Ladle slag-resistant coating based on composite magnesium-based high-temperature-resistant coating and preparation method of ladle slag-resistant coating

Abstract

The invention relates to the technical field of coatings, in particular to a ladle slag-resistant coating based on a composite magnesium-based high-temperature-resistant coating and a preparation method of the ladle slag-resistant coating. The coating is prepared from fused magnesite, composite modified graphite, silicon carbide whiskers, calcium zirconate powder, a sodium silicate solution, aluminum sol, an aluminum dihydrogen phosphate solution, calcium-zirconium copolymerized complex sol, phenolic resin, sodium hexametaphosphate and the like according to a specific proportion. The graphite surface is subjected to multi-component composite modification, and a plurality of high-temperature binders and interface barrier materials are prepared step by step, so that high compactness, excellent slag corrosion resistance and thermal shock resistance of the coating are realized. The prepared coating can effectively block slag liquid permeation under the extremely high temperature and strong alkaline slag environment, the service life and safety of the ladle lining are remarkably improved, and the coating is suitable for the high-temperature metallurgical industry such as steel and iron.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of coating technology, and particularly relates to a molten iron ladle slag-resistant coating based on a composite magnesium-based high-temperature-resistant coating and a preparation method thereof. BACKGROUND

[0002] In the iron-making process, the molten iron ladle, as a key equipment for transporting and storing molten iron, needs to withstand an extremely high temperature environment of up to 1500 DEG C or above and chemical corrosion of strong alkaline slag. With the rapid development of the steel industry and the continuous improvement of product quality requirements, the service conditions of the molten iron ladle are becoming more and more harsh, and the high-temperature resistance and slag erosion resistance of the inner lining coating of the molten iron ladle are put forward with more strict technical requirements.

[0003] The traditional molten iron ladle coating is mainly based on magnesia refractory, which has certain refractory performance, but when facing the increasingly complex slag composition and higher operating temperature in modern metallurgical processes, it exposes many technical defects. First, the single magnesium phase structure is prone to grain coarsening and phase transformation under high temperature conditions, resulting in loose microstructure of the coating, providing a channel for slag liquid penetration, and seriously affecting the slag erosion resistance of the coating Secondly, the thermal expansion coefficient of the traditional coating has poor matching with the matrix material, and is prone to thermal stress concentration under repeated thermal shock, causing coating cracking and peeling, which seriously shortens the service life of the molten iron ladle.

[0004] Although the commonly used carbon additive in the prior art can improve the slag wetting resistance of the coating to some extent, ordinary graphite is prone to ablation in a high-temperature oxidizing atmosphere and cannot provide long-lasting protection. At the same time, the surface inertness of traditional graphite limits its bonding strength with the inorganic matrix, and it is easy to fall off during use, reducing the overall performance of the coating. Although there are various surface-modified carbon materials on the market, most of the modification methods are single and cannot achieve multifunctional synergistic modification, making it difficult to meet the comprehensive performance requirements under complex working conditions.

[0005] In terms of phase composition, the existing coating system generally lacks effective interface reaction barrier mechanism. Under the erosion of high-alkaline slag, a violent chemical reaction will occur between the coating and the slag liquid, generating a low-melting-point liquid phase, which further accelerates the destruction of the coating. The traditional additive formula cannot form a stable reaction barrier layer on the surface of the coating, so that the slag liquid can continuously penetrate into the deep layer of the coating, causing structural damage.

[0006] The binder system is also a weak link in the prior art. The traditional sodium silicate binder is prone to decomposition at high temperatures, and the bonding strength decreases sharply, which cannot maintain the structural integrity of the coating. Although some studies attempt to use phosphate or aluminum sol as a high-temperature binder, the single binder system often has problems such as shrinkage cracking and insufficient thermal stability, making it difficult to achieve ideal high-temperature bonding effect.

[0007] In addition, the chemical compatibility and process matching between different components are often ignored in the existing preparation process. Simple physical mixing method is difficult to realize the uniform dispersion and effective combination of each component at the microscale, resulting in composition segregation and structural defects in the coating, which seriously affects the performance of the coating. Especially in the multi-component composite system, the reaction activity and condensation time sequence of different components are not matched, which is easy to produce internal stress and micro-cracks, and becomes the starting point of coating failure. SUMMARY

[0008] Therefore, the purpose of the present application is to provide a composite magnesium-based high-temperature-resistant coating-based ladle slag-resistant coating and a preparation method thereof, so as to develop a ladle slag-resistant coating which can effectively resist high-temperature alkaline slag erosion and maintain structural stability and excellent thermal shock performance under extreme temperature conditions.

[0009] In order to achieve the above purpose, the present application provides a composite magnesium-based high-temperature-resistant coating-based ladle slag-resistant coating, which comprises the following components by weight: 6600-7000 parts of fused magnesite, 900-1100 parts of modified graphite, 350-450 parts of silicon carbide whisker, 250-350 parts of calcium zirconate powder, 3400-4000 parts of sodium silicate solution, 800-1200 parts of aluminum sol, 700-900 parts of aluminum dihydrogen phosphate solution, 900-1100 parts of calcium zirconium copolymer complex sol, 80-120 parts of phenolic resin and 40-60 parts of sodium hexametaphosphate.

