JP3254146B2 - High strength martensitic stainless steel for oil country tubular goods with excellent stress corrosion cracking resistance and high temperature tensile properties. - Google Patents
High strength martensitic stainless steel for oil country tubular goods with excellent stress corrosion cracking resistance and high temperature tensile properties.Info
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- JP3254146B2 JP3254146B2 JP28684996A JP28684996A JP3254146B2 JP 3254146 B2 JP3254146 B2 JP 3254146B2 JP 28684996 A JP28684996 A JP 28684996A JP 28684996 A JP28684996 A JP 28684996A JP 3254146 B2 JP3254146 B2 JP 3254146B2
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Description
【０００１】[0001]
【発明の属する技術分野】この発明は、原油または天然
ガスの油井、ガス井に使用される油井管用の鋼材に関
し、特に炭酸ガス（CO2)、塩素イオン（Cl- ) 、硫化水
素 (H2Ｓ）などを含む腐食環境が極めて厳しい油井、ガ
ス井用として好適な、優れた耐食性と耐応力腐食割れ
性、さらには高温引張り特性を有するマルテンサイト系
ステンレス鋼に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel material for oil country tubular goods used in oil and gas wells of crude oil or natural gas, and particularly to carbon dioxide (CO 2 ), chlorine ion (Cl − ), hydrogen sulfide (H 2 The present invention relates to a martensitic stainless steel having excellent corrosion resistance, stress corrosion cracking resistance, and high-temperature tensile properties, which is suitable for oil and gas wells having extremely severe corrosion environments including S).
【０００２】[0002]
【従来の技術】近年に至り、原油価格の高騰や近い将来
に予想される石油資源の枯渇化を目前にして、従来は顧
みられなかったような深層油田や、開発が一旦は放棄さ
れた腐食性の強いサワーガス田等に対する開発が、世界
的規模で盛んになっている。このような油田、ガス田
は、一般に深度が極めて深く、またその雰囲気は高温で
かつ、CO2 、Cl- 、H2Ｓ等を含む厳しい腐食環境となっ
ている。従って、このような油田、ガス田の採掘に使用
される油井管としては、高温下においても高強度で、し
かも耐食性、耐応力腐食割れ性を兼ね備えた材質が要求
される。さらに最近では、高温でかつ深い井戸の開発を
考慮して、高強度でかつ高温引張り特性を備えることも
重要視されている。2. Description of the Related Art In recent years, in the face of soaring crude oil prices and the depletion of petroleum resources expected in the near future, deep oil fields that have not been neglected and corrosion that has been once abandoned have been developed. The development of strong sour gas fields, etc. is active on a global scale. Such oil fields and gas fields generally have extremely deep depths, and their atmospheres are at high temperatures and have severe corrosive environments including CO 2 , Cl − , H 2 S, and the like. Therefore, oil well pipes used for mining such oil fields and gas fields are required to be made of a material which has high strength even at high temperatures, and also has corrosion resistance and stress corrosion cracking resistance. More recently, in consideration of the development of deep wells at high temperatures, it is also important to provide high strength and high temperature tensile properties.
【０００３】一般に、CO2 、Cl- を含む環境下では、耐
CO2 腐食性、耐CO2 応力腐食割れ性および耐孔食性に優
れた13％Crマルテンサイト系ステンレス鋼管が使用され
るのが普通である。しかしながら、この13％Crマルテン
サイト系ステンレス鋼は、耐硫化物応力腐食割れ性に劣
ることから、H2Ｓが共存する環境では使用できず、この
場合には、高価な２相ステンレス鋼が用いられているの
が実情である。[0003] In general, CO 2, Cl - in an environment containing, resistant
A 13% Cr martensitic stainless steel pipe excellent in CO 2 corrosion resistance, CO 2 stress corrosion cracking resistance and pitting corrosion resistance is usually used. However, this 13% Cr martensitic stainless steel cannot be used in an environment where H 2 S coexists because of its poor sulfide stress corrosion cracking resistance. In this case, an expensive duplex stainless steel is used. That is the fact.
【０００４】このため、耐CO2 腐食性、耐CO2 応力腐食
割れ性および耐孔食性に優れるのは言うまでもなく、耐
硫化物応力腐食割れ性に優れ、しかも高温での引張り特
性が高い油井管用の鋼材の開発が強く望まれていた。[0004] For this reason, it is needless to say that it has excellent resistance to CO 2 corrosion, resistance to CO 2 stress corrosion cracking and pitting corrosion, as well as excellent resistance to sulfide stress corrosion cracking and high tensile properties at high temperatures. The development of steel products was strongly desired.
【０００５】[0005]
【発明が解決しようとする課題】この発明は、上記の実
情に鑑み開発されたもので、前述したような CO2、C
l-、さらにはH2Ｓ等を含む苛酷な腐食環境下においても
優れた耐食性、耐孔食性、耐応力腐食割れ性をそなえ、
しかも高温引張り特性にも優れた油井管用鋼材を提案す
ることを目的とする。SUMMARY OF THE INVENTION The present invention has been developed in view of the above-mentioned circumstances, and has the above-described CO 2 , C 2
l -, and even includes excellent corrosion resistance, pitting corrosion resistance, stress corrosion cracking resistance under severe corrosive environment containing H 2 S or the like,
Moreover, an object of the present invention is to propose a steel material for an oil country tubular good having excellent high-temperature tensile properties.
