JP3560907B2

JP3560907B2 - NiTi-based alloy wire, method for producing the same, and guide wire for catheter using the NiTi-based alloy wire

Info

Publication number: JP3560907B2
Application number: JP2000268535A
Authority: JP
Inventors: 豊延田中; 宏堀川; 魁助城山; 賢悟水戸瀬
Original assignee: Furukawa Electric Co Ltd; Furukawa Techno Material Co Ltd
Current assignee: Furukawa Electric Co Ltd; Furukawa Techno Material Co Ltd
Priority date: 2000-09-05
Filing date: 2000-09-05
Publication date: 2004-09-02
Anticipated expiration: 2020-09-05
Also published as: JP2002069555A

Description

【０００１】
【発明の属する技術分野】
本発明は、カテーテル（医療）用ガイドワイヤなどに適したＮｉＴｉ系合金ワイヤおよびその製造方法に関する。
【０００２】
【従来の技術】
ＮｉＴｉ系合金ワイヤは、その形状記憶効果または超弾性効果を利用して、カテーテル用ガイドワイヤ、アクチュエータ用材料、アンテナ用芯線、バネ材料などに広く使用されている。
【０００３】
前記カテーテル用ガイドワイヤには、（ａ）血管の末端近くまでワイヤを送り込めるプッシャビリティ（耐座屈性）を有すること、（ｂ）手元の回転をワイヤ先端に伝える操縦性（トルク伝達性）に優れること、（ｃ）きつく曲がった血管内を通しても曲がりぐせが残らずワイヤを血管の奧まで挿入できる形状回復性に優れることが要求される。そして、（ａ）のプッシャビリティは、引張応力−ひずみ曲線で降伏点が無い場合に優れ、（ｂ）の操縦性は、応力ヒステリシスＨが小さく、かつ熱処理（形状記憶熱処理）で十分な真直度（直線性）が得られる場合に優れ、（ｃ）の形状回復性は残留ひずみが小さい場合に優れる。なお、前記熱処理は、通常、引張強さの５％以下の張力を５００℃の温度で１〜２分間付与して施されていた。
【０００４】
ところで、前記カテーテル用ガイドワイヤには、ＮｉＴｉ系合金ワイヤを用いた（１）超弾性型ワイヤ（特公平２−２４５４８号公報、特公平４−６０６７５号公報）、（２）加工硬化型ワイヤ（特公平６−８３７２６号公報）、（３）広ひずみ範囲高弾性型ワイヤ（特願平１０−３１６６９０号公報、特願平１１−２７３４７０号公報）が知られているが、いずれにも欠点がある。即ち（１）の超弾性型ワイヤは、図５（イ）の引張応力−ひずみ曲線から判るように降伏点Ｆを有するためプッシャビリティに劣り、応力ヒステリシスＨが大きく、また熱処理で十分な真直度が得られないため操縦性もやや劣る。（２）の加工硬化型ワイヤは、図５（ロ）から判るように応力ヒステリシスＨが大きく、また熱処理で十分な真直度が得られないため操縦性に劣る。さらにひずみが４％を超えて大きくなると残留ひずみが大きくなり（図示せず）形状回復性にも劣るようになる。（３）の広ひずみ範囲高弾性型ワイヤは、実質的に応力誘起マルテンサイト変態または逆変態を生じないもので、プッシャビリティやトルク伝達性は優れているが、図５（ハ）から判るように残留ひずみＺが存在するため形状回復性に劣る。
