Modified chrome-corundum ramming mix, preparation and construction process thereof

Abstract

The application relates to a modified chrome-corundum ramming mixture and a preparation and construction process, and belongs to the technical field of chrome-corundum ramming mixtures. The ramming mixture comprises A material, B material and C material, the A material comprises chrome-corundum aggregates, titanium dioxide-coated alumina microspheres, calcium sulfide dihydrate and porous silicon carbide microspheres; the B material comprises chromium oxide-zirconium oxide composite nano powder, sodium thiosulfate pentahydrate, tricalcium phosphate and hexagonal boron nitride flaky crystals; and the C material comprises an aluminum dihydrogen phosphate-magnesium hydroxide compound, a calcium fluoride-alumina eutectic body and a silane coupling agent. The preparation process comprises pretreatment of components, preparation of composite powder and layered preparation; and the construction process comprises the steps of pretreatment, wet mixing, layered ramming, negative pressure infiltration, medium-temperature reaction, spraying and curing and overall sintering. The application can effectively inhibit the generation of hexavalent chromium, significantly improve the thermal shock resistance, mechanical strength and heat conduction performance of the material, and has the advantages of good environmental protection, long service life, excellent construction performance and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of chrome corundum ramming mass, and particularly relates to a modified chrome corundum ramming mass and a preparation and construction process. BACKGROUND

[0002] As an important part of the refractory industry, chrome corundum ramming mass plays an irreplaceable role in the field of modern high-temperature industry. This kind of material is mainly composed of chrome corundum particles, binders and various functional additives, and through specific proportioning and preparation process, it forms a composite material with excellent refractory performance. The core component of chrome corundum ramming mass is chrome corundum, which has a very high melting point and good chemical stability, so that it can maintain structural integrity and functional stability in extreme high-temperature environments. The material is mainly used for furnace lining protection in industries such as metallurgy, steel and non-ferrous metal smelting, and can resist the chemical corrosion and physical erosion of molten metal in extreme high-temperature environments, ensuring the long-term stable operation of industrial furnaces. The core component of chrome corundum ramming mass is chrome corundum, which has a high melting point and good chemical stability, so that it can maintain structural integrity under high-temperature conditions. However, traditional chrome corundum ramming mass has a series of inherent defects in high-temperature oxidizing environments, which not only limits its performance, but also brings serious environmental and health risks.

[0003] In high-temperature application scenarios, traditional chrome corundum ramming mass is prone to oxidation of chromium elements, leading to the generation of hexavalent chromium compounds. Hexavalent chromium is a highly carcinogenic substance that poses a significant threat to the environment and human health. Its strong oxidizing property can cause respiratory diseases and skin corrosion, and it can accumulate in the environment for a long time, causing persistent pollution of soil and water. In addition, the existing ramming mass has poor thermal shock resistance and is prone to cracking and peeling in frequent cold and hot cycles, significantly shortening the service life of the material. Structurally, the porosity of traditional materials is high, and oxidizing media can easily penetrate the pores to the inside, accelerating the oxidation process of chromium and reducing the overall density. In addition, the existing ramming mass is prone to softening or failure at high temperatures and cannot withstand long-term thermal stress. Poor thermal conductivity leads to uneven temperature distribution in the furnace, affecting thermal efficiency and accelerating local material degradation. In terms of construction process, the existing method is difficult to achieve deep compounding and uniform distribution of components, and the interlayer bonding force is weak, which is prone to interface peeling. These problems together limit the comprehensive performance of traditional ramming mass, which cannot meet the increasingly stringent environmental standards and high-performance requirements.

[0004] Therefore, it is of great significance to develop an environmentally friendly modified chrome corundum ramming mass and a preparation process that improves the comprehensive performance. SUMMARY

[0005] To solve the problems in the background art, the present application provides a modified chrome corundum ramming mass, which comprises three components of A material, B material and C material in terms of weight fraction, wherein:

[0006] Material A includes: 45-55 parts of chromium corundum aggregate Cr2O3·Al2O3; 8-12 parts of titanium dioxide-coated alumina microspheres TiO2@Al2O3; 2-4 parts of calcium sulfide dihydrate CaS·2H2O; and 3-5 parts of porous silicon carbide microspheres β-SiC.

[0007] Material B includes: chromium oxide-zirconia composite nanopowder Cr2O3-ZrO2: 12-18 parts; sodium thiosulfate pentahydrate Na2S2O3·5H2O: 3-6 parts; tricalcium phosphate Ca3(PO4)2: 4-8 parts; hexagonal boron nitride plate crystals h-BN: 2-4 parts;

[0008] Material C includes: aluminum dihydrogen phosphate-magnesium hydroxide complex Al(H2PO4)3-Mg(OH)2: 8-15 parts; calcium fluoride-alumina eutectic CaF2-Al2O3: 2-5 parts; γ-methacryloyloxypropyltrimethoxysilane KH-570: 0.5-1.5 parts.

[0009] In the preferred embodiment, chromium corundum aggregate Cr2O3·Al2O3 is prepared by electrofusion method: chromium oxide Cr2O3 and alumina Al2O3 are mixed in a molar ratio of 1:3-1:5 and melted in an electric arc furnace at 1800-2000℃ for 4-6 hours. During the melting process, reducing agent coke is added to control the chromium oxide content. After melting, it is cast into ingots, cooled and crushed to a particle size of 0.5-3mm to obtain chromium corundum aggregate with a chromium oxide content of 15-25%.

[0010] Calcium sulfide dihydrate (CaS·2H2O) is prepared by reacting calcium hydroxide with hydrogen sulfide: calcium hydroxide powder (Ca(OH)2) is placed in a reactor, and hydrogen sulfide (H2S) gas is introduced at 80-120℃ for 2-4 hours. During the reaction, the pH value is controlled at 8-9. After the reaction is completed, the mixture is filtered and washed, and then dried at 60-80℃ for 12-24 hours to obtain calcium sulfide dihydrate with a purity ≥98% and a particle size of 200-400 mesh.

[0011] Porous silicon carbide microspheres (β-SiC) were prepared using a sol-gel method: tetraethyl orthosilicate (Si(OC2H5)4) and phenolic resin were mixed in a molar ratio of 1:2, and deionized water and hydrochloric acid catalyst were added. The mixture underwent hydrolysis and condensation at 60°C to form a gel. The precursor microspheres were obtained by spray drying and then carbonized at 1400-1500°C under a nitrogen atmosphere for 3-4 hours to obtain microspheres with a porosity of 35-45%, an average pore size of 5-15 μm, and a specific surface area of ​​8-15 m². 2 / g of porous silicon carbide microspheres;

[0012] Chromium oxide-zirconia composite nanopowder Cr2O3-ZrO2 was prepared by coprecipitation method: chromium trichloride CrCl3·6H2O and zirconium oxychloride ZrOCl2·8H2O were mixed in a molar ratio of 3:1-5:1 to form a mixed solution. Ammonia water was added under vigorous stirring to adjust the pH to 8-9 to form a coprecipitate. After filtration and washing, the solution was dried at 110℃ for 24 hours and then calcined at 1200-1300℃ for 2-4 hours to obtain α-type chromium oxide and monoclinic zirconium oxide composite nanopowder with an average particle size of 20-50 nm.

[0013] Hexagonal boron nitride plate-like crystals (h-BN) are prepared by reacting boric acid with ammonia: boric acid (H3BO3) powder is placed in a graphite crucible, and under a protective atmosphere of ammonia (NH3), the temperature is increased to 1000-1200℃ at a heating rate of 5℃ / min, and held for 4-6 hours. The ammonia flow rate is controlled at 200-300mL / min. After the reaction is completed, the mixture is naturally cooled to room temperature and then mechanically ground and dispersed to obtain hexagonal boron nitride plate-like crystals with a diameter of 10-50μm and a thickness of 0.5-2μm.

[0014] This invention provides a preparation process for modified chromium corundum ramming mix, comprising the following steps:

[0015] S1, Preparation of titanium dioxide-coated alumina microspheres: α-Al2O3 microspheres with a particle size of 1-3 μm were pretreated to remove surface impurities and then placed in a fluidized bed reactor. The reactor was preheated to 400℃, and then titanium tetrachloride (TiCl4) vapor and water vapor (H2O) were introduced. The molar ratio of titanium tetrachloride to water vapor was controlled at 1:2-1:4. Chemical vapor deposition reaction was carried out at a temperature of 450-550℃ for 60-90 minutes. During the reaction, the fluidizing gas flow rate was controlled at 0.8-1.2 m / s, and the reaction pressure was atmospheric pressure. Alumina microspheres with a uniform surface coating of titanium dioxide with a thickness of 50-100 nm were obtained.

[0016] S2, Preparation of chromium oxide-zirconia composite nanopowder: Chromium oxide Cr2O3 nanopowder and zirconia ZrO2 nanopowder are accurately weighed and mixed at a mass ratio of 3:1-5:1, and deionized water is added to prepare a slurry with a solid content of 50-60%. The slurry is fed into a ball mill with zirconia balls as the grinding medium, a ball-to-material ratio of 3:1-5:1, a rotation speed of 200-300 r / min, and ball milling for 24-36 hours until the particle size is uniform. The slurry is spray-dried to remove moisture and calcined at 1200-1300℃ for 2-4 hours with a heating and cooling rate controlled at 5℃ / min to obtain well-crystallized chromium oxide-zirconia composite nanopowder.

[0017] S3, Preparation of aluminum dihydrogen phosphate-magnesium hydroxide composite: Add aluminum hydroxide Al(OH)3 powder to a reaction vessel, slowly add 85% phosphoric acid H3PO4 solution, and react aluminum hydroxide and phosphoric acid at a molar ratio of 1:3. React for 4-6 hours at a temperature of 25-35℃ and a stirring speed of 300-500r / min to obtain aluminum dihydrogen phosphate solution. Then add magnesium hydroxide Mg(OH)2 powder and continue stirring for 2 hours to disperse it evenly. Finally, dry at 60-80℃ for 24-48 hours to obtain aluminum dihydrogen phosphate-magnesium hydroxide composite.

[0018] S4, Preparation of calcium fluoride-alumina eutectic: Calcium fluoride (CaF2) and alumina (Al2O3) are mixed evenly in a precise molar ratio of 1:1 and placed in a platinum crucible. Under an argon protective atmosphere, the mixture is heated to 1400-1500℃ and melted for 2-3 hours. During the melting process, the mixture is intermittently stirred to ensure complete reaction. After the reaction is completed, the mixture is rapidly cooled to room temperature at a cooling rate of 50-100℃ / min. The mixture is then coarsely crushed using a jaw crusher and finely ground to 100-300 mesh using a ball mill to obtain the calcium fluoride-alumina eutectic.

[0019] S5, Preparation of A material: Chromium corundum aggregate, titanium dioxide-coated alumina microspheres prepared in step S1, calcium sulfide dihydrate CaS·2H2O, and silicon carbide porous microspheres β-SiC are put into a forced mixer and dry-mixed at room temperature for 10-15 minutes. The mixing speed is controlled at 60-80 r / min. The mixture is added in 3 batches during the mixing process, with an interval of 2-3 minutes between each batch, to obtain A material with uniform component distribution.

[0020] S6, Preparation of B material: The chromium oxide-zirconia composite nanopowder prepared in step S2, sodium thiosulfate pentahydrate Na2S2O3·5H2O, tricalcium phosphate Ca3(PO4)2, and hexagonal boron nitride plate crystals h-BN are put into a mixing device and dry-mixed for 8-12 minutes under nitrogen protection. The temperature is controlled not to exceed 40℃ during the mixing process to obtain B material with stable chemical composition.

[0021] Preparation of S7, C material: The aluminum dihydrogen phosphate-magnesium hydroxide composite prepared in step S3, the calcium fluoride-alumina eutectic prepared in step S4, and γ-methacryloyloxypropyltrimethoxysilane KH-570 are sequentially added to the reactor. First, the silane coupling agent is mixed with the composite for 3 minutes, and then the eutectic is added and stirred evenly for 5 minutes. The stirring speed is controlled at 100-150 r / min to obtain C material with good bonding performance.

[0022] In the preferred embodiment, in step S1, the chemical vapor deposition reaction is carried out in a temperature zone within the reactor: the preheating zone temperature is 350-400℃, the reaction zone temperature is 450-550℃, and the post-treatment zone temperature is 300-350℃. High-purity nitrogen is used as the carrier gas, with a flow rate of 100-200 mL / min. The coating thickness is monitored in real time during the reaction, and the reaction is stopped when it reaches 50-100 nm, resulting in uniformly coated and firmly bonded titanium dioxide-coated alumina microspheres.

[0023] In the preferred embodiment, in step S2, the ball milling process is divided into two stages: coarse milling and fine milling. The coarse milling is carried out for 12 hours at a speed of 200 r / min, and the fine milling is carried out for 12-24 hours at a speed of 250-300 r / min. The particle size distribution is checked every 6 hours during the ball milling process. The ball milling is ended when the D90 particle size reaches 100-200 nm. The inlet air temperature of the spray drying is 180-220℃, and the outlet air temperature is 80-100℃, so as to obtain composite nanopowder with good dispersibility and uniform particle size.

