CuCr contact and preparation method thereof

Abstract

The invention discloses a CuCr contact and a preparation method thereof, and belongs to the field of alloy contact manufacturing, the CuCr contact is divided into an arc contact area, a transition area and a conductive connection area, and the Cr content of each area is in gradient distribution and is sequentially reduced, so that interface stress concentration can be avoided, and the structural compatibility and mechanical reliability of the whole contact are improved; meanwhile, integrated forming is achieved through the 3D printing technology, the size and the component boundary of each area can be accurately controlled, the complex structure design requirement of the contact is met, and the problems that in the prior art, performance gradient cannot be achieved according to the function requirements of different parts of the contact, and the material utilization rate is low are solved; the printed contact does not have the phenomena of composition segregation, agglomeration, uneven pores and the like, and the problems that in the prior art, Cr elements are difficult to distribute uniformly in a Cu matrix, Cr particles are prone to segregation and agglomeration, local ablation resistance is insufficient, and burning resistance is low are solved.

Description

Technical Field

[0001] This invention relates to the field of alloy contact manufacturing, and more particularly to a CuCr contact and its preparation method. Background Technology

[0002] Chromium-copper alloy (CuCr) is widely used in welding, electrical and other fields due to its good electrical conductivity, thermal conductivity, wear resistance and ablation resistance. For example, it is used to manufacture switch contacts, which can effectively break and connect circuits.

[0003] Existing processes for preparing CuCr contacts mainly include arc melting, melt infiltration, or solid-state sintering. However, the resulting CuCr contacts often exhibit uneven Cr distribution within the Cu matrix, leading to Cr particle segregation and agglomeration. This results in insufficient localized ablation resistance and low anti-burning performance. Furthermore, existing processes cannot achieve performance gradients tailored to the functional requirements of different contact areas, and material utilization is low. Summary of the Invention

[0004] The main objective of this invention is to provide a CuCr contact and its preparation method, aiming to solve the problems in the prior art where the Cr element in the CuCr contact is difficult to distribute uniformly in the Cu matrix, and Cr particles are prone to segregation and agglomeration, resulting in insufficient local ablation resistance and low anti-burning performance of the contact, as well as the inability to achieve performance gradient according to the functional requirements of different parts of the contact and low material utilization.

[0005] To achieve the above objectives, the present invention provides a method for preparing a CuCr contact, wherein the CuCr contact sequentially comprises an arc contact region, a transition region, and a conductive connection region; the preparation method includes: A first mixed powder, a second mixed powder, and a third mixed powder are prepared in a uniform manner. Each mixed powder includes Cu powder and Cr powder. The Cr content in the first mixed powder is greater than the Cr content in the second mixed powder, and the Cr content in the second mixed powder is greater than the Cr content in the third mixed powder. Using 3D printing equipment, under preset printing conditions, the arc contact area is printed based on the first mixed powder; the transition area is printed based on the second mixed powder; and the conductive connection area is printed based on the third mixed powder, to obtain a CuCr contact green body. The CuCr contact green body was subjected to degreasing and vacuum sintering treatment in sequence to obtain CuCr contact green body; The CuCr contact blank is subjected to vacuum heat treatment to obtain the CuCr contact.

[0006] Optionally, the second mixed powder comprises mixed powders with different proportions of multiple components; The printing of the transition zone based on the second mixed powder includes: Based on the direction from the arc contact area to the conductive connection area, and in descending order of Cr content, the transition area is printed using mixed powders with different proportions of multi-components.

[0007] Optionally, the Cr content of the arc contact area is 20% to 60%, the Cr content of the transition area is 5% to 40%, and the Cr content of the conductive connection area is 5% to 20%.

[0008] Optionally, the first mixed powder further includes rare earth elements, and the third mixed powder further includes Ag elements. The content of rare earth elements in the first mixed powder is 0.5%~1.0%, and the particle size is 1μm~3μm. The content of Ag elements in the third mixed powder is 0.3%~0.5%, and the particle size is 5μm~10μm.

[0009] Optionally, the preset printing conditions include: The binder used in 3D printing is a modified phenolic resin-based binder with a solid content of 50%~55% and a jetting volume of 0.05mL / g~0.1mL / g; The thickness of the slice in the arc contact area is 50μm~80μm, the powder spreading pressure is 0.8MPa~1.0MPa, and the platform temperature is 150℃~200℃; The slice thickness in the transition zone is 90μm~140μm, the powder spreading pressure is 0.6MPa~0.8MPa, and the platform temperature is 100℃~140℃. The thickness of the conductive connection region slice is 150μm~200μm, the powder spreading pressure is 0.5MPa~0.7MPa, and the platform temperature is 80℃~120℃.

[0010] Optionally, the degreasing treatment method includes: Under an inert gas atmosphere, the temperature is increased at a rate of 4℃ / min to 6℃ / min. When the temperature reaches 200℃ to 300℃, it is held for 1 to 2 hours. Then, the temperature is increased to 400℃ to 600℃ at a rate of 7℃ / min to 10℃ / min, and held for 2 to 4 hours.

[0011] Optionally, the vacuum sintering process includes: At a vacuum degree of 10 -3 Pa~10 -5 Under the condition of Pa, heat at a heating rate of 1℃ / min to 10℃ / min, and when the temperature reaches 600℃ to 1000℃, hold for 2h to 3h; then heat to 1050℃ to 1150℃ and hold for 2h to 6h.

[0012] Optionally, the vacuum heat treatment method includes: The arc contact area is kept at 700℃~800℃ for 1.5h~2.0h; The conductive connection area is kept at 300℃~400℃ for 1.0h~1.5h. The CuCr contact blank is subjected to isothermal quenching treatment at a cooling rate of 45℃ / min ~ 55℃ / min.

[0013] Optionally, the Cu powder has a particle size of 15 μm to 45 μm, and the Cr powder has a particle size of 20 μm to 60 μm.

[0014] To achieve the above objectives, the present invention also provides a CuCr contact, which is prepared by the above-described preparation method.

[0015] Compared with the prior art, the beneficial effects that the present invention can achieve are as follows: 1. In the technical solution of this invention, the CuCr contact sequentially includes an arc contact area, a transition area, and a conductive connection area, and the Cr content of the arc contact area, the transition area, and the conductive connection area is distributed in a gradient and decreases sequentially. This avoids the problem of interface stress concentration caused by direct bonding of each area, and improves the overall structural compatibility and mechanical reliability of the contact, reducing the risk of cracking caused by differences in thermal expansion coefficients during service. Secondly, by using 3D printing technology to achieve the integral molding of the arc contact area, the transition area, and the conductive connection area, the size and composition boundaries of each area can be precisely controlled, meeting the complex structural design requirements of the contact and solving the problems of performance gradient and low material utilization in the prior art.

