JP6302722B2 - High-strength duplex stainless steel wire excellent in spring fatigue characteristics, its manufacturing method, and high-strength duplex stainless steel wire excellent in spring fatigue characteristics - Google Patents
High-strength duplex stainless steel wire excellent in spring fatigue characteristics, its manufacturing method, and high-strength duplex stainless steel wire excellent in spring fatigue characteristics Download PDFInfo
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- 229910001039 duplex stainless steel Inorganic materials 0.000 title claims description 26
- 238000004519 manufacturing process Methods 0.000 title claims description 14
- 229910000831 Steel Inorganic materials 0.000 claims description 56
- 239000010959 steel Substances 0.000 claims description 56
- 229910001566 austenite Inorganic materials 0.000 claims description 39
- 239000002245 particle Substances 0.000 claims description 38
- 238000010438 heat treatment Methods 0.000 claims description 27
- 229910000859 α-Fe Inorganic materials 0.000 claims description 24
- 229910000734 martensite Inorganic materials 0.000 claims description 22
- 229910001220 stainless steel Inorganic materials 0.000 claims description 22
- 239000002184 metal Substances 0.000 claims description 17
- 229910052751 metal Inorganic materials 0.000 claims description 17
- 238000005096 rolling process Methods 0.000 claims description 16
- 238000001816 cooling Methods 0.000 claims description 7
- 239000012535 impurity Substances 0.000 claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- 238000001556 precipitation Methods 0.000 claims description 5
- 239000000126 substance Substances 0.000 claims description 5
- 239000000047 product Substances 0.000 description 17
- 230000000694 effects Effects 0.000 description 12
- 238000000034 method Methods 0.000 description 11
- 239000013078 crystal Substances 0.000 description 9
- 239000000463 material Substances 0.000 description 8
- 239000000203 mixture Substances 0.000 description 8
- 239000010935 stainless steel Substances 0.000 description 8
- 229920006395 saturated elastomer Polymers 0.000 description 6
- 239000002244 precipitate Substances 0.000 description 5
- 238000012545 processing Methods 0.000 description 5
- 238000005452 bending Methods 0.000 description 4
- 230000007797 corrosion Effects 0.000 description 4
- 238000005260 corrosion Methods 0.000 description 4
- 230000005415 magnetization Effects 0.000 description 4
- 229910052758 niobium Inorganic materials 0.000 description 4
- 229910052720 vanadium Inorganic materials 0.000 description 4
- 238000005491 wire drawing Methods 0.000 description 4
- 229910052726 zirconium Inorganic materials 0.000 description 4
- 239000000835 fiber Substances 0.000 description 3
- 238000000445 field-emission scanning electron microscopy Methods 0.000 description 3
- 238000005098 hot rolling Methods 0.000 description 3
- 230000035882 stress Effects 0.000 description 3
- 229910052715 tantalum Inorganic materials 0.000 description 3
- 238000009864 tensile test Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 229910000963 austenitic stainless steel Inorganic materials 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 238000000265 homogenisation Methods 0.000 description 2
- 230000001771 impaired effect Effects 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 150000004767 nitrides Chemical class 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 229910052717 sulfur Inorganic materials 0.000 description 2
- 239000000654 additive Substances 0.000 description 1
- 230000000996 additive effect Effects 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- LBDSXVIYZYSRII-IGMARMGPSA-N alpha-particle Chemical compound [4He+2] LBDSXVIYZYSRII-IGMARMGPSA-N 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000009661 fatigue test Methods 0.000 description 1
- 230000005307 ferromagnetism Effects 0.000 description 1
- 229910052733 gallium Inorganic materials 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 229910000765 intermetallic Inorganic materials 0.000 description 1
- 229910052745 lead Inorganic materials 0.000 description 1
- 230000005291 magnetic effect Effects 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
- 238000010309 melting process Methods 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 230000005298 paramagnetic effect Effects 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 238000009628 steelmaking Methods 0.000 description 1
- 238000005482 strain hardening Methods 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 150000003568 thioethers Chemical class 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 229910052725 zinc Inorganic materials 0.000 description 1
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Description
本発明は、ばね疲労特性に優れた高強度複相ステンレス鋼線材およびその製造方法、ならびに前記高強度複相ステンレス鋼線材を用いた高強度複相ステンレス鋼線に関するものである。 The present invention relates to a high-strength duplex stainless steel wire excellent in spring fatigue characteristics, a method for producing the same, and a high-strength duplex stainless steel wire using the high-strength duplex stainless steel wire.
従来、ばね疲労特性に優れた高強度ステンレス製品は、ＳＵＳ３０４、ＳＵＳ３１６を代表とするオーステナイト系ステンレス鋼線材、鋼線を素材として加工・成型され製造されてきた。これら製品は、例えばコイルばねとして用いられる場合、特に鋼線の繰り返し曲げ方向、または、ねじり変形方向の疲労特性が求められる。しかしながら、上記のようなオーステナイト系ステンレス鋼線材から加工、製造されたステンレス製品は普通鋼材から製造された製品に比べ劣るという欠点があった。 Conventionally, high-strength stainless steel products having excellent spring fatigue characteristics have been manufactured and formed using austenitic stainless steel wires, such as SUS304 and SUS316, and steel wires as materials. When these products are used as, for example, coil springs, fatigue characteristics in the direction of repeated bending of steel wires or the direction of torsional deformation are particularly required. However, a stainless product processed and manufactured from the austenitic stainless steel wire as described above has a disadvantage that it is inferior to a product manufactured from ordinary steel.
上記課題に対して、強度と疲労特性の向上を目的として、加工誘起マルテンサイト（加工誘起α’）や金属間化合物による強化を利用する技術が検討されている（例えば、特許文献１、２）。しかしながら当該技術では、多量のマルテンサイト（α’）を利用するため得られる製品の靭性に劣る。 In order to improve the strength and fatigue characteristics, techniques using strengthening by work-induced martensite (work-induced α ′) or intermetallic compounds have been studied (for example, Patent Documents 1 and 2). . However, this technique is inferior in the toughness of the product obtained because a large amount of martensite (α ′) is used.
また、上記技術によって得られるステンレス鋼は希少金属の高価なＮｉを多く含有しており、製造コストの観点から望ましくない。そのため、近年では、ステンレス鋼に対し、低Ｎｉ化による低コスト化の要求が強くなってきている。 Further, the stainless steel obtained by the above technique contains a large amount of rare metal expensive Ni, which is not desirable from the viewpoint of manufacturing cost. For this reason, in recent years, there has been an increasing demand for cost reduction by reducing Ni for stainless steel.
低Ｎｉ化の方策として、高Ｍｎ系ステンレス鋼が提案されてきた。そして、高Ｍｎ系ステンレスの強度を向上させる手法として、金属組織の複相組織化が挙げられる（例えば、特許文献３）。
特許文献３に記載の技術は、複相組織のうちオーステナイト（γ）量を制御し、高強度化を図っている。しかしながら、特許文献３に記載の技術では、さらなる高強度化を望む近年の要求強度を満たしてないばかりか、疲労特性が十分でない。
High-Mn stainless steel has been proposed as a measure for reducing Ni. And as a technique for improving the strength of high-Mn stainless steel, there is a multiphase organization of a metal structure (for example, Patent Document 3).
The technique described in Patent Document 3 controls the amount of austenite (γ) in the multiphase structure to increase the strength. However, the technique described in Patent Document 3 does not satisfy the recent required strength for further enhancement of strength but also has insufficient fatigue characteristics.
また、特許文献３に記載の技術は、高い強度を必要とする構造用部材に用いられる鋼板に好適な技術であって、鋼線材に対し複相組織化を利用する技術は未だ検討されていない。 In addition, the technique described in Patent Document 3 is a technique suitable for a steel plate used for a structural member that requires high strength, and a technique that uses a multiphase structure for a steel wire has not yet been studied. .
これまでの低Ｎｉ系・高Ｍｎ系の安価素材のステンレス鋼線材や鋼線は、ばね用として幅広く使用されておらず、さらに従来のばね用素材では、強度と疲労特性の向上が不十分であった。 Conventional low-Ni and high-Mn low-cost stainless steel wires and steel wires have not been widely used for springs, and conventional spring materials are not sufficient to improve strength and fatigue characteristics. there were.
本発明の課題は、ばね疲労特性に優れる廉価低Ｎｉ・高Ｍｎ系高強度複相ステンレス鋼線材、及びその製造方法、ならびにばね疲労特性に優れた高強度ステンレス鋼線を提供することにある。 An object of the present invention is to provide an inexpensive low Ni / high Mn-based high-strength duplex stainless steel wire excellent in spring fatigue characteristics, a manufacturing method thereof, and a high-strength stainless steel wire excellent in spring fatigue characteristics.
本発明では高Ｍｎ、低Ｎｉ系の廉価な素材で、フェライト相、オーステナイト相及びマルテンサイト相から構成される複相組織（以下、α／γ／α’相とも称する）の比率と、α及びγの平均粒径を微細に制御することで、優れた強度とばね疲労特性を示す複相系ステンレス鋼線および線材とすることができる。また、当該線材を製造する際、線材製造プロセス特有の高減面率圧延を有効に活用することで、本発明に係る。高強度複相ステンレス鋼線材を製造できる。
本発明の要旨は下記のとおりである。
In the present invention, a high-Mn, low-Ni inexpensive material, a ratio of a multiphase structure composed of a ferrite phase, an austenite phase and a martensite phase (hereinafter also referred to as α / γ / α ′ phase), α and By finely controlling the average particle diameter of γ, it is possible to obtain a duplex stainless steel wire and wire exhibiting excellent strength and spring fatigue characteristics. Moreover, when manufacturing the said wire, it concerns on this invention by utilizing effectively the high area reduction rolling peculiar to a wire manufacturing process. High strength duplex stainless steel wire can be manufactured.
