Modified chrome corundum ramming material as well as preparation and construction processes thereof

Abstract

The invention relates to a modified chrome corundum ramming material and a preparation and construction process thereof, and belongs to the technical field of chrome corundum ramming materials. The ramming material comprises a material A, a material B and a material C, wherein the material A comprises chrome corundum aggregate, titanium dioxide coated aluminum oxide microspheres, calcium sulfide dehydrate and silicon carbide porous microspheres; the material B comprises chromium oxide-zirconium oxide composite nano powder, sodium thiosulfate pentahydrate, tricalcium phosphate and hexagonal boron nitride flaky crystals; and the material C comprises an aluminum dihydrogen phosphate-magnesium hydroxide compound, a calcium fluoride-aluminum oxide co-melt and a silane coupling agent. The preparation process comprises the steps of pretreatment of all the components, preparation of composite powder and layered preparation. The construction process comprises the steps of pretreatment, wet-process mixing, layered ramming, negative-pressure permeation, medium-temperature reaction, spraying curing, integral firing and the like. Generation of hexavalent chromium can be effectively inhibited, the thermal shock resistance, the mechanical strength and the heat-conducting property of the material are remarkably improved, and the material has the advantages of being good in environment friendliness, long in service life, excellent in 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] The A material comprises: 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; porous silicon carbide microspheres β-SiC: 3-5 parts;

[0007] The B material comprises: chromium oxide-zirconium oxide composite nano powder Cr2O3-ZrO2: 12-18 parts; sodium thiosulfate pentahydrate Na2S2O3·5H2O: 3-6 parts; tricalcium phosphate Ca3(PO4)2: 4-8 parts; hexagonal boron nitride flake crystal h-BN: 2-4 parts;

[0008] The C material comprises: aluminum dihydrogen phosphate-magnesium hydroxide composite 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.

[0009] In a preferred scheme, the chromium corundum aggregate Cr2O3·Al2O3 is prepared by the fused method: chromium oxide Cr2O3 and alumina Al2O3 are dosed according to a molar ratio of 1:3-1:5, melted in an electric arc furnace at 1800-2000°C for 4-6 hours, and a reducing agent coke is added during the melting process to control the chromium oxide content. After melting, the ingot is cast, cooled, and broken into 0.5-3mm particles to obtain a chromium corundum aggregate with a chromium oxide content of 15-25%;

[0010] The calcium sulfide dihydrate CaS·2H2O is prepared by reacting calcium hydroxide with hydrogen sulfide: calcium hydroxide Ca(OH)2 powder is placed in a reactor, hydrogen sulfide H2S gas is introduced at 80-120°C, and the reaction time is 2-4 hours. During the reaction, the pH value is controlled at 8-9. After the reaction is completed, filtration and washing are performed, and drying is carried out at 60-80°C for 12-24 hours to obtain calcium sulfide dihydrate with a purity of ≥98% and a particle size of 200-400 mesh;

[0011] The porous silicon carbide microspheres β-SiC are prepared by the sol-gel method: tetraethyl orthosilicate Si(OC2H5)4 and phenolic resin are mixed according to a molar ratio of 1:2, deionized water and hydrochloric acid catalyst are added, and hydrolysis and polycondensation are carried out at 60°C to form a gel. The precursor microspheres are prepared by spray drying, and carbonization treatment is carried out at 1400-1500°C in a nitrogen atmosphere for 3-4 hours to obtain porous silicon carbide microspheres with a porosity of 35-45%, an average pore size of 5-15μm, and a specific surface area of 8-15m 2 / g;

[0012] The chromium oxide-zirconia composite nanopowder Cr2O3-ZrO2 is prepared by a co-precipitation method: chromium chloride CrCl3.6H2O and zirconium oxychloride ZrOCl2.8H2O are prepared into a mixed solution according to a molar ratio of 3:1-5:1, ammonia water is added under stirring to adjust pH to 8-9, co-precipitation is formed, after filtration and washing, drying is carried out at 110 DEG C for 24 hours, then calcination is carried out at 1200-1300 DEG C for 2-4 hours, and the chromium oxide of alpha type and the monoclinic zirconia composite nanopowder with an average particle size of 20-50 nm is obtained;

[0013] The hexagonal boron nitride flaky crystal h-BN is prepared by the reaction of boric acid and ammonia gas: boric acid H3BO3 powder is placed in a graphite crucible, under the protection of ammonia gas NH3 atmosphere, the temperature is raised to 1000-1200 DEG C at a heating rate of 5 DEG C / min, the temperature is kept for 4-6 hours, the ammonia gas flow is controlled at 200-300 mL / min, after the reaction is completed, the temperature is naturally cooled to room temperature, and mechanical grinding and dispersion are carried out, and the hexagonal boron nitride flaky crystal with a flake diameter of 10-50 um and a thickness of 0.5-2 um is obtained.

[0014] The application provides a preparation process of modified chromium corundum ramming mixture.

[0015] S1, preparing titanium dioxide coated alumina microspheres: after the pretreatment of removing surface impurities, the alpha-Al2O3 microspheres with a particle size of 1-3 um are placed in a fluidized bed reactor, preheated to 400 DEG C, then titanium tetrachloride TiCl4 vapor and water vapor H2O are introduced, the molar ratio of titanium tetrachloride to water vapor is controlled at 1:2-1:4, the chemical vapor deposition reaction is carried out at a temperature of 450-550 DEG C for 60-90 minutes, the flow rate of fluidized gas is controlled at 0.8-1.2 m / s during the reaction, and the reaction pressure is normal pressure, and the alumina microspheres coated with a titanium dioxide layer with a thickness of 50-100 nm on the surface are obtained;

[0016] S2, preparing chromium oxide-zirconia composite nanopowder: the chromium oxide Cr2O3 nanopowder and the zirconia ZrO2 nanopowder are accurately weighed and mixed according to a mass ratio of 3:1-5:1, deionized water is added to prepare slurry with a solid content of 50-60%, the slurry is put into a ball mill, the zirconia balls are used as grinding media, the ball-to-material ratio is 3:1-5:1, the rotating speed is 200-300 r / min, ball milling is carried out for 24-36 hours until the particle size is uniform, water is removed by spray drying, and the chromium oxide-zirconia composite nanopowder with complete crystallization is obtained by calcination at 1200-1300 DEG C for 2-4 hours, and the temperature rising and falling speed is controlled at 5 DEG C / min;

[0017] S3, Preparation of aluminum dihydrogen phosphate-magnesium hydroxide composite: aluminum hydroxide Al(OH)3 powder is added into a reaction kettle, 85% phosphoric acid H3PO4 solution is slowly added, aluminum hydroxide reacts with phosphoric acid at a molar ratio of 1:3, an aluminum dihydrogen phosphate solution is prepared under the conditions of a temperature of 25-35℃ and a stirring speed of 300-500 r / min for 4-6 hours, then magnesium hydroxide Mg(OH)2 powder is added, and stirring is continued for 2 hours to make it uniformly dispersed, and finally drying is carried out at 60-80℃ for 24-48 hours to obtain an aluminum dihydrogen phosphate-magnesium hydroxide composite;

[0018] S4, Preparation of calcium fluoride-aluminum oxide eutectic: calcium fluoride CaF2 and aluminum oxide Al2O3 are accurately mixed at a molar ratio of 1:1, and then uniformly mixed, and then loaded into a platinum-gold crucible, and then melted and reacted at 1400-1500℃ under an argon protective atmosphere for 2-3 hours, and then intermittently stirred during the melting process to ensure complete reaction, and then quickly cooled to room temperature at a cooling rate of 50-100℃ / min, and then coarsely broken by using a jaw crusher and then finely ground by using a ball mill to 100-300 mesh to obtain a calcium fluoride-aluminum oxide 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 porous silicon carbide microspheres β-SiC are put into a forced mixer, dry mixed at room temperature for 10-15 minutes, the mixing speed is controlled at 60-80 r / min, and the components are added in three times with an interval of 2-3 minutes during the mixing process to obtain A material with uniform component distribution;

[0020] S6, Preparation of B material: chromium oxide-zirconium oxide composite nano-powder prepared in step S2, sodium thiosulfate pentahydrate Na2S2O3·5H2O, tricalcium phosphate Ca3(PO4)2, and hexagonal boron nitride flaky crystal h-BN are put into a mixing device, and dry mixing is carried out under nitrogen protection for 8-12 minutes, and the temperature is controlled to be not more than 40℃ during the mixing process to obtain B material with stable chemical composition;

[0021] S7, Preparation of C material: aluminum dihydrogen phosphate-magnesium hydroxide composite prepared in step S3, calcium fluoride-aluminum oxide eutectic prepared in step S4, and γ-methacryloxypropyltrimethoxysilane KH-570 are sequentially added into a reaction kettle, the silane coupling agent is first mixed with the composite for 3 minutes, and then the eutectic is added and uniformly stirred for 5 minutes at a stirring speed of 100-150 r / min to obtain C material with good bonding performance.

[0022] In the preferred solution, in step S1, the chemical vapor deposition reaction is carried out in a reactor with temperature zoning, the preheating zone temperature is 350-400 DEG C, the reaction zone temperature is 450-550 DEG C, the post-processing zone temperature is 300-350 DEG C, the carrier gas is high-purity nitrogen, the flow rate is 100-200 mL / min, the coating thickness is monitored in real time during the reaction, and the reaction is stopped when the coating thickness reaches 50-100 nm, thereby obtaining the titanium dioxide coated alumina microspheres with uniform coating and firm combination.

[0023] In the preferred solution, in step S2, the ball milling process is divided into two stages of coarse milling and fine milling, the coarse milling is carried out at a speed of 200 r / min for 12 hours, the fine milling is carried out at a speed of 250-300 r / min for 12-24 hours, the particle size distribution is checked every 6 hours during the ball milling, the ball milling is stopped when the D90 particle size reaches 100-200 nm, the inlet air temperature of the spray drying is 180-220 DEG C, and the outlet air temperature is 80-100 DEG C, thereby obtaining the composite nano powder with good dispersibility and uniform particle size.

[0024] In the preferred solution, in step S3, the reaction of the aluminum hydroxide and the phosphoric acid is carried out in a dropwise manner, the dropwise adding speed of the phosphoric acid is 2-5 mL / min, the system temperature is controlled to be not more than 40 DEG C during the dropwise adding, the pH value is reduced from 12 to 2-3 during the reaction, the pH value is increased to 6-7 after the addition of the magnesium hydroxide, the drying process is carried out by vacuum drying, the pressure is controlled to be-0.08 to-0.1 MPa, and thereby the aluminum dihydrogen phosphate-magnesium hydroxide composite with stable structure and uniform dispersion is obtained.

[0025] In the preferred solution, in step S4, the melting reaction is carried out in a high-temperature furnace, the heating rate is controlled to be 10 DEG C / min, the argon flow rate is 5-10 L / min during the melting, the stirring is carried out every 30 minutes, each time for 1-2 minutes, the complete melting is indicated by the uniform and transparent melt, the rapid cooling is carried out by using a metal mold, the coarse crushing is carried out first to 10-20 mm, and then the fine grinding is carried out to the required particle size, and thereby the calcium fluoride-alumina eutectic body with compact structure and good activity is obtained.

[0026] The application also provides a construction process of the modified chrome-corundum ramming mixture.

[0027] Q1, A material pretreatment: the A material is placed in a muffle furnace, and pre-sintering is carried out in an oxidizing atmosphere, the gas flow rate is controlled to be 5-10 L / min, the heating rate is 5 DEG C / min, the pre-sintering is carried out at 1100-1150 DEG C for 25-35 minutes, the thickness of the loaded material is not more than 50 mm, and the pre-sintering is completed by natural cooling to room temperature, and the jaw crusher is used to crush to 3-5 mm particle size, thereby obtaining the pretreated A material with enhanced strength and improved activity.

