JP6398415B2 - Method for producing electrode material - Google Patents

Description

  The present invention relates to a composition control technique for electrode materials.

  Electrode materials used for electrodes such as vacuum interrupter (VI) include (1) large breaking capacity, (2) high withstand voltage performance, (3) low contact resistance, and (4) welding resistance. It is required to satisfy the following characteristics: (5) low contact consumption, (6) low cutting current, (7) excellent workability, (8) high mechanical strength, etc. .

  A copper (Cu) -chromium (Cr) electrode has characteristics such as a large breaking capacity, a high withstand voltage performance, and a high welding resistance, and is widely used as a contact material for a vacuum interrupter. In the Cu-Cr electrode, it has been reported that the smaller the particle size of the Cr particles, the better in terms of breaking current and contact resistance (for example, Non-Patent Document 1).

  As a method for producing a Cu—Cr electrode material, generally, two methods of solid phase sintering and infiltration are well known (for example, Patent Documents 1-4). The solid-phase sintering method mixes Cu with good conductivity and Cr with excellent arc resistance at a constant ratio, presses the mixed powder, and then sinters in a non-oxidizing atmosphere such as in a vacuum. To produce a sintered body. The solid-phase sintering method has an advantage that the composition of Cu and Cr can be freely selected.

  On the other hand, the infiltration method is a method in which Cr powder is pressure-molded (or not molded), filled into a container, and heated to a temperature higher than the melting point of Cu in a non-oxidizing atmosphere such as in a vacuum. Cu is infiltrated into the electrode to produce an electrode. The infiltration method cannot freely select the composition ratio of Cu and Cr, but has the advantage that a material with less gas and voids can be obtained and the mechanical strength is higher than the solid phase sintering method.

  In recent years, the use conditions of vacuum interrupters have become stricter, and the application of vacuum interrupters to capacitor circuits has been expanded. In the capacitor circuit, since a voltage 2 to 3 times the normal voltage is applied between the electrodes, it is considered that the contact surface is remarkably damaged by an arc at the time of current interruption or current switching and re-ignition is likely to occur. Therefore, an electrode material having a withstand voltage performance and a current interruption performance superior to conventional Cu—Cr electrodes is required.

  As a method for producing a Cu-Cr-based electrode material with good electrical characteristics such as current interruption performance and withstand voltage performance, a Cr powder that improves electrical characteristics and a finer Cr particle are made into Cu powder as a base material. After mixing heat-resistant element (molybdenum (Mo), tungsten (W), niobium (Nb), tantalum (Ta), vanadium (V), zirconium (Zr), etc.) powder, the mixed powder is inserted into a mold and added. There is a method of manufacturing an electrode that is compacted to form a sintered body (for example, Patent Documents 1 and 2).

  Specifically, a heat-resistant element is added to a Cu—Cr-based electrode material made from Cr having a particle size of 200 to 300 μm, and Cr is refined through a microstructure technique. That is, alloying of Cr and a heat-resistant element is promoted, and precipitation of fine Cr—X (X is a heat-resistant element) particles is increased inside the Cu base material structure. As a result, Cr particles having a diameter of 20 to 60 μm are uniformly dispersed in the Cu base structure in a form having a heat-resistant element therein.

  Also, an electrode manufacturing method in which a plurality of types of heat-resistant elements are solid-phase diffused to form a solid solution containing a plurality of types of heat-resistant elements, a powder obtained by pulverizing the solid solution and a copper powder are mixed, and sintered after pressure forming (For example, Patent Document 4). In this manufacturing method, heat resistant elements such as Cr and Mo are contained in the electrode structure without applying the fine structure technique.

JP 2012-7203 A JP 2002-180150 A Japanese Patent Laid-Open No. 2004-211173 Japanese Patent Laid-Open No. 4-334832

RIEDER, F. ua, “The Influence of Composition and Cr Particle Size of Cu / Cr Contacts on Chopping Current, Contact Resistance, and Breakdown Voltage in Vacuum Interrupters”, IEEE Transactions on Components, Hybrids, and Manufacturing Technology, Vol. 12, 1989, 273-283

  The present invention is to provide an electrode material having a withstand voltage performance and a current interruption performance superior to those of a conventional Cu-Cr electrode. In particular, it is difficult to obtain a fine material that is difficult to obtain by conventional solid solution die press molding. An object is to provide an electrode material having a heat-resistant element.

