A high-hardness copper-chromium alloy and a method for preparing the same

Abstract

The application relates to the technical field of alloy materials, in particular to a high-hardness copper-chromium alloy and a preparation method thereof, which comprises the following steps: S1. raw material pretreatment, S2. smelting and pouring, S3. composite modification treatment, S4. rolling processing, and S5. finished product heat treatment; the application solves key problems such as component segregation, coarse grains, large residual stress, insufficient hardness and wear resistance and the like in the preparation of the existing copper-chromium alloy by optimizing and coordinating the whole-process technology, fundamentally. From the specific process steps, each step can solve the defects of the previous process or the material itself; from the overall scheme, each process forms a layer-by-layer optimization logic, the raw material pretreatment provides high-quality raw materials for smelting, the smelting and pouring provides high-quality ingots for the modification treatment, and the core modification and heat treatment process finally realizes the regulation of the structure and the performance, thereby producing a synergistic effect. The application has stable and reliable technology, and has significant technical value and market prospect.

Description

Technical Field

[0001] This invention relates to the field of alloy materials technology, specifically to a high-hardness copper-chromium alloy and its preparation method. Background Technology

[0002] Copper-chromium alloys, thanks to the excellent electrical and thermal conductivity of copper and the high strength and wear resistance of chromium, are widely used in key areas such as high-voltage switch contacts and precision mechanical wear-resistant components. As industries such as power and aerospace move towards high-end applications, higher demands are being placed on the hardness, wear resistance, and structural stability of copper-chromium alloys. However, existing copper-chromium alloy manufacturing technologies still face numerous bottlenecks, hindering their application in high-end scenarios.

[0003] In the raw material processing stage, traditional processes are not thorough enough in degreasing electrolytic copper, leaving residual oil and moisture, which can lead to defects such as porosity during smelting. Grinding of alloys such as chromium and iron often employs a single ball milling method, resulting in uneven particle size distribution and potential compositional segregation during subsequent smelting. In the smelting and casting stage, conventional heating methods can easily cause localized overheating, and the turbulent flow of liquid metal during directional solidification can exacerbate the problem of porous internal structure in the ingot.

[0004] Modification treatment, a crucial step in enhancing alloy hardness, is currently hampered by existing technologies that employ a single isothermal process. This makes it difficult to precisely control the precipitation of strengthening phases, often resulting in chromium phase agglomeration and coarse grains, thus failing to fully realize the strengthening effect. In the finished product heat treatment stage, traditional isothermal heating and natural cooling methods easily generate significant residual stress within the alloy, leading to poor microstructural stability and ultimately insufficient wear resistance, failing to meet the service life requirements of high-end applications. Currently, the industry urgently needs a systematic solution to address these problems and achieve stable preparation of high-hardness, high-wear-resistant copper-chromium alloys. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and to propose a high-hardness copper-chromium alloy and its preparation method.

[0006] The specific technical solution is as follows: A method for preparing a high-hardness copper-chromium alloy, comprising the following steps: S1. Raw material pretreatment: Select electrolytic copper, electrolytic chromium, pure iron, pure zinc, pure lead, pure nickel and cadmium as raw materials. Dry and degrease the electrolytic copper. Grind and refine the electrolytic chromium, pure iron, pure zinc, pure lead, pure nickel and cadmium to a particle size of 50-100μm. S2. Melting and Casting: The pretreated electrolytic copper is added to a vacuum induction melting furnace and heated to 1150-1200℃ to completely melt it. Then, finely ground electrolytic chromium, pure iron, and pure nickel are added in sequence. The mixture is kept at the temperature and stirred for 20-30 minutes at a stirring rate of 150-200 r / min. Then, pure zinc, pure lead, and cadmium are added and the mixture is kept at the temperature and stirred for another 5-10 minutes. After that, the temperature is rapidly reduced to 1050-1100℃ for casting to obtain an ingot. S3. Composite Modification Treatment: The ingot is placed in a heat treatment furnace and a segmented temperature-controlled modification process is adopted. First, the temperature is raised to 850-900℃ and held for 2-3 hours for solution treatment, during which argon gas is purged by cyclone blowing at a rate of 3-5 L / min and a cyclone speed of 100-150 r / min. Then, the temperature is lowered to 750-780℃ at a rate of 5-8℃ / min and held for 30-40 minutes for the first stage of modification, which promotes the initial precipitation of Cr-Fe-Ni intermetallic compounds. Then, the temperature is lowered to 650-700℃ at a rate of 3-5℃ / min and held for 1-2 hours for the second stage of modification, which allows the chromium phase to precipitate uniformly with intermetallic compounds as the core, thus completing the composite modification treatment. The purity of argon gas is ≥99.999% throughout the process, and the furnace pressure is maintained at 0.1-0.12 MPa. S4. Rolling process: The ingots that have undergone composite modification treatment are hot rolled at a temperature of 700-750℃ and a rolling deformation of 30-40%, and then cold rolled at a deformation of 20-30% to obtain the sheet material. S5. Finished product heat treatment: The rolled plate is placed in a heat treatment furnace and heated to 450-500℃ under an argon protective atmosphere for 1-1.5 hours. Then it is air-cooled to room temperature to obtain a high-hardness copper-chromium alloy finished product. The chemical composition of the high-hardness copper-chromium alloy finished product by mass fraction is: chromium 10.19%, iron 0.006%, zinc 0.005%, lead 0.005%, nickel 0.002%, cadmium 0.0001%, and copper balance.

[0007] As a further technical solution, in step S1, the drying and degreasing treatment of electrolytic copper is as follows: first, dry at 120-150℃ for 30-40 minutes to remove surface moisture, then use an alkaline degreasing agent to ultrasonically degrease at 60-70℃ for 20-30 minutes. The alkaline degreasing agent consists of 20-30 g / L sodium hydroxide, 10-15 g / L sodium carbonate, and 5-8 g / L sodium phosphate, with the remainder being water. The ultrasonic power is 500-800 W. Finally, rinse with deionized water 3-5 times, each time for 5-8 minutes. After rinsing, dry at 100-120℃ for 20-30 minutes. After drying, passivation treatment is performed. The passivation solution is a 5-8 g / L potassium dichromate solution, the passivation temperature is 40-50℃, and the passivation time is 10-15 minutes.

[0008] As a further technical solution, in step S1, the grinding and refining process adopts a staged ball milling process. The first stage of ball milling uses zirconia balls with a diameter of 10 mm, a ball-to-material ratio of 15:1, a rotation speed of 200 r / min, and ball milling for 1.5-2 hours. The second stage of ball milling uses zirconia balls with a diameter of 5 mm, a ball-to-material ratio of 10:1, a rotation speed of 300 r / min, and ball milling for 1-2 hours. Anhydrous ethanol is added as a dispersant during the ball milling process, and the amount of dispersant is 5-10% of the raw material mass. After ball milling, vacuum drying is carried out at a drying temperature of 80-100℃ for 1-1.5 hours.

