Submerged arc furnace tap hole repairing paste and preparation method thereof

Abstract

The invention discloses a repairing paste for a tap hole of a submerged arc furnace and a preparation method thereof in the technical field of metallurgical refractory materials, and the method comprises the following steps: mixing silicon carbide aggregate, metal silicon powder, chromium-doped calcium aluminum chromate, titanium zirconium boron solid solution and other components in a kneading machine step by step, and adding a liquid asphalt binder for wet mixing; and carrying out compression molding and cooling to obtain the repairing paste. Wherein the chromium-doped calcium aluminochromate is prepared from calcium carbonate, aluminum oxide and chromium oxide through ball milling and high-temperature calcination; the titanium-zirconium-boron solid solution is prepared by ball-milling and mixing zirconium powder, titanium powder and amorphous boron powder and then directly hot-pressing and sintering at high temperature. According to the repairing paste, two newly designed inorganic modified compounds are introduced into a traditional repairing paste matrix, so that the high-temperature strength, the slag corrosion resistance and the thermal shock resistance of the material are remarkably improved, and the service life and the maintenance period of the taphole of the submerged arc furnace are prolonged.

Description

Technical Field

[0001] This invention relates to the field of metallurgical refractory materials technology, specifically to repair paste for tapholes of submerged arc furnaces and its preparation method. Background Technology

[0002] As the core smelting equipment for ferroalloys and calcium carbide and other metallurgical and chemical products, the taphole area of ​​the submerged arc furnace is subjected to extremely harsh operating conditions for a long time. During the smelting process, the taphole is repeatedly subjected to the intense scouring and erosion of high-temperature molten iron and slag, accompanied by frequent opening and closing operations. This results in the refractory material in this area facing severe periodic thermal shock, mechanical wear, and complex chemical corrosion. This combined destructive effect makes the taphole the weakest link in the entire furnace lining structure, and its maintenance directly affects the operating rate, energy consumption, and production safety of the submerged arc furnace. Therefore, developing a taphole repair material that can withstand high temperatures, resist erosion, possess excellent thermal shock stability, and is easy to construct and maintain has always been an important research direction in the field of metallurgical refractory materials.

[0003] Traditional repair pastes for tapholes in submerged arc furnaces generally employ a system using silicon carbide and carbonaceous materials as aggregates and coal tar pitch as a binder. This system relies on the high thermal conductivity and good thermal shock resistance of silicon carbide, as well as the non-wetting properties of carbon materials with molten slag, to provide basic performance. However, this traditional system has several inherent drawbacks. First, its high-temperature strength is often insufficient; under prolonged high temperatures or severe erosion, the material structure is prone to softening and erosion, leading to widening of the grooves. Second, the carbon component in the material has poor stability under high-temperature oxidizing atmospheres, easily undergoing oxidation and loss, resulting in a loose structure and reduced strength. Furthermore, the pitch binder decomposes at high temperatures, releasing large amounts of fumes, which not only pollute the environment and endanger the health of operators, but also leaves behind a carbon network structure with limited bonding strength. In addition, the traditional formulation has limited resistance to alkaline slag erosion, and its thermal shock stability needs improvement; frequent and drastic temperature changes can easily cause cracks and spalling, shortening the service life after repair.

[0004] To address the aforementioned issues, existing technologies have attempted improvements from multiple angles. These include partially replacing asphalt with more environmentally friendly synthetic resins, optimizing the gradation of silicon carbide particles to increase bulk density, and introducing metallic silicon powder to generate oxides that enhance bonding at high temperatures. Some studies have also focused on adding specific non-oxide or oxide additives, such as borides, nitrides, or specific composite oxides, in an attempt to improve a particular performance indicator of the material. However, these improvements are mostly adjustments to the components of the existing system or the introduction of a single functional phase, failing to address the fundamental synergistic design and strengthening of the microstructure at the interface between the material matrix and aggregate. Most improvement schemes, while enhancing one performance characteristic, often fail to simultaneously address other key performance aspects, or, due to poor physicochemical compatibility between the introduced phase and the matrix, cannot maintain long-term stability under extreme operating conditions. Therefore, developing a novel modified material system that can synergistically enhance matrix strength, optimize interfacial bonding, and comprehensively improve erosion resistance, thermal shock resistance, and high-temperature stability at the microscopic level has become a key breakthrough in solving the long-term maintenance problem of the taphole in submerged arc furnaces. Summary of the Invention

[0005] The purpose of this invention is to provide a repair paste for the taphole of an electric arc furnace and its preparation method, which solves the technical problems of existing repair pastes for the taphole of electric arc furnaces, such as insufficient strength at extreme high temperatures, poor resistance to slag erosion, low thermal shock stability, and environmental and health hazards caused by the use of coal tar pitch.

