JP2661875B2 - Superplastic duplex stainless steel with low deformation resistance and excellent elongation properties - Google Patents
Superplastic duplex stainless steel with low deformation resistance and excellent elongation propertiesInfo
- Publication number
- JP2661875B2 JP2661875B2 JP6152270A JP15227094A JP2661875B2 JP 2661875 B2 JP2661875 B2 JP 2661875B2 JP 6152270 A JP6152270 A JP 6152270A JP 15227094 A JP15227094 A JP 15227094A JP 2661875 B2 JP2661875 B2 JP 2661875B2
- Authority
- JP
- Japan
- Prior art keywords
- superplastic
- stainless steel
- duplex stainless
- less
- phase
- 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 - Fee Related
Links
- 229910001039 duplex stainless steel Inorganic materials 0.000 title claims description 35
- 229910000831 Steel Inorganic materials 0.000 claims description 8
- 239000000203 mixture Substances 0.000 claims description 8
- 239000010959 steel Substances 0.000 claims description 8
- 229910052804 chromium Inorganic materials 0.000 claims description 6
- 229910052750 molybdenum Inorganic materials 0.000 claims description 6
- 229910052759 nickel Inorganic materials 0.000 claims description 6
- 229910052748 manganese Inorganic materials 0.000 claims description 5
- 229910052757 nitrogen Inorganic materials 0.000 claims description 5
- 229910052710 silicon Inorganic materials 0.000 claims description 5
- 229910052799 carbon Inorganic materials 0.000 claims description 3
- 239000012535 impurity Substances 0.000 claims description 3
- 229910052802 copper Inorganic materials 0.000 claims description 2
- 230000001105 regulatory effect Effects 0.000 claims 1
- 239000000463 material Substances 0.000 description 30
- 230000000694 effects Effects 0.000 description 23
- 230000007797 corrosion Effects 0.000 description 17
- 238000005260 corrosion Methods 0.000 description 17
- 230000003647 oxidation Effects 0.000 description 15
- 238000007254 oxidation reaction Methods 0.000 description 15
- 238000001556 precipitation Methods 0.000 description 11
- 229910052761 rare earth metal Inorganic materials 0.000 description 9
- 229910001220 stainless steel Inorganic materials 0.000 description 9
- 238000000034 method Methods 0.000 description 6
- 230000001747 exhibiting effect Effects 0.000 description 5
- 238000002474 experimental method Methods 0.000 description 5
- 230000006872 improvement Effects 0.000 description 5
- 238000000465 moulding Methods 0.000 description 5
- 239000002244 precipitate Substances 0.000 description 5
- 239000010935 stainless steel Substances 0.000 description 5
- 238000012545 processing Methods 0.000 description 4
- 230000035945 sensitivity Effects 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 229910001566 austenite Inorganic materials 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- 239000011159 matrix material Substances 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- 238000009864 tensile test Methods 0.000 description 3
- 229910000859 α-Fe Inorganic materials 0.000 description 3
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 238000005097 cold rolling Methods 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 229910000765 intermetallic Inorganic materials 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000010791 quenching Methods 0.000 description 2
- 230000000171 quenching effect Effects 0.000 description 2
- 229910052684 Cerium Inorganic materials 0.000 description 1
- 229910001122 Mischmetal Inorganic materials 0.000 description 1
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- 229910001069 Ti alloy Inorganic materials 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- 238000000071 blow moulding Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000005304 joining Methods 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000013011 mating Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 239000013535 sea water Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
Landscapes
- Heat Treatment Of Steel (AREA)
Description
【０００１】[0001]
【産業上の利用分野】この発明は、既知の超塑性２相ス
テンレス鋼に比べ、比較的低温度領域での成形加工であ
っても変形抵抗が小さくかつ伸び特性に優れる超塑性２
相ステンレス鋼についての提案である。BACKGROUND OF THE INVENTION The present invention relates to a superplastic stainless steel having a small deformation resistance and excellent elongation characteristics even in a forming process in a relatively low temperature range, as compared with a known superplastic duplex stainless steel.
It is a proposal for duplex stainless steel.
【０００２】[0002]
【従来の技術】従来、超塑性を発現するステンレス鋼と
しては、SUS 329J4Lなどに代表される、耐孔食２相ステ
ンレス鋼が良く知られている。本来、海水中などの使用
環境下における耐食性向上を意図して設計された，この
２相ステンレス鋼は、オーステナイトおよびフェライト
の２相組織からなり、これら２相が互いに粒成長を抑制
する作用を及ぼし合うことで、高温変形中に微細再結晶
粒を維持し、このことによって、良好な超塑性特性を発
現するものと考えられている。2. Description of the Related Art Conventionally, as a stainless steel exhibiting superplasticity, a pitting resistant duplex stainless steel represented by SUS 329J4L or the like is well known. Originally designed to improve the corrosion resistance in a service environment such as seawater, this duplex stainless steel has a two-phase structure of austenite and ferrite, and these two phases have an effect of suppressing grain growth with each other. It is believed that the mating maintains fine recrystallized grains during high temperature deformation, thereby exhibiting good superplastic properties.
【０００３】このSUS 329J4L系２相ステンレス鋼を、超
塑性が要求される用途、例えば、流し台やゴルフクラブ
ヘッドのような、複雑形状を有する一体成形加工品など
に供する場合、1000℃以上の温度で成形 (超塑性成形)
することが必要である。なぜなら、これよりも低温で成
形すると、変形に際して硬質の金属間化合物であるσ相
が析出するからである。このσ相は、「粒の成長を抑え
るので超塑性性能を高める」という説と、「硬質である
ため変形抵抗を大きくして超塑性性能を劣化させる」と
いう説があるが、常温で材料中に存在すると、材料の靱
性を著しく劣化させることから、結局、最終的には材料
中から完全に消失させる必要がある。そのための手段と
して、σ相の析出温度域より高い温度で超塑性成形した
のち急冷する方法、あるいは、超塑性成形した後、材料
をσ相の析出温度域より高い温度に保持し、急冷する方
法がある。しかしながら、超塑性材料は、高温で極めて
やわらかいために、熱処理中に形状が変化し易く、実際
には成形後の熱処理は不可能である。したがって、２相
ステンレス鋼を超塑性材料として利用するには、σ相が
析出しない温度域での成形が必要となるのである。[0003] When this SUS 329J4L duplex stainless steel is used for applications requiring superplasticity, for example, as an integrally molded product having a complicated shape such as a sink or a golf club head, a temperature of 1000 ° C or more is required. Molding (superplastic forming)
It is necessary to. This is because, if the molding is performed at a lower temperature, a σ phase, which is a hard intermetallic compound, precipitates upon deformation. This σ phase has a theory that “it increases the superplastic performance because it suppresses the growth of grains” and a theory that “it is hard to increase the deformation resistance and degrade the superplastic performance”. In the case of, the toughness of the material is significantly degraded, so that it is necessary to eventually completely eliminate the material from the material. As a means for this, a method of superplastic forming at a temperature higher than the precipitation temperature range of the σ phase and then quenching, or a method of maintaining the material at a temperature higher than the precipitation temperature range of the σ phase after superplastic forming and quenching There is. However, since superplastic materials are very soft at high temperatures, their shapes tend to change during heat treatment, and heat treatment after forming is not actually possible. Therefore, in order to use the duplex stainless steel as a superplastic material, it is necessary to form in a temperature range in which the σ phase does not precipitate.
