Silver-based composite powder containing reinforcing phase, method for preparing same, and electrical contact material

Abstract

This application discloses a silver-based composite powder containing a reinforcing phase, its preparation method, and an electrical contact material. The silver-based composite powder containing the reinforcing phase comprises first sphericity particles with a sphericity greater than 0.85, second sphericity particles with a sphericity of 0.6~0.85, and third sphericity particles with a sphericity less than 0.6. In the silver-based composite powder containing the reinforcing phase, the proportion of first sphericity particles is W1, the proportion of second sphericity particles is W2, and the proportion of third sphericity particles is W3, wherein 4.56 ≥ (W1 + W2) / W3 ≥ 3.00. Since the first sphericity particles can withstand electric arc impact, and the second sphericity particles can balance the requirements of conductivity and corrosion resistance, the high content of first and second sphericity particles in the silver-based composite powder containing the reinforcing phase improves the overall arc erosion resistance of the electrical contact material prepared using it as a raw material.

Description

Technical Field

[0001] This application relates to the field of electrical contact materials technology, specifically to a silver-based composite powder containing a reinforcing phase, its preparation method, and electrical contact materials. Background Technology

[0002] Silver-based electrical contact materials are widely used in switching equipment such as circuit breakers and relays, where they withstand arc thermal shock and mechanical wear during circuit switching. Several mature silver-based electrical contact material systems have been developed, including silver-cadmium oxide (AgCdO), silver-tin oxide (AgSnO2), silver-nickel (AgNi), silver-tungsten (AgW), and silver-graphite (AgC). As electrical equipment develops towards higher performance and longer lifespan, higher requirements are being placed on the overall performance of silver-based electrical contact materials.

[0003] To improve the arc erosion resistance and fusion welding resistance of silver-based electrical contact materials, it is usually necessary to introduce a reinforcing phase. The reinforcing phase can improve the hardness and wear resistance of the material, but introducing a reinforcing phase that is different from the matrix material will face a prominent contradiction: the particle shape of the reinforcing phase powder is usually irregular, for example, its microstructure is an irregular polyhedron, and its sharp parts or edges will cause a sharp increase in contact resistance, which will make the arc erosion resistance of the silver-based electrical contact material worse. Summary of the Invention

[0004] This application provides a silver-based composite powder containing a reinforcing phase, a method for preparing the same, and an electrical contact material, aiming to improve the problem of deteriorated arc erosion resistance of silver-based electrical contact materials.

[0005] This application provides a silver-based composite powder containing a reinforcing phase, wherein the silver-based composite powder containing the reinforcing phase includes a first sphericity particle, a second sphericity particle, and a third sphericity particle; the sphericity of the first sphericity particle is greater than 0.85, the sphericity of the second sphericity particle is 0.6~0.85, and the sphericity of the third sphericity particle is less than 0.6; in the silver-based composite powder containing the reinforcing phase, the proportion of the first sphericity particle is W1, the proportion of the second sphericity particle is W2, and the proportion of the third sphericity particle is W3, wherein 4.56≥(W1+W2) / W3≥3.00.

[0006] Optionally, in some embodiments of this application, W1 / W2 < 0.4.

[0007] Optionally, in some embodiments of this application, W1 is greater than or equal to 15%, W2 is greater than or equal to 50%, and W3 is less than or equal to 25% and greater than 0%.

[0008] Optionally, in some embodiments of this application, the silver-based composite powder containing the reinforcing phase includes silver particles, first reinforcing phase particles, and composite particles. The composite particles include second reinforcing phase particles and a silver layer attached to the surface of the second reinforcing phase particles. The first sphericity particles, the second sphericity particles, and the third sphericity particles are composed of the composite particles, the silver particles, and the first reinforcing phase particles.

[0009] Optionally, in some embodiments of this application, the number of composite particles is multiple, and at least some of the composite particles have a core-shell structure; and / or, Based on the total number of the first reinforcing phase particles and the composite particles, the number of composite particles accounts for more than 50%.

[0010] Optionally, in some embodiments of this application, the composite particles further include an intermediate layer located between the second reinforcing phase particles and the silver layer, the intermediate layer comprising a first metal, the melt of which can wet the silver and / or the second reinforcing phase particles.

[0011] Optionally, in some embodiments of this application, the materials of the first reinforcing phase particles and the second reinforcing phase particles are reinforcing components, wherein the reinforcing components include at least one of tungsten and tungsten carbide; and / or, The first metal includes at least one of cobalt and nickel.

[0012] Optionally, in some embodiments of this application, the D50 particle size of the silver-based composite powder containing the reinforcing phase is 1 μm to 2 μm; and / or, The D90 particle size of the silver-based composite powder containing the reinforcing phase is 2μm~3μm; and / or, The minimum particle size of the silver-based composite powder containing the reinforcing phase is greater than or equal to 0.2 μm; and / or, The maximum particle size of the silver-based composite powder containing the reinforcing phase is greater than or equal to 5 μm; and / or, The silver-based composite powder containing the reinforcing phase has an average aspect ratio of 1.0 to 2.2; and / or, The silver-based composite powder containing the reinforcing phase is a silver-tungsten carbide composite powder.

[0013] Optionally, in some embodiments of this application, the silver-based composite powder containing the reinforcing phase includes silver particles, first reinforcing phase particles, composite particles, and graphene particles; the first sphericity particles, the second sphericity particles, and the third sphericity particles are composed of the silver particles, the first reinforcing phase particles, the composite particles, and the graphene particles.

[0014] Accordingly, this application also provides a method for preparing a silver-based composite powder containing a reinforcing phase, for preparing the aforementioned silver-based composite powder containing a reinforcing phase, comprising: A mixed powder is provided, the mixed powder comprising reinforcing components, silver powder and sintering aid; The mixed powder is subjected to liquid phase sintering treatment to melt the silver powder and adhere it to the surface of the reinforcing component, and then cooled and solidified to obtain a sintered material; the sintering temperature of the liquid phase sintering treatment is 962℃~1200℃, and the sintering time is 0.5h~4h. The sintered material is crushed to obtain silver-based composite powder containing the reinforcing phase.

[0015] Optionally, in some embodiments of this application, the mixed powder further includes graphene powder, wherein the mass percentage of the reinforcing component in the mixed powder is 50wt%~99wt%, the mass percentage of the graphene powder is 0.5wt%~1.0wt%, the mass percentage of the sintering aid is 0.1wt%~2wt%, and the balance is the silver powder.

[0016] Optionally, in some embodiments of this application, the reinforcing component includes tungsten carbide powder, the tungsten carbide powder having an average particle size of 1 μm to 5 μm; and / or, The silver powder has an average particle size of 10 μm to 30 μm; and / or, The graphene powder is graphene nanosheets, and the number of layers in the graphene nanosheets is 1 to 30; and / or, The sintering aid includes at least one of Ni and Co; and / or, The provision of the mixed powder includes: The reinforcing component, the silver powder, and the sintering aid are subjected to a first mixing process to obtain a first mixture. The first mixture and the graphene powder are mixed and ultrasonically dispersed to obtain the second mixture; The second mixture is dried and sieved to obtain the mixed powder.

[0017] Optionally, in some embodiments of this application, the liquid phase sintering treatment is performed under an oxygen-free protective atmosphere; and / or, The crushing process includes high-energy ball milling; and / or, The method for preparing the silver-based composite powder containing the reinforcing phase further includes: performing airflow classification treatment on the powder obtained from the crushing process.

[0018] Accordingly, this application also provides an electrical contact material, wherein the raw materials for preparing the electrical contact material include the aforementioned silver-based composite powder containing a reinforcing phase or the silver-based composite powder containing a reinforcing phase prepared by the aforementioned method.

[0019] Optionally, in some embodiments of this application, the density of the electrical contact material is 9.61 g / cm³. 3 ~9.63g / cm 3 ; and / or, The electrical contact material has a conductivity of 54.84% IACS to 55.35% IACS; and / or, The Brinell hardness of the electrical contact material is 65.14 HBW ~ 66.37 HBW.

[0020] In addition, this application also provides an electrical device comprising the aforementioned electrical contact material.

[0021] In the silver-based composite powder containing a reinforcing phase provided in this application embodiment, the ratio of the total number of powder particles with a sphericity φ greater than or equal to 0.6 (i.e., first and second sphericity particles) to the total number of powder particles with a sphericity φ less than 0.6 (i.e., third sphericity particles) is 3.00 to 4.56. That is, in the silver-based composite powder containing a reinforcing phase, the total number of first and second sphericity particles is 3.00 to 4.56 times the number of third sphericity particles. Since the first sphericity particles can be used to withstand electric arc impact, while the second sphericity particles can be used to balance conductivity and corrosion resistance requirements, the high content of first and second sphericity particles in the silver-based composite powder containing a reinforcing phase can improve the overall arc erosion resistance of the electrical contact material prepared using it as a raw material. Attached Figure Description

[0022] Figure 1 This is a scanning electron microscope image of the AgWC composite powder provided in Example 5 of this application. Detailed Implementation

[0023] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0024] This application provides a silver-based composite powder containing a reinforcing phase, a method for preparing the same, and an electrical contact material. These are described in detail below. It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". The terms first, second, third, etc., are used merely as illustrative and do not impose numerical requirements or establish an order. Various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a rigid limitation on the scope of the invention; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any referenced number (fraction or integer) within the indicated range.

