JP3491148B2 - High strength and high toughness seamless steel pipe for line pipe - Google Patents

High strength and high toughness seamless steel pipe for line pipe

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Publication number
JP3491148B2
JP3491148B2 JP2000123596A JP2000123596A JP3491148B2 JP 3491148 B2 JP3491148 B2 JP 3491148B2 JP 2000123596 A JP2000123596 A JP 2000123596A JP 2000123596 A JP2000123596 A JP 2000123596A JP 3491148 B2 JP3491148 B2 JP 3491148B2
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JP
Japan
Prior art keywords
strength
toughness
steel pipe
seamless steel
pipe
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Fee Related
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JP2000123596A
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Japanese (ja)
Other versions
JP2001288532A (en
Inventor
由紀夫 宮田
光男 木村
高明 豊岡
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JFE Steel Corp
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JFE Steel Corp
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Description

【発明の詳細な説明】Detailed Description of the Invention

【0001】[0001]

【発明の属する技術分野】本発明は、ラインパイプ用高
強度高靱性継目無鋼管に関し、とくに、API−5Lの
X80級のラインパイプ用高強度高靱性継目無鋼管に関す
る。
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high strength and high toughness seamless steel pipe for line pipes, and more particularly to a high strength and high toughness seamless steel pipe for API-5L X80 line pipes.

【0002】[0002]

【従来の技術】原油や天然ガスを輸送するためのパイプ
ラインやライザー用として、要求特性に応じ種々の鋼管
が開発され、実用化されている。その中で、X80級の強
度(降伏強さYS:551 MPa 以上、引張り強さTS: 6
20〜 827MPa )を有する継目無鋼管も開発されている
が、現状、靱性レベルは溶接部も含めると破面遷移温度
がせいぜい-60 ℃である。
2. Description of the Related Art Various steel pipes have been developed and put into practical use for pipelines and risers for transporting crude oil and natural gas according to required characteristics. Among them, X80 class strength (yield strength YS: 551 MPa or more, tensile strength TS: 6
A seamless steel pipe having 20 to 827 MPa) has also been developed, but at present, the toughness level is -60 ° C at the fracture surface transition temperature including the weld.

【0003】しかしながら、近年の油井環境の過酷化、
開発費の節約の観点から、材料にはさらなる高強度高靱
性が要求されるようになっている。また、X80級の強度
を有する継目無鋼管は、通常、次の熱処理方法により強
度調整される。 継目無鋼管製造後一旦冷却し、再加熱して焼入れ、そ
の後焼き戻すいわゆる再加熱焼入れ−焼戻し(RQ−
T) 継目無鋼管製造後直ちに焼入れ、その後焼き戻すいわ
ゆる直接焼入れ−焼戻し(DQ−T)
However, the severer environment of oil wells in recent years,
From the viewpoint of saving development costs, materials are required to have higher strength and toughness. A seamless steel pipe having a strength of X80 class is usually adjusted in strength by the following heat treatment method. After manufacturing seamless steel pipe, it is cooled once, reheated and quenched, and then tempered so-called reheating quenching-tempering (RQ-
T) Quenching immediately after manufacturing seamless steel pipe, then tempering, so-called direct quenching-tempering (DQ-T)

【0004】[0004]

【発明が解決しようとする課題】しかしながら、同じ組
成の鋼でも、サイズによって冷却速度が異なるので、焼
入れ後の強度は異なり、そのため、焼戻し条件を変更し
て対応することになる。したがって、適度な焼戻し軟化
抵抗性を確保することが課題となっていた。そこで、本
発明は、X80級の高強度と破面遷移温度−60℃以下の低
温靱性を有し、しかも適度な焼戻し軟化抵抗性を有する
ラインパイプ用の継目無鋼管を提供することを目的とす
る。
However, even steels having the same composition have different cooling rates depending on their sizes, and therefore have different strengths after quenching. Therefore, it is necessary to change the tempering conditions. Therefore, it has been a subject to secure appropriate temper softening resistance. Therefore, an object of the present invention is to provide a seamless steel pipe for a line pipe which has high strength of X80 grade and low temperature toughness of a fracture surface transition temperature of −60 ° C. or less, and has appropriate temper softening resistance. To do.