[0024] In a preferred embodiment, in step S3, the reaction between aluminum hydroxide and phosphoric acid is carried out by dropwise addition, with the phosphoric acid being added at a rate of 2-5 mL / min. During the dropwise addition, the system temperature is controlled to not exceed 40°C. During the reaction, the pH value drops from 12 to 2-3, and after the addition of magnesium hydroxide, the pH value rises back to 6-7. The drying process is carried out by vacuum drying, with the pressure controlled at -0.08 to -0.1 MPa, to obtain a structurally stable and uniformly dispersed aluminum dihydrogen phosphate-magnesium hydroxide complex.

[0025] In the preferred embodiment, in step S4, the melting reaction is carried out in a high-temperature furnace, with the heating rate controlled at 10℃ / min. During the melting process, the argon flow rate is 5-10L / min, and the mixture is stirred once every 30 minutes for 1-2 minutes each time. The complete melting is indicated by the melt being uniformly transparent. Rapid cooling is achieved using a metal mold, and the crushing process involves first coarse crushing to 10-20mm, and then fine grinding to the required particle size to obtain a dense and highly active calcium fluoride-alumina eutectic.

[0026] This invention also provides a construction process for modified chromium corundum ramming mix, comprising the following steps:

[0027] Q1, Pretreatment of Material A: Material A is placed in a muffle furnace and pre-sintered in an oxidizing atmosphere. The gas flow rate is controlled at 5-10 L / min, the heating rate is 5℃ / min, and the pre-sintering is carried out at 1100-1150℃ for 25-35 minutes. The thickness of the charge does not exceed 50 mm. After pre-sintering, the material is naturally cooled to room temperature and crushed to a particle size of 3-5 mm using a jaw crusher to obtain pre-treated Material A with enhanced strength and improved activity.

[0028] Q2, Wet mixing of A material: Add deionized water to the pretreated A material in batches, with the water-to-material mass ratio controlled at 6-8%. The water addition process is carried out in 3-4 times, with an interval of 30-60 seconds between each addition. Mix in a mixer at a speed of 60-100 r / min for 3-5 minutes. Monitor the uniformity of moisture content during the mixing process to obtain a wet A material with uniform moisture content and good plasticity.

[0029] Q3, Layered tamping of Material A: The moistened Material A is layered onto the cleaned furnace bottom, with each layer strictly controlled to a thickness of 15-20mm. A pneumatic tamping machine is used for compaction, with tamping pressure controlled at 0.4-0.6MPa. The number of tamping passes per square meter is no less than 50, achieving a tamping density of 2.8-3.2g / cm³. 3 The interlayer bonding is achieved by serration treatment, resulting in a dense, uniform, and bubble-free A material;

[0030] Q4, Activation treatment of material B: Dissolve sodium hydroxide (NaOH) and disodium hydrogen phosphate (Na2HPO4) in deionized water in a certain proportion. The concentration of sodium hydroxide is 0.1-0.3 mol / L and the concentration of disodium hydrogen phosphate is 0.05-0.15 mol / L. Adjust the pH value to 8.5-9.2. Mix material B with the activation solution at a liquid-to-material mass ratio of 12-15%. After mixing evenly in a stirrer, let it stand for 15-20 minutes to obtain the activated material B slurry.

[0031] Q5, Negative Pressure Permeation of Material B: The activated material B slurry is loaded into the permeation tank, and the negative pressure is adjusted to -0.015 to -0.025 MPa. The slurry is injected into material A through the permeation pipe. The permeation time is controlled at 10-20 minutes, and the permeation depth is 60-80% of the thickness of material A, so as to obtain an intermediate that is well composited with material B and material A.

[0032] Q6, Medium-temperature reaction treatment: Place material A that has been permeated with material B in a medium-temperature furnace and heat it to 350-450℃ at a heating rate of 2-3℃ / min. Keep it at this temperature for 80-100 minutes. During the reaction, introduce a small amount of water vapor to maintain humidity. The reaction atmosphere is weakly oxidizing. After the reaction is completed, slowly cool it to room temperature to obtain a preliminarily combined composite structure.

[0033] Q7, C material dispersion treatment: Add C material to deionized water to prepare a suspension with a mass concentration of 25-35%, and disperse it using an ultrasonic disperser for 12-18 minutes. During the dispersion process, control the temperature to not exceed 60℃, and stop for 1 minute every 3 minutes of dispersion to prevent overheating, so as to obtain a uniformly dispersed C material suspension without agglomeration.

[0034] Q8, C material spraying and curing: Using specialized spraying equipment, the dispersed C material suspension is evenly sprayed onto the surface of the intermediate in an atomized manner. The spraying pressure is controlled at 0.2-0.4MPa, the spraying distance is maintained at 20-30cm, and the spraying thickness is 2-3mm. After spraying, it is cured at 180-220℃ for 60-90 minutes. Dry air is introduced during the curing process to obtain a smooth and firmly bonded protective layer.

[0035] Q9, Overall Firing: The product coated with C material is fired according to a strict heating curve. The first stage is 20-300℃ with a heating rate of 1℃ / min to remove physical water and organic matter. The second stage is 300-800℃ with a heating rate of 2℃ / min to carry out chemical reactions and preliminary sintering. The third stage is 800-1250℃ with a heating rate of 1.5℃ / min to complete high-temperature sintering. The product is held at 1250℃ for 4-6 hours and fired in a weakly reducing atmosphere of carbon monoxide. The total firing time is 24-30 hours to obtain the modified chromium corundum ramming mix product.

[0036] In the preferred embodiment, in step Q1, the pre-sintering process adopts programmed temperature control, with an initial heating rate of 3℃ / min to 500℃, and then a rate of 5℃ / min to the pre-sintering temperature. The oxygen content in the pre-sintering atmosphere is controlled at 18-21%. The linear change rate of the sample is measured every 10 minutes during the pre-sintering process. When the linear change rate is stable within ±0.1%, the pre-sintering is completed, and a pre-sintered material A with stable dimensions and suitable strength is obtained.

[0037] In step Q2, the mixing process uses a planetary mixer with a main shaft speed of 60-100 r / min and an auxiliary mixing paddle speed of 2-3 times the main shaft speed. The mixing uniformity is checked every minute during the mixing process. When the difference in moisture content at different locations is less than 0.5%, the mixing is considered complete, resulting in a moist A material with uniform moisture distribution and good workability.

[0038] In step Q4, the activation solution is prepared by a stepwise dissolution method. Sodium hydroxide is completely dissolved first, and then disodium hydrogen phosphate is added. The temperature is controlled at 20-30℃ during the dissolution process. After preparation, the solution is left to stand for 2-4 hours to allow it to become completely clear. During the activation process, the solution is stirred every 5 minutes at a speed of 100-200 r / min. During the standing process, a film is covered to prevent moisture evaporation, resulting in a chemically activated B slurry.

[0039] In the preferred embodiment, in step Q5, the negative pressure permeation equipment includes a vacuum pump, a pressure regulating valve, a permeation tank, and a monitoring system. Before permeation, material A is pretreated under vacuum for 30-60 seconds. During the permeation process, the permeation depth is monitored in real time. When the permeation resistance suddenly increases, the negative pressure value is appropriately increased. After the permeation is completed, the negative pressure state is maintained for 5-10 minutes to ensure sufficient permeation, resulting in a composite layer structure with uniform permeation depth and tight bonding.

[0040] In step Q9, the temperature deviation during the firing process is controlled within ±5℃. During the heat preservation stage, the phase change of the sample is measured once per hour. When the expected high-temperature phase is detected, the heat preservation is completed. During the cooling process, the cooling rate is strictly controlled at 50-100℃ / h to 800℃. Then, the sample is naturally cooled to room temperature to obtain a finished modified chromium corundum ramming mix with a dense structure and excellent performance.

[0041] The beneficial effects achieved by this invention are as follows:

[0042] First, this invention designs three components: component A serves as the base aggregate providing high-temperature stability; component B acts as a functional component, exerting a chemical reduction effect to inhibit the formation of hexavalent chromium; and component C acts as a protective component, forming a dense barrier. These components complement each other, working synergistically to block oxidation pathways, inhibit hexavalent chromium formation through chemical reduction, and seal gas permeation channels. In the formula, titanium dioxide-coated alumina microspheres form a uniform and dense rutile protective film on the surface of the chromium corundum aggregate, physically preventing direct contact between oxygen and chromium. Sodium thiosulfate pentahydrate, as a highly efficient reducing medium, undergoes controlled decomposition during the intermediate-temperature reaction stage. The released active sulfur ions selectively complex with any potentially generated hexavalent chromium, transforming it into stable chromium sulfide compounds. Silicon carbide porous microspheres, through their precisely controlled pore structure, provide directional channels for the permeation of component B, and their β-phase crystal structure maintains stable physicochemical properties at high temperatures. Material C employs a synergistic system of aluminum dihydrogen phosphate-magnesium hydroxide composite and calcium fluoride-alumina eutectic. During high-temperature sintering, a low-permeability composite ceramic phase is generated in situ. The quartz-type crystal structure formed by aluminum dihydrogen phosphate, together with the magnesium oxide derivative, constructs a dense microscopic barrier. The molecular bridging effect of the silane coupling agent significantly enhances the interfacial bonding strength between heterogeneous layers by establishing chemical bonds at the organic-inorganic interface. The high electronegativity of fluoride ions forms a charge-protective layer on the outermost layer of the material, further inhibiting the diffusion and penetration of oxidizing media.

[0043] Secondly, in the preparation process, this invention employs chemical vapor deposition technology to achieve uniform growth of nanoscale titanium dioxide coatings by precisely controlling the temperature zones of the fluidized bed and the ratio of reactant gases. The silicon carbide porous microspheres prepared by the sol-gel method exhibit tunable pore size distribution and high specific surface area. The chromium oxide-zirconia composite nanopowder prepared by co-precipitation combined with high-energy ball milling fully utilizes the toughening effect of zirconia phase transformation and the surface effect of nanoparticles. The calcium fluoride-alumina eutectic formed by the melt-quench process retains the high reactivity of the non-equilibrium state, providing an excellent liquid phase medium for the sintering process.

[0044] Third, in the construction process, pre-sintering treatment removes impurities from the aggregate surface and forms active sites through a controlled oxidation process. Layered tamping combined with pneumatic compaction technology ensures a uniform distribution of the pore structure in the base layer, while scoring enhances the mechanical interlocking between layers. The negative pressure infiltration process utilizes a pressure gradient to drive deep diffusion of functional components, and its infiltration depth control mechanism enables component B to form a three-dimensional network structure within component A. The segmented firing regime, by matching the physicochemical changes in different temperature ranges, ultimately forms a stable ceramic structure with fine grains and fused interfaces.

[0045] Fourth, the modified chromium corundum ramming mix of this invention solves the environmental problems of traditional chromium corundum materials while significantly improving performance, showing broad application prospects. Hexavalent chromium pollution generated during the production and use of traditional chromium corundum refractories has always been a major environmental problem facing the industry. This invention reduces the hexavalent chromium content by more than 95%, which is of great significance for protecting the ecological environment and human health. Verification shows that the hexavalent chromium content of the modified chromium corundum ramming mix of this invention is controlled below 2 mg / kg, an average reduction of more than 95% compared to the control group, achieving effective inhibition of hexavalent chromium. In terms of performance, thermal shock resistance is increased by 50-80%, mechanical strength by 25-40%, thermal conductivity by 35-45%, and service life is extended by 1.5-2.0 times, with significant improvements in all indicators. Attached Figure Description

[0046] Figure 1 This is a comparison chart of the mechanical and physical properties of Examples 1-4 and the average values ​​of each comparative example group;

[0047] Figure 2 This is a comparison chart of the environmental performance and structural performance of Examples 1-4 and the average values ​​of each comparative example group;

[0048] Figure 3 This is a comparison chart of the key performance improvement of Examples 1-4 relative to the average value of the corresponding group comparison examples;

[0049] Figure 4 This is a comparison chart of the long-term performance of Examples 1-4 and the average values ​​of each comparative example group;

[0050] Figure 5 This is a flowchart illustrating the preparation and construction process of the modified chromium corundum ramming mix of the present invention. Detailed Implementation

[0051] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. In addition, the forms of the various structures described in the following embodiments are merely illustrative. The present invention is not limited to the structures described in the following embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0052] This invention provides a modified chromium corundum ramming mix, comprising material A, material B, and material C in parts by weight; wherein:

[0053] Material A includes: 45-55 parts of chromium corundum aggregate Cr2O3·Al2O3; 8-12 parts of titanium dioxide-coated alumina microspheres TiO2@Al2O3; 2-4 parts of calcium sulfide dihydrate CaS·2H2O; and 3-5 parts of porous silicon carbide microspheres β-SiC.

[0054] Material B includes: chromium oxide-zirconia composite nanopowder Cr2O3-ZrO2: 12-18 parts; sodium thiosulfate pentahydrate Na2S2O3·5H2O: 3-6 parts; tricalcium phosphate Ca3(PO4)2: 4-8 parts; hexagonal boron nitride plate crystals h-BN: 2-4 parts;

[0055] Material C includes: aluminum dihydrogen phosphate-magnesium hydroxide complex Al(H2PO4)3-Mg(OH)2: 8-15 parts; calcium fluoride-alumina eutectic CaF2-Al2O3: 2-5 parts; γ-methacryloyloxypropyltrimethoxysilane KH-570: 0.5-1.5 parts.

