High-activity and high-tap-density tungsten-copper composite powder as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of tungsten-copper composite powder, and particularly relates to high-activity and high-tap-density tungsten-copper composite powder, a preparation method and application. The preparation method comprises the following steps: mixing micron-sized tungsten trioxide and micron-sized copper powder to obtain a mixture; the mixture is subjected to low-speed dynamic pre-reduction in a rotary furnace, and a primary reduction material is obtained; the primary reduction material is fully reduced through dry hydrogen, and reduced powder is obtained; performing isostatic pressing on the reducing powder to form a block, and crushing the block to obtain crushed powder; and screening the crushed powder after low-temperature presintering. The composite powder with the core-shell structure is prepared by combining tungsten with the grain sizes of 0.3-0.5 mu m and 1-2 mu m and copper with the grain sizes of 3-6 mu m through the process design of wet hydrogen pre-reduction, secondary reduction, crushing treatment after isostatic pressing, low-temperature pre-sintering and the like, and the powder is low in oxygen content, high in activity, high in tap density, excellent in flowability and high in conductivity and can be used for preparing the composite powder with the core-shell structure. And the injection molding process requirements in subsequent processing can be met.

Description

Technical Field

[0001] The present invention belongs to the technical field of tungsten-copper composite powders, and particularly relates to a high-activity and high-tap-density tungsten-copper composite powder, a preparation method and uses thereof. Background Art

[0002] Tungsten-copper composite powder is a two-phase pseudo-alloy material composed of tungsten and copper, which combines the high melting point, high hardness, low thermal expansion coefficient of tungsten and the excellent electrical and thermal conductivity of copper. It can be applied to high-voltage electrical contacts, rocket nozzle throats, electrical discharge machining electrodes and electronic packaging heat dissipation substrates, and is particularly suitable for high-end fields such as nuclear fusion divertors and high-power integrated circuits.

[0003] Problems exist when preparing tungsten-copper composite powder by the traditional mechanical mixing method as follows: the density of tungsten is 19.35 g / cm³, and the density of copper is 8.89 g / cm³. The significant difference between the two leads to the easy floating of light copper powder and the sinking of tungsten powder, making it difficult to disperse evenly, resulting in composition segregation and low overall activity; tungsten powder is prone to adsorb oxygen to form an oxide layer, resulting in too high oxygen content in the powder, usually >0.2 wt%, reducing the activity and hindering sintering densification, resulting in low tap density and poor processing fluidity, and it is difficult to meet the requirements of injection molding process. In addition, generally, micron-sized tungsten powder has low surface activity, regular particles, good fluidity and relatively high tap density; nano-sized tungsten powder has high surface activity, is prone to agglomeration, irregular particles, poor fluidity, and easy formation of pores between particles, resulting in low tap density. Summary of the Invention

[0004] To solve the problems existing in the prior art, the present invention provides a high-activity and high-tap-density tungsten-copper composite powder, a preparation method and uses thereof.

[0005] The specific technical solution is as follows: A preparation method of a high-activity and high-tap-density tungsten-copper composite powder, the steps are as follows: S1. Raw material mixing: Mix micron-sized tungsten trioxide and micron-sized copper powder to obtain a mixed material; S2. Wet hydrogen pre-reduction: The mixed material is slowly and dynamically pre-reduced in a rotary furnace to obtain a primary reduced material; S3. Secondary reduction: The primary reduced material is fully reduced with dry hydrogen to obtain a reduced powder; S4. Isostatic pressing and post-crushing treatment: The reduced powder is isostatically pressed into a block, and the block is crushed to obtain crushed powder; S5. Low-temperature pre-sintering: The crushed powder is subjected to low-temperature pre-sintering and then sieved.

[0006] Preferably, the particle size of tungsten trioxide is 4 - 8 μm; the copper powder is gas-atomized copper powder with a particle size of 3 - 6 μm.