[0016] 2. In the CuCr contact preparation method disclosed in this invention, under preset 3D printing conditions, the internal pores of the obtained CuCr contact green body are uniformly distributed, avoiding phenomena such as component segregation, agglomeration, and uneven pore size. Through subsequent degreasing and sintering treatments, residual pores and impurities inside the green body can be effectively removed, improving the density of the contact and further enhancing its mechanical strength and conductivity. Vacuum heat treatment then refines the grains and induces the precipitation of strengthening phases in the arc contact area, ensuring high hardness and wear resistance. Simultaneously, the conductive connection area forms a low-stress, high-conductivity microstructure, solving the problem in existing technologies where Cr elements are difficult to distribute uniformly in the Cu matrix, easily leading to Cr particle segregation and agglomeration, resulting in insufficient local ablation resistance and low burn resistance of the contact. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the process for preparing the CuCr contact of the present invention. Detailed Implementation

[0018] 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 a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] To address the problems in existing CuCr contacts where the Cr element is difficult to distribute uniformly in the Cu matrix, leading to Cr particle segregation and agglomeration, resulting in insufficient local ablation resistance, low burn resistance, and the inability to achieve performance gradients and low material utilization based on the functional requirements of different parts of the contact, this invention provides a method for preparing a CuCr contact. The CuCr contact sequentially includes an arc contact region, a transition region, and a conductive connection region, such as... Figure 1 As shown, the preparation method includes: S10. Prepare a uniformly mixed first mixed powder, a second mixed powder, and a third mixed powder, each of the mixed powders comprising Cu powder and Cr powder, wherein the Cr content in the first mixed powder is greater than the Cr content in the second mixed powder, and the Cr content in the second mixed powder is greater than the Cr content in the third mixed powder; S20. Using a 3D printing device, under preset printing conditions, the arc contact area is printed based on the first mixed powder; the transition area is printed based on the second mixed powder; and the conductive connection area is printed based on the third mixed powder to obtain a CuCr contact green body. S30. The CuCr contact green body is subjected to degreasing and vacuum sintering treatments in sequence to obtain CuCr contact green body; S40. The CuCr contact blank is subjected to vacuum heat treatment to obtain the CuCr contact; Optionally, the purity of Cu powder in the above-mentioned raw materials is greater than 99.9%, and the purity of Cr powder is greater than 99.5%.

[0020] Optionally, the method for preparing the uniformly mixed first mixed powder, second mixed powder, and third mixed powder described above can be as follows: Under an inert gas atmosphere, the grinding speed is 100 r / min to 200 r / min, and the grinding time is 30 min to 60 min. The drying temperature is 80℃~120℃, and the drying time is 2h~4h.

[0021] Optionally, when preparing the various mixed powders, the grinding equipment can be a planetary ball mill, the ball-to-powder ratio can be 5:1, the grinding media can be alumina balls, and the inert gas can be argon.

[0022] It should be understood that when the Cr content in the above mixed powders is distributed in a gradient, when grinding with a planetary ball mill, it is necessary to prepare mixed powders with different Cr contents according to the different Cr contents.

[0023] It should be noted that during the above-mentioned raw material preparation process, grinding at a medium-low speed of 100-200 rpm for 30-60 minutes ensures uniform dispersion of the alloy powder. This avoids excessive powder breakage or overly fine grains caused by excessively high speeds, which could lead to cold welding. After grinding, the powder will adsorb a small amount of inert gas or residual moisture. Further drying at 80-120℃ for 2-4 hours effectively removes adsorbed water and residual gas without altering the powder particle size or chemical properties, while also preventing powder agglomeration due to insufficient drying.

[0024] It should be understood that the Cr content ratio in each of the above mixed powders is determined based on the gradient distribution of Cr in the above-mentioned arc contact region, transition region and conductive connection region.

[0025] It should be understood that the aforementioned arc contact area is close to the surface of the electric arc, while the transition area and conductive connection area are close to the terminal.

[0026] In one possible implementation, the second mixed powder comprises a mixed powder with multiple components in different proportions; The printing of the transition zone based on the second mixed powder includes: Based on the direction from the arc contact area to the conductive connection area, and following the order of decreasing Cr content, the transition area is printed using mixed powders with different proportions of the multi-components.

[0027] It should be understood that the aforementioned second mixed powder includes mixed powders with different proportions of multiple components, and the Cr content exhibits a nuclear gradient distribution.

[0028] In one possible implementation, the Cu powder has a particle size of 15 μm to 45 μm, and the Cr powder has a particle size of 20 μm to 60 μm.

[0029] In one possible implementation, the first mixed powder further includes rare earth elements, and the third mixed powder further includes Ag elements. The rare earth element content in the first mixed powder is 0.5%~1.0%, and the particle size is 1μm~3μm. The Ag element content in the third mixed powder is 0.3%~0.5%, and the particle size is 5μm~10μm.

[0030] It should be understood that when the rare earth element content in the first mixed powder is 0.5%~1.0% and the particle size is 1μm~3μm; and the Ag element content in the third mixed powder is 0.3%~0.5% and the particle size is 5μm~10μm, under the condition that the arc contact area is printed based on the first mixed powder and the conductive connection area is printed based on the third mixed powder, then the rare earth element content in the arc contact area is 0.5%~1.0% and the particle size is 1μm~3μm; and the Ag element content in the conductive connection area is 0.3%~0.5% and the particle size is 5μm~10μm.

[0031] It should be understood that when the first mixed powder also includes rare earth elements and the third mixed powder also includes Ag elements, then during the preparation of the mixed powder, a mixed powder containing Cr powder, copper powder and rare earth elements can be prepared according to the content ratio of rare earth elements or Ag, as well as a mixed powder containing Cr powder, copper powder and Ag powder.

[0032] It should be noted that when the Cu powder in the above-mentioned mixed powder has a particle size of 15μm~45μm and the Cr powder has a particle size of 20μm~60μm, during the 3D printing process, defects such as pores and agglomeration in the powder layer caused by excessively large powder particle size can be avoided, thereby ensuring the surface smoothness and dimensional accuracy of the obtained green body. At the same time, the rare earth element has a particle size of 1μm~3μm, which can achieve a nano- to micron-level dispersed distribution in the CuCr matrix in the arc contact area, rather than agglomerating into large particles, making the grain refining and grain boundary purification effects of rare earth significant. In addition, when the Ag element has a particle size of 5μm~10μm, it can be uniformly dispersed in the conductive connection area, while avoiding excessive growth during sintering due to excessively small particle size, which would affect conductivity.

[0033] Optionally, the aforementioned rare earth element can be lanthanum (La) or cerium (Ce) rare earth element.

[0034] Optionally, when the above rare earth element is La or Ce, it can be La2O3 (lanthanum oxide) or CeO2 (cerium dioxide).

[0035] In one possible implementation, the above-mentioned preset printing conditions include: The adhesive is a modified phenolic resin-based adhesive with a solid content of 50%~55% and a spraying rate of 0.05mL / g~0.1mL / g; The thickness of the slice in the arc contact area is 50μm~80μm, the powder spreading pressure is 0.8MPa~1.0MPa, and the platform temperature is 150℃~200℃; The slice thickness in the transition zone is 90μm~140μm, the powder spreading pressure is 0.6MPa~0.8MPa, and the platform temperature is 100℃~140℃. The thickness of the conductive connection region slice is 150μm~200μm, the powder spreading pressure is 0.5MPa~0.7MPa, and the platform temperature is 80℃~120℃.

[0036] Alternatively, the printing equipment used for 3D printing can be a binder jetting (BJ) equipment.

[0037] Optionally, in the above-mentioned modified phenolic resin-based adhesive, the modifier can be polyvinyl butyral (PVB), and the addition amount can be 10%~15%; the modified phenolic resin-based adhesive can be composed of phenolic resin, polyvinyl butyral and ethanol solvent.

[0038] It should be noted that in the above-mentioned preset printing conditions, the solid content of the binder is 50%~55%. Within this solid content range, both the flowability and bonding strength of the binder can be balanced. If the solid content is less than 50%, insufficient bonding force will result in the green body being prone to cracking and disintegration; if the solid content is greater than 55%, the viscosity of the binder will increase, making it easy to clog the nozzle during spraying, and resulting in a higher residual carbon content after subsequent degreasing. When the spraying amount is 0.05mL / g~0.1mL / g, it matches the specific surface area of ​​each alloy powder mixture, ensuring effective bonding between powder particles without causing excessively low porosity in the green body due to excessive binder.

