JP3744426B2

JP3744426B2 - Method and apparatus for measuring slag oxidation

Info

Publication number: JP3744426B2
Application number: JP2002006750A
Authority: JP
Inventors: 健加藤木; 幸生寺内; 一治花崎; 正則岩瀬
Original assignee: ヘレウス・エレクトロナイト株式会社
Priority date: 2002-01-15
Filing date: 2002-01-15
Publication date: 2006-02-08
Anticipated expiration: 2022-01-15
Also published as: JP2003207480A

Description

【０００１】
【発明の属する技術分野】
本発明は、精錬工程において溶融金属層の上層に形成されるスラグの酸化度を測定する方法とその装置に関する。
【０００２】
【従来の技術】
鉄鋼精錬においては、溶鋼中に含まれる不純物の成分調整は、溶鋼の上層に形成されるスラグ層の成分制御を通じて行われる。なかでも酸化度の制御は特に重要であり、このためスラグ層を構成するスラグの酸化度を測定する手法の確立が求められている。
【０００３】
酸化度測定としては溶鋼を対象とした酸化度測定が既に周知である。これは固体電解質を用いた酸素センサを搭載したプローブを溶鋼中に投入して前記固体電解質を溶鋼層内に位置づけ、発生した起電力から酸化度を算出するというものである。スラグ層を構成するスラグの酸化度測定を意図するとき、まずこの技術の利用が考えられるが、この技術はそのままでは、スラグの酸化度測定には転用できない。何故なら、スラグ層が溶鋼層に比べて薄いため、固体電解質をスラグ層内に正確に位置づけることが困難であることに加えて、固体電解質を用いて酸化度を算出する場合に不可欠となるスラグ温度を、スラグの腐食性に耐えて測定できる安価な測温素子が見あたらないためである。
【０００４】
このため、従来は、例えば本出願人による特公平７−１５４４９号公報に開示されるように、実操業における転炉の代わりに実験炉を用い、銀などの特定金属を用いて、実験室レベルのスラグ中の酸素分圧を測定し、この測定値から実操業における酸素分圧を推定していた。しかし、実操業環境と実験室環境とは異なるので、その推定にも限界があるうえに、このような測定手法では、測定結果をスラグ改質操作にフィードバックするのに遅れが生じ、変動する炉内状況に対応することができない。
【０００５】
このような状況のなかで本出願人は特開２０００−２１４１２７において、スラグ中の酸化度を迅速に測定でき、測定結果をスラグ改質操作にフィードバックできるスラグの酸化度測定装置を提案している。これはプローブ先端にスラグ捕捉用の空間を設けてこの中に固体電解質を配置した構成であり、その使用方法は、大気中からスラグ層を通過させて溶鋼層にまでプローブ先端を到達させ、溶鋼層に滞在しながらスラグ層通過時に捕捉したスラグを用いて起電力の測定を行い、滞在中の溶鋼層の温度をスラグ温度とみなして、前記起電力からスラグの酸化度を算出するというものである。
【０００６】
【発明が解決しようとする課題】
前記技術により、スラグのオンライン測定が可能となり、測定結果を即座にスラグの改質操作に遅延なく適用できる環境が整ったのであるが、固体電解質を用いているため、コスト低減がはかりにくく、測定頻度を高めてより精密な制御を行ううえでの障害となっていた。本発明は、かかる現況に鑑みてなされたものであり、高価な固体電解質を用いることなく、スラグ中の酸化度を測定する技術を提供せんとするものであり、さらに、測定された酸化度に基づいてスラグ改質を行う際に、投入すべき還元剤や酸化剤の量を決定するために必要となるスラグ厚みを、酸化度測定に用いたプローブの構成を共用して測定できる技術をも提供せんとするものである。
スラグの酸化度測定の重要性は鉄鋼精錬に限定されないことから、本技術の応用範囲は溶融金属一般に及ぶものである。
【０００７】
【課題を解決するための手段】
本発明者は上記課題を解決するにあたって、スラグ層と溶鋼層のそれぞれに電極を接触させた時、これら両電極間に起電力の発生があることに着目した。そして研究の結果、この起電力の大きさがスラグの酸化度と密接なかかわりがあることを見いだし、さらにそのかかわりは、一方が特定されると他方がほぼ特定できる一義的関係にあることも見いだした。そしてその一義的関係は、温度条件に依存しない可能性があることも見いだした。本発明はこれら知見に基づくものである。
【０００８】
上記課題を解決した本発明の測定方法は、スラグ層を通って溶融金属層と大気中との間を昇降するプローブに第１電極を設けるとともに、溶融金属層に通電させて第２電極を設け、スラグ層内に位置づけた前記第１電極と前記第２電極との間で発生する起電力を測定し、この起電力の大きさを、予め別の手段で求めておいたスラグ酸化度と起電力値との相関関係に当てはめて、スラグ酸化度を算出するという方法である。
本発明では、スラグは電解質として機能し、スラグ層と溶鋼層及びこれら両層と接触させた２つの電極とで、事実上の酸素濃淡電池が構成されていると判断される。そのため両電極間で発生する起電力からスラグの酸化度を特定することができる。
【０００９】
この測定方法の原理に基づき構成される測定装置は、スラグ層を通って溶融金属層と大気中との間を昇降するプローブに設けた第１電極と、溶融金属層に電気的に導通させて設けた第２電極、並びに前記第１電極と第２電極間で発生する起電力を測定する起電力測定部とを設けてプローブ側装置を構成する。第２電極は溶融金属層との間を導通状態、即ち電流が流れうる状態となるようにして設けられるが、この箇所に電流が流れるか、否かは、プローブに設けた第１電極の所在によって変わる。
一方、このプローブ側装置が出力する起電力から酸化度を算出する酸化度算出部を備えさせる。この酸化度算出部は、予め別の手段で求めておいたスラグ酸化度と起電力値との相関関係に前記測定された起電力の値を当てはめて酸化度を算出する機能を有している。
このような測定方法及び装置を用いることによってスラグ中の酸化度を、固体電解質を用いることなく測定できるようになる。しかも測定結果は固体電解質を用いたときと同様、迅速に得られるから、測定結果をスラグの改質操作に遅延なくフィードバックすることができる。更に本測定方法による測定結果には温度条件は無視できる可能性が高く、このためスラグの測温が不要となり、従来に比べて格段に装置構成の簡易な酸化度測定装置を提供できる。
【００１０】
酸化度測定の測定結果はスラグの改質操作に利用するが、そのためにはスラグのボリューム（容量）がわかっている必要がある。本発明の第二は、前記酸化度測定用のプローブ構成をスラグ厚みの測定に共用するものである。この酸化度測定とスラグ厚み測定が共に可能な測定方法とその装置は次の内容である。
即ち、スラグ層を通って溶融金属層と大気中との間を昇降するプローブに第１電極を設けるとともに、溶融金属層と通電する第２電極を設け、前記第１電極と前記第２電極との間の電気特性を監視し続ける。そしてその状態が次の三つの状態のうち、いずれの状態にあるかを検知する。その三つの状態とは、導電状態、発電状態および絶縁状態である。導電状態は、第１電極が溶融金属層内に位置して、この第１電極と第２電極との間に溶融金属層が電気的に介在して、その導電性によって前記両電極間を電気的に短絡させている状態である。発電状態とは、第１電極がスラグ層内に位置して、この第１電極と第２電極との間にスラグ層と溶融金属層が電気的に介在して、スラグ層の発電性と溶融金属層の導電性との複合によって前記両電極間に電位差を生じさせている状態である。また絶縁状態とは、第１電極が大気中に位置して、この第１電極と第２電極との間に大気、スラグ層及び溶融金属層が電気的に介在して、大気の絶縁性によって前記両電極間を絶縁している状態である。
そして、導電状態から発電状態に移行する境界位置から溶融金属層とスラグ層との界面位置を、発電状態から絶縁状態に移行する境界位置からスラグ層と大気との界面位置を検出し、これら両界面位置の差からスラグ厚さを算出する。
【００１１】
また、この酸化度算出とスラグ厚み測定との両方を行う測定方法を具体化した装置は、スラグ層を通って溶融金属層と大気中との間を昇降するプローブに設けた第１電極と、溶融金属層に接する導電性容器を接地させて構成した第２電極とを備えさせ、第１電極と第２電極との間で発生する起電力を測定し続ける起電力測定手段とを備えさせ、前記測定された起電力の大きさから特定される第１電極と第２電極との間の電気特性が、導電状態から発電状態に移行する境界位置から溶融金属層とスラグ層との界面位置を、発電状態から絶縁状態に移行する境界位置からスラグ層と大気との界面位置を検出する境界位置とを検出するとともに、これら両境界位置の差からスラグ厚さを算出する厚み算出部とを備えさせる。そして、前記両電極間の電気特性が発電状態であるときに検出された起電力値を、予め別の手段で求めておいたスラグ酸化度と起電力値との相関関係に当てはめて、測定された起電力の大きさに対応するスラグ酸化度を算出する酸化度算出部とを備えさせる。
【００１２】
第２電極は、プローブに設けてもよいが、溶融金属層とスラグ層を収容する容器に導電性を与え、この容器を、を第２電極等することが好ましい。この場合、容器は、操業状態において前記溶融金属層と大地との間に介在して、これら両者間を通電させることになる。
【００１３】
容器を第２電極として用いる場合、容器は操業状態において導電性を有していればよい。例えば鉄製の容器外壁と地金被覆状態である容器内壁とにまたがって地金が付着することにより前記容器の導電性が実現される場合などが実際の形態である。
【００１４】
第２電極をプローブに設けるときには、第１電極がスラグ層内に位置するとき、第２電極が溶融金属層内に位置するような配置関係となるようにする。モールドは、狭義には容器ではないが、溶融金属が満たされるという意味では本発明では容器の一種として取り扱うことができる。
【００１５】
本発明の測定装置はプローブとこのプローブから出力される起電力を外部処理する処理装置とから構成される。プローブの構成は極めて単純であり、先端に第１電極を有し、この第１電極と第２電極との間に発生する起電力を外部へ導出する端子を備えた構成が、その基本的構成である。
【００１６】
【発明の実施の形態】
本発明の測定方法は、溶融金属の上層に形成されるスラグ中の酸化度を測定するものである。以下の説明では、溶鋼を例に挙げて説明するが、溶融金属は鉄に限定されず、銅やアルミなど、その他金属も対象となる。また精錬設備だけでなく、産業廃棄物から金属資源を回収するプラズマ溶融設備なども対象となる。
以下、本発明の詳細を図面に基づき説明する。図１、図２および図３は本発明の測定方法および測定装置の各実施例を示している。図中Ｗは容器、Ｐはプローブ、Ｍは溶鋼層、Ｓはスラグ層、Ａは大気である。ここで容器とは、転炉、タンディッシュ、取鍋、トピード、モールド、プラズマ溶融炉などである。尚、以下の説明では溶鋼層とこれを構成する溶鋼とを共にＭで表記し、またスラグ層とスラグも共にＳで表記し、両者を特に区別しないこととする。またここでは転炉を例に挙げて話を進める。
【００１７】
プローブは耐熱保護管や紙管によって外装されており、自動投入機などにより、スラグ層を通って溶鋼層と大気との間を昇降するようになっている。また、自動投入機にはエンコーダが装備され、その昇降量を計測できるようになっている。プローブＰの先端には第１電極Ｕ１が設けられている。電極の素材に特に限定はない。一方、前記第１電極に対応する第２電極Ｕ２が溶鋼層Ｍの溶鋼に電気的に導通させて設けられる。電気的に導通させる方法はさまざまであり、図１に示すように大地に接地した転炉を通じて通電回路を形成し、転炉内壁を実質上の第２電極Ｕ２とする場合、図２に示すようにプローブＰとは独立した支持部材Ｈの先端に電極を設けて、この電極を溶鋼層Ｍに位置付けて第２電極Ｕ２とする場合、図３に示すように、第１電極Ｕ１をプローブＰの長手方向途中位置に設け、プローブ先端に例えばリング状の第２電極Ｕ２を設けることなどが例示できる。
また溶鋼が収容されている容器が、タンディッシュである場合には、このタンディッシュを第２電極として取り扱うことができる。
また、転炉やタンディッシュなどの容器を第２電極として用いるのではなくプローブ先端に、第１電極と電気的に独立して存在する導電性部材を第２電極として利用することも考慮される。例えば、熱電対保護管やストッパー部材をアルミナグラファイトやジルコニアボライト（ニホウ化ジルコニウム）などの導電性セラミックを用いて製作し、これを第２電極として用いることなどである。
【００１８】
転炉内壁を第２電極Ｕ２として使用する場合、転炉（容器Ｗ）の内壁と外壁とが通電していなければならない。転炉は外壁は鉄製であり内壁は耐火煉瓦製であるため、転炉内外は本来導電状態にはない。しかしながら、操業過程で内壁には地金が付着して全面にわたって被覆状態となっており、さらに転炉を傾動させて行う溶鋼の移し替え操作によって口縁部に地金が付着するので、転炉内外は実質上、導電状態となっている。転炉内壁を第２電極Ｕ２として使用する場合、前記地金による被覆状態が安定していることが絶対の条件である。地金の被覆状態の安定化が困難である場合は、転炉内壁を第２電極とはせず、導電性セラミック製の熱電対保護管やストッパー部材を用いて、これらを第２電極とすべきである。これらは溶融金属層と確実に接触させることができるため、転炉内壁の地金の被覆状態に影響を受けない測定が可能となる。
