Casting alpha-Al2O3-beta-Al2O3-CA6 refractory material and preparation method thereof

Abstract

The invention relates to the technical field of high-temperature functional composite materials, and discloses a fused-cast alpha-Al2O3-beta-Al2O3-CA6 refractory material and a preparation method thereof.The refractory material comprises, by mass, 85%-95% of Al2O3-beta-Al2O3-CA6, 5%-95% of Al2O3-beta-Al2O3-CA6, 5%-10% of 2%-4% of CaO; 1%-3% of Na2O; 0.5%-1.0% of ZrO2; 0.5% to 1.0% of SrO or BaO; and 0.3%-0.6% of CeO2. Preferably, the aluminum alloy further comprises 0.1%-0.3% of B2O3 and 0.5%-2.0% of trace additives. The trace additive is selected from one or more of T < iO2 >, MgO and S < iO2 >. According to the invention, B2O3, MgO, Al2O3 and a small amount of glass phase adjusting components are introduced, and micro-scale closed pores and sealed pore interfaces are formed in a high-temperature sintering process, so that the integration of multiple functions of enhancing crack propagation resistance and improving slag corrosion resistance is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of high-temperature functional composite materials, in particular to a fused-cast α-Al2O3-β-Al2O3-CA6 refractory material and a preparation method thereof. Background Art

[0002] Functional composite materials operating under high-temperature and complex conditions, particularly those used in metallurgy, energy, or high-temperature structural components, face degradation issues caused by the synergistic effects of multiple environments, such as crack propagation under thermal stress and structural erosion due to high-temperature slag corrosion. These failure mechanisms often overlap, significantly shortening the material's service life and becoming a key bottleneck limiting its application performance.

[0003] Existing high-temperature composite materials have significant limitations in terms of structural control and performance matching. Traditional material design often focuses on improving a single property, such as mechanical strength, but overlooks the synergistic effects of cracking and liquid slag corrosion in high-temperature environments. The lack of integrated design of the overall structure and interfaces makes them susceptible to structural instability or premature failure under multiple stresses or corrosion, making them difficult to meet long-term service requirements.

[0004] On the other hand, at the material microstructure level, existing technologies lack a deep understanding and effective utilization of pore control, interface stability, and interaction mechanisms. For example, while some slag-resistant materials have a certain degree of corrosion resistance, they are prone to forming open pores on their surfaces, allowing high-temperature slag to quickly penetrate and destroy the internal structure.

[0005] Furthermore, crack control mechanisms in existing materials often rely on the simple introduction of external reinforcement phases or fillers, lacking systematic design based on interface regulation and energy dissipation mechanisms. This means that once cracks are generated, they tend to rapidly propagate along brittle pathways, leading to overall structural fracture or performance degradation. Faced with these multiple performance bottlenecks, a composite material system is urgently needed that can comprehensively optimize microstructure, interface configuration, and multiphase synergy to simultaneously achieve synergistic improvements in high-temperature crack stability and corrosion resistance, meeting the requirements for long-term stable service in high-temperature environments. Summary of the Invention

[0006] In response to the deficiencies in the prior art, the present invention provides a fused-cast α-Al2O3-β-Al2O3-CA6 refractory material and a preparation method thereof, which solves the problem of insufficient structural stability of the existing materials under the synergistic destruction of high-temperature crack propagation, slag erosion, etc.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0008] A first aspect of the present invention provides a fused-cast α-Al2O3-β-Al2O3-CA6 refractory material comprising the following components, calculated by mass percentage:

[0009] Al2O385%~95%;

[0010] CaO 2%~4%;

[0011] Na2O 1%~3%;

[0012] ZrO2 0.5%~1.0%;

[0013] SrO or BaO 0.5% ~ 1.0%;

[0014] CeO20.3%~0.6%.

[0015] The Al2O3 in the present invention is the main raw material component and constitutes the main crystal phase of the material, mainly existing in two forms: α-Al2O3 and β-Al2O3. α-Al2O3 has high density and excellent high temperature stability, and provides a basic refractory framework as the main skeleton phase; while β-Al2O3 is partially converted into refractory ... + The introduction of ions creates a stable structure, with a certain degree of ion migration and layered structural characteristics, which helps improve the material's thermal shock response behavior. By precisely controlling cooling conditions, the α and β phases precipitate synergistically, creating a microstructure that combines rigidity and cushioning, which is the basis for improving thermal shock stability and structural integrity.

[0016] The amount of CaO added is controlled at 2% to 4%. Its main function is to react with Al2O3 to generate a small amount of CA6 (i.e. CaAl 12 O 19 ) crystal phase. This crystal phase usually precipitates in the form of flakes or plates and has good crack deflection and energy absorption capabilities. Since the formation reaction of CA6 is strongly dependent on the temperature window, by introducing CaO in a precise amount and combining it with slow cooling, staggered CA6 lamellae can be generated between the α-Al2O3 and β-Al2O3 crystal phases, thereby constructing a multi-scale mismatch interface structure, effectively enhancing the complexity of the crack propagation path and improving fracture toughness. At the same time, avoiding the introduction of large proportions of CaO also reduces the structural instability caused by its potential hydration or volume expansion problems at high temperatures.

[0017] The designed introduction of Na2O is 1% to 3%. Unlike the traditional practice of treating Na2O as an impurity, the present invention uses it as a functional flux. Na2O can reduce the melt viscosity at high temperatures, promote uniform melting of raw materials, and promote the formation of β-Al2O3 phase during the cooling process. In addition, the presence of an appropriate amount of Na2O can also regulate the grain growth rate, inhibit the formation of coarse grains of α-Al2O3, and help maintain the uniformity and fine density of the material structure. The key innovation lies in the positive utilization of Na2O, that is, to achieve its structural regulation and phase field equilibrium while controlling its content so as not to lead to glass phase enrichment. This strategy is still rare in traditional fused-cast refractories.

