JP3740999B2 - Hot-rolled steel strip of high-strength martensitic stainless steel - Google Patents
Hot-rolled steel strip of high-strength martensitic stainless steel Download PDFInfo
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Description
【０００１】
【発明の属する技術分野】
この発明は、熱間圧延鋼帯を巻き取ってコイル状としたマルテンサイト系ステンレス鋼帯及びその製造方法に関し、特に、コイルの中心部や外周部等コイルの各位置において均質で優れた強度特性が得られるもの及びその製造方法に関する。
【０００２】
【従来の技術】
石油、天然ガスの輸送用ラインパイプに用いられる鋼材には、使用環境に応じた耐食性と現地溶接性に優れていることが要求される。近年、耐食性の観点から、ステンレス鋼の使用が検討されるようになってきたが、既存のステンレス鋼はラインパイプ用として必ずしも十分な性能ではなく、新たな開発が望まれてきた。
【０００３】
例えば、０．２Ｃ−１３Ｃｒ系は溶接を必要としない油井管用であり、溶接割れ防止のため、高い予熱、後熱温度を必要とし、現地溶接性が重視されるラインパイプには適当でない。また、２２Ｃｒ等の２相ステンレス鋼は、予熱後熱処理は必要でないが、素材として高価で、大量の鋼材を必要とするパイプラインには使用し難い。
【０００４】
そこで、特開平６−１００９４３号公報、特開平４−２６８０１８号公報、特開平８−１００２６６号公報等により、Ｃ量を低下させ、溶接性を改善させた１３Ｃｒ系が提案され、ラインパイプへの適用拡大が検討されるようになってきた。
【０００５】
特に、最近、電縫溶接とレーザ溶接を組み合わせて用いるレーザ溶接電縫鋼管が実用化されたことにより、コイル状の１３Ｃｒ系ステンレス鋼帯をアンコイルし、多段の成形ロールにより、連続的にオープンパイプを成形した後、オープンパイプの相対する両エッジ部を溶接して製造する電縫鋼管への適用が増大しつつある。
【０００６】
１３Ｃｒステンレス鋼の適用においては、素材そのものの焼入れ性が高く、熱間圧延後の空冷によりマルテンサイト組織となるため、コイル状に巻き取った後、所望の材質特性とする熱処理を行った後、各種鋼管とされている。
【０００７】
【発明が解決しようとする課題】
しかしながら、上述した製造方法により電縫鋼管を製造した場合、しばしば目的とする強度が得られず、再度の熱処理を必要とする場合が生じていた。
【０００８】
再熱処理においては、数トンから数１０トンのコイル状の素材を均一に熱処理するため１０数時間から５０時間の長時間を要し、その負担は大きく試行錯誤も限られることより、適切な製造指針が要望されていた。
【０００９】
そこで、本発明では、熱間圧延し、コイル状に巻き取り、熱処理後において所望の強度が安定して得られる高強度マルテンサイト系ステンレス鋼帯およびその製造方法を提供することを目的とする。
【００１０】
【課題を解決するための手段】
本発明者らは、熱間圧延後、２相域加熱し、焼戻しを行った１３Ｃｒ系マルテンサイト系ステンレス鋼の熱延鋼帯を対象に、材質、特に強度に及ぼす成分組成、製造条件の影響について鋭意検討を行った。
【００１１】
その結果、コイル状とした素材の熱処理に必要な長時間加熱の場合、ＡｌＮが析出し、該ＡｌＮの析出により焼戻し軟化抵抗として有効Ｎ量が減少し、強度の低下することを見出した。本発明は以上の知見を基に更に検討を加えてなされたものであり、すなわち本発明は、
１．鋼組成が、質量％で、Ｃ：０．０２％以下、Ｓｉ：０．１〜０．３％、Ｍｎ：０．１〜０．３％、Ｃｒ：１１〜１５％、Ｎｉ：１〜７％、ｓｏｌ．Ａｌ：０．０６％以下、Ｎ：０．００８〜０．０３％、Ｓ：０．００２％以下、Ｔｉ：０．０７％以下、残部がＦｅおよび不可避的不純物からなり、かつ熱間圧延後の熱処理にて制御される鋼中の有効量Ｎ（Ｘ）が６０ｐｐｍ以上であることを特徴とする高強度マルテンサイト系ステンレス鋼の熱延鋼帯。
但し、有効量（Ｘ）＝ｔｏｔａｌＮ−ＮａｓＴｉＮ−ＮａｓＡｌＮ
【００１３】
２．質量％で、Ｎｂ：０．０１〜０．２％，Ｖ：０．０１〜０．２％の一種または二種を含有する１記載の高強度マルテンサイト系ステンレス鋼の熱延鋼帯。