【００１９】
また図３のように、プローブ長手方向に位置をずらして第１電極Ｕ１と第２電極Ｕ２を設ける場合、第１電極Ｕ１がスラグ層Ｓ内に位置づけられるとき、第２電極Ｕ２は溶鋼層Ｍ内に位置づけられるように両電極の配置関係を設定しておく必要がある。
前記３例のうちでは、図１として示したものが、プローブの構造が簡易になる点や取扱いが容易になる点において優れている。また図２として示すものも、転炉に付着している地金の状態の影響を受けないという点において優れている。
【００２０】
このような測定装置を用いて酸化度を測定するには、第１電極Ｕ１をスラグ層Ｓ内に位置付けた状態で、溶鋼層Ｍ内の溶鋼と電気的に導通する第２電極Ｕ２と前記第１電極Ｕ１との間で発生する起電力を測定し、測定された起電力からスラグの酸化度を算出する。酸化度の算出は、予め別の手段で求めておいたスラグ酸化度と起電力値との相関関係に当てはめることによって行う。この相関関係は、実測データの集積としてのデータテーブルで与えられてもよいし、これらデータを回帰分析して得られる近似式であってもよいし、また理論式であってもよい。またデータを得るための酸化度測定手段としては、固体電解質用いるものや、その他、公知の手段が利用できる。
【００２１】
本発明者の研究によれば、前記起電力の大きさとスラグ中の酸化度とは密接な関係を有している。例えば、スラグ中の主たる酸化物であるＦｅＯと起電力との関係は図６で示したグラフで表現される関係にあり、そこには明らかに相関性があることが理解される。そしてその相関性は比較的単純な近似式で表現できると推測される。尚、他の酸化物（例えばＣａＯ）などをも総合した全酸化物の濃度と起電力との関係も前記ＦｅＯ単独の時と同様の傾向示すことを、本発明者は実験によって確認している。また、本発明者は、異なる温度条件下で、起電力と酸化物の濃度との関係を測定したところ、測定結果は温度環境が変わってもほとんど同じであるという興味深い結果が得られた。この結果から、当該方法による酸化度の測定では、測定環境の温度を無視できる可能性があることを意味している。測定結果が温度環境に依存しないのであれば、温度測定を不要にでき、測定作業の簡素化と測定装置のより一層の簡略化が行なえる。
【００２２】
前記測定方法を実施する装置は、プローブと、このプローブが出力する起電力を処理するための処理装置とから構成される。プローブには少なくとも第１電極が設けられる。第２電極はプローブに設ける場合もあれば、プローブ外に設ける場合もある。起電力を処理するための装置には、第１電極と第２電極間の起電力を測定する起電力測定部と、この起電力値から酸化度を算出する酸化度算出部とを装備させる。これらは専用回路を用いてハードウェア的に構成してもよいし、同様の機能をコンピューターのプログラムによって実現してもよい。
【００２３】
酸化度を測定する目的は、スラグの改質を通じて溶鋼の成分調整を行うことである。したがって、必要となる還元剤や酸化剤の投入量を決定するには、スラグ層の厚みを測定してスラグ層のボリューム（容量）を知る必要がある。本発明ではその応用形態として、酸化度の測定に加えてスラグ厚みも算出できる方法と装置を提案する。この装置はプローブ側の装置構成を複雑化することなく実現するものであり、実用に適した装置である。
この装置を用いた測定では、プローブ側構成は基本的に前述の酸化度測定に用いたプローブと同じものを用いることができ、何ら新たな構造の付加を必要としない。その測定方法は、スラグ層Ｓを通って溶鋼層Ｍと大気Ａとの間をプローブＰを上昇又は下降させ、これら異種媒質間を移動する第１電極Ｕ１と、常に溶鋼層Ｍに電気的に導通して配置された第２電極Ｕ２との間で発生する起電力の変化を監視し、起電力が質的に変化する位置をとらえて、これを異種媒質の界面と判断するものである。起電力の質的変化とは電気的な異種状態への移行を指し、具体的には、導電状態、発電状態及び絶縁状態相互間の移行である。
【００２４】
図面に即して説明すると、例えば、図４に示すように第１電極Ｕ１が溶鋼層Ｍ中にあるプローブＰを、スラグ層Ｓを通って大気Ａ中へと引き上げる場合、第１電極Ｕ１と第２電極である容器Ｗとの間に発生する起電力波形は図５に示すように、最初ゼロ電位にあったものがｔ１で立ち上がってＶｓの正電位をもつようになり、次いでｔ２で立ち下がってマイナス無限大を示すようになる。これらは導電状態、発電状態および絶縁状態と表現できる。導電状態は、溶鋼層中に滞在する第１電極Ｕ１と容器Ｗである第２電極との間に溶鋼Ｍが直接介在して両電極間に導電性を与える状態である。また発電状態は、スラグ層中に滞在する第１電極Ｕ１と第２電極との間にスラグ層Ｓと溶鋼層Ｍとが介在し、電解質であるスラグ層Ｓの発電性によって両電極間に発電性を与える状態である。更に絶縁状態は、大気Ａ中に滞在する第１電極Ｕ１と第２電極との間に大気Ａ、スラグ層Ｓ及び溶鋼層Ｍとが介在し、大気Ａの存在により両電極間に絶縁性が与えられた状態である。そしてこれら電気的状態が異なる状態相互間の境界位置が界面位置を示していることになる。即ちｔ１が溶鋼層とスラグ層との界面であり、ｔ２がスラグ層と大気の界面である。
【００２５】
このようにプローブを上昇させながら起電力の変化を監視し、電気的状態の質的変化があった境界位置を検知して異相間の界面位置を特定する。界面位置が特定されればこれら両者間の距離差からスラグ厚みが算出できる。距離差の検出はプローブの昇降装置にエンコーダを取り付ける等して検出すればよい。尚、ここでは、プローブを上昇させながら起電力の変化を監視したが、プローブを下降させながら起電力を監視してもよい。その場合は、スラグ層通過後に溶鋼層に到達することになるので、スラグ層通過時に付着したスラグが第１電極を被覆して第１電極と溶鋼との接触との障害となることを避ける工夫しなければならない。
【００２６】
このスラグ厚みの測定方法を実施する測定装置は、プローブ側の構成は酸化度測定装置に用いるプローブがそのまま利用でき、プローブが出力する信号処理する装置側に、新たな処理部を付加するだけでよい。この処理部には、第１電極と第２電極間で発生起電力を測定し続ける起電力測定部の機能と、両電極間の電気的状態を検知する機能と、前記電気的状態間の移行に関する情報からスラグ厚みを算出する機能とを備えさせるものである。スラグ厚みの算出は、先ず、発電状態及び絶縁状態のいずれであるかを検知し、かつこれら状態間移行における境界位置を検出して界面位置を特定し、さらに最初の界面位置と次の界面位置との距離差からスラグ厚みを求めるようにする。これらは専用回路を用いたハードウェア構成で実現してもよいし、コンピュータープログラムを用いてソフトウェア的に実現してもよい。
【００２７】
このスラグの厚み測定方法は酸化度測定と一体的に取り扱うことができる。即ち、プローブを溶鋼層内から引上げながら起電力を監視し続け、両電極間の電気的状態が発電状態となれば、その起電力の大きさからスラグの酸化度を求め、両電極間の電気的状態が前記発電状態から絶縁状態となるまでの距離を測ってスラグ厚みを特定するというものである。
このような手順に従えば、第１電極の滞在位置がリアルタイムに把握することができるので、第１電極がスラグ層内に位置していることを確認したうえ酸化度の測定を行うことができるので、酸化度測定を確実に行うことができるようになる。またスラグ層の厚みがわかるから、酸化度の測定結果に基づいてスラグ改質を図る場合、還元剤や酸化剤などの必要量も知ることができる。
【００２８】
【発明の効果】
本発明の酸化度測定方法及びその装置は、スラグ層に位置づけた第１電極と溶鋼層と電気的に導通させた第２電極との間の起電力を測定して、その起電力値を、予め別の手段で求めておいた酸化度と起電力との相関関係に当てはめてスラグの酸化度を算出することとしたから、高価な固体電解質を用いた酸素センサを必要とせず、しかも消耗品であるプローブの構造は極めて単純なものにできるから、測定コストの大幅な削減が図れ、多頻度の測定を行なえる経済的環境が整うことになる。また本発明方法による酸化度の測定には温度環境は影響しないと考えられることから、測温素子を不要にできる可能性がある。
【００２９】
請求項２又は７に係る発明のように、プローブを上昇または下降させて起電力の変化を検出し、その電気的状態が変わる境界位置から界面位置を特定し、さらにこのようにして特定された溶鋼レベルとスラグレベルの差からスラグ厚みを算出するようにした場合には、当該スラグ厚みの測定を行う中で酸化度測定を一緒に行うことができるので、第１電極がスラグ層に位置づけられたことを確認して酸化度の測定を行うことができるようになる。またスラグ厚みがわかることで、算出された酸化度に基づいてスラグ改質を行うための還元剤や酸化剤の投入量を算出することができる。
【００３０】
請求項３に係る発明のように、容器を実質的に第２電極として機能させたときには、プローブに設ける電極数が減るので、プローブの構造が簡単になるとともに、プローブから引き出す配線も単純化できる。
【図面の簡単な説明】
【図１】容器を第２電極とした実施例を示す説明図。
【図２】プローブとは独立した第２電極を設けた実施例を示す説明図。
【図３】プローブの長手方向途中部に第２電極を設けた実施例を示す説明図。
【図４】プローブを溶鋼層内から大気中へと引き上げる過程で各層に滞在するプローブを表した説明図。
【図５】プローブの上昇に伴って変化する起電力の大きさを示す説明図
【図６】スラグ中の代表的酸化物であるFeO濃度と起電力の出力電圧との関係を示すグラフ
【符号の説明】
Ａ大気
Ｓスラグ層（スラグ）
Ｍ溶鋼層（溶鋼）
Ｐプローブ
Ｗ容器
Ｈ支持部材
Ｕ１第１電極
Ｕ２第２電極[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and apparatus for measuring the degree of oxidation of slag formed on an upper layer of a molten metal layer in a refining process.
[0002]
[Prior art]
In steel refining, the component adjustment of impurities contained in molten steel is performed through component control of a slag layer formed in the upper layer of the molten steel. In particular, control of the degree of oxidation is particularly important, and therefore, establishment of a method for measuring the degree of oxidation of slag constituting the slag layer is required.
[0003]
As the degree of oxidation measurement, the degree of oxidation measurement for molten steel is already well known. In this method, a probe equipped with an oxygen sensor using a solid electrolyte is introduced into molten steel, the solid electrolyte is positioned in the molten steel layer, and the degree of oxidation is calculated from the generated electromotive force. When the measurement of the oxidation degree of the slag constituting the slag layer is intended, the use of this technique can be considered first, but this technique cannot be diverted to the measurement of the oxidation degree of slag. This is because the slag layer is thinner than the molten steel layer, making it difficult to accurately position the solid electrolyte within the slag layer. In addition, slag is indispensable when calculating the oxidation degree using the solid electrolyte. This is because there is no inexpensive temperature measuring element that can measure the temperature withstanding the corrosiveness of the slag.
