JP2006024476A - Manufacturing method of contact material for vacuum valve - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a contact material for a vacuum valve excellent in a breaking property and withstand voltage characteristics. <P>SOLUTION: The manufacturing method of a contact material for a vacuum valve comprises a first process of mixing Cu powder with an average particle size of 20 to 200 μm, Cr powder with an average particle size of 40 to 200 μm, and powder of auxiliary components like W having a melting point higher than that of Cu and an average particle size of 0.3 to 10 μm within a range of 0.1 to 2 vol% against the total volume of the powder; a second process of forming a fused body by fusing the Cu powder and a whole or a part of Cr powder in the mixed powder in a heat resistant container by raising the temperature of the mixed powder obtained by the first process to that of not lower than the melting point of Cu and not higher than that of the auxiliary components, and cooling the fused body in the heat resistant container or by filling the fused body in a mold; and a third process of forming a plurality of contact materials by processing the fused body cooled at the second process. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a contact material for a vacuum valve, and more specifically, to a method for producing a contact material having both excellent large current interruption characteristics and withstand voltage characteristics.

  The vacuum valve contacts are roughly classified into the following four types.

1) Contact for large current interruption represented by CuBi and CuTeSe 2) Contact used for high voltage applications such as Cu-W 3) Contact having low surge characteristics such as Ag-WC 4) To some extent such as Cu-Cr Of these, the following three methods are generally well known as methods for producing CuCr contacts.

1) Solid-phase sintering method Usually, Cr particles having an average particle diameter of about 40 to 200 μm and Cu particles are mixed and molded, and then sintered at a temperature below the melting point of Cu. And sintering is repeated several times. There is an advantage that the Cu / Cr composition ratio can be freely selected. On the other hand, the gas content is likely to increase as compared with the infiltration method of 2).

2) Infiltration method Usually, Cr particles having an average particle diameter of about 40 to 200 μm are put in a container and Cu is infiltrated into the voids of the Cr particles. In some cases, after forming the Cr particles, the Cu is formed into the voids of the Cr compact. This is a manufacturing method for infiltration. It has a feature that it is easier to obtain a material having a higher density than the solid phase sintering method of 1), and hence the gas content is also easily reduced.

3) Arc melting method Cu and Cr raw materials are rapidly heated and quenched by arc heating to form a fine structure. It has a structure with a high mechanical strength and excellent withstand voltage characteristics.

An example of this arc melting method is disclosed in Patent Document 1.
Japanese Patent No. 3382000

  Since Cu and Cr constituting the CuCr contact point have a large density difference, the manufacturing by the melting method requires rapid solidification, and only the method such as the arc melting method is possible. However, this method inevitably increases the manufacturing cost and is industrially difficult. Further, in the infiltration method in which only Cu is dissolved, it is necessary to sufficiently increase the Cr content so that the Cr particles do not flow in advance, and the Cu / Cr composition ratio is limited to about 25 to 60% of Cu. . On the other hand, in solid phase sintering, this composition ratio can be freely selected, but the particle size of the Cr particles in the structure reflects the particle size of the raw material as it is, and generally has a structure in which coarse Cr particles are dispersed. For this reason, if the amount of Cr, which is a component that improves the breakdown voltage characteristics, decreases, the breakdown voltage is insufficient. In order to improve pressure resistance, when fine Cr particles are used as the raw material, the gas content increases and the interruption characteristics deteriorate. Therefore, the solid phase sintering method has both excellent interruption performance and withstand voltage characteristics. There was a limit to doing it.

  The present invention has been made in view of such conventional points, and an object of the present invention is to provide a method for producing a contact material for a vacuum valve that has both excellent breaking performance and withstand voltage characteristics.

  In order to achieve the above object, the method for producing a contact material for a vacuum valve according to the present invention is a Cu powder having an average particle size of 20 to 200 μm, a Cr powder having an average particle size of 40 to 200 μm, and a powder of 0. A first step of mixing auxiliary component powder having an average particle size of 0.3 to 10 μm and a melting point higher than the melting point of Cu in the range of 1 to 2 vol%, and the mixed powder obtained in this first step is Cu After the temperature is raised to a temperature equal to or higher than the melting temperature of the auxiliary component and below the melting point of the auxiliary component, a part or all of the Cu powder and Cr powder in the mixed powder is dissolved in a heat-resistant container to form a solution, From the second step of cooling in a heat-resistant container or filling the mold in a batch and cooling, and the third step of taking out a plurality of contact materials by processing the melt after finishing the second step It is characterized by comprising.

