U.S. patent application number 10/569484 was filed with the patent office on 2007-10-11 for method for producing metallic flat wires or strips with a cube texture.
Invention is credited to Joerg Eickemeyer, Bernhard Holzapfel, Ralph Opitz, Dietmar Selbmann, Horst Wendrock.
Application Number | 20070234542 10/569484 |
Document ID | / |
Family ID | 34258275 |
Filed Date | 2007-10-11 |
United States Patent
Application |
20070234542 |
Kind Code |
A1 |
Eickemeyer; Joerg ; et
al. |
October 11, 2007 |
Method for Producing Metallic Flat Wires or Strips with a Cube
Texture
Abstract
Method for producing metallic flat wires or strips with a cube
texture that can be used, for example, as a base for
physical-chemical coatings. The products can be produced after the
last forming step in their finished width without further
processing of the edges. The method includes processing a material
based on nickel, copper, gold, or silver into a wire by a cold
drawing method, achieving a total cross-sectional reduction
.epsilon..sub.g.gtoreq.75% or a logarithmic deformation
.phi..sub.g.gtoreq.1.4, and the wire is then further processed by
further forming and annealing methods into a flat wire or a strip
with a cube texture and having a width that can be adjusted in a
defined manner.
Inventors: |
Eickemeyer; Joerg; (Dresden,
DE) ; Selbmann; Dietmar; (Colmnitz, DE) ;
Opitz; Ralph; (Dresden, DE) ; Holzapfel;
Bernhard; (Kreischa, DE) ; Wendrock; Horst;
(Kleinthiemig, DE) |
Correspondence
Address: |
GREENBLUM & BERNSTEIN, P.L.C.
1950 ROLAND CLARKE PLACE
RESTON
VA
20191
US
|
Family ID: |
34258275 |
Appl. No.: |
10/569484 |
Filed: |
August 20, 2004 |
PCT Filed: |
August 20, 2004 |
PCT NO: |
PCT/EP04/51853 |
371 Date: |
December 14, 2006 |
Current U.S.
Class: |
29/33F |
Current CPC
Class: |
C22F 1/08 20130101; Y10T
29/5187 20150115; B21C 1/003 20130101; H01L 39/2454 20130101; C22F
1/14 20130101; C22F 1/10 20130101 |
Class at
Publication: |
029/033.00F |
International
Class: |
B21C 1/00 20060101
B21C001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 25, 2003 |
DE |
103 39 867.8 |
Claims
1. Method for producing metallic flat wires or strips with a cube
texture, comprising processing a material based on nickel, copper,
gold, or silver into a wire having an essentially circular cross
section by a cold drawing method with high-grade forming over
multiple drawing stages, achieving a total cross-sectional
reduction .epsilon..sub.g.gtoreq.75% or a logarithmic deformation
.phi..sub.g.gtoreq.1.4, and then further processing the wire by
further forming and annealing methods into a flat wire or a strip
with a cube texture and having a width that can be adjusted in a
defined manner, the defined width being determined and adjusted by
the wire cross section and degrees of forming of further forming
steps for the wire.
2. The method according to claim 1, wherein the cold drawing method
is implemented with a total cross-sectional reduction of
.epsilon..sub.g.gtoreq.90% or a logarithmic deformation of
.phi..sub.g.gtoreq.2.3.
3. The method according to claim 1, wherein the cold drawing method
is implemented as slip drawing by drawing dies having drawing
angles 2.alpha.=2.degree.-20.degree..
4. The method according to claim 3, wherein the cold drawing is
implemented using drawing angles of 2.alpha..ltoreq.12.degree..
5. The method according to claim 1, wherein the cold drawing method
is carried out in respectively alternating drawing directions
(reversibly).
6. The method according to claim 1, not including an intermediate
treatment of the wire before the further forming and annealing
methods.
7. The method according to claim 2, wherein the cold drawing method
is implemented as slip drawing by drawing dies having drawing
angles 2.alpha.=2.degree.-20.degree..
8. The method according to claim 7, wherein the cold drawing is
implemented using drawing angles of 2.alpha.<12.degree..
9. The method according to claim 2, wherein the cold drawing method
is implemented as slip drawing by drawing dies having drawing
angles 2.alpha.=2.degree.-20.degree..