[0028] Q2, Wet mixing of A material: Add deionized water to pretreated A material in batches, control the water-material mass ratio at 6-8%, add water in 3-4 times, each time interval 30-60s, mix in the mixer at 60-100r / min for 3-5 minutes, monitor the uniformity of moisture content during mixing, get wet A material with uniform moisture content and good plasticity;

[0029] Q3, Layered tamping of A material: Lay wet A material on the cleaned furnace bottom in layers, strictly control the thickness of each layer at 15-20mm, use pneumatic tamper to tamp, control the tamping pressure at 0.4-0.6MPa, tamping frequency per square meter is not less than 50 times, tamping density reaches 2.8-3.2g / cm 3 , use notch treatment for interlayer bonding, get dense and uniform A material without air bubbles;

[0030] Q4, Activation treatment of B material: Dissolve sodium hydroxide NaOH and disodium hydrogen phosphate Na2HPO4 in deionized water according to the proportion, the concentration of sodium hydroxide is 0.1-0.3mol / L, the concentration of disodium hydrogen phosphate is 0.05-0.15mol / L, adjust the pH value to 8.5-9.2, mix B material with the activation liquid according to the liquid-material mass ratio of 12-15%, mix uniformly in the stirrer and then stand for 15-20 minutes, get B material slurry with enhanced activity;

[0031] Q5, Negative pressure infiltration of B material: Put the activated B material slurry into the infiltration tank, adjust the negative pressure to-0.015 to-0.025MPa, inject the slurry into A material through the infiltration pipe, control the infiltration time at 10-20 minutes, the infiltration depth is 60-80% of the thickness of A material, get the intermediate body with good composite of B material and A material;

[0032] Q6, Intermediate temperature reaction treatment: Put the A material with infiltrated B material into the intermediate temperature furnace, heat at a rate of 2-3℃ / min to 350-450℃, keep the temperature at this temperature for 80-100 minutes, introduce a small amount of water vapor to maintain humidity during the reaction, the reaction atmosphere is weakly oxidizing, slowly cool to room temperature after the reaction is completed, get the preliminary combined composite structure;

[0033] Q7, Dispersion treatment of C material: Add C material to deionized water to prepare a suspension with a mass concentration of 25-35%, use ultrasonic disperser for dispersion treatment, dispersion time is 12-18 minutes, control the temperature during dispersion not to exceed 60℃, stop for 1 minute every 3 minutes to prevent overheating, get uniformly dispersed and non-agglomerated C material suspension;

[0034] Q8, C material spraying and curing: using special spraying equipment, the dispersed C material suspension is sprayed on the surface of the intermediate body in atomized manner, the spraying pressure is controlled at 0.2-0.4 MPa, the spraying distance is kept at 20-30 cm, the spraying thickness is 2-3 mm, and after the spraying is completed, curing treatment is carried out at 180-220 °C for 60-90 minutes, dry air is introduced during the curing process, and a smooth and firm protective layer is obtained;

[0035] Q9, overall firing: the C material coated product is fired according to a strict temperature rising curve, the first stage is 20-300 °C at a temperature rising rate of 1 °C / min to remove physical water and organic matter; the second stage is 300-800 °C at a temperature rising rate of 2 °C / min to carry out chemical reaction and preliminary sintering; the third stage is 800-1250 °C at a temperature rising rate of 1.5 °C / min to complete high temperature sintering, and the firing is carried out in a weak reducing atmosphere of carbon monoxide, the total firing time is 24-30 hours, and the modified chrome corundum ramming material product is obtained.

[0036] In the preferred scheme, in step Q1, the pre-sintering process adopts programmed temperature rising, the initial temperature rising rate is 3 °C / min to 500 °C, and then it is raised to the pre-sintering temperature at a rate of 5 °C / 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, and when the linear change rate is stable within ±0.1%, the pre-sintering is completed, and the pre-sintered A material with stable size and appropriate strength is obtained;

[0037] In step Q2, the mixing process adopts a planetary mixer, the main shaft rotating speed is 60-100 r / min, and the auxiliary stirring paddle rotating speed is 2-3 times of the main shaft rotating speed, the mixing uniformity is checked every 1 minute during the mixing process, and when the water content difference at different positions is less than 0.5% through sampling determination, it is considered that the mixing is completed, and the wet A material with uniform water distribution and good working performance is obtained;

[0038] In step Q4, the preparation of the activation liquid adopts a step-by-step dissolution method, sodium hydroxide is completely dissolved first, and then disodium hydrogen phosphate is added, the temperature is controlled at 20-30 °C during the dissolution process, and after the preparation is completed, it is placed for 2-4 hours to make it completely clear, the stirring is carried out every 5 minutes during the activation process, the stirring speed is 100-200 r / min, and a thin film is covered during the standing process to prevent water evaporation, and the B material slurry with fully excited chemical activity is obtained.

[0039] In the preferred scheme, in step Q5, the negative pressure infiltration equipment comprises a vacuum pump, a pressure regulating valve, an infiltration tank and a monitoring system, the A material is subjected to vacuum pretreatment for 30-60s before infiltration, the infiltration depth is monitored in real time during the infiltration process, the negative pressure value is appropriately increased when the infiltration resistance suddenly increases, and the negative pressure state is maintained for 5-10 minutes after the infiltration is completed to ensure that the infiltration is sufficient, so that a composite layer structure with uniform infiltration depth and tight combination is obtained;

[0040] In step Q9, the temperature deviation of the sintering process is controlled within ±5℃, the phase change of the sample is determined once per hour during the holding stage, the holding is completed when the expected high-temperature phase is detected, the cooling process is strictly controlled to have a cooling rate of 50-100℃ / h to 800℃, and then natural cooling to room temperature, so that the modified chrome-corundum ramming material product with dense structure and excellent performance is obtained.

[0041] The present application has the following beneficial effects:

[0042] Firstly, the present application designs three kinds of ingredients, wherein the A material provides high-temperature stability as a basic aggregate, the B material plays a chemical reduction role to inhibit the generation of hexavalent chromium as a functional material, and the C material forms a dense barrier as a protective material, the components form a complementary function and realize the blocking of the oxidation path, the chemical reduction of the inhibition of the formation of hexavalent chromium, and the closure of the gas permeation channel; in the adopted formula composition, the titanium dioxide coated alumina microspheres form a uniform and dense rutile protective film on the surface of the chrome-corundum aggregate, which physically blocks the direct contact of oxygen and chromium elements. The sodium thiosulfate pentahydrate acts as an efficient reducing medium and undergoes controllable decomposition in the medium-temperature reaction stage, the released active sulfur ions selectively complex with the possible generated hexavalent chromium to form stable chromium sulfide compounds. The porous silicon carbide microspheres provide a directional channel for the B material penetration through the precisely controlled pore structure, and the beta phase crystal structure remains stable in physical and chemical properties at high temperature. The C material adopts a synergistic system of aluminum dihydrogen phosphate-magnesium hydroxide compound and calcium fluoride-alumina eutectic, which generates a low-permeability composite ceramic phase in situ during the high-temperature sintering process, wherein the quartz-type crystal structure formed by aluminum phosphate and the magnesium oxide derivative jointly construct a dense microscopic barrier. The molecular bridging effect of the silane coupling agent significantly enhances the interfacial bonding strength between the heterogeneous layers by establishing chemical bonding at the organic-inorganic interface. The high electronegativity of the fluoride ion forms a charge protection layer at the outermost layer of the material, further inhibiting the diffusion and penetration of the oxidizing medium.

[0043] Second, in the preparation process, the application realizes the uniform growth of the nanoscale titanium dioxide coating layer by precisely controlling the temperature zoning of the fluidized bed and the proportion of the reaction gas through chemical vapor deposition technology. The sol-gel method prepared porous silicon carbide microspheres have adjustable pore size distribution and high specific surface area characteristics. The chromium oxide-zirconia composite nano powder prepared by co-precipitation combined with high-energy ball milling technology fully plays the phase transformation toughening effect of zirconia and the surface effect of nano particles. The calcium fluoride-alumina eutectic formed by the melt quenching process retains the high reactivity of the non-equilibrium state, providing an excellent liquid medium for the sintering process.

[0044] Third, in the construction process, the pre-sintering treatment removes impurities on the aggregate surface and forms active sites through a controlled oxidation process. The layered tamping process combined with pneumatic compaction technology ensures the uniform distribution of the pore structure of the base layer. The notch treatment enhances the mechanical interlocking effect between the layers. The negative pressure infiltration process uses pressure gradient to drive the deep diffusion of functional components. The penetration depth control mechanism forms a three-dimensional network structure of B material inside A material. The staged sintering schedule matches the physical and chemical changes in different temperature ranges to finally form a stable ceramic structure with fine grains and interface fusion.

[0045] Fourth, the modified chromium corundum tamping material solves the environmental problem of traditional chromium corundum materials, significantly improves the performance, and has a broad application prospect. The hexavalent chromium pollution generated during the production and use of traditional chromium corundum refractory materials has been a major environmental problem faced by the industry. The application technology reduces the content of hexavalent chromium by more than 95%, which is of great significance to the protection of the ecological environment and human health. According to the test, the content of hexavalent chromium in the modified chromium corundum tamping material is controlled below 2mg / kg, which is more than 95% lower than the average of the comparative examples, realizing the effective inhibition of hexavalent chromium. In terms of performance, the thermal shock resistance is improved by 50-80%, the mechanical strength is improved by 25-40%, the thermal conductivity is improved by 35-45%, and the service life is prolonged by 1.5-2.0 times, all of which are significantly improved. BRIEF DESCRIPTION OF DRAWINGS

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

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

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

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

[0050] Figure 5 is the preparation and construction process flow chart of the modified chrome corundum ramming mixture of the application. DETAILED DESCRIPTION

[0051] The technical solutions in the application will be described clearly and completely below in combination with the drawings in the application, and in addition, the forms of each structure described in the following embodiments are only examples, and the application is not limited to each structure described in the following embodiments, and all other embodiments obtained by those of ordinary skill in the art without creative labor belong to the protection scope of the application.

[0052] The application provides a modified chrome corundum ramming mixture, which comprises A material, B material and C material in parts by weight, wherein:

[0053] The A material comprises: chrome 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; porous silicon carbide microspheres β-SiC: 3-5 parts;

[0054] The B material comprises: chromium oxide-zirconium oxide composite nano powder Cr2O3-ZrO2: 12-18 parts; sodium thiosulfate pentahydrate Na2S2O3·5H2O: 3-6 parts; tricalcium phosphate Ca3(PO4)2: 4-8 parts; hexagonal boron nitride flake crystal h-BN: 2-4 parts;

[0055] The C material comprises: aluminum dihydrogen phosphate-magnesium hydroxide composite Al(H2PO4)3-Mg(OH)2: 8-15 parts; calcium fluoride-alumina eutectic CaF2-Al2O3: 2-5 parts; gamma-methacryloxypropyltrimethoxysilane KH-570: 0.5-1.5 parts.