【０００５】
【発明が解決しようとする課題】
このように、前記（１）〜（３）型のガイドワイヤは、いずれも何らかの欠点があるため、本発明者等は、前記（ａ）〜（ｃ）の特性を全て満足する新しいタイプのカテーテル用ガイドワイヤの開発に向けて種々研究を行った。その結果、（３）型のガイドワイヤの残留ひずみＺは、熱処理を所定条件で施すことにより消滅することを見いだし、さらに研究を重ねて本発明を完成させるに至った。本発明は、プッシャビリティ、操縦性、形状回復性に優れ、カテーテル用ガイドワイヤなどに適したＮｉＴｉ系合金ワイヤ、その製造方法および前記ＮｉＴｉ系合金ワイヤを用いたカテーテル用ガイドワイヤの提供を目的とする。
【０００６】
【課題を解決するための手段】
請求項１記載の発明は、引張応力−ひずみ曲線にひずみ４％まで応力ステージ部が無く、垂下法による真直度が１０ｍｍ／２ｍ以下であり、室温で丸棒に半周巻き付けて８．３％の曲げひずみを３０秒負荷したのちの変形角度が８°以下であることを特徴とするＮｉＴｉ系合金ワイヤである。
請求項２記載の発明は、酸化膜の厚さが３μｍ以下の冷間伸線上がりのＮｉＴｉ系合金線材を用いたＮｉＴｉ系合金ワイヤであって、引張応力−ひずみ曲線にひずみ４％まで応力ステージ部が無く、垂下法による真直度が１０ｍｍ／２ｍ以下であり、室温で丸棒に半周巻き付けて８．３％の曲げひずみを３０秒負荷したのちの変形角度が８°以下であることを特徴とするＮｉＴｉ系合金ワイヤである。
【０００７】
請求項３記載の発明は、酸化膜の厚さが３μｍ以下の冷間伸線上がりのＮｉＴｉ系合金線材に、その引張強さの２０〜７０％の張力を３００〜４５０℃の温度で５秒以上１分以下負荷する熱処理を施すことを特徴とする引張応力−ひずみ曲線にひずみ４％まで応力ステージ部が無く、垂下法による真直度が１０ｍｍ／２ｍ以下であり、室温で丸棒に半周巻き付けて８．３％の曲げひずみを３０秒負荷したのちの変形角度が８°以下のＮｉＴｉ系合金ワイヤの製造方法である。
請求項４記載の発明は、酸化膜の厚さが３μｍ以下の冷間伸線上がりのＮｉＴｉ系合金線材に、その引張強さの２０〜７０％の張力とともに５〜３０％のねじり剪断ひずみを３００〜４５０℃の温度で５秒以上１分以下負荷する熱処理を施すことを特徴とする引張応力−ひずみ曲線にひずみ４％まで応力ステージ部が無く、垂下法による真直度が１０ｍｍ／２ｍ以下であり、室温で丸棒に半周巻き付けて８．３％の曲げひずみを３０秒負荷したのちの変形角度が８°以下のＮｉＴｉ系合金ワイヤの製造方法である。
【０００８】
請求項５記載の発明は、請求項１記載のＮｉＴｉ系合金ワイヤを用いたことを特徴とするカテーテル用ガイドワイヤである。
請求項６記載の発明は、請求項２記載のＮｉＴｉ系合金ワイヤを用いたことを特徴とするカテーテル用ガイドワイヤである。
【０００９】
【発明の実施の形態】
本発明のＮｉＴｉ系合金ワイヤは、図１にその引張応力−ひずみ曲線を示すように、ひずみ４％まで応力ステージ部（図５イ参照）が無いためプッシャビリティに優れる。また垂下法による真直度は１０ｍｍ／２ｍ以下であり操縦性に優れる。さらに室温で丸棒に半周巻き付けて８．３％の曲げひずみを３０秒負荷したのちの変形角度は８°以下であり形状回復性に優れる。上記本発明のＮｉＴｉ系合金ワイヤの特長を従来のものと比較して示すと、表１のようになる。即ち、カテーテル用ガイドワイヤに要求されるプッシャビリティ、操縦性、形状回復性の全てを満足するのは、本発明のＮｉＴｉ系合金ワイヤのみであり、本発明のＮｉＴｉ系合金ワイヤが、カテーテル用ガイドワイヤとして極めて有用であることが明瞭に判る。
【００１０】
【表１】

