Copper base-copper chromium contact composite material and preparation method thereof

Abstract

The invention discloses a copper base-copper chromium contact composite material and a preparation method thereof, and belongs to the technical field of copper chromium contact materials. The preparation method comprises the following steps that a nanometer aluminum oxide coating layer is formed on the surface of chromium powder through a sol-gel method, and coated chromium powder is obtained; the coated chromium powder and the copper powder are subjected to vacuum induction gas atomization treatment, and spherical copper-chromium alloy powder is obtained; the spherical copper-chromium alloy powder is printed on the surface of the copper-based material, and a prefabricated body of the copper-based-copper-chromium contact composite material is obtained; and after the contact layer is subjected to hot isostatic pressing treatment, the prefabricated body is subjected to annealing treatment, and the contact is prepared. According to the method, the high conductivity of the base material and the high wear resistance of the contact layer can be coordinated, so that the arc ablation resistance is improved; through the combination of electron beam printing and hot isostatic pressing, the porosity of the material can be remarkably reduced, and the material is suitable for high-performance contact components in the fields of high-voltage switches, rail transit and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of copper-chromium contact, and particularly relates to a copper-based-copper-chromium contact composite material and a preparation method thereof. BACKGROUND

[0002] As a key conductive contact component in the fields of power systems and rail transit, the performance of copper-based contact materials directly affects the safety, reliability and service life of equipment. An ideal contact material needs to meet three core requirements: high electrical conductivity (reducing contact resistance and energy consumption), excellent arc ablation resistance (resisting high-temperature arc during switching) and high wear resistance (reducing failure caused by mechanical wear).

[0003] However, the existing copper-based contact materials still have significant defects in performance matching and preparation process. For example, pure copper material has excellent electrical conductivity, but its hardness is low and its arc ablation resistance is poor, which cannot meet the use requirements of high-voltage switches and other scenes. For example, copper-chromium alloy improves wear resistance and arc ablation resistance by introducing chromium elements, but the addition of chromium significantly reduces the electrical conductivity, and when the Cr content exceeds 30%, the material becomes brittle and the processing performance deteriorates. In addition, copper-chromium alloys with high chromium content (such as 50wt%) not only have high costs (the price of chromium is about 5 to 8 times that of copper), but also have the problem of excessive consumption of chromium resources, making it difficult to balance economy and performance. The existing copper-chromium contact preparation process, such as infiltration method, is prone to residual pores in the material due to uneven distribution of chromium skeleton pores, thereby accelerating material ablation and electrical breakdown; for example, the powder metallurgy method also causes low sintering density due to oxidation of chromium particles during sintering, thereby reducing the voltage resistance of the material.

[0004] Therefore, there is an urgent need for a method that can improve the density and stability of the material and has high preparation efficiency. SUMMARY

[0005] To solve the defects of the prior art, the application provides a copper-based-copper-chromium contact composite material and a preparation method thereof, which can improve the hardness, arc ablation resistance and density of the contact material on the basis of a high-conductivity matrix and a high-wear-resistance contact layer.

[0006] To achieve the above purpose, the application provides a preparation method of a copper-based-copper-chromium contact composite material, which comprises the following steps: A nano-aluminum oxide coating layer is formed on the surface of chromium powder by a sol-gel method to obtain coated chromium powder; The coated chromium powder and copper powder are subjected to vacuum induction gas atomization treatment to obtain spherical copper-chromium alloy powder; The spherical copper-chromium alloy powder is subjected to printing treatment on the surface of a copper-based substrate to obtain a preform of the copper-based-copper-chromium contact composite material; wherein the preform comprises a base layer and a contact layer, and the contact layer comprises a surface layer and a transition layer connected to the base layer. After the hot isostatic pressing treatment of the contact layer, the preform is annealed to obtain a copper-chromium contact piece. The material of the base layer is copper base material, the material of the contact layer is copper-chromium alloy, the chromium content of the surface layer is 25wt%-30wt%, and the chromium content of the transition layer is 10wt%-15wt%.

[0007] Further, the sol-gel method comprises the following steps: Add aluminum isopropyl alcohol into the ethanol solution and stir until dissolved to obtain an aluminum source solution; Add nitric acid solution to the aluminum source solution to adjust the pH value to 2-3, and continuously stir to form a transparent sol; Add chromium powder to the transparent sol, ultrasonic dispersion, and centrifugal separation to obtain coated powder; The coated powder is subjected to low-temperature annealing and curing treatment to obtain coated chromium powder; The aluminum content in the aluminum source solution is 0.1mol / L-0.2mol / L, and the solid-liquid ratio of chromium powder to transparent sol is 1g:(5-10)mL.

[0008] Further, the centrifugal separation speed is 3000rpm-5000rpm, and the time is 5min-10min; The ultrasonic dispersion power is 200W-300W, and the time is 2h-4h; The low-temperature annealing and curing treatment temperature is 300℃-400℃, the holding time is 1h-2h, and the heating rate is 5℃ / min-10℃ / min.

[0009] Further, the particle size of the spherical copper-chromium alloy powder is 15μm-75μm, and the thickness of the contact layer is 0.8mm-1.8mm.

