JPH0288728A - Manufacture of contact point material - Google Patents

Abstract

PURPOSE:To obtain a contact point material having a little inner defect and to minimize generating frequency of reignition by infiltrating an infiltration material applying refining on arc-resistant material manufactured with the specific method. CONSTITUTION:In the infiltration process, as a countermeasure to gas emitted from the arc-resistant material containing at least one element of Cr and Ti, sintering is executed at higher temp. than the temp. melting the whole infiltration material at the stage of beforehand manufacturing a skeleton of the arc- resistant material to emit the gas and restrain the gas emission from the arc- resistant material at the time of infiltrating. On the other hand, in order to reduce gas emitted from the infiltration material containing at least one element of Ag, Cu and Bi, it can be obtd. be beforehand degassing the infiltration material with zone-refining under high vacuum atmosphere than 10<-3>Torr. The infiltration material applying the refining is infiltrated to the arc-resistant material manufactured in such a way in the range of the sintering temp. Therefore, the total emitted gas quantity can be reduced at the time of infiltrating, and the inner defect and the remained gas quantity of the contact point material are reduced and the generating frequency of the reignition can be minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a method of manufacturing a contact material suitable for reducing the incidence of restriking of a vacuum breaker.

(Prior Art) FIG. 3 is a longitudinal sectional view showing the structure of a vacuum valve. In FIG. 3, the circuit breaker 1 includes an insulating container 2 formed of an insulating material such as ceramic into a substantially cylindrical shape, and metal lids 4 and 5 provided at both ends of the container via sealing mechanisms 3 and 3a. vacuum-tightly sealed. A pair of electrode rods 6°7 are provided so as to penetrate through the metal lids 4 and 5 of this breaker 1, and a fixed electrode 8 and a movable electrode 9 are fixed to the mutually opposing ends of these electrode rods, respectively. has been done. Further, a bellows 10 is attached to the electrode rod 7 of the movable electrode 9, and the pair of electrodes 8 and 9 can be opened and closed by reciprocating movement of the electrode rod 7 while keeping the interior of the breaker chamber 1 vacuum-tight. There is.

The bellows 10 is covered with a hood 11 to prevent deposition of arc vapor, and the breaker 1 further includes:
A cylindrical metal container 12 is provided to prevent arc vapor from adhering to the insulating container 2.

On the other hand, as the enlarged structure of the movable electrode 9 is shown in FIG. 4, the movable electrode 9 is fixed to the electrode rod 7 with a brazing material 13, or is crimped and connected to the electrode rod 7 by caulking (not shown).
A movable contact 14 is bonded thereon by a brazing material 15.

Furthermore, the fixed electrode 8 is also the same except that the direction is reversed, and the fixed contact 14a is connected to this.

The contact material used in this vacuum valve has welding resistance,
Voltage resistance and high breaking properties are required.

However, these three requirements require contradictory physical properties, so it is difficult to ideally balance them.The priority requirements of the applied circuit should be prioritized first, and the other requirements should be set aside slightly. The current situation is that we are responding by making sacrifices.

For example, in high-voltage, large-capacity vacuum breakers, as shown in Japanese Patent Publication No. 41-12131, a Cu alloy containing 5% by weight or less of welding prevention components (Bi, Te, Pb, etc.) is used as an electrode contact. There is.

However, withstand voltage is not sufficient to meet the recent demand for higher voltage. In other words, the vacuum breaker is small and lightweight.
It has superior features compared to other circuit breakers, such as being maintenance-free and environmentally friendly.

Therefore, the scope of application of vacuum breakers has been expanded from the 36kV or less circuits conventionally used for boat fishing to even higher voltage circuits, and the demand for opening and closing special circuits, such as capacitor circuits, has also rapidly increased. Because of what I am doing,
- It is necessary for the layer to withstand high voltage.

Now, one of the important factors that poses a problem when trying to make vacuum circuit breakers withstand high voltages is the re-ignition phenomenon. Although it is considered important, not only prevention techniques but also the direct cause of its occurrence have not yet been clarified.

