JPH0192000A - Rubber mold for forming cip - Google Patents

Abstract

PURPOSE:To prevent the generation of a crack in a formed body without reducing a pressure reducing speed by combining a tubular rubber mold made of a hard rubber and the material easy to peel from the formed body having lower elastic restoring force compared to the material not fixing to the formed body or a hard rubber made rubber mold. CONSTITUTION:A tubular rubber mold 1 is made in a cylindrical shape, a pair of plugs 2 are engaged with its upper and lower opening parts and a rubber sheet 4 is also inserted to the inside of the upper plug 2 opposing to the cavity 3 of the tubular rubber mold 1 inside. In this case, the rubber mold is made by using an urethane rubber for the cylindrical tubular rubber mold 1, a chloroprene rubber for the plug 2 and an isoprene rubber for the rubber sheet 4, for instance. A strong fixture is therefore generated between the forming body and rubber mold face on each face of P2, P3 in the state of the pressurizing time, but no fixture is caused between the plug 2 and P1, hence no stress is generated on the forming body even in the process of transferring to a load removing state and a crack can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention is applicable to industrial fields that handle powder, such as powder metallurgy and ceramics.
Regarding the rubber molds used during ostatic press (cold isostatic press) molding, high-quality CIP is used to prevent cracking of molded products without reducing efficiency.
The present invention relates to the above-mentioned rubber mold for producing a molded article.

(Prior Art) A CIP device is often used as a means for solidifying various powders such as metal powders and ceramics to a density of about 60 to 90%. FIG. 5 shows an outline of such a CIP device, and as shown in the figure, the top and bottom are the upper lid θω, the lower! It is composed of a pressure vessel (9) which is capped with a rubber type ( 1) Powder (
5) is closed with a stopper (2) and sealed with sealing tape (6), and then placed in the pressure medium filled in the pressure vessel (9) from the pressure medium tank (12), and the pressure medium is transferred to the pressure intensifier. By increasing the pressure by (13), the powder (5) in the rubber mold (1) is isotropically compression-molded by the action of the pressure medium, and then the pressure medium is reduced to normal pressure. It can be recovered as a dense molded body.

By the way, one of the problems with such CIP processing is
One is to control the shape of the molded object to the desired shape.
For this purpose, we maintain the same shape in order to prevent the shape of the cavity from deforming.

It is said to be effective to use a rubber mold made of hard rubber, such as polyurethane, which is easy to control.

However, such hard rubber molds have a larger elastic restoring force than soft rubber molds, such as natural rubber, so the molded product may be destroyed by the elastic force of the rubber when unloading after compression molding. It causes the problem of being easy. FIG. 6 is a diagram schematically showing this. When pressurized in the process (B), the inner surface of the rubber mold (1) is pressed against the surface of the molded body by the action of the pressure medium. A part of the rubber bites into the surface layer of the molded body, and the two are fixed at <P', P as shown in the figure (C), resulting in a partially bonded state. Therefore, when the rubber mold tries to restore its original shape due to elastic force when unloading, (C
) As shown in iM, there is a tensile stress (f) inside the molded body.
This causes cracks (7) to occur in the molded article (M) as seen in process (D).

Therefore, it is necessary to address and solve this problem (a method has been proposed in which the rate of decompression of the pressure medium during unloading is slowed down to gradually promote peeling between the molded body and the rubber mold during unloading and prevent cracking). has been done.

However, according to our knowledge, the presence or absence of cracks in the molded body described above is determined by the magnitude relationship of the strength of the molded body, the elastic restoring force of the rubber mold, and the adhesion force between the rubber mold and the molded body. Ru. In other words, if either the restoring force of the rubber mold or the adhesion force between the rubber mold molded bodies is the smallest among the three, cracks will not occur and the strength of the molded body will be smaller than either of the other two. Cracks will occur regardless of the unloading method.

Moreover, on the other hand, as a recent technological trend, the number of powder particles having regular shapes such as spheres is increasing, but such regularly shaped powders cannot be expected to bond through entanglement between the powder particles. Therefore, moldability is poor and the strength of the molded product itself is low. Therefore, when trying to mold such regularly shaped powder, it is necessary to increase the molding pressure as much as possible, but the higher the molding pressure, the more the rubber mold bites into the surface layer of the molded product, and the more the molded product The adhesion force between rubber molds tends to increase.

