JPH08143955A - Production of thick-walled high tensile strength steel uniformized in strength in plate thickness direction - Google Patents
Production of thick-walled high tensile strength steel uniformized in strength in plate thickness directionInfo
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- JPH08143955A JPH08143955A JP28569594A JP28569594A JPH08143955A JP H08143955 A JPH08143955 A JP H08143955A JP 28569594 A JP28569594 A JP 28569594A JP 28569594 A JP28569594 A JP 28569594A JP H08143955 A JPH08143955 A JP H08143955A
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- Prior art keywords
- strength
- temperature
- plate thickness
- steel
- thickness direction
- Prior art date
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Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、引張強さ５９０ＭＰａ
以上の強度を有し、低温靱性に優れ、かつ板厚方向に材
質（強度および靱性）が均一な厚肉高張力鋼の製造方法
に関するものである。FIELD OF THE INVENTION The present invention has a tensile strength of 590 MPa.
The present invention relates to a method for producing a thick high-strength steel having the above strength, excellent low temperature toughness, and uniform material (strength and toughness) in the plate thickness direction.
【０００２】[0002]
【従来の技術】近年、エネルギー需要が年々増加し、そ
れに伴い溶接構造物も大型化し、使用される鋼材の板厚
も増大の傾向にあり、安全性がより重要な課題となって
きている。従って、これらに使用される鋼材には、板厚
中心部まで高強度でかつ高靱性が要求されており、さら
に溶接性を具備することが望まれている。2. Description of the Related Art In recent years, the demand for energy has been increasing year by year, the welded structure has been increased in size, and the plate thickness of the steel material used has been increasing, and safety has become a more important issue. Therefore, the steel materials used for these materials are required to have high strength and high toughness even in the central portion of the plate thickness, and further it is desired to have weldability.
【０００３】従来から、高強度鋼の熱処理としては焼入
れ焼戻し法がある。これは、焼入れによりマルテンサイ
トまたは下部ベイナイトの変態組織とし、その後の焼戻
し処理により過飽和固溶炭素を炭化物として析出させる
ものである。この熱処理法は、圧延した鋼板について再
加熱焼入れ処理を必要とするために経済性が低下すると
いう欠点があった。Conventionally, as a heat treatment for high strength steel, there is a quenching and tempering method. In this, a transformation structure of martensite or lower bainite is obtained by quenching, and supersaturated solid solution carbon is precipitated as a carbide by subsequent tempering treatment. This heat treatment method has a drawback in that the economical efficiency is lowered because the reheated quenching treatment is required for the rolled steel sheet.
【０００４】しかし、最近になって、このような再加熱
焼入れ焼戻し法の欠点を補うべく、圧延後一旦冷却する
ことなく直ちに焼入れを行う直接焼入れ技術が開発さ
れ、経済性を低下させることなく強度も増大できるとい
うことから注目されるようになってきた。特に厚肉材に
対しては、板厚中心まできちんと焼きを入れ、良好な強
度、靱性を得るために、少ない合金元素で焼入れ性の向
上を計る方法として、Ｂによる焼入れ性向上効果を活用
する方法が多く適用されている。例えば、特公昭６０−
２５４９４号公報に記載されるように、熱間圧延した
後、焼入れまでの間に再結晶を起こさせ、Ｂを粒界に偏
析させた後、水焼入れし、その後焼戻しを行うことによ
り、強度、靱性の優れた高張力鋼が得られる。また、特
公平５−３３２８６号公報に記載されるように、Ａｌ、
ＢおよびＮの量的バランスを確保し、かつ圧延終了から
焼入れまでの時間を一定値以上確保すれば、目的の強
度、靱性が得られる。However, recently, in order to make up for the drawbacks of such a reheating quenching and tempering method, a direct quenching technique has been developed in which quenching is performed immediately after rolling without once cooling, and the strength is maintained without lowering the economical efficiency. Has also come to the attention because it can be increased. Especially for thick-walled materials, in order to obtain good strength and toughness, quenching is done to the center of the plate thickness, and as a method of improving the quenching ability with a small amount of alloying elements, the effect of improving the quenching ability of B is utilized. Many methods are applied. For example,
As described in Japanese Patent No. 25494, after hot rolling, recrystallization is caused until quenching, B is segregated at grain boundaries, water quenching is performed, and then tempering is performed to obtain strength, A high strength steel with excellent toughness can be obtained. In addition, as described in Japanese Patent Publication No. 5-33286, Al,
If the quantitative balance between B and N is secured and the time from the end of rolling to the quenching is secured at a certain value or more, the desired strength and toughness can be obtained.
【０００５】一方、Ｂの焼入れ性を利用しない方法とし
ては、特公平３−１６５２３号公報に記載されるよう
に、Ｎｉ量を２．０％以上に調整し、圧延工程において
圧延条件、圧延後の冷却条件と析出処理を適切に制御す
ることにより、微細なフェライト組織あるいはアシキュ
ラーフェライト組織を生成させた、板厚５０ｍｍ以上の
板厚中心部の靱性に優れたＣｕ析出型高張力鋼の製造方
法がある。On the other hand, as a method that does not utilize the hardenability of B, as described in Japanese Patent Publication No. 3-16523, the Ni content is adjusted to 2.0% or more, and the rolling conditions in the rolling process and after rolling Of Cu precipitation high-strength steel with excellent toughness at the center of plate thickness of 50 mm or more, in which a fine ferrite structure or acicular ferrite structure is generated by appropriately controlling the cooling conditions and precipitation treatment of There is a way.
