JPH066741B2 - Manufacturing method of structural steel plate with high toughness - Google Patents

Manufacturing method of structural steel plate with high toughness

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Publication number
JPH066741B2
JPH066741B2 JP1177185A JP1177185A JPH066741B2 JP H066741 B2 JPH066741 B2 JP H066741B2 JP 1177185 A JP1177185 A JP 1177185A JP 1177185 A JP1177185 A JP 1177185A JP H066741 B2 JPH066741 B2 JP H066741B2
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Japan
Prior art keywords
less
temperature
rolling
steel slab
total
Prior art date
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Expired - Lifetime
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JP1177185A
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Japanese (ja)
Other versions
JPS61174328A (en
Inventor
宏 三村
康 森山
博文 森川
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Nippon Steel Corp
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Nippon Steel Corp
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Priority to JP1177185A priority Critical patent/JPH066741B2/en
Publication of JPS61174328A publication Critical patent/JPS61174328A/en
Publication of JPH066741B2 publication Critical patent/JPH066741B2/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Description

【発明の詳細な説明】 （産業上の利用分野） 本発明は高靭性を持つ構造用厚鋼板の製造法に係わり、
特に鋼管、鋼構造物、ガスまた液体の貯蔵装置等に用い
られる靭性が高く主として厚さ２５mm〜１００mm程度の
比較的断面厚みの大きい構造用厚鋼板の製造法に関する
ものである。The present invention relates to a method for manufacturing a structural thick steel plate having high toughness,
In particular, the present invention relates to a method for producing a structural thick steel plate having a high toughness and mainly having a relatively large cross-sectional thickness of about 25 mm to 100 mm, which is used for steel pipes, steel structures, gas or liquid storage devices and the like.

（従来の技術および問題点） 一般に、強度４０〜１００Kgf／mm2級の構造用鋼は、従
来圧延まま、圧延後焼準、焼入れ焼戻し等の熱処理、更
に最近では制御圧延、制御冷却、直接焼入焼戻し等各種
の製造法によって製造されているが、特に厚手断面の鋼
板を対象とする場合、これら通常行われる加熱、圧延に
よる製造方法ではその後に熱処理や制御冷却などの処理
を行っても、板厚中央部の靭性が表層部に比較して小さ
くなり、構造用鋼として必ずしも良好なものと云えず、
これを改善する手段として多くの合金元素の添加を行っ
たり、熱処理を繰り返したりする等の方法がとられ、い
たずらに溶接性の劣化や、工程の煩雑化などを招く結果
となっていた。(Prior Art and Problems) Generally, structural steel having a strength of 40 to 100 Kgf / mm 2 grade is used as it is in conventional rolling, heat treatment such as normalizing after rolling, quenching and tempering, and more recently, controlled rolling, controlled cooling and direct quenching. Although manufactured by various manufacturing methods such as tempering and tempering, particularly when targeting a steel plate with a thick cross section, these usually performed heating, in the manufacturing method by rolling, even after such a heat treatment or controlled cooling, The toughness of the central part of the plate thickness becomes smaller than that of the surface part, and it cannot be said that it is necessarily good as a structural steel.
As a means for improving this, a method of adding many alloying elements, repeating heat treatment, or the like has been adopted, resulting in unnecessarily degrading the weldability and complicating the process.

一方、これら構造用鋼に対する市場の要求は、使用温度
の低下や構造物の大型化の傾向から板厚の大きなしか
も、靭性の良好なものへと移ってゆくようになってい
る。従って上記板厚中央部を含めた靭性の向上対策が一
層必要となっていた。On the other hand, the market demands for these structural steels are shifting to those having a large plate thickness and good toughness due to the tendency of lowering the operating temperature and increasing the size of the structure. Therefore, it is further necessary to take measures to improve the toughness including the center part of the plate thickness.

即ち、先ず従来の鋼片の加熱方法は、圧延形状と圧延の
容易性を重視して、加熱速度を小さくし、しかも余熱段
階、加熱段階を経た後、均熱段階を設け鋼片の表、裏、
断面中央部を充分に均熱せしめたのち加熱炉から抽出し
圧延を行うと云う方法が普通であった。従って加熱時
間、即ち鋼片の加熱炉への装入から抽出迄の時間は通
常、冷片加熱の場合鋼片厚み２００〜２５０mmの場合で
２〜３時間、温片加熱（装入温度５００〜５５０℃）の
場合で約２時間であり、これが全体の圧延能力を制約す
ると同時に鋼片のオーステナイト粒度を粗大にし、その
後の制御圧延、更には制御冷却の際粒度の微細化が必ず
しも充分でなくまた圧延中の板厚方向の温度差に起因す
る制御圧延の効果の差で板厚方向の組織と粒度の差が生
じ、特に断面厚みの大きい厚鋼板では、板厚中央部の切
欠靭性が表層部に比して劣ると云う欠点が生じた。That is, first of all, the conventional method for heating a billet emphasizes the rolled shape and the ease of rolling, reduces the heating rate, and further, after the preheating stage and the heating stage, a soaking stage is provided on the table of billets, back,
A common method is to uniformly heat the central portion of the cross section, then extract from the heating furnace and perform rolling. Therefore, the heating time, that is, the time from the charging of the steel slab into the heating furnace to the extraction is usually 2 to 3 hours when the steel slab thickness is 200 to 250 mm in the case of the cold slab heating, and the heating slab heating (the charging temperature of 500 to In the case of (550 ° C.), it takes about 2 hours, which restricts the overall rolling ability and at the same time coarsens the austenite grain size of the steel slab, and the grain size refinement is not always sufficient during the subsequent controlled rolling and further controlled cooling. Also, the difference in the effect of control rolling due to the temperature difference in the plate thickness direction during rolling causes a difference in the microstructure and grain size in the plate thickness direction.In particular, for thick steel plates with a large cross-sectional thickness, the notch toughness at the center of the plate thickness is the surface layer. There was a defect that it was inferior to the department.

（問題点を解決するための手段） 本発明者らは、種々検討を重ねた結果、板厚方向の組織
および粒度を鋼片の加熱段階から制御し、鋼板の均熱工
程を意識的にとらず鋼片の表面と断面中央部の加熱温度
の差がついたまま圧延工程に入り、圧延温度、圧下量を
規制することで上記の問題点を解消することが可能にな
ることを見出した。(Means for Solving Problems) As a result of various studies, the present inventors controlled the structure and grain size in the plate thickness direction from the heating stage of the steel slab, and consciously considered the soaking process of the steel plate. It was found that the above problems can be solved by starting the rolling process with a difference in heating temperature between the surface of the steel slab and the central portion of the cross section and controlling the rolling temperature and the reduction amount.

即ち、本発明者らはこの問題を解消する手段として鋼片
の加熱加速を大きくし、特に５００〜１０００℃間の変
態域とその上下の加熱速度を大きくすることと、最高加
熱温度における保持時間を最短にすることで結晶粒の成
長を極力抑制することが可能であることを見出した。こ
の場合、鋼片の厚み方向の温度差は当然ながら大きくな
り、鋼片厚手方向の結晶粒度差がつき、また鋼片の中央
部は場合によってはフェライトとオーステナイトの二相
域のままで加熱工程を終えてもよく、いずれにしても所
定の加熱速度、温度内であればその後の制御、圧延、或
いはさらに制御冷却を加えた場合、細粒化効果の差でこ
の鋼片加熱時の断面方向の粒度差は解消されることが確
認された。即ち、鋼片を圧延によって厚鋼板とする際、
抜熱は表面から行われるから圧延作業の全工程にわたっ
て表面側が中央部に比して低温となる。この状態で圧延
を行うと同一圧下量の場合低温である程圧下後の再結晶
したオーステナイト粒度は細かく、また未再結晶域にお
ける圧延でもオーステナイト中に生じる変形帯は低温で
ある程発達するから結果的に低温での圧下程細粒化が著
るしいい。これが前述の鋼片加熱直後の鋼片厚み方向の
結晶粒度の差異を解消せしめ結果的に板厚方向の靭性差
の少い高靭性鋼の製造が可能となる。That is, the inventors of the present invention increase the heating acceleration of the steel slab as a means for solving this problem, particularly increase the transformation region between 500 to 1000 ° C. and the heating rate above and below it, and hold time at the maximum heating temperature. It has been found that it is possible to suppress the growth of crystal grains as much as possible by making the shortest. In this case, the temperature difference in the thickness direction of the slab naturally becomes large, there is a difference in grain size in the thickness direction of the slab, and the center part of the slab is sometimes heated in the two-phase region of ferrite and austenite in the heating process. In any case, within the prescribed heating rate and temperature, if the subsequent control, rolling, or further controlled cooling is applied, due to the difference in the grain refining effect, this cross-sectional direction during heating It was confirmed that the difference in particle size was eliminated. That is, when rolling the billet into a thick steel plate,
Since the heat is removed from the surface, the temperature of the surface side is lower than that of the central part during the whole rolling process. If rolling is performed in this state, the recrystallized austenite grain size after rolling is finer as the temperature is lower at the same reduction amount, and the deformation zone generated in austenite also develops at lower temperature even in rolling in the non-recrystallization region. In particular, the finer the grain size, the better the reduction at low temperature. This eliminates the above-mentioned difference in grain size in the thickness direction of the billet immediately after heating the billet, and as a result, it becomes possible to manufacture a high toughness steel having a small difference in toughness in the thickness direction.

また、更にこの効果を大きくするため特に板厚の大きい
厚鋼板の場合圧延作業に入る前に鋼片の表面から水冷し
鋼板の表面温度を中央部のそれより意識的に温度を下げ
て圧延を開始するともっと効果的であることも知見し
た。従って目的とする最高加熱温度に到達した後の圧延
は制御圧延が必須であり、制御圧延を行った後は製造し
ようとする厚鋼板の化学成分や機械的性質に応じて制御
圧延まま、制御水冷或いは直接焼入れ焼戻しなどの各種
工程をとればよいことも明らかとなった。In order to further increase this effect, especially in the case of thick steel plates with a large plate thickness, water is cooled from the surface of the steel slab before starting the rolling work, and the surface temperature of the steel plate is consciously lowered from that in the central part before rolling. It was also found to be more effective when started. Therefore, controlled rolling is indispensable for rolling after reaching the target maximum heating temperature, and after controlled rolling, controlled rolling as it is, controlled water cooling depending on the chemical composition and mechanical properties of the thick steel plate to be manufactured. Alternatively, it has become clear that various steps such as direct quenching and tempering may be taken.

