U.S. patent application number 13/138554 was filed with the patent office on 2012-04-19 for core wire for guide wire and method for manufacturing the same.
Invention is credited to Akihisa Furukawa, Kiyohito Ishida, Takeshi Ishikawa, Kiyonori Takezawa, Mitsuya Takezawa, Kiyoshi Yamauchi.
Application Number | 20120094123 13/138554 |
Document ID | / |
Family ID | 42709699 |
Filed Date | 2012-04-19 |
United States Patent
Application |
20120094123 |
Kind Code |
A1 |
Yamauchi; Kiyoshi ; et
al. |
April 19, 2012 |
Core wire for guide wire and method for manufacturing the same
Abstract
Provided is a core wire for guide wire in which high rigidity
can be attained even with a fine wire diameter so that pushability
is improved while the core wire is prevented from fatigue
deformation, and a method for manufacturing the core wire. This
core wire 15 for guide wire is made of a Ti--Ni based alloy and has
a wire diameter not larger than 0.5 mm and a Young's modulus not
lower than 50 GPa. According to the manufacturing method, first,
wire drawing is performed on a raw material M.sub.0 so that the raw
material M.sub.0 is passed through a wire drawing dice 2 to be
drawn to a certain length while the wire diameter of the core wire
is reduced. Thus, a primary processed material M.sub.1 is formed.
After that, the primary processed material M.sub.1 is hammered and
drawn by swaging dices 5 and 5 so that a secondary processed
material M.sub.2 is formed. In this manner, the core wire 15 having
a wire diameter not larger than 0.5 mm and a Young's modulus not
lower than 50 GPa is manufactured.
Inventors: |
Yamauchi; Kiyoshi; (Miyagi,
JP) ; Furukawa; Akihisa; (Miyagi, JP) ;
Ishida; Kiyohito; (Miyagi, JP) ; Ishikawa;
Takeshi; (Kanagawa, JP) ; Takezawa; Kiyonori;
(Fukui, JP) ; Takezawa; Mitsuya; (Fukui,
JP) |
Family ID: |
42709699 |
Appl. No.: |
13/138554 |
Filed: |
March 2, 2010 |
PCT Filed: |
March 2, 2010 |
PCT NO: |
PCT/JP2010/053324 |
371 Date: |
November 30, 2011 |
Current U.S.
Class: |
428/401 ;
72/286 |
Current CPC
Class: |
Y10T 428/298 20150115;
A61M 25/09 20130101; A61M 2025/09108 20130101; B21C 37/045
20130101; C21D 7/10 20130101; B21C 1/003 20130101; C21D 8/06
20130101; A61M 2025/09075 20130101; B21J 9/06 20130101 |
Class at
Publication: |
428/401 ;
72/286 |
International
Class: |
D02G 3/00 20060101
D02G003/00; B21C 9/00 20060101 B21C009/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 4, 2009 |
JP |
2009-051274 |
Claims
1. A core wire for guide wire, wherein the core wire is made of a
Ti--Ni based alloy, has a wire diameter not larger than 0.5 mm and
has a Young's modulus not lower than 50 GPa, and wherein wire
drawing and swaging are performed on the core wire.
2. (canceled)
3. The core wire of claim 1, wherein the Ti--Ni based alloy is a
work-hardened Ti--Ni based alloy whose texture has a
microcrystalline structure.
4. The core wire of claim 1, wherein heat treatment as well as the
wire drawing and the swaging is performed on the core wire.
5. A method for manufacturing the core wire of claim 1, the method
comprising: drawing a raw material made of a Ti--Ni based alloy,
and then carrying out swaging to obtain a core wire having a wire
diameter not larger than 0.5 mm and a Young's modulus not lower
than 50 GPa.
6. The method of claim 4, further comprising: performing heat
treatment after the swaging.
Description
TECHNICAL FIELD
[0001] The present invention relates to a core wire for guide wire
which serves as a material of a guide wire for use in introduction
of a catheter etc., and a method for manufacturing the core
wire.
BACKGROUND ART
[0002] In the background art, contrast media or medical agents are
dosed through a catheter for inspection or treatment in a tubular
organ such as a blood vessel or a trachea. The catheter is inserted
to an intended place through a narrow and soft guide wire. For
radiography or treatment in a coronary artery, a cerebral artery or
another narrow tubular organ whose diameter is reduced due to
disease, a microscopic catheter is used and a microscopic guide
wire is also used correspondingly.
[0003] The guide wire is required to have properties such as
pushability with which a pushing force on the operating side can be
transmitted to a front end portion of the guide wire or torque
transmission characteristic with which a blood vessel can be
selected in a bifurcated vessel.
[0004] Stainless steel, Ti--Ni based alloy, etc. may be used as the
material of such a guide wire.