【０００６】[0006]
【発明が解決しようとする課題】しかしながら、Ｂの焼
入れ性向上効果を利用する方法でも、圧延終了から直接
焼入れするまでの経過時間によって、Ｂの粒界への偏析
状態と結晶粒の再結晶挙動が相互に作用しあい、鋼板の
焼入れ性が複雑に変化するため、板厚方向各位置の焼入
れ処理後の変態組織が変化する。このため、ＨＴ５９０
クラス（引張強さ５９０ＭＰａ級）の厚肉材において
は、表層下から板厚１／４ｔ（ｔは全厚）部はＢの焼入
れ性向上によりマルテンサイトと下部ベイナイトの混合
組織が得られても、板厚中心部においては粗粒の上部ベ
イナイト組織の生成により十分な靱性が得られず、この
結果、板厚方向の強度差も大きい。さらに、ＨＴ７８０
クラス（引張強さ７８０ＭＰａ級）の厚肉材において
は、板厚中心部の焼入れ性向上に伴い、マルテンサイト
と下部ベイナイトの混合組織が得られ高靱性が得られる
が、板厚表層下は必然的に粗粒の完全マルテンサイト組
織になるために高強度が得られても靱性が低下し、板厚
方向にも強度差が生じるなどの問題がある。また、Ｂの
焼入れ性向上効果も板厚の増大により限界があり、合金
元素も増加するため、溶接性が強度、靱性に伴わないと
いう問題があった。However, even in the method of utilizing the effect of improving the hardenability of B, the segregation state of B into the grain boundary and the recrystallization behavior of the crystal grain depend on the elapsed time from the end of rolling to the direct quenching. Interact with each other and the hardenability of the steel sheet changes in a complicated manner, so that the transformation structure after the quenching treatment at each position in the sheet thickness direction changes. Therefore, HT590
In the thick-walled material of class (tensile strength of 590 MPa class), even if a mixed structure of martensite and lower bainite is obtained by improving the hardenability of B from the surface layer to the plate thickness 1/4 t (t is the total thickness). In the central part of the plate thickness, sufficient toughness cannot be obtained due to the formation of the coarse bainite structure, and as a result, the strength difference in the plate thickness direction is large. Furthermore, HT780
In the thick-walled material of class (tensile strength 780 MPa class), with the improvement of the hardenability of the central part of the plate thickness, a mixed microstructure of martensite and lower bainite is obtained, and high toughness is obtained, but underneath the plate thickness surface layer is inevitable. However, even if high strength is obtained, the toughness is deteriorated due to the coarse grained perfect martensite structure, and there is a problem that a strength difference occurs also in the plate thickness direction. Further, the effect of improving the hardenability of B is limited due to the increase in the plate thickness, and the alloying elements also increase, so that there is a problem that the weldability is not accompanied by the strength and the toughness.
【０００７】一方、Ｂの焼入れ性を利用しないＣｕ析出
強化鋼においては、板厚中心部ではアシキュラーフェラ
イト組織が得られても、表層部ではそれよりやや焼きの
入ったベイナイト組織が生成し、Ｃｕ析出強化を狙って
板厚方向全体に実質的に均一な焼戻しを受けた組織を形
成しても板厚方向に強度差を生じる。これらいずれの技
術でも焼戻し処理においては、徐加熱を前提として焼戻
し温度が一定、すなわち板厚方向にほぼ均一な焼戻し条
件（焼戻し温度領域滞留時間）で処理している。厚肉材
の場合、焼入れままで板厚方向に変態組織が変化するた
め、それ故、ほぼ均一な焼戻し条件では板厚方向に強度
差を生じるという問題があった。On the other hand, in the Cu precipitation-strengthened steel not utilizing the hardenability of B, even if an acicular ferrite structure is obtained in the center part of the plate thickness, a slightly hardened bainite structure is generated in the surface part, Even if a structure that is subjected to substantially uniform tempering is formed in the entire plate thickness direction aiming at Cu precipitation strengthening, a strength difference occurs in the plate thickness direction. In any of these techniques, the tempering process is performed under the condition that the tempering temperature is constant, that is, the tempering condition (tempering temperature region residence time) is substantially uniform in the sheet thickness direction in the tempering process. In the case of a thick-walled material, the transformation structure changes in the plate thickness direction as it is quenched, and therefore there is a problem that a strength difference occurs in the plate thickness direction under substantially uniform tempering conditions.
【０００８】[0008]
【課題を解決するための手段】本発明は、上記課題を解
決した、板厚方向に強度が均一な厚肉高張力鋼の製造方
法を提供することを目的とするものである。本発明者ら
は、板厚方向に強度および靱性が均一な厚肉高張力鋼を
開発することを目的として、鋼および製造方法について
種々実験した結果、Ｍｏ、Ｎｉを添加した比較的低い炭
素含有量の低合金鋼片を、熱間圧延工程において制御圧
延−直接焼入れし、板厚方向にオーステナイト結晶粒を
細粒化させて微細な焼入れ組織とした後、あらかじめ高
温に設定した炉に厚肉の焼入れ鋼板を装入すると、板厚
中心部と表層部に温度差が生じて、中心部の温度が適正
な焼戻し温度範囲に対し、表層部の温度がそれ以上Ａｃ
1 点以下に到達し、板厚方向に温度差をつけた状態で抽
出する焼戻し処理を施すと、従来の均一な焼戻し温度の
徐加熱に比べ、昇温速度が速いことと板厚方向に温度差
があることから、板厚方向の強度および靱性が均一化し
た鋼板が製造できることを知見した。SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for manufacturing thick high-strength steel having uniform strength in the plate thickness direction, which solves the above problems. The inventors of the present invention conducted various experiments on steel and a manufacturing method for the purpose of developing a thick high-strength steel having uniform strength and toughness in the plate thickness direction, and as a result, relatively low carbon content containing Mo and Ni was added. A controlled amount of low alloy steel slabs in the hot rolling process-direct quenching, austenite crystal grains are refined in the plate thickness direction to form a fine quenched structure, and then thick-walled in a furnace set to a high temperature in advance. When the hardened steel sheet of No. 1 is charged, a temperature difference occurs between the central portion of the plate thickness and the surface layer portion, and the temperature of the central portion exceeds the appropriate tempering temperature range.
When a tempering process is performed in which the temperature reaches one point or less and a temperature difference is applied in the plate thickness direction, the temperature rising rate is faster and the temperature in the plate thickness direction is higher than that of the conventional gradual heating with a uniform tempering temperature. Because of the difference, it was found that a steel sheet with uniform strength and toughness in the sheet thickness direction can be manufactured.
