JPH0543905A - Powder molding method - Google Patents

Abstract

PURPOSE:To reduce a change of shape in degreasing and sintering and to equalize sintered goods by performing degreasing and sintering of the extruded parts of kneaded material of metal or alloy powder in a ceramic filter body. CONSTITUTION:Kneaded material 1 which metal or alloy powder is kneaded with an organic binder, etc., to prepare is extruded from a nozzle and the green 2 or relatively long size thus obtained is as it is and immediately inserted into the opening of a ceramic filter body 3 so that the whole circumference of the green 2 except both the ends may be enclosed by the filter body 3, and under these conditions, degreasing and sintering are performed. Thereby, since radiation heat on degreasing and sintering is not directly radiated to the green 2, the heating of the green 2 is made much more uniform compared with the conventional method. Besides, the whole circumference of the green 2 except both the ends is protected by the filter body 3, muffle effect is obtained. And the degreasing process is made uniform by filter effect.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder molding method. More specifically, the present invention has a uniform quality of the sintered product, and a small change in shape during degreasing and sintering,
The present invention relates to an improved powder molding method by extrusion from a metal or alloy powder kneaded material.

[0002]

2. Description of the Related Art In recent years, a powder molding method in which a metal or alloy powder is kneaded with an organic binder or the like, extruded or injection-molded, and then degreased and sintered at high temperature has been attracting attention. This method is not only excellent in molding efficiency and good in productivity, but also in extrusion molding,
It is characterized in that it is easy to mold a long material, a wire, and the like, and in injection molding, even a product having a complicated shape and difficult to machine such as cutting can be easily molded.

Although the powder molding method has such excellent characteristics and advantages as described above, the degreasing and sintering steps of using an organic binder and removing and sintering the organic binder are indispensable. It has been an important issue to make uniform and secure a predetermined size. Particularly, in extrusion molding, this problem is important because a relatively long molded body is degreased and sintered.

For example, in extrusion molding, as illustrated in FIG. 1, a kneaded material (a) of a metal or alloy powder and an organic binder or the like is extruded from a nozzle (a),
A formed body (green) (c) having a predetermined shape and length is formed, placed on a ceramic plate (d) or the like, heated, degreased and sintered. In this degreasing process, H
2 Gas atmosphere or inert gas atmosphere is adopted, and the sintering process is carried out in vacuum or inert gas atmosphere.

In such a conventional production process, the molded product (green) (c) of the kneaded product is easily broken when the ceramic plate (d) or the like is installed, and therefore the content of the organic binder is inevitable. There is a problem that it will increase. This is because the presence of a large amount of binder makes the load of the degreasing process larger and the dimensional change after degreasing and sintering becomes large, which is unavoidable.

Further, in the conventional process, since the molded body (c) is directly exposed to the heat radiation from the heating source during the degreasing and sintering process, the progress of degreasing and sintering becomes non-uniform and the firing It is difficult to ensure the uniformity of the quality of the product and the strength is not uniform. Therefore, it is difficult to secure the reliability of the physicochemical properties of the sintered product, and it is difficult to predict the dimensional change.

The present invention has been made in view of the market as described above, eliminates the drawbacks of the conventional powder molding method by extrusion molding, ensures the uniform quality of the sintered product, and has a size. The aim is to provide an improved powder compaction process, which can be less variable.

[0008]

In order to solve the above problems, the present invention is characterized in that a kneaded material of metal or alloy powder is extruded and molded, and then the molded body is degreased and sintered in a ceramic filter body. A powder molding method is provided. That is, in the method of the present invention, for example, as illustrated in FIG. 2, a kneaded material (1) prepared by kneading a metal or alloy powder with an organic binder or the like is extruded from a nozzle to obtain a comparatively obtained product. The long shaped body (green) (2) is immediately inserted as it is into the opening (4) of the ceramic filter body (3), and the entire circumference of the shaped body (2) is the same except for both ends. Surrounded by the body (3). Then, in this state, degreasing and sintering are performed.

As is clear from the above steps, in the method of the present invention, the radiant heat at the time of degreasing and sintering does not directly impinge on the molded body (2), so that the molded body (2) is heated by the conventional method. Much more uniform than. Further, since the entire peripheral surface of the molded body (2) except for both ends thereof is surrounded and protected by the ceramic filter body (3), a muffle effect can be obtained. Moreover, the debinding process of the debinding process is homogenized by the filter effect. When H ₂ gas, N ₂ gas, etc. are used during this degreasing, these gases flow in from the end of the open ceramic filter body (3) and the discharge of binder gas is smoothly promoted. It will be.

Therefore, degreasing and sintering proceed uniformly and more efficiently. Further, in the present invention, as shown in FIG. 2, since the ceramic filter bodies (3) can be stacked and sintered, the number of moldings that can be processed in one step is significantly increased as compared with the conventional method. For this reason, the throughput of the method of the present invention is, in fact, more than 10 times that of the conventional one per unit time.

