JP2006111956A - Electrical contact material and general-purpose switch obtained by using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrical contact material in which the increase in temperature caused by the instability of contact resistance in the conventional electrical contact material and the respective characteristics of deposition resistance, consumption resistance and workability are improved without using Cd in connection with an environmental problem. <P>SOLUTION: The Ag-oxide-based electrical contact material used for a general-purpose switch controlling a load of an 80 to 300 V AC voltage and a 5 to 25 A rated current is composed of, by weight, 3.8 to 10.5% CuO and 1.0 to 6.0% ZnO, and the balance Ag. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to an electrical contact material suitable for a general-purpose switch used in so-called home appliances, homes and office automation equipment. Naturally, it is an electrical contact material that does not contain Cd related to environmental problems. Even when the switch is miniaturized, it is excellent in welding resistance and wear resistance, and has low contact resistance. The present invention relates to an electrical contact material capable of suppressing a temperature rise as much as possible.

  An electrical contact that mechanically opens and closes an electrical circuit is generally called an electrical contact. This electrical contact is a metal-to-metal contact that allows the current and signal flowing through the contact to be transmitted without any problems, or when the electrical contact is disconnected. It is necessary to satisfy the characteristics that can be separated without any problem. Although this electrical contact is structurally simple, it is known that various physical or chemical phenomena occur on the contact surface. For example, adsorption, oxidation, sulfurization, synthesis of organic compounds, It is accompanied by very complicated phenomena such as melting, evaporation, consumption, and transition accompanying electric discharge, and there are many unexplained points from an academic viewpoint. When these phenomena occur, the contact function of the electrical contact is hindered, and in some cases, the contact function stops (for example, welding), and the performance and life of an electrical product or the like incorporating the electrical contact is determined. This means that the electrical contact is one of the important components that determine the life and performance of an electrical product or the like.

  Among them, general-purpose switches used in so-called home appliances, homes, office automation equipment, etc., have been rapidly downsized in recent years, and electrical contact materials using conventional technologies are standards for welding resistance, pressure resistance, and temperature rise. There was clearly a limit in satisfying

  Currently, Ag-CdO-based contact materials are almost always used for this general-purpose switch. This Ag—CdO-based contact material is well known as being well balanced in terms of welding resistance, wear resistance, and stability of contact resistance, which are contacts required for general-purpose switches.

General purpose switches are often used with continuous energization because of their use, and there is a risk of burns and fire due to heat generation due to voltage drop at the contact point during energization, so the temperature rise characteristics of the contact part are very important. ing. It is widely known that Ag—CdO-based contact materials are particularly excellent in this temperature rise characteristic because of their low and stable contact resistance when the contacts are closed. This temperature rise characteristic is stipulated in the UL standard that the temperature rise when the rated current of the switch is continuously supplied must be 30 ° C. or less from the ambient temperature.

However, Cd is an element harmful to the human body, and its production and use are not preferred because of the recent environmental problems. Further, since July 2006, use in Europe has been prohibited, and a contact material that replaces the Ag—CdO-based contact material is required for general-purpose switches.

Next, as an electrical contact material not using Cd, an Ag—SnO ₂ —In ₂ O ₃ —NiO-based electrical contact material is known. This Ag—SnO ₂ —In ₂ O ₃ —NiO-based electrical contact material is excellent in welding resistance and wear resistance when used in relays. It has been pointed out that the resistance is unstable. It has also been found that when these electrical contact materials are actually applied to switches, the UL standard that the temperature rise is 30 ° C. or less cannot be satisfied.

  Further, Ag-CuO-based electrical contact materials are known as electrical contact materials that have low contact resistance and are stable. This Ag-CuO-based electrical contact material has a low and low contact resistance when used in a switch, and is an excellent material that can satisfy the UL standard with respect to temperature rise. However, since the material does not have sufficiently satisfactory characteristics regarding the welding resistance and wear resistance, how to improve the welding resistance and wear resistance has been a technical issue.

In response to this technical problem, for example, as disclosed in Patent Document 1, a method of adding a third metal element such as In or Sn, or as disclosed in Patent Document 2, a first method such as Mn, Sb, Ge, or the like. A method of adding three metal elements has been developed. However, these prior arts have many unsatisfactory properties in practical use as compared with Ag-CdO-based contact materials, and actually, there are almost no examples of use as substitutes for Ag-CdO-based contact materials.
JP 51-136171 A JP 51-137873 A

The present invention as the background circumstances described above has been made, the present invention provides environmental problems Ag-CdO-based electric contact material that has been conventionally _{used, Ag-SnO 2 -In 2 O} 3 -NiO Electric contact that has improved all of the problems of temperature rise due to instability of contact resistance, which is a disadvantage of electrical contact materials, and welding resistance and wear resistance, which are disadvantages of Ag-CuO electrical contact materials The material is provided. Then, by using the electrical contact material of the present invention, a general-purpose switch having excellent welding resistance, wear resistance, low contact resistance and the like even if it is further reduced in size is provided.

