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JP4337712B2 - Martensitic stainless steel - Google Patents

Martensitic stainless steel Download PDF

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JP4337712B2
JP4337712B2 JP2004335241A JP2004335241A JP4337712B2 JP 4337712 B2 JP4337712 B2 JP 4337712B2 JP 2004335241 A JP2004335241 A JP 2004335241A JP 2004335241 A JP2004335241 A JP 2004335241A JP 4337712 B2 JP4337712 B2 JP 4337712B2
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martensitic stainless
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JP2006144069A (en
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秀樹 高部
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Nippon Steel Corp
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Sumitomo Metal Industries Ltd
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Priority to PCT/JP2005/019685 priority patent/WO2006054430A1/en
Priority to EP05799225A priority patent/EP1826285B1/en
Priority to CNB2005800396559A priority patent/CN100549204C/en
Priority to US11/791,015 priority patent/US20080213120A1/en
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    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18Hardening; Quenching with or without subsequent tempering
    • C21D1/25Hardening, combined with annealing between 300 degrees Celsius and 600 degrees Celsius, i.e. heat refining ("Vergüten")
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00Heat treatment of ferrous alloys
    • C21D6/004Heat treatment of ferrous alloys containing Cr and Ni
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/02Ferrous alloys, e.g. steel alloys containing silicon
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/04Ferrous alloys, e.g. steel alloys containing manganese
    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22CALLOYS
    • C22C38/00Ferrous alloys, e.g. steel alloys
    • C22C38/18Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • CCHEMISTRY; METALLURGY
    • C21METALLURGY OF IRON
    • C21DMODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00Microstructure comprising significant phases
    • C21D2211/008Martensite

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Description

本発明は、マルテンサイト系ステンレス鋼に関し、さらに詳しくは、硫化水素、炭酸ガス、塩素イオンといった腐食性物質を含む腐食環境で使用されるマルテンサイト系ステンレス鋼に関する。   The present invention relates to martensitic stainless steel, and more particularly to martensitic stainless steel used in a corrosive environment containing corrosive substances such as hydrogen sulfide, carbon dioxide, and chlorine ions.

油井やガス井の深井戸化に伴い、油井管等の油井用鋼材として使用されるマルテンサイト系ステンレス鋼には高強度及び高靭性が求められる。そのため、降伏応力(0.2%耐力)が758〜860MPa(以下、110ksi級と称する)のマルテンサイト系ステンレス鋼や、110ksi級以上の高強度を有するマルテンサイト系ステンレス鋼が開発されている。   With the deepening of oil wells and gas wells, martensitic stainless steel used as oil well steel materials such as oil well pipes is required to have high strength and high toughness. Therefore, martensitic stainless steel having a yield stress (0.2% yield strength) of 758 to 860 MPa (hereinafter referred to as 110 ksi class) and martensitic stainless steel having high strength of 110 ksi class or higher have been developed.

油井用のマルテンサイト系ステンレス鋼はさらに、耐SCC(Stress Corrosion Cracking)性や耐SSC(Sulfide Stress Cracking)性といった高い耐食性も要求される。油井やガス井は腐食環境であり、硫化水素、炭酸ガス、塩素イオンといった腐食性物質を含むためである。つまり、油井用のマルテンサイト系ステンレス鋼には、高強度、高靭性及び高耐食性が求められる。   The martensitic stainless steel for oil wells is also required to have high corrosion resistance such as SCC (Stress Corrosion Cracking) resistance and SSC (Sulfide Stress Cracking) resistance. This is because oil wells and gas wells are corrosive environments and contain corrosive substances such as hydrogen sulfide, carbon dioxide, and chlorine ions. In other words, martensitic stainless steel for oil wells is required to have high strength, high toughness, and high corrosion resistance.

高強度及び高耐食性を有するマルテンサイト系ステンレス鋼として下記特許文献1(特開2003−3243号公報)が開示されている。この文献に開示されたマルテンサイト系ステンレス鋼は、Mo含有量を質量%で1.5%以上にすることにより、従来のマルテンサイト系ステンレス鋼よりも高い耐SSC性を有する。   The following patent document 1 (Unexamined-Japanese-Patent No. 2003-3243) is disclosed as martensitic stainless steel having high strength and high corrosion resistance. The martensitic stainless steel disclosed in this document has a higher SSC resistance than conventional martensitic stainless steel by setting the Mo content to 1.5% by mass or more.

ところで、Mo含有量が高い場合、110ksi級の強度が得られる焼き戻し温度の範囲(以下、焼き戻し温度範囲と称する)が非常に小さくなる。図2はMo含有量が高いマルテンサイト系ステンレス鋼(以下、高Moマルテンサイト系ステンレス鋼と称する)の降伏応力と焼き戻し温度との関係を示す図である。図2の高Moマルテンサイト系ステンレス鋼は、質量%で0.0016%のC、11.8%のCr、7.2%のNi、2.9%のMoを含み、残部はFe及び不純物である。図2を参照して、降伏応力が758〜860MPaの範囲における焼き戻し曲線C10の勾配は大きい。そのため、高Moマルテンサイト系ステンレス鋼の強度を110ksi級にするには焼き戻し温度を約580〜約600℃の範囲内に設定しなければならない。つまり、強度を110ksi級にするための焼き戻し温度範囲ΔTは非常に小さい。   By the way, when Mo content is high, the range of the tempering temperature (henceforth a tempering temperature range) from which 110 ksi grade intensity | strength is obtained becomes very small. FIG. 2 is a diagram showing the relationship between the yield stress and the tempering temperature of martensitic stainless steel having a high Mo content (hereinafter referred to as high Mo martensitic stainless steel). The high Mo martensitic stainless steel of FIG. 2 contains 0.0016% C, 11.8% Cr, 7.2% Ni, 2.9% Mo by mass% with the balance being Fe and impurities. It is. Referring to FIG. 2, the tempering curve C10 has a large slope in the range where the yield stress is in the range of 758 to 860 MPa. Therefore, the tempering temperature must be set in the range of about 580 to about 600 ° C. in order to make the strength of the high Mo martensitic stainless steel 110 ksi class. That is, the tempering temperature range ΔT for making the strength 110 ksi class is very small.

焼き戻し温度範囲ΔTが小さければ、生産性が低下する。通常、高Moマルテンサイト系ステンレス鋼は数百t連続して製造される。この場合、高Moマルテンサイト系ステンレス鋼は複数のヒート(1回の製鋼工程で得られた溶鋼)から製造されるが、各ヒートの化学組成は完全に一致せず、若干変動する。焼き戻し温度範囲ΔTが小さい場合、鋼の強度を110ksi級にするために、化学組成が変動するたびに焼き戻し温度を変更しなければならない。要するに、強度を110ksi級にするためにはヒートごとに焼き戻し温度の設定を変更する必要がある。このような焼き戻し温度の設定変更は生産性を低下させる。
特開2003−3243号公報 国際公開WO2004/57050
If the tempering temperature range ΔT is small, the productivity decreases. Usually, high Mo martensitic stainless steel is manufactured continuously for several hundred tons. In this case, the high Mo martensitic stainless steel is manufactured from a plurality of heats (molten steel obtained in one steel making process), but the chemical composition of each heat does not completely match and varies slightly. When the tempering temperature range ΔT is small, the tempering temperature must be changed every time the chemical composition changes in order to make the steel have a strength of 110 ksi. In short, to set the strength to 110 ksi class, it is necessary to change the setting of the tempering temperature for each heat. Such a change in setting of the tempering temperature decreases productivity.
JP 2003-3243 A International Publication WO2004 / 57050

本発明の目的は、758〜860MPaの降伏応力が得られる焼き戻し温度の範囲が大きいマルテンサイト系ステンレス鋼を提供することである。   An object of the present invention is to provide a martensitic stainless steel having a large tempering temperature range in which a yield stress of 758 to 860 MPa is obtained.

課題を解決するための手段及び発明の効果Means for Solving the Problems and Effects of the Invention

本発明者は種々の実験及び検討の結果、以下の知見を得た。   As a result of various experiments and examinations, the present inventor has obtained the following knowledge.

