JP2023152264A - Cu-Ti-BASED COPPER ALLOY PLATE, MANUFACTURING METHOD THEREOF, ENERGIZATION MEMBER AND HEAT DISSIPATION COMPONENT - Google Patents

Abstract

To provide a Cu-Ti-based copper alloy plate having strength, conductivity, flexure workability and stress relaxation property in combination at a high level, and reduced density (specific gravity).SOLUTION: A copper alloy plate comprising, in mass%, Ti: 1.0 to 5.0%, Al: 0.5 to 3.0%, Ag: 0 to 0.3%, B: 0 to 0.3%, Be: 0 to 0.15%, Co: 0 to 1.0%, Cr: 0 to 1.0%, Fe: 0 to 1.0%, Mg: 0 to 0.5%, Mn: 0 to 1.5%, Nb: 0.0 to 0.5%, Ni: 0 to 1.0%, P: 0 to 0.2%, Si: 0 to 0.5%, Sn: 0 to 1.5%, V: 0 to 1.0%, Zn: 0 to 2.0%, Zr: 0 to 1.0%, S: 0 to 0.2%, rare earth elements: 0 to 3.0%, and the remainder essentially consists of Cu, wherein a maximum width of a grain boundary reaction type precipitate existing region is 1000 nm or less, a KAM value is 3.0 degrees or less with a crystal orientation difference of 15 degrees or more by EBSD measurement (step size 0.1 μm) as the grain boundary, and the tensile strength in a rolling direction is 850 MPa or more.SELECTED DRAWING: Figure 5

Description

The present invention relates to a Cu--Ti based copper alloy plate material with reduced density (specific gravity), a method for manufacturing the same, and current-carrying parts using the plate material.

Cu-Ti copper alloy (titanium copper) has the highest strength level among various copper alloys and has good stress relaxation resistance, so it is widely used as electrically conductive parts and spring parts such as connectors, relays, and switches. There is. BACKGROUND ART In recent years, as mobile terminals such as smartphones and electronic devices for automobiles have become more sophisticated, there has been an increasing demand for their individual components to be lighter. In order to meet this demand, it is important to reduce the weight of copper alloy materials used in current-carrying parts while maintaining their original good characteristics.

Patent Document 1 discloses that in a Cu-Ti based copper alloy, a process combining preliminary aging treatment (precursor treatment) and aging treatment at a relatively low temperature suppresses the formation of grain boundary reaction type precipitates and improves strength. , techniques for improving bending workability, stress relaxation resistance, and fatigue resistance have been disclosed.

Patent Document 2 describes, in Cu-Ti copper alloys, hot rolling to increase the rolling reduction in a high temperature range, solution treatment at a relatively high temperature, and aging treatment to control the temperature near the maximum hardness. A technique has been disclosed that adjusts the texture to a predetermined texture through a process that combines these steps, and improves the bending workability after notching.

Japanese Patent Application Publication No. 2014-185370 Japanese Patent Application Publication No. 2010-126777

With the techniques disclosed in Patent Documents 1 and 2 mentioned above, it is now possible to industrially obtain Cu--Ti based copper alloy sheets with improved desired properties depending on the intended use. However, a method for effectively reducing the density (specific gravity) of alloys has not been established. For example, in the technologies of Patent Documents 1 and 2, it is said that Al, which has a smaller atomic weight than Cu, can be added up to a maximum of 1.0% by mass, but the Al content of the materials shown in the examples is 0. 0.08% (Patent Document 1, Invention Example 6) and 0.14% (Patent Document 2, Example 9), and the density reduction effect is insufficient with this level of Al content. In addition, when attempting to manufacture a Cu-Ti alloy sheet material in which 0.5% or more of Al is added using the manufacturing process disclosed in Patent Documents 1 and 2, it is possible to stably achieve both strength and bending workability at a high level. That is difficult.

An object of the present invention is to provide a Cu-Ti based copper alloy plate material that has a high level of strength, conductivity, bending workability, and stress relaxation properties in a well-balanced manner, and has a reduced density (specific gravity). .

As a result of detailed study, the inventors performed the process of "solution treatment + intermediate cold rolling" twice on a Cu-Ti based copper alloy containing a predetermined amount of Al to reduce the density (specific gravity). By adopting a manufacturing process that is subsequently subjected to aging treatment, it is possible to obtain a plate material with a structure in which there is little generation of coarse grain boundary reaction type precipitates and a moderate lattice strain, thereby making it possible to obtain a plate material that contains aluminum. It has been found that it is possible to impart excellent strength, electrical conductivity, bending workability, and stress relaxation properties despite the above properties.
In order to achieve the above object, the following invention is disclosed in this specification.

