A copper-tungsten alloy and its preparation method

Abstract

This invention discloses a copper-tungsten alloy and its preparation method, belonging to the technical field of copper-tungsten alloys. The method involves placing ultrafine tungsten powder in a composite degreasing agent and ultrasonically separating it; pouring a first modified electroplating solution and the degreased ultrafine tungsten powder into an electroplating tank, repeating ultrasonic electroplating 4-6 times, adding modified buffer solution after each cycle, and then separating again; adding a second modified electroplating solution and performing amplitude pulse electroplating to obtain copper-coated tungsten powder; mixing and granulating to obtain copper-coated tungsten powder particles; reducing to obtain reduced copper-coated tungsten powder; and cold pressing to obtain the copper-tungsten alloy. This invention abandons the traditional strong alkali acid washing pretreatment process and uses an environmentally friendly composite degreasing agent composed of anhydrous ethanol and N-methylpyrrolidone to ultrasonically degrease the tungsten powder, achieving a green, environmentally friendly, low-consumption, and high-efficiency preparation of the copper-tungsten alloy.

Description

Technical Field

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

[0002] Copper-tungsten alloys, as a composite alloy of tungsten and copper, combine the high melting point, high resistance to arc erosion, high strength, and low coefficient of thermal expansion of tungsten with the high electrical and thermal conductivity of copper. They are widely used in medium and high voltage switch contact materials, electrical discharge machining electrodes, electronic packaging materials, and heat sink materials. Due to the high melting point of tungsten, the preparation of this alloy can only be carried out using powder metallurgy-related processes.

[0003] According to the search, Chinese patent CN112708794B describes a pretreatment of tungsten powder by alkaline washing and acid washing to improve the surface properties of tungsten powder and enhance the electroplating coating effect. This treatment can effectively remove oil and oxide layer from the surface of tungsten powder, improve the adhesion between the coating and the substrate, make the coating more uniform and dense, and also make the surface of tungsten powder form a rough microstructure to enhance the coating effect.

[0004] However, the aforementioned patented alkaline washing uses a composite degreasing agent containing sodium hydroxide, sodium dodecyl sulfonate, and sodium phosphate, while the acid washing uses a nitric acid solution. During the treatment process, a large amount of high-concentration wastewater is generated. The strong alkaline components can easily disrupt the acid-base balance of the water body, phosphates can easily cause eutrophication of the water body, and nitrate ions can be converted into nitrites, which will bring the risk of water pollution.

[0005] To address the aforementioned shortcomings, the industry has explored various environmentally friendly pretreatment methods, primarily categorized into organic solvent cleaning and plasma cleaning. Ultrasonic degreasing using single solvents such as ethanol, acetone, and isopropanol is effective for removing light oil contaminants, but it is insufficient for cleaning the dense oxide layer and polar contaminants on the tungsten powder surface, easily leading to low adhesion and poor uniformity of the subsequent copper plating. While low-pressure plasma etching purifies the tungsten powder surface, achieving high cleanliness and eliminating waste liquid discharge, it requires significant equipment investment, has low processing efficiency, and faces challenges in achieving uniform powder processing, hindering large-scale industrial application.

[0006] Based on this, the present invention designs a copper-tungsten alloy and its preparation method to solve the above problems. Summary of the Invention

[0007] To address the aforementioned shortcomings of existing technologies, this invention provides a method for preparing a copper-tungsten alloy, comprising the following steps:

[0008] S1: Place the ultrafine tungsten powder into a composite degreasing agent, which is a mixture of anhydrous ethanol and N-methylpyrrolidone, and then treat it with ultrasound to separate and obtain degreased ultrafine tungsten powder.

[0009] S2: Pour the first modified electroplating solution and degreased ultrafine tungsten powder into the electroplating tank, repeat ultrasonic electroplating 4-6 times, add modified buffer solution once per cycle, and separate to obtain electroplated tungsten powder.

[0010] S3: Pour the second modified electroplating solution and the first electroplating tungsten powder into the electroplating tank for amplitude pulse electroplating, with a positive pulse current density of 9-11 A / dm. 2 The electroplating time is 25-35 seconds, and the reverse pulse current density is 3.5-4.5 A / dm³. 2 The electroplating time is 12-18s, and copper-coated tungsten powder is obtained by separation.