[0010] Further, the copper base material is pretreated before printing, including: Grind the surface of the copper base material with 400-600 mesh sandpaper; Ultrasonic clean the treated copper base material with acetone solution at a power of 100W-600W for 3min-10min.

[0011] Further, the printing method is electron beam printing, comprising the following steps: Under the condition of <5*10 -3 Pa, input high-purity argon as protective gas, and preheat the copper base material to 400℃-600℃; After preheating, electron beam printing is performed at a power of 3kW, a scanning speed of 6mm / s-15mm / s, and a spot diameter of 3mm.

[0012] Further, the printing method is 3D printing, the power of the 3D printing is 1.5 kW, the scanning speed is 800 mm / s-1600 mm / s, and the powder layer thickness is 0.035 mm-0.1 mm.

[0013] Further, the temperature of the hot isostatic pressing treatment is 900 DEG C-1050 DEG C, the pressure of the hot isostatic pressing treatment is 100 MPa-120 MPa, and the holding time of the hot isostatic pressing treatment is 1 h-2 h.

[0014] Further, the annealing treatment comprises a first annealing treatment, a second annealing treatment and a cooling treatment, wherein, the temperature of the first annealing treatment is 750 DEG C-850 DEG C, and the holding time is 1 h-1.5 h; the temperature of the second annealing treatment is 500 DEG C-600 DEG C, and the holding time is 2 h-3 h; the cooling method is high-pressure nitrogen quenching cooling, the pressure of the cooling treatment is 2 MPa-5 MPa, the cooling speed is 50 DEG C / s-200 DEG C / s, and the temperature after the cooling treatment is 30 DEG C-100 DEG C.

[0015] The application further discloses a copper-based-copper-chromium contact composite material obtained by the preparation method.

[0016] In summary, the application has the following advantages: 1. The preparation method of the application prepares a composite material comprising a substrate layer, a transition layer and a surface layer, so that the substrate layer retains the high conductivity (conductivity ≥98% IACS) of pure copper, meeting the core requirement of low contact resistance; the contact layer has a gradient distribution of chromium content through the surface layer and the transition layer, so that the surface hardness and the arc ablation resistance are improved, the interface thermal stress is relieved through the transition layer, the increase of material brittleness caused by high chromium content is avoided, and the inherent contradiction between the insufficient wear resistance of pure copper and the poor conductivity of high chromium alloy is solved.

[0017] 2. The preparation method of the application forms a nano-coating layer on the surface of chromium powder by a sol-gel method, which can effectively inhibit the oxidation and segregation of chromium at high temperature and reduce the influence of oxidation inclusions on the density; secondly, the spherical copper-chromium alloy powder prepared by vacuum induction gas atomization has excellent flowability, which is combined with precise forming of electron beam printing or 3D printing to reduce the pore defects of traditional infiltration or powder metallurgy; finally, the hot isostatic pressing treatment further eliminates pores, so that the material density is improved to more than 99% (porosity ≤1%), which is significantly better than the traditional powder metallurgy (porosity 10%-30%), thereby reducing the risk of electrical breakdown caused by pores and improving the voltage resistance performance.

[0018] In summary, the preparation method of the application combines structural gradient, process precision and material functionalization, while ensuring high electrical conductivity, significantly improves the wear resistance, arc ablation resistance and density of the contact material, while reducing the cost and resource consumption, and is suitable for high-voltage switches, rail transit and other fields with strict requirements on contact performance. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 Element distribution diagram of the copper-based-copper-chromium contact composite material of Example 1 of the application. DETAILED DESCRIPTION

[0020] The principles and characteristics of the application are described below in conjunction with examples, which are used only to explain the application and not to limit the scope of the application. If the specific conditions are not specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0021] The common copper-based contact materials in the prior art are pure copper materials and copper-chromium alloys, but the pure copper material has low hardness (HV≤80) and poor arc ablation resistance, and is easy to weld and wear under the action of arc, with high wear rate, which cannot meet the use requirements in high-voltage switch and other scenes. Therefore, in order to meet the use requirements, the use of copper-chromium alloy is more widespread. Although the copper-chromium alloy contact improves the wear resistance and arc ablation resistance by introducing chromium elements, the addition of chromium will significantly reduce the electrical conductivity. Generally speaking, the electrical conductivity is reduced by 0.8%~1.2% for every 1wt% of chromium added.

[0022] The common preparation methods of the copper-chromium alloy contact in the prior art are infiltration method and powder metallurgy method. Among them, the infiltration method refers to forming a composite material by infiltrating copper liquid into a porous chromium skeleton, but this process is easy to cause uneven distribution of pores in the chromium skeleton, resulting in 10%~30% of pores remaining in the material. These pores will become "weak points" under the action of arc, accelerating the ablation and electrical breakdown of the material. The powder metallurgy method is to directly press and sinter copper-chromium mixed powder, which can control the uniformity of the composition, but the chromium particles are easy to oxidize (form Cr2O3 inclusions) during sintering, and the sintering density is usually lower than 90%, resulting in a decrease in the voltage resistance of the material.