[0009] As a further technical solution, in step S2, a vacuum gradient heating melting process is adopted, specifically: after adding electrolytic copper to the vacuum induction melting furnace, the vacuum is first evacuated to below 0.005 Pa, then the temperature is raised to 800℃ at a rate of 50-60℃ / min, held for 10-15 min, and then raised to 1150-1200℃ at a rate of 30-40℃ / min to completely melt it; the holding and stirring process adopts electromagnetic stirring, and the vacuum degree is maintained at 0.001-0.005 Pa during the stirring process; after adding electrolytic chromium, pure iron, and pure nickel, a staged stirring rate is adopted: the first stage is 150 r / min. The stirring speed is maintained at 100 r / min for 10 min in the first stage, 200 r / min for 10-20 min in the second stage, and 180 r / min for 5 min in the third stage. After adding pure zinc, pure lead, and cadmium, the stirring speed is reduced to 150 r / min and stirred at the same temperature for 5-10 min. The casting process adopts directional solidification and electromagnetic braking technology, with a solidification rate of 2-5℃ / s. The mold preheating temperature is 300-400℃. The inner wall of the mold is coated with a 0.5-1 mm thick layer of boron nitride release agent. During the directional solidification process, an electromagnetic braking magnetic field of 0.03-0.05T is applied to suppress the turbulent flow of liquid metal.

[0010] As a further technical solution, in the composite modification treatment of step S3, a gradient swirling gas flow and ultrasonic vibration synergistic process is adopted. The gradient swirling gas flow specifically refers to the following: in the solid solution treatment stage, the argon gas flow rate is 5L / min and the swirling speed is 100r / min. In the first stage, the modification gas flow rate is linearly increased from 5L / min to 10L / min and the swirling speed is linearly increased from 100r / min to 120r / min. In the second stage, the modification gas flow rate is 10L / min and the swirling speed is constant at 120r / min. The ultrasonic vibration is applied synchronously with a vibration frequency of 15-25kHz. In the first stage, the modification frequency is uniformly increased from 15kHz to 20kHz, and in the second stage, the modification frequency is kept constant at 20kHz, thereby achieving the synergistic refinement effect of airflow and ultrasound.

[0011] As a further technical solution, the power of the ultrasonic vibration is 800-1200W, and the vibration direction is at a 45° angle to the argon gas swirling direction; an intermittent vibration mode is adopted, with vibration lasting 30 seconds and stopping for 10 seconds in a cycle.

[0012] As a further technical solution, in step S4, the hot rolling process adopts a multi-pass temperature-controlled rolling process, specifically: the first pass rolling temperature is 750℃, with a deformation of 5%; the second to fifth passes rolling temperatures are 730-740℃, with a deformation of 6-7% per pass; the last pass rolling temperature is 700-720℃, with a deformation of 8%; the interval between adjacent passes is 5-10 minutes, during which infrared heating is used for temperature compensation, with a compensation power of 3-5kW, to ensure that the rolling temperature is not lower than 700℃; after hot rolling, an online intermediate annealing treatment is performed, with an annealing temperature of 750-800℃, and the holding temperature is... The rolling time is 30-40 minutes, followed by cooling to room temperature at a rate of 10-15℃ / min. Before cold rolling, the hot-rolled sheet is surface polished to remove oxide scale, with a polishing precision of Ra≤0.8μm. Cold rolling adopts a progressive deformation + intermediate stress relief process, with the deformation amount of each pass gradually increasing from 5% to 8%. After every 3 passes of cold rolling, a stress relief annealing is performed at a temperature of 200-250℃ and a holding time of 20-30 minutes. Rolling oil is used for lubrication during cold rolling, with the rolling oil temperature controlled at 20-30℃ and the rolling oil pressure at 0.3-0.5MPa.

[0013] As a further technical solution, in step S5, a gradient heating heat treatment process is adopted, specifically: the temperature is increased from room temperature to 300℃ at a rate of 5-8℃ / min, held for 30min, and then increased to 450-500℃ at a rate of 10-15℃ / min, held for 1-1.5h; during the holding process, argon gas is dynamically circulated at a rate of 8-10L / min, and the plate is subjected to uniform temperature treatment at the same time, and the temperature difference between different parts of the plate is controlled within ±3℃.

[0014] As a further technical solution, the air cooling process adopts a segmented forced ventilation method. In the first stage, the plate temperature is 500-300℃, the ventilation rate is 3m / s, and the ventilation direction is at a 30° angle to the plate surface. In the second stage, the plate temperature is 300-200℃, and the ventilation rate is reduced to 2m / s. In the third stage, the plate temperature is below 200℃, and the ventilation rate is reduced to 1m / s. After cooling to room temperature, a low-temperature tempering treatment is performed. The tempering temperature is 180-220℃, the tempering time is 2-4 hours, and the pressure of the argon protective atmosphere is maintained at 0.1-0.15MPa during the tempering process. After tempering, the plate is naturally cooled to room temperature at a rate of 2-3℃ / min.

[0015] The preparation method yields a high-hardness copper-chromium alloy.

[0016] Compared with the prior art, the present invention has the following beneficial effects: This invention lays a solid foundation for subsequent preparation processes through a refined raw material pretreatment process. For electrolytic copper, a combined process of drying, ultrasonic degreasing, and passivation is employed. First, surface moisture and oil are removed to prevent gas defects during smelting. Then, passivation forms a dense oxide film to prevent secondary oxidation of the raw material. For alloy elements such as chromium and iron, a graded ball milling process combined with anhydrous ethanol dispersion is used to refine the particles to a uniform particle size of 50-100 μm, increasing the specific surface area of ​​the raw material. This pretreatment scheme not only accelerates the dissolution rate of alloying elements during subsequent smelting but also reduces component segregation, thus providing an early guarantee for the uniformity of the alloy microstructure. Simultaneously, the synergistic process of vacuum gradient heating and directional solidification-electromagnetic braking used in the smelting stage—first evacuating to below 0.005 Pa before gradient heating—avoids localized overheating of the molten copper. Electromagnetic braking effectively suppresses turbulent flow of the liquid metal, reducing defects such as porosity and gas bubbles within the ingot, further optimizing the initial microstructure quality of the ingot.