[0056] Chromium corundum aggregate Cr2O3·Al2O3 is prepared by electrofusion method: chromium oxide Cr2O3 and alumina Al2O3 are mixed in a molar ratio of 1:3-1:5 and melted in an electric arc furnace at 1800-2000℃ for 4-6 hours. During the melting process, reducing agent coke is added to control the chromium oxide content. After melting, it is cast into ingots, cooled and crushed to a particle size of 0.5-3mm to obtain chromium corundum aggregate with a chromium oxide content of 15-25%.

[0057] Calcium sulfide dihydrate (CaS·2H2O) is prepared by reacting calcium hydroxide with hydrogen sulfide: calcium hydroxide powder (Ca(OH)2) is placed in a reactor, and hydrogen sulfide (H2S) gas is introduced at 80-120℃ for 2-4 hours. During the reaction, the pH value is controlled at 8-9. After the reaction is completed, the mixture is filtered and washed, and then dried at 60-80℃ for 12-24 hours to obtain calcium sulfide dihydrate with a purity ≥98% and a particle size of 200-400 mesh.

[0058] Porous silicon carbide microspheres (β-SiC) were prepared using a sol-gel method: tetraethyl orthosilicate (Si(OC2H5)4) and phenolic resin were mixed in a molar ratio of 1:2, and deionized water and hydrochloric acid catalyst were added. The mixture underwent hydrolysis and condensation at 60°C to form a gel. The precursor microspheres were obtained by spray drying and then carbonized at 1400-1500°C under a nitrogen atmosphere for 3-4 hours to obtain microspheres with a porosity of 35-45%, an average pore size of 5-15 μm, and a specific surface area of ​​8-15 m². 2 / g of porous silicon carbide microspheres;

[0059] Chromium oxide-zirconia composite nanopowder Cr2O3-ZrO2 was prepared by coprecipitation method: chromium trichloride CrCl3·6H2O and zirconium oxychloride ZrOCl2·8H2O were mixed in a molar ratio of 3:1-5:1 to form a mixed solution. Ammonia water was added under vigorous stirring to adjust the pH to 8-9 to form a coprecipitate. After filtration and washing, the solution was dried at 110℃ for 24 hours and then calcined at 1200-1300℃ for 2-4 hours to obtain α-type chromium oxide and monoclinic zirconium oxide composite nanopowder with an average particle size of 20-50 nm.

[0060] Hexagonal boron nitride plate-like crystals (h-BN) are prepared by reacting boric acid with ammonia: boric acid (H3BO3) powder is placed in a graphite crucible, and under a protective atmosphere of ammonia (NH3), the temperature is increased to 1000-1200℃ at a heating rate of 5℃ / min, and held for 4-6 hours. The ammonia flow rate is controlled at 200-300mL / min. After the reaction is completed, the mixture is naturally cooled to room temperature and then mechanically ground and dispersed to obtain hexagonal boron nitride plate-like crystals with a diameter of 10-50μm and a thickness of 0.5-2μm.

[0061] In material A, the chromium corundum aggregate Cr2O3·Al2O3 serves as a refractory component, providing high-temperature structural strength and corrosion resistance. Titanium dioxide-coated alumina microspheres (TiO2@Al2O3) form a dense oxide protective film at high temperatures, effectively blocking direct contact between external oxygen and chromium, thus inhibiting the oxidation of hexavalent chromium at its source. Calcium sulfide dihydrate (CaS·2H2O) acts as a chemical trapping agent, combining with potentially generated hexavalent chromium ions to form stable sulfide complexes, achieving in-situ solidification of harmful ions. Silicon carbide porous microspheres (β-SiC), through their unique porous structure, regulate the porosity and permeability of the entire base layer, providing a suitable pore network for the penetration of subsequent intermediate functional layers.

[0062] The chromium oxide-zirconia composite nanopowder Cr2O3-ZrO2 in material B enhances the material's density and thermal shock resistance through its nano-effect, while the stabilizing effect of zirconium oxide helps suppress the unstable transformation of the chromium phase. Sodium thiosulfate pentahydrate Na2S2O3·5H2O is a key chemical reducing agent, rapidly reducing any formed hexavalent chromium to low-toxicity trivalent chromium under intermediate temperature conditions, ensuring the material's environmental safety. Tricalcium phosphate Ca3(PO4)2 acts as a pH buffer, maintaining the entire system within a suitable pH range and providing a stable chemical environment for the reduction reaction. Hexagonal boron nitride plate-like crystals h-BN, with their excellent thermal conductivity and plate-like structure, form a highly efficient thermal channel network, ensuring uniform heat transfer and distribution within the material.

[0063] The aluminum dihydrogen phosphate-magnesium hydroxide composite Al(H2PO4)3-Mg(OH)2 in material C undergoes a dehydration reaction at high temperature to form a dense aluminum phosphate ceramic phase, exhibiting excellent chemical stability and low permeability, effectively preventing the penetration and diffusion of external oxidizing gases into the inner layer. The calcium fluoride-alumina eutectic CaF2-Al2O3, as a fluxing agent, lowers the reaction temperature during sintering and promotes densification between components; simultaneously, the presence of fluoride ions further inhibits the oxidation reaction of chromium. γ-methacryloyloxypropyltrimethoxysilane KH-570, as a molecular-level interface modifier, establishes chemical bridges between organic and inorganic interfaces through its bifunctional structure, significantly improving the interfacial bonding strength between different layers and the integrity of the overall structure.

[0064] Material A is the basic aggregate of the entire ramming mix. Chromium corundum aggregate Cr2O3·Al2O3 serves as the refractory component, where chromium oxide (Cr2O3) and alumina (Al2O3) form a solid solution structure. This spinel-type structure exhibits excellent high-temperature stability and corrosion resistance. At high temperatures, the solid solution structure effectively inhibits the free migration of chromium ions, reducing the thermodynamic driving force for hexavalent chromium formation from a crystallographic perspective. The design of titanium dioxide-coated alumina microspheres (TiO2@Al2O3) is based on a heterogeneous core-shell structure protection mechanism. The Al2O3 microspheres act as the core, providing structural support, while the outer TiO2 coating layer exhibits excellent chemical inertness in high-temperature oxidizing atmospheres. The rutile crystal structure of TiO2 forms a dense oxide protective film at high temperatures, effectively blocking direct contact between external oxygen molecules and internal chromium elements, thus fundamentally inhibiting Cr oxidation. 3+ To Cr 6+ The oxidation transformation reaction.

[0065] Calcium sulfide dihydrate (CaS·2H2O) acts as a unique chemical scavenger, its mechanism of action based on the strong affinity between sulfide ions and hexavalent chromium. Under high-temperature conditions, CaS undergoes a thermal decomposition reaction: CaS·2H2O → CaS + 2H2O↑, releasing sulfur dioxide (S). 2- Ions and possible Cr 6+ Ions undergo chemical complexation reactions to form stable CrS3 complexes or other chromium sulfide compounds. These sulfides exhibit good thermodynamic stability at high temperatures, achieving in-situ solidification of harmful hexavalent chromium ions and preventing their release into the environment. The introduction of silicon carbide porous microspheres β-SiC is based on its unique porous structure regulation mechanism. β-SiC (cubic silicon carbide) has a tetrahedral coordinated crystal structure, and the porous structure formed during the preparation process through the sol-gel method precisely controls the pore size distribution. The porous network not only regulates the porosity and permeability of the entire base layer, but more importantly, it provides a directional pore network for the subsequent penetration of B material, ensuring that chemically active components effectively penetrate into the interior of the base layer.

[0066] The design of the chromium oxide-zirconia composite nanopowder Cr2O3-ZrO2 in material B is based on the synergistic effect of nanocomposite materials, in which the introduction of ZrO2 (zirconia) plays a key stabilizing role. ZrO2 exhibits polymorphic transformation characteristics, existing as monoclinic and tetragonal phases at high temperatures. The phase transformation process is accompanied by volume changes, generating a micro-stress field within the material, which helps to suppress the unstable transformation of the chromium phase. Simultaneously, the nanoscale particle size effect enhances the material's density and thermal shock resistance. Sodium thiosulfate pentahydrate Na2S2O3·5H2O is a key component of the entire reduction system, and its molecular structure contains S2O3. 2-Sodium thiosulfate (Na₂S) ions have strong reducing properties. Under moderate temperature conditions (around 400°C), sodium thiosulfate undergoes thermal decomposition, producing Na₂S, which has an even stronger reducing ability, capable of reducing any Cr₂S formed. 6+ Rapidly reduced to low-toxicity Cr 3+ The thermodynamic spontaneity of the reduction reaction ensures the effective elimination of hexavalent chromium. Tricalcium phosphate (Ca3(PO4)2) plays an important role as a pH buffer in the system, as its molecular structure contains PO4. 3- (Phosphate) ions exhibit amphoteric properties in aqueous solutions, reacting with H+. + or OH - Ions combine to form different hydrogen phosphate ions. Through... and The equilibrium reaction is maintained within a suitable pH range, providing a stable chemical environment for the reduction reaction. The introduction of hexagonal boron nitride (h-BN) plate-like crystals is based on its unique layered structure and excellent thermal conductivity. h-BN has a graphite-like layered structure with strong covalent BN bonds within the layers and van der Waals forces between the layers, giving it excellent thermal conductivity perpendicular to the layers. At the same time, the plate-like morphology forms a network of thermally conductive channels in the material, ensuring uniform heat transfer and distribution within the material and avoiding phase transitions and performance degradation caused by local overheating.

[0067] The design of the aluminum dihydrogen phosphate-magnesium hydroxide composite Al(H2PO4)3-Mg(OH)2 in material C is based on the in-situ generation of a high-temperature ceramic phase. Al(H2PO4)3 undergoes a dehydration condensation reaction at high temperature: Al(H2PO4)3 → AlPO4 + 2H3PO4. The resulting AlPO4 has a quartz-type crystal structure, which exhibits excellent chemical stability and low permeability at high temperatures. Simultaneously, Mg(OH)2 decomposes during heating: Mg(OH)2 → MgO + H2O↑. The generated MgO reacts with phosphoric acid to form Mg3(PO4)2. The composite ceramic phase structure effectively prevents the penetration and diffusion of external oxidizing gases into the inner layer.

[0068] The calcium fluoride-alumina eutectic CaF2-Al2O3, acting as a fluxing agent, operates through a low-temperature liquid-phase sintering mechanism based on the eutectic system. CaF2, with its fluorite-type crystal structure and melting point of approximately 1418℃, forms a eutectic with Al2O3 at high temperatures, significantly reducing the system's sintering temperature. More importantly, F... -It possesses strong electronegativity and a small ionic radius, forming a dense fluoride protective layer on the material surface, further inhibiting oxygen diffusion and chromium oxidation. γ-Methacryloxypropyltrimethoxysilane KH-570 is a bifunctional silane coupling agent with the molecular structure CH2=C(CH3)COO(CH2)3Si(OCH3)3, containing both the organic functional group methacryloyloxy and the inorganic functional group trimethoxysilyl. On the material surface, the trimethoxysilyl group reacts chemically with the hydroxyl groups on the inorganic oxide surface:

[0069] The reaction ≡Si-OCH3+HO-M≡→≡Si-OM≡+CH3OH forms a stable silicon-oxygen bond, while the organic functional groups undergo cross-linking reactions with the organic components, thereby establishing a chemical bridge between the organic and inorganic interfaces, significantly improving the interfacial bonding strength between different layers and the integrity of the overall structure.

[0070] Reference Figure 5 The present invention also provides a preparation process for modified chromium corundum ramming mix, comprising the following steps:

[0071] S1, Preparation of titanium dioxide-coated alumina microspheres: α-Al2O3 microspheres with a particle size of 1-3 μm were pretreated to remove surface impurities and then placed in a fluidized bed reactor. The reactor was preheated to 400℃, and then titanium tetrachloride (TiCl4) vapor and water vapor (H2O) were introduced. The molar ratio of titanium tetrachloride to water vapor was controlled at 1:2-1:4. Chemical vapor deposition reaction was carried out at a temperature of 450-550℃ for 60-90 minutes. During the reaction, the fluidizing gas flow rate was controlled at 0.8-1.2 m / s, and the reaction pressure was atmospheric pressure. Alumina microspheres with a uniform surface coating of titanium dioxide with a thickness of 50-100 nm were obtained.

[0072] S2, Preparation of chromium oxide-zirconia composite nanopowder: Chromium oxide Cr2O3 nanopowder and zirconia ZrO2 nanopowder are accurately weighed and mixed at a mass ratio of 3:1-5:1, and deionized water is added to prepare a slurry with a solid content of 50-60%. The slurry is fed into a ball mill with zirconia balls as the grinding medium, a ball-to-material ratio of 3:1-5:1, a rotation speed of 200-300 r / min, and ball milling for 24-36 hours until the particle size is uniform. The slurry is spray-dried to remove moisture and calcined at 1200-1300℃ for 2-4 hours with a heating and cooling rate controlled at 5℃ / min to obtain well-crystallized chromium oxide-zirconia composite nanopowder.

