JPH07188746A - Production of thick-walled steel tube having high toughness and low yield ratio - Google Patents

Production of thick-walled steel tube having high toughness and low yield ratio

Info

Publication number
JPH07188746A
JPH07188746A JP33175793A JP33175793A JPH07188746A JP H07188746 A JPH07188746 A JP H07188746A JP 33175793 A JP33175793 A JP 33175793A JP 33175793 A JP33175793 A JP 33175793A JP H07188746 A JPH07188746 A JP H07188746A
Authority
JP
Japan
Prior art keywords
temperature range
less
cooling
solal
steel
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.)
Pending
Application number
JP33175793A
Other languages
Japanese (ja)
Inventor
Moriyasu Nagae
守康 長江
Osamu Hirano
攻 平野
Yutaka Osanawa
裕 長縄
Takayuki Honda
孝行 本多
Junichiro Kawasaki
順一郎 川崎
Original Assignee
Nkk Corp
日本鋼管株式会社
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Nkk Corp, 日本鋼管株式会社 filed Critical Nkk Corp
Priority to JP33175793A priority Critical patent/JPH07188746A/en
Publication of JPH07188746A publication Critical patent/JPH07188746A/en
Pending legal-status Critical Current

Links

Abstract

PURPOSE:To produce the steel tube by subjecting a steel, in which composition and the parameter representing the tendency of island martensite formation at the time of heating in two phase region are respectively specified, to hot rolling and to reheating up to specific temp., starting and finishing bending in respectively specified temp. regions, and then applying cooling at specific velocity. CONSTITUTION:A steel, having a composition consisting of, by weight, 0.03-0.20% C, 0.01-0.50% Si, 0.5-2.0% Mn, 0.005-0.10% sol.Al, and the balance Fe, is used. In this steel, the value of the parameter PMA representing the tendency of island martensite formation at the time of heating in two phase region and computed from the equation, is regulated to <=120. This steel is hot-rolled, and the resulting steel plate is reheated up to a temp. in the two phase temp. region between Ac1 and Ac3. Bending is started at a temp. in the region not lower than Ar, and finished at a temp. in the region not lower than Ar1. Then, cooling is done at a cooling velocity noC lower than air cooling velocity. Moreover, one or more kinds among respectively prescribed amounts of the following (a), (b), and (c) can be further incorporated into the above steel: (a) one or more elements among Nb, V, and Ti; (b) one or more elements among Cu, Ni, Cr, and Mo; and (c) B and/or Ca.

