JPH09228012A - Shape memory alloy leaf spring and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an Ni-Ti alloy leaf spring in which the wide degree of freedom in design can be taken in the case of combined use with a bias spring or the like. SOLUTION: The leaf spring is the one in which a sheet material cut out of a rolling stock obtd. by rolling an ingot of an Ni-Ti alloy in which, in an Ni-Ti alloy composed of, by atom, 49.5 to 52.0% Ni and 50.5 to 48.0% Ti or an Ni-Ti alloy composed of 49.5 to 52.0% Ni and 50.5 to 48.0% Ti, a part of Ni or/and Ti is substituted with one or >=two kinds of elements among V, Cr, Fe and Co in the range of 0.01 to 0.5% is allowed to shape-memorize into a prescribed bent shape. The total working ratio from the ingot of the sheet material is regulated to >=90%, and the angle θ between the rolling direction of the sheet material and the bending direction of the leaf spring is regulated to >=45 deg..

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to springs, clips,
The present invention relates to various mechanical parts such as actuators, electronic parts such as IC sockets for burn-in, Ni-Ti-based shape memory alloy leaf springs applied to the medical field such as micromachines, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Ni-Ti-based shape memory alloy leaf springs include rectangular leaf springs (a) and arc leaf springs (b) illustrated in FIGS.
, A leaf spring (c) composed of a straight line and an arc, and these are used as an actuator or the like for performing a bidirectional operation in combination with a bias spring. By the way, the actuators and the like are uniformly designed on the basis of the apparent longitudinal elastic modulus which is approximately obtained from the load generated by the phase transformation of the Ni-Ti alloy leaf spring, the deflection, and the size. However, regarding the apparent longitudinal elastic modulus, for example, refer to the literature (mechanical properties of shape memory alloys; Yoshihisa Tanaka et al., P56, Figure 3.14,
The relationship between longitudinal elastic modulus and temperature, Yokendo, 1993) shows that the longitudinal elastic modulus at high temperature (austenite phase, hereinafter referred to as A phase) is about 70.
00kgf / mm ² , the longitudinal elastic modulus at low temperature (rombohedral phase, hereinafter referred to as R phase) is described as about 2000kgf / mm ² , but there is no anisotropy of longitudinal elastic modulus depending on the rolling direction of the plate. Not touched. For this reason, it has been difficult to grasp the clue for expanding the degree of freedom in designing the shape memory alloy leaf spring. Here, the design freedom of the leaf spring is to increase the stroke of the leaf spring, increase the working load of the leaf spring, reduce the size of the leaf spring and increase the generated load per unit weight, For example, the height of the leaf spring is reduced to narrow the accommodation space, and the spring constant of the bias spring when used in combination with the bias spring is reduced.

[0003]

As one of the methods for increasing the degree of freedom in designing a Ni-Ti alloy leaf spring, the apparent longitudinal elastic modulus of the A phase is increased and the apparent longitudinal elastic modulus of the R phase is increased. It is possible to make it smaller. Therefore, the present inventors have conducted earnest research on a method of increasing the difference in longitudinal elastic modulus between the A phase and the R phase. As a result, we found that the apparent longitudinal elastic modulus is affected by the processing conditions of the rolled plate, and that the apparent longitudinal elastic modulus has anisotropy with respect to the rolling direction of the leaf spring material. The present invention has been completed. It is an object of the present invention to provide a Ni—Ti based alloy leaf spring and a method for manufacturing the same, which allows a wide degree of design freedom when used in combination with a bias spring.

[0004]

According to the first aspect of the present invention,
Ni consisting of Ni 49.5-52.0 at% and Ti 50.5-48.0 at%
-Ti-based alloy, or Ni49.5-52.0at%, Ti50.5-4
Ni or / and T of a Ni-Ti alloy consisting of 8.0 at%
Part of i is 0.01 to 0.5 at% in the range of V, Cr, Fe,
Ni substituted with any one element or two or more elements of Co
-A leaf spring in which a plate material cut from a rolled material obtained by rolling an ingot of a Ti-based alloy into a predetermined shape is memorized in a predetermined bending shape, and the total processing rate of the plate material from the ingot is 90 % Or more, the angle θ formed by the rolling direction of the plate material and the bending direction of the plate spring is 45 ° or less, which is a shape memory alloy plate spring.

