JP2014192007A - Electric contact material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that, in a conventional electric contact material obtained by composing a refractory material such as W, WC or Mo only with a high-electroconductivity material such as Ag or Cu, arc generation points are concentrated in current cutoff and the refractory material may be dropped or worn by melting the high-electroconductivity material.SOLUTION: An electric contact material is provided which reduces cubic volume consumption caused by current cutoff. An oxyboride of which the job function is low and which does not inhibit calcination of the electric contact material is added to a conventional electric contact material and by diffusing arc generation points, an electric contact material improved in consumption resistance can be obtained.

Description

  The present invention relates to an electrical contact material used for a contact of an electrical device or an electrical circuit, and more particularly to an electrical contact material optimum for a contact of various switching devices such as a circuit breaker, a disconnecting switch and a switch of a DC electrical circuit.

For circuit breakers, disconnectors and switches used in high-voltage, high-current circuits such as power transmission and distribution networks, tungsten (hereinafter referred to as W) and copper (hereinafter referred to as Cu) composite materials, W and silver (hereinafter referred to as Ag) Many proposals have been made on composite materials, electrical contacts using a composite material of tungsten carbide (hereinafter referred to as WC) and Ag.

  When a large current is opened and closed, an arc is generated between the two electrical contacts that are opened and closed.

Once an arc is generated by opening and closing a contact, it takes time to extinguish the arc. The contact portions that are both ends of the arc are continuously exposed to high heat until the arc is extinguished. This phenomenon is not solved even if the inside of the apparatus is filled with an atmosphere in which an arc is likely to disappear (for example, in SF ₆ gas).

  The contact material must be a good conductor. In addition, the electrical contact must be made of a material that is not easily melted or evaporated by the arc. It is difficult to solve the problem using a single material. Therefore, Cu-W materials, Ag-W materials, and Ag-WC materials, which are a combination of a good conductor and a material having a high melting point and a high boiling point, are mainly used for the application.

  Ag-WC material with excellent oxidation resistance is a medium load aerial switch, Ag-W material with relatively superior oxidation resistance is a high load aerial switch, and oxidation resistance is inferior However, Cu-W materials having excellent wear resistance exhibit excellent functions in oil, gas, and vacuum circuit breakers.

  On the other hand, materials such as Cu or Ag are used as energization contacts that do not interrupt current. Among low-pressure air circuit breakers and wiring circuit breakers, those having a large capacity use Ag-W materials, Ag-WC materials, or the like as arcing chips. As the main contact (main contact), Ag-nickel (hereinafter referred to as Ni) is used. Further, as an arc / current-carrying contact having a medium capacity or less, an Ag-WC material, an Ag-cadmium oxide (hereinafter referred to as CdO) material having excellent current-carrying properties and welding resistance are frequently used.

  In addition, there are an increasing number of cases where direct current interruption such as power generation using natural energy such as wind power and sunlight, direct current power transmission with low power loss, and in-vehicle relays used in electric vehicles and the like is performed.

The problem that has not been solved is that the evaporation / consumption due to the arc opening / closing of the electrical contacts is large and the life is not sufficient.

Patent Document 1 and Patent Document 2 both attempt to disperse the arc generation point by adding boride. However, when boride is used, firing of the high-melting-point material is inhibited, and spots are formed inside the electric contact material. As a result, the problem of poor wear resistance remains.

JP 2002-294384 A JP 2003-203543 A

The technical problem of the present invention is to obtain an electrical contact material that is less consumed by an arc generated by opening and closing the electrical contact.

The electrical contact material of the present invention is a material used for electrical equipment and electrical circuit contacts, and is selected from a first component selected from W and WC, which are high melting point materials, and Cu or Ag, which is a high electrical conductivity material. At least one selected from a second component to be selected and a low work function material of calcium (hereinafter referred to as Ca), strontium (hereinafter referred to as Sr), barium (hereinafter referred to as Ba), magnesium (hereinafter referred to as Mg) and rare earth metals. The third component of the species, and carbon (hereinafter C), chromium (hereinafter Cr), cobalt (hereinafter Co), Ni, iron (hereinafter Fe), phosphorus (hereinafter referred to as materials) that improve contact strength and reduce contact resistance. P), vanadium (hereinafter referred to as V) and at least one or two or more fourth components selected from the group consisting of these compounds.