(A)マルテンサイト系ステンレス鋼のAc1変態点が高くなるような化学組成にすれば、降伏応力を758〜860MPaになる焼き戻し温度範囲が広くなる。Ac1変態点が低ければ、高温焼き戻し中にオーステナイトが生成され、これにより強度が低下するからである。 If the chemical composition as (A) A c1 transformation point of martensitic stainless steel is high, the tempering temperature range becomes the yield stress in 758~860MPa widens. This is because, if the Ac1 transformation point is low, austenite is generated during high-temperature tempering, thereby reducing the strength.

(B)Ac1変態点を高くするだけでなく、C含有量を低くする。これにより、降伏応力を758〜860MPaになる焼き戻し温度範囲がさらに広くなる。C含有量が高いほど、758〜860MPaの降伏応力範囲内における焼き戻し曲線の勾配が大きくなるからである。 (B) Not only increase the A c1 transformation point, but also decrease the C content. Thereby, the tempering temperature range in which the yield stress becomes 758 to 860 MPa is further widened. This is because the higher the C content, the greater the gradient of the tempering curve within the yield stress range of 758 to 860 MPa.

(C)C含有量を低くすれば、δフェライトが生成されやすくなり、鋼の強度及び靭性に影響を与える。110ksi級のマルテンサイトステンレス鋼は外気が0℃を下回る環境でも使用されるため、高強度とともに高靭性も必要である。Ac1変態点を高くし、かつ、C含有量を低下しても鋼の組織をマルテンサイト化できるような化学組成にすれば、δフェライトの生成を抑制でき、110ksi級の強度を保ちながら靭性の低下を防止できる。   (C) If the C content is lowered, δ ferrite is easily generated, which affects the strength and toughness of the steel. Since 110 ksi grade martensitic stainless steel is used even in an environment where the outside air is below 0 ° C., it requires high strength and high toughness. By making the steel composition martensitic even if the Ac1 transformation point is increased and the C content is decreased, the formation of δ ferrite can be suppressed, and the toughness can be maintained while maintaining the strength of 110 ksi class. Decline can be prevented.

以上の知見に基づいて検討した結果、C含有量を0.01%以下にし、かつ、式(1)及び式(2)を満足すれば、降伏応力が758〜860MPaになる焼き戻し温度範囲を従来よりも大きくできることを見出した。   As a result of examination based on the above knowledge, if the C content is 0.01% or less and the expressions (1) and (2) are satisfied, the tempering temperature range in which the yield stress becomes 758 to 860 MPa is obtained. We found that it can be made larger than before.

922.6−554.5C−50.9Mn+2944.8P+1.056Cr−81.1Ni+95.8Mo−1584.9Al−376.1N≧600 (1)   922.6-554.5C-50.9Mn + 2944.8P + 1.056Cr-81.1Ni + 95.8Mo-1584.9Al-376.1N ≧ 600 (1)

30C+0.5Mn+Ni−1.5Si−Cr−Mo+7.9≧0 (2)   30C + 0.5Mn + Ni-1.5Si-Cr-Mo + 7.9 ≧ 0 (2)

ここで、式中の記号は各元素の含有量(質量%)である。   Here, the symbol in a formula | equation is content (mass%) of each element.

式(1)の左辺(以降、式(1)の左辺=F1とする)は本発明のマルテンサイト系ステンレス鋼のAc1変態点を予測する式である。前述のとおり、Ac1変態点を高くすれば、焼き戻し中に残留オーステナイトが析出するのを抑制できるため、降伏応力が急激に低下するのを防止できる。換言すれば、降伏応力が758〜860MPaの範囲の焼き戻し曲線の勾配を小さくできる。 The left side of equation (1) (hereinafter, the left side of equation (1) = F1) is an equation for predicting the A c1 transformation point of the martensitic stainless steel of the present invention. As described above, if the Ac1 transformation point is increased, it is possible to suppress the precipitation of retained austenite during tempering, and thus it is possible to prevent the yield stress from rapidly decreasing. In other words, the gradient of the tempering curve when the yield stress is in the range of 758 to 860 MPa can be reduced.

F1≧600としたのは、600℃以下の焼き戻し温度で焼き戻し処理が実行されるからである。焼き戻し温度を600℃以上にすれば、鋼中の微細炭化物や金属間化合物が粗大化し、返って強度が低下し、さらに靭性も低下する。焼き戻し温度が600℃以下のためF1値は600℃以上であれば足りる。   The reason why F1 ≧ 600 is that the tempering process is executed at a tempering temperature of 600 ° C. or lower. If the tempering temperature is set to 600 ° C. or more, fine carbides and intermetallic compounds in the steel become coarse, and the strength is lowered and the toughness is further lowered. Since the tempering temperature is 600 ° C. or lower, it is sufficient that the F1 value is 600 ° C. or higher.

式(2)の左辺は焼き戻し後の鋼をマルテンサイト化するための式である。オーステナイト形成元素であるC、Mn、Niの含有量と、フェライト形成元素であるSi、Cr、Moの含有量とが式(2)の関係を満たせば、組織がマルテンサイトになり、δフェライトの生成を防止できる。そのため強度の低下を防止し、かつ、高靭性を維持できる。   The left side of Equation (2) is an equation for martensifying the steel after tempering. If the content of C, Mn, and Ni that are austenite forming elements and the content of Si, Cr, and Mo that are ferrite forming elements satisfy the relationship of formula (2), the structure becomes martensite, and δ ferrite Generation can be prevented. Therefore, strength reduction can be prevented and high toughness can be maintained.

なお、マルテンサイト系ステンレス鋼がTiを含有する場合、式(1)の代わりに式(3)を満たせばよい。また、オーステナイト形成元素Cuを含有する場合、式(2)の代わりに式(4)を満たせばよい。   In addition, what is necessary is just to satisfy | fill Formula (3) instead of Formula (1), when a martensitic stainless steel contains Ti. Moreover, what is necessary is just to satisfy | fill Formula (4) instead of Formula (2), when it contains the austenite formation element Cu.

922.6−554.5C−50.9Mn+2944.8P+1.056Cr−81.1Ni+95.8Mo−125.1Ti−1584.9Al−376.1N≧600 (3)   922.6-554.5C-50.9Mn + 2944.8P + 1.056Cr-81.1Ni + 95.8Mo-125.1Ti-1584.9Al-376.1N ≧ 600 (3)

30C+0.5Mn+Ni+0.5Cu−1.5Si−Cr−Mo+7.9≧0 (4)   30C + 0.5Mn + Ni + 0.5Cu-1.5Si-Cr-Mo + 7.9 ≧ 0 (4)

これらの式を満たせば、図1に示す曲線C1のような焼き戻し曲線を得ることができ、758〜860MPaの降伏応力範囲における焼き戻し曲線の勾配を従来よりも小さくできる。そのため、降伏応力が758〜860MPaとなる焼き戻し温度範囲ΔT1は、従来の焼き戻し曲線C2の焼き戻し温度範囲ΔT2よりも大きくなる。そのため、操業中の焼き戻し温度の設定変更に基づく生産性の低下を抑制できる。   If these equations are satisfied, a tempering curve such as the curve C1 shown in FIG. 1 can be obtained, and the gradient of the tempering curve in the yield stress range of 758 to 860 MPa can be made smaller than before. Therefore, the tempering temperature range ΔT1 in which the yield stress is 758 to 860 MPa is larger than the tempering temperature range ΔT2 of the conventional tempering curve C2. Therefore, it is possible to suppress a decrease in productivity based on a setting change of the tempering temperature during operation.

以上の知見に基づいて、本発明者は、以下の発明を完成させた。   Based on the above findings, the present inventor has completed the following invention.