As described above, as a recent trend, the strength of the molded product is decreasing more and more, while the adhesion force between the rubber mold and the molded product is increasing. No matter how slow the speed is, it is becoming difficult to prevent cracking.

Furthermore, even if the strength of the molded product can be secured to a certain extent, i.e., the strength of the molded product can exceed the adhesion force with the rubber mold, reducing the decompression speed during unloading will significantly reduce production efficiency. This is not a good thing as it may lead to

(Problems to be Solved by the Invention) In view of the above-mentioned circumstances, the present invention has developed a rubber mold that can prevent cracks in molded bodies without reducing the CIP processing source pressure speed. The challenge is to form

In considering the formation of such a rubber mold, the present inventors
We also considered soft rubber molds, and found in the process that while soft rubber molds do not cause cracks, they do have problems with shape control.

However, it has been found that such a soft rubber mold is sufficient to cover the weaknesses of the conventional hard rubber mold, and depending on how it is used, it can be useful for improving the conventional hard rubber mold.

Thus, the present invention takes advantage of the hard rubber type described above.

The purpose of this invention is to provide an improved rubber mold for CIP molding by skillfully combining the advantages of soft rubber molds, thereby eliminating the drawbacks of conventional hard rubber molds.

(Means for Solving the Problems) Therefore, the rubber mold for molding of the present invention, which is suitable for the above-mentioned purpose, has the following features: (1) A movable rubber plate or foil is placed inside the hard rubber mold, and the molded product is placed on this rubber plate. Or, by fixing it to rubber foil, only the outer rubber mold is restored when loaded.

[2) The plugs at both ends of the hard rubber mold are made of metal to prevent the molded body from sticking to these parts.

(3) A soft rubber bag is placed inside the hard rubber mold, and the molded body is fixed to the soft rubber bag with a weak restoring force, so that only the hard rubber mold on the outer periphery is restored during loading.

This is the main focus and is based on this, and its characteristics are the above-mentioned tubular hard rubber mold and a pair of plugs that fit into the openings at both ends of the tubular rubber mold. In addition to forming the basic structure, the inner surface of the tubular rubber mold and/or the inner surface of at least one of the plugs, which are in contact with the molded body during molding, are made of a material to which the molded body does not adhere, or/and the tubular rubber mold The reason is that the elastic restoring force is smaller than that of the molded body, and a material that is easily peeled is interposed in the molded body.

More specifically, they can be roughly divided into (1) a tubular hard rubber mold, a plate-shaped or foil-shaped rubber plate inserted through the openings at both ends of the tubular rubber mold, and a rubber mold made of tubular hard rubber; Consisting of a pair of rubber plugs inserted into the opening (2) Consisting of a tubular hard rubber mold and a pair of metal plugs fitted into the openings at both ends of the tubular rubber mold (3) Consisting of a tubular hard rubber mold, a rubber or metal plug fitted into the openings at both ends, and a bag-shaped soft rubber mold inserted into the tubular rubber mold. (4) Consisting of a tubular hard rubber mold, rubber or metal plugs fitted into the openings at both ends, and a soft rubber lining applied along the inner surface of the tubular rubber mold. These are the various configurations, such as what will be done.

In any of the above cases, the cross-sectional shape of the tubular rubber mold can be any shape as long as it is compatible with the shape of the target product, and the material and hardness of the rubber mold can be adjusted according to the target molded product. The value is appropriately selected depending on the strength of the material, and the value is not particularly limited.

(Operation) Next, the operation mode of the present invention having the above configuration will be explained.

First, regardless of its aspect, the rubber mold of the present invention includes a rubber mold made of hard rubber as a constituent element. This is determined by considering both the shrinkage rate when compressed into a molded body, but if the hardness of the rubber mold is too soft, the center part will swell into a drum shape during powder filling.
Alternatively, during compression molding, local shrinkage rates vary depending on non-uniformity of filling, making it difficult to maintain and control the shape of the molded product, such as unevenness on the surface of the product.

