JP3710572B2 - Heating furnace control device - Google Patents

Description

ただし、
Ｌ₂ ：スラブが焼き上がる時刻ｔ_H のスラブの先端から加熱炉抽出口までの距離。
Ｖ₂ ：スラブを搬送する時のテーブル速度
である。
Ｌ₂ には図３から分かるように以下の関係がある。
Ｌ₂ ＝Ｌ_F −Ｌ_S −Ｌ₁ ＝Ｌ_F −Ｌ_S −Ｔ₁ ・Ｖ₁ …（３）
ただし
Ｌ_F ：加熱炉長、
Ｌ_S ：スラブ長、
Ｌ₁ ：スラブの尾端が炉に装入された後、加熱時間Ｔ₁ に
スラブが進んだ距離
Ｖ₁ ：加熱時間Ｔ₁ でのテーブル速度
である。
（１）〜（３）式から、加熱時間Ｔ₁ 及び均熱時間Ｔ₂ は以下のように計算できる。
【００２４】
【数２】

材料加熱時間演算装置１２は以上の（４），（５）式を用いて加熱時間Ｔ₁ と均熱時間Ｔ₂ とを求める。
なお、上式の導入の過程においては、テーブルの加減速時間を考慮しないかたちになっているが、考慮すれば、より厳密な値が求まるけれどもその影響は少なく、上式で十分である。
【００２５】
次に、設定炉温演算装置１４は、スラブが目標の抽出温度になるように加熱炉の最適な設定炉温を演算する装置である。設定炉温を決めるには、スラブの温度予測演算が必要である。そこで、設定炉温演算装置１４は、スラブ温度演算モデル式と最適な設定炉温を演算する最適炉温演算モデル式を使って設定炉温を演算する。
そこで、スラブ温度演算モデル式から説明する。
加熱炉内のスラブの温度は（６）式のフーリェの熱伝導微分方程式で演算できる。
【００２６】
【数３】

ただし、
θ：スラブ温度
ｃ：スラブの比熱
ρ：スラブの密度
Ｘ：Ｘ軸方向（スラブ厚み方向）の深さ
ｋ：スラブの熱伝導率
ｔ：時間
である。
【００２７】
上式を解くのに、図４に示すように、スラブを厚み方向に等分に分割し、各分割境界点の温度を差分方程式で解くことができる。図４はスラブの厚み方向を６分割した例で、温度の計算位置を７点とした場合で、通常、４から８分割すれば十分である。
このようにスラブを分割した場合、スラブ内部の任意の分割境界点ｉの温度θ_i （ｉ＝２〜６）は、下式で計算できる。
【００２８】
【数４】

上記（７）式は、時刻ｔのスラブ分割境界温度θ_i （ｔ）から時間刻み△ｔ後のスラブの分割境界点ｉの温度θ_i （ｔ＋Δｔ）を計算する式である。なお、△Ｘはスラブを厚み方向に分割した距離である。
一方、スラブの表面点温度θ_i （ｉ＝１＝７）は下式で演算できる。
【００２９】
【数５】

上記（８）式でＱはスラブ表面から入る熱流束で、下式のステファンボルツマンの熱輻射の式が適応できる。
Ｑ＝σ・Φ_G ・｛（θ_G ＋２７３）⁴ −（θ_i ＋２７３）⁴ ｝…（９）
ただし、
σ：ステファンボルツマン定数
Φ_G ：加熱炉内の総括熱吸収率
θ_G ：炉温で、加熱時間では加熱期間での炉温θ_G.1 、均熱時間では均熱期間
での炉温θ_G.2
である。
【００３０】
以上の（７）式から（９）式を使い、炉温θ_G とスラブが加熱炉に装入される時の初期温度（この初期温度に関しては、次の炉装入材料初期温度演算装置１３で述べる）とを与えれば、スラブが加熱炉に装入されてから抽出されるまでの時間すなわち材料加熱時間演算装置１２で演算された加熱時間Ｔ₁ と均熱時間Ｔ₂ とにわたってスラブの温度を予測計算できる。
【００３１】
この設定炉温演算装置１４では（９）式の炉温θ_G を求めるのが目的である。（９）式に試行錯誤的に炉温を与え、スラブ温度の計算を（７）〜（９）式の演算を実施し、スラブが目標温度になるように繰り返し演算すれば良いが、繰り返しが膨大となり、実際のプラントのオンライン制御では無理がある。しかも、操業上、エネルギー消費最小のもとで、スラブを目標の抽出温度以上に焼き上げ、しかも均熱度をある値以下にしなければならない等の条件がある。
そこで、効率良く、省エネギーを考慮し、最適な炉温を求めるのに、最適炉温演算モデル式として最適化手法である線形計画法により、最適な炉温を演算する。
【００３２】
炉温を決定する上での条件は、先ず、抽出温度を目標の値以上に加熱しなければならない。抽出温度よりあまり高いと加熱炉の燃料消費が大きくなり、好ましくないので、燃料消費は最低にした上で抽出温度を確保しなければならない。また、前述したように、抽出時のスラブ内の温度差を指定した温度内におさめなければならない。この条件で、加熱時間での最適な設定炉温θ_G.1 と均熱時間での最適な設定炉温θ_G.2 を決定するのが、設定炉温演算装置１４の最適化炉温演算モデル式である。以下、具体的に最適炉温の求め方を示す。
【００３３】
線形計画法では、システムの評価関数Ｊと制約条件とを定義することにより、周知の解法手法で計算され、最適な解が得られる。
そこで、先ず、評価関数Ｊとして、消費エネルギー最小を選ぶ。消費エネルギー最小は消費燃料を最小にすれば良いが、燃料と炉温は密接に関係し、炉温を高くすれば燃料を多く消費し、炉温を低くすれば燃料が少なくなる関係にある。そこで、評価関数は燃料最小を炉温最小として良いことになり、その評価関数を（１０）式に示す。
Ｊ＝α・θ_G.1 ＋β・θ_G.2 …（１０）
ただし
α，β：重み係数
である。
【００３４】
一般に加熱時間の方が均熱時間より長く、しかも加熱時間での炉温は均熱時間での炉温より高いので、重みαの値はβより大きい値の一定値である。
制約条件としては、次の（１１）〜（１３）式とする。
【００３５】
【数６】

（１１）式は加熱炉抽出時のスラブの平均温度θ_out を目標の抽出平均温度θ_out.r に焼き上げるという条件である。
【００３６】
スラブの平均温度は図４の例の場合、次式で計算できる。
【００３７】
【数７】

