JPH08132298A - Production of green compact for sintering, apparatus for production and production of rubber mold and sintered compact - Google Patents

Abstract

PURPOSE: To form a green compact of fine powder without using an injection molding method and without using a binder and lubricant. CONSTITUTION: The fine powder 5 is packed at a high density into a rubber mold 10 at least lateral part of which consists of rubber. The rubber mold 10 and the fine powder 5 packed into the rubber mold 10 are compressed by the punch of a die press. The fine powder is packed at a high density into the rubber mold 10 by oscillation or pressing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding a green compact for sintering, and more specifically, it is a green compact forming method which improves the ordinary die press method to enable fine powder compaction. The present invention relates to a green compact molding apparatus, a rubber mold, and a sintered body manufacturing method. In the powder metallurgy technology, by reducing the particle size of the powder used, not only the density of the sintered body becomes high, but also the crystal grain size of the sintered body becomes finer. The binding material significantly improves the mechanical strength, and the iron-based soft magnetic material improves the magnetic properties. However, the improvement of the strength and reliability of the sintered body due to this fine powdering leads to a decrease in the fluidity of the powder. When the die is naturally filled with a powder having a small particle size and a low fluidity, the powder is apt to cause a crosslinking phenomenon in the die, and the packing density largely varies. As a result, the unit weight of the green compact becomes extremely large and the average packing density also decreases.

[0002]

2. Description of the Related Art For the above reasons, fine powder cannot be compacted by an ordinary die press method. Therefore, in order to compact fine powder, an organic binder is used.
The injection molding method must be used to mold a slurry added as much as 0%. However, in this method, it takes several days to remove the binder, and the decomposition products of the organic binder remain as carbon in the sintered product and deteriorate the properties of the product.

Further, since the specific surface area of the fine powder increases, the fine powder becomes extremely active and is prone to oxidative deterioration in the atmosphere. Al-L for which high reliability is required especially for aircraft
Fine powders such as i alloys and Ti alloys are rapidly oxidized in the atmosphere and spontaneously ignite in extreme cases. In addition, it becomes extremely sensitive to an ignition source, and when the lubrication between the die and the punch is reduced due to dusting or the like in the die press method, sparks are generated due to friction, and thus there is a high risk of ignition.

There is a limit to the shape of the product that can be molded by the die press most commonly used for powder molding. Shapes that have constrictions or irregularities such as screws, or molded products that are too long and narrow cannot be molded with a die press. As an improved method for making the powder compression isotropic in the die press, a rubber mold is installed on the die and the elastic deformation of the rubber filled with the powder is used to make the powder move from the direction perpendicular to the punch moving direction. A compression method has been devised (for example, Japanese Patent Laid-Open No. 49-13580).
No. 5). This method is hereinafter referred to as a rubber mold die press method. With the rubber mold die press method, it is possible in principle to mold irregularly shaped products, but the deformation of the rubber tends to be uneven, and cracks and chips and deformation of the molded product frequently occur. CI for obtaining a molded product having a uniform density by hydrostatically compressing powder contained in a bag such as rubber in a liquid
The P method has low efficiency and is not suitable for high-efficiency continuous production of green compacts.

[0005]

SUMMARY OF THE INVENTION It is difficult to produce a fine powder compact by using a conventional ordinary die press method without using a binder. Therefore, even with materials such as aluminum, which are originally soft and easy to raise the density of compacts, low density compaction has been carried out by using coarse powder with a large particle size.
Accepts a low sintered density.

On the other hand, in the injection molding method, it is possible to manufacture a powder compact of fine powder and use this to manufacture a high-density sintered compact having a density of 90% or more, but the binder removal time is remarkable. Since it takes a long time, the productivity is remarkably low by the ordinary die press method. Furthermore, the product obtained by sintering the green compact has a large amount of impurities such as carbon, and in the case of a Ti alloy, the mechanical properties of the sintered product deteriorate. Conventionally, a process such as sizing was required to densify a product obtained by sintering a green compact. But sizing was only possible for soft materials. Therefore, it is an object of the present invention to provide a method and apparatus for molding fine powder with a productivity equivalent to that of a normal die pressing method. Furthermore, the present invention aims to obtain high density products of various materials by sintering only.

[0007]

According to the method of the present invention, a rubber mold having at least a lateral portion made of rubber is naturally filled with the fine powder, and then the fine powder is substantially deformed without substantially deforming the rubber mold. It is characterized in that it is densely packed and a rubber mold and fine powder are compressed by a punch of a die press machine.

In the present invention, a fine powder has a density of 90.
% Powder having an average particle size of 50 μm or less, which can provide a sintered body of at least 50%. Desirably, a powder compact having a particle size of 30 μm or less, more preferably 20 μm or less is used to make a powder compact, and the powder compact is sintered to obtain a high density sintered body having a true density of 90 to 95% or more.

Even if a coarse particle, that is, a powder having an average particle diameter of more than 50 μm is molded by using a rubber mold, the size and volume ratio of the voids in the green compact become very large.
The voids do not easily shrink during sintering, and as a result, the shrinkage of the compact due to sintering is about 1% by volume, which is extremely low, and a high-density sintered compact cannot be obtained. For example, when an iron-based soft magnetic material is sintered by this method, a sintered body density of less than 90% is obtained.

In the present invention, powder means Fe, Co, N
In addition to metals and alloys such as i, Cu, Mo, Al, and Ti, powders of compounds such as TiC and WC are also included. As the Fe-based fine powder, atomized powder with water or an inert gas is often used, and in some cases, carbonyl powder is also used. Gas atomized powder is used as the Al-based fine powder. As the Ti-based fine powder, a powder made by repeating hydrogen storage treatment and dehydrogenation is often used. Also used is a fine powder produced by a mechanical grinding method. Further, it is a feature of the method of the present invention that even fine powders such as Fe-Co and Ti alloys that are hard and have poor formability are formed without adding a binder or a lubricant. Moreover, since the rubber mold is used in the method of the present invention, the fine powder does not directly contact the die,
No dusting like normal die press occurs. Therefore, it is not necessary to use a lubricant. That is, no binder is added to avoid the above-mentioned adverse effects of residual carbon from the binder and the like. However, if carbon or the like is allowed to remain in the sintered product, 1% by weight or less of a binder may be used.

Such fine powder has particularly poor fluidity,
When the rubber is naturally filled, the filling density becomes uneven in the rubber mold. Generally, for filling the powder into the die, a shaker or the like is used to perform natural filling in which the powder is dropped by weight. In the method using a shaker type feeder, the box containing the powder is slid on the table including the die, the powder is dropped into the die hole by natural dropping, and the swelling part of the powder in the die hole is scraped off by leaving the box. Is.

When the fine powder naturally filled in the rubber mold is then compressed by a die press, the fine powder is compressed by the elastic deformation of the rubber mold both in the moving direction of the punch and in the direction orthogonal thereto, that is, in a so-called pseudo-hydrostatic pressure. Therefore, the fluctuation of the powder density in one green compact becomes small.

However, when the naturally-filled fine powder is compression-molded in a rubber mold, cracks, chips, and deformation always occur in the powder compact. In the die press method using a rubber mold, the cause of cracking when powder is filled to such a natural packing density will be described with reference to FIG.

In the present application, the material forming the upper surface of the rubber mold is referred to as the lid portion, the material forming the lower surface is referred to as the bottom portion, and the material forming the side surface portion of the inner surface is referred to as the side portion. In many cases, the natural packing density is about 11 to 13%, and the dimensional shrinkage ratio of the powder by compression molding reaches as high as 30 to 40%. Then, the rubber mold 10 is largely deformed as shown in (c) of FIG. 32 due to a frictional force which moves between the rubber mold members 10s, 10k, 10u and between the rubber mold 10 and the die. Among these deformations, the non-uniform deformation dy generated in the lid portion 10u and the bottom portion 10k of the rubber mold promotes the generation of the crack 5d in the direction parallel to the pressing direction by the punch, and the non-uniform deformation dx generated in the side portion of the rubber mold is It promotes the generation of cracks 5e in the direction perpendicular to the pressure applied by the punch. Further, the non-uniform deformation dx described above causes severe "elephant foot" deformation at the edge portion of the molded body. In order to prevent such cracking, chipping and deformation, it is necessary to fill the rubber mold with a high density of fine powder before press molding in the rubber mold die pressing method.

The "high density" in the high density packing is at least 1.15 times the natural packing density or more, and is preferably 1.3 for a long product and a molded product with severe irregularities.
More than double. However, it is necessary to avoid high-density filling to such an extent that the rubber mold is deformed due to press-fitting of fine powder during filling, and a molded product having a desired shape cannot be obtained. Therefore, the density is preferably 60% or less of the true density.

In densely filling the rubber mold with the fine powder, it is desirable that the fine powder is first naturally filled and then highly densely filled without substantially deforming the rubber mold. More specifically, for high-density filling, the density is increased by applying vibration to the fine powder naturally filled in the rubber mold. Alternatively, the packing density is increased by pressing or crushing the fine powder naturally filled in the rubber mold with a pusher. Alternatively, the packing density can be increased by pressing with a pusher after vibration.

In order to fill the upper end of the rubber mold with the fine powder, a larger amount of the fine powder than the inner volume of the rubber mold is put in the natural filling state, and the fine powder overflows from the rubber mold as it is. Therefore, use the guide frame to fill the fine powder to a position higher than the upper surface of the rubber mold,
Then, apply vibration or push it in with a pusher to match the upper surface of the fine powder with the upper surface of the rubber mold. At this time, the deformation of the rubber mold caused by the pressing of the guide frame or the pressing by the pusher does not affect the filling state of the fine powder in the mold. That is, it is not a substantial deformation.

On the other hand, when high density packing is performed, the rubber mold is deformed, for example, the rubber mold is compressed by a punch to change the powder from the natural packed state to the high density packed state, and then the compression is temporarily stopped and then further compressed. When the powder compact is obtained by continuing the compression by the punch, the density distribution of the powder becomes non-uniform in the filling state obtained in the previous stage of this method, and the deformation amount of the rubber mold is large, so that the powder compact is not cracked or deformed. The problem arises.

In the method of the present invention, it is desirable that the series of steps from natural filling to high density filling be performed outside the die press machine. Since the punch moves up and down in the die press machine, for example, the apparatus for vibrating and pressing the powder according to claim 2 is installed in the die press machine to perform the forced high density filling. Since it becomes complicated, it is not used in the present invention. Further, it is possible to vibrate the rubber mold together with the die in the die press machine, but this is not realistic.

On the other hand, as a method of filling the fine powder with high density without substantially deforming the rubber mold, the inner punch 9a which can press only the fine powder on the upper punch as shown in FIG. 33 is used. A two-layer structure consisting of an outer side portion 9b capable of pressing only the rubber mold is used, and after the fine powder 5 is pressed into the rubber mold by using the inner punch, the rubber mold 1 is formed by using both the outer punch 9b and the inner punch 9a.
0 and fine powder 5 are compressed and molded. According to this method, it is not always necessary to fill the fine powder outside the die press.

The applicant of the present invention filed a patent application on February 14, 1991 for molding a permanent magnet powder in a magnetic field using a rubber mold, but in the present application, the molding in the magnetic field is not performed. Next, the vibration method will be specifically described with reference to FIG.
The fine powder 5 whose weight has been measured in advance is naturally filled from the powder pan 90 into the rubber mold 10 having the guide frame 100 fixed to the upper part (see FIG. 1A). The fine powder 5 is deposited further above the upper surface of the rubber mold 10. Subsequently, the rubber mold 10 is placed on the vibration exciter 41, and vibration is applied (see (b) of FIG. 1). As the vibrator 41, a vibrator that generates horizontal or vertical vibration by an electromagnetic or crank vibrator can be used. The frequency of vibration is not particularly limited, but is, for example, 1 to 60 Hz. The vibration may be performed after the powder feeding, or after the powder feeding is completed.

After that, when the fine powder 5 rises above the rubber mold 10, the pusher 10
The upper surface of the fine powder 5 is pushed down to the upper surface of the rubber mold 10 by 2 (see (c) of FIG. 1). Subsequently, the pusher 102 and the guide frame 100 are pulled up from the rubber mold 10 (see (d) of FIG. 1). The guide frame 100 may be a plate having the same cross section as the rubber mold 10 as shown in FIG. 1, or a cylindrical body having the same inner dimension as the opening of the rubber mold as shown in FIG. 2, or as shown in FIG. The tip of the tubular body may be fitted in the upper portion of the rubber mold 10. When naturally filling the rubber mold with fine powder,
Although it is possible to prevent the fine powder from overflowing from the rubber mold by using the guide frame, if the fine powder having extremely poor fluidity is filled in the rubber mold by using the shaker type feeder, the filling amount varies significantly. Therefore, if a predetermined amount of fine powder that has been weighed in advance is introduced through a rubber mold, it is possible to control the unit volume of the powder compact very accurately, and the fine powder has a shrinkage ratio during sintering. Is constant, it is possible to stably produce a net-shape sintered body.

In FIG. 4 showing a preferred embodiment, the fine powder 5 is once passed through the conveyor 2 and then weighed by the weighing machine 6.
It is dropped on the vibrating mesh 3 linked with. Since the fine powder 5 has a low fluidity, it easily agglomerates, and if dropped directly into the container 4, it falls into a lump and falls, making it difficult to accurately control the weight. Therefore, a certain amount of the fine powder 7 is collected while crushing the agglomerate of the fine powder by the vibrating mesh 3 and monitoring the weight of the fine powder in the container 4 by the measuring device 6.