【０００６】[0006]
【課題を解決するための手段】さて、発明者らは、上記
の目的を達成すべく、代表的なマルテンサイト系ステン
レス鋼である13％Cr鋼をベースとして、種々の合金成分
について、CO2 、Cl-およびH2Ｓを含む環境下での耐硫
化物応力腐食割れ性に及ぼす影響について調査した。そ
の結果、従来よりもＣを低減した13％Cr鋼において、適
量のNi, Mo, Nb, Ｖを添加すると共に、Ｓ，Si, Al, Ｏ
を所定レベルまで低減することによって、熱間加工性が
確保されると共に、上述した環境下での耐硫化物応力腐
食割れ性並びに高温引張り特性が著しく改善されること
の知見を得た。この発明は、上記の知見に立脚するもの
である。Means for Solving the Problems In order to achieve the above-mentioned object, the present inventors have developed various alloy components based on 13% Cr steel, which is a typical martensitic stainless steel, using CO 2. , Cl - it was investigated the effect on the sulfide stress corrosion cracking resistance in an environment containing and H 2 S. As a result, in a 13% Cr steel with a lower C than before, an appropriate amount of Ni, Mo, Nb, V was added and S, Si, Al, O
It has been found that by reducing to a predetermined level, the hot workability is ensured and the sulfide stress corrosion cracking resistance and the high temperature tensile properties under the above-mentioned environment are remarkably improved. The present invention is based on the above findings.
【０００７】すなわち、この発明は、 Ｃ：0.027 mass％以下、 Si：0.50mass％以下、 Mn：0.30〜1.50mass％、 Ｐ：0.03mass％以下、 Ｓ：0.005 mass％以下、 Cr：11.0〜17.0mass％、 Ni：3.0 〜7.0 mass％、 Mo：0.5 〜5.0 mass％、 Al：0.05mass％以下、 Ｎ：0.01〜0.15mass％、 Ｏ：0.005 mass％以下 を含み、かつ Nb：0.20mass％以下、 Ｖ：0.20mass％以下 のうちから選んだ少なくとも１種を含有し、残部は実質
的にFeからなる組成であって、次式 (1)〜(3) 0.02 ≦0.8(Nb%) + (Ｖ%)≦ 0.20 --- (1) (Cr%)＋3.2(Mo%) + 16(Ｎ%)＋0.5(Ni%)−5(Ｃ%)≧17 --- (2) 1.1｛(Cr%) ＋1.5(Si%)＋(Mo%) ｝−(Ni%) −0.5(Mn%)−30｛ (Ｃ%) + (Ｎ%)｝≦11.63 --- (3) の関係を満足することを特徴とする耐応力腐食割れ性お
よび高温引張り特性に優れた油井管用高強度マルテンサ
イト系ステンレス鋼（第１発明）である。That is, the present invention provides: C: 0.027 mass% or less, Si: 0.50 mass% or less, Mn: 0.30 to 1.50 mass%, P: 0.03 mass% or less, S: 0.005 mass% or less, Cr: 11.0 to 17.0 mass%, Ni: 3.0 to 7.0 mass%, Mo: 0.5 to 5.0 mass%, Al: 0.05 mass% or less, N: 0.01 to 0.15 mass%, O: 0.005 mass% or less, and Nb: 0.20 mass% or less , V: at least one selected from 0.20 mass% or less, and the balance is substantially composed of Fe, and the following formulas (1) to (3): 0.02 ≦ 0.8 (Nb%) + ( V%) ≦ 0.20 --- (1) (Cr%) + 3.2 (Mo%) + 16 (N%) + 0.5 (Ni%)-5 (C%) ≧ 17 --- (2) 1.1 ｛(Cr%) +1.5 (Si%) + (Mo%)｝ − (Ni%) −0.5 (Mn%) − 30 ｛(C%) + (N%)｝ ≦ 11.63 --- (3) Is a high-strength martensitic stainless steel for oil country tubular goods excellent in stress corrosion cracking resistance and high-temperature tensile properties (first invention) characterized by satisfying the following relationship:
【０００８】また、この発明は、 Ｃ：0.027 mass％以下、 Si：0.50mass％以下、 Mn：0.30〜1.50mass％、 Ｐ：0.03mass％以下、 Ｓ：0.005 mass％以下、 Cr：11.0〜17.0mass％、 Ni：3.0 〜7.0 mass％、 Mo：0.5 〜5.0 mass％、 Al：0.05mass％以下、 Ｎ：0.01〜0.15mass％、 Ｏ：0.005 mass％以下 を含み、かつ Nb：0.20mass％以下、 Ｖ：0.20mass％以下 のうちから選んだ少なくとも１種を含有し、さらに Cu：0.22〜3.5 mass％、 Ti：0.3 mass％以下、 Zr：0.2 mass％以下、 Ca：0.0005〜0.01mass
％、 Ｂ：0.0005〜0.01mass％、 Ｗ：3.0 mass％以下 のうちから選んだ１種または２種以上を含有し、残部は
実質的にFeからなる組成であって、次式 (1)〜(3) ′ 0.02 ≦0.8(Nb%) + (Ｖ%)≦ 0.20 --- (1) (Cr%)＋3.2(Mo%) + 16(Ｎ%)＋0.5(Ni%)−5(Ｃ%)≧17 --- (2) 1.1｛(Cr%) ＋1.5(Si%)＋(Mo%) ｝−(Ni%) − 0.5｛(Mn%) + (Cu%) ｝−30｛ (Ｃ%) + (Ｎ%)｝≦11.63 --- (3)′ の関係を満足することを特徴とする耐応力腐食割れ性お
よび高温引張り特性に優れた油井管用高強度マルテンサ
イト系ステンレス鋼（第２発明）である。Further, the present invention provides: C: 0.027 mass% or less, Si: 0.50 mass% or less, Mn: 0.30 to 1.50 mass%, P: 0.03 mass% or less, S: 0.005 mass% or less, Cr: 11.0 to 17.0 mass%, Ni: 3.0 to 7.0 mass%, Mo: 0.5 to 5.0 mass%, Al: 0.05 mass% or less, N: 0.01 to 0.15 mass%, O: 0.005 mass% or less, and Nb: 0.20 mass% or less , V: at least one selected from 0.20 mass% or less, Cu: 0.22 to 3.5 mass%, Ti: 0.3 mass% or less, Zr: 0.2 mass% or less, Ca: 0.0005 to 0.01 mass
%, B: 0.0005 to 0.01 mass%, W: 3.0 mass% or less, and the balance is substantially Fe, and the following formula (1) to (3) '0.02 ≤ 0.8 (Nb%) + (V%) ≤ 0.20 --- (1) (Cr%) + 3.2 (Mo%) + 16 (N%) + 0.5 (Ni%) -5 (C%) ≧ 17 --- (2) 1.1 ｛(Cr%) +1.5 (Si%) + (Mo%)｝ − (Ni%) − 0.5 ｛(Mn%) + (Cu%)｝ − 30% (C%) + (N%) ≤ 11.63 --- (3) 'High strength martensite for oil country tubular goods with excellent stress corrosion cracking resistance and high temperature tensile properties Stainless steel (second invention).
