JP3645306B2

JP3645306B2 - Electric furnace equipment

Info

Publication number: JP3645306B2
Application number: JP07673995A
Authority: JP
Inventors: 浩之千葉
Original assignee: Nisshin Steel Co Ltd
Current assignee: Nippon Steel Nisshin Co Ltd
Priority date: 1995-03-31
Filing date: 1995-03-31
Publication date: 2005-05-11
Anticipated expiration: 2020-05-11
Also published as: JPH08273826A

Description

【０００１】
【産業上の利用分野】
本発明は、スクラップ、各種合金、鉱石などの金属材料や、各種造滓材、コークスなどの材料からなる原料を装入して溶解または熔融する電気炉に送電すべき電力量について、原料の種類に応じて最適な目標値を予め決定するための電気炉設備に関する。
【０００２】
【従来の技術】
種々の金属材料や金属類や鉱石などの溶解、溶融、精錬または製錬工程、特にステンレス鋼等を含む特殊鋼や高合金鉄などを溶製する製鉄や製鋼工程においては、様々な金属溶解炉や金属溶解・溶融炉や金属製錬炉などが用いられる。このうちの電気炉では、主に屑鉄ヤフェロアロイや鉱石など種々の金属分を含有する主原料と、主に精錬やスラグ塩基度調整用としての造滓材や加炭材や還元材などを含む副原料などからなる原料の溶解または溶融、さらに精錬などに用いられる。現在、使用されている電気炉は、その多くが次第に大型化され、大容量を有し、交流電源または直流電源を用いるアーク加熱式電気炉である。このような電気炉内に、種々の事情や実情に合わせて溶銑や溶鋼などの液状主原料を固体主副原料と抱き合わせて装入することもあるけれども、通常、前述のように、種々の主副原料が配合された固体原料を装入する。電気炉に備えられている電極に通電するとアーク放電が始まり、このアーク放電により発生した熱によってかかる固体原料が溶解または溶融されて種々の金属や合金などの溶湯、溶銑または溶鋼など、すなわち広義の金属溶湯とスラグとが溶解または熔融されて溶製される。そして、溶解または溶融された金属溶湯とスラグとは、適宜精錬され、電気炉本体から次工程へ向けて出湯かつ出滓される。
【０００３】
このようにして用いられる電気炉は、通常、前述のような固体の主副原料の装入から、溶製された金属溶湯とスラグとの出湯および出滓に至るまでの過程を、１つのバッチとして、次々とバッチ処理を繰り返して、連続的に操業される。このような操業形態を採る電気炉においては、近年、特に高能率・高生産性や経済性を重視して、大型化や大容量化が図られている。１回のバッチ処理で極力多量の金属溶湯を出湯可能にしようとしても、固体原料は一般にかさばるので、１回のみでは１バッチ分の処理に必要な全ての原料を電気炉内に装入することができない場合が多い。このような場合は、原料の大半を通電開始前に初期装入し、これがある程度加熱によって溶解または溶融して、そのかさが減少した時点で、残りの必要量の原料を通常１回、あるいは２〜３回程度に分けて追加装入して加熱し、溶解または溶融させる。
【０００４】
現在広く使用されている電気炉には、三相交流を用いるエルー式三相アーク炉などがある。エルー式アーク炉は、炉蓋を通して炉上部から炉内に装入された電極と、炉内に装入されている屑鉄などのスクラップを含む主原料や、石灰などの精錬用や造滓用のスラグ形成に用いる副原料などを含む装入物との間を若干離した状態で、電極に通電する際に発生するアークによる熱によって装入物を溶解・精錬する。金属の溶解速度など電気炉操業の制御は、電極に供給される電力によって行われており、１回のバッチ式操業において電極に供給すべき最適目標総送電量は、最終的に出銑される金属溶湯の予定重量に、たとえば経験的に求められる一定の係数を乗算して演算され決定される。
【０００５】
【発明が解決しようとする課題】
前述のような最適目標総送電量の演算方法では、最適目標総送電量は金属溶湯の予定出銑量だけを基準に決定されており、装入物の変動、たとえば主原料および副原料の種類あるいは装入量の変化などによる装入物の総重量および配合の変化などには無関係に決定されている。しかしながら、多量に繰り返して装入する原料を、毎回同一条件で準備することは極めて困難である。たとえば、スクラップは性状や成分が変動し易く、鉱石は産地によって品位に差が生じる。
【０００６】
装入原料が比較的溶解または溶融しやすい種類や配合であったり、既に溶解または熔融している液状の主原料を含むような場合には、前述のような最適目標送電量を基準として制御すると、供給される電力量が過剰となり、装入物が全て溶解してもなお電極への送電が続けられる。このため、必要以上の電力および時間が消費され、電力ロスを生じる。また炉内温度が必要以上に上昇し、さらに電極から発生するアークが直接炉壁を覆う耐火物などに熱負荷を与えるため、耐火物層など電気炉設備の負荷が増加し、損耗が速く進む。
【０００７】
逆に、装入原料が比較的溶解または溶融しにくい種類や配合であったり、装入原料の総重量が通常よりも多い場合には、前述の最適目標総送電量で制御すると、供給される電力量は不足し、装入原料を充分に溶解することができず、溶け残りを生じる。これによって、目標とする出銑量を確保することができなかったり、精錬不足で石灰や硫黄等の副原料が金属溶湯中に残存したりする。また、出銑しる金属溶湯の成分にバラツキが生じて、目標成分の範囲から外れ、製品の品質が低下する。さらに、再び電力を供給して溶け残った装入原料を溶解あるいは溶融する必要があり、一旦炉蓋を開けてから再加熱するような場合は、熱ロスや時間ロスを生じ、能率や生産性が低下する。さらに原料を配合する工程以後の脱ガス工程あるいは鋳造工程などと電気炉による溶解・精錬工程を組合わせた一連の生産ラインの操業予定を混乱させ、あるいは停滞させることになる。
【０００８】
本発明の目的は、１回の操業において電気炉に供給される最適目標総送電量を過不足なく決定することができ、耐火物の異常損耗や送電量の過不足を生じることのない電気炉設備を提供することである。
