JP4579348B1 - Electrical contact material - Google Patents

Abstract

An electrical contact material that can reduce the wear rate after a break test by an overload test such as a breaker or a short circuit test, and an electrical contact material that can prevent welding after a break test by a short circuit test such as a breaker provide. The electrical contact material (31) according to one aspect contains 4% by mass to 7% by mass of graphite, the balance is made of silver and inevitable impurities, the deflection is 0.5 mm or more, the Vickers hardness is 55 or more, oxygen Content is 100 ppm or less. The electrical contact material (31) preferably further contains tungsten carbide. It is preferable that the average particle diameter of tungsten carbide is 40 nm or more and 3 μm or less, and the content of tungsten carbide is 2 mass% or more and 4 mass% or less. The electrical contact material (31) according to another aspect includes 0.5% by mass or more and 2% by mass or less of graphite, the balance is made of silver and inevitable impurities, the deflection is 0.8 mm or more, and the Vickers hardness is 40. As described above, the oxygen content is 100 ppm or less.
[Selection] Figure 1

Description

  The present invention generally relates to an electrical contact material, and more particularly to an electrical contact material used for a circuit breaker (breaker) made of a silver-graphite (Ag-Gr) -based material.

  Conventionally, an electrical contact material made of a silver-graphite-based material is well known.

  For example, JP-A-8-239724 (hereinafter referred to as Patent Document 1) discloses a material for an electrical contact made of silver, a silver alloy or a silver composite material containing 0.05 to 7% by weight of carbon. ing. In this material for electrical contacts, carbon is added to the silver, silver alloy or silver composite powder in the form of carbon black with an average primary particle size of less than 150 nm, and this mixture is cold isostatically compressed by extrusion. Sintered.

  Japanese Patent No. 3138965 (hereinafter referred to as Patent Document 2) discloses a composite for electrical contact comprising silver, an alloy containing silver, or a composite material containing silver and 0.5 to 10% by weight of carbon. Material is disclosed. In this composite material for electrical contacts, carbon powder combined with carbon fiber is powder metallurgy processed together with powdered metal composition so that the average length of carbon fiber is more than twice the average diameter of carbon powder particles. It is formed in a certain material.

  Japanese Unexamined Patent Application Publication No. 2007-169701 (hereinafter referred to as Patent Document 3) discloses an electrical contact material that is a molded sintered body of a composite powder mainly composed of silver powder. In this electrical contact material, carbon fine powder is dispersed and mixed in silver powder, and a main material mainly composed of silver powder and carbon fine powder are mixed by mechanical alloying to obtain a mixed powder. The composite powder is manufactured by a step of forming a composite body and a step of sintering the formed body.

JP-A-8-239724 Japanese Patent No. 3138965 JP 2007-169701 A

  When a breaker is configured using an electrical contact material made of a silver-graphite-based material, the electrical contact material has high conductivity, so that it is difficult to generate heat, and there is almost no adverse effect due to heat generation. However, in the circuit breaker short circuit interruption test using the electrical contact material made of silver-graphite-based material, there is a problem that the consumption rate of the electrical contact material after the test is large due to thermal shock and mechanical impact applied to the electrical contact material. There is.

  Accordingly, an object of the present invention is to provide an electrical contact material capable of reducing the wear rate after an interruption test by an overload test such as a breaker or the like and a short circuit test.

  Another object of the present invention is to provide an electrical contact material capable of preventing welding after a breaking test by a short circuit test such as a breaker.

  The present inventors have studied various causes of the consumption rate of the electrical contact material after the short-circuit breaking test of the breaker using the electrical contact material made of a silver-graphite-based material.

  First, since a breaker for large current having a rated current value of about 100 to 3200 A has a large breaking current, a relatively large current flows through an electrical contact material incorporated in the breaker. Therefore, this electrical contact material is required to have higher heat resistance than conductivity. In order to satisfy this requirement, an electrical contact material having a relatively low silver content and a relatively high graphite content in the silver-graphite-based material is used for a high-current breaker. Specifically, the electrical contact material used for the breaker for large current contains 4% by mass or more and 7% by mass or less of graphite, and the balance is made of silver and inevitable impurities.

  In the breaking test of a large current breaker, contact consumption after a short circuit test in which an operation from on to off is performed with a large breaking current is important. The reason why the electrical contact material is consumed in this short-circuit test is that the operation is instantaneously performed from on to off under the condition that the breaking current is large. Therefore, the thermal energy and machine applied to the electrical contact material during one short-circuit interruption test It was thought that there was a great impact.

  However, as a result of intensive research on the cause of the consumption of the electrical contact material after the short-circuit test of the high-current breaker, the present inventors have made at least the hardness of the electrical contact material at room temperature relatively higher than a certain value. In addition, the electrical contact material is made so that the amount of deflection is relatively large above a certain value, the oxygen content is kept below a certain value, and it is not deformed in a state where heat is generated by flowing a large current (high temperature). It was found that the amount of wear after the short-circuit test can be reduced by configuring. Based on this knowledge, the electrical contact material according to one aspect of the present invention has the following characteristics.

  The electrical contact material according to one aspect of the present invention contains 4% by mass to 7% by mass of graphite, the balance contains silver and unavoidable impurities, the deflection is 0.5 mm or more, the Vickers hardness is 55 or more, oxygen Content is 100 ppm or less.

  In the electrical contact material according to one aspect of the present invention, the bending strength is preferably 210 MPa or more.

  In the electrical contact material according to one aspect of the present invention, the average particle size of graphite is preferably 40 nm or more and 8 μm or less.

  Furthermore, in order to prevent welding after the interruption test by the short circuit test, the electrical contact material according to one aspect of the present invention preferably further contains tungsten carbide.

  In this case, it is preferable that the average particle diameter of tungsten carbide is 40 nm or more and 3 μm or less, and the content of tungsten carbide is 2 mass% or more and 4 mass% or less. The average particle size of tungsten carbide is more preferably 40 nm or more and 150 nm or less.

  Next, since a breaker for small current having a rated current value of about 1 to 60 A has a small breaking current, a relatively small current flows through an electrical contact material incorporated in the breaker. Therefore, the electrical contact material is required to have higher conductivity than heat resistance. In order to satisfy this requirement, an electrical contact material having a relatively high silver content and a relatively low graphite content in the silver-graphite-based material is used for a small current breaker. Specifically, the electrical contact material used for the breaker for small current contains 0.5% by mass or more and 2% by mass or less of graphite, and the balance is made of silver and inevitable impurities.

  In the breaking test of a breaker for small current, contact wear after an overload test in which the operation from on to off is repeated many times with a small breaking current is important. However, in the breaking test of the breaker for small current, since the operation is instantaneously performed from on to off under the condition that the breaking current is small, the mechanical impact applied to the electrical contact material during one overload test is small. Conventionally, it was thought that the electrical contact material was less damaged by mechanical impact.

