Preparation method of tungsten-copper moving knife contact material with complex structure

Abstract

The invention discloses a preparation method of a tungsten-copper moving knife contact material with a complex structure, and the preparation method comprises the following steps: S1, structure modeling and process planning, S2, tungsten skeleton slurry preparation, S3, 3DP printing forming, S4, infiltration assembly and pretreatment, S5, vacuum infiltration, and S6, precise post-treatment.The method adopts a three-dimensional modeling dynamic slicing technology, a tungsten skeleton green body is prepared through a 3DP printing technology, and the tungsten-copper moving knife contact material with the complex structure is obtained; metallurgical bonding of a copper alloy and a tungsten framework is achieved by combining a vacuum infiltration process, the density of the framework is improved by optimizing the particle size ratio of tungsten powder, the copper liquid infiltration rate is controlled by adopting a gradient heating infiltration system, and a traditional degreasing and sintering link is omitted. Compared with a traditional mold pressing technology, the material utilization rate is increased, the machining period is shortened, the technical problems of short electrical life and the like caused by difficult forming of a complex structure and insufficient bonding strength are solved, and the method is suitable for high-reliability scenes such as high-voltage electric appliance switches and new energy automobile motors.

Description

TECHNICAL FIELD

[0001] The application relates to a tungsten-copper moving knife contact preparation technology field, in particular to a preparation method of a tungsten-copper moving knife contact material with a complex structure. BACKGROUND

[0002] The high-frequency opening and closing moving knife contact which is widely used in the fields of high-voltage electrical equipment and new energy vehicles needs to withstand 10 3 -10 4 K arc high-temperature burning and extreme working conditions, and the material thereof must have excellent electrical conductivity, heat conductivity, arc erosion resistance and mechanical strength. A traditional preparation method adopts a tungsten powder compact and a copper alloy substrate co-sintering process, a part blank is prepared through die forming or injection molding, and subsequent mechanical processing is relied on to realize complex structure forming. Such a process has the following significant technical bottlenecks: on the one hand, tungsten-copper alloy is difficult to cut due to high hardness and brittleness, the material removal rate is as high as 50% or more, and complex cavities and special-shaped runners are difficult to accurately process, and the tool is severely worn; on the other hand, the traditional process needs to go through multiple links such as degreasing, sintering, infiltration and machining, and the process is long and it is difficult to guarantee the size precision of deep cavities, narrow seams and other fine structures, resulting in insufficient product electrical life and increased risk of local thermal cycle failure. In addition, although injection molding can reduce the amount of machining, the cost of developing a precision mold is high, usually 5-50 thousand yuan, and the design cycle is as long as 1-6 months, so the cost of a single piece is difficult to reduce in small batch production; meanwhile, it is limited by the structure of the mold.

[0003] In the prior art, the patent with the number CN202011098009.2 improves the injection molding effect by mixing spherical tungsten powder and wax-based binder, so that the material utilization rate of the complex-shaped contact is increased to 83%, but it still needs subsequent turning and milling to remove the sintering neck and relies on high-temperature infiltration to compensate for the copper distribution uniformity problem. However, this process still has inherent defects when facing special structures such as deep cavity runners and special-shaped surfaces of the moving knife contact: the size tolerance accumulation effect caused by mechanical processing, the size tolerance of the existing technology can only be controlled within ±0.1 mm, which cannot meet the consistency requirements of the contact surface for 50,000 times of electrical life. SUMMARY

[0004] The existing tungsten-copper moving knife contact preparation method has the problems of complex structure forming difficulty, serious material waste and insufficient bonding strength leading to short electrical life. In view of the above technical problems, the application provides a preparation method of a tungsten-copper moving knife contact material with a complex structure.

[0005] The technical scheme of the application is a preparation method of a tungsten-copper moving knife contact material with a complex structure, comprising the following steps: S1, structure modeling and process planning: The three-dimensional model containing the shape of the tool head is built by SolidWorks / UG, and the thickness of the slicing layer is dynamically adjusted according to the complexity of the structure: 50-100 μm is used for simple regions, and 20-50 μm is used for complex regions; S2, preparing a tungsten skeleton slurry: Take tungsten powder with a purity of ≥99.9% as aggregate, and ball-mill mix 5-15% of a binder, 0.5-2% of a dispersant, and the balance of the aggregate for 4-8 h; dilute with anhydrous ethanol or deionized water at room temperature until the target viscosity is 500-2000 mPa·s, to obtain a tungsten skeleton slurry; S3, 3DP printing forming: The piezoelectric tungsten skeleton slurry is sprayed to form, the tungsten skeleton slurry prepared in S2 is atomized into tiny droplets, and then sprayed layer by layer to solidify on the substrate, the solidification time of each layer is 10-30 s, and the green body is obtained after printing and air drying at room temperature for 2-4 h; S4, infiltration assembly and pretreatment: Calculate the pore volume of the tungsten skeleton green body in S3, the weight of the copper alloy added is 1.05-1.2 times the pore volume, the weight of the copper alloy block is obtained according to the pore volume of the tungsten skeleton green body, the copper alloy block and the tungsten skeleton green body are assembled in a mold, the assembly gap is ≤0.1 mm, the roughness of the joint surface is polished to Ra≤0.8 μm, and then dried after ultrasonic cleaning with anhydrous ethanol for 15-20 min, to obtain an assembly component; S5, vacuum infiltration: Under a vacuum degree of 1×10 -3 -5×10 -3 Pa, the assembly component in S4 is heated to 1100-1250℃ at a heating rate of 10-15℃ / h, kept for 2-5 h, and then cooled to room temperature at a cooling rate of 5-8℃ / h, to obtain a 3DP printing sintered product; S6, precise post-processing: The 3DP printing sintered product is finished and deburred to obtain a moving knife tungsten copper contact.