Since the fine powder put on the vibrating mesh 3 hardly drops downward from the vibrating mesh 3 while the vibration of the vibrating mesh 3 is stopped, the vibration of the vibrating mesh 3 is repeatedly turned on and off. This makes it possible to control the amount of drop into the container 4 with extremely high precision.
Further, instead of measuring the weight of the fine powder, the volume may be measured and controlled. Instead of the container 4, a rubber mold or a rubber mold with a guide frame may be installed and the weight of the fine powder may be measured together with the rubber mold and the fine powder may be filled in the rubber mold.

According to the methods of claims 3 to 5, even a fine powder having poor fluidity can be filled in a rubber mold with high weight accuracy without adding an organic lubricant. If the packing density of the fine powder in the rubber mold is very high, or if the rubber mold returns to its original shape after the punch load is removed, depending on the degree of unevenness of the molded body, the gap between the molded body and the rubber mold Sufficient voids are not formed, and it becomes impossible or extremely difficult to remove the molded product from the rubber mold. In that case, the rubber mold 10 can be used as split molds 10a and 10b as shown in FIG. That is, at least the side portion of the rubber mold is divided into two or more split molds, which are separated after molding to take out the powder compact 20 from the rubber mold 10. Alternatively, as shown in FIG. 5B, a cut 11 may be provided on a side portion of the rubber mold, and the rubber mold may be opened from the cut surface to remove the molded body. Further, as shown in FIG. 6, the side portion, the bottom portion, and the side portions may be divided. However, when a split mold is used, fine powder is likely to be caught in the split surface of the rubber mold, and uneven deformation such as twisting of the rubber mold is likely to occur, which may result in deformation or cracking of the molded product. Furthermore, time is required to set the split mold on the die.

As a countermeasure against this, after the fine powder is compression-molded, the load is removed, and then the inner surface of the rubber mold is pressurized and / or the outer surface of the rubber mold is depressurized to increase the pressure on the inner surface side. Is effective to expand the gap between the molded body and the rubber mold, and then take out the molded body from the rubber mold. In this embodiment of the method, as shown in FIG. 7, a cylindrical cover 12 is fixed to the top side of the rubber mold 10 with a bottom, and the space between the two is sealed. The rubber mold 10 is expanded by introducing a pressurized gas of about 1 to 5 atm into the cylindrical cover 12.
Then, the suction tube 14 that has been inserted into the tubular cover in advance.
The tip of the powder compact is pressed against the upper surface of the powder compact 20 and is sucked to take out the powder compact 20. When the powder compact 20 is a magnetic substance, it may be taken out by suction with an electromagnet instead of suction. Unlike the above-described embodiment, the rubber mold 10 may be expanded by reducing the pressure in the vacuum chamber having the outer surface of the rubber mold as a part, as shown in FIG.

In FIG. 8, 8 is a lower punch, 14 is a sealing cover, 14a is an exhaust hole, 15a and 15b are O-rings, and 17 is an electromagnet. The sealing cover 14 is pressed against the die 1 via the O-ring 15b and directly against the rubber mold 10 by pushing up the lower punch 8. An O-ring 15a is fitted between the lower punch 8 and the die 1. Therefore, the exhaust hole 14 is provided outside the rubber mold.
A vacuum space 18 is created by exhausting air from a. After the rubber mold 10 is expanded, the powder compact 2 is formed by the electromagnet 17.
Aspirate 0.

After die-press molding, the rubber mold may be turned upside down, the inner surface of the rubber mold may be pressurized or the outer surface may be depressurized, and the molded body may be taken out from the expanded rubber mold by dropping it from the lower side. The method using the split mold is inferior to the depressurization method (FIGS. 7 and 8) in terms of efficiency, but this method enables taking out even if it is difficult to take out the powder compact.

Molded articles such as flat gears whose height along the direction of pressing by the punch is smaller than the dimension in the direction perpendicular to the direction are used to form cemented carbide, Fe--Co, Ti alloys or various intermetallic compounds. In order to mold using a fine powder of a material that is brittle and has poor moldability, rubber that forms at least one of the upper and lower surfaces of the rubber mold (the rubber that forms the upper surface is the lid, the rubber that forms the lower surface is the bottom) It is preferable to use a rubber mold configured to be harder than Contrary to this configuration, when the bottom portion is soft and the side portion is hard, as shown in FIG.
The bottom part 10k tries to shrink due to the deformation of the
It occurs on the 0k surface. This wrinkle becomes a starting point of a crack, and the green compact 5'is broken. Further, in the soft material, powder is likely to be caught on the surface, and friction between the green compact and the mold is large. Further, when the pressure from the punch is removed, the soft bottom portion 10k tries to return to the lower shape and is reversely deformed, but at this time, the rubber at the bottom portion is caught in the green compact 5'to try to follow the reverse deformation. , The powder compact 5'is cracked. These cause cracking of the green compact. When the side portions 10s and the bottom portion 10k have the same hardness, the risk of cracking increases as the amount of compression by the punch increases. Therefore, in the present invention, the bottom portion and / or the lid portion is made of rubber harder than the side portions, or the bottom portion and / or the lid portion is made of metal or hard resin.

The thickness (t, unit: mm) of at least one of the lid and the bottom of the rubber mold is expressed by the formula: t≤16h / D.
(Where h is the thickness of the green compact and D is the positive square root of the cross-sectional area of the green compact). Here, the thickness of the lid or bottom and the thickness of the green compact mean the thickness in the pressing direction by the punch, and the cross-sectional area of the green compact means the cross-sectional area of the green compact perpendicular to the pressing direction by the punch. . The larger the area of the green compact (the smaller the right side of the equation), the greater the force when the rubber reversely deforms, and the more easily the green compact breaks. Therefore, the thickness of the lid and bottom of the rubber mold should be reduced. Make it smaller. FIG. 1 showing that the thickness of the bottom portion 10k is reduced.
At 0, the bottom portion 10k is pressed down by the pressing force Pa of the upper punch 1a and its reaction Pb. On the other hand, the force that makes the bottom portion 10k wrinkle The side portion 10s of the rubber mold and the power Pc that reduces the powder 5 so as to reduce the cross-sectional area.
Is. As the thickness of the bottom portion 10k becomes smaller, the pressing force Pa, Pb of the former becomes larger, and when it exceeds the force Pc of the latter, wrinkles do not occur. Also, the coefficient 16 in the above equation
As a result of the following experiment, was found to be critical with respect to the presence or absence of cracking. A rubber mold (dimensions 30 × 30 × 5 mm, h) having the shapes of (e) and (g) of FIG.
/D=0.17) with an average particle size of 10 μm Fe-C
o The powder was molded at a pressure of 1.0 t / cm ² . In this molding, the bottom thickness (t) of the rubber mold is 0.5 to 3.5 m.
Perform 10 times for each thickness by changing in the range of m
Individual molded bodies were produced. As a result, the following number of cracks was obtained. t = 0.5, 1.0, 1.5 mm, 0; t =
2.0 mm, 1 piece; t = 2.5 mm, 4 pieces; t = 3.0
mm, 10 pieces. From the crack investigation result, the above coefficient 16
Was asked.

Instead of making the bottom and the lid of the rubber mold hard, the rubber mold having an open upper part and / or lower part can be directly pressed by a metal punch to substitute the hard part for the punch. An example of a rubber mold embodying the above-mentioned two methods, that is, (a) hard rubber, metal or hard resin for the bottom and / or lid (b) thin rubber satisfying the above formula, is shown in FIG. Shown in. Hatching in the figure indicates metal or hard rubber. (A) is an example in which the upper lid 10u is made of soft rubber, the side portions 10s are made of soft rubber, and the bottom portion 10k is made of hard rubber or metal. (B) is an example in which the upper lid 10u is made of soft rubber, the side portions 10s are made of soft rubber, and the bottom portion 10k is made of hard rubber or metal. (C) is an example in which the top lid 10u is made of soft rubber (hereinafter, simply referred to as "thin") that satisfies the above formula, the side portions 10s are made of soft rubber, and the bottom portion 10k is made of hard rubber or metal. (D) is an example in which the upper lid 10u is a thin (hereinafter simply referred to as "thin") soft rubber that satisfies the above formula, and the side portions 10s and the bottom portion 10k are an integral soft rubber. (E) is an example in which the upper lid 10u is made of hard rubber or metal, and the side portions 10s and the bottom portion 10k are made of soft rubber. (F) is an example in which the upper lid 10u is made of soft rubber and the side portions 10s and the thin bottom portion 10k are made of soft rubber. (G) is an example in which the upper lid 10u is made of hard rubber or metal, and the side portions 10s and the thin bottom portion 10k are made of integral soft rubber. (H) is an example in which the top lid 10u is made of thin soft rubber, and the side portions 10s and the thin bottom portion 10k are made of integral soft rubber. (I) shows the upper lid 10u made of hard rubber or metal,
In this example, the side portion 10s is made of soft rubber and the bottom portion 10k is made of hard rubber or metal. (J) has no top lid, side part 10s
Is a soft rubber, the bottom portion 10k is a soft rubber, and the bottom portion 10k is a hard rubber or a metal fixed to a side cutout. (K) is an example in which the bottom portion 10k made of hard rubber or metal is surrounded by the side portions 10s from the side surface and the lower surface. If the bottom is thin, the bottom bottom can be reinforced with a harder material than the bottom top, such as metal or hard rubber. (L)
(I) is an example in which a downward projection is provided on the upper lid 10u, the powder is compressed to a high density outside the press machine by the upper lid, and the powder is pressed in the state shown in (1).

FIG. 12 (a) shows a rubber mold having the same function as that of FIG. 11 (e). In the rubber mold (a), the upper punch 1a acts as the upper lid 10u to prevent the green compact from cracking (the method of claim 11). Further, in FIG. 12B, the upper lid 10u in FIG.
An example of a mold in which the upper punch 1a and the lower punch 1b respectively perform the action of the bottom portion 10k is shown. Further, FIG. 12 (c) shows a mold in which the upper punch 1a and the punch 1b are made of a hard material and serve as a hard upper lid 10u (for example, see FIG. 11 (e)).

When molding a long product, a phenomenon completely opposite to that of a flat product occurs. That is, in the flat object, the influence of the rubber mold is dominant from the upper and lower end surfaces having a large area, so cracking was prevented by making at least one of the upper and lower end surfaces hard. However, the influence of the rubber mold from the side becomes dominant in long products. Therefore, if the sides are made soft, layered cracks will occur this time according to the principle illustrated in FIG. 9 (FIG. 1).
3). Therefore, in order to prevent layered cracks, the material on at least one of the upper and lower sides where the rubber mold faces the upper and lower punches of the die press is softer than the rubber on the side facing the die of the die press. It is preferable that it is configured as described above.

It is relatively soft like Al and Fe,
When fine powder having good moldability is molded with a soft rubber mold, the rubber mold may not be separated from the outer surface of the molded body even if the side wall of the powder rubber mold is caught and the load is removed. In this case, the hard rubber mold is unlikely to bite, but if the entire rubber mold is made of hard rubber, it becomes difficult to expand the rubber mold and take out the powder compact. Therefore, at least the side surface of the rubber mold has a two-layer structure, and only the side facing the fine powder is made of a hard material, so that it is possible to prevent the fine powder from being caught while maintaining the flexibility of the entire rubber mold. It is advantageous.
The lid portion and the bottom portion may have a similar two-layer structure. Further, such a two-layer structure may be formed by casting or injection molding a two-layer material, or a hard material may be coated on the inner surface of a rubber mold prepared in advance. Instead of the hard rubber, a resin or rubber containing a lubricant such as molybdenum disulfide, or a material having a low friction coefficient such as tetrafluoroethylene resin can be used for the inner layer to obtain the same effect.

In the method of manufacturing a hollow body such as a ring, the rubber mold is provided with a mandrel made of a material harder than the rubber mold for forming the hollow portion. If the mandrel is soft contrary to this configuration, the mandrel contracts in the radial direction together with the green compact due to the pressing force of the punch, and then the punch is retracted and added to the rubber mold and the green compact. When the load is removed, the mandrel 10m expands so as to expand the central hole of the contracted green compact 5 '(see FIG. 14). As a result, cracking occurs in the green compact 5 '. Therefore, the mandrel 10m (see FIG. 14) is preferably harder than the side portion 10s.

FIG. 15 shows a concrete example of a molding method for producing a green compact having two hollow parts as shown in FIG. 16 by using a mandrel. The mandrels 10m and 10m 'are made of metal and The upper punch 9 into the recess 9 '
Is formed inside. When making a hollow molded body as shown in FIG. 17, a part of the hard mandrel penetrates to the side surface of the molded body. With the method of the present invention, the compression is much more isotropic than with a normal die press and there is no friction between the mold and the powder due to the presence of the rubber mold. Therefore, even if the upper punch alone is pressed, the powder is uniformly formed without being biased. This greatly simplifies the press.