[0023] Based on this, in a first aspect, the application provides a preparation method of a copper-based-copper-chromium contact composite material, comprising the following steps: S1, forming a nano-alumina coating layer on the surface of chromium powder by sol-gel method to obtain coated chromium powder.

[0024] In the above scheme, the elemental chromium powder is coated first, and then the spherical copper-chromium alloy powder is prepared, so that the chromium powder is coated with nano-alumina before mixing, thereby avoiding oxidation of chromium during the atomization process. The alumina coating layer can act as a barrier material to hinder the migration of chromium atoms during alloy melting, thereby reducing the chromium segregation phenomenon during printing. In addition, the surface of the elemental chromium powder is smooth, making the coating process easier to form a continuous nano layer, thereby improving the uniformity of the coating.

[0025] As an optional embodiment of the present application, the sol-gel method comprises the following steps: S101, add aluminum isopropoxide ([Al(OC3H7)3]) to an ethanol solution and stir at 50-60°C for 1-2h until dissolved to obtain an aluminum source solution. The aluminum content in the aluminum source solution is 0.1-0.2mol / L, and the volume ratio of ethanol to water in the ethanol solution is 3:1.

[0026] S102, add nitric acid solution to the aluminum source solution to adjust the pH value to 2-3, and continuously stir to form a transparent sol.

[0027] S103, add chromium powder to the transparent sol, ultrasonically disperse, and then centrifuge to obtain coated powder. The solid-liquid ratio of chromium powder to transparent sol is 1g:(5-10)mL. The ultrasonic dispersion power is 200-300W, and the time is 2-4h to avoid over-thickening of the coating layer due to the time process. The centrifugation speed is 3000-5000rpm, and the time is 5-10min.

[0028] S104, perform low-temperature annealing and curing treatment on the coated powder to obtain coated chromium powder.

[0029] The low-temperature annealing and curing treatment is performed at a temperature of 300-400°C for 1-2h, with a heating rate of 5-10°C / min, and in a nitrogen or argon atmosphere. The low-temperature annealing and curing treatment can remove organic residues in the sol, promote the condensation of Al-O bonds to form amorphous Al2O3, and avoid secondary oxidation of the chromium powder by keeping the annealing temperature below the oxidation initiation temperature of chromium (the oxidation temperature range of chromium metal in air is about 600-1200°C). The cooperation of the sol-gel method and low-temperature annealing and curing can form a uniform and dense nano-shaped Al2O3 coating layer on the surface of the chromium powder, effectively inhibiting the oxidation and segregation of chromium at high temperatures, and improving the density of the printed layer.

[0030] As an optional embodiment of the present application, the chromium powder needs to be pretreated to remove the oxide layer and impurities before being added to the transparent sol. The pretreatment method can include conventional ultrasonic dispersion, deionized water cleaning, vacuum drying (60℃-80℃, 1h-2h), and the like.

[0031] S2, the coated chromium powder and the copper powder are subjected to vacuum induction gas atomization treatment to obtain spherical copper-chromium alloy powder.

[0032] In the specific embodiment, the particle size of the spherical copper-chromium alloy powder is 15μm-75μm, and the thickness of the contact layer is 0.8mm-1.8mm.

[0033] In the specific embodiment, the atmosphere for the vacuum induction gas atomization treatment is high-purity nitrogen (purity >99.99%), which can prevent the coating layer from being oxidized. The melting temperature is 1400℃-1500℃, and the atomization pressure is 8MPa-10MPa, which can ensure that the sphericity of the powder is >95%. Among them, the coating layer remains stable at the atomization high temperature, which can form a Cr-Al2O3core-shell structure, and then mixed with copper liquid for atomization, finally forming a copper matrix and dispersed Cr-Al2O3composite phase in the alloy powder, which can not only inhibit the oxidation of chromium, but also enhance the interfacial bonding force through Al2O3particles. And the vacuum induction gas atomization method for preparing spherical copper-chromium alloy powder can significantly reduce the oxygen content and inclusion rate, while avoiding the impurities introduced by traditional mechanical alloying.

[0034] S3, the spherical copper-chromium alloy powder is subjected to printing treatment on the surface of the copper base material to obtain a preform of the copper base-copper-chromium contact composite material.

[0035] Among them, the preform includes a base layer and a contact layer, and the contact layer includes a surface layer and a transition layer connected with the base layer. The material of the base layer is a copper base material (pure copper, purity >99.99%), which can maintain the high conductivity of pure copper, and the material of the contact layer is a copper-chromium alloy, the chromium content of the surface layer is 25wt%-30wt%, which can improve the wear resistance; the chromium content of the transition layer is 10wt%-15wt%, which can relieve thermal stress.