【０００９】
【課題を解決するための手段】
本発明は、複数種類の原料を装入し、電極の高さを電流が一定になるように調整しながら溶解させる電気炉設備において、
原料の各種類毎に、重量と、
電気炉の運転パターンであって少なくとも原料の装入期から、順次、電極への通電を開始する点弧期、ボーリング期、湯溜形成期、主溶解期、溶解末期、溶落、昇熱期、出銑に至る溶解および精錬工程を含む運転パターンに対する係数であって溶解しにくい原料ほど大きくなり、装入物の温度の高いときには小さく、前記温度の低いときには大きくなる係数との積を演算し、
演算結果の総和を最適目標総送電量として算出する演算手段と、
電気炉に供給される電力量を計測する計測手段と、
計測手段からの出力に応答して、演算手段が算出する最適目標総送電量に計測値が到達したら操業を停止する制御手段と、
電極に供給される電圧を検出し、前記装入期から、点弧期、ボーリング期、湯溜形成期、主溶解期、溶解末期、溶落、昇熱期、出銑に至る溶解および精錬工程を含む運転パターンから外れるときの電圧であって電極に供給される電圧が低下するとき増加させ、前記電圧が高くなるとき低下させる補正量によって、前記演算手段が算出する最適目標総送電量を補正する補正手段と、
電気炉からの出銑温度を検出する検出手段と、
検出手段からの出力に応答し、出銑温度を予め定める基準温度と比較し、出銑温度と基準温度との偏差が小さくなるように出銑温度が基準温度より高いとき次回の操業において前記補正手段の補正量を減少させ、逆に出銑温度が基準温度より低いときは次回の操業において前記補正手段の補正量を増加させる調整手段を含むことを特徴とする電気炉設備である。
また本発明は、前記演算手段は、ステンレス鋼あるいは高合金鉄を溶製するための諸原料の種類と、原料の装入回数と、出銑量と、出銑される溶鋼の組成と、出銑温度とに応じて、過去の操業実績データから、または溶解試験を行って前記係数を予め設定することを特徴とする。
【００１３】
【作用】
本発明に従えば、複数種類の原料を装入し、電極の高さを電流が一定になるように調整しながら溶解させる電気炉設備内に、原料の重量と、電気炉の運転パターンであって少なくとも原料の装入期から、順次、電極への通電を開始する点弧期、ボーリング期、湯溜形成期、主溶解期、溶解末期、溶落、昇熱期、出銑に至る溶解および精錬工程を含む運転パターンに対する係数であって溶解しにくい原料ほど大きくなり、装入物の温度の高いときには小さく、前記温度の低いときには大きくなる係数との積を各種類毎に演算し、演算結果の総和として最適目標総送電量を算出する演算手段と、電気炉に供給される電力量を計測する計測手段と、計測手段からの出力に応答して、計測値が演算手段が算出する最適目標総送電量に到達したら操業を停止する制御手段と、電極に供給される電圧を検出し、前記装入期から、点弧期、ボーリング期、湯溜形成期、主溶解期、溶解末期、溶落、昇熱期、出銑に至る溶解および精錬工程を含む運転パターンから外れるときの電圧であって電極に供給される電圧が低下するとき増加させ、前記電圧が高くなるとき低下させる補正量によって、前記演算手段が算出する最適目標総送電量を補正する補正手段と、電気炉からの出銑温度を検出する検出手段と、検出手段からの出力に応答し、出銑温度を予め定める基準温度と比較し、出銑温度と基準温度との偏差が小さくなるように出銑温度が基準温度より高いとき次回の操業において前記補正手段の補正量を減少させ、逆に出銑温度が基準温度より低いときは次回の操業において前記補正手段の補正量を増加させる調整手段とを備えるので、原料の溶け残しあるいは電力の供給過剰などを有効に防止することができる。しかも原料の溶け残し、あるいは電力の供給過剰などの不都合の発生をさらに減少させることができる。
【００１５】
また好ましくは、前記演算手段は、ステンレス鋼あるいは高合金鉄などを溶製するための諸原料の種類と、原料の装入回数と、出銑量と、出銑される溶鋼の組成と、出銑温度とに応じて、過去の実績データから、または溶解試験を行って前記係数を予め設定するので、ステンレス鋼あるいは高合金鉄などの製品としての成分割合などの品質を一定に保ち、また各合金に適した係数を決定することができる。
【００１６】
【実施例】
図１は、本発明の一実施例の電気炉設備の簡略化した電気炉構成を示すブロック図である。図２は、図１の電気炉の簡略化した正面断面図である。図３は、図１の電気炉の操業過程を示す工程図である。図４は、金属溶湯の出銑温度と目標温度との差と、供給電力量の補正量との関係を示すグラフである。図５は、電気炉に供給される電力の時間変化を示すグラフである。図６は、図１の実施例の最適目標総送電量演算動作を示すフローチャートである。図７は、装入物温度と係数ｃｉとの関係を示すグラフである。図８は、本発明の他の実施例の最適目標総送電量演算動作を示すフローチャートである。
【００１７】
図１および図２に示すように、電気炉設備は主として電気炉１、電圧調整手段８、電圧測定手段１０、電流測定手段１１、計測手段１２、演算手段１３、補正手段１４、調整手段１６、検出手段１７および制御手段１５を含んで構成される。
【００１８】
電気炉１は、一般に、電極４が昇降手段５によって昇降自由に取付けられた炉蓋２と、作業口および除滓口が設けられる炉壁３ａ、および底吹ノズル３ｃが取付けられる炉床３ｂなどの構成を有する炉本体３とを含む。また、電気炉１内には、各種原料が溶解または溶融して、金属溶湯６およびスラグ７が貯留される。炉本体３内表面は、高温の金属溶湯６およびスラグ７に接するので、耐火物層が設けられている。
【００１９】
電圧調整手段８で電圧を調整された電流は、ケーブル９を介して電極４に供給される。ケーブル９には、電圧測定手段１０および電流測定手段１１が取付けられており、電極４に供給される電流および電圧の値を計測している。電流測定手段１１からの信号は、昇降手段５および計測手段１２に入力される。また、電圧測定手段１０からの信号は、計測測定手段１２および補正手段１４に入力される。
【００２０】
