JPH10296499A - Press forming method of green compact and press forming die - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a press molding method for molding a green compact having a chamfered portion on an inner peripheral surface or an outer surface from a powder and a press die used for the same, wherein a step or a step is provided in the chamfered portion. Provided are a molding method that is not formed and a mold therefor. SOLUTION: In a method of press-forming a hollow green compact having a chamfered portion on an inner peripheral surface, a method for press-forming a die is provided between an inner surface of a through hole of a die, an end surface of a pair of upper and lower outer punches in the through hole, The filling powder surrounded by the upper and lower outer punches having a pair of upper and lower inner punches having a tapered chamfered molding surface having a tapered end face is pressed between the upper and lower outer punches to form a green compact. I do.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a press forming method for forming a green compact having a chamfered portion on an inner peripheral surface or an outer surface and a press die used for the method. The present invention relates to a molding method that is not formed and a mold thereof.

[0002]

2. Description of the Related Art In the process of manufacturing a ceramic sintered product or a sintered alloy product using ceramic or metal powder as a starting material, a green compact is formed into a desired shape by a compression molding method using a press before sintering. Depending on the shape of the sintered product or the like, the green compact may be formed in a ring shape with a chamfer at the corner on the inner peripheral surface side of the end, or in a cylindrical or disk shape. There is one in which a chamfered portion is formed at an outer corner.

[0003] As described above, when a green compact is compression-molded in a mold from a powder, a chamfered portion is simultaneously formed on the inner peripheral surface side or the outer surface side of the peripheral body. In the conventional method for forming a ring-shaped green compact, as shown in FIG. 8A, hollow punches 4 and 5 are inserted into a die 1 having a through hole 11 from above and below. The core rod 6 is inserted through the hollow portion of the die 5 to form a mold, and the powder filled between the upper and lower punches 4 and 5 in the die 1 is compressed by the pressing force between the upper and lower punches. The method of compacting to 9 was used. The end faces of the upper and lower punches 4 and 5 have tapered surfaces 46 protruding toward the core rod 6 at the center of the end faces so as to correspond to the end face 92 of the green compact and the shape of the chamfer 94 adjacent to the end face. , 56 are formed, and the green compact 9 compressed by the upper and lower punches has a ring shape having a hollow portion 95 formed by the core rod 6 as shown in FIG. Inner peripheral surface 9
On the third side, the chamfered portions 9 corresponding to the tapered surfaces 46 and 56 are provided.
4, 94 are shaped.

On the other hand, in the case of a green compact having a chamfer on the outside of the peripheral body, as shown in FIG. A flat surface 40 having a flat central portion at one of the end surfaces of the punches 4 and 5 of FIG.
9A is formed on the green compact formed by pressing the powder between the upper and lower punches 4 and 5 at the periphery of the end surface 97 of the peripheral body. As shown in (), a chamfered portion 94 by the tapered surface 46 is formed.

As another method, as shown in FIGS. 9C and 9D, a narrowed portion having a tapered surface 14 on the inner surface of the through hole 11 of the die having a hollow portion is formed. End faces 40 of upper and lower punches 4 and 5 having different outer diameters at the upper and lower sides.
A mold is used that can be arranged so that 50 faces each other across the tapered surface 14 of the narrowed portion. By filling and compressing the powder between the upper and lower punches 4, 5, the chamfered portion 9 is formed by the narrowed portion.
No. 4 is a method for forming a shaped green compact 9.

[0006]

Basically, these compacting methods have an advantage that the compact can be easily formed by a mold composed of a die, upper and lower punches and a core rod.

However, these conventional methods for forming a green compact have a problem that a step, that is, a step 941, is necessarily formed in a chamfered portion of the formed green compact. As shown in FIG. 8B, the green compact 9 having the chamfered portion on the inner peripheral surface of the ring has a step 941 perpendicular to the inner peripheral surface between the chamfered portion 94 and the inner peripheral surface 93. Is done. This is because the tapered surfaces 46 and 56 projecting toward the inside of the end surfaces of the upper and lower punches 4 and 5 have flat ends 46 and 56.
1,561, it is preferable that the protruding end is formed at an acute angle. However, since the formed protruding end is likely to be broken during the compression operation, the strength and life of the punch end surface are ensured. In view of the above, the protruding ends of the tapered surfaces 46 and 56 need to be flat end surfaces 461 and 561 with their tips cut off, and the shape of the end surface of the punch may cause the step 941 to be formed on the green compact 9. Had become.

