WO2004055222A1

WO2004055222A1 - METHOD OF THERMO-MECHANICAL-TREATMENT FOR Fe-Mn-Si SHAPE-MEMORY ALLOY DOPED WITH NbC

Info

Publication number: WO2004055222A1
Application number: PCT/JP2003/016189
Authority: WO
Inventors: Takehiko Kikuchi; Setsuo Kajiwara; Alberto Baruj; Kazuyuki Ogawa; Norio Shinya
Original assignee: National Institute For Materials Science
Priority date: 2002-12-18
Filing date: 2003-12-17
Publication date: 2004-07-01
Also published as: EP1574587A4; US20050236077A1; JP2004197161A; CN100342039C; DE60322260D1; JP3950963B2; EP1574587B1; KR20050083601A; CN1692163A; EP1574587A1

Abstract

Means for thermo-mechanical-treatment of an Fe-Mn-Si shape-memory alloy of specified composition doped with NbC comprises performing a mechanical treatment prior to aging treatment at a mechanical treatment ratio falling within a specified range so that the mechanical treatment can be carried out at room temperature, in place of the old method of performing training as a mechanical treatment prior to aging treatment and in place of the prior method of performing a mechanical treatment at 500 to 800°C prior to aging treatment.

Description

Specification

NbC-added Fe-Mn_Si-type shape memory alloy thermomechanical processing method

The present invention relates to a method for thermomechanical processing of an NbC-added Fe_Mn_Si-based shape memory alloy. More specifically, the present invention provides a method of processing and heat-treating NbC-added Fe—Mn—Si-based shape memory alloy that can exhibit the shape memory characteristics of the above alloy and improve its performance without training. It is about. Background art

It has been a long time since the Fe-Mn-Si-based shape memory alloy was proposed and invented, but its use has not yet been fully utilized, and it has not yet reached the stage of practical application. there were. The main reason for this is that this alloy does not show a sufficient shape memory effect without a special thermomechanical heat treatment called training. Here, training refers to a series of shape memory processing operations in which a process of applying 2-3% deformation at room temperature and then heating near 600 ° C above the reverse transformation point is repeated several times. In view of the situation of the prior art, which required the complicated training process described above, the inventors of the present inventors have conducted intensive research to develop a simple operation, particularly a machining operation that does not require training. That is, frequent training processing operations are performed by adding a small amount of Nb and C elements to the Fe_Mn-Si-based shape memory alloy, performing appropriate aging heat treatment, and precipitating fine NbC carbides in the alloy composition. They found that they exhibited a sufficiently good shape memory effect even without them, and filed a patent application earlier (see Patent Document 1). Furthermore, as a result of research on the thermomechanical treatment of this Nb / C-added alloy, the Fe-Mn_Si-based shape memory alloy of It was discovered that even better aging after working in the temperature range of 00 to 800 ° C resulted in even better shape memory properties, and patent applications were also filed for this (see Patent Documents 2 and 3). Patent Document 1;

Japanese Patent Laid-Open No. 20-1226226

Patent Document 2;

Japanese Patent Application No. 2001-296901

Patent Document 3;

Japanese Patent Application No. 2002-79295 Based on the proposals of the preceding applications, we are convinced that the shape memory alloy technology will make dramatic progress, greatly contribute to practical application in the future, and greatly contribute to the development of industry. There was still room for improvement in the proposals themselves. In other words, even with respect to the latter two prior patent applications (Patent Documents 2 and 3), the invention based on these proposals has an advantage in that the shape memory performance of the alloy itself is lower than that of the conventional technology based on so-called training. The machining operation becomes extremely simple with the improvement of the quality, and its significance is extremely large. In addition, the shape memory performance has been dramatically improved, and the degree of practicality has been significantly improved. It can be said that the operation and effect are extremely remarkable. However, there was still a problem in that heat treatment at a high temperature of 500 to 800 ° C was required, and there was difficulty in using the heat treatment, and it was undeniable that there was a factor that hindered practical application. Disclosure of the invention

The present invention basically seeks to solve this problem.