[0025] In a first aspect, embodiments of this application provide a silver-based composite powder containing a reinforcing phase, which can be used to prepare electrical contact materials. The electrical contact material can be prepared using the silver-based composite powder containing the reinforcing phase as a single raw material, or it can be prepared using the silver-based composite powder containing the reinforcing phase as an additive along with other materials as raw materials.

[0026] Specifically, the silver-based composite powder containing the reinforcing phase includes first sphericity particles, second sphericity particles, and third sphericity particles. The first sphericity particles have a sphericity greater than 0.85, the second sphericity particles have a sphericity of 0.6~0.85, and the third sphericity particles have a sphericity less than 0.6. In the silver-based composite powder containing the reinforcing phase, the proportion of first sphericity particles is W1, the proportion of second sphericity particles is W2, and the proportion of third sphericity particles is W3, where 4.56 ≥ (W1 + W2) / W3 ≥ 3.00.

[0027] Silver-based composite powder containing a reinforcing phase is a composite material formed by introducing a reinforcing phase into a silver-based material. The silver-based material is a material with silver (Ag) as its matrix. Since the silver-based material contains at least silver in its composition, the silver-based composite powder containing the reinforcing phase contains at least silver and a reinforcing component in its composition. Optionally, the reinforcing component includes at least one of tungsten (W) and tungsten carbide (WC).

[0028] Furthermore, the silver-based composite powder containing the reinforcing phase is a powder composed of powder particles, including first-sphericity particles, second-sphericity particles, and third-sphericity particles. Here, the powder particles constituting the silver-based composite powder containing the reinforcing phase are divided into first-sphericity particles, second-sphericity particles, and third-sphericity particles according to their morphology (specifically, sphericity). It should be noted that the material of the first-sphericity particles includes at least one of silver and a reinforcing component; the material of the second-sphericity particles includes at least one of silver and a reinforcing component; and the material of the third-sphericity particles includes at least one of silver and a reinforcing component. The material composition of any pair of first-sphericity particles, second-sphericity particles, and third-sphericity particles can be the same or different, and this is not limited here. As an example, the material of the first-sphericity particles includes silver and a reinforcing component; the material of the second-sphericity particles includes silver or includes silver and a reinforcing component; and the material of the third-sphericity particles includes silver or a reinforcing component.

[0029] Sphericity φ is a geometric parameter that measures how close a particle's shape is to a perfect sphere. Simply put, it describes how "round" a particle is. The higher the sphericity, the closer the particle's shape is to a perfect sphere. Sphericity φ = Surface area of ​​a sphere with the same volume as the particle / Actual surface area of ​​the particle. The value of sphericity φ is always less than or equal to 1. The closer the sphericity φ value is to 1, the more perfect and smooth the shape of the particle; the smaller the value, the more irregular the shape and the rougher the surface. As an example, powder particle A with a sphericity of approximately 0.95 is a smooth spherical particle, while powder particle B with a sphericity of approximately 0.3 is a flake-like or dendritic particle.

[0030] The sphericity φ of the powder particles constituting the silver-based composite powder containing the reinforcing phase can be estimated using image analysis. Specifically, a two-dimensional projection image of the powder particles is captured using a scanning electron microscope (SEM) or an optical microscope; the area (A) and perimeter (P) of the projected powder particles are calculated using image processing software; and then, empirical formulas related to two-dimensional shape are substituted into these formulas, such as Roundness = 4πA / P. 2 This roundness value is used as an approximate reference value for sphericity.

[0031] Specifically, the first sphericity particle refers to a particle with a sphericity φ greater than 0.85, the second sphericity particle refers to a particle with a sphericity φ between 0.6 and 0.85, and the third sphericity particle refers to a particle with a sphericity φ less than 0.6. The first sphericity particle having a higher sphericity than the second sphericity particle refers to sphericity, and the second sphericity particle having a higher sphericity than the third sphericity particle refers to sphericity. In silver-based composite powders containing reinforcing phases, the sphericity of the powder particles exhibits a gradient distribution. This is beneficial for the silver-based composite powders containing reinforcing phases to achieve optimal performance in different application scenarios: the first sphericity particles (φ greater than 0.85) have a near-equiaxed shape, uniform electric field distribution, and low thermal stress concentration, which are used to withstand electric arc impact; the second sphericity particles (φ 0.6~0.85) have both good packing performance and moderate stress distribution, which are used to balance the requirements of conductivity and corrosion resistance; the third sphericity particles (φ < 0.6) maintain certain angular characteristics, which can increase the mechanical interlocking with the silver matrix and improve the interfacial bonding stability.

[0032] As can be seen, in the silver-based composite powder containing the reinforcing phase provided in this application embodiment, the ratio of the total number of powder particles with a sphericity φ greater than or equal to 0.6 (i.e., first sphericity particles and second sphericity particles) to the total number of powder particles with a sphericity φ less than 0.6 (i.e., third sphericity particles) is 3.00~4.56. That is, in the silver-based composite powder containing the reinforcing phase, the total number of first sphericity particles and second sphericity particles is 3.00 times to 4.56 times the number of third sphericity particles. Since the first sphericity particles can be used to withstand electric arc impact, while the second sphericity particles can be used to balance the requirements of conductivity and corrosion resistance, the high content of first and second sphericity particles in the silver-based composite powder containing the reinforcing phase can improve the overall arc erosion resistance of the electrical contact material prepared using them as raw materials; at the same time, the silver-based composite powder containing the reinforcing phase also contains a certain amount of third sphericity particles to ensure the interfacial bonding stability of the electrical contact material.

[0033] In addition, particles with excessively high sphericity have high economic costs in actual production, and particles with high sphericity have relatively small specific surface areas and low sintering activity, requiring higher sintering temperatures or the use of activated sintering, which in turn affects the performance of electrical contact materials. Particles with low sphericity are prone to mechanical interlocking, resulting in high friction between particles, which can lead to increased pressing pressure during the preparation of electrical contact materials and is not conducive to the densification of electrical contact materials.

[0034] Therefore, controlling the total number of first and second spherical particles to be 3.00 to 4.56 times the number of third spherical particles can enable electrical contact materials to have good arc erosion resistance, cost advantage, and density.

[0035] In some embodiments of this application, W1 / W2 < 0.4. That is, in the silver-based composite powder containing the reinforcing phase, the ratio of the proportion of first spherical particles to the proportion of second spherical particles is less than 0.4. By further increasing the proportion of second spherical particles in the silver-based composite powder containing the reinforcing phase, both the electrical conductivity and corrosion resistance of the electrical contact material are considered.

[0036] In some embodiments of this application, in the silver-based composite powder containing the reinforcing phase, the proportion of first spherical particles is greater than or equal to 15%, i.e., W1 ≥ 15%. As examples, the proportion of first spherical particles is 15%, 20%, 25%, 30%, or 35%. In the silver-based composite powder containing the reinforcing phase, the proportion of second spherical particles is greater than or equal to 50%, i.e., W2 ≥ 50%. As examples, the proportion of second spherical particles is 50%, 55%, 60%, or 65%. In the silver-based composite powder containing the reinforcing phase, the proportion of third spherical particles is less than or equal to 25% and greater than 0%, i.e., 0% < W3 ≤ 25%. As examples, the proportion of third spherical particles is 1%, 5%, 10%, 15%, 20%, or 25%.

[0037] In silver-based composite powder containing reinforcing phase, the total number of first-sphericity particles and second-sphericity particles accounts for more than or equal to 75%, while the number of third-sphericity particles accounts for less than or equal to 25%. This can greatly improve the arc erosion resistance of electrical contact materials.

[0038] In some embodiments of this application, the silver-based composite powder containing the reinforcing phase includes silver particles, first reinforcing phase particles, and composite particles. The composite particles include second reinforcing phase particles and a silver layer attached to the surface of the second reinforcing phase particles. The first sphericity particles, the second sphericity particles, and the third sphericity particles are composed of composite particles, silver particles, and the first reinforcing phase particles.

[0039] Silver-based composite powder containing a reinforcing phase is a powder material composed of powder particles. This includes silver particles, first reinforcing phase particles, and composite particles. Here, the powder particles constituting the silver-based composite powder containing a reinforcing phase are classified into silver particles, first reinforcing phase particles, and composite particles based on their material composition.