  ADVANTAGE OF THE INVENTION According to this invention, the contact material for vacuum valves which has the outstanding interruption | blocking performance and a withstand voltage characteristic can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

In view of the current state of manufacturing methods for CuCr contacts as described in the section of the problem to be solved by the invention, the inventors firstly applied a solid phase without rapid solidification and without selecting a Cu / Cr ratio. As a result of repeated research aimed at producing a CuCr-based contact material having the same breaking characteristics as a CuCr contact produced by a sintering method, the method of the present invention has been found.

Moreover, the manufacturing method aimed at increasing the yield rate of the contact material obtained by the present invention was added, and the conditions were found.

Furthermore, the inventors have used this method to obtain a CuCr-based contact material having a withstand voltage characteristic that cannot be achieved with a solid-phase CuCr contact at a Cu / Cr composition ratio in the vicinity of Cr 25 wt%, which has excellent interruption characteristics. Succeeded in manufacturing.

  The method for producing a contact material for a vacuum valve according to the first embodiment of the present invention includes a Cu powder having an average particle size of 20 to 200 μm, a Cr powder having an average particle size of 40 to 200 μm, and 0.1 to 0.1 of the entire powder. A first step of mixing auxiliary component powder having an average particle size of 0.3 to 10 μm and a melting point higher than the melting point of Cu in the range of 2 vol%, and the mixed powder obtained in the first step is fused with Cu After heating up to a temperature above the temperature and below the melting point of the auxiliary component and dissolving part or all of the Cu powder and Cr powder in the mixed powder in a heat-resistant container to form a solution, the solution is heat-resistant A second step of cooling in a container or filling the mold in a batch and cooling; and a third step of taking out a plurality of contact materials by cutting or cutting the melt after completion of the second step It consists of a process.

  In the manufacturing method of the contact material for a vacuum valve according to the first embodiment, the auxiliary component fine particles in the mixed powder are mixed with a Cu liquid phase and a Cr solid phase when the mixed powder is held at a melting temperature of Cu or higher. The separation of the two due to the difference in density between the two particles is suppressed, and Cr particles are finely dispersed in the Cu liquid phase. This effect is due to the Cr dissolved in the Cu liquid phase crystallizing on the auxiliary component particles.

  According to a second embodiment of the present invention, in the method for manufacturing a contact material for a vacuum valve according to the first embodiment, the auxiliary component has a specific resistance increment of 3 μΩcm with respect to pure Cu when 1 atomic% is added to pure Cu. / A component that is not more than atomic% is selected.

  In the present invention, since the Cu particles are melted, a component that increases the specific resistance of the Cu phase by dissolving in the Cu liquid phase is inappropriate as an auxiliary component. That is, when the increment of the specific resistance with respect to the pure Cu when the auxiliary component is added to the pure Cu exceeds 3 μΩcm / atomic%, the electrical conductivity is remarkably impaired, so that the interruption characteristic is deteriorated.

According to a third embodiment of the present invention, in the method for manufacturing a contact material for a vacuum valve according to the first or second embodiment, the density of the liquid phase of Cu (883 ° C.) when the density of the auxiliary component is just above the melting point (883 ° C.). Greater than 0.000 g / cm ³ ).

  In the present invention, Cr having a low density with respect to the Cu liquid phase is crystallized on the auxiliary component. However, when the density of the auxiliary component is small, the auxiliary component itself is separated from the Cu phase before the crystallization of Cr. In order to prevent this, a method of crystallizing Cr having a low density on an auxiliary component having a high density relative to the Cu phase is effective.

  According to a fourth embodiment of the present invention, in the method for manufacturing a contact material for a vacuum valve according to any one of the first to third embodiments, the auxiliary component is at least one of W, Mo, Ta, or a carbide thereof. It is selected from these. Specific examples of the auxiliary component that satisfies the conditions of the second or third embodiment include these substances.

  The fifth embodiment of the present invention is a method of manufacturing a contact material for a vacuum valve according to any one of the first to fourth embodiments, and measures Cu and auxiliary components to be blended in the first step, The total amount of the auxiliary component fine particles and 0.2 to 5.0 times the volume of the Cu particles are mixed to obtain a first mixed powder. The remaining Cu is added to the first mixed powder as appropriate, mixed, and then the second mixed powder. It is characterized in that Cr particles are appropriately added to the second mixed powder and mixed to obtain a third mixed powder.