  However, as a result of extensive research conducted by the inventors on the cause of electric contact material consumption after an overload test of a small current breaker, at least the deflection amount of the electric contact material is relatively increased to a certain value or more. Furthermore, the electrical contact material is made to withstand mechanical impacts repeated many times by relatively increasing the hardness of the electrical contact material at room temperature to a certain value or higher and suppressing the oxygen content to a specified value or less. It has been found that the amount of wear after the overload test can be reduced by configuring. Based on this knowledge, the electrical contact material according to another aspect of the present invention has the following characteristics.

  The electrical contact material according to another aspect of the present invention contains 0.5% by mass or more and 2% by mass or less of graphite, the balance contains silver and unavoidable impurities, the deflection is 0.8 mm or more, and the Vickers hardness is 40. As described above, the oxygen content is 100 ppm or less.

  In the electrical contact material according to another aspect of the present invention, the bending strength is preferably 120 MPa or more.

  In the electrical contact material according to another aspect of the present invention, the average particle size of graphite is preferably 40 nm or more and 8 μm or less.

  As described above, according to the present invention, the electrical contact material incorporated in the breaker for large current can reduce the consumption rate after the short-circuit test, and the electrical contact material incorporated in the breaker for small current can be excessive. The consumption rate can be reduced after the load test. Moreover, in the electrical contact material incorporated in the breaker for large currents, welding can be prevented after the interruption test by the short circuit test by further including tungsten carbide.

It is a side view which shows the arrangement | positioning relationship in the closed state of the stationary side contact member and movable side contact member which comprise the breaker in which the electrical contact material as one embodiment of this invention was integrated. It is a side view which shows the arrangement | positioning relationship in the open state of the stationary side contact member and movable side contact member which comprise the breaker in which the electrical contact material as one embodiment of this invention was integrated.

  First, the configuration of a breaker incorporating an electrical contact material as one embodiment of the present invention will be described.

  As shown in FIGS. 1 and 2, the breaker 10 can contact the fixed contact member 30 and the fixed contact member 30, or can be separated from the fixed contact member 30. The movable-side contact member 20 is disposed so as to be movable repeatedly. The stationary contact member 30 is composed of a joined body of an electrical contact material 31 and a base metal 32. The movable contact member 20 is composed of a joined body of an electrical contact material 21 and a base metal 22. The electrical contact material 31 according to the embodiment of the present invention is used for a part of the stationary contact member 30 of the breaker 10. The electrical contact material 31 shown in FIGS. 1 and 2 is an example of the “electrical contact material” according to the present invention.

  In the stationary contact member 30, the electrical contact material 31 and the base metal 32 are joined to each other via the brazing material 4 with the upper surface of the joint portion 32 a formed integrally on the base metal 32 side as the joint surface. Yes. In the movable contact member 20, the electrical contact material 21 and the base metal 22 are joined to each other via the brazing material 4 with the upper surface of the joint portion formed integrally on the base metal 22 side as the joint surface. .

  Since the movable contact member 20 and the fixed contact member 30 are configured in this way, the electric contact of the movable contact member 20 with respect to the electric contact material 31 of the fixed contact member 30 as shown in FIG. When a current exceeding the allowable current value of the breaker 10 flows for a predetermined time from a state in which the material 21 is in contact (closed state), a built-in contact trip device (not shown) is activated, and FIG. As shown in the figure, the electric contact member 21 of the movable contact member 20 is instantaneously separated from the electric contact member 31 of the fixed contact member 30 in the direction of the arrow Q, and the current is cut off. . As shown in FIGS. 1 and 2, the end side of the base metal 32 on which the electrical contact material 31 is not provided is connected to the primary side (power supply side) terminal of the breaker 10 among the fixed side contact members 30. In addition, of the movable contact member 20, the end portion of the base metal 22 on which the electrical contact material 21 is not provided is connected to the secondary side (load side) terminal of the breaker 10.

  First, in one aspect of the present invention, the movable-side electrical contact material 21 incorporated in the high-current breaker 10 having a rated current value of about 100 to 3200 A is made of a silver-tungsten carbide (Ag-WC) material, The fixed-side electrical contact material 31 is made of a silver-graphite (Ag-Gr) -based material, containing 4% by mass to 7% by mass of graphite, the balance containing silver and inevitable impurities, and a deflection of 0.5 mm or more. The Vickers hardness is 55 or more and the oxygen content is 100 ppm or less.

  In this way, at least the hardness of the electrical contact material 31 at room temperature is relatively increased to a certain value or more, and further, the deflection amount is relatively increased to a certain value or more, and the oxygen content is suppressed to a specified value or less. Thus, by configuring the electrical contact material 31 so as not to be deformed in a state where heat is generated by flowing a large current (high temperature), it is possible to reduce the amount of wear after the short circuit test.

  Increasing the graphite content in silver-graphite (Ag-Gr) based materials strengthens the material because the finely dispersed graphite particles in the material provide a pinning effect. This increases the hardness and bending strength of the material. If the graphite content is less than 4% by mass, the pinning effect cannot be obtained. When the content of graphite exceeds 7% by mass, the pinning effect becomes excessive, so that the amount of deflection becomes small.

  A short circuit test for large current uses a large impact, so a material with relatively high strength is required. However, in order to withstand repeated opening and closing (repetitive impact) of the breaker in an overload test, the amount of deflection is 0.5 mm or more. Need to be. If the amount of deflection is less than 0.5 mm, the toughness of the material is low, so that cracks occur in the electrical contact material 31 due to the repeated impacts described above. However, the amount of deflection is preferably 2 mm or less because of difficulty in manufacturing. Here, “manufacturing difficulty” means that no matter how much the deflection amount is increased, 2 mm is a manufacturing limit.

  In a short circuit test for large current applications, the impact is large. To withstand the impact, a Vickers hardness of 55 or more is required. When the Vickers hardness is less than 55, the contact point is insufficient due to insufficient material hardness in the short circuit test with a large contact load. The shape cannot be maintained. In the overload test, since the contact load is small, the contact shape is hardly affected by the Vickers hardness. However, the Vickers hardness is preferably 150 or less because the contact resistance between the contacts increases if the hardness is too high.

  When the oxygen content exceeds 100 ppm, oxygen present in the material becomes a gas due to high heat of several thousand degrees generated during the short circuit test, so that a part of the base material of the electrical contact material 31 is scattered. Thereby, the rate at which the electrical contact material 31 is consumed increases. In the overload test, since the contact load is small, the rate at which the electrical contact material 31 is consumed is hardly affected by the oxygen content. However, the oxygen content is preferably 20 ppm or more for reasons of difficulty in production. Here, “difficulty in production” means that no matter how small the oxygen content is, 20 ppm is a production limit.