In the present invention, the bending direction of the leaf spring is the direction in which the leaf spring bends when transforming from the R phase to the A phase as shown in FIG. The angle θ formed by the rolling direction of the plate material and the bending direction of the plate spring is the angle shown in FIG. In the present invention, the sufficiently large degree of freedom in designing the plate spring, the ratio of the longitudinal elastic modulus E _R of the apparent modulus of longitudinal elasticity E _A and R-phase of the apparent phase A of Ni-Ti-based alloy plate springs [ It is desirable that E _A / E _R ] be 7.0 or more.

The invention according to claim 3 is Ni 49.5 to 52.0 at
%, Ni-Ti based alloy consisting of Ti50.5 to 48.0 at%, or N consisting of Ni49.5 to 52.0 at% and Ti50.5 to 48.0 at%.
Part of Ni or / and Ti in the i-Ti alloy is 0.01 to
In a range of 0.5 at%, ingot of Ni-Ti alloy substituted with any one or more elements of V, Cr, Fe, and Co, hot rolling and warm or / and cold After rolling, if necessary, dough annealing and cold finish rolling are performed to obtain Ni-
A method for producing a shape memory alloy leaf spring, which comprises producing a rolled Ti-based alloy, cutting the plate into a predetermined shape from the rolled material, restraining the plate in a predetermined bending shape, and performing shape memory heat treatment. The hot rolling and the total working rate in the warm or / and cold rolling is 90% or more, and the cutting of the plate material from the rolled material is performed in the rolling direction of the rolled material and the bending direction during the shape memory heat treatment of the plate material. The method for manufacturing a shape memory alloy leaf spring according to claim 1 or 2, wherein the angle θ formed by and is 45 ° or less.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the invention according to claim 1, the alloy composition is Ni 49.5 to 52.0 at% and Ti 50.5 to 48.0 at% because the Ni content is 52.0 at% even if the Ni content is less than 49.5 at%. Even if it exceeds%, not only the shape memory effect is not exhibited, but also troubles such as cracks occur in the material during the rolling process, which makes the process difficult. When a part of the above Ni or / and Ti is replaced with one or more elements of V, Cr, Fe and Co, the characteristics as a shape memory alloy are not impaired,
The transformation temperatures of the A phase and R phase can be controlled in various ways, and the strength and workability of the alloy can be improved. The substitution element amount is 0.01 to 0.5 at
The reason for limiting to 0.1% is that if it is less than 0.01 at%, the effect cannot be sufficiently obtained, and if it exceeds 0.5 at%, the rolling workability is deteriorated.

In the present invention, the total processing rate of the rolled plate is 90%.
% And the angle θ between the rolling direction of the plate material and the bending direction of the leaf spring is 45 ° or less, the reason why the angle θ is 45 ° or less even if the total processing rate is less than 90% 45 also ° beyond is the total working rate of 90% or more, Ni-Ti-based ratio [E _a the modulus of longitudinal elasticity E _R of the apparent modulus of longitudinal elasticity E _a and R-phase of the apparent phase a of the alloy This is because / E _R ] becomes small.
This means that the degree of freedom in designing the leaf spring when used in combination with the bias spring is reduced.

According to the invention of claim 3, if necessary,
While subjected to finish rolling between fabrics annealing and cold in the leaf spring material after cold rolling, in this case, when the working ratio 20% or more [E _A /
E _R ] is significantly improved. The leaf spring material is as shown in FIGS.
The shape memory heat treatment is performed while restraining the bending shape as shown in FIG. Ni for intermediate annealing, dough annealing, shape memory heat treatment, etc.
-It is performed under normal heating conditions adopted for Ti-based alloys.

In the present invention, the leaf spring includes a leaf material obtained by cutting a leaf material into a narrow ribbon shape from a rolled material and memorizing the shape. The leaf spring of the present invention can also be manufactured by subjecting a rolled material to shape memory heat treatment and cutting it into a predetermined shape.

