Ladle nozzle pocket block added with regenerated Cr2O3-ZrO2-Al2O3 composite powder and preparation method of ladle nozzle pocket block

Abstract

The invention discloses a ladle nozzle pocket block added with regenerated Cr2O3-ZrO2-Al2O3 composite powder and a preparation method of the ladle nozzle pocket block, and belongs to the technical field of refractory materials. The refractory material comprises the following raw materials in percentage by weight: 60-64% of 97.2 fused magnesia particles; 35%-39% of co-ground powder; the sum of the weight percentages of the 97.2 fused magnesia particles and the co-grinding powder is 100%; a thermosetting phenolic resin binder accounting for 4-5% of the total weight of the raw materials is added; the co-grinding powder comprises the following components in percentage by weight: 6%-18% of 97.2 fused magnesite fine powder, 10%-18% of regenerated Cr2O3-ZrO2-Al2O3 composite powder, 5%-8% of alpha-Al2O3 fine powder, 5%-8% of metal aluminum powder and 1%-2% of metal silicon powder; the regenerated Cr2O3-ZrO2-Al2O3 composite powder is prepared from the following chemical components in percentage by weight: 83% of Cr2O3, 5.65% of ZrO2, 0.15% of SiO2 and 0.2% of Fe2O3, and the regenerated Cr2O3-ZrO2-Al2O3 composite powder is prepared from the following raw materials in percentage by weight: 83wt% of Cr2O3, 5.65% of ZrO2, 0.15% of SiO2 and 0.2% The high-temperature mechanical property, erosion resistance and thermal shock resistance of the product are remarkably improved, and the service life of the product is remarkably prolonged.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of refractory materials, and more particularly relates to a ladle nozzle seat brick added with regenerated Cr2O3-ZrO2-Al2O3 composite powder and a preparation method thereof. BACKGROUND

[0002] In the steel smelting process, the ladle nozzle seat brick is a key refractory component connecting the ladle and the sliding nozzle system, and its performance directly affects the quality of molten steel, production safety and refractory material consumption. The traditional nozzle seat brick material is mainly corundum or magnesia-carbon. These materials are subjected to long-term high-temperature molten steel scouring, erosion and thermal shock on the upper end face during use, and are prone to peeling, cracking and other problems. Once the molten steel penetrates into the cracks, it is easy to cause serious production accidents such as steel penetration and steel penetration, which not only affects continuous production, but also brings safety hazards.

[0003] For example, a patent document with the Chinese patent application number CN202411828218.6 and the publication date of March 7, 2025 discloses a composite high-life ladle nozzle seat brick for steelmaking refining and a preparation method thereof. The ladle nozzle seat brick includes a seat brick inner core, the inner core is cylindrical, a flow steel hole is provided in the center of the inner core from top to bottom, the inner core includes an upper inner core and a lower inner core which are fitted in position, the upper inner core and the lower inner core are formed by machine pressing, a pouring part is provided on the outer side of the inner core, the pouring part is flush with the top end face of the inner core, the pouring part extends downward from the bottom of the inner core, a mounting hole is provided in the center of the bottom of the pouring part, the diameter of the mounting hole is larger than the diameter of the flow steel hole, and the mounting hole is coaxial with the flow steel hole. In this scheme, the pouring part is made of corundum material as the main body, which has the problems of long-term high-temperature molten steel scouring, erosion and thermal shock on the upper end face, and is prone to peeling, cracking and other problems.

[0004] Therefore, it is a technical problem to be solved in the field to develop a nozzle seat brick with higher high-temperature strength, better erosion resistance, thermal shock resistance and longer service life. SUMMARY

[0005] 1. Problem to be solved In view of the problem that the performance of the existing ladle nozzle seat brick cannot meet the long-term high-temperature molten steel scouring, the application provides a ladle nozzle seat brick added with regenerated Cr2O3-ZrO2-Al2O3 composite powder and a preparation method thereof. By introducing the regenerated composite powder which is subjected to special pretreatment, and optimizing the raw material ratio and preparation process, the high-temperature mechanical properties, erosion resistance, thermal shock stability and service life of the product are significantly improved.

[0006] 2. Technical scheme To solve the above problems, the application adopts the following technical scheme.

