JP2004100042A - Method for producing copper alloy stock - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for imparting excellent mechanical strength and thermal and electric properties to a copper alloy. <P>SOLUTION: Secondary elements which hardly enter into a solid solution such as Cr (chromium), zirconium (Zr), beryllium (Be), titanium (Ti) and boron (B) are dissolved into a solid solution with a base material metal (Cu) by solution heat treatment, and thereafter rapid cooling is performed to obtain a stock in a supersaturated state. If required, aging treatment is subsequently performed. Then, strain equivalent to an elongation of ≥200%, preferably of 220%, is applied to the stock to attain the fining of crystals (to a mean crystal grain size of ≤20 μm). Simultaneously with the application of the strain or thereafter, aging treatment is applied to promote the precipitation of the secondary elements between the crystal grains. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for producing a copper alloy suitable for a welding electrode material, a connector material of an electric vehicle, and the like.
[0002]
[Prior art]
As automobiles become EVs (electric vehicles), the amount of connectors used as connecting parts for harnesses and wires tends to increase. In addition, the purpose of EV is to secure safety and fuel efficiency with electronic control technology.
Connectors used in automobiles are used under extreme conditions of high temperature and vibration, and therefore, connection reliability and contact stability are required. Further, as the use of EVs progresses, a copper-based spring material having a small energy loss, that is, a high conductivity is desired.
Further, as for the electrode material for welding, all of mechanical strength, thermal properties and electrical properties are required to be equal to or higher than a predetermined value.
[0003]
As means for improving the mechanical strength of a metal material, miniaturization of the crystal structure is known as Hall-Petch's law.
For example, when a metal or alloy material is deformed, the material strength increases due to work hardening. This is because various defects (point defects, dislocations, stacking faults, etc.) accumulate in the material due to processing (plastic deformation), and as a result of the interaction of these defects, the introduction and movement of new defects becomes difficult. It is understood that it will have resistance.
[0004]
In order to apply plastic deformation (strain) to a metal material, extrusion, drawing, shearing, rolling, forging, and the like have been conventionally performed.
More specifically, the material is thinned by rolling, a high pressure torsion (HPT) method, a CEC (Cyclic Extrusion Compression) method of repeatedly passing through a constricted pipe, and a metal sheet thinned by rolling is cut and stacked. An ARB (Accumulative Roll Bonding) method of performing repetitive rolling is proposed, and specific methods for miniaturization of an aluminum alloy are disclosed in Patent Document 1, Patent Document 2, Patent Document 3, Patent Document 4, and the like. An ECAE method has been proposed in which shear deformation is provided by lateral extrusion without reducing the cross section of a material.
[0005]
On the other hand, for copper alloys, methods disclosed in Patent Literature 5, Patent Literature 6, and the like have been proposed. In this prior art, among copper alloys, dynamic recrystallization by hot extrusion is used to improve the properties (cutting properties and dezincification corrosion) of brass (Cu-Zn) used as a material for faucet fittings and the like. Is caused to obtain a finer crystal and a specific crystal structure ratio (the ratio of α phase, β phase, and γ phase).
[0006]
Also, an age hardening type copper alloy to which an element which does not form a solid solution or hardly forms a solid solution at room temperature, such as chromium (Cr), zirconium (Zr), beryllium (Be), boron (B) and titanium (Ti) is added. In order to bring out the predetermined characteristics, the element is first solid-dissolved at a high temperature by solution treatment, then rapidly cooled to a supersaturated state, and then supersaturated by aging at a predetermined temperature. The additive element in the state is precipitated.
[0007]
[Patent Document]
Patent Document 1: JP-A-9-137244 Patent Document 2: JP-A-10-258334 Patent Document 3: JP-A-11-114618 Patent Document 4: JP-A-2000-271621 Patent Document 5: JP-A-Hei Patent Document 6: JP-A-2000-355746
[Problems to be solved by the invention]
The above-mentioned work hardening or aging treatment for aluminum alloys and copper alloys is directly applied to age hardening type copper alloys added with chromium (Cr), zirconium (Zr), beryllium (Be), titanium (Ti) or boron (B). Even if it is applied, all of the mechanical strength, thermal characteristics and electrical characteristics cannot be compatible.
