JPS6362583B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a TiNi alloy pseudoelastic spring.

[Prior art]

TiNi alloys are known to exhibit a remarkable shape memory effect accompanying the reverse transformation of thermoelastic martensitic transformation. It is also known that it also exhibits a pseudoelastic effect.

Pseudo-elastic effect means that when stress is applied to the same alloy at a temperature higher than its reverse transformation completion temperature (hereinafter abbreviated as Af), plastic deformation of several to 10% appears, but at the same time as unloading. It has the property of completely returning to its original state.

This property has attracted attention as a spring material for medical purposes such as orthodontic wires and catheters.

Currently, a piano wire helical coil spring is used as a catheter. The required functions are torque transferability and flexibility at temperatures close to body temperature (35°C). Furthermore, the catheter
for insertion into a blood vessel, at least one to
It is required to show a straight line within a range of 1.5m.

TiNi alloy pseudoelastic materials are generally obtained by homogenization treatment at 800 to 1000°C, but this results in a low stress level for apparent plastic deformation.
The temperature range in which the pseudoelastic effect occurs is also narrow.

The guiding principles for a method of performing treatment without recrystallization at a relatively low temperature after cold working are presented by Buenler (Wire J, Vol. 2,
June 1969 pp41-49).

The detailed research results are published in Japanese Patent Publication No. 58-161753.
It is written in Even with these studies, the above characteristics required for a spring material for a catheter are not satisfied.

[Purpose of the invention]

An object of the present invention is to provide a pseudoelastic spring that exhibits high deformation stress at temperatures near body temperature and has a continuous linear shape.

[Structure of the invention]

A TiNi alloy consisting of 50.5at% Ni (remaining Ti) is cold worked (processing rate 30%) and then continuously annealed under tension at 300 to 450°C, resulting in high deformation stress (60Kg/ mm ² or more) and has a linear shape.

[Action/effect of the invention]

The pseudoelastic spring according to the present invention has high torque transmission properties,
Since it exhibits high deformation stress at temperatures close to body temperature and exhibits a linear shape, when used as a catheter, it is not necessary to use a helical coil like conventional piano wire, and it has the advantage of being able to reduce the wire cross-sectional area. have

The following will explain based on examples.

Example 1 Ti-51.0at%Ni alloy was wire-drawn,
0.7mm by cold working after homogenizing at 800-1000℃
Finished in φ. This was annealed at a temperature of 370° C. while applying tension at a speed of 1 m/10 minutes (1 m soaking zone of the furnace).

Regarding this, stress-strain curves were determined in the temperature range of 0 to 50°C. The results are shown in FIG.

Figure 2 shows the results of measuring the deformation stress (stress indicating apparent plastic deformation) at 30°C with varying cold working rates. Figure 3 shows the results of measuring the deformation stress and residual strain amount when the cold working rate was kept constant and the annealing temperature was changed.

For comparison, Fig. 4 shows the measurement results of the deformation stress of a material homogenized at 800°C and a material subsequently annealed at 400°C.

As is clear from these results, the higher the cold working rate, the higher the deformation stress. Annealing conditions are 300
It can be said that ~450°C is appropriate. However, in practice, it is sufficient if the cold working rate exceeds 30%, but preferably it exceeds 40%.

Example 2 TiNi alloys made of 50, 50.5, and 51.5 at% Ni were wire-drawn, homogenized at 800 to 1000°C, and then cold worked to a diameter of 0.7 mm.

1 while applying tension at a temperature of 370℃.
Annealing was carried out at a speed of m/10 min (soaking zone of the furnace 1 m). The deformation stress and residual strain at 30°C were measured for these. The results are shown in FIG.

This result shows that good pseudoelastic effects can be obtained for TiNi alloy wires with Ni exceeding 50.5 at%. Furthermore, as the Ni concentration increases, the deformation stress tends to increase, but the workability (cold) deteriorates as the Ni concentration increases. Therefore, the practical limit of Ni concentration is 51.5 at%.

Regarding the linear shape of the spring after annealing, the maximum lifting dimension of the 1.5 m cut sample of the spring according to the method of the present invention among the examples was 10 mm.

According to the present invention, it is possible to make the pseudoelastic temperature range and deformation stress constant regardless of the alloy components (Ni concentration) by combining the cold working rate and annealing conditions (temperature and time).

In this way, the present invention can provide a pseudoelastic spring material that maintains a linear shape and has high deformation stress. This is expected to be applied not only to linear spring materials that require a certain length such as medical catheters, but also to other industrial products.

[Brief explanation of drawings]

Figure 1 shows an alloy consisting of Ti-51.0at%Ni that was annealed after cold working (cold working rate 51%) at 370°C at a winding speed of 1m/10 minutes (furnace soaking zone 1m). Stress-strain curve measured for mm ² φ material in the temperature range of 0 to 40°C. Figure 2 is a graph showing the relationship between the stress that causes apparent plastic deformation and the cold working rate ((conditions are material wire diameter 0.7 mmφ, composition: Ti-
51at%Ni, annealing: 400℃ x 1m/10 minutes (soaking zone 1
m, measurement temperature: 30℃). FIG. 3 is a graph showing the relationship between apparent plastic deformation stress and residual strain when the same material as in FIG. 1 is annealed at different temperatures. Measurement conditions were 30℃. Figure 4 uses the same material as Figure 1, 800
3 is a graph showing the relationship between apparent plastic deformation stress and measured temperature when homogenization treatment was performed at 400°C and then heat treatment was performed at 400°C. Figure 5 is 370℃×
It is a graph showing the Ni concentration dependence of the apparent plastic deformation stress and the amount of residual strain when annealed at 1 m/10 minutes. (Measurement temperature 30℃).

Claims (1)

[Claims] 1 After cold working (processing rate 30%) a TiNi alloy showing thermoelastic martensitic transformation consisting of 50.5at% Ni (remaining Ti),
Continuous annealing is performed while applying tension, and temperature (35
A method for producing a pseudoelastic spring characterized by obtaining a continuous linear spring exhibiting pseudoelastic properties with high stress at a temperature near ℃).