The gist of the present invention is as follows.
［１］ 質量％で、
Ｃ ：０．２１％以下、
Ｓｉ：０．０５〜３．２％、
Ｍｎ：1％超〜１５％、
Ｎｉ：０．５％以上、５％未満、
Ｃｒ：１０〜２５％、
Ｍｏ:３．０％以下、
Ｃｕ：３．０％以下、
Ｎ ：０．０２〜０．３５％を含有し、残部Ｆｅおよび不可避的不純物からなり、
金属組織がフェライト相及びオーステナイト相を備え、前記オーステナイト相率が３０〜７７ｖｏｌ.％であり、下記（ａ）式で示される前記オーステナイト相中のＭｄ３０値が−１５〜４５であり、前記フェライト相、前記オーステナイト相において、線材の横断面方向の平均粒径が１０μｍ以下であることを特徴とするばね疲労特性に優れた高強度複相ステンレス鋼線材。
Ｍｄ３０＝５５１−４６２（Ｃ＋Ｎ）−９．２Ｓｉ−８．１Ｍｎ−２９（Ｎｉ＋Ｃｕ）−１３．７Ｃｒ―１８．５Ｍｏ ・・・・ （a）
但し、式中の元素記号は、当該元素の鋼中における含有質量％を意味する。
［２］ 質量％で、
Ｍｏ：２．５％以下
であることを特徴とする上記［１］に記載のばね疲労特性に優れた高強度複相ステンレス鋼線材。
［３］ 更に質量％で、
Ｃｏ：２．５％以下、
Ａｌ：０．００１〜２．０％以下、
Ｂ ：０．０１２％以下
の内、１種類以上を含有することを特徴とする上記［１］または［２］に記載のばね疲労特性に優れた高強度複相ステンレス鋼線材。
［４］ 更に質量％で、
Ｗ :２．５％以下、
Ｓｎ：２．５％以下
の内、１種類以上を含有することを特徴とする上記［１］〜［３］の何れか一項に記載のばね疲労特性に優れた高強度複相ステンレス鋼線材。
［５］ 更に質量％で、
Ｔｉ：１．０％以下、
Ｖ ：２．５％以下、
Ｎｂ:２．５％以下、
Ｔａ：２．５％以下
の内、１種類以上を含有することを特徴とする上記［１］〜［４］の何れか一項に記載のばね疲労特性に優れた高強度複相ステンレス鋼線材。
［６］ 更に質量％で、
Ｃａ：０．０１２％以下、
Ｍｇ：０．０１２％以下、
Ｚｒ：０．０１２％以下、
ＲＥＭ：０．０５％以下
の内、１種類以上を含有することを特徴とする上記［１］〜［５］のいずれか一項に記載のばね疲労特性に優れた高強度複相ステンレス鋼線材。
[1] By mass%
C: 0.21% or less,
Si: 0.05-3.2%
Mn: more than 1% to 15%,
Ni: 0.5% or more, less than 5%,
Cr: 10 to 25%,
Mo: 3.0% or less,
Cu: 3.0% or less,
N: 0.02 to 0.35%, consisting of the balance Fe and inevitable impurities,
The metal structure comprises a ferrite phase and an austenite phase, the austenite phase ratio is 30 to 77 vol.%, The Md30 value in the austenite phase represented by the following formula (a) is -15 to 45, and the ferrite A high-strength dual-phase stainless steel wire excellent in spring fatigue characteristics, characterized in that, in the austenite phase, the average particle size in the cross-sectional direction of the wire is 10 μm or less.
Md30 = 551-462 (C + N) -9.2Si-8.1Mn-29 (Ni + Cu) -13.7Cr-18.5Mo (a)
However, the element symbol in a formula means the content mass% in the steel of the said element.
[2] By mass%
Mo: 2.5% or less
The high-strength duplex stainless steel wire material having excellent spring fatigue characteristics as described in [1] above.
[ 3 ] Furthermore, in mass%,
Co: 2.5% or less,
Al: 0.001 to 2.0% or less,
B: The high-strength duplex stainless steel wire rod having excellent spring fatigue characteristics according to the above [1] or [2] , which contains one or more of 0.012% or less.
[ 4 ] Further, by mass%,
W: 2.5% or less,
Sn: A high-strength duplex stainless steel wire rod excellent in spring fatigue characteristics according to any one of the above [1] to [3] , comprising one or more of 2.5% or less .
[ 5 ] Further, by mass%,
Ti: 1.0% or less,
V: 2.5% or less,
Nb: 2.5% or less,
Ta: A high-strength duplex stainless steel wire rod excellent in spring fatigue characteristics according to any one of [1] to [ 4 ] above, which contains at least one of 2.5% or less .
[ 6 ] Further, by mass%,
Ca: 0.012% or less,
Mg: 0.012% or less,
Zr: 0.012% or less,
REM: 0.05% or less, one or more types are included, The high-strength duplex stainless steel wire rod having excellent spring fatigue characteristics according to any one of the above [1] to [ 5 ] .
［７］ 上記［１］〜［６］の何れか一項に記載の高強度複相ステンレス鋼線材の製造方法であって、
ビレットを１０００〜１２８０℃で３００分以内在炉させることで加熱し、前記加熱後の前記ビレットを熱間線材圧延で９９.０％以上の減面率で熱間加工した後、水冷、または、溶体化処理として９５０〜１１５０℃で６００ｓ以下のインライン熱処理を施して水冷することを特徴とするばね疲労特性に優れた高強度複相ステンレス鋼線材の製造方法。
[ 7 ] The method for producing a high-strength duplex stainless steel wire according to any one of [1] to [ 6 ],
The billet is heated at 1000 to 1280 ° C. within 300 minutes, and the billet after the heating is hot-worked with a reduction in area of 99.0% or more by hot wire rolling, water cooling, or A method for producing a high-strength duplex stainless steel wire rod excellent in spring fatigue characteristics, characterized by subjecting to an in-line heat treatment at 950 to 1150 ° C. for 600 s or less as a solution treatment and water cooling.
［８］ 上記［１］〜［６］のいずれか一項に記載の化学成分を有し、
引張強さが１６００〜２３００ＭＰａで、
金属組織が、フェライト相、オーステナイト相及び加工誘起マルテンサイト相から構成される複相組織を有し、前記フェライト相率が２０〜７０ｖｏｌ.％、前記加工誘起マルテンサイト相率が１〜４０ｖｏｌ.％、残部金属組織が前記オーステナイト相及び不可避的析出相からなり、
前記複相組織の鋼線の横断面方向の平均粒径が５μｍ以下であることを特徴とするばね疲労特性に優れた高強度複相ステンレス鋼線。
[ 8 ] The chemical component according to any one of [1] to [ 6 ] above,
Tensile strength is 1600-2300 MPa,
The metal structure has a multiphase structure composed of a ferrite phase, an austenite phase and a work-induced martensite phase, the ferrite phase ratio is 20 to 70 vol.%, And the work-induced martensite phase ratio is 1 to 40 vol.%. The balance metal structure consists of the austenite phase and the inevitable precipitation phase,
A high-strength duplex stainless steel wire excellent in spring fatigue characteristics, characterized in that the average grain size in the cross-sectional direction of the steel wire having a multiphase structure is 5 μm or less.
本発明によれば、ばね疲労特性に優れる廉価低Ｎｉ・高Ｍｎ系高強度複相ステンレス鋼線材、及びその製造方法、ならびにばね疲労特性に優れた高強度ステンレス鋼線を提供できる。
また、本発明による高強度複相ステンレス線材及びステンレス鋼線は、廉価かつ強度とばね疲労特性に優れるため、当該鋼線をばね部品等に適用することで、強度と耐疲労特性に優れたばね等の部品を安価に提供する効果を持つ。
According to the present invention, it is possible to provide an inexpensive low Ni / high Mn high strength duplex stainless steel wire excellent in spring fatigue characteristics, a manufacturing method thereof, and a high strength stainless steel wire excellent in spring fatigue characteristics.
Moreover, since the high-strength double-phase stainless steel wire and stainless steel wire according to the present invention are inexpensive and excellent in strength and spring fatigue characteristics, by applying the steel wire to spring parts, etc., springs having excellent strength and fatigue resistance characteristics, etc. This has the effect of providing low cost parts.
