U.S. patent application number 09/894126 was filed with the patent office on 2001-12-13 for high strength clad material with excellent molding properties.
Invention is credited to Ishio, Masaaki.
Application Number | 20010051283 09/894126 |
Document ID | / |
Family ID | 27617204 |
Filed Date | 2001-12-13 |
United States Patent
Application |
20010051283 |
Kind Code |
A1 |
Ishio, Masaaki |
December 13, 2001 |
High strength clad material with excellent molding properties
Abstract
An object of the present invention is to provide a three-layer
clad material in which stainless steel is used as the substrate, Ni
or an Ni alloy is monolithically pressure-welded to either
principal plane of the substrate, and Cu is monolithically
pressure-welded to the other principal plane, or a two- or
three-layer clad material in which Ni or an Ni alloy is
monolithically pressure-welded to at least one principal plane of
the substrate, wherein this high-strength, high-drawability clad
material allows the thickness ratio of the stainless steel to be
further increased, mechanical strength (tensile strength) to be
raised above that of a conventional two- or three-layer clad
material, and the thickness of the entire clad material to be
reduced. Uniform tension can be created across the entire thin
sheet, folding or creasing can be prevented from occurring during
pressure welding, the thickness of the thin Ni and Cu sheets prior
to pressure welding can be reduced to about 5 .mu.m, and the
thickness ratio of each of the thin sheets in the three-layer clad
material for cell cases can be reduced to about 0.5% of the entire
thickness by adopting a method in which specially configured and
sized tension bridle rolls are placed upstream of pressure rolls,
and Ni, Cu, and other thin sheets are fed to the pressure rolls
through the agency of these tension bridle rolls.
Inventors: |
Ishio, Masaaki; (Osaka,
JP) |
Correspondence
Address: |
DYKEMA GOSSETT PLLC
FRANKLIN SQUARE, THIRD FLOOR WEST
1300 I STREET, NW
WASHINGTON
DC
20005
US
|
Family ID: |
27617204 |
Appl. No.: |
09/894126 |
Filed: |
June 29, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09894126 |
Jun 29, 2001 |
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09463620 |
Jan 28, 2000 |
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09463620 |
Jan 28, 2000 |
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PCT/JP98/01760 |
Apr 17, 1998 |
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Current U.S.
Class: |
428/680 ;
428/685 |
Current CPC
Class: |
B32B 15/015 20130101;
C23C 30/00 20130101; Y10S 428/925 20130101; B23K 20/023 20130101;
Y10S 428/924 20130101; Y10T 428/12979 20150115; Y10T 428/12944
20150115; B23K 2101/06 20180801; B23K 20/227 20130101; Y10S 428/94
20130101 |
Class at
Publication: |
428/680 ;
428/685 |
International
Class: |
B32B 015/18 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 31, 1997 |
JP |
9-220826 |
Mar 13, 1998 |
JP |
10-82667 |
Claims
1. A high-strength, high-drawability clad material, comprising
stainless steel as a substrate; Ni or an Ni alloy monolithically
pressure-welded to either principal plane of said substrate; and Cu
monolithically pressure-welded to the other principal plane, said
stainless steel having a thickness greater than 92% but no more
than 99% of the total thickness of the clad material, and said clad
material having a tensile strength of 70 kgf/mm.sup.2 or
higher.
2. A high-strength, high-drawability clad material as defined in
claim 1, comprising a plating composed of Sn, Sn-Pb, or In on the
Cu surface.
3. A high-strength, high-drawability clad material as defined in
claim 1 or 2, having a total thickness of 0.05 mm to 0.100 mm.
4. A high-strength, high-drawability clad material as defined in
claim 1, 2, or 3, said material designed for constructing the anode
case of a cell.
5. A high-strength, high-drawability clad material, comprising
stainless steel as a substrate; and Ni or an Ni alloy
monolithically pressure-welded to either principal plane of said
substrate, said stainless steel having a thickness greater than 98%
but no more than 99.5% of the total thickness of the clad
material.
6. A high-strength, high-drawability clad material, comprising
stainless steel as a substrate; and Ni or an Ni alloy
monolithically pressure-welded to both principal planes of said
substrate, said stainless steel having a thickness greater than 96%
but no more than 99% of the total thickness of the clad
material.
7. A high-strength, high-drawability clad material as defined in
claim 5 or 6, having a total thickness of 0.05 mm to 0.100 mm.