[0005] The stainless steel is hard and has high rigidity.
Therefore, a narrow-diameter guide wire formed of the stainless
steel is superior in pushability. However, since the stainless
steel is brought into fatigue deformation easily, the original
performance and function of the stainless steel guide wire is apt
to be spoiled in the course of use.
[0006] On the other hand, the Ti--Ni based alloy is superior in
flexibility so as to be prevented from fatigue deformation.
However, since the Ti--Ni based alloy is softer and lower in
rigidity than stainless steel, the microscopic guide wire formed of
the Ti--Ni based alloy is apt to be insufficient in pushability,
torque transmission characteristic, etc. Thus, there have been some
proposals for guide wires made of Ti--Ni based alloys with enhanced
rigidity.
[0007] For example, Patent Document 1 discloses a catheter guide
wire including a core material and a coating portion applied on the
surface of the core material, wherein the core material is formed
of a Ti--Ni based alloy containing 45 to 52 at % Ni, and at least
one of an exothermic amount and an endothermic amount of the Ti--Ni
based alloy caused by martensitic transformation and martensitic
reverse transformation is not higher than 0.80 cal/g.
[0008] Patent Document 2 discloses catheter guide wire including a
Ti--Ni alloy core wire and an outer circumferential member applied
on the core wire from outside, wherein a sectional area of a front
end portion of the core wire is smaller than that of any other
portion of the core wire by a chemical process and/or a mechanical
process. An example of the aforementioned mechanical process is
swaging or rolling.
[0009] Patent Document 3 discloses a method for manufacturing a
catheter guide wire in which a sectional area of a front end
portion of a Ti--Ni alloy core wire having superelasticity in a
temperature range of from 0.degree. C. to 40.degree. C. is made
smaller than that of any other portion of the core wire by at least
one process selected from a group consisting of etching processing,
cutting/grinding and swaging, and the core wire obtained thus is
coated with an outer circumferential member from outside.
PRIOR TECHNICAL DOCUMENTS
Patent Documents
[0010] Patent Document 1: JP-H05-293175-A
[0011] Patent Document 2: JP-H06-165822-A
[0012] Patent Document 3: JP-H11-128363-A
SUMMARY OF THE INVENTION
Problems that the Invention is to Solve
[0013] Since the guide wire of Patent Document 1 has a Young's
modulus of about 40 GPa as shown in its test example, sufficient
rigidity to be used for microscopic blood vessel may not be
obtained.
[0014] In Patent Document 2, the front end portion of the core wire
in the guide wire is processed to be narrower than any other
portion of the core wire by a chemical process and/or a mechanical
process. When the front end portion of the core wire is processed
by a mechanical process, the rigidity of the front end portion of
the core wire is enhanced by work hardening. However, an
intermediate portion and a base end portion of the core wire are
not processed at all but remain soft. The rigidity of the core wire
as a whole is not enhanced. Thus, a pushing force acting at the
base end portion of the core wire cannot be transmitted to the
front end portion efficiently, and there is a problem in terms of
pushability.
[0015] Also in Patent Document 3, only the front end portion of the
core wire is processed by cutting, swaging etc. The rigidity in the
intermediate portion and the base end portion of the core wire
cannot be enhanced, and there is a problem in terms of pushability
as in Patent Document 2.
[0016] An object of the present invention is to provide a core wire
for guide wire in which high rigidity can be attained even with a
fine wire diameter so that pushability is improved while the core
wire is prevented from fatigue deformation, and a method for
manufacturing the core wire.
Means for Solving the Problems
[0017] A first invention provides a core wire for guide wire,
wherein the core wire is made of a Ti--Ni based alloy, has a wire
diameter not larger than 0.5 mm and has a Young's modulus not lower
than 50 GPa.
[0018] According to the above invention, the core wire has high
rigidity to be not lower than 50 GPa in Young's modulus while the
core wire has the fine wire diameter not larger than 0.5 mm. Thus,
the core wire has high pushability which is required when the core
wire is inserted into a tubular organ, and the core wire is
prevented from fatigue deformation. Accordingly, the core wire can
be used suitably for guide wire, for example, to be inserted into a
narrow blood vessel of a heart, a brain, etc.
[0019] A second invention provides, based on the first invention,
the core wire, wherein wire drawing and swaging are performed on
the core wire.
[0020] According to the above invention, the two processes of wire
drawing and swaging are performed so that the working degree of the
core wire is improved. Thus, high rigidity can be attained in spite
of the fine wire diameter.
[0021] A third invention provides, based on the first or second
invention, the core wire, wherein the Ti--Ni based alloy is a
work-hardened Ti--Ni based alloy whose texture has a
microcrystalline structure.
