Electric contact and vacuum valve having electric contact

Abstract

The present disclosure aims to provide an electrical contact containing a low-boiling-point metal that can simultaneously ensure mechanical strength and electrical conductivity. The electrical contact comprises a base material composed of Cu, high-melting-point material particles, at least one of which are particles of a high-melting-point metal or particles of a carbide of a high-melting-point metal, dispersed and arranged in the base material, and Te and Ti dispersed and arranged in the base material. Te is added in an amount of 3.5% to 14.5% by mass, with the total amount being 100% by mass, and a Ti / Te ratio of 0.12 to 0.38.

Description

Technical Field

[0001] The present disclosure relates to a vacuum valve used in a vacuum circuit breaker, which is one type of high-voltage power distribution equipment, an electric contact used in the vacuum valve, and a method for manufacturing the electric contact. Background Art

[0002] Vacuum circuit breakers, used in high-voltage power distribution equipment, are used to interrupt current in the event of a fault or abnormality in the equipment. They include a vacuum valve that interrupts current. The vacuum valve consists of a fixed electrode and a movable electrode coaxially arranged within an insulating container maintained at a high vacuum.

[0003] When an overload or short-circuit current occurs in power distribution equipment, the current is interrupted by momentarily opening the movable electrode from the fixed electrode. However, due to the arc generated between the electrodes, the current is not interrupted instantaneously by opening. When interrupting the AC current, the arc weakens as the AC current decreases, extinguishing the arc and achieving disconnection. The instantaneous interruption of the current before the AC current reaches zero is called interruption.

[0004] When disconnecting, a large surge voltage known as a switching surge is generated. If the equipment connected to the power distribution system is capacitive or inductive, this large surge voltage may damage the connected equipment. To reduce the surge voltage, the current at the moment of disconnection, or the chopping current, must be reduced. This can be achieved by allowing the arc generated between the electrodes during opening to continue until near the zero point of the AC current.

[0005] The duration of the arc depends on the number of particles present in the vacuum. To maintain the arc, particles must be supplied into the vacuum during interruption. These particles can be metal particles or thermal electrons. Conventional electrical contact materials with low interruption current characteristics typically consist of a mixture of the conductive component Ag and a high-melting-point metal or its carbide, such as WC. This is because the heating of the electrode caused by the generated arc promotes the evaporation of the conductive component Ag and the emission of thermal electrons from the high-melting-point metal or its carbide, thus maintaining the arc.

[0006] The Richardson-Dashman equation, which expresses thermionic electron emission capacity in terms of current density, shows that thermionic electron emission capacity depends on the material's work function and temperature. Temperature, in particular, has a significant contribution. Therefore, high-melting-point metals and their carbides are widely used due to their high melting points. Based on this perspective, vacuum valves using Ag-WC electrical contacts, which exhibit excellent low-off current characteristics, have been developed and put into practical use.

[0007] In conventional vacuum valves, for low cost, copper has been used as the conductive component in place of Ag in electrical contact materials. Stable low chopping current characteristics have been achieved by adding, for example, Te or Se (see, for example, Patent Documents 1 and 2). This is because Te and Se are low-boiling-point metals, with extremely low boiling points among metals. The arc heats the electrodes, causing the low-boiling-point metals to evaporate in large quantities, thus maintaining the arc.

[0008] The addition of low-boiling-point metals can achieve low cutoff current characteristics, but the selective evaporation of low-boiling-point metals can also be understood as material consumption of the electrical contacts. Therefore, as the number of switching cycles increases, the low-boiling-point metal is consumed, the supply of metal vapor to the space between the electrical contacts decreases, and the low cutoff current characteristics deteriorate. Therefore, in order to suppress the degradation of the low cutoff current characteristics, increasing the amount of low-boiling-point metal added is considered. However, if Te, a low-boiling-point metal, is added excessively to the electrical contacts, Cu2Te, an intermetallic compound of Te and Cu, is generated, making the electrical contacts brittle.

[0009] Therefore, an appropriate amount of Mn is added to ensure the mechanical strength of the electric contact (see, for example, Patent Document 3).

[0010] Prior art literature

[0011] Patent Literature

[0012] Patent Document 1: Japanese Patent Application Laid-Open No. 2014-56784

[0013] Patent Document 2: Japanese Patent Application Laid-Open No. 2007-332429

[0014] Patent Document 3: Japanese Patent No. 6497491 Summary of the Invention

[0015] Problems to be solved by the invention

[0016] However, while mechanical strength is ensured, Mn and Cu form a solid solution with each other, which reduces the conductivity of the electrical contacts. This poses a problem in that the temperature of the vacuum valve to which it is applied may rise when electricity is applied.

[0017] The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to provide an electrical contact to which a low-boiling-point metal is added, which can satisfy both mechanical strength and electrical conductivity without using Mn.

