JPH03188248A - Superelastic alloy wire for guide wire and its production - Google Patents

Abstract

PURPOSE:To produce a superelastic alloy wire for guide wire which has a part having a low elastic modulus and a part having a high elastic modulus alternately in a long wire by constituting this wire of an Ni-Ti alloy and alternately providing a part having a high apparent elastic modulus and a part having a low apparent elastic modulus in the longitudinal direction of the wire. CONSTITUTION:A wire 1 is subjected to low-temp. primary heat treatment in a flying furnace 2 and passed through dancer rollers 7, and tension is applied to this wire 1 by means of tension applying devices 8, 8' and high-temp. secondary heat treatment is exerted by means of a batch-type heater 6. In this manner, the wire is constituted of an Ni-Ti alloy and a part having a high apparent elastic modulus and a part having a low apparent elastic modulus are alternately provided in the longitudinal direction of the wire. The part having a high apparent elastic modulus and the part having a low apparent elastic modulus are regulated to 3500-8000kgf/mm<2> and 2500-4500kgf/mm<2>, respectively. The primary heat treatment is carried out at 250-450 deg.C for 1sec-25hr and the secondary heat treatment is carried out at 400-750 deg.C for 1sec-24hr intermittently. By this method, the wire simultaneously having flexibility and strength to bending deformation at the end and in the other part can be provided.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a superelastic alloy wire used for catheter guide wires, etc., in which the tip and other parts of the wire have different apparent elastic modulus, and a method for manufacturing the same. It is related to.

[Conventional technology and its issues]

A catheter guidewire used for insertion into the human body has at least flexibility at the tip and sufficient strength against bending deformation in areas other than the tip in order to improve the guidewire's operability. Two characteristics are required at the same time.

In particular, the tip is tapered to make it thinner and flexible, making it easier to insert.For example, 0,5 mrnφ
A wire with a diameter of about 0.12 amφ is used by tapering a 100 to 200 m portion of the tip of the wire.

Conventionally, this taper processing was first performed by mechanical polishing, but the Ni-Ti superelastic alloy commonly used for catheter guide wires has the disadvantage that its superelasticity is lost when mechanically polished. CH,C
A method of electrolytic polishing is carried out in which the tip is immersed in an electrolytic solution of 001192%, f(C/!048%) while energizing the wire.

However, in the above electrolytic polishing method, each piece is immersed in electrolytic polishing solution using a hatch method and polished while moving up and down, resulting in large variations in the shape of the tapered part, and requires a large number of man-hours, resulting in high costs. There was a problem. In addition, the user
When coating with resin in the next process, there is a problem in that it is difficult to coat a part of the taper and the cost is high.

[Problem to be solved by the invention]

As a result of studies on the above-mentioned problems, the present invention has been developed to provide a guide wire for catheters that has flexibility and strength against bending deformation at the tip and other parts at the same time, that is, partially has a high elastic modulus and a low elastic modulus. A superelastic alloy wire for guide wires having alternating coefficients and a method for manufacturing the same have been developed.

[Means and effects for solving the problem] The present invention has N
A superelastic alloy wire for a guide wire, which is made of an i-Ti alloy and has alternating portions with high and low apparent elastic modulus in the longitudinal direction of the wire, and is also made of a Ni-Ti alloy. After cold working the wire at a processing rate of 10% or more, heat treatment is performed at a temperature of 250 to 450°C for a holding time of 1 second to 24 hours as a first heat treatment, and then a temperature of 400 to 750'C is performed as a secondary heat treatment. , the primary heat treatment temperature is 2
lower than the next heat treatment temperature), holding time 1 second to 2
This is a method for manufacturing a superelastic alloy wire for a guide wire, which is characterized in that heat treatment for 4 hours is intermittently applied to one portion in the longitudinal direction of the wire.