[0006] The present invention achieves the above objectives through the following technical solutions: A method for preparing a repair paste for the taphole of a submerged arc furnace, comprising the following steps: S1. By weight, crush silicon carbide and pass it through a three-layer vibrating screen to obtain silicon carbide with particle size of 8-5mm, 5-3mm, and 3-0mm. Mix 25-35 parts of 8-5mm silicon carbide, 18-25 parts of 5-3mm silicon carbide, and 15-22 parts of 3-0mm silicon carbide to obtain silicon carbide aggregate. Add silicon carbide aggregate, 15-25 parts of metallic silicon powder, 3-8 parts of chromium-doped calcium aluminum chromate, and 2-6 parts of titanium zirconium boron solid solution to a kneader preheated to 115-125℃, dry mix, heat to 145-155℃, add 15-30 parts of liquid asphalt preheated to 135-145℃, heat to 150-180℃, wet mix to obtain a well-kneaded paste. S2. Pour the mixed paste into a mold preheated to 98-102℃, and press it under 50-60MPa pressure to obtain the molded blank; cool the molded blank to room temperature.

[0007] The improved overall performance of the repair paste for the taphole of an electric arc furnace in this invention stems from the orderly integration of its components during preparation and the stable microstructure formed by a series of beneficial chemical reactions occurring under high-temperature service conditions. During the mixing process in the preparation stage, preheated three-grade silicon carbide aggregate, metallic silicon powder, and two modified compound powders are first dry-mixed, achieving physical mixing and preliminary embedding of the reinforcing phase and matrix raw materials at multiple scales (coarse, medium, and fine). Subsequently, preheated liquid asphalt is added as a temporary binder, uniformly coating and wetting the surface of all solid particles under the action of heat and shear force, forming a paste with good plasticity. This process ensures the homogeneity and density of the material before molding. When the molded blank is placed in the high-temperature environment of the electric arc furnace taphole, a dynamic "reaction sintering" process begins. The liquid asphalt first undergoes pyrolysis and carbonization, forming a strong carbon skeleton network that initially binds the solid particles. Simultaneously, the metallic silicon powder oxidizes at high temperature, generating active silicon dioxide. The newly formed silica reacts with the surface of chromium-doped calcium aluminum chromate particles, forming a high-viscosity silicate liquid phase at the particle boundaries. This liquid phase effectively wets the silicon carbide aggregate and carbon network, promotes particle rearrangement through capillary forces, fills micropores, and solidifies into a robust ceramic bonding phase upon cooling, thus greatly strengthening the matrix. Simultaneously, the titanium zirconium boron solid solution particles dispersed in the system, due to their extremely high thermal stability and chemical inertness, remain intact at high temperatures, acting as hard reinforcing points embedded in the matrix and forming a robust physical bond with the silicon carbide aggregate, directly bearing and dispersing the mechanical erosion and chemical corrosion stresses of molten iron and slag. Chromium-doped calcium aluminum chromate optimizes the sinterability and continuity of the matrix through its induced liquid phase, while the titanium zirconium boron solid solution strengthens the material's framework and interfaces through its intrinsic high-temperature properties. The two work together, from the two levels of "optimizing the bonding phase" and "strengthening the dispersed phase", to finally construct a composite material system with high-strength matrix, solid interface and excellent thermal shock resistance, thus achieving the fundamental goal of long-term and stable service of taphole repair paste.

[0008] According to a preferred embodiment of the present invention, in step S1, the dry mixing time is 15-20 min; the wet mixing time is 45-50 min.

[0009] According to a preferred embodiment of the present invention, in step S2, the pressure holding time at 50-60 MPa is 3-5 minutes.

[0010] According to a preferred embodiment of the present invention, the method for preparing the chromium-doped calcium aluminum chromate includes: A1. Place calcium carbonate, aluminum oxide, and chromium oxide into a ball mill jar, add zirconium oxide grinding balls and anhydrous ethanol, and ball mill to obtain a slurry; A2. Dry the slurry in an oven at 78-82℃, sieve it to obtain the undersize; place the undersize in a crucible, heat it to 1345-1355℃ in air atmosphere and hold it there; cool it to room temperature in the furnace to obtain a block product; crush the block product, ball mill it again, dry it, and sieve it.

[0011] In this invention, the synthesis of chromium-doped calcium aluminum chromate is a chemical process based on high-temperature solid-state reaction, with the core objective of obtaining a structurally stable single-phase solid solution through ion substitution. The process begins with the precise mixing and activation of three raw material powders: calcium carbonate, alumina, and chromium oxide. Under prolonged high-energy ball milling, the three raw materials not only achieve uniform dispersion at the microscale, but their crystal structure is also activated by strong mechanical forces, resulting in a significant increase in surface energy and enhanced atomic migration ability, laying the kinetic foundation for subsequent high-temperature reactions. High-temperature calcination of the uniformly mixed precursor powders is a crucial step in forming the target product. During the heating process, calcium carbonate first undergoes thermal decomposition, releasing carbon dioxide and generating highly reactive calcium oxide. As the temperature continues to rise to the reaction threshold, solid-state diffusion and chemical reactions begin at the interface between the calcium oxide, alumina, and chromium oxide particles. Because the trivalent chromium ions in chromium oxide have a similar ionic radius to trivalent aluminum ions, they can enter the calcium hexaaluminate crystal framework generated by the reaction of alumina and calcium oxide through substitution solid solution. This doping behavior is not a simple physical mixing, but rather a profound lattice reconstruction. Trivalent chromium ions partially replace trivalent aluminum ions in the aluminum-oxygen octahedral layer of the calcium hexaaluminate lattice. Due to the slight difference in their ionic radii, the cell parameters expand, introducing controllable lattice distortion and stress fields within the crystal. Simultaneously, to maintain electroneutrality, this process may also involve the formation of oxygen vacancies. These microstructural changes result in chromium-doped calcium aluminum chromate that not only retains the excellent high-temperature stability and corrosion resistance of calcium hexaaluminate itself, but also exhibits enhanced crystal structure activity due to the introduction of defects. This allows it to interact more effectively with other oxide phases in the matrix when used as a repair paste component, thus fulfilling its core function of reinforcing the matrix.

