JPH0458130B2 - - Google Patents

Description

[Detailed description of the invention]

[Field of Application of the Invention] The present invention relates to a vacuum circuit breaker, and in particular, the electrodes of the vacuum circuit breaker are made of a cast alloy suitable for improving low disconnection current characteristics, high withstand voltage characteristics, and welding resistance. The present invention relates to a method of manufacturing a vacuum circuit breaker having the above structure. [Background of the Invention] The basic requirements for the electrode contacts of vacuum circuit breakers include high withstand voltage, low breaking current value, high breaking current, and welding resistance. It will be done. Abrasion resistance is also an important condition. Conventionally, vacuum melted Cu alloys, sintered and infiltrated alloys, etc., have often been used as electrode materials for vacuum circuit breakers. However, some of these basic requirements are contradictory, and it is impossible to satisfy all requirements with a single metal species. For this reason, many electrode materials that have been put into practical use are made by combining two or more types of elements that mutually compensate for the insufficient performance, and are used for specific purposes. For example, a Cr--Cu alloy disclosed in Japanese Patent Publication No. 45-35101 is attracting attention as a material with high voltage resistance. this is,
This is a pre-sintered Cr body made using powder metallurgy and infiltrated with Cu. However, since Cr itself has a very high affinity for oxygen (O ₂ ), management of the Cr powder or compact becomes a problem. Temporary sintering of Cr, infiltration of Cu, etc. are usually performed in vacuum or in purified hydrogen (H ₂ ), but even then, oxide residues are likely to be present and properties tend to vary. On the other hand, this infiltrated alloy is preferable because it has excellent withstand voltage and breaking current values, but it is difficult to provide low breaking current characteristics, which is one of the important characteristics as an electrode material for vacuum circuit breakers. Improvements are desired. [Object of the Invention] The object of the present invention is to enable an electrode to have excellent low breaking current characteristics, to improve high withstand voltage characteristics and welding resistance, and to reduce the occurrence of defects such as cracks. The purpose of the present invention is to provide a method for manufacturing a vacuum circuit breaker that enables the following. [Summary of the Invention] In order to achieve the above object, the present invention provides a method for manufacturing a vacuum circuit breaker in which a pair of electrodes are movably arranged facing each other at a predetermined distance _{. 3} , Al ₂ O ₃ , Cr ₂ O ₃ , BeO, ZrO ₂ , TiO ₂ oxide particles of one or more types averaged by volume ratio
The casting alloy is made of a cast alloy containing more than 0.5% and less than 20% Cu, and the oxide particles are poured on the pouring surface with a plunger so that the concentration of the oxide particles decreases from the surface side of the electrode contacts facing each other to the opposite side. It is formed by solidifying under pressure. According to the research conducted by the inventors, it was considered that the variation in properties of Cr--Cu based infiltration materials is caused by the fact that they are produced using powder metallurgy. In other words, it is a major problem that the suction gas in the sintered body and the oxidation of the Cr particle surface are not completely removed even after the infiltration is completed. As a result of various research into the material, we found that it contained a trace amount of Ti.
We have discovered a new material in which various oxide particles are dispersed in molten Cu alloy. In other words, it was found that fine oxide particles dispersed in the Cu alloy matrix structure exhibited excellent withstand voltage characteristics and low cutting current characteristics. Further details are as follows. The material used for the electrodes of the vacuum circuit breaker in the present invention is based on highly conductive Cu, with oxide particles appropriately dispersed by the pressure casting method described later. The concentration of the oxide changes toward the inside. By creating a concentration gradient of oxide particles in this way, the surface layer can have the specified high voltage resistance and welding resistance, while the internal or joint parts can have high conductivity that is almost like that of pure copper. . That is, not only the performance as an electrode but also the brazing property is very good. In the cast alloy of the present invention, a small amount of Ti is added, and this Ti is a dispersion aid for dispersing oxide particles into the molten Cu alloy. Incidentally, when Ti is not added, the oxide particles do not disperse into the molten Cu alloy but float to the surface of the molten metal. The dispersion mechanism is that Ti disperses into the Cu alloy molten metal by improving the wettability between the oxide particle surface and the molten metal. Therefore, physical and chemical deposits on the oxide particle surface are removed by Ti, leaving a clean particle surface.
Dispersed in Cu alloy. This means that Cr-Cu based electrode materials produced by powder metallurgy
The particle surfaces are cleaned even more and a gas-free material can be obtained. It is sufficient that the amount of Ti added is 0.05 to 0.7% by weight based on the amount of oxide particles dispersed in the present invention. Even if it is added in an amount of 0.7% or more, it has no effect on dispersing the oxide particles, and is not preferable because it dissolves in the matrix and lowers the electrical conductivity. Further, the same effect can be obtained by adding Ci, Zr, V, and Ni in addition to Ti. Bi contributes to lowering the breaking current and improving welding resistance. In particular, the synergistic effect with oxide particles significantly improves the cutting current characteristics. An effective amount of Bi added is 0.01 to 2% by weight. When it is 0.01% or less, Bi exhibits its effect in terms of welding resistance. If it exceeds 2%, it is impossible to prevent segregation due to the density difference with the matrix, and segregation tends to occur in the lower part of the ingot.
