Electrical contact material and production method therefor

Abstract

An electrical contact material according to the present disclosure comprises: a base material (1) composed of Ag; WC constituting first arc-resistant component particles (2) dispersed in the base material 1; and VC constituting second arc-resistant component particles (3) connected in the energization direction, and disposed in the base material (1) having WC constituting the first arc-resistant component particles (2) dispersed therein.

Description

Electrical Contact Material and Method for Producing the Same

[0001] The present disclosure relates to an electrical contact material and a method for producing the same.

[0002] As an electrical contact material used for air circuit breakers, switches, etc. with a rated current exceeding 100 A, Ag-WC (tungsten carbide) obtained by mixing Ag and metal carbide has been used. These have the advantage of being superior in weld resistance and arc resistance during high-current interruption compared to Ag-SnO2 contacts and Ag-CdO contacts obtained by mixing Ag and metal oxides. Ag is responsible for the current-carrying part, and WC is responsible for the arc-resistant component. Since the adhesion between Ag and WC, which is a carbide, is not very good, even if it is lightly welded by an arc, it can be peeled off.

[0003] The method for producing Ag-WC contacts is roughly classified into a powder sintering method and an infiltration method. The powder sintering method is a method in which Ag powder and WC powder are mixed, then placed in a mold, pressure is applied for molding, and then sintered to produce contacts. In the powder sintering method, it is important to apply a relatively high pressure during molding to minimize internal pores. When Gr (graphite) is added to the contacts, the infiltration method cannot be used, so it is produced by the powder sintering method. On the other hand, the infiltration method has the same operation of mixing Ag powder and WC powder for molding, but pores are deliberately left in the molded body during molding, and in the next heat treatment step, Ag is infiltrated into the pores of the molded body to produce contacts. When molding the molded body, Ag powder with a reduced amount of Ag to be infiltrated later is used. Compared with the powder sintering method of solid-phase sintering, the infiltration method is a liquid-phase sintering, so the processing temperature is high, and it is characterized by being easy to increase the density of the contacts.

[0004] When looking at Ag-WC contacts macroscopically, it has a structure in which WC particles are dispersed in the sea of Ag. This is because powders are used as raw materials. If Ag and WC are continuously formed in the current-carrying direction, it can contribute to maintaining the mechanical strength when the contacts are closed and to the weld resistance and resistance stability even when consumed.

[0005] As an example of an electrical contact material, Patent Document 1 discloses a contact manufactured by providing a visually verifiable through-hole in a conductive block portion several centimeters in size, inserting an arc-resistant auxiliary material into the hole, and then drawing it thinly in a wire drawing process. Patent Document 2 also discloses a contact in which carbon nanotubes with metal carbides on their surface are oriented in one direction along the direction of current flow as an arc-resistant component.

[0006] Japanese Patent Publication No. 2005-232502, Japanese Patent Publication No. 2004-10978

[0007] However, electrical contact materials with configurations like those in Patent Documents 1 and 2 can be manufactured when the arc-resistant component is a pure metal such as W or Ni, but there is a problem in that they are difficult to manufacture when the raw material is one in which the particles do not deform, such as carbides.

[0008] This disclosure is made to solve the above-mentioned problems and aims to provide a high-performance electrical contact material and a method for manufacturing the same, while maintaining the good welding resistance of Ag-WC contacts and suppressing contact wear and deformation.

[0009] The electrical contact material according to this disclosure is characterized by comprising a substrate made of a conductor, first arc-resistant component particles dispersed in the substrate, and second arc-resistant component particles arranged on the substrate on which the first arc-resistant component particles are dispersed and connected in the direction of current flow.

[0010] The present disclosure provides a method for manufacturing an electrical contact material, comprising: a first step of coating carbon fibers with a metal that forms the basis of metal carbides, which are second arc-resistant component particles; a second step of forming a molded body containing a mixed powder of first arc-resistant component particles made of metal carbides and conductive particles, and including the metal-coated carbon fibers formed in the first step in a linear manner in the direction of current flow; and a third step of dissolving the same conductive material as the conductive particles into the molded body formed in the second step, thereby carbonizing the metal-coated carbon fibers contained in the molded body.