8. A high-strength, high-drawability clad material as defined in
claim 5, 6, or 7, said material designed for constructing the
cathode case of a cell.
Description
TECHNICAL FIELD
[0001] The present invention relates to a thin, high-strength clad
material that has a tensile strength of 70 kgf/mm.sup.2 or higher,
possesses excellent press forming, and can be deep-drawn by
performing prescribed plating; and more particularly to a
three-layer clad material which can be used, in particular, as a
clad material for forming the anode case of a button cell or the
like and in which stainless steel is used as the substrate, Ni or
an Ni alloy is monolithically pressure-welded to either principal
plane of the substrate, and Cu is monolithically pressure-welded to
the other principal plane; and to a two- or three-layer clad
material which can be used as a clad material for forming a cathode
case and in which stainless steel is used as the substrate, and Ni
or an Ni alloy is monolithically pressure-welded to at least one
principal plane of the substrate.
BACKGROUND ART
[0002] Efforts to create smaller and lighter devices have recently
intensified in the field of electric equipment, creating an urgent
need for developing smaller and thinner cells for use with this
equipment. For example, coin cells, button cells, and other cells
are being widely used.
[0003] Cases for such cells are required to have adequate corrosion
resistance, electrical conductivity, and deep drawability. Examples
of materials used for anode cases include so-called three-layer
clad materials in which stainless steel is used as the substrate,
Ni is integrated with one principal plane of this substrate, and Cu
is integrated with the other principal plane. In addition,
so-called two- or three-layer clad materials in which stainless
steel is used as the substrate, and Ni is integrated with one or
both principal planes of this substrate are used for cathode
cases.
[0004] With such button cells, battery life is determined by the
amount of electrochemical reagent stored in the case, requiring
that the capacity of the case be increased in order to extend
battery life.
[0005] Some applications, however, impose restrictions on the
outside dimensions of cells, forcing researchers to increase the
actual case capacity by using thinner cases. It was impossible,
however, to obtain case materials that would satisfy these
requirements in terms of maintaining the mechanical strength of
cases per se, preventing electrochemical reagents from leaking, or
the like, making the aforementioned goal unattainable.
[0006] As a means of overcoming such shortcomings, it has been
proposed to create button cells in which, in particular, the case
capacity for accommodating electrochemical reagents is
substantially increased by using as an anode case a three-layer
clad material in which stainless steel is used as the substrate, Ni
is integrated with one principal plane of the substrate, and Cu is
integrated with the other principal plane, and setting the weight
ratio of the stainless steel in the three-layer clad material to
between 77% and 91% of the total amount of clad material
(corresponds to a thickness ratio of 79% to 92%); and by using as a
cathode case a three-layer clad material in which stainless steel
is used as the substrate, Ni is integrated with both principal
plane of the substrate, and the temper number of this three-layer
clad material is set to a prescribed level (3.5) (Japanese
Unexamined Patent Application (Kokai) 8-315869; U.S. Pat. Nos.
5,567,538, 5,582,930, and 5,591,541).
[0007] In such button cells, strength per unit of thickness of the
clad material can be increased and the thickness reduced while the
molding properties needed to form an anode case by pressing or the
like can be maintained by increasing the ratio of the stainless
steel constituting the substrate of the three-layer clad material
that forms the anode case; and the capacity of the anode case can
be increased while the strength, stiffness, and crushing resistance
required for an anode case are maintained.
[0008] Although button cells constructed using anode cases and
cathode cases composed of the above-described three-layer clad
materials have much longer cell lives than conventional button
cells, a need exists for a further increase in battery life and a
creation of smaller and lighter cells, and further improvements in
three-layer clad materials are desired. At present, however, it is
difficult to achieve further increases in the weight ratio
(thickness ratio) of the stainless steel constituting the
aforementioned substrate.
[0009] A structure in which the Ni, Cu, or the like integrated with
the principal planes of the stainless steel constituting the
substrate is formed by plating is disclosed for the proposed anode
case and cathode case described above.
[0010] In commercial-scale production, however, cold welding is
commonly used to achieve fabrication because of considerations
related to productivity, the costs incurred in handling plating
equipment or plating solutions, and the like. Specifically, thin Ni
or Cu sheets of prescribed thickness are superposed on the
principal planes of stainless steel (substrate), and the sheets are
pressure-welded and integrated at the same time with the aid of
pressure rolls, rolling a three-layer clad material of prescribed
thickness.