[0012] According to a preferred embodiment of the present invention, in step A1, the ball milling time is 6-8 hours.

[0013] According to a preferred embodiment of the present invention, in step A2, the time for holding the temperature at 1345-1355°C is 4-6 hours.

[0014] According to a preferred embodiment of the present invention, the method for preparing the titanium-zirconium-boron solid solution includes: B1. Place zirconium powder, titanium powder and amorphous boron powder into a ball mill jar, add grinding balls and hexane, and ball mill under an argon atmosphere to obtain a ball-milled slurry; dry the ball-milled slurry in a vacuum drying oven at 58-62℃, and sieve to obtain a mixed powder; B2. The mixed powder is loaded into a mold and placed in a vacuum hot press furnace for sintering: the temperature is raised to 1595-1605℃, the pressure is applied to 18-22MPa, and the temperature and pressure are maintained under argon protection; after sintering, the mixture is cooled to 185-195℃ with the furnace to obtain a block; the block is crushed, ball-milled, dried, and then sieved.

[0015] In this invention, the preparation of the titanium-zirconium-boron solid solution follows the principle of direct elemental reaction synthesis and densification in powder metallurgy, aiming to obtain a single-phase ultra-high temperature ceramic reinforcing phase with precise composition, dense structure, and uniformity. This mechanism begins with the high-energy mechanical alloying pretreatment of three elemental raw materials—zirconium powder, titanium powder, and amorphous boron powder—under a protective atmosphere. A prolonged ball milling process repeatedly compresses, collides, crushes, and cold-welds these three metal and non-metal powders with different plasticity or brittleness, ultimately forming a highly uniform composite powder. During this process, the powder particles are continuously refined, with grain size reduced to the nanometer or submicron level, resulting in a huge surface area and abundant crystal defects, significantly lowering the thermodynamic barrier required for subsequent synthesis reactions. When this highly activated composite powder is placed in a hot press furnace for sintering, a series of complex solid-state diffusion and chemical reactions occur under the combined drive of high temperature and pressure. As the temperature rises, boron atoms, due to their smaller atomic radius and higher diffusion rate, first diffuse into the interior of the zirconium and titanium metal particles through grain boundaries and lattice. When the temperature reaches the critical reaction point, exothermic reactions begin to form corresponding boride nuclei at the zirconium-boron and titanium-boron interfaces. Since zirconium boride and titanium boronide are identical in crystal structure and have similar lattice parameters, they can dissolve mutually to form a continuous solid solution. Under the synergistic effect of sustained high temperature and applied pressure, the newly formed boride nuclei grow and connect with each other, while porosity within the system is rapidly eliminated. Titanium atoms dissolve in the zirconium boride lattice, forming a titanium-zirconium-boron solid solution. This solid solution strengthening effect not only maintains the intrinsic properties of zirconium boride's ultra-high melting point and high hardness but also further enhances its strength and toughness through lattice distortion caused by the dissolved atoms. The resulting dense bulk material has a uniform microstructure and clean grain boundaries, providing a key reinforcing phase with high strength, high thermal conductivity, and excellent oxidation resistance for the repair paste.

[0016] According to a preferred embodiment of the present invention, in step B1, the ball milling time under an argon atmosphere is 8-10 hours.

[0017] According to a preferred embodiment of the present invention, in step B2, the temperature is raised to 595-605°C and held for 1-2 hours.

[0018] The present invention also provides a repair paste for the taphole of an electric arc furnace prepared according to the preparation method of the repair paste for the taphole of the electric arc furnace.

[0019] The beneficial effects of this invention are as follows: The repair paste for the taphole of an electric arc furnace and its preparation method provided by this invention have achieved significant and synergistic technical effects by introducing two newly designed inorganic modified compounds and optimizing the overall preparation process, fundamentally overcoming many performance bottlenecks of traditional repair materials.