10. The method according to claim 7, wherein the cold drawing is
implemented using drawing angles of 2.alpha.<12.degree..
11. The method according to claim 2, wherein the cold drawing
method is carried out in respectively alternating drawing
directions (reversibly).
12. The method according to claim 2, not including an intermediate
treatment of the wire before the further forming and annealing
methods.
13. The method according to claim 3, not including an intermediate
treatment of the wire before the further forming and annealing
methods.
14. The method according to claim 4, not including an intermediate
treatment of the wire before the further forming and annealing
methods.
15. The method according to claim 5, not including an intermediate
treatment of the wire before the further forming and annealing
methods.
Description
FIELD OF THE INVENTION
[0001] The invention relates to the field of materials science and
to a method for producing metallic flat wires or strips with a cube
texture that can be used, for example, as a base for
physical-chemical coatings having a high-grade microstructural
orientation. The texture is hereby used as the basis for
crystallographically oriented growth of the deposited layers on the
substrate. Such bases are suitable, for example, as substrates for
metallic or ceramic coatings as used in the field of
high-temperature superconductivity. Such substrate strips for
coated superconductors may be used in superconducting magnets,
transformers, motors, tomography instruments, or superconducting
current paths, i.e., cables. Such textured metal strips may also be
used as magnetic materials, such as highly permeable nickel-iron
alloys, for example.
PRIOR ART
[0002] It is known that polycrystalline metals having cube
face-centered lattices, such as copper, nickel, gold, and under
certain conditions, silver, after a previous intense cold forming
may form a pronounced texture having a cubic layer in the
subsequent recrystallization by rolling of sheets or flat strips
(G. Wassermann: Texturen metallischer Werkstoffe [Textures of
Metallic Materials], Springer, Berlin, 1939; H. Hu et al.: Trans.
ASM 224 (1962) 96-105). The underlying studies (W. Koster: Z.
Metallkde. 18 (1926) 112-116) as well as the continuing
investigations (R. D. Doherty et al.: Mater. Sci. Eng. A257 (1998)
18-36) were carried out using strip mill rollers followed by
annealing.
[0003] In this manner, by rolling under the conditions of plane
strain deformation and subsequent annealing, textured metal strips,
in particular nickel and silver strips, are currently used as a
base for metallic coatings, ceramic buffer layers, and ceramic
superconductor layers (A. Goyal et al.: U.S. Pat. No. 5,741,377,
Apr. 21, 1998). The suitability of such metal strips as substrate
materials depends primarily on the achievable degree of texturing,
and the quality thereof directly on the surface.
[0004] In addition to the influences of chemical alloys on the
texture quality, the formation of the recrystallization cube
texture is above all linked to specific mechanical requirements for
forming techniques. A high minimum degree of forming is
indispensable in cold rolling, a fine-grained starting structure of
the shaped article being advantageous. The minimum degree of
forming for copper is 82% (O. Dahl, F. Pawlek: Z. Metallkde. 28
(1936) 266-271). To achieve high-grade texturing, however,
significantly higher degrees of forming are employed which
sometimes involve greater than 99% reduction in thickness. This
manufacturing technology requiring very complex forming techniques
is currently put up with, since alternative techniques have not
been seen in decades. Therefore, in actual practice forming
processes other than rolling currently do not play a role in the
production of metal strips with a cube texture.
[0005] Recently, however, it has been demonstrated that the forming
of strip materials using a drawing process with subsequent
annealing can also produce a cube texture (J. Eickemeyer, D.
Selbmann, R. Opitz, B. de Boer, B. Holzapfel, L. Schultz: 8. Saxon
Symposium in Shaping Technology, Dec. 4-5, 2001, TU Bergakademie
Freiberg/Sa., pages. 99-106). This procedure has thus far not
become established in practice.
[0006] There is no universally valid theory concerning the effects
of strain and deformation states on the formation of forming and
annealing textures of metals, or in particular for nickel, copper,
gold, and silver. Therefore, it is not possible to reliably
estimate the effectiveness of a forming process for the formation
of the shaped and annealed textures. In addition, the friction
conditions between the shaped piece and the forming tool also
influence the texture formation in strips, in particular thin
strips, in a manner which heretofore has not been predictable.