【０００４】一方、２相ステンレス鋼について、より低
い温度域，例えば 900℃程度において、超塑性が発現す
るものが求められている。というのは、低温で超塑性を
発現させることができれば、高温での成形加工条件が緩
和され、より安定した成形加工を実現できる上、その設
備設計を容易かつ安価に実施し得ることから、加工コス
トの削減や成形サイクルの短縮に役立つからである。On the other hand, there is a demand for a duplex stainless steel that exhibits superplasticity in a lower temperature range, for example, about 900 ° C. That is, if superplasticity can be developed at low temperatures, the forming conditions at high temperatures can be relaxed, and more stable forming can be realized, and the equipment design can be easily and inexpensively implemented. This is because it helps to reduce costs and shorten the molding cycle.
【０００５】[0005]
【発明が解決しようとする課題】ところで、従来の一般
的な２相ステンレス鋼は、主として耐食性の改善を目的
として開発されており、いわゆる超塑性の発現とその向
上を目的として設計されたものではない。従って、上述
した要請にも拘わらず、従来の２相ステンレス鋼は、依
然として低温で超塑性を発現させる技術が確立されてい
ないのが実情である。Incidentally, conventional general duplex stainless steels have been developed mainly for the purpose of improving corrosion resistance, and are not designed for the purpose of expressing so-called superplasticity and improving the same. Absent. Therefore, in spite of the above-mentioned demands, the fact is that the conventional duplex stainless steel has not yet established a technique for exhibiting superplasticity at low temperatures.
【０００６】そこで、この発明の主たる目的は、超塑性
特性をより一層向上させることにあり、そしてこの発明
の他の目的は、ステンレス鋼本来の特性である耐食性を
維持しつつ、従来に比べてより低い温度域で優れた超塑
性を発現させることができる超塑性２相ステンレス鋼を
提案することにある。Therefore, a main object of the present invention is to further improve the superplastic properties, and another object of the present invention is to maintain the corrosion resistance which is an inherent property of stainless steel, while maintaining the conventional properties. An object of the present invention is to propose a superplastic duplex stainless steel capable of exhibiting excellent superplasticity in a lower temperature range.
【０００７】[0007]
【課題を解決するための手段】さて、900 ℃程度の低い
温度域で優れた超塑性を発現させるためには、その低温
度域で、変形に必要な応力，すなわち流動応力が低く、
歪速度感受性指数，すなわちｍ値が高く、しかもσ相が
析出しない材料であることが必要である。なお、ｍ値と
は、下記式に示す関係にあるｍの数値のことをいう。 ｌｎδ＝ｍ×ｌｎε＋Ｃ （δ；応力、ε；歪み速度、Ｃ；定数） また、たとえ超塑性特性の向上を主目的としているとは
いえ、超塑性成形後の材料が適度な耐食性を示さなけれ
ばステンレス鋼としての特徴を失うことになるから、あ
る程度の耐食性を維持することも必要である。すなわ
ち、900 ℃程度の低い温度域で流動応力が低く、優れた
伸びを示し、かつ耐食性に優れた材料が求められてい
る。Means for Solving the Problems In order to develop excellent superplasticity in a low temperature range of about 900 ° C., the stress required for deformation, that is, the flow stress, is low in the low temperature range.
It is necessary that the material has a high strain rate sensitivity index, that is, an m value, and does not precipitate the σ phase. Note that the m value refers to a numerical value of m having a relationship represented by the following equation. lnδ = m × lnε + C (δ; stress, ε; strain rate, C; constant) Even if the main purpose is to improve superplastic properties, if the material after superplastic forming does not show appropriate corrosion resistance, Since the characteristics of stainless steel are lost, it is necessary to maintain a certain level of corrosion resistance. That is, there is a demand for a material having a low flow stress in a low temperature range of about 900 ° C., exhibiting excellent elongation, and having excellent corrosion resistance.
【０００８】そこで、発明者らは、これらの前提を踏ま
え、上記目的実現に向け種々の合金成分について鋭意検
討した。その結果、 900℃程度の低い温度域で優れた超
塑性特性を有し、σ相の析出がなく、しかも実用的な耐
食性を有する超塑性２相ステンレス鋼を開発した。Accordingly, the present inventors have made intensive studies on various alloy components to achieve the above-mentioned object based on these premise. As a result, a superplastic duplex stainless steel with excellent superplastic properties in a low temperature range of about 900 ° C, no precipitation of σ phase, and practical corrosion resistance was developed.
【０００９】すなわち、この発明は、 Ｃ：0.05wt％以下、 Si：1.5 wt％以下、Mn：3.
0 wt％以下、 Cr：17.0〜26.0wt％、Ni：3.0 〜10.0
wt％、 Mo：0.1 〜2.0 wt％、Ｎ：0.08〜0.20wt％、
Ｓ：0.002 wt％以下、Ｂ：0.0005〜0.01wt％を含み、残
部Feおよび不可避的不純物からなる変形抵抗が小さくか
つ伸び特性に優れる超塑性２相ステンレス鋼（第１発
明）。 上記に記載の発明における基本成分に加えて、さ
らに、Cuを 0.1〜2.0 wt％含有させた組成からなる変形
抵抗が小さくかつ伸び特性に優れる超塑性２相ステンレ
ス鋼（第２発明）。 上記またはに記載の発明における基本成分に加
えて、さらに、REM （希土類元素）を0.005 〜0.05wt％
含有させた組成からなる変形抵抗が小さくかつ伸び特性
に優れる超塑性２相ステンレス鋼（第３発明）。 Cr、Ni、Mo、Si、Ｃ、Mn、CuおよびＮの含有量を、
下記式(1) で定義されるCreqと下記式(2) で定義される
Nieqとの差〔Creq−Nieq〕が、12.0〜17.0を満足する範
囲に規制する上記第１、第２または第３発明に記載の変
形抵抗が小さくかつ伸び特性に優れる超塑性２相ステン
レス鋼（第４発明）。 記 Creq＝Cr＋Mo＋0.5 Si ・・・(1) Nieq＝Ni＋30Ｃ＋0.5 Mn＋0.5 Cu＋20Ｎ ・・・(2)That is, according to the present invention, C: 0.05 wt% or less, Si: 1.5 wt% or less, Mn: 3.
