Magnesian ladle nozzle brick for tire cord steel and preparation method thereof

Abstract

The invention discloses a magnesian ladle nozzle brick for tire cord steel. The magnesian ladle nozzle brick comprises the following components in percentage by weight: 47-54% of 97 fused magnesite; 7%-9% of forsterite; 12%-18% of fused spinel; 4%-6% of high-temperature burning promoting powder; 5%-8% of a ceramic plastic adhesive; 1%-3% of carbon-containing powder; 1%-3% of graphite; 1%-3% of boron carbide; 4%-6% of aluminum magnesium alloy powder; 2%-4% of silicon powder; 4%-6% of resin and 0.4%-0.5% of a resin reinforcing agent are additionally added. The invention aims to provide the magnesium ladle nozzle brick for the tire cord steel and the preparation method of the magnesium ladle nozzle brick. The magnesium ladle nozzle brick has the advantages that the porosity is reduced, the erosion resistance and wear resistance are improved, the internal thermal stress of the blank is reduced, microcracks are avoided, and the thermal shock resistance stability is improved.

Description

Technical Field

[0001] This invention relates to the field of refractory materials based on inorganic materials, and more specifically to a magnesia steel ladle nozzle brick for cord steel and its preparation method. Background Technology

[0002] Cord steel, as the core skeleton material of tire radial tires, has extremely stringent requirements for the purity of molten steel, the control of inclusions, and the stability of casting. Currently, the mainstream ladle nozzle bricks in the industry mainly include aluminum-zirconium-carbon, aluminum-carbon, and zirconia-ring-embedded nozzle bricks. However, they face insurmountable technical bottlenecks in the casting of high-end steel: Although aluminum-zirconium-carbon nozzle bricks exhibit good thermal shock resistance and wear resistance in ordinary steel casting, when casting calcium-treated steel, the Al2O3 and SiO2 they contain easily react with CaO in the molten steel at low temperatures to form low-melting substances. After being washed by the molten steel, this can easily cause steel inclusions in the nozzle, seriously affecting the quality of the molten steel; although zirconia nozzle bricks have excellent corrosion resistance and oxidation resistance, they still have melting loss problems in the casting of aluminum-killed steel, and the high price of zirconia raw materials leads to high refractory material costs per ton of steel, making large-scale promotion difficult. While existing magnesia-based nozzle bricks possess a cost advantage in raw materials, they are limited by the inherent characteristics of periclase—high thermal expansion coefficient and high sintering difficulty—resulting in poor thermal shock resistance, insufficient high-temperature strength, and short service life. They cannot meet the requirements for continuous and stable casting of high-end steels such as cord steel, and are only used in small quantities in Europe, with the domestic market virtually nonexistent. The industry has long faced the dual technical challenges of "balancing erosion resistance with cost" and "coordinating thermal shock resistance with high-temperature strength," urgently requiring the development of a new type of nozzle brick that combines high performance, low cost, and long service life to overcome the technical bottleneck of refractory materials used in high-end steel casting. Summary of the Invention

[0003] To address the aforementioned problems, the present invention aims to provide a magnesium steel ladle sprue brick for cord steel that reduces porosity, improves erosion and wear resistance, reduces internal thermal stress in the billet, avoids microcracks, and enhances thermal shock resistance, as well as its preparation method.

[0004] According to one aspect of the present invention, a magnesia-steel ladle nozzle brick for cord steel is provided, comprising, by weight percentage, the following components: 97% fused magnesia: 47%–54%; Forsterite: 7%–9%; Fused spinel: 12%–18%; High-temperature calcining accelerator powder: 4%–6%; Ceramic adhesive: 5%–8%; Carbon powder content: 1%–3%; Graphite: 1%–3%; Boron carbide: 1%–3%; Aluminum-magnesium alloy powder: 4%–6%; Silicon powder: 2%–4%; In addition, 4% to 6% resin and 0.4% to 0.5% resin reinforcing agent need to be added.

[0005] In some embodiments, the particle size distribution of each component adopts a gradient synergistic design, with the following specific requirements: 97 Fused Magnesia: It adopts a four-grade gradient design, with 3-1mm particles accounting for 10%-15%, 2-1mm particles accounting for 10%-17%, 1-0.5mm particles accounting for 9%-12%, and ≥200 mesh fine powder accounting for 12%-16%, with the total proportion of the four grades of particles being 35%-38%. Forsterite: 1-0 mm grains; Fused spinel: 0.5–0 mm fine grains; High-temperature sintering powder, ceramic adhesive, boron carbide, aluminum-magnesium alloy powder, silicon powder: ≥180 mesh; Contains carbon powder and graphite: 325 mesh.

