JP3433683B2 - Powder mold and powder molding method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder molding die for compressing powder for sintering into a predetermined shape and a method for molding the powder.

[0002]

2. Description of the Related Art Generally, powder molding is carried out by filling powder in a space of an integral molding die and pressurizing it, but in the case of compacting a compact by using powder which easily adheres to the die. Alternatively, if the strength of the molded product is low and cracking is likely to occur during extraction, it is conceivable to use a split mold (hereinafter referred to as split die). By opening the split die when the molded product is removed, the load applied to the molded product is greatly reduced.
This is because it is possible to prevent the molded body from sticking or cracking on the split die. However, since the dividing die has a dividing portion, the powder may invade and accumulate in the gap between the dividing portions. When the powder accumulates in the gap between the split dies, the split dies do not completely close, and if compression molding of the powder is continued in this state, split lines with a low density remain on the surface of the compact and the shape accuracy of the compact deteriorates. To do.

In order to solve the above problem, as shown in FIG. 4, a plate 6 having elasticity is installed inside the split die 2 to close the gap S formed in the split portion 2c of the split die 2. There is a powder molding die 1 (Russia: SU-A-
1315135). The elastic plate 6 is bent into a cylindrical shape so as to follow the opening and closing of the split die 2, and both end surfaces 6t of the plate 6 abut each other in the closed state of the split die 2. In the figure, 5 is a substantially cylindrical core, and the powder H is filled between the core and the plate 6. The filled powder H is compressed by a punch (not shown) descending to form a disk-shaped compact. When the molded body is taken out, the split die 2 is expanded, but since the gap S of the split portion 2c is covered by the plate 6, it is difficult for the residual powder to enter the gap S.

[0004]

However, since the powder molding die 1 has a structure in which the plate 6 is brought into close contact with the inside of the split die 2 due to the elasticity of the plate 6, the plate 6 with respect to the split die 2 is aged over time. When the adhesion is lowered, the powder penetrates between the two and 6, and the powder easily enters the gap S of the split die 2. Furthermore, since there is no means for removing the powder that has entered the gap S of the split die 2 in the powder molding die 1, it is difficult to remove the powder that has once entered the gap S.
Therefore, even in the powder molding die 1, the powder gradually accumulates in the gap S between the split dies 2, and the split dies 2 do not completely close due to the powder over time. In addition, both end surfaces 6t of the plate 6
It is very difficult to make the surface contact with each other completely, and a step remains at the both end surfaces 6t in the molded body.

An object of the present invention is to ensure that the dividing die can always be closed by providing means for removing the powder that has entered the gap between the dividing dies before closing the dividing die.

[0006]

The above-mentioned problems can be solved by a powder molding die and a powder molding method having the following features. That is, the powder mold according to claim 1, the powder mold der for molding into a predetermined shape by compressing powder for sintering
What is divided in the circumferential direction, and divided die cavity powder in the center is accommodated is formed, a die holder which state or expanded closed the split die is held in a state as possible, the divided A punch for compressing the powder contained in the cavity with the die closed and a die formed between the die holder and the split die, and the split portion of the split die when the split die is expanded. And a passage communicating with the gap formed in the passage and a negative pressure in the passage .
DOO has and a pressure variation means capable, said passageway,
Formed along the dividing part of the dividing die to cover the dividing part
It is characterized by being.

According to the present invention, the pressure in the passage is made negative by the pressure changing means, so that the powder that has entered the gap of the split die can be sucked through the passage. That is, the powder that has entered the gap between the split dies can be easily removed by the action of the passage and the pressure varying means.
Therefore, by removing the powder in the gap before closing the dividing die, the dividing die can be completely closed. Therefore, dividing lines having low density do not remain on the surface of the molded body due to the compression molding of the powder, and the shape accuracy of the molded body is improved.

The invention of claim 2 is the powder according to claim 1.
It is a mold and the split die is installed on the mold base.
On the upper surface of the mold base,
A powder escape groove is formed directly below to allow the powder to escape.
It is characterized by being. Therefore, the split die
The powder that has entered the gap of the split part falls into the powder escape groove by its own weight.
It becomes difficult to collect in the above gap. The invention of claim 3 is
The powder molding die according to claim 1 or 2.
So, on the split die, cover the split part of the split die.
It is characterized in that a powder intrusion prevention plate is placed.
For this reason, when filling the cavity with powder,
Does not enter the gap between the split parts.

