JPH08100202A - Injection molding core, injection molding die device, and method for manufacturing sintered product - Google Patents

Abstract

(57) [Summary] [Purpose] To simplify the manufacturing process of sintered products and shorten the time required for core removal. [Structure] An injection molding core 1 is formed of a synthetic resin material having a hollow portion 4 for mounting the pre-sintered molded body in a molding die 2 or 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding core used for forming a pre-sintered compact of a sintered product made of powder of metal, ceramic or the like, and an injection using the core. The present invention relates to a molding die device and a method for manufacturing a sintered product using the die device.

[0002]

2. Description of the Related Art In order to manufacture a molded product from metal or ceramics, machining has been applied. In recent years, however, powder sinter molding has been applied by applying plastic injection molding technology.
It has come to be adopted because it has good workability as compared with metal working and can be mass-produced.

That is, in the above powder sinter molding, a mixture of a raw material powder consisting of fine powder of metal or ceramics and a binder (binding material) is made into a kneading body, which is injected from an injection molding machine into a predetermined mold. After obtaining the preformed body by molding, the binder is removed by heating the preformed body at a temperature equal to or lower than the melting point of the raw material powder, and then the binder-removed formed body is sintered at a high temperature. It is a method of filling the voids after binder removal and manufacturing a contracted powder-sintered molded product having a shape similar to that of a mold.

However, when manufacturing a powder-sintered molded product having a complicated shape having a hollow portion inside by the above-mentioned powder-sintering molding, a core corresponding to the shape of the hollow portion is arranged in the mold. After obtaining the pre-sintered compact by injection molding in the state, a step of removing the core from the pre-sintered compact is required.

Many proposals have been made in the past for removing the core in the above-mentioned powder sinter molding, and as a typical means therefor, the core is formed of a low melting point metal such as bismuth or bismuth soot alloy. , This core,
A method of melting and removing from the pre-sintered compact in parallel with the binder removal treatment or prior to the binder removal treatment (Japanese Patent Application Laid-Open No. Hei 4-
No. 99082) and an organic resin that is soluble in an organic solvent, and a core is formed from the pre-sintered compact by immersing the core in the organic solvent prior to the binder removal treatment. Method of removal (JP-A-4-1795)
No. 01) and the like.

[0006]

However, in the method described in Japanese Patent Laid-Open No. 4-99082, there is a possibility that the core and the raw material powder may react with each other depending on the material of the raw material powder to cause alloying. In some cases, a core removing step is newly added, which causes a problem of increasing cost.

Further, in the method described in the above-mentioned Japanese Patent Laid-Open No. 4-179501, not only a core removing step is newly added, but also this core removing step requires a long time of 10 hours or more, and the solvent tank is used. However, there is a problem that the equipment will be oversized and the working environment will be deteriorated.

The present invention has been made to solve the above-mentioned problems, and an object thereof is to simplify the manufacturing process of a sintered product and shorten the removal time of the core. The object is to provide a molding core, an injection molding die device, and a method for manufacturing a sintered product.

[0009]

In order to achieve the above object, the injection molding core of the invention according to claim 1 has a hollow portion for attaching the pre-sintered molded body to a molding die. It is characterized by being formed of a synthetic resin material.

According to a second aspect of the present invention, there is provided a mold apparatus for injection molding, wherein a kneaded material of raw material powder and a binder is injected into a mold including a core to form a pre-sintered molded body. In the mold device, the core is formed of a synthetic resin material having a mounting hollow portion, and the mounting hollow portion is externally inserted into a protrusion formed in a mold inner space portion forming a cavity. It is characterized in that it is detachably attached to the mold.

According to a third aspect of the present invention, there is provided the injection molding die apparatus according to the second aspect, wherein the protrusion is provided so as to protrude from a die matching surface of the die.

According to a fourth aspect of the present invention, there is provided the injection molding die apparatus according to the second aspect, wherein the protrusion is formed so as to form a part of the internal space of the die. It is characterized in that it is provided in a concave portion which is opened by opening on the mold matching surface.