[0006] In some implementations, by weight percentage: 97 Fused Magnesia: MgO content ≥ 97%; Forsterite: SiO2 content ≤ 40%, MgO content ≥ 45%; Fused spinel: Al2O3 content ≥72%, MgO content ≥21%; Sintering powder: SiO2 content ≤30%, Al2O3 content ≥72%, refractoriness >1800℃; Carbon powder content: 85% residual carbon; Graphite: C content ≥97%; Boron carbide: B4C content ≥90%; Aluminum-magnesium alloy powder: Al content 50±3%, active metals Al and Mg content 7.0%; Silicon powder: Si content ≥ 97%; Resin: Residual carbon content 45±4%, solid content 75~80%, viscosity 15000~18000mpa.

[0007] According to one aspect of the present invention, a method for preparing magnesia steel ladle nozzle bricks for cord steel is provided, characterized by comprising the following steps: S1, gradient mixing; S2, High-pressure forming; S3, gradient drying; S4, Precision firing; S5. Processing; S6. Finished product inspection.

[0008] In some implementations, the gradient mixing in step S1 includes the following steps: Add 97 fused magnesia particles (3-1mm, 2-1mm, 1-0.5mm) to a high-speed mixer and dry mix for 3-6 minutes to form a uniform skeleton; Add resin and resin reinforcing agent, mix well for 5-8 minutes to ensure that the liquid binder evenly coats the surface of the particles; Add 97% fused magnesia fine powder, forsterite, fused spinel, high-temperature sintering powder, ceramic binder, carbon powder, graphite, boron carbide, aluminum-magnesium alloy powder, and silicon powder in sequence, and continue mixing for 10-30 minutes to form a uniform and dense mud, ensuring full contact between the interfaces of each component.

[0009] In some implementations, high-pressure molding in S2 involves using a spiral brick press with a capacity of 1000 tons or more to accurately weigh the clay according to preset dimensions and add it to a custom mold for high-pressure molding.

[0010] In some implementations, the brick blanks formed in step S2 also need to undergo full-size inspection of each brick: external dimensions, flatness, diagonal, and 10% of the products are randomly checked for unit weight, porosity and bulk density each shift. Unqualified products are immediately scrapped and the cause is traced to ensure the consistency of the blanks.

[0011] In some implementations, gradient drying in step S3 includes the following steps: The molded blank is first allowed to dry naturally for 8-12 hours to release surface moisture; The product is then transferred to a drying kiln for gradient heating and drying, with a total duration of 40–60 hours: the temperature is raised to 80°C at a uniform rate within 1 hour and held for 12 hours; then the temperature is raised to 190°C at a uniform rate within the next 24 hours and held for 20 hours.

[0012] In some implementations, the precise firing process in step S4 includes the following steps: The dried green body is pushed into a medium-high temperature tunnel kiln and heated to 580℃±20℃ at a uniform rate within 15 to 20 hours, and then held at that temperature for 15 to 20 hours. In some implementations, the processing in step S5 includes: finishing the brick body and encasing the finished brick in an iron shell.

[0013] This invention discloses a magnesia-steel ladle sprue brick for tire cord steel and its preparation method. Compared with the prior art, it utilizes a four-grade gradient stacking design to achieve dense filling of aggregate and fine powder, reduce porosity, and improve erosion resistance and wear resistance. It develops a gradient drying and precision firing process, and through precise temperature control, reduces internal thermal stress in the green body, avoids the generation of microcracks, and ensures product stability. It adds a steel shell treatment to the finished product to form a "refractory matrix-steel shell protection" composite structure, which further improves thermal shock resistance and service life.

[0014] Furthermore, it exhibits excellent corrosion resistance: the reaction rate between the magnesium-based main material and CaO is significantly lower than that of aluminum-carbon and aluminum-zirconium-carbon materials. The magnesium-rich spinel has outstanding wear resistance, effectively resisting the erosion of high-temperature molten steel, and its service life is extended by more than 50% compared with traditional magnesium-based sprue bricks. Excellent thermal shock resistance: The coefficient of thermal expansion is less than that of corundum material, and the elastic modulus is between that of zirconium plate and corundum. Microcracks are formed during the heating and cooling process to buffer thermal stress and can withstand the drastic temperature changes in the early stage of steel casting. High purity of molten steel: Avoids aluminum inclusions introduced by traditional high-alumina nozzles, and the Al content of molten steel is stably controlled below 0.003%, meeting the requirements for the production of cord steel; Significant cost advantages: Magnesium raw materials are cheaper than zirconium corundum, product lifespan is extended and refractory material consumption per ton of steel is reduced, and the overall cost is 30% to 40% lower than that of zirconia sprue bricks. Detailed Implementation

[0015] The present invention will be further described below with reference to specific embodiments.

