JP2009167450A - Copper alloy and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a copper alloy which has both of high strength and high electric conductivity comparatively by effectively precipitating an element solid-dissolved in a Cu mother phase. <P>SOLUTION: This copper alloy is composed of 0.01-3 mass% precipitation strengthening element and 0.01-5 mass% precipitation promoting element and the balance Cu with inevitable impurities. Then, at least a part of the precipitation strengthening element, is precipitated together with the precipitation promoting element and the electric conductivity is ≥40% IACS. As the above precipitation strengthening element, for example, at least one side of Ti or Cr can be used. Further, as the above precipitation promoting element, for example, at least one side of Fe or Co may be used. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a copper alloy and a method for producing the same. In particular, the present invention relates to a copper alloy having high strength and high conductivity and a method for producing the same.

Cu-Ti alloys are known as high-strength copper alloys and are often used as lead frame materials for semiconductors and connector materials for electronic devices. Cu-Ti alloy is a so-called precipitation-strengthened copper alloy that usually contains about 3% Ti, and has been strengthened by the precipitation of Ti (Cu ₄ Ti) dispersed in the Cu matrix. . Such a Cu-Ti alloy is generally produced by solution treatment of a cast body in which Ti is added to Cu to produce a supersaturated solid solution in which Ti is dissolved, and this solid solution is subjected to aging treatment in a Cu matrix. It is obtained by precipitating Ti precipitates. On the other hand, the solid solubility limit of Ti in a Cu-Ti alloy at around 500 ° C, which is a general aging temperature, is about 1% by mass. Since the solid solution is about 1.0% by mass, the conductivity of the Cu-Ti alloy is 20% IACS or less.

  Moreover, the technique regarding such a Cu-Ti alloy is described in patent document 1, for example. In Patent Document 1, the Cu-Ti alloy is added with 0.01 to 0.5% by mass of at least one element of Fe, Co, Ni, Cr, V, Zr, B and P as a third element. A technique for increasing the strength is described. For example, the conductivity of the copper alloy described in Patent Document 1 (No. 1 described in Table 1) is estimated to be 20% IACS or less from the description of Patent Document 2 (No. 11 described in Tables 1 and 3). As in the prior art, it is considered that Ti is dissolved in the Cu matrix by about 0.5% by mass to 1.0% by mass.

JP 2004-176162 A JP 2002-356726 A

  However, recently, copper alloys having not only high strength but also high conductivity have been demanded, and conventional alloys have not been able to meet the demand. For example, for a signal wire of an automobile wire harness, a copper alloy having a tensile strength of 400 MPa or more and a conductivity of 40% IACS or more is required.

  The present invention has been made in view of the above circumstances, and one of the objects of the present invention is to effectively precipitate an additive element that dissolves in a Cu matrix, thereby achieving high strength and high conductivity. The object is to provide a copper alloy that is compatible. Another object of the present invention is to provide a wire harness electric wire using the copper alloy as a conductor. Another object of the present invention is to provide a method for producing this copper alloy.

  As described above, precipitation-strengthened copper alloys such as Cu-Ti alloys increase the strength by precipitation of additive elements that dissolve in the Cu matrix, but a certain amount of additive elements are added to the Cu matrix. It remains in solid solution, and the electrical conductivity decreases. Therefore, if the additive elements that dissolve in the Cu matrix can be effectively precipitated and the amount of additive elements in the Cu matrix can be reduced, it is possible to achieve both high strength and high conductivity. It is believed that there is.

  Therefore, in order to achieve the above object, the present inventors add a precipitation promoting element to Cu in addition to the precipitation strengthening element, and this precipitation promoting element takes in the precipitation strengthening element and precipitates, resulting in a decrease in conductivity. The inventors have found that the effect of improving the strength is exhibited while suppressing the above, and have completed the present invention.

  In addition, a precipitation strengthening element is an element which expresses the function which improves the intensity | strength of Cu alloy by precipitating in a Cu parent phase. The precipitation promoting element is an element that takes in a precipitation strengthening element that dissolves in the Cu matrix during precipitation and promotes precipitation of the precipitation strengthening element.