[0011] The creasing or the like of the thin Ni or Cu sheets during
pressure welding is prevented by applying a specific amount of
tension in the direction upstream of the pressure rolls with the
aid of the rolls or other components for feeding these thin sheets,
but these thin sheets commonly have a width of about 100 mm to 600
mm and a thickness of about 0.1 mm to 1.0 mm when produced on a
commercial scale, so it is difficult to apply uniform tension
across the entire thin sheet at a lower sheet thickness.
[0012] Consequently, the thin Ni and Cu sheets produce folds and
creases when welded under pressure to stainless steel (substrate),
ultimately creating surface defects and resulting in inadequate
bonding with the substrate. It is therefore impossible to reduce
the thickness of a thin Ni or Cu sheet below a certain limit, and,
as a result, it is difficult to increase the weight ratio
(thickness ratio) of stainless steel in the entire clad material
above a certain level.
[0013] With an anode case, for example, the total thickness of the
clad material is commonly required to be 0.30 mm or less.
Conventional methods are therefore capable of ensuring that the
weight ratio of Ni in relation to the total amount of clad material
is 2% (thickness ratio: 2%), but are less successful in ensuring,
in particular, that the weight ratio of Cu in relation to the total
amount of clad material is less than 7% (less than 6% in terms of
thickness ratio) and, ultimately, that the weight ratio of the
combined amount of Ni and Cu in relation to the total amount of
clad material is less than 9% (less than 8% in terms of thickness
ratio).
[0014] It was thus assumed that the weight ratio (thickness ratio)
of stainless steel (substrate) had insurmountable limitations and
that it was difficult to increase battery life beyond that of a
button cell having the above-described proposed structure, that is,
a button cell in which the weight ratio of stainless steel was 77%
to 91% (corresponds to a thickness ratio of 79% to 92%) of the
total amount of clad material.
DISCLOSURE OF THE INVENTION
[0015] An object of the present invention is to overcome the
above-described shortcomings and to provide a three-layer clad
material which can be used, in particular, as a clad material for
forming the anode case of a button cell or the like and in which
stainless steel is used as the substrate, Ni or an Ni alloy is
monolithically pressure-welded to either principal plane of the
substrate, and Cu is monolithically pressure-welded to the other
principal plane, wherein this high-strength, high-drawability clad
material allows the thickness ratio of the stainless steel to be
further increased, mechanical strength (tensile strength) to be
raised above that of a conventional three-layer clad material, and
the thickness of the entire clad material to be reduced.
[0016] Another object of the present invention is to provide a two-
or three-layer clad material which can be used as a clad material
for forming the cathode case of a button cell or the like and in
which stainless steel is used as the substrate, and Ni or an Ni
alloy is monolithically pressure-welded to at least one principal
plane of the substrate, wherein this high-strength,
high-drawability clad material allows the thickness ratio of the
stainless steel to be further increased, mechanical strength
(tensile strength) to be raised above that of a conventional two-
or three-layer clad material, and the thickness of the entire clad
material to be reduced.
[0017] To attain the stated objects, the inventors conducted
extensive research into means for preventing folding or creasing
from occurring when Ni, Cu, or other thin sheets are bonded under
pressure to substrates composed of stainless steel. It became
possible, for example, to create uniform tension across the entire
thin sheet and to prevent folding or creasing from occurring during
pressure welding by adopting a method in which specially configured
and sized tension bridle rolls were placed upstream of pressure
rolls, and Ni, Cu, and other thin sheets were fed to these pressure
rolls through the agency of these tension bridle rolls.
[0018] As a result, the thickness of the thin Ni and Cu sheets
prior to pressure welding was reduced to about 5 .mu.m, and the
thickness ratio of each of the thin sheets in the three-layer clad
material for cell cases could be reduced to about 0.5% of the
entire thickness. Specifically, it was possible to achieve a
maximum of 99% for the thickness ratio of stainless steel in an
anode case. Any conventional method for manufacturing three-layer
clad materials can be substantially adopted in addition to the
above-described method for feeding Ni, Cu, or other thin sheets to
pressure rolls.