[0040] In other words, the powder particles constituting the silver-based composite powder containing the reinforcing phase can be classified into first-sphericity particles, second-sphericity particles, and third-sphericity particles according to different classification dimensions, or they can be classified into silver particles, first-reinforcing phase particles, and composite particles. First-sphericity particles, second-sphericity particles, and third-sphericity particles are composed of composite particles, silver particles, and first-reinforcing phase particles; that is, composite particles, silver particles, and first-reinforcing phase particles can be further divided into first-sphericity particles, second-sphericity particles, and third-sphericity particles based on their sphericity. More specifically, first-sphericity particles include at least one of composite particles, silver particles, and first-reinforcing phase particles; second-sphericity particles include at least one of composite particles, silver particles, and first-reinforcing phase particles; and third-sphericity particles include at least one of composite particles, silver particles, and first-reinforcing phase particles.

[0041] The composite particles comprise a second reinforcing phase particle and a silver layer, with the silver layer attached to the surface of the second reinforcing phase particle. The silver layer can be a continuous film structure, or it can comprise multiple island-like protrusions attached to the surface of the second reinforcing phase particle. These island-like protrusions can be connected or separated from each other. Alternatively, the silver layer can completely encapsulate the second reinforcing phase particle, in which case the composite particle has a core-shell structure, with the second reinforcing phase particle as the core and the silver layer as the shell. Of course, the silver layer can also only cover part of the surface of the second reinforcing phase particle, leaving some of the particle's surface exposed outside the silver layer.

[0042] As mentioned above, the silver-based composite powder containing a reinforcing phase includes at least silver and reinforcing components in its material composition. When the silver-based composite powder containing a reinforcing phase includes silver particles, first reinforcing phase particles, and composite particles, the material of the silver layer of the silver particles and composite particles is silver, and the second reinforcing phase particles of the first reinforcing phase particles and composite particles are reinforcing phase powder particles, the material of which is the reinforcing component.

[0043] For silver-based composite powders containing a reinforcing phase, the microstructure of the reinforcing phase powder particles is an irregular polyhedron, and their sharp or angular portions can cause a sharp increase in the contact resistance of the electrical contact material. To address this, a silver layer is attached to the surface of the second reinforcing phase particles. This silver layer completely or partially covers the surface of the second reinforcing phase particles, blunting the sharp edges and transforming the originally angular particles into sub-spherical composite particles. Compared to the second reinforcing phase particles, the sphericity φ of the composite particles is significantly improved. Composite particles with high sphericity φ exhibit uniform electric field distribution and low thermal stress concentration in applications, which is beneficial for improving the arc erosion resistance of electrical contact materials prepared using silver-based composite powders containing a reinforcing phase as raw materials.

[0044] Optionally, the first reinforcing phase particles and the second reinforcing phase particles are made of the same material, but the first reinforcing phase particles are second reinforcing phase particles without a silver coating, and the sphericity φ of the first reinforcing phase particles is lower than that of the composite particles. As an example, the first reinforcing phase particles are third-sphericity particles, and the composite particles are either first-sphericity particles or second-sphericity particles. Increasing the content of composite particles in the silver-based composite powder containing the reinforcing phase can increase the total content of first-sphericity particles and second-sphericity particles in the silver-based composite powder containing the reinforcing phase, thereby improving the arc erosion resistance of the silver-based composite powder containing the reinforcing phase.

[0045] In some embodiments of this application, based on the total number of the first reinforcing phase particles and composite particles, the proportion of composite particles is greater than 50%, optionally, the proportion of composite particles is 73.8%~78.9%. The reinforcing phase in the silver-based composite powder containing the reinforcing phase includes first reinforcing phase particles and second reinforcing phase particles. The surface of the second reinforcing phase particles is covered (fully or partially covered) with a silver layer. The number of second reinforcing phase particles is equal to the number of composite particles. The proportion of composite particles is greater than 50%, indicating that at least half of the reinforcing phase is covered by the silver layer. This ensures that the total content of the first and second spherical particles in the silver-based composite powder containing the reinforcing phase is high, thereby ensuring the arc erosion resistance of the electrical contact material. When the proportion of composite particles is less than 50%, the improvement effect of composite particles is not significant, and the average sphericity of the silver-based composite powder containing the reinforcing phase is close to the sphericity of the original powder. When the proportion of composite particles is greater than 50%, it proves that the silver layer and the second reinforcing phase particles are well-encapsulated, which is beneficial to the subsequent improvement of the electrical contact material performance. Under the condition of slightly increasing the contact resistance, the burn-off rate decreases. When the proportion of composite particles is less than 50%, it indicates that the silver layer has a poor coating effect on the second reinforcing phase particles, and the sphericity of the composite particles is difficult to improve effectively. As an example, based on the total number of first reinforcing phase particles and composite particles, the proportion of composite particles is 50%, 55%, 60%, 65%, 70%, 73.8%, 74.0%, 74.5%, 75.0%, 75.5%, 76.0%, 76.5%, 77.0%, 77.5%, 78.0%, 78.5%, 78.9%, 80%, 85%, or 90%.

[0046] In some embodiments of this application, there are multiple composite particles, with at least some of them having a core-shell structure. In the core-shell composite particles, the irregularly shaped second reinforcing phase particles are completely encapsulated within a silver layer, resulting in a generally higher sphericity of the composite particles. Ideally, all composite particles would have a core-shell structure. The core of this core-shell composite particle is a second reinforcing phase particle, and the shell is a silver layer attached to the surface of the second reinforcing phase particle.

[0047] In some embodiments of this application, the composite particles further include an intermediate layer located between the second reinforcing phase particles and the silver layer. The intermediate layer includes a first metal, the melt of which can wet the silver and / or the second reinforcing phase particles.

[0048] The intrinsic physicochemical differences between the reinforcing phase and the silver matrix result in poor interfacial bonding between the silver layer and the second reinforcing phase particles in the composite particles.

[0049] To address this, by introducing an intermediate layer between the second reinforcing phase particles and the silver layer in the composite particles, during the process of preparing the electrical contact material by sintering, the first metal melts to form a melt. The melt of the first metal can indirectly improve the wettability between the second reinforcing phase particles and the silver by wetting the silver used to form the silver layer, and / or the melt of the first metal can indirectly improve the interfacial bonding quality between the silver layer and the second reinforcing phase particles in the obtained composite particles.

[0050] In some embodiments of this application, the materials of the first reinforcing phase particles and the second reinforcing phase particles are reinforcing components, including at least one of tungsten and tungsten carbide.

[0051] When the reinforcing component is tungsten, the silver-based composite powder containing the reinforcing phase is a silver-tungsten (AgW) composite powder. When the reinforcing component is tungsten carbide, the silver-based composite powder containing the reinforcing phase is a silver-tungsten carbide (AgWC) composite powder. When the reinforcing components include both tungsten and tungsten carbide, the silver-based composite powder containing the reinforcing phase is a silver-tungsten carbide-tungsten (AgWCW) composite powder.

[0052] The following explanation uses tungsten carbide as an example of a reinforcing component. Tungsten carbide, due to its high melting point, high hardness, and excellent wear resistance, is a commonly used reinforcing component in silver-based electrical contact materials. When tungsten carbide is directly added as a reinforcing phase to silver-based electrical contact materials, the traditional method only mechanically bonds the tungsten carbide particles to the silver matrix. However, tungsten carbide particles have inherent defects: silver and tungsten carbide are immiscible systems with poor wettability, resulting in a simple mechanical bond at the interface. The bonding force between the tungsten carbide particles and the silver matrix is ​​weak, and the particles are prone to peeling off under repeated electric arcing, making it difficult to fully realize the reinforcing effect. Furthermore, the irregular, angular shape of tungsten carbide particles leads to uneven stress distribution at the interface with the silver matrix. The introduction of tungsten carbide particles often results in an imbalance between contact resistance and burn-off resistance, affecting the overall performance improvement of silver-based electrical contact materials.

[0053] Unlike traditional methods, the silver-tungsten carbide composite powder provided in this application includes silver particles, tungsten carbide particles, and silver-tungsten carbide (AgWC) composite particles. The AgWC composite particles include tungsten carbide particles and a silver layer attached to the surface of the tungsten carbide particles. The presence of AgWC composite particles can significantly improve the aforementioned problems caused by tungsten carbide particles in traditional methods. Specifically, the silver layer is attached to the surface of the tungsten carbide particles, resulting in better bonding between the silver layer and the tungsten carbide particles. This bonding quality is further enhanced when the AgWC composite particles also include an intermediate layer. Secondly, the sphericity φ of the AgWC composite particles is higher than that of the exposed tungsten carbide particles. AgWC composite particles with high sphericity φ exhibit a more uniform electric field distribution and lower thermal stress concentration in applications, which is beneficial for improving the arc erosion resistance of electrical contact materials.

[0054] In some embodiments of this application, the first metal includes at least one of cobalt (Co) and nickel (Ni).

