JPH058094A - Forming mold for cold isostatic press forming - Google Patents

Abstract

PURPOSE:To prevent the development of 'elephant foot' phenomenon at the time of coil isostatic press forming by using a porous rubber distributing the specific pores in the inner part as a material for ring. CONSTITUTION:This mold is provided with a core rod 3 on the center part of a cylindrical shaped rubber mold 2 and seals both ends with covers 1, rubbers 5 for sealing and tapes 4 for sealing and is arranged with the porous rubber rings 7 having 30-70vol.% porosity between powder material 6 and the covers 1. At one end of this cylindrical shaped rubber mold 2, the ring 7 provided with the same outside diameter as the small diameter part of cover 1 and the porosity and composed of elastic material reducing the vol. at the time of pressurizing is fitted and sealed with the cover 1, rubber 5 for sealing and tape 4 for sealing, and after penetrating the core rod 3, the powdery material 6 is fitted to the fixed quantity and further, at the other end, the ring 7 is fitted and sealed with the cover 1, the rubber 5 for sealing and tape 4 for sealing and after preventing the falling of the powdery material 5 and the intrusion of pressure medium into the rubber mold 2, the cold isostatic pressing is executed to the rubber mold 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a forming die for cold isostatic pressing.

[0002]

2. Description of the Related Art Conventionally, it is well known that a cold isostatic pressing device is used as a device for press-compacting a powder material. For example, as a cold isostatic press molding die for producing a cylindrical shape long in the axial direction, there are those as shown in FIGS. 2 and 3.

In the conventional example shown in FIG. 2, both ends of a rubber mold 2 containing a powder material 6 are closed by a lid 1, and a core rod 3 penetrates the lid 1. Therefore, the lid 1 is further stopped by the sealing rubber 5 and the sealing tape 4.

In the conventional example shown in FIG. 3, a core rod 3 is arranged at the center of a rubber mold 2 containing a powder material 6, and the rubber mold 2 and the core rod 3 are closed by a lid 1. However, it is further stopped with the sealing tape 4.

The molding die shown in FIG. 3 performs compression control in the vertical axis direction only by the core rod. The molding die shown in FIG. 2 has a thin core rod and only the core rod is compressed in the vertical axis direction. Since it cannot be controlled with, the through hole is made in the lid so that the core rod can move freely during compression.

FIG. 4 is a schematic diagram when the molding die shown in FIG. 2 is filled with the powder material and the steps of pressurizing and depressurizing are performed. As shown in FIG. 4, the end of the molded body is broken. The reason for this breakage is that the powder molding force is defeated by the force of the rubber mold pushing the molded body in the depressurizing step. As a countermeasure against this breakage, it is known to insert a rubber 10 similar to a rubber mold between the end of the small-diameter portion 8 of the lid and the powder material 6 when the powder is filled, as shown in FIG. Has been. As a result, the occurrence of breakage can be reduced.

[0007]

However, when the molding die shown in FIGS. 3 and 5 is used for cold isostatic pressing, a molding as shown in FIG. 6 is formed. As shown in FIG. 6, the molded body is molded into a shape in which the outer diameter increases toward the end surface, and in general, an elephant foot phenomenon occurs. This has been a cause of chipping, cracking, and reduction in weight yield of the molded body.

In view of the above, it is an object of the present invention to provide a forming die for cold isostatic press forming which prevents the elephant foot phenomenon.

[0009]

SUMMARY OF THE INVENTION According to the present invention, a rubber-type opening for accommodating a powder material is detachably covered by a metal lid, and an elastic material is provided between the lid and the powder material. In a forming die for cold isostatic pressing, in which a ring is formed, the material of the ring is 30 to 70% by volume inside.
The porous rubber in which the pores are distributed is used.

The reason why the porous rubber having 30 to 70% by volume of pores is used is that the volume of the rubber changes as much as the volume of the raw material (about 50%) when compressed under pressure. is there.

