JPS6336090B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vacuum shield contact having excellent large current characteristics and high withstand voltage performance.

Vacuum sheath breakers have advantages such as maintenance-free, non-polluting properties, and excellent sheath breaker performance, so the scope of their application is rapidly expanding. In addition, along with this, demands for higher voltage resistance and larger current are becoming more severe. On the other hand, the performance of a vacuum shield breaker is determined to a large extent by the contact material inside the vacuum container.

Satisfactory characteristics of the vacuum shield and disconnection contacts include:
(1) Large shearing capacity, (2) High withstand voltage, (3) Low contact resistance, (4) Low welding force, (5) Low contact wear, (6) ) have a small cutting current value, (7) have good workability, and (8) have sufficient mechanical strength.

In actual contacts, it is quite difficult to satisfy all of these characteristics, and in general, materials are used that satisfy particularly important characteristics depending on the application, sacrificing other characteristics to some extent. is the actual situation.

Conventionally, this type of contact has been made using copper-bismuth (hereinafter referred to as
Displayed as Cu―Bi. Alloys made of other elements and combinations of elements are similarly indicated by element symbols. ), Cu-Cr-Bi, Cu-Co-Bi, Cu-Cr
etc. were used.

However, in the case of alloy contacts containing low-melting point metals such as Cu-Bi, some of the metals diffuse and evaporate from within the contacts due to the high temperature heating during the evacuation process, and adhere to the metal shield or insulating container inside the vacuum container. This is one of the major factors that degrades the withstand voltage of vacuum shields and disconnectors. In addition, when the load is switched on and off or when a large current is interrupted, evaporation and scattering of low-melting point metals occur, resulting in deterioration of withstand voltage and deterioration of shearing performance. Even though Cu-Cr-Bi is added with Cr, Co, etc., which have excellent vacuum withstand voltage, to eliminate the above-mentioned drawbacks, the above-mentioned drawbacks due to low melting point metals are not fundamentally solved, and it cannot be used at high voltages and large currents. cannot be handled. On the other hand, materials such as Cu-Cr, which are made of a combination of metals (Cr, Co, etc.) with excellent vacuum withstand voltage and Cu, which has excellent electrical conductivity, are inferior to contacts containing low-melting point metals in terms of welding resistance. Although it is slightly inferior in comparison, it is often used in high voltage and large current ranges because it has excellent shearing performance and withstand voltage performance. Furthermore, since there is a limit to the shearing performance of Cu-Cr alloys, we can create a magnetic field by devising the shape of the contact and manipulating the current path of the contact, and this force can generate a large current. Efforts have been made to forcefully drive the arc to improve shearing performance.

However, the demands for higher voltage and larger current have become even more demanding, making it difficult for conventional contacts to sufficiently satisfy the required performance. Furthermore, in order to reduce the size of vacuum shields and disconnectors, conventional contact performance is not sufficient, and there is a need for contact materials with even superior performance.

The present invention was made to eliminate the above-mentioned drawbacks of the conventional products, and its object is to provide a contact for a vacuum circuit breaker that has excellent large current characteristics and high withstand voltage performance.

We fabricated prototype contact materials by adding various metals, alloys, and intermetallic compounds to Cu, and conducted various experiments by incorporating them into vacuum shields and disconnectors. As a result,
Contact alloys in which “Cu, Cr, and Nb” are distributed as single metals, “ternary or binary” alloys, “ternary or binary” intermetallic compounds, or composites thereof are extremely sensitive. It was found that the cutting performance was excellent. The vacuum shield contact of the present invention has Cu as the first component, and other components include Cr of 35% by weight or less and Nb of 40% by weight or less, and each of Cu, Cr, and Nb is It is characterized by being distributed as a metal, a ``ternary or binary'' alloy, a ``tripartite or binary'' intermetallic compound, or a complex thereof.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a structural diagram of a vacuum switch tube, in which electrodes 4 and 5 are installed inside a container formed by a vacuum insulating container 1 and end plates 2 and 3 that close both ends of the vacuum insulating container 1, and an electrode rod 6, respectively. and 7 are arranged to face each other at one end. The electrode 7 is joined to the end plate 3 via a bellows 8 so as to be movable in the axial direction without compromising airtightness. Shields 9 and 10 cover the inner surface of the vacuum insulating container 1 and the bellows 8, respectively, so that the inner surface of the vacuum insulating container 1 and the bellows 8 are not contaminated by vapor generated by the arc. The structure of electrodes 4 and 5 is shown in FIG. The electrode 5 is brazed to the electrode rod 7 on the back side thereof with a brazing material 51 inserted therein. The electrodes 4 and 5 are made of a Cu--Cr--Nb alloy according to the present invention.

