U.S. patent application number 10/079824 was filed with the patent office on 2002-10-17 for method of producing microstructured metal sheets.
This patent application is currently assigned to Ballard Power Systems AG.. Invention is credited to Ruck, Joachim, Tischler, Alois, Weisser, Marc.
Application Number | 20020148269 10/079824 |
Document ID | / |
Family ID | 7675071 |
Filed Date | 2002-10-17 |
United States Patent
Application |
20020148269 |
Kind Code |
A1 |
Ruck, Joachim ; et
al. |
October 17, 2002 |
Method of producing microstructured metal sheets
Abstract
In a method of producing microstructured metal sheets,
microstructures are made in a metal sheet surface in a continuous
embossing step on one side of the metal sheet, while the surface
structure of the other side is essentially not changed. The
embossing step is carried out by means of an embossing roller which
has a negative of the microstructure to be embossed. The flanks of
the microstructure form an angle of at least 5.degree. with respect
to the perpendicular line, and the negative contains compensating
structures in the regions surrounding the microstructure for
rendering the forming uniform along the roller slit.
Inventors: |
Ruck, Joachim; (Heidenheim,
DE) ; Tischler, Alois; (Dorfen, DE) ; Weisser,
Marc; (Owen/Teck, DE) |
Correspondence
Address: |
CROWELL & MORING LLP
INTELLECTUAL PROPERTY GROUP
P.O. BOX 14300
WASHINGTON
DC
20044-4300
US
|
Assignee: |
Ballard Power Systems AG.
|
Family ID: |
7675071 |
Appl. No.: |
10/079824 |
Filed: |
February 22, 2002 |
Current U.S.
Class: |
72/197 |
Current CPC
Class: |
F28F 13/185 20130101;
B01J 2219/00873 20130101; H01M 2008/1095 20130101; H01M 8/0206
20130101; H01M 2300/0082 20130101; B01J 2219/00783 20130101; H01M
8/0263 20130101; C01B 2203/0405 20130101; F28F 2260/00 20130101;
B01J 2219/00835 20130101; B01J 2219/00907 20130101; C01B 3/501
20130101; B21H 8/005 20130101; B01J 19/0093 20130101; F28F 3/04
20130101; Y02P 70/50 20151101; Y02E 60/50 20130101; H01M 8/026
20130101 |
Class at
Publication: |
72/197 |
International
Class: |
B21B 001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 22, 2001 |
DE |
101 08 469.2-14 |
Claims
What is claimed:
1. Method of producing microstructured metal sheets, comprising:
making microstructures in a metal sheet surface in a continuous
embossing step on one side of the metal sheet, while a surface on
the other side is essentially not changed, carrying out the
embossing step by means of an embossing roller which has a negative
of the microstructure to be embossed, wherein flanks of the
microstructure form an angle of at least 5.degree. with respect to
the perpendicular line, and the negative contains compensating
structures in regions surrounding the microstructures for rendering
forming uniform along a roller slit.
2. Method according to claim 1, further comprising heating the
metal sheet before the embossing step.
3. Method according to claim 1, further comprising carrying out the
embossing step in at least of a force-controlled and
path-controlled manner.
4. Method according to claim 1, wherein roller pressure of the
embossing step is in a range of approximately 30 to 1,000 tons.
5. Method according to claim 1, wherein, after the embossing step,
the metal sheet is subjected to a calibrating step.
6. Method according to claim 5, wherein the calibrating step is
followed by at least one annealing step for reducing internal
tensions of the microstructured metal sheet.
7. Method according to claim 6, wherein the annealing process is
carried out with the exclusion of oxygen.
8. Method according to claim 5, wherein, after at least one of the
calibrating and annealing steps, the microstructured metal sheet is
subjected to a straightening at room temperature.
9. Method according to claim 1, wherein the microstructures
preferably have a depth of from approximately 0.1 to 0.5 mm.
10. Method according to claim 1, further comprising thinning the
metal sheet by approximately 50%.
11. Use of the method according to claim 1, preferably for the
production of a microreactor, a micro heat exchanger, an
oil-heated, catalytically or hot-gas heated evaporator, of a
membrane module for the separation of H.sub.2 or of a fuel
cell.
12. A method of producing a microstructured metal sheet,
comprising: embossing a microstructure and compensating structures
surrounding the microstructure on a surface on only one side of a
metal sheet, wherein flanks of the microstructure form an angle of
at least 5.degree. with respect to the perpendicular line.
13. The method according to claim 12, further comprising heating
the metal sheet before embossing.
14. The method according to claim 12, further comprising carrying
out the embossing step in at least one of a force-controlled manner
and a path-controlled manner.
15. The method according to claim 12, comprising applying a force
in the range of approximately 30 to 1,000 tons to the surface of
the metal sheet in the embossing step.
16. The method according to claim 12, comprising applying a force
in the range of approximately 50 to 500 tons to the surface of the
metal sheet in the embossing step.
17. The method according to claim 12, comprising calibrating the
metal sheet after the embossing step.
18. The method according to claim 17, comprising cutting the metal
sheet in sheets of desired sizes.
