Low-carbon magnesium-zirconium-carbon upper nozzle brick and preparation method thereof

Abstract

The invention discloses a low-carbon magnesium-zirconium-carbon upper nozzle brick and a preparation method thereof, and belongs to the technical field of refractory materials. The upper nozzle brick comprises the following components in percentage by weight: 70%-75% of granular aggregate and 25%-30% of co-grinding powder, and the total percentage is 100%. The granular aggregate comprises the following components in percentage by weight: 25-30% of magnesia particles and 70-75% of fused magnesium-zirconium sand; adding 3-4% of phenolic resin; wherein the co-grinding powder is prepared by uniformly mixing 6%-10% of magnesia powder, 5%-8% of fused magnesium-zirconium sand powder, 3%-5% of metal aluminum powder, 5%-8% of 898 graphite and 1%-3% of silicon carbide powder; the surfaces of the fused magnesium-zirconium sand particles are coated with a coating layer, and the coating layer is provided with a coating layer containing hydrated calcium aluminate and alumina gel. The upper nozzle brick prepared by the method can solve the contradictions that the traditional magnesia-carbon material is poor in thermal shock resistance and the alumina-carbon material is not resistant to high alkalinity erosion, and the comprehensive performance and the service life of the product are remarkably improved while the carbon content is reduced.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials technology, specifically relating to a refractory material for steel ladles, and more specifically, to a low-carbon magnesium zirconium carbonaceous top nozzle brick and its preparation method. Background Technology

[0002] The ladle inlet is a key refractory component embedded in the bottom brick of the ladle. Its core function is to provide a stable flow channel for molten steel from the ladle to the tundish, while simultaneously providing three key safeguards: first, it isolates air to prevent secondary oxidation of the molten steel, reducing temperature loss and splashing; second, it controls the flow rate and stability of the molten steel, precisely enabling the continuous casting process; and third, some permeable inlets generate uniform bubbles through their porous structure, helping inclusions to float and improving the cleanliness of the molten steel. Its performance directly determines the continuity, safety, and billet quality of the continuous casting process.

[0003] Currently, the main materials for steel ladle nozzles in China are aluminocarbon and magnesiacarbon. When facing high-basicity slag or calcium-containing steel, the Al2O3 in aluminocarbon nozzles readily reacts with Ca, CaO in the molten steel, and components in the slag to form low-melting-point phases, leading to rapid melting of the refractory material and contamination of the molten steel. In actual casting of steel grades such as SPHD and SPHE, this results in a short service life, making it difficult to meet the demands of long-cycle production. While ordinary magnesiacarbon nozzles exhibit strong resistance to high-basicity slag and calcium-containing steel, and do not generate low-melting-point corrosion products, their corrosion rate is far lower than that of aluminocarbon materials under the same operating conditions. However, magnesia oxide has a high coefficient of thermal expansion and low thermal conductivity, making it prone to thermal stress under rapid heating and cooling conditions during smelting. This can easily lead to cracking, spalling, or even direct bursting, requiring stringent preheating processes; inadequate preheating will significantly shorten its service life. Summary of the Invention

[0004] 1. The problem to be solved To address the issue of substandard performance of existing alumina-carbon and magnesia-carbon top nozzle bricks, this invention provides a low-carbon magnesia-zirconium-carbon top nozzle brick and its preparation method. This invention resolves the contradictions of poor thermal shock stability of traditional magnesia-carbon materials and poor resistance to high alkalinity corrosion of alumina-carbon materials. While reducing carbon content, it significantly improves the overall performance and service life of the product.

[0005] 2. Technical Solution To solve the above problems, the present invention adopts the following technical solution.