[0073] S3, Preparation of aluminum dihydrogen phosphate-magnesium hydroxide composite: Add aluminum hydroxide Al(OH)3 powder to a reaction vessel, slowly add 85% phosphoric acid H3PO4 solution, and react aluminum hydroxide and phosphoric acid at a molar ratio of 1:3. React for 4-6 hours at a temperature of 25-35℃ and a stirring speed of 300-500r / min to obtain aluminum dihydrogen phosphate solution. Then add magnesium hydroxide Mg(OH)2 powder and continue stirring for 2 hours to disperse it evenly. Finally, dry at 60-80℃ for 24-48 hours to obtain aluminum dihydrogen phosphate-magnesium hydroxide composite.

[0074] S4, Preparation of calcium fluoride-alumina eutectic: Calcium fluoride (CaF2) and alumina (Al2O3) are mixed evenly in a precise molar ratio of 1:1 and placed in a platinum crucible. Under an argon protective atmosphere, the mixture is heated to 1400-1500℃ and melted for 2-3 hours. During the melting process, the mixture is intermittently stirred to ensure complete reaction. After the reaction is completed, the mixture is rapidly cooled to room temperature at a cooling rate of 50-100℃ / min. The mixture is then coarsely crushed using a jaw crusher and finely ground to 100-300 mesh using a ball mill to obtain the calcium fluoride-alumina eutectic.

[0075] S5, Preparation of A material: Chromium corundum aggregate, titanium dioxide-coated alumina microspheres prepared in step S1, calcium sulfide dihydrate CaS·2H2O, and silicon carbide porous microspheres β-SiC are put into a forced mixer and dry-mixed at room temperature for 10-15 minutes. The mixing speed is controlled at 60-80 r / min. The mixture is added in 3 batches during the mixing process, with an interval of 2-3 minutes between each batch, to obtain A material with uniform component distribution.

[0076] S6, Preparation of B material: The chromium oxide-zirconia composite nanopowder prepared in step S2, sodium thiosulfate pentahydrate Na2S2O3·5H2O, tricalcium phosphate Ca3(PO4)2, and hexagonal boron nitride plate crystals h-BN are put into a mixing device and dry-mixed for 8-12 minutes under nitrogen protection. The temperature is controlled not to exceed 40℃ during the mixing process to obtain B material with stable chemical composition.

[0077] Preparation of S7, C material: The aluminum dihydrogen phosphate-magnesium hydroxide composite prepared in step S3, the calcium fluoride-alumina eutectic prepared in step S4, and γ-methacryloyloxypropyltrimethoxysilane KH-570 are sequentially added to the reactor. First, the silane coupling agent is mixed with the composite for 3 minutes, and then the eutectic is added and stirred evenly for 5 minutes. The stirring speed is controlled at 100-150 r / min to obtain C material with good bonding performance.

[0078] In step S1, the chemical vapor deposition reaction is carried out in a temperature zone within the reactor. The temperature of the preheating zone is 350-400℃, the temperature of the reaction zone is 450-550℃, and the temperature of the post-treatment zone is 300-350℃. High-purity nitrogen is used as the carrier gas with a flow rate of 100-200 mL / min. The coating thickness is monitored in real time during the reaction. When it reaches 50-100 nm, the reaction is stopped, resulting in uniformly coated and firmly bonded titanium dioxide-coated alumina microspheres.

[0079] In step S2, the ball milling process is divided into two stages: coarse milling and fine milling. Coarse milling lasts for 12 hours at a speed of 200 r / min, and fine milling lasts for 12-24 hours at a speed of 250-300 r / min. During the ball milling process, the particle size distribution is checked every 6 hours. The ball milling ends when the D90 particle size reaches 100-200 nm. The inlet air temperature of the spray drying is 180-220℃, and the outlet air temperature is 80-100℃, resulting in composite nanopowder with good dispersibility and uniform particle size.

[0080] In step S3, the reaction between aluminum hydroxide and phosphoric acid is carried out by dropwise addition at a rate of 2-5 mL / min. During the dropwise addition, the system temperature is controlled to not exceed 40°C. During the reaction, the pH value drops from 12 to 2-3. After the addition of magnesium hydroxide, the pH value rises back to 6-7. The drying process is carried out by vacuum drying with the pressure controlled at -0.08 to -0.1 MPa, resulting in a structurally stable and uniformly dispersed aluminum dihydrogen phosphate-magnesium hydroxide complex.

[0081] In step S4, the melting reaction is carried out in a high-temperature furnace with a heating rate controlled at 10℃ / min. During the melting process, the argon flow rate is 5-10L / min, and the mixture is stirred once every 30 minutes for 1-2 minutes each time. The complete melting is indicated by the melt being uniform and transparent. Rapid cooling is achieved using a metal mold. The crushing process involves first coarse crushing to 10-20mm, and then fine grinding to the required particle size to obtain a dense and highly active calcium fluoride-alumina eutectic.

[0082] The preparation of titanium dioxide-coated alumina microspheres employs chemical vapor deposition (CVD), a surface modification method based on gas-phase reactions. In a fluidized bed reactor, α-Al₂O₃ microspheres, acting as seed particles, are suspended in a high-temperature gas stream. Titanium tetrachloride (TiCl₄) vapor and water vapor undergo a hydrolysis reaction on the particle surface: TiCl₄ + 2H₂O → TiO₂ + 4HCl↑. The reaction is carried out within a temperature range of 450-550℃ to ensure complete reaction and avoid sintering and agglomeration caused by excessively high temperatures. The TiO₂ generated during the reaction is deposited amorphously on the Al₂O₃ surface, gradually crystallizing into a rutile phase as the reaction progresses, forming a coating layer of controllable thickness. Controlling the flow rate of the fluidizing gas is crucial for the uniformity of the coating layer; an appropriate flow rate ensures uniform particle distribution and good heat and mass transfer within the reactor.

[0083] The preparation of chromium oxide-zirconia composite nanopowder is based on a solid-state reaction mechanism using a mechanochemical method. High-energy ball milling achieves uniform mixing and partial solid solution of different phase components at the nanoscale. During ball milling, zirconia balls, acting as the grinding media, exert strong mechanical forces on the powder particles under high-speed impact. This mechanical force not only refines the particle size but, more importantly, generates numerous defects and active sites at the particle interface, promoting diffusion and reaction between different phases. The ball-to-powder ratio affects the contact probability and impact strength between the grinding media and the powder; an excessively high ratio may lead to excessive wear, while a too low ratio affects the refining effect. The subsequent high-temperature calcination process aims to eliminate the stress and defects introduced during mechanical alloying, while simultaneously promoting the improvement of the crystal structure and the stability of the phase composition. Spray drying technology is used to rapidly remove moisture, prevent agglomeration, and maintain the powder's dispersibility.

[0084] The preparation of the aluminum dihydrogen phosphate-magnesium hydroxide composite is based on the chemical synthesis mechanism of acid-base reaction. The reaction between aluminum hydroxide (Al(OH)3) and phosphoric acid (H3PO4) is an exothermic process: Al(OH)3 + 3H3PO4 → Al(H2PO4)3 + 3H2O. Strict temperature and stirring conditions are maintained during the reaction to ensure complete reaction and product homogeneity. The addition of magnesium hydroxide (Mg(OH)2) not only adjusts the pH but, more importantly, its lamellar structure forms a reinforcing phase in the composite, improving the material's mechanical properties. The drying process employs appropriate temperature and time to thoroughly remove moisture and avoid decomposition and phase transitions caused by overheating.

[0085] The preparation of the calcium fluoride-alumina eutectic is based on the phase diagram principle of high-temperature melting reaction. The CaF₂-Al₂O₃ binary system forms various intermediate compounds and a eutectic phase at high temperatures. The melting reaction is carried out under an argon protective atmosphere to prevent the volatilization and oxidation of fluorides at high temperatures. The reaction temperature is selected based on the temperature range of the liquidus region in the phase diagram; within the range of 1400-1500℃, the system forms a homogeneous liquid phase, promoting sufficient reaction and diffusion between components. Rapid cooling aims to suppress crystal growth, maintain the fine-grained structure of the eutectic, and exhibit better reactivity in subsequent applications.

[0086] The formulation of each component follows the basic principles of powder engineering. By controlling the mixing time, speed, and environmental conditions, the uniform distribution of the components is ensured. Component A is prepared using a dry mixing method to avoid the influence of the liquid phase on the subsequent permeation process. Component B is prepared under nitrogen protection to prevent the oxidative deterioration of reducing components such as sodium thiosulfate. Component C is formulated considering the reactivity of the silane coupling agent. By adding it in steps and controlling the reaction time, the coupling agent is ensured to fully exert its interfacial modification effect.

[0087] This invention also provides a construction process for modified chromium corundum ramming mix, comprising the following steps:

[0088] Q1, Pretreatment of Material A: Material A is placed in a muffle furnace and pre-sintered in an oxidizing atmosphere. The gas flow rate is controlled at 5-10 L / min, the heating rate is 5℃ / min, and the pre-sintering is carried out at 1100-1150℃ for 25-35 minutes. The thickness of the charge does not exceed 50 mm. After pre-sintering, the material is naturally cooled to room temperature and crushed to a particle size of 3-5 mm using a jaw crusher to obtain pre-treated Material A with enhanced strength and improved activity.

[0089] Q2, Wet mixing of A material: Add deionized water to the pretreated A material in batches, with the water-to-material mass ratio controlled at 6-8%. The water addition process is carried out in 3-4 times, with an interval of 30-60 seconds between each addition. Mix in a mixer at a speed of 60-100 r / min for 3-5 minutes. Monitor the uniformity of moisture content during the mixing process to obtain a wet A material with uniform moisture content and good plasticity.

[0090] Q3, Layered tamping of Material A: The moistened Material A is layered onto the cleaned furnace bottom, with each layer strictly controlled to a thickness of 15-20mm. A pneumatic tamping machine is used for compaction, with tamping pressure controlled at 0.4-0.6MPa. The number of tamping passes per square meter is no less than 50, achieving a tamping density of 2.8-3.2g / cm³. 3 The interlayer bonding is achieved by serration treatment, resulting in a dense, uniform, and bubble-free A material;

[0091] Q4, Activation treatment of material B: Dissolve sodium hydroxide (NaOH) and disodium hydrogen phosphate (Na2HPO4) in deionized water in a certain proportion. The concentration of sodium hydroxide is 0.1-0.3 mol / L and the concentration of disodium hydrogen phosphate is 0.05-0.15 mol / L. Adjust the pH value to 8.5-9.2. Mix material B with the activation solution at a liquid-to-material mass ratio of 12-15%. After mixing evenly in a stirrer, let it stand for 15-20 minutes to obtain the activated material B slurry.

[0092] Q5, Negative Pressure Permeation of Material B: The activated material B slurry is loaded into the permeation tank, and the negative pressure is adjusted to -0.015 to -0.025 MPa. The slurry is injected into material A through the permeation pipe. The permeation time is controlled at 10-20 minutes, and the permeation depth is 60-80% of the thickness of material A, so as to obtain an intermediate that is well composited with material B and material A.

[0093] Q6, Medium-temperature reaction treatment: Place material A that has been permeated with material B in a medium-temperature furnace and heat it to 350-450℃ at a heating rate of 2-3℃ / min. Keep it at this temperature for 80-100 minutes. During the reaction, introduce a small amount of water vapor to maintain humidity. The reaction atmosphere is weakly oxidizing. After the reaction is completed, slowly cool it to room temperature to obtain a preliminarily combined composite structure.

[0094] Q7, C material dispersion treatment: Add C material to deionized water to prepare a suspension with a mass concentration of 25-35%, and disperse it using an ultrasonic disperser for 12-18 minutes. During the dispersion process, control the temperature to not exceed 60℃, and stop for 1 minute every 3 minutes of dispersion to prevent overheating, so as to obtain a uniformly dispersed C material suspension without agglomeration.

[0095] Q8, C material spraying and curing: Using specialized spraying equipment, the dispersed C material suspension is evenly sprayed onto the surface of the intermediate in an atomized manner. The spraying pressure is controlled at 0.2-0.4MPa, the spraying distance is maintained at 20-30cm, and the spraying thickness is 2-3mm. After spraying, it is cured at 180-220℃ for 60-90 minutes. Dry air is introduced during the curing process to obtain a smooth and firmly bonded protective layer.

[0096] Q9, Overall Firing: The product coated with C material is fired according to a strict heating curve. The first stage is 20-300℃ with a heating rate of 1℃ / min to remove physical water and organic matter. The second stage is 300-800℃ with a heating rate of 2℃ / min to carry out chemical reactions and preliminary sintering. The third stage is 800-1250℃ with a heating rate of 1.5℃ / min to complete high-temperature sintering. The product is held at 1250℃ for 4-6 hours. The firing is carried out in a weakly reducing atmosphere with the carbon monoxide concentration controlled at 0.5-1.5%. The total firing time is 24-30 hours to obtain modified chromium corundum ramming mix products with excellent performance.

[0097] In step Q1, the pre-sintering process adopts programmed temperature control. The initial heating rate is 3℃ / min to 500℃, and then it is increased to the pre-sintering temperature at 5℃ / min. The oxygen content in the pre-sintering atmosphere is controlled at 18-21%. The linear change rate of the sample is measured every 10 minutes during the pre-sintering process. When the linear change rate is stable within ±0.1%, the pre-sintering is completed, and a pre-sintered material A with stable dimensions and suitable strength is obtained.