[0011] S4: Mix copper-coated tungsten powder with a modified granulating agent, wherein the modified granulating agent is a compound of hydroxypropyl methylcellulose and polyethylene glycol, add water to granulate, and dry to obtain copper-coated tungsten powder particles;

[0012] S5: Reduce copper-coated tungsten powder particles under hydrogen to obtain reduced copper-coated tungsten powder;

[0013] S6: The reduced copper-coated tungsten powder is pre-pressed and the pressure is increased and held to obtain a copper-coated tungsten powder green blank;

[0014] S7: The cold-pressed green billet is first heated to 650-750℃ under vacuum and held at that temperature while applying pressure. Then it is heated to 1030-1170℃ and held at that temperature while applying pressure. After cooling, the pressure is released to obtain a copper-tungsten alloy.

[0015] Furthermore, S1 specifically involves: placing ultrafine tungsten powder into a composite degreasing agent, wherein the composite degreasing agent is a mixture of anhydrous ethanol and N-methylpyrrolidone in a volume ratio of 4-6:1, and the volume ratio of the composite degreasing agent to the ultrafine tungsten powder is 3-4:1. The mixture is ultrasonically treated at 200-300W and 40-60℃ for 10-20 minutes, and then separated by vacuum filtration to obtain degreased ultrafine tungsten powder. The composite degreasing agent is recycled after distillation.

[0016] Furthermore, S2 specifically involves: pouring the first modified electroplating solution and degreased ultrafine tungsten powder into an ultrasonic electroplating tank, with the degreased ultrafine tungsten powder loading being 18-22 g / dm³. 2 Stir at 250-350 rpm for 1.5-4.5 min at room temperature, then let stand for 2.5-5.5 min, at a current density of 2-4 A / dm³. 2 Under a DC power supply and an ultrasonic power of 250-350W, ultrasonic electroplating is performed for 3-5 minutes, repeated 4-6 times. For each cycle, 1 / 10-1 / 8 of the volume of the first modified electroplating solution is added as modified buffer. After electroplating, the mixture is separated by vacuum filtration to obtain first-electroplated tungsten powder.

[0017] Furthermore, the modified buffer solution is prepared by mixing maleic acid and boric acid in a molar ratio of 1:1-1.2, and the concentration of boric acid is 0.7-1.0 mol / L.

[0018] Furthermore, the first modified electroplating solution includes copper pyrophosphate at a concentration of 90-110 g / L, triammonium citrate at a concentration of 4-6 g / L, aminosulfonic acid at a concentration of 35-50 g / L, sodium α-olefin sulfonate at a concentration of 0.15-0.25 g / L, and polyvinylpyrrolidone at a concentration of 0.1-0.2 g / L.

[0019] Furthermore, S3 specifically involves: pouring the second modified electroplating solution and the primary electroplating tungsten powder into the electroplating tank, with the primary electroplating tungsten powder loading being 9-11 g / dm³. 2 Variable amplitude pulse electroplating was performed at 19-21℃, with a forward pulse current density of 9-11 A / dm². 2 The electroplating time is 25-35 seconds, and the reverse pulse current density is 3.5-4.5 A / dm³. 2 The electroplating time is 12-18s, the pulse frequency is 800-1200Hz, and after electroplating, the copper-coated tungsten powder is obtained.

[0020] Furthermore, the second modified electroplating solution includes basic copper carbonate at a concentration of 55-75 g / L, methylbenzotriazole at a concentration of 55-75 g / L, aluminum hypophosphite at a concentration of 1.5-1.8 g / L, and potassium antimony tartrate at a concentration of 2-3 g / L.

[0021] Furthermore, S4 specifically involves: mixing copper-coated tungsten powder with a modified granulator at a mass ratio of 100:0.4-0.7, wherein the modified granulator is a compound of hydroxypropyl methylcellulose and polyethylene glycol 400 at a mass ratio of 3-5:1; adding 8-15% of the total mass of the copper-coated tungsten powder and the modified granulator to deionized water; granulating the mixture using a granulator to obtain particles with a particle size of 0.1-0.3 mm; and drying the mixture to obtain copper-coated tungsten powder particles.

