JPH04285141A - Manufacture of ferrous sintered body - Google Patents

Abstract

PURPOSE:To manufacture of ferrous sintered body having high density and excellent in shapeability by adding a specified ratio of copper powder with specified grain diameter to ferrous powder with specified grain diameter, and executing compacting and sintering. CONSTITUTION:By pts.wt., 0.2 to 5 copper powder with 1 to 18mum average grain diameter is added to 100 powder with 1 to 18mum average grain diameter essentially consisting of an iron series, which is mixed with a required binder, and after that, compacting and sintering are executed. At this time, the above copper powder has the m.p. lower than that of iron, and the strength of the green compact at the time of removing the binder is improved to prevent its deformation and to promote the sintering of the iron powder. In this way, the ferrous sintered body good in dimensional accuracy and having high density can be obtd.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing iron-based sintered bodies by powder metallurgy.

0002

BACKGROUND OF THE INVENTION Powder metallurgy is characterized by the ability to easily mass-produce parts that are difficult to manufacture by melting and casting. In conventional powder metallurgy, powder with an average particle size of 60 to 100 μm is used for compression molding, but the sintered density ratio of the sintered body is about 90%, and the mechanical properties are poor compared to melted and cast materials. and had poor magnetic properties.

On the other hand, recent advances in powder metallurgy technology have made it easier to use fine powder. When fine powder with an average particle size of 18 μm or less is used, the sinterability is improved, and a sintered density of 90% or more, and even 95% or more can be obtained. Molding methods include compression molding, injection molding, and slip casting, each of which processes the raw material powder by granulation, compounding with thermoplastic resin, and slurry to increase mold filling fluidity and improve industrial performance. It allows molding.

However, when molding and sintering such fine powder to produce a high-density sintered body, there is a problem in that it is difficult to maintain the shape of the sintered body in a sound state. With conventional powder metallurgy, metal powder particles are bonded together through compression molding, creating a molded body with a certain degree of strength. In the conventional case, when a molded body is sintered, sintering always starts with the strength maintained at about the initial strength of the molded body, so there is little problem of deformation. However, in the case of fine powder, the strength of the compact is maintained using a binder as an auxiliary agent, and since the binder is removed before sintering progresses, the compact passes through a stage during which the strength of the compact becomes extremely weak. Therefore, undesirable deformation occurs due to the molded body's own weight, and the final shape of the sintered body is likely to be deformed.

[0005]

[Problems to be Solved by the Invention] It is an object of the present invention to obtain a high-density iron-based sintered body by using fine powder mainly made of iron with an average particle size of 18 μm or less, and to obtain an iron-based sintered body with excellent shapeability. The purpose of this study is to propose a method for producing a sintered body.

[0006]

[Means for Solving the Problems] That is, in the present invention, 0.2 to 100 parts by weight of copper powder having an average particle size of 1 to 18 μm is added to 100 parts by weight of a powder mainly made of iron and having an average particle size of 1 to 18 μm.
This is a method for producing an iron-based sintered body, characterized in that 5 parts by weight of the iron-based sintered body is added, and then molded and sintered.

[0007]

[Operation] When sintering iron-based powders, copper often has a positive effect on the mechanical properties of the sintered body, or at least has no negative effect. Since copper has a lower melting point than iron, it has the effect of promoting sintering at relatively low temperatures. Therefore, if fine copper powder is mixed with iron-based powder and then molded and sintered, the molded body becomes brittle from the removal of the binder to the start of sintering of the iron-based powder.
Copper partially acts as an adhesive for the iron-based powder particles, improving the strength of the compact at that point and preventing deformation due to its own weight.

[0008] In this case, the iron-based powder has an average particle size of 1 to 18 μm.
As a fine powder of m, the final sintered density can be made sufficiently high. In addition, iron-based powder does not necessarily have to be a single type of powder; for example, it can be a mixture of iron powder and nickel powder,
It may also be a material that becomes an iron-based alloy after sintering. The copper powder added has an average particle size of 1 to 18 μm. The amount of copper powder added is 0.2 to 100 parts by weight of iron-based powder or iron-based powder mixture.
5 parts by weight.