  In the electrical contact material 31 according to one aspect of the present invention, since the impact is large in the short-circuit test for a large current application, the bending strength is preferably 210 MPa or more in order to withstand the impact. When the bending strength is less than 210 MPa, the electrical contact material 31 is broken due to insufficient mechanical strength of the material in a short-circuit test with a large contact load. In the overload test, since the contact load is small, it is hardly affected by the bending strength. However, the bending strength is preferably 300 MPa or less because of difficulty in production. Here, “difficulty in production” means that no matter how much the bending strength is increased, 300 MPa is a production limit.

  In the electrical contact material 31 according to one aspect of the present invention, the average particle size of graphite is preferably 40 nm or more and 8 μm or less. If the average particle diameter of graphite is less than 40 nm, the graphite particles are too fine, and the graphite particles are tightly packed between the silver particles. For this reason, the area which silver particles contact is extremely small. Originally, silver plays a role of maintaining the strength of the electrical contact material 31, but even if pressure is applied in a state where the contact surfaces of the silver particles are extremely small, the silver cannot maintain the strength. Therefore, it becomes difficult to form a molded body. As a result, it becomes difficult to manufacture the electrical contact material 31. Moreover, when the average particle diameter of graphite exceeds 8 micrometers, the hardness and bending strength of the electrical contact material 31 will fall.

  Furthermore, in order to prevent welding after the interruption test by the short circuit test, the electrical contact material 31 according to one aspect of the present invention preferably further includes tungsten carbide. When the electrical contact material 31 further includes tungsten carbide (WC), the hardness and the bending strength of the electrical contact material 31 can be further increased. For example, the Vickers hardness is 70 or more and the bending force is 230 MPa or more. be able to. Thereby, the consumption after a short circuit test can be reduced more effectively.

  In a silver-graphite (Ag-Gr) -based material, the graphite particles are dispersed in a fibrous form, for example. When the contacts come into contact with each other in the short-circuit test, high heat of several thousand degrees is generated, so that silver is easily eluted. As a result, the contacts are welded together. Therefore, when the electrical contact material 31 made of a silver-graphite-tungsten carbide (Ag-Gr-WC) -based material further containing tungsten carbide is used, silver can be prevented from floating on the surface of the electrical contact material 31. Therefore, even if the contacts are brought into contact with each other in the short circuit test and high heat is generated, silver is hardly eluted. As a result, it is possible to prevent welding after the interruption test by the short circuit test.

  In this case, it is preferable that the average particle diameter of tungsten carbide is 40 nm or more and 3 μm or less, and the content of tungsten carbide is 2 mass% or more and 4 mass% or less. When the average particle size of tungsten carbide is less than 40 nm, it is difficult to produce tungsten carbide powder. When the average particle diameter of tungsten carbide exceeds 3 μm, the strength varies depending on the location of the electrical contact material 31. When low strength parts are connected, the electrical contact material 31 is selectively consumed after the short circuit test. If the content of tungsten carbide is less than 2% by mass, elution of silver cannot be suppressed, so that the welding performance is inferior and the effect of increasing the hardness of the electrical contact material 31 is small. When the content of tungsten carbide exceeds 4% by mass, the electrical conductivity of the electrical contact material 31 is deteriorated, so that heat is easily generated. For this reason, the consumption amount when the electrical contact material 31 short-circuits increases.

  The average particle size of tungsten carbide is more preferably 40 nm or more and 150 nm or less. When the average particle diameter of tungsten carbide is not less than 40 nm and not more than 150 nm, the tungsten carbide particles can be uniformly dispersed in silver, so that elution of silver can be more effectively suppressed. Thereby, the welding after the interruption | blocking test by a short circuit test can be prevented. That is, the welding resistance performance of the electrical contact material 31 can be enhanced. If the average particle diameter of tungsten carbide exceeds 150 nm, a large amount of tungsten carbide particles are present on the surface of the electrical contact material 31, so that heat is likely to be generated. For this reason, the consumption amount when the electrical contact material 31 short-circuits increases.

  When the electrical contact material 31 is made from a silver-graphite-tungsten carbide (Ag-Gr-WC) -based material further containing tungsten carbide, it is more preferable that the average particle size of the graphite is 1 μm or more and 5 μm or less. When the average particle diameter of the graphite is 1 μm or more and 5 μm or less, the graphite can be uniformly dispersed in the electric contact material, so that the electric contact material can be strengthened. Thereby, the hardness and the bending strength of the electrical contact material can be increased. When the average particle diameter of graphite is less than 1 μm, fine graphite particles and tungsten carbide particles are closely packed between silver particles after mixing raw material powders. For this reason, the area which silver particles contact is extremely small. Originally, silver plays a role of maintaining the strength of the electrical contact material 31, but even if pressure is applied in a state where the contact surfaces of the silver particles are extremely small, the silver cannot maintain the strength. Therefore, it becomes difficult to form a molded body. In this case, the minimum allowable particle size of the graphite particles compared to the silver-graphite-based material containing only the graphite particles because the fine tungsten carbide particles that inhibit the contact between the silver particles as well as the graphite particles are present. The diameter increases. If the average particle diameter of the graphite exceeds 5 μm, the number of graphite particles serving as a lubricant for contacting the silver particles with the tungsten carbide particles decreases, so that the tungsten carbide particles are not uniformly dispersed when the raw material powder is mixed. It becomes difficult to form an electrical contact material in which tungsten carbide is uniformly dispersed. For this reason, there exists a possibility that the effect of preventing the welding after the interruption | blocking test by a short circuit test may not be acquired by suppressing the effect by adding tungsten carbide, ie, the elution of silver more effectively.

  Next, in another aspect of the present invention, the movable-side electrical contact material 21 incorporated in the small current breaker 10 having a rated current value of about 1 to 60 A is made of a silver-tungsten carbide (Ag-WC) based material. The fixed-side electrical contact material 31 is made of a silver-graphite (Ag-Gr) -based material, contains 0.5% by mass to 2% by mass of graphite, and the balance is made of silver and unavoidable impurities. 0.8 mm or more, Vickers hardness of 40 or more, and oxygen content of 100 ppm or less.

  In this way, at least the deflection amount of the electrical contact material 31 is relatively increased to a specific value or more, and the hardness of the electrical contact material at room temperature is relatively increased to a specific value or more to specify the oxygen content. The consumption after the overload test can be reduced by configuring the electrical contact material 31 so as to be able to withstand a mechanical shock repeated many times while being suppressed below the value.

  Increasing the graphite content in silver-graphite (Ag-Gr) based materials strengthens the material because the finely dispersed graphite particles in the material provide a pinning effect. This increases the hardness and bending strength of the material. If the graphite content is less than 0.5% by mass, the pinning effect cannot be obtained. If the content of graphite exceeds 2% by mass, the pinning effect becomes excessive, and the amount of deflection becomes small.

