U.S. patent application number 13/021371 was filed with the patent office on 2011-08-18 for copper alloy material for electric/electronic parts.
This patent application is currently assigned to THE FURUKAWA ELECTRIC CO., LTD.. Invention is credited to Tatsuhiko EGUCHI, Ryosuke MATSUO, Kuniteru MIHARA.
Application Number | 20110200479 13/021371 |
Document ID | / |
Family ID | 41663649 |
Filed Date | 2011-08-18 |
United States Patent
Application |
20110200479 |
Kind Code |
A1 |
MIHARA; Kuniteru ; et
al. |
August 18, 2011 |
COPPER ALLOY MATERIAL FOR ELECTRIC/ELECTRONIC PARTS
Abstract
A copper alloy material for electric/electronic parts,
containing Co and Si as additive elements, wherein, a compound A is
dispersed, which is composed of Co and Si and has an average
particle diameter of 5 nm or more but less than 50 nm, and at least
one compound is dispersed, which is selected from: a compound B
which does not contain one or any of Co and Si and has an average
particle diameter from 50 to 500 nm, a compound C which contains
both of Co and Si and another element and has an average particle
diameter from 50 to 500 nm, and a compound D which is composed of
Co and Si and has an average particle diameter from 50 to 500 nm; a
grain size of the copper alloy matrix is 3 to 35 .mu.m; and an
electrical conductivity is 50% IACS or more.
Inventors: |
MIHARA; Kuniteru; (Tokyo,
JP) ; MATSUO; Ryosuke; (Tokyo, JP) ; EGUCHI;
Tatsuhiko; (Tokyo, JP) |
Assignee: |
THE FURUKAWA ELECTRIC CO.,
LTD.
Tokyo
JP
|
Family ID: |
41663649 |
Appl. No.: |
13/021371 |
Filed: |
February 4, 2011 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2009/063615 |
Jul 30, 2009 |
|
|
|
13021371 |
|
|
|
|
Current U.S.
Class: |
420/470 ;
420/477; 420/485; 420/489; 420/490 |
Current CPC
Class: |
C22C 9/06 20130101; H01B
1/026 20130101; C22F 1/08 20130101 |
Class at
Publication: |
420/470 ;
420/490; 420/477; 420/489; 420/485 |
International
Class: |
C22C 9/02 20060101
C22C009/02; C22C 9/10 20060101 C22C009/10; C22C 9/04 20060101
C22C009/04 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 5, 2008 |
JP |
2008-202467 |
Claims
1. A copper alloy material for electric/electronic parts,
comprising Co and Si as additive elements, wherein, in the copper
alloy material, a compound A is dispersed, which is composed of Co
and Si and which has an average particle diameter of 5 nm or more
but less than 50 nm, and at least one compound is dispersed, in
which said at least one compound is selected from the group
consisting of a compound B which does not contain one of Co and Si
or any of those and which has an average particle diameter from 50
nm to 500 nm, a compound C which contains both of Co and Si and
another element and which has an average particle diameter from 50
nm to 500 nm, and a compound D which is composed of Co and Si and
which has an average particle diameter from 50 nm to 500 nm,
wherein a grain size of the copper alloy of the matrix is 3 to 35
.mu.m, and wherein an electrical conductivity is 50% IACS or
more.
2. The copper alloy material for electric/electronic parts
according to claim 1, comprising Co and Si as additive elements,
with the balance being Cu and unavoidable impurities.
3. The copper alloy material for electric/electronic parts
according to claim 2, wherein the content of Co is 0.4 to 2.0 mass
%, and the content of Si is 0.1 to 0.5 mass %.
4. The copper alloy material for electric/electronic parts
according to claim 1, wherein the content of Co is 0.4 to 2.0 mass
%, and the content of Si is 0.1 to 0.5 mass %.
5. The copper alloy material for electric/electronic parts
according to claim 1, further comprising at least one selected from
Fe, Cr, Ni, Zr, and Ti in an amount of 0.05 to 1.0 mass % in total,
with the balance being Cu and unavoidable impurities.
6. The copper alloy material for electric/electronic parts
according to claim 5, wherein the content of Co is 0.4 to 2.0 mass
%, and the content of Si is 0.1 to 0.5 mass %.
7. The copper alloy material for electric/electronic parts
according to claim 1, further comprising at least one selected from
Al, Ag, Sn, Zn, Mg, Mn, and In in an amount of 0.05 to 1.0 mass %
in total, with the balance being Cu and unavoidable impurities.
8. The copper alloy material for electric/electronic parts
according to claim 7, wherein the content of Co is 0.4 to 2.0 mass
%, and the content of Si is 0.1 to 0.5 mass %.
9. The copper alloy material for electric/electronic parts
according to claim 7, further comprising at least one selected from
Fe, Cr, Ni, Zr, and Ti in an amount of 0.05 to 1.0 mass % in total,
with the balance being Cu and unavoidable impurities.
10. The copper alloy material for electric/electronic parts
according to claim 9, wherein the content of Co is 0.4 to 2.0 mass
%, and the content of Si is 0.1 to 0.5 mass %.
11. The copper alloy material for electric/electronic parts
according to claim 1, wherein, in the production of an ingot, an
average cooling speed from the solid state temperature to
500.degree. C. is 5 to 100.degree. C./second.
12. A copper alloy material for electric/electronic parts,
comprising Co and Si as additive elements, wherein, a compound A
which is composed of Co and Si and which has an average particle
diameter of 5 nm or more but less than 50 nm, a compound B which
does not contain one of Co and Si or any of those and which has an
average particle diameter from 50 nm to 500 nm, a compound C which
contains both of Co and Si and another element and which has an
average particle diameter from 50 nm to 500 nm, and a compound D
which is composed of Co and Si and which has an average particle
diameter from 50 nm to 500 nm, are dispersed in the copper alloy
material, wherein the ratio of dispersion densities of the
compounds A, B, C, and D satisfies the relationship:
0.0001.ltoreq.{(dispersion density of the compound B+dispersion
density of the compound C+dispersion density of the compound
D)/dispersion density of the compound A}.ltoreq.0.1, wherein a
grain size of the copper alloy of the matrix is 3 to 35 .mu.m, and
wherein an electrical conductivity is 50% IACS or more.
13. The copper alloy material for electric/electronic parts
according to claim 12, comprising Co and Si as additive elements,
with the balance being Cu and unavoidable impurities.
14. The copper alloy material for electric/electronic parts
according to claim 13, wherein the content of Co is 0.4 to 2.0 mass
%, and the content of Si is 0.1 to 0.5 mass %.
15. The copper alloy material for electric/electronic parts
according to claim 12, wherein the content of Co is 0.4 to 2.0 mass
%, and the content of Si is 0.1 to 0.5 mass %.
16. The copper alloy material for electric/electronic parts
according to claim 12, further comprising at least one selected
from Fe, Cr, Ni, Zr, and Ti in an amount of 0.05 to 1.0 mass % in
total, with the balance being Cu and unavoidable impurities.
17. The copper alloy material for electric/electronic parts
according to claim 16, wherein the content of Co is 0.4 to 2.0 mass
%, and the content of Si is 0.1 to 0.5 mass %.
18. The copper alloy material for electric/electronic parts
according to claim 12, further comprising at least one selected
from Al, Ag, Sn, Zn, Mg, Mn, and In in an amount of 0.05 to 1.0
mass % in total, with the balance being Cu and unavoidable
impurities.
19. The copper alloy material for electric/electronic parts
according to claim 18, wherein the content of Co is 0.4 to 2.0 mass
%, and the content of Si is 0.1 to 0.5 mass %.
20. The copper alloy material for electric/electronic parts
according to claim 18, further comprising at least one selected
from Fe, Cr, Ni, Zr, and Ti in an amount of 0.05 to 1.0 mass % in
total, with the balance being Cu and unavoidable impurities.
21. The copper alloy material for electric/electronic parts
according to claim 20, wherein the content of Co is 0.4 to 2.0 mass
%, and the content of Si is 0.1 to 0.5 mass %.
22. The copper alloy material for electric/electronic parts
according to claim 12, wherein, in the production of an ingot, an
average cooling speed from the solid state temperature to
500.degree. C. is 5 to 100.degree. C./second.
Description
TECHNICAL FIELD
[0001] The present invention relates to a copper alloy material
that is applied to an electric/electronic part, such as a connector
or terminal material for an electric/electronic equipment,
particularly a high-frequency relay or switch where high electrical
conductivity is desired, or a connector or terminal material to be
mounted on an automotive vehicle, and a lead frame.
