JPH10177821A - Electric contact and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric contact used for distribution circuit breaker rated at 10A or more or used for a leakage circuit breaker etc. SOLUTION: Within the range from 8μm to 80μm of an electric contact surface 5, a surface layer 1 is composed of a 0% to 6% cadmium(Cd), a 0.1% to 1.5% tin(Sn), a 0.15% to 1.2% nickel(Ni), and a less than 0.2% silver alloy for rest impure elements, while its inside of surface layer 1 is composed of a 14% to 19% cadmium(Cd), a 0.3% to 1.5% tin(Su,) a 0.22% to 1.2% nickel(Ni), and a less than 0.2% silver alloy for rest impure elements, which constitutes an inner layer 2, which has a double layer structure composed of the surface layer 1 and inner layer 2, and is desirable to have the micro Vicker's hardness with 45mHv to 125mHv for both surface layer 1 and inner layer 2. It is possible to produce the electric contact by the molding method of spraying the surface layer 1 or the molding method of and inner layer 2. It is possible to produce the electric contact by the molding method of sprying the surface layer 1 or evaporating the target material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a circuit breaker for power distribution,
The present invention relates to an electric contact used for an earth leakage breaker or the like.

[0002]

2. Description of the Related Art In general, electrical contacts are provided for power distribution circuit breakers, no-fuse breakers, earth leakage breakers, circuit protectors, safety breakers, and other breakers used for distribution boards (hereinafter collectively referred to simply as breakers). Is used. Ag alloys are widely used as electrical contacts for these breakers. This Ag alloy is Ag
It is usually an oxide dispersion strengthened alloy in which In oxide, Sn oxide, Cd oxide, Bi oxide, Co oxide, Ni oxide, Sb oxide, Ca oxide and the like are dispersed. .

[0003] The characteristics required of this electrical contact include:
There are welding resistance, initial temperature characteristics, temperature characteristics after an overload test, temperature characteristics after a durability test, insulation characteristics after a cutoff test, and the like. However, some of these characteristics have mutually opposite characteristics. For example, there is a trade-off relationship between the temperature characteristic and the welding resistance, and therefore, in order to improve the temperature characteristic, the welding resistance must be sacrificed.

Until now, it has been impossible to select a contact that sufficiently satisfies all of these required characteristics due to the above trade-off.

[0005] Above all, the rated current is 200 A, 400 A
For a breaker contact of 100 A or more, mainly for A, it was difficult to achieve both temperature characteristics (particularly initial temperature characteristics and temperature characteristics after an overload test) and welding resistance. For example, even if the welding resistance is good, the initial temperature performance is deteriorated, and the initial temperature (the lower the better) shows a high value, or the state where the good and bad cases occur irregularly occurs in a so-called large variation state. Was.

Japanese Unexamined Patent Publication Nos. 62-97213 and 58-189913 disclose an electric contact having a two-layer structure which is laminated on top and bottom. A two-layer structure composed of a material having good conductivity and a material having high hardness, or a two-layer structure composed of a conductor having wear resistance and welding resistance and a conductor having good arc breaking is handled.

[0007]

Some of the above-mentioned contact characteristics have mutually opposite characteristics, and it is difficult to develop an electric contact having good characteristics for all of the characteristics. there were. In particular, in the case of an electrical contact for a breaker with a rated current of 100 A or more, especially 225 A, 400 A, which the present application recommends to use for its application, both welding resistance and temperature characteristics (the smaller the temperature rise due to energization, the better). It was difficult.

[0008] The reason is that it is difficult to develop an electrical contact that satisfies both characteristics that are originally in a trade-off relationship, and that the ideal contact alloy composition and structure required to satisfy the individual required characteristics are required. Had not been elucidated. For example, in the case of a contact having a rated current of 225 A, how should a combination of a contact alloy composition and a structure necessary for improvement of welding resistance be, and a contact alloy composition and a structure required for improvement of initial temperature characteristics? It was not always clear how the combination should be and how it differs from the optimal combination when the rated current is 50A.

Further, since the optimum contact alloy composition and structure for the initial temperature characteristic and the optimum contact alloy composition and structure for the welding resistance are different, it is difficult to have the different contact alloy composition and structure simultaneously. It is. Even if a two-layer method such as that of the present application is adopted to have the same combination, the most suitable combination thereof, for example, what kind of contact alloy composition, what ratio, and what state are combined It was unknown.