0 wt% or less, Cr: 17.0 to 26.0 wt%, Ni: 3.0 to 10.0
wt%, Mo: 0.1 to 2.0 wt%, N: 0.08 to 0.20 wt%,
Superplastic duplex stainless steel containing 0.002 wt% or less of S and 0.0005 to 0.01 wt% of B and having a small deformation resistance composed of the balance of Fe and unavoidable impurities and having excellent elongation properties (first invention). Superplastic duplex stainless steel having a small deformation resistance and excellent elongation properties, which is composed of a composition containing 0.1 to 2.0 wt% of Cu in addition to the basic components in the above-described invention (second invention). In addition to the basic components in the above or the invention described above, REM (rare earth element) is further added in an amount of 0.005 to 0.05 wt%.
A superplastic duplex stainless steel having a low deformation resistance and excellent elongation characteristics, which is made of a composition contained therein (third invention). The contents of Cr, Ni, Mo, Si, C, Mn, Cu and N are
Creq defined by the following equation (1) and defined by the following equation (2)
The difference between the Ni eq [Cr eq -Ni eq] is the first to regulate the range satisfying the 12.0 to 17.0, superplastic 2 phase excellent in deformation resistance is small and elongation properties described in the second or third invention Stainless steel (the fourth invention). Note Cr eq = Cr + Mo + 0.5 Si (1) Ni eq = Ni + 30C + 0.5 Mn + 0.5 Cu + 20N (2)
【００１０】[0010]
【作用】以下、この発明に従う２相ステンレス鋼におけ
る、各合金組成の含有量を前記の範囲に限定した理由に
ついて説明する。 Ｃ：0.05wt％以下 Ｃは、その含有量が0.05wt％を超えると、粒界腐食感受
性が増大し、耐孔食性が劣化するとともに、炭化物の析
出により熱間加工性が低下する。しかも、超塑性材料と
してみても、Ｃが0.05wt％を超えると冷間圧延に際して
硬化をきたすため、その後の加工などにおける取扱いを
困難にする。従って、Ｃは、0.05wt％を上限とする。The reason why the content of each alloy composition in the duplex stainless steel according to the present invention is limited to the above range will be described below. C: 0.05 wt% or less If C content exceeds 0.05 wt%, intergranular corrosion susceptibility increases, pitting corrosion resistance deteriorates, and hot workability decreases due to precipitation of carbides. Moreover, even if it is considered as a superplastic material, if C exceeds 0.05% by weight, hardening occurs during cold rolling, which makes handling in subsequent processing and the like difficult. Therefore, the upper limit of C is 0.05 wt%.
【００１１】Si：1.5 wt％以下 Siは、金属間化合物であるσ相の構成元素であるため、
このSi量が増えるにしたがってσ相が析出する速度が速
くなり、析出温度範囲の上限温度の上昇が見られる。そ
こで、 900℃前後でもσ相が析出しないようにするため
に、このSiは、1.5 wt％以下とする必要がある。Si: 1.5 wt% or less Since Si is a constituent element of the σ phase which is an intermetallic compound,
As the amount of Si increases, the rate at which the σ phase precipitates increases, and the upper limit temperature of the precipitation temperature range increases. Therefore, in order to prevent the σ phase from being precipitated even at around 900 ° C., this Si needs to be 1.5 wt% or less.
【００１２】Mn：3.0 wt％以下 Mnは、溶解，精錬時に脱酸元素として作用すると共に、
Ｓと化合して硫黄化物を生成し、熱間脆性の発生を防止
するのに有効な元素であるが、3.0 wt％を超えると耐酸
化性が劣化する。従って、このMnは、3.0 wt％以下とす
る必要がある。Mn: 3.0 wt% or less Mn acts as a deoxidizing element during melting and refining,
The element combines with S to form a sulfide and is effective in preventing the occurrence of hot brittleness. However, if it exceeds 3.0 wt%, the oxidation resistance deteriorates. Therefore, this Mn needs to be 3.0 wt% or less.
【００１３】Cr：17.0〜26.0wt％ Crは、フェライト形成元素であり、かつσ相構成元素で
もある。このCrの含有量が26wt％を超えると、σ相の析
出が顕著となり、σ相の析出を促進するSiなどの元素を
少なくしても 900℃前後でσ相の析出が生じる結果、熱
間加工性およびσ相形成温度域における超塑性が劣化す
るため、上限を26.0wt％とする。一方、Cr含有量が17.0
wt％未満では、下記Niと同様に、オーステナイト量が増
大するために、α相によるγ粒成長の抑制効果が消失
し、超塑性性能の劣化を招くと共に、鋼の耐酸化性が低
下し、超塑性成形における高温長時間保持による材料の
酸化が著しく、良好な伸びを得ることができないため、
下限は17.0wt％とする。Cr: 17.0 to 26.0 wt% Cr is a ferrite forming element and a sigma phase constituent element. If the Cr content exceeds 26 wt%, the precipitation of the σ phase becomes remarkable, and even if the elements such as Si that promote the precipitation of the σ phase are reduced, the precipitation of the σ phase occurs at around 900 ° C. Since the workability and the superplasticity in the σ phase forming temperature range deteriorate, the upper limit is set to 26.0 wt%. On the other hand, the Cr content is 17.0
If the content is less than wt%, the austenite content increases, as in the following Ni, so that the effect of suppressing the growth of γ grains by the α phase is lost, and the superplastic performance is deteriorated, and the oxidation resistance of the steel is reduced, Since the oxidation of the material due to high temperature and long time holding in superplastic forming is remarkable and good elongation cannot be obtained,
The lower limit is 17.0 wt%.
