JP4399927B2

JP4399927B2 - Apparatus and method for measuring oxygen partial pressure in slag

Info

Publication number: JP4399927B2
Application number: JP32533299A
Authority: JP
Inventors: 博昭小坂; 洋志岩村; 貴之乙重
Original assignee: ヘレウス・エレクトロナイト株式会社
Priority date: 1998-11-17
Filing date: 1999-11-16
Publication date: 2010-01-20
Anticipated expiration: 2019-11-16
Also published as: JP2000214127A

Description

【０００１】
【発明の属する技術分野】
本発明は、転炉内の溶鋼に酸素を吹き付ける吹錬工程において、該溶鋼の表面付近に形成されるスラグ層の酸素分圧を測定する酸素分圧測定装置およびその測定方法に関する。
【０００２】
【従来の技術】
製鋼プロセスにおいては、高炉から出た銑鉄に含まれる炭素、燐、珪素およびマンガンなどの不純物を除去する精錬工程に、転炉が広く使われている。この転炉内に、溶融している銑鉄と一緒にスクラップや石灰などを入れて、酸素を高速で吹き付けると、溶鋼中の前記不純物が酸素と結合して熱を発して燃え、溶鋼中から除去される。この工程を吹錬工程という。吹錬工程においては、溶鋼の上にＳｉＯ₂、ＣａＯ、Ａｌ₂Ｏ₃、ＦｅＯ、ＭｎＯ若しくはＭｇＯなどの酸化物を含有するスラグ層が形成される。このスラグ層は、溶鋼が空気と直接接触するのを防ぐものであり重要な役割を果たす。また、このスラグ層中の酸素分圧は、前記スラグ層中の酸化物若しくは溶鋼中の不純物の組成に影響を与えることから、その調節は極めて重要である。そして、その酸素分圧を適宜制御することにより、種々の元素を溶鋼相、スラグ相またはガス相へ移行させて、所定の組成を有する鉄鋼材料を作ることができることから、スラグ層中の酸素分圧の正確な測定手段が求められている。
【０００３】
【発明が解決しようとする課題】
しかしながら、従来から、実操業における転炉内の溶鋼の酸素分圧測定は行われてきたが、スラグ層の酸素分圧測定は難しかった。これは以下の理由による。図９は、溶鋼の酸素分圧を測定するのに用いた酸素分圧測定プローブ５０の鉄製カバー部材５１の一部を切り欠いた状態を示す概略図である。この酸素分圧測定プローブ５０の先端部には、内部に熱電対５２ａを配設された保護管５２ｂからなる測温センサ５２と、標準電極（図示せず）を内装した酸素イオン伝導性を有する固体電解質５４と、当該先端部外周を囲む環状電極（対照電極）５５と、当該先端部を覆う鉄製カバー部材５１とが設けられている。このような酸素分圧測定プローブ５０を転炉中のスラグ層を貫通させて溶鋼中にまで浸漬すると、カバー部材５１が溶解して、固体電解質５４と測温センサ５２が溶鋼中に露出する。そのカバー部材５１は、保護管５２ｂがスラグと反応し浸蝕するのを防ぐものである。次いで、環状電極５５と標準電極との間に、標準電極の酸素分圧と固体電解質５４に接する溶鋼中の酸素分圧との差に対応した起電力が測定され、測温センサ５２により溶鋼温度が測定されて、これら起電力と溶鋼温度とに基づいて溶鋼の酸素分圧が算出される。
【０００４】