[0022] In the case where either the wire drawing or the swaging
alone is performed alone, the texture has a structure close to an
amorphous structure. When both the wire drawing and the swaging are
performed as in the core wire, the texture has a microcrystalline
structure. As a result, prevention from fatigue deformation can be
attained even in the processed state of the core wire while the
mechanical characteristics are improved to keep the rigidity. Thus,
the core wire can be used suitably for microscopic guide wire.
[0023] A fourth invention provides, based on the second or third
invention, the core wire, wherein heat treatment as well as the
wire drawing and the swaging is performed on the core wire.
[0024] According to the above invention, the heat treatment is
performed so that strain or residual stress caused by the wire
drawing and the swaging can be relaxed. Thus, the linearity which
is essential as a core wire for guide wire can be enhanced while
the rigidity is attained.
[0025] A fifth invention provides, based on any one of the first to
fourth inventions, a method for manufacturing the core wire
including: drawing a raw material made of a Ti--Ni based alloy, and
then carrying out swaging to obtain a core wire having a wire
diameter not larger than 0.5 mm and a Young's modulus not lower
than 50 GPa.
[0026] According to the above invention, the two processes of wire
drawing and swaging are performed. Thus, a core wire which has high
rigidity to be not lower than 50 GPa in Young's modulus and which
is prevented from fatigue deformation can be obtained.
[0027] A sixth invention provides, based on the fifth invention,
the method further including: performing heat treatment after the
swaging.
[0028] According to the above invention, strain or residual stress
caused by the wire drawing and the swaging can be eliminated by the
heat treatment. Thus, it is possible to obtain a core wire which
has rigidity and is prevented from fatigue deformation and which
has high linearity.
Effect of the Invention
[0029] According to the invention, the core wire has high rigidity
to be not lower than 50 GPa in Young's modulus while the core wire
has a fine wire diameter not larger than 0.5 mm. Thus, the core
wire has high pushability and is prevented from fatigue
deformation, and the core wire can be used suitably for guide wire
to be inserted into a narrow blood vessel of a heart, a brain,
etc.
BRIEF DESCRIPTION OF THE DRAWINGS
[0030] FIG. 1 is sectional view showing an embodiment of a core
wire for guide wire according to the invention.
[0031] FIGS. 2A to 2C illustrate a method for manufacturing the
guide wire according to the invention, FIG. 2A illustrating a state
before wire drawing, FIG. 2B illustrating a state where the wire
drawing is being performed, FIG. 2C illustrating a state where
swaging is being performed.
[0032] FIG. 3 is a stress-strain diagram of Comparative Examples 1
to 3 for examining influence of heat treatment on materials
subjected to wire drawing.
[0033] FIG. 4 is a stress-strain diagram of Comparative Examples 4
to 6 for examining influence of heat treatment on materials
subjected to swaging.
[0034] FIG. 5 is a stress-strain diagram of Comparative Example
land Examples 1 to 3 for examining influence of heat treatment on
materials subjected to both wire drawing and swaging.
[0035] FIG. 6 is a stress-strain diagram of Comparative Example 7
and Examples 4 and 5 for examining influence of kind of swaging on
materials subjected to wire drawing.
[0036] FIGS. 7A and 7B show an observed texture of Example 1 by a
transmission electron microscope, FIG. 7A being a photograph of the
texture, FIG. 7B being an electron diffraction pattern.
[0037] FIGS. 8A and 8B show an observed texture of Example 1 by the
transmission electron microscope at a different place from that in
FIGS. 7A and 7B, FIG. 8A being a photograph of the texture, FIG. 8B
being an electron diffraction pattern.
[0038] FIGS. 9A and 9B show an observed texture of Comparative
Example 1 by the transmission electron microscope, FIG. 9A being a
photograph of the texture, FIG. 9B being an electron diffraction
pattern.
[0039] FIGS. 10A and 10B show an observed texture of Comparative
Example 4 by the transmission electron microscope, FIG. 10A being a
photograph of the texture, FIG. 10B being an electron diffraction
pattern.
[0040] FIG. 11 is a graph showing results of Vickers hardness tests
on Comparative Examples 1 and 4 and Example 1.
MODE FOR CARRYING OUT THE INVENTION
[0041] An embodiment of a core wire for guide wire according to the
invention will be described below with reference to the
drawings.
[0042] This core wire for guide wire (hereinafter referred to as
"core wire") is used so as to be disposed in an internal center of
a guide wire. For example, the core wire can be applied to a guide
wire 10 shown in FIG. 1. The guide wire 10 in this embodiment
includes a core wire 15 according to the invention and a resin
layer 17 applied on an outer circumference of the core wire 15. A
front end portion of the core wire 15 is tapered off with a
diameter gradually reduced toward the tip.