【0005】[0005]

【課題を解決するための手段】本発明者らは、前記目的
を達成するために、鋭意考究・実験を重ね、以下に挙げ
る重要な知見を得た。高強度を確保するには、C量を高
めることが有効であるが、一方で低温靱性を著しく劣化
させてしまう。また、溶接性の確保のためには、C量は
低いほど好ましい。
[Means for Solving the Problems] In order to achieve the above-mentioned object, the present inventors have earnestly studied and conducted experiments, and have obtained the following important findings. To secure high strength, it is effective to increase the C content, but on the other hand, the low temperature toughness is significantly deteriorated. Further, in order to secure weldability, the lower the amount of C, the more preferable.

【0006】C量を低く抑えたうえで、高強度を確保す
るには、Mn、Ni、Moなどの合金元素の添加が有効であ
る。なお、低C鋼の焼入れ性改善にはBの微量添加が有
効であることが知られているが、Bには溶接部の靱性に
悪影響を与えるという負の作用があり、しかも、その影
響はNやTiなどの析出物生成元素の含有量に大きく左右
されるため、Bの微量添加によるのでは靱性の安定確保
が困難である。
Addition of alloying elements such as Mn, Ni and Mo is effective for securing high strength while suppressing the amount of C to a low level. It is known that the addition of a small amount of B is effective for improving the hardenability of a low C steel, but B has a negative effect of adversely affecting the toughness of the welded portion, and its effect is Since it largely depends on the content of precipitate forming elements such as N and Ti, it is difficult to secure stable toughness by adding a trace amount of B.

【0007】低温靱性を確保したうえで、X80級の強度
を得るための焼入れ性を確保するには、Mo量とV量とを
図1に示す適正範囲に制御する必要がある。さらに、焼
戻し条件の変更による強度調整を容易ならしめるため、
焼戻し軟化抵抗性を適正化する必要があり、そのために
は、Nb量とV量とを図2に示す適正範囲に制御する必要
がある。
In order to secure the low temperature toughness and also the hardenability for obtaining the strength of X80 grade, it is necessary to control the amounts of Mo and V within the proper ranges shown in FIG. Furthermore, in order to facilitate strength adjustment by changing tempering conditions,
It is necessary to optimize the temper softening resistance, and for that purpose, it is necessary to control the Nb amount and the V amount within the appropriate range shown in FIG.

【0008】本発明は、これらの知見に基づいて完成さ
れたものであり、その要旨とするところは、質量%で、
C:0.03〜0.06%、Si:0.05〜0.15%、Mn:1.6 〜2.0
%、Al:0.010 〜0.10%、Ni:0.3 〜0.7 %、Mo:0.10
〜0.40%、V:0.06%以下、Nb:0.03%以下、Ti:0.00
3 〜0.020 %、N:0.0010〜0.0100%を含有し、かつ、
Mo+5V≧0.4 %、2Nb−V≦0%、なる関係を満足
し、残部Feおよび不可避的不純物からなるラインパイプ
用高強度高靱性継目無鋼管にある。
The present invention has been completed based on these findings, and the gist of the invention is mass%
C: 0.03 to 0.06%, Si: 0.05 to 0.15%, Mn: 1.6 to 2.0
%, Al: 0.010 to 0.10%, Ni: 0.3 to 0.7%, Mo: 0.10.
~ 0.40%, V: 0.06% or less, Nb: 0.03% or less, Ti: 0.00
3 to 0.020%, N: 0.0010 to 0.0100%, and
Mo + 5V ≧ 0.4%, 2Nb−V ≦ 0%, which is a high-strength, high-toughness seamless steel pipe for a line pipe, the balance of which is Fe and inevitable impurities.