[0011] According to this disclosure, it is possible to suppress contact wear and deformation by maintaining resistance to arc welding at the contact surface and strengthening the three-dimensional structure, thereby providing a high-performance electrical contact material.

[0012] Figure 1 is a plan cross-sectional view showing the configuration of the electrical contact material according to Embodiment 1. Figure 2 is a side cross-sectional view showing the configuration of the electrical contact material according to Embodiment 1. Figure 3 is a flowchart of the manufacturing method of the electrical contact material according to Embodiment 1. Figure 4 is a flowchart of the manufacturing method of the electrical contact material according to Embodiment 1. Figure 5 is a flowchart of the manufacturing method of the electrical contact material according to Embodiment 1. Figure 6 is a flowchart of the manufacturing method of the electrical contact material according to Embodiment 1. Figure 7 is a diagram showing a film deposition apparatus used in manufacturing the electrical contact material according to Embodiment 1. Figure 8 is a diagram for explaining the manufacturing method of the electrical contact material according to Embodiment 1. Figure 9 is a diagram for explaining the manufacturing method of the electrical contact material according to Embodiment 1. Figure 10 is a diagram for explaining the manufacturing method of the electrical contact material according to Embodiment 1. Figure 11 is a cross-sectional view of a fused body made using the manufacturing method of the electrical contact material according to Embodiment 1. Figures 12A and 12B are diagrams illustrating the process of cutting a fused body made using the manufacturing method of the electrical contact material according to Embodiment 1. Figure 13 is a diagram showing the relationship between the concentration of the second arc-resistant component and the grid spacing of the electrical contact material according to Embodiment 1. Figure 14 is a model diagram of the electrical contact material according to Embodiment 1, in which VC particles arranged in a columnar shape are approximated as a rectangular prism, and these are uniformly dispersed in the contact.

[0013] Embodiment 1. Figure 1 is a plan cross-sectional view showing the configuration of the electrical contact material 200 according to Embodiment 1. Figure 2 is a cross-sectional view taken along the line AA in Figure 1.

[0014] As shown in Figures 1 and 2, the electrical contact material 200 consists of a base material 1 made of a conductor, first arc-resistant component particles 2 dispersed in the base material 1, and second arc-resistant component particles 3 provided on the base material 1 on which the first arc-resistant component particles 2 are dispersed, and are linearly connected in the direction of current flow.

[0015] The base material 1 is made of silver (Ag) or copper (Cu). The first arc-resistant component particle 2 is made of tungsten carbide (WC), and the second arc-resistant component particle 3 is made of vanadium carbide (VC).

[0016] WC maintains resistance to arc welding at the contact surface, while VC acts as a framework to reinforce the three-dimensional structure; both possess arc-resistant properties.

[0017] Next, a method for manufacturing the electrical contact material 200 according to Embodiment 1 will be described. Figure 3 is a flowchart of the method for manufacturing the electrical contact material 200 according to Embodiment 1. As shown in Figure 3, the method for manufacturing the electrical contact material 200 according to Embodiment 1 includes the steps of: coating the surface of carbon fibers with V to form V-coated carbon fibers that will be the basis for VC, which is the second arc-resistant component particle 3 (step S301 in Figure 3); mixing WC particles, which are the first arc-resistant component particles 2, with Ag particles, which are conductors, to form a molded body containing the V-coated carbon fibers (step S302 in Figure 3); and dissolving Ag chips, which are conductors, into the molded body to carbonize the V-coated carbon fibers (step S303 in Figure 3).

[0018] Figures 4 to 6 are detailed flowcharts of the steps for forming V-coated carbon fibers (step S301), forming a molded body containing V-coated carbon fibers (step S302), and carbonizing the V-coated carbon fibers by dissolving Ag (step S303), respectively. Figure 7 is a diagram showing a wet film deposition apparatus by plating used in the step for forming V-coated carbon fibers. Figures 8 and 9 are diagrams illustrating the procedure for adding V-coated carbon fibers in the step for forming a molded body containing V-coated carbon fibers.

[0019] In the process of forming V-coated carbon fibers, Embodiment 1 uses a wet coating method for carbon fibers with V. In addition to the wet coating method, there is also a dry coating method using sputtering and vapor deposition in a vacuum. However, because sputtering and vapor deposition have strong directional properties, the film will not be deposited on the back surface of the carbon fiber, which is in shadow. Therefore, it is necessary to make adjustments to the apparatus, such as changing the position of the carbon fiber while depositing the film, and to repeat the film deposition process while changing the position of the fiber.