[0010] The modified graphite is flake graphite modified by hydrochloric acid dopamine, gamma-glycidoxypropyltrimethoxysilane, boric acid and 1-naphthalene boronic acid. Preferably, the weight ratio of the flake graphite, hydrochloric acid dopamine, gamma-glycidoxypropyltrimethoxysilane, boric acid and 1-naphthalene boronic acid is 1000:15-25:38-62:8-12:12-18.

[0011] Preferably, the fused magnesite is FM98, which has a three-stage grading, and the three-stage grading has a mass ratio of average particle size 13mm:average particle size 0.11mm:average particle size≤88µm of 55:25:20.

[0012] Preferably, the average diameter of the silicon carbide whisker is 0.5μm, and the average length is 20μm.

[0013] Preferably, the average particle size of the calcium zirconate powder is 1.5μm.

[0014] Preferably, the sodium silicate solution has a Baume degree of 40°Bé and a modulus of 3.3.

[0015] Preferably, the aluminum sol is prepared by reacting aluminum isopropoxide in anhydrous 2-propanol with aqueous nitric acid.

[0016] Preferably, the weight ratio of the aluminum isopropoxide, the anhydrous 2-propanol and the aqueous nitric acid is 28-32:84-96:180-220.

[0017] Preferably, the concentration of the aqueous nitric acid is 0.1 mol / L.

[0018] Preferably, the calcium-zirconium copolymerization complex sol is prepared by reacting zirconium oxychloride octahydrate, calcium nitrate tetrahydrate and citric acid in deionized water.

[0019] Preferably, the weight ratio of the zirconium oxychloride octahydrate, the calcium nitrate tetrahydrate, the citric acid and the deionized water is 28-32:22.4-25.6:11-13:90-110.

[0020] Preferably, the preparation process of the modified graphite comprises: preparing A liquid by dispersing flake graphite and dopamine hydrochloride in an alkaline buffer; preparing B liquid by hydrolyzing γ-glycidoxypropyltrimethoxysilane in an ethanol-water mixture; adding B liquid into A liquid, then adding boric acid and 1-naphthalene boronic acid, and finally adding γ-glycidoxypropyltrimethoxysilane, and then filtering, washing and drying to obtain the modified graphite.

[0021] Preferably, the weight ratio of γ-glycidoxypropyltrimethoxysilane in the B liquid raw material and the added γ-glycidoxypropyltrimethoxysilane is 30-50:8-12.

[0022] Preferably, the phenolic resin is thermosetting, the average particle size is 15 μm, and the softening point is 110℃.

[0023] The application also provides a preparation method of a composite magnesium-based high-temperature-resistant coating-based ladle slag-resistant paint, comprising the following steps: (1) graphite surface composite modification: dispersing flake graphite and dopamine hydrochloride in an alkaline buffer under ultrasonic for 10-20 min, stirring at 25℃ for 100-140 min to obtain A liquid; preparing B liquid by hydrolyzing γ-glycidoxypropyltrimethoxysilane in an ethanol-water mixture; adding B liquid into A liquid, stirring for 25-35 min, then adding boric acid and 1-naphthalene boronic acid, stirring for 15-25 min, finally adding γ-glycidoxypropyltrimethoxysilane, stirring for 10 min, and then filtering, washing and drying to obtain modified graphite; (2) preparing aluminum sol: adding aluminum isopropoxide into anhydrous 2-propanol, stirring at 40℃ for 30 min, adding aqueous nitric acid dropwise, controlling the temperature to be less than 35℃, after the addition is completed, aging at 25℃ for 45-75 min; (3) Preparation of calcium zirconium copolymer complex sol: zirconium oxychloride octahydrate, calcium nitrate tetrahydrate are added to deionized water, stirred at 35℃ for 30min, citric acid is added, stirred at 80℃ for 60min, cooled to room temperature; (4) Preparation of slurry: fused magnesia, modified graphite, silicon carbide whisker and calcium zirconate powder are dry mixed for 10min, sodium silicate solution, aluminum sol, aluminum dihydrogen phosphate solution, aluminum sol, calcium zirconium copolymer complex sol are added in sequence for stirring or shearing, finally phenolic resin, sodium hexametaphosphate, defoaming agent and deionized water are added for shearing to obtain the slurry; (5) Defoaming and aging: the slurry is defoamed at a vacuum degree of 0.08-0.095MPa for 8-12min, and is left to stand and age for 50-70min to obtain the ladle slag-resistant coating based on the composite magnesium-based high-temperature-resistant coating.

[0024] Preferably, the alkaline buffer solution in step (1) is prepared from deionized water, tris-hydroxymethyl aminomethane and hydrochloric acid with a concentration of 37wt%.

[0025] Preferably, the aluminum sol in step (4) is added in two times, after the sodium silicate solution and after the aluminum dihydrogen phosphate solution, and the weight ratio of the two times is 5-7:3-5.

