U.S. patent application number 13/021444 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 | 20110200480 13/021444 |
Document ID | / |
Family ID | 41663648 |
Filed Date | 2011-08-18 |
United States Patent
Application |
20110200480 |
Kind Code |
A1 |
MATSUO; Ryosuke ; et
al. |
August 18, 2011 |
COPPER ALLOY MATERIAL FOR ELECTRIC/ELECTRONIC PARTS
Abstract
A copper alloy material for electric/electronic parts,
containing Co in an amount of 0.7 to 2.5 mass % and Si in an amount
that gives a mass ratio of Co and Si (Co/Si ratio) within the range
from 3.5 to 4.0, with the balance being Cu and unavoidable
impurities, wherein the grain size is 3 to 15 .mu.m.
Inventors: |
MATSUO; Ryosuke; (Tokyo,
JP) ; MIHARA; Kuniteru; (Tokyo, JP) ; EGUCHI;
Tatsuhiko; (Tokyo, JP) |
Assignee: |
THE FURUKAWA ELECTRIC CO.,
LTD.
Tokyo
JP
|
Family ID: |
41663648 |
Appl. No.: |
13/021444 |
Filed: |
February 4, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2009/063614 |
Jul 30, 2009 |
|
|
|
13021444 |
|
|
|
|
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; 420/489; 420/477; 420/485 |
International
Class: |
C22C 9/10 20060101
C22C009/10; C22C 9/01 20060101 C22C009/01; C22C 9/02 20060101
C22C009/02; C22C 9/04 20060101 C22C009/04; C22C 9/06 20060101
C22C009/06 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 5, 2008 |
JP |
2008-202469 |
Claims
1. A copper alloy material for electric/electronic parts,
comprising Co in an amount of 0.7 to 2.5 mass % and Si in an amount
that gives a mass ratio of Co and Si (Co/Si ratio) within the range
from 3.5 to 4.0, with the balance being Cu and unavoidable
impurities, wherein the grain size is 3 to 15 .mu.m.
2. A copper alloy material for electric/electronic parts,
comprising Co in an amount of 0.7 to 2.5 mass %, at least one
selected from the group consisting of Cr, Ni, Fe, Zr, Ti, Al, Sn,
Mg, and Zn in an amount of 0.01 to 0.15 mass %, and Si in an amount
that gives a mass ratio of the total mass of Co and at least one
(X) selected from the group consisting of Cr, Ni, Fe, Zr, and Ti to
Si ((Co+X)/Si ratio) within the range from 3.5 to 4.0, wherein the
grain size is 3 to 15 .mu.m.
Description
TECHNICAL FIELD
[0001] The present invention relates to a copper alloy material for
an electric/electronic part.
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 (C70250), and the
like, have been used for parts for electric/electronic equipments
(specifically, for example, connectors, terminals, relays, and
switches). 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 becomes high,
metallic materials to be used in the parts for electric/electronic
equipments have been required to have a higher electrical
conductivity. So-called Corson-series copper alloys are high in
electrical conductivity, but Cu--Co--Si-based alloys containing Co
and Si are studied, as copper alloys which have an electrical
conductivity higher than that of conventional Corson-series copper
alloys, as well as a high tensile strength and a resistance to
bending (for example, Patent Literatures 1 and 2). [0004] Patent
Literature 1: JP-A-2008-88512 ("JP-A" means unexamined published
Japanese patent application) [0005] Patent Literature 2:
JP-A-2008-56977
DISCLOSURE OF INVENTION
Technical Problem
[0006] While the parts for electronic/electric equipments are
required to have a high degree of resistance to bending, together
with electrical conductivity and tensile strength, it cannot be
said that the Cu--Co--Si-based alloys described in Patent
Literatures 1 and 2 satisfy all of tensile strength, resistance to
bending, and electrical conductivity (thermal conductivity), each
at a high level.
