JPS6327417B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a heat-resistant and conductive dispersion-strengthened copper alloy material used for spot welding electrode materials, etc., which require high conductivity and high resistance to high temperature softening. . Generally used as electrode material for spot welding.
Age-hardenable copper alloys such as Cu-Cr, Cu-Ti-Cr, and Cu-Be are well known, but the aging temperature of these age-hardenable copper alloys is below 500℃, and at higher temperatures, the Since it softens, it does not have sufficient high temperature softening resistance.

On the other hand, it is well known that the recrystallization temperature of dispersion-strengthened copper alloys that utilize the dispersion strengthening phenomenon is as high as 900°C to 950°C. Therefore, it does not soften even when heated to 900°C, and has much higher high temperature softening resistance (hereinafter referred to as heat resistance) than the above-mentioned age hardenable copper alloys.

Dispersion strengthened alloys are characterized by the fact that fine submicron ceramic particles that do not react with the matrix metal at high temperatures are uniformly dispersed in the matrix at micron intervals. For this purpose, mechanical mixing methods, chemical coprecipitation methods, internal oxidation methods, etc. are generally used as methods for producing dispersion strengthened alloys. Each of these methods has advantages and disadvantages. For example, the mechanical mixing method is an economical method with simple manufacturing conditions, but it is difficult to prevent the agglomeration of the dispersed material even if the starting material is fine particles, making it difficult to obtain a product with a uniform composition. . On the other hand, although the chemical coprecipitation method enables uniform dispersion of fine dispersion materials, it is a wet method and therefore involves problems such as waste liquid treatment. Next, although the internal oxidation method has the disadvantage that the process is complicated, it is possible to finely and uniformly disperse the dispersion material. The present invention relates to an improvement in a method for producing a dispersion-strengthened copper alloy by an internal oxidation method using aluminum oxide as a dispersion matrix of pure copper. In the production of dispersion-strengthened copper alloys, it is necessary to selectively oxidize aluminum in Cu-Al alloy powder. In this case, techniques using oxygen gas and copper oxide as an oxidizing agent in internal oxidation are known. The former requires complicated adjustment of the oxygen gas partial pressure, while the latter thermally decomposes copper oxide and generates oxygen, which selectively oxidizes Al, making it easy to adjust the degree of oxidation. The composition of the oxidizing agent after decomposition differs from the composition of the internally oxidized Cu--Al alloy powder, resulting in non-uniformity in the composition of the manufactured material, resulting in problems such as reduced heat resistance.

As a way to solve this problem, for example,
Publication No. 55-39617 describes the use of Cu ₂ O as an oxidizing agent.
Al(NO ₃ ) ₃・9H ₂ O is used as raw material to produce Al(NO ₃ ) ₃
A method is disclosed that uses a composite powder of Cu ₂ O-Al 2 O ₃ obtained by thermal decomposition to Al ₂ O ₃ as _an oxidizing agent, and equalizes the composition of the alloy powder after internal oxidation and the oxidizing agent after thermal decomposition. has been done. However, this method is a wet method and is a more complicated method. Furthermore, in the above-mentioned publication, prior to internal oxidation, the alloy powder is analyzed by ASTM according to the grain size.
By recrystallizing to No. 6 or higher, it is possible to prevent solute metal oxides from gathering around the powder during internal oxidation. However, this recrystallization must be performed in an inert atmosphere, which not only causes agglomeration of the alloy powder but also increases costs.

The purpose of the present invention is to
It is an object of the present invention to provide a method for producing a heat-resistant and conductive dispersion-strengthened copper alloy material that can reliably control the degree of internal oxidation with good reproducibility in a simple manner by using an appropriate oxidizing agent.

The purpose of the present invention is to provide a Cu-
The first step of producing Al alloy powder by water spraying,
The second step is to oxidize the Cu-Al alloy powder to make a copper oxide-aluminum oxide composite powder oxidizing agent. This is achieved by a method for manufacturing a dispersion-strengthened copper alloy that combines a third step of forming, a fourth step of internally oxidizing the green compact, a fifth step of reducing excess oxide, and a sixth step of hot extrusion. .

First, the basic idea of the present invention will be explained.

