High slag resistance magnesium calcium carbon brick and preparation process thereof

Abstract

This invention discloses a high-slag-erosion-resistant magnesia-calcium-carbon brick and its preparation process, belonging to the field of green special refractory materials technology. The magnesia-calcium-carbon brick comprises a chromium-free magnesia-calcium-carbon brick matrix and a slag-adhesion-resistant, self-cleaning ceramic composite layer disposed on the hot surface of the matrix. The matrix raw material consists of a green magnesia-calcium matrix, composite carbonaceous components, boride and nitride antioxidant and slag-resistant components, and free calcium stabilizing and in-situ slag-resistant phase components. The composite layer includes a ceramicized sealing layer penetrating the surface of the hot surface and a low-wetting, anti-adhesion ceramic coating covering its outer surface. The preparation process uses an industrial control system or factory control system to collect process parameters and perform closed-loop control. This invention, without introducing chromium contamination, enables the components to synergistically improve slag erosion and penetration resistance, giving the hot surface anti-slag adhesion self-cleaning properties, and improves batch consistency through industrial control.

Description

Technical Field

[0001] This invention belongs to the field of green special refractory materials technology, and particularly relates to a magnesium-calcium-carbon brick with high slag erosion resistance and its preparation process. Background Technology

[0002] Magnesia-calcium-carbon bricks are alkaline refractory materials with magnesium oxide and calcium oxide as the main components and composite carbonaceous components. Due to their good chemical compatibility with alkaline refining slag, they are widely used as linings for steel refining furnaces, ladles, and related high-temperature metallurgical containers, playing a crucial role in the smelting of clean steel. During use, these refractory materials are subjected to long-term chemical erosion, mechanical scouring, and repeated thermal cycling by high-temperature molten slag. Their resistance to slag erosion, oxidation, and hydration, as well as their adhesion behavior to molten slag on the working surface, directly determine the service life of the lining and the stability of the smelting process.

[0003] Some existing magnesia-calcium or magnesia-chromium refractories incorporate chromium raw materials to improve slag erosion resistance. However, chromium raw materials pose a risk of generating harmful high-valent chromium during high-temperature service and disposal, which may endanger the environment and human health, making it difficult to meet the development requirements of green and chromium-free refractories. Therefore, current technologies lack a green special refractory ceramic that can maintain excellent slag erosion resistance without relying on chromium raw materials, making it difficult to balance environmental friendliness and performance.

[0004] While the carbonaceous components in magnesia-calcium-carbon bricks help inhibit slag wetting and penetration, carbon is easily oxidized by penetrating oxygen across different temperature ranges. Carbon loss weakens the dense structure of the matrix and provides pathways for slag penetration and erosion. Existing technologies often struggle to provide gradient protection for carbon throughout the entire service temperature range of carbon-containing refractories, and also find it difficult to generate high-melting-point anti-slag phases in situ to seal pores and cut off slag penetration paths while being eroded, thus limiting further improvements in slag erosion and penetration resistance.

[0005] Furthermore, the free calcium oxide contained in magnesium-calcium raw materials is prone to absorbing moisture and undergoing hydration expansion during storage and early use, which in turn leads to cracks and damages the dense working surface of the brick. Existing technologies for stabilizing free calcium oxide largely rely on treatment methods that involve water or easily introduce impurities. These methods are neither sufficient to inhibit hydration nor safe to introduce harmful elements into the molten steel, making it difficult to simultaneously meet the requirements of hydration resistance and metallurgical cleanliness.

[0006] Regarding slag adhesion, existing magnesia-calcium-carbon bricks lack a stable low-wetting and anti-adhesion structure on their working surfaces. Slag easily adheres to and solidifies on the working surface, and is difficult to detach on its own after cooling. Repeated slag adhesion and cleaning exacerbate wear on the working surface. Current technology lacks an anti-slag adhesion self-cleaning material that prevents the working surface from wetting the slag and allows the adhered slag layer to detach on its own under thermal cycling, making it difficult to achieve self-cleaning of the working surface and long service life.

[0007] In terms of preparation and quality control, the production of traditional magnesia-calcium-carbon bricks relies heavily on manual experience to control processes such as batching, mixing, pressing, impregnation, and spraying. This lack of online acquisition and closed-loop feedback of key process parameters leads to significant variations in bulk density and slag erosion resistance between batches, resulting in low yields. Current technologies lack a method for closed-loop control of the preparation process using industrial or factory control systems, and for alarming and locking abnormal batches, making it difficult to guarantee the consistency and stability of product quality.

[0008] Therefore, it is necessary to provide a magnesium-calcium-carbon brick with high slag erosion resistance and its preparation process, so as to improve the slag erosion resistance, oxidation resistance and hydration resistance without introducing chromium raw materials, and to give the working surface a self-cleaning property that resists slag adhesion. At the same time, batch consistency can be improved through industrial control, thus overcoming the shortcomings of the above-mentioned prior art. Summary of the Invention

[0009] This application provides a high slag erosion magnesia-calcium-carbon brick, comprising a magnesia-calcium-carbon brick matrix and a slag adhesion-resistant self-cleaning ceramic composite layer disposed on the hot surface of the magnesia-calcium-carbon brick matrix; all raw materials of the magnesia-calcium-carbon brick matrix are chromium-free; the raw materials of the magnesia-calcium-carbon brick matrix consist of group A green magnesia-calcium matrix, group B composite carbonaceous components, group C borides and nitrides anti-oxidation and anti-slag components, and group D free calcium stabilizing and in-situ anti-slag phase components, in parts by mass:

[0010] Group A, Green Magnesium-Calcium Base Material:

[0011] 25-40 parts by weight of fused magnesia;

[0012] 20-35 parts by weight of sintered magnesium calcium sand;

[0013] 8-20 parts by weight of recycled magnesium-calcium-carbon brick particles;

[0014] 5-15 parts by weight of fine magnesium calcium sand powder;

[0015] Group B, composite carbonaceous components:

[0016] 4-9 parts by weight of flake graphite;

[0017] Acetylene black 0.5–3 parts by weight;

[0018] 2-5 parts by weight of thermosetting phenolic resin;

[0019] Group C, borides and nitrides as antioxidant and slag-resistant components:

[0020] Calcium hexaboride 0.6–3.0 parts by weight;

[0021] Zirconium diboride 0.5–2.5 parts by weight;

[0022] Titanium diboride 0.3–2.0 parts by weight;

[0023] Aluminum nitride, 0.5–3.0 parts by weight;

[0024] 0.5–2.5 parts by weight of hexagonal boron nitride;

[0025] Boron carbide 0.3–2.0 parts by weight;

[0026] Group D, free calcium-stabilized and in-situ anti-slag phase components:

[0027] 0.2–1.2 parts by weight of anhydrous citric acid;

[0028] Aluminum dihydrogen phosphate, 0.5–2.0 parts by weight;

[0029] Stearic acid 0.1–0.8 parts by weight;

[0030] 1-5 parts by weight of calcium zirconate;

[0031] 2-8 parts by weight of magnesium aluminum spinel;

[0032] The anti-slag adhesion self-cleaning ceramic composite layer includes a ceramicized sealing layer that penetrates into the hot surface layer, and a low-wetting anti-adhesion ceramic coating that covers the outer surface of the ceramicized sealing layer.

[0033] Preferably, the purity of calcium hexaboride, zirconium diboride, titanium diboride, and boron carbide is not less than 95%, and the particle size is not greater than 45 micrometers; the particle size of aluminum nitride and hexagonal boron nitride is not greater than 10 micrometers; aluminum dihydrogen phosphate is prepared by reacting aluminum hydroxide and phosphoric acid at a molar ratio of aluminum to phosphorus of 1:3; the recycled magnesium calcium carbon brick particles are obtained by sorting, magnetic separation to remove iron, crushing, and sieving of used magnesium calcium carbon bricks, and the surface of the recycled magnesium calcium carbon brick particles is coated with a hydrophobic stabilizing film formed by the stearic acid; after a static contact test of refining slag at 1600℃, the hot surface of the anti-slag self-cleaning ceramic composite layer has a wetting contact angle of more than 90 degrees with the refining slag, and the attached slag layer can be completely peeled off after cooling.