[0007] Patent Literature 1 describes the results of a bending test
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. Patent Literature 2 describes the results of a
bending test in a 90.degree. V-bending test at a bending radius of
0.3 mm.
[0008] However, it is thought that with the level of this extent,
definitely there will be instances where the resulting alloys are
not capable of coping with the resistance to bending demanded in
the future. Thus, it is necessary to develop a copper alloy
material for electric/electronic parts that can pass severe bending
tests.
[0009] The present invention is contemplated for providing a copper
alloy material for electric/electronic parts, which has high
electrical conductivity and high tensile strength, as well as
excellent resistance to bending.
Solution to Problem
[0010] The inventors of the present invention, having studied
keenly, have found that a copper alloy material, which contains
predetermined amounts of Co and Si, with the mass ratio of Co and
Si being in a predetermined range, and which has a grain size in a
predetermined range, has high electrical conductivity and high
tensile strength, and can pass a sever bending test. The present
invention is attained based on this finding.
[0011] According to the present invention, there is provided the
following means:
[0012] (1) A copper alloy material for electric/electronic parts,
comprising Co in an amount of 0.7 to 2.5 mass % and Si in an amount
that gives a mass ratio of Co and Si (Co/Si ratio) within the range
from 3.5 to 4.0, with the balance being Cu and unavoidable
impurities, wherein the grain size is 3 to 15 .mu.m.
[0013] (2) A copper alloy material for electric/electronic parts,
comprising Co in an amount of 0.7 to 2.5 mass %, at least one
selected from the group consisting of Cr, Ni, Fe, Zr, Ti, Al, Sn,
Mg, and Zn in an amount of 0.01 to 0.15 mass %, and Si in an amount
that gives a mass ratio of the total mass of Co and at least one
(X) selected from the group consisting of Cr, Ni, Fe, Zr, and Ti to
Si ((Co+X)/Si ratio) within the range from 3.5 to 4.0, wherein the
grain size is 3 to 15 .mu.m.
Advantageous Effects of Invention
[0014] According to the present invention, a copper alloy material
for electric/electronic parts can be provided, which is excellent
in electrical conductivity and tensile strength, and which passes a
severe bending test.
[0015] Other and further features and advantages of the invention
will appear more fully from the following description.
BEST MODE FOR CARRYING OUT THE INVENTION
[0016] Preferable embodiments of the alloy composition of the
copper alloy material of the present invention for
electric/electronic parts, will be described in detail. Herein, the
term "copper alloy material" means a product obtained after a
copper alloy of a composition is worked into a given shape (for
example, sheet, strip, foil, rod, or wire). 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.
[0017] First, a first copper alloy material for electric/electronic
parts of the present invention will be described.
[0018] In the first copper alloy material for electric/electronic
parts of the present invention, Co and Si are essential elements.
Co and Si in a copper alloy mainly form a precipitate of Co.sub.2Si
intermetallic compound. By adjusting the proportion of this
precipitate to fall in a specific range, it is possible to provide
a copper alloy material for electric/electronic parts high in
tensile strength and electrical conductivity.
[0019] In the copper alloy material for electric/electronic parts
of the present invention, Co is 0.7 to 2.5 mass %, and preferably
0.8 to 2.2 mass %, more preferably 0.9 to 1.7 mass %. When the
amount of Co is within this range, a copper alloy material for
electric/electronic parts high in tensile strength and electrical
conductivity can be obtained.
[0020] In the present invention, if the amount of Co is too small,
a less amount of the precipitate of the Co.sub.2Si intermetallic
compound is formed, and thus a copper alloy material for
electric/electronic parts high in tensile strength and electrical
conductivity cannot be obtained. If the amount of Co is too large,
its effect is saturated. In regard to Si, it is preferable to add
an amount appropriate for Co, so as to maintain the stoichiometric
ratio of the Co.sub.2Si intermetallic compound. If the amount of Si
is inadequate, the same state as in the case where the amount of Co
is inadequate occurs. That is, if the amount of Si is too small, a
less amount of the precipitate of the Co.sub.2Si intermetallic
compound is formed, and a copper alloy material for
electric/electronic parts high in tensile strength and electrical
conductivity cannot be obtained. If the amount of Si is too large,
its effect is saturated.