[0043] The core wire in this embodiment is made of a Ti--Ni based
alloy subjected to wire drawing and swaging. The core wire is
formed to have a wire diameter not larger than 0.5 mm and a Young's
modulus not lower than 50 GPa.
[0044] A Ti--Ni based alloy which is good in biocompatibility and
suitable for a guide wire, such as Ti--Ni, Ti--Ni--Cu, Ti--Ni--Fe,
Ti--Ni--Nb, etc., is used as the material of the core wire. In
addition, alloy elements such as V, Cr, Mn, Co, etc. may be added
to the Ti--Ni based alloy (each of the alloy elements has a role of
reducing transformation temperature).
[0045] The core wire made of the aforementioned Ti--Ni based alloy
is further subjected to wire drawing and swaging. In the "wire
drawing", a raw material is drawn out through a dice with a certain
hole shape or the raw material is inserted into the hole of the
dice and extruded therefrom, thereby processing the raw material
into a wire with a certain shape. In the "swaging", an outer
circumference of the raw material is hammered and drawn using a
rotating dice, thereby processing the raw material into a desired
shape.
[0046] A working ratio P.sub.1 when the raw material is drawn is
preferably not lower than 10%, more preferably not lower than 20%,
and the most preferably not lower than 30%. When the working ratio
P.sub.1 is lower than 10%, the work hardening of the raw material
is insufficient so that the rawmaterial cannot have satisfactory
rigidity. The working ratio P.sub.1 mentioned herein can be derived
from the following Expression (i), in which A.sub.0 designates a
sectional area of the raw material and A.sub.1 designates a
sectional area of the raw material (primary processed material)
subjected to wire drawing. Although it is preferable that the
working ratio is higher, a contrivance for processing may be
necessary when the working ratio is higher than 60%.
Working Ratio P.sub.1(%)={(A.sub.0-A.sub.1)/A.sub.0}.times.100
(i)
[0047] The processing order is not limited as long as the core wire
is subjected to both the wire drawing and the swaging, but it is
preferable that after wire drawing (primary process) is performed
on the raw material, swaging (secondary process) is performed on
the raw material (primary processed material) subjected to the wire
drawing. In this case, a working ratio P.sub.2 when the primary
processed material is swaged is preferably not lower than 5%.
Further, a total working ratio (P.sub.1+P.sub.2) of this working
ratio P.sub.2 and the aforementioned working ratio P.sub.1 is
preferably not lower than 50%. When the working ratio P.sub.2 is
lower than 5%, the work hardening of the raw material is
insufficient so that the raw material cannot have satisfactory
rigidity. The working ratio P.sub.2 mentioned herein can be derived
from the following Expression (ii), in which A.sub.1 designates a
sectional area of the primary processed material and A.sub.2
designates a sectional area of the raw material (secondary
processed material) subjected to swaging.
Working Ratio P.sub.2(%)={(A.sub.1-A.sub.2)/A.sub.1}.times.100
(ii)
[0048] The core wire subjected to the two processes of the wire
drawing and the swaging is formed to have a wire diameter not
larger than 0.5 mm and a Young's modulus not lower than 50 GPa. As
shown in FIG. 1, in the core wire 15 according to this embodiment,
any other portion than the tapered front end portion has a wire
diameter D.sub.2 not larger than 0.5 mm. When the wire diameter of
the core wire is larger than 0.5 mm, the core wire can be used for
the aorta etc., but it is difficult to use the core wire for
coronary intervention (PTCA), a peripheral system, etc. A practical
wire diameter applied to PTCA or a peripheral system in an existing
guide wire is 0.24 to 0.34 mm.
[0049] The core wire having a wire diameter not larger than 0.5 mm
is made to have a Young's modulus not lower than 50 GPa. The
Young's modulus mentioned herein shows a value when the strain of
the core wire is 2%. That is, this core wire has high rigidity to
be not lower than 50 GPa in spite of the fine wire diameter not
larger than 0.5 mm. When the Young's modulus of the core wire is
lower than 50 GPa, the core wire is apt to come short of
pushability or torque transmission characteristic which is however
required when the core wire is inserted into the microscopic blood
vessel such as a coronary artery or a cerebral artery. Thus, the
core wire having the Young's modulus lower than 50 GPa is not
suitable as a core wire according to the invention. In addition, it
is preferable that the Young's modulus is higher.
[0050] In this manner, the core wire in this embodiment is
subjected to the two processes of wire drawing and swaging, so that
the working ratio of the core wire can be improved as compared with
the case where the core wire is subjected to the wire drawing alone
or the case where the core wire is subjected to the swaging alone.
Thus, the core wire can attain high rigidity to be not lower than
50 GPa in Young's modulus in spite of a fine wire diameter not
larger than 0.5 mm.