[0006] Description: This method is suitable for red copper, chromium bronze, copper chromium zirconium and other copper alloys, and the infiltration is customized by "one alloy at one temperature", such as copper chromium zirconium at 1200℃ to inhibit high Cr segregation, which expands the application of products in different conductivity and strength demand scenarios; The process has high stability, and key parameters such as viscosity, vacuum degree, and heating rate can be monitored in real time, and the performance fluctuation between batches is less than 5%; The green body is directly infiltrated after air drying, without the need for degreasing and sintering, reducing energy consumption and environmental pollution, and meeting the trend of green manufacturing.

[0007] Furthermore, the simple region described in S1 is a planar structure or a regular curved surface structure, while the complex region is a thin-walled structure, a sharp-corner structure, or a microgroove structure.

[0008] Explanation: Clearly defining the division between simple and complex regions makes dynamic adjustment of slice thickness more targeted, avoids ambiguous operations, ensures that complex features are accurately shaped with thin layers, and simple regions are improved with thick layers, thus guaranteeing the structural fidelity of the cutting tool from the source.

[0009] Furthermore, by mass percentage, the tungsten powder in S2 consists of 30-50% fine tungsten powder and the remainder coarse tungsten powder, wherein the fine tungsten powder has a particle size of 3-20 μm and the coarse tungsten powder has a particle size of 10-20 μm.

[0010] Explanation: Fine tungsten powder fills the gaps between coarse tungsten powder, increasing the packing density of the skeleton; coarse powder reduces particle agglomeration and lowers slurry viscosity. The two work together to optimize the permeability and melting efficiency of the skeleton, avoiding insufficient density or uncontrolled viscosity caused by a single particle size.

[0011] Furthermore, the binder in S2 is a compound of polyvinyl alcohol (PVA) and sodium carboxymethyl cellulose (CMC) in a mass ratio of 2-3:1; the dispersant is sodium polyacrylate.

[0012] Note: The PVA and CMC compound binder in a 2-3:1 ratio reduces hygroscopicity and improves green strength; sodium polyacrylate dispersant inhibits particle agglomeration, ensuring uniform and stable slurry and providing a good flowability basis for 3DP spray molding.

[0013] Furthermore, the ball mill in S2 uses zirconia balls with a diameter of 3-5 mm, the mass ratio of the zirconia balls to the tungsten skeleton slurry is 3-5:1, and the rotation speed is 200-300 rpm.

[0014] Note: A ball mill with a zirconia ball to slurry mass ratio of 3-5:1 and a rotation speed of 200-300 rpm is used to achieve uniform mixing of tungsten powder and additives, avoid over-grinding which would cause a sudden increase in viscosity, and control the particle size distribution to achieve a target viscosity of 500-2000 mPa·s.

[0015] Furthermore, the diameter of the microdroplets described in S3 is 50-120 μm.

[0016] Note: The droplet diameter of 50-120μm is adapted to the spraying precision of the piezoelectric nozzle, ensuring that the slurry is evenly covered layer by layer, avoiding clogging or gaps between layers. Combined with a layer thickness of 20-100μm, it can achieve fine shaping of complex contours such as the curvature of a cutting edge.

[0017] Furthermore, the ultrasonic cleaning in S4 has a frequency of 40kHz and a power of 200W; the drying process uses an oven with a temperature of 55-65℃ and a drying time of 1.5-2.5h.

[0018] Note: 40kHz, 200W ultrasonic cleaning effectively removes oil and impurities from the assembly surface. Drying at 55-65℃ for 1.5-2.5h avoids residual moisture that could cause melting and splashing, while also preventing high-temperature deformation and ensuring interface cleanliness and bonding strength.

[0019] Furthermore, the copper alloy block described in S4 is one of copper, chromium bronze, or copper-chromium-zirconium.

[0020] Note: Copper, chromium bronze, and copper-chromium-zirconium are available as options, respectively to meet the high conductivity requirements of copper, the high strength requirements of chromium bronze, and the high wear resistance requirements of copper-chromium-zirconium. This expands the application range of the moving contact in high-load scenarios suitable for chromium bronze and high-speed cutting scenarios suitable for copper-chromium-zirconium.

[0021] Furthermore, the vacuum infiltration heating temperature mentioned in S5 is related to the composition of the copper alloy block. Specifically, the infiltration temperature of the copper is 1100-1150℃, the infiltration temperature of the chromium bronze is 1150℃, and the infiltration temperature of the copper-chromium-zirconium alloy is 1200℃. The holding time of the assembly component is positively correlated with the thickness of the tungsten skeleton green billet in the assembly component. When the overall average thickness of the tungsten skeleton green billet is <5mm, the holding time is 2h; when the overall average thickness of the tungsten skeleton green billet is >10mm, the holding time is 5h; and when the overall average thickness of the tungsten skeleton green billet is between 5-10mm, the holding time is linearly interpolated by increasing by 0.5h per millimeter.

[0022] Note: Temperature is set according to alloy type to avoid oxidation and hard, brittle phases; holding time is positively correlated with thickness to ensure complete melting and penetration of the thick skeleton and improve metallurgical bonding strength.

[0023] Further, the specific method of precision post-processing described in S6 is as follows: First, the dimensions of the 3DP printed and sintered product are corrected. For complex contours, diamond turning is used, with layered cutting at 2000 rpm and a feed rate of 0.02 mm / r on a CNC lathe, gradually correcting to the design dimensions. For flat or regular surfaces such as the bottom surface of the contact and the mounting surface, diamond grinding is used with a WA600# grinding wheel at a linear speed of 20 m / s for fine grinding, eliminating macroscopic deviations through micro-grinding depth of 0.002-0.01 mm. After dimensional correction, the product enters the polishing process, using diamond polishing paste ranging from W1.5 to W0.5 to achieve a gradient transition from coarse to fine particle size. Polishing is performed continuously on a polishing machine at a pressure of 0.1-0.2 MPa and a speed of 25-35 rpm for 30-60 minutes, during which deionized water is used to remove grinding debris until there are no obvious scratches on the surface. After polishing, Taylor... The surface roughness is measured using a Hobson surface profilometer to ensure that Ra≤0.2μm, thus obtaining the moving tungsten copper contact.