[0020] In the method of coating carbon fibers with V using a wet process, first, a carbon fiber tow 9, which is a bundle of carbon fibers, is prepared (step S401 in Figure 4). The carbon fiber tow 9 consists of 12,000 filaments with a diameter of 7 μm bundled together, with a density of 1.8 g / cm³. 3 Use polyacrylnitrile (PAN) carbon fiber. The carbon fiber tow 9 is cut to a length of about 15 cm and both ends are secured with metal clips to prevent unraveling.

[0021] A lower graphitization rate (graphite content) of the carbon fiber used is desirable because it provides greater flexibility against deformation. Since carbon fibers generally have a diameter of 5-10 μm, 5 μm, 7 μm, or 10 μm fibers may also be used. In this case, the film formation state of V will change, so this can be addressed by adjusting the electrolysis current and current. If the diameter is too large, carbide formation takes longer, while using carbon fibers that are too thin presents challenges such as breakage during handling.

[0022] Next, the carbon fiber tow 9 is washed (step S402 in Figure 4). The carbon fiber tow 9 is immersed in acetone for 10 minutes, and while gently agitating it, the sizing agent (carbon fiber consolidating agent: a coating agent that firmly bundles the tow, suppresses fuzzing caused by thread breakage, and also provides the flexibility necessary for processing) on ​​the fiber surface is dissolved. Since it is difficult to completely remove the sizing agent with just one wash, it is rinsed with water and then immersed in acetone again. This is repeated three or more times.

[0023] Next, after a final rinse, the carbon fiber tow 9 is held in place by being clipped with a metal clip and dried in a drying oven at 50°C for 12 hours (step S403 in Figure 4).

[0024] Next, copper plates 6, which will serve as cathodes, are attached to both ends of the carbon fiber tow 9 (step S404 in Figure 4). As preparation for attaching the copper plates 6, the ends of the carbon fiber tow 9, where the sizing agent has not yet dissolved, are cut off. Then, the carbon fiber tow 9 is placed on the copper plate so that both ends rest on it, and the fibers are spread out. A room-temperature drying type conductive paste is applied on top, and then another copper plate is placed on top to sandwich it. The conductive paste is placed in a 40°C oven and allowed to harden for about 30 minutes. Care should be taken when handling the spread carbon fibers to avoid cutting them.

[0025] Finally, V is plated onto the surface of the carbon fiber tow 9 using the wet film deposition apparatus 100 shown in Figure 7 (step S405 in Figure 4). Since carbon fibers oxidize in acidic chemicals, a weakly alkaline aqueous solution is used for vanadium deposition. Ammonium vanadate powder (NH4VO3) is dissolved in water to make an ammonium vanadate aqueous solution 11 with a concentration of 0.1 mol / liter. The pH is adjusted to between 8 and 9. Sodium borate and nitric acid are used as pH adjusters. In the pH range of 8 to 9, vanadate ions in the aqueous solution are H2VO4 - In this state, the aqueous solution becomes colorless.

[0026] As shown in Figure 7, the carbon fiber tow 9, which serves as the cathode, is immersed in an ammonium vanadate aqueous solution 11 via wiring 12 to the negative electrode of the DC power supply 5. At this time, the carbon fiber is slowly immersed in the solution so as not to damage it. Care is taken not to immerse the copper plate 6, which is bonded with conductive paste, directly into the solution. The platinum plate 7, which serves as the anode, is immersed in wiring 13 to the positive electrode of the DC power supply 5, and the silver chloride electrode 8 is immersed as the reference electrode. Electrolysis is performed at room temperature, and the aqueous solution is continuously stirred with a stirrer during electrolysis. The current density during electrolysis is 1 to 5 mA / cm². 2 Using a very small amount, metallic vanadium is deposited onto the cathode carbon fibers over a period of more than two hours, with an average film thickness of approximately 1.5 to 3 μm.

[0027] After electrolysis, the carbon fiber tow 9 is removed, washed with water, and then placed in a drying oven set to approximately 80-100°C for 24 hours to dry the carbon fiber and V. In this way, the V-coated carbon fiber 23 is formed.