[0036] In the above scheme, the contact layer is directly formed on the surface of the copper substrate by printing technology, without the need for the heterogeneous material welding step in the traditional process (such as silver-copper solder connection), thereby reducing the solder cost and the risk of interface brittleness; at the same time, the chromium content of the contact layer is controlled at 10wt%-30wt%, which is 30%-50% less than the traditional high-chromium alloy (such as CuCr50), thereby reducing the raw material cost (the price of chromium is 5-8 times that of copper); in addition, the synergistic process of nano-alumina coating, hot isostatic pressing and gradient annealing reduces the number of post-processing steps and shortens the process cycle, thereby improving the production efficiency. Moreover, in the preform after printing, the gradient composition design of the transition layer can reduce the difference in the thermal expansion coefficients of the base layer and the surface layer, thereby reducing the interface stress concentration in the cold and hot cycle; the nano-alumina coating layer can remain stable during high-temperature printing and hot isostatic pressing, which not only enhances the interface bonding force between the chromium particles and the copper matrix, but also inhibits the agglomeration and growth of the chromium particles, so that the microstructure of the contact layer is more uniform, thereby improving the fatigue resistance and service life of the material.

[0037] As an optional embodiment of the present application, the copper substrate is pretreated before printing, including: polishing the surface of the copper substrate with 400-600 mesh sandpaper; and ultrasonic cleaning the treated copper substrate with an acetone solution at a power of 100-600 W for 3-10 min.

[0038] In the above scheme, sandpaper polishing can remove the oxide layer on the surface of the copper substrate, so that the fresh copper surface directly participates in the combination with the contact layer, thereby enhancing the interface metallurgical bonding or mechanical embedding effect, and avoiding problems such as current concentration and local overheating caused by poor interface bonding. The acetone ultrasonic cleaning can efficiently remove the metal debris, oil stains and air pollutants remaining after polishing, prevent the generation of gas due to the decomposition of the pollutants in the subsequent high-temperature printing, avoid the formation of pores in the material, and further reduce the porosity in cooperation with the hot isostatic pressing process.

[0039] As an optional embodiment of the present application, the printing method is electron beam printing, including the following steps: inputting high-purity argon gas (purity > 99.99%) as a protective gas under the condition of <5*10 -3 Preheat the copper substrate to 400-600°C; after preheating, perform electron beam printing at a power of 3 kW, a scanning speed of 6-15 mm / s and a spot diameter of 3 mm.

[0040] The above scheme is carried out under high vacuum environment and high-purity argon protection, can effectively avoid powder oxidation, cooperate with 400-600°C substrate preheating, can reduce the thermal stress in the printing process, promote the full fusion of the powder and the substrate interface, reduce the porosity, and improve the bonding strength of the contact layer and the copper substrate. Higher spot diameter and lower scanning speed enable energy concentration and long action time, which is suitable for forming a thicker contact layer (such as the overall forming of the transition layer and the surface layer) on the substrate surface, and ensures the stability of the interlayer bonding. It is suitable for scenarios with high requirements for contact layer thickness (such as the need for a thicker transition layer to buffer the performance gradient), and strict requirements for density and interface bonding strength, such as high-voltage switches, rail transit high-power contactors and other devices that can withstand high current impact and mechanical wear for a long time.

[0041] As another optional embodiment of the present application, the printing process is 3D printing, the power of 3D printing is 1.5kW, the scanning rate is 800-1600mm / s, and the powder layer thickness is 0.035-0.1mm.

[0042] The low powder thickness and high scanning rate of the above scheme can realize the fine structure design of the contact layer (such as the optimization of the surface microstructure), and are suitable for preparing contact surfaces with complex shapes or specific functional textures. Among them, the high scanning speed can shorten the printing time, and the "near net shape" feature of 3D printing can reduce the subsequent machining allowance, and the lower power of 1.5kW can be more energy-efficient in thin contact layer printing. It is suitable for precise control of the composition gradient of the transition layer and the surface layer, and realizes the smooth transition of chromium content through layered powder laying, and reduces the stress concentration caused by performance mutation. Compared with electron beam printing, it is more suitable for scenarios with high requirements for contact size accuracy and surface structure complexity, such as small-sized relays, conductive contacts in precision instruments, or devices that need to improve arc extinguishing performance through surface microstructure.

[0043] S4, after the contact layer is subjected to hot isostatic pressing treatment, the preform is subjected to annealing treatment, and is prepared.

[0044] As an optional embodiment of the present application, the temperature of the hot isostatic pressing treatment is 900-1050°C, the pressure of the hot isostatic pressing treatment is 100-120MPa, and the holding time of the hot isostatic pressing treatment is 1-2h.

[0045] As an optional embodiment of the present application, the annealing treatment comprises a first annealing treatment, a second annealing treatment, and a cooling treatment. The first annealing treatment has a temperature of 750-850℃ and a holding time of 1-1.5h, which can promote the uniform precipitation of chromium phase. The second annealing treatment has a temperature of 500-600℃ and a holding time of 2-3h, which can eliminate residual stress and restore electrical conductivity. The cooling treatment is high-pressure nitrogen quenching cooling, the cooling treatment has a pressure of 2-5MPa and a cooling speed of 50-200℃ / s, and the temperature after the cooling treatment is 30-100℃. The high-pressure nitrogen can accelerate heat conduction through forced convection heat exchange, thereby increasing the cooling speed, achieving rapid heat dissipation, refining the grains, improving the hardness, avoiding material embrittlement, and optimizing the high electrical conductivity and high wear resistance.