[0034] Preferably, the ceramicized sealing layer is formed by vacuum impregnation and heat treatment under a protective atmosphere using an inorganic ceramic precursor solution of ethanol-water system. The inorganic ceramic precursor solution comprises, by weight, 15-30 parts magnesium acetate, 5-20 parts zirconium acetate, 2-8 parts aluminum dihydrogen phosphate, 1-5 parts nano-magnesium oxide, 20-40 parts anhydrous ethanol, and 10-25 parts deionized water. The zirconium oxide generated by the thermal decomposition of zirconium acetate reacts with the calcium oxide on the hot-surface layer to form calcium zirconate, making the main phases of the ceramicized sealing layer magnesium oxide and zirconium oxide. The ceramicized sealing layer extends 0.2–2.0 mm from the hot surface into the brick body, consisting of a calcium aluminate and aluminum phosphate bonded phase. The low-wetting, anti-adhesion ceramic coating is formed by spraying, drying, and ceramizing a ceramic slurry under preheating or early service conditions to create a continuous ceramic bonded coating. The ceramic slurry comprises, by weight, 30–55 parts magnesium aluminum spinel, 15–35 parts calcium zirconate, 10–30 parts magnesium oxide, 1–6 parts hexagonal boron nitride, and 3–12 parts aluminum dihydrogen phosphate. The dry film thickness of the low-wetting, anti-adhesion ceramic coating is 50–500 micrometers.

[0035] This invention also provides a process for preparing magnesia-calcium-carbon bricks with high slag erosion resistance, which uses an industrial control system or factory control system to collect process parameters and perform closed-loop control of the production process, including the following steps:

[0036] S1, the recycled magnesium-calcium refractory raw material is recycled and the components of Group A, Group B, Group C and Group D are measured;

[0037] S2, the raw material weighing control unit weighs and records the mass of each component and the order of feeding;

[0038] S3, after dry mixing of each component, add the thermosetting phenolic resin for wet mixing, collect the mixing torque by the mixing state acquisition unit and determine the mixing endpoint accordingly to obtain the mixed material.

[0039] S4, the mixture is pressed into brick blanks, the bulk density of the brick blanks is measured online by the pressing control unit, and the final pressure and holding time of the subsequent brick blanks are adjusted in a closed loop within the preset pressure upper and lower limits.

[0040] S5, the brick blank is heated and cured in sections to obtain cured brick blank;

[0041] S6, vacuum impregnate the hot surface of the cured brick blank with the inorganic ceramic precursor liquid, remove the liquid and heat-treat it under a protective atmosphere to form a ceramic sealing layer.

[0042] S7, the ceramic slurry is sprayed onto the surface of the ceramic sealing layer. The spraying control unit adjusts the spraying flow rate and spray gun movement speed according to the unit area coating weight increase closed loop. After drying, a low wetting and anti-adhesion ceramic coating is formed.

[0043] S8, the coated brick blanks are dried and preheated in sections to obtain a slag-resistant self-cleaning ceramic composite layer;

[0044] S9, through the central industrial controller, aggregates parameters from each process, alarms and locks batches that exceed the set process window, and completes online classification.

[0045] Further, step S1 includes:

[0046] S11, the used magnesium-calcium-carbon bricks are manually sorted to remove the slag layer, then magnetically separated to remove iron, and then crushed and screened to obtain recycled magnesium-calcium-carbon brick particles.

[0047] S12, the recycled magnesium-calcium-carbon brick particles are immersed in the ethanol solution of stearic acid, taken out and dried, and a hydrophobic stabilizing film is formed on the surface of the particles to obtain surface-stabilized recycled magnesium-calcium-carbon brick particles.

[0048] S13, the calcium hexaboride, zirconium diboride, titanium diboride, aluminum nitride, hexagonal boron nitride and boron carbide are sieved respectively, and the surfaces are coated with paraffin wax. They are then measured and prepared according to the formula to obtain the functional components for anti-oxidation pretreatment.

[0049] Further, in step S3, the components of group A, group C, and group D, as well as the flake graphite and acetylene black, are first dry-mixed evenly, and then the thermosetting phenolic resin is added for wet mixing. The mixing state acquisition unit collects the mixing torque at set time intervals. When the continuous acquisition results satisfy the following formula, it is determined that the mixing has reached the endpoint and the mixing is stopped, resulting in a uniformly dispersed mixture:

[0050] ;

[0051] In the formula, the symbol This indicates the absolute value operation; For the first The mixing torque at each sampling moment; For the first The mixing torque at each sampling moment; The time interval between two adjacent samples; This is the preset threshold for the rate of change of torque.

[0052] Further, in step S4, the mixture is loaded into a mold and pressed into brick blanks. The bulk density of the brick blanks is measured online. The pressing control unit determines the final pressing pressure of the next brick blank according to the following formula and presses accordingly, so that the bulk density of the brick blanks tends to the target value:

[0053] ;

[0054] In the formula, For the first The final pressure of the brick blank; For the first The final pressure of the brick blank; This is the preset pressure adjustment coefficient; Target bulk density (g / cm³) 3 ); For the first The measured bulk density of the brick blank; and make Limited to a preset lower limit With preset upper limit Between, when the bulk density of multiple consecutive brick blanks is... An alarm will be triggered and the batch will be locked when the deviation exceeds the preset tolerance.

[0055] Further, in step S6, the hot surface of the cured brick blank is immersed in the inorganic ceramic precursor liquid and a vacuum is drawn. The impregnation is controlled according to a pre-calibrated negative pressure-time-weight gain curve. After impregnation, the leachate is removed, and the impregnation weight gain rate is calculated using the following formula:

[0056] ;

[0057] In the formula, The weight gain rate after impregnation; The mass of the cured brick blank before impregnation; The mass of the cured brick blank after impregnation, removal of the asphalt, and drying to constant weight; when If the preset target range is not reached, repeat the impregnation or adjust the impregnation negative pressure and impregnation time for the next batch. After reaching the preset target range, perform heat treatment under a protective atmosphere to form the ceramic sealing layer.

[0058] Further, in step S7, the ceramic slurry is sprayed onto the surface of the ceramicized sealing layer. The coating weight gain per unit area is calculated by the spraying control unit according to the following formula. When the coating weight gain per unit area reaches a preset value corresponding to a dry film thickness of 50-500 micrometers, the spraying is stopped and the coating is dried to form the low-wetting, anti-adhesion ceramic coating.

[0059] ;

[0060] In the formula, Increased weight per unit area due to coating; The quality of the brick blank before coating; To ensure the quality of the coated brick blank; The coating area of ​​the hot surface; in step S5, the brick blank is heated and cured in a segmented heating method; in step S8, it is first dried at low temperature and then preheated; and the curing and drying control unit adjusts the heating rate according to the rate of change of the brick blank's mass; when the mass of the brick blank no longer decreases, the drying ends.

[0061] Furthermore, the industrial control system or factory control system includes a raw material weighing control unit, a mixing state acquisition unit, a pressing control unit, an impregnation control unit, a spraying control unit, a curing and drying control unit, and a central industrial controller composed of a programmable logic controller, a distributed control system, or an industrial computer and linked with the manufacturing execution system; each control unit is equipped with a weighing sensor, a torque sensor, a pressure sensor, a vacuum pressure sensor, and a temperature sensor, as well as weighing, pressing, impregnation, and spraying actuators; the central industrial controller acquires the mass and feeding sequence of each component, mixing torque, final pressure and holding time, brick bulk density, impregnation negative pressure and impregnation weight gain rate, coating weight gain per unit area, and curing and drying temperatures, and accordingly performs closed-loop control of the production process from steps S3 to S8, as well as over-limit alarms and batch locking.

[0062] The beneficial effects of this invention are as follows:

[0063] The raw materials of the magnesium-calcium-carbon brick matrix of this invention are all free of chromium. Chromium trioxide exists only as an unavoidable impurity. A chromium-free formula is formed by the combination of green magnesium-calcium matrix, composite carbonaceous components, borides and nitrides for oxidation and slag resistance, and free calcium stabilizing and in-situ slag-resistant phase components. This makes the product a green special refractory ceramic, avoiding the formation of harmful high-valent chromium during service and disposal. While maintaining excellent performance, it achieves the greening and environmental friendliness of refractory materials. The matrix incorporates recycled magnesium-calcium-carbon brick particles obtained from the recycling of used magnesium-calcium-carbon bricks to replace part of the virgin magnesium-calcium raw materials. A hydrophobic stabilizing film is formed on the surface of the recycled particles, thereby reducing the consumption of virgin resources and inhibiting the hydration of the recycled particles. This achieves resource utilization of solid waste while ensuring the stability of the formula.