  The copper alloy of the present invention contains 0.01% by mass to 3% by mass of a precipitation strengthening element, 0.01% by mass to 5% by mass of a precipitation promoting element, and the balance consists of Cu and inevitable impurities. And at least one part of the said precipitation strengthening element precipitates with the said precipitation promotion element, and electrical conductivity is 40% IACS or more, It is characterized by the above-mentioned.

  According to the copper alloy of the present invention, at least a part of the precipitation strengthening element is precipitated together with the precipitation promoting element, so that the solid solution amount of the precipitation strengthening element in the Cu matrix is reduced and the conductivity is improved. On the other hand, the precipitation amount of the precipitation strengthening element in the Cu matrix increases and the strength improves.

  When the content of the precipitation strengthening element is less than 0.01% by mass, the precipitation amount of the precipitation strengthening element is small, and a sufficient strength improvement effect cannot be obtained. When it exceeds 3 mass%, the precipitation amount of the precipitation strengthening element is large, and the workability is lowered. On the other hand, when the content of the precipitation promoting element is less than 0.01% by mass, the precipitation strengthening element dissolved in the Cu matrix cannot be sufficiently precipitated, and a sufficient conductivity improvement effect cannot be obtained. If it exceeds 5% by mass, the precipitation promoting element is precipitated in a large amount and the workability is lowered.

  The upper limit of the content of the precipitation strengthening element is preferably less than 2.0% by mass, more preferably less than 1.5% by mass, further preferably 1.0% by mass or less, and the lower limit is preferably 0.1% by mass or more, more preferably 0.5% by mass or more. More preferred. The preferable content of the precipitation promoting element is preferably 4.0% by mass or less, more preferably 3.0% by mass or less, and the lower limit is preferably 0.1% by mass or more, more preferably 0.5% by mass or more.

  It is preferable that the content of the precipitation strengthening element is smaller than the content of the precipitation promoting element.

  In the present invention, the precipitation promoting element takes in and precipitates the precipitation strengthening element in which the solid solution is dissolved in the Cu matrix, so that a precipitate containing the precipitation strengthening element is effectively generated. Even if the content of the precipitation strengthening element is small, the strength reduction can be sufficiently suppressed. Moreover, it is easy to make it react with a precipitation strengthening element because there is much content of a precipitation promoting element. More preferably, the ratio of the content of the precipitation strengthening element and the precipitation promoting element is 0.5 or less.

  It is preferable that the precipitation strengthening element is at least one of Ti or Cr, and the precipitation promoting element is at least one of Fe or Co.

  Ti and Cr have a great effect of improving strength by precipitating in the Cu matrix. Fe and Co easily react with the precipitation strengthening element and have a large effect of promoting the precipitation of the precipitation strengthening element.

  The copper alloy of this invention is excellent in the balance of intensity | strength and electrical conductivity, and can be utilized suitably for the conductor of the electric wire for wire harnesses of this invention. An electric wire for a wire harness provided with this conductor can satisfy a tensile strength of 400 MPa or more. Furthermore, this wire harness electric wire is excellent in toughness, and an elongation of 10% or more may be obtained.

  By having such mechanical characteristics, even when subjected to pulling, impact, or vibration during wiring, installation work or use, it is difficult to break. In addition, it has a conductivity of 40% IACS or higher and has low resistance.

  Moreover, the copper alloy of this invention can be manufactured, for example with the manufacturing method of this invention shown below.

The manufacturing method of the copper alloy of 1st this invention is equipped with the following process, It is characterized by the above-mentioned.
(1) A step of preparing a composite molten metal in which a precipitation strengthening element and a precipitation promoting element are added to Cu
(2) A step of rapidly solidifying the molten composite to produce a solidified body containing the precipitation strengthening element in an amount of 0.01% by mass to 3% by mass and the precipitation promoting element in an amount of 0.01% by mass to 5% by mass.
(3) A step of subjecting the solidified body to plastic working and an aging treatment In the solidifying step, the molten composite is rapidly cooled at a cooling rate of 150 ° C./sec or more so that the precipitation strengthening element and the precipitation promoting element are solidified. Let it be a solidified body.
In the aging treatment step, the plastically processed workpiece is held at 300 ° C. or higher and 600 ° C. or lower for 1 hour or longer and 16 hours or shorter, and at least a part of the precipitation strengthening element is precipitated together with the precipitation promoting element.