[0018] The addition amount of ZrO2 is controlled between 0.5% and 1.0%, and its main function is to refine the grains and improve thermal stability. ZrO2 has extremely high thermal stability and reductive corrosion resistance at high temperatures. In the molten state, it can precipitate at the grain boundaries or partially dissolve in the main crystal phase, which plays a role in inhibiting grain growth, especially helping to maintain the dimensional stability of α-Al2O3 grains. In addition, the introduction of ZrO2 can improve the thermal stress relief ability at the microscopic level, hinder the initiation and expansion of cracks, and is one of the key auxiliary components for building high-temperature stability and thermal shock resistance.

[0019] The amount of SrO or BaO introduced is 0.5% to 1.0% (either one is optional), and its function is to act as a "eutectic regulator" to optimize the local melting point distribution. Under high-temperature operating conditions, this type of alkaline earth metal oxide can eutectic with Al2O3, Na2O, etc. at the grain boundaries or in micro-regions to form local dense areas, realizing the "micro-region self-densification" process, thereby repairing micro cracks that may occur during operation and improving the overall density and slag corrosion resistance. At the same time, its introduction has little effect on the basic structure of the main crystal phase. While constructing a synergistic multiphase system, it maintains the consistency of high-temperature performance, showing the conceptual differentiation of the present invention in the multi-phase regulation path.

[0020] The addition amount of CeO2 is controlled at 0.3% to 0.6%, and its role in the present invention is mainly to improve the overall high-temperature stability of the material. CeO2 also has a certain sintering aid effect, which can promote close bonding between crystal phases during high-temperature annealing or heat treatment, thereby enhancing the interfacial bonding strength. Compared with the traditional design of using MgO or TiO2 as a crystal phase regulator, the function of CeO2 is more inclined to the composite function of "high-temperature structural stabilization auxiliary agent" and "high-temperature performance buffer", showing an improvement in the environmental adaptability of the material.

[0021] Through the above-mentioned multi-component coordinated regulation, the present invention constructs a molten-cast α-Al2O3-β-Al2O3-CA6 composite material system with a multi-scale regulation mechanism. Its core innovation lies in the positive functional design and coordinated utilization of trace additives such as Na2O, CaO, ZrO2, SrO / BaO and CeO2. It breaks through the idea of relying solely on the optimization of the main crystal phase in traditional molten-cast materials, and instead constructs a "thermal stress buffering + structural toughening + high-temperature stability" triple mechanism through fine-tuning of the auxiliary phase, forming a set of comprehensive refractory material design paths for multi-condition heat load environments. This solution achieves functional upgrades based on the original crystal phase system (α / β-Al2O3+CA6), providing new ideas for high-performance refractory materials.

[0022] Preferably, 0.1% to 0.3% of B2O3 is also included.

[0023] The present invention incorporates an extremely low content of B2O3, which acts as a volatile vaporization regulator and thermal stress buffer. During the high-temperature melting process, some of the B2O3 vaporizes and escapes, with the remaining portion forming a localized glass phase or, with components such as Na2O, a low-melting-point phase region, inducing the formation of closed or semi-closed pores on a microscopic scale. This microporous structure mitigates crack strain concentration caused by crystal phase transitions or thermal stress during the cooling phase, acting as a "stress release point."

[0024] Unlike traditional approaches that treat B2O3 as an impurity or confine it to molten glass systems, the present invention introduces it at a limited low level, without significantly reducing the material's refractoriness or softening temperature. This allows for localized structural adjustment, aiding in the formation of a transition interface between the hierarchical porous structure and the dense matrix. Particularly in environments subject to frequent high thermal shock, the micropore distribution induced by B2O3 effectively disperses heat flux and mechanical impact, further enhancing the material's cyclic stability and service life.

[0025] Preferably, 0.5% to 2.0% of trace additives are also included.

[0026] In the present invention, 0.5% to 2.0% of trace additives are further introduced. The additives are selected from one or more of TiO2, MgO, and SiO2. The mechanism of action is to achieve multiple functional adjustment paths such as crystal phase structure regulation, grain size stabilization, and grain boundary energy optimization through multi-element doping, thereby enhancing the service stability of the material under complex working conditions.

[0027] TiO2, as a lattice dopant, can partially enter α-Al2O3 lattice sites during the melting process, forming a solid solution structure and exerting a lattice distortion-strengthening effect. Furthermore, TiO2 acts as an active phase at grain boundaries, promoting inter-grain bonding and improving the material's overall density and high-temperature thermal shock resistance. The appropriate addition of TiO2 effectively controls the rate of grain coarsening and enhances grain boundary migration activity, ensuring a stable microstructure in the melt during high-temperature annealing or operation.

[0028] The introduction of MgO mainly plays the role of inhibiting abnormal grain growth and stabilizing the interface structure of CA6 phase. 2+ Ions have difficulty diffusing at high temperatures, creating a dislocation pinning effect at grain boundaries, hindering the abnormal growth of α-Al2O3 grains and thus maintaining microstructural uniformity. MgO also forms a composite phase interface with some CaO and Al2O3, acting as an interface stabilizer during the formation of CA6 lamellae, improving the distribution stability and microcrack deflection capabilities of CA6 and enhancing the composite's crack resistance.

[0029] SiO2 acts as a liquid phase regulator and intergranular wetting agent in the material. During the melting-cooling process, SiO2 synergizes with components such as Na2O and B2O3 to form a low-melting-point glass phase. This forms a thin layer or network structure at the grain boundaries, which can enhance interphase bonding strength and soften thermal stress. Without destroying the main crystalline phase structure, the SiO2-induced improvement in interfacial wettability helps to establish a continuous and dense grain boundary network, reduce the probability of internal microcrack initiation, and improve overall anti-disintegration capabilities.

[0030] Although these trace additives are used in relatively small quantities, they significantly optimize the composite material's organizational coordination and thermodynamic stability by regulating grain interface behavior, stabilizing the crystal phase structure, and improving interfacial bonding quality. This design does not rely on the structural reinforcement of a single functional component, but rather, through the synergistic mechanism of composite trace components, forms a multi-level, multi-scale structurally stable system, representing another innovative aspect of the present invention in terms of microscopic phase field design and multifunctional compounding.

