JP2001003124A - Manufacture of iron-copper composite powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing an inexpensive Fe-Cu composite powder in which the amount of free copper powder is reduced and the increase in the hardness of a coating copper layer is suppressed. SOLUTION: The process of manufacturing the Fe-Cu composite powder, having <=100 HV hardness of a coating copper layer and <=10% free copper content (the proportion of free copper content to the total copper content), comprises the steps of: mixing a copper powder of >=2000 cm2/g specific surface area and a copper oxide which is composed of copper oxide (CuO) powder or cuprous oxide (Cu2O) powder or a powder mixture thereof and has <=10 μm average particle size with an iron powder in such a way that the mixing ratio between the copper powder and the copper oxide becomes (20 to 80):(80 to 20) (by mass ratio) expressed in terms of copper and further copper content becomes 10 to mass%; heat-treating the resultant mixture in a reducing atmosphere at 700 to 1000 deg.C; pulverizing the mixture; and carrying out screening.

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 Fe-Cu composite powder in which copper is uniformly diffused and adhered to the surface of iron powder, and is suitable mainly as a raw material powder for Fe-Cu powder metallurgy products. is there.

[0002]

2. Description of the Related Art In recent years, in order to prevent segregation of copper or to reduce sliding resistance in Fe-Cu powder metallurgy products, especially in Fe-Cu sintered bearings, copper is uniformly adhered to the surface of iron powder. Demand for Fe-Cu based composite powders is increasing. Conventionally, two methods for producing the Fe-Cu composite powder having such a form are known: a wet method and a dry method.

The wet method disclosed in Japanese Patent Publication No. 51-29486 is a method in which iron powder is immersed in a solution containing copper ions, and copper is electrochemically deposited on the surface of the iron powder. Although the surface of the powder can be relatively uniformly coated with copper, there is a disadvantage that the obtained powder is oxidized if the produced Fe—Cu composite powder is not sufficiently washed and dried, and this is completely performed. Therefore, the manufacturing cost is increased. More recently, manufacturing costs have been further increased due to environmental measures such as waste liquid treatment. For this reason, Fe-
Cu composite powder has not been practically used. on the other hand,
The dry method has long been known in which iron powder and copper fine powder are mixed and heat-treated in a reducing atmosphere to diffuse and adhere copper fine powder to iron powder.However, solid-phase diffusion deposits copper fine powder on the surface of iron powder. It is difficult to make it adhere uniformly, and in particular, there is a problem that a large amount of free copper powder is generated in the crushing and pulverizing steps of the heat-treated cake.

As a method for solving this problem, Japanese Patent Publication No. Sho 59-1
No. 764 and JP-A-8-92604 propose a method of mixing fine powder of copper oxide with iron powder and heat-treating the mixture in a reducing atmosphere. Although this method almost solved the problem of the generation of free copper powder, in this method, a redox reaction between iron and copper oxide occurred before copper oxide was reduced by a reducing atmosphere during heat treatment, Since a large amount of iron dissolves in copper, there is a problem that the hardness of the copper part increases. For example, when a sintered bearing is manufactured using such a powder,
The conformability between the bearing and the shaft becomes poor, and the sliding resistance increases. In addition, when producing a general sintered machine part, the compressibility at the time of compacting is reduced.

[0005]

DISCLOSURE OF THE INVENTION The present invention provides an inexpensive Fe--C having a small amount of free copper powder and suppressing an increase in hardness of a coated copper layer.
The purpose of the present invention is to provide a u-composite powder and a method for producing the same.

[0006]

According to the present invention, iron powder is mixed with copper powder and copper oxide, and the mixture is mixed in a reducing atmosphere at 700 to 1000 ° C.
The hardness of the obtained coated copper layer is H
V100 or less, the free copper content (the ratio of the free copper content to the total copper content) is 10% or less, Fe-Cu composite powder, and copper powder so that the iron content becomes 10 to 70 mass% in copper content. The mixed powder of copper oxide is mixed,
After heat treatment at 00 to 1000 ° C., pulverized and sieved F
This is a method for producing an e-Cu composite powder.

The inventors of the present invention have prepared and examined sintered parts such as bearings using various Fe-Cu composite powders. As a result, the hardness of the coated copper layer was HV100 or less, and the free copper content (total copper content) If the ratio of the amount of free copper to the shaft is 10% or less, the conformability between the shaft and the bearing is improved, the sliding resistance is reduced, and the compressibility during compression molding is also good. It was confirmed that no segregation occurred.