[0009]
That is, for example, in order to make the copper alloy exhibit the thermal and electrical properties required as an electrode material, it is necessary to deposit as much as possible of the solid solution additive element. It is necessary to raise the aging temperature in order to precipitate a large amount. However, when the temperature is increased, the grain growth proceeds and the mechanical properties are reduced. That is, there is a trade-off relationship between mechanical strength and thermal / electrical characteristics.
[0010]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a method for producing a copper alloy material according to the present invention comprises: first, a solution treatment is performed to convert a base metal (Cu) into Cr (chromium), zirconium (Zr), beryllium (Be), titanium ( A second element that hardly forms a solid solution, such as Ti) and boron (B), is dissolved, and then aging treatment is performed as necessary. As the material before applying strain, the desired performance can be obtained even after the solution treatment, but it is more preferable that the material is subjected to aging after the solution treatment and the second element is precipitated between crystal grains. .
Then, a strain corresponding to elongation of 200% or more, preferably 220% is given to the above-mentioned material to refine the crystal (average crystal grain size is 20 μm or less), and aging is performed simultaneously with or after applying the strain. A treatment is performed to promote the precipitation of the second element between the crystal grains.
[0011]
According to the above method, a copper alloy having preferable characteristics as an electrode material such as spot welding, arc welding, or plasma welding or a connector incorporated in an electric vehicle can be obtained. Suitable properties are a hardness of 30 (HRB) or more, preferably 40 (HRB) or more, a conductivity of 85 (IACS%) or more, preferably 90 (IACS%) or more, and a thermal conductivity of 350 (W / (m · K). )) Or more, preferably 360 (W / (m · K)) or more.
When the hardness is 30 (HRB) or more, the tip of the electrode material can be prevented from being deformed and generating heat, and when the conductivity is 85 (IACS%) or more, it reacts with the steel sheet and sticks. When the thermal conductivity is 350 (W / (m · K)) or more, the cooling efficiency is increased, and welding of the electrode material during welding can be prevented.
[0012]
Extrusion, drawing, shearing, rolling, forging, and the like can be considered as means for imparting strain to the material. Particularly in the case of lateral extrusion, aging treatment can be performed simultaneously by setting the material temperature to 400 to 1000 ° C, the mold temperature to 400 to 500 ° C, and the extrusion speed to 0.5 to 2.0 mm / sec. become.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram for explaining a process for obtaining a copper alloy according to the present invention. First, Cr: 0.1 to 1.4 wt% is melted in a base material (Cu), and this is rapidly cooled to supersaturate Cr in Cu. To obtain a solid solution material. Next, a strain corresponding to elongation of 200% or more is given to this material. It is preferable that the material be subjected to an aging treatment after the solution treatment.
When the additive element is Zr, it is 0.15 to 0.5 wt%, when it is Be, it is 0.1 to 3.0 wt%, when it is Ti, it is 0.1 to 6.0 wt%, and when it is B, it is 0.1 to 0.5 wt%. 01 to 0.5 wt%.
[0014]
FIG. 2 shows a mold for giving strain using a Cu tube. The mixture is filled in a Cu tube, the mold temperature is set to 400 to 500 ° C., and the extrusion speed is about 1 mm / sec. EACE processing). Thus, a strain is given to the copper alloy material in which Cr is dissolved in supersaturation. By this operation, the crystal grain size becomes 200 μm or less from 200 μm.
[0015]
Here, Δe: strain amount, Δ: １ ／ of the joining inner angle, ERR: area ratio before and after processing, A0: cross-sectional area before processing, A: cross-sectional area after processing, EAR: equivalent cross-sectional area before and after processing Rate, EE: Assuming equivalent strain (elongation), the following relationship is established.
Δe = 2 / {3 cotan}
ERR = A0 / A = exp (Δe)
EAR = (1-1 / ERR) × 100
EE = (ERR-1) × 100
[0016]
The crystal structure is refined by the lateral extrusion (EACE treatment). Since the extrusion conditions overlap with the aging treatment, the precipitation of the second element is promoted simultaneously with the refinement.
