Air brick, preparation method and application thereof in production of high manganese steel containing aluminum by medium frequency induction furnace

Abstract

This invention discloses a permeable brick, its preparation method, and its application in the production of aluminum-containing high-manganese steel in a medium-frequency induction furnace, belonging to the field of high-manganese steel production technology. By optimizing the structural formula and preparation process of the permeable brick and slag-forming material, combined with an integrated process of steel smelting, segmented argon blowing, slag forming and segmented aluminum addition, secondary argon blowing in the ladle, and customized heat treatment, the technical challenges of easy aluminum oxidation and high oxygen content in molten steel production are solved. The permeable brick adopts a corundum-mullite-silicon carbide composite formula, manufactured through mixing, pressing, drying, and sintering processes; the slag-forming material is based on Al2O3 and CaO, manufactured through mixing, crushing, screening, and drying. This process can reduce the oxygen content of molten steel to ≤20ppm, increase the service life of the permeable brick to ≥30 cycles, synergistically optimize wear resistance, adapt to wear-resistant parts for mining machinery, and has strong industrial adaptability, resulting in a significant improvement in overall performance compared to traditional processes.

Description

Technical Field

[0001] This invention belongs to the field of high manganese steel preparation technology, specifically relating to a permeable brick, its preparation method, and its application in the production of aluminum-containing high manganese steel in a medium-frequency induction furnace. Background Technology

[0002] High manganese steel, due to its excellent work hardening properties, impact toughness, and wear resistance, is widely used in the manufacture of wear-resistant parts in mining machinery, metallurgical equipment, and building material crushing, such as crusher liners, hammers, and ball mill liners. As industrial equipment develops towards higher loads and higher efficiency, higher requirements are placed on the comprehensive performance of high manganese steel parts. Traditional high manganese steel suffers from insufficient toughness and limited wear resistance, making it difficult to meet the demands of extreme working conditions.

[0003] To optimize the performance of high-manganese steel, the industry commonly uses the addition of alloying elements for modification. Aluminum, as a cheap and effective alloying element, has attracted widespread attention for its application in high-manganese steel. Aluminum can refine grain size, improve impact toughness and wear resistance, and can also synergistically optimize the toughness of materials with elements such as Cu and N, addressing the weakness of insufficient toughness in traditional high-manganese steel. Under proper control, aluminum can also deoxidize and purify molten steel, reducing the inclusion of other harmful oxides.

[0004] However, aluminum is highly chemically reactive and has a low melting point (660℃), making it extremely prone to oxidation during medium-frequency induction furnace smelting, forming Al2O3 inclusions. This problem has become a core bottleneck restricting the industrial production of aluminum-containing high-manganese steel. On the one hand, aluminum oxidation results in extremely low yields, with traditional processes yielding only 60-70% Al. This not only increases production costs but also leads to excessive fluctuations in steel composition, affecting product performance consistency. On the other hand, Al2O3 inclusions are hard and stable, making them difficult to completely remove from molten steel using conventional processes. Residual inclusions significantly weaken the strength, toughness, and fatigue life of high-manganese steel, leading to defects such as cracks and pitting on the casting surface, and making it prone to early failure under high-load impact conditions.

[0005] Currently, the industry has tried various conventional solutions to address the issues of aluminum oxidation and inclusion control during the smelting of aluminum-containing high-manganese steel, but all have significant limitations and have failed to fundamentally overcome the technical bottlenecks. Regarding furnace protection, most companies use conventional argon blowing processes to isolate air in an attempt to reduce aluminum oxidation loss. However, due to the lack of dedicated ventilation equipment, the argon blowing effect is greatly reduced. Conventional argon blowing often uses ordinary corundum permeable bricks, which have low apparent porosity, poor pore connectivity, and uneven pore size distribution. This results in argon gas not diffusing evenly after introduction, creating localized argon blowing blind zones. In some areas of the furnace, molten steel remains in full contact with air, and aluminum oxidation loss is not effectively controlled. Simultaneously, argon gas accumulates to form large bubbles with a small contact area with the molten steel, resulting in low degassing efficiency and inability to completely remove dissolved oxygen from the molten steel, leading to secondary aluminum oxidation later.

[0006] In terms of inclusion removal, current production processes mostly use ordinary slag-forming agents to assist in impurity removal. However, these slag-forming agents lack targeted design and are mostly general-purpose metallurgical slag-forming materials, failing to achieve the synergistic functions of adsorbing inclusions, preventing oxidation, and stabilizing the slag phase. Ordinary slag-forming agents are mostly composed of CaO and SiO2, with a single composition, unreasonable alkalinity control, poor fluidity, and insufficient contact with molten steel, thus failing to fully adsorb Al2O3 inclusions. These slag-forming agents lack effective reducing components and cannot inhibit secondary oxidation of aluminum; residual Al2O3 inclusions will still seriously affect product performance.

[0007] In terms of heat treatment processes, existing technologies mostly use traditional heat treatment parameters for high-manganese steel without adapting and optimizing them for the compositional characteristics of aluminum-containing high-manganese steel, resulting in the inability to fully realize the material's comprehensive performance. In aluminum-containing high-manganese steel, aluminum reacts with elements such as C and N. If the heat treatment parameters are inappropriate, brittle phases such as AlN and Al4C3 are easily formed. The presence of these brittle phases significantly reduces the material's toughness, resulting in a lack of significant improvement in impact toughness after heat treatment, or even a decrease in toughness. At the same time, traditional heat treatment processes cannot compensate for performance defects caused by inclusions remaining during the smelting process. Residual Al2O3 inclusions become stress concentration points during heat treatment, leading to problems such as cracking and deformation in castings, further reducing the product qualification rate.

[0008] Existing permeable bricks are mostly made of a single corundum material, which has insufficient high-temperature compressive strength and is easily damaged under the high-temperature conditions of medium-frequency furnace smelting. Furthermore, they have low apparent porosity and poor pore connectivity, leading to the accumulation of large bubbles during argon blowing, resulting in a small contact area with molten steel and poor degassing and oxygen isolation effects. On the other hand, the current process uses a single method for aluminum addition, often adding it all at once, which further exacerbates aluminum oxidation loss. Moreover, the slag-forming and aluminum-addition processes lack synergistic design, failing to form a closed-loop control system of "anti-oxidation - adsorption of inclusions - stable composition."

[0009] In summary, existing processes for producing aluminum-containing high-manganese steel suffer from numerous technical defects: the permeable bricks have low apparent porosity and poor connectivity, leading to uneven argon blowing and high oxygen content in the molten steel; the slag-forming materials lack targeted design, failing to achieve the synergistic functions of adsorbing inclusions, preventing oxidation, and stabilizing the slag phase, resulting in low oxygen removal rates; the aluminum addition method is unreasonable, leading to low Al recovery and large compositional fluctuations; the heat treatment process has poor compatibility with the aluminum-containing composition, preventing the full realization of the material's comprehensive performance; and the lack of synergistic design among various process steps prevents the formation of a closed-loop oxygen reduction and inclusion control system. Therefore, developing a method for producing aluminum-containing high-manganese steel using a medium-frequency induction furnace that can precisely control the oxygen content and inclusions in molten steel and improve the overall performance of the material has significant industrial application value. Summary of the Invention

[0010] This invention aims to address the problems in existing aluminum-containing high-manganese steel production processes, such as easy oxidation of aluminum, high oxygen content in molten steel, excessive inclusions, insufficient overall material performance, and poor process synergy. It provides a permeable brick, its preparation method, and its application in the production of aluminum-containing high-manganese steel in a medium-frequency induction furnace. By optimizing the permeable brick formula and preparation process, designing dedicated protective slag-forming materials, and constructing a synergistic process system, precise control of oxygen content in molten steel and efficient removal of inclusions are achieved, ultimately producing high-toughness, high-wear-resistance, and stable aluminum-containing high-manganese steel suitable for large-scale industrial production.

[0011] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0012] A breathable brick, the raw materials are formulated in the following mass fractions: corundum 60-65%, mullite 20-25%, silicon carbide 5-8%, chromium oxide 3-5%, and bentonite 1-2%.

[0013] Preferably, the permeable brick has the following raw material purity: Al2O3 ≥ 95% in corundum, Al2O3·2SiO2 ≥ 90% in mullite, silicon carbide ≥ 98%, chromium oxide ≥ 99%, and high-purity binder-grade bentonite.