Accordingly, the present inventors have conducted intensive research to determine whether effective shape memory characteristics can be obtained and secured even under processing at a temperature as low as possible for a shape memory alloy having a specific composition, and this is possible. That is, shape memory characteristics even at room temperature Has been found to be sufficient to achieve the stated purpose. In other words, the basic operation of processing an Fe-Mn-Si-based shape memory alloy to which Nb and C are added at room temperature and then subjecting it to heat aging treatment to precipitate NbC carbide is applied. It has been found that the alloy has an unexpected effect that it can exhibit the shape memory characteristic 1 "of the alloy. In other words, it has succeeded in achieving the above-mentioned object. This was done based on success, and the solutions are shown in (1) to (7) below.

(1) Fe-Mn-Si-based shape memory alloy made by adding Nb and C is caulked at room temperature by 5 to 40% and then subjected to aging heat treatment to precipitate NbC carbide. The method for thermomechanical treatment of NbC-added Fe-Mn_Si-based shape memory alloys.

(2) Fe-Mn-Si-based shape memory alloys are composed of Mn: 15 to 40% by weight, Si: 3 to: L: 5% by weight, Nb: 0 .:! To 1. 5% by weight, C: 0.01 to 0.2% by weight, the balance consisting of Fe and unavoidable impurities, and the atomic ratio NbZC of Nb to C is 1 or more. 1) The method for thermomechanical treatment of NbC-added caro Fe-Mn-Si-based shape memory alloys described in item 1).

(3) Nb C-added Fe—Mn—Si-based shape memory alloy has the following alloy components: Mn: 15 to 40% by weight, Si: 3 to 15% by weight, Cr::! -20% by weight, Nb: 0.1-1.5% by weight, C: 0.01-0.2% by weight, the balance consisting of 6 and inevitable impurities, atomic ratio of Nb to C NbZC Wherein the NbC-added Fe—Mn_Si-based shape memory alloy according to the above item (1) is characterized in that the ratio is 1 or more. (4) Nb Ci ¾PF e -Mn-Si type shape memory alloy, as alloy components, Mn: 15-40% by weight, Si: 3 to 15% by weight, Cr::! %, Ni: 0.1 to 20% by weight, Nb: 0 .:! To 1.5% by weight, C: 0.01 to 0.2% by weight, the balance consisting of Fe and inevitable impurities The method according to item (1), wherein the atomic ratio NbZC between Nb and C is 1 or more, wherein the Nb and C-added Fe_Mn-Si-based shape memory alloy is heat-treated.

(5) The Nb according to any one of (2) to (4), wherein the atomic ratio of Nb and C is preferably set in a range of 1.0 to 1.2. C-added calo Fe-Mn-Si A method for thermomechanical processing of shape memory alloys. .

(6) Nb C-added Fe-Fe-Mn_Si-based shape memory alloy contains, as impurities, Cu: 3% by weight or less, Mo: 2% by weight or less, A1: 10% by weight or less, and Co: 30% by weight. The method for thermomechanical treatment of NbC-added Fe—Mn—Si-based shape memory alloy according to any one of (2) to (5), wherein N: 5000 ppm or less is contained.

(7) The method according to any one of (1) to (6), wherein the aging heat treatment is performed in a temperature range of 400 to 1000 ° C. for 1 minute to 2 hours. Of NbC-added Fe-Mn-Si-based shape memory alloy. The invention's effect