The microstructure of the copper alloy obtained by this EACE treatment is shown in the micrograph of FIG. The microstructure before the EACE treatment is shown in the micrograph of FIG. From these micrographs, it can be seen that the added element is precipitated between the fine crystal particles by the EACE treatment (black dots in the photograph).
[0017]
FIG. 4 is a graph showing the relationship between mold temperature and hardness during the EACE process, FIG. 5 is a graph showing the relationship between mold temperature and electrical conductivity, and FIG. 6 is a diagram showing the relationship between mold temperature and thermal conductivity. It is a graph showing that the copper alloy obtained by the method according to the present invention from these graphs has characteristics required for an electrode material such as a welding tip, that is, a hardness of 30 (HRB) or more and a conductivity of 85 (IACS%). As described above, it is understood that the thermal conductivity is 350 (W / (m · K)) or more.
[0018]
That is, from FIGS. 4 to 6, the material not subjected to the EACE treatment (solution treatment + aging treatment) has a high hardness, but is inferior in electric conductivity and thermal conductivity, and the material subjected to only the solution treatment is subjected to the EACE treatment. Although the hardness of the material which has been treated is low, it has excellent electrical conductivity and thermal conductivity, and the material which has been subjected to the aging treatment after the solution treatment has been subjected to the EACE treatment. You can see that it is excellent.
[0019]
As can be seen from the photograph, when aging is performed by applying strain, the second element reacts with impurities such as C, O, B, and N in the components, as is apparent from the photograph, compared to the conventional method in which the aging treatment was simply performed. , Carbides, oxides, borides and nitrides. It is considered that the element other than copper in the component is reduced by increasing the aging precipitate compared to the conventional one, and the matrix becomes a component close to pure copper, and the above-mentioned characteristics are considered to be improved. For the same reason, a phenomenon in which the hardness is reduced can be understood.
[0020]
FIG. 7 is a graph comparing the weldability of the copper alloy obtained by the method according to the present invention and the conventional copper alloy with or without spatter generation and sticking. The copper alloy according to the present invention is alumina-dispersed copper and before aging treatment. The appropriate current conditions are the same as those of the copper alloy, and no sticking occurs.
[0021]
FIG. 8 is a graph comparing the weldability of the copper alloy according to the present invention and the conventional copper alloy by the number of continuous hit points. When the copper alloy according to the present invention was used as a welding tip, 1475 hit points were possible. .
[0022]
Next, titanium (Ti) was selected as an additive element, and a copper alloy was obtained in the same manner as described above. The obtained results are shown in FIGS.
FIG. 9 is a graph showing the relationship between the amount of Ti added and the conductivity. The maximum solid solubility of Ti is not so large as about 8 wt% from the beginning, but from FIG. It remains as a state. This is considered to be the cause of the solid solution of Ti lowering the conductivity of the copper alloy.
[0023]
FIG. 10 is a graph showing the electrical conductivity of a copper alloy that has been subjected to aging treatment at 470 ° C. for 2 hours, and then subjected to heavy working (giving a strain equivalent to 200% elongation) and a copper alloy that has just been subjected to aging treatment. . From this graph, it can be seen that the conductivity of the strongly worked copper alloy has been greatly improved. This is considered to be due to the precipitation of Ti, which was dissolved as a solid solution, by heavy working.
[0024]
FIG. 11 is a graph comparing the hardness of a copper alloy that has been subjected to heavy working and a copper alloy that has only been subjected to aging treatment. From this graph, the hardness of the hardened copper alloy is lower than the hardness of the copper alloy which has just been aged. This is considered to be because Ti that had contributed to solid solution strengthening was precipitated by strong working.
[0025]
FIG. 12 is a fluff showing the relationship between hardness, electrical conductivity, and the temperature of heavy working. From this graph, it can be seen that the conductivity is inferior when the hard working is not performed, and the hardness decreases but the conductivity increases as the temperature of the strong working increases. It is considered that this was also due to the fact that Ti, which contributed to solid solution strengthening as described above, was precipitated by strong working.
