A steel ladle top nozzle brick and its preparation method

Abstract

This invention discloses a top nozzle brick for steel ladles and its preparation method, belonging to the field of refractory materials. It comprises: 1) 25-60 parts by weight of granular aggregate, wherein the granular aggregate consists of 15-35 parts by weight of recycled magnesia-chrome sand particles and 10-25 parts by weight of recycled magnesia-alumina spinel particles; 2) 19-35 parts by weight of co-ground powder, wherein the co-ground powder consists of 8-15 parts by weight of recycled magnesia-chrome sand fine powder, 5-10 parts by weight of recycled magnesia-alumina spinel fine powder, and 6-10 parts by weight of α-Al₂O₃ micro powder; 3) 0.6-1.2 parts by weight of fiber, wherein the fiber consists of 0.5-1 parts by weight of metallic aluminum fiber and 0.1-0.2 parts by weight of polypropylene explosion-proof fiber; and 4) a modified composite curing agent comprising 4 wt%-6 wt% of the total weight of the granular aggregate, co-ground powder, and fiber.

Description

Technical Field

[0001] This invention belongs to the field of refractory materials, and more specifically, relates to a top nozzle brick for steel ladles and its preparation method. Background Technology

[0002] With the continuous development of steelmaking technology, the flow control system in the casting or continuous casting process is now primarily based on the sliding gate flow control system, replacing the stopper rod flow control system. The ladle flow control sliding gate system consists of a dedicated sliding mechanism installed at the bottom of the ladle, a matching hydraulic drive device, a pressure transmission linkage device, a hydraulic cylinder, and refractory materials (upper nozzle brick, upper and lower sliding plates, lower nozzle brick, and joint mortar). Pressure is provided by a hydraulic station, and the linkage transmits the pressure to drive the hydraulic cylinder, which in turn moves the sliding frame within the mechanism. The sliding plate, installed within the sliding frame, moves up and down with the frame, thus controlling the flow during the casting process. The sliding gate flow control system precisely regulates the flow rate of molten steel from the ladle to the continuous casting or ingot casting process, protecting the equipment and personnel below the ladle. It controls the temperature and flow rate of the molten steel, ensuring the molten steel level in the tundish is at a suitable position, and plays a crucial role in the safe and efficient operation of continuous casting and ingot casting.

[0003] The upper nozzle brick for steel ladles is a very important component of the ladle flow control sliding nozzle system. During use, it is fixedly installed inside the ladle nozzle seat brick (connected by special joint mortar), and the large end face is bonded to the upper sliding plate with mortar. The upper nozzle brick is mainly affected by the following factors during use: (1) During the steel pouring process, the high temperature and high speed of the flowing molten steel and steel slag continuously erode and wash away the upper nozzle brick of the ladle; (2) Due to the frequent replacement of the sliding plate during hot maintenance operations, the upper nozzle brick is exposed to the air, which increases carbon oxidation, increases the amount of the deteriorated layer, and makes it easy to be eroded and peeled off when it continues to be used; (3) Each time the sliding plate is replaced during hot maintenance, it is necessary to use mechanical methods to clean the residual mortar, steel slag, cold steel, etc. on the end face of the upper nozzle brick, which continuously damages the upper nozzle brick. Due to the influence of the above factors, the upper nozzle brick has problems such as high material consumption and short service life, which brings economic and environmental pressure to steel enterprises.

[0004] To solve the above problems, a search was conducted:

[0005] Chinese Patent Document 1: Publication No. CN101747062A, Publication Date 2010-06-23, discloses a ladle nozzle brick for steelmaking, which uses fused white corundum as the main raw material and adds 8-14% of fused zirconium mullite by weight of the raw material to the raw material.

[0006] Chinese Patent Document 2: Publication No. CN209157112U, Publication Date 2019-07-26, discloses a top nozzle brick for steel ladles. This top nozzle brick for steel ladles has a zirconia ring brick embedded in the steel flow hole at the upper end of the brick body. The excellent anti-corrosion ability and thermal shock resistance of the zirconia ring brick effectively improve the service life of the top nozzle brick.

[0007] Chinese Patent Document 3: Publication No. CN112456986A, Publication Date 2021-03-09, discloses a high-life steel ladle top nozzle brick for calcium-treated steel and its preparation method. The top nozzle brick includes fine powder, and the fine powder contains modified graphite fine powder made from intercalated graphite and active aluminum-silicon alloy powder. The intercalated graphite content is 25-45% by weight, and the remainder is active aluminum-silicon alloy powder.

[0008] The aforementioned patents employ fused zirconia mullite, zirconium oxide, or magnesia spinel particles to improve service life. However, there are no reports on how to recycle magnesia spinel bricks and magnesia chrome bricks for use in inlet lining bricks. Currently, there are some successful examples and technological foundations. For instance, an Iranian copper smelter used recycled magnesia chrome bricks to prepare castables for anode furnaces, casting wheels, and tapping troughs, demonstrating good performance. Domestically, some refractory material plants have also recycled waste magnesia spinel bricks, selecting, crushing, and screening them to produce recycled magnesia spinel sand, which is used to manufacture refractory products such as ladle lining bricks and ladle castables.