【００１４】
３．質量％で、Ｃａ：０．００５％以下，Ｚｒ：０．００５％以下，Ｍｇ：０．００５％以下の一種または二種以上を含有する１又は２記載の高強度マルテンサイト系ステンレス鋼の熱延鋼帯。
【００１５】
４．質量％で、Ｃｕ：０．１〜３％を含有する１乃至３の何れか一つに記載の高強度マルテンサイト系ステンレス鋼の熱延鋼帯。
【００１６】
５．質量％で、Ｍｏ：０．３〜３％を含有する１乃至４の何れか一つに記載の高強度マルテンサイト系ステンレス鋼の熱延鋼帯。
【００１８】
６．１乃至５何れか一つに記載の高強度マルテンサイト系ステンレス鋼の熱延鋼帯を素材とするレーザ電縫鋼管。
【００２０】
７．熱間圧延後の鋼帯の２相域加熱および／または焼戻し時の昇温速度により、鋼中の有効Ｎ量の析出量を調整することを特徴とする１乃至６何れか一つに記載の高強度マルテンサイト系ステンレス鋼の熱延鋼帯の製造方法。
【００２１】
【発明の実施の形態】
本発明の成分限定理由について述べる。
【００２２】
Ｃ
Ｃは、マルテンサイト組織を得るため重要で、鋼中のＣｒなど炭化物生成元素と炭化物を形成し、強度を向上させるため添加する。一方、過剰に添加すると耐食性に有効なＣｒ量を減少させ、溶接熱影響部の硬さを上昇させ、溶接後熱処理が必要となるため０．０２％以下とする。
【００２３】
Ｓｉ
Ｓｉは脱酸剤として添加する。０．１％未満ではその効果がなく、一方、０．３％を超えるとその効果が飽和し、また、デルタフェライトが晶生し、相バランスを保つためＮｉ量の増加が必要となるため、０．１〜０．３％（０．１％以上、０．３％以下）とする。
【００２４】
Ｍｎ
Ｍｎは製鋼上、脱硫剤として添加する。０．１％未満では効果がなく、熱間加工性も低下する。一方、０．３％を超えて添加すると炭酸ガス下での耐食性が劣化するため、０．１〜０．３％とする。
【００２５】
Ｃｒ
Ｃｒは湿潤炭酸ガスを含む環境下での耐食性向上に有効なため添加する。１１％未満では効果がなく、一方、１５％を超えると他の成分元素を調整してもマルテンサイト組織が得られないため、１１〜１５％とする。
【００２６】
Ｎｉ
Ｎｉはオーステナイト相を形成し、マルテンサイト組織を得るため、Ｃｒ量に応じて適量添加する。１％未満では相安定に不十分であり、また溶接部の材質を損なう。一方、７％を超えるとその効果が飽和し、素材コストも上昇するため、１〜７％とする。
【００２７】
ｓｏｌ．Ａｌ
Ａｌは脱酸元素、および組織微細化のため添加する。ｓｏｌ．Ａｌが０．０６％を超えると、アルミナ系介在物および窒化物が増加し、製造性および靭性が低下するため、０．０６％以下とする。
【００２８】
Ｎ
Ｎは強度を確保し、強度の熱処理依存性を抑制するため０．００８％以上とする。一方、０．０３％を超えて過剰に添加すると、鋼中のＣｒと化合物を形成し、耐食性に有効なＣｒを減少させるため、０．００８〜０．０３％とする。
【００２９】
ＡｌＮ
ＡｌＮは、Ｃｒ ２ Ｎの析出量に影響を与える析出物であり、６０ｐｐｍ以上で過剰な場合、製品の最終強度が低下するため、その析出量を６０ｐｐｍ未満とすることが望ましい。ＡｌＮの析出量が多い場合、固溶Ｎが減少し、焼戻し時においてＣｒ ２ Ｎやその他炭窒化物、窒化物の析出量が減少し軟化抵抗が損なわれるためと思われるが詳細は不明である。
【００３０】
ＡｌＮの析出量は、熱間圧延後の熱処理で制御することが可能であるが、強度調整のための焼戻し時の昇温速度、特に４００℃以上で５０℃／ｈとすることで制御することが好ましい。
【００３１】
尚、ＡｌＮ析出量の測定は、鋼帯の製品領域の板厚中心で求めるものとする。
【００３２】
有効Ｎ量
有効Ｎは焼戻し熱処理において、固溶しあるいは、微細Ｃｒ ２ Ｎさらに通常の抽出分析法で計測されない微細析出物を形成し、軟化を防止する。本発明では、ＡＰＩＸ８０の強度、靭性特性を満足するように、６０ｐｐｍ以上とする。
【００３３】
尚、有効Ｎ量は、チェック分析により、鋼中のｔｏｔａｌＮ量を測定した値から、１０％臭素−メタノール法により抽出したＡｌ，ＴｉをＩＣＰを用いて定量したのち、ＡｌＮ、ＴｉＮとして存在するＮ量を算出し、有効Ｎ量（Ｘ）＝ｔｏｔａｌＮ−ＮａｓＴｉＮ−ＮａｓＡｌＮとして求めた。
【００３４】
本発明の基本成分組成および鋼中析出物に関する規定は以上のとおりであるが、更に所望する特性に応じて、以下の元素を一種または二種以上選択的に添加することが可能である。
【００３５】
Ｎｂ、Ｖ
