JPH07115231B2 - High temperature fluid pressure compression method for materials - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method of densifying mainly the inner surface quality of various materials to be compressed by performing high temperature isotropic pressure treatment.

[Conventional technology]

There are many known methods for forming a powder material into a solid. The most common method is cold pressing and then sintering at high temperature, but the sintered material parts obtained by such a method usually have a density of 100% or a value close to it. The drawback is that there are often none.

In order to improve the density to 100% or a value close to 100%, it is necessary to give a high compressibility at high temperature by forging, rolling, extruding, etc., or to apply high isotropic pressure at high temperature by HIP (hot isotropic compression). is necessary.

For parts with complicated shapes, HIP using argon or nitrogen gas as a pressure medium is suitable, but it has the drawback of being costly due to the complicated mechanism, effective gas usage and long cycle time. However, it is currently applied only to high-grade parts.

As a method that can greatly reduce the cycle time, hydraulic HIP using a liquid as a pressure medium (Japanese Patent Laid-Open No. 58-22307)
However, there are problems with the heat resistance of the material used for the press container and the sealing property against the high-temperature liquid between the punch and the cylinder part, so it seems that much improvement efforts are needed to put it to practical use. Be done.

In order to eliminate these drawbacks of HIP, a series of technologies collectively called pseudo-HIP was developed (The International Jour.
nal of Powder Metallurgy and Powder Technology JUL
It is explained in detail in Y1985. ) For example, the Ceracon method that uses ceramic particles as the pressure medium, the metal that has fluidity at high temperature, and the RO that uses the pressure medium such as ceramic particles.
The C law is a representative example.

The Ceracon method is a method in which ceramic particles and materials heated to a required temperature are charged into a pressing container and then pressed, which has the advantage that the operation is simple and the cycle time is extremely short compared to HIP. HIP with uniform pressure distribution
It is difficult to achieve a moderate isotropic pressure.

Further, in the ROC method, the material is cooled as it is together with the pressure medium, so that the work of removing the medium later is complicated and causes a cost increase.

[Problems to be solved by the invention]

The present invention contemplates the development of a new process using hydraulic pressure that is isotropic, has a short cycle time, and does not require or is a cumbersome sealing mechanism.

[Means and actions for solving problems]

According to the present invention, a material to be compressed heated to a required temperature is charged in a pressing container having an opening hole of a cylinder part where a pressing punch slides upward, and a fluid heated to a required temperature is charged. When compressing isotropically as a pressure medium, a layer of granular material is present between the punch and the fluid, so that the punch does not come into contact with the fluid at least in the initial stage of compression, and the characteristic is that the punch compresses. And

As for the material to be compressed, when molding ordinary metal materials and when molding fine (10 mm or less) grain ceramics, the conditions of high temperature isotropic pressure treatment are temperature range 500 ℃ -2000 ℃, pressure range 500 kg / cm It is about ^{2 to} 5000 kg / cm ² . When a liquid heated to the processing temperature is used as the pressure medium, the heat resistance of the material and the sealing property between the punch and the cylinder arise as described above.

It is said that Ni-based superalloys and Co-based superalloys are the best among the commonly used metallic heat-resistant materials, and some have a creep strength of about 1000 kg / cm ² at 1000 ° C. .

Non-metallic materials include ceramics and carbon.
Some of them have excellent heat resistance at around 00 ° C, but there is concern about impact characteristics and thermal strain characteristics. For use as a pressure vessel, for example, the heat resistance of thick wall cooled ceramics or carbon A special device to cover with metal material is required.

Although the heat resistance problem can be overcome by using the above-mentioned materials, there is a high possibility that the equipment will be uneconomical, and the application will be limited to the production of special high-grade materials.

Therefore, for ordinary materials that need to be manufactured at low cost, the liquid that is the pressure medium is heated while it is still in the press container. It is desirable to remove it from the pressing container as soon as possible.

Next, regarding sealability, gaskets made of metallic materials such as copper or copper alloys are usually used for high-temperature fluid sealing, but it is often difficult to apply for a long time for applications exceeding 700 ° C. . Therefore, it is necessary to prevent the high temperature and high pressure liquid from directly contacting the seal portion between the punch and the cylinder, or to shorten the contact time as much as possible.

For that purpose, a low temperature substance may be allowed to enter between the liquid and the punch. The simplest way to do this is to inject a cold body into the liquid surface immediately before pressing, ideally for the cold body to remain cool throughout the press.

Practically, this cold object is preferably the same substance as the hot liquid and is granular. This is because the same substance does not need to be separated after recovery, and the granular form is easy to handle and has an excellent ability to cover the entire surface of the high temperature liquid.

Of course, to enable this, the melting point or softening temperature of this material must be between the hot liquid and the cold body. Further, the low temperature is preferably room temperature or room temperature in terms of work.