[0010]

Means for Solving the Problems From the surface of an electric contact used for a circuit breaker (breaker) having a rated current of 100 A or more,
Cadmium (Cd) of 0% or more and 6% or less and tin (Sn) of 0.1% by weight%
1.5% or less, nickel (Ni) is 0.15% or more and 1.2% or less, and the balance is a silver alloy having an impurity element of 0.2% or less. Cadmium (Cd) is 14% or more and 19% or less, and tin (Sn) is 0.1% or more.
3% or more and 1.5% or less, nickel (Ni) 0.22%
It has a two-layered structure composed of a silver alloy of at least 1.2% and a balance of at least 0.2% of an impurity element, and the micro Vickers hardness of the surface layer and the inner layer is from 45 mHv to 125 mHv.
The following are used.

Further, antimony (Sb) is 0% by weight.
% To 2%, calcium (Ca) is 0% to 0.3
%, Bismuth (Bi) is 0% or more and 1% or less, cobalt (Co) is 0% or more and 0.5% or less, and indium (I
It is also preferable to use a silver alloy in which n) is 0% or more and 5% or less. The method of manufacturing the electric contact of the present invention includes a spraying method, a rolling method of a thin plate, a vapor deposition method, a method of immersing and washing in an acidic solution, followed by diffusion annealing of alloy elements, hot isostatic pressing (HIP) or hot extrusion. The surface layer can be formed by various methods.

According to the present invention, the electrical contact has a two-layer structure, the temperature characteristics are improved in the surface layer, the welding resistance is improved in the inner layer, and a contact alloy suitable for the two-layer structure with improved characteristics is provided. A composition is disclosed.

That is, since the surface layer has the effect of improving the temperature characteristic, the temperature characteristic is improved by the surface layer,
Conventionally, high Cd and S that degrade temperature characteristics
This is because it has been found that good temperature characteristics can be obtained even at n and Ni concentrations. As described above, in the present application, while achieving the required characteristics while improving the temperature characteristics in the surface layer, on the other hand, it has succeeded in obtaining high welding resistance by setting the contact alloy composition to a high Cd, Sn, and Ni concentration. is there.

In other words, the present invention cannot provide a sufficient effect only with the two-layer structure, and cannot provide a sufficient effect only by setting the contact alloy composition within the composition range indicated by the present invention. If the contact alloy composition is not in the above range even if it has a two-layer structure, high welding resistance cannot be realized unless the contact alloy composition alone has the composition range of the present invention. Does not happen. Therefore,
In the present invention, the combination of the contact alloy composition and the two-layer structure is extremely important, and has a relationship mutually complementing the characteristics to be improved.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention discloses the results of a study on the ideal two-layer structure and electrical contact composition of a contact suitable for a breaker having a rated current of 100 A or more, particularly 225 A, 400 A. The inventor has searched for an optimal contact alloy composition and structure for a contact for 225A, and as a result,
It has been found that the structure of the electric contact is preferably a two-layer structure as shown in FIG.

In FIG. 1, from the surface to the inside of A μm
In the inner layer 2 (deep portion), Cd is 14% or more and 19% or less, Sn is 0.3% or more and 1.5% or less,
Ni is 0.22% or more and 1.2% or less. (%
Is% by weight. same as below. ) More preferably, Cd
Is preferably 16% or more and 18% or less, Sn is preferably 0.4% or more and 1.4% or less, and Ni is preferably 0.24% or more and 1.0% or less.

On the other hand, in the surface layer 1 which is a portion shallower than A μm from the surface, Cd is 0% or more and 6% or less, Sn is 0.1% or more and 1.5% or less, and Ni is 0.15% or more and 1.2%. It is as follows.

The value of A is from 8 to 80 μm, preferably from 20 to 60 μm. Therefore, the surface layer 1 thinner than A μm described in the present invention does not refer to, for example, the modification of the surface layer thinner than a few μm from the surface in plating, which is usually applied to contacts. A thickness is 80
When the thickness exceeds μm, a part of the temperature characteristics is deteriorated, and the welding resistance is deteriorated. On the contrary, when the thickness is less than 8 μm, the effect shown in the present application is hardly recognized and the temperature characteristics are deteriorated. Also 2
As a result of repeating the trial production test, it was clarified that the temperature characteristics and the welding resistance characteristics exhibited the best values at 0 to 60 μm.