【０００９】本発明は、このような知見に基づいて構成
されたもので、その要旨とするところは、重量％でＣ：
０．０３〜０．１５％、Ｓｉ：０．０２〜０．５０％、
Ｍｎ：０．３〜２．０％、Ｎｉ：０．１〜５．０％、Ｍ
ｏ：０．１〜１．５％、Ｃｒ：０．１〜１．５％、Ａ
ｌ：０．０１〜０．１０％、Ｎ：０．００６０％以下を
含有し、さらにＣｕ：０．１〜１．５％、Ｖ：０．０１
〜０．１％、Ｎｂ：０．００５〜０．０５％、Ｔｉ：
０．００５〜０．０３％、Ｂ：０．０００５〜０．００
２０％からなる強度・靱性改善元素群の１種または２種
以上を含有し、および／または介在物形態制御作用のあ
るＣａ：０．０００５〜０．００５％含有し、残部がＦ
ｅおよび不可避的不純物からなる鋼片を、１０００〜１
２５０℃に加熱した後、熱間圧延において９５０℃以下
の温度で６０％以上の圧下率で圧延し、次いでＡｒ3 点
以上の温度から水冷する焼入れ処理を施し、引き続いて
８００〜１０５０℃に保持された炉に装入し、表層部温
度が５５０℃〜Ａｃ1 点に到達後、直ちに抽出する焼戻
し処理を施すことを特徴とする板厚方向に強度が均一な
厚肉高張力鋼の製造方法にある。The present invention is constructed on the basis of such knowledge, and the gist of the present invention is C in weight%:
0.03 to 0.15%, Si: 0.02 to 0.50%,
Mn: 0.3-2.0%, Ni: 0.1-5.0%, M
o: 0.1 to 1.5%, Cr: 0.1 to 1.5%, A
1: 0.01 to 0.10%, N: 0.0060% or less, further Cu: 0.1 to 1.5%, V: 0.01
~ 0.1%, Nb: 0.005-0.05%, Ti:
0.005-0.03%, B: 0.0005-0.00
It contains one or more elements of the strength / toughness improving element group consisting of 20%, and / or Ca having an effect of controlling the morphology of inclusions: 0.0005 to 0.005%, and the balance F
Steel pieces consisting of e and unavoidable impurities are 1000 to 1
After heating to 250 ° C., hot rolling is performed at a temperature of 950 ° C. or lower at a reduction rate of 60% or more, then water quenching is performed from a temperature of Ar 3 points or higher, and subsequently maintained at 800 to 1050 ° C. To a thickened high-strength steel having uniform strength in the plate thickness direction, which is characterized by performing a tempering treatment in which the material is charged into a furnace and the surface layer temperature reaches 550 ° C. to Ac 1 point and then immediately extracted. It is in.
【００１０】[0010]
【作用】以下、本発明を作用とともに詳細に説明する。
まず、本発明に適用する鋼を上記のような鋼成分に限定
した理由について述べる。 Ｃ：Ｃは焼入れ性を向上させ、強度を容易に上昇させる
のに有効な元素である。しかし、０．０３％未満では強
度的に不十分であり、０．１５％を超えると靱性および
溶接性が低下する。従って、Ｃ含有量の範囲を０．０３
〜０．１５％とした。The operation of the present invention will be described in detail below.
First, the reason why the steel applied to the present invention is limited to the above steel components will be described. C: C is an element effective for improving hardenability and easily increasing strength. However, if it is less than 0.03%, the strength is insufficient, and if it exceeds 0.15%, the toughness and weldability deteriorate. Therefore, the range of C content is 0.03
˜0.15%.
【００１１】Ｓｉ：Ｓｉは脱酸元素として、また鋼の強
度向上に有効であるが、０．０２％未満ではその効果は
ない。しかし、０．５０％を超えると靱性が低下する。
従って、Ｓｉ含有量の範囲を０．０２〜０．５０％とし
た。 Ｍｎ：Ｍｎは焼入れ性を向上させ、強度確保に有効であ
るが、０．３％未満では十分な効果が得られない。しか
し、２．０％を超えると焼戻し脆性が大きくなって靱性
が低下する。従って、Ｍｎ含有量を０．３〜２．０％と
した。Si: Si is effective as a deoxidizing element and for improving the strength of steel, but if it is less than 0.02%, it is not effective. However, if it exceeds 0.50%, the toughness decreases.
Therefore, the range of the Si content is set to 0.02 to 0.50%. Mn: Mn improves hardenability and is effective in securing strength, but if it is less than 0.3%, a sufficient effect cannot be obtained. However, if it exceeds 2.0%, the temper brittleness increases and the toughness decreases. Therefore, the Mn content is set to 0.3 to 2.0%.
【００１２】Ｎｉ：Ｎｉは鋼の低温靱性の向上および焼
入れ性を高めて強度を向上させるのに有効な元素であ
る。本発明においては、Ｎｉは焼戻し処理時の昇温速度
が速い場合は、焼入れ処理で得られた転位の消滅を抑制
し、また炭化物析出を微細化させる作用があるため、厚
肉材の板厚中心部の強度および靱性を向上させる。０．
１％未満ではその効果がなく、また５．０％を超えると
強度の割には靱性改善の効果が小さくコスト上昇を招
く。従って、Ｎｉ含有量を０．１％〜５．０％とした。Ni: Ni is an element effective for improving the low temperature toughness and the hardenability of steel to improve the strength. In the present invention, Ni has a function of suppressing disappearance of dislocations obtained in the quenching process and refining carbide precipitation when the temperature rising rate in the tempering process is fast, and thus the plate thickness of the thick material Improve the strength and toughness of the central part. 0.
If it is less than 1%, the effect is not obtained, and if it exceeds 5.0%, the effect of improving the toughness is small relative to the strength, and the cost is increased. Therefore, the Ni content is set to 0.1% to 5.0%.
【００１３】Ｍｏ：Ｍｏは焼入れ性を向上させ、強度確
保および焼戻し脆性の防止に有効である。また、Ｍｏは
本発明の重要な元素である。すなわち、Ｍｏは高温の焼
戻し温度域まで析出硬化が保持できるために、本発明の
ように昇温速度が速い場合は、靱性を低下させることな
く、より高強度を得ることができる。０．１％未満では
その効果が小さく、また１．５％を超えると強度は飽和
し、かえって粗大Ｍｏ 2 Ｃ炭化物が増加して靱性を低下
させる。従って、Ｍｏ含有量を０．１〜１．５％とし
た。Mo: Mo improves the hardenability and ensures strength.
It is effective in maintaining and preventing temper brittleness. Also, Mo is
It is an important element of the present invention. That is, Mo is a high temperature
Since precipitation hardening can be maintained up to the returning temperature range,
If the heating rate is fast, as in
In addition, higher strength can be obtained. Below 0.1%
The effect is small, and when it exceeds 1.5%, the strength is saturated.
