JP4109407B2 - Method and apparatus for controlling flatness of metal plate - Google Patents

Method and apparatus for controlling flatness of metal plate Download PDF

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JP4109407B2
JP4109407B2 JP2000234717A JP2000234717A JP4109407B2 JP 4109407 B2 JP4109407 B2 JP 4109407B2 JP 2000234717 A JP2000234717 A JP 2000234717A JP 2000234717 A JP2000234717 A JP 2000234717A JP 4109407 B2 JP4109407 B2 JP 4109407B2
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width
residual stress
stress
temperature
flatness
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JP2002045907A (en
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透 明石
源一 是枝
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日鐵プラント設計株式会社
新日本製鐵株式会社
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【0001】
【発明の属する技術分野】
本発明は、鉄、アルミニウム,チタン等金属板のトップ部(長さ方向先端)巾方向エッジ部において、巾方向の温度偏差が原因となって発生する耳波を、圧延最終段に付与する幅方向残留応力の制御により防止し、かつ金属板の平坦度を制御する方法及び装置に関し、特に熱延鋼板や厚板鋼板の平坦度制御方法及び装置に関するものである。
【0002】
【従来の技術】
従来、金属材料特に鋼材は、圧延工程から次工程の冷却工程を経て冷却後に発生する鋼板波(耳波)は、熱間圧延機、或いは圧延後の熱間矯正機で幅方向中央部に若干の鋼板波(中波)を発生させることにより、鋼板波を過補償して防止する方法を採用していた。また、この方法でも鋼板波制御が十分でない場合は、別途精整工程で矯正加工を施すことが必要であった。このようなことから、これまで鋼板波を防止するための方法が種々提案されている。
【0003】
例えば、特開平5−269527号公報では金属ストリップの平坦度形状制御方法として、冷却完了後に金属ストリップを巻き取る前にテンションレベラーを設置して平坦度矯正を行う方法に於いて、テンションレベラーの最終ロール直前のロールを金属ストリップの張力の巾方向分布が測定可能な形状検出ロールとし、形状検出ロールからの金属ストリップの平坦度情報を基に形状検出ロールの押し込み量設定を変更して金属ストリップの平坦度形状を制御する方法が提案されている。また、特開平10−263658号公報では熱間仕上圧延機の出側に設置した平坦度計による平坦度情報と巻き取り機前に設置した平坦度計によって測定される巻き付く前の平坦度情報より、伸び率差を求めて仕上圧延機のベンダー制御にフィードバックすることによって金属ストリップの平坦度形状を制御する方法が提案されている。
【0004】
【発明が解決しようとする課題】
しかしながら、上述した特開平5−269527号公報或いは特開平10−263658公報記載の金属ストリップの平坦度形状制御方法では、平坦度形状制御の基準となる情報が平坦度或いは伸び歪み差であり、板巾方向にわたる温度分布情報に基づいたものではない。圧延工程で常温近くまで冷却すれば板巾方向にわたる温度分布はフラットであるが、通常、殆どの材料は材質の作り込みのために高温で巻き取るために、板巾方向に亘る温度分布は板端部が中央部に比べて低くなる温度偏差が発生する。従って、一旦このような方法で伸び歪み差が解消されたとしても、この時点での温度偏差が常温になる熱応力として残留してしまうため、平坦度の改善には結びつかない。
【0005】
本発明は、上述した従来技術の有する問題点を解決するもので、金属材料のトップ部に対し、冷却後の金属板の巾方向エッジ部に発生する耳波を防止し、平坦度を向上させる方法及び装置を提供することを目的とする。
【0006】
【課題を解決するための手段】
本発明は、上述した課題を解決するためになされたもので、その要旨とするところは以下のとおりである。
(1)熱間タンデムミルである仕上げ圧延機の間で、または仕上げ圧延機出側において、金属ストリップの表面温度を測定し、前記表面温度に基づき常温時に発生する熱応力残留応力を推定し、その残留応力が波形状を発生させないように仕上げ圧延機によって幅方向に付与する残留応力の制御を行うことを特徴とする金属板の平坦度制御方法。
(2)熱間リバーシングミルである仕上げ圧延機入側或いは出側において、金属板の表面温度を測定し、前記表面温度に基づき常温時に発生する熱応力残留応力を推定し、その残留応力が波形状を発生させないように仕上げ圧延機によって幅方向に付与する残留応力の制御を行うことを特徴とする金属板の平坦度制御方法。
(3)ストリップ或いは金属板の冷却後の熱応力残留応力推定値に対し、最終パスの圧延機にて制御する残留応力を重ね合わせた合応力を本来の残留応力とし、前記合応力を使って座屈計算し、座屈しないように最終パスの残留応力を制御することを特徴とする前記(1)または(2)に記載の金属板の平坦度制御方法。
(4)板幅センターからエッジ間の前記合応力に対し、2次〜6次の何れかからなる近似式を用い、その近似式の最大と最小の差が極小値となるように制御することを特徴とする前記(3)に記載の金属板の平坦度制御方法。
(5)ストリップ又は金属板の仕上げ圧延機入側又は出側に幅方向の温度測定手段と、前記幅方向の測定温度に基づき常温時に発生する熱応力残留応力を計算し、前記熱応力残留応力が波形状を発生させないように仕上げ圧延機によって付与する幅方向の残留応力を計算する演算手段と、前記幅方向の残留応力を仕上げ圧延機に付与する制御手段を有することを特徴とする金属板の平坦度制御装置。
(6)前記仕上げ圧延機入側又は出側に幅方向の形状測定手段を有し、前記制御手段は前記熱応力残留応力と幅方向の測定形状に基づき仕上げ圧延機によって付与する幅方向の残留応力を計算することを特徴とする前記(5)記載の金属板の平坦度制御装置。
(7)前記演算手段は熱応力残留応力推定値を計算する際に前記幅方向の測定温度と最終パスの圧延機にて制御する残留応力に基づいて計算することを特徴とする前記(5)又は(6)記載の金属板の平坦度制御装置。
にある。
【0007】
【発明の実施の形態】
本発明者らは、平坦度悪化のメカニズム及び平坦度を向上させるための方策について種々の検討を行った。以下、図面に基づいて、本発明の原理について説明する。
