JPH0860276A - Nickel-titanium-base alloy spectacle member and its production - Google Patents

Abstract

PURPOSE: To develop a material compsn. and a producing method capable of obtaining good superplasticity even in cold working at <=20% working degree and to enable the corresponding thereof to the production of spectacles members of all shapes and designs. CONSTITUTION: An Ni-Ti alloy obtd. by blending 1.0 to 2.5 atomic% Co into an Ni-Ti alloy in which the ratio of Ni to Ti (Ni/Ti) by atomic% is regulated to 0.97 to 1.04 is subjected to solution heat treatment at 600 to 900 deg.C for 10 to 120min, is rapidly cooled, is applied with plastic deformation at 5 to 20% working ratio and is molded into a final shape, which is next subjected to heat treatment at 325 to 450 deg.C for 10 to 120min to dispersedly precipitate Ni.Ti aging precipitates.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spectacle member made of a NiTi-based alloy exhibiting superelasticity and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, metal eyeglass frame members (hereinafter referred to as
(Temporarily referred to as eyeglass members and collectively referred to as temples, bridges, etc.) have been manufactured from nickel silver, Ni alloy, monel metal, beryllium copper alloy, titanium or alloys thereof with good workability. However, the spectacle members are also required to have higher functionality, and materials for these metal spectacle frames that are easily deformed and have a higher elastic limit have been demanded.

Therefore, the atomic ratio of Ni to Ti is about 1: 1.
Attempts have long been made to apply the excellent superelasticity or pseudoelasticity of Ti alloys to eyeglass frames. FIG.
2 shows two typical basic configurations of each spectacle member in the present invention, FIG. 1 (a) is a perspective view showing a two-bridge type spectacle member, and FIG. 1 (b) is It is a perspective view which shows the spectacles member of 1 bridge type.

In FIG. 1 (a), the spectacle frame is composed of a temple 1, an upper bridge 2 and a lower bridge 3, and each of these members is made of a shape memory alloy. In the case of FIG. 1 (b), it is an example provided with one bridge 4.

By the way, alloys called shape memory alloys such as NiTi alloys show an austenite structure which is a cubic structure in the parent phase of the high temperature phase, but become monoclinic martensite below the transformation temperature (Ms point). Be transformed. When a stress is applied to the martensite structure, it easily shows an apparent plastic deformation. It has the characteristic of recovering its original shape when heated above the transformation temperature (Af point), which is called the shape memory effect.

Such a shape memory effect is used in various industrial applications. Further, it is well known that a large elastic deformation, which cannot be considered by a normal metal material that applies stress in the state of austenite as a matrix phase, is exhibited. This is called superelasticity or pseudoelasticity.
When stress is applied to the austenite structure, stress-induced martensitic transformation (SIM transformation) occurs. In the stress range where slip transformation does not occur, superelasticity is observed and a large elastic deformation is observed by supplementing the deformation strain with the crystal structure change called transformation.

This superelastic property has a great industrial value and is used in many applications as a material which is hard to deform such as eyeglass members, orthodontic wires, brassieres wires, shoulder pad wires.

Most NiTi alloy superelastic members including eyeglass members are subjected to large plastic deformation in the cold to generate dislocation structure inside the material, and finally undergo heat treatment at a recrystallization temperature or lower at which dislocation structure does not disappear. The method of obtaining superelasticity is adopted. The heat treatment finally performed here is a heat treatment performed while restraining the shape of the member, and is intended for rearrangement of the crystal structure disordered by cold working.
The rearrangement of this crystal causes the above-mentioned SIM transformation.

As disclosed in Japanese Patent Publication No. 2-51976, in an austenite structure having a dislocation structure, the stress or strain limit of possible superelasticity due to SIM transformation occurring when stress is applied is Since it is higher than that of an austenite structure having no dislocation structure, a large cold plastic deformation is used as a general method for manufacturing a superelastic NiTi alloy member. Further, in this manufacturing method, the amount of plastic deformation required is a cold working rate of over 20%.

