Preparation method of low-cost CuCr25 contact material

Abstract

The invention provides a preparation method of a low-cost CuCr25 contact material, and relates to the technical field of preparation of electrical materials, and the preparation method comprises the following steps: preparing and weighing CuCr25 contact raw materials, mixing the CuCr25 contact raw materials, carrying out compression molding on the CuCr25 contact raw materials, sintering a green body, processing and preparing a CuCr25 contact, and cleaning and inspecting the CuCr25 contact. The water atomized copper powder and the aluminothermy chromium powder are adopted as main raw materials, quantitative recycled powder is innovatively added, the cost of the raw materials is successfully and greatly reduced, the optimized solid-phase sintering process ensures that the material forms a uniform and compact microscopic structure, meanwhile, the production energy consumption of the material is effectively reduced, and the production cost is reduced. The key performance of the prepared CuCr25 contact material completely meets the application standard of low-voltage electrical appliances, the conductivity and strength are perfectly balanced, the product advantages of low cost and high performance are constructed, the green manufacturing concept is reflected through waste recycling, and collaborative improvement of economic benefits and product performance is effectively achieved.

Description

Technical Field

[0001] This invention relates to the field of electrical material preparation technology, and in particular to a method for preparing a low-cost CuCr25 contact material. Background Technology

[0002] This invention relates to a high-performance CuCr25 alloy bulk contact material, and more specifically, to a CuCr25 alloy bulk material for high-power vacuum circuit breaker contacts and its preparation method. CuCr25 alloy contacts have advantages such as high breaking current capacity, high voltage resistance, and low arc burn-off rate. They are currently widely used in the manufacture of high-power vacuum circuit breakers both domestically and internationally, and are key components that play a decisive role in the performance of the switches.

[0003] However, while existing pre-alloyed powder mixing and sintering methods can produce high-performance CuCr contacts, the pre-alloyed powders are usually prepared by atomization, which is costly and results in expensive final products with low cost-effectiveness. Traditional mechanical powder mixing methods are cheaper, but they are prone to component segregation due to large differences in the density of chromium and copper, resulting in poor microstructure uniformity and coarsening of chromium particles, which affects the electrical performance and service life of the contacts. In order to reduce costs, the industry has tried to reduce the chromium content or use cheap raw materials, but this often comes at the cost of sacrificing key performance characteristics. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a low-cost method for preparing CuCr25 contact material.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: a method for preparing low-cost CuCr25 contact material, comprising the following steps: S1, CuCr25 contact raw material preparation and weighing: according to the proportioning requirements, copper powder, chromium powder and recycled powder are weighed and prepared using an electronic scale, wherein the recycled powder is derived from processing waste of contact material of the same composition;

[0006] S2, CuCr25 contact material mixing treatment: Weighed copper powder, chromium powder and a predetermined proportion of recycled powder are fully mixed under a protective atmosphere to form a mixed powder. The proportion of chromium powder ensures that the chromium content in the mixed powder is within the standard composition range of CuCr25.

[0007] S3, CuCr25 contact raw material pressing molding: The mixed powder of copper powder, chromium powder and recycled powder is pressed into a green blank.

[0008] S4. Green sintering: The green blank is vacuum sintered. Vacuum sintering is carried out in a specific temperature range below the melting point of copper and held for a period of time to obtain a dense sintered body.

[0009] S5 and CuCr25 contact processing and preparation: The sintered body is machined to transform the roughly shaped and sized sintered blank into CuCr25 contact material that meets the requirements of the product drawings.

[0010] S6. CuCr25 contact cleaning inspection: Remove micro-burrs and metal shavings generated on the edge of the processed CuCr25 contact material during machining. Then, use ultrasonic cleaning to clean the CuCr25 contact material. After cleaning, the CuCr25 contact material is inspected for compliance.

[0011] In a preferred embodiment, in step S1, the copper powder is water-atomized copper powder, the chromium powder is chromium powder produced by the aluminothermic reduction method, and the recycled powder originates from solid waste generated during the preparation of CuCr25 contact material with the same composition as the target product. The solid waste includes, but is not limited to, waste blanks generated during the pressing and molding stage, waste chips generated during the mechanical processing stage after sintering, and grinding powder. The recycled powder is collected, cleaned, crushed, and screened to obtain a particle size distribution suitable for mixing and pressing.