To solve this problem, as shown in FIG. 8C, a tapered narrowed portion is formed in the middle of a core rod for forming a hollow portion of the green compact, and the narrowed portion of the narrowed portion is formed. Tapered surface 66
There is also a method of eliminating the step by forming the chamfered portion 94 of the green compact in the above, but in this case, the problem that the step 941 is still formed in the other chamfered portion of the green compact remains. Was.

[0009] Similarly, in the case of a green compact having a chamfered portion on the outer surface side, the method shown in FIG. The target strength is weak, and there is a risk of breakage in the press forming process, which causes a reduction in the life of the mold.Therefore, it is necessary to set the obtuse angle. Steps are formed.

Further, in the conventional method shown in FIG.
If the narrowed part of the through hole of the die is narrow, a gap may occur between the lower punch and the narrowed part of the through hole due to factors such as adjustment accuracy of the press and wear, or the lower punch and the narrowed part may be formed due to biting of powder. 9D, it is difficult to adjust the gap between the end face 97 and the chamfered portion 94 of the green compact 9, and a step 942 perpendicular to the end face may occur as shown in FIG. 9D.

When a step is formed in the chamfered portion of the sintered product after firing, for example, a ceramic ring fired in a sectional shape as shown in FIG. In a wire guide ring used for passing through, there is a fear that the wire may be broken at the corner of the step or wear may be accelerated. Furthermore, in an application in which a shaft member is inserted into the hollow portion of the ring, for example, the step 941 of the chamfered portion hinders the insertion of the member. Therefore, it is necessary to make corrections such as polishing the steps to make them smooth. However, the steps of the green compacts are brittle and cannot be polished. In addition, the number of man-hours in the sintering process increased, which affected productivity.

In view of the above problems, the present invention first provides a method for press-molding a green compact having a chamfered portion on the inner peripheral surface side, in which no step is attached to the chamfered portion. It is the purpose. Also, the present invention
An object of the present invention is to provide a press die for press-molding a green compact in which no step is attached to a chamfered portion provided on the inner peripheral surface side of the green compact.

Still another object of the present invention is to provide a method for press-molding a green compact having a chamfered portion on the outer surface side, in which no step is attached to the chamfered portion. Further, the present invention provides a press die for press-molding a green compact in which no step is attached to a chamfered portion provided on the outer surface side of the green compact.

[0014]

According to the first aspect of the present invention, there is provided a method for press-molding a hollow green compact having a chamfered portion on an inner peripheral surface thereof, comprising: A die surrounded by a space between the end faces of a pair of upper and lower outer punches in the through hole and an outer peripheral surface of a pair of upper and lower inner punches having tapered chamfered surfaces for chamfering molding on the end side and end faces abutting each other. Characterized in that the filling powder in the through hole is pressed between upper and lower outer punches to form a green compact.

That is, a conventional press-molding die includes a die, a pair of hollow upper and lower punches each having a tapered surface for forming a chamfered portion on an end face inserted into a through-hole of the die, and these punches. The present invention, as shown in FIG. 1, uses a pair of upper and lower punches having a pair of punch end faces 20a, 2b.
A pair of upper and lower outer punches having a substantially flat end face
The hollow portions of the green compact 9 are formed as a pair of upper and lower inner punches 3a and 3b in which both end surfaces 92 of the green compact are formed as a and 2b, and the core rod is divided into two parts vertically so that the end surfaces 30 can contact each other. Is formed, and both of these inner punches 3a and 3b are
Tapered tapered surfaces 34 and 34 are provided on the end side for chamfering, and a chamfered portion 94 is formed in a hollow portion 95 of the green compact 9.

