JPH0351250B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to an improvement in a method for manufacturing a contact material for a vacuum valve using a Cu-Cr alloy or a Cu-Ti alloy. [Technical background of the invention and its problems] The properties required for contact materials for vacuum valves include three basic requirements: welding resistance, voltage resistance, and shear resistance, as well as temperature rise and contact resistance. Low resistance and stability are important requirements. However, since some of these requirements are contradictory, it is impossible to satisfy all requirements with a single metal species. For this reason, in many contact materials in practical use,
Contact materials have been developed that combine two or more elements that mutually compensate for the lack of performance, and are suitable for specific applications such as large current or high voltage applications, and have reasonably excellent properties. However, the reality is that a sufficient contact material for valves that satisfies the ever-increasing demands for higher withstand voltage and larger current has not yet been obtained. For example, a Cu-Bi alloy containing less than 5% of a welding prevention component such as Bi is known as a contact material intended for large currents (Special Publications Publication No. 41).
-12131 Publication) has problems such as extremely low solubility of Bi in the Cu matrix, which often causes polarization, large surface roughness after shingling, and difficulty in processing and forming. . Further, a Cu--Te alloy is also known as another contact material intended for high current (Japanese Patent Publication No. 23751/1983). Although this alloy alleviates the above-mentioned problems of the Cu-Bi alloy, it is more sensitive to the atmosphere than the Cu-Bi alloy and therefore lacks stability in terms of contact resistance and the like. Furthermore, a common feature of these Cu-Te, Cu-Bi, etc. contacts is that they have excellent welding resistance, but even if the withstand voltage characteristics are sufficient for application to the conventional medium voltage class, It has become clear that this method is not necessarily satisfactory for applications in the field of high voltages. On the other hand, as a contact material aimed at high voltage resistance,
A sintered alloy of Cr and a highly conductive component such as Cu (or Ag) is known. However, since Cu is a metal that is extremely easily oxidized, it goes without saying that the management of the powder or compact is important.
Atmospheric conditions during preliminary sintering and infiltration also affect material properties. For example, even though Cu-Cr alloys are obtained by carefully controlling the temperature and time during pre-sintering and infiltration, there are variations and instability in contact resistance and temperature rise characteristics, and these variations can be corrected. What is desired is something that is stable and can be removed. [Object of the invention] The present invention has been made in view of the above circumstances, and
An object of the present invention is to provide a method for manufacturing a contact material for a vacuum valve that can stabilize contact resistance characteristics and temperature rise characteristics. [Summary of the Invention] The present invention provides an arc-resistant material made of 10 to 90% by weight of Cr or/and Ti which has been sufficiently degassed and whose surface has been cleaned, and a conductive material made of the balance made of Cu or/and Ag. A pre-process of sintering the vacuum valve material formed from the rubber material and infiltrating it with an infiltrant material, and cooling the vacuum valve material treated in this pre-process, and during this cooling process, the vacuum valve material is Cooling that improves the temperature rise characteristics of the vacuum valve material during the cooling temperature range of 800°C to 400°C during the cooling process by cooling the material at a cooling rate of 0.6°C to 6°C per minute. It has a process. Further, the present invention cools the vacuum valve material treated in the previous step, and during this cooling process, the vacuum valve material is heated to a temperature within the cooling temperature range of 800°C to 400°C. The method includes a heating and holding step of heating and holding for at least 0.25 hours to increase the conductivity of the vacuum valve material. In addition, the present invention includes a cooling process in which the vacuum valve material treated in the previous process is cooled to room temperature, and after the completion of this cooling process, a cooling temperature range from 800°C to 800°C.
and a reheating step of reheating the vacuum valve material at a temperature of 400°C for at least 0.25 hours. Furthermore, the present invention includes a cooling process in which the vacuum valve material treated in the previous process is cooled at a cooling rate that improves the temperature rise characteristics of the vacuum valve material, and a cooling process in which the vacuum valve material is cooled after this cooling process is completed. A heating and holding step in which the material for the vacuum valve is heated and held for a period of time to increase the conductivity of the material for the vacuum valve at a predetermined temperature in the cooling temperature range, and after this heating and holding step, the material for the vacuum valve is heated to a predetermined temperature in the cooling temperature range in the cooling step. and a reheating step of reheating the mixture. [Embodiments of the Invention] Hereinafter, a method for manufacturing a contact material for a vacuum valve according to the present invention will be described. Before specifically explaining the embodiments, the process leading up to the present invention will be briefly explained. In the following explanation, for convenience,
A vacuum valve material formed from a conductive material made of Cu or/and Ag and an arc-resistant material made of Cr or/and Ti will be described as a Cu-Cr type material. According to research, the above-mentioned instability of Cu-Cr-based contact materials is caused by compositional fluctuations in the Cu-Cr alloy, Cr particle size, particle size distribution, degree of segregation, and degree of porosity present in the alloy. It turned out to be dependent. Although these solutions were found to be effective through the selection of the raw material Cr and the control of the sintering technology, the above-mentioned steps were necessary to further improve the maintenance of stability.