[0004]
For this reason, conventionally, for example, as disclosed in Japanese Patent Publication No. 7-15449 by the present applicant, a laboratory furnace is used instead of a converter in actual operation, and a specific metal such as silver is used at a laboratory level. The partial pressure of oxygen in the slag was measured, and the partial pressure of oxygen in actual operation was estimated from this measured value. However, since the actual operating environment is different from the laboratory environment, there is a limit to the estimation, and in such a measurement method, there is a delay in feeding back the measurement result to the slag reforming operation, and the fluctuating furnace It is not possible to respond to the internal situation.
[0005]
Under such circumstances, the present applicant has proposed in Japanese Patent Application Laid-Open No. 2000-214127 a slag oxidation degree measuring apparatus capable of quickly measuring the oxidation degree in slag and feeding back the measurement result to the slag reforming operation. . This is a configuration in which a space for capturing slag is provided at the tip of the probe and a solid electrolyte is disposed therein. The method of use is to allow the probe tip to reach the molten steel layer through the slag layer from the atmosphere. The electromotive force is measured using the slag captured when passing through the slag layer while staying in the layer, the temperature of the molten steel layer during stay is regarded as the slag temperature, and the slag oxidation degree is calculated from the electromotive force. is there.
[0006]
[Problems to be solved by the invention]
The above technology enables online measurement of slag, and the environment has been set up so that measurement results can be immediately applied to the slag reforming operation without delay. However, since a solid electrolyte is used, it is difficult to achieve cost reduction and measurement. It was an obstacle to higher frequency and more precise control. The present invention has been made in view of the present situation, and aims to provide a technique for measuring the degree of oxidation in slag without using an expensive solid electrolyte. The technology that can measure the slag thickness necessary to determine the amount of reducing agent and oxidant to be added when performing slag reforming based on the configuration of the probe used for measuring the degree of oxidation. It is to be provided.
Since the importance of measuring the oxidation degree of slag is not limited to steel refining, the scope of application of this technology extends to molten metal in general.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present inventor has paid attention to the fact that when an electrode is brought into contact with each of the slag layer and the molten steel layer, an electromotive force is generated between these electrodes. As a result of research, we have found that the magnitude of this electromotive force is closely related to the degree of oxidation of slag, and that it is also found that there is an unambiguous relationship in which one can be specified and the other can be specified. It was. It was also found that the unambiguous relationship may not depend on temperature conditions. The present invention is based on these findings.
[0008]
In the measuring method of the present invention that has solved the above problems, the first electrode is provided on the probe that moves up and down between the molten metal layer and the atmosphere through the slag layer, and the second electrode is provided by energizing the molten metal layer. The electromotive force generated between the first electrode and the second electrode positioned in the slag layer is measured, and the magnitude of the electromotive force is determined in advance by another means and the slag oxidation degree and the electromotive force. This is a method of calculating the degree of slag oxidation by applying the correlation with the power value.
In the present invention, the slag functions as an electrolyte, and it is determined that the slag layer, the molten steel layer, and the two electrodes brought into contact with both layers constitute a practical oxygen concentration cell. Therefore, the oxidation degree of slag can be specified from the electromotive force generated between both electrodes.
[0009]
The measuring device configured based on the principle of this measuring method is configured to electrically connect the molten metal layer with a first electrode provided on a probe that moves up and down between the molten metal layer and the atmosphere through the slag layer. The probe-side device is configured by providing the provided second electrode and an electromotive force measuring unit that measures an electromotive force generated between the first electrode and the second electrode. The second electrode is provided so as to be in a conductive state with the molten metal layer, that is, a state in which a current can flow. Whether or not a current flows in this portion depends on the location of the first electrode provided in the probe. It depends on.
On the other hand, an oxidation degree calculation unit for calculating the oxidation degree from the electromotive force output from the probe side device is provided. The oxidation degree calculation unit has a function of calculating the oxidation degree by applying the measured electromotive force value to the correlation between the slag oxidation degree and the electromotive force value obtained in advance by another means. .