[0011]

The present invention will be described below in detail with reference to examples. (Example 1) Ni-Ti alloys having various compositions shown in Table 1 were vacuum melt-cast by a conventional method to form an ingot having a thickness of 30 mm, a width of 160 mm and a length of 500 mm. Was hot-rolled into a hot-rolled material having a thickness of 3 mm, and the hot-rolled material was repeatedly annealed and cold-rolled to give a rolled material having a thickness of 0.6 mm.
The total rolling rate from the ingot to the rolled material is 98%. A plate material was cut into a predetermined size from this rolled material. A leaf spring was manufactured by performing shape memory heat treatment at 450 ° C for 1 hour while constraining the cut plate material to the bent shape consisting of straight lines and arcs shown in Fig. 1c. The angle θ formed by the rolling direction of the plate material and the bending direction of the plate spring was 0 °.

The obtained leaf spring was examined for shape recovery and ingot rolling workability. The results are also shown in Table 1. The shape recovery depends on whether the leaf spring is subjected to bending deformation with a maximum strain of 5% at the temperature of the R phase, and then heated to reverse transform into the A phase to recover the shape, at which time residual strain occurs. evaluated. The case where the residual strain did not occur was represented by O, and the case where the residual strain occurred was represented by X. For rolling workability, ○ indicates that the material did not crack, and × indicates that the material did not crack.
It was expressed by.

[0013]

[Table 1] Note) Unit: at%, cutting angle θ = 0 °

As is clear from Table 1, the product of the present invention (N
o.1-28) had good shape recovery and workability. On the other hand, the comparative examples (Nos. 29 to 33) were out of the alloy composition of the present invention, so that the shape recoverability and the workability were all poor.

(Embodiment 2) N of the compositions of Nos. 2, 9 and 13 in Table 1
The i-Ti alloy is vacuum melt cast by a conventional method to obtain a thickness of 5
~ 30mm, width 160mm, length 500mm, ingot, after external cutting, hot-rolled at 850 ℃ to make hot-rolled material with thickness of 3mm. A rolled material having a thickness of 0.6 mm was obtained. In the cold rolling, annealing of 650 ° C. × 1 Hr was added as needed. Overall processing rate from ingot to rolled material is 88-98%
It is. A plate material was cut into a predetermined size from this rolled material. 450 while restraining the cut plate material into the bent shape shown in Fig. 1c.
A leaf spring was manufactured by performing shape memory heat treatment at 1 ° C. for 1 hour. The angle θ formed by the rolling direction of the plate and the bending direction of the plate was changed variously.

The spring characteristics of the obtained leaf spring were examined. Longitudinal elastic coefficient of the apparent phase A (80 ℃) E _A, R-phase (25
℃) apparent longitudinal elastic modulus E _R , the ratio of the two [E _A /
E _R ] is shown in Table 2. The spring characteristics of shape memory alloy are
Generally, it is evaluated by obtaining any one of the load-deflection characteristic in the constant temperature state, the temperature-load characteristic in the constant deflection state, and the temperature-deflection characteristic in the constant load state. When the shape memory alloy spring is applied to an actuator or the like in combination with a bias spring, or is adopted. Here is adopted. The evaluation method is, for example, by applying a fixed deflection δ to the point C of the leaf spring stored in the sectional shape shown in FIG. 4 and measuring the load P generated at the point C with temperature change, Ceremony (Source: “Spring” 3rd edition, edited by Spring Technology Research Group, P302, 19
82, Maruzen) to calculate the apparent longitudinal elastic modulus E. δ = PL ³ cos ² α / 3EI + (Prcos ² α / EI) [L ²
β + 2Lr (1 - cosβ) + (r 2/2) (β-sin 2 β / 2)]. However, I is the second moment of area. FIG. 5 illustrates the relationship between the generated load and the temperature.

[0017]

[Table 2]

As is apparent from Table 2, the product of the present invention (No.
34-45) Both, E _A is high, E _R is low, hence their ratio [E _A / E _R] was a large value. On the other hand, since the processing rate of the comparative example No. 46, 48 was less than 90%,
No.47,49 the cutting angle θ is increased both E _R for exceeds 45 °, the ratio of the two [E _A / E _R] is lowered.