[0024] Description: Step-by-step dimension correction diamond turning of complex contours, grinding of regular surfaces and gradient polishing are combined to achieve high precision with tolerance ≤ ±0.03mm and Ra≤0.2μm, meeting the requirements of low friction and long life of the moving tool contact. The inspection process ensures quality control.

[0025] The beneficial effects of this invention are: This invention dynamically adopts slice layer thicknesses of 50-100μm and 20-50μm based on the differences between simple regions and regular curved surfaces, and complex regions and thin-walled sharp-cornered microgrooves, precisely adapting to the fine features of the moving blade contact. This overcomes the limitations of traditional powder metallurgy pressing and sintering in forming complex structures. In slurry preparation, high-purity tungsten powder is used as aggregate, combined with 5% to 15% binder and 0.5% to 2% dispersant. The mixture is ball-milled for 4 to 8 hours and the viscosity is adjusted to 500 to 2000 mPa·s to ensure slurry fluidity and skeleton formability. The reasonable ratio of fine and coarse tungsten powder optimizes the skeleton packing density and permeability, laying the foundation for subsequent melting and infiltration. 3DP molding uses piezoelectric slurry spraying, atomizing the slurry into tiny droplets and spraying and curing it layer by layer. The curing time for each layer is 10 to 30 seconds. After printing, the green body is obtained by air drying at room temperature for 2 to 4 hours, eliminating the debinding and sintering step of traditional binder spraying and significantly shortening the cycle. In the melt infiltration assembly, the weight of copper alloy added is determined to be 1.05 to 1.2 times the pore volume by calculating the pore volume of the green blank. Assembly gaps are ≤0.1 mm in the mold, and the mating surfaces are ground to a roughness Ra≤0.8 micrometers and then ultrasonically cleaned and dried to ensure interfacial bonding strength. Vacuum melt infiltration is performed at 1×10⁻⁶. -3 Up to 5×10 -3 Under a vacuum of 10 to 15°C per hour, the temperature is increased to 1100 to 1250°C and held for 2 to 5 hours, then decreased by 5 to 8°C per hour. This process avoids tungsten oxidation and copper volatilization, and reduces the formation of hard and brittle phases through precise temperature and time control, thereby improving machinability. Precision post-processing removes burrs from the product, ultimately achieving high dimensional accuracy and surface quality of the moving tool contact. The coordinated parameters throughout the process ensure high freedom of forming complex structures and simultaneous optimization of material properties and process efficiency. Attached Figure Description

[0026] Fig. 1 This is a front view of the end face of the sample structure prepared according to mold pattern a in Embodiment 1 of the present invention; Fig. 2 This is a front view of the end face of the sample structure prepared according to mold pattern b in Embodiment 2 of the present invention; Fig. 3 This is a side view of the sample structure prepared according to the c mold pattern in Embodiment 3 of the present invention. Detailed Implementation

[0027] To further illustrate the methods and effects of this invention, the technical solution of this invention will be clearly and completely described below in conjunction with experiments.