[0014] This invention also provides a method for preparing permeable bricks, comprising the following steps:

[0015] (1) Raw material mixing: Put each raw material into a planetary mixer and mix for 30-40 minutes, with the mixing speed controlled at 60-80 r / min;

[0016] (2) Pressing and molding: A hydraulic brick press is used to press the uniformly mixed raw materials into shape under a pressure of 20~25MPa, and the holding time is 5~8s;

[0017] (3) Drying of the green body: Place the formed green body in a normal temperature environment and let it dry naturally for 24 hours;

[0018] (4) Sintering treatment: The dried green body is sintered at 1600~1650℃ for 3~4h, wherein the heating rate is controlled at 5~8℃ / min and the cooling rate is controlled at 3~5℃ / min. After sintering, honeycomb interconnected permeable bricks are obtained.

[0019] This invention also provides an application of permeable bricks in the production of aluminum-containing high-manganese steel in a medium-frequency induction furnace, comprising the following steps:

[0020] (1) Raw material preparation: The raw materials for molten steel are proportioned by mass as follows: C: 0.90~1.20%, Si: 0.35~0.45%, Mn: 10.00~18.00%, Cr: 0.60~0.75%, Al: 0.30~4.50%, Cu: 0.60~0.75%, N: 0.015~0.025%, Nb: 0.03~0.045%, La+Ce: 0.02~0.06%, S≤0.035%, P≤0.035%, with the remainder being Fe and unavoidable impurities;

[0021] (2) Medium-frequency furnace smelting and argon blowing: The molten steel raw material is put into the medium-frequency furnace, and the permeable bricks are installed in the center of the furnace bottom. Argon is blown in stages at a flow rate of 0.3~0.5m. 3 / h, insulation stage 0.15~0.25m 3 / h, adjust to 0.4~0.6m 30 minutes before tapping. 3 / h, smelting to 1520~1550℃;

[0022] (3) Slag formation and aluminum addition: Add 1.2-1.8% of protective slag-forming material by weight of molten steel into the furnace, stir to form a 5-8 mm slag layer, let stand for 15-20 min, add 2 / 3 aluminum material and keep warm for 10-15 min, and then coat the remaining 1 / 3 aluminum material with graphite powder and put it into the ladle at 800-850℃.

[0023] (4) Secondary argon blowing into the ladle: Transfer the molten steel into the ladle and blow argon at a rate of 0.2~0.3m. 3 Argon blowing at a flow rate of / h for 8~12min, then let stand for 20~25min;

[0024] (5) Heat treatment: After casting, the casting is shot blasted to remove the surface oxide scale, held at 650~680℃ for 2~3h, heated to 1050~1080℃ and held for 1.5~2h, cooled to room temperature by water, and then tempered at 270~290℃ for 2~2.5h, and cooled to room temperature by water.

[0025] Preferably, in step (1), the aluminum material is aluminum blocks with Al ≥ 99.5% and aluminum particles in a 3:1 ratio, with the aluminum particle size being 2~5mm; Mn is added in the form of high carbon ferromanganese with Mn ≥ 85%, Cr is added in the form of ferrochrome with Cr ≥ 60%, Nb is added in the form of ferroniobium with Nb ≥ 65%, N is added in the form of chromium nitride master alloy with N ≥ 6%, and La+Ce is added in the form of mixed rare earth ferrosilicon alloy with a total rare earth content ≥ 20%.

[0026] Preferably, in step (1), the Mn content is adjusted according to the wear resistance requirement gradient: 10~14% for low wear resistance scenarios and 14~18% for high wear resistance scenarios; the Al content is adjusted according to the gradient: 0.30~0.80% for low aluminum, 1.00~2.50% for medium aluminum, and 3.00~4.50% for high aluminum.

[0027] Preferably, in step (1), C powder is graphite powder with a fixed carbon content of ≥90%; in step (3), the mass ratio of aluminum material coated with graphite powder is aluminum material: graphite powder = 100: 3~5.

[0028] Preferably, the medium-frequency furnace mentioned in step (2) is a 5~50t medium-frequency induction furnace, with optimized compatibility between the permeable bricks and the furnace structure, and can be installed and used without modifying the furnace body.

[0029] Preferably, in step (3), after the slag-forming material is added, it is mixed by mechanical stirring at a speed of 30-50 r / min and a stirring time of 3-5 min to ensure that the slag layer evenly covers the surface of the molten steel.

[0030] Preferably, the water cooling rate in step (5) is ≥50℃ / min, and the water cooling rate to room temperature after tempering is 20~30℃ / min.

[0031] Compared with the prior art, the technical advantages of the present invention are as follows:

[0032] 1. High apparent porosity permeable bricks achieve efficient oxygen reduction, significantly lowering the oxygen content in molten steel.

[0033] This invention addresses the problems of low apparent porosity, uneven argon blowing, poor oxygen reduction, insufficient flexural strength, and short lifespan associated with traditional permeable bricks. It optimizes the permeable brick formula and manufacturing process by using a corundum-mullite-silicon carbide composite formula and a precise sintering process, increasing the apparent porosity to 26-30% with interconnected honeycomb-like pores. Simultaneously, it achieves excellent strength properties: a flexural strength of 35-39 MPa at room temperature and 25-28 MPa at 1600℃, with significantly enhanced thermal shock resistance and abrasion resistance. The synergistic effect of high apparent porosity, excellent pore connectivity, and high strength ensures uniform diffusion of argon gas throughout the molten steel, eliminating blind spots and significantly improving oxygen isolation and degassing effects. Combined with a segmented argon blowing process, the oxygen content in the molten steel is reduced from 45-55 ppm in traditional processes to ≤25 ppm (in the furnace stage), and finally stabilized at ≤20 ppm after secondary argon blowing in the ladle. Meanwhile, the permeable bricks utilize a corundum-chromium oxide composite system, exhibiting excellent resistance to molten high-manganese steel corrosion and a service life of ≥30 cycles. After ≥30 cycles, the apparent porosity decreases by ≤5%, and the flexural strength decreases by ≤8%, significantly reducing production costs and brick replacement frequency. This advantage solves the problems of high oxygen content in molten steel and easy wear and tear on permeable bricks in existing technologies, laying a foundation for low-oxygen and stable equipment in subsequent processes.

[0034] 2. Specialized slag-forming materials achieve triple synergy, improving the removal rate of inclusions.

[0035] The protective slag-forming material designed in this invention achieves a triple synergistic function of "preventing secondary aluminum oxidation, stabilizing the slag phase, and protecting the permeable bricks" compared to existing general-purpose slag-forming materials. The slag-forming material uses Al2O3 and CaO as its core components, along with MgO, CaF2, and other components, controlling the slag phase alkalinity at 1.0~1.2 and adjusting the slag viscosity to 0.8~1.2 Pa·s. This allows it to form a dense protective slag layer on the molten steel surface, effectively isolating air and inhibiting secondary aluminum oxidation. Simultaneously, the slag exhibits excellent stability, reducing erosion and scouring of the permeable bricks, preventing surface wear and strength reduction, and extending their service life. Adding 2.5~3.5% high-fixed carbon (C) powder to the slag-forming material further enhances the slag layer's reducibility, reducing the erosion of the permeable bricks and aluminum by oxidizing components. MgO and CaO synergistically improve the high-temperature stability of the slag, preventing secondary contamination of the molten steel and damage to the permeable bricks after slag decomposition. A SiO2 content ≤1.5% prevents reaction with permeable brick components, ensuring the structural integrity and strength stability of the permeable bricks. This advantage solves the problem that existing slag-forming materials have limited functionality and no protective effect on permeable bricks, achieving the dual goals of preventing oxidation of molten steel and extending equipment life.

[0036] 3. The synergistic process of segmented aluminum addition and argon blowing significantly optimizes the uniformity and stability of molten steel composition.