On the contrary, coarse Mo 2Carbon carbide increases and toughness decreases
Let Therefore, the Mo content is set to 0.1 to 1.5%.
Was.
【００１４】Ｃｒ：Ｃｒは焼入れ性を向上させ、強度確
保に有効である。しかし、０．１％未満ではその効果が
なく、また１．５％を超えると溶接性が低下する。従っ
て、Ｃｒ含有量を０．１〜１．５％とした。 Ａｌ：Ａｌは脱酸のために必要な元素であると同時に、
鋼片加熱時に窒化物を形成してオーステナイト粒の細粒
化に有効である。しかし、０．０１％未満ではその効果
が小さく、また０．１０％を超えるとアルミナ系介在物
が増加して靱性を低下させる。従って、Ａｌ含有量を
０．０１〜０．１０％とした。Cr: Cr improves the hardenability and is effective in securing the strength. However, if it is less than 0.1%, the effect is not obtained, and if it exceeds 1.5%, the weldability is deteriorated. Therefore, the Cr content is set to 0.1 to 1.5%. Al: Al is an element necessary for deoxidation, and at the same time,
It is effective in forming a nitride during heating of the steel billet and making the austenite grains finer. However, if it is less than 0.01%, its effect is small, and if it exceeds 0.10%, alumina-based inclusions increase and the toughness decreases. Therefore, the Al content is set to 0.01 to 0.10%.
【００１５】Ｎ：ＮはＡｌやＴｉと結合して窒化物を形
成し、オーステナイト粒の粗大化防止に有効に働く。し
かし、Ｎ量が多くなると溶接性が低下するため、Ｎ含有
量を０．００６０％以下とした。 本発明では、上記成分の他に、Ｃｕ、Ｖ、Ｎｂ、Ｔｉ、
Ｂからなる強度・靱性改善元素群の１種または２種以上
を添加し、および／または介在物形態制御作用のあるＣ
ａを添加して所望の強度・靱性を得ることが可能であ
る。N: N combines with Al or Ti to form a nitride, which effectively acts to prevent coarsening of austenite grains. However, since the weldability decreases as the N content increases, the N content is set to 0.0060% or less. In the present invention, in addition to the above components, Cu, V, Nb, Ti,
One or more elements of the strength / toughness improving element group consisting of B is added, and / or C having an effect of controlling inclusion morphology
It is possible to obtain desired strength and toughness by adding a.
【００１６】Ｃｕ：Ｃｕは焼入れ性向上および焼戻し処
理の析出効果により強度向上に有効である。しかし、
０．１％未満ではその効果がなく、また１．５％を超え
ると靱性が低下する。従って、Ｃｕ含有量を０．１〜
１．５％とした。 Ｖ：Ｖは焼戻処理の析出硬化により鋼の強度を高めるの
に有効である。しかし、０．０１％未満ではその効果が
なく、また０．１０％を超えると靱性を低下させる。従
って、Ｖ含有量を０．０１〜０．１０％とした。Cu: Cu is effective in improving the hardenability and the strength due to the precipitation effect of the tempering treatment. But,
If it is less than 0.1%, the effect is not obtained, and if it exceeds 1.5%, the toughness decreases. Therefore, the Cu content is 0.1 to
It was set to 1.5%. V: V is effective in increasing the strength of steel by precipitation hardening in tempering. However, if less than 0.01%, there is no effect, and if more than 0.10%, the toughness decreases. Therefore, the V content is set to 0.01 to 0.10%.
【００１７】Ｎｂ：Ｎｂは微細なＮｂ（Ｃ、Ｎ）を形成
し、圧延後のオーステナイト粒の微細化と焼戻し処理の
析出硬化のために添加するもので強度、靱性をともに向
上させる。しかし、０．００５％未満ではその効果がな
く、また０．０５％を超えると溶接性が低下する。従っ
て、Ｎｂ含有量を０．００５〜０．０５％とした。 Ｔｉ：Ｔｉは微細なＴｉＮを形成し、加熱オーステナイ
ト粒および溶接熱影響部の組織の細粒化により靱性向上
に有効である。しかし、０．００５％未満ではその効果
が小さく、また０．０３％を超えると靱性を低下させ
る。従って、Ｔｉ含有量を０．００５〜０．０３％とし
た。Nb: Nb forms fine Nb (C, N) and is added for refining austenite grains after rolling and for precipitation hardening in tempering treatment, and improves both strength and toughness. However, if it is less than 0.005%, the effect is not obtained, and if it exceeds 0.05%, the weldability is deteriorated. Therefore, the Nb content is set to 0.005 to 0.05%. Ti: Ti forms fine TiN, and is effective for improving toughness by making the austenite grains heated and the microstructure of the weld heat affected zone fine. However, if less than 0.005%, the effect is small, and if more than 0.03%, the toughness decreases. Therefore, the Ti content is set to 0.005 to 0.03%.
【００１８】Ｂ：Ｂは鋼の焼入れ性を高め、強度、靱性
を向上させるのに有効である。しかし、０．０００５％
未満ではその効果が上がらず、また０．００２０％を超
えるとＢの析出物が増加して靱性を低下させる。従っ
て、Ｂ含有量を０．０００５〜０．００２０％とした。 Ｃａ：Ｃａは非金属介在物の球状化に有効であり、靱性
の異方性を小さくする効果がある。そのためには０．０
００５％以上の添加が必要であるが、０．００５０％を
超えると介在物の増加により靱性が低下する。従って、
Ｃａ含有量を０．０００５〜０．００５０％とした。B: B is effective for enhancing the hardenability of steel and improving the strength and toughness. However, 0.0005%
If it is less than 0.005%, the effect is not improved, and if it exceeds 0.0020%, the precipitates of B increase to lower the toughness. Therefore, the B content is set to 0.0005 to 0.0020%. Ca: Ca is effective for spheroidizing non-metallic inclusions, and has the effect of reducing the anisotropy of toughness. 0.0 for that
It is necessary to add 005% or more, but if it exceeds 0.0050%, the toughness decreases due to the increase of inclusions. Therefore,
The Ca content was 0.0005 to 0.0050%.