[0022] Furthermore, S7 specifically involves placing the cold-pressed green blank into a graphite mold and then placing it in a vacuum hot-pressing sintering furnace. The vacuum level inside the furnace is first evacuated to 5 × 10⁻⁶. -3 -8×10 -4 Pa employs a segmented sintering process. First, the temperature is raised to 650-750℃ at a heating rate of 6-8℃ / min and held for 0.3-0.5h, while a pressure of 7-13MPa is applied. Then, the temperature is raised to 1030-1170℃ at a heating rate of 4-6℃ / min and held for 0.6-1.4h, while the pressure is increased to 35-45MPa. After sintering, the furnace is cooled at a cooling rate of 3-5℃ / min. The pressure is released after the furnace temperature drops below 200℃ to obtain a copper-tungsten alloy.

[0023] A copper-tungsten alloy prepared according to the method.

[0024] Compared with the prior art, the beneficial effects of this invention are as follows:

[0025] 1. This invention abandons the traditional strong alkali acid washing pretreatment process and uses an environmentally friendly composite degreasing agent of anhydrous ethanol and N-methylpyrrolidone to perform ultrasonic degreasing of tungsten powder, so as to achieve green, environmentally friendly, low-consumption and high-efficiency preparation of copper-tungsten alloy, and avoid the risks of water pollution and eutrophication caused by pollutants such as strong alkali, phosphate, and nitrate.

[0026] 2. This invention uses a two-step modified electroplating and modified buffer replenishment process to efficiently remove the dense oxide layer and polar contaminants on the surface of tungsten powder, improve the adhesion and uniformity of the coating, and simultaneously improve the room temperature tensile strength, elongation after fracture and hardness of copper-tungsten alloy, giving the alloy excellent mechanical properties. At the same time, the process is simple and low in cost. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0028] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0030] Example 1: This example provides a method for preparing a copper-tungsten alloy, including the following steps:

[0031] S1: Ultrafine tungsten powder (0.4μm) is placed in a composite degreasing agent, which is a mixture of anhydrous ethanol and N-methylpyrrolidone in a volume ratio of 4:1. The volume ratio of the composite degreasing agent to the ultrafine tungsten powder is 3:1. The mixture is ultrasonically treated at 200W and 40℃ for 10 minutes, and then separated by vacuum filtration to obtain degreased ultrafine tungsten powder. The composite degreasing agent is recycled after distillation.

[0032] S2: Pour the first modified electroplating solution and degreased ultrafine tungsten powder into the ultrasonic electroplating tank. The loading amount of degreased ultrafine tungsten powder is 18g / dm³. 2 Stirred at 250 rpm for 1.5 min at room temperature, then let stand for 2.5 min, at a current density of 2 A / dm³ 2 Under a DC power supply and an ultrasonic power of 250W, ultrasonic electroplating was performed for 3 minutes, repeated 4 times. For each cycle, 1 / 10 of the volume of the first modified electroplating solution was added as a modified buffer. After electroplating, the tungsten powder was separated by vacuum filtration to obtain the first electroplated tungsten powder.

[0033] The modified buffer solution is prepared by mixing maleic acid and boric acid in a molar ratio of 1:1, with the concentration of boric acid being 0.7 mol / L.

[0034] The first modified electroplating solution includes copper pyrophosphate at a concentration of 90 g / L, triammonium citrate at a concentration of 4 g / L, aminosulfonic acid at a concentration of 35 g / L, sodium α-olefin sulfonate at a concentration of 0.15 g / L, and polyvinylpyrrolidone at a concentration of 0.1 g / L.

[0035] S3: Pour the second modified electroplating solution and the primary electroplating tungsten powder into the electroplating tank. The loading amount of the primary electroplating tungsten powder is 9 g / dm³. 2 Amplitude pulse electroplating was performed at 19℃ with a forward pulse current density of 9 A / dm². 2 The electroplating time was 25 seconds, and the reverse pulse current density was 3.5 A / dm³. 2 The electroplating time was 12 seconds and the pulse frequency was 800 Hz. After electroplating, the copper-coated tungsten powder was obtained by separation.

[0036] The second modified electroplating solution includes basic copper carbonate at a concentration of 55 g / L, methylbenzotriazole at a concentration of 55 g / L, aluminum hypophosphite at a concentration of 1.5 g / L, and potassium antimony tartrate at a concentration of 2 g / L.

