JP2633743B2 - Manufacturing method of thick steel plate with fine grain size - Google Patents
Manufacturing method of thick steel plate with fine grain sizeInfo
- Publication number
- JP2633743B2 JP2633743B2 JP3104266A JP10426691A JP2633743B2 JP 2633743 B2 JP2633743 B2 JP 2633743B2 JP 3104266 A JP3104266 A JP 3104266A JP 10426691 A JP10426691 A JP 10426691A JP 2633743 B2 JP2633743 B2 JP 2633743B2
- Authority
- JP
- Japan
- Prior art keywords
- rolling
- pass
- temperature
- sheet thickness
- reduction
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
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- Heat Treatment Of Steel (AREA)
Description
【０００１】[0001]
【産業上の利用分野】本発明は結晶粒径の微細な厚鋼板
の製造法に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a steel plate having a fine crystal grain size.
【０００２】[0002]
【従来の技術】海洋構造物や橋梁等の構造部材として使
用される厚鋼板の材質は化学成分や熱処理により決ま
る。最近では低温での圧延を主体とした制御圧延法およ
び圧延後に引続いて冷却を行う加速冷却法により良好な
強度、靭性を有する厚鋼板の製造が可能となってきた。
こういった技術に特公昭４９−７２９１号公報、特公昭
５７−２１００７号公報、さらに特公昭５９−１４５３
５号公報等がある。2. Description of the Related Art The material of steel plates used as structural members such as offshore structures and bridges is determined by chemical components and heat treatment. Recently, it has become possible to manufacture thick steel plates having good strength and toughness by a controlled rolling method mainly performed at low temperature and an accelerated cooling method in which cooling is performed after rolling.
Such techniques are disclosed in JP-B-49-7291, JP-B-57-21007, and JP-B-59-1453.
No. 5 publication.
【０００３】[0003]
【発明が解決しようとしている課題】一般的な制御圧延
では、高温域においてオーステナイトを圧延再結晶によ
り微細化し、さらに低温域においてオーステナイトを未
再結晶状態のまま十分に延伸せしめ、その後の変態過程
で微細なフェライトを得る方法がとられている。しかる
に、高温域の圧延においては、オーステナイト粒径は例
え再結晶により微細化しても引続き生ずる粒成長により
再び粗大化し、圧延再結晶による微細化効果を十分に享
受できないという欠点があった。また、オーステナイト
を未再結晶状態で圧延する場合は、高温域の圧延終了後
の長時間にわたる温度低下待ち時間中にオーステナイト
が粒成長してしまい、靭性が劣化すると同時に生産性も
著しく阻害されるという欠点があった。制御圧延後に引
続いて冷却を行う加速冷却法の場合でもこれらの問題点
は基本的に同じである。In a general controlled rolling, austenite is refined by rolling recrystallization in a high temperature range, and austenite is sufficiently stretched in an unrecrystallized state in a low temperature range. A method of obtaining fine ferrite has been adopted. However, in the high-temperature rolling, there is a disadvantage that even if the austenite grain size is reduced by recrystallization, the austenite grain size is again coarsened by the subsequent grain growth, and the refining effect by rolling recrystallization cannot be sufficiently enjoyed. Further, when austenite is rolled in a non-recrystallized state, austenite grains grow during a long temperature drop waiting time after completion of rolling in a high-temperature region, and toughness is deteriorated and productivity is significantly impaired. There was a disadvantage. These problems are basically the same even in the case of the accelerated cooling method in which cooling is performed after controlled rolling.
【０００４】[0004]
【課題を解決するための手段】本発明は上記のような従
来法の欠点を有利に排除しうる、結晶粒径の微細な厚鋼
板の製造法であり、その要旨とするところは次の通りで
ある。 （１）重量％で Ｃ：０．０２〜０．３０％、Ｓｉ：０．０１〜２．０
％、Ｍｎ：０．３０〜３．５％、残部がＦｅおよび不可
避的不純物からなる鋼を、鋳造後Ａｒ3 点以下の温度ま
で冷却することなくそのままあるいはＡｃ3 点以上の温
度域に加熱後圧延を開始し、連続する２パス以上の圧延
でかつ少なくとも一つのパス間で水冷を行い、各パスで
下式を満足する圧延温度と圧下率の関係で圧延すること
を特徴とする結晶粒径の微細な厚鋼板の製造法。 ７２０００／（７１．３＋８．１×ｌｎ（−ｌｎ（１−Ｒi ）))＋２０≧Ｔi ≧７２０００／（７１．３＋８．１×ｌｎ（−ｌｎ（１−Ｒi ）))−２０ ただし、Ｔi ：ｉ番目の圧延パスの圧延温度（Ｋ）、 Ｒi ：ｉ番目の圧延パスの圧下率＝（入側板厚−出側板厚）／入側板厚 （２）重量％で Ｃ：０．０２〜０．３０％、Ｓｉ：０．０１〜２．０
％、Ｍｎ：０．３０〜３．５％、残部がＦｅおよび不可
避的不純物からなる鋼を、鋳造後Ａｒ3 点以下の温度ま
で冷却することなくそのままあるいはＡｃ3 点以上の温
度域に加熱後圧延を開始し、連続する２パス以上の圧延
でかつ少なくとも一つのパス間で水冷を行い、各パス
が、まず（１）式を満足する圧延温度と圧下率の関係で
ｎパス圧延し、しかる後に引続き（２）式を満足する圧
延温度と圧下率の関係で圧延することを特徴とする結晶