[0028] In the process of forming a molded body containing V-coated carbon fibers, first, Ag particles 21, WC particles 22, and Ni particles 24 are prepared (step S501 in Figure 5). For the Ag particles 21, chemically reduced silver powder with an average particle size of 3 μm is used. For the WC particles 22, powder with an average particle size of 1 μm is used, and for the Ni particles 24, powder with an average particle size of 2 to 3 μm is used. The Ni particles 24 are additives used as a sintering aid for the WC particles 22. The target composition of the contact points after Ag immersion is 61Ag-36WC-2.8VC-0.2Ni by weight (67.4Ag-26.7WC-5.6VC-0.3Ni by volume), and Ag particles 21, WC particles 22, and Ni particles 24 are added in a weight ratio of 46:49:0.3 so that the porosity of the molded body after molding is about 30%, and a mixed powder 20 is prepared using a mortar and pestle.

[0029] Next, a mold 15 is prepared for molding the mixed powder 20 and V-coated carbon fibers 23 (step S502 in Figure 5). A manual uniaxial press molding die with a rectangular cross-sectional area of ​​8 mm in length and 16 mm in width is used for molding the molded body. The material used is SKD11 steel (a steel material mainly for cold molds as indicated in JIS G 4404 (alloy tool steel)). For the mold 15, high-speed steel (a steel material made by hot rolling and forging as indicated in JIS G 4403 (high-speed tool steel)) or cemented carbide (WC-Co or WC-Ni material as indicated in JIS B 4054) may also be used. A thin layer of lubricant is applied to the inner wall of the die 15a and the contact surfaces of the punches 15b and 15c of the mold 15 to prevent the molded body from sticking to the inner wall of the mold 15.

[0030] Next, the mixed powder 20 and V-coated carbon fibers 23 are placed in the mold (step S503 in Figure 5). The Ag / WC / Ni mixed powder 20 is weighed so that the thickness of the molded body after molding will be approximately 6 mm with a porosity of 30%. For more accurate control, since there is a volume shrinkage of about 20% when the V-coated carbon fibers 23 change to VC, the porosity is set taking this shrinkage into account. Also, using an electronic balance, the V-coated carbon fibers 23 are weighed so that the weight of the Ag / WC / Ni mixed powder 20 and the weight of the cut V-coated carbon fibers 23 are in a ratio of 96:4 (adjusting so that the weight ratio of the molded body is approximately Ag:WC:V-coated carbon fiber:Ni = 46:49:3.8:0.3).

[0031] The V-coated carbon fiber 23 is made by cutting a V-coated carbon fiber tow 9 to a length of 16 mm so that it fits along the long side of the mold. If the final contact thickness is, for example, 1.5 mm, the length of the V-coated carbon fiber 23 along the thickness direction will be approximately 1.5 mm. As the average particle size of the powder is several to 10 μm as described above, the length of the V-coated carbon fiber 23 will be at least 100 times the particle size of the powder.

[0032] Figures 8 and 9 show the procedure for placing the mixed powder 20 and V-coated carbon fibers 23 into the mold 15. As shown in Figure 8, the mixed powder 20 is spread on the punch 15c incorporated into the hole of the die 15a of the mold 15, and as shown in Figure 9, the V-coated carbon fibers 23 are laid on top of it so as to be parallel to the long side of the rectangular hole of the mold 15. This is repeated about 10 times to create a mixture of the mixed powder 20 and V-coated carbon fibers 23 inside the mold 15. Care should be taken because if the carbon fibers are unevenly distributed, the molded body will be prone to breaking when it is removed from the mold after molding.

[0033] After placing the mixed powder 20 and V-coated carbon fibers 23 into the mold 15, pressure is applied to the mixture (step S504 in Figure 5). A punch 15b is inserted from above into the hole of the die 15a of the mold 15, and a pressure of 400 to 500 MPa is applied to form the molded body. The molding pressure is adjusted as needed so that the thickness of the molded body is about 6 mm (assuming a rectangle with a contact size of 8 mm x 6 mm after cutting). Since degassing is also performed during heat treatment, care should be taken not to press too hard and crush the vent holes for gas release. In this way, a molded body containing V-coated carbon fibers 23 is formed.