  In order to solve the above-mentioned problems, the present inventors have conducted intensive research and have come up with the following electrical contact materials. Specifically, in an Ag-oxide based electrical contact material used for a general-purpose switch that controls a load having an AC voltage of 80 V to 300 V and a rated current of 5 to 25 A, 3.8 to 10.5 wt% CuO and 1.0 to 6.0% by weight of ZnO and the balance Ag. In addition, the electrical contact material according to the present invention internally oxidizes an Ag—Cu—Zn alloy composed of 3.04 to 8.66 wt% Cu, 0.82 to 4.94 wt% Zn and the balance Ag. It is obtained by doing. And the electrical contact material which concerns on this invention becomes a very suitable thing as an electrical contactor of a general purpose switch.

  In the electrical contact material according to the present invention, an Ag-CuO-based electrical contact material in which CuO is dispersed in Ag is improved. In the previous study, the inventors have found that it is effective to add Te or Bi in order to improve the welding resistance of the Ag-CuO-based electrical contact material, and further add Te or Bi. In addition, it has been found that it is effective to add In or Zn, respectively, in order to improve the deterioration of workability caused by.

  Thereafter, the present inventors searched for a practically optimal electrical contact material composition for use in a general-purpose switch, which has a balance of both characteristics of welding resistance and wear resistance. At that time, it was assumed that the general-purpose switch was not required to have a higher level of characteristics than that of a relay. In other words, since the spring force is used to interrupt the contact in relays, etc., the pull-out force of the miniaturized relay is smaller, and in the ultra-small relay, the pull-out force is 10 g or less, and it has excellent welding resistance. Need to be. On the other hand, since a general-purpose switch is normally operated manually by a human, a pulling force of 50 g or more can be easily secured. For this reason, it has been found that the electrical contact material used for the general-purpose switch need not have a high level of welding resistance as required in the case of a relay.

  That is, the characteristics required for electrical contact materials suitable for general-purpose switches are (1) low contact resistance and stable contact resistance value during the use period of the switch, and (2) during the use period of the switch. Less consumption of the electrical contact material, that is, less consumption is directly correlated to the length of the durable life, and less consumption powder maintains the withstand voltage characteristics. (3) And welding resistance It has been found that sex is not required to be as high as required for relays.

In consideration of the characteristics required for the electrical contact material of such a general-purpose switch, the present inventors added TeO ₂ , Bi ₂ O ₃ , In ₂ O ₃ , and ZnO to the Ag—CuO-based electrical contact material, respectively. In addition, the influence on the above three characteristics and processing characteristics was examined. The results are shown in Table 1. Among the above four oxides, the present inventors have a good balance of characteristics with stability of contact resistance, wear resistance, and workability, and a total balance of four characteristics including welding resistance. From the viewpoint of stabilizing the contact resistance, it was found that the oxide that can be used as the electrical contact material is ZnO, and that the other three oxides may not be added. . And based on this investigation result, the present inventors developed the electrical contact material which concerns on this invention.

  When the amount of CuO is less than 3.8% by weight, it is difficult for the electrical contact material according to the present invention to have an electric contact material having a practical level of characteristics. As the amount of wear during opening and closing increases, the withstand voltage deterioration becomes significant when used in a switch. Practically, it is more preferably in the range of 3.0 to 7.0% by weight.

  ZnO as an electrical contact material according to the present invention is an additive that improves wear resistance without greatly deteriorating the stability of contact resistance. However, if it exceeds 6.0%, the contact resistance becomes unstable. Further, if it is less than 1.0%, practically sufficient wear resistance cannot be obtained. Practically, it is more preferably in the range of 2.0 to 5.0% by weight.

  The electrical contact material according to the present invention internally oxidizes an Ag—Cu—Zn alloy composed of 3.04 to 8.66 wt% Cu, 0.82 to 4.94 wt% Zn and the balance Ag. By doing so, the oxide of CuO and ZnO of the said content range can be contained in Ag, and it can be set as the electrical contact material in which the above-mentioned three characteristics and the total balance of processing characteristics were taken.

  According to the present invention, the contact resistance can be stably maintained at a low level, it has a very excellent wear resistance, has a welding resistance suitable for a general-purpose switch, and has a total of four characteristics excellent in processing characteristics. It is a balanced electrical contact material. And if an electrical contact is comprised with the electrical contact material of this invention, even if it is a switch miniaturized rather than before, it will become possible to aim at stability and long life of a contact resistance.

  One embodiment of the present invention will be described based on examples described below. Examples 1 and 2 are electrical contact materials having the composition (% by weight) shown in Table 2, and Comparative Examples 1 and 2 and Conventional Examples 1 to 5 show electrical contact materials for comparison with the examples. .

