Production formula of high-temperature wear-resistant and acid-base-resistant fused zirconium mullite brick

Abstract

The invention discloses a production formula of a high-temperature wear-resistant and acid-base-resistant fused zirconium mullite brick, and belongs to the technical field of high-performance refractory materials. The invention provides a novel formula and an ultra-slow cooling process. The formula is composed of a matrix forming material, a kyanite / andalusite structure synergistic regulating agent and a rare earth-alkaline earth metal-boron composite functional additive, and the melt property is regulated through the synergistic effect of a specific proportion. The preparation method comprises the steps of burdening, smelting, casting and ultra-slow cooling treatment, namely the average cooling rate of a casting from the high temperature to 800 DEG C is controlled to be smaller than or equal to 0.5 DEG C / min. The process guides the interior of the material to form a synergistic structure of a compact matrix and a high-proportion stable stress buffer unit, so that the product has excellent thermal shock resistance and excellent molten salt permeability resistance while keeping high volume density and high strength, is especially suitable for extremely severe environments such as a sponge titanium magnesium electrolytic bath and a tapping tank, and has a wide application prospect. And the service life of equipment can be obviously prolonged.

Description

Technical Field

[0001] This invention relates to the field of high-performance refractory materials technology, and in particular to a production formula for electrofused zircon mullite bricks that are high-temperature wear-resistant and acid and alkali resistant. Background Technology

[0002] In fields such as non-ferrous metal metallurgy (e.g., sponge titanium production), special steel slide rails, and chemical waste incineration, the refractory linings of key high-temperature equipment endure multiple severe stresses over long periods: intense chemical corrosion from high temperatures (typically >800℃), molten salts (e.g., magnesium chloride) or alkali metal oxides, physical erosion and wear from materials, and frequent thermal shocks caused by process start-ups and shutdowns and power fluctuations. Similarly, for heavy industrial environments like special steel plants, wear-resistant slide rails subjected to constant stress, deformation impacts, and frictional losses must be high-temperature and corrosion-resistant products that combine wear resistance and corrosion resistance. Refractory materials produced by the electrofusion method, due to the complete transformation of raw materials into a homogeneous melt followed by recrystallization at high temperatures, possess advantages such as high purity, high density, and stable phase composition, exhibiting excellent resistance to corrosion and wear.

[0003] However, the fatal weakness of traditional electrofused refractories (such as electrofused zirconia-corundum bricks and electrofused mullite bricks) lies in their poor thermal shock resistance. This is mainly due to their inherent process characteristics: during rapid cooling and solidification, the melt tends to form a coarse and directly bonded crystal structure, resulting in a high internal elastic modulus and a large coefficient of thermal expansion. Simultaneously, the pores generated by solidification shrinkage are mostly concentrated shrinkage cavities or irregularly shaped holes. These pores not only fail to effectively buffer thermal stress but also easily become stress concentration points. Therefore, when subjected to rapid heating and cooling, the enormous thermal stress has nowhere to dissipate or release, easily leading to brittle cracking or spalling of the material, causing unplanned equipment downtime and significant economic losses.

[0004] For a long time, attempts to improve the thermal shock resistance of fused materials, such as introducing small amounts of additives or simply extending the holding time, have often yielded little result, or even at the expense of their core corrosion resistance. The fundamental reason lies in the failure to systematically resolve the contradiction between high density and high corrosion resistance and high toughness and strong thermal shock resistance from the source of material design—namely, the synergy between formulation design and process pathways. Specifically, this manifests as the inability to maintain a high-density matrix in the fused material while actively constructing a stable, dispersed reinforcement structure within it that can effectively dissipate heat stress. Therefore, developing a novel fused material and its preparation method that can synergistically achieve the above-mentioned properties has become a pressing technical challenge in this field. Summary of the Invention

[0005] (a) Purpose of the invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a novel electrofused zirconia-mullite brick and its electrofused casting preparation method. This method aims to actively construct a synergistic structure within the material, consisting of a high-strength, dense matrix and a high proportion of stable stress-buffering units, through an innovative raw material formulation system and a precisely controlled melting-casting-ultra-slow cooling process. This fundamentally solves the problem of poor thermal shock resistance in traditional electrofused materials, enabling them to maintain excellent resistance to molten salt erosion and high strength while achieving superior thermal shock fatigue resistance, ultimately significantly extending their service life under extreme operating conditions.

