JP2013012328A - Method of manufacturing contact point for vacuum valve - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing a contact point for a vacuum valve, by which the contact point for a vacuum valve having less pores inside and high in density is obtained.SOLUTION: A method of manufacturing a contact point for a vacuum valve comprises: a green compact molding step of molding a green compact; a skeleton forming step of forming a plate-like Cr skeleton 1 by sintering the green compact; a cutting step of forming a sheared surface by cutting the Cr skeleton 1 into two parts along the center of its thickness; a placing step of placing a Cu plate 2 at the center of the sheared surface; and an infiltrating step of infiltrating fused Cu, which is acquired by heating the Cu plate 2, into the Cr skeleton 1.

Description

  The present invention relates to a method for manufacturing a contact for a vacuum valve that is particularly required to have a high pressure resistance.

For vacuum valve contacts for high pressure resistance, Cu-Cr materials in which Cr having high pressure resistance properties are dispersed in Cu, which is a high conductor, and Ag-Cr materials, in which Cr is dispersed in Ag, which is a high conductor. Is often used.
As the manufacturing method, Cr powder is mixed with Cu powder or Ag powder and sintered, or a skeleton mainly composed of Cr powder is sintered in advance and Cu or Ag is infiltrated into the skeleton. Methods are known.
In order to obtain high pressure resistance performance, it is necessary to increase the contact density by reducing the pores inside the contact, and the infiltration method tends to be more dense than the sintering method. (See, for example, Patent Documents 1 and 2).

JP-A-60-114502 JP-A-5-101752

In the manufacture of a Cu-Cr-based vacuum valve contact by the conventional infiltration method, in the process of infiltrating Cu into a skeleton composed mainly of Cr powder, a reduction functioning as a reducing action on the Cr oxide film inside. For example, when there is hydrogen gas as the sex gas, the number of pores inside the contact tends to be larger than in vacuum.
In the case of infiltration in a vacuum, even if a closed pore is locally formed in the process of molten Cu penetrating into the skeleton of Cr, a certain amount of the internal pore is vacuum. As time passes, molten Cu enters the portion and closes the inside of the pore.
On the other hand, in the case of infiltration in hydrogen gas, once the closed pore is formed, the inside of the pore is hydrogen gas, so the molten Cu remains in it even if the atmospheric pressure becomes an obstacle and time passes. This is thought to be because the pores could not be penetrated and many pores remained.

In order to solve this problem, in the method for manufacturing a contact for a vacuum valve described in Patent Document 2, the final solidified portion at the time of Cu infiltration is stacked by setting two skeletons of Cr vertically. Attempts have been made to relatively reduce the concentration of pores on the contact surface side by coming to the boundary portion, concentrating defects in the portion, cutting the boundary portion, and not using the portion.
FIG. 4A is a diagram showing one step of the manufacturing method of the contact for a vacuum valve described in Patent Document 2, in which a Cr skeleton 1, a Cu plate 2 and a Cr skeleton 1 are laminated on a pedestal 7, and Cu It is a figure before is infiltrated.

  According to this manufacturing method, it is important that the amount of Cu to be infiltrated is not excessive, and if the Cu is excessive, it tends to wet the periphery of the skeleton faster than filling the inside of the Cr skeleton 1, As a result, the inventors of Patent Document 2 point out that pores are randomly formed inside the Cr skeleton 1 (see paragraph 0043 of Patent Document 2).

However, this is a phenomenon that occurs when the outer diameter of the Cu plate 2 to be infiltrated is larger than the Cr skeleton 1. If the outer diameter of the Cu plate 2 is smaller than the Cr skeleton 1, the molten Cu Since this is quickly absorbed from the installation surface on the Cr skeleton 1 by the action of capillary action, such a problem does not occur.
Rather, as shown in FIG. 4B, after Cu infiltration, the Cu solidified layer 5 which is the boundary between the infiltration skeletons 4 in which Cu is infiltrated into the Cr skeleton 1 is deficient in Cu. The shrinkage nest 6 is generated, and there is a problem that a sound joined state cannot be obtained.

  An object of the present invention is to provide a vacuum valve contact manufacturing method capable of obtaining a high-density vacuum valve contact with few internal pores and to solve the above problems. For the purpose.