[0019] In addition, it was possible to increase the thickness ratio
of stainless steel in a three-layer clad material by adopting the
above-described means, to increase the mechanical strength (tensile
strength) of the three-layer clad material beyond that of a
conventional three-layer clad material by repeating the annealing
and temper rolling at a certain temperature, for example shin-pass
rolling or another treatment, and in certain cases to increase the
strength 10% to 50% above that of a conventional three-layer clad
material by adopting a preferred structure.
[0020] Specifically, the present invention provides a
high-strength, high-drawability clad material which is preferred,
in particular, as a material for forming the anode case of a cell
or the like and in which stainless steel is used as the substrate,
Ni or an Ni alloy is monolithically pressure-welded to either
principal plane of the substrate, and Cu is monolithically
pressure-welded to the other principal plane, this clad material
being such that the thickness of the stainless steel is greater
than 92% but no more than 99% of the total thickness of the clad
material, and the tensile strength is 70 kgf/mm.sup.2 or
higher.
[0021] With the high-strength clad material thus configured, it is
also possible to provide a high-strength, high-drawability clad
material whose drowing properties are further improved and which
can be molded by deep drawing as a result of the fact that a
plating composed of Sn, Sn-Pb, or In is formed on the surface of
Cu.
[0022] The present invention also provides a high-strength,
high-drawability clad material which is preferred, in particular,
as a material for forming the cathode case of a cell and in which
stainless steel is used as the substrate, and Ni or an Ni alloy is
monolithically pressure-welded to at least one principal plane of
the substrate, this clad material being such that the thickness of
the stainless steel is greater than 98% but no more than 99.5% of
the total thickness of the clad material; and a high-strength,
high-drawability clad material in which stainless steel is used as
the substrate, and Ni or an Ni alloy is monolithically
pressure-welded to both principal planes of the substrate, this
clad material being such that the thickness of the stainless steel
is greater than 96% but no more than 99% of the total thickness of
the clad material.
[0023] Also proposed is a high-strength, high-drawability clad
material of the above-described structure, having a total thickness
of 0.05 mm to 0.100 mm.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIGS. 1a and 1b are perspective views illustrating models
for evaluating press formability.
BEST MODE FOR CARRYING OUT THE INVENTION
[0025] Although any conventional material may be used as the
stainless steel that constitutes the substrate of the high-strength
clad material of the present invention, it is preferable to use
austenitic stainless steel, ferritic stainless steel, two-phase
stainless steel, precipitation-harden alle stainless steel, or the
like because of considerations related to corrosion resistance,
drawability, mechanical properties, seal strength, and the like,
particularly when the material is used for a cell case.
[0026] Although the material for the Ni or Ni alloy to be
monolithically pressure-welded to a substrate composed of stainless
steel may be selected in accordance with the intended application,
it is preferable to use pure nickel because of considerations
related to contact resistance, electrical resistance, corrosion
resistance, weldability, and the like, particularly when the
material is used for the anode case or cathode case of a cell. An
Ni alloy to which a specific amount of one or more of Cr, Cu, Be,
Nb, C, W, and the like has been added is commonly used within a
range of about 2 to 3 wt % because of considerations related to
prevention of surface scratch, improved appearance (luster), and
the like.
[0027] Although the Cu to be monolithically pressure-welded to a
substrate composed of stainless steel may be selected in accordance
with the intended application, it is preferable to use
maximum-purity Cu because of considerations related to corrosion
resistance, reactivity toward the electrolyte solution, suppression
of gas generation, and the like, particularly when the material is
used as the anode case of a cell. The effects of the present
invention can also be achieved by using a conventional material
containing a certain amount of impurities. From the standpoint of
dispensing with mercury or the like, it is also possible to use
materials obtained by plating or coating the Cu surface with Sn,
Sn-Pb, In, or the like.
[0028] The press formability of the clad material of the present
invention can be improved and an anode case shaped deeper than the
bore diameter can be easily molded by plating the Cu surface with
Sn, Sn-Pb, In, or the like.
[0029] As noted above, the thickness of the monolithic pressure
welding of Ni, an Ni alloy, Cu, or the like to the clad material of
the present invention can be markedly reduced, and the thickness of
the stainless steel (substrate) relative to the entire clad
material significantly increased.
[0030] For example, the amount of stainless steel can be increased
to 92-99% of the total amount of the clad material obtained by the
monolithic pressure welding of Ni and Cu, which is the preferred
clad material for anode cases.