As a means of thermomechanical treatment of Fe_Mn_Si-based shape memory alloys having a specific composition obtained by adding Nb and C, conventional processing performed prior to aging is performed by training. Alternatively, in the prior art, the processing performed prior to the aging treatment was performed in a temperature range of 500 to 800 ° C. In the present invention, the processing performed prior to the aging treatment is specified. By setting the processing rate within this range, processing can be performed at room temperature regardless of high temperature, that is, the processing was successful. The technical significance is that the difference between the subjects is clear when compared with the premise of the prior art and the prior art, and it is clear that there is an extremely large difference. That is, the present invention has succeeded in significantly improving shape memory properties for the first time by setting and combining a specific alloy composition, a workability at room temperature, and an aging condition within a certain range. The operation shows a shape recovery rate equivalent to that of the training-processed sample due to the extremely common processing heat treatment of room temperature processing and aging, and the shape recovery power is significantly larger than that of the training-processed sample. In any case, the present invention is expected to be further accelerated for practical use in various fields in the future. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a view showing the relationship between the shape recovery rate and the initial deformation amount of a NbC-added Fe_Mn—Si-based shape memory alloy according to the present invention due to thermomechanical treatment.

FIG. 2 is a diagram showing the relationship between shape recovery force and recovery strain of a NbC-added kneaded Fe-Mn-Si-based shape memory alloy according to the present invention due to thermomechanical treatment. BEST MODE FOR CARRYING OUT THE INVENTION

Here, the reason why the processing rate at room temperature is specified as 5 to 40% is that if it is less than 5%, it does not contribute to the improvement of shape memory characteristics effectively, and if it exceeds 40%, the sample becomes too hard and aging treatment This is because subsequent deformation becomes extremely difficult. Further, as shown in the previous application, the alloy component targeted by the method for thermomechanical treatment of the NbC-added kneaded Fe-Mn_Si-based shape memory alloy of the present invention is, as shown in the previous application, Mn: 15 to 40% by weight. . /. , S i: 3-15 weight. /. , Nb: 0.1 to 1.5% by weight, C: 0.01 to 0.2% by weight, and the balance is Fe and unavoidable impurities, and the atomic ratio Nb / C of Nb / C is 1 or more. An alloy. The alloy components of the Nb-C-added Fe-Mn-Si-based shape memory alloy are as follows: Mn: 15 to 40% by weight, Si: 3 to: 15% by weight, Cr: 1 to 20% by weight. , Nb: 0.:! ~ 1.5 wt%, C: 0. 0:! Include ~ 0.2 wt%, the balance F _e及Pi consists unavoidable impurities thereof, an alloy atomic ratio Nb / C of Nb to C is 1 or more, Further, Mn: 15 to 40% by weight, Si: 3 to 15% by weight, Cr ::! To 20% by weight, Ni: 0.1 to 20% by weight. / ₀ , Nb: 0.1 to 1.5% by weight, C: 0.01 to 0.2% by weight, the balance consists of Fe and unavoidable impurities, and the atomic ratio of Nb / C Nb / C is 1 The above alloys are also alloys targeted by the present invention. In any of the Fe-Mn-Si-based shape memory alloys added with NbC, the atomic ratio NbZC of Nb to C in the alloy is preferably 1.0 to 1.2. Further, in the alloy component of interest in the method of thermomechanical treatment of the NbC-added kneaded Fe-Mn-Si-based shape memory alloy of the present invention, as an impurity, 3% by weight or less of Cu and 2% by weight or less are contained as impurities. It is permissible to contain at least one or more of Mo, Al up to 10% by weight, Co up to 30% by weight, or N up to 5000 ppm. Embodiment of the Invention

Hereinafter, the present invention will be specifically described with reference to FIGS. However, the examples shown here are merely for the purpose of assisting the understanding of the present invention easily, and are not intended to limit the present invention. Example;

First, a Fe-28Mn_6Si—5Cr—0.53Nb-0.06C alloy (numerical value is% by weight) prepared by adding NbC of the present invention was prepared by melting. After rolling the obtained shape memory alloy at room temperature, it is subjected to aging treatment by heating for 1 minute to 2 hours in a temperature range of 400 to 1000 ° C to show how the shape memory property can be improved. It is shown below.