[0098] In step Q2, the mixing process uses a planetary mixer with a main shaft speed of 60-100 r / min and an auxiliary mixing paddle speed of 2-3 times the main shaft speed. The mixing uniformity is checked every minute during the mixing process. When the difference in moisture content at different locations is less than 0.5%, the mixing is considered complete, resulting in a moist A material with uniform moisture distribution and good workability.

[0099] In step Q4, the activation solution is prepared by a stepwise dissolution method. Sodium hydroxide is completely dissolved first, and then disodium hydrogen phosphate is added. The temperature is controlled at 20-30℃ during the dissolution process. After preparation, the solution is left to stand for 2-4 hours to allow it to become completely clear. During the activation process, the solution is stirred every 5 minutes at a speed of 100-200 r / min. During the standing process, a film is covered to prevent moisture evaporation, resulting in a chemically activated B slurry.

[0100] In step Q5, the negative pressure permeation equipment includes a vacuum pump, a pressure regulating valve, a permeation tank, and a monitoring system. Before permeation, material A is vacuum pretreated for 30-60 seconds. During the permeation process, the permeation depth is monitored in real time. When the permeation resistance suddenly increases, the negative pressure value is appropriately increased. After the permeation is completed, the negative pressure state is maintained for 5-10 minutes to ensure sufficient permeation, resulting in a composite layer structure with uniform permeation depth and tight bonding.

[0101] In step Q9, the temperature deviation during the firing process is controlled within ±5℃. During the heat preservation stage, the phase change of the sample is measured once per hour. When the expected high-temperature phase is detected, the heat preservation is completed. During the cooling process, the cooling rate is strictly controlled at 50-100℃ / h to 800℃. Then, the sample is naturally cooled to room temperature to obtain a finished modified chromium corundum ramming mix with a dense structure and excellent performance.

[0102] The pretreatment of aggregate A is based on a thermal activation mechanism. The pre-sintering process creates appropriate defects and active sites on the surface of the aggregate particles, which is beneficial for subsequent chemical reactions. The selection of the pre-sintering temperature seeks a balance between material activation and over-sintering; too low a temperature will not generate sufficient activity, while too high a temperature may lead to sintering shrinkage and pore closure. An oxidizing atmosphere is used to remove organic impurities and carbon deposits from the surface, ensuring surface cleanliness. The wet mixing process regulates the plasticity and flowability of the material by controlling the moisture content. A suitable moisture content ensures good formability during tamping while avoiding cracking and shrinkage caused by excessive moisture.

[0103] The layered tamping process is based on the theory of powder compaction. By controlling the thickness of the material layer and tamping parameters, it achieves uniform compaction of the material. Controlling the thickness of each layer is crucial to the final density and uniformity; excessively thick layers make it difficult to achieve sufficient internal compaction, while excessively thin layers affect construction efficiency and interlayer bonding. The use of a pneumatic tamping machine provides stable impact energy, and achieving the required tamping density is the foundation for the success of subsequent process steps. Interlayer scoring enhances the bonding strength between layers by increasing the contact area and mechanical interlocking.

[0104] The activation treatment of component B is based on the pH regulation mechanism of solution chemistry. Sodium hydroxide (NaOH) provides an alkaline environment, while disodium hydrogen phosphate (Na2HPO4) acts as a buffer. Together, they maintain the system within a suitable pH range. The alkaline environment is conducive to the dissolution and diffusion of functional components, enhancing their chemical activity. The settling process allows the activation reaction to proceed fully, reaching a state of chemical equilibrium among the components.

[0105] Negative pressure infiltration is a pressure gradient-driven mass transfer process. By applying negative pressure to the surface of material A, a pressure gradient is created from the surface inwards, driving the slurry of material B to infiltrate into the pore network. Controlling the infiltration depth is crucial for the final protective effect; too shallow an infiltration will not form an effective protective layer, while too deep an infiltration may damage the structural integrity of the base layer. Real-time monitoring during the infiltration process and timely adjustment of process parameters ensure consistent infiltration results.

[0106] The intermediate-temperature reaction treatment is based on the principles of solid-state reaction kinetics. Within a temperature range of 350-450℃, chemical reactions and interfacial bonding occur between the components. The selection of the temperature range takes into account the thermodynamic and kinetic factors of the reaction, ensuring the full progress of the reaction and avoiding undesirable phase transitions caused by excessively high temperatures. The introduction of trace amounts of water vapor during the reaction process facilitates certain hydration reactions while preventing crack formation due to excessive dehydration. A weakly oxidizing atmosphere promotes certain oxidation reactions, and the oxygen content is strictly controlled to prevent excessive oxidation of chromium.

[0107] The dispersion treatment of material C is based on the stability principle of colloidal chemistry. Ultrasonic dispersion technology is used to break up particle agglomerations, forming a stable suspension system. The cavitation effect of ultrasound generates strong mechanical shear force, effectively dispersing particle agglomerates and improving dispersion uniformity. The temperature during the dispersion process is strictly controlled to avoid excessively high temperatures that could lead to rapid solvent evaporation and particle re-agglomeration.

[0108] The spray curing process is based on the thin film formation principle, achieving uniform coating of the protective layer through atomized spraying. Control of spraying parameters includes multiple aspects such as pressure, distance, and travel speed. During the curing process, the solvent evaporates, and the particles gradually approach each other to form a continuous solid film. A suitable curing temperature promotes the cross-linking reaction of the silane coupling agent, enhancing the adhesion between the coating and the substrate.

[0109] The overall firing process employs a segmented heating approach to correspond to different physicochemical processes. The first segment, low-temperature heating, is used to remove physically adsorbed water and thermally decompose organic components. The heating rate is controlled at a slow level to avoid cracking caused by rapid volume changes. The second segment, medium-temperature heating, corresponds to the chemical reaction and preliminary sintering process. Solid-state reactions occur between the components, forming new compound phases, while the material begins to shrink and densify. The third segment, high-temperature sintering, completes the final densification of the material, grain growth, and elimination of porosity, forming a dense ceramic structure. The holding process ensures the reaction proceeds fully, eliminates internal stress, and improves the structural stability of the material.

[0110] Controlling the weakly reducing atmosphere is crucial to preventing the formation of hexavalent chromium. Carbon monoxide (CO), as a reducing gas, reacts with the potentially formed hexavalent chromium, while the presence of CO also inhibits further oxidation of chromium in the material. Precise atmosphere control is achieved through an automated system that monitors and adjusts the gas composition in real time to ensure the stability and reproducibility of the firing process.

[0111] Through the above process, the present invention forms a modified chromium corundum ramming mix with excellent anti-oxidation, anti-permeability and high strength properties, which solves the technical problems faced by traditional chromium corundum ramming mix in high-temperature applications and provides a reliable technical solution for related industrial applications.

[0112] Example 1: This example describes the preparation of a modified chromium corundum ramming mix with excellent resistance to hexavalent chromium formation for use in the bottom of a 1600℃ high-temperature electric arc furnace. According to the formula of this invention, the components were accurately weighed as follows: Component A includes 50 parts of chromium corundum aggregate Cr2O3·Al2O3, 10 parts of titanium dioxide-coated alumina microspheres TiO2@Al2O3, 3 parts of calcium sulfide dihydrate CaS·2H2O, and 4 parts of porous silicon carbide microspheres β-SiC. Component B includes 15 parts of chromium oxide-zirconia composite nanopowder Cr2O3-ZrO2, 4.5 parts of sodium thiosulfate pentahydrate Na2S2O3·5H2O, 26 parts of tricalcium phosphate Ca3(PO4), and 3 parts of hexagonal boron nitride plate crystals h-BN. The C component includes 12 parts of aluminum dihydrogen phosphate-magnesium hydroxide complex Al(H2PO4)3-Mg(OH)2, 3.5 parts of calcium fluoride-alumina eutectic CaF2-Al2O3, and 1.0 parts of γ-methacryloyloxypropyltrimethoxysilane KH-570.

[0113] Chromium corundum aggregate was prepared by electrofusion method, in which chromium oxide (Cr2O3) and alumina (Al2O3) were mixed in a molar ratio of 1:4 and melted in an electric arc furnace at 1900℃ for 5 hours. Coke was added as a reducing agent during the melting process, and the chromium oxide content was controlled at 20%. After cooling, the aggregate was crushed to an average particle size of 1.5 mm. For the preparation of titanium dioxide-coated alumina microspheres, α-Al2O3 microspheres with a particle size of 2 μm were preheated to 400℃ in a fluidized bed reactor. The molar ratio of TiCl4 to H2O was controlled at 1:3, and a CVD reaction was carried out at 500℃ for 75 minutes with the fluidizing gas flow rate maintained at 1.0 m / s, resulting in composite microspheres with a coating thickness of 75 nm.

[0114] In the preparation of chromium oxide-zirconia composite nanopowder, Cr₂O₃ and ZrO₂ were mixed at a mass ratio of 4:1, the slurry solid content was 55%, ball-milled for 30 hours at 250 r / min, and calcined at 1250℃ for 3 hours to obtain composite nanopowder with an average particle size of 35 nm. In the preparation of aluminum dihydrogen phosphate-magnesium hydroxide composite, the molar ratio of aluminum hydroxide to phosphate was 1:3, reacted at 30℃ for 5 hours with a stirring speed of 400 r / min, and after adding magnesium hydroxide, stirring continued for 2 hours, followed by vacuum drying at 70℃ for 36 hours. The calcium fluoride-alumina eutectic was melted at 1450℃ for 2.5 hours with an argon flow rate of 7 L / min and a cooling rate of 75℃ / min.

[0115] The construction process is as follows: Material A is pre-sintered at 1125℃ for 30 minutes with an oxygen content of 20%, and then crushed to a particle size of 4mm. During wet mixing, the water-to-material mass ratio is controlled at 7%, the planetary mixer spindle speed is 80 r / min, and mixing lasts for 4 minutes. Layered tamping is performed, with each layer 18mm thick, a tamping pressure of 0.5MPa, and tamping 55 times per square meter until a density of 3.0 g / cm³ is achieved. 3For material B, the activation treatment involved a NaOH concentration of 0.2 mol / L, a Na₂HPO₄ concentration of 0.1 mol / L, a pH adjusted to 9.0, a liquid-to-material mass ratio of 13.5%, and a standing period of 18 minutes. Negative pressure osmosis was applied at -0.02 MPa for 15 minutes, achieving a osmosis depth of 70% of the thickness of material A. The medium-temperature reaction was carried out at 400℃ for 90 minutes with a heating rate of 2.5℃ / min, maintaining humidity with trace amounts of water vapor in a weakly oxidizing atmosphere. Material C, with a suspension mass concentration of 30%, was ultrasonically dispersed for 15 minutes, sprayed at a pressure of 0.3 MPa at a distance of 25 cm, achieving a thickness of 2.5 mm, and cured at 200℃ for 75 minutes. The overall firing process employed a three-stage heating method: the first stage reached 300℃ at a heating rate of 1℃ / min, the second stage reached 800℃ at a heating rate of 2℃ / min, and the third stage reached 1250℃ at a heating rate of 1.5℃ / min, with a holding time of 5 hours, a CO concentration of 1.0%, and a total firing time of 27 hours.

[0116] Comparative Example 1 differs from Example 1 in that it uses a traditional single-component chromium corundum ramming mix formulation, comprising 85 parts chromium corundum aggregate, 10 parts tricalcium phosphate, and 5 parts phosphate binder, without any antioxidant components. During preparation, the components are directly dry-mixed for 10 minutes, 8% water is added, and conventional ramming is performed. The mixture is then fired at 1200°C with a heating rate of 5°C / min, held at that temperature for 2 hours, and fired in air. All other aspects are the same as in Example 1.

[0117] Comparative Example 2 differs from Example 1 in that it incorporates conventional antioxidants in a traditional formulation, including 75 parts chromium corundum aggregate, 8 parts tricalcium phosphate, 3 parts metallic chromium powder, 4 parts silicon carbide powder, and 10 parts phosphate binder. The preparation process is similar to Comparative Example 1, but the firing temperature is increased to 1220°C, held for 3 hours, and in a weakly reducing atmosphere. Everything else is the same as in Example 1.

[0118] Comparative Example 3 differs from Example 1 in that it employs a two-component structure design. Component A comprises 60 parts chromium corundum aggregate, 10 parts zirconium oxide, and 5 parts tricalcium phosphate. Component B comprises 15 parts chromium oxide and 10 parts phosphate binder. Components A and B are mixed separately and then compounded at a mass ratio of 8:2, simplifying the construction process. The mixture is fired at 1180°C for 4 hours. All other aspects are the same as in Example 1.

[0119] This invention designs a performance comparison experiment, employing multiple standardized testing procedures to evaluate the performance of the embodiments and comparative examples, as detailed below:

[0120] The determination of hexavalent chromium content was performed according to standard HJ687-2014. Samples were kept at 1200℃ in an oxidizing atmosphere for 4 hours before testing. Thermal shock resistance testing was conducted according to GB / T30873-2014 standard, evaluating the material's thermal stability through repeated high-temperature and low-temperature cycles. Mechanical strength testing was performed according to YB / T2208-1998 standard, measuring compressive strength at both room temperature and 1200℃. Thermal conductivity testing was performed according to YB / T4130-2005 standard, measuring the thermal conductivity of each sample at 800℃. To verify the long-term performance of the material, thermal fatigue cycling testing was also conducted, performing hot and cold cycles between 1200℃ and 200℃ according to YB / T4018-1991 standard. Slag erosion resistance testing was performed according to JISR2213 standard, using standard slag to erode at 1500℃ for 6 hours before measuring the erosion depth. The environmental safety assessment was conducted using leaching toxicity tests according to HJ / T299-2007, "Leaching Methods for Solid Waste". The experimental results are as follows:

[0121] The hexavalent chromium content was determined according to standard HJ687-2014. After being kept at 1200℃ in an oxidizing atmosphere for 4 hours, the hexavalent chromium content in Example 1 was 1.2 mg / kg, compared to 28.5 mg / kg in Comparative Example 1, 15.8 mg / kg in Comparative Example 2, and 12.3 mg / kg in Comparative Example 3. The hexavalent chromium inhibition rate reached 95.8% in Example 1 (relative to Comparative Example 1).