[0037] This invention employs a "two-stage aluminum addition + segmented argon blowing + slag-forming synergy" process system, which significantly improves the uniformity and stability of molten steel composition compared to single-stage aluminum addition and single argon blowing processes. Before the first aluminum addition, slag is formed to create a protective slag layer, preventing direct contact between aluminum and air and reducing oxidation losses. The second aluminum addition uses graphite powder coating and is added to the preheated ladle to further inhibit oxidation and ensure uniform aluminum dissolution, preventing compositional segregation caused by excessively high local concentrations. The segmented argon blowing process adjusts the flow rate according to the oxidation risk at different stages of smelting, ensuring oxygen isolation while avoiding steel splashing and compositional fluctuations caused by excessive argon. Simultaneously, the two-stage argon blowing and slag-forming work synergistically to form a closed-loop oxygen reduction system, with the oxygen content of the molten steel fluctuating within a range of ≤±2ppm, ensuring consistent product performance in mass production and preventing partial product failure due to compositional fluctuations. This advantage solves the problems of large fluctuations and poor uniformity in molten steel composition in existing processes, making it suitable for industrial-scale production needs.

[0038] 4. Customized heat treatment processes adapted to aluminum-containing compositions, resulting in synergistic optimization of overall material performance.

[0039] This invention designs a two-stage customized heat treatment process for aluminum-containing high-manganese steel, achieving synergistic optimization of material toughness and wear resistance compared to existing general heat treatment processes. The first stage, a holding treatment at 650-680℃, effectively eliminates melting stress and prevents the formation of brittle phases such as AlN and Al4C3 by Al with C and N, solving the problem of insufficient toughness caused by brittle phases in traditional heat treatment processes. A solution treatment at 1050-1080℃ allows for the full dissolution of elements such as Al, Cu, and Nb, suppressing aluminum segregation and improving material strength. A water cooling rate of ≥50℃ / min prevents the precipitation of brittle carbides, ensuring material toughness. The second stage, a tempering treatment at 270-290℃, eliminates quenching stress and simultaneously causes some Al and Cu to precipitate, forming dispersed strengthening phases, synergistically improving material hardness and wear resistance.

[0040] 5. It has strong process adaptability, requires no modification to existing equipment, and has a low threshold for industrial application.

[0041] The process system of this invention is highly compatible with existing medium-frequency induction furnace production lines. The permeable brick design is adapted to the furnace structure of 5-50t medium-frequency furnaces, allowing for installation and use without furnace body modifications. Compared to existing technologies requiring specialized equipment, this significantly reduces industrialization conversion costs. The slag-forming materials are conventional metallurgical raw materials (Al2O3, CaO, MgO, etc.), readily available and inexpensive, with a simple preparation process enabling large-scale production. The segmented aluminum addition, argon blowing, and heat treatment processes all utilize conventional equipment, requiring only parameter optimization for implementation, and are easily mastered by operators. Furthermore, the process system of this invention is adaptable to the production of aluminum-containing high-manganese steel with varying Al and Mn content gradients. The formula and process parameters can be adjusted according to the performance requirements of different components, achieving "one process, multiple products," and is suitable for the production of various wear-resistant components such as crusher liners, hammers, and ball mill liners. In addition, the process emits no harmful gases, meeting environmental protection requirements and possessing excellent industrial application prospects and promotional value. This advantage solves the problems of poor industrial adaptability and high conversion costs of existing technologies, facilitating large-scale promotion and application. Detailed Implementation

[0042] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of this invention.

[0043] In this embodiment of the invention, the breathable brick is made of the following raw materials in the following mass fractions: corundum 60-65%, mullite 20-25%, silicon carbide 5-8%, chromium oxide 3-5%, and bentonite 1-2%. The purity requirements for the raw materials are: Al2O3 ≥ 95% in corundum, Al2O3·2SiO2 ≥ 90% in mullite, silicon carbide ≥ 98%, chromium oxide ≥ 99%, and high-purity binder-grade bentonite.

[0044] The preparation method of this permeable brick is as follows:

[0045] (1) Raw material mixing: Add each raw material into a planetary mixer according to the above proportions and mix for 30~40 minutes. The mixing speed is controlled at 60~80 r / min to ensure that the raw materials are mixed evenly without segregation, which lays the foundation for subsequent molding and uniformity of pores.

[0046] (2) Pressing and molding: A hydraulic brick press is used to press the mixed raw materials into shape under a pressure of 20~25MPa. The holding time is 5~8s. The pressure and holding time are precisely matched to avoid the pores being over-compacted or the density being insufficient, which would affect the air permeability and strength.

[0047] (3) Green body drying: After molding, the green body is placed in a normal temperature environment for natural drying for 24 hours to fully remove free moisture and prevent the green body from cracking and the pore structure from being disordered due to moisture evaporation during subsequent sintering.

[0048] (4) Sintering treatment: The dried green body is sintered at 1600~1650℃ for 3~4h, and the heating rate is controlled at 5~8℃ / min and the cooling rate is controlled at 3~5℃ / min to obtain honeycomb interconnected permeable brick.

[0049] In this embodiment of the invention, the slag-forming material comprises the following raw materials in the following mass fraction ratios: Al2O3: 38-42%, CaO: 42-48%, MgO: 6-7%, CaF2: 4-5%, C powder: 2.5-3.5%, and SiO2 ≤ 1.5%.

[0050] The preparation method of this slag-forming material is as follows:

[0051] (1) Raw material mixing: Put each proportion of raw materials into a planetary mixer, set the mixing time to 25 min and the mixing speed to 50 r / min, and continue mixing until there are no visible particles in the raw materials, the mixture is uniform and there is no segregation, to ensure that the components are dispersed in a consistent manner.

[0052] (2) Crushing and screening: The uniformly mixed raw materials are fed into a universal crusher for crushing. After crushing, they are screened through a standard sieve to select particles with a size of 1~3mm. Oversized or undersized particles are removed to ensure that the particle size of the slag-forming material is uniform.

[0053] (3) Drying treatment: The sieved slag-forming material particles are sent into an electric heating constant temperature drying oven, the temperature is controlled at 800℃, and the drying is carried out at a constant temperature for 2 hours. During the process, the moisture content is monitored in real time to ensure that the moisture content after drying is ≤0.5%;

[0054] (4) Cooling and storage: After drying, the slag-forming material is naturally cooled to room temperature and stored in a dry and sealed container to avoid moisture absorption for later use.

[0055] A method for producing aluminum-containing high-manganese steel in a medium-frequency induction furnace includes the following steps:

[0056] (1) Raw material preparation

[0057] The raw materials for molten steel are proportioned by mass fraction as follows: C: 0.90~1.20%, Si: 0.35~0.45%, Mn: 10.00~18.00%, Cr: 0.60~0.75%, Al: 0.30~4.50%, Cu: 0.60~0.75%, N: 0.015~0.025%, Nb: 0.03~0.045%, La+Ce: 0.02~0.06%, S≤0.035%, P≤0.035%, with the remainder being Fe and unavoidable impurities. The Mn content is adjusted according to wear resistance requirements: 10~14% for low wear resistance scenarios and 14~18% for high wear resistance scenarios; the Al content is adjusted according to gradients: 0.30~0.80% for low-alumina segments, 1.00~2.50% for medium-alumina segments, and 3.00~4.50% for high-alumina segments, to adapt to different performance requirements under various working conditions.

[0058] The raw material addition forms must meet the following requirements: Mn is added in the form of high-carbon ferromanganese with Mn≥85%, Cr is added in the form of ferrochrome with Cr≥60%, Nb is added in the form of ferroniobium with Nb≥65%, N is added in the form of chromium nitride master alloy with N≥6%, Al is added in the form of aluminum blocks and aluminum granules with Al≥99.5% in a 3:1 ratio (aluminum granule particle size 2~5mm), and La+Ce is added in the form of mixed rare earth ferrosilicon alloy with a total rare earth content ≥20%, to ensure the yield and compositional stability of each alloying element.

[0059] (2) Medium frequency furnace melting and segmented argon blowing

[0060] Add the molten steel raw material to a 5-50t medium-frequency induction furnace according to the specified ratio. Install the prepared permeable bricks in the center of the furnace bottom, ensuring a good seal between the permeable bricks and the furnace bottom to prevent air leakage from affecting the argon blowing effect. Start the medium-frequency furnace and melt and blow argon in stages according to the following process parameters:

[0061] Melting stage: When the melting temperature reaches 1450~1500℃, argon blowing is started, with the flow rate controlled at 0.3~0.5m³. 3 / h, relying on the high apparent porosity of the permeable brick to achieve uniform diffusion of argon gas, suppressing the oxidation of aluminum in the early stage of raw material melting, at which time the oxygen content of molten steel is controlled at 35~40ppm;

[0062] Insulation phase: When the temperature rises to 1520~1550℃, adjust the argon blowing flow rate to 0.15~0.25m³. 3 / h, maintain the inert atmosphere in the furnace and stabilize the composition of the molten steel. At this time, the oxygen content of the molten steel is stabilized below 30ppm.