Ｎｂ、Ｖは、いずれも鋼中のＣやＮと炭化物、窒化物、炭窒化物を形成し結晶粒微細化や析出強化により鋼の強度を向上させる。これらの元素を添加する場合は、０．０１％未満では効果が十分でなく、一方、０．２％を超えても炭窒化物を形成する炭素、窒素が不足して強化機能が飽和するので、それぞれ、０．０１〜０．２％とする。
【００３６】
Ｃａ，Ｚｒ，Ｍｇ
Ｃａ，Ｚｒ，Ｍｇは、鋼中のＡｌＮの析出を遅延させる傾向を有する。しかし、これらの元素は、０．００５％を超えると酸化物系介在物を形成し、靭性を劣化させるため、各々、添加量は０．００５％以下とする。
【００３７】
Ｃｕ
Ｃｕはオーステナイト相を安定化し、靭性も改善する。０．１％未満ではその効果が得られず、一方、３％を超える過剰な添加は靭性を低下させるので、０．１〜３％とする。
【００３８】
Ｍｏ
Ｍｏは耐食性を改善する。０．３％未満ではその効果が得られず、一方、３％を超えるとその効果が飽和し、強度が上昇し、冷間での塑性変形による加工が困難となるため、０．３〜３％とする。
【００３９】
Ｔｉ
Ｔｉは、鋼中のＣやＮと炭化物、窒化物、炭窒化物を形成し結晶粒微細化や析出強化により鋼の強度を向上させる場合添加するが、過剰な添加は製造安定性を損なうため、０．０７％を上限として添加する。
【００４０】
本発明に係る鋼帯は、転炉、電気炉またはそれらの合わせ湯などで溶製した後、連続鋳造機または鋳型でスラブとし、熱間圧延で所定形状に加工後、熱処理で有効Ｎ量析出量を制御し、目標の強度とする。
【００４１】
熱間圧延後の熱処理としては、結晶粒径を微細化するための２相域再加熱後、焼戻しを行うことが望ましく、有効Ｎ量はＡｌＮ析出量の調整により行うことが望ましい。
【００４２】
本発明鋼帯を素材として、すなわち、コイル状の１３Ｃｒ系ステンレス鋼帯をアンコイルし、多段の成形ロールにより、連続的にオープンパイプを成形した後、オープンパイプの相対する両エッジ部を電縫溶接とレーザ溶接を組み合わせて製造するレーザ電縫鋼管を製造することが可能である。
【００４３】
【実施例】
（実施例１）
表１に示す化学成分の鋼を真空溶解炉を用いて溶製し、加熱温度１２００℃、仕上圧延温度９００℃の熱間圧延により板厚１２ｍｍの鋼板とした後、焼きならし、焼戻しを行った。実操業を想定し、熱延後の鋼板を７８０℃、７５０℃に２相域加熱後、６２０℃、６５０℃、６８０℃のいずれかの温度で焼戻しを行った。
【００４４】
熱処理後、引張試験（ＪＩＳＺ２２０３）により機械的性質としてＹＳ，ＴＳを求めた。引張試験の残材の一部から、有効Ｎ量を測定した。
【００４５】
表２に試験結果を示す。有効Ｎ量が６０ｐｐｍ以上となる本発明鋼の場合、いずれの２相域温度や焼戻し温度でも、ＹＳが５７０Ｍｐａ以上となり、熱処理条件の変動によらず安定して高強度が得られた。
【００４６】
【表１】
【表２】
（実施例２）
表３に示す化学成分の鋼を真空溶解炉を用いて溶製し、加熱温度１２００℃、仕上圧延温度９００℃の熱間圧延により板厚１２ｍｍの鋼板とした後、２相域加熱後、焼戻しを行った。実操業を想定し、熱延後の鋼板を７５０℃で２相域加熱後、６２０℃、６５０℃のいずれかの温度で焼戻しを行った。
【００４９】
熱処理後、引張試験（ＪＩＳＺ２２０３）により機械的性質としてＹＳ，ＴＳを求めた。引張試験の残材の一部から、有効Ｎ量を測定した。
【００５０】
表４に試験結果を示す。有効Ｎ量が６０ｐｐｍ以上となる本発明鋼の場合、いずれの２相域温度や焼戻し温度でも、ＹＳが５７０Ｍｐａ以上となり、熱処理条件の変動によらず安定して高強度が得られた。
【００５１】
【表３】
【表４】
【発明の効果】
本発明によれば、高強度で材質安定性の高い高強度マルテンサイト系ステンレス鋼帯およびその製造方法が得られ、産業上、極めて有用である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a martensitic stainless steel strip coiled by winding a hot-rolled steel strip and a manufacturing method thereof, and in particular, uniform and excellent strength characteristics at each position of the coil such as a central portion and an outer peripheral portion of the coil. It is related with what can be obtained, and its manufacturing method.