Since the oxide particles are dispersed, Bi in the range of 0.01 to 2% can be uniformly dispersed in a fine state between the oxide particles, thereby preventing segregation. Also, Bi
In addition, low melting point materials such as Pb, Sb, Cd, Te, Se, In, etc.
I am convinced that vapor pressure resistant elements have a similar effect. One or more types of oxide particles such as Y ₂ O ₃ , Al ₂ O ₃ , CrO ₃ , BeO, ZrO ₂ , TiO ₂ and the like greatly contribute to improving the withstand voltage characteristics. The average particle size of these oxide particles, which are components with voltage resistance characteristics, is preferably in the range of 0.03 to 7 μm, which is also related to the manufacturing method described below. The thickness is preferably 0.03 μm or more in order to prevent particle agglomeration and achieve uniform dispersion, and preferably 7 μm or less in order to provide appropriate particle spacing and good electrode characteristics. Furthermore, by utilizing the fact that the electrode material of the present invention is a cast alloy, it is possible to control the distribution state of oxide particles dispersed in the matrix. In other words, by controlling the solidification rate, it is possible to create a concentration gradient from the blocking surface toward the inside. According to the research conducted by the inventors, the surface layer of the blocking surface, which has the necessary characteristics as an electrode material, is approximately 5 mm deep from the blocking surface.
A thickness of about mm is sufficient. By using pure copper for other electrode materials, it is possible to replace conventional Cr-Cu.
It has been found that the conductivity is improved compared to the infiltrated electrode material, and the electrodes can be bonded very easily. The amount of oxide particles dispersed within 5 mm of the surface layer of the contact surface can be arbitrarily dispersed in a volume ratio of 0.01 to 90%, but a dispersed amount of 0.5% or less has little effect on withstand voltage characteristics. Furthermore, if the amount of dispersion exceeds 80%, the conductivity decreases, making it unsuitable as an electrode material. Therefore, the range of effective dispersion amount for withstand voltage characteristics is 0.5 to 80% by volume. [Example] An example of the present invention will be described below. Regarding the manufacturing method of the electrode material, first, a predetermined amount of Cu metal is melted in a graphite crucible, 0.5% Ti is added to this molten metal,
Maintain the molten metal at approximately 1200℃. Next, while stirring the molten metal, oxide particles are added from the surface of the molten metal and uniformly dispersed in the molten metal, and then Bi is added. This molten metal is poured into a separately prepared mold, and a plunger pressurizes the molten metal from the top of the mold. That is, an ingot of the oxide particle-dispersed composite electrode material is obtained by a type of pressure casting method. Since the pressure casting method is used, no casting defects occur in the ingot, and a sound cast alloy can be obtained. Thereafter, it is processed into a predetermined shape to form an electrode. In addition, in order to create a concentration gradient of oxide particles from the surface layer to the inside, in the case of the processing casting method, the oxide particles added to the molten metal are uniformly dispersed by stirring the molten metal, but when the molten metal stands still, the oxide particles are dispersed at the top of the molten metal. surface. Because it can be rapidly solidified by applying pressure,
This is possible by adjusting the floating speed and the pressurizing time after pouring the molten metal into the mold. In other words, by controlling the coagulation time and pressurization time, it is possible to provide a predetermined concentration gradient of oxide particles and Bi. The electrode material produced in this way was an ingot having the composition shown in Table 1. Regarding the measurement of impulse withstand voltage value, cutting current value, and breaking limit current value, a test piece of a predetermined shape is cut out from the ingot of the above electrode material, and the impulse withstand voltage value (KV) is determined by the method described below for each material. The breaking current value (A) and the breaking limit current value (KV) were each measured. First, as shown in Figure 1, the experimental device used in this test consists of two fixed electrodes placed opposite each other and each having an electrode 1 shaped as shown in Figure 2 attached to its tip. A holder 4a and two movable holders 4b are provided, and the two fixed holders 4a and 2 are provided.
The movable holders 4b are sealed within two raileds 2 made of stainless steel tubes, and the two shields 2 are surrounded by two side plates 6 that fix the glass tube 3 and its both ends. It is sealed. Further, the sliding gap between the two movable holders 4b and the side plate 6 is blocked by a bellows 7, and an exhaust pipe 5 is provided on the side plate 6 between the two movable holders 4b. The purpose is to simply open and close the electrode 1 by discharging air, without using an actual vacuum valve, to examine the cutoff characteristics. In this test, the degree of vacuum in the space formed by the glass tube 3 and the two side plates 6 was set to 1×10 ^-6
It is maintained at ~1× ^-7 Torr. In addition, when testing each characteristic, measure the minimum and maximum values when testing 10 times. Set the gap between electrodes 1 to 2.5 mm, and measure the minimum discharge voltage while applying impulse voltage in 5 KV steps. The impulse voltage needs to have a high minimum value, and the smaller the difference between the minimum and maximum, the smaller the variation in characteristics is and the better. The current is adjusted to obtain the maximum cutting current, and the waveform at the time of current cutting is stored in digital memory, and then reproduced on a synchroscope to measure the cutting current value. Note that the cutting current should preferably be one that can cut with a small current. In addition, the frequency of the cut-off current was adjusted to about 50 Hz, and the frequency of the re-EMF voltage was adjusted to about 10 KHz, and the voltage was applied in steps of 300 to 600 V so that the cut-off current increased in steps of 500 to 1000 A, and the cut-off limit value was adjusted. put out.