[0031] According to experiments performed by the inventors, the
same effect as that demonstrated by a conventional structure can be
obtained when the aforementioned thickness ratio is less than 92%,
and fine pores and cracks develop in Ni, Cu, and other layers when
the ratio exceeds 99%. In particular, hydrogen gas is produced by
reaction with the contained solution and the cell leaks, making it
impossible to attain the intended object when the material is used
for the anode case of a cell. For these reasons, the thickness
ratio is set between 92% and 99%.
[0032] A clad material having a tensile strength of 70 kgf/mm.sup.2
or higher, and preferably 75 kgf/mm.sup.2 or higher, is provided in
order to maintain workability at least at the same level as in the
past. The tensile strength may be optionally raised to 90
kgf/mm.sup.2 or higher, and preferably 95 kgf/mm.sup.2 or higher,
by performing a specific type of skin-pass rolling.
[0033] It is possible to provide a clad material whose total
thickness is kept at 0.05 mm to 0.3 mm while the aforementioned
thickness ratio of stainless steel is maintained. A range of 0.05
to 0.100 mm is preferred for effectively utilizing the merits of
the present invention, and a clad material ranging from 0.07 mm to
0.100 mm is particularly preferred for the anode case of a cell
when reduction in thickness is taken into account together with
press formability and the like.
[0034] As noted above, good monolithic pressure welding can be
achieved when the thin Ni sheet not yet pressure-welded has a
thickness of about 5 .mu.m, making it possible to achieve the same
effect with respect to the structure of a clad material obtained by
the monolithic pressure welding of Ni or an Ni alloy to at least
one principal plane of stainless steel in the same manner as in the
above-described structure.
[0035] In a clad material in which Ni or an Ni alloy is
monolithically pressure-welded to either principal plane of the
stainless steel substrate, the thickness of the stainless steel can
be made greater than 98% but no more than 99.5% of the total
thickness of the clad material; and in a clad material in which Ni
or an Ni alloy is monolithically pressure-welded to both principal
planes of the stainless steel substrate, the thickness of the
stainless steel can be made greater than 96% but no more than 99%
of the total thickness of the clad material, making it possible to
provide a high-strength clad material whose tensile strength is
equal to or greater than that of a conventional structure.
[0036] This material structure can also yield a clad material whose
total thickness is kept at 0.05 mm to 0.3 mm while the
aforementioned thickness ratio of stainless steel is maintained. A
range of 0.05 to 0.100 mm is preferred for effectively utilizing
the merits of the present invention, and a clad material ranging
from 0.07 mm to 0.100 mm is particularly preferred for the cathode
case of a cell when reduction in thickness is taken into account
together with press formability and the like.
[0037] In any of the above-described clad materials, hardness, the
Erichsen value, and the like can be adjusted as needed in addition
to the thickness ratio, total thickness, tensile strength, and the
like of each material. With cell cases in particular, various
desired clad materials can be obtained by selecting optimum
conditions from within the scope of the following claims in
accordance with workability, shape, size, and other factors
determining case capacity (which is an important parameter of
battery life).
Embodiments
[0038] Embodiment 1
[0039] Table 1 shows the results of a comparison between the
tensile strength of a conventional clad material fabricated in
accordance with a convectional manufacturing method (without the
use of tension bridle rolls), and that of the clad material of the
present invention, which was fabricated in accordance with a
manufacturing method (using tension bridle rolls) performed using
the means described above and applied to a structure in which Ni
was monolithically pressure-welded to either principal plane of a
stainless steel substrate, and Cu was monolithically
pressure-welded to the other principal plane in order to confirm
the merits of the present invention. Similar to the conventional
clad material, the clad material of the present invention had a
total thickness of 0.09 mm.
[0040] An SUS 304 equivalent (JIS G4307) was used as the stainless
steel for the substrate, a VNiR equivalent (JIS H4501) was used as
the Ni, and a C1020 equivalent (JIS H3100) was used as the Cu. The
tensile strength, hardness, and Erichsen value were measured in
accordance with JIS Z2241, JIS Z2251, and JIS Z2247,
respectively.