【００１１】
この発明において、前記垂下法による真直度の測定は、図２に示すように、長さ方向が床面に垂直になるように配置したＳＵＳ製チューブ（内径０．３８ｍｍ、外径０．５ｍｍ、長さ５０ｍｍ）１に所定長さの試験ワイヤ２の一端を固定し、試験ワイヤ２の先端の位置と、完全に真直な基準ワイヤ３の先端の位置との床面に平行な距離ｂ（ｍｍ）を測定して求める。変形角度は、図３（イ）に示すように、試験ワイヤ２を室温で直径Ｄの丸棒４に半周巻付けて８．３％の曲げひずみを３０秒間負荷したのち、巻付け部分（Ｄπ／２）を切り取り、その一端側を、図３（ロ）に示すように水平面上に配置し、他端側が水平面から最大に離れるときの角度θを測定して求める。なお、丸棒４の直径Ｄ（ｍｍ）は、Ｄ＝１００ｄ／δの式（但し、ｄはワイヤの直径ｍｍ）に、δ＝８．３を代入して求める。
【００１２】
請求項２記載のＮｉＴｉ系合金ワイヤの製造方法は、酸化膜の薄いＮｉＴｉ系合金線材に熱処理を低温短時間で施すことに特徴があり、引張応力−ひずみ曲線で降伏点が無く、応力ヒステリシスＨが小さく、熱処理で十分な真直度が得られ、残留ひずみの無いＮｉＴｉ系合金ワイヤが得られる。
【００１３】
この発明で、熱処理時の張力を線材の引張強さの２０〜７０％に、温度を３００〜４５０℃に、時間を５秒〜１分にそれぞれ規定する理由は、いずれが下限値未満でも、十分な真直度、十分小さな応力ヒステリシスＨ、８°以下の変形角度が得られないためである。
一方、張力が７０％を超えると線細りや断線が生じたりし、温度が４５０℃を超えるとワイヤの変形抵抗が小さくなって線細りが生じ、得られるワイヤは降伏点が現れ、弾性率が小さくなり、時間が１分を超えても同じく降伏点が現れ、弾性率が小さくなるためである。特に熱処理温度が３００〜３７０℃では弾性率が殆ど低下せず、良好なプッシャビリティが得られる。
【００１４】
本発明において、冷間伸線上がりの線材の酸化膜厚さを３μｍ以下に規定する理由は、酸化膜厚さが３μｍを超えると、応力−ひずみ曲線での応力ステージ部を無くそうとすると、変形角度が８°を超え、変形角度を８°以下にしようとすると応力ステージ部が出現するからである。この原因は、酸化膜が熱伝導或いは変形拘束の面で影響を与えているものと推定される。
【００１５】
この発明において、ＮｉＴｉ系合金線材は、例えば、ＮｉＴｉ系合金鋳塊を熱間加工し、次いで冷間伸線加工して製造される。前記冷間伸線加工では適宜中間焼鈍が施されるが、最終中間焼鈍後の冷間伸線加工率は１５〜６０％が適当である。線材表面の酸化膜厚さは、中間焼鈍を無酸化雰囲気で施すなどの方法により３μｍ以下にできる。
【００１６】
この発明では、熱処理を低温短時間で施すため、得られるＮｉＴｉ系合金ワイヤは従来のものより強度が高くなり、線径を細くできる。従って、直線性が要求されるアンテナ用芯線、ガスケット用棒材、メガネ材等に用いて原料費、或いは装飾性の改善が図れる。
【００１７】
請求項３記載の発明は、張力とともに、ねじり剪断ひずみを負荷して熱処理する製造方法で、ねじり剪断ひずみを負荷することにより線材の残留応力が均一に分布するようになり、単に張力を負荷するよりも真直度が向上する。この発明で、前記ねじり剪断ひずみを５〜３０％に規定する理由は、５％未満ではその効果が十分に得られず、３０％を超えるとねじ切れが起き易くなるためである。
【００１８】
本発明のＮｉＴｉ系合金ワイヤには、Ｎｉを５０．２〜５１．５at％含有し残部がＴｉからなるＮｉＴｉ系合金、Ｎｉを４９．８〜５１．５at％含有し、さらにＣｒ、Ｆｅ、Ｖ、Ａｌ、Ｃｕ、Ｃｏ、Ｍｏの中から１種または２種以上を０．１〜２．０at％含有し残部がＴｉからなるＮｉＴｉ系合金、Ｔｉを４９．０〜５１．０at％、Ｃｕを５〜１２at％含有し残部がＮｉからなるＮｉＴｉ系合金などが用いられる。
【００１９】
【実施例】
以下に本発明を実施例により詳細に説明する。
（実施例１）Ｎｉを５１at％含有し残部がＴｉからなるＮｉＴｉ系合金鋳塊に熱間加工および冷間伸線加工（中間焼鈍を含む）を施し、前記冷間伸線加工における最終中間焼鈍後の伸線加工率を４０％として直径０．５ｍｍの線材を得た。次に、前記線材を矯正機により表２に示す条件で直線状に熱処理してＮｉＴｉ系合金ワイヤを製造した。なお、前記中間焼鈍はすべてＡｒガス雰囲気中で施した。前記伸線加工上がりの線材の引張強さは１７００Ｎ／ｍｍ^２であった。前記熱処理は本発明の規定条件内で施した。
【００２０】
（実施例２）張力とねじり剪断ひずみを負荷しながら熱処理した他は、実施例１と同じ方法によりＮｉＴｉ系合金ワイヤを製造した。
【００２１】
（比較例１）中間焼鈍を大気中で施した他は、実施例１と同じ方法によりＮｉＴｉ系合金ワイヤを製造した。伸線加工上がりの線材の酸化膜厚さは６．７μｍであった。
【００２２】
（比較例２）熱処理を本発明規定条件外で施した他は、実施例１と同じ方法によりＮｉＴｉ系合金ワイヤを製造した。
【００２３】
実施例１、２、比較例１、および比較例２で製造した各々のＮｉＴｉ系合金ワイヤについて、引張応力−ひずみ曲線から応力ステージ部の有無を調べた。また示差走査熱測定（ＤＳＣ）を高感度装置を用いて精密に行った。また真直度は図２に示した方法により測定し、変形角度βは図３（イ）、（ロ）に示した方法（丸棒の径は６．０ｍｍ）により測定した。伸線加工上がりの線材の酸化膜厚さは、走査電子顕微鏡（ＳＥＭ）で酸素の濃度分布を測定する方法により求めた。結果を表２に示す。
【００２４】
【表２】