計測手段１２は、電圧測定手段１０および電流測定手段１１から入力された前記電流および電圧の値から、電極に供給された電力量を計測し、制御手段１５に入力する。演算手段１３は、メモリ１３ａを備えている。演算手段１３は、後述するように操業前に予め電極に供給する予定最適目標総送電量および電力供給パターンを演算し、制御手段１５に入力する。補正手段１４は、電圧調整手段１０からの信号あるいは調整手段１６からの信号に応じて最適目標総送電量の補正値を計算し、制御手段１５に入力する。調整手段１６には、測温プローブなどで実現される検出手段１７で検出された金属溶湯６の出銑温度が入力される。調整手段１６では、前記出銑温度と予め定められている目標温度との差が小さくなるように補正手段１４で計算される補正量を調整する。制御手段１５は、計測手段１２、演算手段１３および補正手段１４からの信号に基づき、電圧調整手段８を調整し、また、昇降手段５に電流設定値を入力する。
【００２１】
図１の電気炉１における溶解・精錬工程を図３に示す。装入期ｓ１では、電気炉１の電極４および炉蓋２をそれぞれ上昇・旋回させて、炉本体の上方の空間を何もない状態に開放し、一般にクレーンまたは台車で運搬されるバケットなどで実現される装入手段１８によって炉内に装入物１９を装入する。装入物１９は、主に固体の主副原料であり、かさばるため、１回分のバッチ式操業に必要な装入物１９の全量が初期装入１回だけでは炉内に装入しきれない場合がある。このような場合は、追加装入を１回または２〜３回に分けて行うことで、１回の装入当たりの装入物１９の量を減少させ、装入物１９をある程度溶解させてかさを減少させてから残りの装入物１９を装入する。
【００２２】
点弧期ｓ２では炉蓋２をかぶせて電極４への通電を開始し、装入物１９との間にアークを発生させる。ボーリング期ｓ３から湯溜形成期ｓ４にかけて電極４を徐々に下降させ、電極４と装入物１９との間に流れる電流を一定に保ち、電極４周囲の装入物１９を溶解させ電気炉１に下部金属溶湯６の湯溜を形成する。主溶解期ｓ５では、電極を上下させて電流を一定に保ちつつ、電気炉１内の装入物１９を溶解する。電極に通電している間、電圧測定手段１０および電流測定手段１１によって電極４に供給される電流値および電圧値を検出し、計測手段１２で供給した電力量を計測している。また、主溶解期ｓ５では、電圧測定手段１０で測定した電圧値を検出し、補正手段によって予め定める運転パターンから外れる電圧の変動を用いて最適目標総送電量を補正する場合もある。装入物１９の追加装入を行う場合は、装入物１９のたとえば約８割が溶解した時点で装入期ｓ１に戻り、装入物１９の装入を行う。また、追加装入を行う場合は、既に炉内に金属溶湯６が存在するので、湯溜形成期ｓ４を設ける必要はない。
【００２３】
溶解末期ｓ６では、炉内の装入物１９など固体は、炉壁近辺に少量残るだけとなるため、炉壁へのアークの熱負荷が増大する可能性がある。これを防ぐために、溶解末期ｓ６では、主溶解期ｓ５より電圧を若干低下させ、供給電力量を減少させる。装入物１９が全て溶解した溶落ｓ７を経て、昇熱期ｓ８で炉内に酸素や追加装入する副原料などを供給して、金属溶湯６に含まれる不純物を除去する。昇熱期ｓ８で供給した酸素などと金属溶湯６とが充分に反応した後、計測手段１２で計測した電力量が予め定める最適目標総送電量に達したら、電極４への通電を停止して、取鍋などに対して出銑ｓ９を行う。出銑後、電気炉１への点検および炉修が行われて１回のバッチ式操業が終了する。
【００２４】
出銑された金属溶湯６は、取鍋の表層からスラグなどを除く除滓ｓ１１が行われた後、検出手段１７によって金属溶湯６の出銑温度の測定が行われる。図４に示すように、出銑温度が予め定められた目標温度より高いとき、調整手段１６によって次回の操業において前記補正手段１４の補正量を減少させ、逆に低いときには補正量を増加させるようにしてもよい。金属溶湯６は、その後脱ガス工程あるいは鋳造工程など次工程を行う設備に輸送される。
【００２５】
図５は、図１の実施例を用いて電気炉１に供給される電力供給パターンを示す。図５（１）は、基本的な電力供給パターンである。時刻ｔ０から原料の初期装入を開始する。時刻ｔ１で初期装入を終了し、電極４へ通電して送電を開始する。この後、時刻ｔ１，ｔ２，ｔ３，ｔ４において印加される電圧を段階的に上昇させる。時刻ｔ１からｔ２までの点弧期ｓ２、時刻ｔ２から時刻ｔ３までのボーリング期ｓ３、時刻ｔ３から時刻ｔ４までの湯溜形成期ｓ４、時刻ｔ４から時刻ｔ５までの主溶解期ｓ５の各期では、電極４に供給される電圧は一定に保たれる。供給された電力量が最適目標総送電量に達する時刻ｔ５で、電極への送電を停止して出銑を行う。
【００２６】
図５（２）および図５（３）は、電力供給パターンの他の例である。時刻ｔ１〜ｔ４までは、図５（１）で示す電力供給パターンと同様の挙動を示す。時刻ｔ４から時刻ｔ５までの主溶解期ｓ５では、時刻ｔ６から時刻ｔ７までの間に一時的に電圧を低下、または送電を停止させる。このとき、電圧測定手段１０からの信号に応じて、最適目標総送電量を補正手段１４によって補正してもよい。その後、時刻ｔ７から送電を再開し、補正された最適目標総送電量に達しする時刻ｔ８で電極への送電を停止して出銑を行う。このように、電極への送電を制御することによって、炉内温度などを調整することができる。また、出銑時刻ｔ８を任意の時刻とすることができるので、電気炉によって行う溶解・精錬工程の前後の工程との時間調整を行うこともできる。
【００２７】
図１の実施例の最適目標総送電量演算動作を図６に示す。ステップｎ１で電気炉１に装入される主副原料を構成する、たとえば屑鉄などのスクラップや石灰などの個別原料の種類および各個別原料の重量Ｍｉ（ｉ＝１〜ｎ）など、装入物の配合を読込む。ステップｎ２では、前述の各個別原料に固有の係数ｃｉ（ｉ＝１〜ｎ）をメモリから読込む。前記係数ｃｉは、たとえばステンレス鋼または高合金鉄などを溶製するための個別原料の種類、原料の装入回数、金属溶湯の出銑量と組成、および金属溶湯の出銑温度などに応じて、過去の操業実績データから、または溶解試験などを行って予め決定し、メモリにストアしておく。前記係数ｃｉは、溶解しにくい個別原料に付されたものほど大きくなり、逆に溶融メタルなど固体装入物の溶解を助けるものに付されるものは負の値を取る場合もある。また、この係数ｃｉは図７に示すように、装入物の温度に依存し、装入物の温度の高いときには小さく、また前記温度の低いときには大きくするようにしてもよい。
【００２８】
