An anti-segregation type environment-friendly refractory spray coating suitable for the tundish cover contact surface and a preparation method thereof

Abstract

This invention relates to the field of refractory materials technology, specifically to an anti-slag-adhesion environmentally friendly refractory spray coating adapted to the contact surface of an tundish cover and its preparation method. The dry powder of this spray coating mainly consists of corundum aggregate, modified spinel powder, composite binder, and modified anti-slag additives. Through precise gradation and spatial decoupling of components, a strong and tough skeleton is constructed. During water addition, rheological changes, and baking, the anti-slag additives spontaneously target and migrate outwards, reconstructing a superhydrophobic slag-repellent armor on the slag-facing surface. Combined with the internal spinel-based slag-locking and deformation buffer defense lines, a gradient synergistic defense is achieved. This invention is completely chromium-free and environmentally friendly, completely eliminating the pain point of high-temperature slag adhesion and spalling, extending its service life to 40 heats, and is suitable for large-scale adaptation to special steel continuous casting conditions.

Description

Technical Field

[0001] This invention relates to the field of refractory materials technology, specifically to an anti-slag-adhesion environmentally friendly refractory spray coating adapted to the contact surface of an intermediate ladle cover and its preparation method. Background Technology

[0002] The tundish, often referred to as the heart of the continuous casting machine, has a cover that serves as a crucial support and insulation structure directly over the molten steel at high temperatures. It operates in extremely harsh environments. In actual production, the tundish cover must withstand heat radiation exceeding 1500°C, as well as the frequent impact of highly corrosive splashing molten steel and highly oxidizing, highly alkaline liquid slag. Furthermore, the rapid heating and cooling of the tundish during handling necessitates that the refractory materials on its contact surfaces possess extremely high thermal shock resistance.

[0003] In early industrial applications, magnesia-chromium refractories were widely used to resist the harsh slag buildup and erosion. However, under high-temperature oxidation and alkaline slag conditions, magnesia-chromium refractories readily generate highly toxic and water-soluble hexavalent chromium (Cr). 6+ Chromium-containing compounds cause irreversible and fatal harm to the ecological environment and human health. With the mandatory implementation of environmental protection regulations such as the "Implementation Plan for Ultra-Low Emission Transformation of the Steel Industry," traditional chromium-containing refractory materials have been completely phased out, and chromium-free environmentally friendly refractory materials have become the only development direction for the industry.

[0004] Currently, the industry mainly uses aluminum-magnesium based (such as corundum-spinel) chromium-free castables or spray coatings as alternatives, and often uses the physical addition of rare earth oxide powders (such as CeO2, La2O3) as anti-slag additives to compensate for the inherent deficiencies of chromium-free systems in slag resistance. However, existing technologies have revealed extremely serious bottleneck defects: Firstly, the low concentration of the surface anti-slag agent makes initial slag adhesion and nodule formation extremely easy. Existing preparation processes mostly employ simple dry-wet physical mixing methods, resulting in the extremely expensive rare earth anti-slag powder being homogeneously dispersed within a monolithic coating matrix tens or even hundreds of millimeters thick. This means that the outermost effective surface layer (slag-facing surface), which directly contacts the molten steel and slag, has an extremely low actual concentration of the anti-slag agent, failing to form an effective barrier to alter interfacial tension. In the early stages of continuous casting, the low-viscosity molten slag easily wets and adheres tightly to the coating surface, forming thick, dead slag nodules. Cleaning these nodules often requires strong mechanical stripping, tearing away large amounts of intact coating material and causing extremely severe mechanical damage.

[0005] Secondly, the lack of a deep, secure barrier leads to severe spalling of the altered layer. Once residual slag penetrates into the coating through capillary pores, the existing material lacks a localized reaction mechanism capable of instantly increasing the viscosity of the free slag liquid. The deepening altered layer creates a significant physical mismatch in thermal expansion coefficients with the original brick state. Under alternating thermal shock stress, this easily triggers large-area, blocky spalling, resulting in a sharp reduction in the lifespan of the tundish cover.

[0006] Third, chemical modification and physical hydration processes are mutually exclusive. If an attempt is made to improve water and slag repellency by significantly increasing anti-slag agents or adding strong surfactants, these organic or highly active substances will directly poison the highly hydrophilic calcium aluminate cement, severely encapsulate the hydration crystal nuclei, block the skeletal network, and cause a precipitous decline in the material's mechanical strength.

[0007] In summary, existing chromium-free spray coatings are caught in a zero-sum game where prioritizing mechanical strength results in weak slag resistance, while prioritizing slag resistance leads to structural collapse. Therefore, developing a novel, long-life chromium-free spray coating that can spontaneously form a film on the surface to repel slag, while also providing deep-layer penetration prevention, without sacrificing a dense mechanical framework, is a major technological barrier that urgently needs to be overcome in the field of metallurgical refractory materials. Summary of the Invention

[0008] In view of this, the purpose of this invention is to propose an anti-slag-adhesion environmentally friendly refractory spray coating and its preparation method for the contact surface of the tundish cover, so as to provide a refractory spray coating that has excellent mechanical strength, anti-slag-adhesion, anti-corrosion, thermal shock stability and bonding strength in a completely chromium-free system, thereby solving the problems of slag adhesion, nodule formation, difficulty in slag removal and coating peeling on the contact surface of the tundish cover.