（発明の構成、作用） 本発明は以上の如き知見に基づいてなされたものであっ
て、その要旨とするところは重量％でＣ；0.02〜0.22
％，Ｓｉ；０．５％以下，Ｍｎ；０．３〜２％，Total
Ａｌ０．０８％以下，TotalＮ；0.008％以下を含み、残
部がＦｅおよび不可避的不純物から成る鋼片を、４００
℃以下の温度から加熱を行い、鋼片の５００〜１０００
℃の間の断面平均昇温速度が７℃／分以上になるように
加熱し、鋼片の表面温度が１２５０℃以下で、（イ）し
かも鋼片の表面と厚み方向中央部の温度差があるままの
状態で加熱炉から抽出して圧延を開始するか、または
（ロ）厚み方向中央部が８５０℃以下になり、しかも前
記温度差があるままの状態で加熱炉から抽出して圧延を
開始するか、または（ハ）鋼片の厚み方向中央部が９０
０〜１０５０℃になり、しかも鋼片の表面と厚み方向中
央部の温度差があるままの状態で加熱炉から抽出し、圧
延に入る以前に鋼片表面から水冷を施し、鋼片表面の温
度が鋼片中央部の温度よりも低下して、その温度差が５
０℃以上となった時点で水冷を止め、直ちに圧変を開始
するかの（イ），（ロ），（ハ）のいずれかについて各
々９２０℃以下での累計圧下率が２０％以上となる圧延
を行うことを特徴とする高靭性をもつ構造用厚鋼板の製
造法にある。(Structure and Action of the Invention) The present invention has been made based on the above findings, and the gist of the present invention is C by weight%; 0.02 to 0.22.
%, Si; 0.5% or less, Mn; 0.3 to 2%, Total
A steel slab containing Al 0.08% or less, Total N; 0.008% or less, and the balance Fe and unavoidable impurities
Heating from the temperature below ℃, 500 ~ 1000
The temperature of the surface of the steel slab is 1250 ° C. or lower, and the temperature difference between the surface of the steel slab and the central portion in the thickness direction is Extraction from the heating furnace to start rolling as it is, or (b) Extraction from the heating furnace and rolling at the temperature difference of 850 ° C or less in the center in the thickness direction Or (c) the center of the slab in the thickness direction is 90
The temperature of the slab surface is 0-1050 ° C, and the temperature of the slab surface is extracted by extracting from the heating furnace with the temperature difference between the surface of the slab and the central part in the thickness direction being kept, and water cooling is performed from the surface of the slab before rolling. Is lower than the temperature at the center of the billet, and the temperature difference is 5
When the water cooling is stopped at 0 ° C or higher and the pressure change starts immediately, the cumulative reduction rate at 920 ° C or lower is 20% or more for each of (a), (b), and (c). It is a method of manufacturing a structural thick steel plate having high toughness, which is characterized by rolling.

本発明は、またさらに必要に応じてＣｒ，Ｃｕ，Ｎｉ，
Ｍｏの１種以上を合計で０．２〜４．２％含むことを特
徴とする構造用厚鋼板の製造法であり、同様に必要に応
じて、Ｂ；0.0005〜0.002％，Ｔｉ；0.005〜0.03％，Ｎ
ｂ；0.005〜0.04％，Ｖ；0.005〜0.04％，Ｃａ；0.005
％以下の１種または２種以上を含むことを特徴とする構
造用厚鋼板の製造法である。The present invention also further comprises Cr, Cu, Ni,
A method for manufacturing a structural thick steel plate, characterized in that it contains one or more kinds of Mo in a total amount of 0.2 to 4.2%. Similarly, if necessary, B: 0.0005 to 0.002%, Ti: 0.005 to 0.03%, N
b; 0.005 to 0.04%, V; 0.005 to 0.04%, Ca; 0.005
% Or less, and a method of manufacturing a structural thick steel plate.

以下に本発明を詳細に説明する。The present invention will be described in detail below.

先ず本発明の対象とする構造用厚鋼板の成分範囲の限定
理由についてのべる。First, the reason for limiting the component range of the structural thick steel plate targeted by the present invention will be described.

最初にＣは焼入性および強度を確保するために必要な元
素であるが０．０２％未満ではＣ拡散律速であるフェラ
イト、パーライト、ベイナイト等の変態組織が得られな
いため目標とする強度レベルの構造用鋼が得られない。
また０．２２％を超えると靭性、溶接性が不良となり構
造用鋼としての特性を得ることはむつかしいのでＣは
０．０２〜0.22％とした。このうちで特に良好な範囲は
０．０５〜０．１８％である。First, C is an element necessary to secure hardenability and strength, but if it is less than 0.02%, a transformation structure of ferrite, pearlite, bainite, etc., which is the C diffusion-controlling rate, cannot be obtained, so the target strength level. No structural steel can be obtained.
Further, if it exceeds 0.22%, the toughness and weldability become poor and it is difficult to obtain the characteristics as structural steel, so C was made 0.02 to 0.22%. Of these, a particularly preferable range is 0.05 to 0.18%.

次にＳｉは通常の製鋼法では鋼中に多少は含まれ、固溶
硬化により強度上昇に寄与するが多量に添加すると靭性
が劣化し、０．５％超では特に溶接熱影響部の靭性も著
るしく劣化するため０．５％以下とした。Next, Si is contained in the steel to some extent in the ordinary steelmaking method and contributes to the strength increase due to solid solution hardening, but if added in a large amount, the toughness deteriorates, and if it exceeds 0.5%, the toughness of the weld heat affected zone is also particularly high. Since it significantly deteriorates, it is set to 0.5% or less.

またＭｎは靭性を大きく損わずに強度を上げるのに有効
な元素であり鋼中に通常含有されるものであるが、０．
３％未満では構造用鋼としての強度を確保することが出
来ずまた２％超では大きく溶接性を低下させる原因とな
る。この場合Mnと同様な効果をもたらす元素としてはC
r，Ni，Cu，Moがありこれらはいずれも鋼の変態を遅ら
せ変態温度を下げるのに有効な元素である。その際制御
圧延後空冷を行う場合も、また水冷を行う場合も厚鋼板
の厚み中央部の冷却速度により目標とする強度を得るた
めにはCr，Ni，Cu，Moの１種以上を合計で少くとも０．
２％以上が必要である。なおこれらの各元素のうちNi，
Cuはとくに靭性を向上させるのに効果があり、Cr，Moは
圧延後水冷を行う場合の焼入性の向上効果や炭化物の組
成や形態を改善する等の効果、Moは更に水冷後の焼戻し
を行う場合や強度が６０Kgf／mm2以上の高張力鋼の溶接
部の応力除去焼鈍による脆化を防止する効果等の多くの
効果がある。Further, Mn is an element effective in increasing the strength without significantly impairing the toughness and is usually contained in steel, but
If it is less than 3%, the strength as a structural steel cannot be secured, and if it exceeds 2%, it causes a large decrease in weldability. In this case, C is the element that produces the same effect as Mn.
There are r, Ni, Cu, and Mo, all of which are effective elements for delaying the transformation of steel and lowering the transformation temperature. At that time, in order to obtain the target strength by the cooling rate at the central portion of the thickness of the thick steel plate, whether it is air-cooled after controlled rolling or water-cooled, at least one of Cr, Ni, Cu, Mo is added in total. At least 0.
2% or more is required. Among these elements, Ni,
Cu is particularly effective in improving toughness, and Cr and Mo are effects of improving hardenability when water cooling after rolling, improving composition and morphology of carbides, and Mo is tempering after water cooling. There are many effects including the effect of preventing embrittlement due to stress relieving annealing of a welded part of high-strength steel having a strength of 60 Kgf / mm 2 or more.

しかし、これらの元素をあまり多量に添加することは溶
接性などを損うことになるため合計４．２％以下にとど
めた。However, adding too much of these elements impairs weldability, etc., so the total content was limited to 4.2% or less.

さらにAlは通常脱酸のために鋼中に添加されるものであ
ってＮと結合して加熱時のオーステナイト粒の細粒化に
役立つが添加量がTotal０．０８％を超えると反って粒
の粗大化とAl2O3等の介在物量の増大を招き靭性や加工
性を阻害する場合がある。従ってAl含有量はTotal量で
０．０８％以下とした。Furthermore, Al is usually added to the steel for deoxidization and is combined with N to help refine the austenite grains during heating, but if the addition amount exceeds 0.08%, the grains will be warped. In some cases, coarsening and increase in the amount of inclusions such as Al 2 O 3 impede toughness and workability. Therefore, the total Al content is 0.08% or less.

ＮはAlと結合してAlNとなり鋼片加熱時の結晶粒の粗大
化を防止するために効果があるが、高温状態での鋼片で
は固溶状態となり、Ｂを含有する鋼種の場合、圧延以降
の冷却の際にＢと結びついてBNとなりＢの焼入性効果を
削減することがある。また更に一般的に溶接熱影響部の
靭性を劣化せしめることがありこれらを著るしくする限
界量として０．００８％以下とした。N is combined with Al to become AlN, which is effective for preventing the coarsening of crystal grains when the steel piece is heated, but the steel piece in the high temperature state becomes a solid solution state, and in the case of the steel type containing B, it is rolled. In the subsequent cooling, it may be combined with B to form BN and reduce the hardenability effect of B. Further, generally, the toughness of the weld heat affected zone may be deteriorated, and the limit amount for making them remarkable is set to 0.008% or less.

以上が基本的な元素であるが、さらに本発明の対象とす
る鋼には前記以外の元素として(A)Ｂ，Ti，Nb，Ｖの１
種又は２種以上を鋼板の断面厚みに応じて構造用鋼とし
ての所定の強度と溶接性のバランスを確保する目的で、
または(B)Caを溶接部の靭性を大きく向上する目的で
(A)，(B)いずれか一方又は両方を添加することが出来
る。The above are the basic elements, but in the steel targeted by the present invention, the elements other than the above are (A) B, Ti, Nb, and V.
For the purpose of ensuring a predetermined strength and weldability balance as structural steel according to the cross-sectional thickness of the steel sheet
Or (B) Ca for the purpose of greatly improving the toughness of the weld.
Either or both of (A) and (B) can be added.

先ず(A)群の成分については、Ｂは焼入性の向上効果が
あるが、0.0005％未満ではその効果が少く、０．００２
％超では溶接熱影響部等にＢの化合物が生じ、靭性を著
るしく劣化させる。First, regarding the components of the (A) group, B has an effect of improving hardenability, but if it is less than 0.0005%, the effect is small, and
If it exceeds%, a compound of B is produced in the weld heat affected zone and the toughness is significantly deteriorated.