Description

【発明の詳細な説明】Detailed Description of the Invention
【0001】[0001]
【産業上の利用分野】本発明は高層ビルや海洋構造物な
どの構造部材あるいは高深度海底パイプラインなどに用
いられる高靭性で降伏比が低い肉厚40〜150mm程
度の厚肉鋼管の製造方法に関する。
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a thick-walled steel pipe having a high toughness and a low yield ratio and having a wall thickness of about 40 to 150 mm, which is used for structural members such as high-rise buildings and marine structures or deep-sea submarine pipelines. Regarding
【0002】[0002]
【従来技術】高層ビルや海洋構造物などの構造部材ある
いは高深度海底パイプラインなどに用いられる肉厚鋼管
には、高強度・高靱性・低降伏比・高溶接性などの性能
が要求される。このため比較的薄肉の鋼管は、制御圧延
や制御冷却などのいわゆるTMCP技術を駆使した低成
分系でかつ高強度の鋼板を素材として、冷間曲げ加工に
より成形しているが、加工硬化による材質劣化が生じる
ため必要に応じて応力除去焼鈍などの熱処理によって回
復させている。
2. Description of the Related Art High-strength, high toughness, low yield ratio, high weldability, and other performance are required for thick-walled steel pipes used for structural members such as high-rise buildings and offshore structures, or deep-sea submarine pipelines. . For this reason, relatively thin-walled steel pipes are formed by cold bending using low-constant and high-strength steel sheets that make full use of the so-called TMCP technology such as controlled rolling and controlled cooling. Since deterioration occurs, it is recovered by heat treatment such as stress relief annealing if necessary.
【0003】一方、厚肉鋼管の場合には、プレス装置な
どの曲げ加工能力の観点から冷間加工は不可能であり、
温間ないし熱間加工が採用される。ここで熱間加工を施
す場合にはTMCPによる強化機構が消失してしまうた
め、より高成分系の焼ならし鋼が採用される。従って、
靱性や溶接性の劣化が避けられない。
On the other hand, in the case of a thick-walled steel pipe, cold working is impossible from the viewpoint of bending workability of a press machine or the like,
Warm or hot working is adopted. Here, when hot working is performed, the strengthening mechanism by TMCP disappears, so a higher component normalized steel is adopted. Therefore,
Degradation of toughness and weldability cannot be avoided.
【0004】また温間加工については、特開62−54
018号公報に、制御圧延または制御圧延と加速冷却を
施した鋼板を、750〜400℃のAc1 温度以下に再
加熱して、直ちにあるいは放冷後750〜250℃の温
度域にて加工することにより靱性などの優れた材質特性
が得られる旨提案されている。ここで加工時の再加熱温
度を750℃以下としたのは、Ac1 以下の加熱温度で
は制御圧延や加速冷却の効果が維持され高材質が得られ
るのに対し、Ac1 以上のオーステナイト+フェライト
二相領域に加熱されると組織が変化し、制御圧延や加熱
冷却の効果が消滅して所定の強度・靱性が得られなくな
るためである。
Regarding warm working, JP-A-62-54
No. 018 gazette, a steel sheet that has been subjected to controlled rolling or controlled rolling and accelerated cooling is reheated to an Ac 1 temperature of 750 to 400 ° C. or lower, and immediately or after cooling, processed in a temperature range of 750 to 250 ° C. Therefore, it is proposed that excellent material properties such as toughness can be obtained. Here, the reheating temperature during processing is set to 750 ° C. or lower because the effect of controlled rolling or accelerated cooling is maintained at high heating temperature of Ac 1 or less and a high quality material is obtained, whereas austenite + ferrite of Ac 1 or more is obtained. This is because the structure changes when heated to the two-phase region, the effects of controlled rolling and heating and cooling disappear, and the prescribed strength and toughness cannot be obtained.
【0005】一方、降伏比を下げるための方法として
は、鋼管をAc3 −250℃〜Ac3−20℃の温度域
に加熱し水冷する方法(特開平3−87318号公報)
やAc3 以上に加熱した後に空冷してAc3 −250℃
〜Ac3 −20℃の温度域から水冷する方法(特開平3
−87317号公報)、あるいはこれらの処理後に冷間
で加工歪を付与し焼き戻す方法(特開平3−21901
7号公報、特開平3−219018号公報)、さらには
鋼管をAc3 −200℃以上に加熱し、Ac3 −200
℃以上で歪付与を開始し、Ac3 −200℃〜Ac3
20℃の温度域で歪付与を終了し、水冷した後に焼き戻
す方法(特開平4−321号公報)などが提案されてい
るが、いずれも鋼管に特別な処理を施すことを前提とし
たもので、経済性及び生産性を著しく損なうことにな
る。
On the other hand, as a method for lowering the yield ratio, a steel pipe is heated to a temperature range of Ac 3 -250 ° C. to Ac 3 -20 ° C. and water-cooled (JP-A-3-87318).
Or heated to above Ac 3 and air-cooled to Ac 3 -250 ℃
~ Ac 3 Water cooling from a temperature range of −20 ° C.
No. 87317) or a method of tempering after these treatments by cold working (Japanese Patent Laid-Open No. 3-21901).
No. 7, JP-A-3-219018), and further, heating a steel pipe to Ac 3 -200 ° C. or higher to obtain Ac 3 -200.
℃ to start the strain applied in the above, Ac 3 -200 ℃ ~Ac 3 -
Although a method of finishing the strain application in the temperature range of 20 ° C, tempering after water cooling (Japanese Patent Laid-Open No. 4-321) and the like have been proposed, all of them are based on the premise that the steel pipe is subjected to a special treatment. Therefore, the economical efficiency and the productivity are significantly impaired.
【0006】[0006]
【発明が解決しようとする課題】以上のように冷間加工
では加工硬化により延性や靱性が劣化するため成形後に
応力除去焼鈍が必要となったり、あるいは成形能力の制
約により極厚鋼管の製造は難しく、熱間加工ではTMC
Pの効果が期待できず高成分系となって靱性や溶接性が
劣ることが予想される。一方、Ac1 温度以下に加熱す
る温間成形では、加工中の温度降下を考慮すると変形抵
抗の増加により極厚鋼管の成形は難しくなる傾向にあ
り、また温度降下とともに降伏比の増大が起きて低い降
伏比が得られないといった問題点を有している。また降
伏比を低下させるために鋼管に熱処理を施したり、冷間
加工を加えた後に熱処理を施すなどの処理は経済性を損
ねることになり、鋼管の製造時に所定の強度・靱性・降
伏比を付与させる方法が要望されている。
As described above, in cold working, stress relieving annealing is required after forming because workability deteriorates ductility and toughness, or extra thick steel pipes cannot be produced due to restriction of forming ability. Difficult, TMC in hot working
It is expected that the effect of P cannot be expected and it becomes a high component system, resulting in poor toughness and weldability. On the other hand, in warm forming under heating to an Ac 1 temperature or less, taking into consideration the temperature drop during processing, it tends to be difficult to form an extremely thick steel pipe due to an increase in deformation resistance, and the yield ratio increases with a decrease in temperature. It has a problem that a low yield ratio cannot be obtained. In addition, heat treatment of the steel pipe to reduce the yield ratio, or treatment such as heat treatment after cold working impairs the economic efficiency, and the prescribed strength / toughness / yield ratio cannot be obtained when manufacturing the steel pipe. A method of giving is desired.
【0007】本発明はかかる事情に鑑みてなされたもの
であって、高靭性で降伏比が低く、高強度及び優れた溶
接性をも兼備した厚肉鋼管を生産性及び経済性良く製造
することができる高靭性で降伏比が低い厚肉鋼管の製造
方法を提供することを目的とする。
The present invention has been made in view of the above circumstances, and is to manufacture a thick-walled steel pipe having high toughness, a low yield ratio, high strength and excellent weldability with high productivity and economical efficiency. It is an object of the present invention to provide a method for producing a thick-walled steel pipe which has high toughness and a low yield ratio.
【0008】[0008]
【課題を解決するための手段】本願発明者らは、大きな
曲げ加工の設備能力を必要とせず、靱性の劣化を起こさ
ず、降伏比が著しく高くならない厚肉鋼管の製造方法を