ただし、
θ_i ：抽出時の各分割部分のスラブ温度
Ｎ ：スラブの厚み方向の分割数
である。
【００３８】
（１２）式は抽出時のスラブの均熱度θ_mmを指定した均熱度θ_mm.u以下にするという条件である。スラブの均熱度θ_mmはスラブの厚み方向に対して、最も高い分割境界点温度と最も低い分割境界点温度との差であるので、スラブ表面温度と中心温度との差で計算できる。
【００３９】
（１３）式は、求める炉温は設備上のあるいは操業上の上限値θ_G.1.u 、θ_G.2.u を越えてはならないという条件であり、このθ_G.1.u 、θ_G.2.u の値はテーブル値として持っている。
【００４０】
しかして、上記（１０）式から（１３）式までの評価関数と制約条件、及び（７）〜（９）式のスラブ温度モデルを用いて公知の最適化手法により最適な炉温θ_G.1 ，θ_G.2 が演算できる。
【００４１】
次に炉装入材料初期温度演算装置１３について説明する。
図２の材料の温度履歴に示すように、加熱炉に装入される時の材料の初期温度は加熱炉での加熱時間が短いので、重要である。図１１に示す従来のホットストリップミルの加熱炉は在炉時間が数時間あるので、加熱炉装入時のスラブ内部温度の分布の誤差は抽出温度にほとんど影響を与えない。
一方、新しい加熱炉は在炉時間が短いので、加熱炉装入時のスラブの温度分布は抽出温度に影響する。抽出温度に影響することは、上記の最適な炉温を演算する結果に影響する。そこで、加熱炉に装入される材料の装入初期温度をこの炉装入材料初期温度演算装置１３によって計算する。
【００４２】
初期温度を計算するのに、本実施形態では、連鋳設備から、すなわち、溶鋼からモデルにより加熱炉に装入されるスラブの初期温度を計算する。以下その計算方法を説明する。
このスラブの温度も、基本的に加熱炉内のスラブ温度計算モデル式がそのまま使用できる。すなわち図４に示すようにスラブをその厚み方向を分割し、（７），（８）式で計算できる。
【００４３】
（９）式は加熱炉から輻射でスラブが加熱される式であるのでそのまま使用できない。連鋳設備から加熱炉に装入されるまでに、図２に示すように、表面が冷却される期間とその後の空冷期間があるので、（９）式の代わりに水冷の熱伝達式と空冷の熱伝達式を適用すれば良い。水冷による熱伝達式は次の（１５）式となる。
Ｑ＝−Ｋ・（θｉ−θ_w ） …（１５）
ただし、
Ｑ：スラブの表面から奪われる熱量（マイナスの符号がつく）
θ_w ：冷却水の温度
θ_i ：スラブのラブの表面温度
Ｋ：平均熱伝達係数
である。
【００４４】
空冷期間では、スラブは輻射により自然冷却となり、輻射の式は（９）式のステファンボルツマンの熱輻射の式が適応できる。すなわち、（９）式の炉温θ_G の代わりに外気温度θ_a を用いた次式を適用すれば良い。
Ｑ＝−σ・Φ・｛（θ_i ＋２７３）⁴ −（θ_a ＋２７３）⁴ ｝…（１６）
ただし、
Ｑ：スラブ表面から奪われる熱量（マイナスの符号がつく）
σ：ステファンボルツマン定数、
Φ：総括熱吸収率
θ_a ：外気温度、
θ_i ：スラブ表面温度
である。
【００４５】
すなわち、（８），（９），（１５），（１６）式を使い、連鋳速度で決まる時間すなわち溶鋼からスラブが加熱炉に入る時間までスラブの温度が計算でき、加熱炉装入スラブ初期温度が演算できることになる。このように、連鋳設備から加熱炉まで連続したモデルでスラブの分割数も同じとすれば、正確な温度計算ができることになる。本実施形態の炉装入材料初期温度演算装置１３による温度計算は鋼種、連鋳速度、厚みなどが同じ条件であれば、１回計算しておけば良く、同じ条件のスラブの初期温度に適用できる。
【００４６】
次に、設定炉温記憶装置１５と炉温設定タイミング演算装置１６について説明する。
設定炉温演算装置１４で演算される炉温は、あらかじめスラブが加熱炉に入る前に計算できるものである。通常、連鋳速度、スラブの厚みなどは一定であり、シャーで切断されるスラブの長さなどはあらかじめ圧延計画でわかるので、スラブが加熱炉に入る前に計算できる。
【００４７】
設定炉温記憶装置１５は設定炉温演算装置１４で計算された炉温を記憶し、出力する装置である。記憶された炉温は次に述べる炉温設定タイミング演算装置１６により起動がかけられ実際の炉温制御装置４に設定される。
【００４８】
一方、炉温設定タイミング演算装置１６は、加熱炉の応答時間を考慮するために設けた装置であり、図５を使ってこの装置を説明する。
加熱炉は炉温設定値を変化させた場合、瞬時に炉温は変わらず、ある応答時間を持って応答する。そこで、スラブの尾端が加熱炉に装入されるタイミングの場合を例にとると、図５に示すように、スラブの尾端が加熱炉に装入されるタイミングで、設定炉温演算装置１４で演算された炉温に加熱炉の温度が達成されているようなタイミングを計算する装置である。スラブの尾端が加熱炉に装入される時刻はあらかじめトラッキング装置１１からもらい、加熱炉の応答時間を考慮し、応答時間Ｔ_RFだけ早く炉温の設定値を変更すれば良いことになる。加熱炉の応答は別途測定した値をテーブル値として持っておけば良い。図５ではスラブが加熱炉に装入される例で示したが、均熱時間での均熱炉温を設定する場合も同様に加熱炉の応答を考慮して設定する。このように、設定炉温演算装置１４で求めた最適な設定炉温は、一度、設定炉温記憶装置１５に記憶され、炉温設定タイミング演算装置１６により起動がかけられ、各加熱帯の炉温制御装置４に送られ、各加熱帯の温度が制御され、スラブが目標温度に加熱される。
【００４９】
以上、材料加熱時間演算装置１２、炉装入材料初期温度演算装置１３、設定炉温演算装置１４、設定炉温記憶装置１５及び炉温設定タイミング演算装置１６の詳細な動作を、その原理と併せて説明したが、図１に示した全体的な動作を以下に説明する。
【００５０】
連鋳設備で生産された材料は、シャー７によって所定の長さに切断されて、スラブ６となる。このスラブ６はテーブルローラ８によって加熱炉１に装入される。そして、スラブ６は加熱炉１にてテーブルローラ８で搬送されながら、目標の温度に加熱されて抽出され、後工程の圧延機９にて圧延される。テーブルローラ８はテーブル制御装置１０によって制御される。
【００５１】
材料加熱時間演算装置１２は、スラブ６が加熱炉１に装入される前に、スラブ６の在炉時間からスラブ６を目標の平均温度に加熱する時間Ｔ₁ と均熱時間Ｔ₂ とを（４）式と（５）式とから演算する。材料加熱時間演算装置１２はこの計算した時間を設定炉温演算装置１４に送ると同時に、トラッキング装置１１に図３で示したスラブを焼き上げる時刻信号ｔ_H を送る。トラッキング装置１１はライン上のスラブ６のトラッキングをすると同時に時間をも管理し、テーブル制御装置１０の起動制御をも行う。炉装入材料初期温度演算装置１３は（８），（９），（１５），（１６）式を使用し、スラブ６が加熱炉１に装入される前に加熱炉装入材料初期温度を演算する。演算された加熱炉装入材料初期温度は設定炉温演算装置１４に送られる。
【００５２】
設定炉温演算装置１４はこのスラブ初期温度と、材料加熱時間演算装置１２で演算された加熱時間Ｔ₁ と均熱時間Ｔ₂ と、スラブの抽出目標温度と、均熱条件とから、（７）〜（９）式を使ったスラブ温度演算モデル式と、線形計画法の基本式（１０）〜（１３）式を使った最適炉温演算モデル式とから省エネルギーを図った加熱炉の最適設定温度（加熱時間では加熱期間での最適炉音θ_G.1 、均熱時間では均熱期間の最適炉温θ_G.2 ）を演算する。演算した結果は設定炉温記憶装置１５に送られ記憶される。
【００５３】
炉温設定タイミング演算装置１６はスラブ６が加熱炉１に装入される時刻ｔ_inより前に加熱炉１の応答を考慮し、炉温設定値を炉温制御装置４に送るタイミングを設定炉温記憶装置１５に指令する。その結果、スラブ６の尾端が加熱炉１に装入されるタイミングで、材料加熱時間演算装置１２にて演算された炉温（加熱期間での最適炉温θ_G.1 ）が達成され、スラブ６は加熱炉内をテーブルローラ８により移動せしめられながら目標の平均温度に加熱される。
【００５４】
スラブ６が焼き上がる時刻ｔ_H になると、トラッキング装置１１はテーブル制御装置１０を起動し、スラブ６を加熱炉１の下流の加熱帯を通過させ、スラブ６は指定された均熱度で抽出され、圧延機９に送られる。このスラブ６が焼き上がる時刻ｔ_H から抽出されるまでの均熱時間では設定炉温記憶装置１５にて記憶された均熱期間での最適炉温θ_G.2 がスラブ６の炉内位置に応じた加熱帯に設定され、スラブ６が均熱されることになる。この均熱期間での最適炉温θ_G.2 の炉温の設定においても、加熱炉の応答を考慮し、スラブ６が焼き上がる時刻ｔ_H より早めに炉温制御装置４に送られる。このタイミングも前述したと同様に炉温設定タイミング演算装置１６で管理される。このようにして、スラブ６は指定された時刻に、均熱条件を満足した抽出目標温度で抽出される。
【００５５】
なお、この実施形態では、スラブ長が長く、スラブ６が第１の加熱帯と第２の加熱帯に跨がる場合は、言うまでもなく第１の加熱帯及び第２の加熱帯の各炉温を同じ炉温θ_G.1 に設定する。
【００５６】
かくして、第１の実施形態によれば、圧延生産量に基づく圧延計画に対応し、省エネルギーのもとで、スラブを圧延に適した温度に精度良く加熱することができる。
【００５７】
図６は本発明の第２の実施形態の構成を示すブロック図である。図中、図１と同一の要素には同一の符号を付してその説明を省略する。この第２の実施形態は加熱炉１の一つの加熱帯に複数のスラブ６が在炉する場合の構成例で、設定炉温記憶装置１５Ａが、図１に示した設定炉温記憶装置１５の機能の他に、一つの加熱帯に材炉する複数のスラブ６に対して、最も高い設定炉温を炉温制御装置４に与える機能を備えた点が図１と構成を異にしている。これは図７に示すように、スラブ６の長さが短いケースで、第１の加熱帯にスラブＡとスラブＢとが在炉する場合、設定炉温記憶装置１５Ａには、材料加熱時間演算装置１２で演算されたスラブＡと、スラブＢの両方の設定炉温が記憶されている。設定炉温記憶装置１５Ａでは記憶されている設定炉温の高い炉温設定値を選択し、第１の加熱帯の炉温制御装置４に送り、そこに在炉するスラブを加熱する。スラブは圧延に適した温度まで焼き上げるのが基本であるので、高い圧延温度を要求するスラブを焼き上げ、他のスラブは目標温度よりも高くなるがこれは仕方のないことである。このように、設定炉温記憶装置１５Ａに設定炉温の大小の判別機能を持たせ、全てのスラブ６を目標温度以上に焼き上げることができる。
【００５８】
かくして、第２の実施形態によれば、一つの加熱帯に複数のスラブ６が在炉する場合でも、圧延生産量に基づく圧延計画に対応し、省エネルギーのもとで、スラブを圧延に適した温度に精度良く加熱することができる。
【００５９】
図８は本発明の第３の実施形態の構成を示すブロック図である。図中、図１と同一の要素には同一の符合を付してその説明を省略する。この実施形態は加熱炉１の材料の入側に炉入側材料温度計１７を設け、炉装入材料初期温度演算装置１３Ａに対して、図１中の炉装入材料初期温度演算装置１３の機能の他に、炉装入初期温度の補正機能を持たせた点が図１と構成を異にしている。以下、この実施形態の動作について、図１と構成を異にする部分について、図９をも参照して説明する。
【００６０】
この実施形態は前述したようにスラブの温度をモデルで計算する際、このモデルによる誤差を解消することを目的としており、図９にて黒丸●で示したのがモデルによるスラブの温度分布であり、モデルによる表面温度計算値をθ₁ とする。炉入側材料温度計１７による検出値をθ_1.D とする。これらの表面温度の差Δθ₁ ＝θ_1.D −θ₁ を使い、モデルで計算した各分割境界点温度を一律にΔθ₁ だけ白丸○に示したように補正する。これは、スラブの厚み方向の温度分布は二次曲線で表せるという解析結果に基づくものである。これによって、スラブの加熱炉装入初期温度の高精度化が可能となり、設定炉温演算装置１４で計算するスラブ温度計算の高精度化が図られる。
【００６１】
かくして、第３の実施形態によれば、スラブを圧延に適した温度に加熱する精度を第２の実施形態よりも高めることができる。
【００６２】
なお、炉装入材料初期温度演算装置１３の代わりに炉装入材料初期温度演算装置１３Ａを用いることは、図１に示した第１の実施形態に適用するだけでなく、図２に示した第２の実施形態にも適用可能である。
【００６３】
図１０は本発明の第４の実施形態の構成を示すブロック図である。図中、図３と同一の要素には同一の符合を付してその説明を省略する。この実施形態は加熱炉１の出側に材料温度計１８が設けられ、フィードバック装置１９が材料温度計１８による実測値と抽出目標温度との差を演算すると共に、この差を零にする温度補正値を演算し、加算器２０を介して、設定炉温記憶装置１５から出力される設定値を補正して、炉温制御装置４に加えるようにした点が図８と構成を異にしている。
【００６４】
以下、図８と構成が異なる部分の動作を以下に説明する。
第１乃至第３の実施形態は温度予測に基づくフィードフォワード制御である。このフィードフォワード制御の場合、予測計算したスラブの抽出温度が必ずしも、目標の抽出温度にならない場合がある。そこで、加熱炉１の出側に材料温度計１８を設置し、その検出値を使用して設定炉温を補正し、スラブの抽出温度の高精度化を図るものである。
【００６５】
いま、炉出側材料温度計１８によるスラブの温度の検出値をθ_out.D とし、スラブの抽出目標温度をθ_out.r とすると、その差Δθ_out ＝θ_out.r −θ_out.D に応じた量、すなわち、次式によって得られる量を設定炉温にフィードバックする。
Δθ_SET ＝Ｃ・Δθ_out …（１７）
ここで、Ｃは係数である。
このように、実績温度と目標値との差に応じた値をフィードバックすることにより、同じロットの後行材のスラブの抽出温度の高精度化が図られる。
【００６６】
かくして、第４の実施形態によれば、スラブを圧延に適した温度に加熱する精度を第３の実施形態よりも高めることができる。
【００６７】
なお、スラブの温度検出値と抽出目標温度と差に応じた量量を設定炉温にフィードバックする機能は、第３の実施形態に限らず、第１及び第２の実施形態にも適用することができる。
【００６８】
一方、第１乃至第４の各実施形態では、それぞれ独立した装置によって、加熱炉１の制御装置を構成したが、これらの要素がもつ機能のいくつか、又は、その殆どを計算機にもたせることも可能である。
【００６９】
【発明の効果】
以上の説明によって明らかなように、本発明によれば、圧延計画に基づき、省エネルギーを図りつつ、材料を目標温度に精度良く焼き上げることができる。
【図面の簡単な説明】
【図１】本発明の第１の実施形態の構成を示すブロック図。
【図２】図１に示した実施形態の動作を説明するために、連続鋳造設備から加熱炉の出側までの材料の温度と時間との関係を示した線図。
【図３】図１に示した実施形態の動作を説明するために、加熱炉での加熱時間及び均熱時間と加熱炉の長さとの関係を示す線図。
【図４】図１に示した実施形態の動作を説明するために、スラブ温度モデルにおけるスラブの厚み方向の分割例を示した図。
【図５】図１に示した実施形態の動作を説明するために、炉温を設定する場合のタイミングを示した図。
【図６】本発明の第２の実施形態の構成を示すブロック図。
【図７】図６に示した実施形態の動作を説明するために、加熱炉の一つの加熱帯に二つのスラブが在炉する例を示した図。
【図８】本発明の第３の実施形態の構成を示すブロック図。
【図９】図８に示した実施形態の動作を説明するために、スラブ温度計の検出値による温度計算結果の修正方法の説明図。
【図１０】本発明の第４の実施形態の構成を示すブロック図。
【図１１】従来のホットストリップミルラインのレイアウト図。
【図１２】本発明の適用対象のホットストリップミルラインのレイアウト図。
【符号の説明】
１ 加熱炉
２ 加熱帯
３ バーナー
４ 炉温制御装置
５ 炉温計
６ スラブ
７ シャー
８ テーブルローラ
９ 圧延機
１０ テーブル制御装置
１１ トラッキング装置
１２ 材料加熱時間演算装置
１３，１３Ａ 炉装入材料初期温度演算装置
１４ 設定炉温演算装置
１５，１５Ａ 設定炉温記憶装置
１６ 炉温設定タイミング演算装置
１７ 炉入側材料温度計
１８ 炉出側材料温度計
１９ フィードバック装置
２０ 加算器[0001]
BACKGROUND OF THE INVENTION
The present invention relates to control of a heating furnace installed on a hot strip mill line, and relates to a control apparatus for a heating furnace that heats a material to be heated (hereinafter simply referred to as a material) to a temperature suitable for rolling.
[0002]
[Prior art]
An example of the layout of a conventional hot strip mill line is shown in FIG. In the same figure, the slab heating furnace 31 which heats a slab is installed in the upstream part. On the downstream side, a rough rolling mill 33 and a finish rolling mill 34 for rolling the slab 32 extracted from the slab heating furnace 31 are arranged in order, and a coiler 35 for winding the rolled material is installed on the most downstream side. The slab heating furnace 31 is arranged in a direction perpendicular to the line. From the material charging side, a slab 32 having a thickness of about 230 mm and a length of about 10 m is charged, and the slab 32 is heated to about 1200 ° C. over several hours. Heat to extract. In this case, the slab heating furnace 31 generally includes a plurality of furnaces, and 40 to 50 slabs are placed in one furnace.