TiはＮを固定し、Ｂを有効化させる性質をもつため０．
００５％以上添加することが有効である。しかしながら
Tiが０．０３％を超えた場合は地鉄中に固溶することが
あり著るしく靭性を劣化させる。Since Ti has the property of fixing N and enabling B, Ti.
It is effective to add 005% or more. However
If Ti exceeds 0.03%, it may form a solid solution in the base metal, resulting in marked deterioration of toughness.

NbおよびＶはいずれも制御圧延の際の未再結晶域の上限
温度を上昇させ圧延の細粒化効果域を拡大させるのと制
御冷却後の焼戻時のNbやＶの炭・窒化物の析出による強
化をもたらすための重要元素であるが、それぞれ０．０
０５％未満の少量であると所期の効果が得られず、一方
０．０４％を超えても上記効果は飽和するのみならず溶
接熱影響部や溶着鋼の切欠靭性を低下させる要因とな
る。したがってNb，Ｖ共０．００５〜０．０４％を限界
量と決めた。Nb and V both increase the upper limit temperature of the non-recrystallized region during controlled rolling to expand the grain refining effect region of rolling and Nb and V charcoal / nitride during tempering after controlled cooling. It is an important element for strengthening by precipitation, but each is 0.0
If the amount is less than 05%, the desired effect cannot be obtained. On the other hand, if the amount exceeds 0.04%, the above effect is not only saturated, but also becomes a factor that reduces the notch toughness of the weld heat affected zone and the welded steel. . Therefore, 0.005 to 0.04% for both Nb and V was determined as the limit amount.

又、(B)群の成分であるCaは、硫化物の形態制御を行
い、圧延方向に直角な方向の切欠靭性や溶接熱影響部の
切欠靭性を向上させるため添加されると有効であるが
０．００５％を超えると表面および内部欠陥が多発す
る。Further, Ca, which is a component of the (B) group, is effective when added to improve the notch toughness of the weld heat affected zone and the notch toughness in the direction orthogonal to the rolling direction by controlling the morphology of the sulfide, If it exceeds 0.005%, many surface and internal defects occur.

次に本発明の製造条件の規定についてその理由を説明す
る。Next, the reason for the definition of the manufacturing conditions of the present invention will be described.

先ず、本発明において鋼片を加熱する際、400℃以下か
らとしたのは、鋳造まま、或いは減厚圧延、分塊圧延を
行った後の熱鋼片または冷却途中の鋼片でも、未だオー
ステナイト→フェライトおよびパーライト、又はベイナ
イト変態が終了していない場合、本発明のオーステナイ
ト→フェライト＋パーライト変態域を通過させる細粒化
効果および逆に本発明の構成要素の一つであるフェライ
ト＋パーライト、又はフェライト＋パーライト＋ベイナ
イト→オーステナイト変態域を急速加熱することによる
オーステナイト粒の粗大化防止の効果が期待出来ないた
め、鋼片加熱時鋼片全体がAc1点（鋼材の化学成分によ
り異なるが７００〜７１０℃）より以下の温度から急速
に加熱することが必要なためである。なお鋼片の厚みと
冷却速度を考慮して余裕をもって４００℃以下と規定し
た。First, when heating a steel slab in the present invention, what was made from 400 ℃ or less, as-cast, or reduced thickness rolling, hot slab after slabbing or even a slab in the middle of cooling, still austenite → When ferrite and pearlite or bainite transformation is not completed, austenite of the present invention → grain refining effect of passing through ferrite + pearlite transformation region and conversely ferrite + pearlite which is one of the constituent elements of the present invention, or Ferrite + pearlite + bainite → The effect of preventing coarsening of austenite grains by rapid heating in the austenite transformation region cannot be expected, so when the billet is heated, the entire billet has an Ac 1 point (700 to 700 depending on the chemical composition of the steel material). This is because it is necessary to rapidly heat from a temperature below 710 ° C). In addition, considering the thickness of the steel slab and the cooling rate, the margin was specified to be 400 ° C. or less.

なお、加熱前の鋼片の冷却については通常空冷かあるい
は場合によっては脱水等その他の目的で積み重ねた状態
での空冷が行われるが、鋼片の加熱後のオーステナイト
粒度を細かくする目的から云えば、この加熱前の鋼片の
フェライト粒度を出来るだけ小さくした方が効果的であ
り、そのためには鋼片を水冷、気水冷却、衝風冷却など
の手段によって出来るだけ強制冷却するのが好ましい。
また、鋳造後減厚圧延を行ったり、鋳造ままでも出来る
だけ厚みの小さい鋼片を選んで冷却速度の増大とその後
の加熱過程の加熱速度の増大を図るのが本発明の目的と
しては効果的である。Regarding the cooling of the steel slab before heating, air cooling is usually performed in the state of being stacked for other purposes such as dehydration or dehydration in some cases, but for the purpose of making the austenite grain size after heating the steel slab finer, It is effective to make the ferrite grain size of the steel slab before heating as small as possible, and for that purpose, it is preferable that the steel slab is forcibly cooled by means such as water cooling, steam cooling, and wind cooling.
Further, it is effective for the purpose of the present invention to carry out reduction rolling after casting, or to select a steel slab as thin as possible even as cast to increase the cooling rate and the heating rate in the subsequent heating process. Is.

次に鋼片の昇温速度を特定した温度範囲を500〜１００
０℃としたのは、この範囲が便宜上決めた鋼の変態制御
に最も妥当な管理温度範囲であってAc1点よりおよそ２
００℃低い温度からAc3点よりおよそ１００〜１５０℃
高い温度域を示し、本発明に規定する化学成分の鋼の変
態域はすべてこの温度範囲に入るからである。またこの
温度範囲の昇温速度は便宜上直線的と仮定する。次にこ
の温度範囲での昇温速度を７℃／分以上としたのはこの
昇温速度未満の緩い昇温速度では加熱後のオーステナイ
ト粒度が本発明の主旨に沿う粒度にならず、その後の制
御圧延を行っても切欠靭性特に断面中央部の切欠靭性が
満足に改良されず、板厚方向の靭性の差となるばかりで
なく、靭性の絶体値そのものが不足するからである。Next, set the temperature range that specified the rate of temperature rise of the billet to 500 to 100.
0 ℃ that is given to approximately 2 than Ac 1 point of this range is the most appropriate control temperature range in transformation control for convenience decided steel
Approximately 100-150 ° C from Ac 3 point from a temperature of 00 ° C
This is because it shows a high temperature range, and the transformation range of the steel having the chemical composition defined in the present invention is all within this temperature range. Further, it is assumed that the heating rate in this temperature range is linear for convenience. Next, the rate of temperature rise in this temperature range was set to 7 ° C./min or more because the austenite grain size after heating did not become the grain size according to the gist of the present invention at a slow temperature rise rate lower than this temperature rise rate. This is because the notch toughness, particularly the notch toughness in the central portion of the cross section, is not satisfactorily improved even if the controlled rolling is performed, and not only the toughness difference in the plate thickness direction is caused, but also the absolute value itself of the toughness is insufficient.

次に鋼片の加熱温度を表面温度で１２５０℃以下とした
のは以下の理由による。即ち、前述の７℃／分以上の昇
温速度で加熱を行った場合、鋼片中心部と表面部は少く
とも１００℃以上の温度差がつく。しかるに、本発明に
規制される化学成分範囲の鋼では、オーステナイト粒の
異常成長温度はAl，Nb，Ti，Ｖ等の粒成長抑制元素の含
有量によって変化するものの安全をみて１１５０℃と考
えられるから鋼片中心部の粒異常成長を防止するため鋼
片表面温度で１２５０℃を上限とした。なお、表面温度
の下限は規定しないが、特に厚みの大きな厚板の場合に
は、圧延時の温度低下が比較的小さいので制御圧延の効
果の大きい表面温度で９２０℃以下の温度に持ち込むた
めの待ち時間が最小になるように鋼片の加熱温度を低く
することが好ましい。一方、厚みの小さな厚鋼板の場合
は、所定の厚み迄圧延するのに時間がかかるので加熱温
度を低くすると鋼板の厚みや単重等に制約が加えられる
ようになるため商用ベースでの製造が困難になり、通常
加熱温度の下限は表面温度で900℃程度となる。Next, the heating temperature of the steel slab was set to 1250 ° C. or lower at the surface temperature for the following reason. That is, when heating is performed at the above-mentioned temperature rising rate of 7 ° C./minute or more, a temperature difference of at least 100 ° C. or more is generated between the central portion and the surface portion of the billet. However, in the steel of the chemical composition range regulated by the present invention, the abnormal growth temperature of austenite grains varies depending on the content of grain growth suppressing elements such as Al, Nb, Ti, and V, but it is considered to be 1150 ° C in view of safety. Therefore, in order to prevent abnormal grain growth in the central portion of the billet, the billet surface temperature was set to 1250 ° C as the upper limit. Although the lower limit of the surface temperature is not specified, especially in the case of a thick plate having a large thickness, since the temperature drop during rolling is relatively small, the surface temperature at which the effect of controlled rolling is great is to bring it to a temperature of 920 ° C or lower. It is preferable to lower the heating temperature of the billet so that the waiting time is minimized. On the other hand, in the case of a thick steel plate with a small thickness, it takes time to roll to a predetermined thickness, so if the heating temperature is lowered, restrictions will be imposed on the thickness and unit weight of the steel plate, etc. It becomes difficult, and the lower limit of the heating temperature is usually about 900 ° C in surface temperature.

ところで、本発明者らは、板厚の特に大きな厚鋼板の場
合の板厚中央部の靭性を向上させるには加熱温度を更に
低目にとり、鋼片の中央部の組織がフェライトとオース
テナイトの混合域の状態から圧延を開始し、圧延中また
は圧延後表面層からの熱の移動による均熱により、オー
ステナイト変態を終了させることを行えば更にオーステ
ナイト粒度が細かくなると云う知見を得ている。従って
特に厚みが５０mmを超えるような厚鋼板の場合は、鋼片
の中央部が８５０℃以下のオーステナイト変態が未だ終
了していない温度域で圧延を開始し、圧下を施こすこと
が有効である。By the way, the inventors of the present invention, in order to improve the toughness of the central part of the plate thickness in the case of a particularly large thick steel plate, the heating temperature is set lower, and the structure of the central part of the steel slab is a mixture of ferrite and austenite. It has been found that if the austenite transformation is finished by starting the rolling from the state of the zone and soaking the heat from the surface layer during or after the rolling, the austenite grain size becomes further fine. Therefore, particularly in the case of a thick steel plate having a thickness of more than 50 mm, it is effective to start rolling in a temperature range in which the austenite transformation at 850 ° C. or less at the center of the steel slab has not yet finished, and to perform rolling reduction. .