粒径の微細な厚鋼板の製造方法。 ７２０００／（７１．３＋８．１×ｌｎ（−ｌｎ（１−Ｒi ）))＋２０≧Ｔi ≧７２０００／（７１．３＋８．１×ｌｎ（−ｌｎ（１−Ｒi ）))−２０ ……………（１） ７２０００／（７４．２＋８．１×ｌｎ（−ｌｎ（１−Ｒj ）))＋２０≧Ｔj ≧７２０００／（７４．２＋８．１×ｌｎ（−ｌｎ（１−Ｒj ）))−２０ ……………（２） ただし、Ｔi ：ｉ番目の圧延パスの圧延温度（Ｋ）、 Ｒi ：ｉ番目の圧延パスの圧下率＝（入側板厚−出側板厚）／入側板厚 Ｔj ：ｊ番目の圧延パスの圧延温度（Ｋ）、 Ｒj ：ｊ番目の圧延パスの圧下率＝（入側板厚−出側板厚）／入側板厚 ｉ≦ｎ、ｊ＞ｎ、ｎ≧１。 （３）重量％で Ｃ：０．０２〜０．３０％、Ｓｉ：０．０１〜２．０
％、Ｍｎ：０．３０〜３．５％さらに、 Ａｌ：０．００５〜０．１０％、Ｔｉ≦０．１０％、Ｃ
ｕ≦３．０％、Ｎｉ≦１０．０％、Ｃｒ≦１０．０％、
Ｍｏ≦３．５％、Ｃｏ≦１０．０％、Ｗ≦２．０％、Ｖ
≦０．１０％、Ｂ≦０．００２５％、Ｒｅｍ≦０．１０
％、Ｃａ≦０．００３０％の１種または２種以上を含有
し、残部がＦｅおよび不可避的不純物からなる鋼を、鋳
造後Ａｒ3 点以下の温度まで冷却することなくそのまま
あるいはＡｃ3 点以上の温度域に加熱後圧延を開始し、
連続する２パス以上の圧延でかつ少なくとも一つのパス
間で水冷を行い、各パスで下式を満足する圧延温度と圧
下率の関係で圧延することを特徴とする結晶粒径の微細
な厚鋼板の製造法。 ７２０００／（７１．３＋８．１×ｌｎ（−ｌｎ（１−Ｒi ）))＋２０≧Ｔi ≧７２０００／（７１．３＋８．１×ｌｎ（−ｌｎ（１−Ｒi ）))−２０ ただし、Ｔi ：ｉ番目の圧延パスの圧延温度（Ｋ）、 Ｒi ：ｉ番目の圧延パスの圧下率＝（入側板厚−出側板厚）／入側板厚 （４）重量％で Ｃ：０．０２〜０．３０％、Ｓｉ：０．０１〜２．０
％、Ｍｎ：０．３０〜３．５％さらに、 Ａｌ：０．００５〜０．１０％、Ｔｉ≦０．１０％、Ｃ
ｕ≦３．０％、Ｎｉ≦１０．０％、Ｃｒ≦１０．０％、
Ｍｏ≦３．５％、Ｃｏ≦１０．０％、Ｗ≦２．０％、Ｖ
≦０．１０％、Ｂ≦０．００２５％、Ｒｅｍ≦０．１０
％、Ｃａ≦０．００３０％の１種または２種以上を含有
し、残部がＦｅおよび不可避的不純物からなる鋼を、鋳
造後Ａｒ3 点以下の温度まで冷却することなくそのまま
あるいはＡｃ3 点以上の温度域に加熱後圧延を開始し、
連続する２パス以上の圧延でかつ 少なくとも一つのパス
間で水冷を行い、各パスが、まず（１）式を満足する圧
延温度と圧下率の関係でｎパス圧延し、しかる後に引続
き（２）式を満足する圧延温度と圧下率の関係で圧延す
ることを特徴とする結晶粒径の微細な厚鋼板の製造方
法。 ７２０００／（７１．３＋８．１×ｌｎ（−ｌｎ（１−Ｒi ）))＋２０≧Ｔi ≧７２０００／（７１．３＋８．１×ｌｎ（−ｌｎ（１−Ｒi ）))−２０ ……………（１） ７２０００／（７４．２＋８．１×ｌｎ（−ｌｎ（１−Ｒj ）))＋２０≧Ｔj ≧７２０００／（７４．２＋８．１×ｌｎ（−ｌｎ（１−Ｒj ）))−２０ ……………（２） ただし、Ｔi ：ｉ番目の圧延パスの圧延温度（Ｋ）、 Ｒi ：ｉ番目の圧延パスの圧下率＝（入側板厚−出側板厚）／入側板厚 Ｔj ：ｊ番目の圧延パスの圧延温度（Ｋ）、 Ｒj ：ｊ番目の圧延パスの圧下率＝（入側板厚−出側板厚）／入側板厚 ｉ≦ｎ、ｊ＞ｎ、ｎ≧１。SUMMARY OF THE INVENTION The present invention is a method for producing a thick steel plate having a fine crystal grain size, which can advantageously eliminate the above-mentioned disadvantages of the conventional method. It is. (1) In terms of% by weight, C: 0.02 to 0.30%, Si: 0.01 to 2.0
%, Mn: 0.30 to 3.5%, the balance being Fe and inevitable impurities, after being cast, without being cooled to a temperature of not more than Ar 3 points, or after being heated to a temperature range of not less than Ac 3 points. Start rolling, rolling two or more consecutive passes
Water-cooling between at least one pass and rolling in each pass with a relationship between a rolling temperature and a rolling reduction satisfying the following formula: 72000 / (71.3 + 8.1 × ln (-ln (1-Ri))) + 20 ≧ Ti ≧ 72000 / (71.3 + 8.1 × ln (-ln (1-Ri)))-20 where Ti: Rolling temperature (K) of the i-th rolling pass, Ri: rolling reduction of the i-th rolling pass = (inlet-side sheet thickness-outlet-side sheet thickness) / inlet-side sheet thickness (2) In weight%, C: 0.02-0. 30%, Si: 0.01 to 2.0
%, Mn: 0.30 to 3.5%, the balance being Fe and inevitable impurities, after being cast, without being cooled to a temperature of not more than Ar 3 points, or after being heated to a temperature range of not less than Ac 3 points. Start rolling, rolling two or more consecutive passes
Water cooling between at least one pass and each pass
However, first, n-pass rolling is performed with the relationship between the rolling temperature and the rolling reduction satisfying the formula (1), and then the rolling is continued with the relationship between the rolling temperature and the rolling reduction satisfying the formula (2). A method for manufacturing thick steel plates with a small diameter. 72000 / (71.3 + 8.1 × ln (−ln (1-Ri))) + 20 ≧ Ti ≧ 72000 / (71.3 + 8.1 × ln (−ln (1-Ri))) − 20 ... (1) 72000 / (74.2 + 8.1 * ln (-ln (1-Rj))) + 20≥Tj≥72000 / (74.2 + 8.1 * ln (-ln (1-Rj)))-20 (2) where, Ti: rolling temperature (K) of the i-th rolling pass, Ri: reduction ratio of the i-th rolling pass = (incoming sheet thickness-outgoing sheet thickness) / incoming sheet thickness Tj: Rolling temperature (K) of the j-th rolling pass, Rj: rolling reduction of the j-th rolling pass = (inlet-side sheet thickness-outlet-side sheet thickness) / inlet-side sheet thickness i ≦ n, j> n, n ≧ 1. (3) In weight%, C: 0.02 to 0.30%, Si: 0.01 to 2.0