[0039] Under the aforementioned preset printing conditions, when the slice thickness of the arc contact area is 50μm~80μm and the powder spreading pressure is 0.8MPa~1.0MPa, it can not only improve the density and surface accuracy of the green body, but also match the high mechanical performance requirements of the arc contact area to resist arc ablation. When the platform temperature is 150℃~200℃, it can accelerate the curing of the binder, avoid warping and deformation of the green body, and ensure the molding stability of the complex structure of the arc contact area. When the slice thickness of the transition area is 90μm~140μm, the powder spreading pressure is 0.6MPa~0.8MPa, and the platform temperature is 100℃~140℃, it can avoid abrupt parameter changes between the arc contact area and the conductive connection area, reduce stress concentration inside the green body, and match the molding requirements of the Cr content gradient distribution, ensuring the continuity of the interface bonding in the transition area. When the thickness of the conductive connection area slice is 150μm~200μm, the powder spreading pressure is 0.5MPa~0.7MPa, and the platform temperature is 80℃~120℃, not only can the molding time and cost be reduced, but the low precision requirements of the conductive connection area can also be taken into account. Furthermore, the excessive curing of the adhesive can be avoided, providing good conditions for subsequent degreasing and ensuring the high conductivity of the conductive area.

[0040] Furthermore, the slice thickness in the above-mentioned technical solution is greater than the maximum powder particle size. This avoids defects such as powder-laying voids and interlayer delamination caused by large powder particles, ensuring the molding advantages of the prepared uniformly mixed powders. In addition, during the printing process, the temperature of the partitioned platform is designed differently, which allows for a lower degree of curing of the binder in the conductive connection area and a higher degree of curing in the arc contact area. In the subsequent degreasing process, a partitioned gradient degreasing effect can be achieved, that is, the binder in the conductive connection area is quickly decomposed and discharged, while the binder in the arc contact area is slowly decomposed, avoiding the problem of green body cracking and ultimately ensuring the consistency of the green body quality after degreasing in different areas.

[0041] In one possible implementation, the above-mentioned degreasing treatment method includes: Under an inert gas atmosphere, the temperature is increased at a rate of 4℃ / min to 6℃ / min. When the temperature reaches 200℃ to 300℃, it is held for 1 to 2 hours. Then, the temperature is increased to 400℃ to 600℃ at a rate of 7℃ / min to 10℃ / min, and held for 2 to 4 hours.

[0042] Alternatively, the inert gas mentioned above can be argon.

[0043] In one possible implementation, the above-described vacuum sintering process includes: At a vacuum degree of 10 -3 Pa~10 -5 Under the condition of Pa, heat at a heating rate of 1℃ / min to 10℃ / min, and when the temperature reaches 600℃ to 1000℃, hold for 2h to 3h; then heat to 1050℃ to 1150℃ and hold for 2h to 6h.

[0044] It should be noted that in the above degreasing process, the initial heating rate is 4℃ / min~6℃ / min. When the temperature reaches 200℃~300℃, it is held for 1h~2h. This method matches the initial decomposition characteristics of the modified phenolic resin-based binder. Slow heating avoids the rapid decomposition of the binder, which generates a large amount of gas and causes blistering, cracking, or delamination of the green body. In an inert gas atmosphere, decomposition products, such as small molecule organic matter, can be carried away, and the oxidation of CuCr powder can be prevented at this stage. At the same time, this stage can remove more than 80% of the binder from the green body without damaging its skeletal structure. Then, the temperature is further increased to 400℃~600℃ at 7℃ / min~10℃ / min and held for 2h~4h. This method targets the difficult-to-decompose components of the binder residue, such as crosslinked resin. At the same time, the rapid heating, shortened low-temperature residence time, and high-temperature holding ensure complete decomposition of the residual binder, avoiding the problem of carbon residue causing a decrease in contact conductivity during subsequent sintering. Ultimately, the residual binder content of the degreased green body is ≤0.5%, and the porosity can be controlled at 40%~50%, providing a uniform infiltration channel for vacuum melting and infiltration.

[0045] In the above technical solution, during vacuum sintering, the vacuum degree is 10... -3 Pa~10 -5 Under the conditions of Pa, the temperature is first increased at a rate of 1℃ / min to 10℃ / min. When the temperature reaches 600℃ to 1000℃, it is held for 2 to 3 hours to further remove adsorbed moisture, residual gases, and trace impurities that were not completely removed during degreasing from the green body. At the same time, preliminary atomic diffusion occurs on the surface of the powder particles in the green body, which improves the strength of the green body skeleton and avoids deformation of the green body in the subsequent high-temperature stage. Then, the temperature is increased to 1050℃ to 1150℃ and held for 2 to 6 hours. This temperature is close to the melting point of Cu and higher than the recrystallization temperature of Cr, which can achieve metallurgical bonding between particles. Specifically, Cu particles soften and flow, thereby filling the pores; while Cr particles are uniformly distributed in the Cu matrix, forming a stable CuCr two-phase structure. Rare earth compounds in the arc contact region, such as La2O3 and CeO2, can be dispersed at the grain boundaries, playing a pinning role to inhibit grain growth; while Ag element powder in the conductive connection region can be dissolved in the Cu matrix, improving conductivity. The final blank has a density of over 99%, and retains a gradient composition structure with high Cr content and rare earth elements in the arc contact area and low Cr content and Ag elements in the conductive area.

[0046] Furthermore, in the technical solution of this invention, during the 3D printing process, the platform temperature in the arc contact area is relatively high, ranging from 150°C to 200°C, resulting in a high degree of binder curing and making it difficult to decompose; while the platform temperature in the conductive connection area is relatively low, ranging from 80°C to 120°C, resulting in a low degree of binder curing and making it easy to decompose. During the degreasing process, by setting segmented heating rates, the decomposition difficulty of the binder in different areas can be matched, avoiding cracking of the blank caused by excessively fast or slow local decomposition.

[0047] Furthermore, during the aforementioned degreasing process, in the first stage, if the heating rate is >6℃ / min, it will cause the binder to boil violently and generate gas, leading to bubbling and cracking of the green body; if the heating rate is <4℃ / min, it will result in residual carbonization of the binder. In the second stage, if the heating rate is <7℃ / min, prolonged residence will lead to powder oxidation; if the heating rate is >10℃ / min, the residual binder will not be completely decomposed. In addition, 200℃~300℃ in the first stage and 400℃~600℃ in the second stage are two critical decomposition temperature windows for modified phenolic resin-based binders. If the temperature is below this range, the binder cannot decompose; if it is above this range, it will cause premature softening and deformation of the green body.

[0048] During vacuum sintering, if the vacuum level is <10 -3 If the vacuum level is less than 10 Pa, the vacuum degree is insufficient, making it impossible to effectively remove impurity gases and easily leading to powder oxidation; if the vacuum degree is greater than 10 Pa, the vacuum degree is insufficient. -5 Pa, on the other hand, would place strict requirements on the equipment and significantly increase costs. Within the first and second temperature ranges of 600℃~1000℃ and 1050℃~1150℃, if the first temperature range is below 600℃, impurities will not be sufficiently removed; if it is above 1000℃, it will cause premature sintering of the green body, pore closure, and hinder subsequent densification in the high-temperature section. If the second temperature range is below 1050℃, Cu particles will not soften and cannot form a metallurgical bond; if it is above 1150℃, the Cu matrix will melt, Cr particles will segregate, and the gradient composition structure will be destroyed.

[0049] In one possible implementation, the above-described vacuum heat treatment method includes: The arc contact area is kept at 700℃~800℃ for 1.5h~2h; The conductive connection area is kept at 300℃~400℃ for 1.0h~1.5h. The CuCr contact blank is subjected to isothermal quenching treatment at a cooling rate of 45℃ / min ~ 55℃ / min.

[0050] Optionally, after vacuum heat treatment, the contact blank can be surface ground and polished to remove the surface oxide layer and burrs, so that the surface roughness Ra of the contact is ≤0.8μm.

[0051] It should be understood that the above-mentioned isothermal quenching treatment of CuCr contact blanks is performed after the vacuum heat treatment of the arc contact area and the conductive connection area is completed.

[0052] Optionally, the above-mentioned vacuum heat treatment equipment can be a local induction heating device.