[0020] Firstly, breakthroughs have been achieved in core high-temperature performance and corrosion resistance. By introducing chromium-doped calcium aluminum chromate as a key matrix reinforcing phase into the system, this compound exhibits extremely high chemical stability and moderate liquid-phase formation capability at high temperatures. Its unique crystal structure not only effectively blocks the penetration and corrosion of molten slag, especially alkaline components, but also integrates well with the silicate phase generated within the material, significantly strengthening the matrix's encapsulation and bonding of aggregates such as silicon carbide, thereby greatly improving the material's structural strength and integrity at high temperatures. Simultaneously, the added titanium-zirconium-boron solid solution, as an ultra-high-temperature reinforcing phase, directly enhances the material's resistance to mechanical erosion and chemical dissolution by high-temperature molten iron and slag due to its extremely high melting point, hardness, and excellent thermal conductivity. The synergistic effect of these two compounds allows the repair paste to maintain structural integrity for extended periods under extreme high-temperature environments, achieving a qualitative leap in corrosion resistance compared to traditional materials.

[0021] Secondly, the thermal shock stability and resistance to thermal stress damage of the material are fundamentally improved. Traditional silicon carbide-based materials, due to differences in the thermal expansion coefficients between phases, are prone to interface crack formation and propagation under severe temperature cycling. In this invention, the titanium-zirconium-boron solid solution, due to its excellent thermal conductivity, facilitates rapid heat dissipation during use, reducing localized thermal stress concentration. More importantly, chromium-doped calcium aluminum chromate can effectively absorb and release thermal stress through slight plastic deformation or the induction of a beneficial microcrack network during temperature changes, preventing the initiation and propagation of fatal macroscopic cracks. The synergistic effect of both "promoting heat transfer" and "optimizing stress release" enables the repair paste to withstand frequent rapid heating and cooling shocks in the taphole area of ​​the submerged arc furnace, exhibiting excellent thermal shock stability and significantly reducing the risk of failure due to thermal shock spalling.

[0022] Finally, this invention also demonstrates significant advantages in terms of overall construction performance, service life, and environmental friendliness. The optimized three-stage silicon carbide aggregate gradation and efficient mixing process ensure good plasticity and filling density of the paste, facilitating on-site tamping and resulting in a uniformly structured repair. Using environmentally friendly liquid asphalt as the core binder ensures sufficient room-temperature adhesion and high-temperature carbonization strength while significantly reducing harm to the environment and operators. Ultimately, the integrated delivery of all these performance improvements directly translates into a substantial extension of the maintenance cycle after taphole repair, reducing the frequency of furnace shutdowns for maintenance, improving the operating rate and production continuity of the submerged arc furnace, and simultaneously reducing long-term maintenance costs, resulting in significant economic benefits and application value. Detailed Implementation

[0023] The following detailed embodiments are only used to further illustrate this application and should not be construed as limiting the scope of protection of this application. Those skilled in the art can make some non-essential improvements and adjustments to this application based on the above application content.

[0024] Example 1 Preparation of chromium-doped calcium aluminum chromate: First, accurately weigh the raw materials. Weigh 100.0 g of calcium carbonate (CaCO3), 550.0 g of alumina (Al2O3), and 50.0 g of chromium oxide (Cr2O3). Place the above raw materials together in a 5 L polyethylene ball mill jar. Add 2100 g of zirconia grinding balls with a diameter of 5 mm as grinding media. Then add 1050 mL of anhydrous ethanol as a dispersant. After sealing the ball mill jar, install it on a planetary ball mill and set the revolution speed to 300 rpm for wet ball milling. The ball milling time is 7 h to ensure that the raw materials achieve sufficient micro-mixing and pre-activation. After ball milling, transfer the resulting slurry to a stainless steel tray and place it in a forced-air drying oven to dry at 80 °C for 24 h to completely remove ethanol. Gently break up the dried agglomerates and sieve them using a standard 200 mesh analytical sieve. Collect the fine powder that passes through the sieve and record it as the precursor powder. The powder was placed in a high-purity corundum crucible, which was then placed in a box-type resistance furnace. Under static air atmosphere, the furnace temperature was raised to 1350℃ at a heating rate of 5℃ / min and held at this temperature for 5 hours to complete the solid-state reaction and crystal growth. After the reaction, the power was turned off, and the furnace was allowed to cool naturally to room temperature (approximately 25℃). The sintered product was removed; it was a light green, dense block. The block was initially crushed to a particle size of less than 1 mm using a jaw crusher, and then subjected to wet ball milling for 4 hours. The slurry after the second ball milling was dried and passed through a 325-mesh sieve to obtain chromium-doped calcium aluminum chromate powder with a uniform particle size distribution, which was then set aside.