BACKGROUND ART
[0002] Hitherto, copper alloys, such as brass (C26000) and phosphor
bronze (C51910, C52120, C52100), as well as beryllium copper
(C17200, C17530) and Corson-series copper alloy (hereinafter, also
simply referred to as Corson copper, for example, C70250), and the
like, have been used, for example, for connectors, terminals,
relays, and switches for electric/electronic equipments. Herein,
the term "Cxxxxx" denotes types of copper alloys specified in CDA
(Copper Development Association).
[0003] In recent years, since a frequency of electric current
applied to the electric/electronic equipments using those alloys
becomes high, materials for those have been required to have a high
electrical conductivity. Under the circumstances, although brass
and phosphor bronze each originally are low in electrical
conductivity while Corson copper shows a medium electrical
conductivity (EC nearly equals to 40% IACS) as a connecter
material, a higher electrical conductivity has been required.
Further, it is well known that beryllium copper is expensive. On
the other hand, pure copper (C11000), tin bearing copper (C14410),
and the like, which have a high electrical conductivity, have a
drawback that their mechanical strength is low. Thus, a copper
alloy has been desired which has an electrical conductivity higher
than that of a conventional Corson copper, and a tensile strength
and a bending property at the same level of those of the
conventional Corson copper.
[0004] Herein, the CXXXXX denotes types of copper alloys specified
in CDA (Copper Development Association). The term "% IACS" is a
unit which indicates an electrical conductivity of a material, and
"IACS" is an abbreviation of "International Annealed Copper
Standard".
[0005] Particularly, among the parts for electronic equipments of
recent years, there are many connectors or terminals that have been
subjected to complicated and severe bending, concomitantly with the
size reduction of electronic equipments. This is because although
the size of connectors is also reduced along with the size
reduction, it is desired to take a contact length as long as
possible in order to maintain the reliability of connection. A
connector or terminal having such a design concept is, in many
cases, referred to as a bellows-bent (corrugated) connector or
terminal. That is, there is a strong demand for the mounting and
installation of terminals or connectors that are bent in a
complicated manner in small parts. On the other hand, the material
of connectors and terminals to be used is becoming thinner
concomitantly with the size reduction. This trend is furthered from
the viewpoint of weight reduction and resource saving. Thin
materials are demanded to have higher mechanical strength as
compared with thick materials, in order to maintain the same
contact pressure.
[0006] As a method of increasing the mechanical strength of a
copper alloy material, there are various strengthening methods,
such as solid solution strengthening, work strengthening, and
precipitation strengthening. Generally, the electrical conductivity
and the mechanical strength are properties in an inconsistent
relationship. Among those methods, it is known that precipitation
strengthening is promising, as a method of enhancing the mechanical
strength without decreasing the electrical conductivity of the
copper alloy material. This precipitation strengthening is a
technique of: subjecting an alloy to which elements causing
precipitation have been added, to a heat treatment at high
temperature, to thereby cause solid-solution of these elements into
the copper matrix, and then heat treating the alloy at a
temperature lower than the temperature used for the solid solution,
thereby precipitating the solid-solution elements. For example,
beryllium copper, Corson copper, and the like employ that
strengthening method.
[0007] Meanwhile, the bending property and the mechanical strength
are properties in an inconsistent relationship. In general, a
material high in the mechanical strength is poor in the bending
property, while a material good in the bending property is, on the
contrary, low in the mechanical strength. In order to enhance the
mechanical strength, it is considered effective to increase the
cold-rolling ratio; however, if the cold rolling ratio is
increased, there is a tendency that the bending property is
conspicuously deteriorated. It has hitherto been considered that
beryllium copper, Corson copper, titanium copper, and the like, as
precipitation type copper alloys, have a well balance between
bending property and mechanical strength. However, with respect to
beryllium copper, beryllium, which is an additive element, is
regarded as an environmental burden material, and there is a demand
for a substitute material. Further, Corson copper or titanium
copper generally does not have an electrical conductivity of 50%
IACS or higher. Examples of the applications where a high
electrical conductivity of 50% IACS or higher is required, include
battery terminals and relay contacts to which high current is
applied. Furthermore, since materials having high electrical
conductivity are generally excellent in the thermal conduction
property as well, materials for the sockets or heat sinks of
central processing units (CPU; integrated logic elements), which
require heat emission properties, are also required to have high
electrical conductivity. Particularly, recent hybrid cars or CPUs
handling high speed processing are required to use materials having
high electrical conductivity and high mechanical strength.
[0008] Under such circumstances, copper alloys which have
mechanical strength, bending property, and electrical conductivity
(thermal conductivity), and which utilize intermetallic compounds
containing Co (cobalt) and Si (silicon), are increasingly
attracting attention. Copper alloys containing Co and Si as
essential elements, or techniques related to these, are known as
shown below.
[0009] First, conventional techniques for copper alloys containing
Co and Si as essential elements will be described.
[0010] Patent Literature 1 describes an alloy containing Co, Si, Zn
(zinc), Mg (magnesium), and S (sulfur) as essential elements. The
purpose in Patent Literature 1 is to improve hot workability.
[0011] Patent literature 2 describes an alloy containing Mg, Zn,
and Sn (tin), in addition to Co and Si. Patent literature 3
describes an alloy essentially containing Sn and Zn, in addition to
Co and Si. Further, Patent Literature 2 and Patent Literature 3
describe that the precipitate (compound) of Co and Si is a
Co.sub.2Si compound.
[0012] Patent Literature 4 describes a Cu--Co--Si-based alloy. The
alloy of Patent Literature 4 is applied in lead frames, and it is
described that the kind of the alloy is a precipitation
strengthening type alloy.
[0013] Patent Literature 5 describes a Cu--Co--Si-based alloy, in
which the size of inclusions precipitated is 2 .mu.m or less.
[0014] Patent literature 6 describes a Cu--Co--Si-based alloy, in
which a Co.sub.2Si compound is precipitated.
[0015] The techniques described in Patent Literatures 1 to 6 all
describe only on one kind (or one size) of intermetallic compound
composed of Co and Si. However, in regard to other alloy systems,
particularly the so-called Corson copper which contains Ni and Si
as essential additive elements, it is known that when two or more
kinds of intermetallic compounds are dispersed in the copper alloy,
the bending property and the like are improved. This technique is
known in Patent Literatures 7 to 11.
Patent Literature 1: JP-A-61-87838 ("JP-A" means unexamined
published
[0016] Japanese patent application) [0017] Patent Literature 2:
JP-A-63-307232 [0018] Patent Literature 3: JP-A-02-129326 [0019]
Patent Literature 4: JP-A-02-277735 [0020] Patent Literature 5:
JP-A-2008-88512 [0021] Patent Literature 6: JP-A-2008-56977 [0022]
Patent Literature 7: JP-A-2006-161148 [0023] Patent Literature 8:
JP-A-2006-265731 [0024] Patent Literature 9: JP-A-2007-314847
[0025] Patent Literature 10: JP-A-2008-75151 [0026] Patent
Literature 11: JP-A-2008-75152
DISCLOSURE OF INVENTION
Technical Problem
[0027] However, all of the techniques described in the patent
literatures do not satisfy all of the mechanical strength, bending
property, and electrical conductivity (thermal conductivity), each
at a high level.
[0028] The purpose in Patent Literature 1 is to improve hot
workability, but the Patent Literature 1 has no description on the
precipitate (compound) of Co and Si and has no description on
mechanical strength or electrical conductivity.
[0029] Patent Literature 2 has no description on performing a
recrystallization treatment, and it is thought that the resultant
alloy is poor in bending property.
[0030] Patent Literature 3 shows, in the example section, that the
electrical conductivity is a relatively low value of 30% IACS or
less.
[0031] Patent Literature 4 describes a precipitation strengthening
type alloy, but has no description on the specific compound or its
size. Further, there is no description on performing a
recrystallization treatment, and it is thought that the resultant
alloy is poor in bending property.
[0032] In Patent Literature 5 and Patent Literature 6, examples are
described in which bending property is evaluated under the
conditions of R/t=1, in which an inner bending radius of the
material is represented by R, and a sheet thickness is represented
by t. However, it is thought that with the mechanical strength
level of this extent, definitely there will be instances where the
resulting alloys are not capable of coping with the bending
property demanded in the future.