[0009] According to incomplete statistics, nearly hundreds of thousands of tons of chrome-magnesium bricks and magnesia-alumina spinel bricks are consumed annually nationwide. Many metallurgical enterprises, glass kiln manufacturers, rotary kilns, and mud-making rotary kilns generate large quantities of used and discarded waste chrome-magnesium bricks and magnesia-alumina spinel bricks each year. However, during use, only about one-third to one-half of these bricks are corroded or melted into the earth. Many manufacturers dispose of them by indiscriminately dumping, scattering, or burying them underground. Indiscriminate dumping or burying not only wastes valuable resources but also harms the environment. For example, chrome-magnesium bricks release toxic hexavalent chromium, which is harmful to human health and ecosystems. Recycling these waste bricks can reduce raw material consumption, lower production costs, and also reduce hexavalent chromium emissions, protecting the environment and human health. Summary of the Invention

[0010] 1. The problem to be solved

[0011] To address the aforementioned problems, the present invention aims to provide a ladle inlet brick that solves many of the problems associated with traditional inlet bricks, including: 1) high material consumption and short service life leading to frequent online replacements; and 2) high raw material cost of pure corundum, which brings economic and environmental pressure to steel companies.

[0012] Another object of the present invention is to provide a method for preparing a top nozzle brick for a steel ladle.

[0013] 2. Technical Solution

[0014] To solve the above problems, the technical solution adopted by the present invention is as follows:

[0015] The first aspect of this invention provides a top nozzle brick for steel ladles, comprising:

[0016] 1) 25 to 60 parts by weight of granular aggregate, wherein the granular aggregate is composed of 15 to 35 parts by weight of recycled magnesia-chromium sand particles and 10 to 25 parts by weight of recycled magnesia-alumina spinel particles.

[0017] 2) A co-milled powder with a mass fraction of 19 to 35 parts, wherein the co-milled powder is composed of 8 to 15 parts by mass of recycled magnesium chromium sand fine powder, 5 to 10 parts by mass of recycled magnesium aluminum spinel fine powder, and 6 to 10 parts by mass of α-Al2O3 micro powder.

[0018] 3) 0.6 to 1.2 parts by weight of fiber, wherein the fiber is composed of 0.5 to 1 part by weight of metallic aluminum fiber and 0.1 to 0.2 parts by weight of polypropylene explosion-proof fiber;

[0019] 4) A modified composite curing agent comprising 4wt% to 6wt% of the total weight of the granular aggregate, co-ground powder, and fiber. The modified composite curing agent is composed of modified nano-silica powder and thermosetting phenolic resin mixed in a weight ratio of 1:100. The modified nano-silica powder is obtained by uniformly mixing nano-silica, titanium dioxide, and alumina salt solution in a certain proportion. Heating causes chemical precipitation of the alumina salt solution. After filtration, washing, and drying, modified nano-silica is obtained. Modified nano-silica can improve the dispersion stability of nano-silica, prevent agglomeration, improve the compatibility of the nano-silica solution, and enhance the adhesion between the binder and the substrate. The average particle size of the nano-silica is 30nm, and the SiO2 content is ≥99.5wt%. The modified nano-silica in the composite curing agent can fill the voids in the phenolic resin, improving the strength and density of the phenolic resin, and enhancing its high-temperature resistance and thermal stability.

[0020] According to any embodiment of the first aspect of the present invention, the recycled magnesia-chromium sand particles are composed of three particle sizes: 5-3 mm, 3-1 mm, and 1-0 mm, with the following mass fractions: 5-10 parts of recycled magnesia-chromium sand particles with a particle size of 5-3 mm, 5-15 parts of recycled magnesia-chromium sand particles with a particle size of 3-1 mm, and 5-10 parts of recycled magnesia-chromium sand particles with a particle size of 1-0 mm; the particle size of the recycled magnesia-chromium sand fine powder is 325 mesh.

[0021] According to any embodiment of the first aspect of the present invention, the content of MgO+Cr2O3 in the recycled magnesia-chromium sand particles and recycled magnesia-chromium sand fine powder is ≥80.0wt%.

[0022] According to any embodiment of the first aspect of the present invention, the recycled magnesium aluminum spinel particles are composed of three particle sizes: 5-3 mm, 3-1 mm, and 1-0 mm, with the following mass fractions: 0-5 parts of recycled magnesium aluminum spinel particles with a particle size of 5-3 mm, 5-10 parts of recycled magnesium aluminum spinel particles with a particle size of 3-1 mm, and 5-10 parts of recycled magnesium aluminum spinel particles with a particle size of 1-0 mm; the particle size of the recycled magnesium aluminum spinel fine powder is 325 mesh.

[0023] According to any embodiment of the first aspect of the present invention, the content of MgO+Al2O3 in the recycled magnesium aluminum spinel particles and recycled magnesium aluminum spinel fine powder is ≥95.0wt%.

[0024] According to any embodiment of the first aspect of the present invention, the particle size of the α-Al2O3 micro powder is 0-2 μm; wherein the α-Al2O3 micro powder contains: Al2O3 content ≥99.0 wt%, SiO2 content ≤0.1 wt%, Fe2O3 content ≤0.08 wt%, and Na2O+K2O content ≤0.3 wt%.

[0025] According to any embodiment of the first aspect of the present invention, the aluminum fiber has a diameter of 0.2 mm and a length of 3-4 mm; the aluminum fiber contains ≥99.8 wt% Al.

[0026] According to any embodiment of the first aspect of the present invention, the phenolic resin is a thermosetting phenolic resin with a viscosity of 15-25 (25°C Pas), a solid content (%) ≥70, a residual carbon content (%) ≥40, and free phenol (%) <10.

