JPH05200711A - Method for molding powder - Google Patents

Abstract

(57) [Summary] [Structure] A process of casting a slurry in which a metal or ceramic powder is dispersed in a dispersion medium whose main component is a melting point of 0 to 100 ° C into a porous mold by casting, and cooling the slurry. step of the solidified molded product, after filling the porous mold directly or this medium powder was charged into the pressure medium, at 1 kg / cm ² or more 10000 kg / cm ² or less of external pressure It comprises a step of isostatically or quasi-isotropically pressing such a compact to consolidate the compact, and a step of thermally decomposing and removing the dispersion medium remaining in the compact subjected to such treatment. [Effect] A degreased molded product that is sound and has a uniform density and high dimensional accuracy can be obtained in an extremely short time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder molding method in which a slurry in which metal or ceramic powder is dispersed is cast into a porous mold by casting.

[0002]

2. Description of the Related Art Sludge casting can be roughly classified into the following two types depending on the method of solidifying sludge.

That is, one of them uses a liquid-absorptive mold made of gypsum or porous resin or the like, and absorbs a part of the liquid of the sludge cast in the mold, thereby causing shape retention. After that, the molded product is obtained by demolding.

Another method is to use a non-absorbent mold of metal, rubber or the like, cool this mold in advance to a temperature below the melting point of the liquid constituting the mold, and cast the slurry into it. This is a method in which the liquid is solidified by cooling to a temperature below the melting point of the liquid at room temperature, the shape-retaining property is thereby generated, and then the liquid is released to obtain a molded product.

The dispersion medium in the slurry is removed by drying or thermal decomposition (degreasing) from the molded body that has been molded.
When removing by drying, the temperature and humidity of the atmosphere are controlled, and the dispersion medium is slowly removed over a very long time. In the case of thermal decomposition and removal, various means such as pressurizing the degreasing atmosphere in order to produce a sound molded body free from cracks and defects, devising the heating rate so that the evaporation rate of organic substances becomes constant, etc. Is used.

The molded body from which the dispersion medium has been removed by drying or thermal decomposition (degreasing) is densified in the sintering process to obtain a sintered body. An outline of this process is shown in FIG.

The present inventor first casts a slurry, in which metal powder or ceramic powder is dispersed in a dispersion medium, into a porous mold, and heats the slurry in the porous mold to evaporate the dispersion medium. A method for producing a molded body of metal powder or ceramic powder, which is characterized by thermally decomposing and removing, has been developed (JP-A-3-24204).

By the way, when metal powder, ceramic powder, or mixed powder of ceramic and metal is used to cast a particularly large part, the density tends to be low or uneven. Therefore, in order to improve the density of the compact and prevent the non-uniformity of the density, a method is known in which the slurry is cast while being pressurized.

[0009]

However, in this case, it is necessary to use an expensive mold or a BN mold for the mold used for molding, and the pressure applied because the pressurization is performed from the casting port. There are still problems such as a limit, and the density distribution of the obtained molded body is likely to occur. The density non-uniformity once generated in this way is difficult to improve in the subsequent drying or thermal decomposition step, and in some cases, causes cracks or cracks during drying, thermal decomposition or firing. .. As means for eliminating such non-uniformity of density, for example, JP-A 1-2304
No. 82 publication describes a method of coating an elastic film on the surface of a molded body after degreasing, followed by cold hydrostatic pressure treatment to remove internal defects and improve the density of the molded body. Since the strength of the molded body is reduced, it is difficult to perform cold hydrostatic pressure treatment without breaking the molded body, and it is preferable to eliminate such non-uniformity of density before degreasing if possible. ..

On the other hand, the dispersion medium in the molded product that has been molded must be removed by drying or thermal decomposition (degreasing).

When the product is dried and removed, it is necessary to strictly control the temperature and humidity of the atmosphere and to slowly remove the dispersion medium over a very long period of time. Because of this, cracks and cracks occur. Therefore, it is difficult to say that this is a highly productive method because it requires a vast area for drying.