【００２５】
表２に示すように、本発明例のＮｏ．１〜１０は、いずれも、ひずみ４％まで応力ステージ部が無く、プッシャビリティに優れるものであった。特に熱処理温度が３２０〜３７０℃のものは弾性率が低くなることもなくより良好なプッシャビリティが得られた。ＤＳＣを測定した結果では、いずれにもマルテンサイト相と母相間の変態を示す吸熱または発熱のピークがブロードではあるが認められ（図４参照）、このことから本発明例のワイヤは応力誘起マルテンサイト変態を起こすものと考えられる。また本発明例のワイヤは真直度および変形角度が、本発明規定値を満足し操縦性および形状回復性に優れるものである。熱処理時に張力とともにねじり剪断ひずみを負荷したＮｏ．７、８は真直度が特に良好であった。なお、本発明例のＮｉＴｉ系合金ワイヤをカテーテル用ガイドワイヤとして用いたところ、プッシャビリティ、操縦性、形状回復性に優れ、良好に用いることができた。これに対し、比較例のＮｏ．１１〜１４は、線材の酸化膜が厚かったため、Ｎｏ．１５は熱処理時の温度が低かったため、いずれも真直度と変形角度が本発明規定値を外れた。Ｎｏ．１６は、熱処理時の温度が高かったため、Ｎｏ．１７は熱処理時間が長かったため、いずれも応力ステージ部が現れた。Ｎｏ．１８は熱処理時の張力が低かったため真直度が低下した。Ｎｏ．１９は前記張力が高かったため熱処理中に断線が生じた。
【００２６】
【発明の効果】
以上に述べたように、本発明のＮｉＴｉ系合金ワイヤは、引張応力−ひずみ曲線においてひずみ４％まで応力ステージ部が無く、また垂下法による真直度が１０ｍｍ／２ｍ以下、曲げひずみ負荷後の変形角度が８°以下といずれも小さいので、プッシャビリティ、操縦性、形状回復性に優れ、カテーテル用ガイドワイヤなどに好適である。前記ＮｉＴｉ系合金ワイヤは、酸化膜厚さの薄い線材に張力、温度、時間を規定して熱処理を施すことにより容易に製造できる。前記熱処理では張力とともにねじり剪断ひずみを負荷することにより特性が向上する。依って、工業上顕著な効果を奏する。
【図面の簡単な説明】
【図１】本発明のＮｉＴｉ系合金ワイヤの引張応力−ひずみ曲線の実施形態を示す説明図である。
【図２】真直度を測定する方法の説明図である。
【図３】（イ）、（ロ）は変形角度を測定する方法の説明図である。
【図４】本発明のＮｉＴｉ系合金ワイヤの（イ）降温時および（ロ）昇温時の熱量変化図である。
【図５】従来のＮｉＴｉ系合金ワイヤの引張応力−ひずみ曲線の説明図で、（イ）は超弾性型ワイヤ、（ロ）は加工硬化型ワイヤ、（ハ）は広ひずみ範囲高弾性型ワイヤである。
【符号の説明】
１ＳＵＳ製チューブ
２試験ワイヤ
３完全に真直な基準ワイヤ
４丸棒[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a NiTi-based alloy wire suitable for a catheter (medical) guide wire and the like, and a method for manufacturing the same.
[0002]
[Prior art]
The NiTi-based alloy wire is widely used as a guide wire for a catheter, a material for an actuator, a core wire for an antenna, a spring material, etc. by utilizing its shape memory effect or superelastic effect.
[0003]
The catheter guide wire has (a) pushability (buckling resistance) for feeding the wire near the end of the blood vessel, and (b) maneuverability (torque transmission) for transmitting hand rotation to the wire tip. (C) It is required that the wire has a good shape recovery property that allows the wire to be inserted deep into the blood vessel without leaving a bent even through a tightly bent blood vessel. The pushability of (a) is excellent when there is no yield point in the tensile stress-strain curve, and the maneuverability of (b) has a small stress hysteresis H and a sufficient straightness by heat treatment (shape memory heat treatment). (Linearity) is excellent, and the shape recovery of (c) is excellent when the residual strain is small. The heat treatment was usually performed by applying a tension of 5% or less of the tensile strength at a temperature of 500 ° C. for 1 to 2 minutes.
[0004]
By the way, as the catheter guide wire, a NiTi-based alloy wire is used (1) a super-elastic wire (JP-B-2-24548 and JP-B-4-60675), and (2) a work-hardening wire ( Japanese Patent Application Publication No. 6-83726) and (3) High elasticity type wires having a wide strain range (Japanese Patent Application Nos. 10-316690 and 11-273470) are known, but all have drawbacks. is there. That is, the super-elastic wire of (1) has a yield point F as shown in the tensile stress-strain curve of FIG. 5 (a) and thus has poor pushability, a large stress hysteresis H, and a sufficient straightness by heat treatment. , The maneuverability is slightly inferior. The work hardening type wire (2) has a large stress hysteresis H, as can be seen from FIG. 5 (b), and is inferior in maneuverability because sufficient straightness cannot be obtained by heat treatment. Further, when the strain increases beyond 4%, the residual strain increases (not shown), and the shape recoverability also deteriorates. The wide strain range high elasticity type wire of (3) does not substantially cause stress-induced martensitic transformation or reverse transformation, and has excellent pushability and torque transmission, as can be seen from FIG. Is poor in shape recovery due to the presence of residual strain Z.
[0005]
[Problems to be solved by the invention]