Furthermore, as the withstand voltage increases, contact materials are also required to have characteristics such as high withstand voltage and low occurrence of restriking phenomenon. In this case, in order to achieve high pressure resistance and non-re-ignition of the contact material, it is necessary to minimize the amount of the fragile welding prevention component that causes defects in pressure resistance, avoid excessive concentration, and avoid gas It is desirable to reduce impurities, pinholes, etc. as much as possible, and to increase the strength of the contact alloy itself.

Therefore, from these points of view, the above-mentioned Cu-B
1 alloy is not satisfactory.

On the other hand, in fields where high voltage resistance and large current interruption are required, Cu-Cr alloys are sometimes used as contact materials.

Unlike other contact materials, this Cu-Cr alloy has the advantage that it can be expected to exhibit uniform performance because there is no difference in vapor pressure between the constituent materials, and its characteristics can be fully utilized depending on how it is used. .

However, the occurrence of the restriking phenomenon has not yet been sufficiently alleviated, and improvements are needed, particularly from the viewpoint of downsizing the vacuum valve.

(Problems to be Solved by the Invention) Since the above-mentioned Cu-Cr alloy is generally produced by powder metallurgy, the physical and chemical conditions of the raw material powder, the chemical condition of the infiltration material, and the sintering of the contact alloy are It is thought that technology and other factors are deeply involved in the occurrence of restriking.

The inventors of the present application conducted detailed observations on the process of heating and sintering the raw material Cr powder to produce a skeleton, and found that 2
It was discovered that there was a stage of gas release. One is gas release due to contamination on the Cr surface from room temperature to around 350°C. The second is Cr, which is generated around 1000℃.
This is gas release due to partial decomposition of oxides.

On the other hand, when focusing on Cu, which is an infiltration material, 2
Stage gas release was observed. One of them is the Cu
The second is the release of gas due to dirt on the surface, and the second is the release of gas dissolved in Cu, which is observed near the melting point of Cu.

When an attempt was made to manufacture a Cu-Cr contact using these raw materials, the following problems occurred, which is considered to be the cause of the restriking phenomenon.

That is, "
By sintering at a temperature lower than the melting point of Cu, for example, 1000°C, C
When a skeleton is manufactured, at the stage where Cu is melted in the process of infiltrating Cu, gas release from C still continues, and as the Cu melts, internal gas that was solidly dissolved in it is also generated at the same time. , defects in partially uninfiltrated areas tend to occur frequently, and the amount of gas remaining in the contacts also increases.

In addition, in this [method for manufacturing contact material for vacuum breaker], the infiltration temperature is higher than the pre-sintering temperature, so the porosity of the Cr skeleton produced by pre-sintering varies as it decreases during the infiltration process. , it becomes difficult to obtain a uniform amount of Cu.

The present invention was made to solve the above-mentioned problems, and an object of the present invention is to provide a method for manufacturing a contact paste that has few internal defects and can minimize the frequency of restriking.

[Structure of the invention]

(Means for Solving the Problems) The present invention makes a skeleton by sintering an arc-resistant material containing at least one of Cr and Ti, and infiltrate the infiltration material containing a small amount (one of both) of Ag5Cu and Bi. A method for manufacturing a contact material that is infiltrated into a skeleton, comprising the steps of: (a) sintering the arc-resistant material at a temperature higher than that at which all of the infiltration material melts or vaporizes to form the skeleton; and (b) the infiltration. A step of zone refining the material in a vacuum atmosphere higher than 10'Torr, and a step of producing the infiltrated material in step C1 within the sintering temperature range of step a. It is characterized by comprising a step of infiltrating the skeleton produced in step a.

(Function) As mentioned above, at the stage of infiltrating the arc-resistant material with the infiltration material, the difference between the gas released from the arc-resistant material and the gas released from the infiltration material is 2fiI! There are types. In order to reduce this released gas, in the present invention, the gas released from the arc-resistant material during the infiltration process is pre-incinerated at the infiltration temperature or higher temperature at the stage of making the skeleton of the arc-resistant material. This suppresses the gas released from the arc-resistant material during infiltration.

On the other hand, in order to reduce the gas released from the infiltrated material, this is made possible by degassing the infiltrated material beforehand by zone refining in an atmosphere with a higher vacuum than 10@-3 Torr.