  For the electrical contact materials of Examples 1-2, Comparative Examples 1-2, and Conventional Examples 1-4, an ordinary high-frequency melting furnace was used to cast an Ag alloy of each composition into an ingot after melting. Next, the ingot was processed into a wire with a diameter of 6 mm by a hot extrusion method. Subsequently, the wire was processed to φ2 mm while being repeatedly annealed and drawn, and was cut at a length of 2 mm to produce a chip of φ2 mm × 2 mmL. This chip was subjected to internal oxidation treatment at an oxygen pressure of 5 atm and a temperature of 700 ° C. for 48 hours, and the chips after the internal oxidation treatment were collected and compression-molded to form a φ50 mm cylindrical billet.

  Subsequent to this compression processing, sintering was performed at 850 ° C. for 4 hours. This compression process and sintering process were repeated 6 times. Table 3 shows the composition (% by weight) after internal oxidation of each material.

  The billet subjected to the compression processing and sintering treatment was again made into a φ6 mm wire by a hot extrusion method. Subsequently, a wire rod having a diameter of 2.3 mm was processed by wire drawing, and a rivet contact having a head diameter of 3.5 mm and a head thickness of 1 mm was created by a header machine.

  The rivet contact described above is incorporated in a temperature rise measuring tester having an opening / closing mechanism with a contact force of 100 g, and after performing a pre-opening / closing operation of 12,000 times with a resistance load of AC250V, 20A, The temperature rise value was measured. Two measurements were made for each contact material. In addition, since the contact point at the time of contact closing changes for every opening and closing, it measured 3 times about each sample. It has been confirmed that these measured values of temperature rise are almost the same as the values obtained with an actual general-purpose switch.

Table 4 shows the temperature rise measurement results. In the UL standard, if one temperature rise exceeds 30 ° C., it cannot be certified, so it is necessary to evaluate the maximum temperature rise measured value for temperature rise characteristics. As can be seen from Table 4, Examples 1, 2 and Comparative Example 2 and Conventional Examples 1 and 2 are practically usable levels, but Conventional Examples 4 and 5 have a high temperature rise value of 69 ° C. It was. This indicates that it is difficult for Ag—SnO ₂ —In ₂ O ₃ —NiO and Ag—SnO ₂ -based electrical contact materials to satisfy the temperature rise standard when applied to a switch. In addition, in the Ag—ZnO—CuO-based contact material of this example, the temperature rise characteristics deteriorated as the added amount of ZnO increased, and the result stabilized as the amount of CuO increased.

  Further, when the amount of wear during opening and closing with the actual load described above was investigated, it was confirmed that Examples 1 to 4 had no practical problem, and in particular, in Examples 2 and 3, the wear resistance was excellent. .

  Finally, the results of observation of the metal cross-sectional structure (magnification 400 times) will be described. 1 shows a cross-sectional structure of Example 1, and FIGS. 2 and 3 show cross-sectional structures of Conventional Examples 1 and 4, respectively. In the cross-sectional structure of Example 1 shown in FIG. 1, it is confirmed that a relatively large oxide is dispersed. This structure has a cross section similar to that of the Ag—CdO electrical contact material of Conventional Example 1 shown in FIG. It turned out to be an organization. On the other hand, it was observed that the cross-sectional structure of Conventional Example 4 shown in FIG. 3 is a state in which very fine oxides are dispersed. In general, when the contact surface is melted by an arc generated during opening and closing of the contact, it is said that fine oxides are more likely to cause aggregation of the oxide, and that aggregation causes a temperature rise. It is considered that the validity of the theory was supported by the results of the tissue observation.

  The electrical contact material of Example 1 is considered advantageous for the temperature rise accompanying energization because relatively large oxides are dispersed. And in order to ensure the wear resistance in addition to having good characteristics against such temperature rise, by adding Zn to such an extent that the good temperature rise characteristics are not impaired, the conventional Ag-CuO system The present invention has realized a suitable electrical contact material for general-purpose switches that eliminates the problems of wear resistance and welding resistance in electrical contact materials.

  In summary, the electrical contact material according to the present invention has an environmental problem (no cadmium is used), a temperature rise problem (contact resistance is stable), and a wear resistance problem ( It can be said to be an excellent electrical contact material suitable for a general-purpose switch that can solve these four problems at the same time.

The metal cross-section structure | tissue observation result of Example 3. FIG. The metal cross-section structure | tissue observation result of the prior art example 1. FIG. The metal cross-section structure | tissue observation result of the prior art example 4. FIG.

Claims (3)

In an Ag-oxide-based electrical contact material used for a general-purpose switch that controls a load having an AC voltage of 80 V to 300 V and a rated current of 5 to 25 A,
An electrical contact material comprising 3.8 to 10.5% by weight of CuO, 1.0 to 6.0% by weight of ZnO, and the balance Ag. 2. The alloy according to claim 1, which is obtained by internal oxidation of an Ag—Cu—Zn alloy comprising 3.04 to 8.66 wt% Cu, 0.82 to 4.94 wt% Zn, and the balance Ag. Electric contact material. A general-purpose switch using the electrical contact material according to claim 1 as an electrical contact.

Images