With respect to the contact alloy composition of the inner layer 2, if the Cd is less than 14%, the welding resistance is lowered, and if it exceeds 18%, the production becomes more difficult as the Cd becomes higher.
This is because, if not more than that, the production cannot be performed, but a portion called an agglomeration where the oxide is deposited tends to be generated inside the contact, which is not preferable in terms of temperature characteristics. Sn is 0.3
%, The welding resistance is low, and if it exceeds 1.5%,
The experimental results showed that the initial temperature characteristics and the temperature characteristics after the overload test deteriorated among the temperature characteristics. Regarding Ni, if it is less than 0.22%, the welding resistance is low, and
If it is 2% or more, the production becomes difficult and the temperature characteristics deteriorate.

In the surface layer 1, if Cd exceeds 6%, the temperature characteristics deteriorate, which is not preferable. Experimental results clearly show that when Sn is less than 0.1%, the welding resistance is low, and when Sn exceeds 1.5%, the initial temperature characteristics and the temperature characteristics after the overload test are deteriorated among the temperature characteristics. Became. Regarding Ni, if it is less than 0.15%, the welding resistance is low, and 1.2%
If it is more than the above, the temperature characteristics deteriorate.

Ni of the inner layer 2 is 0.22% or more and 1.2% or more.
Among the following, it is desirable that it is desirably 0.25% or more and 0.6% or less. This is because it has been found that the effect of improving the welding resistance is remarkable at 0.25% or more. Also, it is desirable for the temperature characteristic to be 0.6% or less.

Sb of the surface layer 1 and the inner layer 2 is 0% or more and 2
% Or less, Ca is 0% or more and 0.3% or less, Bi is 0% or more and 1% or less, Co is 0% or more and 0.5% or less, and In is 0% or more and 5% or less. These elements can be used for
Cd, Sn, N
As long as the concentration of i is within the above range, the intended 100
It has been found that contact performance suitable for a breaker of A or more can be expected.

Of course, if the standard values in the performance evaluation of the breaker (the above-mentioned standard values of the temperature and the welding resistance) are relaxed,
For example, Sn having a value of 0.3% or less, or 1.5% or more does not mean that it is not usable, but 0.3% or less.
Although it can be used even if the value is 5% or more, if considering that the breaker is an important device for safety and that there are variations in any product in actual use, It is desirable to be in the above Sn range. The same applies to Cd and Ni.

The elements contained in the electric contact are the above-mentioned elements, but it is easy to expect that the same effect can be expected in the case of the two-layer structure shown in the present invention even if a small amount of other elements is added. It can be imagined.

Surface layer 1 from the surface of the electrical contact to A μm
Has a Cd content of 0% or more and 6% or less, a Sn content of 0.1% or more and 1.5% or less, and a Ni content of 0.15% or more and 1.2% or less. As long as it is in the range
Sb is 0% to 2%, Ca is 0% to 0.3%, Bi is 0% to 1%, Co is 0% to 0.5%.
Hereinafter, it was confirmed that the same effect can be obtained even when an Ag alloy containing 0% or more and 5% or less of In is used. For example, In improves the initial temperature characteristics, but this effect is based on the effect of the present invention.

Sn, Ni, Sb, Ca, B of the surface layer 1
The i, Co, and In concentrations do not necessarily have to be lower than the concentration of the inner layer 2. Further, it is not necessary to use an expensive element such as Au for the surface portion. In addition, an Ag layer used for a normal Ag-based electrical contact (a pure Ag layer disposed on the opposite side to the contact surface for the purpose of improving the bondability with the Cu base metal, and also having a function different from the surface layer described in the present application) The position to perform is also different.).

As a result of investigating a method of forming a two-layer structure, evaporation, thermal spraying under reduced pressure, rolling and bonding of thin plates,
Regardless of the method of diffusion homogenization of elements by pickling and annealing, HIP diffusion bonding of thin sheets, and the method of extrusion, the same applies as long as the structure of the electrical contact and the contact alloy composition are within the range of the structure and contact alloy composition indicated by the present invention. Clarified that the effect of can be expected. Actually, a combination of the above methods can be considered,
It is not always necessary for performance and is not practical in terms of cost.