なお、通常厚みの大きな鋼板の場合、中央部の約５０％
の範囲で靭性が劣ることが多いことから、特に５０mm超
の厚鋼板では鋼片の加熱時でも鋼片の中央部約５０％の
範囲が８５０℃以下となることが好ましい。この場合鋼
片中央部の温度は予め鋼片中央部に穿孔挿入した熱電対
による測温結果と加熱操炉条件との関係や表面温度の推
移からの計算で知ることが出来る。In the case of a steel plate with a large thickness, about 50% of the center
Since the toughness is often inferior in the range of 50 mm, it is particularly preferable that, in the case of a thick steel plate having a thickness of more than 50 mm, the range of about 50% in the central part of the slab becomes 850 ° C. or less even when the slab is heated. In this case, the temperature of the central part of the steel slab can be known by calculation from the relationship between the temperature measurement result by a thermocouple preliminarily inserted into the central part of the slab and the heating and operating conditions, and the transition of the surface temperature.

また、特に５０mmを超えるような厚鋼板の場合、前記の
手段の他に鋼片を加熱して表面温度が1250℃以下で且つ
鋼片の厚み方向中央部の温度が900〜１０５０℃にな
り、しかも鋼片の表面温度と厚み方向中央部の温度差が
あるままの状態で加熱炉より抽出し、圧延が開始される
前に水冷により表面温度を低下させ、鋼片中央部の温度
が逆に表面温度より５０℃以上高くなった状態から圧延
を開始することもできる。Further, particularly in the case of a thick steel plate that exceeds 50 mm, in addition to the above-mentioned means, the steel piece is heated to have a surface temperature of 1250 ° C. or lower and the temperature of the thickness direction central portion of the steel piece becomes 900 to 1050 ° C., Moreover, the temperature difference between the surface temperature of the steel slab and the temperature in the center in the thickness direction is extracted from the heating furnace, and the surface temperature is lowered by water cooling before the rolling is started. It is also possible to start rolling from a state where the surface temperature is 50 ° C. or higher.

この理由は鋼板中央部の制御圧延の効果を大きくするた
め鋼片中央部を一旦Ac3点より高い温度に急速加熱した
後、鋼片の表面温度を下げ熱伝達係数を大きくしてから
鋼片中央部の温度低下を容易にさせ、圧延と同時に制御
冷却を効果的にするもので、鋼片加熱温度を鋼片厚み中
央部で９００〜１０５０℃にしたのは、この温度範囲が
鋼片の圧延が可能でしかも出来るかぎり低い温度であ
り、さらに圧延時に制御冷却を行う場合でも充分オース
テナイト領域を保つ温度域からの冷却が可能な温度範囲
であるからである。この場合９００℃未満であると圧延
中に温度降下によりAr3変態点を切り、フェライト変態
が生じてフェライト、オーステナイトの二相域圧延を行
う可能性が大きくなり板厚方向の靭性劣化の危険性が生
じる。また１０５０℃超では厚み中央部の制御圧延を有
効にするための９２０℃以下の温度に到達させるための
待ち時間を大きく必要とし、高能率の圧延が出来にくく
なるためである。The reason for this is that in order to increase the effect of controlled rolling in the central portion of the steel sheet, the central portion of the billet is rapidly heated to a temperature higher than the Ac 3 point, and then the surface temperature of the billet is lowered to increase the heat transfer coefficient and The temperature drop in the central portion is facilitated, and the controlled cooling is effectively performed simultaneously with rolling. The heating temperature of the billet is 900 to 1050 ° C in the central portion of the thickness of the billet. This is because it is a temperature range in which rolling is possible, and the temperature is as low as possible, and even when controlled cooling is performed during rolling, it is a temperature range in which cooling can be performed from a temperature range that maintains a sufficient austenite region. In this case, if the temperature is less than 900 ° C, the Ar 3 transformation point is cut due to the temperature drop during rolling, ferrite transformation occurs, and there is a high possibility that ferrite and austenite two-phase rolling will occur, and the risk of deterioration of toughness in the plate thickness direction Occurs. On the other hand, if it exceeds 1050 ° C, a long waiting time is required to reach the temperature of 920 ° C or lower for making the controlled rolling in the central portion of the thickness effective, which makes it difficult to perform high efficiency rolling.

尚水冷によって表面温度が鋼片中央部温度より低下し
て、その温度差が５０℃以上となるよう規定したのは、
表面の熱伝達係数を鋼片中央部より大きくし、中央部か
らの抜熱を有効にならしめるためで５０℃以上の差をつ
けた場合に初めてこれが効果的となるからである。By water cooling, the surface temperature is lower than the central temperature of the billet, and the temperature difference is specified to be 50 ° C or more.
This is because the heat transfer coefficient of the surface is made larger than that of the central portion of the steel slab and the heat removal from the central portion is made effective so that this becomes effective only when a difference of 50 ° C. or more is provided.

本発明においては以上のような各種工程を経たのち圧延
を開始するのであるが、この場合圧延時の圧下量として
９２０℃以下での累計圧下量を２０％以上としたのは、
本発明に規定する化学成分の鋼では未再結晶域を含む制
御圧延有効温度域が９２０℃如以下であるからで、この
温度より低い温度域での累計圧下量が２０％以上の場
合、本発明の目的とする高靭性厚鋼板の必要とする細粒
の組織となるからで、圧下率が２０％に未たないとこの
効果が小さく、靭性のすぐれた構造用鋼は得られない。
従って９２０℃以下の累計圧下量を２０％以上と限定し
た。In the present invention, the rolling is started after the various steps as described above. In this case, the rolling reduction amount at the time of rolling at 920 ° C. or less is 20% or more.
This is because the controlled rolling effective temperature range including the non-recrystallized region is 920 ° C. or less in the steel of the chemical composition defined in the present invention, and when the cumulative reduction amount in the temperature range lower than this temperature is 20% or more, This is because the fine grain structure required for the high toughness steel plate, which is the object of the invention, is obtained, and if the rolling reduction is not less than 20%, this effect is small and a structural steel having excellent toughness cannot be obtained.
Therefore, the cumulative reduction amount at 920 ° C or lower is limited to 20% or more.

次に本発明の効果を実施例につきさらに具体的に説明す
る。Next, the effects of the present invention will be described more specifically with reference to examples.

（実施例） 第１表に示す化学成分を有する鋼を溶製し、同表欄外に
示す鋳造条件で連続鋳造、又は普通造塊−分塊圧延を行
い、連続鋳造の場合は鋳造まま、または減厚圧延後第２
表に示す製造条件にそった製造を行い、各種厚みの厚鋼
板よりその厚み方向の1/4の位置から引張試験片を、1/4
と1/2の位置からシャルピー試験片を採取しそれぞれ試
験を行った。これらの試験結果を第２表に併記して示
す。(Example) Steel having the chemical composition shown in Table 1 is melted, and continuous casting is performed under the casting conditions shown in the margin of the table, or ordinary ingot-slabbing rolling is performed, in the case of continuous casting, as-cast, or Second after thickness reduction rolling
Producing according to the manufacturing conditions shown in the table, the tensile test piece from the 1/4 position in the thickness direction from the thick steel plate of various thickness, 1/4
Charpy test pieces were sampled from positions 1/2 and 1/2, and the respective tests were performed. The results of these tests are also shown in Table 2.

これらによると本発明によるNo.１〜No.３２の鋼はいず
れも切欠靭性が良好でしかも板厚1/4と1/2の位置の値が
極めて接近した厚鋼板が得られていることがわかる。According to these, the steels No. 1 to No. 32 according to the present invention all have good notch toughness, and the thick steel plates in which the values at the positions of 1/4 and 1/2 are extremely close are obtained. Recognize.

これに対しNo.３３〜３５は化学成分が本発明の規定値
より外れたもの、No.３６〜４７は化学成分が本発明の
規定に入っているものの本発明の規定する製造条件に外
れているため、いずれも強度並びに靭性、特に板厚中心
部の靭性が非常に劣る結果を示しており鋼片の急速加熱
や、鋼片の加熱終了時点での厚み方向の温度勾配の効果
が発揮された本発明との差が明瞭に現れている。On the other hand, Nos. 33 to 35 are those whose chemical components are outside the specified values of the present invention, and Nos. 36 to 47 are those whose chemical components are within the specifications of the present invention, but are outside the manufacturing conditions specified by the present invention. As a result, the strength and toughness, especially the toughness at the center of the plate thickness, are very poor, demonstrating the effects of rapid heating of the slab and the temperature gradient in the thickness direction at the end of heating the slab. The difference from the present invention is clearly shown.

（発明の効果） 以上の実施例からみても明らかな如く本発明によれば、
従来法により得られた鋼に比して靭性が良好で、しかも
厚み方向の靭性差の極めて少い鋼材を製造しうることが
可能となるものであり、産業上の効果は顕著なものがあ
る。(Effects of the Invention) As apparent from the above examples, according to the present invention,
Compared with the steel obtained by the conventional method, it is possible to manufacture a steel material that has good toughness and a very small difference in toughness in the thickness direction, and the industrial effect is remarkable. .