[1] In mass%, Ti: 1.0 to 5.0%, Al: 0.5 to 3.0%, Ag: 0 to 0.3%, B: 0 to 0.3%, Be: 0 ~0.15%, Co: 0-1.0%, Cr: 0-1.0%, Fe: 0-1.0%, Mg: 0-0.5%, Mn: 0-1.5% , Nb: 0.0-0.5%, Ni: 0-1.0%, P: 0-0.2%, Si: 0-0.5%, Sn: 0-1.5%, V: 0 to 1.0%, Zn: 0 to 2.0%, Zr: 0 to 1.0%, S: 0 to 0.2%, and among the above elements, Ag, B, Be, Co, Cr, The total content of Fe, Mg, Mn, Nb, Ni, P, Si, Sn, V, Zn, Zr and S is 3.0% or less, the balance is Cu and inevitable impurities, and the plate The maximum width of the grain boundary reaction type precipitate existing region is 1000 nm or less on the observation plane parallel to the plate surface, and measurement is performed with a step size of 0.1 μm by EBSD (electron beam backscatter diffraction method) on the observation plane parallel to the plate surface. A copper alloy sheet material having a KAM value of 3.0° or less when a boundary with a crystal orientation difference of 15° or more is regarded as a grain boundary, and a tensile strength in the rolling direction of 850 MPa or more.
[2] The copper alloy sheet material according to [1] above, further having a composition containing rare earth elements in a total amount of 3.0% by mass or less.
[3] The above, wherein the number density of fine precipitate particles with a major diameter of 5 to 100 nm in the observation plane parallel to the plate surface is 1.0 × 10 ⁸ pieces/mm ² or more and 1.0 × 10 ¹² pieces/mm ² or less The copper alloy plate material according to [1] or [2].
[4] The copper alloy sheet material according to any one of [1] to [3] above, which has an average crystal grain size of 2 to 20 μm when measured by a cutting method according to JIS H0501-1986 in an observation plane parallel to the sheet surface.
[5] The ratio MBR/t of the minimum bending radius without cracking to the plate thickness t, MBR/t, is 2.0 or less according to the W bending test at B.W. according to the Japan Copper Brass Association technical standard JCBA T307:2007. , the copper alloy plate material according to any one of [1] to [4] above.
[6] The copper alloy plate material according to any one of [1] to [5] above, which has an electrical conductivity of 10.0% IACS or higher.
[7] The copper alloy plate material according to any one of [1] to [6] above, which has a density of 8.53 g/cm ³ or less.
[8] The copper alloy plate material according to any one of [1] to [7] above, having a plate thickness of 0.02 to 0.50 mm.
[9] The intermediate product sheet material having the composition specified in [1] above is subjected to first solution treatment, first intermediate cold rolling, second solution treatment, second intermediate cold rolling, and aging treatment in the above order. In the process of manufacturing copper alloy plate material by applying
The first solution treatment is carried out in a temperature range of 750 to 950°C and held for 10 to 600 seconds,
Performing the first intermediate cold rolling at a rolling ratio of 70% or more,
The second solution treatment is carried out at a temperature range of 750 to 900°C for 10 to 600 seconds,
A second intermediate cold rolling is performed at a rolling ratio of 15 to 50%,
Aging treatment is performed at an aging temperature of 300 to 470°C.
The method for producing a copper alloy plate material according to any one of [1] to [8] above.
[10] The method for producing a copper alloy plate material according to [9] above, wherein the intermediate product plate material further has a composition containing a rare earth element in a total amount of 3.0% by mass or less.
[11] After the aging treatment, a step of manufacturing a copper alloy plate material by further performing finish cold rolling and low-temperature annealing in the above order,
Finish cold rolling is performed at a rolling rate of 50% or less,
Low-temperature annealing is performed under conditions of holding the material in a temperature range of 350 to 550°C for 60 seconds or less.
The method for producing a copper alloy plate material according to [9] or [10] above.
[12] A current-carrying component using the copper alloy plate material according to any one of [1] to [8] above.
[13] A heat dissipation component using the copper alloy plate material according to any one of [1] to [8] above.

In this specification, the term "plate material" refers to a sheet-like metal material formed by utilizing the malleability of metal. A thin sheet-shaped metal material is sometimes called "foil," and such "foil" is also included in the "plate material" referred to here. A long sheet metal material wound into a coil shape is also included in the term "plate material." In this specification, the thickness of a sheet-like metal material is referred to as "plate thickness." Further, the "plate surface" is a surface perpendicular to the thickness direction of the plate material. The "plate surface" is sometimes called the "rolled surface."
In this specification, the notation "n1 to n2" indicating a numerical range means "not less than n1 and not more than n2". Here, n1 and n2 are numerical values satisfying n1<n2.

A Cu--Ti based copper alloy usually exhibits a metal structure in which a precipitated phase exists in a matrix (metal base). The precipitated phases include "grain boundary reaction type precipitates" that precipitate at grain boundaries, and "granular precipitates" that precipitate at other locations. These precipitated phases are mainly composed of Cu-Ti intermetallic compounds, but depending on the type and amount of alloying elements added, they may be Ni-Ti, Co-Ti, Fe-Ti, or Cu-Ti. Intermetallic compounds such as Ti--Al may also be present. Among the granular precipitates, very fine ones contribute to improving the strength. Here, fine granular precipitate particles with a major diameter of 5 to 100 nm are referred to as "fine precipitate particles." Grain boundary reaction type precipitates exist as a group of layered particles at grain boundaries. The way the layered particles appear on the observation surface varies depending on the angle at which the observation surface cuts through a group of layered particles.

[How to find the maximum width of the region where grain boundary reaction type precipitates exist]
In an SEM (scanning electron microscope) image of an observation plane parallel to the plate surface, layered particles can be detected from any point on the outline of one grain boundary reaction type precipitate existing region consisting of a group of adjacent layered particles. The longest distance among the distances to the contour line on the grain side opposite to the contour line is defined as the width of the grain boundary reaction type precipitate existing region. At this time, the width of the grain boundary reaction type precipitate existence area observed in the observation area (one randomly selected field or multiple non-overlapping fields of view) that includes a total of 10 or more grain boundary reaction type precipitate existence areas. The maximum value of these is the maximum width of the grain boundary reaction type precipitate existing region for the plate material.

Figures 1 to 3 illustrate SEM images of the observation plane parallel to the plate surface of a Cu-Ti based copper alloy plate material (Comparative Example No. 45 described later) in which grain boundary reaction type precipitates were excessively generated. be. FIG. 3 is an enlarged image of a portion including a region where grain boundary reaction type precipitates exist. In FIG. 3, the outline of the region where grain boundary reaction type precipitates exist is shown by a broken line. The distance from point P ₁ on the contour line to the contour line on the crystal grain side opposite to the contour line with the layered grain in between is represented by the length of the line segment P ₁ Q ₁ . Point Q ₁ is the closest point to point P ₁ on the contour line on the crystal grain side facing point P ₁ . Similarly, the distance from point P ₂ on the contour to the contour on the crystal grain side that faces the contour with the layered grain in between is represented by the length of line segment P ₂ Q ₂ . Point Q ₂ is the closest point to point P ₂ on the contour line on the grain side facing point P ₂ . When the distance from all points on the contour line to the contour line on the crystal grain side facing the above contour line across the layered grains is determined, the maximum value of the distance is determined as the area where the grain boundary reaction type precipitate exists. It becomes the width. In addition, the "contour line of the opposing crystal grain side" is clearly defined, such as at the edge of the region where grain boundary reaction type precipitates exist, where the crystal grains on both sides of the layered grain are in direct contact through the grain boundary, and in the vicinity thereof. For a contour portion that cannot be specified, the “distance to the contour on the opposing crystal grain side” at a point on the contour of that portion may be considered to be 0 (zero).