【００１９】上記の成分の他に、不可避的不純物元素と
して、Ｐ、Ｓなどは靱性を低下させる有害な元素である
からその量は少ない方がよく、好ましくは、Ｐは０．０
１％以下、Ｓは０．００５％以下である。次に、本発明
のもう一つの骨子である製造方法について述べる。上記
のような鋼成分であっても厚肉材の板厚方向の強度およ
び靱性を均一化させるには製造方法が適切でなければな
らない。ここで、鋼片の加熱、圧延、冷却および焼戻し
条件の限定理由について説明する。In addition to the above components, as inevitable impurity elements, P, S, etc. are harmful elements that reduce toughness, so the amount should be small, preferably P is 0.0.
1% or less and S is 0.005% or less. Next, a manufacturing method which is another essence of the present invention will be described. Even with the above steel components, the manufacturing method must be appropriate in order to make the strength and toughness of the thick material in the plate thickness direction uniform. Here, the reasons for limiting the conditions for heating, rolling, cooling, and tempering the steel bill will be described.
【００２０】まず、上記成分組成の鋼片を１０００〜１
２５０℃に加熱して熱間圧延を行う。この加熱は、加熱
オーステナイト粒の細粒化と、焼戻し処理時にＭｏ、Ｃ
ｒ、Ｖなどの微細炭窒化物による析出強化を活用するた
めのもので、鋼片の状態でこれらの炭窒化物を十分に固
溶化させておく必要がある。従って、加熱温度が１００
０℃未満の低い温度では固溶化作用が不十分となる。一
方、加熱温度が１２５０℃を超える温度では、炭窒化物
は十分固溶するものの、加熱オーステナイト粒が粗大化
し、その後のオーステナイト粒が細粒化しにくく、靱性
低下の原因ともなる。First, a steel slab having the above-mentioned composition is used in an amount of 1000-1
Hot rolling is performed by heating to 250 ° C. This heating is performed by refining the heated austenite grains and Mo and C during the tempering treatment.
This is for utilizing the precipitation strengthening by fine carbonitrides such as r and V, and it is necessary to sufficiently dissolve these carbonitrides in the state of a steel slab. Therefore, the heating temperature is 100
At a low temperature of less than 0 ° C, the solid solution action becomes insufficient. On the other hand, when the heating temperature exceeds 1250 ° C., although carbonitrides are sufficiently dissolved, the heated austenite grains are coarsened and the subsequent austenite grains are less likely to be fine grained, which also causes a decrease in toughness.
【００２１】次に、このように加熱された鋼片を、熱間
圧延において９５０℃以下の温度で６０％以上の圧下率
で圧延を行う。これは、圧延によりオーステナイト粒を
細粒化させるためであり、９５０℃を超える温度からの
圧延では板厚方向全位置に細粒化が不十分であり、また
圧下率６０％未満では板厚中心部を細粒化することがで
きず、いずれも靱性低下の原因となる。Next, the thus heated steel slab is hot-rolled at a temperature of 950 ° C. or lower at a rolling reduction of 60% or more. This is because the austenite grains are made finer by rolling, and rolling at a temperature higher than 950 ° C. does not result in sufficient fineness at all positions in the sheet thickness direction. The part cannot be made finer, and any of these causes deterioration in toughness.
【００２２】次に、圧延完了後Ａｒ3 点以上の温度から
水冷する焼入れ処理を行う。これは、細粒化されたオー
ステナイトを板厚中心部まで転位密度の多いマルテンサ
イトやベイナイト（下部ベイナイトおよび上部ベイナイ
ト）に変態させ、より高強度を得るためである。しか
し、Ａｒ3 点未満の温度からの水冷、あるいは冷却が空
冷、徐冷ではフェライトの生成および転位密度の消失が
起こり、板厚中心部の強度、靱性が著しく低下する。ま
た、水冷は通常、板厚方向全てが１５０℃以下に達する
まで行われるが、本発明においては表面層が１５０℃以
下であれば板厚中心部が２００℃程度であっても、後の
焼戻し時に板厚方向に均一な材質が得られるのでかまわ
ない。Next, after the completion of rolling, quenching treatment is carried out by cooling with water at a temperature of Ar 3 or higher. This is for transforming the fine-grained austenite into martensite and bainite (lower bainite and upper bainite) having a high dislocation density up to the center of the plate thickness to obtain higher strength. However, when water cooling from a temperature below the Ar 3 point, or air cooling or slow cooling occurs, ferrite is generated and dislocation density disappears, and the strength and toughness at the center of the plate thickness are significantly reduced. Water cooling is usually carried out until the temperature reaches 150 ° C. or less in the plate thickness direction, but in the present invention, if the surface layer is 150 ° C. or less, even if the center part of the plate thickness is about 200 ° C., the subsequent tempering is performed. It does not matter since a uniform material can be obtained in the plate thickness direction.
【００２３】次に、熱間圧延後水冷された厚鋼板を、そ
の後８００〜１０５０℃に保持された炉に装入し、表層
部（表面から１／８ｔ程度までの表層）温度が５５０℃
〜Ａｃ1 点に到達後、直ちに抽出する焼戻し処理を行
う。この焼戻し処理は、本発明にとって重要な処理であ
る。すなわち、従来の焼戻し処理は、温度の精度を保っ
て可能な限り鋼板厚み方向均一に加熱するのが常識とな
っているが、本発明では意識的に鋼板厚み方向に温度差
をつけ、表層部は中心部よりも高い焼戻し温度としてい
る点が特徴である。厚肉材の場合、焼入れ処理で板厚方
向の焼入れ組織が変化し、表層部は十分焼きの入ったマ
ルテンサイト主体組織となるが、中心部になるほど下部
ベイナイトと上部ベイナイト組織、またはこれらの混合
組織が生成する。この焼入れ変態後の組織差は焼入れま
まで強度差を持つため、従来の均一加熱の焼戻し方法で
はその強度差が保持される。一方、焼戻し温度の変化に
より強度を調整することができる。図１は、表１に示す
鋼Ｌについて、圧延後水冷までを本発明範囲の製造条件
で製造した鋼板を焼戻し処理する際に、焼戻し昇温速度
を本発明法と徐加熱の比較法で焼戻し温度を変化させた
場合の表層部の強度の影響について調査したものであ
る。本発明法の場合、従来の加熱法に比べて加熱速度が
速いことから、より高温まで焼戻し軟化を抑制できるた
めに、表層部は中心部より焼きの入った組織であるた
め、板厚方向に均一な強度を得るためには焼戻し温度を
中心部よりも高温化できる。その結果、図２に示すよう
に、本発明法は比較法に比べ板厚方向の強度が均一化さ
れる。Next, the hot-rolled and water-cooled thick steel plate was charged into a furnace kept at 800 to 1050 ° C., and the surface layer temperature (surface layer from the surface to about 1/8 t) was 550 ° C.