  One aspect of the electrode material of the present invention that achieves the above object is a solid solution powder obtained by mixing a heat-resistant element and a Cr powder having a particle size of 45 μm or less, and pulverizing the solid solution obtained by heating, Cu powder, An electrode material obtained by sintering a molded body obtained by molding a mixed powder in which Cu is mixed, and the electrode material has a weight ratio of 40 to 80% Cu and 2 to 30% Cr. The heat-resistant element is contained in an amount of 10 to 54%, and the content of the heat-resistant element is larger than the content of Cr in a weight ratio.

  Another aspect of the electrode material of the present invention that achieves the above object is that, in the electrode material, the solid solution powder has lost a peak corresponding to Cr element in the X-ray diffraction measurement of the solid solution powder. It is a feature.

  According to the above invention, the withstand voltage performance and the current interruption performance of the electrode material are improved.

It is a flowchart of the manufacturing method of the electrode material which concerns on embodiment of this invention. It is a schematic sectional drawing of the vacuum interrupter which has the electrode material which concerns on embodiment of this invention. It is a figure which shows the measurement result of the XRD measurement of the MoCr solid solution which concerns on the electrode material of Example 1. FIG. It is a figure which shows the measurement result of the XRD measurement of the MoCr solid solution which concerns on the electrode material of Example 1. FIG. 2 is an electron micrograph of the electrode material of Example 1. 4 is an electron micrograph of an electrode material of Comparative Example 1.

  The electrode material which concerns on embodiment of this invention is demonstrated in detail with reference to figures. In the description of the embodiment, unless otherwise specified, the average particle diameter (median diameter d50), particle diameter, and volume relative particle amount are measured by a laser diffraction particle size distribution measuring apparatus (Cirrus Corporation: Cirrus 1090L). Value.

  The present invention relates to an electrode material containing copper (Cu), chromium (Cr), and a heat-resistant element (Mo, etc.), and a technique for controlling the composition so as to have a structure in which a solid solution of Cr and the heat-resistant element is finely dispersed in the electrode material. It is about. By controlling the composition in this way, an electrode material excellent in breaking performance and withstand voltage performance and mass productivity is obtained.

  In particular, the electrode material of the present invention is a heat-resistant element under conditions that can be industrially implemented by mixing the weight ratio of the heat-resistant element and Cr at a ratio of heat-resistant element> Cr when forming a solid solution of the heat-resistant element and Cr. And a solid solution powder of Cr can be obtained. Further, in the X-ray diffraction measurement of the solid solution powder of the heat-resistant element and Cr, by reacting the heat-resistant element with Cr until the Cr element peak substantially disappears, the resistance of the electrode material is reduced without impairing the mechanical strength and workability. The voltage performance and current interruption performance can be improved.

  As the Cu powder, for example, a commercially available electrolytic copper powder is used. The shape of the Cu powder is not necessarily a dendritic shape, and may be a spherical shape such as an atomized powder or an irregular shape. In addition, the particle size of the Cu powder is not particularly limited, and Cu powder having a particle size generally used in the sintering method may be used. By containing 40 to 80% by weight of Cu with respect to the electrode material, the contact resistance of the electrode material can be reduced without impairing the withstand voltage performance and the current interruption performance. If the Cu content exceeds 80%, the mechanical strength of the electrode material may be reduced, and if the Cu content is less than 40%, the current interruption performance may be reduced due to a decrease in the conductivity of the electrode material. This is because there is a fear. Note that the total of Cu, Cr and heat-resistant elements added to the electrode material does not exceed 100% by weight.