本発明者らは熱延鋼板の製造工程において金属板の平坦度悪化のメカニズムを把握するために実機実験を実施した。図1は熱延鋼板の製造工程における仕上げ圧延機以降の製造設備概要図である。まず、熱延鋼板は仕上げ圧延機1を経て所定の製造サイズに圧延され、ランアウトテーブル(ROT)2によって通板され、所定の材質に作り込むためにROT冷却装置3によって所定の板温度まで冷却され、コイラー4によってコイル状に巻き取られる。
【0008】
巻き取る板温度は材質によって色々異なるが100〜750℃まであり、本発明において問題としている平坦度は、このコイル温度が室温まで下がった時点で巻き解くとトップ部(長手方向先端)のエッジ部に耳波と呼ばれる波状の面外変形を起こした場合である。多くの熱延鋼板において起る平坦度悪化は耳波であり、本発明は、この耳波を改善することを意図している。それ以外の場合は、コイラー4の軸やピンチロール(PR)が凸で、巻き取り張力が異常に大きい場合は、エッジではなくセンター部に波の出る中波が発生する場合があるが、これは本発明の対象外である。
【0009】
図2に耳波の定義を示す。エッジ部の波高さHを波のピッチLで割り、100倍して、パーセント表示で表す。
本発明は、圧延機によって波形状を隆起させないように積極的に板断面内の長手方向の塑性歪み(残留応力)を加えることにある。本発明者らの検討では高温時のクリープ歪みが小さいもの、ストリップで言えば巻き取り張力が掛からない部分或いは厚鋼板等はそのまま圧延機で加えた、塑性歪みは残留することが判っている。また、前述のように板の波形状は基本的に圧延終了後、冷却前の温度分布にほぼ相関があることが判っており、そう言った意味で温度分布によって計算される冷間状態での熱歪み(冷間残留応力)を用いて形状を評価することが可能である。測温に基づく常温時ユニットテンションの無い場合の各温度測定点の熱残留応力は下記(1)〜(4)式により計算できる。
【0010】
σf (x)=α×E×T(x) …(1)
F =Σ(σf(x)×bb(x)×t)…(2)
σave =F/(B×t) …(3)
σf'(x)=σf (x)− σave …(4)
また、測定点以外でも応力分布を必要とする場合は温度測定点の間の値は内挿する。
(記号、単位の説明)
σf (x)[kg/mm2]:幅方向位置xにおける常温時の熱歪みによる予測発生応力
α [1/ ℃] :熱膨張係数 =11.6×10-6
E [kg/mm2] :ヤング率 =21000
T [℃] :幅方向位置xにおける温度
t [mm] :金属材料の板厚
F [kg] :板幅方向断面に働く力の総和
bb(x)[mm] :幅方向位置xにおける温度測定点のピッチ
σave [kg/mm2] :板幅方向断面に働く平均応力
B [mm] :板幅
σf'(x)[kg/mm2]:ユニットテンション無し時の各温度測定点の予測熱残留応力
従って、この温度分布から推定される冷間残留応力に最終パスの圧延機による残留応力を加え、熱残留応力に重ね合わせることで圧延機によって波形状を隆起させないように積極的に板断面内の長手方向の塑性歪み(残留応力)を加える方法が有効であることが判明した。前述のものは最終圧延機によって残留応力を加えるが、その残留応力の見積もりには圧延機出側板形状計で形状を測り、残留応力を2〜6次のべき乗関数に置き換えることで残留応力を定義し、制御を行う。(1)の発明はこの原理をストリップに適用したものである。
【0011】
ストリップの表面温度の測定は,冷却後の金属材料の残留応力は圧延後の温度分布に依存するため、正確な平坦度予測をするために仕上げ圧延機最終スタンド前後の冷却前、タンデムミルである仕上げ圧延機間で実施し、好ましくは最終圧延機とその1段前の圧延機間で実施する。また、設備の取り合いや既に設置しているなら、仕上げ圧延機出側で測温しても良い。測温は放射温度計、サーモビュアー等により実施できる。
【0012】
本発明は、ROT冷却前の鋼板幅方向表面温度分布を板厚の0.5〜10倍のピッチ等間隔で測定することが好ましく、その測定ピッチに対応する冷間時の熱歪みを板長手方向の残留応力σとして推定する。以下は図3〜図5を対比しながら説明する。
<モデル>
1.制御用の固有応力は、σK(x)=−σf'(B)β×(x/B)4 …(5)
で定義し、その際のβを制御パラメータと置く。一般に圧延機において、式で示したように制御固有歪みをσK(x) [kg/mm2] を2〜6次の形で与えることは圧延機のベンダー機能やペアクロスミルによる圧延の制御によって可能である(非対称成分を加えてもよい)。ここで、Bは圧延時の板幅サイズの半幅長であり、xは板センター部を0とした幅方向の位置を示しており、鋼板の板幅温度測定点と同じ位置を代入して計算する。またσf'(B)[kg/mm2]は前述の式(4)に示すように測温したポイントB[mm](板幅最エッジ部)でのユニットテンション無し時の各温度測定点の予測熱残留応力である。図3に例としてユニットテンション無し時の各温度測定点の予測熱残留応力を示す。
2.圧延機で加える制御歪みは幅方向に分布のある歪みは加えても幅方向に積分すれば±0となるような歪みしか金属材料の圧延方向には掛けられないため、上述の制御用の固有応力σK(x) [kg/mm2] についてはその板幅方向の応力の積分が0となるように書き換えて制御の評価操作を進める(オフセット分を除く)。σK'(x) [kg/mm2]は巾方向で積分すると0となる圧延機から加わる制御用の固有応力σK(x)である。制御用の固有応力を単位巾当たりで定義するとすれば、
FF=Σ(σK (x)×t) …(6)
σKave=FF/(B×t) …(7)
σK'(x) =σK(x)−σKave …(8)
FF [kg] :板幅方向断面に働く力の総和
σKave [kg/mm2] :板幅方向断面に働く平均応力
例として、制御用の固有応力分布σK'(x) を図4に示す。
3.圧延後温度測温によって予測される冷却完了後の熱残留応力σf'(x)に対し、 冷却完了後の熱残留応力の応力偏差を小さくするために制御用の固有応力を重ね合わせることによって制御が加わった最終的な残留応力分とする。σ'(x) [kg/mm2] は形状制御された結果、予測される冷却完了後の熱残留応力である。
【0013】
σ'(x)=σf'(x)+σK'(x) …(9)
4.上述のσ'(x)を3次元FEMによって波形状の座屈解析を行い、合応力と波形状の評価から波形状が発生しない又は最小となるように加える制御固有応力σK(x)を決定する。例えば、制御パラメータをβとして上下に振らせることにより制御固有応力σK(x)を任意に決定することができる。例として、その際の合応力が冷却して予測される最終的な熱残留応力例を図5を示す。
5.また実際に固有応力は実ライン上では判らず、形状として表れるので形状計で実際に加わった歪みを推定する。形状計はレーザー変位計で直接3次元的な測定し、幅方向の伸び歪み差として固有応力とするのがBESTであり、具体的には下記のように計算する。
【0014】
例えばフラットな板平面に対し、3次元的に測定した板形状は図8のようになっている。この板形状に対し、板巾センターを基準位置0[mm]と置いた場合、各板巾方向位置x[mm]で圧延方向に断面で切り取ると波になる図9の波を線積分し、フラット板の圧延方向長さL[mm]に対する線積分長さL’[mm]を用いて巾方向位置x[mm]での歪みを表す。
【0015】
ε(x)=(L‘―L)/L …(10)