[0026] The application further provides a coating prepared from the above-mentioned ladle slag-resistant coating based on the composite magnesium-based high-temperature-resistant coating, and the specific preparation steps are as follows: the coating is layered on the surface of the ladle lining by batch scraping, the thickness is 2.0-3.0mm, and the coating is dried at 60℃, heat treated at 200℃, heated to 750℃ and heat treated, finally sintered in situ at 1300℃ to obtain the coating.

[0027] The application has the following beneficial effects: Excellent slag erosion resistance: by constructing a composite phase structure with fused magnesia as the skeleton and calcium zirconate as the interface barrier layer, the coating can react with the alkaline slag to form a dense reaction layer under high temperature conditions, effectively blocking the penetration channel of the slag liquid to the inside of the coating. The continuous calcium zirconate phase generated in situ from the calcium zirconium copolymer complex sol during the sintering process forms a stable chemical barrier, significantly improving the erosion resistance of the coating to high-alkalinity slag systems. The introduction of modified graphite further reduces the wettability of the slag liquid and the interface of the coating, reduces the residence time of the slag, and fundamentally inhibits the deep erosion of the slag liquid.

[0028] Significant improvement of thermal shock resistance: The composite magnesium-based high-temperature resistant coating realizes excellent thermal shock resistance through multi-scale toughening mechanism. Silicon carbide whiskers, as fibrous reinforcing phase, form a three-dimensional network structure in the coating matrix, effectively preventing crack propagation. The organic-inorganic hybrid layer formed on the surface of modified graphite can build a gradient interface, relieving stress concentration caused by thermal expansion mismatch. The borosilicate glass phase is generated during heating and solidified after cooling, plugging micro-pores and improving the density and thermal shock resistance of the coating.

[0029] Persistent and stable bonding strength: The binder system prepared by step-by-step complex sol technology realizes the step-by-step cross-linking reaction of silicate-phosphate-aluminum sol, forming a continuous and stable ceramic network structure. The process design of aluminum sol addition avoids local rapid gelation and stress concentration, ensuring the uniformity of the internal structure of the coating. The silane coupling agent on the surface of modified graphite provides chemical bridging between the organic and inorganic phases, significantly enhancing the interfacial bonding strength and preventing delamination of the coating during use.

[0030] Optimized comprehensive performance: By precisely controlling the ratio and reaction sequence of each component, the refractoriness, slag resistance, thermal shock resistance, and mechanical strength of the coating are coordinated and unified. The three-stage grading design of fused magnesia optimizes the bulk density and pore structure, providing a good bearing skeleton. The combined use of boric acid and naphthalene boronic acid ensures sufficient boron source supply and uniform dispersion, and the formed borosilicate glass phase has excellent self-repairing ability. The entire formulation system meets the requirements of high-temperature use, while taking into account the normal temperature mechanical properties and construction operation performance, providing a reliable guarantee for the long-period stable operation of the ladle. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description.

[0032] Figure 1 The preparation process flow chart of the ladle slag-resistant coating based on the composite magnesium-based high-temperature resistant coating in the present application.

[0033] Figure 2 The X-ray diffraction spectrum of the coating in Example 2 of the present application. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical scheme and advantages of the present application more clear and obvious, the following will further describe the present application in combination with specific embodiments.

[0035] Example 1: Step 1: Composite modification of graphite surface An alkaline buffer solution was prepared with 10000 g of deionized water, 100 g of tris-hydroxymethyl aminomethane and 15 g of hydrochloric acid with a concentration of 37 wt%, 15 g of dopamine hydrochloride and 1000 g of flake graphite (average particle size of 300 mesh) were added, ultrasonic dispersion was performed for 10 min, stirring was performed at 25 °C for 100 min, and A liquid was obtained; 30 g of γ-glycidoxypropyltrimethoxysilane was added to a mixture of 200 g of anhydrous ethanol and 20 g of deionized water, 1.5 g of hydrochloric acid with a concentration of 37 wt% was further added, and hydrolysis was performed by stirring at 25 °C for 30 min to obtain B liquid; B liquid was added to A liquid, stirring was performed at 25 °C for 25 min, 8 g of boric acid and 12 g of 1-naphthalene boronic acid were further added, stirring was performed at 25 °C for 15 min, 8 g of γ-glycidoxypropyltrimethoxysilane was further added, stirring was performed at 25 °C for 10 min, filtration was performed, washing was performed with deionized water and anhydrous ethanol for 3 times, and drying was performed at 110 °C for 180 min to obtain modified graphite; Step 2: Preparation of aluminum sol 280 g of aluminum isopropyl alcohol was added to 840 g of anhydrous 2-propanol, stirring was performed at 40 °C for 30 min, 1800 g of nitric acid aqueous solution with a concentration of 0.1 mol / L was further added dropwise, the temperature was controlled to be less than 35 °C during the dropwise addition, after the dropwise addition was completed, aging was performed at 25 °C for 45 min, and aluminum sol was obtained; Step 3: Preparation of calcium-zirconium copolymer complex sol 280 g of zirconium oxychloride octahydrate and 224 g of calcium nitrate tetrahydrate were added to 900 g of deionized water, stirring was performed at 35 °C for 30 min, 110 g of citric acid was further added, stirring was performed at 80 °C for 60 min, and cooling was performed to room temperature to obtain calcium-zirconium copolymer complex sol; Step 4: Preparation of slurry Mix 6600 g of electrically fused magnesia (FM98, three-grade distribution, 13 mm:0.11 mm:≤88 µm at 55:25:20 by mass percentage), 900 g of modified graphite, 350 g of silicon carbide whisker (average diameter 0.5 µm, average length 20 µm) and 250 g of calcium zirconate powder (average particle size 1.5 µm) to obtain a mixture, dry-mix for 10 min at 200 rpm, then add 3400 g of sodium silicate solution (40°Bé, modulus SiO2 / Na2O 3.3, solid content 40 wt%), stir for 5 min at 100 rpm, then add 500 g of aluminum sol, shear for 8 min at 1500 rpm, then add 700 g of aluminum dihydrogen phosphate solution with a concentration of 50 wt%, shear for 5 min at 1500 rpm, then add 300 g of aluminum sol, shear for 5 min at 1500 rpm, then add 900 g of calcium-zirconium copolymer complex sol, stir for 10 min at 150 rpm, then add 80 g of phenolic resin (thermosetting type, average particle size 15 µm, softening point 110 °C), tumble for 3 min, finally add 40 g of sodium hexametaphosphate, 15 g of defoaming agent BYK-024 and 20 g of deionized water, shear for 3 min at 1500 rpm to obtain a slurry; Step 5: defoaming and aging Defoam the slurry at a vacuum degree of 0.08 MPa for 8 min, and let it stand for 50 min to obtain a ladle slag-resistant coating based on a composite magnesium-based high-temperature-resistant coating.