The invention of claim 4 is from claim 1 to claim 3.
Powder molding method using the powder molding die according to any one of 1.
Method, by means of pressure fluctuation means before closing the split die.
The pressure inside the reflow passage is reduced to a negative pressure,
It is characterized in that gas is caused to flow in the formed gap. others
Therefore, the gap between the split dies can be cleaned before the split dies are closed , and the split dies can be closed in the absence of powder in the gap. Therefore, it is possible to close the split die always full.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, based on FIGS. 1 to 3,
A powder molding die and a powder molding method according to an embodiment of the present invention will be described. The powder molding die according to the present embodiment is a mold for producing a cylindrical molded body by compressing a powder obtained by adding wax to a mixed powder of titanium powder and aluminum alloy powder, which are sintering materials, FIG. 1A shows a vertical sectional view of the powder molding die, and FIG. 1B shows a plane sectional view thereof. 2 and 3 are vertical cross-sectional views showing a process of manufacturing the molded body using the powder molding die. The powder molding die 10 is provided with a die base 12, and an inverted frustoconical dividing die 14 is installed on the die base 12.

The dividing die 14 is divided into three equal parts in the circumferential direction, and in a state in which the respective dividing pieces 14r, 14s, 14t are combined, the dividing die 14 has a first axial direction (vertical direction). Two through holes 14k are formed. The second through hole 14k is a portion that constitutes the cavity C, and is held concentrically with the third through hole 12k of the same size formed in the mold base 12. Then, the lower punch 15 is vertically slidably inserted from the third through hole 12k of the die base 12 into the second through hole 14k of the split die 14 from below. Further, on the upper surface of the die base 12, a powder escape groove 12u for escaping the powder dropped from the division parts 14c of the division die 14 is formed just below the division parts 14c.

Each divided piece 14 constituting the divided die 14
r, 14s, 14t (hereinafter simply referred to as split die 14)
Is bound by the die holder 18. The die holder 18 is a member that holds the split die 14 in a closed state or in a state in which the split die 14 can be expanded by a predetermined size, and the split die 1 is operated by a main lifting device (not shown).
Move up / down with 4. In addition, the split die 14 functions as an auxiliary lifting device (not shown) to operate the die holder 1
You can move up against 8. A holder hole 18 for accommodating the split die 14 is provided in the center of the die holder 18.
h is formed, and the taper of the holder hole 18h is set to be equal to the taper of the outer peripheral surface of the split die 14.
That is, the wall surface of the holder hole 18h of the die holder 18 and the outer peripheral surface of the split die 14 are in surface contact with each other.

Therefore, when the die holder 18 moves upward with respect to the split die 14, the holder hole 18 of the die holder 18 slides upward with respect to the outer peripheral surface of the split die 14, and the action of the taper of both splits the split. The die 14 is a die holder 18
Receives uniform pressing force in the radial direction. As a result, each of the divided pieces 14r,
14s and 14t are in close contact with each other, and the dividing die 14 is closed. When the split die 14 moves upward with respect to the die holder 18 by the action of the auxiliary lifting device, the split die 14
Does not receive the pressing force from the die holder 18, and expands radially outward by a certain size.

A suction groove 18m is formed on the wall surface of the holder hole 18 of the die holder 18 at a position corresponding to each divided portion 14c of the divided die 14. The suction groove 18m is vertically formed along the dividing portion 14c appearing on the outer peripheral surface of the dividing die 14 so as to cover the dividing portion 14c. The center of each suction groove 18m in the height direction is the lateral passage 18y.
It is connected to the. The lateral passage 18y is a die holder 18
Of the suction device (not shown) is connected to the opening. With this structure, by operating the suction device, the powder that has entered the gap S of the split portion 14c of the split die 14 is sucked into the suction groove 1.
8 m, it can be discharged to the outside via the lateral passage 18y. Here, since the lateral passage 18y is connected to the center of the suction groove 18m in the height direction, the powder can be sucked substantially uniformly from the gap S. That is, the suction groove 18m
The horizontal passage 18y corresponds to the passage communicating with the gap between the split dies in the present invention, and the suction device corresponds to the pressure fluctuation means of the present invention.