For this reason, the tubular rubber type is made of hard rubber. However, the ease with which the above-mentioned blistering occurs varies greatly depending on the specific gravity and weight of the powder to be filled, as well as the ratio of the length and cross-sectional area of the tubular rubber mold. The longer the hair is, the more likely it is that blistering will occur. This also applies to the occurrence of irregularities on the surface of the molded article.

Therefore, it is possible to prevent this, but in order to do so, the main thing is to provide the side wall of the tubular rubber mold with sufficient strength to support the powder. If the strength of the side wall of the tubular rubber mold is excessively high, the pressure of the pressure medium will not be sufficiently propagated to the molded product during C[P molding, resulting in problems such as insufficient molding, so care must be taken.

Therefore, the material and hardness of the tubular rubber mold should be determined according to the above conditions, and are not particularly limited.

Next, we will discuss the causes of cracking during CIP molding.

The cause of cracking during CIP molding is due to the elastic restoring force of the rubber mold as described above, and the following cases are generally considered as the manner in which cracking occurs.

In the first form, the molded body is strongly adhered to the inner surface of the rubber stopper that closes both ends of the tubular rubber mold, and tensile stress is applied inside the molded body in a direction parallel to the longitudinal direction of the tubular rubber mold when the pressure is reduced during the CIP process. , cracks occur in the direction perpendicular to the longitudinal direction of the compact,
In extreme cases, the molded product may be divided into layers.

In the second form, the molded body is fixed to the inner surface of the tubular rubber mold, and the C
This is the case when a longitudinal stress is generated inside the molded body in a direction perpendicular to the longitudinal direction when the pressure is reduced during the IP treatment, causing radial cracks inside the molded body.

Furthermore, a third form is the above-mentioned first form. This is the case with the second form of mixing.

By the way, it is not possible to make a general statement as to which of the above-mentioned first to third forms the cracks take, as it is determined by the properties of the powder and the material of the rubber mold.
Empirically, it often takes the first form, and then the first form.
．． It has been found through experiments that there are many cases in which the two forms are mixed and the molded product cracks in a pomegranate shape (third form).

Therefore, the present invention has been developed by inserting plate-like or foil-like rubber plates into the openings at both ends of the tubular rubber mold, or by making a pair of plugs fitted into the openings at both ends of the tubular rubber mold made of metal. Of these, the first form, which is the most likely to occur, is mainly prevented.

That is, in the former method, a plate-shaped or foil-shaped rubber is placed inside the stopper, and the molded product is fixed to this, and when the pressure is reduced during the CIP process, the plate-like or foil-like rubber and the stopper are easily separated, forming a tubular shape. This facilitates the elastic restoration of the rubber mold, and prevents the generation of tensile stress in the longitudinal direction in the molded body, and thus prevents the occurrence of cracks.

On the other hand, in the latter case, the stopper itself is made of metal to prevent the occurrence of sticking and achieve the same effect as above.

The material of the rubber plate, rubber foil, or metal stopper is not particularly limited, but any material that meets the above objective 1 is sufficient. Further, although one rubber plate or rubber foil may be used, a plurality of rubber plates or rubber foils may be used as necessary.

As mentioned above, there is a slight difference in the action between a rubber plate or rubber foil and a metal stopper, but the effects are largely the same, and especially when a metal stopper is used, the deformation of the rubber mold near the stopper is decreases, and the strength of the molded article in this area tends to decrease slightly.

Next, in the present invention, the use of soft rubber inside the tubular rubber mold is mainly for preventing the occurrence of cracks in the second and third embodiments.

That is, by covering the entire surface of the molded body with a soft rubber having a weak restoring force, this soft rubber is fixed to the entire surface of the molded body during compression during CIP treatment, and only the hard rubber on the outer periphery of the soft rubber is restored when the pressure is reduced. , the stress generated inside the molded body is kept to a minimum (less than the strength of the molded body) and cracking is prevented.

Therefore, in each of the above cases, when the molded product that becomes the product is separated from the tubular rubber mold with rubber plates, rubber foil, or soft rubber fixed to both ends and/or sides, the fixed rubber plates, rubber foil, or The soft rubber can be peeled off relatively easily by manual operation or the like.