本実施形態に係るばね疲労特性に優れた高強度複相ステンレス鋼線材（以下、単に、高強度複相ステンレス鋼線材またはステンレス鋼線材、もしくは単に線材ともいう。）は、質量％で、Ｃ：０．２１％以下、Ｓｉ：０．０５〜３．２％、Ｍｎ：1％超〜１５％、Ｎｉ：０．５％以上、５％未満、Ｃｒ：１０〜２５％、Ｍｏ:３．０％以下、Ｃｕ：３．０％以下、Ｎ ：０．０２〜０．３５％を含有し、残部Ｆｅおよび不可避的不純物からなり、金属組織がフェライト相及びオーステナイト相を備え、前記オーステナイト相率が３０〜８０ｖｏｌ.％であり、下記（ａ）式で示される前記オーステナイト相中のＭｄ３０値が−１５〜４５であり、前記フェライト相、前記オーステナイト相において、線材の横断面方向の平均粒径が１０μｍ以下であることを特徴とする。
Ｍｄ３０＝５５１−４６２（Ｃ＋Ｎ）−９．２Ｓｉ−８．１Ｍｎ−２９（Ｎｉ＋Ｃｕ）−１３．７Ｃｒ―１８．５Ｍｏ ・・・・ （a）
但し、式中の元素記号は、当該元素の鋼中における含有質量％を意味する。
以下に、先ず、成分組成の限定理由について説明する。
The high-strength double-phase stainless steel wire rod (hereinafter simply referred to as a high-strength double-phase stainless steel wire rod or a stainless steel wire rod or simply a wire rod) excellent in spring fatigue characteristics according to the present embodiment is C%: 0.21% or less, Si: 0.05 to 3.2%, Mn: more than 1% to 15%, Ni: 0.5% or more and less than 5%, Cr: 10 to 25%, Mo: 3.0 %: Cu: 3.0% or less, N: 0.02 to 0.35%, balance Fe and inevitable impurities, the metal structure has a ferrite phase and an austenite phase, the austenite phase ratio is 30 to 80 vol.%, The Md30 value in the austenite phase represented by the following formula (a) is -15 to 45, and in the ferrite phase and the austenite phase, the average particle size in the cross-sectional direction of the wire is 10 μm or less It is characterized in.
Md30 = 551-462 (C + N) -9.2Si-8.1Mn-29 (Ni + Cu) -13.7Cr-18.5Mo (a)
However, the element symbol in a formula means the content mass% in the steel of the said element.
Below, the reason for limitation of a component composition is demonstrated first.
Ｃは、伸線加工後に高強度を得るために、０．２１％以下（以下は全て質量％）添加する。しかしながら、Ｃを０．１４％を超えて添加すると、粒界に粗大Ｃｒ炭化物が析出し、疲労亀裂の起点となり、ばね疲労特性（以下、単に疲労特性ともいう。）が低下傾向となるおそれがあるため、Ｃ量は０．１４％以下とすることが好ましい。また、Ｃ量が０．０１％未満となると強度不足となるおそれがある。以上から、Ｃ量の好ましい範囲は、０．０１〜０．１４％である。 C is added in an amount of 0.21% or less (the following is all by mass%) in order to obtain high strength after wire drawing. However, if C is added in excess of 0.14%, coarse Cr carbide precipitates at the grain boundaries, which becomes the starting point of fatigue cracks, and there is a possibility that the spring fatigue characteristics (hereinafter also simply referred to as fatigue characteristics) tend to decrease. Therefore, the C content is preferably 0.14% or less. Further, if the C content is less than 0.01%, the strength may be insufficient. From the above, the preferable range of the C amount is 0.01 to 0.14%.
Ｓｉは、脱酸を行い、脱酸生成物を少なくして疲労特性を確保するために０．０５％以上添加する。しかしながら、Ｓｉを３．２％を超えて添加するとその効果は飽和するばかりか製造性が悪くなり、また、線材、鋼線の疲労特性を劣化させるため、上限を３．２％にする。Ｓｉ量の好ましい範囲は、０．２〜１．５％である。 Si is added in an amount of 0.05% or more in order to deoxidize, reduce the amount of deoxidation products, and ensure fatigue characteristics. However, if Si is added in excess of 3.2%, the effect is not only saturated, but the manufacturability deteriorates, and the fatigue properties of the wire and steel wire are deteriorated, so the upper limit is made 3.2%. A preferable range of the amount of Si is 0.2 to 1.5%.
Ｍｎは、Ｎｉの代替元素として有効であり、かつ高強度化に有効な加工誘起双晶を得るのに有効な元素である。これらの効果を享受するためＭｎ量は1％超にする。しかしながら、Ｍｎを１５％を超えて添加すると線材、鋼線の靱性が低下して疲労特性を劣化させるため、Ｍｎ量の上限を１５％に限定する。Ｍｎ量の好ましい範囲は、５％超、１５％以下である。 Mn is an effective element for obtaining a work-induced twin that is effective as a substitute element for Ni and effective for increasing the strength. In order to enjoy these effects, the amount of Mn is made more than 1%. However, if Mn is added in excess of 15%, the toughness of the wire rod and steel wire is lowered to deteriorate the fatigue characteristics, so the upper limit of the Mn content is limited to 15%. A preferable range of the amount of Mn is more than 5% and 15% or less.
Ｎｉは、延靱性を確保して疲労特性を確保するため、０．５％以上添加する。しかしながら、５．０％以上添加すると、オーステナイト（γ）相中のMｄ３０値が低くなり、強度特性に劣るばかりか、本発明の低Ｎｉ化の特徴が損なわれる。そのため、Ｎｉ量の上限を５％未満にする。Ｎｉ量の好ましい範囲は、１．０〜４．５％である。 Ni is added in an amount of 0.5% or more in order to ensure ductility and fatigue characteristics. However, if added in an amount of 5.0% or more, the Md30 value in the austenite (γ) phase is lowered and the strength characteristics are inferior, and the low Ni feature of the present invention is impaired. Therefore, the upper limit of the Ni amount is less than 5%. A preferable range of the amount of Ni is 1.0 to 4.5%.
Ｃｒは、耐食性を確保するため、１０．０％以上添加する。しかしながら、Ｃｒを２５％を超えて添加すると、γ相中のMｄ３０値が低くなり、強度特性に劣るばかりか、本発明の低Ｎｉ化の特徴が損なわれるため、Ｃｒ量の上限を２５％にする。Ｃｒ量の好ましい範囲は、１３．０〜２４．０％である。 Cr is added in an amount of 10.0% or more to ensure corrosion resistance. However, if Cr is added in excess of 25%, the Md30 value in the γ phase is lowered and the strength characteristics are inferior, and the characteristics of the low Ni content of the present invention are impaired, so the upper limit of Cr content is 25%. To do. A preferable range of the Cr content is 13.0 to 24.0%.
Ｍｏは、耐食性を向上させるのに有効な元素である。しかしながら、Ｍｏを３．０％を超えて含有すると、その効果は飽和するばかりか、逆に疲労特性が劣化する。そのため、Ｍｏは３．０％以下の範囲で含有させる。Ｍｏ量の好ましい範囲は、０．０５〜２．５％である。 Mo is an element effective for improving the corrosion resistance. However, when Mo is contained in excess of 3.0%, the effect is saturated, and conversely, fatigue characteristics deteriorate. Therefore, Mo is contained in a range of 3.0% or less. A preferable range of the Mo amount is 0.05 to 2.5%.
Ｃｕは、微細Ｃｕ析出物として強度や疲労特性の向上に寄与する元素である。しかしながら、Ｃｕを３．０％を超えて含有すると、線材、鋼線の強度が低下する。そのため、Ｃｕは３．０％以下の範囲で含有させる。Ｃｕ量の好ましい範囲は、０．０５〜２．５％である。 Cu is an element that contributes to improvement of strength and fatigue characteristics as a fine Cu precipitate. However, when Cu is contained exceeding 3.0%, the strength of the wire and the steel wire is lowered. Therefore, Cu is contained in the range of 3.0% or less. A preferable range of the amount of Cu is 0.05 to 2.5%.
Ｎは、伸線加工後に高強度を得るために、０．０２％以上添加する。しかしながら、Ｎを０．３５％を超えて添加すると、粒界に粗大Ｃｒ窒化物が析出し、疲労亀裂の起点となるばかりか、製鋼プロセスで窒素のブローホールが生成して製造性を大幅に劣化させる。そのため、Ｎ量の上限を０．３５％とする。Ｎ量の好ましい範囲は、０．０４〜０．３０％である。 N is added in an amount of 0.02% or more in order to obtain high strength after wire drawing. However, when N is added in excess of 0.35%, coarse Cr nitride precipitates at the grain boundary, which becomes the starting point of fatigue cracks, and nitrogen blowholes are generated in the steelmaking process, greatly improving productivity. Deteriorate. Therefore, the upper limit of the N amount is set to 0.35%. A preferable range of the N amount is 0.04 to 0.30%.
本発明のステンレス線材及び鋼線は、上述してきた元素以外は、Ｆｅ及び不可避的不純物からなる。
代表的な不可避的不純物としては、Ｏ，Ｓ，Ｐなどが挙げられ、通常、鉄鋼の製造プロセスで不可避的不純物として０．０００１〜０．１％の範囲で混入する。
また、上述してきた元素以外の任意添加元素について、代表的なものを上記［２］〜［５］にて説明したが、詳細を以下で説明する。なお、本明細書中に記載されていない元素であっても、本発明の効果を損なわない範囲で含有させることが出来る。
The stainless steel wire and steel wire of the present invention are composed of Fe and inevitable impurities other than the elements described above.
Typical inevitable impurities include O, S, P and the like, and usually mixed in the range of 0.0001 to 0.1% as inevitable impurities in the steel manufacturing process.
Moreover, although typical things were demonstrated by said [2]-[5] about arbitrary addition elements other than the element mentioned above, the detail is demonstrated below. In addition, even if it is an element which is not described in this specification, it can be contained in the range which does not impair the effect of this invention.