[0063] Pre-tapping strengthening stage: 30 minutes before tapping, adjust the argon blowing flow rate to 0.4~0.6 m³ / min. 3 The process is accelerated to enhance degassing and oxygen reduction, lowering the oxygen content of molten steel to ≤25ppm. Temperature control accuracy during smelting is ±5℃, and argon blowing flow rate control accuracy is ±0.05m³ / h.3 / h, ensuring process stability and creating conditions for reducing secondary argon blowing in the ladle to below 20ppm.

[0064] (3) Slag formation and segmented aluminum addition

[0065] After the molten steel is melted to 1520~1550℃, 1.2~1.8% of protective slag-forming material by weight of the molten steel is added to the furnace and mixed using mechanical stirring at a speed of 30~50 r / min for 3~5 minutes, so that the slag-forming material is evenly spread to form a protective slag layer of 5~8 mm thickness. After standing for 15~20 minutes, the isolation and phase-stabilizing effect of the slag-forming material reduces the contact between the molten steel and air, while also reducing the erosion of the permeable bricks by the slag, thus helping to extend the service life of the permeable bricks.

[0066] Then, add 2 / 3 of the aluminum material and hold at that temperature for 10-15 minutes to promote uniform dissolution of the aluminum and prevent localized agglomeration that could lead to accelerated oxidation. The remaining 1 / 3 of the aluminum material is coated with graphite powder (aluminum:graphite powder = 100:3-5) and added to a ladle preheated to 800-850℃. The anti-oxidation properties of the graphite powder help prevent aluminum oxidation loss during tapping, ensuring the Al content of the molten steel meets the standards, while also reducing the erosion of the permeable brick surface by oxidation products.

[0067] (4) Secondary argon blowing in the ladle

[0068] The molten steel in the furnace is transferred to a ladle. Submerged permeable bricks are installed at the bottom of the ladle. Secondary argon blowing is initiated, with the argon flow rate controlled at 0.2~0.3 m³ / s. 3 Argon blowing is carried out at a rate of 8-12 minutes per hour to further lift fine Al2O3 inclusions that have not been adsorbed by the slag-forming material, while simultaneously removing residual oxygen. After argon blowing, the mixture is allowed to stand for 20-25 minutes to ensure complete separation of slag and steel, with a slag-to-steel separation rate ≥95%, an inclusion flotation rate ≥90%, and the oxygen content of the molten steel ultimately stabilizing at ≤20ppm.

[0069] (5) Customized heat treatment

[0070] After the molten steel is cast, the casting is shot-blasted to remove the surface oxide scale. This is followed by a two-stage heat treatment:

[0071] The first stage is water quenching: the casting is placed in a heat treatment furnace and heated to 650~680℃ and held for 2~3 hours to eliminate melting stress and prevent aluminum from forming brittle phases with other elements; then the temperature is raised to 1050~1080℃ and held for 1.5~2 hours to allow the alloying elements to fully dissolve and suppress aluminum segregation; after holding, the casting is water cooled to room temperature at a rate ≥50℃ / min to prevent the precipitation of brittle carbides.

[0072] The second stage of tempering treatment: The quenched casting is placed back into the heat treatment furnace and heated to 270~290℃, held for 2~2.5h to eliminate quenching stress and enhance the toughness and wear resistance of the material with the help of aluminum and copper elements; after tempering, it is water-cooled to room temperature, and the cooling rate is controlled at 20~30℃ / min to avoid deformation of the casting.

[0073] Technical principle of the invention:

[0074] 1. Principles of Breathable Brick Formulation and Preparation Process

[0075] Corundum, as the main aggregate of permeable bricks, possesses excellent high-temperature stability and corrosion resistance. An Al2O3 content ≥95% ensures that the permeable bricks do not decompose under high-temperature conditions above 1600℃, preventing secondary contamination of molten steel. Mullite (Al2O3·2SiO2) works synergistically with corundum to optimize the pore structure of the permeable bricks, improve pore connectivity, and enhance their mechanical strength, preventing damage during use. Silicon carbide (SiC) has high thermal conductivity and wear resistance; adding 5%... Adding 1-8% can improve the thermal shock resistance of permeable bricks, reduce cracking caused by sudden temperature changes, and refine the pore size, allowing argon gas to form microbubbles and increase the contact area with molten steel; chromium oxide (Cr2O3) can improve the corrosion resistance of permeable bricks to high-manganese steel, extend service life, and prevent steel contamination caused by damage to permeable bricks; bentonite, as a binder, can ensure the formability of raw materials when added at 1-2%, and at the same time, some of it volatilizes during sintering, forming micropores and further improving the apparent porosity.

[0076] In the manufacturing process, excessively low pressure leads to insufficient density and poor strength in the permeable bricks, with the room temperature flexural strength easily falling below 30 MPa. Excessively high pressure, on the other hand, compacts the pores, causing the apparent porosity to drop below 20%, thus negating the advantage of high apparent porosity. Sintering is carried out at 1600~1650℃ and held for 3~4 hours. This parameter combination ensures sufficient reaction of all raw materials, forming a stable crystal phase structure, while controlling pore growth, ensuring a stable apparent porosity of 26~30%, and a room temperature flexural strength ≥35 MPa and a high temperature flexural strength ≥25 MPa. This apparent porosity and strength characteristic is superior to traditional permeable bricks, allowing argon gas to diffuse evenly throughout the molten steel, eliminating argon blowing blind zones, and increasing the contact area between argon gas and molten steel by more than 30%. This significantly enhances oxygen isolation and degassing effects, reducing the oxygen content in the molten steel from 45~55 ppm in traditional processes to ≤25 ppm (in-furnace stage), laying the foundation for subsequent secondary argon blowing and extending the service life of the permeable bricks.

[0077] 2. Synergistic effect principle of protective slag-forming materials

[0078] Al2O3, as the core adsorbent phase of the slag-forming material, has the same crystal structure as the Al2O3 inclusions in the molten steel. It can efficiently adsorb the Al2O3 inclusions in the molten steel through interfacial interactions, while forming a solid solution to fix the inclusions in the slag and prevent them from re-dissolving into the molten steel. CaO and Al2O3 synergistically adjust the slag phase basicity to 1.0~1.2. This basicity range allows the slag to have suitable fluidity and adsorption capacity. If the basicity is too high, the slag will have poor fluidity and insufficient contact with the molten steel; if the basicity is too low, the slag will have poor stability and be prone to decomposition and failure.

[0079] Adding 6-7% MgO can improve the high-temperature stability of the slag, preventing excessive melting and loss of fluidity caused by the slag over-melting at smelting temperatures of 1520-1550℃. It also inhibits the erosion of the permeable bricks by the slag, reduces surface wear, and extends their service life. Adding 4-5% CaF2 as a flux can adjust the slag viscosity to 0.8-1.2 Pa·s, enhancing the slag's ability to cover the molten steel surface and reducing the impact of slag splashing on the permeable bricks during argon blowing. C powder (fixed carbon ≥90%) can form a reducing atmosphere on the slag surface, inhibiting secondary aluminum oxidation and reducing the corrosion of the permeable bricks by oxidizing components of the slag. Strictly controlling the SiO2 content to ≤1.5% is crucial because SiO2 readily reacts with the corundum components in the permeable bricks, weakening their structural strength. Low content control prevents rapid attenuation of the permeable bricks' flexural strength.

[0080] 3. The principle of synergistic optimization of molten steel composition

[0081] The precise proportions and addition methods of molten steel directly determine the overall performance of aluminum-containing high-manganese steel. Controlling the carbon content to 0.90~1.20% ensures material toughness while improving hardness and wear resistance, avoiding increased brittleness due to excessive carbon content. A silicon content of 0.35~0.45% provides deoxidation and improves steel fluidity, preventing excessive silicon from forming a brittle phase with aluminum. Mn, as the core element of high-manganese steel, has a content of 10.00~18.00% to ensure work hardening properties; gradient adjustments can adapt to different wear resistance requirements. The addition of high-carbon ferromanganese avoids Mn oxidation loss, ensuring stable Mn yield.

