JPH0474405B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing an electrical contact material, and more particularly, to a method for manufacturing a harmless sintered material for electrical contacts with excellent welding resistance. Conventionally, AgCdO-based sintered materials, which have been widely used as electrical contact materials in the medium load range, have excellent contact performance, but because they are made from harmful Cd, they contain Cd during the manufacturing process and during use. There is a risk that it will turn into dust and cause pollution, and it also has the disadvantage of being expensive due to the high Ag content.
On the other hand, AgNi-based sintered materials have been put into practical use as harmless electrical contact materials that do not contain Cd.
AgNi-based sintered materials have a problem in that they have inferior adhesion resistance compared to AgCdO-based materials. The purpose of the present invention is to improve the welding resistance, which is a drawback of conventional AgNi-based sintered materials, and to make it possible to manufacture inexpensive electrical contact materials that have contact performance equivalent to or better than AgCdO-based electrical contact materials. That is. The gist of the present invention is to press and mold a mixed powder consisting of 10 to 30% Ni, 1.7 to 10% Cu oxide in terms of Cu, 0.1 to 0.5% C, and the balance substantially Ag, and then The present invention provides a method for producing an electrical contact material, which comprises sintering in an atmosphere and reducing at least a portion of the oxide to form a solid solution in Ag and Ni in the form of metal. To explain the reason why the composition of the sintered material for electrical contacts according to the present invention is limited as described above, Ni is added to improve wear resistance, but if Ni is less than 10%, this effect is not achieved. Moreover, if it exceeds 30%, workability will deteriorate, so it was set at 10 to 30%. Cu oxide is added to improve contact resistance and Ni dispersibility, and the amount added is calculated in terms of metallic Cu.
If it is less than 1.7%, no improvement in Ni dispersibility is observed, and 10
If it exceeds 1.7 to 10%, the welding resistance will deteriorate.
And so. In addition, C is added to improve welding resistance, and if the amount added is less than 0.1%, the effect of addition will not be fully achieved, and if it exceeds 0.5%, workability will deteriorate, so 0.1 to 0.5 %. The electrical contact material according to the method of the present invention having the above-mentioned composition has significantly improved adhesion resistance compared to conventional AgNi-based sintered materials, and exhibits adhesion resistance equal to or higher than that of AgCdO-based sintered materials. Regarding contact resistance,
Adding Ni to Ag increases contact resistance, but Cu
By sintering while adding oxide and C to coexist, it is possible to make the size smaller than that of the AgCdO type. Furthermore, regarding wear resistance,
Although it is slightly inferior to the AgCdO type, it is not a difference that would cause a practical problem. Moreover, the electrical contact material according to the method of the present invention is more effective than the AgCdO-based sintered material.
Since the Ag content can be reduced, it can be manufactured at low cost, and since it does not contain harmful Cd, it does not cause pollution. According to the present invention, the electrical contact material uses fine powders of Ag, Ni, Cu oxide, and C as raw materials, blends these in a predetermined ratio, and presses and molds the materials, followed by decomposed ammonia gas (N ₂ +H ₂ ) is manufactured by sintering at 700 to 800°C for 1 to 20 hours in a reducing atmosphere, but this method uses Ag, Ni, and metal Cu as raw materials.
Compared to the case where Ag and C are used, at least a part of the oxide is reduced and dissolved in Ni during the sintering process, and the Ni alloy is refined. This is because the distribution in the matrix can be obtained. In addition, after sintering,
It is preferable to subject the obtained sintered body to reprocessing such as sizing and coining. As the raw material powder, powders of 0.1 to 10 ³ μm, preferably 0.5 to 20 μm can be used, and commercially available powders may be used as they are. Examples of the present invention will be described below. Example Raw material powder was Ag (average particle size: 1.08μ) 70% by weight,
Ni (average particle size: 2.2μ) 19.7% by weight, Cu ₂ O (average particle size: 5μ) 10% by weight (Cu conversion), C (average particle size: 5μ)
Blend at a ratio of 0.3% by weight, mix uniformly in a ball mill, and crush the mixed powder under a pressure of 4t/cm ² to a diameter
The resulting molded body was heated and sintered at 750° C. for 2 hours in a reducing gas atmosphere (N ₂ + H ₂ ) to obtain a sintered body for an electrical contact. This sintered body was heated to 700 to 800℃, and then extruded into a sintered body with a diameter of 6 mm.
After forming it into a rod-shaped body of mm in diameter, it was processed using a wire drawing header, and the obtained contact was assembled into a relay and used as a test product. Comparative Example 1 Using the Ag and CdO powder used in the example as raw materials, a sintered body of Ag-12%CdO was obtained in the same manner as in the example and used as a contact, and this was incorporated into a relay to make a sample. And so. Comparative Example 2 Using the Ag and Ni powders used in the examples as raw materials, they were mixed at a weight ratio of 70% Ag and 30% Ni, and in the same manner as in the examples, an AgNi diameter sintered body was obtained and used as a contact, This was assembled into a relay and used as a sample. Comparative Example 3 The raw material powder Ag and Ni used in the example were replaced with metal Cu.
Along with C, Ag70%, Ni19.7%, Cu metal powder (average particle size: 5μ) 10%, C (average particle size: 5μ) 0.3%
A sintered body was obtained as a contact point in the same manner as in the example, and this was incorporated into a relay as a sample. The contact resistance, abrasion resistance, and welding properties of the samples obtained in each of the Examples and Comparative Examples described above were measured under the following conditions. The results are shown in the table. Regarding wear resistance, when opened and closed 350,000 times,
It is expressed as the number of relays whose contact force was 5 g or less. [Test conditions] Sample: 5 relays (2C) each Voltage: AC220V Current: 4A Load: Resistive load Contact force: Initial 20-30g Opening/closing frequency: 30 times/min

[Table] As is clear from the results shown in Table 1, the electrical contact material according to the present invention has significantly improved welding resistance compared to those of Comparative Examples 2 and 3, and is equivalent to that of Comparative Example 1. It shows the above characteristics. Furthermore, it can be seen that the contact resistance is superior to all comparative examples. Furthermore, the abrasion resistance is equivalent to Comparative Examples 2 and 3, and although it is slightly inferior to that of Comparative Example 1, it can be seen that the difference is such that it does not pose much of a problem in practice.

Claims (1)

[Claims] 1 Ni 10-30%, Cu oxide Cu equivalent 1.7-10%,
After pressure-molding a mixed powder consisting of 0.1 to 0.5% C and the remainder substantially Ag, it is sintered in a neutral or reducing atmosphere, and at least a portion of the oxide is reduced to produce Ag and A method for producing an electrical contact material, characterized by dissolving Ni in the form of a metal.