[0056] The chrome corundum aggregate Cr2O3·Al2O3 is prepared by an electric melting method: chromium oxide Cr2O3 and alumina Al2O3 are dosed in a molar ratio of 1:3-1:5, melted in an electric arc furnace at 1800-2000℃ for 4-6 hours, a reducing agent coke is added during the melting process to control the content of chromium oxide, and after the melting is completed, the ingot is cast, cooled and broken to 0.5-3mm particle size, to obtain the chrome 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 Ca(OH)2 powder is placed in a reactor, hydrogen sulfide H2S gas is introduced at 80-120℃, the reaction time is 2-4 hours, the pH value is controlled at 8-9 during the reaction, after the reaction is completed, it is filtered and washed, and dried at 60-80℃ for 12-24 hours, to obtain calcium sulfide dihydrate with a purity of ≥98%, and a particle size of 200-400 mesh;

[0058] Silicon carbide porous microspheres β-SiC are prepared by sol-gel method: tetraethyl orthosilicate Si(OC2H5)4 and phenolic resin are mixed according to a molar ratio of 1:2, deionized water and hydrochloric acid catalyst are added, hydrolysis and polycondensation are carried out at 60℃ to form a gel, precursor microspheres are prepared by spray drying, and carbonization treatment is carried out at 1400-1500℃ in a nitrogen atmosphere for 3-4 hours, to obtain silicon carbide porous microspheres with a porosity of 35-45%, an average pore size of 5-15μm, and a specific surface area of 8-15m 2 / g;

[0059] Chromium oxide-zirconia composite nano powder Cr2O3-ZrO2 is prepared by coprecipitation method: chromium trichloride CrCl3·6H2O and zirconium oxychloride ZrOCl2·8H2O are prepared into a mixed solution according to a molar ratio of 3:1-5:1, ammonia water is added under vigorous stirring to adjust the pH to 8-9, and coprecipitation is formed, after filtration and washing, drying is carried out at 110℃ for 24 hours, and then calcination is carried out at 1200-1300℃ for 2-4 hours, to obtain α-type chromium oxide and monoclinic zirconia composite nano powder with an average particle size of 20-50nm;

[0060] Hexagonal boron nitride flaky crystal h-BN is prepared by reacting boric acid with ammonia gas: boric acid H3BO3 powder is placed in a graphite crucible, heated to 1000-1200℃ at a heating rate of 5℃ / min in an ammonia gas NH3 protective atmosphere, and kept for 4-6 hours, the ammonia gas flow is controlled at 200-300mL / min, after the reaction is completed, it is naturally cooled to room temperature, and mechanically ground and dispersed, to obtain hexagonal boron nitride flaky crystal with a flake diameter of 10-50μm and a thickness of 0.5-2μm.

[0061] The Cr2O3·Al2O3 of the A material provides high temperature structural strength and erosion resistance as a refractory component. The TiO2@Al2O3 forms a dense oxide protective film at high temperatures, effectively blocking the direct contact of external oxygen and chromium elements, and inhibiting the oxidation of hexavalent chromium from the source. The CaS·2H2O as a chemical capture agent combines with the possible hexavalent chromium ions to form stable sulfide complexes, achieving in-situ solidification of harmful ions. The porous β-SiC microspheres adjust the porosity and air permeability of the entire base layer through their unique porous structure, providing a suitable pore network for the subsequent permeation of the intermediate functional layer.

[0062] The Cr2O3-ZrO2 of the B material enhances the density and thermal shock resistance of the material through its nano effect, and the stabilizing effect of zirconia helps to inhibit the unstable transformation of the chromium phase. The Na2S2O3·5H2O is a key chemical reducing agent that rapidly reduces any formed hexavalent chromium to low-toxicity trivalent chromium at medium temperature conditions, ensuring the environmental safety of the material. The Ca3(PO4)2 acts as a pH buffer, maintaining the entire system within a suitable pH range, providing a stable chemical environment for the reduction reaction. The h-BN sheet crystal forms an efficient heat conduction channel network due to its excellent thermal conductivity and sheet structure, ensuring uniform heat transfer and distribution within the material.

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

[0064] A material is the basic aggregate of the entire ramming material, and the chromium corundum aggregate Cr2O3·Al2O3 is used as a refractory component. The chromium oxide Cr2O3 and the aluminum oxide Al2O3 form a solid solution structure, and the spinel structure has excellent high-temperature stability and corrosion resistance. In a high-temperature environment, the solid solution structure effectively inhibits the free migration of chromium ions, and from the crystallographic point of view, the thermodynamic driving force for the formation of hexavalent chromium is reduced. The design of the TiO2@Al2O3 alumina microsphere coated with titanium dioxide is based on the protection mechanism of the heterogeneous core-shell structure, in which the Al2O3 microsphere provides structural support, and the outer TiO2 coating layer exhibits excellent chemical inertness in a high-temperature oxidation atmosphere. The rutile crystal structure of TiO2 forms a dense oxide protective film at high temperatures, effectively blocking the direct contact between external oxygen molecules and internal chromium elements, and inhibiting the oxidation conversion reaction of Cr 3+ to Cr 6+ .

[0065] Calcium sulfide CaS·2H2O as a special chemical capture agent, its mechanism of action is based on the strong affinity of sulfur ions and hexavalent chromium. Under high-temperature conditions, CaS undergoes thermal decomposition reaction: CaS·2H2O→CaS+2H2O↑, and the released S 2- ions and the possible Cr 6+ ions undergo chemical complexation reaction to form stable CrS3 complex or other chromium sulfide compounds. These sulfides have 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 porous silicon carbide microspheres β-SiC is based on its unique porous structure adjustment mechanism. β-SiC (cubic silicon carbide) has a tetrahedral coordination crystal structure, and the porous structure formed by the sol-gel method during preparation precisely controls the pore size distribution; the porous network not only adjusts the porosity and air permeability of the entire base layer, but more importantly, it provides a directional pore network for the subsequent penetration of B material, ensuring that the chemically active components effectively penetrate into the interior of the base layer.

[0066] The design of the chromium oxide-zirconia composite nano-powder Cr2O3-ZrO2 of B material is based on the synergistic effect of nanocomposites, and the introduction of ZrO2 (zirconia) plays a key stabilizing role. ZrO2 has polymorphic transformation characteristics, existing in monoclinic and tetragonal phases at high temperatures, and the phase transition process is accompanied by volume change, which helps to inhibit the unstable transformation of chromium phase, and the nanoscale particle size effect enhances the density and thermal shock resistance of the material. Sodium thiosulfate pentahydrate Na2S2O3·5H2O is a key component of the entire reduction system, and its molecular structure contains S2O3 2-sulfate) ion, which has strong reducing property. At medium temperature (about 400°C), sodium thiosulfate is thermally decomposed, and the generated Na2S has stronger reducing ability to reduce any formed Cr 6+ quickly to low-toxic 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, and contains PO4 3- (phosphate) ion in its molecular structure, which exhibits amphoteric characteristics in aqueous solution, and combines with H + or OH - ions to form different hydrogen phosphate ions. Through the equilibrium reaction of and , the system is maintained in a suitable pH range, providing a stable chemical environment for the reduction reaction. The introduction of hexagonal boron nitride flake crystals h-BN is based on its unique layered structure and excellent thermal conductivity. h-BN has a graphite-like layered structure, with strong covalent bonds between B-N bonds within the layer and van der Waals forces between layers, making it have excellent thermal conductivity in the direction perpendicular to the layer. At the same time, the flaky morphology forms a network of thermal conduction channels in the material, ensuring uniform heat transfer and distribution within the material, avoiding phase transition and performance degradation caused by local overheating.

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

[0068] Calcium fluoride-aluminum oxide eutectic CaF2-Al2O3 as a flux component, its mechanism is based on the low-temperature liquid phase sintering mechanism of the eutectic system. CaF2 has a fluorite-type crystal structure, and its melting point is about 1418°C. At high temperatures, it forms a eutectic with Al2O3, significantly reducing the sintering temperature of the system. More importantly, F -The strong electronegativity and small ion radius form a dense fluoride protective layer on the surface of the material, further inhibiting the diffusion of oxygen and the oxidation reaction of chromium. γ-methacryloxypropyl trimethoxysilane KH-570 is a bifunctional silane coupling agent, and its molecular structure is CH2=C(CH3)COO(CH2)3Si(OCH3)3, which contains both organic functional groups methacryloxy and inorganic functional groups trimethoxysilane groups. On the surface of the material, the trimethoxysilane group reacts with the hydroxyl group on the surface of the inorganic oxide:

[0069] ≡Si-OCH3+HO-M≡→≡Si-O-M≡+CH3OH, forming a stable silicon-oxygen bond, and the organic functional group is crosslinked with the organic component, thereby establishing a chemical bridge between the organic-inorganic interface, significantly improving the interfacial bonding strength and the integrity of the overall structure.

[0070] Referring to Figure 5 The application also provides a preparation process of the modified chromium corundum ramming mixture, comprising the following steps:

[0071] S1, preparing titanium dioxide coated alumina microspheres: after pretreatment to remove surface impurities, α-Al2O3 microspheres with a particle size of 1-3 μm are placed in a fluidized bed reactor, preheated to 400°C, and then titanium tetrachloride TiCl4 vapor and water vapor H2O are introduced, the molar ratio of titanium tetrachloride to water vapor is controlled at 1:2-1:4, and the chemical vapor deposition reaction is carried out at a temperature of 450-550°C for 60-90 minutes, the flow rate of the fluidizing gas is controlled at 0.8-1.2 m / s during the reaction, and the reaction pressure is atmospheric pressure, to obtain alumina microspheres uniformly coated with a titanium dioxide layer with a thickness of 50-100 nm on the surface;

[0072] S2, preparing chromium oxide-zirconium oxide composite nano powder: chromium oxide Cr2O3 nano powder and zirconium oxide ZrO2 nano powder are accurately weighed and mixed according to a mass ratio of 3:1-5:1, deionized water is added to prepare a slurry with a solid content of 50-60%, and the slurry is put into a ball mill with zirconia balls as the grinding medium, the ball-to-material ratio is 3:1-5:1, and the rotation speed is 200-300 r / min, and the slurry is ball milled for 24-36 hours until the particle size is uniform, the water is removed by spray drying, and the chromium oxide-zirconium oxide composite nano powder is calcined at 1200-1300°C for 2-4 hours, with a temperature rising rate controlled at 5°C / min, to obtain well-crystallized chromium oxide-zirconium oxide composite nano powder;

[0073] S3, Preparation of aluminum dihydrogen phosphate-magnesium hydroxide composite: aluminum hydroxide Al(OH)3 powder is added into a reaction kettle, 85% phosphoric acid H3PO4 solution is slowly added, aluminum hydroxide reacts with phosphoric acid at a molar ratio of 1:3, an aluminum dihydrogen phosphate solution is prepared under the conditions of a temperature of 25-35℃ and a stirring speed of 300-500 r / min for 4-6 hours, then magnesium hydroxide Mg(OH)2 powder is added, and stirring is continued for 2 hours to make it uniformly dispersed, and finally drying is carried out at 60-80℃ for 24-48 hours to obtain an aluminum dihydrogen phosphate-magnesium hydroxide composite;

[0074] S4, Preparation of calcium fluoride-aluminum oxide eutectic: calcium fluoride CaF2 and aluminum oxide Al2O3 are accurately mixed at a molar ratio of 1:1, and then uniformly mixed, and then loaded into a platinum-gold crucible, and then melted and reacted at 1400-1500℃ under an argon protective atmosphere for 2-3 hours, and then intermittently stirred during the melting process to ensure complete reaction, and then quickly cooled to room temperature at a cooling rate of 50-100℃ / min, and then coarsely broken by using a jaw crusher and then finely ground by using a ball mill to 100-300 mesh to obtain a calcium fluoride-aluminum oxide 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 porous silicon carbide microspheres β-SiC are put into a forced mixer, dry mixed at room temperature for 10-15 minutes, the mixing speed is controlled at 60-80 r / min, and the components are added in three times with an interval of 2-3 minutes during the mixing process to obtain A material with uniform component distribution;

[0076] S6, Preparation of B material: chromium oxide-zirconium oxide composite nanometer powder prepared in step S2, sodium thiosulfate pentahydrate Na2S2O3·5H2O, tricalcium phosphate Ca3(PO4)2, and hexagonal boron nitride flaky crystal h-BN are put into a mixing device, and dry mixing is carried out under nitrogen protection for 8-12 minutes, and the temperature is controlled to be not more than 40℃ during the mixing process to obtain B material with stable chemical composition;

[0077] S7, Preparation of C material: aluminum dihydrogen phosphate-magnesium hydroxide composite prepared in step S3, calcium fluoride-aluminum oxide eutectic prepared in step S4, and γ-methacryloxypropyltrimethoxysilane KH-570 are sequentially added into a reaction kettle, the silane coupling agent is first mixed with the composite for 3 minutes, and then the eutectic is added and uniformly stirred for 5 minutes at a stirring speed of 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 reactor with temperature zoning, the preheating zone temperature is 350-400℃, the reaction zone temperature is 450-550℃, the post-treatment zone temperature is 300-350℃, the carrier gas is high-purity nitrogen, the flow rate is 100-200 mL / min, the coating thickness is monitored in real time during the reaction, and the reaction is stopped when the coating thickness reaches 50-100 nm, thereby obtaining titanium dioxide-coated alumina microspheres with uniform coating and firm bonding.