When the hardness of pure annealed copper is measured by a micro Vickers hardness tester, HV (0.5 gf) 40 to
On the other hand, the micro-Vickers hardness of the coated copper layer of the Fe—Cu composite powder produced by the conventional method of mixing iron powder and copper oxide powder is HV (0.5 gf) 130 to 14
It reaches about 0. As described above, the composite powder having the hard coated copper layer increases the deformation resistance and causes a decrease in the compressibility or, when baked on the bearing, causes a decrease in the conformability between the bearing and the shaft.

When the free copper content exceeds 10%, F
It is considered that a part where the copper layer is missing occurs in a part of the e-Cu composite powder, or a large amount of the copper layer adheres to a part thereof. When it is manufactured, not only conformability and sliding resistance but also strength varies, which is not preferable. In the present invention, in order to suppress the oxidation-reduction reaction between iron and copper oxide, which cause such solid solution strengthening of the copper layer, a part of the copper oxide powder is replaced with copper powder, so that free copper is removed. The present inventors succeeded in suppressing the content (the ratio of the amount of free copper to the total copper content) to 10% or less and at the same time suppressing the hardness of the coated copper layer to HV (0.5 gf) 100 or less.

In the production method of the present invention, the hardness of the copper part rapidly decreases when the mixing ratio of the copper powder is up to 20 mass% in terms of copper, and then gradually decreases as the mixing ratio of the copper powder increases. . On the other hand, the production ratio of free copper powder increases with an increase in the mixing ratio of copper powder, but the degree of increase is relatively gentle when the mixing ratio of copper powder is 80 mass% or less in terms of copper, but exceeds 80 mass%. It increases rapidly from around. Therefore, the mixing ratio of copper powder and copper oxide is
A range of 20 to 80:80 to 20 (mass ratio) in terms of copper is appropriate.

The heat treatment is performed in a reducing atmosphere at 700 to 100
Perform at 0 ° C. When the heat treatment temperature is 700 ° C. or lower, the amount of residual oxygen in the powder increases, and the generation rate of free copper powder increases. On the other hand, when the temperature exceeds 1000 ° C., the sintering of the powder proceeds, and a large amount of energy is required for pulverizing the heat-treated cake. At the same time, the solubility of iron in copper increases, so that the hardness of the copper portion on the surface of the powder decreases. Increase.

The copper content is suitably from 10 to 70 mass%, and if it is 70 mass% or more, the amount of free copper powder increases. On the other hand, if it is less than 10 mass%, it is not preferable because the surface of the iron powder cannot be completely covered.

The finer the particle size of the copper powder mixed in the copper oxide used in the production method of the present invention, the better. It is preferable to use fine copper powder having a specific surface area (BET method) of at least 2000 cm ² / g. If it is less than 2000 cm ² / g, the production ratio of free copper powder increases.

Similarly, copper oxide used in the production method of the present invention to reduce free copper powder may be copper oxide (CuO) powder, cuprous oxide (Cu ₂ O) powder, or a mixed powder thereof. Good. However, their average particle size is 10 μm
The following is preferred. If the average particle size exceeds 10 μm, the oxidation-reduction reaction with iron powder does not proceed smoothly, and the production ratio of free copper powder increases.

[0015]

Next, embodiments of the present invention will be described below.

(Example 1) Copper oxide (CuO) powder or copper suboxide (Cu) having an average particle size of 3 μm in a reduced iron powder for powder metallurgy having a particle size of −150 μm so that the copper content is 50 mass%.
₂ O) powder and electrolytic copper powder having a specific surface area of 2700 cm ² / g in a predetermined ratio (80:20, 50: 50,2)
0:80) and 30 minutes at 800 ° C. in a hydrogen stream.
Heat treated. Subsequently, the obtained heat-treated cake was pulverized by a cutter mill, further pulverized by a high-speed hammer mill, and sieved to produce an Fe-Cu composite powder having a particle size of -180 µm. Table 1 shows the results of measuring the micro Vickers hardness of the copper part of the obtained powder and the free copper content by a self-made magnetic separator.