[0018] Means for solving problems

[0019] The electrical contact according to the present disclosure includes: a base material composed of Cu; high-melting-point material particles, which are at least one of particles of a high-melting-point metal or particles of a carbide of a high-melting-point metal, dispersed and arranged in the base material; and Te and Ti dispersed and arranged in the base material. When the total is taken as 100 mass%, Te is added at 3.5 mass% to 14.5 mass%, and Ti / Te is 0.12 to 0.38, and at least a portion of the Te and Ti forms an intermetallic compound of Te and Ti.

[0020] The present disclosure provides a vacuum valve having an electrical contact comprising: a base material composed of Cu; high-melting-point material particles, which are at least one of particles of a high-melting-point metal or particles of a carbide of a high-melting-point metal, dispersed and arranged in the base material; and Te and Ti dispersed and arranged in the base material, wherein Te is added at a rate of 3.5 mass% to 14.5 mass% (with the total amount being 100 mass%), Ti / Te is 0.12 to 0.38, and at least a portion of the Te and Ti form an intermetallic compound of Te and Ti.

[0021] Effects of the Invention

[0022] According to the electrical contact of the present disclosure, regarding Ti and Te, by setting Te to 3.5 mass % or more and 14.5 mass % or less and further setting Ti / Te to 0.12 or more and 0.38 or less, mechanical strength and conductivity can be ensured without adding Mn.

[0023] According to the vacuum valve having electric contacts according to the present disclosure, regarding Ti and Te, by setting Te to 3.5 mass % or more and 14.5 mass % or less and further setting Ti / Te to 0.12 or more and 0.38 or less, mechanical strength and electrical conductivity can be ensured without adding Mn.

[0024] According to the method for producing an electrical contact according to the present disclosure, an electrical contact having secured mechanical strength and conductivity can be produced by mixing Ti powder and Te powder at 3.5 mass % to 14.5 mass % of Te powder and adjusting Ti / Te to 0.12 to 0.38. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic cross-sectional view of the vacuum valve according to the first embodiment of the present disclosure.

[0026] Figure 2 This is a table showing the compositions of the electric contacts of Examples 1 to 4 and Comparative Examples 1 to 3 according to the first embodiment of the present disclosure.

[0027] Figure 3This is a table showing the compositions of the electric contacts of Examples 5 to 9 and Comparative Examples 4 and 5 according to the first embodiment of the present disclosure.

[0028] Figure 4 This is a table showing the compositions of the electric contacts of Examples 10 to 13 and Comparative Examples 6 to 8 according to the first embodiment of the present disclosure.

[0029] Figure 5 This is a cross-sectional view showing the internal structure of the electric contact produced in Example 3 according to Embodiment 1 of the present disclosure.

[0030] Figure 6 This is a phase diagram of Ti—Te according to the first embodiment of the present disclosure.

[0031] Figure 7 It is a diagram showing the state of the electric contact of Comparative Example 2 according to Embodiment 1 of the present disclosure.

[0032] Figure 8 This is a SEM observation of the state of precipitation of Ti and its compounds in the Cu remaining in the infiltrated material in Comparative Example 2.

[0033] Figure 9 This is a table showing the compositions of the electric contacts of Examples 14 to 16 and Comparative Examples 9 and 10 according to the first embodiment of the present disclosure.

[0034] Figure 10 This is a table showing the compositions of the electric contacts of Examples 17 to 19 and Comparative Examples 11 and 12 according to the first embodiment of the present disclosure.

[0035] Figure 11 This is a table showing the configurations of the electric contacts of Examples 20 to 22 according to the first embodiment of the present disclosure. DETAILED DESCRIPTION

[0036] Implementation method 1.

[0037] Figure 1 Schematic cross-sectional view of a vacuum valve according to Embodiment 1. The vacuum valve 1 of this embodiment includes a shutoff chamber 2 .

[0038] The isolation chamber 2 is composed of a cylindrical insulating container 3 and metal covers 5a and 5b. The ends of the metal covers 5a and 5b are fixed by sealing metal fittings 4a and 4b, and the interiors of the metal covers 5a and 5b are kept vacuum-tight.

[0039] Inside the isolation chamber 2, a fixed electrode rod 6 and a movable electrode rod 7 are installed facing each other. A fixed electrode 8 and a movable electrode 9 are welded to the ends of the fixed electrode rod 6 and the movable electrode rod 7, respectively. Furthermore, a fixed electrical contact 10 and a movable electrical contact 11 are welded to the contact portions of the fixed electrode 8 and the movable electrode 9, respectively. The electrical contact according to this embodiment is used for at least one of the fixed electrical contact 10 and the movable electrical contact 11.

[0040] A bellows 12 is attached to the movable electrode rod 7. The bellows 12 maintains the interior of the isolation chamber 2 in a vacuum-tight manner while enabling axial movement of the movable electrode 9. This axial movement of the movable electrode 9 allows the movable electrode 9 to come into contact with or separate from the fixed electrode 8.