[0027] A second aspect of the present invention provides a method for preparing a top nozzle brick for a steel ladle, the method comprising the steps of:

[0028] 1) Preparation of recycled raw material pellets;

[0029] 2) Mixture preparation: According to the mass proportions, the recycled magnesium chromate sand particles and recycled magnesium chromate sand fine powder, recycled magnesium aluminum spinel particles and recycled magnesium aluminum spinel fine powder, α-Al2O3 micro powder, metallic aluminum fiber and polypropylene explosion-proof fiber are fully premixed in a high-speed mixer at a speed of 150-250 r / min and a premixing time of 10-15 min.

[0030] 3) Sludge preparation: Add the mixture from step two to a high-speed roller mill for crushing and mixing, add a modified composite curing agent, the weight of which is 4wt% to 6wt% of the weight of the premixed material, and stir for 10 to 15 minutes until the mixture is uniformly mixed to obtain sludge.

[0031] 4) Machine pressing: The clay is added to the molding mold and formed by a 1000T press. The high-pressure molding forms brick blanks, which are then naturally air-dried for 24 hours.

[0032] 5) Drying and curing: After being air-dried for 24 hours, the brick blanks are placed in an electric dryer for drying. The drying process is as follows: the temperature is increased from room temperature to 110℃ at a rate of 20℃ / h and held for 24 hours; then the temperature is increased to 220℃ at a rate of 15℃ / h and held for 10 hours; then the temperature is increased to 350℃ at a rate of 12℃ / h and held for 18 hours; finally, the temperature is cooled to room temperature at a rate of 20℃ / h to obtain the finished product.

[0033] According to any embodiment of the second aspect of the present invention, the step of preparing the recycled raw material pellets includes:

[0034] 11) Select waste magnesium aluminum spinel bricks and magnesium chrome bricks, remove impurities and attachments, and then manually or mechanically remove the slag layer and transition layer to reduce the content of low melting point phases;

[0035] 12) After the preliminary treatment of waste magnesium aluminum spinel bricks and magnesium chrome bricks is selected, they are sent to the crusher for coarse and fine crushing to crush the material to a particle size of less than 25mm.

[0036] 13) The crushed material is fed into a magnetic separator for magnetic separation to remove iron impurities and improve the purity of the raw material; the particles after impurity removal are fed into a planetary roller mill for crushing to remove false particles and improve the overall bulk density of the recycled raw material. The crushing time is 7 to 10 minutes.

[0037] 14) The crushed material is fed into a vibrating screen and screened to obtain recycled magnesium aluminum spinel particles with particle sizes of 5-3mm, 3-1mm, and 1-0mm and recycled magnesium chromium sand particles with particle sizes of 5-3mm, 3-1mm, and 1-0mm.

[0038] 15) Grind the particles with a particle size of 1-0 mm obtained by sieving into uniform 325-mesh recycled magnesium aluminum spinel powder and 325-mesh recycled magnesium chromium sand powder using a ball mill.

[0039] 3. Beneficial effects

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] (1) The ladle inlet bricks of the present invention utilize waste magnesium-aluminate spinel bricks and magnesium-chrome bricks through recycling and reuse, avoiding the indiscriminate dumping or landfilling of large quantities of waste bricks and reducing environmental pollution. This has positive environmental significance in preventing the release of toxic substances, such as hexavalent chromium, which can harm the human body and the ecosystem.

[0042] (2) The steel ladle top nozzle brick of the present invention reduces the demand for raw materials in production: by recycling, the demand for new materials is reduced, the exploitation and consumption of natural resources are reduced, which helps to build a circular economy model and slows down the rate of resource depletion.

[0043] (3) The steel ladle top outlet brick of the present invention successfully transforms waste magnesium aluminum spinel bricks and magnesium chrome bricks into recycled raw materials through recycling processes such as selection, cleaning, crushing, screening and fine grinding, reducing the demand for high-cost raw materials, achieving efficient recycling and maximizing the utilization of resources.

[0044] (4) The steel ladle top nozzle brick of the present invention reduces production costs: steel ladle top nozzle bricks are prepared by using recycled raw materials, which can significantly reduce production costs compared with traditional production methods; through recycling and regeneration, the high cost of fresh raw materials is avoided, and the competitiveness of the product is improved.

[0045] (5) The ladle top nozzle brick of the present invention introduces a new type of composite curing agent. By adding the modified composite curing agent, the high temperature strength and corrosion resistance of the brick can be effectively improved. Attached Figure Description

[0046] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. However, it should be understood that these drawings are designed for illustrative purposes only and are not intended to limit the scope of the present invention. Furthermore, unless specifically indicated, these drawings are intended only to conceptually illustrate the structural construction described herein and are not necessarily drawn to scale.

[0047] Figure 1 This is a product image of the inlet brick for steel ladles according to the present invention. Detailed Implementation

[0048] The following is a detailed description of exemplary embodiments of the present invention. Although these exemplary embodiments are described in sufficient detail to enable those skilled in the art to implement the present invention, it should be understood that other embodiments are possible and various changes can be made to the present invention without departing from the spirit and scope of the present invention.

[0049]

Top nozzle brick for ladle

[0050] The top nozzle brick for ladle of the present invention comprises granular aggregate, co-ground powder, fiber, and a modified composite curing agent.

[0051] Among them, the co-ground powder can fill the pores between the granular aggregate and the fiber, especially the pores between the granular aggregates, effectively reducing the apparent porosity and increasing the bulk density of the top nozzle brick; the fiber plays a toughening role in the top nozzle brick, effectively enhancing the service strength of the top nozzle brick; the modified composite curing agent is used to bond the granular aggregate and reduce the carbon content in the top nozzle brick.