[0025] Preparation of titanium-zirconium-boron solid solution: First, accurately weigh the raw materials. Weigh 400.0 g of zirconium powder (Zr, purity ≥99.5%), 100.0 g of titanium powder (Ti, purity ≥99.5%), and 125.0 g of amorphous boron powder (B, purity ≥95.0%). Place the above elemental powders together in a glove box filled with argon gas, and then place it into a 5 L hard stainless steel ball mill jar. Add 2500 g of 10 mm diameter hard alloy grinding balls to the jar. Add 1250 mL of hexane as a process control agent to prevent excessive cold welding. Seal the ball mill jar to ensure airtightness, and then transfer it to a high-energy ball mill. Under a continuously purged argon atmosphere, mechanical alloying is performed at a speed of 250 rpm for 9 hours. After ball milling, the slurry was poured into an evaporating dish inside a glove box and transferred to a vacuum drying oven, where it was dried at 60°C and -0.1 MPa for 36 hours. The dried composite powder was then sieved through a 150-mesh sieve to obtain activated mixed powder. 500 g of this mixed powder was weighed and placed into a graphite mold with an inner diameter of 50 mm. The mold was then placed entirely into a vacuum hot-pressing sintering furnace. The furnace door was closed, and a vacuum of 5 × 10⁻⁵ MPa was applied. -3 After Pa, the programmed heating began. Direct heating was performed at a rate of 10℃ / min to 1600℃. When the temperature reached 1200℃, axial pressure was applied and gradually stabilized at 20MPa upon reaching 1600℃. The temperature and pressure were maintained at 1600℃ and 20MPa for 2 hours. After sintering, heating was stopped, and the furnace was cooled to below 190℃ while maintaining pressure. Then, the pressure was released, and cooling continued to room temperature. The dense sintered block was removed, crushed, ball-milled twice for 6 hours, dried, and sieved through a 400-mesh sieve to obtain a grayish-black titanium-zirconium-boron solid solution fine powder for later use.

[0026] Preparation of repair paste for the taphole of an electric arc furnace: First, process the aggregate. Take 10 kg of lumpy black silicon carbide (SiC≥97%) and crush it using a jaw crusher until it all passes through a 20 mm screen. Then, feed the crushed material into a three-layer vibrating screen to separate it into three particle sizes: 8-5 mm, 5-3 mm, and 3-0 mm. Accurately weigh 3000 g of 8-5 mm silicon carbide, 2200 g of 5-3 mm silicon carbide, and 1800 g of 3-0 mm silicon carbide, and manually premix them in a mixing tank for 3 minutes to obtain a total weight of 7000 g of graded silicon carbide aggregate. Preheat the jacket of the kneader (double-shaft meshing type) with steam to stabilize the temperature of the kneader body at 120℃. All 7000g of silicon carbide aggregate, 2000g of metallic silicon powder (Si≥98.5%, 200 mesh), 500g of the aforementioned chromium-doped calcium aluminum chromate powder, and 400g of the aforementioned titanium zirconium boron solid solution powder were sequentially added to a kneader. Stirring was started for dry mixing for 17 minutes. After dry mixing, the jacket steam pressure was increased to raise the material temperature to 150℃ within 5 minutes. 1500g of liquid asphalt was preheated to 140℃ in another container and then poured into the kneader at a uniform rate. After adding the asphalt, heating and stirring continued to raise the paste temperature to 165℃ within 10 minutes, and wet mixing was continued at this temperature for 47 minutes, for a total wet mixing time of approximately 57 minutes. The paste temperature remained at 160℃ throughout the entire kneading process. After kneading, a hot paste with uniform texture and good plasticity was obtained. Preheat the molding die (150mm×150mm×300mm) to 100℃. Quickly transfer the hot paste into the die and press it using a hydraulic press at a pressure of 55MPa for 4 minutes. After demolding, a dense repair paste blank is obtained. Place the blank on a ventilated cooling conveyor and allow it to cool naturally to below 30℃ at room temperature to obtain the finished repair paste for the taphole of the submerged arc furnace.

[0027] Example 2 The specific implementation method is the same as in Example 1, except that the preparation of chromium-doped calcium aluminum chromate is as follows: 120.0 g of calcium carbonate, 660.0 g of alumina, and 60.0 g of chromium oxide are accurately weighed. The raw materials are placed in a 5L polyethylene ball mill jar, and 2520 g of zirconia grinding balls with a diameter of 5 mm and 1260 mL of anhydrous ethanol are added. The mixture is ball-milled at 300 rpm for 6 hours in a planetary ball mill. The slurry is dried in an 80℃ forced-air drying oven for 24 hours and then sieved through a 200-mesh sieve to obtain precursor powder. The powder is placed in a corundum crucible and heated to 1350℃ at a rate of 5℃ / min in air atmosphere, held at that temperature for 5 hours, and then cooled with the furnace. The calcined block is crushed, ball-milled again for 4 hours, dried, and then sieved through a 325-mesh sieve to obtain chromium-doped calcium aluminum chromate powder for later use.

[0028] Preparation of titanium-zirconium-boron solid solution: Accurately weigh 320.0 g of zirconium powder, 80.0 g of titanium powder, and 100.0 g of amorphous boron powder. Place the raw materials in an argon-filled glove box and then into a 5 L stainless steel ball mill jar. Add 2000 g of 10 mm diameter cemented carbide grinding balls and 1000 mL of hexane. After sealing, transfer to a ball mill and ball mill at 250 rpm for 8 h under argon protection. Dry the slurry at 60 °C and -0.1 MPa vacuum for 36 h, and pass it through a 150 mesh sieve to obtain a mixed powder. Weigh 500 g of the mixed powder and place it into a Φ50 mm graphite mold, then place it in a vacuum hot press furnace. Evacuate to 5 × 10⁻⁶ m³ / h. -3 The temperature was increased to 1600℃ at a rate of 10℃ / min, while pressure was applied simultaneously. The temperature and pressure were maintained at 1600℃ and 20MPa for 2 hours. The furnace was then cooled to below 190℃ to release the pressure. After cooling to room temperature, the block was removed. After crushing, it was ball-milled again for 6 hours, dried, and passed through a 400-mesh sieve to obtain titanium-zirconium-boron solid solution powder for later use.