[0007] A steel ladle nozzle seat brick with added recycled Cr2O3-ZrO2-Al2O3 composite powder, the raw material composition by weight percentage includes: 97.2 fused magnesia particles: 60%-64%; co-ground powder: 35%-39%; the sum of the weight percentages of the 97.2 fused magnesia particles and the co-ground powder is 100%; and an additional 4% to 5% thermosetting phenolic resin binder is added to the total weight of the raw materials. The co-milled powder comprises 6%–18% of 97.2 fused magnesia fine powder, 10%–18% of regenerated Cr2O3-ZrO2-Al2O3 composite powder, 5%–8% of α-Al2O3 fine powder, 5%–8% of metallic aluminum powder and 1%–2% of metallic silicon powder. The chemical composition and content of the regenerated Cr2O3-ZrO2-Al2O3 composite powder are as follows: Cr2O3 content is 83%, ZrO2 content is 5.65%, SiO2 content is 0.15%, and Fe2O3 content is 0.2%.

[0008] Furthermore, the raw material composition and weight percentage of the 97.2 fused magnesia particles are as follows: 27%-30% 97.2 fused magnesia with a particle size of 5-3 mm, 16%-18% 97.2 fused magnesia with a particle size of 3-1 mm, and 15%-19% 97.2 fused magnesia with a particle size of 1-0 mm. Furthermore, the chemical composition and content of the 97.2 fused magnesia particles and 97.2 fused magnesia fine powder are as follows: MgO content is 97.35%, CaO content is 1.28%, SiO2 content is 1.12%, and Fe2O3 content is 0.28%.

[0009] Furthermore, the particle size of the 97.2 fused magnesia fine powder is 325 mesh.

[0010] Furthermore, the particle size of the regenerated Cr2O3-ZrO2-Al2O3 composite powder is 500 mesh.

[0011] Furthermore, the particle size of the α-Al2O3 fine powder is 0-2 μm; the chemical composition and content of the α-Al2O3 micro powder are as follows: Al2O3 content ≥99.0%, SiO2 content ≤0.1%, Fe2O3 content ≤0.08%, and Na2O+K2O content ≤0.3%.

[0012] Furthermore, the aluminum powder contains 99.5% Al, 0.18% Fe, 0.2% Si, and 0.1% Cu; the particle size of the aluminum powder is 200 mesh.

[0013] Furthermore, the chemical composition and content of the silicon metal powder are as follows: Si content is 98.6%, Fe content is 0.54%, Al content is 0.49%, and Ca content is 0.36%; the particle size of the silicon metal powder is 325 mesh.

[0014] A method for preparing a ladle nozzle seat brick with added recycled Cr2O3-ZrO2-Al2O3 composite powder includes the following steps: (1) Preparation of co-milled powder: Mix 97.2 fused magnesia fine powder, regenerated Cr2O3-ZrO2-Al2O3 composite powder, α-Al2O3 fine powder, metallic aluminum powder and metallic silicon powder evenly according to the formula; (2) Particle batching: Mix 97.2 fused magnesia particles of different sizes evenly according to the proportion; (3) Mixing: First, dry mix the granules for 2-3 minutes, then slowly add the thermosetting phenolic resin binder and wet mix for 5-8 minutes, and finally add the co-grinding powder. After mixing for 40-50 minutes, the mixture is discharged from the mill to obtain the mixture. (4) Molding: Pressing the mixture into a blank; (5) Drying: After the green body is naturally air-dried for 24 hours, it is placed in a drying kiln and dried according to the preset temperature curve; (6) Packaging: After drying, the product is removed from the kiln and cooled to room temperature. After passing inspection, it is packaged.

[0015] Further, the temperature curve in step (5) is as follows: the initial temperature is 30℃, the temperature is increased to 80℃ in 0-3 hours, the temperature is increased from 80℃ to 120℃ in 3-6 hours, the temperature is increased from 120℃ to 150℃ in 6-8 hours, the temperature is increased from 150℃ to 180℃ in 8-10 hours, and the temperature is increased from 180℃ to 210℃ in 10-12 hours and kept at that temperature for 10 hours.

