Method for preparing drainage sand by using waste skateboard bricks and drainage sand

Abstract

The application relates to the technical field of fire-resistant material recycling and reusing, and particularly discloses a method for preparing drainage sand by using waste slide panel bricks and the drainage sand. The method for preparing the drainage sand by using the waste slide panel bricks comprises the following steps: crushing the waste slide panel bricks, adopting controlled impact stripping to cooperate with airflow classification and separation of the oxidized erosion layer, and adopting magnetic separation treatment on the remaining aggregate; mechanically shaping the purified aggregate, adding inorganic nano powder in the mechanical shaping process, and obtaining regenerated aggregate; taking the regenerated aggregate as a core, continuously coating an anti-sintering inner shell layer and a sintering-controlling outer shell layer on the surface of the aggregate from inside to outside to form a composite particle; and performing heat curing treatment on the composite particle, and performing hydrophobization treatment on the surface of the particle in the curing process. The application aims to convert the waste slide panel bricks into high-performance drainage sand which has excellent fluidity and controllable sintering behavior at high temperature.

Description

Technical Field

[0001] This application relates to the field of refractory material recycling and reuse technology, and more specifically, it relates to a method for preparing diversion sand using waste sliding bricks and the diversion sand itself. Background Technology

[0002] Slide block bricks, as core refractory materials in continuous casting control systems for steel, possess high aluminum content, high mechanical strength, and strong corrosion resistance, making waste slide block bricks generated after service highly valuable for recycling. Crushing and screening waste slide block bricks and using them as aggregate to prepare guide sand is an important way for the steel metallurgical industry to achieve solid waste recycling, reduce production costs, and practice green manufacturing. Guide sand, as a key filler for the sliding gate of the steel ladle, directly determines the automatic start-up rate during continuous casting and is a core material for ensuring the safety and efficiency of continuous steel production.

[0003] However, existing recycling processes for waste slide block bricks generally suffer from the following drawbacks: First, traditional simple mechanical crushing results in highly irregular shapes of recycled aggregates (mostly needle-like or flaky, or gravelly), with a large angle of repose, leading to poor flowability of the guide sand and incomplete filling within the nozzle. Second, the surface of waste slide block bricks is covered with a large amount of residual steel slag, oxide erosion layers, and metallic iron. These impurities fluctuate greatly in composition and are difficult to remove. If purification is incomplete, they can easily cause chemical fluctuations in the guide sand at high temperatures. Most seriously, due to the high surface activity and microcracks of the recycled aggregates, their sintering window is extremely narrow: on the one hand, premature bonding and burning between particles can easily occur, leading to casting failure; on the other hand, if the sintering strength is insufficient, molten steel leakage is likely to occur. This contradiction between "poor flowability" and "uncontrollable sintering behavior" limits the large-scale application of recycled guide sand in the production of high-quality steel grades. Summary of the Invention

[0004] To address the aforementioned problems, this application provides a method for preparing diversion sand using waste sliding bricks, and the diversion sand itself.

[0005] The first part of this application provides a method for preparing diversion sand using waste sliding bricks, which adopts the following technical solution: A method for preparing diversion sand using waste sliding bricks includes the following steps: (1) Purification: The waste sliding bricks are crushed and the oxidation and erosion layer is separated by controlled impact stripping and airflow grading. The remaining aggregates are purified by magnetic separation process with magnetic induction intensity ≥1.2T. (2) Rounding: The purified aggregate is mechanically shaped, and inorganic nanoparticles accounting for 0.5%-5% of the aggregate mass are added during the mechanical shaping process to obtain recycled aggregate; (3) Coating: Using the recycled aggregate as the core, a continuous anti-sintering inner shell layer and a controlled sintering outer shell layer are constructed on the surface of the aggregate from the inside out through a coating process to form a multi-layer core-shell structure composite particle; wherein, the anti-sintering inner shell layer contains graphite and carbonaceous binder, and the controlled sintering outer shell layer contains quartz sand and sintering accelerator. (4) Curing: The coated particles are subjected to thermal curing treatment, and the particle surface is hydrophobically treated by introducing a vapor phase modifier during the curing process.