Here, as shown in FIG.
The outer peripheral surfaces of a and 3b have a tapered surface 34 on the end side and a small-diameter peripheral surface 33 ahead of the tapered surface 34, and chamfered portions 94, 94 on both sides in the hollow portion of the compact 9 and an inner peripheral surface 93 therebetween. Steps that are formed and associated with the chamfer are not formed. And the reason why the inner punch is divided into a pair of upper and lower parts is that the hollow part is formed in the green compact, and then the inner punches 3a and 3b can be pulled up and down from the green compact after molding, This is for facilitating the release of the green compact. further,
Since the end faces of the pair of upper and lower punches 2a, 2b, 3a, 3b may be flat end faces or flat shapes close thereto, the mechanical strength of the punches at the end faces is large, and the punches are long even in long-term press operations. The advantage of prolonging the life is recognized.

Next, the second invention relates to a method of molding a green compact having a chamfered portion on the outer surface side, wherein the inner surface of the hollow portion of the outer lower punch inserted from below into the through hole of the die, An upper end surface of an inner lower punch inserted from below into a hollow portion of the punch, and a concave portion for chamfer formation provided inside the lower end surface of an upper punch inserted from above into a through hole of a die;
Is characterized in that the filling powder surrounded by is pressed between the inner lower punch and the upper punch to form a green compact.

That is, while the conventional die is a die composed of a die and an upper and lower punch inserted into a die through hole, the die of the present invention is, as shown in FIG. Has a double structure of an outer lower punch 2b and an inner lower punch 3b inserted into a hollow portion of the outer lower punch.
b is the outer edge 40 of the lower end surface of the upper punch 4.
The powder 90 is pressed and compressed between the lower end surface of the upper punch and the recess 48 formed inside the outer edge and the upper end surface 30b of the inner lower punch in a state where the powder 90 is in contact with the upper punch. , End face 97 and chamfer 9 formed by recess 48
4 to form a green compact.

In the present invention, the through-hole of the die is a guide hole for the outer lower punch and the upper punch without directly participating in the compacting, and is formed at the time of forming.
The outer peripheral surface or side surface of the green compact is formed on the inner surface of the hollow portion b, and the concave portion 48 on the lower end surface of the upper punch 4 has the flat end surface 4 inside.
The end surface or outer surface 97 of the green compact 9 and the chamfered portion 96 at its corner are formed by the tapered surface 7 and the peripheral tapered surface 46. Further, the outer edge portion 40 formed outside the concave portion 48 on the lower end surface of the upper punch 4 abuts on the annular upper end surface 20b of the hollow outer lower punch 2b. Is not formed, and the outer edge 40
Since the thickness can be ensured to be wide, the strength at the end face can be secured, damage such as breakage can be avoided, and the life can be prolonged. Further, since the strength of the outer edge portion 40 is large, the inner surface shape of the concave portion 48 of the upper punch can be freely formed, and therefore, the size or surface area of the chamfered portion 96 of the green compact 9 can be reduced. It is also possible to enlarge it to occupy a considerable portion, thereby forming a trapezoidal or truncated cone-shaped compact, and thus a sintered product, so that the chamfered part is a truncated cone. Also becomes easier.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION With regard to molding of a green compact having a chamfered portion on the inner peripheral surface side, a mold used for this will be described first. As shown in FIGS. , A die 1 having a through hole, and an inner surface of the through hole 11
Is also a forming surface that forms the outer peripheral surface 91 of the above. A pair of upper and lower hollow punches 2a and 2b are slidably inserted into the through holes 11 of the die, and these outer punches are provided with end faces 20a and 20b respectively forming both end faces of the green compact 9. Have. Inside the hollow portion of the pair of upper and lower outer punches 2a and 2b, a pair of upper and lower inner punches 3a and 3b are inserted so that the end faces 30 thereof can contact with each other and slidably. 3a and 3b, a tapered tapered surface 34 and a small-diameter peripheral surface 33 at the tapered end of the tapered surface are formed on the end side. The inner peripheral surface 93 of the portion is formed, and the tapered surfaces 34, 34
Chamfers 94 are formed on both sides of the hollow portion 95 of the green compact 9.