[0007] With the growing interest in substantially ideal annealed
textures for the use of strips as very long, quasi-monocrystalline
substrates (superconducting layer conductors), at the same time
there is the requirement for the most perfect texture possible, not
only in the strip interior, but in particular on the surface of
such coating bases. For this reason, all influences which may
interfere with the texture formation are to be evaluated critically
and avoided if possible. This applies not least of all to the
optimum process conditions for material forming, which thus far
have essentially been limited to the influencing variables for the
rolling of strips and sheets.
Explanation of the Essence of the Invention
[0008] The object of the invention is to provide a method for
producing metallic flat wires or strips with a cube texture, by
means of which the products have a high-grade cube texture after
the last forming step and the final annealing treatment.
[0009] The object is attained by the invention as stated in the
claims. Further developments are the subject of the subordinate
claims.
[0010] In the method according to the invention for producing
metallic flat wires or strips with a cube texture, a material based
on nickel, copper, gold, or silver is processed into a wire having
an essentially circular cross section by means of a cold drawing
method with high-grade forming over multiple drawing stages,
achieving a total cross-sectional reduction
.epsilon..sub.g.gtoreq.75% or a logarithmic deformation
.phi..sub.g.gtoreq.1.4. The wire is then further processed by means
of further forming and annealing methods into a metallic flat wire
or a strip with a cube texture and having a width that can be
adjusted in a defined manner, the defined width being determined
and adjusted by means of the wire cross section and the degrees of
forming of the further forming steps for the wire.
[0011] The cold drawing method advantageously is implemented with a
total cross-sectional reduction of .epsilon..sub.g.gtoreq.90% or a
logarithmic deformation of .phi..sub.g.gtoreq.2.3.
[0012] It is likewise advantageous to implement the cold drawing
method as slip drawing by means of drawing dies having drawing
angles 2.alpha.=2.degree.-20.degree., drawing angles of
2.alpha..ltoreq.12.degree. being even more advantageous.
[0013] Furthermore, it is advantageous to carry out the cold
drawing method in respectively alternating drawing directions
(reversibly).
[0014] It is also advantageous to omit an intermediate treatment of
the wire before the further forming and annealing methods.
[0015] As starting material for the production of the metallic flat
wire or strip, the method according to the invention uses metallic
base materials which tend to form the cube texture after cold
forming and subsequent recrystallization. These include metallic
materials with cube face-centered lattices, such as nickel, copper,
gold, and, under certain conditions, silver, as well as some of the
alloys thereof.
[0016] According to the invention, these metallic base materials
are processed by a high-grade cold drawing to produce a wire
material having an essentially circular cross section. These wires
are further processed by the methods, known per se, of roll drawing
using feely rotatable rollers, or drawing through drawing jaws
arranged in parallel, or rolling to produce a metallic flat wire or
a metallic strip, the cube texture being formed during the
subsequent final recrystallization annealing known per se.
[0017] In the scope of the present invention, metallic flat wires
are understood to mean articles produced from wires by means of
cold forming, the width and thickness being primarily determined by
the starting wire diameter and the degree of forming employed.
[0018] Metallic strips are understood to mean articles produced
from precursor products by cold forming, the strip width being
obtained by longitudinal division of wider products.
[0019] The high-grade cold drawing is carried out first by drawing
the starting materials through drawing dies as commonly used in
wire manufacturing. The subsequent forming may be performed by
rolling to produce strips, or by drawing of strips by use of
rolling tools or drawing jaws.
[0020] Cold drawing as slip drawing through drawing dies is
advantageously performed by use of drawing dies having drawing
angles between 2.degree. and 20.degree., and particularly
advantageously with drawing angles .ltoreq.12.degree., Cold drawing
of the wire may thereby be carried out in the same direction
(unidirectionally), or advantageously with respectively alternating
drawing directions (reversibly).
[0021] Furthermore, the method according to the invention requires
no intermediate treatments of the wire after drawing of the wire
and before the further forming into metallic flat wires and
metallic strips, which offers technological benefits.
[0022] The method according to the invention, using cold drawing to
produce a wire and further forming into a flat wire or strip and
final annealing, for comparable reductions in thickness achieves at
least the relative degree of texture of the cube layer as that
resulting from the use of the cold rolling used heretofore, as well
as from the cold drawing using rolling tools or drawing jaws. The
intensive wire drawing results in a structural state that is
particularly favorable for forming the subsequent recrystallization
cube texture.