[0037] S4: Mix copper-coated tungsten powder and modified granulating agent at a mass ratio of 100:0.4. The modified granulating agent is a compound of hydroxypropyl methylcellulose and polyethylene glycol 400 at a mass ratio of 3:1. Add 8% of the total mass of copper-coated tungsten powder and modified granulating agent in deionized water. Granulate the mixture into particles with a particle size of 0.1 mm using a granulator. Dry the particles (at 40°C and a wind speed of 2.0 m / s for 2 hours) to obtain copper-coated tungsten powder particles.

[0038] S5: Place the copper-coated tungsten powder particles into a hydrogen furnace, introduce hydrogen gas at a flow rate of 0.6 L / min, and reduce at 300℃ for 1 h to obtain reduced copper-coated tungsten powder;

[0039] S6: Place the reduced copper-coated tungsten powder into a cold press mold, pre-press it at 7MPa for 1.5min, then increase the cold pressing pressure to 70MPa, hold the pressure for 4min, and press it to form a copper-coated tungsten powder blank.

[0040] S7: Place the cold-pressed green body into a graphite mold and put it into a vacuum hot pressing sintering furnace. First, evacuate the vacuum level in the furnace to 5×10. -3 Pa was subjected to segmented sintering. First, the temperature was raised to 650℃ at a heating rate of 6℃ / min and held for 0.3h, while a pressure of 7MPa was applied. Then, the temperature was raised to 1030℃ at a heating rate of 4℃ / min and held for 0.6h, while the pressure was increased to 35MPa. After sintering, the furnace was cooled at a cooling rate of 3℃ / min. After the furnace temperature dropped below 200℃, the pressure was released to obtain a copper-tungsten alloy.

[0041] Example 2: This example provides a method for preparing a copper-tungsten alloy, including the following steps:

[0042] S1: Ultrafine tungsten powder (0.4μm) is placed in a composite degreasing agent, which is a mixture of anhydrous ethanol and N-methylpyrrolidone in a volume ratio of 6:1. The volume ratio of the composite degreasing agent to the ultrafine tungsten powder is 4:1. The mixture is ultrasonically treated at 300W and 60℃ for 20 minutes, and then separated by vacuum filtration to obtain degreased ultrafine tungsten powder. The composite degreasing agent is recycled after distillation.

[0043] S2: Pour the first modified electroplating solution and degreased ultrafine tungsten powder into the ultrasonic electroplating tank. The loading amount of degreased ultrafine tungsten powder is 22g / dm³. 2 Stirred at 350 rpm for 4.5 min at room temperature, then let stand for 5.5 min, and then at a current density of 4 A / dm³. 2 Under a DC power supply and an ultrasonic power of 350W, ultrasonic electroplating was performed for 5 minutes, repeated 6 times. Each time, 1 / 8 of the volume of the first modified electroplating solution was added as a modified buffer. After electroplating, the tungsten powder was separated by vacuum filtration to obtain the first electroplated tungsten powder.

[0044] The modified buffer solution is prepared by mixing maleic acid and boric acid in a molar ratio of 1:1.2, and the concentration of boric acid is 1.0 mol / L.

[0045] The first modified electroplating solution includes copper pyrophosphate at a concentration of 110 g / L, triammonium citrate at a concentration of 6 g / L, aminosulfonic acid at a concentration of 50 g / L, sodium α-alkenyl sulfonate at a concentration of 0.25 g / L, and polyvinylpyrrolidone at a concentration of 0.2 g / L.

[0046] S3: Pour the second modified electroplating solution and the primary electroplating tungsten powder into the electroplating tank. The loading amount of the primary electroplating tungsten powder is 11 g / dm³. 2Amplitude pulse electroplating was performed at 21℃ with a forward pulse current density of 11 A / dm². 2 The electroplating time was 35 seconds, and the reverse pulse current density was 4.5 A / dm³. 2 The electroplating time was 18 seconds, the pulse frequency was 1200 Hz, and after electroplating, the copper-coated tungsten powder was obtained by separation.

[0047] The second modified electroplating solution includes basic copper carbonate at a concentration of 75 g / L, methylbenzotriazole at a concentration of 75 g / L, aluminum hypophosphite at a concentration of 1.8 g / L, and potassium antimony tartrate at a concentration of 3 g / L.