[0082] The Al content is designed in a gradient range of 0.30% to 4.50%, which can be adjusted according to performance requirements: the low-aluminum segment focuses on improving toughness, the medium-aluminum segment achieves a balance between toughness and wear resistance, and the high-aluminum segment focuses on improving wear resistance. The addition of aluminum blocks and aluminum granules in a 3:1 ratio optimizes the dissolution rate of aluminum and avoids accelerated oxidation caused by excessive local concentration. Cu and N work synergistically. Cu 0.60% to 0.75% can improve the toughness and corrosion resistance of the material, while N 0.015% to 0.025% is added in the form of chromium nitride, which can refine the grains and work synergistically with Al to optimize toughness and avoid embrittlement caused by excessive Al.

[0083] The synergistic effect of Nb and La+Ce composite rare earth elements: Nb (0.03~0.045%) refines grains, improving strength and wear resistance; La+Ce (0.02~0.06%) modifies Al2O3 inclusions, transforming needle-like and blocky inclusions into spherical shapes, reducing the disruptive effect of inclusions on material properties, and improving compositional uniformity. Cr (0.60~0.75%) enhances corrosion resistance and wear resistance, and synergistically strengthens surface properties with Al; strict control of S≤0.035% and P≤0.035% prevents harmful elements from forming brittle phases with aluminum, ensuring material toughness.

[0084] 4. Principle of Collaborative Control of Process Parameters

[0085] The segmented argon blowing gradient flow design adapts to the differences in oxidation risk at each stage of steel smelting, achieving a dynamic balance between inert atmosphere control and degassing efficiency. During the melting stage, the raw materials have a large surface area and high oxidizing activity; a larger flow of argon can quickly replace the air in the furnace, constructing a dense inert protective layer and inhibiting the oxidation of aluminum and other alloying elements from the source. During the holding stage, the steel composition tends to stabilize, and the oxidation risk is significantly reduced; a smaller flow of argon can maintain the inert environment in the furnace while avoiding excessive argon agitation that could cause steel splashing and composition fluctuations. In the pre-tapping degassing stage, increasing the argon flow increases the contact area between argon and molten steel, accelerating the removal of dissolved oxygen and gaseous impurities from the steel, forming a gradient control system of "oxidation inhibition - composition stabilization - deep degassing," laying a low-oxygen foundation for subsequent secondary argon blowing.

[0086] The synergistic process of adding aluminum twice and slag formation relies on physical isolation and chemical assistance to inhibit aluminum oxidation loss while improving compositional uniformity. The dense slag layer formed by the protective slag-forming material creates a physical barrier between the molten steel and air, reducing the probability of aluminum contact with oxygen, and simultaneously removing some oxidation products in advance through slag adsorption. Graphite powder-coated aluminum material has both chemical inert coating and auxiliary deoxidation functions, isolating air during the tapping process and inhibiting secondary oxidation of aluminum through the reducing properties of graphite powder, while promoting uniform dissolution of aluminum material and avoiding excessive oxidation caused by localized high concentrations. The secondary argon blowing in the ladle and the argon blowing in the furnace are linked, utilizing the buoyancy effect of argon to enhance the flotation of fine inclusions, constructing a closed-loop system of "full-process oxygen isolation + deep deoxidation + inclusion removal".

[0087] The two-stage heat treatment process is precisely adapted to the compositional characteristics of aluminum-containing high-manganese steel. Temperature control prevents the formation of brittle phases while optimizing the microstructure to achieve a synergistic improvement in toughness and wear resistance. Low-temperature preheating and holding effectively eliminates internal stress generated during melting, inhibiting the formation of brittle phases such as AlN and Al4C3 by Al and C / N elements during subsequent high-temperature treatment, thus preventing material toughness degradation. High-temperature solution treatment breaks the segregation of alloying elements, promoting the full integration of Al, Cu, Nb, and other elements into the austenite matrix, improving compositional uniformity and solid solution strengthening effect. Rapid water cooling inhibits the precipitation of brittle carbides during cooling, preserving the toughness advantages of the austenite microstructure. Low-temperature tempering eliminates quenching stress and simultaneously promotes the precipitation of some Al and Cu to form dispersed strengthening phases, improving material hardness and wear resistance while ensuring toughness, achieving precise control of microstructure and properties.

[0088] The present invention will be further illustrated below through specific embodiments and comparative examples.

[0089] (I) Preparation and performance optimization of permeable bricks

[0090] Example 1

[0091] A breathable brick, by mass fraction, comprises the following raw materials: 60% corundum, 25% mullite, 8% silicon carbide, 5% chromium oxide, and 2% bentonite.

[0092] The preparation process of the permeable brick includes the following steps:

[0093] (1) Raw material mixing: Add each raw material into a planetary mixer according to the above proportions, mix for 30 minutes, and control the mixing speed at 60 r / min to ensure that the raw materials are mixed evenly without segregation, which lays the foundation for subsequent molding and uniformity of pores.

[0094] (2) Pressing and molding: A hydraulic brick press is used to press the mixed raw materials into shape under a pressure of 20MPa. The holding time is 5s. The pressure and holding time are precisely matched to avoid the pores being over-compacted or the density being insufficient, which would affect the air permeability and strength.

[0095] (3) Green body drying: After molding, the green body is placed in a normal temperature environment for natural drying for 24 hours to fully remove free moisture and prevent the green body from cracking and the pore structure from being disordered due to moisture evaporation during subsequent sintering.

[0096] (4) Sintering treatment: The dried green body is sintered at 1600℃ for 4h, and the heating rate is controlled at 5℃ / min and the cooling rate is controlled at 3℃ / min to obtain honeycomb interconnected permeable brick.

[0097] Example 2

[0098] A breathable brick, by mass fraction, comprises the following raw materials: 63% corundum, 23% mullite, 7% silicon carbide, 5% chromium oxide, and 2% bentonite.

[0099] The preparation process of the permeable brick includes the following steps:

[0100] (1) Raw material mixing: Add each raw material to the planetary mixer according to the above proportions, mix for 35 minutes, and control the mixing speed at 70 r / min to ensure that the raw materials are mixed evenly without segregation, which lays the foundation for subsequent molding and uniformity of pores.

[0101] (2) Pressing and molding: A hydraulic brick press is used to press the mixed raw materials into shape under a pressure of 22MPa and a holding time of 6s. The pressure and holding time are precisely matched to avoid the pores being over-compacted or the density being insufficient, which would affect the air permeability and strength.

[0102] (3) Green body drying: After molding, the green body is placed in a normal temperature environment for natural drying for 24 hours to fully remove free moisture and prevent the green body from cracking and the pore structure from being disordered due to moisture evaporation during subsequent sintering.

[0103] (4) Sintering treatment: The dried green body was sintered at 1620℃ for 3.5h, and the heating rate was controlled at 6℃ / min and the cooling rate was controlled at 4℃ / min to obtain honeycomb interconnected permeable brick.

[0104] Example 3

[0105] A breathable brick, by mass fraction, comprises the following raw materials: 65% corundum, 22% mullite, 6% silicon carbide, 5% chromium oxide, and 2% bentonite.

[0106] The preparation process of the permeable brick includes the following steps:

[0107] (1) Raw material mixing: Add each raw material to the planetary mixer according to the above proportions, mix for 40 minutes, and control the mixing speed at 80 r / min to ensure that the raw materials are mixed evenly without segregation, which lays the foundation for subsequent molding and uniformity of pores.

[0108] (2) Pressing and molding: A hydraulic brick press is used to press the mixed raw materials into shape under a pressure of 25MPa and a holding time of 8s. The pressure and holding time are precisely matched to avoid the pores being over-compacted or the density being insufficient, which would affect the air permeability and strength.

[0109] (3) Green body drying: After molding, the green body is placed in a normal temperature environment for natural drying for 24 hours to fully remove free moisture and prevent the green body from cracking and the pore structure from being disordered due to moisture evaporation during subsequent sintering.

[0110] (4) Sintering treatment: The dried green body was sintered at 1650℃ for 3h, and the heating rate was controlled at 8℃ / min and the cooling rate was controlled at 5℃ / min to obtain honeycomb interconnected permeable brick.

[0111] Comparative Example 1 (Preparation of breathable bricks lacking mullite)

[0112] Raw material ratio (mass fraction): corundum 88%, silicon carbide 6%, chromium oxide 5%, bentonite 1%.

[0113] The preparation process is the same as in Example 3.

[0114] Comparative Example 2 (Preparation of permeable bricks lacking silicon carbide and containing more than 2% bentonite)

[0115] Raw material ratio (mass fraction): corundum 69%, mullite 22%, chromium oxide 5%, bentonite 4%.