[How to find KAM value]
The plate surface (rolled surface) of the plate material sample to be measured is buffed and then ion milled to obtain a smooth observation surface. An observation area (for example, a rectangular area of 240 x 180 μm) with a field of view corresponding to an observation magnification of 500 times is randomly set within the observation plane, and a step size of 0. Collect crystal orientation data by irradiating with an electron beam at 1 μm, and based on that data, use EBSD data analysis software to consider boundaries where the crystal orientation difference between adjacent measurement points is 15° or more as grain boundaries. Calculate the KAM (Kernel Average Misorientation) value when The KAM value is determined by measuring all the crystal orientation differences between adjacent spots (hereinafter referred to as "adjacent spot orientation differences") for electron beam irradiation spots arranged at a pitch of 0.1 μm, and determining the difference in crystal orientation between adjacent spots that is less than 15°. This corresponds to extracting only the measured values of the spot azimuth difference and calculating their average value. In calculating the KAM value, twin boundaries are also regarded as grain boundaries.

[How to determine the number density of fine precipitate particles]
After electrolytically polishing the plate surface under the following electrolytic polishing conditions, the observation surface obtained by ultrasonic cleaning in ethanol for 20 minutes was observed at a magnification of 100,000 times using an FE-SEM (field emission scanning electron microscope). An observation field is randomly set in which part or all of particles having a major diameter of 1.0 μm or more are not included in the field of view. With respect to the observation field, the number of precipitate particles having a major axis of 5 to 100 nm is counted among particles whose entire contours are visible. This operation is performed for 10 or more observation fields whose areas do not overlap, and the total number of counts in all the observed fields N _TOTAL is divided by the total area of the observation field, and the value is converted to the number per 1 ^mm2 . Let be the number density (pieces/mm ² ) of fine precipitate particles. Here, the "major axis" of a certain particle is expressed as the diameter of the smallest circumscribed circle surrounding the particle on the image.
(Electrolytic polishing conditions)
・Electrolyte: Distilled water, phosphoric acid, ethanol, and 2-propanol mixed in a volume ratio of 10:5:5:1 ・Liquid temperature: 20°C
・Voltage: 15V
・Electrolysis time: 20 seconds

According to the present invention, it is possible to realize a Cu-Ti based copper alloy sheet material that has a high level of well-balanced strength, conductivity, bending workability, and stress relaxation properties, but has a reduced density (specific gravity) of the alloy. It became.

SEM photograph of the observed surface of the Cu-Ti alloy plate obtained in Comparative Example No. 45 prepared by electrolytic polishing. An SEM photograph showing an enlarged partial area of Fig. 1. SEM photograph of a partial region of FIG. 2 enlarged. SEM photograph of the observed surface of the Cu-Ti alloy plate obtained in Invention Example No. 1 prepared by electrolytic polishing. SEM photograph of a partial region of FIG. 4 enlarged. SEM photograph of a partial region of FIG. 5 enlarged.

[Chemical composition]
Hereinafter, "%" regarding alloy components means "% by mass" unless otherwise specified.

Ti (titanium) is an element that causes the formation of a Ti modulation structure through spinodal decomposition and the formation of fine second phase particles through precipitation, contributing to an increase in the strength of the Cu--Ti based copper alloy. It also contributes to improving stress relaxation resistance and reducing density (specific gravity). Here, alloys with a Ti content of 1.0% or more are targeted. From the viewpoint of precipitation strengthening, the Ti content is more preferably 2.5% or more. Excessive Ti content causes deterioration in hot workability and cold workability as well as deterioration in bending workability, so the Ti content is set to 5.0% or less. It may be controlled to 4.5% or less, or 4.0% or less.

Al (aluminum) is an element effective in reducing the density (specific gravity) of a Cu-Ti based copper alloy. In order to fully exhibit this effect, Al content of 0.5% or more is required. It is more effective to set it to 0.7% or more, and even more effective to set it to 1.0% or more. When 0.5% or more of Al is added to a Cu-Ti based copper alloy, there is generally a problem that it becomes difficult to achieve both strength and bending workability. However, this problem can be solved by the manufacturing method described below. However, if the Al content becomes too large, the conductivity will decrease, so the Al content is limited to 3.0% or less. The Al content is preferably 2.75% or less.

Ag (silver), B (boron), Be (beryllium), Co (cobalt), Cr (chromium), Fe (iron), Mg (magnesium), Mn (manganese), Nb (niobium), Ni (nickel), P (phosphorus), Si (silicon), Sn (tin), V (vanadium), Zn (zinc), Zr (zirconium), and S (sulfur) are optional elements. One or more of these can be contained as necessary. For example, Ni, Co, Fe, and Nb form intermetallic compounds with Ti and contribute to improving strength. In addition, since the intermetallic compounds of these elements suppress the coarsening of crystal grains, solution treatment at higher temperatures is possible in the production of copper alloy sheets, which is advantageous for sufficiently dissolving Ti. Become. Sufficient solid solution of Ti can be expected to suppress the formation of grain boundary reaction type precipitates and increase the number of second phase particles that contribute to higher strength. Sn has a solid solution strengthening effect and an effect of improving stress relaxation resistance. Zn improves solderability and strength, and is also effective in improving castability. Mg has an effect of improving stress relaxation resistance and a function of removing S. Si can form a compound with Ti, which contributes to pinning during recrystallization in the production of copper alloy sheets, and can reduce the crystal grain size. Cr and Zr are effective in dispersion strengthening and suppressing coarsening of crystal grains. Mn and V tend to form a high melting point compound with S and the like, and B and P have the effect of refining the casting structure, so each can contribute to improving hot workability.

The contents of the above arbitrary elements are Ag: 0 to 0.3%, B: 0 to 0.3%, Be: 0 to 0.15%, Co: 0 to 1.0%, and Cr: 0 to 1. 0%, Fe: 0-1.0%, Mg: 0-0.5%, Mn: 0-1.5%, Nb: 0-0.5%, Ni: 0-1.0%, P: 0-0.2%, Si: 0-0.5%, Sn: 0-1.5%, V: 0-1.0%, Zn: 0-2.0%, Zr: 0-1.0 %, S: can be in the range of 0 to 0.2%. Further, the total content of these Ag, B, Be, Co, Cr, Fe, Mg, Mn, Ni, P, S, Si, Sn, V, Zn, and Zr is desirably 3.0% or less, It is more preferably 1.0% or less, and may be controlled to 0.8% or less.