That is, FIG. 1 is a graph showing the difference in shape recovery ratio between the case where only aging is performed (rolling ratio 0%) and the case where 10%, 20% and 30% rolling is performed at room temperature. The aging process is All were performed at 800 ° C for 10 minutes. For comparison, the results of an as-annealed sample and a sample trained five times are also shown for Fe-28Mn-6Si-5Cr alloy without NbC added. The horizontal axis is the amount of deformation (%) due to tensile deformation at room temperature, and the vertical axis is the shape recovery rate (%) when the sample is heated to 600 ° C. When heated to 400 ° C, almost the same shape recovery rate can be obtained. The test pieces used in this experiment were prepared with a thickness of 0.6 mm, a width of l to 4 mm, and a length (gauge length) of 15 mm. As can be seen from the figure, the 10% rolled sample has about the same or slightly inferior shape memory recovery as the alloy trained five times without NbC. . The amount of deformation necessary for practical use is about 4%, but even at this amount of deformation, a shape memory recovery rate of about 90% strongly suggests that it can be used as a practical alloy. I have. Considering that at least five trainings are required to obtain the same shape recovery rate with a normal Fe-Mn-Si based shape memory alloy without NbC addition, the effect is extremely excellent. I have. When the rolling reduction increases and reaches 20%, the shape recovery rate is almost the same or slightly better than that in the case of no processing (only aging). Furthermore, when the rolling reduction is 30%, the shape recovery rate is worse at a place where the initial strain is larger than when only aging is performed. On the other hand, as shown in Fig. 2, the shape-restoring force, one of the important shape-memory characteristics for practical use, is significantly higher for the samples that have been aged at 20% and 30% at room temperature after rolling at 30%. Has improved. Fig. 2 shows the degree of improvement of the shape recovery force in comparison with the case of only aging (rolling ratio 0%) and the case of aging treatment after rolling 10% at room temperature. The recovery force when the recovery strain on the horizontal axis is zero means the stress generated when both ends are fixed, heated to above the reverse transformation temperature after tensile deformation at room temperature, and then returned to room temperature again. Further, the recovery force when the recovery strain is 2%, for example, means the generated stress measured by fixing both ends after the recovery of the strain by 2%. First given at room temperature The phase strain was tested at 4-6%. The test specimens used were the same as those used to obtain the results shown in Fig. 1. In FIG. 2, the recovery strain on the horizontal axis is, in a practical example, the diameter of the allowable clearance between the pipe and the fastener (shape memory alloy) when used for the fastener of the pipe. Corresponds to the value expressed as a percentage (%). This shape recovery force is remarkably improved at a high rolling reduction. When the rolling reduction at room temperature is 20 to 30%, a recovery force of 310 MPa at a recovery strain of 0% and a recovery force of 20 OMPa can be obtained even at a recovery strain of 2%. Also, it was found that even at a rolling reduction of 10%, exactly the same shape recovery force as in the case of training was obtained. In other words, it is understood from the results in this figure that the shape recovery force is significantly increased at high rolling reductions (20%, 30%) compared to the rolling reductions of 0% and 10%. . For comparison, FIG. 2 shows the shape recovery force of the solution-treated sample without NbC addition and the sample trained five times, but the recovery force is considerably higher than that according to the embodiment of the present invention. I knew it was small. As described above, the present invention relates to a processing performed prior to the aging treatment on a Fe-Mn-Si-based shape memory alloy having a specific composition obtained by adding Nb and C. However, it was the first time that processing was possible at room temperature within a specific processing rate range. The technical significance is that the conventional technology, which is the premise of the technology, is different from the conventional technology in that it requires training with complicated operations and high-temperature processing at 500 to 800 ° C in the prior art. Is clear and obvious. That is, the present invention has succeeded in significantly improving shape memory properties for the first time by setting a specific alloy composition, a workability at room temperature, and an aging condition within a certain range and combining them. The operation is performed at the same level of shape recovery rate as that of the sample that has been subjected to the training treatment by the extremely extensive processing heat treatment of room temperature processing and aging. And the shape resilience is significantly greater than that of the sample that has been subjected to the training process. Dai can be used and used as a fastening member for all purposes up to the fastening of oil pipes, and its economic effect is immense. Of course, the uses as the fastening members exemplified in the above are merely one end of the embodiment, and the present invention is not limited to such uses and fields, and the present invention will be applied to various fields in various fields in the future. It is expected to be put to practical use for various applications. Industrial applicability