A method for manufacturing a vacuum valve contact according to the present invention is as follows.
A green compact molding process in which a powder mainly composed of a high pressure resistant material is pressed with a mold to form a green compact;
A skeleton forming step of sintering the green compact to form a plate-shaped skeleton;
A split cutting process in which this skeleton is cut into two at the thickness center to form a cut surface;
A placing step of placing an infiltrant made of a highly conductive material at the center of the cut surface;
And an infiltration process for infiltrating the melted infiltrate into the inside of the skeleton.

  According to the method for manufacturing a contact for a vacuum valve according to the present invention, an infiltrant is placed immediately above a low-density region exposed on the cut surface of the skeleton, and the infiltrant melted by heating is removed from the low-density region to the inside of the skeleton. By permeating into the surface, a region left locally from infiltration does not occur, and a healthy contact with few pores can be obtained.

It is a figure which shows the behavior which fuse | melted Cu osmose | permeates the inside of Cr skeleton. It is sectional drawing which shows the division | segmentation cutting process of Cr skeleton in the manufacturing method of the contact for vacuum valves of Embodiment 1 of this invention. It is sectional drawing which shows Cu infiltration process in the manufacturing method of the contact for vacuum valves of Embodiment 1 of this invention. FIG. 4A is a cross-sectional view showing a process before Cu infiltration in a conventional vacuum valve contact manufacturing method, and FIG. 4B is a cross-sectional view showing a process after Cu infiltration.

Embodiment 1 FIG.
The inventor of the present application investigated in detail the penetration mechanism of molten Cu in order to clarify the cause of pores remaining due to infiltration of Cu.
That is, as shown in FIG. 1, the Cu plate 2 was placed on the Cr skeleton 1 and heated in a hydrogen gas atmosphere to melt the Cu plate 2, and the behavior of molten Cu penetrating into the Cr skeleton 1 was examined.
Then, when the molten Cu from the Cu plate 2 penetrates in the direction of arrow A from the top, the molten Cu soaks into the surface layer of the upper surface first, and then penetrates into the center of the interior earlier than the arrow. As shown by B, it was found that there was a phenomenon that the Cr skeleton 1 penetrated into the surface of the side surface and then wrapped around the surface of the bottom surface.
Due to this phenomenon, the pores in the central part of the Cr skeleton 1 are confined, and a low density region 3 that is a frequent region of closed pores is generated in the central part of the Cr skeleton 1, and this causes a low density contact point. It can be said that it is a cause of manufacturing.

In addition, the infiltration of molten Cu at the inner center of the Cr skeleton 1 is slower than the surroundings because the density at the inner central part of the Cr skeleton 1 is lower than that of the surroundings, and the action force of capillary action is relative. This is thought to be due to the small size.
The low density region 3 is generated in the central portion of the inside of the Cr skeleton 1 when the green compact is formed by compressing the Cr powder in the manufacturing process of the Cr skeleton 1. This is considered to be due to the fact that the pressure was not sufficiently transmitted to the center of the interior due to the fluidity of the powder, although it was compressed by receiving pressure from the bottom and side surfaces.

As a result of examining the penetration mechanism of the molten Cu in detail in this way, the inventor of the present application has found that the low density region 3 is generated at the central portion inside the Cr skeleton 1.
Then, paying attention to this point, the following manufacturing method of the vacuum valve contact according to the first embodiment of the present invention was invented.
First, a powder mainly composed of Cr, which is a high pressure resistant material, is pressed with a mold to form a green compact.
After the green compact forming step, the green compact is sintered in a hydrogen gas atmosphere as a reducing gas to form a plate-like Cr skeleton 1.
After this skeleton forming step, as shown in FIG. 2, the Cr skeleton 1 is cut into two parts so as to cross the low density region 3 formed in the central portion of the plate thickness to form a cut surface.
After this divided cutting step, the Cu plate 2 that is an infiltrated body made of a highly conductive material is placed on the cut surface so as to face the low density region 3.
After this placing step, the Cu plate 2 is heated in an atmosphere of hydrogen gas, and the Cu plate 2 is melted and penetrated into the Cr skeleton 1 as shown in FIG.
After this infiltration step, the Cr skeleton 1 is cooled to obtain a Cu—Cr based contact.