[0079] In step S2, the ball milling process is divided into two stages of coarse milling and fine milling, the coarse milling is carried out at a speed of 200 r / min for 12 hours, the fine milling is carried out at a speed of 250-300 r / min for 12-24 hours, the particle size distribution is checked every 6 hours during the ball milling process, the ball milling is stopped when the D90 particle size reaches 100-200 nm, the inlet air temperature of the spray drying is 180-220℃, the outlet air temperature is 80-100℃, and a composite nano-powder with good dispersibility and uniform particle size is obtained.

[0080] In step S3, the reaction of aluminum hydroxide and phosphoric acid is carried out by dropwise addition, the dropwise addition rate of phosphoric acid is 2-5 mL / min, the system temperature is controlled not to exceed 40℃ during the dropwise addition process, the pH value decreases from 12 to 2-3 during the reaction process, the pH value rises to 6-7 after the addition of magnesium hydroxide, vacuum drying is used in the drying process, the pressure is controlled at -0.08 to -0.1 MPa, and a stable and uniformly dispersed aluminum dihydrogen phosphate-magnesium hydroxide composite is obtained.

[0081] In step S4, the melting reaction is carried out in a high-temperature furnace, the heating rate is controlled at 10℃ / min, the argon flow rate during the melting process is 5-10 L / min, the stirring is carried out every 30 minutes for 1-2 minutes each time, the complete melting is indicated by the uniform and transparent melt, the rapid cooling is carried out using a metal mold, the coarse crushing is carried out to 10-20 mm first, and then the fine grinding is carried out to the required particle size, thereby obtaining a calcium fluoride-alumina eutectic body with compact structure and good activity.

[0082] The preparation of titania-coated alumina microspheres adopts chemical vapor deposition (CVD) technology, which is a surface modification method based on gas-phase reaction. In the fluidized bed reactor, α-Al2O3 microspheres are kept in suspension in the high-temperature gas stream as seed particles, and the hydrolysis reaction of titanium tetrachloride TiCl4 vapor and water vapor occurs on the surface of the particles: TiCl4 + 2H2O → TiO2 + 4HCl↑. The reaction is carried out at a temperature range of 450-550°C to ensure sufficient reaction and avoid sintering and agglomeration caused by excessively high temperature. The TiO2 generated during the reaction is deposited on the surface of Al2O3 in an amorphous state, and gradually crystallizes into rutile phase as the reaction proceeds, forming a controllable coating layer. The flow rate control of the fluidizing gas is crucial to the uniformity of the coating layer, and the appropriate flow rate ensures the uniform distribution of particles in the reactor and good heat and mass transfer effect.

[0083] The preparation of chromium oxide-zirconia composite nanopowder is based on the solid-phase reaction mechanism of mechanical chemistry, and the uniform mixing and partial solid solution of different phase components at the nanoscale are achieved through high-energy ball milling. During the ball milling process, zirconia balls act as grinding media and produce strong mechanical force on the powder particles under high-speed impact. The mechanical force not only refines the particle size, but more importantly, it generates a large number of defects and active sites at the particle interface, promoting diffusion and reaction between different phases. The selection of ball-to-powder ratio affects the contact probability and impact strength between grinding media and powder. Excessive ball-to-powder ratio may cause excessive wear, while too low ball-to-powder ratio affects the refinement effect. The subsequent high-temperature calcination process aims to eliminate the stress and defects introduced during mechanical alloying, and promote the perfection of crystal structure and stability of phase composition. The application of spray drying technology quickly removes water to prevent agglomeration and maintain the dispersibility of the powder.

[0084] The preparation of 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. The temperature and stirring conditions are strictly controlled during the reaction to ensure the complete reaction and uniformity of the product. The addition of magnesium hydroxide Mg(OH)2 not only plays a role in pH adjustment, but more importantly, its lamellar structure forms a reinforcing phase in the composite, improving the mechanical properties of the material. The drying process uses appropriate temperature and time to fully remove water, avoiding decomposition and phase change caused by excessive heating.

[0085] The preparation of calcium fluoride-alumina eutectic is based on the phase diagram principle of high-temperature melting reaction. The CaF2-Al2O3 binary system forms a variety of intermediate compounds and eutectic phases at high temperatures. The melting reaction is carried out in an argon protective atmosphere to prevent the volatilization and oxidation of fluorides at high temperatures. The selection of reaction temperature is based on the temperature range of the liquid phase in the phase diagram. In the range of 1400-1500℃, the system forms a uniform liquid phase, promoting sufficient reaction and diffusion between components. The purpose of rapid cooling is to inhibit the growth of crystals and maintain the fine crystal structure of the eutectic, which exhibits better reaction activity in subsequent applications.

[0086] The preparation process of each component follows the basic principles of powder engineering, and by controlling the mixing time, speed and environmental conditions, the uniform distribution of components is ensured. The preparation of A material adopts dry mixing method to avoid the influence of liquid phase on the subsequent infiltration process. The preparation of B material is carried out under nitrogen protection to prevent oxidation of reducing components such as sodium thiosulfate. The preparation of C material considers the reactivity of silane coupling agent, and by adding it step by step and controlling the reaction time, it ensures that the coupling agent fully plays its interfacial modification role.

[0087] The present application also provides a construction process for modified chrome corundum ramming material, comprising the following steps:

[0088] Q1, A material pretreatment: Put A material into a muffle furnace and pre-sinter in an oxidizing atmosphere, control the gas flow at 5-10 L / min, the heating rate is 5℃ / min, pre-sinter at 1100-1150℃ for 25-35 minutes, the thickness of the charge should not exceed 50mm, after pre-sintering, cool naturally to room temperature, break to 3-5mm particle size with a jaw crusher, get pretreated A material with enhanced strength and improved activity;

[0089] Q2, A material wet mixing: Add deionized water to the pretreated A material in batches, control the water to material mass ratio at 6-8%, the water adding process is divided into 3-4 times, each time interval is 30-60s, mix in a mixer at 60-100r / min for 3-5 minutes, monitor the uniformity of moisture content during mixing, get wet A material with uniform moisture content and good plasticity;

[0090] Q3, A material layering ramming: Lay the wet A material in layers on the cleaned furnace bottom, strictly control the thickness of each layer at 15-20mm, use a pneumatic ramming machine for tamping, control the tamping pressure at 0.4-0.6MPa, the tamping frequency per square meter should not be less than 50 times, the tamping density reaches 2.8-3.2g / cm 3 , the interlayer bonding is treated by scoring, get dense and uniform A material without air bubbles;

[0091] Q4, B material activation treatment: dissolve sodium hydroxide NaOH and disodium hydrogen phosphate Na2HPO4 in deionized water in proportion, the concentration of sodium hydroxide is 0.1-0.3 mol / L, the concentration of disodium hydrogen phosphate is 0.05-0.15 mol / L, adjust the pH value to 8.5-9.2, mix the B material with the activation liquid according to the liquid material mass ratio of 12-15%, mix uniformly in the stirrer, and then stand for 15-20 minutes to obtain the B material slurry with enhanced activity;

[0092] Q5, B material negative pressure infiltration: load the activated B material slurry into the infiltration tank, adjust the negative pressure to-0.015 to-0.025 MPa, inject the slurry into the A material through the infiltration pipe, control the infiltration time to 10-20 minutes, and the infiltration depth is 60-80% of the thickness of the A material, to obtain the intermediate with good compounding of the B material and the A material;

[0093] Q6, medium temperature reaction treatment: place the A material with the infiltrated B material in a medium temperature furnace, heat to 350-450℃ at a heating rate of 2-3℃ / min, and keep the temperature for 80-100 minutes, during the reaction process, a small amount of water vapor is introduced to maintain humidity, the reaction atmosphere is weakly oxidizing, after the reaction is completed, slowly cool to room temperature, to obtain the preliminary combined composite structure;

[0094] Q7, C material dispersion treatment: add the C material into deionized water to prepare a suspension with a mass concentration of 25-35%, and use an ultrasonic disperser for dispersion treatment, the dispersion time is 12-18 minutes, and the temperature is controlled to be not more than 60℃ during the dispersion process, stop for 1 minute every 3 minutes of dispersion to prevent overheating, to obtain the C material suspension which is uniformly dispersed and has no agglomeration;

[0095] Q8, C material spraying and solidification: use a special spraying equipment to uniformly spray the dispersed C material suspension on the surface of the intermediate in an atomized manner, the spraying pressure is controlled to be 0.2-0.4 MPa, the spraying distance is kept at 20-30 cm, the spraying thickness is 2-3 mm, and after the spraying is completed, solidification treatment is carried out at 180-220℃ for 60-90 minutes, dry air is introduced during the solidification process, to obtain the protective layer which is smooth in surface and firmly combined;

[0096] Q9, overall sintering: sinter the product coated with the C material according to a strict temperature rising curve, the first stage is 20-300℃ at a heating rate of 1℃ / min to remove physical water and organic matter; the second stage is 300-800℃ at a heating rate of 2℃ / min for chemical reaction and preliminary sintering; the third stage is 800-1250℃ at a heating rate of 1.5℃ / min to complete high temperature sintering, keep the temperature at 1250℃ for 4-6 hours, the sintering is carried out in a weak reducing atmosphere, the concentration of carbon monoxide is controlled to be 0.5-1.5%, and the total sintering time is 24-30 hours, to obtain the modified chrome corundum ramming material product with excellent performance.

[0097] In step Q1, the pre-sintering process uses a program-controlled temperature rise, the initial temperature rise rate is 3℃ / min to 500℃, then 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 the pre-sintered A material with stable size and appropriate strength is obtained;

[0098] In step Q2, the mixing process uses a planetary mixer, the main shaft speed is 60-100r / min, the auxiliary stirring paddle speed is 2-3 times the main shaft speed, the mixing process is stopped every 1 minute to check the mixing uniformity, when the water content difference in different positions is less than 0.5% through sampling determination, it is considered that the mixing is completed, and the wet A material with uniform water distribution and good working performance is obtained;

[0099] In step Q4, the preparation of the activation solution uses a step-by-step dissolution method, first completely dissolve sodium hydroxide, then add disodium hydrogen phosphate, control the temperature at 20-30℃ during the dissolution process, after preparation, place for 2-4 hours to make it completely clear, stir every 5 minutes during the activation process, the stirring speed is 100-200r / min, cover a film during the standing process to prevent water evaporation, and the B material slurry with fully activated chemical activity is obtained.

[0100] In step Q5, the negative pressure infiltration equipment includes a vacuum pump, a pressure regulating valve, an infiltration tank and a monitoring system, the A material is subjected to vacuum pretreatment for 30-60s before infiltration, the infiltration depth is monitored in real time during the infiltration process, when the infiltration resistance suddenly increases, the negative pressure value is appropriately increased, after the infiltration is completed, the negative pressure state is maintained for 5-10 minutes to ensure sufficient infiltration, and the composite layer structure with uniform infiltration depth and tight bonding is obtained;

[0101] In step Q9, the temperature deviation of the sintering process is controlled within ±5℃, the phase change of the sample is measured every hour during the holding stage, when the expected high-temperature phase is detected, the holding is completed, the cooling process strictly controls the cooling rate to be 50-100℃ / h to 800℃, then naturally cooled to room temperature, and the modified chrome corundum ramming material product with dense structure and excellent performance is obtained.