[0006] By adopting the above technical solutions, the transformation of waste sliding bricks from coarse and scattered solid waste into high-performance functional materials has been achieved. The purification step effectively removes the oxide layer and metallic iron impurities that affect the casting rate through physical sorting, ensuring the purity and stability of the material composition; the rounding step improves the geometric morphology of the recycled aggregate, fundamentally enhancing the fluidity of the guide sand; the encapsulation step constructs a gradient core-shell structure, cleverly resolving the thermodynamic contradiction between anti-sintering and controlled sintering; and the solidification step locks in the physical morphology of the multi-layer structure and endows it with moisture resistance. The synergistic effect of the entire process enables the finished guide sand to reach the level of virgin guide sand in terms of automatic casting rate, impermeable steel performance, and storage stability.

[0007] Optionally, the inorganic nanoparticles are selected from at least one of nano-alumina, nano-silicon dioxide, nano-silicon carbide, or nano-magnesium oxide; the average particle size of the inorganic nanoparticles is 10nm-100nm.

[0008] By employing the above technical solution, it is found that the surface of waste sliding block brick aggregate typically contains numerous microcracks generated by thermal stress. These cracks are the cause of molten steel penetration at high temperatures or further aggregate fragmentation. Nanoparticles can penetrate and fill these microcracks, reducing the stress concentration effect at the crack tips and significantly enhancing the mechanical strength and refractoriness of the aggregate. Simultaneously, the introduction of nanoparticles increases the surface density of the aggregate, reducing ineffective penetration of the binder into the aggregate interior during subsequent coating processes, ensuring the uniformity of the coating layer thickness and the interfacial bonding strength.

[0009] Optionally, the mass ratio of the anti-sintering inner shell layer to the controlled sintering outer shell layer in step (3) is 1:(1.5-4).

[0010] By adopting the above technical solution, the mass ratio of 1:(1.5-4) ensures that the inner layer has sufficient physical isolation thickness to prevent the aggregates from burning together, while ensuring that the outer layer can form a continuous sintering network to block molten steel.

[0011] Optionally, the thermosetting treatment in step (4) is a thermo-crosslinking curing process performed at 120℃-250℃; the vapor phase modifier is an organosilane coupling agent.

[0012] By adopting the above technical solution and setting a thermal crosslinking range of 120℃-250℃, it is ensured that carbonaceous binders such as phenolic resin can fully transform from a liquid state into a stable three-dimensional network structure, thereby firmly locking the functional components onto the aggregate surface and preventing delamination or detachment during transportation and filling. A fumed organosilane coupling agent is introduced for hydrophobic treatment, forming a molecular-level low surface energy film on the outermost layer of the particles. This completely solves the porosity fluctuations and safety hazards caused by the easy absorption of moisture by recycled materials, and significantly reduces the friction coefficient and adhesion between the guide sand and the sprue seat brick wall, preventing the "bridging" phenomenon of the guide sand within the sprue and ensuring the free-fall performance of the guide sand.

[0013] Optionally, the roundness value of the recycled aggregate is greater than 0.75, and the angle of repose is 20°-30°.

[0014] By adopting the above technical solution, the high roundness value significantly reduces the intermeshing resistance of particles during the filling process, allowing the guiding sand to uniformly fill the sliding nozzle in a near-fluid state. The lower angle of repose ensures that the guiding sand can quickly slide and disintegrate under its own weight at the moment the nozzle opens, without forming a stable static equilibrium. The synergistic optimization of these two indicators guarantees the uniform density of the guiding sand inside the nozzle, thus providing a stable pressure section and offering physical and geometric guarantees for improving the automatic pouring rate.

[0015] Optionally, the linear velocity V of the controlled impact peeling in step (1) is set according to the material type of the sliding block: For aluminum-carbon sliding bricks, the impact linear velocity V is 45m / s-55m / s; for aluminum-magnesium-carbon sliding bricks, the impact linear velocity V is 35m / s-45m / s; and for magnesium-carbon sliding bricks, the impact linear velocity V is 30m / s-40m / s.