Since the molded body (2) can be directly received in the ceramic filter body (3), the breakage is not so large as in the conventional case. Therefore, the content of the organic binder can be reduced. This greatly contributes to uniform degreasing and sintering and minimization of dimensional change. Moreover, when the process is performed in a vacuum atmosphere, the amount of gas generated by the organic binder is small, so that the load on the vacuum pump system can be reduced.

In the method of the present invention having the above characteristics and effects, various kinds of metals or alloys similar to the conventional ones can be used. For example, powder of stellite alloy is used. The size of the powder of these metals or alloys can be set appropriately, and usually 5 to 15
Those having a diameter of about μm are preferably used. These powders are kneaded with an organic binder or the like, and in this case, the organic binder is also a thermoplastic polymer, or an oligomer thereof, together with an appropriate additive component such as a plasticizer.

Adjustment of these kneaded materials can be carried out in accordance with a conventional method. The same applies to extrusion. The shape and size of the ceramic filter body (3) into which the molded article after extrusion is inserted is not particularly limited. Further, as the material, an appropriate material such as an alumina-based or zirconia-based oxide or a nitride is used.

The ceramic filter body (3) is porous, and the porosity thereof can be appropriately set to, for example, about 20 to 40%. However, a high heat resistant ceramic that can withstand the heating temperature during sintering is used as the filter body of the present invention.

[0015]

EXAMPLE A powder of Stellite-6 having an average particle diameter of 12 μm was mixed with an organic binder made of a thermoplastic polymer in an amount of 6%, and kneaded using a pressure / heating kneader. This kneaded product was extruded into two types of wire rods having a diameter of 5 mm × 1200 mm and a diameter of 25 mm × 1200 mm.

Each of these was inserted into an opening of a ceramic filter body having the following characteristics. -Alumina content 99% -Bass specific gravity 2.6-Body porosity 35% -Water absorption 14% -Heat-resistant temperature 1400 ° C Degreasing was performed by heating in an H ₂ atmosphere for 1 hour at a temperature of 470 ° C. The temperature rising rate was 30 ° C./Hr.

Next, sintering was performed at a temperature of 1250 ° C. in a vacuum atmosphere for 10 hours. The heating rate at this time was 200 ° C./Hr. And cooled to an N ₂ atmosphere. A sintered product having a diameter of 2 mm and a length of 830 mm was obtained from the molded body having a diameter of 5 mm. In addition, a sintered product having a diameter of 12 mm and a length of 870 mm was obtained from the molded product having a diameter of 25 mm. In each case, by stacking a plurality of filter bodies and degreasing and sintering, the processes from the conventional method of 200 to 2280 were performed in one batch.

The quality and strength of the molded product were uniform and almost no breakage was observed. On the other hand, in the conventional method, generation of cranks after sintering and generation of micropores after degassing were unavoidable. In the above method, the amount of organic binder used could be reduced to 5% or less. On the other hand, in the conventional method, it was difficult to reduce the amount to 10% or less. Moreover, in the case of the conventional method, 5 mm diameter x 1
From the 200 mm long molding, only 1.2 mm diameter x 760 mm length, which was a very large dimensional change, could be obtained.

[0019]

As described in detail above, according to the present invention, it is possible to obtain a highly reliable product having uniform quality and strength of the sintered product. Moreover, the dimensional change after sintering can be small.

[Brief description of drawings]

FIG. 1 is a perspective view illustrating the steps of a conventional method.

FIG. 2 is a perspective view of a main part illustrating the process of the present invention using a semi-filter body.

[Explanation of symbols]

 A Nozzle Kneaded product C Molded product (green) D Ceramic plate 1 Kneaded product 2 Molded product (green) 3 Ceramic filter body

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[Procedure amendment]

[Submission date] September 17, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

Then, sintering was performed at a temperature of 1250 ° C. in a vacuum atmosphere for 1 hour. The heating rate at this time was 200 ° C./Hr. And cooled to an N ₂ atmosphere.
A sintered product having a diameter of 4.5 mm and a length of 830 mm was obtained from the molded body having a diameter of 5 mm. In addition, a sintered product having a diameter of 2.2 mm and a length of 870 mm was obtained from the molded body having a diameter of 2.5 mm. In each case, by stacking a plurality of filter bodies and degreasing and sintering, the processes from the conventional method of 200 to 2280 were performed in one batch.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

The quality and strength of the molded product were uniform and almost no breakage was observed. On the other hand, in the conventional method, generation of cracks after sintering and generation of micropores after degassing were unavoidable. In the above method, the amount of organic binder used could be reduced to 5% or less. On the other hand, in the conventional method, it was difficult to reduce the amount to 10% or less. Moreover, in the case of the conventional method, 5 mm diameter x 12
From the 00 mm long molded body, only the one with a very large dimensional change of 4.0 diameter × 880 mm length could be obtained.

Claims (1)

[Claims] 1. A powder molding method characterized by extruding a kneaded material of metal or alloy powder, and then degreasing and sintering the molded body in a ceramic filter body.