σ' ‘(x) =ε(x)×E(x) …(11)
ここでE(x)は温度に依存したヤング率[kg/mm2],σ' ‘(x)[kg/mm2] は実際に加わった制御歪みの値。
しかし、一般的にはセンターと両エッジの3点の金属材料移動速度と変位を測ることによって長手方向に対してセンターを基準にした波高さ或いはエッジ部を基準にした波高さを計測することが出来る。この状態が計測できれば、センターを基準にしたエッジ部の伸び歪み差或いはエッジ部を基準にしたセンター部の伸び歪み差を計算し、その3点の結果から2次以上のべき乗で近似することも可能である。この場合原理的には例えば耳波の場合、移動速度と経過時間より、板圧延方向位置y[mm]が決まり、それに合わせて板の変位が観測される。これはあたかも巾方向位置をエッジ部を示すx=Bと置いたときの図9のようになる。これを式(8)のようにx=Bとして計算し、その値から導き出されるε(B)=(L‘―L)/Lを使って、歪み分布を例えば2次で仮定すれば式(12)のようになると仮定できる。応力は(9)式から導かれる。
【0016】
ε(x)=ε(B)×(x/B)2 …(12)
6.実際はこの形状計の結果である全巾に渡るσ' ‘(x) を受けて計算して出したσ'(x)の差異を無くすようにフィードバック制御で最終圧延機で形状を加える。
個々の内容は以上説明したとおりであるが、制御のアルゴリズムを図6に、その構成となる機器の配置の例を図7にそれぞれ示した。
【0017】
上記により計算した残留応力σK(x)を圧延機のベンダー装置により付与することにより、常温に冷却されたとき波形状が発生しない金属ストリップを得ることができる。
(2)の発明は厚板等のシート圧延に(1)の発明を適用した場合である。
(3)の発明は精度良く形状を制御するために座屈解析をして圧延機で加える塑性歪みを導き出す方法を示したものである。座屈解析は例えばFEMにより計算できる。
【0018】
座屈しないように、圧延機のベンダー装置により最終仕上げ圧延の残留応力を制御しなければFEMの結果では耳波となる場合は中波となるように制御する(制御固有歪みをセンター部を圧縮、エッジ部を引張応力とするような2〜6次の応力分布の大きさを制御する。
(4)の発明は座屈解析をしなくても合力の近似式を用いその最大と最小の差をミニマムとする制御を加えることで簡易的且つ迅速に対応するものである。
【0019】
合応力の2〜6次の近似式は応力分布が巾方向に等ピッチで把握出来る前提としてセンターからエッジ部までを最小二乗法で決定することができる。この合応力の最大と最小の差が極小値となるように制御するには前述の制御パラメータβを上下に振りその際に応力の最大と最小の値が極値を持つので極値を持ったパラメータβを形状改善の制御値として決定する。
【0020】
(5)〜(7)の発明は上記(1)〜(4)の方法を実施するための装置に関するものである。
温度測定手段は、例えば、測温は放射温度計、サーモビュアー等を使用することができる。所定の幅方向の残留応力を仕上げ圧延機に付与する制御手段として、例えば、ベンダー、ペアクロス等を使用することができる。また、形状測定手段は、例えば、変位計やCCDカメラによる画像処理等を使用することができる。センタ―及び両エッジの3点測定による幅方向の測定形状に基づき計算される仕上げ圧延機に付与する幅方向の残留応力は,前述の(9)と式(10)により求めることができる。
【0021】
【実施例】
本実施例について図を用いて説明する。ROT冷却前の鋼板幅方向表面温度分布を板厚の0.5〜10倍のピッチ等間隔で測定し、その測定ピッチに対応する冷間時の熱歪みを板長手方向の残留応力σとして推定した。制御のアルゴリズムを図6に示し、その構成となる機器の配置を図7に示す。以下は図3と図6を対比しながら説明する。
<モデル>
1.制御用の固有応力はσK(x)=−σf'(B)α(x/B)4 で定義し、その際のαを制御パラメータとして、0〜1と置いた。板巾の半幅Bは圧延サイズによって変わる値であるが例えばB=600とし、板厚t=2、xは板センター部を0とした幅方向の位置を示しており、鋼板の板幅温度測定点と同じ位置を代入して計算した。
2.上述の制御用の固有応力σK(x)についてはその板幅方向の応力の積分が0となるとなるように書き換えて操作する(オフセット分を加える)。
【0022】
FF=Σ(σK (x)×2)
σKave=FF/(2×600)
σK'(x) =σK(x)−σKave
3.従来の残留応力σ(x) に対し、 制御用の固有応力を重ね合わせることによって制御が加わった最終的な残留応力分とした。
【0023】
σ'(x)=σf'(x)+σK'(x)
4.上述のσ'(x)を3次元FEMによって波形状の座屈解析を行い、合応力と波形状の評価から波形状が発生しない又は最小となるように加える制御固有応力σK(x)を決定した。今回は制御パラメータをαとして0.4〜0.6に振らせた。その際の合応力図を図5に示す。
5.また、実際に固有応力は実ライン上では判らず、形状として表れるので形状計で実際に加わった歪みを推定した。センターと両エッジの3点の速度と変位を測ることによって長手方向に波形状測定して急峻度を計算し、その散点の結果から2次以上のべき乗で近似した。この形状計の結果を受けて最終圧延機で形状を加えた。
【0024】
個々の内容は以上のようだが、以上の発明の結果を実際のラインに適用して実施したところ、図10,図11に示すようになった。図10はエッジ部の長手方向に対する高さ方向の変位図である。図11は板幅センター部の長手方向に対する高さ方向の変位図である。このことより、本発明を適用しなければエッジ部に波が発生する耳波でαを0.8以上にすればセンター部が波を発生させてしまう中波になってしまい、板形状をフラットにするためにはαを0.2〜0.6の間に制御すれば良いことが判る。この方法を適用することで平坦度1.0%の耳波の発生率は1000コイル中ゼロであった。
【0025】
【発明の効果】
本発明により、金属材料のトップ部に対し、冷却後の金属板の巾方向エッジ部に発生する耳波を防止し、平坦度を向上させることができた。
【図面の簡単な説明】
【図1】熱延鋼板の製造工程概略図及び本発明の実施例を示した図である。
【図2】平坦度の定義を説明するための図である。
【図3】各巾方向位置で測温した温度をもとに予測した予測熱残留応力図である。
【図4】圧延機から加わる制御用の固有応力分布図である。
【図5】予測熱残留応力と制御用の固有応力分布を重ね合わせた合応力図である。
【図6】制御のアルゴリズムを示した図である。
【図7】構成となる機器の配置の例を示した図である。
【図8】3次元的に板形状を測定した場合の形状図である。
【図9】3次元的に板形状を測定した形状図を所定の巾方向位置で圧延方向断面で切り取った図である。
【図10】エッジ部の板形状を測定した場合の形状図である。
【図11】センター部の板形状を測定した場合の形状図である。
【符号の説明】
1…圧延機
2…ランアウトテーブル
3…ROT冷却装置
4…コイラー
5…温度計
7…鋼板
H…波高さ
L…波のピッチ
[0001]
BACKGROUND OF THE INVENTION