【０００９】[0009]
【発明の実施の形態】以下、この発明において鋼の成分
組成を上記の範囲に限定した理由について説明する。 Ｃ：0.027 mass％以下 Ｃは、マルテンサイト系ステンレス鋼の強度に関係する
重要な元素であるが、後述するNiの添加に起因して、焼
もどし時に鋭敏化が起こり易くなる。この鋭敏化を起こ
させないためには 0.027mass％以下とする必要があるの
で、Ｃ量の上限は 0.027mass％とした。なお、このＣ
は、ラインパイプ用鋼のように溶接施工が前提となる場
合には、より一層低減（例えば0.02mass％以下）する必
要があるが、油井管用としてはこの点に特に考慮を払う
必要はなく、上記した鋭敏化の点さえクリアできれば、
多い方が高強度の点からは有利である。従って、強度ひ
いては高温での引張り特性の観点からは0.02〜0.027 ma
ss％程度が好適である。また、この発明では後述するよ
うに、Ｃの低減による強度の低下はNiの添加によって補
うことができる。BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the reason why the composition of steel in the present invention is limited to the above range will be described. C: 0.027 mass% or less C is an important element related to the strength of martensitic stainless steel, but sensitization is likely to occur during tempering due to the addition of Ni described later. In order not to cause this sensitization, the content needs to be 0.027 mass% or less. Therefore, the upper limit of the C content is set to 0.027 mass%. Note that this C
It is necessary to further reduce (for example, 0.02 mass% or less) when welding is assumed as in steel for line pipe, but it is not necessary to pay particular attention to this point for oil country tubular goods. If you can clear the above sensitization points,
A larger amount is advantageous from the point of high strength. Therefore, from the viewpoint of strength and thus tensile properties at high temperatures, 0.02 to 0.027 ma
About ss% is preferable. In addition, in the present invention, as described later, a decrease in strength due to a decrease in C can be compensated for by adding Ni.
【００１０】Si：0.50mass％以下 Siは、通常の製鋼過程において脱酸剤として有用な元素
であるが、0.50mass％を超えると耐CO2 腐食性が低下
し、また熱間加工性も劣化することから、含有量は0.50
mass％以下に限定した。Si: 0.50 mass% or less Si is an element useful as a deoxidizing agent in a normal steelmaking process, but if it exceeds 0.50 mass%, the CO 2 corrosion resistance decreases and the hot workability also deteriorates. Therefore, the content is 0.50
mass% or less.
【００１１】Mn：0.30〜1.50mass％ Mnは、油井管用マルテンサイト系ステンレス鋼としての
強度を確保するために0.30mass％以上を必要とするが、
1.50mass％を超えると靱性に悪影響を及ぼすので、0.30
〜1.50mass％の範囲に限定した。Mn: 0.30 to 1.50 mass% Mn requires 0.30 mass% or more to secure the strength as martensitic stainless steel for oil country tubular goods.
If it exceeds 1.50 mass%, the toughness is adversely affected.
Limited to the range of ~ 1.50 mass%.
【００１２】Ｐ：0.03mass％以下 Ｐは、耐CO2 腐食性、耐CO2 応力腐食割れ性、耐孔食性
および耐硫化物応力腐食割れ性をともに劣化させる元素
であり、その混入は極力低減することが望ましいが、極
端な低減は製造コストの上昇を招く。そこで、工業的に
比較的安価に実施可能で、しかも耐CO2 腐食性、耐CO2
応力腐食割れ性、耐孔食性および耐硫化物応力腐食割れ
性を劣化させない範囲として、0.03mass％以下に定め
た。P: 0.03% by mass or less P is an element that deteriorates both the resistance to CO 2 corrosion, the resistance to CO 2 stress corrosion cracking, the resistance to pitting corrosion and the resistance to sulfide stress corrosion cracking. It is desirable to perform such a process, but an extreme reduction leads to an increase in manufacturing cost. Therefore, it can be implemented industrially at relatively low cost, and is resistant to CO 2 corrosion and CO 2
0.03 mass% or less is defined as a range that does not deteriorate the stress corrosion cracking resistance, pitting corrosion resistance, and sulfide stress corrosion cracking resistance.
【００１３】Ｓ：0.005 mass％以下 Ｓは、パイプ製造過程においてその熱間加工性を著しく
劣化させる元素であり、その混入は極力低減することが
望ましいが、 0.005mass％以下に低減すれば通常の工程
でのパイプ製造が可能となることから、Ｓはその上限を
0.005 mass％とした。S: 0.005 mass% or less S is an element that significantly deteriorates the hot workability in the pipe manufacturing process, and it is desirable to reduce the contamination as much as possible. Since the pipe can be manufactured in the process, S
0.005 mass%.