  In short-circuit tests for small current applications, the impact is smaller than that for large current applications, and a material with relatively low strength is required to withstand the impact. In order to endure, the amount of deflection needs to be 0.8 mm or more. When the amount of deflection is less than 0.8 mm, the toughness of the material is low, so that cracks occur in the electrical contact material 31 due to the above repeated load. However, the amount of deflection is preferably 2.5 mm or less because of manufacturing difficulties. Here, “difficult to manufacture” means that no matter how much the amount of deflection is increased, 2.5 mm is a manufacturing limit.

  In short circuit tests for small current applications, the impact is smaller than in large current applications, so a Vickers hardness of 40 or more is required to withstand the impact. If the Vickers hardness is less than 40, the material is used in a short circuit test with a large contact load. The contact shape cannot be maintained due to insufficient hardness. In the overload test, since the contact load is small, the contact shape is hardly affected by the Vickers hardness. However, the Vickers hardness is preferably 100 or less because the contact resistance between the contacts increases if the hardness is too high.

  When the oxygen content exceeds 100 ppm, oxygen present in the material becomes a gas due to high heat of several thousand degrees generated during the short circuit test, so that a part of the base material of the electrical contact material 31 is scattered. Thereby, the rate at which the electrical contact material 31 is consumed increases. In the overload test, since the contact load is small, the rate at which the electrical contact material 31 is consumed is hardly affected by the oxygen content. However, the oxygen content is preferably 30 ppm or more for reasons of difficulty in production. Here, “difficulty in production” means that no matter how small the oxygen content is, 30 ppm is a production limit.

  In the electrical contact material 31 according to another aspect of the present invention, in the short-circuit test for small current application, the impact is smaller than that for the large current application, so that the bending strength is 120 MPa or more to withstand the impact. Is preferred. When the bending strength is less than 120 MPa, the electrical contact material 31 is broken due to insufficient mechanical strength of the material in a short-circuit test with a large contact load. In the overload test, since the contact load is small, it is hardly affected by the bending strength. However, the bending strength is preferably 280 MPa or less because of difficulty in production. Here, “difficulty in production” means that no matter how much the bending strength is increased, 280 MPa is a production limit.

  In the electrical contact material 31 according to another aspect of the present invention, the average particle size of graphite is preferably 40 nm or more and 8 μm or less. If the average particle diameter of graphite is less than 40 nm, the graphite particles are too fine, and the graphite particles are tightly packed between the silver particles. For this reason, the area which silver particles contact is extremely small. Originally, silver plays a role of maintaining the strength of the electrical contact material 31, but even if pressure is applied in a state where the contact surfaces of the silver particles are extremely small, the silver cannot maintain the strength. Therefore, it becomes difficult to form a molded body. As a result, it becomes difficult to manufacture the electrical contact material 31. Moreover, when the average particle diameter of graphite exceeds 8 micrometers, the hardness and bending strength of the electrical contact material 31 will fall.

  The electrical contact material 31 made of the silver-graphite (Ag-Gr) -based material of the present invention is manufactured as follows.

  First, silver powder and graphite powder are mixed in a vacuum of, for example, 80 to 150 Pa, for example, for 30 to 60 minutes in accordance with a predetermined composition. Thereafter, a compression molded body is formed by applying a pressure of, for example, 250 to 350 Mpa to the mixed powder. This compression-molded body is temporarily sintered, for example, by holding it in a reducing gas atmosphere such as hydrogen gas at a temperature of 850 to 950 ° C. for 1 to 2 hours, for example. This temporary sintered body is coined, for example, under a pressure of 1000 to 1200 MPa so that the true density becomes 97% or more, for example. The co-processed temporary sintered body is, for example, in an inert gas atmosphere such as nitrogen gas or a reducing gas atmosphere such as hydrogen gas at a temperature of 750 to 850 ° C., or a mixed gas thereof. For example, after preheating by holding for 1 to 2 hours in an atmosphere, an extrusion pressure of 100 to 200 GPa is applied to extrude into a predetermined shape.

  The electrical contact material 31 made of the silver-graphite-tungsten carbide (Ag-Gr-WC) -based material of the present invention containing tungsten carbide is manufactured as follows.

  First, silver powder, graphite powder, and tungsten carbide powder are mixed in a vacuum of 80 to 150 Pa, for example, for 30 to 60 minutes in accordance with a predetermined composition. Thereafter, a compression molded body is formed by applying a pressure of, for example, 250 to 350 Mpa to the mixed powder. This compression-molded body is temporarily sintered, for example, by holding it in a reducing gas atmosphere such as hydrogen gas at a temperature of 850 to 950 ° C. for 1 to 2 hours, for example. This temporary sintered body is coined, for example, under a pressure of 1000 to 1200 MPa so that the true density becomes 97% or more, for example. The co-processed temporary sintered body is, for example, in an inert gas atmosphere such as nitrogen gas or a reducing gas atmosphere such as hydrogen gas at a temperature of 750 to 850 ° C., or a mixed gas thereof. For example, after preheating by holding for 1 to 2 hours in an atmosphere, an extrusion pressure of 100 to 200 GPa is applied to extrude into a predetermined shape.

  As described above, in order to manufacture the electrical contact material 31 from the silver-graphite (Ag-Gr) -based or silver-graphite-tungsten carbide (Ag-Gr-WC) -based material of the present invention, an extrusion method is employed. Is done. When the electrical contact material 31 is manufactured by the extrusion method, the old powder grain boundary in the raw material powder is torn off, so that the most brittle powder grain boundary is strengthened by powder metallurgy in the extruded body. Thereby, the bending strength and deflection of the material can be increased. Further, since the material is densified by the extrusion method, the hardness of the material can be increased. On the other hand, when the sintering method is employed, the old powder grain boundary in the raw material powder remains in the sintered body, so that a sintered body having a lower mechanical strength than that of the extruded body can be obtained.

  In the production method of the present invention, the raw material powder is mixed in a vacuum as described above. Since the specific gravity of the silver powder as the raw material powder is about 4.8 times the specific gravity of the graphite powder, it is difficult to uniformly disperse and mix the silver powder and the graphite powder in the atmosphere. For this reason, since the electrical contact material 31 manufactured using the mixed powder obtained by mixing in the atmosphere cannot obtain the effect of the uniform dispersion strengthening of the particles, the hardness and the bending strength are reduced. On the other hand, the electrical contact material 31 manufactured using the mixed powder obtained by mixing in a vacuum can obtain the effect of uniform dispersion strengthening of particles.

  Moreover, in the manufacturing method of this invention, since the compression molding body is temporarily sintered in reducing gas atmosphere as mentioned above, the oxygen adhering to the surface of raw material powder is removed. As a result, it is possible to reduce the amount of wear after the interruption test by the overload test or the short circuit test of the electrical contact material 31 obtained. On the other hand, when the compression molded body is pre-sintered in an inert gas atmosphere, there is no oxygen mixed during the sintering, but oxygen attached to the surface of the raw material powder is not removed. The amount of wear after the blocking test increases.