[0021] Based on the stoichiometric ratio of the Co.sub.2Si
intermetallic compound, an optimal mass ratio of Co to Si (Co/Si)
is that Co/Si nearly equals to 4.2. In the copper alloy material of
the present invention, the mass ratio of Co to Si (Co/Si) is
adjusted to be within the range from 3.5 to 4.0. Preferably, the
value of Co/Si, in terms of mass ratio, is within the range from
3.70 to 3.95. When the mass ratio of Co and Si (Co/Si ratio) is
adjusted to be within this range, a copper alloy material for
electric/electronic parts which is excellent in both tensile
strength and bending, can be obtained. If the mass ratio of Co and
Si (Co/Si ratio) is too small, Si is in excess, and therefore, a
part of Si that does not form an intermetallic compound with Co is
made into a solid solution, thereby lowering the electrical
conductivity. If the mass ratio of Co and Si (Co/Si ratio) is too
large, Co is in excess, and therefore, a part of Co that does not
form an intermetallic compound with Si is made into a solid
solution, thereby lowering the electrical conductivity.
[0022] When the amount of Co and the amount of Si exceed
predetermined amounts, an alloy material cannot be obtained if the
solution treatment temperature is not raised. Accordingly, if a
heat treatment is carried out at a temperature higher than the
solution treatment temperature usually employed (about
1,000.degree. C.), there occur problems, such as that the product
shape cannot be maintained.
[0023] In the first copper alloy material for electric/electronic
parts of the present invention, the amount of Si is determined so
that the mass ratio of Co to Si (Co/Si) would be within the range
from 3.5 to 4.0, and it is preferable to adjust the amount of Si to
0.2 to 0.7 mass %.
[0024] Next, a second copper alloy material of the present
invention will be described.
[0025] The second copper alloy material of the present invention
contains Co in an amount of 0.7 to 2.5 mass %, and at least one
selected from the group consisting of Cr, Ni, Fe, Zr, Ti, Al, Sn,
Mg, and Zn in an amount of 0.01 to 0.15 mass %, with the balance
being Cu and unavoidable impurities, while the copper alloy
material contains Si in an amount that gives a mass ratio of the
total mass of Co and at least one (X) selected from the group
consisting of Cr, Ni, Fe, Zr, and Ti to Si ((Co+X)/Si ratio) within
the range from 3.5 to 4.0.
[0026] The amount to be added of at least one selected from the
group consisting of Cr, Ni, Fe, Zr, Ti, Al, Sn, Mg, and Zn is
preferably 0.05 to 0.15 mass %. If the amount of addition is too
small, the effect of addition is small. If the amount of addition
is too large, the mechanical strength is lowered, and at the same
time, as the added elements are made into solid solution, the
electrical conductivity is lowered.
[0027] Cr, Ni, Fe, Zr, and Ti form precipitates together with both
or one of Co and Si, or by themselves singly, and bring an effect
of making the grain size finer. At least one (X) selected from the
group consisting of Cr, Ni, Fe, Zr, and Ti has a function of
substituting a part of Co, to form a (Co, X).sub.2Si compound, to
enhance mechanical strength.
[0028] On the other hand, AI, Sn, Mg, and Zn have a feature of
being made into a solid solution in the copper matrix, to
strengthen the resultant alloy. When made into a solid solution,
Al, Sn, Mg, and Zn strengthen the alloy material or bring an
improvement in resistance to stress relaxation. Furthermore, when
both of Sn and Mg are added, the resistance to stress relaxation is
improved synergistically. When the ratio of addition of Sn and Mg
is set at Sn/Mg.gtoreq.1, the stress relaxation resistance is
further improved.