[0016] By adopting the above technical solution, due to the significant differences in matrix bonding strength and oxide layer brittleness among alumina-carbon, alumina-magnesia-carbon, and magnesia-carbon sliding block bricks, differentiated impact linear velocities can achieve precise work distribution. For alumina-carbon bricks with a harder matrix, a higher linear velocity ensures that the firmly bonded oxide layer is broken and peeled off; while for magnesia-carbon bricks with a relatively loose matrix, a lower linear velocity can effectively remove the oxide layer while avoiding over-crushing of high-value magnesia aggregate. This refined classification control not only significantly improves the purity of recycled aggregates but also maximizes the yield and reduces energy consumption from over-crushing during the production process.

[0017] Optionally, the anti-sintering inner shell layer is composed of flake graphite, silicon carbide and thermosetting binder; wherein the average particle size D50 of the silicon carbide is 1um-8um; and the mass ratio of the flake graphite to the micron-sized silicon carbide is (3-8):1.

[0018] By employing the above technical solution, flake graphite provides excellent lubricity and non-wetting properties, preventing direct contact between aggregate surfaces. Micron-sized silicon carbide, with its extremely high hardness and thermal stability, acts as a microscopic support between the graphite flakes, enhancing the inner shell's oxidation resistance and compressive strength at high temperatures. Since both SiC and graphite are non-wetting with molten steel, this inner shell can form a stable, non-reactive interface around the aggregate, ensuring that the core of the guiding sand remains porous under any extreme thermal load.

[0019] Optionally, the controlled sintering outer shell layer is composed of quartz sand, aluminum silicate mineral flux, and borate sintering accelerator; wherein the particle size distribution of the quartz sand is 40um-120um; the mass ratio of the aluminum silicate mineral flux to the borate sintering accelerator is (2-6):1; and the mass percentage of the sintering accelerator in the controlled sintering outer shell layer is 3wt%-10wt%.

[0020] By employing the above technical solution, quartz sand provides the skeletal foundation, while the precise ratio of flux and accelerator allows the outer shell layer to rapidly undergo a eutectic reaction upon reaching a specific temperature range, generating an appropriate amount of high-viscosity liquid phase. This liquid phase forms a silicon-oxygen network bridging structure at the particle contact points, endowing the sintered layer with sufficient mechanical strength to withstand the hydrostatic pressure of molten steel (preventing steel seepage) while maintaining low fracture toughness (ensuring smooth casting). This ternary system design makes the temperature sensitivity of sintering behavior controllable, greatly expanding the adaptability of the guiding sand to different steel grades and casting cycles.

[0021] Secondly, this application provides a diversion sand, the diversion sand particles having a multi-layered gradient core-shell structure, the core of which is a recycled slide block aggregate whose surface microcracks are passivated and filled by inorganic nanoparticles, and is wrapped from the inside out with an anti-sintering inner shell layer, a controlled sintering outer shell layer and a surface hydrophobic film.

[0022] By adopting the above technical solution, the guiding sand possesses, at the microscopic level, a passivated aggregate core, a stable anti-sintering inner layer, an intelligent controlled sintering outer layer, and a hydrophobic surface. This multi-layered coupled structure enables the product to exhibit extremely high flow consistency, chemical inertness, and automatic response capability at high temperatures. It overcomes the persistent problem of performance fluctuations in traditional recycled guiding sand, significantly reduces the frequency of artificial oxygen injection during continuous casting, and improves the continuity and safety of steel production.

[0023] In summary, this application has the following beneficial effects: 1. This application effectively solves industry problems such as large fluctuations in aggregate composition, incomplete oxide layer removal, and poor flowability caused by irregular geometric morphology in recycled waste sliding bricks by employing controlled impact stripping combined with mechanical shaping and nanoparticle passivation processes. Differentiated impact linear velocities achieve precise removal of oxide layers from sliding bricks of different materials, significantly improving aggregate purity. Simultaneously, the use of inorganic nanoparticles to physically fill and stress-passivate microcracks on the aggregate surface not only enhances the mechanical strength of the aggregate but also ensures that the roundness and angle of repose of the recycled aggregate meet the standards of virgin diverting sand, laying a solid physical and geometric foundation for improving the automatic casting rate.