[0006] A low-carbon magnesia-zirconium carbonaceous top-feed brick comprises granular aggregate and co-ground powder. The granular aggregate has a weight percentage of 70%–75%, the co-ground powder has a weight percentage of 25%–30%, and the total percentage is 100%. The granular aggregate is composed of the following weight percentages: 25–30% magnesia sand particles, 70–75% fused magnesia-zirconium sand, and 3%–4% phenolic resin. The co-ground powder is prepared by uniformly mixing 6%–10% magnesia sand powder, 5%–8% fused magnesia-zirconium sand powder, 3%–5% metallic aluminum powder, 5%–8% 898 graphite, and 1%–3% silicon carbide powder. A coating layer is formed on the surface of the fused magnesia-zirconium sand particles, and the coating layer contains hydrated calcium aluminate and aluminum glue.

[0007] Further, the preparation method of the coating layer is as follows: weigh the active calcium-containing aluminate, add water and stir evenly, add the fused magnesium zircon sand particles and stir evenly, stir at 100-150℃ until dry, and obtain particles with a coating layer on the surface; the active calcium-containing aluminate is one or more of aluminate cement, monocalcium aluminate, monocalcium dialuminate, dodecacalcium heptaaluminate and calcium aluminoferrite, and its weight fraction is 2% to 4% of the weight of the fused magnesium zircon sand particles. Furthermore, the average thickness of the coating layer on the surface of the fused magnesium zircon sand particles is 0.2 to 0.5 mm.

[0008] Furthermore, the particle size of the fused magnesia is 5-3 mm, 3-1 mm, and 1-0 mm, and the weight percentage of each particle size is as follows: 10%-15% for fused magnesia with a particle size of 5-3 mm, 5%-10% for fused magnesia with a particle size of 3-1 mm, and 5%-10% for fused magnesia with a particle size of 1-0 mm; the chemical composition and content of the fused magnesia are: MgO ≥ 96.3%, SiO2 ≤ 1.3%, and CaO ≤ 1.5%.

[0009] Furthermore, the fused magnesium zirconium sand has three particle sizes: 3–1 mm, 1–0.5 mm, and 0.5–0 mm, with the following weight percentages: 10%–17% for fused magnesium zirconium sand with a particle size of 3–1 mm; 15%–23% for fused magnesium zirconium sand with a particle size of 1–0.5 mm; and 10%–15% for fused magnesium zirconium sand with a particle size of 0.5–0 mm. The fused magnesium zirconium sand particles and powder contain the following contents: MgO content ≥90%, ZrO2 content ≥4%, SiO2 content ≤2.5%, Fe2O3 content ≤0.6%, and CaO content ≤1.2%.

[0010] Furthermore, the 898 graphite has a fixed carbon content of ≥98%, an ash content of ≤1.8%, and a moisture content of ≤0.4%.

[0011] Furthermore, in the silicon carbide fine powder: the content of SiC is ≥94.5%, the content of Fe2O3 is ≤0.4%, the content of SiO2 is ≤0.6%, the content of free carbon is ≤0.5%, and the content of free silicon is ≤0.6%.

[0012] Furthermore, the particle size of the aluminum powder is 0 to 0.075 mm; the aluminum powder contains: Al content ≥ 99%, Fe content ≤ 0.2%, Si content ≤ 0.2%, and Cu content ≤ 0.1%.

[0013] A method for preparing a low-carbon magnesium zirconium carbonaceous top-feed brick includes the following steps: Step 1: Preparation of co-milled powder: The co-milled powder is prepared by uniformly mixing fused magnesia fine powder, fused magnesia zircon fine powder, 898 graphite, silicon carbide fine powder and metallic aluminum powder according to the formula. Step 2: Granular material batching: Mix fused magnesia and fused magnesia-zirconium sand evenly according to the proportions; Step 3: Mixing: Dry mix the granular material for 3-5 minutes, add 3-4% of liquid phenolic resin by weight and wet mix for 3-6 minutes, then add co-grinding powder and continue mixing for 25-35 minutes. Allow the mixed mud to stand for 12-24 hours. Step 4: Shaping: Add the clay after it has been trapped into the mold, lightly beat it 2-3 times, then remove it from the mold and beat it twice to release the air. Then gradually increase the pressure and beat it 5-8 times. The total number of beatings should not be less than 10 times to obtain a semi-finished brick blank. Step 5: Drying: Dry the semi-finished brick blanks at a temperature of 210±10℃ for 15h~20h. Step Six: High-Temperature Treatment: Firing is carried out in a shuttle kiln under N2 atmosphere at a temperature of 1650±20℃ and held for 15 hours. Step 7: Finishing: After drying or high-temperature treatment, the semi-finished products are encased, their appearance is trimmed, and they are packaged after passing inspection.