[0007] (II) Technical Solution To achieve the above objectives, the present invention adopts the following technical solution: Firstly, a raw material formulation for zircon mullite bricks suitable for electrofusion casting is provided.

[0008] The formulation consists of the following components by weight percentage, each functionally designed based on its role in the formation of the final material structure: Matrix forming material (83-91wt%): constitutes the continuous, high-strength main skeleton of the material.

[0009] Industrial alumina powder (Al2O3 content ≥98.5%): 70-76 wt%. Provides a corundum phase matrix with high refractoriness and chemical inertness, which is the basis for its corrosion resistance.

[0010] Zircon concentrate powder (ZrO2 content ≥65%): 1-6wt%. It decomposes at high temperature to generate active ZrO2 and SiO2. The former, after partial stabilization, can provide potential phase transformation toughening effect, while the latter reacts with Al2O3 to generate a high-strength mullite phase.

[0011] High-purity quartz powder (SiO2 content ≥99%): 10-14wt%. Precise control of the Al2O3 / SiO2 molar ratio ensures the formation of a sufficient quantity of high-quality mullite network, optimizing the material's high-temperature performance.

[0012] Monoclinic zirconia powder (ZrO2 content ≥99%): 1-3wt%. High-purity zirconia is directly introduced to form a stable zirconia dispersion phase with zircon decomposition products, improving the material's resistance to molten salt erosion, and stabilizing its high-toughness crystal form through combination with rare earth oxides.

[0013] Structure synergistic regulator (6-12wt%): Its core function is to regulate the physicochemical properties and solidification behavior of high-temperature melts, creating favorable conditions for subsequent processes. Its composition and proportion are key to achieving structure regulation.

[0014] Kyanite concentrate powder (Al2O3≥58%, particle size D90≤0.074mm): 2.5-7.0wt%.

[0015] andalusite concentrate powder (Al2O3≥58%, particle size D90≤0.15mm): 3.5-8.0wt%.

[0016] Mechanism and Proportion Requirements: Kyanite begins to decompose violently at approximately 1300℃, accompanied by significant volume expansion; while andalusite decomposes at a higher temperature and expands more gently. This invention requires that the weight ratio of the two be strictly controlled at (0.33-1.67):1. During the rapid heating and smelting stage of the electrofusion process, this specific ratio of mixture enables stepwise activation and decomposition. The initial decomposition of kyanite helps to break up the agglomeration of raw material particles in the early stages of melt formation, promoting melting homogenization; the subsequent decomposition of andalusite plays a stabilizing and buffering role. The synergy between the two can effectively influence the viscosity gradient and gas dissolution-precipitation behavior of the melt at high temperatures, laying a physicochemical foundation for obtaining a uniform stress buffer unit distribution through the subsequent ultra-slow cooling process. Imbalance in the ratio will lead to inhomogeneous melt properties or uncontrolled gas behavior.

[0017] Composite functional additives (3-6 wt%, based on final oxides): They play multiple auxiliary roles in the melting, solidification and cooling stages, and optimize the final structure.

[0018] Rare earth oxides (0.6-1.8 wt%): selected from at least one of yttrium oxide (Y₂O₃) and lanthanum oxide (La₂O₃). The main mechanism is the formation of a solid solution with zirconium oxide, inhibiting abnormal growth of zirconium oxide grains and stabilizing them in a highly tough tetragonal phase at room temperature, thus improving matrix toughness. Simultaneously, rare earth ions may accumulate at phase boundaries, optimizing interfacial bonding strength.

[0019] Alkaline earth metal oxides (0.4-1.2 wt%): selected from at least one of magnesium oxide (MgO) and calcium oxide (CaO). Their mechanism of action is to regulate the slag erosion resistance index of the material, and they can form a small amount of high-melting-point compounds at high temperatures, acting as pinning agents to limit excessive migration of the main crystalline phase grain boundaries.