[0028] Example 1: A method for preparing a complex structure tungsten-copper moving knife contact material, comprising the following steps: S1. Structural Modeling and Process Planning: A 3D model containing the tool head shape was built using SolidWorks / UG. The layer thickness was dynamically adjusted according to the structural complexity: 75μm for simple areas and 35μm for complex areas. The simple regions are planar structures or regular curved surface structures, while the complex regions are thin-walled structures, sharp-cornered structures, or micro-groove structures. S2. Preparation of tungsten framework slurry: Using tungsten powder with a purity ≥99.9% as aggregate, 10% binder, 1.2% dispersant, and the remainder aggregate were ball-milled and mixed for 6 hours by mass percentage. The mixture was then diluted with anhydrous ethanol or deionized water at room temperature (25°C) until the target viscosity reached 1200 mPa·s, yielding a tungsten skeleton slurry. Viscosity was measured using a Brookfield DV2T rotational viscometer with rotor #3 and a rotation speed of 60 rpm to ensure the tungsten skeleton slurry had suitable flowability for spraying. By mass percentage, the tungsten powder in S2 consists of 40% fine tungsten powder and the remainder coarse tungsten powder. The fine tungsten powder has a particle size of 10-12 μm, and the coarse tungsten powder has a particle size of 13-16 μm. The fine tungsten powder fills the gaps between the coarse tungsten powder to increase the bulk density, while the coarse tungsten powder reduces the viscosity of the tungsten skeleton slurry. The binder is a mixture of polyvinyl alcohol (PVA) and sodium carboxymethyl cellulose (CMC) at a mass ratio of 2.5:1. The dispersant is sodium polyacrylate. The ball mill uses zirconia balls with a diameter of 4 mm, and the mass ratio of the zirconia balls to the tungsten skeleton slurry is 4:1, with a rotation speed of 250 rpm. S3 and 3DP printing molding: The tungsten skeleton slurry was sprayed onto a substrate layer by layer to form a piezoelectric tungsten skeleton slurry. The tungsten skeleton slurry prepared by S2 was atomized into tiny droplets and then sprayed onto the substrate layer by layer for curing. The curing time for each layer was 20 seconds. After printing, the substrate was air-dried at room temperature for 3 hours to obtain a tungsten skeleton green body. The diameter of the tiny droplets was 80-100 μm. S4. Melting and Infiltration Assembly and Pretreatment: Calculate the pore volume of the tungsten skeleton green blank described in S3. The weight of the added copper alloy is 1.1 times the pore volume. Assemble the copper alloy block and the tungsten skeleton green blank in mold a wrapped with graphite paper. The assembly gap is ≤0.1mm. The surface roughness of the mating surfaces is polished to Ra≤0.8μm. After ultrasonic cleaning with anhydrous ethanol for 18min, the parts are dried. The ultrasonic cleaning frequency is 40kHz and the power is 200W. The drying is carried out in an oven at 60℃ for 2h. The copper alloy block is chromium bronze; by mass percentage, the chromium bronze contains 0.5 wt% Cr, 0.2 wt% Zr, and the balance is copper; S5, Vacuum Melting Infiltration: At a vacuum degree of 2.5 × 10 -3 Under Pa conditions, the temperature was increased to 1200℃ at a heating rate of 12.5℃ / h, held for 3.5h, and then cooled to room temperature at a cooling rate of 7℃ / h to obtain the 3DP printed and sintered product. Vacuum conditions can lower the melting and infiltration temperature, reduce the formation of hard and brittle phases, and have a dual effect on improving the metallurgical bonding strength and machinability of tungsten-copper alloys. The melting and infiltration temperature is matched to the melting point of the copper alloy, and the melting and infiltration temperature is 65℃ higher than the liquidus of the copper alloy. S6. Precision post-processing: The 3DP-printed and sintered product is then finished and deburred to obtain a moving tungsten copper contact. The specific method for this precision post-processing is as follows: First, the dimensions of the 3DP-printed and sintered product are corrected. For complex contours, diamond turning is used with CVD diamond tools at a rake angle of -5° and a clearance angle of 8° to ensure cutting sharpness and resistance to chipping. Layered cutting is performed on a CNC lathe at 2000 rpm and a feed rate of 0.02 mm / r, gradually correcting to the design dimensions. For planar or regular surfaces such as the contact... The bottom surface and mounting surface are precision ground using diamond grinding with a WA600# grinding wheel at a linear speed of 20 m / s. Macroscopic deviations are eliminated through a micro-grinding depth of 0.008 mm. After dimensional correction, the surface proceeds to the polishing process. Diamond polishing paste ranging from W1.5 to W0.5 is used to create a gradient from coarse to fine grit. Polishing is performed continuously for 45 minutes at a pressure of 0.15 MPa and a speed of 30 rpm on a polishing machine, with deionized water used to remove grinding debris until the surface is free of obvious scratches. After polishing, the surface roughness is checked using a Taylor Hobson surface profilometer to ensure Ra ≤ 0.2 μm, with critical areas such as the cutting edge requiring ≤ 0.15 μm. Finally, a coordinate measuring machine is used to verify that the critical dimensional tolerance is ≤ ±0.03 mm, achieving the desired result. Fig. 1 The image shows a smooth-surfaced, precisely sized moving-blade tungsten copper contact.

[0029] Example 2: This example is basically the same as Example 1, except that the copper alloy block and the tungsten skeleton blank are assembled in mold b, which is covered with graphite paper, to obtain the following result. Fig. 2 The moving knife tungsten copper contact shown.

[0030] Example 3: This example is basically the same as Example 1, except that the copper alloy block and the tungsten skeleton blank are assembled in a mold c covered with graphite paper to obtain the following result. Fig. 3 The moving tungsten copper contact shown is made of... Figs. 1-3As can be seen from Examples 1-3, this method can produce moving tungsten copper contacts with different complex structures and high precision according to different industrial needs.