[0014] Furthermore, the heating curve for the high-temperature treatment in step six is ​​as follows: heating from 0 to 600℃ for 10 hours, heating from 600 to 1400℃ for 40 hours, heating from 1400 to 1650℃ for 15 hours, holding at 1650℃ (±20℃) for 15 hours, and then cooling for 80 to 90 hours to below 100℃.

[0015] 3. Beneficial effects Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention provides a low-carbon magnesium zirconium carbonaceous top water inlet brick and its preparation method, using fused magnesium zirconium sand with a coating layer on the surface as the core aggregate. The coating layer can directly improve the erosion and scouring resistance of the aggregate particles in an alkaline environment. On the other hand, the functional layer, as an intermediate buffer layer, can effectively reduce the thermal expansion mismatch between the fused magnesium zirconium sand aggregate and the external matrix, and greatly improve the thermal shock resistance of the product.

[0016] (2) This invention discloses a low-carbon magnesium-zirconium carbonaceous top-end brick and its preparation method. Under a specific process (nitrogen protection, 1650℃), silicon carbide powder and metallic aluminum powder in the co-milled powder react with fused magnesium-zirconium sand powder to generate a Sialon-ZrO2 composite structure in situ. The Sialon phase has excellent properties such as high strength, high hardness, high temperature corrosion resistance, and thermal shock resistance, while ZrO2 has toughening and corrosion resistance properties. This in-situ synthesized composite structure serves as the matrix bonding phase of the product, greatly improving the comprehensive mechanical properties and service life of the top-end brick. Detailed Implementation

[0017] A low-carbon magnesia-zirconium carbonaceous top-feed brick comprises granular aggregate and co-ground powder. The granular aggregate comprises 70%–75% by weight, the co-ground powder comprises 25%–30% by weight, and the total percentage is 100%. The granular aggregate is composed of the following weight percentages: 25–30% magnesia sand particles, 70–75% fused magnesia-zirconium sand, and 3%–4% phenolic resin. The co-ground powder is prepared by uniformly mixing 6%–10% magnesia sand powder, 5%–8% fused magnesia-zirconium sand powder, 3%–5% metallic aluminum powder, 5%–8% 898 graphite, and 1%–3% silicon carbide powder. A coating layer is formed on the surface of the fused magnesia-zirconium sand particles, the coating layer comprising hydrated calcium aluminate and aluminum adhesive.

[0018] The coating layer is prepared as follows: Weigh out the active calcium aluminate and add it to water, stirring until homogeneous. Add the fused magnesium zirconium sand particles and stir until homogeneous. Stir at 100–150°C until dry to obtain particles with a coating layer on the surface. The active calcium aluminate is one or more of aluminate cement, monocalcium aluminate, monocalcium dialuminate, dodecacalcium heptaaluminate, and calcium aluminoferrite, with a weight fraction of 2%–4% of the weight of the fused magnesium zirconium sand particles. The average thickness of the coating layer on the surface of the fused magnesium zirconium sand particles is 0.2–0.5 mm.

[0019] The fused magnesia is available in three particle sizes: 5–3 mm, 3–1 mm, and 1–0 mm. The weight percentages for each particle size are as follows: 10%–15% for 5–3 mm, 5%–10% for 3–1 mm, and 5%–10% for 1–0 mm. The chemical composition and content of the fused magnesia are: MgO ≥ 96.3%, SiO2 ≤ 1.3%, and CaO ≤ 1.5%.

[0020] The fused magnesia-zirconium sand has three particle sizes: 3–1 mm, 1–0.5 mm, and 0.5–0 mm. The weight percentages are as follows: 10%–17% for 3–1 mm particle size; 15%–23% for 1–0.5 mm particle size; and 10%–15% for 0.5–0 mm particle size. The fused magnesia-zirconium sand particles and powder contain: MgO content ≥90%, ZrO2 content ≥4%, SiO2 content ≤2.5%, Fe2O3 content ≤0.6%, and CaO content ≤1.2%.