[0003]
In this conventional hot strip mill line, the slab extracted from the heating furnace is rolled to a thickness of about 20 to 60 mm by a plurality of passes by a plurality of rough rolling mills 33 and then sent to a finishing mill 34. Therefore, although it is a high-productivity mill line, it consumes a large amount of energy and requires a large capital investment for the construction of a new line.
[0004]
Recently, with the progress of continuous casting (hereinafter referred to as continuous casting) technology, it has become possible to produce thin slabs, for example, slabs having a thickness of around 50 mm by continuous casting. For this reason, a continuous heating facility and a hot strip mill are connected, a new heating furnace with a simpler configuration is provided in place of the conventional slab heating furnace, and the hot strip mill is installed with fewer or fewer rough rolling mills. A new mill line called so-called mini mill or compact mill is attracting attention. FIG. 12 shows an example of the layout of the equipment of this new mill line, and the present invention is applied to a new heating furnace of this new mill line.
[0005]
The new mill line is characterized by low production compared to conventional mill lines but low construction costs for hot strip mills and low energy consumption. In this new mill line, the furnace produced by cutting the material produced in the continuous casting equipment 21 to a length determined by the production plan by the shear 7 and heating the obtained short slab 6 to a temperature suitable for rolling in the subsequent process. 1 is installed.
[0006]
Here, the slab 6 is heated to a target extraction temperature while moving on a table roller that is also continuously installed in the heating furnace. Therefore, this heating furnace 1 is a facility that is greatly different from the heating furnace 31 installed in the conventional hot strip mill shown in FIG. 11, for example, the thickness of the material to be heated is different and the heating time is greatly different. It is the structure which can respond to. The conventional heating furnace heated the slab for about 3 hours, but the new heating furnace 1 of the new mill line needs to be baked in a few minutes. In addition, since the new heating furnace 1 is directly connected to the continuous casting equipment 21, when the downstream rolling mill group 9A cannot be operated for some reason, the continuous casting equipment cannot stop production. The furnace must also serve as a buffer to store material. Therefore, the length of the heating furnace 1 is several times longer than the conventional one. Furthermore, the new heating furnace 1 has a structure in which a material is conveyed by a table roller.
As described above, the new heating furnace is a furnace based on a new concept and requires a new control method.
[0007]
[Problems to be solved by the invention]
In the new mill line shown in FIG. 12, the material produced in the continuous casting equipment 21 is cut by the shear 7 to a length based on the rolling plan. The obtained slab 6 predicts and manages the positions of the tip and tail ends of the slab on the line and the passing time of each facility by a tracking technique that is a well-known technique essential for a conventional hot strip mill. Further, the cut slab is transported by the table roller 8 controlled by the table control device omitted in FIG. The slab 6 charged in the heating furnace 1 is baked to the extraction target temperature while being conveyed. In this case, while the slab 6 is in the heating furnace 1, the furnace temperature of each heating zone of the heating furnace is controlled by the furnace temperature control device omitted in FIG. 12 provided for each heating zone. When the extraction time of the slab 6 comes, the slab 6 is extracted and rolled by a rolling mill in the subsequent stroke.
[0008]
In this mill line, since the continuous casting speed is constant, the production amount of the mill is determined by the production amount based on the continuous casting speed. Therefore, even if a quick extraction pitch is requested on the rolling mill side, continuous casting cannot catch up. For example, if the required slab length is 16 m and the continuous casting speed is 4 m / min, the continuous casting cannot keep up even if the rolling pitch is requested to be reduced to 4 minutes or less. If the rolling pitch is 4 minutes, the slab must be baked to the target extraction temperature in 4 minutes and sent to the rolling mill.
[0009]
In this way, in a new heating furnace in a new mill line (hereinafter simply referred to as a new heating furnace), it must be heated in a short time to achieve a temperature suitable for rolling while saving energy. The problem is that the slab must be sent to the rolling mill at a time corresponding to the rolling pitch based on the rolling plan.
[0010]
The present invention has been made to solve the above-mentioned problems, and corresponds to a rolling plan based on a rolling production amount, and controls a heating furnace that accurately heats a slab to a temperature suitable for rolling under energy saving. An object is to provide an apparatus.
[0011]
[Means for Solving the Problems]
  The heating furnace control device according to claim 1, wherein the material cut in a predetermined length after being produced in the continuous casting equipment is passed through the heating furnace while being extracted by the table roller and extracted from the heating furnace. In the heating furnace control device that controls the furnace temperature so that the material extraction temperature becomes a preset extraction target temperature, the temperature of each of the heating zones provided in the material conveyance direction in the heating furnace is controlled. Furnace temperature control means, tracking means for predicting the time when the tail end of the material is charged into the heating furnace, and the time when the tip of the material is extracted from the heating furnace, and prediction of the tracking means A table control means for controlling the conveyance of the table roller, a time when the tail end of the material is inserted into the heating furnace, a time when the tip of the material is extracted from the heating furnace, and the table A heating time for heating the average temperature of the material to the extraction target temperature based on a table speed at which the roller transports the material, and a temperature uniformity that is a temperature difference between the surface temperature of the material and the center temperature. A material heating time calculating means for calculating a soaking time for keeping the temperature within a predetermined temperature, and using the material temperature calculation model for the initial temperature of the heating furnace when the material is charged into the heating furnace The furnace charge material initial temperature calculation means calculated by the above, the heating time and soaking time of the material calculated by the material heating time calculation means, and the heating furnace charge calculated by the furnace charge material initial temperature calculation means A set furnace temperature calculation means for calculating a set furnace temperature of the heating furnace based on an initial charge temperature, a target extraction temperature of the material and a soaking condition at the time of extraction, and the furnace temperature control calculated by the set furnace temperature calculation means Set furnace temperature to be added to the means Setting furnace temperature storage means for storing, and furnace temperature setting timing calculation for adding the set furnace temperature stored in the setting furnace temperature storage means to the furnace temperature control means at a predetermined timing calculated in consideration of the response time of the heating furnace And the furnace temperature control means controls the temperature of each heating zone based on the set furnace temperature applied by the furnace temperature setting timing calculation means.