本発明によるマルテンサイト系ステンレス鋼は、質量%で、C:0.001〜0.01%、Si:0.5%以下、Mn:0.1〜3.0%、P:0.04%以下、S:0.01%以下、Cr:10〜15%、Ni:4〜8%、Mo:2.8〜5.0%、Al:0.001〜0.10%、N:0.07%以下を含有し、残部はFe及び不純物からなり、式(1)及び式(2)を満足し、758〜860MPaの降伏応力を有する。   The martensitic stainless steel according to the present invention is, in mass%, C: 0.001 to 0.01%, Si: 0.5% or less, Mn: 0.1 to 3.0%, P: 0.04%. Hereinafter, S: 0.01% or less, Cr: 10-15%, Ni: 4-8%, Mo: 2.8-5.0%, Al: 0.001-0.10%, N: 0.00. It contains not more than 07%, and the balance consists of Fe and impurities, satisfies the formulas (1) and (2), and has a yield stress of 758 to 860 MPa.

922.6−554.5C−50.9Mn+2944.8P+1.056Cr−81.1Ni+95.8Mo−1584.9Al−376.1N≧600 (1)   922.6-554.5C-50.9Mn + 2944.8P + 1.056Cr-81.1Ni + 95.8Mo-1584.9Al-376.1N ≧ 600 (1)

30C+0.5Mn+Ni−1.5Si−Cr−Mo+7.9≧0 (2)   30C + 0.5Mn + Ni-1.5Si-Cr-Mo + 7.9 ≧ 0 (2)

ここで、式中の記号は各元素の含有量(質量%)である。また、0.2%耐力を降伏応力とする。   Here, the symbol in a formula | equation is content (mass%) of each element. Moreover, 0.2% yield strength is defined as yield stress.

本発明によるマルテンサイト系ステンレス鋼は、C含有量を0.01%以下にすることにより焼き戻し曲線の勾配を小さくできる。さらに、式(1)を満たすことによりAc1変態点を従来よりも高くできる。そのため、焼き戻し曲線の勾配は小さくなり、降伏応力が758〜860MPaとなる焼き戻し温度範囲が従来よりも大きくなる。 The martensitic stainless steel according to the present invention can reduce the gradient of the tempering curve by setting the C content to 0.01% or less. Furthermore, by satisfying the formula (1), the Ac1 transformation point can be made higher than before. Therefore, the gradient of the tempering curve becomes small, and the tempering temperature range in which the yield stress becomes 758 to 860 MPa becomes larger than before.

さらに式(2)を満たすことにより、強度が110ksi未満になるのを防止でき、かつ、高靭性を維持できる。また、Mo含有量が高いため、高耐食性を有する。   Furthermore, by satisfy | filling Formula (2), it can prevent that intensity | strength becomes less than 110 ksi and can maintain high toughness. Moreover, since Mo content is high, it has high corrosion resistance.

本発明によるマルテンサイト系ステンレス鋼は、質量%で、C:0.001〜0.01%、Si:0.5%以下、Mn:0.1〜3.0%、P:0.04%以下、S:0.01%以下、Cr:10〜15%、Ni:4〜8%、Mo:2.8〜5.0%、Al:0.001〜0.10%、N:0.07%以下と、Ti:0.25%以下、V:0.25%以下、Nb:0.25%以下、Zr:0.25%以下のうちの1種以上とを含有し、残部はFe及び不純物からなり、式(2)及び式(3)を満足し、758〜860MPaの降伏応力を有する。 The martensitic stainless steel according to the present invention is, in mass%, C: 0.001 to 0.01%, Si: 0.5% or less, Mn: 0.1 to 3.0%, P: 0.04%. Hereinafter, S: 0.01% or less, Cr: 10-15%, Ni: 4-8%, Mo: 2.8-5.0%, Al: 0.001-0.10%, N: 0.00. And at least one of Ti: 0.25% or less , V: 0.25% or less , Nb: 0.25% or less , Zr: 0.25% or less , with the balance being Fe And impurities, satisfying the expressions (2) and (3), and having a yield stress of 758 to 860 MPa.

30C+0.5Mn+Ni−1.5Si−Cr−Mo+7.9≧0 (2)   30C + 0.5Mn + Ni-1.5Si-Cr-Mo + 7.9 ≧ 0 (2)

922.6−554.5C−50.9Mn+2944.8P+1.056Cr−81.1Ni+95.8Mo−125.1Ti−1584.9Al−376.1N≧600 (3)   922.6-554.5C-50.9Mn + 2944.8P + 1.056Cr-81.1Ni + 95.8Mo-125.1Ti-1584.9Al-376.1N ≧ 600 (3)

ここで、式中の記号は各元素の含有量(質量%)である。なお、式(3)中のTiの数値は0となる場合もある。   Here, the symbol in a formula | equation is content (mass%) of each element. In addition, the numerical value of Ti in Formula (3) may be 0.

この場合、C含有量を0.01%以下にし、かつ、式(3)を満たすことにより758〜860MPaの降伏応力が得られる焼き戻し温度範囲を従来よりも大きくすることができる。さらに式(2)を満たすことにより、強度が110ksi未満になるのを防止でき、かつ、高靭性を維持できる。   In this case, the tempering temperature range in which the yield stress of 758 to 860 MPa can be obtained can be made larger than before by making the C content 0.01% or less and satisfying the formula (3). Furthermore, by satisfy | filling Formula (2), it can prevent that intensity | strength becomes less than 110 ksi and can maintain high toughness.

本発明によるマルテンサイト系ステンレス鋼は、質量%で、C:0.001〜0.01%、Si:0.5%以下、Mn:0.1〜3.0%、P:0.04%以下、S:0.01%以下、Cr:10〜15%、Ni:4〜8%、Mo:2.8〜5.0%、Al:0.001〜0.10%、N:0.07%以下と、Ti:0.25%以下、V:0.25%以下、Nb:0.25%以下、Zr:0.25%以下のうちの1種以上と、Cu:1.0%以下とを含有し、残部はFe及び不純物からなり、式(3)及び式(4)を満足し、758〜860MPaの降伏応力を有する。 The martensitic stainless steel according to the present invention is, in mass%, C: 0.001 to 0.01%, Si: 0.5% or less, Mn: 0.1 to 3.0%, P: 0.04%. Hereinafter, S: 0.01% or less, Cr: 10-15%, Ni: 4-8%, Mo: 2.8-5.0%, Al: 0.001-0.10%, N: 0.00. 07% or less, Ti: 0.25% or less , V: 0.25% or less , Nb: 0.25% or less , Zr: 0.25% or less , and Cu: 1.0% The remainder consists of Fe and impurities, satisfies the formulas (3) and (4), and has a yield stress of 758 to 860 MPa.

922.6−554.5C−50.9Mn+2944.8P+1.056Cr−81.1Ni+95.8Mo−125.1Ti−1584.9Al−376.1N≧600 (3)   922.6-554.5C-50.9Mn + 2944.8P + 1.056Cr-81.1Ni + 95.8Mo-125.1Ti-1584.9Al-376.1N ≧ 600 (3)

30C+0.5Mn+Ni+0.5Cu−1.5Si−Cr−Mo+7.9≧0 (4)   30C + 0.5Mn + Ni + 0.5Cu-1.5Si-Cr-Mo + 7.9 ≧ 0 (4)

ここで、式中の記号は各元素の含有量(質量%)である。なお、式(3)中のTiの数値は0となる場合もある。   Here, the symbol in a formula | equation is content (mass%) of each element. In addition, the numerical value of Ti in Formula (3) may be 0.

この場合、C含有量を0.01%以下にし、かつ、式(3)を満たすことにより758〜860MPaの降伏応力が得られる焼き戻し温度範囲を従来よりも大きくすることができる。さらに式(4)を満たすことにより、強度が110ksi未満になるのを防止でき、かつ、高靭性を維持する。   In this case, the tempering temperature range in which the yield stress of 758 to 860 MPa can be obtained can be made larger than before by making the C content 0.01% or less and satisfying the formula (3). Furthermore, by satisfy | filling Formula (4), intensity | strength can be prevented from becoming less than 110 ksi, and high toughness is maintained.

好ましくはさらに、Ca:0.005%以下、Mg:0.005%以下、La:0.005%以下、Ce:0.005%以下のうちの1種以上を含有する。 Preferably, it further contains at least one of Ca: 0.005% or less , Mg: 0.005% or less , La: 0.005% or less , Ce: 0.005% or less .