By using such a measuring method and apparatus, the degree of oxidation in the slag can be measured without using a solid electrolyte. Moreover, since the measurement result can be obtained quickly as in the case of using the solid electrolyte, the measurement result can be fed back to the slag reforming operation without delay. Furthermore, it is highly possible that the temperature condition is negligible in the measurement result obtained by this measurement method, so that it is not necessary to measure the temperature of the slag, and it is possible to provide a device for measuring the degree of oxidation that is much simpler than the prior art.
[0010]
The measurement result of the degree of oxidation measurement is used for the slag reforming operation. For this purpose, it is necessary to know the volume (capacity) of the slag. In the second aspect of the present invention, the probe configuration for measuring the degree of oxidation is commonly used for measuring the slag thickness. The measuring method and apparatus capable of both measuring the degree of oxidation and measuring the slag thickness are as follows.
That is, the first electrode is provided on the probe that moves up and down between the molten metal layer and the atmosphere through the slag layer, and the second electrode that is energized with the molten metal layer is provided, and the first electrode and the second electrode Continue to monitor the electrical characteristics during. Then, it is detected which state is one of the following three states. The three states are a conductive state, a power generation state, and an insulation state. In the conductive state, the first electrode is located in the molten metal layer, and the molten metal layer is electrically interposed between the first electrode and the second electrode, and the conductivity between the electrodes is electrically connected. Is in a state of being short-circuited. In the power generation state, the first electrode is located in the slag layer, and the slag layer and the molten metal layer are electrically interposed between the first electrode and the second electrode, so that the power generation property and melting of the slag layer are achieved. This is a state in which a potential difference is generated between the electrodes due to the combination with the conductivity of the metal layer. The insulation state means that the first electrode is located in the atmosphere, and the atmosphere, the slag layer and the molten metal layer are electrically interposed between the first electrode and the second electrode. The two electrodes are insulated from each other.
Then, the interface position between the molten metal layer and the slag layer is detected from the boundary position where the conductive state shifts to the power generation state, and the interface position between the slag layer and the atmosphere is detected from the boundary position where the power generation state shifts to the insulation state. The slag thickness is calculated from the difference in interface position.
[0011]
Further, an apparatus embodying a measurement method for performing both the degree of oxidation calculation and the slag thickness measurement includes a first electrode provided on a probe that moves up and down between the molten metal layer and the atmosphere through the slag layer, A second electrode configured by grounding a conductive container that is in contact with the molten metal layer, and an electromotive force measuring unit that continues to measure an electromotive force generated between the first electrode and the second electrode, The electrical characteristics between the first electrode and the second electrode specified from the measured magnitude of electromotive force indicate the interface position between the molten metal layer and the slag layer from the boundary position where the state transitions from the conductive state to the power generation state. A thickness calculating unit for detecting a boundary position for detecting an interface position between the slag layer and the atmosphere from a boundary position for transition from the power generation state to the insulating state, and calculating a slag thickness from a difference between the two boundary positions. Let Then, the electromotive force value detected when the electrical characteristics between the electrodes are in the power generation state is measured by applying the correlation between the slag oxidation degree and the electromotive force value obtained in advance by another means. An oxidization degree calculating unit for calculating the slag oxidation degree corresponding to the magnitude of the electromotive force.
[0012]
The second electrode may be provided on the probe, but it is preferable to provide conductivity to a container that accommodates the molten metal layer and the slag layer, and this container is used as the second electrode or the like. In this case, the container is interposed between the molten metal layer and the ground in an operating state, and energizes between them.
[0013]
When using a container as a 2nd electrode, the container should just have electroconductivity in an operating state. For example, the case where the conductivity of the container is realized by the adhesion of the metal over the outer wall of the iron container and the inner wall of the container that is covered with the metal is an actual form.
[0014]
When the second electrode is provided on the probe, it is arranged such that when the first electrode is located in the slag layer, the second electrode is located in the molten metal layer. The mold is not a container in a narrow sense, but can be handled as a kind of container in the present invention in the sense that the molten metal is filled.
[0015]