[0046] In a second aspect, based on the overall inventive concept, the present application also discloses a copper-based-copper-chromium contact composite material obtained by the above preparation method. The conductivity of the base material in the composite material is ≥98% IACS, the hardness of the contact layer can be increased by 30-50%, and the arc ablation resistance can be increased by about 40%.

[0047] The above technical solutions of the present application will be described in detail below in conjunction with specific embodiments.

[0048] Embodiment 1 The present embodiment provides a preparation method of a copper-based-copper-chromium contact composite material, comprising the following steps: (1) Aluminum isopropoxide is added to an ethanol solution (the volume ratio of ethanol to water is 3:1) and stirred until dissolved to obtain an aluminum source solution with an aluminum content of 0.2mol / L; Nitric acid solution is added dropwise to the aluminum source solution to adjust the pH value to 3, and continuous stirring is performed to form a transparent sol; Chromium powder is added to the transparent sol at a solid-liquid ratio of 1g:10mL, ultrasonic dispersion is performed at a power of 300W for 2h, and then centrifugal separation is performed at a speed of 3000rpm for 5min to obtain coated powder; The coated powder is subjected to low-temperature annealing and curing treatment at a temperature of 400℃ and a temperature increasing rate of 5℃ / min, and the holding time is 1h to obtain coated chromium powder.

[0049] (2) The coated chromium powder and copper powder are subjected to vacuum induction gas atomization treatment to obtain spherical copper-chromium alloy powder with a particle size of 30μm.

[0050] The atmosphere of the vacuum induction gas atomization treatment is high-purity nitrogen (purity >99.99%) to prevent oxidation of the coating. The melting temperature is 1400℃ and the atomization pressure is 8MPa to ensure that the sphericity of the powder is >95%.

[0051] (3) The surface of the copper substrate is polished by 600 mesh sandpaper, and the polished copper substrate is cleaned with an acetone solution at a power of 300 W for 5 min.

[0052] (4) The spherical copper-chromium alloy powder is printed on the surface of the copper substrate to obtain a preform of the copper-based-copper-chromium contact composite material. The preform includes a substrate layer and a contact layer, and the contact layer includes a surface layer and a transition layer connected with the substrate layer. The chromium content of the surface layer is 30 wt%, and the chromium content of the transition layer is 10 wt%.

[0053] The printing method includes: adding <5*10 -3 The copper substrate is preheated to 400 DEG C under the condition of inputting high-purity argon as a protective gas at a pressure of 5*10

[0054] (5) The contact layer is subjected to hot isostatic pressing treatment at a temperature of 1050 DEG C and a pressure of 100 MPa for 1 h.

[0055] (6) The preform is subjected to first annealing treatment at a temperature of 850 DEG C for 1 h, and then subjected to second annealing treatment at a temperature of 600 DEG C for 3 h, and then cooled by high-pressure nitrogen quenching to obtain the copper-based-copper-chromium contact composite material. The cooling pressure is 2 MPa, the cooling speed is 100 DEG C / s, and the temperature after cooling treatment is 30 DEG C. The copper and chromium distribution diagram of the copper-based-copper-chromium contact composite material is shown in Figure 1 . Figure 1 The light pink area is the copper distribution area, and the blue area is the chromium distribution area.

[0056] Example 2 The embodiment provides a preparation method of a copper-based-copper-chromium contact composite material, which comprises the following steps: (1) Aluminum isopropoxide is added into an ethanol solution (the volume ratio of ethanol to water is 3:1) and stirred until dissolved to obtain an aluminum source solution with an aluminum content of 0.1 mol / L; Nitric acid solution is added dropwise into the aluminum source solution to adjust the pH value to 3, and continuous stirring is performed to form a transparent sol; Chromium powder is added into the transparent sol according to a solid-liquid ratio of 1 g:5 mL, ultrasonic dispersion is performed at a power of 200 W for 4 h, and then centrifugal separation is performed at a speed of 5000 rpm for 5 min to obtain coated powder; The coated powder is subjected to low-temperature annealing and curing treatment at a temperature of 400 DEG C at a temperature increasing rate of 8 DEG C / min, and the temperature is kept for 2 h to obtain coated chromium powder.

[0057] (2) The coated chromium powder and copper powder are subjected to vacuum induction gas atomization treatment to obtain spherical copper-chromium alloy powder with a particle size of 50 μm.

[0058] The atmosphere of the vacuum induction gas atomization treatment is high-purity nitrogen (purity > 99.99 %), which can prevent the oxidation of the cladding layer. The melting temperature is 1500 ℃, and the atomization pressure is 8 MPa, which can ensure that the powder sphericity is > 95 %.

[0059] (3) The surface of the copper base material is polished by sandpaper with a mesh size of 400, and the polished copper base material is ultrasonically cleaned with an acetone solution at a power of 500 W for 3 min.

[0060] (4) The spherical copper-chromium alloy powder is printed on the surface of the copper base material to obtain a preform of the copper base-copper-chromium contact composite material. The preform includes a base layer and a contact layer, and the contact layer includes a surface layer and a transition layer connected with the base layer. The chromium content of the surface layer is 25 wt%, and the chromium content of the transition layer is 15 wt%.

