JPH09111342A - Production of low yield ratio steel pipe - Google Patents
Production of low yield ratio steel pipeInfo
- Publication number
- JPH09111342A JPH09111342A JP26425395A JP26425395A JPH09111342A JP H09111342 A JPH09111342 A JP H09111342A JP 26425395 A JP26425395 A JP 26425395A JP 26425395 A JP26425395 A JP 26425395A JP H09111342 A JPH09111342 A JP H09111342A
- Authority
- JP
- Japan
- Prior art keywords
- pipe
- steel
- less
- yield ratio
- low yield
- 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.)
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- Heat Treatment Of Steel (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、管厚が５０ｍｍ以
下、外形が４００〜２０００ｍｍ程度の比較的薄肉の建
築・土木用定降伏比６０キロ級高張力鋼管に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relatively thin-walled high yield strength steel pipe having a constant yield ratio of 60 kg for construction and civil engineering, which has a pipe thickness of 50 mm or less and an outer diameter of 400 to 2000 mm.
【０００２】[0002]
【従来の技術】従来、建築用高張力鋼材としては５０キ
ロ級のものが多用されてきたが、ビルの高層化や構造形
式の複雑化などのため、軽量化が可能な６０キロ級鋼材
を使用する動きが出てきた。また、激震時における建造
物の倒壊防止のために鋼構造の終局限界状態設計が適用
されるようになり、高い塑性変形能の目安となる降伏比
が低いこと、すなわち８０％以下の低降伏比が要求され
るようになっている。さらに、柱としての外観上の見栄
えの良さや、梁取り付けなど構造の自由度の高さから、
従来の角型コラムに代わる丸コラムに対する要求も高ま
っている。2. Description of the Related Art Conventionally, 50 kg class high strength steel materials have been widely used, but 60 kg class steel materials that can be reduced in weight due to the increase in the height of buildings and the complicated structure type have been used. The movement to use came out. In addition, the ultimate limit state design of steel structures has come to be applied to prevent collapse of buildings during severe earthquakes, and the yield ratio, which is a measure of high plastic deformability, is low, that is, a low yield ratio of 80% or less. Is required. In addition, because of the good appearance on the pillars and the high degree of freedom in structure such as beam mounting,
There is also an increasing demand for a round column that replaces the conventional rectangular column.
【０００３】以上のような背景に基づき、厚肉６０キロ
級低降伏比鋼管に対する社会的ニーズが高まっており、
これまでにも管厚１００ｍｍ程度までの厚肉鋼管の製造
方法として以下に示す種々の技術が提案されている。Based on the above background, the social needs for thick-wall 60 kg class low yield ratio steel pipe are increasing,
Various techniques described below have been proposed as a method for producing a thick-walled steel pipe having a pipe thickness up to about 100 mm.
【０００４】特開平３−１７３７１９号公報には、冷間
成形後の鋼管に焼もどしを施す技術が開示されており、
特開平５−６５５３５号、特開平５−１１７７４６号、
特開平５−１１７７４７号の各公報には、鋼板に焼もど
しや二相域加熱焼入処理を施し、さらに鋼管成形後に応
力除去処理（ＳＲ処理）を行う技術が開示されている。
また、特開平６−４９５４０号、特開平６−４９５４１
号、特開平６−１２８６４１号の各公報には、鋼板に熱
処理を施した後、さらに鋼管を焼きならし処理するもの
が開示されている。さらに、特開平６−２６４１４３
号、特開平６−２６４１４４号の各公報には鋼板に焼も
どし処理を施したり、二相域加熱焼入−焼もどし処理を
施して成形前の降伏比を厳しく規制した技術が、特開平
６−３４０９２２号公報には鋼板圧延時の１パス当たり
の圧下量を厳しく規定するものが開示されている。Japanese Unexamined Patent Publication (Kokai) No. 3-173719 discloses a technique of tempering a steel pipe after cold forming.
JP-A-5-65535, JP-A-5-117746,
Japanese Patent Application Laid-Open No. 5-117747 discloses a technique in which a steel sheet is subjected to tempering and two-phase region heating and quenching treatment, and further, stress relieving treatment (SR treatment) is performed after forming a steel pipe.
Further, JP-A-6-49540 and JP-A-6-49541.
JP-A-6-128641 and JP-A-6-128641 disclose a method in which a steel plate is heat-treated and then the steel pipe is further normalized. Furthermore, JP-A-6-264143
JP-A-6-264144 and JP-A-6-264144 disclose a technique in which a steel sheet is tempered or a two-phase heating / quenching treatment is performed to strictly control the yield ratio before forming. Japanese Patent Publication No. 340922 discloses that which strictly regulates the amount of reduction per pass when rolling a steel sheet.
【０００５】しかしながら、これらいずれの技術におい
ても極厚鋼管で６０キロ級の高強度と低降伏比を達成す
るために、時間や費用のかかる熱処理を必要としたり、
圧延能率の低下などの犠牲を強いられる製造方法となら
ざるを得ず、工業的な見地からは改善の余地を多く残し
ている。However, in any of these techniques, in order to achieve a high strength and a low yield ratio of 60 kg in an extra-thick steel pipe, heat treatment that requires time and cost is required,
This is a manufacturing method that must be sacrificed such as a reduction in rolling efficiency, leaving much room for improvement from an industrial standpoint.