In order to automate the method of the present invention, a method of conveying a plurality of rubber molds in a circulating path is desirable. According to the method of the present invention, ne which uses fine powder without cracking or chipping is used.
Since the purpose is to produce a t-shape compact, one way to realize the automation is to measure the fine powder and to perform natural filling using a guide frame, vibration after the natural filling of the fine powder, and / or High-density filling of the rubber mold by pressing with the pusher, die pressing, and taking out of the powder compact from the rubber mold are sequentially repeated in a circulation path that intermittently conveys the rubber mold.
As a device for carrying out this, a measuring machine for fine powder along a circulation path for intermittently conveying the rubber mold, a feeder for naturally filling the rubber mold with the fine powder, and a vibrating device for performing high density filling. It is desirable to use a machine and / or a pusher, and a device in which jigs for taking out the powder compact from the rubber mold are sequentially arranged. Here, if the molding is continuously conveyed, each of the steps 1 to 3 must be performed while the mold is moving, and the feeder, punch, and the like must move together with the mold. Because the fine powder easily causes bridging in the rubber mold, it is not possible to use a powder feeder by free fall grinding, and it is necessary to move the feeder and guide together with the rubber mold to fill the measured powder into the mold. Because. This greatly complicates the device as compared with the case where each jig is fixedly arranged.

According to the method of the present invention, powder feeding, filling,
Since the press is not occupied during the removal of the molded body,
Productivity is greatly improved. One embodiment of the method of transferring the die together with the rubber mold will be described with reference to FIG. The rubber itself of the rubber mold 10i (see FIG. 19) forms a bottomless mold, and the open bottom of the rubber mold is closed to a part of the rotary die 40. Therefore, the rotary die 40 constitutes the bottom of the rubber mold. While the rubber mold 10i sequentially rotates together with the ring-shaped rotary die 40, a series of operations such as filling powder into the rubber mold 10i with a feeder, die pressing with a die press device 60, and removal of a molded product with a molded product removal device 62 (A to D) can be performed.

In A, the fine powder 5 (see FIG. 20) weighed by the quantitative supply device is put into the rubber mold 10 having the guide 100 attached thereto, and vibrated by the vibrator 41 to increase the density. Increase to high density. The die is not shown in FIG. 18B is a preliminary position, and C is pressed by a die press. The rotary die 40 stops moving until the operations at A, B, C and D start and complete. Since the rubber mold 10i returns to its original shape after compaction, a ring-shaped gap 10r is formed around the compact 63. This gap 10r
Is the rubber mold 10i that causes the green compact 63 to be sucked by the suction described above.
Large enough to be removed from. Reference numeral 66 is a conveyor driven by a step motor 67 driven by the control unit 50. After the arm 64 swings above the conveyor 66 and the green compact 63 is placed on the conveyor 66, the conveyor 66 moves. The series of operations is controlled by the control unit 50.

Reference numeral 28 is a rubber mold cleaning device including an air piston 24, an air unit 25, an electromagnet 26, and an electromagnet excitation power source 27. The electromagnet 26 moves above the die cavity after taking out the powder compact from the die, and is excited by the electromagnet power source 27 to attract the residual powder remaining in the rubber mold 10 by the magnetic force, so that the rubber mold needs to be cleaned. By. If the powder is non-magnetic, a cleaning means such as suction can be used. The die may be conveyed along the circulation path together with the rubber mold. That is, in FIG. 18, the ring-shaped turntable 40 is made of inexpensive carbon steel, and the die made of die steel is the rubber mold 1.
It may be configured so as to be attached to and detached from the ring-shaped rotary table 40 together with 0. In order to form a fine powder of highly active alloy, it is preferable to carry the rubber mold in the circulating path in an inert gas chamber. In the circulating path device, since the paths of the fine powder and the compact are constant, the entire device can be made compact, so that it is easy to create an atmosphere. As shown by the chain double-dashed line 30 in FIG. 18, it is possible to selectively store the periphery of the press machine and the path portion in the inert gas container (30).

FIG. 21 is a plan view of an apparatus according to an embodiment of the present invention when only the rubber mold is conveyed and the die moves only along a small part of the circulation path. FIG. 22 is a side view of FIG. FIG. In this device, the die is a disk-shaped rotary die 1a, and a plurality of punched dies (two in the drawing are used).
(Only one is shown, but three or more may be used). The rotary die 1a is rotated by the motor 91 so that each die moves along the circular path, and the upper and lower punches 9 are formed. , 8 are provided at a _first position P ₁ which is vertically inserted into the die, and at a second position P ₂ , a mold loader 7 which is used to insert fine powder into the rotary die together with the rubber mold.
0, and at the third position P ₃ the rotary die 1
Extractors 78 and 84 are provided for taking out the rubber mold including the powder compact from a. The rotary die 1a is sequentially circulated through P ₁ , P ₃ , and P ₂ by a motor 91.

The disk die 1a is not all expensive die steel, and may be used only in the periphery that comes into contact with the punch. Other parts may be made of plastic, iron or the like for weight saving and cost reduction. The mold loader 70 is driven by two hydraulic cylinders 71 and 80. Hydraulic cylinder 7
1 moves forward and backward a hollow rod 79 having a suction port attached to its tip. In the position of FIG. 22, the rubber mold 10 shown on the right side is inserted into the die. Hydraulic cylinder 80
Raises and lowers the cylinder 71 fixed to the piston 92 as a whole. In the raised state, the suction port sucks the rubber mold 10 on the belt conveyor 45, and then the hollow rod 79 advances while moving in the raised state and moves to above the die. After that, the cylinder 71 descends and the rubber mold 10 is inserted into the die. 76 and 81 are hydraulic units. Reference numeral 75 denotes a fixed cam, and when the rotary die 1a rotates, the elevating bottom 1d provided in the die slides along the upper surface contour of the fixed cam 75 as shown in FIG. That is, during pressing, the die is completely separated from the fixed cam 75 (see (a) figure), but next, it rides on the hem of the fixed cam 75 (see (b) figure) and the slope of the mountain. (See (c, d)) and reaches the flat portion at the top, the rubber mold 10 in which the powder compact is placed reaches the same level as the upper surface of the rotary die 1a ((e)). See figure). At this time, the rubber mold has reached the third position P ₃ (see FIG. 22). After that, the elevating bottom 1d descends again, so that the unmolded fine powder can be received in the die (see FIG. (F)). A first conveyor 45 having an end located near the second position P ₂ is provided, and the first conveyor 4 is provided.
The rubber mold filled with the fine powder is conveyed by 5.
A second conveyor 140 having an end located near the third position P ₃ is provided. The rubber mold 10 is the rotary die 1.
It is guided along the rubber mold recovery plate 78 by the rotational movement of a, and then is slightly slid on the fixed base 84 and transferred onto the second conveyor 140.

[0043]

【Example】

Example 1 The rubber mold used is shown in FIG. The upper lid portion 10u was made of hard rubber (hardness 90), the side portion 10s was made of soft rubber (hardness 40), and the bottom portion 10k was made of hard rubber (hardness 90). The inner dimension of the rubber mold cavity is 30 x 30
It was × 3 (mm). The rubber mold was manufactured as follows. A hard urethane plate 34, which has been hardened and cut out in advance, is set on the bottom of a mold 36 having the same shape as the cavity shown in FIG. A two-liquid mixed room temperature curing type) was cast to mold the bottom portion 10k and the side portion 10s.

All rubber molds used in the following examples were prepared according to this method. F as fine powder
e-45 wt% Co atomized powder (average particle size 15 μm,
True density 8.3 g / cc) pressing pressure: 1.0 t / cm ²
It was molded in. The obtained green compact is sintered at a temperature of 1200 ° C.
Sintering was performed for 6 hours. The results are shown in Table 1. No lubricant or binder was added to any of the powders.

(1) In the table, the leftmost data is a comparative example by natural filling. In natural filling, fine powder was allowed to fall freely from the powder box into the rubber mold, and then the raised portion above the rubber mold was scraped off. The weight of the powder was not measured. On the other hand, in all the examples, the weight of the fine powder was measured in advance within the error range of ± 1% for each packing density. (2) Filling method N ・ ・ ・ ・ Natural filling (free cutting after free fall) NV ・ ・ ・ Vibration while dropping the powder into the cavity through the guide, and lightly pushing with a pusher to match the upper surface of the powder with the rubber mold NVP ..Vibration while dropping the powder into the cavity through the guide. Push firmly with the pusher. (3) Criteria for cracking and chipping (n = 50)

○ No cracking or chipping occurs △ Less than 10% of the total number of cracks or chipping occurs × 10% or more of the total number of cracks or chipping occurs

(4) Deformation criterion x Non-uniform deformation is remarkable, dimensional adjustment by post-processing is impossible, improvement is difficult even if the shape of the rubber mold is modified. △ Some non-uniform deformation, but post-processing Or to the extent that can be compensated by dimensional adjustment by sizing ○ Almost no non-uniform deformation. Although some non-uniform deformation remains, a good molded body can be obtained by slightly changing the shape of the inner surface of the rubber mold. The above (1) to (4) are the same for all the examples.

[0048]

[Table 1]

As in the case of Fe-Co powder, Ti powder (hydrolyzed powder (average particle size 10 μm, true density 4.5 g / c
c) was molded under a pressing pressure of 1.0 t / cm ² , and the obtained green compact was sintered at 1150 ° C. for 6 hours. Table 2 shows the results.

[0050]

[Table 2]

Example 2 The upper lid 10u of the rubber mold shown in FIG. 26 is made of hard rubber (hardness 90) and the side portion 10s with a bottom is made of soft rubber (hardness 4).
0), the inner dimension of the cavity is 4 inner diameter x 1 height
It was set to 7 mm. The powder, pressing pressure, and sintering conditions used are as follows, and the results are shown in each table. (1) Fe-2 wt% Si (average particle size 10 μm, true density 7.7 g / cc) Pressing pressure: 1.0 t / cm ² , sintering temperature 1200 ° C. Sintering time: 6 hours (Table 3) (2) Fe -0.3 wt% C (water atomization → hydrogen reduction) (average particle size 20 μm, true density 7.8 g / cc) Pressing pressure: 1.0 t / cm ² , sintering temperature 1200 ° C. Sintering time: 6 hours (Table 4 (3) Fe-0.3 wt% C (water atomization → hydrogen reduction) (average particle size 12 μm, true density 7.8 g / cc) Pressing pressure: 1.0 t / cm ² , sintering temperature 1200 ° C. Sintering time: 6 hours (Table 5) (4) Fe-42 wt% Ni (atomized powder) (average particle size 30 μm, true density 8.1 g / cc) Pressing pressure: 1.0 t / cm ² , sintering temperature 1200 ° C. Sintering time: 6 hours (Table 6) (5) Fe-42 wt% Ni (atomized ) (Average particle size 12 [mu] m, a true density of 8.1 g / cc) Press pressure: 1.0 t / cm ^2, sintering temperature 1200 ° C. Sintering time: 6 hours (Table 7) (6) Ti (hydrogenolysis powder) ( Average particle size 10 μm, true density 4.5 g / cc) Pressing pressure: 1.0 t / cm ² , sintering temperature 1150 ° C. Sintering time: 6 hours (Table 8) (7) Sintering Al (atomized powder) (Average Particle size 10 μm, true density 2.7 g / cc) Pressing pressure: 1.0 t / cm ² , sintering temperature 600 ° C. Sintering time: 6 hours (Table 9)

[0052]

[Table 3]

[0053]

[Table 4]

[0054]

[Table 5]

[0055]

[Table 6]

[0056]

[Table 7]

[0057]

[Table 8]

[0058]

[Table 9]

Example 3 The same rubber mold as in Example 2 was used, and the fine powders of various materials were filled to the filling densities shown in Table 10 using a guide frame, a vibration and a pusher. It pressed under the same conditions and sintered. However, Fe-45% Co was pressed and sintered under the conditions of Example 6 described later. On the other hand, for comparison, when a die press method using a die (die inner diameter 3.9 mm) that can mold almost the same shape as that molded by a rubber mold was performed, the same fine powder used for molding by the rubber mold was fluid. Since it was low, it was impossible to fill the mold. Therefore, the coarse powder shown in Table 10 was used, and after spontaneous filling, it was molded at a pressure of 1.5 t / cm ² , and then sintered under the same conditions as the fine powder. The density of the sintered body is shown in Table 10 and Table 1.
It is shown in FIG.

[0060]

[Table 10]

[0061]

[Table 11]

Example 4 Bolts were molded using the rubber mold shown in FIG. The upper lid 10u and the side portions 10s of the rubber mold are made of soft rubber (hardness 40). The powder used is Fe
-2 wt% Si (average particle size 10 μm, true density 7.7 g /
cc, atomized powder) -Table 12-and Ti powder (average particle size 30 μm, true density 4.5 g / cc, hydrocracked powder-
It was Table 13-. The former powder has a pressing pressure of 1.2 t / c
The powder compact obtained by molding at m ² was sintered at a sintering temperature of 1200.
Sintering was performed under the conditions of ℃ and sintering time of 6 hours. The latter powder was molded under a pressing pressure of 1.4 t / cm ² , and the obtained powder compact was fired under the conditions of a sintering temperature of 1150 ° C. and a sintering time of 6 hours. The results are shown in Tables 12 and 13. In all materials, the screw thread was particularly damaged when it was naturally filled, and it was broken at the boundary between the foot and the head of the screw. It is considered that the damage of the screw thread is caused by the powder not being uniformly filled up to every corner of the groove forming the screw thread of the rubber mold, and the breakage of the molded body is caused by the uneven deformation of the rubber mold.