[0029] Preparation of repair paste for the taphole of an electric arc furnace: Accurately weigh 2500g of 8-5mm particle size silicon carbide, 2500g of 5-3mm particle size silicon carbide, and 2200g of 3-0mm particle size silicon carbide, and mix them to obtain a total weight of 7200g of graded aggregate. Preheat the kneader to 115℃, add all the aggregate, 1500g of metallic silicon powder, 800g of the previously prepared chromium-doped calcium aluminum chromate powder, and 600g of the previously prepared titanium zirconium boron solid solution powder, and dry mix for 15min. Raise the temperature to 145℃, add 1800g of liquid asphalt preheated to 135℃, continue to raise the temperature to 150℃, and wet mix at this temperature for 45min. Pour the paste into a mold preheated to 100℃, and press it under 58MPa pressure for 3min to form the finished product. After demolding, the blank should be naturally cooled to room temperature to obtain the finished product.

[0030] Example 3 The specific implementation method is the same as in Example 1, except that the preparation of chromium-doped calcium aluminum chromate is as follows: 80.0g of calcium carbonate, 440.0g of alumina, and 40.0g of chromium oxide are accurately weighed. The raw materials are placed in a 5L polyethylene ball mill jar, and 1680g of zirconia grinding balls with a diameter of 5mm and 840mL of anhydrous ethanol are added. The mixture is ball-milled at 300rpm for 8 hours in a planetary ball mill. The slurry is dried in an 80℃ forced-air drying oven for 24 hours and then sieved through a 200-mesh sieve to obtain the precursor powder. The powder is placed in a corundum crucible and heated to 1350℃ at 5℃ / min in air atmosphere, held at that temperature for 5 hours, and then cooled with the furnace. The calcined block is crushed, ball-milled again for 4 hours, dried, and then sieved through a 325-mesh sieve to obtain chromium-doped calcium aluminum chromate powder for later use.

[0031] Preparation of titanium-zirconium-boron solid solution: Accurately weigh 480.0 g of zirconium powder, 120.0 g of titanium powder, and 150.0 g of amorphous boron powder. Place the raw materials in an argon-filled glove box and then into a 5 L stainless steel ball mill jar. Add 3000 g of 10 mm diameter cemented carbide grinding balls and 1500 mL of hexane. After sealing, transfer to a ball mill and ball mill at 250 rpm for 10 h under argon protection. Dry the slurry at 60 °C and -0.1 MPa vacuum for 36 h, and pass it through a 150 mesh sieve to obtain a mixed powder. Weigh 500 g of the mixed powder and place it into a Φ50 mm graphite mold, then place it in a vacuum hot press furnace. Evacuate to 5 × 10⁻⁶ m³ / h. -3 The temperature was increased to 1600℃ at a rate of 10℃ / min, while pressure was applied simultaneously. The temperature and pressure were maintained at 1600℃ and 20MPa for 2 hours. The furnace was then cooled to below 190℃ to release the pressure. After cooling to room temperature, the block was removed. After crushing, it was ball-milled again for 6 hours, dried, and passed through a 400-mesh sieve to obtain titanium-zirconium-boron solid solution powder for later use.

[0032] Preparation of repair paste for the taphole of an electric arc furnace: Accurately weigh 3500g of 8-5mm particle size silicon carbide, 1800g of 5-3mm particle size silicon carbide, and 1500g of 3-0mm particle size silicon carbide, and mix them to obtain a total aggregate weight of 6800g. Preheat the mixer to 125℃, add all the aggregate, 2500g of metallic silicon powder, 300g of the previously prepared chromium-doped calcium aluminum chromate powder, and 200g of the previously prepared titanium zirconium boron solid solution powder, and dry mix for 20min. Raise the temperature to 155℃, add 2500g of liquid asphalt preheated to 145℃, and continue to raise the temperature to 180℃ and wet mix at this temperature for 50min. Pour the paste into a mold preheated to 100℃ and press it under 60MPa pressure for 5min to form the finished product. After demolding, the blank should be naturally cooled to room temperature to obtain the finished product.

[0033] Comparative Example 1 The specific implementation method is the same as in Example 1, except that no chromium-doped calcium aluminum chromate and titanium zirconium boron solid solution are added in this comparative example.

[0034] Comparative Example 2 The specific implementation method is the same as in Example 1, except that this comparative example only adds chromium-doped calcium aluminum chromate and does not add titanium zirconium boron solid solution.

[0035] Comparative Example 3 The specific implementation method is the same as in Example 1, except that this comparative example only adds titanium zirconium boron solid solution and does not add chromium-doped calcium aluminum chromate.