In addition to this, it was found that even more detailed control of the sintering technology was required. In other words, it has been found that the instability of the above characteristics is correlated with the slight difference in the amount of Cr contained in Cu. In other words, when estimating the amount of Cr contained in the Cu portion of a Cu-Cr alloy using a semi-quantitative method using
However, by using the technology of the present invention described later, Cu-
For Cr alloys, it was 0.2% or less, with a typical value of 0.1% or less. It is recognized that this difference depends on the thermal history of the Cu-Cr alloy, especially after sintering or infiltration, and by carefully controlling this condition,
It has been shown that this method is highly effective in improving the conductivity of Cu-Cr alloys and reducing its variation. Note that the thermal history after sintering or infiltration referred to herein can be represented by the cooling rate characteristic substantially experienced by the contact point itself. In other words, it refers to controlling the cooling rate, which varies depending on the size of the contact and the characteristics of the furnace, to a predetermined condition. The present inventors have confirmed that, as a method for alleviating such undesirable characteristics, it is effective to improve the electrical conductivity characteristics of the material and to reduce the variation thereof. That is, Cu
In the manufacturing process of the -Cr contact alloy, it has been found that it is preferable to minimize the infiltration of Cr and/or Ti into Cu in order to reduce variations between contacts. Next, the manufacturing method of the present invention will be specifically explained. The raw materials used in the present invention are an arc-resistant material made of Cr and/or Ti powder that has been sufficiently degassed and whose surface has been cleaned, and Cu powder.
and a conductive material consisting of both or one of Ag and Ag. In addition, these Cr, Ti, Cu,
In addition to Ag, Te of about 10% or less depending on the contact application.
Welding-resistant materials such as Bi and Sb, arc-resistant materials such as W, Mo, and V may be added as auxiliary components. Cr,
If the particle size of Ti exceeds 250 μm, the probability of contact between pure Cu and Ag parts increases, which is undesirable in terms of welding problems. There is no lower limit for the diameter, but rather it is determined by handling, such as increasing activity. In addition, the heating conditions for obtaining contact alloys are Cu, Ag.
By applying the conditions according to the method of the present invention in the cooling process or after cooling, both the method of completing the process below the melting point of Cu and Ag and the method of infiltrating it by heating it above the melting point of Cu and Ag. Demonstrate its effectiveness. The latter method, which has a high diffusion rate, makes a large contribution to the contact point. On the other hand, the same effects can be obtained by applying the conditions of the present invention whether the skeleton is made of only Cr and Ti or a skeleton in which a small amount of Cu or Ag is mixed in advance with Cr or Ti. Note that the contact resistance characteristics and temperature rise characteristics in the present invention are determined as follows. The contact resistance characteristic is a curvature radius with the same surface roughness as a 20 mm diameter flat electrode with a surface roughness of 5 μm.
A 100R convex electrode is placed facing the electrode, and both electrodes are installed in a 10 ^-5 Torr vacuum chamber with an opening/closing mechanism and a load of 3 kg is applied. The contact resistance is then determined from the potential drop when a 10A alternating current is applied between the two electrodes. Note that the contact resistance value is a value that includes the resistance or contact resistance of wiring materials, switches, measuring instruments, etc. that constitute the measurement circuit as a circuit constant. On the other hand, the temperature rise characteristics were determined by placing the electrodes facing each other under the same electrode conditions as above, and applying a current of 400A 20 times with a contact force of 30Kg and a separation force of 20Kg in a 10 ^-5 Torr vacuum chamber. Measurements were taken by inserting a thermocouple into a measurement hole with a diameter of 1.5 mm and a depth of 4 mm that was pre-drilled on the side. Furthermore, the temperature value is based on the ambient temperature of approximately 25℃.
This is a comparative value that also includes the influence of the heat capacity of the holder to which the electrode is attached. The numerical values indicate the maximum and minimum of three samples. Next, a first embodiment of the present invention will be described with reference to Table 1.