[0036] Coating preparation: layering on the surface of the ladle lining by batch scraping method, thickness 2.0 mm, 60 °C drying for 90 min, 200 °C for 100 min, then heating to 750 °C at a rate of 4 °C / min and holding for 45 min, and finally sintering in situ at 1500 °C for 100 min at a rate of 4 °C / min to obtain a coating.

[0037] Example 2: Step 1: composite modification of graphite surface An alkaline buffer solution was prepared with 10000 g of deionized water, 120 g of tris-hydroxymethyl aminomethane and 20 g of hydrochloric acid with a concentration of 37 wt%, 20 g of dopamine hydrochloride and 1000 g of flake graphite (average particle size of 300 mesh) were added, ultrasonic dispersion was performed for 15 min, stirring was performed at 25 °C for 120 min, and A liquid was obtained; 40 g of γ-glycidoxypropyltrimethoxysilane was added to a mixture of 200 g of anhydrous ethanol and 20 g of deionized water, 2 g of hydrochloric acid with a concentration of 37 wt% was further added, hydrolysis was performed by stirring at 25 °C for 30 min, and B liquid was obtained; B liquid was added to A liquid, stirring was performed at 25 °C for 30 min, 10 g of boric acid and 15 g of 1-naphthalene boronic acid were further added, stirring was performed at 25 °C for 20 min, 10 g of γ-glycidoxypropyltrimethoxysilane was further added, stirring was performed at 25 °C for 10 min, filtration was performed, washing was performed with deionized water and anhydrous ethanol for 3 times, and drying was performed at 120 °C for 240 min, and modified graphite was obtained; Step 2: Preparation of aluminum sol 300 g of aluminum isopropyl alcohol was added to 900 g of anhydrous 2-propanol, stirring was performed at 40 °C for 30 min, 2000 g of nitric acid aqueous solution with a concentration of 0.1 mol / L was further added dropwise, the temperature was controlled to be less than 35 °C during the dropwise addition process, after the dropwise addition process was completed, aging was performed at 25 °C for 60 min, and aluminum sol was obtained; Step 3: Preparation of calcium-zirconium copolymer complex sol 300 g of zirconium oxychloride octahydrate and 240 g of calcium nitrate tetrahydrate were added to 1000 g of deionized water, stirring was performed at 35 °C for 30 min, 120 g of citric acid was further added, stirring was performed at 80 °C for 60 min, and cooling was performed to room temperature, and calcium-zirconium copolymer complex sol was obtained; Step 4: Preparation of slurry 6800 g of electrically fused magnesia (FM98, three-grade distribution, 13 mm:0.11 mm:≤88 μm at 55:25:20 by mass percent), 1000 g of modified graphite, 400 g of silicon carbide whisker (average diameter 0.5 μm, average length 20 μm) and 300 g of calcium zirconate powder (average particle size 1.5 μm) were mixed at 200 rpm for 10 min to obtain a mixture, 3700 g of sodium silicate solution (40°Bé, modulus SiO2 / Na2O 3.3, solid content 40 wt%) was added and stirred at 100 rpm for 5 min, 600 g of aluminum sol was added and sheared at 1500 rpm for 8 min, 800 g of aluminum dihydrogen phosphate solution with a concentration of 50 wt% was added and sheared at 1500 rpm for 5 min, 400 g of aluminum sol was added and sheared at 1500 rpm for 5 min, 1000 g of calcium-zirconium copolymer complex sol was added and stirred at 150 rpm for 10 min, 100 g of phenolic resin (thermosetting type, average particle size 15 μm, softening point 110 °C) was added and tumbled for 3 min, finally 50 g of sodium hexametaphosphate, 20 g of defoaming agent BYK 024 and 30 g of deionized water were added and sheared at 1500 rpm for 3 min to obtain a slurry; Step 5: defoaming and aging The slurry was defoamed at a vacuum degree of 0.09 MPa for 10 min and aged for 60 min to obtain a composite magnesium-based high-temperature-resistant coating-based ladle slag-resistant coating.