[0012] In a preferred embodiment, the specific steps of S2 are as follows:

[0013] S2.1 Preliminary mixing: First, all the recycled powder produced from the processing waste of the contact material is mixed with some copper powder to form a premixed powder;

[0014] S2.2, Complete Mixing: Place the premixed powder obtained in step S2.1 together with the remaining copper powder and all the chromium powder in a mixing device, and then continuously introduce a protective atmosphere into the mixing device to ensure sufficient mixing time until a uniformly mixed powder is obtained.

[0015] As a preferred embodiment, the mixing process in step S2.2 is as follows: all the premixed powder is loaded into the mixer, the mixing tank is sealed, a vacuum is first drawn, and then high-purity nitrogen or argon is introduced. The atmosphere replacement is repeated several times to ensure that the mixing tank is in an oxygen-free state. Under the protective atmosphere, the mixer is started and run for several hours. Through the violent tumbling and diffusion of the powder in three-dimensional space, uniform mixing is achieved.

[0016] In a preferred embodiment, the specific steps of S3 are as follows:

[0017] S3.1 Mold preparation and powder loading: Load the mixed powder obtained in step S2 into the cavity of the pressing mold that has been cleaned and lubricated.

[0018] S3.2 Initial venting: Apply an initial pre-pressure to the powder in the mold cavity, and then perform a depressurization operation to achieve the first venting and break the bridging effect between powder particles;

[0019] S3.3, Mold main pressing: After the initial venting is completed, a higher main pressing pressure is applied to the mold. The main pressing pressure can cause the powder particles to undergo plastic deformation and tightly bond together, and maintain the pressure for a certain period of time.

[0020] S3.4 Depressurization and Demolding: After pressing is completed, the main pressing pressure on the mold is slowly released, and then the pressed blank is removed from the mold to obtain a green blank with a predetermined shape, size and sufficient mechanical strength.

[0021] As a preferred embodiment, the pressing process in step S3.3 is as follows: the powder is bidirectionally pressed by the upper and lower punches under a set high pressure, causing the mixed powder particles to shift and plastically deform, and tightly bonded by mechanical meshing and cold welding, thereby forming a green blank with a predetermined shape, appropriate strength and density.

[0022] In a preferred embodiment, the specific steps of S4 are as follows:

[0023] S4.1 Loading and Pre-vacuuming: Place the green billets into the vacuum sintering furnace, seal the furnace body, and perform the initial stage of vacuuming to reduce the pressure inside the furnace to a basic high vacuum level.

[0024] S4.2, Staged heating and degassing: Start the heating program, first raise the furnace temperature to an intermediate temperature range at the first heating rate, and keep it in this range to fully remove the gas, moisture and volatile substances adsorbed in the green billet;

[0025] S4.3 High-temperature sintering: After degassing, the furnace temperature is raised to the final sintering temperature below the melting point of copper at the second heating rate, and held for a period of time to allow the powder particles to achieve full metallurgical bonding and densification through the solid-phase atomic diffusion mechanism.

[0026] S4.4 Cooling of sintered body: After the heat preservation is completed, heating is stopped, and the sintered body is cooled to room temperature under a controlled vacuum or a protective atmosphere to obtain a sintered body with uniform and dense microstructure.

[0027] As a preferred embodiment, the specific steps of S5 are as follows:

[0028] S5.1 Establishment of reference planes: Perform initial processing on the sintered billet to prepare one or more reference planes or reference holes on the sintered billet for subsequent precise positioning;

[0029] S5.2 Preliminary forming process: Using the reference plane or reference hole of the sintered blank as the positioning basis, the sintered blank is rough machined to remove most of the machining allowance, so that the outline size of the sintered blank is close to the final size of the product.

[0030] S5.3 Precision machining: Based on the pre-formed sintered blank, the key areas that constitute the working surface of the contact are precision machined to obtain contact material with precise geometric shape, dimensional tolerance and specific surface roughness that meet the requirements of the product drawings.

[0031] S5.4 Functional Structure Machining: Based on the product design, non-working surface functional structures for assembly, positioning, or flow guidance are machined on the contact material.

[0032] In a preferred embodiment, the specific steps of S6 are as follows:

[0033] S6.1 Edge finishing and deburring: Finishing the edges and end faces of the contact material after machining to remove burrs and metal flash generated during machining.

