【発明の詳細な説明】〈産業上の利用分野〉この発明は、湿潤な硫化水素を含んだ所謂“サワー環境
”下で引き起こされる硫化物割れ（以下ＳＳＣと略称す
る）に対して高い抵抗性を示し、特にサワー環境で使用
される油井用鋼として好適な高張力鋼に関するものであ
る。[Detailed Description of the Invention] <Industrial Application Field> The present invention provides high resistance to sulfide cracking (hereinafter abbreviated as SSC) caused in a so-called "sour environment" containing wet hydrogen sulfide. The present invention relates to high-strength steel suitable as oil well steel particularly used in sour environments.
ＳＳＣは、サワー環境下で鋼材に応力が作用して生じる
一種の環境脆化現象で、例えば油井管にこれが起きると
、場合によっては油井の放棄にまで至る大きな経済的損
失を余儀無くされる上、有毒ガスの漏洩等により重大事
故につながる危険も大きい。このため、サワー油井やサ
ワーガス井で用いられる鋼材には、まず第一に優れた耐
ＳＳＣ性が必要とされている。SSC is a type of environmental embrittlement phenomenon that occurs when stress is applied to steel materials in a sour environment. For example, when this happens to oil country tubular goods, it can lead to large economic losses that may even lead to the abandonment of the oil well. There is also a high risk of serious accidents due to leakage of toxic gas. Therefore, first of all, steel materials used in sour oil wells and sour gas wells are required to have excellent SSC resistance.
一方、井戸の設計に当っては、鋼材の自重による引っ張
り応力や使用するリグの能力を考慮する必要があり、こ
のためには鋼材の軽量化、即ち高張力化が要求されるこ
とになり、近年の深井戸開発はこの要求を益々切実なも
のとしている。On the other hand, when designing a well, it is necessary to take into account the tensile stress due to the weight of the steel material and the capacity of the rig used, and for this purpose, the weight of the steel material must be reduced, and in other words, the strength of the steel material must be increased. The recent development of deep wells has made this demand even more urgent.
ところが、−Ｊｌに鋼材の強度と耐ＳＳＣ性とは互いに
両立し難い特性であるため、これまで地層深部のサワー
油井やサワーガス井の開発は大きな制約を受けていた。However, since the strength and SSC resistance of -Jl steel materials are incompatible with each other, the development of sour oil wells and sour gas wells in deep geological formations has been severely constrained.
〈従来技術とその問題点〉ところで、従来、鋼材の耐ＳＳＣ性に影響を及ぼす冶金
学的因子の解明にも多大な努力が払われて来ており、次
に示すような事項が一般的に知られていた。即ち、（ａｌ ｒ４の耐ＳＳＣ特性は材料強度が高くなるほ
ど劣化し、逆に材料強度が低（なるほど向上するが、ロ
ックウェル硬さのＣスケールで２０〜２２（抗張力で７
７〜７９ ｋｇｆ／ｍｍ”）以下の材料では一般にＳＳ
Ｃは生じ難い。<Prior art and its problems> By the way, a great deal of effort has been made to elucidate the metallurgical factors that affect the SSC resistance of steel materials, and the following points have generally been studied: It was known. In other words, (the SSC resistance properties of AL R4 deteriorate as the material strength increases, and conversely, the material strength decreases (although it improves, it is 20 to 22 on the Rockwell hardness C scale (7 in tensile strength).
7 to 79 kgf/mm”) is generally SS.
C is unlikely to occur.
（ｂ） 同一強度レベルで比較した場合、鋼材組織と
して”焼戻しマルテンサイト組織”を有する材料が最も
耐ＳＳＣ性が良好であり、これは組織の均質性が高いこ
とによるものである。また、鋼材をこのような組織とす
れば、比較的少量の合金元素の添加で高強度が得られる
利点もある。(b) When compared at the same strength level, the steel material having a "tempered martensitic structure" has the best SSC resistance, and this is due to the high homogeneity of the structure. Further, if the steel material has such a structure, there is an advantage that high strength can be obtained with the addition of a relatively small amount of alloying elements.
そして、焼入れ・焼戻し処理で鋼材組織を均質化するに
は、まず完全に焼きを入れて組織をマルテンサイト化す
る必要があり、そのためにはＣ１Ｃ１５ｉＸ、 Ｃｒ、
、Ｍｏ及びＢの添加が有効である。In order to homogenize the steel structure through quenching and tempering, it is first necessary to completely quench the structure to make it martensite, and for that purpose, C1C15iX, Cr,
, Mo and B are effective.
（Ｃ１焼戻し温度は、Ａｃ、変態点を越えない範囲で高
温はど耐ＳＳＣ性向上に有利であり、これは転位等の内
部歪の減少と炭化物の球状化によると考えられる。(The C1 tempering temperature is advantageous for improving SSC resistance as long as it does not exceed the Ac or transformation point. This is thought to be due to the reduction of internal strains such as dislocations and the spheroidization of carbides.
（ｄ） −般に結晶粒が細かいほど鋼材の耐ＳＳＣ性
は向上するので、Ｎｂ等の添加や、急速加熱焼入れ等の
熱処理による細粒化が耐ＳＳＣ性の改善に有効である。(d) - In general, the finer the crystal grains, the better the SSC resistance of the steel material, so adding Nb or the like or making the grains finer by heat treatment such as rapid heating quenching is effective in improving the SSC resistance.
（ｅ） 鋼材中の不純物元素に関しては、介在吻や粒
界偏析の増大により耐ＳＳＣ性を劣化させる場合が多く
、特にＰやＳは低い方が良い。(e) Concerning impurity elements in steel materials, they often deteriorate SSC resistance due to increased intercalation and grain boundary segregation, and in particular, the lower the content of P and S, the better.
以上のように、耐ＳＳＣ性と冶金学的因子との関係は十
分とは言えないまでも定性的にはかなり明らかとなって
きており、ＡＰＩ（米国石油協会）において、これらを
考慮したサワー環境用油井管の規格化が“Ｃ−９０グレ
ード（降伏強度： ６３．３〜７３．８ｋｇｆ／ｍｍｚ
）”の強度レベルのものについてまでなされるに至って
いる。As described above, the relationship between SSC resistance and metallurgical factors has become qualitatively clear, although it cannot be said to be complete, and the API (American Petroleum Institute) has established a sour environment The standardization of oil country tubular goods for commercial use is “C-90 grade (yield strength: 63.3 to 73.8 kgf/mmz
)” strength level has even been developed.