得るべく種々検討を重ねた結果、以下のような知見を得
た。
Means for Solving the Problems The inventors of the present invention have variously studied to obtain a method for producing a thick-walled steel pipe that does not require a large bending facility, does not cause deterioration in toughness, and does not significantly increase the yield ratio. As a result, the following findings were obtained.
【0009】すなわち、成分組成を特定範囲に規制する
ことにより、フェライト+オーステナイトの二相域温度
に加熱しその温度域から成形しても島状マルテンサイト
の生成を抑制して靱性の劣化を引き起こさないように
し、この鋼を用いて熱間圧延により鋼板を製造し、これ
を二相域に加熱しかつこの温度域から造管のための曲げ
加工を施し、変態終了温度以上の温度で加工を終了させ
ることにより、従来二相域加熱において問題となってい
た靭性劣化の問題を生じさせずに高靭性低降伏比鋼管が
得られることを見出した。
That is, by restricting the composition of components to a specific range, even if it is heated to the temperature of the two-phase region of ferrite + austenite and molded from that temperature region, the formation of island martensite is suppressed and deterioration of toughness is caused. Steel sheet is manufactured by hot rolling using this steel, heated to a two-phase region, and subjected to bending for pipe making from this temperature region, and processing at a temperature above the transformation end temperature. It has been found that by completing the process, a high-toughness low-yield ratio steel pipe can be obtained without causing the problem of deterioration of toughness that has been a problem in the conventional two-phase region heating.
【0010】ここで特徴的なことは、従来から二相域へ
の加熱により変形抵抗が低下し、低降伏比が得られるこ
とは知られていたが、同時に著しい靱性の劣化を伴うた
めこの温度域での造管加工は行われていなかったが、上
述のように二相域に加熱・加工しても靱性の劣化が起こ
りにくい成分組成の鋼を見出したことにより、二相域加
熱における靱性劣化の問題を解決した点である。
It has been known that heating to the two-phase region lowers the deformation resistance and that a low yield ratio can be obtained, but at the same time, it is accompanied by a remarkable deterioration in toughness, and this temperature is characteristic. Although no pipe forming work was performed in the two-phase region, the toughness in the two-phase region heating was found by finding a steel with a composition that does not easily cause deterioration of the toughness when heated and processed in the two-phase region as described above. This is the point of solving the problem of deterioration.
【0011】本発明はこのような知見に基づいて完成さ
れたものであり、第1に、重量%で、C:0.03〜
0.20%、Si:0.01〜0.50%、Mn:0.
5%〜2.0%、solAl:0.005〜0.10%
を含有し、残部Fe及び不可避的不純物からなり、かつ
以下に示す(1)式で計算される二相域加熱時の島状マ
ルテンサイト生成傾向を表わすパラメータ:PMAの値が
MA≦120となる鋼を、熱間圧延により鋼板とし、A
1 以上でかつAc3 以下の二相域温度範囲に再加熱
し、Ar1 以上の温度域から曲げ加工を開始し、Ar1
以上の温度域で加工を終了し、その後空冷以上の冷却速
度で冷却することを特徴とする高靭性で降伏比が低い厚
肉鋼管の製造方法を提供するものである。
The present invention has been completed on the basis of such findings, and firstly, in% by weight, C: 0.03 to.
0.20%, Si: 0.01 to 0.50%, Mn: 0.
5% to 2.0%, solAl: 0.005 to 0.10%
Containing the balance consisting of Fe and unavoidable impurities, and parameters representative of the (1) shown island martensite tendency in the two-phase region heating which is calculated by the formula below: P values of the MA P MA ≦ 120 Steel to be a steel plate by hot rolling, A
c 1 or more and reheated to Ac 3 following the two-phase region temperature range, it starts bending from Ar 1 above temperature range, Ar 1
The present invention provides a method for producing a thick-walled steel pipe having high toughness and a low yield ratio, which is characterized by terminating processing in the above temperature range and then cooling at a cooling rate of air cooling or higher.
【0012】第2に、重量%で、C:0.03〜0.2
0%、Si:0.01〜0.50%、Mn:0.5%〜
2.0%、solAl:0.005〜0.10%を含有
し、さらにNb:0.005〜0.05%、V:0.0
1〜0.10%、Ti:0.005〜0.10%のうち
1種又は2種以上を含有し、残部Fe及び不可避的不純
物からなり、かつ以下に示す(1)式で計算される二相
域加熱時の島状マルテンサイト生成傾向を表わすパラメ
ータ:PMAの値がPMA≦120となる鋼を、熱間圧延に
より鋼板とし、Ac1 以上でかつAc3 以下の二相域温
度範囲に再加熱し、Ar1 以上の温度域から曲げ加工を
開始し、Ar1 以上の温度域で加工を終了し、その後空
冷以上の冷却速度で冷却することを特徴とする高靭性で
降伏比が低い厚肉鋼管の製造方法を提供するものであ
る。
Secondly, in% by weight, C: 0.03 to 0.2.
0%, Si: 0.01 to 0.50%, Mn: 0.5% to
2.0%, solAl: 0.005 to 0.10%, Nb: 0.005 to 0.05%, V: 0.0
1 to 0.10%, Ti: 0.005 to 0.10%, containing 1 or 2 or more kinds, consisting of the balance Fe and unavoidable impurities, and calculated by the formula (1) shown below. parameters representing the island martensite tendency in the two-phase region heating: steels value of P MA is P MA ≦ 120, and the steel sheet by hot rolling, Ac 1 or more and Ac 3 following the two-phase region temperature reheated to the range, to start the bending from Ar 1 above temperature range, to exit the processing by Ar 1 or more temperature range, the yield ratio in the subsequent high toughness, characterized by cooling with air or a cooling rate The present invention provides a method for manufacturing a thick-walled steel pipe having a low value.
【0013】第3に、重量%で、C:0.03〜0.2
0%、Si:0.01〜0.50%、Mn:0.5%〜
2.0%、solAl:0.005〜0.10%を含有
し、さらにCu:1.5%以下、Ni:1.0%以下、
Cr:1.0%以下、Mo:0.5%以下のうち1種又
は2種以上を含有し、残部Fe及び不可避的不純物から
なり、かつ以下に示す(1)式で計算される二相域加熱
時の島状マルテンサイト生成傾向を表わすパラメータ:
MAの値がPMA≦120となる鋼を、熱間圧延により鋼
板とし、Ac1 以上でかつAc3 以下の二相域温度範囲
に再加熱し、Ar1 以上の温度域から曲げ加工を開始
し、Ar1 以上の温度域で加工を終了し、その後空冷以
上の冷却速度で冷却することを特徴とする高靭性で降伏
比が低い厚肉鋼管の製造方法を提供するものである。
Third, C: 0.03 to 0.2 by weight%.
0%, Si: 0.01 to 0.50%, Mn: 0.5% to
2.0%, solAl: 0.005 to 0.10%, further Cu: 1.5% or less, Ni: 1.0% or less,
Cr: 1.0% or less, Mo: 0.5% or less, one or more kinds are contained, the balance is Fe and inevitable impurities, and two-phase calculated by the formula (1) shown below. Parameters indicating the tendency of island martensite formation during zone heating:
Steels value of P MA is P MA ≦ 120, and the steel sheet by hot rolling, then reheated to and Ac 3 following the two-phase region temperature range at Ac 1 or more, the bending from Ar 1 or more temperature range The present invention provides a method for producing a thick-walled steel pipe having high toughness and a low yield ratio, which is characterized by starting, finishing processing in a temperature range of Ar 1 or higher, and then cooling at a cooling rate of air cooling or higher.
【0014】第4に、重量%で、C:0.03〜0.2
0%、Si:0.01〜0.50%、Mn:0.5%〜
2.0%、solAl:0.005〜0.10%を含有
し、さらにNb:0.005〜0.05%、V:0.0
1〜0.10%、Ti:0.005〜0.10%のうち
1種又は2種以上、及びCu:1.5%以下、Ni:
1.0%以下、Cr:1.0%以下、Mo:0.5%以
下のうち1種又は2種以上を含有し、残部Fe及び不可
避的不純物からなり、かつ以下に示す(1)式で計算さ
れる二相域加熱時の島状マルテンサイト生成傾向を表わ
すパラメータ:PMAの値がPMA≦120となる鋼を、熱
間圧延により鋼板とし、Ac1 以上でかつAc3 以下の
二相域温度範囲に再加熱し、Ar1 以上の温度域から曲
げ加工を開始し、Ar1 以上の温度域で加工を終了し、
その後空冷以上の冷却速度で冷却することを特徴とする
高靭性で降伏比が低い厚肉鋼管の製造方法を提供するも
のである。
Fourth, C: 0.03 to 0.2 by weight%.
0%, Si: 0.01 to 0.50%, Mn: 0.5% to
2.0%, solAl: 0.005 to 0.10%, Nb: 0.005 to 0.05%, V: 0.0