Further, in the method for producing a sintered product according to a fifth aspect of the present invention, the kneaded material of the raw material powder and the binder is injection-molded in a mold including a core, and a pre-sintered molded body is obtained. In the method for producing a sintered product, in which the binder is removed by heating at a temperature equal to or lower than the melting point of the raw material powder, and then the obtained binder-removed molded body is sintered, the core has an attachment hollow portion. And is formed of a synthetic resin material, and the mounting hollow portion is detachably mounted on the mold by being externally inserted into a protrusion formed to project in the mold inner space forming the cavity, After the mold is released from the pre-sintered compact, the core is melted and removed from the pre-sintered compact together with the binder in the binder removal treatment step.

[0014]

Since the inventions according to claims 1 to 5 are configured as described above, they have the following effects.

That is, since the injection-molded core according to the first aspect of the present invention has the mounting hollow portion and is formed of the synthetic resin material, the mutual reaction between the core and the raw material powder in the binder removal treatment step. It is possible to melt and remove the core together with the binder from the pre-sintered molded body, and to form the core with a synthetic resin material in an amount as small as the mounting hollow portion.

According to a second aspect of the present invention, there is provided a mold apparatus for injection molding, wherein a core having a mounting hollow portion and made of a synthetic resin material has a hollow portion for mounting and a protrusion portion of a space inside the mold. Since it is inserted into the mold and set in the mold, the core can be easily set and released, and the core can be set in a short time without any interaction with the raw material powder in the binder removal process. It is possible to mold a pre-sintered compact that can be removed by.

In the mold apparatus for injection molding according to the third aspect of the present invention, since the protrusion to which the core is fixed is formed so as to project from the mold matching surface of the mold, the core is set and released. It can be done easily.

Further, in the injection-molding die device according to the fourth aspect of the present invention, since the protrusion to which the core is fixed is provided in the concave portion opened on the die matching surface of the die. The protrusions can be protected by avoiding exposure to the outside.

Further, in the method for producing a sintered product according to a fifth aspect of the present invention, the molding core of the pre-sintered compact is formed of a synthetic resin material having a hollow portion for attachment to a mold, After the mold is released from the pre-sintered compact, it is melted and removed from the pre-sintered compact together with the binder in the binder removal processing step, so there is no need to newly provide a core removal step and the mounting hollow Since the amount of synthetic resin is reduced due to the provision of the parts, the core can be quickly removed from the pre-sintered compact.

[0020]

The present invention will be described in detail below with reference to the illustrated embodiments.

FIG. 1 shows an injection molding core 1 as one embodiment, FIG. 2 shows an injection molding die apparatus 2 using this injection molding core 1, and FIG. 3 shows this injection molding. 1 shows a sintered product 3 obtained by a method of manufacturing a sintered product using a mold device 2 for a metal.

The injection molding core 1 is made of a synthetic resin material having a hollow portion 4 for mounting the pre-sintered compact on the molding die.

That is, the injection molding core 1 is formed of a synthetic resin material into a substantially U-shaped solid body corresponding to the hollow portion 5 of the sintered product 3, and both ends of the U-shape are formed. An attachment hollow portion 4 is formed by opening the end surface 1a of the portion.

The synthetic resin material forming the core 1 does not soften at the injection molding temperature, melts at the binder removal processing temperature, and reacts with the material contained in the pre-sintered compact. As long as there is no synthetic resin material, both thermosetting resin and thermoplastic resin can be used. Specifically, as the thermosetting resin, a melamine resin, a phenol resin, an epoxy resin, an unsaturated polyester resin, or an unsaturated polycarbonate resin can be used,
Polystyrene resin or the like can be used as the thermoplastic resin.

The core 1 is formed into a predetermined shape by subjecting these synthetic resin materials to compression molding, powder molding, cast molding or the like.

The injection molding die unit 2 is constructed by assembling the injection molding core 1.

That is, the injection molding die apparatus 2 is shown in FIG.
As shown in FIG. 1, a first split mold 6 having a male die 8 protruding from the mating surface 6a in a U-shaped cross section, and a male die 8 formed by recessing from the mold mating surface 7a in a U-shaped cross section. A second split mold 7 having a female mold 9 that forms a space 10 inside the mold between
The first split mold 6 is obtained by inserting the mounting hollow portion 4 onto the protrusions 13 formed by projecting from the mold matching surfaces 6a on both sides of the male mold 8.
The core 1 is detachably attached to the core 1. Further, the first split mold 6 is provided with a gate 12 having one end 12a opened to the mold matching surface 6a and the other end 12b communicating with an injection molding machine (not shown).