Example 2 Copper oxide (CuO) powder or cuprous oxide (Cu ₂ ) having an average particle size of 3 μm was added to a reduced iron powder for powder metallurgy having a particle size of −150 μm so that the copper content was 50 mass%.
O) Powder and electrolytic copper powder having a specific surface area of 2700 cm ² / g are mixed at a mass ratio of 50:50 in terms of copper, and mixed at a predetermined temperature (700 ° C., 900 ° C., 1000 ° C.) in a hydrogen stream.
min heat treatment. Subsequently, the obtained heat-treated cake was pulverized and sieved in the same manner as in Example 1 to produce an Fe-Cu composite powder having a particle size of -180 µm. Table 1 shows the results of measuring the micro Vickers hardness of the copper part of the obtained powder and the free copper content.

Example 3 Copper oxide (CuO) powder or cuprous oxide (Cu ₂ ) having an average particle size of 3 μm was added to a reduced iron powder for powder metallurgy having a particle size of −150 μm so as to have a predetermined copper content (20, 70).
O) Powder and electrolytic copper powder having a specific surface area of 2700 cm ² / g were mixed at a mass ratio of 50:50 in terms of copper, and heat-treated at 800 ° C. for 30 minutes in a hydrogen stream. Subsequently, the obtained heat-treated cake was pulverized and sieved in the same manner as in Example 1 to obtain -1.
An Fe-Cu composite powder having a particle size of 80 µm was prepared. Table 1 shows the results of measuring the micro Vickers hardness of the copper part of the obtained powder and the free copper content.

[0018]

Comparative Example 1 (Comparative Example 1) Reduced iron powder for powder metallurgy having a particle size of -150 μm was mixed with cuprous oxide powder (Cu ₂ O) having an average particle size of 3 μm so that the copper content was 50 mass%, and a hydrogen stream was applied. Heat treatment was performed at 800 ° C. for 30 minutes. Subsequently, the obtained heat-treated cake was pulverized and sieved in the same manner as in Example 1;
An Fe—Cu composite powder having a particle size of 180 μm was prepared. Table 1 shows the results of measuring the micro Vickers hardness of the copper part of the obtained powder and the free copper content.

Comparative Example 2 Reduced iron powder for powder metallurgy having a particle size of -150 μm and electrolytic copper powder having a specific surface area of 2700 cm ² / g were mixed at a mass ratio of copper in a ratio of 50:50, and mixed in a hydrogen stream at a flow rate of 80:50.
Heat treatment was performed at 0 ° C. for 30 minutes. Subsequently, the obtained heat-treated cake was pulverized and sieved in the same manner as in Example 1 to obtain -180.
An Fe-Cu composite powder having a particle size of μm was produced. Table 1 shows the results of measuring the micro Vickers hardness of the copper part of the obtained powder and the free copper content.

Comparative Example 3 Cuprous oxide powder (Cu ₂ O) having an average particle size of 3 μm and a specific surface area of 270 such that the copper content of the reduced iron powder for powder metallurgy having a particle size of −150 μm was 50 mass%.
0 cm ² / g of electrolytic copper powder is converted to a copper equivalent mass ratio of 50:50.
And heat-treated in a hydrogen stream at 600 ° C. for 30 minutes. Subsequently, the obtained heat-treated cake was pulverized and sieved in the same manner as in Example 1 to obtain Fe-Cu having a particle size of -180 μm.
A composite powder was prepared. Table 1 shows the results of measuring the micro Vickers hardness of the copper part of the obtained powder and the free copper content.

Comparative Example 4 Cuprous oxide powder (Cu ₂ O) having an average particle size of 3 μm and a specific surface area of 270 such that the reduced iron powder for powder metallurgy having a particle size of −150 μm had a copper content of 50 mass%.
0 cm ² / g of electrolytic copper powder is converted to a copper equivalent mass ratio of 50:50.
And heat-treated in a hydrogen stream at 1050 ° C. for 30 minutes. Subsequently, the obtained heat-treated cake was pulverized and sieved in the same manner as in Example 1 to obtain Fe-C having a particle size of -180 μm.
u composite powder was produced. Table 1 shows the results of measuring the micro Vickers hardness of the copper part of the obtained powder and the free copper content.