[Table] First, as a pre-process to apply the manufacturing method of the present invention, Cr with an average diameter of 125 μm is molded at a pressure of 2 tons/cm ² and the molded body obtained is stored in a carbon container and heated at 1000°C in vacuum for 1 hour. Perform preliminary sintering. An infiltration material made of Cu is placed on the underside of this pre-sintered body, and then
Move to the infiltration process, which is carried out in a vacuum at 1200°C for 1 hour. Next, after the infiltration process is completed, the contact alloy material is cooled from 1200°C. Now, in this cooling process, the cooling temperature section is 800℃.
The temperature difference between 100°C and 400°C is cooled at a cooling rate of 0.6°C to 6°C per minute to improve the temperature rise characteristics of Cu-Cr. Comparing the results of cooling with this method with the results of cooling under other conditions, we find that
As shown in Comparative Examples 1 and 2, cooling temperature section 1200℃
After cooling from 800℃ at 3.5℃/min, from 700℃ to 500℃
When cooling at a cooling rate of 80°C/min to 24°C/min between
℃ (characteristics deteriorate), whereas in the present invention, the cooling rate is 6℃/min to 0.6℃/min.
It can be seen that when cooling in minutes (Effect Examples 1 and 2), the temperature rise characteristic is around 80°C or lower, which is lower (preferable) than the former. This trend is observed in the cooling temperature range 1200℃
Even if the cooling rate between 800°C and 800°C was significantly faster at 40°C/min, the same condition was exhibited (Effect Examples 3, 4, and 5). Further cooling from 1200℃ to 800℃, and subsequent cooling
Since it shows an effective tendency even between 700℃ and 500℃ (Effect Example 6), it depends on the cooling rate that passes through the 100℃ temperature difference arbitrarily selected between the cooling temperature range 800℃ and 400℃. It is shown that. In addition, the contact resistance characteristics are similar to the group around 60 μΩ (effect examples 1 to 6).
It is divided into groups of 70μΩ or more (Comparative Examples 1 and 2), which correspond to the temperature rise resistance. Note that productivity is poor if the cooling rate is slower than 0.6°C/min. Cu equivalent to about 5% was mixed in advance with 74 μm Ti powder to obtain a molded product at 2.5 tons/cm ² and heated at 1100°C in vacuum.
Cu is placed on the top of the skeleton obtained by pre-sintering for 2 hours.
The infiltration work is carried out in a vacuum at 1250℃ for 1 hour. In the cooling process after the infiltration process, when the temperature range from 700℃ to 500℃ was cooled at a cooling rate of 3.5℃/min (Effect Example 6), the same area was cooled at 24℃/min (Comparative Example 3). Compared to the Cu-Ti material obtained by cooling at a high speed, the conductivity was improved by 1.35 to 1.47 times. Next, a second embodiment of the present invention will be described with reference to Table 2.

[Table] In this method, the vacuum valve material is heated and held at a predetermined temperature in the cooling temperature range from 800°C to 400°C for a period of time that increases the conductivity of the vacuum valve material, that is, at least 0.25 hours. Specifically, the average particle size
Naturally filling a carbon container with 74μm Cr and placing it in hydrogen
Temporary sintering is performed at 900℃ for 1 hour. After placing an infiltration material made of Cu containing 0.1% Bi on the upper side of this pre-sintered body, the infiltration process is carried out in a vacuum at 1150°C for 1 hour. Next, the contact alloy material after the infiltration process is
Cool from 1150°C to each holding temperature at a rate of 13.3°C/min. After this cooling, the temperature rise characteristics and contact resistance characteristics of each contact piece were determined after being maintained for a predetermined period of time. This is to show that the method of the present invention is the best. As shown in Comparative Example 4, the holding temperature
At 1000℃, the amount of solid solution of Cr in Cu is large, and the conductivity is about 20-25% IACS.
As shown in 8 and 9, the holding temperature is 800℃, 600℃,
At 400°C, the electrical conductivity increases to around 30% IACS or more, mainly due to a decrease in the amount of solid solution of Cr in Cu. In addition, when considering the effect of holding time with the holding temperature constant at 700℃, as shown in Effect Examples 10 and 11, 30% for 1 to 0.25 hours.