[0031] Preferably, the ZrO2 is monoclinic or partially stabilized zirconium oxide.

[0032] In the present invention, the selected ZrO2 is preferably monoclinic or partially stabilized zirconia (PSZ). Its design not only takes into account the basic high-temperature stability of ZrO2, but also focuses on its phase transformation toughening mechanism and microstructure stabilization effect in multiphase composite structures.

[0033] Monoclinic ZrO2 is a thermodynamically stable phase within the high to moderate temperature range (below approximately 1170°C). Its lattice structure remains relatively stable during cooling, and it exhibits good thermal expansion compatibility with the primary crystalline phase, α-Al2O3, making it less susceptible to thermal stress concentration. This makes it suitable as a filler component for grain refinement and enhanced interfacial bonding. Furthermore, monoclinic ZrO2 acts as a "pinning" within grains or at grain boundaries, inhibiting abnormal growth of primary crystalline phase grains and maintaining microstructural uniformity. This makes it a key technical tool for constructing thermally stable microstructures.

[0034] In contrast, some stable ZrO2 (such as Y2O3-stabilized or CaO-stabilized ZrO2) exhibit a reversible t→m (tetragonal to monoclinic) phase transition during high-temperature operation. This process, accompanied by volume expansion, can induce a compressive stress field at the crack tip, resulting in a "phase transformation toughening" effect that blunts the crack and deflects the crack path. This mechanism can significantly improve the material's fracture resistance and thermal shock stability threshold, making it particularly suitable for operating conditions with frequent thermal shock or high stress concentration risks.

[0035] Furthermore, the addition of ZrO2 contributes to the formation of a multiphase distribution and energy-absorbing "barrier layer" structure. In the composite system, it is distributed between α-Al2O3 and CA6 platelets, forming a "third phase barrier" that disrupts the crack propagation path and helps to construct a complex energy dissipation network. In the present invention, combined with the primary and secondary crystalline phases of α / β-Al2O3 and CA6, the synergistic toughening and structural stability provided by ZrO2 enhances the overall material's crack-resistance and toughening properties.

[0036] By optimizing the ZrO2 crystal type and addition method, the present invention achieves multiple enhancements of grain growth, crack control and thermal stress coordination without introducing a high proportion of structural impurities.

[0037] Preferably, the SrO or BaO is its corresponding carbonate, which is formed by decomposition at high temperature.

[0038] In the present invention, SrO or BaO is preferably introduced into the raw material system in the form of its corresponding carbonate (such as SrCO3 or BaCO3). During the high-temperature melting process, a thermal decomposition reaction occurs, releasing CO2 gas and simultaneously generating SrO or BaO oxide. Compared to directly using the oxide form, the introduction of carbonates offers unique functional advantages in multiple aspects.

[0039] First, the decomposition of carbonates, accompanied by the release of gases, helps form localized microbubbles or release channels within the melt, thereby improving the fluidity of the mixture and the diffusion rate of reactants. This process, at the microscopic scale, promotes a more uniform distribution of the liquid phase within the intercrystalline interstices, enhancing the reactivity and mass transfer efficiency of the melt components, and thus contributing to the formation of a denser and more uniform crystal structure.

[0040] Secondly, the in-situ formation of SrO or BaO avoids the compositional segregation issues that can occur with traditional premixing methods. Because the carbonate precursor decomposes within a specific temperature window, SrO / BaO can be gradually released and spatially controlled doping can be achieved, forming a preferred distribution between the α-Al2O3 and β-Al2O3 phases or within the CA6 formation region. This facilitates the formation of Sr / Ba-rich melt zone microstructures at grain boundaries or in subgrain regions, enhancing local density and thermal shock mitigation capabilities.

[0041] Furthermore, the CO2 released by carbonate decomposition can also clean the melt to a certain extent, promoting the migration or escape of inclusions and improving material purity. This process has a certain auxiliary effect on suppressing non-ideal secondary phases during crystal phase formation, thereby improving the formation integrity of the primary crystal phase and grain uniformity.

[0042] More importantly, SrO or BaO, as alkaline earth metal oxides, can form eutectics with Na₂O, B₂O₃, SiO₂, and other materials at high temperatures, acting as a "self-healing layer" at grain boundaries or defect areas, enhancing the self-densification and slag erosion resistance of cracked areas. Compared to directly adding SrO / BaO, the present invention achieves "in-situ reaction generation" through the thermal decomposition of its carbonate precursor, embedding a thermodynamic regulation mechanism within the melting process, demonstrating greater structural integrity and phase boundary self-regulation.

[0043] The second aspect of the present invention provides a method for preparing the fused-cast α-Al2O3-β-Al2O3-CA6 refractory material according to the first aspect, comprising the following steps:

[0044] 1) Weighing each component raw material and mixing them in a ball mill for 6 to 12 hours. Drying the mixed raw materials for 6 to 8 hours to control the moisture content to ≤ 0.5%;

[0045] In this step, first of all, all raw materials need to be weighed in proportion according to the material formula, including Al2O3, CaO, Na2O, ZrO2, SrO or BaO, CeO2 and other component raw materials. Accurate weighing of raw materials is crucial to material performance, which can ensure uniform distribution of components of the final product and avoid unstable material properties due to component errors. Then, the components are placed in a ball mill for mixing, and the ball milling time is controlled within the range of 6 to 12 hours to ensure mixing uniformity. Optimization of the ball-to-material ratio (such as 3:1 to 5:1) can effectively reduce the unevenness of particle size and enhance the overall performance of the material. The choice of alumina balls as grinding media is mainly to avoid impurities in the material and ensure a higher purity.

[0046] The mixed raw materials need to be dried for 6-8 hours, with the moisture content strictly controlled at ≤0.5% to prevent defects such as blistering and cracking in the melt due to water volatilization during the subsequent melting process. The purpose of this step is to ensure the uniformity and appropriate moisture content of the raw materials, providing a stable raw material input for the melting process.