Comparative Example 5 A reduced iron powder for powder metallurgy having a particle size of -150 μm was mixed with cuprous oxide powder (Cu ₂ O) having an average particle size of 3 μm and a specific surface area of 150 so that the copper content was 50 mass%.
0 cm ² / g of electrolytic copper powder is converted to a copper equivalent mass ratio of 50:50.
And heat-treated in a hydrogen stream at 800 ° C. for 30 minutes. Subsequently, the obtained heat-treated cake was pulverized and sieved in the same manner as in Example 1 to obtain Fe-Cu having a particle size of -180 μm.
A composite powder was prepared. Table 1 shows the results of measuring the micro Vickers hardness of the copper part of the obtained powder and the free copper content.

(Comparative Example 6) Cuprous oxide powder (Cu ₂ O) having an average particle diameter of 18 μm and a specific surface area of 27 so that the reduced iron powder for powder metallurgy having a particle diameter of −150 μm has a copper content of 50 mass%.
00 cm ² / g of electrolytic copper powder was converted to a copper equivalent mass ratio of 50: 5.
The mixture was mixed at a ratio of 0 and heat-treated at 800 ° C. for 30 minutes in a hydrogen stream. Subsequently, the obtained heat-treated cake was pulverized and sieved in the same manner as in Example 1 to obtain Fe-C having a particle size of -180 μm.
u composite powder was produced. Table 1 shows the results of measuring the micro Vickers hardness of the copper part of the obtained powder and the free copper content.

[0024]

[Table 1]

As shown in Table 1, the Fe-Cu composite powder obtained under the production conditions of the present invention was obtained from the Fe-Cu composite powder obtained in each comparative example.
Compared to the Cu composite powder, both the hardness of the copper part and the free copper content show numerical values in favorable ranges. On the other hand, in each of the comparative examples, one of them shows a bad numerical value.

[0026]

As is clear from Table 1 above, the Fe-Cu composite powder of the present invention minimizes the production of free copper powder and at the same time suppresses the hardness of the copper portion to a low level. Good compatibility when a sintered bearing is made, and good compressibility during molding. In addition, the production method of the present invention can be provided at very low cost because of the dry method, and is an industrially useful invention. Further, by using the Fe-Cu composite powder of the present invention, a high-performance sintered machine component or a sintered bearing can be manufactured at low cost.

[Procedure amendment]

[Submission date] April 20, 2000 (200.4.2
0)

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction contents]

[0005] The present invention has less free copper powder, in order to provide an inexpensive Fe-Cu composite powder with a reduced increase in the hardness of the coated copper layer is to provide a manufacturing method thereof.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006]

According to the present invention, the specific surface area is 2
000 cm ² / g or more copper powder and copper oxide (Cuo) powder
Or cuprous oxide (Cu ₂ O) powder or a mixed powder thereof
Powder and a copper oxide having an average particle size of 10 μm or less.
And the mixture ratio of copper powder and copper oxide is 20 to 80 in terms of copper:
80 to 20 (mass ratio)
Mix with iron powder so that the content is 10-70 mass%
Then, these mixtures are mixed in a reducing atmosphere at 700 to 100
After heat treatment at 0 ° C, it is crushed and sieved.
The free copper content is less than 100 HV in hardness of the coated copper layer.
(Ratio of free copper amount to total copper content) is 10% or less
This is a method for producing an Fe—Cu composite powder.

Claims (5)

[Claims] An iron powder mixed with a copper powder and a copper oxide and heat-treated at 700 to 1000 ° C. in a reducing atmosphere,
When the hardness of the obtained coated copper layer is HV 100 or less, the free copper content (the ratio of the free copper amount to the total copper content) is 10%.
The following Fe-Cu composite powder. 2. The iron powder has a copper content of 10 to 70 mass%.
A method for producing an Fe—Cu composite powder in which a copper powder and a copper oxide are mixed, heat-treated at 700 to 1000 ° C. in a reducing atmosphere, pulverized and sieved. 3. The mixing ratio of copper powder and copper oxide is 2 in terms of copper.
The method for producing a Fe-Cu composite powder according to claim 2, wherein the ratio is in the range of 0 to 80:80 to 20 (mass ratio). 4. The method for producing an Fe—Cu composite powder according to claim ² , wherein the specific surface area of the copper powder is 2000 cm ² / g or more. 5. The copper oxide is copper oxide (CuO) powder, cuprous oxide (Cu ₂ O) powder or a mixed powder thereof, and their average particle size is 10 μm or less. The method for producing an Fe—Cu composite powder according to claim 2 or 3.