[0021] In addition, 898 graphite has a fixed carbon content ≥98%, ash content ≤1.8%, and moisture content ≤0.4%. In silicon carbide fine powder: SiC content ≥94.5%, Fe2O3 content ≤0.4%, SiO2 content ≤0.6%, free carbon content ≤0.5%, and free silicon content ≤0.6%. The particle size of metallic aluminum powder is 0~0.075mm, and in metallic aluminum powder: Al content ≥99%, Fe content ≤0.2%, Si content ≤0.2%, and Cu content ≤0.1%.

[0022] The preparation method of the above-mentioned low-carbon magnesium zirconium carbonaceous top-end brick includes the following steps: Step 1: Preparation of co-milled powder: The co-milled powder is prepared by uniformly mixing fused magnesia fine powder, fused magnesia zircon fine powder, 898 graphite, silicon carbide fine powder and metallic aluminum powder according to the formula. Step 2: Granular material batching: Mix fused magnesia and fused magnesia-zirconium sand evenly according to the proportions; Step 3: Mixing: Dry mix the granular material for 3-5 minutes, add 3-4% of liquid phenolic resin by weight and wet mix for 3-6 minutes, then add co-grinding powder and continue mixing for 25-35 minutes. Allow the mixed mud to stand for 12-24 hours. Step 4: Shaping: Add the clay after it has been trapped into the mold, lightly beat it 2-3 times, then remove it from the mold and beat it twice to release the air. Then gradually increase the pressure and beat it 5-8 times. The total number of beatings should not be less than 10 times to obtain a semi-finished brick blank. Step 5: Drying: Dry the semi-finished brick blanks at a temperature of 210±10℃ for 15h~20h. Step Six: High-Temperature Treatment: Firing is carried out in a shuttle kiln under N2 atmosphere at a temperature of 1650±20℃ and held for 15 hours. Step 7: Finishing: After drying or high-temperature treatment, the semi-finished products are encased, their appearance is trimmed, and they are packaged after passing inspection.

[0023] The heating curve for the high-temperature treatment in step six is ​​as follows: heating from 0 to 600℃ for 10 hours, heating from 600 to 1400℃ for 40 hours, heating from 1400 to 1650℃ for 15 hours, holding at 1650℃ (±20℃) for 15 hours, and then cooling for 80 to 90 hours to below 100℃.

[0024] This invention pre-treats the core aggregate, fused magnesium zirconium sand, with surface functionalization. By pre-constructing a composite coating layer of hydrated calcium aluminate and alumina gel on the particle surface, new functional properties are endowed to the aggregate. This is not a simple physical coating; this coating layer can act as a physical barrier and chemical buffer layer during high-temperature use, simultaneously improving the material's resistance to erosion and thermal shock at the microstructural level of the "aggregate-matrix interface".

[0025] Furthermore, this invention does not simply add silicon carbide (SiC), metallic aluminum (Al), and fused magnesium zirconium sand (containing ZrO2) as independent components, but rather purposefully designs them into a high-temperature system that can undergo a synergistic reaction under specific conditions. Through a controlled nitrogen atmosphere and a high-temperature treatment process at 1650℃, the above components are driven to generate a Sialon-ZrO2 composite structure in situ. This method, by precisely controlling the components and process parameters, synthesizes a high-performance ceramic phase in situ within the product, fundamentally improving the matrix properties.

[0026] In summary, the low-carbon magnesium-zirconium carbonaceous top-end brick and its preparation method of the present invention solve the problems of aggregate erosion resistance and interfacial thermal stress by using a coated magnesium-zirconium sand, and solve the problems of matrix strength, toughness and erosion resistance by utilizing an in-situ generated Sialon-ZrO2 composite structure. The synergistic effect of these two methods achieves the low-carbon target (5-8% total carbon) while breaking through the bottleneck of traditional materials' inability to simultaneously achieve optimal performance, resulting in unexpectedly excellent comprehensive properties.