〔Effect of the invention〕

As explained above, the present invention contributes to the improvement of excellent low breaking current characteristics, high withstand voltage characteristics and welding resistance, and the electrode The altered layer due to surface dissolution can be made thinner, and the occurrence of defects such as cracks can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing an embodiment of the experimental apparatus of the present invention, and FIG. 2 is an enlarged view of the electrodes shown in FIG. 1. 1... Test electrode.

Claims (1)

[Claims] 1. A method for manufacturing a vacuum circuit breaker in which a pair of electrodes are movably arranged facing each other at a predetermined distance, wherein the electrodes are made of Y ₂ O ₃ , Al ₂ O ₃ , CrO ₃ , BeO,
Contains one or more types of oxide particles such as ZrO ₂ and TiO ₂ in an average of more than 0.5% and less than 20% by volume, with the remainder being
After pouring molten Cu into a mold, the molten metal is solidified under pressure with a plunger so that the concentration of the oxide particles decreases from the surface side of the electrode contacts facing each other to the opposite side. A method for manufacturing a vacuum circuit breaker characterized by: 2. In claim 1, the Y ₂ O ₃ ,
A method for manufacturing a vacuum circuit breaker, characterized in that the diameter of oxide particles of Al ₂ O ₃ , Cr ₂ O ₃ , BeO, ZrO ₂ and TiO ₂ is 0.03 to 7 μm. 3. In claim 1, the concentration gradient of the oxide particles dispersed is 5 mm from the electrode contact surface layer.
A method for manufacturing a vacuum circuit breaker, characterized in that the volume ratio is 0.01 to 90%. 4. A method for manufacturing a vacuum circuit breaker in which a pair of electrodes are movably arranged facing each other at a predetermined distance, wherein the electrodes are made of Y ₂ O ₃ , Al ₂ O ₃ , Cr ₂ O ₃ , BeO,
One or more kinds of oxide particles of ZrO ₂ , TiO ₂ ,
Contains 0.01 to 2% by weight of one or more of Bi, Pb, Sb, Te, Se, and Cd, and 0.01 to 0.7% by weight of one or more of Ti, Zr, Cr, V, and Nb. After pouring the molten metal of Cu into the mold, the volume ratio of the oxide particles is more than 0.5% and less than 20%, and the concentration of the oxide particles decreases from the electrode setting surface side to the opposite side. 1. A method for manufacturing a vacuum circuit breaker, characterized in that the molten metal surface is solidified under pressure using a plunger.