The above is the basic idea for solving the problems of heat resistance and sealing. Next, the basic principle of the present invention will be described with reference to FIG.

Reference numeral 1-1 is a bottom portion of the pressing container, 1-2 is a side surface portion of the pressing container, and 1-4 is a sliding portion of the punch between the punches 2 and 1-2. The material 3 to be compressed and the high-temperature fluid 4 are charged inside such a pressing container.

As the material to be compressed, for example, a material in which capsules are filled with stainless steel powder, or a material in which stainless steel powder is cold compression-molded by a pressing machine or the like is often used. In the figure, 6 is a granular object that is put in immediately before pressing, and is usually at room temperature (room temperature).

Reference numeral 5 denotes a portion where the high-temperature fluid 4 is rapidly cooled and solidified immediately after the granular substance 6 is charged, and has a function of preventing the high-temperature fluid from rising during pressing. Because of this, the punch does not come into direct contact with the hot fluid, at least in the early stages of pressing. For this reason, the sliding part 1-4 does not need a seal mechanism or may be simple.

FIG. 2 shows a method for subjecting a large-sized component to high-temperature and high-pressure treatment with a small-capacity press. If the diameter of the punch is reduced as shown in FIG.
Due to the principle of isotropic pressure in the fluid, the compressive force of the punch required to generate the same amount of isotropic pressure
The drawing is smaller than that in FIG. 1 by the sectional area of the punch.

FIG. 3 shows an example of the structure of a pressing container in which a heating device for raising the temperature of the fluid 4 or keeping it warm is provided. 1-3, an open hole is formed in the thick side wall portion.

In FIG. 3, reference numeral 10 denotes a heating portion containing a heating resistor 11 therein, and reference numeral 12 denotes a press container outer skin portion for preventing heat from escaping to the outside of the press container. As described above, when the pressing container is heated, it is desirable that the bottom part 1-1 and the side part 1-2 which are the inner surface of the pressing container are made of a material having excellent heat resistance such as superalloy, ceramics or carbon. .

In the method described above, the high temperature fluid and the granular material do not have to be made of the same material, but in terms of workability, it is often convenient that both are made of the same material.

Because these substances in the press container,
This is because, even when it is repeatedly used or when it is circulated and repeatedly used, if these pressure media are made of the same material, the work of separating the two becomes unnecessary.

However, in this case, the melting point or softening temperature of this material must be between the temperature of the high temperature fluid and the temperature of the particulate matter. Processing temperature is stainless steel 700 to 130 ℃
It is about 0 ° C.

Therefore, taking the case of stainless steel as an example, the melting point or softening temperature of this pressure medium must be between 700 ° C and 1300 ° C and room temperature. Glass can be given as an example of such a material. For example, the softening temperature of lead soda glass is about 630 ° C, and that of aluminosilicate glass is about 920 ° C. Many glasses with higher softening temperatures are also known.

In order to quickly form the solid layer 5 shown in FIGS. 1 to 3, glass having a material whose softening temperature is directly below the temperature of the high temperature fluid may be used.

FIG. 4 is a diagram showing a method of repeatedly performing a pressing action when a high temperature fluid and a granular substance made of the same material are used.

After each press, excess fluid and particulate matter are removed, and a new high temperature fluid at an appropriate temperature is additionally charged to bring the high temperature fluid in the press container to the required temperature. The fluid is removed from the discharge hole 9 (closed at the time of pressing), for example.

Further, if necessary, the fluid is stirred to improve the soaking degree of the fluid, then a block-shaped material to be compressed is charged, and then an appropriate amount of a granular object is charged and press-compressed.

When performing such an operation, the inside of the pressing container is always heated to a temperature close to the processing temperature. Therefore, cooling the pressing container increases the durability of the material forming the inner surface of the pressing container. FIG. 4 shows a press container cooling section 7 having a circulating water passage 8 built therein.

Note that it is also effective to remove all the high-temperature fluid, the particulate matter, and the block-shaped material after the pressing is completed by tilting the pressing container. In this case, if a system in which the removed high temperature fluid is circulated is used, heat loss can be reduced.

FIG. 5 and FIG. 6 are diagrams of a working method when the large-sized component shown in FIG. 2 is pressed with a small press compression force.

As shown in FIG. 5, after the material 3 to be compressed is heated (a) in the heating furnace 7, the material 3 is taken out and attached to the pedestal 8 (b). After fixing this to the press container lower lid 1-1,
Attach to the pressing container 1-2 (c) and close the lower part of the pressing container.

Next, as shown in FIG. 6, the glass 4 which has been heated to become a fluid is charged, and then the granular glass 6 at room temperature is charged. This state is shown in FIG. 2. In the state shown in FIG. 2, the punch is pushed down to apply a load. Since the high temperature and high pressure process is completed, the lower lid 1-1 is opened and the glass is removed.