  Examples of the heat-resistant element include molybdenum (Mo), tungsten (W), tantalum (Ta), niobium (Nb), vanadium (V), zirconium (Zr), beryllium (Be), hafnium (Hf), and iridium (Ir). In addition, elements selected from elements such as platinum (Pt), titanium (Ti), silicon (Si), rhodium (Rh), and ruthenium (Ru) can be used alone or in combination. In particular, it is preferable to use Mo, W, Ta, Nb, V, or Zr, which has a remarkable effect of refining Cr particles. When the heat-resistant element is used as a powder, the average particle diameter of the heat-resistant element powder is, for example, 2 to 20 μm, and more preferably 2 to 10 μm, so that the electrode material contains particles containing Cr (a solid solution of the heat-resistant element and Cr). Can be finely dispersed and uniformly dispersed. By containing 10 to 54% by weight of the heat-resistant element with respect to the electrode material, it is possible to improve the withstand voltage performance and current interruption performance of the electrode material without impairing the mechanical strength and workability.

  By containing 2 to 30% by weight of Cr with respect to the electrode material, it is possible to improve the withstand voltage performance and the current interruption performance of the electrode material without impairing the mechanical strength and workability. When using Cr powder, for example, by setting the particle size of Cr powder to −325 mesh (particle size of 45 μm or less), an electrode material excellent in withstand voltage performance and current interruption performance can be obtained. Since the particle size of the Cr powder used is small, the remaining Cr particles are refined by Mo or Cu during the main sintering, and the particle size becomes sufficiently small, so that the contact resistance of the electrode surface becomes low. In addition, it is preferable to use a Cr powder having a small particle diameter in order to disperse particles containing fine Cr in the electrode material, but the amount of impurities contained in the electrode material increases as the Cr particles become finer. Current interrupting performance is reduced. An increase in the impurities of the electrode material by reducing the particle size of the Cr particles cannot be avoided when Cr is finely pulverized. However, a Cr powder having a particle size of less than −325 mesh may be used as long as Cr can be made into a fine powder in an inert gas, for example, an inert gas. It is preferable to use a Cr powder having a small particle diameter in order to disperse the particles containing modified Cr.

  A method for manufacturing an electrode material according to an embodiment of the present invention will be described in detail with reference to the flowchart of FIG. In the following description, Mo is exemplified as the heat-resistant element, but the same applies to the case where powder of other heat-resistant elements is used.

  In the mixing step S1, heat-resistant element powder (for example, Mo powder) and Cr powder are mixed. For example, by setting the particle size of Cr powder to be larger than the particle size of Mo powder and −325 mesh, a MoCr solid solution can be formed at a heat treatment temperature and a heat treatment time excellent in mass productivity. In the mixed powder, the weight of Mo is larger than the weight of Cr, more preferably the weight of Mo is 3 or more with respect to the weight of Cr, and more preferably the weight of Mo is 7 or more with respect to the weight of Cr. By mixing the Mo powder and the Cr powder so as to become, in the subsequent pulverization step S3, the force required for pulverization is reduced, and a finer powder can be obtained.

  In the heat treatment step S2, the mixed powder of the Mo powder and the Cr powder obtained in the mixing step S1 is filled in a container (for example, an alumina container) that does not react with Mo and Cr, and a non-oxidizing atmosphere (hydrogen atmosphere or vacuum atmosphere). Etc.) at a predetermined temperature (for example, 1200 ° C. to 1500 ° C.). By performing the heat treatment, a MoCr solid solution in which Mo and Cr are in solution with each other is obtained. In the heat treatment step S2, it is preferable to perform the heat treatment so that the remaining Cr element does not exist. For example, in the heat treatment step S2, the temperature and time of the heat treatment are selected so that the Cr element peak (and the Mo element peak) in the X-ray analysis of the MoCr solid solution disappears.

Further, in the heat treatment step S2, the mixed powder may be pressure-formed (pressed) before the heat treatment. By pressure forming the mixed powder, interdiffusion between Mo and Cr is promoted, and the heat treatment time can be shortened or the heat treatment temperature can be reduced. The pressure at the time of pressure molding is not particularly limited, but is preferably 0.1 t / cm ² or less. When the pressure at the time of pressure molding of the mixed powder is very large, the sintered body after the heat treatment becomes hard, and there is a possibility that the pulverization operation in the subsequent pulverization step S3 may be difficult.