【００１４】Cr：11.0〜17.0mass％ Crは、耐CO2 腐食性、耐CO2 応力腐食割れ性を確保する
ための基本元素であり、かような観点からは11.0mass％
以上を必要とするが、17.0mass％を超えると熱間加工性
が劣化することから、Crは11.0〜17.0mass％の範囲で含
有させるものとした。Cr: 11.0 to 17.0 mass% Cr is a basic element for ensuring the resistance to CO 2 corrosion and the resistance to CO 2 stress corrosion cracking. From such a viewpoint, 11.0 mass%
The above is required, but if it exceeds 17.0 mass%, the hot workability deteriorates. Therefore, Cr is contained in the range of 11.0 to 17.0 mass%.
【００１５】Ni：3.0 〜7.0 mass％ Niは、保護被膜を強固にして、耐CO2 腐食性、耐CO2 応
力腐食割れ性、耐孔食性および耐硫化物応力腐食割れ性
を高めると共に、Ｃの低減に伴う強度の低下を補う上で
も有用な元素である。しかしながら、含有量が 3.0mass
％未満ではその添加効果に乏しく、一方 7.0mass％を超
えるとマルテンサイト組織の安定性を損なうので、Niは
3.0〜7.0 mass％の範囲に限定した。Ni: 3.0 to 7.0 mass% Ni strengthens the protective coating to enhance the resistance to CO 2 corrosion, the resistance to CO 2 stress corrosion cracking, the resistance to pitting corrosion and the resistance to sulfide stress corrosion cracking, It is also an element that is useful in compensating for a decrease in strength due to a decrease in the content. However, the content is 3.0mass
If the content is less than 7.0 mass%, the stability of the martensitic structure is impaired.
Limited to the range of 3.0 to 7.0 mass%.
【００１６】Mo：0.5 〜5.0 mass％ Moは、Cl- による孔食に対して抵抗性を与える元素であ
るが、 0.5mass％未満ではその効果が認められず、一方
5.0mass％を超えるとδフェライトの発生を招き耐CO2
腐食性、耐CO2 応力腐食割れ性および熱間加工性が低下
することから、Moは 0.5〜5.0 mass％の範囲に限定し
た。[0016] Mo: 0.5 ~5.0 mass% Mo is, Cl - is an element that gives the resistance to pitting is less than 0.5 mass% not observed its effect, whereas
If it exceeds 5.0 mass%, δ ferrite is generated and CO 2 resistance
Mo is limited to the range of 0.5 to 5.0 mass% because the corrosion resistance, CO 2 stress corrosion cracking resistance and hot workability are reduced.
【００１７】Al：0.05mass％以下 Alは、強力な脱酸作用を有し、製鋼における脱酸剤とし
て有効に寄与するが、0.05mass％を超えると靱性に悪影
響を及ぼすことから、Alは0.05mass％以下（好ましくは
0.01〜0.04mass％）の範囲に制限した。Al: 0.05 mass% or less Al has a strong deoxidizing effect and effectively contributes as a deoxidizing agent in steelmaking. However, if it exceeds 0.05 mass%, it adversely affects toughness. mass% or less (preferably
0.01 to 0.04 mass%).
【００１８】Ｎ：0.01〜0.15mass％ Ｎは、耐孔食性を著しく向上させる元素であるが、0.01
mass％未満ではその効果が十分ではなく、一方0.15mass
％を超えると種々の窒化物を形成して靱性を劣化させる
ので、0.01〜0.15mass％好ましくは0.02〜0.15mass％の
範囲で含有させるものとした。N: 0.01 to 0.15 mass% N is an element that significantly improves pitting resistance.
If it is less than mass%, the effect is not enough, while 0.15mass
%, Various nitrides are formed and the toughness is degraded. Therefore, the content is set in the range of 0.01 to 0.15 mass%, preferably 0.02 to 0.15 mass%.
【００１９】Ｏ：0.005 mass％以下 Ｏは、本発明鋼の性能を十分に発揮させる上で、極めて
重要な元素である。すなわち、その含有量が多いと種々
の酸化物を形成して熱間加工性、耐CO2 腐食性、耐CO2
応力腐食割れ性、耐孔食性、耐硫化物応力腐食割れ性お
よび靱性を著しく低下させるので、かようなおそれのな
い 0.005mass％以下まで低減することが重要である。O: 0.005 mass% or less O is an extremely important element for sufficiently exhibiting the performance of the steel of the present invention. That is, if its content is large, various oxides are formed and hot workability, CO 2 corrosion resistance, CO 2 resistance
Since the stress corrosion cracking resistance, pitting corrosion resistance, sulfide stress corrosion cracking resistance and toughness are significantly reduced, it is important to reduce them to 0.005 mass% or less, at which there is no such possibility.
【００２０】Nb：0.20mass％以下、Ｖ：0.20mass％以
下、0.02≦0.8(Nb%) + (Ｖ%)≦0.20 Nb，Ｖはいずれも、高温における強度の向上、および耐
応力腐食割れ性の改善に有用な元素であるが、含有量が
0.20mass％を超えると靱性の劣化を招くので、靱性を損
なうことなく高温強度を確保するためには、Nb：0.20ma
ss％以下、Ｖ：0.20mass％以下でかつ、0.02≦0.8(Nb%)
+ (Ｖ%)≦0.20の関係を満足する範囲で含有させること
が重要である。Nb: 0.20 mass% or less, V: 0.20 mass% or less, 0.02 ≦ 0.8 (Nb%) + (V%) ≦ 0.20 Nb and V are both improvements in strength at high temperatures and resistance to stress corrosion cracking. Is an element that is useful for improving
If it exceeds 0.20 mass%, the toughness will be degraded. To ensure high-temperature strength without impairing the toughness, Nb: 0.20 ma
ss% or less, V: 0.20 mass% or less and 0.02 ≦ 0.8 (Nb%)
It is important that the content be within a range satisfying the relationship of + (V%) ≦ 0.20.