%, Mn: 0.30 to 3.5%, Al: 0.005 to 0.10%, Ti ≦ 0.10%, C
u ≦ 3.0%, Ni ≦ 10.0%, Cr ≦ 10.0%,
Mo ≦ 3.5%, Co ≦ 10.0%, W ≦ 2.0%, V
≦ 0.10%, B ≦ 0.0025%, Rem ≦ 0.10
%, Ca ≦ 0.0030% containing one or more kinds, and the balance being Fe and unavoidable impurities, without being cooled to a temperature of not more than Ar 3 point after casting, or without being cooled to 3 points of Ac or more. Start rolling after heating to the temperature range of
Two or more consecutive rolling passes and at least one pass
A method for producing a steel plate having a fine crystal grain size , wherein water is cooled between the rolls and rolling is performed in each pass at a relationship between a rolling temperature and a rolling reduction satisfying the following formula. 72000 / (71.3 + 8.1 × ln (-ln (1-Ri))) + 20 ≧ Ti ≧ 72000 / (71.3 + 8.1 × ln (-ln (1-Ri)))-20 where Ti: Rolling temperature (K) of the i-th rolling pass, Ri: rolling reduction of the i-th rolling pass = (inlet-side sheet thickness-outlet-side sheet thickness) / inlet-side sheet thickness (4) In% by weight, C: 0.02-0. 30%, Si: 0.01 to 2.0
%, Mn: 0.30 to 3.5%, Al: 0.005 to 0.10%, Ti ≦ 0.10%, C
u ≦ 3.0%, Ni ≦ 10.0%, Cr ≦ 10.0%,
Mo ≦ 3.5%, Co ≦ 10.0%, W ≦ 2.0%, V
≦ 0.10%, B ≦ 0.0025%, Rem ≦ 0.10
%, Ca ≦ 0.0030% containing one or more kinds, and the balance being Fe and unavoidable impurities, without being cooled to a temperature of not more than Ar 3 point after casting, or without being cooled to 3 points of Ac or more. Start rolling after heating to the temperature range of
Two or more consecutive rolling passes and at least one pass
Water-cooling is performed between each pass, and each pass is first subjected to n-pass rolling in accordance with the relationship between the rolling temperature and the rolling reduction satisfying the formula (1), and then subsequently to rolling in the relationship between the rolling temperature and the rolling reduction satisfying the formula (2). A method for producing a thick steel plate having a fine crystal grain size. 72000 / (71.3 + 8.1 × ln (−ln (1-Ri))) + 20 ≧ Ti ≧ 72000 / (71.3 + 8.1 × ln (−ln (1-Ri))) − 20 ... (1) 72000 / (74.2 + 8.1 * ln (-ln (1-Rj))) + 20≥Tj≥72000 / (74.2 + 8.1 * ln (-ln (1-Rj)))-20 (2) where, Ti: rolling temperature (K) of the i-th rolling pass, Ri: reduction ratio of the i-th rolling pass = (incoming sheet thickness-outgoing sheet thickness) / incoming sheet thickness Tj: Rolling temperature (K) of the j-th rolling pass, Rj: rolling reduction of the j-th rolling pass = (inlet-side sheet thickness-outlet-side sheet thickness) / inlet-side sheet thickness i ≦ n, j> n, n ≧ 1.
【０００５】以下本発明について詳細に説明する。まず
本発明鋼の成分限定理由について説明する。Ｃは鋼材を
強化するために不可欠の元素であって、０．０２％未満
では所要の高強度が得られにくく、また０．３０％を越
えると溶接部の靭性が損なわれるため０．０２％以上
０．３０％以下に限定した。Ｓｉは脱酸を促進しかつ強
度を上げることで効果的な元素であるので０．０１％以
上添加するが、添加しすぎると溶接性を劣化させるため
２．０％以下にとどめる。Ｍｎは低温靭性を向上させる
元素として有効であるので０．３％以上添加するが、
３．５％以上添加すると溶接割れを促進させるおそれが
あるので、３．５％以下にとどめる。Hereinafter, the present invention will be described in detail. First, the reasons for limiting the components of the steel of the present invention will be described. C is an indispensable element for strengthening the steel material. If it is less than 0.02%, it is difficult to obtain the required high strength, and if it exceeds 0.30%, the toughness of the welded portion is impaired, so that 0.02% It was limited to not less than 0.30%. Since Si is an element effective for promoting deoxidation and increasing the strength, it is added in an amount of 0.01% or more. However, if added too much, the weldability is deteriorated, so that the content is limited to 2.0% or less. Since Mn is effective as an element for improving low-temperature toughness, Mn is added in an amount of 0.3% or more.