[0031] Example 4: This example is basically the same as Example 1, except that it includes the following steps: S1. Structural Modeling and Process Planning: A 3D model containing the tool head shape was constructed using SolidWorks / UG. The layer thickness was dynamically adjusted according to the structural complexity: 50μm for simple areas and 20μm for complex areas. The simple regions are planar structures or regular curved surface structures, while the complex regions are thin-walled structures, sharp-cornered structures, or micro-groove structures. S2. Preparation of tungsten framework slurry: Using tungsten powder with a purity ≥99.9% as aggregate, 5% binder, 0.5% dispersant, and the remainder aggregate are ball-milled and mixed for 4 hours by mass percentage. The mixture is then diluted with anhydrous ethanol or deionized water at room temperature (25°C) until the target viscosity is 500 mPa·s, yielding a tungsten skeleton slurry. Viscosity was measured using a Brookfield DV2T rotational viscometer with rotor #3 and a rotation speed of 60 rpm to ensure the tungsten skeleton slurry has suitable flowability for spraying. By mass percentage, the tungsten powder in S2 consists of 30% fine tungsten powder and the remainder coarse tungsten powder. The fine tungsten powder has a particle size of 3-10 μm, and the coarse tungsten powder has a particle size of 10-15 μm. The fine tungsten powder fills the gaps between the coarse tungsten powder to increase the bulk density, while the coarse tungsten powder reduces the viscosity of the tungsten skeleton slurry. The binder is a mixture of polyvinyl alcohol (PVA) and sodium carboxymethyl cellulose (CMC) in a mass ratio of 2:1. The dispersant is sodium polyacrylate. The ball mill uses zirconia balls with a diameter of 3 mm, and the mass ratio of the zirconia balls to the tungsten skeleton slurry is 3:1, with a rotation speed of 200 rpm. S3 and 3DP printing molding: The tungsten skeleton slurry was sprayed onto a substrate using a piezoelectric tungsten skeleton slurry. The tungsten skeleton slurry prepared by S2 was atomized into tiny droplets and then sprayed onto the substrate layer by layer for curing. The curing time for each layer was 10 seconds. After printing, the substrate was air-dried at room temperature for 2 hours to obtain a tungsten skeleton green body. The diameter of the tiny droplets was 50-80 μm. S4. Melting and Infiltration Assembly and Pretreatment: Calculate the pore volume of the tungsten skeleton green billet described in S3. The weight of the added copper alloy is 1.05 times the pore volume. Based on the pore volume of the tungsten skeleton green billet, determine the weight of the added copper alloy block. Assemble the copper alloy block and the tungsten skeleton green billet in a mold, with an assembly gap ≤ 0.1 mm. Grind the mating surface roughness to Ra ≤ 0.8 μm, and then ultrasonically clean with anhydrous ethanol for 15 min followed by drying. The ultrasonic cleaning frequency is 40 kHz and the power is 200 W. The drying is performed in an oven at 55°C for 1.5 h. The copper alloy block described in S4 is one type of chromium bronze; by mass percentage, the chromium bronze contains 0.4-0.6 wt% Cr, 0.1-0.3 wt% Zr, and the balance is copper; S5, Vacuum Melting Infiltration: At a vacuum degree of 1×10 -3 Under Pa conditions, the temperature is increased to 1100℃ at a heating rate of 10℃ / h, held for 2 hours, and then cooled to room temperature at a cooling rate of 5℃ / h to obtain the 3DP printed and sintered product. Vacuum conditions can lower the melting and infiltration temperature, reduce the formation of hard and brittle phases, and have a dual effect on improving the metallurgical bonding strength and machinability of tungsten-copper alloys. The melting and infiltration temperature is matched to the melting point of the copper alloy, and the melting and infiltration temperature is 50℃ higher than the liquidus of the copper alloy. S6. Precision post-processing: The 3DP-printed and sintered product is then finished and deburred to obtain a moving tungsten copper contact. The specific method for this precision post-processing is as follows: First, the dimensions of the 3DP-printed and sintered product are corrected. For complex contours, diamond turning is used with CVD diamond tools at a rake angle of -5° and a clearance angle of 8° to ensure cutting sharpness and resistance to chipping. Layered cutting is performed on a CNC lathe at 2000 rpm and a feed rate of 0.02 mm / r, gradually correcting to the design dimensions. For planar or regular surfaces such as the contact... The bottom surface and mounting surface are precision ground with diamond grinding using a WA600# grinding wheel at a linear speed of 20m / s. Macroscopic deviations are eliminated by a micro-grinding depth of 0.002mm. After dimensional correction, the surface enters the polishing process. Diamond polishing paste ranging from W1.5 to W0.5 is used to create a gradient transition from coarse to fine grit. Polishing is performed continuously for 30 minutes at a pressure of 0.1MPa and a speed of 30rpm on a polishing machine, during which deionized water is used to remove grinding debris until there are no obvious scratches on the surface. After polishing, the surface roughness is checked using a Taylor Hobson surface profilometer to ensure that Ra≤0.2μm, and ≤0.15μm for critical parts such as the cutting edge. Finally, the critical dimensional tolerance is verified to be ≤±0.03mm using a coordinate measuring machine to obtain a smooth surface and precise dimensions of the moving tungsten copper contact.

[0032] Example 5: This example is basically the same as Example 1, except that it includes the following steps: S1. Structural Modeling and Process Planning: A 3D model containing the tool head shape was constructed using SolidWorks / UG. The layer thickness was dynamically adjusted according to the structural complexity: 100μm for simple areas and 50μm for complex areas. The simple regions are planar structures or regular curved surface structures, while the complex regions are thin-walled structures, sharp-cornered structures, or micro-groove structures. S2. Preparation of tungsten framework slurry: Using tungsten powder with a purity ≥99.9% as aggregate, 15% binder, 2% dispersant, and the remainder aggregate were ball-milled and mixed for 8 hours by mass percentage. The mixture was then diluted with anhydrous ethanol or deionized water at room temperature (25°C) until the target viscosity was 2000 mPa·s, thus obtaining a tungsten skeleton slurry. Viscosity was measured using a Brookfield DV2T rotational viscometer with rotor No. 3 and a rotation speed of 60 rpm to ensure that the tungsten skeleton slurry had suitable flowability for spraying. By mass percentage, the tungsten powder in S2 consists of 50% fine tungsten powder and the remainder coarse tungsten powder. The fine tungsten powder has a particle size of 10-20 μm, and the coarse tungsten powder has a particle size of 15-20 μm. The fine tungsten powder fills the gaps between the coarse tungsten powder to increase the bulk density, while the coarse tungsten powder reduces the viscosity of the tungsten skeleton slurry. The binder is a mixture of polyvinyl alcohol (PVA) and sodium carboxymethyl cellulose (CMC) in a mass ratio of 3:1. The dispersant is sodium polyacrylate. The ball mill uses zirconia balls with a diameter of 5 mm, and the mass ratio of the zirconia balls to the tungsten skeleton slurry is 5:1, with a rotation speed of 300 rpm. S3 and 3DP printing molding: The tungsten skeleton slurry was sprayed onto a substrate layer by layer to form a piezoelectric tungsten skeleton slurry. The tungsten skeleton slurry prepared by S2 was atomized into tiny droplets and then sprayed onto the substrate layer by layer for curing. The curing time for each layer was 30 seconds. After printing, the substrate was air-dried at room temperature for 4 hours to obtain a tungsten skeleton green body. The diameter of the tiny droplets was 100-120 μm. S4. Melting and Infiltration Assembly and Pretreatment: Calculate the pore volume of the tungsten skeleton green blank in S3. The weight of the added copper alloy is 1.2 times the pore volume. Based on the pore volume of the tungsten skeleton green blank, determine the weight of the added copper alloy block. Assemble the copper alloy block and the tungsten skeleton green blank in a mold, with an assembly gap ≤ 0.1 mm. Grind the mating surface roughness to Ra ≤ 0.8 μm, and then ultrasonically clean with anhydrous ethanol for 20 min followed by drying. The ultrasonic cleaning frequency is 40 kHz and the power is 200 W. The drying is performed in an oven at 65℃ for 2.5 h. The copper alloy block is one type of chromium bronze; by mass percentage, the chromium bronze contains 0.6 wt% Cr, 0.3 wt% Zr, and the balance is copper; S5, Vacuum Melting Infiltration: At a vacuum degree of 5×10 -3 Under Pa conditions, the temperature is increased to 1250℃ at a heating rate of 15℃ / h, held for 5h, and then cooled to room temperature at a cooling rate of 8℃ / h to obtain the 3DP printed and sintered product. Vacuum conditions can lower the melting and infiltration temperature, reduce the formation of hard and brittle phases, and have a dual effect on improving the metallurgical bonding strength and machinability of tungsten-copper alloys. The melting and infiltration temperature is matched to the melting point of the copper alloy, and the melting and infiltration temperature is 80℃ higher than the liquidus of the copper alloy. S6. Precision post-processing: The 3DP-printed and sintered product is then finished and deburred to obtain a moving tungsten copper contact. The specific method for this precision post-processing is as follows: First, the dimensions of the 3DP-printed and sintered product are corrected. For complex contours, diamond turning is used with CVD diamond tools at a rake angle of -5° and a clearance angle of 8° to ensure cutting sharpness and resistance to chipping. Layered cutting is performed on a CNC lathe at 2000 rpm and a feed rate of 0.02 mm / r, gradually correcting to the design dimensions. For flat or regular surfaces, such as the contact... The head bottom surface and mounting surface are precision ground with diamond grinding using a WA600# grinding wheel at a linear speed of 20m / s. Macroscopic deviations are eliminated by micro-grinding to a depth of 0.01mm. After dimensional correction, the head enters the polishing process, using diamond polishing paste ranging from W1.5 to W0.5 to create a gradient transition in grit size. Polishing is performed continuously for 60 minutes at a pressure of 0.2MPa and a speed of 30rpm on a polishing machine, during which deionized water is used to remove grinding debris until there are no obvious scratches on the surface. After polishing, the surface roughness is checked using a Taylor Hobson surface profilometer to ensure that Ra≤0.2μm, and ≤0.15μm for critical parts such as the cutting edge. Finally, the critical dimensional tolerance is verified to be ≤±0.03mm using a coordinate measuring machine, resulting in a smooth surface and precise dimensions of the moving tungsten copper contact.

