JPS5942066B2 - Rhenium-cobalt alloy contacts - Google Patents

Description

[Detailed Description of the Invention] The present invention mainly relates to a reed switch for a small reed relay,
The present invention relates to contacts used when controlling the power of large relays, lamps, motors, etc. using one type of switch each having contacts with relatively small contact force such as small relays and switches, and particularly relates to rhenium-cobalt alloy contacts.

In general, miniaturized reed switches, etc. have low contact pressure, and it is difficult to provide a thick contact layer, so when a high melting point metal such as tungsten molybdenum is used as the contact material, it is necessary to prevent an increase in contact resistance. I can't do that.

Therefore, conventionally, contacts plated with noble metals such as rhodium have been widely used.

However, rhodium contacts have the disadvantage that contact resistance increases due to organic gases contained in the atmosphere or organic gases adsorbed on the surface in advance.

In addition, it is not possible to directly plate contact strips or lead pieces made of iron, nickel, etc., which are easily oxidized, and it is necessary to apply a plating layer of gold, silver, copper, etc. As the thickness decreases, the manufacturing process becomes complicated and the processing cost of the contact increases.

The present invention eliminates the drawbacks of the limited contact processing technology as described above and provides a contact with improved performance, and is a rhenium-cobalt alloy contact containing rhenium in an amount of 50 to 70% by weight. It is.

As mentioned above, the contact resistance of rhodium contacts increases due to organic gas, and the function as a contact is greatly reduced.

This is a characteristic shared by transition metals such as platinum metals, and is a phenomenon that occurs when a ruptured film on the surface is removed by an arc or the like, except when the contact surface is operated in an inert atmosphere.

However, in the case of a rhenium-cobalt alloy, since rhenium and cobalt are not transition metals, the organic gas does not increase the contact resistance.

Furthermore, the melting point of rhodium is 1,966°C, whereas the melting point of a cobalt alloy containing 50 to 70% rhenium is extremely high at about 2.100 to 2,300°C, so there is little wear due to arcing.

Therefore, compared to rhodium contacts, the rhenium-cobalt alloy contacts have a longer lifespan when used under conditions where arcs are generated when the contacts are opened and closed, due to changes in the properties of the alloy due to the arc.

In general, contacts made of gold, silver, copper, and tungsten plated with rhenium are known to have low contact resistance and stability, and have improved current cutting ability, but alloys such as iron and nickel are easily oxidized. It is industrially difficult to directly plate the contact bullets, and due to plating technology, plating of rhenium alone is prone to cracking or peeling if it is less than an extremely thin layer, which is sufficiently higher than the arc voltage and higher than the minimum arc current. A single-layer rhenium contact is too thin and unsuitable for applications where current is to be interrupted.

However, rhenium containing less than 70% rhenium by weight
Cobalt alloy contacts contain cobalt, which is easily electrodeposited even on easily oxidized metal surfaces such as iron and nickel, so unlike rhodium and ruthenium, they can be directly plated.

In fact, rhenium, as well as cobalt, is a base metal and is a cheaper material than rhodium, making it possible to simplify the manufacturing process and create extremely high-performance, inexpensive switches without using all precious resources. can be provided.

In addition, because it contains cobalt, which is easy to electrodeposit on metal surfaces that are easily oxidized, such as iron and nickel due to plating technology, it can be used on contact strips and leads that are industrially impossible to use with rhodium or rhenium. A thick rhenium-cobalt alloy layer can be created directly by electrolytic plating.

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 compares the stability of contact resistance with that of a rhodium contact as an example of the present invention.

FIG. 2 is a circuit diagram for measurement, and 21 is a reed switch equipped with a rhenium-cobalt alloy contact or a reed switch equipped with a rhodium (base gold plating layer) contact to be subjected to the test.

22 is a contact that allows current to flow through the circuit when the reed switch contact 21 is closed, and 23 is a power source with a voltage of 48V DC.
, 24 is a load resistance.

In such a circuit, the reed switch 21 is set to 50H.
FIG. 1 shows the relationship between the number of operations and contact resistance when opening and closing at z.

FIG. 1a shows the case of a rhodium contact, and FIG. 1b shows the case of rhenium-cobalt (60% rhenium).

Comparing a and b, it can be seen that the rhenium-cobalt alloy contact exhibits less fluctuation in contact resistance and is extremely stable compared to the rhodium contact even if the number of operations increases.

FIG. 3 compares the current cutting ability of a contact according to an embodiment of the present invention with a conventional rhodium contact and a rhenium-cobalt alloy contact of the present invention, and FIG. 4 is a measurement circuit diagram thereof.

In Fig. 4, 41 is a reed switch with rhenium-cobalt alloy contacts to be tested, a reed switch with rhodium and rhenium contacts, 42 is a contact load resistance of 100 Ω, and 43 is a power source of DC 100 Ω. .

FIG. 3 shows the relationship between the number of operations and the lifespan when the reed switch 41 is opened and closed at 10 Hz.

Here, the straight line A indicates the cumulative incidence of non-separable failures of rhenium-cobalt contacts, and the straight lines A and C indicate the cumulative incidence of non-separable failures of rhodium and rhenium contacts.

As is clear from the figure, rhenium-cobalt contacts are less likely to fail than rhodium and rhenium contacts.

It is even more effective as a multilayer contact in which layers of this rhenium-cobalt alloy are stacked alternately with layers of gold, silver, copper, etc., and that one electrode is made of rhenium-cobalt alloy and the other electrode is also made of gold, silver, or copper. It is also effective when using low melting point metals such as.

It should be noted that the rhenium-cobalt alloy constituting the alloy contact according to the present invention can be manufactured by well-known alloy forming techniques such as the melting method.

For example, in the case of manufacturing an alloy containing 60% rhenium by weight as in the above embodiment, by heating and melting rhenium and cobalt at about 2,100° C., a solid solution alloy can be obtained throughout the entire region.

As explained above, the present invention has a rhenium component ratio of 50
By configuring the contact layer with ~70% rhenium-cobalt alloy, the contact resistance is low and stable even in an atmosphere containing organic gas at low contact force, and the service life is long when switching large amounts of power. We can provide inexpensive contacts.

[Brief explanation of the drawing]

Figure 1a shows a rhodium contact, and Figure 1a shows a rhenium contact.
A diagram showing the relationship between the number of operations and contact resistance of a cobalt contact. FIG. 2 is a test circuit diagram used to measure the relationship between the contact resistance and the number of operations. FIG. 3 is a diagram showing the relationship between the number of operations and the cumulative failure rate of contact failure. FIG. 4 is a test circuit diagram used to measure the number of operations and the cumulative failure rate of non-openable contacts. 21.41...Reed switch, 22...
...Gate contact, 23, 43...Power supply, 24
, 42...Load resistance. :3

Claims (1)

[Claims] 1. A rhenium-cobalt alloy contact characterized by containing a rhenium component ratio of 50 to 70% by weight of the rhenium-cobalt alloy.