[0055] In the above scheme, the first metal is cobalt and / or nickel. When the second reinforcing phase particles are tungsten carbide particles, liquid cobalt and / or nickel exhibit good wettability to the tungsten carbide particles. This good wettability stems from the atomic-level interaction between the liquid cobalt and / or nickel and the tungsten carbide particles. In particular, there is a strong chemical affinity between the melt of cobalt and / or nickel and tungsten carbide, which may form an extremely thin, compositionally graded transition layer at the interface, thereby reducing the solid-liquid interfacial energy.

[0056] In some embodiments of this application, the average aspect ratio of the silver-based composite powder containing the reinforcing phase is 1.0 to 2.2.

[0057] Silver-based composite powder containing reinforcing phase is a powder composed of powder particles. The average aspect ratio of silver-based composite powder containing reinforcing phase refers to the average aspect ratio K of all powder particles.

[0058] When testing the average aspect ratio of silver-based composite powder containing reinforcing phase, the average aspect ratio K of all particles in the scanning electron microscope image was statistically analyzed at the same field magnification.

[0059] The aspect ratio K, also known as the diameter-to-thickness ratio or length-to-diameter ratio, is a key dimensionless parameter describing particle shape. Typically, the aspect ratio K is the ratio of the particle's major axis to its minor axis. The specific formula is: K = L / W, where L is the length of the particle along its longest direction, and W is the maximum width perpendicular to that direction.

[0060] The K value can usually be obtained statistically through image analysis methods (such as scanning electron microscope (SEM) images). The specific steps are as follows: acquire a large number of two-dimensional projection images of particles, calculate the major and minor axes of the circumscribed ellipse for each particle, or obtain the length and width using the minimum bounding rectangle method, calculate the K value, and statistically analyze its distribution.

[0061] When K=1, the particles are nearly circular in a two-dimensional projection, and their shape tends to be isometric. When K>1, the particles are non-isometric, and the larger the value, the more elongated or flattened the shape. When K>>1, the particles are distinctly needle-like, rod-like, plate-like, or fibrous.

[0062] A higher aspect ratio K leads to a difference between the short and long axes, which in turn causes a difference in contact resistance. In the embodiments of this application, the average aspect ratio of the silver-based composite powder containing the reinforcing phase is 1.0 to 2.2, indicating that the shape of the powder particles constituting the silver-based composite powder containing the reinforcing phase is sub-angular to sub-circular. This is beneficial for improving the packing density and isotropy between powder particles, thereby reducing the contact resistance of the electrical contact material.

[0063] In some embodiments of this application, the D50 particle size of the silver-based composite powder containing the reinforcing phase is 1 μm to 2 μm. The D50 particle size of the silver-based composite powder containing the reinforcing phase being 1 μm to 2 μm means that 50% (i.e., half) of the powder particles in the silver-based composite powder containing the reinforcing phase have a particle size smaller than 1 μm to 2 μm. As examples, the D50 particle size of the silver-based composite powder containing the reinforcing phase is 1.0 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, or 2.0 μm.

[0064] In some embodiments of this application, the D90 of the silver-based composite powder containing the reinforcing phase is 2 μm to 3 μm. The D90 of the silver-based composite powder containing the reinforcing phase being 2 μm to 3 μm means that 90% of the powder particles in the silver-based composite powder containing the reinforcing phase have a particle size smaller than 2 μm to 3 μm. As an example, the D90 particle size of the silver-based composite powder containing the reinforcing phase is 2.0 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, or 3.0 μm.

[0065] In some embodiments of this application, the minimum particle size of the silver-based composite powder containing the reinforcing phase is greater than or equal to 0.2 μm; the maximum particle size of the silver-based composite powder containing the reinforcing phase is greater than or equal to 5 μm.

[0066] When the particle size distribution of silver-based composite powder containing reinforcing phase varies, it leads to large performance dispersion. By precisely controlling the various particle size parameters of the silver-based composite powder containing reinforcing phase to the above-mentioned range, the particle size distribution of the powder can be narrowed and made more uniform, which is beneficial to improving the stability and consistency of the electrical contact material performance.

[0067] Furthermore, if the particle size of the silver-based composite powder containing the reinforcing phase is too coarse, its sintering activity will be low. This necessitates increasing the sintering temperature or extending the holding time at the target sintering temperature to achieve the same effect in subsequent electrical contact material preparation, which is not economically advantageous. Conversely, if the particle size of the silver-based composite powder containing the reinforcing phase is too fine, it will be difficult to mix evenly with other powders, easily leading to agglomeration and segregation in the electrical contact material. Moreover, excessively fine silver-based composite powder containing the reinforcing phase requires greater pressure during the pressing and compaction process.

[0068] In some embodiments of this application, the silver-based composite powder containing the reinforcing phase includes silver particles, first reinforcing phase particles, composite particles, and graphene particles; the first sphericity particles, the second sphericity particles, and the third sphericity particles are composed of silver particles, first reinforcing phase particles, composite particles, and graphene particles.

[0069] Graphene particles are further introduced into a silver-based composite powder containing a reinforcing phase, comprising silver particles, a first reinforcing phase particle, and composite particles. The graphene particles also constitute a type of powder particle in the silver-based composite powder containing the reinforcing phase. Thus, the first spherical particle, the second spherical particle, and the third spherical particle are composed of silver particles, the first reinforcing phase particle, the composite particle, and the graphene particle. More specifically, the first spherical particle includes at least one of silver particles, the first reinforcing phase particle, the composite particle, and the graphene particle; the second spherical particle includes at least one of silver particles, the first reinforcing phase particle, the composite particle, and the graphene particle; and the third spherical particle includes at least one of silver particles, the first reinforcing phase particle, the composite particle, and the graphene particle.

[0070] Graphene possesses excellent electrical and thermal conductivity due to its unique two-dimensional structure. Adding a small amount of graphene to a silver matrix can significantly improve the material's electrical conductivity, thermal conductivity, and resistance to arc erosion.

[0071] The above technical solution introduces graphene particles into silver-based composite powder containing reinforcing phases to form a three-dimensional conductive network, which effectively compensates for the increase in resistance caused by the reinforcing phase particles (including the first reinforcing phase particles and the second reinforcing phase particles) and the intermediate layer (if any), so that the electrical contact material can maintain a moderate contact resistance while improving the anti-burning performance.

[0072] Secondly, embodiments of this application also provide a method for preparing a silver-based composite powder containing a reinforcing phase, used to prepare the aforementioned silver-based composite powder containing a reinforcing phase, the method comprising: S10. Provide a mixed powder, which includes reinforcing components, silver powder and sintering aids; S20. The mixed powder is subjected to liquid phase sintering treatment to melt the silver powder and attach it to the surface of the reinforcing component, and then cooled and solidified to obtain a sintered material; wherein the sintering temperature of the liquid phase sintering treatment is 962℃~1200℃, and the sintering time is 0.5h~4h. S30. The sintered material is crushed to obtain silver-based composite powder containing the reinforcing phase.

[0073] In step S10, the mixed powder includes a reinforcing component, which is used to form a reinforcing phase. In the obtained silver-based composite powder containing the reinforcing phase, the reinforcing phase includes first reinforcing phase particles and second reinforcing phase particles, that is, the reinforcing component is used to form the first reinforcing phase particles and the second reinforcing phase particles. Optionally, the reinforcing component includes at least one of tungsten and tungsten carbide. As an example, the reinforcing component includes tungsten carbide powder with an average particle size of 1 μm to 5 μm, such as 1 μm, 2 μm, 3 μm, 4 μm or 5 μm.

[0074] In step S10, the mixed powder also includes silver powder, which is ultimately used to form the silver matrix of the electrical contact material. In the resulting silver-based composite powder containing the reinforcing phase, the silver powder is used to form silver particles and silver layers. As an example, the average particle size of the silver powder is 10 μm to 30 μm, such as 10 μm, 15 μm, 20 μm, 25 μm, or 30 μm.

[0075] In step S10, the mixed powder also includes a sintering aid, which assists in wetting the reinforcing components during the sintering process by forming a melt from the melting of silver powder, thereby allowing the liquid silver to adhere to the surface of the reinforcing components. After sintering, the sintering aid remains in the material. Specifically, after sintering, as the temperature decreases, the liquid silver solidifies to form a silver layer that adheres to the surface of the second reinforcing phase particles formed by the reinforcing components, while the sintering aid forms an intermediate layer connecting the silver layer and the second reinforcing phase particles. Optionally, the sintering aid includes at least one ferrous metal, such as Ni and Co.