[0012] Further, there is a similar problem in removing by thermal decomposition. That is, the binder once solidified is remelted by heating and is accompanied by a large volume expansion. As a result, the molded body may be deformed, warped or cracked. In order to avoid this, the rate of temperature rise until remelting is extremely slow, or the temperature is increased by embedding in embedding powder.However, especially for long objects and large objects, deformation due to their own weight is avoided. Absent.

Further, it is necessary that the decomposition gas generated by the thermal decomposition is discharged to the outside of the molded body faster than the generation rate. In other words, if the decomposition gas is generated too fast, it accumulates inside the compact and the compact swells,
This is because it may cause cracking or peeling. Therefore, the temperature rising rate at the time of thermal decomposition must be extremely slowed, and even if the size is about the same as a turbocharger, it usually takes a long time of about 3 weeks. In order to shorten this, various measures have been taken such as pressurizing the degreasing atmosphere and devising the heating rate so that the evaporation rate of the organic matter becomes constant, but it is still insufficient. It is said that the maximum thickness of the molded body that can be produced by such thermal decomposition is about 15 mm at the maximum. Further, it is known that the soundness of a molded body after pyrolysis largely depends on the density of the molded body, and if the density is low, cracks and cracks are likely to occur even when treated with the same thermal decomposition pattern. ..

The present invention has been made to solve the above problems in the cast molding of powders, and the compact density obtained in the slurry cast molding technique in a short time without any inconvenience to the compact. The purpose is to improve and uniformize the oil content and shorten the degreasing time.

[0015]

Means for Solving the Problems That is, the present inventors
A step of casting a slurry in which a metal or ceramic powder is dispersed in a dispersion medium containing a substance having a melting point of 0 to 100 ° C. as a main component into a porous mold by casting, a step of solidifying the slurry by cooling to form a shaped body, after embedding the porous mold directly or which the pressure medium powder, pressurized and charged into the pressure medium, isotropic or quasi-molded body according at 1 kg / cm ² or more 10000 kg / cm ² or less of external pressure It is possible to solve the above-mentioned problems by going through a step of isostatically pressing the compact and compacting the compact, and a step of removing the dispersion medium remaining in the compact subjected to such treatment by thermal decomposition. They found out and completed the present invention.

The powder formed by the method of the present invention contains 2% N
i-98% Fe mixture, SUS316 powder, metal powder such as high speed steel, ceramic powder such as silicon nitride and silicon carbide, tungsten carbide-cobalt mixture powder, titanium carbide-nickel mixture powder and other metal-ceramics mixture powder is there. The particle size of these powders is about 0.1 to 100 μm.

The dispersion medium in which the metal or ceramic powder is dispersed is mainly composed of a substance having a melting point of 0 to 100 ° C., and examples of this substance include water or stearyl alcohol, cetyl alcohol and t-butyl alcohol. Examples thereof include alcohols, carboxylic acids such as stearic acid, amides or esters such as stearic acid amide, and hydrocarbons such as paraffin having a melting point in the above range. In this case, if the melting point is too low, the facility for producing a low-temperature refrigerant for solidifying the slurry becomes large, which is not preferable. On the other hand, if the melting point is too high, the viscosity becomes high, and the fixation of the slurry increases when the equipment is stopped, and cleaning is not easy, which is not preferable. Therefore, it is preferable that the substance having a melting point of 0 to 100 ° C. be the main component, that is, 90% by weight or more be contained. In order to give the slurry proper fluidity,
At least one of these is mixed with various commercially available dispersants and lubricants, or polyvinyl alcohol, polyvinyl butyral, methyl cellulose, ethyl cellulose, phenols, amines, liquid paraffin, etc. as thickeners to adjust the fluidity and viscosity. be able to. As a measure of proper fluidity, the viscosity of the slurry is in the range of 50 to 10 ⁴ centipoise.