[0041] A metal bellows arc shield 13 is installed above the bellows 12. Bellows arc shield 13 prevents arc vapor from adhering to the bellows 12. Furthermore, a metal insulating container arc shield 14 is installed within the isolation chamber 2 to cover the fixed electrode 8 and the movable electrode 9. Insulating container arc shield 14 prevents arc vapor from adhering to the inner wall of the insulating container 3.

[0042] Generally, the fixed electrode 8 and the movable electrode 9 as well as the fixed electric contact 10 and the movable electric contact 11 have a disc-like shape. Hereinafter, a case where the electric contact of this embodiment has a disc-like shape will be described.

[0043] First, the method for manufacturing the electrical contact of this embodiment will be described. The electrical contact of this embodiment is manufactured through the following steps: mixing raw material powders and pressing them with a predetermined die to form a compact; calcining the compact to obtain a sintered body; infiltrating the resulting sintered body with Cu to obtain an infiltrated body; and finally processing the resulting infiltrated body into a predetermined shape to obtain the electrical contact.

[0044] Hereinafter, the method for manufacturing the electric contact according to the present embodiment will be described in detail.

[0045] In the process of mixing raw material powders and molding them with a predetermined die to produce a molded body, Cu powder as a base material serving as a conductive component, Cr powder as a high-melting-point metal serving as an arc-resistant component, and Ti powder and Te powder as low-boiling-point metals for sustaining the arc are mixed, and the resulting mixed powder is compression-molded by a press, thereby obtaining a Cu-Cr-Ti-Te molded body.

[0046] When the mass of the mixed powder is set to 100 mass % (hereinafter referred to as wt %), the mass of the Ti powder is 20 to 80 wt %, the mass of the Te powder is 3.5 to 14.5 wt %, and the remainder is the mass of the Cu powder and the Cr powder. In this case, the Ti / Te mass ratio is 0.12 to 0.38.

[0047] The experiments conducted to determine the values ​​of the above-mentioned substances will be described later.

[0048] When a relatively hard, non-plastically deformable powder like Cr particles is made finer, the specific surface area of ​​the powder increases. Consequently, during compression molding, numerous voids form near the contact points between the powders, making densification difficult. When the particle size is too small, the compression molding pressure required to obtain a molded body with the desired density increases excessively, sometimes causing cracks during compression molding. Therefore, the average particle size of the Cr powder is preferably greater than 0.1 μm.

[0049] If the average particle size of the Cr powder is large, fluctuations may occur during disconnection, and the low chopping current characteristics may become unstable. Therefore, the average particle size of the Cr powder is preferably 120 μm or less.

[0050] In addition, as the average particle size of the raw material powder, for example, the average particle size in the particle size distribution measured by a laser diffraction particle size distribution device is used.

[0051] In the process of calcining the molded body to obtain a sintered body, the molded body is heated in a hydrogen atmosphere or 1×10 -5 The Cu-Cr-Ti-Te compact is sintered at 500 to 950° C. under vacuum at a pressure of Pa or less.

[0052] The sintering temperature may be at least 30°C lower than 988°C, which is the boiling point of Te.

[0053] In the process of infiltrating Cu into the sintered body to obtain the infiltrated body, the -5 Under vacuum of Pa or less, a Cu circular plate or Cu square plate of the same or smaller size as the sintered body is placed directly below the sintered body, and infiltration is performed at a temperature of 1083°C or higher and lower than 1140°C, which is the melting point of Cu.

[0054] If the infiltration temperature is above 1140°C, the saturated vapor pressure of the low-boiling-point metal present in the sintered body increases, and as a result, the sintered body sometimes expands due to the initial sublimation of Te and a dense electrical contact cannot be obtained, or the Cu in the sintered body sometimes melts and the shape of the sintered body collapses.

[0055] In addition, regarding the arrangement of the Cu circular plate or the Cu square plate and the sintered body, either one may be on top. Alternatively, the sintered body may be arranged by sandwiching it between two Cu circular plates from above and below.

[0056] In the process of processing the infiltrated material into the desired shape to obtain the electrical contact, the contact material is ground to the required thickness and diameter for the design, as a fixed or movable electrical contact for a vacuum valve. Finally, the electrical contact is obtained by taper processing or surface grinding at the end.

[0057] In the process of forming the infiltrated material into a predetermined shape to obtain an electrical contact, the contact material is ground down to the required thickness and diameter for the design, either as a fixed or movable electrical contact for a vacuum valve. Finally, the end portion is tapered or the surface is polished to obtain the electrical contact.

[0058] Next, examples and comparative examples are given and described in more detail.

[0059] [Example 1]

[0060] In Example 1, a uniform mixed powder was prepared by mixing Cu powder with an average particle size of 10 μm, Cr powder with an average particle size of 40 μm, Te powder with an average particle size of 40 μm, and Ti powder with an average particle size of 30 μm using a ball mill or V-type mixer for at least 30 minutes. The mixed powder was placed in a steel mold with an inner diameter of 23 mm and compression-molded using a hydraulic press at a pressure of 20 to 100 MPa to produce a compact with a thickness of 5 mm.