[0052]

Granular aggregate

[0053] The granular aggregate of the present invention has a mass fraction of 25 - 60 parts, and the granular aggregate is composed of recycled magnesia-chrome sand particles with a mass fraction of 15 - 35 parts and recycled magnesia-aluminum spinel particles with a mass fraction of 10 - 25 parts.

[0054] Among them, the particle size of the recycled magnesia-chrome sand particles consists of three particle gradations of 5 - 3mm, 3 - 1mm, and 1 - 0mm, and their mass fractions are respectively: 5 - 10 parts of recycled magnesia-chrome sand particles with a particle size of 5 - 3mm, 5 - 15 parts of recycled magnesia-chrome sand particles with a particle size of 3 - 1mm, and 5 - 10 parts of recycled magnesia-chrome sand particles with a particle size of 1 - 0mm.

[0055] Among them, the particle size of the recycled magnesia-aluminum spinel particles consists of three particle gradations of 5 - 3mm, 3 - 1mm, and 1 - 0mm, and their mass fractions are respectively: 0 - 5 parts of recycled magnesia-aluminum spinel particles with a particle size of 5 - 3mm, 5 - 10 parts of recycled magnesia-aluminum spinel particles with a particle size of 3 - 1mm, and 5 - 10 parts of recycled magnesia-aluminum spinel particles with a particle size of 1 - 0mm.

[0056] The above three of 5 - 3mm, 3 - 1mm, and 1 - 0mm are frequency distributions, respectively representing: 3 < X ≤ 5mm; 1 < X ≤ 3mm; 0 < X ≤ 1mm, where X represents the particle size.

[0057] Through the three particle gradations of the recycled magnesia-chrome sand particles and the three particle gradations of the recycled magnesia-aluminum spinel particles, the bulk density of the top nozzle brick can reach the optimum, ensuring the service strength of the top nozzle brick.

[0058] Furthermore, the content of MgO+Cr2O3 in the recycled magnesia-chromium sand particles and recycled magnesia-chromium sand fine powder is ≥80.0wt%; and the content of MgO+Al2O3 in the recycled magnesia-alumina spinel particles and recycled magnesia-alumina spinel fine powder is ≥95.0wt%.

[0059] The specific preparation steps for recycled magnesia-chromium sand particles, recycled magnesia-chromium sand fine powder, recycled magnesia-alumina spinel particles, and recycled magnesia-alumina spinel fine powder include:

[0060] 11) Select waste magnesium aluminum spinel bricks and magnesium chrome bricks, remove impurities and attachments, and then manually or mechanically remove the slag layer and transition layer to reduce the content of low melting point phases;

[0061] 12) After the preliminary treatment of waste magnesium aluminum spinel bricks and magnesium chrome bricks is selected, they are sent to the crusher for coarse and fine crushing to crush the material to a particle size of less than 25mm.

[0062] 13) The crushed material is fed into a magnetic separator for magnetic separation to remove iron impurities and improve the purity of the raw material; the particles after impurity removal are fed into a planetary roller mill for crushing to remove false particles and improve the overall bulk density of the recycled raw material. The crushing time is 7 to 10 minutes.

[0063] 14) The crushed material is fed into a vibrating screen and screened to obtain recycled magnesium aluminum spinel particles with particle sizes of 5-3mm, 3-1mm, and 1-0mm and recycled magnesium chromium sand particles with particle sizes of 5-3mm, 3-1mm, and 1-0mm.

[0064] 15) Grind the particles with a particle size of 1-0 mm obtained by sieving into uniform 325-mesh recycled magnesium aluminum spinel powder and 325-mesh recycled magnesium chromium sand powder using a ball mill.

[0065] This invention recycles waste magnesia-chrome bricks and magnesia-alumina spinel bricks from steel plants and processes these waste materials using recycling technology. Specifically, the eroded and damaged parts of the materials are screened to remove impurities and attachments, while the remaining parts are subjected to recycling processes such as crushing, washing, screening, and grinding to obtain suitable particles and fine powders, which can then be reused as raw materials for the preparation of refractory materials.

[0066] However, the recycling of waste magnesia-chrome bricks and magnesia-alumina spinel bricks will cause several problems: 1) During high-temperature use, the organic solvents in waste magnesia-chrome bricks and magnesia-alumina spinel bricks are low-melting-point phases, which are very easy to cause perforation, increasing the erosion of the top nozzle brick by molten steel. At the same time, the top nozzle brick is prone to cracks along the edge of the perforation when heated, thus accelerating the cracking problem of the top nozzle brick; 2) Although waste magnesia-chrome bricks and magnesia-alumina spinel bricks are crushed, the original binder binds the particles together to form pseudo particles. These pseudo particles have low strength and are very easy to crack when heated, which brings safety hazards to the use of the top nozzle brick.

[0067] This invention employs a rolling process to remove false particles and increase the overall bulk density of the recycled raw material. Simultaneously, 0.3–0.5% hydrated alumina and 0.2–0.5% fused alumina by weight of the recycled material can be added during the rolling process. The hydrated alumina has a particle size of 0–2 μm, and the fused alumina has a particle size of 5–3 mm. The hydrated alumina has a Mohs hardness of 3.5–4 and is relatively soft, enabling it to crush organic solvents during rolling. Subsequent sieving reduces the amount of organic solvents in the recycled material, lowering the risk of perforation. Furthermore, it serves as a source of alumina with the α-Al₂O₃ micropowder in the co-milled powder, participating in chemical reactions. The fused alumina has a Mohs hardness of 7.5–8, enabling it to crush harder false particles and accelerate their breakage. The fused alumina can also be used as a raw material.

