JPS6059978B2 - electrical contact materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to electrical contact materials used in equipment that conducts current and switches on and off.

In particular, the purpose is to improve the properties of Ag-WC alloys.

Conventionally, Ag=WC alloys have been widely used as contacts in equipment such as air vents, new products, and switches due to their excellent arc resistance and welding resistance. However, recently, equipment such as no-fuse brakes, new products, and switches have become smaller and more sophisticated, and as a result, the load on contact materials has become severer, and contact performance has become worse. Improvement is strongly required. In addition, as equipment becomes smaller, contact dimensions tend to become smaller and contact pressure decreases, which increases wear and tear that occurs when current flows or breaks, and leads to welding of contacts and deterioration of equipment insulation.
Furthermore, there is a problem in that the temperature tends to rise when switching at the rated current. Graphite (Gr
) was developed. In this contact, the arc heat generated during opening and closing turns Gr into a reducing gas, which prevents oxidation of WC and suppresses temperature rise, and has the effect of increasing welding resistance due to the lubricity of Gr. However, the addition of Gr had disadvantages such as consumption and deterioration of insulation properties. For this reason, in small, high-performance Shiya Shinsei products and switches, the movable contacts are made of Ag-
For the WC contacts and fixed contacts, it was necessary to use a combination of Ag-WC-Gr contacts. However, changing and combining materials for the movable part and the fixed part makes parts management extremely troublesome. Furthermore, even when using such a combination, the contact pressure is small in recent small and high-performance devices, and the arc heat generated during opening and closing causes abnormal temperature rises, deterioration of insulation, and frequent welding, and further improvements in contact performance are required. It is requested. The present invention has been made in view of the above points, and it is an object to provide a contact alloy having excellent welding resistance, wear resistance, and insulation resistance, and having low temperature rise and excellent practicality.

Furthermore, the alloy of the present invention provides an inexpensive contact alloy that can be used as a contact even when the amount of expensive silver is considerably reduced.
The alloy according to the present invention has IVa, Va, and V in ferrous metal and silver.
This is an electrical contact material characterized in that it contains a carbide of a group LA metal and graphite dispersed therein, and the carbide is dispersed in a ferrous metal and silver.

The characteristics of the alloy according to the present invention will be explained below. The inventors conducted various studies on alloys in which iron group metals and various carbides were added to silver, and found that alloys in which carbides were dispersed in iron group metals and silver were consumed and scattered by the arc heat generated when the current was turned on and off. It has been found that this method has an extremely small amount of damage, and is effective in reducing insulation deterioration and welding of equipment.

It is known in the field of cemented carbide that carbide solid solution in iron group metals has excellent strength and bonding at high temperatures, but the inventors have developed a combination of Ag and Gr. It has been found that the performance as a contact point is significantly improved when made into an alloy. In addition, solid solution reactions between iron group metals and carbides generally occur only at high temperatures, but if Ag is present, Ag
It was found that - becomes a liquid phase, and the reaction is promoted through this liquid phase.

However, iron group metals and carbides have poor oxidation resistance and are oxidized by the arc heat generated during opening and closing, increasing contact resistance and increasing the temperature of the equipment. There is.

Therefore, when Gr, which has excellent reducing properties, is added to the above contact alloy to prevent the oxidation of iron group metals and carbides, Gr decomposes with the heat of electrical switching and generates reducing gas, preventing the oxidation of iron group metals and carbides. prevent contact resistance and reduce equipment temperature rise. It was found that the welding resistance was improved due to the lubricity of Gr. In other words, carbides with excellent mechanical strength and bond strength at high temperatures and carbides of iron group metals are dissolved in silver to improve wear resistance and welding resistance, and also have excellent reducing and lubricating properties. By adding Gr, the alloy has high performance welding resistance, abrasion resistance, insulation resistance, and temperature rise characteristics that could not be expected with conventional Ag-WC or N-WC-Gr contacts. I was able to get

The iron group metals include Fe, CO, Nl, etc., and the amount thereof is preferably 5 to 6% by weight, preferably 20 to 5% by weight.