The present invention is a width that imparts an ear wave generated due to a temperature deviation in the width direction to the final stage of rolling in the top portion (tip in the length direction) and the width direction edge portion of a metal plate such as iron, aluminum, and titanium. More particularly, the present invention relates to a method and an apparatus for controlling the flatness of a hot-rolled steel plate or a thick steel plate.
[0002]
[Prior art]
Conventionally, in the case of metal materials, particularly steel materials, a steel plate wave (ear wave) generated after cooling from the rolling process to the next cooling process is slightly applied to the center in the width direction by a hot rolling mill or a hot straightening machine after rolling. The method of overcompensating and preventing the steel plate wave by generating the steel plate wave (medium wave) was adopted. Further, if the steel plate wave control is not sufficient even with this method, it is necessary to perform a straightening process separately in a refining process. For this reason, various methods for preventing the steel plate wave have been proposed so far.
[0003]
For example, in Japanese Patent Application Laid-Open No. 5-269527, as a method for controlling the flatness shape of a metal strip, a method of correcting the flatness by installing a tension leveler before winding up the metal strip after cooling is completed. The roll immediately before the roll is a shape detection roll capable of measuring the width distribution of the tension of the metal strip, and the push amount setting of the shape detection roll is changed based on the flatness information of the metal strip from the shape detection roll. A method for controlling the flatness shape has been proposed. Japanese Patent Laid-Open No. 10-263658 discloses flatness information by a flatness meter installed on the exit side of a hot finish rolling mill and flatness information before winding measured by a flatness meter installed before the winder. Thus, there has been proposed a method for controlling the flatness shape of the metal strip by obtaining an elongation difference and feeding back to the vendor control of the finishing mill.
[0004]
[Problems to be solved by the invention]
However, in the above-described metal strip flatness shape control method described in Japanese Patent Application Laid-Open No. 5-269527 or Japanese Patent Application Laid-Open No. 10-263658, information serving as a reference for flatness shape control is flatness or elongation strain difference. It is not based on temperature distribution information across the width direction. If it is cooled to near room temperature in the rolling process, the temperature distribution in the plate width direction is flat, but usually most materials are wound up at a high temperature to make the material, so the temperature distribution in the plate width direction is A temperature deviation is generated in which the end portion is lower than the central portion. Therefore, even if the difference in elongation strain is once eliminated by such a method, the temperature deviation at this time remains as a thermal stress that reaches room temperature, and thus does not lead to improvement in flatness.