[0009] To achieve the above objectives, the present invention provides an anti-slag-sticking environmentally friendly refractory spray coating adapted to the contact surface of the tundish cover, wherein the coating is formed by mixing dry powder and water. The dry powder is composed of the following raw materials by weight percentage: 45%-60% corundum aggregate, 21.5%-25% brown corundum fine powder, 8%-15% modified spinel powder, 3%-8% activated alumina micro powder, 3.9%-6% environmentally friendly composite binder, 1%-3% modified anti-slag additive, and 0.1%-0.5% dispersant; The preparation steps of the modified spinel powder are as follows: spinel raw powder is activated by disodium ethylenediaminetetraacetate, impregnated and deposited with lanthanum trichloride, and then subjected to alkaline hydrolysis polymerization with tetraethyl orthosilicate and template agent, followed by calcination to form mesoporous modified spinel powder. Finally, the mesoporous modified spinel powder is obtained by supercritical fluid deposition of cerium nitrate and pyrolysis treatment. The modified anti-slag additive is obtained by modifying hydroxylated cerium oxide nanoparticles with silane coupling agent KH560 and octa(aminophenyltrioxosilane).

[0010] Preferably, the weight ratio of the spinel powder, disodium ethylenediaminetetraacetate, lanthanum trichloride, tetraethyl orthosilicate, and template agent is 1800-2200g:45-55g:180-220g:180-220g:70-90g.

[0011] Preferably, the template agent is a mixture of polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer and hexadecyltrimethylammonium bromide in a weight ratio of 1:1.

[0012] Preferably, the activation temperature is 55-65℃ and the activation time is 3.5-4.5h.

[0013] Preferably, the ultrasonic power of the impregnation deposition is 280-320W, and the time is 40-60min.

[0014] Preferably, the hydrolysis polymerization temperature is 35-45℃ and the time is 22-26h.

[0015] Preferably, the alkaline pH is 8.5-9.5.

[0016] Preferably, the calcination temperature is 530-570℃ and the time is 3-4 hours.

[0017] Preferably, the weight ratio of the mesoporous modified spinel powder to cerium nitrate is 1800-2200g:180-220g.

[0018] Preferably, the supercritical fluid deposition is carried out at a pressure of 9.5-10.5 MPa, a temperature of 240-260 °C, and a time of 2.5-3.5 h.

[0019] Preferably, the pyrolysis temperature is 780-820℃ and the time is 1.5-2.5h.

[0020] Preferably, the weight ratio of the hydroxylated nano-cerium oxide powder, silane coupling agent KH560, and octa(aminophenyltrioxosilane) is 280-320g:8-12g:280-320g.

[0021] Preferably, the grafting reaction temperature is 70-80℃ and the time is 10-14h.

[0022] Preferably, the hydroxylated cerium oxide nanoparticles are obtained by treating cerium oxide nanoparticles with hydrogen peroxide.

[0023] Preferably, the weight ratio of the dry powder to water is 100:12-15.

[0024] Preferably, the corundum aggregate has a particle size of 0.1-5 mm, wherein 1-5 mm particles account for 30%-40% and 0.1-1 mm particles account for 60%-70%; Preferably, the brown fused alumina fine powder has a particle size of 50-70 μm.

[0025] Preferably, the spinel powder has a particle size of 20-45 μm.

[0026] Preferably, the particle size of the activated alumina micro powder is 1-5 μm.

[0027] Preferably, the average particle size of the nano-cerium oxide powder is 20-40 nm.

[0028] Preferably, the environmentally friendly composite binder is a compound system of calcium aluminate cement and polyaluminum phosphate, with a mass ratio of 3-2:1.

[0029] Preferably, the dispersant is one or a mixture of two of sodium tripolyphosphate and sodium hexametaphosphate.

[0030] Furthermore, the present invention also provides a method for preparing an anti-slag-adhesive environmentally friendly refractory spray coating adapted to the contact surface of the tundish cover, comprising: dry mixing corundum aggregate, brown corundum fine powder, modified spinel powder, and activated alumina micro powder to form a mixed aggregate; subsequently adding an environmentally friendly composite binder, a modified anti-slag additive, and a dispersant and mixing to form a dry powder; finally mixing the dry powder with water to obtain an anti-slag-adhesive environmentally friendly refractory spray coating adapted to the contact surface of the tundish cover.

