JP2002282985A - Member made of shape memory alloy and manufacturing method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a member made of a shape memory alloy and manufacturing method therefor capable of effectively imparting a shape memory property, usable as it is especially when a processing material is a cast material, without requiring a cutting process for removing such a defect as a shrinking cavity or crack, and imparting not only a diameter increasing process or diameter reducing process to a tubular processing material but a desired shape to the inner face and the outer face thereof. SOLUTION: A rotary plastic process is applied to a shape memory alloy material by cold forming, and a shape memory property is imparted thereto. The rotary plastic process has a spinning process and a flam forming process or a ring rolling process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shape memory alloy member used as a fastening member such as a pipe joint and other members, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Shape memory alloys are functional materials applied to various uses. As a general use form, after the material of the shape memory alloy is coldly deformed, the material is heated in the next step, and the property of returning to the original shape, that is, the property of returning to the original shape is used. Therefore, it is an essential step to apply a cold deformation beforehand.

[0003] As a specific means for imparting cold deformation to a shape memory alloy material, means for expanding the diameter through a mandrel and means for expanding the split mold are disclosed in Japanese Patent Application Laid-Open No. 10-280061. Have been. Japanese Patent Application Laid-Open No. H10-153280 discloses a means for expanding the diameter by bulging using hydraulic pressure or urethane rubber.

[0004] A training process in which deformation is imparted in the cold and then heating to an appropriate temperature and cold deformation is repeated is known as an effective means for improving the shape memory effect of an iron-based shape memory alloy. Technology.

[0005] When manufacturing a shape memory alloy member, various methods such as melting the alloy material and casting into a desired shape, or rolling and extruding after casting, and further welding a rolled plate material as necessary are used. is there. In particular, a tubular body such as a pipe joint is generally manufactured by casting, and in this case, it is preferable that it can be used as a product as cast. There are various casting methods for casting a tubular body, and a centrifugal casting method utilizing centrifugal force has excellent shape memory characteristics.

However, the tubular body manufactured by the centrifugal casting method is cooled from the outer surface side, and the final solidified portion is located on the inner surface side of the tubular body. There is a problem that a crack is generated starting from the defective portion at the time and grows to cause a crack (break). Therefore, when such a tubular body is used as a pipe joint, it is necessary to perform a cutting process to remove a defective portion on the inner surface side, and therefore, at the time of casting, it is necessary to cast a thicker film in consideration of a machining allowance. The problem also existed.

[0007]

DISCLOSURE OF THE INVENTION The present inventors have studied a method for imparting the shape memory characteristics of the above-mentioned conventional shape memory alloy member, and have conducted various tests. As a means of imparting a shape, it is possible to effectively impart shape memory characteristics by performing so-called rotational plastic working, and it can be used as it is without the need for cutting work to remove defects such as sink marks and cracks in cast materials Further, it has been found that not only the diameter expansion processing or the diameter reduction processing for the processing material of the tubular body, but also that a desired shape can be imparted to the inner surface and the outer surface thereof, and the present invention has been achieved. .

[0008]

That is, the present invention provides a shape memory alloy member characterized by imparting shape memory characteristics to a shape memory alloy material by cold rolling plastic working. Provide a way.

The rotational plastic working includes spinning,
Although there is a flow forming process or a ring rolling process, in particular, according to the ring rolling process, simultaneously with imparting shape memory characteristics, not only simply expanding or reducing the diameter of the material of the tubular body, but also forming the tubular body. The inner surface and the outer surface can be processed into a groove shape, processed into irregularities, or provided with various shapes. In addition, since no cutting is required, there is an advantage that the yield is good, the processing can be performed in a short time, and the productivity is excellent.

As described above, in the ring rolling process, various shapes can be formed on the inner surface and the outer surface of the tubular body. However, when the tubular body is a cast material, it is necessary to perform a pre-treatment such as a cutting process without any pretreatment. It is convenient because it can be used as a material. Particularly, a tubular body cast by a centrifugal casting method is more preferable because it has excellent shape memory characteristics.

On the other hand, according to the spinning process and the flow forming process, it is possible to impart a shape memory property by pressing a forming roll against not only a tubular body but also a sheet material of a shape memory alloy.

The method of the present invention is most effective when applied to an iron-based shape memory alloy.
It can also be applied to shape memory alloys.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an example in which ring rolling is performed as rotational plastic working according to the method of the present invention. A tubular body 1 made of an iron-based shape memory alloy as a working material is formed between a forming roller 2 and a mandrel 3. Pressure is applied by the pressure roller 4 while being sandwiched and rotated, and the diameter is expanded in the cold to impart shape memory characteristics. At this time, it is possible to form a projection shape, a groove shape, and the like on the inner surface and the outer surface of the tubular body 1. Further, even if the tubular body 1 as a processing material has a defective portion such as sink marks or slight cracks in the cast material, ring rolling can be performed without preliminary processing such as cutting. In the drawing, reference numeral 5 denotes a support roller attached to the distal end of the clamp arm 6, which plays a role of rotatably supporting the tubular body 1 in a stable posture during ring rolling.

