JP2687841B2 - Low yield ratio high strength steel pipe manufacturing method - Google Patents
Low yield ratio high strength steel pipe manufacturing methodInfo
- Publication number
- JP2687841B2 JP2687841B2 JP13068293A JP13068293A JP2687841B2 JP 2687841 B2 JP2687841 B2 JP 2687841B2 JP 13068293 A JP13068293 A JP 13068293A JP 13068293 A JP13068293 A JP 13068293A JP 2687841 B2 JP2687841 B2 JP 2687841B2
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- Prior art keywords
- yield ratio
- steel pipe
- quenching
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- hot
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Description
【０００１】[0001]
【産業上の利用分野】本発明は、建造物、橋梁、タンク
等の鋼構造物の建築材料として使用するのに好適な、降
伏比：80％以下、引張強さ：590N/mm2以上の低降伏比高
張力鋼管の製造方法に関する。INDUSTRIAL APPLICABILITY The present invention has a yield ratio of 80% or less and a tensile strength of 590 N / mm 2 or more, which is suitable for use as a building material for steel structures such as buildings, bridges and tanks. The present invention relates to a method for manufacturing a high yield steel pipe having a low yield ratio.
【０００２】[0002]
【従来の技術】従来より、建造物、橋梁、タンク等の鋼
構造物は徐々に大型化される傾向にあり、かかる大型化
に対応するため、鋼構造物の建築材料である鋼材には、
高強度化および厚肉化が求められている。求められる強
度のレベルは引張強さ：590N/mm2以上である。2. Description of the Related Art Conventionally, steel structures such as buildings, bridges, and tanks have been gradually increased in size.
Higher strength and thicker wall are required. The required strength level is a tensile strength of 590 N / mm 2 or more.
【０００３】また、鋼構造物に生じる脆性破壊を防止す
るため、上記の鋼材には降伏比 [引張強さに対する降伏
強さ (降伏点または耐力) の割合] が低いことも要求さ
れている。求められる降伏比のレベルは降伏比：80％以
下である。このような低降伏比高張力鋼材を製造する方
法が従来より種々提案されている。Further, in order to prevent brittle fracture occurring in a steel structure, the above steel materials are also required to have a low yield ratio [ratio of yield strength (yield point or proof stress) to tensile strength]. The required yield ratio level is a yield ratio of 80% or less. Various methods for producing such a high yield steel material having a low yield ratio have been conventionally proposed.
【０００４】特開平２−205626号公報には、Ｃ：0.02〜
0.20％、Si：0.02〜0.50％、Mn：0.20〜2.00％およびA
l：0.010 〜0.100 ％と、さらにCu：0.10〜2.00％、N
b：0.005 〜0.10％、Ｖ：0.005 〜0.10％、Ti：0.005
〜0.10％のうちの１種または２種以上、さらに必要に応
じて、Ni：0.10〜2.00％、Cr：0.10〜1.00％、Mo：0.05
〜0.50％およびＢ：0.0003〜0.0030％のうちの１種また
は２種以上を、次式Japanese Unexamined Patent Publication No. 2-205626 discloses C: 0.02 to
0.20%, Si: 0.02-0.50%, Mn: 0.20-2.00% and A
l: 0.010 to 0.100%, Cu: 0.10 to 2.00%, N
b: 0.005 to 0.10%, V: 0.005 to 0.10%, Ti: 0.005
~ 0.10% of 1 or 2 or more, if necessary, Ni: 0.10 ~ 2.00%, Cr: 0.10 ~ 1.00%, Mo: 0.05
To 0.50% and B: 0.0003 to 0.0030%, one or more of
【０００５】[0005]
【数２】 ＤI ＝ (17−0.1Nr)×８√Ｃ×(0.7Si＋１) ×(3.3Mn＋１) ×(0.4Cu＋１) × ( 0.4Ni ＋１) ×(2.2Cr＋１) ×(3.0Mo＋１) ×(1.8Ｖ＋１) ×(200Ｂ＋１) ≦ex p(0.015t＋2.0) ただし、Nr：焼入れ時のASTMオーステナイト粒度番号 ｔ：板厚(mm) を満たすように含有し、残部Feおよび不可避的不純物か
らなる鋼片に熱間圧延を行った後、焼入れ焼戻し処理ま
たは直接焼入れ焼戻し処理を行うことにより、タンクや
ペンストック等の溶接構造物用材料に適した低降伏比高
張力鋼板を製造する方法が提案されている。D I = (17−0.1Nr) × 8√C × (0.7Si + 1) × (3.3Mn + 1) × (0.4Cu + 1) × (0.4Ni + 1) × (2.2Cr + 1) × (3.0Mo + 1) × ( 1.8V + 1) x (200B + 1) ≤ ex p (0.015t + 2.0) However, Nr: ASTM austenite grain size number at the time of quenching t: Steel contained so as to satisfy the plate thickness (mm), with the balance Fe and unavoidable impurities A method has been proposed for producing a low-yield ratio, high-strength steel sheet suitable for materials for welded structures such as tanks and penstocks by performing hot-quenching or direct quenching and tempering after hot rolling the piece. ing.
【０００６】この方法は、略述すれば、引張強さ：588N
/mm2級以上の鋼板の降伏比を低減する手段として、 (フ
ェライト＋オーステナイト) ２相域からの焼入れ工程を
含む多段熱処理、具体的にはＱ−Ｑ' −Ｔ、ＤＱ−Ｑ'
−ＴおよびＤＱ' −Ｔ [ただし、Ｑ：オーステナイト域
焼入れ、Ｑ' ： (フェライト＋オーステナイト) ２相域
焼入れ、ＤＱ：オーステナイト域直接焼入れ、ＤＱ' ：
(フェライト＋オーステナイト) ２相域直接焼入れ、
Ｔ：焼戻し] の３法によってフェライトと硬質の第２相
との混合組織を生成させることが可能となることを利用
し、ＤI で表わされる焼入性を特定のレベルに抑え、そ
の一方で鋼板にCu、Nb、Ｖ、Ti等の析出強化元素を添加
してＱ−ＴまたはＤＱ−Ｔを行うことにより、低降伏比
でかつ所定の高強度を有し、さらに溶接性も優れた低降
伏比高張力鋼板を製造する方法である。This method can be summarized as follows: Tensile strength: 588N
As a means to reduce the yield ratio of steel sheets of grade / mm 2 or higher, a multi-step heat treatment including a quenching process from the (ferrite + austenite) 2 phase region, specifically Q-Q'-T, DQ-Q '
-T and DQ'-T [where Q: austenite quenching, Q ': (ferrite + austenite) two-phase quenching, DQ: austenite direct quenching, DQ':
(Ferrite + austenite) 2 phase area direct quenching,
T: utilizing the fact that it is possible to produce a mixed structure of the second phase ferrite and the hard by 3 methods tempering, reduced to a particular level of hardenability represented by D I, on the other hand By performing Q-T or DQ-T by adding precipitation strengthening elements such as Cu, Nb, V, and Ti to the steel sheet, it has a low yield ratio and a predetermined high strength, and also has excellent weldability. It is a method of manufacturing a high tensile strength steel plate having a yield ratio.