[0017] The core synergistic effect of the invention's main processes lies in achieving the regulation and microstructure optimization of the strengthening phase. The synergistic effects of gradient swirling ventilation and ultrasonic vibration, segmented temperature-controlled modification, and gradient heating and segmented forced ventilation air-cooling in the finished product heat treatment are particularly crucial. The segmented temperature-controlled modification process, through precise control of three temperature stages, first achieves full dissolution of alloying elements at 850-900℃, then cools to 750-780℃ to promote the initial precipitation of Cr-Fe-Ni intermetallic compounds, and finally allows the chromium phase to grow uniformly around the intermetallic compounds at 650-700℃, thus mechanistically avoiding the problem of strengthening phase agglomeration. The synergy of gradient swirling ventilation and ultrasonic vibration further enhances the modification effect. During the solution treatment stage, the constant ventilation and swirling rate ensure uniform argon gas coverage of the ingot, expelling internal impurities. During the modification stage, the ventilation rate and swirling speed are linearly increased, combined with gradient adjustment of the ultrasonic vibration frequency. The cavitation effect of ultrasound breaks down coarse grains, while the acoustic flow effect accelerates element diffusion, resulting in a more uniform and dispersed distribution of the strengthening phase. The gradient heating process for finished product heat treatment gradually raises the temperature from room temperature to the target temperature, avoiding thermal stress caused by excessive temperature differences. Segmented forced ventilation air cooling adjusts the ventilation rate according to different temperature ranges, precisely controlling the cooling rate to ensure more complete microstructural transformation and reduce residual stress. Due to the synergistic effect of these three core processes, a uniform and fine distribution of reinforcing phases forms within the alloy, significantly improving grain density. This not only greatly enhances the alloy's hardness but also strengthens its microstructural stability, providing microstructural support for excellent wear resistance.

[0018] In summary, this invention fundamentally solves key problems in existing copper-chromium alloy preparation, such as compositional segregation, coarse grains, high residual stress, and insufficient hardness and wear resistance, through optimized design and synergistic coordination of the entire process. From the perspective of specific process steps, each step specifically addresses the defects of preceding processes or the materials themselves. From the perspective of the overall scheme, the processes form a progressive optimization logic: raw material pretreatment provides high-quality raw materials for smelting, smelting and casting provides high-quality ingots for modification treatment, and the core modification and heat treatment processes ultimately achieve the control of microstructure and properties, producing a synergistic effect. The process of this invention is stable and reliable, with controllable operation, suitable for industrial mass production, and can meet the application needs of high-end fields such as high-voltage switches and precision machinery, possessing significant technical value and market prospects. Attached Figure Description

[0019] Figure 1 This is a flowchart of a method for preparing a high-hardness copper-chromium alloy. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] The high-hardness copper-chromium alloys prepared in the various embodiments and comparative examples of this invention have the following chemical composition by mass fraction: chromium 10.19%, iron 0.006%, zinc 0.005%, lead 0.005%, nickel 0.002%, cadmium 0.0001%, and copper balance.

[0022] Example 1: The high-hardness copper-chromium alloy preparation method of this embodiment includes the following steps: S1. Raw Material Pretreatment: Electrolytic copper, electrolytic chromium, pure iron, pure zinc, pure lead, pure nickel, and cadmium were selected as raw materials. Electrolytic copper underwent drying and degreasing treatment, specifically: first, it was dried at 120℃ for 40 minutes to remove surface moisture; then, it was ultrasonically degreased at 60℃ for 30 minutes using an alkaline degreasing agent composed of 20 g / L sodium hydroxide, 15 g / L sodium carbonate, and 5 g / L sodium phosphate, with the remainder being water. The ultrasonic power was 500 W. Finally, it was rinsed three times with deionized water, each rinsing time being 8 minutes. After rinsing, it was dried at 100℃ for 30 minutes. After drying, passivation treatment was performed using a 5 g / L potassium dichromate solution. The passivation temperature was 40℃ and the passivation time was 15 min. Electrolytic chromium, pure iron, pure zinc, pure lead, pure nickel, and cadmium were ground and refined using a staged ball milling process. The first stage of ball milling used 10 mm diameter zirconia balls with a ball-to-material ratio of 15:1, a rotation speed of 200 r / min, and ball milling for 1.5 h. The second stage of ball milling used 5 mm diameter zirconia balls with a ball-to-material ratio of 10:1, a rotation speed of 300 r / min, and ball milling for 2 h. Anhydrous ethanol was added as a dispersant during the ball milling process, and the amount of dispersant was 5% of the raw material mass. After ball milling, vacuum drying was carried out at a drying temperature of 80℃ for 1.5 h. Finally, the particles were ground and refined to a particle size of 50 μm.

[0023] S2. Melting and Casting: A vacuum gradient heating melting process is adopted. Pretreated electrolytic copper is added to a vacuum induction melting furnace. First, the vacuum is evacuated to below 0.005 Pa, then the temperature is increased to 800℃ at a rate of 50℃ / min and held for 15 min. Then, the temperature is increased to 1150℃ at a rate of 30℃ / min to ensure complete melting. Next, finely ground electrolytic chromium, pure iron, and pure nickel are added sequentially, and the mixture is held at this temperature and stirred for 20 min. Electromagnetic stirring is used during the stirring process, maintaining a vacuum of 0.005 Pa. A staged stirring rate is adopted: the first stage is 150 r / min, maintained at 10... The process involved three stages: a first stage of stirring at 200 rpm for 5 minutes, a second stage at 180 rpm for 5 minutes, and a third stage at 180 rpm for 5 minutes. Then, pure zinc, pure lead, and cadmium were added, the stirring speed was reduced to 150 rpm, and stirring was continued for 10 minutes. Afterward, the temperature was rapidly reduced to 1050℃ for casting. The casting process employed directional solidification and electromagnetic braking, with a solidification rate of 2℃ / s. The mold preheating temperature was 300℃, and the inner wall of the mold was coated with a 0.5mm thick layer of boron nitride release agent. During directional solidification, a 0.03T electromagnetic braking magnetic field was applied to suppress turbulent flow of the liquid metal, resulting in the ingot.

[0024] S3. Composite Modification Treatment: The ingot is placed in a heat treatment furnace, employing a segmented temperature-controlled modification process, combined with a gradient swirl gas flow and ultrasonic vibration process. The argon purity is ≥99.999% throughout the process, and the furnace pressure is maintained at 0.1 MPa. Specifically: First, the temperature is raised to 850℃ and held for 3 hours for solution treatment, during which argon gas swirl purging is used. The gradient swirl gas flow rate during this stage is 5 L / min, and the swirl speed is 100 r / min. Simultaneously, ultrasonic vibration is applied at a frequency of 15 kHz and a power of 800 W, with the vibration direction at a 45° angle to the argon gas swirl direction. An intermittent vibration mode is used, with a 30-second vibration followed by a 10-second pause. Then, the temperature is reduced to 750℃ at a cooling rate of 5℃ / min and held for 40 seconds. The first stage of modification is carried out to promote the initial precipitation of Cr-Fe-Ni intermetallic compounds. In this stage, the gradient swirl ventilation rate is linearly increased from 5 L / min to 10 L / min, and the swirl speed is linearly increased from 100 r / min to 120 r / min. The ultrasonic vibration frequency is uniformly increased from 15 kHz to 20 kHz, while other vibration parameters remain unchanged. Then, the temperature is reduced to 650 ℃ at a cooling rate of 3 ℃ / min, and the temperature is maintained for 2 hours for the second stage of modification, so that the chromium phase is uniformly precipitated with intermetallic compounds as the core. In this stage, the gradient swirl ventilation rate is kept constant at 10 L / min, the swirl speed is kept constant at 120 r / min, the ultrasonic vibration frequency is kept constant at 20 kHz, and other vibration parameters remain unchanged, thus completing the composite modification treatment.

