Copper tungsten carbide electric contact material and preparation method thereof

Abstract

According to the copper-tungsten carbide electric contact material and the preparation method thereof, a nano titanium carbide transition layer capable of forming strong metallurgical bonding with WC and Cu is generated on the surface of tungsten carbide particles in situ through a collaborative process of ball milling coating and reduction diffusion reaction. According to the gradient interface structure, loads can be efficiently transmitted, WC particles are effectively prevented from being peeled off from a base body under electric arc impact, the electric arc ablation resistance of the material is improved by 70% or above compared with a traditional CuWC material, and the service life of a contact is greatly prolonged.

Description

Technical Field

[0001] This invention relates to the field of electrical contact materials, specifically to a copper tungsten carbide electrical contact material and its preparation method. Background Technology

[0002] Copper-tungsten carbide (CuWC) composites hold an important position in the field of electrical contact materials due to their excellent electrical conductivity and wear resistance. However, CuWC materials prepared by the traditional mechanical mixing-melting method have inherent defects: poor interfacial wettability between WC and Cu, weak interfacial bonding, and under repeated arc erosion, WC particles are easily peeled off from the Cu matrix, resulting in a high arc erosion rate and limited service life.

[0003] A search and analysis of existing technologies revealed that Chinese patent CN111411280A discloses a copper-tungsten carbide-diamond composite electrical contact material using cobalt as a binder. While this method enhances the interfacial bonding between tungsten carbide and the copper matrix to some extent with the help of cobalt, the introduction of cobalt significantly reduces the material's conductivity. More critically, under the continuous action of a high-energy electric arc, cobalt easily forms a low-melting-point eutectic structure with copper, generating alloy nodules on the contact surface, severely affecting arc breaking stability and contact service life. Another technical approach, as shown in this patent, involves directly adding diamond to improve wear resistance; however, diamond lacks sufficient thermal stability at the high temperatures of an electric arc and is highly susceptible to graphitization. Graphitization not only leads to the failure of the reinforcing phase but also introduces soft defect regions, further exacerbating arc erosion and causing contact performance degradation.

[0004] Chinese patent CN119876726A proposes introducing modified carbon fibers and polydopamine to modify Ti3C2 to improve the density and overall performance of tungsten carbide copper composites. However, the modification process involved in this scheme is complex, requiring multiple steps of organic functionalization and liquid phase treatment. This not only results in a long process cycle and high cost, but also may introduce impurities and residual functional groups, posing a potential risk to the uniformity and stability of the material's electrical properties, which is not conducive to large-scale preparation and the application of high-reliability electrical contacts. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings and deficiencies of the existing technology and to provide a copper tungsten carbide electrical contact material and its preparation method.

[0006] The technical solution adopted in this invention is as follows: The first aspect of this invention provides a method for preparing a copper tungsten carbide electrical contact material, characterized by comprising the following steps: S1. Tungsten carbide powder and titanium powder are ball-milled in a protective atmosphere so that the titanium powder is dispersed and coated on the surface of the tungsten carbide particles to obtain activated mixed powder; S2. Under a reducing atmosphere, the activated mixed powder is kept at 900-1050℃ for 3-8 hours to promote the diffusion of titanium to the tungsten carbide grain boundaries to form a TiC transition layer, thus obtaining diffusion-treated powder; S3. After crushing and sieving the diffusion-treated powder, mix it with copper powder to obtain composite powder; S4. The composite powder is made into copper tungsten carbide electrical contact material.

[0007] Preferably, in step S1, the average particle size of the tungsten carbide powder is 0.5 to 5 μm, and the average particle size of the titanium powder is 0.1 to 5 μm.

[0008] Preferably, in step S1, the content of titanium powder in the activated mixed powder is 0.03 to 0.08 wt%.

[0009] Preferably, in step S1, tungsten carbide powder and titanium powder are ball-milled in a high-energy ball mill for 10 to 24 hours, with a ball-to-material ratio of 5:1 to 10:1 and a rotation speed of 200 to 400 rpm.

[0010] Preferably, in step S3, the diffusion-treated powder is crushed and then passed through a 300-500 mesh sieve, and the average particle size of the copper powder is 30-80 μm.

[0011] Preferably, step S4 specifically includes the following steps: S4-1. Add a sintering agent to the composite powder, mix, sieve, dry, sinter at 1150-1250℃, and then granulate to obtain granulated powder; S4-2. Add a molding agent to the granulated powder and mold to prepare a preform with a porosity of 18% to 35%; S4-3. The pressed preform is heated to 600-650°C at a rate of 3-10°C / min under a hydrogen atmosphere and held for 1-3 hours to remove the molding agent and obtain a degreased preform. S4-4. The degreased blank is embedded in the filler and kept at 1050-1150℃ for 1-3 hours in a hydrogen atmosphere to form a pre-fired skeleton; S4-5. A pure copper sheet with a thickness of 0.1 to 0.5 mm is laid on the surface of the pre-fired skeleton and melt-infiltrated in a hydrogen atmosphere at 1250 to 1400°C for 2 to 4 hours to obtain copper tungsten carbide electrical contact material.

