JP4169652B2 - Method for producing copper composite material - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a copper composite material suitable as a welding electrode material or a connector used in an electric vehicle.
[0002]
[Prior art]
A copper alloy in which an oxide such as alumina is dispersed in a copper matrix is excellent in electrical conductivity and heat resistance, and thus is widely used as an electrical component material. Many proposals have been made to improve the characteristics and manufacturing method of this copper alloy.
For example, proposals have been made to improve conductivity and softening properties by adding not only aluminum as an element to be internally oxidized but also tin as a third element. (Patent Document 1)
[0003]
Further, it has been proposed that particles having a particle size of 50 μm or less become 70% by weight or more by using a copper alloy powder in which an easily oxidizable metal such as aluminum of 300 μm or less manufactured by an atomizing method is used as a solid solution. (Patent Document 2)
[0004]
Moreover, after Cu-Al alloy powder was internally oxidized to Al to Al ₂ O ₃ , the surface of this alloy powder was smoothed, and then compacted to form a compact, which was molded at 600 to 1000 ° C. A hot forging method has been proposed. (Patent Document 3)
[0005]
Moreover, after internally oxidizing the plate-like copper alloy containing Al to make Al into Al ₂ O ₃ , this plate-like alloy is made into a coil shape, this coil-like alloy is sealed in a metal tube, and this metal tube is formed into a desired shape. A method of hot working at 900 ° C. has been proposed. (Patent Document 4)
[0006]
Further, a method has been proposed in which an alloy powder obtained by internally oxidizing a Cu—Al alloy chip is filled in a carbon mold and hot pressed at 900 ° C. and a pressure of 400 kg / cm ² . (Patent Document 5)
[0007]
In addition, a method has been proposed in which a sinterability is enhanced so that an Al ₂ O ₃ annular hard layer is present inside the Cu—Al alloy powder. (Patent Document 6)
[0008]
Further, although it is not a copper alloy but an aluminum alloy, in order to refine the structure and enhance the toughness, a shear deformation having a strain corresponding to an elongation of 200% or more or 220% or more in one extrusion to the aluminum alloy is performed at 300 ° C. The method of giving at the following temperature is proposed. (Patent Literature 7, Patent Literature 8)
[0009]
[Patent Literature]
Patent Document 1: Japanese Patent Application Laid-Open No. 59-150043 Patent Claim 2: Japanese Patent Application Laid-Open No. 60-141802 Patent Document 3: Japanese Patent Application Laid-Open No. 63-241126, page 2, upper right column 6 Line 11 to Patent Document 4: JP-A-2-385541, page 3, upper right column, line 16 to lower left column, last line Patent Document 5: JP-A-2-93029, page 3, lower right column, line 15 to page 4. Patent Document 6: Japanese Patent Laid-Open No. 4-80301 Patent Document 7: Japanese Patent Laid-Open No. 9-137244 Patent Document 8: Japanese Patent Laid-Open No. 11-114618
[Problems to be solved by the invention]
Among the above-mentioned prior arts, Patent Documents 1 to 6 all perform hot working at high temperatures, and therefore tend to coarsen the structure due to grain growth, and are used as electrode materials for welding and connectors for electric vehicles. A product that satisfies the required characteristics at the same time cannot be obtained.
On the other hand, according to Patent Documents 7 and 8, a refined structure is obtained. However, this document does not disclose any copper alloy, and in particular, what kind of manufacturing method is used for a composite material in which ceramic is mixed with copper. There is no suggestion about what to do.
[0011]
In view of this, the inventors of the present invention previously described Japanese Patent Application No. 2003-000919 by mixing copper powder and ceramic powder (alumina or titanium boride) to make this mixed powder a primary shape body. Although proposals have been made to extrude while imparting strain, a method for producing a copper composite material with improved properties is desired.
[0012]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention comprises a method for producing a copper composite material in which titanium boride is dispersed in a copper matrix from the following steps (1) to (4).
(1) A step of mixing a copper powder, a titanium powder and a boron powder into a primary shape.
(2) A step of applying thermal energy to the primary shaped body to react the titanium powder and boron powder to form titanium boride in a copper matrix.