As described above, since the guidewires of the above-mentioned types (1) to (3) all have some disadvantages, the present inventors have proposed a new type of catheter that satisfies all the above-mentioned characteristics (a) to (c). Research for the development of guide wire As a result, it has been found that the residual strain Z of the (3) type guide wire disappears when heat treatment is performed under predetermined conditions, and further studies have been made to complete the present invention. The present invention, pushability, maneuverability, good shape recovery, NiTi-based alloy wire that is suitable, such as a catheter guide wire, and aims to provide a catheter guide wire using the manufacturing method and the NiTi-based alloy wire I do.
[0006]
[Means for Solving the Problems]
Invention of claim 1, wherein, the tensile stress - strain stress stage section up to 4% strain curve rather free straightness by hanging method is not more than 10 mm / 2m, 8.3% wound half a round bar at room temperature A deformation angle after applying a bending strain of 30 seconds to 8 ° or less.
According to a second aspect of the present invention, there is provided an NiTi-based alloy wire using a cold-drawn NiTi-based alloy wire having an oxide film thickness of 3 μm or less , wherein a tensile stress-strain curve shows a strain of up to 4%. There is no part, the straightness by the hanging method is 10mm / 2m or less, and the deformation angle after winding around a round bar at room temperature and applying a 8.3% bending strain for 30 seconds is 8 ° or less. it is a NiTi alloy wire ya to.
[0007]
According to the third aspect of the present invention, a cold-drawn NiTi alloy wire having an oxide film thickness of 3 μm or less is subjected to a tension of 20 to 70% of its tensile strength at a temperature of 300 to 450 ° C. for 5 seconds. The tensile stress-strain curve is characterized by being subjected to a heat treatment of not more than 1 minute. The tensile stress-strain curve has no stress stage portion up to 4% of strain, the straightness by the hanging method is 10 mm / 2m or less, and is wound around a round bar at room temperature for half a round. This method is for producing a NiTi alloy wire having a deformation angle of 8 ° or less after a bending strain of 8.3% is applied for 30 seconds .
According to a fourth aspect of the present invention, a cold-drawn NiTi-based alloy wire having an oxide film thickness of 3 μm or less has a torsional shear strain of 5 to 30% together with a tension of 20 to 70% of its tensile strength. The tensile stress-strain curve is characterized by applying a heat treatment at a temperature of 300 to 450 ° C. for 5 seconds or more and 1 minute or less, without a stress stage portion up to a strain of 4%, and a straightness by a hanging method of 10 mm / 2 m or less. This is a method for producing a NiTi alloy wire having a deformation angle of 8 ° or less after winding around a round bar at room temperature for half a round and applying a bending strain of 8.3% for 30 seconds .
[0008]
According to a fifth aspect of the present invention, there is provided a guide wire for a catheter, wherein the NiTi-based alloy wire according to the first aspect is used .
According to a sixth aspect of the present invention, there is provided a guide wire for a catheter, wherein the NiTi alloy wire according to the second aspect is used .
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
As shown in the tensile stress-strain curve of FIG. 1, the NiTi alloy wire of the present invention has excellent pushability because there is no stress stage portion (see FIG. 5A) up to a strain of 4% . Further, the straightness by the hanging method is 10 mm / 2 m or less, which is excellent in maneuverability. Further, after being wound around a round bar at room temperature for half a round and subjected to a bending strain of 8.3% for 30 seconds, the deformation angle is 8 ° or less, which is excellent in shape recovery. Table 1 shows the characteristics of the NiTi-based alloy wire of the present invention in comparison with the conventional one. That is, only the NiTi alloy wire of the present invention satisfies all of the pushability, maneuverability, and shape recovery required for a catheter guide wire, and the NiTi alloy wire of the present invention It is clearly seen that it is extremely useful as a wire.
[0010]
[Table 1]