フロントページの続き (51)Int.Cl.5 識別記号 庁内整理番号 ＦＩ 技術表示箇所 Ｃ２２Ｃ 38/54 Continuation of the front page (51) Int.Cl. 5 Identification code Office reference number FI technical display location C22C 38/54

Claims (22)

【特許請求の範囲】[Claims] 【請求項１】重量％でＣ０．０２〜０．２２％，Ｓｉ
０．５％以下，Ｍｎ０．３〜２％，TotalＡｌ０．０８
％以下，TotalＮ０．００８％以下を含み、残部がＦｅ
および不可避的不純物から成る鋼片を、４００℃以下の
温度から加熱を行い、鋼片の５００〜１０００℃の間の
断面平均昇温速度が７℃／分以上になるように加熱し、
鋼片の表面温度が１２５０℃以下で、しかも鋼片の表面
と厚み方向中央部の温度差があるままの状態で加熱炉か
ら抽出して圧延を開始し、９２０℃以下での累計圧下率
が２０％以上となる圧延を行うことを特徴とする高靭性
をもつ構造用厚鋼板の製造法。1. C0.02 to 0.22% by weight, Si
0.5% or less, Mn 0.3 to 2%, TotalAl 0.08
% Or less, Total N 0.008% or less, balance Fe
And a steel slab composed of unavoidable impurities are heated from a temperature of 400 ° C. or lower so that the average cross-section temperature rising rate of the steel slab between 500 and 1000 ° C. is 7 ° C./min or more,
When the surface temperature of the steel slab is 1250 ° C or lower, and the temperature difference between the surface of the steel slab and the central portion in the thickness direction remains, extraction is started from the heating furnace and rolling is started. A method for manufacturing a structural thick steel plate having high toughness, which comprises rolling at 20% or more. 【請求項２】重量％でＣ０．０２〜０．２２％，Ｓｉ
０．５％以下，Ｍｎ０．３〜２％，TotalＡｌ０．０８
％以下，TotalＮ0.008％以下を含み、さらにＣｒ，Ｃ
ｕ，Ｎｉ，Ｍｏの１種以上を合計で０．２〜４．２％を
含み、残部がＦｅおよび不可避的不純物から成る鋼片
を、４００℃以下の温度から加熱を行い、鋼片の５００
〜１０００℃の間の断面平均昇温速度が７℃／分以上に
なるように加熱し、鋼片の表面温度が１２５０℃以下
で、しかも鋼片の表面と厚み方向中央部の温度差がある
ままの状態で加熱炉から抽出して圧延を開始し、９２０
℃以下での累計圧下率が２０％以上となる圧延を行うこ
とを特徴とする高靭性をもつ構造用厚鋼板の製造法。2. C0.02 to 0.22% by weight%, Si
0.5% or less, Mn 0.3 to 2%, TotalAl 0.08
% Or less, Total N 0.008% or less, Cr, C
A steel slab containing at least one of u, Ni and Mo in a total amount of 0.2 to 4.2% and the balance of Fe and unavoidable impurities is heated from a temperature of 400 ° C. or less to give 500
The temperature of the surface of the steel slab is 1250 ° C. or less, and there is a temperature difference between the surface of the steel slab and the central part in the thickness direction. As it is, extract it from the heating furnace and start rolling.
A method for manufacturing a structural thick steel plate having high toughness, which comprises performing rolling such that a cumulative rolling reduction at 20 ° C. or less is 20% or more. 【請求項３】重量％でＣ０．０２〜０．２２％，Ｓｉ
０．５％以下，Ｍｎ０．３〜２％，TotalＡｌ０．０８
％以下，TotalＮ0.008％以下を含み、さらにＴｉ0.005
〜０．０３を含み、残部がＦｅおよび不可避的不純物か
ら成る鋼片を、４００℃以下の温度から加熱を行い、鋼
片の５００〜１０００℃の間の断面平均昇温速度が７℃
／分以上になるように加熱し、鋼片の表面温度が１２５
０℃以下で、しかも鋼片の表面と厚み方向中央部の温度
差があるままの状態で加熱炉から抽出して圧延を開始
し、９２０℃以下での累計圧下率が２０％以上となる圧
延を行うことを特徴とする高靭性をもつ構造用厚鋼板の
製造法。3. C0.02-0.22% by weight, Si
0.5% or less, Mn 0.3 to 2%, TotalAl 0.08
% Or less, Total N 0.008% or less, and Ti 0.005
~ 0.03, the balance consisting of Fe and unavoidable impurities, the steel slab is heated from a temperature of 400 ℃ or less, the cross-sectional average temperature rise rate of the steel slab between 500 ~ 1000 ℃ is 7 ℃.
The surface temperature of the steel slab is 125
Rolling is performed by extracting from the heating furnace at a temperature of 0 ° C or lower and with the temperature difference between the surface of the steel slab and the central portion in the thickness direction being maintained, and then rolling at a total reduction of 20% or more at 920 ° C or lower. A method of manufacturing a structural thick steel plate having high toughness, which is characterized by performing 【請求項４】重量％でＣ０．０２〜０．２２％，Ｓｉ
０．５％以下，Ｍｎ０．３〜２％，TotalＡｌ０．０８
％以下，TotalＮ0.008％以下を含み、さらにＮｂ0.005
〜０．０４％，Ｖ0.005〜０．０４％の１種または２種
を含み、残部がＦｅおよび不可避的不純物から成る鋼片
を、４００℃以下の温度から加熱を行い、鋼片の５００
〜１０００℃の間の断面平均昇温速度が７℃／分以上に
なるように加熱し、鋼片の表面温度が１２５０℃以下
で、しかも鋼片の表面と厚み方向中央部の温度差がある
ままの状態で加熱炉から抽出して圧延を開始し、９２０
℃以下での累計圧下率が２０％以上となる圧延を行うこ
とを特徴とする高靭性をもつ構造用厚鋼板の製造法。4. C0.02 to 0.22% by weight, Si
0.5% or less, Mn 0.3 to 2%, TotalAl 0.08
% Or less, Total N 0.008% or less, and Nb 0.005
~ 0.04%, V0.005 ~ 0.04% of 1 or 2 kinds, the balance consisting of Fe and unavoidable impurities, the steel slab is heated from the temperature of 400 ℃ or less, 500 of the steel slab.
The temperature of the surface of the steel slab is 1250 ° C. or less, and there is a temperature difference between the surface of the steel slab and the central part in the thickness direction. As it is, extract it from the heating furnace and start rolling.
A method for manufacturing a structural thick steel plate having high toughness, which comprises performing rolling such that a cumulative rolling reduction at 20 ° C. or less is 20% or more. 【請求項５】重量％でＣ０．０２〜０．２２％，Ｓｉ
０．５％以下，Ｍｎ０．３〜２％，TotalＡｌ０．０８
％以下，TotalＮ0.008％以下を含み、さらにＣｒ，Ｃ
ｕ，Ｎｉ，Ｍｏの１種以上を合計で０．２〜４．２％を
含み、さらにＮｂ0.005〜0.04％，Ｖ0.005〜0.04％の１
種または２種を含み、残部がＦｅおよび不可避的不純物
から成る鋼片を、４００℃以下の温度から加熱を行い、
鋼片の５００〜１０００℃の間の断面平均昇温速度が７
℃／分以上になるように加熱し、鋼片の表面温度が１２
５０℃以下で、しかも鋼片の表面と厚み方向中央部の温
度差があるままの状態で加熱炉から抽出して圧延を開始
し、９２０℃以下での累計圧下率が２０％以上となる圧
延を行うことを特徴とする高靭性をもつ構造用厚鋼板の
製造法。5. C0.02 to 0.22% by weight, Si
0.5% or less, Mn 0.3 to 2%, TotalAl 0.08
% Or less, Total N 0.008% or less, Cr, C
u, Ni, Mo of one or more kinds in total of 0.2 to 4.2%, and Nb of 0.005 to 0.04% and V0.005 to 0.04% of 1
, Or two, with the balance being Fe and unavoidable impurities, the steel slab is heated from a temperature of 400 ° C. or lower,
The average cross-section temperature rising rate between 500 and 1000 ° C of the steel slab is 7
The surface temperature of the steel slab is 12
Rolling at a temperature of 50 ° C or lower, and with the temperature difference between the surface of the steel slab and the central portion in the thickness direction being kept, extracting from the heating furnace and starting rolling, and the cumulative rolling reduction at 920 ° C or lower being 20% or more. A method of manufacturing a structural thick steel plate having high toughness, which is characterized by performing 【請求項６】重量％でＣ０．０２〜０．２２％，Ｓｉ
０．５％以下，Ｍｎ０．３〜２％，TotalＡｌ０．０８
％以下，TotalＮ0.008％以下を含み、さらにＣａ0.005
％以下を含み、残部がＦｅおよび不可避的不純物から成
る鋼片を、４００℃以下の温度から加熱を行い、鋼片の
５００〜１０００℃の間の断面平均昇温速度が７℃／分
以上になるように加熱し、鋼片の表面温度が１２５０℃
以下で、しかも鋼片の表面と厚み方向中央部の温度差が
あるままの状態で加熱炉から抽出して圧延を開始し、９
２０℃以下での累計圧下率が２０％以上となる圧延を行
うことを特徴とする高靭性をもつ構造用厚鋼板の製造
法。6. C0.02 to 0.22% by weight, Si
0.5% or less, Mn 0.3 to 2%, TotalAl 0.08
% Or less, Total N 0.008% or less, and Ca 0.005
% Or less, and the balance consisting of Fe and unavoidable impurities is heated from a temperature of 400 ° C. or lower so that the average cross-section temperature rising rate between 500 and 1000 ° C. is 7 ° C./min or more. So that the surface temperature of the steel slab is 1250 ° C
In the following, and with the temperature difference between the surface of the steel slab and the central portion in the thickness direction remaining, extraction from the heating furnace was started and rolling was started.
A method for producing a structural thick steel plate having high toughness, which comprises rolling at a cumulative reduction of 20% or more at 20 ° C or less. 【請求項７】重量％でＣ０．０２〜０．２２％，Ｓｉ
０．５％以下，Ｍｎ０．３〜２％，TotalＡｌ０．０８
％以下，TotalＮ0.008％以下を含み、さらにＮｂ0.005
〜０．０４％，Ｖ０．００５〜０．０４％の１種または
２種を含み、さらにＢ0.0005〜０．００２％を含み、残
部がＦｅおよび不可避的不純物から成る鋼片を、４００
℃以下の温度から加熱を行い、鋼片の500〜1000℃の間
の断面平均昇温速度が７℃／分以上になるように加熱
し、鋼片の表面温度が１２５０℃以下で、しかも鋼片の
表面と厚み方向中央部の温度差があるままの状態で加熱
炉から抽出して圧延を開始し、９２０℃以下での累計圧
下率が２０％以上となる圧延を行うことを特徴とする高
靭性をもつ構造用厚鋼板の製造法。7. C0.02 to 0.22% by weight, Si
0.5% or less, Mn 0.3 to 2%, TotalAl 0.08
% Or less, Total N 0.008% or less, and Nb 0.005
To 0.04%, V0.005 to 0.04% of 1 or 2 types, further B0.0005 to 0.002%, and the balance consisting of Fe and inevitable impurities.