1 to 0.10%, Ti: 0.005 to 0.10%, one or more kinds, and Cu: 1.5% or less, Ni:
1.0% or less, Cr: 1.0% or less, Mo: 0.5% or less, one or more types are contained, the balance is Fe and inevitable impurities, and the formula (1) is shown below. parameters representing the island martensite tendency in the two-phase region heating in calculated: the value of P MA is a steel which is a P MA ≦ 120, and the steel sheet by hot rolling, and Ac 3 following the Ac 1 or more reheated to a two-phase region temperature range, it starts bending from Ar 1 above temperature range, to exit the processing by Ar 1 or more temperature range,
The present invention provides a method for producing a thick-walled steel pipe having high toughness and a low yield ratio, which is characterized by cooling at a cooling rate higher than air cooling.
【0015】第5に、重量%で、C:0.03〜0.2
0%、Si:0.01〜0.50%、Mn:0.5%〜
2.0%、solAl:0.005〜0.10%、C
a:0.0005〜0.0050%を含有し、残部Fe
及び不可避的不純物からなり、かつ以下に示す(1)式
で計算される二相域加熱時の島状マルテンサイト生成傾
向を表わすパラメータ:PMAの値がPMA≦120となる
鋼を、熱間圧延により鋼板とし、Ac1 以上でかつAc
3 以下の二相域温度範囲に再加熱し、Ar1 以上の温度
域から曲げ加工を開始し、Ar1 以上の温度域で加工を
終了し、その後空冷以上の冷却速度で冷却することを特
徴とする高靭性で降伏比が低い厚肉鋼管の製造方法を提
供するものである。
Fifth, by weight%, C: 0.03 to 0.2
0%, Si: 0.01 to 0.50%, Mn: 0.5% to
2.0%, solAl: 0.005-0.10%, C
a: 0.0005 to 0.0050%, balance Fe
And becomes unavoidable impurities, and represents the island martensite tendency in the two-phase region heating is calculated by the following equation (1) Parameters: Steels value of P MA is P MA ≦ 120, heat Steel plate by hot rolling, Ac 1 or more and Ac
3 was reheated to the following two-phase region temperature ranges, characterized in that to start the bending from Ar 1 above temperature range, to exit the processing by Ar 1 or more temperature range, and then cooled in air over a cooling rate And a method of manufacturing a thick-walled steel pipe having a high toughness and a low yield ratio.
【0016】第6に、重量%で、C:0.03〜0.2
0%、Si:0.01〜0.50%、Mn:0.5%〜
2.0%、solAl:0.005〜0.10%を含有
し、さらにNb:0.005〜0.05%、V:0.0
1〜0.10%、Ti:0.005〜0.10%のうち
1種又は2種以上、及びB:0.0005〜0.003
0%、Ca:0.0005〜0.0050%のうち1種
又は2種を含有し、残部Fe及び不可避的不純物からな
り、かつ以下に示す(1)式で計算される二相域加熱時
の島状マルテンサイト生成傾向を表わすパラメータ:P
MAの値がPMA≦120となる鋼を、熱間圧延により鋼板
とし、Ac1 以上でかつAc3 以下の二相域温度範囲に
再加熱し、Ar1 以上の温度域から曲げ加工を開始し、
Ar1 以上の温度域で加工を終了し、その後空冷以上の
冷却速度で冷却することを特徴とする高靭性で降伏比が
低い厚肉鋼管の製造方法を提供するものである。
Sixth, in% by weight, C: 0.03 to 0.2
0%, Si: 0.01 to 0.50%, Mn: 0.5% to
2.0%, solAl: 0.005 to 0.10%, Nb: 0.005 to 0.05%, V: 0.0
1 to 0.10%, Ti: 0.005 to 0.10%, one or more kinds, and B: 0.0005 to 0.003.
0%, Ca: 0.0005 to 0.0050%, containing one or two kinds, consisting of the balance Fe and unavoidable impurities, and heating in the two-phase region calculated by the following formula (1) Parameter indicating the tendency of island martensite formation: P
Steels value of MA is P MA ≦ 120, and the steel sheet by hot rolling, reheating to Ac 1 or more and Ac 3 following the two-phase region temperature range, start the bending from Ar 1 or more temperature range Then
The present invention provides a method for producing a thick-walled steel pipe having high toughness and a low yield ratio, which is characterized by terminating processing in a temperature range of Ar 1 or higher and then cooling at a cooling rate of air cooling or higher.
【0017】第7に、重量%で、C:0.03〜0.2
0%、Si:0.01〜0.50%、Mn:0.5%〜
2.0%、solAl:0.005〜0.10%を含有
し、さらにCu:1.5%以下、Ni:1.0%以下、
Cr:1.0%以下、Mo:0.5%以下のうち1種又
は2種以上、及びB:0.0005〜0.0030%、
Ca:0.0005〜0.0050%のうち1種又は
2種以上を含有し、残部 Fe及び不可避的不純物から
なり、かつ以下に示す(1)式で計算される二相域加熱
時の島状マルテンサイト生成傾向を表わすパラメータ:
MAの値がPMA≦120となる鋼を、熱間圧延により鋼
板とし、Ac1 以上でかつAc3 以下の二相域温度範囲
に再加熱し、Ar1 以上の温度域から曲げ加工を開始
し、Ar1以上の温度域で加工を終了し、その後空冷以
上の冷却速度で冷却することを特徴とする高靭性で降伏
比が低い厚肉鋼管の製造方法を提供するものである。
Seventh, in% by weight, C: 0.03 to 0.2.
0%, Si: 0.01 to 0.50%, Mn: 0.5% to
2.0%, solAl: 0.005 to 0.10%, further Cu: 1.5% or less, Ni: 1.0% or less,
One or more of Cr: 1.0% or less and Mo: 0.5% or less, and B: 0.0005 to 0.0030%,
Ca: Island containing one or more of 0.0005 to 0.0050%, the balance Fe and unavoidable impurities, and the two-phase region heating calculated by the following formula (1) Parameters that indicate the tendency to form martensite in the form of:
Steels value of P MA is P MA ≦ 120, and the steel sheet by hot rolling, then reheated to and Ac 3 following the two-phase region temperature range at Ac 1 or more, the bending from Ar 1 or more temperature range The present invention provides a method for producing a thick-walled steel pipe having high toughness and a low yield ratio, which is characterized by starting, finishing processing in a temperature range of Ar 1 or higher, and then cooling at a cooling rate of air cooling or higher.
【0018】第8に、重量%で、C:0.03〜0.2
0%、Si:0.01〜0.50%、Mn:0.5%〜
2.0%、solAl:0.005〜0.10%を含有
し、さらにNb:0.005〜0.05%、V:0.0
1〜0.10%、Ti:0.005〜0.10%のうち
1種又は2種以上、Cu:1.5%以下、Ni:1.0
%以下、Cr:1.0%以下、Mo:0.5%以下のう
ち1種又は2種以上、及びB:0.0005〜0.00
30%、Ca:0.0005〜0.0050%のうち1
種又は2種を含有し、残部Fe及び不可避的不純物から
なり、かつ以下に示す(1)式で計算される二相域加熱
時の島状マルテンサイト生成傾向を表わすパラメータ:
MAの値がPMA≦120となる鋼を、熱間圧延により鋼
板とし、Ac1 以上でかつAc3 以下の二相域温度範囲
に再加熱し、Ar1 以上の温度域から曲げ加工を開始
し、Ar1 以上の温度域で加工を終了し、その後空冷以
上の冷却速度で冷却することを特徴とする高靭性で降伏
比が低い厚肉鋼管の製造方法を提供するものである。
Eighth, C: 0.03 to 0.2 by weight%
0%, Si: 0.01 to 0.50%, Mn: 0.5% to
2.0%, solAl: 0.005 to 0.10%, Nb: 0.005 to 0.05%, V: 0.0
1 to 0.10%, Ti: 0.005 to 0.10%, one or more kinds, Cu: 1.5% or less, Ni: 1.0
% Or less, Cr: 1.0% or less, Mo: 0.5% or less, one or more, and B: 0.0005 to 0.00
30%, Ca: 1 out of 0.0005 to 0.0050%
Parameter indicating the island-like martensite formation tendency at the time of heating in the two-phase region, which contains one or two kinds, is composed of the balance Fe and unavoidable impurities, and is calculated by the following formula (1):
Steels value of P MA is P MA ≦ 120, and the steel sheet by hot rolling, then reheated to and Ac 3 following the two-phase region temperature range at Ac 1 or more, the bending from Ar 1 or more temperature range The present invention provides a method for producing a thick-walled steel pipe having high toughness and a low yield ratio, which is characterized by starting, finishing processing in a temperature range of Ar 1 or higher, and then cooling at a cooling rate of air cooling or higher.
【0019】 PMA=325×[C%]+9×[Si%]+40×[Mn%]+ 3×[solAl%]+380×[Nb%]……(1) 次に、本発明に係る厚肉鋼管の製造方法について、成分
組成、製造条件に分けて詳細に説明する。
P MA = 325 × [C%] + 9 × [Si%] + 40 × [Mn%] + 3 × [solAl%] + 380 × [Nb%] (1) Next, the thickness according to the present invention The method of manufacturing a thick steel pipe will be described in detail by dividing the composition and manufacturing conditions.