この場合、マルテンサイト系ステンレス鋼の熱間加工性が向上する。なお、これらの元素を含有しても、上記発明の効果に影響はない。   In this case, the hot workability of martensitic stainless steel is improved. Even if these elements are contained, the effect of the invention is not affected.

以下、図面を参照し、本発明の実施の形態を詳しく説明する。図中同一又は相当部分には同一符号を付してその説明は繰り返さない。   Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

1.化学組成
本発明の実施の形態によるマルテンサイト系ステンレス鋼は、以下の組成を有する。以降、元素に関する%は質量%を意味する。
1. Chemical Composition The martensitic stainless steel according to the embodiment of the present invention has the following composition. Hereinafter, “%” related to elements means “% by mass”.

C:0.001〜0.01%
過剰にCを含有すれば、焼き戻し曲線の勾配が急峻になり、758〜860MPaの降伏応力を有する鋼が安定して得られない。C含有量は低く制限すべきである。一方、C含有量を0.001%未満にすれば製造コストが高くなる。そのため、C含有量は0.001〜0.01%にする。好ましいC含有量は0.001〜0.008%である。
C: 0.001 to 0.01%
If C is contained excessively, the gradient of the tempering curve becomes steep, and a steel having a yield stress of 758 to 860 MPa cannot be stably obtained. The C content should be limited low. On the other hand, if the C content is less than 0.001%, the production cost increases. Therefore, the C content is 0.001 to 0.01%. A preferable C content is 0.001 to 0.008%.

Si:0.5%以下
Siは脱酸剤として有効である。一方、Siは鋼を硬化するためSi含有量が高すぎると鋼の靭性及び加工性が劣化する。また、Siはフェライト形成元素であるため、鋼のマルテンサイト化を妨げる。そのため、Si含有量は0.5%以下にする。好ましいSi含有量は0.3%以下である。
Si: 0.5% or less Si is effective as a deoxidizer. On the other hand, since Si hardens steel, if the Si content is too high, the toughness and workability of the steel deteriorate. Moreover, since Si is a ferrite forming element, it prevents the martensite formation of steel. Therefore, the Si content is 0.5% or less. A preferable Si content is 0.3% or less.

Mn:0.1〜3.0%
Mnは鋼の熱間加工性の向上に寄与する。さらに、Mnはオーステナイト形成元素であり、組織のマルテンサイト化に寄与する。ただし、過剰にMnを含有すれば靭性が低下する。そのため、Mn含有量は0.1〜3.0%にする。好ましいMn含有量は0.3〜1.0%である。
Mn: 0.1 to 3.0%
Mn contributes to the improvement of hot workability of steel. Further, Mn is an austenite-forming element and contributes to the martensitic transformation of the structure. However, if Mn is contained excessively, the toughness is lowered. Therefore, the Mn content is 0.1 to 3.0%. A preferable Mn content is 0.3 to 1.0%.

P:0.04%以下
Pは不純物である。PはSSCを発生させるため、P含有量をなるべく低く制限する。具体的には、P含有量を0.04%以下にする。
P: 0.04% or less P is an impurity. Since P generates SSC, the P content is limited as low as possible. Specifically, the P content is set to 0.04% or less.

S:0.01%以下
Sは不純物である。Sは熱間加工性を低下する。そのため、S含有量をなるべく低く制限する。具体的には、S含有量を0.01%以下にする。
S: 0.01% or less S is an impurity. S decreases hot workability. Therefore, the S content is limited as low as possible. Specifically, the S content is set to 0.01% or less.

Cr:10〜15%
Crは湿潤炭酸ガス環境での耐食性の向上に寄与する。一方、Crはフェライト形成元素であるため、過剰に含有すれば焼き戻しマルテンサイトが形成されにくくなり、強度及び靭性が低下する。そのためCr含有量は10〜15%にする。好ましいCr含有量は11〜14%である。
Cr: 10-15%
Cr contributes to improvement of corrosion resistance in a wet carbon dioxide environment. On the other hand, since Cr is a ferrite-forming element, if it is excessively contained, tempered martensite is difficult to be formed, and strength and toughness are reduced. Therefore, the Cr content is 10 to 15%. A preferable Cr content is 11 to 14%.

Ni:4〜8%
Niはオーステナイト形成元素であり、焼き戻し後の組織をマルテンサイトにするために必要である。Ni含有量が低すぎる場合、焼き戻し後の組織はフェライトを多く含む。一方、Ni含有量が多すぎる場合、焼き戻し後の組織はオーステナイトを多く含む。そのため、Ni含有量は4〜8%にする。好ましいNi含有量は4〜7%である。
Ni: 4-8%
Ni is an austenite-forming element and is necessary to make the structure after tempering martensite. When the Ni content is too low, the structure after tempering contains a large amount of ferrite. On the other hand, when there is too much Ni content, the structure | tissue after tempering contains much austenite. Therefore, the Ni content is 4 to 8%. A preferable Ni content is 4 to 7%.

Mo:2.8〜5.0%
Moは耐SSC性及び強度の向上に寄与する重要な元素である。本実施の形態によるマルテンサイト系ステンレス鋼では、高い耐SSC性を得るためMo含有量の下限を2.8%にする。一方、Moはフェライト形成元素であるため、過剰な添加は組織のマルテンサイト化を妨げる。そのためMo含有量の上限を5.0%にする。好ましいMo含有量は2.8〜4.0%である。
Mo: 2.8 to 5.0%
Mo is an important element contributing to the improvement of SSC resistance and strength. In the martensitic stainless steel according to the present embodiment, the lower limit of the Mo content is set to 2.8% in order to obtain high SSC resistance. On the other hand, since Mo is a ferrite-forming element, excessive addition hinders the formation of martensite in the structure. Therefore, the upper limit of the Mo content is 5.0%. A preferable Mo content is 2.8 to 4.0%.

Al:0.001〜0.10%
Alは脱酸剤として有効である。一方、Al含有量が多すぎると多数の介在物が生成され、耐食性が低下する。そのため、Al含有量は0.001〜0.10%にする。好ましいAl含有量は0.001〜0.06%である。
Al: 0.001 to 0.10%
Al is effective as a deoxidizer. On the other hand, when there is too much Al content, many inclusions will be produced | generated and corrosion resistance will fall. Therefore, the Al content is 0.001 to 0.10%. A preferable Al content is 0.001 to 0.06%.

N:0.07%以下
Nは窒化物を形成し耐食性を低下する。そのため、N含有量は0.07%以下にする。
N: 0.07% or less N forms nitrides and reduces corrosion resistance. Therefore, the N content is 0.07% or less.

なお、残部はFe及び不純物で構成される。不純物は製造過程の種々の要因等により含まれる。   The balance is composed of Fe and impurities. Impurities are included due to various factors in the manufacturing process.

本実施の形態によるマルテンサイト系ステンレス鋼はさらに、必要に応じてTi、V、Nb、Zrのうちの1種以上を含有する。   The martensitic stainless steel according to the present embodiment further contains at least one of Ti, V, Nb, and Zr as necessary.

Ti:0.25%以下
V:0.25%以下
Nb:0.25%以下
Zr:0.25%以下
Ti、V、Nb、Zrは選択元素である。これらの元素はCを固定し、強度のばらつきを低減する。一方、これらの元素を過剰に含有すると焼き戻し後の組織のマルテンサイト化が妨げられる。そのため、これらの元素の含有量をそれぞれ0.25%以下にする。好ましい含有量は、Ti:0.005〜0.25%、V:0.005〜0.25%、Nb:0.002〜0.25%、Zr:0.0003〜0.25%であり、さらに好ましい含有量の上限値は、それぞれ0.20%である。
Ti: 0.25% or less V: 0.25% or less Nb: 0.25% or less Zr: 0.25% or less Ti, V, Nb, and Zr are selective elements. These elements fix C and reduce variations in strength. On the other hand, when these elements are contained excessively, the structure after tempering is prevented from becoming martensite. Therefore, the content of these elements is set to 0.25% or less . Preferred contents are Ti: 0.005-0.25%, V: 0.005-0.25%, Nb: 0.002-0.25%, Zr: 0.0003-0.25% , more preferably the upper limit of the content is, respectively is 0. 20%.