[0016] Magnesium steel cladding nozzle bricks for steel cords, by weight percentage, comprise the following components: 97 fused magnesia: 47%–54%, used as core aggregate to ensure erosion resistance; Forsterite: 7%–9% serves to regulate the thermodynamic stability of the system; Fused spinel: 12%–18% is used to optimize thermal shock resistance and wear resistance; High-temperature sintering accelerator powder: 4%–6% acts as an innovative sintering strengthening component; Ceramic adhesive: 5%–8% acts as a novel inorganic plasticizing and reinforcing component; Carbon powder: 1% to 3% is used to optimize the carbon bonding structure; Graphite: 1%–3% is used to enhance antioxidant properties; Boron carbide: 1%–3% serves to refine the microstructure and enhance interfacial bonding; Aluminum-magnesium alloy powder: 4%–6% serves to promote in-situ reaction and strengthen the bonding phase; Silicon powder: 2%–4% is used to optimize the sintering densification process; The sum of the weights of all the above components is 100%. An additional 4% to 6% resin and 0.4% to 0.5% resin reinforcing agent are added in a liquid state to improve the bonding strength and stability.

[0017] The particle size distribution of each component adopts a gradient synergistic design, with the following specific requirements: 97 fused magnesia: It adopts a four-level gradient design, with 3-1mm particles accounting for 10%-15%, 2-1mm particles accounting for 10%-17%, 1-0.5mm particles accounting for 9%-12%, and ≥200 mesh fine powder accounting for 12%-16%, with the total proportion of the four-level particles being 35%-38%, thereby achieving dense packing; Forsterite: 1-0mm particles, ensuring interfacial bonding with other components; Fused spinel: 0.5-0mm fine particles, uniformly filling the gaps in the skeleton; High-temperature sintering powder, ceramic binder, boron carbide, aluminum-magnesium alloy powder, silicon powder: ≥180 mesh, to ensure uniform reaction during sintering; Contains carbon powder and graphite: 325 mesh, optimizing carbon phase distribution and bonding effect.

[0018] By weight percentage: 97 Fused Magnesia: MgO content ≥97%, ensuring basic anti-corrosion properties; Forsterite: SiO2 content ≤40%, MgO content ≥45%, balancing thermodynamic stability and reactivity; Fused spinel: Al2O3 content ≥72%, MgO content ≥21%, ensuring core performance against thermal shock; Sintering accelerator powder: SiO2 content ≤30%, Al2O3 content ≥72%, refractoriness >1800℃, to ensure sintering promotion effect; Ceramic adhesive: bulk density of approximately 450 g / L, ensuring synergistic effects of plasticization and reinforcement; Carbon powder: 85% residual carbon, optimized carbon bonding structure; Graphite: C content ≥97%, optimized carbon bonding structure; Boron carbide: B4C content ≥90%; Aluminum-magnesium alloy powder: Al content 50±3%, active metals Al and Mg content 7.0%; Silicon powder: Si content ≥97% to ensure sufficient in-situ reaction; Resin: Residual carbon content 45±4%, solid content 75~80%, viscosity 15000~18000mpa, ensuring bonding strength and residual carbon stability.

[0019] According to one aspect of the present invention, a method for preparing magnesia steel ladle nozzle bricks for cord steel is provided, characterized by comprising the following steps: S1, gradient mixing; S2, High-pressure forming; S3, gradient drying; S4, Precision firing; S5. Processing; S6. Finished product inspection.

[0020] The gradient mixing process in step S1 includes the following steps: Add 97 fused magnesia particles (3-1mm, 2-1mm, 1-0.5mm) to a high-speed mixer and dry mix for 3-6 minutes to form a uniform skeleton; Add resin and resin reinforcing agent, mix well for 5-8 minutes to ensure that the liquid binder evenly coats the surface of the particles; Add 97% fused magnesia fine powder, forsterite, fused spinel, high-temperature sintering powder, ceramic binder, carbon powder, graphite, boron carbide, aluminum-magnesium alloy powder, and silicon powder in sequence, and continue mixing for 10-30 minutes to form a uniform and dense mud, ensuring full contact between the interfaces of each component.

[0021] S2 medium-high pressure molding involves using a spiral brick press with a capacity of 1000 tons or more, accurately weighing the clay according to preset dimensions, and then adding it to a custom mold for medium-high pressure molding.