[0002]
[Prior art]
Steel materials used for oil and natural gas transportation line pipes are required to have excellent corrosion resistance and on-site weldability according to the usage environment. In recent years, the use of stainless steel has been studied from the viewpoint of corrosion resistance, but existing stainless steel does not necessarily have sufficient performance for line pipes, and new development has been desired.
[0003]
For example, the 0.2C-13Cr system is for oil well pipes that do not require welding, and is not suitable for line pipes that require high preheating and post-heating temperatures to prevent weld cracking, and where on-site weldability is important. Also, duplex stainless steel such as 22Cr does not require heat treatment after preheating, but is expensive as a material and difficult to use for pipelines that require a large amount of steel.
[0004]
Accordingly, JP-A-6-1000094, JP-A-4-268018, JP-A-8-1000026, etc. propose a 13Cr system in which the amount of C is reduced and weldability is improved. Expansion of application has been considered.
[0005]
In particular, recently, a laser welded ERW steel pipe using a combination of ERW welding and laser welding has been put to practical use, so that a coiled 13Cr stainless steel strip is uncoiled and continuously opened by a multi-stage forming roll. After molding, the application to the ERW steel pipe manufactured by welding both opposing edge portions of the open pipe is increasing.
[0006]
In application of 13Cr stainless steel, since the hardenability of the raw material itself is high and it becomes a martensite structure by air cooling after hot rolling, after being wound in a coil shape, after performing a heat treatment with desired material characteristics, Various steel pipes are used.