According to the method for manufacturing a vacuum valve contact according to the first embodiment of the present invention, the low density region 3 is exposed on the cut surface of the Cr skeleton 1, and the infiltration Cu plate 2 is placed immediately above the low density region 3. Therefore, Cu melted during heating enters from the low density region 3 and penetrates toward the outer peripheral portion of the Cr skeleton 1.
For this reason, since the phenomenon shown in FIG. 1, that is, the penetration of molten Cu does not proceed preferentially from the outer peripheral portion of the Cr skeleton 1, there is no region left locally from the infiltration of Cu. For this reason, a healthy contact with few pores can be obtained.

Hereinafter, an example of the manufacturing method of the vacuum valve contact according to the first embodiment of the present invention will be described in detail.
Example 1.
The Cr powder is passed through sieves having a pore size of 45 μm and 20 μm to obtain a particle size of 20 μm or more and 45 μm or less. After adding a small amount of Cu powder having a particle size of several μm as a binder, the mixture is stirred and mixed. The mold was filled and pressed at 100 MPa to form a green compact with an outer diameter of 90 mm.
The thickness of the green compact was adjusted by changing the filling amount to obtain a green compact with a thickness of 15 to 19 mm.
The obtained green compact was sintered at 1100 ° C. for 2 hours in a hydrogen gas atmosphere to produce a Cr skeleton mainly composed of Cr having a predetermined porosity.
The obtained Cr skeleton was horizontally cut from the center of the plate thickness and divided.
Thereafter, a Cu plate having an outer diameter of 75 mm is placed with the cut surface facing upward, heated in a hydrogen gas atmosphere at 1150 ° C. for 1 hour, the Cu plate is melted and penetrated into the Cr skeleton, and an outer diameter of 90 mm × plate An infiltration sample of 60 wt% Cu-40 wt% Cr having a thickness of 7 to 9 mm was obtained.

  Further, for comparison, an infiltration Cu plate having an outer diameter of 75 mm is placed on the upper portion without dividing the Cr skeleton, and heated at 1150 ° C. for 1 hour in a hydrogen gas atmosphere. It melt | dissolved and the molten Cu was osmose | permeated inside this skeleton, and the 60 wt% Cu-40 wt% Cr infiltration sample of 90 mm of outer diameter x 15-19 mm in plate thickness was obtained.

Three samples were prepared for each type of plate thickness: for observation of internal structure (pore state), for density measurement, and for pressure resistance performance evaluation (for breakdown voltage measurement).
In observing the internal structure, the sample was cut in the diameter direction and observed with an optical microscope, and the total area of pores seen in the area of the cross section central portion 2 mm × 2 mm was measured from the photographed photo.
In the density measurement, a disc having an outer diameter of 80 × 5.5 mm in thickness was cut out from the central portion in the plate thickness direction, the density was evaluated using the Archimedes method, and the density ratio was determined in comparison with the true density.
In the pressure resistance test, a disk with an outer diameter of 20 mm x a plate thickness of 5.5 mm was cut out from the center in the plate thickness direction, assembled into a vacuum valve, and the breakdown voltage was increased while gradually increasing the impulse voltage under the condition of a contact distance of 2 mm. Was measured, the increase profile of the breakdown voltage with the increase in the number of applied voltages was measured, and the withstand voltage performance was evaluated from the saturation value. In addition, AC100 kV voltage conditioning was performed before measurement of the breakdown voltage.

Table 1 shows the evaluation results.
As shown in Examples 1- (1 to 3) of Table 1, in the contact obtained by dividing the Cr skeleton of the present invention and infiltrating Cu, the total area of the internal pores is small, and the high value of the density ratio of 99% or more is high. Obtained.
On the other hand, as seen in Comparative Example 1- (1 to 3), the contact area in which Cu is infiltrated without dividing the Cr skeleton has a large total area of pores present therein, and has a high density of 99% or more. Was not obtained.

  As shown in the saturation value of breakdown voltage in Table 1, the withstand voltage performance is about 150 to 153 kV in Examples 1- (1 to 3), which is very high compared to other comparative examples. It was.

As described above, in this Example 1, the Cr skeleton is horizontally cut from the central portion of the plate thickness and divided, and the Cu plate for infiltration is disposed immediately above the low density region exposed on the cut surface. Sometimes the molten Cu enters from the low density region and penetrates outward.
For this reason, since the molten Cu does not permeate preferentially from the outer peripheral portion as in the prior art, a region left locally from infiltration does not occur.
Therefore, a sound contact with few pores can be obtained inside, and a high pressure resistance performance can be obtained with the vacuum valve.