  In the temperature rising process until the Cu powder is melted, when the auxiliary component is in contact with the Cr particles, the auxiliary component is fixed to the Cr surface. Therefore, in order to crystallize Cr on the auxiliary component particles in a finely dispersed state after melting, it is necessary to avoid this sticking as much as possible. For this purpose, it is effective to reduce the contact between Cr and auxiliary components during mixing, and it is important to first uniformly disperse auxiliary component particles in Cu particles by mixing according to the above procedure.

  According to a sixth embodiment of the present invention, in the method for manufacturing a contact material for a vacuum valve according to any one of the first to fifth embodiments, the ratio of the Cu powder in the first step to the entire mixed powder is 60. It is -83 vol%.

  According to the present embodiment, in the material having a Cr content of about 25 wt% (22 vol%) by the solid-phase sintering method, which has an excellent breaking performance but has insufficient withstand voltage characteristics, it is excellent due to the effect of refinement of the structure. It is also possible to combine the withstand voltage characteristics.

  According to a seventh embodiment of the present invention, in the method for manufacturing a contact material for a vacuum valve according to any one of the first to sixth embodiments, a solution is formed between the second step and the third step. On the other hand, the method includes a step of performing at least one processing of compression, rolling, or forging.

  By this processing, fine defects contained in the melt are crushed and the electrical conductivity is increased, so that it is possible to have excellent current-carrying characteristics.

  In an eighth embodiment of the present invention, in the method for manufacturing a contact material for a vacuum valve according to any one of the first to seventh embodiments, the dissolution is performed between the second step and the third step. It has the process of hold | maintaining a body at the temperature of the range of 700-900 degreeC.

  Improvement of the current-carrying characteristics can also be obtained by such heat treatment.

According to a ninth embodiment of the present invention, in the method for producing a contact material for a vacuum valve according to any one of the first to eighth embodiments, a mixed powder is provided between the first step and the second step. It has the process of shape | molding with the pressure of the range of 5-8 ton / cm < ² >.

  In the method according to any one of the first to eighth embodiments, a non-defective part that can be expected to have good electrical characteristics is formed only in a limited part of the entire solution. However, as in the ninth embodiment, this non-defective part can be greatly enlarged by pressurizing the mixed powder in advance before raising it to a temperature equal to or higher than the melting temperature of Cu. However, when this applied pressure is excessive, it prevents the gas confined in the compact from being released during the dissolution of Cu, leading to a decrease in the shut-off performance.

  The tenth embodiment of the present invention was molded at the above pressure when forming a solution by raising the temperature in the second step in the method for manufacturing a contact material for a vacuum valve according to the ninth embodiment. The whole or part of the region sandwiched between two parallel surfaces perpendicular to the center line of the green compact is heated to a temperature not lower than the melting temperature of Cu and not higher than the melting point of the auxiliary component, It is made to move toward the other end from one end, and it is set as the melt | dissolution body which a part or all of Cu powder in a molded object fuse | melted.

  As described above, since the composition variation of Cu and Cr in a wide range can be suppressed even by partially dissolving and solidifying the green compact, the non-defective product can be enlarged.

  Examples of the present invention will be specifically described below.

<Configuration of sample vacuum valve>
First, the configuration of a test vacuum valve to which the contact material for a vacuum valve manufactured according to the present invention is applied will be described.

  FIG. 1 is a cross-sectional view for explaining a configuration example of a test vacuum valve, and FIG. 2 is an enlarged cross-sectional view of an electrode portion of FIG.

  In FIG. 1, the shut-off chamber 1 is vacuum-tight with an insulating container 2 formed in a substantially cylindrical shape by an insulating material, and metal lids 4 a and 4 b provided at both ends via sealing metal fittings 3 a and 3 b. It is configured.

  In the blocking chamber 1, a pair of electrodes 7 and 8 attached to opposite ends of the conductive rods 5 and 6 are disposed. The upper electrode 7 is a fixed electrode and the lower electrode 8 is a movable electrode. A bellows 9 is attached to the conductive rod 6 of the electrode 8 so that the electrode 8 can be moved in the axial direction while keeping the inside of the blocking chamber 1 in a vacuum-tight state. A metal arc shield 10 is provided on the top of the bellows 9 to prevent the bellows 9 from being covered with arc vapor. Further, a metal arc shield 11 is provided in the blocking chamber 1 so as to cover the electrodes 7 and 8, thereby preventing the insulating container 2 from being covered with the arc vapor.

