JP2530865B2 - Ag-oxide composite contact strip - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an Ag-
The present invention relates to an oxide-based composite contact strip.

[Conventional technology]

Conventionally, there has been a so-called Ag-oxide type contact strip material in which an oxide such as Cd, Sb, Sn, Zn or In is added to Ag, an Ag alloy or Ag as a material for a medium load contact. The contact strip material is mainly used in a region of medium current or higher because it has excellent contact properties such as welding resistance, wear resistance and contact stability.

Ag-oxide-based contact strips are more likely to generate an arc because the arc voltage and current are lower than Ag and Ag-Ni, and oxides and the like, which are components of the contact, are volatilized by this arc, Improved contact surface cleaning and arc blowout effects,
It is said that this provides excellent contact characteristics.

[Problems to be solved by the invention]

As described above, the Ag-oxide-based contact strip is 5 to 20 Wt in Ag.
% Of the oxide is dispersed to improve the contact characteristics, but the workability is remarkably reduced, and it becomes difficult to process the strip with an increase in the amount of the oxide.

Therefore, as one method, it is conceivable to form an Ag layer on the outer periphery of the Ag-oxide-based contact strip and to facilitate the processing of the strip using the excellent workability of Ag. However, a contact made of this Ag-coated composite strip, for example, a rivet type contact, is subjected to a heading process as shown in FIG. 3, and as a result, the head surface of the contact is mostly on the contact surface as shown in (d). It will occupy the area of, and will be very easy to weld.

When the present inventor examined this phenomenon, it takes a form in which the arc generated because the Ag-oxide-based contact strip is closed to Ag moves in the outer peripheral direction and disappears in a short time. It turned out to be difficult.

Therefore, in the contact made of the Ag-oxide composite contact strip, the arc residence time at the time of opening and closing becomes long, Ag is held at a high temperature, and finally welding is performed.

[Means for solving problems]

In the present invention, an Ag layer is formed on the outer periphery of an Ag-oxide-based contact strip, and a discontinuous portion is formed at one or a plurality of locations in the cross section of the Ag layer, and the area ratio of the Ag layer to the cross section is 5 or less. It is characterized by having been set to ~ 35%.

[Action]

According to the above configuration, since the discontinuous portion is provided in the Ag layer on the outer periphery of the Ag-oxide composite contact strip, the arc foot generated when the contact is opened and closed flows from the discontinuous portion to the outer peripheral portion and quickly. It can be prevented that the contacts disappear and are kept at a high temperature.

The reason why the ratio of Ag in the cross section is set to 5 to 35% is as follows.
If the content is less than 5%, the coating of the strip becomes unstable, and the effect of improving the workability is reduced. If the content is more than 35%, particularly the contact resistance among the contact characteristics becomes a problem.

〔Example〕

 Examples of the present invention will be described below.

17.3 kg of Ag, 2.4 kg of Cd, and 0.3 kg of Sn were dissolved in a total of 20 kg in a high frequency furnace, and the molten metal was powdered by water atomization.

This powder was molded and sintered after internal oxidation, inserted into an Ag cylinder, and welded with an Ag lid to form a composite billet.

The composite billet was heated to 850 ° C., extruded into a bar having a diameter of 15 mm by a hot extruder, and repeatedly subjected to annealing and drawing to obtain a composite wire having a diameter of 3.5 mm.

This composite wire is, for example, shown in FIGS. 2 (a), (b) and (c).
Draw out with a die having a protrusion on the inner surface as shown in Fig. 3, and then with a circular die with a diameter of 3 mm to make a strip with as many discontinuities as the number of protrusions in the Ag layer, and then Ag-oxide composite contact It was made into strip material.

In addition, the thickness of the Ag cylinder is 3 mm
Was set to be around 0.1 mm.

Next, as shown in FIGS. 1 (a) and 1 (b), the strip was formed into a rivet-like shape by a header machine, fixed to the base by caulking, assembled into a contact tester, and subjected to a voltage of 20 volts.
An opening and closing test was performed under the conditions of 0 V and a current of 50 A.

Therefore, a strip having two discontinuous portions was used as sample No. 1,
The strip having four discontinuous portions was designated as Sample No. 2.

For comparison, a strip with the same composition without an Ag layer on the surface was designated as sample No. 3, and a strip with an Ag layer on the surface without discontinuity was designated as sample No. 4 using the same method as above. Manufactured.

 The results of the above switching test are shown in the following table.

As shown in the above table, the strip material without Ag layer on the surface like Sample No. 3 has good welding resistance, but cracks are likely to occur during contact formation. No sample No.4
Has a problem in welding resistance.

On the other hand, Sample No. 1 of the present invention having a discontinuous portion,
Sample No. 2 has good workability and excellent welding resistance.

〔The invention's effect〕

According to the present invention described in detail above, by providing a discontinuous portion in the Ag layer on the outer periphery of the Ag-oxide-based composite contact strip,
The foot of the arc generated when the contact is opened and closed flows from this discontinuity, and is quickly extinguished to prevent the contact from being maintained at a high temperature, which has the effect of obtaining excellent contact characteristics.

[Brief description of drawings]

FIG. 1 is a plan view showing a state where a contact is headed, FIG. 2 is a plan view showing an example of a die, and FIG. 3 is a perspective view showing a state where a contact is headed in a conventional example.

Claims (1)

(57) [Claims] 1. An Ag-oxide-based contact strip material having an Ag layer formed on the outer periphery thereof, and a discontinuous portion formed at one or more locations of the Ag layer in the cross section, and the area ratio of the Ag layer occupying the cross section. 5 to 35%, Ag-oxide composite contact strip material.