[0076] In step S20, the mixed powder is sintered, specifically a liquid-phase sintering process. Specifically, during this liquid-phase sintering process, as the sintering temperature rises above the melting point of silver, the silver powder in contact with the reinforcing phase particles (e.g., tungsten carbide particles) melts into a liquid phase under the action of sintering aids (such as Ni, Co, etc.). The silver liquid phase wets and covers the surface of the reinforcing phase particles. As the sintering and holding process continues, the molten liquid silver, utilizing its liquid phase fluidity and surface tension, spreads across the sharp edges of the reinforcing phase particles. The liquid silver can coat small reinforcing phase particles, while for larger particles, it forms island-like structures on their surfaces, thus producing a "passivation" effect, gradually transforming the originally angular reinforcing phase particles into a sub-angular to sub-rounded composite phase. This composite phase, after subsequent cooling and solidification, forms composite particles in the silver-based composite powder containing the reinforcing phase. Furthermore, the silver between the composite particles may form bridges connecting them. It should be noted that due to factors such as the distribution of reinforcing components, silver powder and sintering aids in the mixed powder, there may be some independent reinforcing phase particles. The surface of these reinforcing phase particles will not be covered with liquid silver, and some liquid silver may exist independently instead of being attached to the surface of the reinforcing phase particles. Thus, after cooling and solidification, these reinforcing phase particles form free reinforcing phase particles, and at the same time, the liquid silver forms free silver.

[0077] In step S20, the sintering temperature for liquid phase sintering is 962℃~1200℃, and the sintering time is 0.5h~4h. For example, the sintering temperature for liquid phase sintering is 962℃, 1000℃, 1050℃, 1100℃, 1150℃, or 1200℃, and the sintering time is 0.5h, 1h, 2h, 3h, or 4h. The sintering temperature for liquid phase sintering must be higher than the melting point of silver. When the sintering temperature is lower than the melting point of silver, the silver will not melt and cannot coat the reinforcing phase particles to achieve passivation. Increasing the sintering temperature is beneficial for improving the sphericity of the composite particles. When the sintering temperature is too high (above 1200℃), the viscosity of silver increases, which may cause it to flow from the voids to the lower layer, causing agglomeration. Furthermore, excessively high sintering temperatures may also lead to the evaporation of the silver liquid, resulting in changes in the overall composition of the material. When the sintering temperature is too low, although the silver has melted, there is not enough time for diffusion, resulting in poor coating of the reinforcing phase particles and an overall sphericity close to the original sphericity of the reinforcing phase particles. When the sintering time is too long, it may lead to grain coarsening, the formation of compounds at the interface that affect interfacial bonding, and poor economic efficiency.

[0078] In the liquid-phase sintering process of step S20, silver powder melts and then solidifies upon cooling to obtain a sintered material. Since the silver particles may form bridges connecting the composite particles, this sintered material possesses a certain strength, thus requiring crushing. In step S30, crushing can break down large-diameter particles, reducing the overall particle size of the powder to a smaller range. However, crushing has a destructive effect on the sintered material obtained from liquid-phase sintering, potentially causing the composite particles to become sharp again or disrupting their structure, transforming them back into free silver powder and reinforcing phase particles. The free silver powder forms silver particles in the silver-based composite powder containing the reinforcing phase, and the free reinforcing phase particles form the first reinforcing phase particles in the silver-based composite powder containing the reinforcing phase.

[0079] The method for preparing silver-based composite powder containing a reinforcing phase provided in the application embodiment utilizes the edge-blunting effect during liquid-phase sintering to transform the originally angular reinforcing phase particles into sub-spherical composite particles, significantly improving sphericity. Spherical composite particles exhibit uniform electric field distribution and low thermal stress concentration in applications, which is beneficial for improving the arc erosion resistance of electrical contact materials. Liquid-phase sintering allows silver to form an effective coating layer on the surface of the reinforcing phase particles. Combined with the action of sintering aids, the interfacial bonding changes from mechanical bonding to a wetting-coating type. Under repeated arc impacts, the reinforcing phase particles are less prone to peeling off, significantly improving erosion resistance.

[0080] Based on the above-mentioned reasonable sintering temperature range and sintering time, under the influence of sintering aids, we can obtain first sphericity particles with a sphericity greater than 0.85, second sphericity particles with a sphericity of 0.6~0.85, and third sphericity particles with a sphericity less than 0.6. At the same time, in the silver-based composite powder containing the reinforcing phase, the proportions of the first, second, and third sphericity particles satisfy the following relationship: 4.56≥(W1+W2) / W3≥3.00.

[0081] In some embodiments of this application, in step S20, the liquid-phase sintering process is performed under an oxygen-free protective atmosphere. Optionally, the oxygen-free protective atmosphere comprises at least one of hydrogen, nitrogen, and argon. As an example, the gas flow rate is 200 sccm.

[0082] In some embodiments of this application, the crushing process in step S30 includes high-energy ball milling. High-energy ball milling can refine the particle size and also allow free Ag and reinforcing phase particles to form a mechanical bond. As an example, the grinding balls and the inner wall of the grinding jar used in the high-energy ball milling process are made of cemented carbide; the ball-to-material ratio is (5~10):1, for example, 5:1, 6:1, 7:1, 8:1, 9:1, or 10:1; the ball milling speed is 200rpm~400rpm, for example, 200rpm, 250rpm, 300rpm, 350rpm, or 400rpm; the ball milling time is 2h~8h, for example, 2h, 3h, 4h, 5h, 6h, 7h, or 8h; and the grinding medium is anhydrous ethanol or gasoline, etc. Of course, in other embodiments, the crushing process includes airflow crushing.

[0083] In some embodiments of this application, the method for preparing silver-based composite powder containing the reinforcing phase further includes: performing airflow classification treatment on the powder obtained from the crushing process.

[0084] During liquid-phase sintering, Ag connected to the reinforcing phase particles (e.g., WC particles) liquefies, and liquid silver passivates the edges of the reinforcing phase particles and forms a wettable bond with the help of sintering aids, thus coating or covering the reinforcing phase particles. Large droplets formed by the interconnection of Ag particles are distributed between the reinforcing phase particles, and finally, after being broken up by ball milling, they adhere to the surface of the reinforcing phase particles or composite particles in a mechanical bonding manner.

[0085] After liquid phase sintering, the powder particles (e.g., composite particles) almost retain their original particle size. Subsequently, they are crushed (e.g., high-energy ball milling) and air classified. The crushing and air classification processes do not break the composite particles after liquid phase sintering into individual reinforcing phase particles. The role of the crushing process is to break the composite structure block formed after liquid phase sintering into small composite particles. Most of these composite particles still retain the core-shell structure of Ag-coated reinforcing phase, while the non-reinforcing phase particles are separated from Ag.

[0086] The function of airflow classification is to screen the particle size of the powder obtained from crushing, so as to achieve precise control of the particle size of composite powder and obtain silver-based composite powder with a narrow particle size distribution and uniform size containing reinforcing phase.

[0087] By combining crushing (e.g., high-energy ball milling) with air classification, precise control of the particle size of silver-based composite powder containing reinforcing phases can be achieved, resulting in a narrow and uniform particle size distribution. A uniform particle size distribution is beneficial to the stability and consistency of the electrical contact material properties.

[0088] As an example, the air classifier process includes: slowly feeding the crushed powder into the spiral feed inlet of an air classifier to classify the powder, thereby obtaining silver-based composite powder with a controllable particle size containing a reinforcing phase. The fine powder produced by the air classifier is within the controllable range of 0.1 μm to 5 μm.

[0089] Airflow classification has no effect on the microstructure of powder particles; it only removes large, non-compliant particles as required.

[0090] In some embodiments of this application, the powder obtained from the crushing process can also be screened by sieving through a sieve to remove unqualified large particles.

[0091] In some embodiments of this application, the mixed powder also includes graphene powder. The introduction of graphene can form a three-dimensional conductive network in the silver matrix, effectively compensating for the increase in resistance caused by the reinforcing components and sintering aids, so that the electrical contact material maintains a moderate contact resistance while improving its resistance to burn-off.

[0092] In some embodiments of this application, the mass percentage of the reinforcing component in the mixed powder is 50wt%~99wt%, the mass percentage of graphene powder is 0.5wt%~1.0wt%, the mass percentage of the sintering aid is 0.1wt%~2wt%, and the balance is silver powder.

[0093] The proportions of the mixed powders affect the composition of the resulting silver-based composite powder containing the reinforcing phase, and consequently, the composition of the electrical contact material. In electrical contact materials, there are intrinsic differences in physicochemical properties between the reinforcing phase and the silver matrix. Excessive reinforcing phase content significantly increases the contact resistance of the electrical contact material, affecting its conductivity; conversely, insufficient reinforcing phase content makes it difficult to fully realize the anti-burn-off effect. Furthermore, the uniformity of the heterogeneous reinforcing phase distribution and the quality of interfacial bonding within the silver matrix are difficult to precisely control, leading to unstable performance of the electrical contact material.

[0094] Graphene has a large specific surface area. Adding too much graphene is not conducive to material mixing and molding, while too little graphene cannot compensate for the conductivity of electrical contact materials.

[0095] Adding too much sintering aid is detrimental to the overall electrical conductivity of the material, while adding too little sintering aid will affect the coating effect.

[0096] By controlling the formulation of the mixed powder, electrical contact materials can have good resistance to burn-off and stable performance.