[0025] S4. Rolling Process: The composite modified ingot is hot-rolled using a multi-pass temperature-controlled rolling process. Specifically: the first pass is rolled at 750℃ with a deformation of 5%; the second to fifth passes are rolled at 730℃ with a deformation of 6% per pass; and the final pass is rolled at 700℃ with a deformation of 8%. There is a 10-minute interval between adjacent passes, during which infrared heating with a power of 3kW is used to compensate for the temperature difference, ensuring that the rolling temperature does not fall below 700℃. After hot rolling, an online intermediate annealing process is performed at 750℃ for 40 minutes, followed by a temperature increase of 10℃ / min. The hot-rolled sheet was cooled to room temperature at a rate of min. After hot rolling, it was cold-rolled. Before cold rolling, the surface of the hot-rolled sheet was polished to remove oxide scale. The polishing accuracy was Ra≤0.8μm. The cold rolling adopted a progressive deformation + intermediate stress relief process. The deformation amount of each pass gradually increased from 5% to 8%. After every 3 passes of cold rolling, a stress relief annealing was performed. The annealing temperature was 200℃ and the holding time was 30min. Rolling oil was used for lubrication during the cold rolling process. The rolling oil temperature was controlled at 20℃ and the rolling oil pressure was 0.3MPa. The cumulative deformation amount of hot rolling was 30% and the cumulative deformation amount of cold rolling was 20% to obtain the sheet.

[0026] S5. Finished Product Heat Treatment: The rolled sheet is placed in a heat treatment furnace and subjected to a gradient heating process under an argon protective atmosphere. Specifically, the temperature is increased from room temperature to 300℃ at a rate of 5℃ / min, held for 30 min, and then increased to 450℃ at a rate of 10℃ / min, held for 1.5 h. During the holding process, dynamic argon circulation is used at a circulation rate of 8 L / min, while simultaneously homogenizing the sheet, controlling the temperature difference between different parts of the sheet within ±3℃. The sheet is then air-cooled to room temperature, using a segmented forced ventilation method. In the first stage, the plate temperature is 500-300℃, the ventilation rate is 3m / s, and the ventilation direction is at a 30° angle to the plate surface. In the second stage, the plate temperature is 300-200℃, and the ventilation rate is reduced to 2m / s. In the third stage, the plate temperature is below 200℃, and the ventilation rate is reduced to 1m / s. After cooling to room temperature, a low-temperature tempering treatment is performed. The tempering temperature is 180℃, the tempering time is 4 hours, and the pressure of the argon protective atmosphere is maintained at 0.1MPa during the tempering process. After tempering, the plate is naturally cooled to room temperature at a rate of 2℃ / min to obtain a high-hardness copper-chromium alloy finished product.

[0027] Example 2: The high-hardness copper-chromium alloy preparation method of this embodiment includes the following steps: S1. Raw Material Pretreatment: Electrolytic copper, electrolytic chromium, pure iron, pure zinc, pure lead, pure nickel, and cadmium were selected as raw materials. Electrolytic copper underwent drying and degreasing treatment, specifically: first, it was dried at 135℃ for 35 minutes to remove surface moisture; then, an alkaline degreasing agent was used for ultrasonic degreasing at 65℃ for 25 minutes. The alkaline degreasing agent consisted of 25 g / L sodium hydroxide, 12 g / L sodium carbonate, and 6.5 g / L sodium phosphate, with the remainder being water. The ultrasonic power was 650 W. Finally, it was rinsed four times with deionized water, each rinsing time being 6.5 minutes. After rinsing, it was dried at 110℃ for 25 minutes. After drying, passivation treatment was performed using a 6.5 g / L potassium dichromate solution. The passivation temperature was 45℃ and the passivation time was 12 min. Electrolytic chromium, pure iron, pure zinc, pure lead, pure nickel, and cadmium were ground and refined using a staged ball milling process. The first stage of ball milling used 10 mm diameter zirconia balls with a ball-to-material ratio of 15:1, a rotation speed of 200 r / min, and a milling time of 1.75 h. The second stage of ball milling used 5 mm diameter zirconia balls with a ball-to-material ratio of 10:1, a rotation speed of 300 r / min, and a milling time of 1.5 h. Anhydrous ethanol was added as a dispersant during the ball milling process, with the amount of dispersant being 7.5% of the raw material mass. After ball milling, vacuum drying was performed at a drying temperature of 90℃ for 1.25 h. Finally, the particles were ground and refined to a particle size of 75 μm.

[0028] S2. Melting and Casting: A vacuum gradient heating melting process is adopted. Pretreated electrolytic copper is added to a vacuum induction melting furnace. First, the vacuum is evacuated to below 0.005 Pa, then the temperature is increased to 800℃ at a rate of 55℃ / min and held for 12.5 min. Then, the temperature is increased to 1175℃ at a rate of 35℃ / min to ensure complete melting. Next, finely ground electrolytic chromium, pure iron, and pure nickel are added sequentially, and the mixture is held at this temperature and stirred for 25 min. Electromagnetic stirring is used during the stirring process, maintaining a vacuum of 0.003 Pa. A staged stirring rate is adopted: the first stage is 150 r / min for 10 min. In the second stage, the stirring speed was maintained at 200 r / min for 10 min, and in the third stage, it was maintained at 180 r / min for 5 min. Then, pure zinc, pure lead, and cadmium were added, and the stirring speed was reduced to 150 r / min. The stirring was continued at this temperature for 7.5 min. After that, the temperature was rapidly reduced to 1075℃ for casting. The casting process adopted directional solidification and electromagnetic braking technology. The solidification rate was 3.5℃ / s, the mold preheating temperature was 350℃, and the inner wall of the mold was coated with a 0.75mm thick layer of boron nitride release agent. During the directional solidification process, an electromagnetic braking magnetic field of 0.04T was applied to suppress the turbulent flow of liquid metal and obtain the ingot.

[0029] S3. Composite Modification Treatment: The ingot is placed in a heat treatment furnace, employing a segmented temperature-controlled modification process, combined with a gradient swirl gas flow and ultrasonic vibration process. The argon purity is ≥99.999% throughout the process, and the furnace pressure is maintained at 0.11 MPa. Specifically: First, the temperature is raised to 875℃ and held for 2.5 hours for solution treatment, during which argon gas swirl purging is used. The gradient swirl gas flow rate during this stage is 5 L / min, and the swirl speed is 100 r / min. Simultaneously, ultrasonic vibration is applied at a frequency of 20 kHz and a power of 1000 W, with the vibration direction at a 45° angle to the argon gas swirl direction. An intermittent vibration mode is used, with a 30-second vibration followed by a 10-second pause. Then, the temperature is reduced to 765℃ at a cooling rate of 6.5℃ / min and held. The first stage of modification was carried out for 35 minutes to promote the initial precipitation of Cr-Fe-Ni intermetallic compounds. During this stage, the gradient swirl ventilation rate was linearly increased from 5 L / min to 10 L / min, and the swirl speed was linearly increased from 100 r / min to 120 r / min. The ultrasonic vibration frequency was uniformly increased from 15 kHz to 20 kHz, while other vibration parameters remained unchanged. The temperature was then reduced to 675 ℃ at a cooling rate of 4 ℃ / min, and the temperature was maintained for 1.5 hours for the second stage of modification, which allowed the chromium phase to precipitate uniformly with intermetallic compounds as the core. During this stage, the gradient swirl ventilation rate was kept constant at 10 L / min, the swirl speed was kept constant at 120 r / min, the ultrasonic vibration frequency was kept constant at 20 kHz, and other vibration parameters remained unchanged, thus completing the composite modification treatment.