The measuring apparatus according to the present invention includes a probe and a processing device that externally processes an electromotive force output from the probe. The structure of the probe is very simple, and the basic structure is a structure having a first electrode at the tip and a terminal for deriving an electromotive force generated between the first electrode and the second electrode to the outside. It is.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The measuring method of this invention measures the oxidation degree in the slag formed in the upper layer of a molten metal. In the following description, molten steel will be described as an example, but the molten metal is not limited to iron, and other metals such as copper and aluminum are also targeted. In addition to refining facilities, plasma melting facilities that recover metal resources from industrial waste are also targeted.
Hereinafter, the details of the present invention will be described with reference to the drawings. 1, 2 and 3 show embodiments of the measuring method and measuring apparatus of the present invention. In the figure, W is a container, P is a probe, M is a molten steel layer, S is a slag layer, and A is the atmosphere. Here, the container is a converter, tundish, ladle, topped, mold, plasma melting furnace or the like. In the following description, both the molten steel layer and the molten steel constituting this are denoted by M, and both the slag layer and slag are denoted by S, and the two are not particularly distinguished. Also, here we will talk about a converter.
[0017]
The probe is covered with a heat-resistant protective tube and a paper tube, and is moved up and down between the molten steel layer and the atmosphere through the slag layer by an automatic charging machine or the like. Also, the automatic feeder is equipped with an encoder so that the amount of elevation can be measured. A first electrode U1 is provided at the tip of the probe P. There is no particular limitation on the electrode material. On the other hand, the second electrode U2 corresponding to the first electrode is provided in electrical conduction with the molten steel of the molten steel layer M. As shown in FIG. 2, there are various methods for electrical conduction. In the case where an energization circuit is formed through a converter grounded to the ground as shown in FIG. 1 and the inner wall of the converter is substantially the second electrode U 2, as shown in FIG. When an electrode is provided at the tip of the support member H independent of the probe P, and this electrode is positioned on the molten steel layer M to serve as the second electrode U2, the first electrode U1 is connected to the probe P as shown in FIG. For example, the ring-shaped second electrode U2 may be provided at a position in the middle of the longitudinal direction and the probe tip may be provided.
Moreover, when the container in which the molten steel is accommodated is a tundish, this tundish can be handled as the second electrode.
In addition, it is also considered to use a conductive member that exists electrically independent of the first electrode at the probe tip as the second electrode, instead of using a container such as a converter or tundish as the second electrode. . For example, a thermocouple protective tube and a stopper member are manufactured using a conductive ceramic such as alumina graphite or zirconia bolite (zirconium diboride), and this is used as the second electrode.
[0018]
When the converter inner wall is used as the second electrode U2, the inner wall and the outer wall of the converter (container W) must be energized. Since the converter has an outer wall made of iron and an inner wall made of refractory brick, the inside and outside of the converter are not inherently conductive. However, in the operation process, the inner wall adheres to the inner wall and is covered over the entire surface, and further, the ingot is attached to the rim by the transfer operation of the molten steel performed by tilting the converter. The inside and outside are substantially conductive. When the converter inner wall is used as the second electrode U2, it is an absolute condition that the covering state with the metal is stable. When it is difficult to stabilize the covering state of the metal bar, the inner wall of the converter is not used as the second electrode, and a thermocouple protective tube made of conductive ceramic or a stopper member is used as the second electrode. Should. Since these can be reliably brought into contact with the molten metal layer, the measurement can be performed without being affected by the covering state of the metal on the converter inner wall.
[0019]
Further, as shown in FIG. 3, when the first electrode U1 and the second electrode U2 are provided by shifting the position in the probe longitudinal direction, when the first electrode U1 is positioned in the slag layer S, the second electrode U2 is the molten steel layer M. It is necessary to set the arrangement relationship of both electrodes so that they can be positioned within.
Among the three examples, the one shown in FIG. 1 is excellent in that the structure of the probe is simple and the handling is easy. Moreover, what is shown as FIG. 2 is excellent in the point that it is not influenced by the state of the metal which has adhered to the converter.
[0020]
In order to measure the degree of oxidation using such a measuring device, the first electrode U1 is positioned in the slag layer S, and the second electrode U2 electrically connected to the molten steel in the molten steel layer M The electromotive force generated between one electrode U1 is measured, and the slag oxidation degree is calculated from the measured electromotive force. The degree of oxidation is calculated by applying the correlation between the degree of slag oxidation obtained in advance by another means and the electromotive force value. This correlation may be given by a data table as an accumulation of actually measured data, an approximate expression obtained by regression analysis of these data, or a theoretical expression. In addition, as means for measuring the degree of oxidation for obtaining data, those using a solid electrolyte and other known means can be used.