In such a mold, both the outer punch and the inner punch can be separated up and down, and their end faces can be moved up and down outside the through holes of the die. The press is connected to mechanical or hydraulic pressurizing means, for example, a hydraulic cylinder (not shown) so as to be pressurized. In particular, since the outer upper punch 2a and the inner upper punch 3a are moved up and down in cooperation with each other as described later, as shown in FIGS.
Preferably, a and 2b are provided with an interlocking device 4. In this example, the gap between the upper end flange 28a of the outer upper punch 2a and the pressing plate 42 connected to the flange is provided in the inner upper punch 3a. The flange 38a on the upper end side is interposed with play for up and down movement, and the up and down movement of the pressing plate 41 enables the up and down movement of the inner upper punch 3a.

In the step of the press forming method of the present invention, an outer lower punch is provided inside the through hole of the die, and an inner lower punch having a tapered surface for chamfering at the upper end in the hollow portion of the outer lower punch. After the arrangement, a filling step of supplying a required amount of powder to the inside of the die through-hole, and a lower end surface of the inner upper punch 3a having a tapered tapered surface for chamfering molding on a lower end side and an upper end surface of the inner lower punch are formed. In the abutted state, the inner punch lowering step of burying the double-sided forming surface of the inner punch in the powder, and then the pressing step of pressing the powder between the upper and lower outer punch end faces to form a green compact, And releasing the upper and lower inner and outer punches out of the through-hole of the die to release the molded body.

Each step of the press forming method will be described in more detail with reference to FIGS. 2 and 3. The filling step is, as shown in FIG. 2A, an outer upper punch 2a and an inner upper punch 2a. With 3a raised and retracted,
The upper end surface 30 of the inner lower punch 3b is
0, and the lower outer punch 2b is arranged below the upper surface 10 of the die 1 so that the space formed inside the through hole 11 of the die has a predetermined volume. Is positioned at the upper end surface 20b.

The powder 90 moves the feeder container 7 having the lower bottom open to the upper portion of the through hole 11 so that the lower bottom slides on the upper surface 10 of the die, and is supplied to the empty space in the through hole 11 of the die. Then, when the powder 90 is rubbed in the through hole by sliding the feeder container 7, a predetermined amount of the powder 90 is filled in the empty space, and the powder 90 is formed on the upper surface 10 of the die and the inner lower punch. It is flush with the upper end surface 30.

In the next inner punch lowering step, as shown in FIG. 2B, of the outer and inner upper punches 2a and 3a, the lower end face 30 of the inner upper punch 3a is placed inside the through hole of the die. Inside lower punch 3 looking into the upper surface of the filled powder 90
b, the upper and lower inner punches 3a, 3a
2B, and then, as shown in FIG. 2C, the end of the outer upper punch 2a is inserted into the through hole 11 of the die, and the ends of the upper and lower inner punches 3a, 3b are inserted. The constricted portion 37 formed by the two tapered surfaces 34, 34 near the portion and the small-diameter peripheral surfaces 33, 33 therebetween is buried in the powder 90.

Further, in the next compression step, a pressure is applied between the upper and lower outer punches 2a and 2b to thereby form the tapered surface 34,
The powder 90 flows and satisfies the constricted portion 37 between the upper and lower outer punches 2a and 2b as shown in FIG.
The powder 90 is compressed until the end faces 20a, 20b of the upper and lower outer punches coincide with the ridgeline 35 formed by the tapered surface 34 and the outer peripheral surface of the upper and lower inner punches 3a, 3b. And In FIG. 3, when the pressing plate 42 of the linking device 4 comes into contact with the flange 38 a of the inner upper punch 3 a in FIG. 3, the ridge line 35 coincides with the lower end surface 20 a of the outer upper punch 2 a. By adjusting the adjusting tool 41 in advance as described above, this can be easily achieved.

In order to release the green compact 9, the through hole 1 of the die is used.
The green compact 9 can be separated by lifting each punch from 1 and unloading the space between the upper and lower outer punches and pulling the upper and lower inner punches 3a and 3b up and down to separate them.