However, the cold workability of NiTi alloy is extremely poor, and it is necessary to repeatedly perform heat treatment, that is, strain relief annealing, at a temperature not lower than the recrystallization temperature every time cold workability deteriorates. In the processing of members that require complicated shapes such as eyeglass members, it is difficult to manufacture members of various shapes by performing cold working in excess of 20%. Therefore, there is a drawback that the designs that can be manufactured by the conventional method are greatly limited for members having complicated shapes.

In order to solve this, a Ni-Ti-Co alloy (Co: 1 to 6% by weight) having a specified constituent structure has been used as a method for obtaining superelasticity characteristics without cold working (Japanese Patent Laid-Open No. 5-58200). −5168
2)), a Ni-Ti alloy in which an intermetallic compound (Ni ₃ Ti) is dispersed and precipitated in a matrix phase (see Japanese Patent Laid-Open No. 59-28548).
Is proposed. According to these methods, it has become possible to obtain superelasticity characteristics only by heat treatment without cold working, but the fatigue characteristics are not sufficient for application to members such as eyeglass frame parts that are subjected to repeated stress. In addition, the eyeglasses did not have sufficient strength to satisfy the wearing sensation at the spectacle use environment temperature (-5 ° C to 30 ° C).

[0012]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned drawbacks of the conventional method by performing a mild cold working of 20% or less and then performing a heat treatment for aging precipitation of Ni ₃ Ti. Is to develop a material composition and manufacturing method capable of obtaining excellent superelasticity, and to develop a technology capable of supporting manufacturing of spectacle members of any shape and design.

[0013]

[Means for Solving the Problems] Thus, the inventors of the present invention have conducted various studies to solve the above-mentioned problems, and have made an alloy containing Ni-based alloy with 1.0 to 2.5% Co in atomic%. The present invention has been completed based on the knowledge that good superelasticity can be achieved by using and preforming, followed by aging precipitation of Ni ₃ Ti, even under a light pressure of 20% or less.

The gist of the present invention is that the atomic ratio of Ni and Ti (Ni / Ti) is 0.97 or more and 1.04 or less.
NiTi obtained by dispersing Ni ₃ Ti aging precipitates, which is obtained by mixing 1.0 to 2.5 atomic% of Co in NiTi alloy.
It is a base alloy eyeglass member.

From another aspect, the present invention provides an atomic%
And NiTi whose ratio of Ni and Ti (Ni / Ti) is 0.97 or more and 1.04 or less
NiTi-based alloy, which is a mixture of 1.0 at% to 2.5 at% Co, is added to the alloy at 600 ℃ or more and 900 ℃ or less for 10 minutes or more 12
Solution heat treatment for 0 minutes or less, plastic deformation with a working rate of 5% or more and 20% or less to form the final shape, and then heat treatment for 10 minutes or more and 120 minutes or less at 325 ° C or more and 450 ° C or less Ni ₃ T
i A method for producing a NiTi-based alloy eyeglass member, characterized in that superelasticity is obtained by dispersing and precipitating an aging precipitate. In a preferred aspect of the present invention, swaging may be performed prior to the solution heat treatment.

[0016]

There are roughly two means for solving the problems in the present invention, one relates to the optimum alloy composition, and the other relates to a manufacturing method by an appropriate combination of cold working and heat treatment. It is a thing.

That is, the optimum alloy composition is Ni with an atomic ratio of Ni and Ti (Ni / Ti) of 0.97 or more and 1.04 or less.
It is a Ti alloy mixed with 1.0 at% to 2.5 at% of Co.

If necessary, the alloy is swaged in advance, and then solution heat-treated at 600 ° C. or higher and 900 ° C. or lower for 10 minutes or longer and 120 minutes or shorter to obtain a working rate of 5% or higher.
Plastic deformation of 20% or less is applied to form the final shape, then 32
Superelasticity is obtained by performing heat treatment at 5 ° C or higher and 450 ° C or lower for 10 minutes or longer and 120 minutes or shorter to disperse and precipitate Ni ₃ Ti aging precipitates. As described above, temples and bridges are typically used as the spectacle frame member, and a suitable manufacturing method is specified for each.