[0038] Coating preparation: layering on the surface of the ladle lining with batch scraping method, thickness 2.5 mm, 60 °C drying for 120 min, 200 °C for 120 min, then heating to 750 °C at a rate of 5 °C / min and holding for 60 min, and finally sintering in situ at 1300 °C at a rate of 5 °C / min for 120 min to obtain a coating.

[0039] Example 3: Step 1: composite modification of graphite surface An alkaline buffer solution was prepared by using 10000 g of deionized water, 140 g of tris-hydroxymethyl aminomethane and 25 g of hydrochloric acid with a concentration of 37 wt%, 25 g of dopamine hydrochloride and 1000 g of flake graphite (average particle size of 300 mesh) were added, ultrasonic dispersion was performed for 20 min, stirring was performed at 25 °C for 140 min, and A liquid was obtained; 50 g of γ-glycidoxypropyltrimethoxysilane was added to a mixture of 200 g of anhydrous ethanol and 20 g of deionized water, 2.5 g of hydrochloric acid with a concentration of 37 wt% was further added, hydrolysis was performed by stirring at 25 °C for 30 min, and B liquid was obtained; B liquid was added to A liquid, stirring was performed at 25 °C for 35 min, 12 g of boric acid and 18 g of 1-naphthalene boronic acid were further added, stirring was performed at 25 °C for 25 min, 12 g of γ-glycidoxypropyltrimethoxysilane was further added, stirring was performed at 25 °C for 10 min, filtration was performed, washing was performed with deionized water and anhydrous ethanol for 3 times, and drying was performed at 130 °C for 300 min, and modified graphite was obtained; Step 2: Preparation of aluminum sol 320 g of aluminum isopropyl alcohol was added to 960 g of anhydrous 2-propanol, stirring was performed at 40 °C for 30 min, 2200 g of nitric acid aqueous solution with a concentration of 0.1 mol / L was added dropwise, the temperature was controlled to be less than 35 °C during the dropwise addition, after the dropwise addition was completed, aging was performed at 25 °C for 75 min, and aluminum sol was obtained; Step 3: Preparation of calcium-zirconium copolymer complex sol 320 g of zirconium oxychloride octahydrate and 256 g of calcium nitrate tetrahydrate were added to 1100 g of deionized water, stirring was performed at 35 °C for 30 min, 130 g of citric acid was further added, stirring was performed at 80 °C for 60 min, and cooling was performed to room temperature, and calcium-zirconium copolymer complex sol was obtained; Step 4: Preparation of slurry 7000 g of electrically fused magnesia (FM98, three-grade distribution, 13 mm:0.11 mm:≤88 µm at 55:25:20 by mass percent), 1100 g of modified graphite, 450 g of silicon carbide whisker (average diameter 0.5 µm, average length 20 µm), and 350 g of calcium zirconate powder (average particle size 1.5 µm) were mixed to obtain a mixture, which was dry-mixed at 200 rpm for 10 min. Then, 4000 g of sodium silicate solution (40°Bé, modulus SiO2 / Na2O 3.3, solid content 40 wt%) was added, and stirred at 100 rpm for 5 min. Then, 700 g of aluminum sol was added, and sheared at 1500 rpm for 8 min. Then, 900 g of aluminum dihydrogen phosphate solution with a concentration of 50 wt% was added, and sheared at 1500 rpm for 5 min. Then, 500 g of aluminum sol was added, and sheared at 1500 rpm for 5 min. Then, 1100 g of calcium-zirconium copolymerization complex sol was added, and stirred at 150 rpm for 10 min. Then, 120 g of phenolic resin (thermosetting type, average particle size 15 µm, softening point 110 °C) was added, and tumbled for 3 min. Finally, 60 g of sodium hexametaphosphate, 25 g of defoaming agent BYK-024, and 40 g of deionized water were added, and sheared at 1500 rpm for 3 min to obtain a slurry. Step 5: defoaming and aging The slurry was defoamed at a vacuum degree of 0.095 MPa for 12 min, and aged for 70 min to obtain a composite magnesium-based high-temperature-resistant coating-based ladle slag-resistant coating.

[0040] Coating preparation: layering was performed on the surface of the ladle lining using the batch scraping method, with a thickness of 3.0 mm, drying at 60 °C for 150 min, heat preservation at 200 °C for 150 min, then heating to 750 °C at a rate of 6 °C / min, heat preservation for 75 min, finally in-situ sintering at 1300 °C at a rate of 6 °C / min for 140 min to obtain a coating.

[0041] Comparative Example 1: Comparative Example 1 differs from Example 2 in that boric acid is replaced by equimolar amount of 1-naphthalene boronic acid; the rest of the conditions are consistent with Example 2.