  In the pulverization step S3, the MoCr solid solution is pulverized using a pulverizer (for example, a planetary ball mill) to obtain a powder containing the MoCr solid solution (hereinafter referred to as MoCr powder). The pulverizing atmosphere in the pulverizing step S3 is preferably a non-oxidizing atmosphere, but may be pulverized in the air. The pulverization conditions may be such that the particles (secondary particles) in which the MoCr solid solution particles are bonded to each other are pulverized. In addition, in the pulverization of the MoCr solid solution, the longer the pulverization time, the smaller the average particle diameter of the MoCr solid solution particles. Therefore, for example, in the MoCr powder, by setting the pulverization conditions such that the volume relative particle amount of particles having a particle size of 30 μm or less (more preferably, particles having a particle size of 20 μm or less) is 50% or more, MoCr particles ( Particles in which Mo and Cr are dissolved and dissolved in each other) and an electrode material in which the Cu structure is uniformly dispersed (that is, an electrode material excellent in withstand voltage performance) can be obtained.

In the Cu powder mixing step S4, the MoCr powder obtained in the pulverizing step S3 and the Cu powder are mixed. After mixing, a mixed powder of MoCr powder and Cu powder (hereinafter referred to as MoCr-Cu powder) is pressure-molded. The molding pressure at the time of molding is, for example, a molding pressure (for example, 1 to 4 t / cm ² ) generally used in a sintering method.

  In the sintering step S5, the molded MoCr—Cu powder is sintered to obtain the electrode material according to the embodiment of the present invention. Sintering is performed in a non-oxidizing atmosphere (for example, in a hydrogen atmosphere or a vacuum atmosphere) at a temperature not higher than the melting point of Cu (1083 ° C.).

  In addition, a vacuum interrupter can be comprised using the electrode material which concerns on embodiment of this invention. As shown in FIG. 2, a vacuum interrupter 1 having an electrode material according to an embodiment of the present invention includes a vacuum vessel 2, a fixed electrode 3, a movable electrode 4, and a main shield 10.

  The vacuum vessel 2 is configured by sealing both open end portions of the insulating cylinder 5 with a fixed side end plate 6 and a movable side end plate 7, respectively.

  The fixed electrode 3 is fixed in a state of passing through the fixed side end plate 6. One end of the fixed electrode 3 is fixed so as to face one end of the movable electrode 4 in the vacuum vessel 2, and the end of the fixed electrode 3 facing the movable electrode 4 is in accordance with the embodiment of the present invention. An electrode contact material 8 which is an electrode material is provided.

  The movable electrode 4 is provided on the movable side end plate 7. The movable electrode 4 is provided coaxially with the fixed electrode 3. The movable electrode 4 is moved in the axial direction by an opening / closing means (not shown), and the fixed electrode 3 and the movable electrode 4 are opened and closed. An electrode contact material 8 is provided at the end of the movable electrode 4 facing the fixed electrode 3. A bellows 9 is provided between the movable electrode 4 and the movable side end plate 7, and the movable electrode 4 is moved up and down while keeping the inside of the vacuum vessel 2 in a vacuum, so that the fixed electrode 3 and the movable electrode 4 can be opened and closed. Done.

  The main shield 10 is provided so as to cover a contact portion between the electrode contact material 8 of the fixed electrode 3 and the electrode contact material 8 of the movable electrode 4, and is insulated from an arc generated between the fixed electrode 3 and the movable electrode 4. Protect 5

[Example 1]
A specific example is given and the electrode material which concerns on embodiment of this invention is demonstrated in detail. The electrode material of Example 1 is an electrode material produced according to the flowchart shown in FIG.

  Mo powder having a particle size of 0.8 to 6 μm was used. The average particle size of the Mo powder was measured by the Fischer method and found to be 3.3 μm. As the Cr powder, powder classified by −325 mesh (a sieve opening of 45 μm), that is, a powder having a particle size of 45 μm or less was used. As the Cu powder, a commercially available electrolytic copper powder was used.