[0029] In the second copper alloy material of the present
invention, the mass ratio of the total mass of Co and at least one
(X) selected from the group consisting of Cr, Ni, Fe, Zr, and Ti to
Si ((Co+X)/Si ratio) is from 3.5 to 4.0. Preferably, the value of
the (Co+X)/Si ratio is, in terms of mass ratio, within the range
from 3.70 to 3.95. When the (Co+X)/Si ratio is adjusted to be
within this range, a copper alloy material for electric/electronic
parts which is excellent in both tensile strength and bending, can
be obtained. If the (Co+X)/Si ratio is too small, Si is in excess,
and therefore, a part of Si that does not form an intermetallic
compound with Co and X is made into a solid solution, thereby
lowering the electrical conductivity. If the (Co+X)/Si ratio is too
large, Co or X is in excess, and therefore, a part of Co or X that
does not form an intermetallic compound with Si is made into a
solid solution, thereby lowering the electrical conductivity.
[0030] In the second copper alloy material for electric/electronic
parts of the present invention, the amount of Si is determined so
that the mass ratio of the sum of Co and the at least one (X)
selected from the group consisting of Cr, Ni, Fe, Zr, and Ti to Si
((Co+X)/Si ratio) would be within the range from 3.5 to 4.0, and it
is preferable to adjust the amount of Si to 0.2 to 0.7 mass %.
[0031] In the first and second copper alloy materials of the
present invention, if the content of elements, such as H, O, and S,
as unavoidable impurities is less than 5 ppm mass %, the copper
alloy material for electric/electronic parts can be obtained
without impairing the purport of the present invention.
[0032] It is important to have a grain size of 3 to 15 .mu.m in the
copper alloy material of the present invention. According to the
present invention, the grain size means a value measured by JIS H
0501 (cutting method). When the grain size is adjusted to be within
the range of 3 to 15 .mu.m, it is possible to obtain a copper alloy
material for electric/electronic parts excellent in resistance to
bending. When the grain size is less than 3 .mu.m, the remaining
worked structure is confirmed, which has an adverse effect on the
resistance to bending. On the other hand, when the grain size is
coarser than 15 .mu.m, significant bending or cracks occurs in the
grain boundary, and as a result, the resultant resistance to
bending is lowered. The grain size is preferably 4 to 10 .mu.m. In
order to adjust the grain size to 3 to 15 such a grain size can be
realized, for example, by controlling the amounts of addition of
elements, such as Co and Si, each within a specific range;
controlling the ranges of the heat treatment conditions and rolling
conditions in the respective steps to be carried out till the final
recrystallization heat treatment, each within a specific range; or
controlling the thermal history control conditions (a speed of
temperature raising, and retention temperature and time period) of
the recrystallization heat treatment, within a specific range.
[0033] There is a preferable range in a relationship between the
amount to be added of Co and the temperature at which the
recrystallization heat treatment is carried out. For example, when
the amount to be added of Co is 0.7 to 1.0 mass %, the temperature
at which the recrystallization heat treatment is carried out is
preferable to be within a range of 850 to 900.degree. C.; and when
the amount to be added of Co is 1.0 to 2.5 mass %, the temperature
at which the recrystallization heat treatment is carried out is
preferable to be within a range of 900 to 1,025.degree. C. The
upper limit temperature is more preferably 1,000.degree. C. When
the recrystallization heat treatment is carried out within this
temperature range, the recrystallization heat treatment can be
carried out surely, and deformation of the alloy material can be
prevented.
[0034] Next, a preferable method for producing the copper alloy
material of the invention is exemplified, for example, in the
following embodiment. An outline of the main production steps for
the copper alloy material of the present invention includes:
melting.fwdarw.casting.fwdarw.hot rolling.fwdarw.face
milling.fwdarw.cold rolling.fwdarw.solution and recrystallization
heat treatment.fwdarw.rapid cooling.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 of
the final step may be omitted.