【００１４】Ni：3.0 〜10.0wt％ Niは、オーステナイト形成元素であり、3.0 wt％未満に
なると、他のフェライト形成元素やオーステナイト形成
元素によって調整しても、γ( オーステナイト) 相の比
率が30wt％以下となり、超塑性変形中にα( フェライ
ト）相の粒成長を抑制するという効果が低下し、超塑性
特性の劣化を招くため、下限を3.0 wt％とする。一方、
10wt％を超えると、逆にγ相の比率が高くなり、γ相の
粒成長速度が増大して材料の高温での流動応力の上昇を
招くため、上限を10.0wt％とする。Ni: 3.0 to 10.0 wt% Ni is an austenite-forming element. When the content of Ni is less than 3.0 wt%, the ratio of the γ (austenite) phase is 30 wt% even when adjusted by other ferrite-forming elements or austenite-forming elements. % Or less, the effect of suppressing the grain growth of the α (ferrite) phase during superplastic deformation is reduced, and the superplastic properties are degraded. Therefore, the lower limit is set to 3.0 wt%. on the other hand,
If it exceeds 10% by weight, on the contrary, the ratio of the γ-phase becomes high, and the grain growth rate of the γ-phase increases to cause an increase in the flow stress of the material at a high temperature, so the upper limit is made 10.0% by weight.
【００１５】Mo：0.1 〜2.0 wt％ Moは、２相ステンレス超塑性材料において極めて重要な
役割を担う元素である。なぜなら、Moは、加工後におけ
る耐孔食性や耐隙間腐食性などの耐食性の向上に寄与す
る元素であり、耐食性２相ステンレス鋼においては欠く
ことのできない重要な元素だからである。しかしなが
ら、２相ステンレス鋼の超塑性特性に関する発明者らの
実験によれば、このMoは、σ相の析出を促進する働きが
あり、流動応力（超塑性変形における変形抵抗）を著し
く上昇させることが判った。特に、この流動応力の上昇
は、900 ℃近傍の低温度域において著しく、また添加量
が2.0 wt％を超えると顕著になる。従って、Moは、上限
を2.0 wt％とする。一方で、このMoは、材料の高温での
耐酸化性を著しく向上させる働きがある。そのため、Mo
を添加しない材料では、流動応力は低いものの高温に長
時間さらされるために、超塑性伸びでは良好な結果が得
られない。この点、発明者らの実験によれば、Moを 0.1
wt％以上添加すると、超塑性伸びが著しく改善されるこ
とが判った。従って、Moは、下限を 0.1wt％とする。Mo: 0.1-2.0 wt% Mo is an element that plays a very important role in a duplex stainless steel superplastic material. This is because Mo is an element that contributes to the improvement of corrosion resistance such as pitting corrosion resistance and crevice corrosion resistance after processing, and is an important element that is indispensable in corrosion-resistant duplex stainless steel. However, according to the inventors' experiments on the superplastic properties of the duplex stainless steel, this Mo has a function of accelerating the precipitation of the σ phase and significantly increases the flow stress (deformation resistance in superplastic deformation). I understood. In particular, the increase in the flow stress is remarkable in a low temperature range around 900 ° C., and becomes remarkable when the added amount exceeds 2.0 wt%. Therefore, Mo has an upper limit of 2.0 wt%. On the other hand, Mo has a function of significantly improving the oxidation resistance of the material at high temperatures. Therefore, Mo
In a material without addition of, although the flow stress is low, good results cannot be obtained by superplastic elongation because the material is exposed to high temperature for a long time. In this regard, according to the experiments performed by the inventors, Mo was 0.1%.
It was found that the superplastic elongation was remarkably improved by adding at least wt%. Therefore, the lower limit of Mo is 0.1 wt%.
【００１６】Cu： 0.1〜2.0 wt％ 一般に、超塑性成形は、複雑な形状への対応、ならびに
金型費用の低減を図るため、通常の成形加工よりも加圧
力が低いガス圧力によるブロー成形を採用している。従
って、超塑性２相ステンレス鋼を実用化するためには、
その材料の流動応力を低くすることが必要である。とこ
ろが、この２相ステンレス鋼は、超塑性成形の温度を従
来の1000℃から 900℃に下げると、流動応力の増加が著
しい。従って、超塑性２相ステンレス鋼の実用化にとっ
ては、流動応力の低減が最も重要な課題であった。そこ
で、発明者らは、２相ステンレス鋼の超塑性特性に関す
る研究を行ったところ、Cuは、一般に耐食性、隙間腐食
性の改善に寄与する元素であるが、流動応力を小さくす
る効果もあることに気付いた。このCuは、2.0 wt％を超
えて含有すると、超塑性伸びの低下を招き、実用上好ま
しくない。従って、Cuは、 2.0wt％を上限とし、流動応
力改善の効果が現れ始める 0.1wt％を下限とする。好ま
しくは、流動応力の顕著な低減効果がみられる1.0 wt％
以上を含有することが望ましい。上述したようなCuの効
果により、超塑性２相ステンレス鋼はより実用的なもの
となった。なお、このCuによる流動応力低減の詳細な機
構については未だ明らかではないが、Cuが粒界に偏析し
て粒界滑りを容易にすることで、流動応力を小さくする
ものと考えている。Cu: 0.1 to 2.0 wt% In general, superplastic forming is performed by blow molding with a gas pressure that is lower than the normal forming process in order to cope with complicated shapes and reduce the cost of the mold. Has adopted. Therefore, in order to commercialize superplastic duplex stainless steel,
It is necessary to reduce the flow stress of the material. However, when the temperature of superplastic forming is lowered from 1000 ° C. to 900 ° C. in the conventional duplex stainless steel, the flow stress increases remarkably. Therefore, reduction of flow stress was the most important issue for practical use of superplastic duplex stainless steel. Therefore, the present inventors conducted research on the superplastic properties of duplex stainless steel.Cu is generally an element that contributes to the improvement of corrosion resistance and crevice corrosion, but it also has the effect of reducing flow stress. Noticed. If the content of Cu exceeds 2.0 wt%, the superplastic elongation is lowered, which is not preferable in practical use. Therefore, the upper limit of Cu is 2.0 wt%, and the lower limit is 0.1 wt%, at which the effect of improving the flow stress starts to appear. Preferably, 1.0 wt%, at which a remarkable effect of reducing flow stress is observed.
It is desirable to contain the above. The effect of Cu as described above has made superplastic duplex stainless steels more practical. Although the detailed mechanism of the reduction of the flow stress by Cu is not clear yet, it is considered that the flow stress is reduced by segregating Cu at the grain boundaries to facilitate grain boundary sliding.
