JPS62240111A - Working method for ni-ti group shape memory alloy - Google Patents

Abstract

PURPOSE:To obtain the secondary work in a correct shape without the camber and torsion in the longitudinal direction by giving a tension by holding the alloy worked in the necessary shape at more than the prescribed temp. in the work stage of a Ni-Ti group shape memory alloy. CONSTITUTION:The shape memory alloy (a) rolled in the necessary shape is passed to a heating device 3 by providing the heating device 3 at the outlet side of a rolling mill 1 in the rolling of an Ni-Ti group shape memory alloy (a). The heating device 3 holds the shape memory alloy (a) at the temp. >=100 deg.C, then it is wound by a winding machine 2 by adding a tension thereto. This method is applied for the shape memory alloy subjected to a roll forming as well and the preferable roll forming temp. is taken within the range from the temp. >=50 deg.C higher than the Af point of a martensite transformation upto 200 deg.C. In this way the secondary work in a correct shape without the camber and torsion in the longitudinal direction can be manufactured.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a processing method for Ni-Ti based shape memory alloy (hereinafter abbreviated as NT gold alloy), and specifically solves the problems of warpage and twisting caused by processing. be.

[Conventional technology]

NT gold alloy is an alloy whose main components are Ni and Li, and it has a shape memory effect in which deformation in the martensitic phase returns to its original shape in the matrix by heating above the As point of martensitic transformation, and martensitic transformation. In the matrix above the AS point of
It has a superelastic effect that allows it to return to its original shape even if a strain of several percent is applied, and it also exhibits a vibration damping effect due to hysteresis during alloy transformation. This characteristic is an effect not seen in ordinary metals, and its use in various actuators, fasteners, etc. is being considered.
It has been put into practical use in some areas.

[Problem that the invention attempts to solve]

When viewed from general metals, NT alloys belong to the category of materials that are difficult to work, and are extremely work hardened and have poor ductility. For this reason, it takes a considerable amount of man-hours just to process an ingot into round or square wire with a diameter of several mm, and the scope of use of NT gold alloy as secondary processed products is limited to coil material, which is relatively easy to process. Almost. However, although plate materials and the like have recently been processed, little is known about the processing.

Generally, when metal materials are processed, it is extremely rare for the material to stretch uniformly in the longitudinal direction, resulting in defects in the longitudinal shape of the resulting processed product, such as warping and twisting. For this reason, the straightness of the processed product is ensured by applying tension to the processed product on the output side of the process or by repeatedly applying tension targets using a tension leveler or the like. However, the repeated tension target is often an independent device, which may deteriorate the cross-sectional shape of some processed products, and is also problematic in terms of cost.

Depending on the metal material, sufficient straightness may be obtained by elongation in the longitudinal direction simply by applying tension to the workpiece at the exit side of processing, but NT gold alloys tend to become straight when processed in the temperature range of the martensitic phase. However, when the temperature is raised to a temperature higher than the As point of martensitic transformation, the shape of the processed product is restored due to the deformation of martensite, and the straightness of the processed product is significantly deteriorated. Furthermore, when processing is performed in the temperature range of the matrix, even if tension is applied, the elongation in the longitudinal direction is almost elastic elongation, and warping and twisting of the processed product cannot be improved. In addition, if the NT gold alloy is heated to the recrystallization temperature and tension is applied, as with general metal materials, residual stress and distortion can be removed, and warpage and twist can be removed. However, this method causes problems in terms of properties such as surface oxidation and reduction in mechanical strength.

[Means to solve the problem]

In view of this, as a result of various studies, the present invention has developed an NT gold alloy processing method that can remove warpage and twisting of processed products without deteriorating their properties.

One of the processing methods of the present invention is characterized in processing the NT gold alloy by maintaining the alloy processed into a desired shape at a temperature of 100° C. or higher and applying tension.

Another processing method of the present invention is to roll form a pulled plate <NT gold alloy by passing it through a forming roll and using a pulling machine, in which a heating device is provided between the forming roll and the pulling machine, and the rolled alloy is
It is characterized by maintaining the temperature above ℃ and applying tension.

Yet another processing method of the present invention is in the roll forming process of N-alloy, which is passed through a forming roll and pulled out by a pulling machine, a heating device is provided between the forming roll and the pulling machine, and the A-f point of martensitic transformation is 50
It is characterized by applying tension to an alloy that has been roll-formed in a temperature range from 100°C or higher to 200°C while maintaining the temperature at 100°C or higher.

That is, in the present invention, when NT gold alloy is processed into a desired shape by cold rolling, wire drawing, roll forming, etc. of the same type as general metals, the processed product will not warp or twist, although this will vary depending on the NT gold alloy blending ratio and processing conditions. occurs. This is heated to 100℃
By holding it above and applying tension in the longitudinal direction,
This is a product that has been corrected for warping or twisting. For example, the first
As shown in the figure, a heating device (3) is installed between the rolling mill (1) and the winder (2) on the exit side, and the rolled NT gold alloy a) is passed through the heating device (3) to a temperature of 100°C or higher. Hold and winder (
2) applies tension to the NT gold alloy a). As shown in the figure, there are capstans (4) before and after the heating device (3).
, (5) and passing it through the heating device (3) a)
Tension may be applied to.

In addition, as shown in Figure 2, in the roll forming process, a heating device (3) is provided between the final forming stand (b) and the take-off stand (7), and the roll-formed NT gold alloy a) is placed in the heating device (3). The NT gold alloy a) is maintained at 100°C or higher through the
Add tension to.

In the figure, (8) indicates an inert gas introduction pipe. Furthermore, in the above roll forming process, the roll forming process is performed in a temperature range from 50°C or more higher than the Af point of the martensitic transformation of the NT gold alloy to 200°C, and this is maintained at 100°C or higher () to form the longitudinal Add tension in the direction.