[0061] The obtained compact was sintered at 900° C. for 2 hours in a hydrogen atmosphere to prepare a sintered body.

[0062] The sintered body was then placed on a Cu disc of approximately 2 mm in thickness and 20 mm in diameter, and infiltrated at 1110°C for 2 hours in a hydrogen atmosphere to obtain the electrical contact of Example 1. In the case where the Cu infiltrated material was not melted, the temperature was increased by 10°C at a time and the infiltration treatment was repeated. The temperature at which Cu melts during the infiltration treatment is defined as the infiltration temperature. The composition of the electrical contact obtained in Example 1 is shown in FIG. Figure 2 in the table.

[0063] [Examples 2 to 13]

[0064] In Examples 2 to 13, the same steps as in Example 1 were used to make electrical contacts and verify the effect of Ti concentration. However, the mass ratio of each powder in the mixed powder was adjusted to change the composition ratio of the electrical contacts. In Examples 2 to 4, the Te concentration was fixed at 3.5 wt%. Figure 2The composition of the electric contact is shown in the table. In Examples 5 to 9, the Te concentration was fixed at 9 wt %, and the compositions of the obtained electric contacts were shown in the table. Figure 3 In Examples 10 to 13, the Te concentration was fixed at 14.5 wt%, and the compositions of the electrical contacts were shown in Figure 4 middle.

[0065] [Comparative Examples 1 to 8]

[0066] In Comparative Examples 1 to 8, the same steps as in Example 1 were used to make electric contacts. The effect of Ti concentration was verified. However, the mass ratio of each powder during the preparation of the mixed powder was adjusted to change the composition ratio of the electric contacts. The Te concentration was fixed at 3.5 wt % in Comparative Examples 1 and 2, 2.5 wt % in Comparative Example 3, 9 wt % in Comparative Examples 4 and 5, 14.5 wt % in Comparative Examples 6 and 7, and 15.5 wt % in Comparative Example 8. The compositions of the electric contacts of Comparative Examples 1 to 3 are shown in FIG. Figure 2 The compositions of the electrical contacts of Comparative Examples 4 and 5 are shown in Figure 3 The compositions of the electric contacts of Comparative Examples 6 to 8 are shown in FIG. Figure 4 , explain them separately.

[0067] In this embodiment, Examples 1 to 13 and Comparative Examples 1 to 8 were evaluated from the perspectives of manufacturability, low chopping current characteristics, and off-state characteristics. Furthermore, the electrical conductivity was also checked for its quality. These will be described in detail in order.

[0068] First, manufacturability will be described. Manufacturability is an evaluation of whether an electric contact can be manufactured. There are two points to evaluate the manufacturability of an electric contact.

[0069] The first evaluation point is when the density ratio of the electrical contact exceeds 95% of the density ratio required for use as an electrical contact. In this embodiment, the density ratio is calculated by dividing the density of the prototype electrical contact by the theoretical density calculated from the composition. If the density ratio is below 95% during the brazing process during vacuum valve assembly, the presence of voids within the electrical contact increases the likelihood of the solder being absorbed by the voids through capillary action, potentially increasing the frequency of soldering failures. Therefore, a density ratio exceeding 95% is preferred for practical purposes; electrical contacts with a density ratio below 95% are considered defective.

[0070] The second evaluation factor is that the mechanical strength of the electrical contact produced by the infiltration process is strong enough to be cut into a predetermined shape by machining. Electrical contacts with low mechanical strength have good weldability and are therefore considered good electrical contacts. However, if the mechanical strength is too low, cracks may form during machining, making processing difficult. Therefore, mechanical strength above the minimum required to prevent cracking is required.

[0071] In the present embodiment, a case where no cracks were generated during machining was judged as acceptable, and a case where cracks were generated was judged as defective.

[0072] Next, the evaluation of low chopping current characteristics and disconnection characteristics is described. The evaluation of low chopping current characteristics and disconnection characteristics is based on the results obtained by performing chopping current tests and disconnection current tests using the electrical contacts obtained in each example and comparative example as test contacts.

[0073] The 5mm thick, 23mm diameter electrical contacts obtained in each of the Examples and Comparative Examples were machined to produce test contacts 3mm thick and 20mm in diameter. Furthermore, the surface of the test contact was tapered approximately 15° from the end to 2mm inward. Two tapered test contacts were fabricated and assembled into an evaluation vacuum valve, using them as the fixed and movable contacts, respectively. Using the evaluation vacuum valves fabricated according to each of the Examples and Comparative Examples, chopping current and breaking current tests were conducted to evaluate low chopping current and breaking characteristics.