[0064] This invention utilizes boride and nitride antioxidant and anti-slag components to provide gradient protection for carbon in carbon-containing refractory materials across their entire service temperature range. In the low-to-medium temperature range, some components are preferentially oxidized before carbon, consuming infiltrated oxygen and releasing boron oxides to form a low-viscosity glassy phase that seals pores. In the high-temperature range, other components oxidize and react in situ with calcium oxide or magnesium oxide in the matrix to generate high-melting-point anti-slag phases such as calcium zirconate, calcium titanate, and magnesium aluminum spinel, accompanied by micro-expansion that seals pores. This cuts off the slag penetration channels and improves resistance to slag erosion and penetration. The free calcium stabilizing and in-situ anti-slag phase components of this invention inhibit the hydration expansion of free calcium oxide and replenish the high-melting-point anti-slag phase through chelation film formation and inorganic bonding, thereby ensuring that the dense working surface is not damaged by hydration cracks. The above-mentioned gradient anti-oxidation, in-situ densification and free calcium stabilization technologies work together and are mutually conditional, so that the resulting magnesium-calcium-carbon bricks have higher resistance to slag erosion and impermeability than the simple sum of the individual effects of each component, thus achieving a synergistic effect of mutual superposition and protection.

[0065] This invention provides an anti-slag adhesion self-cleaning ceramic composite layer on the hot surface of a magnesium-calcium-carbon brick matrix. The composite layer comprises a ceramicized sealing layer penetrating the surface of the hot surface and a low-wetting, anti-adhesion ceramic coating covering its outer surface. The ceramicized sealing layer is formed by vacuum impregnation and heat treatment of an inorganic ceramic precursor liquid in an ethanol-water system. The zirconium oxide generated by its thermal decomposition reacts in situ with calcium oxide on the hot surface to form calcium zirconate, achieving interfacial ceramicization. This seals the surface pores and enhances the bond between the sealing layer and the coating. The low-wetting, anti-adhesion ceramic coating uses a high-melting-point anti-slag phase as its framework and provides a non-wetting surface with components that are not wetted by molten slag. Simultaneously, its multi-scale rough structure reduces the actual contact area with the molten slag, thereby preventing the working surface from wetting the refining slag and allowing the slag layer adhering to it to be peeled off entirely after cooling. This imparts anti-slag adhesion self-cleaning properties to the working surface and reduces the wear caused by repeated slag adhesion and cleaning.

[0066] The preparation process of this invention uses an industrial control system or factory control system to collect preparation process parameters and perform closed-loop control of the production process. It collects key parameters such as mixing torque, final pressure, brick bulk density, impregnation weight gain, and coating weight gain online through each control unit. The central industrial controller then makes closed-loop adjustments to processes such as mixing, pressing, impregnation, and spraying based on these parameters. At the same time, it alarms and locks batches that exceed the set process window, thereby making the bulk density and slag erosion resistance of batches more consistent. This improves product quality consistency and yield while achieving stable and controllable preparation process and online grading. Attached Figure Description

[0067] Figure 1 These are comparison charts of slag erosion resistance index and slag penetration depth between Examples 1 to 4 and Comparative Examples 1 to 8, where (a) is a comparison chart of slag erosion resistance index and (b) is a comparison chart of slag penetration depth.

[0068] Figure 2 This is a scatter plot comparing the measured improvement and the linear superposition predicted improvement of the slag erosion resistance index of Comparative Examples 2 to 8 with Example 1.

[0069] Figure 3 The graphs show the changes in the slag layer self-detachment rate as a function of the number of thermal cycles for Examples 1 to 4 and Comparative Examples 1, 8, and 9.

[0070] Figure 4 The figures are discretization comparisons of bulk density and slag erosion resistance index for Example 1 and Comparative Example 10, where (a) is a box plot of bulk density and (b) is a box plot of slag erosion resistance index.

[0071] Figure 5 This is a process flow diagram of the preparation process of a magnesium-calcium-carbon brick with high slag erosion resistance according to the present invention. Detailed Implementation

[0072] The technical solutions of this invention will be clearly and completely described below. In addition, the forms of the various structures described in the following embodiments are merely illustrative. This invention is not limited to the structures described in the following embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0073] This specific embodiment describes a high-slag-erosion-resistant magnesia-calcium-carbon brick, its formulation, and preparation process. The magnesia-calcium-carbon brick comprises a magnesia-calcium-carbon brick matrix and a slag-adhesion-resistant, self-cleaning ceramic composite layer disposed on the hot surface of the magnesia-calcium-carbon brick matrix. None of the raw materials in the magnesia-calcium-carbon brick matrix contain chromium; chromium trioxide is present only as an unavoidable impurity, thus classifying the product as a green special refractory ceramic. The raw materials of the magnesia-calcium-carbon brick matrix, by mass, consist of group A (green magnesia-calcium matrix), group B (composite carbonaceous components), group C (borides and nitrides for oxidation and slag resistance), and group D (free calcium stabilizing and in-situ slag-resistant phase components). Each component is a definite single substance. The formulation design aims to reduce resource consumption by replacing some virgin raw materials with recycled magnesia-calcium raw materials, and to achieve synergistic effects of multiple functional components at different temperature ranges and failure stages, thus considering slag erosion resistance, oxidation resistance, hydration resistance, and slag adhesion-resistant self-cleaning.

[0074] Group A green magnesia-calcium matrix includes fused magnesia, sintered magnesia-calcium sand, recycled magnesia-calcium-carbon brick particles, and fine magnesia-calcium sand powder. Fused magnesia, with periclase as the main crystalline phase, provides a framework to resist alkaline slag, and its preferred dosage is 25–40 parts by mass. Sintered magnesia-calcium sand provides free calcium oxide to improve chemical compatibility with alkaline refining slag and participates in the subsequent in-situ formation of anti-slag phases; its preferred dosage is 20–35 parts by mass. Recycled magnesia-calcium-carbon brick particles are derived from used magnesia-calcium-carbon bricks and are used to replace part of the primary magnesia-calcium sand to reduce unit material consumption; its preferred dosage is 8–20 parts by mass. Fine magnesia-calcium sand powder is used to fill the matrix and adjust sintering and density; its preferred dosage is 5–15 parts by mass. The particle size of the fused magnesia and the sintered magnesia-calcium sand is selected according to conventional refractory aggregate gradation to ensure a continuous packing of coarse, medium, and fine particles.

[0075] Group B composite carbonaceous components include flake graphite, acetylene black, and thermosetting phenolic resin. Flake graphite is non-wetting by slag and has high thermal conductivity, used to inhibit slag penetration and improve thermal shock resistance; its preferred dosage is 4–9 parts by weight. Acetylene black has a fine particle size, used to fill the micropores of the matrix and supplement the carbon network; its preferred dosage is 0.5–3 parts by weight. Thermosetting phenolic resin acts as a binder, cross-linking and curing during the low-temperature curing stage and providing residual carbon; its preferred dosage is 2–5 parts by weight. To reduce free phenol release, modified thermosetting phenolic resins with low free phenol and low free formaldehyde content are preferred.