For example, for temples, if necessary, the alloy round wire is swaged, then repeatedly flattened by a press and heat-treated for stress relief,
After processing to a specified thickness and width, solution heat treatment is performed at 600 ℃ or more and 900 ℃ or less for 10 minutes to 120 minutes, and further plasticity by cold press flat working of 5% to 20% depending on the thickness change. It is deformed and molded into the final shape, then 325 ℃
Heat treatment at 450 ℃ or less for 10 minutes to 120 minutes
By ₃ Ti aging precipitation was dispersed and precipitated it is to obtain a temple having a superelasticity.

In the case of the upper bridge, the round wire made of the alloy is subjected to solution heat treatment at 600 ° C. or higher and 900 ° C. or lower for 10 minutes or longer and 120 minutes or shorter, and cold pressed at 5% or higher and 20% or lower depending on the thickness change. Superplasticity was achieved by plastically deforming by flattening to form the final shape, and then heat-treating at 325 ° C to 450 ° C for 10 minutes to 120 minutes to disperse Ni ₃ Ti aging precipitates. You get the upper bridge.

Further, regarding the lower bridge, the alloy round wire is subjected to solution heat treatment at 600 ° C. or higher and 900 ° C. or lower for 10 minutes or longer and 120 minutes or shorter, and the cross-sectional area reduction rate is 5% or higher and 20% or lower. Swaging or hole die wire drawing is applied for plastic deformation, and then bending is performed to form the final shape, followed by heat treatment at 325 ° C to 450 ° C for 10 minutes to 120 minutes, and Ni ₃ Ti aging precipitate Thus, the lower bridge having superelasticity is obtained by dispersing and precipitating.

In the present invention, the superelastic property specifically required for the eyeglass member is 6% at -5 ° C to 30 ° C.
That is, the residual strain is 1% or less when the above strain is applied. As described above, the present invention aims to achieve the object by reducing the burden of cold working as much as possible when manufacturing eyeglass members having complicated shapes with the above-mentioned required characteristics, and by combining with age precipitation hardening by heat treatment. Is.

In the present invention, the alloy composition of interest is
The reasons defined as above are as follows. Ni / Ti
This is because when the ratio is less than 0.97, aging precipitation does not occur, and when it exceeds 1.04, the workability is significantly deteriorated. Also, the Co content is
If it is less than 1.0 atomic%, the transformation temperature Af point after aging heat treatment is 0 ° C.
This is because the appearance temperature of superelasticity deviates to the high temperature side from the intended temperature range, and if it exceeds 2.5%, the workability deteriorates. The preferable blending amount is 1.0 to 2.0%.

The heat treatment conditions include solution heat treatment before cold working and aging heat treatment performed in the final shape. The solution heat treatment is performed for the purpose of removing accumulated cold work strain in the cold work which the material has undergone before the solution heat treatment, and further solid-dissolving various precipitates. If the temperature is 600 ° C or higher, the purpose of solution treatment is sufficiently achieved, but if it exceeds 900 ° C, problems such as oxidation and coarsening of crystal grains occur. It is desirable to perform in an active atmosphere. It is preferably 600 to 750 ° C.

The heating time is 10 to 120 minutes. If it is shorter than 10 minutes, solution treatment is not sufficient, while if it exceeds 120 minutes, the problem of coarsening of crystal grains occurs. It is preferably 20 to 60 minutes.
The solution treatment refers to a treatment of performing rapid cooling such as water cooling after heat treatment.

The cold working may be any method such as hole die wire drawing, swaging and press rolling, and requires 5 to 20%, preferably 5 to 15% of plastic working. Aging heat treatment is one of the important factors of the present invention.
For Ti-Co ternary alloys, a specific aging heat treatment
It was found that the Ni-excess intermetallic compound of Ni ₃ Ti was finely dispersed and precipitated in the NiTi compound and exhibited excellent superelasticity with excellent fatigue properties.