The temperature of the steel slab is heated to a temperature of 500 ° C to 1000 ° C so that the average cross-section temperature rising rate is 7 ° C / min or more. It is characterized in that it is extracted from the heating furnace in a state where there is a temperature difference between the surface of the piece and the central portion in the thickness direction, rolling is started, and rolling at a cumulative rolling reduction of 20% or more at 920 ° C. or less is performed. Manufacturing method of structural steel plate with high toughness. 【請求項８】重量％でＣ０．０２〜０．２２％，Ｓｉ
０．５％以下，Ｍｎ０．３〜２％，TotalＡｌ０．０８
％以下，TotalＮ0.008％以下を含み、さらにＣｒ，Ｃ
ｕ，Ｎｉ，Ｍｏの１種以上を合計で０．２〜４．２％を
含み、さらにＮｂ0.005〜0.04％，Ｖ0.005〜0.04％の１
種または２種を含み、さらにＢ０．０００５〜０．００
２％を含み、残部がＦｅおよび不可避的不純物から成る
鋼片を、４００℃以下の温度から加熱を行い、鋼片の５
００〜１０００℃の間の断面平均昇温速度が７℃／分以
上になるように加熱し、鋼片の表面温度が１２５０℃以
下で、しかも鋼片の表面と厚み方向中央部の温度差があ
るままの状態で加熱炉から抽出して圧延を開始し、920
℃以下での累計圧下率が２０％以上となる圧延を行うこ
とを特徴とする高靭性をもつ構造用厚鋼板の製造法。8. C0.02 to 0.22% by weight%, Si
0.5% or less, Mn 0.3 to 2%, TotalAl 0.08
% Or less, Total N 0.008% or less, Cr, C
u, Ni, Mo of one or more kinds in total of 0.2 to 4.2%, and Nb of 0.005 to 0.04% and V0.005 to 0.04% of 1
Or two kinds, further B0.0005-0.00
A steel slab containing 2% and the balance consisting of Fe and unavoidable impurities was heated from a temperature of 400 ° C. or lower to give 5
It is heated so that the average cross-section temperature rising rate between 00 and 1000 ° C is 7 ° C / min or more, the surface temperature of the steel slab is 1250 ° C or less, and the temperature difference between the surface of the steel slab and the central portion in the thickness direction is Extract it from the heating furnace as it is and start rolling,
A method for manufacturing a structural thick steel plate having high toughness, which comprises performing rolling such that a cumulative rolling reduction at 20 ° C. or less is 20% or more. 【請求項９】重量％でＣ０．０２〜０．２２％，Ｓｉ
０．５％以下，Ｍｎ０．３〜２％，TotalＡｌ０．０８
％以下，TotalＮ0.008％以下を含み、さらにＮｂ0.005
〜０．０４％，Ｖ０．００５〜０．０４％の１種または
２種を含み、さらにＴｉ０．００５〜０．０３％を含
み、残部がＦｅおよび不可避的不純物から成る鋼片を、
４００℃以下の温度から加熱を行い、鋼片の５００〜１
０００℃の間の断面平均昇温速度が７℃／分以上になる
ように加熱し、鋼片の表面温度が１２５０℃以下で、し
かも鋼片の表面と厚み方向中央部の温度差があるままの
状態で加熱炉から抽出して圧延を開始し、９２０℃以下
での累計圧下率が２０％以上となる圧延を行うことを特
徴とする高靭性をもつ構造用厚鋼板の製造法。9. C0.02 to 0.22% by weight, Si
0.5% or less, Mn 0.3 to 2%, TotalAl 0.08
% Or less, Total N 0.008% or less, and Nb 0.005
A steel slab containing 0.0 to 0.04% and 0.005 to 0.04% of V, or 0.002 to 0.03% of Ti, and the balance of Fe and inevitable impurities.
Heating from the temperature of 400 ℃ or less, 500 ~ 1
Heating so that the average cross-section temperature rising rate between 000 ° C is 7 ° C / min or more, the surface temperature of the steel slab is 1250 ° C or less, and there is a temperature difference between the surface of the steel slab and the central portion in the thickness direction. The method for producing a structural thick steel sheet having high toughness, which comprises extracting from a heating furnace in the above state, starting rolling, and performing rolling such that the cumulative rolling reduction at 920 ° C. or less is 20% or more. 【請求項１０】重量％でＣ０．０２〜０．２２％，Ｓｉ
０．５％以下，Ｍｎ０．３〜２％，TotalＡｌ０．０８
％以下，TotalＮ0.008％以下を含み、さらにＣｒ，Ｃ
ｕ，Ｎｉ，Ｍｏの１種以上を合計で０．２〜４．２％を
含み、さらにＮｂ0.005〜0.04％，Ｖ0.005〜0.04％の１
種または２種を含み、さらにＴｉ０．００５〜０．０３
％を含み、残部がＦｅおよび不可避的不純物から成る鋼
片を、４００℃以下の温度から加熱を行い、鋼片の５０
０〜１０００℃の間の断面平均昇温速度が７℃／分以上
になるように加熱し、鋼片の表面温度が１２５０℃以下
で、しかも鋼片の表面と厚み方向中央部の温度差がある
ままの状態で加熱炉から抽出して圧延を開始し、９２０
℃以下での累計圧下率が２０％以上となる圧延を行うこ
とを特徴とする高靭性をもつ構造用厚鋼板の製造法。10. C0.02 to 0.22% by weight, Si
0.5% or less, Mn 0.3 to 2%, TotalAl 0.08
% Or less, Total N 0.008% or less, Cr, C
u, Ni, Mo of one or more kinds in total of 0.2 to 4.2%, and Nb of 0.005 to 0.04% and V0.005 to 0.04% of 1
Or two kinds, and further Ti 0.005-0.03
%, And the balance consisting of Fe and unavoidable impurities is heated to a temperature of 400 ° C. or lower to obtain 50
Heating is performed so that the average cross-section temperature rising rate between 0 to 1000 ° C is 7 ° C / min or more, the surface temperature of the steel slab is 1250 ° C or less, and the temperature difference between the surface of the steel slab and the central portion in the thickness direction is Extract from the heating furnace as it is and start rolling,
A method for manufacturing a structural thick steel plate having high toughness, which comprises performing rolling such that a cumulative rolling reduction at 20 ° C. or less is 20% or more. 【請求項１１】重量％でＣ０．０２〜０．２２％，Ｓｉ
０．５％以下，Ｍｎ０．３〜２％，TotalＡｌ０．０８
％以下，TotalＮ0.008％以下を含み、さらにＣｒ，Ｃ
ｕ，Ｎｉ，Ｍｏの１種以上を合計で０．２〜４．２％を
含を、さらにＴｉ0.005〜０．０３％を含み、さらにＣ
ａ０．００５％以下を含み、残部がＦｅおよび不可避的
不純物から成る鋼片を、４００℃以下の温度から加熱を
行い、鋼片の５００〜１０００℃の間の断面平均昇温速
度が７℃／分以上になるように加熱し、鋼片の表面温度
が１２５０℃以下で、しかも鋼片の表面と厚み方向中央
部の温度差があるままの状態で加熱炉から抽出して圧延
を開始し、９２０℃以下での累計圧下率が２０％以上と
なる圧延を行うことを特徴とする高靭性をもつ構造用厚
鋼板の製造法。11. C0.02 to 0.22% by weight, Si
0.5% or less, Mn 0.3 to 2%, TotalAl 0.08
% Or less, Total N 0.008% or less, Cr, C
u, Ni, or Mo, in a total amount of 0.2 to 4.2%, Ti 0.005 to 0.03%, and C
a a steel slab containing 0.005% or less of which the balance is Fe and unavoidable impurities is heated from a temperature of 400 ° C. or less, and the average cross-section temperature rising rate of the steel slab between 500 and 1000 ° C. is 7 ° C. / Heating so that the surface temperature of the steel slab is 1250 ° C. or lower, and there is a temperature difference between the surface of the steel slab and the central portion in the thickness direction, extraction from the heating furnace is started, and rolling is started. A method for producing a structural thick steel plate having high toughness, which comprises rolling at a cumulative reduction of 20% or more at 920 ° C or less. 【請求項１２】重量％でＣ０．０２〜０．２２％，Ｓｉ
０．５％以下，Ｍｎ０．３〜２％，TotalＡｌ０．０８
％以下，TotalＮ0.008％以下を含み、さらにＣｒ，Ｃ
ｕ，Ｎｉ，Ｍｏの１種以上を合計で０．２〜４．２％を
含み、さらにＮｂ0.005〜0.04％，Ｖ0.005〜0.04％の１
種または２種を含み、さらにＴｉ０．００５〜０．０３
％を含み、さらにＣａ０．００５％以下を含み、残部が
Ｆｅおよび不可避的不純物から成る鋼片を、４００℃以
下の温度から加熱を行い、鋼片の５００〜１０００℃の
間の断面平均昇温速度が７℃／分以上になるように加熱
し、鋼片の表面温度が１２５０℃以下で、しかも鋼片の
表面と厚み方向中央部の温度差があるままの状態で加熱
炉から抽出して圧延を開始し、９２０℃以下での累計圧
下率が２０％以上となる圧延を行うことを特徴とする高
靭性をもつ構造用厚鋼板の製造法。12. C0.02 to 0.22% by weight, Si
0.5% or less, Mn 0.3 to 2%, TotalAl 0.08
% Or less, Total N 0.008% or less, Cr, C
u, Ni, Mo of one or more kinds in total of 0.2 to 4.2%, and Nb of 0.005 to 0.04% and V0.005 to 0.04% of 1
Or two kinds, and further Ti 0.005-0.03
%, Further containing 0.005% or less of Ca, the balance consisting of Fe and unavoidable impurities is heated from a temperature of 400 ° C. or lower to increase the average cross-sectional temperature of the steel slab between 500 and 1000 ° C. Heated to a speed of 7 ° C / min or more, extracted from the heating furnace while the surface temperature of the steel slab is 1250 ° C or less, and the temperature difference between the surface of the steel slab and the central portion in the thickness direction remains. A method for producing a structural thick steel sheet having high toughness, which comprises starting rolling and performing rolling such that a cumulative reduction rate at 920 ° C or lower is 20% or more. 【請求項１３】重量％でＣ０．０２〜０．２２％，Ｓｉ
０．５％以下，Ｍｎ０．３〜２％，TotalＡｌ０．０８
％以下，TotalＮ0.008％以下を含み、さらにＣｒ，Ｃ
ｕ，Ｎｉ，Ｍｏの１種以上を合計で０．２〜４．２％を
含み、さらにＮｂ0.005〜0.04％，Ｖ0.005〜0.04％の１
種または２種を含み、さらにＴｉ０．００５〜０．０３
％を含み、さらにＢ0.0005〜0.002％を含み、さらにＣ
ａ0.005％以下を含み、残部がＦｅおよび不可避的不純
物から成る鋼片を、４００℃以下の温度から加熱を行
い、鋼片の５００〜１０００℃の間の断面平均昇温速度
が７℃／分以上になるように加熱し、鋼片の表面温度が
１２５０℃以下で、しかも鋼片の表面と厚み方向中央部
の温度差があるままの状態で加熱炉から抽出して圧延を