[0102] The pretreatment of A material is based on the thermal activation mechanism. The pre-sintering process makes the surface of the aggregate particles have appropriate defects and active sites, which is beneficial to the subsequent chemical reaction. The selection of pre-sintering temperature seeks a balance point between material activation and excessive sintering. Too low temperature cannot produce enough activity, and too high temperature may lead to sintering shrinkage and pore closure. The use of oxidizing atmosphere is to remove organic impurities and carbonaceous deposits on the surface to ensure the cleanliness of the surface. The wet mixing process controls the water content to adjust the plasticity and fluidity of the material. The appropriate water content ensures good formability during tamping, while avoiding cracking and shrinkage caused by excessive water.

[0103] The layered tamping process is based on the powder densification theory. By controlling the laying thickness and tamping parameters, the material is uniformly and densely packed. The control of the thickness of each layer is crucial to the final density and uniformity. Too thick single layer is difficult to achieve internal full densification, and too thin layer affects the construction efficiency and interlayer bonding. The use of pneumatic tamping machine provides stable impact energy, and the tamping density meets the standard, which is the basis for the success of the subsequent process steps. The interlayer scoring treatment enhances the interlayer bonding strength by increasing the contact area and mechanical engagement.

[0104] The activation treatment of B material is based on the pH regulation mechanism of solution chemistry. Sodium hydroxide NaOH provides an alkaline environment, and sodium phosphate dibasic Na2HPO4 acts as a buffer. Both of them work together to maintain the system in an appropriate pH range. Alkaline environment is conducive to the dissolution and diffusion of functional components, improving their chemical activity. The standing process allows the activation reaction to proceed fully, and the components reach a state of chemical equilibrium.

[0105] Negative pressure infiltration is a mass transfer process driven by pressure gradient. By applying negative pressure to the surface of A material, a pressure gradient from the surface to the inside is formed, driving the B material slurry to penetrate into the pore network. The control of the penetration depth is crucial to the final protection effect. Too shallow penetration cannot form an effective protective layer, and too deep penetration may damage the structural integrity of the base layer. Real-time monitoring during the infiltration process adjusts the process parameters in time to ensure the consistency of the infiltration effect.

[0106] The moderate temperature reaction treatment is based on the principle of solid phase reaction kinetics. In the temperature range of 350-450℃, chemical reactions and interfacial bonding occur between components. The selection of temperature range considers the thermodynamic and kinetic factors of the reaction to ensure the full reaction and avoid adverse phase changes caused by high temperature. The trace amount of water vapor introduced during the reaction process helps the hydration reaction of some components, while preventing cracks caused by excessive dehydration. The weak oxidizing atmosphere promotes the oxidation reaction of some components, and the oxygen content is strictly controlled to avoid excessive oxidation of chromium.

[0107] The dispersion treatment of C material is based on the stability principle of colloid chemistry, and the agglomeration between particles is broken by ultrasonic dispersion technology to form a stable suspension system. The cavitation effect of ultrasonic wave produces strong mechanical shear force, effectively disperses the particle agglomerates, and improves the uniformity of dispersion. The temperature in the dispersion process is strictly controlled to avoid the rapid evaporation of the solvent and the re-agglomeration of the particles caused by high temperature.

[0108] The spray curing process is based on the principle of thin film formation, and the uniform coating of the protective layer is realized by atomizing spraying. The control of spraying parameters includes pressure, distance, moving speed and other aspects, and the curing process makes the solvent evaporate, the particles gradually approach and form a continuous solid film, and the appropriate curing temperature promotes the crosslinking reaction of the silane coupling agent and enhances the bonding force between the coating and the substrate.

[0109] The whole sintering process adopts the way of segmented heating corresponding to different physical and chemical processes. The first low-temperature heating is used to remove physically adsorbed water and thermal decomposition of organic components, and the heating rate is controlled at a slow level to avoid cracking caused by rapid volume change. The second medium-temperature heating corresponds to the chemical reaction and preliminary sintering process, and solid-phase reactions occur between components to form new compound phases, while the material begins to shrink and densify. The third high-temperature sintering completes the final densification of the material, grain growth and pore elimination, forming a dense ceramic structure. The holding process makes the reaction fully proceed, eliminates internal stress, and improves the structural stability of the material.

[0110] The control of weak reducing atmosphere is crucial to prevent the generation of hexavalent chromium. Carbon monoxide CO as a reducing gas reacts with the possible hexavalent chromium, and the presence of CO also inhibits the further oxidation of chromium in the material. The precise control of the atmosphere is realized by an automatic system, which monitors and adjusts the gas composition in real time to ensure the stability and reproducibility of the sintering process.

[0111] Through the above process, the modified chrome corundum ramming mass with excellent oxidation resistance, permeation resistance and high strength characteristics is formed, which solves the technical problems faced by traditional chrome corundum ramming mass in high temperature application, and provides a reliable technical solution for related industrial applications.

[0112] Example 1, this embodiment is directed to the application of 1600℃ high temperature electric arc furnace bottom, prepared with excellent resistance to hexavalent chromium generation performance of modified chromium corundum ramming material. According to the formulation of the present application, the components are accurately weighed as follows: A material components include chromium corundum aggregate Cr2O3·Al2O350 parts, titanium dioxide coated alumina microspheres TiO2@Al2O310 parts, calcium sulfide CaS·2H2O3 parts, porous silicon carbide microspheres β-SiC4 parts. B material components include chromium oxide-zirconium oxide composite nano powder Cr2O3-ZrO215 parts, sodium thiosulfate Na2S2O3·5H2O4.5 parts, tricalcium phosphate Ca3(PO4)26 parts, hexagonal boron nitride flake crystal h-BN3 parts. C material components include aluminum dihydrogen phosphate-magnesium hydroxide complex Al(H2PO4)3-Mg(OH)212 parts, calcium fluoride-alumina eutectic CaF2-Al2O33.5 parts, γ-methacryloxypropyltrimethoxysilane KH-5701.0 parts.

[0113] Chromium corundum aggregate is prepared by electric melting method, chromium oxide Cr2O3 and alumina Al2O3 are dosed according to the molar ratio of 1:4, melted in the electric arc furnace at 1900℃ for 5 hours, and coke is added as a reducing agent during the melting process, the chromium oxide content is controlled at 20%, and after cooling, it is broken to an average particle size of 1.5mm. When preparing the titanium dioxide coated alumina microspheres, α-Al2O3 microspheres with a particle size of 2μm are preheated to 400℃ in a fluidized bed reactor, the molar ratio of TiCl4 to H2O is controlled at 1:3, and CVD reaction is carried out at 500℃ for 75 minutes, the flow rate of fluidizing gas is maintained at 1.0m / s, and the composite microspheres with a coating thickness of 75nm are obtained.

[0114] When preparing the chromium oxide-zirconium oxide composite nano powder, Cr2O3 and ZrO2 are mixed according to the mass ratio of 4:1, the slurry solid content is 55%, ball milling for 30 hours at a speed of 250r / min, and calcination at 1250℃ for 3 hours to obtain a composite nano powder with an average particle size of 35nm. During the preparation of the aluminum dihydrogen phosphate-magnesium hydroxide complex, the molar ratio of aluminum hydroxide to phosphoric acid is 1:3, the reaction is carried out at 30℃ for 5 hours, the stirring speed is 400r / min, after adding magnesium hydroxide, the stirring is continued for 2 hours, and vacuum drying is carried out at 70℃ for 36 hours. The calcium fluoride-alumina eutectic is melted at 1450℃ for 2.5 hours, the argon flow rate is 7L / min, and the cooling rate is 75℃ / min.

[0115] The construction process is as follows: A material is pre-sintered at 1125℃ for 30 minutes, the oxygen content is 20%, and it is broken to a particle size of 4mm. The water material mass ratio is controlled at 7% during wet mixing, the main shaft speed of the planetary mixer is 80r / min, and the mixing time is 4 minutes. The thickness of each layer is 18mm during layering and ramming, the ramming pressure is 0.5MPa, the ramming frequency is 55 times per square meter, and the density reaches 3.0g / cm 3The B material activation treatment is carried out at a NaOH concentration of 0.2 mol / L, a Na2HPO4 concentration of 0.1 mol / L, a pH value of 9.0, a liquid-to-material mass ratio of 13.5%, and a standing time of 18 minutes. The negative pressure infiltration pressure is -0.02 MPa, the infiltration time is 15 minutes, and the infiltration depth is 70% of the thickness of the A material. The medium-temperature reaction is carried out at 400 ℃ for 90 minutes, the heating rate is 2.5 ℃ / min, trace water vapor is used to maintain humidity, and a weak oxidizing atmosphere is used. The C material suspension has a mass concentration of 30%, ultrasonic dispersion is carried out for 15 minutes, the spraying pressure is 0.3 MPa, the distance is 25 cm, the thickness is 2.5 mm, and curing is carried out at 200 ℃ for 75 minutes. The overall firing is carried out in three stages, the first stage is heated to 300 ℃ at a rate of 1 ℃ / min, the second stage is heated to 800 ℃ at a rate of 2 ℃ / min, the third stage is heated to 1250 ℃ at a rate of 1.5 ℃ / min, the holding time is 5 hours, the CO concentration is 1.0%, and the total firing time is 27 hours.

[0116] Comparative Example 1 is different from Example 1 in that a traditional single-component chrome-corundum ramming material formula is used, which includes chrome-corundum aggregate 85 parts, tricalcium phosphate 10 parts, and phosphoric acid binder 5 parts, and does not contain any antioxidant components. During preparation, the components are directly dry-mixed for 10 minutes, 8% water is added, conventional ramming construction is carried out, and firing is carried out at 1200 ℃, the heating rate is 5 ℃ / min, the holding time is 2 hours, and firing is carried out in an air atmosphere. Other conditions are the same as in Example 1.

[0117] Comparative Example 2 is different from Example 1 in that a conventional antioxidant is added to the traditional formula, which includes chrome-corundum aggregate 75 parts, tricalcium phosphate 8 parts, metallic chromium powder 3 parts, silicon carbide powder 4 parts, and phosphoric acid binder 10 parts. The preparation process is similar to that in Comparative Example 1, but the firing temperature is increased to 1220 ℃, the holding time is 3 hours, and firing is carried out in a weak reducing atmosphere. Other conditions are the same as in Example 1.

[0118] Comparative Example 3 is different from Example 1 in that a two-component structure design is used, the A material includes chrome-corundum aggregate 60 parts, zirconia 10 parts, and tricalcium phosphate 5 parts. The B material includes chromium oxide 15 parts and phosphoric acid binder 10 parts. During preparation, the A material and the B material are mixed separately, then compounded in a mass ratio of 8:2, the construction process is simplified, and firing is carried out at 1180 ℃ for 4 hours. Other conditions are the same as in Example 1.