If it is added in an amount of 3.5% or more, there is a possibility that welding cracks may be promoted. Therefore, the content is limited to 3.5% or less.
【０００６】Ａｌは脱酸剤として有効であるので０．０
０５％以上添加しても良いが、過量のＡｌは材質にとっ
て有害な介在物を生成するため上限を０．１％とした。
Ｔｉは微量の添加で結晶粒の微細化に有効であるので、
溶接部靭性を劣化させない程度の量を添加しても良い。
そのため添加量の上限は０．１０％とする。Ｃｕ，Ｎ
ｉ，Ｃｒ，Ｍｏ，Ｃｏ，Ｗはいずれも焼入れ性を向上さ
せる元素として知られており本発明鋼に添加した場合鋼
の強度を上昇させることができるが、過度の添加は溶接
性を損なうことになるため、Ｃｕは３．０％以下、Ｎｉ
は１０％以下、Ｃｒは１０％以下、Ｍｏは３．５％以
下、Ｃｏは１０％以下、Ｗは２％以下に限定した。Since Al is effective as a deoxidizing agent,
Although it may be added in an amount of 05% or more, an excessive amount of Al generates inclusions harmful to the material, so the upper limit is set to 0.1%.
Since Ti is effective in refining crystal grains by adding a small amount,
An amount that does not deteriorate the weld toughness may be added.
Therefore, the upper limit of the amount added is 0.10%. Cu, N
i, Cr, Mo, Co, and W are all known as elements for improving hardenability, and when added to the steel of the present invention, can increase the strength of the steel. However, excessive addition impairs weldability. Therefore, Cu is 3.0% or less, Ni
Is 10% or less, Cr is 10% or less, Mo is 3.5% or less, Co is 10% or less, and W is 2% or less.
【０００７】Ｖは析出効果により強度の上昇に有効であ
るが、過度の添加は靭性を損なうことになるため、上限
を０．１０％とした。Ｂは焼入れ性を向上させる元素と
して知られており本発明鋼に添加した場合鋼の強度を上
昇させることができるが、過度の添加はＢの析出物を増
加させて靭性を損なうことになるため、上限を０．００
２５％とした。ＲｅｍとＣａはＳの無害化に有効である
が、過度の添加は靭性を損なうことになるため、上限を
それぞれ０．１０％，０．００３０％とした。[0007] V is effective for increasing the strength due to the precipitation effect, but excessive addition impairs the toughness, so the upper limit was made 0.10%. B is known as an element that improves the hardenability and can increase the strength of the steel when added to the steel of the present invention, but excessive addition increases the precipitates of B and impairs the toughness. , With an upper limit of 0.00
25%. Rem and Ca are effective for detoxifying S, however, since excessive addition impairs toughness, the upper limits are set to 0.10% and 0.0030%, respectively.
【０００８】次に本発明の根幹をなす技術思想について
述べる。従来、厚鋼板の靭性を向上させる加工方法とし
ては、オーステナイトの再結晶温度域における圧延で結
晶粒を再結晶により微細化し、引続き未再結晶温度域に
おける圧延において結晶粒を十分に延伸せしめ、そのま
まの状態で変態させることが有効とされてきた。しか
し、これまでの圧延法では、特開昭５３−４０６２０，
４０６２１号公報、特開昭５９−１８２９１６号公報、
特開昭６０−５６０１７号公報のように、圧延中に温度
制御をする方法はあったものの、圧延中の金属組織の逐
次変化に基づいて、圧延パス間時間、圧下率および圧延
温度を圧延パス毎に制御することがなかったために、高
温での圧延で再結晶した粒はパス間時間内の粒成長によ
り再び粗大化する場合が多い。さらに、再結晶温度域か
ら未再結晶温度域まで温度が低下する間の待ち時間中に
結晶粒が粒成長により粗大化する傾向があり、上記の圧
延法の効果を十分に享受することができなかった。Next, the technical idea which forms the basis of the present invention will be described. Conventionally, as a processing method for improving the toughness of thick steel plate, the crystal grains are refined by recrystallization by rolling in the recrystallization temperature range of austenite, and subsequently the crystal grains are sufficiently stretched in rolling in the non-recrystallization temperature range, and It has been considered effective to transform in this state. However, in the conventional rolling method, JP-A-53-40620,
JP 40621, JP-A-59-182916,
As disclosed in Japanese Patent Application Laid-Open No. 60-56017, there was a method of controlling the temperature during rolling. However, the time between rolling passes, the rolling reduction, and the rolling temperature were determined based on the sequential change of the metal structure during rolling. Since control was not performed every time, the grains recrystallized by rolling at a high temperature often become coarse again due to grain growth within the time between passes. Furthermore, during the waiting time during which the temperature decreases from the recrystallization temperature range to the non-recrystallization temperature range, the crystal grains tend to become coarse due to grain growth, and the effects of the above-described rolling method can be sufficiently enjoyed. Did not.