[0097] As an example, in the mixed powder, the mass percentage of the reinforcing component is any one or any two of the following: 50wt%, 60wt%, 65wt%, 70wt%, 75wt%, 80wt%, 90wt%, 95wt%, and 99wt%; the mass percentage of graphene powder is any one or any two of the following: 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, and 1.0wt%; the mass percentage of the sintering aid is any one or any two of the following: 0.1wt%, 0.5wt%, 1.0wt%, 1.5wt%, and 2wt%; and the balance is silver powder.

[0098] In some embodiments of this application, the mass percentage of reinforcing components in the mixed powder is 50wt%~95wt%, the mass percentage of graphene powder is 0.5wt%~1.0wt%, the mass percentage of sintering aid is 1.0wt%~2.0wt%, and the mass percentage of silver powder is 3.5wt%~47.5wt%.

[0099] The silver-based composite powder containing the reinforcing phase prepared by the above-mentioned mixed powder is mainly composed of spherical particles with a high average sphericity of about 0.62~0.80.

[0100] As an example, in the mixed powder, the mass percentage of silver powder is any one or any two of the following: 3.5wt%, 8wt%, 10wt%, 17.5wt%, 22.5wt%, 27.5wt%, 32.0wt%, 37.5wt%, and 47.5wt%.

[0101] In some embodiments of this application, the graphene powder is graphene nanosheets. Graphene nanosheets are small thin sheets formed by stacking single-layer or multi-layer graphene (single-layer carbon atoms). The more layers of graphene nanosheets, the closer their performance is to graphite, but they cannot effectively compensate for the influence of Ni and Co on the conductivity of the silver matrix. The fewer layers of graphene nanosheets, the better their performance, but they are more prone to aggregation and difficult to form an effective three-dimensional conductive network in the silver matrix. Therefore, in the embodiments of this application, the number of graphene nanosheets is between 1 and 30 layers. As an example, the number of graphene nanosheets is 1, 3, 6, 9, 12, 15, 18, 21, 24, 27, or 30 layers.

[0102] In some embodiments of this application, a mixed powder is provided, comprising: The reinforcing components, silver powder, and sintering aids are subjected to a first mixing treatment to obtain a first mixture. The first mixture and graphene powder were mixed and then ultrasonically dispersed to obtain the second mixture; The second mixture is dried and sieved to obtain a mixed powder.

[0103] The first mixing, ultrasonic dispersion, and drying and sieving processes do not have a significant impact on the morphology of the powder; they mainly only change the mixing and distribution state of the powder.

[0104] As an example, the preparation method of the mixed powder includes: adding reinforcing components, silver powder, and sintering aids to a three-dimensional motion mixer for a first mixing treatment, with a mixing time of 2h~8h and a rotation speed of 20rpm~50rpm, to obtain a uniformly mixed first mixture. The uniformly mixed first mixture is then subjected to multiple short-time ultrasonic dispersion treatments with graphene powder under a medium, with a settling period after each ultrasonic dispersion treatment, to obtain a second mixture; wherein the ultrasonic dispersion medium is anhydrous ethanol, and each ultrasonic dispersion is performed for 0.5h~1h followed by a 0.5h settling period, with 3~5 dispersion cycles, an ultrasonic frequency range of 400W~800W, and an ultrasonic temperature of room temperature. The second mixture is then washed, dried, and sequentially sieved through 80-mesh, 150-mesh, and 300-mesh sieves for later use.

[0105] In some embodiments of this application, the silver-based composite powder containing the reinforcing phase is AgWC composite powder, and the preparation method of AgWC composite powder is as follows: Tungsten carbide powder, silver powder, and sintering aids are mixed to obtain the first mixture; The first mixture is mixed with graphene powder and ultrasonically dispersed to obtain the second mixture; The second mixture is dried and then sieved to obtain a mixed powder. The mixed powder was subjected to liquid-phase sintering treatment, and then cooled and solidified to obtain sintered material; The sintered material was subjected to high-energy ball milling. The powder after high-energy ball milling is subjected to airflow classification to form a graphene-reinforced AgWC composite powder.

[0106] The AgWC composite powder uses tungsten carbide as the main structural component. Through a process combining liquid-phase sintering and high-energy ball milling, the microstructure of tungsten carbide is optimized and controlled, thereby enhancing the interfacial bonding between silver and tungsten carbide.

[0107] The above-mentioned method for preparing AgWC composite powder involves pre-compositing tungsten carbide and silver to form a reinforcing phase powder. Liquid-phase sintering is then used to melt and coat the tungsten carbide with silver to improve interfacial bonding. High-energy ball milling and airflow classification are then used to control the particle morphology and size distribution, resulting in a silver-tungsten carbide composite powder with optimized microstructure. Furthermore, a small amount of sintering aid is added to this reinforcing phase powder as a wetting agent to improve the wettability between silver and tungsten carbide, and a small amount of graphene is added to optimize electrical conductivity.

[0108] This application also provides an electrical contact material, the raw materials for which include the aforementioned silver-based composite powder containing a reinforcing phase or the silver-based composite powder containing a reinforcing phase prepared by the aforementioned method.

[0109] In some embodiments of this application, the raw materials for preparing the electrical contact material include only silver-based composite powder containing a reinforcing phase, that is, only silver-based composite powder containing a reinforcing phase is used as a raw material to directly prepare the electrical contact material.

[0110] In some embodiments of this application, silver-based composite powder containing a reinforcing phase can also be combined with other silver-based electrical contact materials for the preparation of electrical contact materials. As an example, silver-based composite powder containing a reinforcing phase can be used as a third phase in traditional silver-based electrical contact materials (e.g., AgWC12C3) to effectively stabilize contact resistance while improving the burn-off resistance of the electrical contact material, thus achieving an optimized balance of overall performance.

[0111] In some embodiments of this application, the density of the electrical contact material is 9.61 g / cm³. 3 ~9.63g / cm 3 For example, 9.61 g / cm³ 3 9.62 g / cm 3 Or 9.63 g / cm 3 .

[0112] In some embodiments of this application, the conductivity of the electrical contact material is 54.84% IACS to 55.35% IACS, for example 54.84% IACS, 54.90% IACS, 55.00% IACS, 55.10% IACS, 55.20% IACS, 55.30% IACS or 55.35% IACS.

[0113] In some embodiments of this application, the Brinell hardness of the electrical contact material is 65.14HBW to 66.37HBW, for example 65.14HBW, 65.50HBW, 66.00HBW or 66.37HBW.

[0114] In addition, this application also provides an electrical device comprising the aforementioned electrical contact material.

[0115] In some embodiments of this application, the electrical device includes at least one of a relay, a disconnecting device, and a controller. Optionally, the disconnecting device includes at least one of a circuit breaker, a contactor, and a switch.

[0116] The following description is based on specific embodiments.

[0117] Example 1 This embodiment provides an AgWC composite powder, the preparation process of which is as follows: S1. Ingredients: Take tungsten carbide powder (WC), silver powder (Ag), sintering aid and graphene powder (Gr) and mix them according to the proportions shown in Table 1. The mass proportions of tungsten carbide powder, silver powder, sintering aid and graphene are 50wt%, 47.5wt%, 1.5wt% and 1.0wt% respectively. The sintering aid is nickel powder (Ni).

[0118] S2. Mixing: Add tungsten carbide powder, silver powder and sintering aid to a three-dimensional motion mixer and mix at 30 rpm for 4 hours to obtain a uniformly mixed powder.

[0119] S3. Ultrasonic dispersion: The uniformly mixed powder and graphene powder are subjected to multiple short-time ultrasonic dispersions in a medium (specifically anhydrous ethanol). The ultrasonic dispersion frequency is 600W, each ultrasonic dispersion lasts for 40 minutes, and the ultrasonic dispersion is performed 4 times. Each ultrasonic dispersion is followed by a 30-minute interval between each dispersion and a period of stillness.

[0120] S4. Drying and sieving: Wash and dry the ultrasonically dispersed powder (drying method is vacuum drying, temperature is 60℃, time is 12h), and then pass it through 80 mesh, 150 mesh and 300 mesh sieves in sequence for later use.

[0121] S5. Liquid phase sintering: The sieved powder is loaded into an alumina crucible, which is placed in a tube furnace. An oxygen-free protective atmosphere (hydrogen protective atmosphere) is introduced, and the temperature of the tube furnace is raised to 980°C at a heating rate of 5°C / min. The holding time is 1.5h. In liquid phase sintering, molten Ag partially or completely coats WC and Gr particles and fills the gaps.

[0122] S6. High-energy ball milling: After the liquid phase sintering powder is crushed, it is loaded into a planetary ball mill for ball milling (ball-to-material ratio 8:1, rotation speed 300 rpm, time 4 h, grinding balls and inner wall of the ball mill are made of hard alloy). After ball milling, it is passed through a 300-mesh sieve to obtain composite powder.

[0123] S7. Air classification: The composite powder is slowly fed into the spiral feed port of the air classifier to classify the AgWC composite powder and obtain AgWC composite powder with controllable particle size. The fine powder range is D50=2μm.