[0047] 2) placing the dried mixture in a high-purity alumina crucible and melting it at 1850° C. to 1950° C. for 1.5 to 2.5 hours;

[0048] The core of this step is the high-temperature melting process. Choosing a high-purity alumina crucible as the melting container can minimize the reaction between the melt and the crucible material while improving the purity of the melt. The melting temperature is controlled between 1850°C and 1950°C. This temperature range can effectively promote the reaction of the various components and ensure that the melt viscosity of the material is low at this temperature, which is conducive to the uniform mixing of the components. The melting time of 1.5 to 2.5 hours is to ensure that all components are completely melted and promote the formation of various crystal phases.

[0049] It is particularly important to note that temperature control during the melting process has a significant impact on the material's microstructure. If the temperature is too high or too low during this step, it may lead to grain growth or incomplete melt formation. Therefore, temperature and time must be strictly controlled to ensure that all components react fully under ideal conditions to form the desired composite material structure.

[0050] 3) Pour the melt into a metal mold preheated to 800℃~1000℃ and cool naturally at room temperature;

[0051] Pouring the melt into a metal mold preheated to 800°C to 1000°C helps control the material's cooling rate, avoiding excessive thermal stress caused by excessive cooling, which could affect the internal structure and mechanical properties of the final product. Preheating the metal mold not only reduces thermal stress during the pouring process but also minimizes the temperature difference between the metal mold and the melt, preventing excessive thermal expansion of the mold surface when in contact with the melt, which could cause cracking or defects.

[0052] After pouring, the casting is allowed to cool naturally to room temperature. This process is designed to ensure the structural stability of the product. Natural cooling avoids the rapid contraction stress caused by strong external cooling, thereby maintaining the microstructural stability of the material and preventing cracks or defects.

[0053] 4) Annealing the cooled ingot at a temperature of 1250°C to 1400°C for 6 to 12 hours;

[0054] Annealing is a critical step in the preparation of the present material, aiming to improve the ingot's grain structure and microstructure. Heating the cooled ingot to an annealing temperature of 1250°C to 1400°C for 6 to 12 hours promotes grain growth, improves inter-grain bonding, and eliminates residual stresses caused by stress concentration during the cooling process. Annealing not only enhances the material's stability but also improves its toughness and thermal shock resistance.

[0055] During this process, the choice of annealing temperature and holding time directly impacts the material's grain refinement and interfacial bonding. Excessively high temperatures can lead to excessive grain growth, while too low temperatures can result in ineffective annealing. Therefore, optimizing annealing temperature and time is crucial for improving the material's high-temperature performance.

[0056] 5) Mechanical processing to form the final product;

[0057] After cooling and annealing, the ingot often requires machining to remove surface irregularities and precisely control the size and shape of the final product. Machining, including turning, grinding, and cutting, can further improve surface finish and refine the material's microstructure, ensuring it meets application requirements.

[0058] Furthermore, machining can eliminate microcracks or porosity that may exist on the material surface, further enhancing its performance. During machining, care must be taken to avoid secondary damage to the material caused by excessive cutting or high-temperature friction. A sound machining process helps ensure that the final product's performance meets the desired requirements.

[0059] Preferably, the ball-to-material ratio during ball milling is 3:1 to 5:1, and the grinding medium used is alumina balls.

[0060] During ball milling, a ball-to-material ratio of 3:1 to 5:1 helps improve grinding efficiency and optimize the particle distribution of the material. This ratio ensures effective collision and friction between the material and the milling media, avoiding inadequate grinding due to a low ball-to-material ratio or energy waste and equipment burden due to a high ball-to-material ratio.

[0061] Alumina balls are chosen as grinding media because of their high hardness, good wear resistance and strong chemical stability, which can avoid the appearance of unnecessary impurities during the grinding process, thereby ensuring the purity and consistency of the final product.

[0062] Preferably, the melting process adopts a step-by-step heating method, including: heating to 1500°C at 10°C / min in the first stage, and heating to 1850-1950°C at 5°C / min in the second stage.

[0063] The step-by-step heating method can effectively avoid excessive temperature gradients caused by rapid heating, thereby reducing thermal stress during the melting process. Furthermore, the temperature increase process also facilitates the uniform melting of the various components in the material and their mutual reactions. When the temperature is raised to 1500°C, the first stage primarily ensures basic melting, while the second stage, through a more gradual heating to 1850-1950°C, achieves uniform high-temperature reactions and thorough mixing of the components, further improving the physical and chemical stability of the material.

[0064] Preferably, the heating rate during the annealing process is 3-5°C / min, and the cooling rate is 2-3°C / min.

[0065] During the annealing process, controlling the heating and cooling rates directly affects grain growth and the release of internal stress in the material. Excessively rapid heating can lead to excessive grain growth, affecting the material's microstructure; while excessive cooling rates can cause thermal cracking. Therefore, during annealing, a heating rate of 3-5°C / min and a cooling rate of 2-3°C / min can effectively control the material's microstructure and reduce stress concentration caused by rapid temperature changes.

[0066] Preferably, in step 2), an induction furnace or an electric arc furnace is used as the melting equipment, and the melting process is carried out in air or a weakly oxidizing atmosphere.

[0067] Induction furnaces or electric arc furnaces, as melting equipment, can provide stable melting conditions at high temperatures while avoiding material composition shifts caused by an oxidizing environment. Using air or a weakly oxidizing atmosphere helps control the degree of material oxidation and avoid the effects of excessive oxidation on the final product properties, especially at high temperatures where oxidation of the melt can easily lead to material property degradation.

[0068] Preferably, the method further comprises performing a pore sealing treatment on the surface after step 5), wherein the pore sealing treatment adopts silica sol or alumina coating, and the treatment temperature is 400°C to 600°C.

[0069] Pore sealing is an additional process in this invention, designed to improve the casting's surface sealing and resistance to slag erosion. Sealing micropores with a silica sol or alumina coating effectively prevents external slag or gas from eroding the material's internal structure, extending its service life. The treatment temperature is controlled within the 400°C to 600°C range, ensuring a strong bond between the coating and the substrate without causing phase changes or thermal cracking in the substrate structure.