(Function) The processing method of the present invention replaces the conventional processing at the recrystallization temperature, which causes property deterioration, by processing at the martensitic phase and then
By applying tension in the longitudinal direction while maintaining the temperature within a temperature range of ℃ or higher, which is applicable to cold processing machines, it is possible to remove warpage and twisting of the processed product.

However, holding the temperature above 100℃ and applying tension is
Although warping and twisting of processed products can be effectively removed,
This is because in the end vortices, even if the tension is increased, warping and twisting are not sufficiently removed. In addition, in roll forming, if the pipe is not welded and the forming is performed in the cold (martensitic phase), some shape recovery will occur in the temperature range of the matrix phase.
A gap is created in the butt part. To solve this problem, either use roll forming to bend the shape strongly in advance by an amount corresponding to the amount of shape restoration, or roll form at a temperature that is 50°C or more higher than the Af point of martensitic transformation.
By carrying out the process in a temperature range of 00°C, it is possible to eliminate the shape recovery of the parent phase in the temperature range. However, if the temperature is less than 50°C from the Af point of martensitic transformation, shape recovery cannot be eliminated, and if the temperature exceeds 200°C, the characteristics of the alloy will deteriorate due to oxidation or the like.

<Example (1)> NT gold alloy Like general metals, warping and twisting occur during cold rolling, and the degree of warpage varies depending on the blending ratio of the alloy and processing conditions. Then, the width obtained by rolling was 10# and the thickness was 0.
An NT gold alloy with a thickness of 3M, a length of 500 mm, and a radius of curvature of 100 mm was prepared, and as shown in Figure 3, the NT gold alloy a) was
) was attached with a weight (10) that moves up and down within the guide (11) at the lower end, and the radius of curvature after heating the NT gold alloy a) to a constant temperature for 1 second was measured. The results are shown in FIG.

As is clear from the figure, increasing the heating temperature to 100°C or higher had a significant effect on reducing warpage.

This effect becomes greater when the weight (tension) is increased, but excessive tension leads to breakage or deformation of the cross-sectional shape. Furthermore, the torsion was greatly improved by heating and maintaining it at 100° C. or higher while being straightened by a weight guide.

Next, width 10 shoes, thickness 0.3. , NT with radius of curvature 100#
The alloy tape was heated at 2771/m using both capstans (temperature: 300°C, furnace length: 500°) as shown in Figure 1.
Tension was applied to the alloy tape at a linear speed of 1.5 in (tension: 5 kg). As a result, it was possible to make the radius of curvature of DESO -9 = 10 m or more.

<Example (2)> Generally, in roll forming, warping is likely to occur due to the difference in trajectory length between the edge and the bottom during the forming process. So N
When a round oven tube with a diameter of 3# was created by roll forming a T alloy tape, a warp with a radius of curvature of about 500 seconds occurred on the side opposite to the mating part. On the other hand, as shown in FIG. 2, a heating device was placed between the final molding stand and the take-up stand, and the roll-formed NT alloy tape was passed through the roll-formed NT alloy tape at a heating temperature of 200° C. and a tension of 5 kg. As a result, we were able to increase the radius of curvature to approximately 10,000 m. For comparison, the sample was passed through a heating device without applying tension, but no improvement in the radius of curvature was observed.

If the tube is not welded and is formed in the cold (martensitic phase), some shape recovery may occur in the temperature range of the parent phase, and an opening may occur at the mating portion. In such a case, either bend the NT alloy tape strongly in advance by roll forming in accordance with the amount of shape restoration, or bend the NT alloy tape under deformation by 50 degrees from the A'f point of martensitic transformation during roll forming. If the temperature is maintained at a temperature higher than 200°C, the joining portion will not open even if heated to 200°C or higher with a heating device, and the radius of curvature can be improved.

(Effects of the Invention) According to the present invention, instead of the conventional processing at recrystallization temperatures that leads to deterioration of characteristics, it is possible to eliminate warpage and twist in the longitudinal direction, and to produce a secondary product with an accurate shape. It has remarkable effects on T leaves, such as being able to provide processed products extremely easily.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an example of the processing method of the present invention, Fig. 2 is an explanatory diagram showing another example of the processing method of the present invention, and Fig. 3 is an explanatory diagram showing an example of the processing method of the present invention. Fig. 4 is a diagram showing the relationship between the radius of curvature and the heating temperature, showing an example of the test results. a. Formed NT gold alloy, rolling mill 2, winding machine 3, heating device 4.5 .Capstan 6, final molding stand 7, take-up stand 9, support part 10, weight 11, weight guide Fig. 1 Fig. 2 Fig. 3 Fig. 4

Claims (3)

[Claims] (1) A method for processing a Ni-Ti-based shape memory alloy, characterized in that the alloy processed into a desired shape is held at 100° C. or higher and tension is applied. (2) In the roll forming process of a Ni-Ti based shape memory alloy that is passed through a forming roll and drawn by a pulling machine, a heating device is installed between the forming roll and the pulling machine to maintain the roll-formed alloy at 100°C or higher. Ni-T is characterized by applying tension by
Processing method for i-based shape memory alloy. (3) In the roll forming process of Ni-Ti-based shape memory alloy, which is pulled through a forming roll and pulled by a pulling machine, a heating device is installed between the forming roll and the pulling machine, and the temperature is 50°C or more higher than the Af point of martensitic transformation. A method for processing a Ni-Ti-based shape memory alloy, which comprises applying tension to an alloy that has been roll-formed in a temperature range from 100°C to 200°C while maintaining the temperature at 100°C or higher.