[0033] Furthermore, the techniques described in Patent Literatures
7 to 11 each are related to the so-called Corson copper containing
Ni and Si as main additive elements. Corson copper and
Cu--Co--Si-based alloys differ from each other in the alloying
elements, and have differences, for example, in different
temperature of carrying out a solution heat treatment. For example,
in the case of Corson copper, when the amount of Ni is 3 mass % or
more, a solution heat treatment temperature of about 900.degree. C.
is required; while, in the case of a Cu--Co--Si alloy, it has been
known that at a solution heat treatment temperature of about
900.degree. C., alloys having an amount of Co of about 1.0 to 1.2
mass % only can be sufficiently treated by a solution heat
treatment. Furthermore, in the case of a Corson copper having an
amount of Ni of 3 mass % or more, when it is tried to enhance the
mechanical strength and improve the bending property, it is
practically difficult to obtain an electrical conductivity of 20%
IACS or more, and a copper alloy having high electrical
conductivity cannot be obtained. That is, the Corson copper and the
Cu--Co--Si alloys have significant differences in the solution heat
treatment temperature or the properties of alloy, so there is a
demand for a new technique which is not an extension of the
conventional techniques.
SOLUTION TO PROBLEM
[0034] In view of the above, in order to simultaneously satisfy
high electrical conductivity, high mechanical strength, and
satisfactory bending property in copper alloy materials, the
inventors of the present invention found a specifically preferable
relationship of those properties with the grain size, by dispersing
a precipitate (compound) of two or more kinds in a Cu--Co--Si-based
copper alloy, and controlling the size of such a precipitate (if
necessary, including its density). By conducting further
investigations, the inventors attained the present invention.
[0035] According to the present invention, there is provided the
following means:
[0036] (1) A copper alloy material for electric/electronic parts,
comprising Co and Si as additive elements,
[0037] wherein, in the copper alloy material, a compound A is
dispersed, which is composed of Co and Si and which has an average
particle diameter of 5 nm or more but less than 50 nm, and at least
one compound is dispersed, in which said at least one compound is
selected from the group consisting of a compound B which does not
contain one of Co and Si or any of those and which has an average
particle diameter from 50 nm to 500 nm, a compound C which contains
both of Co and Si and another element and which has an average
particle diameter from 50 nm to 500 nm, and a compound D which is
composed of Co and Si and which has an average particle diameter
from 50 nm to 500 nm,
[0038] wherein a grain size of the copper alloy of the matrix is 3
to 35 .mu.m, and
[0039] wherein an electrical conductivity is 50% IACS or more.
[0040] (2) A copper alloy material for electric/electronic parts,
comprising Co and Si as additive elements,
[0041] wherein, a compound A which is composed of Co and Si and
which has an average particle diameter of 5 nm or more but less
than 50 nm, a compound B which does not contain one of Co and Si or
any of those and which has an average particle diameter from 50 nm
to 500 nm, a compound C which contains both of Co and Si and
another element and which has an average particle diameter from 50
nm to 500 nm, and a compound D which is composed of Co and Si and
which has an average particle diameter from 50 nm to 500 nm, are
dispersed in the copper alloy material,
[0042] wherein the ratio of dispersion densities of the compounds
A, B, C, and D satisfies the relationship:
0.0001.ltoreq.{(dispersion density of the compound B+dispersion
density of the compound C+dispersion density of the compound
D)/dispersion density of the compound A)}.ltoreq.1,
[0043] wherein a grain size of the copper alloy of the matrix is 3
to 35 .mu.m, and
[0044] wherein an electrical conductivity is 50% IACS or more.
[0045] (3) The copper alloy material for electric/electronic parts
as described in item (1) or (2), further comprising at least one
selected from Al, Ag, Sn, Zn, Mg, Mn, and In in an amount of 0.05
to 1.0 mass % in total, with the balance being Cu and unavoidable
impurities.
[0046] (4) The copper alloy material for electric/electronic parts
as described in any one of items (1) to (3), further comprising at
least one selected from Fe, Cr, Ni, Zr, and Ti in an amount of 0.05
to 1.0 mass % in total, with the balance being Cu and unavoidable
impurities.
[0047] (5) The copper alloy material for electric/electronic parts
as described in item (1) or (2), comprising Co and Si as additive
elements, with the balance being Cu and unavoidable impurities.
[0048] (6) The copper alloy material for electric/electronic parts
as described in any one of items (1) to (5), wherein the content of
Co is 0.4 to 2.0 mass %, and the content of Si is 0.1 to 0.5 mass
%.
[0049] (7) The copper alloy material for electric/electronic parts
as described in any one of items (1) to (6), wherein, in the
production of an ingot, an average cooling speed from the solid
state temperature to 500.degree. C. is 5 to 100.degree.
C./second.
[0050] Herein, the term "average particle diameter (size) of a
precipitate (compound)" is the average particle size of a
precipitate in interest determined by the method described below.
The term "grain size" means a value measured according to JIS-H0501
(cutting method) described below.
ADVANTAGEOUS EFFECTS OF INVENTION
[0051] According to the present invention, a copper alloy material
can be provided, which has an optimized grain size, which is high
in electrical conductivity, high in mechanical strength, and
excellent in bending property, and which is favorable for the use
in electric/electronic parts, by controlling two or more kinds of
precipitates (compounds) in a Cu--Co--Si alloy which exhibits a
high electrical conductivity.
[0052] Other and further features and advantages of the invention
will appear more fully from the following description.
BEST MODE FOR CARRYING OUT THE INVENTION
[0053] Preferable embodiments of the copper alloy material of the
present invention will be described in detail. Herein, the term
"copper alloy material" means a product obtained after a copper
alloy base material (herein, the "copper alloy base material" means
a mixture of component elements of a copper alloy not having the
concept of shape) is worked into a predetermined shape (for
example, sheet, strip, foil, rod, or wire). Further, the term
"copper alloy of matrix" means a copper alloy not having the
concept of shape.
[0054] Although explanation will be given on a sheet material and a
strip material as preferable specific examples of the copper alloy
material, but the shape of the copper alloy material is not limited
to the sheet material or the strip material.
[0055] First, the technical idea of the present invention will be
described. The inventors of the present invention found, by
studying keenly, that, in order to obtain a copper alloy material
high in mechanical strength, high in electrical conductivity, and
favorable in bending property, two or more kinds of precipitates
(compounds) having different sizes are needed in a Cu--Co--Si-based
alloy, and that it is important to control the grain size of the
copper alloy of the matrix to 3 to 35 .mu.m. Further, the inventors
found that it is preferable to control the density of the
precipitates (compounds) so as to control the grain size of the
copper alloy of the matrix to 3 to 35 .mu.m. Furthermore, the
inventors found that, between two kinds of precipitates having
different sizes, a giant (coarse) compound having an average
particle diameter from 50 nm to 500 nm can be obtained preferably
by appropriately setting the cooling speed in the production of an
ingot.
[0056] Furthermore, for a copper alloy material appropriate
favorable for the use in electric/electronic parts, the electrical
conductivity is 50% IACS or more, and, with regard to the
relationship between tensile strength and bending property, it is
preferable that when the tensile strength is 550 MPa or more but
less than 650 MPa, R/t.ltoreq.0.5, in which R/t serves as an index
for bending property; when the tensile strength is 650 MPa or more
but less than 700 MPa, R/t.ltoreq.1; when the tensile strength is
700 MPa or more but less than 750 MPa, R/t.ltoreq.2; and when the
tensile strength is 750 MPa or more but less than 800 MPa,
R/t.ltoreq.3.
[0057] Herein, the term "R/t" means a result obtained by conducting
a W bending test at a bending angle of 90.degree. according to the
"Standard test method of bend formability for sheets and strips of
copper and copper alloys (JBMA T307)" of the Japan Copper and Brass
Association Technical Standards, and is a value obtained by
subjecting a sheet material cut out in a direction perpendicular to
rolling, to a bending test under the condition of a predetermined
bending radius (R), determining the R value of the limit at which
any crack (breakage) does not occur at the top, and normalizing the
value by the sheet thickness (t). In general, a smaller value of
R/t gives more satisfactory bending property.
[0058] In the copper alloy material of the present invention for
electric/electronic parts, the electrical conductivity of the
copper alloy material is set at 50% IACS or higher. The electrical
conductivity is more preferably 55% IACS or more, and further
preferably 60% IACS or more, and it is preferable that the
electrical conductivity is as high as possible, but the upper limit
is generally approximately 75% IACS. In the copper alloy material
for electric/electronic parts of the present invention, it is
preferable that the tensile strength and the bending property (R/t)
have the relationship described above. Further, the lower limit of
the bending property (R/t) is 0.