【０００６】一方、圧延まま・冷間成形ままでも低降伏
比を具備する鋼管が特開平５−１５６３５７号公報に開
示されているが、強度レベルは５０キロ級に限定されて
いる。On the other hand, a steel pipe having a low yield ratio even as rolled or cold formed is disclosed in Japanese Patent Laid-Open No. 5-156357, but the strength level is limited to 50 kg class.
【０００７】[0007]
【発明が解決しようとする課題】ところで、鋼管柱の１
種として、鋼管の内部にコンクリートを充填し、合成構
造として剛性、耐力を確保する新しいタイプの柱の実用
化が検討されており、この場合は鋼管とコンクリートと
の複合材となるため、同じ耐荷重性能を得るための鋼管
の厚さは、鋼管単体の場合の約１／２とすることが可能
となる。このような用途を考慮した場合、例えば肉厚５
０ｍｍ以下の比較的薄肉の６０キロ級低降伏比鋼管が必
要となってくる。By the way, one of the steel pipe columns is used.
As a seed, a new type of column that is filled with concrete inside the steel pipe to secure rigidity and yield strength as a composite structure is being considered for practical use.In this case, it is a composite material of steel pipe and concrete, so the same resistance The thickness of the steel pipe for obtaining the load performance can be about 1/2 of that of the steel pipe alone. Considering such applications, for example, wall thickness 5
A relatively thin 60 kg class low yield ratio steel pipe of 0 mm or less is required.
【０００８】しかしながら、上述した厚肉鋼管製造技術
をこのような鋼管の製造に適用することは経済性および
生産性の観点から問題がある。したがって、薄肉の６０
キロ級低降伏比鋼管を安価にかつ大量に製造し得る新た
な技術が必要となる。However, applying the above-mentioned thick-walled steel pipe manufacturing technique to the manufacture of such a steel pipe is problematic from the viewpoint of economical efficiency and productivity. Therefore, thin 60
A new technology is needed to manufacture low-yield, low-yield-class steel pipes in large quantities at low cost.
【０００９】本発明はかかる事情に鑑みてなされたもの
であって、コンクリート充填型複合鋼管柱などに用いる
ことができる管厚５０ｍｍ程度までの６０キロ級鋼管
を、安価で大量に安定して製造することができる低降伏
比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 it is possible to stably manufacture a 60 kg class steel pipe up to a pipe thickness of about 50 mm, which can be used as a concrete-filled composite steel pipe column, in a large amount at a low cost. An object of the present invention is to provide a method for producing a low yield ratio steel pipe that can be manufactured.
【００１０】[0010]
【課題を解決するための手段】本発明者らは、圧延後や
造管後に鋼板ないし鋼管を熱処理することなく、圧延ま
ま、造管ままで低降伏比の６０キロ級鋼管を製造するた
めに、圧延・加速冷却条件ならびに成形時の拡管率を検
討した結果、以下の知見を得た。DISCLOSURE OF THE INVENTION The inventors of the present invention intend to produce a 60 kg class steel pipe having a low yield ratio as-rolled and as-formed without heat-treating a steel plate or steel pipe after rolling or pipe-making. As a result of examining the rolling / accelerated cooling conditions and the pipe expansion ratio during forming, the following findings were obtained.
【００１１】すなわち、特定の化学組成を有する鋼を、
特定の圧延・加速冷却条件で圧延で圧延することによ
り、圧延ままで０キロ級の強度と８０％以下の低降伏比
を達成し、さらに拡管率を適性化することにより、造管
時の加工硬化による降伏比の上昇が抑制され、成形まま
で管軸方向の低降伏比を達成することができる。That is, a steel having a specific chemical composition is
By rolling by rolling under specific rolling and accelerated cooling conditions, as-rolled strength of 0 kg and a low yield ratio of 80% or less are achieved, and by further optimizing the pipe expansion ratio, processing during pipe manufacturing An increase in the yield ratio due to hardening is suppressed, and a low yield ratio in the axial direction of the pipe can be achieved as formed.
【００１２】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：０．０５〜
０．２０％、Ｓｉ：０．０１〜０．５％、Ｍｎ：０．５
〜２．０％、Ｐ：０．０５％以下、Ｓ：０．０１％以
下、ｓｏｌ．Ａｌ：０．００５〜０．１０％、Ｎ：０．
００１〜０．０１０％を含有し、さらにＮｂ：０．００
５〜０．０５％、Ｖ：０．０１〜０．１０％、Ｔｉ：
０．００５〜０．１０％の１種または２種以上を含有す
る鋼に対し、再結晶温度以下かつＡｒ3 以上の温度域に
おいて累積圧が３０％以上の熱間圧延を施した後、Ａｒ
3 −５０℃±３０℃の温度まで空冷し、その後１〜２０
℃／ｓｅｃの冷却速度で４００〜６００℃の温度範囲ま
で加速冷却を施した鋼板を鋼管に成形し、造管最終工程
における拡管率を０．４％以上とすることを特徴とす
る、管軸方向の引張試験における降伏比が８０％以下の
低降伏比６０キロ級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. Firstly, in% by weight, C: 0.05 to.