In the present invention, in the fourth step, the Cu-Al alloy powder is internally oxidized and thermal decomposition of the oxidizing agent occurs.
In order to equalize the composition of both at the end of the fourth step, if the Cu-Al alloy powder itself is oxidized in the first step to become a copper oxide-aluminum oxide composite powder oxidizing agent, after internal oxidation in the fourth step, , Cu-Al
The alloy powder and the thermally decomposed oxidizing agent become a Cu-Al ₂ O ₃ composite powder, and it is possible to make both powders the same composition by a simple method. Looking at the fourth step in more detail, the oxygen released by thermal decomposition of the copper oxide oxidizer during internal oxidation treatment diffuses into the Cu-Al alloy powder.
It reacts with Al dissolved in Cu to form Al ₂ O ₃ .
When Al ₂ O ₃ is generated in this reaction, the solid solution Al concentration near Al ₂ O ₃ decreases, and Al diffuses into that position from the surroundings. Assuming that the Cu-Al alloy powder is spherical and consists of a single crystal, oxygen
Volumetric diffusion occurs from the surface of the Al alloy powder to the inside.
First, it reacts with solid solution Al near the surface to form Al ₂ O ₃ . Then, since the solid solution Al concentration in this vicinity decreases relatively, the solid solution Al diffuses from the inside of the Cu-Al alloy powder to the vicinity of the surface according to the second law of thermodynamics.
Such oxidation and diffusion reactions occur continuously, and as a result, the Al ₂ O ₃ concentration produced becomes non-uniform near the surface and inside the internally oxidized Cu—Al alloy powder. That is, there is a phenomenon in which the Al ₂ O ₃ concentration is higher near the surface. To prevent this phenomenon, solid solution
It is desirable to shorten the Al diffusion distance, that is, to reduce the particle size of the Cu--Al alloy powder.

Although we considered the case where the Cu--Al alloy powder consists of a single crystal, the actual Cu--Al alloy powder is polycrystalline. In the case of polycrystals, the grain boundaries are metallurgically active areas, so the oxygen released by thermal decomposition of the oxidizing agent diffuses preferentially from the grain boundaries into the Cu-Al alloy powder, further increasing the crystallization. Diffuses into the grain. Therefore,
In this case, the finer the grain size of the polycrystal, the more
The concentration distribution of the generated Al ₂ O ₃ becomes uniform. In this way, fine crystal grains and/or fine powder grains are
When internal oxidation is performed using Cu/Al alloy powder and the copper oxide/aluminum monoxide composite oxidizing agent of the present invention, a dispersion-strengthened copper alloy having sufficient heat resistance can be easily produced.

The reasons for the limitations of the present invention will be described below, and a more detailed explanation will be added.

First step It is necessary to increase the cooling rate during spraying to produce fine Cu--Al alloy powder as much as possible. Since the cooling rate of the water spray method is higher than that of the gas spray method, it is necessary to use the water spray method to finely divide the Cu--Al alloy molten metal into powder with a predetermined particle size. The crystal grain size is also influenced by the grain size of the produced Cu--Al alloy powder. That is,
As the Cu-Al alloy powder particle size increases, the crystal grain size tends to increase. Therefore, the particle size of the Cu--Al alloy powder must be -70 mesh or less, preferably -100 mesh.

Furthermore, if the Al concentration in the Cu--Al alloy powder is less than 0.1% by weight, the proportion of Al ₂ O ₃ , which is a dispersant after internal oxidation, is small and sufficient heat resistance cannot be obtained. Al concentration
If it exceeds 1.0% by weight, the proportion of Al ₂ O ₃ will be excessive and the conductivity and ductility will decrease, so the Al concentration in the Cu--Al alloy powder is preferably 0.1 to 1.0% by weight.

