JP6753022B2 - Electrical contacts and contacts - Google Patents

Description

The present invention relates to an electrical contact that can be used in an opening / closing device such as a breaker or a magnet switch, and a contact using this electrical contact.

In order to extend the life of switching equipment such as magnet switches, the best shortcut is to improve the wear resistance of the electrical contacts themselves against arcs when the current is repeatedly cut off, and to extend the life of the equipment. , Various research and development have been carried out to improve the wear resistance of the electrical contacts themselves.

Among them, Ag-SnO _{2-In 2} O ₃ system Ag oxide-based electrical contacts have a high frequency of current interruption by opening and closing like magnet switches and relays, and long life is strongly required due to their usage conditions. In this case, it is known that the method of joining the base material of the electric contact and the contact and the quality of the joining state have a great influence on the life of the electric contact itself.

As a method for joining such an Ag oxide-based electric contact and a base material, a method is generally used in which an electric contact having a pure Ag layer formed on one side of the electric contact material is used and the pure Ag layer and the base material are joined. (For example, Patent Document 1 and Patent Document 2). This is because when the electrical contact material is directly bonded to the base material of the contactor, the electrical contact material itself is made so that it is difficult to weld to the adjacent member, so that the mechanical strength is increased at the bonding interface with the base material. This is because it cannot be obtained.

Further, it is known that when the electric contact is joined to the base material, the joining state greatly affects the life of the electric contact during use. If the bonding condition is poor, it will be insufficient to release the arc heat from the electrical contacts to the base material and contacts when the current is repeatedly cut off, and the temperature of the contact surface will rise, which will reduce the wear resistance during opening and closing, resulting in electricity. It adversely affects the durability of contacts. In addition, there is a risk that the electrical contacts may come off due to insufficient joint strength with the base material. As described above, since the quality of the joint leads to the long and short life of the electrical contact and the reliability in terms of safety, it has been required to manage the optimum joint strength.

Further, in recent years, in switching devices such as magnet switches and relays, the miniaturization of the devices has progressed, and the shape of the electrical contacts themselves has tended to be designed to be small, and the usage environment of the electrical contacts has become more severe. Under these circumstances, Ag-SnO _{2-In 2} O ₃ system Ag oxide-based electrical contacts are required to have a longer life by improving wear resistance performance more than before.

Japanese Unexamined Patent Publication No. 2006-241596 Japanese Unexamined Patent Publication No. 2008-152971

Ag-SnO _{2-In 2} O ₃ based Ag oxide-based electrical contact material is made of Ag-Sn-In based internally oxidizing alloy by subjecting it to internal oxidation treatment, and is responsible for wear resistance and welding resistance. _It is an electrical contact material having an internal oxidized structure in which oxides such as ₂ and In ₂ O ₃ or composite oxides are dispersed in the Ag matrix. A microscopic observation of the inside of the center of this electrical contact material shows that at the end of the internal oxidation treatment, a layer (dilute oxide layer) with a thin oxide and close to pure Ag was formed in the center of the material. It has an oxidized structure. However, in practical use of switching equipment, when the electrical contact material is consumed by the arc during repeated current interruption and the oxide dilute layer is exposed on the outermost surface of the contact, the welding resistance and wear resistance are temporarily deteriorated and unstable. Therefore, it cannot be said that there are no safety problems.

Furthermore, in recent years, from the viewpoint of reducing the material price and improving the wear resistance by saving Ag, there is a tendency to increase the amount of oxide instead of reducing the amount of Ag in the Ag oxide-based electrical contact material, but on the other hand, the amount of oxide increases. Then, the difference in the expansion coefficient of the volume before and after the internal oxidation becomes large, and the shape of the electrical contact material tends to collapse before and after the internal oxidation. This tends to be the same even when an internally oxidizing alloy having a pure Ag layer formed on one side is subjected to an internal oxidation treatment. Due to this tendency, when the electrical contacts are brazed to the base material, the flatness of the joint surface of the electrical contacts becomes unstable, and it is becoming difficult to fix the electrical contacts to the contacts completely horizontally. is there. In addition to brazing, diffusion in a furnace is also used as the joining method. However, even in this method, since the joint surface of the electric contact and the base material is bonded by solid phase diffusion in a heat treatment furnace under an inert atmosphere, a more precise and flat joint surface is required. If the electrical contacts are not fixed horizontally to the contacts, the form of wear due to the arc when using the opening / closing device will be biased, so the electrical contacts will not be consumed evenly, and as a result, the life of the electrical contacts will be shortened. is there.