<Melt-Casting>
[0035] A copper alloy ingot is obtained, by melting Cu, Co, Si, and
the like, which are the raw materials of the target copper alloy,
followed by pouring the resultant melt into a mold, and casting
under cooling at a cooling speed from 10 to 30 K/sec (K is for
"Kelvin" which represents the absolute temperature; hereinafter,
the same). Herein, the following description will be made with an
ingot of a size: width 160 mm, thickness 30 mm, and length 180
mm.
<Hot Rolling/Face-Milling/Cold Rolling>
[0036] Then, the resultant ingot is kept at a temperature of 900 to
1,000.degree. C. for 30 to 60 min, followed by working by hot
rolling to thickness 8 to 15 mm (a rolling reduction 50 to 73%),
quenching by water cooling (rapid cooling) immediately,
face-milling the rolled surface by approximately 1 mm for each
side, to remove an oxide layer on the surface, and working by cold
rolling to thickness about 0.1 to 0.3 mm. The rolling reduction is
set to be 95% or more (preferably, 99.5% or less).
<Recrystallization Heat Treatment>
[0037] Then, to cause solution and recrystallization, a
recrystallization heat treatment is carried out for a given time
period (e.g. for 30 sec) in a salt bath (salt bath furnace) kept at
a temperature of 800 to 1,025.degree. C., followed by quenching by
water cooling. In the recrystallization heat treatment, the heat
treatment is carried out by adjusting the temperature raising speed
by interposing the subject between stainless steel plates different
in plate thickness. A preferable temperature raising speed in this
occasion is 10 to 300 K/sec at a temperature of 300.degree. C. or
higher. Further, a preferable cooling speed is 30 to 200 K/sec.
<Aging Heat Treatment>
[0038] Then, for the purpose to cause aging precipitation, an aging
heat treatment is carried out at a temperature from 400 to
600.degree. C. for 30 to 300 min. The temperature raising speed
from room temperature to the highest temperature in that occasion
is within the range from 3 to 25 K/min. With regard to temperature
lowering, cooling is carried out inside the furnace at a speed
within the range from 1 to 2 K/min until the temperature reaches
300.degree. C., which is a temperature sufficiently lower than the
temperature zone considered to affect the precipitation.
<Finish Rolling>
[0039] The copper alloy material, to which the aging heat treatment
has been completed for subjecting, is further subjected to a cold
rolling at a working ratio of 20%, and thus a finish
rolled-material is obtained. The finish rolling can be omitted.
<Strain-Relieving Annealing>
[0040] After the completion of the aging heat treatment (in the
case of conducting the finish rolling, after the completion of the
finish rolling), the copper alloy material is subjected to
strain-relieving annealing, according to the necessity.
[0041] The bending property can be evaluated by perpendicular
bending (R/t=0) in a 90.degree. W bending test, under the
conditions of a yield stress (YS) value of 600 MPa or more and an
electrical conductivity of 60% IACS or more. 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. The "R/t" can be determined, 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, the smaller the value of R/t
is, the more satisfactory the resistance to bending is.
[0042] The copper alloy material of the present invention is
excellent in the electrical conductivity and the tensile strength,
and can pass a bending test under sever conditions.
EXAMPLES
[0043] 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 Nos. 1 to 13 and Comparative Example Nos. 14 to 40
[0044] Alloys containing elements as shown in Table 1, with the
balance being Cu and unavoidable impurities, were melted with a
high-frequency melting furnace, followed by casting at a cooling
speed of 10 to 30 K/sec, to obtain ingots, respectively, with width
160 mm, thickness 30 mm, and height 180 mm. The cooling speed was
set under the conditions which would not cause any cracks or the
like in the ingot.
[0045] The thus-obtained ingots were kept at a temperature of
1,000.degree. C. for 30 min, followed by hot rolling to give
hot-rolled sheets with thickness t=12 mm.