しかしながら、鋼材の冶金学的因子と耐ＳＳＣ性との間
の関係がある程度解明されたとは言っても、ＳＳＣ対策
を完璧ならしめるほど十分に的を得た知見は得られてお
らず、その後の研究は、（ａ”）８食環境や応力条件が
厳しくなると低強度鋼であってもＳＳＣを生じることが
明らかとなり、上述したｒｓｓｃ防止のための強度上限
の基準」は、サワー環境での使用に際しての単に一般的
な材料選択の目安に過ぎないもので、耐ＳＳＣ性改善の
指針を与えるものではない、（ｂ′）焼戻しマルテンサイト組織を有する鋼材が良好
な耐ＳＳＣ性を示すとは言っても、高強度鋼の場合には
、単に焼戻しマルテンサイト組織とするだけでは必ずし
も実用的に十分な耐ＳＳＣ性を付与出来ない。また焼入
れ性の改善は均質な焼戻しマルテンサイト組織を得て良
好な耐ＳＳＣ性を実現するために有効な手段であり、Ｃ
％ Ｓｉ、 Ｍｎ、Ｃｒ、 Ｍｏ及びＢの添加によって
焼入れ性を改善することはこれまでの油井用鋼にも利用
されてきた手段ではあるが、前記元素はその添加量によ
っては耐ＳＳＣ性を劣化させる場合が多く、焼入れ性の
改善と耐ＳＳＣ性の向上とを両立させることは実際上極
めて困難である、（Ｃ′）焼戻し温度を高くすると耐ＳＳＣ性が向上する
とは言っても、高温で焼戻すことは材料強度を低下させ
ることになり、高温焼戻しで如何に必要な強度を確保す
るかは実際上極めて困難な問題である。このため各種の
固溶元素や炭化物形成元素を添加することが考えられる
が、耐ＳＳＣ性を確保する上で必要な元素の種類や添加
量についての明確な知見はない、（ｄ′）結晶粒の微細化は確かに耐ＳＳＣ性向上に有効
ではあるか、これは鋼材の耐ＳＳＣ性改善の必要条件で
はあっても十分条件ではない、（ｅ′）不純物元素であ
るＰやＳの低減も鋼材の耐ＳＳＣ性改善の必要条件では
あっても十分条件ではない、ことを明らかとし、強度グレードが規格化されたものよ
りも更に高くなると従来の知見に基づくのみでは十分な
耐ＳＳＣ性が安定して達成できないことを示唆するとと
もに、更なる研究は、既ζこ規格化されたグレードのも
のであっても局部的な塑性変形を受けると耐ＳＳＣ性が
大幅に劣化して実用に耐えない場合があることをも明ら
かにしたのである。However, even though the relationship between metallurgical factors and SSC resistance of steel materials has been elucidated to some extent, sufficient targeted knowledge has not been obtained to perfect SSC countermeasures, and subsequent Research has shown that (a)8 SSC can occur even in low-strength steels when the food environment or stress conditions are severe, and the above-mentioned upper strength standard for preventing rssc is not suitable for use in sour environments. (b') It is not true that steel materials with a tempered martensitic structure exhibit good SSC resistance. However, in the case of high-strength steel, simply forming a tempered martensitic structure does not necessarily provide practically sufficient SSC resistance. In addition, improving hardenability is an effective means to obtain a homogeneous tempered martensitic structure and achieve good SSC resistance.
% Si, Mn, Cr, Mo, and B are added to improve hardenability, which has been used in oil well steels to date, but these elements can degrade SSC resistance depending on the amount added. (C') Although increasing the tempering temperature improves SSC resistance, it is actually extremely difficult to achieve both improvements in hardenability and SSC resistance. Tempering reduces the strength of the material, and it is actually an extremely difficult problem to secure the necessary strength through high-temperature tempering. For this reason, it is possible to add various solid solution elements and carbide-forming elements, but there is no clear knowledge of the types and amounts of elements necessary to ensure SSC resistance. (d') Crystal grains Is refinement of the steel material certainly effective in improving SSC resistance? Although this is a necessary condition for improving the SSC resistance of steel materials, it is not a sufficient condition. (e') Reduction of impurity elements P and S is also effective. It has become clear that although this is a necessary condition for improving the SSC resistance of steel materials, it is not a sufficient condition, and if the strength grade is higher than the standardized one, sufficient SSC resistance will not be stable based only on conventional knowledge. In addition to suggesting that this cannot be achieved, further research has shown that even with already standardized grades, SSC resistance deteriorates significantly when subjected to local plastic deformation, rendering them unsuitable for practical use. It also became clear that there are cases.
例えば、油井管では、冷間変形を避けるため細心の注意
を払って製造し、かつ取り扱ったとしても、油井現場に
おいてこれを継手で接続する際などではある程度の局部
的塑性変形は避は難いものである。従って、これらを考
慮するとサワー用途には塑性変形に対して耐ＳＳＣ性の
劣化の小さい鋼が必要になるが、従来の鋼ではこの劣化
が大きく、しかも高強度になるほど塑性変形の形容を受
は易いと言う問題を回避できなかった。For example, even if oil country tubular goods are manufactured and handled with the utmost care to avoid cold deformation, some degree of local plastic deformation is unavoidable when connecting them with joints at oil well sites. It is. Therefore, taking these into consideration, a steel with low deterioration in SSC resistance due to plastic deformation is required for sour applications, but with conventional steel, this deterioration is large, and the higher the strength, the less it is susceptible to plastic deformation. I couldn't avoid the easy problem.
く問題点を解決するための手段〉本発明者等は、上述のような観点から、優れた耐ＳＳＣ
性と高強度とを兼ね備え、しかも塑性変形による耐ＳＳ
Ｃ性の劣化を伴うことのない高張力油井用鋼を提供すべ
（更なる研究を重ねた結果、以下に示される如き知見が
得られたのである。Means for Solving the Problems> From the above-mentioned viewpoint, the present inventors have developed a method with excellent SSC resistance.
It has both high strength and high strength, and also has SS resistance due to plastic deformation.
It is necessary to provide a high tensile strength oil well steel that does not suffer from deterioration of carbon properties (as a result of further research, the following findings were obtained).