[0007] Preferably, in step S2, the rotary kiln rotates at a speed of 8 to 12 revolutions per hour, the temperature is 650 to 800 °C, the wet hydrogen flow rate is controlled at 1 to 2 L / min, and the dew point of the wet hydrogen is controlled at 0 to 20 °C.

[0008] Preferably, in step S3, the hydrogen purity is greater than or equal to 99.95%, the gas flow rate is controlled at 1 to 3 L / min, and the temperature is 850 to 950 °C.

[0009] Preferably, in step S4, the pressing parameters used for isostatic pressing are 150 to 250 MPa.

[0010] Preferably, in step S4, crushing is carried out by dry ball milling in a rolling ball mill, the rotation speed is 80 to 120 rpm, and the ball-to-material ratio is 2 to 3:1.

[0011] Preferably, in step S5, the temperature for low-temperature pre-sintering of the crushed powder is 1000 to 1100 °C, the pre-sintering time is 1 to 2 h, and the pre-sintering is carried out in a hydrogen atmosphere.

[0012] A high-activity and high-tap-density tungsten-copper composite powder, the tungsten-copper composite powder prepared by the above method, and the tungsten-copper composite powder includes a core-shell structure with copper as the core and tungsten as the shell.

[0013] Preferably, the tungsten-copper composite powder is a composite powder composed of tungsten with grain sizes of 0.3 to 0.5 μm and 1 to 2 μm and copper with a grain size of 3 to 6 μm.

[0014] The tungsten-copper composite powder prepared in this application is suitable for the batch preparation of injection-molded products, and the injection-molded products include, but are not limited to, micro-precision electronic packaging parts, high-thermal-conductivity micro-channel heat dissipation substrates, and complex-shaped electrical contacts.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. By constructing a core-shell structure with copper as the core and tungsten as the shell through a wet hydrogen pre-reduction process, the powder is given a high tap density and excellent flow characteristics, ensuring uniform filling of complex cavities during injection molding.

[0016] 2. The synergistic effect of the wet hydrogen pre-reduction, secondary reduction, and low-temperature pre-sintering processes reduces the oxygen content, improves the surface activity, and significantly reduces the porosity during the low-temperature sintering process, making the final product have both high density and interface bonding strength.

[0017] 3. For the prepared tungsten-copper composite powder, tungsten powder with a particle size of 0.3 - 0.5 μm is uniformly adsorbed on the surface of copper powder with a particle size of 3 - 6 μm, forming a core-shell structured powder with copper as the core and tungsten as the shell. Tungsten powder with a particle size of 1 - 2 μm is independently distributed, and the tap density is 7.0 - 7.5 g / cm³, and the oxygen content is ≤0.1 wt%.

[0018] 4. This powder is particularly suitable for the batch preparation of injection-molded products such as micro-precision electronic packages, high thermal conductivity microchannel heat dissipation substrates, and complex-shaped electrical contacts. In the fields of 5G communication, power semiconductors, and microelectromechanical systems (MEMS), it can replace the traditional pressing-sintering process to achieve high-precision and near-net-shape manufacturing.

[0019] Through process designs such as wet hydrogen pre-reduction, secondary reduction, crushing after isostatic pressing, and low-temperature pre-sintering, this application prepares a composite powder with a core-shell structure composed of tungsten with grain sizes of 0.3 - 0.5 μm and 1 - 2 μm and copper with a grain size of 3 - 6 μm. This powder has a low oxygen content, high activity, high tap density, excellent fluidity, and high electrical conductivity, and can meet the requirements of the injection molding process in subsequent processing. Description of the Drawings

[0020] Figure 1 It is the SEM image of the tungsten-copper composite powder prepared by the present invention. Detailed Embodiments

[0021] To facilitate the understanding of the present invention, the present invention will be described in more detail below with reference to the drawings and specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described in this specification. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosed content of the present invention more thorough and comprehensive.