[0034] S6.2 Ultrasonic cleaning: The deburred contact material is placed in an ultrasonic cleaning device and cleaned with a cleaning medium for at least one cycle of ultrasonic oscillation to remove fine particles, oil and fingerprint contaminants adhering to the surface of the contact material.

[0035] S6.3 Drying treatment: Dry the cleaned contact material to ensure that there is no residual cleaning medium or moisture on the surface and inside of the contact material;

[0036] S6.4 Finished Product Inspection: The dried contact material is subjected to a comprehensive inspection of its dimensions, surface morphology, and cleanliness. If it passes the inspection, a low-cost CuCr25 contact material is obtained.

[0037] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0038] This invention utilizes water-atomized copper powder and aluminothermic chromium powder as main raw materials, and innovatively adds a certain amount of recycled powder, successfully achieving a significant reduction in raw material costs. Moreover, the optimized solid-state sintering process ensures the formation of a uniform and dense microstructure while effectively reducing the energy consumption of material production. The key performance of the prepared CuCr25 contact material fully meets the standards for low-voltage electrical applications, perfectly balancing conductivity and strength. This not only creates a low-cost, high-performance product advantage, but also embodies the concept of green manufacturing through waste recycling, effectively achieving a synergistic improvement in economic benefits and product performance. Attached Figure Description

[0039] Figure 1This is a schematic diagram of the process structure for preparing a low-cost CuCr25 contact material provided by the present invention.

[0040] Figure 2 A schematic diagram illustrating the specific process structure of a low-cost CuCr25 contact material preparation method provided by the present invention. Detailed Implementation

[0041] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0042] Example 1

[0043] like Figure 1-2 As shown, the present invention provides a technical solution: a method for preparing a low-cost CuCr25 contact material, comprising the following steps:

[0044] S1, CuCr25 contact raw material preparation and weighing: According to the mixing ratio requirements, use an electronic scale to weigh copper powder, chromium powder and recycled powder. The recycled powder comes from the processing waste of the same composition of contact material.

[0045] S2, CuCr25 contact material mixing treatment: Weighed copper powder, chromium powder and a predetermined proportion of recycled powder are fully mixed under a protective atmosphere to form a mixed powder. The proportion of chromium powder ensures that the chromium content in the mixed powder is within the standard composition range of CuCr25.

[0046] S3, CuCr25 contact raw material pressing molding: The mixed powder of copper powder, chromium powder and recycled powder is pressed into a green blank.

[0047] S4. Green sintering: The green blank is vacuum sintered. Vacuum sintering is carried out in a specific temperature range below the melting point of copper and held for a period of time to obtain a dense sintered body.

[0048] S5 and CuCr25 contact processing and preparation: The sintered body is machined to transform the roughly shaped and sized sintered blank into CuCr25 contact material that meets the requirements of the product drawings.

[0049] S6. CuCr25 contact cleaning inspection: Remove micro-burrs and metal chips generated on the edge of the processed CuCr25 contact material during the machining process, and then use ultrasonic cleaning to clean the CuCr25 contact material. After cleaning, the CuCr25 contact material is inspected for compliance.

[0050] In step S1, the copper powder is water-atomized copper powder, the chromium powder is chromium powder produced by the aluminothermic reduction method, and the recycled powder originates from solid waste generated during the preparation of CuCr25 contact material with the same composition as the target product. The solid waste includes, but is not limited to, waste blanks generated during the pressing and molding stage, waste chips generated during the mechanical processing stage after sintering, and grinding powder. The recycled powder is collected, cleaned, crushed, and screened to obtain a particle size distribution suitable for mixing and pressing.

[0051] In the above, by selecting water-atomized copper powder and chromium powder produced by aluminothermic reduction as raw materials, and combining the recycling of recycled powder, the water-atomized copper powder has regular particle shape and good flowability, which is conducive to achieving uniform filling and densification during mixing and pressing. The chromium powder produced by aluminothermic reduction has high purity and good sintering activity, which can promote solid-phase diffusion and metallurgical bonding during the sintering stage. The recycled powder comes from solid waste of CuCr25 contact material of the same composition. After the solid waste is collected, cleaned, crushed and screened, recycled powder with controllable particle size distribution is obtained, which significantly reduces the cost of raw materials. By recycling waste, resource waste and environmental burden are reduced. At the same time, the uniformity of mixed powder and green strength are ensured, which provides a basis for the subsequent mixing in step S2, pressing in step S3 and sintering in step S4. It avoids pressing defects or uneven sintering caused by powder particle size mismatch, thereby improving production efficiency and product consistency.