[0034] In the process of dissolving Ag and carbonizing the V-coated carbon fibers, first, a molded body containing the molded V-coated carbon fibers 23 is placed on a carbon tray (step S601 in Figure 6).

[0035] Next, to fill 30% of the voids in the molded body, Ag chips or Ag blocks are weighed and placed on top of the molded body (step S602 in Figure 6). Figure 10 shows the state with Ag chips 25 placed on top of the molded body 30. Ag tape may be used instead of Ag chips 25. With Ag tape, for example, a strip 5 mm wide, 0.3 mm thick, and several tens of centimeters to 1 m long is made, cut to the required length and weight, rolled up and placed on the molded body.

[0036] Next, the molded body 30 with the Ag chips 25 placed on it is placed in a 100% hydrogen furnace while still on the carbon tray, and heat treatment is performed in four steps: (1) drying, (2) degassing of moisture, (3) reduction of the oxidized V portion, and (4) Ag dissolution and VC formation reaction (step S603 in Figure 6).

[0037] First, in step (1), the physically adsorbed moisture is evaporated again at 200°C for 2 hours. Next, in step (2), the chemically adsorbed moisture is evaporated at 500°C for 30 minutes. Then, in step (3), the temperature is raised to about 850°C, which is about 100°C lower than the melting point of Ag, and held for 12 hours to reduce the vanadium oxide remaining in the carbon fiber coating V to metal V.

[0038] Up to step (3), the Ag chips 25 placed on the molded body 30 do not dissolve, so the voids are not filled, and unwanted components can be removed from the molded body 30. Care must be taken to proceed to step (4) only after steps (1) to (3) have been completed, otherwise the molded body 30 may swell or burst. Then, in step (4), the temperature is raised to 1000°C and held for 12 hours to simultaneously infiltrate the Ag into the molded body 30 and carbonize the V.

[0039] After the dissolution of Ag and carbonization of V are completed, the fused body 40 with Ag 26 shown in Figure 11 is removed from the hydrogen furnace (step S604 in Figure 6). Figure 11 shows a cross-sectional view of the obtained fused body 40. The removed fused body 40 is then subjected to barrel polishing or SiC sandpaper to remove any remaining undissolved Ag, altered surface layer, and carbon deposits.

[0040] Finally, the fused material 40, measuring approximately 6 mm in length, 8 mm in width, and 16 mm in thickness, is cut into multiple pieces with a thickness of 1.5 mm using wire electrical discharge machining (step S605 in Figure 6). Approximately eight pieces of electrical contact material 200 can be cut from the fused material 40. Note that this is not the only method for cutting the fused material 40; it may also be cut using a precision wet cutting machine. In this case, since the fused material 40 contains hard particles such as WC and VC, it is advisable to use a diamond cutting blade. Figures 12A and 12B show an example of cutting the fused material 40 using a cutting blade 41.

[0041] When the cut electrical contact material 200 was observed using a cross-sectional SEM (Scanning Electron Microscope), as shown in Figure 2, VC grains, which act as second arc-resistant component particles 3, were arranged in rows in the locations where carbon fibers had been.

[0042] The cut electrical contact material 200 was joined to the base portions of the movable and fixed contacts of a 200A rated circuit breaker using silver solder. At this time, it is desirable to use Ni-containing silver solder such as BAg-3 or BAg-4 in order to improve the adhesion between the electrical contact material 200 and the copper base.

[0043] As described above, according to the electrical contact material 200 according to the first embodiment, the base material 1 made of Ag, the WC which is the first arc-resistant component particles 2 dispersed in the base material 1, and the base material 1 in which the WC which is the first arc-resistant component particles 2 are dispersed are provided with VC which is the second arc-resistant component particles 3 connected in the energization direction. Therefore, not only can the welding resistance to the arc be maintained on the contact surface by WC and the contact consumption amount and deformation be suppressed by strengthening the three-dimensional structure by VC, but also excellent arc resistance performance can be obtained.