ｉ）油井用鋼においては、所望強度と焼入れ性を確保す
るため所定量のＣ５５ｔ、 Ｍｎ、 Ｃｒ及びＭｏの添
加は不可欠である上、耐ＳＳＣ性向上のために均質性の
高い焼戻しマルテンサイトを主体とした組織が必要であ
るが、塑性変形による耐ＳＳＣ性の劣化は焼戻し組織中
の炭化物分布に大きく左右されるものであり、前記強度
確保成分であるＳｉ、ＭｎＸＣｒ及びＭｏはこの炭化物
分布を不均一にしがちであるので、それらの含有量は総
合的に十分な調整を行う必要があること。i) In steel for oil wells, it is essential to add a certain amount of C55t, Mn, Cr and Mo to ensure the desired strength and hardenability, and it is also necessary to add highly homogeneous tempered martensite to improve SSC resistance. However, the deterioration of SSC resistance due to plastic deformation is largely influenced by the carbide distribution in the tempered structure, and the strength-ensuring components Si, MnXCr, and Mo control this carbide distribution. Since they tend to be non-uniform, it is necessary to comprehensively and sufficiently adjust their contents.
ｉｉ ）つまり、鋼材内部歪の減少と炭化物を球状化し
て靭性を改善するためには、油井用鋼材の焼戻しはでき
るだけ高温で行う必要があるが、従来の油井用鋼では高
温焼戻しにより旧オーステナイト粒界の炭化物が粗大化
する傾向にあり、塑性変形を受けるとその近傍に歪が集
中して耐ＳＳＣ性の大幅な劣化が引き起こされるもので
あること。ii) In other words, in order to reduce the internal strain of the steel and make carbides spheroidal to improve toughness, oil well steel must be tempered at as high a temperature as possible, but in conventional oil well steel, high temperature tempering reduces prior austenite grains. The carbides in the area tend to become coarse, and when subjected to plastic deformation, strain concentrates in the vicinity, causing a significant deterioration of SSC resistance.
しかも、上記炭化物の粗大化傾向には、鋼中のＳｉ、Ｍ
ｎｓ Ｃｒ及びＭｏｆｉが大きな影８を与えており、こ
れらの含有量が多くなると粗大炭化物の形成傾向も強（
なること。Moreover, the coarsening tendency of carbides is caused by Si, M in steel.
ns Cr and Mofi cast a large shadow 8, and as their content increases, the tendency to form coarse carbides becomes stronger (
To become a.
ｉｉｉ ）従って、高温焼戻しを行ったとしても、旧オ
ーステナイト粒界の炭化物の粗大化を抑えれば塑性変形
による耐ＳＳＣ性の劣化が極力抑制されるものであり、
そのためには前記Ｓｉｓ Ｍｎｓ Ｃｒ及びＭｏの含有
量を制限するのが有効であること、ｉｖ）ところで、Ｓ
ｉ、 Ｍｎ、、Ｃｒ及びＭｏの含有量を制限すると鋼材
に所望の強度、焼入れ性を確保出来なくなる恐れがある
が、これに適量のＢを添加するとともに、Ｚｒ又はＩｆ
を含有させると、Ｂによる焼入れ性改善効果が加味され
て前記懸念が緩和される上、Ｚｒ又はＨｆは微細な窒化
物を形成して旧オーステナイト粒界の炭化物の粗大化を
防止するのでＳｉｓ Ｍｎｓ Ｃｒ及びと。の含有量制
限も幾分緩和されるので、強度や焼入れ性に対する実際
上の不都合は無くなること。iii) Therefore, even if high-temperature tempering is performed, if the coarsening of carbides at prior austenite grain boundaries is suppressed, the deterioration of SSC resistance due to plastic deformation can be suppressed as much as possible.
For this purpose, it is effective to limit the contents of Sis Mns Cr and Mo; iv) By the way, S
If the content of i, Mn, Cr, and Mo is limited, there is a risk that the desired strength and hardenability of the steel material cannot be secured, but in addition to adding an appropriate amount of B, Zr or If
When Sis Mns is contained, the above-mentioned concerns are alleviated due to the hardenability improving effect of B, and Zr or Hf forms fine nitrides and prevents coarsening of carbides at prior austenite grain boundaries. Cr and. Since the restriction on the content of is also somewhat relaxed, there will be no practical disadvantages regarding strength and hardenability.
■）更に、細粒のオーステナイト粒組織を前身とする焼
戻し組織では炭化物分布が均一化しているので耐ＳＳＣ
性に好結果をもたらされるものであり、また不可避不純
物中のＳやＰは勿論のことＮｉ、 Ｎ％ Ｏ及びＣｕも
鋼材の耐ＳＳＣ性に悪影啓を及ぼすので、前述した対策
に加え、旧オーステナイト粒径を極力抑えるとともに上
記不純物元素の含有量をも総合規制すると局部的塑性変
形の有無に関わらず鋼材の耐ＳＳＣ性は一段と改善され
、・実際上十分に満足できる強度と耐ＳＳＣ性とを備え
た油井用鋼材が得られること。■) Furthermore, in the tempered structure whose predecessor is fine-grained austenite grain structure, the carbide distribution is uniform, so it is resistant to SSC.
In addition to the above-mentioned measures, in addition to the above-mentioned measures, S and P, as well as Ni, N% O, and Cu, which are unavoidable impurities, have a negative impact on the SSC resistance of steel materials. By minimizing the prior austenite grain size and comprehensively regulating the content of the impurity elements mentioned above, the SSC resistance of the steel material will be further improved regardless of the presence or absence of local plastic deformation, resulting in practically satisfactory strength and SSC resistance. Steel materials for oil wells can be obtained.
ｖｉ）その上、上記対策を施した油井用鋼材にＣａ又は
希土類元素（ＲＥＭ）の所定量を添加すると、鋼中の硫
化物系介在物の形状が球状化されることによる耐ＳＳＣ
性改善効果も加味され、耐ＳＳＣ性が一層優れた油井用
鋼材が得られること。vi) Furthermore, when a predetermined amount of Ca or rare earth elements (REM) is added to oil well steel materials that have undergone the above measures, the shape of sulfide-based inclusions in the steel becomes spheroidized, resulting in improved SSC resistance.
It is possible to obtain a steel material for oil wells with even better SSC resistance, taking into account the effect of improving the properties of steel.