[0033] Example 6: This example is basically the same as Example 1, except that the tungsten powder in S2 is composed of 30% fine tungsten powder and the remainder coarse tungsten powder. The fine tungsten powder has a particle size of 3-10 μm and the coarse tungsten powder has a particle size of 10-15 μm.

[0034] Example 7: This example is basically the same as Example 1, except that the tungsten powder in S2 is composed of 50% fine tungsten powder and the remainder coarse tungsten powder. The fine tungsten powder has a particle size of 10-20 μm and the coarse tungsten powder has a particle size of 15-20 μm.

[0035] Example 8: This example is basically the same as Example 1, except that the binder in S2 is a mixture of polyvinyl alcohol (PVA) and sodium carboxymethyl cellulose (CMC) in a mass ratio of 2:1; and the dispersant is sodium polyacrylate.

[0036] Example 9: This example is basically the same as Example 1, except that the binder in S2 is a compound of polyvinyl alcohol (PVA) and sodium carboxymethyl cellulose (CMC) in a mass ratio of 3:1; and the dispersant is sodium polyacrylate.

[0037] Example 10: This example is basically the same as Example 1, except that the ball mill in S2 uses zirconia balls with a diameter of 3 mm, the mass ratio of the zirconia balls to the tungsten skeleton slurry is 3:1, and the rotation speed is 200 rpm.

[0038] Example 11: This example is basically the same as Example 1, except that the ball mill in S2 uses zirconia balls with a diameter of 5 mm, the mass ratio of the zirconia balls to the tungsten skeleton slurry is 5:1, and the rotation speed is 300 rpm.

[0039] Example 12: This example is basically the same as Example 1, except that the diameter of the microdroplets in S3 is 50-70 μm.

[0040] Example 13: This example is basically the same as Example 1, except that the diameter of the microdroplets in S3 is 100-120μm.

[0041] Example 14: This example is basically the same as Example 1, except that the copper alloy block in S4 is red copper; the red copper contains Cu ≥ 99.95% and impurities ≤ 0.05%.

[0042] Example 15: This example is basically the same as Example 1, except that the copper alloy block in S4 is copper-chromium-zirconium; the Cr content in the copper-chromium-zirconium is 1wt%, the Zr content is 0.2wt%, and the balance is copper.

[0043] Example 16: This example is basically the same as Example 1, except that the copper alloy block in S4 is copper-chromium-zirconium; the Cr content in the copper-chromium-zirconium is 0.8wt%, the Zr content is 0.1wt%, and the balance is copper.

[0044] Example 17: This example is basically the same as Example 1, except that the copper alloy block in S4 is copper-chromium-zirconium; the Cr content in the copper-chromium-zirconium is 1.2wt%, the Zr content is 0.3wt%, and the balance is copper.

[0045] Comparative Example 1: The difference between this embodiment and Example 1 is that the tungsten powder particle size in S2 is uniformly 10-15 μm.

[0046] Comparative Example 2: The difference between this embodiment and Example 1 is that the ball mill in S2 uses zirconia balls with a diameter of 8 mm, the mass ratio of the zirconia balls to the tungsten skeleton slurry is 6:1, and the rotation speed is 400 rpm.

[0047] Comparative Example 3: The difference between this embodiment and Example 1 is that in S5, the vacuum degree is 5×10 -3 At Pa, the temperature is increased to 1150℃ at a heating rate of 15℃ / h and held for 5h; the vacuum melting and infiltration heating temperature is related to the composition of the copper alloy block, wherein the melting and infiltration temperature of the copper is 1150℃; the holding time of the assembly is positively correlated with the thickness of the tungsten skeleton green billet in the assembly, the overall average thickness of the tungsten skeleton green billet is 8mm, and linear interpolation is performed at 0.5h per millimeter.