[0005]
The present invention solves the above-mentioned problems of the prior art, and prevents the ear wave generated at the edge in the width direction of the metal plate after cooling with respect to the top portion of the metal material, thereby improving the flatness. It is an object to provide a method and apparatus.
[0006]
[Means for Solving the Problems]
The present invention has been made to solve the above-described problems, and the gist thereof is as follows.
(1) Measure the surface temperature of the metal strip between finish rolling mills that are hot tandem mills or on the exit side of the finishing mill, and estimate the thermal stress residual stress generated at room temperature based on the surface temperature, A method for controlling the flatness of a metal plate, wherein the residual stress applied in the width direction by a finish rolling mill is controlled so that the residual stress does not generate a wave shape.
(2) Measure the surface temperature of the metal plate on the entry side or exit side of the finishing mill, which is a hot reversing mill, and estimate the thermal stress residual stress generated at room temperature based on the surface temperature. A method for controlling the flatness of a metal plate, wherein the residual stress applied in the width direction is controlled by a finish rolling mill so as not to generate a wave shape.
(3) The combined stress obtained by superimposing the residual stress controlled by the rolling mill in the final pass against the estimated value of the thermal stress after cooling of the strip or metal plate is used as the original residual stress. The method for controlling flatness of a metal plate according to (1) or (2), wherein buckling is calculated and residual stress in the final pass is controlled so as not to buckle.
(4) Using an approximate expression consisting of any of the second to sixth orders for the resultant stress between the sheet width center and the edge, and controlling the difference between the maximum and minimum of the approximate expression to a minimum value. The method for controlling the flatness of a metal plate according to (3), wherein:
(5) A thermal measurement residual stress generated at normal temperature is calculated based on the temperature measuring means in the width direction on the entry side or the exit side of the finishing mill of the strip or metal plate, and the measurement temperature in the width direction, and the thermal stress residual stress is calculated. Characterized in that the metal plate has calculation means for calculating the residual stress in the width direction applied by the finishing mill so as not to generate a wave shape, and control means for applying the residual stress in the width direction to the finishing mill. Flatness control device.
(6) A width direction shape measuring means is provided on the entry side or the exit side of the finish rolling mill, and the control means is a width direction residual applied by the finish mill based on the thermal stress residual stress and the width measurement shape. The flatness control device for a metal plate according to (5), wherein the stress is calculated.
(7) The calculation means calculates the thermal stress residual stress estimated value based on the measured temperature in the width direction and the residual stress controlled by the rolling mill in the final pass. Or the flatness control apparatus of the metal plate of (6) description.
It is in.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
The present inventors have made various studies on the mechanism of flatness deterioration and the measures for improving the flatness. The principle of the present invention will be described below with reference to the drawings.
The present inventors performed an actual machine experiment in order to grasp the mechanism of deterioration of the flatness of the metal plate in the manufacturing process of the hot-rolled steel sheet. FIG. 1 is a schematic diagram of manufacturing equipment after a finish rolling mill in a manufacturing process of a hot-rolled steel sheet. First, a hot-rolled steel sheet is rolled to a predetermined production size through a finish rolling mill 1, passed through a run-out table (ROT) 2, and cooled to a predetermined plate temperature by a ROT cooling device 3 to make a predetermined material. The coiler 4 winds up the coil.
[0008]
The plate temperature to be wound varies depending on the material, but is up to 100 to 750 ° C. The flatness which is a problem in the present invention is the edge portion of the top portion (longitudinal tip) when unrolled when the coil temperature is lowered to room temperature. This is a case where a wavy out-of-plane deformation called an otowave occurs. The flatness deterioration that occurs in many hot-rolled steel sheets is ear waves, and the present invention is intended to improve the ear waves. In other cases, if the axis of the coiler 4 and the pinch roll (PR) are convex and the take-up tension is abnormally large, a medium wave that generates a wave at the center portion instead of the edge may occur. Is outside the scope of the present invention.
[0009]
FIG. 2 shows the definition of the ear wave. The wave height H of the edge portion is divided by the wave pitch L, multiplied by 100, and expressed in percentage.
An object of the present invention is to positively apply a plastic strain (residual stress) in the longitudinal direction in the cross section of the plate so as not to raise the wave shape by a rolling mill. According to the study by the present inventors, it has been found that the plastic strain remains small when the creep strain at a high temperature is small, that is, the portion where the winding tension is not applied or the thick steel plate is applied as it is with a rolling mill. In addition, as described above, it is known that the wave shape of the plate is basically correlated with the temperature distribution before cooling after the end of rolling, and in that sense, in the cold state calculated by the temperature distribution The shape can be evaluated using thermal strain (cold residual stress). The thermal residual stress at each temperature measurement point when there is no unit tension at normal temperature based on temperature measurement can be calculated by the following equations (1) to (4).
[0010]
σf (x) = α × E × T (x) (1)
F = Σ (σf (x) × bb (x) × t) (2)
σave = F / (B × t) (3)
σf ′ (x) = σf (x) −σave (4)
In addition, when a stress distribution is required at a point other than the measurement point, the value between the temperature measurement points is interpolated.