【０００７】また、特開平３−219012号公報には、Ｃ：
0.03〜0.10％、Si：0.05〜0.60％、Mn：0.60〜2.00％、
Mo：0.10〜0.50％、Ｐ：0.030 ％以下、Ｓ：0.020 ％以
下を含み、さらにNi：1.00％以下、Cr：0.70％以下、C
u：0.70％以下、Ｖ：0.06％以下、Nb：0.05％以下およ
びＢ：0.0050％以下のうちから選ばれた一種以上、必要
に応じてTi：0.003 〜0.05％、残部Feおよび不可避的不
純物からなり、かつＰCM(％) ＝Ｃ＋Si/30 ＋Mn/20 ＋N
i/60 ＋Cr/20 ＋Cu/20 ＋Mo/15 ＋Ｖ/10 ＋５Ｂが0.16
〜0.21％である鋼を熱間圧延後、直ちに300 〜550 ℃ま
で急冷するか、もしくは空冷後Ac3 点以上の温度に再加
熱した後300 〜550 ℃まで急冷した後、室温まで空冷
し、さらにAc1 〜Ac3 変態点間の二相域温度に加熱保持
した後、空冷以上の冷却速度で焼入れを行い、その後45
0 〜600 ℃の温度で焼戻しを行うことにより、溶接割れ
感受性が小さく予熱が不要で、降伏比が80％以下、引張
強さが588N/mm2以上の低降伏比高張力鋼板を製造する方
法が提案されている。Further, in Japanese Patent Laid-Open No. 3-219012, C:
0.03 to 0.10%, Si: 0.05 to 0.60%, Mn: 0.60 to 2.00%,
Mo: 0.10 to 0.50%, P: 0.030% or less, S: 0.020% or less, Ni: 1.00% or less, Cr: 0.70% or less, C
u: 0.70% or less, V: 0.06% or less, Nb: 0.05% or less and B: 0.0050% or less, if necessary, Ti: 0.003 to 0.05%, balance Fe and unavoidable impurities. And P CM (%) = C + Si / 30 + Mn / 20 + N
i / 60 ＋ Cr / 20 ＋ Cu / 20 ＋ Mo / 15 ＋ V / 10 ＋ 5B is 0.16
~ 0.21% steel is hot-rolled and then immediately quenched to 300-550 ℃, or air-cooled and reheated to a temperature of Ac 3 points or higher, and then rapidly cooled to 300-550 ℃, and then air-cooled to room temperature. Furthermore, after heating and holding at the two-phase region temperature between the Ac 1 to Ac 3 transformation points, quenching is performed at a cooling rate of air cooling or higher, and then 45
A method for producing a high-strength steel sheet with a low yield ratio and a yield strength of 80% or less and a tensile strength of 588 N / mm 2 or less, which has a low susceptibility to welding cracks, requires no preheating, and is tempered at a temperature of 0 to 600 ° C. Is proposed.
【０００８】すなわち、この方法は、Ｃ含有量を0.10％
以下に低減し合金元素を添加した上記の組成を有する鋼
で、二相焼入れ前の組織を若干粗い組織として焼入れ焼
戻し処理を施す方法である。That is, this method has a C content of 0.10%.
This is a method of performing quenching and tempering treatment on the steel having the above-described composition with the alloying elements reduced and having the following composition, with the structure before the two-phase quenching being made slightly rough.
【０００９】さらに、特開昭61−288018号公報には、熱
間圧延後あるいは高温度に再加熱された鋼管を高温度か
ら急冷した後、高周波加熱法で鋼管の表面硬化層のみに
局部焼戻し処理あるいは局部焼戻し急冷処理を行うこと
により、高強度でかつ低降伏比鋼管 (引張強さ：634N/m
m2以上、降伏比：83.0％以下) を製造する方法が提案さ
れている。Further, in JP-A-61-288018, a steel pipe after hot rolling or reheated to a high temperature is rapidly cooled from a high temperature and then locally tempered only to a surface hardened layer of the steel pipe by a high frequency heating method. Steel pipe with high strength and low yield ratio (tensile strength: 634 N / m
m 2 or more, a yield ratio: 83.0% or less) A method for producing have been proposed.
【００１０】[0010]
【発明が解決しようとする課題】しかし、これらの従来
の方法によっても、降伏比が80％以下である588N/mm2以
上の低降伏比高張力鋼管を製造することはできない。特
開平２−205626号公報または特開平３−219012号公報に
より提案された方法によれば、確かに熱延鋼板段階で目
標とする引張強度および降伏比を達成することはでき
る。しかし、この熱延鋼板に冷間で製管加工を行って鋼
管を製造すると、鋼管の降伏比が80％超となり、所望の
低降伏比高張力鋼管を製造することができない。すなわ
ち、製管加工を行った後も降伏比を80％以下に抑制する
必要がある。However, even with these conventional methods, it is not possible to manufacture a high-strength steel pipe having a low yield ratio of 588 N / mm 2 or more and a yield ratio of 80% or less. According to the method proposed in JP-A-2-205626 or JP-A-3-219012, it is possible to certainly achieve the target tensile strength and yield ratio in the hot rolled steel sheet stage. However, when this hot-rolled steel sheet is subjected to cold pipe forming to produce a steel pipe, the yield ratio of the steel pipe exceeds 80%, and a desired low yield ratio high-strength steel pipe cannot be produced. That is, it is necessary to suppress the yield ratio to 80% or less even after performing the pipe manufacturing process.
【００１１】一方、特開昭61−288018号公報により提案
された方法によれば、確かに降伏比を低減することは可
能であるが、製管加工後の鋼管に急冷、焼戻しという２
度にわたる熱処理を行う必要があり、コストおよび納期
の点で問題である。さらに、得られる鋼管の強度が590
N/mm2 以上となり過大になってしまう。すなわち、熱処
理工程を簡略化してコストダウンを図るとともに強度レ
ベルを590 N/mm2 級に調整する必要がある。On the other hand, according to the method proposed in Japanese Patent Laid-Open No. 61-288018, although it is possible to surely reduce the yield ratio, it is necessary to perform quenching and tempering on the steel pipe after pipe forming.
It is necessary to perform heat treatment repeatedly, which is a problem in terms of cost and delivery time. Furthermore, the strength of the obtained steel pipe is 590.