  Furthermore, in the manufacturing method of the present invention, as described above, since the presintered body is subjected to extrusion after coining, the density of the material at the time of preheating becomes 98% or more. For this reason, the amount of oxygen entering the material from the inside of the heating furnace during the preheating can be reduced. Thereby, for example, in the electrical contact material 31 finally obtained, the oxygen content can be controlled to 20 ppm or more and 100 ppm or less. On the other hand, when the pre-sintered body is not coined, the density of the material is about 90%, so that the amount of oxygen entering the material from the heating furnace during preheating increases. For this reason, since oxidation of silver advances, the oxygen content in the electrical contact material 31 finally obtained increases.

  Hereinafter, comparative experiments by Examples and Comparative Examples conducted for confirming the effects of the above-described embodiment will be described.

[Example A]
In this example, as an example corresponding to the above-described embodiment, the fixed-side electrical contact material 31 according to the following Examples A1 to A9 was manufactured. In addition, the fixed-side electrical contact material 31 according to Comparative Examples A1 to A8, in which the graphite content, deflection, Vickers hardness, and oxygen content were outside the scope of the present invention, was prepared in the same manner as in the examples of the present invention. . Furthermore, as a comparative example corresponding to the conventional example, an electrical contact material 31 on the fixed side by the following comparative examples A11 to A16, A21 to A26, A31 to A36, and A41 to A46 was produced. An interruption test by an overload test and a short-circuit test was performed using each of the breakers for a large current having a rated current value of 100 A configured by incorporating each of these electrical contact materials 31. The movable-side electrical contact material 21 was made of a material containing 50% by mass of silver and the balance being tungsten carbide.

  The average particle diameter of the graphite (Gr) powder, the content of graphite (Gr) in the prepared electrical contact material 31, the electrical contact used in the examples and comparative examples of the present invention to produce the electrical contact material 31 The deflection, the bending strength, the hardness, the oxygen content and the density of the material 31 are shown in the following Table 1. Also, the consumption rate of the electrical contact material 31 after the overload test and the consumption rate of the electrical contact material 31 after the short circuit test The evaluation results for are also shown in Table 1. It should be noted that the numerical values underlined in Table 1 indicate that they are outside the scope of the present invention.

  It should be noted that the method of measuring the deflection, bending strength, hardness, oxygen content and density of the electrical contact material 31, the method of the interruption test by the overload test and the short-circuit test of the breaker for high current, the wear rate after these interruption tests Evaluation will be described later.

(Examples A1 to A9) (Comparative Examples A1 to A8)
In Examples A1 to A9 and Comparative Examples A1 to A8, an electrical contact material 31 made of a silver-graphite (Ag-Gr) -based material containing graphite (Gr) with the content shown in Table 1 was produced as follows.

  A graphite (Gr) powder having an average particle diameter shown in Table 1 and a silver (Ag) powder having an average particle diameter of 3 μm were vacuum-treated (100 Pa) using a ball mill so as to have the graphite content shown in Table 1. Mix for 30 minutes. By applying a pressure of 300 MPa to the obtained mixed powder with a press, a disk-shaped compression molded body having a thickness of 300 mm and an outer diameter of 80 mm was formed. This compression-molded body was pre-sintered by holding it in hydrogen gas at a temperature of 950 ° C., which is a reducing gas atmosphere, for 1 hour. This temporary sintered body was coined under a pressure of 1100 MPa so that the true density was 97% or more. The presintered body that has been subjected to coining processing is preheated by holding in an inert gas atmosphere of nitrogen gas at a temperature of 800 ° C. for 2 hours, and then an extrusion pressure of 100 GPa is applied, whereby the cross section is 10 mm square. Extrusion was performed to form a rod-like body. The obtained rod-shaped body was cut into a thickness of 1 mm to produce an electrical contact material 31. In addition, although it tried to produce an electrical contact material by said method using the graphite powder whose average particle diameter is 10 nm, it was not able to manufacture.

(Comparative Examples A11 to A16)
In Comparative Examples A11 to A16, except that the step of coining the temporary sintered body is not performed, graphite (Gr) is contained in the content shown in Table 1 according to the same steps as in the above Examples A1 to A9. The electrical contact material 31 of the silver-graphite (Ag-Gr) system material containing was produced.

(Comparative Examples A21 to A26)
In Comparative Examples A21 to A26, graphite (Gr) is contained at the contents shown in Table 1 according to the same steps as in Examples A1 to A9, except that silver powder and graphite powder are mixed in the atmosphere. An electrical contact material 31 made of a silver-graphite (Ag-Gr) material was produced.

(Comparative Examples A31 to A36)
Comparative Examples A31 to A36 are the same as Examples A1 to A9 except that the compression molded body was pre-sintered by holding it in a protective gas atmosphere at a temperature of 950 ° C. for 1 hour. According to the process of, the electrical contact material 31 of the silver-graphite (Ag-Gr) type | system | group material containing a graphite (Gr) with content shown in Table 1 was produced.

(Comparative Examples A41 to A46)
In Comparative Examples A41 to A46, the electrical contact material 31 made of a silver-graphite (Ag-Gr) -based material containing graphite (Gr) with the content shown in Table 1 was produced as follows.

  The graphite (Gr) powder having the average particle size shown in Table 1 and the silver (Ag) powder having the average particle size of 3 μm are manually mixed in the atmosphere for 30 minutes so as to have the graphite content shown in Table 1. did. A plate-like compression-molded body having a planar shape of 10 mm square and a thickness of 1 mm was formed by applying a pressure of 300 MPa to the obtained mixed powder with a press. This compression-molded body was pre-sintered by holding in a vacuum at a temperature of 900 ° C. for 1 hour. This temporary sintered body was coined under a pressure of 500 MPa so that the true density was 97% or more. Thus, the electrical contact material 31 was obtained.

(Deflection)
The deflection [mm] of the produced electrical contact material was measured according to JIS H5501.

(Drag strength)
A sample for a bending test having a size of 5 mm × 2 mm × 30 mm was produced from the same material as the produced electrical contact material. Using this sample, the bending strength [MPa] was measured under the conditions of a distance between supporting points of 15 mm and a head speed of 1 mm / min.

(hardness)
Using a Vickers hardness meter, the Vickers hardness [HV] of the produced electrical contact material was measured according to JIS Z 2244.

(Oxygen content)
The oxygen content remaining in the produced electrical contact material was measured by an infrared absorption method using an oxygen analyzer (model BMGA520) manufactured by Horiba, Ltd.

(density)
The density (relative density) of the produced electrical contact material was calculated by dividing the weight of the electrical contact material by the volume of the electrical contact material (calculated value obtained by product of vertical dimension × horizontal dimension × thickness dimension). The density was calculated by dividing by the theoretical density of each material.