この発明は、上記知見に基づいてなされたものであり、油井用鋼を、Ｃ： ０．１５〜０．４５％（以下、成分割合を表す％
は重量割合とする）、Ｓｉ ： ０．１〜０．８％、Ｍｎ ： ０．２〜０．
８％、Ｃｒ ： ０．２％以上１．０％未満、Ｍｏ ：
０．０５〜０．８％、Ａβ： ０．００５〜０．０６０％、Ｂ ： ０．０００１〜０．００３０％を含み、更にＺｒ ： ０．０１〜０．１５％、）Ｉｆ ： ０．００１ 〜０．１５０ ％の１種以
上と、Ｎｂ ： ０．０１〜０．１５％、Ｖ ： ０．０１〜０．１５％、Ｔｉ ： ０．０１〜０．１５％のうちの１種以上とを含有するか、或いは更に、Ｃａ
： ０．００１〜０．１５％、希土類元素： ０．００１〜０．０３０％の１種以上を
も含有するとともに残部が実質的にＦｅから成る成分組
成で、しかも不可避不純物として規制されるＰ％ ３％
Ｃｕｓ Ｎｉｓ Ｎ及びＯの含有量がそれぞれＰ：０．０１％以下、 Ｓ ： ０．００５％以下、Ｃ
ｕ ： ０．１５％未満、 Ｎｉ ： ０．０５％以下
、Ｎ ： ０．０１５０％以下、Ｏ： ０．００５０％
以下を満足しており、かつ“平均粒径：１６μｍ以下の
オーステナイト粒”を前身とする焼戻しマルテンサイト
を主体とした組織を有する如（に構成することによって
、焼戻し温度や局部的な塑性変形に格別な影響を受ける
ことなく優れた耐ＳＳＣ性と高強度とを発揮せしめ得る
ようにした点、に特徴を有するものである。This invention was made based on the above knowledge, and the steel for oil wells is made of C: 0.15 to 0.45% (hereinafter referred to as % representing component ratio
are weight percentages), Si: 0.1-0.8%, Mn: 0.2-0.
8%, Cr: 0.2% or more and less than 1.0%, Mo:
0.05-0.8%, Aβ: 0.005-0.060%, B: 0.0001-0.0030%, further Zr: 0.01-0.15%, ) If: 0. 001 to 0.150%, and one or more of Nb: 0.01 to 0.15%, V: 0.01 to 0.15%, Ti: 0.01 to 0.15%. or further contains Ca
: 0.001 to 0.15%, Rare earth element: 0.001 to 0.030%, and has a component composition in which the balance is substantially Fe, and P, which is regulated as an unavoidable impurity. % 3%
Cus Nis The content of N and O is P: 0.01% or less, S: 0.005% or less, C
u: less than 0.15%, Ni: 0.05% or less, N: 0.0150% or less, O: 0.0050%
By satisfying the following requirements and having a structure mainly composed of tempered martensite whose predecessor is "austenite grains with an average grain size of 16 μm or less," the structure is resistant to tempering temperatures and local plastic deformation. It is characterized by being able to exhibit excellent SSC resistance and high strength without being particularly affected.
次いで、この発明において鋼の成分割合及び旧オーステ
ナイト粒の平均粒径を前記の如くに数値限定した理由を
説明する。Next, the reason why the component ratio of the steel and the average grain size of the prior austenite grains are numerically limited as described above in this invention will be explained.
Ａ）鋼の成分割合ａ）ＣＣ成分には、鋼に油井用鋼として必要な強度を付与する
とともに焼入れ性を向上させる作用があるが、その含有
量が０．１５％未満では前記作用に所望の効果が得られ
ず、−方、０．４５％を越えて含有させると靭性に悪影
響がでてくる上、焼入れ時に焼き割れを生じ易（なるこ
とから、Ｃ含有量は０．１５〜０．４５％と定めた。但
し、より安定な性能を確保し、かつ製造が容易であると
の観点からは、Ｃ含有量を０．２５〜０．３５％に調整
することが好ましい。A) Component ratio of steel a) C The C component has the effect of imparting the necessary strength to steel as steel for oil wells and improving hardenability, but if its content is less than 0.15%, this effect will not be achieved. On the other hand, if the C content exceeds 0.45%, the desired effect will not be obtained, and the toughness will be adversely affected, and quench cracking will easily occur during quenching. However, from the viewpoint of ensuring more stable performance and easy production, it is preferable to adjust the C content to 0.25 to 0.35%.
ｂ）ＳｉＳｉ成分は鋼の脱酸剤としでも焼入れ性向上元素としで
も必要なものであるが、その含有量が０．１％未満では
所望の脱酸効果並びに焼入れ性向上効果を得ることがで
きず、−方、０．８％を越えて含有させると結晶粒の粗
粒化を招いて耐ＳＳＣ性や靭性を劣化することから、Ｓ
ｉ含有量は０．１〜０．８％と定めた。但し、好ましく
は、Ｓｉ含を量は０．１５％以上に調整するのが良い。b) Si The Si component is necessary both as a deoxidizing agent for steel and as an element for improving hardenability, but if its content is less than 0.1%, it is difficult to obtain the desired deoxidizing effect and hardenability improving effect. On the other hand, if the S content exceeds 0.8%, it will cause coarsening of crystal grains and deteriorate SSC resistance and toughness.
The i content was determined to be 0.1 to 0.8%. However, it is preferable to adjust the Si content to 0.15% or more.
ｃ）ＭｎＭｎ成分は主として強度と焼入れ性を高めるために添加
されるものであり、その含有量が０．２％未満では所望
の効果が確保できない。−方、０．８％を越えてＭｎを
含有せしめると鋼中で偏析して局部的に硬化組織を生じ
、耐ＳＳＣ性を劣化させるため、Ｍｎ含有量は０．２〜
０．８％と定めた。c) Mn The Mn component is added mainly to improve strength and hardenability, and if its content is less than 0.2%, the desired effect cannot be ensured. - On the other hand, if Mn is contained in an amount exceeding 0.8%, it will segregate in the steel and cause a locally hardened structure, deteriorating the SSC resistance.
It was set at 0.8%.
ｄ）ＣｒＣｒ成分にも強度と焼入れ性を高める作用があるが、そ
の含有量が０．２％未満では前記作用に所望の効果が得
られず、−方、１．０％以上含有させると、高温焼戻し
を施した場合結晶粒界に粗大な炭化物が形成されて耐Ｓ
ＳＣ性が劣化することから、Ｃｒ含有量は０．２％以上
１．０％未満と定めた。d) Cr The Cr component also has the effect of increasing strength and hardenability, but if its content is less than 0.2%, the desired effect cannot be obtained. , when high-temperature tempering is performed, coarse carbides are formed at grain boundaries, resulting in poor S resistance.
Since the SC property deteriorates, the Cr content was set at 0.2% or more and less than 1.0%.