In addition, reduction of oxides in hydrogen,
A micro welding method is also conceivable, and the same effect can be expected as long as the structure of the contact and the contact alloy composition are in the range of the structure and the contact alloy composition shown in the present application, but the cost and the quality are stable in a large amount. It is not desirable in terms of mass production from the viewpoint of manufacturing the product at low cost, and is not always desirable from the viewpoint of maintaining the cleanliness of the bonding interface.

It is desirable that there is no large difference between the hardness of the inner layer and the hardness of the surface layer. This is because if the difference in hardness is large, it is difficult to realize a good bonding state during bonding. It has also been found that if the surface layer is too hard, the contact area will be small when the contacts come together. Further, if the inner layer is too hard than the surface layer, it is not preferable because cracks occur when the contact is used. Therefore, both the surface layer and the inner layer need to have a micro Vickers hardness of 45 to 125 mHv.

In the present application, by controlling the hardness, it is possible to obtain, for the first time, a contact suitable for a breaker having a rated current of 100A class or more, more preferably 200A or more, intended by the present application. Therefore, it is substantially different from JP-A-62-97213, in which a material having good conductivity is used as the second layer (lower layer) and a layer made of a material having high hardness is used as the first layer (upper layer). The first layer is made of Ag-SnO ₂
Instead of or In ₂ O ₃ system, the second layer nor pure Ag.

In the present application, the effect is most exhibited under a use condition in which the rated current is 100 A or more, especially 200 A or more. For example, if the rated current is 100A, 50k at 220V
A. When the rated current is 225A, the contact that exerts its effect when used in a breaker with a rated breaking current of 50kA at 220V is clarified. is not.

The surface layer 1 which is the first layer according to the present invention is
The main purpose is to improve the temperature characteristics, and to improve the welding resistance of the inner layer 2 as the second layer. Therefore, for example, as in Japanese Patent Application Laid-Open No. 58-189913, the first layer is made of a conductor having wear resistance and welding resistance, and the second layer is made of a conductor having a good arc break at short-circuit current. This is clearly different from the case of the present invention, and there is no need to form irregularities on the boundary surface between the first layer and the second layer as in the publication. Another difference is that no silver-lithium-based or silver-indium-based layer is used as the second layer as in the publication.

In general, a gradual concentration gradient from the surface toward the inside is generally observed at the contact which has been internally oxidized. However, the two-layer structure of the present invention, of course, does not exhibit the general concentration gradient observed in the internal oxidation. However, a portion shallower than A μm from the surface has a continuous structure within a few μm width at the boundary surface with the inside, and even though there is a change in chemical composition, the surface is clearly observed, for example, by an optical microscope. This shows the difference in the composition and composition between the part and the inside.

However, since it is an industrial product and the contact alloy composition and the metal structure of any electrical contact show a slight concentration gradient and a change in the metal structure, the internal layer and the surface layer are not changed. In each case, there may be a concentration gradient of the contact alloy composition found in general internal oxidation. The gradient of the hardness distribution accompanying the concentration gradient is also 45 to 1
If the hardness is in the range of 25 mHv (or 80 to 110 mHv), the hardness distribution may have a gradient.

It is known that Ag plating is applied to the contact surface by several μm, but this is not intended by the present invention. The thickness of the surface layer 1 referred to in the present invention is 8 to 80 μm from the surface, preferably 20 to 60 μm.
In addition, this surface layer is not pure Ag but contains other alloying elements, and is not intended for simple Ag plating.

Further, in the manufacturing process of the gas-shaped contact, heat treatment may be performed in a furnace to join the copper base metal and the Ag alloy. In this case, Cd on the surface of the Ag alloy
May be slightly dissipated into the furnace, which may result in a somewhat lower Cd concentration on the surface, which is also not intended by the present application. The layer having a low Cd concentration generated due to the dissipation in such a furnace is usually about 10 μm from the surface, and such a screw-type contact is used at a rated current of 200 A or more at which the present invention effectively exerts its effect. Is rarely done. Even if the rated current is 100A,
This screw-type electrical contact is sometimes used,
Normally only for fixed contacts, rated current 100A
Screw type contacts are rarely used for the above movable contacts.