(High current breaker interruption test (overload test))
In the overload test, a breaking current of 600 A was set at a load voltage of 220V. As a test method, CO duty (test to set a breaker in a circuit through which a cutoff current of 600 A at a load voltage of 220 V flows, and forcibly turn on the switch in the switch OFF state to instantaneously cut off the current) 50 times It was. And the consumption rate of the electrical contact material 31 after an overload test was computed by the following formula | equation. In Table 1, as the evaluation of the consumption rate, “◎” when the calculated consumption rate is 5% or less, “◯” when it is 10% or less, and “×” when it exceeds 10%.

  (Consumption rate of electrical contact material) = [{(thickness of electrical contact material before test) − (thickness of electrical contact material after test)} / (thickness of electrical contact material before test)] × 100 (%) (Equation 1).

(High current breaker interruption test (short circuit test))
In the short circuit test, a breaking current of 5000 A was set at a load voltage of 220V. As test methods, set the breaker to a circuit where a 5000 A cutoff current flows at a load voltage of 220 V and set the breaker in the O OFF state (the test that causes the cutoff current to flow when the breaker switch is ON and cut off the current) and the CO duty The test for forcibly turning on the switch and cutting off the current instantaneously) was performed according to the following procedure. That is, in this short circuit test, one O duty and three CO duties were performed in this order as operation duties. And the consumption rate of the electrical contact material 31 after a short circuit test was computed by said (Formula 1). In Table 1, as the evaluation of the consumption rate, “◎” is shown when the calculated consumption rate is 10% or less, “◯” when it is 40% or less, and “x” when it exceeds 40%.

  From Table 1, in the case of a large current breaker with a rated current value of 100A, at least the Vickers hardness of the electrical contact material at normal temperature is relatively increased to 55 or more, and the deflection is relatively increased to 0.5 mm or more. In addition, by suppressing the oxygen content to 100 ppm or less and configuring the electrical contact material so that it does not deform in a state where heat is generated by flowing a large current (under high temperature), not only the consumption rate after the overload test, It can be seen that the amount of wear after the short-circuit test was also reduced.

[Example B]
In this example, as an example corresponding to the above-described embodiment, the stationary-side electrical contact material 31 according to the following Examples B1 to B9 was manufactured. Further, in the same manner as in the examples of the present invention, the fixed-side electrical contact material 31 was produced according to Comparative Examples B1 to B8 in which the graphite content, deflection, Vickers hardness and oxygen content were outside the scope of the present invention. . Furthermore, as a comparative example corresponding to the conventional example, an electrical contact material 31 on the fixed side by the following comparative examples B11 to B16, B21 to B26, B31 to B36, and B41 to B46 was produced. An interruption test by an overload test and a short-circuit test was performed using each of the small current breakers having a rated current value of 30 A configured by incorporating each of these electrical contact materials 31. The movable-side electrical contact material 21 was made of a material containing 50% by mass of silver and the balance being tungsten carbide.

  The average particle diameter of the graphite (Gr) powder, the content of graphite (Gr) in the prepared electrical contact material 31, the electrical contact used in the examples and comparative examples of the present invention to produce the electrical contact material 31 Deflection, bending strength, hardness, oxygen content and density of the material 31 are shown in the following Table 2. Also, the consumption rate of the electrical contact material 31 after the overload test and the consumption rate of the electrical contact material 31 after the short circuit test The evaluation results for are also shown in Table 2. In addition, the numerical values underlined in Table 2 indicate that they are outside the scope of the present invention.

  The method for measuring the deflection, bending strength, hardness, oxygen content and density of the electrical contact material 31 is the same as in Example A described above. The method of the interruption test by the overload test and the short circuit test of the breaker for small current and the evaluation of the consumption rate after these interruption tests will be described later.

(Examples B1 to B9) (Comparative Examples B1 to B8)
In Examples B1 to B9 and Comparative Examples B1 to B8, an electrical contact material 31 made of a silver-graphite (Ag-Gr) -based material containing graphite (Gr) with the contents shown in Table 2 was produced as follows.

  A graphite (Gr) powder having an average particle diameter shown in Table 2 and a silver (Ag) powder having an average particle diameter of 3 μm were vacuum-treated (100 Pa) using a ball mill so as to have the graphite content shown in Table 2. Mix for 30 minutes. By applying a pressure of 300 MPa to the obtained mixed powder with a press, a disk-shaped compression molded body having a thickness of 300 mm and an outer diameter of 80 mm was formed. This compression-molded body was pre-sintered by holding it in hydrogen gas at a temperature of 950 ° C., which is a reducing gas atmosphere, for 1 hour. This temporary sintered body was coined under a pressure of 1100 MPa so that the true density was 97% or more. The presintered body that has been subjected to coining processing is preheated by holding in an inert gas atmosphere of nitrogen gas at a temperature of 800 ° C. for 2 hours, and then an extrusion pressure of 100 GPa is applied, whereby the cross section is 10 mm square. Extrusion was performed to form a rod-like body. The obtained rod-shaped body was cut into a thickness of 1 mm to produce an electrical contact material 31. In addition, although it tried to produce an electrical contact material by said method using the graphite powder whose average particle diameter is 10 nm, it was not able to manufacture.

(Comparative Examples B11 to B16)
In Comparative Examples B11 to B16, graphite (Gr) is contained at the content shown in Table 2 according to the same steps as in the above Examples B1 to B9, except that the step of coining the temporary sintered body is not performed. The electrical contact material 31 of the silver-graphite (Ag-Gr) system material containing was produced.

(Comparative Examples B21 to B26)
In Comparative Examples B21 to B26, graphite (Gr) is contained in the contents shown in Table 2 according to the same steps as in the above Examples B1 to B9 except that silver powder and graphite powder are mixed in the air. An electrical contact material 31 made of a silver-graphite (Ag-Gr) material was produced.

(Comparative Examples B31 to B36)
Comparative examples B31 to B36 are the same as the above examples B1 to B9, except that the compression molded body was temporarily sintered by holding it in nitrogen gas at a temperature of 950 ° C., which is a protective gas atmosphere, for 1 hour. According to the process of, the electrical contact material 31 of the silver-graphite (Ag-Gr) type | system | group material which contains a graphite (Gr) with content shown in Table 2 was produced.

(Comparative Examples B41 to B46)
In Comparative Examples B41 to B46, the electrical contact material 31 of a silver-graphite (Ag-Gr) -based material containing graphite (Gr) with the content shown in Table 2 was produced as follows.

  The graphite (Gr) powder having an average particle diameter shown in Table 2 and the silver (Ag) powder having an average particle diameter of 3 μm are manually mixed in the atmosphere for 30 minutes so as to have the graphite content shown in Table 2. did. A plate-like compression-molded body having a planar shape of 10 mm square and a thickness of 1 mm was formed by applying a pressure of 300 MPa to the obtained mixed powder with a press. This compression-molded body was pre-sintered by holding in a vacuum at a temperature of 900 ° C. for 1 hour. This temporary sintered body was coined under a pressure of 500 MPa so that the true density was 97% or more. Thus, the electrical contact material 31 was obtained.