[0042] Comparative Example 2: Comparative Example 2 differs from Example 2 in that 1-naphthalene boronic acid is replaced by equimolar amount of boric acid; the rest of the conditions are consistent with Example 2.

[0043] Comparative Example 3: Comparative Example 3 differs from Example 2 in that 50 g of pre-hydrolyzed γ-glycidoxypropyltrimethoxysilane is added to A liquid, and the subsequent addition of 10 g of γ-glycidoxypropyltrimethoxysilane is cancelled; the rest of the conditions are consistent with Example 2.

[0044] Comparative Example 4: Comparative Example 4 differs from Example 2 in that 600 g of aluminum sol was combined with 400 g of aluminum sol to 1000 g, which was added to the sodium silicate solution at one time, and was not divided into two times and sandwiched between the sodium silicate solution and the aluminum dihydrogen phosphate solution; the rest of the conditions were the same as Example 2.

[0045] Comparative Example 5: Comparative Example 5 differs from Example 2 in that no calcium-zirconium copolymerization complex sol was added; the rest of the conditions were the same as Example 2.

[0046] Comparative Example 6: Comparative Example 6 differs from Example 2 in that the calcium zirconate powder was replaced with an equal amount of fused magnesia; the rest of the conditions were the same as Example 2.

[0047] Performance test: X-ray diffraction: an X-ray diffractometer was used for characterization.

[0048] Slag resistance test: according to GB / T 8931-2007, an alkaline slag was prepared according to the standard method and a static cup type corrosion and slag adhesion thickness measurement was carried out, the sample was a layered coating test block (50 mm x 50 mm x 5 mm, the coating thickness was consistent with the sample preparation) on the lining substrate in the ladle, the slag adhesion thickness and corrosion depth were measured after 1500°C for 2h, and the results are shown in Table 1.

[0049] Thermal shock resistance: according to GB / T 30873-2014, 1300°C for 10 min, then water quenching for one cycle, the cycle number before peeling was recorded, the thermal shock stability was determined, and the results are shown in Table 1.

[0050] Cold bending strength and cold compressive strength: bending according to GB / T 3001-2017, three-point bending span 100 mm, loading rate 0.5 MPa / s; compressive strength according to GB / T 5072-2023, loading rate 2.5 MPa / s, results are shown in Table 1.

[0051] Table 1 Performance test results Sample Slime thickness / mm Erosion depth / mm Thermal shock resistance cycles Cold modulus of rupture / MPa Cold compressive strength / MPa Example 1 2.4 0.85 22 11.0 108 Example 2 2.1 0.72 26 12.4 102 Example 3 2.3 0.79 21 11.5 100 Comparative Example 1 2.9 1.20 18 10.6 96 Comparative Example 2 3.1 1.30 17 10.1 94 Comparative Example 3 3.4 1.65 16 9.3 90 Comparative Example 4 3.8 1.80 16 11.2 95 Comparative Example 5 4.9 2.40 17 9.0 88 Comparative Example 6 5.3 2.70 17 8.6 86 Data analysis: As can be seen from the data of examples 1-3 in Table 1, the coating prepared by the ladle slag-resistant coating material based on the composite magnesium-based high-temperature-resistant coating provided by the application exhibits synchronous improvement of slag resistance and erosion resistance, stable mechanical properties after thermal shock, and reliable interface bonding. The main reason is that a multi-scale network is formed after high-temperature sintering, which is a rigid framework supported by fused magnesia, a matrix of continuous ceramic phase converted from silicate-aluminum sol-phosphate, a barrier layer of interface reaction of calcium zirconate, and toughening units of modified graphite and silicon carbide whiskers; the borosilicate glass phase generated during the heating stage and solidified after cooling blocks the micropores and improves wetting, the gradient interface reduces stress concentration caused by thermal expansion mismatch, and the carbon phase reduces slag wettability and inhibits residence, thereby achieving systematic synergistic gain.

[0052] As can be seen from the data of example 2 and comparative example 1 in Table 1, when only the organic boron-containing component with aromatic rings is used and the inorganic boron source is lacking, the levels of slag resistance and erosion resistance decrease and the fluctuation increases. The main reason is that the organic boron-containing component is easily lost during the heating process, resulting in insufficient boron oxide available for reaction at high temperatures, making it difficult to form a continuous borosilicate glass phase and uniform pad layer, and weakening the interface self-healing and densification. Therefore, the combination of inorganic boron source and organic boron-containing component produces synergy in phase quantity guarantee and dispersion pre-adjustment, showing the effect of 1 plus 1 greater than 2.

[0053] As can be seen from the data of example 2 and comparative example 2 in Table 1, when only the inorganic boron source is used and the organic boron-containing component with aromatic rings is lacking, the interface stability and thermal shock retention of the coating decrease. The main reason is that the inorganic boron source particles are unevenly distributed, and the connectivity of the borosilicate glass phase formed at high temperatures is insufficient; the lack of molecular-scale organic boron-containing components for pre-dispersion and wetting regulation of the precursor limits the interface disturbance resistance. Therefore, the synergy of the dual boron source in dispersion and densification is an unexpected gain.