Any slurry may be used as long as it has fluidity so that it can be cast. Its concentration is over 20% by volume, 85
It must be below the volume%. It is preferably 45% by volume or more and 75% by volume or less. If it is less than 20% by volume, the fluidity is excellent, but the shrinkage rate of the slurry becomes large during the process of pressurizing part of the dispersion medium into the porous mold and discharging it to the outside, which reduces the dimensional accuracy of the molded body. To do. On the other hand, if it exceeds 85% by volume, it will be difficult to provide the fluidity required for molding even if the particle size distribution of the powder, the dispersant, etc. are devised.

The porous mold must have strength to withstand the pressure during slurry casting and through holes (through hole density, pore diameter, etc.) through which the dispersion medium can be discharged to the outside. In addition, when the mold is isotropically or quasi-isotropically pressed after the cast molding, the mold itself needs to have such strength that it is isotropically compressed. Further, in order to transfer the shape of the inner surface of the mold to the slurry to form a molded product having good skin, the mold itself must also have good inner skin. In order to produce a mold suitable for such a purpose, the same method as the so-called shell mold used in precision casting can be used.
That is, a pattern (prototype) corresponding to the shape of the mold cavity is made of wax, urea, or the like, and silicon nitride or B is formed on the surface of the pattern except for openings for pattern removal.
Ceramic powders such as N powder, silica flour, zircon flour, polyvinyl alcohol, polyvinyl butyral,
Methyl cellulose, ethyl cellulose, carboxymethyl cellulose, paraffin wax, phenol resin,
After applying a slurry dispersed in water or an organic solvent such as hydrocarbons or alcohols together with one or more kinds of organic binders such as epoxy resin, silica sand, zircon sand, alumina sand, glass powder, etc. Sand the ceramic powder. By repeating this operation, a shell mold having a predetermined thickness and strength can be produced.
Here, the binder of the sanding slurry is preferably an organic binder. Because when using an inorganic binder such as ethyl silicate or its hydrolyzed liquid or colloidal silica, the strength of the shell mold can be greatly increased, but it does not easily deform due to pressure and the mold inside This is because the effect appears. That is, it is difficult to compress the shell mold where the shell mold is hard to be crushed, such that the molded product is not uniformly compressed and deforms. By using an organic binder, deformation due to pressure is facilitated, and when the dispersion medium is pyrolyzed and removed in a later step, the shell mold is also pyrolyzed at the same time and the strength of the shell mold decreases or self-disintegration. Will also be easier. In order to thermally decompose these binders,
The temperature above 400 ℃ and below 1200 ℃ is suitable. However, depending on the shape of the shell mold and the type of organic binder, the organic binder alone may not provide the desired strength. In this case, the strength can be adjusted by mixing the inorganic binder with the organic binder. on the other hand,
In order for the mold itself to have a good inner surface texture, a healthy surface without unevenness or peeling is usually produced by adjusting the solid content concentration in the slurry or optimizing the binder amount. For such a purpose, a porous organic film such as a urethane film may be formed instead of the ceramic slurry applied to the innermost layer. A shell mold is prepared by repeating the application of the slurry and the sanding on the organic film thus formed. As a result, an extremely smooth film can be formed on the innermost layer to realize good transferability, and it is also possible to completely and simultaneously decompose and remove at the stage of thermal decomposition of the dispersion medium. The shell mold thus obtained is subjected to steam treatment, thermal decomposition, washing with water, elution with an organic solvent, etc. to remove the wax resin, urea and the like inside, to obtain a porous shell mold. This mold has the advantage of being able to handle complex shapes.

The slurry is cast and molded from the opening of the porous mold thus formed. The temperature of the slurry at this time may be in the range where the slurry has appropriate fluidity. Further, the porous shell mold may be heated or cooled as long as it does not hinder the fluidity of the slurry. It is an effective means to maintain a certain pressing force immediately after the completion of casting the slurry in order to increase the powder concentration. However, at this time,
If the applied pressure is too large, not only the solid-liquid is separated inside the mold and the density of the molded body becomes non-uniform, but also the mold itself may be damaged. Therefore, the holding pressure of the slurry immediately after casting is preferably 10 kg / cm ² or less. In this way, as the dispersion medium is cooled below the melting point inside the mold, it solidifies and a molded body is obtained.