(Shutdown test for small current breaker (overload test))
In the durability test, a cutoff current of 180 A was set at a load voltage of 220V. As a test method, CO duty (test to set a breaker in a circuit through which a cutoff current of 180 A at a load voltage of 220 V flows, and forcibly turn on the switch in the switch OFF state to instantaneously cut off the current) 50 times It was. And the consumption rate of the electrical contact material 31 after an overload test was computed by said (Formula 1). In Table 2, as the evaluation of the consumption rate, “◎” when the calculated consumption rate is 5% or less, “◯” when it is 10% or less, and “×” when it exceeds 10%.

(Shutdown test for short current breaker (short circuit test))
In the short circuit test, a breaking current of 300 A was set at a load voltage of 220V. As test methods, set the breaker to a circuit where a 300 A cutoff current flows at a load voltage of 220 V, and a CO duty (a test in which a cutoff current flows when the breaker switch is turned on and the current is cut off) and a CO duty (switch voltage is OFF). The test for forcibly turning on the switch and cutting off the current instantaneously) was performed according to the following procedure. That is, in this short circuit test, one O duty and three CO duties were performed in this order as operation duties. And the consumption rate of the electrical contact material 31 after a short circuit test was computed by said (Formula 1). Table 2 shows “消耗” when the calculated consumption rate is 10% or less, “◯” when the calculated consumption rate is 40% or less, and “X” when it exceeds 40%.

  From Table 2, in the case of a breaker for small current with a rated current value of 30A, at least the amount of deflection of the electrical contact material is relatively increased to 0.8 mm or more, and the Vickers hardness at normal temperature of the electrical contact material is relative to 40 or more. In addition to reducing the oxygen content to 100 ppm or less and configuring the electrical contact material to withstand repeated mechanical shocks, not only the wear rate after the short-circuit test but also the overload test It turns out that the amount of later consumption was also reduced.

[Example C]
In this example, as an example corresponding to the above-described embodiment, a fixed-side electrical contact material 31 according to Examples C1 to C20 below was manufactured. In addition, as a comparative example corresponding to the conventional example, an electrical contact material 31 on the fixed side according to the following comparative examples C107, C207, C307, and C407 was manufactured. An interruption test by an overload test and a short-circuit test was performed using each of the breakers for a large current having a rated current value of 100 A configured by incorporating each of these electrical contact materials 31. The movable-side electrical contact material 21 was made of a material containing 50% by mass of silver and the balance being tungsten carbide.

  The average particle diameter of the graphite (Gr) powder used for producing the electrical contact material 31 in the examples and comparative examples of the present invention, the graphite (Gr) content in the produced electrical contact material 31, tungsten carbide ( Table 3 below shows the average particle size of the WC powder, the content of tungsten carbide (WC) in the produced electrical contact material 31, the deflection, bending strength, hardness, oxygen content and density of the electrical contact material 31. . Table 3 also shows the evaluation results of the consumption rate of the electrical contact material 31 after the overload test and the consumption rate of the electrical contact material 31 after the short circuit test. In addition, the numerical value underlined in Table 3 shows that it is outside the scope of the present invention.

  The method for measuring the deflection, bending strength, hardness, oxygen content and density of the electrical contact material 31 is the same as in Example A described above. The method of the interruption test by the overload test and the short-circuit test of the breaker for large current, and the evaluation of the consumption rate after these interruption tests are the same as in the above-described Example A.

(Examples C1 to C20)
In Examples C1 to C20, the electrical contact material 31 of a silver-graphite-tungsten carbide (Ag-Gr-WC) material containing graphite (Gr) and tungsten carbide (WC) with the contents shown in Table 3 is as follows. It was made as follows.

  Graphite (Gr) powder and tungsten carbide (WC) powder having an average particle size shown in Table 3 and silver (Ag) powder having an average particle size of 3 μm have the graphite content and the tungsten carbide content shown in Table 3. In a vacuum mill (100 Pa) using a ball mill for 30 minutes. By applying a pressure of 300 MPa to the obtained mixed powder with a press, a disk-shaped compression molded body having a thickness of 300 mm and an outer diameter of 80 mm was formed. This compression-molded body was pre-sintered by holding it in hydrogen gas at a temperature of 950 ° C., which is a reducing gas atmosphere, for 1 hour. This temporary sintered body was coined under a pressure of 1100 MPa so that the true density was 97% or more. The presintered body that has been subjected to coining processing is preheated by holding in an inert gas atmosphere of nitrogen gas at a temperature of 800 ° C. for 2 hours, and then an extrusion pressure of 100 GPa is applied, whereby the cross section is 10 mm square. Extrusion was performed to form a rod-like body. The obtained rod-shaped body was cut into a thickness of 1 mm to produce an electrical contact material 31.

(Comparative Example C107)
In Comparative Example C107, the same average particle diameter as Example C7 as shown in Table 3 was followed according to the same steps as in Examples C1 to C20 above, except that the step of coining the temporary sintered body was not performed. And an electric contact material 31 of a silver-graphite-tungsten carbide (Ag-Gr-WC) -based material containing graphite (Gr) and tungsten carbide (WC) in a content.

(Comparative Example C207)
Comparative Example C207 is the same as Example C7 as shown in Table 3, according to the same steps as in Examples C1 to C20 above, except that silver powder, graphite powder and tungsten carbide powder were mixed in the atmosphere. An electrical contact material 31 of silver-graphite-tungsten carbide (Ag-Gr-WC) based material containing graphite (Gr) and tungsten carbide (WC) with an average particle size and content was produced.

(Comparative Example C307)
In Comparative Example C307, the same steps as in Examples C1 to C20 described above, except that the compression molded body was pre-sintered by holding it in nitrogen gas at a temperature of 950 ° C., which is a protective gas atmosphere, for 1 hour. As shown in Table 3, the electrical contact of the silver-graphite-tungsten carbide (Ag-Gr-WC) -based material containing graphite (Gr) and tungsten carbide (WC) with the same average particle size and content as in Example C7 A material 31 was produced.

(Comparative Example C407)
In Comparative Example C407, the electrical contact material 31 of a silver-graphite-tungsten carbide (Ag-Gr-WC) -based material containing graphite (Gr) and tungsten carbide (WC) with the contents shown in Table 3 is as follows. Produced.

  A graphite (Gr) powder and a tungsten carbide (WC) powder having an average particle size shown in Table 3 and a silver (Ag) powder having an average particle size of 3 μm in the atmosphere so as to have the graphite content shown in Table 3. Mixed manually for 30 minutes. A plate-like compression-molded body having a planar shape of 10 mm square and a thickness of 1 mm was formed by applying a pressure of 300 MPa to the obtained mixed powder with a press. This compression-molded body was pre-sintered by holding in a vacuum at a temperature of 900 ° C. for 1 hour. This temporary sintered body was coined under a pressure of 500 MPa so that the true density was 97% or more. Thus, the electrical contact material 31 was obtained.