ステップｎ３では、前記各個別原料の重量Ｍｉおよび前記係数ｃｉを用い、次式から１回のバッチ式操業当り、すなわち１チャージ分の最適目標総送電量Ｗを決定する。重量Ｍｉの単位をＴｏｎとすると、係数ｃｉは電力原単位として算出される。
【００２９】
【数１】

【００３０】
これによって、各個別原料毎に異なる溶解し易さの度合、また各個別原料の量の増減に応じた最適目標総送電量を決定することができる。ステップｎ４では、前記最適目標総送電量Ｗを初期装入後の初装期間、追加装入期間など、電気炉操業の各期間に装入される装入物の重量などに応じ、また、溶解末期および昇熱期などに必要な電力量を計算して分配し、各期間別の予定電力量ｗを決定する。ステップｎ５では、ステップｎ４で計算した前記各期間毎の最適目標総送電量Ｗを、点弧期、ボーリング期などの前記期間内の各期毎に必要な電力量に分割する。ステップｎ６では、前記各期毎に必要とされる電圧に応じて供給される電力および通電する時間を計算し、決定する。ステップｎ７では、ステップｎ６で決定された電力および時間から１回の操業に関する電力投入スケジュールを決定する。これによって、装入物の配合に対応して最適な最適目標総送電量を決定することができる。
【００３１】
また図８は、本発明の電力の演算動作の他の実施例である。図８は図７のフローチヤートと類似のものであり、同一のステップには同一の符号を付け、説明は省略する。ステップｎ１ａでは、固体の原料およびスラグなど固体装入物の総重量Ｍｓを読込む。あるいは、個別装入物のうち、固体であるもの重量Ｍｉの総和を計算して総重量Ｍｓを求めてもよい。ステップｎ２ａでは、予め決定されメモリにストアされている一定の係数Ｃを読込む。ステップｎ３では、前記固体装入物の総重量Ｍｓと係数Ｃとを用い、次式から１チャージ当りの最適目標総送電量Ｗを計算する。
【００３２】
Ｗ＝Ｍｓ・Ｃ …（２）
ステップｎ４からステップｎ７までは、図７と同様に進む。これによって、総重量に対して最適な最適目標総送電量を決定できる。
【００３３】
前述の他の実施例を用い、前記係数Ｃを４５０〜４９０（ｋＷＨ／Ｔｏｎ・固体原料）として最適目標総送電量を決定し、操業を行ったところ、金属溶湯の予定出銑量に係数を乗算する従来技術を用いて操業を行った場合と比較して、金属溶湯の出銑温度が約２０℃低下し、出銑された金属溶湯当りの電力源単位は、約２５（ｋＷＨ／Ｔｏｎ・メタル）だけ低減することが確認された。また、炉修材の使用量も低減された。原料の溶け残りなどのトラブル回数の増加も見られなかった。
【００３５】
【発明の効果】
本発明によれば、複数種類の原料を装入し、電極の高さを電流が一定になるように調整しながら溶解させる電気炉設備内に、原料の重量と、電気炉の運転パターンであって少なくとも原料の装入期から、順次、電極への通電を開始する点弧期、ボーリング期、湯溜形成期、主溶解期、溶解末期、溶落、昇熱期、出銑に至る溶解および精錬工程を含む運転パターンに対する係数であって溶解しにくい原料ほど大きくなり、装入物の温度の高いときには小さく、前記温度の低いときには大きくなる係数との積を各種類毎に演算し、演算結果の総和として最適目標総送電量を算出する演算手段と、電気炉に供給される電力量を計測する計測手段と、計測手段からの出力に応答して、計測値が演算手段が算出する最適目標総送電量に到達したら操業を停止する制御手段とを備える。好ましくは、前記電気炉設備内に電極に供給される電圧を検出し、前記運転パターンから外れる電圧であって電極に供給される電圧が低下するとき増加させ、前記電圧が高くなるとき低下させる補正量によって、前記演算手段が算出する最適目標総送電量を補正する補正手段または電気炉からの出銑温度を検出する検出手段と、検出手段からの出力に応答し、出銑温度を予め定める基準温度と比較し、出銑温度と基準温度との偏差が小さくなるように出銑温度が基準温度より高いとき次回の操業において前記補正手段の補正量を減少させ、逆に出銑温度が基準温度より低いときは次回の操業において前記補正手段の補正量を増加させる調整手段とを含む。また、前記演算手段は、ステンレス鋼あるいは高合金鉄を溶製するための諸原料の種類と、原料の装入回数と、出銑量と、出銑される溶鋼の組成と、出銑温度とに応じて、過去の操業実績データから、または溶解試験を行って前記係数を予め設定する。これらによって、原料の溶け残しあるいは電力の供給過剰など、電力消費の低減と電気炉操業に関する不都合の発生防止とを図ることができるので、省エネルギとともに操業工程の停滞などを低減することができる。
【図面の簡単な説明】
【図１】本発明の一実施例の電気炉設備の簡略化した電気的構成を示すブロック図である。
【図２】図１の電気炉の簡略化した正面断面図である。
【図３】図１の電気炉の操業過程を示す工程図である。
【図４】金属溶湯の出銑温度と目標温度との差と、供給電力量の補正量との関係を示すグラフである。
【図５】電気炉に供給される電力の時間変化を示すグラフである。
【図６】図１の実施例の最適目標総送電量演算動作を示すフローチャートである。
【図７】装入原料の温度と、係数ｃｉとの関係を示すグラフである。
【図８】本発明の他の実施例の最適目標総送電量演算動作を示すフローチャートである。
【符号の説明】
１電気炉
２炉蓋
３炉本体
４電極
５昇降手段
６金属溶湯
７スラグ
８電圧調整手段
９ケーブル
１０電圧測定手段
１１電流測定手段
１２計測手段
１３演算手段
１４補正手段
１５制御手段
１６調整手段
１７検出手段
１８装入手段
１９装入物[0001]
[Industrial application fields]
The present invention relates to the amount of power to be transmitted to an electric furnace in which raw materials made of metal materials such as scrap, various alloys and ores, various ironmaking materials and coke are charged and melted or melted. about electric furnaces for predetermining the optimum target value in accordance with.