0.20%, Si: 0.01 to 0.5%, Mn: 0.5
~ 2.0%, P: 0.05% or less, S: 0.01% or less, sol. Al: 0.005-0.10%, N: 0.
001 to 0.010%, and Nb: 0.00
5 to 0.05%, V: 0.01 to 0.10%, Ti:
Steel containing 0.005 to 0.10% of one or two or more is hot-rolled at a cumulative pressure of 30% or more in a temperature range not higher than the recrystallization temperature and not lower than Ar 3 and then Ar.
3 air-cooled to a temperature of -50 ℃ ± 30 ℃, then 20
A pipe axis, characterized in that a steel plate that has been subjected to accelerated cooling to a temperature range of 400 to 600 ° C at a cooling rate of ° C / sec is formed into a steel pipe, and the pipe expansion ratio in the pipemaking final step is 0.4% or more. A method for manufacturing a low yield ratio 60 kg class steel pipe having a yield ratio of 80% or less in a unidirectional tensile test.
【００１３】第２に、重量％で、Ｃ：０．０５〜０．２
０％、Ｓｉ：０．０１〜０．５％、Ｍｎ：０．５〜２．
０％、Ｐ：０．０５％以下、Ｓ：０．０１％以下、ｓｏ
ｌ．Ａｌ：０．００５〜０．１０％、Ｎ：０．００１〜
０．０１０％を含有し、さらにＣｕ：１．５％以下、Ｎ
ｉ：１．０％以下、Ｃｒ：１．０％以下、Ｍｏ：０．５
％以下、Ｎｂ：０．００５〜０．０５％、Ｖ：０．０１
〜０．１０％、Ｔｉ：０．００５〜０．１０％、Ｂ：
０．０００５〜０．００３０％、Ｃａ：０．０００５〜
０．００５０％の１種または２種以上を含有する鋼に対
し、再結晶温度以下かつＡｒ3 以上の温度域において累
積圧が３０％以上の熱間圧延を施した後、Ａｒ3 −５０
℃±３０℃の温度まで空冷し、その後１〜２０℃／ｓｅ
ｃの冷却速度で４００〜６００℃の温度範囲まで加速冷
却を施した鋼板を鋼管に成形し、造管最終工程における
拡管率を０．４％以上とすることを特徴とする、管軸方
向の引張試験における降伏比が８０％以下の低降伏比６
０キロ級鋼管の製造方法を提供するものである。Secondly, C: 0.05 to 0.2 by weight%.
0%, Si: 0.01 to 0.5%, Mn: 0.5 to 2.
0%, P: 0.05% or less, S: 0.01% or less, so
l. Al: 0.005-0.10%, N: 0.001-
0.010%, Cu: 1.5% or less, N
i: 1.0% or less, Cr: 1.0% or less, Mo: 0.5
% Or less, Nb: 0.005 to 0.05%, V: 0.01
~ 0.10%, Ti: 0.005 to 0.10%, B:
0.0005-0.0030%, Ca: 0.0005-
To 0.0050% of one or steel containing two or more, whose accumulated pressure at the recrystallization temperature or lower and than the Ar 3 temperature ranges are subjected to hot rolling of more than 30%, Ar 3 -50
Air-cool to a temperature of ± 30 ° C, then 1-20 ° C / se
A steel plate that has been subjected to accelerated cooling to a temperature range of 400 to 600 ° C. at a cooling rate of c is formed into a steel pipe, and the pipe expansion ratio in the pipe forming final step is 0.4% or more. Low yield ratio 6 with a yield ratio of 80% or less in a tensile test
The present invention provides a method for manufacturing a 0 kg class steel pipe.
【００１４】[0014]
【発明の実施の形態】以下、本発明に係る低降伏比鋼管
の製造方法、組成、圧延条件、造管成形条件に分けて詳
細に説明する。 （組成）本発明では、基本成分元素としてＣ、Ｓｉ、Ｍ
ｎ、ｓｏｌ．Ａｌ、およびＮを含有し、不純物元素とし
てのＰおよびＳを規制し、選択成分として、Ｎｂ，Ｖ，
Ｔｉの少なくとも１種、またはＣｕ，Ｎｉ，Ｃｒ，Ｍ
ｏ，Ｎｂ，Ｖ，Ｔｉ，Ｂ，Ｃａの少なくとも１種が添加
される。BEST MODE FOR CARRYING OUT THE INVENTION A method for producing a low yield ratio steel pipe according to the present invention, composition, rolling conditions, and pipe forming conditions will be described in detail below. (Composition) In the present invention, C, Si, and M are used as basic constituent elements.
n, sol. It contains Al and N, regulates P and S as impurity elements, and uses Nb, V, and
At least one of Ti, or Cu, Ni, Cr, M
At least one of o, Nb, V, Ti, B and Ca is added.