  In the electrical contact material of the present invention, the first component is 20 to 90% by mass, the second component is 80 to 10% by mass, and the third component and the fourth component are 0.1 to 14 in total. It is preferable that it is below mass%.

The material structure of the electrical contact material of the present invention can be roughly classified into the following two.
(Tissue 1) Material structure (tissue 2) having a porous structure in which the first component, the third component, and the fourth component have continuous open pores, and filling the open pores with the second component Material structure in which the first component, the third component, and the fourth component are dispersed in the second component matrix The material structure of the electrical contact material of the present invention may be any of the above.

  In the electrical contact material of the present invention, the porous body preferably has an average particle diameter of the first component and an average particle diameter of the third component of 20 μm or less.

  The electrical contact material of the present invention allows the first component to be doped with at least one element selected from the group consisting of aluminum, potassium, and silicon.

  The electrical contact material of the present invention allows the second component to be alloyed with at least one metal selected from the group consisting of Cr, Co, Ni, Fe, and P.

  The electrical contact material of the present invention preferably has a porosity of 10% or less.

  The electrical contact material of the present invention preferably has a conductivity of 10% IACS or more.

The electrical contact material according to the present invention is particularly suitable for use as an electrical contact for DC current interruption. In that case, the use as a cathode is particularly suitable.

According to the present invention, it is possible to reduce the volume consumption of electrical contacts due to current interruption.

Simplified schematic of the test circuit with the movable side joined as the movable side and fixed side of the electrical switchgear as the anode and the fixed side as the cathode Comparison graph of volume consumption of test piece after performing block test in Fig. 1 Simplified schematic of the test circuit with the movable side joined as the movable side and fixed side of the electrical switchgear as the cathode and the fixed side as the anode Comparison graph of volume consumption of test pieces after performing blocking test in FIGS. 1 and 3

  Hereinafter, embodiments of the present invention will be described in detail.

This electrical contact material includes a first component selected from W and WC which are high melting point materials, a second component selected from Cu and Ag which are high electrical conductive materials, and Ca, Sr, which are materials having a low work function. C, Cr, Co, Ni, Fe, which is a material that affects the strength of the contact material and reduces contact resistance, with at least one third component selected from Ba, Mg, and rare earth metal borates. P, V and at least one or two or more fourth components selected from the group consisting of these compounds are contained.
Although borides and oxides having a low work function are known to improve discharge characteristics, borates provide further improvements in discharge characteristics. Further, borate does not inhibit densification of the electrical contact material compared to boride and oxide. Therefore, the third component was a borate. The reason why the fourth component is added is to provide an appropriate strength to the electrical contact material to prevent damage and deformation, and to reduce the contact resistance of the electrical contact material.
The blending ratio of the first component is 20 to 90% by mass for the first component, 80 to 10% by mass for the second component, and the total of the third component and the fourth component is 0.1% by mass. It is preferable that it is% -14 mass%.

In the electrical contact material according to the present invention, the material structure can be roughly classified into the following two.
(Tissue 1) Material structure in which the first component, the third component, and the fourth component have a porous structure having continuous open pores, and the second component fills the open pores (tissue 2) Material structure in which the first component, the third component, and the fourth component are dispersed in the matrix of the second component The material structure of the electrical contact material according to the present invention may be any of the above.
The porous body preferably has a structure in which the third component and the fourth component are dispersed in the first component.
In particular, the porous body preferably has an average particle diameter of the first component and an average particle diameter of the third component of 20 μm or less.
If the average particle size of the first component of the porous body exceeds 20 μm, the material structure becomes inhomogeneous, and it may be difficult to develop good characteristics. If the average particle size of the third component of the porous body is greater than 20 μm, the variation in arc resistance characteristics may increase. If the average particle size is 10 μm or less, the desired characteristics are more easily obtained.

  When the first component is 20% by mass or more, the arc resistance characteristics can be kept high. On the other hand, when the first component is 90% by mass or less, the electrical conductivity can be maintained at 10% IACS or more. If the blending amount of the first component is 30 to 70% by mass and the second component is 70 to 30% by mass, the desired characteristics are easily obtained.

  If the total of the third component and the fourth component is 14% by mass or less, the material structure is less likely to be inhomogeneous and the variation in characteristics tends to be reduced. If the total of the third component and the fourth component is 0.1% or more, the desired characteristics are easily obtained.

  When the porosity of the electrical contact material of the present invention is 10% or less, arc resistance characteristics are easily obtained. If the porosity is 5% or less, the desired characteristics are easily obtained.