[0061] The printing method includes: inputting high-purity argon as a protective gas under the condition of < 5 * 10 -3 Pa, preheating the copper base material to 500 ℃; after preheating, electron beam printing is performed at a power of 3 kW, a scanning speed of 12 mm / s, and a spot diameter of 3 mm.

[0062] (5) The contact layer is subjected to hot isostatic pressing at a temperature of 950 ℃ and a pressure of 100 MPa for 1 h.

[0063] (6) The preform is subjected to first annealing at a temperature of 750 ℃ for 1.5 h, and then subjected to second annealing at a temperature of 500 ℃ for 2.5 h, and then subjected to high-pressure nitrogen quenching cooling to obtain the copper base-copper-chromium contact composite material. The pressure of the cooling treatment is 2 MPa, the cooling speed is 50 ℃ / s, and the temperature after the cooling treatment is 50 ℃.

[0064] Example 3 The embodiment provides a preparation method of a copper base-copper-chromium contact composite material, which includes the following steps: (1) Aluminum isopropoxide is added to an ethanol solution (the volume ratio of ethanol to water is 3:1) and stirred until dissolved to obtain an aluminum source solution with an aluminum content of 0.15 mol / L; Nitric acid solution is added dropwise to the aluminum source solution to adjust the pH value to 3, and continuous stirring is performed to form a transparent sol; Chromium powder is added to the transparent sol according to a solid-liquid ratio of 1 g:8 mL, ultrasonic dispersion is performed at a power of 300 W for 4 h, and then centrifugal separation is performed at a speed of 3000 rpm for 5 min to obtain coated powder; The coated powder is subjected to low-temperature annealing and curing treatment at a temperature of 400 ℃ and a temperature increasing rate of 10 ℃ / min, and is kept for 1 h to obtain coated chromium powder.

[0065] (2) The coated chromium powder and copper powder are subjected to vacuum induction gas atomization treatment to obtain spherical copper-chromium alloy powder with a particle size of 75 μm.

[0066] The atmosphere for the vacuum induction gas atomization treatment is high-purity nitrogen (purity > 99.99%), which can prevent the coating from being oxidized. The melting temperature is 1450°C, and the atomization pressure is 8 MPa, which can ensure that the sphericity of the powder is > 95%.

[0067] (3) The surface of the copper substrate is polished by sandpaper with a mesh size of 600, and the polished copper substrate is ultrasonically cleaned with an acetone solution at a power of 200 W for 10 min.

[0068] (4) The spherical copper-chromium alloy powder is printed on the surface of the copper substrate to obtain a preform of a copper-based-copper-chromium contact composite material. The preform includes a substrate layer and a contact layer, and the contact layer includes a surface layer and a transition layer connected to the substrate layer. The chromium content of the surface layer is 30 wt%, and the chromium content of the transition layer is 15 wt%.

[0069] The printing method includes: inputting high-purity argon gas as a protective gas under the condition of <5*10 -3 Pa, preheating the copper substrate to 450°C; after preheating, electron beam printing is performed at a power of 3 kW, a scanning speed of 6 mm / s, and a spot diameter of 3 mm.

[0070] (5) The contact layer is subjected to hot isostatic pressing at a temperature of 900°C and a pressure of 100 MPa for 1 h.

[0071] (6) The preform is subjected to first annealing at a temperature of 750°C for 1 h, and then subjected to second annealing at a temperature of 500°C for 3 h; and then prepared by high-pressure nitrogen quenching cooling. The cooling pressure is 2 MPa, the cooling speed is 150°C / s, and the temperature after cooling is 60°C.

[0072] Comparative Example 1 This comparative example provides a preparation method of a copper-based-copper-chromium contact composite material, including the following steps: (1) Aluminum isopropoxide is added to an ethanol solution (the volume ratio of ethanol to water is 3:1) and stirred until dissolved to obtain an aluminum source solution with an aluminum content of 0.2 mol / L; Nitric acid solution is added dropwise to the aluminum source solution to adjust the pH value to 3, and continuous stirring is performed to form a transparent sol; Chromium powder is added to the transparent sol according to a solid-liquid ratio of 1 g:10 mL, ultrasonically dispersed at a power of 300 W for 2 h, and then centrifuged at a speed of 3000 rpm for 5 min to obtain coated powder; The coated powder is subjected to low-temperature annealing and curing treatment at a temperature of 400℃ with a temperature increasing rate of 5℃ / min, and is kept for 1h to obtain the coated chromium powder.

[0073] (2) The coated chromium powder is subjected to vacuum induction gas atomization treatment to obtain spherical copper-chromium alloy powder with a particle size of 15μm-75μm.

[0074] The atmosphere for the vacuum induction gas atomization treatment is high-purity nitrogen (purity > 99.99%) to prevent oxidation of the coating. The melting temperature is 1400℃, and the atomization pressure is 8MPa to ensure that the sphericity of the powder is > 95%.

[0075] (3) The surface of the copper substrate is polished by sandpaper with a mesh size of 600, and the polished copper substrate is ultrasonically cleaned in an acetone solution at a power of 300W for 5min.