[0059] In order to obtain a material high in electrical
conductivity, high in mechanical strength, and excellent in bending
property as a copper alloy material favorable for the use in
electric/electronic parts, it is useful to utilize a technique of
dispersing two or more kinds of intermetallic compounds having
different sizes in a Cu--Co--Si-based alloy.
[0060] First, the background of this technique will be described,
and the copper alloy as mentioned herein is an example of the case
where the intermetallic compound is one kind of compound containing
Co and Si. When Co and Si are added to copper, followed by
subjecting to an adequate heat treatment, to give a so-called
precipitation type copper alloy in which an intermetallic compound
composed of Co and Si precipitates.
[0061] A heat treatment method of developing the function of a
precipitation type copper alloy is generally carried out by
essentially performing the following two kinds of heat treatments.
The first heat treatment is referred to as heat solution (or
recrystallization) treatment or homogenization treatment, and this
heat treatment is carried out at a relatively high temperature for
a shorter time period. The second heat treatment is referred to as
aging heat treatment or precipitation treatment, and this heat
treatment is carried out at a temperature lower than the solution
heat treatment temperature for a longer time period.
[0062] First, the first heat treatment is carried out, by using a
continuous annealing furnace which threads a rolled sheet of a
copper alloy inside the heating furnace. This is because, when a
sheet is heat treated at a high temperature in a state of being
wound in a coil form, adhesion occurs, and because, when the
cooling speed thereafter is slow, the elements made into a solid
solution uncontrollably precipitate, to form a precipitate that
does not contribute to mechanical strength. Further, since there is
a concern about sheet breakage caused by threading inside the
furnace at high temperature, a heat treatment in a short time
period is carried out.
[0063] On the other hand, in regard to the second heat treatment,
since it is intended to finely disperse the precipitate (compound)
that contributes to mechanical strength in the copper alloy, the
sheet of the copper alloy wound into a coil form is subjected to a
heat treatment for a relatively long time period (specifically,
several minutes to several ten hours) in a heating furnace that has
been kept under temperature control, and thus the precipitate
(compound) which is optimal for a solid phase diffusion treatment
is sufficiently dispersed.
[0064] Thus, in a precipitation type copper alloy, the temperature
for the solution heat treatment (the first heat treatment) is
raised as high as possible, and thereby the amount of solute
elements that are made into a solid solution in the copper matrix
is increased. Then, a precipitate (compound) is precipitated, by
utilizing the difference in temperature from the aging heat
treatment (the second heat treatment) performed thereafter, and
thus the copper alloy is strengthened. As the temperature of this
solution heat treatment (the first heat treatment) is raised
higher, the solid solution amount of the solute elements is
increased (thereby, the amount of precipitate that precipitates
upon the later second heat treatment is increased). Thus, it is
advantageous to perform a high temperature heat treatment for the
first heat treatment. However, on the contrary, coarsening of the
texture of the recrystallization, which occurs simultaneously, has
adverse influence on the bending property. If the grain size is
coarse in a copper alloy high in mechanical strength, when the
copper alloy is subjected to bending, cracks (fissure) occurs at
that bent portion, or the surface unevenness of wrinkles (orange
peel surfaces, chalk marks) becomes large. Each of those result in
that necessary contact pressure may not be obtained, or the contact
point becomes unstable, thus the resultant copper alloy material
does not serve favorably for applications, such as connectors and
terminals. Further, the particle diameter becomes larger upon
recrystallization as the temperature is raised higher; and, when
the high temperature heat treatment is carried out as the first
heat treatment so as to increase the amount of the solute elements
as described above, bending property is deteriorated on the
contrary. As such, for a copper alloy material in which the
intermetallic compound is one kind of compound containing Co and
Si, it can be said that it is extremely difficult to satisfy all of
high electrical conductivity, high mechanical strength, and
satisfactory bending property.
[0065] Thus, according to the present invention, the inventors
developed a technique of dispersing two or more kinds of
intermetallic compounds having different sizes in a
Cu--Co--Si-based alloy, to satisfy all of high electrical
conductivity, high mechanical strength, and satisfactory bending
property. A fine compound composed of Co and Si and having a size
of 5 nm or more but less than 50 nm is a compound that contributes
to precipitation strengthening. On the other hand, a coarse
compound having a size from 50 nm to 500 nm is a compound that does
not contribute to precipitation strengthening but exhibits effects
at the time of high temperature solution heat treatment as
described in the above. This coarse compound cannot be made into a
solid solution in the copper matrix even in the high temperature
solution heat treatment, and exists in the copper matrix.
Therefore, even if grain growth occurs, the coarse compound becomes
a barrier and causes a state in which grain boundary movement is
difficult to occur. As a result, coarsening of the grain size is
suppressed.
[0066] In the case of a copper alloy, an ingot obtained by melting
(making into molten) raw materials followed by solidifying, is used
as a starting material, which is subjected to hot rolling and cold
rolling, and various heat treatments, thereby a copper alloy
material exhibiting desired properties is completed. In the course
of the solidification of the ingot, the hot rolling, the cooling
thereafter, the various heat treatments, or the cooling thereafter,
intermetallic compounds of various sizes are formed, and a solution
heat treatment is a treatment to make those intermetallic compounds
into solid solution, again, in the copper matrix. The solution heat
treatment is a treatment carried out prior to an aging heat
treatment, but upon the solution heat treatment, only coarse
compounds remain behind, while others are made into a solid
solution in the copper matrix. That is, what remain behind in the
copper matrix after the solution heat treatment are coarse
compounds only.
[0067] The aging heat treatment of the subsequent step allows
precipitation of fine precipitates (compounds), but at this
temperature, the size and density of the coarse compounds that have
been exposed to a high temperature in the preceding heat treatment,
do not change. There are a cases where the solution heat treatment
and the aging heat treatment are carried out in this successive
order, and another case where a cold rolling step is conducted
between these heat treatments; however, in any of those cases,
there is no change in the size and density of the coarse compounds
upon the heat treatment steps.
[0068] The compound A having an average particle diameter of 5 nm
or more but less than 50 nm, which is a compound that contributes
to precipitation strengthening, is a compound that precipitates
upon the aging heat treatment, to enhance mechanical strength. The
compound A is preferably Co.sub.2Si, but may also contain a
compound that does not fulfill the composition ratio of Co.sub.2Si
(for example, CoSi, or CoSi.sub.2). When the average particle
diameter of the compound A is 5 nm or more, the amount of
precipitation hardening is sufficient, and when the average
particle diameter is less than 50 nm, the mechanical strength is
sufficient, without a loss of coherent strain. Therefore, the size
of the compound A is defined to be 5 nm or more but less than 50
nm, and a preferred size is from 10 nm to 30 nm. However, since
this compound A varies with the observation method, the details of
the observation method will be described in the section "Examples"
shown below.
[0069] Next, the compound B is a compound that does not contain one
of Co and Si or any of them, and the contribution of this compound
to mechanical strength is small. Examples of the composition of the
compound B include Co-x, Si-x, and x-y, in which x and y each
represent an element other than Co and other than Si. When this
compound B is made into a solid solution in the copper matrix at
the solution heat treatment temperature to disappear, the compound
B cannot be utilized in the control of the grain size of the copper
alloy of the matrix. Therefore, this compound B is one having a
melting point higher than the solid solution temperature (that is,
the melting point) of Co.sub.2Si, which is a main component of the
compound A.
[0070] When the average particle diameter of the compound B is from
50 nm to 500 nm, the compound B exhibits an effect of suppressing
(pinning) the grain boundary movement at high temperature. The
compound B is an incoherent compound since it has an average
particle diameter of 50 nm or more, and in order to suppress the
grain boundary movement of the copper alloy of the matrix, the
average particle diameter of the compound B is preferably from 50
nm to 500 nm. The average particle diameter of the compound B is
more preferably from 100 nm to 300 nm. The inventors confirmed by
an observation of the texture after a solution heat treatment, that
the grain growth is suppressed most effectively when the compound B
is dispersed.