[0052] The specific steps of S2 are as follows:

[0053] S2.1 Preliminary mixing: First, all the recycled powder produced from the processing waste of the contact material is mixed with some copper powder to form a premixed powder;

[0054] S2.2, Complete Mixing: Place the premixed powder obtained in step S2.1 together with the remaining copper powder and all the chromium powder in a mixing device, and then continuously introduce a protective atmosphere into the mixing device to ensure sufficient mixing time until a uniformly mixed powder is obtained.

[0055] In the above process, in S2.1 preliminary mixing, all the recycled powder is first premixed with some copper powder. This utilizes the good plasticity and small particle size of copper powder to coat and disperse recycled powder particles that may agglomerate or have irregular shapes due to the recycling process, thus laying the foundation for subsequent uniform mixing. Then, in S2.2 complete mixing, the premixed powder is thoroughly mixed with the remaining copper powder and all the chromium powder in a mixing device. During mixing, a protective atmosphere is continuously introduced into the device. The protective atmosphere can effectively prevent the chromium powder from being oxidized during the mixing process, thereby ensuring the chemical purity and performance of the final sintered material. By mixing for a long time in a protective environment, the uniform distribution of copper, chromium and recycled powder can be achieved, significantly improving the compositional uniformity of the mixed powder. At the same time, due to the uniform incorporation of recycled powder, the raw material cost is effectively reduced.

[0056] The mixing process in step S2.2 is as follows: all the premixed powder is loaded into the mixer, the mixing tank is sealed, a vacuum is first drawn, and then high-purity nitrogen or argon is filled in. The atmosphere replacement is repeated several times to ensure that the mixing tank is in an oxygen-free state. Under the protective atmosphere, the mixer is started and run for several hours. Through the violent tumbling and diffusion of the powder in three-dimensional space, uniform mixing is achieved.

[0057] The specific steps of S3 are as follows:

[0058] S3.1 Mold preparation and powder loading: Load the mixed powder obtained in step S2 into the cavity of the pressing mold that has been cleaned and lubricated.

[0059] S3.2 Initial venting: Apply an initial pre-pressure to the powder in the mold cavity, and then perform a depressurization operation to achieve the first venting and break the bridging effect between powder particles;

[0060] S3.3, Mold main pressing: After the initial venting is completed, a higher main pressing pressure is applied to the mold. The main pressing pressure can cause the powder particles to undergo plastic deformation and tightly bond together, and maintain the pressure for a certain period of time.

[0061] S3.4, Pressure Relief and Demolding: After pressing is completed, the main pressing pressure on the mold is slowly released, and then the pressed blank is removed from the mold to obtain a green blank with a predetermined shape, size and sufficient mechanical strength.

[0062] In the above process, S3.1, surface cleaning and lubrication of the mold cavity effectively reduces friction between the powder and the mold wall and prevents contamination, ensuring that the powder can smoothly and evenly fill the cavity and creating favorable conditions for subsequent demolding. S3.2, the initial venting, involves applying an initial pre-pressure followed by depressurization to expel gas trapped between powder particles and effectively disrupt bridging caused by mutual support, thus preventing the formation of pores or delamination within the green body. S3.3, the main mold pressing, effectively applies a pressure much higher than the pre-pressure. The pressure causes significant plastic deformation of the powder particles, and they achieve a tight bond through mechanical interlocking and cold welding. At the same time, the high pressure is maintained for a period of time to ensure stress relaxation and stability of the particle bonding state, thereby obtaining a high-density and high-strength green body. Finally, in S3.4, the pressure is released and the mold is demolded. The main pressing pressure can be released slowly to avoid cracking of the green body due to drastic stress changes, and the formed green body is completely removed from the mold. Thus, a green body with a predetermined geometry, precise size, relatively uniform and dense internal structure and sufficient mechanical strength to withstand the subsequent handling and sintering process is successfully prepared.