  In the electrode material of Example 1, Mo powder and Cr powder were first mixed at a weight ratio of Mo: Cr = 7: 1, and sufficiently mixed using a V-type mixer.

After mixing, the mixed powder of Mo powder and Cr powder was transferred into an alumina container and heat-treated at 1250 ° C. for 3 hours in a vacuum heating furnace. The degree of vacuum of the vacuum heating furnace after sintering was 3.5 × 10 ⁻³ Pa. In addition, if the degree of vacuum after maintaining for a predetermined time at the heat treatment temperature is 5 × 10 ⁻³ Pa or less, the oxygen content in the electrode material produced using the obtained solid solution decreases, and the current interruption of the electrode material There is no loss of performance.

  After cooling, the MoCr solid solution was taken out from the vacuum heating furnace and pulverized for 10 minutes using a planetary ball mill to obtain MoCr powder. When the average particle size of the pulverized MoCr powder was measured by laser diffraction particle size distribution measurement, it was 10 μm or less. After grinding, X-ray diffraction (XRD) measurement of the MoCr powder was performed. The measurement results are shown in FIG. As shown in FIG. 3, in the MoCr powder according to the electrode material of Example 1, the peak corresponding to Mo (110) and the peak corresponding to Cr (110) disappear, and the Cr raw material powder is in the MoCr powder. It is thought that it does not exist. 3 shows not only the X-ray diffraction measurement result of the MoCr powder related to the electrode material of Example 1, but also the mixing ratio (weight ratio) of Mo and Cr to change the electrode material of Example 1. The X-ray diffraction measurement result of the MoCr powder produced by the same method is also shown.

  FIG. 4 is a diagram showing X-ray diffraction measurement results of MoCr powder produced by the same method as the electrode material of Example 1 by changing the mixing ratio (weight ratio) of Mo and Cr. As apparent from FIGS. 3 and 4, the peak value corresponding to the Cr element increases as the Cr weight increases with respect to the Mo weight. That is, in the mixed powder, when the weight of Cr is larger than the weight of Mo, it is considered that the amount of Cr element remaining after the heat treatment in the heat treatment step S2 increases. Therefore, by mixing Mo and Cr in a weight ratio of Mo and Cr so that Mo> Cr, the MoCr solid solution in which the peak corresponding to the Cr element has almost disappeared after the heat treatment in the heat treatment step S2 is obtained. Can be obtained.

  Moreover, based on the result of the X-ray diffraction measurement of the MoCr powder, the crystal constants of the MoCr powder, the Mo powder, and the Cr powder according to the electrode material of Example 1 were obtained. The lattice constant a of the MoCr powder (Mo: Cr = 7: 1) was 0.3107 nm. The lattice constant a (Mo) of the Mo powder was 0.3151 nm, and the lattice constant a (Cr) of the Cr powder was 0.2890 nm.

  Next, Cu powder and MoCr powder are uniformly mixed at a weight ratio of Cu: MoCr = 4: 1, a molded body is produced by press die molding, and a non-oxidizing atmosphere at 1070 ° C. for 2 hours. The electrode material of Example 1 was produced by sintering in the medium.

  FIG. 5 is a cross-sectional micrograph of the electrode material of Example 1. In FIG. 5, the region that appears relatively white (white portion) is an alloy structure in which Mo and Cr are in a solid solution, and the portion that appears relatively black (gray portion) is a Cu structure. That is, in the electrode material of Example 1, a fine alloy structure (white portion) of 25 μm or less is uniformly refined and dispersed in the Cu phase.

[Comparative Example 1]
The electrode material of Comparative Example 1 is obtained by mixing Cu powder and Cr powder, and sintering the obtained mixed powder after molding by press die molding.