[0063]

[Table 12]

[0064]

[Table 13]

Example 5 Fe-45 wt% Co fine powder (average particle size 12 μm) was obtained using rubber mold A and rubber mold B shown in FIG.
m) was packed at a packing density of 3.70 g / cc. The inside dimension of the cavity is 30 × 30 × 3 for any rubber mold
There was mm. The entire rubber mold A (10u, 10s)
Made from soft rubber (hardness 40)
The side portions were made of the above soft rubber, and the other portions (10u, 10k) were made of hard rubber (hardness 90). As a filling method, a fine powder previously weighed was naturally filled using a guide, and then forcedly filled by a vibration and a pusher. 1 molding with a press pressure of 1.0 t / cm ^2.
When it was carried out 0 times, all the green compacts molded by the rubber mold A were cracked, and all the rubber molds B were good.

Example 6 As shown in FIG. 29, using rubber molds A and B (internal cavity size 4 × 17 mm) made of the following materials, fine powder, filling density, method, pressing condition, and n number were set. Molded under the same conditions as in Example 4. Rubber mold A Rubber mold B Top lid Soft rubber (hardness 40) Hard rubber (hardness 80) Side part Hard rubber (hardness 80) Soft rubber (hardness 40) Bottom soft rubber (hardness 40) Hard rubber (hardness 80) Rubber mold B All of the powder compacts formed in step 1 had lamellar cracking, and all the powder compacts formed by the rubber mold A were good.

Example 7 A rubber mold (A) made of the following material shown in FIG.
Using (B) and (C), aluminum powder (average particle size 30 μm, atomized powder) was molded. Upper lid Side part Inner surface film (10n) Rubber mold (A) Hard rubber No soft rubber (Hardness 90) (Hardness 40) Rubber mold (B) Same as above Same as above Tetrafluoroethylene resin (hardness 80) (t = 0.5mm) Rubber mold (C) Same as above Same as above 40% MoS ₂ (hardness 80) Blended soft rubber (hardness 40) (t = 1.0 mm) In molding using the rubber mold (A), the powder compact is bit into the rubber mold. Even if the mold was turned upside down and the inside of the mold was pressurized with compressed air of 1.0 kg / cm ² , the molded body remained in the mold as it was. In the molding using the rubber molds (B) and (C), no biting occurred at all, and when the rubber mold was inverted and inflated, the molded body easily dropped and could be taken out.

Example 8 Using a rubber mold having a shape shown in FIGS. 31A, 31B and 31C and having a mandrel made of the materials shown in the following table,
Fe-2 wt% Si (atomized powder, particle size 12 μm) was press-molded at 1 t / cm ² , and the number of cracks generated according to the material of the mandrel was examined. Rubber mold (A), (B)
Shape is outer diameter φ33mm × inner diameter φ24mm × height 18m
The shape of m and mandrel 10m is the outer diameter φ12 in the set state.
mm x height 15 mm ((A)), outer diameter φ12 mm
The height was 7.5 mm (in the case of (B)). Rubber mold (C) has an outer diameter of 33 mm, an inner diameter of 24 mm, and a height of 1.
It has a size of 8 mm and a thickness of 1.5 m as a mandrel.
Eight blades of m and 7.5 mm in height were arranged radially. The state of cracking is shown in Table 14 as the number of cracks during molding 10 times.

[0069]

[Table 14] From Table 14, it was confirmed that when the mandrel was soft, the mandrel contracted in the radial direction together with the molded body, and when the mandrel was unloaded in this state, the mandrel returned so as to open the hole of the contracted molded body and cracking occurred. . The most desirable material for the mandrel is metal, followed by high hardness rubber, and it can be said that a material that does not easily deform is suitable.

Example 9 High purity Al and high purity Li were converted into Al-2.84 wt% Li.
After mixing so as to have the composition
Al-Li alloy powder having an average particle size of 8 μm was obtained by gas atomization. Using this powder, the inner dimension is 30φ
A disc-shaped green compact was manufactured by a circular path type green compact manufacturing device (FIG. 18) in which a through rubber mold made of urethane rubber (hardness 60) having a height of 10 mm was fixedly arranged. Here, when molding was performed on an example in which the entire apparatus was exposed to the atmosphere (not placed in the chamber), the powder was frequently ignited and molding was impossible.

On the other hand, when the portion indicated by the alternate long and two short dashes line 30 in FIG. 18 was covered with a dome-shaped chamber and the air in the chamber was replaced with argon gas to carry out molding, molding became possible.

[0072]

According to the method of the present invention, a powder compact of fine powder can be obtained with higher efficiency than the conventional injection molding method. Although the efficiency is inferior, the efficiency is far higher than the case where the debinding process of the injection molding method is performed. Further, according to the method of claim 1, fine powder can be formed without using a binder and a lubricant.

According to the methods of claims 2 and 3, high-density packing can be efficiently performed. According to the methods of claims 4 and 5, it is possible to make the variation of the unit weight of the sintered body extremely small, and to reduce the final machining allowance of the sintered body. According to the methods of claims 6 and 7 and the rubber mold of claim 29, it is easy to take out the powder compact after unloading the punch. The construction of the rubber mold according to claims 8 to 11 and 23 to 29 is particularly effective for molding a powder compact, which is apt to crack.

The structure of the rubber mold according to the twelfth and thirteenth aspects prevents galling of the rubber mold. According to the method of claim 14, the structure of the die press machine can be simplified.
According to the method of claim 15, the hollow body can be molded without cracking. The inventions of claims 16, 17, 19, 20, and 21 utilize high-density packing of a fine powder into a rubber mold outside the die press machine, thereby performing press molding with high efficiency without lowering the efficiency of the die press machine. enable. Claim 18
This method is effective in preventing ignition of the highly active powder.
According to the method of claim 30, a high density sintered body of fine powder can be produced only by sintering.

[Brief description of drawings]

FIG. 1 is a diagram showing a method of filling a rubber mold with a high density of fine powder.

FIG. 2 is a diagram of a guide frame.

FIG. 3 is a diagram of a guide frame.

FIG. 4 is a diagram showing a measuring method for fine powder.

FIG. 5 is a view of a split mold.

FIG. 6 is a view of a split mold.

FIG. 7 is a diagram showing a method of expanding a rubber mold.

FIG. 8 is a diagram showing a method of expanding a rubber mold.

FIG. 9 is an explanatory diagram of cracking of a molded body.

FIG. 10 is a diagram of pressure applied to a rubber mold.

FIG. 11 is a view of various rubber molds.

FIG. 12 is a diagram showing a molding method using a rubber mold in which at least one of upper and lower ends is opened.

FIG. 13 is an explanatory diagram of a layered crack.

FIG. 14 is a view of a rubber mold for molding a hollow body.

FIG. 15 is a view of a rubber mold for molding a hollow body.

FIG. 16 is a view of a hollow body.

FIG. 17 is a view of a hollow body.

FIG. 18 is a diagram of a circuit-circulating device.

19 is a diagram of a rubber mold provided in the device of FIG.

FIG. 20 is a diagram of a rubber mold including a pusher and a vibrator.

FIG. 21 is a diagram of a circular path type device.

22 is a side view and a partial cross-sectional view of the device of FIG. 21. FIG.

FIG. 23 is an operation explanatory view of a cam plate.

FIG. 24 is a view of the rubber mold used in Example 1.

FIG. 25 is a diagram showing a method of manufacturing the rubber mold of FIG. 24.

FIG. 26 is a view of the rubber mold used in Example 3.

27 is a view of the rubber mold used in Example 4. FIG.

28 is a view of the rubber mold used in Example 5. FIG.

29 is a drawing of the rubber mold used in Example 6. FIG.

30 is a view of the rubber mold used in Example 7. FIG.

FIG. 31 is a view of a rubber mold used in Example 8.

[Description of sign]

 1 die 2 conveyor 3 vibrating mesh 4 container 5 fine powder 6 gravimetric measuring instrument 7 fine powder 8 lower punch 9 upper punch 10 rubber mold 11 cut 12 cylindrical cover 14 sealing cover 15 O-ring 17 electromagnet 18 vacuum space 20 powder compacting Body 22 Pusher 30 Inert gas container 31 Hydraulic unit 32 Hydraulic cylinder 33 Core 34 Hard urethane plate 35 Unhardened rubber 36 Mold 40 Ring-shaped rotary table 41 Shaker 42 Feeder 44 Motor 45 Belt conveyor 50 Control unit 60 Die press Device 62 Molded product take-out device 70 Mold loader 71 Hydraulic cylinder 75 Cam 76 Hydraulic unit 78 Rubber mold recovery plate 79 Hollow rod 80 Hydraulic cylinder 81 Hydraulic unit 82 Hydraulic unit 90 Saucepan 91 Motor 92 Pi Ton 100 guide frame 102 pusher

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] March 28, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] Full text

[Correction method] Change

[Correction content]

[Document name] Statement

Title: Manufacturing method, manufacturing apparatus for green compact for sintering,
Method for manufacturing rubber mold and sintered body

[Claims]

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a green compact for sintering. The present invention relates to a green compact manufacturing apparatus, a rubber mold, and a sintered compact manufacturing method. In the powder metallurgy technology, by reducing the particle size of the powder used, not only the density of the sintered body becomes high, but also the crystal grain size of the sintered body becomes finer. The binding material significantly improves the mechanical strength, and the iron-based soft magnetic material improves the magnetic properties. However, the improvement of the strength and reliability of the sintered body due to this fine powdering leads to a decrease in the fluidity of the powder. When the die is naturally filled with a powder having a small particle size and a low fluidity, the powder is apt to cause a crosslinking phenomenon in the die, and the packing density largely varies. As a result, the unit weight of the green compact becomes extremely large and the average packing density also decreases.

[0002]

2. Description of the Related Art For the above reasons, fine powder cannot be compacted by an ordinary die press method. Therefore, in order to compact fine powder, an organic binder is used.
The injection molding method must be used to mold a slurry added as much as 0%. However, in this method, it takes several days to remove the binder, and the decomposition products of the organic binder remain as carbon in the sintered product and deteriorate the properties of the product.

Further, since the specific surface area of the fine powder increases, the fine powder becomes extremely active and is prone to oxidative deterioration in the atmosphere. Al-L for which high reliability is required especially for aircraft
Fine powders such as i alloys and Ti alloys are rapidly oxidized in the atmosphere and spontaneously ignite in extreme cases. Further, the fine powder becomes extremely sensitive to an ignition source, and when the lubrication between the die and the punch is reduced by dusting or the like in the die press method, sparks are generated due to friction, and thus there is a high risk of ignition.

There is a limit to the shape of the product that can be molded by the die press most commonly used for powder molding. Shapes that have constrictions or irregularities such as screws, or molded products that are too long and narrow cannot be molded with a die press. As an improved method for making the powder compression isotropic in the die press, a rubber mold is installed on the die and the elastic deformation of the rubber filled with the powder is used to make the powder move from the direction perpendicular to the punch moving direction. A compression method has been devised (for example, Japanese Patent Laid-Open No. 49-13580).
No. 5). This method is hereinafter referred to as a rubber mold die press method. With the rubber mold die press method, it is possible in principle to mold irregularly shaped products, but the deformation of the rubber tends to be uneven, and cracks and chips and deformation of the molded product frequently occur. CI for obtaining a molded product having a uniform density by hydrostatically compressing powder contained in a bag such as rubber in a liquid
The P method has low efficiency and is not suitable for high-efficiency continuous production of green compacts.

[0005]

SUMMARY OF THE INVENTION It is difficult to produce a fine powder compact by using a conventional ordinary die press method without using a binder. Therefore, even with materials such as aluminum, which are originally soft and easy to raise the density of compacts, low density compaction has been carried out by using coarse powder with a large particle size.
Accepts a low sintered density.

On the other hand, in the injection molding method, it is possible to manufacture a powder compact of fine powder and use this to manufacture a high-density sintered compact having a density of 90% or more, but the binder removal time is remarkable. Since it takes a long time, the productivity is remarkably low by the ordinary die press method. Furthermore, the product obtained by sintering the green compact has a large amount of impurities such as carbon, and in the case of a Ti alloy, the mechanical properties of the sintered product deteriorate. Conventionally, a process such as sizing was required to densify a product obtained by sintering a green compact. But sizing was only possible for soft materials. Therefore, it is an object of the present invention to provide a method and apparatus for molding fine powder with a productivity equivalent to that of a normal die pressing method. Furthermore, the present invention aims to obtain high density products of various materials by sintering only.

[0007]

The method of SUMMARY and effects of the Invention The present invention, fine rubber mold at least the side portion is made of rubber
Fine powder is packed at high density and punched by a die press machine.
A method for compressing a mumold and a fine powder, the method comprising:
The first is high-density filling outside the die press machine, and the second is
When the rubber mold is substantially deformed in the die press machine,
In some cases, punching with a die press machine can be used for high-density filling.
And are characterized. Here, "outside the die press" means
The mu mold is not displaced from the axial position of the punch of the die press machine.
Is in a position where
Of die press equipment consisting of holders and rams
You don't have to go out. "By the punch of the die press machine
"Compress" means that either one or both of the upper and lower punches
More direct or indirect rubber mold and high density filling
By making a compact by compressing fine powder
is there. Here, the punch moves with the compression of the rubber mold.
Direction and the compressive force generated in the direction almost orthogonal to the movement of the punch
Both the compressive force in the direction can be applied to the fine powder
Is required for forming a green compact with uniform density and high
There is .