上記［２］にて記載した成分組成の限定理由について説明する。 The reasons for limiting the component composition described in [2] above will be described.
Ｃｏは、線材、鋼線の疲労特性を向上させるのに有効な元素である。しかしながら、Ｃｏを２．５％を超えて含有すると、その効果は飽和するばかりか、逆に線材、鋼線の疲労特性が劣化するおそれがある。そのため、Ｃｏは必要に応じて２．５％以下の範囲で含有させてもよい。Ｃｏ量のより好ましい範囲は、０．０５〜１．０％であり、更に好ましくは０．１〜０．８％である。 Co is an element effective for improving the fatigue characteristics of wire rods and steel wires. However, if Co is contained in excess of 2.5%, the effect is not only saturated, but conversely, the fatigue properties of the wire and steel wire may be deteriorated. Therefore, Co may be contained in a range of 2.5% or less as necessary. A more preferable range of the amount of Co is 0.05 to 1.0%, and further preferably 0.1 to 0.8%.
Ｂは、粒界強度を向上させて、線材、鋼線の疲労特性を向上させるのに有効な元素である。しかしながら、Ｂを０．０１２％を超えて含有すると、粗大なボライド生成により、逆に疲労特性が劣化するおそれがある。そのため、Ｂは必要に応じて０．０１２％以下の範囲で含有させてもよい。Ｂ量のより好ましい範囲は、０．０００４〜０．０１０％であり、更に好ましくは０．００１〜０．００５％である。 B is an element effective for improving the grain boundary strength and improving the fatigue properties of the wire and the steel wire. However, if B is contained in excess of 0.012%, there is a possibility that the fatigue characteristics are deteriorated conversely due to generation of coarse boride. Therefore, B may be contained within a range of 0.012% or less as necessary. A more preferable range of the B amount is 0.0004 to 0.010%, and further preferably 0.001 to 0.005%.
Ａｌは、脱酸を促進して介在物清浄度レベルを向上させ、線材、鋼線の疲労特性を向上させるのに有効な元素であるため、０．００１％以上含有させてもよい。しかしながら、Ａｌを２．０％を超えて含有すると、その効果は飽和するばかりか、材料自体の疲労特性が劣化するおそれがある。そのため、Ａｌは必要に応じて２．０％以下の範囲で含有させてもよい。Ａｌ量のより好ましい範囲は、０．００３〜１．０％であり、更に好ましくは０．００５〜０．１％である。 Al is an element effective for promoting deoxidation to improve the level of inclusion cleanliness and improving the fatigue properties of wire rods and steel wires. Therefore, Al may be contained in an amount of 0.001% or more. However, if Al is contained in excess of 2.0%, not only the effect is saturated, but the fatigue characteristics of the material itself may be deteriorated. Therefore, Al may be contained in a range of 2.0% or less as necessary. A more preferable range of the amount of Al is 0.003 to 1.0%, and further preferably 0.005 to 0.1%.
次に、上記［３］にて記載した成分組成の限定理由について説明する。 Next, the reasons for limiting the component composition described in [3] above will be described.
Ｗは、耐食性を向上させるのに有効な元素である。しかしながら、Ｗを２．５％を超えて含有すると、その効果は飽和するばかりか、逆に疲労特性が劣化するおそれがある。そのため、Ｗは必要に応じて２．５％以下の範囲で含有させてもよい。Ｗ量のより好ましい範囲は、０．０５〜２．０％であり、更に好ましくは０．１〜１．５％以下である。 W is an element effective for improving the corrosion resistance. However, if W is contained in excess of 2.5%, the effect is not only saturated, but conversely, fatigue characteristics may be deteriorated. Therefore, W may be contained in a range of 2.5% or less as necessary. A more preferable range of the W amount is 0.05 to 2.0%, and more preferably 0.1 to 1.5%.
Ｓｎは、耐食性を向上させるのに有効な元素である。しかしながら、Ｓｎを２．５％を超えて含有すると、その効果は飽和するばかりか、逆に疲労特性が劣化するおそれがある。そのため、Ｓｎは必要に応じて２．５％以下の範囲で含有させてもよい。Ｓｎ量のより好ましい範囲は、０．０１〜１．０％であり、更に好ましくは０．０５〜０．２％以下である。 Sn is an element effective for improving the corrosion resistance. However, if Sn is contained in excess of 2.5%, the effect is not only saturated, but conversely, fatigue characteristics may be deteriorated. Therefore, Sn may be contained in a range of 2.5% or less as necessary. A more preferable range of the Sn amount is 0.01 to 1.0%, and more preferably 0.05 to 0.2%.
次に、上記［４］にて記載した成分組成の限定理由について説明する。 Next, the reasons for limiting the component composition described in [4] above will be described.
Ｔｉ，Ｖ，Ｎｂ，Ｔａは、炭窒化物を形成して結晶粒径を微細にして線材、鋼線の疲労特性を改善するため、必要に応じて、Ｔｉ：１．０％以下，Ｖ：２．５％以下，Ｎｂ：２．５％以下，Ｔａ：２．５％以下の内、１種類以上を含有させてもよい。しかしながら、これら各元素を各規定上限を超えて含有させると粗大介在物が生成し、線材、鋼線の疲労特性が低下するおそれがある。これらのことから、各元素の好ましい範囲は、Ｔｉ：０．０３〜０．７％、Ｖ：０．０４〜１．５％、Ｎｂ：０．０４〜１．５％、Ｔａ：０．０４〜１．５％であり、更に好ましくは、Ｔｉ：０．０５〜０．５％，Ｖ：０．０８〜０．９％，Ｎｂ：０．０８〜０．９％，Ｔａ：０．０８〜０．９％である。 Ti, V, Nb, and Ta form carbonitrides to refine the crystal grain size and improve the fatigue properties of the wire and steel wire. Therefore, if necessary, Ti: 1.0% or less, V: One or more of 2.5% or less, Nb: 2.5% or less, and Ta: 2.5% or less may be contained. However, if these elements are contained in excess of the specified upper limit, coarse inclusions are generated, and the fatigue properties of the wire and steel wire may be reduced. From these facts, preferable ranges of each element are Ti: 0.03-0.7%, V: 0.04-1.5%, Nb: 0.04-1.5%, Ta: 0.04. -1.5%, more preferably, Ti: 0.05-0.5%, V: 0.08-0.9%, Nb: 0.08-0.9%, Ta: 0.08 ~ 0.9%.
次に、上記［５］にて記載した成分組成の限定理由について説明する。
Ｃａ，Ｍｇ，Ｚｒ，ＲＥＭは、脱酸のため、必要に応じて、Ｃａ：０．０１２％以下，Ｍｇ：０．０１２％以下，Ｚｒ：０．０１２％以下，ＲＥＭ：０．０５％以下の１種以上を含有させる。しかしながら、各上限を超えて含有すると粗大介在物が生成して鋼線の疲労特性が低下する。好ましい範囲は、Ｃａ：０．０００４〜０．０１０％、Ｍｇ：０．０００４〜０．０１０％、Ｚｒ：０．０００４〜０．０１０％、ＲＥＭ：０．０００４〜０．０５％であり、更に好ましくはＣａ：０．００１〜０．００５％，Ｍｇ：０．００１〜０．００５％，Ｚｒ：０．００１〜０．００５％，ＲＥＭ：０．００１〜０．０５％である。
Next, the reasons for limiting the component composition described in [5] above will be described.
Ca, Mg, Zr, and REM are for deoxidation, and as required, Ca: 0.012% or less, Mg: 0.012% or less, Zr: 0.012% or less, REM: 0.05% or less 1 or more types of are included. However, when it contains exceeding each upper limit, a coarse inclusion will produce | generate and the fatigue characteristic of a steel wire will fall. Preferred ranges are Ca: 0.0004 to 0.010%, Mg: 0.0004 to 0.010%, Zr: 0.0004 to 0.010%, REM: 0.0004 to 0.05%, More preferably, they are Ca: 0.001-0.005%, Mg: 0.001-0.005%, Zr: 0.001-0.005%, REM: 0.001-0.05%.
以上説明した各元素の他にも、本発明の効果を損なわない範囲で含有させることが出来る。その他の成分について本発明では特に規定するものではないが、一般的な不純物元素であるＰ、Ｓ、Ｚｎ、Ｂｉ、Ｐｂ、Ｓｅ、Ｓｂ、Ｈ、Ｇａ等は可能な限り低減することが好ましい。これらの元素は、本発明の課題を解決する限度にいて、その含有割合が制御され、必要に応じて、Ｐ≦４００ｐｐｍ、Ｓ≦１００ｐｐｍ、Ｚｎ≦１００ｐｐｍ、Ｂｉ≦１００ｐｐｍ、Ｐ≦１００ｐｐｍ、Ｓｅ≦１００ｐｐｍ、Ｓｂ≦１００ｐｐｍ、Ｈ≦１０ｐｐｍ、Ｇａ≦１００ｐｐｍの１種以上を含有する。 In addition to the elements described above, the elements of the present invention can be contained within a range not impairing the effects of the present invention. Other components are not particularly defined in the present invention, but it is preferable to reduce general impurity elements such as P, S, Zn, Bi, Pb, Se, Sb, H, and Ga as much as possible. These elements are limited to solve the problems of the present invention, and the content ratio is controlled, and P ≦ 400 ppm, S ≦ 100 ppm, Zn ≦ 100 ppm, Bi ≦ 100 ppm, P ≦ 100 ppm, Se ≦ as necessary. Contains one or more of 100 ppm, Sb ≦ 100 ppm, H ≦ 10 ppm, Ga ≦ 100 ppm.