【００１７】Ｎ：0.08〜0.20wt％ Ｎは、Ｃと同様にオーステナイト形成元素であり、その
ため優れた超塑性特性を得るためには、このＮの含有量
は、他のフェライト形成元素との兼ね合いのもとで組織
バランスを十分勘案して定める必要がある。なぜなら、
後述するように、超塑性特性の発現に必要な結晶粒の微
細化は、γ相とα相の量に最も大きく依存するからであ
る。具体的には、〔Creq−Nieq〕の値が12.0から17.0の
範囲におさまるようなＮ量が好ましい。また、このＮ
は、耐孔食性を向上させるという効果もある。この効果
を得るためには、Ｎの含有量は、少なくとも0.08wt％以
上とする必要がある。しかしながら、Ｎ含有量が0.20wt
％を超えると熱間加工性が極めて悪くなる。従って、こ
のＮは、0.08〜0.20wt％とする。N: 0.08 to 0.20 wt% N is an austenite-forming element like C. Therefore, in order to obtain excellent superplastic properties, the content of N must be balanced with other ferrite-forming elements. It is necessary to take into account the organizational balance under the rules. Because
This is because, as will be described later, the refinement of crystal grains required for the development of superplastic properties depends most on the amounts of the γ phase and the α phase. Specifically, the amount of N is preferably such that the value of [Cr eq -Ni eq ] falls within the range of 12.0 to 17.0. Also, this N
Has the effect of improving pitting resistance. To obtain this effect, the N content must be at least 0.08 wt% or more. However, N content is 0.20wt
%, The hot workability becomes extremely poor. Therefore, this N is set to 0.08 to 0.20 wt%.
【００１８】Ｓ：0.002 wt％以下 Ｓは、粒界に偏析して２相ステンレス鋼の熱間加工性を
著しく劣化させることが知られている。そのため、実用
上、0.002 wt％以下に抑えて、熱間加工性を確保するこ
とが好ましい。S: not more than 0.002 wt% S is known to segregate at the grain boundaries and significantly degrade the hot workability of the duplex stainless steel. For this reason, it is practically preferable to keep the workability at 0.002 wt% or less to ensure hot workability.
【００１９】Ｂ：0.0005〜0.01wt％ Ｂは、粒界に偏析して粒界を強化することが知られてい
るが、流動応力の上昇を引き起こすことから、従来、超
塑性の向上に不利とされていた。しかしながら、発明者
らの実験によれば、0.0005wt％以上を添加すれば、以外
にも極めて高い伸びが得られ、超塑性の向上に有効であ
ることが判った。すなわち、このＢは、この発明におい
て極めて重要な役割を担う元素であり、この作用効果
は、酸化の影響のないAr雰囲気中で顕著にみられた。具
体的には、0.0005wt％以上の添加で超塑性伸び向上の効
果が確認され、さらに好ましくは 0.005 wt ％以上が望
ましい添加量と言える。しかしながら、0.01wt％を超え
てＢを添加すると、粒界にＢ化合物が析出して流動応力
の急激な上昇を招き、超塑性伸び向上の効果が見られな
くなる。従って、このＢの含有量は0.0005〜0.01wt％の
範囲に限定した。B: 0.0005 to 0.01 wt% B is known to segregate at the grain boundaries to strengthen the grain boundaries. However, since B causes an increase in flow stress, it is conventionally disadvantageous for improving superplasticity. It had been. However, according to experiments by the inventors, it was found that if 0.0005 wt% or more was added, extremely high elongation could be obtained, and it was effective in improving superplasticity. That is, B is an element that plays an extremely important role in the present invention, and this effect was remarkably observed in an Ar atmosphere that was not affected by oxidation. Specifically, the effect of improving superplastic elongation is confirmed by adding 0.0005 wt% or more, and more preferably 0.005 wt% or more is a desirable addition amount. However, when B is added in an amount exceeding 0.01 wt%, a B compound precipitates at the grain boundaries, causing a rapid increase in flow stress, and the effect of improving superplastic elongation cannot be seen. Therefore, the content of B was limited to the range of 0.0005 to 0.01 wt%.
【００２０】REM ：0.005 〜0.05wt％ 先に述べたように、一般に、超塑性２相ステンレス鋼の
超塑性成形は、その加工温度が 900〜1000℃程度と極め
て高い。そのため、成形時間に長時間を要する場合に
は、材料そのものに、ある程度の耐酸化性が要求され
る。その理由は、耐酸化性がないと、材料の変形にとも
ない、材料内部にまで酸化が進行し、ボイドの発生、材
料の破断が生じてしまい、実用性が乏しくなるからであ
る。この点に関し発明者らは、超塑性２相ステンレス鋼
の耐酸化性の向上に寄与する元素として、REM （希土類
元素のうちから選ばれるいずれか１種またはミッシュメ
タルのような２種以上の混合物であり、特に La,Ceおよ
びＹが好適である。）に着目した。従来、このREM の添
加による耐酸化性の向上に関する研究は、数多く報告さ
れているが（例えば、日本金属学会会報 vol.18, p192,
1979 等が参照される）、主としてフェライト系の鉄鋼
材料に関するものであり、２相ステンレス鋼については
ほとんど例がない。なぜなら、REM の耐酸化性効果が一
般に酸化スケールの密着性を改善する点にあることか
ら、熱膨張差の大きいα相とγ相が共存する２相ステン
レス鋼では、繰り返し酸化などの試験によっては前記効
果が実質認められないためと考えられる。この点、発明
者らが行った超塑性伸びの実験では、材料が一定温度に
保持されて実施されるので、２相ステンレス鋼において
もREM の効果が顕著に現れ、その結果、材料の耐酸化性
が大幅に向上し、優れた超塑性伸びを示す材料が得られ
ることが判った。以上説明したように、REM は、超塑性
加工において、耐酸化性の向上に寄与する元素である
が、0.05wt％を超えて添加すると、表面疵の原因となっ
たり、非金属介在物となって鋼中に残留して耐食性劣化
の原因となる。そのため、0.05wt％を上限とし、耐酸化
性改善の効果が現れ始める0.005 wt％を下限とする。REM: 0.005 to 0.05 wt% As described above, generally, the superplastic forming of superplastic duplex stainless steel has an extremely high processing temperature of about 900 to 1000 ° C. Therefore, when a long molding time is required, the material itself is required to have a certain degree of oxidation resistance. The reason for this is that if the material does not have oxidation resistance, oxidation proceeds inside the material as the material is deformed, voids are generated, and the material is broken, resulting in poor practicality. In this regard, the inventors have proposed that REM (any one selected from rare earth elements or a mixture of two or more kinds such as misch metal) as an element contributing to the improvement of the oxidation resistance of superplastic duplex stainless steel. And La, Ce and Y are particularly suitable.) Conventionally, many studies on the improvement of oxidation resistance by the addition of REM have been reported (for example, Bulletin of the Japan Institute of Metals vol.18, p192,
1979 etc.), mainly concerning ferritic steel materials, and there are few examples of duplex stainless steels. The reason is that the oxidation resistance effect of REM is generally to improve the adhesion of the oxide scale.Therefore, in a duplex stainless steel in which an α phase and a γ phase with a large difference in thermal expansion coexist, depending on tests such as repeated oxidation, etc. It is considered that the effect was not substantially observed. In this regard, in the experiment of superplastic elongation performed by the inventors, since the material is maintained at a constant temperature, the effect of REM is remarkably exhibited even in the duplex stainless steel, and as a result, the oxidation resistance of the material is reduced. It was found that a material having significantly improved properties and excellent superplastic elongation was obtained. As explained above, REM is an element that contributes to the improvement of oxidation resistance in superplastic working. However, if it is added in excess of 0.05 wt%, it may cause surface flaws or become nonmetallic inclusions. And remains in the steel, causing deterioration of corrosion resistance. Therefore, the upper limit is 0.05 wt%, and the lower limit is 0.005 wt%, at which the effect of improving the oxidation resistance starts to appear.