[0053] Optionally, when the above-mentioned vacuum heat treatment equipment is a local induction heating device, the power of the induction coil in the arc contact area can be 20kW~30kW, the power of the induction coil in the conductive connection area can be 10kW~15kW, and the transition area is kept at the same temperature as the furnace. The cooling medium for isothermal quenching can be nitrogen, the cooling rate can be 45℃ / min~55℃ / min, and the quenching termination temperature can be 150℃~200℃.

[0054] It should be noted that under the aforementioned vacuum treatment conditions, the arc contact area is held at 700℃~800℃ for 1.5h~2h. This is because the arc contact area contains high Cr content and rare earth compounds, and 700℃~800℃ falls within the recrystallization temperature range of CuCr alloys. At this temperature, the Cu matrix undergoes dynamic recrystallization, refining the grains. Simultaneously, rare earth compound particles pin the grain boundaries, inhibiting abnormal grain growth and forming a uniform fine-grained structure. The refined grains and dispersed rare earth second phase significantly improve the hardness and high-temperature stability of the arc contact area, preventing fusion welding, plastic deformation, or electrical wear under the high-temperature impact of the electric arc, thus extending the service life of the contact. The 1.5h~2h holding time ensures sufficient recrystallization without causing grain growth due to excessive holding time. If the temperature exceeds 800℃ or the time exceeds 2h, it will lead to grain coarsening, which will reduce the mechanical properties of the contact.

[0055] For the conductive connection region, holding at 300℃~400℃ for 1.0h~1.5h results in a low Cr content region with added Ag. Since 300℃~400℃ is far below its recrystallization temperature, holding at this temperature does not alter the microstructure of the Cu-Ag solid solution; it only eliminates residual internal stress generated during vacuum sintering, preventing cracking of the contacts due to stress release during service. Furthermore, this temperature range prevents Ag atoms from segregating at grain boundaries, ensuring uniform Ag dissolution within the Cu matrix, thereby maintaining high conductivity in the conductive connection region and reducing contact resistance and heat loss during current transmission.

[0056] After vacuum heat treatment of the arc contact area and conductive connection area, the CuCr contact blank is subjected to isothermal quenching at a rate of 45℃ / min to 55℃ / min. This rapidly cools the contact from the holding temperature to room temperature, suppressing the precipitation of brittle phases in the CuCr alloy while preserving a fine-grained structure and a uniform solid solution structure. This avoids grain coarsening and phase segregation caused by slow cooling. Furthermore, quenching quickly fixes the microstructure of each region of the contact, reducing interfacial stress in the transition zone and preventing cracking risks caused by differences in thermal expansion coefficients between different regions, thus ensuring the structural integrity of the contact. In isothermal quenching, if the cooling rate is below 45℃ / min, grain growth and phase precipitation cannot be effectively suppressed; if it is above 55℃ / min, excessive quenching internal stress will be generated due to rapid cooling, leading to microcracks in the contact.

[0057] To achieve the above objectives, the present invention also provides a CuCr contact, which is prepared by the above-described preparation method.

[0058] Optionally, the thickness of the arc contact area can be 2mm to 5mm, the thickness of the transition area can be 1mm to 3mm, and the thickness of the conductive connection area can be 3mm to 6mm.

[0059] In one possible implementation, the Cr content of the arc contact area is 20% to 60%, the Cr content of the transition area is 5% to 40%, and the Cr content of the conductive connection area is 5% to 20%.

[0060] It should be understood that the proportions of Cr content in the aforementioned arc contact area, transition area, and conductive connection area are calculated as mass ratios.

[0061] Optionally, the method for determining the Cr content in the arc contact area, transition area and conductive connection area can be as follows: during the preparation of the mixed powder, CuCr alloy powders with different Cr mass ratios are obtained by batch grinding using a grinding equipment, and then 3D printing is performed, so that the Cr content in the arc contact area, transition area and conductive connection area is distributed in a gradient.

[0062] Optionally, in order to achieve a gradient distribution of Cr content from the arc contact area, transition area, and conductive connection area during the 3D printing process described above, and to ensure that the Cr content gradually decreases from the arc contact area to the conductive connection area, the present invention can use a binder jetting 3D printing device with multiple independent material storage bins and automatic powder path switching. During the printing process, partitioned printing is performed; simultaneously, layered printing is performed when printing each area, thereby ensuring that the Cr content in each area is gradient-distributed, and that the Cr content gradually decreases from the arc contact area to the conductive connection area.

[0063] It should be understood that, in order to achieve a Cr content of 20%~60% in the arc contact area, 5%~40% in the transition area, and 5%~20% in the conductive connection area during 3D printing, the printing method can be as follows: In SolidWorks / UG, the arc contact area, transition area, and conductive area are functionally divided, and the geometric boundaries and Cr content ranges of each area are marked. The transition area can be further divided into 2~3 sub-layers, and a decreasing gradient of Cr from the arc contact area end to the conductive area end can be set, with a decreasing range of 60%~5%. Furthermore, during the printing process, the printer's multi-feeder system separately loads the first mixed powder for the arc contact area, the second mixed powder for the transition area, and the third mixed powder for the conductive area.

[0064] In the technical solution of this invention, the thicknesses of the arc contact area, transition area, and conductive connection area can be determined according to the actual required dimensions of the CuCr contact. When the thickness of the arc contact area of ​​the obtained CuCr contact is 2mm~5mm, it ensures an effective bearing layer against arc erosion while avoiding excessive thickness that would increase the overall weight and reduce conductivity. The thickness of the transition area is 1mm~3mm, which avoids excessive thickness that would extend the conductive path and alleviate the abrupt change in performance between the arc contact area and the conductive connection area. The thickness of the conductive connection area is 3mm~6mm, which ensures an effective cross-sectional area for current transmission.

[0065] Cr is the core element determining the mechanical and electrical properties of CuCr contacts. Higher Cr content results in stronger hardness and resistance to arc erosion, but poorer conductivity; conversely, lower Cr content leads to excellent conductivity but weaker mechanical properties. In the CuCr contacts obtained in this invention, the Cr content in the arc contact zone is 20%~60%, which significantly improves the wear resistance and ablation resistance of Cr, matching the core service requirements of the arc contact zone; the Cr content in the transition zone is 5%~40%, achieving a smooth transition from high to low Cr content and avoiding a decrease in interfacial bonding force caused by abrupt changes in composition; the Cr content in the conductive connection zone is 5%~20%, minimizing the impact of Cr on conductivity while ensuring basic mechanical strength, and further improving conductivity through Ag doping.

[0066] Furthermore, in the arc contact area of ​​the aforementioned CuCr contact, the high Cr content resists welding and erosion, while rare earth elements refine the grains and purify the grain boundaries, improving high-temperature stability. When its thickness is 2mm~5mm, it ensures that the contact still has a sufficient effective working layer after multiple arc impacts, significantly improving contact life. In the conductive connection area, the low Cr content reduces the obstruction of electron transport by the hard matrix, while Ag elements dissolved in the Cu matrix further improve conductivity. When its thickness is 3mm~6mm, it can increase the current carrying area, reduce current density, reduce heat loss, and prevent contact failure due to overheating.