[0024] 2. This application employs a multi-layered gradient structure of an anti-sintering inner shell and a controlled-sintering outer shell, along with a specific ternary eutectic sintering system, to resolve the thermodynamic contradiction between the anti-seepage steel and high-speed casting of the guiding sand under high-temperature conditions. By introducing micron-sized silicon carbide with steric hindrance effect and graphite to synergistically construct a high-temperature isolation barrier in the inner layer, the porosity of the core aggregate is ensured. The outer layer, through a eutectic liquid phase formed by aluminum silicate flux and borate-based accelerator, instantly constructs a high-viscosity silicon-oxygen network bridging structure upon contact with molten steel. This gradient functional design allows for controlled sintering layer thickness and extremely low fracture toughness, greatly expanding the adaptability of the guiding sand to different steel grades and smelting cycles.

[0025] 3. The method of this application not only significantly reduces the production cost of steelmaking enterprises, but also improves the continuity and safety of continuous casting operations, providing industrial promotion value for the recycling of refractory materials. Detailed Implementation

[0026] The following detailed description of this application is provided in conjunction with the embodiments. It should be noted that: unless otherwise specified, the conditions in the following embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following embodiments are all from commercially available sources.

[0027] Example 1 A process for preparing diversion sand using waste sliding plate bricks: The raw material source was waste aluminum-carbon sliding plate bricks replaced in the continuous casting workshop of a steel plant. Testing revealed that this batch of sliding plate bricks had a residual carbon content of 12 wt%, and its main chemical components were Al2O3 and C. A jaw crusher was used to pre-crush the waste sliding plate bricks into coarse blocks with a particle size of 30mm-50mm.

[0028] Coarse materials are fed into a vertical shaft impact crusher. Based on the alumina-carbon material properties, the rotor impact linear velocity V is set to 50 m / s. The crushed material enters an air classifier, where the low density and fine particle size characteristics of the pulverized oxide layer are utilized to completely separate it from the matrix aggregate, and the material is collected by a dust removal system. The sorted aggregate undergoes high-gradient magnetic separation with a magnetic induction intensity of 1.6T to remove inclusions of fine metallic iron and iron-containing slag.

[0029] The purified aggregate was fed into a horizontal shaping machine for mechanical grinding and polishing. During the shaping process, 2.75% by weight of nano-alumina powder was added. The average particle size of the nano-powder was 55 nm. The resulting recycled aggregate was measured to have a roundness value of 0.82 and an angle of repose of 25°. Using recycled aggregate as the core, a high-efficiency mixing and granulation machine is employed to spray and coat flake graphite (20μm particle size), micron-sized silicon carbide (D50 of 4.5μm), and liquid thermosetting phenolic resin in a specific ratio. The mass ratio of flake graphite to silicon carbide is set at 5.5:1.

[0030] Before the inner layer has solidified, the outer layer material continues to coat it. The outer layer consists of quartz sand (particle size distribution of 80μm), aluminum silicate mineral flux (potassium feldspar powder), and borate sintering accelerator.

[0031] The total mass ratio of the anti-sintering inner shell layer to the controlled sintering outer shell layer is set to 1:2.75.

[0032] The mass ratio of flux to accelerator is set at 4:1.

[0033] The sintering accelerator accounts for 6.5 wt% of the total shell layer.

[0034] The coated granules are fed into a fluidized bed drying oven, and the curing temperature is set to 185℃. The temperature is maintained for 45 minutes to allow the resin to fully crosslink. After curing and cooling to 150℃, an atomized organosilane coupling agent (KH-550) is introduced into the fluidized bed. Utilizing the residual heat of the granules, a continuous molecular-level hydrophobic film is formed on the outermost layer of the guiding sand through vapor deposition.

[0035] Drainage sand was obtained by using waste sliding plate bricks.

[0036] Example 2 A process for preparing diversion sand using waste sliding plate bricks: The difference from Example 1 is that magnesium carbonaceous waste sliding plate bricks are used as raw materials. In step (1) during the purification process, the rotor impact linear velocity V is reduced to 35 m / s.