If the electrical contact material of the present invention has an electrical conductivity of 10% IACS or more, heat generation during energization is reduced, and thus a temperature rise resistance property is more easily obtained.

Next, an example of the manufacturing method of the electrical contact material according to the present invention will be described.

  First, at least one selected from a powder of a first component selected from any of W and WC, which are high melting point materials, and each borate of Ca, Sr, Ba, Mg, and rare earth metals, which are materials having a low work function. A third component powder and at least one selected from the group consisting of C, Cr, Co, Ni, Fe, P, V, and these compounds, which are materials that affect the strength of the material and reduce contact resistance Alternatively, after mixing and molding two or more kinds of fourth component powders, in an inert gas atmosphere such as nitrogen or argon, a reducing gas atmosphere such as hydrogen, or a vacuum atmosphere Firing is performed to produce a porous body in which the third component and the fourth component are dispersed in the first component. The fourth component may be the simple substance or a compound such as NiP or VC.

  About the borate powder, the borate powder selected from the borate described above is prepared.

  The borate powder of this embodiment is a mixture of Ca, Sr, Ba, Mg, rare earth metal oxide or carbonate and a boron-containing substance such as boron carbide or boron carbonate, and heat-treated in an oxidizing atmosphere. Can be obtained by:

  The first component powder is preferably one having an average particle diameter of 1 to 20 μm.

  The powder of the third component is preferably one having an average particle diameter of 1 to 20 μm.

  The firing temperature is preferably 1000 to 1500 ° C. when the first component is W, and 800 to 1300 ° C. when the first component is WC. When the firing temperature is produced under the firing conditions, it is easy to obtain good mechanical properties.

  Next, the porous body and any one of Cu and Ag are selected, and the second component having any one of a powder form, a particle form, a pellet form and a plate form is accommodated in a container such as a crucible, for example, Infiltrating the second component into the porous body by heating at an appropriate temperature in an inert gas atmosphere such as argon, a reducing gas atmosphere such as hydrogen, or a vacuum atmosphere. To produce an electrical contact material.

  The heating temperature for infiltrating the second component is preferably 1080 ° C. or higher when the second component is Cu, and 960 ° C. or higher when the second component is Ag. When the second component is Cu, if the heating temperature is less than 1080 ° C., it is difficult to sufficiently infiltrate Cu into the porous body. When the second component is Ag, it is difficult to sufficiently infiltrate Ag into the porous body when the heating temperature is less than 960 ° C. If the temperature is too high, pores are likely to be generated inside the material. Therefore, when the second component is Cu, it is preferably 1800 to 1180 ° C., and when the second component is Ag, it is preferably 960 to 1060 ° C.

  In addition, the electrical contact material according to the present invention mixes and molds the first component, the second component, the third component, and the fourth component, and then forms an inert gas atmosphere such as nitrogen or argon, such as hydrogen. It can also be manufactured by firing at a temperature of, for example, 900 to 1000 ° C. in either a reducing gas atmosphere or a vacuum atmosphere.

  As described above, according to the present invention, the first component, which is a high melting point material, the second component, which is a highly electrically conductive material, and the fourth component, which is a material that affects the strength and contact resistance of contacts. In this system, a borate having a low work function as the third component and a high electron emission characteristic is blended, for example, dispersed in the first component to disperse the arc, so that the second component Cu or Since the selective loss of Ag can be suppressed and the dropout and wear of the first component can be greatly reduced, the arc resistance can be improved.

  In the case of direct current interruption with a constant polarity, the arc resistance can be improved by dispersing the arc by using an electrical contact containing a borate having a low work function on the cathode side that emits electrons.

  In addition, since the main material is the first component, which is a high melting point material, and the second component, which is a high electrical conductive material, it has excellent welding resistance, low contact resistance, and good electrical conductivity.

Therefore, according to the present invention, it is possible to provide an electrical contact material having excellent welding resistance, low contact resistance, good electrical conductivity, and excellent arc resistance.

(Preparation of electrical contact material sample)
Hereinafter, preferred embodiments of the electrical contact material according to the present invention will be described.

  First, W powder having an average particle diameter of 4 μm, powdered Ni having an average particle diameter of 1 μm, and powdered strontium borate powder having an average particle diameter of 7 μm were prepared.