1 TABLE 1 Tensile SUS Sam- Thickness Increase strength hard-
Erichsen ple ratio in SUS (kgf/ ness value No. Ni:SUS:Cu (%)
mm.sup.2) H.sub.V (mm) Conventional 1 8:76:16 100 65 170 12
material 2 8:84:8 110 68 170 12 3 2:91:7 120 71 170 12 Material 4
2:92.5:5.5 121 72 170 12 of 5 2:94:4 124 73 170 12 present 6 2:96:2
126 74 170 12 invention 7 1:98:1 129 75 170 12 8 0.5:99:0.5 130 76
170 12 Material 9 2:92.5:5.5 121 94 330 8 of 10 0.5:99:0.5 130 98
330 9 present invention
[0041] Note 1: "Increase in SUS" designates the SUS thickness of
each sample, assuming that the SUS thickness of sample No.1, which
is a conventional clad material, is 100.
[0042] Note 2: Sample Nos. 9 and 10 were obtained by subjecting
clad material sample Nos. 4 and 8, respectively, to skin-pass
rolling.
[0043] It can be seen in Table 1 that a clad material of the
present invention has better tensile strength than a conventional
clad material. In addition, the Erichsen value remains about the
same as that of a conventional clad material, indicating that deep
drawability remains as good as that of a conventional clad
material.
[0044] Embodiment 2
[0045] Table 2 shows the results of a comparison between the
tensile strength of a conventional clad material and that of the
clad material of the present invention, whose thickness was varied
in order to confirm the merits of the present invention. The
stainless steel (substrate), Ni, and Cu were the same materials as
those in Example 1.
2 TABLE 2 Thick- ness of clad Increase Tensile Erich- Sam- mater-
Thickness in strength sen ple ial ratio SUS (kgf/ value No. (mm)
Ni:SUS:Cu (%) mm.sup.2) (mm) Conventional 11 0.15 8:76:16 100 65 12
material 12 0.15 2:91:7 120 71 12 Material 13 0.30 0.5:99:0.5 130
76 12 of 14 0.20 0.5:99:0.5 130 76 12 present 15 0.15 0.5:99:0.5
130 76 12 invention 16 0.13 0.5:99:0.5 130 76 12 17 0.10 0.5:99:0.5
130 76 12 18 0.08 0.5:99:0.5 130 76 12 19 0.07 0.5:99:0.5 130 76 12
20 0.05 0.5:99:0.5 130 76 10 21 0.10 2:92.5:5.5 121 72 12 22 0.10
2:94:4 124 73 12 23 0.10 2:96:2 126 74 12 24 0.10 1:98:1 129 75 12
Material 25 0.10 2:92.5:5.5 121 94 8 of 26 0.10 0.5:99:0.5 130 98 9
present invention
[0046] Note 1: "Increase in SUS" designates the SUS thickness of
each sample, assuming that the SUS thickness of sample No. 11,
which is a conventional clad material, is 100.
[0047] Note 2: Sample Nos. 25 and 26 were obtained by subjecting
clad material sample Nos. 21 and 17, respectively, to skin-pass
rolling.
[0048] It can be seen in Table 2 above that a clad material of the
present invention has better tensile strength than does a
conventional clad material and that the thickness of the proposed
clad material can be reduced by about 5% to 50% when its tensile
strength is about the same as that of the conventional clad
material. When, for example, the proposed material is used for the
anode case of a cell, the capacity of the case can be increased by
reducing the thickness of the case while preserving the same
outside dimensions thereof. Longer battery life can be achieved as
a result.
[0049] Embodiment 3
[0050] Table 3 shows the results of a comparison between the
tensile strength of a conventional clad material fabricated in
accordance with a convectional manufacturing method (without the
use of tension bridle rolls), and that of the clad material of the
present invention, which was fabricated by a manufacturing method
(using tension bridle rolls) performed using the means described
above and applied to a structure in which Ni was monolithically
pressure-welded to one or both principal planes of a stainless
steel substrate in order to confirm the merits of the present
invention.
[0051] Similar to the conventional clad material, the clad material
of the present invention had a total thickness of 0.09 mm. An SUS
304 equivalent (JIS G4307) was used as the stainless steel for the
substrate, and a VNiR equivalent (JIS H4501) was used as the Ni.
The tensile strength was measured on the basis of JIS Z2241.