In the present invention, a fine powder has a density of 90.
% Powder having an average particle size of 50 μm or less, which can provide a sintered body of at least 50%. Desirably, a powder compact having a particle size of 30 μm or less, more preferably 20 μm or less is used to make a powder compact, and the powder compact is sintered to obtain a high density sintered body having a true density of 90 to 95% or more.

Even if a coarse particle, that is, a powder having an average particle diameter of more than 50 μm is molded by using a rubber mold, the size and volume ratio of the voids in the green compact become very large.
The voids do not easily shrink during sintering, and as a result, the shrinkage of the compact due to sintering is about 1% by volume, which is extremely low, and a high-density sintered compact cannot be obtained. For example, when an iron-based soft magnetic material is sintered by this method, a sintered body density of less than 90% is obtained.

In the present invention, powder means Fe, Co, N
In addition to metals and alloys such as i, Cu, Mo, Al, and Ti, powders of compounds such as TiC and WC are also included. As the Fe-based fine powder, atomized powder with water or an inert gas is often used, and in some cases, carbonyl powder is also used. Al-based fine powder is gas atomized or
Quenched powder is used. As the Ti-based fine powder, a powder made by repeating hydrogen storage treatment and dehydrogenation is often used. Also used is a fine powder produced by a mechanical grinding method. Further, it is a feature of the method of the present invention that even fine powders such as Fe-Co and Ti alloys that are hard and have poor formability are formed without adding a binder or a lubricant. In addition, since the rubber mold is used in the method of the present invention, the fine powder does not come into direct contact with the die, and powder entrainment unlike ordinary die press does not occur. Therefore, it is not necessary to use a lubricant. That is, no binder is added to avoid the above-mentioned adverse effects of residual carbon from the binder and the like. However, if carbon or the like is allowed to remain in the sintered product, 1% by weight or less of a binder may be used.

Such fine powder has particularly poor fluidity,
Since natural filling causes the density of the packing in the rubber mold to be high or low, in the present invention, high density is required before molding by the die press machine.
It is essential to perform filling once . Generally, for filling the powder into the die, a shaker or the like is used to perform natural filling in which the powder is dropped by weight. In the method using a shaker type feeder, the box containing the powder is slid on the table including the die, the powder is dropped into the die hole by natural dropping, and the swelling part of the powder in the die hole is scraped off by leaving the box. Is.

When the fine powder naturally filled in the rubber mold is then compressed by a die press, the fine powder is compressed by the elastic deformation of the rubber mold both in the moving direction of the punch and in the direction orthogonal thereto, that is, in a so-called pseudo-hydrostatic pressure. Therefore, the fluctuation of the powder density in one green compact becomes small.

However, when the naturally-filled fine powder is compression-molded in a rubber mold, cracks, chips, and deformation always occur in the powder compact. In the die press method using a rubber mold, the cause of cracking when powder is filled to such a natural packing density will be described with reference to FIG.

In the present application, the material forming the upper surface of the rubber mold is called the lid portion, the material forming the lower surface is the bottom portion, and the material forming the side portions of the inner surface is called the side portion. In many cases, the natural packing density is about 11 to 13%, and the dimensional shrinkage ratio of the powder by compression molding reaches as high as 30 to 40%. Then, the rubber mold 10 is largely deformed as shown in (c) of FIG. 32 due to a frictional force which moves between the rubber mold members 10s, 10k, 10u and between the rubber mold 10 and the die. Among these deformations, the non-uniform deformation dy generated in the lid portion 10u and the bottom portion 10k of the rubber mold promotes the generation of the crack 5d in the direction parallel to the pressing direction by the punch, and the non-uniform deformation dx generated in the side portion of the rubber mold is It promotes the generation of cracks 5e in the direction perpendicular to the pressure applied by the punch. Further, the non-uniform deformation dx described above causes severe "elephant foot" deformation at the edge portion of the molded body. In order to prevent such cracking, chipping and deformation, it is necessary to fill the rubber mold with a high density of fine powder before press molding in the rubber mold die pressing method.

The "high density" in the high density packing is at least 1.15 times the natural packing density or more, and is preferably 1.3 for a long product and a molded product with severe irregularities.
More than double. However, it is necessary to avoid high-density filling to such an extent that the rubber mold is deformed due to press-fitting of fine powder during filling, and a molded product having a desired shape cannot be obtained. Therefore, the density is preferably 60% or less of the true density.

According to the first aspect of the present invention, when the high density filling of the fine powder into the rubber mold is performed, the fine powder is automatically removed once.
After filling it with a high density, or filling it with rubber,
High-density filling is performed simultaneously with filling the mold. Daipre
As a concrete high-density filling method outside the machine, rubber molding
Vibration is applied to the fine powder that is naturally filled in the rubber;
Compacting or pushing a fine powder which is naturally filled into the field by the pusher; followed pressurized Funochi pusher natural filling
Press the rubber mold; do not vibrate the rubber mold at the same time as powdering
Which is possible. If necessary, combine these or
You may go back and forth .

In order to fill the upper end of the rubber mold with the fine powder, a larger amount of the fine powder than the inner volume of the rubber mold is put in the natural filling state, and the fine powder overflows from the rubber mold as it is. Therefore, use the guide frame to fill the fine powder to a position higher than the upper surface of the rubber mold,
Then, apply vibration or push it in with a pusher to match the upper surface of the fine powder with the upper surface of the rubber mold. At this time, the deformation of the rubber mold caused by the pressing of the guide frame or the pressing by the pusher is caused by the fine powder in the mold.
It does not cause the packing density to vary (see Fig. 32).
There is .

On the other hand , according to the second aspect of the present invention, the dip
Deformation of the rubber mold when high-density filling is performed inside the machine
Is accompanied by . For example, if a rubber mold is compressed by a punch to change the powder from a natural filling state to a high density filling state, the compression is temporarily stopped, and then the punching is continued to obtain a powder compact, which is obtained in the preceding stage of this method. In the filled state, the density distribution of the powder is non-uniform and the deformation of the rubber mold is large, which causes problems such as cracking and deformation of the green compact .
In the second aspect of the present invention, the substantial deformation of the rubber mold
It is necessary to perform high-density packing without causing

In the present invention, the high density filling step is performed by die pressing.
The first method performed outside the machine is the second method performed inside the die press machine.
Preferred over law. The punch moves up and down in the die press machine
In order to vibrate and press the powder in order to
It is not possible to install it in the machine and perform forced high-density filling.
Since the structure of the entire press machine becomes very complicated,
Flaw, rubber mold with die in die press machine
Because it is not realistic to vibrate the die press machine
The means of high-density packing inside is very limited, and
Difficult to fill the measuring powder in the die press machine
That is the reason.

As a second specific method of the present invention for filling the fine powder with a high density without substantially deforming the rubber mold, as shown in FIG. 33, the upper punch is an inner side capable of pressing only the fine powder. 9a and an outer part 9b capable of pressing only the rubber mold, and a fine powder 5 is press-fit into the rubber mold by using an inner punch, and then the rubber mold 1 is formed by using both the outer punch 9b and the inner punch 9a.
0 and fine powder 5 are compressed and molded.

The applicant of the present invention filed a patent application on February 14, 1991 for molding a permanent magnet powder in a magnetic field using a rubber mold, but in the present application, the molding in the magnetic field is not performed. Next, the vibration method will be specifically described with reference to FIG.
The fine powder 5 whose weight has been measured in advance is naturally filled from the powder pan 90 into the rubber mold 10 having the guide frame 100 fixed to the upper part (see FIG. 1A). The fine powder 5 is deposited further above the upper surface of the rubber mold 10. Subsequently, the rubber mold 10 is placed on the vibration exciter 41, and vibration is applied (see (b) of FIG. 1). As the vibrator 41, a vibrator that generates horizontal or vertical vibration by an electromagnetic or crank vibrator can be used. The frequency of vibration is not particularly limited, but is, for example, 1 to 60 Hz. Excitation is performed from the time of powder feeding and it falls on the rubber mold.
Powder may be given a higher density, or
The vibration may be performed after the natural filling state is reached once.
In the following description, high density packing is mainly performed after natural packing.
The embodiment will be described.

After that, when the fine powder 5 rises above the rubber mold 10, the pusher 10
The upper surface of the fine powder 5 is pushed down to the upper surface of the rubber mold 10 by 2 (see (c) of FIG. 1). Subsequently, the pusher 102 and the guide frame 100 are pulled up from the rubber mold 10 (see (d) of FIG. 1). The guide frame 100 may be a plate having the same cross section as the rubber mold 10 as shown in FIG. 1, or a cylindrical body having the same inner dimension as the opening of the rubber mold as shown in FIG. 2, or as shown in FIG. The tip of the tubular body may be fitted in the upper portion of the rubber mold 10. The guide frame opening is made of rubber on the bottom side of the guide frame.
If it has almost the same shape as the upper opening of the mold
For example, the opening of the guide frame should be
It may be slightly widened on the upper surface side . When naturally filling the rubber mold with fine powder, it is possible to prevent the fine powder from overflowing from the rubber mold by using a guide frame, but the fine powder with extremely poor fluidity is filled into the rubber mold by using a shaker-type feeder. Then, the variation of the filling amount becomes remarkable. Therefore, if a predetermined amount of fine powder that has been weighed in advance is introduced through the guide into the rubber mold, the unit amount of the powder compact can be controlled extremely accurately,
Also, since the fine powder has a constant shrinkage during sintering, ne
A t-shape sintered body can be stably produced.

In FIG. 4 showing a preferred embodiment, the fine powder 5 is once passed through the conveyor 2 and then weighed by the weighing machine 6.
It is dropped on the vibrating mesh 3 linked with. Since the fine powder 5 has a low fluidity, it easily agglomerates, and if dropped directly into the container 4, it falls into a lump and falls, making it difficult to accurately control the weight. Therefore, a certain amount of the fine powder 7 is collected while crushing the agglomerate of the fine powder by the vibrating mesh 3 and monitoring the weight of the fine powder in the container 4 by the measuring device 6.

Since the fine powder put on the vibrating mesh 3 hardly drops downward from the vibrating mesh 3 while the vibration of the vibrating mesh 3 is stopped, the vibration of the vibrating mesh 3 is repeatedly turned on and off. This makes it possible to control the amount of drop into the container 4 with extremely high precision.
Further, instead of measuring the weight of the fine powder, the volume may be measured and controlled. Instead of the container 4, a rubber mold or a rubber mold with a guide frame may be installed and the weight of the fine powder may be measured together with the rubber mold and the fine powder may be filled in the rubber mold.

According to the methods of claims 3 to 5, even a fine powder having poor fluidity can be filled in a rubber mold with high weight accuracy without adding an organic lubricant. If the packing density of the fine powder in the rubber mold is very high, or if the rubber mold returns to its original shape after the punch load is removed, depending on the degree of unevenness of the molded body, the gap between the molded body and the rubber mold Sufficient voids are not formed, and it becomes impossible or extremely difficult to remove the molded product from the rubber mold. In that case, the rubber mold 10 can be used as split molds 10a and 10b as shown in FIG. That is, at least the side portion of the rubber mold is divided into two or more split molds, which are separated after molding to take out the powder compact 20 from the rubber mold 10. Alternatively, as shown in FIG. 5B, a cut 11 may be provided on a side portion of the rubber mold, and the rubber mold may be opened from the cut surface to remove the molded body. Further, as shown in FIG. 6, the side portion, the bottom portion, and the side portions may be divided. However, when a split mold is used, fine powder is likely to be caught in the split surface of the rubber mold, and uneven deformation such as twisting of the rubber mold is likely to occur, which may result in deformation or cracking of the molded product. Furthermore, time is required to set the split mold on the die.

As a countermeasure against this, after crushing the fine powder, the load is removed, and then the inner surface of the rubber mold is filled with gas or the like.
And / or depressurize the outer surface of the rubber mold to give a pressure difference so that the pressure on the inner surface side becomes higher, expand the gap between the molded body and the rubber mold, and then remove the molded body from the rubber mold. The method is effective. In the embodiment of this method, as shown in FIG. 7, a cylindrical cover 12 is fixed on the top side of a rubber mold 10 with a bottom, and both 1
The space between 0 and 12 is sealed. By introducing a pressurized gas of about 1 to 5 atm into the cylindrical cover 12, the rubber mold 1
Inflate 0. Then, the tip of the suction tube 14 which has been projected into the tubular cover in advance is pressed against the upper surface of the powder compact 20 and is sucked to remove the powder compact 20. When the powder compact 20 is a magnetic substance, it may be taken out by suction with an electromagnet instead of suction. Unlike the above-described embodiment, the rubber mold 10 may be expanded by reducing the pressure in the vacuum chamber having the outer surface of the rubber mold as a part, as shown in FIG.