At this time, the protrusion 13 is formed in the die space portion 1 formed by combining the first and second split dies 6 and 7.
The core 1 which is formed so as to project to 0 and is fixed to the protrusion 13 is located in the space 10 inside the mold and communicates with the gate 12 between the male mold 8 and the female mold 9. To form a cavity 10a.

Injection-molding die device 2 having the above structure
Means that the protrusion 13 to which the core 1 is fixed is the mold matching surface 6 of the mold.
Since it is formed so as to project from a, the core 1 can be easily set and released, and the pre-sintered compact can be easily molded.

The following manufacturing method is used to obtain a sintered product 3 using the injection molding die device 2.

First, a molding material is prepared. The molding material is a mixture of raw material powder and binder, that is, fine metal powder such as copper, aluminum, steel, nickel and various alloys,
Alternatively, a raw material powder such as glass, enamel or the like and ceramics fine powder, and a binder such as polyethylene or acrylic resin that functions to bind these raw material powders are mixed at a temperature equal to or higher than the melting point of the binder. Therefore, the compounding ratio of the raw material powder and the binder in this kneaded product is usually set in the range of 5 to 30 parts by weight of the binder with respect to 100 parts by weight of the raw material powder.

The kneaded material thus adjusted is used for the gate 12 of the injection molding die unit 2 using an injection molding machine (not shown).
Is injection-molded into the cavity 10a through the, and a pre-sintered compact is injection-molded. Then, the first and second split molds 6
The molds of 7 and 7 are opened, and the pre-sintered compact is released from the core 1. In the pre-sintering molding which is released, the core 1 is filled inside.

Next, the pre-sintered compact is sent to a binder removal tank for binder removal processing. This binder removal treatment is performed at 400 to 600 in a vacuum state, an inert gas atmosphere such as argon and a reducing atmosphere such as a hydrogen atmosphere.
It is carried out by heating for 10 to 20 hours under the condition that the temperature is gradually raised to a temperature of ℃, preferably about 500 ℃.

In the binder removal treatment step, the core 1 made of the binder and the synthetic resin material contained in the pre-sintered compact is melted and effectively removed from the pre-sintered compact, and thereafter the same as described above. The binder-removed molded body is formed by cooling in the reducing atmosphere.

The binder-removed compact thus obtained is then sent to a sintering treatment step and sintered or fired at a temperature of 600 to 2200 ° C. for 3 to 10 hours to melt the raw material powder and remove the binder. After processing, the fine voids are filled, and the sintered product 3 shown in FIG. 3 can be obtained. The sintered product 3 is a U-shaped pipe body in which the hollow portion 5 is formed by melting and removing the core 1.

In this method for producing a sintered product, since the core 1 is made of a synthetic resin material, the binder and the core are simultaneously formed in the binder removal processing step without causing a reaction with the raw material powder of the pre-sintered compact. It becomes possible to melt and remove, and the manufacturing process can be simplified without adding one step for removing the core 1, and the core 1 has a hollow portion 4 for attaching to the mold. Since the core 1 is formed with a small amount of the synthetic resin material only in the hollow portion 4, the time required for removing the core 1 in the binder removal processing step can be shortened.

FIG. 4 shows an injection molding die apparatus 20 as another embodiment. This injection molding die device 20 has a recess 14 formed by opening the die matching surface 15a of the first split mold 15 so that the protrusion 13 forms a part of the space 10 inside the die. It is provided and the gate 12 is formed in the central portion of the second split mold 16 so as to correspond to the bent portion 1b of the core 1, and other configurations are different. It is formed similarly to the mold device 2.

The injection molding die apparatus 20 is capable of performing injection molding of a pre-sintered compact which can simplify the manufacturing process and shorten the removal time of the core 1 similarly to the die apparatus 2. In addition to this, a kneaded material as a molding material can be easily and uniformly filled from the gate 12 into the cavity 10a, and a sintered product 3 of stable quality can be obtained.