It becomes N / mm 2 or more and becomes excessive. That is, it is necessary to simplify the heat treatment process to reduce the cost and adjust the strength level to 590 N / mm 2 .
【００１２】ここに、本発明の目的は、建造物、橋梁、
タンク等の鋼構造物の建築材料として使用するのに好適
な、降伏比：80％以下、引張強さ：590N/mm2以上の低降
伏比高張力鋼管の製造方法を提供することにあり、定量
的には、耐力(0.2％YS) ≧440N/mm2、引張強さTS：590
〜740N/mm2、降伏比YR≦80％、伸びEl≧20％、シャルピ
ー吸収エネルギーvE0 ≧27Ｊの機械的特性を備えた低降
伏比高張力鋼管を製造することにある。The object of the present invention is to construct buildings, bridges,
To provide a method for manufacturing a high-strength steel pipe having a low yield ratio of 80% or less and a tensile strength of 590 N / mm 2 or more, which is suitable for use as a building material for steel structures such as tanks, Quantitatively, yield strength (0.2% YS) ≧ 440N / mm 2 , tensile strength TS: 590
It is to manufacture a low yield ratio high tensile steel pipe having mechanical properties of ˜740 N / mm 2 , yield ratio YR ≦ 80%, elongation El ≧ 20%, Charpy absorbed energy vE 0 ≧ 27J.
【００１３】[0013]
【課題を解決するための手段】前述のように、熱間圧延
を終了した段階、すなわち熱延鋼板の段階では所望の特
性 (YR：80％以下、TS：590N/mm2以上) を有していて
も、製管加工を終了した段階、すなわち鋼管の段階では
加工硬化により耐力が上昇してしまうため、必然的に降
伏比が80％を超えてしまう。[Means for Solving the Problems] As described above, at the stage where hot rolling is completed, that is, at the stage of hot-rolled steel sheet, the desired properties (YR: 80% or less, TS: 590 N / mm 2 or more) are obtained. However, the yield ratio exceeds 80% inevitably because the yield strength increases due to work hardening at the stage where the pipe manufacturing process is completed, that is, at the stage of the steel pipe.
【００１４】本発明者は、このような製管加工による降
伏比の上昇を改善する手段を鋭意検討し、(i) 製管加工
後に鋼管に熱処理を行ってYR：80％以下、TS：590N/mm2
以上を満足する方法、(ii)製管加工による耐力の上昇を
予め見込んで熱間圧延後の熱延鋼板の耐力、引張強さ、
降伏比等を目標値の下限付近に抑制し、製管加工後に目
標値を満足する方法の二つに着目した。The present inventor diligently studied a means for improving the yield ratio increase due to such pipe forming work, and (i) heat-treating the steel pipe after pipe forming to make YR: 80% or less, TS: 590N. / mm 2
A method that satisfies the above, (ii) the yield strength of the hot-rolled steel sheet after hot rolling in anticipation of an increase in yield strength due to pipe forming, the tensile strength,
We paid attention to two methods of suppressing the yield ratio and the like near the lower limit of the target value and satisfying the target value after pipe manufacturing.
【００１５】(i) の方法の考え方には、前述の特開昭61
−288013号公報により提案された方法も包含されるが、
製管加工後に急冷、焼戻しという２度にわたる熱処理を
行う必要があり、コストおよび納期の点で問題である。
そこで、本発明者は、(ii)の方法を利用して低降伏比高
張力鋼管を製造する方法を検討した。The concept of the method (i) is based on the above-mentioned Japanese Patent Laid-Open No.
Although the method proposed by −288013 publication is also included,
It is necessary to perform heat treatment twice, that is, quenching and tempering, after pipe making, which is a problem in terms of cost and delivery time.
Therefore, the present inventor studied a method for producing a high yield steel pipe with a low yield ratio by utilizing the method (ii).
【００１６】本発明者は、(ii)の方法により鋼管を製造
した場合の問題について検討した結果、製管加工によ
る表面歪のために鋼管の表面が著しく硬化すること、お
よび降伏比がばらついてしまうことという問題がある
ことがわかった。そこで、本発明者はさらに検討した結
果、下記(a) 項および(b) 項にそれぞれまとめた内容の
知見を得た。The present inventor has studied the problem in the case of manufacturing a steel pipe by the method (ii), and as a result, the surface of the steel pipe is significantly hardened due to the surface strain due to the pipe manufacturing process, and the yield ratio varies. It turns out that there is a problem of getting lost. Therefore, as a result of further studies, the present inventor has obtained the findings summarized in the following items (a) and (b).
【００１７】(a) 焼入れまま(As Ｑ) の表面におけるオ
ーステナイト結晶粒度と表面硬度との間には、従来から
知られているように、一定の相関関係がある。図１は、
Ｃ：0.13％、Si：0.15％、Mn：1.50％、さらに、Cu：0.
20％、Ni：0.20％、Nb：0.015％、Ｖ：0.04％、残部Fe
および不可避的不純物であって、炭素当量Ｃeq(W) が0.
39％である鋼片を素材とした鋼管 (厚さ：55mm、直径：
900mm)の表面のビッカース硬さ(Hv10kgf) と降伏比YR
(％) との関係を示すグラフである。すなわち、鋼板の
表裏面では加熱によりオーステナイト粒が粗大化するの
に対し、焼入れままでは表裏面の硬度が著しく高まって
しまい、後続して行われる熱処理 (二相域焼入れ、焼戻
し) によっても解消されずに残り、さらに製管加工によ
り著しく高まり、降伏比YRの上昇をもたらしてしまう。
同図に示すグラフから、鋼管の降伏比を80％以下に抑制
するには、鋼管表面のビッカース硬さ(Hv 10kgf)を200
以下に抑制する必要がある。(A) There is a certain correlation between the austenite grain size and the surface hardness on the as-quenched (As Q) surface, as is conventionally known. FIG.
C: 0.13%, Si: 0.15%, Mn: 1.50%, and further Cu: 0.
20%, Ni: 0.20%, Nb: 0.015%, V: 0.04%, balance Fe
And unavoidable impurities with a carbon equivalent Ceq (W) of 0.
Steel pipe made from 39% steel billet (thickness: 55 mm, diameter:
900 mm surface Vickers hardness (Hv10 kgf) and yield ratio YR
6 is a graph showing the relationship with (%). In other words, the austenite grains on the front and back surfaces of the steel sheet become coarse due to heating, whereas the hardness of the front and back surfaces increases significantly when the steel is left as it is, and it is eliminated by subsequent heat treatment (two-phase region quenching and tempering). However, it will remain unremoved and will be significantly increased by the pipe manufacturing process, resulting in an increase in the yield ratio YR.