[0074] For the chopping current test, a circuit was assembled with a 20Ω resistor connected in series with the evaluation vacuum valve. Using an AC200V power supply, a current of 10A was applied. The current measured from the moment the evaluation vacuum valve was closed to the moment the arc current reached zero upon opening was defined as the chopping current. The chopping current test was conducted 1000 times using the same evaluation vacuum valve, and the average value was used as the chopping current value for each Example and Comparative Example.

[0075] In order to avoid damage to electrical equipment due to surge voltage rise generated during disconnection, the chopping current value must be 1 A or less. In this test, the test was considered passed when the chopping current value was 1 A or less.

[0076] For the opening test, a circuit is assembled, connecting a thyristor in series with an evaluation vacuum valve. With the evaluation vacuum valve closed, a current is passed, utilizing the discharge from the capacitor bank. When the evaluation vacuum valve is opened, the test is judged to determine if the circuit breaker successfully opens. The capacitor bank is charged using an external power supply. The opening test is repeated by increasing the current by 1 kA from 2 kA. Passing the test is determined when the circuit breaker successfully completes the opening test at 4 kA. A successful opening test means that no restriking or arcing occurs when the evaluation vacuum valve is opened.

[0077] Next, the evaluation of the electrical conductivity of the produced electrical contacts will be described. Since electrical contacts are current-carrying components, they require high electrical conductivity. As a benchmark for electrical conductivity, the internationally adopted annealed standard soft copper (volume resistivity: 1.7241×10 -2 The electrical conductivity of 100 μΩm is defined as the value of 100% IACS (International Annealed Copper Standard, IACS).

[0078] In this embodiment, the conductivity of Ag-WC contacts, which are widely used as low-surge contacts, is used as a standard, and a conductivity higher than 20% IACS is considered acceptable.

[0079] Figure 5 3 is a cross-sectional view showing the internal structure of the electric contact produced in Example 3 of this embodiment. Figure 5 This is a cross-sectional photograph of an electrical contact observed using a scanning electron microscope (SEM). The composition distribution of the internal structure was determined using the composition analysis function of the scanning electron microscope using wavelength dispersive X-ray spectroscopy or energy dispersive X-ray spectroscopy.

[0080] like Figure 5 As shown in FIG, Cr particles 16 as particles of a high melting point substance and Ti—Te intermetallic compound particles 17 formed by Ti and Te forming an intermetallic compound are dispersed and arranged in a base material 15 having Cu as a conductive component.

[0081] Furthermore, the composition analysis function of wavelength dispersive X-ray spectroscopy or energy dispersive X-ray spectroscopy attached to the SEM was used to measure the composition distribution of the internal structure of the Ti-Te intermetallic compound particles 17. As a result, the atomic weight ratio of Ti to Te was 1:2 or 3:4.

[0082] Figure 6 for Figure 5 The state diagram of the Ti-Te junction shown in FIG. Figure 6 Since the Ti—Te intermetallic compound contains a TiTe 2 intermetallic compound 18 or a Ti 3 Te 4 intermetallic compound 19 , it is considered that the Ti powder and the Te powder react with each other during the process of mixing and heating to form the intermetallic compound.

[0083] To maintain mechanical strength sufficient for machining of the electrical contact, an amount of Ti is added that does not form Cu2Te, which causes brittleness. To form Ti-Te intermetallic compound particles 17, a Ti:Te ratio of 1:2 or 3:4 is preferred, expressed in terms of atomic weight. Therefore, a Ti / Te ratio of 0.5 or greater is considered necessary, and a Ti / Te ratio of 0.17 or greater is necessary in terms of mass ratio. The following description uses mass ratios.

[0084] The results of Examples 1 to 13 and Comparative Examples 1 to 8 will be described in order.

[0085] First, use Figure 2 Examples 1 to 4 and Comparative Examples 1 and 2 will be described.

[0086] From the viewpoint of density ratio for manufacturability, in Examples 1 to 4 and Comparative Example 1, Cu was infiltrated up to an infiltration temperature of 1140° C., and thus, trial production of electric contacts was possible.

[0087] From the viewpoint of mechanical strength for manufacturability, Examples 1 to 4 and Comparative Example 1 were machined. As a result, cracks partially occurred in Comparative Example 1.

[0088] In Comparative Example 2, Cu was hardly infiltrated, Cu in the infiltrated material remained, and the density ratio did not reach 95%, so that the electric contact could not be manufactured.

[0089] From the above results, it is known that the Ti / Te value formed by the TiTe2 intermetallic compound or the Ti3Te4 intermetallic compound can be obtained even if the Ti / Te value is not greater than 0.17 as long as the Ti / Te value is greater than 0.12. Figure 6 The Ti-Te phase diagram is considered to be due to the fact that: from the lever principle, even if Ti / Te is below 0.17, it can be inferred that TiTe2 intermetallic compounds are formed.

[0090] In other words, it is believed that not all Te forms a TiTe2 intermetallic compound or a Ti3Te4 intermetallic compound, but that by forming a portion of the Te into a Ti-Te intermetallic compound, mechanical strength sufficient to withstand electrical contact failure can be achieved. The examples show that cracks occur when the Ti / Te ratio is 0.09 or less, so it can be said that production is possible even with a Ti / Te ratio of 0.12 or more.