Second step Next, the Cu-Al alloy powder containing 0.1 to 1.0% by weight of Al is completely oxidized to produce a composite oxide of copper oxide and Al ₂ O ₃ , which is used as the oxidizing agent in the fourth step. . The oxidation treatment may be performed by heating in the air at a temperature of 400°C to 700°C for 0.5 to 1.5 hours. Although oxidation reactions occur below 400°C, it takes a long time to complete the oxidation, and
Since the oxidation time is not significantly shortened even if heated to a temperature higher than ℃, it is necessary to heat at 400℃ to 700℃ for 0.5 to 1.5 hours. After oxidation, it is necessary to grind it to a fine powder of -250 mesh or less, preferably -325 mesh or less. If the oxidizing agent is coarse, the internal oxidation described below will not be performed uniformly.

Third step: Cu--Al alloy powder and oxidizing agent are mixed, and the ratio varies depending on the Al concentration. In order to internally oxidize 0.1 to 1.0% by weight of Al contained in the Cu-Al alloy, it is necessary to add 0.5 to 7.0% by weight of an oxidizing agent to the entire alloy. The Cu-Al alloy powder and the oxidizing agent are mixed using a mixer, such as V
A mold, double cone mold, etc. is sufficient, but during mixing
A mixer that works hardens Cu-Al alloy powder,
For example, a ball mill is not preferred because it reduces the compressibility of the mixed powder.

Next, the mixed powder of Cu-Al alloy powder and oxidizer powder needs to be compression molded to a relative density of 80% or more. If the relative density is less than 80%, the amount of plastic deformation during hot extrusion, which will be described later, will be small and uniformity of the structure will be hindered. Furthermore, if the relative density is less than 80%, the efficiency during hot extrusion may decrease, so the relative density must be 80% or more. In order to obtain a relative density of 80% or more, a molding pressure of 4000 to 6000 Kgf/cm ² is preferable.

4th step Next, Cu is compression molded to a relative density of 80% or more.
Inert mixed powder of Al alloy powder and oxidizer powder
Internal oxidation treatment is performed by heating in Ar gas. The heating temperature may be higher than the temperature at which the oxidizing agent, copper oxide, is thermally decomposed to generate oxygen. in particular
Heating to 700°C or higher is sufficient, but since internal oxidation treatment requires a long time, it is necessary to heat at a higher temperature in order to accelerate the rate of oxygen diffusion into the Cu-Al alloy powder. It is appropriate to heat at 850°C to 1000°C for 20 to 60 minutes. If the heating temperature exceeds 1000°C, Al ₂ O ₃ generated by internal oxidation will become coarse, which is not preferable.

Fifth step Next, reduction is performed after internal oxidation treatment. Cu for internally oxidizing 0.1 to 1.0 wt% Al in the third step above.
It has been stated that the appropriate amount of the oxidizing agent added to the Al alloy powder is 0.5 to 7.0% by weight, but this value is greater than the chemical equivalent to the Al concentration in the Cu--Al alloy powder. This was determined in consideration of the fact that oxygen generated by thermal decomposition of copper oxide in the internal oxidation process diffuses out of the compact, and is also related to the relative density of the compact. From this, conversely, the chemical equivalent of oxygen becomes larger than the chemical equivalent of Al in the Cu--Al alloy powder, so it reacts with the matrix Cu during cooling after internal oxidation to form Cu ₂ O. _Cu2O
is not preferable because it causes a decrease in conductivity and ductility. Therefore, it is necessary to perform reduction to remove excess oxygen after internal oxidation.
The reduction temperature may be set so that the oxygen generated by thermal decomposition of Cu ₂ O undergoes a reduction reaction. Specifically 700℃~900
Carry out the reduction reaction for 0.5-1 Hr at °C. The atmosphere for the reduction reaction is preferably hydrogen or decomposed ammonia gas.

Sixth Step Next, after the reduction reaction, the green compact is sealed in a copper container in a neutral atmosphere. The purpose of sealing in a neutral atmosphere is to prevent oxidation during heating during hot extrusion, which will be described later.

Hot extrusion must be carried out at an extrusion ratio of 10:1 or more. If the extrusion ratio is less than 10:1, there will be less plastic flow and uniformity of the structure will be hindered, so the extrusion ratio should be
A ratio of 10:1 or more is required, preferably 15:1 to 30:1. Moreover, the temperature of hot extrusion is preferably 850°C to 950°C.