As described above, according to the present invention, 1 to 18 μm
By adding copper powder of 1 to 18 μm to the iron-based powder and molding and sintering, the molded body is prevented from becoming brittle during sintering, and as a result, deformation of the shape of the sintered body due to its own weight etc. is suppressed. Can be done. If the average particle size of the iron-based and copper-based fine powders used is smaller than 1 μm, the manufacturing cost will be high;
On the other hand, if the average diameter is larger than 18 μm, the sinterability will be insufficient, so the average diameter is set in the range of 1 to 18 μm.

[0010] If the amount of copper powder added is less than 0.2 parts by weight per 100 parts by weight of the iron-based powder, the above-mentioned strength improvement effect during sintering will not be observed, and on the contrary, if it exceeds 5 parts by weight, Since it lowers the density of the sintered body, the amount is set in the range of 0.2 to 5 parts by weight.

[0011]

[Example] Example 1 Average particle size 1.3, 4.9, 8.3, 11.6, 1
High-pressure water atomized iron powder with sizes of 5.2, 17.0, 18.8, and 23.6 μm and electrolytic steel powder with an average particle size of 3.7 μm were prepared. Each type of iron powder does not contain copper powder, and iron powder does not contain copper powder.
A sample containing 2.0 parts by weight of copper powder per 100 parts by weight was prepared separately. 2% (wt%) camphor was added to each mixture, and a rectangular parallelepiped molded body having a length of 35 mm, a width of 10 mm, and a height of 5 mm was molded at a molding pressure of 2 t/cm 2 .

[0012] The molded body was placed so as to straddle alumina plates placed at intervals of 25 mm, heated at a rate of 5°C/min in a hydrogen atmosphere, and held at 1250°C for 1 hour. After cooling, the density of the sintered body was measured using the Archimedes method. In addition, the distance that the central portion of the sintered body in the longitudinal direction sank downward due to its own weight was measured as the amount of deformation. Table 1 shows the measurement results. When copper powder is added, deformation due to its own weight is clearly suppressed. This effect is relatively small when the particle size of the iron powder is as small as 1 μm, but it becomes more noticeable as the particle size increases. However, if the particle size of the iron powder exceeds 18 μm, the density of the sintered body will not increase, and the effect of suppressing deformation due to the addition of copper powder will be reduced.

[0013]

[Table 1]

Example 2 High-pressure water atomized iron powder with an average particle size of 11.6 μm and average particle sizes of 1.2, 3.7, 10.1, 16.9, 20.
3. Electrolytic copper powder of 31.6 μm was prepared. Each copper powder was mixed with iron powder at a weight ratio of 100:2.0, molded and sintered in the same manner as in Example 1, and the density and deformation amount were measured.

Table 2 shows the measurement results. The finer the particle size of the copper powder, the greater the deformation suppressing effect. When the particle size exceeds 18 μm, the density of the sintered body decreases and the deformation suppressing effect becomes insufficient.

[0016]

[Table 2]

Example 3 High-pressure water atomized iron powder with an average particle size of 11.6 μm and electrolytic copper powder with an average particle size of 3.7 μm were prepared. iron powder 100
Copper powder is 0.1, 0.2, 1.0, based on weight part.
A mixture was prepared by mixing 2.0, 4.0, 8.0, and 15.0 parts by weight. Each was molded in the same manner as in Example 1,
After sintering, the density and deformation amount were measured.

Table 3 shows the results. The amount of copper powder added is 0.
The deformation suppressing effect is large when the amount is 2 to 8 parts by weight. However, if the amount of copper powder added exceeds 5 parts by weight, the density decreases significantly, which is not preferable. Furthermore, if an excessive amount of copper powder is added, the amount of liquid phase during sintering becomes excessive, causing roughness and cavities in the sintered body, making it unsuitable for manufacturing parts.

[0019]

[Table 3]

[0020]

[Effects of the Invention] As shown above, according to the present invention,
Since it is possible to produce a high-density iron-based sintered body with good dimensional accuracy, it is highly useful as a technology for manufacturing parts with complex shapes.

Claims (1)

[Claims] Claim 1: Mainly iron-based particles with an average diameter of 1 to 18μ
Average particle size 1 to 18 μm per 100 parts by weight of m powder
1. A method for producing an iron-based sintered body, which comprises adding 0.2 to 5 parts by weight of copper powder, followed by molding and sintering.