(3) A step of plastically deforming the primary shape body on which the titanium boride is formed to give a strain to form a secondary shape body.
As described above, rather than mixing titanium boride with copper powder, titanium powder and boron powder, which become titanium boride, are formed in the copper matrix by reaction, thereby increasing the mechanical strength by making fine particles. Can do.
For example, if the average particle diameter of titanium powder and boron powder is 0.3 to 10 μm, the average particle diameter of the base material of the obtained secondary shape body is 20 μm or less, and the average particle diameter of titanium boride particles is 400 nm or less. It is possible to obtain a welding electrode material that is small in deformation due to pressurization during welding (because the compressive strength of the material is low).
[0013]
In addition, when applying heat energy to the primary shape body, some titanium and boron dissolve in copper, but if this solid solution of titanium and boron remains unreacted, the conductive and thermal It will be inferior in characteristics. Therefore, it is preferable to heat-treat the secondary shaped body in the same step as the step of plastically deforming and applying the strain, or the subsequent step, to precipitate unreacted solid solution elements (titanium and boron).
[0014]
As the plastic deformation, for example, a strain corresponding to an elongation of 200% or more is applied. Examples of means for imparting plastic deformation include extrusion, drawing, shearing, rolling, forging, and the like. For example, the material temperature is set to 400 ° C. to 1000 ° C., a mold of 400 ° C. to 500 ° C. is used, and the extrusion rate is 0.5. Side extrusion performed at ˜2.0 mm / sec is effective, and the number of extrusions needs to be repeated 10 to 20 times.
[0015]
The extrusion material temperature was set to 400 ° C. to 1000 ° C. When the temperature was less than 400 ° C., the deformation resistance was large and extrusion became difficult, and sufficient bonding strength between the matrix (matrix) and the particles could not be obtained. If it exceeds, the melting point of copper will be exceeded and melting will not be possible. The mold temperature is set to 400 ° C. to 500 ° C. because extrusion becomes difficult when the mold temperature becomes too low, and the mold itself is annealed when the mold temperature becomes too high. .
Further, the higher the extrusion speed, the easier the distortion occurs. However, the reason for setting it to 0.5 to 2.0 mm / sec is not preferable because it takes less time to manufacture if it is less than 0.5 mm / sec. The above range is preferable because the friction with the mold is increased and the mold life is extremely shortened.
Further, in order to perform the extrusion, the alloy powder needs to be in a predetermined shape (primary shape). For this purpose, means such as compacting or filling the mixed powder into a tube can be considered.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a diagram for explaining a process for obtaining a copper composite material according to the present invention. In either case, titanium (Ti) powder and boron (B) powder are mixed with a base material (Cu powder) as a starting material. The mixing ratio is 0.1 wt% to 5.0 wt% for both titanium powder and boron powder. If it is less than 0.1 wt%, the wear resistance is not improved, and if it exceeds 5.0 wt%, the conductivity is lowered and the life of the mold is shortened, so that the above range is satisfied.
[0017]
Subsequently, in order to extrude said mixed powder sideways, it is set as a primary shape body. There are two steps to obtain a primary shape. When the target product is a small object such as a connector or electrode rod, the Cu tube is filled with the above mixture to form a primary shape. On the other hand, when the target product is long or large, it is formed into a primary shape body by compacting.
[0018]
Next, the primary shape body is sintered. The added titanium (Ti) and boron (B) react with the thermal energy associated with the sintering to produce titanium boride. FIG. 3 shows the state of the structure after sintering. From this figure, it can be seen that titanium boride that was not produced before sintering was produced in the copper matrix after sintering.
In the embodiment, sintering was performed as a means for applying thermal energy, but thermal energy may be applied by means other than this.
[0019]
The sintered primary shape obtained as described above is subjected to side extrusion to give a strain corresponding to an elongation of 200% or more, preferably about 220%.
FIG. 2 illustrates an example using a Cu tube. In the figure, the diameter of the Cu tube is larger than the diameter of the insertion hole formed in the side extrusion mold. The diameter is substantially equal to the diameter of the insertion hole formed in the mold, and is supported by using a jig or the like so that the Cu tube does not fall when the Cu tube is pushed by a punch.