Moreover, since the projection 13 is provided in the recess 14 in the injection molding die device 20, the projection 13 can be protected from being exposed to the outside, and the durability is improved. Has become.

Experimental Example: Next, the effect of the present invention will be further described by an experimental example.

Copper powder having a particle size of 5 to 30 μm was prepared as a raw material powder.

On the other hand, polystyrene 2 to 2 is used as a binder.
5 parts by weight, acrylic resin 2-5 parts by weight, polyethylene 1
˜3 parts by weight, 0.5 to 1.5 parts by weight of paraffin wax and 0.1 to 0.5 parts by weight of stearic acid were mixed to prepare a binder.

Then, 90% by weight of the copper powder and 10% by weight of the mixed binder were kneaded to prepare a molding material.

As the injection molding die apparatus, the injection molding die apparatus 2 shown in FIG. 2 was prepared as the apparatus of the present invention, and the injection molding die apparatus 100 shown in FIG. 5 was prepared as the comparison apparatus.
The mold apparatus 100 is composed of split molds 101 and 102, and a mold inner space portion 104 is formed by matching the split molds 101 and 102, and the split mold 101 has a gate 105.
And a core 106 that forms a hollow portion of the sintered product is arranged in the space 104 inside the mold. The core 106 is formed as a U-shaped solid body corresponding to the hollow shape of the sintered product, and both ends 106a of the core 106 are fitted into the recesses 101a formed in the mold matching surface to fit into the metal. The split mold 101 is disposed in the mold space 104.
And 102, a cavity 104a communicating with the gate 105 is formed.

That is, both cores 1 and 106 have the same shape except for the presence or absence of the mounting hollow portion 4, and both mold devices 2 and 20 have the projection 13 (mold device 2) and the recess 101a.
It has the same structure except that it is different from the (die unit 20).

Further, the cores 1 and 106 used in the mold apparatuses 2 and 100, respectively, were molded by casting the same unsaturated polycarbonate.

Then, the above-mentioned molding material is supplied to an injection molding machine in which the screw temperature is set to 180 ° C., and is poured into a mold apparatus 2 (the apparatus of the present invention) to inject a pre-sintered molded body including the core 1. Molded.

The pre-sintered compact thus obtained was then embedded in a binder removal treatment tank filled with activated carbon,
Under a nitrogen gas atmosphere, the temperature was gradually raised from room temperature to 500 ° C. to remove the binder.

In this binder removal processing step, the core 1 is melted and removed together with the binder from the pre-sintered compact,
A binderless molded body was obtained.

Next, the binder-removed molded body was gradually heated from room temperature to 1050 ° C. in a nitrogen gas atmosphere over 10 hours, kept at 1050 ° C. for 4 hours, and then cooled to have a diameter shown in FIG. a: 5 to 10 mm, hollow diameter b: 3 to
A bifurcated pipe sintered product 3 having a height of 8 mm and a height h of 15 to 50 mm was obtained.

On the other hand, for comparison, an injection molding die apparatus 1
No. 00 is used to obtain a pre-sintered compact including the core 106 with the same compacting material, and the binder removal process and the sintering process are performed under the same conditions as described above, and the sintering is performed in the same shape and size as described above. Item 3 was obtained.

Cores 1 and 10 used in the injection molding die apparatus 2 (invention apparatus) and 100 (comparative apparatus) at this time.
Table 1 shows the weight of No. 6 and the melting removal time (degreasing time) from the pre-sintered compact in the debindering process of the cores 1 and 106.

[0053]

[Table 1] As can be seen from Table 1, the core 1 used in the device of the present invention can be formed with a smaller amount of resin than the core 106 due to the provision of the mounting hollow portion 4, and due to this small amount of resin, The degreasing time in the binder removal treatment step can be greatly shortened.

[0054]

As described in detail above, the present invention has the following effects.