[0068] Furthermore, the inventors discovered that after hydrated alumina absorbs water from the air, its surface undergoes hydroxylation, resulting in partial dissolution and rapid formation of pseudo-boehmite gel that covers the exposed surface. Some of the pseudo-boehmite gel undergoes a crystallization reaction to generate Bayerite and a small amount of boehmite. These disordered, interlocking Bayerite and gel can cover part of the surface of the top water inlet brick, effectively reducing the failure of some modified nano-silica powder + phenolic resin composite curing agent.

[0069] This invention fully utilizes the excellent corrosion resistance, oxidation resistance, and thermal shock resistance of magnesium aluminum spinel bricks and magnesium chrome bricks. Through optimization and improvement of the production process, these bricks are recycled and applied to the top nozzle bricks of steel ladles, which can significantly improve the performance and service life of the top nozzle bricks, thereby reducing the production costs of steel enterprises and improving the quality of steel billets.

[0070] The recycling process proposed in this invention not only solves various problems of traditional top nozzle bricks, but also realizes the rational utilization of waste material resources. The reduction of hydrated alumina can effectively fill the apparent pores in the granular aggregate, effectively reduce the overall porosity of the top nozzle brick, and improve the strength of the top nozzle brick. When heated at high temperature (molten steel in a ladle), the hydrated alumina decomposes into alumina, which causes environmental pollution, reflecting a positive response to sustainable development and resource recycling.

[0071]

Co-ground powder

[0072] The co-milled powder of the present invention has a mass fraction of 19 to 35 parts, and the co-milled powder is composed of 8 to 15 parts by mass of recycled magnesium chromate fine powder, 5 to 10 parts by mass of recycled magnesium aluminum spinel fine powder, and 6 to 10 parts by mass of α-Al2O3 micro powder.

[0073] The particle size of the recycled magnesium chromium sand fine powder is 325 mesh; the particle size of the recycled magnesium aluminum spinel fine powder is 325 mesh.

[0074] The particle size of the α-Al2O3 micro powder is 0-2 μm; the α-Al2O3 micro powder contains: Al2O3 content ≥99.0 wt%, SiO2 content ≤0.1 wt%, Fe2O3 content ≤0.08 wt%, and Na2O+K2O content ≤0.3 wt%.

[0075] The α-Al₂O₃ possesses excellent high-temperature resistance, with a melting point of 2054℃. Adding α-Al₂O₃ micropowder to refractory bricks can improve their refractoriness, enabling them to be used for extended periods at high temperatures.

[0076]

fiber

[0077] The fiber of the present invention has a mass fraction of 0.6 to 1.2 parts, and the fiber is composed of 0.5 to 1 parts by mass of metallic aluminum fiber and 0.1 to 0.2 parts by mass of polypropylene explosion-proof fiber; the diameter of the metallic aluminum fiber is 0.2 mm and the length is 3 to 4 mm; the content of Al in the metallic aluminum fiber is ≥99.8 wt%.

[0078] Modified composite curing agent

[0079] The modified composite curing agent is composed of modified nano-silica powder and thermosetting phenolic resin mixed in a weight ratio of 1:100. The modified nano-silica powder is obtained by uniformly mixing nano-silica, titanium dioxide, and alumina salt solution in a certain proportion. Heating causes chemical precipitation of the alumina salt solution. After filtration, washing, and drying, modified nano-silica is obtained. Modified nano-silica can improve the dispersion stability of nano-silica, prevent agglomeration, improve the compatibility of the nano-silica solution, and enhance the adhesion between the binder and the substrate. The average particle size of the nano-silica is 30 nm, and the SiO2 content is ≥99.5 wt%. The modified nano-silica in the composite curing agent can fill the voids in the phenolic resin, improving the strength and density of the phenolic resin. Furthermore, it improves the high-temperature resistance and thermal stability of the phenolic resin. It accounts for 4 wt% to 6 wt% of the total weight of the aggregate, co-ground powder, and fiber.

[0080] Preparation method of top nozzle bricks for steel ladles

[0081] The preparation method of the present invention includes the following steps:

[0082] 1) Preparation of recycled raw material pellets;

[0083] 2) Mixture preparation: According to the mass proportions, the recycled magnesium chromate sand particles and recycled magnesium chromate sand fine powder, recycled magnesium aluminum spinel particles and recycled magnesium aluminum spinel fine powder, α-Al2O3 micro powder, metallic aluminum fiber and polypropylene explosion-proof fiber are fully premixed in a high-speed mixer at a speed of 150-250 r / min and a premixing time of 10-15 min.

[0084] 3) Sludge preparation: Add the mixture from step two to a high-speed roller mill for crushing and mixing, add a modified composite curing agent, the weight of which is 4wt% to 6wt% of the weight of the premixed material, and stir for 10 to 15 minutes until the mixture is uniformly mixed to obtain sludge.

[0085] 4) Machine pressing: The clay is added to the molding mold and formed by a 1000T press. The high-pressure molding forms brick blanks, which are then naturally air-dried for 24 hours.