[0070] The sealing layer can also play a role in repairing microcracks, especially when the microstructure of the material is fatigued after long-term service. The presence of the sealing layer provides a restorative buffer for secondary use and has a certain self-healing function.

[0071] In summary, the preparation method of the present invention, based on the traditional melting and casting process, constructs a closed-loop processing system from raw material mixing to structural strengthening through refined control of each step, atmosphere selection, temperature adjustment and post-processing optimization, ensuring the comprehensive improvement of the material in high-temperature performance, organizational stability and structural density, etc., reflecting the systematic innovation and engineering adaptability advantages of the present invention in the design of the preparation process system.

[0072] The present invention provides a melt-cast α-Al2O3-β-Al2O3-CA6 refractory material and a preparation method thereof. It has the following beneficial effects:

[0073] 1. This invention utilizes a multi-level structural system constructed by introducing B2O3, ZrO2, and trace dopants (such as TiO2, MgO, and SiO2) to effectively suppress thermal stress concentration and rapid crack propagation between crystalline phases. The microporous structure induced by B2O3 during high-temperature melting and the phase-transformation toughening effect of ZrO2 synergize to provide the material with excellent thermal shock resistance, making it suitable for demanding applications subject to frequent heating and cooling cycles.

[0074] 2. This invention introduces trace amounts of functional doping components and oxides formed by the decomposition of Sr / Ba precursors, promoting the formation of transitional buffer zones and multi-layer bonding between grain boundaries and subgrain regions. This structural design effectively enhances the bonding quality between the primary and secondary crystalline phases, significantly improving the overall structural integrity and mechanical impact resistance of the material, and achieving a coordinated transition from microstructure to macroscopic performance.

[0075] 3. This invention, through the selection of ZrO2 polymorphs and the closed-pore structure formed by B2O3 within the composite material system, constructs a complex energy absorption and conduction pathway. Cracks are effectively deflected and passivated when encountering multiphase interfaces, microporous regions, and third-phase distribution layers, significantly improving the material's durability and fatigue resistance under cyclic loading and long-term operation.

[0076] 4. This invention introduces SrO or BaO through the thermal decomposition of carbonate precursors, achieving in-situ release and controlled spatial distribution of the oxides, thus avoiding the heterogeneity issues associated with traditional direct oxide doping. Simultaneously, a phased heating, atmosphere-controlled melting, and annealing strategy ensures controlled phase transitions and adjustable grain growth, resulting in greater engineering controllability and batch consistency in material preparation.

[0077] 5. The present invention realizes the evolution from single component strengthening to multi-mechanism coordinated evolution in material function construction, which not only improves performance indicators such as thermal shock resistance and slag corrosion resistance, but also improves the thermodynamic stability and adaptability to multiple working conditions of the material through microstructure regulation paths. DETAILED DESCRIPTION

[0078] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0079] Example 1:

[0080] The embodiment of the present invention provides a method for preparing a melt-cast α-Al2O3-β-Al2O3-CA6 refractory material, comprising the following steps:

[0081] 1) Weigh the raw materials of each component according to mass percentage: α-Al2O3 65%, CaCO3 18%, ZrO2 (partially stabilized) 6%, SrCO3 3%, CeO2 1%, B2O3 2%, SiO2 2%, TiO2 1%, Na2CO3 2%.

[0082] The raw materials were wet-milled in a ball mill for 12 hours at a ball-to-material ratio of 4:1 using alumina balls as the grinding medium. The mixture was then dried for 8 hours to a final moisture content of ≤0.5%.

[0083] 2) The dried mixture was placed in a high-purity alumina crucible and melted in an induction furnace using a stepwise heating process: the first stage was heated to 1500°C at 10°C / min, and the second stage was heated to 1900°C at 5°C / min, with the temperature maintained for 2 hours. The melting atmosphere was a weakly oxidizing atmosphere.

[0084] 3) The molten mixture is poured into a steel metal mold preheated to 900°C and naturally cooled to room temperature.

[0085] 4) The cooled ingot was annealed in air atmosphere: the temperature was raised to 1300°C at 4°C / min, kept at that temperature for 8 hours, and then cooled to room temperature at 2.5°C / min.

[0086] 5) The annealed samples are subjected to mechanical cutting, grinding and other processing to obtain refractory products of regular shape.

[0087] 6) The surface of the final product is sealed with silica sol at a temperature of 500°C for 2 hours.

[0088] Example 2:

[0089] The embodiment of the present invention provides a method for preparing a melt-cast α-Al2O3-β-Al2O3-CA6 refractory material, comprising the following steps:

[0090] 1) Weigh the raw materials of each component by mass percentage: α-Al2O3 60%, CaCO3 20%, ZrO2 (monoclinic) 8%, BaCO3 4%, CeO2 2%, B2O3 2%, TiO2 1%, Na2CO3 2%, MgO 1%.

[0091] The mixed raw materials were ground in a ball mill for 6 hours at a ball-to-material ratio of 5:1, using alumina balls as the grinding medium. The mixture was dried at 100°C for 6 hours to control the moisture content to ≤0.5%.

[0092] 2) The dried mixture was placed in a high-purity alumina crucible and melted in an electric arc furnace: heating at 10°C / min to 1500°C in the first stage and 5°C / min to 1950°C in the second stage, holding at this temperature for 2.5 hours. The melting atmosphere was air.

[0093] 3) After melting, quickly pour it into a metal mold preheated to 1000℃ and place it outside the furnace to cool naturally.

[0094] 4) Annealing: Heat to 1400°C at 3°C / min, keep at this temperature for 12 hours, and cool to room temperature at 3°C / min.

[0095] 5) After annealing, the product undergoes machining processes such as grinding, edge trimming, and drilling to form a standard size sample.

[0096] 6) The final product is sealed with alumina sol at a temperature of 600°C for 1 hour to improve corrosion resistance and resistance to slag erosion.