【００２１】以上、必須成分について説明したが、この
発明ではさらに以下に述べる元素についても、必要に応
じて適宜添加することができる。 Cu：0.22〜3.5 mass％ Cuは、保護皮膜を強固にして鋼中への水素の侵入を抑制
し、耐硫化物応力腐食割れ性を高める元素であるが、0.
22mass％未満ではその効果に乏しく、一方 3.5mass％を
超えると高温でCuＳが粒界析出し、熱間加工性の低下を
招くことから、Cuは0.22〜3.5 mass％の範囲で含有させ
るものとした。Although the essential components have been described above, in the present invention, the following elements can be further added as needed. Cu: 0.22 to 3.5 mass% Cu is an element that strengthens the protective film, suppresses the intrusion of hydrogen into steel, and increases sulfide stress corrosion cracking resistance .
When the content is less than 22 mass%, the effect is poor. On the other hand, when the content exceeds 3.5 mass%, CuS precipitates at the high temperature at the grain boundary and causes deterioration in hot workability. Therefore, Cu is contained in the range of 0.22 to 3.5 mass%. And
【００２２】Ca：0.0005〜0.01mass％ Caは、ＳをCaＳとして固定しＳ系介在物を球状化するこ
とにより、介在物の周囲のマトリックスの格子歪を小さ
くして、水素のトラップ能を下げる作用がある。その効
果は、含有量が0.0005mass％未満では顕著ではなく、一
方0.01mass％を超えるとCaＯの増加を招き、耐CO2 腐食
性、耐孔食性の低下を招くことから、Caは0.0005〜0.01
mass％好ましくは0.0010〜0.0050mass％の範囲で含有さ
せるものとした。Ca: 0.0005 to 0.01 mass% Ca fixes S as CaS and spheroidizes S-based inclusions, thereby reducing the lattice distortion of the matrix around the inclusions and lowering the hydrogen trapping ability. There is action. The effect is not as pronounced in content is less than 0.0005 mass%, whereas when it exceeds 0.01 mass% leads to an increase in CaO, resistance CO 2 corrosion, since it leads to a decrease in pitting resistance, Ca is 0.0005 to 0.01
mass%, preferably in the range of 0.0010 to 0.0050 mass%.
【００２３】Ti：0.3 mass％以下、Zr：0.2 mass％以
下、Ｂ：0.0005〜0.01mass％、Ｗ：3.0mass％以下 Ti，Zr，ＢおよびＷはいずれも、強度の向上のみなら
ず、耐応力腐食割れ性を改善する上でも有用な元素であ
るが、Tiは 0.3mass％を超えると、Zrは 0.2mass％を超
えると、Ｗは 3.0mass％を超えるとそれぞれ靱性の劣化
を招き、またＢは0.0005mass％未満では効果が無く、一
方0.01mass％を超えるとやはり靱性の劣化を招くので、
それぞれTi：0.3 mass％以下、Zr：0.2 mass％以下、
Ｂ：0.0005〜0.01mass％、Ｗ：3.0 mass％以下の範囲で
含有させるものとした。Ti: 0.3 mass% or less, Zr: 0.2 mass% or less, B: 0.0005 to 0.01 mass%, W: 3.0 mass% or less All of Ti, Zr, B and W not only improve strength but also endurance. It is a useful element in improving stress corrosion cracking, but when Ti exceeds 0.3 mass%, Zr exceeds 0.2 mass%, and W exceeds 3.0 mass%, the toughness deteriorates. B has no effect if it is less than 0.0005 mass%, while if it exceeds 0.01 mass%, it also causes deterioration of toughness.
Ti: 0.3 mass% or less, Zr: 0.2 mass% or less,
B: 0.0005 to 0.01 mass%, W: 3.0 mass% or less.
【００２４】この発明の鋼は、以上のような成分組成を
有するものであるが、耐食性、耐応力腐食割れ性改善の
観点から添加元素量をさらに限定した。すなわち、本発
明鋼の硫化物応力腐食割れは、孔食状の起点から主とし
て水素脆性によって割れが伝播していくのであるが、割
れの起点となる孔食状の腐食は不働態皮膜の欠陥または
組織上の不均一が原因で発生する。この点、 (Cr%)＋3.2(Mo%) + 16(Ｎ%)＋0.5(Ni%)−5(Ｃ%)≧17 の範囲に制限すれば、孔食状の欠陥の成長および水素の
侵入が抑制され、不働態皮膜の欠陥部からの割れが抑制
されて、耐硫化物応力腐食割れ性の向上を図ることがで
きる。 (Cr%)＋3.2(Mo%) + 16(Ｎ%)＋0.5(Ni%)−5(Ｃ%)
が上記の範囲を外れた場合には、不働態皮膜欠陥部から
の割れが成長して硫化物応力腐食割れが発生し易くな
る。The steel of the present invention has the above-mentioned composition, but the amount of added elements is further limited from the viewpoint of improving corrosion resistance and stress corrosion cracking resistance. That is, in the sulfide stress corrosion cracking of the steel of the present invention, the cracks propagate from the pit-like starting point mainly due to hydrogen embrittlement, but the pitting-like corrosion serving as the starting point of the crack is a defect of the passive film or Caused by uneven tissue. In this regard, if it is limited to the range of (Cr%) + 3.2 (Mo%) + 16 (N%) + 0.5 (Ni%)-5 (C%) ≧ 17, the growth of pit-like defects and Intrusion of hydrogen is suppressed, cracking of the passive film from a defective portion is suppressed, and sulfide stress corrosion cracking resistance can be improved. (Cr%) + 3.2 (Mo%) + 16 (N%) + 0.5 (Ni%)-5 (C%)
Is out of the above range, cracks from the passive film defects are grown and sulfide stress corrosion cracking is likely to occur.