From the graph shown in the figure, in order to suppress the yield ratio of the steel pipe to 80% or less, the Vickers hardness (Hv 10 kgf) of the steel pipe surface is 200
It is necessary to suppress the following.
【００１８】本発明者は、降伏比の上昇は、このよう
に、表面のオーステナイト粒の粗大化が焼入れ性を増す
ことにつながるためであると考え、これを解消して表面
のオーステナイト粒の粗大化を防ぎ降伏比を80％以下と
するには、圧延時の圧下量を抑制して軽圧下を行えばよ
いとの知見を得た。図２は、Ｃ：0.13％、Si：0.15％、
Mn：1.50％、さらに、Cu：0.20％、Ni：0.20％、Nb：0.
015 ％、Ｖ：0.04％、残部Feおよび不可避的不純物であ
って、炭素当量Ｃeq(W) が0.39％である鋼片に、900 ℃
以上の温度域における１パス当たりの圧下率[(１パスに
おける圧下量)/(全圧下量) ×100]が２％、４％および
６％の３水準となるようにして熱間圧延を行って所定の
板厚の熱延鋼板とし、該熱延鋼板に、Ac3 点 (約 862
℃) 以上の温度域から焼入れを行い、引き続き [Ac1 点
(約 684℃) 以上 Ac3点 (約 862℃)以下] の２相温度
域に再加熱して前記２相温度域から焼入れを行い、さら
に焼戻しを行って得た熱延鋼板の表面におけるオーステ
ナイト粒径 (mm) または前記熱延鋼管を素材とした鋼管
(厚さ：55mm、直径：900mm)のビッカース硬さと、900
℃以上の１パス当たりの圧下率 (％) との関係を示すグ
ラフである。図２に示すグラフから、オーステナイトγ
粒の粗大化が著しい900 ℃以上の温度域における１パス
当たりの圧下率を４％以下とすれば鋼管表面のビッカー
ス硬さ(Hv 10kgf)を200 以下に抑制できることがわか
る。 (b) 製管加工後の降伏比のばらつきを抑制するために
は、組成、特に特に下記式により規定される炭素当量
Ｃeq(W) が大きく影響する。The present inventor believes that the increase in the yield ratio is because the coarsening of the austenite grains on the surface leads to an increase in the hardenability, and this is eliminated to improve the coarseness of the austenite grains on the surface. It was found that the reduction amount during rolling should be suppressed and a light reduction should be performed in order to prevent the formation of steel and reduce the yield ratio to 80% or less. Fig. 2 shows C: 0.13%, Si: 0.15%,
Mn: 1.50%, Cu: 0.20%, Ni: 0.20%, Nb: 0.
015%, V: 0.04%, balance Fe and unavoidable impurities and a carbon equivalent Ceq (W) of 0.39% to a steel slab at 900 ° C.
Hot rolling was carried out so that the reduction rate per pass [(reduction amount in one pass) / (total reduction amount in one pass) x 100] in the above temperature range was 3% of 2%, 4% and 6%. To obtain a hot-rolled steel sheet having a predetermined thickness, and the hot-rolled steel sheet has Ac 3 points (about 862
Quenching is performed from the temperature range above, and then [Ac 1 point
Austenite on the surface of hot-rolled steel sheet obtained by reheating to a two-phase temperature range of (about 684 ° C) or more and Ac 3 point (about 862 ° C or less), quenching from the two-phase temperature range, and further tempering. Grain size (mm) or steel pipe made from the hot rolled steel pipe
Vickers hardness of (thickness: 55 mm, diameter: 900 mm) and 900
It is a graph which shows the relationship with the rolling reduction (%) per 1 pass above ° C. From the graph shown in FIG. 2, austenite γ
It can be seen that the Vickers hardness (Hv 10 kgf) on the surface of the steel pipe can be suppressed to 200 or less by setting the rolling reduction per pass in the temperature range of 900 ° C or more where the grain coarsening is remarkable to 4% or less. (b) In order to suppress the variation of the yield ratio after the pipe manufacturing, the composition, particularly the carbon equivalent Ceq (W) defined by the following formula has a great influence.
【００１９】[0019]
【数３】 (Equation 3)
【００２０】図３は、Ｃ：0.14〜0.20％、Si：0.15％、
Mn：1.50％、さらに、Cu：0.20％、Ni：0.20％、Nb：0.
015 ％、Ｖ：0.04％、残部Feおよび不可避的不純物であ
って、炭素当量Ｃeq(W) が0.40％、0.44％、0.45％およ
び0.46％の４水準の鋼片に、900 ℃以上の温度域におけ
る１パス当たりの圧下率が３％となるようにして熱間圧
延を行って所定の板厚の熱延鋼板とし、該熱延鋼板に、
Ac3 点以上の温度域から焼入れを行い、引き続き Ac1点
以上 Ac3点以下の２相温度域に再加熱して前記２相温度
域から焼入れを行い、さらに焼戻しを行って得た熱延鋼
板、および該熱延鋼板を素材とした鋼管 (厚さ：55mm、
直径：900mm)について、炭素当量Ｃeq(W) (％) と降伏
比YR (％) との関係を示すグラフである。図３に示すグ
ラフから、鋼管の降伏比YRを80％以下に抑制するには、
炭素当量Ｃeqを0.45％以下に抑制すればよい。本発明者
は、これらの知見に基づいてさらに検討を重ねて、本発
明を完成するに至った。FIG. 3 shows C: 0.14 to 0.20%, Si: 0.15%,
Mn: 1.50%, Cu: 0.20%, Ni: 0.20%, Nb: 0.
015%, V: 0.04%, balance Fe and unavoidable impurities, and carbon equivalent Ceq (W) of 0.40%, 0.44%, 0.45% and 0.46% in four levels of steel billets in a temperature range of 900 ℃ or more. Hot rolling is performed so that the rolling reduction per pass in 3 is 3% to obtain a hot rolled steel sheet having a predetermined plate thickness, and the hot rolled steel sheet is
Quenching is performed from a temperature range of Ac 3 points or higher, and subsequently, reheating is performed to a 2-phase temperature range of Ac 1 point to Ac 3 points and lower, and quenching is performed from the 2-phase temperature range. Steel plate and steel pipe made of the hot rolled steel plate (thickness: 55 mm,
It is a graph which shows the relationship between carbon equivalent Ceq (W) (%) and yield ratio YR (%) about a diameter: 900 mm. From the graph shown in FIG. 3, in order to suppress the yield ratio YR of the steel pipe to 80% or less,
The carbon equivalent Ceq should be suppressed to 0.45% or less. The present inventor has conducted further studies based on these findings and completed the present invention.