[0097] Example 3:

[0098] The embodiment of the present invention provides a method for preparing a melt-cast α-Al2O3-β-Al2O3-CA6 refractory material, comprising the following steps:

[0099] 1) The raw materials are mixed in the following proportions: α-Al2O3 73%, CaCO3 15%, ZrO2 (partially stabilized) 4%, SrCO3 2%, CeO2 0.5%, B2O3 1%, Na2CO3 1.5%, SiO2 2%, TiO2 1%.

[0100] The ball milling time is 6 hours, the ball-to-material ratio is 3:1, and alumina balls are used as the grinding medium. After mixing, the raw materials are dried for 6 hours and the moisture content is controlled below 0.5%.

[0101] 2) The melting process was carried out in an induction furnace. The temperature was raised to 1500°C at a rate of 10°C / min in the first stage and to 1850°C at a rate of 5°C / min in the second stage, with the temperature maintained for 1.5 hours. The melting atmosphere was air.

[0102] 3) The melt was poured into a metal mold preheated to 800°C and then naturally cooled to room temperature.

[0103] 4) Annealing: heating rate 5°C / min, temperature set to 1250°C, keep at this temperature for 6 hours, then slowly cool to room temperature at 2°C / min.

[0104] 5) The samples are simply polished and shaped to ensure uniform size and smooth edges and corners.

[0105] 6) Finally, silica sol is used to perform surface sealing treatment at 450° C. for 1 hour.

[0106] Comparative Example 1:

[0107] Compared with Example 1, the difference is that the ZrO2 component is not added, and the other raw material proportions and preparation steps remain the same.

[0108] Comparative Example 2:

[0109] Compared with Example 1, the difference is that the staged heating process is omitted, and the temperature is quickly raised to 1900°C for melting at 10°C / min throughout the process, and the other process conditions remain unchanged.

[0110] Comparative Example 3:

[0111] Compared with Example 1, the difference is that no B2O3 component is added, and the other raw material ratios and parameters are consistent.

[0112] Comparative Example 4:

[0113] Compared with Example 1, the difference is that the final step of silica sol sealing treatment is not performed, and the other processes and components remain the same.

[0114] Test Example 1: Thermal Shock Stability Test

[0115] The test steps are as follows:

[0116] 1. Sample Preparation

[0117] Refractory material samples prepared according to Example 1 and Comparative Example 1 were selected respectively to ensure that the shapes and sizes of the samples were basically the same (about 40 mm×40 mm×10 mm), and the edges were mechanically polished to prevent initial cracks from interfering with the test results.

[0118] 2. Preheating

[0119] All samples were preheated in a drying oven at 120 °C for 2 h to ensure that there was no moisture remaining on the surface to eliminate interfering factors such as water vapor burst during the thermal shock process.

[0120] 3. Thermal shock cycle test process

[0121] The sample was placed in a high-temperature box furnace and heated to 1100°C. After keeping warm for 10 minutes, it was quickly taken out using a clamp and immediately placed in clean water at room temperature to cool, completing a thermal shock cycle.

[0122] 4. Cyclic testing and damage determination

[0123] Repeat the thermal shock cycle steps above until the sample shows through cracks, obvious edge collapse, or structural damage. Inspect the sample appearance after each cycle and record the number of cycles.

[0124] 5. Data recording and statistics

[0125] The number of thermal shock cycles each sample group can withstand is counted, and the average value is calculated as a basis for comparison. The number of samples in each group is set to 5 to ensure representative test results.

[0126] The experimental results are shown in Table 1:

[0127] Table 1 Comparison of the effects of ZrO2 addition on thermal shock cycle resistance of composite materials

[0128]

[0129]

[0130] The experimental results show that Example 1 with the introduction of ZrO2 exhibits significantly better thermal stability than Comparative Example 1 in the thermal shock cycle test, with an average thermal shock cycle resistance of nearly 28 times, while the average number of thermal shock cycles for samples without the addition of ZrO2 is only 13 times, and the former's tolerance is more than doubled.

[0131] This performance advantage stems from the metastable phase transformation toughening mechanism of ZrO2 in high-temperature environments. During heating and cooling, ZrO2 undergoes a martensitic phase transformation from tetragonal to monoclinic. The accompanying volume expansion effectively blocks stress concentration at the crack tip, thereby inhibiting crack propagation. Furthermore, the stress field disturbance zone induced by this mechanism helps deflect and blunt the crack path, improving overall fracture resistance.

[0132] Combined with the microporous structure induced by B₂O₃, ZrO₂ contributes to the construction of a multi-scale energy dissipation network, continuously deflecting, absorbing energy, and terminating crack propagation, significantly delaying structural failure in the material under drastic thermal-cold cycles. This thermal shock protection system, synergistically constructed through multiphase composite strengthening and localized toughening mechanisms, is one of the key innovations in the material design of this invention.

[0133] Experimental data also confirms the incompleteness of the multiphase system when ZrO2 is missing, causing cracks to propagate in a straight line at high speed within the material, making it difficult to achieve structural slow-release and defensive reactions, thereby reducing thermal shock resistance. This highlights the structural control value and engineering practicality of this invention's material composition strategy.

[0134] Test Example 2: Tissue uniformity and structural density test

[0135] The test steps are as follows:

[0136] 1. Sample Preparation and Processing

[0137] Samples prepared according to Example 1 and Comparative Example 2 were selected with the same size (40 mm×40 mm×10 mm). All samples were polished to remove surface oxide layers and impurities to ensure that the test was conducted on the internal structure.

[0138] 2. Bulk Density Determination

[0139] The bulk density test was performed using the Archimedes method. Before the test, the sample was vacuum immersed in degassed water for 1 hour to ensure that the pores were completely filled. The dry weight, suspended weight in water, and saturated wet weight were then recorded to calculate the density value.

[0140] 3. Ultrasonic propagation velocity test

[0141] The longitudinal wave propagation velocity was tested using a pulse reflection ultrasonic detector at a frequency of 1 MHz. The time difference between the ultrasonic waves passing through each sample was recorded and the wave velocity was converted based on the sample thickness. A higher wave velocity indicates a denser structure and fewer defects.