[0076] Group C, consisting of boride and nitride antioxidant and anti-slag components, includes calcium hexaboride, zirconium diboride, titanium diboride, aluminum nitride, hexagonal boron nitride, and boron carbide. This composition is designed to progressively protect carbon and generate an anti-slag phase in situ across the entire service temperature range of carbon-containing refractory materials. In the medium- and low-temperature range, calcium hexaboride, zirconium diboride, titanium diboride, and boron carbide are more easily oxidized than carbon, preferentially consuming infiltrated oxygen to protect the carbon network and releasing boron trioxide to form a low-viscosity glassy phase that seals pores and cuts off early slag penetration channels. In the high-temperature range, zirconium dioxide generated from the oxidation of zirconium diboride reacts in situ with calcium oxide in the matrix to form calcium zirconate with a melting point of approximately 2345℃. Titanium dioxide generated from the oxidation of titanium diboride reacts with calcium oxide in the matrix to form high-melting-point calcium titanate. Aluminum oxide generated from the oxidation of aluminum nitride reacts in situ with magnesium oxide to form magnesium aluminum spinel, accompanied by micro-expansion to seal pores. Hexagonal boron nitride is distributed on the working surface as a phase that is not wetted by slag, thus reducing slag adhesion. Calcium hexabode provides a boron source while also providing calcium compatible with the magnesium-calcium matrix, and zirconium diboride provides zirconium. The combination of these two components allows calcium zirconate to be formed more quickly at lower temperatures. The preferred proportions of each component are: calcium hexabode 0.6–3.0 parts by mass, zirconium diboride 0.5–2.5 parts by mass, titanium diboride 0.3–2.0 parts by mass, aluminum nitride 0.5–3.0 parts by mass, hexagonal boron nitride 0.5–2.5 parts by mass, and boron carbide 0.3–2.0 parts by mass.

[0077] Group D, the free calcium stabilizing and in-situ anti-slag phase component, includes anhydrous citric acid, aluminum dihydrogen phosphate, stearic acid, calcium zirconate, and magnesium aluminum spinel. This component is designed to inhibit the hydration of free calcium oxide in magnesium calcium carbon bricks and supplement a high-melting-point anti-slag phase. Anhydrous citric acid chelates with calcium oxide and magnesium oxide on the particle surface to form insoluble calcium citrate and magnesium citrate films, inhibiting hydration expansion during storage and early use, and providing clean carbonization and replenishing residual carbon during heating. Its preferred dosage is 0.2–1.2 parts by mass. Aluminum dihydrogen phosphate provides inorganic bonding at low temperatures and reacts with free calcium oxide to form a stable phosphate phase. The residual aluminum phosphate after heating also serves as a bonding phase. Its preferred dosage is 0.5–2.0 parts by mass. Stearic acid forms a hydrophobic film on the particle surface to further inhibit hydration. Its preferred dosage is 0.1–0.8 parts by mass. Calcium zirconate is introduced as a seed crystal for the high-melting-point anti-slag phase, and its preferred dosage is 1–5 parts by mass. Magnesium aluminum spinel is used as an anti-slag micro-powder and synergistically densifies with spinel generated in situ from aluminum nitride, with a preferred dosage of 2-8 parts by mass. The aluminum dihydrogen phosphate is placed within the brick matrix, away from the final molten slag contact surface, to avoid introducing harmful phosphorus into the molten steel.

[0078] The four components mentioned above work synergistically in the formulation. Group A provides the green matrix and free calcium oxide; Group B provides the carbon network and binding phase; Group C provides gradient protection for carbon at different temperature ranges and generates calcium zirconate, magnesium aluminum spinel, and borate glass phases in situ; and Group D stabilizes the free calcium oxide and supplements the high-melting-point anti-slag phase. The boron trioxide released by Group C can lower the in-situ formation temperature of magnesium aluminum spinel, while the stabilization of free calcium oxide by Group D ensures that the dense, non-wetting working surface constructed by Groups A and C is not damaged by hydration cracks. Thus, the effects of each component are superimposed and mutually protective, resulting in magnesium-calcium-carbon bricks with slag erosion and impermeability resistance higher than the simple sum of the individual effects of each component.

[0079] For the preparation and pretreatment of uncommon components, the purity of calcium hexaboride, zirconium diboride, titanium diboride, and boron carbide is preferably not less than 95%, and the particle size is preferably not greater than 45 μm. The particle size of aluminum nitride and hexagonal boron nitride is preferably not greater than 10 μm. Before batching, calcium hexaboride, zirconium diboride, titanium diboride, aluminum nitride, hexagonal boron nitride, and boron carbide are sieved and coated with paraffin wax to obtain functional components with anti-oxidation pretreatment. Paraffin wax, rather than binder resin, is used as the coating medium to ensure that the coating amount is independent of the thermosetting phenolic resin used in wet mixing and avoids duplicate measurement. Aluminum dihydrogen phosphate is prepared by mixing aluminum hydroxide and phosphoric acid at a molar ratio of aluminum to phosphorus of 1:3, reacting under heating and stirring until a transparent viscous state is reached, and then drying and pulverizing. The recycled magnesium-calcium-carbon brick particles are obtained by manually sorting and removing the slag layer, magnetically separating and removing iron from used magnesium-calcium-carbon bricks, crushing and sieving, then immersing them in an ethanol solution of stearic acid and drying them to form a hydrophobic stabilizing film on the surface of the particles. The residual carbon mass fraction is preferably not less than 2%.

[0080] The anti-slag adhesion self-cleaning ceramic composite layer includes a ceramicized sealing layer penetrating the hot-surface surface and a low-wetting, anti-adhesion ceramic coating covering the outer surface of the ceramicized sealing layer. The ceramicized sealing layer is formed by vacuum impregnation and heat treatment under a protective atmosphere using an inorganic ceramic precursor solution of an ethanol-water system. The inorganic ceramic precursor solution includes, by mass, magnesium acetate, zirconium acetate, aluminum dihydrogen phosphate, nano-magnesium oxide, anhydrous ethanol, and deionized water. The use of an ethanol-water system, replacing nitrates and zirconium oxychloride with acetate, aims to reduce the water activity of the system to inhibit the hydration of free calcium oxide in the magnesium-calcium system and avoid residual chloride ions from the carbonaceous components of nitrates and zirconium oxychloride when heated. The zirconium dioxide generated by the thermal decomposition of zirconium acetate reacts in situ with the calcium oxide on the hot-surface surface to form calcium zirconate, making the main phases of the ceramicized sealing layer a combination of magnesium oxide, calcium zirconate, and aluminum phosphate. The ceramicized sealing layer preferably extends 0.2 mm to 2.0 mm from the hot-surface surface into the brick body. The low-wetting, anti-adhesion ceramic coating is formed by spraying, drying, and ceramizing a ceramic slurry under preheating or early service conditions to create a continuous ceramic-bonded coating. The ceramic slurry, by weight, comprises magnesium aluminum spinel, calcium zirconate, magnesium oxide, hexagonal boron nitride, and aluminum dihydrogen phosphate, with a preferred dry film thickness of 50 μm to 500 μm. This ceramic composite layer uses magnesium aluminum spinel, calcium zirconate, and magnesium oxide to form a high-melting-point anti-slag framework, hexagonal boron nitride to provide a surface that is not wetted by molten slag, and micron-sized ceramic particles and nano-components to form a multi-scale rough surface, reducing the actual contact area with the molten slag. This results in a wetting contact angle greater than 90° with the refining slag at 1600°C on the working surface, and the adhered slag layer can be completely peeled off after cooling.

[0081] This invention also designs a preparation process for magnesia-calcium-carbon bricks with high slag erosion resistance, such as... Figure 5As shown, the overall preparation process employs an industrial control system or factory control system to collect process parameters and implement closed-loop control of the production process, including steps S1 to S9. Step S1 involves recycling the recycled magnesia-calcium refractory raw materials and metering the components of groups A, B, C, and D according to the stated proportions. Step S1 further includes steps S11 to S13. In step S11, the used magnesia-calcium-carbon bricks are manually sorted to remove the slag layer, magnetically separated to remove iron, crushed, and sieved to obtain recycled magnesia-calcium-carbon brick particles. In step S12, the recycled magnesia-calcium-carbon brick particles are immersed in an ethanol solution of stearic acid and then removed and dried to obtain surface-stabilized recycled magnesia-calcium-carbon brick particles. In step S13, the calcium hexaboride, zirconium diboride, titanium diboride, aluminum nitride, hexagonal boron nitride, and boron carbide are sieved, coated with paraffin wax, and metered according to the proportions for later use. In step S2, the raw material weighing control unit weighs each component and records the mass and feeding sequence. Step S3: After dry mixing of all components, thermosetting phenolic resin is added for wet mixing. First, components A, C, and D, along with flake graphite and acetylene black, are dry-mixed until uniform. Then, thermosetting phenolic resin is added for wet mixing. The mixing torque is collected by the mixing state acquisition unit to determine the mixing endpoint, resulting in a mixed material. Step S4: The mixed material is pressed into brick blanks. The pressing control unit measures the bulk density of the brick blanks online and adjusts the final pressure and holding time of subsequent brick blanks within a preset pressure range using a closed-loop method. Step S5: The brick blanks are cured in stages to obtain cured brick blanks. Step S6: The hot surface of the cured brick blanks is vacuum impregnated with the inorganic ceramic precursor liquid. After removing the liquid, it is heat-treated under a protective atmosphere to form a ceramic sealing layer. Step S7: The ceramic slurry is sprayed onto the surface of the ceramic sealing layer. The spraying control unit adjusts the spraying flow rate and spray gun movement speed according to the coating weight gain per unit area using a closed-loop method, and the coating is dried to form a low-wetting, anti-adhesion ceramic coating. Step S8 involves segmented drying and preheating of the coated brick blanks to obtain an anti-slag adhesion self-cleaning ceramic composite layer. Step S9 involves the central industrial controller summarizing the parameters of each process, alarming and locking batches that exceed the set process window, and completing online classification.