【００２１】ここに、本発明の要旨とするところは、
Ｃ：0.02〜0.20％、Si：0.02〜0.50％、Mn：0.50〜2.00
％、さらに、Cu：0.10〜1.5 ％、Ni：0.10〜0.50％、N
b：0.005 〜0.10％およびＶ：0.005 〜0.10％からなる
群から選ばれた１種または２種以上、残部Feおよび不可
避的不純物であって、式により規定される炭素当量Ｃ
eq(W) が0.38％以上0.45％以下である鋼片に、900 ℃以
上の温度域における１パス当たりの圧下率が４％以下と
なるようにして熱間圧延を行って所定の板厚の熱延鋼板
とし、該熱延鋼板に、Ac3 点以上の温度域から焼入れを
行い、引き続き(Ac1点以上 Ac3点以下) の２相温度域に
再加熱して２相温度域から焼入れを行い、さらに焼戻し
を行ってから、製管加工を行うことを特徴とする低降伏
比高張力鋼管の製造方法である。The gist of the present invention is as follows.
C: 0.02-0.20%, Si: 0.02-0.50%, Mn: 0.50-2.00
%, Cu: 0.10 to 1.5%, Ni: 0.10 to 0.50%, N
b: 0.005 to 0.10% and V: 0.005 to 0.10%, one or more selected from the group consisting of the balance Fe and inevitable impurities, and a carbon equivalent C defined by the formula.
Steel strips with eq (W) of 0.38% or more and 0.45% or less were hot-rolled with a reduction ratio of 4% or less per pass in the temperature range of 900 ℃ or more and hot rolled. A hot-rolled steel sheet is obtained by quenching the hot-rolled steel sheet from a temperature range of Ac 3 points or higher, and then reheating to a 2-phase temperature zone of (Ac 1 point or higher and Ac 3 points or lower) to quench from the 2-phase temperature range. And a tempering process, and then a pipe manufacturing process.
【００２２】[0022]
【作用】以下、本発明を作用効果とともに詳述する。ま
ず、本発明で用いる鋼片の組成、および炭素当量を上述
のように限定する理由を説明する。Hereinafter, the present invention will be described in detail together with the functions and effects. First, the composition of the steel billet used in the present invention and the reason for limiting the carbon equivalent as described above will be described.
【００２３】Ｃ：0.02〜0.20％ Ｃは、強度確保のために0.02％以上の添加が必要である
が、0.20％を超えて過剰に添加すると溶接性を損なう。
そこで、本発明では、Ｃ含有量は0.02％以上0.20％以下
と限定する。 C: 0.02 to 0.20% C needs to be added in an amount of 0.02% or more to secure the strength, but if added in excess of 0.20%, the weldability is impaired.
Therefore, in the present invention, the C content is limited to 0.02% or more and 0.20% or less.
【００２４】Si：0.02〜0.50％ Siは、主に鋼の脱酸のために添加され、通常その添加量
は0.02％以上であり、また降伏比の低減にも有効であ
る。しかし、0.50％を超えて過剰に添加すると靱性を劣
化させるので好ましくない。そこで、本発明では、Si含
有量は0.02％以上0.50％以下と限定する。 Si: 0.02 to 0.50% Si is added mainly for deoxidizing steel, and the addition amount is usually 0.02% or more, and it is also effective for reducing the yield ratio. However, if added in excess of 0.50%, the toughness deteriorates, which is not preferable. Therefore, in the present invention, the Si content is limited to 0.02% or more and 0.50% or less.
【００２５】Mn：0.50〜2.00％ Mnは、強度確保のために0.50％以上の添加が必要である
が、2.00％を超えて過剰に添加すると溶接性を損なう。
そこで、本発明では、Mn含有量は0.50％以上2.00％以下
と限定する。 Mn: 0.50 to 2.00% Mn needs to be added in an amount of 0.50% or more to secure the strength, but if added in excess of 2.00%, the weldability is impaired.
Therefore, in the present invention, the Mn content is limited to 0.50% or more and 2.00% or less.
【００２６】さらに、本発明では、高強度化を図るため
に、Cu：0.10〜1.5 ％、Ni：0.10〜0.50％、Nb：0.005
〜0.10％およびＶ：0.005 〜0.10％からなる群から選ば
れた１種または２種以上を含有する。以下、これらの元
素についても組成の限定理由を説明する。Further, in the present invention, in order to increase the strength, Cu: 0.10 to 1.5%, Ni: 0.10 to 0.50%, Nb: 0.005.
.About.0.10% and V: 0.005 to 0.10%, and one or more kinds selected from the group consisting of. The reasons for limiting the composition of these elements will be described below.
【００２７】Cu：0.10〜1.5 ％ Cuは、0.10％以上の添加により高強度化に有効である
が、1.5 ％を超えて過剰に添加すると溶接性を損なうと
ともに熱間割れも生ずる。そこで、Cuを添加する場合に
は、その含有量は0.10％以上1.5 ％以下と限定すること
が望ましい。 Cu: 0.10 to 1.5% Cu is effective in increasing the strength by adding 0.10% or more, but if added in excess of 1.5%, the weldability is impaired and hot cracking occurs. Therefore, when Cu is added, its content is preferably limited to 0.10% or more and 1.5% or less.
【００２８】Ni：0.10〜0.50％ Niは、0.10％以上の添加により強度上昇に有効である
が、過剰に添加すると溶接性および低温靱性がともに劣
化する。特に、Niは高価な元素であり0.50％超添加する
と経済性の点で問題がある。そこで、Niを添加する場合
には、その含有量は0.10％以上0.50％以下と限定するこ
とが望ましい。 Ni: 0.10 to 0.50% Ni is effective in increasing the strength by adding 0.10% or more, but if added in excess, both weldability and low temperature toughness deteriorate. In particular, Ni is an expensive element, and if added in excess of 0.50%, there is a problem in terms of economy. Therefore, when Ni is added, its content is preferably limited to 0.10% or more and 0.50% or less.
【００２９】Nb：0.005 〜0.10％ Nbは、0.005 ％以上の添加により特に直接焼入れ焼戻し
法において高強度化に有効であるが、0.10％を超えて過
剰に添加すると靱性および溶接性がともに劣化する。そ
こで、Nbを添加する場合には、その含有量は0.005 ％以
上0.10％以下と限定することが望ましい。 Nb: 0.005 to 0.10% Nb is effective for increasing the strength particularly in the direct quenching and tempering method by adding 0.005% or more, but if added in excess of 0.10%, both toughness and weldability deteriorate. . Therefore, when Nb is added, its content is preferably limited to 0.005% or more and 0.10% or less.
