JPH0776401B2 - Superelastic alloy material and superelastic element - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a superelastic alloy material and a superelastic element used for an inexpensive superelastic spring having excellent workability.

[Prior Art] It is well known that, in general, TiNi alloys exhibit a remarkable shape memory effect and a pseudoelastic effect accompanying the reverse transformation of the thermoelastic martensitic transformation.

When a TiNi alloy is used as a shape memory spring with a small hysteresis, it is known that after cold working, it is annealed at 400 to 500 ° C and a mesophase transformation is utilized by leaving a cold worked structure. The same method is used for pseudo elastic springs.

These are being put to practical use for home appliances like actuators, orthodontic wires, guide wires, brassieres, etc., but all of them were used near body temperature (about 35 ° C).

[Problems to be Solved by the Invention]

Room temperature (below 20 ℃) especially 0 ℃ using shape memory alloy
The TiNi binary alloy requires a short treatment (5-10 minutes) at a temperature of 500-550 ° C. in order to obtain a spring that works in the front-back direction. In this case, since the processing time was short, the spring back could not be ignored, and there was a problem in moldability. In addition, under the heat treatment condition exceeding 500 ° C., since the worked structure given by cold working disappears, there is a problem that hysteresis becomes large.

A spring exhibiting pseudo-elasticity around O ° C can be obtained by treatment at 400 to 450 ° C for a short time (5 to 10 minutes). However, similar to the above, the spring back was large and it was difficult to mold the coil spring.

Overcoming these difficulties and enabling the production of elements that operate at room temperature or below are extremely important for practical application of pseudo-elastic springs for actuators such as refrigerators and ventilation holes for homes, automobiles, clothing, and medicine. It's important.

On the other hand, it is well known that such TiNi alloy has poor workability. This TiNi alloy is usually hot worked to a diameter of about 5-10 mm and then cold worked to the desired dimensions. The TiNi alloy wire undergoes severe work hardening, and therefore requires repeated annealing holes. Therefore, the cost required for cold working occupies most of the cost of TiNi alloy wire.

The technical problem of the present invention is to solve these problems, to provide a superelastic alloy material and a superelastic element that maintain superelastic characteristics at room temperature or lower and have improved cold workability.

Means for Solving the Problems] According to the present invention, a TiNi alloy consisting of 44 to 50 at% (not including 50) Ni and the balance substantially Ti, wherein a part of the Ti is 0.5 Within the range of up to 5 at%, a superelastic alloy material is obtained which is substituted with Fe and has a cold workability of 30% or more per pass.

Further, according to the present invention, a superelastic element is obtained, which is obtained by subjecting the above-mentioned superelastic alloy material to cold working and then heat treating it at a temperature in the range of 350 ° C to 600 ° C.

In the present invention, the substitution amount of the Fe component of the TiNi alloy is set to 0.5 to 5 atomic percent (at%) because the effect of adding Fe is less than 0.5 at%, and when the amount exceeds 5 at%, the content is significantly higher. It depends on the elasticity and the difficulty.

The lower limit of Ni is 44 atomic percent (at%).
In the NiNi alloy, as Ni decreases, the transformation temperature rises,
It becomes difficult to obtain superelasticity at room temperature or lower. Similar thing is TiNiFe
This is also true for alloys.

The heat treatment temperature is set to 350 to 600 ° C.
This is because sufficient superelastic properties cannot be obtained, and if the temperature exceeds 600 ° C., superelastic properties can be obtained, but it becomes weak against repeated deformation such as bending and stretching.

〔Example〕

 Examples of the present invention will be described.

Table 1 shows the processing characteristics of the TiNiFe superelastic alloy material and the superelastic starting temperature of the superelastic element according to the examples of the present invention.

As a comparative example, the measurement results of the TiNi superelastic alloy material containing no Fe and the superelastic element are also shown.

In this table, the cold workability test is performed with the work rates of the alloy material samples in one pass being 20%, 30%, 40% and 50%. The circles in the table are acceptable even if you pass 3 times, Δ
The mark indicates that one or two passes are allowed after three passes, and the mark x indicates that all three passes are not allowed after three passes. Samples containing 0.5 at% or more of Fe (2-5 and 7-10) have a processing rate of 50% per pass.
It was possible. On the other hand, in the superelastic alloy material samples (11 to 13) according to the comparative example, the processing rate of one pass was limited to about 30%, and it was found that the processing was a little difficult at 40% or more. Here, “somewhat difficult” means that a workability test of about 3 times breaks once or twice and it is not always possible to work, but in actual work, it is not necessarily an appropriate working method that it is easily broken. From a safety point of view, the processing rate of TiNi alloy material can be suppressed to 30% or less.

In addition, the superelasticity starting temperature in Table 1 is −2 after heat-treating the TiNiFe superelastic alloy material according to the example for 30 minutes at 400 ° C.
It was measured from the stress-strain curve at each temperature by raising the temperature every 0 ° C to 5 ° C.

As a comparative example, the measurement results of the superelasticity starting temperature after cold working of the TiNi superelastic alloy material containing no Fe are also shown.

From this table, the temperature showing superelasticity decreased with an increase in the amount of Fe added, and the superelastic alloy elements (Samples 4 and 9) added with 5 at% were 0 ° C or lower. On the other hand, the comparative example of Fe was 7 at
%, The superelastic alloy elements (Samples 5 and 10) were not good in superelastic characteristics.

In addition, the comparative examples (Samples 11 to 13) exhibited a superelastic temperature of room temperature or higher.

The superelastic alloy material and the superelastic element according to the example were manufactured as follows.

Prepare TiNiFe alloys with the composition shown in Table 1 by high frequency vacuum melting, and then homogenize them for 2 hours at a temperature of 900 ° C, then use a hot hammer, a hot roll, and then cold drawing. By processing to 2.0 mm, a super elastic alloy linear material (Samples 1 to 10 in Table 1) was obtained.

When this superelastic alloy material is cold-worked and heat-treated in the range of 350 ° C. to 600 ° C., superelastic starting temperature measurement samples 1 to 10 in Table 1 of the superelastic element are formed. Also, the superelastic alloy material and the elastic element according to the comparative example were manufactured by the same method as that of the example.

〔The invention's effect〕

As described above, according to the present invention, there is provided a superelastic alloy material and a superelastic element which have excellent cold workability, can significantly reduce the processing cost, and retain the superelastic characteristics at room temperature or lower. Is possible.

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Claims (2)

[Claims] 1. A TiNi alloy comprising 44 to 50 at% (not including 50) of Ni and the balance substantially consisting of Ti, wherein a part of the Ti is contained within the range of 0.5 to 5 at% by Fe. Is replaced by
A superelastic material having a cold workability of 30% or more. 2. A superelastic element obtained by heat-treating the superelastic alloy material according to claim 1 at a temperature in the range of 350 to 600 ° C. after cold working.