[0011]
In the present invention, the measurement of straightness by the drooping method is, as shown in FIG. 2, a SUS tube (inner diameter 0.38 mm, outer diameter 0.5 mm, One end of a test wire 2 of a predetermined length is fixed to 1 (length 50 mm) 1 and a distance b (mm) parallel to the floor surface between the position of the tip of the test wire 2 and the position of the tip of the completely straight reference wire 3. ) Is measured and determined. As shown in FIG. 3A, the deformation angle is determined by winding the test wire 2 around the round bar 4 having a diameter D at room temperature for half a round, applying a bending strain of 8.3% for 30 seconds, and then winding the portion (Dπ / 2) is cut out, one end side thereof is arranged on a horizontal plane as shown in FIG. 3 (b), and the angle θ when the other end side is farthest from the horizontal plane is measured and obtained. The diameter D (mm) of the round bar 4 is obtained by substituting δ = 8.3 into an equation of D = 100 d / δ (where d is the diameter of the wire mm).
[0012]
Method for producing a NiTi-based alloy wire according to claim 2 is characterized in that the heat treatment in a thin NiTi alloy wire with oxide film at a low temperature short time, tensile stress - yield point in strain curve is rather free, stress The hysteresis H is small, sufficient straightness is obtained by heat treatment, and a NiTi-based alloy wire without residual strain is obtained.
[0013]
In the present invention, the reason for setting the tension at the time of heat treatment to 20 to 70% of the tensile strength of the wire, the temperature to 300 to 450 ° C., and the time to 5 seconds to 1 minute, respectively, This is because a sufficient straightness, a sufficiently small stress hysteresis H, and a deformation angle of 8 ° or less cannot be obtained.
On the other hand, if the tension exceeds 70%, wire thinning or disconnection may occur, and if the temperature exceeds 450 ° C., the deformation resistance of the wire decreases and wire thinning occurs, and the resulting wire has a yield point and elastic modulus. This is because even if the time becomes longer than 1 minute, the yield point similarly appears and the elastic modulus becomes small. In particular, when the heat treatment temperature is 300 to 370 ° C., the elasticity hardly decreases and good pushability is obtained.
[0014]
In the present invention, the reason for defining the oxide film thickness of the cold-drawn wire rod to be 3 μm or less is that if the oxide film thickness exceeds 3 μm, the stress stage portion in the stress-strain curve is eliminated. This is because a stress stage portion appears when the deformation angle exceeds 8 ° and the deformation angle is set to 8 ° or less. It is presumed that the cause is that the oxide film has an effect on heat conduction or deformation constraint.
[0015]
In the present invention, the NiTi-based alloy wire is manufactured by, for example, hot working a NiTi-based alloy ingot and then cold drawing. In the cold drawing, intermediate annealing is appropriately performed, and the cold drawing rate after the final intermediate annealing is suitably 15 to 60%. The thickness of the oxide film on the surface of the wire can be reduced to 3 μm or less by, for example, performing intermediate annealing in a non-oxidizing atmosphere.
[0016]
In the present invention, since the heat treatment is performed at a low temperature in a short time, the obtained NiTi-based alloy wire has a higher strength and a smaller wire diameter than the conventional wire. Therefore, the raw material cost or the decorativeness can be improved by using the antenna core wire, the gasket rod material, the eyeglass material, etc., which require linearity.
[0017]
The invention according to claim 3 is a manufacturing method in which torsion shear strain is applied together with tension to perform a heat treatment. By applying torsional shear strain, the residual stress of a wire is uniformly distributed, and tension is simply applied. Straightness is improved. In the present invention, the reason why the torsional shear strain is specified to be 5 to 30% is that if it is less than 5%, the effect is not sufficiently obtained, and if it exceeds 30%, thread breakage is apt to occur.
[0018]
The NiTi-based alloy wire of the present invention contains 50.2 to 51.5 at% of Ni and the balance is Ti. The NiTi-based alloy wire contains 49.8 to 51.5 at% of Ni, and further contains Cr, Fe, and V. , Al, Cu, Co, Mo, a NiTi-based alloy containing 0.1 to 2.0 at% of one or more kinds and the balance being Ti; 49.0 to 51.0 at% of Ti; For example, a NiTi-based alloy containing 5 to 12 at% and a balance of Ni is used.
[0019]
【Example】
Hereinafter, the present invention will be described in detail with reference to Examples.
(Example 1) Hot working and cold drawing (including intermediate annealing) are applied to a NiTi-based alloy ingot containing 51 at% of Ni and the balance being Ti, and final intermediate annealing in the cold drawing is performed. A wire having a diameter of 0.5 mm was obtained by setting the subsequent drawing rate to 40%. Next, the wire was heat-treated linearly by a straightener under the conditions shown in Table 2 to produce a NiTi-based alloy wire. The intermediate annealing was all performed in an Ar gas atmosphere. The wire after the wire drawing had a tensile strength of 1700 N / mm ² . The heat treatment was performed within the specified conditions of the present invention.
[0020]
(Example 2) A NiTi-based alloy wire was manufactured in the same manner as in Example 1, except that heat treatment was performed while applying tension and torsional shear strain.
[0021]
(Comparative Example 1) A NiTi-based alloy wire was manufactured in the same manner as in Example 1 except that the intermediate annealing was performed in the air. The oxide film thickness of the wire after the drawing was 6.7 μm.
[0022]
(Comparative Example 2) A NiTi-based alloy wire was manufactured in the same manner as in Example 1 except that the heat treatment was performed outside the conditions specified in the present invention.
[0023]
Examples 1 and 2, the NiTi-based alloy wire of each prepared in Comparative Example 1, and Comparative Example 2, tensile stress - examined the existence of the stress stage portion from strain curve. Further, differential scanning calorimetry (DSC) was precisely performed using a high-sensitivity apparatus. The straightness was measured by the method shown in FIG. 2, and the deformation angle β was measured by the method shown in FIGS. 3A and 3B (the diameter of the round bar was 6.0 mm). The oxide film thickness of the wire after the drawing was determined by a method of measuring the oxygen concentration distribution by using a scanning electron microscope (SEM). Table 2 shows the results.
[0024]
[Table 2]