ｅ）Ｍ。e) M.
Ｍｏも強度と焼入れ性を向上させるために添加するもの
で、特に高温焼戻しによって必要な強度を確保するため
に欠かせないものであるが、その含有量が０．０５％未
満では所望の効果を得ることができず、−方、０．８％
を越えて含有させると粗大炭化物が形成されて耐ＳＳＣ
性の劣化を招くので、Ｍｏ含有量は０．０５〜０．８％
と定めた。Mo is also added to improve strength and hardenability, and is indispensable to ensure the necessary strength especially during high-temperature tempering, but if its content is less than 0.05%, the desired effect will not be achieved. Unable to obtain - 0.8%
If the content exceeds the
Mo content is 0.05 to 0.8% because it causes deterioration of properties.
It was determined that
ｆ）ＡＩＡｌ成分は鋼の脱酸と細粒化のために添加されるもので
あるが、その含有量が０．００５％未満では所望の効果
をうろことができず、−方、０．０６０％を越えて含有
せしめると酸化物系の非金属介在物が増加し耐ＳＳＣ性
が劣化することから、へ！含有量は０．００５〜０．０
６０％と定めた。f) AI Al component is added for deoxidizing steel and refining the grain, but if the content is less than 0.005%, the desired effect cannot be achieved; If the content exceeds 0.060%, oxide-based nonmetallic inclusions will increase and SSC resistance will deteriorate. Content is 0.005-0.0
It was set at 60%.
ｇ） ＢＢ成分には微量添加で鋼の焼入れ性を顕著に改善する作
用があり、この発明の鋼の場合には焼入れ性向上に存効
なＳｉ、 Ｍｎ、Ｃｒ及びＭｏの添加量が耐ＳＳＣ性の
点から制限されるため、これらに変わって所望の焼入れ
性を確保する上で不可欠なものである。しかし、その含
有量が０．００１％未満では上記作用に所望の効果が得
られず、−方、０．００３０％を越えて含有させると結
晶粒界に粗大な炭化物が形成されて耐ＳＣＣ性と靭性が
劣化することから、Ｓ含有量は０．００１〜０．００３
０％と定めた。g) B The B component has the effect of significantly improving the hardenability of steel when added in small amounts, and in the case of the steel of this invention, the added amounts of Si, Mn, Cr, and Mo, which are effective in improving the hardenability, are Since it is limited in terms of SSC properties, it is indispensable in place of these to ensure desired hardenability. However, if the content is less than 0.001%, the desired effect cannot be obtained in the above action, and on the other hand, if the content exceeds 0.0030%, coarse carbides are formed at grain boundaries, resulting in poor SCC resistance. The S content is 0.001 to 0.003 because the toughness deteriorates.
It was set as 0%.
ｈ）Ｚｒ、及び）Ｉｆこれらの成分には、微細な窒化物を形成して粒界炭化物
の粗大化を防ぐことにより耐ＳＳＣ性を向上させる作用
を発揮するので、それぞれ単独で或いは両者を複合して
添加されるものであるが、その含有量がＺｒの場合には
０．０１％未満になると、そしてＨｆの場合には０．０
０１％未満になると前記作用に所望の効果が得られず、
−方、Ｚｒ及びｌｌｆとも０．１５％を越えて含有させ
てもそれ以上の耐ＳＳＣ性改善効果が達せられないばか
りか、逆に靭性劣化を招くことから、Ｚｒ含有量は０．
０１〜０．１５％と、Ｉｆ含有量は０．００１〜０．１
５０％とそれぞれ定めた。h) Zr and) If These components have the effect of improving SSC resistance by forming fine nitrides and preventing coarsening of grain boundary carbides, so they may be used alone or in combination. However, if the content is less than 0.01% in the case of Zr, and 0.0% in the case of Hf.
If it is less than 0.01%, the desired effect cannot be obtained,
On the other hand, even if both Zr and ILF are contained in amounts exceeding 0.15%, not only will no further improvement in SSC resistance be achieved, but conversely, toughness will deteriorate, so the Zr content should be 0.15%.
01-0.15%, If content is 0.001-0.1
Each was set at 50%.
１）Ｎｂ、Ｖ、及びＴｉこれらの成分には、いずれも鋼組織の微細化と強度向上
作用があるので１種又は２種以上添加されるものである
が、いずれの成分も０．０１％未満では前記作用に所望
の効果が得られず、−方、それぞれ０．１５％を越えて
含有させると靭性の劣化を招くことから、Ｎｂ、■及び
Ｔｉ含有量はそれぞれ０．０１〜０．１５％と定めた。1) Nb, V, and Ti Each of these components has the effect of refining the steel structure and improving strength, so one or more of these components are added, but the content of each component is 0.01%. If the content is less than 0.15%, the desired effect cannot be obtained, and if the content exceeds 0.15%, the toughness deteriorates. It was set at 15%.
ｊ）ＰＰは鋼の結晶粒界に偏析して耐ＳＳＣ性を劣化させる傾
向を示す不純物元素であるが、その含有量が０．０１５
％以下であれば実際上格別な問題を生じないことから、
Ｐ含有量は０．０１５％以下と定めた。j) P P is an impurity element that tends to segregate in the grain boundaries of steel and deteriorate SSC resistance, but if its content is 0.015
% or less, no particular problem will arise in practice, so
The P content was determined to be 0.015% or less.
ｋ） ＳＳは硫化物系介在物を増加して鋼の耐ＳＳＣ性を劣化さ
せる不純物元素であるが、その含有量が０．０１５％以
下であれば上記不都合を容認できることから、Ｓ含有量
は０．０１５％以下と定めた。k) S S is an impurity element that increases sulfide inclusions and deteriorates the SSC resistance of steel, but if the content is 0.015% or less, the above disadvantages can be tolerated, so the S content was set at 0.015% or less.
１）ＣｕＣｕは鋼の圧延加熱時に粒界を脆化させる不純物元素で
あるが、その含有量が０．１５％未満であれば実際上該
不都合を容認できることから、Ｃｕ含有量は０．１５％
未満と定めた。1) Cu Cu is an impurity element that embrittles grain boundaries during rolling heating of steel, but if its content is less than 0.15%, this disadvantage can be tolerated in practice, so the Cu content is 0.15%. %
It is set as less than
ｍ） ＮｉＮｉはサワー環境下での孔食発生を助長して耐ＳＳＣ性
を劣化させる不純物元素であるが、その含有量が０．０
５％以下であれば実際上の不都合を容認できることから
、Ｎｉ含有量は０．０５％以下と限定した。m) Ni Ni is an impurity element that promotes pitting corrosion in a sour environment and deteriorates SSC resistance, but if its content is 0.0
Since practical inconveniences can be tolerated if it is 5% or less, the Ni content is limited to 0.05% or less.
