JPS5825444A - Electric contact material - Google Patents

Abstract

PURPOSE:To obtain an Ag oxide compound electric contact material which has elevated melt-stick resistance, arc resistance and resistance, by uniformly dispersing a specific quantity of ZnO, SnO2 and Li2O into an Ag base. CONSTITUTION:Powder consisting of 5-30wt% Zn ZnO, 0.5-10% Sn of SnO2, and the Ag is mixed. This mixed powder is immersed into a solution of LiNO3, and while basing on LiO2, 0.001-1% Li is made to adhere. This mixed powder is molded and sintered, by which an electric contact material is obtained. As for this contact material, ZnO and a composite oxide Zn2SnO4 are subjected to be spher and are dispersed into an Ag base uniformly and finely, therefore, it is excellent in its thermal stability, also low in its contact resistance, is excellent in its melt-stick resistance, and also is rich in its workability.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to silver oxide-based contact materials, particularly silver-zinc oxide and tin monoxide-based electrical contact materials.

Requirements for contact materials include ■welding resistance, ■arc resistance,
Abrasion resistance, ■Low contact resistance.

Silver-zinc oxide contact materials are contacts with excellent contact resistance characteristics, but they have drawbacks such as welding resistance and oil resistance, so they have sufficient characteristics to be used as contact materials for medium loads such as electromagnetic switches and no-fuse breakers. There was a problem that was difficult to obtain.

This silver-zinc oxide contact material can be manufactured by either an internal oxidation method or a powder method. In the internal oxidation method, the maximum amount of zinc oxide that can be contained in the silver base is about 8% by weight in terms of metal weight when internal oxidation is carried out in an atmosphere of 1 atm and 0□.

This limit can be further reduced by adding other third elements to improve wear resistance and welding resistance. Therefore, in the internal oxidation method, it is not possible to contain the oxide and the amount of oxide necessary to improve the wear resistance and welding resistance in the silver base.

In addition, because the oxide particles are coarse and their distribution is uneven, the welding resistance and abrasion resistance are poor.On the other hand, when manufacturing by the powder method, there are limitations that occur when using the internal oxidation method.
The combination and amount of alloy compositions are free, but the sinterability is poor. Due to the residual p, the wear characteristics are inferior to those made using the internal oxidation method, and the insulation characteristics between the contacts are also generally inferior. .

For these reasons, silver-zinc oxide based electrical contact materials are not currently used as contact materials for small to large loads.

The present invention was made for the purpose of improving the performance of silver-zinc oxide alloys.

The material of the present invention relates to a silver-zinc oxide alloy made by a powder method, and by adding oxidation and tin to the silver-zinc oxide alloy, the welding resistance, arc resistance, and abrasion resistance are significantly improved. The present invention provides an electrical contact material in which the sinterability of silver-zinc oxide and tin oxide alloys is improved by further adding lithium oxide.

The present invention is a material consisting of zinc oxide, tin oxide, lithium oxide/residue, and the metal proportion of the oxide is 5 to 80% by weight of zinc.
It is an electrical contact material characterized by containing 0.5 to 10% by weight of tin and 0.001 to 1.0% by weight of lithium, and having a structure in which oxides are uniformly dispersed in a silver base. The present invention will be explained in detail below.

Like cadmium oxide, the silver-zinc oxide alloy contains zinc oxide, which easily sublimates and evaporates at relatively low temperatures, so it is difficult to aggregate on the surface layer of the contact after the contact is opened and closed. Therefore, it has excellent low contact resistance characteristics and good current conductivity.

However, the welding resistance and arc resistance are inferior compared to silver-cadmium oxide alloys and silver-tin oxide alloys.

When tin oxide is added to the silver-zinc oxide tin monoxide alloy, zinc oxide and tin oxide react to form a composite oxide of Zn2SnO. This is because, as shown in Figure 1, when the tin oxide added by sintering has a higher zinc oxide content, it reacts with the zinc oxide contained in a larger amount to form a composite oxide Zn2SnO. Almost no remains. Since Zn25nO is more thermally stable than ZnO, it is thought to improve wear resistance, arc resistance, and welding resistance.

It is thought that lithium oxide reacts with the composite oxide Zn25n04 and zinc oxide, prevents evaporation loss of zinc oxide at the sintering temperature (880°C to 930°C), and promotes sintering. On the other hand, zinc oxide particles are grown and their shape is made spherical to reduce the contact interface between the oxide and silver. For this reason, the hardness of the alloy decreases, but the workability such as rollability improves.
It is thought that wear resistance and arc resistance can be improved.

Lithium may be added in powder form, such as lithium carbonate, or in liquid form, dissolved in a suitable solvent for ease of mixing, such as an aqueous lithium nitrate solution.