[0051] In addition, the texture of this core wire has a
microcrystalline structure because the two processes of wire
drawing and swaging are performed on the core wire. This will be
described with reference to FIGS. 9A and 9B (the case where wire
drawing is performed alone) and FIGS. 10A and 10B (the case where
swaging is performed alone). In the case where wire drawing is
performed alone as shown in FIG. 9B and the case where swaging is
performed alone as shown in FIG. 10B, an image of unclear rings
whose outlines are intermittent is observed in an electron
diffraction pattern of each core wire. This electron diffraction
pattern is an image peculiar to an amorphous structure (so-called
halo pattern). In the case where wire drawing is performed alone
and the case where swaging is performed alone, the texture of each
core wire has an amorphous structure, as is also confirmed with
reference to pictures of textures shown in FIGS. 9A and 10A.
[0052] On the other hand, an electron diffraction pattern of a core
wire according to the invention is obtained by using and imaging
one and the same sample as electron diffraction at two places. As a
result, as shown in FIGS. 7B and 8B, an image of clear rings can be
observed in the electron diffraction pattern. Thus, the core wire
has a microcrystalline structure, as is also confirmed clearly with
reference to pictures of the textures shown in FIGS. 7A and 8A.
[0053] In this manner, the textures of the core wire change from a
metastable amorphous structure to a stable microcrystalline
structure respectively due to both the wire drawing and the swaging
performed on the core wire. Thus, the working degree (for example,
hardness) increases, and mechanical characteristics such as tensile
strength are improved.
[0054] The core wire in this embodiment is further subjected to
heat treatment so that strain, bending or residual stress caused by
processing can be eliminated. For example, the heat treatment can
be carried out on the core wire at a temperature of 200 to
400.degree. C. for 1 to 60 minutes while the core wire is retained
in a certain shape.
[0055] Next, a method for manufacturing a core wire for guide wire
according to the invention will be described with reference to
FIGS. 2A to 2C. The aforementioned core wire for guide wire can be
manufactured by this method for manufacturing a core wire for guide
wire (hereinafter referred to as "manufacturing method").
[0056] This manufacturing method includes a primary process for
drawing a raw material M.sub.0 into a primary processed material
M.sub.1 and a secondary process for swaging the primary processed
material M.sub.1 into a secondary processed material M.sub.2 after
the primary process, so as to manufacture a core wire which has a
wire diameter not larger than 0.5 mm and a Young's modulus not
lower than 50 GPa.
[0057] First, as shown in FIG. 2A, the raw material M.sub.0 having
a wire diameter D.sub.0 and made of a Ti--Ni based alloy is
inserted into a hole 2 formed in a wire-drawing dice 1 and extruded
from the hole 2, or the raw material M.sub.0 is drawn out through
the hole 2 of the wire-drawing dice 1. Thus, as shown in FIG. 2B,
wire drawing is performed on the raw material M.sub.0 so as to draw
the raw material M.sub.0 into a certain length while reducing the
diameter of the raw material M.sub.0. As a result, the primary
processed material M.sub.1 having a wire diameter D.sub.1 is
shaped.
[0058] The inner diameter of the hole 2 of the wire drawing dice 1
is set so that a working ratio P.sub.1 when the raw material
M.sub.0 is drawn is made preferably not lower than 10%, more
preferably not lower than 20%, and most preferably not lower than
30%.
[0059] Next, swaging is performed on the primary processed material
M.sub.1. An apparatus used for the swaging in this embodiment has a
pair of swaging dices 5 and 5 as shown in FIG. 2C. The pair of
swaging dices 5 and 5 are formed to rotate in certain directions
around the primary processed material M.sub.1 while colliding with
and separating from the primary processed material M.sub.1
repeatedly. In addition, the swaging dices 5 and 5 move sliding
forward and backward along an axial direction of the primary
processed material M.sub.1.
[0060] Then, the primary processed material M.sub.1 is rotated in a
certain direction, and the pair of swaging dices 5 and 5 hammer and
draw the primary processed material M.sub.1 while rotating on the
periphery of the primary processed material M.sub.1 in a certain
direction. At the same time, the same swaging dices 5 move over a
certain range in the axial direction of the primary processed
material M.sub.1. Thus, a secondary processed material M.sub.2
having a wire diameter D.sub.2 not larger than 0.5 mm is shaped. In
this embodiment, an unnecessary portion of the secondary processed
material M.sub.2 is then further cut off, and a front end portion
of the secondary processed material M.sub.2 is processed into a
tapered shape with a reduced diameter. Thus, the core wire 15
having the wire diameter D.sub.2 not larger than 0.5 mm as shown in
FIG. 1 is manufactured. The secondary processed material M.sub.2
may be used as the core material 15 as it is.