[0067] Example 1 A method for preparing a CuCr contact includes the following steps: S10. Using a planetary ball mill, mixed alloy powders for the arc contact region, transition region, and conductive connection region are prepared separately under an argon atmosphere, specifically through steps S101~S103: S101. Weigh out Cu powder with a purity greater than 99.9%, Cr powder with a purity greater than 99.5%, and La2O3 powder according to the mass ratio of Cr content of 20%~50%, La2O3 content of rare earth element 0.8%, and the balance being Cu. Set the mill speed to 150 r / min and the grinding time to 45 min. After grinding, dry at 100℃ for 3 h to obtain multiple groups of CuCr / rare earth mixed powders with Cr content of 20%~50%. Among them, the particle size of Cu powder is 15μm~30μm, the particle size of Cr powder is 20μm~40μm, and the particle size of La2O3 is 1μm~3μm. S102. Weigh out Cu powder with a purity greater than 99.9% and Cr powder with a purity greater than 99.5% according to the mass ratio of Cr content in the transition zone being 5%~25% and the balance being Cu; set the mill speed to 150 r / min and the grinding time to 45 min; after grinding, dry at 100℃ for 3 h to obtain multiple groups of CuCr mixed powders with a Cr content of 5%~25%; wherein the particle size of Cu powder is 15μm~30μm and the particle size of Cr powder is 20μm~40μm; S103. Weigh out Cu powder with a purity greater than 99.9%, Cr powder with a purity greater than 99.5%, and Ag powder according to the mass ratio of Cr content of 5%~10%, Ag content of 0.4%, and the balance being Cu. Set the grinding speed to 150 r / min and the grinding time to 45 min. After grinding, dry at 100℃ for 3 h to obtain multiple groups of CuCr / Ag mixed powders with a Cr content of 5%~10%. The particle size of Cu powder is 15μm~30μm, the particle size of Cr powder is 20μm~40μm, and the particle size of Ag powder is 5μm~8μm. S20. Using 3D printing equipment, under preset printing conditions, the alloy mixture powders obtained in S10 are printed to obtain CuCr contact green blanks, specifically: The adhesive used is a modified phenolic resin-based adhesive with a solid content of 52% and a spraying rate of 0.08 mL / g; Start the metal powder binder jet molding 3D printer, which is equipped with 3-4 independent powder hoppers, corresponding to the arc contact area, transition area and conductive connection area respectively. Load the multiple groups of CuCr / rare earth mixed powder, CuCr mixed powder and CuCr / Ag mixed powder prepared in S10 into the corresponding hoppers, preheat them, remove the adsorbed water on the powder surface and improve the powder flowability. The data of the CuCr contact 3D model, with an arc contact area thickness of 3mm, a transition area thickness of 2mm, and a conductive connection area thickness of 4mm, was imported into the printer control software. The software was then divided into slices according to these areas: 60μm for the arc contact area, 120μm for the transition area, and 180μm for the conductive connection area. Printing parameters for each area were then set: 0.9MPa powder spreading pressure and 180℃ for the arc contact area; 0.7MPa powder spreading pressure and 120℃ for the transition area; and 0.6MPa powder spreading pressure and 100℃ for the conductive connection area. The printing path was set to bidirectional cross-scan to reduce internal stress in the green body. Then, printing is carried out according to the set printing conditions. During the printing process, printing is carried out in sections. When printing each section, printing is carried out in layers according to the Cr content range of each section. After printing is completed, the forming platform temperature is kept at 100℃ for 2 hours to allow the adhesive to fully cure. After the platform cools to room temperature, the green blank is taken out from the forming cylinder and the loose powder that is not bonded on the surface is removed with a soft brush to obtain CuCr contact green blank. The dimensional accuracy is controlled within ±0.1mm. S30. The CuCr contact green body obtained in S20 is subjected to degreasing and vacuum sintering treatments in sequence to obtain the CuCr contact green body, specifically as follows: Degreasing treatment: Place the CuCr contact green blank obtained from S20 in a graphite crucible, with a graphite felt pad at the bottom of the green blank to prevent direct contact with the crucible and adhesion. Close the furnace door and introduce argon gas into the furnace to replace the air inside. Start the heating program at a heating rate of 5℃ / min, raising the temperature from room temperature to 250℃, and then hold for 1.5 hours. This stage mainly removes low-molecular-weight volatiles from the binder. After completion, adjust the heating rate to 8℃ / min, raising the temperature from 250℃ to 500℃, and then hold for 3 hours. This stage decomposes the resin crosslinking network in the binder, which can remove large-molecule organic matter. After degreasing, turn off the heating system and allow the furnace to cool to room temperature. Vacuum sintering: Place the mold containing the green blanks into the sintering furnace chamber, close the furnace door, and start the vacuum pump to first evacuate to a low vacuum of 10. -1 Pa, then start the molecular pump to evacuate to a high vacuum, and finally stabilize the vacuum level at 1×10. -4Pa; Start the heating program at a rate of 5℃ / min, raising the temperature from room temperature to 800℃, and then hold for 2.5 hours. During this stage, argon and trace amounts of moisture adsorbed on the powder surface are removed, while the initial diffusion of atoms on the powder particle surface is promoted, strengthening the green body skeleton. After completion, maintain the heating rate of 5℃ / min, raising the temperature from 800℃ to 1100℃, and then hold for 4 hours. During this stage, Cu particles soften and flow, filling pores, Cr particles are uniformly distributed in the Cu matrix, rare earth La2O3 disperses and pins grain boundaries, and Ag elements are dissolved in the Cu matrix. After the high-temperature holding is completed, turn off the heating system and cool the furnace to room temperature. S40. The CuCr contact blank obtained in S30 is subjected to vacuum heat treatment to obtain the CuCr contact, specifically as follows: Vacuum heat treatment is performed using a zoned induction heating vacuum heat treatment furnace; The contact blank is fixed on the tooling fixture, ensuring that the arc contact area is directly opposite the first induction coil, the conductive connection area is directly opposite the second induction coil, and the transition area is in the temperature-dependent region between the two coils. The furnace door is closed, a vacuum is drawn, and the first induction coil is started with a power of 25kW to locally heat the arc contact area. The temperature of the arc contact area is monitored by a temperature probe and raised to 750℃. After stabilization, the temperature is held for 1.8 hours. Simultaneously, the second induction coil is started with a power of 12kW to locally heat the conductive connection area. The temperature of the conductive connection area is monitored and raised to 350℃. After stabilization, the temperature is held for 1.2 hours. During this period, no additional heating is applied to the transition area, which is naturally kept at the furnace temperature. After the heat treatment and heat preservation are completed, the vacuum degree inside the furnace is maintained, the quenching system is started, preheated nitrogen is introduced into the furnace, and the cooling rate is controlled at 50℃ / min to make the microstructure of each area of ​​the contact uniformly transformed. Through the above steps S10~S40, a CuCr contact is obtained, which has an arc contact area thickness of 3mm, a transition area thickness of 2mm, and a conductive connection area thickness of 4mm.