次に、本実施形態に係る線材の金属組織について説明する。
線材の金属組織において、オーステナイト相率を３０〜８０vol.％に限定する。オーステナイト相率が３０vol.％未満では、強度特性に劣るばかりか、熱間製造性を得られない。一方、オーステナイト相率が８０vol.％を超えると粒径が大きくなり、疲労特性が劣化する。そのため、オーステナイト相率の上限を８０vol.％に限定する。オーステナイト相率の好ましい範囲は４０〜７３vol.％以下である。
Next, the metal structure of the wire according to this embodiment will be described.
In the metal structure of the wire, the austenite phase ratio is limited to 30 to 80 vol.%. If the austenite phase ratio is less than 30 vol.%, Not only the strength properties are inferior, but also hot manufacturability cannot be obtained. On the other hand, when the austenite phase ratio exceeds 80 vol.%, The particle size increases and the fatigue characteristics deteriorate. Therefore, the upper limit of the austenite phase rate is limited to 80 vol.%. A preferable range of the austenite phase ratio is 40 to 73 vol.% Or less.
また、線材において、オーステナイト相以外の残部金属組織の大部分がフェライト相である。さらに、不可避的析出相からなる線材とする。
なお、本実施形態に係る線材を用いて製造された鋼線の金属組織については後述することとする。
Moreover, in the wire, most of the remaining metal structure other than the austenite phase is the ferrite phase. Furthermore, it is set as the wire which consists of an unavoidable precipitation phase.
In addition, suppose that it mentions later about the metal structure of the steel wire manufactured using the wire which concerns on this embodiment.
次に、Ｍｄ値について説明する。
本実施形態に係る線材において、オーステナイト相中のＭｄ値は、−１５〜４０に限定する。
Ｍｄ３０値は、伸線後の加工誘起マルテンサイト量と成分の関係をそれぞれ調査して得られた指標であり、高強度と鋼線の疲労特性を安定的に確保するために制御する必要がある。
Next, the Md value will be described.
In the wire according to the present embodiment, the Md value in the austenite phase is limited to -15 to 40.
The Md30 value is an index obtained by investigating the relationship between the amount of work-induced martensite after drawing and the component, and it is necessary to control the strength in order to stably secure the fatigue strength of the steel wire. .
Ｍｄ３０値は、下記式（ａ）より求められる値であり、オーステナイト相中のこの値が−１５未満の場合、オーステナイト相の安定度が増し、伸線加工では高強度化し難くなる。一方、Ｍｄ３０値が４５を超えると、オーステナイト相が不安定となり、伸線加工で加工誘起マルテンサイト相が４０体積％以上に生成してしまい、疲労特性が劣化する。そのため、Ｍｄ３０値を−１５〜４０に限定する。Ｍｄ値の好ましい範囲は、−１０〜４０である。 The Md30 value is a value obtained from the following formula (a). When this value in the austenite phase is less than −15, the stability of the austenite phase increases, and it is difficult to increase the strength by wire drawing. On the other hand, if the Md30 value exceeds 45, the austenite phase becomes unstable, and the work-induced martensite phase is generated to 40% by volume or more in the wire drawing, resulting in deterioration of fatigue characteristics. Therefore, the Md30 value is limited to -15 to 40. A preferable range of the Md value is −10 to 40.
Ｍｄ３０＝５５１−４６２（Ｃ＋Ｎ）−９．２Ｓｉ−８．１Ｍｎ−２９（Ｎｉ＋Ｃｕ）−１３．７Ｃｒ−１８．５Ｍｏ ・・・ （ａ） Md30 = 551-462 (C + N) -9.2Si-8.1Mn-29 (Ni + Cu) -13.7Cr-18.5Mo (a)
次に、フェライト（α）相及びオーステナイト（γ）相の結晶粒径について説明する。
α粒径、γ粒径において、粒径の微細化は疲労特性の向上に寄与する。つまり、α相及びγ相の平均粒径が１０μm以下の場合、疲労特性は良好になる。しかし、α相及びγ相の平均粒径が１０μｍを超えると疲労特性の劣化に加え、強度も劣位となる。そのため、α相及びγ相の平均粒径を１０μｍ以下に限定する。α相及びγ相の平均粒径好ましい範囲は５μｍ以下とする。なお、α相及びγ相の平均粒径の下限は特に限定せず、小さければ小さいほど上記効果を十分に享受できる。
Next, the crystal grain sizes of the ferrite (α) phase and the austenite (γ) phase will be described.
In the α particle size and the γ particle size, refinement of the particle size contributes to improvement of fatigue characteristics. That is, when the average particle size of the α phase and the γ phase is 10 μm or less, the fatigue characteristics are good. However, when the average particle size of the α phase and the γ phase exceeds 10 μm, the strength becomes inferior in addition to the deterioration of the fatigue characteristics. Therefore, the average particle size of the α phase and the γ phase is limited to 10 μm or less. The preferable range of the average particle diameter of the α phase and γ phase is 5 μm or less. In addition, the minimum of the average particle diameter of (alpha) phase and (gamma) phase is not specifically limited, The said effect can fully be enjoyed, so that it is small.
「α相及びγ相の平均粒径」は、線材の横断面をFE-SEMで観察し、繊維方向に直角となる直線Ｌ（μｍ）を引き、その直線に存在した粒(αもしくはγ)の数Ｎから下記（Ｆ）式を用いて算出することができる。
α相及びγ相の平均粒径（μm）＝Ｌ／Ｎ ・・・ （Ｆ）
“Average particle diameter of α phase and γ phase” means that the cross section of the wire is observed with FE-SEM, and a straight line L (μm) perpendicular to the fiber direction is drawn, and the grains (α or γ) existing in the straight line It can be calculated using the following formula (F) from the number N of:
Average particle diameter of α phase and γ phase (μm) = L / N (F)
次に、本実施形態に係る線材の製造方法について説明する。
本実施系形態に係る高強度複相ステンレス鋼線材を廉価に得るには、α、γ結晶粒径を微細にするように線材製造条件を制御することが重要である。
Next, the manufacturing method of the wire which concerns on this embodiment is demonstrated.
In order to obtain the high-strength duplex stainless steel wire according to the present embodiment at low cost, it is important to control the wire production conditions so that the α and γ crystal grain sizes are made fine.
まず、線材圧延用のビレット加熱条件について説明する。
上記化学成分を有するビレットと加熱する際、加熱温度が１０００℃未満では線材圧延時の割れが生じてしまう。一方、加熱温度が１２８０℃を超えると結晶粒が発達し、粗大結晶粒が残存し、鋼線の疲労特性を劣化させる。そのため、ビレットの加熱温度が１０００〜１２８０℃の範囲内とする。
また、加熱する際のビレットの在炉時間が３００分を超えても鋼線において粗大結晶粒が残存する。従って、ビレットを加熱する際は、加熱温度範囲を１０００〜１２８０℃の範囲内とするとともに、在炉時間が３００分以内となるように厳格に管理することが必要である。
なお、ビレット加熱時の条件の好ましい範囲は、加熱温度１０００〜１２８０℃で、在炉時間２００分以内である。
First, billet heating conditions for wire rod rolling will be described.
When heating with the billet which has the said chemical component, if the heating temperature is less than 1000 degreeC, the crack at the time of wire rod rolling will arise. On the other hand, when the heating temperature exceeds 1280 ° C., crystal grains develop, coarse crystal grains remain, and the fatigue characteristics of the steel wire are deteriorated. Therefore, the heating temperature of the billet is set within the range of 1000 to 1280 ° C.
Moreover, even if the billet furnace time during heating exceeds 300 minutes, coarse crystal grains remain in the steel wire. Therefore, when heating the billet, it is necessary to strictly control the heating temperature range to be in the range of 1000 to 1280 ° C and to keep the in-furnace time within 300 minutes.
In addition, the preferable range of the conditions at the time of billet heating is 1000-1280 degreeC of heating temperature, and is in-furnace time within 200 minutes.
次に、加熱後のビレットを熱間線材圧延で９９.０％以上の減面率で熱間加工する。
熱間線材圧延での減面率の合計が９９％未満になると材料の粒径の均一化が不足し、疲労特性が劣位になる。そのため、熱間線材圧延での減面率を９９％以上とし、更に、好ましくは９９．５〜９９．９９％とする。
Next, the billet after heating is hot-worked with a reduction in area of 99.0% or more by hot wire rolling.
If the total area reduction in hot wire rolling is less than 99%, the particle size of the material is insufficiently uniform, and the fatigue characteristics become inferior. Therefore, the area reduction rate in hot wire rolling is 99% or more, more preferably 99.5 to 99.99%.