[0012]
The control device for a heating furnace according to claim 2, wherein when a plurality of materials are present in one heating zone of the heating furnace, the furnace temperature of the heating zone is the highest setting furnace temperature among the set furnace temperatures for each material. A function for setting the temperature is added to the set furnace temperature storage means.
[0013]
The heating furnace control apparatus according to claim 3 is provided with a thermometer for measuring the material temperature on the material charging side of the heating furnace, and using the measured value, the furnace charging material initial temperature calculating means performs prediction calculation. The function of internally correcting the material temperature is added to the furnace charge material initial temperature calculating means.
[0014]
According to a fourth aspect of the present invention, there is provided a heating furnace control device comprising: a thermometer for measuring a material temperature on a material extraction side of the heating furnace; and a value corresponding to a difference between a measured value of the thermometer and a target extraction temperature of the material. Feedback means for correcting the set furnace temperature applied to the furnace temperature control means is further provided.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on preferred embodiments shown in the drawings.
FIG. 1 is a block diagram showing the configuration of the first embodiment of the present invention. In the figure, 1 is a heating furnace to be controlled, and this heating furnace 1 has a plurality of heating zones 2 (hereinafter also referred to simply as heating zones) 2 in the material transport direction, and each heating zone 2 has a burner. 3. A furnace temperature control device 4 and a furnace thermometer 5 are provided, and the furnace temperature control device 4 controls the fuel supply amount of the burner 3 so that the detected value of the furnace thermometer 5 follows the set furnace temperature. ing.
[0016]
Further, a shear 7 is provided on the material charging side of the heating furnace 1, and the material produced in the continuous casting facility is cut into a slab 6 having a predetermined length. The cut slab 6 is heated to a target temperature while being conveyed by the table roller 8, extracted from the heating furnace 1, and rolled by a rolling mill 9 in a subsequent process. The table roller 8 is divided so that a predetermined number forms one set, and the speed is controlled by the table control device 10 for each set. In this case, the table control device 10 controls the table roller 8 in accordance with a conveyance command from a conveyance control device (not shown) and a command from the tracking device 11. The tracking device 11 is a device that predicts the time at which the leading and trailing ends of the material pass through the main equipment on the line including each heating zone of the heating furnace, and at the same time manages the time and commands the activation of the table control device 10. .
[0017]
On the other hand, the material heating time calculation device 12 calculates a time for heating the slab to the target temperature from the in-furnace time of the slab 6 before the slab 6 is inserted into the heating furnace 1, and calculates the calculation result as a set furnace temperature calculation. At the same time as sending to the device 14, a slab baking time signal is given to the tracking device 11. The furnace charging material initial temperature calculation device 13 calculates a heating furnace charging slab initial temperature, which will be described in detail later, and adds it to the set furnace temperature calculation device 14 before the slab 6 is charged into the heating furnace 1. is there.
[0018]
The set furnace temperature calculation device 14 is based on the heating time of the slab 6 calculated by the material heating time calculation device 12, the heating furnace charging slab initial temperature calculated by the furnace charging material initial temperature calculation device 13, and the rolling schedule. The optimum set furnace temperature of each heating zone 2 of the heating furnace 1 is calculated based on the determined extraction target temperature, and the calculation result is sent to the set furnace temperature storage device 15 and stored therein. Based on the tracking result of the tracking device 11, the furnace temperature setting timing calculation device 16 takes into account the temperature control response of the heating furnace 1 before the time when the slab 6 is inserted into the heating furnace 1, and stores the set furnace temperature. The timing at which the furnace temperature set value stored in the device 15 is applied to the furnace temperature control device 4 is determined, and an output command is given.
[0019]
Regarding the first embodiment configured as described above, the principle and operation of main components will be described, and then the overall operation will be described.
When a slab is heated in a heating furnace, the surface temperature is increased because it is heated from the surface as is well known, and a temperature difference (called a soaking degree) occurs between the surface temperature and the center temperature. If this temperature difference is large, it is not preferable for rolling, and it is necessary to reduce this temperature difference. Therefore, a heating time T for heating the average temperature of the slab to the extraction target temperature in order to reduce the temperature difference of the slab during extraction by performing temperature analysis of the material.₁And soaking time T to keep the soaking degree within the specified temperature₂Focus on dividing it into
[0020]
FIG. 2 is an example of a temperature analysis, and is a diagram showing a rough change of the material temperature from the molten steel temperature of the continuous casting until the slab is extracted from the heating furnace with time on the horizontal axis. In FIG. 2, the center temperature, the surface temperature and the average temperature in the thickness direction of the material, and the heating time T₁Furnace temperature at_G.1, Soaking time T₂Furnace temperature at_G.2Is shown. In Fig. 2, the in-furnace time T of the material_FIs determined by the rolling plan, but the time T determined by this rolling plan_FTo heating time T₁And soaking time T₂It is the material heating time calculation device 12 that calculates.
[0021]
Using FIG. 3, the heating time T₁And soaking time T₂Explain how to decide.
First, the slab furnace time T_FIs defined. In this embodiment, the time from when the tail end of the slab is inserted into the heating furnace to when the tip of the slab is extracted from the heating furnace is defined as the in-furnace time.
The length of the slab is determined by the rolling plan, and the time t when the slab is charged into the heating furnace after being cut by the shear 7_inIs grasped by the tracking device 11 based on the rolling plan. Also, the time t at which the slab should be extracted for rolling in the subsequent process_0UTIs also decided. That is, the time T for allowing the slab to stay in the heating furnace_FIs decided. Therefore, this time T_FThe slab can be heated with a to secure the target soaking degree and extraction temperature. As described above, the material heating time calculation device 12 has T_FTo heating time T₁And soaking time T₂It is what decides.
[0022]
In this case, the heating time T₁And soaking time T₂Is the in-furnace time T_FTherefore, the following equation (1) is established.
T₁+ T₂= T_F                              ... (1)
Soaking time T₂Is the time t when the average temperature of the slab is baked to the extraction target temperature_HIt can be seen that the most efficient operation is to immediately transport the slab with a table roller and extract it from the heating furnace. That is, T₂May be determined by the following equation (2).
[0023]
[Expression 1]