On the other hand, in an electric contact having a pure Ag layer formed on one side, when the number of times of opening and closing in the switch device is repeated, the bonding interface between the electric contact material and the pure Ag layer may become the starting point of peeling. Of course, if peeling occurs, there is a risk that the electrical contact material will fall off, and it will be insufficient to release the arc heat to the base material and contacts, which will cause the temperature of the contact surface to rise and withstand opening and closing. There is also a problem that the wearability is lowered and the wear of the electric contacts is increased (hereinafter referred to as peeling wear).

Therefore, the present invention provides an inexpensive electrical contact that has no oxide dilute layer, has a flat joint surface, and can prolong the service life by improving wear resistance performance more than before by reducing peeling wear. It is an object of the present invention to provide a contactor using this.

The structure of the electrical contact according to the present invention can be manufactured by performing a special internal oxidation treatment. In the conventional internal oxidation treatment, Sn, In, etc., which are solute elements contained in the Ag—Sn—In-based internal oxidizing alloy under high temperature and high oxygen partial pressure, permeate into Ag from the surface layer of the internal oxidizing alloy. By combining with the stored oxygen, it is precipitated as an oxide such as SnO ₂ or In ₂ O _{3 in the} Ag matrix. At this time, a phenomenon occurs in which solute elements such as Sn and In diffuse from the inside of the internally oxidizing alloy toward the outer surface layer.

This phenomenon of solute element diffusion is caused by an internal oxide layer having an internal oxide structure formed of oxides precipitated inward from the surface of the internal oxidizing alloy, and oxide precipitation has not occurred over time. This is a phenomenon in which the concentration of solute elements differs from that of the oxide layer, and the solute elements diffuse from the non-oxidized layer to the surface layer in order to fill this concentration gradient. Therefore, at the end of the internal oxidation treatment, a dilute oxide layer in which the oxide is diluted is formed because the solute element that diffuses is insufficient in the central part of the material.

Therefore, in the present invention, in this internal oxidation treatment, an internal oxide layer is formed only on one side of the internally oxidizing alloy having the same composition, and oxygen permeation from the other side of the internally oxidizing alloy is inhibited. It is characterized by forming an unoxidized layer directly below the inhibition surface.

That is, the structure of the present invention is an electrical contact having a structure in which an internal oxide layer is formed only on one side of an internally oxidizing alloy having the same composition and an unoxidized layer is provided on the other side. With the electrical contacts having such a structure, the oxide dilute layer is not formed in the center inside the material, and the non-oxidized layer can play a role of bonding the contact with the base material. In addition, there is virtually no bonding interface between the internal oxide layer and the non-oxidized layer, and there is no risk of peeling wear starting from the bonding interface.

Here, the definition of the unoxidized layer in the present invention is a layer in the internal oxidizing alloy that is different from the internal oxide layer and in which no oxide is precipitated, and is a surface on which the internal oxide layer is formed. An unoxidized layer located on the opposite surface, preferably in the range of 50% or less in terms of the cross-sectional ratio of electrical contacts. The cross-sectional ratio referred to here is a value expressed as a percentage (%) obtained by dividing the layer thickness of the unoxidized layer by the total thickness of the electrical contacts.

Although it depends on the thickness of the electrical contacts and the usage environment of the opening / closing device, the non-oxidized layer itself that does not contain oxide has almost no wear resistance, so if the cross-sectional ratio of the non-oxidized layer exceeds 50%, There is a concern that the durability of the electrical contacts will decrease due to the decrease in the cross-sectional ratio of the internal oxide layer. In addition, the height difference from the height position of the non-oxidized layer, which has no wear resistance, is smaller than the height position of the oxide dilute layer at the electrical contact where the oxide thin layer is formed, which is a conventional technique. This is because the advantageous effect of obtaining the stable wear resistance of the present invention is reduced. The lower limit of the cross-sectional ratio is not particularly limited as long as the non-oxidized layer, which plays the role of bonding to the base material, has a minimum cross-sectional ratio that satisfies the bonding strength required by the type of opening / closing device.

During the internal oxidation treatment of the present invention, an oxide is precipitated in the Ag matrix from one side of the material to form an internal oxide layer, which causes an expansion force of volume increase, but the surface on the opposite side of the internal oxide layer. Since there is an unoxidized layer having appropriate ductility and mechanical strength, the unoxidized layer cancels out this expansion force, and as a result, the internal oxidation treatment is completed without breaking the shape of the electrical contacts. As a result, the flatness of the non-oxidized layer used for the joint surface with the base material becomes horizontal.

Further, since the Ag content of the unoxidized layer used for the joint surface is smaller than that of the conventional electric contact forming the pure Ag layer, it is possible to provide an inexpensive electric contact by reducing the amount of expensive Ag used.