[0142] 4. Data statistics and comparison

[0143] Each group of test samples consisted of 5 pieces. The density and ultrasonic velocity were recorded separately, and the average and fluctuation analysis within the group was performed. The structural density and tissue consistency of the two groups of samples were compared.

[0144] The experimental results are shown in Table 2:

[0145] Table 2 Comparison of the effects of staged heating process on the structural density and uniformity of composite materials

[0146] Sample number <![CDATA[Volume density (g / cm 3 )]]> Ultrasonic speed (m / s) Visible structural features Example 1-1 3.24 5170 Dense, no visible defects Example 1-2 3.21 5220 Uniform structure Examples 1-3 3.26 5140 Micro-closed pores Examples 1-4 3.22 5195 No obvious structural stratification Examples 1-5 3.25 5150 Structural integrity Comparative Example 2-1 3.11 4870 Obvious grain unevenness Comparative Example 2-2 3.08 4935 There are crystalline inclusion bands Comparative Examples 2-3 3.12 4810 Many coarse particles Comparative Examples 2-4 3.14 4865 Too many internal pores Comparative Examples 2-5 3.1 4790 Insufficient local density

[0147] This experiment shows that the sample group using the staged heating process performs better in terms of volume density and ultrasonic propagation velocity, with the density concentrated in the range of 3.21 to 3.26 g / cm 3The wave velocity is between 5140 and 5220 m / s, indicating a dense structure, few defects, and good internal uniformity. However, the density of the comparative samples using a single heating rate fluctuates greatly, and the ultrasonic propagation velocity is generally reduced. Combined with the observation results, it shows that the grain coarsening and structural inhomogeneity are more obvious.

[0148] The fundamental reason for this is that the multi-stage heating strategy provides a reaction buffer window and crystal phase reconstruction adjustment time during the melting process, promoting sufficient diffusion and reaction between the primary and secondary crystalline phases, and avoiding the accumulation of defects caused by local overheating or uneven crystallization. In particular, controlling the heating rate during the high-temperature stage helps the grains grow gradually in the melt rather than suddenly, thus forming a more detailed and coherent crystal network structure.

[0149] The staged heating also effectively regulates the release behavior of oxide precursors during melting, ensuring that auxiliary phase components such as SrO and BaO are evenly distributed within the melt. This uniform distribution further enhances the synergistic matching between multiphase interfaces, reduces thermal stress gradients between crystal phases, inhibits the initiation of microcrack sources, and significantly improves structural density and microstructural consistency.

[0150] In contrast, the comparative sample, due to its rapid heating rate, failed to provide sufficient time for reaction and crystallization adjustment, resulting in loose connections between crystals, significant phase boundary mutations, poor local density, and ultimately low macroscopic density and acoustic velocity response. This demonstrates the importance of melt-stage heat treatment strategies in material structure construction and highlights the innovative highlights and application significance of this invention in process optimization and coordinated crystal phase regulation.

[0151] Test Example 3: Crack Propagation and Energy Dissipation Capacity Test

[0152] The test steps are as follows:

[0153] 1. Sample Preparation and Pretreatment

[0154] Samples prepared according to Example 1 and Comparative Example 3 were selected respectively with uniform size (about 20 mm×20 mm×5 mm), and standard Vickers hardness indentation (load 10 kg, loading time 10 s) was applied to the surface of the specimens to induce and observe the crack propagation path.

[0155] 2. Crack extension observation test

[0156] After 24 hours of stabilization after indentation, the crack morphology around the indentation was observed using an optical microscope, the average crack length was recorded, and the relative crack extension ratio was calculated to determine the material's ability to inhibit crack propagation.

[0157] 3. Load-unload cycle test

[0158] The samples were subjected to mechanical loading-unloading cycle tests, and 10 cycles were performed in the low load range (20–50% of the ultimate load) using a universal material testing machine. The energy dissipation curve and deformation recovery were monitored to evaluate the toughness and energy dissipation characteristics of the material under micro-damage.

[0159] 4. Data Collection and Comparative Analysis

[0160] Three samples were tested in each group, and the average crack length and energy dissipation during the cyclic test were summarized to compare the differences in crack resistance and structural energy dissipation performance between the example and comparative example samples.

[0161] The experimental results are shown in Table 3:

[0162] Table 3 Comparison of the effects of B2O3 introduction on the crack resistance and energy dissipation of composite materials

[0163]

[0164]

[0165] The experimental results show that the crack length in Example 1 is significantly shorter than that in Comparative Example 3, and the crack morphology exhibits typical deflection and termination characteristics, indicating that crack propagation is significantly hindered. Furthermore, during the load-unload cycle test, the energy dissipation capacity of the Example is approximately 1.7 times that of the Comparative Example, demonstrating higher toughness and structural energy absorption capacity.

[0166] The key to this performance improvement lies in the active behavior of B₂O₃ during the melting process, which induces the formation of microscale closed pores within the material. These pores act as "energy absorbers" or "deflection nodes" along the crack propagation path, effectively redirecting the crack and weakening areas of stress concentration, thereby preventing rapid crack penetration. Furthermore, the microporous regions absorb energy transmitted from the crack tip, delaying the onset of localized structural damage.

[0167] Furthermore, the glassy phase separation mechanism involving B2O3 promotes the formation of highly cohesive multiphase interfacial regions. These regions slowly release internal stress under stress, exhibiting good elastic-plastic behavior. Combined with the loading-unloading cyclic performance, this structural design significantly improves the material's stability in response to repeated loading, making it a crucial component in constructing an integrated multi-point energy dissipation and crack suppression structure.

[0168] In contrast, the lack of B₂O₃ in Comparative Example 3 demonstrates a lack of effective crack propagation and slow-release channels within the internal structure. Cracks primarily propagate in a linear pattern, with short paths and low energy consumption, making them susceptible to structural fatigue and premature failure under repeated loading. This demonstrates the theoretical basis and practical application of the present invention's material composition design for crack behavior regulation.