【００３０】Ｖ：0.005 〜0.10％ Ｖは、0.005 ％以上の添加で鋼の強度を高めるが、0.10
％を超えて過剰に添加すると効果が飽和するばかりでな
く、溶接性を劣化させる。そこで、Ｖを添加する場合に
は、その含有量は0.005 ％以上0.10％以下と限定するこ
とが望ましい。上記以外の組成は、Feおよび不可避的不
純物である。 V: 0.005 to 0.10% V increases the strength of steel by adding 0.005% or more, but 0.10% to 0.10%
If it is added excessively in excess of%, not only the effect is saturated, but also the weldability is deteriorated. Therefore, when V is added, its content is preferably limited to 0.005% or more and 0.10% or less. Compositions other than the above are Fe and unavoidable impurities.
【００３１】Ｃeq：0.38％以上0.45％以下 炭素当量Ｃeqは、前述の図３に示す関係に基づき、鋼管
での降伏比を80％以下とするため、0.45％以下とする。
しかし、炭素当量Ｃeqを0.38％未満と著しく低下すると
強度の低下を招く。そこで、本発明では、炭素当量Ｃeq
は0.38％以上0.45％以下と限定する。 Ceq: 0.38% or more and 0.45% or less Carbon equivalent Ceq is set to 0.45% or less in order to set the yield ratio in the steel pipe to 80% or less based on the relationship shown in FIG. 3 described above.
However, if the carbon equivalent Ceq is significantly reduced to less than 0.38%, the strength is lowered. Therefore, in the present invention, the carbon equivalent Ceq
Is limited to 0.38% to 0.45%.
【００３２】900 ℃以上の加工温度における１パス当た
りの圧下率：４％以下 本発明では、かかる組成および炭素当量を有する鋼片
に、熱間圧延を行うが、熱間圧延では、900 ℃以上の加
工温度における１パス当たりの圧下率を４％以下と限定
する。 One pass at a processing temperature of 900 ° C. or higher
In the present invention, a steel strip having such a composition and carbon equivalent is hot-rolled in the present invention. In hot-rolling, the reduction rate per pass at a working temperature of 900 ° C or higher is 4%. % Or less.
【００３３】すなわち、900 ℃以上の加工温度における
１パス当たりの圧下率は、熱延鋼板の表面のオーステナ
イト粒の成長を抑制するのに重要であり、本発明の重要
なポイントである。前述の図２のグラフに示すように、
再結晶が起こるオーステナイト粒径が著しく粗大化し易
い900 ℃以上においては圧下率を４％以下と抑制して熱
延鋼板の表面のオーステナイト粒を微細化し、焼きが入
り難くして表面の硬度の上昇を抑制し、引いては製管加
工後の硬度上昇を抑制することができるため、低降伏比
の鋼管を製造することが可能となる。このため、900 ℃
以上の加工温度での圧下率を４％以下と限定した。That is, the rolling reduction per pass at the processing temperature of 900 ° C. or higher is important for suppressing the growth of austenite grains on the surface of the hot rolled steel sheet, and is an important point of the present invention. As shown in the graph of FIG. 2 above,
At 900 ° C or higher where recrystallization occurs where the austenite grain size is likely to be significantly coarsened, the rolling reduction is suppressed to 4% or less to refine the austenite grains on the surface of the hot rolled steel sheet, making it difficult to quench and increasing the surface hardness. Since it is possible to suppress the increase in hardness and the increase in hardness after the pipe manufacturing, it is possible to manufacture a steel pipe having a low yield ratio. Therefore, 900 ℃
The rolling reduction at the above processing temperature was limited to 4% or less.
【００３４】なお、圧下率は、 (１パスにおける圧下
量）／（全圧下量）×100 ％により算出される。また、
圧下率は各パスを通じて一定である必要はない。すなわ
ち、本発明では、各パスの圧下率の最大値を４％と限定
している。The rolling reduction is calculated by (rolling down amount in one pass) / (total rolling down amount) × 100%. Also,
The reduction rate does not have to be constant throughout each pass. That is, in the present invention, the maximum value of the rolling reduction of each pass is limited to 4%.
【００３５】本発明では、熱間圧延の際には、上記の圧
下率以外の限定は不要である。熱間圧延の開始温度は11
00〜1000℃程度、仕上温度は 800〜700 ℃程度、熱間圧
延時の総圧下率は66〜96％程度を例示することができ
る。In the present invention, during hot rolling, no limitation other than the above-mentioned reduction is necessary. The starting temperature for hot rolling is 11
For example, the finishing temperature is about 800 to 700 ° C., and the total rolling reduction during hot rolling is about 66 to 96%.
【００３６】Ac3 点以上からの焼入れ、Ac1 点〜Ac3 点
の２相域からの焼入れ、焼戻し 本発明では、熱間圧延を終了した熱延鋼板の強度を確保
するため、Ac3 点以上の温度域からの焼入れを行う。焼
入れ温度がAc3 点未満であると、所望の強度を確保する
ことができないからである。焼入れの態様は特に限定を
要さない。水焼入れ、油焼入れ等を適宜行えばよい。 Quenching from Ac 3 points or more, Ac 1 point to Ac 3 points
In the present invention, in order to secure the strength of the hot-rolled steel sheet that has finished hot rolling, quenching is performed from a temperature range of Ac 3 or higher. This is because if the quenching temperature is less than Ac 3 point, desired strength cannot be secured. The mode of quenching is not particularly limited. Water quenching, oil quenching, etc. may be appropriately performed.
【００３７】次に、本発明では、Ac1 点〜Ac3 点の２相
域からの焼入れを行い、軟質フェライト相および硬質ベ
イナイト相を析出して低降伏比化を図るとともに、軟質
フェライト相および硬質ベイナイト相の析出に起因した
靱性劣化を防止するため、焼戻しを行う。焼戻しは、通
常の温度 (500 〜600 ℃程度) で行えばよい。Next, in the present invention, quenching is carried out from the two-phase region of Ac 1 point to Ac 3 point to precipitate a soft ferrite phase and a hard bainite phase to achieve a low yield ratio, and to obtain a soft ferrite phase and Tempering is performed to prevent deterioration of toughness due to precipitation of hard bainite phase. Tempering may be performed at a normal temperature (500 to 600 ° C).
【００３８】本発明では、このようにして熱処理を終え
た熱延鋼板を素材として製管加工を行い、鋼管を製造す
る。製管加工の方法は特定の手段には限定されない。例
えば、電縫鋼管、鍛接鋼管さらにはＵＯＥ鋼管等の溶接
鋼管の製管加工法を適用できる。In the present invention, the hot-rolled steel sheet thus heat-treated is used as a raw material for pipe manufacturing to manufacture a steel pipe. The pipe manufacturing method is not limited to a particular means. For example, a method for producing a welded steel pipe such as an electric resistance welded pipe, a forged steel pipe, and a UOE steel pipe can be applied.