[0063] The pressing process in step S3.3 is as follows: the powder is pressed bidirectionally by the upper and lower punches under a set high pressure, causing the mixed powder particles to shift and plastically deform. Through mechanical meshing and cold welding, they are tightly combined to form a green blank with a predetermined shape, appropriate strength and density.

[0064] The specific steps of S4 are as follows:

[0065] S4.1 Loading and Pre-vacuuming: Place the green billets into the vacuum sintering furnace, seal the furnace body, and perform the initial stage of vacuuming to reduce the pressure inside the furnace to a basic high vacuum level.

[0066] S4.2, Staged heating and degassing: Start the heating program, first raise the furnace temperature to an intermediate temperature range at the first heating rate, and keep it in this range to fully remove the gas, moisture and volatile substances adsorbed in the green billet;

[0067] S4.3 High-temperature sintering: After degassing, the furnace temperature is raised to the final sintering temperature below the melting point of copper at the second heating rate, and held for a period of time to allow the powder particles to achieve full metallurgical bonding and densification through the solid-phase atomic diffusion mechanism.

[0068] S4.4 Cooling of sintered body: After the heat preservation is completed, heating is stopped, and the sintered body is cooled to room temperature under a controlled vacuum or a protective atmosphere to obtain a sintered body with uniform and dense microstructure.

[0069] In the above process, by placing the green billet in a vacuum sintering furnace and pre-evacuating it to reduce the furnace pressure to a basic high vacuum level, active gases such as oxygen in the furnace and on the surface of the green billet can be removed to the maximum extent before heating. This creates an oxygen-free inert environment, preventing the oxidation of copper and chromium powder particles during subsequent high-temperature sintering. This avoids the formation of oxide impurities that could damage the conductivity and mechanical properties of the material, thus laying a pure atmosphere for high-quality metallurgical reactions in the subsequent sintering process. The staged heating and degassing in step S4.2 first raises the temperature to an intermediate temperature at a first heating rate and holds it there, allowing sufficient time for the gases, moisture, and volatile substances introduced during the process to slowly and completely escape from the interior of the green billet. Instead of cracking or creating pores in the green body due to rapid vaporization during rapid heating, the high-temperature sintering in step S4.3 first involves holding the green body at a sintering temperature below the melting point of copper for an extended period of time. This allows the atoms at the contact points of the powder particles to gain sufficient kinetic energy. Then, through the solid-phase atomic diffusion mechanism, they migrate across the interface to achieve metallurgical bonding between the particles. This is accompanied by material migration and pore shrinkage, transforming the originally mechanically bonded green powder into a dense sintered body with strong metallurgical bonding, high density, and high strength. At the same time, it ensures the uniform distribution of the chromium and copper phases, thereby maintaining the electrical properties required for the CuCr25 material. The cooling of the sintered body in step S4.4, by controlling the cooling rate to room temperature under a continuous protective atmosphere, can effectively avoid thermal stress and microcracks caused by excessive internal and external temperature differences.

[0070] In this embodiment, the raw materials are first prepared and compounded. Water atomized copper powder and aluminothermic chromium powder, which have lower costs, are selected as the main raw materials. Then, recycled powder of the same composition, which has been pretreated by cleaning, crushing and screening, is mixed in. The copper powder, chromium powder and recycled powder are accurately weighed according to the CuCr25 composition requirements and predetermined ratio. Then, the prepared powder is poured into a mixing device and fully mixed under the protection of inert gas, so as to achieve a macroscopic and microscopic uniform distribution of copper, chromium and recycled powder particles, forming a composite powder with uniform composition, and effectively preventing powder oxidation, thus obtaining a homogeneous product.

[0071] After mixing, the powder is densified and shaped. The uniformly mixed composite powder is loaded into the cavity of a precision mold and then pressed under high pressure. This causes the powder particles to shift, rearrange, and plastically deform. Then, through mechanical meshing and van der Waals forces, they are tightly combined to eliminate most of the pores, thereby forming a green body with a predetermined geometric shape, a certain mechanical strength, and density.

[0072] After pressing, the green body is placed in a sintering furnace, and the furnace temperature is raised to the medium and low temperature range at a gradual heating rate and then kept at the temperature for a sufficient period of time. This allows for the complete removal of water vapor, gas and organic impurities adsorbed on the surface of the mixed powder particles without causing significant shrinkage, thus purifying the particle surface and creating a clean interface for subsequent atomic diffusion. At the same time, it also initially establishes weak connections between particles, thereby improving the strength of the green body.