[0016] 3. Beneficial effects Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention relates to a steel ladle nozzle seat brick with added recycled Cr2O3-ZrO2-Al2O3 composite powder and its preparation method, which creatively introduces recycled Cr2O3-ZrO2-Al2O3 composite powder as a key component (content 10%-18%). This powder is derived from the recycling of waste or by-products, which not only achieves efficient recycling of resources and reduces production costs, but also, through a special high-temperature firing and acid washing pretreatment process (as described in claims 4 and 5), it obtains the characteristics of well-developed grains, uniform structure, and high purity. This pretreatment is the key to this invention, which enables the composite powder to form a suitable amount of liquid phase of 9%-17% at a service temperature of 1480℃, which is not an effect that can be achieved by simply adding similar raw materials in the prior art. This liquid phase can effectively promote sintering densification and fill pores, thereby significantly improving the bulk density of the product (up to 3.19 g / cm³) and reducing the apparent porosity (down to 8.39%).

[0017] (2) This invention relates to a steel ladle nozzle seat brick with added recycled Cr2O3-ZrO2-Al2O3 composite powder and its preparation method, which designs a multi-component synergistic system. Among them, the α-Al2O3 fine powder synergistically with the components in the recycled composite powder to further optimize the high-temperature liquid phase behavior and enhance the slag corrosion resistance; the addition of metallic aluminum powder and metallic silicon powder undergoes oxidation and reaction during high-temperature use, generating silica gel and mullite phase in situ. This dual strengthening mechanism (gel reinforcement and ceramic combination) significantly improves the high-temperature strength (compressive strength up to 70 MPa) and thermal shock stability of the product. This design, which optimizes the microstructure and performance by initiating in situ reactions through a specific additive combination, is non-obvious.

[0018] (3) The present invention provides a steel ladle nozzle seat brick with added recycled Cr2O3-ZrO2-Al2O3 composite powder and its preparation method. Compared with the existing aluminum-carbon / corundum nozzle seat bricks, it has made leapfrog progress in key performance indicators: the average service life has been greatly increased from about 75 times of the existing products to 125-135 times, with an improvement rate of more than 60%; the average erosion rate has been reduced to ≤0.5 mm / time, which is significantly lower than ≥0.66 mm / time of the existing products; the apparent porosity has been greatly reduced, and the bulk density and room temperature compressive strength have been significantly improved; no steel leakage, breakage or serious cracks have been found in the finished products, which solves the technical problem of easy peeling and cracking leading to steel penetration in the existing technology.

[0019] (4) The present invention relates to a steel ladle nozzle seat brick with added recycled Cr2O3-ZrO2-Al2O3 composite powder and its preparation method. In the preparation method, the specific mixing sequence (dry mixing of particles first, wet mixing with binder, and finally co-milling powder) is conducive to the uniform coating of particles and powder by binder, and optimizes the formability. The precisely controlled drying regime (natural air-drying for 24 hours first, and then using a phased slow heating curve) effectively avoids the cracking of the green body caused by rapid evaporation of moisture and temperature stress, ensuring the product yield and quality stability, and realizing stable industrial production. Detailed Implementation

[0020] Exemplary embodiments of the present invention are described in detail below. While these exemplary embodiments have been described in sufficient detail to enable those skilled in the art to practice the invention, it should be understood that other embodiments may be implemented and various changes may be made to the invention without departing from its spirit and scope. The more detailed description of embodiments of the invention below is not intended to limit the scope of the claimed invention, but is merely illustrative and does not limit the description of the features and characteristics of the invention, in order to suggest the best mode for carrying out the invention and to enable those skilled in the art to practice it. Therefore, the scope of the invention is defined only by the appended claims.

[0021] Table 1 shows the particle shape and percentage of the ingredients used in each embodiment of the present invention; Table 2 shows the physicochemical properties and average service life parameters of the ladle nozzle seat brick with added recycled Cr2O3-ZrO2-Al2O3 composite powder obtained in Examples 1 to 4 and the existing ladle nozzle seat brick.

[0022] Example 1 A steel ladle nozzle seat brick with added recycled Cr2O3-ZrO2-Al2O3 composite powder has the following composition and weight percentages: 61% 97.2 fused magnesia, 39% co-ground powder, totaling 100% by weight, plus 4% thermosetting phenolic resin binder by weight. The co-ground powder is prepared by uniformly mixing 12% 97.2 fused magnesia fine powder, 15% Cr2O3-ZrO2-Al2O3 composite powder, 8% α-Al2O3 micro powder, 2% metallic aluminum powder, and 2% metallic silicon powder.