In FIG. 8, 8 is a lower punch, 14 is a sealing cover, 14a is an exhaust hole, 15a and 15b are O-rings, and 17 is an electromagnet. The sealing cover 14 is pressed against the die 1 via the O-ring 15b and directly against the rubber mold 10 by pushing up the lower punch 8. An O-ring 15a is fitted between the lower punch 8 and the die 1. Therefore, the exhaust hole 14 is provided outside the rubber mold.
A vacuum space 18 is created by exhausting air from a. After the rubber mold 10 is expanded, the powder compact 2 is formed by the electromagnet 17.
Aspirate 0.

After die-press molding, the rubber mold may be turned upside down, the inner surface of the rubber mold may be pressurized or the outer surface may be depressurized, and the molded body may be taken out from the expanded rubber mold by dropping it from the lower side. The method using the split mold is inferior to the depressurization method (FIGS. 7 and 8) in terms of efficiency, but this method enables taking out even if it is difficult to take out the powder compact.

Molded articles such as flat gears whose height along the direction of pressing by the punch is smaller than the dimension in the direction perpendicular to the direction are used to form cemented carbide, Fe--Co, Ti alloys or various intermetallic compounds. for molding using a fine powder of brittle molding having poor material, lid materials <br/> forming the material (upper surface forming at least one of the upper and lower surfaces of the rubber mold inner surface, forming the lower surface the material is referred to as the bottom) is Gomumo
It is preferable to use a rubber mold configured to be harder than the rubber that forms the lateral portion of the fold . Contrary to this configuration, when the bottom portion is soft and the side portions are hard, the bottom portion 10k tends to shrink as the side portions 10s are deformed and wrinkles are formed on the bottom portion, as schematically shown in FIG. It occurs on the surface of 10k. This wrinkle becomes a starting point of a crack, and the green compact 5'is broken. Further, in the soft material, powder is likely to be caught on the surface, and friction between the green compact and the mold is large. Further, when the pressure by the punch is removed, the soft bottom portion 10k tries to return to its original shape and is reversely deformed. At this time, the rubber at the bottom portion is caught in the green compact 5'to try to follow the reverse deformation. , The powder compact 5'is cracked. These cause cracking of the green compact. Lateral part 10
If the hardness of s is the same as that of the bottom portion 10k, the risk of cracking increases as the amount of compression by the punch increases. Therefore, in the present invention, the bottom portion and / or the lid portion is made of rubber harder than the side portions, or the bottom portion and / or the lid portion is made of metal or hard resin.

The thickness (t, unit: mm) of at least one of the lid and the bottom of the rubber mold is expressed by the formula: t≤16h / D.
(Where h is the thickness of the green compact and D is the positive square root of the cross-sectional area of the green compact). Here, the thickness of the lid or bottom and the thickness of the green compact mean the thickness in the pressing direction by the punch, and the cross-sectional area of the green compact means the cross-sectional area of the green compact perpendicular to the pressing direction by the punch. . The larger the area of the green compact (the smaller the right side of the equation), the greater the force when the rubber reversely deforms, and the more easily the green compact breaks. Therefore, the thickness of the lid and bottom of the rubber mold should be reduced. Make it smaller. FIG. 1 showing that the thickness of the bottom portion 10k is reduced.
At 0, the bottom portion 10k is pressed down by the pressing force Pa of the upper punch 1a and its reaction Pb. On the other hand, the force that makes the bottom portion 10k wrinkle The side portion 10s of the rubber mold and the power Pc that reduces the powder 5 so as to reduce the cross-sectional area.
Is. As the thickness of the bottom portion 10k becomes smaller, the pressing force Pa, Pb of the former becomes larger, and when it exceeds the force Pc of the latter, wrinkles do not occur. Also, the coefficient 16 in the above equation
As a result of the following experiment, was found to be critical with respect to the presence or absence of cracking. A rubber mold (dimensions 30 × 30 × 5 mm, h) having the shapes of (e) and (g) of FIG.
/D=0.17) with an average particle size of 10 μm Fe-C
o The powder was molded at a pressure of 1.0 t / cm ² . In this molding, the bottom thickness (t) of the rubber mold is 0.5 to 3.5 m.
Perform 10 times for each thickness by changing in the range of m
Individual molded bodies were produced. As a result, the following number of cracks was obtained. t = 0.5, 1.0, 1.5 mm, 0; t =
2.0 mm, 1 piece; t = 2.5 mm, 4 pieces; t = 3.0
mm, 10 pieces. From the crack investigation result, the above coefficient 16
Was asked.

Instead of making the bottom and the lid of the rubber mold hard, the rubber mold having an open upper part and / or lower part can be directly pressed by a metal punch to substitute the hard part for the punch. An example of a rubber mold embodying the above-mentioned two methods, that is, (a) hard rubber, metal or hard resin for the bottom and / or lid (b) thin rubber satisfying the above formula, is shown in FIG. Shown in. Hatching in the figure indicates metal or hard rubber. (A) is an example in which the upper lid 10u is made of soft rubber, the side portions 10s are made of soft rubber, and the bottom portion 10k is made of hard rubber or metal. (B) is an example in which the upper lid 10u is made of soft rubber, the side portions 10s are made of soft rubber, and the bottom portion 10k is made of hard rubber or metal. (C) is an example in which the top lid 10u is made of soft rubber (hereinafter, simply referred to as "thin") that satisfies the above formula, the side portions 10s are made of soft rubber, and the bottom portion 10k is made of hard rubber or metal. (D) is an example in which the upper lid 10u is a thin (hereinafter simply referred to as "thin") soft rubber that satisfies the above formula, and the side portions 10s and the bottom portion 10k are an integral soft rubber. (E) is an example in which the upper lid 10u is made of hard rubber or metal, and the side portions 10s and the bottom portion 10k are made of soft rubber. (F) is an example in which the upper lid 10u is made of soft rubber and the side portions 10s and the thin bottom portion 10k are made of soft rubber. (G) is an example in which the upper lid 10u is made of hard rubber or metal, and the side portions 10s and the thin bottom portion 10k are made of integral soft rubber. (H) is an example in which the top lid 10u is made of thin soft rubber, and the side portions 10s and the thin bottom portion 10k are made of integral soft rubber. (I) shows the upper lid 10u made of hard rubber or metal,
In this example, the side portion 10s is made of soft rubber and the bottom portion 10k is made of hard rubber or metal. (J) has no top lid, side part 10s
Is a soft rubber, the bottom portion 10k is a soft rubber, and the bottom portion 10k is a hard rubber or a metal fixed to a side cutout. (K) is an example in which the bottom portion 10k made of hard rubber or metal is surrounded by the side portions 10s from the side surface and the lower surface. If the bottom is thin, the bottom bottom can be reinforced with a harder material than the bottom top, such as metal or hard rubber. (L)
(I) is an example in which a downward projection is provided on the upper lid 10u, the powder is compressed to a high density outside the press machine by the upper lid, and the powder is pressed in the state shown in (1).

FIG. 12 (a) shows a rubber mold having the same function as that of FIG. 11 (e). In the rubber mold (a), the upper punch 1a acts as the upper lid 10u to prevent the green compact from cracking (the method of claim 11). Further, in FIG. 12B, the upper lid 10u in FIG.
An example of a mold in which the upper punch 1a and the lower punch 1b respectively perform the action of the bottom portion 10k is shown. Further, in FIG. 12 (c), the upper punch 1a and the lower punch 1b are made of a hard material, and the hard upper lid 10u (for example, see FIG. 11 (e)).
A mold that performs the action of is shown. In addition, here
The hard material of the punch is attached to the tip of the metal punch.
It may be hard rubber or resin.

When molding a long product, a phenomenon completely opposite to that of a flat product occurs. That is, in the flat object, the influence of the rubber mold is dominant from the upper and lower end surfaces having a large area, so cracking was prevented by making at least one of the upper and lower end surfaces hard. However, the influence of the rubber mold from the side becomes dominant in long products. Therefore, if the side portions are made soft, layered cracks will occur this time according to the principle illustrated in FIG. 9 (see FIG. 13). Therefore, in order to prevent layered cracks, the material on at least one of the upper and lower sides where the rubber mold faces the upper and lower punches of the die press is softer than the rubber on the side facing the die of the die press. It is preferable that it is configured as described above.

It is relatively soft like Al and Fe,
When fine powder having good moldability is molded by a soft rubber mold, the powder may bite the side wall of the rubber mold and the rubber mold may not be separated from the outer surface of the molded body even if the load is removed. In this case, the hard rubber mold is unlikely to bite, but if the entire rubber mold is made of hard rubber, it becomes difficult to expand the rubber mold and take out the powder compact. Therefore, at least the side surface of the rubber mold has a two-layer structure, and only the side facing the fine powder is made of a hard material, so that it is possible to prevent the fine powder from being caught while maintaining the flexibility of the entire rubber mold. It is advantageous. The lid portion and the bottom portion may have a similar two-layer structure. Also,
Such a two-layer structure may be made by casting or injection-molding the two-layer material, or a hard material may be coated on the inner surface of a preformed rubber mold. Instead of the hard rubber, a resin or rubber containing a lubricant such as molybdenum disulfide, or a material having a low friction coefficient such as tetrafluoroethylene resin can be used for the inner layer to obtain the same effect.

In the method of manufacturing a hollow body such as a ring, the rubber mold is provided with a mandrel made of a material harder than the rubber mold for forming the hollow portion. If the mandrel is soft contrary to this configuration, the mandrel contracts in the radial direction together with the green compact due to the pressing force of the punch, and then the punch is retracted and added to the rubber mold and the green compact. When the load is removed, the mandrel 10m expands so as to expand the central hole of the contracted green compact 5 '(see FIG. 14). As a result, cracking occurs in the green compact 5 '. Therefore, the mandrel 10m (see FIG. 14) is preferably harder than the side portion 10s.

FIG. 15 shows a concrete example of a molding method for producing a green compact having two hollow parts as shown in FIG. 16 by using a mandrel. The mandrels 10m and 10m 'are made of metal and The upper punch 9 into the recess 9 '
Is formed inside. When making a hollow molded body as shown in FIG. 17, a part of the hard mandrel penetrates to the side surface of the molded body. With the method of the present invention, the compression is much more isotropic than with a normal die press and there is no friction between the mold and the powder due to the presence of the rubber mold. Therefore, even if the upper punch alone is pressed, the powder is uniformly formed without being biased. This greatly simplifies the press.

In order to automate the method of the present invention, a method of conveying a plurality of rubber molds in a circulating path is desirable. According to the method of the present invention, ne which uses fine powder without cracking or chipping is used.
Since the purpose is to produce a t-shape molded body, one way to realize the automation is to measure fine powder and feed it to a rubber mold using a guide frame.
Flour, high density filling of the rubber mold by vibration Dooyobi / or pusher pressing fine powder, die pressing, and taken out of the green compact from the rubber mold successively repeated in circular path for intermittently transporting the rubber mold. As an apparatus for carrying out this, a measuring machine for fine powder along a circulating path for intermittently conveying the rubber mold,
High-quantity and high-density consisting of a feeder that supplies fine powder to a rubber mold and a pusher for high-density filling.
The filling section (a), die press machine (b), and powder compact
It is desirable to use an apparatus in which the take-out parts (c), which are jigs for taking out from the mold, are sequentially arranged. The exciter can be arranged instead of or with the pusher. The shaker can be installed in the same position as the feeder or it can be placed between the feeder and die press. If the molding is continuously conveyed, the steps (a) to (c) must be performed while the mold is moving, and the feeder, punch, etc. must move together with the mold. Because the fine powder easily causes bridging in the rubber mold, it is not possible to use a powder feeder by free fall grinding, and it is necessary to move the feeder and guide together with the rubber mold to fill the measured powder into the mold. Because. This greatly complicates the device as compared with the case where each jig is fixedly arranged.

According to the method of the present invention, powder feeding, filling,
Since the press is not occupied during the removal of the molded body,
Productivity is greatly improved. One embodiment of the method of transferring the die together with the rubber mold will be described with reference to FIG. The rubber itself of the rubber mold 10i (see FIG. 19) forms a bottomless mold, and the open bottom of the rubber mold is closed to a part of the rotary die 40. Therefore, the rotary die 40 constitutes the bottom of the rubber mold. While the rubber mold 10i sequentially rotates together with the ring-shaped rotary die 40, a series of operations such as filling powder into the rubber mold 10i with a feeder, die pressing with a die press device 60, and removal of a molded product with a molded product removal device 62 (A to D) can be performed.

In A, the fine powder 5 (see FIG. 20) weighed by the quantitative supply device is put into the rubber mold 10 having the guide 100 attached thereto, and vibrated by the vibrator 41 to increase the density. Increase to high density. As in this method, it is preferable that the supply of the fine powder to the rubber mold and the high-density filling of the rubber mold are performed at the same place. If the supply to the rubber mold and the high density filling to the rubber mold are performed in different places, the guides 100 must be moved from the powder feeding place to the pushing place, and the number of guides 100 increases, and the device becomes complicated. Invite. The die is not shown in FIG. 18B is a preliminary position, and C is pressed by a die press. A,
The rotary die 40 stops moving until the operations at B, C and D start and complete. Since the rubber mold 10i returns to its original shape after compaction, a ring-shaped gap 10r is formed around the compact 63. The gap 10r is large enough to take out the green compact 63 from the rubber mold 10i by the above-mentioned suction. 66 is the control unit 5
It is a conveyor driven by a step motor 67 driven by 0. After the arm 64 swings above the conveyor 66 and the green compact 63 is placed on the conveyor 66, the conveyor 66 moves. The series of operations is controlled by the control unit 50.