[0011]

In the cold isostatic pressing, the pressing force is applied to the entire molding die filled with the powder material. At that time, in the conventional technique, the upper and lower lids and the core rod are made of a material such as metal that does not deform when pressed, and the outer peripheral portion is made of a material such as rubber that elastically deforms when pressed. Composed of materials. However, the powder material, which is the object to be molded, is a material that changes in volume as pressure is increased.If the end surface of the powder material is made of a metal material that does not undergo elastic deformation or volume change, the elephant foot phenomenon occurs. It is difficult to prevent the occurrence of.

According to the means adopted by the present invention, by arranging a ring made of a material whose volume decreases like the powder material at the time of pressurization at the place where the powder material comes into contact with the upper and lower parts at the time of pressurization, At the end of the molded body, the part where the diameter becomes larger than the central part of the molded body toward the end face, so-called elephant foot phenomenon does not occur, and the powder material of the end face part and the ring in contact with it are both Since the volume is reduced during pressurization, the flow of the raw material inside the powder material is less likely to occur due to unnecessary shear stress inside the powder raw material, and it is possible to produce a molded body having a more uniform molding density.

[0013]

FIG. 1 is a sectional view of an embodiment according to the present invention. A molding die which has a core rod 3 at the center of a cylindrical rubber die 2 and whose both ends are covered with a lid 1, a sealing rubber 5 and a sealing tape 4, and which is between the powder material 6 and the lid 1. Has a ring 7 made of porous rubber having a predetermined porosity.

A ring 7 made of an elastic material, which has the same outer diameter as the small diameter portion 8 of the lid 1 and has the porosity shown in Table 1 and whose volume is reduced when pressurized, is provided at one end of the cylindrical rubber mold 2. Put, lid 1,
Stopping with the sealing rubber 5 and the sealing tape 4, after passing through the core rod 3, filling a certain amount of the powder material 6, and further inserting the ring 7 at the other end, the lid 1, the sealing rubber 5 and the sealing tape 4
To prevent the powder material from spilling out and the pressure medium liquid from entering the rubber mold 2, and then put the rubber mold 2 in the pressure container of the cold isostatic press for 2 minutes until the predetermined pressure is reached. And pressurize for 2 minutes, then 300kg / cm ²
Rapidly decelerates to 10kg for 300kg / cm ² or less
/ Slowed in cm ² / 1sec rate of. After the molding was completed, the rubber mold was taken out from the pressure vessel, the sealing tape, the sealing rubber, the lid and the ring were removed, and the molded body was taken out from the rubber mold. The state of occurrence of the elephant foot phenomenon of the molded body at this time was investigated. In this method, as shown in FIG. 7, the diameter of the central portion is a, the diameter of the end portion is b, and the value of b when a is 100 is shown in Table 1.

[0015]

[Table 1]

As can be seen from Table 1, the porosity is 30%.
In the range of up to 70%, the elephant foot phenomenon could be suppressed within 10% in terms of the external dimension ratio.

[0017]

According to the present invention, the elephant foot phenomenon can be eliminated. As a result, the molded body can be molded at a constant density, the molded body is free from chipping and cracking, and the weight yield can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment according to the present invention.

FIG. 2 is a cross-sectional view of a conventional example.

FIG. 3 is a cross-sectional view of another conventional example.

FIG. 4 is a schematic diagram of a molding process.

FIG. 5 is a cross-sectional view of another conventional example.

FIG. 6 is a cross-sectional view of a conventional molded body.

FIG. 7 is a schematic view of a molded body.

[Explanation of symbols]

 1 Lid 2 Rubber type 3 Core rod 4 Sealing tape 5 Sealing rubber 6 Powder material 7 Ring 8 Small diameter part of lid 9 Large diameter part of lid 10 Rubber

Claims (1)

Claim: What is claimed is: 1. A rubber-type opening for accommodating a powder material is detachably covered by a metal lid, and a ring made of an elastic material is provided between the lid and the powder material. In a forming die for cold isostatic pressing, in which a porous rubber having 30 to 70% by volume of pores distributed therein is used as a material of the ring. Mold for press molding.