  Furthermore, as shown in an enlarged view in FIG. 2, the electrode 8 is fixed to the conductive rod 6 by a brazing portion 12 or is crimped and connected by caulking. The contact 13 a is attached to the electrode 8 by brazing 14. The contact 13b is attached to the electrode 7 by brazing.

<Production method of contact material>
The contact material manufacturing process in the vacuum valve contact material manufacturing method according to the present invention will be described.

  First, the contact manufacturing process of Examples 1 to 21 and Comparative Examples 1 to 18 will be described.

[First step]
First, Cr powder, Cu powder and auxiliary component powder having a predetermined particle diameter are mixed in any of the following procedures.

  A: Mix all powders at once and mix.

  B: Cr powder and auxiliary component powder are mixed, and Cu powder is mixed with this mixed powder.

  C: First, the total amount of the auxiliary component powder and the same amount of Cu powder are mixed, and after mixing this mixed powder and the remaining Cu powder, Cr powder is further mixed.

  D: First, the total amount of the auxiliary component powder and the same amount of Cu powder are mixed, and the same amount of Cu powder as this mixed powder is further added and mixed. This operation is repeated, and at each time when new Cu powder is added, if the remaining Cu powder becomes less than the amount of mixed powder, this remaining Cu powder is further added and mixed, and then Cr powder is mixed. Then, the mixing step is completed.

  E: Only Cu powder and Cr powder are mixed.

[Second step]
Next, this mixed powder is put into a melting crucible having a diameter of 60 mm and melted at a temperature equal to or higher than the melting point of Cu by high-frequency induction heating in a vacuum (dissolution method A). The melt is then cooled in the crucible.

[Third step]
Further, the melt is taken out from the crucible, and a contact of φ40 mm is processed and taken out. In these examples and comparative examples, the conditions shown below were used as standard manufacturing conditions, and the case where any of these conditions was changed as a parameter was examined.

・ Raw material average particle size:
Cu: 100 μm
Cr ... 100μm
Auxiliary component: 1 μm
・ Auxiliary ingredient… W
・ Raw material volume ratio:
Cu: Cr: auxiliary component = 71.2: 28.3: 0.5
In Example 22, the columnar melt was taken out of the crucible, forged into a prismatic shape, and further rolled into a plate shape.

  In Examples 23 to 24 and Comparative Examples 19 to 20, after the melt was taken out of the crucible, the melt was held at a temperature in the range of 600 to 1000 ° C. in a vacuum.

In Examples 25 to 26 and Comparative Examples 21 to 22, before the mixed powder was put into the crucible, it was molded at a pressure in the range of ^{3 to} 10 ton / cm ² and this molded body was set in the crucible.

  In Example 27, in the second step, the entire powder was not melted at once, and an area sandwiched between two parallel surfaces perpendicular to the center line of the green compact was inductively heated as shown in FIG. Only the Cu powder is melted by raising the temperature to a temperature equal to or higher than the melting temperature of Cu and equal to or lower than the melting point of the auxiliary component, and the Cu powder in the molded body is moved by moving this region from one end to the other end of the molded body. It melted sequentially and it was set as the solution (dissolution method B). That is, as shown in FIG. 3, the green compact 15 is put in a crucible (heat-resistant container) 20, and a region sandwiched between two parallel surfaces 18 perpendicular to the center line 21 of the green body 15 is induction-dissolved. The coil 17 is induction-heated to raise the temperature to a temperature equal to or higher than the melting temperature of Cu and lower than the melting point of the auxiliary component to melt only the Cu powder to form a molten layer 16 and sandwiched between the parallel surfaces 18. The Cu powder in the compact was sequentially melted by moving the region to be heated by induction from one end of the compact toward the other end to obtain a melt. In addition, in order to move the area | region which is pinched | interposed by the parallel surface 18 and is induction-heated with the induction melting coil 17, the induction melting coil 17 may be moved, or the crucible (heat-resistant container) 20 which accommodated the molded object 15 is moved. You may let them.

<Evaluation method and conditions>
Next, evaluation methods and evaluation conditions for obtaining data explaining examples and comparative examples of the present invention will be described.