[0002]
[Prior art]
Various metal melting furnaces are used for melting, melting, refining or smelting various metal materials, metals and ores, especially in steelmaking and steelmaking processes where special steel and high alloy iron including stainless steel are melted. And metal melting / melting furnaces and metal smelting furnaces are used. Of these, the electric furnace mainly contains main raw materials containing various metals such as scrap iron YAFERO alloy and ore, and mainly ironmaking, carburizing and reducing materials for refining and slag basicity adjustment. Used for melting or melting raw materials composed of auxiliary raw materials, etc., and for refining. Currently, many of the electric furnaces used are arc-heating electric furnaces that are gradually increased in size, have a large capacity, and use an AC power source or a DC power source. In such an electric furnace, a liquid main raw material such as hot metal or molten steel may be charged in combination with a solid main auxiliary material according to various circumstances and circumstances. A solid material mixed with auxiliary materials is charged. When an electrode provided in the electric furnace is energized, an arc discharge starts, and the solid raw material is melted or melted by the heat generated by the arc discharge, so that molten metals such as various metals and alloys, hot metal or molten steel, etc. The molten metal and slag are melted or melted to be melted. Then, the molten or melted molten metal and slag are appropriately refined and discharged and discharged from the electric furnace main body for the next process.
[0003]
The electric furnace used in this way usually has a single batch of processes from the charging of the solid main auxiliary material as described above to the discharge and discharge of molten metal and slag. As described above, the batch processing is repeated one after another and the operation is continuously performed. In recent years, electric furnaces adopting such an operation form have been increased in size and capacity with an emphasis on high efficiency, high productivity, and economic efficiency. Even if it is possible to discharge a large amount of molten metal as much as possible in one batch process, the solid raw materials are generally bulky, so that all the raw materials required for one batch of processing should be charged into the electric furnace only once. There are many cases where this is not possible. In such a case, most of the raw materials are initially charged before the start of energization, and when this is dissolved or melted to some extent by heating and the bulk is reduced, the remaining necessary amount of raw materials is usually once or twice. Separately add about 3 times, heat and melt or melt.
[0004]
An electric furnace that is widely used at present is an ERU type three-phase arc furnace using a three-phase alternating current. The Eruc type arc furnace is used for the main raw materials including scraps such as scrap iron and the like, and smelting and slagging for lime, etc. The charge is melted and refined by the heat generated by the arc generated when the electrode is energized in a state of being slightly separated from the charge including the auxiliary material used for slag formation. The electric furnace operation such as the melting rate of the metal is controlled by the electric power supplied to the electrode, and the optimum target total transmission amount to be supplied to the electrode in one batch operation is finally output. It is calculated and determined by multiplying the predetermined weight of the molten metal by, for example, a certain coefficient determined empirically.
[0005]
[Problems to be solved by the invention]
In the calculation method of the optimum target total power transmission amount as described above, the optimum target total power transmission amount is determined based only on the expected amount of molten metal, and the fluctuation of the charge, for example, the type of main raw material and auxiliary raw material Alternatively, it is determined regardless of the total weight of the charged material and the change in the composition due to the change in the charged amount. However, it is extremely difficult to prepare raw materials that are repeatedly charged in large quantities under the same conditions each time. For example, the properties and components of scrap are likely to vary, and the quality of ore varies depending on the production area.
[0006]
If the charging raw material is of a type or composition that is relatively easy to dissolve or melt, or if it contains a liquid main raw material that has already been dissolved or melted, control it based on the optimal target power transmission amount as described above. Even if the amount of power supplied becomes excessive and all of the charge is dissolved, power transmission to the electrode is still continued. This consumes more power and time than necessary, causing power loss. In addition, the furnace temperature rises more than necessary, and the arc generated from the electrode directly applies heat load to the refractory that covers the furnace wall, increasing the load on the electric furnace equipment such as the refractory layer, leading to faster wear. .
[0007]
On the other hand, when the charged raw material is of a kind or composition that is relatively difficult to dissolve or melt, or when the total weight of the charged raw material is larger than usual, it is supplied by controlling with the above-mentioned optimum target total power transmission amount. The amount of electric power is insufficient, and the charged raw material cannot be sufficiently dissolved, resulting in undissolved residue. As a result, the target amount of brewing cannot be secured, or auxiliary materials such as lime and sulfur remain in the molten metal due to insufficient refining. In addition, the components of the molten metal that come out vary, deviating from the target component range, and the quality of the product decreases. In addition, it is necessary to supply power again to melt or melt the remaining raw material. If the furnace lid is opened once and then reheated, heat loss and time loss occur, resulting in efficiency and productivity. Decreases. Furthermore, the operation schedule of a series of production lines that combine the degassing process or casting process after the raw material mixing process and the melting and refining process using an electric furnace is disrupted or stagnated.
[0008]
An object of the present invention, once the optimum target total power amount supplied to the electric furnace can be determined without excess or deficiency in the operation, the refractory of the abnormal wear and transmission of it to such electroforming resulting excess or deficiency It is to provide a furnace.
[0009]
[Means for Solving the Problems]
The present invention, in an electric furnace equipment charged with a plurality of types of raw materials, and melted while adjusting the height of the electrode so that the current is constant,
For each type of raw material ,
The operation pattern of the electric furnace, starting from the charging period of the raw materials, and starting the energization of the electrodes in sequence, starting period, boring period, puddle formation period, main melting period, end of melting period, falling, and heating period It is a coefficient for the operation pattern including the melting and refining processes leading to tapping, and it is calculated as the product of the coefficient that increases as the raw material that is difficult to dissolve, decreases when the temperature of the charge is high, and increases when the temperature is low. ,
A calculation means for calculating the sum of the calculation results as the optimum target total transmission amount;
Measuring means for measuring the amount of power supplied to the electric furnace;
In response to the output from the measuring means, a control means for stopping the operation when the measured value reaches the optimum target total power transmission amount calculated by the calculating means ,
The voltage supplied to the electrode is detected, and the melting and refining processes from the charging period to the starting period, the boring period, the hot water pool forming period, the main melting period, the last melting period, the falling, the heating period, and the tapping The optimal target total power transmission amount calculated by the calculation means is corrected by a correction amount that increases when the voltage supplied to the electrode decreases and decreases when the voltage supplied to the electrode decreases. Correction means to
Detection means for detecting the temperature of the tapping from the electric furnace;
In response to the output from the detection means, the output temperature is compared with a predetermined reference temperature, and when the output temperature is higher than the reference temperature so that the deviation between the output temperature and the reference temperature is small, the correction is performed in the next operation. The electric furnace equipment includes an adjusting means for decreasing the correction amount of the means and conversely increasing the correction amount of the correction means in the next operation when the output temperature is lower than the reference temperature .