Table 1 shows the results of a diameter expansion test of a plurality of tubular body samples subjected to ring rolling using the rolling diameter expander having the basic configuration shown in FIG. 1, and Table 2 shows the results. 9 shows shape memory characteristics of a sample subjected to a diameter treatment.

A sample of a tubular body as a processing material has a nominal diameter of 150 and a weight percentage of C0.05%, Mn28%, Si6
%, Cr 5%, and the balance substantially made of iron is manufactured by centrifugal casting.
A solution treatment at 1 ° C. × 1 hr was performed. Furthermore, cut to 45 mm as a ring width to make multiple samples,
It was used for diameter expansion. However, the sample was as-cast, unprocessed, and had a wall thickness (tube thickness) of 14 mm (sample No. 3-A).
And 3-B), without as-cast processing, with a wall thickness (pipe thickness) of 17 m
m (Sample Nos. 4-A and 4-B) and 17 mm in thickness were subjected to internal cutting to have a wall thickness (tube thickness) of 14 mm (Samples No. 1-A, 1-B,
2-A) and 2-B). Further, as a comparative example, a mandrel having a wall thickness (pipe thickness) of 14 mm, which was manufactured under the same material and under the same conditions under the same conditions and which had been subjected to a conventional mandrel diameter expansion (sample Nos. 5-A and 5-) B) was added.

The rolling expander has a pressure roller pressure of 15M.
The diameter was expanded under the following conditions: pa, a forming roller original pressure of 3.5 Mpa, and a forming roller rotation rate of 200 rpm. The diameter expansion is two levels of 6% and 8% based on the inner diameter. In addition, the sample No.
For 4-A and 4-B, each was 12 based on the inner diameter.
%, 14%.

As can be seen from Table 1, the results of the diameter expansion test of the tubular sample described above did not show any cracks or the like in any of the three types of samples subjected to ring rolling. On the other hand, in the sample No. of the comparative example in which the mandrel diameter was increased. For 5-A and 5-B, cracks occurred at the time of diameter expansion. From this, it is understood that the diameter expansion by the ring rolling process is superior to the mandrel expansion method.

Next, with respect to the sample subjected to the diameter expansion process, the expanded tubular sample was subjected to a temperature of 300.degree.
Table 2 shows the results of evaluating the shape memory characteristics by heating under the conditions of minutes and allowing to cool, measuring the inner diameter, obtaining the diameter reduction ratio, and evaluating the shape memory characteristics. As a comparative example, the diameter reduction ratio was determined under the same heating conditions for the ones manufactured under the same material and under the same conditions (however, the inner surface was cut) and the mandrel diameter was expanded (samples Nos. 11 and 12). Added. As a result, the diameter reduction rate (change rate) was almost 3.0% in all cases, and the shape memory characteristics were equivalent.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

As described above, according to the present invention,
It can effectively impart shape memory properties, especially when the material to be processed is a cast material, and can be used as it is without the need for cutting work to remove defects such as sink marks and cracks,
Further, it is possible not only to expand or reduce the diameter of the processed material of the tubular body, but also to impart a desired shape to the inner surface and the outer surface thereof.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a basic configuration of a ring rolling process for implementing a method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tubular body 2 Forming roller 3 Mandrel 4 Pressure roller 5 Supporting roller

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kimio Nakamura 1-12-19 Kitahorie, Nishi-ku, Osaka City, Osaka Prefecture Inside Kurimoto Iron Works Co., Ltd. (72) Kosaku Umemoto 1-chome Kitahorie, Nishi-ku, Osaka City, Osaka No. 12-19 Inside Kurimoto Iron Works Co., Ltd. Former Hasekura 35th Kawauchi Residence 11-204 F-term (reference) 4E087 AA01 BA02 BA24 CA41 CB03 HB08

Claims (6)

[Claims] 1. A member made of a shape memory alloy, wherein a shape memory alloy material is given a shape memory characteristic by cold rolling plastic working to a shape memory alloy material. 2. A method of manufacturing a member made of a shape memory alloy, wherein a shape memory alloy material is imparted to a shape memory alloy material by performing cold rotational plastic working. 3. The method according to claim 1, wherein the rotational plastic working comprises spinning,
3. The method for producing a shape memory alloy member according to claim 2, wherein the member is a flow forming process or a ring rolling process. 4. The method according to claim 2, wherein the material is a cast material of a shape memory alloy. 5. The method according to claim 4, wherein the cast material is formed by centrifugal force casting. 6. The method according to claim 2, wherein the shape memory alloy is an iron-based shape memory alloy.