[0020] Boron oxide (B2O3) (0.1-0.6wt%): As a highly efficient flux, its core mechanism is to significantly reduce the viscosity and surface tension of high-temperature melts. This not only facilitates component diffusion and homogenization during the melting process and promotes gas removal, but more importantly, at the end of solidification, it promotes the good wetting and filling of a small amount of residual liquid phase between the forming crystal framework, helping to seal the dispersed micropores, promoting the formation of isolated, spherical stress buffer units, and improving the sintering densification of the material.

[0021] The wt% of each component above refers to its weight percentage in the formula, and does not refer to purity or effective content; for the distinction, purity or effective content is expressed as %.

[0022] Secondly, a method for preparing fused zircon mullite bricks using the above-mentioned formula is provided.

[0023] The above formulation is combined with a multi-stage, precisely controlled process, particularly by introducing a crucial ultra-slow cooling stage to guide the material structure's evolution along a predetermined path. The specific steps are as follows: S1. Ingredient mixing and deep homogenization Accurately weigh all powder raw materials according to the above formula. Place the weighed raw materials in a high-efficiency mixing device (such as a three-dimensional mixer or a V-type mixer) and perform dry mixing for no less than 60 minutes until the material achieves absolute uniformity in color and composition distribution at both the macroscopic and microscopic scales.

[0024] Mechanism Explanation: Initial homogeneity of raw materials is the primary prerequisite for obtaining a final product with uniform composition and structure. Deep homogenization ensures synchronous reactions during subsequent melting and avoids localized component segregation, which is the foundation for achieving consistent and repeatable material properties.

[0025] S2. Staged smelting and refining homogenization Add the uniformly mixed furnace charge into the electric arc furnace and perform a staged melting process: Rapid melting period: Higher arc voltage and current are used to rapidly melt the furnace charge to form a molten pool, reducing heat loss and component volatilization.

[0026] Low-temperature refining period: After the furnace charge has fully melted, reduce the input power appropriately and precisely control the melt temperature at 2050-2200℃, and maintain the temperature within this range for 60-120 minutes for refining.

[0027] Mechanism explanation: A higher refining temperature ensures good melt fluidity, which is beneficial for removing dissolved gases and light impurities; a sufficiently long refining time ensures that all components, especially high-melting-point zirconium oxide and rare earth oxides, can diffuse fully and achieve molecular-level compositional homogeneity. This is a key step in obtaining a defect-free, high-performance melt.

[0028] S3. Temperature-controlled casting and initial solidification management Adjust the temperature of the refined melt to 1950-2100℃ (that is, about 150-250℃ higher than its theoretical liquidus temperature).

[0029] Pour the molten material smoothly into a mold that has been preheated to 100-300°C. The inner wall of the mold must be coated with a refractory coating to prevent sticking.

[0030] After casting is completed, immediately use a special tool to gently and continuously stir the riser area of ​​the casting for about 1-3 minutes.

[0031] Cover the surface of the riser with a layer of high-efficiency thermal insulation material (such as aluminum silicate fiber cotton or composite thermal insulation covering agent).

[0032] Mechanism Explanation: A suitable superheat (1950-2100℃) ensures the melt maintains good fluidity during casting, allowing it to fill complex areas of the mold cavity. Mold preheating slows down the rapid cooling rate when the melt contacts the mold, preventing surface cooling that could cause cold shuts or cracks. Post-pouring tamping of the riser utilizes hydrodynamics to help expel rising gases and light inclusions from the mold cavity to the riser, reducing porosity defects inside the casting. Covering with insulating material slows down the solidification rate at the riser, prolonging its liquid feeding time and preventing concentrated shrinkage cavities inside the casting due to solidification shrinkage.

[0033] S4. Ultra-slow cooling treatment The castings, after casting and initial treatment, are transferred together with the mold to a slow cooling facility with precise programmed temperature control (such as a computer-controlled insulated pit or tunnel-type slow cooling kiln) to perform the following ultra-slow cooling regime: Starting from the casting temperature, cooling is performed in a programmed manner to ensure that the average cooling rate of the casting during the entire high-temperature stage from the casting temperature to 800°C is no greater than 0.5°C / min.