[0007]
[Problems to be solved by the invention]
However, when the ERW steel pipe is manufactured by the above-described manufacturing method, the intended strength is often not obtained, and there is a case where the heat treatment is required again.
[0008]
In re-heat treatment, it takes a long time of 10 to 50 hours to uniformly heat a coil-shaped material of several tons to several tens of tons, and the burden is large and trial and error is limited. Guidelines were requested.
[0009]
Therefore, an object of the present invention is to provide a high-strength martensitic stainless steel strip that can be hot-rolled, wound into a coil, and stably obtain desired strength after heat treatment, and a method for producing the same.
[0010]
[Means for Solving the Problems]
The present inventors are subject to the effects of component composition and manufacturing conditions on material, particularly strength, for hot rolled steel strip of 13Cr martensitic stainless steel that has been subjected to two-phase region heating and tempering after hot rolling. We conducted an intensive study.
[0011]
As a result, it has been found that in the case of long-time heating necessary for heat treatment of the coiled material, AlN is precipitated, and the effective N amount is reduced as the temper softening resistance due to the precipitation of AlN, and the strength is reduced. The present invention has been made based on further studies based on the above findings, that is, the present invention
1. Steel composition is mass%, C: 0.02% or less, Si: 0.1-0.3%, Mn: 0.1-0.3%, Cr: 11-15%, Ni: 1-7 %, Sol. Al: 0.06% or less, N: 0.008 to 0.03%, S: 0.002% or less, Ti: 0.07% or less, the balance is Fe and inevitable impurities , and after hot rolling A hot-rolled steel strip of high-strength martensitic stainless steel, wherein the effective amount N (X) in the steel controlled by the heat treatment is 60 ppm or more.
However, effective amount (X) = totalN-NasTiN-NasAlN
[0013]
2 . The hot-rolled steel strip of high-strength martensitic stainless steel according to 1, which contains one or two of Nb: 0.01 to 0.2% and V: 0.01 to 0.2% in mass%.
[0014]
3 . The heat of high-strength martensitic stainless steel according to 1 or 2 , containing one or more of Ca: 0.005% or less, Zr: 0.005% or less, and Mg: 0.005% or less in mass%. Steel strip .
[0015]
4 . The hot-rolled steel strip of high-strength martensitic stainless steel according to any one of 1 to 3 , which contains Cu: 0.1 to 3% by mass%.
[0016]
5 . The hot-rolled steel strip of high-strength martensitic stainless steel according to any one of 1 to 4 , containing Mo: 0.3 to 3% by mass%.
[0018]
6 . A laser-welded steel pipe made of the hot-rolled steel strip of high-strength martensitic stainless steel according to any one of 1 to 5 .
[0020]
7 . The heating rate during 2-phase region heating and / or tempering of the steel strip after hot rolling, according to any one 1 to 6, characterized in that adjusting the amount of precipitation of the effective N amount in steel Manufacturing method of hot-rolled steel strip of high-strength martensitic stainless steel .
[0021]
DETAILED DESCRIPTION OF THE INVENTION
The reasons for limiting the components of the present invention will be described.
[0022]
C
C is important for obtaining a martensite structure, and is added to form a carbide and a carbide-forming element such as Cr in the steel and to improve the strength. On the other hand, if added excessively, the Cr amount effective for corrosion resistance is decreased, the hardness of the weld heat affected zone is increased, and post-weld heat treatment is required, so the content is made 0.02% or less.
[0023]
Si
Si is added as a deoxidizer. If it is less than 0.1%, the effect is not obtained. On the other hand, if it exceeds 0.3%, the effect is saturated, and delta ferrite is crystallized. 0.1 to 0.3% (0.1% or more and 0.3% or less).
[0024]
Mn
Mn is added as a desulfurizing agent in steelmaking. If it is less than 0.1%, there is no effect, and hot workability is also lowered. On the other hand, if added over 0.3%, the corrosion resistance under carbon dioxide gas deteriorates, so the content is made 0.1 to 0.3%.
[0025]
Cr
Cr is added because it is effective for improving the corrosion resistance in an environment containing wet carbon dioxide. If it is less than 11%, there is no effect. On the other hand, if it exceeds 15%, a martensite structure cannot be obtained even if other component elements are adjusted.