[0031] The beneficial effects of this invention are: This invention does not employ conventional physical blending. Instead, it covalently grafts octa(aminophenyltrioxosilane), which possesses a large three-dimensional spatial structure, with pre-stimulated hydroxylated nano-cerium oxide, thereby endowing the modified anti-slag additive with extremely strong steric repulsion and peripheral hydrophobicity. During the water-added pulping, molding, baking, and dehydration rheological processes, the additive is subjected to interphase repulsion and compression within the strongly hydrophilic gelling system. Accompanied by capillary water evaporation, it spontaneously and continuously undergoes directional reconstruction and enrichment towards the contact interface (slag-facing surface). This repulsive targeted migration mechanism allows extremely small amounts of polar anti-slag agent to concentrate at the forefront of service, preventing initial steel slag adhesion and nodulation, and completely eliminating the need for manual mechanical damage caused by violent slag cleaning.

[0032] This invention employs extremely precise mesoporous placement and elemental infusion treatment of spinel, the core component of the matrix. After chemically etching away surface magnesium ions, lanthanum is ultrasonically anchored and embedded into the deep lattice. Then, supercritical fluid mass transfer technology is used to forcibly infuse an in-situ crystallized cerium layer onto the mesoporous silica outer skin. Under extreme conditions, when micro-wear or trace residues penetrate and erode inwards, the free slag is initially isolated and tension-reduced by cerium islands upon contact with the mesoporous outer skin. This instantaneous reaction forms a high-melting-point, high-viscosity isolating phase, effectively locking the highly fluid slag within the shallow surface and completely blocking long-range erosion into the matrix interior. Simultaneously, pre-designed nanoscale mesoporous vesicles construct an excellent three-dimensional microscopic expansion space, greatly dissipating and resolving the thermal mismatch stress caused by rapid heating and cooling, thus fundamentally solving the problem of planar spalling between the altered layer and the matrix.

[0033] This invention ingeniously designs a spatial decoupling and temporal composite mechanism for pre-treatment powder preparation and post-treatment standardized dry-wet mixing. By independently completing the grafting of anti-slag molecules in the pre-treatment reactor, the poisoning and retarding effects of surfactant in-situ blending on the early hydration nuclei of calcium aluminate are completely avoided, ensuring that the strong cementitious network can be smoothly overlapped and cross-linked without any organic interference. At the same time, the addition of a strict discontinuous gradation of coarse and fine aggregates not only constructs the most compact physical packing model, but also scientifically combines dry mixing with forced high-shear wet mixing, completely eliminating the phenomenon of micro-encapsulation and agglomeration of powder, releasing a smooth reconstruction channel for the external discharge anti-slag agent, and ultimately endowing the coating with an indestructible ultra-long service life, mechanical toughness, and unbreakable adhesion to the base plate.

[0034] This invention, by completely eliminating traditional toxic substances and achieving a chromium-free environmentally compliant system, successfully constructs an extremely dense macroscopic physical framework with stress buffering capacity through material optimization and modification, supplemented by precise discontinuous gradation and batching processes. This not only fundamentally prevents slag erosion and avoids mechanical damage and breakage of the coating caused by violent slag cleaning, but also seamlessly adapts to the efficient industrial construction process of conventional stirring and spraying in mainstream steel plants. Ultimately, it greatly extends the safe service life of the continuous casting tundish cover to the industrial-grade upper limit of 40 heats, solving the industry problem of traditional chromium-free materials being prone to nodule formation and peeling. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0036] The sources or properties of the raw materials used in the embodiments and comparative examples of this invention are as follows: Spinel powder: particle size 35μm; Polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer: Sigma-Aldrich, item number 435465; Nano cerium oxide powder: average particle size 30nm; Octa(aminophenyltrioxosilane): Zhengzhou Huiju (Alpha) Chemical Products Co., Ltd., item number A359825.