Example 2
The Cr powder is passed through sieves with a pore size of 45 μm and 20 μm to obtain a particle size of 20 μm or more and 45 μm or less. The mold was filled and pressed at a predetermined pressure to form a green compact having an outer diameter of 75 mm and a plate thickness of 15 mm. The porosity inside the green compact was adjusted by changing the applied pressure in the range of 80 to 250 MPa to obtain green compacts having various porosity.
The obtained green compact was sintered at 1100 ° C. for 2 hours in a hydrogen gas atmosphere to prepare Cr skeletons mainly composed of Cr having various porosity.
The obtained Cr skeleton was cut horizontally from the center of the plate thickness and divided into 7 mm thicknesses.
Thereafter, an infiltration Cu plate having an outer diameter of 70 mm is placed with the cut surface facing upward, heated in a hydrogen gas atmosphere at 1150 ° C. for 1 hour, and the Cu plate is melted and penetrated into the Cr skeleton. Cu-Cr infiltrated samples having different compositions were obtained.

  For comparison, a green compact was formed at a pressure of 60 MPa, and then an infiltration sample of 70 wt% Cu-30 wt% Cr was obtained through the same process as described above.

Three samples were prepared for each type of composition, one for observing the internal structure (pore state), one for measuring density, and one for evaluating withstand voltage performance (for measuring breakdown voltage).
In observing the internal structure, the sample was cut in the diameter direction and observed with an optical microscope, and the total area of pores seen in the area of the cross section central portion 2 mm × 2 mm was measured from the photographed photo.
In the density measurement, a disc having an outer diameter of 70 mm × a thickness of 5.5 mm was cut out from the center in the thickness direction, the density was evaluated using the Archimedes method, and the density ratio was determined by comparing with the true density.
In the pressure resistance test, a disk with an outer diameter of 20 mm x a plate thickness of 5.5 mm was cut out from the center in the plate thickness direction, assembled into a vacuum valve, and the breakdown voltage was increased while gradually increasing the impulse voltage under the condition of a contact distance of 2 mm. Was measured, the increase profile of the breakdown voltage with the increase in the number of applied voltages was measured, and the withstand voltage performance was evaluated from the saturation value. In addition, AC100 kV voltage conditioning was performed before measurement of the breakdown voltage.

Table 2 shows the evaluation results.
As shown in Example 2- (1-7) in Table 2, when the Cr composition of the sample was 35 to 65 wt%, the total area of the internal pores was small, and a high value with a density ratio of 99% or more was obtained.
On the other hand, as seen in Comparative Example 2-1, when the Cr composition was 30 wt%, the total area of pores present inside suddenly increased, and a high density of 99% or more could not be obtained.
As shown in the saturation value of the breakdown voltage in Table 2, the withstand voltage performance shows a value of about 147 to 161 kV in Example 2- (1-7), which is very high compared to Comparative Example 2-1. all right.

From the above, in this Example 2, the Cr skeleton was horizontally cut from the central part of the plate thickness and divided, and the Cu plate for infiltration was disposed immediately above the low density region exposed on the cut surface. At the time of immersion, molten Cu enters from the low density region and penetrates outward.
For this reason, since the molten Cu does not permeate preferentially from the outer peripheral portion as in the prior art, a region left locally from infiltration does not occur.
Therefore, even when the Cr composition is in the range of 35 to 65 wt%, it is possible to obtain a high-density Cu—Cr contact having almost no pore inside, and as a result, the vacuum valve can obtain high pressure resistance.
Note that when the Cr composition is 30 wt%, the pores increase and the density decreases. This is because the Cr composition is too low to make it difficult to maintain the skeleton structure of Cr, and the structure is locally uneven inside. It is considered that a portion is generated and the infiltrating property of the molten Cu becomes non-uniform.