Figure 3 shows a photograph of the metallographic structure of a conventional Cu-Cr alloy contact as a comparative example. This is a Cu-Cr alloy obtained by mixing Cu powder and Cr powder at 75% by weight and 25% by weight, molding, and sintering.

Figure 4 shows Cu-Cr-Nb as an example of the present invention.
A photograph of the metallographic structure of the alloy is shown. This is a Cu-Cr-Nb alloy obtained by mixing, molding, and sintering a mixed powder containing Cu powder and Cr powder of 75% by weight and 25% by weight, respectively, and 5% by weight of Nb. be. Note that sintering was performed at about 1100° C. under conditions such that part of Cr and Nb reacted to form Cr ₂ Nb.

Figure 5 shows Cu-Cr-Nb as an example of the present invention.
This figure shows a photograph of the metallographic structure of an alloy sintered at a relatively low temperature that makes it difficult for Cr and Nb to form an alloy or an intermetallic compound. This is an alloy obtained by molding and sintering a Cu--Cr--Nb mixed powder having the same blending ratio as the example shown in FIG. It can be seen that in the alloy shown in Figure 4, Cr, Nb, and Cr ₂ Nb are uniformly and finely distributed in Cu. Also, the alloy in Figure 5 is Cu
Cr and Nb are mainly distributed as single metals,
_Cr2Nb is rarely seen.

The results of various measurements or tests will be explained below.

First, from our experimental results, we found that in a contact alloy consisting of a binary alloy of Cu and Cr, the amount of Cr is 20 to 30% by weight.
We have confirmed that various types of performance are extremely excellent in the range of
The changes in various properties of the alloy when the amount is varied are shown.

Figure 6 shows the relationship between the amount of Nb added to an alloy with a fixed weight ratio of 75:25 and electrical conductivity, and shows that the electrical conductivity decreases as the amount of Nb increases. However, if the weight ratio of Cu and Cr in the alloy is fixed at 75:25, there is no practical problem even if the amount of Nb is increased to 20% by weight. Note that the vertical axis in FIG. 6 shows the ratio when the electric conductivity of Cu-Cr is set to 1, and the horizontal axis shows the amount of Nb added. Figure 7 shows the relationship between the amount of Nb added and the contact resistance when the weight ratio of Cu and Cr in the alloy was fixed at 75:25.
It shows the same tendency as electrical conductivity. The vertical axis in Figure 7 shows the value of the conventional Cu-25%Cr alloy by 1.
The ratio is shown below. Figure 8 shows Nb added to an alloy with a fixed weight ratio of Cu and Cr at 75:25.
It shows the relationship between the amount of shearing capacity and the shearing capacity, and it can be seen that the shearing performance of the Nb-added product is significantly improved compared to the conventional product (Cu-25 wt% Cr alloy).

The vertical axis in Figure 8 is Cu-25% by weight of the conventional product.
The ratio is shown with the value of Cr alloy as 1. As is clear from Figure 8, as the amount of Nb added increases, the shearing capacity increases, and at 5 wt% Nb, it is 1.8
If Nb is added beyond this point, the shear shear capacity will decrease. That is, Nb and Cr coexist,
This interaction increases the shearing performance, but when Nb and Cr are increased beyond a certain level, Cu, which has good conductivity, decreases in the alloy, reducing the electrical conductivity and thermal conductivity of the alloy, causing an arc This is because it becomes difficult to quickly dissipate the heat input caused by this, and conversely, the shear breaking performance deteriorates. FIG. 9 similarly shows the relationship between the amount of Nb added and the withstand voltage performance. As is clear from the figure, when the amount of Nb is 3% by weight or less, there is no difference from the conventional product (Cu-25% by weight Cr alloy), but if more than that is added, the withstand voltage performance increases as the amount of Nb added increases. can be seen.