[0020]
As specific conditions for the side extrusion, ECAE (equal-channel-angular) is extruded 12 times with a material temperature of 400 to 1000 ° C., a mold temperature of 400 to 500 ° C., an extrusion speed of about 1 mm / sec. -Extrusion) process. By repeating this process, the matrix phase is refined and the titanium boride formed in the copper matrix is crushed and dispersed.
[0021]
FIG. 4 is a diagram showing the relationship between the electrical conductivity with and without strong processing (giving a strain corresponding to an elongation of 220%) and the amount of TiB added. It turned out to improve. This is because the heat treatment produces conductive titanium boride, but the added titanium and boron do not react stoichiometrically, and the solid solution titanium and boron remain unreacted in the copper. It remains in the matrix, and this causes the electrical conductivity to not be increased. Therefore, it is considered that unreacted solid solution elements (titanium and boron) are precipitated and the electrical conductivity is improved when strongly processed.
[0022]
FIG. 5 is a graph comparing the weldability of the copper composite material according to the present invention and the conventional copper composite material by the number of continuous hit points, and a commercially available copper composite material in which alumina is dispersed in copper is used as a welding tip. The number of hitting points is about 1200, whereas the alumina-dispersed copper composite material subjected to ECAE (equal-channel-angular-extrusion) treatment has a hitting number of about 1600 and the copper according to the present invention in which titanium boride is dispersed. In the case where the composite material was a welding tip, 1900 dots were possible.
[0023]
【The invention's effect】
As described above, according to the method for producing a copper composite material according to the present invention, since solution treatment is not a starting point, there is no limit due to a solid solution limit, and titanium and boron added to copper are arbitrarily set. It is possible to obtain characteristics that could not be obtained with conventional copper composite materials.
In particular, titanium boride is not added directly to copper, but titanium and boron before reaction are added, and by adding thermal energy to this, titanium boride is generated in the copper matrix by reaction, Refinement of the tissue (nano order: several hundred nm or less) is promoted, and the mechanical strength is improved.
[Brief description of the drawings]
FIG. 1 illustrates a method for producing a copper composite material according to the present invention. FIG. 2 illustrates a method for producing a copper composite material by filling a copper pipe.
FIG. 3 is a micrograph showing the state of the structure after sintering. FIG. 4 is a diagram showing the relationship between the electrical conductivity with and without strong processing and the added amounts of Ti and B. FIG. 5 relates to the present invention. A graph comparing the weldability of copper composites obtained by the manufacturing method and conventional copper composites in terms of the number of consecutive dots

Claims (7)

A method for producing a copper composite material in which titanium boride is dispersed in a copper matrix, comprising the following steps (1) to (3).
(1) A step of mixing a copper powder, a titanium powder and a boron powder into a primary shape.
(2) A step of applying thermal energy to the primary shaped body to react the titanium powder and boron powder to form titanium boride in a copper matrix.
(3) A step of plastically deforming the primary shape body on which the titanium boride is formed to give a strain to form a secondary shape body. 2. The method of manufacturing a copper composite material according to claim 1, wherein the secondary shape body is subjected to a heat treatment in the same step as the step of plastically deforming and applying the strain, or in a subsequent step. Production method. 3. The method for producing a copper composite material according to claim 1, wherein the plastic deformation imparts a strain corresponding to an elongation of 200% or more. 4. The method for producing a copper composite material according to claim 1, wherein the plastic deformation is extrusion performed at a material temperature of 400 ° C. to 1000 ° C. 5. 4. The method for producing a copper composite material according to claim 1, wherein the plastic deformation is extrusion performed at a mold temperature of 400 ° C. or more and 500 ° C. or less. 5. 6. The method for producing a copper composite material according to claim 1, wherein the primary shape body is obtained by compacting or filling a tube with mixed powder. The method for producing a copper composite material according to any one of claims 1 to 6, wherein the ceramic powder has an average particle size of 0.3 to 10 µm, and an average particle size of the base material of the obtained secondary shape body is 20 µm or less. The method for producing a copper composite material, wherein the titanium boride particles have an average particle size of 500 nm or less.

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