A powder intrusion prevention plate 19 is placed on the dividing die 14 to cover the dividing portion 14c of the dividing die 14. The powder intrusion prevention plate 19 is an undivided integral disc, and each of the divided pieces 14r, 14 of the division die 14 is formed.
It is connected to s and 14t with a bolt (not shown). The connecting portion can be relatively moved in the radial direction without making the powder intrusion prevention plate 19 separate from the split die 14 in the vertical direction by making the bolt hole a long hole, for example. A substantially cylindrical projection 19t is formed at the center of the lower surface of the powder intrusion prevention plate 19, and the projection 19t is formed by the split die 1
4 is fitted in the recess 14x formed in the upper part of the second through hole 14k.

A first through hole 19k is formed at the center of the powder intrusion prevention plate 19 so as to vertically penetrate the portion of the projection 19t, and the inner diameter of the first through hole 19k is the second of the split die 14. Only the inner diameter of the through hole 14k is set to be slightly larger. And the powder intrusion prevention plate 19
The upper punch 20 is vertically slidably inserted from above into the second through hole 14k of the split die 14 through the first through hole 19k. That is, the powder H is compression-molded in the space (cavity C) defined by the second through hole 14k, the upper punch 20, and the lower punch 15.

Next, a powder molding method using the powder molding die 10 will be described with reference to FIGS. First, the suction device is operated. As a result, a negative pressure is applied to the gap S formed in the split portion 14c of the split die 14 via the lateral passage 18y of the die holder 18 and the suction groove 18m, and the powder that has entered the gap S is sucked by the suction device. . The suction of the powder by the suction device is continuously performed until the molding of the powder is completed. As shown in FIG. 2A, the die holder 18 and the split die 14 are held at the lower limit position, and the lower punch 15 has the third through hole 12k of the die base 12 and the second through hole of the split die 14. It is housed in the hole 14k and the first through hole 19k of the powder intrusion prevention plate 19.

In this state, the main lifting device operates, first the die holder 18 moves upward with respect to the split die 14, and then the die holder 18 and the split die 14 integrally rise to a predetermined position (see FIG. 2 ( See B)). In this way, the die holder 1
When the die 8 moves upward with respect to the dividing die 14, the dividing die 14 is uniformly pressed inward in the radial direction by the die holder 18, and the dividing die 14 is closed. Further, as the die holder 18 and the split dies 14 rise, the lower punch 15 at the lower limit position is pulled out from the split dies 14 and the like. Next, the powder H for sintering is placed in the cavity C of the split die 14.
Is filled.

When the cavity C is filled with the powder H for sintering, as shown in FIG.
Is inserted into the second through hole 14k of the split die 14 from the first through hole 19k of the powder intrusion prevention plate 19, and the powder in the cavity C is compressed. Next, as shown in FIG. 3A, the upper punch 20 is pulled out from the second through hole 14k and the like of the split die 14, and the auxiliary lifting device operates to move the split die 14 above the die holder 18. Move. As a result, the split die 14 does not receive the restraining force from the die holder 18 and expands radially outward by a certain dimension.

Next, the main elevating device is operated, and as shown in FIG.
As shown in FIG. 5, the die holder 18, the split die 14 and the like are lowered to the lower limit position, and the lower punch 15 is pushed into the second through hole 14k of the split die 14 from the third through hole 12k of the die base 12. As a result, the compact H in the cavity C is extruded to the outside by the lower punch 15, and the molding of the powder H is completed.

As described above, according to the powder molding die 10 of the present embodiment, the powder that has entered the gap S of the split die 14 can be sucked by the suction device before the split die 14 is closed. The split die 14 can be completely closed. Therefore, the dividing line having a low density does not remain on the surface of the molded body H due to the compression molding of the powder,
The shape accuracy of the molded body H is improved. In the powder molding method according to the present embodiment, the suction device is constantly operated to suck the periphery of the split portion 14c of the split die 14, so that the gap S and its periphery are always kept clean. .

On the upper surface of the mold base 12, the split die 1 is provided.
A powder escape groove 12u is formed at a position directly below the fourth divided portion 14c. Therefore, even if the powder that has entered the lower portion of the gap S of the split die 14 is not sucked by the suction device,
The powder does not collect in the gap S because it falls into the powder escape groove 12u by its own weight. Also, the split die 1
4, the powder intrusion prevention plate 19 is placed,
When filling the cavity H with the powder H for sintering, the powder does not spill onto the split die 14,
The powder H does not enter the gap S from the upper surface of the.