In addition, the content of the above arbitrary elements is Ag: 0-0.1%, B: 0-0.03%, Be: 0-0.05%, Co: 0-0.1%, Cr: 0-0. 0.1%, Fe: 0-0.2%, Mg: 0-0.25%, Mn: 0-0.2%, Nb: 0-0.04%, Ni: 0-0.2%, P: 0-0.03%, S: 0-0.03%, Si: 0-0.15%, Sn: 0-0.8%, V: 0-0.03%, Zn: 0-0 .2%, Zr: more preferably in the range of 0 to 0.5%.

In addition, the content of the above arbitrary elements is Ag: 0-0.08%, B: 0-0.02%, Be: 0-0.03%, Co: 0-0.08%, Cr: 0-0. 0.08%, Fe: 0-0.18%, Mg: 0-0.2%, Mn: 0-0.18%, Nb: 0-0.03%, Ni: 0-0.18%, P: 0-0.02%, S: 0-0.02%, Si: 0-0.12%, Sn: 0-0.6%, V: 0-0.02%, Zn: 0-0 .18%, Zr: may be controlled within the range of 0 to 0.4%.

A rare earth element (REM) can be included as an element other than the above. The rare earth elements are Sc (scandium), Y (yttrium), and lanthanoid elements of Group 3 of the periodic table. Inclusion of rare earth elements is effective in making crystal grains finer and dispersing precipitates. In order to achieve a good balance between the surface properties, strength, and conductivity of the plate material, the total content of rare earth elements is preferably 3.0% or less by mass, and more preferably 1.5% or less. , 0.8% or less, or 0.5% or less.

Specific rare earth element content ranges include, in mass %, La (lanthanum): 2.0% or less, Ce (cerium): 1.8% or less, Pr (praseodymium): 0.3% or less, Contains one or more selected from Nd (neodymium): 0.8% or less, Sm (samarium): 2.5% or less, and Y (yttrium): 2.5% or less, and the total content of rare earth elements is 3. A range of .0% or less can be mentioned.

The content range of rare earth elements in consideration of economic efficiency and manufacturability is, for example, in mass %, La: 0.8% or less, Ce: 0.7% or less, Pr: 0.1% or less, Nd: 0. .2% or less, Sm: 1.0% or less, and Y: 1.0% or less, and the total content of rare earth elements is 1.5% or less. . More preferable rare earth element content ranges in consideration of economic efficiency and manufacturability include, for example, in terms of mass %, La: 0.35% or less, Ce: 0.32% or less, Pr: 0.04% or less, The range includes one or more selected from Nd: 0.1% or less, Sm: 0.5% or less, and Y: 0.5% or less, and the total content of rare earth elements is 0.8% or less. be able to.

[Maximum width of grain boundary reaction type precipitate existing region]
In Cu-Ti based copper alloys, grain boundary reaction type precipitates are likely to be generated. Grain boundary reaction type precipitates become a factor that reduces bending workability. If the structure is adjusted to be soft, bending workability can be maintained to some extent even if a large amount of grain boundary reaction type precipitates are generated. However, in order to achieve both high levels of strength and bending workability in Cu-Ti copper alloy sheets, it is important to control the metal structure so that the maximum width of the region where grain boundary reaction type precipitates exist is small. I found out something. Specifically, in the copper alloy sheet material of the present invention, the grain boundary reaction type precipitates in the observation plane parallel to the plate surface are A tissue state in which the maximum width of the existing region is 1000 nm or less is adopted. In order to reduce the maximum width of the region where grain boundary reaction type precipitates exist, it is extremely effective to employ the manufacturing process described below that can make the crystal grain size finer. In addition, if the region where grain boundary reaction type precipitates exist is not observed in the SEM image explained above in "How to determine the maximum width of the region where grain boundary reaction type precipitates exist," The maximum width of the region is 1000 nm or less."

[KAM value]
In order to achieve both high levels of strength and bending workability, it is also important that the KAM value does not become too high. The KAM value is one of the indicators that can evaluate lattice strain within crystal grains. As a result of the study, the copper alloy sheet material of the present invention has a structure in which the KAM value is 3.0° or less according to the above-mentioned "How to Determine the KAM Value". As long as sufficient strength can be obtained, the lower limit of the KAM value is not particularly limited, but it can usually be adjusted within a range of 0.5° or more. From the viewpoint of achieving both strength and bending workability and manufacturability, the KAM value is more preferably in the range of 0.6 to 2.0.

[Tensile strength]
The tensile strength in the rolling direction of the copper alloy sheet material of the present invention is preferably 850 MPa or more, more preferably 880 MPa or more. It is also possible to adjust the tensile strength in the rolling direction to a strength level of 1000 MPa or more. The upper limit of the tensile strength is not particularly limited, but may be adjusted within a range of, for example, 1400 MPa or less, or may be adjusted within a range of 1200 MPa or less.

[Number density of fine precipitate particles]
Fine precipitate particles with a major diameter of 5 to 100 nm contribute to improving strength by being dispersed in the matrix (metal base). The number density of fine precipitate particles having a major diameter of 5 to 100 nm is preferably 1.0×10 ⁸ particles/mm ² or more. On the other hand, if the number of fine precipitate particles is too large, it may have an adverse effect on bending workability, so the number density of fine precipitate particles with a major axis of 5 to 100 nm is within the range of 1.0 × 10 ¹² /mm ² or less. It is preferable that Note that the amount of fine precipitate particles produced tends to increase as the Ti content increases.

[Average grain size]
The smaller the average grain size, the more dispersed the formation sites of grain boundary reaction type precipitates are during aging treatment in the production of copper alloy sheet materials, and the more the above-mentioned maximum width of the grain boundary reaction type precipitate existing region can be reduced. It is advantageous. It is also advantageous for improving strength. The copper alloy sheet material of the present invention preferably has an average crystal grain size of, for example, 20 μm or less, more preferably 16 μm or less, and 5 μm or less when measured by a cutting method according to JIS H0501-1986 in an observation plane parallel to the sheet surface. It is more preferable that Excessive refinement of the average grain size is not preferable from the viewpoint of increasing process load. Usually, the average crystal grain size may be in the range of 2 μm or more. The manufacturing process described below in which solution treatment is performed twice is effective for refining crystal grains. In addition, the cutting method prescribed in JIS H0501-1986 states that "the average value of the cutting length (mm) is indicated," but the crystal grain size targeted by the present invention is extremely small in relation to this default display unit. Therefore, here, measurement is performed in accordance with the method of the standard in an observation field of higher magnification, and the average crystal grain size in μm is determined.