However,
L₂: Time t when slab is baked_HThe distance from the tip of the slab to the furnace outlet.
V₂: Table speed when transporting slab
It is.
L₂As can be seen from FIG.
L₂= L_F-L_S-L₁= L_F-L_S-T₁・ V₁  ... (3)
However,
L_F: Furnace length,
L_S: Slab length,
L₁: After the tail end of the slab is charged into the furnace, the heating time T₁In
Distance traveled by the slab
V₁: Heating time T₁Table speed at
It is.
From the formulas (1) to (3), the heating time T₁And soaking time T₂Can be calculated as follows:
[0024]
[Expression 2]

The material heating time calculation device 12 uses the above equations (4) and (5) to calculate the heating time T₁And soaking time T₂And ask.
In the process of introducing the above equation, the acceleration / deceleration time of the table is not taken into consideration. However, if it is taken into account, a more exact value can be obtained, but the influence is small, and the above equation is sufficient.
[0025]
Next, the set furnace temperature calculation device 14 is a device that calculates the optimum set furnace temperature of the heating furnace so that the slab reaches the target extraction temperature. In order to determine the set furnace temperature, a slab temperature prediction calculation is required. Therefore, the set furnace temperature calculation device 14 calculates the set furnace temperature using the slab temperature calculation model expression and the optimum furnace temperature calculation model expression for calculating the optimum set furnace temperature.
Therefore, the slab temperature calculation model formula will be described.
The temperature of the slab in the heating furnace can be calculated by the Fourier heat conduction differential equation (6).
[0026]
[Equation 3]