[0030] S4. Rolling Process: The composite-modified ingot is hot-rolled using a multi-pass temperature-controlled rolling process. Specifically: the first pass is rolled at 750℃ with a deformation of 5%; the second to fifth passes are rolled at 735℃ with a deformation of 6.5% per pass; and the final pass is rolled at 710℃ with a deformation of 8%. There is a 7.5-minute interval between adjacent passes, during which infrared heating is used to compensate for the temperature difference (4kW) to ensure the rolling temperature does not fall below 700℃. After hot rolling, an online intermediate annealing process is performed at 775℃ for 35 minutes, followed by a 12.5-degree rotation. Cooling to room temperature at a rate of ℃ / min; after hot rolling, cold rolling is performed. Before cold rolling, the surface of the hot-rolled sheet is polished to remove oxide scale, and the polishing accuracy is Ra≤0.8μm. The cold rolling adopts a progressive deformation + intermediate stress relief process, with the deformation amount of each pass gradually increasing from 5% to 8%. After every 3 passes of cold rolling, stress relief annealing is performed at a temperature of 225℃ and a holding time of 25min. Rolling oil lubrication is used during the cold rolling process, with the rolling oil temperature controlled at 25℃ and the rolling oil pressure at 0.4MPa. The cumulative deformation amount of hot rolling is 35%, and the cumulative deformation amount of cold rolling is 25%, to obtain the sheet.

[0031] S5. Finished Product Heat Treatment: The rolled sheet is placed in a heat treatment furnace and subjected to a gradient heating process under an argon protective atmosphere. Specifically, the temperature is increased from room temperature to 300℃ at a rate of 6.5℃ / min, held for 30 min, and then increased to 475℃ at a rate of 12.5℃ / min, held for 1.25 h. During the holding process, dynamic argon circulation is used at a circulation rate of 9 L / min, and the sheet is simultaneously subjected to temperature homogenization treatment, with the temperature difference between different parts of the sheet controlled within ±3℃. The sheet is then air-cooled to room temperature, using a segmented forced ventilation method. In the first stage, the plate temperature is 500-300℃, the ventilation rate is 3m / s, and the ventilation direction is at a 30° angle to the plate surface. In the second stage, the plate temperature is 300-200℃, and the ventilation rate is reduced to 2m / s. In the third stage, the plate temperature is below 200℃, and the ventilation rate is reduced to 1m / s. After cooling to room temperature, a low-temperature tempering treatment is performed. The tempering temperature is 200℃, the tempering time is 3 hours, and the pressure of the argon protective atmosphere is maintained at 0.125MPa during the tempering process. After tempering, the plate is naturally cooled to room temperature at a rate of 2.5℃ / min to obtain a high-hardness copper-chromium alloy finished product.

[0032] Example 3: The high-hardness copper-chromium alloy preparation method of this embodiment includes the following steps: S1. Raw Material Pretreatment: Electrolytic copper, electrolytic chromium, pure iron, pure zinc, pure lead, pure nickel, and cadmium were selected as raw materials. Electrolytic copper underwent drying and degreasing treatment, specifically: first, it was dried at 150℃ for 30 minutes to remove surface moisture; then, it was ultrasonically degreased at 70℃ for 20 minutes using an alkaline degreasing agent composed of 30 g / L sodium hydroxide, 10 g / L sodium carbonate, and 8 g / L sodium phosphate, with the remainder being water. The ultrasonic power was 800 W. Finally, it was rinsed 5 times with deionized water, each rinsing time being 5 minutes. After rinsing, it was dried at 120℃ for 20 minutes. After drying, passivation treatment was performed using an 8 g / L potassium dichromate solution. The passivation temperature was 50℃ and the passivation time was 10 min. Electrolytic chromium, pure iron, pure zinc, pure lead, pure nickel, and cadmium were ground and refined using a staged ball milling process. The first stage of ball milling used 10 mm diameter zirconia balls with a ball-to-material ratio of 15:1, a rotation speed of 200 r / min, and ball milling for 2 h. The second stage of ball milling used 5 mm diameter zirconia balls with a ball-to-material ratio of 10:1, a rotation speed of 300 r / min, and ball milling for 1 h. Anhydrous ethanol was added as a dispersant during the ball milling process, and the amount of dispersant was 10% of the raw material mass. After ball milling, vacuum drying was carried out at a drying temperature of 100℃ for 1 h. Finally, the particles were ground and refined to a particle size of 100 μm.

[0033] S2. Melting and Casting: A vacuum gradient heating melting process is adopted. Pretreated electrolytic copper is added to a vacuum induction melting furnace. First, the vacuum is evacuated to below 0.005 Pa, then the temperature is increased to 800℃ at a rate of 60℃ / min and held for 10 min. Then, the temperature is increased to 1200℃ at a rate of 40℃ / min to ensure complete melting. Next, finely ground electrolytic chromium, pure iron, and pure nickel are added sequentially, and the mixture is held at this temperature and stirred for 30 min. Electromagnetic stirring is used during the stirring process, maintaining a vacuum of 0.001 Pa. A staged stirring rate is adopted: the first stage is 150 r / min, maintained at 1... The first stage was 0 min, the second stage was 200 r / min for 15 min, and the third stage was 180 r / min for 5 min. Then pure zinc, pure lead, and cadmium were added, the stirring rate was reduced to 150 r / min, and stirring was continued for 5 min. After that, the temperature was rapidly reduced to 1100℃ for casting. The casting process adopted directional solidification and electromagnetic braking technology, with a solidification rate of 5℃ / s. The mold preheating temperature was 400℃, and a 1 mm thick layer of boron nitride release agent was coated on the inner wall of the mold. During the directional solidification process, an electromagnetic braking magnetic field of 0.05T was applied to suppress the turbulent flow of liquid metal and obtain the ingot.