The strontium borate is obtained by mixing SrBO ₃ and B ₂ O ₃ having an average particle diameter of 5 μm at a mass ratio of 2: 1 and firing at 1050 ° C. for 30 minutes in an air atmosphere. used.

  These powders were mixed with a Henschel mixer for 30 minutes to obtain a mixed powder. At this time, six types of powders were manufactured by changing the blending amount of strontium borate.

  Next, the mixed powder was die-pressed at a pressure of 50 MPa to obtain a plate-like molded body.

A porous body having continuous open pores is obtained by providing a concave portion where the molded body can be sufficiently accommodated in a heat-resistant container, placing the molded body therein, and performing sintering for 60 minutes at 1150 ° C. in an H ₂ atmosphere. It was.

On this porous body, a sufficient amount of plate-like Cu was installed for infiltration, and in this state, infiltration was performed at H ₂ atmosphere at 1100 ° C. for 20 minutes, and the continuous open pores were filled with Cu. The structure electrical contact material was obtained.

  Excessive Cu that could not be infiltrated from the obtained material was removed, and cutting was performed with a milling machine to form a rectangular parallelepiped test piece, and an electrical contact used for the test was produced. The total mass of W and Ni was 70 mass%, and the infiltrated Cu was 30 mass%. Moreover, W and Ni were 69.6 mass% and 0.4 mass%, respectively. The porosity of this test piece was less than 3%. When the electrical conductivity of this test piece was measured, the electrical conductivity was 50% IACS.

  The strontium borate contained in the electrical contact is 0% by mass as a comparative sample 1, and 0.1% by mass, 0.5% by mass, 1.0% by mass, 1.5% by mass and 2.0% by mass are added. The obtained samples were designated as Sample 1 to Sample 5, respectively.

When the cross sections of Samples 1 to 5 were compositionally analyzed by XRD (X-ray diffraction), Ni could not be observed as a simple substance. When the borate was measured by XRD, 90% Sr ₂ B ₂ O ₅ and 10% SrB ₂ O ₄ were found in the peak intensity ratio.

Two types of electrical tests were carried out using Comparative Example 1 and Sample Examples 1 to 5 as a test piece that was brazed to a brass pedestal having a rectangular parallelepiped shape with a brazing material BAg-24 defined by JIS standards.

Example 1
In Example 1, the movable side is the anode, the fixed side is the cathode, the same test piece is used, the test voltage is 230 VAC, the test current is 2500 A, the energization time is 0.5 cycles, the test interval is 30 seconds, and the contact size is 2 mm × 5 mm × 5 mm. The blockage test was conducted 5 times under the condition, and the volume wear rate was calculated from the mass wear amount of the test piece and compared (FIGS. 1 and 2).

Compared with comparative sample 1, the cathode of sample 1 is clearly less consumed, the cathode of sample 2 is about 65%, and the cathodes of samples 3 to 5 are about 40% of consumption, especially sample 4 is the least consumed. As a result. Although not shown in the figure, a sample in which 5% by mass of strontium borate was added to the comparative sample was manufactured and the same test was performed. As a result, the amount of consumption was about 80% that of Comparative Sample 1. .

(Example 2)
In order to compare the influence of the polarity and the influence of the movable side fixed side, the same test as in Example 1 was performed using Sample 4 (1.5% by mass of strontium borate) and changing the polarity. (Figs. 3 and 4)
From the test results, it was found that the volume consumption on the cathode side was suppressed to 60% to 70% compared to the volume consumption on the anode side, regardless of the movable fixation.

(Example 3)
As Example 3, the movable side is the anode, the fixed side is the cathode, the same test piece as in Example 1 is used, the test voltage is 230 VAC, the test current is 100 A, the energization time is 1 second, the test interval is 2 seconds, the test piece size is 2 mm × The open / close test was performed 20,000 times under the condition of 8 mm × 8 mm, and the contact resistances of the test pieces were compared.

In Samples 1 to 5, the increase in contact resistance was lower than that in Comparative Sample 1, and the contact resistance value after opening and closing 20,000 times was reduced to about 70% of Comparative Sample 1.
In any of the tests of Examples 1 to 3, no welding occurred.

Example 4
The test was carried out using the test piece obtained by replacing the W portion of the test piece used in Example 1 with WC as Comparative Sample 2 and Samples 6-10.
The cathode of sample 6 is clearly less consumed than comparative sample 2, the cathode of sample 7 is about 65%, and the cathodes of samples 8 to 10 are about 40%, especially sample 4 is the least consumed. As a result.

