JP2915183B2 - Manufacturing method of powder molded product - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a powder molded product.

[0002]

2. Description of the Related Art Research has been made on adding a new function and value by forming the inside and the surface of a substance with different materials, and has been applied to many products at present. For example, plating has been practically used as a technique for forming a film of a material different from the base material electrochemically on the base material surface, and has improved decorativeness, corrosion resistance, and conductivity.

Further, recently, a coating forming method by a PVD method represented by vacuum evaporation and sputtering has been put into practical use,
It is applied to lenses and the like. In the method of forming a film on the surface of the base material, peeling of the film becomes a serious problem.
In order to solve these problems, attempts have been made to modify the surface of the base material itself in addition to improving the adhesion strength between the base material and the film. For example, Japanese Patent Publication No. 61-45698
In the gazette, by heating the brass material under reduced pressure,
It has been proposed that, of the copper and zinc constituting brass, a material having a copper surface and a brass inside without a bonding interface is produced by removing zinc, which is a high vapor pressure component, from the surface.

However, in this conventional example, only the surface layer is modified to the last, and it is not possible to modify the defects of the base material. For example, in the case of brass, the surface is coppered, but the inside remains brass, and the vulnerability to stress corrosion cracking of brass is maintained as it is, and to improve it, the growth of brass structure is suppressed There is a need to.
As a result, restrictions on equipment such as rapid heating and rapid cooling are required, and further, it is extremely difficult to arbitrarily obtain the thickness of the surface layer due to restrictions on heating conditions.

In this conventional example, since the brass material is treated, the degree of freedom of the shape is extremely small, and if this material is used for processing, brass as a base material appears on the processed surface. . As a result, stress corrosion cracking from the surface where brass appears may easily progress. Furthermore, also in electrical characteristics, the surface layer is copper, but the inside is only brass,
Due to restrictions on heating conditions for suppressing crystal growth, the copper layer on the surface becomes extremely thin, and the effect of reducing the electrical resistance as a whole is very small. The present invention has been made in order to solve such problems, and the object is to form the surface layer and the base material from different materials without a problem of peeling, and to use the different materials also at the crystal grain boundaries of the base material. An object of the present invention is to provide a composite material which has been introduced and has also improved the disadvantages of the base material.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a method for forming an alloy powder by forming an alloy powder comprising at least two components by any means, and then heating the alloy powder under reduced pressure. The method is characterized in that low vapor pressure components are precipitated on the surface layer of the product and crystal grain boundaries by bonding the particles while evaporating the high vapor pressure components therein.

[0007] The invention is characterized in that the alloy powder is a brass material. In the above, it is characterized in that the dimensional accuracy of the powder molded product is increased by recompressing means, and holes formed by evaporation of a high vapor pressure component on the surface layer are closed. The molding means is injection molding using a material obtained by kneading an alloy powder and a molding aid. The molding means is a sheet shape molding method such as a doctor blade method or an extrusion molding method. It is characterized in that sintering is performed after the sheet-shaped molded product is punched into a predetermined shape. When punching the sheet-shaped molded product into a predetermined shape, or after punching, insert a part of a material different from the molded product into the molded product,
Thereafter, sintering is performed. When the sheet-shaped molded product is punched into a predetermined shape, powder of a material different from that of the molded product is molded into the molded product, and thereafter, sintering is performed.

[0008] An alloy powder composed of at least two components is heated under reduced pressure to evaporate a high vapor pressure component in the components constituting the alloy to precipitate a low vapor pressure component on the surface of the powder. It is characterized in that a low vapor pressure component is precipitated on the surface layer of the product and the crystal grain boundaries by forming and sintering. After heating the alloy powder composed of at least two components under reduced pressure to evaporate the high vapor pressure component in the components constituting the alloy to precipitate the low vapor pressure component on the powder surface layer, different types of powder , Mixed by any means, and then sintered.

[0009]

According to the above construction, in the present invention, after forming an alloy powder composed of two or more components, the molded product is heated under reduced pressure to reduce the high vapor pressure component in the components constituting the alloy. Bonding between the particles while evaporating, or heating the alloy powder under reduced pressure, evaporating the high vapor pressure component to precipitate the low vapor pressure component on the surface layer, then molding, and then sintering Or, further, after heating the alloy powder under reduced pressure, evaporating the high vapor pressure component and depositing the low vapor pressure component on the surface layer, mixing with different types of powder and molding, then By sintering, the surface layer and the base material are composed of different materials without any problem of peeling,
It is possible to introduce a different material into the crystal grain boundary of the base material, and it is possible to improve the defects of the base material.