【００１５】これら成分元素の限定理由を以下に説明す
る。なお、以下の説明において％表示はすべて重量％を
示す。 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０．０５％は必要である。しかし、０．２
０％を超えると低温割れや高温割れ等が発生しやすくな
って溶接性や靭性を損なう。このため、Ｃ含有量を０．
０５〜０．２０％の範囲とする。The reasons for limiting these constituent elements will be described below. In the following description, all percentages are% by weight. C: To secure the strength of this type of steel inexpensively and effectively, C is required to be 0.05%. However, 0.2
If it exceeds 0%, cold cracking and hot cracking are likely to occur, and the weldability and toughness are impaired. Therefore, the C content is 0.
The range is from 05 to 0.20%.
【００１６】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招く。こ
のため、Ｓｉ含有量を０．０１〜０．５０％の範囲とす
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 set to the range of 0.01 to 0.50%.
【００１７】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。このため、Ｍｎ含有量を０．５〜
２．０％の範囲とする。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
The range is 2.0%.
【００１８】Ｐ： 本発明においてＰは不純物元素であ
り、０．０５％以上含有すると溶接高温割れが発生しや
すくなる。したがって、Ｐ含有量の上限を０．０５％と
する。P: In the present invention, P is an impurity element, and if it is contained in an amount of 0.05% or more, weld hot cracking is likely to occur. Therefore, the upper limit of the P content is set to 0.05%.
【００１９】Ｓ： 本発明においてＰは不純物元素であ
り、０．０１％以上含有するとＭｎＳに起因する溶接時
の水素割れが発生しやすくなる。したがって、Ｓ含有量
の上限を０．０１％とする。S: In the present invention, P is an impurity element, and if it is contained in an amount of 0.01% or more, hydrogen cracking during welding due to MnS is likely to occur. Therefore, the upper limit of the S content is 0.01%.
【００２０】ｓｏｌ．Ａｌ： ｓｏｌ．Ａｌは脱酸のた
めに添加されるが、０．００５％未満では十分な脱酸効
果が得られず、また０．１０％でその効果が飽和し、そ
れより多く添加することは経済的な面から望ましくな
い。このため、ｓｏｌ．Ａｌ含有量を０．００５〜０．
１０％の範囲とする。Sol. Al: sol. Al is added for deoxidation, but if it is less than 0.005%, a sufficient deoxidizing effect cannot be obtained, and if it is 0.10%, the effect is saturated, and it is economical to add more than that. It is not desirable from the aspect. Therefore, sol. Al content is 0.005 to 0.
The range is 10%.
【００２１】Ｎ： Ｎは窒化物を形成して高温強度を向
上させるが、０．００１％未満ではその効果が小さく、
また０．０１％を超えると靭性低下につながる。このた
め、Ｎ含有量を０．００１〜０．０１％の範囲とする。N: N forms a nitride to improve high temperature strength, but if less than 0.001%, its effect is small,
On the other hand, if it exceeds 0.01%, the toughness is lowered. Therefore, the N content is set in the range of 0.001 to 0.01%.
【００２２】以上が基本成分であるが、選択成分の限定
理由は以下の通りである。 Ｎｂ，Ｖ，Ｔｉ： これらの元素は析出強化や焼入れ性
増大効果による強度上昇あるいは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、これらの含有量をＮｂ：０．
００５％〜０．０５％、Ｖ：０．０１〜０．１０％、Ｔ
ｉ：０．００５〜０．１０％の範囲とする。The above are the basic components, but the reasons for limiting the selective components are as follows. Nb, V, Ti: These elements bring about an increase in strength due to the effect of precipitation strengthening and an increase in hardenability, or an improvement in toughness due to the refinement of crystal grains. However, when the addition amount increases, the toughness of the welded portion is deteriorated. If the content is Nb: 0.
005% to 0.05%, V: 0.01 to 0.10%, T
i: The range is 0.005 to 0.10%.
【００２３】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
を大きく損なわずに強化を図ることができるが、溶接性
および経済性の観点から、これらの含有量をＣｕ：１．
５％以下、Ｎｉ：１．０％以下、Ｃｒ：１．０％以下、
Ｍｏ：０．５％以下の範囲とする。Cu, Ni, Cr, Mo: These elements can be strengthened without significantly impairing toughness through solid solution strengthening and structural change due to increase in hardenability, but from the viewpoint of weldability and economy, these elements The content of Cu: 1.
5% or less, Ni: 1.0% or less, Cr: 1.0% or less,
Mo: 0.5% or less.
【００２４】Ｂ： 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が、その含有量が０．００
０５％未満ではその効果が小さく、また０．００３０％
を超えると溶接性を損なうため、その含有量を０．００
０５〜０．００３０％の範囲とする。B: B increases the hardenability of steel and exerts a great effect on the strength increase, but its content is 0.00
If less than 05%, the effect is small, and 0.0030%
If it exceeds 1.0, the weldability will be impaired, so its content should be 0.00
The range is from 05 to 0.0030%.