[0048] S4: Mix copper-coated tungsten powder and modified granulating agent at a mass ratio of 100:0.7. The modified granulating agent is a compound of hydroxypropyl methylcellulose and polyethylene glycol 400 at a mass ratio of 5:1. Add 15% of the total mass of copper-coated tungsten powder and modified granulating agent in deionized water. Granulate the mixture into particles with a particle size of 0.3 mm using a granulator. Dry the particles (at 40°C and a wind speed of 2.0 m / s for 2 hours) to obtain copper-coated tungsten powder particles.

[0049] S5: Place the copper-coated tungsten powder particles into a hydrogen furnace, introduce hydrogen gas at a flow rate of 1.8 L / min, and reduce at 450℃ for 1.7 h to obtain reduced copper-coated tungsten powder;

[0050] S6: Place the reduced copper-coated tungsten powder into a cold press mold, pre-press it at 13MPa for 2.5min, then increase the cold pressing pressure to 90MPa, hold the pressure for 5min, and press it to form a copper-coated tungsten powder blank.

[0051] S7: Place the cold-pressed green body into a graphite mold and put it into a vacuum hot pressing sintering furnace. First, evacuate the vacuum level in the furnace to 8×10. -4 Pa was subjected to segmented sintering. First, the temperature was raised to 750°C at a heating rate of 8°C / min and held for 0.5 hours while applying a pressure of 13 MPa. Then, the temperature was raised to 1170°C at a heating rate of 6°C / min and held for 1.4 hours while increasing the pressure to 45 MPa. After sintering, the furnace was cooled at a cooling rate of 5°C / min. After the furnace temperature dropped below 200°C, the pressure was released to obtain a copper-tungsten alloy.

[0052] Example 3: This example provides a method for preparing a copper-tungsten alloy, including the following steps:

[0053] S1: Ultrafine tungsten powder (0.4μm) is placed in a composite degreasing agent, which is a mixture of anhydrous ethanol and N-methylpyrrolidone in a volume ratio of 5:1. The volume ratio of the composite degreasing agent to the ultrafine tungsten powder is 3:1. The mixture is ultrasonically treated at 240W and 48℃ for 13 minutes, and then separated by vacuum filtration to obtain degreased ultrafine tungsten powder. The composite degreasing agent is recycled after distillation.

[0054] S2: Pour the first modified electroplating solution and degreased ultrafine tungsten powder into the ultrasonic electroplating tank. The loading amount of degreased ultrafine tungsten powder is 19 g / dm³. 2 Stirred at 320 rpm for 2 minutes at room temperature, then let stand for 2.5 minutes, and then at a current density of 4 A / dm³. 2 Under a DC power supply and an ultrasonic power of 250W, ultrasonic electroplating was performed for 3 minutes, repeated 4 times. For each cycle, 1 / 10 of the volume of the first modified electroplating solution was added as a modified buffer. After electroplating, the tungsten powder was separated by vacuum filtration to obtain the first electroplated tungsten powder.

[0055] The modified buffer solution is prepared by mixing maleic acid and boric acid in a molar ratio of 1:1.2, and the concentration of boric acid is 0.7 mol / L.

[0056] The first modified electroplating solution includes copper pyrophosphate at a concentration of 95 g / L, triammonium citrate at a concentration of 4 g / L, aminosulfonic acid at a concentration of 40 g / L, sodium α-alkenylsulfonate at a concentration of 0.15 g / L, and polyvinylpyrrolidone at a concentration of 0.13 g / L.

[0057] S3: Pour the second modified electroplating solution and the primary electroplating tungsten powder into the electroplating tank. The loading amount of the primary electroplating tungsten powder is 9 g / dm³. 2 Amplitude pulse electroplating was performed at 20℃, with a forward pulse current density of 11 A / dm². 2 The electroplating time was 32 seconds, and the reverse pulse current density was 3.5 A / dm³. 2 The electroplating time was 15 seconds, the pulse frequency was 800 Hz, and after electroplating, the copper-coated tungsten powder was obtained by separation.

[0058] The second modified electroplating solution includes basic copper carbonate at a concentration of 68 g / L, methylbenzotriazole at a concentration of 70 g / L, aluminum hypophosphite at a concentration of 1.7 g / L, and potassium antimony tartrate at a concentration of 2.2 g / L.