[0034] S3. Composite Modification Treatment: The ingot is placed in a heat treatment furnace, employing a segmented temperature-controlled modification process, combined with a gradient swirl gas flow and ultrasonic vibration process. The argon purity throughout the process is ≥99.999%, and the furnace pressure is maintained at 0.12 MPa. Specifically: First, the temperature is raised to 900℃ and held for 2 hours for solution treatment, during which argon gas swirl purging is used. The gradient swirl gas flow rate during this stage is 5 L / min, and the swirl speed is 100 r / min. Simultaneously, ultrasonic vibration is applied at a frequency of 25 kHz and a power of 1200 W, with the vibration direction at a 45° angle to the argon gas swirl direction. An intermittent vibration mode is used, with a 30-second vibration followed by a 10-second pause. Then, the temperature is reduced to 780℃ at a cooling rate of 8℃ / min and held for 3 hours. The first stage of modification was carried out at 0 min to promote the initial precipitation of Cr-Fe-Ni intermetallic compounds. During this stage, the gradient swirl ventilation rate was linearly increased from 5 L / min to 10 L / min, and the swirl speed was linearly increased from 100 r / min to 120 r / min. The ultrasonic vibration frequency was uniformly increased from 15 kHz to 20 kHz, while other vibration parameters remained unchanged. The temperature was then reduced to 700 ℃ at a cooling rate of 5 ℃ / min, and the temperature was maintained for 1 h for the second stage of modification, so that the chromium phase was uniformly precipitated with intermetallic compounds as the core. During this stage, the gradient swirl ventilation rate was kept constant at 10 L / min, the swirl speed was kept constant at 120 r / min, the ultrasonic vibration frequency was kept constant at 20 kHz, and other vibration parameters remained unchanged, thus completing the composite modification treatment.

[0035] S4. Rolling Process: The composite modified ingot is hot-rolled using a multi-pass temperature-controlled rolling process. Specifically: the first pass is rolled at 750℃ with a deformation of 5%; the second to fifth passes are rolled at 740℃ with a deformation of 7% per pass; and the final pass is rolled at 720℃ with a deformation of 8%. There is a 5-minute interval between adjacent passes, during which infrared heating is used to compensate for the temperature difference (5kW) to ensure the rolling temperature does not fall below 700℃. After hot rolling, an online intermediate annealing process is performed at 800℃ for 30 minutes, followed by a temperature increase of 15℃ / m. The hot-rolled sheet is cooled to room temperature at a rate of 100°C. After hot rolling, it is cold-rolled. Before cold rolling, the surface of the hot-rolled sheet is polished to remove oxide scale. The polishing accuracy is Ra≤0.8μm. The cold rolling adopts a progressive deformation + intermediate stress relief process. The deformation amount of each pass is gradually increased from 5% to 8%. After every 3 passes of cold rolling, a stress relief annealing is performed. The annealing temperature is 250°C and the holding time is 20min. Rolling oil is used for lubrication during the cold rolling process. The rolling oil temperature is controlled at 30°C and the rolling oil pressure is 0.5MPa. The cumulative deformation amount of hot rolling is 40%, and the cumulative deformation amount of cold rolling is 30%, to obtain the sheet.

[0036] S5. Finished Product Heat Treatment: The rolled sheet is placed in a heat treatment furnace and subjected to a gradient heating process under an argon protective atmosphere. Specifically, the temperature is increased from room temperature to 300℃ at a rate of 8℃ / min, held for 30 min, and then increased to 500℃ at a rate of 15℃ / min, held for 1 h. During the holding process, dynamic argon circulation is used at a circulation rate of 10 L / min, while simultaneously homogenizing the sheet, controlling the temperature difference between different parts of the sheet within ±3℃. The sheet is then air-cooled to room temperature, using a segmented forced ventilation method. In the first stage, the plate temperature is 500-300℃, the ventilation rate is 3m / s, and the ventilation direction is at a 30° angle to the plate surface. In the second stage, the plate temperature is 300-200℃, and the ventilation rate is reduced to 2m / s. In the third stage, the plate temperature is below 200℃, and the ventilation rate is reduced to 1m / s. After cooling to room temperature, a low-temperature tempering treatment is performed. The tempering temperature is 220℃, the tempering time is 2h, and the pressure of the argon protective atmosphere is maintained at 0.15MPa during the tempering process. After tempering, the plate is naturally cooled to room temperature at a rate of 3℃ / min to obtain a high-hardness copper-chromium alloy product.

[0037] Comparative Example 1: The method for preparing high-hardness copper-chromium alloy in this comparative example is exactly the same as that in Example 2, except that the gradient swirling airflow and ultrasonic vibration synergistic process is not used in step S3 composite modification treatment.

[0038] Step S3, the composite modification treatment, is as follows: The ingot is placed in a heat treatment furnace, and a segmented temperature-controlled modification process is adopted; the argon purity is ≥99.999% throughout the process, and the furnace pressure is maintained at 0.11MPa; specifically: first, the temperature is raised to 875℃ and held for 2.5h for solution treatment, during which argon is purged at a uniform rate of 5L / min without swirling; then, the temperature is lowered to 765℃ at a cooling rate of 6.5℃ / min and held for 35min for the first stage of modification; then, the temperature is lowered to 675℃ at a cooling rate of 4℃ / min and held for 1.5h for the second stage of modification, completing the composite modification treatment; no ultrasonic vibration is applied throughout the process.

[0039] Comparative Example 2: The method for preparing high-hardness copper-chromium alloy in this comparative example is exactly the same as that in Example 2, except that the segmented temperature-controlled modification process is not used in step S3, which is replaced by constant temperature modification.

[0040] Step S3, the composite modification treatment, is as follows: The ingot is placed in a heat treatment furnace and subjected to a constant-temperature modification process, simultaneously employing a gradient swirl gas flow and ultrasonic vibration synergistic process. The argon purity is ≥99.999% throughout the process, and the furnace pressure is maintained at 0.11 MPa. Specifically, the temperature is first raised to 875℃ and held for 2.5 hours for solution treatment, during which argon gas swirl purging is used. The gradient swirl gas flow rate during this stage is 5 L / min, and the swirl speed is 100 r / min. Ultrasonic vibration is applied simultaneously at a frequency of 20 kHz and a power of 1000 W, with the vibration direction at a 45° angle to the argon gas swirl direction. An intermittent vibration mode is used, with a 30-second vibration followed by a 10-second pause and repeat. Then, the temperature is directly lowered to 675℃ and held at this constant temperature for 2.5 hours for modification treatment. During this stage, the gradient swirl gas flow rate is constant at 10 L / min, and the swirl speed is constant at 120 r / min. The ultrasonic vibration frequency remains constant at 20 kHz, while other vibration parameters remain unchanged, completing the composite modification treatment.

[0041] Comparative Example 3: The preparation method of the high-hardness copper-chromium alloy in this comparative example is exactly the same as that in Example 2, except that the gradient heating and segmented forced ventilation air cooling process is not used in the heat treatment of the finished product in step S5.

[0042] Step S5, the heat treatment of the finished product, is as follows: The rolled plate is placed in a heat treatment furnace and heated directly from room temperature to 475°C under an argon protective atmosphere, and held at that temperature for 1.25 hours. During the holding process, static argon protection is used without dynamic circulation. Then, it is naturally cooled to room temperature without segmented forced ventilation. After cooling to room temperature, a low-temperature tempering treatment is performed. The tempering temperature is 200°C, the tempering time is 3 hours, and the pressure of the argon protective atmosphere is maintained at 0.125 MPa during the tempering process. After tempering, it is naturally cooled to room temperature at a rate of 2.5°C / min to obtain the copper-chromium alloy finished product.