[0082] In step S3, the mixing state acquisition unit acquires the mixing torque at set time intervals. When the continuous acquisition results satisfy the following formula, it is determined that the mixing has reached the end point and the mixing is stopped, resulting in a uniformly dispersed mixture.

[0083] ;

[0084] In the formula, the symbol This indicates the absolute value operation; For the first The mixing torque (N·m) at each sampling time; For the first The mixing torque (N·m) at each sampling time; The time interval (s) between two consecutive samples; The preset torque change rate threshold (N·m / s) is used as the criterion. This criterion uses the stabilization of the mixing torque over time as an indicator of uniform dispersion, which facilitates the determination of the mixing endpoint without substituting specific values.

[0085] In step S4, the pressing control unit measures the bulk density of the brick blank online and determines the final pressing pressure of the next brick blank according to the following formula, pressing it accordingly to make the bulk density of the brick blank approach the target value.

[0086] ;

[0087] In the formula, For the first Final pressure of the brick blank (MPa); For the first Final pressure of the brick blank (MPa); The preset pressure adjustment coefficient (MPa·cm) 3 / g); Target bulk density (g / cm³) 3 ); For the first Measured bulk density of brick blank (g / cm³) 3 ); and make Limited to a preset lower limit (MPa) and preset upper limit Between (MPa), when the bulk density of multiple consecutive brick blanks is and When the deviation exceeds the preset tolerance, an alarm is triggered and the batch is locked. This formula adjusts the final pressure proportionally based on the density deviation and sets upper and lower limits to ensure that the volumetric density between batches is consistent and does not exceed the limits.

[0088] In step S6, the hot surface of the cured brick blank is immersed in the inorganic ceramic precursor liquid and a vacuum is drawn. The impregnation is controlled according to a pre-calibrated negative pressure-time-weight gain curve. After impregnation, the leachate is removed, and the impregnation weight gain rate is calculated using the following formula.

[0089] ;

[0090] In the formula, The weight gain rate after impregnation (%). The mass (g) of the cured brick blank before impregnation; The mass (g) of the cured brick blank after impregnation, removal of the leaching liquid, and drying to constant weight. If the preset target range is not reached, repeat the immersion process or adjust the immersion negative pressure and immersion time for the next batch. After reaching the preset target range, heat treat under a protective atmosphere to form the ceramic sealing layer. Remove the leachate and dry it to constant weight before weighing and calculating the weight gain rate, so that this parameter can be stably measured in the industrial field.

[0091] In step S7, the coating control unit calculates the coating weight gain per unit area using the following formula. When the weight gain reaches a preset value corresponding to the dry film thickness, the coating process stops and drying begins.

[0092] ;

[0093] In the formula, Weight gain per unit area of ​​coating (g / cm³) 2 ); The mass (g) of the brick blank before coating; The mass (g) of the coated brick blank; The coating area of ​​the hot surface (cm²) 2 The coating thickness is characterized by the weight gain per unit area, making the amount of coating controllable by weighing in the industrial setting.

[0094] The industrial control system or factory control system includes a raw material weighing control unit, a mixing state acquisition unit, a pressing control unit, an impregnation control unit, a spraying control unit, a curing and drying control unit, and a central industrial controller composed of a programmable logic controller, a distributed control system, or an industrial computer and linked to the manufacturing execution system. Each control unit is equipped with a weighing sensor, a torque sensor, a pressure sensor, a vacuum pressure sensor, and a temperature sensor, as well as corresponding weighing, pressing, impregnation, and spraying actuators. The central industrial controller performs closed-loop control of the production process from steps S3 to S8 based on the collected parameters, and provides over-limit alarms and batch locking, ensuring that the parameters of each process are under control and thereby reducing the dispersion between batches.

[0095] The magnesium-calcium-carbon bricks obtained according to the above formula and process have a lower decarburized layer thickness and lower apparent porosity due to the gradient oxidation resistance of group C and the formation of in-situ calcium zirconate and magnesium aluminum spinel. Due to the stability of free calcium oxide by group D, hydration cracking is less likely to occur during storage and early use. The hot-surface anti-slag adhesion self-cleaning ceramic composite layer causes the molten slag to be discretely distributed and detach itself during thermal cycling. The use of recycled raw materials and a chromium-free, low-free-phenol system meets the requirements of green special refractory ceramics. Furthermore, the closed-loop control of key processes by the industrial control system ensures that the bulk density and slag resistance of the products tend to be consistent between batches. Those skilled in the art can implement the above technical solution based on the above formula composition, the standardized names and dosage ranges of each component, the preparation methods of uncommon components, and steps S1 to S9 and the corresponding formulas.

[0096] Example 1: The magnesium-calcium-carbon brick matrix formulation in this example, by weight, is as follows: fused magnesia 32, sintered magnesium-calcium sand 28, recycled magnesium-calcium-carbon brick particles 14, magnesium-calcium sand fine powder 10, flake graphite 6, acetylene black 1.5, thermosetting phenolic resin 3.5, calcium hexaboride 1.8, zirconium diboride 1.5, titanium diboride 1.0, aluminum nitride 1.8, hexagonal boron nitride 1.5, boron carbide 1.0, anhydrous citric acid 0.6, aluminum dihydrogen phosphate 1.2, stearic acid 0.4, calcium zirconate 3, and magnesium aluminum spinel 5.

[0097] The preparation process is as follows. S1 involves raw material processing and metering, where S11 involves sorting, magnetically separating to remove iron from used magnesium-calcium-carbon bricks, crushing, and sieving to obtain recycled magnesium-calcium-carbon brick particles with a particle size of 1mm to 5mm. S12 involves immersing these particles in a 2% (w / w) stearic acid ethanol solution, then removing and drying them to form a hydrophobic stabilizing film. S13 involves sieving calcium hexaboride, zirconium diboride, titanium diboride, aluminum nitride, hexagonal boron nitride, and boron carbide separately and coating them with paraffin wax. S2 involves weighing each material sequentially by a raw material weighing control unit and recording the order of addition. S3 involves dry mixing of each component followed by wet mixing with thermosetting phenolic resin. The mixing torque is collected by a mixing state acquisition unit, and mixing is stopped according to the mixing endpoint criterion. S4 involves pressing and molding, with a final pressure of 150MPa and a target bulk density of 3.02g / cm³. 3 The pressing control unit adjusts the final pressure and holding time of subsequent brick blanks according to the closed-loop incremental control law of final pressing. S5 involves segmented heating and curing at 200℃. S6 involves vacuum impregnating the hot surface of the working surface with an ethanol-water system inorganic ceramic precursor liquid. The precursor liquid, by mass, consists of 22 parts magnesium acetate, 12 parts zirconium acetate, 5 parts aluminum dihydrogen phosphate, 3 parts nano magnesium oxide, 30 parts anhydrous ethanol, and 18 parts deionized water. After removing the leachate, heat treatment is performed under a protective atmosphere to form a ceramic sealing layer. S7 involves spraying a ceramic slurry onto the surface of the sealing layer to form a low-wetting, anti-adhesion ceramic coating. The ceramic slurry, by mass, consists of 42 parts magnesium aluminum spinel, 25 parts calcium zirconate, 18 parts magnesium oxide, 4 parts hexagonal boron nitride, and 8 parts aluminum dihydrogen phosphate. The dry film thickness of the coating is approximately 200μm. S8 involves segmented drying and preheating. S9 involves the central industrial controller summarizing parameters and determining the classification.