19. The method according to claim 17, comprising annealing the
microstructured metal sheet to reduce internal tensions after the
calibrating step.
20. The method according to claim 19, comprising annealing the
microstructured metal sheet with the exclusion of oxygen.
21. The method according to claim 19, comprising straightening the
microstructured metal sheet at room temperature after at least one
of the calibrating and annealing steps.
22. The method according to claim 12, wherein the microstructures
preferably have a depth of from approximately 0.1 to 0.5 mm.
23. The method according to claim 12, further comprising thinning
the metal sheet by approximately 50%.
24. The method according to claim 12, wherein the compensating
structure has at least one of ribs and grooves having a criss-cross
configuration.
25. The method according to claim 12, wherein the compensating
structure has a mesa-like configuration.
Description
BACKGROUND AND SUMMARY OF THE INVENTION
[0001] This application claims the priority of German Patent
Document No. 101 08 469.2-14, filed Feb. 22, 2001, the disclosure
of which is expressly incorporated by reference herein.
[0002] The invention relates to a method of producing
microstructured metal sheets as well as to the use of the
method.
[0003] German Patent Document DE 198 01 374 A1 discloses methods
which are suitable for producing microstructured metal sheets, such
as etching, milling, embossing, punching or wire-EDM.
[0004] In the prior art, microstructured metal sheets have been
produced by galvanic methods (removal or build-up of material),
chemical methods (etching), electrical methods (eroding),
electrochemical methods (ECM), mechanical methods (HSC milling,
engraving) or laser removal methods. The disadvantage of all
above-mentioned methods is the high production costs. The last two
of the above-mentioned methods have the disadvantage of a high
carrying-in of heat which warps the metal sheets. In the case of
the galvanic, chemical and electrochemical methods, costly disposal
or recycling of the used materials is necessary. Furthermore, at
the conclusion of the respective process, another process step,
finish rolling, has to be added in order to obtain highly parallel
metal sheets, which are required for the further course of the
production. In addition, in the case of mechanical methods
(etching), for reasons of corrosion, it is not possible to use just
any material for the production of metal sheets. High-alloy Cr--Ni
steel and Ni base alloys respectively are not suitable for etching
and more expensive materials must therefore be used.
[0005] It is therefore an object of the invention to provide a
cost-effective method which is suitable for mass production and has
a high dimensional accuracy of the metal sheets while the influence
of heat during the embossing is only minimal.
[0006] To achieve this object, the present invention provides a
method of producing microstructured metal sheets, which is
described hereinafter.
[0007] In the method according to the invention, a very good
surface quality can be attained in a particularly advantageous
manner, which surface quality does not promote the corrosion caused
by aggressive media. In the case of etching, on the other hand, the
grain boundaries are exposed and promote corrosion. Furthermore,
the method is not harmful to the environment.
[0008] Other objects, advantages and novel features of the present
invention will become apparent from the following detailed
description of the invention when considered in conjunction with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1a is a schematic view of the embossing of a metal
sheet by means of a structured embossing roller; and
[0010] FIG. 1b is a cutout of FIG. 1a;
[0011] FIG. 2a illustrates a compensating structure that has ribs
and/or grooves having the criss-cross configuration;
[0012] FIG. 2b illustrates a compensating structure that has a
mesa-like configuration;
[0013] FIG. 3a is a schematic view of a possible arrangement of a
negative structure on an embossing roller which, on the one hand,
contains the microstructure and, on the other hand, contains the
compensating structures; and
[0014] FIG. 3b is a cutout of FIG. 3a.
DETAILED DESCRIPTION OF THE DRAWINGS
[0015] A method according to the invention is directed to the
microstructuring of metal sheets. Microstructures are made in a
continuous embossing step into the surface on one side of a metal
sheet, while the surface of the other side is essentially not
changed. The embossing step is carried out by means of an embossing
roller 1 which has a negative of the microstructure 3 to be
embossed. The flanks 5 of the microstructure form an angle of at
least 5.degree. with respect to the perpendicular line. The regions
of the roller surrounding the microstructures have the negative of
compensating structures 4 to make the embossed metal sheet uniform
along the roller slit. This is schematically illustrated in FIGS.
1a and 1b.
[0016] The microstructure 3 may have any suitable structures. For
example, the microstructure may have grooves and/or ribs that are
arranged in any suitable manner. In the illustrated embodiment, the
microstructure 3 includes grooves and/or ribs that form a plurality
of concentrically arranged rectangles. When embossed, the area of
the metal sheet containing the microstructure 3 is plastified, and
the grains of the metal material are crushed into finer grains due
to the thinness of the metal sheet and the high degree of
deformation.
[0017] The compensating structures 4 preferably are used to make
the force or pressure applied to the metal sheet 2 during embossing
substantially uniform in all areas of the metal sheet 2, so that
the areas of the metal sheet 2 surrounding the microstructure 3 are
also pressed and plastified to crush the grains of the metal
material into finer grains. Without the compensating structures 4
the areas of the microstructures 3 would have relatively small
grains, while the areas surrounding the microstructures 3 would
have relatively large grains. The interface between the large and
small grain areas may damage the metal sheet 2.