【００２５】Ｃａ： Ｃａは介在物の形態を球状化さ
せ、これにより水素誘起割れやラメラテアなどを防止す
る効果があるが、０．０００５％未満ではその効果が得
られず、０．００５％を超えて添加してもその効果は飽
和するため、Ｃａ含有量を０．０００５〜０．００５％
の範囲とする。Ca: Ca has the effect of spheroidizing the morphology of inclusions, thereby preventing hydrogen-induced cracking, lamellatea, etc. However, if it is less than 0.0005%, that effect cannot be obtained, and 0.005% is added. Even if added in excess, the effect is saturated, so the Ca content should be 0.0005-0.005%.
Range.
【００２６】（圧延条件）本発明においては、上述のよ
うな組成を有する鋼に対し、再結晶温度以下かつＡｒ3
以上の温度域において累積圧が３０％以上の熱間圧延を
施した後、Ａｒ3−５０℃±３０℃の温度まで空冷し、
その後１〜２０℃／ｓｅｃの冷却速度で４００〜６００
℃の温度範囲まで加速冷却を施す。これにより鋼板段階
で圧延方向の引張特性として６０キロ級の高強度と８０
％以下の低降伏比を得る。(Rolling Conditions) In the present invention, for the steel having the above composition, the recrystallization temperature is not higher than Ar 3
After hot rolling with a cumulative pressure of 30% or more in the above temperature range, air cooling to a temperature of Ar 3 −50 ° C. ± 30 ° C.,
Then 400 to 600 at a cooling rate of 1 to 20 ° C / sec.
Accelerated cooling to a temperature range of ℃. As a result, at the steel plate stage, tensile strength in the rolling direction is as high as 60 kg and 80%.
A low yield ratio of less than or equal to% is obtained.
【００２７】ここで、再結晶温度以下で３０％以上の累
積圧下率としたのは、未再結晶域で十分な圧延を行うこ
とにより制御圧延の効果を発揮させて微細なオーステナ
イト粒を得るためである。また、Ａｒ3 以上の温度域で
熱間圧延を行うため、圧延終了温度も当然にＡｒ3 以上
となるが、このようにしたのは、集合組織の発達を抑制
して、超音波探傷の測定精度に悪影響を及ぼす音響異方
性をなくすためである。Here, the reason why the cumulative rolling reduction is 30% or more at the recrystallization temperature or lower is that the effect of the controlled rolling is exerted by obtaining sufficient austenite grains by performing sufficient rolling in the unrecrystallized region. Is. Also, since hot rolling is performed in a temperature range of Ar 3 or higher, the rolling end temperature naturally becomes Ar 3 or higher, but this is done by suppressing the development of texture and measuring ultrasonic flaw detection. This is to eliminate acoustic anisotropy that adversely affects accuracy.
【００２８】なお、再結晶温度は成分系によって異なる
が、目安としてＮｂ無添加系で９００℃程度、Ｎｂ添加
系で９５０℃程度である。また、Ａｒ3 もＣやＭｎなど
の含有量によって異なるが、７５０℃程度が目安とな
る。The recrystallization temperature varies depending on the component system, but as a guide, it is about 900 ° C. in the Nb-free system and about 950 ° C. in the Nb-containing system. Ar 3 also varies depending on the content of C, Mn, etc., but about 750 ° C. is a standard.
【００２９】また、圧延終了後直ちに加速冷却を施さず
にＡｒ3 −５０℃±３０℃の温度まで空冷するのはフェ
ライトを一部析出させるためであり、その後の加速冷却
により残りのオーステナイトをベイナイト組織とし、最
終的にフェライト＋ベイナイトの二相混合組織として低
降伏比を達成する。ここで加速冷却開始温度がＡｒ3−
２０℃より高温になるとフェライトの生成が不十分とな
り、Ａｒ3 −８０℃未満になるとフェライト分率が高く
なりすぎて６０キロ級の強度を得難くなる。なお、±３
０℃は実製造時のばらつきを考慮したものである。Immediately after the completion of rolling, air cooling to a temperature of Ar 3 −50 ° C. ± 30 ° C. without performing accelerated cooling is for the purpose of precipitating a part of ferrite, and the remaining austenite is converted to bainite by subsequent accelerated cooling. As a structure, a low yield ratio is finally achieved as a two-phase mixed structure of ferrite and bainite. Here, the accelerated cooling start temperature is Ar 3 −.
If the temperature is higher than 20 ° C., the formation of ferrite becomes insufficient, and if it is less than Ar 3 −80 ° C., the ferrite fraction becomes too high and it becomes difficult to obtain the strength of 60 kg class. In addition, ± 3
0 ° C. takes into consideration variations during actual manufacturing.