[0010]

[Example 1]

As the powder, brass having a component composition of 70% Cu + 30% Zn was used. In this case, zinc has a boiling point of 930 ° C. and copper has a boiling point of 2582 ° C. under atmospheric pressure, and it is possible to selectively remove only zinc by appropriately setting heating conditions and pressure. The above powder used had an average particle size of about 70 to 120 μm, and stearic acid was added at a weight ratio of 2 to 3% before molding. After the above materials were adjusted, they were molded using a direct pressure press under a molding pressure of 1 to 7 ton / cm ² .

The molded article was heated according to the temperature pattern shown in FIG. In this temperature pattern, in a temperature range of 200 ° C., stearic acid is melted and removed by decomposition, and
In the temperature range of ℃, zinc on the surface of the powder is removed and 900
In the temperature range of ° C., at the same time as bonding between powders, the evaporation of zinc from the surface of the molded article is promoted to form a complete copper layer. In this case, the degree of vacuum of the atmosphere is 10 ⁻² to 10 ⁻⁴ torr.
The vacuum was maintained at about r.

In the molded article manufactured according to this embodiment, the surface layer is made of copper and the inside is made of brass. Moreover, in the brass structure, as shown in FIG. 2, copper precipitates at the crystal grain boundaries, thereby inhibiting the growth of the brass structure. Such a material is excellent in stress corrosion cracking resistance because a brass structure is not grown, and also has improved conductivity because copper is precipitated in a matrix along grain boundaries.

Example 2 As powder, brass having a component composition of 70% Cu + 30% Zn was used. The above powder having an average particle size of about 10 μm was kneaded with a molding aid composed of dibutyl phthalate, paraffin wax, polyethylene, and an ethylene-vinyl acetate copolymer under heating before molding. The mixing ratio was such that powder: molding aid = 55: 45 in volume ratio. Next, a material obtained by kneading the above alloy powder and a forming aid
Was molded using an injection molding machine as shown in FIG. That is,
The above-mentioned material is put into the hopper 12, and the
In the axial direction by the rotation of
It was injected and filled at a pressure of 700 kg / cm ² . The molded product was heated to 450 ° C. over 24 hours in a nitrogen atmosphere to remove the molding aid, and then 10 ⁻² to 10 ⁻⁴ torr.
Heating was performed in a temperature pattern shown in FIG. 3 under a vacuum of about r.

The molded article produced by this method has a copper surface area and brass inside. Moreover, in the brass structure, as shown in FIG. 2, copper precipitates at the crystal grain boundaries, thereby inhibiting the growth of the brass structure. Such a material is excellent in stress corrosion cracking resistance because a brass structure is not grown, and also has improved conductivity because copper is precipitated in a matrix along grain boundaries.

[Embodiment 3] In Embodiment 1 described above, FIG.
As shown in (a), a sintered product 10 obtained by sintering a molded product
As shown in FIG. 4B, pores 11 generated by evaporation of zinc are present in the surface layer 10a of the sintered product 10. this,
As shown in FIG. 4 (c), the direct pressure type press is again used for 1 to 7 to
Pressure was applied at a pressure of n / cm ² . As a result, as shown in FIG. 4D, the holes 11 existing in the surface layer 10a of the sintered product 10 are closed, and the copper density of the surface layer 10a further increases, so that gloss appears, and Can be used.

Example 4 As powder, brass having a component composition of 70% Cu + 30% Zn was used. The above powder had an average particle size of about 10 μm, and was mixed in a ball mill together with a molding aid composed of polyvinyl alcohol and methylcellosolve in a ball mill for 1 to 2 hours before molding. Next, the above-mentioned material is
The amount of material on the spreader roller 16 as shown in
Is adjusted by the blade 17 by the doctor blade method.
It was formed into a sheet.

Example 5 The composition of the powder was 70
Brass of% Cu + 30% Zn was used. The above powder had an average particle size of about 10 μm, and was mixed in a ball mill together with a molding aid composed of polyvinyl alcohol and methylcellosolve in a ball mill for 1 to 2 hours before molding. Next, as shown in FIG. 6, the above-mentioned material was formed into a sheet by a doctor blade method in which the amount of the material on the roller 16 of the spreader was adjusted by a blade 17. After leaving the molded product 18 in the air to remove water, it is punched into a predetermined shape by a press, and then 10 ⁻² to 10 ⁻⁴ ton.
Heating was performed under a vacuum of about rr according to the temperature pattern shown in FIG. The surface layer of the molded article produced by this method is copper all around, and the inside is brass, and there is no precipitation of brass on the end face unlike the conventional example.