(Material property evaluation)
(1) Relative density The density was measured by the Archimedes method, the true density was determined from the composition ratio, and converted to the relative density. As a result, the value of Comparative Example 1 was relatively compared with 1.00, and 0.95 or more was regarded as acceptable.

(2) Hardness variation Rockwell hardness was measured, and the value of Example 1 was relatively compared as 1.00, and less than 2.00 was accepted.

(Electrical characteristics evaluation)
(1) Breaking characteristic The breaking test was conducted according to the JEC standard No. 5 test, thereby evaluating the breaking characteristic.

(2) Dielectric strength characteristics Evaluated based on the probability of re-ignition in advanced small current tests. The current is 500 A and the recovery voltage is 12.5 kV. The number of tests is 2000. The relative value when the re-ignition occurrence probability of Example 17 is 1.0 is shown, and the relative value of 1.2 or less was accepted.

(3) Energization characteristics Conductivity is evaluated by eddy current measurement, displayed as a relative value to the measurement of Example 1, and this value is 1 in consideration of application to switchgear used in a large current energization region. .1 or higher was accepted.

(Mass productivity evaluation)
(1) Non-defective product ratio The ratio of the area | region which can satisfy | fill all of material property evaluation item (1), (2) and electrical property evaluation item (1) among melt | dissolution was investigated. The contact diameter r to be evaluated was made constant, the diameter of the melt was changed, and the lower limit R of the melt diameter satisfying the above conditions was determined and calculated by (r / R) ² . From the viewpoint of mass productivity, the acceptable product rate was 0.9 or more.

<Examples and Comparative Examples>
Next, the manufacturing conditions of each contact, its problems, and the corresponding material characteristics and electrical characteristics data will be discussed with reference to FIGS.

  First, in Examples 1 to 19 and Comparative Examples 1 to 15, the relative density and hardness variation of the material, which are evaluation items of the soundness of the manufactured material, are examined, and in addition to this, a CuCr contact should be provided. The blocking performance, which is a basic characteristic, was evaluated.

(Examples 1-2 and Comparative Examples 1-2)
The characteristics were evaluated by changing the ratio of Cr: auxiliary component in the standard production conditions from 28.8: 0 to 24.8: 4.0. In Example 1 and Example 2 in which the amount of auxiliary component is in the range of 0.1 to 2 vol%, a contact with relatively little variation is obtained and the interruption characteristic is passed, but in Comparative Example 1 that does not include an auxiliary component, Since Cr is in a state separated from Cu, variation in hardness (particularly, variation between different contacts) is large, and the interruption performance is also rejected. Further, in Comparative Example 2 where the amount of the auxiliary component is as large as 4 vol%, the interruption characteristic is rejected due to a decrease in the interruption performance due to local heating of the auxiliary component.

(Examples 3-5 and Comparative Examples 3-4)
The average particle size of the Cu powder under the standard production conditions was changed in the range of 10 to 400 μm, and the characteristics were evaluated. In Examples 3 to 5 in which the average particle diameter of the Cu powder is in the range of 20 to 200 μm, contacts with relatively little variation are obtained and the interruption characteristics are passed, but the comparison is made with the average particle diameter of Cu being 10 μm. In Example 3, since the gas content of the contact material is too high, the interruption characteristic is rejected. Further, Comparative Example 4 having a large average particle diameter of Cu of 400 μm is in a state where defects are dispersed in the contact material, so that the electrical conductivity is low and the interruption characteristic is insufficient.

(Examples 6-8 and Comparative Examples 5-6)
The average particle diameter of Cr powder under the standard production conditions was changed in the range of 20 to 400 μm, and the characteristics were evaluated. In Examples 6 to 8 in which the average particle diameter of the Cr powder is in the range of 40 to 200 μm, contacts with relatively little variation are obtained and the interruption characteristics are passed, but the comparison is made with the average particle diameter of Cr being 20 μm. In Example 5, since the gas content of the contact material is too high, the interruption characteristic is rejected. Further, Comparative Example 6 having a large average particle size of Cr of 400 μm is in a state in which defects are dispersed in the contact material, so that the electrical conductivity is low and the interruption characteristic is insufficient.