[0086] 5) Drying and curing: After air-drying for 24 hours, the brick blanks are placed in an electric dryer for drying. The drying process is as follows:

[0087] The brick is heated from room temperature to 110℃ at a rate of 20℃ / h and held for 4 hours. The main purpose of this stage is to rapidly evaporate the moisture in the brick and gradually cross-link the molecular chains in the binder. Then, the temperature is increased to 220℃ at a rate of 15℃ / h and held for 10 hours. The main purpose of this stage is to completely evaporate the moisture in the brick and further cross-link the molecular chains in the binder. Next, the temperature is increased to 350℃ at a rate of 12℃ / h and held for 18 hours. The main purpose of this stage is to completely cross-link the molecular chains in the binder and to bring the brick to its final strength and performance. Finally, the temperature is cooled to room temperature at a rate of 20℃ / h. This stage ensures uniform and stable cooling to prevent cracking of the brick during rapid cooling, resulting in the final product.

[0088] 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 the invention. Therefore, the scope of the invention is defined only by the appended claims.

[0089] Example 1

[0090] The preparation method of the top nozzle brick for steel ladle in this embodiment includes the following steps:

[0091] Step 1: Preparation of the mixture: According to the following mass proportions, 5 parts of recycled magnesia-chrome sand particles (5-3mm), 15 parts of recycled magnesia-chrome sand particles (3-1mm), 8 parts of recycled magnesia-chrome sand particles (1-0mm), 6 parts of recycled magnesia-chrome sand 325-mesh fine powder, 5 parts of recycled magnesia-alumina spinel particles (5-3mm), 5 parts of recycled magnesia-alumina spinel particles (3-1mm), 5 parts of recycled magnesia-alumina spinel particles (1-0mm), 5 parts of recycled magnesia-alumina spinel particles 325-mesh fine powder, 6 parts of α-Al2O3 micro powder, 0.5 parts of metallic aluminum fiber, and 0.1 parts of polypropylene explosion-proof fiber are thoroughly premixed using a high-speed mixer at a speed of 150-250 r / min for 10-15 min to obtain the mixture.

[0092] Step 2, mud preparation: Add the mixture from Step 2 to a high-speed roller mill for crushing and mixing, add a modified composite curing agent, the weight of which is 4% to 6% of the weight of the premixed material, and stir for 10 to 15 minutes until uniformly mixed to obtain a semi-finished mud.

[0093] Step 3, machine pressing: The clay is added to the molding mold and formed in a 1000T press. After high-pressure molding, the brick blanks are naturally air-dried for 24 hours.

[0094] Step 4: Drying and Curing: After air-drying for 24 hours, the brick blanks are placed in an electric dryer for drying. The drying process is as follows: the temperature is increased from room temperature to 110℃ at a rate of 20℃ / h and held for 24 hours; then the temperature is increased to 220℃ at a rate of 15℃ / h and held for 10 hours; then the temperature is increased to 350℃ at a rate of 12℃ / h and held for 18 hours; finally, the temperature is cooled to room temperature at a rate of 20℃ / h to obtain the finished product.

[0095] Example 2

[0096] The preparation method of the top nozzle brick for steel ladle in this embodiment includes the following steps:

[0097] Step 1: Preparation of the mixture: According to the following mass proportions, 7 parts of recycled magnesia-chrome sand particles (5-3mm), 10 parts of recycled magnesia-chrome sand particles (3-1mm), 5 parts of recycled magnesia-chrome sand particles (1-0mm), 5 parts of recycled magnesia-chrome sand 325-mesh fine powder, 5 parts of recycled magnesia-alumina spinel particles (5-3mm), 10 parts of recycled magnesia-alumina spinel particles (3-1mm), 10 parts of recycled magnesia-alumina spinel particles (1-0mm), 8 parts of recycled magnesia-alumina spinel particles 325-mesh fine powder, 8 parts of α-Al2O3 micro powder, 0.5 parts of metallic aluminum fiber, and 0.1 parts of polypropylene explosion-proof fiber are thoroughly premixed using a high-speed mixer at a speed of 150-250 r / min for 10-15 min to obtain the mixture.

[0098] Step 2, mud preparation: Add the mixture from Step 2 to a high-speed roller mill for crushing and mixing, add a modified composite curing agent, the weight of which is 4% to 6% of the weight of the premixed material, and stir for 10 to 15 minutes until uniformly mixed to obtain a semi-finished mud.

[0099] Step 3, machine pressing: The clay is added to the molding mold and formed in a 1000T press. After high-pressure molding, the brick blanks are naturally air-dried for 24 hours.

[0100] Step 4: Drying and Curing: After air-drying for 24 hours, the brick blanks are placed in an electric dryer for drying. The drying process is as follows: the temperature is increased from room temperature to 110℃ at a rate of 20℃ / h and held for 24 hours; then the temperature is increased to 220℃ at a rate of 15℃ / h and held for 10 hours; then the temperature is increased to 350℃ at a rate of 12℃ / h and held for 18 hours; finally, the temperature is cooled to room temperature at a rate of 20℃ / h to obtain the finished product.

[0101] Example 3

[0102] The preparation method of the top nozzle brick for steel ladle in this embodiment includes the following steps:

[0103] Step 1: Preparation of the mixture: According to the following mass proportions, 10 parts of recycled magnesia-chrome sand particles (5-3mm), 15 parts of recycled magnesia-chrome sand particles (3-1mm), 10 parts of recycled magnesia-chrome sand particles (1-0mm), 10 parts of recycled magnesia-chrome sand 325-mesh fine powder, 2 parts of recycled magnesium aluminum spinel particles (5-3mm), 5 parts of recycled magnesium aluminum spinel particles (3-1mm), 7 parts of recycled magnesium aluminum spinel particles (1-0mm), 8 parts of recycled magnesium aluminum spinel particles 325-mesh fine powder, 10 parts of α-Al2O3 micro powder, 1 part of metallic aluminum fiber, and 0.2 parts of polypropylene explosion-proof fiber are thoroughly premixed using a high-speed mixer at a speed of 150-250 r / min for 10-15 min to obtain the mixture.