Next, this porous mold is directly or after being embedded in pressure medium powder, it is charged into a pressure medium and the molded body is isotropically or pseudo-isotropically pressed from the outside.

When the porous mold is directly pressurized, the pressure medium is usually water or gas such as N ₂ , Ar, He, H ₂ or the like or an organic solvent such as ethanol or carbon tetrachloride. When a solvent having a property of dissolving the dispersion medium is used as the pressurizing medium, a part of the dispersion medium can be further eluted and removed during pressurization, which is also effective for shortening the thermal decomposition time. In this case, various combinations of the dispersion medium and the pressure medium are conceivable. For example, when paraffin is used as the dispersion medium, the pressure medium may be hexane, ethyl alcohol, or THF. Of course, it is not limited to this.

The pressure is 1 kg / cm²More than 10000kg / cm²The following ranges
Is selected for the fence. The reason for this is 1 kg / cm ²The pressure below
This is because there is almost no effect of improving the powder density by pressure.
, 10,000 kg / cm²The above pressure is excessive and the device
It is not practical because it increases in size. Therefore 5kg / cm²More than 50
00kg / cm²The following pressure is more desirable, 1000kg / cm²More than 50
00kg / cm²The following pressures are particularly desirable. Pressure is in this range
It may be appropriately selected depending on the size and thickness of the object to be processed. Well
Also, the pressure is gradually increased to the maximum pressure within this range.
Or, it may be changed up and down. Pressurized medium
When using a solvent that has the property of dissolving the dispersion medium
Move the dispersion medium to the outside of the molded body due to this pressure fluctuation.
Is particularly effective as it is promoted.

The pressurizing device is not particularly limited.
It is preferable to use a pressure medium powder that can be used as described below, to which pressure can be applied, and a uniaxial press device, a CIP device, an ordinary pressure furnace using gas as a pressure medium, or the like can be used. Further, an apparatus in which the casting apparatus and the pressure apparatus are combined may be used so that the casting apparatus and the subsequent pressurizing operation can be performed by the same apparatus.

Even when the porous mold is embedded in the pressure medium powder and then pressure is applied, the effect of compacting the powder can be expected as in the above case, although the dispersion medium is not removed. As the pressure medium powder, not only powder but also powder dispersed in a material having plasticity such as wax may be used as long as it can be deformed during the pressure treatment. Examples of such powders include zircon flour, silica flour, zircon sand, alumina sand and other precision casting materials having a particle size of about 20 to 1000 μm, powdered polyethylene, polystyrene, polypropylene, water absorbing polymers, oil absorbing polymers, etc. Particle size is 100-500
Examples thereof include an organic polymer material having a particle size of about 0 μm, ceramic powder such as alumina and silicon nitride having a particle size of about 0.1 to 5 μm, and the like.

These pressurizing operations may be repeated twice or more. This can be expected to improve the powder density and make it uniform.

Next, the shell mold which has been subjected to the pressure treatment is subjected to a thermal decomposition step. There are no particular restrictions on this method. The thermal decomposition furnace may be any furnace capable of raising the temperature to a temperature at which the binder in the dispersion medium and the shell mold can be thermally decomposed and controlling the atmosphere. As the thermal decomposition condition, the temperature may be equal to or higher than the thermal decomposition point of the binder, but usually about 400 to 600 ° C. is suitable. The temperature rising rate can be greatly increased as compared with the conventional method, and can be 100 ° C./hr or more. Usually 1-10
It is selected from the range of ° C / hr. Pyrolysis is carried out in the atmosphere or in an atmosphere such as nitrogen, and 95% or more of the binder, preferably 97
Perform until about 99% can be removed from the molded body. After the thermal decomposition is completed, a molded product is obtained through a demolding process.

The compact is made into a dense sintered body through a sintering process. A flow chart of the process of the present invention is shown in FIG.