(Example 3) No. 2 Ni-Ti alloy in Table 1 was vacuum melt cast by a conventional method to obtain a thickness of 30 mm and a width of 160 m.
After making an ingot of m and length of 500 mm, after cutting it, hot rolling at 850 ℃ to hot rolled material with thickness of 3 mm, and then cold rolling this hot rolled material with thickness of 0.6 mm I got the material. If necessary
Annealing was performed at 650 ° C x 1 hr. The total processing rate from ingot to rolled material is 98%. Next, after dough annealing, this was finish cold-rolled in the same direction as cold-rolling to obtain a finish material. The working ratio after annealing of the dough was varied between 10 and 51%. A plate material was cut into a predetermined size from this finish material. A leaf spring was manufactured by subjecting the cut leaf material to a shape memory heat treatment at 450 ° C for 1 hour while restraining the bent shape shown in Fig. 1c. The angle θ formed by the rolling direction of the finish material and the bending direction of the plate material was variously changed.

[0020] The obtained plate spring, by the same evaluation methods as in Example 2, a longitudinal elastic coefficient of the apparent phase A (80 ° C.) E _A longitudinal elastic modulus of apparent R-phase (25 ° C.) E _R, And the ratio of both [E _A / E _R ] were determined. The results are shown in Table 3.

[0021]

[Table 3] Note) Alloy No. 2.

As is clear from Table 3, the N
o.50~55 are all reduced E _R is more, both the ratio of [E
_A / E _R ] was significantly improved. In Nos. 56 and 57, the work ratio of finish cold rolling was low, so the ratio of the two did not improve so much.

[0023]

As described above, according to the present invention,
Since the leaf spring characteristics of the Ni-Ti alloy are improved, the degree of freedom in designing the leaf spring in the actuator or the like combined with the bias spring is expanded, and a remarkable effect is industrially achieved.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a Ni—Ti alloy leaf spring of the present invention.

FIG. 2 is an explanatory view of a bending direction of a leaf spring according to the present invention.

FIG. 3 is an explanatory view of an angle θ formed by a rolling direction of a rolled material and a bending direction of a plate material cut from the rolled material in the present invention.

FIG. 4 is an explanatory diagram of a leaf spring when obtaining leaf spring characteristics of a shape memory alloy.

FIG. 5 is an explanatory diagram showing a relationship between generated load and temperature.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takeo Nakamura 2-6-1, Marunouchi, Chiyoda-ku, Tokyo Furukawa Electric Co., Ltd.

Claims (3)

[Claims] 1. Ni 49.5 to 52.0 at%, Ti 50.5 to 48.0 at
% Ni-Ti alloy, or Ni49.5-52.0at
%, N of Ni-Ti based alloy consisting of Ti 50.5 to 48.0 at%
i or / and a part of Ti in the range of 0.01 to 0.5 at%,
A plate material cut into a predetermined shape from a rolled material obtained by rolling an ingot of a Ni—Ti alloy substituted with any one or more elements of V, Cr, Fe, and Co is formed into a predetermined bent shape. A shape-memorized leaf spring, the total processing rate from the ingot of the plate material is 90% or more, the angle θ formed by the rolling direction of the plate material and the bending direction of the plate spring is 45 ° or less. Characteristic shape memory alloy leaf spring. 2. The ratio [E _A / E _R ] of the apparent longitudinal elastic modulus E _A of the austenite phase and the apparent longitudinal elastic modulus E _R of the rhombohedral phase of the leaf spring is 7.0 or more. The shape memory alloy leaf spring according to item 1. 3. Ni49.5-52.0at%, Ti50.5-48.0at
% Ni-Ti alloy, or Ni49.5-52.0at
%, N of Ni-Ti based alloy consisting of Ti 50.5 to 48.0 at%
i or / and a part of Ti in the range of 0.01 to 0.5 at%,
Hot rolling an ingot of a Ni—Ti based alloy substituted with any one or more of V, Cr, Fe and Co elements;
Performing warm or / and cold rolling, further subjecting to dough annealing and cold finish rolling to produce a Ni-Ti alloy rolled material, and then cutting a plate material into a predetermined shape from the rolled material, A method for producing a shape memory alloy leaf spring, which comprises subjecting this plate material to a predetermined bending shape and performing a shape memory heat treatment, comprising: a hot rolling and a total working rate in warm or / and cold rolling.
90% or more, the cutting of the plate material from the rolled material is performed so that the angle θ formed by the rolling direction of the rolled material and the bending direction during shape memory heat treatment of the plate material is 45 ° or less. The method for manufacturing the shape memory alloy leaf spring according to claim 1 or 2.