[0023] 97.2 fused magnesia and 97.2 fused magnesia fine powder are industrial 97.2 fused magnesia, composed of flotation concentrate powder, release agent, and magnesite ore particles. These materials are mixed in a roller mill according to the formula ratio, compacted and granulated into pellets, and then naturally dried. The dried concentrate pellets are then transported to a buffer silo and gradually fed into an electric furnace for smelting. The voltage is generally 200-280V, and the current is generally controlled at 10000-15000A. After smelting, the material undergoes cooling crystallization, demolding, cooling, crushing, and sorting processes to produce a product with high bulk density, high mineral phase content, well-developed grains, uniform structure, stable quality, and good resistance to erosion, spalling, slag corrosion, and thermal shock.

[0024] The particle size of 97.2 fused magnesia is 5–3 mm, 3–1 mm, and 1–0 mm, with the following weight percentages for each particle size: 30% for 5–3 mm, 16% for 3–1 mm, and 15% for 1–0 mm. The chemical composition and content of 97.2 fused magnesia are as follows: 97.35% MgO, 1.28% CaO, 1.12% SiO2, and 0.28% Fe2O3.

[0025] The particle size of 97.2 fused magnesia fine powder is 325 mesh, and its weight percentage is 12%. The chemical composition and content of 97.2 fused magnesia fine powder are as follows: MgO content is 97.35%, CaO content is 1.28%, SiO2 content is 1.12%, and Fe2O3 content is 0.28%.

[0026] The particle size of the recycled Cr2O3-ZrO2-Al2O3 composite powder is 500 mesh. The chemical composition and content of the recycled Cr2O3-ZrO2-Al2O3 composite powder are as follows: Cr2O3 content is 83%, ZrO2 content is 5.65%, SiO2 content is 0.15%, and Fe2O3 content is 0.2%.

[0027] The particle size of α-Al2O3 micro powder is 0-2μm. The chemical composition and content of α-Al2O3 micro powder are as follows: Al2O3 content ≥99.0%, SiO2 content ≤0.1%, Fe2O3 content ≤0.08%, and Na2O+K2O content ≤0.3%.

[0028] The aluminum powder contains 99.5% Al, 0.18% Fe, 0.2% Si, and 0.1% Cu, and has a particle size of 200 mesh.

[0029] The chemical composition and content of the metallic silicon powder are as follows: Si content is 98.6%, Fe content is 0.54%, Al content is 0.49%, Ca content is 0.36%, and the particle size of the metallic silicon powder is 325 mesh.

[0030] The preparation method of the steel ladle nozzle seat brick with the above-mentioned addition of recycled Cr2O3-ZrO2-Al2O3 composite powder includes the following steps: (1) Preparation of co-milled powder: 97.2 electrofused magnesia fine powder, α-Al2O3 micro powder, zircon fine powder and metallic silicon powder were mixed evenly according to weight percentage to obtain co-milled powder; (2) Particle batching: 97.2 fused magnesia with a particle size of 5-3 mm, 97.2 fused magnesia with a particle size of 3-1 mm, and 97.2 fused magnesia with a particle size of 1-0 mm are uniformly mixed according to the weight percentage to obtain the particle batching; (3) Mixing: Dry mix the granular aggregate with a wet mill for 2-3 minutes, then slowly add the thermosetting phenolic resin binder and wet mix for 5-8 minutes, and finally add the co-grinding powder. After mixing for 50-60 minutes, the mixture is discharged from the mill to obtain the mixture. (4) Molding: The mixture is pressed into a semi-finished blank on a 630t electric screw press brick machine; (5) Drying: After the billet is naturally air-dried for 8 hours, it is placed in a tunnel natural gas drying kiln and dried according to the set curve. The initial temperature of the billet entering the kiln is 30℃. In the first 0-4 hours, the temperature increases from 30℃ to 80℃; in the 4-7 hours, the temperature increases from 80℃ to 120℃; in the 7-9 hours, the temperature increases from 120℃ to 150℃; in the 9-11 hours, the temperature increases from 150℃ to 180℃; in the 11-13 hours, the temperature increases from 180℃ to 210℃ and is held at this temperature for 16 hours. The total drying time is 37 hours. After the product is removed from the kiln, it is inspected and products that meet the size and appearance requirements are selected to proceed to the next process. (6) Packaging: After drying, remove from the kiln and let it air dry to room temperature. Check the size and appearance according to the drawing requirements and appearance standards, and pack it into boxes after it passes the inspection.