[Embodiment 6] As shown in FIGS. 8A to 8C, the sheet-like molded product 18 in the above-described embodiment 5 is processed into a stud shape when punching out a predetermined shape with a punching die 19. The silver contact part 20 was inserted. Thereafter, sintering was performed under the same temperature conditions as in Example 5. In the molded article produced by this method, the silver part 20 shrinks when the sheet-like molded article is sintered.
It was fixed in a crimped state, and an alloy was formed at the contact portion between copper and silver. Generally, a contact portion of a relay or the like is formed by caulking a silver-based material contact with a copper-based material. However, at the time of caulking, the contact surface is contaminated with oil or the like attached to a mold, and requires cleaning. However, the contact portion made according to this embodiment is
Contaminants are removed in the process of sintering at a high temperature, and an extremely clean contact surface can be provided.

[Embodiment 7] As shown in FIGS. 9 (a) and 9 (b), the sheet-like molded product in the above-mentioned embodiment 5 is punched into a predetermined shape by a punching die 19, and then the sheet-shaped molded article is punched out of FIG. ), Using a powdered silver 21 in a predetermined position,
At 2, a stud-like shape was formed. Thereafter, sintering was performed under the same temperature conditions as in Example 5. In this case, the amount of the molding aid added to the silver powder was adjusted so that the shrinkage after sintering was smaller than the shrinkage of the sheet-shaped molded product. In the molded product manufactured by this method, as shown in FIG. 9 (e), when the sheet-shaped molded product is sintered, it shrinks and the silver portion 23 is fixed in a caulked state, and copper and silver are fixed together. The alloy was shaped at the contact portion of No. 1. Generally, a contact portion of a relay or the like is formed by caulking a silver-based material contact with a copper-based material. However, at the time of caulking, the contact surface is contaminated with oil or the like attached to a mold and requires cleaning.

However, the contaminants are removed during the sintering process at a high temperature in the contact portion manufactured according to the present embodiment, and it is possible to provide an extremely clean contact surface. Also, the degree of freedom of the contact shape can be increased as compared with the conventional caulking.

Example 8 The composition of the powder was 70
Brass of% Cu + 30% Zn was used. The average particle diameter of the above powder is about 70 to 120 μm, and 10 ⁻² to 1
By heating at 600 ° C. for 10 to 30 minutes under a vacuum of 0 ⁻⁴ torr, zinc on the powder surface was evaporated to form a copper layer. At that time, the powder was constantly moved by a barrel or the like to prevent aggregation and fusion.

To this powder, 2-3% by weight of stearic acid was added. After the above materials were adjusted, they were molded using a direct pressure press under a molding pressure of 1 to 7 ton / cm ² . This molded product was heated according to the temperature pattern shown in FIG. In this temperature pattern, in the temperature range of 200 ° C., stearic acid is melted and removed by decomposition, and further, 900 ° C.
In this temperature range, the powders are bonded together, and at the same time, the evaporation of zinc from the surface of the molded article is promoted to form a complete copper layer.
In this case, the degree of vacuum of the atmosphere was kept at a vacuum of about 10 ^-2 to 10 ^-4 torr.

In the molded article produced by this method, the surface layer is made of copper and the inside is made of brass. Moreover, in the brass structure, as shown in FIG. 2, copper precipitates at the crystal grain boundaries, thereby inhibiting the growth of the brass structure. Such a material is excellent in stress corrosion cracking resistance because the brass structure does not grow, and the conductivity is also improved because copper is precipitated in a matrix along the grain boundaries.

Example 9 The composition of the powder was 70
Brass of% Cu + 30% Zn was used. The average particle diameter of the above powder is about 70 to 120 μm, and 10 ⁻² to 1
By heating at 600 ° C. for 10 to 30 minutes under a vacuum of 0 ⁻⁴ torr, zinc on the powder surface was evaporated to form a copper layer. At that time, the powder was constantly moved by a barrel or the like to prevent aggregation and fusion.

To this powder, 90-95% by weight of iron powder and 2-3% of stearic acid were added. After adjusting the above materials, using a direct pressure type press, molding pressure 1 to 7 ton / c
It was molded in the range of m ^2. This molded product was heated according to the temperature pattern shown in FIG. In this temperature pattern, 20
In a temperature range of 0 ° C., stearic acid is melted and removed by decomposition, and in a temperature range of 1300 ° C., powder is bonded.
In this case, the degree of vacuum of the atmosphere was kept at a vacuum of about 10 ^-2 to 10 ^-4 torr.