本実施の形態によるマルテンサイト系ステンレス鋼はさらに、必要に応じてCuを含有する。   The martensitic stainless steel according to the present embodiment further contains Cu as necessary.

Cu:1.0%以下
Cuは選択元素である。CuはNiと同様にオーステナイト形成元素であり、焼き戻し後の組織のマルテンサイト化に有効である。一方、過剰にCuを含有すると熱間加工性が低下する。そのため、Cu含有量は、1.0%以下、好ましくは、0.02〜1.0%にする。
Cu: 1.0% or less Cu is a selective element. Cu, like Ni, is an austenite forming element and is effective for martensite formation after tempering. On the other hand, when Cu is contained excessively, hot workability will fall. Therefore, the Cu content is 1.0% or less, preferably 0.02 to 1.0%.

本実施の形態によるマルテンサイト系ステンレス鋼はさらに、必要に応じてCa、Mg、La、Ceのうちの1種以上を含有する。   The martensitic stainless steel according to the present embodiment further contains one or more of Ca, Mg, La, and Ce as necessary.

Ca:0.005%以下
Mg:0.005%以下
La:0.005%以下
Ce:0.005%以下
Ca、Mg、La、Ceはいずれも選択元素である。これらの元素は熱間加工性の向上に寄与する。一方、これらの元素を過剰に含有すると粗大な酸化物が生成され、耐食性が低下する。そのため、これらの元素の含有量はそれぞれ0.005%以下、好ましくは、0.0002〜0.005%にする。これらの元素のうち、熱間加工性の向上に特に寄与する元素はCa及びLaである。
Ca: 0.005% or less Mg: 0.005% or less La: 0.005% or less Ce: 0.005% or less Ca, Mg, La, and Ce are all selective elements. These elements contribute to the improvement of hot workability. On the other hand, when these elements are contained excessively, coarse oxides are generated, and the corrosion resistance is lowered. Therefore, the content of these elements is 0.005% or less, preferably 0.0002 to 0.005% . Among these elements, Ca and La are elements that particularly contribute to the improvement of hot workability.

2.製造方法
上記化学組成の鋼を溶製し、周知の精錬工程により精錬する。続いて溶鋼を連続鋳造法により連続鋳造材にする。連続鋳造材とはたとえばスラブやブルームやビレットである。又は、溶鋼を造塊法によりインゴットにする。
2. Manufacturing method Steel having the above chemical composition is melted and refined by a well-known refining process. Subsequently, the molten steel is made into a continuous cast material by a continuous casting method. The continuous cast material is, for example, a slab, bloom or billet. Alternatively, the molten steel is made into an ingot by the ingot-making method.

スラブやブルーム、インゴットを熱間加工してビレットにする。このとき、熱間圧延によりビレットにしてもよいし、熱間鍛造によりビレットにしてもよい。   Hot-work slabs, blooms, and ingots into billets. At this time, the billet may be formed by hot rolling or may be formed by hot forging.

連続鋳造又は熱間加工により得られたビレットを熱間加工して油井管にする。熱間加工としてたとえばマンネスマン法を実施する。熱間加工としてユジーン−セジュネル方式等の熱間押出を実施してもよいし、エルハルト方式等の鍛造管製造方法を実施してもよい。熱間加工後の油井管に焼き入れ及び焼き戻し処理を実施する。焼き入れ処理は周知の方法で実施する。たとえば、焼き入れ温度は900〜950℃とする。ただし、他の温度範囲であってもよい。   A billet obtained by continuous casting or hot working is hot worked into an oil well pipe. For example, the Mannesmann method is performed as hot working. As the hot working, a hot extrusion such as a Eugene-Segenel method may be performed, or a forged pipe manufacturing method such as an Erhardt method may be performed. Quench and temper the oil well pipe after hot working. The quenching process is performed by a known method. For example, the quenching temperature is 900 to 950 ° C. However, other temperature ranges may be used.

焼き戻し処理において、好ましい焼き戻し温度の下限は500℃である。一方、焼き戻し温度が高すぎると、残留オーステナイトが析出し、降伏応力を758〜860MPaとすることができない。そのため、好ましい焼き戻し温度の上限は600℃である。   In the tempering treatment, a preferable lower limit of the tempering temperature is 500 ° C. On the other hand, if the tempering temperature is too high, retained austenite precipitates and the yield stress cannot be 758 to 860 MPa. Therefore, the upper limit of the preferable tempering temperature is 600 ° C.

さらに、本発明の実施の形態によるマルテンサイト系ステンレス鋼は、以下の式(1)及び(2)を満たす。   Furthermore, the martensitic stainless steel according to the embodiment of the present invention satisfies the following formulas (1) and (2).

922.6−554.5C−50.9Mn+2944.8P+1.056Cr−81.1Ni+95.8Mo−1584.9Al−376.1N≧600 (1)   922.6-554.5C-50.9Mn + 2944.8P + 1.056Cr-81.1Ni + 95.8Mo-1584.9Al-376.1N ≧ 600 (1)

30C+0.5Mn+Ni−1.5Si−Cr−Mo+7.9≧0 (2)
式(1)を満たせば、Ac1変態点を高くなるため、降伏応力が758〜860MPaの範囲での焼き戻し曲線の勾配を小さくできる。また、式(2)を満たせば、組織のマルテンサイト化を促進できる。そのため、式(1)及び式(2)を満たせば、758〜860MPaの降伏応力が得られる焼き戻し温度範囲を従来よりも大きくすることができる。そのため、操業中の焼き戻し温度の設定変更に基づく生産性の低下を抑制できる。
30C + 0.5Mn + Ni-1.5Si-Cr-Mo + 7.9 ≧ 0 (2)
It satisfies the equation (1), since the higher the transformation point A c1, the yield stress can be reduced the gradient of the tempering curves in the range of 758~860MPa. Moreover, if the formula (2) is satisfied, the formation of martensite in the structure can be accelerated. Therefore, if the formulas (1) and (2) are satisfied, the tempering temperature range in which a yield stress of 758 to 860 MPa can be obtained can be made larger than before. Therefore, it is possible to suppress a decrease in productivity based on a setting change of the tempering temperature during operation.

さらに、式(2)を満足することにより油井用鋼材として必要な高い靭性を得ることもできる。   Furthermore, high toughness required as oil well steel can be obtained by satisfying the formula (2).

なお、本実施の形態よるマルテンサイト系ステンレス鋼がTiを含有する場合、式(1)の代わりに式(3)を満たす。また、マルテンサイト系ステンレス鋼がCuを含有する場合、式(2)の代わりに式(4)を満たす。   In addition, when the martensitic stainless steel by this Embodiment contains Ti, Formula (3) is satisfy | filled instead of Formula (1). Moreover, when a martensitic stainless steel contains Cu, Formula (4) is satisfy | filled instead of Formula (2).

922.6−554.5C−50.9Mn+2944.8P+1.056Cr−81.1Ni+95.8Mo−125.1Ti−1584.9Al−376.1N≧600 (3)   922.6-554.5C-50.9Mn + 2944.8P + 1.056Cr-81.1Ni + 95.8Mo-125.1Ti-1584.9Al-376.1N ≧ 600 (3)

30C+0.5Mn+Ni+0.5Cu−1.5Si−Cr−Mo+7.9≧0 (4)   30C + 0.5Mn + Ni + 0.5Cu-1.5Si-Cr-Mo + 7.9 ≧ 0 (4)

なお、上記ではマルテンサイト系ステンレス鋼を鋼管にしたが、マルテンサイト系ステンレス鋼を鋼板にしてもよい。   In the above description, martensitic stainless steel is used as the steel pipe, but martensitic stainless steel may be used as the steel plate.