[0048] Comparative Example 4: The difference between this embodiment and Example 1 is that the assembly gap in S4 is >0.2mm.

[0049] Comparative Example 5: The difference between this embodiment and Example 1 is that polishing is not performed in S6.

[0050] To investigate the performance of the tungsten-copper moving contact in the above embodiments and control examples, the main materials were determined according to the experimental formula, and samples were obtained for testing. Density was determined using the Archimedes displacement method. The pore volume was calculated by measuring the difference between the mass of saturated water and the dry weight of the sample, and the relative density was obtained as (sample measured density / theoretical density) × 100%. Material utilization (wt%) was calculated based on the feed-to-finished product mass ratio, i.e., (actual finished product mass / total feed mass) × 100%, reflecting the degree of material waste during 3DP printing and melting processes. Thermal conductivity was tested using the laser flash method. The sample surface was heated by laser pulses, and the temperature rise curve on the back side was detected. The thermal diffusivity was calculated by combining density and specific heat capacity, and finally, the thermal conductivity was calculated. Dimensional accuracy was measured using a coordinate measuring machine to detect key parts such as the cutting edge thickness and the position of the mounting holes. The tolerance range (e.g., ≤ ±0.03 mm) characterizes the level of dimensional deviation after processing. The results are shown in Table 1. Specific investigations are as follows: Table 1 Performance test results of tungsten copper moving knife contact samples from Examples 1-17 and Comparative Examples 1-5

[0051] 1. Investigate the influence of tungsten powder ratio parameters on the performance of tungsten-copper moving knife contacts: A comparison of Examples 1, 4, and 5 with Control Example 1 shows that the tungsten powder ratio plays a decisive role in material performance. Example 1, using a ratio of 40% fine powder + 60% coarse powder, achieved a density of 99.2% and a material utilization rate of 83%, demonstrating optimal overall performance. Example 4 reduced the fine powder ratio to 30%, slightly decreasing the density to 99.3%, but increasing the material utilization rate to 89%, indicating that reducing the fine powder can optimize utilization. Control Example 1, without optimized ratio, showed a significant decrease in density to 97.5%, proving that insufficient fine powder leads to insufficient bulk density. Furthermore, Example 5, using 50% fine powder and 50% coarse powder, achieved a density of 98.9%, higher than Control Example 1 but still lower than Example 1, indicating that the fine powder ratio needs to be controlled within a reasonable range of 30-40% to achieve the best balance between density and utilization.

[0052] 2. Investigating the influence of ball milling process parameters on the properties of tungsten skeleton slurry: A comparison of Examples 1, 10, and 11 with Control Example 2 shows that ball milling parameters directly affect slurry flowability and skeleton density. Example 1 used 4mm zirconia balls at a rotation speed of 250 rpm, achieving a density of 99.2%. Example 10 reduced the ball diameter to 3mm and increased the rotation speed to 200 rpm, while maintaining a density of 99.2%, indicating that smaller ball diameters can refine tungsten powder particle size. Control Example 2 increased the rotation speed to 400 rpm, resulting in over-grinding of tungsten powder, an increase in the proportion of particles <3μm, uncontrolled slurry viscosity >3000 mPa·s, and a decrease in density to 98.3%. Furthermore, Example 11 used 5mm large balls at a high rotation speed of 300 rpm, achieving a density of 99.5%, indicating that large ball diameters can still maintain a certain degree of dispersibility at high rotation speeds, but strict speed control is necessary to avoid over-grinding.

[0053] 3. Investigate the effects of melting temperature and copper alloy type on metallurgical bonding strength: The comparison between Examples 14-17 and Comparative Example 4 highlights the synergistic effect of copper alloy composition and melting temperature. Example 15 uses chromium bronze with 0.5wt% Cr and 0.2wt% Zr, melted at 1200℃, achieving a density of 98.8%, a material utilization rate of 83%, and a thermal conductivity of 266.7 W / (MK), suitable for applications requiring high thermal conductivity. Comparative Example 4 has an assembly gap >0.2mm, a melting temperature of 1200℃, a density of 98.6%, a thermal conductivity of 264.9 W / m·K, and a dimensional accuracy of ±0.03mm. It is speculated that the excessive assembly gap led to insufficient melting in certain areas and uneven porosity distribution. Example 17 uses a copper-chromium-zirconium alloy with high Cr 1.2wt% and high Zr 0.3wt%, melted at 1250℃, achieving a maximum density of 99.7%, but the thermal conductivity drops to 255.2 W / m·K, reflecting that the addition of alloying elements has a certain inhibitory effect on thermal conductivity.

[0054] 4. Investigate the effect of post-treatment processes on surface quality and dimensional accuracy: The comparison between Example 5 and Control Example 5 verifies the criticality of the polishing process. Example 5 uses gradient polishing, achieving a surface roughness Ra ≤ 0.2 μm, dimensional accuracy ± 0.03 mm, and cutting edge Ra ≤ 0.15 μm. Control Example 5, without polishing, has a surface roughness Ra > 0.2 μm and dimensional accuracy ± 0.04 mm. Furthermore, Example 1 combines diamond turning at 2000 rpm (0.02 mm / r) with grinding with a WA600# wheel at 20 m / s to eliminate macroscopic deviations, while Control Example 5, without optimized post-treatment, suffers a ≥ 40% reduction in electrical life due to surface defects. Therefore, a polishing pressure of 0.15 MPa and a time of 45 minutes is the optimal parameter combination, balancing efficiency and surface quality.