(Examples 9-11 and Comparative Examples 7-8)
The average particle size of the auxiliary component powder under the standard production conditions was changed in the range of 0.1 to 10 μm, and the characteristics were evaluated. In Examples 9 to 11 in which the average particle diameter of the auxiliary component powder is in the range of 0.3 to 3 μm, contacts with relatively little variation are obtained, and the interruption characteristics are also passed. In Comparative Example 7 having a thickness of 0.1 μm, the auxiliary component particles agglomerate and become large composite particles. Therefore, the dispersion of Cr is insufficient, and the gas content is increased. It has become. Further, in Comparative Example 8 in which the average particle size of the auxiliary component is as large as 10 μm, separation of Cr and Cu is remarkable, so that the contact material structure is inhomogeneous and the interruption characteristic is insufficient.

(Example 12 and Comparative Example 9)
Contacts were produced using Ag and W as auxiliary components for the standard production conditions, and the characteristics were evaluated. In Example 12, where the auxiliary component is W, a contact with relatively little variation was obtained and the interruption characteristic was also passed. However, in Comparative Example 9 in which Ag was used as the auxiliary component, Ag was completely dissolved in Cu. Therefore, the fine dispersion of Cr does not occur, and the separation of Cr and Cu becomes remarkable, so that the material structure becomes inhomogeneous and the barrier property is rejected.

(Examples 13 to 14 and Comparative Example 10)
Contacts were manufactured using Nb, Mo and WC as auxiliary components for the standard manufacturing conditions, and the characteristics were evaluated. In Examples 13 to 14 where the auxiliary components are Mo and WC, respectively, contacts with relatively little variation are obtained and the interruption characteristics are also passed. However, in Comparative Example 10 using Nb as the auxiliary component, Cu is changed to Cu. Due to the influence of the decrease in the conductivity due to the solid solution of Nb, the interruption characteristic is rejected.

(Example 15 and Comparative Example 11)
Contacts were manufactured using TiC and Ta as auxiliary components of the standard manufacturing conditions, and the characteristics were evaluated. In Example 15 where the auxiliary component is Ta, contacts with relatively little variation are obtained and the interruption characteristics are also passed. However, in Comparative Example 11 using TiC as the auxiliary component, TiC having a low density is on the Cu liquid phase. As a result, the Cr is not finely dispersed and the separation of Cr and Cu becomes remarkable, so that the material structure becomes inhomogeneous and the barrier property is rejected.

(Examples 16 to 17 and Comparative Examples 12 to 13)
Characteristic evaluation was performed by changing the standard production conditions and the mixing procedure of powders A to D. In Example 16 and Example 17 using procedures C and D, a contact with relatively little variation was obtained and the interruption characteristics passed, but in Comparative Examples 12 and 13 using Procedures A and B, Since the auxiliary component W adheres to the surface of the Cr particles, the fine dispersion of Cr does not occur, the separation of Cr and Cu becomes remarkable, the material structure becomes inhomogeneous, and the barrier property is rejected.

(Examples 18 to 19 and Comparative Examples 14 to 15)
Characteristic evaluation was performed by changing the ratio of the Cu powder volume to the W powder volume in the initial mixing of the Cu powder and the W powder in the powder mixing procedure D in the range of 0.1 to 10. In Examples 18 and 19 in which the ratio of the volume of Cu powder to the volume of W powder is in the range of 0.2 to 5, a contact with a relatively small variation in hardness is obtained, and the breaking characteristics are also passed. In Comparative Example 14 having a ratio of 0.1 and Comparative Example 15 having a ratio of 0.1, since the dispersion of the auxiliary components W and Cu is insufficient, some W particles adhere to the Cr particles. Is insufficient, and the shut-off characteristics are rejected.

  In the above embodiments, the quality of the characteristics is judged by the interruption characteristics, but the CuCr contacts are often applied to switchgears used in a high voltage region. Therefore, in the following examples, conditions for satisfying the withstand voltage characteristics at the same time were evaluated.

(Examples 20 to 21 and Comparative Examples 16 to 17)
The characteristics were evaluated by changing the Cu: Cr ratio of the standard production conditions from 49.9: 49.6 to 88.5: 11.0. In Examples 20 and 21 in which the Cu amount is in the range of 60 to 83 vol%, contacts with relatively little variation are obtained, and both the breaking characteristics and the withstand voltage characteristics pass, but the Cu amount is 49.6 vol%. In comparative example 16 with a small amount, the amount of Cr is large and the thermal conductivity is low, so the interruption performance is unacceptable. Further, in Comparative Example 17 where the amount of Cu is as large as 88.5 vol%, the amount of Cr dispersed particles is small, and a part of the surface of W of the auxiliary component particles is not covered with crystallized Cr. The voltage characteristics are rejected.