[0091] In addition, in the cross-sectional analysis of Comparative Example 1 where Ti / Te was 0.09 or less, a large amount of Cu2Te, which is the cause of brittleness, was detected. This is believed to be due to insufficient Ti for forming the Ti—Te intermetallic compound.

[0092] In Examples 1 to 4, good results were obtained also in the circuit breaking test and the disconnection test.

[0093] In addition, in Examples 1 to 4, cross-sectional analysis of the Ti component dissolved in Cu revealed that the Ti component was as little as 1 wt % or less, and the electrical conductivity was 20% IACS or more.

[0094] Therefore, it can be said that the electrical contacts of Examples 1 to 4 of the present embodiment have improved electrical conductivity and can suppress heat generation during current flow.

[0095] Second, use Figure 7 and Figure 8 The reasons why Cu remains in Comparative Example 2 are explained in two points.

[0096] The first point is that the wettability between the sintered body and Cu in the infiltration material deteriorates due to the addition of Ti. Figure 7 : is a diagram showing the appearance of the electric contact of Comparative Example 2. Figure 7 It is possible to confirm the molten Cu22 that did not penetrate into the sintered body but flowed out of the sintered body, the Cu23 that solidified as droplets on the surface, and the Cu21 of the infiltration material. Figure 7 It is considered that when Ti is excessively added as shown in Comparative Example 2, the wettability of the sintered body with Cu of the infiltration material deteriorates, so that the molten Cu does not penetrate into the sintered body and flows out as droplets.

[0097] The second point is the increase in infiltration temperature caused by the addition of Ti. Figure 8 This is a SEM observation of the precipitation of Ti and its compounds in the Cu of the infiltrated material remaining in Comparative Example 2. Figure 8 In the figure, sintered body 24 and Cu 25 of the infiltration material can be identified. Ti 26 is sparsely distributed within Cu 25. It is believed that the addition of Ti, with a Ti / Te ratio of 0.12, necessary for the Ti3Te4 intermetallic compound, creates a state in which Ti, with a melting point of 1668°C (higher than the melting point of Cu at 1083°C), is present in the Cu of the infiltration material, raising the normal melting point of Cu. In this embodiment, as shown in Example 4, if the Ti / Te ratio is 0.38 or less, infiltration can be performed at an infiltration temperature of up to 1140°C.

[0098] That is, in the present embodiment, from Examples 1 to 4 and Comparative Examples 1 and 2, if Ti / Te is 0.38 or less, infiltration can be performed at an infiltration temperature up to 1140°C.

[0099] In Comparative Example 2, the heating temperature was 1150° C. to fully melt Cu having a high melting point. However, since Cu was also used in the molded body, the Cu in the molded body also melted, making it difficult to maintain the shape of the electrical contact.

[0100] Furthermore, Te exists as an intermetallic compound with Ti. This raises its melting point, but due to its very low saturated vapor pressure, it is likely to partially evaporate during high-temperature infiltration. This evaporation of Te reduces the density of the molded body, making it impossible to manufacture the molded body at temperatures above 1150°C.

[0101] From the above, it was found that adding Ti in an amount that does not form Cu2Te, which causes brittleness, is effective. On the other hand, excessive addition of Ti makes the manufacturability of the electrical contact difficult.

[0102] Next, Comparative Example 3 will be described. Comparative Example 3 has a Ti / Te ratio similar to that of Example 3, but with a Te concentration of 2.5 wt %. In Comparative Example 3, the infiltrated body has a density ratio of 95% or higher, and Ti—Te intermetallic compounds can be confirmed by cross-sectional analysis.

[0103] The low chopping current characteristics of the evaluation vacuum valve were evaluated, and the chopping current exceeded 1A, resulting in a failure. This is believed to be due to insufficient Te, a low-boiling-point metal required to ensure low surge resistance. Therefore, it is believed that a Te content of 3.5 wt% or more is necessary to achieve stable low chopping current characteristics.

[0104] Depend on Figure 6 From the state diagram of Ti and Te shown in the figure and the results of Examples 1 to 4 and Comparative Examples 1 to 3 described above, it is believed that if the Ti / Te range of the Ti-Te intermetallic compound is set to be greater than 0.12 and less than 0.38, TiTe2 or Ti3Te4 will be generated. Figure 6 The phase diagram of Ti / Te shows that the range of Ti / Te is preferably 0.17 or more and 0.3 or less.

[0105] Summarize Figure 2 As a result, it can be said that in the Ti and Te of the electric contact that satisfy the manufacturability, low chopping current characteristics and electrical conductivity, Te is 3.5 wt% or more and Ti / Te is 0.12 or more and 0.38 or less.

[0106] Next, the results of Examples 5 to 13 and Comparative Examples 4 to 8 will be described.