[0071] Next, the compound C is a compound that contains both of Co
and Si and another element, and this compound also is small in
contribution to mechanical strength. The difference between the
compounds C and B is that the compound C has a composition, for
example, Co-Si-x, or Co-Si-x-y, in which x and y each represent an
element other than Co and other than Si. Since it is also
preferable, as in the case of the compound B, for the compound C
not to be made into a solid solution in the copper matrix upon the
high temperature solution heat treatment to disappear, the compound
C is one having a melting point higher than the solid solution
temperature (that is, the melting point) of Co.sub.2Si. The average
particle diameter of the compound C is preferably from 50 nm to 500
nm, to exhibit the same effect as the compound B. The average
particle diameter of the compound C is more preferably from 100 nm
to 300 nm.
[0072] There are the cases where the compound B or C is present in
a size of an average particle diameter of 5 nm or more but less
than 50 nm, which is the same as the average particle diameter of
the compound A. In the case of a compound which has an average
particle diameter of 5 nm or more but less than 50 nm and which has
a composition similar to that of the compound B or C, when the
elements, which have been once made into solid solution by a
solution heat treatment, undergo precipitation, the elements
substitute Co, which is a main element, and form compounds with Si,
thereby contributing to enhancement of mechanical strength. For
example, Fe, Ni, and Cr among the additive elements each have a
function of substituting a part of Co in the main precipitate phase
and forming (Co, x).sub.2Si compounds (x=Fe, Ni, or Cr), thereby
enhancing mechanical strength.
[0073] Finally, the compound D is a compound composed only of Co
and Si, and has the same components as those of the compound A.
However, the compound D has a different size, and it also includes
compounds that do not have the composition ratio of Co.sub.2Si (for
example, CoSi, and CoSi.sub.2). The compound D is different from
the compound A in the following point. Since the size of the
compound D is coarse, the time period is not sufficient for the
compound D to be made into a solid solution in the matrix in the
high temperature solution heat treatment of a short time period,
and as a result, the compound D remains in the copper matrix and
exhibits the function of suppressing grain growth. Although this
compound D has an angular shape in many cases, but its particle
size is defined as the average particle diameter.
[0074] Therefore, since the compound D is utilized to exhibit the
same effect as the compound B or C, the average particle diameter
of the compound D is also preferably from 50 nm to 500 nm. The
average particle diameter of the compound D is more preferably from
100 nm to 300 nm.
[0075] The compound B, the compound C, and the compound D are
subjected to a component analysis with an EDS (energy dispersive
spectrometer) attached to a transmission electron microscope (SEM),
and thereby it is determined which compound (precipitate) is which.
Thus, the size of each of the compounds can be measured.
[0076] Further, in the present invention, the grain size of the
copper alloy of the matrix is set within the range of 3 to 35
.mu.m. This is because, when the grain size is 3 .mu.m or more,
recrystallization is sufficient, there is no risk that there could
be mixed grains including unrecrystallization where insufficiently
recrystallized portions are observed, and the bending property is
favorable. Furthermore, when the grain size is 35 .mu.m or less,
the grain boundary density is high, the bending stress (applied
strain) can be sufficiently absorbed, and the bending property is
favorable. The grain size of the copper alloy is preferably from 10
to 30 .mu.m.
[0077] Further, in the present invention, the electrical
conductivity of the material is set to be 50% IACS or more. This
property is obtained, by precipitating an intermetallic compound of
Co.sub.2Si by, for example, adjusting preferably the content of Co
to 0.4 to 2.0 mass % and the content of Si to 0.1 to 0.5 mass
%.
[0078] The reason is described why adjusting the ratio of the
dispersion densities of the compounds preferably to:
0.0001.ltoreq.{(the dispersion density of the compound B+the
dispersion density of the compound C+the dispersion density of the
compound D)/the dispersion density of the compound A}.ltoreq.0.1.
First, the coarse compounds B, C, and D that suppress the grain
boundary movement of the copper alloy of the matrix, may be exist
in two or more kinds of those together with the compound A, but the
ratio of their dispersion densities is preferably 0.0001
.ltoreq.{(the dispersion density of the compound B+the dispersion
density of the compound C+the dispersion density of the compound
D)/the dispersion density of the compound A}.ltoreq.0.1. When the
ratio of dispersion density is within this range, the effect of
suppressing the grain boundary movement is high, and the proportion
of the coarse precipitates (compounds) is small, which do not
contribute to mechanical strength but which suppress movement.
Thus, the purpose of high mechanical strength can be sufficiently
achieved. The ratio of the dispersion density of the respective
compounds is preferably: 0.0001.ltoreq.{(the dispersion density of
the compound B+the dispersion density of the compound C+the
dispersion density of the compound D)/the dispersion density of the
compound A}.ltoreq.0.01, and more preferably: 0.0001.ltoreq.{(the
dispersion density of the compound B+the dispersion density of the
compound C+the dispersion density of the compound D)/the dispersion
density of the compound A}.ltoreq.0.001.
[0079] If the number of compounds B, C, and D (particularly, the
total number of those) is too small, for example, deterioration in
bendability of the resultant copper alloy material may occur due to
grain coarsening, and the like.
[0080] In the copper alloy material of the present invention, as
the number of precipitates of the compound A increases, that is,
the dispersion density of the compound A in the copper alloy
material increases, the mechanical strength is enhanced. Further,
as the number of precipitates of the compound B, C, and D
(particularly, the total number of these) is larger, that is, the
(the dispersion density of the compound B+the dispersion density of
the compound C+the dispersion density of the compound D) in the
copper alloy material is higher, a copper alloy material can be
obtained, which has a favorable bendability, with respect to
mechanical strength enhancement. In regard to the number of these
compounds (and the dispersion density thereof), it is thought that,
generally, the larger the amounts of the additive alloying elements
is, the more the number of resultant compounds is, as long as the
conditions for the solution heat treatment or aging treatment are
appropriately controlled.
[0081] In regard to the amounts of addition of Co and Si in the
copper alloy material of the present invention, the amount of
addition of Co is set at 0.4 to 2.0 mass %, since, when the amount
of addition of Co is 0.4 mass % or more, a desired mechanical
strength can be obtained, and, when the amount of addition of Co is
2.0 mass % or less, the solution heat treatment temperature is
within an appropriate range and no production technique with an
extremely high degree of difficulty is needed. On the other hand,
in regard to Si, since the stoichiometric ratio of Co.sub.2Si,
which is the precipitation strengthening phase of this Cu--Co--Si
alloy, is the ratio Co/Si nearly equals to 4.2, the range of the
amount of addition of
[0082] Si is set according to this ratio. As long as the value of
the ratio Co/Si is 3.5 or more but 4.8 or less, no problem arises
for practical use. When the respective elements of Fe, Ni and Cr
substitute a part of Co in the main precipitate phase to form a
(Co, x).sub.2Si compound (in which x is Fe, Ni, or Cr), the
calculation of the ratio is as follows: the ratio (Co+x)/Si nearly
equals to 4.2 (in which x is Fe, Ni, or Cr). Even in that case,
there is no problem for practical use, as long as the ratio
(Co+x)/Si nearly equals to 3.5 to 4.8.
[0083] The copper alloy material of the present invention may
contain elements other than Co and other than Si.
[0084] Al, Ag, Sn, Zn, Mg, Mn, and In have a feature of being made
into a solid solution in the copper matrix to strengthen the
resultant alloy. When the amount of addition of the elements is
0.05 mass % or more in total, the effect is obtained, and when the
amount of addition is 1.0 mass % or less in total, the electrical
conductivity is not inhibited. A preferred amount of addition is at
least one of these elements in an amount of 0.2 to 0.4 mass % in
total.
[0085] In addition to the above, Zn has an effect of improving
solder adhesiveness, and Mn has an effect of improving hot
workability. Further, the addition of Sn and Mg has an effect of
improving the stress relaxation resistance. Individual addition of
Sn or Mg also provides the effect, but when those two elements are
added, the elements exhibit the effect synergistically. When the
amount of addition is 0.1 mass % or more in total, the effect is
provided, and when the amount of addition is 1.0 mass % or less,
the electrical conductivity is not inhibited, and an electrical
conductivity of 50% IACS or more is secured. On the other hand,
there is also a finding on the ratio of addition of Sn and Mg. When
Sn/Mg.gtoreq.1, excellent results on the stress relaxation
resistance are obtained in many cases. Further, since the
respective elements of Zn, Mn, Sn, and Mg also have the function of
serving as x and y of the compounds B and C, the effect of
suppressing grain boundary movement as the compounds B and C is
exhibited.