Example 3
The Cr powder is passed through sieves with a pore size of 45 μm and 20 μm to give a particle size of 20 μm or more and 45 μm or less. And was pressed at 100 MPa to form a green compact with an outer diameter of 30 to 105 mm and a plate thickness of 15 mm.
The obtained green compact was sintered at 1100 ° C. for 2 hours in a hydrogen gas atmosphere to produce a Cr skeleton mainly composed of Cr having a predetermined porosity.
The obtained Cr skeleton was cut horizontally from the center of the plate thickness and divided into 7 mm thicknesses.
Then, the Cu plate for infiltration is placed with the cut surface facing upward, heated in a hydrogen gas atmosphere at 1150 ° C. for 1 hour, the Cu plate is melted, and the molten Cu is infiltrated into the skeleton. 60 wt% Cu-40 wt% Cr infiltration samples having different thicknesses of 7 mm were obtained.
The Cu plate was used by changing the outer diameter according to the size of the skeleton, and specifically, the Cu plate having an outer diameter smaller than that by 5 to 15 mm depending on the outer diameter of the skeleton.
Three samples were prepared for each type of outer diameter: for observation of internal structure (pore state), for density measurement, and for pressure resistance performance evaluation (for breakdown voltage measurement).
In observing the internal structure, the sample was cut in the diameter direction and observed with an optical microscope, and the total area of pores seen in the area of the cross section central portion 2 mm × 2 mm was measured from the photographed photo.
Further, in the density measurement, a disk having an outer diameter of 25 mm and a plate thickness of 5.5 mm was cut out from the central portion in the plate thickness direction, the density was evaluated using the Archimedes method, and the density ratio was obtained by comparison with the true density.
Also, in the pressure resistance performance test, a disk with an outer diameter of 20 mm x a thickness of 5.5 mm was cut out from the center in the thickness direction, assembled into a vacuum valve, and destroyed while gradually increasing the impulse voltage under the condition of a distance of 2 mm between the contacts. The voltage was measured, the increase profile of the breakdown voltage with the increase in the number of applied voltages was measured, and the withstand voltage performance was evaluated from the saturation value. In addition, AC100 kV voltage conditioning was performed before measurement of the breakdown voltage.

Table 3 shows the evaluation results.
As shown in Examples 3- (1 to 6) of Table 3, it was found that, in any outer diameter sample, the total area of the internal pores was small, and a high value with a density ratio of 99% or more was obtained.
As shown in the saturation value of the breakdown voltage in Table 3, the breakdown voltage performance showed a high value of about 147 to 154 kV.

As described above, in this Example 3, the Cr skeleton is horizontally cut from the central portion of the plate thickness and divided, and the Cu plate for infiltration is disposed immediately above the low density region exposed on the cut surface. Cu melted at the time of immersion penetrates from the low density region and penetrates outside.
For this reason, since the molten Cu does not permeate preferentially from the outer peripheral portion as in the prior art, a region left locally from infiltration does not occur.
Therefore, even when the outer diameter of the contact is in the range of 30 to 105 mm, it is possible to obtain a high-density Cu—Cr contact having almost no pore inside. As a result, the vacuum valve can obtain high pressure resistance.

Example 4
The Cr powder is passed through sieves with a pore size of 45 μm and 20 μm to obtain a particle size of 20 μm or more and 45 μm or less. The mold was filled and pressed at 100 MPa to form a green compact having an outer diameter of 90 mm and a plate thickness of 17 mm.
Further, the Cr powder is passed through sieves having a pore size of 75 μm and 45 μm to obtain a particle size of 45 μm or more and 75 μm or less. 90 molds were filled and pressed at 90 MPa to form a green compact with an outer diameter of 90 mm and a plate thickness of 17 mm.
Further, the Cr powder is passed through sieves having a pore size of 125 μm and 75 μm to obtain a particle size of 75 μm or more and 125 μm or less. A 90 mold was filled and pressed at 80 MPa to form a green compact having an outer diameter of 90 mm and a plate thickness of 17 mm.
The obtained green compact was sintered in a hydrogen gas atmosphere at 1100 ° C. for 2 hours to produce a skeleton mainly composed of Cr having a predetermined porosity.
The obtained Cr skeleton was cut horizontally from the center of the plate thickness and divided into 8 mm thicknesses.
Then, the Cu plate for infiltration is placed with the cut surface facing up, heated in a hydrogen gas atmosphere at 1150 ° C. for 1 hour, and the Cu plate is melted and infiltrated into the skeleton. Different 60 wt% Cu-40 wt% Cr infiltration samples were obtained.
Three samples were prepared for each type of Cr powder particle size: for observation of internal structure (pore state), for density measurement, and for pressure resistance performance evaluation (for breakdown voltage measurement).
In observing the internal structure, the sample was cut in the diameter direction and observed with an optical microscope, and the total area of pores seen in the area of the cross section central portion 2 mm × 2 mm was measured from the photographed photo.
Further, in the density measurement, a disk having an outer diameter of 80 mm and a plate thickness of 5.5 mm was cut out from the central portion in the plate thickness direction, the density was evaluated using the Archimedes method, and the density ratio was obtained by comparison with the true density.
In the pressure resistance test, a disk with an outer diameter of 20 mm x a plate thickness of 5.5 mm was cut out from the center in the plate thickness direction, assembled into a vacuum valve, and the breakdown voltage was increased while gradually increasing the impulse voltage under the condition of a contact distance of 2 mm. Was measured, the increase profile of the breakdown voltage with the increase in the number of applied voltages was measured, and the withstand voltage performance was evaluated from the saturation value. In addition, AC100 kV voltage conditioning was performed before measurement of the breakdown voltage.