The amount of each constituent element added to the Ag—Sn—In based internal oxidizing alloy to which the technical idea of the present invention is applied contains Sn and In in a total amount of 3 to 14% by mass, and Zn, Cu, Sb, and Ni. , Bi, Co and Fe are preferably selected from the group and contain at least 1 to 4% by mass in total, and the balance is composed of Ag and unavoidable impurities.

Here, the reason why Sn and In are set to 3 to 14% by mass in total is that if it is less than 3% by mass, the wear resistance is insufficient due to the lack of oxide, and the unoxidized layer is closer to pure Ag. This is because the mechanical strength is insufficient and the expansion force of the internal oxide layer cannot be offset. This is because if it exceeds 14% by mass, the precipitated oxide becomes excessive and aggregates, so that the contact resistance increases, which is not preferable as a characteristic of the electric contact. In addition, the unoxidized layer tends to be unable to completely cancel the expansion force of the volume increase during the internal oxidation treatment due to the excess oxide.

The reason why at least one selected from the group of Zn, Cu, Sb, Ni, Bi, Co and Fe was set to 1 to 4% by mass in total is that if it is less than 1% by mass, the internal oxide structure is refined. This is because the mechanical strength of the unoxidized layer is insufficient and the expansion force of the internal oxide layer cannot be offset. This is because if it exceeds 4% by mass, an oxide film is formed on the surface layer and the formation of a uniform internal oxidized structure is inhibited.

The present invention has a structure in which an internally oxidizing alloy composed of a specific additive element and a specific composition has an internal oxide layer on one side surface layer of the material and an unoxidized layer on the other side adjacent to the internal oxide layer. It was used as a contact point. With such a configuration, there is no risk of peeling wear because there is virtually no bonding interface between the internal oxide layer and the non-oxidized layer, and the dilute oxide layer is not formed in the center inside the material. Stable oxidation and wear resistance can be obtained. Further, since the unoxidized layer having a lower Ag content than the conventional pure Ag layer can play the role of the bonding surface of the contact with the base material, it is possible to provide an inexpensive electric contact material. Furthermore, since the non-oxidized layer suppresses the shape collapse of the electrical contact material and maintains the flatness of the joint surface to enable horizontal and strong bonding with the base material, the length due to stable consumption of the electrical contact is long. The life can be extended.

Explanatory drawing which shows the cross section of the electric contact by this invention Explanatory drawing showing the cross section of the electric contact by the prior art Explanatory drawing which shows the cross section of an electric contact and a contact according to this invention.

1 Internal oxide layer 2 Unoxidized layer 3 Oxide dilute layer 4 Pure Ag layer 5 Contact base material

Examples and conventional examples of the present invention are shown in Table 1, and the processing steps of these electrical contacts will be described. The embodiment of the present invention is not limited to the following examples, and can be appropriately adjusted according to the dimensions and characteristics of the target electrical contact.

It contains a total of 3 to 14% by mass of Sn and In, and a total of 1 to 4% by mass of at least one selected from the group of Zn, Cu, Sb, Ni, Bi, Co and Fe, and has a balance. An ingot was obtained by a compounding and dissolution method so as to form an internally oxidizing alloy composed of Ag and unavoidable impurities. Then, surface milling, rolling, annealing and cutting were repeated to prepare an internally oxidizing alloy plate having a plate thickness of 1.5 mm, a width of 100 mm and a length of 400 mm. By repeating a plurality of steps of applying anhydrous boron oxide only to this one surface and performing heat treatment at 475 ° C. in an argon atmosphere, a thick oxide film is formed on the surface coated with anhydrous boron oxide, and then internal oxidation treatment is performed. It was. Here, the reason why the oxide film is formed on only one surface is that the formation of the oxide film inhibits the occlusion of oxygen during the internal oxidation treatment and forms the unoxidized layer directly under the oxide film.

As the conditions for the internal oxidation treatment, it is preferable to select the optimum temperature and pressure according to the composition of the internal oxidizing alloy and the characteristics required for the switching device, but here, internal oxidation is performed for comparative evaluation with each example. The treatment conditions were unified at a temperature of 800 ° C. and an oxygen partial pressure of 1 MPa, and the treatment time was adjusted so that the cross-sectional ratio of the unoxidized layer was 10%.

After internal oxidation treatment, the entire peripheral edge of the plate is cut, grinding and barrel polishing are performed to remove the oxide film, and the plate is punched into a 10 mm square square shape by press punching to form a single-sided surface layer of the material. An electrical contact having a structure shown in FIG. 1 having an internal oxide layer and an unoxidized layer on the other side adjacent to the internal oxide layer was used (Examples 8 to 14).

The plurality of electrical contacts thus obtained were joined to a base material made of oxygen-free Cu by diffusion in a furnace to produce movable contacts and fixed contacts for a magnet switch (FIG. 3). The conditions for diffusion in the furnace were 750 ° C. × 20 min in a nitrogen atmosphere.