By infiltrating the arc-resistant material produced as described above with the infiltration material subjected to sofalining, the total amount of gas released during infiltration can be reduced, and internal defects in the contact and the amount of residual gas can also be reduced. The frequency of restriking can be minimized.

(Example) FIG. 1 is a process diagram showing an embodiment of the present invention.

That is, in step 1.01, a mesh of Cr having an average particle size of 100 to 400 is placed in a carbon crucible that has been degassed in advance.
Tap filling the powder followed by I in step 102
Temporary sintering is performed for 60 minutes at 1150° C., which is higher than the melting point of Cu (1083° C.), under a vacuum condition higher than X 10 ′ Torr to form a skeleton. On the other hand, in step 103, zone refining Cu, which is an infiltration material, is subjected to zone refining under a vacuum condition higher than I×10' Torr, and in step 104, it is cut into appropriate dimensions, and the surface coating is removed. The infiltration material is made by washing.

Furthermore, in step 105, I
Infiltration takes 45 minutes at 1130° C., which is above the melting point of Cu and below the sintering temperature when producing the Cr skeleton, under a vacuum condition higher than R. Steps 101 and 102 in FIG. 1 correspond to step a of the present invention, and steps 103 and 10
4 corresponds to the process of the present invention, and step 105 corresponds to the process C of the present invention.

The advantages of zone rearing Cu-based infiltration materials will now be described.

The oxygen content of commercially available oxygen-free copper is expressed by the formula 1)
pm, and when vacuum melting is performed using this material, the oxygen content is slightly lower than that of oxygen-free copper, but it is still several pm.
It is pm. On the other hand, when oxygen-free copper is used as a material and subjected to zone refining, the oxygen content is extremely low to 1 ppm or less. This is because in the case of vacuum melting, the Cu solidifies from the surroundings with the gas involved, whereas in the case of zone refining, the Cu solidifies gradually from one direction, so it can solidify without trapping gas inside the Cu. It is.

As a result, Cu has fewer internal defects and less restriking phenomenon.
-Cr base contact material is obtained, but regarding this evaluation,
The number of internal defects and the probability of re-ignition occurrence were determined using the following method for contacts manufactured using the method shown in Figure 1 (hereinafter referred to as examples) and contacts manufactured under various conditions (hereinafter referred to as comparative examples). It was evaluated by

a1 Number of Internal Defects After polishing and etching the contacts, use the number of holes that can be confirmed in 10 arbitrary fields of view (one field of view is 60×90IIIn) at 200x magnification using an optical microscope.

b. Re-ignition occurrence rate A disc-shaped contact piece with a diameter of 30 mm and a thickness of 5 mm was attached to a day mount pull type vacuum valve, and the re-ignition frequency was measured when a 6 kVX500A circuit was interrupted 2000 times. The variation width (maximum and minimum) of two circuit breakers (six valves) is shown. When attaching the contacts, only baking heating (450° C., 30 minutes) was performed, and no brazing material or accompanying heating was performed.

Examples and comparative examples will be compared below.

First, zone refining Cu was used in the examples, whereas oxygen-free Cu was used as a comparative example.

The number of internal defects and the number of re-ignition occurrences when vacuum melted Cu was used and the pre-sintering conditions and infiltration conditions were the same were as follows.
It was as shown in the diagram in the figure. That is, Comparative Example 1,
Example 2 showed high values for both the number of internal defects and the probability of restriking occurrence, whereas Example 1 showed good characteristics with both the number of internal defects and the probability of restriking occurrence being small.

Next, Example 2 is a contact in which the same zone refining Cu as in the above example was used, and the pre-sintering conditions were 1260°C x 60 minutes and the infiltration conditions were 1200°C x 45 minutes. Comparative Example 3 is a contact using 1000°C x 60 minutes and 1130°C x 45 minutes as the infiltration condition, and a contact using 1150°C x 60 minutes as the pre-sintering condition and 1189°C x 45 minutes as the infiltration condition. The number of internal defects and the number of re-ignition occurrences in Comparative Example 4 were as shown in the chart of FIG. As is clear from this chart, when the infiltration temperature is higher than the pre-sintering temperature, the number of internal defects is larger and the probability of restriking is also higher, whereas when the infiltration temperature is lower than the pre-sintering temperature, the infiltration temperature is lower than the pre-sintering temperature. Example 2 showed good characteristics in both the number of internal defects and the probability of restriking occurrence.