(Example 5)
The test was carried out using the test piece obtained by replacing the W portion of the test piece used in Example 3 with WC as Comparative Sample 2 and Samples 6-10.
The samples 6 to 10 had a lower increase in contact resistance than the comparative sample 2, and the contact resistance value after opening and closing 20,000 times was reduced to about 70% of the comparative sample 2.
In any of the tests of Examples 4 and 5, no welding occurred.

(Example 6)
First, W powder (first component) having an average particle size of 2 μm, Ag (second component) having an average particle size of 2 μm, strontium borate powder (third component) having an average particle size of 7 μm, and an average particle size of 100 μm The following C powder and VC powder (fourth component) having an average particle diameter of 2 μm were mixed with a Henschel mixer for 30 minutes to obtain a mixed powder. At this time, six types of powders were manufactured by changing the blending amount of strontium borate.

  Next, the mixed powder was die-pressed at a pressure of 50 MPa to obtain a plate-like molded body.

By providing a concave portion where the molded body can be sufficiently accommodated in a heat-resistant container, placing the molded body therein, and sintering for 60 minutes at 1150 ° C. in an H ₂ atmosphere, W particles and strontium borate particles in Ag And a material having a structure in which C particles are dispersed.
The obtained material was put into a mold and pressed to increase the density, and then cut with a milling machine to form a rectangular parallelepiped test piece, thereby producing an electrical contact used for the test. The total mass of WC and the fourth component was 21 mass% (WC 12 mass%, C 3 mass%, VC 6 mass%), and the mass of Ag was 79 mass%. The test piece porosity was less than 3%. When the electrical conductivity of this test piece was measured, the electrical conductivity was 40% IACS.

  The strontium borate contained in the electrical contact is 0% by mass as a comparative sample 3 compared to the first component and the second component, 0.1% by mass, 0.5% by mass, 1.0% by mass, and 1. They are 5 mass%, 2.0 mass%, and 5.0 mass%, and are designated as Sample 11 to Sample 16, respectively.

When the cross sections of the samples 11 to 16 were observed with an EPMA (electron beam microanalyzer), it was confirmed that most of the borate was present at the grain boundaries of Ag and WC. When the borate was measured by XRD, 90% Sr ₂ B ₂ O ₅ and 10% SrB ₂ O ₄ were found in the peak intensity ratio.

The same test as in Example 1 was performed using Comparative Example 3 and Sample Examples 11-16.
As a result of the test, the sample 11 is hardly changed compared to the comparative sample 3, the sample 12 is about 90%, the samples 13 to 16 are about 80%, and the sample 16 is about 90%. There was little consumption.

The samples 11 to 16 showed a lower increase in contact resistance than the comparative sample 3, and the contact resistance value after opening and closing 20,000 times decreased to about 80% of the comparative sample 4.
In Samples 11 to 16, no welding occurred in any of the tests.

Claims (9)

A material used for electrical contacts,
A first component selected from W and WC;
A second component selected from Cu and Ag;
At least one or two or more third components selected from any borate of Ca, Sr, Ba, Mg and rare earth metals;
An electrical contact material containing at least one selected from the group consisting of C, Cr, Co, Ni, Fe and P alone or a compound consisting of any two or more thereof, and a fourth component selected from two or more. The electrical contact material according to claim 1, wherein the electrical contact material is a direct current blocking electrical contact material. The electrical contact material according to claim 2, wherein the electrical contact material is a cathode material of an electrical contact for interrupting a direct current. 20 to 90% by mass of the first component,
80 to 20% by mass of the second component,
The electrical contact material according to any one of claims 1 to 3, wherein the third component and the fourth component together are 0.1 mass% or more and 14 mass% or less. 5. The electrical contact material according to claim 1, wherein an average particle diameter of the first component and an average particle diameter of the third component are both 20 μm or less. The first component, the third component and the fourth component have a shape of a porous body having continuous open pores,
The electrical contact material according to any one of claims 1 to 5, having a structure in which the second component is filled in open pores. In the matrix of the second component,
The electrical contact material according to claim 1, wherein the electrical contact material has a structure in which the first component, the third component, and the fourth component are dispersed. The electrical contact material according to any one of claims 1 to 7, wherein the porosity is 10% or less. The electrical contact material according to any one of claims 1 to 8, wherein the electrical conductivity is 10% IACS or more.

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