【0009】この継目無鋼管は、X80級の強度、破面遷
移温度−60℃以下の低温靱性、および、600 ℃×30分の
焼戻しと650 ℃×30分の焼戻しでの降伏強さの差が30〜
70MPa になる焼戻し軟化抵抗性を有することが特徴的で
ある。
This seamless steel pipe has a strength of X80 grade, a low temperature toughness at a fracture surface transition temperature of −60 ° C. or less, and a difference in yield strength between tempering at 600 ° C. × 30 minutes and tempering at 650 ° C. × 30 minutes. Is 30 ~
Characteristically, it has temper softening resistance of 70 MPa.

【0010】[0010]

【発明の実施の形態】本発明において鋼の組成(化学成
分)を上記のように限定した理由を以下に述べる。な
お、化学成分含有量(濃度)を表す%は質量%を意味す
る。 C:0.03〜0.06% Cは、鋼の強度に関係する重要な元素であり、焼入れ性
を高めてX80級の強度を確保するために0.03%以上を必
要とするが、一方、0.06%を超えると溶接割れ感受性を
高めるため、0.03〜0.06%とする。
BEST MODE FOR CARRYING OUT THE INVENTION The reasons for limiting the composition (chemical composition) of steel in the present invention as described above will be described below. In addition,% showing a chemical component content (concentration) means mass%. C: 0.03 to 0.06% C is an important element related to the strength of steel, and 0.03% or more is required to improve the hardenability and secure the strength of X80 class, while it exceeds 0.06%. And 0.03 to 0.06% in order to increase the sensitivity to welding cracks.

【0011】Si:0.05〜0.15% Siは、製鋼における脱酸剤として、また高強度化のため
に必要であり、0.05%未満ではその効果に乏しく、一
方、0.15%を超えると母材、HAZの靱性劣化や溶接性
の低下を招来するため、0.05〜0.15%とする。 Mn:1.6 〜2.0 % Mnは、焼入れ性を高めて高強度化するために必要であ
り、また母材およびHAZの靱性を向上させる働きもあ
るが、1.6 %未満ではこれらの諸効果を得難く、一方、
2.0 %を超えて添加しても効果は飽和するため、1.6 〜
2.0 %とする。
Si: 0.05 to 0.15% Si is necessary as a deoxidizing agent in steelmaking and for enhancing the strength. If it is less than 0.05%, its effect is poor. On the other hand, if it exceeds 0.15%, the base metal and HAZ are poor. Since it causes deterioration of toughness and deterioration of weldability, it is set to 0.05 to 0.15%. Mn: 1.6 to 2.0% Mn is necessary for enhancing the hardenability and strength, and also has the function of improving the toughness of the base metal and HAZ, but if it is less than 1.6%, it is difficult to obtain these effects. ,on the other hand,
The effect is saturated even if added over 2.0%, so 1.6 ~
2.0%

【0012】Al:0.010 〜0.10% Alは、製鋼における脱酸剤として作用するとともに、N
と結合してAlN を形成し結晶粒を微細化し靱性を向上さ
せる効果を有している。この効果を得るために0.010 %
以上の添加を必要とするが、0.070 %を超えるとAl2O3
系介在物が増加し靭性を劣化させるとともに、表面欠陥
が多発する懸念がある。そのため、Alは0.010 〜0.10%
とする。なお、安定した表面品質を確保する観点からは
0.010 〜0.050 %が好ましい。
Al: 0.010 to 0.10% Al acts as a deoxidizing agent in steelmaking, and N
Has the effect of forming AlN by combining with Al to form finer crystal grains and improving toughness. 0.010% for this effect
The above additions are required, but if 0.070% is exceeded, Al 2 O 3
There is a concern that the number of system inclusions will increase and the toughness will deteriorate, and that many surface defects will occur. Therefore, Al is 0.010 to 0.10%
And From the perspective of ensuring stable surface quality,
0.010 to 0.050% is preferable.