A detailed examination of the aging heat treatment conditions revealed that
It was clarified that below 325 ° C, the aging was not sufficient and the superelastic effect did not appear, and above 450 ° C, overaging occurred and the superelasticity was not obtained. Heat treatment time is 10
If it is less than 10 minutes, there is concern that the characteristics may vary, and if it exceeds 120 minutes, the work efficiency is poor, so it was set to 10 to 120 minutes. It is preferably 20 to 60 minutes.

[0028]

【Example】

Example 1 A NiTi-based alloy having the chemical composition shown in Table 1 was vacuum melted and cast, and then hot forged, hot rolled, and cold drawn to form a round wire having a diameter of 2.0 mm. Next, the obtained round wire is heat-treated at 700 ° C. for 20 minutes and then rapidly cooled,
As shown in Table 1, plastic reduction of 0%, 5%, 10%, 15% and 20% was applied by cold swaging.

The cold-worked wire thus obtained was further subjected to the aging heat treatment shown in Table 1 to obtain a linear test piece. Each test piece was subjected to a tensile test at room temperature of 25 ° C. After applying a load to both ends and applying a strain of 6%, it was unloaded and the residual amount remained The presence or absence of elasticity was confirmed.

The cold workability evaluation test was conducted with a 2 mm round wire 70
After heat treatment at 0 ° C. for 20 minutes, rapid cooling and swaging were performed to confirm whether cold working with a surface reduction rate of 20% was possible.

Further, with the components shown in Table 1, the cold working ratio,
The aging-treated wire was subjected to a fatigue test at room temperature (25 ° C) with a strain of 1.5% at a strain of 1.5% by a hunter type rotary bending fatigue tester, and the fatigue fracture frequency was investigated to confirm the fatigue properties. The obtained results are summarized in Table 2.

In the column of superelasticity, the case of residual strain of 0.7% or less is indicated by "⊚", the case of residual strain of 1% or less is indicated by "○", and the case of residual strain of more than 1% is indicated by "x". ”Indicated. In the column of cold workability, "○" indicates that surface reduction rate reduction of up to 20% is possible, and "X" indicates that cracking occurred when the cold work reduction rate was less than 20%. Show.

Further, in the column of fatigue characteristics, the number of fatigue ruptures of 3000 times or more is indicated by “◯”, particularly 3500 times or more is indicated by “⊚”, and less than 3000 times is indicated by “x”. If even one of these characteristics had "x", it was evaluated as "x" as a comprehensive evaluation.

In the examples of the present invention, superelasticity, cold workability,
Furthermore, it was verified that the fatigue characteristics were good. The overall evaluation is "◎" or "○". The photograph shown in FIG. 2 is an electron micrograph showing the metal structure of the Ni-excess intermetallic compound of Ni ₃ Ti which appeared in the NiTi matrix by the aging heat treatment at 420 ° C. for 30 minutes. It is considered that the precipitation of such a fine Ni-excess intermetallic compound Ni ₃ Ti suppresses the generation of new dislocations at the time of deformation and produces good superelasticity.

FIG. 3 (a) is the same elongation-stress graph after solution heat treatment for alloy E of this example, FIG. 3 (b) is after 10% cold press molding, and FIG. It is a graph which shows the elongation-stress relationship by the tensile test result in the test piece after a process. Further, FIG. 3 (d) shows the results of the tensile test in the case where the solution heat treatment was performed without cold working and the direct aging heat treatment was performed.

As shown in FIG. 3 (d), a large elastic recovery was observed as compared with a normal metal material without cold working, and it can be seen that the eyeglass frame functions sufficiently. However, as shown in Fig. 3 (c), by combining cold working and aging precipitation, perfect superelasticity due to SIM transformation peculiar to shape memory alloys can be obtained. Therefore, the effect that the spectacle frame exhibits a flexible wearing feeling can be seen.

Further, the materials A to D and E1 to E6 of the present invention.
In the range of −5 ° C. to 30 ° C., a stress value of 500 MPa or more was shown at a strain of 2% or more, and it was confirmed that the strength was sufficient to satisfy the wearing feeling of the spectacle frame.

