JPS6067631A - Preparation of cu-cr contact for vacuum breaker - Google Patents

Abstract

PURPOSE:To inexpensively prepare a Cu-Cr contact for a vacuum circuit breaker reduced in occluded gas, by adding a Cr23C6 powder to an electrolytic Cr- powder to mix both of them while sintering the resulting mixture, and infiltrating oxygen free Cu into the obtained sintered body. CONSTITUTION:5-30wt%, pref. 5-15wt% of a Cr23C6 powder is added to a commercial inexpensive electrolytic Cu-powder and both of them are sufficiently mixed and sintered. Subsequently, oxygen free Cu sufficiently degassed by vacuum melting is infiltrated into the obtained sintered body. By this method, a Cu- Cr contact for a vacuum circuit breaker reduced in occluded gas and prevented from the loss of extinction characteristics of arc and insulating characteristics in vacuum is obtained.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a vacuum breaker for reducing storage gas (1:u
-Regarding a method for manufacturing a Cr contact.

[Prior art and its problems]

Conventionally, the contact phase materials used in vacuum circuit breakers that require large current breaking performance include Cu-B1 alloys, C
U-13i alloys are excellent in terms of breaking performance and welding resistance, but the Bi contained in this contact alloy is said to be a factor in deteriorating the ML pressure resistance characteristics of vacuum circuit breakers. It has shortcomings.

On the other hand, Cu-(:r-based alloys have relatively excellent breaking performance, withstand voltage characteristics, and current cutting properties, and Cr, which is a constituent element of this contact, has a getter action that absorbs gas. It is generally accepted that this is an effective contact for vacuum circuit breakers.

In this Cu-(:r alloy, Cu and Cr are originally difficult to melt together, so usually Cu and Cr powders are mixed together.
H■ It is made by the solid-phase sintering method in which the mixture is weighed and mixed in a certain ratio, pressure-formed, and then sintered in a vacuum or reducing atmosphere, and it contains 40 to 60 weight n% of Cr. In this case, first a sintered body of Cr is made, and then Cu
By infiltrating the voids in the Cr sintered body, the
- A sintering and infiltration method is used to produce the Cr contact powder.

On the other hand, a vacuum breaker performs current interruption in a vacuum container, and therefore has superior arc-extinguishing and insulation properties, as well as high breaking performance, compared to other layered devices.

Therefore, it is preferable that the amount of gas absorbed in the contacts used in the vacuum breaker be as small as possible. In other words, when the amount of gas occluded in the contact increases, metal vapor is generated and the occluded gas is dissipated into the vacuum container each time the contact opens and closes, which deteriorates the degree of vacuum and reduces the quenching characteristics. This is because the insulation properties are impaired. For medium- to low-capacity air circuit breakers that are frequently switched on and off, gas occlusion in the contacts is a particularly serious problem.

The amount of gas absorbed in the contact is closely related to the manufacturing method of the contact. For example, in the sinter infiltration method mentioned above, 7+,
9 Because the process is carried out in an atmosphere, the reducing ability of the oxide is lower than in a hydrogen atmosphere, and C
Since Ba oxide is formed on the surface of the r powder in the form of Cr 203, the gas contained inside is diffused to the surface when the Cr powder is sintered, and less firewood is released to the outside. C
Since the Cu to be infiltrated into the sintered body is of high purity and has been sufficiently degassed by vacuum melting, the amount of dissolved gases such as oxygen, nitrogen, and hydrogen injected into the Cu is less than Oppm, and The amount of gas occluded in the Cr powder that forms the sintered body is very small, so the amount of gas does not increase by infiltrating Cu in the sintering infiltration method. The amount of gas remaining in the Cu-Cr contact is controlled exclusively by the amount of gas occluded in the raw material powder.For example, the electrolytic Cr powder used as the raw material has an oxygen content of 6.300.
ppm, nitrogen approx. 330 ppm, hydrogen approx. 1100 p
p.

Cu-Cr contacts made from this raw material contain a total of about 7,000 ppm of gas, and a considerably large amount of gas is occluded in the Cu-Cr contacts, but as a contact for a vacuum breaker, the content is less than 2,000 ppm. It is desired that

On the other hand, from Hamura's point of view, the conventional manufacturing method for reducing the amount of occluded gas in Cu-Cr contacts is to grind high-purity Cr that has been vacuum melted and degassed, and then undergo further reduction treatment to produce Cr powder. Although it is also used as an original sashimi,
In this method, the Vi raw material powder becomes very expensive, and since Cr is a metal that is inherently easily oxidized, it is also difficult to handle. In addition, commercially available electrolytic Cr powder is cheaper than vacuum melted powder, but as mentioned above, it costs about 7,000
Since it stores 0.00 ppm of gas, when using Cr powder, the blending ratio must be determined so that the contact phase material has as low a Cr content as possible. Contacts have drawbacks such as the inability to guarantee desired electrical characteristics.

[Purpose of the invention]

The purpose of the present invention is to eliminate the above-mentioned drawbacks and to produce Cu-C which is produced using commercially available %w4Cr powder which occludes a large amount of gas.
Cu that can reduce the amount of gas remaining at the r contact
-Providing a method for manufacturing a Cr contact.