[0037] Example 3 A process for preparing diversion sand using waste skateboard bricks: The difference from Example 1 is that in the rounding process, nano-alumina is replaced with nano-silica, and its average particle size is set to 25nm.

[0038] Example 4 A process for preparing diversion sand using waste sliding plate bricks: The difference from Example 1 is that the mass ratio of the anti-sintering inner shell layer to the controlled sintering outer shell layer is changed. The mass ratio of the inner and outer shell layers is adjusted to 1:1.8.

[0039] Example 5 A process for preparing guide sand using waste sliding plate bricks: The difference from Example 1 lies in changing the concentration of the sintering accelerator and the proportion of the flux. The mass percentage of the sintering accelerator (borate) is increased to 9.5 wt%.

[0040] Example 6 A process for preparing diversion sand using waste sliding plate bricks: The difference from Example 1 is that aluminum-magnesium-carbon waste sliding plate bricks are used as raw materials. During the purification process, the rotor impact linear velocity V is set to 40 m / s.

[0041] Example 7 A process for preparing diversion sand using waste skateboard bricks: The difference from Example 1 is that nano-silicon carbide powder, accounting for only 0.5 wt% of the aggregate mass, is added during the rounding process.

[0042] Example 8 A process for preparing diversion sand using waste sliding plate bricks: The difference from Example 1 lies in changing the mass ratio of flake graphite to micron-sized silicon carbide. When constructing the anti-sintering inner layer, the mass ratio of graphite to silicon carbide is set to 3:1.

[0043] Example 9 A process for preparing diversion sand using waste sliding plate bricks: The difference from Example 1 is the change in the thermosetting temperature. During the curing process, the thermal crosslinking temperature is set to 250°C.

[0044] Example 10 A process for preparing diversion sand using waste sliding plate bricks: The difference from Example 1 is that the mass ratio of aluminum silicate mineral flux to borate accelerator is changed. The mass ratio of flux to accelerator is set to 6:1.

[0045] Example 11 A process for preparing diversion sand using waste skateboard bricks: The difference from Example 1 is that the thermal crosslinking temperature is set to 120°C during the curing process.

[0046] Example 12 A process for preparing diversion sand using waste sliding plate bricks: The difference from Example 1 is that the total mass ratio of the anti-sintering inner shell layer to the controlled sintering outer shell layer is changed. The total mass ratio of the inner and outer shell layers is set to 1:4.

[0047] Example 13 A process for preparing diversion sand using waste skateboard bricks: The difference from Example 1 is that nano-magnesium oxide powder accounting for 5 wt% of the aggregate mass is added during the rounding process.

[0048] Example 14 A process for preparing diversion sand using waste skateboard bricks: The difference from Example 1 is that when constructing the outer shell layer, high-purity quartz sand with a particle size distribution of 120μm is selected.

[0049] Comparative Example 1 The difference from Example 1 is that the waste sliding plate bricks are only subjected to conventional jaw crushing and screening, without the use of controlled impact stripping and magnetic separation processes.

[0050] Comparative Example 2 The difference from Example 1 is that no nano-alumina powder is added during the mechanical shaping process, while the other parameters remain the same.

[0051] Comparative Example 3 The difference from Example 1 is that instead of constructing an anti-sintering inner shell layer, the "controlled sintering outer shell layer" described in Example 1 is directly wrapped on the surface of the recycled aggregate.

[0052] Comparative Example 4 The difference from Example 1: The anti-sintering inner shell contains only flake graphite and binder, without adding micron-sized silicon carbide.

[0053] Comparative Example 5 The difference from Example 1 is that the mass percentage of sintering accelerator in the controlled sintering outer shell layer is increased to 15 wt%.

[0054] Comparative Example 6 The difference from Example 1 is that no organosilane coupling agent is introduced during the curing and cooling process, while the other curing conditions remain unchanged.