[0037] Example 1: A method for preparing an anti-slag-adhesive environmentally friendly refractory spray coating adapted to the contact surface of an tundish cap, the specific steps of which are as follows: (1) 1800g of spinel powder was dispersed in 10000mL of deionized water containing 45g of disodium ethylenediaminetetraacetate. The mixture was vigorously stirred mechanically for 3.5h in a constant temperature water bath at 55℃. After centrifugation and washing three times with deionized water, activated spinel wet powder was obtained. The powder was resuspended in 5000mL of aqueous solution containing 180g of lanthanum trichloride. The mixture was ultrasonically vibrated at 280W for 40min. After vacuum filtration and drying at 100℃, the powder was resuspended in 18000mL of deionized water. 35g of polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer and 35g of cetyltrimethylammonium bromide were added. 180g of tetraethyl orthosilicate was slowly added dropwise at a constant temperature of 35℃. At the same time, ammonia was added dropwise to adjust the pH to 8.5. The hydrolysis reaction was carried out for 22h. After the reaction was completed, the product was placed in a tube furnace and calcined in air at 530℃ for 3h to form mesoporous modified spinel powder. (2) 1800g of mesoporous modified spinel powder was loaded into a supercritical fluid permeation vessel, and 3000mL of methanol solution containing 180g of cerium nitrate heptahydrate crystals was injected. The vessel was sealed and pressurized to 9.5MPa and heated to 240℃ and held at pressure for 2.5h. After slowly depressurizing, the vessel was rapidly heat-treated at 780℃ in air atmosphere for 1.5h to obtain mesoporous gradient modified spinel powder. (3) Weigh 280g of high-purity cerium oxide nanoparticles and disperse them in 3000mL of deionized water containing 45g of hydrogen peroxide. Maintain a slight boiling state and continue reflux stirring for 3.5h. After the reaction is completed, centrifuge and wash with deionized water until neutral vacuum drying to form hydroxylated cerium oxide nanoparticles. Then, take 2800mL of anhydrous ethanol as solvent in a reactor equipped with a reflux condenser, add 28g of octa(aminophenyltrioxosilane) and 8g of silane coupling agent KH560, stir and disperse, then add 280g of hydroxylated cerium oxide nanoparticles. Re-flux reaction with ultrasonic assistance at 70℃ for 10h. After the reaction is completed, centrifuge the obtained product to remove excess unreacted material, wash with anhydrous ethanol and dry to obtain modified anti-slag additive. (4) 4500g of corundum aggregate (30% of 1-5mm particle size and 70% of 0.1-1mm particle size), 2500g of brown corundum fine powder, 1500g of modified spinel powder and 800g of activated alumina micro powder are sequentially added into a high-strength mixing tank and dry-mixed for 15min to obtain a preliminary uniform aggregate. Then, 260g of high-purity calcium aluminate cement, 130g of polyaluminum phosphate powder, 300g of modified anti-slag additive and 10g of sodium hexametaphosphate powder are sequentially added to the aggregate. The stirring cage is started and strong countercurrent mixing is continued for 20min to obtain a uniform dry powder. Finally, the dry powder is mixed with tap water and added to a variable frequency high-shear forced mixer and continuously stirred for 15min to form a uniform slurry. The target product, anti-slag environmentally friendly refractory spray coating, can be obtained.

[0038] Example 2: A method for preparing an anti-slag-adhesive environmentally friendly refractory spray coating adapted to the contact surface of an tundish cap, the specific steps of which are as follows: (1) 2000g of spinel powder was dispersed in 10000mL of deionized water containing 50g of disodium ethylenediaminetetraacetate. The mixture was vigorously stirred mechanically in a constant temperature water bath at 60℃ for 4h. After centrifugation and washing three times with deionized water, activated spinel wet powder was obtained. The powder was resuspended in 5000mL of aqueous solution containing 200g of lanthanum trichloride and ultrasonically vibrated at 300W for 50min. After vacuum filtration and drying at 100℃, the powder was resuspended in 20000mL of deionized water. 40g of polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer and 40g of cetyltrimethylammonium bromide were added. 200g of tetraethyl orthosilicate was slowly added dropwise at a constant temperature of 40℃. Ammonia was added dropwise to adjust the pH to 9. The hydrolysis reaction was carried out for 24h. After the reaction was completed, the product was placed in a tube furnace and calcined in an air atmosphere at 550℃ for 3.5h to form mesoporous modified spinel powder. (2) 2000g of mesoporous modified spinel powder was loaded into a supercritical fluid permeation vessel, and 3000mL of methanol solution containing 200g of cerium nitrate heptahydrate crystals was injected. The vessel was sealed and pressurized to 10MPa and heated to 250℃ and held at pressure for 3h. After slowly depressurizing, the vessel was rapidly heat-treated at 800℃ in air atmosphere for 2h to obtain mesoporous gradient modified spinel powder. (3) Weigh 300g of high-purity cerium oxide nanoparticles and disperse them in 3000mL of deionized water containing 50g of hydrogen peroxide. Maintain a slight boiling state and continue reflux stirring for 4h. After the reaction is completed, centrifuge and wash with deionized water until neutral vacuum drying to form hydroxylated cerium oxide nanoparticles. Then, take 3000mL of anhydrous ethanol as solvent in a reactor equipped with a reflux condenser, add 30g of octa(aminophenyltrioxosilane) and 10g of silane coupling agent KH560, stir and disperse, then add 300g of hydroxylated cerium oxide nanoparticles. Recycle at 75℃ with ultrasonic-assisted oscillation for 12h. After the reaction is completed, centrifuge the obtained product to remove excess unreacted material, wash with anhydrous ethanol and dry to obtain modified anti-slag additive. (4) 5300g of corundum aggregate (35% of 1-5mm particle size and 65% of 0.1-1mm particle size), 2300g of brown corundum fine powder, 1200g of modified spinel powder and 550g of activated alumina micro powder are sequentially added into a high-strength mixing tank and dry-mixed for 20min to obtain a preliminary uniform aggregate. Then, 280g of high-purity calcium aluminate cement, 140g of polyaluminum phosphate powder, 200g of modified anti-slag additive and 30g of sodium hexametaphosphate powder are sequentially added to the aggregate. The stirring cage is started and strong countercurrent mixing is continued for 25min to obtain a uniform dry powder. Finally, the dry powder is mixed with tap water and added to a variable frequency high-shear forced mixer and continuously stirred for 20min to form a uniform slurry. The target product, anti-slag environmentally friendly refractory spray coating, can be obtained.