【００２１】〔Creq−Nieq〕：12.0〜17.0 従来、２相ステンレス鋼の超塑性の発現機構に関する研
究報告は多く、中でも、合金元素の影響、加工状態の影
響、σ相析出の影響などについての研究報告が多い。発
明者らは、２相ステンレス鋼の超塑性変形において最も
重要な役割を果たしていると考えられる、α／γ粒界の
影響を調べるために、幅広いα／γ比の組成の２相ステ
ンレス鋼について実験を行った。その結果、α／γ比と
超塑性特性の一つである歪速度感受性指数（ｍ値）との
間に強い相関があることを見出した。すなわち、上記α
／γ比は〔Creq−Nieq〕で示すことができるが、この値
を好適範囲にすると、高いｍ値が得られ、それよりαが
多くても少なくても、ｍ値は減少する傾向にあることが
判った。さて、「Progress in Materials Science 」
(Vol.33(1989) p.169) によれば、微細化超塑性材の特
徴として、その構成する２相によるZener 効果により、
超塑性変形の途中において、互いに粒成長を抑制し合っ
て、微細再結晶粒の維持を通じ、粒界面積を減少させず
に、粒界すべりを活発化する点が挙げられる。そして、
異相の粒成長を抑制するには、２相の組織比率を50：50
にするのが望ましいことにも言及しているが、これは、
２相の強度レベルが同等か、またはそれに近いことが前
提となる。しかし、超塑性変形下のαおよびγ各相間で
は、γ相の強度が高くなっているため、変形抵抗の減少
を考慮したとき、硬質母相より軟質母相とすることの方
が有利となる。従って、αおよびγ相の比は、軟質のα
相を１：１よりも高くすることが、必要と言える。そこ
で、αおよびγ相の比の指標である、上記〔Creq−N
ieq〕を12.0〜17.0を満足する範囲に規制することとし
た。すなわち、〔Creq−Nieq〕を12.0以上とすることに
よって、母相を軟質化することができ、一方〔Creq−Ni
eq〕が17.0以下であれば、異相の粒成長抑制効果を阻害
することはない。[Cr eq -Ni eq ]: 12.0-17.0 Conventionally, there have been many research reports on the mechanism of superplasticity development of duplex stainless steels. Among them, the effects of alloying elements, the effects of working conditions, the effects of σ phase precipitation, etc. There are many research reports on In order to investigate the influence of α / γ grain boundaries, which are considered to play the most important role in the superplastic deformation of the duplex stainless steel, the present inventors have studied a duplex stainless steel having a composition with a wide α / γ ratio. An experiment was performed. As a result, they found that there is a strong correlation between the α / γ ratio and the strain rate sensitivity index (m value), which is one of the superplastic properties. That is, the above α
The / γ ratio can be represented by [Cr eq -Ni eq ], but when this value is in a suitable range, a high m value is obtained, and the m value tends to decrease with more or less α. It was found to be. By the way, "Progress in Materials Science"
According to (Vol.33 (1989) p.169), the feature of the miniaturized superplastic material is that the Zener effect of its two phases
In the course of superplastic deformation, grain growth is suppressed by each other, and grain boundary sliding is activated without reducing the grain boundary area by maintaining fine recrystallized grains. And
In order to suppress the hetero-phase grain growth, the structure ratio of the two phases should be 50:50.
But it is desirable to use
It is assumed that the intensity levels of the two phases are equal or close. However, between the α and γ phases under superplastic deformation, since the strength of the γ phase is high, it is more advantageous to use a soft matrix than a hard matrix when considering reduction in deformation resistance. . Thus, the ratio of the α and γ phases is
It may be necessary to make the phase higher than 1: 1. Therefore, the above [Cr eq −N
i eq ] is restricted to a range satisfying 12.0 to 17.0. That is, by setting [Cr eq -Ni eq ] to 12.0 or more, the matrix can be softened, while [Cr eq -Ni eq]
eq ] is 17.0 or less, there is no hindrance to the effect of inhibiting the heterogeneous grain growth.
【００２２】[0022]
【実施例】以下に、この発明の実施例を比較例と併せて
説明する。表１に示す成分組成からなる10kgの２相ステ
ンレス鋼を、大気雰囲気下で高周波炉にて誘導溶解した
後、10kgの金型に鋳造し、次いで1150〜1200℃の温度域
で熱間鍛造して10mmの厚さとし、その後、1000〜1200℃
の温度域で溶体化処理を施し、脱スケール後に圧下率84
％の冷間圧延を施し、板厚を1.6 mmに調整して試験片を
作製した。なお、試験片形状は、平行部長さが10mm、幅
５mmである。EXAMPLES Examples of the present invention will be described below together with comparative examples. 10 kg of duplex stainless steel having the composition shown in Table 1 was induction-melted in a high-frequency furnace in the air atmosphere, cast into a 10 kg mold, and then hot forged in a temperature range of 1150 to 1200 ° C. To a thickness of 10 mm, then 1000-1200 ° C
Solution treatment in the temperature range of
% Cold rolling was performed to adjust the sheet thickness to 1.6 mm to produce a test piece. The test piece had a parallel portion length of 10 mm and a width of 5 mm.