[0098] For easier comparison, the functional components of the magnesium-calcium-carbon brick matrix formulation are divided into the following modules: Module I: Gradient boride antioxidant components, including calcium hexaboride, zirconium diboride, titanium diboride, and boron carbide. Module II: In-situ densification and non-wetting components, including aluminum nitride, hexagonal boron nitride, calcium zirconate, and magnesium aluminum spinel. Module III: Free calcium stabilizing and anti-hydration components, including anhydrous citric acid, aluminum dihydrogen phosphate, and stearic acid.

[0099] Example 2 differs from Example 1 in that the functional components of Module I, Module II, and Module III are all used at their lower limits, namely 0.6g calcium hexaboride, 0.5g zirconium diboride, 0.3g titanium diboride, 0.5g aluminum nitride, 0.5g hexagonal boron nitride, 0.3g boron carbide, 0.2g anhydrous citric acid, 0.5g aluminum dihydrogen phosphate, 0.1g stearic acid, 1g calcium zirconate, and 2g magnesium aluminum spinel. The final pressure of S4 is 130MPa, and the dry film thickness of the coating in S7 is approximately 80μm. The rest is the same as in Example 1.

[0100] Example 3 differs from Example 1 in that the functional components of Module I, Module II, and Module III are all used at their maximum dosage, namely, calcium hexaboride 3.0, zirconium diboride 2.5, titanium diboride 2.0, aluminum nitride 3.0, hexagonal boron nitride 2.5, boron carbide 2.0, anhydrous citric acid 1.2, aluminum dihydrogen phosphate 2.0, stearic acid 0.8, calcium zirconate 5, and magnesium aluminum spinel 8. The final pressure of S4 is 170 MPa, and the dry film thickness of the coating in S7 is approximately 450 μm. The rest is the same as in Example 1.

[0101] Example 4 differs from Example 1 in that it increases the green substitution rate. The amount of recycled magnesium-calcium-carbon brick particles is 20, the amount of fused magnesia is 28, the amount of sintered magnesium-calcium sand is 26, the amount of functional components is moderate, and the rest is the same as in Example 1.

[0102] Comparative Examples 1 to 8 are used for the collaborative decomposition of the three material modules, while Comparative Examples 9 and 10 are used for the contribution of the isolation precursor liquid system and the control method, respectively. The parts that are the same as those in the examples will not be described again.

[0103] Comparative Example 1, a benchmark magnesia-calcium-carbon brick, contains only the matrix components of fused magnesia, sintered magnesia-calcium sand, recycled magnesia-calcium-carbon brick particles, magnesia-calcium sand fine powder, flake graphite, acetylene black, and thermosetting phenolic resin. It does not contain the functional components of Module I, Module II, and Module III, and does not undergo S6 impregnation and S7 coating. It does not have a hot-surface self-cleaning ceramic composite layer. The remaining processes are the same as in Example 1.

[0104] Comparative Examples 2 to 7 were based on Comparative Example 1, with different modules added respectively. Comparative Example 2 added Module I, Comparative Example 3 added Module II, Comparative Example 4 added Module III, Comparative Example 5 added Module I and Module II, Comparative Example 6 added Module I and Module III, and Comparative Example 7 added Module II and Module III. The amount of each added module component was the same as in Example 1, and S6 and S7 were not performed.

[0105] Comparative Example 8 is based on Comparative Example 1, with the addition of Module I, Module II and Module III, i.e., using the complete material formulation, but without S6 impregnation and S7 coating, and without a hot-side self-cleaning ceramic composite layer, the rest is the same as Example 1.

[0106] Comparative Example 9 differs from Example 1 in that the S6 precursor solution is replaced with a traditional water-based nitrate and zirconium oxychloride system, which consists of magnesium nitrate hexahydrate, aluminum nitrate nonahydrate, zirconium oxychloride octahydrate, nano magnesium oxide, and deionized water by mass. The rest is the same as in Example 1.

[0107] Comparative Example 10 differs from Example 1 in that it does not employ an industrial control closed loop. The S3 mixing endpoint, S4 final pressure, and holding time are all set based on manual experience, while the rest are the same as Example 1.

[0108] Example 1, Slag Erosion Resistance Index and Slag Penetration Depth, used the methods of Examples 1 to 4 and Comparative Examples 1 to 8 for sample preparation. Slag resistance tests were conducted in a refining slag environment using the static crucible method, according to the slag resistance test method for refractory materials. The slag erosion resistance index is a relative value with the erosion amount of Comparative Example 1 as 100; a smaller value indicates better slag erosion resistance. The slag penetration depth is the maximum depth to which the slag penetrates the brick below the slag line after the sample is cut open, expressed in mm. The experimental results are as follows: Figure 1 As shown, Figure 1 (a) shows the comparison of slag erosion resistance indices. Figure 1 (b) shows the comparison of slag penetration depth; the data are shown in Table 1.

[0109] Table 1. Measured data of slag erosion resistance index and slag penetration depth of Examples 1 to 4 and Comparative Examples 1 to 8:

[0110]

[0111] From Table 1 and Figure 1 As can be seen from Table (a), the slag erosion resistance indices of Examples 1 to 4 are 40, 43, 38, and 44, respectively; Comparative Example 1 is 100; Comparative Examples 2, 3, and 4, which contain only a single module, are 82, 78, and 94, respectively; and Comparative Example 8, which contains a complete material formulation, is 47. From Table 1 and... Figure 1 As can be seen in (b), the slag penetration depth of the embodiments is 2.3 mm to 3.0 mm, compared to 9.5 mm in Comparative Example 1 and 3.5 mm in Comparative Example 8. It can be seen that the slag erosion resistance index and slag penetration depth of the embodiments are significantly lower than those of all comparative examples. The improvement from adding Module I, Module II or Module III alone is limited, and the embodiment with all three modules and a hot-face self-cleaning layer has the lowest improvement.

[0112] In Module I, calcium hexaboride, zirconium diboride, titanium diboride, and boron carbide are more easily oxidized than carbon. In the medium and low temperature range, they preferentially consume the infiltrated oxygen to protect the carbon network and release boron trioxide to form a low-viscosity glass phase to seal the pores, reducing the thickness of the decarburized layer and the slag penetration channels. In Module II, aluminum nitride forms magnesium aluminum spinel in situ at high temperature and is accompanied by micro-expansion and densification. Together with calcium zirconate, it forms a high-melting-point anti-slag skeleton. Hexagonal boron nitride reduces the spread of slag on the working surface as a phase that is not wetted by slag. The sealing layer formed in step S6 of this invention penetrates into the hot surface to seal the pores. The low-wetting and anti-adhesion ceramic coating formed in step S7 further blocks the slag on the outermost layer, making it difficult for slag to wet and penetrate. The slag erosion resistance index and penetration depth decrease simultaneously.

[0113] Example 2: Cooperative decomposition of the slag erosion resistance index; samples were prepared using the methods of Comparative Examples 1 to 8 and Example 1, and the slag erosion resistance index obtained in Example 1 was used. The improvement was defined as 100 minus the slag erosion resistance index. Comparative Examples 2, 3, and 4 contained only Module I, Module II, and Module III, respectively, and their improvement values ​​of 18, 22, and 6 were taken as single-module improvements. The linear superposition prediction improvement of each combination was equal to the sum of the improvements of each of its individual modules, and the measured improvement was obtained from its respective slag erosion resistance index. Figure 2 The graph uses the predicted improvement from linear superposition as the x-axis and the measured improvement as the y-axis. The dashed line represents the baseline for linear superposition where the measured improvement equals the predicted improvement. Points falling on the baseline indicate that the measured improvement of the combination is equal to the predicted improvement, while points above the baseline indicate positive synergy. The vertical distance from the point to the baseline is the synergy gain. Experimental results are as follows: Figure 2 As shown, the data are presented in Table 2.