[0059] S4: Mix copper-coated tungsten powder with a modified granulator at a mass ratio of 100:0.5. The modified granulator is a compound of hydroxypropyl methylcellulose and polyethylene glycol 400 at a mass ratio of 5:1. Add 12% of the total mass of copper-coated tungsten powder and modified granulator to deionized water. Granulate the mixture into particles with a particle size of 0.1 mm using a granulator. Dry the particles (at 40°C and a wind speed of 2.0 m / s for 2 hours) to obtain copper-coated tungsten powder particles.

[0060] S5: Place the copper-coated tungsten powder particles into a hydrogen furnace, introduce hydrogen gas at a flow rate of 1.6 L / min, and reduce at 320℃ for 1 h to obtain reduced copper-coated tungsten powder;

[0061] S6: Place the reduced copper-coated tungsten powder into a cold press mold, pre-press it at 10MPa for 2.5min, then increase the cold pressing pressure to 75MPa, hold the pressure for 4min, and press it to form a copper-coated tungsten powder blank.

[0062] S7: Place the cold-pressed green body into a graphite mold and put it into a vacuum hot pressing sintering furnace. First, evacuate the vacuum level in the furnace to 5×10. -3 Pa was subjected to segmented sintering. First, the temperature was raised to 680℃ at a heating rate of 6℃ / min and held for 0.5h, while a pressure of 10MPa was applied. Then, the temperature was raised to 1060℃ at a heating rate of 5℃ / min and held for 1.2h, while the pressure was increased to 42MPa. After sintering, the furnace was cooled at a cooling rate of 5℃ / min. After the furnace temperature dropped below 200℃, the pressure was released to obtain a copper-tungsten alloy.

[0063] Testing showed that the copper-tungsten alloys prepared in Examples 1-3 all met the following requirements: electrical conductivity ≥ 54% IACS, thermal conductivity ≥ 220 W / (m·K), and coefficient of thermal expansion ≤ 10. -6 The arc burning time is ≤5s under the following conditions: ℃, AC 220V / 10A.

[0064] Comparative Example 1: The difference between this comparative example and Example 3 is that in S2, the components of the first modified electroplating solution are replaced with 100 g / L anhydrous copper sulfate, 2.5 g / L glacial acetic acid, 40 g / L concentrated sulfuric acid, 0.2 g / L sodium dodecyl sulfonate, and 0.1 g / L polyethylene glycol.

[0065] Comparative Example 2: The difference between this comparative example and Example 3 is that, in S2, no modified buffer solution is added after each cycle.

[0066] Comparative Example 3: The difference between this comparative example and Example 3 is that in S3, the second modified electroplating solution does not contain potassium antimony tartrate.

[0067] Comparative Example 4: The difference between this comparative example and Example 3 is that S1 is replaced with the traditional acid and alkali washing steps. The alkali washing step is as follows: ultrafine tungsten powder is immersed in a degreasing agent with a volume ratio of degreasing agent to ultrafine tungsten powder of 4:1. The composition and content of the degreasing agent are: sodium hydroxide 10wt%, sodium dodecyl sulfonate 1wt%, sodium phosphate 4wt%, and the balance is water. It is cleaned under ultrasonic conditions at 75°C for 30 minutes, the ultrafine tungsten powder is filtered using a centrifuge, and it is repeatedly rinsed with clean water until the pH value is neutral, and then dried. The acid washing step is as follows: ultrafine tungsten powder after alkali washing is immersed in a 5% nitric acid solution with a volume ratio of nitric acid solution to ultrafine tungsten powder of 3:1, and it is cleaned under ultrasonic conditions at 25°C for 10 minutes. The ultrafine tungsten powder is filtered using a centrifuge, and it is repeatedly rinsed with clean water until the pH value is neutral, and then dried and vacuum stored.

[0068] Comparative Example 5: The difference between this comparative example and Example 3 is that S2 uses conventional DC electroplating without ultrasonic assistance.

[0069] Comparative Example 6: This comparative example differs from Example 3 in that conventional pulse electroplating was performed at 20°C with a current density of 11 A / dm³. 2 The electroplating time was 47 seconds, the pulse frequency was 800 Hz, and variable amplitude pulses were not used.

[0070] Comparative example: The copper-tungsten alloy prepared according to Example 13 of Chinese Patent CN112708794B.