[0119] The performance comparison experiment is designed, a plurality of standardized test procedures are used to evaluate the performance of the examples and the comparative examples, and the specific conditions are as follows:

[0120] The determination of hexavalent chromium content was performed according to the standard HJ687-2014, and the sample was detected after being kept at 1200℃ in an oxidizing atmosphere for 4 hours. The thermal shock resistance test was performed according to the standard GB / T30873-2014, and the thermal stability of the material was evaluated by repeated high and low temperature alternating cycles. The mechanical strength test was performed according to the standard YB / T2208-1998 to determine the compressive strength, and the test was performed at room temperature and 1200℃ high temperature conditions, respectively. The thermal conductivity test was performed according to the standard YB / T4130-2005, and the thermal conductivity of each sample was determined at 800℃. In order to verify the long-term performance of the material, a thermal fatigue cycle test was also performed, and the cold and hot cycles were performed between 1200℃ and 200℃ according to the standard YB / T4018-1991. The slag corrosion resistance test was performed according to the standard JISR2213, and the corrosion depth was determined after being corroded by standard slag at 1500℃ for 6 hours. The environmental safety evaluation was performed according to the standard "Solid waste leaching toxicity leaching method" HJ / T299-2007. The experimental results are as follows:

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

[0122] The thermal shock resistance was tested according to GB / T30873-2014, and the thermal shock resistance of Example 1 was 18 times, and the thermal shock resistance of Comparative Example 1 was 7 times, the thermal shock resistance of Comparative Example 2 was 10 times, and the thermal shock resistance of Comparative Example 3 was 12 times. Example 1 was improved by 157% compared with Comparative Example 1, showing a significant advantage. The compressive strength was determined according to YB / T2208-1998, and the compressive strength of Example 1 at room temperature was 85.2MPa, and the compressive strength at 1200℃ was 48.3MPa, and the compressive strength of Comparative Example 1 was 65.8MPa and 32.1MPa, respectively, the compressive strength of Comparative Example 2 was 71.4MPa and 36.8MPa, respectively, and the compressive strength of Comparative Example 3 was 76.2MPa and 41.5MPa, respectively.

[0123] The thermal conductivity test was performed according to YB / T4130-2005, and the thermal conductivity of Example 1 at 800℃ was 3.85W / m·K, and the thermal conductivity of Comparative Example 1 was 2.68W / m·K, the thermal conductivity of Comparative Example 2 was 3.12W / m·K, and the thermal conductivity of Comparative Example 3 was 3.45W / m·K, and Example 1 was improved by 43.7% compared with Comparative Example 1. The apparent porosity test results showed that the apparent porosity of Example 1 was 14.2%, the apparent porosity of Comparative Example 1 was 18.6%, the apparent porosity of Comparative Example 2 was 16.8%, and the apparent porosity of Comparative Example 3 was 15.4%, and the bulk density of Example 1 was 3.25g / cm 3 , and the bulk density of Comparative Example 1 was 2.98g / cm3 .

[0124] Example 2, this example is directed to the application requirements of the medium temperature induction furnace lining at 1400℃, the component dosage in the moderate matching range is used. The A material components include chromium corundum aggregate Cr2O3·Al2O348 parts, titanium dioxide coated alumina microspheres TiO2@Al2O39 parts, calcium sulfide dihydrate CaS·2H2O 2.5 parts, porous silicon carbide microspheres β-SiC 3.5 parts. The B material components include chromium oxide-zirconium oxide composite nano powder Cr2O3-ZrO214 parts, sodium thiosulfate pentahydrate Na2S2O3·5H2O 4 parts, tricalcium phosphate Ca3(PO4)25 parts, and hexagonal boron nitride flake crystal h-BN 2.5 parts. The C material components include aluminum dihydrogen phosphate-magnesium hydroxide complex Al(H2PO4)3-Mg(OH)210 parts, calcium fluoride-alumina eutectic CaF2-Al2O33 parts, and γ-methacryloxypropyltrimethoxysilane KH-570 0.8 parts.

[0125] The preparation process parameters are moderately adjusted to adapt to medium temperature applications, the fused temperature of chromium corundum aggregate is 1850℃, the melting time is 4.5 hours, the chromium oxide content is controlled to be 18%, and the broken particle size is 1.0mm. In the titanium dioxide coating process, the molar ratio of TiCl4 to H2O is 1:2.5, the reaction temperature is 480℃, the CVD time is 70 minutes, and the coating layer thickness is 65nm. The mass ratio of chromium oxide-zirconium oxide composite powder Cr2O3 to ZrO2 is 3.5:1, ball milling is performed for 28 hours, the calcination temperature is 1220℃, and the average particle size is 30nm.

[0126] The construction process is optimized for medium temperature applications, the A material pre-sintering temperature is 1110℃, the pre-sintering time is 28 minutes, and the broken particle size is 3.5mm. The water material mass ratio is 6.5%, the mixing time is 3.5 minutes, the ramming pressure is 0.45MPa, the ramming frequency is 52 times per square meter, and the density is 2.9g / cm 3 . The B material activation liquid NaOH concentration is 0.15mol / L, the Na2HPO4 concentration is 0.08mol / L, the pH value is 8.8, and the liquid material mass ratio is 12.5%. The negative pressure infiltration is -0.018MPa, the infiltration time is 12 minutes, the medium temperature reaction temperature is 380℃, and the holding time is 85 minutes. The C material spraying thickness is 2.2mm, the solidification temperature is 190℃, and the time is 70 minutes. The overall firing is performed at 1220℃ for 4.5 hours, the CO concentration is 0.8%, and the total time is 25 hours.

[0127] Comparative Example 4, different from Example 2, a traditional formula with high chromium content is used, chromium corundum aggregate 90 parts (chromium oxide content 30%), tricalcium phosphate 5 parts, phosphoric acid binder 5 parts, and water 10%, fired at 1150℃ for 3 hours in an air atmosphere. The same as Example 2.

[0128] Comparative Example 5, which is different from Example 2 in that a carbon antioxidant is added in the conventional formula, 78 parts of chrome corundum aggregate, 5 parts of graphite powder, 2 parts of carbon black, 10 parts of tricalcium phosphate, 5 parts of phosphate binder, fired at 1180°C, reducing atmosphere. The same as Example 2.

[0129] Comparative Example 6, which is different from Example 2 in that a simplified three-component structure is used, each component is prepared according to a mass ratio of 6:3:1, the total formula is 70 parts of chrome corundum aggregate, 10 parts of zirconia powder, 15 parts of phosphate binder, 5 parts of silica powder, and the construction process is simplified. The same as Example 2.

[0130] Performance test results comparison

[0131] The hexavalent chromium content test shows that Example 2 is 1.8 mg / kg, Comparative Example 4 is 35.2 mg / kg, Comparative Example 5 is 22.6 mg / kg, and Comparative Example 6 is 18.9 mg / kg. The hexavalent chromium inhibition rate of Example 2 reaches 94.9%, which is significantly better than each comparative example. The thermal shock resistance of Example 2 is 16 times, that of Comparative Example 4 is 6 times, that of Comparative Example 5 is 8 times, and that of Comparative Example 6 is 11 times. Example 2 is improved by 45.5% compared with the best comparative example.

[0132] The cold compressive strength of Example 2 is 82.6 MPa, the high-temperature compressive strength is 45.8 MPa, the cold compressive strength of Comparative Example 4 is 62.4 MPa and 29.8 MPa respectively, the cold compressive strength of Comparative Example 5 is 68.7 MPa and 34.2 MPa, and the cold compressive strength of Comparative Example 6 is 73.8 MPa and 38.6 MPa. The thermal conductivity of Example 2 at 800°C is 3.62 W / m·K, and that of Comparative Example 4 is 2.45 W / m·K, which is improved by 47.8%. The apparent porosity of Example 2 is 13.8%, and the bulk density is 3.18 g / cm 3 , which are better than each comparative example.

[0133] Example 3, which is aimed at 1500°C refining furnace application, uses the following raw materials: A material components include chrome corundum aggregate Cr2O3·Al2O3 52 parts, titanium dioxide coated alumina microspheres TiO2@Al2O3 11 parts, calcium sulfide dihydrate CaS·2H2O 3.5 parts, porous silicon carbide microspheres β-SiC 4.5 parts. B material components include chromium oxide-zirconia composite nano powder Cr2O3-ZrO2 16 parts, sodium thiosulfate pentahydrate Na2S2O3·5H2O 5 parts, tricalcium phosphate Ca3(PO4)2 7 parts, hexagonal boron nitride flake crystal h-BN 3.5 parts. C material components include aluminum dihydrogen phosphate-magnesium hydroxide complex Al(H2PO4)3-Mg(OH)2 13 parts, calcium fluoride-alumina eutectic CaF2-Al2O3 4 parts, γ-methacryloxypropyltrimethoxysilane KH-570 1.2 parts.

[0134] The preparation process is strengthened for high temperature application, the electric melting temperature of chrome corundum aggregate is 1950℃, the melting time is 6 hours, the chromium oxide content is 22%, and the aggregate is crushed to 2.0mm particle size. The CVD coating reaction temperature is 520℃, the time is 80 minutes, and the coating layer thickness is 85nm. The mass ratio of chromium oxide-zirconium oxide composite powder is 4.5:1, the ball milling time is 32 hours, the calcination temperature is 1280℃, and the average particle size is 40nm. The reaction time of aluminum dihydrogen phosphate-magnesium hydroxide composite is extended to 6 hours, the drying temperature is 75℃, and the time is 48 hours.

[0135] The construction process parameters are as follows: pre-sintering temperature 1140℃, time 32 minutes, water aggregate mass ratio 7.5%, ramming pressure 0.55MPa, and density 3.1g / cm 3 . The concentration of the B material activation solution is increased, NaOH 0.25mol / L, Na2HPO40.12mol / L, pH value 9.1, and liquid aggregate mass ratio 14%. The negative pressure infiltration is -0.022MPa, the medium temperature reaction temperature is 420℃, and the holding time is 95 minutes. The C material spraying thickness is 2.8mm, the solidification temperature is 210℃, and the time is 85 minutes. The firing temperature is 1280℃, the holding time is 5.5 hours, and the CO concentration is 1.2%.

[0136] Comparative Example 7, which is different from Example 3, uses an ultra-high chromium content formula, 95 parts of chrome corundum aggregate (chromium oxide content 35%), 5 parts of phosphoric acid binder, and firing at 1100℃ for 2 hours, aiming for the highest refractory performance but ignoring environmental protection requirements. The others are the same as Example 3.

[0137] Comparative Example 8, which is different from Example 3, uses a composite of multiple antioxidants, including 75 parts of chrome corundum aggregate, 3 parts of metallic Al powder, 6 parts of SiC powder, 2 parts of graphite powder, 10 parts of tricalcium phosphate, 4 parts of phosphoric acid binder, and firing in a strong reducing atmosphere. The others are the same as Example 3.

[0138] Comparative Example 9, which is different from Example 3, uses a ceramic binder system, 80 parts of chrome corundum aggregate, 10 parts of alumina micropowder, 5 parts of silica fume, and 5 parts of clay binder, and firing at 1300℃. The others are the same as Example 3.

[0139] Performance test results comparison

[0140] The hexavalent chromium content of Example 3 is only 0.8mg / kg, while that of Comparative Example 7 is as high as 42.6mg / kg, that of Comparative Example 8 is 28.3mg / kg, and that of Comparative Example 9 is 25.1mg / kg. The inhibitory effect of Example 3 is the most significant. The thermal shock resistance of Example 3 reaches 20 times, while that of Comparative Example 7 is 5 times, that of Comparative Example 8 is 9 times, and that of Comparative Example 9 is 13 times. Example 3 still improves by 53.8% compared to the best comparative example.

[0141] The mechanical strength of Example 3 is 88.5 MPa at room temperature and 51.2 MPa at high temperature, while the mechanical strength of Comparative Example 7 is 59.3 MPa and 27.6 MPa, the mechanical strength of Comparative Example 8 is 74.8 MPa and 38.9 MPa, and the mechanical strength of Comparative Example 9 is 81.2 MPa and 44.7 MPa. The thermal conductivity of Example 3 is 4.15 W / m·K at 1000℃, while the thermal conductivity of Comparative Example 7 is 2.82 W / m·K, which is increased by 47.2%. The apparent porosity is 13.5%, and the bulk density is 3.32 g / cm 3 , and the structure is more compact.