[0104] Step 2, mud preparation: Add the mixture from Step 2 to a high-speed roller mill for crushing and mixing, add a modified composite curing agent, the weight of which is 4% to 6% of the weight of the premixed material, and stir for 10 to 15 minutes until uniformly mixed to obtain a semi-finished mud.

[0105] Step 3, machine pressing: The clay is added to the molding mold and formed in a 1000T press. After high-pressure molding, the brick blanks are naturally air-dried for 24 hours.

[0106] Step 4: Drying and Curing: After air-drying for 24 hours, the brick blanks are placed in an electric dryer for drying. The drying process is as follows: the temperature is increased from room temperature to 110℃ at a rate of 20℃ / h and held for 24 hours; then the temperature is increased to 220℃ at a rate of 15℃ / h and held for 10 hours; then the temperature is increased to 350℃ at a rate of 12℃ / h and held for 18 hours; finally, the temperature is cooled to room temperature at a rate of 20℃ / h to obtain the finished product.

[0107] Example 4

[0108] The preparation method of the top nozzle brick for steel ladle in this embodiment includes the following steps:

[0109] Step 1: Preparation of the mixture: According to the following mass proportions, 8 parts of recycled magnesia-chrome sand particles (5-3mm), 12 parts of recycled magnesia-chrome sand particles (3-1mm), 5 parts of recycled magnesia-chrome sand particles (1-0mm), 8 parts of recycled magnesia-chrome sand 325-mesh fine powder, 3 parts of recycled magnesium aluminum spinel particles (5-3mm), 10 parts of recycled magnesium aluminum spinel particles (3-1mm), 10 parts of recycled magnesium aluminum spinel particles (1-0mm), 6 parts of recycled magnesium aluminum spinel particles 325-mesh fine powder, 5 parts of α-Al2O3 micro powder, 1 part of metallic aluminum fiber, and 0.2 parts of polypropylene explosion-proof fiber are thoroughly premixed using a high-speed mixer at a speed of 150-250 r / min for 10-15 min to obtain the mixture.

[0110] Step 2, mud preparation: Add the mixture from Step 2 to a high-speed roller mill for crushing and mixing, add a modified composite curing agent, the weight of which is 4% to 6% of the weight of the premixed material, and stir for 10 to 15 minutes until uniformly mixed to obtain a semi-finished mud.

[0111] Step 3, machine pressing: The clay is added to the molding mold and formed in a 1000T press. After high-pressure molding, the brick blanks are naturally air-dried for 24 hours.

[0112] Step 4: Drying and Curing: After air-drying for 24 hours, the brick blanks are placed in an electric dryer for drying. The drying process is as follows: the temperature is increased from room temperature to 110℃ at a rate of 20℃ / h and held for 24 hours; then the temperature is increased to 220℃ at a rate of 15℃ / h and held for 10 hours; then the temperature is increased to 350℃ at a rate of 12℃ / h and held for 18 hours; finally, the temperature is cooled to room temperature at a rate of 20℃ / h to obtain the finished product.

[0113] Table 2 shows the performance of the ladle nozzle bricks obtained in Examples 1-4 and their service life at a certain steel plant.

[0114]

[0115] The invention relates to a ladle top nozzle brick, which was tested on a steel plant's ladle under the following conditions: ladle capacity 150t, molten steel pouring temperature 1580-1590℃, average tapping time 30 minutes. The main steel produced was carbon steel, killed steel, and cord steel. The original ladle top nozzle lifespan was around 25 heats. The newly developed top nozzle lifespan, as tested, is significantly improved and is now basically synchronized with the lifespan of the existing top nozzle bricks. This significantly reduces the pressure on ladle turnover and improves steelmaking efficiency.

[0116] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for producing a nozzle brick for a ladle, characterized by, The steel ladle upper nozzle brick comprises: 1) 25-60 parts by mass of granular aggregate, which is composed of 15-35 parts by mass of recycled magnesite-chrome sand particles and 10-25 parts by mass of recycled magnesium-aluminum spinel particles; 2) 19-35 parts by mass of co-milled powder, which is composed of 8-15 parts by mass of recycled magnesite-chrome sand fine powder, 5-10 parts by mass of recycled magnesium-aluminum spinel fine powder, and 6-10 parts by mass of α-Al2O3 micro powder; 3) 0.6-1.2 parts by mass of fibers, which is composed of 0.5-1 part by mass of metal aluminum fibers and 0.1-0.2 part by mass of polypropylene explosion-proof fibers; 4) and 4 wt%-6 wt% of the total weight of the granular aggregate, the co-milled powder and the fibers of a modified composite curing agent, which is composed of modified nano-silica powder and thermosetting phenolic resin mixed at a weight ratio of 1:100; the modified nano-silica powder is obtained by uniformly mixing nano-silica, titanium dioxide and an aluminum salt solution at a certain ratio, chemically precipitating the aluminum salt solution after heating, and then filtering, washing and drying; the modified nano-silica improves the dispersion stability of nano-silica, prevents agglomeration, improves the compatibility of the nano-silica solution, and improves the adhesion between the binder and the substrate; the average particle size of the nano-silica is 30 nm, and the content of SiO2 is ≥99.5 wt%; the modified nano-silica fills the voids in the phenolic resin, improves the strength and density of the phenolic resin, and improves the high-temperature resistance and thermal stability of the phenolic resin; the method comprises the following steps: 1) recycled raw material granular material preparation; the volume density of the recycled raw material as a whole is improved by using rolling treatment to remove false granules; at the same time, 0.3-0.5% of hydrated aluminum oxide and 0.2-0.5% of electrically fused spinel based on the total weight of the recycled material are added during the rolling process; 2) mixture preparation: the recycled magnesite-chrome sand particles and the recycled magnesite-chrome sand fine powder, the recycled magnesium-aluminum spinel particles and the recycled magnesium-aluminum spinel fine powder, and the α-Al2O3 micro powder, the metal aluminum fibers and the polypropylene explosion-proof fibers are pre-mixed by a high-speed mixer at a speed of 150-250 r / min for 10-15 min; 3) preparation of the mud: the mixture of step 2 is added to a high-speed roller mill for rolling, stirring and adding the modified composite curing agent, the weight of which is 4 wt%-6 wt% of the weight of the pre-mixed material, and the stirring time is 10-15 min to obtain the mud; 4) machine pressing: the mud is added to a molding mold and formed into a brick billet on a 1000T press, and then naturally air-dried for 24 h. 5) Dry curing: the brick blank which is naturally aired for 24 hours is dried in the electric dryer, and the drying process is as follows: from room temperature to 110℃ at a rate of 20℃ / h, and then kept for 24 hours; then to 220℃ at a rate of 15℃ / h, and then kept for 10 hours; then to 350℃ at a rate of 12℃ / h, and then kept for 18 hours; finally, cooled to room temperature at a rate of 20℃ / h, and then the finished product is obtained.