しかし、このような酸素分圧測定プローブ５０は、カバー部材５１を除いても、スラグ層の酸素分圧測定に直接使うことはできない。これは、（１）前記保護管５２ｂは、スラグと反応し浸蝕するので、スラグ温度を直接測定することはできず、（２）前記２つのセンサを用いてスラグ温度と、酸素分圧に対応する起電力とを正確に測定するには数秒の時間を要するが、数秒間、薄いスラグ層中にセンサを位置させるのが難しい、という２つの理由からである。特に、近年、スラグ層を薄くする精錬工法（スラグレス工法）が採用されつつあるので、薄いスラグ層中にセンサを位置させることは益々困難になりつつある。
【０００５】
従って、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った。
【０００６】
以上の事情に鑑み、本発明が解決しようとするところは、実操業における転炉内のスラグ層の酸素分圧測定を精度良く行う点にある。
【０００７】
【課題を解決するための手段】
前記課題を解決すべく、本発明の酸素分圧測定装置は、筒状本体部の先端面に形成した凹所内に、標準電極を内装した酸素イオン伝導性を有する棒状の固体電解質を立設し、この固体電解質を囲む位置にスラグ付着性の良好な材質の対照電極を設けて構成した酸素センサと、この酸素センサに隣接し、その感温部を筒状本体部の軸方向において前記酸素センサより先端側に位置付けた溶鋼温度測定用の測温センサと、からなる酸素分圧測定プローブを備えると共に、前記酸素センサの標準電極と対照電極間に生起するスラグ中の酸素分圧に対応する起電力と、前記測温センサから出力される熱起電力に対応する溶鋼温度とに基づいて、この溶鋼温度をスラグ温度とみなしてスラグ中の酸素分圧を算出する演算部を備えることを特徴としたものである。
【０００８】
ここで、前記測温センサがスラグと反応し浸蝕するのを防ぐには、当該測温センサをカバー部材で覆うことが好ましい。
【０００９】
また、このような装置を用いたスラグ中の酸素分圧測定方法は、筒状本体部の先端面に形成した凹所内に、標準電極を内装した酸素イオン伝導性を有する棒状の固体電解質を立設し、この固体電解質を囲む位置にスラグ付着性の良好な材質の対照電極を設けて構成した酸素センサと、この酸素センサに隣接し、その感温部を筒状本体部の軸方向において前記酸素センサより先端側に位置づけた溶鋼温度測定用の測温センサと、からなる酸素分圧測定プローブを用い、この酸素分圧測定プローブ先端面をスラグ層を通過させ、この通過時に凹所内に流入したスラグを保持したまま、測温センサの感温部を溶鋼層所定深さ位置にまで到達させて停止させ、当該停止姿勢において凹所内のスラグを介して酸素センサの標準電極と対照電極間に生起する起電力を測定する共に、測温センサを用いて溶鋼温度を測定し、前記溶鋼温度をスラグ温度とみなしてスラグ中の酸素分圧を測定してなるものである。
【００１０】
ここで、前記測温センサがスラグと反応し浸蝕するのを防ぐ場合は、スラグとの反応防止用カバー部材で覆われた前記測温センサをスラグ層を通過させ、溶鋼に浸漬させて、前記カバー部材が溶解し、露出した測温センサにより溶鋼温度を測定するのが好ましい。
【００１１】
【発明の実施の形態】
以下に、本発明に係る酸素分圧測定装置の実施形態を図面を参照しながら説明する。
【００１２】
図１は、本発明に係る酸素分圧測定装置の酸素分圧測定プローブの鉄製カバー部材の一部を切り欠いた要部説明図である。本実施形態の酸素分圧測定プローブ１は、筒状本体部２の先端面に形成され、環状内壁３を有する凹所４内に立設し、標準電極（図示せず）を内装した棒状の固体電解質５と、この固体電解質５を軸心にして配設したスラグ付着性の良好な鉄製の環状電極（対照電極）６とからなる酸素センサと、当該先端面において、前記酸素センサと隣接して配設され、鉄製のカバー部材７で覆われたアーチ状の測温センサ８とから構成される。