[0076] (4) The spherical copper-chromium alloy powder is printed on the surface of the copper substrate to obtain a preform of the copper-based-copper-chromium contact composite material. The preform includes a substrate layer and a contact layer (chromium content 30wt%).

[0077] The printing method includes: inputting high-purity argon as a protective gas under a pressure of <5*10 -3 Pa, preheating the copper substrate to 400℃; and after preheating, performing electron beam printing at a power of 3kW, a scanning speed of 8mm / s, and a spot diameter of 3mm.

[0078] (5) The contact layer is subjected to hot isostatic pressing treatment at a temperature of 1050℃ and a pressure of 100MPa for 1h.

[0079] (6) The preform is subjected to first annealing treatment at a temperature of 850℃ for 1h, and then subjected to second annealing treatment at a temperature of 600℃ for 3h, and then prepared by high-pressure nitrogen quenching cooling. The cooling pressure is 2MPa, the cooling speed is 100℃ / s, and the temperature after cooling treatment is 30℃.

[0080] Comparative Example 2 This comparative example provides a preparation method of a copper-based-copper-chromium contact composite material, including the following steps: (1) The chromium powder and the copper powder are subjected to vacuum induction gas atomization treatment to obtain spherical copper-chromium alloy powder with a particle size of 30μm.

[0081] The atmosphere for the vacuum induction gas atomization treatment is high-purity nitrogen (purity > 99.99%) to prevent oxidation of the coating. The melting temperature is 1400℃, and the atomization pressure is 8MPa to ensure that the sphericity of the powder is > 95%.

[0082] (2) The surface of the copper substrate is polished by 600 mesh sandpaper, and the polished copper substrate is cleaned with an acetone solution at a power of 300 W for 5 min.

[0083] (3) The spherical copper-chromium alloy powder is printed on the surface of the copper substrate to obtain a preform of the copper-based-copper-chromium contact composite material. The preform includes a substrate layer and a contact layer, and the contact layer includes a surface layer and a transition layer connected with the substrate layer. The chromium content of the surface layer is 30 wt%, and the chromium content of the transition layer is 10 wt%.

[0084] The printing method includes: <5*10 -3 The copper substrate is preheated to 400℃ under the condition of inputting high-purity argon gas as a protective gas at a pressure of 5*10

[0085] (4) The contact layer is subjected to hot isostatic pressing at a temperature of 1050℃ and a pressure of 100 MPa for 1 h.

[0086] (5) The preform is subjected to first annealing at a temperature of 850℃ for 1 h, and then subjected to second annealing at a temperature of 600℃ for 3 h, and then cooled by high-pressure nitrogen quenching to obtain the copper-based-copper-chromium contact composite material. The cooling pressure is 2 MPa, the cooling speed is 100℃ / s, and the temperature after cooling is 30℃.

[0087] Comparative Example 3 The present comparative example provides a preparation method of a copper-based-copper-chromium contact composite material, including the following steps: (1) Aluminum isopropoxide is added to an ethanol solution (the volume ratio of ethanol to water is 3:1) and stirred until dissolved to obtain an aluminum source solution with an aluminum content of 0.2 mol / L; Nitric acid solution is added dropwise to the aluminum source solution to adjust the pH value to 3, and continuous stirring is performed to form a transparent sol; Chromium powder is added to the transparent sol according to a solid-liquid ratio of 1 g:10 mL, ultrasonic dispersion is performed at a power of 300 W for 2 h, and then centrifugal separation is performed at a speed of 3000 rpm for 5 min to obtain coated powder; The coated powder is subjected to low-temperature annealing and curing treatment at a temperature of 400℃ with a heating rate of 5℃ / min, and the temperature is maintained for 1 h to obtain coated chromium powder.

[0088] (2) The coated chromium powder and copper powder are mixed to obtain copper-chromium alloy powder.

[0089] (3) The surface of the copper substrate is polished by 600 mesh sandpaper, and the polished copper substrate is cleaned with an acetone solution at a power of 300 W for 5 min.

[0090] (4) printing the copper-chromium alloy powder on the surface of the copper base material to obtain a preform of the copper base-copper chromium contact composite material. The preform includes a base layer and a contact layer, and the contact layer includes a surface layer and a transition layer connected with the base layer. The chromium content of the surface layer is 30wt%, and the chromium content of the transition layer is 10wt%.

[0091] The printing method includes: inputting high-purity argon as a protective gas under a pressure of <5*10 -3 The copper base material is preheated to 400℃ under the input of high-purity argon as a protective gas under a pressure of Pa, and then electron beam printing is performed at a power of 3kW, a scanning speed of 8mm / s and a spot diameter of 3mm.

[0092] (5) The contact layer is subjected to hot isostatic pressing at a temperature of 1050℃ and a pressure of 100MPa for 1h.

[0093] (6) The preform is subjected to first annealing at a temperature of 850℃ for 1h, and then subjected to second annealing at a temperature of 600℃ for 3h, and then obtained by high-pressure nitrogen quenching cooling. The cooling pressure is 2MPa, the cooling speed is 100℃ / s, and the temperature after cooling treatment is 30℃.