表1に示す化学組成を有する供試材を製造し、各供試材において、降伏応力が758〜860MPaになる焼き戻し温度範囲を調査した。さらに、各供試材の靭性及び耐食性を調査した。

Figure 0004337712
Test materials having the chemical composition shown in Table 1 were produced, and the tempering temperature range in which the yield stress was 758 to 860 MPa was investigated in each test material. Furthermore, the toughness and corrosion resistance of each specimen were investigated.
Figure 0004337712

表1に示す化学組成を有する鋼を溶製した。表1に示すように、供試材1〜11の化学組成は本発明の化学組成の範囲内であった。   Steel having the chemical composition shown in Table 1 was melted. As shown in Table 1, the chemical compositions of the test materials 1 to 11 were within the range of the chemical composition of the present invention.

ここで、式(1)の左辺をF1、式(2)の左辺をF2とし、各供試材のF1及びF2を求めた。このとき、Tiを含有する供試材に対してはF1の代わりに式(3)の左辺=F3を求めた。また、Cuを含有する供試材に対してはF2の代わりに式(4)の左辺=F4を求めた。   Here, F1 and F2 of each test material were obtained with the left side of Formula (1) as F1 and the left side of Formula (2) as F2. At this time, the left side of formula (3) = F3 was obtained instead of F1 for the test material containing Ti. Further, for the specimen containing Cu, the left side of formula (4) = F4 was determined instead of F2.

供試材1〜供試材11はいずれもF1〜F4が本発明の範囲内であった。具体的にはF1及びF3が600以上であり、F2及びF4が0以上であった。   As for the test material 1-the test material 11, all F1-F4 was in the range of this invention. Specifically, F1 and F3 were 600 or more, and F2 and F4 were 0 or more.

一方、供試材12及び13では、化学組成が本発明の範囲内であるものの、F3値が600未満であった。供試材14〜16ではC含有量が本発明の上限値を超えた。さらに、供試材14はF3値が600未満であり、供試材15はF4値が0未満であった。   On the other hand, in the test materials 12 and 13, although the chemical composition was within the range of the present invention, the F3 value was less than 600. In the test materials 14 to 16, the C content exceeded the upper limit of the present invention. Further, the sample material 14 had an F3 value of less than 600, and the sample material 15 had an F4 value of less than 0.

供試材1〜16の溶鋼を鋳造して連続鋳造材にした。製造した連続鋳造材を熱間鍛造及び熱間圧延して厚さ15mm、幅120mm、長さ1000mmの複数の鋼板にした。熱間鍛造及び熱間圧延後の鋼板は常温まで空冷した。得られた鋼板を用いて以下の試験を実施した。   The molten steels of test materials 1 to 16 were cast into continuous cast materials. The manufactured continuous cast material was hot forged and hot rolled into a plurality of steel plates having a thickness of 15 mm, a width of 120 mm, and a length of 1000 mm. The steel sheet after hot forging and hot rolling was air-cooled to room temperature. The following test was implemented using the obtained steel plate.

1.焼き戻し温度範囲
初めに、得られた複数の鋼板を焼き入れした。このとき、焼き入れ温度は910℃にした。続いて、焼き入れした鋼板に対して焼き戻しを実施した。このとき、焼き戻し温度を450〜650℃の温度範囲内で変化させた。各焼き戻し温度で焼き戻しを実施した鋼板を用いて引張試験を実施した。具体的には、鋼板から平行部の直径が6.35mm、平行部の長さが25.4mmの丸棒試験片を作製した。作製した丸棒試験片を用いてJIS Z2241に基づいて常温で引張試験を実施し、降伏応力を求めた。引張試験後、各供試材について降伏応力が758〜860MPaの範囲内となる焼き戻し温度範囲ΔTを求めた。なお、0.2%耐力を降伏応力とした。
1. Tempering temperature range First, the obtained steel sheets were quenched. At this time, the quenching temperature was 910 ° C. Subsequently, tempering was performed on the quenched steel sheet. At this time, the tempering temperature was changed within a temperature range of 450 to 650 ° C. Tensile tests were performed using steel plates tempered at each tempering temperature. Specifically, a round bar test piece having a parallel part diameter of 6.35 mm and a parallel part length of 25.4 mm was prepared from the steel plate. A tensile test was performed at room temperature based on JIS Z2241 using the prepared round bar test piece, and yield stress was obtained. After the tensile test, a tempering temperature range ΔT in which the yield stress was in the range of 758 to 860 MPa was determined for each specimen. The 0.2% yield strength was defined as the yield stress.

表2に各供試材における降伏応力が758〜860MPaとなる焼き戻し温度範囲を示す。

Figure 0004337712
Table 2 shows the tempering temperature range in which the yield stress in each specimen is 758 to 860 MPa.
Figure 0004337712

表2中のΔTは各供試材の降伏応力が758〜860MPaとなる焼き戻し温度のうちの最高温度と最低温度との差分値である。なお、単位は℃である。   ΔT in Table 2 is a difference value between the highest temperature and the lowest temperature among the tempering temperatures at which the yield stress of each specimen becomes 758 to 860 MPa. The unit is ° C.

表2に示すように、供試材1〜11はいずれもΔTが40℃以上であった。一方、供試材12及び13はF3値が600未満であったため、ΔTが40℃未満となった。供試材14はC含有量が高く、かつ、F3値が600未満であったためΔTが40℃未満となった。供試材15及び16はC含有量が高いため、ΔTが40℃未満となった。   As shown in Table 2, all of the test materials 1 to 11 had ΔT of 40 ° C. or higher. On the other hand, since the test materials 12 and 13 had an F3 value of less than 600, ΔT was less than 40 ° C. Since the specimen 14 had a high C content and an F3 value of less than 600, ΔT was less than 40 ° C. Since the test materials 15 and 16 had a high C content, ΔT was less than 40 ° C.

図1に供試材1と供試材14における焼き戻し温度と降伏応力の関係を示す。図1に示すように、F3値が600以上である供試材1の焼き戻し曲線C1は758〜860MPaの降伏応力範囲での勾配が小さく、焼き戻し温度範囲ΔT1は110℃であった。一方、F3値が600未満であった供試材14の758〜860MPaの降伏応力範囲での焼き戻し曲線C2の勾配は大きく、焼き戻し温度範囲ΔT2は20℃と小さかった。   FIG. 1 shows the relationship between the tempering temperature and the yield stress in the specimen 1 and specimen 14. As shown in FIG. 1, the tempering curve C1 of the specimen 1 having an F3 value of 600 or more had a small gradient in the yield stress range of 758 to 860 MPa, and the tempering temperature range ΔT1 was 110 ° C. On the other hand, the slope of the tempering curve C2 in the yield stress range of 758 to 860 MPa of the specimen 14 having an F3 value of less than 600 was large, and the tempering temperature range ΔT2 was as small as 20 ° C.

2.靭性
表3に各供試材の靭性値を求めた結果を示す。

Figure 0004337712
2. Toughness Table 3 shows the results of determining the toughness value of each specimen.
Figure 0004337712

靭性試験は以下のとおり実施した。得られた鋼板を910℃で焼き入れし、続いて降伏応力が表3に示す値となるように焼き戻しを実施した。焼き戻しを実施した鋼板からJISZ2202に基づく10mm幅のVノッチ試験片を作製した。   The toughness test was conducted as follows. The obtained steel plate was quenched at 910 ° C. and subsequently tempered so that the yield stress was a value shown in Table 3. A 10 mm wide V-notch test piece based on JISZ2202 was produced from the tempered steel plate.

作製したVノッチ試験片を用いてJIS Z2242に基づいて−40℃にてシャルピー衝撃試験を実施し、吸収エネルギを求めた。   A Charpy impact test was performed at −40 ° C. based on JIS Z2242 using the prepared V-notch test piece, and the absorbed energy was obtained.

表3中の吸収エネルギの単位はJである。供試材1〜11はいずれもF2又はF4値が0以上であるため、吸収エネルギが100Jを超え、高い靭性を示した。一方、供試材15はF4値が0未満であったため、吸収エネルギが低かった。   The unit of absorbed energy in Table 3 is J. Since all of the test materials 1 to 11 had an F2 or F4 value of 0 or more, the absorbed energy exceeded 100 J and exhibited high toughness. On the other hand, since the sample material 15 had an F4 value of less than 0, the absorbed energy was low.