  In addition, since the CuCr contact is also applied to a switching device used in a large current energizing region, in the following examples, various conditions for simultaneously satisfying the energizing characteristics in addition to the breaking characteristics were evaluated.

(Example 22 and Comparative Example 18)
Characteristic evaluation of both the case where the forging and rolling step of the melt was put between the second step and the third step of the standard production conditions and the case where it was not put was performed. In Example 22 in which the forging and rolling process was added, contacts with relatively little variation were obtained, and both the breaking characteristics and the current-carrying characteristics passed, but in Comparative Example 18 in which this process was not added, there was a built-in defect. In order to reduce heat conduction, the current-carrying characteristics are rejected.

(Examples 23 to 24 and Comparative Examples 19 to 20)
The melt was subjected to a heat treatment step between the second step and the third step under the standard production conditions, and the characteristics were evaluated by changing the heat treatment temperature. In Example 23 and Example 24 where the heat treatment temperature is in the range of 700 to 900 ° C., contacts with relatively little variation are obtained, and both the breaking characteristics and the energization characteristics pass, but the heat treatment temperature is 600 ° C. In the low comparative example 19, since the precipitation of Cr dissolved in the Cu phase is insufficient, the current-carrying characteristics are rejected. Further, in Comparative Example 20, where the heat treatment temperature is as high as 1000 ° C., the amount of Cr dissolved in the Cu phase is increased during the heat treatment, and thus the energization characteristics are unacceptable.

In the above example, evaluation was performed by taking out a contact of φ40 mm from a melt of φ60 mm. However, in consideration of mass productivity, it is also necessary to evaluate the unused portion. Then, the ratio of the area | region which can satisfy | fill all of material property evaluation item (1), (2) and electrical property evaluation item (1) among melt | dissolution was investigated. The contact diameter r to be evaluated was made constant, the diameter of the melt was changed, the lower limit R of the melt diameter that satisfies the above conditions was determined, and the yield rate was calculated from (r / R) ² .

(Examples 25-26 and Comparative Examples 21-22)
A mixed powder forming step was inserted between the first step and the second step under the standard production conditions, and the characteristics were evaluated by changing the forming pressure. In Examples 25 and Example 26 the molding pressure is in the range of 5~8ton / cm ^2, but the yield rate is passed 90% or more, the low molding pressure and 3 ton / cm ² Comparative Example 21, Cu Since the movement of Cr particles occurs at the initial stage of the powder particles, the current-carrying characteristics are rejected. Further, in Comparative Example 22 where the molding pressure is as high as 10 ton / cm ² , the gas in the powder cannot be completely removed when the Cu powder is melted, so that the cutoff characteristic is unacceptable.

(Example 27 and Comparative Example 23)
In Comparative Example 23, in which the entire powder is dissolved at the same time in the second step, and the region sandwiched between two parallel surfaces perpendicular to the center line of the green compact is not heated at the same time. Only the Cu powder is melted by raising the temperature to a temperature equal to or higher than the melting temperature of Cu and equal to or lower than the melting point of the auxiliary component, and the Cu powder in the molded body is moved by moving this region from one end to the other end of the molded body. Comparative evaluation was made with Example 27, which was sequentially melted to form a solution. In Example 27 in which the powder was sequentially dissolved, the non-defective product ratio passed 90% or more, but in Comparative Example 23 in which the powder was dissolved at one time, the gas in the powder was not completely removed when the Cu powder was melted. As a result, the yield rate is decreasing.

(Other examples)
Similar effects can be obtained when Mo ₂ C, TaC is used as an auxiliary component in addition to the auxiliary components shown in the above-described embodiments.

(Effect of Example)
As described above, in the embodiment of the present invention, the molten Cu and Cr particles exist without being separated by the action of the auxiliary component, and the fine Cr particles are finely dispersed between the Cr particles introduced from the raw material. It was possible to provide a method for manufacturing a material. In addition, according to the embodiment of the present invention, by setting the amount of Cr in an appropriate range, it has excellent breaking performance and withstand voltage performance that could not be realized with a contact material manufactured by a conventional solid phase sintering method. We made it possible to provide contact materials. In addition, by applying a process such as forging and rolling and a heat treatment process to this basic manufacturing method, it was possible to combine current-carrying characteristics. Furthermore, by forming the powder before dissolution and performing the dissolution partially and continuously, a production method with a high yield rate suitable for mass production could be provided.