【００２３】このようにして得られた試験片は、超塑性
成形温度である900 ℃に加熱してから、この温度に約70
分間保持した後、引張試験に供し、超塑性特性を評価し
た。この引張試験には、通常のクロスヘッド速度が一定
の一軸引張試験ではなく、高温強度試験法の一つとして
行われているステップ・ストレイン・レイト法を採用し
た。これは、当初、極低速のクロスヘッド速度(0.005mm
/min) で引張を開始して、応力のピークを迎えた時点で
クロスヘッド速度を段階的に順次上昇させて行き、各ク
ロスヘッド速度での応力ピークを求め、この操作を20mm
／min まで続けることによって、変形抵抗（流動応力）
および歪速度感受性指数（ｍ値）などを比較的簡便に求
めることができる試験法である。The test piece thus obtained was heated to a superplastic forming temperature of 900 ° C., and then heated to about 70 ° C.
After holding for 10 minutes, it was subjected to a tensile test to evaluate superplastic properties. For this tensile test, a step strain rate method, which is performed as one of the high-temperature strength test methods, was adopted instead of a normal uniaxial tensile test in which the crosshead speed was constant. This was initially due to the extremely low crosshead speed (0.005mm
/ min), and at the time when the stress peaks, the crosshead speed is gradually increased, and the stress peak at each crosshead speed is determined.
/ Min, deformation resistance (flow stress)
And a strain rate sensitivity index (m value) can be determined relatively easily.
【００２４】なお、超塑性についての明確な定義はない
が、これまでのところ、一般には、伸びが 200％以上お
よび上記ｍ値が0.3 以上となるときに、超塑性を示すと
判断してよいとされている。この二つの指標以外に、実
際の超塑性加工において重要な要素として、変形抵抗
（流動応力）がある。従って、超塑性特性は、流動応
力、ｍ値および伸びの３指標をもって評価した。その結
果を表１に示す。表１に示す実施結果から明らかなよう
に、発明鋼は、流動応力が 900℃で20 MPa以下と小さ
く、ｍ値＞0.75と大きく、しかも、伸びは1000％以上と
大きく、上記３指標のいずれも良好な数値を示した。こ
れに対し、発明鋼の成分組成範囲から逸脱した比較鋼
は、超塑性特性の発現は認められるものの、流動応力，
ｍ値または伸びの少なくともいずれかの指標が悪く、そ
れ故に、発明鋼の方が優れた超塑性特性を示すことが明
らかとなった。Although there is no clear definition of superplasticity, so far, generally, it may be determined that superplasticity is exhibited when the elongation is 200% or more and the m value is 0.3 or more. It has been. In addition to these two indices, there is deformation resistance (flow stress) as an important factor in actual superplastic working. Therefore, the superplastic properties were evaluated using three indices of flow stress, m value and elongation. Table 1 shows the results. As is clear from the working results shown in Table 1, the invented steel has a low flow stress at 900 ° C. of 20 MPa or less, a large m-value> 0.75, and a large elongation of 1000% or more. Also showed good numerical values. On the other hand, the comparative steels deviating from the composition range of the invention steels exhibited superplastic properties, but the flow stress,
It has been clarified that at least one of the indices of the m-value and the elongation is poor, and therefore the inventive steel exhibits better superplastic properties.
【００２５】[0025]
【表１】 [Table 1]
【００２６】次に、流動応力または伸びに及ぼすＢ添加
の影響について試験した。その結果を図１，図２に示
す。これらの図に示す結果から明らかなように、伸び
は、Ｂ添加によって向上する傾向が見られ、一方で、流
動応力は、Ｂ添加量の増加に伴って増加することが確認
された。以上の結果から、伸びと流動応力、ｍ値のバラ
ンスを考慮すると、0.0005〜0.01wt％の範囲内であれ
ば、成形上の問題を起こすことなく、 900℃前後の低い
温度域での超塑性加工を実現し得る。Next, the effect of B addition on the flow stress or elongation was examined. The results are shown in FIGS. As is clear from the results shown in these figures, the elongation tended to be improved by the addition of B, while the flow stress was confirmed to increase as the amount of B added increased. From the above results, considering the balance between elongation, flow stress and m value, if it is in the range of 0.0005 to 0.01 wt%, there is no forming problem and superplasticity in low temperature range around 900 ° C. Processing can be realized.
【００２７】また、ｍ値に及ぼす〔Creq−Nieq〕の影響
についても試験した。その結果を図３に示す。この図に
示す結果から明らかなように、ｍ値は、〔Creq−Nieq〕
が12〜17の範囲で高くなり、その範囲で良好な超塑性特
性が得られることが判った。The effect of [Cr eq -Ni eq ] on the m value was also tested. The result is shown in FIG. As is clear from the results shown in this figure, the m value is [Cr eq -Ni eq ]
Was increased in the range of 12 to 17, and it was found that good superplastic properties were obtained in that range.
【００２８】[0028]
【発明の効果】以上説明したようにこの発明の超塑性２
相ステンレス鋼は、900 ℃前後でのσ相の析出がなく、
しかも流動応力が低く、高いｍ値を有する材料であるの
で、 900℃前後の低い温度域での超塑性加工を実現し得
る。しかも、この発明によれば、加工後の製品にはσ相
がないので、脆化、耐食性の劣化などの問題の生じない
極めて実用的な製品が得られる。従って、この発明は、
鉄基超塑性材料の適用範囲を一層拡大することに寄与
し、さらに、Ti合金などとの超塑性接合といった，従来
は成形温度の違いから不可能であった製造方法をも可能
とするものである。As described above, the superplasticity of the present invention 2
Duplex stainless steel has no precipitation of σ phase around 900 ° C.
In addition, since the material has a low flow stress and a high m value, superplastic working in a low temperature range of about 900 ° C. can be realized. Moreover, according to the present invention, since there is no σ phase in the processed product, an extremely practical product free from problems such as embrittlement and deterioration of corrosion resistance can be obtained. Therefore, the present invention
This contributes to further expanding the range of application of iron-based superplastic materials, and also enables manufacturing methods such as superplastic joining with Ti alloys, which were not possible due to differences in molding temperatures. is there.
【図面の簡単な説明】[Brief description of the drawings]
【図１】流動応力とＢ添加量との関係を示すグラフであ
る。FIG. 1 is a graph showing the relationship between flow stress and the amount of B added.
【図２】伸びとＢ添加量との関係を示すグラフである。FIG. 2 is a graph showing the relationship between elongation and the amount of B added.
【図３】歪速度感受性指数（ｍ値）と〔Creq−Nieq〕と
の関係を示すグラフである。FIG. 3 is a graph showing a relationship between a strain rate sensitivity index (m value) and [Cr eq −Ni eq ].