Here, we will explain how the flexibility or stiffness of the line is related to the mechanical properties of the material, especially the apparent elastic properties of the stress-strain diagram. Explain the reason for defining it. As shown in the stress-strain diagram of a superelastic alloy in Figure 1, when tensile strain is applied to the line, the stress increases linearly from point 0 to point A in the diagram.
When further strain is applied, the stress reaches point B while exhibiting a substantially constant value from point A. When the tensile strain is stopped at point B and the load is unloaded, it passes through point 0, point D, and returns to point 0. (Generally, the strain at point B is 4 to 6%.) This is a stress-strain diagram of a superelastic alloy.

Now, in Figure 1, the stress σ at point A is the strain ε.

The average elastic modulus divided by It can be seen that the strength of

On the other hand, regarding the relationship between the superelasticity memory heat treatment conditions and the apparent elastic modulus, as shown in FIG. 3, it was found that the apparent elastic modulus is small when the heat treatment temperature is low and becomes large when the heat treatment temperature is high.

The present invention was made based on the above knowledge, and the 10%
The long wire that has undergone the above cold working is first subjected to primary heat treatment at a low temperature so that the apparent elastic modulus takes a small value, leaving one part of the wire where you want it to be flexible. By further performing secondary heat treatment at a high temperature so that the apparent elastic coefficient (hereinafter simply referred to as elastic coefficient) of the other parts takes a high value, parts with high and low elastic coefficients are separated in the longitudinal direction of the wire. A superelastic alloy wire having alternating .

However, the above-mentioned portion with a high elastic modulus is 3500 to 80
00kgf/m4, lower part 2500-4500
It has an elastic modulus of kgf/-.

In addition, as a superelastic alloy having the above elastic modulus, Ni-
A part of Ti alloy or one or both of Ni and Ti is F
e, Cr, ■, Co, Si, Nb.

A Ni-Ti alloy substituted with one or more elements such as Al, Cu, Mo, and Mn can be used.

The manufacturing method is to process the above-mentioned Ni-Ti alloy wire at a processing rate of 10% or more, and then perform a primary heat treatment at a temperature of 250 to 450'C for a holding time of 1 second to 24 hours, followed by a secondary heat treatment. Heat treatment at a temperature of 400 to 750℃ (
However, the temperature of the first heat treatment is lower than the temperature of the second heat treatment), and heat treatment is intermittently applied to one portion in the longitudinal direction of the wire for a holding time of 1 second to 24 hours.

The above heat treatment may be carried out continuously using a continuous heat treatment apparatus, or may be carried out using a batch heat treatment apparatus, or both may be carried out in combination.

Next, the present invention will be explained in more detail with reference to the drawings.

As shown in Fig. 4, in order to give the wire (1) flexibility, that is, a low elastic modulus, the wire (1) is fed from the supply bobbin (3) through a running furnace (2) at a low temperature in advance. It is passed through and wound up on a winding bobbin (4), and subjected to primary heat treatment. Next, as shown in FIG. 5, a predetermined portion of the wire (1) is subjected to a secondary heat treatment by applying electricity through current terminals (5) and (5') while applying an appropriate tension. In this method of secondary heat treatment, as shown in FIG. 6, it is also possible to perform the secondary heat treatment on the required portion of the wire (11) at an appropriate temperature using a batch type heater (6) that allows the wire to be taken in and taken out. In the bunch type heat treatment, a fixed length batch type heater can be moved, and the wire can be moved in and out of the batch type heater.

In order to efficiently perform the above-mentioned primary heat treatment and secondary heat treatment, as shown in Fig. 8, wire (1) must be connected to the supply bobbin
3), undergoes low-temperature primary heat treatment in a running furnace (2), passes through a dancer roll (7), applies tension to the wire using tensioning devices (8) and (8'), and punches the wire. It is preferable to use a continuous heat treatment apparatus that performs high-temperature secondary heat treatment on a predetermined portion using a type heater (6).