[0046] Then, each of the surfaces of the hot-rolled sheets were
face-milled by 1 mm in each side, to thickness t=10 mm, followed by
cold rolling to finish to sheet thickness t=0.25 mm. Then, the
resultant sheets were subjected to a recrystallization heat
treatment at a temperature from 870 to 1,000.degree. C.
[0047] The recrystallization heat treatment was carried out by
raising the temperature in a manner dependent on how large the
amount to be added of Co was. Specifically, when the amount to be
added of Co was 0.9 mass %, the temperature was 870.degree. C.;
when the amount to be added of Co was 1.2 mass %, the temperature
was 915.degree. C.; when the amount to be added of Co was 1.4 mass
%, the temperature was 940.degree. C.; when the amount to be added
of Co was 1.65 mass %, the temperature was 965.degree. C.; when the
amount to be added of Co was 1.9 mass %, the temperature was
980.degree. C.; and when the amount to be added of Co was 2.4 mass
%, the temperature was 1,000.degree. C. Furthermore, also in the
case where additives other than Co and other than Si were contained
(Alloys Nos. 4, and 7 to 11), the temperature for the
recrystallization heat treatment was set in the same manner as in
the case where additives other than Co and other than Si were not
contained. In regard to Comparative Example Nos. 37 to 40, the
temperature of the recrystallization heat treatment was set at
940.degree. C., 1,050.degree. C., 775.degree. C., and 790.degree.
C., respectively, to change the grain size.
[0048] Then, the thus-prepared materials after the
recrystallization heat treatment were subjected to the following
process, to produce test specimens which correspond to the final
products. The sheet thickness of the test specimens was set to
t=0.2 mm.
[0049] Process: Recrystallization heat treatment--Aging heat
treatment (at a temperature of 525.degree. C. for 2 hours)--Cold
working (20%)
[0050] Measurement of the following items was carried out with
respect to those test specimens. The composition table and grain
size of the copper alloys are shown in Table 1, and the evaluation
results on the tensile strength and bending properties of the
copper alloy materials are shown in Table 2.
a. Grain size (GS):
[0051] After a cross-section perpendicular to the rolling direction
of the respective 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 H0501. Then, the measurement parameter was set at 200, and the
arithmetic mean was determined. This value was designated as the
arithmetic mean of the grain size. The results are shown in Table
1.
b. Yield Stress (YS):
[0052] Two test pieces of JIS Z2201 No. 5, which were cut in
parallel to the rolling direction of the respective test specimen,
were measured according to JIS Z2241, to determine the average
value. According to an offset method, the proof strength in the
case where the permanent elongation was 0.2%, was calculated from
formula (I), as the yield stress. The results are shown in Table
2.
.sigma..sub.0.2=F.sub.0.2/A.sub.0 formula (1)
[0053] In the formula,
[0054] .sigma. represents a proof stress (N/mm.sup.2) calculated by
the offset method; and
[0055] F represents a force, which was determined, by obtaining a
relationship curve diagram between a force and the resultant
elongation, with using an elongation meter, drawing a line parallel
to the straight line portion of the early stage of the test, from
the point on the axis of elongation corresponding to the
predetermined permanent elongation (.epsilon.%), and determining
the force shown at the point at which the parallel line intersects
the curve diagram.
c. Electrical Conductivity (EC):
[0056] 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 Table 2. The distance
between the terminals was 100 mm.
d. Bending Property A:
(1) W Bending
[0057] A test piece of sheet thickness t=0.20 (mm), sheet width
w=10 (mm),
[0058] and length I=35 (mm) was cut from the respective test
specimens, according to JIS Z2248, and the surface of the test
piece was lightly polished with metallic polishing powders, to
remove an oxide layer. Then, 90.degree. W bending in which an inner
radius of bending would be R=0 mm, was performed in two directions
of: bending parallel to the rolling direction (Good-way bending:
hereinafter, "GW bending"); and bending perpendicular to the
rolling direction (Bad-way bending: hereinafter, "BW bending"). The
value of R/t at this time was 0.