[0061] It is also preferable that the size of an arc-like recess
formed in a front end portion of each swaging dice is set so that a
working ratio P.sub.2 when the primary processed material is swaged
can be made not lower than 5%. Further, it is preferable that
setting is done so that a total working ratio (P.sub.1+P.sub.2) of
the working ratio P.sub.1 and the working ratio P.sub.2 can be made
not lower than 50%.
[0062] According to this manufacturing method, the two processes of
wire drawing and swaging are performed so that the working ratio of
the core wire is improved, as compared with the case where wire
drawing is performed alone or the case where swaging is performed
alone. As a result, the hardness increase caused by work hardening
becomes larger. And, it is possible to obtain a core wire which has
high rigidity to be not lower than 50 GPa in Young's modulus while
having the fine wire diameter not larger than 0.5 mm and which is
prevented from fatigue deformation.
[0063] Preferably, in this manufacturing method, heat treatment is
performed on the core wire after the aforementioned swaging. For
example, the heat treatment is performed on the core wire 15 such
that the core wire 15 is kept at a temperature 200.degree. C. to
400.degree. C. for 1 to 60 minutes. Since strain, bending, and
residual stress caused by the wire drawing and the swaging are
eliminated from the core wire 15 through the heat treatment, it is
possible to obtain a core wire which has rigidity and is prevented
from fatigue deformation and which has high linearity (not bending
but keeping a straight posture in its initial shape).
[0064] The core wire according to the invention manufactured by the
aforementioned manufacturing method has the following operation and
effect.
[0065] That is, due to the two processes of wire drawing and
swaging performed on the core wire according to the invention, the
working ratio of the core wire is improved as compared with the
case where wire drawing is performed alone or the case where
swaging is performed alone. Thus, the hardness increase caused by
work hardening becomes larger than in the case where one of the
aforementioned processings is performed alone. Therefore, the core
wire according to the invention can attain high rigidity to be not
lower than 50 GPa in Young's modulus while having the fine wire
diameter not larger than 0.5 mm.
[0066] Since the core wire according to the invention has high
rigidity while having the fine wire diameter, the core wire is high
in pushability which is required when the core wire is inserted
into a tubular organ and in toque transmission characteristic which
is requested for selection of a blood vessel, and the core wire can
be prevented from fatigue deformation. Thus, for example, the core
wire according to the invention can be used suitably for guide wire
to be inserted into a narrow blood vessel of a heart, a brain,
etc.
[0067] In the background art, a raw material is drawn and then cut
or ground so as to obtain a core wire for guide wire with a narrow
size. However, the cost may be increased due to a large waste of
the material because the drawn raw material is cut. Further, the
hardness and the rigidity may be low because a work-hardened layer
produced in the surface of the raw material by the wire drawing is
cut.
[0068] On the other hand, the wire diameter of the core wire is
made not larger than 0.5 mm by the swaging in which the raw
material is hammered and drawn. Thus, the yield of the material can
be improved to reduce the cost, as compared with the case where the
raw material is cut into a certain size. Further, since the swaging
is performed after the wire drawing in this embodiment, a
work-hardened layer produced by the wire drawing can be prevented
from being cut, but the work hardening is further advanced. Thus, a
core wire having high rigidity to be not lower than 50 GPa in
Young's modulus can be obtained.
EXAMPLES
[0069] Mechanical characteristics, textures and hardness of various
core materials were evaluated.
(Prerequisite) Composition of Ti--Ni Based Alloy
[0070] Examples and Comparative Examples which will be described
below were manufactured using an alloy of Ti-51Ni (at %).
(1) Manufacturing of Comparative Examples and Examples
Comparative Example 1
[0071] A linear raw material was cut out from a Ti--Ni based alloy
having the aforementioned composition, and wire drawing was
performed on the raw material. Thus, Comparative Example 1 was
manufactured. The wire diameter was 0.475 mm, and the working ratio
rate was 55%.
Comparative Example 2
[0072] A certain length of the raw material was cut out from
Comparative Example 1, and heat treatment was applied to the raw
material such that the raw material was kept at 200.degree. C. for
30 minutes. Thus, Comparative Example 2 was manufactured. The
working ratio was the same as that of Comparative Example 1, and
the wire diameter was 0.478 mm (The wire diameter varies depending
on oxides during the heat treatment. It is also the same in
Comparative Example 3 and Examples 2 and 3).
Comparative Example 3
[0073] A certain length of the raw material was cut out from
Comparative Example 1, and heat treatment was applied to the raw
material such that the raw material was kept at 300.degree. C. for
30 minutes. Thus, Comparative Example 2 was manufactured. The
working ratio was the same as that of Comparative Example 1, and
the wire diameter was 0.482 mm.