[0116] The preparation process is the same as in Example 3.

[0117] Comparative Example 3 (Preparation of permeable bricks lacking chromium oxide)

[0118] Raw material ratio (mass fraction): corundum 70%, mullite 22%, silicon carbide 6%, bentonite 2%.

[0119] The preparation process is the same as in Example 3.

[0120] Comparative Example 4 (Preparation of permeable bricks with deviation in molding pressure)

[0121] This comparative example is based on Example 3, except that the molding pressure is changed to 18MPa (below the range of 20~25MPa), and the rest of the process is the same as in Example 3.

[0122] Comparative Example 5 (Preparation of permeable bricks with sintering temperature deviation)

[0123] This comparative example is based on Example 3, except that the sintering temperature is changed to 1580℃ (below the range of 1600~1650℃), and the rest of the process is the same as in Example 3.

[0124] To verify the comprehensive performance of the permeable bricks prepared in this invention, performance tests and comparative analyses were conducted on samples from Examples 1-3 and Comparative Examples 1-5. Specifically, the apparent porosity was tested according to YB / T 5200-1993 "Test Method for Apparent Porosity and Bulk Density of Dense Refractory Castables"; the high-temperature compressive strength was tested according to GB / T 34218-2017 "Test Method for High-Temperature Compressive Strength of Refractory Materials"; the high-temperature flexural strength was tested according to GB / T 3002-2017 "Test Method for High-Temperature Flexural Strength of Refractory Materials"; and the oxygen content of the molten steel was tested according to GB / T 11261-2006 "Determination of Oxygen Content in Iron and Steel - Pulse Heating Inert Gas Melting-Infrared Absorption Method". Detailed data are shown in Table 1.

[0125]

[0126] Conclusion Analysis:

[0127] 1. Mullite optimizes pore connectivity and synergistically enhances mechanical strength with corundum. Without it (Comparative Example 1), the apparent porosity of the permeable brick decreased to 22.4% (below the target range of 26-30%), with uneven pore size distribution. The high-temperature flexural strength at 1600℃ was only 20.2 MPa, a 28.6% decrease compared to Example 3. The service life was shortened to 8 cycles, only 25% of the optimal solution. Furthermore, the oxygen content in the molten steel increased to 38.5 ppm, significantly weakening the oxygen reduction effect. This confirms the supporting role of mullite in pore structure and strength. Silicon carbide mainly improves… The absence of chromium oxide significantly reduced the thermal shock resistance and porosity of the permeable bricks (Comparative Example 2), resulting in a high-temperature flexural strength of 21.5 MPa, a 24.0% decrease compared to Example 3. The bricks cracked after only 10 heats, making them unsuitable for the rapid high-temperature changes in the medium-frequency furnace. Chromium oxide is responsible for improving the permeable bricks' resistance to corrosion from molten high-manganese steel. Its absence (Comparative Example 3) reduced the high-temperature compressive strength to 48.6 MPa, causing severe surface corrosion. The bricks failed after 7 heats, with a 1.8% decrease in apparent porosity. This indicates that chromium oxide is a key component for extending the service life of permeable bricks.

[0128] 2. The preparation process parameters must be strictly controlled within the specified range; deviations will prevent the achievement of the target performance. The molding pressure directly determines the density and porosity retention capacity of the permeable brick. When the pressure is below 20 MPa (Comparative Example 4), the apparent porosity rises to 32.5%, resulting in insufficient density and a high-temperature compressive strength of only 45.3 MPa. The brick breaks after 6 heats, and the excessively loose pores lead to uneven argon diffusion and poor oxygen reduction effect. When the sintering temperature is below 1600℃ (Comparative Example 5), the raw materials cannot fully react to form a stable crystalline phase, resulting in an apparent porosity of 23.1% and a high-temperature flexural strength of 20.7 MPa. The brick cracks after 8 heats, and the unstable crystalline phase causes the strength decay rate to double. This further proves that a molding pressure of 20~25 MPa and a sintering temperature of 1600~1650℃ are the core process parameters to ensure the performance of the permeable brick.

[0129] 3. Example 3 exhibits the best overall performance and strongest stability, with an apparent porosity of 30.0%, a high-temperature compressive strength of 65.3 MPa at 1600℃, a high-temperature flexural strength of 28.3 MPa, and a service life of 32 cycles, far exceeding the target requirement of ≥30 cycles. The oxygen content in the molten steel in the furnace is reduced to 20.5 ppm. After 32 heats, the apparent porosity decreases by only 4.2%, and the flexural strength decreases by only 5.1%. It has the best corrosion resistance and thermal shock resistance, and can achieve uniform argon diffusion, laying the foundation for subsequent deep oxygen reduction.

[0130] (II) Preparation and performance optimization of slag-forming materials

[0131] Example 4

[0132] A slag-forming material, in terms of mass fraction, comprises the following raw materials: Al2O3 38%, CaO 48%, MgO 6%, CaF2 4%, C powder 2.5%, and SiO2 1.5%.

[0133] The preparation process of the slag-forming material includes the following steps:

[0134] (1) Raw material mixing: Put each proportion of raw materials into a planetary mixer, set the mixing time to 25 min and the mixing speed to 50 r / min, and continue mixing until there are no visible particles in the raw materials, the mixture is uniform and there is no segregation, to ensure that the components are dispersed in a consistent manner.

[0135] (2) Crushing and screening: The uniformly mixed raw materials are fed into a universal crusher for crushing. After crushing, they are screened through a standard sieve to select particles with a size of 1~3mm. Oversized or undersized particles are removed to ensure that the particle size of the slag-forming material is uniform.

[0136] (3) Drying treatment: The sieved slag-forming material particles are sent into an electric heating constant temperature drying oven, the temperature is controlled at 800℃, and the constant temperature drying is carried out for 2 hours. The drying parameters are precisely controlled, and the moisture content is reduced to 0.25% after drying to avoid;

[0137] (4) Cooling and storage: After drying, the slag-forming material is naturally cooled to room temperature and stored in a dry and sealed container to avoid moisture absorption for later use.

[0138] (5) Performance test: Melting point 1390℃, suitable for smelting temperature of 1520~1550℃, can quickly melt and form slag layer at high temperature; suitable for 50t medium frequency furnace high aluminum high manganese steel smelting, no obvious slag formation or slag splashing phenomenon, smooth operation, can stably cover the surface of molten steel; spreadability is suitable for basic smelting requirements, the spread area accounts for 78% of the surface of molten steel at room temperature, and can achieve uniform coverage by auxiliary mechanical stirring at high temperature; can react mildly with steelmaking residue, can effectively adsorb free Al2O3 inclusions in the residue, the reaction rate is moderate, each furnace can adsorb 68% of the inclusions in the residue, and no harmful gases are produced; compared with the original steel ladle simply covering the heat preservation agent, the average temperature drop of each furnace of steel is reduced by 8℃, the heat preservation effect is better than the traditional heat preservation agent, and the energy consumption of secondary heating of molten steel can be reduced.

[0139] Example 5

[0140] A slag-forming material, in terms of mass fraction, comprises the following raw materials: Al2O3 40%, CaO 44%, MgO 6.8%, CaF2 4.7%, C powder 3.3%, and SiO2 1.2%.

[0141] The preparation process of the slag-forming material includes the following steps:

[0142] (1) Raw material mixing: Put each proportion of raw materials into a planetary mixer, set the mixing time to 30 min and the mixing speed to 60 r / min, extend the mixing time to improve the mixing uniformity, eliminate the risk of component segregation, and ensure that each functional component is evenly distributed.

[0143] (2) Crushing and screening: The mixed raw materials are fed into a universal crusher for crushing. After crushing, they are screened through a standard sieve to select particles with a size of 3-4 mm. The particle size range is strictly controlled to ensure the fluidity and spreadability of the slag.

[0144] (3) Drying treatment: The qualified slag-forming material particles are sent into an electric heating constant temperature drying oven, the temperature is set at 800℃, and the drying is carried out at a constant temperature for 2 hours. The drying parameters are precisely controlled, and the moisture content is reduced to 0.22% after drying.

[0145] (4) Cooling and storage: After drying, cool naturally to room temperature, pack into a dry and sealed container for storage to prevent moisture absorption from affecting performance.