Although the conductivity is close to or higher than IACS, as shown in Comparative Example 5, when the holding time is 0.1 hour, the solid solution state of Cr in Cu is still maintained, so the conductivity is 30% IACS. It is as follows. The temperature rise characteristics also correspond to the difference in conductivity, and are divided into a group of 80°C or lower (Effect Examples 7 to 11) and a group of 90°C or higher (Comparative Examples 4 and 5). In addition, the contact resistance characteristics are also 60 μΩ or less (effect examples 7 to 11).
and 70μΩ or higher group (Comparative Examples 4 and 5). If the holding temperature is lower than 400°C, it is not a good idea because a longer holding time is required. In addition, as shown in Table 2, there are differences in electrical conductivity, temperature rise characteristics, and contact resistance characteristics due to differences in holding time, as shown in the contacts with almost the same Cu content (Effect Example 12) and (Comparative Example 6) in the Cu-Ti alloys. is observed, and the effects of the present invention are also exhibited in Cu-Ti alloys. Next, a third embodiment of the present invention will be described with reference to Table 3.

[Table] In this method, after the cooling process of the vacuum valve material is completed, the material is reheated for at least 0.25 hours at a reheating temperature within the cooling temperature range of 400°C to 800°C. To explain specifically, the average particle size is 44μ
A Cu lump was placed on top of the Cu powder of m, and the whole was stored in a carbon container, and after temporary sintering at 950℃ in vacuum for 3 hours, the temperature was continued to be raised to 125℃ in vacuum without cooling, and infiltration was performed for 1 hour. do the work. Next, the contact material is obtained by cooling to room temperature at an average cooling rate of 24°C/min. When this contact material was reheated from room temperature to each predetermined holding temperature as shown in Table 3, the reheating temperature
By reheating between 400°C and 800°C, the conductivity before reheating, which was around 26.0 to 30.9% IACS, increased to around 40% IACS due to the precipitation of Cr from Cu ( Effect examples 16-18). However, when the reheating temperature was further increased to 900 and 1000°C, the conductivity remained at around 30% IACS, although it showed a slight increase (Comparative Examples 8 and 9). Note that, as shown in Comparative Example 10, when the reheating temperature was 200° C., the movement of Cr from the Cu was still insufficient, and no effect was observed within the heating time of this experiment. As mentioned above, the above applies to Cu
This corresponds well to the amount of Cr present in the sample. The temperature rise characteristics are classified into groups near or below 70°C, each corresponding to the conductivity behavior. Further, the contact resistance characteristics are similarly classified into a group around 50 μΩ (Effect Examples 16 to 18) and a group around 60 μΩ or more (Comparative Examples 8 to 10), each corresponding to the conductivity behavior. The retention time during reheating is 37% if it is 0.25 hours or more as shown in effect examples 13 to 15.
It maintains a temperature rise property near or above 70°C with a conductivity of IACS or higher, and a contact resistance property of 50 μΩ or less, while the holding time is 0.1 as in Comparative Example 7.
Time is not enough to obtain the above characteristics. In addition, for Cu-Ti alloys, as shown in Table 3, the holding temperature during reheating using the same Cu-Ti contacts is
At 700°C (Effect Example 19) and 1000°C (Comparative Example 11), the former had better properties as shown in the same table, and the effects of the present invention were recognized. From the above, it is possible to improve the characteristics by reheating after cooling, but the temperature is 400℃ to 800℃.
It was found that the retention time was more than 0.25 hours. Next, a fourth embodiment of the present invention will be described with reference to Table 4.

[Table] This manufacturing method adds a heating holding step and a reheating step to the vacuum valve material after the infiltration step. In other words, a mixture of 149μm Cr powder and Cu powder of the same diameter at a ratio of 95:5 is 1.5μm.
Temporary sintering is performed at 1150°C in a vacuum molded at ton/cm ² , and then inserted into an alumina boat together with a Cu alloy ingot containing 0.1% Sb and infiltrated in a vacuum at 1200°C. After this infiltration is completed, the temperature is increased from 1200℃ to 800℃ for 24 hours.
After cooling at a rate of 3.5° C./min, the cooling temperature range from 800° C. to 600° C. is further cooled to 600° C. at a cooling rate of 3.5° C./min as in Effect Example 3. Effect example 7 during this cooling
When fabricated using a holding temperature of 600°C as shown in Figure 2, stable properties were obtained as shown in Effect Example 20. Thereafter, the above sample was cooled and then reheated at 500°C, but similarly stable characteristics were obtained (Example 21). From the above results, adjusting the cooling rate after the infiltration step to a predetermined condition and then superimposing the heating holding step and reheating treatment step was effective in further improving and stabilizing the properties. As explained above, in the embodiment of the present invention, within the cooling temperature range 800°C to 400°C,
A cooling means that cools 100°C at a cooling rate of 0.6°C per minute, a heating holding means that maintains heating at any temperature in a cooling temperature range of 800°C to 400°C for at least 0.25 hours, and a cooling temperature range of 400°C to 800°C.