After this, the one in which the material 3 and the pedestal 8 are integrated is removed from the lower lid 1-1. This completes one cycle, returning to FIG. 4, the material 3 is taken out from the heating furnace 7, and the same process is repeated.

In the above description, it has been assumed that the high temperature fluid 4 is composed of the same component, but a granular substance having a small melting point volume compression rate and a high melting point (for example, ceramic grains) may be mixed in this portion. By doing so, the volumetric compression rate of the high temperature fluid portion under load can be apparently reduced, and the stroke of the punch can be reduced. It is more effective if the same high melting point substance particles are mixed with the granular substance 6.

In the above description, the required temperature in the description of the high temperature fluid heated to the required temperature may not be the same as the processing temperature of the material to be subjected to the high temperature and high pressure processing.

That is, when the material is heated outside the press container, and the fluid heated to the required temperature is charged into the press container after the material is charged, the pressing operation is usually a short time of the order of several minutes. This is because even if the temperature of the high temperature fluid is slightly different from the temperature of the material, the temperature of the material does not greatly change.

Applying this principle allows to some extent the same hot fluid to be used for materials heated to different temperatures.

〔Example〕

Example 1 SUS304 stainless steel powder having a grain size of -100 mesh was compressed to a density of 90% by a cold press. The size of this compression molded product is 10
It is mmφ x 10 mm high.

This was pressed by the isotropic method shown in FIG.

Aluminosilicate glass was used as the high temperature fluid and the room temperature particulate material. The average particle size of the granular glass is 1 mm.

The high temperature fluid temperature is 1200 ℃ and the press compression force is 10t. However, the punch diameter is 40 mmφ. The height of the high temperature fluid layer is 100 mm, and the thickness of the granular glass layer immediately after charging is 30 mm.

Pressing for 5 minutes under these conditions results in a density of approximately 10
0% moldings were obtained. This is the same effect on the internal quality as obtained with HIP.

Example 2 Continuous operation was manually performed by tilting the pressing container of Example 1 each time pressing was completed to eliminate the blocks of high temperature glass and stainless steel.

As a result, 2 minutes for press preparation work such as high temperature glass charging, granular glass charging and stainless steel block charging,
It was demonstrated that one cycle was possible with a press compaction time of 5 minutes and 3 minutes for the removal of hot glass and stainless blocks after the press was completed, for a total of 10 minutes.

Example 3 The same press container and punch as in Example 1 were used. Aluminosilicate glass as a high-temperature fluid, B with a particle size of 1 mmφ
A mixture of 5% N particles was used.

The high temperature fluid temperature is 1200 ℃ and the press compression force is 10t. However, the punch diameter is 40 mmφ. The height of the high temperature fluid layer is 100 mm, and the thickness of the granular glass layer immediately after charging is 30 mm.

Pressing for 5 minutes under these conditions results in a density of approximately 10
0% moldings were obtained. This is the same effect on the internal quality as obtained with HIP.

〔The invention's effect〕

As described above, it was proved that a molded product having the same quality as that obtained by the conventional HIP can be obtained in the order of 10 minutes per cycle. This is a remarkable effect when compared with the conventional HIP, which took one hour or more for one cycle.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of the present invention, FIGS. 2 to 4 are explanatory diagrams showing an application of the present invention, and FIGS. 5 to 6 are explanatory diagrams showing procedures for realizing the method of FIG. is there. 1-1: Bottom of press container 1-2: Side of press container 1-3: Thick part of press container side 1-4: Punch sliding part 2: Punch 3: Block material 4: High temperature fluid 5: High temperature Solid part where fluid is rapidly cooled 6: Granular object 7: Press container cooling part 8: Cooling water flow passage 9: High temperature fluid discharge hole 10: Press container heating part 11: Heating resistor 12: Press container skin Department

Claims (3)

[Claims] 1. A fluid heated to a required temperature is loaded with a material to be compressed, which has been heated to a required temperature, in a pressing container having an opening hole of a cylinder portion on which a pressing punch slides. When isotropically press-compressing as a pressure medium, a layer of granular material is present between the punch and the fluid so that the punch does not come into contact with the fluid at least in the initial stage of compression, and thus the press-compression is performed. High-temperature fluid pressure compression method for characteristic materials. 2. A high temperature fluid pressure compression method for a material according to claim 1, wherein the same material whose melting point or softening temperature is an intermediate value between the temperature at which the fluid is heated and the room temperature is used as the fluid and the granular substance. 3. A powder having a melting point or a softening temperature higher than the temperature of the hot fluid and having a volume compressibility smaller than that of the hot fluid is mixed in the hot fluid,
The method for compressing a material under high temperature fluid pressure according to claim 1, which reduces the volumetric compressibility of the high temperature fluid during pressing.