JPH0216369B2 - - Google Patents
Info
- Publication number
- JPH0216369B2 JPH0216369B2 JP60249957A JP24995785A JPH0216369B2 JP H0216369 B2 JPH0216369 B2 JP H0216369B2 JP 60249957 A JP60249957 A JP 60249957A JP 24995785 A JP24995785 A JP 24995785A JP H0216369 B2 JPH0216369 B2 JP H0216369B2
- Authority
- JP
- Japan
- Prior art keywords
- shape memory
- less
- deformation
- present
- properties
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
Description
（産業上の利用分野）
本発明は高強度、高靭性で必要な場合には耐熱
性や耐食性を有するFe−Mn−Si系形状記憶合金
の形状記憶能を向上させる方法に関するものであ
る。
（従来の技術）
特願昭59−187403号、同60−40561号に示され
ているように、Fe−Mn−Si系形状記憶合金は、
通常の真空溶解や大気溶解で鋳塊を製造し熱間圧
延、温間圧延により板等所望の形状に加工し、適
当な熱処理を施すと40°曲げでほぼ100％の形状回
復を示す。しかし４％の引張歪を与えて形状回復
機能を調べると60％程度しか回復しない。これは
４％という歪が本材料の形状記憶量の限界を越え
たため回復率が低下したものと考えられる。
形状記憶合金を実用に供する場合、４％程度あ
るいはそれ以上の歪を受ける用途も多いので、こ
のような厳しい変形に対しても100％の回復を示
せば使用範囲の拡大が期待できる。
（発明が解決しようとする問題点）
本発明はFe−Mn−Si系形状記憶合金において
歪を加えた状態でも優れた形状記憶特性を発揮さ
せるための特性向上方法に関するものである。
（問題点を解決するための手段）
本発明合金の形状記憶作用は、Md点（応力で
マルテンサイトが生成しはじめる温度）以下で変
形させることによつてγ→ε変態を起させ、その
後Af点（マルテンサイトが母相に逆変態してし
まう温度）以上に加熱することによつてε→γ変
態で元の構造に戻る工程で得られている。ところ
が、変形量が大きくなると、γ→ε変態だけでは
なく、γのすべり変形が生じてしまう。つまり、
γのすべり変形に対する抵抗を大きくしてやれ
ば、それだけ大きい変形をγ→ε変態で対応でき
ることになり、形状記憶効果の生じる歪量が増大
すると考えられる。
一般に材料のすべり変形に対する抵抗は材料中
に転位を導入することによつて上昇することが知
られており、従来の形状記憶合金でもくり返し形
状回復を行ううちに材料中に転位が導入され、マ
トリツクスのすべり変形に対する抵抗力が上昇
し、形状記憶特性の向上することがトレーニング
効果として知られている。本発明者らはFe−Mn
−Si系形状記憶合金においても同様の効果が得ら
れると考え、Af点直上に加熱温度を選定し、γ
→ε→γ変態を反覆させたところ、γの加工硬化
が極度に進行し、形状記憶効果は全く改善されな
いか、あるいはむしろ低下する傾向さえみられ
た。そこで本発明者らは、この加工硬化が形状回
復効果を阻害する原因と考え、変形回復温度を
Af点（本発明鋼では200℃前後）よりも高温で一
定時間加熱すれば形状回復率が向上すると考え、
変形→高温加熱回復→変形サイクルを繰返したと
ころ形状記憶効果が向上し、４％歪でもほぼ100
％の回復を示すことを見出した。
本発明はこのような知見に基くもので、重量％
でMn20〜40％、Si3.5〜８％を含有した鉄基合金
または前記成分に10％以下のCr、Ni、Co、２％
以下のMo、１％以下のＣ、Al、Cuの１種または
２種以上を含有させた鉄基合金または前記各成分
に、さらにCaあるいは希土類元素を0.01％以下添
加した鉄基合金からなる形状記憶合金に、20％以
下の加工と400℃以上の加熱を１回以上与えるこ
とを特徴とするFe−Mn−Si系形状記憶合金の特
性向上方法に関するものである。
そこで先ず本発明における各成分とその量の限
定理由について説明する。
Mnは20％未満では応力誘起によつてε相の生
成とともにα′相も導入され形状記憶効果を低下さ
せる。また40％を越えるとγが安定化されγ→ε
変態よりも、γのすべり変形が優先的に生じるよ
うになる。そこで20〜40％とした。
Siはγ→ε変態を促進させる元素であり、その
充分な効果は3.5％以上の添加によつて得られる。
また８％を越えると合金の加工性、成形性がそこ
なわれるので、その範囲を3.5〜８％とした。
Crはγ→ε変態を容易にし、形状記憶特性を
向上させる上、耐食性の向上にも役立つが10％を
越えて添加すると、Siと低融点の金属間化合物を
作り、合金の溶製が不可能になる。
Niは形状記憶特性を劣化させることなく靭性
の向上に寄与するが、10％を越えて添加すると熱
間加工性が悪くなる。
Coは形状記憶効果を向上させ、熱間加工性も
向上させるが、高価であり、また多量に添加して
も効果が顕著ではないので、その上限を10％とし
た。
Moは形状記憶効果を向上させるとともに耐熱
性をも向上させるが、２％を越えると熱間加工性
が悪くなり形状記憶特性も低下する。
Ｃは形状記憶効果を向上させるが１％を越える
と靭性が著しく劣化する。
Alは脱酸剤として作用するとともに形状記憶
効果を向上させるが、１％以上添加しても効果に
変化がない。
Cuは形状記憶効果を劣化させることなく耐食
性を向上させるが、その添加は上限１％で十分で
ある。
CaはMnSの形状制御により形状記憶効果を向
上させるが、過剰の添加は靭性、疲労特性などを
損うので上限を0.01％とした。
稀土類元素（REM）はCaと同様に、MnSの形
状制御により形状記憶効果を向上させるが、過剰
に添加すると、靭性、疲労特性などを損うので、
上限を0.01％とした。
なお本発明においてはMnSの形状制御効果を
確実にするためＳおよびＰをそれぞれ0.003％以
下にすることが好ましい。
次に本発明の特徴とする処理について説明す
る。
加工の上限を20％とした理由は、20％を超える
変形では材料内部に割れを生じてしまい、その後
の加熱によつて回復が不可能となるためである。
なお、加工の下限は形状記憶効果が現われる0.5
％程度である。
また加工後、400℃以上に加熱する理由は、変
形のうちγ→ε変態で生じたεを消してγ一相と
し、さらにγの加工硬化の一部を取り除き、形状
記憶特性を向上させるためである。しかし加熱温
度が400℃以下の場合には回復の度合が小さくな
るため400℃以上の加熱が必要である。また上限
は1350℃程度である。なお、この際の加熱時間は
１〜60分程度が望ましい。
また20％以下の加工と400℃以上の加熱を繰返
すと１回の場合に比べて形状記憶効果はさらに改
善される。
（実施例）
次に本発明の実施例について説明する。
実施例 １
第１表はFe−30％Mn−5.5％Si形状記憶合金に
対して本発明方法を実施した場合の結果を比較法
とともに示すものである。
表中、プロセスNo.１〜５は本発明法、No.６〜８
は比較法である。
比較の基準となるプロセスNo.６においては20％
変形に対する形状記憶効果は100％であるが、40