  From Table 3, the Vickers hardness at least at the normal temperature of the electrical contact material is obtained even in the case of a breaker for a large current having a rated current value of 100 A using the electrical contact material 31 made of silver-graphite-tungsten carbide (Ag-Gr-WC). In a state (high temperature) where heat is generated by flowing a large current by relatively increasing to 55 or more, further increasing the deflection amount to 0.5 mm or more, and suppressing the oxygen content to 100 ppm or less. It can be seen that by configuring the electrical contact material so as not to be deformed, not only the consumption rate after the overload test but also the consumption amount after the short circuit test can be reduced.

[Example D]
In this example, as an example corresponding to the above-described embodiment, the fixed-side electrical contact material 31 according to the following Examples D1 to D9 was manufactured. The fixed-side electrical contact material 31 according to Comparative Examples D1 to D4 in which the average particle size of the tungsten carbide powder and the content of tungsten carbide were outside the preferred range of the present invention was produced in the same manner as in the example of the present invention. A welding test was carried out using each of the breakers for a large current having a rated current value of 100 A, which was constructed by incorporating each of these electrical contact materials 31. The movable-side electrical contact material 21 was made of a material containing 50% by mass of silver and the balance being tungsten carbide.

  The average particle diameter of the graphite (Gr) powder used for producing the electrical contact material 31 in the examples and comparative examples of the present invention, the graphite (Gr) content in the produced electrical contact material 31, tungsten carbide ( Table 4 below shows the average particle diameter of the WC) powder and the content of tungsten carbide (WC) in the produced electrical contact material 31. Also, the evaluation results for the welding test are shown in Table 4. In addition, the numerical value underlined in Table 4 shows that it is outside the preferable range of this invention.

  The method for measuring the deflection, bending strength, hardness, oxygen content and density of the electrical contact material 31 is the same as in Example A described above. The method of welding test of the breaker for high current and the evaluation of the welding test will be described later.

(Examples D1-D9) (Comparative Examples D1-D4)
In Examples D1 to D9 and Comparative Examples D1 to D4, electrical contacts of silver-graphite-tungsten carbide (Ag-Gr-WC) -based materials containing graphite (Gr) and tungsten carbide (WC) with the contents shown in Table 4 The material 31 was produced as follows.

  The graphite (Gr) powder and the tungsten carbide (WC) powder having the average particle diameter shown in Table 4 and the silver (Ag) powder having the average particle diameter of 3 μm have the graphite content and the tungsten carbide content shown in Table 4. In a vacuum mill (100 Pa) using a ball mill for 30 minutes. By applying a pressure of 300 MPa to the obtained mixed powder with a press, a disk-shaped compression molded body having a thickness of 300 mm and an outer diameter of 80 mm was formed. This compression-molded body was pre-sintered by holding it in hydrogen gas at a temperature of 950 ° C., which is a reducing gas atmosphere, for 1 hour. This temporary sintered body was coined under a pressure of 1100 MPa so that the true density was 97% or more. The presintered body that has been subjected to coining processing is preheated by holding in an inert gas atmosphere of nitrogen gas at a temperature of 800 ° C. for 2 hours, and then an extrusion pressure of 100 GPa is applied, whereby the cross section is 10 mm square. Extrusion was performed to form a rod-like body. The obtained rod-shaped body was cut into a thickness of 1 mm to produce an electrical contact material 31.

(Welding test of breaker for high current)
In the welding test, a breaking current of 5000 A was set at a load voltage of 265V. As test methods, set the breaker to a circuit where a 5000 A cutoff current flows at a load voltage of 265 V, and set the breaker in the O OFF state (a test in which a cutoff current flows when the breaker switch is ON and the current is cut off) The test for forcibly turning on the switch and cutting off the current instantaneously) was performed according to the following procedure. That is, in this welding test, one O duty and five CO duties were performed in this order as operation duties. And the welding condition of the electrical contact material 31 during a welding test or after a welding test was evaluated. Table 4 shows the evaluation of the welding condition, “◎” when the contacts are not welded at all, and when the breaker is easily removed by ON / OFF of the breaker (light welding) “○”, simply by ON / OFF of the breaker When it does not come off (heavy welding), it is indicated by “x”.

  From Table 4, in the breaker for large current having a rated current value of 100A, silver-graphite-tungsten carbide having an average particle size of tungsten carbide of 40 nm to 150 nm and a content of tungsten carbide of 2 mass% to 4 mass%. It can be seen that the welding after the interruption test by the short circuit test could be prevented by configuring the electrical contact material with the system material.

  It should be considered that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is shown not by the above embodiments and examples but by the scope of claims, and is intended to include all modifications and variations within the meaning and scope equivalent to the scope of claims. .

  For example, in the above embodiments and examples, an example in which the electrical contact material 31 of the present invention is applied to the stationary contact member 30 of the breaker 10 has been described. However, the present invention is not limited to this example, and the breaker is not limited thereto. The electric contact material of the present invention may be used for any of the ten movable side contact members 20 or the fixed side contact member 30.

  In the above-described embodiment and examples, an example in which the electrical contact material 31 of the present invention is used for the breaker 10 as an example of a switch is shown, but the present invention is not limited to this example. The electrical contact material of the present invention may be used for a switch (switch device) other than a breaker such as an electromagnetic switch.

  The electrical contact material of the present invention is used by being incorporated into a breaker for large current having a rated current value of 100 to 3200A or a breaker for small current having a rated current value of 1 to 60A.

  10: Breaker, 21, 31: Electrical contact material.

Claims (9)

  An electrical contact material comprising 4% by mass to 7% by mass of graphite, the balance containing silver and inevitable impurities, a deflection of 0.5 mm or more, a Vickers hardness of 55 or more, and an oxygen content of 100 ppm or less.   The electrical contact material according to claim 1, wherein the bending strength is 210 MPa or more.   The electrical contact material according to claim 1, wherein the average particle diameter of the graphite is 40 nm or more and 8 μm or less.   The electrical contact material according to claim 1, further comprising tungsten carbide.   The electrical contact material according to claim 4, wherein the tungsten carbide has an average particle size of 40 nm or more and 3 μm or less, and the tungsten carbide content is 2 mass% or more and 4 mass% or less.   The electrical contact material according to claim 5, wherein the tungsten carbide has an average particle size of 40 nm or more and 150 nm or less.   An electrical contact material containing 0.5% by mass or more and 2% by mass or less of graphite, the balance containing silver and inevitable impurities, a deflection of 0.8 mm or more, a Vickers hardness of 40 or more, and an oxygen content of 100 ppm or less.   The electrical contact material according to claim 7, wherein the bending strength is 120 MPa or more.   The electrical contact material according to claim 7, wherein the average particle diameter of the graphite is 40 nm or more and 8 μm or less.

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