ｎ）Ｎ鋼中に不純物元素であるＮが多量に含まれると粗大窒化
物の増加を招いて耐ＳＳＣ性を劣化させるが、その含有
量が０．０１５０％までは許容限度を越えた不都合を引
き起こすことがないので、Ｎ含有量は０．０１５０％以
下と定めた。n) N If a large amount of N, an impurity element, is contained in steel, it will cause an increase in coarse nitrides and deteriorate SSC resistance, but if the content is up to 0.0150%, problems exceeding the allowable limit will occur. The N content was set at 0.0150% or less since this would not cause any damage.
鋼中に不純物元素であるＯが多量に含まれると酸化物系
介在物が増加して耐ＳＳＣ性を劣化させるが、その含有
量が０．００５０％までは許容限度を越えた不都合を引
き起こすことがないので、０含有量は０．００５ｏ％以
下と定めた。If a large amount of O, an impurity element, is contained in steel, oxide-based inclusions will increase and deteriorate SSC resistance, but if the content is up to 0.0050%, it will cause problems beyond the permissible limit. Therefore, the zero content was determined to be 0.005o% or less.
ｐ）Ｃａ、及び希土類元素（ＲＥＭ）これらの成分は、いずれも硫化物系介在物の形状を球状
化して鋼の耐ＳＳＣ性を改善する作用を有しているので
必要に応じて１種以上含有せしめられるものであるが、
いずれも０．００１％未満では前記作用に所望の効果が
得られず、−方、Ｃａの場合には０．０１０％を越えて
、また希土類元素の場合には０．０３０％を越えて含有
させると、いずれの場合も鋼中の介在物が増加して逆に
耐ＳＳＣ性や靭性を劣化させるようになることから、Ｃ
ａ含有量は０．００１〜０．０１０％と、そして希土類
元素は０．００１〜０．０３０％とそれぞれ定めた。p) Ca and rare earth element (REM) Each of these components has the effect of spheroidizing the shape of sulfide inclusions and improving the SSC resistance of steel, so one or more of these components may be used as necessary. Although it can be contained,
If the content is less than 0.001%, the desired effect cannot be obtained; on the other hand, if the content exceeds 0.010% in the case of Ca, and if it exceeds 0.030% in the case of rare earth elements, In either case, inclusions in the steel increase and conversely deteriorate SSC resistance and toughness.
The a content was determined to be 0.001 to 0.010%, and the rare earth element was determined to be 0.001 to 0.030%.
Ｂ）旧オーステナイト粒の平均粒径焼戻しマルテンサイトの前身である旧オーステナイト粒
の平均粒径が１６μｍを越えていると、焼戻し後の鋼材
の粒界炭化物が粗大化して耐ＳＳＣ性の劣化を招くこと
から、綱の組織を“平均粒径が１６μｍ以下のオーステ
ナイト粒を前身とする焼戻しマルテンサイト組織”と限
定した。B) Average grain size of prior austenite grains If the average grain size of prior austenite grains, which is the predecessor of tempered martensite, exceeds 16 μm, grain boundary carbides in the steel after tempering will become coarse, leading to deterioration of SSC resistance. Therefore, the structure of the steel was limited to "a tempered martensitic structure whose predecessor is austenite grains with an average grain size of 16 μm or less."
なお、１６μｍ以下の旧オーステナイト粒は、焼入れ時
の加熱を数”Ｃ／ｓｅｃ〜数十’Ｃ／ｓｅｃの加熱速度
で急速に行う方法や、焼入れを２回以上繰り返して行う
方法で達成できることが知られているが、本発明では、
合金成分の種類と添加量を適正に調整すること及び焼入
れ時の加熱温度を比較的低くすることにより旧オーステ
ナイト粒を１６μｍ以下とすることを可能にした。It should be noted that prior austenite grains of 16 μm or less can be achieved by heating during quenching rapidly at a heating rate of several ''C/sec to several tens of C/sec, or by repeating quenching two or more times. Although known, in the present invention,
By appropriately adjusting the types and amounts of alloy components added and by lowering the heating temperature during quenching, it was possible to reduce the prior austenite grains to 16 μm or less.
鋼を以上のような構成とすることにより、局部的な組成
変形を受けても耐ＳＳＣ性劣化の極めて小さい、即ちサ
ワー環境での耐久性や実用上の取り扱い性が非常に良好
な高張力油井用鋼を得ることができるが、このような効
果は、咳鋼中にそれぞれ０．５％以下のＴａｓ Ｓｎｓ
Ｓｂ−、ＡＳ％ Ｔｅｓ ８１％ Ｓｅ、Ｚｎ、 Ｐ
ｂ、 Ｍｇ、 Ｙ及びＧｏの１種以上が含まれていても
何ら損なわれることがない。また、鋼中にＷが含まれる
と粗大炭化物を形成して耐ＳＳＣ性を劣化する傾向が見
られるので１、Ｗの含有は極力避けるのが良（、不純物
として混入する場合でもその量は０．００４％未満に止
めるのが好ましい。By configuring the steel as described above, it is possible to create a high-tensile oil well with very little deterioration in SSC resistance even when subjected to local compositional deformation, which means that it has very good durability in sour environments and practical handling. However, such an effect can be obtained by adding less than 0.5% of each Tas Sns in the cough steel.
Sb-, AS% Tes 81% Se, Zn, P
Even if one or more of Go, Mg, Y, and Go are included, no damage will be caused. In addition, if W is included in steel, it tends to form coarse carbides and deteriorate SSC resistance, so it is best to avoid containing W as much as possible (even if it is mixed as an impurity, the amount should be 0. It is preferable to keep it below .004%.
次に、この発明を実施例により比較例と対比しながら説
明する。Next, the present invention will be explained using examples and comparing with comparative examples.
