Metal treatment – Stock – Copper base
Reexamination Certificate
1999-06-25
2001-12-11
Ip, Sikyin (Department: 1742)
Metal treatment
Stock
Copper base
C148S402000, C148S563000, C428S547000, C428S610000, C428S690000
Reexamination Certificate
active
06328822
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a copper-based, functionally graded alloy having uniform composition and diameter and continuously or stepwise changing properties such as hardness, modulus elongation, etc. and a method for producing such an alloy, and use of such an alloy in guide wires, catheters, etc.
Functionally graded alloys are materials having continuously or stepwise changing properties such as hardness, elasticity, thermal conductivity, electric conductivity, etc. without gradient in size given by mechanical working such as cutting, etc. or chemical treatments such as etching, etc. Functionally graded materials developed so far are mostly such two-component composites as SiC/C, ZrO/W, TiC/Ni, ZrO/Ni, etc., which have gradually changing mixing ratios.
Conventional functionally graded materials having gradually changing mixing ratios have been produced by mixing different material powders at gradually changing mixing ratios to prepare a plurality of mixed powder sheets having gradually changing mixing ratios, laminating the mixed powder sheets along the gradually changing mixing ratios, compacting and sintering them. For example, Japanese Patent Laid-Open No. 5-278158 discloses a functionally graded, binary metal material produced by laminating and sintering W powder and Mo powder at a gradually changing mixing ratio.
However, the functionally graded materials produced by such a method cannot be rolled or drawn, and they can be formed to desired shapes only by cutting. Thus, they are not only very expensive but also cannot be formed into complicated shapes. Accordingly, the conventional functionally graded materials are used mainly in highly expensive applications, such as spacecraft, nuclear power generators, etc. It is thus highly desired to develop less expensive and easy-to-form functionally graded materials.
Also, alloys having shape recovery properties and superelasticity are widely used in various applications such as guide wires, catheters, etc. To introduce the catheter into the blood vessel and place it at a desired site in the blood vessel, a guide wire for guiding the catheter is first introduced into the desired site in the blood vessel, and the catheter is guided to the desired site in the blood vessel along the guide wire. Because human blood vessels are winding and branching differently depending on individuals, guide wires having high introduction operability and torque conveyance are required to insert the guide wires without damaging the blood vessel walls.
For this purpose, the guide wire is composed of a core wire comprising a tip end portion which is made soft by reducing its diameter, and a body portion which is relatively rigid, and a coating layer formed on the core wire, the coating layer being made of synthetic resins which do not cause any damage to the human body, such as polyamides, thermoplastic polyurethanes, fluoroplastics, etc.
The guide wire is usually constituted by a coil-shaped metal wire made of stainless steel, carbon steel, etc. However, wires of such materials are easily bent, superelastic metals such as Ni—Ti alloys, etc. are used for the core wires of the guide wires (Japanese Patent Publication No. 2-24549).
However, because superelastic Ni—Ti alloys lack rigidity, though they are sufficiently soft. Therefore, they are not well inserted into the blood vessel, sometimes making it difficult to place them at a desired place in the blood vessel.
Also, because Ni—Ti alloys are relatively poor in cold working, they are not easily formed into thin wires suitable for guide wires, etc. With respect to the gradient of properties by heat treatment, it is difficult to provide the guide wire with such a gradient as to control the torque conveyance of the guide wire.
The same is true of catheters made of Ni—Ti alloys. The Ni—Ti alloy catheters are not well inserted into the blood vessel. Also, Ni—Ti alloys are not easily formed into thin wires or pipes. Further, the Ni—Ti alloys are poor in weldability and adhesion, posing problems when combined with other materials.
OBJECT AND SUMMARY OF THE INVENTION
An object of the present invention is to provide an inexpensive functionally graded alloy having excellent workability and a method for producing such a functionally graded alloy.
Another object of the present invention is to provide a core wire for a guide wire comprising a soft tip end portion and a properly elastic and rigid body portion, excellent in insertion operability, torque conveyance, and workability, and a guide wire comprising such a core wire.
A further object of the present invention is to provide a catheter comprising a soft tip end portion and a properly elastic and rigid body portion, excellent in insertion operability, torque conveyance, and workability.
As a result of research on the previously proposed shape memory Cu—Al—Mn alloy having a &bgr;-phase structure (Japanese Patent Laid-Open No. 7-62472), the inventors have found that when the shape memory Cu—Al—Mn alloy having a &bgr;-phase structure is partially heated at particular temperatures or at gradually changing temperatures, the shape memory Cu—Al—Mn alloy is provided with a partially different crystal structure, which shows remarkably gradient properties. The inventors have also found that by giving gradually changing properties to the Cu—Al—Mn alloy by a heat treatment at a proper temperature gradient, the guide wire and the catheter can be produced from such Cu—Al—Mn alloy with extremely improved insertion operability and torque conveyance. The present invention has been completed based upon these findings.
The functionally graded alloy of the present invention has a composition comprising 3-10 weight % of Al, 5-20 weight % of Mn, the balance being substantially Cu and inevitable impurities, and comprises a first portion composed essentially of a &bgr;-phase, a second portion composed essentially of an &agr;-phase and a Heusler phase, and a third portion having a crystal structure continuously or stepwise changing from the first portion to the second portion.
The method for producing the functionally graded alloy according to the present invention comprises the steps of:
(a) forming a copper-based alloy having a composition comprising 3-10 weight % of Al, 5-20 weight % of Mn, the balance being substantially Cu and inevitable impurities, into a desired shape;
(b) keeping the copper-based alloy at 500° C. or higher and rapidly cooling it to transform a crystal structure thereof substantially to a &bgr;-phase; and
(c) subjecting the copper-based alloy to an aging treatment by a heater having a temperature gradient, thereby heating the first portion to lower than 250° C., the second portion to 250-350° C., and the third portion at a temperature continuously or stepwise changing from the heating temperature of the first portion to the heating temperature of the second portion.
The core wire for a guide wire according to the present invention comprises a body portion having high rigidity and a tip end portion having a lower rigidity than that of the body portion, at least part of the core wire being made of a copper-based alloy comprising 3-10 weight % of Al, and 5-20 weight % of Mn, the balance being substantially Cu and inevitable impurities.
The guide wire according to the present invention comprises a core wire comprising a body portion having high rigidity and a tip end portion having a lower rigidity than that of the body portion, at least part of the core wire being made of a copper-based alloy comprising 3-10 weight % of Al, and 5-20 weight % of Mn, the balance being substantially Cu and inevitable impurities.
The catheter according to one embodiment of the present invention is at least partially constituted by a metal pipe, the metal pipe being, at least in a tip end portion, made of a copper-based alloy comprising 3-10 weight % of Al, and 5-20 weight % of Mn, the balance being substantially Cu and inevitable impurities.
The catheter according to another embodiment of the present invention contains a reinforcing metal member in a
Ishida Kiyohito
Ishii Yoshikazu
Kainuma Ryosuke
Ip Sikyin
Ishida Kiyohito
LandOfFree
Functionally graded alloy, use thereof and method for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Functionally graded alloy, use thereof and method for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Functionally graded alloy, use thereof and method for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2558387