In addition, the present invention exhibits its effect regardless of the pressure reduction speed at the time of pressure reduction during CIP processing, and therefore does not reduce the pressure reduction speed, without sacrificing production efficiency. First, it is made possible to prevent cracking of the molded body.

(Example) The present invention will be described in detail below with further reference to the accompanying drawings.

FIG. 1(A) shows an example of the rubber mold according to the present invention, in which the tubular rubber mold (1) has a cylindrical shape, and a pair of plugs (2) are fitted into the upper and lower openings of the mold. Tubular rubber mold (1)
A rubber plate (4) is inserted inside the upper stopper (2) facing the internal cavity (3).

Figure 1 (B) shows the state (A) immediately after filling powder (5) when using the rubber mold as described above.

When pressurizing inside the CIP device (B) and when unloading the pressure medium (
Each state of C) is schematically shown.

That is, in the pressurized state (B), strong adhesion occurs between the molded body (M) and the rubber mold surface on each surface of PZ+P3 in the figure, but there is no adhesion between P and the plug (2). Since this does not occur, stress is not generated in the molded body even in the process of transitioning to the unloaded state (C), and cracking can be prevented.

The effect of the rubber plate (]) can be confirmed in I1, but if another rubber plate is placed on the 23rd side in Fig. 1 (D), the lower plug (2) and the molded body (M) This is even more effective since it can prevent the particles from sticking together.

Furthermore, although there is no particular meaning in inserting three or more rubber plates, the same effect can be obtained after all, so the number of rubber plates used is not limited.

Further, as mentioned above, the thickness of the rubber plate (4) should be such that one side sticks to the molded body but the other side does not stick to the stopper (2), and in fact, a foil of about 0.1 mm is sufficient. Any material having a thickness from 100 to 100% can be used.

Note that (6) in the figure indicates a sealing tape.

Next, based on the configuration of the above example, we will clarify the experimental situation.

Urethane rubber (JIS hardness 80) is used for the cylindrical tubular rubber mold (1), and chloroprene rubber (JIS hardness 60) is used for the plug (2).
), isoprene rubber (JIS hardness 40) on the rubber plate (4)
A rubber mold shown in FIG.
-8Fe-4Cr alloy powder (average particle size 50 μm) was CIP-molded at 5000 kg/cfr.

First, when we conducted a CIP molding experiment without inserting the rubber plate (4), we observed layered cracks as shown in Figure 6. It was also confirmed in this case.

Next, a similar experiment was conducted with one rubber plate (4) inserted at the top and bottom, and no cracking was observed even when depressurization was performed at the maximum speed (2000 atm/sec or more).
The effect of inserting the rubber plate (4) was fully confirmed.

FIG. 2 shows a modification of the rubber mold of the present invention, in which the tubular rubber mold (1) is cylindrical and the stopper (2) is made of metal.

In this case, by using the metal plug (2), it is possible to prevent the inner surface of the plug from adhering to the surface of the molded body, so that the same effect as described above can be obtained.

However, since the metal stopper (2) does not substantially deform even when pressurized, the molded body (M) becomes drum-shaped as shown in FIG. 2 (III), and the molding strength at both ends of the molded body is Some decline is inevitable.

FIG. 3 shows another modification of the present invention, in which a rubber mold (7) consisting of a soft rubber bag is separably inserted into a tubular rubber mold (1).

In this case, the molded body (M) does not stick on any surface other than the surface indicated by P4 in the figure, which is extremely effective in preventing cracking when molding powder that tends to stick to the inner surface of the tubular rubber mold (1). Effective.

Regarding the embodiment shown in FIG. 3, an experiment was actually conducted in the same manner as shown in FIG.

The cylindrical tubular rubber mold (1) is made of urethane rubber (hardness 80), and the plug (2) is made of chloroprene rubber (hardness 60).

Furthermore, a rubber mold of the present invention was created using isoprene rubber (hardness 30) as the rubber bag (7).

A, ff-20 created by inert gas atomization method
Since the 3i-6Cu-1-6Cu-4 alloy is brittle, it exhibited pomegranate-shaped cracks when CIP-molded using a conventional rubber mold, but no cracks were observed with the rubber mold of the present invention.
The effectiveness of the rubber bag (7) was confirmed.

