form mullite. Furthermore, it achieves the optimal combination of aluminum ions, silicon ions, and... The fine powder adheres tightly to the surface of the carbon fiber, forming a sol-coated carbon fiber. The specific silicon-to-aluminum ratio of the aluminum-silicon sol (≥1 / 3) allows silicon ions to form C-Si bonds with the carbon fiber during the initial sintering process. During subsequent heat treatment, these silicon ions preferentially react to form SiC whiskers, while the remaining aluminum and silicon ions... Under the promoting effect of the formation of mullite whiskers, while preventing SiC whiskers from being oxidized, the furnace cover is strengthened and toughened, giving it excellent high-temperature strength, thermal shock resistance and erosion resistance, and the ability to not peel off after long-term use. As a result, it can be widely used in various types of electric arc furnaces.

[0023] 3. This invention achieves the preparation of a low thermal conductivity and high corrosion resistance refractory material for an electric arc furnace lid with a gradient structure through a specific sintering process. The upper surface of the lid remains in contact with the air atmosphere, where the carbon fibers are oxidized at high temperatures to form pores, effectively reducing the thermal conductivity and providing insulation. The other surfaces of the lid are protected by clay and alumina powder, preventing oxidation and the formation of SiC whiskers. The low impurities and specific material-to-water ratio of the clay allow for effective oxygen isolation and easy scraping after sintering. The 70-150 mesh alumina powder effectively isolates oxygen while preventing it from sintering with the clay slurry, making it easy to clean. The resulting electric arc furnace lid refractory material possesses the characteristics of a dense, highly corrosion-resistant surface and a relatively high porosity and low thermal conductivity on the non-corroded surface, giving the lid both excellent corrosion resistance and good insulation properties. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention will be clearly and completely described below.

[0025] Example 1: A method for preparing a gradient structure electric arc furnace cover with low thermal conductivity and high corrosion resistance, comprising the following steps:

[0026] (1) The carbon fibers were ultrasonically dispersed in the aluminosilicate sol for 1 hour, and then 0.1% of the mass of the aluminosilicate sol was added. Fine powder was ultrasonically dispersed for 30 minutes, then vacuum-dried for 30 minutes and dried at 50°C for 4 hours. Finally, it was sintered in a vacuum furnace at 300°C for 2 hours to obtain sol-coated carbon fibers. The carbon fibers had a diameter of 5-10 μm, a length of 5-10 mm, and a C content of 95 wt%. The aluminosilicate sol had a pH of 2.0, a solid content of 30 wt%, and a silicon-to-aluminum ratio of 1 / 3. The fine powder is of analytical grade and has a particle size ≤1μm;

[0027] (2) Take the following raw materials by mass percentage: 65wt% high-purity fused white corundum particles, 20wt% activated alumina fine powder, 10wt% calcium aluminate cement, 5wt% sol-coated carbon fiber, and then take 1% of the raw material mass of water-reducing agent and mix them evenly together. Then add 2% of the raw material mass of water and mix evenly. After casting and drying, the furnace cover green blank is obtained. The fine powder is of analytical grade, with a particle size ≤1μm. High-purity fused white corundum particles. Content ≥99.6wt%; Activated alumina fine powder The content is ≥99.8wt%, and the crystal form is α phase; the impurity content of calcium aluminate cement is ≤0.5wt%.

[0028] (3) Coat the sides and bottom of the furnace cover blank with 5-10 mm of clay slurry, then place the furnace cover blank in 70-150 mesh alumina powder. Except for the upper surface which is in contact with air, the sides and bottom of the furnace cover blank are buried in 70-150 mesh alumina powder. Keep it at 1600℃ for 4 hours, then scrape off the clay layer to obtain the finished product. The clay slurry is made by mixing clay and water at a material-to-water ratio of 1:3. The clay impurity content is ≤5wt%, and the specific surface area is 42-54 m2 / g. The impurity content of the 70-150 mesh alumina powder is less than 0.05wt%. .