[0142] Example 4 is directed to the application of a 1350℃ ladle refining furnace working layer, and the raw materials used are as follows: the A material components include chromium corundum aggregate Cr2O3·Al2O347 parts, titanium dioxide coated alumina microspheres TiO2@Al2O38.5 parts, calcium sulfide dihydrate CaS·2H2O 2.8 parts, and porous silicon carbide microspheres β-SiC 3.2 parts. The B material components include chromium oxide-zirconium oxide composite nano powder Cr2O3-ZrO213 parts, sodium thiosulfate pentahydrate Na2S2O3·5H2O 3.5 parts, tricalcium phosphate Ca3(PO4)24.5 parts, and hexagonal boron nitride flaky crystals h-BN 2.2 parts. The C material components include aluminum dihydrogen phosphate-magnesium hydroxide composite Al(H2PO4)3-Mg(OH)29 parts, calcium fluoride-alumina eutectic CaF2-Al2O32.8 parts, and γ-methacryloxypropyltrimethoxysilane KH-570 0.6 parts.

[0143] The preparation process parameters are moderate, the chromium corundum aggregate is fused at 1880℃ for 4.2 hours, the chromium oxide content is 17%, and the particle size is 0.8 mm. The CVD coating temperature is 460℃, the time is 65 minutes, and the coating thickness is 60 nm. The composite nano powder mass ratio is 3.2:1, the ball milling time is 26 hours, the calcination temperature is 1200℃, and the particle size is 25 nm. The composite preparation reaction time is 4.5 hours, the drying temperature is 65℃, and the drying time is 30 hours. The eutectic melting temperature is 1420℃, and the melting time is 2.2 hours.

[0144] The construction process is optimized to improve construction efficiency, the pre-sintering temperature is 1100℃, the pre-sintering time is 25 minutes, and the particle size is 3.2 mm. The water material ratio is 6.2%, the mixing time is 3.2 minutes, the ramming pressure is 0.42 MPa, and the ramming frequency is 50 times / m 2 , the density is 2.85 g / cm 3 . The activation liquid is NaOH 0.12 mol / L and Na2HPO40.07 mol / L, the pH is 8.6, the liquid material ratio is 12%. The infiltration pressure is -0.016 MPa, the infiltration time is 10 minutes, the reaction temperature is 365℃, and the reaction time is 80 minutes. The spraying thickness is 2.0 mm, the solidification temperature is 185℃, and the solidification time is 65 minutes. The firing temperature is 1200℃, the holding time is 4.2 hours, and the CO content is 0.7%.

[0145] Comparative Example 10, which is different from Example 4, is an economic formula for cost optimization, with 82 parts of chrome corundum aggregate, 13 parts of tribasic calcium phosphate, and 5 parts of phosphoric acid binder, simplified preparation process, and sintering temperature of 1150°C with 2.5 hours of holding. The other aspects are the same as those in Example 4.

[0146] Comparative Example 11, which is different from Example 4, is based on a traditional formula with the addition of some modified components, with 70 parts of chrome corundum aggregate, 8 parts of zirconia powder, 4 parts of silicon carbide powder, 12 parts of tribasic calcium phosphate, and 6 parts of phosphoric acid binder, with slightly optimized process. The other aspects are the same as those in Example 4.

[0147] Comparative Example 12, which is different from Example 4, adopts a double-layer structure design, with a dense layer (85 parts of chrome corundum aggregate and 15 parts of binder) as the bottom layer and a functional layer (with the addition of antioxidant components) as the surface layer, with layered construction but without achieving deep composition of components. The other aspects are the same as those in Example 4.

[0148] The content of hexavalent chromium in Example 4 is 1.5 mg / kg, that in Comparative Example 10 is 31.8 mg / kg, that in Comparative Example 11 is 19.4 mg / kg, and that in Comparative Example 12 is 16.7 mg / kg, with an inhibition rate of 95.3% for Example 4. The thermal shock resistance is 15 times, and that of the comparative examples is 6 times, 9 times, and 11 times, respectively, with obvious advantages of Example 4.

[0149] The compressive strength of Example 4 is 80.8 MPa at room temperature and 44.6 MPa at high temperature, that of Comparative Example 10 is 63.5 MPa and 30.4 MPa, that of Comparative Example 11 is 69.2 MPa and 35.8 MPa, and that of Comparative Example 12 is 74.6 MPa and 40.2 MPa. The thermal conductivity coefficient at 800°C is 3.48 W / m·K, which is increased by 38.1% compared with 2.52 W / m·K of Comparative Example 10. The apparent porosity is 14.8%, and the bulk density is 3.12 g / cm 3 .

[0150] To verify the long-term use performance of the examples, a thermal fatigue cycle test was performed. As shown in Figure 4 , according to the YB / T4018-1991 standard, cold and hot cycles were performed at 1200°C ↔ 200°C. The thermal fatigue life of Examples 1-4 is 126 times, 118 times, 135 times, and 112 times, respectively, while the average cycle number of each comparative example is in the range of 60-80 times, with an increase of 50-80% in the thermal fatigue life of the examples.

[0151] The slag resistance test was performed according to the standard JISR2213, using standard slag to erode at 1500℃ for 6 hours. The erosion depths of examples 1-4 were 2.8mm, 3.2mm, 2.5mm, 3.0mm respectively, while the erosion depths of the comparative examples were generally in the range of 4.5-6.2mm, the erosion resistance of the examples was improved by 35-45%.

[0152] The line change rate test results showed that the line change rates of examples 1-4 during high temperature use were all controlled within ±0.3%, while the line change rates of the comparative examples generally reached ±0.5-0.8%, the examples showed better dimensional stability. The mass loss rate test showed that the mass loss rates of the examples were controlled at 0.8-1.2%, while the comparative examples were 1.5-2.8%, proving that the examples had better high temperature stability.

[0153] The experimental results are shown in Table 1 and Figures 1-4 .

[0154] Table 1 Comparison of main performance indicators of examples and comparative examples

[0155] As can be seen from Table 1 and Figure 1 , the cold pressure strength of examples 1-4 was generally in the range of 80-88MPa, while the average value of the comparative examples was mostly between 62-76MPa. In terms of high temperature pressure strength, the values of the examples were concentrated in 44-51MPa, while the comparative examples were in the range of 28-41MPa. In terms of thermal conductivity, the thermal conductivity of the examples was significantly higher than that of the comparative examples, the examples were between 3.48-4.15W / m·K, while the comparative examples were mostly in the range of 2.45-3.78W / m·K. In terms of apparent porosity, the examples showed lower values, generally between 13.5-14.8%, while the apparent porosity of the comparative examples was relatively high, in the range of 15.4-20.1%.

[0156] Figure 2 The examples showed the advantages of the examples in environmental performance, the content of hexavalent chromium of the examples was significantly lower than that of the comparative examples, the content of hexavalent chromium of examples 1-4 was controlled at a very low level of 0.8-1.8mg / kg, while the average value of the comparative examples was as high as 12.3-42.6mg / kg. In the comparison of thermal shock resistance, the examples showed stronger thermal shock stability, the number was between 15-20 times, while the comparative examples was only 5-13 times. In terms of bulk density, the examples reached 3.12-3.32g / cm 3 , higher than the comparative examples of 2.89-3.18g / cm 3 .

[0157] Figure 3The performance improvement of the examples relative to the comparative examples is visually displayed in percentage form. The improvement in cold pressure strength and high temperature pressure strength is generally in the range of 20-40%, the reduction in hexavalent chromium content is more than 90%, and the improvement in thermal shock resistance varies between 50-300%, showing the comprehensive performance advantages of examples 1-4.

[0158] Figure 4 The excellent performance of the examples in long-term use is disclosed. The thermal fatigue cycle life of the examples is 112-135 times, while that of the comparative examples is only 60-75 times, with an improvement of about 70-80%. In the molten slag erosion resistance test, the erosion depth of the examples is controlled at 2.5-3.2 mm, and the erosion depth of the comparative examples is 5.0-5.5 mm, showing stronger erosion resistance of the examples.

[0159] It can be seen that the modified chrome corundum ramming mixture of the present application has achieved remarkable advantages in environmental protection performance, mechanical strength, physical properties and long-term stability. The substantial reduction of hexavalent chromium content indicates that the environmental protection goal has been effectively achieved, the improvement of mechanical strength and thermal conductivity proves that the performance has been comprehensively improved, and the improvement of thermal shock resistance and thermal fatigue life shows that the material has better long-term stability. The performance improvement is mainly due to the synergistic effect of the three materials of the present application. The titanium dioxide coated alumina microspheres in A material form a dense rutile protective film on the surface of chrome corundum aggregate through chemical vapor deposition technology, which physically blocks the direct contact of oxygen and chromium elements, and inhibits the oxidation reaction of hexavalent chromium from the source. As a chemical capture agent, calcium sulfide dihydrate reacts with the possible 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 a directional channel for the penetration of B material, ensuring that the functional components can effectively penetrate into the interior of the base layer. The sodium thiosulfate pentahydrate in B material releases active sulfur ions under medium temperature conditions, which selectively reduces any hexavalent chromium to convert it into low-toxicity trivalent chromium. The chromium oxide-zirconia composite nano-powder utilizes the phase change toughening effect of zirconia and the surface effect of nano-particles to significantly improve the density and thermal shock resistance of the material. The hexagonal boron nitride sheet crystal forms an efficient heat conduction channel network with its layered structure, ensuring uniform heat transfer within the material. Tricalcium phosphate plays a pH buffering role, maintaining the system within a suitable pH range to provide a stable chemical environment for the reduction reaction. The aluminum dihydrogen phosphate-magnesium hydroxide compound in C material undergoes dehydration and polycondensation reaction in-situ to generate low-permeability aluminum phosphate ceramic phase during high-temperature sintering, effectively preventing the penetration of external oxidizing gas into the inner layer. The calcium fluoride-alumina eutectic as a fluxing agent reduces the reaction temperature and promotes the densification of the components during sintering, while the high electronegativity of fluoride ions forms a charge protection layer on the surface of the material to further inhibit the oxidation reaction. The silane coupling agent establishes a chemical bridge between the organic-inorganic interface through its bifunctional structure, significantly enhancing the interfacial bonding strength between the heterogeneous layers.

[0160] The layered ramming and penetration technology used in the preparation process realizes the three-dimensional network distribution of different functional components in the material, forming a gradient protection structure, which comprehensively inhibits the generation of hexavalent chromium through the triple mechanism of blocking the oxidation path, chemical reduction inhibition and sealing the gas penetration channel, while achieving the synergistic improvement of mechanical properties and physical properties.

[0161] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A modified chrome-corundum ramming mix, characterized in that It comprises three components of A material, B material and C material by weight parts, wherein: A material comprises: 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; porous silicon carbide microspheres β-SiC: 3-5 parts; B material comprises: chromium oxide-zirconium oxide composite nano powder Cr2O3-ZrO2: 12-18 parts; sodium thiosulfate pentahydrate Na2S2O3·5H2O: 3-6 parts; tricalcium phosphate Ca3(PO4)2: 4-8 parts; hexagonal boron nitride flaky crystal h-BN: 2-4 parts; C material comprises: aluminum dihydrogen phosphate-magnesium hydroxide composite Al(H2PO4)3-Mg(OH)2: 8-15 parts; calcium fluoride-alumina eutectic CaF2-Al2O3: 2-5 parts; γ-methacryloylpropyltrimethoxysilane KH-570: 0.5-1.5 parts.