[0094] Test example The copper base-copper chromium contact composite materials prepared in Examples 1-3 and Comparative Examples 1-3 are subjected to performance tests, and the results are shown in Table 1.

[0095] Table 1

[0096] As can be seen from Table 1, the density of the copper base-copper chromium contact composite material prepared in Examples 1-3 is increased to more than 99% by hot isostatic pressing, and the porosity is reduced to less than 0.8%, which significantly reduces the weak point of arc ablation. At the same time, the chromium powder is coated by the sol-gel method to inhibit oxidation during atomization and printing, and the density is increased to more than 99% by hot isostatic pressing. It can also be seen that the conductivity of the traditional CuCr50 is only 70%IACS~75%IACS, while the contact layer of the example still maintains ≥98% IACS of the base material conductivity when the chromium content is 25wt%~30wt%, and the hardness is increased by 30%~50%, which breaks through the limitation of increasing chromium to reduce conductivity.

[0097] Although the specific embodiments of the present application are described in detail, it should not be understood as limiting the scope of protection of the present application. Various modifications and variations made by those skilled in the art within the scope described in the claims are still within the scope of protection of the present application.

Claims

1. A method of making a copper base-copper chromium contact composite material, characterized by, The method comprises the following steps: forming a nano-alumina coating layer on the surface of chromium powder by a sol-gel method to obtain coated chromium powder; performing vacuum induction gas atomization treatment on the coated chromium powder and copper powder to obtain spherical copper-chromium alloy powder; performing printing treatment on the surface of a copper substrate by using the spherical copper-chromium alloy powder to obtain a preform of a copper substrate-copper-chromium contact composite material; wherein the preform comprises a substrate layer and a contact layer, and the contact layer comprises a surface layer and a transition layer connected with the substrate layer; performing hot isostatic pressing treatment on the contact layer, and then performing annealing treatment on the preform to obtain a copper substrate-copper-chromium contact composite material; wherein the material of the substrate layer is a copper substrate, the material of the contact layer is a copper-chromium alloy, the chromium content of the surface layer is 25wt%-30wt%, and the chromium content of the transition layer is 10wt%-15wt%.

2. The production method according to claim 1, characterized by, The sol-gel method comprises the following steps: adding aluminum isopropoxide into an ethanol solution and stirring until dissolved to obtain an aluminum source solution; adding nitric acid solution dropwise into the aluminum source solution to adjust the pH value to 2-3, and continuously stirring to form a transparent sol; adding chromium powder into the transparent sol, ultrasonic dispersing, and then centrifugal separation to obtain coated powder; performing low-temperature annealing solidification treatment on the coated powder to obtain coated chromium powder; wherein the aluminum content in the aluminum source solution is 0.1mol / L-0.2mol / L, and the solid-liquid ratio of the chromium powder to the transparent sol is 1g:(5-10)mL.

3. The preparation method according to claim 2, characterized in that, The centrifugal separation is performed at a speed of 3000rpm-5000rpm for 5min-10min; the ultrasonic dispersing is performed at a power of 200W-300W for 2h-4h; the low-temperature annealing solidification treatment is performed at a temperature of 300℃-400℃ for 1h-2h, and the heating rate is 5℃ / min-10℃ / min.

4. The preparation method according to claim 1, characterized in that, The particle size of the spherical copper-chromium alloy powder is 15μm-75μm, and the thickness of the contact layer is 0.8mm-1.8mm.

5. The preparation method according to claim 1, characterized in that, The copper substrate is pretreated before the printing treatment, comprising: polishing the surface of the copper substrate by using 400-600 mesh sandpaper; ultrasonic cleaning the treated copper substrate in acetone solution at a power of 100W-600W for 3min-10min.

6. The method of claim 1, wherein, The printing treatment is performed by electron beam printing, comprising the following steps: at <5*10 -3 The copper substrate is preheated to 400-600°C under the input of high-purity argon gas as a protective gas under the condition of Pa. after preheating, performing electron beam printing at a power of 3kW, a scanning speed of 6mm / s-15mm / s, and a spot diameter of 3mm.

7. The preparation method according to claim 1, characterized in that, The printing treatment is performed by 3D printing, and the power of the 3D printing is 1.5kW, the scanning speed is 800mm / s-1600mm / s, and the powder layer thickness is 0.035mm-0.1mm.

8. The method of claim 1, wherein, The temperature of the hot isostatic pressing treatment is 900℃-1050℃, the pressure of the hot isostatic pressing treatment is 100MPa-120MPa, and the holding time of the hot isostatic pressing treatment is 1h-2h.

9. The method of claim 1, wherein, The annealing treatment comprises first annealing treatment, second annealing treatment, and cooling treatment, wherein, the temperature of the first annealing treatment is 750℃-850℃, and the holding time is 1h-1.5h; The temperature of the second annealing treatment is 500-600 DEG C, and the holding time is 2-3 hours. The cooling treatment is high-pressure nitrogen quenching, the pressure of the cooling treatment is 2-5 MPa, the cooling speed is 50-200 DEG C / s, and the temperature after the cooling treatment is 30-100 DEG C.

10. A copper base-copper chromium contact composite material characterized by, The preparation method according to any one of claims 1-9.

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