Cu powder and Cr powder were mixed at a weight ratio of Cu: Cr = 4: 1 and mixed well using a V-type mixer until uniform. The same Cu powder as in Example 1 was used. As the Cr powder, a particle size of 80 μm or less (classified with an 80 μm sieve) was used. After mixing, a mixed powder of Cu powder and Cr powder is press-molded at a press pressure of 4 t / cm ² to produce a molded body, and this molded body is sintered in a non-oxidizing atmosphere at 1070 ° C. for 2 hours. The electrode material of Comparative Example 1 was produced.

  6 is a photomicrograph showing a cross section of the electrode material of Comparative Example 1. FIG. From FIG. 6, it can be seen that in the electrode material of Comparative Example 1, Cr particles are scattered in the Cu phase.

[Comparative Example 2]
The electrode material of Comparative Example 2 is an electrode material produced by the same method as the electrode material of Example 1 except that the mixing ratio of Mo powder and Cr powder is different.

  More specifically, Mo powder and Cr powder were mixed at a weight ratio of Mo: Cr = 1: 4, and sufficiently mixed using a V-type mixer so as to be uniform.

After mixing, the mixed powder of Mo powder and Cr powder was transferred into an alumina container, and the mixed powder was heat-treated at 1250 ° C. for 3 hours in a vacuum heating furnace. The degree of vacuum of the vacuum heating furnace after sintering at 1250 ° C. for 3 hours was 3.5 × 10 ⁻³ Pa.

  After cooling, the MoCr solid solution was taken out from the vacuum heating furnace and pulverized for 10 minutes using a planetary ball mill to obtain MoCr powder. When the average particle diameter of the pulverized MoCr powder was measured by laser diffraction particle size distribution measurement, it was about 40 μm.

  Moreover, the result of having performed the X-ray-diffraction measurement of MoCr powder is shown in FIG. As shown in FIG. 4, in the X-ray diffraction measurement of the MoCr powder according to the electrode material of Comparative Example 2, it was confirmed that a peak corresponding to the Cr element was present.

  Next, Cu powder and MoCr powder are uniformly mixed at a weight ratio of Cu: MoCr = 4: 1 to produce a molded body by press die molding, and in a non-oxidizing atmosphere at 1070 ° C. for 2 hours. The electrode material of Comparative Example 2 was produced by sintering. Since the electrode material of Comparative Example 2 is rich in Cr, it has been found that the hardness is high and the energy required for pulverization is high, which affects mass productivity.

  Table 1 shows the electrode material processing conditions and electrode characteristics of Example 1 and Comparative Examples 1 and 2.

  As shown in Table 1, the electrode material of Example 1 can realize miniaturization of the arc resistance component, which was difficult by the conventional sintering method.

  Moreover, when Example 1 and Comparative Example 2 are compared, in Comparative Example 2, the grindability is difficult. This is considered to be caused by the fact that Cr is sintered together during temporary sintering. In the electrode material of Example 1, the average particle diameter after pulverization is 10 μm, whereas in the electrode material of Comparative Example 2, the average particle diameter after pulverization is 40 μm. This is probably because, in Comparative Example 2, in the mixed powder of Mo and Cr, the weight of Cr powder is larger than the weight of Mo powder, so that the amount of Cr particles diffused is small and the amount of remaining Cr element is large. . And it is thought that the contact resistance of the electrode surface becomes high in the electrode material of Comparative Example 2 by increasing the amount of the remaining Cr element. Moreover, since the mixing property of Cr powder and Cu powder is poor, it is considered that the dispersibility of Cr in the electrode structure is lowered even if the Cr particles are made fine. In Comparative Example 2, it is conceivable to reduce the particle size of the Cr particles dispersed in the electrode material by setting the particle size of the raw material Cr powder as small as possible (for example, 10 μm or less). If the particle size of the electrode material is reduced, the oxygen content of the electrode material increases, and the current blocking performance of the electrode material may be reduced.

[Comparative Example 3]
The electrode material of Comparative Example 3 is an electrode material produced using Cr powder having a particle size of 80 μm or less (Cr powder classified by an 80 μm sieve). In addition, the same powder as the electrode material of Example 1 was used for Mo powder and Cu powder.

  More specifically, Mo powder and Cr powder were mixed at a weight ratio of Mo: Cr = 9: 1 and sufficiently mixed using a V-type mixer so as to be uniform.