Next, Cr powder was simply filled into the crucible and Cr powder was lightly pressurized after filling.
U-Cr contacts were manufactured and evaluated as Examples 3 and 4, the results of which are shown in FIG.

According to this, it can be seen that both the number of internal defects and the probability of occurrence of restriking are small in all Examples. Therefore, even if the Cr content varies within the range of 35 to 70% by weight, it is judged that it does not significantly affect the number of internal defects and the probability of restriking.

Next, whereas the above Examples 1 to 4 each use zone refining Cu as the infiltration material, 0.1% Bi was used as the infiltration material.
The same conditions as in Example 1 were carried out using a Cu-B1-based infiltration material containing 1.5% by weight of Bi and subjected to zone refining, and a Cu-B1-based infiltration material containing 1.5% by weight of Bi and subjected to zone refining. The Cu-Cr contact made in Example 5゜6 is made by vacuum melting and containing 1.0% Bi.
Comparative Example 5 is a Cu-Cr contact fabricated using u-B1 based infiltration material under the same conditions as Example 1, and the evaluation results are shown in FIG. According to the evaluation results, those infiltrated with Cu-B1 manufactured by vacuum melting have a high probability of internal defects and restriking, whereas those infiltrated with Cu-B1 manufactured by zone refining It can be seen that, irrespective of the amount of Bi, all of them have few internal defects and have a low probability of restriking.

Next, as another combination, Cr30 is used as arc-resistant feed.
．． After mixing Cr5Ti powder to have a concentration of 1% in solid state and 15.3% Ti and tapping it into a carbon crucible, it was pre-sintered and refined in the same process as in Example 1.
In Example 7, a contact with a low internal defect rate and a low probability of restriking can be obtained.

Next, 28.3% was treated with sofa lining as an infiltration material.
Cu-Ag and refined Ag were pre-sintered at 1100°C for 60 minutes,
Contacts infiltrated for 45 minutes are shown as Examples 8 and 9, respectively. In this case as well, the number of internal defects,
A contact point with a low probability of restriking can be obtained.

As is clear from the above description, step a of creating a skeleton by sintering the arc-resistant material at a temperature higher than the melting temperature of the infiltration material;
When the infiltration feed is produced by zone refining in a vacuum atmosphere higher than 103 Torr, the infiltration feed produced in this step is produced in step a within the sintering temperature range of step a. By infiltrating the skeleton thus obtained, a contact with a small number of internal defects and a low probability of restriking can be obtained.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, after a skeleton is manufactured by sintering the infiltrated material at a temperature higher than the temperature at which all of the infiltrated material melts, the infiltrated material subjected to zone refining is sintered to form the skeleton. Since the infiltration is performed within a temperature range, internal defects in the contact and the probability of restriking can be minimized.

[Brief explanation of the drawing]

Fig. 1 is a process diagram showing one embodiment of the present invention, and Fig. 2 is a diagram showing a comparison between other contact materials under various conditions in order to evaluate the contact material according to the same embodiment. , 3rd
The figure is a longitudinal cross-sectional view of a vacuum valve to which the contact material according to the present invention is applied, and FIG. 4 is an enlarged cross-sectional view of the main parts of this vacuum valve. 1... Breaker, 2... Insulating container, 3, 3a...
Sealing mechanism, 4, 5... Metal lid body, 6, 7... Electrode rod, 8... Fixed electrode, 9... Movable electrode, 14...
Movable contact, 14a... fixed contact.

Claims (1)

[Claims] A contact in which a skeleton is made by sintering an arc-resistant material containing at least one of Cr and Ti, and an infiltration material containing at least one of Ag, Cu, and Bi is infiltrated into the skeleton. The method for manufacturing the material includes: a. Sintering the arc-resistant material at a temperature higher than that at which all of the infiltration material melts to form the skeleton; b. Sintering the infiltration material at a temperature of 10^-^3 Torr. (c) The infiltration material produced in step b above is produced in step a within the sintering temperature range of step a above. 1. A method for producing a contact material, comprising: a step of infiltrating a skeleton formed by the method.