[0022] In step S2, each brick blank undergoes a full-size inspection: external dimensions, flatness, and diagonal. 10% of the products are randomly checked each shift for unit weight, porosity, and bulk density. Unqualified products are immediately scrapped and the cause is traced to ensure the consistency of the blank.

[0023] The gradient drying process in step S3 includes the following steps: The molded blank is first allowed to dry naturally for 8-12 hours to release surface moisture; The product is then transferred to a drying kiln for gradient heating and drying, with a total duration of 40–60 hours: the temperature is raised to 80°C at a uniform rate within 1 hour and held for 12 hours; then the temperature is raised to 190°C at a uniform rate within the next 24 hours and held for 20 hours.

[0024] In step S4, precise firing includes the following steps: The dried green body is pushed into a medium-high temperature tunnel kiln and heated to 580℃±20℃ at a uniform rate within 15 to 20 hours, and then held at that temperature for 15 to 20 hours. In some implementations, the processing in step S5 includes: finishing the brick body and encasing the finished brick in an iron shell.

[0025] Example 1 Raw material specifications: 97 Fused magnesia (MgO≥97%), forsterite (SiO2≤40%, MgO≥45%), fused spinel (Al2O3≥72%, MgO≥21%), high-temperature sintering powder (SiO2≤30%, Al2O3≥72%), ceramic adhesive (bulk density approximately 450g / L), carbon powder (residual carbon content 85%), graphite (C≥97%), boron carbide (B4C≥90%), aluminum-magnesium alloy powder (Al 50±3%, active metal ≥97.0%), silicon powder (Si≥97%), resin (residual carbon content 45±4%, solid content 75~80%, viscosity 15000~18000mpa).

[0026] Formula (by weight): 97. Fused magnesia: 3-1mm 13%, 2-1mm 13%, 1-0.5mm 12%, ≥200 mesh 16%; Forsterite (1-0mm): 10%; Fused spinel (0.5~0mm): 12%; High temperature burning powder (≥200 mesh): 5%; Ceramic adhesive (≥180 mesh): 5%; Contains carbon powder (325 mesh): 2%; Graphite (325 mesh): 2%; Boron carbide (≥180 mesh): 2%; Aluminum-magnesium alloy powder (≥180 mesh): 5%; Silica powder (≥180 mesh): 3%; Added resin 4% and resin reinforcing agent 0.4%.

[0027] Preparation process: 1. Weigh each component according to the formula. First, add 97 fused magnesia particles to a high-speed mixer and dry mix for 4 minutes. Then add the resin and reinforcing agent and mix for 6 minutes. Finally, add the remaining fine powder and mix for 20 minutes. 2. The 1000-ton spiral brick press is used for forming, and the external dimensions, flatness, and other indicators are tested. 3. After air drying for 10 hours, transfer to a drying kiln: heat to 80℃ for 1 hour and hold for 12 hours, then heat to 190℃ for 20 hours after 24 hours. 4. The tunnel kiln is heated to 580℃ in 18 hours, held at that temperature for 15 hours, and then cooled down at a uniform rate for 20 hours. 5. After being fitted with a steel shell, the finished product is inspected and put into storage.

[0028] Performance metrics: C content: 5.53%; MgO content: 60.2%; Pressure resistance at room temperature: 79.6 MPa; Body density at room temperature: 2.91 g / cm³; Porosity at room temperature: 5.6%; Flexural strength at 1400℃: 9.7MPa, with optimal overall performance.

[0029] Examples 2-3: According to the component ratios and particle size distribution of Formula 2 and Formula 3 in Table 1, the same preparation process as in Example 1 was used. The products prepared all met the usage requirements, and the physicochemical properties are shown in Table 2.

[0030] Table 1: Component ratios and particle size distribution of Formula 2 and Formula 3 Table 2: Physicochemical properties of Formula 2 and Formula 3 The above descriptions are merely some embodiments of the present invention. It should be noted that those skilled in the art can make other modifications and improvements without departing from the inventive concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A magnesium steel-clad sprue brick for use with steel cord, characterized in that, By weight percentage, it includes the following components: 97% fused magnesia: 47%–54%; Forsterite: 7%–9%; Fused spinel: 12%–18%; High-temperature calcining accelerator powder: 4%–6%; Ceramic adhesive: 5%–8%; Carbon powder content: 1%–3%; Graphite: 1%–3%; Boron carbide: 1%–3%; Aluminum-magnesium alloy powder: 4%–6%; Silicon powder: 2%–4%; In addition, 4% to 6% resin and 0.4% to 0.5% resin reinforcing agent need to be added.