The reason why the content of alloying elements is limited to the above range in the present invention is as follows. Zinc oxide is 5% by metal weight
If it is less than 30% by weight, the effect of improving the welding resistance will be small, and if it exceeds 30% by weight, the abrasion resistance will deteriorate and the contact resistance will increase, making it undesirable as a contact material. If tin oxide is less than 0.5% by weight of the metal, the amount of the composite oxide Zn2Sn04 produced by reaction with zinc oxide will be small, and the effect of improving arc resistance, wear resistance, and welding resistance will be small.

Moreover, if it exceeds 10% by weight, the workability of the contact material deteriorates, and the contact resistance increases significantly. If the amount of lithium oxide is less than 0.001% by weight of the metal, the effect of improving sinterability will be small. If lithium were to exist in the form of lithium oxide, it would be highly hygroscopic and would absorb moisture from the atmosphere, making it undesirable as a contact material. Also, since lithium is a substance with a low work function, it easily releases electrons. For this reason, if the contacts are uniformly distributed over the contact surface, the contacts will wear out on average, which will actually improve the wear resistance.
Too much will accelerate wear and tear. Although it cannot be specifically defined, if it exceeds 1.0% by weight, moisture absorption and wear and tear of the contacts will increase.

As described above, the electrical contact material of the present invention has zinc oxide/composite oxide Zn25n04 spheroidized and is uniformly and finely dispersed in the silver base, so it has excellent welding resistance, arc resistance, and abrasion resistance, and is easy to process. rich in

Next, examples of the present invention will be described.

<Example 1> Electrolytic Av powder, commercially available zinc oxide, and tin oxide at 75·=20=
A total of 500 parts were blended at a weight ratio of 5 parts. After mixing this in a ball mill, 0.2% in terms of lithium oxide was added by immersion treatment in an aqueous lithium nitrate solution.

After sintering at 880 to 930°C for 1 hour, the material was hot rolled to obtain an electrical contact material with a thickness of 0.7 mm.

<Example 2> Electrolytic A2 powder, commercially available zinc oxide, and tin oxide in a ratio of 75:15:1
A total of 500 tr was blended at a weight ratio of 0. An electrical contact material was obtained in the same manner as in Example 1 except for the above.

<Example 3> Electrolytic A9 powder, commercially available zinc oxide, and tin oxide in a ratio of 66:82:2
A total of 500 tr was blended at a weight ratio of . This was mixed with an attritor for 5 hours and then immersed in a lithium nitrate A aqueous solution to add 0.5% in terms of lithium oxide. This mixed powder was embossed at B t /cd, and 6
Preliminary sintering was carried out at 50°C for 40 minutes. Next, the vacuum 1O-2To
#-1 After sintering at 880 to 980°C for 1.5 hours at Shichijogyo, hot forging and machining were performed to obtain an electrical contact material with a thickness of 0.7 wire.

The electrical contact material obtained in the above example was incorporated into a commercially available safety breaker and subjected to temperature rise after overload-endurance test and overload-short circuit test under the conditions shown in Table 1 to reach dielectric strength and welding. The number of times until The results are shown in Table 2. For comparison, the results for the contact point A, -10% cdo are also listed in Table 2. Table 1 Temperature rise Overload test AC220V, 150A, power factor 0
．． 8 tests Opening/closing times 50 times Endurance test AC220V, 2OA Opening/closing times 5000 times Above test, temperature rise measured Short circuit test After overload test, AC220V, 1500A.

At power factor 0.75, 1 pole 0 → C0-2 poles 0-CO-2 poles CO
Repeat until welding.

As is clear from the results in Table 2, the above-mentioned electrical contact materials have excellent thermal stability, low contact resistance, and excellent welding resistance, so their industrial value is great. .

[Brief explanation of drawings]

FIG. 1 is an X-ray diffraction diagram showing oxides produced by sintering the alloy of the present invention. 1: Ay, 2: ZnO, 3: Zn25n
O. Left 1 Letter of amendment to figure procedure September 21, 1980 Haruki Shimada, Commissioner of the Japan Patent Office 2 Name of the invention and device Electrical contact material 3 Relationship to the case of the person making the amendment Patent applicant address 5-15 Kitahama, Higashi-ku, Osaka name(
213) Representative and President of Sumitomo Electric Industries, Ltd. Masao Kamei 4, Agent Address: 1-1-3 Shimaya, Konohana-ku, Osaka City, Sumitomo Electric Industries, Ltd. Drawing 7, Contents of the Amendment Revised the drawing as shown in the attached sheet. I will.

Claims (1)

[Claims] (1) A material consisting of zinc oxide, tin oxide, lithium oxide, and leftover food, in which the metal proportion of the above oxides is 5 to 30% by weight of zinc,
An electrical contact material containing 0.5 to 10% by weight of tin, 0.001 to 1.0% by weight of lithium, and having a structure in which oxides are uniformly dispersed in the A2 base.