また、線材の結晶粒径を抑制するには、熱間線材圧延後に水冷、もしくは溶体化処理として、短時間の連続したインライン熱処理後に水冷することが好ましい。この時、熱間線材圧延直後、または、インライン熱処理直後に水冷しないと炭窒化物が生成してしまうため、鋼線の疲労特性が劣化し易い。
また、熱処理温度９５０℃未満のインライン熱処理でも炭窒化物が生成し、鋼線の疲労特性が劣化し易い。一方、１１５０℃超や６００ｓを超えた条件でインライン熱処理すると、結晶粒径が粗大化する。また、熱間線材圧延後にオフライン熱処理を施す場合も同様に結晶粒径が粗大化する。そのため、溶体化処理としてインライン処理と行う場合、熱処理条件を９５０〜１１５０℃、６００ｓ以下とする。なお、好ましいインライン熱処理条件の範囲は、１０００〜１１００℃、３００ｓ以下である。
In order to suppress the crystal grain size of the wire, it is preferable to perform water cooling after hot wire rolling, or water cooling after continuous in-line heat treatment as a solution treatment. At this time, if it is not water-cooled immediately after hot wire rolling or after in-line heat treatment, carbonitrides are generated, so the fatigue characteristics of the steel wire are likely to deteriorate.
In addition, carbonitrides are generated even by in-line heat treatment at a heat treatment temperature of less than 950 ° C., and the fatigue characteristics of the steel wire are likely to deteriorate. On the other hand, when the in-line heat treatment is performed under conditions exceeding 1150 ° C. or exceeding 600 s, the crystal grain size becomes coarse. Similarly, when the off-line heat treatment is performed after hot wire rolling, the crystal grain size becomes coarse. Therefore, when performing an in-line process as a solution treatment, heat processing conditions shall be 950-1150 degreeC and 600 s or less. In addition, the range of preferable in-line heat processing conditions is 1000-1100 degreeC and 300 s or less.
次に、本実施形態に係る線材を用いた製造した高強度複相ステンレス鋼線について説明する。
本実施形態に係る鋼線は、引張強さが１６００〜２３００ＭＰａで、金属組織が、フェライト相、オーステナイト相及び加工誘起マルテンサイト相から構成される複相組織を有し、フェライト相率が２０〜７０ｖｏｌ.％、加工誘起マルテンサイト相率が１〜４０%、残部金属組織がオーステナイト相及び不可避的析出相からなり、複相組織の鋼線の横断面方向の平均粒径が５μｍ以下である。
以下、各構成要件について説明する。
Next, the manufactured high-strength duplex stainless steel wire using the wire according to this embodiment will be described.
The steel wire according to the present embodiment has a tensile strength of 1600 to 2300 MPa, a metal structure having a multiphase structure composed of a ferrite phase, an austenite phase, and a work-induced martensite phase, and a ferrite phase ratio of 20 to 70 vol.%, The processing induced martensite phase ratio is 1 to 40%, the remaining metal structure is composed of an austenite phase and an inevitable precipitation phase, and the average particle size in the cross-sectional direction of the steel wire having a multiphase structure is 5 μm or less.
Hereinafter, each component will be described.
鋼線の引張強さは１６００〜２３００ＭＰａである。引張強さについて、１６００ＭＰａ未満では、高強度ばね製品として必要な強度を満足せず、価値が格段に低下する。一方、引張強さが２３００ＭＰａを超えると、鋼線のねじり加工性及び疲労特性が安定せずに劣る。そのため、上限を２３００ＭＰａにする。鋼線の引張強さの好ましい範囲は、１７００以上、２０００ＭＰａ未満である。
なお、引張強さの測定方法は、圧延方向と平行方向にＪＩＳ１３Ｂ引張試験片を用いてＪＩＳ Ｚ ２２４１に準拠した引張試験により測定することができる。Ｎ数は３以上として平均値をとることとしてよい。
The tensile strength of the steel wire is 1600-2300 MPa. When the tensile strength is less than 1600 MPa, the strength required as a high-strength spring product is not satisfied, and the value is significantly reduced. On the other hand, if the tensile strength exceeds 2300 MPa, the twistability and fatigue characteristics of the steel wire are not stable and are inferior. Therefore, the upper limit is set to 2300 MPa. A preferable range of the tensile strength of the steel wire is 1700 or more and less than 2000 MPa.
In addition, the measuring method of tensile strength can be measured by the tensile test based on JISZ2241 using a JIS13B tensile test piece in a direction parallel to a rolling direction. The N number may be 3 or more and an average value may be taken.
鋼線の金属組織は、フェライト相、オーステナイト相及び加工誘起マルテンサイト相から構成される複相組織である。
加工誘起マルテンサイト量について、１vol.％未満では、強度を得られないため、加工誘起マルテンサイト相率は１vol.％以上とする。一方、４０vol.％を超えると靭性が劣化し、疲労特性に劣る。そのため、加工誘起マルテンサイト相率の上限を４０vol.％に限定する。加工誘起マルテンサイト相率の好ましい範囲は、１〜３５vol.％以下である。
The metal structure of the steel wire is a multiphase structure composed of a ferrite phase, an austenite phase, and a work-induced martensite phase.
Regarding the amount of work-induced martensite, if less than 1 vol.%, Strength cannot be obtained, so the work-induced martensite phase ratio is 1 vol.% Or more. On the other hand, if it exceeds 40 vol.%, The toughness deteriorates and the fatigue properties are inferior. Therefore, the upper limit of the processing induced martensite phase ratio is limited to 40 vol.%. A preferable range of the processing-induced martensite phase ratio is 1 to 35 vol.% Or less.
鋼線のフェライト量について、２０vol.％未満では、粒径の粗大化のため靭性及び疲労特性を劣化させるため、フェライト相率は２０vol.％以上とする。一方、フェライト相率が７０％を超えると強度及び熱間加工性を劣化させる。そのため、フェライト相率の上限を５０vol.％に限定する。フェライト相率の好ましい範囲は、２０〜５０vol.％以下である。 If the amount of ferrite in the steel wire is less than 20 vol.%, The toughness and fatigue characteristics are deteriorated due to the coarsening of the particle size, so the ferrite phase ratio is set to 20 vol.% Or more. On the other hand, if the ferrite phase ratio exceeds 70%, the strength and hot workability deteriorate. Therefore, the upper limit of the ferrite phase ratio is limited to 50 vol.%. A preferable range of the ferrite phase ratio is 20 to 50 vol.% Or less.
オーステナイト相の一部は、冷間加工によって、加工誘起マルテンサイト相へ変態することが望ましい。靭性を高水準に保ちながら強度を増加させる働きおよび、衝撃吸収能が期待できるからである。フェライト相及び加工誘起マルテンサイト相以外の残部金属組織の大部分がオーステナイト相ならびに不可避的析出相である。この理由は、ステンレス鋼線中には添加元素の組み合わせによっては炭化物、硫化物及び窒化物などの析出物が析出したり、脱酸時に生成した酸化物が不可避的に残存したりする場合があるためである。 It is desirable that a part of the austenite phase is transformed into a work-induced martensite phase by cold working. This is because the work to increase the strength while maintaining the toughness at a high level and the shock absorbing ability can be expected. Most of the remaining metal structure other than the ferrite phase and the work-induced martensite phase is the austenite phase and the inevitable precipitation phase. This is because, depending on the combination of additive elements, precipitates such as carbides, sulfides and nitrides may be deposited in the stainless steel wire, or oxides generated during deoxidation may inevitably remain. Because.
なお、フェライト相および加工誘起マルテンサイト相は、強磁性を有し、一方、オーステナイト相の常磁性であるので、相率の測定には、電磁気的測定方法を用い、フェライト相および加工誘起マルテンサイト相を体積％で求めることができる。不可避的析出物相の量は無視できるので、オーステナイト相量は、１００％からもしくはフェライト相または加工誘起マルテンサイト相の体積％を引いた値となる。 The ferrite phase and the work-induced martensite phase have ferromagnetism, while the austenite phase is paramagnetic. Therefore, the phase ratio is measured using an electromagnetic measurement method. The phase can be determined in volume%. Since the amount of inevitable precipitate phase is negligible, the amount of austenite phase is 100% or a value obtained by subtracting the volume% of the ferrite phase or the work-induced martensite phase.
また、複相組織の鋼線の横断面方向の平均粒径は５μｍ以下とする。
鋼線のα、γ、α’平均粒径（複相組織の平均粒径）において、粒径の微細化は疲労特性の向上に寄与する。つまり、α、γ、α’平均粒径が５μm以下の場合、疲労特性は良好になる。α、γ、α’平均粒径が５μｍを超えると疲労特性の劣化に加え、強度も劣位となる。そのため、α、γ、α’平均粒径を５μｍ以下に限定する。α、γ、α’平均粒径の好ましい範囲は２μｍ以下とする。
Moreover, the average particle diameter of the cross-sectional direction of the steel wire of a multiphase structure shall be 5 micrometers or less.
In the α, γ, α ′ average particle diameter (average particle diameter of the multiphase structure) of the steel wire, refinement of the particle diameter contributes to improvement of fatigue characteristics. That is, when the α, γ, α ′ average particle diameter is 5 μm or less, the fatigue characteristics are good. When the average particle size of α, γ, α ′ exceeds 5 μm, the fatigue properties are deteriorated and the strength is inferior. Therefore, the α, γ, α ′ average particle diameter is limited to 5 μm or less. The preferable range of α, γ, α ′ average particle diameter is 2 μm or less.
なお、鋼線の粒径の測定方法は、鋼線の横断面をFE-SEMで観察し、繊維方向に直角となる直線Ｌ（μｍ）を引き、その直線に存在した粒(α、α’もしくはγ)の数Ｎから下記（Ｆ）式を用いて算出した。
平均粒径（μm）＝Ｌ／Ｎ ・・・ （Ｆ）
The steel wire grain size is measured by observing the cross-section of the steel wire with FE-SEM, drawing a straight line L (μm) perpendicular to the fiber direction, and the grains existing on the straight line (α, α ′ Alternatively, it was calculated from the number N of γ) using the following formula (F).