[0055] 1. Sphericity Measurement of Recycled Aggregate The determination was performed using microscopic image analysis. The specific steps were as follows: 500 particles of the recycled aggregate sample were randomly selected, and digital images of the particles were acquired using an industrial stereomicroscope. The perimeter (P) and area (A) of the projected surface of each particle were automatically extracted using image processing software, and then calculated using the formula C = 4πA / P. 2The roundness value of a single particle is calculated. The final result is the arithmetic mean of the roundness values ​​of 500 particles. The closer this value is to 1.0, the closer the aggregate geometry is to a sphere.

[0056] 2. Angle of Repose Detection The angle of repose of surfactant powders and particles was determined using the injection method, in accordance with the national standard GB / T11986-1989, "Determination of Angle of Repose of Surfactant Powders and Particles". During the test, the guide sand sample was allowed to fall naturally from a specified height through a standard funnel (outlet diameter 10 mm) and accumulate on a horizontal circular plate. After the accumulation stabilized, the angle between the inclined surface of the cone and the bottom plane was measured. Five consecutive measurements were taken, and the average value was recorded. A smaller angle of repose indicates better flowability of the guide sand.

[0057] 3.1 Static Sintered Layer Thickness Measurement at 1600℃ A high-temperature crucible simulation method was employed. 500g of the guiding sand sample was placed in a high-purity graphite crucible with an inner diameter of 50mm, and a constant hydrostatic pressure of 0.1MPa (to simulate the hydrostatic pressure of molten steel) was applied to the surface of the guiding sand. The crucible was placed in a high-temperature tube furnace and heated to 1600℃ under an argon atmosphere. After holding at this temperature for 2 hours, the furnace was cooled to room temperature. After sampling, the average thickness of the hardened sintered layer formed on the top was measured using vernier calipers at at least five points, and the average value was taken.

[0058] 4. Simulated Automatic Opening Rate Detection A laboratory sprue simulation device was used for hot-state testing. The ladle opening operation was simulated at a simulated high temperature of 1600℃. Drainage sand was filled into the simulated sprue, and after 2 hours, the bottom slide gate was opened. If the drainage sand could instantly collapse and flow out due to its own weight and the simulated pressure above, it was considered a "successful automatic pouring start"; if manual intervention (such as oxygen supply) was required for it to flow out, it was considered a "failed pouring start". Each embodiment was repeated 200 times, and the percentage of successful pouring starts was calculated.

[0059] 5. Surface hydrophobic contact angle detection (WaterContactAngle) The contact angle was measured using a contact drop method with a contact angle measuring instrument. Drainage sand particles were evenly laid on a glass slide to form a dense plane, and 3 μL of deionized water was dropped onto the surface using a precision sampler. The wetting morphology of the droplet on the particle surface was captured by a high-speed camera, and the contact angle at the liquid / solid interface was measured using the tangential method. A contact angle greater than 90° was considered hydrophobic, and greater than 130° was considered strongly hydrophobic.

[0060] Table 1 Detection Data Example 1 0.82 25.0 8.5 99.5 135 Example 2 0.81 26.0 9.0 99.0 132 Example 3 0.85 22.0 8.2 99.5 136 Example 4 0.82 25.5 6.2 99.5 134 Example 5 0.82 25.0 11.5 98.5 135 Example 6 0.81 26.5 8.8 99.0 133 Example 7 0.76 29.0 8.7 98.0 130 Example 8 0.81 25.5 10.5 99.0 135 Example 9 0.82 25.0 8.4 99.5 142 Example 10 0.82 25.5 5.5 99.5 135 Example 11 0.80 27.0 8.9 97.5 115 Example 12 0.83 24.5 11.8 98.5 137 Example 13 0.88 21.0 8.1 99.5 138 Example 14 0.79 28.0 7.5 99.5 132 Comparative Example 1 0.72 34.0 15.2 65.0 110 Comparative Example 2 0.68 38.0 9.0 88.0 105 Comparative Example 3 0.81 25.5 Fully sintered (>30) 0.0 131 Comparative Example 4 0.81 26.0 12.5 91.0 130 Comparative Example 5 0.82 25.0 22.0 45.0 135 Comparative Example 6 0.82 25.0 8.8 92.0 (Dampness) <10 Combining Example 1 and Comparative Examples 1 and 2 with Table 1, it can be seen that: Comparative Example 1 did not employ controlled impact stripping and high-gradient magnetic separation processes, resulting in a large amount of residual oxidative erosion layer on the aggregate surface, with a roundness value of only 0.72 and an angle of repose as high as 34.0°, proving that residual impurities severely damaged the geometric regularity of the aggregate. Comparative Example 2 lacked nanoparticle filling during shaping, further deteriorating the roundness to 0.68 and increasing the angle of repose to 38.0°, far inferior to Example 1. This indicates that this application, through the synergistic effect of controlled impact—mechanical shaping—nanopassivation, can effectively repair microcracks on the surface of waste brick aggregate and eliminate geometric defects, enabling the recycled aggregate to exhibit excellent sphericity and flowability, providing a physical basis for high casting rates.