Further, according to the present invention, the calculation means includes the types of raw materials for melting stainless steel or high alloy iron, the number of raw material charges, the amount of feed, the composition of the molten steel to be fed, According to the soot temperature, the coefficient is set in advance from past operation result data or by performing a dissolution test .
[0013]
[Action]
According to the invention, charged with a plurality of types of raw materials, the height current in an electric furnace equipment to dissolve while adjusting so as to be constant electrode, and the weight of the raw materials, meet the operation pattern of the electric furnace At least from the charging stage of the raw material, the ignition period, the boring period, the sump formation period, the main dissolution period, the end of melting period, the melting, the heating period, as raw material is difficult to dissolve a coefficient against the driving pattern including a refining step increases, small when high temperature charge, calculates the product of the coefficient becomes large when low the temperature for each type, operation An arithmetic means for calculating the optimum target total power transmission amount as the sum of the results, a measuring means for measuring the amount of electric power supplied to the electric furnace, and an optimum that the arithmetic means calculates the measured value in response to the output from the measuring means When it reaches the target total power transmission, And control means for stopping, detects a voltage supplied to the electrode, from the instrumentation Iriki, Tenkoki, boring stage, the basin formative years, mainly lytic phase, dissolving the end, burn through, Noborinetsuki, tapping The voltage calculated when the operation pattern including the melting and refining processes leading to is increased, is increased when the voltage supplied to the electrode is decreased, and is calculated by the correction amount that is decreased when the voltage is increased. A correction means for correcting the target total power transmission amount, a detection means for detecting the output temperature from the electric furnace, and responding to an output from the detection means, comparing the output temperature with a predetermined reference temperature, When the output temperature is higher than the reference temperature so that the deviation from the reference temperature is small, the correction amount of the correction means is decreased in the next operation, and conversely, when the output temperature is lower than the reference temperature, the correction is performed in the next operation. Correction amount of correction means Because and an adjusting means for increasing, it is possible to effectively prevent the raw material of the melt leaving or power supply excess etc.. Moreover, it is possible to further reduce the occurrence of inconveniences such as unmelted raw materials or excessive supply of electric power.
[0015]
Preferably, the calculation means includes various types of raw materials for melting stainless steel or high alloy iron, the number of raw material charges, the amount of feed, the composition of the molten steel to be fed, and the output. Depending on the temperature, the coefficient is set in advance from past performance data or by performing a dissolution test, so the quality of the component ratio as a product such as stainless steel or high alloy iron is kept constant, A suitable coefficient for the alloy can be determined.
[0016]
【Example】
FIG. 1 is a block diagram showing a simplified electric furnace configuration of an electric furnace facility according to an embodiment of the present invention. FIG. 2 is a simplified front cross-sectional view of the electric furnace of FIG. FIG. 3 is a process diagram showing an operation process of the electric furnace of FIG. FIG. 4 is a graph showing the relationship between the difference between the molten metal tapping temperature and the target temperature and the amount of power supply correction. FIG. 5 is a graph showing the time change of the electric power supplied to the electric furnace. FIG. 6 is a flowchart showing the optimum target total power transmission amount calculation operation of the embodiment of FIG. FIG. 7 is a graph showing the relationship between the charge temperature and the coefficient ci. FIG. 8 is a flowchart showing an optimum target total power transmission amount calculation operation according to another embodiment of the present invention.
[0017]
As shown in FIG. 1 and FIG. 2, the electric furnace equipment is mainly composed of an electric furnace 1, a voltage adjusting means 8, a voltage measuring means 10, a current measuring means 11, a measuring means 12, a calculating means 13, a correcting means 14, a adjusting means 16, The detection unit 17 and the control unit 15 are included.
[0018]
In general, the electric furnace 1 includes a furnace lid 2 in which an electrode 4 is mounted freely by a lifting means 5, a furnace wall 3a in which a work port and a removal port are provided, and a hearth 3b in which a bottom blowing nozzle 3c is mounted. And a furnace body 3 having the following structure. In the electric furnace 1, various raw materials are melted or melted, and the molten metal 6 and the slag 7 are stored. Since the inner surface of the furnace body 3 is in contact with the high-temperature molten metal 6 and the slag 7, a refractory layer is provided.
[0019]
The current whose voltage is adjusted by the voltage adjusting means 8 is supplied to the electrode 4 via the cable 9. A voltage measuring means 10 and a current measuring means 11 are attached to the cable 9 to measure the values of current and voltage supplied to the electrode 4. A signal from the current measuring unit 11 is input to the elevating unit 5 and the measuring unit 12. A signal from the voltage measuring unit 10 is input to the measuring / measuring unit 12 and the correcting unit 14.
[0020]
The measuring unit 12 measures the amount of electric power supplied to the electrode from the values of the current and voltage input from the voltage measuring unit 10 and the current measuring unit 11 and inputs them to the control unit 15. The computing means 13 includes a memory 13a. As will be described later, the calculation means 13 calculates the scheduled optimum target total power transmission amount and power supply pattern to be supplied to the electrodes in advance before operation, and inputs them to the control means 15. The correction unit 14 calculates a correction value of the optimum target total power transmission amount according to the signal from the voltage adjustment unit 10 or the signal from the adjustment unit 16 and inputs the correction value to the control unit 15. The adjusting means 16 receives the temperature of the molten metal 6 detected by the detecting means 17 realized by a temperature measuring probe or the like. The adjusting unit 16 adjusts the correction amount calculated by the correcting unit 14 so that the difference between the output temperature and a predetermined target temperature is small. The control unit 15 adjusts the voltage adjusting unit 8 based on signals from the measuring unit 12, the calculating unit 13, and the correcting unit 14, and inputs a current set value to the elevating unit 5.
[0021]
The melting and refining process in the electric furnace 1 of FIG. 1 is shown in FIG. In the charging period s1, the electrode 4 and the furnace lid 2 of the electric furnace 1 are lifted and swung, respectively, to open the space above the furnace body to a state in which there is nothing, and generally with a bucket or the like transported by a crane or a carriage A charge 19 is charged into the furnace by the charging means 18 realized. Since the charge 19 is mainly a solid main auxiliary material and is bulky, the entire amount of the charge 19 required for one batch operation cannot be charged into the furnace by one initial charge. There is a case. In such a case, the additional charging is performed once or in two to three times to reduce the amount of the charge 19 per charge and dissolve the charge 19 to some extent. The remaining charge 19 is charged after the bulk is reduced.