[0043] test: Experiment 1: Hardness test; Test Method: The hardness of the alloy products in each embodiment and comparative example was tested using a Vickers hardness tester. Five standard specimens were prepared from different parts of the alloy products. Three points were tested at different locations on each specimen. The average value of 15 test data was taken as the final hardness value of the sample. The test load was 1000g, and the load holding time was 15s. The test results are shown in Table 1 below: Table 1

[0044] As shown in Table 1, the Vickers hardness of the high-hardness copper-chromium alloy products prepared in Examples 1-3 is all above 385HV, indicating that the preparation method of the present invention can effectively improve the hardness of copper-chromium alloys. Comparing Example 2 with the comparative examples: The hardness of Comparative Example 1 was only 312 HV. This was because the lack of a gradient swirling airflow and ultrasonic vibration synergistic process resulted in uneven argon gas distribution during the solution treatment stage, and impurities inside the alloy could not be fully removed. At the same time, the chromium phase precipitation was uneven and the grains were coarse during the modification stage, making it impossible to form a uniform and fine Cr-Fe-Ni intermetallic compound strengthening phase, thus significantly reducing the alloy hardness. The hardness of Comparative Example 2 was 298 HV. The core reason was the lack of a segmented temperature-controlled modification process. The isothermal modification could not achieve the initial precipitation of Cr-Fe-Ni intermetallic compounds and the subsequent uniform precipitation of the chromium phase. The chromium phase was prone to agglomeration, and the strengthening effect was greatly weakened. The hardness of Comparative Example 3 was 335 HV. This was mainly because the finished product heat treatment lacked a gradient heating and segmented forced ventilation air cooling process. Direct heating led to uneven distribution of thermal stress inside the alloy. The natural air cooling rate could not be precisely controlled, resulting in local coarsening of the alloy structure. After tempering, the internal stress could not be effectively eliminated, thus affecting the hardness performance.

[0045] Test 2: Abrasion resistance test; Sliding wear tests were conducted using an MMW-1 universal friction and wear testing machine. Alloy products from each embodiment and comparative example were machined into standard wear specimens of 5mm × 10mm × 20mm. GCr15 bearing steel (hardness 62HRC) was selected for the wear pair. The test load was 50N, the sliding speed was 0.5m / s, the test time was 60min, and the test environment was a dry room temperature environment. Before the test, the specimen mass was weighed using an electronic balance (accuracy 0.1mg), and after the test, the specimen mass was weighed again to calculate the mass wear amount. Simultaneously, the width and depth of the wear trajectory were measured to calculate the volumetric wear amount. Each sample was tested in parallel three times, and the average value was taken as the final test result. The test results are shown in Table 2 below. Table 2

[0046] As shown in Table 2, the high-hardness copper-chromium alloy products prepared in Examples 1-3 exhibit excellent wear resistance, with mass wear amounting to less than 8.5 mg and volume wear amounting to less than 1.1 mm. 3 The mass wear and volume wear of Comparative Example 1 reached 18.6 mg and 2.38 mm, respectively. 3 The reason is that the lack of gradient swirling airflow and ultrasonic vibration synergistic process leads to a decrease in alloy hardness and poor microstructure uniformity. During sliding wear, the surface is prone to plastic deformation and material shedding, resulting in a significant increase in wear. Comparative Example 2 showed the largest wear, with a mass wear of 22.3 mg and a volume wear of 2.86 mm. 3The core issue is that isothermal degradation leads to chromium phase agglomeration, coarse microstructure, and a significant decrease in hardness. During wear, an effective wear-resistant surface layer cannot be formed, resulting in rapid material loss. Comparative Example 3 showed a mass wear of 15.4 mg and a volume wear of 1.97 mm. 3 The main reason for this is that improper heat treatment of the finished product leads to residual stress inside the alloy, resulting in poor microstructure stability. During wear, stress release causes the surface microstructure to peel off, exacerbating the wear. In summary, the preparation method of this invention, through the synergistic effect of various key processes, enables the alloy to obtain a uniform and fine microstructure and high hardness, thereby significantly improving its wear resistance.

[0047] In summary, this invention, through the synergistic combination of a series of processes including raw material pretreatment, vacuum gradient heating melting and casting, segmented temperature-controlled composite modification, multi-pass temperature-controlled rolling, and gradient heating heat treatment of the finished product, can effectively prepare copper-chromium alloys with high hardness and high wear resistance. The performance test results of Examples 1-3 show that the preparation method is stable and reliable, and the prepared alloy products exhibit excellent comprehensive performance.

[0048] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not describe all details exhaustively, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification.

Claims

1. A method for preparing a high-hardness copper-chromium alloy, characterized in that, Includes the following steps: S1. Raw material pretreatment: Select electrolytic copper, electrolytic chromium, pure iron, pure zinc, pure lead, pure nickel and cadmium as raw materials. Dry and degrease the electrolytic copper. Grind and refine the electrolytic chromium, pure iron, pure zinc, pure lead, pure nickel and cadmium to a particle size of 50-100μm. S2. Melting and Casting: The pretreated electrolytic copper is added to a vacuum induction melting furnace and heated to 1150-1200℃ to completely melt it. Then, finely ground electrolytic chromium, pure iron, and pure nickel are added in sequence. The mixture is kept at the temperature and stirred for 20-30 minutes at a stirring rate of 150-200 r / min. Then, pure zinc, pure lead, and cadmium are added and the mixture is kept at the temperature and stirred for another 5-10 minutes. After that, the temperature is rapidly reduced to 1050-1100℃ for casting to obtain an ingot. S3. Composite Modification Treatment: The ingot is placed in a heat treatment furnace and a segmented temperature-controlled modification process is adopted. First, the temperature is raised to 850-900℃ and held for 2-3 hours for solution treatment, during which argon gas is purged by cyclone blowing at a rate of 3-5 L / min and a cyclone speed of 100-150 r / min. Then, the temperature is lowered to 750-780℃ at a rate of 5-8℃ / min and held for 30-40 minutes for the first stage of modification, which promotes the initial precipitation of Cr-Fe-Ni intermetallic compounds. Then, the temperature is lowered to 650-700℃ at a rate of 3-5℃ / min and held for 1-2 hours for the second stage of modification, which allows the chromium phase to precipitate uniformly with intermetallic compounds as the core, thus completing the composite modification treatment. The purity of argon gas is ≥99.999% throughout the process, and the furnace pressure is maintained at 0.1-0.12 MPa. S4. Rolling process: The ingots that have undergone composite modification treatment are hot rolled at a temperature of 700-750℃ and a rolling deformation of 30-40%, and then cold rolled at a deformation of 20-30% to obtain the sheet material. S5. Finished product heat treatment: The rolled plate is placed in a heat treatment furnace and heated to 450-500℃ under an argon protective atmosphere for 1-1.5 hours. Then it is air-cooled to room temperature to obtain a high-hardness copper-chromium alloy finished product. The chemical composition of the high-hardness copper-chromium alloy finished product by mass fraction is: chromium 10.19%, iron 0.006%, zinc 0.005%, lead 0.005%, nickel 0.002%, cadmium 0.0001%, and copper balance.