【００２５】また、後述する実施例にも示したとおり、 第１発明： 1.1｛(Cr%) ＋1.5(Si%)＋(Mo%) ｝−(Ni%) −0.5(Mn%)−30｛ (Ｃ%) + (Ｎ%)｝≦11.63 、 第２発明： 1.1｛(Cr%) ＋1.5(Si%)＋(Mo%) ｝−(Ni%) − 0.5｛(Mn%) + (Cu%) ｝−30｛ (Ｃ%) + (Ｎ%)｝≦11.63 の範囲に制限することにより、組織上の不均一をなくし
て割れの起点となる孔食状の腐食を抑制することがで
き、耐硫化物応力腐食割れの発生を防止することができ
る。関係式が上記の範囲を外れた場合には、割れの起点
となる孔食状の腐食が発生し易くなり、耐硫化物応力腐
食割れ性が低下する。Further, as shown in the examples described later, the first invention: 1.1 ｛(Cr%) + 1.5 (Si%) + (Mo%)｝ − (Ni%) − 0.5 (Mn%) − 30 ｛(C%) + (N%)｝ ≦ 11.63 , Second invention: 1.1 ｛(Cr%) + 1.5 (Si%) + (Mo%)｝ − (Ni%) − 0.5 ｛(Mn%) + (Cu%)｝ -30 ｛(C%) + (N%)｝ ≤ 11.63 to eliminate non-uniformity on the structure and suppress pit-like corrosion, which is the starting point of cracking And the occurrence of sulfide stress corrosion cracking can be prevented. When the relational expression is out of the above range, pitting corrosion, which is a starting point of cracking, is likely to occur, and sulfide stress corrosion cracking resistance is reduced.
【００２６】また、この発明では、熱間加工性の観点か
らＳ，Si，Al，Ｏを著しく低減して熱間加工性を向上さ
せている。従って、この鋼を用いて油井管を製造する場
合には、通常の工程に何ら手を加えることなく製造する
ことができる。すなわち、シームレスパイプあるいは電
縫鋼管に成形後、圧延のまま、または 950〜1050℃の温
度に加熱して水冷または空冷により冷却した後、油井鋼
管として必要な強度を得るべく 550〜650 ℃の温度範囲
で焼戻すのが通常である。In the present invention, from the viewpoint of hot workability, S, Si, Al, and O are significantly reduced to improve hot workability. Therefore, when producing an oil country tubular goods using this steel, it is possible to produce the oil country tubular goods without any modification to a normal process. That is, after forming into a seamless pipe or ERW steel pipe, as it is rolled, or after being heated to a temperature of 950 to 5050 ° C and cooled by water cooling or air cooling, a temperature of 550 to 650 ° C to obtain the necessary strength as an oil well steel pipe It is usual to temper in a range.
【００２７】[0027]
【実施例】表１に示す成分組成になる溶鋼を、十分に脱
ガスした後、 100キロ鋼塊とし、研究用モデルシームレ
ス圧延機により外径：3.3 inch（83.82 mm）、肉厚：0.
5inch（12.7mm）のパイプを作製した。ついで各パイプ
から試験片素材を切出し、1000℃で１時間加熱後、空冷
した。さらに焼き戻しを施し、降伏強度を125grade(125
〜140ksi) のレベルに調整した。このように焼き戻した
試験片素材から、厚さ：３mm、幅：30mm、長さ：40mmの
腐食試験片、厚さ：２mm、幅：20mm、長さ：75mmのＵ曲
げ応力腐食割れ試験片および平行部の直径が 6.4mmφの
定荷重引張応力腐食割れ試験片を機械加工によって作製
した。Ｕ曲げ応力腐食割れ試験片は、曲げ治具により曲
率半径が８mmとなるように板厚（ｔ＝２mm) に対して曲
げ応力を付与した状態で試験に供した。EXAMPLE Molten steel having the composition shown in Table 1 was thoroughly degassed to obtain a 100 kg steel ingot. The outer diameter was 3.3 inches (83.82 mm) and the wall thickness was 0.1 mm using a model seamless rolling mill for research.
A 5 inch (12.7 mm) pipe was manufactured. Then, a test piece material was cut out from each pipe, heated at 1000 ° C. for 1 hour, and air-cooled. After further tempering, the yield strength is 125 grade (125
~ 140 ksi). From the test piece material thus tempered, a corrosion test piece having a thickness of 3 mm, a width of 30 mm and a length of 40 mm, a U-bending stress corrosion cracking test piece having a thickness of 2 mm, a width of 20 mm and a length of 75 mm A constant load tensile stress corrosion cracking test piece having a parallel portion diameter of 6.4 mmφ was prepared by machining. The U-bending stress corrosion cracking test piece was subjected to a test in a state where bending stress was applied to a plate thickness (t = 2 mm) so that a radius of curvature was 8 mm by a bending jig.