[0036] Performance testing The repair pastes prepared for the tapholes of submerged arc furnaces in Examples 1-3 and Comparative Examples 1-3 were subjected to performance tests according to the following method, which included the following steps: All samples were prepared following a uniform procedure: the finished repair pastes obtained from each example and comparative example were placed in a steel mold and pressed at 55 MPa for 4 minutes to form standard sample blanks. The blank types included: cubes with a side length of 50 mm for pressure resistance testing, strips with dimensions of 40 mm × 40 mm × 160 mm for flexural strength testing, and cylinders with a diameter of 50 mm and a height of 50 mm for slag resistance testing. The formed blanks were first placed in a forced-air drying oven and dried at 110°C for at least 24 hours to remove moisture. Subsequently, the dried blanks were placed in a high-temperature sintering furnace and heated to 1400°C at a rate of 5°C / min under a nitrogen protective atmosphere, and held at this temperature for 3 hours. Finally, they were cooled to room temperature with the furnace to obtain the final samples for each performance test.

[0037] The room-temperature compressive strength test was conducted on a universal testing machine. A prepared 50mm cube specimen was placed in the center of the lower platen of the testing machine, and continuous, uniform pressure was applied at a loading rate of 0.5 MPa / s until the specimen broke. The maximum pressure value at specimen failure was recorded, and the compressive strength was calculated by dividing this value by the bearing area of ​​the specimen. Five specimens were tested in parallel for each group of samples, and the final result was the arithmetic mean of the five test values.

[0038] High-temperature flexural strength testing was performed using a three-point bending test apparatus equipped with a high-temperature furnace. A 40mm × 40mm × 160mm specimen was placed on alumina support rollers spaced 125mm apart. The high-temperature furnace was heated to 1400℃ at a rate of 10℃ / min, and the specimen was allowed to homogenize at this temperature for 30 minutes. Subsequently, a load was applied to the center of the specimen span through the upper pressure roller at a stress increase rate of 0.15MPa / s until fracture. The maximum load at fracture was recorded, and the flexural strength was calculated using the three-point bending formula. Three specimens were tested in parallel for each group, and the results were averaged.

[0039] The static crucible method was used to test the slag erosion resistance. A hole with a diameter of 30 mm and a depth of 35 mm was pre-drilled at the center of the top of the cylindrical sample. 10.0 g of synthetic slag powder, prepared by mixing calcium oxide, silicon dioxide, aluminum oxide, and ferrous oxide in a mass ratio of 40:35:15:10, was precisely filled into the hole. The sample containing the slag was placed in a high-temperature furnace and heated to 1600 °C at a rate of 10 °C / min under a reducing carbon monoxide atmosphere, and held at that temperature for 3 hours. After the procedure, the sample was longitudinally cut along its central axis, and the maximum depth and area of ​​the slag erosion zone were measured. Using the average erosion area of ​​the sample in Comparative Example 1 as a baseline (defined as 100%), the relative erosion resistance index of other samples was calculated; a lower index indicates better erosion resistance.

[0040] Thermal shock stability testing was performed using the water quenching method. The specimen was held in a muffle furnace at 1100°C for 30 minutes, then rapidly removed and completely immersed in flowing water at 25°C for 3 minutes before being removed again. The specimen was then dried in a drying oven at 110°C for 2 hours. This process was recorded as one complete thermal shock cycle. This process was repeated 10 times for the same specimen. The compressive strength at room temperature was tested before and after 10 cycles. The strength retention rate after thermal shock was defined as the percentage of the strength after thermal shock to the original strength before thermal shock.

[0041] Environmental indicators are assessed by determining the total content of polycyclic aromatic hydrocarbons (PAHs). 2.00 g of the dried repair paste sample is accurately weighed and subjected to Soxhlet extraction using toluene as the solvent, with extraction continuing for 24 hours. The extract is concentrated and purified, and then qualitatively and quantitatively analyzed using gas chromatography-mass spectrometry (GC-MS). The sum of the contents of 16 PAH monomers is detected and calculated, and the total content is reported.

[0042] Test results: Table 1: Test results of each embodiment and comparative example ; As can be seen from Table 1, the formulation system represented by Examples 1-3 of the present invention effectively and comprehensively solves the various technical problems faced by the existing repair paste for tapholes of submerged arc furnaces by synergistically introducing two newly designed inorganic modified compounds: chromium-doped calcium aluminum chromate and titanium zirconium boron solid solution.

[0043] Regarding high-temperature strength, Example 1 achieved a room-temperature compressive strength of 45.2 MPa and a high-temperature flexural strength of 9.1 MPa, significantly higher than Comparative Example 1 (35.6 MPa and 5.2 MPa, respectively) without any modified compounds, and also superior to Comparative Examples 2 and 3 (which only added a single compound). This fully demonstrates that the combined effect of the two modified compounds, through solid solution strengthening of the matrix and optimization of the particle interface, fundamentally improves the mechanical properties of the material at both room temperature and extreme high temperatures, thus solving the problem of insufficient high-temperature strength.