(2) 180.degree. Bending
[0059] In the same manner as in the W bending, 180.degree. bending
was performed, except for placing an object twice the given inner
radius (herein, R=0.1 mm) according to JIS Z2248, and pushing the
two ends of the test piece one another. The same evaluation as in
the 90.degree. W bending was performed. The value of R/t at this
time was R/t=(0.1/0.2)=0.5, based on R=0.1 (mm) and t=0.2 (mm).
(3) Evaluation of Whether Cracks Occurred or not in the Bent
Portion
[0060] 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). For both of the 90.degree. W bending and 180.degree.
bending, if there were no cracks on the surface of the test piece
in at least one of the GW bending and the BW bending, the specimen
was judged to be ".smallcircle. (good)"; and if cracks were
observed in both of the bending tests, the specimen was judged to
be "x (poor)". Further, for any one of the 90.degree. W bending and
180.degree. bending, if cracks occurred in both of the GW bending
and BW bending, the overall judgment was "x (poor)". The results
are shown in Tables 1 and 2.
e. Bending Property B
[0061] The test was performed according to the W bending test
specified in JIS Z2248, using a strip-shape sample of width 10 mm.
The bending direction was set at the Good Way and the Bad Way,
respectively, and the bending radius R/sheet thickness t was set to
1.0. For the test piece after bending, whether cracks occurred or
not, was observed with an optical microscope, on the surface and
cross-section of the bent portion. If no cracks occurred in both of
the Good Way and the Bad Way, the sample was judged to be
".smallcircle. (good)"; and if cracks occurred in both or one of
the Good Way and the Bad Way, the sample was judged to be "x
(poor)". The results are shown in Table 2.
TABLE-US-00001 TABLE 1 Elements I to be added (Co + X)/Si Alloy Co
Si Elements II in which X = GS No. mass % mass % Co/Si to be added
Cr, Ni, Fe, Zr, Ti .mu.m Example 1 0.91 0.26 3.50 -- -- 11
according 2 0.91 0.24 3.79 -- -- 12 to 3 0.90 0.23 3.91 -- -- 13
this 4 1.21 0.34 -- Ni: 0.1 mass % 3.85 12 invention 5 1.22 0.31
3.94 -- -- 13 6 1.41 0.38 3.71 -- -- 14 7 1.65 0.44 3.75 Mg: 0.1
mass % -- 12 8 0.90 0.26 -- Cr: 0.1 mass % 3.85 7 9 1.40 0.40 --
Cr: 0.1 mass % 3.75 8 10 0.90 0.28 -- Ti: 0.15 mass % 3.75 10 11
1.40 0.40 -- Zr: 0.05 mass % 3.63 13 12 2.40 0.62 3.87 -- -- 5 13
0.85 0.23 3.70 -- -- 15 Comparative 14 0.90 0.19 4.74 -- -- 22
example 15 1.40 0.32 4.38 -- -- 20 16 1.65 0.36 4.58 -- -- 23 17
1.91 0.41 4.66 -- -- 18 18 0.90 0.16 5.63 -- -- 17 19 0.91 0.31
2.94 -- -- 14 20 1.21 0.22 5.50 -- -- 25 21 1.20 0.40 3.00 -- -- 12
22 1.42 0.28 5.07 -- -- 24 23 1.40 0.52 2.69 -- -- 14 24 1.65 0.33
5.00 -- -- 22 25 1.64 0.62 2.65 -- -- 13 26 1.89 0.36 5.25 -- -- 24
27 1.90 0.65 2.92 -- -- 12 28 0.60 0.16 3.75 -- -- 42 29 3.00 0.80
3.75 -- -- 4 30 0.32 0.08 4.00 -- -- 60 31 4.20 1.15 3.65 -- --
Un-recrystallized (<3 .mu.m) 32 0.90 0.19 -- Cr: 0.2 mass % 5.79
8 33 0.90 0.55 -- Cr: 0.1 mass % 1.82 6 34 1.40 0.30 -- Cr: 0.2
mass % 5.33 6 35 1.40 0.90 -- Cr: 0.1 mass % 1.67 6 36 1.40 0.82 --
Cr: 0.5 mass % 2.32 6 37 0.91 0.26 3.50 -- -- 35 38 1.41 0.38 3.71
-- -- 50 39 0.91 0.26 3.50 -- -- Un-recrystallized (<3 .mu.m) 40
1.41 0.38 3.71 -- -- Un-recrystallized (<3 .mu.m)
TABLE-US-00002 TABLE 2 Alloy YS EC Bending Bending No. MPa % IACS
property A property B Example 1 622 66 .smallcircle. .smallcircle.