[0071] Experimental Example 1: The tensile strength (MPa) and elongation after fracture (%) of the copper-tungsten alloy prepared in this invention were tested at room temperature (25℃) and at 600℃ according to GB / T 228.2-2015 "Metallic materials - Tensile testing - Part 2: High temperature test method".

[0072] Experimental Example 2: The hardness (HRA) of the copper-tungsten alloy prepared in this invention at room temperature and 600℃ was tested according to GB / T 3849.

[0073] The results are shown in the table below:

[0074]

[0075] As shown in the table above, the copper-tungsten alloy prepared by this invention has an average tensile strength of over 340 MPa at room temperature (25°C), an average elongation after fracture of over 22%, and an average hardness of over 60.5 HRA. Under high-temperature testing conditions of 600°C, the average tensile strength of the alloy in the example remains above 220 MPa, and the average hardness remains above 24 HRA, with minimal degradation in various properties.

[0076] In Comparative Example 1, the copper coating on the tungsten powder surface was poorly bonded and the uniformity of the coating was reduced due to the replacement with a traditional copper sulfate electroplating solution, resulting in a general decrease in overall mechanical properties. In Comparative Example 2, the pH and composition of the electroplating system fluctuated because no modified buffer solution was added during the electroplating process, leading to a decrease in coating quality and slightly inferior performance compared to the example. In Comparative Example 3, the high-temperature performance decreased the most because the second modified electroplating solution lacked potassium antimony tartrate.

[0077] Comparative Example 4 replaced ultrasonic degreasing with a composite degreasing agent with a traditional strong alkali pickling pretreatment process. Traditional alkali pickling contains strong alkali and phosphates, while acid pickling uses nitric acid solution, generating highly polluting wastewater and causing a significant decline in the room-temperature and high-temperature mechanical properties of the copper-tungsten alloy. Comparative Example 5 eliminated ultrasonic assistance in process S2, using only conventional DC electroplating. Without ultrasonic action, the ultrafine tungsten powder easily agglomerates, resulting in uneven deposition of copper ions on the tungsten powder surface, leading to a decrease in the alloy's room-temperature mechanical properties and a significant reduction in high-temperature tensile strength and hardness. Comparative Example 6 replaced the amplitude-modulated pulse electroplating in S3 with conventional pulse electroplating, without current amplitude control, resulting in poorer high-temperature resistance of the copper coating and a reduced retention rate of the alloy's high-temperature tensile strength and hardness.

[0078] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a copper-tungsten alloy, characterized in that, Includes the following steps: S1: Place the ultrafine tungsten powder into a composite degreasing agent, which is a mixture of anhydrous ethanol and N-methylpyrrolidone, and then treat it with ultrasound to separate and obtain degreased ultrafine tungsten powder. S2: Pour the first modified electroplating solution and degreased ultrafine tungsten powder into the electroplating tank, repeat ultrasonic electroplating 4-6 times, add modified buffer solution once per cycle, and separate to obtain electroplated tungsten powder. S3: Pour the second modified electroplating solution and the first electroplating tungsten powder into the electroplating tank for amplitude pulse electroplating, with a positive pulse current density of 9-11 A / dm. 2 The reverse pulse current density is 3.5-4.5 A / dm². 2 Copper-coated tungsten powder was obtained by separation; S4: Mix copper-coated tungsten powder with a modified granulating agent, wherein the modified granulating agent is a compound of hydroxypropyl methylcellulose and polyethylene glycol, add water to granulate, and dry to obtain copper-coated tungsten powder particles; S5: Reduce copper-coated tungsten powder particles under hydrogen to obtain reduced copper-coated tungsten powder; S6: The reduced copper-coated tungsten powder is pre-pressed and the pressure is increased and held to obtain a copper-coated tungsten powder green blank; S7: The cold-pressed green billet is first heated to 650-750℃ under vacuum and held at that temperature while applying pressure. Then it is heated to 1030-1170℃ and held at that temperature while applying pressure. After cooling, the pressure is released to obtain a copper-tungsten alloy.

2. The method for preparing copper-tungsten alloy according to claim 1, characterized in that, S1 specifically involves: placing ultrafine tungsten powder into a composite degreasing agent, wherein the composite degreasing agent is a mixture of anhydrous ethanol and N-methylpyrrolidone in a volume ratio of 4-6:1, and the volume ratio of the composite degreasing agent to the ultrafine tungsten powder is 3-4:

1. The mixture is ultrasonically treated at 200-300W and 40-60℃ for 10-20 minutes, and then separated by vacuum filtration to obtain degreased ultrafine tungsten powder. The composite degreasing agent is recycled after distillation.