[0061] Combining Example 1 and Comparative Example 3 with Table 1, it can be seen that in Comparative Example 3, despite having similar original aggregate physical properties to Example 1 due to the complete absence of the anti-sintering inner shell layer, the thickness of the 1600℃ high-temperature sintering layer exceeded 30mm, resulting in an overall "dead burning" phenomenon and a simulated automatic casting rate of 0.0%. This fully demonstrates that the inner shell layer composed of graphite and silicon carbide plays a crucial role in physical steric hindrance and chemical isolation under high-temperature conditions, preventing the liquid phase of the outer shell layer from penetrating into the aggregate core. Only by constructing a continuously coated gradient core-shell structure can the loose state of the guiding sand core be ensured.

[0062] Combining Examples 1 and 5 and Comparative Example 5 with Table 1, it can be seen that when the concentration of the sintering accelerator is within the range of 3wt%-10wt% as defined in this application, the sintered layer thickness is controlled at 8.5mm and 11.5mm respectively, and the automatic casting rate remains above 98.5%. However, when the accelerator concentration in Comparative Example 5 is increased to 15%, due to the excessive low-melting eutectic liquid phase generated at high temperature and its decreased viscosity, the sintered layer thickness increases sharply to 22.0mm, causing the automatic casting rate to plummet to 45.0%. This confirms that the composition ratio of the sintering system in this application ensures that the necessary impermeable barrier is formed without losing the casting function due to over-sintering.

[0063] Combining Example 1 and Comparative Example 4 with Table 1, it can be seen that: Comparative Example 4, which used only graphite in the inner shell layer and lacked micron-sized silicon carbide, resulted in an increase in the thickness of the sintered layer at 1600℃ to 12.5 mm, and a decrease in the casting rate to 91.0%. A single graphite layer is prone to physical collapse or oxidation and thinning when subjected to the static pressure impact of molten steel and trace oxygen erosion. However, the silicon carbide added in Example 1, with its high hardness and chemical stability, acts as a "microscopic support pillar" between the graphite sheets, significantly enhancing the compressive strength and chemical inertness of the inner shell layer.

[0064] Combining Example 1 and Comparative Example 6 with Table 1, it can be seen that after modification with fumed organosilane, Example 1 exhibits a surface contact angle of 135°, demonstrating strong hydrophobicity; while Comparative Example 6, lacking this process, has a contact angle of less than 10°. Under simulated humid conditions, the "bridging" and adhesion phenomena observed in Comparative Example 6 led to a decrease in its casting rate to 92.0% with significant fluctuations. This indicates that fumed modification is not simply surface treatment, but rather eliminates the safety hazards caused by moisture absorption through micropores in the recycled material by constructing a molecular-level hydrophobic isolation membrane. Furthermore, combining Examples 9 and 11, it can be seen that thermosetting within the range of 120℃-250℃ effectively ensures the structural strength of the coating layer, with the high-temperature curing in Example 9 being more conducive to the formation of the fumed deposition film.

[0065] Combining Examples 1, 7, and 13 with Table 1, it can be seen that as the amount of nanoparticles added increases from 0.5 wt% to 2.75 wt% and then to 5 wt%, the roundness value of the recycled aggregate shows a significant linear upward trend, while the angle of repose decreases accordingly. This demonstrates that nanoparticles can significantly improve the tribomechanical behavior between aggregates by repairing microcracks. Even at the lower limit of 0.5 wt%, the present invention can still maintain a roundness baseline of 0.76, proving the wide applicability of this technical route under different cost requirements.