For reference, experiments were also conducted on the rubber molds shown in Figures 1 and 2 at the same time, but some cracks were observed in the product after CIP molding due to the brittleness of the alloy. The use of bag (7) was found to be effective.

FIG. 4 shows a soft rubber bag (
7) shows a case in which a rubber plate (4) is placed in the opening.

In this case, the entire surface of the molded body (M) is adhered to the soft rubber, but since no adhesion occurs to the outer peripheral part made of hard rubber, which has a large restoring force, the occurrence of cracks can be completely prevented. In addition to the above, the present invention also includes a separable lining of a soft rubber mold along the inner surface of the tubular rubber mold instead of the soft rubber bag.

In each of the above cases, the rubber adhered to the molded body can be easily peeled off by peeling it off manually after recovering the molded body, and the peeled rubber can also be reused. Also, in some cases, rubber may be bonded together by pressure, and in this case, stearic acid is added to the contact surface of the rubber.

It is effective to apply a release agent such as zinc oxide.

(Effects of the Invention) The present invention is a rubber mold for CEP molding as described above, and includes a tubular hard rubber mold and a material that does not adhere to the molded product or has an elastic restoring force compared to the hard rubber mold. When performing CIP treatment on powders with poor moldability and low molded body strength, by combining a material that is low and easy to peel off from the molded body, it is possible to maintain and control the internal shape of the cavity due to hard rubber. In addition, it is possible to prevent the occurrence of stress and even cracks in the molded body without reducing the depressurization rate during CIP processing, improving production efficiency during CIP molded body manufacturing and reducing the incidence of defective products. A significant reduction effect is expected.

[Brief explanation of the drawing]

1 to 4 show each embodiment of the present invention, (A) is a schematic sectional view of each rubber mold, and (17) is a state immediately after powder filling using each corresponding rubber mold (A). ). When pressurizing inside the CIP device (B) and when unloading the pressure medium (
It is a schematic diagram which shows each state of C). Further, FIG. 5 is a schematic diagram of a CIP apparatus, and FIG. 6 is a schematic diagram of each state during CIP molding, showing problems in the conventional technology. (1)...Tubular rubber type, (2)...Plug. (4)...Rubber plate, (5)...Powder. (7)...Rubber bag, (M)...Molded object patent applicant
Kobe Steel, Ltd. - No. 1 Edict (B) A B C No. 2
Figure (a) Figure 3 (a) (b) A 5 C
$4 ward ゝ2 (b)

Claims (1)

[Scope of Claims] 1. An inner surface of the tubular rubber mold that is provided with a tubular hard rubber mold and a pair of plugs that fit to close the opening of the tubular rubber mold, and that is in contact with the molded product during molding. or/and the inner surface of at least one of the plugs is made of a material to which the molded body does not adhere; or/and the inner surface is made of a material that has a smaller elastic restoring force than the tubular rubber mold and is easily peeled off from the molded body. A rubber mold for CIP molding, characterized in that it is made by interposing. 2. A rubber mold consisting of a tubular hard rubber mold and a pair of rubber plugs that close the opening of the tubular rubber mold. A rubber mold for CIP molding according to claim 1, in which a foil-like rubber plate is inserted. 3. A rubber mold for CIP molding according to claim 1, which comprises a tubular hard rubber mold and a pair of metal plugs that are fitted to close the openings at both ends of the tubular rubber mold. 4. Claim No. 4, wherein a bag-like rubber mold made of soft rubber is inserted separably from the tubular rubber mold into the rubber mold consisting of a tubular hard rubber mold and plugs that close the openings at both ends of the rubber mold. A rubber mold for CIP molding according to item 1. 5. CI according to claim 4, wherein the stopper is a rubber stopper
Rubber mold for P molding. 6. CI according to claim 4, wherein the stopper is a metal stopper
Rubber mold for P molding. 7. According to any one of claims 1 to 6, a soft rubber lining that is separable from the tubular rubber mold is provided along the inner surface of the tubular hard rubber mold. C of
Rubber mold for IP molding.