[0034] In particular, in the critical temperature range of 1200℃ to 800℃, which is most sensitive to material phase transformation and residual stress formation, the cooling rate needs to be further slowed down and strictly controlled within the range of 0.2-0.4℃ / min.

[0035] The entire slow cooling process should last no less than 100 hours, until the core temperature of the casting safely drops below 150°C before subsequent operations can proceed.

[0036] This step is the crucial process for achieving a high-proportion stable stress buffer unit structure in this invention. The extremely slow cooling rate (≤0.5℃ / min) produces multiple synergistic effects: Promoting gas aggregation and spheroidization: Gases dissolved in the melt (such as those produced by the decomposition of raw materials or dissolved from the air) have ample time to slowly diffuse out, aggregate, and grow. Slow cooling allows sufficient time for the gas expansion pressure and the surface tension of the melt to reach equilibrium, thus forming nearly spherical isolated pores, rather than needle-like or branched pores formed during rapid cooling.

[0037] Achieving sufficient stress relaxation: During the cooling process, the different thermal expansion coefficients of various phases (such as corundum, mullite, and zirconium oxide) and the temperature difference between the inside and outside of the material generate enormous internal stress. Ultra-slow cooling provides these stresses with sufficient time to relax and release through mechanisms such as dislocation movement and grain boundary slip, preventing stress freezing. This ensures that the final material's internal pores (stress buffer units) are softly bonded to the dense matrix rather than rigidly connected, and the pores themselves do not become crack initiators.

[0038] Guiding equilibrium solidification and phase transformation: Slow cooling makes the solidification and solid-state phase transformation process closer to the thermodynamic equilibrium state, which is conducive to the formation of a phase with uniform composition and stable structure, and reduces the generation of segregation and non-equilibrium brittle phases.

[0039] S5. Post-processing and machining After the casting has completely cooled to room temperature, it is demolded. The gating and riser system is removed. The brick blank is then machined using diamond tools through grinding, cutting, and drilling to achieve the precise dimensions, shape, and surface finish required by the design drawings. Finally, a pre-assembly inspection is performed.

[0040] Thirdly, a high-performance electrofused zircon-mullite brick prepared by the above method is provided.

[0041] This study addresses the performance optimization of fused zirconium-mullite bricks used in electrolytic cells of sponge titanium plants and the improvement of wear resistance coefficients in wear-resistant slide rail bricks used in special steel plants. It systematically analyzes the influence mechanism of introducing kyanite group minerals (kyanite, andalusite, and sillimanite) on the thermal shock stability, wear resistance, high-temperature resistance, and corrosion resistance of the materials. The resulting brick is not a simple product of densification, but rather a composite material with an optimized internal structure obtained through the aforementioned specific process, exhibiting an apparent porosity ≤2.5% and a bulk density ≥3.08 g / cm³. 3 The compressive strength at room temperature is ≥268MPa, the number of water-cooled thermal shock cycles at 1100℃ is ≥25, the linear thermal expansion coefficient at 1000℃ is ≤0.62%, and the average molten salt penetration depth after static immersion in molten anhydrous magnesium chloride at 850℃ for 48 hours is ≤1.2mm. Details are as follows: Physical structural properties: High bulk density (≥3.05 g / cm³) 3 This indicates that its matrix is ​​highly dense, with an apparent porosity of ≤2.5%, and the permeation test proves that it is basically closed-cell, which acts as an effective stress buffer unit uniformly dispersed in the dense matrix.

[0042] Mechanical and thermomechanical properties: With a compressive strength of ≥250MPa at room temperature, it demonstrates robust load-bearing capacity. Breakthrough thermal shock resistance has been achieved; in a stringent water-quenched thermal shock cycle test from 1100℃ to room temperature, it withstands at least 25 cycles without fracture, proving that its internal structure effectively absorbs and dissipates heat from shock impacts.

[0043] Chemical corrosion resistance: In tests simulating the extreme corrosive environment of a magnesium electrolytic cell (static immersion in molten anhydrous magnesium chloride at 850℃ for 48 hours), the average penetration depth of the molten salt was limited to less than 1.2 mm, which is far superior to traditional products, indicating that its dense matrix and stable internal structure effectively block the capillary penetration channels of the molten salt.