％変形に対する形状記憶効果は50％である。
これに対し、本発明方法のプロセスNo.１は加工
量20％以下、加熱温度400℃以上、繰返し回数１
の場合であるが、形状記憶効果は20％変形の場合
は100％であることは勿論のこと、40％変形に対
する形状記憶効果も80％となり、No.６より優れて
いる。またプロセスNo.２〜５は、加工−加熱の繰
返し回数２、３、４、５の場合であるが、40％変
形に対する形状記憶効果は繰返し回数２の場合は
90％、３〜５回の場合では100％に到達する。
また比較法No.７は加工量が本発明方法の範囲
外、またNo.８は加熱温度が本発明方法の範囲外で
あるため形状記憶効果は改善されない。
(Field of Industrial Application) The present invention relates to a method for improving the shape memory ability of an Fe-Mn-Si shape memory alloy that has high strength, high toughness, and if necessary, heat resistance and corrosion resistance. (Prior art) As shown in Japanese Patent Application Nos. 59-187403 and 60-40561, Fe-Mn-Si shape memory alloys are
When an ingot is produced by conventional vacuum melting or atmospheric melting, then processed into a desired shape such as a plate by hot rolling or warm rolling, and then subjected to appropriate heat treatment, it shows almost 100% shape recovery after 40° bending. However, when we examine the shape recovery function by applying 4% tensile strain, only about 60% recovery occurs. This is considered to be because the recovery rate decreased because the strain of 4% exceeded the limit of the shape memory capacity of this material. When shape memory alloys are put into practical use, they are often subjected to distortions of around 4% or more, so if they can show 100% recovery even after such severe deformation, the range of use can be expected to expand. (Problems to be Solved by the Invention) The present invention relates to a method for improving the properties of a Fe-Mn-Si shape memory alloy to exhibit excellent shape memory properties even under strain. (Means for solving the problem) The shape memory effect of the alloy of the present invention is achieved by causing γ→ε transformation by deforming it below the Md point (the temperature at which martensite begins to form due to stress), and then Af It is obtained through the process of returning to the original structure through ε→γ transformation by heating above the point (temperature at which martensite reversely transforms into the parent phase). However, when the amount of deformation becomes large, not only γ→ε transformation but also γ slip deformation occurs. In other words,
It is thought that if the resistance to the sliding deformation of γ is increased, the larger deformation can be handled by the γ→ε transformation, and the amount of strain at which the shape memory effect occurs increases. It is generally known that the resistance to sliding deformation of a material increases by introducing dislocations into the material, and even in conventional shape memory alloys, dislocations are introduced into the material during repeated shape recovery, and the matrix It is known that the training effect increases resistance to sliding deformation and improves shape memory properties. The inventors have discovered that Fe-Mn
- Considering that a similar effect can be obtained with Si-based shape memory alloys, we selected a heating temperature just above the Af point, and
When the →ε→γ transformation was repeated, the work hardening of γ progressed extremely, and the shape memory effect did not improve at all, or even tended to decrease. Therefore, the present inventors believe that this work hardening is the cause of inhibiting the shape recovery effect, and the deformation recovery temperature is