Further, the decrease in the Cd concentration on the extreme surface observed when the sample is passed through the furnace is often accompanied by a decrease in the Sn concentration. However, the present invention is different from this, and the Sn concentration is high. It is intended to provide a contact alloy composition different from the contact alloy composition obtained in the furnace treatment.

In the present invention, Sb is 0% or more and 2% or more.
Hereinafter, Ca is 0% or more and 0.3% or less, and Bi is 0% or more and 1% or less.
% Or less, Co is 0% or more and 0.5% or less, and In is 0% or more and 5% or less even if it is an Ag alloy as long as it belongs to the scope of Claim 1. Similarly, other elements such as Ce usually added at 0.001% or more and 5% or less, Sb added at 0.1% or more and 6.2% or less, and 0.01% or more and 5% or less are added. L
i, Si added at 0.05% or more and 10% or less;
Fe added at not less than 01% and not more than 0.5%, 0.05%
Pb added at 0.1% or less, Cr and Sr added at 0.001% or more and 5% or less, Ti added at 0.5% or more and 5% or less, 0.5% or more and 5% or less , Te added at 0.5% to 5%, and Mn added at 0.5% to 5%.
AlF ₃ , MgF ₂ , C added at not less than 01% and not more than 3%
rF ₃ , CaF ₂ , Z added at 0.5% or more and 5% or less
n, Ge, Ga added at 1% or more and 3% or less, 0.0
It does not prevent the addition of Mg added at 1% or more and 0.1% or less.

In these cases, the effects of the contact alloy composition, hardness, and two-layer structure shown in claim 1 are the same as those without these elements, as long as they fall within the scope of claim 1. This is because the effect of can be expected. In other words, the present application does not prohibit the addition of a trace amount of an additive element to such an extent that the effect of the present application is not impaired within the range of the contact structure and the contact alloy composition of Cd, Sn, and Ni shown in the present application.

Example 1 A pair of 8 mm long, 6 mm wide, 2.5 mm thick and 6 mm long, 6 mm wide, 2 mm thick (the movable contact 6 and the fixed contact 7 attached to the base 4 in FIG.
Corresponds to. FIG. 2 (II) shows the fixed contact 7 for explanation.
Indicated by. Although FIG. 2 (II) shows a circular contact, a square contact or the like also applies. Each of the electrical contacts has a pure Ag layer 3 with a thickness of 10%, and the contact alloy composition is as shown in Tables 1 and 2 ("Plasma" in the column of "Method").
Applicable. Tables 3-6 are the same. ), And an alloy powder having a composition shown in Tables 3 and 4 was sprayed on the surface thereof (the surface opposite to the pure Ag) in an Ar + H ₂ atmosphere by a reduced pressure plasma spraying method. .

[0041]

[Table 1]

[0042]

[Table 2]

[0043]

[Table 3]

[0044]

[Table 4]

Prealloy powder was used as a raw material, and powder having a particle size of submicron to 2 μm was used. Ar was used as a carrier gas for the feed. During the thermal spraying, the tip of the thermal spraying gun is swung under automatic control to form the surface layer 1 by the uniform thermal spraying layer and to form the inside of the contact as a contact base material (often called a substrate). In order to increase the adhesion of the surface layer 1 by the layer 2 and the sprayed layer,
The substrate was exposed to a plasma flame and heated to perform thermal spraying.

Tables 5 and 6 show the resulting two-layer structure and hardness of the oxidized contact. The rated current of these contacts is 1
220V, 50k with various breakers over 00A
The breaking test, the initial temperature measurement, the temperature characteristics after the overload test, the temperature characteristics after the durability test, and the temperature characteristics after the short-circuit test were evaluated using the breaking current of A. The overload test condition was 5 times the rated current, and the test was performed 50 times, and the durability test was performed 5000 times at the rated current. Tables 5 and 6 show the test results. In addition, since the evaluation results differed depending on the evaluation breaker, the overall evaluation was shown as 5-1. The best result was indicated by 5, the lower limit of use was indicated by 3, and the worst result was indicated by 1.