[0031] Example 2 This embodiment describes a steel ladle nozzle seat brick with added recycled Cr2O3-ZrO2-Al2O3 composite powder. Its composition and weight percentage are as shown in Table 1, and the preparation method is the same as in Example 1.

[0032] Example 3 This embodiment describes a steel ladle nozzle seat brick with added recycled Cr2O3-ZrO2-Al2O3 composite powder. Its composition and weight percentage are as shown in Table 1, and the preparation method is the same as in Example 1.

[0033] Example 4 This embodiment describes a steel ladle nozzle seat brick with added recycled Cr2O3-ZrO2-Al2O3 composite powder. Its composition and weight percentage are as shown in Table 1, and the preparation method is the same as in Example 1.

[0034] Table 1. Particle type and percentage of ingredients used in various embodiments of the present invention

[0035] Table 2. Physicochemical properties and average service life parameters of the ladle nozzle seat bricks with added recycled Cr2O3-ZrO2-Al2O3 composite powder obtained in Examples 1-4 compared with existing ladle nozzle seat bricks.

[0036] Table 2 shows that the ladle nozzle seat bricks of this invention, which incorporate recycled Cr2O3-ZrO2-Al2O3 composite powder, were tested on large steel ladles. After the test, the ladle nozzle seat bricks of this invention were analyzed against existing products for issues such as pore enlargement and cracking. The average service life was 125 cycles / brick, the pore enlargement rate was an average of 30 mm / brick, and the average erosion rate was 0.25 mm / cycle. Through batch use, the results were statistically compared with existing products. The average erosion rate of the ladle nozzle seat bricks of this invention was ≤0.5 mm / cycle, which is lower than the erosion rate of existing aluminum-carbon products (≥0.66 mm / cycle). The pore enlargement and internal condition of the disassembled lower-line seat bricks were good, with no steel leakage, breakage, or cracks observed.

[0037] In summary, this invention discloses a ladle nozzle seat brick with added recycled Cr2O3-ZrO2-Al2O3 composite powder and its preparation method. By using specially pretreated recycled Cr2O3-ZrO2-Al2O3 composite powder as the core functional component, and creatively combining it with α-alumina, metallic aluminum powder, and metallic silicon powder to form a multiphase synergistic strengthening system, combined with optimized machine pressing and drying processes, a ladle nozzle seat brick with comprehensive performance far exceeding existing technologies is prepared. This technical solution effectively solves the industry problems of poor erosion resistance, insufficient thermal shock stability, and easy cracking and spalling leading to safety accidents in traditional nozzle seat bricks. Simultaneously, it achieves solid waste resource utilization, achieving unexpected technical effects. It demonstrates outstanding substantial characteristics and significant progress in improving performance, extending service life, ensuring safety, and reducing costs. The examples described herein are merely preferred embodiments of the invention and are not intended to limit the concept and scope of the invention. Any modifications and improvements made by those skilled in the art to the technical solutions of the invention without departing from the design concept of the invention should fall within the protection scope of the invention.

Claims

1. A steel ladle nozzle seat brick with added recycled Cr2O3-ZrO2-Al2O3 composite powder, characterized in that, The raw material composition, by weight percentage, includes: 97.2 fused magnesia particles: 60%-64%; co-ground powder: 35%-39%; the sum of the weight percentages of the 97.2 fused magnesia particles and the co-ground powder is 100%; and an additional thermosetting phenolic resin binder accounting for 4% to 5% of the total weight of the raw materials. The co-milled powder comprises 6%–18% of 97.2 fused magnesia fine powder, 10%–18% of regenerated Cr2O3-ZrO2-Al2O3 composite powder, 5%–8% of α-Al2O3 fine powder, 5%–8% of metallic aluminum powder and 1%–2% of metallic silicon powder. The chemical composition and content of the regenerated Cr2O3-ZrO2-Al2O3 composite powder are as follows: Cr2O3 content is 83%, ZrO2 content is 5.65%, SiO2 content is 0.15%, and Fe2O3 content is 0.2%.