[0107] Depend on Figure 3 In Examples 5 to 9 and Comparative Examples 4 to 5, the Te concentration was fixed at 9 wt % so that Ti / Te was 0.08 or more and 0.43 or less.

[0108] In Examples 5 to 9, it was possible to produce infiltrated bodies having a density ratio of 95% or more, and machining was possible without any problems. Furthermore, the electrical conductivity was 20% IACS, and both low chopping current characteristics and interruption characteristics were good.

[0109] In Comparative Example 4 where Ti / Te was smaller than 0.09, Cu in the infiltrated material melted at 1110°C, but a large amount of Cu2Te, which causes brittleness, was detected in cross-sectional analysis, and some cracks occurred during machining.

[0110] In Comparative Example 5, sufficient infiltration was not achieved at infiltration temperatures up to 1130° C. This is considered to be due to the same reason as in Comparative Example 2.

[0111] Will Figure 3 The results are summarized as follows: among the Ti and Te of the electrical contact that satisfy manufacturability, low chopping current characteristics and electrical conductivity, it can be said that Te is 9 wt% and Ti / Te is 0.12 or more and 0.37 or less.

[0112] Next, the results of Examples 10 to 13 and Comparative Examples 6 to 8 will be described.

[0113] Depend on Figure 4 In Examples 10 to 13 and Comparative Examples 6 to 7, the Te concentration was fixed at 14.5 wt % so that Ti / Te was greater than or equal to 0.09 and less than or equal to 0.42.

[0114] As a result, the same results as those of Examples 1 to 9 and Comparative Examples 1 to 5 described above were obtained.

[0115] Furthermore, in Comparative Example 8, the Te concentration was increased to 15.5 wt% to confirm the upper limit of the Te concentration. Although electrical contacts could be fabricated in Comparative Example 8, the evaporation of Te, a low-boiling-point metal, increased during testing of low chopping current and tripping characteristics, resulting in sporadic occurrences of tripping failures at 4 kA. Therefore, it is believed that a Te content of less than 15 wt% is practically acceptable.

[0116] Summarize Figure 4 As a result, it can be said that the Te content is 14.5 wt % and the Ti / Te ratio is 0.12 or more and 0.36 or less in the electric contact that satisfies the manufacturability, low chopping current characteristics, and electrical conductivity.

[0117] Next, in order to study the content of Cr as an arc-proof component, Examples 14 to 16 and Comparative Examples 9 and 10 were carried out. Figure 9 The table shows the composition and results of the electric contacts of Examples 14 to 16 and Comparative Examples 9 to 10. Figure 9 In the examples and comparative examples, the Te concentration was set to 9 wt %, the Ti / Te ratio was kept constant at 0.29, and the Cr concentration was varied.

[0118] In Examples 14 to 16, Ti—Te intermetallic compounds were formed and mechanical processing was possible.

[0119] Furthermore, good results were obtained in the evaluation of low chopping current characteristics and disconnection characteristics.

[0120] The amount of Cr is correlated with the electrical conductivity. The less the amount of Cr, the higher the electrical conductivity tends to be. Figure 9 It was confirmed that the IACS was 20% or more even in Example 16, which had the highest Cr concentration of 60 wt % among Examples 14 to 16.

[0121] Figure 9 Comparative Example 9, with a Cr content of 15 wt%, failed to open at 4 kA in the interruption test. Cross-sectional analysis confirmed that the low Cr content, a high-melting-point substance that serves as an arc-proof component, resulted in traces of Cu cladding. Therefore, it is believed that low Cr content prevents the electrical contact from functioning properly.

[0122] Figure 9 In Comparative Example 10, where the Cr content was 70 wt %, it was difficult to form a molded body. Due to the addition of hard Cr, slight cracks occurred on the side surfaces of the molded body when it was removed from the die.

[0123] Summarize Figure 9 As a result, in an electrical contact that satisfies manufacturability, low chopping current characteristics, and electrical conductivity, it can be said that when the Te concentration is 9 wt % and the Ti / Te ratio is 0.29, the Cr concentration is 20 wt % or more and 60 wt % or less.

[0124] Next, in order to examine the particle size of Cr used, Examples 17 to 19 and Comparative Examples 11 and 12 were carried out. Figure 10 The table shows the composition and results of the electric contacts of Examples 17 to 19 and Comparative Examples 11 to 12. Figure 10 In the examples and comparative examples, the Te concentration was kept constant at 9 wt %, the Ti / Te ratio was kept constant at 0.29, and the Cr particle size was varied.

[0125] In Example 17, when the Cr particle size was 1 μm, press molding was possible. In Examples 18 and 19, press molding was also possible.

[0126] In Comparative Example 11, when the Cr particle size was 0.1 μm, cracks occurred on the side surfaces of the molded body. This is presumably because the pressure during molding was increased in order to obtain a predetermined density of the molded body.