[0022] The preparation method of a high-activity and high-tap-density tungsten-copper composite powder is as follows: S1. Raw material mixing: Mix tungsten trioxide and copper powder in a mass ratio of 1 - 2:1 for 2 - 4 h to obtain a mixed material. Among them, the particle size of tungsten trioxide is 4 - 8 μm, the copper powder is gas-atomized copper powder, and the particle size of the copper powder is 3 - 6 μm; S2. Wet hydrogen pre-reduction: The mixed material is slowly and dynamically pre-reduced in a rotary furnace to obtain a primary reduced material. Among them, the rotation speed of the rotary furnace is 8 - 12 revolutions per hour, the temperature is 650 - 800 °C, the wet hydrogen flow rate is controlled at 1 - 2 L / min, the dew point of the wet hydrogen is controlled at 0 - 20 °C, and the time is 2 - 4 h; S3. Secondary reduction: The primary reduced material is fully reduced with dry hydrogen to obtain a reduced powder. Among them, the hydrogen purity is greater than or equal to 99.95%, the gas flow rate is controlled at 1 - 3 L / min, the temperature is 850 - 950 °C, and the time is 2 - 3 h; S4. Crushing treatment after isostatic pressing: The reduced powder is isostatically pressed into a block, and the block is crushed to obtain crushed powder. Among them, the pressing parameters used for isostatic pressing are 150 - 250 MPa, the pressure holding time is 10 - 15 s, the crushing is carried out by dry grinding with a rolling ball mill, the rotation speed is 80 - 120 rpm, the ball-to-material ratio is 2 - 3:1, and the ball milling time is 20 - 60 min; S5. Low-temperature pre-sintering: The temperature for low-temperature pre-sintering of the crushed powder is 1000 - 1100 °C, the pre-sintering time is 1 - 2 h, the pre-sintering atmosphere is a hydrogen atmosphere, and after pre-sintering, it is sieved through a 200-mesh sieve to obtain a tungsten-copper composite powder with high activity and high tap density.

[0023] Example 1: Preparation method of a tungsten-copper composite powder with high activity and high tap density, preparation steps S1. Mixing: Tungsten trioxide with a particle size of 4 - 8 μm and gas-atomized copper powder with a particle size of 3 - 6 μm are mixed at a mass ratio of 6:4 using a vertical stirrer for 3 hours. S2. Wet hydrogen pre-reduction: The rotation speed of the rotary furnace is 10 revolutions per hour, at 650 °C for 3 h, the wet hydrogen flow rate is controlled at 1.5 L / min, and the dew point of the wet hydrogen is controlled at 10 °C to generate composite particles. S3. Secondary reduction: Dry hydrogen with a hydrogen purity of greater than or equal to 99.95%, at 900 °C for 2.5 h, and the gas flow rate is controlled at 2 L / min. S4. Isostatic pressing and crushing: Maintain a pressure of 200 MPa for 12 seconds. After isostatic pressing and forming, it is dry-milled by rolling ball milling for 40 minutes with a ball-to-material ratio of 2.5:1 and a rotation speed of 100 rpm. S5. Pre-sintering: At 1050 °C for 1.5 h, in a hydrogen atmosphere, and sieved through a 200-mesh vibrating sieve to obtain a tungsten-copper composite powder with high activity and high tap density.

[0024] Performance results: Tap density: 7.2 g / cm³, oxygen content: 0.08 wt%, sintered density: 96.8%, electrical conductivity 53.0% IACS, hardness 170 HB.

[0025] Example 2: This example is a high-temperature rapid reduction scheme. Compared with Example 1, the parameter adjustments are as follows: The wet hydrogen pre-reduction temperature is increased to 780 °C and the time is shortened to 2 h; the secondary reduction temperature is 950 °C for 2 h; the ball milling time is shortened to 30 minutes.