Comparative Example 4
[0074] A linear raw material was cutout from a Ti--Ni based alloy
having the aforementioned composition, and swaging was performed on
the raw material. Thus, Comparative Example 4 was manufactured. The
wire diameter was 0.360 mm, and the working ratio was 98.9%.
Comparative Example 5
[0075] A certain length of the raw material was cutout from
Comparative Example 4, and heat treatment was applied to the raw
material such that the raw material was kept at 200.degree. C. for
30 minutes. Thus, Comparative Example 5 was manufactured. The
working ratio and the wire diameter were the same as those of
Comparative Example 4.
Comparative Example 6
[0076] A certain length of the raw material was cut out from
Comparative Example 4, and heat treatment was applied to the raw
material such that the raw material was kept at 300.degree. C. for
30 minutes. Thus, Comparative Example 6 was manufactured. The
working ratio and the wire diameter were the same as those of
Comparative Example 4.
Comparative Example 7
[0077] In the same manner as Comparative Example 1, a linear raw
material was cut out from a Ti--Ni based alloy having the
aforementioned composition, and wire drawing was performed on the
raw material. Thus, Comparative Example 7 was manufactured. The
wire diameter was 0.602 mm, and the working ratio was 43.8%.
Example 1
[0078] A certain length of the raw material was cut out from
Comparative Example 1, and swaging was performed on the raw
material. Thus, Example 1 was manufactured. The wire diameter was
0.423 mm and the working ratio after the swaging was 64%.
Example 2
[0079] A certain length of the raw material was cut out from
Example 1, and heat treatment was applied to the raw material such
that the raw material was kept at 200.degree. C. for 30 minutes.
Thus, Example 2 was manufactured. The working ratio was the same as
that of Example 1 and the wire diameter was 0.416 mm.
Example 3
[0080] A certain length of the raw material was cut out from
Example 1, and heat treatment was applied to the raw material such
that the raw material was kept at 300.degree. C. for 30 minutes.
Thus, Example 3 was manufactured. The working ratio was the same as
that of Example 1 and the wire diameter was 0.420 mm.
Example 4
[0081] A certain length of the raw material was cut out from
Comparative Example 7, and swaging was performed on the raw
material with three swaging dices. Thus, Example 4 was
manufactured. The wire diameter was 0.486 mm and the working ratio
after the swaging was 64%.
Example 5
[0082] A certain length of the raw material was cut out from
Comparative Example 7, and swaging was performed on the raw
material with two swaging dices. Thus, Example 5 was manufactured.
The wire diameter was 0.512 mm and the working ratio after the
swaging was 59%.
(2) Evaluation of Mechanical Characteristics
[0083] (a) Test Method
[0084] Each of Comparative Examples 1 to 7 and Examples 1 to 5 was
processed so that a test piece with a gauge length of 50 mm was
manufactured. Each of these test pieces was set in a Tensilon
tensile tester to repeat a cycle (load application, load removal,
load application, . . . ) of applying a tensile load to the test
piece at a room temperature and with a test speed of 1 mm/min so as
to produce an elongation strain in the test piece, and then
removing the tensile load from the test piece. The relation between
tensile stress (MPa) and strain (%) was measured in each test
piece. The results are shown in FIGS. 3 to 6 and in Table 1. The
Young's modulus on this occasion was calculated from the tensile
stress at the strain of 2%.
[0085] In addition, Comparative Examples 1 to 3 are provided for
examining influence of heat treatment on materials subjected to
wire drawing (see FIG. 3), and Comparative Examples 4 to 6 are
provided for examining influence of heat treatment on materials
subjected to swaging (see FIG. 4). On the other hand, Examples 1 to
3 are provided for examining influence of heat treatment on
materials subjected to both wire drawing and swaging (see FIG. 5),
and Examples 4 and 5 are provided for examining influence of kind
of swaging (two dices or three dices) on materials subjected to
swaging (see FIG. 6).