[0039] Example 3: A method for preparing an anti-slag-adhesive environmentally friendly refractory spray coating adapted to the contact surface of an tundish cap, the specific steps of which are as follows: (1) 2200g of spinel powder was dispersed in 10000mL of deionized water containing 55g of disodium ethylenediaminetetraacetate. The mixture was vigorously stirred mechanically in a constant temperature water bath at 65℃ for 4.5h. After centrifugation and washing three times with deionized water, activated spinel wet powder was obtained. The powder was resuspended in 5000mL of aqueous solution containing 220g of lanthanum trichloride and ultrasonically vibrated at 320W for 60min. After vacuum filtration and drying at 100℃, the powder was resuspended in 22000mL of deionized water. 45g of polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer and 45g of cetyltrimethylammonium bromide were added. 220g of tetraethyl orthosilicate was slowly added dropwise at a constant temperature of 45℃. At the same time, ammonia was added dropwise to adjust the pH to 9.5. The hydrolysis reaction was carried out for 26h. After the reaction was completed, the product was placed in a tube furnace and calcined in air at 570℃ for 4h to form mesoporous modified spinel powder. (2) 2200g of mesoporous modified spinel powder was loaded into a supercritical fluid permeation vessel, and 3000mL of methanol solution containing 220g of cerium nitrate heptahydrate crystals was injected. The vessel was sealed and pressurized to 10.5MPa and heated to 260℃ and held at pressure for 3.5h. After slowly depressurizing, the vessel was rapidly heat-treated at 820℃ in air atmosphere for 2.5h to obtain mesoporous gradient modified spinel powder. (3) Weigh 320g of high-purity cerium oxide nanoparticles and disperse them in 3000mL of deionized water containing 55g of hydrogen peroxide. Maintain a slight boiling state and continue refluxing and stirring for 4.5h. After the reaction is completed, centrifuge and wash with deionized water until neutral vacuum drying to form hydroxylated cerium oxide nanoparticles. Then, take 3200mL of anhydrous ethanol as solvent in a reactor equipped with a reflux condenser, add 32g of octa(aminophenyltrioxosilane) and 12g of silane coupling agent KH560, stir and disperse, and then add 320g of hydroxylated cerium oxide nanoparticles. Refrigerate at 80℃ with ultrasonic assistance for 14h. After the reaction is completed, centrifuge the obtained product to remove excess unreacted material, wash and dry with anhydrous ethanol to obtain modified anti-slag additive. (4) 6000g of corundum aggregate (40% of 1-5mm particle size and 60% of 0.1-1mm particle size), 2150g of brown corundum fine powder, 800g of modified spinel powder and 300g of activated alumina micro powder are sequentially added into a high-strength mixing tank and dry-mixed for 20 minutes to obtain a preliminary uniform aggregate. Then, 400g of high-purity calcium aluminate cement, 200g of polyaluminum phosphate powder, 100g of modified anti-slag additive and 50g of sodium hexametaphosphate powder are sequentially added to the aggregate. The stirring cage is started and strong countercurrent mixing is continued for 30 minutes to obtain a uniform dry powder. Finally, the dry powder is mixed with tap water and added to a variable frequency high-shear forced mixer and continuously stirred for 20 minutes to form a uniform slurry. The target product, anti-slag type environmentally friendly refractory spray coating, can be obtained.

[0040] Comparative Example 1: The difference from Example 2 is that in step (4), the modified spinel powder is replaced with spinel raw powder, and the modified anti-slag additive is replaced with high-purity cerium oxide nanopowder. The remaining steps are the same as in Example 2.

[0041] Comparative Example 2: The difference from Example 2 is that the activation treatment of disodium ethylenediaminetetraacetate and the lanthanum trichloride impregnation deposition step (1) are omitted. The remaining steps are the same as those in Example 2.

[0042] Comparative Example 3: The difference from Example 2 is that the supercritical fluid deposition step is omitted in step (2), and the modified spinel powder in step (4) is replaced with mesoporous modified spinel powder. The remaining steps are the same as in Example 2.

[0043] Comparative Example 4: The difference from Example 2 is that octa(aminophenyltrioxosilane) is not added in step (2), while the rest of the steps are the same as in Example 2.

[0044] Comparative Example 5: The difference from Example 2 is that step (1) was completely eliminated in which the polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer was replaced with an equal amount of hexadecyltrimethylammonium bromide. The remaining steps are the same as in Example 2.

[0045] Comparative Example 6: The difference from Example 2 is that the proportion of 1-5mm particle size of corundum aggregate in step (4) is 100%, while the other steps are the same as in Example 2.

[0046] Comparative Example 7: The difference from Example 2 is that in step (4), all raw materials and water are directly mixed without stepwise mixing, while the remaining steps are the same as in Example 2.