Example 2 Example 2 shows an example of manufacturing a temple member. Using the material having the chemical composition of alloy E shown in Table 1, a temple member was manufactured according to the manufacturing process shown in FIG.

First, a circular wire having a diameter of 2 mm (φd1) shown in FIG. 4 (a) is repeatedly swaged and annealed at 700 ° C. for 20 minutes in a cold state to obtain a taper shape (one end A member having a diameter of φd1 = 2.0, a diameter of the central portion of φd2 = 1.65, and a diameter of the other end of φd3 = 1.4 mm) was obtained. Next, after carrying out annealing heat treatment at 700 ° C for 20 minutes, cold press working (primary press working) and annealing heat treatment at 700 ° C for 20 minutes were repeated, and as shown in Fig. 4 (c).
Rectangular shape (thickness at one end t1 = 1.45, width w1 = 2.4,
The width w2 of the central part was 1.9 and the diameter of the other end was φd3 = 1.4 mm.

Here, the final solution treatment, 700 ° C., 20
After heat treatment for 10 minutes, quenching is performed, then 10% cold plastic working is performed by the final press working, and the shape shown in Fig. 4 (d) is obtained.
(Thickness t2 at one end = 1.3, width w3 = 2.7, width w4 at the center =
2.2, the other end diameter φd3 = 1.4 mm), and aging heat treatment at 420 ° C. for 20 minutes to prepare a temple for an eyeglass frame.
It was confirmed that the obtained temples exhibited excellent superelasticity between -5 and 30 ° C.

(Third Embodiment) A third embodiment is an example showing a manufacturing example of the upper bridge member. Using the material having the chemical composition of alloy E shown in Table 1, the upper bridge member was manufactured according to the manufacturing process shown in FIG.

First, a round wire having a diameter of 1.5 mm is annealed at 700 ° C. for 20 minutes to form a linear member (diameter φ) shown in FIG. 5 (a).
d4 = 1.5 mm) was obtained. Next, cold pressing (primary pressing) was performed to obtain the rectangular shape (end thickness t3) shown in Fig. 5 (b).
= 1.4 and the same width w5 = 1.55 mm). To this 700
After heat treatment at ℃ for 20 minutes and then quenching, 10% cold plastic working was performed by final pressing, and the shape shown in Fig. 5 (c) (end thickness t4 = 1.35, same width w6 = 1.7 mm) and 42
An aging heat treatment was performed at 0 ° C for 20 minutes to fabricate an upper bridge for an eyeglass frame. It was confirmed that the obtained upper bridge exhibited excellent superelasticity between −5 and 30 ° C.

Example 4 Example 4 shows an example of manufacturing the lower bridge member. Using the material having the chemical composition of alloy E shown in Table 1, the lower bridge member was manufactured according to the manufacturing process shown in FIG.

First, a round wire having a diameter of 1.25 mm (φd5) in FIG. 6 (a) is heat-treated at 700 ° C. for 20 minutes and then rapidly cooled, and then swaging is performed to obtain a diameter of 1.20 mm (φd5) shown in FIG. 6 (b). φ
The straight line of d6) (reduction rate of cold working = 7.8%) was adopted. Next, the U-shape shown in Fig. 6 (c) (φd6 = 1.2, L1 = 20, L2 = 15 m
Bending was applied to m), and finally aging heat treatment was performed at 420 ° C. for 20 minutes to produce a lower bridge for an eyeglass frame. It was confirmed that the obtained lower bridge exhibits excellent superelasticity between −5 and 30 ° C.

(Embodiment 5) Embodiment 5 is an example of manufacturing a single bridge member. Using the material having the chemical composition of alloy E shown in Table 1, a single bridge member was manufactured according to the manufacturing process shown in FIG.