【０００９】しかるに、本発明者らは上記の限界を打破
することを可能とする新しい事実を発見し、結晶粒の微
細な厚鋼板の製造法を発明した。本発明者らは、通常の
厚板圧延の圧延パス間時間、圧下率および圧延温度と金
属組織との関係を詳細に調査した結果、通常の圧延パス
間時間ちょうどに圧延再結晶を完了させるための条件と
して圧延温度と圧下率の関係が（１）式の不等式で表さ
れることを見出した。 ７２０００／（７１．３＋８．１×ｌｎ（−ｌｎ（１−Ｒ）))＋２０≧Ｔ≧ ７２０００／（７１．３＋８．１×ｌｎ（−ｌｎ（１−Ｒ）))−２０ ……………（１） また、通常の圧延パス間時間内では再結晶が開始しない
（オーステナイトが未再結晶状態である）ための条件と
して圧延温度と圧下率の関係が（２）式の不等式で表さ
れることを見出した。 ７２０００／（７４．２＋８．１×ｌｎ（−ｌｎ（１−Ｒ）))＋２０≧Ｔ≧ ７２０００／（７４．２＋８．１×ｌｎ（−ｌｎ（１−Ｒ）))−２０ ……………（２） ただし（１）式、（２）式とも、Ｔ：圧延温度（Ｋ）、 Ｒ：各圧延パスの圧下率＝（入側板厚−出側板厚）／入
側板厚。However, the present inventors have discovered a new fact that makes it possible to overcome the above-mentioned limitations, and have invented a method for producing a thick steel plate having fine crystal grains. The present inventors have investigated in detail the relationship between the metallographic structure and the rolling pass time, rolling reduction and rolling temperature of normal plate rolling, and completed the rolling recrystallization just in the normal rolling pass time. It has been found that the relationship between the rolling temperature and the rolling reduction is represented by the inequality of the equation (1) as the condition (1). 72000 / (71.3 + 8.1 × ln (−ln (1-R))) + 20 ≧ T ≧ 72000 / (71.3 + 8.1 × ln (−ln (1-R))) − 20 ... (1) In addition, as a condition for recrystallization not to start within the normal rolling pass time (austenite is in an unrecrystallized state), the relationship between the rolling temperature and the rolling reduction is expressed by the inequality of equation (2). I found that. 72000 / (74.2 + 8.1 × ln (−ln (1-R))) + 20 ≧ T ≧ 72000 / (74.2 + 8.1 × ln (−ln (1-R))) − 20 ... (2) However, in both of the expressions (1) and (2), T: rolling temperature (K), R: reduction ratio of each rolling pass = (inlet-side plate thickness-outlet-side plate thickness) / inlet-side plate thickness.
【００１０】すなわち、圧延再結晶による微細化を狙う
場合には、（１）式の圧延温度と圧下率の関係を満たす
圧延条件を選定することにより、オーステナイトは次パ
スの圧延直前に再結晶を完了する。これにより再結晶に
引続いて生ずる粒成長を完全に回避することができる。
一方、未再結晶圧延によるオーステナイトの延伸を狙う
場合には、（２）式の圧延温度と圧下率の関係を満たす
圧延条件を選定することにより、オーステナイトを完全
に未再結晶状態に保つことが可能となる。これにより、
従来のような長時間におよぶ温度低下待ちは不要とな
り、その間の粒成長の削除、さらには生産性の大幅な向
上も可能となる。In other words, when miniaturization by rolling recrystallization is aimed at, austenite is subjected to recrystallization immediately before rolling in the next pass by selecting rolling conditions that satisfy the relationship between the rolling temperature and the rolling reduction in the equation (1). Complete. As a result, grain growth following recrystallization can be completely avoided.
On the other hand, when aiming for austenite stretching by non-recrystallization rolling, it is possible to maintain austenite in a completely non-recrystallized state by selecting rolling conditions that satisfy the relationship between the rolling temperature and the rolling reduction in equation (2). It becomes possible. This allows
It is not necessary to wait for a long time to lower the temperature as in the related art, and it is possible to eliminate the grain growth during that time and to further improve the productivity.
【００１１】次に本発明の製造条件の限定理由を詳細に
説明する。本発明においては鋳造後冷片にすることなく
鋳片を直接圧延しても良いしまた鋳造後冷片としたもの
を再加熱して用いても良い。加熱温度はＡｃ3 点以上と
し、特に上限を定める必要はない。高温域の圧延では、
圧延再結晶によるオーステナイトの微細化を狙うため、
（１）式の圧延温度と圧下率の関係を満たす圧延条件を
選定する。ただし、９００℃以下では粒成長速度が遅く
実質的に粒成長による靭性劣化が見られないため、９０
０℃以上の圧延温度域では（１）式を満たす必要があ
る。また引続きオーステナイトの未再結晶圧延を狙う場
合は、（２）式の圧延温度と圧下率の関係を満たす圧延
条件を選定する。（１）及び（２）式を満足させるため
には、連続する２パス以上の圧延でかつ少なくとも一つ
の圧延パス間において冷却することが望ましいが、冷却
手段としては、パス間時間の短縮と再結晶終了後の結晶
粒の粗大化を回避するために、水冷方式を採用すること
が必要である。また本発明では、圧延終了後に放冷、加
速冷却、直接焼入れ、焼戻しなどのいずれの手段を用い
ても有効である。Next, the reasons for limiting the manufacturing conditions of the present invention will be described in detail. In the present invention, the cast slab may be directly rolled without being cast and then cooled, or the cast flake may be reheated before use. The heating temperature is set to three or more Ac, and it is not necessary to set an upper limit. In high temperature rolling,
In order to refine austenite by rolling recrystallization,
A rolling condition that satisfies the relationship between the rolling temperature and the rolling reduction in equation (1) is selected. However, at a temperature of 900 ° C. or lower, the grain growth rate is slow, and substantially no toughness deterioration due to grain growth is observed.
In the rolling temperature range of 0 ° C. or more, it is necessary to satisfy the expression (1). In the case where the austenitic non-recrystallization rolling is to be continued, the rolling conditions satisfying the relationship between the rolling temperature and the rolling reduction in the equation (2) are selected. In order to satisfy the expressions (1) and (2), it is necessary to perform rolling in two or more consecutive passes and at least one
It is desirable to cool between rolling passes of
Means include shortening the time between passes and recrystallization
Use a water-cooled system to avoid grain coarsening
Is required . In the present invention, it is effective to use any means such as cooling after cooling, accelerated cooling, direct quenching, and tempering.