2. The magnesium steel ladle nozzle brick for cord steel according to claim 1, characterized in that, The particle size distribution of each component adopts a gradient synergistic design, with the following specific requirements: 97 Fused Magnesia: It adopts a four-grade gradient design, with 3-1mm particles accounting for 10%-15%, 2-1mm particles accounting for 10%-17%, 1-0.5mm particles accounting for 9%-12%, and ≥200 mesh fine powder accounting for 12%-16%, with the total proportion of the four grades of particles being 35%-38%. The forsterite: 1-0 mm particles; The fused spinel: fine particles of 0.5–0 mm; The high-temperature sintering powder, ceramic plastic binder, boron carbide, aluminum-magnesium alloy powder, and silicon powder are ≥180 mesh. The carbon powder and graphite contained are 325 mesh.

3. The magnesium steel ladle nozzle brick for cord steel according to claim 2, characterized in that, By weight percentage: The 97 fused magnesia has an MgO content of ≥97%. The forsterite has the following composition: SiO2 content ≤ 40%, MgO content ≥ 45%; The fused spinel has an Al2O3 content ≥72% and an MgO content ≥21%. The calcining powder has the following characteristics: SiO2 content ≤30%, Al2O3 content ≥72%, and refractoriness >1800℃. The plastic adhesive has a bulk density of 450 g / L; The carbon powder contains 85% residual carbon. The graphite has a C content ≥97%; The boron carbide has a B4C content ≥90%; The aluminum-magnesium alloy powder contains 50±3% Al and 7.0% active metals Al and Mg. The silicon powder has a Si content of ≥97%. The resin has the following characteristics: residual carbon content 45±4%, solid content 75-80%, and viscosity 15000-18000 MPa.

4. The method for preparing the magnesia steel ladle nozzle brick for cord steel according to any one of claims 1-3, characterized in that, Includes the following steps: S1, gradient mixing; S2, High-pressure forming; S3, gradient drying; S4, Precision firing; S5. Processing; S6. Finished product inspection.

5. The method for preparing the magnesia steel ladle nozzle brick for cord steel according to claim 4, characterized in that, The gradient mixing in step S1 includes the following steps: Add 97 fused magnesia particles (3-1mm, 2-1mm, 1-0.5mm) to a high-speed mixer and dry mix for 3-6 minutes to form a uniform skeleton; Add resin and resin reinforcing agent, mix well for 5-8 minutes to ensure that the liquid binder evenly coats the surface of the particles; Add 97% fused magnesia fine powder, forsterite, fused spinel, high-temperature sintering powder, ceramic binder, carbon powder, graphite, boron carbide, aluminum-magnesium alloy powder, and silicon powder in sequence, and continue mixing for 10-30 minutes to form a uniform and dense mud, ensuring full contact between the interfaces of each component.

6. The method for preparing the magnesia steel ladle nozzle brick for cord steel according to claim 4, characterized in that, The high-pressure molding in S2 is as follows: using a spiral brick press with a capacity of 1000 tons or more, the clay material is accurately weighed according to the preset size and added to a customized mold for high-pressure molding.

7. The method for preparing the magnesia steel ladle nozzle brick for cord steel according to claim 5, characterized in that, In step S2, the formed brick blanks must undergo full-size inspection of each brick: external dimensions, flatness, diagonal. 10% of the products are randomly checked each shift for unit weight, porosity, and bulk density. Unqualified products are immediately scrapped and the cause is traced to ensure the consistency of the blanks.

8. The method for preparing the magnesia steel ladle nozzle brick for cord steel according to claim 4, characterized in that, The gradient drying process in step S3 includes the following steps: The molded blank is first allowed to dry naturally for 8-12 hours to release surface moisture; The product is then transferred to a drying kiln for gradient heating and drying, with a total duration of 40–60 hours: the temperature is raised to 80°C at a uniform rate within 1 hour and held for 12 hours; then the temperature is raised to 190°C at a uniform rate within the next 24 hours and held for 20 hours.

9. The method for preparing the magnesia steel ladle nozzle brick for cord steel according to claim 4, characterized in that, In step S4, precise firing includes the following steps: The dried green body is pushed into a medium-high temperature tunnel kiln and heated to 580℃±20℃ at a uniform rate within 15 to 20 hours, and then held at that temperature for 15 to 20 hours. A uniform cooling process is used to slowly cool the material down to room temperature within 20 hours.

10. The method for preparing the magnesia steel ladle nozzle brick for cord steel according to claim 4, characterized in that, The processing in step S5 includes: fine processing of the brick body and encasing the finished brick in an iron shell.

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