After mixing, the mixed powder of Mo powder and Cr powder was transferred into an alumina container, and the mixed powder was heat-treated at 1150 ° C. for 6 hours in a vacuum heating furnace. The degree of vacuum of the vacuum heating furnace after sintering at 1150 ° C. for 6 hours was 3.5 × 10 ⁻³ Pa.

  After cooling, the MoCr solid solution was taken out from the vacuum heating furnace and pulverized for 10 minutes using a planetary ball mill to obtain MoCr powder. When the average particle size of the pulverized MoCr powder was measured by laser diffraction particle size distribution measurement, it was about 10 μm.

  Further, as a result of X-ray diffraction measurement of the MoCr powder, it was confirmed in the X-ray diffraction measurement of the MoCr powder according to the electrode material of Comparative Example 3 that a peak corresponding to the Cr element exists.

  Next, Cu powder and MoCr powder are uniformly mixed at a weight ratio of Cu: MoCr = 4: 1 to produce a molded body by press die molding, and in a non-oxidizing atmosphere at 1070 ° C. for 2 hours. The electrode material of Comparative Example 3 was produced by sintering. Since the electrode material of Comparative Example 3 was rich in Mo, the filling rate was as low as 85% or less, which affected the brazeability and was found to be inapplicable as a VI electrode material.

  Although the electrode material of Comparative Example 3 had a large weight of Mo powder mixed with Cr powder, residual Cr particles were confirmed in the obtained MoCr solid solution powder. In other words, when the particle size of the Cr powder mixed with the Mo powder is large (for example, 80 μm), even if the weight of the Mo powder mixed with the Cr powder is increased, it is not possible to obtain the MoCr powder with less residual Cr element. There is. In addition, although the electrode material of the comparative example 3 differs in the sintering temperature of the mixed powder of the Mo powder and the Cr powder from the examples and other comparative examples, the same sintering conditions as the examples and other comparative examples ( In the case of sintering at 1250 ° C.-3 h), Cr peak was confirmed, and Cr particles remained.

  According to the electrode material according to the embodiment of the present invention as described above, the content (weight ratio) of Mo powder and Cr powder forming the MoCr solid solution is Mo> Cr, so that MoCr in the electrode structure is obtained. Solid solution particles can be finely and uniformly dispersed. As a result, electrical characteristics such as current interruption performance and withstand voltage performance of the electrode material are improved. In addition, since the Cu portion that is a highly conductive component phase and the MoCr alloy phase that is an arc resistant component are both uniformly and finely dispersed, the contact resistance of the electrode surface decreases.

  That is, by increasing the content of the heat-resistant element with respect to the electrode material, it is possible to obtain an electrode material excellent in withstand voltage performance and current interruption performance. By making the weight of Mo larger than the weight of Cr, not only MoCr powder with little residual Cr element can be obtained, but also the sintering reaction between Cr particles during MoCr solid solution formation is suppressed, and the MoCr solid solution can be easily pulverized. Thus, the MoCr solid solution can be pulverized with a smaller force.

  Moreover, by setting the particle size of the Cr powder to 45 μm or less, the Cr particles can be completely (substantially) dissolved in Mo by heat treatment. For example, in the X-ray diffraction measurement, a MoCr powder in which a peak corresponding to the Cr element has substantially disappeared (that is, a MoCr powder in which no Cr element remains) can be obtained. As a result, an electrode material having a structure in which MoCr solid solution particles having a fine particle diameter are dispersed on the electrode surface can be obtained. By setting the particle size of the Cr powder to 45 μm or less, even if Cr particles remain by heat treatment, the Cr particles are further refined by Mo or Cu during the main sintering step (sintering step S5). The increase in contact resistance on the electrode surface can be suppressed. On the other hand, when the particle size of the Cr powder is larger than 45 μm, even if the content of the Mo powder and the Cr powder is Mo> Cr, the Cr particles are not completely dissolved in the Mo, and as the Cr element It will remain. The presence of such large Cr particles on the electrode surface may increase the contact resistance between the electrodes. Accordingly, it is necessary to reduce the contact resistance between the electrodes by performing heat treatment until the remaining Cr element disappears or increasing the electrode diameter.