【0020】[成分組成]本発明では、C,Si,M
n、及びsolAlを基本成分とし、(a)Nb,V,
Tiのうち1種または2種以上、(b)Cu,Ni,C
r,Moのうち1種または2種以上、(c)Ca,Bの
うち1種または2種、を選択成分として、対象とする鋼
を基本成分のみ、又は基本成分とこの(a)〜(c)の
うち1種または2種以上とを含有するものとする。な
お、上記(c)のみを基本成分に添加する場合にはCa
単独に限られる。
[Component composition] In the present invention, C, Si, M
n and solAl as basic components, (a) Nb, V,
One or more of Ti, (b) Cu, Ni, C
One or two or more of r and Mo, and one or two of (c) Ca and B are selected as the selected components, and the target steel is the basic component alone or the basic components and these (a) to (). One or more of c) are to be contained. In addition, when only the above (c) is added to the basic component, Ca
Limited to a single person.
【0021】さらに本発明では、後述するように、 PMA=325×[C%]+9×[Si%]+40×[M
n%]+3×[solAl%]+380×[Nb%] で表されるパラメータを120以下とすることにより二
相域加熱時の島状マルテンサイトの生成傾向を著しく低
下させることができる。
Further, in the present invention, as will be described later, P MA = 325 × [C%] + 9 × [Si%] + 40 × [M
By setting the parameter represented by [n%] + 3 × [solAl%] + 380 × [Nb%] to 120 or less, the tendency of island martensite formation during heating in the two-phase region can be significantly reduced.
【0022】以下に各成分範囲の限定理由について説明
する。なお、以下の説明において%表示はすべて重量%
を示す。
The reasons for limiting the range of each component will be described below. In the following explanation, all percentages are% by weight.
Indicates.
【0023】C: この種の鋼の強度を安価にかつ効果
的に確保するためにはCは0.03%は必要である。し
かし、0.20%を超えると低温割れや高温割れなどの
溶接性を損なう。従って、C含有量を0.03〜0.2
0%の範囲に規定する。
C: To secure the strength of this type of steel inexpensively and effectively, C is required to be 0.03%. However, if it exceeds 0.20%, the weldability such as cold cracking and hot cracking is impaired. Therefore, the C content is 0.03 to 0.2.
Specify in the range of 0%.
【0024】Si: Siは脱酸のために添加される
が、0.01%未満では十分な脱酸効果が得られず、一
方0.50%を超えると靭性や溶接性の劣化を引き起こ
す。従って、Si含有量を0.01〜0.50%の範囲
に規定する。
Si: Si is added for deoxidation, but if it is less than 0.01%, a sufficient deoxidizing effect cannot be obtained, while if it exceeds 0.50%, toughness and weldability are deteriorated. Therefore, the Si content is specified in the range of 0.01 to 0.50%.
【0025】Mn: Mnは鋼の強度および靭性の向上
に有効な鋼の基本元素として添加されるが、0.5%未
満ではその効果が小さく、また2.0%を超えると溶接
性が著しく劣化する。従って、Mn含有量を0.5〜
2.0%の範囲に規定する。
Mn: Mn is added as a basic element of steel effective for improving the strength and toughness of the steel, but if it is less than 0.5%, its effect is small, and if it exceeds 2.0%, the weldability is remarkable. to degrade. Therefore, the Mn content is 0.5 to
Specified within the range of 2.0%.
【0026】solAl: solAlは鋼の脱酸のた
めに添加されるが、0.005%未満では十分な効果が
得られず、一方0.10%でその効果が飽和する。従っ
て、Al0.005〜0.10%の範囲に規定する。
SolAl: SolAl is added for deoxidation of steel, but if it is less than 0.005%, a sufficient effect cannot be obtained, while if it is 0.10%, the effect is saturated. Therefore, Al is specified in the range of 0.005 to 0.10%.
【0027】以上は基本成分の限定理由であるが、以下
上記(a)〜(c)に示した選択成分の限定理由につい
て説明する。
The reasons for limiting the basic components have been described above. The reasons for limiting the selective components shown in (a) to (c) above will be described below.
【0028】(a)Nb、V、Ti: これらの元素
は、析出強化による強度上昇や結晶粒微細化による靭性
の改善をもたらすが、添加量が増大すると溶接部の靭性
などを劣化させるため、Nb:0.005〜0.05
%、V:0.01〜0.10%、Ti:0.005〜
0.10%の範囲に規定する。
(A) Nb, V, Ti: These elements bring about an increase in strength due to precipitation strengthening and an improvement in toughness due to the refinement of crystal grains, but when the addition amount increases, the toughness of the welded portion and the like deteriorate. Nb: 0.005-0.05
%, V: 0.01 to 0.10%, Ti: 0.005 to
It is specified in the range of 0.10%.
【0029】(b)Cu、Ni、Cr、Mo: これら
の元素は固溶強化と焼入れ性増大による組織変化を通じ
て靭性を損なわずに強化が図れるが、溶接性および経済
性の観点からCuは1.5%以下、Ni、Crは1.0
%以下、Moは0.5%以下に規定する。
(B) Cu, Ni, Cr, Mo: These elements can be strengthened without impairing toughness through solid solution strengthening and structural change due to increase in hardenability, but Cu is 1 from the viewpoint of weldability and economy. 0.5% or less, Ni, Cr 1.0
%, And Mo is specified to be 0.5% or less.
【0030】(c)B、Ca: Bは鋼の焼入れ性を増
大させ強度上昇に大きな効果をもたらすものの、0.0
005%未満ではこの効果が小さく、また0.0030
%を超えると溶接性を損なうため、0.0005〜0.
0030%の範囲に規定する。また、Caは介在物の形
態を球状化させて水素誘起割れやラメラテアなどの防止
に有効であるが、0.0005%未満ではその効果が得
られず、0.0050%を超えて添加してもその効果は
飽和するため、0.0005〜0.0050%の範囲に
規定する。
(C) B, Ca: B increases the hardenability of steel and exerts a great effect on the increase in strength, but 0.0
If it is less than 005%, this effect is small, and 0.0030
%, The weldability is impaired, so 0.0005 to 0.
Specified within the range of 0030%. Further, Ca is effective in preventing hydrogen-induced cracking and lamellathea by spheroidizing the form of inclusions, but if less than 0.0005%, the effect cannot be obtained, and if added in excess of 0.0050%. However, the effect is saturated, so the range is defined as 0.0005 to 0.0050%.
【0031】PMA: 二相域に加熱しその温度から成形
を開始した際の島状マルテンサイトの生成傾向に及ぼす
合金元素の影響を定量的に検討した結果、図1に示すよ
うに次の式で計算されるパラメータPMAと良い相関を持
つことが明らかとなった。
P MA : The effect of alloying elements on the tendency to form island martensite when heating in the two-phase region and starting the molding from that temperature was quantitatively examined, and as shown in FIG. It became clear that it has a good correlation with the parameter P MA calculated by the formula.
【0032】PMA=325×[C%]+9×[Si%]
+40×[Mn%]+3×[solAl%]+380×
[Nb%] また靱性と島状マルテンサイトの面積分率は良い相関が
あり、例えば図2に示すように島状マルテンサイトの面
積分率が5%以下とすることによりシャルピー衝撃試験
の0℃における吸収エネルギーは100J以上となって
良好な靱性が達成される。ここで島状マルテンサイトの
面積分率を5%以下とするためには、図1からPMA≦1
20とする必要がある。従って、本発明ではPMA≦12
0に規定している。
P MA = 325 × [C%] + 9 × [Si%]
+40 x [Mn%] +3 x [solAl%] +380 x
[Nb%] Further, there is a good correlation between the toughness and the area fraction of island martensite. For example, as shown in FIG. 2, by setting the area fraction of island martensite to 5% or less, the Charpy impact test was performed at 0 ° C. The absorbed energy at 100 J is 100 J or more and good toughness is achieved. Here, in order to reduce the area fraction of island martensite to 5% or less, from FIG. 1, P MA ≦ 1
It should be 20. Therefore, in the present invention, P MA ≦ 12
It is defined as 0.
【0033】[製造条件]本発明では、熱間圧延後、A
1 以上Ac3 以下のいわゆる二相域温度領域に再加熱
し、Ar1 以上の温度域から造管のための曲げ加工を開
始し、Ar1 以上の温度域で加工を終了し、その後空冷
以上の冷却条件で冷却することを必須条件としている。
[Manufacturing conditions] In the present invention, after hot rolling, A
