JPS5956080A - Crucible for infiltrating metal - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a crucible used in the infiltration process of a copper-chromium contact for a vacuum breaker obtained by singly sintering chromium powder and infiltrating silk into the sintered chromium body.

Generally, a vacuum breaker has the following characteristics.

1. Since the current is cut off in a vacuum vessel, the ionization effect at the natural zero value of the current is due to the diffusion of electrons in a high vacuum, which is significantly greater than those using other arc-extinguishing principles, resulting in excellent cutoff performance. 02 indicates that the arc is not exposed when cut off, so there is no risk of fire or explosion and it is safe.

3. Compact and lightweight, helping to save labor during maintenance and inspection 04.
There is little noise when shutting off.

5. Since the contacts are sealed in a vacuum, they are not affected by ambient air and do not require maintenance.

6. No special auxiliary equipment or accessories are required other than the equipment that opens and closes the contacts.

Due to the many features mentioned above, the use of vacuum breakers has increased significantly, starting with pole transformers and being used in power receiving and distribution equipment in buildings and factories, and the use of vacuum breakers is expected to expand further. It is being

It is extremely important to select an appropriate material for the contacts used in this vacuum breaker and to establish processing technology, and the contact materials are required to have the following properties: (1) Sufficient degassing thing.

(2) Good electrical and thermal conductivity.

(3) Do not weld.

(4) Less wear and tear.

(5) Excellent breaking performance.

(6) The contact resistance is low and the current carrying capacity is uniform.

(7) High pressure resistance.

(8) The current cut-off value is small.

Many contact materials that meet these required properties have been developed, but in particular, contacts that contain 40 to 60 tI6 of chromium and the rest is copper have higher breaking and Wj than other contacts.
It has been demonstrated that it is highly useful as a contact for vacuum circuit breakers because it has excellent pressure and current cutting characteristics, and chromium has a getter action that absorbs gas. This (g)
Chrome contacts are usually manufactured by sinter infiltration method, and the manufacturing process is as follows. First, a graphite crucible is filled with chromium powder, and then held in a vacuum of 10'''' torr or less at a temperature in the range of 1200° C. to 1400° C. for about 1 hour to sinter the chromium powder. Next, as shown in Figure i1, copper 2 is placed on top of the chromium sintered body 1, and these are placed in a graphite crucible 3.
Alternatively, as shown in Fig. 2, a chromium sintered body 1 with copper 2 placed on it is placed on a Y graphite plate 4, and the whole is less than 10-'t, or r. The chromium sintered body 1 is infiltrated with tF12 by maintaining the temperature in the vacuum of 1100° C. to 1300° C. for about several tens of minutes.

The thus obtained copper-chromium alloy is then machined into the desired contact shape. However, there were problems as described below when infiltrating copper into the chromium sintered body in the above process.

(1) In the method shown in FIG. 1, molten steel tends to adhere to the graphite crucible, and when it is peeled off, the graphite crucible is damaged. Therefore, there is a large economic loss due to damage to the crucible. (2) In the method shown in Figure 2, molten steel often flows out into the surroundings and makes the inside of the vacuum furnace dirty.

(3) Graphite easily adsorbs gas while the device is in the atmosphere, and this adsorbed gas becomes a factor that causes deterioration of the degree of vacuum during the infiltration process.

(4) Graphite rutsuho has poor workability and low strength, so it is easily damaged during handling such as setup.

The object of the present invention is to provide a crucible for metal infiltration which eliminates the two disadvantages and has high strength and less gas adsorption.

The process of achieving the present invention and the structure of the present invention will be briefly described below.