[0025]
As shown in Table 2, the No. of the present invention example. 1-10 are both stress stage section up to 4% strain rather free, it was excellent in-flop Sshabiriti. In particular, when the heat treatment temperature was from 320 to 370 ° C, better pushability was obtained without lowering the elastic modulus. According to the DSC measurement results, the endothermic or exothermic peak indicating the transformation between the martensitic phase and the parent phase was broad (see FIG. 4), indicating that the wire of the present invention exhibited stress-induced martensite. It is considered to cause site metamorphosis. The straightness and deformation angle of the wire of the present invention satisfy the specified values of the present invention, and are excellent in maneuverability and shape recovery. No. 1 was loaded with torsional shear strain together with tension during heat treatment. Nos. 7 and 8 had particularly good straightness. In addition, when the NiTi-based alloy wire of the present invention was used as a guide wire for a catheter, it was excellent in pushability, maneuverability and shape recovery, and could be used favorably. On the other hand, in Comparative Example No. Nos. 11 to 14 were Nos. 1 to 14 because the oxide film of the wire was thick. In No. 15, since the temperature at the time of heat treatment was low, the straightness and the deformation angle were out of the specified values of the present invention. No. No. 16 had a high temperature at the time of heat treatment. In No. 17, since the heat treatment time was long, a stress stage portion appeared in each case. No. Sample No. 18 had low straightness due to low tension during heat treatment. No. In No. 19, the wire was broken during the heat treatment due to the high tension.
[0026]
【The invention's effect】
As described above, the NiTi-based alloy wire of the present invention has no stress stage portion up to a strain of 4% in the tensile stress-strain curve, has a straightness of 10 mm / 2 m or less by the hanging method, and has a deformation after bending strain load. Since the angle is as small as 8 ° or less, the pushability, the maneuverability, and the shape recovery are excellent, and it is suitable for a guide wire for a catheter. The NiTi-based alloy wire can be easily manufactured by subjecting a wire having a thin oxide film thickness to a heat treatment with a specified tension, temperature and time. In the heat treatment, characteristics are improved by applying torsional shear strain together with tension. Therefore, a remarkable industrial effect is achieved.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an embodiment of a tensile stress-strain curve of a NiTi-based alloy wire of the present invention.
FIG. 2 is an explanatory diagram of a method of measuring straightness.
FIGS. 3A and 3B are explanatory diagrams of a method for measuring a deformation angle.
FIG. 4 is a diagram showing a change in calorie of the NiTi alloy wire of the present invention when (a) lowering the temperature and (b) when raising the temperature.
FIG. 5 is an explanatory diagram of a tensile stress-strain curve of a conventional NiTi-based alloy wire, where (a) is a superelastic wire, (b) is a work hardening wire, and (c) is a wide strain range high elastic wire. It is.
[Explanation of symbols]
1 SUS tube 2 Test wire 3 Completely straight reference wire 4 Round bar