Sectional drawing which shows an example of the vacuum valve to which the contact material for vacuum valves manufactured by this invention is applied. The principal part expanded sectional view of FIG. Sectional drawing of the crucible which accommodated the molded object for demonstrating Example 27 of this invention. The table | surface which shows Examples 1-15 and the manufacturing conditions (part) of Comparative Examples 1-11. The table | surface which shows Examples 1-15 and the manufacture conditions (remainder) and evaluation result of Comparative Examples 1-11. The table | surface which shows Example 16-27 and the manufacturing conditions (part) of Comparative Examples 12-23. The table | surface which shows the manufacturing conditions (remainder) and evaluation result of Examples 16-27 and Comparative Examples 12-23.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Shut-off chamber 2 ... Insulation container 3a, 3b ... Sealing metal fittings 4a, 4b ... Lid bodies 5, 6 ... Conductive rod 7, 8 ... Electrode 9 ... Bellows 12 ... Brazing part 10, 11 ... Arc shield 13a, 13b ... Contact 14 ... Brazing layer 15 ... Molded body 16 ... Molten layer 17 ... Induction melting coil 18 ... Two surfaces 20 parallel to the center line of the molded body ... Crucible (heat-resistant container)
21 ... Molded body center line

Claims (10)

  Cu powder having an average particle diameter of 20 to 200 μm, Cr powder having an average particle diameter of 40 to 200 μm, and an average particle diameter of 0.3 to 10 μm and a melting point of Cu in the range of 0.1 to 2 vol% of the whole powder The first step of mixing the powder of the higher auxiliary component, and the mixed powder obtained in the first step is heated to a temperature not lower than the melting temperature of Cu and lower than the melting point of the auxiliary component. A second step of melting a part or all of the Cu powder and Cr powder in a heat-resistant container to form a melt, and then cooling the melt in the heat-resistant container or filling it in a mold and cooling it. And a third step of taking out a plurality of contact materials by processing the melt after finishing the second step, and a method for producing a contact material for a vacuum valve.   2. The vacuum valve component according to claim 1, wherein the auxiliary component is selected such that an increment of specific resistance with respect to pure Cu when added at 1 atomic% to pure Cu is 3 μΩcm / atomic% or less. Manufacturing method of contact material.   The method for producing a contact material for a vacuum valve according to claim 1 or 2, wherein the density of the auxiliary component is larger than the density of the liquid phase of Cu immediately above the melting point.   The method for manufacturing a contact material for a vacuum valve according to any one of claims 1 to 3, wherein the auxiliary component is selected from at least one of W, Mo, Ta, and carbides thereof.   Cu and auxiliary components to be blended in the first step are weighed, and the total amount of auxiliary component fine particles and Cu particles of 0.2 to 5.0 times the volume thereof are mixed to form a first mixed powder, The remaining Cu is appropriately added to the first mixed powder and mixed to obtain a second mixed powder, and Cr particles are appropriately added to the second mixed powder and mixed to obtain a third mixed powder. The manufacturing method of the contact material for vacuum valves in any one of Claim 1 thru | or 4.   6. The method for producing a contact material for a vacuum valve according to claim 1, wherein a ratio of the Cu powder to the entire mixed powder in the first step is 60 to 83 vol%.   7. The method according to claim 1, further comprising a step of performing at least one processing of compression, rolling, and forging on the melt between the second step and the third step. The manufacturing method of the contact material for vacuum valves in any one.   8. The method according to claim 1, further comprising a step of holding the melt at a temperature in a range of 700 to 900 ° C. between the second step and the third step. The manufacturing method of the contact material for vacuum valves of description. 9. The method according to claim 1, further comprising a step of forming the mixed powder at a pressure in a range of 5 to 8 ton / cm < ² > between the first step and the second step. A method for producing a contact material for a vacuum valve according to claim 1.   In the second step, when forming a melt by raising the temperature, the whole or part of the region sandwiched between two parallel surfaces perpendicular to the center line of the compact formed by the pressure is Cu. The molten body is heated to a temperature equal to or higher than the melting temperature of the auxiliary component and equal to or lower than the melting point of the auxiliary component, the region is moved from one end of the molded body toward the other end, and a part or all of Cu powder in the molded body is melted. The manufacturing method of the contact material for vacuum valves of Claim 9 characterized by the above-mentioned.

Images