【0013】Ni:0.3 〜0.7 % Niは、母材およびHAZの靱性を向上させる働きがあ
る。この効果は0.3 %以上の添加で顕現する。しかし、
0.7 %を超えて添加しても靱性、耐食性の向上効果が飽
和し、徒にコスト高を招く結果となって不利である。こ
のためNi量は0.3〜0.7 %とする。
Ni: 0.3 to 0.7% Ni has the function of improving the toughness of the base material and HAZ. This effect becomes apparent with the addition of 0.3% or more. But,
Even if added in excess of 0.7%, the effect of improving toughness and corrosion resistance saturates, which is disadvantageous because it results in a high cost. Therefore, the Ni content is 0.3 to 0.7%.

【0014】Mo:0.10〜0.40% Moは、焼入れ性向上および固溶強化のために必須に添加
され、その効果を得るには0.10%以上を必要とするが、
0.40%を超える添加は特に溶接部の靱性の劣化を招くた
め、0.10〜0.40%とする。 V:0.06%以下 Vは、炭窒化物として基地中に析出させて焼戻し軟化抵
抗を適正化に資するために必須に添加されるが、0.06%
を超えると特に溶接部の靱性を劣化させるため、0.06%
以下に限定する。
Mo: 0.10 to 0.40% Mo is indispensable for improving hardenability and solid solution strengthening, and 0.10% or more is required to obtain the effect,
The addition of more than 0.40% causes deterioration of the toughness of the welded portion, so the content is made 0.10 to 0.40%. V: 0.06% or less V is indispensably added in order to contribute to the optimization of temper softening resistance by precipitating in the matrix as carbonitride, but 0.06%
Exceeding 0.06% deteriorates the toughness of the weld, so 0.06%
Limited to:

【0015】Nb:0.03%以下 Nbは、炭窒化物として基地中に析出させて焼戻し軟化抵
抗の適正化に資するために必須に添加されるが、0.03%
を超えて添加すると焼戻し軟化抵抗が過大となるため0.
03%以下に限定する。 Ti:0.003 〜0.020 % Tiは、炭化物を形成し結晶粒を微細化し靱性を向上させ
るとともに、基地中に析出して強度を増加させて高強度
化に寄与する。その効果は0.003 %以上の添加で発現す
るが、一方、0.020 %を超えて添加すると、焼入れ性の
確保が難しくなるとともに靭性も劣化する。このため、
Tiは0.003 〜0.020 %とする。なお、より好ましくは0.
010 〜0.018 %である。
Nb: 0.03% or less Nb is essentially added as carbonitride to precipitate in the matrix and contribute to the optimization of temper softening resistance, but 0.03%
If added in excess of 0, the temper softening resistance becomes excessive, so 0.
Limited to less than 03%. Ti: 0.003 to 0.020% Ti forms carbides and refines crystal grains to improve toughness, and precipitates in the matrix to increase strength and contribute to high strength. The effect is exhibited by addition of 0.003% or more, while if added over 0.020%, it becomes difficult to secure hardenability and the toughness deteriorates. For this reason,
Ti is 0.003 to 0.020%. Incidentally, more preferably 0.
It is 010 to 0.018%.