【００２８】各試験の実施条件は次のとおりである。 ・腐食試験 NaCl：10％水溶液、 CO2：30気圧、温度：200 ℃、期
間：２週間 ・Ｕ曲げ応力腐食割れ性 NaCl：10％水溶液、 CO2：30気圧、温度：200 ℃、期
間：２週間 ・定荷重引張応力腐食割れ試験 ５％NaCl水溶液、H2Ｓ分圧：0.1 気圧(CO2バランス) 、
pH：3.8 (0.5％CH3COOH ＋CH3COONaの添加により調
整）、負荷応力：1.0 σy 、温度：24℃、期間：１か月 評価方法は、腐食試験においてはそれらの重量減から計
算した腐食速度および10倍ルーペ観察による孔食発生の
有無、またＵ曲げ応力腐食割れ試験においては肉眼観察
および断面の光学顕微鏡観察による割れ発生の有無（耐
Ｕ曲げＳＣＣ性）、さらに定荷重引張応力腐食割れ試験
においては所定時間内の破断の有無（耐ＳＳＣ性）とし
た。 ・高温引張り試験 丸棒引張り試験片を用いて 150℃、 200℃の条件で引張
り試験を行い、常温におけるY.S.と高温引張り試験で求
めたY.S.との比をとって評価した。得られた結果を整理
して表２に示す。The operating conditions for each test are as follows. - Corrosion test NaCl: 10% aqueous solution, CO 2: 30 atmospheres, a temperature: 200 ° C., duration: 2 weeks · U bending stress corrosion cracking resistance NaCl: 10% aqueous solution, CO 2: 30 atmospheres, a temperature: 200 ° C., period: 2 weeks ・ Constant load tensile stress corrosion cracking test 5% NaCl aqueous solution, H 2 S partial pressure: 0.1 atm (CO 2 balance)
pH: 3.8 (adjusted by the addition of 0.5% CH 3 COOH + CH 3 COONa), applied stress: 1.0 σy, temperature: 24 ° C, duration: 1 month The evaluation method is the corrosion calculated from the weight loss in the corrosion test. Presence or absence of pitting corrosion by speed and 10-fold loupe observation. In U-bending stress corrosion cracking test, presence or absence of cracking by visual observation and optical microscopic observation of cross section (U-bending SCC resistance), and constant load tensile stress corrosion cracking In the test, the presence or absence of breakage within a predetermined time (SSC resistance) was determined. -High-temperature tensile test A tensile test was performed at 150 ° C and 200 ° C using a round bar tensile test piece, and the ratio of YS at room temperature to YS determined by the high-temperature tensile test was evaluated. Table 2 summarizes the obtained results.
【００２９】[0029]
【表１】 [Table 1]
【００３０】[0030]
【表２】 [Table 2]
【００３１】同表から明らかなように、発明鋼はいずれ
も、耐CO2 腐食性、耐CO2 応力腐食割れ性および耐硫化
物応力腐食割れ性に優れている。また 150℃、 200℃の
高温においても、Y.S.の低下程度が少なく、高強度であ
ることが確かめられた。従って、本発明鋼はH2Ｓを含む
油井環境での油井鋼管として十分使用可能であることが
判る。As is clear from the table, all of the inventive steels have excellent resistance to CO 2 corrosion, resistance to CO 2 stress corrosion cracking and resistance to sulfide stress corrosion cracking. Even at high temperatures of 150 ° C and 200 ° C, it was confirmed that the degree of YS reduction was small and the strength was high. Therefore, it is understood that the steel of the present invention can be sufficiently used as an oil well steel pipe in an oil well environment containing H 2 S.
【００３２】[0032]
【発明の効果】かくして、この発明によれば、CO2 、Cl
- 、H2Ｓ等を含む厳しい腐食環境下においても十分な耐
食性および耐応力腐食割れ性を示し、しかも高温下にお
いても高強度を確保し得るマルテンサイト系ステンレス
鋼を得ることができる。従って、この発明によれば、苛
酷な環境で使用し得る油井管を安価に供給することがで
き、産業の発達に寄与するところ極めて大である。Thus, according to the present invention, CO 2 , Cl
-, H 2 S or the like also exhibits sufficient corrosion resistance and stress corrosion cracking resistance under severe corrosive environments containing, it is possible to obtain a martensitic stainless steel is also capable of ensuring the high strength at high temperatures. Therefore, according to the present invention, an oil country tubular good that can be used in a severe environment can be supplied at a low cost, and it is extremely large that it contributes to industrial development.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 北幅 由一 愛知県半田市川崎町１丁目１番地 川崎 製鉄株式会社 知多製造所内 (56)参考文献 特開 平３−75337（ＪＰ，Ａ) 特開 平７−62499（ＪＰ，Ａ) 特開 昭62−177124（ＪＰ，Ａ) 特開 昭63−171856（ＪＰ，Ａ) 特開 平10−130785（ＪＰ，Ａ) 特開 平７−233445（ＪＰ，Ａ) 特開 平７−62499（ＪＰ，Ａ) 特表 平10−503809（ＪＰ，Ａ) 国際公開96／3532（ＷＯ，Ａ１) (58)調査した分野(Int.Cl.7，ＤＢ名) C22C 38/00 - 38/60 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yuichi Kitazawa 1-1-1, Kawasaki-cho, Handa-shi, Aichi Prefecture Kawata Steel Corporation Chita Works (56) References JP-A-3-75337 (JP, A) JP-A-7-62499 (JP, A) JP-A-62-177124 (JP, A) JP-A-63-171856 (JP, A) JP-A-10-130785 (JP, A) JP-A-7-233445 ( JP, A) JP-A-7-62499 (JP, A) JP-T10-503809 (JP, A) WO 96/3532 (WO, A1) (58) Fields investigated (Int. Cl. 7 , DB) Name) C22C 38/00-38/60
Claims (2)
的にFeからなる組成であって、次式 (1)〜(3) 0.02 ≦0.8(Nb%) + (Ｖ%)≦ 0.20 --- (1) (Cr%)＋3.2(Mo%) + 16(Ｎ%)＋0.5(Ni%)−5(Ｃ%)≧17 --- (2) 1.1｛(Cr%) ＋1.5(Si%)＋(Mo%) ｝−(Ni%) −0.5(Mn%)−30｛ (Ｃ%) + (Ｎ%)｝≦11.63 --- (3) の関係を満足することを特徴とする耐応力腐食割れ性お
よび高温引張り特性に優れた油井管用高強度マルテンサ
イト系ステンレス鋼。C: 0.027 mass% or less, Si: 0.50 mass% or less, Mn: 0.30 to 1.50 mass%, P: 0.03 mass% or less, S: 0.005 mass% or less, Cr: 11.0 to 17.0 mass%, Ni : 3.0 to 7.0 mass%, Mo: 0.5 to 5.0 mass%, Al: 0.05 mass% or less, N: 0.01 to 0.15 mass%, O: 0.005 mass% or less, and Nb: 0.20 mass% or less, V: 0.20 mass% or less, and the balance is substantially composed of Fe, and the following formulas (1) to (3): 0.02 ≦ 0.8 (Nb%) + (V%) ≦ 0.20 --- (1) (Cr%) + 3.2 (Mo%) + 16 (N%) + 0.5 (Ni%)-5 (C%) ≥ 17 --- (2) 1.1 ｛(Cr% ) +1.5 (Si%) + (Mo%)｝ − (Ni%) −0.5 (Mn%) − 30 ｛(C%) + (N%)｝ ≦ 11.63 --- Satisfies (3) High-strength martensitic stainless steel for oil country tubular goods with excellent stress corrosion cracking resistance and high-temperature tensile properties.