[0047]

[Table 5]

[0048]

[Table 6]

Example 2 Each of a pair of electrical contacts having a length of 8 mm, a width of 6 mm, a thickness of 2.5 mm and a length of 6 mm, a width of 6 mm, and a thickness of 2 mm was provided with a pure Ag layer having a thickness of 10%. , Tables 1 and 2 (the description of “deposition” in the column of “method” applies. The same applies to Tables 3 to 6). The surface of the contact base material to be the internal layer 2 of the electric contact having the contact alloy composition.
On the surface opposite to the pure Ag, vapor deposition was performed by a magnetron sputtering method using a target having a contact alloy composition shown in Tables 3 and 4. The temperature of the substrate is maintained at 200 ° C. to prevent re-evaporation of Sn, and the pressure of the Ar atmosphere is several t
orr to several tens torr.

In order to improve the adhesion between the inner layer 2 of the contact as the base material and the surface layer 1 as the vapor deposition layer, the surface of the inner layer 2 of the contact is previously cleaned by ions generated by high frequency. After that, vapor deposition was performed. Then, the electrical contact obtained after the internal oxidation is subjected to a breaking test, an initial temperature measurement, a temperature characteristic after an overload test, a temperature characteristic after an overload test, and a temperature characteristic after a short circuit test in the same manner as in Example 1. Tables 5 and 6 show the evaluation results together with the hardness.

Example 3 The contact alloy compositions were as shown in Tables 1 and 2.
(The description of "sheet" in the column of the method corresponds.
Same for 6. ) Is prepared, and an Ag alloy foil having the composition shown in Tables 3 and 4 is coated on the upper surface thereof in an Ar atmosphere for 60 hours.
Bonded at 0 ° C. Pure Ag is further added to the obtained two-layer alloy plate.
The layer was heated at 600 ° C. in an Ar atmosphere and then rolled to produce a three-layer alloy plate, which was punched out into a chip-shaped 8 mm long, 6 mm wide, 2.5 mm thick, 6 mm long, 6 mm wide.
A pair of electrical contacts having a thickness of 2 mm and a thickness of 2 mm were prepared.

The contacts obtained after the internal oxidation were subjected to a breaking test, initial temperature measurement, temperature characteristics after an overload test, temperature characteristics after an overload test, and temperature characteristics after a short circuit test in the same manner as in Example 1. Are shown in Tables 5 and 6 together with the hardness value.

Example 4 The contact alloy compositions were as shown in Tables 1 and 2.
(The description of "acid + baked" in the column of the method corresponds.
Same for 6. ), An oxidation contact with a pure Ag layer was prepared, and the outer portion was immersed in an acidic solution to remove stains on the surface, and then annealed to promote diffusion of alloy elements. Thus, alloys having the compositions shown in Tables 3 and 4 were formed on the contact surfaces. Tables 5 and 6 show the structure and hardness of the resulting two-layer structure contact.

The contacts obtained after internal oxidation were subjected to a breaking test under the same conditions as in Example 1, initial temperature measurement, temperature characteristics after an overload test, temperature characteristics after an overload test, and temperature after a short circuit test. The properties were evaluated.

(Example 5) The contact alloy compositions were as shown in Tables 1 and 2.
(The description of "HIP" in the column of the method corresponds.
Same for 6. ), A plate having the composition shown in Tables 3 and 4 was adhered to the surface of the plate, and the joining surfaces were welded so that the two plates were airtight.

Thereafter, 700 ° C. × 1800 Kg / cm ² ×
Hot isostatic pressing (HIP) was performed in Ar gas under the condition of 2 h, a pure Ag layer was bonded to this two-layer plate, and the obtained plate was rolled and punched out to obtain a chip-shaped 8 mm long, horizontal chip. 6
mm, thickness 2.5mm, length 6mm, width 6mm, thickness 2
mm was made. Then, the contact obtained after internal oxidation is subjected to a breaking test under the same conditions as in Example 1, and an initial temperature measurement, a temperature characteristic after an overload test, a temperature characteristic after an overload test, and a temperature characteristic after a short circuit test are evaluated. did.

Example 6 The contact alloy compositions were as shown in Tables 1 and 2.
(The description of "extrusion" in the column of the method is applicable. Tables 3 to 6
The same is true. ) The powder obtained by oxidizing the powder was prepared by press molding to form a cylindrical member, and the powder having the composition shown in Tables 3 and 4 was oxidized therearound and integrated with the members shown in Tables 1 and 2 by press molding. And the cross-sectional shape when integrated is 80 diameter.
A cylindrical billet having a diameter of 80 mm and a length of 200 mm was prepared.