However,
θ: Slab temperature
c: Specific heat of slab
ρ: Slab density
X: Depth in the X-axis direction (slab thickness direction)
k: Thermal conductivity of slab
t: time
It is.
[0027]
To solve the above equation, as shown in FIG. 4, the slab can be divided equally in the thickness direction, and the temperature at each dividing boundary point can be solved by a difference equation. FIG. 4 shows an example in which the thickness direction of the slab is divided into six. In the case where the temperature calculation position is seven points, it is usually sufficient to divide into four to eight.
When the slab is divided in this way, the temperature θ at an arbitrary dividing boundary point i inside the slab_i(I = 2 to 6) can be calculated by the following equation.
[0028]
[Expression 4]

The above equation (7) is the slab division boundary temperature θ at time t._iTemperature θ at the dividing boundary point i of the slab after time step Δt from (t)_iIt is a formula for calculating (t + Δt). ΔX is a distance obtained by dividing the slab in the thickness direction.
On the other hand, the surface point temperature θ of the slab_i(I = 1 = 7) can be calculated by the following equation.
[0029]
[Equation 5]

In the above equation (8), Q is a heat flux entering from the surface of the slab, and the following Stefan-Boltzmann thermal radiation equation can be applied.
Q = σ · Φ_G・ {(Θ_G+273)^Four− (Θ_i  +273)^Four} ... (9)
However,
σ: Stefan Boltzmann constant
Φ_G: Overall heat absorption rate in the heating furnace
θ_G: Furnace temperature, heating time is the furnace temperature θ during the heating period_G.1In soaking time, soaking period
Furnace temperature at_G.2
It is.
[0030]
Using the above equations (7) to (9), the furnace temperature θ_GAnd the initial temperature when the slab is charged into the heating furnace (this initial temperature will be described in the next furnace charging material initial temperature arithmetic unit 13), the slab is charged into the heating furnace. Time until extraction, that is, heating time T calculated by the material heating time calculation device 12₁And soaking time T₂The slab temperature can be predicted and calculated.
[0031]
In this set furnace temperature calculation device 14, the furnace temperature θ of the equation (9)_GIs the purpose. The furnace temperature is given to the equation (9) by trial and error, and the calculation of the slab temperature is performed by calculating the equations (7) to (9), so that the slab becomes the target temperature. It becomes enormous and it is impossible for online control of an actual plant. In addition, there is a condition that, for operation, the slab must be baked to a target extraction temperature or higher and the soaking degree must be lower than a certain value with a minimum energy consumption.
Therefore, in order to obtain the optimum furnace temperature efficiently in consideration of energy saving, the optimum furnace temperature is calculated by the linear programming method which is an optimization technique as the optimum furnace temperature calculation model formula.
[0032]
The condition for determining the furnace temperature is that the extraction temperature must first be heated to a target value or higher. If the temperature is higher than the extraction temperature, the fuel consumption of the heating furnace increases, which is not preferable. Therefore, the fuel consumption must be minimized and the extraction temperature must be secured. Further, as described above, the temperature difference in the slab at the time of extraction must be kept within a specified temperature. Under this condition, the optimum furnace temperature θ for the heating time_G.1And optimal furnace temperature θ for soaking time_G.2Is determined by the optimized furnace temperature calculation model formula of the set furnace temperature calculation device 14. The method for obtaining the optimum furnace temperature will be specifically described below.
[0033]
In the linear programming method, by defining the evaluation function J and the constraint condition of the system, calculation is performed by a well-known solution method, and an optimal solution is obtained.
Therefore, first, the minimum energy consumption is selected as the evaluation function J. The minimum energy consumption can be achieved by minimizing the fuel consumption. However, the fuel and the furnace temperature are closely related, and if the furnace temperature is increased, more fuel is consumed, and if the furnace temperature is lowered, the fuel is decreased. Therefore, the evaluation function may be set such that the minimum fuel is the minimum furnace temperature, and the evaluation function is shown in Equation (10).
J = α ・ θ_G.1+ Β ・ θ_G.2                        (10)
However,
α, β: Weighting factor
It is.
[0034]
In general, since the heating time is longer than the soaking time, and the furnace temperature at the heating time is higher than the furnace temperature at the soaking time, the value of the weight α is a constant value greater than β.
As a constraint condition, the following equations (11) to (13) are used.
[0035]
[Formula 6]

Equation (11) is the average temperature θ of the slab at the time of furnace extraction._outThe target extraction average temperature θ_out.rThe condition is to bake it.
[0036]
In the case of the example of FIG. 4, the average slab temperature can be calculated by the following equation.
[0037]
[Expression 7]