Claims

Tensile stress - stress stage section up to 4% strain strain curve rather free straightness by hanging method is not more than 10 mm / 2m, and room temperature flexural wound half a round bar of 8.3% strain load 30 seconds A NiTi-based alloy wire having a deformation angle of 8 ° or less.

A NiTi-based alloy wire using a cold-drawn NiTi-based alloy wire having an oxide film thickness of 3 μm or less, and has no stress stage portion up to a strain of 4% in a tensile stress-strain curve, and is straightened by a drooping method. degree is not more than 10 mm / 2m, NiTi alloy wire ya, characterized in that the deformation angle After wound half a round bar load bending strain of 8.3% 30 seconds at room temperature is 8 ° or less.

A heat treatment of applying a tension of 20 to 70% of the tensile strength at a temperature of 300 to 450 ° C. for 5 seconds to 1 minute on a cold-drawn NiTi alloy wire having an oxide film thickness of 3 μm or less. The tensile stress-strain curve is characterized by having no stress stage portion up to a strain of 4%, a straightness of not more than 10 mm / 2m by the hanging method, and a bending strain of 8.3% when wound around a round bar at room temperature for half a round. Of a NiTi-based alloy wire having a deformation angle of 8 ° or less after loading for 30 seconds .

A cold-drawn NiTi-based alloy wire having an oxide film thickness of 3 μm or less is subjected to a torsional shear strain of 5 to 30% together with a tensile strength of 20 to 70% of its tensile strength at a temperature of 300 to 450 ° C. The tensile stress-strain curve has a stress stage portion up to 4% of strain in a tensile stress-strain curve, and has a straightness of not more than 10 mm / 2 m by a drooping method. A method for producing a NiTi-based alloy wire having a deformation angle of 8 ° or less after winding and applying a bending strain of 8.3% for 30 seconds.

A guide wire for a catheter, comprising the NiTi alloy wire according to claim 1.

A guide wire for a catheter, comprising the NiTi-based alloy wire according to claim 2.