We believe that the shape recovery rate will improve if heated for a certain period of time at a higher temperature than the Af point (approximately 200℃ for the steel of the present invention).
By repeating the deformation → high-temperature heating recovery → deformation cycle, the shape memory effect improved, and even with 4% strain, it became almost 100
% recovery. The present invention is based on this knowledge, and the weight %
Iron-based alloy containing 20 to 40% Mn and 3.5 to 8% Si, or 10% or less of Cr, Ni, Co, and 2% of the above components
A shape made of an iron-based alloy containing one or more of the following Mo, 1% or less of C, Al, and Cu, or an iron-based alloy that further contains Ca or a rare earth element of 0.01% or less to each of the above components. The present invention relates to a method for improving the properties of an Fe-Mn-Si shape memory alloy, which comprises subjecting the memory alloy to processing of 20% or less and heating to 400°C or more once or more. Therefore, first, the reasons for limiting each component and its amount in the present invention will be explained. When the Mn content is less than 20%, the α' phase is also introduced along with the formation of the ε phase due to stress induction, reducing the shape memory effect. Moreover, when it exceeds 40%, γ is stabilized and γ→ε
γ slip deformation occurs preferentially over transformation. Therefore, it was set at 20-40%. Si is an element that promotes γ→ε transformation, and its sufficient effect can be obtained by adding 3.5% or more.
Moreover, if it exceeds 8%, the workability and formability of the alloy will be impaired, so the range is set to 3.5 to 8%. Cr facilitates the γ → ε transformation, improves shape memory properties, and is also useful for improving corrosion resistance, but when added in excess of 10%, it forms a low melting point intermetallic compound with Si, making it impossible to melt the alloy. It becomes possible. Ni contributes to improving toughness without deteriorating shape memory properties, but if added in excess of 10%, hot workability deteriorates. Although Co improves the shape memory effect and hot workability, it is expensive and the effect is not significant even when added in large amounts, so the upper limit was set at 10%. Mo improves the shape memory effect and also improves heat resistance, but if it exceeds 2%, hot workability deteriorates and shape memory properties also deteriorate. C improves the shape memory effect, but if it exceeds 1%, the toughness deteriorates significantly. Al acts as a deoxidizing agent and improves the shape memory effect, but there is no change in the effect even if it is added in an amount of 1% or more. Cu improves corrosion resistance without deteriorating the shape memory effect, but an upper limit of 1% is sufficient for its addition. Ca improves the shape memory effect by controlling the shape of MnS, but excessive addition impairs toughness, fatigue properties, etc., so the upper limit was set at 0.01%. Like Ca, rare earth elements (REM) improve the shape memory effect by controlling the shape of MnS, but when added in excess, it impairs toughness, fatigue properties, etc.