[Bending workability]
Bending is often involved when processing current-carrying parts. For Cu-Ti alloys, the ratio MBR/t of the minimum bending radius MBR without cracking and the plate thickness t is 2 in the W bending test at B.W. according to the Japan Copper Brass Association technical standard JCBA T307:2007. If the bending workability is .5 or less, it can be applied to many current-carrying parts, but in the present invention, as an even stricter standard, the above-mentioned MBR/t is 2.0 or less. The goal is B.W. (Bad Way) means that the bending axis is parallel to the rolling direction. The MBR/t of the copper alloy plate material of the present invention is preferably 1.0 or less, more preferably 0.7 or less, and even more preferably 0.0.

Note that JCBA T307:2007 states, "This standard is applied to the evaluation of bending workability of copper and copper alloy thin sheets and strips with a thickness of 0.1 mm or more and 0.8 mm or less." According to the inventors' studies, it is possible to evaluate the bending workability of Cu-Ti copper alloy sheets with a thickness of less than 0.1 mm by W bending tests using the method described in the standard. This was confirmed. Therefore, in the present invention, the W bending test method in B.W. shown in JCBA T307:2007 is extended to cases where the plate thickness is less than 0.1 mm (for example, 0.02 mm or more and less than 0.1 mm). Apply as is.

[conductivity]
Considering the use of the Cu-Ti based copper alloy plate material, it is desirable that the conductivity is 10.0% IACS or more. The upper limit of the electrical conductivity is not particularly limited, but it may normally be adjusted within a range of 20.0% IACS or less.

[Stress relaxation properties]
Considering the use of the Cu-Ti based copper alloy sheet material, it is desirable that the stress relaxation rate after being held at 250° C. for 100 hours is 15% or less. Although the lower limit of the stress relaxation rate is not particularly limited, the stress relaxation rate is usually 3% or more.

[density]
Since the atomic weight order of Cu, Ti, and Al is Cu>Ti>Al, increasing the Al content is most effective in reducing the density (specific gravity) of the Cu-Ti based copper alloy. , the influence of Ti content cannot be ignored. The content of Al and Ti is limited in order to maintain strength, bendability, conductivity, and stress relaxation properties within the above-mentioned favorable ranges, but according to the present invention, the density at 20°C can be reduced to 8. It can be reduced to 53 g/cm ³ or less. In Cu-Ti based copper alloys, reducing the density to 8.53 g/cm ³ or less while maintaining strength, bending workability, conductivity, and stress relaxation properties within the above-mentioned favorable ranges is an impossible task compared to conventional methods. This was difficult with technology. Note that the lower limit of the density is not particularly limited, but may be adjusted within a range of 7.8 g/cm ³ or more, for example.

[Production method]
The copper alloy plate material explained above can be manufactured, for example, by the following manufacturing process.
Melting/casting → billet heating → hot working → rough cold rolling → first solution treatment → first intermediate cold rolling → second solution treatment → second intermediate cold pressure → aging treatment → (finish cold rolling) Rolling) → (Low temperature annealing)
In the above, steps in parentheses can be omitted. Although not described in the above steps, surface cutting is performed as necessary after hot working, and pickling, polishing, or further degreasing is performed as necessary after each heat treatment. Each of the above steps will be explained below.

[Melting/Casting]
A slab having the chemical composition specified in the present invention may be manufactured using a crucible furnace or the like. In order to prevent oxidation of Ti and Al, it is preferable to carry out the process in an inert gas atmosphere or in a vacuum melting furnace.

[Slab heating]
The slab can be heated before hot working, for example, by holding it at 900 to 960°C for 0.5 to 5 hours.

[Hot working, rough cold rolling]
The hot working method is not particularly limited. Usually, hot forging or hot rolling is used. In the case of hot rolling, the total hot rolling rate may be, for example, 60 to 99%. After the hot working is completed, it is preferable to rapidly cool the material by water cooling or the like. Next, cold rolling is performed. Cold rolling at this stage is referred to as "rough cold rolling" in this specification. The rolling ratio in rough cold rolling can be, for example, 50 to 99%. In this way, an intermediate product plate material to be subjected to the first solution treatment can be obtained.
Here, the rolling rate is expressed by the following formula (1).
Rolling ratio (%) = 100 x (t ₀ - t ₁ )/t ₀ (1)
t ₀ : Plate thickness before rolling (mm)
_t1 : Plate thickness after rolling (mm)

[First solution treatment]
A first solution treatment is performed on the above intermediate product plate material. In this solution treatment, the strain introduced during hot working and rough cold rolling is used to recrystallize and remove coarse grain boundary reaction type precipitates and granular precipitates generated after casting and during hot working. Sufficient solid solution. If the solid solution of the precipitates is insufficient in this first solution treatment stage, the precipitates will remain until the final step, making it impossible to obtain desired characteristics. In the first solution treatment, it is advantageous to increase the amount of thermal energy introduced in order to give priority to solid solution treatment. In this case, although recrystallized grains tend to grow, there is no problem because the crystal grains are made finer in the subsequent second solution treatment. The first solution treatment can be carried out under conditions of holding at a temperature range of 750 to 950°C for 10 to 600 seconds, and more preferably under conditions of holding at 800 to 900°C for 20 to 600 seconds.

[First intermediate cold rolling]
The cold rolling performed on the material that has undergone the first solution treatment is called first cold rolling. The purpose of the first cold rolling is to introduce strain in addition to reducing the plate thickness. If strain is insufficiently introduced, sufficient nucleation sites for recrystallization cannot be secured in the subsequent second solution treatment, making it difficult to refine crystal grains. For the above reasons, it is necessary to set the rolling ratio in the first intermediate cold rolling to 70% or more. It is more effective to set it to 85% or more, and even more effective to set it to 90% or more. The upper limit of the rolling ratio is not particularly limited, but it may be normally set within a range of 99% or less depending on the capacity of the cold rolling mill.