[0047] Performance testing Mechanical property testing: According to GB / T 3001-2017 "Test Method for Flexural Strength of Refractory Materials at Room Temperature" and GB / T 5072-2023 "Test Method for Compressive Strength of Refractory Materials at Room Temperature", the spray coatings obtained in the examples and comparative examples were vibrated and molded into standard test rectangles under specified pressure. After static curing, they were transferred to a forced-air drying oven at 110℃ for 24 hours to dehydrate. Then, they were heated to 1500℃ in a silicon molybdenum rod high-temperature furnace according to the heating curve and held at the center point for 3 hours for post-firing calibration. After cooling, they were tested by a computer servo universal testing machine. Slag erosion resistance test: According to GB / T 32179-2015 "Test method for slag resistance of refractory materials", the uniform slurry obtained from the examples and comparative examples was vibrated and cast into a standard cubic sample with an outer dimension of 70mm×70mm×70mm. At the same time, a volume-fixing blind hole (crucible groove) with a diameter of Φ35mm×depth of 35mm was reserved (or drilled) in the center of the top surface. After the specimen was naturally cured for 24 hours and demolded, it was placed in a 110℃ forced-air drying oven for 24 hours to remove free water. 30g of highly corrosive high-calcium crystallizer slag retained on site from the continuous casting tundish was accurately weighed and filled into each dried crucible blind groove. The specimen was placed in a high-temperature muffle furnace containing silicon molybdenum rods and heated to 1500°C at a heating rate of 5°C / min. The temperature was maintained for 3 hours. After the furnace cooled to room temperature, the crucible was removed and vertically cut along the central axis of the blind hole using a high-precision diamond cutter. The cross-section was photographed at high resolution, and the area of ​​the slag penetrating into the substrate and the area of ​​erosion and dissolution were accurately calculated using image processing software. The erosion rate (%) = total eroded and penetrated area / effective cross-sectional area of ​​the original blind hole × 100%. At the same time, a high-temperature optical contact angle measuring instrument was used to record and measure the macroscopic spreading contact angle of the three-phase interface point where the molten slag droplets contacted the substrate of the example material at 1500°C. Thermal shock stability test: According to YB / T 376.1-1995 "Test method for thermal shock resistance of refractory products (water quenching method)", the test specimens of the same specifications prepared by spray coating obtained from the examples and comparative examples were placed in a high temperature resistance furnace at 1100℃ and kept at a constant temperature until the internal and external heat was uniform for 30 minutes. Then, they were quickly picked up with steel tongs and thrown into a deep tank of flowing cold water with a large flow rate and strong circulation to generate ultra-strong micro-stress, which caused rapid cooling. The application and removal of heat load were repeated in cycles and monitored in real time until the test specimen showed continuous through-type micro-cracks visible to the naked eye or the total mechanical strength was reduced to the point of being unusable. Adhesion strength test: The slurry obtained in the examples and comparative examples was uniformly sprayed onto the surface of the steel substrate using compressed air. The thickness of the sprayed reference film was controlled to be 30 mm. After curing at room temperature for 24 hours, it was placed in a 110°C drying oven for continuous baking for 24 hours. On the baked coating surface, a stainless steel standard test cylinder (spindle) with a diameter of Φ50 mm was vertically bonded using high-strength epoxy resin structural adhesive. After curing for 24 hours, the substrate was fixed on a vertical computer servo universal tensile testing machine. The spindle was connected using a universal joint, and a tensile force was applied vertically upward at a uniform rate of 0.05 MPa / s until the interface between the coating and the steel plate completely peeled off. The maximum tensile load (F) at the moment of failure was recorded. The adhesion strength value was calculated according to the formula: Adhesion strength (MPa) = maximum tensile force (N) / cross-sectional area of ​​cylinder. Actual service life test: The test site was set in the workshop of the national-level main special steel continuous casting branch. The test carrier was a standard 120-ton continuous casting tundish cover. The coating materials of the example and comparative examples were fully covered on the slag-facing working surface of the tundish cover by the on-site spraying machine with a construction thickness of 40mm. The hot preparation was carried out in strict accordance with the standard furnace baking curve of steelmaking plant, which is first baked at 150℃ for dehydration and then rapidly preheated at 1000℃. The tundish cover was put into online continuous casting operation. The single pouring time (one heat) was 45 minutes. It was subjected to the impact of molten steel splashing at 1500℃. When the tundish was turned off the line, it had to undergo a severe thermal shock cycle from 1500℃ to room temperature. Inspection and Standards: After each turnover, on-site workers use conventional mechanical pry bars to peel off and clean the cold dead residue adhering to the surface, and track and record the macroscopic anti-peeling and slag resistance of the coating throughout the process. Retirement Standard (End of Service): Continuously accumulate continuous casting cycle counts. Material failure is determined and counting is terminated when any of the following conditions occur: 1. Coating peeling caused by violent cleaning or thermal shock, resulting in continuous large-area peeling (single sheet peeling area > 200cm²). 2 1) Structural degradation and peeling; 2) Local residual coating thickness eroded and worn down to less than 10mm, posing a safety hazard of steel shell burn-through; The test results are shown in Table 1.