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

3. Process for the production of a modified chrome-corundum ramming mix according to any one of claims 1 to 2, characterized in that It comprises the following steps: S1, preparation of titanium dioxide coated alumina microspheres: the particle size of 1-3 μm α-Al2O3 microspheres is pretreated to remove surface impurities, then placed in a fluidized bed reactor, preheated to 400℃, then four chlorine titanium TiCl4 vapor and water vapor H2O are introduced, the molar ratio of titanium tetrachloride to water vapor is controlled at 1:2-1:4, the chemical vapor deposition reaction is carried out at a temperature of 450-550℃ for 60-90 minutes, the flow rate of fluidizing gas is controlled at 0.8-1.2 m / s during the reaction, the reaction pressure is atmospheric pressure, and alumina microspheres coated with a uniform titanium dioxide layer with a thickness of 50-100 nm are obtained; S2, preparation of chromium oxide-zirconia composite nano powder: chromium oxide Cr2O3 nano powder and zirconia ZrO2 nano powder are accurately weighed and mixed according to a mass ratio of 3:1-5:1, deionized water is added to prepare a slurry with a solid content of 50-60%, and the slurry is put into a ball mill with zirconia balls as the grinding medium, the ball-to-material ratio is 3:1-5:1, and the rotation speed is 200-300 r / min, ball milling for 24-36 hours until the particle size is uniform, then spray drying to remove water, and calcining at 1200-1300℃ for 2-4 hours with a temperature rising rate of 5℃ / min to obtain well-crystallized chromium oxide-zirconia composite nano powder; S3, preparation of aluminum dihydrogen phosphate-magnesium hydroxide composite: aluminum hydroxide Al(OH)3 powder is added to a reaction kettle, 85% phosphoric acid H3PO4 solution is slowly added, and the aluminum hydroxide and phosphoric acid are reacted at a molar ratio of 1:3, an aluminum dihydrogen phosphate solution is prepared by reacting at a temperature of 25-35℃ and a stirring speed of 300-500 r / min for 4-6 hours, then magnesium hydroxide Mg(OH)2 powder is added, and stirring is continued for 2 hours to disperse uniformly, and finally drying at 60-80℃ for 24-48 hours to obtain an aluminum dihydrogen phosphate-magnesium hydroxide composite; S4, preparation of calcium fluoride-alumina eutectic: calcium fluoride CaF2 and alumina Al2O3 are accurately mixed according to a molar ratio of 1:1, and then placed in a platinum gold crucible, melted at 1400-1500℃ under an argon protective atmosphere for 2-3 hours, and the reaction is completed by intermittent stirring during the melting process, and the reaction is completed by rapid cooling to room temperature at a cooling rate of 50-100℃ / min, and then coarsely broken by a jaw crusher and finely ground by a ball mill to 100-300 mesh to obtain a calcium fluoride-alumina eutectic; S5, A material preparation: chromium corundum aggregate, titanium dioxide coated alumina microspheres prepared in step S1, calcium sulfide dihydrate CaS·2H2O, and porous silicon carbide microspheres β-SiC are put into a forced mixer, dry mixed at room temperature for 10-15 minutes, the mixing speed is controlled at 60-80 r / min, and the components are uniformly distributed by adding 3 times during the mixing process with an interval of 2-3 minutes to obtain A material. S6, B material preparation: the chromium oxide-zirconium oxide composite nano-powder prepared in step S2, sodium thiosulfate Na2S2O3.5H2O, tricalcium phosphate Ca3(PO4)2, and hexagonal boron nitride flake crystal h-BN were put into a mixing device, and dry mixing was carried out under nitrogen protection for 8-12 minutes, and the temperature was controlled to be not more than 40 DEG C during the mixing process, so that the B material with stable chemical composition was obtained; S7, C material preparation: the aluminum dihydrogen phosphate-magnesium hydroxide composite prepared in step S3, the calcium fluoride-aluminum oxide eutectic prepared in step S4, and gamma-methacryloxypropyltrimethoxysilane KH-570 were sequentially added into a reaction kettle, the silane coupling agent was mixed with the composite for 3 minutes, and then the eutectic was added and uniformly stirred for 5 minutes, and the stirring speed was controlled to be 100-150 r / min, so that the C material with good bonding performance was obtained.

4. The manufacturing process of claim 3, wherein, In step S1, the chemical vapor deposition reaction is carried out in a reactor with temperature zoning, the preheating zone temperature is 350-400 DEG C, the reaction zone temperature is 450-550 DEG C, the post-treatment zone temperature is 300-350 DEG C, the carrier gas is high-purity nitrogen, the flow rate is 100-200 mL / min, the coating thickness is monitored in real time during the reaction, and the reaction is stopped when the coating thickness reaches 50-100 nm, so that the titanium dioxide coated aluminum oxide microspheres with uniform coating and firm bonding are obtained.

5. The manufacturing process of claim 3, wherein, In step S2, the ball milling process is divided into two stages of coarse milling and fine milling, the coarse milling is carried out at a speed of 200 r / min for 12 hours, the fine milling is carried out at a speed of 250-300 r / min for 12-24 hours, the particle size distribution is checked every 6 hours during the ball milling process, the ball milling is stopped when the D90 particle size reaches 100-200 nm, the inlet air temperature of the spray drying is 180-220 DEG C, and the outlet air temperature is 80-100 DEG C, so that the composite nano-powder with good dispersibility and uniform particle size is obtained.

6. The manufacturing process of claim 3, wherein, In step S3, the reaction of aluminum hydroxide and phosphoric acid is carried out in a dropwise manner, the dropwise adding speed of phosphoric acid is 2-5 mL / min, the temperature of the system is controlled to be not more than 40 DEG C during the dropwise adding process, the pH value of the reaction system decreases from 12 to 2-3 during the reaction process, the pH value rises to 6-7 after the addition of magnesium hydroxide, vacuum drying is adopted in the drying process, and the pressure is controlled to be-0.08 to-0.1 MPa, so that the aluminum dihydrogen phosphate-magnesium hydroxide composite with stable structure and uniform dispersion is obtained.

7. The manufacturing process of claim 3, wherein, In step S4, the melting reaction is carried out in a high-temperature furnace, the heating rate is controlled to be 10 DEG C / min, the argon flow rate during the melting process is 5-10 L / min, the stirring is carried out every 30 minutes for 1-2 minutes each time, the complete melting is indicated by the uniform and transparent appearance of the melt, the rapid cooling is carried out by using a metal mold, the coarse crushing is carried out first to 10-20 mm, and then the fine grinding is carried out to the required particle size, so that the calcium fluoride-aluminum oxide eutectic with compact structure and good activity is obtained.

8. A process for the construction of a modified chrome-corundum ramming mix according to any one of claims 1 to 2, characterized in that The following steps are included: Q1, Pretreatment of A material: Put A material into a muffle furnace and pre-sinter in an oxidizing atmosphere, with gas flow controlled at 5-10 L / min and heating rate of 5 ℃ / min, pre-sinter at 1100-1150 ℃ for 25-35 min, the thickness of the loaded material should not exceed 50 mm, after pre-sintering, naturally cool to room temperature, break into 3-5 mm particles using a jaw crusher, and obtain pretreated A material with enhanced strength and activity; Q2, Wet mixing of A material: Add deionized water to the pretreated A material in batches, with water to material mass ratio controlled at 6-8%, add water in 3-4 times with 30-60 s interval, mix in a mixer at 60-100 r / min for 3-5 min, monitor the uniformity of water content during mixing, and obtain wet A material with uniform water content and good plasticity; Q3, A material layering ramming: the wet A material is layered on the cleaned furnace bottom, the thickness of each layer is strictly controlled at 15-20 mm, pneumatic ramming machine is used for tamping, the tamping pressure is controlled at 0.4-0.6 MPa, the tamping frequency per square meter is not less than 50 times, and the tamping density reaches 2.8-3.2 g / cm 3 , the interlayer bonding is treated by scoring, and the A material is obtained which is dense, uniform and bubble-free; Q4, Activation treatment of B material: Dissolve sodium hydroxide NaOH and disodium hydrogen phosphate Na2HPO4 in deionized water in proportion, with sodium hydroxide concentration of 0.1-0.3 mol / L and disodium hydrogen phosphate concentration of 0.05-0.15 mol / L, adjust pH to 8.5-9.2, mix B material with the activation liquid at liquid to material mass ratio of 12-15%, mix uniformly in a stirrer, and then stand for 15-20 min, to obtain B material slurry with enhanced activity; Q5, Negative pressure infiltration of B material: Load the activated B material slurry into an infiltration tank, adjust the negative pressure to -0.015 to -0.025 MPa, inject the slurry into A material through an infiltration tube, control the infiltration time at 10-20 min, and the infiltration depth at 60-80% of the thickness of A material, to obtain an intermediate with good B material and A material composite; Q6, Intermediate temperature reaction treatment: Place the A material with infiltrated B material into an intermediate temperature furnace, heat to 350-450 ℃ at a heating rate of 2-3 ℃ / min, and keep the temperature for 80-100 min, during which, inject a small amount of water vapor to maintain humidity, and the reaction atmosphere is weakly oxidizing, after reaction, slowly cool to room temperature, to obtain a preliminary combined composite structure; Q7, Dispersion treatment of C material: Add C material into deionized water to prepare a suspension with mass concentration of 25-35%, and use an ultrasonic disperser for dispersion treatment, with dispersion time of 12-18 min, and control the temperature during dispersion not to exceed 60 ℃, stop for 1 min every 3 min to prevent overheating, to obtain uniformly dispersed and non-agglomerated C material suspension; Q8, Spraying and solidification of C material: Use a special spraying equipment to uniformly spray the dispersed C material suspension on the surface of the intermediate in an atomized manner, with spraying pressure controlled at 0.2-0.4 MPa, spraying distance maintained at 20-30 cm, and spraying thickness of 2-3 mm, after spraying, perform solidification treatment at 180-220 ℃ for 60-90 min, during which, inject dry air, to obtain a smooth and firmly combined protective layer. Q9, whole body sintering: the C material coated product is sintered according to a strict temperature rising curve, the first section is 20-300℃ with a temperature rising rate of 1℃ / min, physical water and organic matter are removed; the second section is 300-800℃ with a temperature rising rate of 2℃ / min, chemical reaction and preliminary sintering are carried out; the third section is 800-1250℃ with a temperature rising rate of 1.5℃ / min, high temperature sintering is completed, and the sintering is carried out in a weak reducing atmosphere of carbon monoxide, the total sintering time is 24-30 hours, and the modified chromium corundum ramming material product is obtained.

9. The construction process of claim 8, wherein, In step Q1, the pre-sintering process adopts a program-controlled temperature rising, the initial temperature rising rate is 3℃ / min to 500℃, then it is increased 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, and when the linear change rate is stable within ±0.1%, the pre-sintering is completed, and pre-sintered A material is obtained; In step Q2, the mixing process adopts a planetary mixer, the main shaft rotating speed is 60-100r / min, and the auxiliary stirring paddle rotating speed is 2-3 times of the main shaft rotating speed, the mixing process is stopped every 1 minute to check the mixing uniformity, the mixing is considered to be completed when the water content difference in different positions is less than 0.5% through sampling determination, and the wet A material with uniform water distribution and good working performance is obtained; In step Q4, the preparation of the activation liquid adopts a step-by-step 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, the activation liquid is placed for 2-4 hours after preparation to make it completely clear, the activation process is stirred every 5 minutes, the stirring speed is 100-200r / min, and a thin film is covered during the standing process to prevent water evaporation, and the B material slurry with fully excited chemical activity is obtained.

10. The construction process of claim 8, wherein, In step Q5, the negative pressure infiltration equipment includes a vacuum pump, a pressure regulating valve, an infiltration tank and a monitoring system, the A material is subjected to vacuum pretreatment for 30-60s before infiltration, the infiltration depth is monitored in real time during the infiltration process, the negative pressure value is appropriately increased when the infiltration resistance suddenly increases, and the negative pressure state is maintained for 5-10 minutes after the infiltration is completed to ensure sufficient infiltration, and the composite layer structure with uniform infiltration depth and tight bonding is obtained. In step Q9, the temperature deviation of the sintering process is controlled within ±5℃, the phase change of the sample is measured every hour during the holding stage, the holding is completed when the expected high temperature phase is detected, the temperature decreasing rate is strictly controlled at 50-100℃ / h to 800℃ during the cooling process, and then the product is naturally cooled to room temperature, and the finished product is obtained.

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