【００１２】[0012]
【実施例】次に本発明を実施例にもとづいて説明する。
まず表１に示す成分の本発明鋼について表２に示す本発
明方法および比較方法を適用した場合、表３に示したオ
ーステナイト結晶粒径、強度、靭性となる。ただしオー
ステナイト結晶粒径は圧延直後に焼入れることにより観
察したもので、材質試験片を採取した厚鋼板と同じ設定
条件で圧延した厚鋼板から試験片を採取した。表３よ
り、明らかに本発明鋼は優れた特性を示し、本発明は有
効である。Next, the present invention will be described based on embodiments.
First, when the method of the present invention and the comparative method shown in Table 2 are applied to the steel of the present invention having the components shown in Table 1, the austenite grain size, strength and toughness shown in Table 3 are obtained. However, the austenitic crystal grain size was observed by quenching immediately after rolling, and a test piece was sampled from a thick steel sheet rolled under the same setting conditions as the thick steel sheet from which the material test piece was sampled. Table 3 clearly shows that the steel of the present invention has excellent properties, and the present invention is effective.
【００１３】[0013]
【表１】 [Table 1]
【００１４】[0014]
【表２】 [Table 2]
【００１５】[0015]
【表３】 [Table 3]
【００１６】[0016]
【表４】 [Table 4]
【００１７】[0017]
【発明の効果】本発明は上記の通り構成されているの
で、次に記載する効果を奏する。請求項１および３の厚
鋼板の製造方法においては、所定の成分の鋼の圧延再結
晶後の粒成長を完全に回避することにより、結晶粒径の
微細な厚鋼板を得ることができ、厚鋼板の機械的性質を
効率的に向上させることが可能となる。請求項２および
４の厚鋼板の製造方法においては、所定の成分の鋼の圧
延再結晶後の粒成長を完全に回避することにより、オー
ステナイトの結晶粒径を微細とし、さらに引続きオース
テナイトを完全未再結晶状態に保ったまま変態させるこ
とにより粒径の微細な変態後の金属組織を得ることがで
き、厚鋼板の機械的性質を効率的に向上させることが可
能となる。請求項５の厚鋼板の製造方法は、請求項２乃
至４に記載された条件を具現化するための一製造方法を
示したもので、これにより結晶粒径の微細な厚鋼板を得
ることができ、厚鋼板の機械的性質を効率的に向上させ
ることができる。Since the present invention is constituted as described above, the following effects can be obtained. In the method for manufacturing a steel plate according to claims 1 and 3, a steel plate having a fine grain size can be obtained by completely avoiding grain growth after rolling and recrystallization of steel having a predetermined component. It is possible to efficiently improve the mechanical properties of the steel sheet. In the method for manufacturing a steel plate according to claims 2 and 4, by completely avoiding grain growth after rolling and recrystallization of steel having a predetermined component, the crystal grain size of austenite is reduced, and further, austenite is completely removed. By performing transformation while maintaining the recrystallized state, it is possible to obtain a transformed metal structure with a fine grain size, and it is possible to efficiently improve the mechanical properties of the thick steel plate. The method for manufacturing a thick steel plate according to claim 5 is an example of a manufacturing method for realizing the conditions described in claims 2 to 4, whereby a thick steel plate having a fine grain size can be obtained. As a result, the mechanical properties of the thick steel plate can be efficiently improved.
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平２−15121（ＪＰ，Ａ) 特開 平２−77521（ＪＰ，Ａ) 特開 平４−358021（ＪＰ，Ａ) ────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-2-15121 (JP, A) JP-A-2-77521 (JP, A) JP-A-4-358021 (JP, A)
Claims (4)
％、Ｍｎ：０．３０〜３．５％、残部がＦｅおよび不可
避的不純物からなる鋼を、鋳造後Ａｒ3 点以下の温度ま
で冷却することなくそのままあるいはＡｃ3 点以上の温
度域に加熱後圧延を開始し、連続する２パス以上の圧延
でかつ少なくとも一つのパス間で水冷を行い、各パスで
下式を満足する圧延温度と圧下率の関係で圧延すること
を特徴とする結晶粒径の微細な厚鋼板の製造法。 ７２０００／（７１．３＋８．１×ｌｎ（−ｌｎ（１−Ｒi ）))＋２０≧Ｔi ≧７２０００／（７１．３＋８．１×ｌｎ（−ｌｎ（１−Ｒi ）))−２０ ただし、Ｔi ：ｉ番目の圧延パスの圧延温度（Ｋ）、 Ｒi ：ｉ番目の圧延パスの圧下率＝（入側板厚−出側板厚）／入側板厚C .: 0.02 to 0.30% by weight, Si: 0.01 to 2.0% by weight
%, Mn: 0.30 to 3.5%, the balance being Fe and inevitable impurities, after being cast, without being cooled to a temperature of not more than Ar 3 points, or after being heated to a temperature range of not less than Ac 3 points. Start rolling, rolling two or more consecutive passes
Water-cooling between at least one pass and rolling in each pass with a relationship between a rolling temperature and a rolling reduction satisfying the following formula: 72000 / (71.3 + 8.1 × ln (-ln (1-Ri))) + 20 ≧ Ti ≧ 72000 / (71.3 + 8.1 × ln (-ln (1-Ri)))-20 where Ti: Rolling temperature (K) of the i-th rolling pass, Ri: rolling reduction of i-th rolling pass = (incoming plate thickness-outgoing plate thickness) / incoming plate thickness
％、Ｍｎ：０．３０〜３．５％、残部がＦｅおよび不可
避的不純物からなる鋼を、鋳造後Ａｒ3 点以下の温度ま
で冷却することなくそのままあるいはＡｃ3 点以上の温
度域に加熱後圧延を開始し、連続する２パス以上の圧延
でかつ少なくとも一つのパス間で水冷を行い、各パス
が、まず（１）式を満足する圧延温度と圧下率の関係で
ｎパス圧延し、しかる後に引続き（２）式を満足する圧
延温度と圧下率の関係で圧延することを特徴とする結晶
粒径の微細な厚鋼板の製造方法。 ７２０００／（７１．３＋８．１×ｌｎ（−ｌｎ（１−Ｒi ）))＋２０≧Ｔi ≧７２０００／（７１．３＋８．１×ｌｎ（−ｌｎ（１−Ｒi ）))−２０ ……………（１） ７２０００／（７４．２＋８．１×ｌｎ（−ｌｎ（１−Ｒj ）))＋２０≧Ｔj ≧７２０００／（７４．２＋８．１×ｌｎ（−ｌｎ（１−Ｒj ）))−２０ ……………（２） ただし、Ｔi ：ｉ番目の圧延パスの圧延温度（Ｋ）、 Ｒi ：ｉ番目の圧延パスの圧下率＝（入側板厚−出側板厚）／入側板厚 Ｔj ：ｊ番目の圧延パスの圧延温度（Ｋ）、 Ｒj ：ｊ番目の圧延パスの圧下率＝（入側板厚−出側板厚）／入側板厚 ｉ≦ｎ、ｊ＞ｎ、ｎ≧１。2. C: 0.02 to 0.30% by weight, Si: 0.01 to 2.0% by weight.