[0169] Test Example 4: High Temperature Slag Corrosion Test

[0170] The test steps are as follows:

[0171] 1. Sample preparation and pretreatment

[0172] The sintered samples corresponding to Example 1 and Comparative Example 4 were selected and cut into blocks with a size of approximately 20 mm × 20 mm × 10 mm. All samples were surface-polished to the same roughness level (Ra≈0.8 μm) to eliminate the influence of surface morphology on slag corrosion behavior.

[0173] 2. Slag sample preparation and arrangement

[0174] Prepare artificial simulated high-temperature slag, primarily composed of the CaO–SiO₂–Fe₂O₃–Al₂O₃ system with a melting point of approximately 1280°C. Place the sample in a refractory crucible and cover it with a certain amount of slag powder, ensuring full contact between the sample's upper surface and the slag.

[0175] 3. High temperature corrosion treatment

[0176] The crucible was placed in a high-temperature furnace at a heating rate of 10°C / min, heated to 1350°C, and held at this temperature for 3 hours. During this holding period, the slag melted and reacted with the sample, simulating the slag corrosion environment under actual use conditions.

[0177] 4. Cooling and sample handling

[0178] After the test, the samples were naturally cooled to room temperature, taken out, sectioned, and the surface slag residue was cleaned. The samples were sliced using a vertical metallographic cutting machine for cross-sectional analysis.

[0179] 5. Erosion depth and structure assessment

[0180] A stereo microscope and image analysis software were used to measure the depth of the slag layer and record the characteristics of the penetration interface to comprehensively evaluate the improvement in corrosion resistance achieved by the sealing treatment. Each group of samples was tested on at least three specimens to ensure representative data.

[0181] The experimental results are shown in Table 4:

[0182] Table 4 Comparison of the effects of surface sealing treatment on the slag erosion resistance of composite materials

[0183]

[0184]

[0185] Experimental data shows that the slag corrosion depth of Example 1 samples is significantly lower than that of Comparative Example 4, averaging less than 0.5 mm. The interface morphology is intact, and the structure shows no significant damage. Comparative Example 4, on the other hand, exhibits deep penetration exceeding 1.3 mm, with significant surface flaking, dissolution of crystal boundaries, and concentrated cracks at multiple points. This demonstrates that the sealing treatment is significantly effective in inhibiting high-temperature slag corrosion.

[0186] This performance improvement is primarily attributed to the sealing treatment, which creates a dense, chemically stable protective interface on the material's surface. This sealing layer exhibits low reactivity with molten slag at high temperatures, effectively shielding the internal structure from molten slag and reducing the tendency of active components in the slag to corrode the primary crystalline phase. The continuous, dense interface formed in the sealed area also provides a certain degree of mechanical buffering, maintaining structural integrity under thermal expansion and contraction stresses and preventing crack initiation.

[0187] Furthermore, the sealing layer significantly reduces the wettability between the slag and the material surface by regulating the surface porosity and contact interface energy, thereby reducing the slag liquid adhesion area and residence time, further improving the overall slag erosion resistance. This interface regulation mechanism, combined with the internal multiphase synergistic system, effectively implements a composite structural protection strategy from the surface to the substrate.

[0188] The comparative sample, which had no pore sealing treatment and had open pores on its surface, allowed molten slag to quickly penetrate the internal structure along these pores at high temperatures, accelerating interfacial reactions and destroying the crystalline phase, ultimately leading to overall structural degradation of the material. This result fully validates the innovative concept of optimizing the pore sealing process and regulating interface engineering in this invention, which is of great significance for extending the material's service life in high-temperature corrosive environments.

[0189] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A melt-cast α-Al2O3-β-Al2O3-CA6 refractory material, characterized in that: Calculated by mass percentage, it includes the following components: Al2O385%~95%; CaO 2%~4%; Na2O 1%~3%; ZrO2 0.5%~1.0%; SrO or BaO 0.5% ~ 1.0%; CeO20.3%~0.6%.

2. The fused-cast α-Al2O3-β-Al2O3-CA6 refractory material according to claim 1, characterized in that: It also includes 0.1% to 0.3% B2O3.

3. The fused-cast α-Al2O3-β-Al2O3-CA6 refractory material according to claim 1, characterized in that: It also includes 0.5% to 2.0% of trace additives.

4. The fused-cast α-Al2O3-β-Al2O3-CA6 refractory according to claim 3, characterized in that: The trace additive is selected from one or more of TiO2, MgO, and SiO2.

5. The fused-cast α-Al2O3-β-Al2O3-CA6 refractory material according to claim 1, characterized in that: The ZrO2 is monoclinic or partially stabilized zirconium oxide.

6. The fused-cast α-Al2O3-β-Al2O3-CA6 refractory material according to claim 1, characterized in that: The SrO or BaO is its corresponding carbonate, which is decomposed at high temperature.

7. A method for preparing the melt-cast α-Al2O3-β-Al2O3-CA6 refractory material according to any one of claims 1 to 6, characterized in that: The following steps are involved: 1) Weighing each component raw material and mixing them in a ball mill for 6 to 12 hours. Drying the mixed raw materials for 6 to 8 hours to control the moisture content to ≤ 0.5%; 2) placing the dried mixture in a high-purity alumina crucible and melting it at 1850° C. to 1950° C. for 1.5 to 2.5 hours; 3) Pour the melt into a metal mold preheated to 800℃~1000℃ and cool naturally at room temperature; 4) Annealing the cooled ingot at a temperature of 1250°C to 1400°C for 6 to 12 hours; 5) The final product is formed by mechanical processing.

8. The preparation method according to claim 7, characterized in that The ball-to-material ratio during ball milling is 3:1-5:1, and the grinding medium used is alumina balls.

9. The preparation method according to claim 7, characterized in that The melting process adopts a step-by-step heating method, including: heating to 1500° C. at 10° C. / min in the first stage, and heating to 1850-1950° C. at 5° C. / min in the second stage.

10. The preparation method according to claim 7, characterized in that The heating rate during the annealing process is 3-5°C / min, and the cooling rate is 2-3°C / min.

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