3 TABLE 3 Increase in Tensile Sample Thickness ratio SUS strength
No. Ni:SUS:Ni (%) (kgf/mm.sup.2) Conventional 27 2:98:0 100 75 clad
material Clad 28 1.5:98.5:0 101 85 material of 29 1.0:99.0:0 101 86
present 30 0.5:99.5:0 102 87 invention Clad 31 2:96:2 100 74
material of present invention Conventional 32 1.75:96.5:1.75 101 80
clad material 33 1.0:98.0:1.0 102 81 34 0.5:99.0:0.5 103 82
[0052] Note 1: "Increase in SUS" designates the SUS thickness of
sample Nos. 28 to 30 and 32 to 34, assuming that the SUS thickness
of sample No. 27 or 31, which is a conventional clad material, is
100.
[0053] The clad material of the present invention in Table 3 was
obtained by skin-pass rolling. It can be seen that the clad
material of the present invention has better tensile strength than
does the conventional clad material. It could also be confirmed
that even without undergoing skin-pass rolling, the proposed clad
material has at least the same tensile strength as the conventional
clad material.
[0054] Embodiment 4
[0055] To confirm that the clad material of the present invention
could be used as the anode case of a cell, the clad material (total
thickness: 0.09 mm) pertaining to the present invention and
consisting of sample Nos. 4 to 10 (Ni/SUS/Cu) in Example 1 was
drawn by press-working into a bottomed cylinder with an outside
diameter of 7 mm and a height of 6 mm (FIG. 1a) such that the inner
peripheral surface thereof was Cu. The results are shown in Table
4. The material yielded a regularly shaped case which had a high
degree of roundness and was devoid of cracks, fractures, or the
like.
4 TABLE 4 nner-layer Total material thick- during ness Sample
Thickness ratio pressure Press (mm) No. Ni:SUS:Cu forming
formability Clad 0.09 4 2:92.5:5.5 Cu Good material 0.09 5 2:94:4
Cu Good of 0.09 6 2:96:2 Cu Good present 0.09 7 1:98:1 Cu Good
invention 0.09 8 0.5:99:0.5 Cu Good 0.09 9 2:92.5:5.5 Cu Good 0.09
10 0.5:99:0.5 Cu Good
[0056] Embodiment 5
[0057] To confirm that the clad material of the present invention
could be used as the cathode case of a cell, the clad material
(total thickness: 0.09 mm) pertaining to the present invention and
consisting of sample Nos. 28 to 30 (Ni/SUS) and Nos. 32 to 34
(Ni/SUS/Ni) in Example 3 was drawn by press-working into a bottomed
cylinder with an outside diameter of 7 mm and a height of 6 mm
(FIG. 1a). The results are shown in Table 5. Sample Nos. 28 to 30
were formed such that the inner peripheral surfaces thereof were
SUS. The material yielded a regularly shaped case which had a high
degree of roundness and was devoid of cracks, fractures, or the
like.
5 TABLE 5 Inner- layer Total material thick- during ness Sample
Thickness ratio pressure Press (mm) No. Ni:SUS:Wi forming
formability Clad 0.09 28 1.5:98.5:0 SUS Good material 0.09 29
1.0:99.0:0 SUS Good of 0.09 30 0.5:99.5:0 SUS Good present 0.09 32
1.75:96.5:1.75 Ni Good invention 0.09 33 1.0:98.0:1.0 Ni Good 0.09
34 0.5:99.0:0.5 Ni Good
[0058] Embodiment 6
[0059] Drawing was performed under even more stringent conditions
than in Examples 4 and 5 in order to confirm that press formability
could be improved by plating the clad material of the present
invention. Specifically, the clad material (total thickness: 0.09
mm) pertaining to the present invention and consisting of sample
Nos. 4 to 10 (NilSUS/Cu) in Example 1, as well as clad materials
obtained by plating the Cu surface of this clad material with Sn,
Sn-Pb, or In (thickness: 2 .mu.m), were drawn by press-working into
bottomed cylinders with an outside diameter of 3 mm and a height of
10 mm (FIG. 1b) such that the inner peripheral surface was the Cu
side. The results are shown in Table 6. The following grading
system is adopted in Table 6 for evaluating press formability:
"{circle over (.smallcircle.)}" indicates good formability,
".largecircle." indicates cases in which slight shape defects have
developed, and "X" indicates cases in which the material have
fractured and cannot be press-formed.