[0018] The compensating structure may have any suitable
configurations. For example, the compensating structure may have
ribs and/or grooves having the criss-cross configuration shown in
FIG. 2a, or it may have the mesa-like configuration shown in FIG.
2b.
[0019] Preferably, the width of the patterns on the roller is
greater than the width of the metal sheet to ensure that all areas
of the metal sheet are embossed. In addition, the depth and width
of the patterns of the compensating structure are similar to or the
same as those of the patterns of the microstructure.
[0020] Metal sheets 2 suitable for use with the invention are
metallic and may be made of, for example, steel, particularly
stainless steel, such as Cr--Ni steel, and of aluminum, Ni, Ni
alloys, Pd, Pd alloys, Cu, Cu alloys.
[0021] Before embossing, the metal sheet (2) can be heated by means
of inductive heating or by means of infrared radiators, and the
temperature may be in the range of room temperature to 300.degree.
C. and may depend on the material. During the subsequent embossing
step, the so-called cold-rolling at room temperature to 300.degree.
C., the material is completely plastified. In other words, the
grains of the metal material are smashed as a result of the narrow
material thickness and the high degree of deformation. The roller
pressure of the embossing step is in the range of approximately 30
to 1,000 tons, preferably in the range of from 50 to 500 tons.
During embossing, a reduction of the material to be embossed takes
place, and the material is also highly compacted in the roller
slit. To reduce the possibility of the material becoming jammed
when passing through the roller slit, the embossing
(microstructure) 3 on the roller 1 has an angle of at least
5.degree. at the flanks 5, and the negative in the regions
surrounding the microstructure contains compensating structures 4
which render the forming uniform along the roller slit and along
the metal sheet width respectively and therefore lead to uniform
advancing. As a result, cracks in the metal sheet are
advantageously avoided and a good surface evenness is ensured
because the material flows uniformly forward along the width of the
roller slit. FIG. 3a is a schematic illustration of, and FIG. 3b is
a sectional view of, the roller with a uniform arrangement of the
microstructures and the compensating structures 4. However, the
high deformation necessarily leads to internal tensions in the
metal sheet. Therefore, the embossing roller 1 itself may have a
crowned shape.
[0022] With respect to the embossing step, the method can be
implemented in a force-controlled and/or path-controlled manner. In
the case of a force-controlled implementation of the method, the
roller force is kept constant by way of a contact and control
mechanism. The roller slit height can be variably adjusted as a
function of the local degree of forming and the input cross-section
of the metal sheet. In contrast, in the case of a path-controlled
implementation of the method, the roller slit height is kept
constant by way of a contact and control mechanism, whereas the
roller force is variably adjustable as a function of the local
degree of forming and the input cross-section of the metal sheet.
The method may also be a combination of a force-controlled and
path-controlled implementation. During embossing, a new grain
formation (recrystallization) takes place which is comparable to
the old grain structure.
[0023] After the embossing step, the metal sheet is subjected to a
calibrating step. This calibrating pass is used for equalizing the
embossing profile. In the calibrating step, embossed metal sheet 2
is treated with a plane roller to adjust the thickness and
dimension of the embossed metal sheet.
[0024] After the calibrating step, die cutting may be performed and
the metal sheet 2 may be cut into designed sizes. Each cut metal
sheet preferably contains the microstructure 3 and may also contain
the compensating structures 4.
[0025] To reduce internal tensions of the microstructured metal
sheet, the calibrating step is followed by at least one annealing
step. The temperatures during the annealing process are in the
range of from approximately 500 to 1,200.degree. C. depending on
the type of the material to be embossed. The annealing process is
carried out with the exclusion of oxygen, preferably in a
hydrogen-containing and/or nitrogen-containing atmosphere, for
reducing or preventing an oxide skin formation on the surface of
the material.
[0026] Subsequently, after the calibrating and/or annealing step,
the microstructured metal sheet is subjected to a straightening
process at room temperature. The continuous process can be
uncoupled between the embossing and the calibrating step, and the
process steps occurring after the embossing step can be continued
in a separate system.
[0027] The microstructures produced according to the method of the
invention have a depth of approximately from 0.1 to 0.5 mm, the
metal sheet experiencing a thinning by approximately 50% during the
process.
[0028] The method is preferably used for producing a microreactor,
a micro heat exchanger, an oil-heated, catalytically or hot-gas
heated evaporator, a membrane module for the separation of H.sub.2
or a fuel cell, particularly a polymer electrolyte membrane fuel
cell, in which case the devices produced according to the method of
the invention are equally suitable for hydrogen fuel cells,
reformate-operated fuel cells or direct methanol fuel cells.
[0029] The foregoing disclosure has been set forth merely to
illustrate the invention and is not intended to be limiting. Since
modifications of the disclosed embodiments incorporating the spirit
and substance of the invention may occur to persons skilled in the
art, the invention should be construed to include everything within
the scope of the appended claims and equivalents thereof.
* * * * *