[0122] According to GB / T30873-2014, the thermal shock resistance of Example 1 was tested after 18 thermal shock cycles, compared to 7 cycles for Comparative Example 1, 10 cycles for Comparative Example 2, and 12 cycles for Comparative Example 3. Example 1 showed a 157% improvement over Comparative Example 1, demonstrating a significant advantage. The compressive strength was measured according to YB / T2208-1998. The compressive strength of Example 1 at room temperature was 85.2 MPa, and at 1200℃ it was 48.3 MPa. Comparative Example 1 showed 65.8 MPa and 32.1 MPa respectively, Comparative Example 2 showed 71.4 MPa and 36.8 MPa, and Comparative Example 3 showed 76.2 MPa and 41.5 MPa respectively.

[0123] Thermal conductivity tests were performed according to YB / T4130-2005. Example 1 had a thermal conductivity of 3.85 W / m·K at 800℃, Comparative Example 1 had 2.68 W / m·K, Comparative Example 2 had 3.12 W / m·K, and Comparative Example 3 had 3.45 W / m·K. Example 1 showed a 43.7% improvement over Comparative Example 1. Apparent porosity tests showed 14.2% for Example 1, 18.6% for Comparative Example 1, 16.8% for Comparative Example 2, and 15.4% for Comparative Example 3. The bulk density for Example 1 was 3.25 g / cm³. 3 Comparative Example 1 showed a concentration of 2.98 g / cm³.3 .

[0124] Example 2: This example addresses the application requirements of a 1400℃ medium-frequency induction furnace lining, employing a moderate range of component proportions. Component A includes 48 parts of chromium corundum aggregate (Cr2O3·Al2O3), 9 parts of titanium dioxide-coated alumina microspheres (TiO2@Al2O3), 2.5 parts of calcium sulfide dihydrate (CaS·2H2O), and 3.5 parts of porous silicon carbide microspheres (β-SiC). Component B includes 14 parts of chromium oxide-zirconia composite nanopowder (Cr2O3-ZrO2), 4 parts of sodium thiosulfate pentahydrate (Na2S2O3·5H2O), 25 parts of tricalcium phosphate (Ca3(PO4)), and 2.5 parts of hexagonal boron nitride plate crystals (h-BN). The C component includes 10 parts of aluminum dihydrogen phosphate-magnesium hydroxide complex Al(H2PO4)3-Mg(OH)2, 3 parts of calcium fluoride-alumina eutectic CaF2-Al2O3, and 0.8 parts of γ-methacryloyloxypropyltrimethoxysilane KH-570.

[0125] The preparation process parameters were moderately adjusted to suit medium-temperature applications. The electrofusion temperature of the chromium corundum aggregate was 1850℃, the melting time was 4.5 hours, the chromium oxide content was controlled at 18%, and the crushed particle size was 1.0 mm. In the titanium dioxide coating process, the molar ratio of TiCl4 to H2O was 1:2.5, the reaction temperature was 480℃, the CVD time was 70 minutes, and the coating thickness was 65 nm. The chromium oxide-zirconia composite powder had a Cr2O3 to ZrO2 mass ratio of 3.5:1, was ball-milled for 28 hours, calcined at 1220℃, and had an average particle size of 30 nm.

[0126] The construction process was optimized for medium-temperature applications. The pre-sintering temperature for material A was 1110℃, the pre-sintering time was 28 minutes, and the crushed particle size was 3.5mm. The water-to-material mass ratio was 6.5%, the mixing time was 3.5 minutes, the tamping pressure was 0.45MPa, the number of tamping cycles was 52 times / square meter, and the density was 2.9g / cm³. 3 Material B's activation solution has a NaOH concentration of 0.15 mol / L, a Na₂HPO₄ concentration of 0.08 mol / L, a pH of 8.8, and a liquid-to-material mass ratio of 12.5%. Negative pressure permeation is applied at -0.018 MPa for 12 minutes, with a medium-temperature reaction at 380℃ and a holding time of 85 minutes. Material C is sprayed with a thickness of 2.2 mm, cured at 190℃ for 70 minutes. The entire process is then fired at 1220℃ for 4.5 hours with a CO concentration of 0.8%, for a total time of 25 hours.

[0127] Comparative Example 4 differs from Example 2 in that it uses a traditional formula with high chromium content: 90 parts chromium corundum aggregate (30% chromium oxide content), 5 parts tricalcium phosphate, 5 parts phosphate binder, and 10% water. It is fired at 1150°C for 3 hours in an air atmosphere. Everything else is the same as in Example 2.

[0128] Comparative Example 5 differs from Example 2 in that a carbon antioxidant is added to the conventional formula. The formula includes 78 parts chromium corundum aggregate, 5 parts graphite powder, 2 parts carbon black, 10 parts tricalcium phosphate, and 5 parts phosphate binder. It is calcined at 1180°C in a reducing atmosphere. Everything else is the same as in Example 2.

[0129] Comparative Example 6 differs from Example 2 in that it employs a simplified three-component structure, with each component formulated in a mass ratio of 6:3:1. The total formula consists of 70 parts chromium corundum aggregate, 10 parts zirconium oxide powder, 15 parts phosphate binder, and 5 parts silica fume powder. The construction process is also simplified. Everything else is the same as in Example 2.

[0130] Performance test results comparison

[0131] The hexavalent chromium content test showed that Example 2 had a content of 1.8 mg / kg, Comparative Example 4 had 35.2 mg / kg, Comparative Example 5 had 22.6 mg / kg, and Comparative Example 6 had 18.9 mg / kg. Example 2 achieved a hexavalent chromium inhibition rate of 94.9%, significantly better than the comparative examples. The thermal shock resistance test showed that Example 2 underwent 16 shocks, Comparative Example 4 underwent 6 shocks, Comparative Example 5 underwent 8 shocks, and Comparative Example 6 underwent 11 shocks, with Example 2 showing a 45.5% improvement over the optimal comparative example.

[0132] The room temperature compressive strength of Example 2 was 82.6 MPa, and the high temperature compressive strength was 45.8 MPa. Comparative Example 4 showed 62.4 MPa and 29.8 MPa, respectively; Comparative Example 5 showed 68.7 MPa and 34.2 MPa; and Comparative Example 6 showed 73.8 MPa and 38.6 MPa. The thermal conductivity at 800℃ was 3.62 W / m·K in Example 2, compared to 2.45 W / m·K in Comparative Example 4, representing an increase of 47.8%. The apparent porosity of Example 2 was 13.8%, and the bulk density was 3.18 g / cm³. 3 All of them are better than the proportions of each pair.

[0133] Example 3, this example is for application in a 1500℃ refining furnace, using the following raw materials: Component A includes 52 parts of chromium corundum aggregate Cr2O3·Al2O3, 11 parts of titanium dioxide-coated alumina microspheres TiO2@Al2O3, 3.5 parts of calcium sulfide dihydrate CaS·2H2O, and 4.5 parts of porous silicon carbide microspheres β-SiC. Component B includes 16 parts of chromium oxide-zirconia composite nanopowder Cr2O3-ZrO2, 5 parts of sodium thiosulfate pentahydrate Na2S2O3·5H2O, 27 parts of tricalcium phosphate Ca3(PO4), and 3.5 parts of hexagonal boron nitride plate crystals h-BN. The C component includes 13 parts of aluminum dihydrogen phosphate-magnesium hydroxide complex Al(H2PO4)3-Mg(OH)2, 4 parts of calcium fluoride-alumina eutectic CaF2-Al2O3, and 1.2 parts of γ-methacryloyloxypropyltrimethoxysilane KH-570.

[0134] The preparation process was enhanced for high-temperature applications. The chromium corundum aggregate was melted at 1950℃ for 6 hours, achieving a chromium oxide content of 22%, and crushed to a particle size of 2.0 mm. The CVD coating reaction was carried out at 520℃ for 80 minutes, resulting in a coating layer thickness of 85 nm. The chromium oxide-zirconia composite powder had a mass ratio of 4.5:1, was ball-milled for 32 hours, calcined at 1280℃, and had an average particle size of 40 nm. The reaction time for the aluminum dihydrogen phosphate-magnesium hydroxide composite was extended to 6 hours, and the drying temperature was 75℃ for 48 hours.

[0135] The construction process parameters are as follows: pre-sintering temperature 1140℃, time 32 minutes, water-to-material ratio 7.5%, tamping pressure 0.55MPa, and density 3.1g / cm³. 3 The concentration of the activation solution for component B was increased: NaOH 0.25 mol / L, Na₂HPO₄ 0.12 mol / L, pH 9.1, and a liquid-to-material mass ratio of 14%. Negative pressure permeation was applied at -0.022 MPa, with a medium-temperature reaction temperature of 420℃ and a holding time of 95 minutes. Component C was sprayed to a thickness of 2.8 mm, with a curing temperature of 210℃ and a curing time of 85 minutes. The firing temperature was 1280℃, with a holding time of 5.5 hours and a CO concentration of 1.2%.

[0136] Comparative Example 7 differs from Example 3 in that it uses an ultra-high chromium content formulation, with 95 parts of chromium corundum aggregate (35% chromium oxide content) and 5 parts of phosphate binder, and is fired at 1100°C for 2 hours, aiming for the highest refractory performance but neglecting environmental protection requirements. Everything else is the same as in Example 3.

[0137] Comparative Example 8 differs from Example 3 in that it uses a composite of multiple antioxidants, including 75 parts chromium corundum aggregate, 3 parts metallic Al powder, 6 parts SiC powder, 2 parts graphite powder, 10 parts tricalcium phosphate, and 4 parts phosphate binder, and is sintered in a strongly reducing atmosphere. Everything else is the same as in Example 3.

[0138] Comparative Example 9 differs from Example 3 in that it uses a ceramic binder system, comprising 80 parts chromium corundum aggregate, 10 parts alumina micro powder, 5 parts silica fume, and 5 parts clay binder, and is sintered at a high temperature of 1300℃. All other aspects are the same as in Example 3.

[0139] Performance test results comparison

[0140] Example 3 showed a hexavalent chromium content of only 0.8 mg / kg, compared to 42.6 mg / kg in Comparative Example 7, 28.3 mg / kg in Comparative Example 8, and 25.1 mg / kg in Comparative Example 9. Example 3 exhibited the most significant inhibitory effect. Regarding thermal shock resistance, Example 3 achieved 20 cycles, compared to 5 cycles in Comparative Example 7, 9 cycles in Comparative Example 8, and 13 cycles in Comparative Example 9. Example 3 still showed a 53.8% improvement over the optimal comparative example.

[0141] Regarding mechanical strength, Example 3 exhibits a room temperature compressive strength of 88.5 MPa and a high temperature strength of 51.2 MPa, compared to 59.3 MPa and 27.6 MPa in Comparative Example 7, 74.8 MPa and 38.9 MPa in Comparative Example 8, and 81.2 MPa and 44.7 MPa in Comparative Example 9. The thermal conductivity of Example 3 at 1000℃ is 4.15 W / m·K, compared to 2.82 W / m·K in Comparative Example 7, representing an improvement of 47.2%. The apparent porosity is 13.5%, and the bulk density is 3.32 g / cm³. 3 The structure is more compact.

[0142] Example 4. This example is for application in the working layer of a 1350℃ ladle refining furnace. The raw materials used are as follows: Component A includes 47 parts of chromium corundum aggregate Cr2O3·Al2O3, 8.5 parts of titanium dioxide-coated alumina microspheres TiO2@Al2O3, 2.8 parts of calcium sulfide dihydrate CaS·2H2O, and 3.2 parts of porous silicon carbide microspheres β-SiC. Component B includes 13 parts of chromium oxide-zirconia composite nanopowder Cr2O3-ZrO2, 3.5 parts of sodium thiosulfate pentahydrate Na2S2O3·5H2O, 24.5 parts of tricalcium phosphate Ca3(PO4), and 2.2 parts of hexagonal boron nitride plate crystals h-BN. The C component includes 29 parts of aluminum dihydrogen phosphate-magnesium hydroxide complex Al(H2PO4)3-Mg(OH), 2.8 parts of calcium fluoride-alumina eutectic CaF2-Al2O3, and 0.6 parts of γ-methacryloyloxypropyltrimethoxysilane KH-570.

[0143] The preparation process parameters were moderate: chromium corundum aggregate was electrofused at 1880℃ for 4.2 hours, with a chromium oxide content of 17% and a particle size of 0.8 mm. CVD coating was performed at 460℃ for 65 minutes, resulting in a coating thickness of 60 nm. The composite nanopowder had a mass ratio of 3.2:1, was ball-milled for 26 hours, calcined at 1200℃, and had a particle size of 25 nm. The composite preparation reaction lasted 4.5 hours, followed by drying at 65℃ for 30 hours. The eutectic was melted at 1420℃ for 2.2 hours.