[0146] (5) Performance test: The melting point is 1360℃, which is optimally compatible with the smelting temperature of 1520~1550℃. It melts quickly at high temperature and does not require additional heating. It is suitable for smelting aluminum-containing high-manganese steel in various medium frequency furnaces of 5~50t. There is no slag formation, foaming or slag splashing. It is easy to operate and can stably cover the surface of molten steel throughout the process. It has good synergy with the segmented argon blowing and aluminum addition process. It has excellent spreadability. At room temperature, the spread area accounts for 88% of the surface of molten steel. The viscosity at high temperature is suitable. It can quickly form a dense and uniform 5~8mm slag layer without mechanical stirring. It can react quickly with steelmaking residues and efficiently adsorb 88% of free Al2O3 inclusions and harmful impurities. The reaction products are stable and do not pollute the molten steel. Compared with the original heat preservation agent, the temperature drop of each furnace can be reduced by 12℃, and the heat preservation and energy saving effect is significant.

[0147] Example 6

[0148] A slag-forming material, in terms of mass fraction, comprises the following raw materials: Al2O3 42%, CaO 42%, MgO 7%, CaF2 4.5%, C powder 3.5%, and SiO2 1.0%.

[0149] The preparation process of the slag-forming material includes the following steps:

[0150] (1) Raw material mixing: Put each proportion of raw materials into a planetary mixer, set the mixing time to 30 min and the mixing speed to 60 r / min, to ensure that each raw material is fully mixed, especially C powder is evenly dispersed, to avoid local over-mixing that could lead to subsequent foaming;

[0151] (2) Crushing and screening: The uniformly mixed raw materials are fed into a universal crusher for crushing. After crushing, they are screened through a standard sieve to select particles with a particle size of 3-5mm to ensure that the particle size meets the requirements for use, taking into account both flowability and coverage.

[0152] (3) Drying treatment: The sieved slag-forming material particles are sent into an electric heating constant temperature drying oven, the temperature is controlled at 800℃, and the drying is carried out at a constant temperature for 2 hours. The drying parameters are precisely controlled, and the moisture content is reduced to 0.20% after drying.

[0153] (4) Cooling and storage: After drying, allow the product to cool naturally to room temperature, then place it in a dry, sealed container to prevent moisture absorption and store for later use.

[0154] (5) Performance test: Melting point 1350℃, suitable for smelting temperature of 1520~1550℃, melting speed is fast at high temperature, and protective slag layer can be formed quickly; suitable for 50t medium frequency furnace smelting of high aluminum and high manganese steel, due to the high C powder content there is slight foaming phenomenon, which can be effectively avoided by adjusting the stirring speed, no obvious slag formation, and the whole can achieve full coverage protection of molten steel; good spreadability, the spread area accounts for 85% of the surface of molten steel at room temperature, the viscosity is suitable at high temperature, the spread rate is fast, and a uniform slag layer can be formed quickly; it can react with steelmaking residue, can efficiently adsorb Al2O3 inclusions in the residue, the reaction rate is fast, and each furnace can adsorb 80% of the inclusions in the residue, and the reaction products have no harmful components; compared with the original steel ladle simply covering the heat preservation agent, the average temperature drop of each furnace steel is reduced by 10℃, the heat preservation effect is excellent, and the energy saving effect is outstanding.

[0155] (III) Integration and Application Verification

[0156] Example 7 (Optimal permeable brick + optimal slag-forming material)

[0157] The permeable bricks use the product from Example 3, and the slag-forming material uses the product from Example 5, as detailed below:

[0158] A method for producing aluminum-containing high-manganese steel using a medium-frequency induction furnace, comprising the following steps: (The method utilizes the permeable bricks prepared in Example 3 and the slag-forming material prepared in Example 5 in conjunction with the medium-frequency induction furnace.)

[0159] (1) Preparation of raw materials for molten steel

[0160] The raw materials for molten steel are proportioned by mass fraction as follows: C: 1.0%, Si: 0.4%, Mn: 14.00%, Cr: 0.7%, Al: 3.0%, Cu: 0.65%, N: 0.02%, Nb: 0.04%, La+Ce: 0.04%, S: 0.02%, P: 0.02%, with the remainder being Fe and unavoidable impurities.

[0161] (2) Medium frequency furnace melting and segmented argon blowing

[0162] The molten steel raw materials are fed into a 50t medium-frequency induction furnace according to the specified ratio. The prepared permeable bricks are installed in the center of the furnace bottom, ensuring a good seal between the permeable bricks and the furnace bottom. The medium-frequency furnace is started, and the melting temperature is raised to 1450℃. Argon blowing is initiated, with the flow rate controlled at 0.4 m³ / h. 3 / h; when the temperature rises to 1550℃, adjust the argon blowing flow rate to 0.2m³ / h. 3 / h, maintain an inert atmosphere inside the furnace; 30 minutes before tapping, adjust the argon blowing flow rate to 0.5m. 3 / h, to enhance the degassing and oxygen reduction effect.

[0163] (3) Slag formation and segmented aluminum addition

[0164] After the molten steel is melted to 1550℃, 1.5% of the protective slag-forming material by weight of the molten steel is added to the furnace and mixed mechanically at a speed of 40 r / min for 5 minutes to ensure the slag-forming material is evenly spread to form a 5 mm thick protective slag layer. The mixture is then allowed to stand. Next, 2 / 3 of the aluminum material is added and held at this temperature for 15 minutes. The remaining 1 / 3 of the aluminum material is coated with graphite powder (aluminum material: graphite powder = 100:3) and added to a ladle preheated to 800℃. The anti-oxidation properties of the graphite powder are used to prevent aluminum oxidation loss during tapping.

[0165] (4) Secondary argon blowing in the ladle

[0166] The molten steel in the furnace is transferred to a ladle. Submerged permeable bricks are installed at the bottom of the ladle. Secondary argon blowing is initiated, with the argon flow rate controlled at 0.25 m³ / s. 3 Argon blowing is carried out at a rate of 10 min / h to further float up fine Al2O3 inclusions that have not been adsorbed by the slag-forming material, while removing residual oxygen. After argon blowing, the mixture is allowed to stand for 25 min.

[0167] (5) Customized heat treatment

[0168] After the molten steel is cast, the casting is shot-blasted to remove surface oxide scale. The casting is then placed in a heat treatment furnace, heated to 650℃ and held for 2.5 hours; subsequently, the temperature is increased to 1050℃ and held for 2 hours; after holding, it is water-cooled to room temperature at a rate ≥50℃ / min to prevent the precipitation of brittle carbides. The quenched casting is then placed back into the heat treatment furnace, heated to 280℃ and held for 2 hours; after tempering, it is water-cooled to room temperature at a rate controlled at 25℃ / min.

[0169] Comparative Example 6 (Non-optimal permeable bricks + optimal slag-forming materials)

[0170] The permeable bricks used were the product of Comparative Example 3 (lacking chromium oxide), the slag-forming material used was the product of Example 5, and the production process was the same as that of Example 7.

[0171] Comparative Example 7 (Optimal permeable brick + non-optimal slag-forming material)

[0172] The permeable bricks are made using the product of Example 3, the slag-forming material is made using the product of Example 4 (basic formula), and the production process is the same as that of Example 7.

[0173] Comparative Example 8 (Non-optimal permeable bricks + non-optimal slag-forming materials)

[0174] The permeable bricks used were the product of Comparative Example 5 (sintering temperature deviation), the slag-forming material used was the product of Example 4 (basic formula), and the production process was the same as that of Example 7.

[0175] To verify the comprehensive performance of the aluminum-containing high-manganese steel prepared by the present invention, performance tests and comparative analyses were conducted on the samples of Example 7 and Comparative Examples 6-8.

[0176] The oxygen content of the molten steel was determined according to GB / T 11261-2006 "Determination of Oxygen Content in Iron and Steel - Pulse Heating Inert Gas Melting-Infrared Absorption Method"; the impact toughness was determined according to GB / T5680-2023 "Austenitic Manganese Steel Castings"; the hardness was determined according to GB / T 230.1-2018 "Metallic Materials - Rockwell Hardness Test - Part 1: Test Method"; and the high-temperature flexural strength was tested according to GB / T 3002-2017 "Refractory Materials - High-Temperature Flexural Strength Test Method". Detailed data are shown in Table 2.