[0086] Fe, Cr, Ni, Zr, and Ti are elements that substitute Co to
form compounds with Si, to contribute to enhancement of mechanical
strength. That is, the respective elements of Fe, Ni, Cr, Zr, and
Ti have a function of substituting a part of Co in the main
precipitate phase to form a (Co, z).sub.2Si compound (in which z is
Fe, Ni, Cr, Zr, or Ti), thereby enhancing mechanical strength. With
respect to the amount of addition, when at least one of these
elements is added in an amount of 0.05 mass % or more in total, the
effect is exhibited, and when added in an amount of 1.0 mass % or
less, the elements do not cause crystallization upon casting, or do
not form intermetallic compounds that do not contribute to the
mechanical strength. Since the respective elements of Fe, Cr, Ni,
Zr, and Ti also have a function of serving as x and y of the
compounds B and C, the elements exhibit the effect of suppressing
the grain boundary movement as the compounds B and C. These
elements exhibit almost the same effects when added in combination
with two or more of those, or added singly. A preferred amount of
addition is 0.5 to 0.8 mass % in total for at least one of these
elements.
[0087] Furthermore, even if at least one of the elements of the
group consisting of Al, Ag, Sn, Zn, Mg, Mn, and In and at least one
of the elements of the group consisting of Fe, Cr, Ni, Zr, and Ti
are added in combination, as long as the respective amounts of
addition are within the ranges described above, the properties of
the individual elements will not be inhibited.
[0088] Examples of the unavoidable impurities in the copper alloy
material for electric/electronic parts of the present invention
include H, C, O, S, and the like.
[0089] Next, the copper alloy material of the present invention
will be described from the viewpoint of the production method.
[0090] The copper alloy material of the present invention can be
produced by, for example, the following steps. An outline of the
main production steps for the copper alloy material of the present
invention includes: melting.fwdarw.casting.fwdarw.homogenization
treatment.fwdarw.hot rolling.fwdarw.face milling.fwdarw.cold
rolling.fwdarw.solution heat treatment.fwdarw.aging heat
treatment.fwdarw.final cold-rolling.fwdarw.low-temperature
annealing. The aging heat treatment and the final cold-rolling may
be in a reversed order. Further, the low-temperature annealing
(stress relief annealing) of the final step may be omitted. In
regard to the conditions of the respective steps, the steps can be
carried out in a usual manner, except for the steps especially
mentioned herein.
[0091] In the present invention, the fact that the average cooling
speed from the solid state temperature to 500.degree. C., in the
production of the copper alloy ingot, is 5 to 100.degree. C./sec,
also contributes to the precipitation of the compound B, C, and D
in appropriate sizes and amounts. When this average cooling speed
is from 5 to 100.degree. C./sec, the compounds B, C, and D are
appropriately formed, and as a result, the grain size of the copper
alloy of the matrix can be adjusted to an adequate range. Herein,
the solid state temperature is the temperature at which
solidification is initiated, and since a temperature lower than
500.degree. C. falls in a temperature zone in which the compound A
is precipitated, the lower limit of the temperature range is
determined 500.degree. C.
[0092] If the cooling speed after the casting is too slow, the
mechanical strength may be lowered, owing to an increase of coarse
precipitates.
[0093] The solution heat treatment temperature is preferably, when
the amount of Co is 0.4 to 1.2 mass %, the temperature is
800.degree. C. to 950.degree. C.; when the amount is 1.0 to 1.5
mass %, the temperature is 900.degree. C. to 950.degree. C.; and
when the amount is 1.3 to 2.0 mass %, the temperature is 900 to
1,000.degree. C. Then, solution and recrystallization can be
sufficiently carried out for the respective cases. The grain size
of the copper alloy of the matrix is determined by the heat
treatment at these temperatures. Further, it is preferable to
conduct rapid cooling with the cooling speed of 50.degree. C. /sec
or more from the solution heat treatment temperature. If the rapid
cooling is not conducted, the element solution-heat-treated at the
high temperature may precipitate. The particles (compounds)
precipitated upon this cooling are incoherent precipitates, which
do not contribute to the mechanical strength, and which give an
adverse effect to the characteristics, by contributing as nucleus
forming sites in forming coherent precipitates in the subsequent
aging heat treatment step (or the aging heat treatment step after
the cold rolling step subsequent to the solution heat treatment),
thereby to accelerate precipitation at the sites. The
above-mentioned cooling speed means an average speed from the
solution heat treatment temperature at high temperature to
300.degree. C. At a temperature 300.degree. C. or lower, a
significant change in the texture does not occur, and the cooling
speed to this temperature may be set at a predetermined cooling
speed.
[0094] According to the present invention, after the solution heat
treatment (recrystallization is also carried out, along with the
solution, by this heat treatment), an aging heat treatment is
carried out, to form compounds of Co and Si in the copper alloy.
This heat treatment may also be carried out after the solution heat
treatment, and even after a predetermined cold rolling is carried
out after the solution heat treatment. The conditions for this
aging heat treatment are preferably at a temperature of 500.degree.
C. to 600.degree. C. for 1 to 4 hours, in the case of performing
the aging heat treatment after the solution heat treatment but
before the final cold-rolling; and preferably at a temperature of
450.degree. C. to 550.degree. C. for 1 to 4 hours, in the case of
performing the aging heat treatment after the final cold-rolling
after the solution heat treatment. Further, the cooling speed after
this aging heat treatment has a preferred range. When the cooling
speed is in the range of 20 to 100.degree. C./hour, increase of the
electrical conductivity is sufficiently achieved. If the cooling
speed is faster than 100.degree. C./hour, increase of the
electrical conductivity is not achieved sufficiently; and if the
cooling speed is slower than 20.degree. C./hour, the target changes
in the properties do not occur but only the heat treatment time is
prolonged, which is not economical. On the other hand, the
temperature range associated with the cooling speed is the range of
cooling from the respective heat treatment temperature to
300.degree. C. If the lower limit of the temperature range is
higher than 300.degree. C., the target high electrical conductivity
cannot be obtained; and if the lower limit of the temperature range
is set at a much lower value than 300.degree. C., there is no
change in the obtained electrical conductivity.
[0095] The cooling speed after the aging heat treatment can be
adjusted by controlling the temperature at a heating furnace.
Further, in the case where it is required to conduct a rapid
cooling, the rapid cooling can be conducted by taking out the
subject from a heating zone of the heating furnace and subjecting
the subject to forced air cooling or water quenching.
EXAMPLES
[0096] The present invention will be described in more detail based
on examples given below, but the invention is not meant to be
limited by these.
Example 1
[0097] Alloys (Example Nos. 1 to 35, Comparative Example Nos. 101
to 128) containing elements as shown in Tables 1 and 2, with the
balance of Cu and unavoidable impurities, were melted with a
high-frequency melting furnace, followed by casting at a cooling
speed of 5 to 100.degree. C. /sec, to obtain ingots, respectively,
with thickness 30 mm, width 100 mm, and height 150 mm. At that
time, a thermocouple was placed in the vicinity of the mold wall,
and casting and melting were carried out to obtain the ingots,
while measuring any time.
[0098] The thus-obtained ingots were kept at a temperature from 930
to 1,050.degree. C. for 0.5 to 1.0 hour, followed by hot rolling to
give hot-rolled sheets with sheet thickness t=12 mm, face-milling
each surface in 1 mm in each to thickness t=10 mm, cold rolling to
finish to sheet thickness t=0.3 mm, and subjecting to a solution
heat treatment at a temperature from 700 to 950.degree. C. The
thus-prepared materials were subjected to any one of the following
two processes, to produce test specimens of the final products.
[0099] Process A: (The solution heat treatment)--Aging heat
treatment (at a temperature from 500 to 600.degree. C. for 2 to 4
hours)--Cold working (working ratio: 5 to 25%) [0100] Then,
according to the necessity, strain-relieving annealing was
conducted at a temperature from 300 to 400.degree. C. for 1 to 2
hours.
[0101] Process B: (The solution heat treatment)--Cold rolling
(working ratio: 5 to 25%)--Aging heat treatment (at a temperature
from 450 to 550.degree. C. for 2 to 4 hours)
[0102] The resultant test specimens were evaluated by the following
property testing. The results of Examples are shown in Table 1, and
the results of Comparative Examples are shown in Table 2. In Tables
1 and 2, the expression "E+08" and the like in the items of
compound density represents the power of 10 (e.g. in the case of
"E+08", it means ".times.10.sup.8").
a. Tensile Strength [TS]:
[0103] Three test pieces were cut out from the respective test
specimen (test piece) in the direction parallel to the rolling
direction, according to JIS Z2201-13B, followed by measuring,
according to JIS Z2241, to obtain the average value as shown.
b. Measurement of Electrical Conductivity [EC]:
[0104] With respect to two respective test pieces, the electrical
conductivity was measured in a thermostat controlled at 20.degree.