[Key points of the invention]

The present invention uses chromium carbide powder (Cr2) in addition to electrolytic Cr powder.
This is a method for manufacturing a Cu-Cr contact in which 5 to 30% by weight of 3C6) is added to reduce residual gas in a C11-Cr contact obtained by a sinter infiltration method.

[Embodiments of the invention]

The present invention will be explained below based on examples. First, chromium carbide added as a reducing agent to electrolytic Cr powder contains CryC.
a * There are Cr5Cz, Cr23C6, etc., but as a result of a separate experiment, it was concluded that Cr2306 is the best, and 1+, Cr powder with -100 to +325 mesh and 1300 mesh Cr23C6 powder were mixed well in a mortar. After that, the mixture was transferred to a V-type mixer and mixed for 2 hours. In this way, seven types of mixed powders with different amounts of Cr23C6 added were prepared, and the mixed powders were filled into a graphite melting tube that had been sufficiently heated and degassed, and this was held in a vacuum furnace at 1250°C for 1 hour. Sintering was performed under two conditions: and holding at 1400° C. for 1 hour.

Table 1 shows the analysis results of the amount of oxygen contained in the obtained sintered body. 'fk, solutionThe gas occluded in Cr powder is mostly oxygen, as mentioned above, so Table 1 lists the analytical values for only oxygen, and for comparison, it also includes those without adding Cr23C6. As shown in Table 1, by adding 1 lotus of Cr23C6 powder, the sintering conditions were changed to 1250℃ in vacuum,
In the case of holding for 1 hour, the amount of residual oxygen in the Cr sintered body decreased by 23 units compared to the one without fibers, and when 5% by weight was added, the amount of residual oxygen in the Cr sintered body decreased by 1.
/2 or less. Furthermore, when the amount of Cr23C6 added is increased, the amount of oxygen decreases to 1280 pp+n at 10% by weight, but when more than that is added (1i1=K), the amount of residual oxygen begins to gradually increase, and at 40%, it finally reaches 1280 pp+n without the addition of Cr23C6. It will be at almost the same level. This tendency is observed when the sintering conditions are 1400°C in vacuum.

The same is true when holding for 1 hour. 4) Cr23C61 heavy i
% addition, the amount of oxygen remaining in the Cr sintered body becomes about 2/3 of that without addition, and when 5-fold fA is added, the amount of oxygen remaining in the Cr sintered body becomes 1/3 or less at once. Furthermore, Cr23C6
If the amount of oxygen added is increased to 10% by weight, the amount of residual oxygen will be 3
00 ppm, which is a significant decrease. But no more Cr2
As the amount of 3C6 added increases, the sintering conditions become 1 in vacuum.
As in the case of holding at 250° C. for 1 hour, the amount of oxygen increases, but the higher the sintering temperature, the greater the amount of oxygen removed from the Cr sintered body.

As described above, according to the present invention, the appropriate amount of Cr23C6 to be added is 5 to 301 parts per electrolytic Cr powder, and
If the weight is below -, there is less contact interface between Cr powder and Cr23C6, the reaction between the two is limited, and degassing is not achieved sufficiently.
Furthermore, if 30M or more of Cr23C6 is added, electrolytic Cr
Excess Cr23CI+ that does not contribute to the reaction with the powder remains as it is. (The amount of oxygen stored in J23C6 powder is extremely large compared to Cr powder, about 16.0
00 ppm, so if Cr23C6 is left as is, depending on the amount added, the amount of occluded acid in the Cr powder sintered body will actually increase by 1.0 ppm. That is, the amount of Cr23C6 powder added to the Cr powder is preferably around 10% by weight, which is a range that allows the reduction reaction to proceed in just the right amount with Cr2O3, and is preferably 5 to 15% by weight.

For example, after adding 10% by weight of Cr23C6 powder to electrolytic Cr powder and sintering this mixed powder at 1400°C in vacuum, the total amount of gas remaining in the 50Cu-50Cr contact infiltrated with oxygen-free ('u) is approximately 200 ppm. Compared to several thousand ppm in the conventional method that does not add Cr23C6, it has been significantly reduced.When used in a vacuum breaker, frost on the contacts and similar characteristics are reduced. It has been confirmed that the specifications are fully met.

The reason why the addition of Cr23C6 effectively contributes to the degassing of the Cr powder bed sintered body is because it does not prevent the oxygen formed on the Cr powder surface from diffusing to the surface and being released. The reaction process with the following formula is also effective in reducing the gas value in the Cu-Cr contact.

〔Effect of the invention〕

As explained in the examples above, vacuum 1- and ^Cu-Cr
When manufacturing contacts by the sinter infiltration method, by using electrolytic Cr powder as a raw material and adding 5 to 30 g of K Cr23C6 powder, the amount of oxygen stored in the Cr sintered body can be greatly increased. The gas dissipation from two points, which is a major problem in vacuum circuit breakers, does not affect the breaking performance or insulation properties of the tube, and the economical effects are great.

Ear-containing person Itoriju Yamaguchi

Claims (1)

[Claims] 1) A cu-cr contact for an X-standby circuit breaker, characterized in that Cr23C6 powder is added and mixed with electrolytic Cr powder to form a sintered body, and then the sintered body is infiltrated with oxygen-free Cu. 02, the method according to claim 1, in which Cr2
The amount of 3C6 powder added is 5 to 30% by weight, preferably 5 to 30% by weight.
Cu for vacuum breaker which is 15 years old
-Method of screwing Cr contacts.