It should be noted that none of the movable contacts and fixed contacts after joining by diffusion in the furnace had electrical contacts not fixed horizontally to each contact.

Further, except that the internally oxidizing alloy having a composition range different from that of the present invention is used, as a result of producing electrical contacts in the same processing process as described above and joining them to each contact, the flatness of the joint surface is impaired. , There were a plurality of electrical contacts whose electrical contacts were not fixed horizontally to each contactor (Examples 1 to 7).

Conventional Example An ingot was obtained by a compounding and melting method so as to obtain an internally oxidizing alloy similar to that of the Example, and then face-cutting, rolling, annealing and cutting were performed to obtain a desired plate. A pure Ag plate was composited on one side of this plate by hot rolling clad, and the obtained composite material was rolled to prepare an internally oxidizing alloy plate having a plate thickness of 1.5 mm, a width of 100 mm, and a length of 400 mm. Internal oxidation treatment is applied to this, and after cutting the entire peripheral edge of the plate and barrel polishing, it is further punched into a 10 mm square square shape by press punching to form an internal oxide layer on one side of the material and the inside of the internal oxide layer. An electrical contact having a structure shown in FIG. 2 having a dilute oxide layer in the center and a pure Ag layer on the other side adjacent to the internal oxide layer was used (conventional examples 1 to 8).

As the conditions for the internal oxidation treatment, the treatment time was adjusted so that there was no unoxidized layer inside the internally oxidizing alloy, and complete internal oxidation was performed. For comparative evaluation with Examples, the temperature and oxygen partial pressure during the internal oxidation treatment were set to 800 ° C. and oxygen partial pressure of 1 MPa under the same conditions as in Examples, and the thickness of the pure Ag layer was unoxidized in Examples. The cross-sectional ratio of the layer was the same as 10%.

The plurality of electrical contacts thus obtained were joined to a base material made of oxygen-free Cu by diffusion in a furnace to produce movable contacts and fixed contacts for a magnet switch. The conditions for diffusion in the furnace were 750 ° C. × 20 min in a nitrogen atmosphere.

In addition, among the movable contacts and fixed contacts after joining by diffusion in the furnace, there were a plurality of movable contacts and fixed contacts in which the electrical contacts were not horizontally fixed to each contact due to the impaired flatness of the joint surface.

Comparative evaluation method between the present invention and the prior art The compositions of the internally oxidizing alloys in Examples and Conventional Examples are shown in Table 1. In addition, the flatness of the unoxidized layer or the pure Ag layer used for the joint surface of the contact with the base material was investigated before and after the internal oxidation treatment of the example or the conventional example. As a method for investigating the flatness, the internally oxidizing alloy plate before the internal oxidation treatment in the conventional example or the embodiment is placed on the surface plate, and spacers are inserted into the four corners of the internal oxidizing alloy plate to determine the joint surface. The gap between the board and the surface was measured. Further, even after the internal oxidation treatment, the voids at the same location were measured in the same manner. Those having no difference in voids before and after the internal oxidation treatment, that is, those having no change in the flatness of the joint surface are evaluated as A, and those having a change are evaluated as B, which are also shown in Table 1.

10 movable contacts and 10 fixed contacts with electrical contacts (Examples 1 to 14 and conventional examples 1 to 8), excluding those that are not horizontally fixed to each contact, are commercially available magnets with a rating of 80 A. Table 1 also shows the average value (mg) of consumption after opening and closing 1 million times in the AC3 class test (according to JIS C 8201-3 and JIS C 8201-4-1), which are incorporated in each switch. The average value of wear (mg) is the average value per 10 weight differences obtained by subtracting the weight before the AC3 class test by the weight after the test in the contacts with the electrical contacts joined, and this value is used to determine the wear resistance. evaluated. In addition, the presence or absence of peeling wear after the completion of the test was investigated.

As a result, it was confirmed that the present invention has no oxide thin layer and no peeling wear, and is superior in wear resistance to the prior art.

Claims (3)

It contains Sn and In in total of 3 to 14% by mass, contains at least one selected from the group of Zn, Cu, Sb, Ni, Bi, Co and Fe in total of 1 to 4% by mass, and the balance is unavoidable with Ag. An electrical contact characterized by comprising an internal oxide layer formed on one side of an internally oxidizing alloy composed of impurities and an unoxidized layer formed on the opposite surface adjacent to the internal oxide layer. The electrical contact according to claim 1, wherein the unoxidized layer has a cross-sectional ratio of 50% or less of the entire electrical contact. A contactor for an opening / closing device, which is configured by joining the non-oxidized layer of the electrical contact according to claim 1 or 2 to a base material of the contactor.

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