according to 2 619 66 .smallcircle. .smallcircle. this 3 615 67
.smallcircle. .smallcircle. invention 4 665 64 .smallcircle.
.smallcircle. 5 660 64 .smallcircle. .smallcircle. 6 674 63
.smallcircle. .smallcircle. 7 682 61 .smallcircle. .smallcircle. 8
645 63 .smallcircle. .smallcircle. 9 691 62 .smallcircle.
.smallcircle. 10 632 65 .smallcircle. .smallcircle. 11 683 60
.smallcircle. .smallcircle. 12 695 60 .smallcircle. .smallcircle.
13 602 68 .smallcircle. .smallcircle. Comparative 14 589 66 x
.smallcircle. example 15 643 64 x .smallcircle. 16 652 63 x
.smallcircle. 17 664 62 x .smallcircle. 18 671 61 x .smallcircle.
19 538 55 .smallcircle. .smallcircle. 20 567 58 x .smallcircle. 21
542 52 .smallcircle. .smallcircle. 22 573 52 x .smallcircle. 23 552
51 .smallcircle. .smallcircle. 24 565 53 x .smallcircle. 25 567 49
.smallcircle. .smallcircle. 26 555 51 x .smallcircle. 27 577 47
.smallcircle. .smallcircle. 28 515 71 x .smallcircle. 29 692 52
.smallcircle. .smallcircle. 30 488 72 .smallcircle. .smallcircle.
31 695 51 x .smallcircle. 32 588 56 .smallcircle. .smallcircle. 33
562 48 .smallcircle. .smallcircle. 34 594 60 .smallcircle.
.smallcircle. 35 615 52 .smallcircle. .smallcircle. 36 577 52
.smallcircle. .smallcircle. 37 525 61 x .smallcircle. 38 607 58 x
.smallcircle. 39 489 66 x .smallcircle. 40 565 62 x
.smallcircle.
[0062] As shown in Tables 1 and 2, Examples according to the
present invention each exhibited a high electrical conductivity,
with the electrical conductivity being 60% IACS or more, and a
yield stress (YS) of 600 MPa or more. Further, Examples exhibited
excellent results even under the severe bending test conditions, in
which the value of R/t in the 90.degree. bending was 0, and the
value of R/t in the 180.degree. bending was 0.5 or less. On the
contrary, Comparative Examples each did not pass in one or more of
the following points: the electrical conductivity was less than 60%
IACS; the yield stress (YS) was less than 600 MPa; the value of R/t
in the 90.degree. bending did not satisfy 0; and the value of R/t
in the 180.degree. bending did not satisfy 0.5 or less. Further, as
in the cases of Alloy Nos. 15 to 18, some alloys exhibited a high
electrical conductivity such as an electrical conductivity of 60%
IACS or more, and a yield stress (YS) of 600 MPa or more; however,
although those alloys passed the W bending test with R/t=1.0, they
failed to pass the W bending test with the value of R/t being 0, or
the 180.degree. bending with the value of R/t being 0.5.
[0063] 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.
[0064] This non-provisional application claims priority under 35
U.S.C. .sctn.119 (a) on Patent Application No. 2008-202469 filed in
Japan on Aug. 5, 2008, which is entirely herein incorporated by
reference.
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