[0144] Construction process optimization to improve efficiency: pre-sintering at 1100℃ for 25 minutes, particle size 3.2mm; water-to-material ratio 6.2%; mixing time 3.2 minutes; tamping at 0.42MPa, 50 times / m. 2 Density 2.85 g / cm³ 3 The activation solution consisted of 0.12 mol / L NaOH and 0.07 mol / L Na₂HPO₄, with a pH of 8.6 and a liquid-to-solid ratio of 12%. The process involved penetration at -0.016 MPa for 10 minutes, followed by a reaction at 365°C for 80 minutes. A 2.0 mm thick coating was then applied, cured at 185°C for 65 minutes. Finally, the coating was fired at 1200°C for 4.2 hours, with a CO₂ content of 0.7%.

[0145] Comparative Example 10 differs from Example 4 in that it uses a cost-optimized economical formulation, comprising 82 parts chromium corundum aggregate, 13 parts tricalcium phosphate, and 5 parts phosphate binder. The preparation process is simplified, with a firing temperature of 1150°C and a holding time of 2.5 hours. Everything else is the same as in Example 4.

[0146] Comparative Example 11 differs from Example 4 in that it incorporates some modified components based on the traditional formula: 70 parts chromium corundum aggregate, 8 parts zirconium oxide powder, 4 parts silicon carbide powder, 12 parts tricalcium phosphate, and 6 parts phosphate binder. The process is slightly optimized. Everything else is the same as in Example 4.

[0147] Comparative Example 12 differs from Example 4 in that it employs a double-layer structure design. The bottom layer is a dense layer (85 parts chromium corundum aggregate and 15 parts binder), and the surface layer is a functional layer (with added antioxidant components). While the layers are applied, deep component integration is not achieved. Otherwise, it is the same as Example 4.

[0148] Example 4 showed a hexavalent chromium content of 1.5 mg / kg, compared to 31.8 mg / kg in Comparative Example 10, 19.4 mg / kg in Comparative Example 11, and 16.7 mg / kg in Comparative Example 12. Example 4 achieved an inhibition rate of 95.3%. In terms of thermal shock resistance, after 15 cycles, the comparative examples showed 6, 9, and 11 cycles respectively, demonstrating a clear advantage for Example 4.

[0149] The compressive strength of Example 4 was 80.8 MPa at room temperature and 44.6 MPa at high temperature; Comparative Example 10 showed 63.5 MPa and 30.4 MPa; Comparative Example 11 showed 69.2 MPa and 35.8 MPa; and Comparative Example 12 showed 74.6 MPa and 40.2 MPa. The thermal conductivity at 800℃ was 3.48 W / m·K, an increase of 38.1% compared to 2.52 W / m·K in Comparative Example 10. The apparent porosity was 14.8%, and the bulk density was 3.12 g / cm³. 3 .

[0150] To verify the long-term performance of the embodiments, thermal fatigue cycle tests were conducted. Figure 4 As shown, according to the YB / T4018-1991 standard, thermal cycling was performed at 1200℃↔200℃. The thermal fatigue lives of Examples 1-4 were 126, 118, 135, and 112 cycles, respectively, while the average number of cycles for each comparative example was in the range of 60-80 cycles. The thermal fatigue life of the examples was improved by 50-80%.

[0151] The slag erosion resistance test was conducted according to JIS R2213 standard, using standard slag and erosion at 1500℃ for 6 hours. The erosion depths of Examples 1-4 were 2.8 mm, 3.2 mm, 2.5 mm, and 3.0 mm, respectively, while the erosion depths of the comparative examples were generally in the range of 4.5-6.2 mm. The erosion resistance of the examples was improved by 35-45%.

[0152] The linear change rate test results show that the linear change rate of Examples 1-4 during high-temperature use was controlled within ±0.3%, while the linear change rate of the comparative examples generally reached ±0.5-0.8%, indicating that the examples exhibited better dimensional stability. The mass loss rate test shows that the mass loss rate of the examples was controlled within 0.8-1.2%, while that of the comparative examples was 1.5-2.8%, proving that the examples have better high-temperature stability.

[0153] The results of each experiment are shown in Table 1 and Figures 1-4 As shown.

[0154] Table 1 Comparison of key performance indicators between the examples and comparative examples.

[0155]

[0156] From Table 1 and Figure 1 It can be seen that the room temperature pressure resistance of Examples 1-4 is generally in the range of 80-88 MPa, while the average value of the comparative examples is mostly between 62-76 MPa. Regarding high temperature pressure resistance, the values ​​of the examples are concentrated in the range of 44-51 MPa, while those of the comparative examples are in the range of 28-41 MPa. In terms of thermal conductivity, the thermal conductivity of the examples is significantly higher than that of the comparative examples, with the examples ranging from 3.48-4.15 W / m·K, while the comparative examples are mostly in the range of 2.45-3.78 W / m·K. Regarding apparent porosity, the examples show lower values, generally between 13.5-14.8%, while the comparative examples have relatively higher apparent porosity, ranging from 15.4-20.1%.

[0157] Figure 2 The examples demonstrate advantages in environmental performance. Regarding hexavalent chromium content, the examples are significantly lower than the comparative examples. The hexavalent chromium content in Examples 1-4 is controlled at an extremely low level of 0.8-1.8 mg / kg, while the comparative examples have an average of 12.3-42.6 mg / kg. In the comparison of thermal shock resistance, the examples exhibit stronger thermal shock stability, with a cycle count between 15-20, compared to only 5-13 in the comparative examples. Regarding bulk density, the examples achieve 3.12-3.32 g / cm³. 3 This is higher than the 2.89-3.18 g / cm³ of the comparative example. 3 .

[0158] Figure 3The performance improvement of the embodiments compared to the comparative examples is intuitively shown in percentage form. The improvement in room temperature pressure resistance and high temperature pressure resistance is generally in the range of 20-40%, the reduction in hexavalent chromium content is even more than 90%, and the improvement in thermal shock resistance varies between 50-300%, showing the comprehensive performance advantages of embodiments 1-4.

[0159] Figure 4 The results reveal the superior long-term performance of the embodiments. In terms of thermal fatigue cycle life, the embodiments achieved 112-135 cycles, while the comparative examples only achieved 60-75 cycles, representing an improvement of approximately 70-80%. In the slag erosion resistance test, the erosion depth of the embodiments was controlled at 2.5-3.2 mm, while the erosion depth of the comparative examples reached 5.0-5.5 mm, demonstrating that the embodiments exhibited stronger erosion resistance.

[0160] It can be seen that the modified chromium corundum ramming mix of this invention has achieved significant advantages in various aspects, including environmental performance, mechanical strength, physical properties, and long-term stability. The substantial reduction in hexavalent chromium content indicates that environmental goals have been effectively achieved; the improved mechanical strength and thermal conductivity demonstrate a comprehensive improvement in performance; and the increased thermal shock resistance and thermal fatigue life indicate better long-term stability. The performance improvement mainly stems from the synergistic effect of the three components of this invention. In component A, titanium dioxide-coated alumina microspheres form a dense rutile protective film on the surface of the chromium corundum aggregate through chemical vapor deposition, physically blocking direct contact between oxygen and chromium, thus inhibiting the oxidation reaction of hexavalent chromium at its source. Calcium sulfide dihydrate acts as a chemical trapping agent; its sulfide ions react with potentially generated hexavalent chromium ions to form stable chromium sulfide compounds, achieving in-situ solidification of harmful ions. The unique pore structure of silicon carbide porous microspheres provides directional channels for the penetration of component B, ensuring that functional components can effectively penetrate into the base layer. In component B, sodium thiosulfate pentahydrate undergoes thermal decomposition under intermediate temperature conditions, releasing active sulfur ions that selectively reduce any formed hexavalent chromium, converting it into low-toxicity trivalent chromium. Chromium oxide-zirconia composite nanopowder utilizes the phase transformation toughening effect of zirconia and the surface effect of nanoparticles to significantly improve the material's density and thermal shock resistance. Hexagonal boron nitride plate-like crystals, with their layered structure, form a highly efficient thermally conductive channel network, ensuring uniform heat transfer within the material. Tricalcium phosphate acts as a pH buffer, maintaining a stable chemical environment for the reduction reaction within a suitable pH range. In component C, the aluminum dihydrogen phosphate-magnesium hydroxide composite undergoes dehydration and condensation during high-temperature sintering, generating a low-permeability aluminum phosphate ceramic phase in situ, effectively preventing external oxidizing gases from penetrating into the inner layer. Calcium fluoride-alumina eutectic acts as a flux, lowering the reaction temperature during sintering and promoting densification between components. Simultaneously, the high electronegativity of fluoride ions forms a charge-protective layer on the material surface, further inhibiting oxidation. Silane coupling agents establish chemical bridging at the organic-inorganic interface through their bifunctional structure, significantly enhancing the interfacial bonding strength between heterogeneous layers.

[0161] The layered tamping combined with negative pressure infiltration technology used in the preparation process realizes the three-dimensional network distribution of different functional components inside the material, forming a gradient protection structure. Through the triple mechanism of blocking oxidation pathways, inhibiting chemical reduction, and sealing gas permeation channels, the formation of hexavalent chromium is comprehensively suppressed, while achieving synergistic improvement of mechanical and physical properties.

[0162] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A modified chromium corundum ramming mix, characterized in that, It consists of three components, A, B, and C, in parts by weight, wherein: Material A includes: Chromium corundum aggregate Cr2O3·Al2O3: 45-55 parts; Titanium dioxide-coated alumina microspheres (TiO2@Al2O3): 8-12 parts; Calcium sulfide dihydrate CaS·2H2O: 2-4 parts; Silicon carbide porous microspheres β-SiC: 3-5 parts; Material B includes: Chromium oxide-zirconia composite nanopowder Cr2O3-ZrO2: 12-18 parts; Sodium thiosulfate pentahydrate Na2S2O3·5H2O: 3-6 parts; Tricalcium phosphate (Ca3(PO4)2): 4-8 parts; Hexagonal boron nitride plate-like crystals h-BN: 2-4 parts; Material C includes: Aluminum dihydrogen phosphate-magnesium hydroxide complex Al(H2PO4)3-Mg(OH)2: 8-15 parts; Calcium fluoride-alumina eutectic CaF2-Al2O3: 2-5 parts; γ-Methacryloxypropyltrimethoxysilane KH-570: 0.5-1.5 parts.

2. The modified chromium corundum ramming mix according to claim 1, characterized in that, Chromium corundum aggregate Cr2O3·Al2O3 is prepared by electrofusion method: chromium oxide Cr2O3 and alumina Al2O3 are mixed in a molar ratio of 1:3-1:5 and melted in an electric arc furnace at 1800-2000℃ for 4-6 hours. During the melting process, reducing agent coke is added to control the chromium oxide content. After melting, it is cast into ingots, cooled and crushed to a particle size of 0.5-3mm to obtain chromium corundum aggregate with a chromium oxide content of 15-25%. Calcium sulfide dihydrate (CaS·2H2O) is prepared by reacting calcium hydroxide with hydrogen sulfide: calcium hydroxide powder (Ca(OH)2) is placed in a reactor, and hydrogen sulfide (H2S) gas is introduced at 80-120℃ for 2-4 hours. During the reaction, the pH value is controlled at 8-9. After the reaction is completed, the mixture is filtered and washed, and then dried at 60-80℃ for 12-24 hours to obtain calcium sulfide dihydrate with a purity ≥98% and a particle size of 200-400 mesh. Porous silicon carbide microspheres (β-SiC) were prepared using a sol-gel method: tetraethyl orthosilicate (Si(OC2H5)4) and phenolic resin were mixed in a molar ratio of 1:2, and deionized water and hydrochloric acid catalyst were added. The mixture underwent hydrolysis and condensation at 60°C to form a gel. The precursor microspheres were obtained by spray drying and then carbonized at 1400-1500°C under a nitrogen atmosphere for 3-4 hours to obtain microspheres with a porosity of 35-45%, an average pore size of 5-15 μm, and a specific surface area of ​​8-15 m². 2 / g of porous silicon carbide microspheres; Chromium oxide-zirconia composite nanopowder Cr2O3-ZrO2 was prepared by coprecipitation method: chromium trichloride CrCl3·6H2O and zirconium oxychloride ZrOCl2·8H2O were mixed in a molar ratio of 3:1-5:1 to form a mixed solution. Ammonia water was added under vigorous stirring to adjust the pH to 8-9 to form a coprecipitate. After filtration and washing, the solution was dried at 110℃ for 24 hours and then calcined at 1200-1300℃ for 2-4 hours to obtain α-type chromium oxide and monoclinic zirconium oxide composite nanopowder with an average particle size of 20-50 nm. Hexagonal boron nitride plate-like crystals (h-BN) are prepared by reacting boric acid with ammonia: boric acid (H3BO3) powder is placed in a graphite crucible, and under a protective atmosphere of ammonia (NH3), the temperature is increased to 1000-1200℃ at a heating rate of 5℃ / min, and held for 4-6 hours. The ammonia flow rate is controlled at 200-300mL / min. After the reaction is completed, the mixture is naturally cooled to room temperature and then mechanically ground and dispersed to obtain hexagonal boron nitride plate-like crystals with a diameter of 10-50μm and a thickness of 0.5-2μm.