Next, we will show how the characteristics of the alloy change when the weight ratio of Cr to Cu is changed while the amount of Nb in the alloy is fixed at 25% by weight. Figure 10 shows Cu
The relationship between the weight ratio of Cr and electrical conductivity is shown.

Next, the amount of Nb added in the alloy was changed to 0, 1.3, 5, 10,
Fixed at 20, 30, and 40% by weight, and
Regarding the relationship between shearing performance and Cr weight ratio when changing the weight ratio of Cr to Cu, the 11th article
As shown in the figure. The vertical axis is the conventional product (Cu-25% by weight)
The horizontal axis shows the ratio with the value of Cu (Cr alloy) as 1.
Shows the weight ratio of Cr to As can be seen from the figure, the conventional Cu-Cr binary alloy has a Cr content of 20~
There is a peak of shear shear capacity in the 30% weight range.
A similar tendency exists when the amount of Nb is fixed at 1 to 5% by weight. Furthermore, when the Nb amount is fixed at 5% by weight, the Cr weight ratio increases from about 11% by weight to 25% by weight, exceeding that of the conventional product (Cu-25% Cr alloy).
A remarkable increase in the shear cutting performance can be seen. On the other hand, when the Nb content is fixed at 20% by weight, the peak of the shear breaking capacity is in the range of 5 to 15% by weight of Cr, and the peak value is slightly higher than that of alloys with 5% by weight of Nb. Inferior.

Figure 12 shows that in a binary alloy of Cu and Nb, Nb
Figure 13 shows the relationship between Cu and electrical conductivity.
The relationship between Cr content and electrical conductivity in a binary Cr alloy is shown. Both figures show that as Nb and Cr increase, the electrical conductivity decreases, and for Nb, it decreases at about 40% by weight.
Furthermore, at 40% by weight, Cr reaches the limit of the electrical conductivity generally required for a contact for a breaker, and increasing Nb and Cr beyond this point will have a negative effect on current conduction, rupture, etc. in practice. Furthermore, as is clear from Fig. 11, when coexisting with Nb, an improvement in shear cutting performance is seen when the amount of Cr is 35% by weight or less, and no effect can be obtained even if the amount of Cr is increased beyond that. do not have. on the other hand,
As for Nb, when it coexists with Cr, even a small amount of addition can improve the cracking performance, and it is practical when the amount of Nb is 40% by weight or less. In addition, the amount of Nb is 40% by weight.
The above seems to have an effective range in terms of shearing performance, but firstly, it is difficult to achieve with the normal sintering method due to manufacturing reasons, and secondly, as is clear from Figure 12, 40
If the weight% Nb or more is used, the electrical conductivity is low and the contact resistance increases, making it difficult to put it into practical use as a circuit breaker for other than special purposes.

Furthermore, from Figure 11, the range in which the shearing performance is significantly improved (more than 1.5 times) compared to the conventional product is when the Cr content is ~33% by weight and the Nb content is 1 to 30% by weight.
% by weight is preferred.

In the above example, an intermetallic compound consisting of Cr and Nb, that is, Cr ₂ Nb, is formed, and Cu contains
We have shown various properties of alloys in which Cr, Nb and Cr ₂ Nb are uniformly and finely distributed.
Alloys in which Cu, Cr, and Nb are distributed almost as single substances show almost the same tendency, and compared to conventional
It has significantly greater shearing performance than Cu-25wt% Cr alloy. However, when mixed with the same composition,
In the formed and sintered Cu-Cr-Nb alloy, Cr and Nb
It was found that those that form intermetallic compounds have better cutting performance.