[0044] Macroscopic structural characteristics: The material cross-section is uniform and dense, without any visible concentrated shrinkage cavities, cracks, or large defects. Its performance is attributed to the synergistic structure of the dense matrix and dispersed stable stress buffer units jointly constructed by the aforementioned formulation and process.

[0045] (III) Beneficial Effects Compared with the prior art, the present invention has the following significant advantages and positive effects: 1. This invention utilizes the synergistic expansion control mechanism of kyanite and andalusite: both kyanite (phase transformation expansion of approximately 18%) and andalusite (phase transformation expansion of approximately 5%) transform into mullite at high temperatures. By limiting the specific ratio of the two, the violent expansion of kyanite is buffered and dispersed by the gentle expansion of andalusite, transforming destructive concentrated expansion into uniform micro-expansion. With sufficient time provided by ultra-slow cooling, this micro-expansion effectively fills micropores and promotes crystal interweaving, thereby significantly reducing the overall thermal expansion coefficient of the product and enhancing matrix bonding strength without sacrificing density (low porosity). Using kyanite alone results in uncontrolled expansion, leading to a loose structure and a surge in porosity; using andalusite alone provides insufficient control and limited performance improvement.

[0046] 2. Traditional rapid cooling (>5℃ / min) addresses the problems of frozen thermal stress and phase transformation stress, microcrack formation, and increased coefficient of thermal expansion. This invention employs ultra-slow cooling at ≤0.5℃ / min, which has the following characteristics: (a) it allows sufficient gas escape from the melt, reducing shrinkage cavities; (b) it provides sufficient kinetic conditions for the synergistic phase transformation of kyanite / andalusite, achieving stress relaxation and homogenization; and (c) it promotes uniform grain growth, resulting in a stable microstructure with low internal stress. These are the decisive process factors for achieving a synergistic leap in both low coefficient of thermal expansion and high thermal shock resistance.

[0047] 3. This invention also utilizes multi-component additives for auxiliary optimization of porosity and density: yttrium oxide can stabilize the zirconium oxide phase and refine the grains; magnesium oxide and boron oxide, as sintering aids and grain boundary modifiers, help optimize the grain boundary structure during slow cooling, further improving the high-temperature performance and corrosion resistance of the material.

[0048] 4. This invention breaks through the limitations of traditional electrofused bricks, which suffer from poor thermal shock resistance due to high density. It achieves three lows and one high: low porosity (≤2.5%), low thermal expansion (≤0.62% at 1000℃), low erosion rate, and high thermal shock resistance (≥25 cycles), comprehensively exceeding national high-quality product standards. It is particularly suitable for extreme environments with frequent thermal shock and severe molten salt corrosion. This invention is not only suitable for linings of sponge titanium-magnesium electrolytic cells but can also be applied to hot spots in glass kilns, chemical waste incinerators, steel refining equipment, and any other extreme environment simultaneously subjected to high temperatures, corrosion, thermal shock, and abrasion, possessing broad market prospects. Attached Figure Description

[0049] Figure 1 This is a comparison of the surface erosion of the product brick in Example 1 and the product brick in Comparative Example 1 after 18 months of use. Figure 1 Photo 'a' shows the surface erosion of the brick product from Example 1. Figure 1 b is a photograph showing the surface erosion of the brick in Comparative Example 1. Detailed Implementation

[0050] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0051] I. Product Formula and Process: Prepare materials according to the weight percentage formula shown in Table 1 below. All powder raw materials must be passed through a sieve of the appropriate mesh size to ensure particle size and mixed for 90 minutes using a three-dimensional mixer.

[0052] Table 1: Raw material formulations for examples and comparative examples

[0053] Preparation process: A method for preparing erosion-resistant and thermal shock-resistant fused zirconia-mullite bricks, using the formula in Table 1, and including the following steps: S1. Ingredients and homogenization: Weigh each ingredient according to the formula and mix them evenly; S2. Melting: Place the mixture in an electric arc furnace for melting. After complete melting, refine at 2050-2200℃ for 60-120 minutes. S3. Casting and initial treatment: Cool the melt to 1950-2100℃ and pour it into a mold preheated to 100-300℃. After casting, stir the riser and cover it with insulation material. S4. Ultra-slow cooling treatment: The casting is subjected to programmed slow cooling after casting, so that the average cooling rate of the casting from the casting temperature to 800℃ is not greater than 0.5℃ / min, and the total slow cooling time is not less than 100 hours. S5. Post-processing: Demold the fully cooled casting and machine it to the specified dimensions.