According to the present invention, as a means for subjecting a Fe_Mn_Si type shape memory alloy having a specific composition obtained by adding Nb and C to a thermomechanical treatment to a thermomechanical treatment, it has been conventionally aged. In the prior art, the processing performed by training or, in the prior art, the processing performed prior to the aging process was performed in a temperature range of 500 to 800 ° C. In the above, the present inventors succeeded in making it possible to perform processing performed prior to aging processing within a specific processing rate, regardless of high temperature, that is, at room temperature. The technical significance of the present invention is clear when compared with the configurations of the prior art and the prior art on which it is based, and it is clear that there is an extremely large difference. In other words, the present invention has succeeded in significantly improving shape memory properties for the first time by setting a specific alloy composition, a workability at room temperature, and an aging condition within a certain range and combining them. The operation showed a shape recovery rate equivalent to that of the sample that had been subjected to the training treatment by the extremely common processing heat treatment of room temperature aging and aging, and the shape recovery force was significantly larger than that of the sample that had been subjected to the training treatment. In any case, it is expected that the present invention will be further accelerated toward practical use in various fields in the future.

Claims

The scope of the claims

1. Fe-Mn-Si-based shape memory alloy made by adding Nb and C is processed at 5-40% at room temperature, and then heat-aged to precipitate NbC carbide. The method of thermomechanical treatment of NbC-added Fe-Mn-Si-based shape memory alloy.

2. Fe-Mn-Si-based shape memory alloys have the following alloy components: Mn: 15 to 40% by weight, Si: 3 to: 15% by weight, Nb: 0.1 to: 1.5% by weight. , C: 0.01 to 0.2% by weight, the balance consisting of Fe and unavoidable impurities, and the atomic ratio NbZC of Nb to C is 1 or more, NbC according to claim 1, Addition Fe E Mn—Si Thermomechanical processing method for shape memory alloys.

3. Nb C »F e -Mn-Si type shape memory alloy is composed of Mn: 15 to 40% by weight, Si: 3 to: 15% by weight, Cr: 1 to 20% by weight, Nb: 0.

1 to 1.5% by weight, C: 0.01 to 0.2% by weight, balance Fe and inevitable impurities, and atomic ratio of Nb to C NbZC is 1 or more The method for thermomechanical treatment of NbC-added Fe—Mn—Si-based shape memory alloy according to claim 1.

4. Nb C¾S¾PF e-Mn-S i based shape memory alloy is composed of Mn: 15 to 40% by weight, Si: 3 to 15% by weight, Cr ::! To 20% by weight, Ni: 0.

1 to 20% by weight, Nb: 0 .:! To 1.5% by weight, C: 0.01 to 0.2% by weight, the balance consisting of Fe and unavoidable impurities, atomic ratio of Nb to C NbZC The method for thermomechanical treatment of Nb- and C-added FeFe_Mn_Si-based shape memory alloys according to claim 1, characterized in that the value is 1 or more.

5. The NbC-added Fe according to any one of claims 2 to 4, wherein the atomic ratio of Nb and C is preferably set in a range of 1.0 to 1.2. —Mn

'I A method for thermomechanical treatment of Si-based shape memory alloys.

6. The Nb-C-added Fe-Mn-Si-based shape memory alloy contains 3% by weight or less of Cu, 2% by weight or less of Mo, and 10% by weight of A1 as impurities. /. The NbC-added Fe-Mn-Si-based shape memory alloy according to any one of claims 2 to 5, wherein Co: 30% by weight or less and N: 500 ° ppm or less. Processing heat treatment method.

7. The addition of NbC according to any one of claims 1 to 6, wherein the aging heat treatment is performed in a temperature range of 400 to 1000 ° C for 1 minute to 2 hours. F e—Mn—Si A method for thermomechanical treatment of shape memory alloys.