[0012] Preferably, when the copper content in the target copper tungsten carbide electrical contact material is 9.8–15 wt%, the porosity is 18–25%. When the copper content in the target copper-tungsten carbide electrical contact material is 15-20 wt%, the porosity is 23-30%. When the copper content in the target copper-tungsten carbide electrical contact material is 20–24.95 wt%, the porosity is 28–35%.

[0013] Preferably, in step S4-2, the molding agent is polyvinyl alcohol and / or paraffin, and the amount of the molding agent added is 3-8 wt%.

[0014] Preferably, in step S4-4, the filler is graphite powder and / or alumina powder.

[0015] A second aspect of the present invention provides a copper tungsten carbide electrical contact material, which is prepared by the preparation method described above.

[0016] The beneficial effects of this invention are as follows: 1. Significantly Enhanced Interfacial Bonding Strength: Through a synergistic process of high-energy ball milling coating and reduction-diffusion reaction, a nano-titanium carbide transition layer with strong metallurgical bonding to both WC and Cu is generated in situ on the surface of tungsten carbide particles. This gradient interface structure can efficiently transfer loads and effectively prevent WC particles from peeling off from the matrix under arc impact, improving the material's arc erosion resistance by more than 70% compared to traditional CuWC materials, and significantly extending the contact life.

[0017] 2. High-level synergy between conductivity and wear resistance: By precisely controlling the amount of titanium added to 0.03–0.08 wt%, most of it reacts with carbon to form a high-hardness TiC phase, greatly reducing the solid solubility of titanium in the copper matrix. This design endows the material with excellent wear resistance while ensuring the high conductivity continuity of the copper matrix, giving the material both excellent conductivity and resistance to arc erosion.

[0018] 3. High process stability and product consistency: By precisely designing the compact porosity to control the final copper content, and combining this with a sintering process under filler protection, the technical challenges of easy deformation and difficult forming of high tungsten carbide content materials during preparation are effectively solved. This process is stable, and the prepared products have high dimensional accuracy and uniform microstructure, making them suitable for large-scale industrial production. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0020] Figure 1 The image shows a cross-sectional metallographic image of the copper tungsten carbide electrical contact material prepared in Example 2 of this invention, as observed under a metallographic microscope. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0022] Example 1 This embodiment provides a CuWC85 electrical contact material and its preparation method, which includes the following steps: (1) Activation and mixing: Weigh 9500g of tungsten carbide powder with an average particle size of 2-4μm and 4.7g of titanium powder with an average particle size of 1-3μm. Put both powders and cemented carbide balls into a powder mixer with a ball-to-material ratio of 8:1. High-energy ball milling is carried out for 20 hours under argon protection at a speed of 300rpm to obtain tungsten carbide composite powder with titanium coating on the surface. (2) Reduction diffusion: The titanium-coated tungsten carbide composite powder is unloaded, alloy balls are sieved out, the composite powder obtained by sieving is loaded into a graphite boat and kept at 1000°C for 5 hours in a hydrogen atmosphere to obtain tungsten carbide powder with a TiC transition layer. (3) Copper powder composite: Tungsten carbide powder with TiC transition layer is crushed and passed through a 400-mesh sieve and then mixed with 495.3g of copper powder with an average particle size of 60μm in a powder mixer for 4 hours to obtain copper-tungsten carbide composite powder; (4) Powder granulation: After mixing copper-tungsten carbide composite powder with sintering agent, the mixture is sieved, dried, loaded into a material boat, sintered at 1150℃ and then granulated to obtain granular composite powder. (5) Compression molding: 5wt% paraffin is added to the granular composite powder as a molding agent, and a porous compact with a single weight of 0.894g and a porosity of 24.08% is prepared by compression molding; (6) Degreasing: The porous compact is heated to 600°C at a rate of 5°C / min under a hydrogen atmosphere and held for 3 hours to remove the molding agent and obtain a degreased compact. (7) Skeleton sintering: The degreased blank is embedded in graphite powder filler and held at 1000℃ for 1 to 3 hours in a hydrogen atmosphere to obtain a pre-sintered skeleton; (8) Melting and infiltration strengthening: 0.106g of pure copper sheet is laid on the surface of the pre-sintered skeleton and melted and infiltrated in a hydrogen atmosphere at 1300℃ for 4 hours to obtain a dense copper tungsten carbide electrical contact material blank. (9) Post-processing: The dense copper tungsten carbide electrical contact material blank is cleaned and refined to obtain the final CuWC85 finished product.