[0029]

In the method of the present invention, a substance having a melting point of 0 to 100 ° C. is used as a main component of a dispersion medium to facilitate solidification and liquefaction of a slurry in which metal or ceramic powder is dispersed to form a compact. It is easy to do. By making the mold porous, the dispersion medium can be absorbed and discharged to the outside. The above slurry is cast into this porous mold, and after cooling and solidifying the slurry, this is externally applied at 1 kg / cm ² or more 10,000 k
By pressurizing at a pressure of g / cm ² or less, the pressurizing medium enters the pores of the porous mold and acts directly on the molded body. The molded body is isotropically pressed and consolidated to form a molded body having a high density and a uniform density distribution, and fine defects such as sink marks are removed. Further, when the dispersion medium of the slurry is in the plasticized region due to pressure, rearrangement of the powder occurs,
Uniformity of the density is achieved together with improvement of the powder density. When the compacted body is heated together with the porous mold to raise the temperature to the melting point of the dispersion medium, the dispersion medium causes a rapid volume expansion in most cases. At this time, the binder in an amount corresponding to the expanded volume is discharged to the outside by the capillary force of the pores of the shell mold. Moreover, since the strength of the shell mold does not decrease at about the melting temperature of the binder, the molded body is held from the outside to prevent the molded body from being deformed or cracked. Furthermore, when the temperature rises, the thermal decomposition of the binder in the shell mold and the residual dispersion medium in the object to be processed simultaneously proceed. During thermal decomposition, the shell mold undergoes strength reduction or self-disintegration, which facilitates its removal from the molded body.

[0030]

【Example】

Example 1 A cylinder made of silicon nitride was produced. First, the average particle size is 0.7 μm
Si ₃ N ₄ 93.0 parts by weight, Al ₂ O ₃ 2.0 having an average particle size of 0.5 μm
56 parts by weight, 5.0 parts by weight of Y ₂ O _{3 having} an average particle size of 0.5 μm, melting point 56
℃ paraffin 10.5 parts by weight, stearic acid 3.5 parts by weight,
2.0 parts by weight of a commercially available ester-based dispersant was added and the mixture was kneaded under vacuum for 24 hours. On the other hand, a cavity-shaped shell mold corresponding to the cylinder shown in FIG. 2 was prepared from a slurry in which 50.0 parts by weight of polyvinyl alcohol was dispersed in 100.0 parts by weight of Si ₃ N ₄ powder and alumina sand. The above slurry was cast into this shell mold at 80 ° C. at a casting pressure of 3 kg / cm ² .
With the start of casting, the casting pressure temporarily dropped, but after recovering to 3 kg / cm ² , the casting pressure was maintained for 10 minutes for cooling and solidification. This was embedded in silica flower. These were placed in a thin rubber bag and vacuum sealed. This was put into a CIP device, kept at 3000 kg / cm ² for 5 minutes, and then taken out.
After removing the layer of silica flour, it was placed in a pressure degreasing furnace at room temperature. The atmosphere was nitrogen and the temperature was raised at a heating rate of 100 ° C./hr while flowing at a gas pressure of 5 kg / cm ² . After reaching 500 ° C., the temperature was kept as it was for 1 hour, then allowed to cool and returned to atmospheric pressure. As a result, the mold was extremely brittle and could be easily removed. A molded product obtained was sound, and no deformation of the molded product was observed. Table 1 shows the diameters of the molded bodies measured at the positions A to D shown in FIG.

[0031]

[Table 1]

It can be seen that it is almost constant in the height direction. This was filled with 50% by weight of AIN and 50% by weight of NB, charged into a sintering furnace, heated to 1350 ° C. in a vacuum and held for 2 hours. Then, while flowing nitrogen gas at a gas pressure of 9.5 kg / cm ² , the temperature was further raised to 1750 ° C. and maintained for 5 hours. While maintaining the gas pressure, it was cooled to 1200 ° C., returned to normal pressure and allowed to cool. As a result, a healthy sintered body having a theoretical density ratio of 98.5% was obtained.