Next, with respect to the compacting of a compact having a chamfered portion on the outer surface side of the second invention, a specific example of a mold used for the compacting will be described first with reference to FIGS. 5A and 5B. As described above, the mold includes the die 1 having the through hole 11, the lower outer punch 2 b is inserted into the through hole 11 of the die 1 from below, and the outer lower punch has a hollow portion 32 and Is formed. There is an inner lower punch 3b which is slidably inserted from below into the hollow portion of the outer lower punch 2b.
It has an upper end surface 30b that forms the wider end surface 92 of the compact. On the other hand, the upper punch 4 is inserted into the through-hole 11 of the die from above, and the lower end surface of the upper punch 4 has an outer edge portion 40 that is a flat surface that comes into contact with the ring-shaped upper end surface 20b of the outer lower punch. Inside, there is a concave portion 48 consisting of a flat end surface 47 depressed inward and a tapered surface 46 that expands around the flat end surface 47, and an end surface or outer surface 97 of the green compact 9;
A chamfer 96 at the corner is formed.

As shown in FIGS. 5A and 5C, the upper punch 4 and the inner lower punch 3b are formed with a small diameter through hole 4 as shown in FIGS.
5 and 35, the core rod 6 is inserted from below into the through-hole, and during molding, the core rod 6 is penetrated into the powder 90 to form a hollow portion 95 in the compact 9.

According to the method for press-molding the green compact 9 of the present invention, a hollow lower outer punch is disposed inside a through hole of a die, and an inner lower punch is disposed such that an upper end surface is located in a hollow portion of the outer lower punch. A filling step of supplying a required amount of powder into the hollow portion of the inner lower punch, and a state in which the outer edge of the lower end surface of the upper punch having a concave portion on the lower end surface is in contact with the upper end surface of the outer lower punch. Then, a punch lowering step of pressing the upper punch and the outer lower punch into the die penetration, and pressing the powder between the concave portion on the lower end surface of the upper punch and the upper end surface of the outer lower punch to form a green compact And a release step of pushing up and down the punches out of the through hole of the die to separate the molded body from the through hole.

As shown in FIG. 5 (C), a more specific molding method is as follows. In the filling step, the upper punch 4 is retracted upward, and the upper surface 10 of the die 1 and the upper end surface of the outer lower punch 2b are removed. The upper end surface 30b of the inner lower punch 3b is placed at a predetermined position in the hollow portion of the outer lower punch 2b while holding the upper surface 20b flush, and in this example, the core rod 6 passes through the through hole of the inner lower punch 3b. The point 60 is arranged at the same level as the upper surface 10 of the die 1. In this state, in FIG. 6A, the lower bottom of the feeder container 7 is slid over the upper surface 10 of the die 1 so that the powder 90 is supplied into the hollow portion of the outer lower punch 2b, and the feeder container 7 is slid. , And the powder is filled in a predetermined amount.

In the punch lowering step, as shown in FIG. 6B, the outer edge 40 of the lower end surface of the upper punch 4 is lowered so as to contact the upper end surface 20b of the outer lower punch 2b.
It is pushed into the through hole of the die 1. At this time the lower punch 3 inside
The core rod 6 extending from the through hole b is adjusted to be inserted into the through hole 45 penetrating the upper punch 4.

In the compression step, as shown in FIG. 6C, the upper punch 4 and the inner lower punch 2b are pressed while the lower end surface 40 of the upper punch 4 and the upper end surface of the outer lower punch 2b are in contact with each other. Thus, the powder 90 fills the upper end surface 20b of the inner lower punch 2b and the concave portion 48 of the lower end surface of the upper punch 4 to become the green compact 9 in which the shape of the concave portion 48 is shaped. In the release process, FIG.
As shown in (D), when the space between the punches is unloaded, the upper punch 4 is raised, and the upper end surfaces of the inner and outer lower punches 2b, 3b and the core rod 6 are aligned with the upper surface of the die. Separated.

The green compact formed as described above is sent to a firing step to form a dense sintered product, as in the prior art, but a step or step is formed in the chamfered portion of the green compact. Since it is not formed, grinding and polishing processes for removing steps in the sintered product are not required,
There is an advantage that the purification process of the sintered product can be simplified.

In the above-described example, the molding method of the present invention has been described with reference to a peripheral body having a circular cross section. However, the present invention is not limited to this. For example, a green compact having a rectangular or rectangular cross section may be used. Can be applied. As an example of such a rectangular sintered product, a ceramic copy paper guide is shown in FIG. 7 (A). The copy paper guide is formed in a rectangular shape on the lower surface and in a semi-cylindrical shape. There is a chamfered portion 96 on which an inclined surface is formed.
Is used for applications where copy paper travels. Thus, the molding method of the present invention can be widely applied to not only the outer surface of the peripheral body but also a green compact having a chamfered portion on the outer surface.