[Second solution treatment]
In the material that has undergone the first intermediate cold rolling, the precipitates are already sufficiently dissolved in solid solution, and strain has been introduced into the crystals of the matrix (metal base). A plate material having such a structure is subjected to a second solution treatment. In this solution treatment, the strain introduced in the first intermediate cold rolling is used to generate new recrystallization from many locations, thereby refining the crystal grains. Since the main purpose is not to form a solid solution of precipitates but to refine grains by recrystallization, the upper limit of the allowable heating temperature is lower than in the first solution treatment. Specifically, it can be carried out under conditions of holding the temperature in a temperature range of 750 to 900°C for 10 to 600 seconds. When the temperature exceeds 900° C., grain growth accompanied by movement of grain boundaries between recrystallized grains tends to occur, and crystal grains may become coarse. Furthermore, if the temperature is lower than 750°C, precipitation rather than recrystallization tends to occur, making it difficult to sufficiently generate fine precipitates in the aging treatment described below. The second solution treatment is more preferably carried out at a temperature range of 750 to 880°C for 10 to 300 seconds, and even more preferably carried out at a temperature range of 750 to 860°C for 10 to 150 seconds. In addition, from the viewpoint of suitably achieving the purpose of the second solution treatment, which is to refine the crystal grains, it is more effective that the heating temperature 2 in the second solution treatment is lower than the heating temperature 1 in the first solution treatment. and when the heating temperature 2 is higher than the heating temperature 1, the difference is 50°C or less and the holding time 2 at the heating temperature 2 of the second solution treatment is longer than that of the first solution. It is more effective that the holding time at the heating temperature 1 of the chemical treatment is one-third or less of the holding time 1.

[Second intermediate cold rolling]
The cold rolling performed on the material that has undergone the second solution treatment is called second intermediate cold rolling. In the second intermediate cold rolling, appropriate strain is introduced so that the formation of fine precipitates within the crystal grains is promoted in the subsequent aging treatment. This strain also contributes to improving the strength. If the amount of strain introduced is too large, the resulting structure will have a KAM value that is too high, which may lead to a decrease in bending workability. Therefore, the rolling rate of the second intermediate cold rolling cannot be set as high as that of the first intermediate cold rolling. Specifically, the rolling ratio of the second intermediate cold rolling needs to be in the range of 15 to 50%. It is more preferably in the range of 15 to 40%, and may be controlled in the range of 15 to 35%.

[Aging treatment]
The material that has undergone the second intermediate cold rolling is subjected to an aging treatment at 300 to 470°C, preferably 320 to 450°C, to generate fine precipitates that contribute to strength. Grain boundary reaction type precipitates are also generated by aging treatment, but since the crystal grains have already been refined, the generation sites of grain boundary reaction type precipitates are dispersed throughout the material, resulting in the above-mentioned ``grain boundary reaction type precipitates''. A metal structure with a small "maximum width of existing region" can be obtained. The aging treatment time (holding time at 300 to 470°C) can usually be set within the range of 1 to 24 hours to obtain a sufficient effect. The aging treatment time is preferably set within a range of 8 to 20 hours, for example.

[Final cold rolling, low temperature annealing]
After the aging treatment, cold rolling and low-temperature annealing can be performed as necessary for the purpose of adjusting plate thickness, improving strength, and the like. Cold rolling at this stage is called "finish cold rolling." If the rolling rate in finish cold rolling is too high, the KAM value will be too high, leading to a decrease in bending workability. In the finish cold rolling, the rolling ratio needs to be 50% or less, more preferably 30% or less, and may be controlled within the range of 25% or less. In order to improve strength, it is effective to ensure a rolling ratio of 5% or more, and more effective to ensure a rolling ratio of 10% or more. Low-temperature annealing can be carried out under conditions of holding the material in a temperature range of 350 to 550°C, preferably 400 to 500°C, for a period of 60 seconds or less. It is effective to ensure a holding time of 15 seconds or more in the above temperature range.
The final plate thickness can range from 0.02 to 0.50 mm, for example.

[Electricity-carrying parts]
The copper alloy sheet material of the present invention described above has a high level of well-balanced strength, electrical conductivity, bending workability, and stress relaxation properties, and has a reduced density (specific gravity). The current-carrying components used in this work meet the demands for higher functionality in mobile terminals and automotive electronic equipment in recent years.

[Heat dissipation parts]
The copper alloy sheet material of the present invention described above has a high level of well-balanced strength, electrical conductivity, bending workability, and stress relaxation properties (materials with excellent electrical conductivity generally have excellent heat dissipation properties). ), and the density (specific gravity) is reduced, so heat dissipation parts using this plate material meet the demands for higher functionality of mobile terminals and automotive electronic devices in recent years.

A copper alloy having the chemical composition shown in Table 1 was melted and cast. In Inventive Example No. 14, misch metal (mixture of rare earth elements) was added as a rare earth element addition source at a ratio of 0.32% by mass to the total amount of the copper alloy raw material. The mass ratio of the main rare earth elements contained in this misch metal was La:Ce:Pr:Nd=28:50:5:17.

The obtained slabs were heated at the temperatures and times shown in Tables 2 and 3. Except for some examples (Comparative Example Nos. 40 and 41), the slabs were taken out of the heating furnace, hot-rolled to the thickness shown in Tables 2 and 3, and cooled with water. The total hot rolling rate is 87.5 to 95%. After hot rolling, the surface oxide layer was removed by mechanical polishing (face cutting), and each hot rolled material was cold rolled to the thickness listed in the "Rough Cold Rolling" column of Tables 2 and 3. did.

Thereafter, except for some examples (Comparative Example No. 31, 38, 39, 40, 41, 45), the first solution treatment, the first intermediate cold rolling, and the second Solution treatment, second intermediate cold rolling, and aging treatment were performed in the above order. The aging treatment was performed in a nitrogen atmosphere using a batch heat treatment furnace. Regarding Invention Examples Nos. 4, 5, and 11 and Comparative Example 37, finish cold rolling and low-temperature annealing were performed under the conditions listed in Tables 2 and 3 after the aging treatment. The symbol "-" (hyphen) in Tables 2 and 3 means that a step was omitted. For Nos. 31, 39, and 45, the first intermediate cold rolling and the second solution treatment were omitted. In No. 38, a preliminary aging treatment (precursor treatment) was performed after the solution treatment, and then the aging treatment was performed through cold rolling at a light rolling reduction. No. 40 is a process in which the slab subjected to homogenization heat treatment is directly subjected to aging treatment, and hot rolling and cold rolling are not performed. No. 41 is a slab that has been heat-treated for homogenization, cold-rolled at a rolling rate of 85% to a plate thickness of 0.10 mm, and then subjected to solution treatment and aging treatment. No hot rolling was performed. Tables 2 and 3 show the thicknesses of the finally obtained plates. This plate material was used as a test material for the following investigation. Since the example No. 40 did not go through the rolling process, the test piece was prepared by cutting out a sample from the aged material and adjusting the plate thickness to 0.08 mm by etching. Note that the density (specific gravity) was measured using a block sample cut from the material after heating the slab.