The method for producing a copper alloy according to the second aspect of the present invention comprises the following steps, wherein a copper alloy having a conductivity of 40% IACS or more is obtained.
(1) A step of preparing a cast body containing 0.01% to 3% by mass of precipitation strengthening elements, 0.01% to 5% by mass of precipitation promoting elements, and the balance being Cu and inevitable impurities
(2) A step of producing a solid solution by solution treatment of the cast body
(3) A step of performing an aging treatment after performing plastic working on the solid solution In the solution treatment step, the casting material is held at 800 ° C. or higher and 1000 ° C. or lower for 10 minutes or longer and 10 hours or shorter, and the precipitation strengthening element And the precipitation promoting element is dissolved in the Cu matrix.
In the aging treatment step, the plastically processed workpiece is held at 300 ° C. or higher and 600 ° C. or lower for 1 hour or longer and 16 hours or shorter, and at least a part of the precipitation strengthening element is precipitated together with the precipitation promoting element.

  In the first production method, the molten alloy is rapidly cooled to obtain a solidified body in which the additive element is in a solid solution state, and the solidified body is subjected to an aging treatment to disperse fine precipitates uniformly. Can be manufactured. This makes it possible to obtain a copper alloy having a conductivity of 40% IACS or more. Further, in the second production method, the cast material is subjected to a solution treatment, so that the solid solution state of the additive element is a uniform solid solution, and the aging treatment is applied to the solid solution, whereby fine precipitates are uniformly dispersed. Copper alloys with electrical conductivity of 40% IACS or higher can be manufactured.

  In the solidification process, if the cooling rate is 150 ° C / sec or more, a copper alloy having a certain level or more of characteristics (for example, conductivity of 40% IACS or more) can be obtained without performing solution treatment. Even when the speed is less than 150 ° C./sec, a copper alloy having a certain level or more can be obtained by performing a solution treatment. Of course, the solution treatment may be performed even when the cooling rate is 150 ° C./sec or more. In the solution treatment step, when the heating temperature is less than 800 ° C., it is difficult to sufficiently dissolve the additive element, and when the heating temperature exceeds 1000 ° C., the cast material is softened, which is not preferable. In the solution treatment step, when the holding time is less than 10 minutes, it is difficult to obtain a solid solution in which the additive element is in a solid solution state, and when the holding time exceeds 10 hours, the productivity is lowered. In the aging treatment step, when the heating temperature is out of the range of 300 to 600 ° C., it is difficult to obtain a sufficient conductivity improving effect. Further, in the aging treatment step, if the holding time is less than 1 hour, it is difficult to obtain a sufficient conductivity improvement effect, and if the holding time exceeds 16 hours, the productivity is lowered.

  In the solidification step, the cooling rate is preferably 175 ° C./sec or more. In the solution treatment step, the heating temperature is preferably 800 ° C. or higher and 950 ° C. or lower, and the holding time is preferably 30 minutes or longer and 3 hours or shorter. In the aging treatment step, the heating temperature is preferably 400 ° C. or more and 550 ° C. or less, and the holding time is preferably 2 hours or more and 10 hours or less.

  When producing a composite molten metal or solidifying it, it is preferably performed in an inert gas atmosphere or in a vacuum. The solution treatment and aging treatment are preferably performed in a non-oxidizing atmosphere.

  Examples of plastic working include forging, metal pressing, rolling, extrusion, wire drawing, drawing, drawing, and the like.

  The copper alloy of the present invention is a copper alloy that realizes unprecedented strength and electrical conductivity of 40% or more by precipitating at least part of the precipitation strengthening element together with the precipitation promoting element, and contributes as a new electronic component material. It is expected.

  Copper alloys having different compositions (Sample Nos. 1 to 5) were prepared, and the mechanical properties (tensile strength, elongation) and electrical properties (conductivity) of each copper alloy were examined. Each copper alloy was produced as follows.