6 TABLE 6 Total Cladding Sam- cladding thickness ple thickness
Plating and ratio Press No. (mm) thickness Ni:SUS:Cu formability
Clad 4 0.09 None 2:92.5:5.5 .largecircle. material 5 0.09 None
2:94:4 .largecircle. of 6 0.09 None 2:96:2 .largecircle. present 7
0.09 None 1:98:1 .largecircle. invention 8 0.09 None 0.5:99:0.5
.largecircle. 9 0.09 None 2:92.5:5.5 X 10 0.09 None 0.5:99:0.5 X
Clad 35 0.09 Sn 2 .mu.m 2:92.5:5.5 .circleincircle. material 36
0.09 Sn 2 .mu.m 2:94:4 .circleincircle. of 37 0.09 Sn 2 .mu.m
2:96:2 .circleincircle. present 38 0.09 Sn 2 .mu.m 1:98:1
.circleincircle. invention 39 0.09 Sn 2 .mu.m 0.5:99:0.5
.circleincircle. 40 0.09 Sn 2 .mu.m 2:92.5:5.5 .circleincircle. 41
0.09 Sn 2 .mu.m 0.5:99:0.5 .circleincircle. Clad 42 0.09 Sn-Pb 2
.mu.m 2:92.5:5.5 .circleincircle. material 43 0.09 Sn-Pb 2 .mu.m
2:94:4 .circleincircle. of 44 0.09 Sn-Pb 2 .mu.m 2:96:2
.circleincircle. present 45 0.09 Sn-Pb 2 .mu.m 1:98:1
.circleincircle. invention 46 0.09 Sn-Pb 2 .mu.m 0.5:99:0.5
.circleincircle. 47 0.09 Sn-Pb 2 .mu.m 2:92.5:5.5 .circleincircle.
48 0.09 Sn-Pb 2 .mu.m 0.5:99:0.5 .circleincircle. Clad 49 0.09 In 2
.mu.m 2:92.5:5.5 .circleincircle. material 50 0.09 In 2 .mu.m
2:94:4 .circleincircle. of 51 0.09 In 2 .mu.m 2:96:2
.circleincircle. present 52 0.09 In 2 .mu.m 1:98:1 .circleincircle.
invention 53 0.09 In 2 .mu.m 0.5:99:0.5 .circleincircle. 54 0.09 In
2 .mu.m 2:92.5:5.5 .circleincircle. 55 0.09 In 2 .mu.m 0.5:99:0.5
.circleincircle.
[0060] Unplated sample Nos. 4 to 8 did not have cracks, fractures,
or the like but their press formability could not be considered
satisfactory. It was also possible to confirm that unplated sample
Nos. 9 and 10 had cracks, fractures, and the like, and that the
press forming itself was difficult to perform.
[0061] The clad materials obtained by plating the Cu surfaces of
sample Nos. 4 to 10 with Sn, Sn-Pb, or In, on the other hand, were
free of cracks, fractures, or the like and yielded regularly shaped
cases with a high degree of roundness. It was confirmed that the
range of applications of the clad material of the present invention
could be further broadened by performing adequate press forming on
sample Nos. 9 and 10, which have high tensile strength and are
normally unsuitable for drawing.
INDUSTRIAL APPLICABILITY
[0062] It is evident from the examples described above that the
clad material of the present invention allows the thickness ratio
of stainless steel to be further increased, a mechanical strength
(tensile strength) equal to or greater than that of a conventional
clad material to be obtained, and the total thickness of the clad
material to be reduced in a three-layer clad material in which
stainless steel is used as the substrate, Ni or an Ni alloy is
monolithically pressure-welded to either principal plane of the
substrate, and Cu is monolithically pressure-welded to the other
principal plane; or in a two- or three-layer clad material in which
stainless steel is used as the substrate, and Ni or an Ni alloy is
monolithically pressure-welded to at least one principal plane of
the substrate, making it possible to increase the capacity of the
anode case, cathode case, or the like for a button cell or the
like, to substantially increase the capacity of the product for
storing electrochemical reagents, to yield smaller and lighter
products, and to extend battery life while preserving the strength,
stiffness, and crushing resistance required of the case when the
material is used for forming this case.
[0063] In the particular case of a three-layer clad material having
a Cu layer, press formability can be improved by plating the Cu
surface with Sn, Sn-Pb, In, or the like, making it possible to
further broaden the range of applications for the clad material of
the present invention as a result of a synergistic effect with the
above-described effect.
* * * * *