Average particle diameter (μm) = L / N (F)
以下に本発明の実施例について説明するが、本発明は、以下の実施例で用いた条件に限定されるものではない。
表１、表２に実施例の鋼の化学組成、Ｍｄ３０値を示す。なお、表中の下線は本発明範囲から外れているものと示す。
Examples of the present invention will be described below, but the present invention is not limited to the conditions used in the following examples.
Tables 1 and 2 show the chemical compositions and Md30 values of the steels of the examples. The underline in the table indicates that it is out of the scope of the present invention.
これらの化学組成の鋼は、ステンレス鋼の安価溶製プロセスであるＡＯＤ溶製を想定し、１００ｋｇの真空溶解炉にて溶解し、φ１８０ｍｍの鋳片に鋳造した。そしてその鋳片を１１００℃で２００分の加熱後、φ５．５ｍｍまで熱間の線材圧延（減面率：９９．９％）を行い、１０５０℃で熱間圧延を終了した。その直後に水冷、または熱間圧延終了から連続して、溶体化処理として１０５０℃で３分のインライン熱処理を実施して水冷し、酸洗を行い線材とした。
その後、φ４．０ｍｍまで冷間で伸線加工を施し、１０５０℃で３分の中間ストラウンド焼鈍を施し、引き続き２．０ｍｍまで冷間で伸線加工を施した。その後、大気にて４００℃で３０分の時効処理を行い、高強度ステンレス鋼線の製品とした。
The steels of these chemical compositions were melted in a 100 kg vacuum melting furnace and cast into a slab of φ180 mm assuming AOD melting, which is a low-cost melting process for stainless steel. The slab was heated at 1100 ° C. for 200 minutes, and then hot wire rod rolling (reduction rate: 99.9%) was performed up to φ5.5 mm, and the hot rolling was terminated at 1050 ° C. Immediately after that, continuously from the end of water-cooling or hot rolling, in-line heat treatment was performed at 1050 ° C. for 3 minutes as a solution treatment, water-cooled, and pickled to obtain a wire.
Thereafter, the wire was drawn cold to φ4.0 mm, subjected to intermediate stroke annealing at 1050 ° C. for 3 minutes, and then cold drawn to 2.0 mm. Thereafter, an aging treatment was performed in the atmosphere at 400 ° C. for 30 minutes to obtain a high-strength stainless steel wire product.
そして、線材製品のα相、γ相における平均粒径（α、γ粒径）、オーステナイト相率（γ分率）、引張強さ、ならびに鋼線製品の引張強さ、加工誘起マルテンサイト量（α’量），α量，α／γ／α’粒径（複相組織平均粒径）、疲労特性を評価した。
その評価結果を表４〜６に示す。オーステナイト相率（γ分率）については表１及び表２に示す。
And the average particle size (α, γ particle size), austenite phase rate (γ fraction), tensile strength, and tensile strength of steel wire products, the amount of work-induced martensite ( α ′ amount), α amount, α / γ / α ′ particle diameter (double-phase structure average particle diameter), and fatigue characteristics were evaluated.
The evaluation results are shown in Tables 4-6. The austenite phase ratio (γ fraction) is shown in Tables 1 and 2.
次に、α、γ粒径に及ぼすビレット加熱条件と熱間線材圧延での熱間加工率および、その後の均一化熱処理温度の影響を調査した。
表１及び表２に示す成分組成の鋼Ａ及び鋼Ｅのφ１８０ｍｍの鋳片を、表３に示すビレット加熱温度と保持時間（ビレット加熱時間）でビレットを加熱し、各線材圧延減面率で熱間線材圧延し、１０００℃で熱間圧延を終了した。その後、溶体化処理（均一化熱処理）として９００℃、１０００℃、１０５０℃、１１５０℃、１２００℃のいずれかの温度で３００ｓ保持した後に水冷し、酸洗を行い線材とした。
そして、得られた線材のα、γ粒径を測定した。その評価結果を表３に示す。粒径が5μｍ以下の場合を（◎），５〜１０μmの場合を(○)、１０μｍを超える場合を（×）として評価した。
Next, the effects of billet heating conditions, hot working rate in hot wire rolling, and subsequent homogenization heat treatment temperature on α and γ grain sizes were investigated.
The billet is heated at the billet heating temperature and holding time (billet heating time) shown in Table 3 for the steel A and steel E slabs having the component compositions shown in Table 1 and Table 2, and each wire rod rolling reduction in area Hot wire rolling was performed, and the hot rolling was finished at 1000 ° C. Thereafter, as a solution treatment (homogenization heat treatment), the substrate was kept at a temperature of 900 ° C., 1000 ° C., 1050 ° C., 1150 ° C., or 1200 ° C. for 300 s, then cooled with water, pickled, and used as a wire.
And the alpha and gamma particle size of the obtained wire was measured. The evaluation results are shown in Table 3. The case where the particle size was 5 μm or less was evaluated as (◎), the case where the particle size was 5 to 10 μm (◯), and the case where the particle size exceeded 10 μm was evaluated as (×).
鋼線の引張強さは、ＪＩＳ Ｚ ２２４１の引張試験での引張強さと破断絞りにて評価した。
表４〜６に示すとおり、本発明例の鋼線の製品では、全て１６００〜２１００ＭＰａあり、強度特性に優れていた。
The tensile strength of the steel wire was evaluated by the tensile strength in the tensile test of JIS Z 2241 and the drawing at break.
As shown in Tables 4 to 6, all the steel wire products of the examples of the present invention had 1600 to 2100 MPa and were excellent in strength characteristics.
鋼線のα’量とα（γ）量は、「製品」と「製品を１０５０℃×３分の熱処理した材料」を直流磁束計にて１００００ Ｏｅの磁場を付与した時の飽和磁化値を測定し、以下の（Ａ）〜（Ｅ）式にて求めた。
α’量（vol.％）=｛（σｓ−σ1050）／σｓ（ｂｃｃ）｝×１００ ・・・ （Ａ）
α 量（vol.％）=｛σ1050／σｓ（ｂｃｃ）｝×１００ ・・・ （Ｂ）
γ 量（vol.％）=１００−｛σ1050／σｓ（ｂｃｃ）×１００｝ ・・・ （Ｃ）
ここで、σｓ：製品の飽和磁化値（Ｔ），σ1050：製品を１０５０℃×３分の熱処理した材料の飽和磁化値（T），σs(ｂｃｃ)：γが１００％マルテンサイト（α’）変態した時の飽和磁化値（計算値）
σｓ（ｂｃｃ）=２．１４−０．０３０Ｃｒｅｑ ・・・ （Ｄ）
Creq=Cr+1.8Si+Mo+0.5Ni+0.9Mn+3.6(C+N)+1.25P+2.91S+1.85Al+1.07V・・（Ｅ）
表４〜６に示すとおり、本発明の線材の線品では、γ量は３０〜８０体積％であり、鋼線の製品では、α’量は１〜４０体積％であり、α量は２０〜７０体積％であった。
The amount of α ′ and α (γ) of the steel wire is the saturation magnetization value when the magnetic field of 10000 Oe is applied to the “product” and “material obtained by heat-treating the product at 1050 ° C. × 3 minutes” with a DC magnetometer. It measured and calculated | required with the following (A)-(E) type | formula.
α ′ amount (vol.%) = {(σ s −σ 1050 ) / σ s (bcc)} × 100 (A)
α amount (vol.%) = {σ 1050 / σ s (bcc)} × 100 (B)
γ amount (vol.%) = 100− {σ 1050 / σ s (bcc) × 100} (C)
Where σ s is the saturation magnetization value (T) of the product, σ 1050 is the saturation magnetization value (T) of the material obtained by heat-treating the product at 1050 ° C. for 3 minutes, σ s (bcc) is γ is 100% martensite ( α ') Saturation magnetization value when transformed (calculated value)
σ s (bcc) = 2.14−0.030Creq (D)
Creq = Cr + 1.8Si + Mo + 0.5Ni + 0.9Mn + 3.6 (C + N) + 1.25P + 2.91S + 1.85Al + 1.07V ・ ・ (E)
As shown in Tables 4 to 6, in the wire rod of the present invention, the γ amount is 30 to 80% by volume, and in the steel wire product, the α ′ amount is 1 to 40% by volume and the α amount is 20%. It was -70 volume%.
鋼線の疲労特性は、中村式の回転曲げ疲労試験にて、回転曲げ応力５００および６００Ｎ／ｍｍ２を負荷して１０5回の回転を負荷させて鋼線が破断するか否かで評価した。両応力とも破断しない場合を非常に良い（◎），５００Ｎ／ｍｍ２のみ破断しない場合を良い（○），いずれも破断した場合を悪い（×）として評価した。
表４〜６に示すとおり、本発明の範囲内であるＮｏ．１〜８、１５〜５６の鋼線の疲労特性は◎または○であり、疲労特性に優れていた。特に、回転曲げ応力６００Ｎ／ｍｍ２で破断しないことは、ピアノ線相当以上の耐疲労特性を有することを示すものであり、従来ステンレス鋼線では難しいとされていたピアノ線代替として使用できる可能性のあるものである。そのため、産業上非常に有効である。
The fatigue characteristics of the steel wire were evaluated by whether or not the steel wire was broken by applying a rotation bending stress of 500 and 600 N / mm 2 and applying 10 5 rotations in a Nakamura-type rotary bending fatigue test. The case where both the stresses were not broken was evaluated as very good (（), the case where only 500 N / mm 2 was not broken was good (（), and the case where both were broken was evaluated as bad (×).