c 1 above Ac 3 was reheated to below the so-called two-phase region temperature region starts bending for forming tubes from Ar 1 above temperature range, to exit the processing by Ar 1 or more temperature range, followed by air cool Cooling under the above cooling conditions is an essential condition.
【0034】ここで二相域温度に加熱したのは、大きな
設備能力を必要とせず容易に曲げ加工を行うためと、二
相域加熱・成形により降伏比を低下させるためである。
また加工終了温度は、Ar1 以上の二相域温度に設定す
る。この範囲で加工を終了することにより、冷間加工時
に比べて約1/3の小さな変形抵抗ならびに80%以下
の低い降伏比が期待される。また加工後の冷却は空冷以
上の冷却速度であればよく、水冷であっても構わない。
空冷であるか水冷であるかは、設備能力や作業性・経済
性の視点から選択される。なおここでいう空冷以上の冷
却速度とは、0.05℃/sec以上の速度をいう。
The heating to the two-phase region temperature is performed in order to easily perform the bending without requiring a large facility capacity and to reduce the yield ratio by the two-phase region heating / forming.
The processing end temperature is set to a two-phase region temperature of Ar 1 or higher. By finishing the work in this range, a small deformation resistance of about 1/3 and a low yield ratio of 80% or less are expected as compared with the cold work. Further, the cooling after processing may be a cooling rate of air cooling or more, and may be water cooling.
Whether it is air-cooled or water-cooled is selected from the viewpoints of facility capacity, workability, and economic efficiency. The cooling rate of air cooling or more as referred to herein means a rate of 0.05 ° C./sec or more.
【0035】なお、熱間圧延は、通常この分野で用いら
れる一般的な手法を採用すればよい。また、曲げ加工
は、プレスベンドやベンディングロールなどの通常の円
筒状に曲げる手法が採用されるが、特に限定されるもの
ではない。
For the hot rolling, a general method usually used in this field may be adopted. Further, as the bending process, a general method of bending into a cylindrical shape such as a press bend or a bending roll is adopted, but it is not particularly limited.
【0036】[0036]
【作用】ここで本発明を用いることにより、二相域に加
熱しその温度域から成形しても靱性劣化を引き起こさな
いのは以下の作用による。すなわち、化学成分のうち多
量の添加により島状マルテンサイトの生成を促進する元
素としてC,Si,Mn,solAl,Nbの5種類を
抽出し、これら元素の二相域加熱時の島状マルテンサイ
ト生成に対する相対的な寄与率を求め、これをパラメー
タPMAとして表し、この値を120以下とすることによ
り島状マルテンサイトの面積分率を5%以下とすること
ができ、これにより二相域加熱を行っても著しい靱性の
劣化を防ぐことができるのである。
By using the present invention, the following action does not cause deterioration of toughness even if the material is heated in the two-phase region and molded from that temperature region. That is, C, Si, Mn, solAl, and Nb are extracted as five elements that promote the formation of island martensite by adding a large amount of chemical components, and island martensite of these elements during heating in the two-phase region is extracted. The relative contribution to the generation is obtained and expressed as a parameter P MA . By setting this value to 120 or less, the area fraction of island martensite can be set to 5% or less. Even if heating is performed, significant deterioration of toughness can be prevented.
【0037】[0037]
【実施例】表1に示す成分組成の鋼を、熱間圧延により
鋼板にした後、800℃に再加熱して直ちにプレスベン
ドにより円筒状に成形し、成形を690℃で終了して空
冷ないし水冷して鋼管を製造した。このように製造した
鋼管の機械的性質を表1に示す。またPMA=325×
[C%]+9×[Si%]+40×[Mn%]+3×
[solAl%]+380×[Nb%]で計算されるパ
ラメータPMAの値ならびに板厚40mm、予熱温度10
0℃で実施した斜めy形溶接割れ試験の結果を併せて示
す。
EXAMPLE Steels having the chemical compositions shown in Table 1 were hot-rolled into steel sheets, then reheated to 800 ° C. and immediately formed into a cylindrical shape by press bend. The forming was completed at 690 ° C. and air-cooled. Water cooling was performed to manufacture a steel pipe. Table 1 shows the mechanical properties of the steel pipe manufactured in this manner. Also, P MA = 325 ×
[C%] + 9 × [Si%] + 40 × [Mn%] + 3 ×
Value of parameter P MA calculated by [solAl%] + 380 × [Nb%], plate thickness 40 mm, preheating temperature 10
The results of the oblique y-type weld cracking test conducted at 0 ° C are also shown.
【0038】なお、表1中、鋼番号1〜17は本発明鋼
であり、鋼番号18〜22は比較鋼である。
In Table 1, steel numbers 1 to 17 are steels of the present invention, and steel numbers 18 to 22 are comparative steels.
【0039】[0039]
【表1】 表1に示すように、本発明鋼では、溶接割れ試験におい
て割れが発生せず良好な溶接性を有するとともに、引張
強さもすべて500N/mm2 以上の高い値を示した。
また降伏比はいずれも70%以下の低い値を示してお
り、二相域加熱成形の十分な効果が認められた。さらに
二相域加熱成形にもかかわらず0℃でのシャルピー衝撃
値はすべて100J以上の良好な靱性を示し、高強度・
高靱性・高溶接性ならびに低降伏比が同時に達成されて
いることが確認された。
[Table 1] As shown in Table 1, in the steels of the present invention, cracks did not occur in the weld crack test, good weldability was exhibited, and all tensile strengths were high values of 500 N / mm 2 or more.
In addition, the yield ratios were all low values of 70% or less, and a sufficient effect of the two-phase region thermoforming was confirmed. Furthermore, despite the two-phase region hot forming, the Charpy impact values at 0 ° C all show good toughness of 100 J or more, and high strength /
It was confirmed that high toughness / weldability and low yield ratio were simultaneously achieved.
【0040】一方、比較鋼の場合にはいずれも高強度と
低降伏比は達成されているものの、溶接性および靱性に
問題があり、特に靭性については0℃のシャルピー衝撃
値が21J以下と極めて低くなっている。これは二相域
加熱成形時に生成した粗大な島状マルテンサイトによる
もので、PMAを120以下に制限することの重要性を示
唆している。
On the other hand, in the case of the comparative steels, both high strength and low yield ratio have been achieved, but there are problems in weldability and toughness, and in particular regarding toughness, the Charpy impact value at 0 ° C. is 21 J or less, which is extremely low. It's getting low. This is due to the coarse island-like martensite formed during the two-phase region hot forming, suggesting the importance of limiting PMA to 120 or less.
【0041】[0041]
【発明の効果】以上説明したように、本発明によれば、
肉厚が40〜150mm程度の厚肉鋼管を、大きな設備
能力を必要とせず、靱性の劣化を起こさずに高強度・高
溶接性・低降伏比といった性質を具備させたまま経済的
に製造することが可能となった。
As described above, according to the present invention,
Economically manufacture thick-walled steel pipes with a wall thickness of 40 to 150 mm while not requiring large facility capacity and having properties such as high strength, high weldability, and low yield ratio without causing deterioration of toughness. It has become possible.
【図面の簡単な説明】[Brief description of drawings]
【図1】パラメータPMAと島状マルテンサイトの面積分
率との相関を示す図。
FIG. 1 is a diagram showing a correlation between a parameter P MA and an area fraction of island martensite.
【図2】マルテンサイトの面積分率とシャルピー衝撃試
験の0℃における吸収エネルギーとの関係を示す図。
FIG. 2 is a diagram showing a relationship between an area fraction of martensite and absorbed energy at 0 ° C. in a Charpy impact test.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 本多 孝行 東京都千代田区丸の内一丁目1番2号 日 本鋼管株式会社内 (72)発明者 川崎 順一郎 東京都千代田区丸の内一丁目1番2号 日 本鋼管株式会社内 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takayuki Honda Inventor Marunouchi 1-2-2 Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Junichiro Kawasaki Inventor 1-2-1 Marunouchi, Chiyoda-ku, Tokyo Nippon Steel Tube Co., Ltd.