TABLE-US-00001 TABLE 1 Wire Drawing Swaging Wire Young's Working
Working Heat Diameter Modulus Target Drawing Sample Ratio (%) Ratio
(%) Treatment (mm) (GPa) Note Influence of Heat Treatment FIG. 3
CE1 55 -- -- 0.475 49.2 -- on Materials Subjected to CE2 '' --
200.degree. C. .times. 30 min 0.478 43.8 heat treatment on sample
Wire Drawing obtained from CE1 CE3 '' -- 300.degree. C. .times. 30
min 0.482 32.6 heat treatment on sample obtained from CE1 Influence
of Heat Treatment FIG. 4 CE4 -- .sup. 98.9 -- 0.360 58.9 -- on
Materials Subjected to CE5 -- '' 200.degree. C. .times. 30 min ''
58.2 heat treatment on sample Swaging obtained from CE4 CE6 -- ''
300.degree. C. .times. 30 min '' 49.6 heat treatment on sample
obtained from CE4 influence of Heat Treatment FIG. 5 Ex1 55 64 --
0.423 63.4 wire drawing and swaging on on Materials Subjected to
sample obtained from CE1 Wire Drawing and Swaging Ex2 '' ''
200.degree. C. .times. 30 min 0.416 70.2 heat treatment on sample
obtained from Ex1 Ex3 '' '' 300.degree. C. .times. 30 min 0.420
60.5 heat treatment on sample obtained from Ex1 Influence of Kind
of Swaging FIG. 6 CE7 .sup. 43.8 -- -- 0.602 40.7 same conditions
as CE1 (with Three Dices or Two (different sample) Dices) on
Materials Ex4 '' 64 -- 0.486 60.9 3-dice swaging on sample
Subjected to Wire Drawing obtained from CE7 Ex5 '' 59 -- 0.512 60.7
2-dice swaging on sample obtained from CE7 (CE = Comparative
Example) (Ex = Example)
[0086] (b) Discussion of Test Results
[0087] As shown in FIG. 3, it is understood that the Young's
modulus is reduced when heat treatment is performed after wire
drawing (Comparative Examples 2 and 3). The higher the temperature
of the heat treatment is, the more conspicuous that tendency is.
The same tendency is confirmed in the case where heat treatment is
performed after swaging as shown in FIG. 4.
[0088] FIG. 5 shows a stress-strain diagram of Examples 1 to 3. As
is understood from the result of Example 1, the material subjected
to the two processes of wire drawing and swaging has a high
rigidity of 63.4 GPa in Young's modulus in spite of a fine wire
diameter of 0.423 mm.
[0089] In Comparative Examples shown in FIGS. 3 and 4, heat
treatment leaded to reduction in Young's modulus. On the other
hand, there was obtained a result in Example 2 shown in FIG. 5 that
the Young's modulus was improved in spite of heat treatment
performed. That is, obtained was the finding that the Young's
modulus was improved by heat treatment on the material subjected to
the two processes of wire drawing and swaging while the Young's
module was reduced by heat treatment on the material subjected to
wire drawing or swaging only. This is because the metal texture has
a microcrystalline structure due to the combination of wire drawing
and swaging. That is, heat treatment performed after wire drawing
or heat treatment performed after swaging leads to loss in energy
(reduction in Young's modulus) due to recrystallization, while heat
treatment performed after wire drawing and swaging leads to no loss
in energy (no reduction in Young's modulus).
[0090] FIG. 6 shows Young's modulus in the case where swaging was
performed with three dices (Example 4) and Young's modulus in the
case where swaging was performed with two dices (Example 5). The
number of dices had little influence, but it could be confirmed
that the Young's modulus was improved in each case.
(3) Evaluation of Textures
[0091] Textures and electron diffraction patterns of Comparative
Examples 1 and 4 and Example 1 were observed with a transmission
electron microscope (TEM). The results are shown in FIGS. 7A to 8B
(Example 1), FIGS. 9A and 9B (Comparative Example 1) and FIGS. 10A
and 10B (Comparative Example 4). Incidentally, Example 1 was
observed in two different positions (FIGS. 7A to 8B).
[0092] As shown in FIGS. 9B and 10B, the electron diffraction
patterns of Comparative Examples 1 and 4 have unclear images
peculiar to an amorphous structure. Also from FIGS. 9A and 10A, it
is understood that structures in Comparative Examples 1 and 4 are
amorphous.
[0093] On the other hand, as shown in FIGS. 7B and 8B, the electron
diffraction pattern of Example 1 has a clear ring-like image
peculiar to a crystalline structure. Further as shown in FIGS. 7A
and 8B, it is also understood from the texture pictures that the
texture of Example 1 has a microcrystalline structure. Thus, the
two processes of wire drawing and swaging lead to a
microcrystalline structure in the texture.
(4) Evaluation of Hardness
[0094] Vickers hardness (Hv) was measured in Comparative Examples 1
and 4 and Example 1 whose textures were observed in (3). Vickers
hardness was measured outside the texture and inside the texture in
each sample with a load of 200 kg. The results are shown in FIG.
11.
[0095] As shown in FIG. 11, the Vickers hardness in Comparative
Example 1 subjected to wire drawing only is comparatively low, and
the Vickers hardness in Comparative Example 2 subjected to swaging
only is comparatively high but varies widely. On the other hand, in
Example 1 subjected to wire drawing and swaging, the Vickers
hardness is high both inside the texture and outside the texture,
and low in variation. It is therefore understood that the texture
structure of Example 1 is highly stable.
DESCRIPTION OF REFERENCE NUMERALS AND SIGNS
[0096] 10 guide wire [0097] 15 core wire for guide wire (core
wire)
* * * * *