[0054] The smelting and casting process involves adding the mixture to a 1-ton electric arc furnace. The furnace is then powered to melt the mixture, and after complete melting, it is refined at (2100±50)℃ for 90 minutes. The melt is then cooled to (2000±20)℃ and poured into a special cast iron mold preheated to 700℃. Immediately after casting, the riser is gently tamped, and the mold is covered with aluminosilicate fiber felt.

[0055] Examples 1-3 strictly followed the above steps, while Comparative Examples 1-3 differed only in the cooling process: Examples 1-3: Strictly implement the ultra-slow cooling process of this invention. Move the casting to a programmable temperature-controlled insulation pit, and set the average cooling rate from the casting temperature to 800°C to be approximately 0.4°C / min (approximately 0.3°C / min in the 1200-800°C range), with a total slow cooling time of approximately 110 hours, until the core temperature is below 150°C.

[0056] Comparative Examples 1-3: Using the traditional method. After casting and covering, the material was placed in a workshop environment to cool naturally, and its average cooling rate from high temperature to 800℃ was much greater than 5℃ / min.

[0057] II. Performance Testing and Result Analysis: Various performance tests were conducted on the brick samples after cooling to room temperature and processing, and the results are summarized in Table 2. All performance tests were conducted according to relevant national standards: bulk density and apparent porosity were determined according to GB / T 2997; room temperature compressive strength was determined according to GB / T 5072; flexural strength was determined according to GB / T 3001; thermal shock resistance (water cooling at 1100℃) was tested according to GB / T 30873; resistance to molten magnesium erosion was determined by immersion in a static crucible at 850℃ for 48 hours to measure the penetration depth; linear thermal expansion coefficient was determined according to GB / T 7320; and thermal conductivity was determined according to GB / T 5990. Standard samples after processing were also tested.

[0058] Successful verification of Examples 1-3: All three examples achieved the invention objectives and the national standard for high-quality fused zirconia mullite bricks. They exhibit low porosity (≤2.5%) and high bulk density (≥3.08 g / cm³). 3 The high strength (pressure resistance ≥268MPa, flexural strength ≥52MPa) indicates that the material has formed a highly dense microstructure. Excellent thermal shock resistance (≥25 cycles) is directly related to its low coefficient of thermal expansion (≤0.62% at 1000℃) and suitable thermal conductivity, indicating that internal thermal stress is effectively suppressed. Simultaneously, outstanding resistance to molten salt penetration (≤0.95mm) confirms the effective barrier of the dense and intact matrix against corrosive media. This is the result of the combined effects of kyanite / andalusite synergistic phase composition regulation in the formulation, yttrium oxide and other additives optimizing high-temperature performance, and the ultra-slow cooling process.

[0059] Comparative Example 1: No structure modifier and natural rapid cooling process. Although it has the highest density and strength, its coefficient of thermal expansion is significantly higher (0.75% at 1000℃), and its thermal conductivity is lower, resulting in extremely poor thermal shock resistance (9 times). The rapid cooling process easily generates micro-stress concentration and potential microcracks at grain boundaries. Although some of these are masked by the high density, they become crack initiation points under thermal shock conditions. The high molten salt penetration depth (1.80 mm) also indicates that its microstructure has shortcomings in corrosion resistance.

[0060] Comparative Example 2 used only kyanite, and Comparative Example 3 used only andalusite; neither achieved the performance level of the examples. In Comparative Example 2, excessive expansion of kyanite led to increased porosity, decreased density and strength, and a loose structure, resulting in insufficient resistance to erosion and thermal shock. Comparative Example 3 outperformed Comparative Example 2, but its coefficient of thermal expansion and thermal shock resistance were still inferior to the examples, demonstrating that a single raw material cannot achieve the comprehensive effect of synergistically controlling phase composition and thermal expansion behavior through a specific ratio of kyanite and andalusite.