[0048] Table 1 Performance Test Results Data Analysis: As can be seen from the data in Examples 1-3 of Table 1, the anti-slag-forming environmentally friendly refractory spray coating prepared by this invention has achieved excellent and balanced comprehensive performance in all key service indicators. This demonstrates that, under the premise of completely eliminating traditional toxic substances and achieving a fully chromium-free environmentally compliant system, this invention, through the modified cerium oxide anti-slag additive with huge resistance and hydrophobic traction power, and the mesoporous spinel powder with deep-seated lanthanum element locking, exhibits unparalleled gradient stepwise and chemical synergy capabilities during liquid-phase formation and high-temperature service. Furthermore, with precise discontinuous gradation and batching processes, an extremely dense macroscopic physical framework with stress buffering capacity is successfully constructed. This not only fundamentally prevents slag erosion and avoids mechanical damage and breakage of the coating caused by violent slag removal, but also seamlessly adapts to the efficient industrial construction process of conventional stirring and spraying in mainstream steel plants. Ultimately, it greatly extends the safe service life of the continuous casting tundish cover to the industrial-grade upper limit of 40 heats, solving the industry problem of easy nodule formation and peeling of traditional chromium-free materials.

[0049] As can be seen from the data in Example 2 and Comparative Example 1 in Table 1, the traditional physical mixing method is simply unable to form a protective armor with an effective concentration in the contact layer. However, through the innovative chemical grafting and mesoporous construction, the material is endowed with the ability of spontaneous gradient step-by-step and high synergy. The giant nucleus exclusion modified cerium oxide is precisely forced back to the outermost layer to reconstruct a pure cerium slag-repellent armor, while the mesoporous spinel in the inner layer acts as a lanthanum-locking fortress. The two work together to completely overcome the core pain points of traditional chromium-free materials, such as easy slag adhesion on the surface and easy deterioration and collapse inside.

[0050] As can be seen from the data of Example 2 and Comparative Example 2 in Table 1, there is a significant gap between the two in terms of slag erosion resistance rate and actual service life. The possible mechanism is that when the deep spinel lattice formation and lanthanum element deadlock deposition process are omitted, the gradient synergistic defense is missing. With the inevitable microscopic wear of the surface sacrificial armor in the later stage of service, the trace residues that penetrate into the coating depth can no longer be intercepted by the high melting point lanthanum element. The slag liquid flows freely along the pores, causing local severe metamorphic layer mismatch and peeling. This fully demonstrates that the tiered synergy of outer slag rejection and deep slag locking is indispensable for long-term service under extreme working conditions.

[0051] As can be seen from the data of Example 2 and Comparative Example 3 in Table 1, Comparative Example 3, which did not undergo supercritical fluid permeation and cerium coating treatment, showed significant deterioration in core anti-corrosion indicators such as slag erosion resistance and slag-liquid contact angle. The possible mechanism is that after omitting the supercritical high-temperature and high-pressure mass transfer localization and anchoring step, the outermost mesoporous channels of the spinel powder were completely exposed, resulting in the loss of the synergistic isolation and tension reduction effect of the high-melting-point cerium element on the mesoporous skin. This increased the local slag wettability, and under frequent alternating thermal shock scouring, the slag-liquid easily penetrated and destroyed the stress buffer vesicle structure of the material body, ultimately leading to the simultaneous disintegration of the system's thermal shock resistance and deep anti-corrosion capability. This demonstrates the irreplaceable role of supercritical fluid technology in constructing microscopic mesoporous barriers and improving the overall gradient defense line.

[0052] As can be seen from the data of Example 2 and Comparative Example 4 in Table 1, Comparative Example 4 exhibits a very special characteristic: a slight improvement in basic mechanical properties, but a precipitous drop in slag resistance and service life. The possible mechanism is that, due to the removal of the spatial steric bridging of this large, rigid inorganic cluster, calcium aluminate cement and aggregate achieve extremely pure physical compact packing. This results in the modified slag-resistant additive being firmly trapped inside the slurry, completely losing its ability to spontaneously migrate and reconstruct to the outermost edge of the coating. Consequently, the slag-facing surface is prone to slag adhesion and nodule formation because it cannot form a high-concentration, pure cerium-resistant, robust armor.

[0053] As can be seen from the data in Example 2 and Comparative Example 5 in Table 1, when the polyethylene glycol-polypropylene glycol-polyethylene glycol triblock copolymer was removed and replaced entirely with an equal amount of hexadecyltrimethylammonium bromide, the overall performance of the material deteriorated. The possible mechanism is that, lacking the broad macroporous backbone constructed by the macromolecular block copolymer, the single micro-mesopores induced by the small molecule surfactant are prone to large-area thermal collapse under high-temperature calcination and service. Furthermore, the excessively narrow pore size severely hinders the supercritical fluid from carrying cerium nitrate to deep local anchorage, resulting in a large amount of cerium element being forced to accumulate disorderly on the outermost surface of the powder, accelerating the deterioration and mechanical collapse of the coating.