C. (.+-.1.degree. C.) by using the four-terminal method, to obtain
the average value (% IACS) as shown in Tables 1 to 2. The distance
between the terminals was 100 mm.
c. Bending property:
[0105] Respective test pieces were cut out from the test specimens
in a direction perpendicular to the rolling direction into a size
of width 10 mm and length 35 mm. The resultant test pieces were
subjected to W-bending at 90.degree. (Bad-way bending), with a
bending radius R of 0 to 0.5 (mm), at six levels with interval 0.1
mm, in which the bending axis was set to be parallel to the rolling
direction. Then, the bent portions were observed, to confirm
whether cracks were occurred or not at the bent portion, in which
the observation was made with the naked eye with an optical
microscope with a magnification of 50.times., and with a scanning
electron microscope (SEM). In "R/t" in Table 1, R represents the
bending radius, and t represents the sheet thickness. The smaller
the value is, the more favorable the bending property is.
d. Grain size [GS]:
[0106] After a cross-section perpendicular to the rolling direction
of the respective test specimen (test piece) was finished into a
mirror surface by wet polishing and buff polishing, the
thus-polished surface was corroded with a liquid of: chromic
acid:water=1:1, for several seconds. Then, photographs of the
resultant polished and corroded surface were taken, with a
magnification of 200.times. to 400.times. with an optical
microscope, or with a magnification of 500.times. to 2,000.times.
with a scanning electron microscope (SEM) using a secondary
electronic image by the SEM, to measure a grain size on the
cross-section, according to the cutting method of JIS-H-0501. The
magnification of the photographs was changed depending upon the
size of the grains observed. The term "mixed grain" in the tables
means a texture, in which both of a recrystallized region and an
unrecrystallized region (the state of the rolling worked structure
remained therein) are co-present; and in the case of mixed grain,
no particle size was measured. It is known that if an
unrecrystallized region exists, the bending property of the
resultant alloy is poor. Thus, the mixed grain is an undesirable
texture.
e. Cooling speed after aging heat treatment
[0107] The cooling speed was adjusted by changing the weight of the
material that was subjected to the heat treatment, or adjusted by
controlling the temperature with the heating furnace utilized. By
using the same heating furnace (batch type), for example, to obtain
a faster cooling speed, the amount of simultaneously performing the
heat treatment was decreased, while to obtain a slower cooling
speed, a dummy test piece was placed to increase the amount that
was simultaneously subjected to the heat treatment, and thereby the
respective heat treatments were carried out. Further, when
performing rapid cooling, the sample was taken out from the heating
zone of the heating furnace and was subjected to forced air cooling
or water quenching. The adjustment of the cooling speed was also
carried out, by controlling the temperature in the heating furnace.
In the case where the number of samples was particularly small, or
in the case where the cooling speed was very low, the cooling speed
was adjusted, by controlling the temperature in the heating
furnace.
f. Size, the number, and dispersion density of compound
[0108] The size (average particle size) of the precipitate
(compound) was measured using a transmission electron microscope
(TEM). Since it is difficult to observe the precipitate in the
final product under the influence of working strain, observation
was made with respect to the texture of the material after the
aging heat treatment. A test piece for TEM was cut out from any
site of the heat treated material, followed by electro-polishing
(by a twin jet-type electro-polishing apparatus) at a temperature
in the range of -20 to -25.degree. C. by using a methanol solution
of nitric acid (20%), to obtain a test piece for observation.
[0109] Then, the resultant test piece was observed with an
accelerating voltage of 300 kV, to adjust the incident direction of
an electron beam in the vicinity of (001), and three sheets of
photographs were arbitrarily taken with a magnification of
100,000.times.. Using the photographs, the number of compounds A
(about 100 particles) satisfying the defined size was
determined.
[0110] Further, the compounds B, C, and D were respectively
subjected to a component analysis with an EDS (energy dispersive
spectrometer) attached to a transmission electron microscope, and
then three sheets of photographs were arbitrarily taken with a
magnification of 1,000.times. to 5,000.times.. Using the
photographs, the number of compounds satisfying the defined size
was determined. The number of particles was 10 to 100.
[0111] From these values, the respective dispersion densities
(/mm.sup.2) of the compounds A, B, C, and D were determined. In the
following tables, the dispersion density is simply abbreviated as
density. Further, the "densities of compounds B, C, and D
(/mm.sup.2)" represents the sum of the dispersion densities
(/mm.sup.2) of the compounds B, C and D, and it is needless to say
that if a certain compound(s) is not present, the term density
represents the dispersion density of the remaining compound alone
or the sum of the dispersion densities of the remaining two kinds
of compounds. The term "(B+C+D)/A" is an abbreviation of "{(the
dispersion density of the compound B+the dispersion density of the
compound C+the dispersion density of the compound D)/the dispersion
density of the compound A}".
[0112] (Note) Abbreviations in the following tables not mentioned
in the above are: "Ingot cooling speed" is the cooling speed of the
ingot; "Sol. temp." is the temperature in the solution heat
treatment; "Aging temp." and "Aging time" are the temperature and
the time period in the aging heat treatment, respectively; "Density
Comp. A" is the dispersion density of the compound A; and "Density,
Comp. B, C, D" is the sum total of the dispersion densities of the
compounds B, C, and D (/mm.sup.2, i.e. the number of compounds per
square millimeter).
TABLE-US-00001 TABLE 1 Ingot Density Other cooling Sol. Aging Aging
Density Comp. B, Bending Co Si elements speed temp. Pro- temp. time
GS Comp. A/ C, D/ (B + C + TS EC property No. mass % .degree. C./h
.degree. C. cess .degree. C. h .mu.m mm.sup.2 mm.sup.2 D)/A MPa %
IACS R/t 1 0.51 0.153 Cr = 0.1 28 760 A 530 2 19 3.5E+08 3.2E+05