As understood from the above, one feature of the present invention is that fine Cu-Al alloy powder is obtained by water spraying in the first step, and grain coarsening treatment such as recrystallization treatment is performed before the fourth step. It lies in not doing it. Although recrystallization inevitably occurs during the internal oxidation in the fourth step, since no recrystallization treatment was performed in the previous step, the crystal grain size in the final product is very small.

Figures 1 and 2 are photographs of the metallographic structure of Cu-Al alloy powder. Figure 1 shows the structure after water spraying, with an average crystal grain size of 7.13 microns (σ = 1.01 microns). It was hot. Figure 2 shows the structure after recrystallization after heating at 880°C for 1 hour, with an average crystal grain size of 19.7 microns (σ =
2.44 microns). Therefore, the present invention improves the crystal grain size after the internal oxidation treatment in the fourth step.
It is fully possible to reduce the thickness to 30 microns or less,
The grain size of the final product can be kept very small, resulting in a uniform Al ₂ O ₃ concentration distribution.

Examples will be described below for further explanation.

Example 1 In an induction furnace, Cu-0.1% by weight Al, Cu-0.4
An alloy having a composition of % Al and Cu-1.0% Al by weight was melted and powdered by water spraying, and sieved into a 100-mesh size. A part of this powder was further sieved to -250 mesh, oxidized at 600°C for 1 hour in the atmosphere, ground in a ball mill, and sieved to -325 mesh to obtain an oxidizing agent. The ratio of the above Cu-Al alloy powder and oxidizing agent is 0.5% by weight oxidizing agent for 0.1% Al, 2.5% oxidizing agent for 0.4% Al, and 6.5% for 1.0% Al.
Each weight percent of oxidizing agent was added and mixed for 30 minutes using a V-type mixer. After mixing, the mixture was compacted at a molding pressure of 6000 kgf/cm ² . The relative density of the green compact was 89% in the case of 0.1 wt% Al, 87% in the case of 0.4 wt% Al, and 84% in the case of 1.0 wt% Al. The obtained green compact
Internal oxidation treatment was performed by heating at 950°C for 30 minutes in Ar gas. Thereafter, it was heated in hydrogen at 800°C for 1 hour for reduction. After reduction, it was sealed in a Cu container in Ar gas, and hot extrusion was performed at an extrusion ratio of 20:1 and an extrusion temperature of 900°C.
Extruded material from 100℃ to 1000℃ in 100℃ increments
The hardness was measured by heating in Ar gas for 1 hour. The results are shown in Figure 3. In Figure 3, -〇-,
―●― and ―×― lines are 0.1, 0.4, and 1.0% by weight, respectively.
Indicates Al. It was revealed that none of the extruded materials softened much at heating temperatures up to 900°C. In addition, the conductivity of the extruded material is 87% IACS for 0.1 wt% Al;
In the case of 0.4 wt% Al, the IACS was 79%, and in the case of 1.0 wt% Al, it was 60% IACS.

Comparative Example 1 A Cu-0.4% by weight Al alloy powder was prepared in the same manner as in Example 1 and sieved into -40 mesh + 70 mesh. In other respects, the extruded material was produced in the same manner as in Example 1. The extruded material using the Cu-0.4 wt% Al alloy powder of Example 1 and the extruded material produced in Comparative Example 1 were
The hardness was measured by heating at 700°C in Ar gas for 100 hours, and the results are shown in FIG. 4 by the --- and --- lines, respectively. From the results shown in Figure 4, it can be seen that the coarser the grain size of the Cu--Al alloy powder, the greater the decrease in hardness.

Comparative Example 2 Cu-0.4 wt% Al alloy powder of Example 1 (-100
molding pressure 2500Kgf/cm ²
A mixed powder of Cu-0.4 wt% Al alloy powder and 0.5 wt% oxidizing agent was compression molded to a relative density of 74%. Other steps were the same as in Example 1. The extruded material using the Cu-0.4 wt% Al alloy powder produced in Example 1 and the extruded material produced in Comparative Example 2 were heated at 800°C in Ar gas.
After heating for 30 hours, a tensile test was conducted. The extruded material of Example 1 has a tensile strength of 52Kgf/ ^mm2 and an elongation of 11%.Comparative Example 2
In the case of the extruded material, it was 39Kgf/mm ² 15%, respectively. Therefore, it is clear that if the relative density of the green compact is less than 80%, the heat resistance will decrease.