[0029] Example 2: A method for preparing a gradient structure electric arc furnace cover with low thermal conductivity and high corrosion resistance, comprising the following steps:

[0030] (1) The carbon fibers were ultrasonically dispersed in the aluminosilicate sol for 1.5 h, and then 0.3% of the mass of the aluminosilicate sol was added. Fine powder was ultrasonically dispersed for 40 min, then vacuum-dried for 40 min, and dried at 65℃ for 6 h. Finally, it was sintered in a vacuum furnace at 500℃ for 2.5 h to obtain sol-coated carbon fibers. The carbon fibers had a diameter of 5-10 μm, a length of 5-10 mm, and a C content of 96 wt%. The aluminosilicate sol had a pH of 1.5, a solid content of 40 wt%, and a silicon-aluminum ratio of 2 / 5. The fine powder is of analytical grade and has a particle size ≤1μm;

[0031] (2) Take the following raw materials by mass percentage: 80wt% high-purity fused white corundum particles, 10wt% activated alumina fine powder, 8wt% calcium aluminate cement, 2wt% sol-coated carbon fiber, and then take 1.5% of the raw material mass of water-reducing agent and mix them evenly together. Then add 3% of the raw material mass of water and mix evenly. After casting and drying, the furnace cover green blank is obtained. The fine powder is of analytical grade, with a particle size ≤1μm. High-purity fused white corundum particles. Content ≥99.6wt%; Activated alumina fine powder The content is ≥99.8wt%, and the crystal form is α phase; the impurity content of calcium aluminate cement is ≤0.5wt%.

[0032] (3) Coat the sides and bottom of the furnace cover blank with 5-10mm of clay slurry, then place the furnace cover blank in 70-150 mesh alumina powder. Except for the upper surface which is in contact with air, the sides and bottom of the furnace cover blank are buried in 70-150 mesh alumina powder. Keep it at 1700℃ for 6 hours, then scrape off the clay layer to obtain the finished product. The clay slurry is made by mixing clay and water at a material-to-water ratio of 1:5. The clay impurity content is ≤5wt%, and the specific surface area is 42-54m2 / g. The impurity content of the 70-150 mesh alumina powder is less than 0.05wt%. .

[0033] Example 3: A method for preparing a gradient structure electric arc furnace cover with low thermal conductivity and high corrosion resistance, comprising the following steps:

[0034] (1) The carbon fibers were ultrasonically dispersed in the aluminosilicate sol for 2 hours, and then 0.5% of the mass of the aluminosilicate sol was added. Fine powder was ultrasonically dispersed for 60 min, then vacuum-dried for 60 min, and dried at 80℃ for 8 h. Finally, it was sintered in a vacuum furnace at 800℃ for 3 h to obtain sol-coated carbon fibers. The carbon fibers had a diameter of 5-10 μm, a length of 5-10 mm, and a C content of 98 wt%. The aluminosilicate sol had a pH of 1, a solid content of 50 wt%, and a silicon-to-aluminum ratio of 2 / 3. The fine powder is of analytical grade and has a particle size ≤1μm;

[0035] (2) Take the following raw materials by mass percentage: 67wt% high-purity fused white corundum particles, 25wt% activated alumina fine powder, 5wt% calcium aluminate cement, 3wt% sol-coated carbon fiber, and then take 2% of the raw material mass of water-reducing agent and mix them evenly together. Then add 5% of the raw material mass of water and mix evenly. After casting and drying, the furnace cover green blank is obtained. The fine powder is of analytical grade, with a particle size ≤1μm. High-purity fused white corundum particles. Content ≥99.6wt%; Activated alumina fine powder The content is ≥99.8wt%, and the crystal form is α phase; the impurity content of calcium aluminate cement is ≤0.5wt%.

[0036] (3) Coat the sides and bottom of the furnace cover blank with 5-10mm of clay slurry, then place the furnace cover blank in 70-150 mesh alumina powder. Except for the upper surface which is in contact with air, the sides and bottom of the furnace cover blank are buried in 70-150 mesh alumina powder and kept at 1750℃ for 8 hours. Then scrape off the clay layer to obtain the finished product. The clay slurry is made by mixing clay and water at a material-to-water ratio of 1:7, wherein the clay impurity content is ≤5wt% and the specific surface area is ≤5wt%. 70-150 mesh alumina powder has an impurity content of less than 0.05 wt%, which is... .