[0177]

[0178] Conclusion Analysis:

[0179] 1. A significant synergistic effect exists between the optimal permeable brick and the optimal slag-forming material. Combining them allows for the full utilization of their respective functional advantages, achieving a synergistic effect greater than the sum of its parts (1+1>2). Example 7 integrates the optimal permeable brick (Example 3) with the optimal slag-forming agent (Example 5), combined with a synergistic process of segmented argon blowing, segmented aluminum addition, and customized heat treatment. The overall performance is significantly superior to all comparative examples. The oxygen content in the molten steel is stably controlled at 19.2 ppm, meeting the target requirement of ≤20 ppm, representing a reduction of 30.9% and 29.2% compared to 27.8 ppm in Comparative Example 6 and 27.1 ppm in Comparative Example 8, respectively; the impact toughness reaches 150.4 J / cm². 2 Compared to 110.2 J / cm² in Comparative Example 6 2 Comparative Example 7: 125.3 J / cm 2 Comparative Example 8: 100.1 J / cm 2 The wear resistance was increased by 36.5%, 20.2%, and 50.2% respectively; the wear resistance relative wear amount was only 0.6, which was 29.4%, 20.0%, and 34.8% higher than that of Comparative Example 6 (0.85), Comparative Example 7 (0.75), and Comparative Example 8 (0.92), respectively, demonstrating excellent comprehensive performance.

[0180] 2. The use of suboptimal components significantly reduces overall process performance, with the most significant impact coming from permeable bricks lacking key components. For example, in Comparative Example 6, permeable bricks lacking chromium oxide were used. Even with the optimal slagging agent, the permeable bricks eroded and failed after only 7 heats, with a 22.6% decrease in high-temperature flexural strength. This directly led to the failure of the oxygen reduction effect, preventing the oxygen content of the molten steel from reaching the target range, and causing a significant decline in steel performance. The impact of suboptimal slagging materials was relatively milder. For instance, in Comparative Example 7, the optimal permeable bricks were used with a basic formula slagging agent. Although the oxygen content of the molten steel could be reduced to 19.9 ppm (close to the target value), the weak adsorption capacity of inclusions and insufficient protection of the permeable bricks resulted in lower impact toughness and wear resistance of the steel compared to the optimal combination, and the rate of strength decay of the permeable bricks was also significantly accelerated.

[0181] 3. The integrated process of this invention constructs a closed-loop system of "anti-oxidation - deep degassing - inclusion removal - performance optimization" by organically combining the optimal permeable bricks, the optimal slag-forming materials and synergistic processes. It can stably produce high-performance aluminum-containing high-manganese steel with oxygen content ≤20ppm, low inclusions.

[0182] The above content should not be construed as limiting the specific implementation of this invention to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of this invention, and all such deductions or substitutions should be considered as falling within the patent protection scope defined by the submitted claims.

Claims

1. A breathable brick, characterized in that, The raw materials are proportioned by mass as follows: corundum 60-65%, mullite 20-25%, silicon carbide 5-8%, chromium oxide 3-5%, and bentonite 1-2%.

2. The breathable brick according to claim 1, characterized in that, Raw material purity: Al2O3 ≥ 95% in corundum, Al2O3·2SiO2 ≥ 90% in mullite, silicon carbide ≥ 98%, chromium oxide ≥ 99%, and bentonite is high-purity binder-grade bentonite.

3. A method for preparing a breathable brick according to claim 1 or 2, characterized in that, Includes the following steps: (1) Raw material mixing: Put each raw material into a planetary mixer and mix for 30-40 minutes, with the mixing speed controlled at 60-80 r / min; (2) Pressing and molding: A hydraulic brick press is used to press the uniformly mixed raw materials into shape under a pressure of 20~25MPa, and the holding time is 5~8s; (3) Drying of the green body: Place the formed green body in a normal temperature environment and let it dry naturally for 24 hours; (4) Sintering treatment: The dried green body is sintered at 1600~1650℃ for 3~4h, wherein the heating rate is controlled at 5~8℃ / min and the cooling rate is controlled at 3~5℃ / min. After sintering, honeycomb interconnected permeable bricks are obtained.

4. The application of a permeable brick prepared according to claim 3 in the production of aluminum-containing high-manganese steel in a medium-frequency induction furnace, characterized in that, Includes the following steps: (1) Raw material preparation: The raw materials for molten steel are proportioned by mass as follows: C: 0.90~1.20%, Si: 0.35~0.45%, Mn: 10.00~18.00%, Cr: 0.60~0.75%, Al: 0.30~4.50%, Cu: 0.60~0.75%, N: 0.015~0.025%, Nb: 0.03~0.045%, La+Ce: 0.02~0.06%, S≤0.035%, P≤0.035%, with the remainder being Fe and unavoidable impurities; (2) Medium-frequency furnace smelting and argon blowing: The molten steel raw material is put into the medium-frequency furnace, and the permeable bricks are installed in the center of the furnace bottom. Argon is blown in stages at a flow rate of 0.3~0.5m. 3 / h, insulation stage 0.15~0.25m 3 / h, adjust to 0.4~0.6m 30 minutes before tapping. 3 / h, smelting to 1520~1550℃; (3) Slag formation and aluminum addition: Add 1.2-1.8% of protective slag-forming material by weight of molten steel into the furnace, stir to form a 5-8 mm slag layer, let stand for 15-20 min, add 2 / 3 aluminum material and keep warm for 10-15 min, and then coat the remaining 1 / 3 aluminum material with graphite powder and put it into the ladle at 800-850℃. (4) Secondary argon blowing into the ladle: Transfer the molten steel into the ladle and blow argon at a rate of 0.2~0.3m. 3 Argon blowing at a flow rate of / h for 8~12min, then let stand for 20~25min; (5) Heat treatment: After casting, the casting is shot blasted to remove the surface oxide scale, held at 650~680℃ for 2~3h, heated to 1050~1080℃ and held for 1.5~2h, cooled to room temperature by water, and then tempered at 270~290℃ for 2~2.5h, and cooled to room temperature by water.

5. The application of the permeable brick according to claim 4 in the production of aluminum-containing high-manganese steel in a medium-frequency induction furnace, characterized in that, In step (1), the aluminum material is aluminum blocks with Al ≥ 99.5% and aluminum granules in a 3:1 ratio, with the aluminum granules having a particle size of 2~5mm; Mn is added in the form of high carbon ferromanganese with Mn ≥ 85%, Cr is added in the form of ferrochrome with Cr ≥ 60%, Nb is added in the form of ferroniobium with Nb ≥ 65%, N is added in the form of chromium nitride master alloy with N ≥ 6%, and La+Ce is added in the form of mixed rare earth ferrosilicon alloy with a total rare earth content ≥ 20%.

6. The application of the permeable brick according to claim 4 in the production of aluminum-containing high-manganese steel in a medium-frequency induction furnace, characterized in that, In step (1), the Mn content is adjusted according to the wear resistance requirements: 10~14% for low wear resistance scenarios and 14~18% for high wear resistance scenarios; the Al content is adjusted according to the gradient: 0.30~0.80% for low aluminum, 1.00~2.50% for medium aluminum, and 3.00~4.50% for high aluminum.

7. The application of the permeable brick according to claim 4 in the production of aluminum-containing high-manganese steel in a medium-frequency induction furnace, characterized in that, In step (1), C powder is graphite powder with fixed carbon content ≥90%; in step (3), the mass ratio of aluminum material coated with graphite powder is aluminum material: graphite powder = 100: 3~5.

8. The application of the permeable brick according to claim 4 in the production of aluminum-containing high-manganese steel in a medium-frequency induction furnace, characterized in that, The medium-frequency furnace mentioned in step (2) is a 5~50t medium-frequency induction furnace. The compatibility between the permeable brick and the furnace body structure is optimized, and it can be installed and used without modifying the furnace body.

9. The method of applying the permeable brick according to claim 4 in the production of aluminum-containing high-manganese steel in a medium-frequency induction furnace, characterized in that, In step (3), after the slag-forming material is added, it is mixed by mechanical stirring at a speed of 30-50 r / min and a stirring time of 3-5 min to ensure that the slag layer evenly covers the surface of the molten steel.

10. The method of applying the permeable brick according to claim 4 in the production of aluminum-containing high-manganese steel in a medium-frequency induction furnace, characterized in that, In step (5), the water cooling rate is ≥50℃ / min, and the water cooling rate to room temperature after tempering is 20~30℃ / min.

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