Comparative Example 1 A cylinder having the same shape and size as in Example 1 was produced. The slurry blending conditions and the shell mold making method were the same as in Example 1. The slurry was cast into a shell mold at 80 ° C. at a casting pressure of 3 kg / cm ² . Similarly, it was held for 10 minutes and then cooled and solidified. This was placed in a pressure degreasing furnace at room temperature without performing CIP treatment. Nitrogen atmosphere, gas pressure 5kg / c
The temperature was raised at a heating rate of 100 ° C./hr while circulating at m ² . Fifty
After reaching 0 ° C., the temperature was maintained for 1 hour, allowed to cool, and returned to atmospheric pressure. As a result, the mold was extremely brittle and could be easily removed, but the molded body was brittle, and part of the surface was peeled off during the process of removing the mold. Also, a small crack was observed on a part of the side surface. AIN 50% by weight, BN
Fill it with 50% by weight of powder and put it in a sintering furnace.
The temperature was raised to ℃ and kept for 2 hours. Then, pressurize nitrogen gas
While circulating at 9.5 kg / cm ² , the temperature was further raised to 1750 ° C. and kept for 5 hours. While maintaining the gas pressure, it was cooled to 1200 ° C., returned to normal pressure and allowed to cool. As a result, a sintered body having a high theoretical density ratio of 98.3% was obtained, but the sintered body was broken apart.

Comparative Example 2 The same slurry as in Example 1 was used. An aluminum mold was used as the mold. The slurry was cast into a mold under the same conditions as in Example 1. It was cooled and solidified and taken out from the mold. Three cylinders were produced by the same method. This was subjected to CIP treatment in the same manner as in Example 1. These were charged into a pressure degreasing furnace, and the effect of the heating rate during degreasing on the soundness of the molded body was investigated. The temperature rising rate is the same as in Example 1, 100 ° C./hr
And a total of 4 levels of 50 ° C / hr, 10 ° C / hr and 5 ° C / hr were selected. The atmosphere was nitrogen, and the temperature was raised at each heating rate while flowing at a gas pressure of 5 kg / cm ² . After reaching 500 ° C., the temperature was kept as it was for 1 hour, then allowed to cool and returned to atmospheric pressure. As a result, when the rate of temperature rise was 100 ° C./hr and 50 ° C./hr, the molded body had large cracks. At 10 ° C / hr, 5 ° C / hr, a molded product without cracks and cracks was obtained, but at 10 ° C / hr
The case was obviously warped. In the case of 5 ° C./hr, the dimension of the molded body was measured as in Example 1. The results are shown in Table 1.
Shown in. The size is larger toward the bottom, suggesting that it is deformed by its own weight.

Example 2 A cylinder having the same shape and size as in Example 1 was produced. The slurry blending conditions and the shell mold making method were the same as in Example 1. The slurry was cast into a shell mold at 80 ° C. at a casting pressure of 3 kg / cm ² . Similarly, it was held for 10 minutes and then cooled and solidified. This mold was placed in a thick rubber mold and filled with ethyl alcohol as a pressure medium, and then the lid was closed and sealed. This was charged into a CIP device, and CIP treatment was performed using water as a pressure medium. First, pressurize to 1.0kg / cm ² and hold for 5 minutes, then pressurize to 2.0kg / cm ² and hold for 5 minutes,
After raising the pressure to 3.0 kg / cm ² and holding for 5 minutes, the pressure was lowered and the product was taken out. The ethyl alcohol filled in the thick rubber mold was white and turbid, and it can be seen that a part of the dispersion medium was extracted by the ethyl alcohol. After the porous mold was dried at 40 ° C. for 24 hours, the same CIP and drying operations were performed again. Then, it was charged into a pressure degreasing furnace at room temperature. The atmosphere was nitrogen, and the temperature was raised at a heating rate of 150 ° C./hr while flowing at a gas pressure of 5 kg / cm ² . After reaching 500 ° C., the temperature was kept as it was for 1 hour, then allowed to cool and returned to atmospheric pressure. After removing the mold,
The molded body was sound and no deformation was observed.