(Average grain size)
The observation surface was prepared by polishing the plate surface of the sample material and etching the surface finished by electropolishing using the electrolytic polishing conditions described in "How to determine the number density of fine precipitate particles" above. . The observation surface was observed with an optical microscope at a magnification of 1000 times, and an observation image was obtained. By drawing a total of three straight lines parallel to the rolling surface and counting the number of grain boundaries cut by each straight line using a cutting method based on JIS H0501-1986, the average value of the grain size in the observation field can be determined. was calculated. This operation was performed for five randomly selected visual fields, and the arithmetic mean value of the average values of the crystal grain sizes obtained in each visual field was adopted as the average crystal grain size of the plate material. Note that LEXT OLS4000 manufactured by OLYMPUS Corporation was used as an optical microscope.

(Maximum width of grain boundary reaction type precipitate existing region)
The plate surface of the test material was polished, and the observation surface, which was finished by electropolishing using the electrolytic polishing conditions described in "How to determine the number density of fine precipitate particles" above, was examined using an SEM (scanning electron microscope). ), and the maximum width of the grain boundary reaction type precipitate existing area was determined according to the above-mentioned "How to determine the maximum width of the grain boundary reaction type precipitate existing area".

(Number density of fine precipitate particles)
The number density of fine precipitate particles was determined according to the above-mentioned "How to determine the number density of fine precipitate particles."

(KAM value)
After buffing the plate surface of the sample cut out from the test material, ion milling polishing was performed to prepare a sample surface for EBSD (electron beam backscatter diffraction) measurement. The surface of the sample was observed using an FE-SEM (JSM-7200F manufactured by JEOL Ltd.) under the conditions of an acceleration voltage of 15 kV and a magnification of 500 times. Crystal orientation data was collected by the EBSD method at a step size of 0.1 μm using an EBSD device (manufactured by Oxford Instruments, Symmetry). Based on the crystal orientation data measured for the measurement area of 5 visual fields, the KAM value was determined according to the above-mentioned "How to determine the KAM value". OIM-Analysis 7.3.1 manufactured by TSL Solutions Co., Ltd. was used as software for EBSD data analysis.

(Tensile strength)
A tensile test piece (JIS No. 5) in the rolling direction (any direction in Example No. 40) was taken from each sample material, and a tensile test was conducted in accordance with JIS Z2241 with the number of tests n = 3 to measure the tensile strength. did. The average value of n=3 was taken as the performance value of the sample material. In addition, the value of 0.2% proof stress determined by this tensile test was used to measure the stress relaxation rate described below.

(conductivity)
The conductivity of each sample material was measured by double bridge and average cross-sectional area method in accordance with JIS H0505.

(MBR/t of 90°W bending)
The ratio MBR/t between the minimum bending radius MBR at which no cracking occurs and the plate thickness t was determined by a W bending test at B.W. according to the Japan Copper Brass Association technical standard JCBA T307:2007. The test piece size was 30 mm in length in the direction perpendicular to rolling and 10 mm in length in rolling direction. However, in Example No. 40, an arbitrary direction was taken as the longitudinal direction. A bending test was performed in which the bending radius was changed in stages, and the number of tests was n = 3 for one bending radius. This is the MBR for the sample material. The presence or absence of cracks on the surface of the bent portion was determined in accordance with JCBA T307:2007. For samples judged to have "large wrinkles" in the appearance observation of the surface of the bent part, a sample was cut perpendicular to the bending axis direction at the deepest wrinkle part, and the polished cross section was observed with an optical microscope. It was checked to see if any cracks had developed into the inside of the plate, and if no such cracks had occurred, it was determined that ``no cracks were observed.''

(stress relaxation rate)
A test piece with a width of 10 mm in the direction perpendicular to the rolling direction (any direction in Example No. 40) was cut from the test material, and the stress relaxation rate was measured using a cantilever method in accordance with the Japan Copper Brass Association technical standard JCBA T309:2004. It was measured. The test piece was set with a load stress equivalent to 80% of the 0.2% proof stress so that the deflection displacement was in the thickness direction, and the stress relaxation rate was measured after holding it at 250°C for 100 hours. . If the stress relaxation rate is 15% or less under these conditions, it can be judged that the sheet material has good stress relaxation resistance as a Cu-Ti based copper alloy plate material.

(density)
Using a block sample with a mass of 10 g cut out from the material after heating the slab, the density at room temperature (20° C.) was measured by the Archimedes method (underwater gravimetric method).
The above results are shown in Tables 4 and 5.

All of the plate materials of the present invention, whose chemical composition and manufacturing conditions were strictly controlled in accordance with the above regulations, have good strength, conductivity, bending workability, and stress relaxation properties, and are also effective in reducing density (specific gravity). It was excellent.

On the other hand, Comparative Example No. 31 was subjected to solution treatment only once, so the maximum width of the grain boundary reaction type precipitate existing region was large, and the bending workability was poor.
In No. 32, the electrical conductivity decreased because the Al content was too high.
In No. 33, since the temperature of the first solution treatment was low, the solid solution of the precipitated phase was insufficient, the maximum width of the grain boundary reaction type precipitate existing region was large, and the bending workability was poor. Furthermore, the amount of fine precipitates was insufficient and the strength was low.
In No. 34, the temperature of the first solution treatment was too high, so the crystal grains became coarse and the strength was low.
In No. 35, since the rolling rate in the first intermediate cold rolling was low, grain refinement could not be achieved in the second solution treatment, and the strength was low.
In No. 36, the rolling ratio in the second intermediate cold rolling was too high, so the KAM value became too large and the bending workability was poor.
In No. 37, the rolling ratio in the finish cold rolling was too high, so the KAM value was too large, and the bending workability was poor.
Since No. 38 does not contain Al, the effect of reducing density (specific gravity) cannot be obtained.
Since No. 39 does not contain Al, the effect of reducing density (specific gravity) cannot be obtained. Furthermore, since the process of performing solution treatment once at high temperature was adopted, the maximum width of the region where grain boundary reaction type precipitates existed became large, resulting in poor bending workability.
No. 40 is an example in which the rolling process was not performed. In this case, since the material was soft, the bending workability was good despite the fact that the maximum width of the grain boundary reaction type precipitate existing region was large. However, the amount of fine precipitates produced was small and the conductivity was low. In addition, the strength was low because there were few fine precipitates and the average crystal grain size was large.
No. 41 did not contain Al but contained Mg, so it was possible to obtain the effect of reducing density (specific gravity). However, high strength has not been achieved.
In No. 42, since the Ti content was low, the amount of fine precipitates produced was insufficient and the strength was low. Further, the effect of reducing density (specific gravity) has not been obtained.
In No. 43, the Ti content was too high, resulting in excessive formation of fine precipitates, resulting in poor bending workability.
In No. 44, since the Al content was low, the effect of reducing the density (specific gravity) was not obtained.
Since No. 45 does not contain Al, the effect of reducing density (specific gravity) cannot be obtained. Furthermore, since the solution treatment was performed only once, the maximum width of the grain boundary reaction type precipitate existing region was increased, resulting in poor bending workability.
In No. 46, since the temperature of the second solution treatment was low, the crystal grains were not sufficiently refined and the strength was low.