[0027] 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.

[0028] Example 1 Objective: Focus on high resistance to corrosion.

[0029] Formula and process: Granular aggregate (73%): Fused magnesia (particle size 5-3mm, accounting for 12.5% ​​of the total weight of raw materials): meets the requirement of MgO≥96.3%.

[0030] Fused magnesia (particle size 3-1mm, accounting for 8% of the total weight of raw materials): meets the requirement of MgO≥96.3%.

[0031] Fused magnesia (particle size 1-0 mm, accounting for 7.5% of the total weight of raw materials): meets the requirement of MgO≥96.3%.

[0032] Surface-coated fused magnesia-zirconium sand (totaling 45% of the raw material weight): 13% of the particles are 3-1mm, 17% are 1-0.5mm, and 15% are 0.5-0mm. The coating layer uses aluminate cement (3% of the particle weight) with an average thickness of 0.3mm. The particles meet the requirements of MgO≥90% and ZrO2≥4%.

[0033] Co-milled powder (27%): Magnesia fine powder (200 mesh, accounting for 6% of the total weight of raw materials): MgO≥96.3%.

[0034] Fused magnesium zircon sand fine powder (200 mesh, accounting for 8% of the total weight of raw materials): MgO≥90%, ZrO2≥4%.

[0035] Aluminum powder (particle size 0-0.075mm, accounting for 3% of the total weight of raw materials): Al≥99%.

[0036] 898 graphite (8% of total raw material weight): Fixed carbon ≥ 98%.

[0037] Silicon carbide fine powder (2% of the total weight of raw materials): SiC≥94.5%.

[0038] Additive: Liquid phenolic resin (3.5% of the total weight of raw materials).

[0039] Preparation method: The preparation steps of the low-carbon magnesium zirconium carbon-based top water inlet brick mentioned above are strictly followed. The total number of impacts during molding is 12. The high-temperature treatment is carried out at 1650℃ (+10℃) for 15 hours under N2 atmosphere.

[0040] Example 2 Objective: To focus on optimizing thermal shock resistance and strength.

[0041] Formula and process: Granular aggregate (72%): Fused magnesia (particle size 5-3mm, accounting for 10% of the total weight of raw materials): meets the requirement of MgO≥96.3%.

[0042] Fused magnesia (particle size 3-1mm, accounting for 10% of the total weight of raw materials): meets the requirement of MgO≥96.3%.

[0043] Fused magnesia (particle size 1-0 mm, accounting for 10% of the total weight of raw materials): meets the requirement of MgO≥96.3%.

[0044] Surface-coated fused magnesium zirconium sand (totaling 42% of the raw material weight): 15% of the particles are 3-1mm, 15% are 1-0.5mm, and 12% are 0.5-0mm. The coating layer uses monocalcium aluminate (2.5% of the particle weight) with an average thickness of 0.2mm. The particles meet the following requirements: MgO ≥ 90%, ZrO2 ≥ 4%.

[0045] Co-milled powder (28%): Magnesia fine powder (200 mesh, accounting for 10% of the total weight of raw materials): MgO≥96.3%.

[0046] Fused magnesium zircon sand fine powder (200 mesh, accounting for 5% of the total weight of raw materials): MgO≥90%, ZrO2≥4%.

[0047] Aluminum powder (particle size 0-0.075mm, accounting for 5% of the total weight of raw materials): Al≥99%.

[0048] 898 graphite (5% of total raw material weight): Fixed carbon ≥ 98%.

[0049] Silicon carbide fine powder (3% of the total weight of raw materials): SiC≥94.5%.

[0050] Additive: Liquid phenolic resin (4% of the total weight of raw materials).

[0051] Preparation method: In step 3, the wet mixing time is extended to 6 minutes, the total number of molding impacts is 15, the high temperature treatment is carried out at 1650℃ for 15 hours under N2 atmosphere, and the cooling time is extended to 90 hours.