(Sample Nos. 1-3)
Pure Cu (OFC), sponge Ti particles as precipitation strengthening elements, and pig iron (Fe-4 mass% C alloy) particles as precipitation promoting elements were placed in a crucible and melted in an arc melting furnace to prepare a composite molten metal. Dissolution was performed in an argon atmosphere to prevent oxidation of the raw material. The composite molten metal was heated to a melting point of pig iron (about 1200 ° C.) or more and stirred with a stirring fin.

  This composite molten metal was cast into a water-cooled Cu mold and rapidly cooled at a cooling rate of 180 ° C./sec to produce a solidified body having a length of 70 mm × width of 40 mm × thickness of 25 mm. This solidified body is designated as sample No. 1.

  Further, a solidified body of sample Nos. 2 and 3 was produced in the same manner as sample No. 1 except that the amounts of sponge Ti particles and pig iron particles to be added were changed.

(Sample No. 4, 5)
Only pure Cu (OFC) and pig iron (Fe-4 mass% C alloy) grains as additive elements were placed in a crucible and melted in an arc melting furnace to prepare a composite molten metal. Dissolution was performed in an argon atmosphere to prevent oxidation of the raw material. The composite molten metal was heated to a melting point of pig iron (about 1200 ° C.) or more and stirred with a stirring fin.

  This composite molten metal was cast into a water-cooled Cu mold and rapidly cooled at a cooling rate of 180 ° C./sec to produce a solidified body having a length of 70 mm × width of 40 mm × thickness of 25 mm. This solidified body is designated as sample No. 4.

  A solidified body of Sample No. 5 was prepared in the same manner as Sample No. 4 except that only sponge Ti particles were used as the additive element.

  Table 1 shows the compositions of sample Nos. 1 to 5. The composition was examined by ICP emission spectroscopic analysis.

  Next, wire drawing was performed on sample Nos. 1 to 5 to produce wire drawing materials, and the tensile strength (MPa), elongation at break (%), and conductivity (% IACS) of each wire drawing material were measured. The wire drawing material was prepared by subjecting a sample to surface cutting to obtain a rod-shaped body having a diameter of φ12 mm, drawing the rod-shaped body to a diameter of φ0.2 mm, and then performing an aging treatment. The aging treatment was performed at a heating temperature of 20 to 550 ° C., a holding time of 8 hours, and cooling was performed by furnace cooling. Each characteristic was measured for each wire drawn by aging treatment at each heating temperature. The results are shown in Table 2.

  Samples Nos. 1 to 5 all had a tendency that the conductivity increased as the heating temperature of the aging treatment increased, peaked at 450 ° C., and then decreased. Therefore, the characteristics of each sample when the heating temperature is 450 ° C. are compared. Sample Nos. 1 to 3 (examples of the present invention) have a conductivity of 70% IACS or higher, while sample No. 5 has a conductivity as low as about 40% IACS. In addition, the inventive example has a tensile strength of 440 MPa or more, whereas the sample No. 4 has a low tensile strength of about 400 MPa.

  FIG. 1 is a graph showing the relationship between tensile strength and electrical conductivity based on the results in Table 2. In FIG. 1, when the region where the conductivity is 40% IACS or higher is seen, the example of the present invention has a significantly improved conductivity compared to Sample No. 5, and has an excellent balance between strength and conductivity. I understand that Further, it can be seen that the example of the present invention has substantially the same conductivity as Sample No. 4, but the strength is improved.

  Next, the cross section of the wire drawing material of Sample No. 3 was observed with an SEM equipped with EDX. FIG. 2 shows the EDX analysis results within the range observed by SEM. As a result of elemental analysis by EDX, FIGS. 2 (I) to (III) show the element mapping of Cu, Ti, and Fe, respectively. In FIGS. The concentration is high, and the element concentration is low in dark (dark) portions. Sample No. 3 has fine precipitates in the Cu matrix from Fig. 2 (I). From Figs. 2 (II) and (III), this precipitate has Ti and Fe as constituent elements. I understand that it contains. In addition, since Ti is concentrated at the position where Fe is precipitated, it is considered that the precipitation of Ti is promoted by Fe taking in Ti and precipitating. Although the details are not clear, it is considered that this precipitate exists in the state of Fe-Ti alloy or Fe-Ti compound.