In the present embodiment, the die holder 18
And the split die 14 are moved up and down by the main lifting device, and the split die 14 can be moved up relative to the die holder 18 by the auxiliary lifting device. However, it suffices that these move relative to each other. For example, the die holder 18 is fixed, and the split die 14, the die base 12, and the lower punch 15 are moved up and down relative to the die holder 18. You can also As the molding procedure in this case, first, the mold plate 12 and the split die 14 are lowered with respect to the die holder 18. In this way, the dividing die 14 is lowered relative to the die holder 18, so that the dividing die 14 is closed inward in the radial direction by the die holder 18. Next, the die holder 18, the split die 14, and the die plate 12 are integrally raised to a predetermined position. On this occasion,
Since the lower punch 15 does not rise, it is pulled out of the mold. After filling the powder in the cavity C and performing compression molding,
The mold plate 12 moves upward to push up the split die 14, and the split die 14 moves upward with respect to the die holder 18. As a result, the split die 14 does not receive the restraining force from the die holder 18, and spreads outward in the radial direction. Next, the lower punch 15 rises, the molded body in the cavity C is extruded to the outside, and the molding is completed.

Here, in the present embodiment, the suction groove 18
Although the example in which m is formed on the die holder 18 side is shown, it is also possible to form m on the outer peripheral surface side of the split die 14.
Further, in the present embodiment, the example in which the powder in the gap S is removed by sucking the periphery of the gap S of the split die 14 has been shown, but the powder is removed by blowing gas into the gap S, for example. Is also possible. Further, since the die is divided in the powder molding die according to the present embodiment,
PVD coating or the like, which usually has a limited coating range, can be applied, and the mold life can be improved.

[0025]

[0026]

According to the present invention, since the dividing die can be completely closed at all times, when the powder is compression-molded, a dividing line having a low density does not remain on the surface of the molded body,
The shape accuracy of the molded body is improved.

[Brief description of drawings]

FIG. 1 (A) is a vertical sectional view of a powder molding die according to an embodiment of the present invention, and FIG. 1 (B) is a plane cross section of a powder molding die according to an embodiment of the present invention. It is a figure.

2A, 2B, and 2C are vertical cross-sectional views showing respective steps of a powder molding method using the powder molding die according to the embodiment of the present invention.

3 (A) and 3 (B) are vertical cross-sectional views showing respective steps of a powder molding method using the powder molding die according to the embodiment of the present invention.

FIG. 4 is a plan view showing a conventional powder molding die.

[Explanation of symbols]

14 split dies 14c Dividing part 14k Second through hole (cavity C) S gap 18 Die holder 18m suction groove (passage) 18y horizontal passage (passage)

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP 57-146499 (JP, A) JP 8-169003 (JP, A) JP 61-283499 (JP, A) JP 4- 45206 (JP, A) Actual Development 2-17529 (JP, U) Actual Development 2-138095 (JP, U) Actual Development 61-69232 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) B30B 11/00-11/02 B22F 3/035 B28B 3/02

Claims (4)

(57) [Claims] 1. A powder molding mold for molding into a predetermined shape by compressing powder for sintering, are divided in the circumferential direction, and divided die cavity powder in the center is accommodated is formed A die holder that holds the split die in a closed state or a state in which the split die can be expanded; a punch that compresses the powder stored in the cavity in the closed state of the split die; and a die holder and the split die. And a passage that communicates with the gap formed in the divided portion of the split die when the split die is expanded, and a pressure fluctuation that can make the pressure in the passage negative. has a means, the passage, the dividing portion covering along the dividing portion of the split die
A powder molding die characterized in that it is formed as described above . 2. The powder molding die according to claim 1, wherein the split die is installed on a die base, and an upper surface of the die base is directly below a split portion of the split die.
A powder escape groove for escaping the falling powder to the position is formed.
A powder molding die characterized in that. 3. The method according to claim 1 or 2.
Of the powder molding die, and the powder impregnation covering the division part of the division die is provided on the division die.
Powder molding characterized by having an entry prevention plate placed
Type. 4. A method of forming a powder to be used a powder mold according to any one of claims 1 to claim 3, before closing the split die, a negative pressure the pressure in the passage by the pressure variation means And a gas is caused to flow through the gap formed in the divided portion of the divided die.