[0052] Example 3 Objective: To balance performance and cost.

[0053] Formula and process: Granular aggregate (70%): Fused magnesia (particle size 5-3mm, accounting for 15% of the total weight of raw materials): meets the requirement of MgO≥96.3%.

[0054] Fused magnesia (particle size 3-1mm, accounting for 5% of the total weight of raw materials): meets the requirement of MgO≥96.3%.

[0055] Fused magnesia (particle size 1-0 mm, accounting for 10% of the total weight of raw materials): meets the requirement of MgO≥96.3%.

[0056] Surface-coated fused magnesium zirconium sand (totaling 40% of the raw material weight): 10% of the particles are 3-1mm, 20% are 1-0.5mm, and 10% are 0.5-0mm. The coating layer uses a mixture of dodecacalcium heptaaluminate and a small amount of calcium aluminoferrite (4% of the total particle weight), with an average thickness of 0.4mm. The particles meet the requirements of MgO≥90% and ZrO2≥4%.

[0057] Co-milled powder (30%): Magnesia fine powder (200 mesh, accounting for 8% of the total weight of raw materials): MgO≥96.3%.

[0058] Fused magnesium zirconium sand fine powder (200 mesh, accounting for 6% of the total weight of raw materials): MgO≥90%, ZrO2≥4%.

[0059] Aluminum powder (particle size 0-0.075mm, accounting for 4% of the total weight of raw materials): Al≥99%.

[0060] 898 graphite (8% of total raw material weight): Fixed carbon ≥ 98%.

[0061] Silicon carbide fine powder (4% of the total weight of raw materials): SiC≥94.5%.

[0062] Additive: Liquid phenolic resin (3% of the total weight of raw materials).

[0063] Preparation method: In step three, the material is trapped for 24 hours, the total number of molding impacts is 10, and the high temperature treatment is carried out at 1640℃ for 16 hours under N2 atmosphere.

[0064] Example 4 Objective: Designed with the lowest carbon content to accommodate the production of ultra-low carbon steel.

[0065] Formula and process: Granular aggregate (75%): Fused magnesia (particle size 5-3mm, accounting for 12% of the total weight of raw materials): meets the requirement of MgO≥96.3%.

[0066] Fused magnesia (particle size 3-1mm, accounting for 8% of the total weight of raw materials): meets the requirement of MgO≥96.3%.

[0067] Fused magnesia (particle size 1-0 mm, accounting for 5% of the total weight of raw materials): meets the requirement of MgO≥96.3%.

[0068] Surface-coated fused magnesium zirconium sand (totaling 50% of the raw material weight): 17% of the particles are 3-1mm, 23% are 1-0.5mm, and 10% are 0.5-0mm. The coating layer uses monocalcium aluminate (2% of the particle weight) with an average thickness of 0.2mm. The particles meet the requirements of MgO≥90% and ZrO2≥4%.

[0069] Co-milled powder (25%): Magnesia fine powder (200 mesh, accounting for 7% of the total weight of raw materials): MgO≥96.3%.

[0070] Fused magnesium zircon sand fine powder (200 mesh, accounting for 7% of the total weight of raw materials): MgO≥90%, ZrO2≥4%.

[0071] Aluminum powder (particle size 0-0.075mm, accounting for 5% of the total weight of raw materials): Al≥99%.

[0072] 898 graphite (5% of total raw material weight): Fixed carbon ≥ 98%.

[0073] Silicon carbide fine powder (1% of the total weight of raw materials): SiC≥94.5%.

[0074] Additive: Liquid phenolic resin (3.5% of the total weight of raw materials).

[0075] Preparation method: Step 6: High temperature treatment is strictly controlled within the range of 1640-1660℃ (±20℃) and kept at that temperature for 15 hours.

[0076] Example 5 Objective: To maximize the addition of metallic aluminum and silicon carbide to enhance in-situ Sialon-ZrO2 formation.

[0077] Formula and process: Granular aggregate (70%): Fused magnesia (particle size 5-3mm, accounting for 13% of the total weight of raw materials): meets the requirement of MgO≥96.3%.