[0054] As can be seen from the data of example 2 and comparative example 3 in Table 1, when only the silane is introduced at the beginning and the subsequent addition is cancelled, the adhesion of the coating and the thermal shock retention decrease simultaneously. The main reason is that single pre-hydrolysis easily leads to silane self-condensation, and the interface bridging density and gradient are difficult to accurately construct; stepwise addition can form a continuous transition layer between the organic modified layer and the inorganic gel, reducing the micro-cracks induced by thermal mismatch. Therefore, the time-sequenced introduction of silane has a synergistic gain in building a gradient interface and inhibiting thermal spalling.

[0055] As can be seen from the data of Example 2 and Comparative Example 4 in Table 1, after two additions of the aluminum sol and once, the anti-adhesion and anti-erosion indexes decrease and the dispersion increases. The main reason is that the aluminum sol is added between silicates and phosphates, which can realize step-by-step neutralization and uniform cross-linking of the network, reduce shrinkage cracking and pore connectivity; one-time addition can easily produce local rapid gel and defect enrichment. Therefore, the process synergy of the sequence coupling of the aluminum sol for the structure uniformity and slag resistance stability is difficult to predict.

[0056] As can be seen from the data of Example 2 and Comparative Example 5 in Table 1, when the calcium zirconate copolymerization complex sol is absent, the coating barrier layer is discontinuous to high-alkali slag, and the erosion resistance and thermal shock resistance decrease. The main reason is that the sol nucleates in situ and refines growth at the pore and interface, forming a continuous calcium zirconate reaction layer that can passivate the slag and matrix interface and cut off the penetration channel; without this component, only particle size reaction is relied on, and a layered structure is difficult to establish. Therefore, the in-situ generation of the sol size and the particle size configuration produce a 1+1>2 densification and barrier synergy.

[0057] As can be seen from the data of Example 2 and Comparative Example 6 in Table 1, after the complete replacement of the calcium zirconate with the electrically fused magnesia, the slag resistance and erosion resistance indexes decrease significantly. The main reason is that the calcium zirconate can react with the components in the slag to form a cohesive and dense reaction layer and increase the interface viscosity, thereby reducing the wettability and migration of the slag; simply relying on the magnesia phase lacks this specific reaction barrier, and the slag is more likely to penetrate under high-alkali conditions. Therefore, the dual-phase combination of the magnesia skeleton and the calcium zirconate exhibits a barrier synergy that cannot be obtained by simple replacement in a high-alkali slag environment.

[0058] As can be seen from the data of Example 2 and Comparative Example 6 in Table 1, after the complete replacement of the calcium zirconate with the electrically fused magnesia, the slag resistance and erosion resistance indexes decrease significantly. The main reason is that the calcium zirconate can react with the components in the slag to form a cohesive and dense reaction layer and increase the interface viscosity, thereby reducing the wettability and migration of the slag; simply relying on the magnesia phase lacks this specific reaction barrier, and the slag is more likely to penetrate under high-alkali conditions. Therefore, the dual-phase combination of the magnesia skeleton and the calcium zirconate exhibits a barrier synergy that cannot be obtained by simple replacement in a high-alkali slag environment. Figure 2 As can be seen from the data of Example 2 and Comparative Example 6 in Table 1, after the complete replacement of the calcium zirconate with the electrically fused magnesia, the slag resistance and erosion resistance indexes decrease significantly. The main reason is that the calcium zirconate can react with the components in the slag to form a cohesive and dense reaction layer and increase the interface viscosity, thereby reducing the wettability and migration of the slag; simply relying on the magnesia phase lacks this specific reaction barrier, and the slag is more likely to penetrate under high-alkali conditions. Therefore, the dual-phase combination of the magnesia skeleton and the calcium zirconate exhibits a barrier synergy that cannot be obtained by simple replacement in a high-alkali slag environment.

[0059] Those skilled in the art should understand that the above discussion of any embodiment is only intended to be exemplary in nature and is not intended to suggest that the present application is limited to these examples; under the concept of the present application, the above embodiments or technical features among different embodiments can be combined, steps can be implemented in any order, and there are many other variations of different aspects of the present application as described above, which are not provided in details for the sake of brevity.

Claims

1. A slag-resistant coating for molten iron ladles based on a composite magnesium-based high-temperature resistant coating, characterized in that, The composition includes the following components in parts by weight: 6600-7000 parts fused magnesia, 900-1100 parts modified graphite, 350-450 parts silicon carbide whiskers, 250-350 parts calcium zirconate powder, 3400-4000 parts sodium silicate solution, 800-1200 parts aluminum sol, 700-900 parts aluminum dihydrogen phosphate solution, 900-1100 parts calcium zirconium copolymer complex sol, 80-120 parts phenolic resin, and 40-60 parts sodium hexametaphosphate. The modified graphite is obtained by composite modification of flake graphite with dopamine hydrochloride, γ-glycidoxypropyltrimethoxysilane, boric acid and 1-naphthaleneboronic acid; the weight ratio of the flake graphite, dopamine hydrochloride, γ-glycidoxypropyltrimethoxysilane, boric acid and 1-naphthaleneboronic acid is 1000:15-25:38-62:8-12:12-18.