(Explanation of symbols and units)
σf (x) [kg / mm 2 ]: Predicted stress α [1 / ° C.] due to thermal strain at normal temperature at the position x in the width direction: Thermal expansion coefficient = 11.6 × 10 −6
E [kg / mm 2 ]: Young's modulus = 21000
T [° C.]: Temperature t [mm] at the position x in the width direction: Plate thickness F [kg] of the metal material: Total force bb (x) [mm] acting on the cross section in the plate width direction: Temperature measurement at the position x in the width direction Point pitch σave [kg / mm 2 ]: Average stress B [mm] acting on the cross section in the plate width direction: Plate width σf '(x) [kg / mm 2 ]: Predicted heat at each temperature measurement point without unit tension Residual stress Therefore, add the residual stress from the rolling mill in the final pass to the cold residual stress estimated from this temperature distribution and superimpose it on the thermal residual stress to prevent the corrugation from rising up by the rolling mill. It was proved that the method of applying the plastic strain (residual stress) in the longitudinal direction is effective. In the case of the above, residual stress is applied by the final rolling mill. To estimate the residual stress, the residual stress is defined by measuring the shape with a plate shape meter on the output side of the rolling mill and replacing the residual stress with a 2-6th power function. And control. The invention of (1) applies this principle to strips.
[0011]
The surface temperature of the strip is measured by a tandem mill before cooling before and after the final stand of the finishing mill to accurately predict the flatness because the residual stress of the metal material after cooling depends on the temperature distribution after rolling. It is carried out between finish rolling mills, preferably between the final rolling mill and the rolling mill one stage before. If the equipment is already installed or already installed, the temperature may be measured on the exit side of the finishing mill. Temperature measurement can be performed with a radiation thermometer, a thermoviewer, or the like.
[0012]
In the present invention, it is preferable to measure the surface temperature distribution in the width direction of the steel plate before ROT cooling at equal intervals of 0.5 to 10 times the plate thickness, and the thermal strain during cold corresponding to the measurement pitch is measured in the longitudinal direction of the plate. Estimated as residual stress σ in the direction. The following will be described with reference to FIGS.
<Model>
1. The inherent stress for control is σK (x) = − σf ′ (B) β × (x / B) 4 (5)
Where β is the control parameter. In general, in rolling mills, as shown in the equation, the inherent strain of control is given as σK (x) [kg / mm 2 ] in the 2nd to 6th order by controlling the rolling function with the bender function of the rolling mill and the pair cross mill. Possible (asymmetric components may be added). Here, B is a half width of the sheet width size at the time of rolling, x indicates the position in the width direction with the sheet center portion being 0, and the calculation is performed by substituting the same position as the sheet width temperature measurement point of the steel sheet. To do. Also, σf '(B) [kg / mm 2 ] is the temperature measurement point without unit tension at the point B [mm] (plate width outermost edge) measured as shown in the above equation (4). Predicted thermal residual stress. FIG. 3 shows the predicted thermal residual stress at each temperature measurement point when there is no unit tension as an example.
2. The control strain applied by the rolling mill can be applied to the rolling direction of the metal material only by applying a strain that is ± 0 when integrated in the width direction even if a strain distributed in the width direction is added. The stress σK (x) [kg / mm 2 ] is rewritten so that the integral of the stress in the sheet width direction becomes zero, and the control evaluation operation is advanced (excluding the offset). σK ′ (x) [kg / mm 2 ] is a control intrinsic stress σK (x) applied from the rolling mill that becomes 0 when integrated in the width direction. If we define the intrinsic stress for control per unit width,
FF = Σ (σK (x) × t) (6)
σ Kave = FF / (B × t) (7)
σK ′ (x) = σK (x) −σKave (8)
FF [kg]: Total force σ Kave [kg / mm 2 ] of force acting on the cross section in the plate width direction: As an example of the average stress acting on the cross section in the plate width direction, a control intrinsic stress distribution σ K ′ (x) is shown in FIG.
3. Control by superimposing control intrinsic stress on thermal residual stress σf '(x) after completion of cooling predicted by temperature measurement after rolling to reduce stress deviation of thermal residual stress after completion of cooling The final residual stress with added σ ′ (x) [kg / mm 2 ] is a thermal residual stress after completion of cooling that is predicted as a result of shape control.
[0013]
σ ′ (x) = σf ′ (x) + σK ′ (x) (9)
4). Waveform buckling analysis of the above-mentioned σ '(x) by three-dimensional FEM, and control intrinsic stress σK (x) to be applied so that the waveform does not occur or is minimized is determined from the evaluation of combined stress and waveform To do. For example, the control intrinsic stress σK (x) can be arbitrarily determined by swinging up and down with the control parameter β. As an example, FIG. 5 shows a final thermal residual stress example in which the resultant stress at that time is predicted by cooling.
5. In fact, the inherent stress is not known on the actual line and appears as a shape, so the strain actually applied is estimated by a shape meter. The shape meter is a three-dimensional measurement directly with a laser displacement meter, and the best stress is an intrinsic stress as an elongation strain difference in the width direction. Specifically, it is calculated as follows.
[0014]
For example, the plate shape measured three-dimensionally with respect to a flat plate plane is as shown in FIG. For this plate shape, when the plate width center is set at the reference position 0 [mm], the wave of FIG. 9 that becomes a wave when the cross section is cut in the rolling direction at each plate width direction position x [mm] is line-integrated, The distortion at the width direction position x [mm] is expressed using the line integral length L ′ [mm] with respect to the rolling direction length L [mm] of the flat plate.
[0015]
ε (x) = (L′−L) / L (10)
σ ′ ′ (x) = ε (x) × E (x) (11)
Where E (x) is the temperature dependent Young's modulus [kg / mm 2 ], and σ '' (x) [kg / mm 2 ] is the value of the control strain actually applied.