[0037] Comparative Example 1: Referring to Example 1, in step (1), carbon fibers were added to a solution at a mass of 0.1% of the solvent. The fine powder was ultrasonically dispersed in aluminosilicate sol for 1 hour, then vacuumed for 30 minutes and dried at 50°C for 4 hours. Finally, it was sintered in a vacuum furnace at 300°C for 2 hours to obtain sol-coated carbon fibers.

[0038] Comparative Example 2: Referring to Example 1, the pH value of the aluminum silica sol was adjusted to 3.

[0039] Comparative Example 3: Referring to Example 1, the furnace cover blank in step (3) was placed directly at 1600℃ for 4 hours without being coated with clay slurry or having any surface buried in 70~150 mesh alumina powder.

[0040] The gradient-structure, low thermal conductivity, and highly corrosion-resistant refractory materials for electric arc furnace covers prepared in Examples 1-3 were compared with the products prepared in Comparative Examples 1, 2, and 3. The thermal shock resistance retention rate after 5 water cooling cycles at 1100℃ is shown in the table below:

[0041]

[0042] The described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for preparing a gradient structure electric arc furnace cover with low thermal conductivity and high corrosion resistance, characterized in that, Includes the following steps: (1) Disperse the carbon fibers in the aluminosilicate sol ultrasonically for 1-2 hours, then add 0.1-0.5% of the mass of the aluminosilicate sol. Fine powder is ultrasonically dispersed for 30-60 minutes, then vacuumed for 30-60 minutes and dried at 50-80℃ for 4-8 hours. Finally, it is sintered in a vacuum furnace at 300-800℃ for 2-3 hours to obtain sol-coated carbon fiber. (2) Take the following raw materials in the following mass percentages: 65~80wt% high-purity fused white corundum particles, 10~25wt% activated alumina fine powder, 5~10wt% calcium aluminate cement, 2~5wt% sol-coated carbon fiber, then take 1~2% of the raw material mass of water-reducing agent and mix them together evenly, then add 2~5% of the raw material mass of water and mix evenly, cast into shape and dry to obtain furnace cover green blank; (3) Coat the sides and bottom of the furnace cover blank with 5-10 mm of clay slurry, then place the furnace cover blank in 70-150 mesh alumina powder. Except for the upper surface which is in contact with air, the sides and bottom of the furnace cover blank are buried in 70-150 mesh alumina powder and kept at 1600-1750℃ for 4-8 hours. Then scrape off the clay layer to obtain the finished product.

2. The method for preparing the gradient structure low thermal conductivity and high corrosion resistance electric arc furnace cover according to claim 1, characterized in that, The carbon fiber has a diameter of 5–10 μm, a length of 5–10 mm, and a C content of ≥95 wt%.

3. The method for preparing the gradient structure low thermal conductivity and high corrosion resistance electric arc furnace cover according to claim 1, characterized in that, The aluminosilicate sol has a pH value of less than or equal to 2.0, a solid content of ≥30wt%, and a silicon-to-aluminum ratio of ≥1 / 3.

4. The method for preparing the gradient structure low thermal conductivity and high corrosion resistance electric arc furnace cover according to claim 1, characterized in that, The The fine powder is of analytical grade and has a particle size ≤1μm.

5. The method for preparing the gradient structure low thermal conductivity and high corrosion resistance electric arc furnace cover according to claim 1, characterized in that, The high-purity fused white corundum particles Content ≥99.6wt%.

6. The method for preparing the gradient structure low thermal conductivity and high corrosion resistance electric arc furnace cover according to claim 1, characterized in that, The activated alumina fine powder Content ≥99.8wt%, crystal form is α phase.

7. The method for preparing the gradient structure low thermal conductivity and high corrosion resistance electric arc furnace cover according to claim 1, characterized in that, The impurity content of the calcium aluminate cement is ≤0.5wt%.

8. The method for preparing the gradient structure low thermal conductivity and high corrosion resistance electric arc furnace cover according to claim 1, characterized in that, The clay slurry is made by mixing clay and water at a material-to-water ratio of 1:3~7, wherein the clay impurity content is ≤5wt% and the specific surface area is 42~54m2 / g.

9. The method for preparing the gradient structure low thermal conductivity and high corrosion resistance electric arc furnace cover according to claim 1, characterized in that, The 70-150 mesh alumina powder has an impurity content of less than 0.05 wt%, which is α. .

Images