[0124] Example 2 This embodiment provides an AgWC composite powder, the preparation process of which is as follows: S1. Ingredients: Take tungsten carbide powder (WC), silver powder (Ag), sintering aid and graphene powder (Gr) and mix them according to the proportions shown in Table 1. The mass proportions of tungsten carbide powder, silver powder, sintering aid and graphene are 60wt%, 37.5wt%, 1.5wt% and 1.0wt% respectively. The sintering aid is nickel powder (Ni).

[0125] S2~S7 are the same as in Example 1.

[0126] Example 3 This embodiment provides an AgWC composite powder, the preparation process of which is as follows: S1. Ingredients: Take tungsten carbide powder (WC), silver powder (Ag), sintering aid and graphene powder (Gr) and mix them according to the proportions shown in Table 1. The mass proportions of tungsten carbide powder, silver powder, sintering aid and graphene are 70wt%, 27.5wt%, 1.5wt% and 1.0wt% respectively. The sintering aid is nickel powder (Ni).

[0127] S2~S7 are the same as in Example 1.

[0128] Example 4 This embodiment provides an AgWC composite powder, the preparation process of which is as follows: S1. Ingredients: Take tungsten carbide powder (WC), silver powder (Ag), sintering aid and graphene powder (Gr) and mix them according to the proportions shown in Table 1. The mass proportions of tungsten carbide powder, silver powder, sintering aid and graphene are 80wt%, 17.5wt%, 1.5wt% and 1.0wt% respectively. The sintering aid is nickel powder (Ni).

[0129] S2~S7 are the same as in Example 1.

[0130] Example 5 This embodiment provides an AgWC composite powder, the preparation process of which is as follows: S1. Ingredients: Take tungsten carbide powder (WC), silver powder (Ag), sintering aid, and graphene powder (Gr) and mix them according to the proportions shown in Table 1. The mass proportions of tungsten carbide powder, silver powder, sintering aid, and graphene are 90wt%, 8.0wt%, 1.5wt%, and 0.5wt%, respectively. The sintering aid includes nickel powder (Ni) and cobalt powder (Co), wherein the mass ratio of nickel powder to cobalt powder is 2:1.

[0131] S2-S7 are the same as in Example 1. The SEM images of the AgWC composite powder prepared in this example are shown below. Figure 1 As shown.

[0132] Example 6 This embodiment provides an AgWC composite powder, the preparation process of which is as follows: S1. Ingredients: Take tungsten carbide powder (WC), silver powder (Ag), sintering aid, and graphene powder (Gr) and mix them according to the proportions shown in Table 1. The mass proportions of tungsten carbide powder, silver powder, sintering aid, and graphene are 95wt%, 3.5wt%, 1.0wt%, and 0.5wt%, respectively. The sintering aid includes nickel powder (Ni) and cobalt powder (Co), wherein the mass ratio of nickel powder to cobalt powder is 1:1.

[0133] S2~S7 are the same as in Example 1.

[0134] Example 7 This embodiment provides an AgWC composite powder, the preparation process of which is as follows: S1. Ingredients: Take tungsten carbide powder (WC), silver powder (Ag), sintering aid and graphene powder (Gr) and mix them according to the proportions shown in Table 1. The mass proportions of tungsten carbide powder, silver powder, sintering aid and graphene are 65wt%, 32wt%, 2.0wt% and 1.0wt%, respectively. The sintering aid includes cobalt powder (Co).

[0135] S2~S7 are the same as in Example 1.

[0136] Example 8 This embodiment provides an AgWC composite powder, the preparation process of which is as follows: S1. Ingredients: Take tungsten carbide powder (WC), silver powder (Ag), sintering aid, and graphene powder (Gr) and mix them according to the proportions shown in Table 1. The mass proportions of tungsten carbide powder, silver powder, sintering aid, and graphene are 75wt%, 22.5wt%, 2.0wt%, and 0.5wt%, respectively. The sintering aid includes nickel powder (Ni) and cobalt powder (Co), wherein the mass ratio of nickel powder to cobalt powder is 1:1.

[0137] S2~S7 are the same as in Example 1.

[0138] Example 9 The difference between this embodiment and Embodiment 1 is that during liquid phase sintering, the temperature of the tubular resistance furnace is raised to 962°C at a heating rate of 5°C / min, and the holding time is 4.0h. The rest is the same as in Embodiment 1.

[0139] Example 10 The difference between this embodiment and Embodiment 1 is that during liquid phase sintering, the temperature of the tubular resistance furnace is raised to 1200°C at a heating rate of 5°C / min, and the holding time is 0.5h. The rest is the same as in Embodiment 1.

[0140] Comparative Example 1 This comparative example provides an AgWC composite powder, the preparation process of which is as follows: S1. Ingredients: Take tungsten carbide powder (WC) and silver powder (Ag) and mix them according to the proportions shown in Table 1. The mass ratios of tungsten carbide powder and silver powder are 70wt% and 30wt%, respectively.

[0141] S2~S7 are the same as in Example 1.

[0142] Table 1

[0143] The AgWC composite powders provided in Examples 1-8 and Comparative Example 1 were characterized for the following properties: 1. Perform laser particle size analysis on the powder to determine the particle size distribution range. The test standard shall be in accordance with GB / T 19077-2024 Particle size analysis - Laser diffraction method.

[0144] 2. The average sphericity, average aspect ratio, and elemental analysis of AgWC composite powders with different compositions were observed using SEM and EDS to semi-quantitatively analyze the coating effect of WC. The coating rate was estimated by analyzing the overlap between Ag and WC elements in the AgWC composite powder using EDS images and image processing software. Scanned images were taken at three locations for each powder group, and at least 20 particles in the images were statistically analyzed. The sphericity φ and aspect ratio K of individual particles were calculated based on the results measured in the SEM images. The formula for calculating sphericity φ is as follows: φ=4πA / P 2 ; In the above formula, A: area (μm) 2 P: perimeter (μm).

[0145] The formula for calculating the aspect ratio K is as follows: K=L / W; In the above formula, L: length (μm), W: width (μm).

[0146] The average sphericity is obtained by averaging the sphericity φ of all individual particles measured.

[0147] The average aspect ratio is obtained by averaging the aspect ratio K of all individual particles measured.

[0148] The percentage of particles with a sphericity greater than 0.85 is W1, the percentage of particles with a sphericity between 0.6 and 0.85 is W2, and the percentage of particles with a sphericity less than 0.6 is W3.

[0149] The results of the above performance characterization are recorded in Tables 2 and 3.

[0150] Table 2

[0151] As can be seen from the characterization results of Examples 1-4 in Table 2, under the condition of adding the same proportion of sintering aid, as the Ag content decreases, the D50 and D90 particle sizes of the AgWC composite powder continuously decrease, the average aspect ratio of the AgWC composite powder continuously increases, and the average sphericity slightly improves. This is mainly because the decrease in Ag causes the system to develop towards a lower surface energy. Ag melts first at the corners of WC and adheres to the surface of WC particles, resulting in an increase in sphericity. During the subsequent ball milling and classification process, the average aspect ratio continues to increase, and silver with weak adhesion or poorly bonded Ag and WC detach, resulting in a slight decrease in sphericity. In addition, the decrease in silver content leads to an increase in the coating rate on the surface of WC particles. This is mainly because excessive silver content may cause Ag to preferentially connect with molten Ag during liquid-phase sintering, resulting in a decrease in coating rate and an increase in D50 and D90.

[0152] Table 3

[0153] The AgWC80 composite powder provided in Example 4 was added as a reinforcing phase to the AgWC12C3 system (Ag:WC:C = 85:12:3, mass ratio). Bulk electrical contact materials of 5.5 × 5.5 × 2.0 mm were prepared using powder metallurgy molding to investigate the effect of the AgWC80 composite powder on the performance of the electrical contact materials. While ensuring that the WC and C contents in AgWC12C3 remained unchanged, WC was added at 0%, 50%, and 100% of the total WC content in AgWC80 and AgWC12C3 (80 wt% WC in the AgWC80 composite powder; 75 wt% Ag, 12 wt% WC, and 3 wt% graphite in the AgWC12C3 electrical contact material). Based on WC, the AgWC12C3 electrical contact material was added at proportions of 0 wt%, 50 wt%, and 100 wt%. The WC in the material is replaced with AgWC80 powder to ensure that the total content of AgWC12C3 remains unchanged in the distribution ratio of each component; 0wt% means that AgWC12C3, Ag, WC, and C are all conventional powders; 50wt% means that half of the 12wt% WC in AgWC12C3 is contributed by the composite powder of AgWC80; 100wt% means that all the WC in AgWC12C3 is contributed by AgWC80. The final Ag content of the system is made up by the same Ag powder, and they are denoted as A1, A2, and A3 respectively.

[0154] A1, A2, and A3 were used as research objects. The density, conductivity, and Brinell hardness of A1, A2, and A3 were characterized and analyzed by a density meter, an eddy current conductivity meter, and a Brinell hardness meter, respectively. The results are shown in Table 4.