〈実施例〉まず、１５０ｋｇの高周波炉で第１表に示される如き成
分組成の鋼を溶製後、熱間圧延によって１２鶴厚の板材
を製造した。続いて、これを８８０℃に加熱して１時間
保持した後水中に焼入れしくなお、鋼番号２１の材料は
鋼番号３のものと同一組成ではあるが、結晶粒度を変え
るために加熱温度を９８０℃としたものである）、更に
６４０〜７２０℃で３０分の焼戻し処理を施して“焼戻
しマルテンサイトを主体とした組織”を有する鋼材とし
た。<Example> First, steel having the composition shown in Table 1 was melted in a 150 kg high-frequency furnace, and then a plate material having a thickness of 12 mm was produced by hot rolling. Subsequently, this was heated to 880°C, held for 1 hour, and then quenched in water.Although the material of Steel No. 21 has the same composition as that of Steel No. 3, the heating temperature was increased to 980°C in order to change the grain size. The steel material was further tempered at 640 to 720°C for 30 minutes to obtain a steel material having a "structure mainly composed of tempered martensite."
このようにして得られた鋼材に関して旧オーステナイト
の結晶粒径、強度及び耐ＳＳＣ性を調査し、その結果を
第２表に示した。Regarding the steel materials thus obtained, the crystal grain size, strength, and SSC resistance of prior austenite were investigated, and the results are shown in Table 2.
耐ＳＳＣ性は、第１図に示されるような“シェルタイブ
試験”と呼ばれる一種の３点曲げ応力付加試験を行って
ＳＳＣの発生する限界付加応力を求め、その値で評価し
た。この試験法は、第２図に示されるような長手方向中
央部にキリ孔を設け２表た試験片１を使用するものであり、中央部の小孔部分が
応力集中により塑性変形するため、実用上の耐ＳＳＣ性
が評価できるものである。なお、試験液としては硫化水
素を飽和した０、５％酢酸溶液（２０℃）が使用され、
浸漬時間は５００時間であった。The SSC resistance was evaluated by performing a type of three-point bending stress adding test called a "shell tie test" as shown in FIG. 1 to determine the critical added stress at which SSC occurs. This test method uses a double-sided test piece 1 with a drilled hole in the center in the longitudinal direction as shown in Figure 2, and the small hole in the center deforms plastically due to stress concentration. This allows evaluation of practical SSC resistance. The test solution used was a 0.5% acetic acid solution (20°C) saturated with hydrogen sulfide.
The immersion time was 500 hours.
第２表に示される結果からも明らかなように、本発明の
条件を満足する鋼はいずれも高い強度と優れた耐ＳＳＣ
性とを兼備しているのに対して、成分組成や旧オーステ
ナイト粒の粒径が本発明で規定する条件から外れている
鋼では十分な耐ＳＳＣ性を示さないことが分かる。As is clear from the results shown in Table 2, all steels that satisfy the conditions of the present invention have high strength and excellent SSC resistance.
However, it can be seen that steels in which the composition and the particle size of prior austenite grains deviate from the conditions specified in the present invention do not exhibit sufficient SSC resistance.
上述のように、この発明によれば、高い強度を有する上
、優れた耐ＳＳＣ性をも安定して発揮する高張力鋼を比
較的コスト安く実現することができ、サワー環境下で使
用される油井部材の性能を一段と向上することが可能と
なるなど、産業上極めて有用な効果がもたらされるので
ある。As described above, according to the present invention, it is possible to produce high-strength steel that not only has high strength but also stably exhibits excellent SSC resistance at a relatively low cost, and is suitable for use in sour environments. This brings about extremely useful effects industrially, such as making it possible to further improve the performance of oil well components.
第１図は、シェルタイブ試験における試験片の支持状態
を示す概略模式図、第２図は、シェルタイブ試験の試験片形状を示しており
、第２図（ａ）はその正面図、第２図中）は側面図であ
る。図面において、１・・・試験片、 ２・・・ガラス丸棒、３・
・・応力付加ボルト。Figure 1 is a schematic diagram showing the supporting state of the test piece in the shell-type test, Figure 2 shows the shape of the test piece in the shell-type test, and Figure 2 (a) is its front view; ) is a side view. In the drawings, 1... test piece, 2... glass round bar, 3...
...Stressed bolt.
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14591386AJPS634046A (en) | 1986-06-20 | 1986-06-20 | High-tensile steel for oil well excellent in resistance to sulfide cracking |
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP14591386AJPS634046A (en) | 1986-06-20 | 1986-06-20 | High-tensile steel for oil well excellent in resistance to sulfide cracking |
| Publication Number | Publication Date |
|---|---|
| JPS634046Atrue JPS634046A (en) | 1988-01-09 |
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP14591386APendingJPS634046A (en) | 1986-06-20 | 1986-06-20 | High-tensile steel for oil well excellent in resistance to sulfide cracking |
| Country | Link |
|---|---|
| JP (1) | JPS634046A (en) |
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7862667B2 (en) | 2007-07-06 | 2011-01-04 | Tenaris Connections Limited | Steels for sour service environments |
| US8002910B2 (en) | 2003-04-25 | 2011-08-23 | Tubos De Acero De Mexico S.A. | Seamless steel tube which is intended to be used as a guide pipe and production method thereof |
| US8221562B2 (en) | 2008-11-25 | 2012-07-17 | Maverick Tube, Llc | Compact strip or thin slab processing of boron/titanium steels |
| US8328960B2 (en) | 2007-11-19 | 2012-12-11 | Tenaris Connections Limited | High strength bainitic steel for OCTG applications |
| US8414715B2 (en) | 2011-02-18 | 2013-04-09 | Siderca S.A.I.C. | Method of making ultra high strength steel having good toughness |
| US8926771B2 (en) | 2006-06-29 | 2015-01-06 | Tenaris Connections Limited | Seamless precision steel tubes with improved isotropic toughness at low temperature for hydraulic cylinders and process for obtaining the same |
| US9644248B2 (en) | 2013-04-08 | 2017-05-09 | Dalmine S.P.A. | Heavy wall quenched and tempered seamless steel pipes and related method for manufacturing said steel pipes |
| US9657365B2 (en) | 2013-04-08 | 2017-05-23 | Dalmine S.P.A. | High strength medium wall quenched and tempered seamless steel pipes and related method for manufacturing said steel pipes |
| US9803256B2 (en) | 2013-03-14 | 2017-10-31 | Tenaris Coiled Tubes, Llc | High performance material for coiled tubing applications and the method of producing the same |
| RU2647061C1 (en)* | 2017-04-27 | 2018-03-13 | Юлия Алексеевна Щепочкина | Steel |
| US9970242B2 (en) | 2013-01-11 | 2018-05-15 | Tenaris Connections B.V. | Galling resistant drill pipe tool joint and corresponding drill pipe |
| US11105501B2 (en) | 2013-06-25 | 2021-08-31 | Tenaris Connections B.V. | High-chromium heat-resistant steel |