[0026] Performance results: Tap density: 7.0 g / cm³; oxygen content: 0.05 wt%; sintered density 97.4%, electrical conductivity 53.7% IACS, hardness 174 HB.

[0027] Example 3: This example is a high-pressure pressing scheme. Compared with Example 1, the parameter adjustments are as follows: The isostatic pressing pressure is increased to 250 MPa and the pressure holding time is 15 seconds; the pre-sintering temperature is 1100 °C for 1 h; the wet hydrogen dew point is adjusted to 20 °C.

[0028] Performance results: Tap density: 7.5 g / cm³; oxygen content: 0.10 wt%; sintered density: 98.1%, electrical conductivity 54.5% IACS, hardness 180 HB.

[0029] In this example, by increasing the isostatic pressure and performing high-pressure densification, the tapped density was further improved.

[0030] Comparative example: Traditional mechanical mixing method. Preparation method: Take tungsten powder with a particle size of 4 - 8 μm and gas-atomized copper powder with a particle size of 3 - 6 μm, and mix them in a mass ratio of 7:3; use a high-speed ball mill for dry mixing for 4 hours, with a ball-to-material ratio of 5:1 and a rotation speed of 300 rpm; directly press into shape, with a pressure of 200 MPa, and sinter at 1250 °C for 2 hours in a hydrogen atmosphere.

[0031] Performance results: Tapped density: 4.8 g / cm³; oxygen content: 0.25 wt%; sintered density: 83%, electrical conductivity: 21.6% IACS, hardness: 103 HB.

[0032] All raw materials used are commercially available.

[0033] The above performance tests were carried out with reference to the following standards: The tapped density was tested according to the standard of GB / T5162 - 2021. The oxygen content was tested according to the standard of GB / T5158.4 - 2011. The sintered density was tested according to the standard of GB / T3850 - 2015. The electrical conductivity was tested according to the standard of GB / T3048.2 - 2007. The hardness was tested according to the standard of GB / T4340.1 - 2009.

[0034] Through comparison, it was found that in Examples 1 - 3, the tapped density was 7.0 - 7.5 g / cm³, the oxygen content ≤ 0.1 wt%, the sintered density ≥ 96%, and the electrical conductivity ≥ 53.0% IACS.

[0035] Electron microscopy scanning and particle size analysis were also carried out. In Example 1, the microstructure: tungsten powder with a size of 0.3 - 0.5 μm was evenly adsorbed on the surface of copper powder with a size of 3 - 6 μm, forming a core-shell structured powder with copper as the core and tungsten as the shell, and tungsten powder with a size of 1 - 2 μm was independently distributed, as Figure 1 shown. In the comparative example, the microstructure: tungsten and copper particles agglomerated separately, with poor interfacial bonding and no core-shell structure.

[0036] Through process designs such as wet hydrogen pre-reduction, secondary reduction, crushing treatment after isostatic pressing, and low-temperature pre-sintering, this application prepared a composite powder with a core-shell structure composed of tungsten with grain sizes of 0.3 - 0.5 μm and 1 - 2 μm and copper with a size of 3 - 6 μm. This powder has a low oxygen content, high activity, high tapped density, excellent fluidity and high electrical conductivity, and can meet the requirements of the injection molding process in subsequent processing.