Ceramic and metal materials are considered to be materials that can be practically used as crucible materials because they have higher strength than graphite and less gas adsorption in the atmosphere. The former hardly reacts with the metal even at high temperatures, but it has the disadvantage that it cannot withstand the thermal stress that occurs during heating and cooling during infiltration and breaks.In contrast, the latter does not break during heating and cooling. Although this phenomenon does not occur, it has the disadvantage that it reacts with the chromium sintered body or molten steel at high temperatures and becomes firmly adhered to each other.Therefore, the inventors of the present invention have combined the advantages of each of the above. We conducted various experiments thinking that this would solve the drawbacks of the prior art described above.As a result, we plated the inner surface of the container with nickel, which is made of a metal material with a higher melting point than copper, and then coated it with ceramic by thermal spraying. It was found that a ceramic coating with a thin coating met the purpose of the present invention.The thickness of the ceramic coating was optimal in the range of 0.1 to Q, 5711F+.This is because the raw material powder used for thermal spraying With a particle size of This is because it has been found that alumina and zirconia are particularly excellent ceramic materials for trench spraying from the viewpoint of thermal shock resistance and non-reactivity with graphite.

As an example, FIG. 3 shows an example of the structure of a crucible when a stainless steel (SUS304) container is coated with alumina. 511 in FIG. I stainless steel container, 6 represents a nickel plating layer, and 7 represents an alumina coating layer. The charge of interest is the same as that shown in Figure 1, and is omitted here. FIG. 4 shows the relationship between temperature, degree of vacuum, and time in the vacuum furnace when this was used as a crucible for copper infiltration and infiltration was performed using the same method as in the past. In Figure 4, curve 8
Curve 9 represents the change in the degree of vacuum over time when a conventional graphite crucible is used, and curve 9 shows the change in the degree of vacuum when the crucible according to the present invention is used.

The temperature sio corresponding to these is also indicated by dotted lines. As can be seen by comparing curves 8 and 9 in Fig. 4, the amount of gas generated using the crucible according to the present invention is smaller than that of the conventionally used graphite crucible, and chromium, a metal that is particularly easily oxidized, etc. It is clear that it is effective against

In addition, even if the crucible according to the present invention was resistant to adhesion of molten copper to the inner wall, there were no cases where the crucible was damaged due to peeling off the molten copper.

As mentioned above, in the present invention, a metal container with a higher melting point than the infiltrated metal and a ceramic coating on the inner surface is used as the crucible, and since it does not contain any graphite material, it cannot be used in conventional graphite crucibles. A remarkable effect was obtained that could not be achieved. That is, the use of the crucible according to the present invention ξ has the following advantages over the case of using a normal graphite crucible.

(1) The amount of gas generated during the infiltration process is small, so there is no oxidation or contamination of the resulting material.

(2) Since the strength of the rutsuho is high, there is no risk of damage during handling, and it can withstand repeated use over a long period of time and is economical.

The present invention also describes the production of contact powder for vacuum breakers. For example, when there are two types of metals that are difficult to fuse together, the powdered sintered body of one metal is infiltrated with the other metal. This is effective when obtaining an alloy of.

[Brief explanation of the drawing]

Figures 1 and 2 are sectional views showing the conventional infiltration method, Figure 3 is a sectional view showing the melting hole according to the present invention, and Figure 4 is the graphite melting method and the melting hole according to the present invention. Situation 11 when used
FIG. 1 is a diagram showing the degree of vacuum between 1j and 1j. 1. Chrome sintered body, 2. Planer, 3. Graphite crucible, 4.
Pyrolead plate, 5 ・Stainless steel container, 6...Nickel plating, 'l ・Ceramic coating. , 1=1 Figure 1 ;! j72 figure time (hl)

Claims (1)

[Claims] 1) A crucible used for infiltrating a porous powder sintered body with metal, characterized by comprising a metal container and a ceramic coating applied to the inner surface of the metal container. Crucible for metal infiltration. 2. A metal melting/immersion crucible according to claim 1, which is used for manufacturing a contact material made by infiltrating a chromium powder sintered body with copper. 3) A crucible for metal infiltration according to claim 1, wherein the ceramic coating is made of alumina. 4) The crucible for metal infiltration according to claim 1, wherein the ceramic coating is made of zirconia. 5) A crucible for metal infiltration according to claim 3 or 4, characterized in that the thickness of the ceramic coating is Q, 1 mm to 0.5 mm.