開始し、９２０℃以下での累計圧下率が２０％以上とな
る圧延を行うことを特徴とする高靭性をもつ構造用厚鋼
板の製造法。13. C0.02 to 0.22% by weight, Si
0.5% or less, Mn 0.3 to 2%, TotalAl 0.08
% Or less, Total N 0.008% or less, Cr, C
u, Ni, Mo of one or more kinds in total of 0.2 to 4.2%, and Nb of 0.005 to 0.04% and V0.005 to 0.04% of 1
Or two kinds, and further Ti 0.005-0.03
%, B 0.0005 to 0.002%, and C
a steel slab containing 0.005% or less and the balance consisting of Fe and unavoidable impurities is heated from a temperature of 400 ° C. or less, and the average cross-section temperature rising rate of the steel slab between 500 and 1000 ° C. is 7 ° C. / Heating so that the surface temperature of the steel slab is 1250 ° C. or lower, and there is a temperature difference between the surface of the steel slab and the central portion in the thickness direction, extraction from the heating furnace is started, and rolling is started. A method for producing a structural thick steel plate having high toughness, which comprises rolling at a cumulative reduction of 20% or more at 920 ° C or less. 【請求項１４】重量％でＣ０．０２〜０．２２％，Ｓｉ
０．５％以下，Ｍｎ０．３〜２％，TotalＡｌ０．０８
％以下，TotalＮ０．００８％以下を含み、残部がＦｅ
および不可避的不純物から成る鋼片を、４００℃以下の
温度から加熱を行い、鋼片の５００〜１０００℃の間の
断面平均昇温速度が７℃／分以上となるように加熱し、
鋼片の表面温度が１２５０℃以下で、かつ厚み方向中央
部が８５０℃以下になり、しかも鋼片の表面と厚み方向
中央部の温度差があるままの状態で加熱炉から抽出して
圧延を開始し、９２０℃以下での累積圧下率が２０％以
上となる圧延を行うことを特徴とする高靭性をもつ構造
用厚鋼板の製造法。14. C0.02 to 0.22% by weight, Si
0.5% or less, Mn 0.3 to 2%, TotalAl 0.08
% Or less, Total N 0.008% or less, balance Fe
And a steel slab composed of unavoidable impurities are heated from a temperature of 400 ° C. or lower so that the average cross-section temperature rising rate of the steel slab between 500 and 1000 ° C. is 7 ° C./min or more,
When the surface temperature of the steel slab is 1250 ° C or lower, the central portion in the thickness direction is 850 ° C or lower, and there is a temperature difference between the surface of the steel slab and the central portion in the thickness direction, the steel is extracted from the heating furnace and rolled. A method for producing a structural thick steel plate having high toughness, which comprises starting and rolling at a cumulative reduction of 20% or more at 920 ° C. or less. 【請求項１５】重量％でＣ０．０２〜０．２２％，Ｓｉ
０．５％以下，Ｍｎ０．３〜２％，TotalＡｌ０．０８
％以下，TotalＮ0.008％以下を含み、さらにＣｒ，Ｃ
ｕ，Ｎｉ，Ｍｏの１種以上を合計で０．２〜４．２％を
含み、残部がＦｅおよび不可避的不純物から成る鋼片
を、４００℃以下の温度から加熱を行い、鋼片の５００
〜１０００℃の間の断面平均昇温速度が７℃／分以上と
なるように加熱し、鋼片の表面温度が1250℃以下で、か
つ厚み方向中央部が８５０℃以下になり、しかも鋼片の
表面と厚み方向中央部の温度差があるままの状態で加熱
炉から抽出して圧延を開始し、９２０℃以下での累積圧
下率が２０％以上となる圧延を行うことを特徴とする高
靭性をもつ構造用厚鋼板の製造法。15. C0.02 to 0.22% by weight, Si
0.5% or less, Mn 0.3 to 2%, TotalAl 0.08
% Or less, Total N 0.008% or less, Cr, C
A steel slab containing at least one of u, Ni and Mo in a total amount of 0.2 to 4.2% and the balance of Fe and unavoidable impurities is heated from a temperature of 400 ° C. or less to give 500
The average surface temperature of cross section between ~ 1000 ° C is 7 ° C / min or more, the surface temperature of the steel slab is 1250 ° C or less, and the central portion in the thickness direction is 850 ° C or less. It is extracted from the heating furnace in a state where there is a temperature difference between the surface of the steel sheet and the central portion in the thickness direction, and the rolling is started, and the rolling at which the cumulative rolling reduction is 20% or more at 920 ° C or less is performed. Manufacturing method of structural steel plate with toughness. 【請求項１６】重量％でＣ０．０２〜０．２２％，Ｓｉ
０．５％以下，Ｍｎ０．３〜２％，TotalＡｌ０．０８
％以下，TotalＮ0.008％以下を含み、さらにＮｂ0.005
〜０．０４％、Ｖ0.005〜０．０４％の１種または２種
を含み、残部がＦｅおよび不可避的不純物から成る鋼片
を、４００℃以下の温度から加熱を行い、鋼片の５００
〜１０００℃の間の断面平均昇温速度が７℃／分以上に
なるように加熱し、鋼片の表面温度が１２５０℃以下
で、かつ厚み方向中央部が８５０℃以下になり、しかも
鋼片の表面と厚み方向中央部の温度差があるままの状態
で加熱炉から抽出して圧延を開始し、９２０℃以下での
累積圧下率が２０％以上となる圧延を行うことを特徴と
する高靭性をもつ構造用厚鋼板の製造法。16. C0.02 to 0.22% by weight, Si
0.5% or less, Mn 0.3 to 2%, TotalAl 0.08
% Or less, Total N 0.008% or less, and Nb 0.005
~ 0.04%, V0.005 ~ 0.04% of 1 or 2 kinds, the balance consisting of Fe and unavoidable impurities, the steel slab is heated from the temperature of 400 ℃ or less, 500 of the steel slab.
To 1000 ° C, the surface temperature of the steel slab is 1250 ° C or less, and the central portion in the thickness direction is 850 ° C or less. It is extracted from the heating furnace in a state where there is a temperature difference between the surface of the steel sheet and the central portion in the thickness direction, and the rolling is started, and the rolling at which the cumulative rolling reduction is 20% or more at 920 ° C or less is performed. Manufacturing method of structural steel plate with toughness. 【請求項１７】重量％でＣ０．０２〜０．２２％，Ｓｉ
０．５％以下，Ｍｎ０．３〜２％，TotalＡｌ０．０８
％以下，TotalＮ0.008％以下を含み、さらにＣｒ，Ｃ
ｕ，Ｎｉ，Ｍｏの１種以上を合計で０．２〜４．２％を
含み、さらにＮｂ0.005〜0.04％、Ｖ0.005〜0.04％の１
種または２種を含み、さらにＢ０．０００５〜0.002％
を含み、残部がＦｅおよび不可避的不純物から成る鋼片
を、４００℃以下の温度から加熱を行い、鋼片の５００
〜１０００℃の間の断面平均昇温速度が７℃／分以上と
なるように加熱し、鋼片の表面温度が１２５０℃以下
で、かつ厚み方向中央部が８５０℃以下になり、しかも
鋼片の表面と厚み方向中央部の温度差があるままの状態
で加熱炉から抽出して圧延を開始し、９２０℃以下での
累積圧下率が２０％以上となる圧延を行うことを特徴と
する高靭性をもつ構造用厚鋼板の製造法。17. C0.02 to 0.22% by weight, Si
0.5% or less, Mn 0.3 to 2%, TotalAl 0.08
% Or less, Total N 0.008% or less, Cr, C
u, Ni, Mo of one or more kinds in a total content of 0.2 to 4.2%, and Nb of 0.005 to 0.04% and V0.005 to 0.04% of 1
Includes two or more species, and B 0.0005 to 0.002%
And a balance of Fe and unavoidable impurities in the balance are heated from a temperature of 400 ° C. or lower to give
To 1000 ° C, the surface temperature of the steel slab is 1250 ° C or less, and the central portion in the thickness direction is 850 ° C or less. It is extracted from the heating furnace in a state where there is a temperature difference between the surface of the steel sheet and the central portion in the thickness direction, and the rolling is started, and the rolling at which the cumulative rolling reduction is 20% or more at 920 ° C or less is performed. Manufacturing method of structural steel plate with toughness. 【請求項１８】重量％でＣ０．０２〜０．２２％，Ｓｉ
０．５％以下，Ｍｎ０．３〜２％，TotalＡｌ０．０８
％以下，TotalＮ０．００８％以下を含み、残部がＦｅ
および不可避的不純物から成る鋼片を、４００℃以下の
温度から加熱を行い、鋼片の５００〜１０００℃の間の
断面平均昇温速度が７℃／分以上になるように加熱し、
鋼片の表面温度が１２５０℃以下で、かつ厚み方向中央
部が９００〜１０５０℃になり、しかも鋼片の表面と厚
み方向中央部の温度差があるままの状態で加熱炉から抽
出し、圧延に入る以前に鋼片表面から水冷を施し、鋼片
表面の温度が鋼片中央部の温度よりも低下して、その温
度差が５０℃以上となった時点で水冷を止め、直ちに圧
延を開始し、９２０℃以下での累計圧下率が２０％以上
となる圧延を行うことを特徴とする高靭性をもつ構造用
厚鋼板の製造法。18. C0.02 to 0.22% by weight, Si
0.5% or less, Mn 0.3 to 2%, TotalAl 0.08
% Or less, Total N 0.008% or less, balance Fe
And a steel slab composed of unavoidable impurities are heated from a temperature of 400 ° C. or lower so that the average cross-section temperature rising rate of the steel slab between 500 and 1000 ° C. is 7 ° C./min or more,
The surface temperature of the steel slab is 1250 ° C. or lower, the central portion in the thickness direction becomes 900 to 1050 ° C., and the temperature difference between the surface of the steel slab and the central portion in the thickness direction is extracted from the heating furnace and rolled. Water cooling from the surface of the billet before entering, the temperature of the billet surface is lower than the temperature of the center of the billet, water cooling is stopped when the temperature difference becomes 50 ° C or more, and rolling is started immediately. Then, a method for producing a structural thick steel sheet having high toughness, which comprises rolling at a total reduction of 20% or more at 920 ° C or less. 【請求項１９】重量％でＣ０．０２〜０．２２％，Ｓｉ