[0026]
Ni
Ni forms an austenite phase and obtains a martensite structure, so an appropriate amount is added according to the amount of Cr. If it is less than 1%, the phase stability is insufficient, and the material of the weld is damaged. On the other hand, if it exceeds 7%, the effect is saturated and the material cost also rises.
[0027]
sol. Al
Al is added for deoxidation element and structure refinement. sol. If Al exceeds 0.06%, alumina inclusions and nitrides increase and manufacturability and toughness decrease, so the content is made 0.06% or less.
[0028]
N
N is made 0.008% or more in order to secure the strength and to suppress the strength heat treatment dependency. On the other hand, if it exceeds 0.03% and is added excessively, it forms a compound with Cr in the steel and decreases Cr effective in corrosion resistance, so 0.008 to 0.03%.
[0029]
AlN
AlN is a precipitate that affects the precipitation amount of Cr 2 N , and when it is excessive at 60 ppm or more, the final strength of the product is lowered. Therefore, the precipitation amount is preferably less than 60 ppm. When the precipitation amount of AlN is large, the solid solution N decreases, and it seems that the precipitation amount of Cr 2 N , other carbonitrides and nitrides decreases during tempering, and softening resistance is impaired, but details are unknown. .
[0030]
The precipitation amount of AlN can be controlled by the heat treatment after hot rolling, but it should be controlled by setting the heating rate during tempering for strength adjustment, particularly 50 ° C / h above 400 ° C. Is preferred.
[0031]
In addition, the measurement of the amount of AlN precipitation shall be calculated | required in the sheet thickness center of the product area | region of a steel strip.
[0032]
Effective N amount Effective N dissolves in the tempering heat treatment or forms fine precipitates which are not measured by ordinary Cr 2 N and further by a normal extraction analysis method, thereby preventing softening. In the present invention, 60 ppm or more is set so as to satisfy the strength and toughness characteristics of APIX80.
[0033]
In addition, the effective N amount is the amount of N present as AlN and TiN after quantifying Al and Ti extracted by 10% bromine-methanol method using ICP from the value obtained by measuring the total N amount in steel by check analysis. The amount was calculated and obtained as an effective N amount (X) = totalN-NasTiN-NasAlN.
[0034]
Although the prescription | regulation regarding the basic component composition of this invention and the precipitate in steel is as above, according to the characteristic further desired, it is possible to selectively add the following element 1 type, or 2 or more types.
[0035]
Nb, V
Nb and V both form C and N in steel and carbide, nitride and carbonitride, and improve the strength of the steel by grain refinement and precipitation strengthening. When these elements are added, if less than 0.01%, the effect is not sufficient. On the other hand, even if it exceeds 0.2%, carbon and nitrogen forming carbonitride are insufficient and the strengthening function is saturated. , 0.01 to 0.2% respectively.
[0036]
Ca, Zr, Mg
Ca, Zr, and Mg have a tendency to delay the precipitation of AlN in the steel. However, when these elements exceed 0.005%, oxide inclusions are formed and the toughness is deteriorated.
[0037]
Cu
Cu stabilizes the austenite phase and improves toughness. If less than 0.1%, the effect cannot be obtained. On the other hand, excessive addition exceeding 3% lowers toughness, so the content is made 0.1 to 3%.
[0038]
Mo
Mo improves corrosion resistance. If the content is less than 0.3%, the effect cannot be obtained. On the other hand, if the content exceeds 3%, the effect is saturated, the strength is increased, and processing by cold plastic deformation becomes difficult. %.
[0039]
Ti
Ti is added when C and N in steel form carbides, nitrides, carbonitrides to improve the strength of steel by grain refinement and precipitation strengthening, but excessive addition impairs production stability. 0.07% is added as the upper limit.
[0040]
The steel strip according to the present invention is melted in a converter, electric furnace, or a combination hot metal, and then slabed with a continuous casting machine or a mold, processed into a predetermined shape by hot rolling, and precipitated with an effective N amount by heat treatment. Control the amount to the target intensity.
[0041]
As the heat treatment after hot rolling, it is desirable to perform tempering after two-phase region reheating to refine the crystal grain size, and the effective N amount is desirably adjusted by adjusting the amount of precipitated AlN.