[0073] The temperature is then raised to a high-temperature range below the melting point of copper but sufficient to activate significant diffusion of chromium atoms, and held at this temperature for an extended period. This allows copper and chromium atoms to gain sufficient kinetic energy, which then diffuses across the particle boundaries via lattice diffusion. Mass migration occurs at the contact points, causing the sintering neck to coarsen continuously. The migration of matter towards the neck leads to a decrease in the center-to-center distance between particles, resulting in overall linear shrinkage of the green body. This gradually closes the interconnected irregular pores, significantly reducing the overall porosity and greatly increasing the material density. Ultimately, a strong metallurgical bond is formed between the mixed powder particles, establishing a continuous electrical conductivity pathway and mechanical strength framework, thus laying the foundation for the material's high conductivity and high hardness.

[0074] Example 2

[0075] like Figure 1-2 As shown, the specific steps of S5 are as follows:

[0076] S5.1 Establishment of reference planes: Perform initial processing on the sintered billet to prepare one or more reference planes or reference holes on the sintered billet for subsequent precise positioning;

[0077] S5.2 Preliminary forming process: Using the reference plane or reference hole of the sintered blank as the positioning basis, the sintered blank is rough machined to remove most of the machining allowance, so that the outline size of the sintered blank is close to the final size of the product.

[0078] S5.3 Precision machining: Based on the pre-formed sintered blank, the key areas that constitute the working surface of the contact are precision machined to obtain contact material with precise geometric shape, dimensional tolerance and specific surface roughness that meet the requirements of the product drawings.

[0079] S5.4 Functional structure processing: Based on the product design, non-working surface functional structures for assembly, positioning or flow guidance are processed on the contact material;

[0080] In the above, by machining a reference plane or reference hole on the sintered billet, precise geometric reference points can be provided for subsequent processes, thereby ensuring the consistency and repeatability of positioning, effectively reducing the cumulative error in the machining process, and improving the overall dimensional accuracy and machining reliability. S5.2 Preliminary forming machining is based on the reference established in S5.1 for rough machining, which can effectively utilize the reference positioning to remove most of the machining allowance, thereby achieving efficient material cutting to quickly bring the billet contour dimensions close to the final product requirements, optimizing time efficiency and resource utilization for subsequent finishing machining. S5.3 Precision machining targets the key areas of the contact working surface for finishing. High-precision cutting processes can control the geometry, dimensional tolerances, and surface roughness, thereby ensuring that the contact material meets strict performance standards, thereby improving electrical contact characteristics, reducing arc erosion, and extending service life. S5.4 Functional structures are added to the non-working surface during machining according to the product design, such as assembly, positioning, or flow guiding structures, which effectively enhance the practicality and adaptability of the contact material, facilitate installation, improve system stability, and optimize fluid dynamics performance, thereby improving the overall quality and economy of the product.

[0081] The specific steps of S6 are as follows:

[0082] S6.1 Edge finishing and deburring: Finishing the edges and end faces of the contact material after machining to remove burrs and metal flash generated during machining.

[0083] S6.2 Ultrasonic cleaning: The deburred contact material is placed in an ultrasonic cleaning device and cleaned with a cleaning medium for at least one cycle of ultrasonic oscillation to remove fine particles, oil and fingerprint contaminants adhering to the surface of the contact material.

[0084] S6.3 Drying treatment: Dry the cleaned contact material to ensure that there is no residual cleaning medium or moisture on the surface and inside of the contact material;

[0085] S6.4 Finished Product Inspection: The dried contact material is subjected to a comprehensive inspection of its dimensions, surface morphology and cleanliness. If it passes the inspection, a low-cost CuCr25 contact material is obtained.

