JPH05320713A - Production of composite sintered compact - Google Patents

Abstract

PURPOSE:To produce a composite sintered compact without any crack at the joining part by adjusting the amt. of a binder to be kneaded with the powder of the material of a different kind to regulate the sintering shrinkage rate, forming a composite compact from the material, degreasing and then sintering the compact. CONSTITUTION:The specified amt. of a binder is kneaded with the one material powder to be sintered, the mixture is injection-molded, and the sintering shrinkage rate of the obtained compact is obtained. The amt. of the binder to be added to the other material powder to be sintered necessary to adjust the shrinkage sintering shrinkage rate to that of the former compd. is obtained, and the binder is mixed. The injection-molded body of the one material powder is set at a specified position in a die, and the kneaded body of the other material is injection-molded into the space of the die and combined with the former injection-molded body. The composite compact thus obtained is degreased and sintered.

Description

Detailed Description of the Invention

[0001]

The present invention relates to an injection molding sintering method (Metal
Injection molding (abbreviated as MIM method) is used to manufacture a composite sintered body made of different materials.

It is customary to use a cutting process to obtain a molded product with good dimensional accuracy using metal, but there are molded products that are hard and brittle and difficult to lathe. For example, iron
This includes magnet bases and motor yokes made of soft magnetic materials made of silicon (Fe-Si) alloys and iron-cobalt (Fe-Co) alloys. The production yield is low and not practical.

Here, the metal powder is mixed with an organic binder, injection-molded into a required shape, placed in a furnace, and gradually heated to decompose the organic binder to remove the binder. Injection molding sintering method (MIM
There is a law).

This method is suitable for processing the above-mentioned materials, can be applied to those having complicated shapes, and has a feature that the yield is high. It should be noted that some metal parts made using the MIM method are not made of a single material due to their use,
In many cases, the partially different case is preferable from the viewpoint of characteristics or cost.

For example, in a magnet base for a wire dot printer used in a printer, a coil is wound to pass an electric current, and a core portion for generating a magnetic flux and a yoke portion for forming a magnetic flux path are not necessarily made of the same magnetic material. It is not necessary to form it, and it is preferable to use different kinds of magnetic materials in terms of characteristics and cost.

The present invention relates to a method for manufacturing such a composite sintered body.

[0007]

2. Description of the Related Art The process of sintering an injection-molded product is performed by mixing materials,
It consists of four steps: injection molding, binder removal, and sintering.

That is, in the kneading, the average particle diameter of the raw material is 10 μm.
After roughly kneading the metal powder and an organic binder such as paraffin wax, a pressure of about 1 ton / cm ² is applied and injection molding is performed to form a molded body.

Next, heating to about 400 ° C. in a non-oxidizing atmosphere such as argon (Ar) or nitrogen (N ₂ ) is carried out to remove the binder to evaporate the binder, and then to a high temperature. A sintered body is formed by sintering.

Here, for the parts used in the electronic equipment, there are cases where it is appropriate to use parts made of different kinds of materials rather than being made of a single material depending on the use and shape. For such applications, conventionally, parts have been manufactured by individually manufacturing by the MIM method and then joining by methods such as screwing, shrink fitting, and brazing.

However, when such a method is applied, there are problems that the shape and material of the joint are limited, the joint strength is generally weak, and the number of steps is increased, so that the manufacturing cost is increased.

[0012]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
It is desirable to apply the IM method to form the composite sintered body, but it is necessary that cracks do not occur in the joint portion at this time, and it is a problem to solve such a problem.

[0013]

[Means for Solving the Problems] The above-mentioned problem is to obtain a sintering shrinkage rate for a molded body obtained by kneading a predetermined amount of a binder into one material powder to be sintered, and to obtain the other material to be sintered. For the powder, the addition amount of the binder necessary to match the above-mentioned sintering shrinkage ratio is obtained, and an injection molded body made of one material powder is set in the mold, and then the other material is placed in the space of this mold. This can be solved by configuring a method for manufacturing a composite sintered body, which is characterized in that the kneaded body is injection-molded to form a composite molded body, and then degreasing and sintering are performed.

[0014]

[Function] When a two-step injection molding is performed using different materials, and the molded body is degreased and then sintered to produce a sintered body, the problem is that the firing shrinkage rate differs depending on the material.
This causes cracks at the joints of the sintered body.

Therefore, it is necessary to match the firing shrinkage rates of both, and the present invention eliminates the occurrence of cracks by adjusting the amount of the binder. The use of such a method causes problems. Will be resolved.

[0016]

[Example] Fe-50% Co with a very high saturation magnetic flux density
Fe-6.5 with improved permeability by improving the magnetism of alloy and pure iron
% Si alloy was used to form a rod-shaped composite sintered body.

Regarding the formation of a Fe-50% Co alloy having an average particle size of 20 μm, the inventors have conventionally added 35% by volume of a polyethylene-based binder and kneaded it to use, which is the standard.

After the binder is debindered at a maximum temperature of 440 ° C. and then sintered in an H ₂ stream at 1450 ° C. for 1 hour, the sintering shrinkage rate is 10.47%. Next, the sintering shrinkage ratio of Fe-6.5% Si alloy with an average particle size of 20 μm was 10.47.
%, The amount of polyethylene binder added was changed from 27% by volume to 40% by volume to form a molded body, and Fe-50
The binder was removed and sintered under the same conditions as in the case of the% Co alloy.

FIG. 1 shows the relationship between the addition amount of the binder thus obtained and the sintering shrinkage ratio. From this figure, Fe-6.5% Si
The amount of binder added to the alloy powder was determined to be 30% by volume.
That is, the sintering shrinkage in this case is 10.64%,
Sintering shrinkage rate of 0.17% is slightly higher than that of -50% Co alloy.

Next, the amount of Fe added was set to 30% by volume.
-Mixing 6.5% Si alloy powder and injection molding 5 x 4 x 50 mm
A rod-shaped piece was prepared, cut into 1/2 lengths, and then inserted again into the mold.

Next, a kneaded body made of a Fe-50% Co alloy was injection-molded in the space of this mold to form a rod-shaped piece of 5 × 4 × 50 mm. FIG. 2 shows the shape and configuration of the rod-shaped piece thus formed.

The molded body was heated at 10 ° C. in a nitrogen (N ₂ ) stream.
After removing the binder by heating it to 440 ° C at a speed of 1 hour, it was transferred to a sintering furnace and heated to 1450 ° C at a speed of 300 ° C / hour in a hydrogen (H ₂ ) stream to make a sintered body. .

As a result, no abnormalities such as cracks were observed at the interface of the composite sintered body, and the joining state was good.

[0024]

EFFECTS OF THE INVENTION By carrying out the present invention in which a composite molded body is formed by adjusting the amount of binder added and adjusting the sintering shrinkage ratio, the occurrence of cracks can be eliminated.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the amount of binder added and the sintering shrinkage rate for Fe-6.5% Si alloy.

FIG. 2 is a shape diagram of an example.

[Explanation of symbols]

 1 Fe-6.5% Si alloy 2 Fe-50% Co alloy

Claims (1)

[Claims] 1. A sintering shrinkage rate is obtained for a molded body obtained by kneading a predetermined amount of a binder with one material powder to be sintered, and the sintering shrinkage rate is obtained for the other material powder to be sintered. The amount of binder required to match the above is determined in advance, an injection molded body made of one material powder is set in the mold, and then a kneaded body of another material is injection molded into the space of the mold to form a composite. A method for producing a composite sintered body, which comprises degreasing and sintering after forming a molded body.