  The average particle size of the heat-resistant element (Mo or the like) can be one factor that determines the particle size of the solid solution powder of the heat-resistant element and Cr. That is, Cr particles are refined by heat-resistant element particles, Cr diffuses into the heat-resistant element particles by a diffusion mechanism, and the heat-resistant element and Cr form a solid solution structure, so the particle size of the heat-resistant element is increased by the heat treatment. . Further, the degree of increase by pre-sintering also depends on the mixing ratio of Cr. Therefore, by setting the average particle diameter of the heat-resistant element powder to, for example, 2 to 20 μm, more preferably 2 to 10 μm, the heat-resistant element and Cr for forming an electrode material having excellent withstand voltage performance and current interruption performance The solid solution powder can be obtained.

  In addition, by providing the electrode material according to the embodiment of the present invention, for example, on at least one of the fixed electrode and the movable electrode of the vacuum interrupter (VI), the withstand voltage performance of the electrode contact of the vacuum interrupter can be improved. When the withstand voltage performance of the electrode contact is improved, the gap length between the fixed electrode and the movable electrode can be made shorter than that of the conventional vacuum interrupter, and the gap between the fixed electrode and the movable electrode and the main shield can be narrowed. Therefore, the structure of the vacuum interrupter can be reduced. As a result, the vacuum interrupter can be reduced in size. In addition, the manufacturing cost of the vacuum interrupter is reduced by downsizing the vacuum interrupter.

  The description of the embodiments of the present invention has been given by way of specific preferred examples. However, the present invention is not limited to the examples, and design changes may be made as appropriate without departing from the characteristics of the invention. Possible and modified forms are also within the technical scope of the present invention.

  For example, in the description of the embodiment of the present invention, the heat treatment temperature in the heat treatment step S2 is 1250 ° C.-3 hours, but the heat treatment temperature in the heat treatment step S2 is 1250 ° C. or more and not more than the melting point of Cr, more preferably By carrying out in the range of 1250 ° C. to 1500 ° C., the mutual diffusion of Mo and Cr sufficiently proceeds, and the subsequent pulverization of the MoCr solid solution using a pulverizer can be performed relatively easily. An electrode material excellent in blocking performance can be manufactured. The heat treatment time varies depending on the heat treatment temperature. For example, heat treatment is performed for 3 hours at 1250 ° C., but heat treatment for 0.5 hour is sufficient at 1500 ° C.

  In addition, the MoCr powder is not limited to those manufactured by the manufacturing method described in the embodiment, and MoCr powder manufactured by a known manufacturing method (for example, a jet mill method or an atomizing method) may be used. .

  In addition, the electrode material of the present invention is not limited to those having only heat-resistant elements, Cr, and Cu as constituent elements, and an element that improves the characteristics of the electrode material may be added. For example, the welding resistance of the electrode material can be improved by adding Te.

DESCRIPTION OF SYMBOLS 1 ... Vacuum interrupter 2 ... Vacuum container 3 ... Fixed electrode 4 ... Movable electrode 5 ... Insulating cylinder 6 ... Fixed side end plate 7 ... Movable side end plate 8 ... Electrode contact material (electrode material)
9 ... Bellows 10 ... Main shield

Claims (1)

A molded body obtained by molding a mixed powder obtained by mixing a solid solution powder obtained by pulverizing a solid solution obtained by mixing a heat-resistant element and Cr powder having a particle size of 45 μm or less, and heating, and a Cu powder is fired. A method for producing a bonded electrode material,
The electrode material is 40 to 80% Cu by weight ratio with respect to the electrode material,
2-30% Cr,
Containing 10-54% of a heat-resistant element,
The content of refractory elements, rather multi than the content of Cr by weight,
The method for producing an electrode material, wherein the solid solution powder has a peak corresponding to Cr element disappeared in X-ray diffraction measurement of the solid solution powder.