As another example, FIG. 7B shows a guide member for feeding a tape or a film, and guide rings at both ends of the guide member are provided with a molding member of the present invention as shown in FIG. 7C. A ring with a beveled outer chamfer 96 is utilized. FIG. 7D and FIG. 7E show a mounting table for drying a semiconductor wafer. The green compact of the present invention is used for four truncated cones fixed on a hot plate. The chamfer is a conical surface. As shown in FIG. 7F, the green compact of the present invention has a groove 951 on the end surface 97 and a chamfered portion 96 on the outer peripheral surface, like a head part of a reading section of a flexible disk. Is also available.

[0037]

According to the method of the present invention, a pair of upper and lower inner punches whose end faces are in contact with each other are provided inside a pair of upper and lower outer punches. On the outer peripheral surface, a tapered surface is formed on the end side and press-molded as a chamfered molding surface, so that a step or step close to the chamfered portion of the inner peripheral surface is formed on the green compact. Sintering process can be simplified. Further, according to the present invention, since the end face of the punch can be made flat, the mechanical strength of the end of the punch can be ensured to be large, and the life of the mold can be extended.

The method for press-molding a green compact having a chamfered portion on the outer surface according to the present invention comprises pressing the green compact between a concave portion for forming a chamfer on the lower end surface of the upper punch and the upper end surface of the inner lower punch. Since it is formed, no steps or steps are formed in the chamfered portion, and the process of purifying the sintered product can be simplified. Also,
The end face of the upper punch can be reinforced by increasing the thickness of the outer edge around the recess, so that the strength of the punch end is large, which contributes to extending the life of the mold. Further, the inner shape of the recess can be enlarged. In addition, it is easy to manufacture various kinds of parts having a chamfered portion having a large conical shape.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a mold for press-molding a hollow green compact having a chamfered portion on an inner peripheral surface according to the present invention (A) and a cross-sectional view of a ring-shaped green compact thereof (B).

FIGS. 2A and 2B are cross-sectional views of a metal mold showing a molding step of a green compact according to an embodiment of the present invention, wherein FIG. 2A shows a filling step, and FIGS. .

FIG. 3 is a cross-sectional view of a metal mold showing a molding step of a green compact according to an embodiment of the present invention, showing a compression step.

FIG. 4 is a cross-sectional view of a mold for press-molding a green compact having a chamfered portion on the outer surface according to the present invention (A) and a cross-sectional view of the green compact (B).

FIG. 5 is a cross-sectional view of a mold for press-molding the green compact according to the embodiment of the present invention, (A) is a cross-sectional view in a compression step, (B) is a cross-sectional view of the green compact, and And (C) show cross-sectional views before powder compaction.

FIG. 6 is a cross-sectional view of a mold showing a molding step of a green compact according to an embodiment of the present invention, where (A) shows a filling step, (B) shows a punch lowering step, and (C) shows a compression step. , (D) show the mold release step, respectively.

FIG. 7 is a component external view illustrating each sintered component that can be formed by the press forming method of the present invention.

FIG. 8 is a cross-sectional view (A, C) of a conventional die for forming a ring-shaped green compact having a chamfered portion on the inner peripheral surface, and a cross-sectional view of a ring-shaped green compact formed by the die ( B, D).

FIG. 9 is a cross-sectional view (A, C) of a conventional die for molding a green compact having a chamfered portion on the outer surface, and a cross-sectional view (B, D) of a green compact formed by the die.