０．５％以下，Ｍｎ０．３〜２％，TotalＡｌ０．０８
％以下，TotalＮ0.008％以下を含み、さらにＮｂ0.005
〜０．０４％、Ｖ０．００５〜０．０４％の１種または
２種を含み、残部がＦｅおよび不可避的不純物から成る
鋼片を、４００℃以下の温度から加熱を行い、鋼片の５
００〜１０００℃の間の断面平均昇温速度が７℃／分以
上になるように加熱し、鋼片の表面温度が１２５０℃以
下で、かつ厚み方向中央部が９００〜１０５０℃にな
り、しかも鋼片の表面と厚み方向中央部の温度差がある
ままの状態で加熱炉から抽出し、圧延に入る以前に鋼片
表面から水冷を施し、鋼片表面の温度が鋼片中央部の温
度よりも低下して、その温度差が５０℃以上となった時
点で水冷を止め、直ちに圧延を開始し、９２０℃以下で
の累計圧下率が２０％以上となる圧延を行うことを特徴
とする高靭性をもつ構造用厚鋼板の製造法。19. A weight percentage of C0.02 to 0.22%, Si
0.5% or less, Mn 0.3 to 2%, TotalAl 0.08
% Or less, Total N 0.008% or less, and Nb 0.005
To 0.04%, V0.005 to 0.04% of 1 or 2 types, and the balance consisting of Fe and unavoidable impurities, a steel slab is heated from a temperature of 400 ° C. or less to obtain 5
Heating is carried out so that the average cross-section temperature rising rate between 00 and 1000 ° C. is 7 ° C./min or more, the surface temperature of the steel slab is 1250 ° C. or less, and the central portion in the thickness direction becomes 900 to 1050 ° C. Extract from the heating furnace with the temperature difference between the surface of the slab and the central part in the thickness direction kept, and perform water cooling from the surface of the slab before rolling begins. Also, the water cooling is stopped when the temperature difference becomes 50 ° C. or more, the rolling is immediately started, and the rolling at a total reduction of 20% or more at 920 ° C. or less is performed. Manufacturing method of structural steel plate with toughness. 【請求項２０】重量％でＣ０．０２〜０．２２％，Ｓｉ
０．５％以下，Ｍｎ０．３〜２％，TotalＡｌ０．０８
％以下，TotalＮ0.008％以下を含み、さらにＮｂ0.005
〜０．０４％，Ｖ０．００５〜０．０４％の１種または
２種を含み、さらにＴｉ０．００５〜０．０３％を含
み、残部がＦｅおよび不可避的不純物から成る鋼片を、
４００℃以下の温度から加熱を行い、鋼片の５００〜10
00℃の間の断面平均昇温速度が７℃／分以上になるよう
に加熱し、鋼片の表面温度が1250℃以下で、かつ厚み方
向中央部が900〜1050℃になり、しかも鋼片の表面と厚
み方向中央部の温度差があるままの状態で加熱炉から抽
出し、圧延に入る以前に鋼片表面から水冷を施し、鋼片
表面の温度が鋼片中央部の温度よりも低下して、その温
度差が５０℃以上となった時点で水冷を止め、直ちに圧
延を開始し、９２０℃以下での累計圧下率が２０％以上
となる圧延を行うことを特徴とする高靭性をもつ構造用
厚鋼板の製造法。20. C0.02 to 0.22% by weight, Si
0.5% or less, Mn 0.3 to 2%, TotalAl 0.08
% Or less, Total N 0.008% or less, and Nb 0.005
A steel slab containing 0.0 to 0.04% and 0.005 to 0.04% of V, or 0.002 to 0.03% of Ti, and the balance of Fe and inevitable impurities.
Heating from a temperature of 400 ℃ or less, 500 ~ 10
Heating so that the average cross-section temperature rising rate between 00 ° C is 7 ° C / min or more, the surface temperature of the steel slab is 1250 ° C or less, and the central portion in the thickness direction is 900 to 1050 ° C. The temperature of the steel slab surface is lower than that of the center of the slab, which is extracted from the heating furnace with the temperature difference between the surface of the slab and the center of the thickness direction still remaining, and water cooling is performed from the surface of the slab before starting rolling. Then, when the temperature difference becomes 50 ° C. or more, water cooling is stopped, rolling is immediately started, and high rolling toughness is characterized by performing rolling such that the cumulative reduction rate at 920 ° C. or less is 20% or more. Manufacturing method of steel plate for structural use. 【請求項２１】重量％でＣ０．０２〜０．２２％，Ｓｉ
０．５％以下，Ｍｎ０．３〜２％，TotalＡｌ０．０８
％以下，TotalＮ0.008％以下を含み、さらにＣｒ，Ｃ
ｕ，Ｎｉ，Ｍｏの１種以上を合計で０．２〜４．２％を
含み、残部がＦｅおよび不可避的不純物からなる鋼片
を、４００℃以下の温度から加熱を行い、鋼片の５００
〜１０００℃の間の断面平均昇温速度が７℃／分以上に
なるように加熱し、鋼片の表面温度が1250℃以下で、か
つ厚み方向中央部が９００〜1050℃になり、しかも鋼片
の表面と厚み方向中央部の温度差があるままの状態で加
熱炉から抽出し、圧延に入る以前に鋼片表面から水冷を
施し、鋼片表面の温度が鋼片中央部の温度よりも低下し
て、その温度差が５０℃以上となった時点で水冷を止
め、直ちに圧延を開始し、９２０℃以下での累計圧下率
が２０％以上となる圧延を行うことを特徴とする高靭性
をもつ構造用厚鋼板の製造法。21. C0.02-0.22% by weight, Si
0.5% or less, Mn 0.3 to 2%, TotalAl 0.08
% Or less, Total N 0.008% or less, Cr, C
A steel slab containing at least one of u, Ni, and Mo in a total amount of 0.2 to 4.2% and the balance of Fe and unavoidable impurities is heated from a temperature of 400 ° C. or less to give 500
The average temperature of cross section between ~ 1000 ℃ is heated to 7 ℃ / min or more, the surface temperature of the steel slab is 1250 ℃ or less, and the thickness direction central part is 900 ～ 1050 ℃, Extracted from the heating furnace with the temperature difference between the surface of the strip and the center of the thickness direction being kept, water cooling was applied from the surface of the strip before rolling, and the temperature of the surface of the strip was higher than that of the center of the strip. High toughness, characterized in that water cooling is stopped when the temperature difference decreases to 50 ° C. or more, rolling is immediately started, and rolling at a total reduction of 20% or more at 920 ° C. or less is performed. For manufacturing structural thick steel plate with. 【請求項２２】重量％でＣ０．０２〜０．２２％，Ｓｉ
０．５％以下，Ｍｎ０．３〜２％，TotalＡｌ０．０８
％以下，TotalＮ0.008％以下を含み、さらにＣｒ，Ｃ
ｕ，Ｎｉ，Ｍｏの１種以上を合計で０．２〜４．２％を
含み、さらにＮｂ0.005〜0.04％，Ｖ0.005〜0.04％の１
種または２種を含み、さらにＴｉ０．００５〜０．０３
％を含み、残部がＦｅおよび不可避的不純物からなる鋼
片を、４００℃以下の温度から加熱を行い、鋼片の５０
０〜１０００℃の間の断面平均昇温速度が７℃／分以上
になるように加熱し、鋼片の表面温度が１２５０℃以下
で、かつ厚み方向中央部が９００〜１０５０℃になり、
しかも鋼片の表面と厚み方向中央部の温度差があるまま
の状態で加熱炉から抽出し、圧延に入る以前に鋼片表面
から水冷を施し、鋼片表面の温度が鋼片中央部の温度よ
りも低下して、その温度差が５０℃以上となった時点で
水冷を止め、直ちに圧延を開始し、９２０℃以下での累
計圧下率が２０％以上となる圧延を行うことを特徴とす
る高靭性をもつ構造用厚鋼板の製造法。22. C0.02-0.22% by weight, Si
0.5% or less, Mn 0.3 to 2%, TotalAl 0.08
% Or less, Total N 0.008% or less, Cr, C
u, Ni, Mo of one or more kinds in total of 0.2 to 4.2%, and Nb of 0.005 to 0.04% and V0.005 to 0.04% of 1
Or two kinds, and further Ti 0.005-0.03
%, And the balance consisting of Fe and unavoidable impurities is heated from a temperature of 400 ° C. or lower to obtain 50
The cross-section average temperature rising rate between 0 to 1000 ° C. is heated to 7 ° C./min or more, the surface temperature of the steel slab is 1250 ° C. or less, and the thickness direction central portion is 900 to 1050 ° C.
Moreover, it is extracted from the heating furnace with the temperature difference between the surface of the slab and the center in the thickness direction remaining, and water cooling is performed from the surface of the slab before starting rolling. When the temperature difference becomes 50 ° C. or more, water cooling is stopped, rolling is immediately started, and rolling at a cumulative reduction of 920 ° C. or less of 20% or more is performed. Manufacturing method of structural steel plate with high toughness.
JP1177185A 1985-01-26 1985-01-26 Manufacturing method of structural steel plate with high toughness Expired - Lifetime JPH066741B2 (en)

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Cited By (2)

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KR20160079163A (en) * 2014-12-25 2016-07-06 주식회사 포스코 Steel having superior brittle crack arrestability and method for manufacturing the steel
WO2018030737A1 (en) * 2016-08-08 2018-02-15 주식회사 포스코 Ultra-thick steel material having excellent resistance to brittle crack propagation and preparing method therefor

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JP4792778B2 (en) * 2005-03-29 2011-10-12 住友金属工業株式会社 Manufacturing method of thick-walled seamless steel pipe for line pipe

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20160079163A (en) * 2014-12-25 2016-07-06 주식회사 포스코 Steel having superior brittle crack arrestability and method for manufacturing the steel
WO2018030737A1 (en) * 2016-08-08 2018-02-15 주식회사 포스코 Ultra-thick steel material having excellent resistance to brittle crack propagation and preparing method therefor

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