However, in general, it is possible to measure the wave height with reference to the center or the edge with respect to the longitudinal direction by measuring the moving speed and displacement of the metal material at three points of the center and both edges. I can do it. If this state can be measured, it is possible to calculate the difference in elongation strain at the edge with respect to the center or the difference in elongation strain at the center with respect to the edge, and approximate it with a power of second order or higher from the result of the three points. Is possible. In principle, for example, in the case of an ear wave, the plate rolling direction position y [mm] is determined from the moving speed and the elapsed time, and the displacement of the plate is observed accordingly. This is as shown in FIG. 9 when the position in the width direction is set to x = B indicating the edge portion. If this is calculated as x = B as shown in equation (8), and ε (B) = (L′−L) / L derived from that value is used, the strain distribution is assumed to be quadratic, for example. 12) can be assumed. The stress is derived from equation (9).
[0016]
ε (x) = ε (B) × (x / B) 2 (12)
6). Actually, the shape is added to the final rolling mill by feedback control so as to eliminate the difference of σ ′ (x) calculated by receiving σ ′ ′ (x) over the entire width as a result of this shape meter.
Although the individual contents are as described above, FIG. 6 shows the control algorithm, and FIG. 7 shows an example of the arrangement of devices constituting the control algorithm.
[0017]
By applying the residual stress σK (x) calculated as described above by a bender device of a rolling mill, a metal strip that does not generate a wave shape when cooled to room temperature can be obtained.
The invention of (2) is a case where the invention of (1) is applied to sheet rolling of thick plates and the like.
The invention of (3) shows a method of deriving plastic strain applied by a rolling mill by buckling analysis in order to control the shape with high accuracy. The buckling analysis can be calculated by FEM, for example.
[0018]
In order to prevent buckling, if the residual stress of the final finish rolling is not controlled by the bender device of the rolling mill, control is performed so that it becomes an intermediate wave when it becomes an ear wave in the FEM result (control inherent distortion is compressed in the center part) The size of the 2nd to 6th order stress distribution is controlled so that the edge portion has a tensile stress.
The invention of (4) can be dealt with simply and quickly by using an approximate expression of the resultant force without performing buckling analysis and by adding a control that minimizes the difference between the maximum and minimum.
[0019]
The approximate expression of the second to sixth orders of the resultant stress can be determined from the center to the edge portion by the least square method on the premise that the stress distribution can be grasped at equal pitches in the width direction. In order to control the difference between the maximum and minimum of the resultant stress to be a minimum value, the control parameter β described above is moved up and down, and the maximum and minimum values of the stress have extreme values at that time. The parameter β is determined as a shape improvement control value.
[0020]
The inventions (5) to (7) relate to an apparatus for carrying out the methods (1) to (4).
As the temperature measuring means, for example, a radiation thermometer, a thermoviewer, or the like can be used for temperature measurement. For example, a vendor, a pair cloth, or the like can be used as a control unit that applies a residual stress in a predetermined width direction to the finishing mill. Further, the shape measuring means can use, for example, image processing by a displacement meter or a CCD camera. The residual stress in the width direction applied to the finishing mill calculated based on the measured shape in the width direction by the three-point measurement of the center and both edges can be obtained by the above-mentioned (9) and equation (10).
[0021]
【Example】
This embodiment will be described with reference to the drawings. The surface temperature distribution in the width direction of the steel plate before ROT cooling is measured at a pitch equal to 0.5 to 10 times the plate thickness, and the thermal strain during cold corresponding to the measured pitch is estimated as the residual stress σ in the plate longitudinal direction. did. FIG. 6 shows a control algorithm, and FIG. 7 shows an arrangement of devices constituting the control algorithm. The following will be described with reference to FIG. 3 and FIG.
<Model>
1. The intrinsic stress for control was defined by σK (x) = − σf ′ (B) α (x / B) 4 , and α at that time was set as 0 to 1 as a control parameter. The half width B of the sheet width is a value that varies depending on the rolling size. For example, B = 600, the sheet thickness t = 2, and x represents the position in the width direction with the sheet center portion set to 0. It was calculated by substituting the same position as the point.
2. The above-described control intrinsic stress σK (x) is rewritten and manipulated so that the integral of the stress in the plate width direction becomes zero (addition of offset).
[0022]
FF = Σ (σK (x) × 2)
σKave = FF / (2 × 600)
σK '(x) = σK (x) −σKave
3. The final residual stress was controlled by superimposing the control inherent stress on the conventional residual stress σ (x).
[0023]
σ ′ (x) = σf ′ (x) + σK ′ (x)
4). Waveform buckling analysis of the above-mentioned σ '(x) by three-dimensional FEM, and control intrinsic stress σK (x) to be applied so that the waveform does not occur or is minimized is determined from the evaluation of combined stress and waveform did. This time, the control parameter was changed to 0.4 to 0.6 as α. The resultant stress diagram at that time is shown in FIG.
5. In addition, since the actual stress is not known on the actual line and appears as a shape, the strain actually applied was estimated with a shape meter. Steepness was calculated by measuring the wave shape in the longitudinal direction by measuring the velocity and displacement at the center and at the three edges, and approximated by a power of second order or higher from the result of the scattered points. Based on the result of this shape meter, the shape was added by the final rolling mill.
[0024]
Although the individual contents are as described above, when the results of the above invention are applied to an actual line, the results are shown in FIGS. FIG. 10 is a displacement diagram in the height direction with respect to the longitudinal direction of the edge portion. FIG. 11 is a displacement diagram in the height direction with respect to the longitudinal direction of the plate width center portion. From this fact, if the present invention is not applied, if the α is 0.8 or more with an ear wave that generates a wave at the edge portion, the center portion becomes a medium wave that generates a wave, and the plate shape is flat. In order to achieve this, it is understood that α should be controlled between 0.2 and 0.6. By applying this method, the incidence of ear waves with a flatness of 1.0% was zero in 1000 coils.
[0025]
【The invention's effect】
According to the present invention, it is possible to prevent the ear waves generated at the edge portion in the width direction of the metal plate after cooling with respect to the top portion of the metal material, and to improve the flatness.