  Table 4 shows the evaluation results. As shown in Example 4- (1 to 3) in Table 4, it was found that in all samples, the total area of the internal pores was small, and a high value with a density ratio of 99% or more was obtained. As shown in the saturation value of the breakdown voltage in Table 4, the breakdown voltage performance showed a high value of about 151 to 155 kV.

As described above, in this Example 4, the Cr skeleton is horizontally cut from the central portion of the plate thickness and divided, and the Cu plate for infiltration is disposed immediately above the low density region exposed on the cut surface. Sometimes the molten Cu infiltrates from the low density region and infiltrates outward.
For this reason, since the molten Cu does not permeate preferentially from the outer peripheral portion as in the prior art, a region left locally from infiltration does not occur.
Therefore, in the case where the powder particle size of Cr is 20 μm or more and 45 μm or less by sieve classification, 45 μm or more and 75 μm or less, or 75 μm or more and 125 μm or less, high-density Cu—Cr having almost no pores inside. A contact can be obtained, and as a result, a high pressure resistance can be obtained in the vacuum valve.

  Embodiment 5 FIG.

The Cr powder is passed through sieves with a pore size of 45 μm and 20 μm to obtain a particle size of 20 μm or more and 45 μm or less. The mold was filled and pressed at 100 MPa to form a green compact having an outer diameter of 100 mm and a plate thickness of 17 mm. The obtained green compact was sintered in a hydrogen gas atmosphere at 1100 ° C. for 2 hours to produce a skeleton mainly composed of Cr having a predetermined porosity.
The obtained Cr skeleton was cut horizontally from the center of the plate thickness and divided into 8 mm thicknesses.
Thereafter, a Cu plate for infiltration was placed with the cut surface facing upward, and heated in a hydrogen gas atmosphere at 1150 ° C. for 1 hour to melt the Cu plate and infiltrate the skeleton. At this time, the infiltration area of the molten Cu into the Cr skeleton was changed by changing the outer diameter size of the Cu plate for infiltration, and a 60 wt% Cu-40 wt% Cr infiltration sample having a thickness of 8 mm with different infiltration processes was obtained. .
For each type, three samples were prepared for observation of the internal structure (pore state), density measurement, and pressure resistance performance evaluation (breakdown voltage measurement).
In observing the internal structure, the sample was cut in the diameter direction and observed with an optical microscope, and the total area of pores seen in the area of the cross section central portion 2 mm × 2 mm was measured from the photographed photo.
Further, in the density measurement, a disk having an outer diameter of 90 mm × a plate thickness of 5.5 mm was cut out from the central portion in the plate thickness direction, the density was evaluated using the Archimedes method, and the density ratio was obtained by comparing with the true density.
Also, in the pressure resistance performance test, a disk with an outer diameter of 20 mm x a thickness of 5.5 mm was cut out from the center in the thickness direction, assembled into a vacuum valve, and destroyed while gradually increasing the impulse voltage under the condition of a distance of 2 mm between the contacts. The voltage was measured, the increase profile of the breakdown voltage with the increase in the number of applied voltages was measured, and the withstand voltage performance was evaluated from the saturation value.
In addition, AC100 kV voltage conditioning was performed before measurement of the breakdown voltage.