[0037] The present invention constructs a core-shell structure with copper as the core and tungsten as the shell through a wet hydrogen pre-reduction process. By enriching fine tungsten particles around coarse tungsten particles, a balance between sintering activity and tap density is achieved, endowing the powder with a high tap density and excellent flow characteristics, ensuring uniform filling of complex cavities during injection molding. The synergistic effects of the wet hydrogen pre-reduction, secondary reduction, and low-temperature pre-sintering processes reduce the oxygen content, increase the surface activity, and significantly reduce the porosity during the low-temperature sintering process, enabling the final product to have both high density and interfacial bonding strength. The prepared tungsten-copper composite powder has tungsten powder with a size of 0.3 - 0.5 μm uniformly adsorbed on the surface of copper powder with a size of 3 - 6 μm, forming a core-shell structured powder with copper as the core and tungsten as the shell. Tungsten powder with a size of 1 - 2 μm is independently distributed, and the tap density is 7.0 - 7.5 g / cm³, and the oxygen content is ≤0.1 wt%. This powder is particularly suitable for the batch preparation of injection molding products such as micro-precision electronic packaging components, high-thermal-conductivity microchannel heat dissipation substrates, and electrical contacts with complex shapes. In the fields of 5G communication, power semiconductors, and microelectromechanical systems (MEMS), it can replace the traditional pressing-sintering process to achieve high-precision, near-net-shape manufacturing.

[0038] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

Claims

1. A method for preparing a high-activity and high-tap density tungsten-copper composite powder, characterized in that: Here are the steps: S1. Raw material mixing: mixing micron-sized tungsten trioxide and micron-sized copper powder to obtain a mixture; S2, wet hydrogen pre-reduction: the mixed material is subjected to slow dynamic pre-reduction in a rotary kiln to obtain a primary reduction material; S3, secondary reduction: the primary reduction raw material is fully reduced with dry hydrogen to obtain reduced powder; S4, crushing treatment after isostatic pressing: the reduced powder is isostatically pressed into blocks, and the blocks are crushed to obtain crushed powder; S5. Low-temperature pre-sintering: The crushed powder is sieved after low-temperature pre-sintering.

2. The method for preparing a high-activity and high-tap density tungsten-copper composite powder according to claim 1, characterized in that: The particle size of tungsten trioxide is 4~8μm; the copper powder is atomized copper powder with a particle size of 3~6μm.

3. The method for preparing a high-activity and high-tap density tungsten-copper composite powder according to claim 1, characterized in that: In step S2, the rotation speed of the rotary kiln is 8-12 revolutions per hour, the temperature is 650-800°C, the wet hydrogen flow rate is controlled to be 1-2 L / min, and the dew point of the wet hydrogen is controlled to be 0-20°C.

4. The method for preparing a tungsten-copper composite powder with high activity and high tap density according to claim 1, characterized in that: In step S3, the purity of hydrogen is ≥99.95%, the gas flow rate is 1-3 L / min, and the temperature is 850-950°C.

5. The method for preparing a tungsten-copper composite powder with high activity and high tap density according to claim 1, characterized in that: In step S4, the pressing parameters used for isostatic pressing are 150-250 MPa.

6. The method for preparing a tungsten-copper composite powder with high activity and high tap density according to claim 1, characterized in that: In step S4, the crushing is carried out by rolling ball mill dry grinding, the rotation speed is 80-120 rpm, and the ball-to-material ratio is 2-3:

1.

7. The method for preparing a tungsten-copper composite powder with high activity and high tap density according to claim 1, characterized in that: In step S5, the temperature of low-temperature pre-sintering of the crushed powder is 1000-1100° C., the pre-sintering time is 1-2 hours, and the pre-sintering adopts a hydrogen atmosphere.

8. High activity and high tap density tungsten-copper composite powder, characterized in that: The tungsten-copper composite powder is prepared by the method according to any one of claims 1 to 7, wherein the tungsten-copper composite powder comprises a core-shell structure with copper as a core and tungsten as a shell.

9. The high-activity and high-tap-density tungsten-copper composite powder according to claim 8, characterized in that: The tungsten-copper composite powder is a composite powder composed of tungsten with grain sizes of 0.3-0.5 μm and 1-2 μm and copper with grain sizes of 3-6 μm.

10. Use of high-activity and high-tap density tungsten-copper composite powder, characterized in that: Used for batch production of injection molded products, including but not limited to micro-precision electronic packages, high thermal conductivity microfluidic heat dissipation substrates and complex-shaped electrical contacts.

Images