[0068] Example 2 A method for preparing a CuCr contact includes the following steps: S10. Using a planetary ball mill, mixed alloy powders for the arc contact region, transition region, and conductive connection region are prepared separately under an argon atmosphere, specifically through steps S101~S103: S101. Weigh out Cu powder with a purity greater than 99.9%, Cr powder with a purity greater than 99.5%, and La2O3 powder according to the mass ratio of Cr content of 20%~60%, La2O3 content of rare earth element 0.5%, and the balance being Cu. Set the mill speed to 100 r / min and the grinding time to 30 min. After grinding, dry at 80℃ for 4 h to obtain multiple groups of CuCr / rare earth mixed powders with a Cr mass content of 20%~60%, wherein the particle size of Cu powder is 15μm~20μm, the particle size of Cr powder is 20μm~30μm, and the particle size of La2O3 is 1μm~3μm. S102. According to the mass ratio of Cr content in the transition zone being 10%~40% and the balance being Cu, Cu powder with a purity greater than 99.9% and Cr powder with a purity greater than 99.5% were weighed separately. The mill speed was set to 100 r / min and the grinding time was 30 min. After grinding, the powder was dried at 80℃ for 4 h to obtain multiple groups of CuCr mixed powders with a Cr content of 10%~40%. Among them, the particle size of Cu powder was 15μm~20μm and the particle size of Cr powder was 20μm~30μm. S103. Weigh out Cu powder with a purity greater than 99.9%, Cr powder with a purity greater than 99.5%, and Ag powder according to the mass ratio of Cr content of 5%~20%, Ag content of 0.3%, and the balance being Cu. Set the grinding speed to 100 r / min and the grinding time to 30 min. After grinding, dry at 80℃ for 4 h to obtain at least 3 groups of CuCr / Ag mixed powder with a Cr content of 5%~20%. Among them, the particle size of Cu powder is 15μm~20μm, the particle size of Cr powder is 20μm~30μm, and the particle size of Ag powder is 5μm~8μm. S20. Using 3D printing equipment, under preset printing conditions, the alloy mixture powders obtained in S10 are printed to obtain CuCr contact green blanks, specifically: The adhesive used is a modified phenolic resin-based adhesive with a solid content of 50% and a spraying rate of 0.05 mL / g; Start the metal powder binder jetting 3D printer, which is equipped with 3-4 independent powder hoppers, corresponding to the arc contact area, transition area and conductive connection area respectively. Load the CuCr / rare earth mixed powder, CuCr mixed powder and CuCr / Ag mixed powder prepared in S10 into the corresponding hoppers, preheat them to remove adsorbed water on the powder surface and improve powder flowability. The data of the CuCr contact 3D model, with an arc contact area thickness of 2mm, a transition area thickness of 1mm, and a conductive connection area thickness of 3mm, was imported into the printer control software. The area was then divided into slices: the arc contact area slice thickness was 50μm, the transition area slice thickness was 90μm, and the conductive connection area slice thickness was 150μm. Printing parameters for each area were then set: powder spreading pressure of 0.8MPa and platform temperature of 150℃ for the arc contact area; powder spreading pressure of 0.6MPa and platform temperature of 100℃ for the transition area; and powder spreading pressure of 0.5MPa and platform temperature of 80℃ for the conductive connection area. The printing path was set to bidirectional cross-scan to reduce internal stress in the green body. Then, printing is carried out according to the set printing conditions. During the printing process, printing is carried out in sections. When printing each section, printing is carried out in layers according to the Cr content range of each section. After printing is completed, the forming platform temperature is kept at 100℃ for 2 hours to allow the adhesive to fully cure. After the platform cools to room temperature, the green blank is taken out from the forming cylinder and the loose powder that is not bonded on the surface is removed with a soft brush to obtain CuCr contact green blank. The dimensional accuracy is controlled within ±0.1mm. S30. The CuCr contact green body obtained in S20 is subjected to degreasing and vacuum sintering treatments in sequence to obtain the CuCr contact green body, specifically as follows: Degreasing treatment: Place the CuCr contact green blank obtained from S20 in a graphite crucible, with a graphite felt pad at the bottom of the green blank to prevent direct contact with the crucible and adhesion. Close the furnace door and introduce argon gas into the furnace to replace the air inside. Start the heating program at a heating rate of 4℃ / min, raising the temperature from room temperature to 200℃, and then hold for 2.0h. This stage mainly removes low-molecular-weight volatiles from the binder. After completion, adjust the heating rate to 7℃ / min, raising the temperature from 200℃ to 400℃, and then hold for 3h. This stage decomposes the resin crosslinking network in the binder, which can remove large-molecule organic matter. After degreasing, turn off the heating system and allow the furnace to cool to room temperature. Vacuum sintering: Place the mold containing the green blanks into the sintering furnace chamber, close the furnace door, and start the vacuum pump to first evacuate to a low vacuum of 10. -1 Pa, then start the molecular pump to evacuate to a high vacuum, and finally stabilize the vacuum level at 1×10. -3 Pa; Start the heating program at a rate of 2℃ / min, raising the temperature from room temperature to 600℃, and then hold for 3.0h. During this stage, argon and trace amounts of moisture adsorbed on the powder surface are removed, while the initial diffusion of atoms on the powder particle surface is promoted, strengthening the green body skeleton. After completion, maintain the heating rate of 5℃ / min, raising the temperature from 600℃ to 1050℃, and then hold for 6h. During this stage, Cu particles soften and flow, filling pores, Cr particles are uniformly distributed in the Cu matrix, rare earth La2O3 disperses and pins grain boundaries, and Ag elements are dissolved in the Cu matrix. After the high-temperature holding is completed, turn off the heating system and cool the furnace to room temperature. S40. The CuCr contact blank obtained in S30 is subjected to vacuum heat treatment to obtain the CuCr contact, specifically as follows: Vacuum heat treatment is performed using a zoned induction heating vacuum heat treatment furnace; The contact blank is fixed on the tooling fixture, ensuring that the arc contact area is directly opposite the first induction coil, the conductive connection area is directly opposite the second induction coil, and the transition area is in the temperature-dependent region between the two coils. The furnace door is closed, a vacuum is drawn, and the first induction coil is started with a power of 25kW to locally heat the arc contact area. The temperature of the arc contact area is monitored by a temperature probe and raised to 700℃. After stabilization, the temperature is held for 2.0h. Simultaneously, the second induction coil is started with a power of 12kW to locally heat the conductive connection area. The temperature of the conductive connection area is monitored and raised to 300℃. After stabilization, the temperature is held for 1.0h. During this period, no additional heating is applied to the transition area, which is naturally kept at the furnace temperature. After the heat treatment and heat preservation are completed, the vacuum degree inside the furnace is maintained, the quenching system is started, preheated nitrogen is introduced into the furnace, and the cooling rate is controlled at 45℃ / min to make the microstructure of each area of ​​the contact uniformly transformed. Through the above S10~S40, a CuCr contact is obtained, which has an arc contact area thickness of 2mm, a transition area thickness of 1mm, and a conductive connection area thickness of 3mm.

[0069] The properties of the CuCr contacts obtained in Examples 1 and 2 were measured in accordance with the national standard GB / T 5089-2008 Test Methods for Electrical Contact Materials.

[0070] The determination method is as follows: Arc contact area hardness: Vickers hardness tester, load 200g, holding time 15s, take the average value of 5 measuring points; Conductivity of conductive connection area: eddy current conductivity meter, test temperature 25℃, converted to International Standard for Annealed Copper (IACS) percentage; Contact resistance: Four-probe method, apply DC current of 100A, and test the contact resistance value of the connection between the contact and the copper conductor; Arc burn resistance: Simulating the working conditions of a high-voltage circuit breaker, rated voltage 10kV, rated current 2000A, the number of times the contact fails after breaking operation; Density: Archimedes' displacement method, measuring the volume and mass of the sample, and calculating the ratio of actual density to theoretical density; Structural integrity: The interface of the transition zone was observed using a metallographic microscope, and the microstructure of the arc contact area and conductive area was observed using a scanning electron microscope (SEM).

[0071] The measurement results are shown in Table 1.

[0072] Table 1

[0073] Analysis of the data in Table 1 shows that the CuCr contact prepared in Example 1 exhibits superior arc contact hardness and ablation resistance. This is because the Cr content in Example 1 is 50%, higher than that in Example 2, and the La content is 0.8%. The high Cr content allows for the formation of more hard Cr phases, improving wear resistance; the high La content more effectively pins grain boundaries, inhibiting CuCr grain growth under the high temperature of the electric arc, thus significantly improving arc ablation resistance. Simultaneously, the vacuum sintering temperature in Example 1 is higher than that in Example 2, resulting in stronger Cu particle fluidity and higher bulk density, further enhancing the mechanical properties of the arc contact. In Example 2, a low Cr content design was adopted. Although the hardness and ablation resistance are lower than those in Example 1, the conductivity is higher, making it more suitable for medium- and low-voltage, low-current electrical equipment applications. Secondly, the Cr content in the conductive connection region of Example 2 is only 5%, lower than the 10% in Example 1, resulting in less Cr hindering electron transport. Simultaneously, the Ag content is 0.3%, close to the 0.4% in Example 1. Since Ag is uniformly dissolved in the Cu matrix, it can form a low-resistance Cu-Ag solid solution. Therefore, the CuCr contact of Example 2 has higher conductivity and lower contact resistance. Furthermore, the superior overall performance of the CuCr contacts in Examples 1 and 2 is due to their partitioned design, dividing the CuCr contact into an arc contact region, a transition region, and a conductive connection region, and employing targeted manufacturing processes for each region. This solves the problem of traditional contacts being either wear-resistant but non-conductive or conductive but not wear-resistant.