-After reaching the Ac 1 point, a tempering process for extracting immediately is performed. This tempering treatment is an important treatment for the present invention. That is, in the conventional tempering process, it is common knowledge that the temperature accuracy is maintained and the steel sheet thickness direction is uniformly heated as much as possible. Is characterized in that it has a tempering temperature higher than that of the central part. In the case of thick-walled materials, the quenching process changes the quenching structure in the plate thickness direction, and the surface layer part has a well-quenched martensite-based structure, but the lower the central part, the lower bainite and upper bainite structure, or a mixture of these. Generated by the organization. Since the difference in structure after the quenching transformation has a difference in strength as quenched, the difference in strength is maintained by the conventional uniform heating tempering method. On the other hand, the strength can be adjusted by changing the tempering temperature. FIG. 1 shows that, with respect to the steel L shown in Table 1, when tempering a steel sheet manufactured under the manufacturing conditions within the scope of the present invention after rolling until water cooling, the tempering temperature rising rate was tempered by a comparative method of the present invention method and gradual heating. This is an investigation of the influence of the strength of the surface layer when the temperature is changed. In the case of the method of the present invention, since the heating rate is higher than that of the conventional heating method, temper softening can be suppressed to a higher temperature. In order to obtain uniform strength, the tempering temperature can be set higher than that of the central part. As a result, as shown in FIG. 2, in the method of the present invention, the strength in the plate thickness direction is made more uniform than in the comparative method.
【００２４】従って、８００℃未満の炉に装入すると板
厚方向の温度差が小さく、加熱速度も遅くなり、板厚方
向の強度差が大きくなる。また、１０５０℃を超えた炉
に装入すると板厚方向の温度差が大きくなり、中心部に
とって適正な焼戻し温度で抽出すると表層部はＡｃ1 点
を超えるため表層部の強度が著しく低下する。また、固
溶Ｍｏ、Ｃｒ、Ｖなどを炭窒化物として転位に析出させ
て強度、靱性を向上させるには、さらに１０℃／ｍｉｎ
以上の昇温速度が望ましい。そして、抽出する板厚方向
の温度で、表層部が５５０℃未満では中心部の温度が低
く焼戻しが不十分となり、降伏強度が低下し、厚み方向
の強度差も大きく靱性も低下する。また、表層部の温度
がＡｃ1 点超では残留オーステナイトが生成し、強度、
靱性が低下する。一方、中心部温度は表層部温度よりも
低い温度差で抽出する必要があり、好ましくは４０〜１
００℃である。４０℃未満では、板厚方向の温度差が小
さく、１００℃超では板厚方向の温度差が大きくなり、
ともに板厚方向の強度差が大きくなる。Therefore, when the furnace is charged at a temperature lower than 800 ° C., the temperature difference in the plate thickness direction is small, the heating rate is slow, and the strength difference in the plate thickness direction is large. Further, if the temperature exceeds 1050 ° C., the temperature difference in the plate thickness direction becomes large, and if the tempering is performed at an appropriate tempering temperature for the center portion, the surface layer portion will exceed Ac 1 point and the strength of the surface layer portion will be significantly reduced. Further, in order to precipitate solid solution Mo, Cr, V, etc. as carbonitrides at dislocations and improve strength and toughness, further 10 ° C./min
The above rate of temperature rise is desirable. When the temperature of the surface layer portion to be extracted is less than 550 ° C., the temperature of the central portion is low and tempering becomes insufficient, yield strength decreases, strength difference in the thickness direction becomes large, and toughness also decreases. In addition, when the temperature of the surface layer exceeds Ac 1 point, retained austenite is generated, and strength,
Toughness decreases. On the other hand, the central temperature needs to be extracted with a temperature difference lower than the surface temperature, and preferably 40 to 1
It is 00 ° C. If it is less than 40 ° C, the temperature difference in the sheet thickness direction is small, and if it exceeds 100 ° C, the temperature difference in the sheet thickness direction becomes large.
In both cases, the strength difference in the plate thickness direction becomes large.
【００２５】このような製造工程で製造された厚鋼板
は、板厚方向に材質が均一であり、靱性を損なうことな
く高強度を保証することができる。なお、厚鋼板の四周
部（先後端部および幅端部）の材質偏差は許容範囲内で
あり、特に問題にはならない。The thick steel plate manufactured by such a manufacturing process is made of a uniform material in the plate thickness direction, and high strength can be guaranteed without impairing toughness. In addition, the material deviation of the four peripheral portions (the front and rear end portions and the width end portion) of the thick steel plate is within the allowable range and does not cause any particular problem.
【００２６】[0026]
【実施例】表１および表２（表１のつづき）に示す組成
を有する鋼を溶製して得た鋼片から、表３、表４（表３
のつづき−１）、表５（表３のつづき−２）および表６
（表３のつづき−３）に示す本発明法と比較法の各々の
製造条件に基づいて、板厚５０〜１８０ｍｍの鋼板を製
造した。なお、水冷停止温度は、本発明法、比較法とも
に表層にて１５０℃以下であった。これらの母材の機械
的性質を表７、表８（表７のつづき−１）、表９（表７
のつづき−２）、表１０（表７のつづき−３）、表１１
（表７のつづき−４）および表１２（表７のつづき−
５）に示す。表１〜表６中の下線部分は、それぞれ本発
明から外れる元素添加範囲および製造条件範囲を示す。EXAMPLES From steel pieces obtained by melting steel having the compositions shown in Tables 1 and 2 (continued from Table 1), Tables 3 and 4 (Table 3
(Continued-1), Table 5 (continued-2 of Table 3) and Table 6
A steel plate having a plate thickness of 50 to 180 mm was manufactured based on the respective manufacturing conditions of the method of the present invention and the comparative method shown in (continued from Table 3-3). The water cooling stop temperature was 150 ° C. or lower at the surface layer in both the method of the present invention and the comparative method. The mechanical properties of these base materials are shown in Table 7, Table 8 (continued from Table 7-1) and Table 9 (Table 7).
Continued-2), Table 10 (continued-3 of Table 7), Table 11
(Continued from Table 7-4) and Table 12 (continued from Table 7-
5). The underlined portions in Tables 1 to 6 show the range of element addition and the range of manufacturing conditions that depart from the present invention.
