JPH02153857A - Production of sintered material - Google Patents

Abstract

PURPOSE:To shorten dewaxing time in dewaxing an injection molded or extrusion molded article comprising metallic or ceramic powder and an organic polymer binder with an organic solvent and sintering, by using a combination of a component soluble in an organic solvent and a component insoluble in the organic solvent as the binder. CONSTITUTION:Metallic or ceramic powder is blended with a binder consisting essentially of an organic polymer, kneaded and pelletized to give a mixture, which is injection molded or extrusion molded to give a molded article of desired shape. In the operation, the organic polymer contained as the binder is a combination of one or more of a solution soluble in a certain organic solvent and a component insoluble in the organic solvent. Only the soluble binder component is extracted by a method such as immersing the molded article in a certain organic solvent and the molded article is sintered to give a sintered product. By this method, the molded article can be dewaxed in a shorter time than by heating dewaxing method and the shape of the molded article will not be damaged because the polymer insoluble in an organic solvent is left.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a method for producing a sintered body of metal or ceramics, and in particular, the present invention relates to a method for producing a sintered body of metal or ceramics, and in particular, a method of manufacturing a sintered body of metal or ceramics, and in particular, a method of manufacturing a sintered body of metal or ceramics, and in particular, a method of manufacturing a sintered body of a metal or ceramic, in which a formed body is mixed with a raw material powder and a binder mainly composed of an organic polymer before sintering. It relates to a method of obtaining a mixture by injection molding or extraction molding a mixture obtained by mixing, kneading, and pelletizing the mixture, and then degreasing the mixture.

[Prior Art] Generally, in the process of producing a sintered body of metal or ceramics, a compact for sintering is obtained as a green compact by compression molding raw material powder. Since this method usually uses punches to apply pressure from above and below, the shape of the molded product obtained is limited to relatively simple shapes such as cylinders and cylinders, and it is difficult to obtain products with more complex shapes. It is necessary to perform post-processing such as cutting and grinding on the sintered product.

In order to improve these problems, various techniques are being studied to make the shape of the molded object more similar to the product, but in the field of ceramic products, mainly so-called engineering ceramics, 10 to 2% Offi is added to the raw material powder. A method has been carried out industrially in which a binder mainly composed of an organic polymer is added, mixed, kneaded, injection molded or extraction molded, and the molded product is degreased and sintered to obtain a product. Injection molding and extraction molding are originally molding methods for thermoplastic organic polymers, but they are suitable for producing products with high dimensional accuracy and in large quantities without post-processing, so they are suitable for solving the problems mentioned above. There are some things worth noting. Supported by the recent development of metal powder manufacturing technology, typified by the atomization method, and the development of binder compounding technology, attempts have been made to apply the above-mentioned method to sintered metal products.

[Problems to be Solved by the Invention] The difference between the method of using this injection or extraction molded body for sintering and the conventional method of sintering a compression molded body is that the molding method is different, but in the former, Since the molded body contains a large amount of binder, it is necessary to perform a binder removal, that is, a degreasing step, before sintering. Incidentally, in the latter case, the molded body does not contain a total heat binder, or even if it does contain it, it is only in a small amount, so it can be directly sintered. The conventional general method for this degreasing step is to gradually heat the molded body to volatilize the binder as a pyrolysis gas. If the temperature increase rate at this time is too high, the generation of pyrolysis gas will be too rapid, causing deformation such as cracks and blisters in the molded body, so it is necessary to set it to about 5 to b. For this reason, raising the temperature from room temperature to 600°C requires a long time of 30 to 120)1 r, which is a factor that hinders the reduction in manufacturing costs.

The technical problem of the present invention was achieved in order to eliminate this drawback, as a result of studying a binder removal method as an alternative to the conventional so-called heat debinding method. It is an object of the present invention to provide a method for manufacturing a sintered body that enables time reduction.