【００３０】加速冷却の適正な冷却速度は成分系によっ
て異なるが、前記の成分範囲でベイナイト組織を得るた
めには１℃／ｓｅｃ以上は必要である。一方、２０℃／
ｓｅｃを超えると、板表面近傍が異常に硬化するような
板厚方向の硬さの不均一が生じ、本発明の特徴である圧
延まま、すなわちテンパーフリーの状態で造管成形を行
うと割れ等の欠陥が発生するため、冷却速度の上限を２
０℃／ｓｅｃとした。The appropriate cooling rate for accelerated cooling differs depending on the component system, but 1 ° C./sec or more is required to obtain the bainite structure in the above component range. On the other hand, 20 ° C /
When it exceeds sec, the hardness in the plate thickness direction becomes uneven such that the vicinity of the plate surface is abnormally hardened, and when the pipe forming is carried out in the as-rolled state, that is, in the temper-free state, which is a feature of the present invention, cracks, etc. Therefore, the upper limit of the cooling rate is 2
It was set to 0 ° C./sec.
【００３１】加速冷却の停止温度を常温とせずに４００
〜６００℃としたが、これも本発明の特徴である圧延ま
ま（テンパーフリー）の状態で造管成形を行うために必
須の条件である。すなわち、冷却停止温度を４００℃未
満とすると、加速冷却時に生成した島状マルテンサイト
が分解せずに残存するため、造管成形時に割れ等の欠陥
が発生する。一方、冷却停止温度が６００℃を超える
と、ベイナイト変態が十分に終了せずに６０キロ級の強
度を確保することが困難となる。If the stop temperature of accelerated cooling is not set to room temperature, 400
Although the temperature is set to ˜600 ° C., this is also an essential condition for performing pipe forming in the as-rolled (temper-free) state, which is a feature of the present invention. That is, when the cooling stop temperature is less than 400 ° C., island-like martensite generated during accelerated cooling remains without being decomposed, and thus defects such as cracks occur during pipe forming. On the other hand, when the cooling stop temperature exceeds 600 ° C., it becomes difficult to secure the strength of 60 kg class without completing the bainite transformation sufficiently.
【００３２】（造管成形条件）造管成形は所定の形状・
寸法が得られる方法であればＵＯＥ、プレスベンド、ロ
ールベンドなどどのような冷間成形法でもかまわない。
ただし、成形ままで低降伏比を得るためには、成形の最
終工程で拡管を施さなければならない。これは拡管によ
る周方向の引張変形は長手方向の圧縮変形をもたらし、
再度長手方向に外力が加わった際に、バウシンガー効果
により降伏強度が低下し、結果として低降伏比が達成さ
れることを狙ったものである。拡管率と降伏比との関係
を図１に示す。図１に示すように、拡管率が０．４％以
上となると８０％以下の低降伏比が容易に達成される。
したがって、拡管率の下限を０．４％とした。(Pipe forming conditions) Pipe forming has a predetermined shape
Any cold forming method such as UOE, press bend, or roll bend may be used as long as the dimensions can be obtained.
However, in order to obtain a low yield ratio as it is, the pipe must be expanded in the final step of molding. This is because the tensile deformation in the circumferential direction due to pipe expansion causes the compressive deformation in the longitudinal direction,
When an external force is applied again in the longitudinal direction, the yield strength is lowered by the Bausinger effect, and as a result, a low yield ratio is achieved. Fig. 1 shows the relationship between the expansion ratio and the yield ratio. As shown in FIG. 1, when the expansion ratio is 0.4% or more, a low yield ratio of 80% or less can be easily achieved.
Therefore, the lower limit of the pipe expansion ratio is set to 0.4%.
【００３３】以上のように、上記成分系、圧延・加速冷
却条件を採用することにより、圧延ままで６０キロ級の
強度と低降伏比を確保することができ、さらに拡管率を
０．４％以上とすることにより造管時の加工硬化による
降伏比の上昇を抑制することができるため、造管成形ま
まで低降伏比を達成することができる。As described above, by adopting the above component system and rolling / accelerated cooling conditions, it is possible to secure a strength of 60 kg class and a low yield ratio as it is rolled, and further, a pipe expansion ratio of 0.4%. With the above, it is possible to suppress an increase in the yield ratio due to work hardening during pipe forming, and thus it is possible to achieve a low yield ratio as it is in pipe forming.
【００３４】[0034]
【実施例】以下、本発明の具体的な実施例について説明
する。 （実施例１）成分系ならびに圧延条件を種々変えて製造
した鋼板を、種々の拡管率を採用して冷間で造管し、管
軸方向の引張特性を調べた。表１に化学組成を示し、表
２、３に圧延・造管条件および引張試験の結果を示す。DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described. (Example 1) Steel sheets manufactured by varying the composition system and rolling conditions were cold-cast with various expansion ratios, and the tensile properties in the pipe axis direction were examined. Table 1 shows the chemical composition, and Tables 2 and 3 show the rolling / pipe forming conditions and the results of the tensile test.
【００３５】[0035]
【表１】 [Table 1]
【００３６】[0036]
【表２】 [Table 2]
【００３７】[0037]
【表３】 [Table 3]
【００３８】表２、３に示すように、本発明の範囲内の
成分系を用い、かつ本発明で規定された圧延条件・造管
条件を採用した鋼番１〜１０は、６０キロ級として十分
な強度と８０％以下の低降伏比が得られ、さらに２７％
以上の優れた伸び延性を示すことが確認された。As shown in Tables 2 and 3, steel Nos. 1 to 10 using the component system within the scope of the present invention and adopting the rolling conditions and pipe forming conditions specified in the present invention are classified as 60 kg class. Sufficient strength and low yield ratio of 80% or less are obtained, and further 27%
It was confirmed that the above excellent elongation and ductility were exhibited.