The upper limit was set at 0.01%. In the present invention, in order to ensure the shape control effect of MnS, it is preferable that S and P be each 0.003% or less. Next, processing that is a feature of the present invention will be explained. The reason why the upper limit of processing is set at 20% is that deformation exceeding 20% will cause cracks inside the material, making recovery impossible by subsequent heating.
The lower limit of processing is 0.5, at which the shape memory effect appears.
It is about %. The reason for heating to 400℃ or higher after processing is to eliminate the ε generated by the γ → ε transformation during deformation, making it a single γ phase, and also to remove part of the work hardening of γ and improve shape memory properties. It is. However, if the heating temperature is below 400°C, the degree of recovery will be small, so heating above 400°C is necessary. Also, the upper limit is about 1350°C. Note that the heating time at this time is preferably about 1 to 60 minutes. In addition, if processing of 20% or less and heating of 400°C or more is repeated, the shape memory effect will be further improved compared to the case of only one processing. (Example) Next, an example of the present invention will be described. Example 1 Table 1 shows the results when the method of the present invention was applied to a Fe-30%Mn-5.5%Si shape memory alloy, together with a comparative method. In the table, Process Nos. 1 to 5 are the methods of the present invention, Nos. 6 to 8
is a comparative method. 20% in Process No. 6, which is the standard for comparison.
The shape memory effect on deformation is 100%, but 40
The shape memory effect on % deformation is 50%. On the other hand, Process No. 1 of the method of the present invention has a processing amount of 20% or less, a heating temperature of 400°C or more, and a repetition rate of 1.
In this case, the shape memory effect is not only 100% for 20% deformation, but also 80% for 40% deformation, which is superior to No. 6. In addition, Process No. 2 to 5 are cases where the number of repetitions of processing and heating is 2, 3, 4, and 5, but the shape memory effect for 40% deformation is when the number of repetitions is 2.
90%, and in 3 to 5 times it reaches 100%. Further, in comparative method No. 7, the processing amount is outside the range of the method of the present invention, and in No. 8, the heating temperature is outside the range of the method of the present invention, so that the shape memory effect is not improved.
【表】
実施例 ２
第２表は、基本成分Fe−32％Mn−６％Si形状
記憶合金に対する合金元素の影響を、本発明方法
の範囲内で添加した場合と、本発明方法の範囲外
で添加した場合を対比して示したものである。表
中No.１〜14は本発明方法、No.15〜21は比較法であ
る。この表から明らかなように比較鋼は形状記憶
効果は良好であるが、熱間加工性、疲労特性など
が劣る。
これに対して本発明方法においては形状記憶効
果のみならず熱間加工性、靭性、疲労特性、その
他の諸特性がすべて良好である。なお第２表にお
ける形状記憶効果はいずれも40％変形に対するも
のである。[Table] Example 2 Table 2 shows the effects of alloying elements on the basic component Fe-32%Mn-6%Si shape memory alloy when added within the scope of the method of the present invention and when added outside the scope of the method of the present invention. This figure shows a comparison of the case where the compound is added. In the table, Nos. 1 to 14 are the methods of the present invention, and Nos. 15 to 21 are the comparative methods. As is clear from this table, the comparative steels have good shape memory effects, but are inferior in hot workability, fatigue properties, etc. In contrast, in the method of the present invention, not only the shape memory effect but also hot workability, toughness, fatigue properties, and other various properties are all good. Note that the shape memory effects in Table 2 are all for 40% deformation.
【表】
（発明の効果）
以上説明したように本発明方法によればFe−
Mn−Si系形状記憶合金の形状記憶機能の向上を
図ることができる。また形状記憶特性に影響を及
ぼすことなく、強度、靭性、熱間加工性、疲労特
性などの諸特性の向上を図ることができ、その結
果形状記憶合金の用途を拡大することができる。[Table] (Effects of the invention) As explained above, according to the method of the present invention, Fe-
The shape memory function of the Mn-Si shape memory alloy can be improved. Moreover, various properties such as strength, toughness, hot workability, and fatigue properties can be improved without affecting shape memory properties, and as a result, the uses of shape memory alloys can be expanded.