  From the above results, it can be seen that the inventive examples (samples Nos. 1 to 3) achieve high strength and high conductivity. Therefore, it is considered that the example of the present invention can be suitably used for the signal wire of the automobile wire harness. In addition, since the electrical conductivity of the present invention example is 70% IACS or higher, it is considered that the present invention can also be used for a power line of an automobile wire harness. In particular, Sample No. 3 has an elongation of 10% or more and excellent toughness, and can be an electric wire that is difficult to break.

  Here, in the example of the present invention, since Fe is added in the state of pig iron, C is also added at the same time. Therefore, when observed by the SEM, it was confirmed that fine TiC was dispersed in the Cu matrix. This TiC is considered to contribute to strength improvement by dispersing in the matrix.

  In addition, this invention is not limited to the above-mentioned Example, It can change suitably in the range which does not deviate from the summary of this invention. For example, the contents of Ti and Fe, the types and contents of precipitation strengthening elements and precipitation promoting elements may be changed, or an aging treatment may be performed before the solidified body is drawn.

  The copper alloy of the present invention is a copper alloy having high strength and high conductivity, and can be used as a new electronic component material. For example, it can be suitably used for a conductor of a signal line of an automobile wire harness.

It is the graph which showed the relationship between the tensile strength and electrical conductivity of sample Nos. 1-5. It is a microscope picture (500,000 times) which shows elemental mapping by EDX of sample No.3 cross section, (I) shows Cu distribution state, (II) shows Ti distribution state, and (III) shows Fe distribution state .

Claims (8)

Contains 0.01% to 3% by weight of precipitation strengthening element, 0.01% to 5% by weight of precipitation promoting element, the balance consists of Cu and inevitable impurities,
At least a part of the precipitation strengthening element is precipitated together with the precipitation promoting element,
Copper alloy characterized by an electrical conductivity of 40% IACS or higher.   The copper alloy according to claim 1, wherein the content of the precipitation strengthening element is less than the content of the precipitation promoting element. The precipitation strengthening element is at least one of Ti or Cr;
The copper alloy according to claim 1 or 2, wherein the precipitation promoting element is at least one of Fe and Co.   An electric wire for a wire harness using the copper alloy according to any one of claims 1 to 3 as a conductor.   The wire for a wire harness according to claim 4, wherein the wire has a tensile strength of 400 MPa or more.   The wire for a wire harness according to claim 5, wherein the wire has an elongation of 10% or more. A step of preparing a composite melt obtained by adding a precipitation strengthening element and a precipitation promoting element to Cu;
Rapidly solidifying the composite molten metal to produce a solidified body containing 0.01% by mass to 3% by mass of the precipitation strengthening element and 0.01% by mass to 5% by mass of the precipitation promoting element;
A step of performing an aging treatment after plastic processing the solidified body,
In the solidification step, the composite molten metal is rapidly cooled at a cooling rate of 150 ° C./sec or more to obtain a solidified body in which the precipitation strengthening element and the precipitation promoting element are dissolved.
In the aging treatment step, a plastically processed workpiece is held at 300 ° C. or more and 600 ° C. or less for 1 hour or more and 16 hours or less, and at least a part of the precipitation strengthening element is precipitated together with the precipitation promoting element. Alloy manufacturing method. A step of preparing a cast body containing a precipitation strengthening element of 0.01 mass% or more and 3 mass% or less, a precipitation promoting element of 0.01 mass% or more and 5 mass% or less, with the balance being Cu and inevitable impurities;
Producing a solid solution by solution treatment of the casting,
A step of performing an aging treatment after plastic working the solid solution,
In the solution treatment step, the casting material is held at 800 ° C. or higher and 1000 ° C. or lower for 10 minutes or longer and 10 hours or shorter, and the precipitation strengthening element and the precipitation promoting element are dissolved in the Cu matrix,
In the aging treatment step, the plastic processed workpiece is held at 300 ° C. or more and 600 ° C. or less for 1 hour or more and 16 hours or less, and at least a part of the precipitation strengthening element is precipitated together with the precipitation promoting element,
A method for producing a copper alloy, comprising producing a copper alloy having a conductivity of 40% IACS or more.