The molded article produced by this method is shown in FIG.
As shown in FIG. 2, copper precipitates at the crystal grain boundaries of iron, and further, brass is dispersed in the copper to form a structure that prevents the progress of cracks at the grain boundaries. Further, the electrical conductivity can be improved by forming copper at the grain boundaries.

Example 10 SUS304 was used as a powder. The above powder used had an average particle size of about 70 to 120 μm, and stearic acid was added at a weight ratio of 2 to 3% before molding. After the above materials were adjusted, they were molded using a direct pressure press under a molding pressure of 1 to 7 ton / cm ² .
This molded product was heated according to the temperature pattern shown in FIG. In this temperature pattern, stearic acid is melted and removed by decomposition in the temperature range of 200 ° C., chromium on the surface of the powder is removed in the temperature range of 1150 ° C., and at the same time, the powder is bonded in the temperature range of 1350 ° C. The chromium concentration on the surface is controlled by promoting the evaporation of chromium from the surface of the molded article.

In this case, the degree of vacuum of the atmosphere is 10 ⁻² to 10
A vacuum of about ^-4 torr was maintained. In the molded article manufactured by this method, the chromium concentration of the surface layer can be arbitrarily controlled. For example, when anodizing treatment or the like is performed, the color tone width can be increased.

[0029]

According to the present invention, the surface layer and the base material can be made of different materials without a problem of separation, and the different materials can be introduced into the crystal grain boundaries of the base material. The composite material which also improved the defect of can be manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram showing temperature conditions in Example 1.

FIG. 2 is a view showing a crystal structure of a molded article in Example 1.

FIG. 3 is a diagram showing temperature conditions in Example 2.

FIGS. 4A to 4D are diagrams illustrating a pressing method according to a third embodiment.

FIG. 5 is a view showing an injection molding machine used in Example 2 .

FIG. 6 is a diagram showing the principle of a doctor blade device used in Example 4 .

FIG. 7 is a diagram showing temperature conditions in Example 5.

8 (a) to 8 (c) are views showing a molding step in Example 6. FIG.

9 (a) to 9 (e) are views showing a molding step in Example 7. FIG.

FIG. 10 is a diagram showing temperature conditions in Example 8.

FIG. 11 is a diagram showing temperature conditions in Example 9.

FIG. 12 is a view showing a crystal structure in Example 9.

FIG. 13 is a diagram showing temperature conditions in Example 10.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Sintered product 11 Void 12 Hopper 13 Screw 14 Die 15 Cavity 17 Blade 18 Sheet-shaped molded product 19 Die die 20 Silver contact part 21 Silver powder 23 Silver part

Claims (10)

(57) [Claims] An alloy powder composed of at least two components is formed by an arbitrary means, and then heated under reduced pressure to evaporate a high vapor pressure component in the components constituting the alloy and bond the particles together. A method for producing a powder molded product, wherein a low vapor pressure component is precipitated on a surface layer and a crystal grain boundary of the product. 2. The method according to claim 1, wherein the alloy powder is a brass material. 3. The powder molded product according to claim 1, wherein the dimensional accuracy of the powder molded product is improved by recompressing means, and a hole formed by evaporation of a high vapor pressure component in a surface layer is closed. Manufacturing method. 4. The method according to claim 1, wherein the molding means is injection molding using a material obtained by kneading an alloy powder and a molding aid. 5. The method according to claim 1, wherein the molding means is a sheet shape molding method such as a doctor blade method or an extrusion molding method. 6. The manufacturing method according to claim 1, wherein
A method for producing a powder molded product, comprising sintering a sheet-shaped molded product after punching it into a predetermined shape. 7. The method according to claim 1, wherein
A method of manufacturing a powder molded product, comprising: inserting a part of a material different from that of the molded product into the molded product when or after punching the sheet-shaped molded product into a predetermined shape; and performing sintering thereafter. 8. The manufacturing method according to claim 1, wherein
A method for manufacturing a powder molded product, comprising: forming a powder of a material different from that of the molded product into the molded product when punching the sheet-shaped molded product into a predetermined shape; and performing sintering thereafter. 9. An alloy powder composed of at least two or more components is heated under reduced pressure to evaporate a high vapor pressure component in the components constituting the alloy to deposit a low vapor pressure component on a surface layer of the powder. A method for producing a powder molded product, wherein a low vapor pressure component is precipitated on a product surface layer and a crystal grain boundary by molding by any means and thereafter sintering. 10. An alloy powder composed of at least two or more components is heated under reduced pressure to evaporate a high vapor pressure component in the components constituting the alloy to deposit a low vapor pressure component on a surface layer of the powder. A method for producing a powder molded product, comprising mixing with a different kind of powder, molding by any means, and thereafter sintering.