3. The method for preparing the copper-tungsten alloy according to claim 1, characterized in that, S2 specifically involves pouring the first modified electroplating solution and degreased ultrafine tungsten powder into an ultrasonic electroplating tank, with the degreased ultrafine tungsten powder loading being 18-22 g / dm³. 2 Stir at 250-350 rpm for 1.5-4.5 min at room temperature, then let stand for 2.5-5.5 min, at a current density of 2-4 A / dm³. 2 Under a DC power supply and an ultrasonic power of 250-350W, ultrasonic electroplating is performed for 3-5 minutes, repeated 4-6 times. For each cycle, 1 / 10-1 / 8 of the volume of the first modified electroplating solution is added as modified buffer. After electroplating, the mixture is separated by vacuum filtration to obtain tungsten powder that has been electroplated once.

4. The method for preparing the copper-tungsten alloy according to claim 3, characterized in that, The modified buffer solution is prepared by mixing maleic acid and boric acid in a molar ratio of 1:1-1.2, and the concentration of boric acid is 0.7-1.0 mol / L.

5. The method for preparing the copper-tungsten alloy according to claim 3, characterized in that, The first modified electroplating solution includes copper pyrophosphate at a concentration of 90-110 g / L, triammonium citrate at a concentration of 4-6 g / L, aminosulfonic acid at a concentration of 35-50 g / L, sodium α-olefin sulfonate at a concentration of 0.15-0.25 g / L, and polyvinylpyrrolidone at a concentration of 0.1-0.2 g / L.

6. The method for preparing the copper-tungsten alloy according to claim 1, characterized in that, S3 specifically involves: pouring the second modified electroplating solution and the primary electroplating tungsten powder into the electroplating tank, with the primary electroplating tungsten powder loading amount being 9-11 g / dm³. 2 Variable amplitude pulse electroplating was performed at 19-21℃, with a forward pulse current density of 9-11 A / dm². 2 The electroplating time is 25-35 seconds, and the reverse pulse current density is 3.5-4.5 A / dm³. 2 The electroplating time is 12-18s, the pulse frequency is 800-1200Hz, and after electroplating, the copper-coated tungsten powder is obtained.

7. The method for preparing the copper-tungsten alloy according to claim 6, characterized in that, The second modified electroplating solution includes basic copper carbonate at a concentration of 55-75 g / L, methylbenzotriazole at a concentration of 55-75 g / L, aluminum hypophosphite at a concentration of 1.5-1.8 g / L, and potassium antimony tartrate at a concentration of 2-3 g / L.

8. The method for preparing the copper-tungsten alloy according to claim 1, characterized in that, S4 specifically involves mixing copper-coated tungsten powder with a modified granulator at a mass ratio of 100:0.4-0.

7. The modified granulator is a compound of hydroxypropyl methylcellulose and polyethylene glycol 400 at a mass ratio of 3-5:

1. 8-15% of the total mass of the copper-coated tungsten powder and the modified granulator is added to deionized water. The mixture is then granulated using a granulator to obtain particles with a diameter of 0.1-0.3 mm, and dried to obtain copper-coated tungsten powder particles.

9. The method for preparing the copper-tungsten alloy according to claim 1, characterized in that, S7 specifically involves placing the cold-pressed green blank into a graphite mold and then placing it in a vacuum hot-pressing sintering furnace. The vacuum level inside the furnace is first evacuated to 5 × 10⁻⁶. -3 -8×10 -4 Pa employs a segmented sintering process. First, the temperature is raised to 650-750℃ at a heating rate of 6-8℃ / min and held for 0.3-0.5h, while a pressure of 7-13MPa is applied. Then, the temperature is raised to 1030-1170℃ at a heating rate of 4-6℃ / min and held for 0.6-1.4h, while the pressure is increased to 35-45MPa. After sintering, the furnace is cooled at a cooling rate of 3-5℃ / min. The pressure is released after the furnace temperature drops below 200℃ to obtain a copper-tungsten alloy.

10. A copper-tungsten alloy prepared by the method according to any one of claims 1-9.

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