The wire heat-treated in this way is, for example, a long piece in which portions having a high elastic modulus and portions having a low elastic modulus are alternately located at desired positions and for a desired length, as shown in FIG. A line is obtained. In order to use the above-mentioned catheter wire, the above-mentioned wire may be cut into wires having a necessary high elastic modulus and a necessary low elastic modulus.

The superelastic alloy wire for guide wires of the present invention can be applied not only to the above-mentioned catheters but also to other applications requiring similar characteristics.

〔Example〕

An embodiment of the present invention will be described below.

Wire diameter 0.48ma + φ Ni 51at%, balance Ti N
Using an iTi alloy wire drawn at a processing rate of 50%, first heat treatment was performed under the following conditions to give the wire a low elastic modulus over its entire length using the continuous heat treatment apparatus shown in FIG.

■Furnace, 114DO'C ■Line speed 2m/min (constant speed) ■Furnace length 2m The stress-strain diagram of the obtained wire rod as shown in Figure 1 is taken, and σ and /ε at point A are As a result of examining , σA/ε
The elastic modulus up to 1.5% strain at A=53 kgf/d/1.5% was 3550 kgf/-.

Next, secondary heat treatment was performed under the following conditions to impart a high elastic modulus only to the necessary length (portion) of this wire.

■ Furnace temperature: 550℃ ■ Holding time: 2 hours ■ Furnace length: 1.8 m, leaving 0.2 m of untreated part (this part already has a low elastic modulus) as shown in Figure 7. Heat treatment was performed every 1.8 m.

A stress-strain diagram is drawn from the obtained line in the same manner as above, and A
As a result of examining the point elongation, /ε4, σA/ε.

-48kgf/mjlo, 85%, the elastic modulus up to 0.85% strain was 5650kgf/mjlo. In this way, a long wire having alternately low and high elastic modulus regions was obtained in one wire.

(Effects) As explained above, according to the present invention, it is possible to obtain a superelastic alloy wire for guide wires having alternating portions with a low elastic modulus and a high elastic modulus in one long wire, which is industrially remarkable. This has the following effects.

[Brief explanation of drawings]

Figure 1 is a diagram showing the stress-strain characteristics of the superelastic alloy wire of the present invention, Figure 2 is a diagram showing the relationship between stiffness and pseudo-elastic modulus, and Figure 3 is a diagram showing the relationship between the stiffness and pseudo-elastic modulus. Figure 4 is a side view showing the heat treatment apparatus used in one embodiment of the present invention, and Figures 5 and 6 are diagrams showing the relationship between heat treatment temperature and heat treatment temperature. FIG. 7 is a perspective view showing the apparatus, FIG. 7 is a side view showing the distribution of line characteristics obtained by the present invention, and FIG. 8 is a side view of another heat treatment apparatus used in one embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Wire, 2... Running furnace, 3... Supply bobbin, 4... Winding bobbin, 5, 5'... Current-carrying terminal, 6... Batch type heater 7... Dancer roll, 88'... tension applying device.

Claims (3)

[Claims] (1) A superelastic alloy wire for a guide wire, which is made of a Ni-Ti alloy and has alternating portions with high and low apparent elastic modulus in the longitudinal direction of the wire. (2) The part with high apparent elastic modulus is 3500 to 800
0kgf/mm^2, low part 2500~4500k
The superelastic alloy wire for a guide wire according to claim 1, having an elastic modulus of gf/mm^2. (3) After cold working the Ni-Ti alloy wire at a processing rate of 10% or more, heat treatment is performed at a temperature of 250 to 450°C for a holding time of 1 second to 24 hours as a primary heat treatment, and then as a secondary heat treatment. Temperature: 400-750°C (however, the primary heat treatment temperature shall be lower than the secondary heat treatment temperature), holding time: 1 second ~
1. A method for producing a superelastic alloy wire for a guide wire, which comprises intermittently applying heat treatment for 24 hours to one portion in the longitudinal direction of the wire.