%, Mn: 0.30 to 3.5%, the balance being Fe and inevitable impurities, after being cast, without being cooled to a temperature of not more than Ar 3 points, or after being heated to a temperature range of not less than Ac 3 points. Start rolling, rolling two or more consecutive passes
Water cooling between at least one pass and each pass
However, first, n-pass rolling is performed with the relationship between the rolling temperature and the rolling reduction satisfying the formula (1), and then the rolling is continued with the relationship between the rolling temperature and the rolling reduction satisfying the formula (2). A method for manufacturing thick steel plates with a small diameter. 72000 / (71.3 + 8.1 × ln (−ln (1-Ri))) + 20 ≧ Ti ≧ 72000 / (71.3 + 8.1 × ln (−ln (1-Ri))) − 20 ... (1) 72000 / (74.2 + 8.1 * ln (-ln (1-Rj))) + 20≥Tj≥72000 / (74.2 + 8.1 * ln (-ln (1-Rj)))-20 (2) where, Ti: rolling temperature (K) of the i-th rolling pass, Ri: reduction ratio of the i-th rolling pass = (incoming sheet thickness-outgoing sheet thickness) / incoming sheet thickness Tj: Rolling temperature (K) of the j-th rolling pass, Rj: rolling reduction of the j-th rolling pass = (inlet-side sheet thickness-outlet-side sheet thickness) / inlet-side sheet thickness i ≦ n, j> n, n ≧ 1.
％、Ｍｎ：０．３０〜３．５％さらに、 Ａｌ：０．００５〜０．１０％、Ｔｉ≦０．１０％、Ｃ
ｕ≦３．０％、Ｎｉ≦１０．０％、Ｃｒ≦１０．０％、
Ｍｏ≦３．５％、Ｃｏ≦１０．０％、Ｗ≦２．０％、Ｖ
≦０．１０％、Ｂ≦０．００２５％、Ｒｅｍ≦０．１０
％、Ｃａ≦０．００３０％の１種または２種以上を含有
し、残部がＦｅおよび不可避的不純物からなる鋼を、鋳
造後Ａｒ3 点以下の温度まで冷却することなくそのまま
あるいはＡｃ3 点以上の温度域に加熱後圧延を開始し、
連続する２パス以上の圧延でかつ少なくとも一つのパス
間で水冷を行い、各パスで下式を満足する圧延温度と圧
下率の関係で圧延することを特徴とする結晶粒径の微細
な厚鋼板の製造法。 ７２０００／（７１．３＋８．１×ｌｎ（−ｌｎ（１−Ｒi ）))＋２０≧Ｔi ≧７２０００／（７１．３＋８．１×ｌｎ（−ｌｎ（１−Ｒi ）))−２０ ただし、Ｔi ：ｉ番目の圧延パスの圧延温度（Ｋ）、 Ｒi ：ｉ番目の圧延パスの圧下率＝（入側板厚−出側板厚）／入側板厚3. C: 0.02 to 0.30% by weight, Si: 0.01 to 2.0% by weight
%, Mn: 0.30 to 3.5%, Al: 0.005 to 0.10%, Ti ≦ 0.10%, C
u ≦ 3.0%, Ni ≦ 10.0%, Cr ≦ 10.0%,
Mo ≦ 3.5%, Co ≦ 10.0%, W ≦ 2.0%, V
≦ 0.10%, B ≦ 0.0025%, Rem ≦ 0.10
%, Ca ≦ 0.0030% containing one or more kinds, and the balance being Fe and unavoidable impurities, without being cooled to a temperature of not more than Ar 3 point after casting, or without being cooled to 3 points of Ac or more. Start rolling after heating to the temperature range of
Two or more consecutive rolling passes and at least one pass
A method for producing a steel plate having a fine crystal grain size , wherein water is cooled between the rolls and rolling is performed in each pass at a relationship between a rolling temperature and a rolling reduction satisfying the following formula. 72000 / (71.3 + 8.1 × ln (-ln (1-Ri))) + 20 ≧ Ti ≧ 72000 / (71.3 + 8.1 × ln (-ln (1-Ri)))-20 where Ti: Rolling temperature (K) of the i-th rolling pass, Ri: rolling reduction of i-th rolling pass = (incoming plate thickness-outgoing plate thickness) / incoming plate thickness
％、Ｍｎ：０．３０〜３．５％さらに、 Ａｌ：０．００５〜０．１０％、Ｔｉ≦０．１０％、Ｃ
ｕ≦３．０％、Ｎｉ≦１０．０％、Ｃｒ≦１０．０％、
Ｍｏ≦３．５％、Ｃｏ≦１０．０％、Ｗ≦２．０％、Ｖ
≦０．１０％、Ｂ≦０．００２５％、Ｒｅｍ≦０．１０
％、Ｃａ≦０．００３０％の１種または２種以上を含有
し、残部がＦｅおよび不可避的不純物からなる鋼を、鋳
造後Ａｒ3 点以下の温度まで冷却することなくそのまま
あるいはＡｃ3 点以上の温度域に加熱後圧延を開始し、
連続する２パス以上の圧延でかつ少なくとも一つのパス
間で水冷を行い、各パスが、まず（１）式を満足する圧
延温度と圧下率の関係でｎパス圧延し、しかる後に引続
き（２）式を満足する圧延温度と圧下率の関係で圧延す
ることを特徴とする結晶粒径の微細な厚鋼板の製造方
法。 ７２０００／（７１．３＋８．１×ｌｎ（−ｌｎ（１−Ｒi ）))＋２０≧Ｔi ≧７２０００／（７１．３＋８．１×ｌｎ（−ｌｎ（１−Ｒi ）))−２０ ……………（１） ７２０００／（７４．２＋８．１×ｌｎ（−ｌｎ（１−Ｒj ）))＋２０≧Ｔj ≧７２０００／（７４．２＋８．１×ｌｎ（−ｌｎ（１−Ｒj ）))−２０ ……………（２） ただし、Ｔi ：ｉ番目の圧延パスの圧延温度（Ｋ）、 Ｒi ：ｉ番目の圧延パスの圧下率＝（入側板厚−出側板厚）／入側板厚 Ｔj ：ｊ番目の圧延パスの圧延温度（Ｋ）、 Ｒj ：ｊ番目の圧延パスの圧下率＝（入側板厚−出側板厚）／入側板厚 ｉ≦ｎ、ｊ＞ｎ、ｎ≧１。4. C: 0.02-0.30% by weight, Si: 0.01-2.0% by weight