【0016】N:0.0010〜0.0100% Nは、AlN の形成やV、Nbの炭窒化物形成のために0.00
10%以上の含有を必要とするが、0.0100%を超える含有
はHAZの靱性を劣化させるので、0.0010〜0.0100%と
する。なお、より好ましくは0.0030〜0.0080%である。 Mo+5V≧0.4 % 個々の成分元素がそれぞれ上記の限定範囲内にあって
も、Mo量とV量の5倍の和が0.4 %未満であると、焼入
れ性が不足してX80級の強度を確保するのが難しくな
る。よって、Mo量とV量とは、Mo+5V≧0.4 %なる関
係を満たす必要がある。(図1参照) 2Nb−V≦0% 個々の成分元素がそれぞれ上記の限定範囲内にあって
も、Nb量の2倍とV量の差が0%を超えると焼戻し軟化
抵抗が過大となり、サイズによらず焼戻し条件を変更す
るだけで強度調整を行うことが困難となる。そのため、
Nb量とV量とは、2Nb−V≦0%なる関係を満たす必要
がある。(図2参照) その他不可避的不純物としてP、S、Oを含有するが、
母材靱性確保の面からできるだけ低減するのが望まし
い。なお、P、S、Oはそれぞれ0.03%、0.01%、0.01
%までは許容できる。
N: 0.0010 to 0.0100% N is 0.00 due to the formation of AlN and carbonitrides of V and Nb.
Although the content of 10% or more is required, the content of more than 0.0100% deteriorates the toughness of the HAZ, so the content is made 0.0010 to 0.0100%. In addition, it is more preferably 0.0030 to 0.0080%. Mo + 5V ≧ 0.4% Even if each component element is within the above limits, if the sum of Mo content and V content is less than 0.4%, hardenability is insufficient and X80 grade strength is secured. Hard to do. Therefore, the amount of Mo and the amount of V must satisfy the relationship of Mo + 5V ≧ 0.4%. (Refer to FIG. 1) 2Nb-V ≦ 0% Even if each component element is within the above-mentioned limited range, if the difference between the double Nb amount and the V amount exceeds 0%, the temper softening resistance becomes excessive, It becomes difficult to adjust the strength simply by changing the tempering conditions regardless of the size. for that reason,
The amount of Nb and the amount of V must satisfy the relationship of 2Nb−V ≦ 0%. (See FIG. 2) P, S, and O are contained as other unavoidable impurities.
From the viewpoint of securing the toughness of the base material, it is desirable to reduce it as much as possible. In addition, P, S, and O are 0.03%, 0.01%, and 0.01, respectively.
Up to% is acceptable.

【0017】次に、本発明鋼管の好ましい製造プロセス
について説明する。上記組成になる鋼を転炉あるいは電
気炉で溶製し、連続鋳造法あるいは造塊法により凝固さ
せ鋳片を得る。その過程で溶鋼の取鍋精錬、真空脱ガス
等は必要に応じて実施する。得られた鋳片をそのまま、
あるいはさらに熱間圧延して鋼管素材とする。
Next, a preferable manufacturing process of the steel pipe of the present invention will be described. Steel having the above composition is melted in a converter or an electric furnace and solidified by a continuous casting method or an ingot making method to obtain a slab. In the process, ladle refining of molten steel, vacuum degassing, etc. are carried out as necessary. The obtained slab is as it is,
Alternatively, it is further hot rolled to obtain a steel pipe material.

【0018】前記鋼管素材をAc3 点以上に加熱し、プラ
グミル方式、マンドレルミル方式等の熱間管圧延により
継目無鋼管とし、あるいはさらにサイザ、ストレッチレ
デューサにより熱間のまま所望の寸法に造管する。造管
後は、所望の強度−靱性バランスを得るために焼入れ−
焼戻し(Q−T)からなる熱処理を行う。焼入れ(Q)
は、造管後の熱間状態から直ちにMs点以下(200 ℃程度
以下)まで冷却する直接焼入れ(DQ)、造管後常温付
近まで放冷しその後γ域に再加熱したうえでMs点以下ま
で冷却する再加熱焼入れ(RQ)のいずれで行ってもよ
い。Q−T後にX80級の強度を得るには、γ域の温度か
ら、好ましくは20℃/s以上の冷却速度で、焼入れた後、
Ac1 点未満(好ましくは550℃以上)の範囲内に適宜設
定した温度で焼き戻せばよい。焼戻し温度での保持時間
は適宜決定すればよく、通常は10〜 120min 程度に設定
される。
[0018] The steel pipe material is heated to Ac 3 point or more and hot-rolled by a plug mill method, a mandrel mill method or the like to obtain a seamless steel tube, or a sizer and a stretch reducer are used to produce a desired size while hot. To do. After pipe forming, quenching to obtain the desired strength-toughness balance-
A heat treatment consisting of tempering (Q-T) is performed. Quenching (Q)
Is direct quenching (DQ) that immediately cools from the hot state after pipe making to a temperature below the Ms point (about 200 ° C or less), after cooling to near room temperature after pipe making, and then reheating to the γ region, then below the Ms point. Any of reheat quenching (RQ) for cooling to In order to obtain X80 class strength after Q-T, after quenching from the temperature in the γ region, preferably at a cooling rate of 20 ° C / s or more,
It may be tempered at a temperature appropriately set within the range of less than Ac 1 point (preferably 550 ° C. or higher). The holding time at the tempering temperature may be appropriately determined and is usually set to about 10 to 120 min.