[0054] As can be seen from the data in Example 2 and Comparative Example 6 in Table 1, a rigorous physical gradation is an important underlying foundation for ensuring that the chemical reconstruction defense line can adhere to the wall for a long time without falling off. The possible mechanism is that the lack of effective penetration and filling of the gaps between the macroscopic coarse aggregate by the fine powder results in a large number of uncontrollable macroscopic interconnected pores left inside the solidified slurry, which weakens the effective support section against external loads and the toughness to resolve the displacement stress of sudden cooling and heating.

[0055] As can be seen from the data in Table 1 for Example 2 and Comparative Example 7, the mixing method that deviates from the strict dry-wet mixing sequence does not achieve the optimal performance of any of the indicators. The possible mechanism is that directly and randomly mixing all aggregates, micro-powders, cementitious materials, and water in a momentary, disordered manner severely restricts the macroscopic long-range free migration of the free modified anti-slag additive during the liquid-phase rheological process. This results in some cerium oxide particles carrying significant steric hindrance being forcibly trapped in localized agglomerates, unable to be completely forced back to the outermost contact surface of the coating.

[0056] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention is limited to these examples; within the framework of the invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A slag-entrapping, environmentally friendly, refractory sprayable coating for adapting the tundish cover contact surface, characterized in that, The refractory spray coating is made by mixing dry powder and water. The dry powder is composed of the following raw materials by weight percentage: 45%-60% corundum aggregate, 21.5%-25% brown corundum fine powder, 8%-15% modified spinel powder, 3%-8% activated alumina micro powder, 3.9%-6% environmentally friendly composite binder, 1%-3% modified anti-slag additive, and 0.1%-0.5% dispersant; The preparation steps of the modified spinel powder are as follows: spinel raw powder is activated by disodium ethylenediaminetetraacetate, impregnated and deposited with lanthanum trichloride, and then subjected to alkaline hydrolysis polymerization with tetraethyl orthosilicate and template agent, followed by calcination to form mesoporous modified spinel powder, which is finally obtained by supercritical fluid deposition and pyrolysis treatment of cerium nitrate. The modified anti-slag additive is obtained by modifying hydroxylated cerium oxide nanoparticles with silane coupling agent KH560 and octa(aminophenyltrioxosilane).

2. The slag-trapping, environmentally friendly refractory coating according to claim 1, characterized in that, The weight ratio of spinel powder, disodium ethylenediaminetetraacetate, lanthanum trichloride, tetraethyl orthosilicate, and template agent is 1800-2200g:45-55g:180-220g:180-220g:70-90g; the template agent is a mixture of polyethylene glycol, polypropylene glycol, polyethylene glycol triblock copolymer, and hexadecyltrimethylammonium bromide in a weight ratio of 1:

1.

3. The slag-trapping, environmentally friendly refractory coating according to claim 1, characterized in that, The calcination temperature is 530-570℃, and the time is 3-4 hours.

4. The slag-trapping, environmentally friendly refractory coating of claim 1, wherein, The weight ratio of the mesoporous modified spinel powder to cerium nitrate is 1800-2200g:180-220g.

5. The slag-trapping, environmentally friendly, refractory coating according to claim 1, characterized in that, The supercritical fluid deposition is carried out at a pressure of 9.5-10.5 MPa, a temperature of 240-260 °C, and a time of 2.5-3.5 h; the pyrolysis is carried out at a temperature of 780-820 °C and a time of 1.5-2.5 h.

6. The slag-trapping, environmentally friendly, refractory coating of claim 1, wherein, The weight ratio of the hydroxylated nano-cerium oxide powder, silane coupling agent KH560, and octa(aminophenyltrioxosilane) is 280-320g:8-12g:280-320g.

7. The slag-trapping, environmentally friendly, refractory coating of claim 1, wherein, The weight ratio of the dry powder to water is 100:12-15.

8. The slag-trapping, environmentally friendly, refractory coating of claim 1, wherein, The corundum aggregate has a particle size of 0.1-5 mm, of which 1-5 mm particles account for 30%-40% and 0.1-1 mm particles account for 60%-70%; the brown corundum fine powder has a particle size of 50-70 μm; and the activated alumina micro powder has a particle size of 1-5 μm.

9. The slag-trapping, environmentally friendly, refractory coating of claim 1, wherein, The environmentally friendly composite binder is a compound system of calcium aluminate cement and polyaluminum phosphate with a mass ratio of 3-2:1; the dispersant is one or a mixture of two of sodium tripolyphosphate and sodium hexametaphosphate.

10. A method for preparing an anti-slag-adhesive environmentally friendly refractory spray coating adapted to the contact surface of an intermediate ladle cap according to any one of claims 1-9, characterized in that, Corundum aggregate, brown corundum fine powder, modified spinel powder, and activated alumina micro powder are dry-mixed to form a mixed aggregate; then an environmentally friendly composite binder, modified anti-slag additive, and dispersant are added and mixed to form a dry powder; finally, the dry powder is mixed with water to obtain an anti-slag environmentally friendly refractory spray coating suitable for the contact surface of the tundish cover.

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