[0061] Regarding the high strength of Comparative Example 1, the results further demonstrate that higher strength is not always better. It employed a traditional high-purity formula and rapid cooling process, achieving a room-temperature compressive strength of 310 MPa, primarily due to the 'fine-grain strengthening' effect caused by rapid cooling and a large amount of 'frozen' internal thermal stress. This high-strength state is inherently metastable and brittle. Its high coefficient of thermal expansion (0.75%) and extremely low thermal shock resistance (9 cycles) are clear evidence of this. When subjected to thermal cycling, the inherent high internal stress of this material becomes the driving force for crack initiation and propagation, leading to rapid failure. This confirms the inherent defects of traditional high-strength materials described in the prior art.

[0062] In summary, the improvement of this invention does not lie in obtaining a higher extreme value of room temperature strength, but in actively designing and precisely controlling the micro-stress state, thermal expansion behavior and microstructure of the material through synergistic innovation of raw materials and processes. Thus, while ensuring a safety margin of strength (far exceeding national standards), the focus of performance optimization is shifted to the thermal shock resistance and structural stability that determine the actual service life, achieving a qualitative leap in comprehensive service performance.

[0063] To further confirm the impact of cooling rate on key material properties, the following tests were specifically designed, as shown in Table 2: Table 2: Impact of Cooling Rate on Key Product Performance

[0064] As shown in Table 2, when the core ultra-slow cooling process of this invention (cooling rate ≤0.5℃ / min) is adopted, the product performance achieves a key leap, with the apparent porosity reduced to ≤2.5% and the thermal shock resistance exceeding 25 cycles, indicating that the pores are essentially closed pores, achieving the excellent performance indicators set by the invention. The data in Table 3 intuitively demonstrate that the ultra-slow cooling process is the decisive process factor in obtaining low porosity, high closed-pore ratio, and high thermal shock resistance. The slow cooling rate is conducive to gas accumulation to form stable closed pores and fully relaxes thermal stress, thereby transforming closed pores from potential crack initiation points into beneficial stress buffer units.

[0065] III. Industrial Application Testing: Comparative masonry was constructed on the sidewalls and corners of an 8kA magnesium electrolytic cell in a sponge titanium plant. One side used the product of Example 1 of this invention, while the other side used commercially available high-quality fused mullite bricks (with performance close to Comparative Example 1). The cell underwent a mid-term inspection after 18 months of cyclical production (including normal start-up, operation, and shutdown).

[0066] The brick of this invention (Example 1): The inner lining surface is generally flat and dense, with an average erosion rate of 0.14 mm / month, extending the brick's lifespan to 36-40 months. No network cracks or flaking were observed on the surface. Figure 1 As shown in a.

[0067] Traditional electrofused bricks: The inner lining surface shows obvious erosion grooves and several thermal shock cracks, with localized flaking of about 5mm thick, such as... Figure 1 As shown in b, its average erosion rate reaches 0.28 mm / month, and there is a risk of accelerated erosion due to thermal shock spalling. The service life of traditional sponge titanium-magnesium electrolytic cells using this brick is about 24 months.

[0068] Test results show that, under the target operating conditions of this invention, its service life can be more than doubled, resulting in significant economic benefits.

[0069] Conclusion: This invention provides a novel design concept and preparation paradigm for fused zirconia-mullite bricks. By constructing a chemical system containing a structural synergistic regulator of kyanite / andalusite in a specific ratio and multifunctional additives, and combining it with a physical process path characterized by ultra-slow cooling, an ideal composite structure of a dense matrix and dispersed stable stress buffer units was successfully constructed within the fused material. This structure enables the material to overcome the bottleneck of poor thermal shock resistance in traditional fused products, achieving synergistic optimization of high erosion resistance, high thermal shock resistance, and high strength. It provides an efficient and reliable technical solution for addressing the long service life problem of refractory materials under extreme high-temperature corrosion and thermal shock coupled environments.