Claims (1)
た鉄基合金に、20％以下の加工と400℃以上の加
熱を１回以上与えることを特徴とするFe−Mn−
Si系形状記憶合金の特性向上方法。 ２ 重量％でMn20〜40％、Si3.5〜８％に加え
て、10％以下のCr、Ni、Co、２％以下のMo、
１％以下のＣ、Al、Cuの１種または２種以上を
含有した鉄基合金に、20％以下の加工と400℃以
上の加熱を１回以上与えることを特徴とするFe
−Mn−Si系形状記憶合金の特性向上方法。 ３ 重量％でMn20〜40％、Si3.5〜８％に加え
て、10％以下のCr、Ni、Co、２％以下のMo、
１％以下のＣ、Al、Cuの１種または２種以上及
びさらに0.01％以下のCa又は希土類元素を含有し
た鉄基合金に、20％以下の加工と400℃以上の加
熱を１回以上与えることを特徴とするFe−Mn−
Si系形状記憶合金の特性向上方法。[Claims] 1. An iron-based alloy containing 20 to 40% Mn and 3.5 to 8% Si by weight is subjected to processing of 20% or less and heating to 400°C or more once or more. Fe−Mn−
Method for improving the properties of Si-based shape memory alloys. 2 In addition to 20 to 40% Mn and 3.5 to 8% Si by weight, 10% or less of Cr, Ni, Co, 2% or less of Mo,
Fe characterized by subjecting an iron-based alloy containing 1% or less of one or more of C, Al, and Cu to processing of 20% or less and heating to 400°C or more once or more.
-Method for improving the properties of Mn-Si shape memory alloys. 3 In addition to 20 to 40% Mn and 3.5 to 8% Si by weight, 10% or less of Cr, Ni, Co, 2% or less of Mo,
Iron-based alloy containing 1% or less of one or more of C, Al, Cu, and 0.01% or less of Ca or rare earth elements is subjected to processing of 20% or less and heating to 400℃ or more at least once. Fe−Mn− characterized by
Method for improving the properties of Si-based shape memory alloys.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60249957A JPS62112720A (en) | 1985-11-09 | 1985-11-09 | Improvement of characteristic fe-mn-si shape memory alloy |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60249957A JPS62112720A (en) | 1985-11-09 | 1985-11-09 | Improvement of characteristic fe-mn-si shape memory alloy |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS62112720A JPS62112720A (en) | 1987-05-23 |
| JPH0216369B2 true JPH0216369B2 (en) | 1990-04-17 |
Family
ID=17200698
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP60249957A Granted JPS62112720A (en) | 1985-11-09 | 1985-11-09 | Improvement of characteristic fe-mn-si shape memory alloy |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS62112720A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0450581U (en) * | 1990-09-05 | 1992-04-28 |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH02149648A (en) * | 1988-12-01 | 1990-06-08 | Nisshin Steel Co Ltd | Shape memory stainless steel and its shape memorizing method |
| US5032195A (en) * | 1989-03-02 | 1991-07-16 | Korea Institute Of Science And Technology | FE-base shape memory alloy |
| JPH0382741A (en) * | 1989-08-25 | 1991-04-08 | Nisshin Steel Co Ltd | Shape memory staiinless steel excellent in stress corrosion cracking resistance and shape memory method therefor |
| US5244513A (en) * | 1991-03-29 | 1993-09-14 | Mitsubishi Jukogyo Kabushiki Kaisha | Fe-cr-ni-si shape memory alloys with excellent stress corrosion cracking resistance |
| JP3950963B2 (en) * | 2002-12-18 | 2007-08-01 | 独立行政法人物質・材料研究機構 | Thermomechanical processing of NbC-added Fe-Mn-Si based shape memory alloy |
| JP4695417B2 (en) * | 2005-03-16 | 2011-06-08 | 新日本製鐵株式会社 | Rail joint member using shape memory alloy |
| CN108359875B (en) * | 2018-04-02 | 2020-02-07 | 四川大学 | Low-nickel FeMnAlNi-based shape memory alloy and processing method thereof |
-
1985
- 1985-11-09 JP JP60249957A patent/JPS62112720A/en active Granted
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0450581U (en) * | 1990-09-05 | 1992-04-28 |
Also Published As
| Publication number | Publication date |
|---|---|
| JPS62112720A (en) | 1987-05-23 |
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