【００３９】このようにして、本発明により、0.2 ％YS
≧440N/mm2、TS：590 〜740N/mm2、YR≦80％、El≧20
％、vE0 ≧27Ｊの機械的特性を有し、建造物、橋梁、タ
ンク等の鋼構造物の建築材料として使用するのに好適な
低降伏比高張力鋼管を製造することが可能となった。さ
らに、本発明を実施例を参照しながら詳述するが、これ
は本発明の例示であり、これにより本発明が限定される
ものではない。Thus, according to the present invention, 0.2% YS
≧ 440N / mm 2 , TS: 590 to 740N / mm 2 , YR ≦ 80%, El ≧ 20
%, VE 0 ≧ 27 J, and it has become possible to manufacture a high yield strength steel pipe with a low yield ratio suitable for use as a building material for steel structures such as buildings, bridges and tanks. . Further, the present invention will be described in detail with reference to examples, but this is an exemplification of the present invention, and the present invention is not limited thereto.
【００４０】[0040]
【実施例】表１に示す鋼組成、Ac1 点 (℃) 、Ac3
(℃) および炭素当量Ｃeqを有する鋼片１ないし鋼片18
に、900 ℃以上の温度域における１パス当たりの圧下率
の最大値が同表に示す値となるようにして熱間圧延を行
って所定の板厚の熱延鋼板とし、該熱延鋼板に、表２の
「製造方法」の欄の左端の数字で示す焼入れ温度で焼入
れを行い、引き続き(Ac1点以上 Ac3点以下) の２相温度
域に再加熱して表２の「製造方法」の欄の真中の数字で
示す焼入れ温度で焼入れを行い、さらに表２の「製造方
法」の欄の右端の数字で示す焼戻し温度で焼戻しを行っ
てから、電縫鋼管の製造法に基づいて製管加工を行い、
表２に示す板厚および外径を備えた電縫鋼管を製造し
た。[Example] Steel composition shown in Table 1, Ac 1 point (° C), Ac 3
(° C) and carbon equivalent Ceq 1 to 18
In addition, hot rolling was performed by hot rolling so that the maximum value of the rolling reduction per pass in the temperature range of 900 ° C or higher was the value shown in the table, and the hot rolled steel sheet with a predetermined thickness was obtained. , Quenching was performed at the quenching temperature indicated by the leftmost number in the "Production method" column of Table 2, followed by reheating to the two-phase temperature range of (Ac 1 point or more and Ac 3 points or less), and "Production method" of Table 2 After quenching at the quenching temperature indicated by the number in the middle of the column, and further at the tempering temperature indicated by the number at the right end of the column of "Production method" in Table 2, based on the method for producing electric resistance welded steel pipe Performs pipe manufacturing,
ERW steel pipes having the plate thicknesses and outer diameters shown in Table 2 were manufactured.
【００４１】[0041]
【表１】 [Table 1]
【００４２】[0042]
【表２】 [Table 2]
【００４３】これらの電縫鋼管から、ｌ方向についてJI
S ４号試験片を切り出して、耐力0.2 ％YS、引張強さT
S、降伏比YRおよび伸びElを測定するとともに、t/4 厚
さ部からｌ方向についてJIS ５号試験片を切り出して、
シャルピー吸収エネルギーｖＥ０（Ｊ）を測定した。結
果を表２にまとめて示す。From these ERW steel pipes, JI
S No. 4 test piece is cut out, yield strength 0.2% YS, tensile strength T
Measure S, yield ratio YR and elongation El and cut out a JIS No. 5 test piece from the t / 4 thickness part in the 1 direction,
Charpy absorbed energy vE 0 (J) was measured. The results are summarized in Table 2.
【００４４】表２における試料Ｎｏ．１ないし試料No.9
は、本発明で規定する条件を全て満足するため、0.2 ％
YS≧440N/mm2、TS：590 〜740N/mm2、YR≦80％、El≧20
％、vE0≧27Ｊという本発明の目標値を全て満足してい
る。Sample No. 1 in Table 2 1 to Sample No. 9
Is 0.2% because it satisfies all the conditions specified in the present invention.
YS ≧ 440N / mm 2 , TS: 590 to 740N / mm 2 , YR ≦ 80%, El ≧ 20
%, VE 0 ≧ 27 J, all of which satisfy the target values of the present invention.
【００４５】これに対し、試料No.10 は、Ｃ含有量が本
発明の範囲の下限を下回っているため、TSが低下した。
試料No.11 は、Si含有量が本発明の範囲の上限を上回っ
ているとともに炭素当量Ｃeqが本発明の範囲の下限を下
回っているため、TSおよびvE0 ともに劣化した。On the other hand, in sample No. 10, the TS content was lowered because the C content was below the lower limit of the range of the present invention.
Sample No. 11 deteriorated in both TS and vE 0 because the Si content was above the upper limit of the range of the present invention and the carbon equivalent Ceq was below the lower limit of the range of the present invention.
【００４６】試料No.12 は、Mn含有量が本発明の範囲の
下限を下回っているとともに炭素当量Ｃeqが本発明の範
囲の下限を下回っているため、0.2 ％YS、TSおよびvE0
がそれぞれ劣化した。試料No.13 は、Nb含有量が本発明
の範囲の上限を上回っているためvE0 が劣化した。In sample No. 12, the Mn content is below the lower limit of the range of the present invention and the carbon equivalent Ceq is below the lower limit of the range of the present invention, so 0.2% YS, TS and vE 0.
Have deteriorated. In Sample No. 13, the Nb content was above the upper limit of the range of the present invention, so vE 0 was deteriorated.
【００４７】試料No.14 は、炭素当量Ｃeqが本発明の範
囲の上限を上回っているとともに900 ℃以上の温度域に
おける１パスの圧下率が本発明の範囲の上限を上回って
おり、さらにAc3 以上からの焼入れ温度が本発明の範囲
の下限を下回っているため、TS、YR、ElおよびvE0 がそ
れぞれ劣化した。In sample No. 14, the carbon equivalent Ceq exceeds the upper limit of the range of the present invention, and the rolling reduction in one pass in the temperature range of 900 ° C. or higher exceeds the upper limit of the range of the present invention. Since the quenching temperature from 3 or more is below the lower limit of the range of the present invention, TS, YR, El and vE 0 were deteriorated respectively.