【００２７】[0027]
【表１】 [Table 1]
【００２８】[0028]
【表２】 [Table 2]
【００２９】[0029]
【表３】 [Table 3]
【００３０】[0030]
【表４】 [Table 4]
【００３１】[0031]
【表５】 [Table 5]
【００３２】[0032]
【表６】 [Table 6]
【００３３】[0033]
【表７】 [Table 7]
【００３４】[0034]
【表８】 [Table 8]
【００３５】[0035]
【表９】 [Table 9]
【００３６】[0036]
【表１０】 [Table 10]
【００３７】[0037]
【表１１】 [Table 11]
【００３８】[0038]
【表１２】 [Table 12]
【００３９】表７〜表１２に見られるように、本発明例
（本発明の鋼組成と本発明の製造条件とを組合わせた製
造条件１、４、６、８、１０、１３、１５、１８、２
１、２３、２５、２７、２９、３１、３３、３５、３
７、３９、４１、４３、４５）の強度と靱性は十分高
く、かつ板厚方向の強度が均一である。これに対して、
製造条件は本発明の範囲内であるが鋼組成が本発明から
逸脱している比較例４７、４８、４９、５０では強度お
よび靱性が低下し、板厚方向の強度差が大きい。As shown in Tables 7 to 12, examples of the present invention (manufacturing conditions 1, 4, 6, 8, 10, 13, 15, which are combinations of the steel composition of the present invention and the manufacturing conditions of the present invention). 18, 2
1, 23, 25, 27, 29, 31, 33, 35, 3
7, 39, 41, 43, 45) and the toughness are sufficiently high, and the strength in the plate thickness direction is uniform. On the contrary,
In Comparative Examples 47, 48, 49, and 50 in which the manufacturing conditions are within the scope of the present invention but the steel composition deviates from the present invention, the strength and toughness are reduced, and the strength difference in the plate thickness direction is large.
【００４０】さらに、本発明の鋼組成であっても比較法
の製造条件の場合において、比較例２、４６では鋼片加
熱温度が高く、細粒化が不十分となり靱性が低下してい
る。比較例３では加熱温度が低いために析出物の固溶化
が不十分となり、強度が低下している。比較例５、３
０、４４では圧延開始温度が高く、細粒化が不十分とな
り、靱性が低下している。比較例７、２２、４２では圧
下率が低く、板厚中心部の細粒化が不十分となり、靱性
が低下している。比較例９、２４、４０では圧延後の水
冷開始温度が低く、板厚中心部の強度、靱性が著しく低
下している。比較例１１、２６、３８では鋼板装入炉温
が低く、このため鋼板昇温速度が遅く、板厚方向の焼戻
し温度差が小さくなり、板厚方向の強度差が大きい。比
較例１２、２８では鋼板装入炉温が高く、このため鋼板
昇温速度が速く、板厚方向の温度差が大きくなり、板厚
表層部の焼戻し温度がＡｃ1 点を超えるため表層部の強
度、靱性が低下している。比較例１４では鋼板昇温速度
が遅く、板厚方向の温度差が小さくなり、板厚方向の強
度差が大きい。比較例１６、３２では炉抽出時の板厚表
層部温度が低く、このため板厚中心部温度が低くなり、
板厚方向の強度差が大きく、かつ靱性も低下している。
比較例１７、３６では炉抽出時の板厚表層部温度がＡｃ
1 点を超えたため残留オーステナイトが生成し、表層部
の強度、靱性が低下している。比較例１９では板厚中心
部温度と板厚表層部との焼戻し温度差が小さく、このた
め板厚方向の強度差が大きい。比較例２０では板厚方向
の温度差が大きく、このため中心部に適正な焼戻し温度
では表層部がＡｃ1 点を超えるため表層部の強度、靱性
が著しく低下している。Further, even with the steel composition of the present invention, under the manufacturing conditions of the comparative method, in Comparative Examples 2 and 46, the billet heating temperature was high, the grain refinement was insufficient, and the toughness was lowered. In Comparative Example 3, since the heating temperature is low, the solid solution of the precipitate is insufficient and the strength is reduced. Comparative Examples 5 and 3
In Nos. 0 and 44, the rolling start temperature was high, the grain refinement was insufficient, and the toughness was lowered. In Comparative Examples 7, 22, and 42, the rolling reduction is low, the grain refinement in the central portion of the plate thickness is insufficient, and the toughness is reduced. In Comparative Examples 9, 24, and 40, the water cooling start temperature after rolling is low, and the strength and toughness of the central portion of the plate thickness are significantly reduced. In Comparative Examples 11, 26, and 38, the steel plate charging furnace temperature is low, so the steel plate temperature rising rate is slow, the tempering temperature difference in the plate thickness direction is small, and the strength difference in the plate thickness direction is large. In Comparative Examples 12 and 28, the steel plate charging furnace temperature was high, and therefore the steel plate heating rate was high, the temperature difference in the plate thickness direction was large, and the tempering temperature of the plate thickness surface layer portion exceeded Ac 1 point, so that Strength and toughness are reduced. In Comparative Example 14, the temperature rising rate of the steel plate is slow, the temperature difference in the plate thickness direction is small, and the strength difference in the plate thickness direction is large. In Comparative Examples 16 and 32, the plate thickness surface layer temperature at the time of furnace extraction was low, and therefore the plate thickness center temperature was low,
The strength difference in the plate thickness direction is large and the toughness is also reduced.
In Comparative Examples 17 and 36, the temperature of the surface layer portion of the plate thickness at the time of furnace extraction was Ac
Since it exceeded 1 point, retained austenite was generated and the strength and toughness of the surface layer part were reduced. In Comparative Example 19, the difference in tempering temperature between the central portion of the sheet thickness and the surface layer portion of the sheet thickness is small, and therefore the difference in strength in the sheet thickness direction is large. In Comparative Example 20, the temperature difference in the plate thickness direction is large. Therefore, at the tempering temperature appropriate for the central portion, the surface layer portion exceeds the Ac 1 point, so that the strength and toughness of the surface layer portion are significantly reduced.
【００４１】[0041]
【発明の効果】本発明により、厚肉材の板厚方向の強度
を均一化でき、強度、靱性バランスの向上した高張力鋼
を経済的に製造できるようになる。According to the present invention, the strength of a thick material in the plate thickness direction can be made uniform, and a high-strength steel having an improved balance of strength and toughness can be economically manufactured.