[0114] Table 2 shows the comparison data of single-module improvement, linear superposition prediction improvement, and measured improvement between Comparative Examples 2 to 8 and Example 1:

[0115]

[0116] As shown in Table 2, the measured improvements of Comparative Examples 2, 3, and 4 (18, 22, and 6) are equal to the improvements predicted by linear superposition. The measured improvements of Comparative Examples 5, 6, and 7 (44, 25, and 29) are slightly higher than the improvements predicted by linear superposition (40, 24, and 28). The measured improvement of Comparative Example 8 (53) is significantly higher than the improvement predicted by linear superposition (46). The measured improvement of Example 1 (60) is 14 higher than the improvement predicted by linear superposition (46). Figure 2 It can be seen that the points of Comparative Examples 2 to 4 fall on the linear superposition baseline, while the points of Comparative Examples 5 to 8 are located above the baseline. The vertical distance from Comparative Example 8 to the baseline is 7, and the vertical distance from Example 1 to the baseline is 14. This demonstrates that the improvement in slag resistance after the three-module combination is greater than the sum of the individual improvements of each module.

[0117] Boron trioxide released by module I upon heating acts as a mineralizer for magnesium aluminum spinel, lowering the in-situ formation temperature of magnesium aluminum spinel in module II and allowing it to densify more fully under the low-temperature, non-sintering conditions of step S5 of this invention. Anhydrous citric acid and aluminum dihydrogen phosphate in module III stabilize free calcium oxide, inhibiting hydration expansion during storage and early use, ensuring that the dense, non-wetting working surface constructed by modules I and II is not damaged by hydration cracks. These three factors are mutually conditional rather than simply additive. In Example 1, approximately 7% of the 14% exceeding the baseline comes from the synergistic effect of the three modules, while the remainder comes from the hot-surface self-cleaning ceramic composite layer formed in steps S6 and S7 of this invention, and the ceramicization of the sealing layer and coating interface resulting from the thermal decomposition of zirconium acetate in the ethanol-water acetate precursor solution and the in-situ formation of calcium zirconate from the hot-surface calcium oxide.

[0118] Experimental Example 3: Slag Layer Self-Shedding Rate After Thermal Cycling; Samples were prepared using the methods of Examples 1 to 4 and Comparative Examples 1, 8, and 9. The slag was first impregnated in refining slag, then thermally cycled between room temperature and 1500°C. The slag layer self-shedding rate was measured every 5 cycles, i.e., the percentage of slag mass that detached spontaneously relative to the initial attached slag mass. A higher value indicates better self-cleaning. Experimental results are as follows: Figure 3 As shown, the data are presented in Table 3.

[0119] Table 3. Slag layer self-detachment rate data of Examples 1 to 4 and Comparative Examples 1, 8, and 9 under 0 to 30 thermal cycles:

[0120]

[0121] From Table 3 and Figure 3 It can be seen that as the number of thermal cycles increases from 0 to 30, the slag layer self-detachment rate of Examples 1 to 4 increases from about 12% to about 90%. Comparative Example 1, lacking a surface layer, remains below 15%, while Comparative Example 8 increases to about 33%, and Comparative Example 9 increases to about 77%. This shows that the examples with a self-cleaning ceramic composite layer on a hot surface have the highest self-detachment rate and increase the fastest with thermal cycles. Comparative Example 8, with only a complete material formulation and no surface layer, has a significantly lower rate, while Comparative Example 9, using a traditional water-based precursor liquid, is in the middle.

[0122] The hot-surface self-cleaning ceramic composite layer formed in steps S6 and S7 of this invention uses hexagonal boron nitride to provide a surface that is not wetted by molten slag, and the multi-scale rough structure formed by micron-sized ceramic particles and nano-components reduces the actual contact area of ​​the molten slag, causing the adhering slag to be distributed in discrete particles or islands. The sealing layer mitigates the difference in thermal expansion between the coating and the substrate, and the interfacial shear stress generated by thermal cycling causes the discrete slag blocks to crack and fall off along the interface. The more cycles, the more complete the detachment. The embodiment is superior to Comparative Example 9 because the in-situ generation of calcium zirconate from the ethanol-water acetate precursor solution further ceramicizes the interface between the sealing layer and the coating, resulting in a weaker bond between the adhering slag and the ceramic surface.

[0123] Experiment 4, the impact of industrial control on consistency: Using the methods of Example 1 and Comparative Example 10, 20 bricks were produced in each batch. Bulk density and slag erosion resistance index were measured, and the coefficient of variation and yield were calculated. The coefficient of variation is the ratio of the standard deviation to the mean; a smaller value indicates better batch consistency. Experimental results are as follows: Figure 4 As shown, Figure 4 (a) is a box plot of bulk density. Figure 4 (b) is a box plot of the slag erosion resistance index, and the statistical values ​​are shown in Table 4.

[0124] Table 4 shows the statistical data on the mean and coefficient of variation of bulk density and slag erosion resistance index, as well as the yield, for industrial control in Example 1 and manual control in Comparative Example 10:

[0125]

[0126] As shown in Table 4, the average bulk density of the industrial control group in Example 1 was 3.02 g·cm³. -3 The coefficient of variation was 1.2%, the average slag erosion resistance index was 40, the coefficient of variation was 4%, and the yield was 96%; the average bulk density of the artificially controlled group in Comparative Example 10 was 3.00 g·cm³. -3 The coefficient of variation is 4.5%, the average slag erosion resistance index is 43, the coefficient of variation is 9%, and the yield is 88%. Figure 4 As can be seen in (a), the volumetric density box of the industrial control unit in Example 1 is narrower and the top and bottom bevels are shorter. Figure 4 As can be seen in (b), the slag erosion resistance index box is also narrower. This indicates that the industrial control group has a more concentrated distribution of bulk density and slag erosion resistance index, a smaller coefficient of variation, and a higher yield.

[0127] In step S4 of this invention, the pressing control unit adjusts the final pressing pressure of the next brick blank according to the volume density deviation based on the final pressing closed-loop incremental control law and limits it within the upper and lower limits, so that the volume density between batches converges to the target value, the density of the brick blanks tends to be consistent, and thus the slag erosion resistance index tends to be consistent; manual control has no feedback adjustment, and the final pressing pressure fluctuates with experience, resulting in large batch dispersion.

[0128] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A magnesium-calcium-carbon brick with high resistance to slag erosion, characterized in that, The product includes a magnesium-calcium-carbon brick matrix and a slag-resistant, self-cleaning ceramic composite layer disposed on the hot surface of the magnesium-calcium-carbon brick matrix; none of the raw materials of the magnesium-calcium-carbon brick matrix contain chromium; the raw materials of the magnesium-calcium-carbon brick matrix consist of group A green magnesium-calcium matrix, group B composite carbonaceous components, group C boride and nitride antioxidant and slag-resistant components, and group D free calcium stabilizing and in-situ slag-resistant phase components, in parts by mass: Group A, Green Magnesium-Calcium Base Material: 25-40 parts by weight of fused magnesia; 20-35 parts by weight of sintered magnesium calcium sand; 8-20 parts by weight of recycled magnesium-calcium-carbon brick particles; 5-15 parts by weight of fine magnesium calcium sand powder; Group B, composite carbonaceous components: 4-9 parts by weight of flake graphite; Acetylene black 0.5–3 parts by weight; 2-5 parts by weight of thermosetting phenolic resin; Group C, borides and nitrides as antioxidant and slag-resistant components: Calcium hexaboride 0.6–3.0 parts by weight; Zirconium diboride 0.5–2.5 parts by weight; Titanium diboride 0.3–2.0 parts by weight; Aluminum nitride, 0.5–3.0 parts by weight; 0.5–2.5 parts by weight of hexagonal boron nitride; Boron carbide 0.3–2.0 parts by weight; Group D, free calcium-stabilized and in-situ anti-slag phase components: 0.2–1.2 parts by weight of anhydrous citric acid; Aluminum dihydrogen phosphate, 0.5–2.0 parts by weight; Stearic acid 0.1–0.8 parts by weight; 1-5 parts by weight of calcium zirconate; 2-8 parts by weight of magnesium aluminum spinel; The anti-slag adhesion self-cleaning ceramic composite layer includes a ceramicized sealing layer that penetrates into the hot surface layer, and a low-wetting anti-adhesion ceramic coating that covers the outer surface of the ceramicized sealing layer.