Comparative Example 3 Cu-0.4 wt% Al alloy powder of Example 1 (-100
Hot extrusion was carried out using a part of the mesh (mesh) and changing the extrusion ratio of hot extrusion to 8:1. The extruded material produced using the Cu-0.4 wt% Al alloy powder produced in Example 1 and the extruded material produced in Comparative Example 3 were heated in Ar gas under the same conditions as Comparative Example 2, and a tensile test was conducted. Ta. The extruded material of Example 1 has a tensile strength of 52 kg.
f/ ^mm2 elongation 11%, and the extruded material of Comparative Example 3, respectively, 36
Kgf/mm ² was 10%. Therefore, the extrusion ratio is 10:1
It has become clear that if it is less than that, the heat resistance will be insufficient.

Comparative Example 4 Using a part of the Cu-0.4 wt% Al powder (-100 mesh) of Example 1, a part of it was oxidized as an oxidizing agent in the same manner as in Example 1, and the oxidizing agent was added to the whole.
The oxidizing agent and the Cu-0.4% by weight Al powder were mixed in a V-type mixer for 30 minutes so that the concentration was 2.5% by weight.
Thereafter, this mixed powder was compacted to a relative density of 46%. Subsequently, the green compact was heated to 950℃ for 30 minutes.
Internal oxidation was performed by heating in Ar gas. After internal oxidation, the green compact is crushed and sieved into 100 mesh pieces.
After filling the powder into a copper container and replacing the air inside the container with Ar gas, the copper container was vacuum sealed and the extrusion ratio was 20:1.
Extrusion was carried out at an extrusion temperature of 900°C.

The extruded material was heated in Ar gas for 1 hour at every 100°C from 100°C to 1000°C, and then the room temperature hardness was measured. The results are shown in Figure 3 by the -△- line. From this, it is clear that when the relative density is low, the heat resistance is insufficient.

From the above explanation, the present invention has excellent heat resistance and conductivity,
It is clear that it is suitable for heat-resistant conductive dispersion-strengthened copper alloys used as electrode materials for spot welding.

[Brief explanation of the drawing]

Figure 1 is a photograph of the metallographic structure of Al-containing copper alloy powder immediately after water spraying (magnification: x500), and Figure 2 is a photograph of the metallographic structure of the powder in Figure 1 after heating it at 880°C for 1 hour (magnification: ×500), and FIG. 3 is a diagram showing the relationship between heating temperature and hardness of the materials of Example 1 and Comparative Example 4 according to the present invention, and FIG. 4 is a diagram comparing Example 1 and Comparative Example 4 according to the present invention. FIG. 3 is a diagram showing the relationship between heating time and hardness of the material in Example 1.

Claims (1)

[Claims] 1 The first step of water spraying an alloy containing 0.1 to 1.0% by weight of Al and the balance consisting of Cu to form a Cu-Al alloy powder of -70 mesh or less, the Cu obtained in the first step.
- Al alloy powder is oxidized in an oxidizing atmosphere at 400°C to 700°C for 0.5 to 1.5 hours and then pulverized to produce a composite powder of copper oxide and aluminum monoxide with a size of -250 mesh or less, which is obtained in the second step and the first step. The copper oxide aluminum monoxide composite powder obtained in the second step is added and mixed with Cu-Al alloy powder at a relative density of 80%.
3rd step of compacting the powder compact obtained in the 3rd step to a temperature of 20 to 60% at 850℃ to 1000℃ in Ar gas.
4th step in which Al in the Cu-Al alloy powder obtained in the 1st step is selectively internally oxidized by the copper oxide aluminum monoxide composite powder obtained in the 2nd step; The fifth step is heating at 700°C to 900°C for 0.5 to 1 hour in a post-reducing atmosphere to reduce excess oxide, and after the reduction in the fifth step, the copper container is sealed in a non-oxidizing atmosphere and the extrusion ratio is 10: A method for producing a heat-resistant, electrically conductive dispersion-strengthened copper alloy material, comprising a sixth step of hot extruding at least one step.