[Brief description of the drawings]
FIG. 1 is a schematic view of a hot-rolled steel sheet manufacturing process and a diagram showing an embodiment of the present invention.
FIG. 2 is a diagram for explaining the definition of flatness.
FIG. 3 is a predicted thermal residual stress diagram predicted based on the temperature measured at each width direction position.
FIG. 4 is a distribution diagram of inherent stress for control applied from a rolling mill.
FIG. 5 is a resultant stress diagram in which the predicted thermal residual stress and the control intrinsic stress distribution are superimposed.
FIG. 6 is a diagram showing a control algorithm.
FIG. 7 is a diagram showing an example of the arrangement of devices that constitute a configuration.
FIG. 8 is a shape diagram when a plate shape is measured three-dimensionally.
FIG. 9 is a view obtained by cutting a shape figure obtained by measuring a plate shape three-dimensionally at a predetermined width direction position along a cross section in the rolling direction.
FIG. 10 is a shape diagram when a plate shape of an edge portion is measured.
FIG. 11 is a shape diagram when the plate shape of the center portion is measured.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Rolling mill 2 ... Run-out table 3 ... ROT cooling device 4 ... Coiler 5 ... Thermometer 7 ... Steel plate H ... Wave height L ... Wave pitch

Claims (7)

  1. 熱間タンデムミルである仕上げ圧延機の間で、または仕上げ圧延機出側において、金属ストリップの表面温度を測定し、前記表面温度に基づき常温時に発生する熱応力残留応力を推定し、その残留応力が波形状を発生させないように仕上げ圧延機によって幅方向に付与する残留応力の制御を行うことを特徴とする金属板の平坦度制御方法。Measure the surface temperature of the metal strip between the finishing mills, which are hot tandem mills, or on the exit side of the finishing mill, and estimate the thermal stress residual stress generated at room temperature based on the surface temperature, and the residual stress A method for controlling the flatness of a metal plate, comprising: controlling a residual stress applied in a width direction by a finish rolling mill so as not to generate a wave shape.
  2. 熱間リバーシングミルである仕上げ圧延機入側或いは出側において、金属板の表面温度を測定し、前記表面温度に基づき常温時に発生する熱応力残留応力を推定し、その残留応力が波形状を発生させないように仕上げ圧延機によって幅方向に付与する残留応力の制御を行うことを特徴とする金属板の平坦度制御方法。On the entrance side or exit side of the finishing mill, which is a hot reversing mill, the surface temperature of the metal plate is measured, the thermal stress residual stress generated at room temperature is estimated based on the surface temperature, and the residual stress has a wave shape. A method for controlling the flatness of a metal plate, wherein the residual stress applied in the width direction is controlled by a finish rolling mill so as not to be generated.
  3. ストリップ或いは金属板の冷却後の熱応力残留応力推定値に対し、最終パスの圧延機にて制御する残留応力を重ね合わせた合応力を本来の残留応力とし、前記合応力を使って座屈計算し、座屈しないように最終パスの残留応力を制御することを特徴とする請求項1または2に記載の金属板の平坦度制御方法。The estimated residual thermal stress after cooling the strip or metal sheet is combined with the residual stress controlled by the rolling mill in the final pass as the original residual stress. The method for controlling flatness of a metal plate according to claim 1 or 2, wherein the residual stress in the final pass is controlled so as not to buckle.
  4. 板幅センターからエッジ間の前記合応力に対し、2次〜6次の何れかからなる近似式を用い、その近似式の最大と最小の差が極小値となるように制御することを特徴とする請求項3に記載の金属板の平坦度制御方法。An approximate expression consisting of any one of the second to sixth orders is used for the resultant stress between the sheet width center and the edge, and the difference between the maximum and minimum of the approximate expression is controlled to be a minimum value. The flatness control method for a metal plate according to claim 3.
  5. ストリップ又は金属板の仕上げ圧延機入側又は出側に幅方向の温度測定手段と、前記幅方向の測定温度に基づき常温時に発生する熱応力残留応力を計算し、前記熱応力残留応力が波形状を発生させないように仕上げ圧延機によって付与する幅方向の残留応力を計算する演算手段と、前記幅方向の残留応力を仕上げ圧延機に付与する制御手段を有することを特徴とする金属板の平坦度制御装置。A temperature measuring means in the width direction on the entry side or the exit side of the finish rolling mill of the strip or metal plate, and the thermal stress residual stress generated at normal temperature based on the measurement temperature in the width direction are calculated. Flatness of a metal plate, characterized by having calculation means for calculating the residual stress in the width direction applied by the finish rolling mill so as not to cause the generation, and control means for applying the residual stress in the width direction to the finish rolling mill Control device.
  6. 前記仕上げ圧延機入側又は出側に幅方向の形状測定手段を有し、前記制御手段は前記熱応力残留応力と幅方向の測定形状に基づき仕上げ圧延機によって付与する幅方向の残留応力を計算することを特徴とする請求項5記載の金属板の平坦度制御装置。There is a shape measurement means in the width direction on the entry side or the exit side of the finish rolling mill, and the control means calculates the residual stress in the width direction applied by the finish rolling mill based on the thermal stress residual stress and the measurement shape in the width direction. The flatness control apparatus for a metal plate according to claim 5, wherein
  7. 前記演算手段は熱応力残留応力推定値を計算する際に前記幅方向の測定温度と最終パスの圧延機にて制御する残留応力に基づいて計算することを特徴とする請求項5又は6記載の金属板の平坦度制御装置。7. The calculation means according to claim 5, wherein the calculation means calculates the thermal stress residual stress estimated value based on the measured temperature in the width direction and the residual stress controlled by a rolling mill in the final pass. 8. Metal plate flatness control device.
JP2000234717A 2000-08-02 2000-08-02 Method and apparatus for controlling flatness of metal plate Expired - Lifetime JP4109407B2 (en)

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