この測温センサ８は、石英などからなるチューブ状保護管８ａの内部に熱電対８ｂを配設したものであり、その頂点付近に熱電対８ｂの測温接点を有した感温部９を備えている。尚、この測温センサ８の感温部９は、後述する理由から、前記の酸素センサの頂点よりも先端側に位置するように配設される。また、前記固体電解質５は酸素イオン導電体であり、一般には、酸化ジルコニウム（ジルコニア）や酸化トリウムを主体とし、必要に応じて、二酸化珪素、アルミナ、酸化チタン若しくは酸化鉄などを所定量（数モル程度）固溶して部分安定化された焼結体であるが、特に部分安定化ジルコニアは、優れた耐熱衝撃性を有すると共に酸素濃度に対する応答速度が早いことから好ましい。このような固体電解質５に内装される標準電極には、クロムと酸化クロム、モリブデンと酸化モリブデン、ニッケルと酸化ニッケルとの混合物などが用いられる。
【００１３】
前記酸素センサとしては、より具体的には、図２（ａ），（ｂ）に示すようなものが挙げられる。同図（ａ），（ｂ）は、酸素センサの概略断面図である。同図（ａ）に示す酸素センサは、環状内壁１０の軸心に配設された固体電解質１１の先端部が、凹所１２からやや突出したものであり、同図（ｂ）に示す酸素センサは、環状内壁１４が後退し且つその軸心に配設された固体電解質１５の先端部が、凹所１６内に位置したものとなっている。
【００１４】
このような酸素分圧測定プローブは、図３に示す形態で用いられる。図３は、上記酸素分圧測定プローブ１を用いて転炉内のスラグ層の酸素分圧を測定している状態を示す模式図である。図中の符号２０は転炉、２１は転炉内の溶鋼層、２２はスラグ層、２４はその先端部に本発明に係る酸素分圧測定プローブ１を設けたサブランス、２５は先端部から下方の溶鋼へ酸素を吹き出すメインランスを示している。サブランス２４は、昇降装置（図示せず）に保持されており、転炉２０の底部は酸素等を含むガス２７を溶鋼中に上吹きさせる羽口２０ａ，２０ｂ，２０ｃを備えている。
【００１５】
そのスラグ層２２の酸素分圧の測定は、以下のように行われる。先ず、駆動装置により酸素分圧測定プローブ１を下方へ移動させ、スラグ層２２を貫通させて溶鋼層２１の中に浸漬させ、溶鋼層の所定深さ位置に停止させる。このとき、図７に示すように、前記のカバー部材７は溶鋼中に溶解して測温センサ８が露出し、酸素センサの凹所４には溶融したスラグ２８が保持され、固体電解質５の全表面と環状電極６とに付着している。このように、凹所４にスラグ２８を流入させて保持しつつ、スラグ付着性の良好な環状電極６にスラグ２８を付着させることにより、固体電解質５の全表面が確実にスラグ２８で覆われて、溶鋼中に酸素分圧測定プローブ１を浸漬しても、固体電解質５の表面の一部が溶鋼中に露出することが無くなるのである。尚、図２（ｂ）に示したように、凹所１６のより内部に固体電解質１５を配置した場合は、固体電解質の表面の一部が溶鋼に露出するのをより確実に防ぐことができる。また、測温センサ８の感温部９を酸素センサよりも先端側に位置付けしていることで、スラグ２８が感温部９に付着し、溶鋼温度測定を阻害するのを防いでいる。
【００１６】
次に、酸素分圧測定プローブ１は、スラグ２８の酸素分圧測定が終了するまでの数秒間、その停止状態を維持される。このとき、溶融状態のスラグ２８は電気伝導性を有するので固体電解質５と環状電極６とが電気的に接続し、固体電解質５に内装された標準電極と環状電極６との間に、その標準電極の酸素分圧と固体電解質５の表面に付着したスラグ中の酸素分圧との差に対応した起電力が発生し、測温センサ８の感温部９により溶鋼温度に対応した熱起電力が発生する。これら起電力および熱起電力は、ホルダー２６に備わる電気接点を通して接続された後方に位置する測定器により検出される。尚、前記の停止状態は、酸素分圧に対応する起電力の変化が平衡状態に移るまでの数秒間、維持されなければならない。