[0074] Example 3 A method for preparing a CuCr contact includes the following steps: S10. Using a planetary ball mill, mixed alloy powders for the arc contact region, transition region, and conductive connection region are prepared separately under an argon atmosphere, specifically through steps S101~S103: S101. Weigh out Cu powder with a purity greater than 99.9%, Cr powder with a purity greater than 99.5%, and La2O3 powder, respectively, according to the mass ratio of Cr content of 30%~60%, La2O3 content of rare earth element 1.0%, and Cu content as the balance. Set the mill speed to 200 r / min and the grinding time to 50 min. After grinding, dry at 120℃ for 2 h to obtain multiple groups of CuCr / rare earth mixed powders with a Cr mass content of 30%~60%, wherein the particle size of Cu powder is 30μm~45μm, the particle size of Cr powder is 40μm~60μm, and the particle size of La2O3 is 1μm~3μm. S102. According to the mass ratio of Cr content in the transition zone being 10%~40% and the balance being Cu, Cu powder with a purity greater than 99.9% and Cr powder with a purity greater than 99.5% were weighed separately. The mill speed was set to 200 r / min and the grinding time was 50 min. After grinding, the powder was dried at 120℃ for 2 h to obtain multiple groups of CuCr mixed powders with a Cr content of 10%~40%, wherein the particle size of Cu powder was 30μm~45μm and the particle size of Cr powder was 40μm~60μm. S103. Weigh out Cu powder with a purity greater than 99.9%, Cr powder with a purity greater than 99.5%, and Ag powder according to the mass ratio of Cr content of 5%~20%, Ag content of 0.5%, and the balance being Cu. Set the grinding speed to 200 r / min and the grinding time to 50 min. After grinding, dry at 120℃ for 2 h to obtain multiple groups of CuCr / Ag mixed powders with a Cr content of 5%~20%. Among them, the particle size of Cu powder is 30μm~45μm, the particle size of Cr powder is 40μm~60μm, and the particle size of Ag powder is 5μm~8μm. S20. Using 3D printing equipment, under preset printing conditions, the alloy mixture powders obtained in S10 are printed to obtain CuCr contact green blanks, specifically: The adhesive used is a modified phenolic resin-based adhesive with a solid content of 55% and a spraying rate of 0.1 mL / g; Start the metal powder binder jetting 3D printer, which is equipped with 3-4 independent powder hoppers, corresponding to the arc contact area, transition area and conductive connection area respectively. Load the CuCr / rare earth mixed powder, CuCr mixed powder and CuCr / Ag mixed powder prepared in S10 into the corresponding hoppers, preheat them to remove adsorbed water on the powder surface and improve powder flowability. The data of the CuCr contact 3D model, with an arc contact area thickness of 5mm, a transition area thickness of 3mm, and a conductive connection area thickness of 6mm, was imported into the printer control software. The software was then divided into slices according to these areas: the arc contact area slice thickness was 80μm, the transition area slice thickness was 140μm, and the conductive connection area slice thickness was 200μm. Printing parameters for each area were then set: powder spreading pressure of 1.0MPa and platform temperature of 200℃ for the arc contact area; powder spreading pressure of 0.8MPa and platform temperature of 140℃ for the transition area; and powder spreading pressure of 0.7MPa and platform temperature of 120℃ for the conductive connection area. The printing path was set to bidirectional cross-scan to reduce internal stress in the green body. Then, printing is carried out according to the set printing conditions. During the printing process, printing is carried out in sections. When printing each section, printing is carried out in layers according to the Cr content range of each section. After printing is completed, the forming platform temperature is kept at 100℃ for 2 hours to allow the adhesive to fully cure. After the platform cools to room temperature, the green blank is taken out from the forming cylinder and the loose powder that is not bonded on the surface is removed with a soft brush to obtain CuCr contact green blank. The dimensional accuracy is controlled within ±0.1mm. S30. The CuCr contact green body obtained in S20 is subjected to degreasing and vacuum sintering treatments in sequence to obtain the CuCr contact green body, specifically as follows: Degreasing treatment: Place the CuCr contact green blank obtained from S20 in a graphite crucible, with a graphite felt pad at the bottom of the green blank to avoid direct contact with the crucible and adhesion. Close the furnace door and introduce argon gas into the furnace to replace the air inside. Start the heating program at a heating rate of 6℃ / min, raising the temperature from room temperature to 300℃, and then hold for 1.0 h. This stage mainly removes low-molecular-weight volatiles from the binder. After completion, adjust the heating rate to 10℃ / min, raising the temperature from 300℃ to 600℃, and then hold for 2 h. This stage decomposes the resin crosslinking network in the binder, which can remove large-molecule organic matter. After degreasing, turn off the heating system and allow the furnace to cool to room temperature. Vacuum sintering: Place the mold containing the green blanks into the sintering furnace chamber, close the furnace door, and start the vacuum pump to first evacuate to a low vacuum of 10. -1 Pa, then start the molecular pump to evacuate to a high vacuum, and finally stabilize the vacuum level at 1×10. -5 Pa; Start the heating program at a rate of 10℃ / min, raising the temperature from room temperature to 1000℃, and then hold for 2.0h. During this stage, argon and trace amounts of moisture adsorbed on the powder surface are removed, while the initial diffusion of atoms on the powder particle surface is promoted, strengthening the green body skeleton. After completion, maintain the heating rate of 10℃ / min, raising the temperature from 1000℃ to 1150℃, and then hold for 2h. During this stage, Cu particles soften and flow, filling pores, Cr particles are uniformly distributed in the Cu matrix, rare earth La2O3 disperses and pins grain boundaries, and Ag elements are dissolved in the Cu matrix. After the high-temperature holding is completed, turn off the heating system and cool the furnace to room temperature. S40. The CuCr contact blank obtained in S30 is subjected to vacuum heat treatment to obtain the CuCr contact, specifically as follows: Vacuum heat treatment is performed using a zoned induction heating vacuum heat treatment furnace; The contact blank is fixed on the tooling fixture, ensuring that the arc contact area is directly opposite the first induction coil, the conductive connection area is directly opposite the second induction coil, and the transition area is in the temperature-dependent region between the two coils. The furnace door is closed, a vacuum is drawn, and the first induction coil is started with a power of 25kW to locally heat the arc contact area. The temperature of the arc contact area is monitored by a temperature probe and raised to 800℃. After stabilization, the temperature is held for 1.5 hours. Simultaneously, the second induction coil is started with a power of 12kW to locally heat the conductive connection area. The temperature of the conductive connection area is monitored and raised to 400℃. After stabilization, the temperature is held for 1.5 hours. During this period, no additional heating is applied to the transition area, which is naturally kept at the furnace temperature. After the heat treatment and heat preservation are completed, the vacuum degree inside the furnace is maintained, the quenching system is started, preheated nitrogen is introduced into the furnace, and the cooling rate is controlled at 55℃ / min to make the microstructure of each area of ​​the contact uniformly transformed. Through the above S10~S40, a CuCr contact is obtained, which has an arc contact area thickness of 2mm, a transition area thickness of 1mm, and a conductive connection area thickness of 3mm.

[0075] Comparative Example 1 Comparative Example 1 was set up under Example 3. In Comparative Example 1, the arc contact area did not contain rare earth elements, and the conductive connection area did not contain Ag elements. In the 3D printing method, instead of setting different printing parameters according to different areas, the slice thickness was uniformly set to 140 μm, the powder spreading pressure to 0.8 MPa, and the platform temperature to 140°C. In the vacuum heat treatment, instead of differentiating the heat treatment design according to different areas, the temperature was uniformly set to be held at 800°C for 3 hours. The remaining steps and process parameters were the same as in Example 3.