[Explanation of symbols]

 Reference Signs List 1 die 11 through hole 2a outer upper punch 2b outer lower punch 3a inner upper punch 3b inner lower punch 30 inner punch end surface 34 tapered surface 37 constricted portion 4 upper punch 46 tapered surface 48 concave portion 9 powder compact 90 powder 94 chamfered portion

Claims (9)

[Claims] 1. A method for press-molding a green compact having a through hole and a chamfered portion on an inner peripheral surface, comprising: a step between an inner surface of a through hole of a die and an end surface of a pair of upper and lower outer punches in the through hole; Filling powder surrounded by the upper and lower outer punches having a pair of upper and lower inner punches having a tapered taper for chamfering molding on the part side and having their leading end surfaces in contact with each other is pressed between the upper and lower outer punches to form a green compact. A method of press-molding a green compact, which comprises molding. 2. A method of press-molding a green compact having a through hole and a chamfered portion on an inner peripheral surface, comprising: a lower outer punch inside a through hole of a die; After arranging an inner lower punch having a tapered tapered surface for chamfering, a filling step of supplying a required amount of powder inside the die through hole, and an inner upper surface having a tapered tapered surface for chamfering on the lower end side An inner punch lowering step of lowering both inner punches and burying the ends including the tapered surface in powder in a state where the lower end surface of the punch and the upper end surface of the inner lower punch are in contact with each other; A compression step of pressing the powder between the end faces of the punch to form a green compact, and a release step of lifting the upper and lower inner and outer punches out of the through holes of the die to release the molded body. A method for press-molding a green compact. 3. The filling step includes disposing the outer lower punch inside a through-hole opening in an upper surface of the die, and inserting the inner lower punch through a hollow portion of the outer lower punch. 3. The method of press-molding a green compact according to claim 2, wherein after the lower punch is disposed such that an upper end surface thereof is substantially flush with an upper surface of the die, a required amount of powder is supplied to the inside of the die through-hole. 4. A press die for molding a green compact having a through hole and a chamfer on an inner peripheral surface, comprising: a die having a through hole for forming an outer peripheral surface of the green compact; A pair of hollow upper and lower outer punches having end surfaces respectively forming both end surfaces of the green compact, slidably inserted into the through holes, and slidably inserted into the hollow portions of these outer punches. A pair of upper and lower inner punches having a tapered surface on the end side for forming a chamfered portion on the inner peripheral surface of the green compact and having end surfaces capable of contacting each other. Type. 5. A method of press-molding a green compact having a chamfered portion on an outer surface, comprising: a hollow inner peripheral surface of an outer lower punch inserted from below into a through hole of a die; An upper end surface of the inserted inner lower punch, a concave portion for chamfering molding of the lower end surface of the upper punch, which is inserted from above into the through hole of the die and whose lower end surface contacts the upper end surface of the outer lower punch, The filling powder surrounded by is pressed between the inner lower punch and the upper punch to form a green compact, and the concave portion on the lower end surface of the upper punch forms a chamfered portion without steps on the outer peripheral surface of the green compact. A method for press-molding a green compact, which is formed. 6. The inner lower punch and the upper punch have small-diameter through holes, and a hollow portion is formed in the green compact by a core rod inserted into the powder through the through holes. Item 6. A method for press-molding a green compact according to Item 5. 7. A method for press-molding a green compact having a chamfered portion on an outer surface, comprising: a hollow outer lower punch inside a through hole of a die; A filling step of arranging a lower punch and supplying a required amount of powder into the hollow portion of the inner lower punch; and an outer edge of the lower end surface of the upper punch having a chamfered concave portion on a lower end surface thereof. A punch lowering step of pressing the upper punch and the outer lower punch into the die through while being in contact with the upper end surface of the punch; and a step between the concave portion of the lower end surface of the upper punch and the upper end surface of the outer lower punch. A pressing step of pressing the powder to form a green compact, and a releasing step of pushing up the upper and lower punches out of the through-hole of the die and separating the molded body from the through-hole. Press molding method for green compacts. 8. A press die for molding a green compact having a chamfered portion on an outer surface, comprising: a die having a through-hole; and an outer peripheral surface of the green compact inserted into the through-hole of the die from below. An outer lower punch having a hollow inner surface to be formed, an inner lower punch having an upper end surface which is slidably inserted into the hollow portion of the outer lower punch from below to form one end surface of the green compact; An upper punch which is inserted into the through hole of the die from above, and has a concave portion for integrally forming a chamfer with the other end surface of the green compact, the lower end surface of the outer lower punch being in contact with the upper end surface, A press die characterized by comprising: 9. The press die according to claim 8, wherein the inner lower punch has a small-diameter through-hole, and has a core rod protruding from the through-hole to form a hollow portion of the green compact. .