Claims (8)

    【特許請求の範囲】[Claims]
  1. 【請求項1】 重量%で、C:0.03〜0.20%、
    Si:0.01〜0.50%、Mn:0.5%〜2.0
    %、solAl:0.005〜0.10%を含有し、残
    部Fe及び不可避的不純物からなり、かつ以下に示す
    (1)式で計算される二相域加熱時の島状マルテンサイ
    ト生成傾向を表わすパラメータ:PMAの値がPMA≦12
    0となる鋼を、熱間圧延により鋼板とし、Ac1 以上で
    かつAc3 以下の二相域温度範囲に再加熱し、Ar1
    上の温度域から曲げ加工を開始し、Ar1 以上の温度域
    で加工を終了し、その後空冷以上の冷却速度で冷却する
    ことを特徴とする高靭性で降伏比が低い厚肉鋼管の製造
    方法。 PMA=325×[C%]+9×[Si%]+40×[Mn%]+ 3×[solAl%]+380×[Nb%]……(1)
    1. C: 0.03 to 0.20% by weight,
    Si: 0.01 to 0.50%, Mn: 0.5% to 2.0
    %, SolAl: 0.005 to 0.10%, the balance Fe and unavoidable impurities, and the island-like martensite formation tendency at the time of heating in the two-phase region calculated by the formula (1) shown below. represents parameters: the value of P MA is P MA ≦ 12
    0 become steel, and the steel sheet by hot rolling, reheating to Ac 1 or more and Ac 3 following the two-phase region temperature range, starts bending from Ar 1 above temperature range, Ar 1 or more temperature A method for producing a thick-walled steel pipe having high toughness and a low yield ratio, which comprises finishing processing in a zone and then cooling at a cooling rate higher than air cooling. P MA = 325 × [C%] + 9 × [Si%] + 40 × [Mn%] + 3 × [solAl%] + 380 × [Nb%] (1)
  2. 【請求項2】 重量%で、C:0.03〜0.20%、
    Si:0.01〜0.50%、Mn:0.5%〜2.0
    %、solAl:0.005〜0.10%を含有し、さ
    らにNb:0.005〜0.05%、V:0.01〜
    0.10%、Ti:0.005〜0.10%のうち1種
    又は2種以上を含有し、残部Fe及び不可避的不純物か
    らなり、かつ以下に示す(1)式で計算される二相域加
    熱時の島状マルテンサイト生成傾向を表わすパラメー
    タ:PMAの値がPMA≦120となる鋼を、熱間圧延によ
    り鋼板とし、Ac1 以上でかつAc3 以下の二相域温度
    範囲に再加熱し、Ar1 以上の温度域から曲げ加工を開
    始し、Ar1 以上の温度域で加工を終了し、その後空冷
    以上の冷却速度で冷却することを特徴とする高靭性で降
    伏比が低い厚肉鋼管の製造方法。 PMA=325×[C%]+9×[Si%]+40×[Mn%]+ 3×[solAl%]+380×[Nb%]……(1)
    2. C: 0.03 to 0.20% by weight,
    Si: 0.01 to 0.50%, Mn: 0.5% to 2.0
    %, SolAl: 0.005-0.10%, Nb: 0.005-0.05%, V: 0.01-
    0.10%, Ti: 0.005 to 0.10%, containing one or more kinds, consisting of the balance Fe and inevitable impurities, and a two-phase calculated by the following formula (1) parameters representing the island martensite propensity to generate time-frequency heating: steels value of P MA is P MA ≦ 120, and the steel sheet by hot rolling, the Ac 1 or more and Ac 3 in the following two-phase region temperature range reheating starts bending from Ar 1 above temperature range, to exit the processing by Ar 1 or more temperature range, low yield ratio at a high toughness, characterized by subsequently cooling air cooling or a cooling rate Method for manufacturing thick steel pipe. P MA = 325 × [C%] + 9 × [Si%] + 40 × [Mn%] + 3 × [solAl%] + 380 × [Nb%] (1)
  3. 【請求項3】 重量%で、C:0.03〜0.20%、
    Si:0.01〜0.50%、Mn:0.5%〜2.0
    %、solAl:0.005〜0.10%を含有し、さ
    らにCu:1.5%以下、Ni:1.0%以下、Cr:
    1.0%以下、Mo:0.5%以下のうち1種又は2種
    以上を含有し、残部Fe及び不可避的不純物からなり、
    かつ以下に示す(1)式で計算される二相域加熱時の島
    状マルテンサイト生成傾向を表わすパラメータ:PMA
    値がPMA≦120となる鋼を、熱間圧延により鋼板と
    し、Ac1 以上でかつAc3 以下の二相域温度範囲に再
    加熱し、Ar1 以上の温度域から曲げ加工を開始し、A
    1 以上の温度域で加工を終了し、その後空冷以上の冷
    却速度で冷却することを特徴とする高靭性で降伏比が低
    い厚肉鋼管の製造方法。 PMA=325×[C%]+9×[Si%]+40×[Mn%]+ 3×[solAl%]+380×[Nb%]……(1)
    3. C: 0.03 to 0.20% by weight,
    Si: 0.01 to 0.50%, Mn: 0.5% to 2.0
    %, SolAl: 0.005 to 0.10%, Cu: 1.5% or less, Ni: 1.0% or less, Cr:
    1.0% or less, Mo: 0.5% or less, one or more kinds are contained, and the balance is Fe and unavoidable impurities.
    And parameters representative of the island martensite tendency in the two-phase region heating is calculated by the following equation (1): Steels value of P MA is P MA ≦ 120, and the steel sheet by hot rolling, Ac Reheat to a two-phase temperature range of 1 or more and Ac 3 or less, and start bending from the temperature range of Ar 1 or more.
    A method for producing a thick-walled steel pipe having high toughness and a low yield ratio, characterized by finishing processing in a temperature range of r 1 or higher and then cooling at a cooling rate of air cooling or higher. P MA = 325 × [C%] + 9 × [Si%] + 40 × [Mn%] + 3 × [solAl%] + 380 × [Nb%] (1)
  4. 【請求項4】 重量%で、C:0.03〜0.20%、
    Si:0.01〜0.50%、Mn:0.5%〜2.0
    %、solAl:0.005〜0.10%を含有し、さ
    らにNb:0.005〜0.05%、V:0.01〜
    0.10%、Ti:0.005〜0.10%のうち1種
    又は2種以上、及びCu:1.5%以下、Ni:1.0
    %以下、Cr:1.0%以下、Mo:0.5%以下のう
    ち1種又は2種以上を含有し、残部Fe及び不可避的不
    純物からなり、かつ以下に示す(1)式で計算される二
    相域加熱時の島状マルテンサイト生成傾向を表わすパラ
    メータ:PMAの値がPMA≦120となる鋼を、熱間圧延
    により鋼板とし、Ac1 以上でかつAc3 以下の二相域
    温度範囲に再加熱し、Ar1 以上の温度域から曲げ加工
    を開始し、Ar1 以上の温度域で加工を終了し、その後
    空冷以上の冷却速度で冷却することを特徴とする高靭性
    で降伏比が低い厚肉鋼管の製造方法。 PMA=325×[C%]+9×[Si%]+40×[Mn%]+ 3×[solAl%]+380×[Nb%]……(1)
    4. C: 0.03 to 0.20% by weight,
    Si: 0.01 to 0.50%, Mn: 0.5% to 2.0
    %, SolAl: 0.005-0.10%, Nb: 0.005-0.05%, V: 0.01-
    0.10%, Ti: 0.005 to 0.10%, one or more kinds, and Cu: 1.5% or less, Ni: 1.0
    % Or less, Cr: 1.0% or less, Mo: 0.5% or less, one or more of them are contained, the balance is Fe and unavoidable impurities, and calculated by the following formula (1). parameters representing the island martensite tendency in the two-phase region heating that: the steel value of P MA is P MA ≦ 120, and the steel sheet by hot rolling, and Ac 3 following two-phase region at Ac 1 or more reheated to a temperature range, starts bending from Ar 1 above temperature range, to exit the processing by Ar 1 or more temperature range, then the yield in high toughness, characterized by cooling with air or a cooling rate Method for manufacturing thick-walled steel pipe with a low ratio. P MA = 325 × [C%] + 9 × [Si%] + 40 × [Mn%] + 3 × [solAl%] + 380 × [Nb%] (1)
  5. 【請求項5】 重量%で、C:0.03〜0.20%、
    Si:0.01〜0.50%、Mn:0.5%〜2.0
    %、solAl:0.005〜0.10%、Ca:0.
    0005〜0.0050%を含有し、残部Fe及び不可
    避的不純物からなり、かつ以下に示す(1)式で計算さ
    れる二相域加熱時の島状マルテンサイト生成傾向を表わ
    すパラメータ:PMAの値がPMA≦120となる鋼を、熱
    間圧延により鋼板とし、Ac1 以上でかつAc3 以下の
    二相域温度範囲に再加熱し、Ar1 以上の温度域から曲
    げ加工を開始し、Ar1 以上の温度域で加工を終了し、
    その後空冷以上の冷却速度で冷却することを特徴とする
    高靭性で降伏比が低い厚肉鋼管の製造方法。 PMA=325×[C%]+9×[Si%]+40×[Mn%]+ 3×[solAl%]+380×[Nb%]……(1)
    5. C: 0.03 to 0.20% by weight,
    Si: 0.01 to 0.50%, Mn: 0.5% to 2.0
    %, SolAl: 0.005 to 0.10%, Ca: 0.
    A parameter indicating the tendency of island-like martensite formation during heating in the two-phase region, which is composed of the balance Fe and unavoidable impurities and contains 0005 to 0.0050%, and is calculated by the following formula (1): P MA A steel having a value of P MA ≦ 120 is hot-rolled into a steel sheet, reheated to a temperature range of two phases of Ac 1 or more and Ac 3 or less, and bending is started from a temperature range of Ar 1 or more, Finish processing in the temperature range above Ar 1 ,