[0076] Comparative Example 2 Comparative Example 2 was set up in Example 3. In Comparative Example 2, the CuCr contact was a whole without the division of the arc contact area, transition area and conductive connection area, and the Cr content in the contact was 50% and uniformly distributed. Therefore, no regional processing was required in the subsequent 3D printing step and vacuum heat treatment step. The scheme of the 3D printing step was that the slice thickness was 140μm, the powder spreading pressure was 0.8MPa, the platform temperature was 140℃, and the vacuum heat treatment method was to hold at 800℃ for 3h. The remaining steps and processes were the same as in Example 3.

[0077] The performance of CuCr contacts prepared in Example 3, Comparative Examples 1 and 2 was measured using the same method as in Example 1. The results are shown in Table 2.

[0078] Table 2

[0079] Analysis of the data in Table 1 shows that the CuCr contact obtained in Example 3 exhibits superior performance. This is because, in the technical solution of Example 3, the Cr content in the arc contact area reaches 60%, combined with 1.0% La2O3, forming a large amount of hard Cr phase. Furthermore, the rare earth oxides disperse and pin the grain boundaries, inhibiting grain growth at high temperatures, thus resulting in optimal hardness and ablation resistance. In the conductive connection area, the 20% Cr + 0.5% Ag content, where Ag is dissolved in the Cu matrix, reduces electron transport resistance, maintaining a high conductivity of 82% IACS even with a relatively high Cr content. Secondly, in 3D printing, setting parameters for different regions can improve the green compact density and forming accuracy, and the gradient transition of parameters in the transition zone avoids interface stress concentration. During the debinding stage, phased heating and holding not only ensure complete binder removal but also promote the full flow of Cu particles to fill the pores, achieving a density of over 99.5%. In Comparative Example 1, because the arc contact area does not contain rare earth elements, the hardness is improved solely by high Cr content. Under the high temperature of the electric arc, the grains tend to coarsen, significantly reducing ablation resistance and hardness. In the conductive connection area, there is no Ag to enhance conductivity, and the 3D printing process does not differentiate printing conditions for different regions, resulting in high green body porosity, reduced conductivity, and increased contact resistance. Furthermore, while overall heat treatment improves the hardness of the conductive area, it exacerbates the difference in thermal expansion between the conductive area and the arc contact area, leading to microcracks at the interface. In Comparative Example 2, the CuCr contacts are uniformly distributed. Although the contact hardness is maintained, conductivity is significantly reduced, and contact resistance increases. In addition, the uniform 3D printing parameters cannot adapt to the functional requirements of different areas, resulting in uneven porosity distribution within the green body. After subsequent processing, the overall performance of the resulting contacts is reduced.

[0080] Analysis of Examples 1-3 and Comparative Examples 1-2 reveals that in the technical solution of this invention, the CuCr contact is designed with a regional structure, resulting in a gradient distribution of Cr content in the arc contact area, transition area, and conductive connection area. Furthermore, the Cr content gradually decreases from the arc contact area to the transition area and then to the conductive connection area. This not only alleviates interfacial stress but also ensures resistance to arc erosion and conductivity in the conductive connection area. Secondly, in the arc contact area, the synergy between rare earth oxides and high Cr enhances wear resistance and ablation resistance through grain boundary pinning and hard phase reinforcement. In the conductive connection area, the synergy between Ag elements and low Cr enhances conductivity through solid solution reinforcement and reduced contact resistance. Furthermore, during the 3D printing process, the slice thickness is always greater than the maximum particle size of the powder, which ensures uniform powder spreading. The high powder spreading pressure and high plateau temperature in the arc contact area match the molding requirements of the high Cr powder content, improving the green body density. The low powder spreading pressure and low plateau temperature in the conductive area prevent excessive oxidation of Ag powder, ensuring the solid solution effect of subsequent sintering. At the same time, subsequent processing steps and parameters are set for different areas, ultimately forming a gradient of process parameters that is completely matched with the gradient of composition and structure throughout the entire process, jointly improving the various performance characteristics of the CuCr contact.

[0081] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A method for preparing a CuCr contact, characterized in that, The CuCr contact sequentially comprises an arc contact region, a transition region, and a conductive connection region; the preparation method includes: A first mixed powder, a second mixed powder, and a third mixed powder are prepared in a uniform manner. Each mixed powder includes Cu powder and Cr powder. The Cr content in the first mixed powder is greater than the Cr content in the second mixed powder, and the Cr content in the second mixed powder is greater than the Cr content in the third mixed powder. Using 3D printing equipment, under preset printing conditions, the arc contact area is printed based on the first mixed powder; the transition area is printed based on the second mixed powder; and the conductive connection area is printed based on the third mixed powder, to obtain a CuCr contact green body. The CuCr contact green body was subjected to degreasing and vacuum sintering treatment in sequence to obtain CuCr contact green body; The CuCr contact blank is subjected to vacuum heat treatment to obtain the CuCr contact.

2. The preparation method according to claim 1, characterized in that, The second mixed powder comprises mixed powders with different proportions of multiple components; The printing of the transition zone based on the second mixed powder includes: Based on the direction from the arc contact area to the conductive connection area, and in descending order of Cr content, the transition area is printed using mixed powders with different proportions of multi-components.

3. The preparation method according to claim 1, characterized in that, The Cr content in the arc contact area is 20%~60%, the Cr content in the transition area is 5%~40%, and the Cr content in the conductive connection area is 5%~20%.

4. The preparation method according to claim 1, characterized in that, The first mixed powder further includes rare earth elements, and the third mixed powder further includes Ag elements. The content of rare earth elements in the first mixed powder is 0.5%~1.0%, and the particle size is 1μm~3μm. The content of Ag elements in the third mixed powder is 0.3%~0.5%, and the particle size is 5μm~10μm.

5. The preparation method according to claim 1, characterized in that, The preset printing conditions include: The binder used in 3D printing is a modified phenolic resin-based binder with a solid content of 50%~55% and a jetting volume of 0.05mL / g~0.1mL / g; The thickness of the slice in the arc contact area is 50μm~80μm, the powder spreading pressure is 0.8MPa~1.0MPa, and the platform temperature is 150℃~200℃; The slice thickness in the transition zone is 90μm~140μm, the powder spreading pressure is 0.6MPa~0.8MPa, and the platform temperature is 100℃~140℃. The thickness of the conductive connection region slice is 150μm~200μm, the powder spreading pressure is 0.5MPa~0.7MPa, and the platform temperature is 80℃~120℃.

6. The preparation method according to claim 1, characterized in that, The degreasing treatment method includes: Under an inert gas atmosphere, the temperature is increased at a rate of 4℃ / min to 6℃ / min. When the temperature reaches 200℃ to 300℃, it is held for 1 to 2 hours. Then, the temperature is increased to 400℃ to 600℃ at a rate of 7℃ / min to 10℃ / min, and held for 2 to 4 hours.

7. The preparation method according to claim 1, characterized in that, The vacuum sintering process includes: At a vacuum degree of 10 -3 Pa~10 -5 Under the condition of Pa, heat at a heating rate of 1℃ / min to 10℃ / min, and when the temperature reaches 600℃ to 1000℃, hold for 2h to 3h; then heat to 1050℃ to 1150℃ and hold for 2h to 6h.

8. The preparation method according to claim 1, characterized in that, The vacuum heat treatment method includes: The arc contact area is kept at 700℃~800℃ for 1.5h~2.0h; The conductive connection area is kept at 300℃~400℃ for 1.0h~1.5h. The CuCr contact blank is subjected to isothermal quenching treatment at a cooling rate of 45℃ / min ~ 55℃ / min.

9. The preparation method according to claim 1, characterized in that, The Cu powder has a particle size of 15μm to 45μm, and the Cr powder has a particle size of 20μm to 60μm.

10. A CuCr contact, characterized in that, The CuCr contact is prepared by the preparation method according to any one of claims 1 to 9.

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