[0044] In terms of resistance to slag erosion, the erosion resistance index of Example 1 was as low as 58%, which was far better than the 100% baseline value of Comparative Example 1, meaning that its erosion resistance was nearly doubled. Even compared with Comparative Example 2 (75%) and Comparative Example 3 (85%), which added only one compound, the Example 1 showed a significant advantage. This indicates that the stable phase and high-viscosity liquid phase formed by chromium-doped calcium aluminum chromate at high temperature can effectively block slag penetration, while the titanium zirconium boron solid solution provides an inert barrier. The two work together to achieve a leap in erosion resistance.

[0045] In terms of thermal shock stability, Example 1 maintained a strength retention rate of up to 90% after 10 severe thermal shock cycles, while Comparative Example 1 only maintained 72%. This is attributed to the high thermal conductivity of the titanium zirconium boron solid solution, which promotes rapid heat diffusion and reduces thermal stress concentration. At the same time, chromium-doped calcium aluminum chromate optimizes the stress release behavior of the matrix. The two work together to significantly enhance the material's ability to resist drastic temperature changes.

[0046] Finally, the total PAH content in all examples and comparative examples was less than 50 mg / kg. This result confirms that the environmentally friendly liquid asphalt binder system used in this invention has successfully replaced traditional coal tar pitch, completely eliminating the resulting toxic emissions and health hazards. In summary, the data clearly demonstrate that this invention not only comprehensively solves the three key technical bottlenecks of strength, erosion resistance, and thermal shock resistance through the synergistic effect of innovative components, but also ensures the environmental friendliness of the product, achieving a dual breakthrough in performance and environmental protection.

[0047] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a repair paste for the taphole of a submerged arc furnace, characterized in that the steps include... include: S1. By weight, crush silicon carbide and pass it through a three-layer vibrating screen to obtain silicon carbide with particle size of 8-5mm, 5-3mm, and 3-0mm. Mix 25-35 parts of 8-5mm silicon carbide, 18-25 parts of 5-3mm silicon carbide, and 15-22 parts of 3-0mm silicon carbide to obtain silicon carbide aggregate. Add silicon carbide aggregate, 15-25 parts of metallic silicon powder, 3-8 parts of chromium-doped calcium aluminum chromate, and 2-6 parts of titanium zirconium boron solid solution to a kneader preheated to 115-125℃, dry mix, heat to 145-155℃, add 15-30 parts of liquid asphalt preheated to 135-145℃, heat to 150-180℃, wet mix to obtain a well-kneaded paste. S2. Pour the mixed paste into a mold preheated to 98-102℃, and press it under 50-60MPa pressure to obtain the molded blank; cool the molded blank to room temperature.

2. The method for preparing the repair paste for the taphole of a submerged arc furnace according to claim 1, characterized in that, In step S1, the dry mixing time is 15-20 min; the wet mixing time is 45-50 min.

3. The method for preparing the repair paste for the taphole of a submerged arc furnace according to claim 1, characterized in that, In step S2, the pressure holding time at 50-60MPa is 3-5 minutes.

4. The method for preparing the repair paste for the taphole of a submerged arc furnace according to claim 1, characterized in that, The preparation method of the chromium-doped calcium aluminum chromate includes: A1. Place calcium carbonate, aluminum oxide, and chromium oxide into a ball mill jar, add zirconium oxide grinding balls and anhydrous ethanol, and ball mill to obtain a slurry; A2. Dry the slurry in an oven at 78-82℃, sieve it to obtain the undersize; place the undersize in a crucible, heat it to 1345-1355℃ in air atmosphere and hold it there; cool it to room temperature in the furnace to obtain a block product; crush the block product, ball mill it again, dry it, and sieve it.

5. The method for preparing the repair paste for the taphole of a submerged arc furnace according to claim 4, characterized in that, In step A1, the ball milling time is 6-8 hours.

6. The method for preparing the repair paste for the taphole of a submerged arc furnace according to claim 4, characterized in that, In step A2, the temperature is raised to 1345-1355℃ and held for 4-6 hours.

7. The method for preparing the repair paste for the taphole of a submerged arc furnace according to claim 1, characterized in that, The method for preparing the titanium-zirconium-boron solid solution includes: B1. Place zirconium powder, titanium powder and amorphous boron powder into a ball mill jar, add grinding balls and hexane, and ball mill under an argon atmosphere to obtain a ball-milled slurry; dry the ball-milled slurry in a vacuum drying oven at 58-62℃, and sieve to obtain a mixed powder; B2. The mixed powder is loaded into a mold and placed in a vacuum hot press furnace for sintering: the temperature is raised to 1595-1605℃, the pressure is applied to 18-22MPa, and the temperature and pressure are maintained under argon protection; after sintering, the mixture is cooled to 185-195℃ with the furnace to obtain a block; the block is crushed, ball-milled, dried, and then sieved.

8. The method for preparing the repair paste for the taphole of a submerged arc furnace according to claim 7, characterized in that, In step B1, the ball milling time under an argon atmosphere is 8-10 hours.

9. The method for preparing the repair paste for the taphole of a submerged arc furnace according to claim 7, characterized in that, In step B2, the temperature is raised to 595-605℃ and held for 1-2 hours.

10. A repair paste for the taphole of a submerged arc furnace, characterized in that, The repair paste for the taphole of the submerged arc furnace is prepared by the method described in any one of claims 1-9.