[0042]
The steel strip of the present invention is used as a raw material, that is, the coiled 13Cr stainless steel strip is uncoiled, and an open pipe is continuously formed by a multi-stage forming roll, and then both opposite edge portions of the open pipe are electro-welded. It is possible to manufacture a laser-welded steel pipe manufactured by combining laser welding.
[0043]
【Example】
Example 1
Steel of chemical composition shown in Table 1 is melted using a vacuum melting furnace, and after hot-rolling at a heating temperature of 1200 ° C. and a finish rolling temperature of 900 ° C. to a steel plate having a thickness of 12 mm, normalizing and tempering are performed. It was. Assuming actual operation, the steel sheet after hot rolling was heated in a two-phase region at 780 ° C. and 750 ° C., and then tempered at any of 620 ° C., 650 ° C., and 680 ° C.
[0044]
After the heat treatment, YS and TS were obtained as mechanical properties by a tensile test (JISZ2203). The effective N amount was measured from a part of the remaining material of the tensile test.
[0045]
Table 2 shows the test results. In the case of the steel of the present invention in which the effective N amount is 60 ppm or more, YS was 570 Mpa or more at any two-phase region temperature or tempering temperature, and high strength was stably obtained regardless of fluctuations in heat treatment conditions.
[0046]
[Table 1]
[Table 2]
(Example 2)
Steels with chemical components shown in Table 3 were melted using a vacuum melting furnace, made into a steel plate with a thickness of 12 mm by hot rolling at a heating temperature of 1200 ° C. and a finish rolling temperature of 900 ° C., and then tempered after heating in two phases. Went. Assuming actual operation, the hot-rolled steel sheet was heated in a two-phase region at 750 ° C., and then tempered at either 620 ° C. or 650 ° C.
[0049]
After the heat treatment, YS and TS were obtained as mechanical properties by a tensile test (JISZ2203). The effective N amount was measured from a part of the remaining material of the tensile test.
[0050]
Table 4 shows the test results. In the case of the steel of the present invention in which the effective N amount is 60 ppm or more, YS was 570 Mpa or more at any two-phase region temperature or tempering temperature, and high strength was stably obtained regardless of fluctuations in heat treatment conditions.
[0051]
[Table 3]
[Table 4]
【The invention's effect】
According to the present invention, a high-strength martensitic stainless steel strip having high strength and high material stability and a method for producing the same can be obtained, which is extremely useful industrially.
Claims (7)
Ｃ：０．０２％以下、
Ｓｉ：０．１〜０．３％、
Ｍｎ：０．１〜０．３％、
Ｃｒ：１１〜１５％、
Ｎｉ：１〜７％、
ｓｏｌ．Ａｌ：０．０６％以下、
Ｎ：０．００８〜０．０３％、
Ｓ：０．００２％以下、
Ｔｉ：０．０７％以下、
残部がＦｅおよび不可避的不純物からなり、かつ熱間圧延後の熱処理にて制御される鋼中の有効量Ｎ（Ｘ）が６０ｐｐｍ以上であることを特徴とする高強度マルテンサイト系ステンレス鋼の熱延鋼帯。
但し、有効量（Ｘ）＝ｔｏｔａｌＮ−ＮａｓＴｉＮ−ＮａｓＡｌＮSteel composition is mass%,
C: 0.02% or less,
Si: 0.1 to 0.3%,
Mn: 0.1 to 0.3%,
Cr: 11-15%,
Ni: 1-7%,
sol. Al: 0.06% or less,
N: 0.008 to 0.03%,
S: 0.002% or less,
Ti: 0.07% or less,
Heat of high-strength martensitic stainless steel, characterized in that the balance is Fe and inevitable impurities , and the effective amount N (X) in the steel controlled by heat treatment after hot rolling is 60 ppm or more Steel strip.
However, effective amount (X) = totalN-NasTiN-NasAlN
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| JPH07258732A (en) * | 1994-03-22 | 1995-10-09 | Nippon Steel Corp | Production of high strength stainless hot rolled steel sheet excellent in workability |
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