[0023] Example 2 This embodiment provides a CuWC75 electrical contact material and its preparation method, which includes the following steps: (1) Activation and mixing: Weigh 9000g of tungsten carbide powder with an average particle size of 1-3μm and 8g of titanium powder with an average particle size of 0.5-2μm. Put both powders and cemented carbide balls into a powder mixer with a ball-to-material ratio of 10:1. High-energy ball milling is carried out for 20 hours under argon protection at a speed of 300rpm to obtain tungsten carbide composite powder with titanium coating on the surface. (2) Reduction diffusion: The titanium-coated tungsten carbide composite powder is unloaded, alloy balls are sieved out, the mixed powder obtained by sieving is loaded into a graphite boat and kept at 1000°C for 6 hours in a hydrogen atmosphere to obtain tungsten carbide powder with a TiC transition layer. (3) Copper powder composite: The tungsten carbide powder with TiC transition layer is crushed and passed through a 400-mesh sieve, and then mixed with 992g of copper powder with an average particle size of 40μm in a powder mixer for 6 hours to obtain copper-tungsten carbide composite powder. (4) Powder granulation: The copper-tungsten carbide composite powder is mixed with sintering agent, sieved, dried, loaded into a material boat, sintered at 1150℃ and granulated to obtain granular composite powder; (5) Compression molding: 6wt% paraffin is added to the granular composite powder as a molding agent, and a porous compact with a single weight of 0.833g and a porosity of 31.13% is prepared by compression molding; (6) Degreasing: The porous compact is heated to 600°C at a rate of 5°C / min under a hydrogen atmosphere and held for 3 hours to remove the molding agent and obtain a degreased compact; (7) Skeleton sintering: The degreased blank is embedded in graphite powder filler and kept at 1000℃ for 3 hours under hydrogen atmosphere to obtain a pre-sintered skeleton; (8) Melting and infiltration strengthening: 0.167g of pure copper sheet is laid on the surface of the pre-sintered skeleton and melted and infiltrated in a hydrogen atmosphere at 1300℃ for 4 hours to obtain a dense copper tungsten carbide electrical contact material blank. (9) Post-processing: The dense copper tungsten carbide electrical contact material blank is cleaned and refined to obtain the final CuWC75 finished product. Figure 1 The image shown is a cross-sectional metallographic image of the copper tungsten carbide electrical contact material prepared in this embodiment, observed under a metallographic microscope.

[0024] Example 3 This embodiment provides a CuWC90 electrical contact material and its preparation method, which includes the following steps: (1) Activation and mixing: Weigh 9700g of tungsten carbide powder with an average particle size of 1-3μm and 6g of titanium powder with an average particle size of 0.5-2μm. Put both powders and cemented carbide balls into a powder mixer with a ball-to-material ratio of 8:1. High-energy ball milling is carried out for 18 hours under argon protection at a speed of 350rpm to obtain tungsten carbide composite powder with titanium coating on the surface. (2) Reduction diffusion: The titanium-coated tungsten carbide composite powder is unloaded, alloy balls are sieved out, the mixed powder obtained by sieving is loaded into a graphite boat and kept at 1000°C for 6 hours in a hydrogen atmosphere to obtain tungsten carbide powder with a TiC transition layer. (3) Copper powder composite: The tungsten carbide powder with TiC transition layer is crushed and passed through a 400-mesh sieve, and then mixed with 294g of copper powder with an average particle size of 30μm in a powder mixer for 6 hours to obtain copper-tungsten carbide composite powder. (4) Powder granulation: The copper-tungsten carbide composite powder is mixed with sintering agent, sieved, dried, loaded into a material boat, sintered at 1150℃ and granulated to obtain granular composite powder; (5) Compression molding: 6 wt% polyvinyl alcohol is added to the granular composite powder as a molding agent, and a porous compact with a single weight of 0.928 g and a porosity of 19.69% is prepared by compression molding. (6) Degreasing: The porous compact is heated to 600°C at a rate of 5°C / min under a hydrogen atmosphere and held for 1 to 3 hours to remove the molding agent and obtain a degreased compact. (7) Skeleton sintering: The degreased blank is embedded in graphite powder filler and kept at 1000℃ for 3 hours under hydrogen atmosphere to obtain a pre-sintered skeleton; (8) Melting and infiltration strengthening: 0.072g of pure copper sheet is laid on the surface of the pre-sintered skeleton and melted and infiltrated in a hydrogen atmosphere at 1300℃ for 4 hours to obtain a dense copper tungsten carbide electrical contact material blank. (9) Post-processing: The dense copper tungsten carbide electrical contact material blank is cleaned and refined to obtain the final CuWC90 finished product.