Although not shown in the figure, Bi, Te,
The above-mentioned example can also be applied to low-sintering vacuum shields and breaker contacts to which low-melting point metals such as Sb, Tl, Pb, Se, Ce, and Ca, alloys, and intermetallic compounds of these are added individually or in combination. It has also been confirmed that it has the effect of increasing shrunken performance and withstand voltage performance. Note that when 20% by weight or more of low melting point metals, alloys thereof, or intermetallic compounds were added individually or in combination, the shearing performance was significantly reduced.

As described above, according to the present invention, Cu is
Cu, Cr, and Nb are each contained as a single metal, an alloy of these three or two, or an intermetallic compound of these three or two, or as other components. Since it is configured to be distributed in a composite state, it is possible to obtain a vacuum shear breaking contact which has excellent shear breaking performance and high withstand voltage performance.

[Brief explanation of drawings]

Figure 1 is a structural diagram between vacuum switches, Figure 2 is an enlarged sectional view of the electrode part, Figure 3 is a photograph of the metallographic structure of a conventional Cu-25 wt% Cr alloy manufactured by the sintering method, and Figure 4 The figure shows a metallographic photograph of an alloy in which 5% by weight of Nb is added to a Cu-25% by weight Cr mother alloy according to an embodiment of the present invention sintered at a high temperature. An alloy structure photograph with a similar composition, Figure 6 shows a weight ratio of Cr to Cu of 75:25.
Figure 7 is a characteristic diagram showing the change in electrical conductivity when the amount of Nb added is changed for an alloy fixed at
A characteristic diagram showing the change in contact resistance when the amount of Nb added is changed for an alloy in which the weight ratio of Cr to Cu is fixed at 75:25. Figure 8 shows the change in contact resistance when the weight ratio of Cr to Cu is fixed at 75:25. A characteristic diagram showing the change in shear capacity when changing the amount of Nb added to a fixed alloy. Figure 9 shows the weight ratio of Cr to Cu at 75:25.
FIG. 3 is a characteristic diagram showing changes in withstand voltage performance when the amount of Nb added is changed for an alloy fixed at . 1st
Figure 0 is a characteristic diagram showing the change in electrical conductivity when the weight ratio of Cr to Cu is changed when the amount of Nb in the alloy is fixed at 25% by weight. Figure 11 is
Nb amount 0, 1, 3, 5, 10, 20, 30, 40% by weight
FIG. 3 is a characteristic diagram showing the change in shear capacity of the alloy when the weight ratio of Cr to Cu is changed when each is fixed to . Figure 12 shows the relationship between the amount of Nb and electrical conductivity in a Cu-Nb binary alloy, and Figure 13 shows the relationship between the amount of Nb and electrical conductivity.
The relationship between Cr content and electrical conductivity in a Cu-Cr binary alloy is shown. DESCRIPTION OF SYMBOLS 1... Vacuum insulation container, 2, 3... End plate, 4, 5... Electrode, 6, 7... Electrode rod, 8... Bellows, 9, 10...
Shield, 51...brazing material. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1 Copper is the first component, and chromium is the other component.
A contact for a vacuum shield, characterized in that it is made of a material in which the total content of chromium and niobium is 35% by weight or less, 40% by weight or less (excluding 0) of niobium, and 10% by weight or more of chromium and niobium. 2. The vacuum shield breaker contact according to claim 1, wherein the chromium content is 32% by weight or less, and the niobium content is in the range of 1 to 30% by weight. 3 Copper, chromium, and niobium each as a single substance, an alloy of these three or two, or an intermetallic compound of these three or two, or
The vacuum shield contact according to claim 1 or 2, characterized in that the contact is distributed as a composite. 4 Bismuth, tellurium, antimony, thallium,
Claims 1 and 2 contain at least 20% by weight of at least one of low melting point metals such as lead, selenium, cerium, and calcium, alloys thereof, or intermetallic compounds thereof.
3. The vacuum breaker contact according to any one of paragraphs 1 and 3.