Claims

1. A method for preparing a complex structure tungsten-copper moving knife contact material, characterized in that, Includes the following steps: S1. Structural Modeling and Process Planning: Construct a 3D model containing the tool head shape using SolidWorks / UG. The slice layer thickness is dynamically adjusted according to the structural complexity: 50-100μm for simple areas and 20-50μm for complex areas. S2. Preparation of tungsten framework slurry: Take tungsten powder with a purity of ≥99.9% as aggregate, and ball mill 5-15% binder, 0.5-2% dispersant and the balance of the aggregate for 4-8 hours by mass percentage; dilute with anhydrous ethanol or deionized water at room temperature until the target viscosity is 500-2000 mPa·s to obtain tungsten skeleton slurry; S3 and 3DP printing molding: The tungsten skeleton slurry was sprayed into micro-droplets by atomizing the tungsten skeleton slurry prepared by S2, and then sprayed onto the substrate layer by layer for curing. The curing time for each layer was 10-30 seconds. After printing, it was air-dried at room temperature for 2-4 hours to obtain the tungsten skeleton green body. S4. Melting and Infiltration Assembly and Pretreatment: Calculate the pore volume of the tungsten skeleton green blank in S3. The weight of the added copper alloy is 1.05-1.2 times the pore volume. Based on the pore volume of the tungsten skeleton green blank, determine the weight of the added copper alloy block. Assemble the copper alloy block and the tungsten skeleton green blank in a mold. The assembly gap is ≤0.1mm. The surface roughness of the mating surface is polished to Ra≤0.8μm. After ultrasonic cleaning with anhydrous ethanol for 15-20min, the assembly is dried to obtain the assembled component. S5, Vacuum Melting Infiltration: At a vacuum degree of 1×10 -3 -5×10 -3 Under Pa conditions, the assembly component described in S4 is heated to 1100-1250℃ at a heating rate of 10-15℃ / h, held at that temperature for 2-5h, and then cooled to room temperature at a cooling rate of 5-8℃ / h to obtain the 3DP printed sintered product. S6. Precision post-processing: The 3DP printed and sintered product is finished and burrs are removed to obtain a moving tungsten copper contact.

2. The method for preparing a complex structure tungsten-copper moving knife contact material according to claim 1, characterized in that, The simple region described in S1 is a planar structure or a regular curved surface structure, while the complex region is a thin-walled structure, a sharp-corner structure, or a microgroove structure.

3. The method for preparing a complex structure tungsten-copper moving knife contact material according to claim 1, characterized in that, By mass percentage, the tungsten powder in S2 consists of 30-50% fine tungsten powder and the remainder coarse tungsten powder, wherein the fine tungsten powder has a particle size of 3-20 μm and the coarse tungsten powder has a particle size of 10-20 μm.

4. The method for preparing a complex structure tungsten-copper moving knife contact material according to claim 1, characterized in that, The binder in S2 is a compound of polyvinyl alcohol (PVA) and sodium carboxymethyl cellulose (CMC) in a mass ratio of 2-3:1; the dispersant is sodium polyacrylate.

5. The method for preparing a complex structure tungsten-copper moving knife contact material according to claim 1, characterized in that, The ball mill described in S2 uses zirconia balls with a diameter of 3-5 mm, and the mass ratio of the zirconia balls to the tungsten skeleton slurry is 3-5:1, with a rotation speed of 200-300 rpm.

6. The method for preparing a complex structure tungsten-copper moving knife contact material according to claim 1, characterized in that, The diameter of the microdroplets described in S3 is 50-120 μm.

7. The method for preparing a complex structure tungsten-copper moving knife contact material according to claim 1, characterized in that, The ultrasonic cleaning in S4 has a frequency of 40kHz and a power of 200W; the drying process uses an oven with a temperature of 55-65℃ and a drying time of 1.5-2.5h.

8. The method for preparing a complex structure tungsten-copper moving knife contact material according to claim 1, characterized in that, The copper alloy block described in S4 is one of copper, chromium bronze, or copper-chromium-zirconium.

9. The method for preparing a complex structure tungsten-copper moving knife contact material according to claim 8, characterized in that, The vacuum infiltration heating temperature described in S5 is related to the composition of the copper alloy block. Specifically, the infiltration temperature of the copper is 1100-1150℃, the infiltration temperature of the chromium bronze is 1150℃, and the infiltration temperature of the copper-chromium-zirconium is 1200℃. The holding time of the assembly component is positively correlated with the thickness of the tungsten skeleton green billet in the assembly component. When the overall average thickness of the tungsten skeleton green billet is <5mm, the holding time is 2h; when the overall average thickness of the tungsten skeleton green billet is >10mm, the holding time is 5h; and when the overall average thickness of the tungsten skeleton green billet is between 5-10mm, the holding time is linearly interpolated by increasing the holding time by 0.5h per millimeter.

10. The method for preparing a complex structure tungsten-copper moving knife contact material according to claim 1, characterized in that, The specific method for precision post-processing described in S6 is as follows: First, the dimensions of the 3DP printed and sintered product are corrected. For complex contours, diamond turning is used, with layered cutting at 2000 rpm and a feed rate of 0.02 mm / r on a CNC lathe, gradually correcting to the design dimensions. For flat or regular surfaces such as the bottom surface of the contact and the mounting surface, diamond grinding is used with a WA600# grinding wheel at a linear speed of 20 m / s for fine grinding, eliminating macroscopic deviations through micro-grinding depth of 0.002-0.01 mm. After dimensional correction, the product enters the polishing process, using diamond polishing paste ranging from W1.5 to W0.5 to achieve a gradient transition from coarse to fine particle size. Polishing is performed continuously on a polishing machine at a pressure of 0.1-0.2 MPa and a speed of 25-35 rpm for 30-60 minutes, during which deionized water is used to rinse away the grinding debris until there are no obvious scratches on the surface. After polishing, the surface roughness is checked with a surface profiler to ensure that Ra≤0.2μm is achieved, obtaining the moving tungsten copper contact.

Images