First, a circular line having a diameter of 1.5 mm (φd7) shown in FIG. 7A is U-shaped as shown in FIG. 7B (φd7 = 1.5, L3 = 20, L4 =
15 mm) was bent. Next, after heat treatment at 700 ° C for 20 minutes, quenching is performed. Then, as shown in Fig. 7 (c), in the figure, only the shaded portion has an elliptical cross-sectional shape with a minor axis of 1.4 mm (φd7
= 1.5, L3 = 20, L4 = 15, t5 = 1.4, w7 = 1.55 mm) was subjected to cold press working (cold working ratio = 13%). After that, after aging heat treatment at 420 ℃ for 20 minutes, 1 for eyeglass frames
This bridge was produced. The obtained one bridge is -5
It was confirmed that it exhibits excellent superelasticity at 30 ° C.

[0047]

[Table 1]

[0048]

[Table 2]

[0049]

EFFECTS OF THE INVENTION According to the present invention, NiTi alloy eyeglass members having excellent superelasticity can be obtained by mild cold working with a working ratio of 20% or less, and members with complicated shapes can be manufactured without difficulty. It was It has become possible to cope with the recent diversification of eyeglass frame designs, and its industrial value is great.

[Brief description of drawings]

FIG. 1 (a) is a schematic perspective view showing the structure of a two-bridge type metal eyeglass frame, and FIG. 1 (b) is a schematic perspective view showing the structure of a one-bridge type metal eyeglass frame.

FIG. 2 is an electron micrograph of a metal structure showing a precipitate after the aging heat treatment in the example of the present invention.

FIG. 3 is a diagram showing an example of a stress hysteresis curve in a tensile test, FIG. 3 (a) is an example after solution treatment, FIG. 3 (b) is an example after 10% cold working, and FIG. 3 (c) shows an example after 10% cold working + aging heat treatment, and FIG. 3 (d) shows an example after solution treatment + aging heat treatment.

FIG. 4 is an explanatory view of an example of a manufacturing process of a temple member, FIG. 4 (a) is a strand shape, FIG. 4 (b) is a shape after swaging, and FIG. 4 (c) is a primary shape. The shape after pressing and the shape after final pressing are shown in FIG. 4 (d).

5A and 5B are explanatory views of an example of a manufacturing process of the upper bridge member. FIG. 5A is a strand shape, FIG. 5B is a shape after primary press working, and FIG. The respective shapes after the final pressing are shown.

6A and 6B are explanatory views of an example of a manufacturing process of the lower bridge member. FIG. 6A is a wire shape, FIG. 6B is a shape after primary press working, and FIG. The respective shapes after the final pressing are shown.

FIG. 7 is an explanatory view of an example of a manufacturing process of one bridge, FIG. 7 (a) is a wire shape, FIG. 7 (b) is a shape after bending, and FIG. 7 (c) is press working. The latter shape (final shape) is shown respectively.

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] November 11, 1994

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

FIG.

[Fig. 2]

[Figure 3]

[Figure 5]

[Figure 4]

[Figure 6]

[Figure 7]

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuyuki Nakasuji 4-53-3 Kitahama, Chuo-ku, Osaka, Sumitomo Metal Industries, Ltd. 1985 Sanyo Special Alloy Co., Ltd.

Claims (3)

[Claims] 1. The atomic ratio of Ni to Ti (Ni / Ti) is 0.
A NiTi-based alloy eyeglass member comprising NiTi alloy of 97 or more and 1.04 or less mixed with 1.0 at% or more and 2.5 at% or less of Co, in which Ni ₃ Ti aging precipitates are dispersed and deposited. 2. The atomic ratio of Ni to Ti (Ni / Ti) is 0.
NiTi-based alloy composed of 97 to 1.04 NiTi alloy with 1.0 at% to 2.5 at% Co at 600 ° C to 90
Perform solution heat treatment for 10 minutes or more and 120 minutes or less at 0 ℃ or less,
A plastic deformation of 5% or more and 20% or less is added to form the final shape, and then heat treatment is performed at 325 ° C or more and 450 ° C or less for 10 minutes or more and 120 minutes or less to disperse and precipitate Ni ₃ Ti aging precipitates. A method for manufacturing a NiTi-based alloy spectacle member characterized by obtaining elasticity. 3. The method according to claim 2, wherein swaging is carried out prior to the solution heat treatment.