[0070] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that, without departing from the principles of the present invention, fine-tuning of the proportions of the formulation components and equivalent substitution of process parameters (such as using other controllable slow cooling equipment) should be considered to fall within the protection scope defined in this specification.

Claims

1. A production formula for high-temperature wear-resistant and acid / alkali-resistant fused zircon mullite bricks, characterized in that, By weight percentage, it consists of the following components: The matrix forming material comprises 83-91%, including: 70-76% industrial alumina powder, 1-6% zircon concentrate powder, 10-14% high-purity quartz powder, and 1-3% monoclinic zirconium oxide powder; The structure synergistic regulator is 6-12%, comprising: 2.5-7.0% kyanite concentrate and 3.5-8.0% andalusite concentrate, with the weight ratio of kyanite to andalusite being (0.33-1.67):1; The composite functional additives comprise 3-6%, including, as oxides: 0.6-1.8% rare earth oxides, 0.4-1.2% alkaline earth metal oxides, and 0.1-0.6% boron oxide; The percentages for each component mentioned above refer to their weight percentage in the formula.

2. The production formula for a high-temperature wear-resistant and acid-alkali-resistant fused zircon mullite brick according to claim 1, characterized in that, The rare earth oxide is yttrium oxide and / or lanthanum oxide; the alkaline earth metal oxide is magnesium oxide and / or calcium oxide.

3. The production formula for a high-temperature wear-resistant and acid-alkali-resistant fused zircon mullite brick according to claim 1, characterized in that, The total ZrO2 content of the zircon concentrate powder and monoclinic zirconium oxide powder accounts for 3-7% of the total weight of the raw material formula.

4. The production formula for a high-temperature wear-resistant and acid-alkali-resistant electrofused zircon mullite brick according to claim 1, characterized in that, The particle size D90 of the kyanite concentrate powder is ≤0.074mm; the particle size D90 of the andalusite concentrate powder is ≤0.15mm.

5. A method for preparing erosion-resistant and thermal shock-resistant fused zirconia-mullite bricks, comprising using the production formula for high-temperature wear-resistant and acid-alkali-resistant fused zirconia-mullite bricks as described in any one of claims 1-4, characterized in that... And includes the following steps: S1. Ingredients and homogenization: Weigh each ingredient according to the formula and mix them evenly; S2. Melting: Place the mixture in an electric arc furnace for melting. After complete melting, refine at 2050-2200℃ for 60-120 minutes. S3. Casting and initial treatment: Cool the melt to 1950-2100℃ and pour it into a mold preheated to 100-300℃. After casting, stir the riser and cover it with insulation material. S4. Ultra-slow cooling treatment: The casting is subjected to programmed slow cooling after casting, so that the average cooling rate of the casting from the casting temperature to 800℃ is not greater than 0.5℃ / min, and the total slow cooling time is not less than 100 hours. S5. Post-processing: Demold the fully cooled casting and machine it to the specified dimensions.

6. The method for preparing an erosion-resistant and heat-shock-resistant fused zircon-mullite brick according to claim 5, characterized in that, In the S4 ultra-slow cooling treatment step, the cooling rate of the casting in the temperature range of 1200℃ to 800℃ is controlled at 0.2-0.4℃ / min.

7. The method for preparing an erosion-resistant and thermally shock-resistant fused zircon-mullite brick according to claim 5, characterized in that, The S2 smelting step is a staged smelting process, which includes a rapid melting period and a low-temperature refining period.

8. The method for preparing an erosion-resistant and thermally shock-resistant fused zircon-mullite brick according to claim 5, characterized in that, In the S3 casting and initial treatment step, the stirring of the riser lasts for 1-3 minutes.

9. An erosion-resistant and heat-shock-resistant fused zircon-mullite brick prepared by the preparation method according to any one of claims 5-8, wherein the properties satisfy the following: apparent porosity ≤ 2.5%, bulk density ≥ 3.08 g / cm³. 3 It has a room temperature compressive strength ≥268MPa, a water-cooled thermal shock cycle count ≥25 times at 1100℃, a linear thermal expansion coefficient ≤0.62% at 1000℃, and an average molten salt penetration depth ≤1.2mm after static immersion in molten anhydrous magnesium chloride at 850℃ for 48 hours.

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