3.耐食性
湿潤炭酸ガス環境下での耐食性は以下の炭酸ガス腐食試験を実施することにより評価した。靭性評価時と同じ条件で焼き入れ及び焼き戻しを実施した鋼板から幅20mm×厚さ3mm×長さ50mmの試験片を切り出した。切り出した試験片の表面を600番エメリー紙により研磨した後、脱脂及び乾燥した。
3. Corrosion resistance Corrosion resistance in a wet carbon dioxide environment was evaluated by carrying out the following carbon dioxide corrosion test. A test piece having a width of 20 mm, a thickness of 3 mm, and a length of 50 mm was cut out from a steel plate that had been quenched and tempered under the same conditions as in toughness evaluation. The surface of the cut test piece was polished with # 600 emery paper, and then degreased and dried.

作製した試験片を9.73気圧のCOガスと0.014気圧のHSとを飽和させた25%NaCl水溶液に720時間浸漬した。なお、試験中は水溶液の温度を165℃に維持した。 The prepared test piece was immersed in a 25% NaCl aqueous solution saturated with 9.73 atm CO 2 gas and 0.014 atm H 2 S for 720 hours. During the test, the temperature of the aqueous solution was maintained at 165 ° C.

試験後、試験片の腐食減量を求めた。具体的には、試験前の試験片の重量から試験後の試験片の重量を差分した値を腐食減量とした。さらに、目視により試験片表面の局部腐食の有無を確認した。腐食減量が7.7g未満であり、かつ、局部腐食が発生していなければ湿潤炭酸ガス環境下での耐食性が高いと判断した。   After the test, the corrosion weight loss of the test piece was determined. Specifically, the value obtained by subtracting the weight of the test piece after the test from the weight of the test piece before the test was taken as the corrosion weight loss. Furthermore, the presence or absence of local corrosion on the surface of the test piece was confirmed visually. If the corrosion weight loss was less than 7.7 g and no local corrosion occurred, it was judged that the corrosion resistance in a wet carbon dioxide environment was high.

さらに、湿潤硫化水素環境下での耐SSC性を以下のSSC試験を実施することにより評価した。靭性評価時と同じ条件で焼き入れ及び焼き戻しを実施した鋼板から平行部の直径6.3mm、平行部の長さ25.4mmの引張試験片を作製した。作製した引張試験片を用いてNACE TM0177−96 Method Aに基づいてプルーフリング試験を実施した。このとき、0.03atmのHS(CObal.)を飽和させた20%NaCl水溶液に試験片を720時間浸漬した。NaCl水溶液のpHは4.5とし、試験中、水溶液の温度を25℃に維持した。試験後、目視にて割れの有無を確認した。 Furthermore, the SSC resistance in a wet hydrogen sulfide environment was evaluated by carrying out the following SSC test. A tensile test piece having a parallel part diameter of 6.3 mm and a parallel part length of 25.4 mm was prepared from a steel sheet which had been quenched and tempered under the same conditions as those during toughness evaluation. A proof ring test was performed based on NACE TM0177-96 Method A using the prepared tensile test pieces. At this time, the test piece was immersed in a 20% NaCl aqueous solution saturated with 0.03 atm of H 2 S (CO 2 bal.) For 720 hours. The pH of the aqueous NaCl solution was 4.5, and the temperature of the aqueous solution was maintained at 25 ° C. during the test. After the test, the presence or absence of cracks was confirmed visually.

表4に耐食性試験の結果を示す。

Figure 0004337712
Table 4 shows the results of the corrosion resistance test.
Figure 0004337712

表中の炭酸ガス腐食試験における「○」は、腐食減量が7.7g以下であり、かつ、局部腐食が発生していないことを示す。また、SSC腐食試験における「○」は割れが発生していないことを示す。供試材1〜11いずれも高い耐食性を有していた。   In the table, “◯” in the carbon dioxide gas corrosion test indicates that the corrosion weight loss is 7.7 g or less and that local corrosion has not occurred. In addition, “◯” in the SSC corrosion test indicates that no crack has occurred. All of the test materials 1 to 11 had high corrosion resistance.

以上、本発明の実施の形態を説明したが、上述した実施の形態は本発明を実施するための例示に過ぎない。よって、本発明は上述した実施の形態に限定されることなく、その趣旨を逸脱しない範囲内で上述した実施の形態を適宜変形して実施することが可能である。   While the embodiments of the present invention have been described above, the above-described embodiments are merely examples for carrying out the present invention. Therefore, the present invention is not limited to the above-described embodiment, and can be implemented by appropriately modifying the above-described embodiment without departing from the spirit thereof.

本発明によるマルテンサイト系ステンレス鋼は、硫化水素、炭酸ガス、塩素イオン等の腐食性物質を含む腐食環境で使用される鋼材として利用可能である。特に、油井やガス井といった湿潤硫化水素環境及び湿潤炭酸ガス環境における生産設備用鋼材、地熱発電設備用鋼材、炭酸ガス除去設備用鋼材、油井管として使用される鋼管に利用可能である。   The martensitic stainless steel according to the present invention can be used as a steel material used in a corrosive environment containing corrosive substances such as hydrogen sulfide, carbon dioxide gas, and chlorine ions. In particular, the present invention is applicable to steel materials for production equipment, steel materials for geothermal power generation equipment, steel materials for carbon dioxide removal equipment, and steel pipes used as oil well pipes in wet hydrogen sulfide environments and wet carbon dioxide environments such as oil wells and gas wells.

本発明の実施例における供試材1と供試材14の降伏応力と焼き戻し温度との関係を示す図である。It is a figure which shows the relationship between the yield stress and tempering temperature of the specimen 1 and the specimen 14 in the Example of this invention. 従来の高Moマルテンサイト系ステンレス鋼の降伏応力と焼き戻し温度との関係を示す図である。It is a figure which shows the relationship between the yield stress and tempering temperature of the conventional high Mo martensitic stainless steel.

Claims (4)