【００３９】これに対して、鋼番１１のように未再結晶
温度域での圧下率が３０％に満たない場合、また鋼番１
２，１５，１７のようにＮｂ，Ｖ，Ｔｉを過剰に添加し
た場合、および鋼番２０のように加速冷却の停止温度が
４００℃未満の場合には、いずれも伸びが２０％未満と
なり、延性が不足していることが確認された。さらに、
圧延仕上温度がＡｒ3 より低い鋼番１３、加速冷却にお
ける冷却速度が１℃／ｓｅｃ未満の鋼番１６、冷却開始
温度Ａｒ3 −８０℃より低い鋼番１９では、いずれも強
度が６０キロ級としては不足していた。さらに、拡管率
が０．４％に満たない鋼番１４や、加速冷却の開始温度
がＡｒ3 −２０℃より高い鋼番１８では、８０％を超え
る高い降伏比となった。On the other hand, when the reduction ratio in the unrecrystallized temperature range is less than 30% as in steel No. 11, steel No. 1
When Nb, V, and Ti are excessively added like Nos. 2, 15 and 17, and when the accelerated cooling stop temperature is less than 400 ° C. like Steel No. 20, the elongation is less than 20%, It was confirmed that the ductility was insufficient. further,
Steel No. 13 having a rolling finishing temperature lower than Ar 3 , Steel No. 16 having a cooling rate of less than 1 ° C./sec in accelerated cooling, and Steel No. 19 having a cooling start temperature Ar 3 −80 ° C. have a strength of 60 kg. Was lacking as Further, in Steel No. 14 having a pipe expansion ratio of less than 0.4% and Steel No. 18 having a start temperature of accelerated cooling higher than Ar 3 −20 ° C., a high yield ratio exceeding 80% was obtained.
【００４０】[0040]
【発明の効果】以上説明したように、本発明によれば、
コンクリート充填型複合鋼管柱などに用いることができ
る管厚５０ｍｍ程度以下の比較的薄肉の低降伏比６０キ
ロ級鋼管を、圧延ままでかつ造管成形ままで得ることが
でき、造管前の鋼板や造管後の鋼管を熱処理しなくても
よいため、安価で大量に安定して製造することができ、
生産性および経済性を著しく高めることができる。As described above, according to the present invention,
A relatively thin-walled, low yield ratio 60 kg class steel pipe with a tube thickness of about 50 mm or less, which can be used for concrete-filled composite steel pipe columns, etc., can be obtained as-rolled and pipe-formed as it is. Since it is not necessary to heat treat steel pipe after pipe making, it is possible to manufacture inexpensively and stably in large quantities.
Productivity and economic efficiency can be significantly increased.
【図１】拡管率と管軸方向の降伏比との関係を示すグラ
フ。FIG. 1 is a graph showing the relationship between the pipe expansion ratio and the yield ratio in the pipe axis direction.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 当麻 英夫 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 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Hideo Toma 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Steel Pipe Co., Ltd.
Claims (2)
Ｓｉ：０．０１〜０．５％、Ｍｎ：０．５〜２．０％、
Ｐ：０．０５％以下、Ｓ：０．０１％以下、ｓｏｌ．Ａ
ｌ：０．００５〜０．１０％、Ｎ：０．００１〜０．０
１０％を含有し、さらにＮｂ：０．００５〜０．０５
％、Ｖ：０．０１〜０．１０％、Ｔｉ：０．００５〜
０．１０％の１種または２種以上を含有する鋼に対し、
再結晶温度以下かつＡｒ3 以上の温度域において累積圧
が３０％以上の熱間圧延を施した後、Ａｒ3 −５０℃±
３０℃の温度まで空冷し、その後１〜２０℃／ｓｅｃの
冷却速度で４００〜６００℃の温度範囲まで加速冷却を
施した鋼板を鋼管に成形し、造管最終工程における拡管
率を０．４％以上とすることを特徴とする、管軸方向の
引張試験における降伏比が８０％以下の低降伏比６０キ
ロ級鋼管の製造方法。1. C: 0.05 to 0.20% by weight,
Si: 0.01 to 0.5%, Mn: 0.5 to 2.0%,
P: 0.05% or less, S: 0.01% or less, sol. A
1: 0.005 to 0.10%, N: 0.001 to 0.0
10%, and Nb: 0.005 to 0.05
%, V: 0.01 to 0.10%, Ti: 0.005 to
For steel containing 0.10% of one or more,
After hot rolling at a cumulative pressure of 30% or more in a temperature range of recrystallization temperature or lower and Ar 3 or higher, Ar 3 −50 ° C. ±
A steel plate obtained by air cooling to a temperature of 30 ° C. and then accelerated cooling to a temperature range of 400 to 600 ° C. at a cooling rate of 1 to 20 ° C./sec is formed into a steel pipe, and the pipe expansion ratio in the pipe making final step is 0.4. % Or more, a low yield ratio 60 kg class steel pipe having a yield ratio of 80% or less in a tensile test in the axial direction of the pipe.