[Means for Solving the Problems] According to the present invention, a mixture obtained by mixing, kneading, and pelletizing metal or ceramic powder with a binder mainly composed of an organic polymer is molded into desired shapes by injection molding or extraction molding. In the method of manufacturing a sintered body by forming a molded body into a shaped body, degreasing it with a predetermined organic solvent, and sintering it, the organic polymer has a soluble component and an insoluble component in the predetermined organic solvent. A method for manufacturing a sintered body is obtained.

That is, the present invention uses a combination of two or more types of organic polymers contained as binders in the injection or extraction molded product, one that is soluble in a certain kind of solvent and one that is not. This method is configured to extract only soluble components using a method of degreasing, and is characterized by being able to perform degreasing in a shorter time than conventional thermal degreasing methods and without causing deformation of the molded product.

Extraction with an organic solvent is effective as a method for separating both organic and inorganic substances from a mixture, but heat degreasing, which is a conventional degreasing method during this manufacturing process, is nothing but an operation for separating organic and inorganic substances.

However, even if an attempt is made to extract the molded object simply by immersing it in an organic solvent that can dissolve the binder, in most cases the molded object collapses as the binder dissolves, so this solvent extraction method is not applicable to this manufacturing process. This is extremely difficult. On the other hand, organic substances and organic polymers, which are the main components of the binder in question here, have a limited number of organic solvents that can dissolve them depending on their chemical structures. From the opposite perspective, a certain type of organic solvent may be a good solvent for one type of organic polymer but a poor solvent for another type of organic polymer, and this property can be exploited. For example, it is possible to selectively extract a specific organic polymer from a mixture of two or more organic polymers.

In view of these facts, the present inventors performed an extraction process on a molded body made of a binder mainly composed of metal or ceramic powder and an organic polymer using an organic solvent while leaving a part of the binder remaining. The present inventors have discovered that a molded body that can be sintered without losing its shape can be obtained by doing so, leading to the present invention.

The powder used in the present invention is not particularly limited as long as it can be made into powder and can be sintered, and examples include various pure metal and alloy powders, and ceramics such as ferrite and alumina. .

Furthermore, as an example of a combination of organic polymers, if polypropylene and acrylic polymer are used, the former is hardly soluble in benzene, but is a good solvent for acrylic polymer and is suitable for the purpose of the present invention. be.

[Example] Examples will be given and explained below.

<Example-1> Fe-50Co powder 91.0 with an average particle size of 9.6 μa manufactured by a water atomization method. Ovt%, high density polyethylene 1.0w1% as binder, vinyl acetate content 25
% ethylene-vinyl acetate copolymer 3, Ovt%, butyl polyacrylate 2.0w1%, paraffin wax with melting point 60°C 2. Ovt%, stearinl! 21.0yt
After adding and kneading the mixture into pellets, injection molding is performed to make pellets with an outer diameter of φ3C1+, an inner diameter of φ20, and a thickness of 5+.
A ring-shaped molded product of am was obtained. When this molded body was immersed in toluene at 60° C. and maintained for 5 hours, the weight loss of the molded body was y, evt%, and no change in dimensions was observed.

In other words, 84.4i% of the binder is extracted with toluene and the remaining 15. Gvt% is considered to be mainly composed of high density polyethylene which is insoluble in toluene. This degreased molded body
Relative density 9 as a result of sintering at 1250℃ x 5 hours in atmosphere 2
A sintered body of 6% was obtained. At this time, the dimensional shrinkage was about 17% for both the outer and inner diameters, and about 12% for the thickness, and no deformation was observed.

Comparative Example 1> A molded article obtained in the same manner as in Example 1 was heated from room temperature to 600° C. in an Ar atmosphere, and degreased by holding the temperature at 600° C. for 511°C.

The heating rate at this time is 5, 10.15, 20.40"C/
Although five conditions of llr were used, degreased bodies without deformation were obtained only under 5°C/llr and 10°C/11r.