[0078] Fused magnesia (particle size 3-1mm, accounting for 7% of the total weight of raw materials): meets the requirement of MgO≥96.3%.

[0079] Fused magnesia (particle size 1-0 mm, accounting for 10% of the total weight of raw materials): meets the requirement of MgO≥96.3%.

[0080] Surface-coated fused magnesia-zirconium sand (totaling 40% of the raw material weight): 12% of the particles are 3-1mm, 18% are 1-0.5mm, and 10% are 0.5-0mm. The coating layer uses a mixture of aluminate cement and monocalcium aluminate (3.5% of the particle weight), with an average thickness of 0.45mm. The particles meet the requirements of MgO≥90% and ZrO2≥4%.

[0081] Co-milled powder (30%): Magnesia fine powder (200 mesh, accounting for 6% of the total weight of raw materials): MgO≥96.3%.

[0082] Fused magnesium zircon sand fine powder (200 mesh, accounting for 8% of the total weight of raw materials): MgO≥90%, ZrO2≥4%.

[0083] Aluminum powder (particle size 0-0.075mm, accounting for 5% of the total weight of raw materials): Al≥99%.

[0084] 898 graphite (6% of total raw material weight): Fixed carbon ≥ 98%.

[0085] Silicon carbide fine powder (5% of the total weight of raw materials): SiC≥94.5%.

[0086] Additive: Liquid phenolic resin (4% of the total weight of raw materials).

[0087] Preparation method: Step 6 High temperature treatment: Hold at 1650℃ (+15℃) for 15 hours under N2 atmosphere. This is to promote the full reaction of aluminum powder, silicon carbide powder and fused magnesium zircon sand powder in the co-milled powder, and generate sufficient Sialon-ZrO2 composite structure in situ to give the product extremely high high temperature strength and hardness.

[0088] These five embodiments demonstrate how, within the weight percentages and composition ranges defined in the claims, targeted or balanced optimization of product performance (erosion resistance, thermal shock resistance, low-carbon adaptability, and high-temperature strength) can be achieved by adjusting particle size distribution, coating composition and thickness, the proportion of each fine powder in the co-milled powder, and process parameters. The water inlet bricks prepared in all embodiments are expected to exhibit superior overall performance and service life compared to existing alumina-carbon or ordinary magnesia-carbon products.

[0089] 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 low-carbon magnesium-zirconium carbonaceous top-feed brick, comprising granular aggregate and co-ground powder, characterized in that, The weight percentage of the granular aggregate is 70%–75%, the weight percentage of the co-ground powder is 25%–30%, and the total percentage is 100%. The composition of the granular aggregate by weight percentage is: 25–30% magnesia particles, 70–75% fused magnesium zirconium sand, and 3%–4% phenolic resin. The co-ground powder is prepared by uniformly mixing 6%–10% magnesia powder, 5%–8% fused magnesium zirconium sand powder, 3%–5% metallic aluminum powder, 5%–8% 898 graphite, and 1%–3% silicon carbide powder. A coating layer is coated on the surface of the fused magnesium zirconium sand particles, and the coating layer contains hydrated calcium aluminate and aluminum glue.

2. The low-carbon magnesium-zirconium carbonaceous top-feed brick according to claim 1, characterized in that, The coating layer is prepared by weighing active calcium aluminate, adding water and stirring evenly, adding fused magnesium zircon sand particles and stirring evenly, stirring at 100-150℃ until dry, and obtaining particles with a coating layer on the surface; the active calcium aluminate is one or more of aluminate cement, monocalcium aluminate, monocalcium dialuminate, dodecacalcium heptaaluminate and calcium aluminoferrite, and its weight fraction is 2%-4% of the weight of fused magnesium zircon sand particles.

3. The low-carbon magnesium-zirconium carbonaceous top-feed brick according to claim 2, characterized in that, The average thickness of the coating layer on the surface of the fused magnesium zircon sand particles is 0.2 to 0.5 mm.