【図１】鋼Ｌについて本発明法と比較法を焼戻し温度を
変化させた場合の表層部の強度の影響について示す図で
ある。FIG. 1 is a diagram showing the influence of the strength of the surface layer portion when the tempering temperature is changed by the method of the present invention and the comparative method for steel L.
【図２】本発明法と比較法について板厚方向の強度を示
した図である。FIG. 2 is a diagram showing the strength in the plate thickness direction for the method of the present invention and the comparative method.
Claims (2)
可避的不純物からなる鋼片を、１０００〜１２５０℃に
加熱した後、熱間圧延において９５０℃以下の温度で６
０％以上の圧下率で圧延し、次いでＡｒ3 点以上の温度
から水冷する焼入れ処理を施し、引き続いて８００〜１
０５０℃に保持された炉に装入し、表層部温度が５５０
℃〜Ａｃ1点に到達後、直ちに抽出する焼戻し処理を施
すことを特徴とする板厚方向に強度が均一な厚肉高張力
鋼の製造方法。1. C: 0.03 to 0.15% by weight%, Si: 0.02 to 0.50%, Mn: 0.3 to 2.0%, Ni: 0.1 to 5.0. %, Mo: 0.1 to 1.5%, Cr: 0.1 to 1.5%, Al: 0.01 to 0.10%, N: 0.0060% or less, the balance being Fe and A steel slab composed of unavoidable impurities is heated to 1000 to 1250 ° C., and then hot rolled at a temperature of 950 ° C. or less for 6
Rolling is performed at a rolling reduction of 0% or more, and then quenching treatment is performed by water cooling from a temperature of Ar 3 points or more, and subsequently 800 to 1
The temperature in the surface layer was 550
A method for producing thick high-strength steel having uniform strength in the plate thickness direction, which comprises subjecting to a tempering treatment in which extraction is performed immediately after the temperature reaches 1 ° C to Ac 1 .
〜１．５％、 Ｖ：０．０１〜０．１％、 Ｎｂ：０．００５〜０．０５％、 Ｔｉ：０．００５〜０．０３％、 Ｂ：０．０００５〜０．００２０％からなる強度・靱性
改善元素群の１種または２種以上および／または介在物
形態制御作用のある Ｃａ：０．０００５〜０．００５％ を含有し、残部がＦｅおよび不可避的不純物からなる鋼
片を、１０００〜１２５０℃に加熱した後、熱間圧延に
おいて９５０℃以下の温度で６０％以上の圧下率で圧延
し、次いでＡｒ3 点以上の温度から水冷する焼入れ処理
を施し、引き続いて８００〜１０５０℃に保持された炉
に装入し、表層部温度が５５０℃〜Ａｃ1点に到達後、
直ちに抽出する焼戻し処理を施すことを特徴とする板厚
方向に強度が均一な厚肉高張力鋼の製造方法。2. C: 0.03 to 0.15% by weight, Si: 0.02 to 0.50%, Mn: 0.3 to 2.0%, Ni: 0.1 to 5.0. %, Mo: 0.1-1.5%, Cr: 0.1-1.5%, Al: 0.01-0.10%, N: 0.0060% or less, and further Cu: 0. .1
-1.5%, V: 0.01-0.1%, Nb: 0.005-0.05%, Ti: 0.005-0.03%, B: 0.0005-0.0020% A steel slab containing one or more of the following elements for improving strength and toughness and / or Ca having an morphology-controlling effect of Ca: 0.0005 to 0.005% and the balance being Fe and inevitable impurities. , 1000 to 1250 ° C., and then hot rolling is performed at a temperature of 950 ° C. or less at a rolling reduction of 60% or more, and then subjected to a quenching treatment of water cooling from a temperature of Ar 3 points or more, and subsequently 800 to 1050. After charging the furnace maintained at ℃, the surface layer temperature reaches 550 ℃ ~ Ac 1 point,
A method for producing thick high-strength steel having uniform strength in the plate thickness direction, which is characterized by performing a tempering treatment for immediate extraction.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP28569594A JPH08143955A (en) | 1994-11-18 | 1994-11-18 | Production of thick-walled high tensile strength steel uniformized in strength in plate thickness direction |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP28569594A JPH08143955A (en) | 1994-11-18 | 1994-11-18 | Production of thick-walled high tensile strength steel uniformized in strength in plate thickness direction |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH08143955A true JPH08143955A (en) | 1996-06-04 |
Family
ID=17694844
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP28569594A Withdrawn JPH08143955A (en) | 1994-11-18 | 1994-11-18 | Production of thick-walled high tensile strength steel uniformized in strength in plate thickness direction |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH08143955A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR20130116202A (en) * | 2012-04-13 | 2013-10-23 | 가부시키가이샤 고베 세이코쇼 | Thick steel plate excellent in ultra low temperature toughness |
| KR101442400B1 (en) * | 2012-03-09 | 2014-09-17 | 가부시키가이샤 고베 세이코쇼 | Thick steel plate excellent in ultra low temperature toughness |
| WO2017208329A1 (en) * | 2016-05-31 | 2017-12-07 | 新日鐵住金株式会社 | High-tensile steel plate having excellent low-temperature toughness |
| CN116254483A (en) * | 2023-02-01 | 2023-06-13 | 桂林理工大学 | High-strength steel plate with excellent low-temperature impact toughness and manufacturing method thereof |
-
1994
- 1994-11-18 JP JP28569594A patent/JPH08143955A/en not_active Withdrawn
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR101442400B1 (en) * | 2012-03-09 | 2014-09-17 | 가부시키가이샤 고베 세이코쇼 | Thick steel plate excellent in ultra low temperature toughness |
| KR20130116202A (en) * | 2012-04-13 | 2013-10-23 | 가부시키가이샤 고베 세이코쇼 | Thick steel plate excellent in ultra low temperature toughness |
| WO2017208329A1 (en) * | 2016-05-31 | 2017-12-07 | 新日鐵住金株式会社 | High-tensile steel plate having excellent low-temperature toughness |
| CN116254483A (en) * | 2023-02-01 | 2023-06-13 | 桂林理工大学 | High-strength steel plate with excellent low-temperature impact toughness and manufacturing method thereof |
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