【0019】[0019]

【実施例】表1に示す組成になる鋼を転炉で溶製し、真
空脱ガス処理を行い、連続鋳造法により凝固させて得た
鋳片をビレット圧延して鋼管素材とした。これら鋼管素
材をマンネスマン−プラグミル方式の管製造設備により
外径219mm ×肉厚11.1mmの継目無鋼管となし、該鋼管を
表2に示す条件で熱処理した。この熱処理は次のように
して行った。 焼入れ ・造管後、オーステナイト温度域から直接水焼入れ(D
Q)、あるいは、 ・一旦室温まで冷却してから再加熱(950 ℃×15分)
し、900 ℃から水焼入れ(RQ) 焼戻し ・600 ℃×30分、および、650 ℃×30分、あるいは、 ・620 ℃×30分 焼入れ後の硬さ、焼戻し後の引張特性(強度:YS,T
S、伸び:El )、シャルピー試験における50%破面遷
移温度(50%FATT )を調査した。また、市販のX80級溶
接材料を用いてTIG溶接(電圧15V 、電流200A、溶接
速度10kJ/min、入熱18kJ/cm )にて鋼管継手を作製しH
AZ(ボンドから1mm )の50%FATT を調査した。それら
の結果を表2に示す。
EXAMPLE Steels having the compositions shown in Table 1 were melted in a converter, subjected to vacuum degassing treatment, and solidified by a continuous casting method. These steel pipe materials were made into seamless steel pipes having an outer diameter of 219 mm and a wall thickness of 11.1 mm by a Mannesmann-plug mill type pipe manufacturing facility, and the steel pipes were heat-treated under the conditions shown in Table 2. This heat treatment was performed as follows. After quenching and pipe forming, water quenching directly from the austenite temperature range (D
Q), or ・ Cooling to room temperature and then reheating (950 ℃ × 15 minutes)
Water quenching (RQ) tempering from 900 ℃ · 600 ℃ × 30 minutes, and 650 ℃ × 30 minutes, or · 620 ℃ × 30 minutes Hardness after quenching, tensile properties after tempering (strength: YS, T
S, elongation: El), and 50% fracture surface transition temperature (50% FATT) in the Charpy test were investigated. Also, using a commercially available X80-class welding material, a steel pipe joint was prepared by TIG welding (voltage 15V, current 200A, welding speed 10kJ / min, heat input 18kJ / cm).
The 50% FATT of AZ (1 mm from bond) was investigated. The results are shown in Table 2.

【0020】[0020]

【表1】 [Table 1]

【0021】[0021]

【表2】 [Table 2]

【0022】表2より、本発明範囲内のもの(本発明
例)では、X80級の強度、優れた低温靱性、および、適
度な焼戻し軟化抵抗性を呈したのに対し、本発明範囲外
のもの(比較例)では、強度、低温靱性、焼戻し軟化抵
抗性の少なくともいずれかが不十分もしくは過度であっ
た。
From Table 2, those within the scope of the present invention (Examples of the present invention) exhibited X80 grade strength, excellent low temperature toughness, and appropriate temper softening resistance, while those outside the scope of the present invention. In the sample (Comparative Example), at least one of strength, low temperature toughness, and temper softening resistance was insufficient or excessive.

【0023】[0023]

【発明の効果】本発明の継目無鋼管は、X80級の強度と
優れた低温靱性を有し、かつ適度な焼戻し軟化抵抗性を
有するので、サイズによらず目標強度を容易に達成で
き、複数サイズの成分統合が可能となってラインパイプ
用鋼管のコストダウンが図れるという優れた効果を奏す
る。
EFFECTS OF THE INVENTION The seamless steel pipe of the present invention has strength of X80 grade, excellent low temperature toughness, and appropriate temper softening resistance, so that the target strength can be easily achieved regardless of size. It is possible to integrate the size components, and it is possible to reduce the cost of steel pipes for line pipes.