[0022]
In the ignition period s 2, energization of the electrode 4 is started by covering the furnace lid 2, and an arc is generated between the charge 19. The electrode 4 is gradually lowered from the boring period s3 to the puddle formation period s4, the current flowing between the electrode 4 and the charge 19 is kept constant, the charge 19 around the electrode 4 is melted, and the electric furnace 1 A hot water reservoir for the molten metal 6 is formed on the bottom. In the main melting period s5, the charge 19 in the electric furnace 1 is melted while moving the electrodes up and down to keep the current constant. While the electrode is energized, the current value and the voltage value supplied to the electrode 4 are detected by the voltage measuring means 10 and the current measuring means 11, and the amount of power supplied by the measuring means 12 is measured. In the main dissolution period s5, the voltage value measured by the voltage measuring unit 10 may be detected, and the optimum target total power transmission amount may be corrected by using a voltage fluctuation that deviates from a predetermined operation pattern by the correcting unit. When additional charging of the charge 19 is performed, for example, when about 80% of the charge 19 is dissolved, the charge period 19 is returned to and the charge 19 is charged. Moreover, when performing additional charging, since the molten metal 6 already exists in the furnace, it is not necessary to provide the hot water reservoir formation period s4.
[0023]
At the end of melting s6, only a small amount of solid such as the charge 19 in the furnace remains in the vicinity of the furnace wall, so that there is a possibility that the heat load of the arc on the furnace wall increases. In order to prevent this, at the end of dissolution period s6, the voltage is slightly lowered from the main dissolution period s5 to reduce the amount of power supplied. Through the melt s7 in which all of the charge 19 is dissolved, oxygen, secondary raw materials to be additionally charged, etc. are supplied into the furnace in the heating period s8, and impurities contained in the molten metal 6 are removed. After the oxygen supplied in the heat-up period s8 and the molten metal 6 have sufficiently reacted, when the amount of power measured by the measuring means 12 reaches the predetermined optimum total power transmission amount, the power supply to the electrode 4 is stopped. Then, s9 is performed for the ladle. After the tapping, inspection and repair of the electric furnace 1 are performed, and one batch operation is completed.
[0024]
After the molten metal 6 is removed from the surface layer of the ladle to remove the slag and the like, the detection means 17 measures the temperature of the molten metal 6. As shown in FIG. 4, when the output temperature is higher than a predetermined target temperature, the adjustment means 16 decreases the correction amount of the correction means 14 in the next operation, and conversely, when it is low, the correction amount is increased. It may be. The molten metal 6 is then transported to equipment for performing the next process such as a degassing process or a casting process.
[0025]
FIG. 5 shows a power supply pattern supplied to the electric furnace 1 using the embodiment of FIG. FIG. 5 (1) shows a basic power supply pattern. Initial charging of the raw material is started from time t0. At time t1, the initial charging is finished, and the electrode 4 is energized to start power transmission. Thereafter, the voltage applied at times t1, t2, t3, and t4 is increased stepwise. In each period of the ignition period s2 from time t1 to t2, the boring period s3 from time t2 to time t3, the hot water pool formation period s4 from time t3 to time t4, and the main dissolution period s5 from time t4 to time t5 The voltage supplied to the electrode 4 is kept constant. At time t5 when the supplied power reaches the optimum target total power transmission, power transmission to the electrode is stopped and output is performed.
[0026]
FIG. 5 (2) and FIG. 5 (3) are other examples of the power supply pattern. From time t1 to t4, the same behavior as the power supply pattern shown in FIG. In the main dissolution period s5 from time t4 to time t5, the voltage is temporarily reduced or power transmission is stopped from time t6 to time t7. At this time, the optimum target total power transmission amount may be corrected by the correcting unit 14 in accordance with a signal from the voltage measuring unit 10. Thereafter, power transmission is resumed from time t7, and power transmission to the electrode is stopped at time t8 when the corrected optimal target total power transmission amount is reached. Thus, the furnace temperature and the like can be adjusted by controlling the power transmission to the electrodes. In addition, since the tapping time t8 can be set to an arbitrary time, it is possible to adjust the time with the steps before and after the melting and refining step performed by the electric furnace.
[0027]
FIG. 6 shows the optimum target total power transmission amount calculation operation of the embodiment of FIG. Charges that constitute the main and auxiliary materials charged into the electric furnace 1 in step n1, such as the types of individual raw materials such as scrap such as scrap iron and lime, and the weight Mi (i = 1 to n) of each individual raw material Read the recipe. In step n2, the coefficient ci (i = 1 to n) specific to each individual raw material is read from the memory. The coefficient ci depends on, for example, the type of individual raw material for melting stainless steel or high alloy iron, the number of times of raw material charging, the amount and composition of the molten metal, the temperature of the molten metal, etc. Then, it is determined in advance from past operation result data or by performing a dissolution test or the like, and is stored in a memory. The coefficient ci becomes larger as it is attached to an individual raw material that is difficult to dissolve, and conversely, a thing attached to an element that aids dissolution of a solid charge such as molten metal may take a negative value. Further, as shown in FIG. 7, the coefficient ci depends on the temperature of the charge, and may be small when the temperature of the charge is high and large when the temperature is low.
[0028]
In step n3, the optimum target total power transmission amount W for one batch operation, that is, one charge is determined from the following equation using the weight Mi of each individual raw material and the coefficient ci. When the unit of the weight Mi is Ton, the coefficient ci is calculated as a power unit.
[0029]
[Expression 1]

[0030]
As a result, it is possible to determine the optimum target total power transmission amount corresponding to the degree of easiness of dissolution different for each individual raw material and the increase or decrease of the amount of each individual raw material. In step n4, the optimum target total power transmission amount W is dissolved according to the weight of the charge charged in each period of the electric furnace operation, such as the initial charge period after the initial charge and the additional charge period. The amount of electric power necessary for the end period and the heat-up period is calculated and distributed, and the planned electric energy w for each period is determined. In step n5, the optimum target total power transmission amount W for each period calculated in step n4 is divided into electric power required for each period in the period such as the firing period and the boring period. In step n6, the power to be supplied and the energization time are calculated and determined according to the voltage required for each period. In step n7, a power input schedule for one operation is determined from the power and time determined in step n6. As a result, it is possible to determine the optimum optimum target total transmission amount corresponding to the composition of the charge.