[0086] The above process involves removing burrs and metal flash formed on the edges and end faces of the contact material during machining through mechanical finishing. This prevents burrs and metal flash from causing arcing, short circuits, or accelerated wear during actual use, thus improving contact surface integrity, reducing failure risks, and extending service life. Next, in the S6.2 ultrasonic cleaning step, ultrasonic oscillation generates a high-frequency cavitation effect in the cleaning medium. The impact force of the bursting microbubbles removes fine particles, oil, and fingerprint contaminants adhering to the contact material surface, achieving a high degree of cleanliness and preventing contaminants from affecting electrical contact performance and reliability. The subsequent S6.3 drying process uses vacuum drying to evaporate and remove residual media and moisture from the cleaning process. This effectively eliminates moisture from the material surface and potential pores, thus preventing material oxidation, corrosion, or electrical short circuits. It ensures that there are no residues inside or outside the contact material, guaranteeing its long-term stability and performance. Finally, the S6.4 finished product inspection process uses measuring tools and visual inspection to comprehensively verify the dimensional accuracy, surface morphology flatness, and cleanliness of the contact material. This process monitors the quality of the obtained material, selects qualified products, and ensures that the low-cost CuCr25 contact material ultimately meets the design requirements and application specifications.

[0087] In this embodiment, after sintering, the sintered body is precision machined to ensure that the dimensional accuracy, geometric tolerances and surface finish of the working surface of the sintered body meet the requirements of the drawings, thereby ensuring the precise assembly of the contacts and electrical components. Then, the sintered body is placed in a finishing mold and pressure is applied to the sintered body for cold re-pressing, thereby further closing residual micropores and correcting minor deformations, effectively improving the consistency of product dimensions and surface quality. Finally, the precision machined CuCr25 contact working surface is firmly metallurgically bonded to the highly conductive copper or copper alloy back conductor through electron beam welding, ensuring the material has excellent breaking performance.

[0088] Finally, the obtained CuCr25 contact material is inspected. Once the inspection is passed, the required low-cost CuCr25 contact material can be obtained.

[0089] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a low-cost CuCr25 contact material, characterized in that, Includes the following steps: S1, CuCr25 contact raw material preparation and weighing: According to the mixing ratio requirements, use an electronic scale to weigh copper powder, chromium powder and recycled powder. The recycled powder comes from the processing waste of the same composition of contact material. S2, CuCr25 contact material mixing treatment: Weighed copper powder, chromium powder and a predetermined proportion of recycled powder are fully mixed under a protective atmosphere to form a mixed powder. The proportion of chromium powder ensures that the chromium content in the mixed powder is within the standard composition range of CuCr25. S3, CuCr25 contact raw material pressing molding: The mixed powder of copper powder, chromium powder and recycled powder is pressed into a green blank. S4. Green sintering: The green blank is vacuum sintered. Vacuum sintering is carried out in a specific temperature range below the melting point of copper and held for a period of time to obtain a dense sintered body. S5 and CuCr25 contact processing and preparation: The sintered body is machined to transform the roughly shaped and sized sintered blank into CuCr25 contact material that meets the requirements of the product drawings. S6. CuCr25 contact cleaning inspection: Remove micro-burrs and metal shavings generated on the edge of the processed CuCr25 contact material during machining. Then, use ultrasonic cleaning to clean the CuCr25 contact material. After cleaning, the CuCr25 contact material is inspected for compliance.

2. The method for preparing a low-cost CuCr25 contact material according to claim 1, characterized in that, In step S1, the copper powder is water-atomized copper powder, the chromium powder is chromium powder produced by the aluminothermic reduction method, and the recycled powder originates from solid waste generated during the preparation of CuCr25 contact material with the same composition as the target product. The solid waste includes, but is not limited to, waste blanks generated during the pressing and molding stage, waste chips generated during the mechanical processing stage after sintering, and grinding powder. The recycled powder is collected, cleaned, crushed, and screened to obtain a particle size distribution suitable for mixing and pressing.

3. The method for preparing a low-cost CuCr25 contact material according to claim 1, characterized in that, The specific steps of S2 are as follows: S2.1 Preliminary mixing: First, all the recycled powder produced from the processing waste of the contact material is mixed with some copper powder to form a premixed powder; S2.2, Complete Mixing: Place the premixed powder obtained in step S2.1 together with the remaining copper powder and all the chromium powder in a mixing device, and then continuously introduce a protective atmosphere into the mixing device to ensure sufficient mixing time until a uniformly mixed powder is obtained.

4. The method for preparing a low-cost CuCr25 contact material according to claim 1, characterized in that, The mixing process in step S2.2 is as follows: all the premixed powder is loaded into the mixer, the mixing tank is sealed, a vacuum is first drawn, and then high-purity nitrogen or argon is introduced. The atmosphere replacement is repeated several times to ensure that the mixing tank is in an oxygen-free state. Under the protective atmosphere, the mixer is started and run for several hours. Through the violent tumbling and diffusion of the powder in three-dimensional space, uniform mixing is achieved.