[0023] The primary advantage of the novel method is that, as a
result of the adjustment of defined wire diameters and the
adjustment of the overall degree of forming in the subsequent
forming steps for the wire, the width of the finished metallic flat
wires or metallic strips becomes adjustable without the
longitudinal division of wide strips which otherwise would be
necessary. In addition, there is no complex edge processing, so
that the equipment for both longitudinal division and edge
processing may be omitted in the assembly line. At the same time,
the method operates without material losses, which necessarily
occur as the result of cutting edge strips, and without
metal-cutting products, which are unavoidable in edge processing.
Technological steps are thereby omitted which also tend to
consistently impair the surface quality of the sensitive
strips.
[0024] Although the wire drawing method is a well-known forming
method, its influence on the forming and annealing textures in
metallic flat wires or metallic bands produced from wires has not
been investigated heretofore.
[0025] The not unfavorable influence of wire drawing on the
production of metallic flat wires or metallic strips having a cube
texture is surprisingly revealed for specialized treatments, such
as achieving a high-grade cube texture. This is quite unexpected
for the reason that drawing textures, as fiber textures, are
fundamentally different from rolling textures, and a positive
influence in terms of the sought recrystallization cube layer,
which is known to result from the rolling texture of certain cube
face-centered metals and their alloys, cannot be assumed. Even the
non-homogeneous strain and deformation state, which is present in
the processing of round wires to flat wires or strips over a wide
dimensional range, surprisingly has no disadvantages for the end
product having a cube texture.
[0026] When the method according to the invention is used for the
production of substrate bands or strips for magnetic applications,
a more effective manufacturing is thus technically possible at
equivalent or improved product quality. This inevitably results in
savings in energy and labor expenditures, as well as cost savings
for specialized equipment which would otherwise be necessary for
longitudinal division and edge processing.
[0027] The melt metallurgical production of the metals and alloys
to be textured is preferably carried out by casting into a copper
mold. As an alternative to melt metallurgical production, powder
metallurgical production using hot and cold isostatic pressing may
also be appropriate for the starting material.
[0028] Before the subsequent conventional heat forming is begun,
the metallurgically produced cast or pressed bodies may acquire an
advantageous starting structure by homogenization annealing, and
the grain size may be adjusted in a controlled manner for the final
intensive cold forming. From the standpoint of good cold
formability, the degree of heat forming as well as the temperature
and duration of annealing may be easily optimized in the subsequent
process by one skilled in the art. The annealing atmosphere for the
recrystallization advantageously is reducing or inert. The
annealing temperatures and times tend towards changed values with
increasing alloy content, and likewise may be easily adjusted by
one skilled in the art.
[0029] Compared to other known approaches, the fundamental
difference in the approach according to the invention is that a
wire having an essentially circular cross section may also be used
as starting product for the flat wire or strip production without
resulting disadvantageous effects on the cube texture in the flat
wire or strip to be ultimately produced. This would not have been
expected according to the prior art. Depending on the type of wire,
the drawing and annealing textures in wires are fiber textures, and
consequently are characterized by a single preferred direction, the
wire axis. It was therefore surprising that a high-grade drawn wire
having a fiber texture could be prepared by means of comparatively
minor subsequent flat forming to form a biaxial recrystallization
cube texture.
MOST ADVANTAGEOUS APPROACH FOR CARRYING OUT THE INVENTION
[0030] The invention is explained in greater detail below, with
reference to examples.
[0031] They show:
[0032] FIG. 1: A structural image obtained by EBSD, and the degree
of texture of a 82 .mu.m thick nickel-iron strip (Ni53Fe47)
produced by unidirectional roll drawing from a diameter of 1.25 mm
(.epsilon.=87.9%), after the starting wire was drawn from O20 mm to
O5 mm (.epsilon.=93.75%), and following an intermediate annealing
was further drawn to O1.25 mm (.epsilon.=93.75%).