Example 3 Next, an example in which a cemented carbide bolt was manufactured is shown. Average particle size
8.0 parts by weight of stearyl alcohol and 0.20 parts by weight of an ester-based dispersant were added to 90 parts by weight of 1.5 μm WC and 10 parts by weight of Co having an average particle size of 1.3 μm, and the mixture was vacuum kneaded at 90 ° C. for 24 hours. To the obtained slurry, 0.5 part by weight of ethyl cellulose, 0.5 part by weight of dibutyl phthalate and 1.0 part by weight of liquid paraffin were added and further kneaded for 2 hours. On the other hand, a bolt-shaped wax pattern shown in FIG. 3 was prepared, and a thickness of about 50 μm was formed on this surface.
To form a porous urethane film. Separately, 100.0 parts by weight of zircon flower was added to 30 parts of isopropyl alcohol.
A slurry dispersed in a mixed solution of 5 parts by weight of a hydrolyzed liquid of ethyl silicate and 1.5 parts by weight of polyvinyl butyral was prepared. After applying this to the surface of the urethane film, the operation of sanding zircon sand having a particle diameter of 0.5 mm was repeated to prepare a mold. Then, the wax pattern in the mold was eluted with water vapor at a pressure of 6 kg / cm ² to obtain a shell mold having a bolt-shaped cavity. next,
Pour the slurry of cemented carbide composition into this mold and the pressure is 6 kg.
Casted at / cm ² . After confirming that the casting pressure had recovered to 6 kg / cm ² , it was further held for 20 minutes for solidification. This mold was placed in a thick rubber mold, filled with water, and then the lid was closed and sealed. This was charged into a CIP device, and CIP treatment was performed using water as a pressure medium. First, pressurize to 0.5kg / cm ² and hold for 5 minutes, then pressurize to 1.0kg / cm ² and hold for 5 minutes,
After raising the pressure to 2.0 kg / cm ² and holding for 5 minutes, the pressure was lowered and the product was taken out. The porous mold was dried at 50 ° C. for 24 hours. Next, this was subjected to a degreasing treatment under the same conditions as in Example 1, and then the mold was removed, whereby a sound molded body having a bolt shape was obtained.

[0037]

In the cast molding of the powder of the present invention,
After casting the slurry into the porous mold and solidifying it, the porous mold is directly or after being embedded in the pressure medium powder, it is charged into a pressure medium and the molded body is isotropically or pseudo-isotropically pressurized. Then, by thermally decomposing the molded body together with the porous mold, it is possible to obtain a degreased body that is sound and has high dimensional accuracy in a short time. This is because the density of the molded body itself is improved by pressure-treating the molded body after casting,
It is not easily affected by the thermal decomposition rate, deformation and cracking are prevented by holding the molded body in the porous mold even during thermal decomposition, and the dispersion medium during melting during heating is kept in the fine mold of the porous mold. This is because the amount of the dispersion medium at the time of thermal decomposition is reduced because it can be efficiently discharged to the outside through the holes.

Further, when a solvent capable of dissolving the dispersion medium in the slurry is used as the pressurizing medium and a pressure is directly applied to the molded body, the dispersion medium can be eluted during the pressurization, so that thermal decomposition is carried out. The time can be further shortened.

[Brief description of drawings]

FIG. 1 is a diagram showing a flow of steps of the method of the present invention.

FIG. 2 is a side view of the cylinders manufactured in Examples 1 and 2.

FIG. 3 is a diagram showing an outer shape of a bolt manufactured in Example 3;

FIG. 4 is a diagram showing a flow of an example of steps of a conventional method.

Claims (1)

[Claims] 1. A step of casting a slurry, in which a metal or ceramic powder is dispersed in a dispersion medium containing a substance having a melting point of 0 to 100 ° C. as a main component, into a porous mold by casting, and B) cooling the slurry. Step of solidifying into a molded body, C) Implanting the porous mold directly or after embedding it in pressure medium powder, and then charging it into a pressure medium, and externally 1 kg / cm ² or more 10,000 kg / cm ^2
The step of consolidating the compact by isostatically or quasi-isotropically pressing the compact with a pressure of ² or less, D) In the compact by thermally decomposing the compact with the porous mold Forming method, characterized by comprising the step of removing the dispersion medium remaining in the powder