Reference numeral 28 is a rubber mold cleaning device including an air piston 24, an air unit 25, an electromagnet 26, and an electromagnet excitation power source 27. The electromagnet 26 moves above the die cavity after taking out the powder compact from the die, and is excited by the electromagnet power source 27 to attract the residual powder remaining in the rubber mold 10 by the magnetic force, so that the rubber mold needs to be cleaned. By. If the powder is non-magnetic, a cleaning means such as suction can be used. The die may be conveyed along the circulation path together with the rubber mold. That is, in FIG. 18, the ring-shaped turntable 40 is made of inexpensive carbon steel, and the die made of die steel is the rubber mold 1.
It may be configured so as to be attached to and detached from the ring-shaped rotary table 40 together with 0. In order to form a fine powder of highly active alloy, it is preferable to carry the rubber mold in the circulating path in an inert gas chamber. In the circulating path device, since the paths of the fine powder and the compact are constant, the entire device can be made compact, so that it is easy to create an atmosphere. As shown by the chain double-dashed line 30 in FIG. 18, it is possible to selectively store the periphery of the press machine and the path portion in the inert gas container (30).

FIG. 21 is a plan view of an apparatus according to an embodiment of the present invention when only the rubber mold is conveyed and the die moves only along a small part of the circulation path. FIG. 22 is a side view of FIG. FIG. In this device, the die is a disk-shaped rotary die 1a, and a plurality of punched dies (two in the drawing are used).
(Only one is shown, but three or more may be used). The rotary die 1a is rotated by the motor 91 so that each die moves along the circular path, and the upper and lower punches 9 are formed. , 8 are provided at a _first position P ₁ which is vertically inserted into the die, and at a second position P ₂ , a mold loader 7 which is used to insert fine powder into the rotary die together with the rubber mold.
0, and at the third position P ₃ the rotary die 1
Extractors 78 and 84 are provided for taking out the rubber mold including the powder compact from a. The rotary die 1a is sequentially circulated through P ₁ , P ₃ , and P ₂ by a motor 91.

The disk die 1a is not all expensive die steel, and may be used only in the periphery that comes into contact with the punch. Other parts may be made of plastic, iron or the like for weight saving and cost reduction. The mold loader 70 is driven by two hydraulic cylinders 71 and 80. Hydraulic cylinder 7
1 moves forward and backward a hollow rod 79 having a suction port attached to its tip. In the position of FIG. 22, the rubber mold 10 shown on the right side is inserted into the die. Hydraulic cylinder 80
Raises and lowers the cylinder 71 fixed to the piston 92 as a whole. In the raised state, the suction port sucks the rubber mold 10 on the belt conveyor 45, and then the hollow rod 79 advances while moving in the raised state and moves to above the die. After that, the cylinder 71 descends and the rubber mold 10 is inserted into the die. 76 and 81 are hydraulic units. Reference numeral 75 denotes a fixed cam, and when the rotary die 1a rotates, the elevating bottom 1d provided in the die slides along the upper surface contour of the fixed cam 75 as shown in FIG. That is, during pressing, the die is completely separated from the fixed cam 75 (see (a) figure), but next, it rides on the hem of the fixed cam 75 (see (b) figure) and the slope of the mountain. (See (c, d)) and reaches the flat portion at the top, the rubber mold 10 in which the powder compact is placed reaches the same level as the upper surface of the rotary die 1a ((e)). See figure). At this time, the rubber mold has reached the third position P ₃ (see FIG. 22). After that, the elevating bottom 1d descends again, so that the unmolded fine powder can be received in the die (see FIG. (F)). A first conveyor 45 having an end located near the second position P ₂ is provided, and the first conveyor 4 is provided.
The rubber mold filled with the fine powder is conveyed by 5.
A second conveyor 140 having an end located near the third position P ₃ is provided. The rubber mold 10 is the rotary die 1.
It is guided along the rubber mold recovery plate 78 by the rotational movement of a, and then is slightly slid on the fixed base 84 and transferred onto the second conveyor 140.

[0043]

Example 1 A rubber mold used is shown in FIG. The upper lid portion 10u was made of hard rubber (hardness 90), the side portion 10s was made of soft rubber (hardness 40), and the bottom portion 10k was made of hard rubber (hardness 90). The inner dimension of the rubber mold cavity is 30 x 30
It was × 3 (mm). The rubber mold was manufactured as follows. A hard urethane plate 34, which has been hardened and cut out in advance, is set on the bottom of a mold 36 having the same shape as the cavity shown in FIG. A two-liquid mixed room temperature curing type) was cast to mold the bottom portion 10k and the side portion 10s.

All rubber molds used in the following examples were prepared according to this method. F as fine powder
e-45 wt% Co atomized powder (average particle size 15 μm,
True density 8.3 g / cc) pressing pressure: 1.0 t / cm ²
It was molded in. The obtained green compact is sintered at a temperature of 1200 ° C.
Sintering was performed for 6 hours. The results are shown in Table 1. No lubricant or binder was added to any of the powders.

(1) In the table, the leftmost data is a comparative example by natural filling. In the case of natural filling, fine powder was allowed to fall freely from the powder box into the rubber mold, and the raised portion above the rubber mold was scraped off. The weight of the powder was not measured. On the other hand, in all the examples, the weight of the fine powder was measured in advance within the error range of ± 1% for each packing density. (2) Filling method N ・ ・ ・ Natural filling (free cutting after free fall) NV ・ ・ ・ Vibration while dropping powder into the cavity through the guide, and lightly pusher to match the upper surface of the powder with the rubber mold after completion of filling powder pusher NVP · · guide powder is vibrated while dropping into the cavity through the filling after completion powder pressing in
The strongly pushed (3) cracking, chipping criteria (n = 50)

○ No cracking or chipping occurs △ Less than 10% of the total number of cracks or chipping occurs × 10% or more of the total number of cracks or chipping occurs

(4) Deformation criterion x Non-uniform deformation is remarkable, dimensional adjustment by post-processing is impossible, improvement is difficult even if the shape of the rubber mold is modified. △ Some non-uniform deformation, but post-processing Or to the extent that can be compensated by dimensional adjustment by sizing ○ Almost no non-uniform deformation. Although some non-uniform deformation remains, a good molded body can be obtained by slightly changing the shape of the inner surface of the rubber mold. The above (1) to (4) are the same for all the examples.

[0048]

[Table 1]

As in the case of Fe-Co powder, Ti powder (hydrolyzed powder (average particle size 10 μm, true density 4.5 g / c
c) was molded under a pressing pressure of 1.0 t / cm ² , and the obtained green compact was sintered at 1150 ° C. for 6 hours. Table 2 shows the results.

[0050]

[Table 2]

Example 2 The upper lid 10u of the rubber mold shown in FIG. 26 is made of hard rubber (hardness 90) and the side portion 10s with a bottom is made of soft rubber (hardness 4).
0), the inner dimension of the cavity is 4 inner diameter x 1 height
It was set to 7 mm. The powder, pressing pressure, and sintering conditions used are as follows, and the results are shown in each table. (1) Fe-2 wt% Si (average particle size 10 μm, true density 7.7 g / cc) Pressing pressure: 1.0 t / cm ² , sintering temperature 1200 ° C. Sintering time: 6 hours (Table 3) (2) Fe -0.3 wt% C (water atomization → hydrogen reduction) (average particle size 20 μm, true density 7.8 g / cc) Pressing pressure: 1.0 t / cm ² , sintering temperature 1200 ° C. Sintering time: 6 hours (Table 4 (3) Fe-0.3 wt% C (water atomization → hydrogen reduction) (average particle size 12 μm, true density 7.8 g / cc) Pressing pressure: 1.0 t / cm ² , sintering temperature 1200 ° C. Sintering time: 6 hours (Table 5) (4) Fe-42 wt% Ni (atomized powder) (average particle size 30 μm, true density 8.1 g / cc) Pressing pressure: 1.0 t / cm ² , sintering temperature 1200 ° C. Sintering time: 6 hours (Table 6) (5) Fe-42 wt% Ni (atomized ) (Average particle size 12 [mu] m, a true density of 8.1 g / cc) Press pressure: 1.0 t / cm ^2, sintering temperature 1200 ° C. Sintering time: 6 hours (Table 7) (6) Ti (hydrogenolysis powder) ( Average particle size 10 μm, true density 4.5 g / cc) Pressing pressure: 1.0 t / cm ² , sintering temperature 1150 ° C. Sintering time: 6 hours (Table 8) (7) Sintering Al (atomized powder) (Average Particle size 10 μm, true density 2.7 g / cc) Pressing pressure: 1.0 t / cm ² , sintering temperature 600 ° C. Sintering time: 6 hours (Table 9)

[0052]

[Table 3]

[0053]

[Table 4]

[0054]

[Table 5]

[0055]

[Table 6]

[0056]

[Table 7]

[0057]

[Table 8]

[0058]

[Table 9]

Example 3 Using the same rubber mold as in Example 2, the average particle size (μ
Example 1 using the guide frame, the vibration, and the pusher to the packing density described in Table 10 for each powder of various materials with different m).
Was filled by the method of NVP , pressed under the same conditions as in Example 2, and sintered. However, Fe-45% Co was pressed and sintered under the conditions of Example 6 described later. On the other hand, for comparison, when a die press method using a die (die inner diameter 3.9 mm) that can mold almost the same shape as that molded by a rubber mold was performed, the same fine powder used for molding by the rubber mold was fluid. Since it was low, it was impossible to fill the mold. Therefore, the coarse powder shown in Table 10 was used, and after spontaneous filling, it was molded at a pressure of 1.5 t / cm ² , and then sintered under the same conditions as the fine powder. Tables 10 and 11 show the densities of the sintered bodies.
Shown in

[0060]

[Table 10]

[0061]

[Table 11]

Example 4 Bolts were molded using the rubber mold shown in FIG. The upper lid 10u and the side portions 10s of the rubber mold are made of soft rubber (hardness 40). The powder used is Fe
-2 wt% Si (average particle size 10 μm, true density 7.7 g /
cc, atomized powder) -Table 12-and Ti powder (average particle size 30 μm, true density 4.5 g / cc, hydrocracked powder-
It was Table 13-. The former powder has a pressing pressure of 1.2 t / c
The powder compact obtained by molding at m ² was sintered at a sintering temperature of 1200.
Sintering was performed under the conditions of ℃ and sintering time of 6 hours. The latter powder was molded under a pressing pressure of 1.4 t / cm ² , and the obtained powder compact was fired under the conditions of a sintering temperature of 1150 ° C. and a sintering time of 6 hours. The results are shown in Tables 12 and 13. In all materials, the screw thread was particularly damaged when it was naturally filled, and it was broken at the boundary between the foot and the head of the screw. It is considered that the damage of the screw thread is caused by the powder not being uniformly filled up to every corner of the groove forming the screw thread of the rubber mold, and the breakage of the molded body is caused by the uneven deformation of the rubber mold.

[0063]

[Table 12]

[0064]

[Table 13]

Example 5 Fe-45 wt% Co fine powder (average particle size 12 μm) was obtained using rubber mold A and rubber mold B shown in FIG.
m) was packed at a packing density of 3.70 g / cc. The inside dimension of the cavity is 30 × 30 × 3 for any rubber mold
There was mm. The entire rubber mold A (10u, 10s)
Made from soft rubber (hardness 40)
The side portions were made of the above soft rubber, and the other portions (10u, 10k) were made of hard rubber (hardness 90). As a filling method, a fine powder previously weighed was naturally filled using a guide, and then forcedly filled by a vibration and a pusher. 1 molding with a press pressure of 1.0 t / cm ^2.
When it was carried out 0 times, all the green compacts molded by the rubber mold A were cracked, and all the rubber molds B were good.

Example 6 As shown in FIG. 29, using rubber molds A and B (internal cavity size 4 × 17 mm) made of the following materials, fine powder, filling density, method, pressing condition, and n number were set. Molded under the same conditions as in Example 4. Rubber mold A Rubber mold B Top lid Soft rubber (hardness 40) Hard rubber (hardness 80) Side part Hard rubber (hardness 80) Soft rubber (hardness 40) Bottom soft rubber (hardness 40) Hard rubber (hardness 80) Rubber mold B All of the powder compacts formed in step 1 had lamellar cracking, and all the powder compacts formed by the rubber mold A were good.

Example 7 A rubber mold (A) made of the following material shown in FIG.
Using (B) and (C), aluminum powder (average particle size 30 μm, atomized powder) was molded. Upper lid Side part Inner surface film (10n) Rubber mold (A) Hard rubber No soft rubber (Hardness 90) (Hardness 40) Rubber mold (B) Same as above Same as above Polytetrafluoroethylene resin (Hardness 80) (t = 0.5mm) Rubber mold (C) Same as above Same as above 40% MoS ₂ (hardness 80) Blended soft rubber (hardness 40) (t = 1.0 mm) In molding using the rubber mold (A), the powder compact is bit into the rubber mold. , rubber and rubber mold upside down
Shaped body even through the beam mold pressurized with compressed air 1.0 kg / cm ² is as remaining in the rubber mold. In the molding using the rubber molds (B) and (C), no biting occurred at all, and when the rubber mold was inverted and inflated, the molded body easily dropped and could be taken out.