【図面の簡単な説明】[Brief description of drawings]

【図1】Mo量とV量の適正範囲を示す領域図である。FIG. 1 is a region diagram showing an appropriate range of Mo amount and V amount.

【図2】Nb量とV量の適正範囲を示す領域図である。FIG. 2 is a region diagram showing an appropriate range of Nb amount and V amount.

───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平9−41074(JP,A) (58)調査した分野(Int.Cl.7,DB名) C22C 38/00 - 38/60 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-9-41074 (JP, A) (58) Fields investigated (Int.Cl. 7 , DB name) C22C 38/00-38/60

Claims (2)

(57)【特許請求の範囲】(57) [Claims] 【請求項1】 質量%で、C:0.03〜0.06%、Si:0.05
〜0.15%、Mn:1.6〜2.0 %、Al:0.010 〜0.10%、N
i:0.3 〜0.7 %、Mo:0.10〜0.40%、V:0.06%以
下、Nb:0.03%以下、Ti:0.003 〜0.020 %、N:0.00
10〜0.0100%を含有し、かつ、Mo+5V≧0.4 %、2Nb
−V≦0%、なる関係を満足し、残部Feおよび不可避的
不純物からなるラインパイプ用高強度高靱性継目無鋼
管。
1. In mass%, C: 0.03 to 0.06%, Si: 0.05
~ 0.15%, Mn: 1.6 to 2.0%, Al: 0.010 to 0.10%, N
i: 0.3 to 0.7%, Mo: 0.10 to 0.40%, V: 0.06% or less, Nb: 0.03% or less, Ti: 0.003 to 0.020%, N: 0.00
Contains 10-0.0100% and Mo + 5V ≧ 0.4%, 2Nb
A high-strength, high-toughness seamless steel pipe for a line pipe, which satisfies the relationship of −V ≦ 0% and consists of the balance Fe and unavoidable impurities.
【請求項2】 X80級の強度、破面遷移温度−60℃以下
の低温靱性、および、600 ℃×30分の焼戻しと650 ℃×
30分の焼戻しでの降伏強さの差が30〜70MPaになる焼戻
し軟化抵抗性を有することを特徴とする請求項1記載継
目無鋼管。
2. Strength of X80 grade, low temperature toughness of fracture transition temperature -60 ° C. or lower, and tempering at 600 ° C. × 30 minutes and 650 ° C. ×
2. The seamless steel pipe according to claim 1, which has tempering softening resistance such that a difference in yield strength after tempering for 30 minutes is 30 to 70 MPa.
JP2000123596A 2000-02-02 2000-04-25 High strength and high toughness seamless steel pipe for line pipe Expired - Fee Related JP3491148B2 (en)

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JP2000-25158 2000-02-02
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BRPI0615215B1 (en) 2005-08-22 2014-10-07 Nippon Steel & Sumitomo Metal Corp SEWLESS STEEL PIPE FOR LINE PIPE AND PROCESS FOR YOUR PRODUCTION
CN103233163A (en) * 2013-05-02 2013-08-07 内蒙古科技大学 X80 RE (rare-earth) pipeline steel containing RE Ce and manufacturing method thereof
CN105256218A (en) * 2015-11-10 2016-01-20 湖南华菱湘潭钢铁有限公司 Production method of ultra-thick low-alloy steel plate
CN109234623B (en) * 2018-09-29 2020-10-27 南京钢铁股份有限公司 X80M deep-sea strain-resistant pipeline steel plate and rolling process
CN109338213B (en) * 2018-09-29 2021-01-26 南京钢铁股份有限公司 X80M deep sea strain-resistant pipeline steel and rolling process
CN109234622B (en) * 2018-09-29 2020-08-18 南京钢铁股份有限公司 X80M deep-sea strain-resistant pipeline steel and smelting process

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