質量%で、C:0.001〜0.01%、Si:0.5%以下、Mn:0.1〜3.0%、P:0.04%以下、S:0.01%以下、Cr:10〜15%、Ni:4〜8%、Mo:2.8〜5.0%、Al:0.001〜0.10%、N:0.07%以下を含有し、残部はFe及び不純物からなり、式(1)及び式(2)を満足し、
758〜860MPaの降伏応力を有するマルテンサイト系ステンレス鋼。
922.6−554.5C−50.9Mn+2944.8P+1.056Cr−81.1Ni+95.8Mo−1584.9Al−376.1N≧600 (1)
30C+0.5Mn+Ni−1.5Si−Cr−Mo+7.9≧0 (2)
ここで、式中の記号は各元素の含有量(質量%)である。
In mass%, C: 0.001 to 0.01%, Si: 0.5% or less, Mn: 0.1 to 3.0%, P: 0.04% or less, S: 0.01% or less, Cr: 10-15%, Ni: 4-8%, Mo: 2.8-5.0%, Al: 0.001-0.10%, N: 0.07% or less, the balance being Fe And satisfying the formula (1) and the formula (2),
Martensitic stainless steel having a yield stress of 758 to 860 MPa.
922.6-554.5C-50.9Mn + 2944.8P + 1.056Cr-81.1Ni + 95.8Mo-1584.9Al-376.1N ≧ 600 (1)
30C + 0.5Mn + Ni-1.5Si-Cr-Mo + 7.9 ≧ 0 (2)
Here, the symbol in a formula | equation is content (mass%) of each element.
質量%で、C:0.001〜0.01%、Si:0.5%以下、Mn:0.1〜3.0%、P:0.04%以下、S:0.01%以下、Cr:10〜15%、Ni:4〜8%、Mo:2.8〜5.0%、Al:0.001〜0.10%、N:0.07%以下と、
Ti:0.25%以下、V:0.25%以下、Nb:0.25%以下、Zr:0.25%以下のうちの1種以上とを含有し、残部はFe及び不純物からなり、式(2)及び式(3)を満足し、
758〜860MPaの降伏応力を有するマルテンサイト系ステンレス鋼。
30C+0.5Mn+Ni−1.5Si−Cr−Mo+7.9≧0 (2)
922.6−554.5C−50.9Mn+2944.8P+1.056Cr−81.1Ni+95.8Mo−125.1Ti−1584.9Al−376.1N≧600 (3)
ここで、式中の記号は各元素の含有量(質量%)である。
In mass%, C: 0.001 to 0.01%, Si: 0.5% or less, Mn: 0.1 to 3.0%, P: 0.04% or less, S: 0.01% or less, Cr: 10-15%, Ni: 4-8%, Mo: 2.8-5.0%, Al: 0.001-0.10%, N: 0.07% or less,
Ti: 0.25% or less , V: 0.25% or less , Nb: 0.25% or less , Zr: one or more of 0.25% or less , and the balance consists of Fe and impurities, Satisfying formula (2) and formula (3),
Martensitic stainless steel having a yield stress of 758 to 860 MPa.
30C + 0.5Mn + Ni-1.5Si-Cr-Mo + 7.9 ≧ 0 (2)
922.6-554.5C-50.9Mn + 2944.8P + 1.056Cr-81.1Ni + 95.8Mo-125.1Ti-1584.9Al-376.1N ≧ 600 (3)
Here, the symbol in a formula | equation is content (mass%) of each element.
質量%で、C:0.001〜0.01%、Si:0.5%以下、Mn:0.1〜3.0%、P:0.04%以下、S:0.01%以下、Cr:10〜15%、Ni:4〜8%、Mo:2.8〜5.0%、Al:0.001〜0.10%、N:0.07%以下と、
Ti:0.25%以下、V:0.25%以下、Nb:0.25%以下、Zr:0.25%以下のうちの1種以上と、
Cu:1.0%以下とを含有し、残部はFe及び不純物からなり、式(3)及び式(4)を満足し、
758〜860MPaの降伏応力を有するマルテンサイト系ステンレス鋼。
922.6−554.5C−50.9Mn+2944.8P+1.056Cr−81.1Ni+95.8Mo−125.1Ti−1584.9Al−376.1N≧600 (3)
30C+0.5Mn+Ni+0.5Cu−1.5Si−Cr−Mo+7.9≧0 (4)
ここで、式中の記号は各元素の含有量(質量%)である。
In mass%, C: 0.001 to 0.01%, Si: 0.5% or less, Mn: 0.1 to 3.0%, P: 0.04% or less, S: 0.01% or less, Cr: 10-15%, Ni: 4-8%, Mo: 2.8-5.0%, Al: 0.001-0.10%, N: 0.07% or less,
One or more of Ti: 0.25% or less , V: 0.25% or less , Nb: 0.25% or less , Zr: 0.25% or less ,
Cu: 1.0% or less , with the balance being Fe and impurities, satisfying formula (3) and formula (4),
Martensitic stainless steel having a yield stress of 758 to 860 MPa.
922.6-554.5C-50.9Mn + 2944.8P + 1.056Cr-81.1Ni + 95.8Mo-125.1Ti-1584.9Al-376.1N ≧ 600 (3)
30C + 0.5Mn + Ni + 0.5Cu-1.5Si-Cr-Mo + 7.9 ≧ 0 (4)
Here, the symbol in a formula | equation is content (mass%) of each element.
請求項1〜請求項のいずれか1項に記載のマルテンサイト系ステンレス鋼であってさらに、Ca:0.005%以下、Mg:0.005%以下、La:0.005%以下、Ce:0.005%以下のうちの1種以上を含有することを特徴とするマルテンサイト系ステンレス鋼。 The martensitic stainless steel according to any one of claims 1 to 3 , further comprising Ca: 0.005% or less , Mg: 0.005% or less , La: 0.005% or less , Ce : Martensitic stainless steel characterized by containing one or more of 0.005% or less .
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Families Citing this family (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2416670C2 (en) * 2006-08-22 2011-04-20 Сумитомо Метал Индастриз, Лтд. Martensite stainless steel
JP5045178B2 (en) * 2007-03-26 2012-10-10 住友金属工業株式会社 Method for manufacturing bend pipe for line pipe and bend pipe for line pipe
CN101956146A (en) * 2010-10-12 2011-01-26 西安建筑科技大学 High strength super-martensitic stainless steel for oil and gas pipelines and preparation method thereof
BR102014005015A8 (en) 2014-02-28 2017-12-26 Villares Metals S/A martensitic-ferritic stainless steel, manufactured product, process for producing forged or rolled bars or parts of martensitic-ferritic stainless steel and process for producing all seamless martensitic-ferritic stainless steel
US10047417B2 (en) * 2015-03-11 2018-08-14 Aktiebolaget Skf Continuous caster roll for a continuous casting machine
RU2698006C9 (en) * 2016-03-04 2019-12-25 Ниппон Стил Корпорейшн Steel material and steel pipe for oil wells
RU2710808C1 (en) * 2016-05-20 2020-01-14 Ниппон Стил Корпорейшн Steel long products for well element and well element
CA3035163A1 (en) * 2016-09-01 2018-03-08 Nippon Steel & Sumitomo Metal Corporation Steel material and oil-well steel pipe
BR112019007842B1 (en) * 2016-10-25 2023-03-14 Jfe Steel Corporation MARTENSITIC STAINLESS STEEL SEAMLESS TUBE FOR TUBULAR PRODUCTS IN THE OIL SECTOR AND ITS PRODUCTION METHOD
AR116495A1 (en) * 2018-09-27 2021-05-12 Nippon Steel Corp MARTENSITIC STAINLESS STEEL MATERIAL
US20220033942A1 (en) * 2018-09-28 2022-02-03 Corning Incorporated Alloyed metals with an increased austenite transformation temperature and articles including the same
EP4006177B1 (en) * 2019-07-24 2024-02-28 Nippon Steel Corporation Martensitic stainless steel pipe and method of manufacturing martensitic stainless steel pipe
JP2023046414A (en) * 2020-01-22 2023-04-05 日鉄ステンレス株式会社 Martensitic stainless steel sheet and martensitic stainless steel member

Family Cites Families (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH05156409A (en) * 1991-11-29 1993-06-22 Nippon Steel Corp High-strength martensite stainless steel having excellent sea water resistance and production thereof
DE69628190T2 (en) * 1995-09-27 2003-11-20 Sumitomo Metal Industries, Ltd. HIGH-STRENGTH, WELDED STEEL STRUCTURES WITH EXCELLENT CORROSION RESISTANCE
CN1243609C (en) * 1997-03-14 2006-03-01 日石三菱株式会社 Mixing device
EP1026273B1 (en) * 1997-07-18 2007-12-19 Sumitomo Metal Industries Limited Martensite stainless steel of high corrosion resistance
JP2000192196A (en) * 1998-12-22 2000-07-11 Sumitomo Metal Ind Ltd Martensitic stainless steel for oil well
JP2001107198A (en) * 1999-10-07 2001-04-17 Nippon Steel Corp Martensitic stainless steel linepipe excellent in ssc resistance and its producing method
US6793744B1 (en) * 2000-11-15 2004-09-21 Research Institute Of Industrial Science & Technology Martenstic stainless steel having high mechanical strength and corrosion
JP2003129190A (en) * 2001-10-19 2003-05-08 Sumitomo Metal Ind Ltd Martensitic stainless steel and manufacturing method therefor
AR042494A1 (en) * 2002-12-20 2005-06-22 Sumitomo Chemical Co HIGH RESISTANCE MARTENSITIC STAINLESS STEEL WITH EXCELLENT PROPERTIES OF CORROSION RESISTANCE BY CARBON DIOXIDE AND CORROSION RESISTANCE BY FISURES BY SULFIDE VOLTAGES
CN100532611C (en) * 2003-07-22 2009-08-26 住友金属工业株式会社 Martensitic stainless steel

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WO2006054430A1 (en) 2006-05-26
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US20080213120A1 (en) 2008-09-04
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