%, Mn: 0.30 to 3.5%, Al: 0.005 to 0.10%, Ti ≦ 0.10%, C
u ≦ 3.0%, Ni ≦ 10.0%, Cr ≦ 10.0%,
Mo ≦ 3.5%, Co ≦ 10.0%, W ≦ 2.0%, V
≦ 0.10%, B ≦ 0.0025%, Rem ≦ 0.10
%, Ca ≦ 0.0030% containing one or more kinds, and the balance being Fe and unavoidable impurities, without being cooled to a temperature of not more than Ar 3 point after casting, or without being cooled to 3 points of Ac or more. Start rolling after heating to the temperature range of
Two or more consecutive rolling passes and at least one pass
Water-cooling is performed between each pass, and each pass is first subjected to n-pass rolling in accordance with the relationship between the rolling temperature and the rolling reduction satisfying the formula (1), and then subsequently to rolling in the relationship between the rolling temperature and the rolling reduction satisfying the formula (2). A method for producing a thick steel plate having a fine crystal grain size. 72000 / (71.3 + 8.1 × ln (−ln (1-Ri))) + 20 ≧ Ti ≧ 72000 / (71.3 + 8.1 × ln (−ln (1-Ri))) − 20 ... (1) 72000 / (74.2 + 8.1 * ln (-ln (1-Rj))) + 20≥Tj≥72000 / (74.2 + 8.1 * ln (-ln (1-Rj)))-20 (2) where, Ti: rolling temperature (K) of the i-th rolling pass, Ri: reduction ratio of the i-th rolling pass = (incoming sheet thickness-outgoing sheet thickness) / incoming sheet thickness Tj: Rolling temperature (K) of the j-th rolling pass, Rj: rolling reduction of the j-th rolling pass = (inlet-side sheet thickness-outlet-side sheet thickness) / inlet-side sheet thickness i ≦ n, j> n, n ≧ 1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3104266A JP2633743B2 (en) | 1991-05-09 | 1991-05-09 | Manufacturing method of thick steel plate with fine grain size |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3104266A JP2633743B2 (en) | 1991-05-09 | 1991-05-09 | Manufacturing method of thick steel plate with fine grain size |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH04358020A JPH04358020A (en) | 1992-12-11 |
| JP2633743B2 true JP2633743B2 (en) | 1997-07-23 |
Family
ID=14376128
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3104266A Expired - Fee Related JP2633743B2 (en) | 1991-05-09 | 1991-05-09 | Manufacturing method of thick steel plate with fine grain size |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2633743B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8882936B2 (en) | 2004-08-24 | 2014-11-11 | Nippon Steel & Sumitomo Metal Corporation | High-tensile steel with excellent weldability and toughness and with tensile strength of 550 MPa class or more and method of production of the same |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH0215121A (en) * | 1988-07-04 | 1990-01-18 | Nippon Steel Corp | Production of steel having good toughness |
| JPH0670248B2 (en) * | 1988-09-13 | 1994-09-07 | 川崎製鉄株式会社 | Manufacturing method of ultra-high-strength steel plate for welding with excellent homogeneity in the thickness direction |
-
1991
- 1991-05-09 JP JP3104266A patent/JP2633743B2/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8882936B2 (en) | 2004-08-24 | 2014-11-11 | Nippon Steel & Sumitomo Metal Corporation | High-tensile steel with excellent weldability and toughness and with tensile strength of 550 MPa class or more and method of production of the same |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04358020A (en) | 1992-12-11 |
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