[0044] Further, according to the manufacturing method of the electrical contact material 200 according to the first embodiment, the first step of coating the carbon fiber with V to form the V-coated carbon fiber 23, the mixed powder of WC particles 22 and Ag particles 21, and the second step of forming a molded body in which the V-coated carbon fiber 23 is arranged in the energization direction, and the third step of infiltrating the Ag chip 25 and carbonizing the V-coated carbon fiber 23 are provided. Therefore, not only can the welding resistance to the arc be maintained on the contact surface by WC and the contact consumption amount and deformation be suppressed by strengthening the three-dimensional structure by VC, but also the electrical contact material 200 having excellent arc resistance performance can be easily manufactured. Furthermore, the manufacturing process can be simplified by simultaneously performing the formation of the carbide and the infiltration of the conductor.

[0045] In the manufacturing method of the electrical contact material 200 according to the first embodiment, the V-coated carbon fiber 23 obtained by coating the carbon fiber with V is used in the step of forming the molded body containing the V-coated carbon fiber. However, the V-coated carbon fiber plated with Ag on the surface of the V-coated carbon fiber 23 may also be used. In this case, when the molded body is formed, the adhesion between the V-coated carbon fiber and the Ag particles is improved, and the molded body is less likely to collapse.

[0046] As an example, in addition to the Ag-WC-VC contact (Example 2) produced by the manufacturing method of the electrical contact material 200 in Embodiment 1, samples were trial-produced by changing the amount of V-coated carbon fiber (Examples 1, 3, and Comparative Example 1). For each comparison, without using V-coated carbon fiber and using VC particles as raw materials, Ag powder, WC powder, and Ni powder were mixed to have the same composition as in Examples 1 to 3, and then press-molded using a manual uniaxial press molding die to form a molded body, and Ag was infiltrated into it (Comparative Examples 2 to 5). Also, a contact was trial-produced by molding a molded body using only WC particles without using VC particles as the material for the arc-resistant component (Comparative Example 6). The contacts of Examples 1 to 3 and Comparative Example 1 were cut after Ag infiltration to obtain the final shape shown in Fig. 12B. For Comparative Examples 2 to 6 that do not use V-coated carbon fiber, the molded body may be formed by pressing for each individual contact so that it has the shape shown in Fig. 12B after Ag infiltration.

[0047] To match the resistance values of these contacts, the addition amounts of WC and VC were adjusted so that the volume ratio of Ag to Ni was the same. These contacts were mounted on a circuit breaker rated at 200 A. Then, a short-circuit interruption test was carried out. The test conditions were an AC power supply with an effective voltage of 300 V and an effective current of 10 kA. The test was started by applying a voltage between the contacts from the open contact state, then the contacts were closed to start current conduction, and automatic interruption was performed by detection by the overcurrent detection circuit in the circuit breaker and then the contacts were opened again. After repeating this three times, the contacts were taken out from the circuit breaker and measured using a non-contact three-dimensional measuring instrument to calculate the consumption amount.

[0048] Table 1 shows the contact composition and the results after short-circuit interruption tests of the electrical contact material 200 used in Examples 1-3 and Comparative Examples 1-6. As shown in Table 1, Examples 1-3 all showed less contact wear compared to Comparative Examples 2-4, which had the same contact composition. Furthermore, in Example 1 and Comparative Example 2, where the amount of added VC was small, Example 1, which used V-coated carbon fiber, showed less wear, but the difference was small. When the amount of columnarly arranged VC particles is less than that of Example 1, the effect of the columnar arrangement is masked by the performance of other parts. Therefore, at the lower limit, contacts with a concentration of columnarly arranged VC particles of less than 2.9% by volume perform similarly to contacts without arrangement, and the effect of the columnar arrangement becomes invisible. Moreover, when comparing Comparative Example 1 and Comparative Example 5, which have the same composition, Comparative Example 1, which used V-coated carbon fiber, showed a higher wear.

[0049]

[0050] Next, using the same circuit breaker, a mechanical durability test was conducted for 8,500 cycles, followed by a current-on durability test of 1,500 cycles at a 500V, 200A rating. The switching frequency was set to 120 times / hour.