[0031]
FIG. 8 shows another embodiment of the power calculation operation of the present invention. FIG. 8 is similar to the flow chart of FIG. 7, and the same steps are denoted by the same reference numerals and description thereof is omitted. In step n1a, the total weight Ms of the solid raw material and the solid charge such as slag is read. Alternatively, the total weight Ms may be obtained by calculating the sum of the weights Mi of the individual charges. In step n2a, a predetermined coefficient C determined in advance and stored in the memory is read. In step n3, the optimum target total power transmission amount W per charge is calculated from the following equation using the total weight Ms of the solid charge and the coefficient C.
[0032]
W = Ms · C (2)
Steps n4 to n7 proceed in the same way as in FIG. Thereby, the optimum target total power transmission amount that is optimal with respect to the total weight can be determined.
[0033]
Using the other examples described above, the optimum target total power transmission amount was determined with the coefficient C set to 450 to 490 (kWH / Ton / solid raw material), and the operation was performed. Compared to the case where the operation is performed using the conventional technique of multiplication, the temperature of the molten metal is reduced by about 20 ° C., and the power source unit per molten metal is about 25 (kWH / Ton · It was confirmed that only metal) was reduced. In addition, the amount of furnace repair material used was reduced. There was no increase in the number of troubles such as unmelted raw materials.
[0035]
【The invention's effect】
According to the present invention, charged with a plurality of types of raw materials, the height current in an electric furnace equipment to dissolve while adjusting so as to be constant electrode, and the weight of the raw materials, meet the operation pattern of the electric furnace At least from the charging stage of the raw material, the ignition period, the boring period, the sump formation period, the main dissolution period, the end of melting period, the melting, the heating period, as raw material is difficult to dissolve a coefficient against the driving pattern including a refining step increases, small when high temperature charge, calculates the product of the coefficient becomes large when low the temperature for each type, operation An arithmetic means for calculating the optimum target total power transmission amount as the sum of the results, a measuring means for measuring the amount of electric power supplied to the electric furnace, and an optimum that the arithmetic means calculates the measured value in response to the output from the measuring means When it reaches the target total power transmission, And a control means for stopping. Preferably, reduced when detecting a voltage supplied to the electrodes in the electric furnace facilities, before increasing when the voltage supplied to a voltage electrode out of the Kiun rolling pattern is reduced, the voltage is increased In response to the output from the correction means for correcting the optimum target total power transmission amount calculated by the calculation means or the output temperature from the electric furnace, and the output from the detection means, the output temperature is set in advance. When the output temperature is higher than the reference temperature so that the deviation between the output temperature and the reference temperature becomes smaller compared to the set reference temperature, the correction amount of the correction means is decreased in the next operation, and conversely the output temperature is Adjusting means for increasing the correction amount of the correcting means in the next operation when the temperature is lower than the reference temperature . In addition, the calculation means includes the types of raw materials for melting stainless steel or high alloy iron, the number of raw material charges, the amount of feed, the composition of the molten steel to be fed, and the temperature of the feed. In accordance with the above, the coefficient is set in advance from past operation result data or by performing a dissolution test . As a result, it is possible to reduce power consumption and prevent inconveniences related to the operation of the electric furnace, such as unmelted raw materials or excessive supply of electric power, so that energy saving and stagnation of the operation process can be reduced.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a simplified electrical configuration of an electric furnace facility according to an embodiment of the present invention.
2 is a simplified front sectional view of the electric furnace of FIG. 1. FIG.
FIG. 3 is a process diagram showing an operation process of the electric furnace of FIG. 1;
FIG. 4 is a graph showing the relationship between the difference between the molten metal tapping temperature and the target temperature and the amount of power supply correction.
FIG. 5 is a graph showing a time change of electric power supplied to the electric furnace.
6 is a flowchart showing an optimum target total transmission amount calculation operation of the embodiment of FIG. 1;
FIG. 7 is a graph showing the relationship between the temperature of the charged raw material and the coefficient ci.
FIG. 8 is a flowchart showing an optimum target total transmission amount calculation operation according to another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Electric furnace 2 Furnace lid 3 Furnace main body 4 Electrode 5 Lifting means 6 Metal melt 7 Slag 8 Voltage adjustment means 9 Cable 10 Voltage measurement means 11 Current measurement means 12 Measurement means 13 Calculation means 14 Correction means 15 Control means 16 Adjustment means 17 Detection Means 18 Charging means 19 Charge

Claims

In an electric furnace facility that charges multiple types of raw materials and melts while adjusting the height of the electrodes so that the current is constant,
For each type of raw material ,
The operation pattern of the electric furnace, at least from the charging period of the raw materials, in order to start the energization to the electrodes, starting period, boring period, puddle formation period, main melting period, end of melting period, falling, heating period It is a coefficient for the operation pattern including the melting and refining processes leading to tapping, and it is calculated as the product of the coefficient that increases as the raw material that is difficult to dissolve, increases when the temperature of the charge is high, and increases when the temperature is low. ,
A calculation means for calculating the sum of the calculation results as the optimum target total transmission amount;
Measuring means for measuring the amount of power supplied to the electric furnace;
In response to the output from the measuring means, the control means for stopping the operation when the measured value reaches the optimum target total power transmission amount calculated by the calculating means ,
The voltage supplied to the electrode is detected, and the melting and refining processes from the charging period to the ignition period, the boring period, the sump formation period, the main melting period, the final melting period, the falling, the heating period, and the tapping The optimal target total power transmission amount calculated by the calculation means is corrected by a correction amount that increases when the voltage supplied to the electrode decreases and decreases when the voltage supplied to the electrode decreases. Correction means to
Detection means for detecting the temperature of the tapping from the electric furnace;
In response to the output from the detection means, the output temperature is compared with a predetermined reference temperature, and when the output temperature is higher than the reference temperature so that the deviation between the output temperature and the reference temperature is small, the correction is performed in the next operation. An electric furnace facility comprising an adjusting means for decreasing the correction amount of the means and conversely increasing the correction amount of the correction means in the next operation when the output temperature is lower than the reference temperature .

The calculation means depends on the types of raw materials for melting stainless steel or high alloy iron, the number of raw material charges, the amount of feed, the composition of the molten steel to be fed, and the feed temperature. The electric furnace equipment according to claim 1 , wherein the coefficient is set in advance from past operation performance data or by performing a dissolution test .