That is, according to the first aspect of the present invention, since the core has the mounting hollow portion and is made of the synthetic resin material,
In the binder removal treatment step, the core can be melted and removed from the pre-sintered compact together with the binder without any interaction between the core and the raw material powder. Since the manufacturing process can be simplified without adding, and the core can be formed with a synthetic resin material of a small amount corresponding to the mounting hollow portion,
It is possible to provide an injection molding core that can reduce the time required for removing the core while saving the synthetic resin material.

According to the second aspect of the present invention, the core having the mounting hollow portion and formed of a small amount of synthetic resin material has the mounting hollow portion outside the protrusion of the inner space of the mold. Since it is inserted and set in the mold, the core can be set and released easily, and the core can be removed in a short time without any interaction with the raw material powder in the binder removal process. A possible pre-sintered molded body can be molded, and as a result, it is possible to provide an injection molding die apparatus which can simplify the manufacturing process and shorten the time for removing the core.

According to the third aspect of the present invention, since the protrusion to which the core is fixed is formed so as to protrude from the die matching surface of the mold, the core can be easily set and released. As a result, in addition to the effect of the invention described in claim 2, it is possible to provide the injection molding die device that facilitates the molding of the pre-sintered molded body.

Further, according to the invention of claim 4, since the projecting portion to which the core is fixed is provided in the recessed hole opened on the die matching surface of the die, the projecting portion is formed. It can be protected by avoiding exposure to the outside, resulting in claim 2.
In addition to the effects of the invention described above, it is possible to provide an injection molding die device in which the durability of the protrusion is improved.

Further, according to the invention of claim 5, the molding core of the pre-sintered compact is formed of a synthetic resin material having a hollow portion for attachment to a mold, and the core is pre-sintered. Since the pre-sintered compact is melted and removed together with the binder in the binder removal step after the mold is released from the mold, there is no need to newly provide the core removal step, and the mounting hollow portion is provided. Since the amount of synthetic resin is small, the core can be removed quickly from the pre-sintered compact, resulting in a simplified manufacturing process and a shorter core removal time. Can be provided.

[Brief description of drawings]

FIG. 1 is a front view of a core as an example.

FIG. 2 is a cross-sectional view of an injection molding die apparatus as one example.

FIG. 3 shows a sintered product as an example, (a) is a front view thereof, and (b) is a partially cutaway bottom view thereof.

FIG. 4 is a cross-sectional view of a mold device for injection molding as another embodiment.

FIG. 5 is a cross-sectional view of an injection molding die device as a comparative example.

[Explanation of symbols]

 1 Injection Molding Core 2, 20 Injection Molding Mold Device 3 Sintered Product 4 Mounting Hollow Part (Injection Molding Core) 6a, 7a, 15a Mold Matching Surface 10 Mold Inner Space 10a Cavity 13 Protrusion Part 14 Recess

Claims (5)

[Claims] 1. An injection molding core, which is made of a synthetic resin material and has a hollow portion for mounting the pre-sintered compact to a molding die. 2. An injection molding die device for forming a pre-sintered compact by injecting a kneaded material of a raw material powder and a binder into a die containing a core, wherein the core has a hollow portion for mounting. It is formed of a synthetic resin material and is detachably attached to the mold by externally inserting the mounting hollow portion into a protrusion formed in a mold inner space portion forming a cavity. A mold apparatus for injection molding, characterized in that 3. The mold apparatus for injection molding according to claim 2, wherein the protrusion is provided so as to project from a mold matching surface of the mold. 4. The injection-molding die apparatus according to claim 2, wherein the protrusion is opened in a die-matching surface of the die so as to form a part of the die inner space. An injection molding die apparatus, which is provided in a recessed portion. 5. The binder is removed by heating a pre-sintered compact obtained by injection molding a kneaded material of the raw material powder and a binder into a mold containing a core at a temperature not higher than the melting point of the raw material powder. In the method for producing a sintered product, the core is formed of a synthetic resin material having a hollow part for attachment, and the binder is attached. The hollow part is detachably attached to the mold by externally inserting it into a protrusion formed in the mold space forming the cavity, and after the core is released from the pre-sintered compact, A method for manufacturing a sintered product, characterized in that the binder is melted and removed from the pre-sintered compact in the binder removal treatment step together with the binder.