As shown in Tables 4-6, No. which is within the scope of the present invention. The fatigue characteristics of the steel wires 1 to 8 and 15 to 56 were ◎ or ◯, and the fatigue characteristics were excellent. In particular, the fact that it does not break at a rotational bending stress of 600 N / mm 2 indicates that it has fatigue resistance equivalent to or higher than that of a piano wire, and can be used as a substitute for a piano wire that has been considered difficult with conventional stainless steel wires. There is something. Therefore, it is very effective in industry.
なお、本実施例において、線材と鋼線の粒径の測定方法は、線材および鋼線の横断面をFE-SEMで観察し、繊維方向に直角となる直線L（μｍ）を引き、その直線に存在した粒(αもしくは(α’+γ)もしくは(α＋α’+γ))の数Nから下記（Ｆ）式を用いて算出した。
平均粒径（μm）＝Ｌ／Ｎ ・・・ （Ｆ）
表４〜６に示すとおり、本発明の線材の線品では、粒径は１０μｍ以下であり、鋼線の製品の粒径は５μｍ以下であった。
In this example, the particle diameter of the wire rod and steel wire is measured by observing the cross section of the wire rod and steel wire with FE-SEM, and drawing a straight line L (μm) perpendicular to the fiber direction. Was calculated from the number N of grains (α or (α ′ + γ) or (α + α ′ + γ)) present in the following formula (F).
Average particle diameter (μm) = L / N (F)
As shown in Tables 4 to 6, in the wire rod of the wire rod of the present invention, the particle size was 10 μm or less, and the particle size of the steel wire product was 5 μm or less.
以上の各実施例から明らかなように、本発明により、強度，疲労特性に優れる廉価な低Ｎｉ・高Ｍｎ系の高強度ステンレス鋼線材、鋼線を安価に製造でき、複雑形状のばねに割れ無く、精度よく成形可能であり、耐久性に優れる高強度複雑形状の精密ばね製品を安価に提供することができ、産業上極めて有用である。 As is clear from the above examples, according to the present invention, an inexpensive low Ni / high Mn high strength stainless steel wire excellent in strength and fatigue characteristics can be produced at low cost, and cracked into a spring having a complicated shape. Therefore, it is possible to provide a high-precision, complex-shaped precision spring product that can be molded with high accuracy and has excellent durability, and is extremely useful in the industry.
Claims (8)
Ｃ ：０．２１％以下、
Ｓｉ：０．０５〜３．２％、
Ｍｎ：1％超〜１５％、
Ｎｉ：０．５％以上、５％未満、
Ｃｒ：１０〜２５％、
Ｍｏ:３．０％以下、
Ｃｕ：３．０％以下、
Ｎ ：０．０２〜０．３５％を含有し、残部Ｆｅおよび不可避的不純物からなり、
金属組織がフェライト相及びオーステナイト相を備え、前記オーステナイト相率が３０〜７７ｖｏｌ.％であり、下記（ａ）式で示される前記オーステナイト相中のＭｄ３０値が−１５〜４５であり、前記フェライト相、前記オーステナイト相において、線材の横断面方向の平均粒径が１０μｍ以下であることを特徴とするばね疲労特性に優れた高強度複相ステンレス鋼線材。
Ｍｄ３０＝５５１−４６２（Ｃ＋Ｎ）−９．２Ｓｉ−８．１Ｍｎ−２９（Ｎｉ＋Ｃｕ）−１３．７Ｃｒ―１８．５Ｍｏ ・・・・ （a）
但し、式中の元素記号は、当該元素の鋼中における含有質量％を意味する。 % By mass
C: 0.21% or less,
Si: 0.05-3.2%
Mn: more than 1% to 15%,
Ni: 0.5% or more, less than 5%,
Cr: 10 to 25%,
Mo: 3.0% or less,
Cu: 3.0% or less,
N: 0.02 to 0.35%, consisting of the balance Fe and inevitable impurities,
The metal structure comprises a ferrite phase and an austenite phase, the austenite phase ratio is 30 to 77 vol.%, The Md30 value in the austenite phase represented by the following formula (a) is -15 to 45, and the ferrite A high-strength dual-phase stainless steel wire excellent in spring fatigue characteristics, characterized in that, in the austenite phase, the average particle size in the cross-sectional direction of the wire is 10 μm or less.
Md30 = 551-462 (C + N) -9.2Si-8.1Mn-29 (Ni + Cu) -13.7Cr-18.5Mo (a)
However, the element symbol in a formula means the content mass% in the steel of the said element.
Ｍｏ：２．５％以下Mo: 2.5% or less
であることを特徴とする請求項１に記載のばね疲労特性に優れた高強度複相ステンレス鋼線材。The high-strength duplex stainless steel wire rod having excellent spring fatigue characteristics according to claim 1.
Ｃｏ：２．５％以下、
Ａｌ：０．００１〜２．０％以下、
Ｂ ：０．０１２％以下
の内、１種類以上を含有することを特徴とする請求項１または２に記載のばね疲労特性に優れた高強度複相ステンレス鋼線材。 In addition,
Co: 2.5% or less,
Al: 0.001 to 2.0% or less,
B: The high-strength dual-phase stainless steel wire rod having excellent spring fatigue characteristics according to claim 1 or 2 , characterized by containing one or more of 0.012% or less.
Ｗ :２．５％以下、
Ｓｎ：２．５％以下
の内、１種類以上を含有することを特徴とする請求項１〜３の何れか一項に記載のばね疲労特性に優れた高強度複相ステンレス鋼線材。 In addition,
W: 2.5% or less,
The high-strength duplex stainless steel wire rod excellent in spring fatigue characteristics according to any one of claims 1 to 3, characterized by containing one or more of Sn: 2.5% or less.
Ｔｉ：１．０％以下、
Ｖ ：２．５％以下、
Ｎｂ:２．５％以下、
Ｔａ：２．５％以下
の内、１種類以上を含有することを特徴とする請求項１〜４の何れか一項に記載のばね疲労特性に優れた高強度複相ステンレス鋼線材。 In addition,
Ti: 1.0% or less,
V: 2.5% or less,
Nb: 2.5% or less,
The high-strength duplex stainless steel wire rod having excellent spring fatigue characteristics according to any one of claims 1 to 4 , wherein Ta: 2.5% or less is contained.
Ｃａ：０．０１２％以下、
Ｍｇ：０．０１２％以下、
Ｚｒ：０．０１２％以下、
ＲＥＭ：０．０５％以下
の内、１種類以上を含有することを特徴とする請求項１〜５のいずれか一項に記載のばね疲労特性に優れた高強度複相ステンレス鋼線材。 In addition,
Ca: 0.012% or less,
Mg: 0.012% or less,
Zr: 0.012% or less,
REM: 0.05% or less, 1 type or more is contained, The high intensity | strength duplex stainless steel wire rod excellent in the spring fatigue characteristic as described in any one of Claims 1-5 characterized by the above-mentioned.
ビレットを１０００〜１２８０℃で３００分以内在炉させることで加熱し、前記加熱後の前記ビレットを熱間線材圧延で９９.０％以上の減面率で熱間加工した後、水冷、または、溶体化処理として９５０〜１１５０℃で６００ｓ以下のインライン熱処理を施して水冷することを特徴とするばね疲労特性に優れた高強度複相ステンレス鋼線材の製造方法。 It is a manufacturing method of the high intensity | strength duplex stainless steel wire as described in any one of Claims 1-6 ,
The billet is heated at 1000 to 1280 ° C. within 300 minutes, and the billet after the heating is hot-worked with a reduction in area of 99.0% or more by hot wire rolling, water cooling, or A method for producing a high-strength duplex stainless steel wire rod excellent in spring fatigue characteristics, characterized by subjecting to an in-line heat treatment at 950 to 1150 ° C. for 600 s or less as a solution treatment and water cooling.
引張強さが１６００〜２３００ＭＰａで、
金属組織が、フェライト相、オーステナイト相及び加工誘起マルテンサイト相から構成される複相組織を有し、前記フェライト相率が２０〜７０ｖｏｌ.％、前記加工誘起マルテンサイト相率が１〜４０ｖｏｌ.％、残部金属組織が前記オーステナイト相及び不可避的析出相からなり、
前記複相組織の鋼線の横断面方向の平均粒径が５μｍ以下であることを特徴とするばね疲労特性に優れた高強度複相ステンレス鋼線。 Having the chemical component according to any one of claims 1 to 6 ,
Tensile strength is 1600-2300 MPa,
The metal structure has a multiphase structure composed of a ferrite phase, an austenite phase and a work-induced martensite phase, the ferrite phase ratio is 20 to 70 vol.%, And the work-induced martensite phase ratio is 1 to 40 vol.%. The balance metal structure consists of the austenite phase and the inevitable precipitation phase,
A high-strength duplex stainless steel wire excellent in spring fatigue characteristics, characterized in that the average grain size in the cross-sectional direction of the steel wire having a multiphase structure is 5 μm or less.
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