[0021]
According to the inventor's research, the magnitude of the electromotive force and the degree of oxidation in the slag have a close relationship. For example, it is understood that the relationship between FeO, which is the main oxide in slag, and the electromotive force is in the relationship represented by the graph shown in FIG. 6, and there is a clear correlation therewith. And it is estimated that the correlation can be expressed by a relatively simple approximate expression. In addition, the present inventor has confirmed through experiments that the relationship between the concentration of all oxides including other oxides (for example, CaO) and the electromotive force also shows the same tendency as in the case of FeO alone. . The inventor measured the relationship between the electromotive force and the oxide concentration under different temperature conditions, and obtained an interesting result that the measurement result was almost the same even when the temperature environment changed. From this result, the measurement of the degree of oxidation by the method means that the temperature of the measurement environment may be negligible. If the measurement result does not depend on the temperature environment, the temperature measurement can be eliminated, and the measurement work can be simplified and the measurement apparatus can be further simplified.
[0022]
An apparatus for performing the measurement method includes a probe and a processing apparatus for processing an electromotive force output from the probe. The probe is provided with at least a first electrode. The second electrode may be provided on the probe or may be provided outside the probe. An apparatus for processing an electromotive force is equipped with an electromotive force measurement unit that measures an electromotive force between the first electrode and the second electrode, and an oxidation degree calculation unit that calculates an oxidation degree from the electromotive force value. These may be configured by hardware using a dedicated circuit, or similar functions may be realized by a computer program.
[0023]
The purpose of measuring the degree of oxidation is to adjust the composition of the molten steel through slag reforming. Therefore, in order to determine the required amount of reducing agent or oxidizing agent, it is necessary to measure the thickness of the slag layer by measuring the thickness of the slag layer. The present invention proposes a method and apparatus capable of calculating the slag thickness in addition to the measurement of the degree of oxidation as an application form thereof. This device can be realized without complicating the device configuration on the probe side, and is a device suitable for practical use.
In the measurement using this apparatus, the same structure as the probe used for the above-described oxidation degree measurement can be basically used for the probe side configuration, and no additional structure is required. The measuring method is that the probe P is raised or lowered between the molten steel layer M and the atmosphere A through the slag layer S, and the first electrode U1 moving between these different media is always electrically connected to the molten steel layer M. A change in electromotive force generated between the second electrode U2 arranged in conduction is monitored, a position where the electromotive force changes qualitatively is determined, and this is determined as an interface of a different medium. The qualitative change of electromotive force refers to a transition to an electrical heterogeneous state, specifically, a transition between a conductive state, a power generation state, and an insulating state.
[0024]
For example, when the probe P having the first electrode U1 in the molten steel layer M as shown in FIG. 4 is pulled up into the atmosphere A through the slag layer S, as shown in FIG. As shown in FIG. 5, the electromotive force waveform generated between the second electrode and the container W rises at t1 to have a positive potential of Vs, and then rises at t2. It goes down and shows minus infinity. These can be expressed as a conductive state, a power generation state, and an insulation state. The conductive state is a state in which the molten steel M is directly interposed between the first electrode U1 staying in the molten steel layer and the second electrode which is the container W to provide conductivity between the two electrodes. Further, the power generation state is that the slag layer S and the molten steel layer M are interposed between the first electrode U1 and the second electrode staying in the slag layer, and the power generation between the two electrodes is caused by the power generation property of the slag layer S that is an electrolyte. It is a state that gives sex. Further, the insulation state is that the atmosphere A, the slag layer S and the molten steel layer M are interposed between the first electrode U1 and the second electrode staying in the atmosphere A, and the insulation between the two electrodes due to the presence of the atmosphere A. It is a given state. The boundary position between the states having different electrical states indicates the interface position. That is, t1 is the interface between the molten steel layer and the slag layer, and t2 is the interface between the slag layer and the atmosphere.
[0025]