5. A method for preparing a low-cost CuCr25 contact material according to claim 1, characterized in that, The specific steps of S3 are as follows: S3.1 Mold preparation and powder loading: Load the mixed powder obtained in step S2 into the cavity of the pressing mold that has been cleaned and lubricated. S3.2 Initial venting: Apply an initial pre-pressure to the powder in the mold cavity, and then perform a depressurization operation to achieve the first venting and break the bridging effect between powder particles; S3.3, Mold main pressing: After the initial venting is completed, a higher main pressing pressure is applied to the mold. The main pressing pressure can cause the powder particles to undergo plastic deformation and tightly bond together, and maintain the pressure for a certain period of time. S3.4 Depressurization and Demolding: After pressing is completed, the main pressing pressure on the mold is slowly released, and then the pressed blank is removed from the mold to obtain a green blank with a predetermined shape, size and sufficient mechanical strength.

6. The method for preparing a low-cost CuCr25 contact material according to claim 1, characterized in that, The pressing process in step S3.3 is as follows: the powder is pressed bidirectionally by the upper and lower punches under a set high pressure, causing the mixed powder particles to shift and plastically deform. Through mechanical meshing and cold welding, they are tightly combined to form a green blank with a predetermined shape, appropriate strength and density.

7. The method for preparing a low-cost CuCr25 contact material according to claim 1, characterized in that, The specific steps of S4 are as follows: S4.1 Loading and Pre-vacuuming: Place the green billets into the vacuum sintering furnace, seal the furnace body, and perform the initial stage of vacuuming to reduce the pressure inside the furnace to a basic high vacuum level. S4.2, Staged heating and degassing: Start the heating program, first raise the furnace temperature to an intermediate temperature range at the first heating rate, and keep it in this range to fully remove the gas, moisture and volatile substances adsorbed in the green billet; S4.3 High-temperature sintering: After degassing, the furnace temperature is raised to the final sintering temperature below the melting point of copper at the second heating rate, and held for a period of time to allow the powder particles to achieve full metallurgical bonding and densification through the solid-phase atomic diffusion mechanism. S4.4 Cooling of sintered body: After the heat preservation is completed, heating is stopped, and the sintered body is cooled to room temperature under a controlled vacuum or a protective atmosphere to obtain a sintered body with uniform and dense microstructure.

8. The method for preparing a low-cost CuCr25 contact material according to claim 1, characterized in that, The specific steps of S5 are as follows: S5.1 Establishment of reference planes: Perform initial processing on the sintered billet to prepare one or more reference planes or reference holes on the sintered billet for subsequent precise positioning; S5.2 Preliminary forming process: Using the reference plane or reference hole of the sintered blank as the positioning basis, the sintered blank is rough machined to remove most of the machining allowance, so that the outline size of the sintered blank is close to the final size of the product. S5.3 Precision machining: Based on the pre-formed sintered blank, the key areas that constitute the working surface of the contact are precision machined to obtain contact material with precise geometric shape, dimensional tolerance and specific surface roughness that meet the requirements of the product drawings. S5.4 Functional Structure Machining: Based on the product design, non-working surface functional structures for assembly, positioning, or flow guidance are machined on the contact material.

9. The method for preparing a low-cost CuCr25 contact material according to claim 1, characterized in that, The specific steps of S6 are as follows: S6.1 Edge finishing and deburring: Finishing the edges and end faces of the contact material after machining to remove burrs and metal flash generated during machining. S6.2 Ultrasonic cleaning: The deburred contact material is placed in an ultrasonic cleaning device and cleaned with a cleaning medium for at least one cycle of ultrasonic oscillation to remove fine particles, oil and fingerprint contaminants adhering to the surface of the contact material. S6.3 Drying treatment: Dry the cleaned contact material to ensure that there is no residual cleaning medium or moisture on the surface and inside of the contact material; S6.4 Finished Product Inspection: The dried contact material is subjected to a comprehensive inspection of its dimensions, surface morphology, and cleanliness. If it passes the inspection, a low-cost CuCr25 contact material is obtained.

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