2. The ladle nozzle seat brick with added recycled Cr2O3-ZrO2-Al2O3 composite powder according to claim 1, characterized in that, The raw material composition and weight percentage of the 97.2 fused magnesia particles are as follows: 27%-30% 97.2 fused magnesia with a particle size of 5-3mm, 16%-18% 97.2 fused magnesia with a particle size of 3-1mm, and 15%-19% 97.2 fused magnesia with a particle size of 1-0mm.

3. The ladle nozzle seat brick with added recycled Cr2O3-ZrO2-Al2O3 composite powder according to claim 1, characterized in that, The chemical composition and content of the 97.2 fused magnesia particles and 97.2 fused magnesia fine powder are as follows: MgO content is 97.35%, CaO content is 1.28%, SiO2 content is 1.12%, and Fe2O3 content is 0.28%.

4. The ladle nozzle seat brick with added recycled Cr2O3-ZrO2-Al2O3 composite powder according to claim 1, characterized in that, The particle size of the 97.2 fused magnesia fine powder is 325 mesh.

5. A steel ladle nozzle seat brick with added recycled Cr2O3-ZrO2-Al2O3 composite powder according to claim 1, characterized in that, The particle size of the regenerated Cr2O3-ZrO2-Al2O3 composite powder is 500 mesh.

6. The ladle nozzle seat brick with added recycled Cr2O3-ZrO2-Al2O3 composite powder according to claim 1, characterized in that, The particle size of the α-Al2O3 fine powder is 0-2μm; the chemical composition and content of the α-Al2O3 micro powder are as follows: Al2O3 content ≥99.0%, SiO2 content ≤0.1%, Fe2O3 content ≤0.08%, and Na2O+K2O content ≤0.3%.

7. A steel ladle nozzle seat brick with added recycled Cr2O3-ZrO2-Al2O3 composite powder according to claim 1, characterized in that, The aluminum powder contains 99.5% Al, 0.18% Fe, 0.2% Si, and 0.1% Cu; the particle size of the aluminum powder is 200 mesh.

8. A steel ladle nozzle seat brick with added recycled Cr2O3-ZrO2-Al2O3 composite powder according to claim 1, characterized in that, The chemical composition and content of the silicon metal powder are as follows: Si content is 98.6%, Fe content is 0.54%, Al content is 0.49%, and Ca content is 0.36%; the particle size of the silicon metal powder is 325 mesh.

9. A method for preparing a ladle nozzle seat brick with recycled Cr2O3-ZrO2-Al2O3 composite powder as described in any one of claims 1-8, characterized in that, Includes the following steps: (1) Preparation of co-milled powder: Mix 97.2 fused magnesia fine powder, regenerated Cr2O3-ZrO2-Al2O3 composite powder, α-Al2O3 fine powder, metallic aluminum powder and metallic silicon powder evenly according to the formula; (2) Particle batching: Mix 97.2 fused magnesia particles of different sizes evenly according to the proportion; (3) Mixing: First, dry mix the granules for 2-3 minutes, then slowly add the thermosetting phenolic resin binder and wet mix for 5-8 minutes, and finally add the co-grinding powder. After mixing for 40-50 minutes, the mixture is discharged from the mill to obtain the mixture. (4) Molding: Pressing the mixture into a blank; (5) Drying: After the green body is naturally air-dried for 24 hours, it is placed in a drying kiln and dried according to the preset temperature curve; (6) Packaging: After drying, the product is removed from the kiln and cooled to room temperature. After passing inspection, it is packaged.

10. The method for preparing a ladle nozzle seat brick with added recycled Cr2O3-ZrO2-Al2O3 composite powder according to claim 9, characterized in that, The temperature curve in step (5) is as follows: the initial temperature is 30℃, the temperature is increased to 80℃ in 0-3 hours, the temperature is increased from 80℃ to 120℃ in 3-6 hours, the temperature is increased from 120℃ to 150℃ in 6-8 hours, the temperature is increased from 150℃ to 180℃ in 8-10 hours, and the temperature is increased from 180℃ to 210℃ in 10-12 hours and held for 10 hours.

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