It has a reheating means for reheating at one of these temperatures for at least 0.25 hours, and since production is carried out by using one or a combination of these means, the temperature increase characteristics of the Cu-Cr alloy and It is possible to improve contact resistance characteristics and also improve stability. As a result, it is possible to obtain the best contact material that can satisfy all the characteristics required for a contact material for a vacuum valve. Note that the present invention is not limited to the above embodiments. For example, even if part or all of Cu is replaced with Ag, the same effects as in the above embodiment can be achieved. As explained above, according to the embodiments of the present invention
The temperature rise characteristics and contact resistance characteristics of the Cu-Cr alloy can be improved, and the stability can also be improved. As a result, it is possible to obtain the best contact material that can satisfy all the characteristics required for a contact material for a vacuum valve. Note that the present invention is not limited to the above embodiments. For example, even if part or all of Cu is replaced with Ag, the same effects as in the above embodiment can be achieved. Furthermore, it has been found that the effects of the present invention can be exerted on alloys having an extremely wide range of ratios of Cu (Ag) and Cr (Ti). On the other hand, other characteristics of contact materials for vacuum valves, such as 90% or more in terms of shearing performance,
Cr (Ti), 90% or more Cu (Ag) in terms of welding resistance
It is best to avoid alloys of [Effects of the Invention] As detailed above, according to the present invention, it is possible to provide a method for manufacturing a contact material for a vacuum valve that can stabilize contact resistance characteristics and temperature rise characteristics.

Claims (1)

[Claims] 1. 10 which has been sufficiently degassed and whose surface has been cleaned.
A vacuum valve material made of an arc-resistant material made of ~90% by weight of Cr or/and Ti and a conductive material with the balance made of Cu or/and Ag is sintered and infiltrated with an infiltrant. The vacuum valve material treated in the previous step is cooled, and during this cooling process, the vacuum valve material is heated to a predetermined temperature within the cooling temperature range of 800°C to 400°C in the cooling process. Temperature difference between 100℃ and cooling rate from 0.6℃ to 6℃ per minute to improve the temperature rise characteristics of the vacuum valve material
1. A method for producing a contact material for a vacuum valve, the method comprising: a cooling step in which the temperature decreases. 2 Sufficiently degassed and surface cleaned10
A vacuum valve material made of an arc-resistant material made of ~90% by weight of Cr or/and Ti and a conductive material with the balance made of Cu or/and Ag is sintered and infiltrated with an infiltrant. A pre-process and the vacuum valve material treated in this pre-process are cooled, and during this cooling process, the vacuum valve material is cooled to any temperature within the cooling temperature range of 800°C to 400°C in the cooling process. A method for manufacturing a contact material for a vacuum valve, comprising the step of heating and holding the material for at least 0.25 hours to increase the conductivity of the material for a vacuum valve at such a temperature. 3 Sufficiently degassed and surface cleaned10
A vacuum valve material made of an arc-resistant material made of ~90% by weight of Cr or/and Ti and a conductive material with the balance made of Cu or/and Ag is sintered and infiltrated with an infiltrant. A pre-process, a cooling process in which the vacuum valve material treated in the pre-process is cooled to room temperature, and after the completion of this cooling process, a cooling temperature range of 800°C to 400°C. A method for producing a contact material for a vacuum valve, comprising a reheating step of reheating the material for a vacuum valve for at least 0.25 hours. 4 Sufficiently degassed and surface cleaned10
A vacuum valve material made of an arc-resistant material made of ~90% by weight of Cr or/and Ti and a conductive material with the balance made of Cu or/and Ag is sintered and infiltrated with an infiltrant. a cooling step in which the vacuum valve material treated in the previous step is cooled at a cooling rate that improves the temperature rise characteristics of the vacuum valve material; and after this cooling step, the vacuum valve material is A heating and holding step in which the vacuum valve material is heated and held at a predetermined temperature in the cooling temperature section for a period of time to increase the conductivity of the vacuum valve material; 1. A method for manufacturing a contact material for a vacuum valve, comprising a reheating step of reheating the material at a predetermined temperature in a cooling temperature range.