In this way, the change in electromotive force is monitored while raising the probe, the boundary position where the qualitative change in the electrical state is detected, and the interface position between the different phases is specified. If the interface position is specified, the slag thickness can be calculated from the distance difference between the two. The distance difference may be detected by attaching an encoder to the probe lifting device. Although the change in electromotive force is monitored while raising the probe here, the electromotive force may be monitored while lowering the probe. In that case, since the molten steel layer is reached after passing through the slag layer, the slag adhered when passing through the slag layer covers the first electrode and prevents the first electrode from contacting the molten steel. Must.
[0026]
The measuring apparatus that implements this slag thickness measuring method can use the probe used for the oxidation degree measuring apparatus as it is on the probe side, and simply add a new processing unit to the signal processing apparatus side that the probe outputs. Good. The processing unit includes a function of an electromotive force measurement unit that continuously measures an electromotive force generated between the first electrode and the second electrode, a function of detecting an electrical state between both electrodes, and a transition between the electrical states. And a function of calculating the slag thickness from the information on the slag. The slag thickness is calculated by first detecting whether it is in the power generation state or the insulation state, and detecting the boundary position in the transition between these states to identify the interface position, and then the first interface position and the next interface position. The slag thickness is obtained from the difference in distance from These may be realized by a hardware configuration using a dedicated circuit, or may be realized by software using a computer program.
[0027]
This slag thickness measurement method can be handled in an integrated manner with the oxidation degree measurement. That is, while monitoring the electromotive force while pulling up the probe from the molten steel layer, and the electrical state between the two electrodes becomes a power generation state, the degree of oxidation of the slag is obtained from the magnitude of the electromotive force, and the electrical The slag thickness is specified by measuring the distance from the power generation state to the insulation state.
According to such a procedure, the stay position of the first electrode can be grasped in real time, so that the degree of oxidation can be measured after confirming that the first electrode is located in the slag layer. As a result, the degree of oxidation can be reliably measured. In addition, since the thickness of the slag layer is known, when the slag is modified based on the measurement result of the degree of oxidation, the necessary amount of reducing agent, oxidizing agent, etc. can be known.
[0028]
【The invention's effect】
The method and apparatus for measuring the degree of oxidation of the present invention measures the electromotive force between the first electrode positioned in the slag layer and the second electrode electrically connected to the molten steel layer, and determines the electromotive force value, Since the slag oxidation degree is calculated by applying the correlation between the oxidation degree and electromotive force obtained in advance by another means, an oxygen sensor using an expensive solid electrolyte is not required, and consumables. Since the structure of the probe can be made extremely simple, the measurement cost can be greatly reduced, and an economic environment in which frequent measurements can be performed is established. Further, since it is considered that the temperature environment does not affect the measurement of the degree of oxidation by the method of the present invention, there is a possibility that the temperature measuring element can be made unnecessary.
[0029]
As in the invention according to claim 2 or 7, the change in electromotive force is detected by raising or lowering the probe, the interface position is identified from the boundary position where the electrical state changes, and further identified in this way. When the slag thickness is calculated from the difference between the molten steel level and the slag level, the oxidation degree measurement can be performed together with the measurement of the slag thickness, so the first electrode is positioned in the slag layer. After confirming this, the degree of oxidation can be measured. Further, by knowing the slag thickness, it is possible to calculate the amount of reducing agent or oxidant input for performing slag reforming based on the calculated degree of oxidation.
[0030]
When the container is made to function substantially as the second electrode as in the invention according to claim 3, the number of electrodes provided on the probe is reduced, so that the structure of the probe is simplified and the wiring drawn from the probe can be simplified. .
[Brief description of the drawings]
FIG. 1 is an explanatory view showing an embodiment in which a container is a second electrode.
FIG. 2 is an explanatory view showing an embodiment in which a second electrode independent of a probe is provided.
FIG. 3 is an explanatory view showing an embodiment in which a second electrode is provided in the middle in the longitudinal direction of the probe.
FIG. 4 is an explanatory diagram showing probes that stay in each layer in the process of pulling up the probe from the molten steel layer to the atmosphere.
FIG. 5 is an explanatory diagram showing the magnitude of electromotive force that changes as the probe rises. FIG. 6 is a graph showing the relationship between the concentration of FeO, which is a representative oxide in slag, and the output voltage of electromotive force. Explanation of]
A Atmosphere S Slag layer (slag)
M Molten steel layer (molten steel)
P probe W container H support member U1 first electrode U2 second electrode