Table 5 shows the evaluation results.
As shown in Example 5- (1 to 4) of Table 5, when the outer diameter of the infiltration Cu plate is in the range of 50 to 100 mm, the total area of the internal pores is small, and a high value with a density ratio of 99% or more is obtained. I understood it.
As for the pressure performance, as shown in the saturation value of the breakdown voltage in Table 5, a high value of about 150 to 154 kV was shown.
On the other hand, when the outer diameter of the infiltration Cu plate was 40 mm, infiltration unevenness occurred inside the contact, and the density of the entire contact was lowered as shown in Comparative Example 5-1.
Further, when the outer diameter of the infiltration Cu plate is larger than the outer diameter of the contact, as shown in Comparative Example 5-2, the molten Cu protrudes to the outer periphery of the contact, and there is a problem that the alumina pedestal and the contact are welded. Occurred.

As described above, in this Example 5, since the Cr skeleton is horizontally cut from the central portion of the plate thickness and divided, and the Cu plate for infiltration is disposed immediately above the low density region exposed on the cut surface, Sometimes the molten Cu enters from the low density region and penetrates outward.
For this reason, since the molten Cu does not permeate preferentially from the outer peripheral portion as in the prior art, a region left locally from infiltration does not occur.
Therefore, in the range where the outer diameter of the infiltration Cu plate is 50 to 100 mm (outer diameter of the infiltration Cu plate / contact outer diameter = 0.5 to 1.0), the inner diameter has a high density with almost no pores. A Cu—Cr contact can be obtained, and as a result, a high pressure resistance can be obtained in the vacuum valve.

In the above embodiments and examples, the Cr skeleton 1 using Cr, which is a high pressure resistant material, is used as the skeleton, and the Cu plate 2, which is a highly conductive material, is used as the infiltrate. It is not limited to this. For example, W or Mo may be used instead of Cr, and Ag may be used instead of Cu.
Further, although hydrogen gas is used as the reducing gas, ammonia gas, for example, may be used.
The present invention can also be applied to a method for manufacturing a contact for a vacuum valve in which a skeleton is formed under a vacuum without a reducing gas, and an infiltrated dissolved in the skeleton is infiltrated.

  1 Cr skeleton (skeleton), 2 Cu plate (infiltrated), 3 low density region, 4 infiltration skeleton, 5 Cu solidified layer, 6 shrinkage nest, 7 pedestal.

Claims (8)

A green compact molding process in which a powder mainly composed of a high pressure resistant material is pressed with a mold to form a green compact;
A skeleton forming step of sintering the green compact to form a plate-shaped skeleton;
A split cutting process in which this skeleton is cut into two at the thickness center to form a cut surface;
A placing step of placing an infiltrant made of a highly conductive material at the center of the cut surface;
A method for manufacturing a contact for a vacuum valve, comprising: an infiltration step in which the infiltrant melted by heating the infiltrant is infiltrated into the skeleton.   The method for manufacturing a contact for a vacuum valve according to claim 1, wherein the green compact is sintered in an atmosphere of a reducing gas.   The method for manufacturing a contact for a vacuum valve according to claim 2, wherein the reducing gas is hydrogen gas.   The method for manufacturing a contact for a vacuum valve according to any one of claims 1 to 3, wherein the high pressure resistant material is Cr and the high conductive material is Cu.   5. The vacuum according to claim 4, wherein the green compact has a molding pressure of 80 to 250 MPa, the Cr has a composition of 35 to 65 wt%, and the Cu has a composition of 65 to 35 wt%. Manufacturing method of contact for valve.   The vacuum valve contact according to claim 4 or 5, wherein the skeleton has an outer diameter of 30 to 105 mm, and the infiltrant has an outer diameter of 5 to 15 mm smaller than the outer diameter of the skeleton. Production method.   The method for manufacturing a contact for a vacuum valve according to any one of claims 4 to 6, wherein the green compact has a powder particle size of 20 to 125 µm.   The ratio (R1 / R2) between the outer diameter R1 of the infiltrated body and the outer diameter R2 of the skeleton is 0.5 to 1.0. The manufacturing method of the contact for vacuum valves as described in a term.

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