Then, after heating in an Ar atmosphere at 800 ° C. × 2 h, hot extrusion was performed with a die having two holes to obtain a plate shape. A pure Ag layer plate having a thickness is laminated and rolled, and punched out of the obtained plate having a three-layer structure, into a chip-shaped 8 mm long and 6 m wide.
m, thickness 2.5mm, length 6mm, width 6mm, thickness 2m
m pair of electrical contacts were produced. Then, the contact obtained after internal oxidation is subjected to a breaking test under the same conditions as in Example 1, and an initial temperature measurement, a temperature characteristic after an overload test, a temperature characteristic after an overload test, and a temperature characteristic after a short circuit test are evaluated. did.

The results of the tests of Examples 1 to 6 are shown in Tables 1 to 6 together with Comparative Examples. That is, the comparative examples in Table 2 are those in which the contact alloy composition of the inner layer is out of the present invention, the comparative examples in Table 4 are those in which the contact alloy composition in the surface layer is out of the present invention, and the comparative examples in Table 6 are the first. No. 11 has the contact alloy composition of the surface layer (including some internal layers), the next six have the contact alloy composition of the internal layer, the next three have the thickness and hardness of the surface layer, and the last comparative example Indicates that the rated current of the evaluation deviates from the present invention. As a result, the electrical contacts according to the present invention showed clearly superior temperature characteristics and welding resistance as compared with the comparative example.

[0060]

The present invention relates to a structure suitable for an electric contact having a rated current of 100 A or more (a surface layer which is shallower than A μm from the surface of the electric contact and an inner layer which is deeper than A μm from the surface of the electric contact). By clarifying the contact alloy composition (contact layer alloy composition of the surface layer and contact layer alloy composition of the inner layer) and hardness, excellent temperature performance (initial, after overload test, after endurance test, and after short-circuit breaking test) and It is possible to provide an electric contact having excellent welding resistance.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross section of an electric contact.

FIG. 2 is a conceptual diagram showing a pair of electric contacts (movable contact, fixed contact).

[Description of Signs] 1: Surface layer 2: Internal layer 3: Pure Ag layer 4: Base 5: Electric contact surface 6: Movable contact 7: Fixed contact

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01H 11/04 H01H 11/04 B

Claims (8)

[Claims] 1. An electrical contact for use in a circuit breaker (breaker) having a rated current of 100 A or more, wherein a surface layer of 8 μm to 80 μm from the surface of the electrical contact has a weight percentage of cadmium (Cd) of 0% to 6%. Hereinafter, tin (Sn) is 0.1
% To 1.5%, nickel (Ni) is 0.15% to 1.2%, and the balance is a silver alloy containing 0.2% or less of an impurity element. % Cadmium (Cd) is 14% or more and 19% or less, tin (Sn)
Is 0.3% or more and 1.5% or less, and nickel (Ni) is 0.1% or more.
It has a two-layer structure composed of a silver alloy of 22% or more and 1.2% or less, with the balance being an impurity element of 0.2% or less, and the surface layer and the inner layer have a micro Vickers hardness of 45 mHv or more and 1 or more.
An electrical contact, wherein the electrical contact is 25 mHv or less. 2. A silver alloy containing 0.2% or less of impurities,
Antimony (Sb) is 0% or more and 2% or less, calcium (Ca) is 0% or more and 0.3% or less, bismuth (B
2. The silver alloy according to claim 1, wherein i) is 0% or more and 1% or less, cobalt (Co) is 0% or more and 0.5% or less, and indium (In) is 0% or more and 5% or less. Electrical contacts. 3. The method according to claim 1, wherein the surface layer is formed by a thermal spraying method. 4. The method according to claim 1, wherein the surface layer is formed by rolling a thin plate. 5. The method according to claim 1, wherein the surface layer is formed by a vapor deposition method. 6. The method for producing an electrical contact according to claim 1, wherein a surface layer is formed by immersion cleaning in an acidic solution and diffusion annealing of an alloy element. 7. The method according to claim 1, wherein the surface layer is formed by hot isostatic pressing (HIP). 8. The method according to claim 1, wherein the surface layer is formed by hot extrusion.