％、 Ｂ：0.0005〜0.01mass％、 Ｗ：3.0 mass％以下 のうちから選んだ１種または２種以上を含有し、残部は
実質的にFeからなる組成であって、次式 (1)〜(3) ′ 0.02 ≦0.8(Nb%) + (Ｖ%)≦ 0.20 --- (1) (Cr%)＋3.2(Mo%) + 16(Ｎ%)＋0.5(Ni%)−5(Ｃ%)≧17 --- (2) 1.1｛(Cr%) ＋1.5(Si%)＋(Mo%) ｝−(Ni%) − 0.5｛(Mn%) + (Cu%) ｝−30｛ (Ｃ%) + (Ｎ%)｝≦11.63 --- (3)′ の関係を満足することを特徴とする耐応力腐食割れ性お
よび高温引張り特性に優れた油井管用高強度マルテンサ
イト系ステンレス鋼。2. C: 0.027 mass% or less, Si: 0.50 mass% or less, Mn: 0.30 to 1.50 mass%, P: 0.03 mass% or less, S: 0.005 mass% or less, Cr: 11.0 to 17.0 mass%, Ni : 3.0 to 7.0 mass%, Mo: 0.5 to 5.0 mass%, Al: 0.05 mass% or less, N: 0.01 to 0.15 mass%, O: 0.005 mass% or less, and Nb: 0.20 mass% or less, V: 0.20 at least one selected from mass% or less, Cu: 0.22 to 3.5 mass%, Ti: 0.3 mass% or less, Zr: 0.2 mass% or less, Ca: 0.0005 to 0.01 mass
%, B: 0.0005 to 0.01 mass%, W: 3.0 mass% or less, and the balance is substantially Fe, and the following formula (1) to (3) '0.02 ≤ 0.8 (Nb%) + (V%) ≤ 0.20 --- (1) (Cr%) + 3.2 (Mo%) + 16 (N%) + 0.5 (Ni%) -5 (C%) ≧ 17 --- (2) 1.1 ｛(Cr%) +1.5 (Si%) + (Mo%)｝ − (Ni%) − 0.5 ｛(Mn%) + (Cu%)｝ − 30% (C%) + (N%) ≤ 11.63 --- (3) 'High strength martensite for oil country tubular goods with excellent stress corrosion cracking resistance and high temperature tensile properties Stainless steel.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP28684996A JP3254146B2 (en) | 1996-10-29 | 1996-10-29 | High strength martensitic stainless steel for oil country tubular goods with excellent stress corrosion cracking resistance and high temperature tensile properties. |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP28684996A JP3254146B2 (en) | 1996-10-29 | 1996-10-29 | High strength martensitic stainless steel for oil country tubular goods with excellent stress corrosion cracking resistance and high temperature tensile properties. |
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| Publication Number | Publication Date |
|---|---|
| JPH10130787A JPH10130787A (en) | 1998-05-19 |
| JP3254146B2 true JP3254146B2 (en) | 2002-02-04 |
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| JP3744254B2 (en) * | 1999-04-27 | 2006-02-08 | 住友金属工業株式会社 | Martensitic stainless steel seamless steel pipe with excellent surface quality |
| JP4035919B2 (en) * | 1999-04-27 | 2008-01-23 | 住友金属工業株式会社 | Martensitic stainless steel seamless steel pipe with excellent surface quality |
| US6793744B1 (en) | 2000-11-15 | 2004-09-21 | Research Institute Of Industrial Science & Technology | Martenstic stainless steel having high mechanical strength and corrosion |
| 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 |
| JP4893196B2 (en) * | 2006-09-28 | 2012-03-07 | Ｊｆｅスチール株式会社 | High strength stainless steel pipe for oil well with high toughness and excellent corrosion resistance |
| JP2010242162A (en) * | 2009-04-06 | 2010-10-28 | Jfe Steel Corp | Cr-CONTAINING STEEL PIPE FOR CARBON DIOXIDE GAS INJECTION AT SUPER CRITICAL-PRESSURE |
| JPWO2024070784A1 (en) * | 2022-09-29 | 2024-04-04 |
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| JPS62177124A (en) * | 1986-01-29 | 1987-08-04 | Nippon Steel Corp | Manufacture of steel pipe for thermal well having low rate of creep deformation |
| JPS63171856A (en) * | 1987-01-09 | 1988-07-15 | Hitachi Ltd | Heat-resisting steel and gas turbine using same |
| JP2791804B2 (en) * | 1989-08-16 | 1998-08-27 | 新日本製鐵株式会社 | Martensitic stainless steel with high strength and excellent corrosion resistance |
| JPH0762499A (en) * | 1993-08-26 | 1995-03-07 | Kawasaki Steel Corp | Martensitic stainless steel for oil well pipe |
| CN1159213A (en) * | 1994-07-21 | 1997-09-10 | 新日本制铁株式会社 | Martensitic stainless steel having excellent hot workability and sulfide stress cracking resistance |
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|---|---|
| JPH10130787A (en) | 1998-05-19 |
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