4. A low-carbon magnesium-zirconium carbonaceous top-feed brick according to claim 1, characterized in that, The fused magnesia has particle sizes of 5–3 mm, 3–1 mm, and 1–0 mm, with the following weight percentages for each particle size: 10%–15% for fused magnesia with a particle size of 5–3 mm, 5%–10% for fused magnesia with a particle size of 3–1 mm, and 5%–10% for fused magnesia with a particle size of 1–0 mm. The chemical composition and content of the fused magnesia are: MgO ≥ 96.3%, SiO2 ≤ 1.3%, and CaO ≤ 1.5%.

5. A low-carbon magnesium-zirconium carbonaceous top-feed brick according to claim 1, characterized in that, The fused magnesium zirconium sand has three particle sizes: 3–1 mm, 1–0.5 mm, and 0.5–0 mm. The weight percentages are as follows: 10%–17% for fused magnesium zirconium sand with a particle size of 3–1 mm; 15%–23% for fused magnesium zirconium sand with a particle size of 1–0.5 mm; and 10%–15% for fused magnesium zirconium sand with a particle size of 0.5–0 mm. The fused magnesium zirconium sand particles and powder contain the following contents: MgO content ≥90%, ZrO2 content ≥4%, SiO2 content ≤2.5%, Fe2O3 content ≤0.6%, and CaO content ≤1.2%.

6. A low-carbon magnesium-zirconium carbonaceous top-feed brick according to claim 1, characterized in that, The 898 graphite has a fixed carbon content of ≥98%, ash content of ≤1.8%, and moisture content of ≤0.4%.

7. The low-carbon magnesium-zirconium carbonaceous top-feed brick according to claim 6, characterized in that, The silicon carbide fine powder contains: SiC content ≥ 94.5%, Fe2O3 content ≤ 0.4%, SiO2 content ≤ 0.6%, free carbon content ≤ 0.5%, and free silicon content ≤ 0.6%.

8. The low-carbon magnesium-zirconium carbonaceous top-feed brick according to claim 1, characterized in that, The aluminum powder has a particle size of 0 to 0.075 mm; the aluminum powder contains: Al content ≥ 99%, Fe content ≤ 0.2%, Si content ≤ 0.2%, and Cu content ≤ 0.1%.

9. A method for preparing a low-carbon magnesium-zirconium carbonaceous top-feed brick according to any one of claims 1-8, characterized in that, Includes the following steps: Step 1: Preparation of co-milled powder: The co-milled powder is prepared by uniformly mixing fused magnesia fine powder, fused magnesia zircon fine powder, 898 graphite, silicon carbide fine powder and metallic aluminum powder according to the formula. Step 2: Granular material batching: Mix fused magnesia and fused magnesia-zirconium sand evenly according to the proportions; Step 3: Mixing: Dry mix the granular material for 3-5 minutes, add 3-4% of liquid phenolic resin by weight and wet mix for 3-6 minutes, then add co-grinding powder and continue mixing for 25-35 minutes. Allow the mixed mud to stand for 12-24 hours. Step 4: Shaping: Add the clay after it has been trapped into the mold, lightly beat it 2-3 times, then remove it from the mold and beat it twice to release the air. Then gradually increase the pressure and beat it 5-8 times. The total number of beatings should not be less than 10 times to obtain a semi-finished brick blank. Step 5: Drying: Dry the semi-finished brick blanks at a temperature of 210±10℃ for 15h~20h. Step Six: High-Temperature Treatment: Firing is carried out in a shuttle kiln under N2 atmosphere at a temperature of 1650±20℃ and held for 15 hours. Step 7: Finishing: After drying or high-temperature treatment, the semi-finished products are encased, their appearance is trimmed, and they are packaged after passing inspection.

10. The method for preparing a low-carbon magnesium-zirconium carbonaceous top-water-gate brick according to claim 9, characterized in that, The temperature rise curve for the high-temperature treatment in step six is ​​as follows: 0-600℃ for 10 hours, 600-1400℃ for 40 hours, 1400-1650℃ for 15 hours, 1650℃ (±20℃) for 15 hours, and then cooling for 80-90 hours to below 100℃.