Ｓｉ：０．０１〜０．５％、Ｍｎ：０．５〜２．０％、
Ｐ：０．０５％以下、Ｓ：０．０１％以下、ｓｏｌ．Ａ
ｌ：０．００５〜０．１０％、Ｎ：０．００１〜０．０
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、Ｎｂ：０．００５〜０．０５％、Ｖ：０．０１〜
０．１０％、Ｔｉ：０．００５〜０．１０％、Ｂ：０．
０００５〜０．００３０％、Ｃａ：０．０００５〜０．
００５０％の１種または２種以上を含有する鋼に対し、
再結晶温度以下かつＡｒ3 以上の温度域において累積圧
が３０％以上の熱間圧延を施した後、Ａｒ3 −５０℃±
３０℃の温度まで空冷し、その後１〜２０℃／ｓｅｃの
冷却速度で４００〜６００℃の温度範囲まで加速冷却を
施した鋼板を鋼管に成形し、造管最終工程における拡管
率を０．４％以上とすることを特徴とする、管軸方向の
引張試験における降伏比が８０％以下の低降伏比６０キ
ロ級鋼管の製造方法。2. C: 0.05 to 0.20% by weight,
Si: 0.01 to 0.5%, Mn: 0.5 to 2.0%,
P: 0.05% or less, S: 0.01% or less, sol. A
1: 0.005 to 0.10%, N: 0.001 to 0.0
10%, Cu: 1.5% or less, Ni:
1.0% or less, Cr: 1.0% or less, Mo: 0.5% or less, Nb: 0.005 to 0.05%, V: 0.01 to
0.10%, Ti: 0.005 to 0.10%, B: 0.
0005-0.0030%, Ca: 0.0005-0.
For steel containing 0050% of one or more,
After hot rolling at a cumulative pressure of 30% or more in a temperature range of recrystallization temperature or lower and Ar 3 or higher, Ar 3 −50 ° C. ±
A steel plate obtained by air cooling to a temperature of 30 ° C. and then accelerated cooling to a temperature range of 400 to 600 ° C. at a cooling rate of 1 to 20 ° C./sec is formed into a steel pipe, and the pipe expansion ratio in the pipe making final step is 0.4. % Or more, a low yield ratio 60 kg class steel pipe having a yield ratio of 80% or less in a tensile test in the axial direction of the pipe.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26425395A JPH09111342A (en) | 1995-10-12 | 1995-10-12 | Production of low yield ratio steel pipe |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26425395A JPH09111342A (en) | 1995-10-12 | 1995-10-12 | Production of low yield ratio steel pipe |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH09111342A true JPH09111342A (en) | 1997-04-28 |
Family
ID=17400614
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP26425395A Pending JPH09111342A (en) | 1995-10-12 | 1995-10-12 | Production of low yield ratio steel pipe |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH09111342A (en) |
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| JP2005060838A (en) * | 2003-07-31 | 2005-03-10 | Jfe Steel Kk | Steel pipe with low yield ratio, high strength, high toughness and superior strain age-hardening resistance, and manufacturing method therefor |
| JP2006183133A (en) * | 2004-12-02 | 2006-07-13 | Jfe Steel Kk | Method for producing steel sheet for high strength steam piping having excellent weld heat affected zone toughness |
| CN104818427A (en) * | 2015-04-17 | 2015-08-05 | 武汉钢铁(集团)公司 | X70 pipeline steel with hydrogen sulfide corrosion resistance for longitudinal welded pipe and production method of X70 pipeline steel |
| 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 |
| CN108914008A (en) * | 2018-08-10 | 2018-11-30 | 武汉钢铁集团鄂城钢铁有限责任公司 | A kind of economical high-ductility 360MPa level structure steel plate and its manufacturing method |
-
1995
- 1995-10-12 JP JP26425395A patent/JPH09111342A/en active Pending
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2005060838A (en) * | 2003-07-31 | 2005-03-10 | Jfe Steel Kk | Steel pipe with low yield ratio, high strength, high toughness and superior strain age-hardening resistance, and manufacturing method therefor |
| JP2006183133A (en) * | 2004-12-02 | 2006-07-13 | Jfe Steel Kk | Method for producing steel sheet for high strength steam piping having excellent weld heat affected zone toughness |
| CN104818427A (en) * | 2015-04-17 | 2015-08-05 | 武汉钢铁(集团)公司 | X70 pipeline steel with hydrogen sulfide corrosion resistance for longitudinal welded pipe and production method of X70 pipeline steel |
| 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 |
| CN108914008A (en) * | 2018-08-10 | 2018-11-30 | 武汉钢铁集团鄂城钢铁有限责任公司 | A kind of economical high-ductility 360MPa level structure steel plate and its manufacturing method |
| CN108914008B (en) * | 2018-08-10 | 2020-11-06 | 宝武集团鄂城钢铁有限公司 | Manufacturing method of economical high-plasticity 360 MPa-level structural steel plate |
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