【００４８】試料No.15 は、炭素当量Ｃeqが本発明の範
囲の上限を上回っているとともに900 ℃以上の温度域に
おける１パスの圧下率が本発明の範囲の上限を上回って
いるため、TS、YR、ElおよびvE0 がそれぞれ劣化した。
試料No.16 は、900 ℃以上の温度域における１パスの圧
下量が本発明の範囲の上限を上回っているため、YRが劣
化した。In sample No. 15, the carbon equivalent Ceq exceeds the upper limit of the range of the present invention, and the rolling reduction in one pass in the temperature range of 900 ° C. or more exceeds the upper limit of the range of the present invention. , YR, El and vE 0 deteriorated.
In Sample No. 16, the YR was deteriorated because the amount of reduction in one pass in the temperature range of 900 ° C. or higher exceeded the upper limit of the range of the present invention.
【００４９】試料No.17 は、二相域からの焼入れ温度が
本発明の範囲の上限を上回っているため、TS、YR、Elお
よびvE0 がそれぞれ劣化した。さらに、試料No.18 は、
二相域からの焼入れ温度が本発明の範囲の下限を下回っ
ているため、vE0 が劣化した。In sample No. 17, the quenching temperature from the two-phase region exceeded the upper limit of the range of the present invention, so that TS, YR, El and vE 0 were deteriorated. Furthermore, Sample No. 18 is
Since the quenching temperature from the two-phase region is below the lower limit of the range of the present invention, vE 0 was deteriorated.
【００５０】[0050]
【発明の効果】以上詳述したように、本発明により、0.
2 ％YS≧440N/mm2、TS：590 〜740N/mm2、YR≦80％、El
≧20％、vE0 ≧27Ｊの機械的特性を有し、建造物、橋
梁、タンク等の鋼構造物の建築材料として使用するのに
好適な低降伏比高張力鋼管を製造することが可能となっ
た。As described above in detail, according to the present invention,
2% YS ≧ 440N / mm 2 , TS: 590 ~740N / mm 2, YR ≦ 80%, El
It has a mechanical property of ≧ 20% and vE 0 ≧ 27J, and it is possible to manufacture a high yield steel pipe with a low yield ratio suitable for use as a building material for steel structures such as buildings, bridges and tanks. became.
【図１】鋼管のビッカース硬さと降伏比との関係を示す
グラフである。FIG. 1 is a graph showing the relationship between the Vickers hardness of a steel pipe and the yield ratio.
【図２】オーステナイト粒径または鋼管のビッカース硬
さと圧下率との関係を示すグラフである。FIG. 2 is a graph showing a relationship between austenite grain size or Vickers hardness of a steel pipe and a rolling reduction.
【図３】鋼管の炭素当量と降伏比との関係を示すグラフ
である。FIG. 3 is a graph showing a relationship between a carbon equivalent of a steel pipe and a yield ratio.
Claims (1)
〜0.50％、Mn：0.50〜2.00％、さらに、Cu：0.10〜1.5
％、Ni：0.10〜0.50％、Nb：0.005 〜0.10％およびＶ：
0.005 〜0.10％からなる群から選ばれた１種または２種
以上、残部Feおよび不可避的不純物であって、下式によ
り規定される炭素当量Ｃeq(W) が0.38％以上0.45％以下
である鋼片に、900 ℃以上の温度域における１パス当た
りの圧下率が４％以下となるようにして熱間圧延を行っ
て所定の板厚の熱延鋼板とし、該熱延鋼板に、Ac3 点以
上の温度域から焼入れを行い、引き続き Ac1点以上 Ac3
点以下の２相温度域に再加熱して前記２相温度域から焼
入れを行い、さらに焼戻しを行ってから、製管加工を行
うことを特徴とする低降伏比高張力鋼管の製造方法。 【数１】 1. C: 0.02 to 0.20% by weight, Si: 0.02
~ 0.50%, Mn: 0.50 to 2.00%, Cu: 0.10 to 1.5
%, Ni: 0.10 to 0.50%, Nb: 0.005 to 0.10% and V:
One or more selected from the group consisting of 0.005 to 0.10%, the balance Fe and unavoidable impurities, and the carbon equivalent Ceq (W) defined by the following formula is 0.38% to 0.45% One piece is hot-rolled so that the rolling reduction per pass in the temperature range of 900 ° C or higher is 4% or less to obtain a hot-rolled steel sheet having a predetermined thickness, and the hot-rolled steel sheet has Ac 3 points. Quenching is performed from the above temperature range, and subsequently Ac 1 point or more Ac 3
A method for producing a low-strength-ratio high-strength steel pipe, comprising reheating to a two-phase temperature region below a point, quenching from the two-phase temperature region, further tempering, and then pipe-making. (Equation 1)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13068293A JP2687841B2 (en) | 1993-06-01 | 1993-06-01 | Low yield ratio high strength steel pipe manufacturing method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP13068293A JP2687841B2 (en) | 1993-06-01 | 1993-06-01 | Low yield ratio high strength steel pipe manufacturing method |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH06340922A JPH06340922A (en) | 1994-12-13 |
| JP2687841B2 true JP2687841B2 (en) | 1997-12-08 |
Family
ID=15040100
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP13068293A Expired - Lifetime JP2687841B2 (en) | 1993-06-01 | 1993-06-01 | Low yield ratio high strength steel pipe manufacturing method |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2687841B2 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20210130219A (en) | 2019-03-29 | 2021-10-29 | 제이에프이 스틸 가부시키가이샤 | Electric resistance welded steel pipe, manufacturing method thereof, and steel pipe pile |
| KR20210132698A (en) | 2019-03-29 | 2021-11-04 | 제이에프이 스틸 가부시키가이샤 | Electric resistance welded steel pipe, manufacturing method thereof, and steel pipe pile |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP4912013B2 (en) * | 2006-03-31 | 2012-04-04 | 株式会社神戸製鋼所 | Manufacturing method of press-bend cold-formed circular steel pipe with excellent earthquake resistance |
| CN103966504B (en) * | 2013-01-24 | 2016-12-28 | 宝山钢铁股份有限公司 | A kind of 500MPa level low yield strength ratio straight weld steel pipe and manufacture method thereof |
| CN103276179A (en) * | 2013-06-07 | 2013-09-04 | 南京钢铁股份有限公司 | Manufacturing method for pipe line steel with characteristics of high steel plasticity and double peak grain distribution |
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-
1993
- 1993-06-01 JP JP13068293A patent/JP2687841B2/en not_active Expired - Lifetime
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20210130219A (en) | 2019-03-29 | 2021-10-29 | 제이에프이 스틸 가부시키가이샤 | Electric resistance welded steel pipe, manufacturing method thereof, and steel pipe pile |
| KR20210132698A (en) | 2019-03-29 | 2021-11-04 | 제이에프이 스틸 가부시키가이샤 | Electric resistance welded steel pipe, manufacturing method thereof, and steel pipe pile |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH06340922A (en) | 1994-12-13 |
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