[0066] Combining Examples 10, 12, and 14 with Table 1, it can be seen that: Example 10 achieved an ultra-thin controlled sintering of 5.5 mm by increasing the flux ratio, while Example 12 achieved a strengthened sintering of 11.8 mm by increasing the total outer layer thickness. Example 14 used 120 μm coarse-grained quartz sand; although the roundness was slightly reduced, its 7.5 mm sintering thickness exhibited excellent brittle fracture characteristics, with a casting open rate of 99.5%.

[0067] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A method for preparing diversion sand using waste sliding plate bricks, characterized in that, Includes the following steps: (1) Purification: The waste sliding bricks are crushed and the oxidation and erosion layer is separated by controlled impact stripping and airflow grading. The remaining aggregates are purified by magnetic separation process with magnetic induction intensity ≥1.2T. (2) Rounding: The purified aggregate is mechanically shaped, and inorganic nanoparticles accounting for 0.5%-5% of the aggregate mass are added during the mechanical shaping process to obtain recycled aggregate; (3) Coating: Using the recycled aggregate as the core, a continuous anti-sintering inner shell layer and a controlled sintering outer shell layer are constructed on the surface of the aggregate from the inside out through a coating process to form a multi-layer core-shell structure composite particle; wherein, the anti-sintering inner shell layer contains graphite and carbonaceous binder, and the controlled sintering outer shell layer contains quartz sand and sintering accelerator. (4) Curing: The coated particles are subjected to thermal curing treatment, and the particle surface is hydrophobically treated by introducing a vapor phase modifier during the curing process.

2. The method for preparing diversion sand using waste sliding plate bricks according to claim 1, characterized in that: The inorganic nanoparticles are selected from at least one of nano-alumina, nano-silicon dioxide, nano-silicon carbide, or nano-magnesium oxide; the average particle size of the inorganic nanoparticles is 10nm-100nm.

3. The method for preparing diversion sand using waste sliding bricks according to claim 1, characterized in that: The mass ratio of the anti-sintering inner shell layer to the controlled sintering outer shell layer in step (3) is 1:(1.5-4).

4. The method for preparing diversion sand using waste sliding bricks according to claim 1, characterized in that: The thermosetting treatment in step (4) is a thermo-crosslinking curing process carried out at 120℃-250℃; the vapor phase modifier is an organosilane coupling agent.

5. The method for preparing diversion sand using waste sliding plate bricks according to claim 1, characterized in that: The roundness value of the recycled aggregate is greater than 0.75, and the angle of repose is 20°-30°.

6. The method for preparing diversion sand using waste sliding bricks according to claim 1, characterized in that: The linear velocity V of the controlled impact peeling in step (1) is set according to the material type of the sliding block: For aluminum-carbon sliding bricks, the impact linear velocity V is 45m / s-55m / s; for aluminum-magnesium-carbon sliding bricks, the impact linear velocity V is 35m / s-45m / s; and for magnesium-carbon sliding bricks, the impact linear velocity V is 30m / s-40m / s.

7. The method for preparing diversion sand using waste sliding plate bricks according to claim 1, characterized in that: The anti-sintering inner shell is composed of flake graphite, silicon carbide and thermosetting binder; wherein the average particle size D50 of the silicon carbide is 1um-8um; and the mass ratio of the flake graphite to the micron-sized silicon carbide is (3-8):

1.

8. The method for preparing diversion sand using waste sliding bricks according to claim 1, characterized in that: The controlled sintering outer shell layer is composed of quartz sand, aluminum silicate mineral flux, and borate sintering accelerator; wherein the particle size of the quartz sand is distributed between 40um and 120um; the mass ratio of the aluminum silicate mineral flux to the borate sintering accelerator is (2-6):1; and the mass percentage of the sintering accelerator in the controlled sintering outer shell layer is 3wt%-10wt%.

9. A type of diversion sand, characterized in that: The diversion sand is prepared by the method described in any one of claims 1-8.