However,
θ_i: Slab temperature of each segment during extraction
N: Number of divisions in the thickness direction of the slab
It is.
[0038]
Equation (12) is the soaking degree θ of the slab during extraction._mmSoaking degree θ specified_mm.uThe condition is as follows. Slab soaking degree θ_mmIs the difference between the highest dividing boundary point temperature and the lowest dividing boundary point temperature in the thickness direction of the slab, and can be calculated by the difference between the slab surface temperature and the center temperature.
[0039]
Equation (13) shows that the required furnace temperature is the upper limit value θ on the equipment or operation._G.1.u, Θ_G.2.uThis condition is that it must not exceed_G.1.u, Θ_G.2.uThe value of has a table value.
[0040]
Thus, the optimum furnace temperature θ by the known optimization method using the evaluation function and the constraint conditions from the above formulas (10) to (13) and the slab temperature model of formulas (7) to (9)._G.1, Θ_G.2Can be calculated.
[0041]
Next, the furnace charge material initial temperature calculation device 13 will be described.
As shown in the temperature history of the material in FIG. 2, the initial temperature of the material when it is charged into the heating furnace is important because the heating time in the heating furnace is short. Since the heating furnace of the conventional hot strip mill shown in FIG. 11 has an in-furnace time of several hours, an error in the distribution of the internal temperature of the slab when the heating furnace is charged hardly affects the extraction temperature.
On the other hand, since the new furnace has a short in-furnace time, the temperature distribution of the slab when the furnace is charged affects the extraction temperature. Influencing the extraction temperature affects the result of calculating the optimum furnace temperature. Therefore, the initial charging temperature of the material charged into the heating furnace is calculated by the furnace charging material initial temperature calculation device 13.
[0042]
In order to calculate the initial temperature, in this embodiment, the initial temperature of the slab charged into the heating furnace is calculated from the continuous casting equipment, that is, from the molten steel by the model. The calculation method will be described below.
Basically, the slab temperature calculation model formula in the heating furnace can be used as it is for the slab temperature. That is, as shown in FIG. 4, the slab can be calculated by the equations (7) and (8) by dividing the slab in the thickness direction.
[0043]
Equation (9) cannot be used as it is because the slab is heated by radiation from a heating furnace. As shown in FIG. 2, there is a period during which the surface is cooled and a subsequent air cooling period until the furnace is charged from the continuous casting equipment. The heat transfer equation can be applied. The heat transfer equation by water cooling is the following equation (15).
Q = −K · (θi−θ_w... (15)
However,
Q: The amount of heat taken from the surface of the slab (with a minus sign)
θ_w: Temperature of cooling water
θ_i: Slab surface temperature of slab
K: Average heat transfer coefficient
It is.
[0044]
In the air-cooling period, the slab is naturally cooled by radiation, and the Stefan-Boltzmann thermal radiation formula (9) can be applied to the radiation formula. That is, the furnace temperature θ in equation (9)_GInstead of outside temperature θ_aThe following equation using the above may be applied.
Q = -σ · Φ · {(θ_i+273)^Four− (Θ_a+273)^Four} ... (16)
However,
Q: The amount of heat taken from the slab surface (with a minus sign)
σ: Stefan Boltzmann constant,
Φ: Overall heat absorption rate
θ_a:Outside air temperature,
θ_i: Slab surface temperature
It is.
[0045]
That is, using the equations (8), (9), (15), and (16), the slab temperature can be calculated from the time determined by the continuous casting speed, that is, the time from the molten steel to the time when the slab enters the furnace. The initial temperature can be calculated. Thus, if the number of slab divisions is the same in a continuous model from the continuous casting equipment to the heating furnace, accurate temperature calculation can be performed. If the steel grade, continuous casting speed, thickness, etc. are the same conditions, the temperature calculation by the furnace charging material initial temperature calculation device 13 of the present embodiment may be calculated once and applied to the initial temperature of the slab under the same conditions. it can.
[0046]
Next, the set furnace temperature storage device 15 and the furnace temperature setting timing calculation device 16 will be described.
The furnace temperature calculated by the set furnace temperature calculation device 14 can be calculated in advance before the slab enters the heating furnace. Usually, the continuous casting speed, the thickness of the slab, etc. are constant, and the length of the slab to be cut by the shear is known in advance in the rolling plan, so that it can be calculated before the slab enters the heating furnace.
[0047]
The set furnace temperature storage device 15 is a device that stores and outputs the furnace temperature calculated by the set furnace temperature calculation device 14. The stored furnace temperature is activated by the furnace temperature setting timing arithmetic unit 16 described below and set in the actual furnace temperature control device 4.
[0048]
On the other hand, the furnace temperature setting timing arithmetic unit 16 is an apparatus provided for considering the response time of the heating furnace, and this apparatus will be described with reference to FIG.
When the furnace temperature setting value is changed, the furnace temperature does not change instantaneously and responds with a certain response time. Therefore, taking the case where the tail end of the slab is charged into the heating furnace as an example, as shown in FIG. 5, the set furnace temperature calculation device at the timing when the tail end of the slab is charged into the heating furnace. 14 is a device that calculates the timing at which the temperature of the heating furnace is achieved to the furnace temperature calculated in 14. The time at which the tail end of the slab is charged into the heating furnace is obtained from the tracking device 11 in advance, and the response time T is considered in consideration of the response time of the heating furnace._RFIt is sufficient to change the set value of the furnace temperature as soon as possible. The response of the heating furnace should have a value measured separately as a table value. Although FIG. 5 shows an example in which the slab is charged into the heating furnace, the setting of the soaking furnace temperature in the soaking time is similarly set in consideration of the response of the heating furnace. Thus, the optimum set furnace temperature obtained by the set furnace temperature calculation device 14 is once stored in the set furnace temperature storage device 15 and activated by the furnace temperature setting timing calculation device 16, and the furnace of each heating zone is set. It is sent to the temperature control device 4, the temperature of each heating zone is controlled, and the slab is heated to the target temperature.
[0049]
The detailed operations of the material heating time calculation device 12, the furnace charging material initial temperature calculation device 13, the set furnace temperature calculation device 14, the set furnace temperature storage device 15, and the furnace temperature setting timing calculation device 16 are combined with the principle thereof. The overall operation shown in FIG. 1 will be described below.
[0050]
The material produced in the continuous casting facility is cut into a predetermined length by the shear 7 to form the slab 6. The slab 6 is charged into the heating furnace 1 by a table roller 8. And while the slab 6 is conveyed with the table roller 8 in the heating furnace 1, it is heated and extracted by target temperature, and is rolled with the rolling mill 9 of a post process. The table roller 8 is controlled by a table control device 10.
[0051]
The material heating time calculation device 12 is a time T for heating the slab 6 to the target average temperature from the in-furnace time of the slab 6 before the slab 6 is charged into the heating furnace 1.₁And soaking time T₂Are calculated from the equations (4) and (5). The material heating time calculation device 12 sends the calculated time to the set furnace temperature calculation device 14 and at the same time, the time signal t for baking the slab shown in FIG._HSend. The tracking device 11 tracks the slab 6 on the line and simultaneously manages the time, and also controls the activation of the table control device 10. The furnace charging material initial temperature calculation device 13 uses the equations (8), (9), (15), (16), and the heating furnace charging material initial temperature before the slab 6 is charged into the heating furnace 1. Is calculated. The calculated heating furnace charging material initial temperature is sent to the set furnace temperature calculation device 14.
[0052]
The set furnace temperature calculation device 14 uses the initial slab temperature and the heating time T calculated by the material heating time calculation device 12.₁And soaking time T₂From the slab extraction target temperature and the soaking condition, the slab temperature calculation model equation using the equations (7) to (9) and the basic equations (10) to (13) of the linear programming were used. Optimum furnace temperature calculation model formula for optimum setting temperature of the heating furnace to save energy (In the heating time, the optimum furnace sound θ in the heating period_G.1In the soaking time, the optimum furnace temperature θ for the soaking period_G.2) Is calculated. The calculated result is sent to and stored in the set furnace temperature storage device 15.
[0053]
The furnace temperature setting timing calculation device 16 is configured to measure the time t when the slab 6 is inserted into the heating furnace 1._inThe timing of sending the furnace temperature set value to the furnace temperature control device 4 is instructed to the set furnace temperature storage device 15 in consideration of the response of the heating furnace 1 before. As a result, at the timing when the tail end of the slab 6 is inserted into the heating furnace 1, the furnace temperature calculated by the material heating time calculation device 12 (optimum furnace temperature θ in the heating period)._G.1The slab 6 is heated to the target average temperature while being moved by the table roller 8 in the heating furnace.
[0054]
Time t when slab 6 is baked_HThen, the tracking device 11 activates the table control device 10 to pass the slab 6 through the heating zone downstream of the heating furnace 1, and the slab 6 is extracted with a specified temperature uniformity and sent to the rolling mill 9. Time t when this slab 6 is baked_HIn the soaking time until extraction from the optimum furnace temperature θ in the soaking period stored in the set furnace temperature storage device 15_G.2Is set to a heating zone corresponding to the position of the slab 6 in the furnace, and the slab 6 is soaked. Optimum furnace temperature θ during this soaking period_G.2In the setting of the furnace temperature, the time t when the slab 6 is baked in consideration of the response of the heating furnace_HIt is sent to the furnace temperature control device 4 earlier. This timing is also managed by the furnace temperature setting timing arithmetic unit 16 as described above. In this way, the slab 6 is extracted at the specified time at the extraction target temperature that satisfies the soaking condition.
[0055]
In this embodiment, when the slab length is long and the slab 6 straddles the first heating zone and the second heating zone, it goes without saying that each furnace temperature of the first heating zone and the second heating zone is used. The same furnace temperature θ_G.1Set to.
[0056]
Thus, according to the first embodiment, the slab can be accurately heated to a temperature suitable for rolling under energy saving, corresponding to the rolling plan based on the rolling production amount.
[0057]
FIG. 6 is a block diagram showing the configuration of the second exemplary embodiment of the present invention. In the figure, the same elements as those in FIG. The second embodiment is a configuration example in the case where a plurality of slabs 6 are present in one heating zone of the heating furnace 1, and the set furnace temperature storage device 15 </ b> A includes the set furnace temperature storage device 15 shown in FIG. 1. In addition to the function, the configuration is different from that shown in FIG. 1 in that a plurality of slabs 6 that are fired in one heating zone have a function of giving the highest set furnace temperature to the furnace temperature control device 4. This is a case where the length of the slab 6 is short as shown in FIG. 7, and when the slab A and the slab B are in the first heating zone, the set furnace temperature storage device 15A has a material heating time calculation. The set furnace temperatures of both the slab A and the slab B calculated by the device 12 are stored. In the set furnace temperature storage device 15A, a stored furnace temperature set value having a high set furnace temperature is selected, sent to the furnace temperature control device 4 in the first heating zone, and the slab existing in the furnace is heated. Since slabs are basically baked to a temperature suitable for rolling, slabs requiring high rolling temperatures are baked, and other slabs are higher than the target temperature, but this is unavoidable. In this way, the set furnace temperature storage device 15A is provided with a function for determining the set furnace temperature, and all the slabs 6 can be baked to a target temperature or higher.
[0058]
Thus, according to the second embodiment, even when a plurality of slabs 6 exist in one heating zone, it corresponds to a rolling plan based on the rolling production amount, and the slab is suitable for rolling under energy saving. The temperature can be accurately heated.
[0059]
FIG. 8 is a block diagram showing the configuration of the third exemplary embodiment of the present invention. In the figure, the same elements as those in FIG. In this embodiment, a furnace entrance-side material thermometer 17 is provided on the material entrance side of the heating furnace 1, and the furnace charge material initial temperature calculation device 13 in FIG. In addition to the function, the configuration of the furnace charging initial temperature is different from that shown in FIG. In the following, the operation of this embodiment will be described with reference to FIG.
[0060]
This embodiment aims to eliminate the error caused by this model when calculating the slab temperature using the model as described above. The black circle ● in FIG. 9 shows the slab temperature distribution by the model. , Calculate the surface temperature calculated by the model₁And The detected value by the furnace entrance side material thermometer 17 is θ_1.DAnd The difference between these surface temperatures Δθ₁= Θ_1.D−θ₁, The temperature of each dividing boundary point calculated by the model is uniformly Δθ₁Only correct as indicated by white circles. This is based on the analysis result that the temperature distribution in the thickness direction of the slab can be expressed by a quadratic curve. As a result, it is possible to increase the accuracy of the initial temperature of the slab in the furnace, and increase the accuracy of the slab temperature calculation calculated by the set furnace temperature calculation device 14.
[0061]
Thus, according to the third embodiment, the accuracy of heating the slab to a temperature suitable for rolling can be improved as compared with the second embodiment.
[0062]
The use of the furnace charge material initial temperature calculation device 13A instead of the furnace charge material initial temperature calculation device 13 is not only applied to the first embodiment shown in FIG. 1, but also shown in FIG. The present invention can also be applied to the second embodiment.
[0063]
FIG. 10 is a block diagram showing the configuration of the fourth exemplary embodiment of the present invention. In the figure, the same elements as those in FIG. In this embodiment, a material thermometer 18 is provided on the outlet side of the heating furnace 1, and a feedback device 19 calculates a difference between an actual measurement value obtained by the material thermometer 18 and an extraction target temperature, and temperature correction that makes this difference zero. The configuration is different from FIG. 8 in that the value is calculated and the set value output from the set furnace temperature storage device 15 is corrected via the adder 20 and added to the furnace temperature control device 4. .
[0064]
Hereinafter, the operation of a portion having a configuration different from that in FIG. 8 will be described.
The first to third embodiments are feedforward control based on temperature prediction. In the case of this feedforward control, the predicted extraction temperature of the slab may not necessarily be the target extraction temperature. Therefore, a material thermometer 18 is installed on the exit side of the heating furnace 1, and the set furnace temperature is corrected using the detected value, so that the extraction temperature of the slab is increased in accuracy.
[0065]
Now, the detected value of the temperature of the slab by the furnace exit side material thermometer 18 is θ_out.DAnd slab extraction target temperature is θ_out.rThen, the difference Δθ_out= Θ_out.r−θ_out.DIs fed back to the set furnace temperature.
Δθ_SET= C · Δθ_out                          ... (17)
Here, C is a coefficient.
In this way, by feeding back a value corresponding to the difference between the actual temperature and the target value, it is possible to increase the accuracy of the extraction temperature of the slab of the succeeding material of the same lot.
[0066]
Thus, according to the fourth embodiment, the accuracy of heating the slab to a temperature suitable for rolling can be improved as compared with the third embodiment.
[0067]
The function of feeding back the amount corresponding to the difference between the temperature detection value of the slab and the extraction target temperature to the set furnace temperature is not limited to the third embodiment, but also applies to the first and second embodiments. Can do.
[0068]
On the other hand, in each of the first to fourth embodiments, the control device of the heating furnace 1 is configured by an independent device, but some or most of the functions of these elements may be given to the computer. Is possible.
[0069]
【The invention's effect】
As is apparent from the above description, according to the present invention, the material can be accurately baked to the target temperature while saving energy based on the rolling plan.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a first embodiment of the present invention.
FIG. 2 is a diagram showing the relationship between the temperature and time of material from the continuous casting equipment to the exit side of the heating furnace in order to explain the operation of the embodiment shown in FIG. 1;
FIG. 3 is a diagram showing the relationship between the heating time and soaking time in the heating furnace and the length of the heating furnace in order to explain the operation of the embodiment shown in FIG. 1;
4 is a diagram showing an example of division in the thickness direction of a slab in a slab temperature model in order to explain the operation of the embodiment shown in FIG. 1; FIG.
FIG. 5 is a diagram showing timing when a furnace temperature is set in order to explain the operation of the embodiment shown in FIG. 1;
FIG. 6 is a block diagram showing a configuration of a second exemplary embodiment of the present invention.
7 is a view showing an example in which two slabs are present in one heating zone of the heating furnace in order to explain the operation of the embodiment shown in FIG. 6;
FIG. 8 is a block diagram showing a configuration of a third exemplary embodiment of the present invention.
FIG. 9 is an explanatory diagram of a method for correcting a temperature calculation result based on a detection value of a slab thermometer in order to explain the operation of the embodiment shown in FIG. 8;
FIG. 10 is a block diagram showing a configuration of a fourth embodiment of the present invention.
FIG. 11 is a layout diagram of a conventional hot strip mill line.
FIG. 12 is a layout diagram of a hot strip mill line to which the present invention is applied.
[Explanation of symbols]
1 Heating furnace
2 Heating zone
3 Burner
4 Furnace temperature control device
5 Furnace thermometer
6 Slab
7 Shah
8 Table roller
9 Rolling mill
10 Table controller
11 Tracking device
12 Material heating time calculation device
13,13A Furnace charging material initial temperature calculation device
14 Setting furnace temperature calculation device
15,15A Set furnace temperature storage device
16 Furnace temperature setting timing calculation device
17 Furnace entry side material thermometer
18 Furnace exit side material thermometer
19 Feedback device
20 Adder