0.00091 588 69 0 2 0.98 0.266 Sn = 0.1, 32 830 A 555 3 18 7.8E+08
2.1E+05 0.00027 654 70 0.75 Mg = 0.1, Ni = 0.2 3 1.208 0.307 Fe =
0.15, 28 930 B 530 2 20 1.2E+09 2.3E+06 0.00192 701 60 1.5 Zr = 0.1
4 1.887 0.456 Sn = 0.1, 42 950 A 540 2 12 6.2E+09 6.4E+06 0.00103
711 55 1.5 Mg = 0.1, Ni = 0.2 5 0.78 0.177 Sn = 0.15, 81 780 A 540
3 10 4.4E+08 4.0E+06 0.00909 590 71 0 Mg = 0.2 6 0.98 0.231 Sn =
0.2, 27 850 A 565 3 19 3.2E+09 2.9E+06 0.00091 643 69 0.5 7 Fe =
0.3 B 530 3 1.9E+09 1.4E+06 0.00074 639 74 0.5 8 1.193 0.279 Mg =
0.1, 26 950 A 560 3 18 2.9E+08 9.0E+06 0.03103 605 65 0 9 Sn = 0.2
B 510 3 3.4E+09 3.0E+06 0.00088 604 66 0 10 1.575 0.386 Mn = 0.06,
42 950 A 580 2 28 7.4E+09 7.0E+06 0.00095 648 64 0.5 Ti = 0.1 11
1.987 0.491 Zn = 0.2, 37 950 B 530 2 14 9.1E+09 9.2E+06 0.00101 729
53 1 Sn = 0.05 12 0.957 0.229 Fe = 0.25 52 750 A 580 4 13 2.4E+09
2.0E+06 0.00083 590 75 0 13 0.955 0.227 Cr = 0.25, 28 900 A 570 2
13 3.5E+09 3.7E+06 0.00106 665 63 0.75 14 Mn = 0.1 B 530 2 4.5E+09
5.0E+06 0.00111 665 61 1 15 1.175 0.279 27 925 A 580 4 10 7.8E+08
8.8E+05 0.00113 649 64 0.5 16 B 530 4 1.2E+09 1.0E+06 0.00083 653
60 0.75 17 0.92 0.33 Mg = 0.1, 30 880 A 550 2 12 2.2E+09 1.4E+06
0.00064 612 61 0 Ni = 0.5 18 0.95 0.42 Mg = 0.15, 44 870 B 525 2 16
2.4E+08 1.0E+06 0.00417 622 59 0 Ni = 0.8 19 1.4 0.48 Mg = 0.1, 58
945 A 550 2 18 6.2E+09 4.9E+06 0.00079 734 58 1 Ni = 0.5 20 1.38
0.52 Mg = 0.2, 65 950 A 550 2 20 7.9E+09 6.4E+06 0.00081 723 57 1
21 Ni = 0.8 B 525 2 4.9E+08 3.0E+06 0.00612 745 55 1 22 1.432 0.364
Sn = 0.1, 31 950 A 580 2 7 6.7E+09 7.7E+06 0.00115 659 66 0.75 Mg =
0.2 23 1.742 0.444 Cr = 0.4, 63 950 A 530 5 9 7.7E+09 7.8E+06
0.00101 722 53 2 Ni = 0.3 24 0.641 0.152 Zn = 0.5, 63 780 A 545 3 9
3.2E+08 3.0E+05 0.00094 565 73 0 25 Cr = 0.2, B 510 3 1.8E+08
2.0E+06 0.01111 572 75 0.5 Ag = 0.1 26 0.902 0.25 72 800 B 485 4 12
5.2E+08 7.0E+06 0.01346 610 64 0 27 0.887 0.2 Mg = 0.1, 73 810 A
560 2 12 8.7E+08 6.6E+05 0.00076 612 65 0 28 Ni = 0.5, A 4 6.7E+08
2.8E+06 0.00418 565 73 0 29 Sn = 0.2 B 515 2 3.3E+09 2.9E+06
0.00088 565 63 0 30 1.2 0.35 Sn = 0.2, 73 830 A 535 2 17 5.4E+08
4.9E+05 0.00091 675 65 0.5 31 Fe = 0.1, A 5 5.3E+08 3.3E+05 0.00062
671 69 1 32 Al = 0.1 B 485 3 1.8E+09 1.9E+06 0.00106 659 72 1 33
1.45 0.38 Sn = 0.1, 63 850 A 570 2 13 2.2E+08 2.0E+05 0.00091 723
73 1.5 34 Zn = 0.5, B 510 3 2.9E+09 2.8E+06 0.00097 731 66 1.75 Ni
= 0.1 35 1.44 0.35 Mg = 0.1, 34 850 A 565 2 9 8.2E+08 8.9E+05
0.00109 729 53 1.5 Ni = 0.5, Cr = 0.1
TABLE-US-00002 TABLE 2 Ingot Density Other cooling Sol. Aging Aging
Density Comp. B, Bending Co Si elements speed temp. Pro- temp. time
GS Comp. A/ C, D/ (B + C + TS EC property No. mass % .degree. C./h
.degree. C. cess .degree. C. h .mu.m mm.sup.2 mm.sup.2 D)/A MPa %
IACS R/t 101 0.38 0.08 Cr = 0.1 83 770 A 530 3 28 3.3E+07 2.0E+05
0.00606 461 76 0.5 102 2.2 0.52 Zn = 0.5, 44 990 A 540 2 29 4.5E+10
3.3E+09 0.07333 833 48 3.5 Sn = 0.2, Fe = 0.1 103 0.824 0.238 Ni =
0.3 83 1000 A 560 2 55 2.5E+09 6.8E+07 0.02720 687 61 2.5 104 1.02
0.212 Ag = 0.3 63 750 B 550 4 Mixed 3.5E+08 2.0E+06 0.00571 687 63
2.5 grain 105 0.928 0.267 128 900 A 580 3 39 3.7E+08 3.0E+04
0.00008 591 60 2 106 1.4 0.3 152 910 B 510 2 37 3.9E+09 3.0E+04
0.00001 594 65 2 107 0.825 0.233 Fe = 0.2 83 900 A 400 2 33 8.9E+07
2.0E+05 0.00225 436 41 0.5 108 0.928 0.211 Mn = 0.1, 32 920 A 620 4
29 4.2E+03 4.0E+01 0.00952 464 74 0.5 Sn = 0.2 109 1.127 0.284 Cr =
0.1, 41 900 B 530 0.5 33 5.8E+07 5.0E+05 0.00862 457 39 0.75 Mg =
0.3 110 0.854 0.227 Al = 0.2 64 900 A 560 0.5 19 6.2E+07 7.0E+05
0.01129 457 47 0.75 111 0.905 0.205 Ag = 0.05, 53 920 B 530 6 23
9.2E+07 9.7E+06 0.10543 458 67 0 Ni = 0.2 112 1.5 0.4 43 985 A 560
5 34 5.8E+07 1.2E+07 0.20690 454 62 0.25 113 0.507 0.127 Sn = 2.5
73 800 A 560 4 23 3.7E+09 2.5E+06 0.00068 591 36 0.5 114 0.878
0.223 Sn = 1.4, 63 850 A 580 3 19 6.2E+09 6.9E+06 0.00111 678 37
0.5 115 Mg = 1 B 530 2 5.8E+08 5.2E+07 0.08966 581 40 0.75 116 1.62
0.435 Zn = 0.03, 53 950 A 580 2 30 2.5E+09 2.4E+04 0.00001 663 54 2
Cr = 0.03 117 1.905 0.505 Zn = 0.02, 43 950 B 530 3 27 6.3E+09
6.8E+04 0.00001 708 51 2.5 Sn = 0.01 118 0.526 0.162 Fe = 2.4 63
750 A 530 3 Mixed 8.2E+09 8.0E+07 0.00976 614 65 2.5 grain 119
0.928 0.235 Cr = 2.1 64 900 A 580 3 Mixed 2.9E+08 2.3E+06 0.00793
671 49 2.5 120 B 530 1 grain 7.2E+08 2.1E+06 0.00292 591 59 2.5 121
1.206 0.278 Ni = 2.5, 63 900 A 580 4 23 6.7E+08 6.9E+07 0.10299 678
42 1 122 Sn = 0.3 B 530 3 1.9E+08 9.1E+05 0.00479 584 41 1.25 123
1.527 0.393 Cr = 0.05 32 950 A 580 2 17 3.9E+08 9.2E+03 0.00002 649
50 1.5 124 1.301 0.321 Cr = 0.03, 32 950 A 560 4 38 9.4E+09 4.4E+04
0.00000 621 59 1.5 Ni = 0.04 125 0.902 0.22 Sn = 0.1, 3 850 A 555 2
39 7.7E+07 7.9E+07 1.02597 476 54 0.5 126 Mg = 0.1 3 880 B 510 2 44
7.8E+07 8.2E+07 1.05128 488 52 0.5 Sn = 0.15, Mg = 0.2 127 1.307
0.302 Sn = 0.2, 232 Cracks occurred in the re-heating before
hot-rolling, and it was impossible to conduct hot-rolling. 128 Zn =
0.3 183 Cracks occurred in the re-heating before hot-rolling, and
it was impossible to conduct hot-rolling. Mg = 0.3
[0113] As shown in Table 1, each of Examples (inventive examples
according to the present invention) satisfied all of mechanical
strength, electrical conductivity, and bending property, each at a
high level in a well-balanced manner. Specifically, the electrical
conductivity (EC) was 50% IACS or more, and in regard to the
relationship between the tensile strength (TS) and the bending
property (R/t), when TS was 550 MPa or more but less than 650 MPa,
R/t.ltoreq.0.5; when TS was 650 MPa or more but less than 700 MPa,
R/t.ltoreq.1; and when TS was 700 MPa or more but less than 800
MPa, R/t.ltoreq.2, thus, a good balance was achieved, with each of
the properties being at a high level. On the contrary, in
Comparative Examples shown in Table 2, at least any one of the
properties of mechanical strength, electrical conductivity, and
bending property was not practical. Among those, Sample Nos. 101,
107 to 112, and 125 to 126 of Comparative Examples had the tensile
strengths of less than 500 MPa, which did not reach a practical
level.
[0114] Having described our invention as related to the present
embodiments, it is our intention that the invention not be limited
by any of the details of the description, unless otherwise
specified, but rather be construed broadly within its spirit and
scope as set out in the accompanying claims.
[0115] This non-provisional application claims priority under 35
U.S.C. .sctn.119 (a) on Patent Application No. 2008-202467 filed in
Japan on Aug. 5, 2008, which is entirely herein incorporated by
reference.
* * * * *