For reference, FIGS. 1 to 3 illustrate SEM photographs of the observed surface of the Cu--Ti alloy plate obtained in Comparative Example No. 45 prepared by electrolytic polishing. Further, FIGS. 4 to 6 illustrate SEM photographs of the observed surface of the Cu--Ti alloy plate obtained in Invention Example No. 1 prepared by electrolytic polishing. The length of the white scale bar at the bottom of each photograph corresponds to 10 μm in FIGS. 1 and 4, and 1 μm in FIGS. 2, 3, 5, and 6.

Claims (13)

In mass%, Ti: 1.0 to 5.0%, Al: 0.5 to 3.0%, Ag: 0 to 0.3%, B: 0 to 0.3%, Be: 0 to 0. 15%, Co: 0-1.0%, Cr: 0-1.0%, Fe: 0-1.0%, Mg: 0-0.5%, Mn: 0-1.5%, Nb: 0.0-0.5%, Ni: 0-1.0%, P: 0-0.2%, Si: 0-0.5%, Sn: 0-1.5%, V: 0-1 .0%, Zn: 0-2.0%, Zr: 0-1.0%, S: 0-0.2%, and among the above elements, Ag, B, Be, Co, Cr, Fe, Mg , Mn, Nb, Ni, P, Si, Sn, V, Zn, Zr and S total content is 3.0% or less, the balance is Cu and unavoidable impurities, and the composition is parallel to the plate surface. The maximum width of the grain boundary reaction type precipitate existing region is 1000 nm or less on the observation plane, and the crystal orientation is determined by EBSD (electron backscatter diffraction) with a step size of 0.1 μm on the observation plane parallel to the plate surface. A copper alloy sheet material having a KAM value of 3.0° or less when boundaries with a difference of 15° or more are regarded as grain boundaries, and a tensile strength in the rolling direction of 850 MPa or more. The copper alloy sheet material according to claim 1, further having a composition containing rare earth elements in a total amount of 3.0% by mass or less. Claim 1 or 2, wherein the number density of fine precipitate particles with a major diameter of 5 to 100 nm in an observation plane parallel to the plate surface is 1.0×10 ⁸ particles/mm ² or more and 1.0×10 ¹² particles/mm ² or less. Copper alloy plate material according to 2. The copper alloy sheet material according to claim 1 or 2, which has an average crystal grain size of 2 to 20 μm when measured by a cutting method according to JIS H0501-1986 in an observation plane parallel to the sheet surface. A claim in which the ratio MBR/t of the minimum bending radius MBR at which cracking does not occur and the plate thickness t is 2.0 or less in a W bending test at B.W. according to the Japan Copper Brass Association technical standard JCBA T307:2007. Copper alloy plate material according to 1 or 2. The copper alloy plate material according to claim 1 or 2, having an electrical conductivity of 10.0% IACS or more. The copper alloy plate material according to claim 1 or 2, having a density of 8.53 g/cm ³ or less. The copper alloy plate material according to claim 1 or 2, having a plate thickness of 0.02 to 0.50 mm. In mass%, Ti: 1.0 to 5.0%, Al: 0.5 to 3.0%, Ag: 0 to 0.3%, B: 0 to 0.3%, Be: 0 to 0. 15%, Co: 0-1.0%, Cr: 0-1.0%, Fe: 0-1.0%, Mg: 0-0.5%, Mn: 0-1.5%, Nb: 0.0-0.5%, Ni: 0-1.0%, P: 0-0.2%, Si: 0-0.5%, Sn: 0-1.5%, V: 0-1 .0%, Zn: 0-2.0%, Zr: 0-1.0%, S: 0-0.2%, and among the above elements, Ag, B, Be, Co, Cr, Fe, Mg , Mn, Nb, Ni, P, Si, Sn, V, Zn, Zr and S total content is 3.0% or less, and the balance consists of Cu and unavoidable impurities. In the step of manufacturing a copper alloy plate material by applying 1 solution treatment, 1st intermediate cold rolling, 2nd solution treatment, 2nd intermediate cold rolling, and aging treatment in the above order,
The first solution treatment is carried out in a temperature range of 750 to 950°C and held for 10 to 600 seconds,
Performing the first intermediate cold rolling at a rolling ratio of 70% or more,
The second solution treatment is carried out at a temperature range of 750 to 900°C for 10 to 600 seconds,
A second intermediate cold rolling is performed at a rolling ratio of 15 to 50%,
Aging treatment is performed at an aging temperature of 300 to 470°C.
A method for manufacturing a copper alloy plate material according to claim 1. 10. The method for manufacturing a copper alloy sheet material according to claim 9, wherein the intermediate product sheet material further has a composition containing a rare earth element in a total amount of 3.0% by mass or less. After the aging treatment, finish cold rolling and low temperature annealing are further performed in the above order to produce a copper alloy plate material,
Finish cold rolling is performed at a rolling rate of 50% or less,
Low-temperature annealing is performed under conditions of holding the material in a temperature range of 350 to 550°C for 60 seconds or less.
The method for manufacturing a copper alloy plate material according to claim 9 or 10. A current-carrying component using the copper alloy plate material according to claim 1 or 2 as a material. A heat dissipation component using the copper alloy plate material according to claim 1 or 2 as a material.