Example 8 Using a rubber mold having a shape shown in FIGS. 31A, 31B and 31C and having a mandrel made of the materials shown in the following table,
Fe-2 wt% Si (atomized powder, particle size 12 μm) was press-molded at 1 t / cm ² , and the number of cracks generated according to the material of the mandrel was examined. Rubber mold (A), (B)
Shape is outer diameter φ33mm × inner diameter φ24mm × height 18m
The shape of m and mandrel 10m is the outer diameter φ12 in the set state.
mm x height 15 mm ((A)), outer diameter φ12 mm
The height was 7.5 mm (in the case of (B)). Rubber mold (C) has an outer diameter of 33 mm, an inner diameter of 24 mm, and a height of 1.
It has a size of 8 mm and a thickness of 1.5 m as a mandrel.
Eight blades of m and 7.5 mm in height were arranged radially. The state of cracking is shown in Table 14 as the number of cracks during molding 10 times.

[0069]

[Table 14] From Table 14, it was confirmed that when the mandrel was soft, the mandrel contracted in the radial direction together with the molded body, and when the mandrel was unloaded in this state, the mandrel returned so as to open the hole of the contracted molded body and cracking occurred. . The most desirable material for the mandrel is metal, followed by high hardness rubber, and it can be said that a material that does not easily deform is suitable.

Example 9 High purity Al and high purity Li were converted into Al-2.84 wt% Li.
After mixing so as to have the composition
Al-Li alloy powder having an average particle size of 8 μm was obtained by gas atomization. Using this powder, the inner dimension is 30φ
A disc-shaped green compact was manufactured by a circular path type green compact manufacturing device (FIG. 18) in which a through rubber mold made of urethane rubber (hardness 60) having a height of 10 mm was fixedly arranged. Here, when molding was performed on an example in which the entire apparatus was exposed to the atmosphere (not placed in the chamber), the powder was frequently ignited and molding was impossible.

On the other hand, when the portion indicated by the alternate long and two short dashes line 30 in FIG. 18 was covered with a dome-shaped chamber and the air in the chamber was replaced with argon gas to carry out molding, molding became possible.

[0072]

According to the methods of claims 1 and 6 , it is possible to obtain a powder compact of fine powder with higher efficiency than the conventional injection molding method. Although it is inferior in efficiency to die press, it is much more efficient than debinding treatment in injection molding. Further, according to the methods of claims 1 and 6 , fine powder can be formed without the need for a binder and a lubricant. According to the methods of claims 2 and 3, high-density packing can be efficiently performed.
According to the methods of claims 4 and 5, it is possible to make the variation of the unit weight of the sintered body extremely small, and to reduce the final machining allowance of the sintered body. Method of claims 7 and 8
According to the rubber mold of the thirty-first aspect , it is easy to take out the green compact after unloading the punch. Claims 9 to 12
The configurations of rubber molds Nos. 25 to 31 are particularly effective for molding a powder compact having a tendency to crack.

The structure of the rubber mold according to the thirteenth and fourteenth aspects prevents galling of the rubber mold. According to the method of claim 15 , the structure of the die press machine can be simplified.
According to the method of claim 16 , the hollow body can be molded without cracking. The inventions of claims 17, 18 , 20 to 23 make it possible to perform press molding with high efficiency without lowering the efficiency of the die press machine by utilizing the fact that the fine powder is packed into the rubber mold at a high density outside the die press machine. To do. The method of claim 19 is effective in preventing ignition of the highly active powder. According to the method of claim 32 , a high-density sintered body of fine powder can be produced only by sintering.

[Brief description of drawings]

FIG. 1 is a diagram showing a method of filling a rubber mold with a high density of fine powder.

FIG. 2 is a diagram of a guide frame.

FIG. 3 is a diagram of a guide frame.

FIG. 4 is a diagram showing a measuring method for fine powder.

FIG. 5 is a view of a split mold.

FIG. 6 is a view of a split mold.

FIG. 7 is a diagram showing a method of expanding a rubber mold.

FIG. 8 is a diagram showing a method of expanding a rubber mold.

FIG. 9 is an explanatory diagram of cracking of a molded body.

FIG. 10 is a diagram of pressure applied to a rubber mold.

FIG. 11 is a view of various rubber molds.

FIG. 12 is a diagram showing a molding method using a rubber mold in which at least one of upper and lower ends is opened.

FIG. 13 is an explanatory diagram of a layered crack.

FIG. 14 is a view of a rubber mold for molding a hollow body.

FIG. 15 is a view of a rubber mold for molding a hollow body.

FIG. 16 is a view of a hollow body.

FIG. 17 is a view of a hollow body.

FIG. 18 is a diagram of a circuit-circulating device.

19 is a diagram of a rubber mold provided in the device of FIG.

FIG. 20 is a diagram of a rubber mold including a pusher and a vibrator.

FIG. 21 is a diagram of a circular path type device.

22 is a side view and a partial cross-sectional view of the device of FIG. 21. FIG.

FIG. 23 is an operation explanatory view of a cam plate.

FIG. 24 is a view of the rubber mold used in Example 1.

FIG. 25 is a diagram showing a method of manufacturing the rubber mold of FIG. 24.

FIG. 26 is a view of the rubber mold used in Example 3.

27 is a view of the rubber mold used in Example 4. FIG.

28 is a view of the rubber mold used in Example 5. FIG.

29 is a drawing of the rubber mold used in Example 6. FIG.

30 is a view of the rubber mold used in Example 7. FIG.

FIG. 31 is a view of a rubber mold used in Example 8.

[Explanation of symbols] 1 die 2 conveyor 3 vibrating mesh 4 container 5 fine powder 6 gravimetric device 7 fine powder 8 lower punch 9 upper punch 10 rubber mold 11 notch 12 cylindrical cover 14 sealing cover 15 O-ring 17 electromagnet 18 vacuum Space 20 Powder compact 22 Pusher 30 Inert gas container 31 Hydraulic unit 32 Hydraulic cylinder 33 Core 34 Hard urethane plate 35 Unhardened rubber 36 Mold 40 Ring-shaped rotary table 41 Vibrator 42 Feeder 44 Motor 45 Belt conveyor 50 Control Unit 60 Die Press Device 62 Molded Body Removing Device 70 Mold Loader 71 Hydraulic Cylinder 75 Cam 76 Hydraulic Unit 78 Rubber Type Recovery Plate 79 Hollow Rod 80 Hydraulic Cylinder 81 Hydraulic Unit 82 Hydraulic Unit 90 Saucepan 91 Mo Motor 92 piston 100 guide frame 102 pusher ─────────────────────────────────────────── ───────────

[Procedure amendment]

[Submission date] February 5, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Fig. 32

[Correction method] Added

[Correction content]

FIG. 32 is a drawing for explaining the condition of cracks that occur in a green compact when it is molded by a rubber mold.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] Fig. 33

[Correction method] Added

[Correction content]

FIG. 33 is a diagram illustrating a method of compacting powder using a punch including an outer punch and an inner punch.

Claims (30)

[Claims] 1. A method for producing a green compact for sintering by molding a green powder compact, wherein a rubber mold having rubber at least on a side portion is naturally filled with the fine powder, and then the rubber mold is formed. Molding of a green compact for sintering characterized in that a fine powder is densely packed without being substantially deformed, and the rubber mold and the fine powder filled in the rubber mold are compressed by a punch of a die press machine. Method. 2. The method for molding a green compact for sintering according to claim 1, wherein the rubber mold is densely filled with fine powder by vibrating and / or pressing. 3. The rubber mold is naturally filled with fine powder through a guide provided in the upper opening of the rubber mold and having an opening of substantially the same size as the opening, and a pusher is installed along the guide. The method for molding a green compact for sintering according to claim 2, characterized in that the compact is pressed into the rubber mold and / or the rubber mold is vibrated together with the guide. 4. The method for molding a green compact for sintering according to claim 3, wherein a predetermined amount of a fine powder that has been previously measured is naturally filled. 5. The pressure for sintering according to claim 3, wherein the weight of the rubber mold and the fine powder is measured during the natural filling of the fine powder, and the natural filling is stopped after the predetermined weight is reached. Powder molding method. 6. The powder compact for sintering according to claim 1, wherein at least a side portion of the rubber mold is divided into two or more or has a cut surface. Body shaping method. 7. Unloading after compression molding of fine powder,
After that, the inner surface of the rubber mold is pressurized and / or the outer surface of the rubber mold is depressurized to provide a pressure difference so that the pressure on the inner surface side becomes higher, and the gap between the powder compact and the rubber mold is expanded. 7. The powder compact formed body is taken out from a rubber mold, according to any one of claims 1 to 6.
A method for molding a green compact for sintering according to the item. 8. The material on at least one of the upper and lower sides of the rubber mold facing the upper and lower punches of the die press machine is harder than the rubber on the side of the die press machine facing the die. The method for molding a green compact for sintering according to any one of claims 1 to 7. 9. The material of at least one of the upper and lower sides of the rubber mold facing the upper and lower punches of the die press machine is softer than the rubber on the side of the die press machine facing the die. The method for molding a green compact for sintering according to any one of claims 1 to 7. 10. The thickness (t, unit: mm) of at least one of the upper lid portion and the bottom plate portion of the rubber mold is represented by the formula: t.
≦ 16 h / D (where, h is the thickness of the green compact, and D is the positive square root of the cross-sectional area of the green compact). A method for molding a green compact for sintering according to the above. 11. The method according to claim 1, wherein at least one of the upper and lower surfaces of the rubber mold having an open upper part is directly pressed with a punch. Method for forming green compact for sintering. 12. The rubber mold according to claim 1, wherein the side of the side portion facing the fine powder is harder than the material of the side facing the die. A method for forming a green compact for sintering. 13. The rubber mold according to claim 1, wherein the side of the side portion facing the powder is made of a material having a smaller friction coefficient than the material of the side facing the die. The method for molding a green compact for sintering according to item 1. 14. The method for molding a green compact for sintering according to any one of claims 1 to 13, wherein a rubber mold installed in a die having a closed bottom is pressed by an upper punch. 15. The compact according to claim 1, wherein the green compact is a hollow body, and the rubber mold is provided with a mandrel made of a material harder than the rubber mold for forming a hollow portion. A method for molding a green compact for sintering according to any one of 1. 16. A rubber mold is intermittently conveyed for a natural filling of a quantitatively measured amount of fine powder into a rubber mold, a high density filling of a rubber mold, a die press, and a removal of a powder compact from the rubber mold. The method for molding a green compact for sintering according to any one of claims 1 to 15, wherein the method is repeated sequentially in a circulating path. 17. The method for molding a green compact for sintering according to claim 16, wherein the die is conveyed along with the rubber mold in the circulating path. 18. The method for molding a green compact for sintering according to claim 16, wherein the rubber mold is conveyed in a circulating path in an inert gas chamber. 19. A weighing machine for fine powder, a feeder for spontaneously filling the rubber mold with the fine powder, and a vibrating machine along a path for intermittently circulating a rubber mold having at least a side surface made of rubber and having a bottom. And / or a pusher and a jig for taking out the green compact from the rubber mold are sequentially arranged, and a compacting device for a green compact for sintering. 20. A rubber mold having at least a side surface made of rubber and a fine powder weighing machine, a feeder for spontaneously filling the rubber mold with the fine powder, and a vibration along a path for intermittently circulating the die of the die press machine. A compacting device for a compact for sintering, characterized in that a machine and / or a pusher, and a jig for taking out the compact from the rubber mold are sequentially arranged. 21. The compacting device for sintering green compacts according to claim 19 or 20, wherein the punch of the die press machine is fixedly arranged on the die press machine. 22. The compacting device for sintering green compacts according to claim 19, wherein the circulating transport path is provided in an inert gas chamber. 23. The material of at least one of the upper and lower sides of the rubber mold facing the upper and lower punches of the die press machine is harder than the rubber on the side of the die press machine facing the die. A rubber mold for fine powder molding. 24. The material of at least one of the upper and lower sides of the rubber mold facing the upper and lower punches of the die press machine is softer than the rubber on the side of the die side of the die press machine facing the die. A rubber mold for fine powder molding. 25. The thickness (t, unit: mm) of at least one of the upper lid and the bottom of the rubber mold is expressed by the formula: t ≦.
16 h / D (wherein h is the thickness of the green compact, and D is the positive square root of the cross-sectional area of the green compact). 26. A rubber mold for fine powder molding, wherein the green compact is a hollow body, and the rubber mold is provided with a mandrel made of a material harder than the rubber mold for forming a hollow portion. . 27. A rubber mold in which at least a side surface portion is made of rubber is a composite rubber mold in which the side facing the powder and the side facing the die are made of different materials, and A rubber mold for fine powder molding, characterized in that the material on the side to be treated is harder than the material on the side to face the die. 28. A rubber mold at least a side surface of which is made of rubber is a composite rubber mold in which the side facing the powder and the side facing the die are made of different materials, and A rubber mold for fine powder molding, characterized in that the material on the side to be treated has a smaller coefficient of friction than the material on the side facing the die. 29. The rubber mold for fine powder molding according to claim 23, wherein at least a side portion is divided into two or more pieces or has a cut surface. 30. A method for producing a sintered body, which comprises sintering the green compact molded by the method according to claim 1. Description: