JPH08155697A - Compact molding method - Google Patents

Abstract

PURPOSE: To mold compacts in various complicated shapes and to pull out a compact from a molding member without damaging the compact. CONSTITUTION: Powder and molding members U1-U5 are filled in the recessed part m1 of a rubber mold (m) attached to a die (d). Then, the powder is compressed which is filled in the recessed part of the rubber mold (m). A compact is obtained by detaching it from the molding members by melting at least a part of the molding member.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to powder or granules filled in a rubber mold attached to a die (hereinafter referred to as
Simply called "powder". ) Is compressed using the pressure applied by the punch and the elastic deformation of the rubber of the rubber mold to form a green compact. The green compact molded by such a method becomes various parts or products used in various industrial fields by sintering treatment, impregnation treatment, curing treatment, or the like.

[0002]

2. Description of the Related Art Conventionally, a rubber mold mounted on a die is filled with powder at a high density, and then, for example, by utilizing pressure applied by punches arranged opposite to each other and elastic deformation of rubber of the rubber mold. Compress the powder filled in the rubber mold,
There is known a powder compacting method in which a compression-molded powder compact is taken out from a rubber mold.

[0003]

In the above-described conventional green compact molding method, it is not possible to mold a green compact having a groove or a recess on the outer or inner circumference or a hollow compact. In addition, in the case of a thin green compact, there is a problem that the green compact will be broken when taken out from the rubber mold. The shape of the powder was limited.

The object of the present invention is to solve the problems of the conventional green compact forming method and to form a green compact having a complicated shape efficiently and highly accurately. It is to provide a molding method.

[0005]

In order to achieve the above-mentioned object, the present invention provides a method for forming a powder compact by a step of loading powder and a mold member into a concave portion of a rubber mold attached to a die. It comprises a step of compressing the powder charged in the concave portion of the mold and a step of separating the green compact and the mold member by melting at least a part of the mold member, and melting the entire mold member. In addition, the mold member is formed of a core mold member and a soluble layer disposed on the surface of the core mold member, and the soluble layer is removed by dissolution. It was done.

First, a prior application filed by the present applicant as an example to which the green compact forming method of the present invention is applied (for example, JP-A-4-363010, JP-A-6-207).
No. 205, etc.) is a vertical sectional view of a green compact forming apparatus similar to the green compact forming apparatus disclosed in FIG. 2, FIG. 3 is a vertical sectional view of a main part of the green compact forming apparatus, etc. 4 is a front view of a possible mold member and FIG. 5 is a vertical cross-sectional view of a green body into which the meltable mold member is incorporated, by way of example, on an inner surface as shown in FIG. An example of forming a nut-shaped green compact C1 having a thread groove c1 formed therein will be described.

M is a cylindrical die d (hereinafter, simply referred to as "die").
Say. ) And the lower punch p1 and the like inserted in the die d so that the upper surface is positioned lower than the upper surface d1 of the die d, and is formed by the lower punch p1 inserted in the die d and the die d. The recess (hereinafter, simply referred to as “die cavity”) 1 has a recess (hereinafter simply, “rubber cavity”) having a predetermined shape corresponding to the shape of the green compact to be molded.
Say. ) A rubber mold m in which m1 is arranged is mounted. In this embodiment, since the nut-shaped green compact C1 having a hexagonal planar shape is molded, the rubber cavity m
1 is formed in the hexagonal column-shaped space.

The lower punch p1 is placed on the auxiliary support plate 2 and fixed to the auxiliary support plate 2 with bolts 3, and the auxiliary support plate 2 to which the lower punch p1 is fixed.
Are bolts 5 on the index table or machine base 4,
It is fixed by 5 '. Reference numeral 6 denotes a backup ring made of hard rubber or the like having an inner hole 6a provided on the upper surface p1 'of the lower punch p1 and made of a die d and the lower punch p.
This is to prevent the rubber mold m from being caught in the gap between the rubber mold 1 and 1. A disc spring 7 is arranged between the lower surface d2 of the die d and the auxiliary support plate 2 so as to surround the lower punch p1. Instead of the disc spring 7, various spring members such as a coil spring, a rubber cushion using hard urethane rubber, and a fluid cylinder having a spring effect can be used.

P2 is an upper punch that can be moved up and down by a plunger or the like (not shown).
Is placed on the upper surface d1 of the die d, and is formed larger than the planar shape of the die cavity 1 so as to cover the die cavity 1. Reference numeral 8 denotes a ring-shaped backup ring made of hard rubber or the like, which is attached to the periphery of a recess 9 having a circular planar shape provided on the lower surface p2 ′ of the upper punch p2,
The backup ring 8 is arranged so as to be flush with the lower surface p2 ′ of the upper punch p2 and also to cover the contact line 10 between the die d and the rubber mold m mounted on the die. The rubber member 11 is provided inside the ring 8 so as to be substantially flush with the lower surface p2 ′ of the upper punch p2.
Is attached.

As shown in FIG. 4, U1 is a thread groove c formed on the outer periphery of the inner surface of a nut-shaped green compact C1.
1 is a mold member having a screw thread u1 corresponding to 1 and a fitting part u2 fitted into the inner hole 6a of the backup ring 6 and a hole m3 formed in the bottom m2 of the rubber mold m. U1 is formed of a wax or a synthetic resin that can be melted at a predetermined temperature, a metal or glass having a low melting point, a synthetic resin that is melted by a predetermined solvent, or a substance that sublimes at a temperature higher than room temperature (hereinafter, this A mold member formed of such a material is referred to as a "dissolvable mold member" or simply "mold member"). As substances that sublime at temperatures higher than room temperature, camphor, naphthalene, etc. are known, and a mold member is made of a material containing polyacetal resin, and a fuming nitric acid is formed after molding a green compact. It is also possible to decompose the polyacetal resin of the mold member by contacting the mold member with the nitrogen dioxide gas generated by utilizing it at a high temperature. Note that such a substance is also referred to as a meltable mold member or simply a mold member.

The meltable mold member U1 is formed by fitting the fitting portion u2 of the mold member U1 into the hole m3 formed in the bottom m2 of the rubber mold m and the inner hole 6a of the backup ring 6. The mold member U1 is arranged in the rubber cavity m1 such that the upper surface u3 of the mold member U1 is equal to or slightly higher than the height of the filled powder. . In this embodiment, since the powder is filled up to the upper surface d1 of the die d and the upper surface m4 of the rubber mold m, the upper surface u3 of the mold member U1 is the upper surface d of the die d as shown in FIG.
1 and the upper surface m4 of the rubber mold m or the die d
The upper surface d1 and the upper surface m4 of the rubber mold m are arranged so as to slightly project.

When compressing the powder densely packed in the rubber cavity m1 of the rubber mold m, first, the upper punch p2 is lowered and the upper punch p2 is placed on the upper surface d1 of the die d. . Next, when the upper punch p2 is further lowered, the die d is lowered together with the upper punch p2 against the disc spring 7 arranged between the die d and the auxiliary support plate 2. In this way, the upper punch p2 and the die d descend, but the lower punch p1 fixed to the index table or the machine base 4 via the auxiliary support plate 2 does not move, so that the die d, the lower punch p1, and the upper punch p2. A space in which the rubber mold m formed by
That is, the depth of the die cavity 1 becomes shallower. Therefore, the die cavity 1 of the rubber mold m mounted in the die cavity 1 contracts inward, and the powder densely packed in the rubber cavity m1 is compressed and compressed. The powder will be molded.

Next, the green compact molding method of the present invention for molding the nut-shaped green compact C1 using the above-described green compact molding apparatus will be described.

First, as described above, the fitting portion u2 of the mold member U1 which can be dissolved is set to the bottom portion m2 of the rubber mold m.
Hole m3 bored in the hole and the inner hole 6 of the backup ring 6
The mold member U1 is arranged in the rubber cavity m1 by fitting it into a. Next, the rubber mold m and the mold member U
The powder is densely packed in the gap v1 formed between the powder and the powder. After that, the upper punch p2 is lowered, and the upper punch p2 is placed on the upper surface d1 of the die d as shown in FIG. Next, when the upper punch p2 is further lowered, the upper punch p2 is lowered together with the die d against the disc spring 7. However, as described above, the lower punch p1 does not move, so that the depth of the die cavity 1 is reduced. Becomes shallower, and the rubber cavity m1 of the rubber mold m mounted in the die cavity 1 contracts inward, so that the powder filled in the gap v1 formed between the rubber mold m and the mold member U1 is It will be compressed.

Although the depth of the die cavity 1 becomes shallower as the upper punch p2 and the die d are lowered, such a change in the depth of the die cavity 1 is reflected on the lower surface p2 'of the upper punch p2. It is absorbed by the compressive deformation of the attached rubber member 11. In other words, in the compression process of the powder filled in the rubber mold m by the lower punch p1 and the upper punch p2, the relative movement of the mold member U1 with respect to the upper punch p2 and the die d is caused by the compression deformation of the rubber member 11. Will be absorbed.

After compression molding of the powder filled in the gap v1 between the rubber mold m and the meltable mold member U1 by the lower punch p1 and the upper punch p2, the upper punch p2 is moved upward, and then, as shown in FIG. As shown in FIG. 5, the powder compact C1 incorporating the mold member U1 is taken out from the rubber cavity m1 of the rubber mold m by an appropriate means such as a vacuum suction machine (not shown). Thereafter, by heating to a predetermined temperature to melt and remove the mold member U1, or by melting and removing the mold member U1 with a suitable solvent, and further sublimating and removing the mold member U1.
A nut-shaped green compact C1 as shown in FIG.

Next, as shown in FIG. 6, in the case of molding a powder compact C2 in which disk-shaped flanges c3, c4 are provided at both ends of a cylindrical portion c2, the powder compact molding is carried out. 7, FIG. 8, FIG. 10 and FIG. 11 which are vertical cross-sectional views of main parts of the apparatus and the like, FIG. 9 which is a perspective view of the meltable mold member U2 and vertical of the powder compact in which the meltable mold member is incorporated. This will be described with reference to FIG. 12, which is a sectional view.

First of all, as shown in FIG.
A rubber mold m having a cylindrical space portion as the rubber cavity m1 is attached to the die cavity 1, and then the rubber cavity m1 of the rubber mold m is densely filled with powder to a predetermined height. The height of the powder filled to this predetermined height corresponds to the thickness of the flange c4 of the green compact C2 to be molded.

Next, as shown in FIG. 9, an inner diameter corresponding to the diameter of the cylindrical portion c2 of the green compact C2 to be molded, an outer diameter corresponding to the inner diameter of the rubber cavity m1, and the green compact C2.
As shown in FIG. 8, a cylindrical meltable mold member U2 having a height corresponding to the height of the cylindrical portion c2 of the above is placed on the powder filled to a predetermined height. Then
As shown in FIG. 10, the inside of the meltable mold member U2 and the upper part of the mold member U2 are densely filled with powder up to the upper surface d1 of the die d and the upper surface m4 of the rubber mold m.

After that, the upper punch p2 is moved down to the position shown in FIG.
As shown in FIG. 1, the upper punch p2 is placed on the upper surface d1 of the die d. Next, when the upper punch p2 is further lowered, the upper punch p2 is lowered together with the die d against the disc spring 7, but as described above, the lower punch p1 does not move. Of the rubber mold m
The powder filled in the rubber cavity m1 is compressed.

After compression molding of the powder filled in the rubber mold m by the lower punch p1 and the upper punch p2, the upper punch p
2 is moved upwards and then, as shown in FIG. 12, a green compact C2 incorporating a meltable mold member U2.
Is removed from the rubber mold m and then heated to a predetermined temperature to melt and remove the mold member U2, or by melting and removing the mold member U2 with an appropriate solvent to further sublimate and remove the mold member U2. By doing
A green compact C2 as shown in FIG. 6 is molded.

As described above, the powder is densely packed in the rubber cavity m1 of the rubber mold m together with the meltable mold members U1 and U2 having appropriate shapes, and then the lower punch p1 inserted into the die d is formed. Between the upper punch p2 facing the lower punch p1, powder is filled and the rubber mold m in which the mold member is arranged is compressed to be meltable.
1, U2 are incorporated into the green compacts C1 and C2, and then the green compacts C1 and C2 in which the meltable mold members U1 and U2 are incorporated are taken out from the rubber mold m, and then,
By melting and removing the mold members U1, U2 by heating to a predetermined temperature, or by melting and removing the mold members U1, U2 with a suitable solvent, and further by sublimating and removing the mold members U1, U2. It is possible to mold green compacts of various shapes.

Next, FIG. 14 and FIG. 15 are vertical cross-sectional views of the main parts of the green compact molding device and the like in the case of molding a thin cylindrical green compact C3 as shown in FIG. And FIG. 16 which is a vertical sectional view of the green compact C3 in which the mold member U3 which can be dissolved is incorporated will be described.

First, a meltable cylindrical mold member U
The die member U3 is arranged in the rubber cavity m1 by fitting the lower end portion of 3 into the hole m3 formed in the bottom portion m2 of the rubber mold m and the inner hole 6a of the backup ring 6. Next, as shown in FIG. 14, powder is densely filled in the gap v2 formed between the rubber mold m and the mold member U3. Then, lower the upper punch p2,
As shown in FIG. 15, the upper punch p2 is placed on the upper surface d1 of the die d. Next, when the upper punch p2 is further lowered, the upper punch p2 is lowered together with the die d, but as described above, the lower punch p1 does not move,
The die cavity 1 becomes shallower and the die cavity 1
Rubber cavity m1 of the rubber mold m mounted on the
Contract inward, so that the rubber mold m and the mold member U3
The powder filled in the gap v2 formed between and is compressed.

Although the depth of the die cavity 1 becomes shallower as the upper punch p2 and the die d are lowered, such a change in the depth of the die cavity 1 is reflected on the lower surface p2 'of the upper punch p2. It is absorbed by the compressive deformation of the attached rubber member 11. In other words, the relative movement of the die member U3 with respect to the upper punch p2 and the die d in the compression process of the powder filled in the rubber mold m by the lower punch p1 and the upper punch p2 is caused by the compression deformation of the rubber member 11. Will be absorbed.

After compressing the powder filled in the gap v2 between the rubber mold m and the meltable mold member U3 by the lower punch p1 and the upper punch p2, the upper punch p2 is moved upward, and then FIG. The thin-walled cylindrical green compact C3 in which the mold member U3 as shown in (3) is incorporated is taken out from the rubber mold m. Then, the mold member U is heated to a predetermined temperature.
3 by melting or removing the mold member U3 by melting and removing the mold member U3 with a suitable solvent.
By sublimating and removing 3, the thin cylindrical green compact C3 as shown in FIG. 13 is molded.

As described above, the green compact C3 is attached to the mold member U.
It is possible to prevent the green compact C3 from being broken by taking it out from the rubber mold m with the green compact 3 still incorporated, and in the subsequent melting and removing process of the mold member U3, the green compact C3 is removed.
In addition, since an external force that damages the green compact C3 is not applied, it is possible to mold the green compact C3 without damage such as chipping or cracking. Such a green compact forming method is particularly suitable for forming a green compact that is easily damaged, and can easily form a green compact that is easily damaged with high yield.

Next, as shown in FIG. 17, a green compact having a truncated cone space c5 inside the truncated cone (hereinafter, simply referred to as "trumpet-like green compact"). C4
18 is a vertical cross-sectional view of a main part of a green compact molding device and the like, and FIG. 19 is a vertical cross-sectional view of a green compact C4 in which a partially meltable mold member is incorporated. To do.

First, a rubber mold m in which an inverted truncated cone-shaped space is formed as the rubber cavity m1 is mounted in the die cavity 1. Then, a wax or synthetic resin that can be melted at a predetermined temperature or a synthetic resin that melts at a predetermined temperature is formed around a core-shaped member u4 having a shape of an inverted truncated cone that is made of a hard synthetic resin or metal that does not dissolve by heat or a solvent. A mold member U4 having a soluble layer u5 formed of a resin or a sublimable substance is prepared, and a protrusion u6 protruding from the lower surface of the core mold member u4 of the mold member U4 is attached to the bottom of the rubber mold m. The mold member U4 is arranged in the rubber cavity m1 by fitting in the recess m5 provided in m2.
The mold member U4 is arranged in the rubber cavity m1 such that the upper surface u7 of the mold member U4 arranged in the rubber cavity m1 is equal to or slightly higher than the height of the powder filled in the rubber cavity m1. To be done. In this embodiment, since the powder is filled up to the upper surface d1 of the die d and the upper surface m4 of the rubber mold m, the upper surface u7 of the mold member U4 is the upper surface d of the die d as shown in FIG.
1 and the upper surface m4 of the rubber mold m or the die d
The upper surface d1 and the upper surface m4 of the rubber mold m are arranged so as to slightly project.

Then, the gap v3 formed between the rubber mold m and the mold member U4 is densely filled with powder up to the upper surface d1 of the die d and the upper surface m4 of the rubber mold m. After that, as described above, the upper punch p2 is lowered to compress the powder filled in the gap v3 formed between the rubber mold m and the mold member U4 to form the green compact C4. Further, as described above, in the compression process of the powder filled in the rubber mold m by the lower punch p1 and the upper punch p2, the relative movement of the die member U4 with respect to the upper punch p2 and the die d is caused by the rubber member 11 and Mold member U4 and lower punch p
It is absorbed by the compressive deformation of the rubber mold m located between the upper surface p1 'and the upper surface p1'.

After the powder filled in the gap v3 between the rubber mold m and the above-mentioned mold member U4 is compressed by the lower punch p1 and the upper punch p2, the upper punch p2 is moved upward, and then FIG. The trumpet-shaped green compact C4 in which the mold member U4 as shown in (1) is incorporated is taken out from the rubber mold m. After that, by heating to a predetermined temperature to melt and remove the soluble layer u5 of the mold member U4 or by melting and removing the soluble layer u5 with a suitable solvent, the soluble layer u5 is further sublimated. By removing the powder compact C4 from the mold member U4, a gap is formed between the powder compact C4 and the core mold member u4 of the mold member U4, and the powder compact C4 is extracted from the mold member U4.

The mold member U4 is composed of a core mold member u4 which is insoluble by heat or solvent and a layer u5 which is soluble by heat, solvent or the like, and a green compact C4 incorporating the mold member U4 is formed into a mold member U4. When removing from the mold, only the dissolvable layer u5 needs to be dissolved and removed, so that the green compact C4 can be extracted from the mold member U4 in a short time.

Next, in the case of molding a rectangular parallelepiped green compact C5 having a hollow inside c6 as shown in FIG. 20, it is a vertical cross-sectional view of an essential part of a green compact molding apparatus or the like. 21.

First, a rubber mold m having a rectangular parallelepiped space as the rubber cavity m1 is mounted in the die cavity 1, and then the rubber cavity m1 of the rubber mold m is densely filled with powder to a predetermined height. . The height of the powder filled to this predetermined height corresponds to the wall thickness of the green compact C5 to be molded. Then, a meltable mold member U5 having substantially the same rectangular parallelepiped shape as the cavity of the inside c6 of the green compact C5.
Is placed on top of the powder that has been filled to a predetermined height. After that, as shown in FIG. 21, powder is densely packed around the meltable mold member U5 up to the upper surface d1 of the die d and the upper surface m4 of the rubber mold m, and after the powder is filled, the above-described process is performed. Thus, the upper punch p2 is lowered to compress the powder filled in the rubber cavity m1 of the rubber mold m.

After the powder filled in the rubber mold m is compressed by the lower punch p1 and the upper punch p2, the upper punch p2 is moved upward, and thereafter, the mold member U5 which can be melted inside is formed.
The green compact C5 provided with is taken out from the rubber mold m. Next, after forming a through hole of an appropriate size in the green compact C5 in which the meltable mold member U5 is disposed, it is heated to a predetermined temperature to melt the mold member U5, and the through hole is formed. By discharging the melted mold member U5 from the above, or by melting the mold member U5 with a suitable solvent and discharging the melted mold member U5 from the through hole, the inside c6 as shown in FIG. A rectangular parallelepiped green compact C5 is molded. The holes formed in the green compact C5 for discharging the molten mold member U5 can be formed by forming needle-like protrusions or rod-like protrusions on the upper surface of the mold member U5. Of course, if the green compact C5 can penetrate the molten mold member U5, it is not necessary to form such a hole. If the mold member U5 is made of a sublimable substance, the holes formed in the green compact C5 may be small needle-shaped holes, and it is necessary to form holes. Nor.

By the method as described above, it is possible to easily and accurately mold a powder compact having a hollow inside, which has been difficult to mold in the past.

As described above, the rubber mold m is filled with the powder at a high density together with the mold members U1 to U5 having an appropriate shape. If the amount of the powder filled in is too small and the powder is not sufficiently filled, shape distortion called elephant foot deformation, cracking, chipping and the like are likely to occur in the green compact. In order to prevent the shape distortion, cracking, and chipping of the green compact, the volume of the portion of the above-described upper punch p2 and the lower punch p1 filled with the powder before compression and the upper punch p1.
It is necessary to minimize the difference in volume of the green compact other than the volumes of the mold members U1 to U5 after being compressed by 2 and the lower punch p1.

Means for filling the powder into the rubber mold with high density include the following means other than pressing the powder with a pusher. (1) By spheroidizing the powder and adjusting the particle size distribution, the powder can be packed in the rubber mold at a high density even by allowing the powder to fall naturally. Even in such a case, by applying vibration or tapping during or after the filling, the powder is further filled at a high density, and the filling is made uniform, which enables more suitable molding of the green compact. Become. (2) By degassing and compressing the powder in advance, it is possible to pack the powder at a much higher density than in a fluffy state in which the powder is filled with air. Deaeration compaction is performed by lightly compressing the powder while removing air from the pump. By using the powder deaerated and compressed in this way (which is in a granular form to some extent), depending on the material of the powder (for example, Ti powder), the powder can be packed into the rubber mold at a high density even by only free fall. can do.

In the above-described embodiment, the nut-shaped powder compact C1, the powder compact C2 in which the disk-shaped flanges c3 and c4 are provided at both ends of the columnar part c2, and the thin-walled cylindrical powder compact C2. The case where the green compact C3, the trumpet-shaped green compact C4, and the rectangular parallelepiped green compact C5 in which the inside c6 is hollow is molded has been described. By appropriately changing the shape, not only the green compacts C1 to C5, but also green compacts having various shapes can be formed.

In the above-mentioned embodiment, when powder is compression-molded by using the meltable mold member, the mold member is also compressed, and the mold member is deformed by the compression so that the pressure is removed, that is, the unloading is performed. At this time, the mold member elastically returns to its original shape, but at this time, the compression-molded green compact may be broken. Therefore, as the material of the mold member, the following two types are preferable. (1) A hard material that is not substantially deformed by compression, (2)
A material that deforms when compressed but does not elastically recover when unloaded. For example, the material of type (1) above is used as the material of the mold member U3 shown in FIG. 14 described above, and the material of type (2) above is shown in FIG. It is used as a material for the mold member U2. Furthermore, when a soft material such as wax is used as the mold member, it is possible to increase the hardness by mixing powder of alumina, iron or the like into the wax, such as in a thin cylinder as shown in FIG. It is effective for molding.

In the above-described embodiment, the rubber mold m mounted in the die cavity 1 and filled with the powder at a high density is placed between the lower punch p1 inserted in the die d and the upper punch p2 which moves up and down. In the example shown in Fig. 1, the upper punch p2 is placed on the rubber mold m, and then the lower punch p1 is moved upward so that the rubber mold m filled with the powder at a high density is formed. It can also be compressed. Further, the die d may be formed as a bottomed cylinder to omit the lower punch p1. In this case, the rubber mold m densely filled with the powder has a bottomed die d and an upper punch p.
It will be compressed between 2 and.

In the following, a nut-shaped green compact C1 as shown in FIG. 1 and a thin-walled cylindrical green compact C3 as shown in FIG. 13 are molded and then sintered to form a nut. A more specific example of manufacturing a thin cylinder will be described.

[First Embodiment] A case will be described in which the nut shown in FIG. 1 is molded in the order as described with reference to FIGS. The powder used was pure titanium (Ti) powder having an average particle size of 12.5 μm.

The mold member U1 shown in FIG. 4 has a melting point of 8
Microcrystalline wax with a penetration of 8 at 9 ° C and 25 ° C, and stainless steel with an average particle size of 60 μm (SUS
-316) The material was prepared by injection molding using a material to which 15% by volume of powder was added.

The rubber mold m has a hardness of 30 (JIS
The silicone rubber of A) was used. The die d, the lower punch p1, and the upper punch p2 are made of stainless steel (SUS-30
4) was used, and the coned disc spring 7 was made of hardened steel.

The molding order of the green compact is as follows. (1) The fitting portion u2 of the mold member U1 is fitted into the hole m3 of the rubber mold m and the inner hole 6a of the backup ring 6, and the mold member U1 is arranged in the rubber cavity m1 of the rubber mold m. (2) A cylindrical guide (not shown) is placed on the upper surface d1 of the die d, the gap v1 formed between the rubber mold m and the mold member U1 is filled with the above-mentioned powder, and then,
Die set M including die d, lower punch p1, upper punch p2, etc.
The cylindrical guide was vibrated to fill the gap v1 with the powder at a high density, and the powder was densely packed with a pusher (not shown) so as to be flush with the upper surface m4 of the rubber mold m. (3) After removing the guides and pushers, the upper punch p2 is lowered to place the upper punch p2 on the upper surface d1 of the die d, and then the upper punch p2 is further lowered to compress the powder with a molding pressure of 6t. Molded. (4) The upper punch p2 is raised to remove the upper punch p2. (5) The green compact C1 incorporating the mold member U1 as shown in FIG. 5 was taken out from the rubber mold m using a vacuum suction pad (not shown). (6) Using the suction type cleaner, the rubber cavity m1 and the hole m3 of the rubber mold m are cleaned, and another mold member U1 is again used.
The fitting portion u2 was fitted into the hole m3 of the rubber mold m and the inner hole 6a of the backup ring 6, and the green compact was molded in the order described above.

The order of (1) to (6) was repeated 100 times to form a green compact. After molding, no cracks or chips were found.

Next, the mold member U as shown in FIG.
The powder compact C1 integrated with 1 is fitted to the fitting part u of the mold member U1.
The fitting part u2 of the mold member U1 was placed on a table having a through hole into which the No. 2 could be inserted so that the fitting part u2 was inserted into the through hole, and then placed in an electric furnace. The temperature of the electric furnace was raised to 100 ° C. The mold member U1 melted down from the through holes of the base when the temperature reached 90 ° C. during the temperature rise.

Next, the green compact C1 in which the mold member U1 has melted down
Was placed in a vacuum sintering furnace. The wax and metal powder that had melted down were reused. The powder compact C1 is vacuumed at 1150 °
Sintering was performed at C for 2 hours. As a result, average density 4.50
A titanium nut of g / cm ³ was made. As a result of using this nut as it was (without machining), the quality was equivalent to the nut made by machining.

As a comparative example, as the material of the mold member U1,
Rubber material and metal (made of brass) of the same material as the rubber mold m
Using, the mold member U1 was made to have the same size as that of the example, and was molded using the above-described green compact molding device. As a result, when a rubber material was used as the mold member U1, all the green compacts were broken. When a metal was used as the mold member U1, there was no cracking or chipping of the powder compact, but the threaded parts of the mold member U1 and the powder compact did not come off, and only the powder compact could not be taken out. , Could not make a product.

As a result of the above, it was confirmed that nuts made of pure titanium can be produced by the embodiment of the present invention.

Conventionally, titanium nuts have been produced by cutting. However, the following nuts are used for cutting.
There was a problem like (4). (1) Titanium alloy has a tensile strength of 100 kgf / m
Since it has m ² or more, a large force is applied to the cutting edge of the tool, the cutting edge is chipped (chipping), and the tool is easily worn. (2) Titanium material has a very low thermal conductivity (similar to stainless steel, which makes it difficult to cut stainless steel), and the heat generated during cutting is difficult to escape and accumulates in tools and workpieces. Then, the heat increases the wear of the tool. (3) Titanium materials have a small Young's modulus (also called longitudinal elastic modulus) that indicates the magnitude of strain when a force is applied (1/2 of steel). It transforms about 2 times. For this reason, a thin processed product may have poor processing accuracy or chatter. (4) When cutting under conditions where a tool that is heavily worn or thin chips are produced, the chips may burn. Titanium material is chemically very active and therefore prone to tool wear. When the cutting speed is increased, a large amount of cutting heat is generated, and the temperature at which the cutting is being performed is increased, which further activates the tool, and the tool is easily worn.

In the embodiment of the present invention, since the titanium nut can be produced regardless of the cutting work, the above-mentioned problematic cutting work can be omitted, and the titanium nut can be mass-produced inexpensively.

Also, a green compact is manufactured by a metal mold forming method to a shape close to a finished product of a titanium nut, and thereafter, a screw hole portion of an inner peripheral portion of a sintered product close to the finished product is cut or forged. Then, a method of manufacturing a titanium nut is known. However, in order to obtain a product having a high density as in the embodiment of the present invention, it is necessary to use fine titanium powder having an average particle size of 20 μm or less. The titanium material is chemically active, and fine titanium powder having a particle size of 20 μm or less is easily welded to the mold and galling easily occurs. In order to prevent galling of the mold, the particle size of the powder should be about 60 μm. When such a large powder of about 60 μm is used, the density of the sintered body after sintering does not increase and 4.1 ±
Only a sintered body having a density of about 0.1 g / cm ³ can be obtained.
When the density is such a low value, sufficient strength cannot be obtained and it cannot be used as a nut. The green compact molding method according to the present invention can produce a high-density, high-strength titanium nut, which has not been obtained conventionally, without post-processing such as grinding or forging.

[Embodiment 2] A case where a thin cylinder as shown in FIG. 13 is molded in the order as described with reference to FIGS. 14 to 16 will be described. The powder used was molybdenum powder having an average particle size of 3 μm.

The cylindrical mold member U3 shown in FIG.
Is a paraffin wax having a melting point of 69 ° C., a penetration of 15 at 25 ° C. and an average molecular weight of 472, and an average particle size of 12 μm.
12% by volume of aluminum powder was added as a material, and injection molding was performed.

The rubber mold m has a hardness of 10 (JIS
The silicone rubber of A) was used. High-strength steel was used for the die d, lower punch p1, and upper punch p2, and spring steel was used for the disc spring 7.

The molding order of the green compact is as follows. (1) The mold member U3 is placed in the rubber cavity m1 of the rubber mold m by fitting the mold member U3 into the hole m3 of the rubber mold m and the inner hole 6a of the backup ring 6. (2) The above-mentioned molybdenum powder was densely filled in the gap v2 formed between the rubber mold m and the mold member U3. (3) Lower the upper punch p2 to lower the upper punch p2 to the die d
Was placed on the upper surface d1 of the above, then the upper punch p2 was further lowered, and the powder was compression-molded at a maximum molding pressure of 20 t. (4) The upper punch p2 is raised to remove the upper punch p2. (5) The green compact C3 incorporating the mold member U3 as shown in FIG. 16 was taken out from the rubber mold m using a vacuum suction pad (not shown). (6) Using a suction type cleaner, the rubber cavity m1 and the hole m3 of the rubber mold m are cleaned, and another mold member U3 is again used.
Was fitted into the hole m3 of the rubber mold m and the inner hole 6a of the backup ring 6, and the green compact was molded in the order described above. (7) The green compact C3 incorporating the mold member U3 was placed in a vacuum sintering furnace and heated to 100 ° C.
Melted down. Next, sintering was performed in hydrogen gas at 1600 ° C. for 2 hours.

The steps (1) to (7) were repeated many times. As a result, average density of 1 with no cracks or chips
A thin walled cylinder of 0.2 g / cm ³ of sintered molybdenum was produced.

As a comparative example, the mold member U3 was formed of metal (made of brass), and a molding test was conducted in the same order as in the above (1) to (7). As a result, cracks and chips were found in the sintered body. Many were seen. These cracks and chips were generated when the mold member U3 (made of brass) and the green compact C3 were separated after molding.

When a material composed of wax and aluminum powder is used as the mold member U3 according to the embodiment of the present invention, the powder compact C3 and the mold member U3 are separated by melting the mold member U3. Since it was carried out without applying any strain or external force to C3, cracking or chipping did not occur in the green compact C3. It has been found that when the mold member U3 of the comparative example is a metal, distortion and an external force are applied to the green compact C3 when the mold member U3 and the green compact C3 are separated, and many molding defects occur.

[0062]

Since the present invention is configured as described above, it has the following effects.

Since the mold member or a part of the mold member is dissolved and removed after molding the powder compact having the mold member incorporated therein, it is possible to mold the powder compact having various shapes having a complicated shape. In addition, the green compact can be extracted from the mold member without damaging the green compact.

[Brief description of drawings]

FIG. 1 is a perspective view of a green compact as an example formed by a green compact forming method of the present invention.

FIG. 2 is a vertical cross-sectional view of a green compact molding apparatus or the like as an example to which the green compact molding method of the present invention is applied.

FIG. 3 is a vertical sectional view of a main part of the green compact molding apparatus and the like shown in FIG.

FIG. 4 is a front view of an exemplary meltable mold member.

FIG. 5 is a vertical cross-sectional view of a green compact with a mold member incorporated therein.

FIG. 6 is a perspective view of another example of a green compact molded by the green compact molding method of the present invention.

FIG. 7 is a vertical cross-sectional view of a main part of a green compact molding device and the like.

FIG. 8 is a vertical cross-sectional view of an essential part of a green compact molding apparatus and the like similar to FIG.

FIG. 9 is a perspective view of an example meltable mold member.

FIG. 10 is a vertical cross-sectional view of a main part of a green compact molding apparatus and the like similar to FIG.

11 is a vertical cross-sectional view of a main part of a green compact molding apparatus and the like similar to FIG. 7.

FIG. 12 is a vertical cross-sectional view of a green compact with a mold member incorporated therein.

FIG. 13 is a perspective view of a powder compact as still another example molded by the powder compact molding method of the present invention.

FIG. 14 is a vertical cross-sectional view of a main part of a green compact molding device and the like.

FIG. 15 is a vertical cross-sectional view of an essential part of a green compact molding apparatus or the like similar to FIG.

FIG. 16 is a vertical cross-sectional view of a green compact with a mold member incorporated therein.

FIG. 17 is a perspective view of a powder compact as still another example molded by the powder compact molding method of the present invention.

FIG. 18 is a vertical cross-sectional view of essential parts of a powder compacting device and the like.

FIG. 19 is a vertical cross-sectional view of a green compact with a mold member incorporated therein.

FIG. 20 is a perspective view of a powder compact as still another example molded by the powder compact molding method of the present invention.

FIG. 21 is a vertical cross-sectional view of essential parts of a powder compacting device and the like.

[Explanation of symbols]

 C1 to C5 ··· Powder compact U1 to U5 ··· Mold member d ····· Die m ····· Rubber mold m1 ···・ ・ ・ Rubber cavity p1 ・ ・ ・ ・ ・ ・ Upper punch p2 ・ ・ ・ ・ ・ ・ Lower punch 1 ・ ・ ・ ・ ・ ・ ・ Die cavity 6,8 ・ ・ ・ ・Ring 7 ... Belleville spring 11 ... Rubber member

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Toshihiro Watanabe 1 Erie Part 2 No. 401, Intermetalix Co., Ltd. 22-22 Matsumuro Ouegami-cho, Nishikyo-ku, Kyoto City, Kyoto Prefecture

Claims (3)

[Claims] 1. A method of loading powder and a mold member into a recess of a rubber mold mounted on a die, compressing the powder loaded in the recess of the rubber mold, and melting at least a part of the mold member. A method for molding a green compact, comprising a step of separating the green compact and the mold member. 2. The green compact molding method according to claim 1, wherein the entire mold member is dissolved and removed. 3. The mold member is formed of a core member and a meltable layer disposed on the surface of the core member, and the meltable layer is dissolved and removed. The green compact molding method according to.