Claims

A method for measuring the degree of oxidation of a slag layer formed on a molten metal layer contained in a container,
The first electrode is provided on the probe that moves up and down between the molten metal layer and the atmosphere through the slag layer, and the second electrode is provided in electrical conduction with the molten metal layer and is positioned in the slag layer. The electromotive force generated between one electrode and the second electrode is measured, and the magnitude of this electromotive force is applied to the correlation between the slag oxidation degree and the electromotive force value obtained in advance by another means. The method for measuring the degree of oxidation of slag to calculate the degree of oxidation of slag.

A method for measuring the degree of oxidation of a slag layer formed on a molten metal layer contained in a container,
A first electrode is provided on the probe that goes up and down between the molten metal layer and the atmosphere through the slag layer, and a second electrode that is electrically connected to the molten metal layer is provided, and the first electrode and the second electrode And continue to monitor the electrical characteristics between
The first electrode is located in the molten metal layer, and the molten metal layer electrically interposed between the first electrode and the second electrode is electrically conductive to electrically short-circuit between the two electrodes due to its conductivity. State and
The first electrode is located in the slag layer, and the slag layer and the molten metal layer electrically interposed between the first electrode and the second electrode are the power generation property of the slag layer as the electrolyte and the molten metal layer. A power generation state in which a potential difference is generated between the two electrodes by combining with the conductivity of
The first electrode is located in the atmosphere, and the atmosphere, the slag layer, and the molten metal layer that are electrically interposed between the first electrode and the second electrode insulate the electrodes from each other by the insulating property of the atmosphere. Insulation state,
The interface position between the molten metal layer and the slag layer is shifted from the boundary position where the conductive state shifts to the power generation state, while the boundary position where the transition state shifts from the power generation state to the insulating state. Detect the interface position between the slag layer and the atmosphere,
The slag thickness is calculated from the difference between these interface positions, and the magnitude of the electromotive force in the power generation state is applied to the correlation between the slag oxidation degree and the electromotive force value obtained by another means in advance. A method for measuring the degree of oxidation of slag to calculate the degree of oxidation.

A container that accommodates the molten metal layer and the slag layer is interposed between the molten metal layer and the ground in an operating state, and has conductivity to energize the two, and this container is substantially used as the second electrode. The slag oxidation degree measuring method according to claim 1, which functions.

The slag oxidation degree measuring method according to claim 3, wherein the conductivity of the container is realized by the adhesion of the metal over the outer wall of the iron container and the inner wall of the container in a covered state.

The slag oxidation degree measuring method according to claim 1, wherein when the first electrode is located in the slag layer, the two electrodes are provided in the same probe in such a positional relationship that the second electrode is located in the molten metal layer.

The method for measuring the slag oxidation degree according to any one of claims 1 to 5, wherein the container is one of a converter, tundish, ladle, topped, mold, and plasma melting furnace.

An apparatus for measuring the degree of oxidation of a slag layer formed on a molten metal layer contained in a container,
A first electrode provided on a probe that moves up and down between the molten metal layer and the atmosphere through the slag layer;
A second electrode provided in electrical conduction with the molten metal layer;
An electromotive force measuring unit for measuring an electromotive force generated between the first electrode positioned in the slag layer and the second electrode conducted to the molten metal layer;
Oxidation for calculating the slag oxidation degree corresponding to the magnitude of the measured electromotive force by applying the measured electromotive force value to the correlation between the slag oxidation degree and the electromotive force value obtained in advance by another means. A degree calculator,
A slag oxidation degree measuring apparatus comprising:

An apparatus for measuring the degree of oxidation of a slag layer formed on a molten metal layer contained in a container,
A first electrode provided on a probe that moves up and down between the molten metal layer and the atmosphere through the slag layer;
A second electrode provided in electrical conduction with the molten metal layer;
An electromotive force means for continuously measuring an electromotive force generated between the first electrode and the second electrode;
The electrical characteristics between the first electrode and the second electrode specified from the measured magnitude of electromotive force indicate the interface position between the molten metal layer and the slag layer from the boundary position where the state transitions from the conductive state to the power generation state. A thickness calculating unit that detects a boundary position that detects an interface position between the slag layer and the atmosphere from a boundary position that shifts from the power generation state to the insulation state, and calculates a slag thickness from a difference between these boundary positions;
The electromotive force value when the electrical characteristics between the electrodes are in the power generation state is applied to the correlation between the slag oxidation degree and the electromotive force value obtained in advance by another means, and the measured electromotive force An oxidation degree calculation unit for calculating the slag oxidation degree corresponding to the thickness,
A slag oxidation degree measuring apparatus comprising:

It is a probe used for the oxidation measurement method of the slag in any one of Claims 1-6,
A probe having a first electrode at the tip and a terminal for deriving an electromotive force generated between the first electrode and the second electrode to the outside.