2. The slag-resistant coating for molten iron ladles based on a composite magnesium-based high-temperature resistant coating according to claim 1, characterized in that, The fused magnesia is FM98, with a three-stage gradation. The three-stage gradation has a mass ratio of 55:25:20 for an average particle size of 13 mm: an average particle size of 0.11 mm: an average particle size ≤88 µm.

3. The slag-resistant coating for molten iron ladles based on a composite magnesium-based high-temperature resistant coating according to claim 1, characterized in that, The silicon carbide whiskers have an average diameter of 0.5 μm and an average length of 20 μm; the calcium zirconate powder has an average particle size of 1.5 μm.

4. The slag-resistant coating for molten iron ladles based on a composite magnesium-based high-temperature resistant coating according to claim 1, characterized in that, The sodium silicate solution has a Baumé degree of 40°Bé and a modulus of 3.

3.

5. The slag-resistant coating for molten iron ladles based on a composite magnesium-based high-temperature resistant coating according to claim 1, characterized in that, The aluminum sol is prepared by reacting aluminum isopropoxide in anhydrous 2-propanol with an aqueous nitric acid solution; the weight ratio of aluminum isopropoxide, anhydrous 2-propanol and aqueous nitric acid solution is 28-32:84-96:180-220; the concentration of the aqueous nitric acid solution is 0.1 mol / L.

6. The slag-resistant coating for molten iron ladles based on a composite magnesium-based high-temperature resistant coating according to claim 1, characterized in that, The calcium-zirconium copolymer complex sol is prepared by reacting zirconium oxychloride octahydrate, calcium nitrate tetrahydrate, and citric acid in deionized water; the weight ratio of zirconium oxychloride octahydrate, calcium nitrate tetrahydrate, citric acid, and deionized water is 28-32:22.4-25.6:11-13:90-110.

7. The slag-resistant coating for molten iron ladles based on a composite magnesium-based high-temperature resistant coating according to claim 1, characterized in that, The preparation process of the modified graphite includes: preparing solution A by mixing flake graphite and dopamine hydrochloride in an alkaline buffer solution; hydrolyzing γ-glycidoxypropyltrimethoxysilane in an ethanol-water mixture to obtain solution B; adding solution B to solution A, then adding boric acid and 1-naphthoic acid, and finally adding γ-glycidoxypropyltrimethoxysilane, followed by filtration, washing, and drying to obtain modified graphite.

8. The slag-resistant coating for molten iron ladles based on a composite magnesium-based high-temperature resistant coating according to claim 7, characterized in that, The weight ratio of γ-glycidoxypropyltrimethoxysilane to the added γ-glycidoxypropyltrimethoxysilane in the raw material of solution B is 30-50:8-12.

9. A method for preparing an anti-slag coating for molten iron ladles based on a composite magnesium-based high-temperature resistant coating according to any one of claims 1-8, characterized in that, Includes the following steps: (1) Graphite surface composite modification: Flake graphite and dopamine hydrochloride were ultrasonically dispersed in alkaline buffer for 10-20 min and stirred at 25℃ for 100-140 min to obtain solution A; γ-glycidoxypropyltrimethoxysilane was hydrolyzed in ethanol-water mixture to obtain solution B; solution B was added to solution A and stirred for 25-35 min, then boric acid and 1-naphthaleneboronic acid were added and stirred for 15-25 min, and finally γ-glycidoxypropyltrimethoxysilane was added and stirred for 10 min. After filtration, washing and drying, modified graphite was obtained. (2) Preparation of aluminum sol: Add aluminum isopropoxide to anhydrous 2-propanol, stir at 40°C for 30 min, add nitric acid aqueous solution dropwise, control the temperature to be less than 35°C, and age at 25°C for 45-75 min after the addition is complete. (3) Preparation of calcium zirconium copolymer complex sol: Zirconium oxychloride octahydrate and calcium nitrate tetrahydrate were added to deionized water, stirred at 35°C for 30 min, citric acid was added, stirred at 80°C for 60 min, and cooled to room temperature; (4) Slurry preparation: fused magnesia, modified graphite, silicon carbide whiskers and calcium zirconate powder are mixed and dry-mixed for 10 min. Sodium silicate solution, aluminum sol, aluminum dihydrogen phosphate solution, aluminum sol and calcium zirconium copolymer complex sol are added in sequence and stirred or sheared. Finally, phenolic resin, sodium hexametaphosphate, defoamer and deionized water are added and sheared to obtain slurry. (5) Degassing and aging: Degas the slurry under a vacuum of 0.08-0.095MPa for 8-12 minutes and let it stand for aging for 50-70 minutes to obtain an anti-slag coating for molten iron ladle based on a composite magnesium-based high-temperature resistant coating.

10. The slag-resistant coating for molten iron ladles based on a composite magnesium-based high-temperature resistant coating according to claim 9, characterized in that, In step (4), the aluminum sol is added in two parts, after the sodium silicate solution and after the aluminum dihydrogen phosphate solution, with a weight ratio of 5-7:3-5.

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