| US11124852B2 (en) | 2016-08-12 | 2021-09-21 | Tenaris Coiled Tubes, Llc | Method and system for manufacturing coiled tubing |
| US11952648B2 (en) | 2011-01-25 | 2024-04-09 | Tenaris Coiled Tubes, Llc | Method of forming and heat treating coiled tubing |
| US12129533B2 (en) | 2015-04-14 | 2024-10-29 | Tenaris Connections B.V. | Ultra-fine grained steels having corrosion- fatigue resistance |
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8002910B2 (en) | 2003-04-25 | 2011-08-23 | Tubos De Acero De Mexico S.A. | Seamless steel tube which is intended to be used as a guide pipe and production method thereof |
| US8926771B2 (en) | 2006-06-29 | 2015-01-06 | Tenaris Connections Limited | Seamless precision steel tubes with improved isotropic toughness at low temperature for hydraulic cylinders and process for obtaining the same |
| US8328958B2 (en) | 2007-07-06 | 2012-12-11 | Tenaris Connections Limited | Steels for sour service environments |
| US7862667B2 (en) | 2007-07-06 | 2011-01-04 | Tenaris Connections Limited | Steels for sour service environments |
| US8328960B2 (en) | 2007-11-19 | 2012-12-11 | Tenaris Connections Limited | High strength bainitic steel for OCTG applications |
| US8221562B2 (en) | 2008-11-25 | 2012-07-17 | Maverick Tube, Llc | Compact strip or thin slab processing of boron/titanium steels |
| US11952648B2 (en) | 2011-01-25 | 2024-04-09 | Tenaris Coiled Tubes, Llc | Method of forming and heat treating coiled tubing |
| US8414715B2 (en) | 2011-02-18 | 2013-04-09 | Siderca S.A.I.C. | Method of making ultra high strength steel having good toughness |
| US9970242B2 (en) | 2013-01-11 | 2018-05-15 | Tenaris Connections B.V. | Galling resistant drill pipe tool joint and corresponding drill pipe |
| US10378074B2 (en) | 2013-03-14 | 2019-08-13 | Tenaris Coiled Tubes, Llc | High performance material for coiled tubing applications and the method of producing the same |
| US9803256B2 (en) | 2013-03-14 | 2017-10-31 | Tenaris Coiled Tubes, Llc | High performance material for coiled tubing applications and the method of producing the same |
| US10378075B2 (en) | 2013-03-14 | 2019-08-13 | Tenaris Coiled Tubes, Llc | High performance material for coiled tubing applications and the method of producing the same |
| US11377704B2 (en) | 2013-03-14 | 2022-07-05 | Tenaris Coiled Tubes, Llc | High performance material for coiled tubing applications and the method of producing the same |
| US9657365B2 (en) | 2013-04-08 | 2017-05-23 | Dalmine S.P.A. | High strength medium wall quenched and tempered seamless steel pipes and related method for manufacturing said steel pipes |
| US9644248B2 (en) | 2013-04-08 | 2017-05-09 | Dalmine S.P.A. | Heavy wall quenched and tempered seamless steel pipes and related method for manufacturing said steel pipes |
| US11105501B2 (en) | 2013-06-25 | 2021-08-31 | Tenaris Connections B.V. | High-chromium heat-resistant steel |
| US12129533B2 (en) | 2015-04-14 | 2024-10-29 | Tenaris Connections B.V. | Ultra-fine grained steels having corrosion- fatigue resistance |
| US11124852B2 (en) | 2016-08-12 | 2021-09-21 | Tenaris Coiled Tubes, Llc | Method and system for manufacturing coiled tubing |
| RU2647061C1 (en)* | 2017-04-27 | 2018-03-13 | Юлия Алексеевна Щепочкина | Steel |
| Publication | Publication Date | Title |
|---|---|---|
| CN109082591B (en) | 125ksi hydrogen sulfide stress corrosion resistant high-strength oil casing steel and preparation process thereof | |
| CN101634001B (en) | CT90-class steel for continuous oil pipe and method for manufacturing same | |
| JP3898814B2 (en) | Continuous cast slab for high strength steel with excellent low temperature toughness and its manufacturing method, and high strength steel with excellent low temperature toughness | |
| JPS61270355A (en) | High strength steel excelling in resistance to delayed fracture | |
| JPS634047A (en) | High-strength oil well steel with excellent sulfide cracking resistance | |
| JPS634046A (en) | High-tensile steel for oil well excellent in resistance to sulfide cracking | |
| JPS62253720A (en) | Production of low-alloy high-tension oil-well steel having excellent resistance to sulfide stress corrosion cracking | |
| CN112126849A (en) | X90 pipeline steel with high strength and toughness and containing rare earth La and Ce elements and rolling method thereof | |
| JPH0253506B2 (en) | ||
| JP3449311B2 (en) | Seamless steel pipe with high toughness and high corrosion resistance | |
| JPH01259124A (en) | Method for manufacturing high-strength oil country tubular goods with excellent corrosion resistance | |
| JPS63230847A (en) | Low alloy steel for oil country tubular goods with excellent corrosion resistance | |
| JPH0253505B2 (en) | ||
| JPH0260748B2 (en) | ||
| CN114086083B (en) | 1100 MPa-grade sulfur-resistant high-pressure gas cylinder steel, high-pressure gas cylinder and manufacturing method thereof | |
| JPH06271975A (en) | High strength steel excellent in hydrogen embrittlement resistance and its production | |
| JPS6164815A (en) | Manufacturing method for high-strength steel with excellent delayed fracture resistance | |
| CN117966019A (en) | X80 grade pipeline steel plate with excellent hydrogen embrittlement resistance and manufacturing method | |
| JP4344126B2 (en) | Induction tempered steel with excellent torsional properties | |
| CN116875880A (en) | A 590MPa-level hydrogen-induced cracking resistant resistance welding oil casing and its manufacturing method | |
| JPH06293914A (en) | Production of low alloy steel plate for line pipe excellent in co2 corrosion resistance and haz toughness | |
| JPS644566B2 (en) | ||
| CN113832415A (en) | X80-grade high-temperature-resistant pipeline steel and manufacturing method thereof | |
| JPS634043A (en) | High-tensile steel for oil well excellent in resistance to sulfide cracking | |
| JPS62202053A (en) | Steel materials for low yield ratio chains |