[0155] Table 4

[0156] As can be seen from the results in Table 4, the three materials A1, A2, and A3 exhibit different physical properties. The higher the proportion of AgWC80, the more its gradient particle size distribution contributes to the densification of AgWC12C3, resulting in lower porosity, higher hardness, and higher conductivity.

[0157] A1, A2, and A3 were used as static contact materials and paired with AgW50 as the moving contact material. Using an electrical performance testing platform, the materials were broken 5000 times under conditions of 220V, 63A, and a power factor of 0.8, and their contact resistance was monitored. After the test, the materials were weighed sequentially on an electronic balance, and the average value was compared with the value before the test to calculate the material loss. The results are shown in Table 5.

[0158] Table 5

[0159] In the electrical performance test, A3 showed a slightly higher average resistance of 0.8068 mΩ, which was 13.56% and 4.05% higher than A1 and A2, respectively. However, it had the lowest material loss of only 0.0323 g, which was 72.51% and 52.01% lower than A1 and A2, respectively. This indicates that the composite silver-based electrical contact material prepared by this method has high material density, good bonding between the silver matrix and the WC interface, long service life, and high cost-effectiveness.

[0160] analyze: (1) The role of spherical AgWC composite particles: In the AgWC composite powder prepared in Examples 1 to 4 above, the AgWC composite powder particles are sub-spherical in shape (average sphericity = 0.72~0.80). Compared with the angular WC particles (average sphericity = 0.58) in the traditional powder mixing process (Comparative Example 1), the spherical particles have a uniform electric field distribution and low thermal stress concentration under the action of electric arc, and are not easy to become the erosion origin point, so the burn loss is significantly reduced.

[0161] (2) The role of the wetting and coating interface: Liquid phase sintering enables Ag to form an effective coating layer on the surface of WC particles, and the interfacial bonding changes from mechanical interlocking to wetting and coating bonding. Under repeated arc impact, WC particles are not easily peeled off from the Ag matrix.

[0162] (3) The role of the graphene conductive network: Graphene forms a three-dimensional conductive network in AgWC composite powder, providing additional channels for electron transport. When AgWC composite powder is added to the AgWC12C3 system, the original graphene and the newly added graphene form complementary conductive pathways, effectively compensating for the increase in contact resistance caused by the addition of WC and sintering aids, keeping the overall contact resistance within an acceptable range.

[0163] (4) Balance of comprehensive performance: Through the optimization and control of WC microstructure and the conductivity compensation of graphene, a good balance is achieved between contact resistance and anti-burn performance, and the comprehensive performance is significantly better than that of traditional powder mixing process.

[0164] The foregoing has provided a detailed description of a silver-based composite powder containing a reinforcing phase, its preparation method, and its electrical contact material, as provided in the embodiments of this application. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A silver-based composite powder containing a reinforcing phase, characterized in that, The silver-based composite powder containing the reinforcing phase includes first spherical particles, second spherical particles, and third spherical particles; the sphericity of the first spherical particles is greater than 0.85, the sphericity of the second spherical particles is 0.6~0.85, and the sphericity of the third spherical particles is less than 0.6; in the silver-based composite powder containing the reinforcing phase, the proportion of the first spherical particles is W1, the proportion of the second spherical particles is W2, and the proportion of the third spherical particles is W3, wherein 4.56≥(W1+W2) / W3≥3.

00.

2. The silver-based composite powder containing a reinforcing phase according to claim 1, characterized in that, W1 / W2 < 0.4; and / or, W1 is greater than or equal to 15%, W2 is greater than or equal to 50%, and W3 is less than or equal to 25% and greater than 0%.

3. The silver-based composite powder containing a reinforcing phase according to claim 1, characterized in that, The silver-based composite powder containing the reinforcing phase includes silver particles, first reinforcing phase particles, and composite particles. The composite particles include second reinforcing phase particles and a silver layer attached to the surface of the second reinforcing phase particles. The first sphericity particles, the second sphericity particles, and the third sphericity particles are composed of the composite particles, the silver particles, and the first reinforcing phase particles.

4. The silver-based composite powder containing a reinforcing phase according to claim 3, characterized in that, The composite particles are multiple, and at least some of the composite particles have a core-shell structure; and / or, Based on the total number of the first reinforcing phase particles and the composite particles, the number of composite particles accounts for more than 50%.

5. The silver-based composite powder containing a reinforcing phase according to claim 3, characterized in that, The composite particles further include an intermediate layer located between the second reinforcing phase particles and the silver layer. The intermediate layer includes a first metal, the melt of which can wet the silver and / or the second reinforcing phase particles.

6. The silver-based composite powder containing a reinforcing phase according to claim 5, characterized in that, The materials of the first reinforcing phase particles and the second reinforcing phase particles are reinforcing components, and the reinforcing components include at least one of tungsten and tungsten carbide; and / or, The first metal includes at least one of cobalt and nickel.

7. The silver-based composite powder containing a reinforcing phase according to claim 1, characterized in that, The silver-based composite powder containing the reinforcing phase includes silver particles, first reinforcing phase particles, composite particles, and graphene particles; the first sphericity particles, the second sphericity particles, and the third sphericity particles are composed of the silver particles, the first reinforcing phase particles, the composite particles, and the graphene particles.

8. The silver-based composite powder containing a reinforcing phase according to any one of claims 1 to 7, characterized in that, The D50 particle size of the silver-based composite powder containing the reinforcing phase is 1 μm to 2 μm; and / or, The D90 particle size of the silver-based composite powder containing the reinforcing phase is 2μm~3μm; and / or, The minimum particle size of the silver-based composite powder containing the reinforcing phase is greater than or equal to 0.2 μm; and / or, The maximum particle size of the silver-based composite powder containing the reinforcing phase is greater than or equal to 5 μm; and / or, The silver-based composite powder containing the reinforcing phase has an average aspect ratio of 1.0 to 2.2; and / or, The silver-based composite powder containing the reinforcing phase is a silver-tungsten carbide composite powder.

9. A method for preparing a silver-based composite powder containing a reinforcing phase, used to prepare the silver-based composite powder containing a reinforcing phase as described in any one of claims 1 to 8, characterized in that, include: A mixed powder is provided, the mixed powder comprising reinforcing components, silver powder and sintering aid; The mixed powder is subjected to liquid phase sintering treatment to melt the silver powder and adhere it to the surface of the reinforcing component, and then cooled and solidified to obtain a sintered material; the sintering temperature of the liquid phase sintering treatment is 962℃~1200℃, and the sintering time is 0.5h~4h. The sintered material is crushed to obtain silver-based composite powder containing the reinforcing phase.

10. The method for preparing silver-based composite powder containing a reinforcing phase according to claim 9, characterized in that, The mixed powder also includes graphene powder. In the mixed powder, the mass percentage of the reinforcing component is 50wt%~99wt%, the mass percentage of the graphene powder is 0.5wt%~1.0wt%, the mass percentage of the sintering aid is 0.1wt%~2wt%, and the balance is silver powder.

11. The method for preparing silver-based composite powder containing a reinforcing phase according to claim 10, characterized in that, The reinforcing component includes tungsten carbide powder, the tungsten carbide powder having an average particle size of 1 μm to 5 μm; and / or, The silver powder has an average particle size of 10 μm to 30 μm; and / or, The graphene powder is graphene nanosheets, and the number of layers in the graphene nanosheets is 1 to 30; and / or, The sintering aid includes at least one of Ni and Co; And / or, The provision of the mixed powder includes: The reinforcing component, the silver powder, and the sintering aid are subjected to a first mixing process to obtain a first mixture. The first mixture and the graphene powder are mixed and ultrasonically dispersed to obtain the second mixture; The second mixture is dried and sieved to obtain the mixed powder.

12. The method for preparing silver-based composite powder containing a reinforcing phase according to any one of claims 9 to 11, characterized in that, The liquid phase sintering treatment is carried out under an oxygen-free protective atmosphere; and / or, The crushing process includes high-energy ball milling; and / or, The method for preparing the silver-based composite powder containing the reinforcing phase further includes: performing airflow classification treatment on the powder obtained from the crushing process.

13. An electrical contact material, characterized in that, The raw materials for preparing the electrical contact material include the silver-based composite powder containing the reinforcing phase as described in any one of claims 1 to 8, or the silver-based composite powder containing the reinforcing phase prepared by the method described in any one of claims 9 to 12.

14. The electrical contact material according to claim 13, characterized in that, The density of the electrical contact material is 9.61 g / cm³. 3 ~9.63g / cm 3 ; and / or, The electrical contact material has a conductivity of 54.84% IACS to 55.35% IACS; and / or, The Brinell hardness of the electrical contact material is 65.14 HBW ~ 66.37 HBW.

15. An electrical device, characterized in that, The electrical device comprises the electrical contact material as described in claim 13 or 14.

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