[0026]
As described above, the solid solution Ti, which could not be precipitated by the aging treatment, is combined with the strong working, so that the solid solution Ti can be precipitated from the copper matrix. By controlling the amount of Ti, the amount of precipitated Ti can be controlled, so that a copper alloy having characteristics suitable for the purpose can be produced.
[0027]
Next, boron (B) was selected as an additive element, and copper alloys were manufactured by various methods. FIG. 13 shows the relationship between boron (TiB) and conductivity of the obtained copper alloy. Here, as a method of obtaining a copper alloy, (1) a solution-treated ingot is prepared, ( ₂ ) TiB ₂ powder is added to copper as a compound (ceramic), and (3) Ti powder and B powder are used alone for copper. Was adopted.
From FIG. 13, it was found that the conductivity was highest when an ingot was selected as the manufacturing method. In any of the production methods, the conductivity decreases with an increase in the proportion of TiB added, and the conductivity increases by performing strong working.
[0028]
【The invention's effect】
As described above, according to the method for producing a copper alloy according to the present invention, since the crystal structure of the copper alloy is refined, it is possible to precipitate a large amount of additional elements between crystal grains. The related mechanical strength and thermal / electrical properties can be compatible.
In particular, characteristics required as an electrode material such as a welding tip, specifically, copper having a hardness of 30 (HRB) or more, a conductivity of 85 (IACS%) or more, and a thermal conductivity of 350 (W / (m · K)) or more An alloy can be obtained.
Further, it is possible to obtain a copper alloy having excellent characteristics as a component such as a connector of an electric vehicle.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a method for producing a copper alloy according to the present invention. FIG. 2 is a diagram illustrating a mold used for an EACE process. FIG. 3A is a diagram illustrating a copper obtained by a method according to the present invention. A micrograph (b) showing the crystal structure of the alloy is a micrograph showing the crystal structure before EACE treatment. [FIG. 4] A graph showing the relationship between mold temperature and hardness. [FIG. 5] The relationship between mold temperature and conductivity. FIG. 6 is a graph showing the relationship between the mold temperature and the thermal conductivity. FIG. 7 is a graph showing the weldability between the copper alloy obtained by the production method according to the present invention and the conventional copper alloy, which shows spatter generation and sticking. FIG. 8 is a graph comparing the weldability of a copper alloy obtained by the production method according to the present invention with a conventional copper alloy by the number of continuous dots. FIG. 9 is a graph showing the relationship between the amount of Ti added and the conductivity. Graph [Figure 10] shows the electrical conductivity of the copper alloy that was subjected to heavy working and the copper alloy that had just been aged. Rough [Fig. 11] A graph comparing the hardness of a hard-worked copper alloy with that of a copper alloy just subjected to aging [Fig. 12] A fluff showing the relationship between hardness, conductivity and the temperature of hard-working [Fig. 13] Graph showing the relationship between the addition method and conductivity

Claims (5)

A second element that does not form a solid solution or hardly forms a solid solution at room temperature is dissolved in a base metal (Cu), and a strain corresponding to elongation of 200% or more is given to this material to achieve crystal refinement. A method for producing a copper alloy material, wherein an aging treatment is performed simultaneously with or after the application of the strain to promote the precipitation of the second element between crystal grains. 2. The method for manufacturing a copper alloy material according to claim 1, wherein the second element is any one of Cr (chromium), zirconium (Zr), beryllium (Be), titanium (Ti), and boron (B). A method for producing a copper alloy material, comprising: 3. The method for producing a copper alloy material according to claim 1, wherein the means for giving a strain to the material is any one of extrusion, drawing, shearing, rolling, and forging. Material manufacturing method. 4. The method for producing a copper alloy material according to claim 3, wherein the extrusion conditions are lateral extrusion, the mold temperature is 400 to 500 ° C., and the extrusion speed is 0.5 to 2.0 mm / sec. Method for producing copper alloy material. The method for manufacturing a copper alloy material according to claim 1, wherein the material is preliminarily subjected to an aging treatment before the material is strained.

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