2. The high slag erosion resistance magnesium-calcium-carbon brick according to claim 1, characterized in that, The purity of the calcium hexaboride, zirconium diboride, titanium diboride, and boron carbide is not less than 95% and the particle size is not greater than 45 micrometers. The particle size of the aluminum nitride and the hexagonal boron nitride is not greater than 10 micrometers. The aluminum dihydrogen phosphate is prepared by reacting aluminum hydroxide and phosphoric acid at a molar ratio of aluminum to phosphorus of 1:

3. The recycled magnesium calcium carbon brick particles are obtained by sorting, magnetic separation to remove iron, crushing, and sieving of used magnesium calcium carbon bricks. The surface of the recycled magnesium calcium carbon brick particles is coated with a hydrophobic stabilizing film formed by the stearic acid.

3. The high slag erosion resistance magnesium-calcium-carbon brick according to claim 1, characterized in that, The ceramicized sealing layer is formed by vacuum impregnation and heat treatment under a protective atmosphere using an inorganic ceramic precursor solution based on an ethanol-water system. The inorganic ceramic precursor solution comprises, by weight, 15-30 parts magnesium acetate, 5-20 parts zirconium acetate, 2-8 parts aluminum dihydrogen phosphate, 1-5 parts nano-magnesium oxide, 20-40 parts anhydrous ethanol, and 10-25 parts deionized water. The zirconium oxide generated by the thermal decomposition of zirconium acetate reacts with the calcium oxide on the hot-surface layer to form calcium zirconate, making magnesium oxide and calcium zirconate the main phases of the ceramicized sealing layer. The ceramicized sealing layer extends 0.2–2.0 mm from the hot surface into the brick body, and is bonded to the aluminum phosphate phase. The low-wetting, anti-adhesion ceramic coating is formed by spraying, drying, and ceramicizing the ceramic slurry under preheating or early service conditions to form a continuous ceramic bond coating. The ceramic slurry comprises, by weight, 30–55 parts magnesium aluminum spinel, 15–35 parts calcium zirconate, 10–30 parts magnesium oxide, 1–6 parts hexagonal boron nitride, and 3–12 parts aluminum dihydrogen phosphate. The dry film thickness of the low-wetting, anti-adhesion ceramic coating is 50–500 micrometers.

4. A process for preparing the high slag erosion resistant magnesium-calcium-carbon brick according to any one of claims 1 to 3, characterized in that, The process involves collecting preparation process parameters using an industrial control system or factory control system and implementing closed-loop control of the production process, including the following steps: S1, the recycled magnesium-calcium refractory raw material is recycled and the components of Group A, Group B, Group C and Group D are measured; S2, the raw material weighing control unit weighs and records the mass of each component and the order of feeding; S3, after dry mixing of each component, add the thermosetting phenolic resin for wet mixing, collect the mixing torque by the mixing state acquisition unit and determine the mixing endpoint accordingly to obtain the mixed material. S4, the mixture is pressed into brick blanks, the bulk density of the brick blanks is measured online by the pressing control unit, and the final pressure and holding time of the subsequent brick blanks are adjusted in a closed loop within the preset pressure upper and lower limits. S5, the brick blank is heated and cured in sections to obtain cured brick blank; S6, vacuum impregnate the hot surface of the cured brick blank with the inorganic ceramic precursor liquid, remove the liquid and heat-treat it under a protective atmosphere to form a ceramic sealing layer. S7, the ceramic slurry is sprayed onto the surface of the ceramic sealing layer. The spraying control unit adjusts the spraying flow rate and spray gun movement speed according to the unit area coating weight increase closed loop. After drying, a low wetting and anti-adhesion ceramic coating is formed. S8, the coated brick blanks are dried and preheated in sections to obtain a slag-resistant self-cleaning ceramic composite layer; S9, through the central industrial controller, aggregates parameters from each process, alarms and locks batches that exceed the set process window, and completes online classification.

5. The process according to claim 4, characterized in that, Step S1 includes: S11, the used magnesium-calcium-carbon bricks are manually sorted to remove the slag layer, then magnetically separated to remove iron, and then crushed and screened to obtain recycled magnesium-calcium-carbon brick particles. S12, the recycled magnesium-calcium-carbon brick particles are immersed in the ethanol solution of stearic acid, taken out and dried, and a hydrophobic stabilizing film is formed on the surface of the particles to obtain surface-stabilized recycled magnesium-calcium-carbon brick particles. S13, the calcium hexaboride, zirconium diboride, titanium diboride, aluminum nitride, hexagonal boron nitride and boron carbide are sieved respectively, and the surfaces are coated with paraffin wax. They are then measured and prepared according to the formula to obtain the functional components for anti-oxidation pretreatment.

6. The process according to claim 4, characterized in that, In step S3, the components of group A, group C, and group D, along with the flake graphite and acetylene black, are first dry-mixed until homogeneous. Then, the thermosetting phenolic resin is added for wet mixing. The mixing state acquisition unit collects the mixing torque at set time intervals. When the continuous acquisition results satisfy the following formula, the mixing is determined to have reached its endpoint and the mixing is stopped, resulting in a uniformly dispersed mixture: ； In the formula, the symbol This indicates the absolute value operation; For the first The mixing torque at each sampling moment; For the first The mixing torque at each sampling moment; The time interval between two adjacent samples; This is the preset threshold for the rate of change of torque.

7. The process according to claim 4, characterized in that, In step S4, the mixture is loaded into a mold and pressed into brick blanks. The bulk density of the brick blanks is measured online. The pressing control unit determines the final pressing pressure of the next brick blank according to the following formula and presses it accordingly, so that the bulk density of the brick blanks tends to the target value: ； In the formula, For the first The final pressure of the brick blank; For the first The final pressure of the brick blank; This is the preset pressure adjustment coefficient; Target bulk density (g / cm³) 3 ); For the first The measured bulk density of the brick blank; and make Limited to a preset lower limit With preset upper limit Between, when the bulk density of multiple consecutive brick blanks is... An alarm will be triggered and the batch will be locked when the deviation exceeds the preset tolerance.

8. The process according to claim 4, characterized in that, In step S6, the hot surface of the cured brick blank is immersed in the inorganic ceramic precursor liquid and a vacuum is drawn. The impregnation is controlled according to a pre-calibrated negative pressure-time-weight gain curve. After impregnation, the leachate is removed, and the impregnation weight gain rate is calculated using the following formula: ； In the formula, The weight gain rate after impregnation; The mass of the cured brick blank before impregnation; The mass of the cured brick blank after impregnation, removal of the asphalt, and drying to constant weight; when If the preset target range is not reached, repeat the impregnation or adjust the impregnation negative pressure and impregnation time for the next batch. After reaching the preset target range, perform heat treatment under a protective atmosphere to form the ceramic sealing layer.

9. The process according to claim 4, characterized in that, In step S7, the ceramic slurry is sprayed onto the surface of the ceramicized sealing layer. The coating weight gain per unit area is calculated by the spraying control unit according to the following formula. When the coating weight gain per unit area reaches a preset value corresponding to a dry film thickness of 50-500 micrometers, the spraying is stopped and the coating is dried to form the low-wetting, anti-adhesion ceramic coating. ； In the formula, Increased weight per unit area due to coating; The quality of the brick blank before coating; To ensure the quality of the coated brick blank; The coating area of ​​the hot surface; in step S5, the brick blank is heated and cured in a segmented heating method; in step S8, it is first dried at low temperature and then preheated; and the curing and drying control unit adjusts the heating rate according to the rate of change of the brick blank's mass; when the mass of the brick blank no longer decreases, the drying ends.

10. The process according to claim 4, characterized in that, The industrial control system or factory control system includes a raw material weighing control unit, a mixing state acquisition unit, a pressing control unit, an impregnation control unit, a spraying control unit, a curing and drying control unit, and a central industrial controller composed of a programmable logic controller, a distributed control system, or an industrial computer and linked with the manufacturing execution system. Each control unit is equipped with a weighing sensor, a torque sensor, a pressure sensor, a vacuum pressure sensor, and a temperature sensor, as well as weighing, pressing, impregnation, and spraying actuators. The central industrial controller collects the mass and feeding sequence of each component, mixing torque, final pressure and holding time, brick bulk density, impregnation negative pressure and impregnation weight gain rate, coating weight gain per unit area, and curing and drying temperatures, and performs closed-loop control of the production process from steps S3 to S8, as well as over-limit alarms and batch locking.

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