<Example-2> Calcined powder of strontium ferrite with an average particle size of 1.0μ, 90.0w1%, 1.0vt% of polypropylene as a binder, and ethylene-vinyl acetate copolymer with a vinyl acetate content of 25%3. 0w1%, polystyrene 3, OvL
915, paraffin wax 2 at m point 60°C, OvL
%, stearic acid 1. Ovt% was added to each, and a pipe with an outer diameter of 36 mm and an inner diameter of 26 yawn was formed by extraction molding, and cut into a length of 30 m+s. When this molded body was immersed in benzene at 60°C and maintained at 511r,
The weight loss of the molded body was 8.7 wt%, and no change in dimensions was observed. In other words, 87.0w1% of the binder is extracted by benzene, and the remaining 13.0w1% is extracted by benzene. Ovt% is considered to be mainly composed of polypropylene which is insoluble in benzene. As a result of sintering this degreased compact at 1200° C. for 2 hours, a sintered compact with a relative density of 97% was obtained.

At this time, the shrinkage of the dimensions is about 12% for both the outer and inner diameters, and the length is about 1
6%, and no deformation was observed.

Comparative Example-2> When the molded body obtained in the same manner as in Example-2 was heated and degreased in the same manner as in Comparative Example-2, the temperature increase rate without deformation was still up to 10°C/II'. Ta.

[Effects of the Invention] As explained in detail above, according to the method for manufacturing a sintered body of the present invention, the degreasing time of a molded body made of metal or ceramic powder and a binder mainly composed of an organic polymer can be significantly reduced. This opens up the possibility of providing high-quality, low-cost sintered products with a large degree of freedom in shape.

This greatly contributes to the expansion of new uses for sintered products, and is of great industrial benefit.

Procedural amendment (voluntary) Heisei/2002 Director General of the Japan Patent Office Yoshi 1) Tsuyoshi Moon 1. Indication of the case Patent Application No. 305157 of 1988 3. Name of the invention Method for manufacturing sintered bodies 3. Amendments to be made Relationship with the Patent Case Patent Applicant Name Tokin 4 Co., Ltd., Agent 〒! 05 Address: 1-4-10 Nishi-Shinbashi, Minato-ku, Tokyo (and 2 others)
Date 6: Contents of the amendment (a) As per the attachment (b), a part of the statement in the detailed description of the invention column of the specification is amended as follows.

1) Change “extraction molding” in line 3 of page 2 of the specification to “extrusion molding”
Correct to.

2) Change “extraction molding” to “extrusion molding” in the first line of page 3 of the specification.
Correct to.

3) "Extraction molding" on page 3, line 3 of the specification is changed to "extrusion molding"
Correct to.

4) In the specification, page 3, line 12, "extraction molding" is corrected to "extrusion molding".

5) In the specification, page 4, line 12, "extraction molding" is corrected to "extrusion molding".

6) On page 4, line 19 of the specification, "extraction molding" is corrected to "extrusion molding".

7) Page 5, line 5 of the specification, “extraction molding” is changed to “extrusion molding”
Correct to.

(Attachment) Claim 1: A mixture obtained by mixing, kneading, and pelletizing metal or ceramic powder with a binder whose main component is an organic polymer is molded into a desired shape by injection molding or extrusion molding. In the method of manufacturing a sintered body by forming a molded body, degreasing it with a predetermined whitening solvent, and sintering it, the organic polymer has a soluble component and an insoluble component in the organic solvent. A method for producing a sintered body, comprising:

Claims (1)

[Claims] 1. A mixture obtained by mixing, kneading, and pelletizing metal or ceramic powder with a binder whose main component is an organic polymer is molded into a desired shape by injection molding or extraction molding, and then mixed with a specified organic solvent. A method for producing a sintered body by degreasing and sintering, wherein the organic polymer has a soluble component and an insoluble component in the organic solvent. .