3. The preparation process of the modified chromium corundum ramming mix according to any one of claims 1-2, characterized in that, Includes the following steps: S1, Preparation of titanium dioxide-coated alumina microspheres: α-Al2O3 microspheres with a particle size of 1-3 μm were pretreated to remove surface impurities and then placed in a fluidized bed reactor. The reactor was preheated to 400℃, and then titanium tetrachloride (TiCl4) vapor and water vapor (H2O) were introduced. The molar ratio of titanium tetrachloride to water vapor was controlled at 1:2-1:

4. Chemical vapor deposition reaction was carried out at a temperature of 450-550℃ for 60-90 minutes. During the reaction, the fluidizing gas flow rate was controlled at 0.8-1.2 m / s, and the reaction pressure was atmospheric pressure. Alumina microspheres with a uniform surface coating of titanium dioxide with a thickness of 50-100 nm were obtained. S2, Preparation of chromium oxide-zirconia composite nanopowder: Chromium oxide Cr2O3 nanopowder and zirconia ZrO2 nanopowder are accurately weighed and mixed at a mass ratio of 3:1-5:1, and deionized water is added to prepare a slurry with a solid content of 50-60%. The slurry is fed into a ball mill with zirconia balls as the grinding medium, a ball-to-material ratio of 3:1-5:1, a rotation speed of 200-300 r / min, and ball milling for 24-36 hours until the particle size is uniform. The slurry is spray-dried to remove moisture and calcined at 1200-1300℃ for 2-4 hours with a heating and cooling rate controlled at 5℃ / min to obtain well-crystallized chromium oxide-zirconia composite nanopowder. S3, Preparation of aluminum dihydrogen phosphate-magnesium hydroxide composite: Add aluminum hydroxide Al(OH)3 powder to a reaction vessel, slowly add 85% phosphoric acid H3PO4 solution, and react aluminum hydroxide and phosphoric acid at a molar ratio of 1:

3. React for 4-6 hours at a temperature of 25-35℃ and a stirring speed of 300-500r / min to obtain aluminum dihydrogen phosphate solution. Then add magnesium hydroxide Mg(OH)2 powder and continue stirring for 2 hours to disperse it evenly. Finally, dry at 60-80℃ for 24-48 hours to obtain aluminum dihydrogen phosphate-magnesium hydroxide composite. S4, Preparation of calcium fluoride-alumina eutectic: Calcium fluoride (CaF2) and alumina (Al2O3) are mixed evenly in a precise molar ratio of 1:1 and placed in a platinum crucible. Under an argon protective atmosphere, the mixture is heated to 1400-1500℃ and melted for 2-3 hours. During the melting process, the mixture is intermittently stirred to ensure complete reaction. After the reaction is completed, the mixture is rapidly cooled to room temperature at a cooling rate of 50-100℃ / min. The mixture is then coarsely crushed using a jaw crusher and finely ground to 100-300 mesh using a ball mill to obtain the calcium fluoride-alumina eutectic. S5, Preparation of A material: Chromium corundum aggregate, titanium dioxide-coated alumina microspheres prepared in step S1, calcium sulfide dihydrate CaS·2H2O, and silicon carbide porous microspheres β-SiC are put into a forced mixer and dry-mixed at room temperature for 10-15 minutes. The mixing speed is controlled at 60-80 r / min. The mixture is added in 3 batches during the mixing process, with an interval of 2-3 minutes between each batch, to obtain A material with uniform component distribution. S6, Preparation of B material: The chromium oxide-zirconia composite nanopowder prepared in step S2, sodium thiosulfate pentahydrate Na2S2O3·5H2O, tricalcium phosphate Ca3(PO4)2, and hexagonal boron nitride plate crystals h-BN are put into a mixing device and dry-mixed for 8-12 minutes under nitrogen protection. The temperature is controlled not to exceed 40℃ during the mixing process to obtain B material with stable chemical composition. Preparation of S7, C material: The aluminum dihydrogen phosphate-magnesium hydroxide composite prepared in step S3, the calcium fluoride-alumina eutectic prepared in step S4, and γ-methacryloxypropyltrimethoxysilane KH-570 are added sequentially to the reaction vessel. First, the γ-methacryloxypropyltrimethoxysilane KH-570 and the aluminum dihydrogen phosphate-magnesium hydroxide composite are mixed for 3 minutes. Then, the calcium fluoride-alumina eutectic is added and stirred evenly for 5 minutes. The stirring speed is controlled at 100-150 r / min to obtain C material with good bonding properties.

4. The preparation process according to claim 3, characterized in that, In step S1, the chemical vapor deposition reaction is carried out in a temperature zone within the reactor. The temperature of the preheating zone is 350-400℃, the temperature of the reaction zone is 450-550℃, and the temperature of the post-treatment zone is 300-350℃. High-purity nitrogen is used as the carrier gas with a flow rate of 100-200 mL / min. The coating thickness is monitored in real time during the reaction. When it reaches 50-100 nm, the reaction is stopped, resulting in uniformly coated and firmly bonded titanium dioxide-coated alumina microspheres.

5. The preparation process according to claim 3, characterized in that, In step S2, the ball milling process is divided into two stages: coarse milling and fine milling. Coarse milling lasts for 12 hours at a speed of 200 r / min, and fine milling lasts for 12-24 hours at a speed of 250-300 r / min. The particle size distribution is checked every 6 hours during the ball milling process. The ball milling ends when the D90 particle size reaches 100-200 nm. The inlet air temperature of the spray drying is 180-220℃, and the outlet air temperature is 80-100℃, resulting in chromium oxide-zirconia composite nanopowder with good dispersibility and uniform particle size.

6. The preparation process according to claim 3, characterized in that, In step S3, the reaction between aluminum hydroxide and phosphoric acid is carried out by dropwise addition at a rate of 2-5 mL / min. During the dropwise addition, the system temperature is controlled to not exceed 40°C. During the reaction, the pH value drops from 12 to 2-3. After the addition of magnesium hydroxide, the pH value rises back to 6-7. The drying process is carried out by vacuum drying with the pressure controlled at -0.08 to -0.1 MPa, resulting in a structurally stable and uniformly dispersed aluminum dihydrogen phosphate-magnesium hydroxide complex.

7. The preparation process according to claim 3, characterized in that, In step S4, the melting reaction is carried out in a high-temperature furnace with a heating rate controlled at 10℃ / min. During the melting process, the argon flow rate is 5-10L / min, and the mixture is stirred once every 30 minutes for 1-2 minutes each time. The complete melting is indicated by the melt being uniform and transparent. Rapid cooling is achieved using a metal mold. The crushing process involves first coarse crushing to 10-20mm, and then fine grinding to the required particle size to obtain a dense and highly active calcium fluoride-alumina eutectic.

8. The construction process of the modified chromium corundum ramming mix as described in any one of claims 1-2, characterized in that, Includes the following steps: Q1, Pretreatment of Material A: Material A is placed in a muffle furnace and pre-sintered in an oxidizing atmosphere. The gas flow rate is controlled at 5-10 L / min, the heating rate is 5℃ / min, and the pre-sintering is carried out at 1100-1150℃ for 25-35 minutes. The thickness of the charge does not exceed 50 mm. After pre-sintering, the material is naturally cooled to room temperature and crushed to a particle size of 3-5 mm using a jaw crusher to obtain pre-treated Material A with enhanced strength and improved activity. Q2, Wet mixing of A material: Add deionized water to the pretreated A material in batches, with the water-to-material mass ratio controlled at 6-8%. The water addition process is carried out in 3-4 times, with an interval of 30-60 seconds between each addition. Mix in a mixer at a speed of 60-100 r / min for 3-5 minutes. Monitor the uniformity of moisture content during the mixing process to obtain a wet A material with uniform moisture content and good plasticity. Q3, Layered tamping of Material A: The moistened Material A is layered onto the cleaned furnace bottom, with each layer strictly controlled to a thickness of 15-20mm. A pneumatic tamping machine is used for compaction, with tamping pressure controlled at 0.4-0.6MPa. The number of tamping passes per square meter is no less than 50, achieving a tamping density of 2.8-3.2g / cm³. 3 The interlayer bonding is achieved by serration treatment, resulting in a dense, uniform, and bubble-free A material; Q4, Activation treatment of material B: Dissolve sodium hydroxide (NaOH) and disodium hydrogen phosphate (Na2HPO4) in deionized water in a certain proportion. The concentration of sodium hydroxide is 0.1-0.3 mol / L and the concentration of disodium hydrogen phosphate is 0.05-0.15 mol / L. Adjust the pH value to 8.5-9.

2. Mix material B with the activation solution at a liquid-to-material mass ratio of 12-15%. After mixing evenly in a stirrer, let it stand for 15-20 minutes to obtain the activated material B slurry. Q5, Negative Pressure Permeation of Material B: The activated material B slurry is loaded into the permeation tank, and the negative pressure is adjusted to -0.015 to -0.025 MPa. The slurry is injected into material A through the permeation pipe. The permeation time is controlled at 10-20 minutes, and the permeation depth is 60-80% of the thickness of material A, so as to obtain an intermediate that is well composited with material B and material A. Q6, Medium-temperature reaction treatment: Place material A that has been permeated with material B in a medium-temperature furnace and heat it to 350-450℃ at a heating rate of 2-3℃ / min. Keep it at this temperature for 80-100 minutes. During the reaction, introduce a small amount of water vapor to maintain humidity. The reaction atmosphere is weakly oxidizing. After the reaction is completed, slowly cool it to room temperature to obtain a preliminarily combined composite structure. Q7, C material dispersion treatment: Add C material to deionized water to prepare a suspension with a mass concentration of 25-35%, and disperse it using an ultrasonic disperser for 12-18 minutes. During the dispersion process, control the temperature to not exceed 60℃, and stop for 1 minute every 3 minutes of dispersion to prevent overheating, so as to obtain a uniformly dispersed C material suspension without agglomeration. Q8, C material spraying and curing: Using specialized spraying equipment, the dispersed C material suspension is evenly sprayed onto the surface of the intermediate in an atomized manner. The spraying pressure is controlled at 0.2-0.4MPa, the spraying distance is maintained at 20-30cm, and the spraying thickness is 2-3mm. After spraying, it is cured at 180-220℃ for 60-90 minutes. Dry air is introduced during the curing process to obtain a smooth and firmly bonded protective layer. Q9, Overall Firing: The product coated with C material is fired according to a strict heating curve. The first stage is 20-300℃ with a heating rate of 1℃ / min to remove physical water and organic matter. The second stage is 300-800℃ with a heating rate of 2℃ / min to carry out chemical reactions and preliminary sintering. The third stage is 800-1250℃ with a heating rate of 1.5℃ / min to complete high-temperature sintering. The product is held at 1250℃ for 4-6 hours and fired in a weakly reducing atmosphere of carbon monoxide. The total firing time is 24-30 hours to obtain the modified chromium corundum ramming mix product.

9. The construction process according to claim 8, characterized in that, In step Q1, the pre-sintering process adopts programmed temperature control. The initial heating rate is 3℃ / min, and the temperature is raised to 500℃. Then, it is raised to the pre-sintering temperature at a rate of 5℃ / min. The oxygen content in the pre-sintering atmosphere is controlled at 18-21%. The linear change rate of the sample is measured every 10 minutes during the pre-sintering process. When the linear change rate is stable within ±0.1%, the pre-sintering is completed, and pre-sintered material A is obtained. In step Q2, the mixing process uses a planetary mixer with a main shaft speed of 60-100 r / min and an auxiliary mixing paddle speed of 2-3 times the main shaft speed. The mixing uniformity is checked every minute during the mixing process. When the difference in moisture content at different locations is less than 0.5%, the mixing is considered complete, resulting in a moist A material with uniform moisture distribution and good workability. In step Q4, the activation solution is prepared by a stepwise dissolution method. Sodium hydroxide is completely dissolved first, and then disodium hydrogen phosphate is added. The temperature is controlled at 20-30℃ during the dissolution process. After preparation, the solution is left to stand for 2-4 hours to allow it to become completely clear. During the activation process, the solution is stirred every 5 minutes at a speed of 100-200 r / min. During the standing process, a film is covered to prevent moisture evaporation, resulting in a chemically activated B slurry.

10. The construction process according to claim 8, characterized in that, In step Q5, the negative pressure permeation equipment includes a vacuum pump, a pressure regulating valve, a permeation tank, and a monitoring system. Before permeation, material A is vacuum pretreated for 30-60 seconds. During the permeation process, the permeation depth is monitored in real time. When the permeation resistance suddenly increases, the negative pressure value is appropriately increased. After the permeation is completed, the negative pressure state is maintained for 5-10 minutes to ensure sufficient permeation, resulting in a composite layer structure with uniform permeation depth and tight bonding. In step Q9, the temperature deviation during the firing process is controlled within ±5℃. During the heat preservation stage, the phase change of the sample is measured once per hour. When the expected high-temperature phase is detected, the heat preservation is completed. During the cooling process, the cooling rate is strictly controlled at 50-100℃ / h, and the temperature is reduced to 800℃. Then, the sample is naturally cooled to room temperature to obtain the finished product.

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