Claims (4)

Extraction temperature of the material when the material cut by the predetermined length after being produced in the continuous casting equipment is passed through the heating furnace while being conveyed by the table roller and extracted from the heating furnace is set in advance. In the control device of the heating furnace that controls the furnace temperature so that
Furnace temperature control means for controlling the temperature of each heating zone provided in the material conveying direction in the heating furnace;
Tracking means for predicting the time when the tail end of the material is charged into the heating furnace and the time when the tip of the material is extracted from the heating furnace;
Table control means for controlling the conveyance of the table roller based on the prediction of the tracking means;
Based on the time at which the tail end of the material is charged into the heating furnace, the time at which the tip of the material is extracted from the heating furnace, and the table speed at which the table roller conveys the material, A material for calculating a heating time for heating the average temperature of the material to the extraction target temperature, and a soaking time for keeping the soaking degree, which is a temperature difference between the surface temperature of the material and the center temperature, within a predetermined temperature. Heating time calculation means;
A furnace charging material initial temperature calculating means for calculating a heating furnace charging initial temperature when the material is charged into the heating furnace using a temperature calculation model of the material;
The heating time and soaking time of the material calculated by the material heating time calculating means, the heating furnace charging initial temperature calculated by the furnace charging material initial temperature calculating means, and the extraction target temperature and extraction of the material A set furnace temperature calculating means for calculating a set furnace temperature of the heating furnace based on a soaking condition at the time,
Set furnace temperature storage means for storing the set furnace temperature calculated by the set furnace temperature calculation means and applied to the furnace temperature control means;
Furnace temperature setting timing calculation means for adding the set furnace temperature stored in the set furnace temperature storage means to the furnace temperature control means at a predetermined timing calculated in consideration of the response time of the heating furnace;
The furnace temperature control means controls the temperature of each heating zone based on the set furnace temperature applied by the furnace temperature setting timing calculation means,
A control apparatus for a heating furnace. When a plurality of materials are present in one heating zone of the heating furnace, the set furnace temperature storage means has a function of setting the furnace temperature of the heating zone to the highest set furnace temperature among the set furnace temperatures for each material. The control apparatus of the heating furnace of Claim 1 added. The thermometer for measuring the material temperature is installed on the material charging side of the heating furnace, and the function of internally correcting the material temperature predicted and calculated by the furnace charging material initial temperature calculating means using the measured value of the thermometer The control apparatus for a heating furnace according to claim 1 or 2, added to the furnace charge material initial temperature calculating means. The thermometer that measures the material temperature on the material extraction side of the heating furnace, and the set furnace temperature applied to the furnace temperature control means are corrected by a value corresponding to the difference between the measured value of the thermometer and the target extraction temperature of the material. The control apparatus of the heating furnace in any one of Claim 1 thru | or 3 further provided with the feedback means to do.

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