[0051] Table 2 shows the contact composition and the results after current-carrying durability tests of the electrical contact material 200 used in Examples 1-3 and Comparative Examples 1-6. As shown in Table 2, Examples 1-3 all showed less contact wear compared to Comparative Examples 2-4. Also, as with Table 1, although Example 1, which used V-coated carbon fiber, showed less wear than Comparative Example 2, the difference was still small. When the amount of columnar arrangement of VC particles is further reduced compared to the amount in Example 1, the effect of the columnar arrangement is masked by the performance of other parts. Therefore, at the lower limit, contacts with a concentration of columnar-arranged VC particles of less than 2.9% by volume perform similarly to contacts without arrangement, and the effect of the columnar arrangement becomes invisible. Furthermore, comparing Comparative Example 1 and Comparative Example 5, Comparative Example 1, which used V-coated carbon fiber, actually showed more wear.

[0052] Comparative Example 1, which uses the highest proportion of V-coated carbon fiber by volume at 11.6%, shows increased wear, likely due to increased contact wear caused by crack expansion. When the contact surface is exposed to an arc, cracks propagate from the contact surface inward. It is known that these cracks do not propagate through the Ag itself, but rather along the interface between the conductive component Ag and the arc-resistant components such as WC and VC. This is because the adhesion between Ag and the arc-resistant components is low.

[0053]

[0054] Figure 13 shows the calculated value of the distance D (unit cell) between columns when the concentration of VC grains changes from 0 (0 arc-resistant component) to 32% by volume, assuming that all arc-resistant components are uniformly dispersed in columnar arrangements. Here, the cross-sectional area of ​​the VC grains is assumed to be 10 × 10 μm, and the 27 prisms are assumed (see Figure 14). When the concentration of the columnar VC grains is 11%, the lattice spacing is 30 μm. As the distance between the prisms decreases, the interface that is prone to delamination comes closer, so it is thought that cracks extending from the contact surface are more likely to connect continuously. In Comparative Example 1, the distance between the columnar VC grains decreased, which is thought to have increased contact wear due to cracks, resulting in a reversal of the wear amount compared to Comparative Example 5. It can be said that the distance between columns that can reduce contact wear compared to a contact with a simple, uniform mixture when the concentration of the second arc-resistant component particles 3 is 11% or less is the range. If the concentration of the second arc-resistant component particle 3 exceeds 11%, the welding resistance cannot be maintained.

[0055] While this application describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but are applicable individually or in various combinations to the embodiments. Accordingly, countless variations not illustrated are envisioned within the scope of the art disclosed herein. For example, these include modifying, adding or omitting at least one component, or even extracting at least one component and combining it with a component from another embodiment.

[0056] 1 Substrate, 2 First arc-resistant component particles, 3 Second arc-resistant component particles, 20 Mixed powder, 21 Ag particles, 22 WC particles, 23 V-coated carbon fiber, 25 Ag chips, 30 Molded body, 200 Electrical contact material.

Claims

1. An electrical contact material comprising: a substrate made of a conductor; first arc-resistant component particles dispersed in the substrate; and second arc-resistant component particles arranged on the substrate on which the first arc-resistant component particles are dispersed and connected in the direction of current flow, wherein the concentration of the second arc-resistant component particles is in the range of 2.9% or more and 11% or less by volume.

2. The electrical contact material according to claim 1, characterized in that the first arc-resistant component particles and the second arc-resistant component particles are made of metal carbides.

3. The electrical contact material according to claim 1 or 2, characterized in that the conductor is Ag or Cu, the first arc-resistant component particles are made of WC, and the second arc-resistant component particles are made of VC.

4. A method for manufacturing an electrical contact material, comprising: a first step of coating carbon fibers with a metal that forms the basis of metal carbides, which are second arc-resistant component particles; a second step of forming a molded body containing a mixed powder of first arc-resistant component particles made of metal carbides and conductive particles, wherein the carbon fibers coated with the metal formed in the first step are arranged in the direction of current conduction; and a third step of dissolving the same conductive material as the conductive particles into the molded body formed in the second step, thereby carbonizing the carbon fibers coated with the metal contained in the molded body.

5. The method for manufacturing an electrical contact material according to claim 4, characterized in that the conductor is Ag or Cu, the first arc-resistant component particles consist of WC, and the second arc-resistant component particles consist of VC.

6. The method for manufacturing an electrical contact material according to claim 4 or 5, characterized in that the length of the metal-coated carbon fiber matches the thickness of the contact.

7. A method for manufacturing an electrical contact material according to any one of claims 4 to 6, characterized in that the surface of the carbon fiber coated with the metal is coated with the same conductor as the conductive particles.

Images