───────────────────────────────────────────────────── フロントページの続き (72)発明者 小出 信也 神奈川県川崎市川崎区小島町４番２号 日本冶金工業株式会社 研究開発本部 技術研究所内 (56)参考文献 特開 昭62−192235（ＪＰ，Ａ) ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Shinya Koide 4-2 Kojimacho, Kawasaki-ku, Kawasaki-shi, Kawasaki Pref. JP, A)
Claims (4)
下、 Mn：3.0 wt％以下、 Cr：17.0〜26.0wt％、 Ni：3.0 〜10.0wt％、 Mo：0.1 〜2.0 wt％、 Ｎ：0.08〜0.20wt％、 Ｓ：0.002 wt％以下、 Ｂ：0.0005〜0.01wt％を含み、残部Feおよび不可避的不
純物からなる変形抵抗が小さくかつ伸び特性に優れる超
塑性２相ステンレス鋼。C: 0.05 wt% or less, Si: 1.5 wt% or less, Mn: 3.0 wt% or less, Cr: 17.0 to 26.0 wt%, Ni: 3.0 to 10.0 wt%, Mo: 0.1 to 2.0 wt%, A superplastic duplex stainless steel containing N: 0.08 to 0.20 wt%, S: 0.002 wt% or less, B: 0.0005 to 0.01 wt%, and has a small deformation resistance composed of the balance of Fe and unavoidable impurities and has excellent elongation characteristics.
下、 Mn：3.0 wt％以下、 Cr：17.0〜26.0wt％、 Ni：3.0 〜10.0wt％、 Mo：0.1 〜2.0 wt％、 Ｎ：0.08〜0.20wt％、 Ｓ：0.002 wt％以下、 Ｂ：0.0005〜0.01wt％を含み、さらに、 Cu： 0.1〜2.0 wt％を含有し、残部Feおよび不可避的不
純物からなる変形抵抗が小さくかつ伸び特性に優れる超
塑性２相ステンレス鋼。2. C: 0.05 wt% or less, Si: 1.5 wt% or less, Mn: 3.0 wt% or less, Cr: 17.0 to 26.0 wt%, Ni: 3.0 to 10.0 wt%, Mo: 0.1 to 2.0 wt%, N: 0.08 to 0.20 wt%, S: 0.002 wt% or less, B: 0.0005 to 0.01 wt%, further contains Cu: 0.1 to 2.0 wt%, and low deformation resistance consisting of balance Fe and unavoidable impurities Superplastic duplex stainless steel with excellent elongation characteristics.
れ、 REMを0.005 〜0.05wt％含有する組成からなる、変
形抵抗が小さくかつ伸び特性に優れる超塑性２相ステン
レス鋼。3. A superplastic duplex stainless steel having low deformation resistance and excellent elongation characteristics, wherein each of the steels according to claim 1 or 2 has a composition containing 0.005 to 0.05% by weight of REM.
含有量を、下記式(1) で定義されるCreqと、下記式(2)
で定義されるNieqとの差〔Creq−Nieq〕が、12.0〜17.0
を満足するように規制することを特徴とする請求項１〜
３のいずれか１つに記載の変形抵抗が小さくかつ伸び特
性に優れる超塑性２相ステンレス鋼。 記 Creq＝Cr＋Mo＋0.5 Si ・・・(1) Nieq＝Ni＋30Ｃ＋0.5 Mn＋0.5 Cu＋20Ｎ ・・・(2)4. The content of Cr, Ni, Mo, Si, C, Mn, Cu and N is determined by the following equation: Cr eq defined by the following formula (1):
The difference from Ni eq defined in (Cr eq- Ni eq ) is 12.0 to 17.0
Claim 1 characterized by regulating so as to satisfy
3. A superplastic duplex stainless steel according to any one of the above items 3, which has low deformation resistance and excellent elongation properties. Note Cr eq = Cr + Mo + 0.5 Si (1) Ni eq = Ni + 30C + 0.5 Mn + 0.5 Cu + 20N (2)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6152270A JP2661875B2 (en) | 1994-07-04 | 1994-07-04 | Superplastic duplex stainless steel with low deformation resistance and excellent elongation properties |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP6152270A JP2661875B2 (en) | 1994-07-04 | 1994-07-04 | Superplastic duplex stainless steel with low deformation resistance and excellent elongation properties |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0813093A JPH0813093A (en) | 1996-01-16 |
| JP2661875B2 true JP2661875B2 (en) | 1997-10-08 |
Family
ID=15536832
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP6152270A Expired - Fee Related JP2661875B2 (en) | 1994-07-04 | 1994-07-04 | Superplastic duplex stainless steel with low deformation resistance and excellent elongation properties |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2661875B2 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5672315A (en) * | 1995-11-03 | 1997-09-30 | Nippon Yakin Kogyo Co., Ltd. | Superplastic dual-phase stainless steels having a small deformation resistance and excellent elongation properties |
| GB2306971B (en) * | 1995-11-08 | 1999-04-14 | Nippon Yakin Kogyo Co Ltd | Superplastic dual-phase stainless steels having a small deformation resistance and excellent elongation properties |
| JP4494245B2 (en) * | 2005-02-14 | 2010-06-30 | 日新製鋼株式会社 | Low Ni austenitic stainless steel with excellent weather resistance |
| WO2016031958A1 (en) * | 2014-08-28 | 2016-03-03 | 国立大学法人豊橋技術科学大学 | Metal material and processing/treatment method |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS62192235A (en) * | 1986-02-20 | 1987-08-22 | Nippon Yakin Kogyo Co Ltd | Direct production for two phase stainless steel thin strip having excellent superplasticity and surface property |
| JPH0814004B2 (en) * | 1987-12-28 | 1996-02-14 | 日新製鋼株式会社 | Method for producing high-ductility and high-strength dual-phase chrome stainless steel strip with excellent corrosion resistance |
| JP2952929B2 (en) * | 1990-02-02 | 1999-09-27 | 住友金属工業株式会社 | Duplex stainless steel and method for producing the same |
| JP2765392B2 (en) * | 1992-08-31 | 1998-06-11 | 住友金属工業株式会社 | Method for manufacturing hot-rolled duplex stainless steel strip |
| JPH06128691A (en) * | 1992-10-21 | 1994-05-10 | Sumitomo Metal Ind Ltd | Duplex stainless steel with good toughness and thick-walled steel pipe made of it |
-
1994
- 1994-07-04 JP JP6152270A patent/JP2661875B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0813093A (en) | 1996-01-16 |
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