    Then, a method for producing a thick-walled steel pipe having high toughness and a low yield ratio, characterized by cooling at a cooling rate higher than air cooling. P MA = 325 × [C%] + 9 × [Si%] + 40 × [Mn%] + 3 × [solAl%] + 380 × [Nb%] (1)
  6. 【請求項6】 重量%で、C:0.03〜0.20%、
    Si:0.01〜0.50%、Mn:0.5%〜2.0
    %、solAl:0.005〜0.10%を含有し、さ
    らにNb:0.005〜0.05%、V:0.01〜
    0.10%、Ti:0.005〜0.10%のうち1種
    又は2種以上、及びB:0.0005〜0.0030
    %、Ca:0.0005〜0.0050%のうち1種又
    は2種を含有し、残部Fe及び不可避的不純物からな
    り、かつ(1)式で計算される二相域加熱時の島状マル
    テンサイト生成傾向を表わすパラメータ:PMAの値がP
    MA≦120となる鋼を、熱間圧延により鋼板とし、Ac
    1 以上でかつAc3 以下の二相域温度範囲に再加熱し、
    Ar1 以上の温度域から曲げ加工を開始し、Ar1 以上
    の温度域で加工を終了し、その後空冷以上の冷却速度で
    冷却することを特徴とする高靭性で降伏比が低い厚肉鋼
    管の製造方法。 PMA=325×[C%]+9×[Si%]+40×[Mn%]+ 3×[solAl%]+380×[Nb%]……(1)
    6. C: 0.03 to 0.20% by weight,
    Si: 0.01 to 0.50%, Mn: 0.5% to 2.0
    %, SolAl: 0.005-0.10%, Nb: 0.005-0.05%, V: 0.01-
    0.10%, Ti: 0.005 to 0.10%, one or more kinds, and B: 0.0005 to 0.0030.
    %, Ca: 0.0005 to 0.0050% of 1 type or 2 types, the balance Fe and unavoidable impurities, and island martens during heating in the two-phase region calculated by the formula (1). Parameter indicating the site generation tendency: The value of P MA is P
    Steel with MA ≤ 120 is hot-rolled into a steel plate, and Ac
    Reheat to a two-phase temperature range of 1 or more and Ac 3 or less,
    A thick-walled steel pipe with high toughness and a low yield ratio characterized by starting bending in a temperature range of Ar 1 or higher, finishing the bending in a temperature range of Ar 1 or higher, and then cooling at a cooling rate of air cooling or higher. Production method. P MA = 325 × [C%] + 9 × [Si%] + 40 × [Mn%] + 3 × [solAl%] + 380 × [Nb%] (1)
  7. 【請求項7】 重量%で、C:0.03〜0.20%、
    Si:0.01〜0.50%、Mn:0.5%〜2.0
    %、solAl:0.005〜0.10%を含有し、さ
    らにCu:1.5%以下、Ni:1.0%以下、Cr:
    1.0%以下、Mo:0.5%以下のうち1種又は2種
    以上、及びB:0.0005〜0.0030%、Ca:
    0.0005〜0.0050%のうち1種又は2種以上
    を含有し、残部Fe及び不可避的不純物からなり、かつ
    (1)式で計算される二相域加熱時の島状マルテンサイ
    ト生成傾向を表わすパラメータ:PMAの値がPMA≦12
    0となる鋼を、熱間圧延により鋼板とし、Ac1 以上で
    かつAc3 以下の二相域温度範囲に再加熱し、Ar1
    上の温度域から曲げ加工を開始し、Ar1 以上の温度域
    で加工を終了し、その後空冷以上の冷却速度で冷却する
    ことを特徴とする高靭性で降伏比が低い厚肉鋼管の製造
    方法。 PMA=325×[C%]+9×[Si%]+40×[Mn%]+ 3×[solAl%]+380×[Nb%]……(1)
    7. C: 0.03 to 0.20% by weight,
    Si: 0.01 to 0.50%, Mn: 0.5% to 2.0
    %, SolAl: 0.005 to 0.10%, Cu: 1.5% or less, Ni: 1.0% or less, Cr:
    1.0% or less, one or more of Mo: 0.5% or less, and B: 0.0005 to 0.0030%, Ca:
    One or more of 0.0005 to 0.0050% is contained, the balance is Fe and unavoidable impurities, and the island-like martensite formation tendency at the time of heating in the two-phase region is calculated by the formula (1). parameters representing the: value of P MA is P MA ≦ 12
    0 become steel, and the steel sheet by hot rolling, reheating to Ac 1 or more and Ac 3 following the two-phase region temperature range, starts bending from Ar 1 above temperature range, Ar 1 or more temperature A method for producing a thick-walled steel pipe having high toughness and a low yield ratio, which comprises finishing processing in a zone and then cooling at a cooling rate higher than air cooling. P MA = 325 × [C%] + 9 × [Si%] + 40 × [Mn%] + 3 × [solAl%] + 380 × [Nb%] (1)
  8. 【請求項8】 重量%で、C:0.03〜0.20%、
    Si:0.01〜0.50%、Mn:0.5%〜2.0
    %、solAl:0.005〜0.10%を含有し、さ
    らにNb:0.005〜0.05%、V:0.01〜
    0.10%、Ti:0.005〜0.10%のうち1種
    又は2種以上、Cu:1.5%以下、Ni:1.0%以
    下、Cr:1.0%以下、Mo:0.5%以下のうち1
    種又は2種以上、及びB:0.0005〜0.0030
    %、Ca:0.0005〜0.0050%のうち1種又
    は2種を含有し、残部Fe及び不可避的不純物からな
    り、かつ(1)式で計算される二相域加熱時の島状マル
    テンサイト生成傾向を表わすパラメータ:PMAの値がP
    MA≦120となる鋼を、熱間圧延により鋼板とし、Ac
    1 以上でかつAc3 以下の二相域温度範囲に再加熱し、
    Ar1 以上の温度域から曲げ加工を開始し、Ar1 以上
    の温度域で加工を終了し、その後空冷以上の冷却速度で
    冷却することを特徴とする高靭性で降伏比が低い厚肉鋼
    管の製造方法。 PMA=325×[C%]+9×[Si%]+40×[Mn%]+ 3×[solAl%]+380×[Nb%]……(1)
    8. C: 0.03 to 0.20% by weight,
    Si: 0.01 to 0.50%, Mn: 0.5% to 2.0
    %, SolAl: 0.005-0.10%, Nb: 0.005-0.05%, V: 0.01-
    0.10%, Ti: 0.005 to 0.10%, one or more, Cu: 1.5% or less, Ni: 1.0% or less, Cr: 1.0% or less, Mo: 1 out of 0.5% or less
    Or two or more, and B: 0.0005 to 0.0030
    %, Ca: 0.0005 to 0.0050% of 1 type or 2 types, the balance Fe and unavoidable impurities, and island martens during heating in the two-phase region calculated by the formula (1). Parameter indicating the site generation tendency: The value of P MA is P
    Steel with MA ≤ 120 is hot-rolled into a steel plate, and Ac
    Reheat to a two-phase temperature range of 1 or more and Ac 3 or less,
    A thick-walled steel pipe with high toughness and a low yield ratio characterized by starting bending in a temperature range of Ar 1 or higher, finishing the bending in a temperature range of Ar 1 or higher, and then cooling at a cooling rate of air cooling or higher. Production method. P MA = 325 × [C%] + 9 × [Si%] + 40 × [Mn%] + 3 × [solAl%] + 380 × [Nb%] (1)
JP33175793A 1993-12-27 1993-12-27 Production of thick-walled steel tube having high toughness and low yield ratio Pending JPH07188746A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP33175793A JPH07188746A (en) 1993-12-27 1993-12-27 Production of thick-walled steel tube having high toughness and low yield ratio

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP33175793A JPH07188746A (en) 1993-12-27 1993-12-27 Production of thick-walled steel tube having high toughness and low yield ratio

Publications (1)

Publication Number Publication Date
JPH07188746A true JPH07188746A (en) 1995-07-25

Family

ID=18247283

Family Applications (1)

Application Number Title Priority Date Filing Date
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Country Link
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106222548A (en) * 2016-07-25 2016-12-14 武汉钢铁股份有限公司 The low yield strength ratio structural steel for bridge of normalizing rolling and production method thereof

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106222548A (en) * 2016-07-25 2016-12-14 武汉钢铁股份有限公司 The low yield strength ratio structural steel for bridge of normalizing rolling and production method thereof

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