If it is less than 5%, the iron group metal will be dispersed in the silver, and solid solution of carbides will not occur, resulting in no improvement in wear resistance.

Moreover, if Gr is added in an amount of 60% or more, the contact resistance does not decrease and there is no effect of improving temperature rise characteristics.

As carbides, IVa, Va, ■1a group carbides such as W, MO, Ta, Nb, Tl, and Gr are effective, and the amount thereof is preferably 5 to 7 weight%, particularly 20 to 50%, which improves the characteristics. is good.

If the carbide content is less than 5%, the amount of carbide in Ag is too small and the welding resistance is insufficient, and if it is more than 70%, the contact resistance does not decrease even if Gr is added, and no improvement in temperature rise characteristics is observed. . Next, the effective range of Gr is 1 to 11% by weight, preferably 3 to 7%. If it is less than 1%, no improvement in temperature increase characteristics will be observed even if the iron group metal or carbide is within the increasing range, and if it is more than 11%, it will be difficult to manufacture the alloy and it will not be practical.

In addition, about 0.1% by weight of Al, which does not impair the purpose of the present invention,
Si, Se, Te, Bi, Zn, Cd, In, Ca, N
There is no problem even if metal elements such as a are included.

Next, the characteristics of the contact alloy according to the present invention will be specifically explained with reference to Examples.

Example 1 Each powder was blended in the proportions shown in Table 1, Table 2, Table 3, and Table 4. After mixing, a molded body was made, and the molded body was baked at a temperature of 1100°C in a hydrogen atmosphere. concluded.

This sintered body was pressurized again to produce an alloy with almost zero porosity. Among the alloys, those in Table 4 are conventional alloys for comparison. A9lO4O4OlOAlOlO6O2Ol 1st
The figure is a micrograph of an example (A4) of the alloy according to the present invention, magnified by 100 magnification.

In Figure 1, the white part is the silver phase, the light gray part is the Ni phase, and the N
The dark gray particles in the i-phase are the WC phase, and the irregularly shaped black parts are the graphite phase. As can be seen in the figure, the iron group metal and the carbide react during the sintering process in the alloy of the present invention, resulting in an alloy microstructure in which the carbide is solidly dissolved in the iron group metal and the carbide is also dispersed in the Ag phase. ing. It is thought that because the hard phase forms a skeleton, it exhibits characteristics of high heat resistance and low arc wear resistance. The alloys prepared as described above were evaluated for current conduction characteristics and wear characteristics using an ASTM tester.

The conditions are: AClOO■, 50A, pf 1.0, contact pressure 200gr, separation force 200gr, contact shape 5x
5×1.5tTfr! n, and was opened and closed 20,000 times.
The results of the voltage variation width and amount of wear after 20,000 times of opening and closing are shown in the fifth column.
Shown in the table.

Example 2 Movable contacts 4 x 7
After cutting the fixed contact into the dimensions of 8 x 8 x 2 wgn, it was joined to the base metal using resistance brazing.
Incorporation of an A-rated wiring sheath breaker The contact performance was evaluated under the test conditions shown below, and Table 6 was obtained.

Test conditions: Overload test: AC22O■, 200Apf5 old durability test: AC22OV, 5OApf 54 times temperature rise test: AC22OV, 5OA2H short circuit test: AC22O
V, 7.5KApfO. 5lPO-CO, 2PO-CO
As shown in Table 6, it can be seen that the alloy of the present invention has contact characteristics with low wear, low temperature rise, and high dielectric strength.

The alloy of the present invention not only has excellent contact performance as described above, but also contains a large amount of iron group metals and carbides, and the amount of expensive silver can be greatly reduced, making it of high industrial value.

Claims (1)

[Claims] 1. 5 to 70% by weight of at least one metal carbide selected from the group consisting of tungsten, molybdenum, tantalum, niobium, titanium, and chromium, and 1 to 11% by weight of graphite.
% by weight, 5 to 60% by weight of iron group metals, the balance being silver,
An electrical contact material characterized in that the carbide is dispersed in an iron group metal and silver. 2. The electrical contact material according to claim 1, wherein the iron group metal is at least one of nickel, iron, and cobalt.