[0025] Comparative Example 1 This comparative example provides a method for preparing CuWC75 material using traditional powder metallurgy technology, and the specific steps are as follows: (1) Raw material mixing: Weigh 7500g of 1-8μm tungsten carbide powder and 2500g of 80μm electrolytic copper powder directly, put them into a mixer and mix for 4 hours; (2) Compression molding: Add 3wt% polyvinyl alcohol binder to the powder obtained in step (1) and press it into a compact weighing 0.833g under a pressure of 300MPa; (3) First sintering: Place the pressed blank obtained in step (2) in a hydrogen-protected furnace and heat it to 1100℃ at 10℃ / min and hold it for 2 hours; (4) Melting treatment: 0.167g of copper sheet is placed on the surface of the sintered billet and melted in a hydrogen atmosphere at 1250℃ for 2 hours to obtain the final CuWC75 product.

[0026] The WC content in the CuWC75 electrical contact materials obtained in Example 2 and Comparative Example 1 is approximately 75%. The density, compactness, hardness, and resistivity of the copper-tungsten electrical contact materials prepared in Example 2 and Comparative Example 1 were tested. The density was tested using the Archimedes' displacement method, and the theoretical density of the material is 12.91 g / cm³. 3 The density was calculated as ρactual / ρtheoretical. The hardness of the electrical contact material was measured using a Webster hardness tester, and the resistivity of the material was measured using a bridge conductivity meter. The test results are shown in Table 1.

[0027] Table 1. Comparison of density, compactness, hardness, and resistivity between Example 2 and the comparative example. The results in Table 1 show that the CuWC75 electrical contact material prepared by this invention has high density, compactness, hardness, and low resistivity. The product prepared in the comparative example suffers from problems such as uneven tungsten carbide distribution, high porosity, poor microstructure, and poor wear resistance.

[0028] The above description discloses only preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A method of making a copper-tungsten carbide electrical contact material, characterized by, The method comprises the following steps: S1. Ball-milling tungsten carbide powder and titanium powder in a protective atmosphere to obtain activated mixed powder; S2. Heating the activated mixed powder at 900-1050℃ for 3-8 hours in a reducing atmosphere to obtain diffusion-treated powder; S3. Mixing the diffusion-treated powder with copper powder after crushing and sieving to obtain composite powder; S4. Preparing copper-tungsten carbide electrical contact material from the composite powder.

2. The method of claim 1, wherein the copper-tungsten carbide electrical contact material is prepared by the steps of: In step S1, the average particle size of the tungsten carbide powder is 0.5-5 μm, and the average particle size of the titanium powder is 0.1-5 μm. ​ 3. The method of claim 1, wherein the copper-tungsten carbide electrical contact material is prepared by the steps of: In step S1, the content of titanium powder in the activated mixed powder is 0.03-0.08 wt%. ​ 4. The method of claim 1, wherein the copper-tungsten carbide electrical contact material is prepared by the steps of: In step S1, the tungsten carbide powder and the titanium powder are ball-milled in a high-energy ball mill for 10-24 hours, the ball-to-material ratio is 5:1-10:1, and the rotation speed is 200-400 rpm. ​ 5. The method of claim 1, wherein the copper-tungsten carbide electrical contact material is prepared by the steps of: In step S3, the diffusion-treated powder is crushed and sieved through a 300-500 mesh sieve, and the average particle size of the copper powder is 30-80 μm. ​ 6. The method for preparing a copper tungsten carbide electrical contact material according to claim 1, characterized in that: Step S4 specifically comprises the following steps: S4-1. Adding sintering agent to the composite powder, mixing, sieving, drying, sintering at a temperature of 1150-1250℃, and granulating to obtain granulated powder; S4-2. Adding molding agent to the granulated powder to prepare green body with a porosity of 18% ~ 35%; S4-3. Heating the green body in a hydrogen atmosphere at a rate of 3~10℃ / min to 600~650℃ and maintaining for 1~3 hours to remove the molding agent and obtain a defatted body; S4-4. Burying the defatted body in filler and maintaining at 1050-1150℃ in a hydrogen atmosphere for 1-3 hours to form a pre-sintered skeleton; S4-5. Laying a pure copper sheet with a thickness of 0.1-0.5 mm on the surface of the pre-sintered skeleton and infiltrating at 1250-1400℃ in a hydrogen atmosphere for 2-4 hours to obtain copper-tungsten carbide electrical contact material.

7. A method of making a copper-tungsten carbide electrical contact material according to claim 6, wherein: In step S4-2, the molding agent is polyvinyl alcohol and / or paraffin wax, and the addition amount of the molding agent is 3-8 wt%. ​ 8. The method of claim 6, wherein the copper-tungsten carbide electrical contact material is prepared by the steps of: In step S4-4, the filler is graphite powder and / or alumina powder. ​ 9. A copper-tungsten carbide electrical contact material characterized by: The copper-tungsten carbide electrical contact material is prepared by the method of any one of claims 1-8.

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