[0127] In Comparative Example 12, when the Cr particle size was 150 μm, sporadic disconnection failures were observed during the disconnection test. This is believed to be because when the particle size of Cr particles, a high-melting-point substance, is 150 μm or larger, the contact surface no longer has a uniform structure, and the generated arc is limited to the Cr particles, a high-melting-point substance.

[0128] Summarize Figure 10 The results show that in an electrical contact that satisfies manufacturability, low interruption current characteristics, and electrical conductivity, when the Te concentration is 9 wt% and the Ti / Te ratio is 0.29, the practical Cr particle size is larger than 0.1 μm and less than 120 μm.

[0129] In addition, Examples 20 to 22 were carried out by changing the arc-proof component to Cr carbide such as Cr3C2, W, and W carbide such as WC. Figure 11 The compositions and results of the electric contacts of Examples 20 to 22 are shown.

[0130] Depend on Figure 11 As a result, even if the arc-proof component is not Cr but Cr carbide, W and W carbide, the same effect can be obtained. This is considered to be because: as arc-proof components, Cr carbide, W and W carbide are high melting point metals, so there is no problem in practical use.

[0131] Therefore, the high-melting-point material particles are not limited to Cr powder. They may be W powder, which is particles of other high-melting-point metals, or Cr3C2 powder, which is a carbide of a high-melting-point metal, such as Cr carbide, or WC powder, which is particles of W carbide. In other words, the high-melting-point material particles may be at least one of particles of a high-melting-point metal or a carbide of a high-melting-point metal. Furthermore, as another example, the high-melting-point metal particles may be Mo powder, similar to Cr powder and W powder, and the high-melting-point metal carbide particles may be Mo carbide particles, such as Mo2C powder, similar to Cr3C2 powder and WC powder.

[0132] In the present embodiment, Ti is used instead of Mn as an additive for maintaining mechanical strength, thereby manufacturing an electric contact capable of maintaining high electrical conductivity.

[0133] Based on the results of the above-described examples and comparative examples, by setting Te to 3.5 wt% or more and 14.5 wt% or less, and furthermore, a Ti / Te ratio of 0.12 or more and 0.38 or less, a portion of the Ti is converted into TiTe2 or Ti3Te4. As a result, Cu2Te, which can cause brittleness, is not formed, and mechanical strength can be maintained. Furthermore, the electrical contacts of this embodiment can satisfy low interruption current characteristics and disconnection characteristics. In other words, it is possible to produce electrical contacts that meet high-current disconnection performance, low surge performance, and current-carrying performance.

[0134] It should be noted that the concentration and particle size of Cr vary depending on other conditions, and the Cr particle size greater than 0.1 μm and less than 120 μm obtained in Examples 1 to 19 and Comparative Examples 1 to 12 is not limited to this as long as it is within the range that achieves the effects of the invention.

[0135] Description of Reference Signs

[0136] 10 Fixed electrical contacts

[0137] 11 Movable electrical contacts

[0138] 15 Cu of base metal

[0139] 16 Cr

[0140] 17 Ti-Te intermetallic compound

[0141] 18 TiTe2 intermetallic compound

[0142] 19 Ti3Te4 intermetallic compound

[0143] 22 Molten Cu

[0144] 23 Solidified Cu

Claims

1. An electrical contact, comprising: A base material composed of Cu; high-melting-point material particles dispersed in the matrix, the particles being at least one of high-melting-point metal particles or carbide particles of the high-melting-point metal; and Te and Ti dispersed and arranged in the base material, When the total is 100 mass %, the Te is added in an amount of 3.5 mass % or more and 14.5 mass % or less, and the Ti / Te is 0.12 or more and 0.38 or less. At least a portion of the Te and at least a portion of the Ti form an intermetallic compound of the Te and Ti, The intermetallic compound forms TiTe2 or Ti3Te4.

2. The electrical contact according to claim 1, wherein: The Cu dissolves the Ti in a solid solution at 1 mass % or less.

3. The electric contact according to claim 1 or 2, characterized in that: The high melting point material particles are at least any one of Cr, Cr carbide, W, W carbide, Mo, and Mo carbide.

4. The electric contact according to claim 1 or 2, characterized in that: When the high-melting-point material particles are Cr, the concentration of the Cr is 20 mass % or more and 60 mass % or less, and the particle size of the Cr is larger than 0.1 μm and 120 μm or less.

5. A vacuum valve comprising an electrical contact, the electrical contact comprising: A base material composed of Cu; high-melting-point material particles dispersed in the matrix, the particles being at least one of high-melting-point metal particles or carbide particles of the high-melting-point metal; and Te and Ti dispersed and arranged in the base material, When the total is 100 mass %, the Te is added in an amount of 3.5 mass % or more and 14.5 mass % or less, and the Ti / Te is 0.12 or more and 0.38 or less. At least a portion of the Te and at least a portion of the Ti form an intermetallic compound of the Te and Ti, The intermetallic compound forms TiTe2 or Ti3Te4.

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