EXAMPLE 1
[0033] A circular rod made of Ni53Fe47 alloy is drawn in the
conventional manner by rod or wire drawing in multiple stages, from
a diameter of 20 mm to a wire having an essentially circular cross
section of 5 mm in diameter (1.sup.st overall reduction of
.epsilon..sub.g=93.75%). After a recrystallization annealing at
850.degree. C., further cold drawing results in a diameter of 1.25
mm (2.sub.nd overall reduction of .epsilon..sub.g=93.75%). This
wire is then further processed by means of unidirectional roll
drawing, with a cross-sectional reduction of .epsilon..sub.g=87.4%,
to a flat wire having a width of 1.89 mm and a thickness of 82
.mu.m. Texture annealing at 1100.degree. C. over a period of 60
minutes results in a high-grade recrystallization cube texture
which constitutes a share of 94.3% in the structure (FIG. 1), 93.1%
of all grain boundaries being small-angle grain boundaries with a
misorientation <10.degree. (white in FIG. 1). In conventional
procedures for continuous strip forming of flat products, such a
texture quality is not achieved until the reduction in strip
thickness is greater than .epsilon..sub.g=99%. Further machining of
the flat wire obtained is not necessary.
EXAMPLE 2
[0034] A circular rod made of Ni53Fe47 alloy is drawn in the
conventional manner by rod or wire drawing in multiple stages, from
a diameter of 20 mm to a wire having an essentially circular cross
section of 5 mm in diameter (1.sup.st overall reduction of
.epsilon..sub.g=93.75%). After a recrystallization annealing at
850.degree. C., further cold drawing results in a diameter of 1.25
mm (2.sub.nd overall reduction of .epsilon..sub.g=93.75%). This
wire is then further processed by means of reversible roll drawing,
with a cross-sectional reduction of .epsilon..sub.g=87.9%, to a
strip having a width of 1.86 mm and a thickness of 77 .mu.m.
Texture annealing at 1100.degree. C. over a period of 60 minutes
results in a high-grade recrystallization cube texture which
constitutes a share of 91.3% in the structure, 92.8% of all grain
boundaries being small-angle grain boundaries (misorientation
<10.degree.). In conventional procedures for continuous strip
forming of flat products, such a texture quality is not achieved
until the reduction in strip thickness is greater than
.epsilon.g=99%. Further machining of the flat wire obtained is not
necessary.
EXAMPLE 3
[0035] A circular rod made of Ni53Fe47 alloy is drawn in the
conventional manner by rod or wire drawing in multiple stages, from
a diameter of 20 mm to a wire having an essentially circular cross
section of 1.25 mm in diameter (1.sup.st overall reduction of
.epsilon..sub.g=99.6%). This wire is then further processed by
means of reversible roll drawing, with a cross-sectional reduction
of .epsilon..sub.g=87.9%, to a strip having a width of 1.83 mm and
a thickness of 80 .mu.m. Texture annealing at 1100.degree. C. over
a period of 60 minutes results in a high-grade recrystallization
cube texture which constitutes a share of 91.6% in the structure,
83.6% of all grain boundaries being small-angle grain boundaries
(misorientation <10.degree.). Further machining of the strip
obtained is not necessary.
EXAMPLE 4
[0036] A circular rod made of Ni53Fe47 alloy is drawn in the
conventional manner by rod or wire drawing in multiple stages, from
a diameter of 20 mm to a wire having an essentially circular cross
section of 5 mm in diameter (1.sup.st overall reduction of
.epsilon..sub.g=93.75%). After a recrystallization annealing at
850.degree. C., further cold drawing results in a diameter of 1.25
mm (2.sub.nd overall reduction of .epsilon..sub.g=93.75%). This
wire is then further processed by means of reversible roll drawing,
with a cross-sectional reduction of .epsilon..sub.g=82.2%, to a
strip having a width of and a thickness of 97 .mu.m. Texture
annealing at 1100.degree. C. over a period of 60 minutes results in
a high-grade recrystallization cube texture which constitutes a
share of 82.9% in the structure, 61.9% of all grain boundaries
being small-angle grain boundaries (misorientation<10.degree.).
Further machining of the strip obtained is not necessary.
EXAMPLE 5
[0037] A nickel wire having an alloy content of 5 atomic-% tungsten
is drawn in multiple stages from a starting diameter of 5 mm to a
diameter of 1 mm (.epsilon..sub.g=96%). The wire is then cold
rolled, without intermediate treatment, into a flat wire having
final dimensions of 1.9 mm width and 60 .mu.m thickness. The flat
wire is finally subjected to a heat treatment at 1100.degree. C.
over a period of 1 hour, forming a sharply defined cube texture as
used for bases for coating with epitactically grown layers.
* * * * *