2. The method of producing a nozzle brick for a ladle according to claim 1, characterized by, The preparation step of the regenerated raw material granules comprises: 6) The waste magnesium-aluminum spinel brick and the waste magnesite-chrome brick are selected, and impurities and attachments are removed, and then the sticky slag layer and the transition layer are manually or mechanically removed; 7) The waste magnesium-aluminum spinel brick and the waste magnesite-chrome brick which are preliminarily treated are sent into a crusher for coarse crushing and fine crushing, and the material is crushed to a particle size of less than 25 mm; 8) The crushed material is sent into a magnetic separator for magnetic separation and iron removal treatment, and the granules after impurity removal are sent into a planetary wheel mill for rolling treatment, and the rolling time is 7-10 minutes; 9) The rolled material is sent into a vibrating screen for screening to obtain regenerated magnesium-aluminum spinel granules with a particle size of 5-3 mm, 3-1 mm and 1-0 mm, and regenerated magnesite-chrome sand granules with a particle size of 5-3 mm, 3-1 mm and 1-0 mm; 10) The granules with a particle size of less than 1-0 mm obtained by screening are finely ground by a ball mill to obtain uniform regenerated magnesium-aluminum spinel fine powder with a mesh of 325 and regenerated magnesite-chrome sand fine powder with a mesh of 325.

3. The method of producing a nozzle brick for a ladle according to claim 1, characterized by, The particle size of the regenerated magnesite-chrome sand granules is composed of three particle gradations of 5-3 mm, 3-1 mm and 1-0 mm, and the mass fractions are as follows: 5-10 parts of the regenerated magnesite-chrome sand granules with a particle size of 5-3 mm, 5-15 parts of the regenerated magnesite-chrome sand granules with a particle size of 3-1 mm, and 5-10 parts of the regenerated magnesite-chrome sand granules with a particle size of 1-0 mm; the particle size of the regenerated magnesite-chrome sand fine powder is 325 mesh.

4. The method of producing a nozzle brick for a ladle according to claim 1, characterized by, The content of MgO+Cr2O3 in the regenerated magnesite-chrome sand granules and the regenerated magnesite-chrome sand fine powder is ≥80.0wt%.

5. The method of producing a nozzle brick for a ladle according to claim 1, characterized by, The particle size of the regenerated magnesium-aluminum spinel granules is composed of three particle gradations of 5-3 mm, 3-1 mm and 1-0 mm, and the mass fractions are as follows: 0-5 parts of the regenerated magnesium-aluminum spinel granules with a particle size of 5-3 mm, 5-10 parts of the regenerated magnesium-aluminum spinel granules with a particle size of 3-1 mm, and 5-10 parts of the regenerated magnesium-aluminum spinel granules with a particle size of 1-0 mm; the particle size of the regenerated magnesium-aluminum spinel fine powder is 325 mesh.

6. The method of producing a nozzle brick for a ladle according to claim 1, characterized by, The content of MgO+Al2O3 in the regenerated magnesium-aluminum spinel granules and the regenerated magnesium-aluminum spinel fine powder is ≥95.0wt%.

7. The method of producing a nozzle brick for a ladle according to claim 1, characterized by, The particle size of the α-Al2O3 micro powder is 0-2 μm; the content of Al2O3 in the α-Al2O3 micro powder is ≥99.0wt%, the content of SiO2 is ≤0.1wt%, the content of Fe2O3 is ≤0.08wt%, and the content of Na2O+K2O is ≤0.3wt%.

8. The method of producing a nozzle brick for a ladle according to claim 1, characterized by, The diameter of the metal aluminum fiber is 0.2 mm, and the length is 3-4 mm; the content of Al in the metal aluminum fiber is ≥99.8wt%.

9. The method of producing a nozzle brick for a ladle according to claim 1, characterized by, The thermosetting phenolic resin has viscosity 15-25 (25℃ Pas), solid content ≥70%, carbon residue content ≥40%, and free phenol <10%.

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