2. The preparation method according to claim 1, characterized in that, In step S1, the drying and degreasing treatment of electrolytic copper is as follows: First, dry at 120-150℃ for 30-40 minutes to remove surface moisture. Then, use an alkaline degreasing agent to ultrasonically degrease at 60-70℃ for 20-30 minutes. The alkaline degreasing agent consists of 20-30 g / L sodium hydroxide, 10-15 g / L sodium carbonate, and 5-8 g / L sodium phosphate, with the remainder being water. The ultrasonic power is 500-800 W. Finally, rinse with deionized water 3-5 times, each time for 5-8 minutes. After rinsing, dry at 100-120℃ for 20-30 minutes. After drying, passivation treatment is performed. The passivation solution is a 5-8 g / L potassium dichromate solution. The passivation temperature is 40-50℃ and the passivation time is 10-15 minutes.

3. The preparation method according to claim 1, characterized in that, In step S1, the grinding and refining process adopts a staged ball milling process. The first stage of ball milling uses zirconia balls with a diameter of 10 mm, a ball-to-material ratio of 15:1, a rotation speed of 200 r / min, and ball milling for 1.5-2 hours. The second stage of ball milling uses zirconia balls with a diameter of 5 mm, a ball-to-material ratio of 10:1, a rotation speed of 300 r / min, and ball milling for 1-2 hours. Anhydrous ethanol is added as a dispersant during the ball milling process, and the amount of dispersant is 5-10% of the raw material mass. After ball milling, vacuum drying is carried out at a drying temperature of 80-100℃ for 1-1.5 hours.

4. The preparation method according to claim 1, characterized in that, In step S2, a vacuum gradient heating melting process is adopted, specifically as follows: after adding electrolytic copper to a vacuum induction melting furnace, the vacuum is first evacuated to below 0.005 Pa, then the temperature is increased to 800℃ at a rate of 50-60℃ / min, held for 10-15 min, and then increased to 1150-1200℃ at a rate of 30-40℃ / min to completely melt it; electromagnetic stirring is used during the holding and stirring process, and the vacuum degree is maintained at 0.001-0.005 Pa during the stirring process; after adding electrolytic chromium, pure iron, and pure nickel, a staged stirring rate is adopted: the first stage is 150 r / min and held for 10-15 min. The first stage involves stirring at 200 rpm for 10 minutes, followed by a second stage at 200 rpm for 10-20 minutes, and a third stage at 180 rpm for 5 minutes. After adding pure zinc, pure lead, and cadmium, the stirring speed is reduced to 150 rpm, and the mixture is kept warm and stirred for 5-10 minutes. The casting process employs directional solidification and electromagnetic braking technology, with a solidification rate of 2-5℃ / s. The mold preheating temperature is 300-400℃, and the inner wall of the mold is coated with a 0.5-1mm thick layer of boron nitride release agent. During directional solidification, an electromagnetic braking magnetic field of 0.03-0.05T is applied to suppress the turbulent flow of the liquid metal.

5. The preparation method according to claim 1, characterized in that, In the composite modification treatment of step S3, a gradient swirling gas flow and ultrasonic vibration synergistic process is adopted. The gradient swirling gas flow specifically refers to the following: in the solid solution treatment stage, the argon gas flow rate is 5 L / min and the swirling speed is 100 r / min. In the first stage, the modification gas flow rate is linearly increased from 5 L / min to 10 L / min and the swirling speed is linearly increased from 100 r / min to 120 r / min. In the second stage, the modification gas flow rate is 10 L / min and the swirling speed is constant at 120 r / min. The ultrasonic vibration is applied synchronously with a vibration frequency of 15-25 kHz. In the first stage, the modification frequency is uniformly increased from 15 kHz to 20 kHz, and in the second stage, the modification frequency is kept constant at 20 kHz, so as to achieve the synergistic refinement effect of airflow and ultrasound.

6. The preparation method according to claim 5, characterized in that, The ultrasonic vibration power is 800-1200W, and the vibration direction is at a 45° angle to the argon gas swirling direction; an intermittent vibration mode is adopted, with vibration lasting 30 seconds and stopping for 10 seconds in a cycle.

7. The preparation method according to claim 1, characterized in that, In step S4, the hot rolling process employs a multi-pass temperature-controlled rolling process, specifically: the first pass rolling temperature is 750℃ with a deformation of 5%; the second to fifth passes rolling temperatures are 730-740℃ with a deformation of 6-7% per pass; and the final pass rolling temperature is 700-720℃ with a deformation of 8%. There is a 5-10 minute interval between adjacent passes, during which infrared heating is used for temperature compensation at a power of 3-5 kW to ensure the rolling temperature does not fall below 700℃. After hot rolling, an online intermediate annealing process is performed at a temperature of 750-800℃ for a holding time of 30- After 40 minutes, the hot-rolled sheet is cooled to room temperature at a rate of 10-15℃ / min. Before cold rolling, the hot-rolled sheet is polished to remove oxide scale, and the polishing accuracy is Ra≤0.8μm. The cold rolling adopts a progressive deformation + intermediate stress relief process, with the deformation amount of each pass gradually increasing from 5% to 8%. After every 3 passes of cold rolling, a stress relief annealing is performed at a temperature of 200-250℃ and a holding time of 20-30 minutes. Rolling oil is used for lubrication during the cold rolling process, with the rolling oil temperature controlled at 20-30℃ and the rolling oil pressure at 0.3-0.5MPa.

8. The preparation method according to claim 1, characterized in that, In step S5, a gradient heating heat treatment process is adopted, specifically: the temperature is increased from room temperature to 300℃ at a rate of 5-8℃ / min, held for 30min, and then increased to 450-500℃ at a rate of 10-15℃ / min, held for 1-1.5h; during the holding process, argon gas is dynamically circulated at a rate of 8-10L / min, and the plate is subjected to uniform temperature treatment at the same time, and the temperature difference between different parts of the plate is controlled within ±3℃.

9. The high-hardness copper-chromium alloy as described in claim 8, characterized in that, The air cooling process employs a segmented forced ventilation method. In the first stage, the plate temperature is 500-300℃, the ventilation rate is 3m / s, and the ventilation direction forms a 30° angle with the plate surface. In the second stage, the plate temperature is 300-200℃, and the ventilation rate is reduced to 2m / s. In the third stage, the plate temperature is below 200℃, and the ventilation rate is reduced to 1m / s. After cooling to room temperature, a low-temperature tempering treatment is performed. The tempering temperature is 180-220℃, the tempering time is 2-4 hours, and the pressure of the argon protective atmosphere is maintained at 0.1-0.15MPa during the tempering process. After tempering, the plate is naturally cooled to room temperature at a rate of 2-3℃ / min.

10. A high-hardness copper-chromium alloy is obtained according to any one of claims 1-9.

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