【００１７】
次に、測定器においては、測温センサ８による熱起電力の値を基にして溶鋼温度が算出され、この溶鋼温度をスラグ温度とみなし、以下の式を用いてスラグ中の酸素分圧（Ｐｏ₂）が算出される。
【００１８】
【数１】

ここで、式中のＥは酸素濃淡電池の平衡状態における起電力，Ｒはガス定数（気体定数），Ｆはファラディ定数，Ｐｅは固体電解質の電子伝導パラメータ，Ｐｏ₂ (ref)は基準電極の酸素分圧，Ｐｏ₂ はスラグ中の酸素分圧である。
【００１９】
そして、測定器においてスラグ中の酸素分圧を算出した後、駆動装置２７を用いてホルダー２６を上昇させ、酸素分圧測定プローブ１を転炉２０内から脱却させる。尚、測定器にマイクロプロセッサを内蔵して、このようにして算出・測定されたスラグ中の酸素分圧とスラグ温度とを用いて、スラグ中の酸素活量を算出したり、予め作成された検量線を用いてスラグ中の炭素量を推定・算出する機能（ソフトウェアなど）を付与することも可能である。また、算出された値をデジタル表示計やＣＲＴなどに表示したり、その値を異常検出に利用することなども、容易に実現できる。
【００２０】
次に、図４〜図６を参照しながら、その先端部に酸素分圧測定プローブ１を設けた複合プローブの一実施形態を簡単に説明する。図４（ａ）は、本発明に係る酸素分圧測定プローブ１を先端に設けた複合プローブの全体側面図であり、同図（ｂ）は、複合プローブを左側から見た正面図であり、同図（ｃ）は、複合プローブを右側から見た背面図である。このような複合プローブは、全長が１，５００〜２，０００ｍｍ、外径が７５〜１００ｍｍの筒状本体部２の先端面に前記酸素センサと測温センサとを有した酸素分圧測定プローブ１と、この酸素分圧測定プローブ１に内嵌接合する全長が４２０〜４５０ｍｍ、外径が５４〜６５ｍｍの中軸管３０と、この中軸管３０に外嵌接合し且つ後方のホルダー（図示せず）に連結する全長が２００〜４００mm、外径が７５〜９０mmのサブスリーブ３１とを備えて構成される。尚、図４（ａ）には、酸素センサと測温センサとは、筒状本体部２の軸心を挟んで並設されているが、本発明ではこれに限らず、図５に示すように、酸素センサ３２とカバー部材３３に覆われた測温センサとが、筒状本体部３４の軸心に対してより偏心した状態で並設されていてもよい。
【００２１】
図６は、前記複合プローブの概略構成を示す要部断面図である。筒状本体部２の構成部材である紙製の外管４０の内部には、固体電解質５を備えた酸素センサ、カバー部材７で覆われた測温センサおよびカーボンセンサが設けられている。酸素センサおよび測温センサの構成は、上述の構成と略同じである。またカーボンセンサは、溶鋼流入口４１を備えた鉄製の脱酸室４２と、この脱酸室４２内に配設されたアルミニウムなどからなるキル材４３と、鉄製の溶鋼採取室４４とを備えており、脱酸室４２においてサポーター４５により固定された棒状の熱電対４６の先端部が溶鋼採取室４４内に配設されたものである。上述したように酸素分圧測定プローブ１が溶鋼中に浸漬すると、前記溶鋼流入口４１から脱酸室入口部４２ａを経て流入した溶鋼がキル材４３で脱酸された後に、溶鋼採取室４４内に流入し、ここで熱電対４６によりその凝固温度が測定され、後方に位置する測定器により溶鋼中の炭素濃度が算出される。また、中軸管３０の内部には、前記のホルダーの電気接点と接続するコネクタ４７が設けられており、酸素センサ、測温センサおよびカーボンセンサから導出したリード線４８ａ，４８ｂ，４８ｃと接続されている。
【００２２】
このような複合プローブのサンプルを１８本作製し、これらサンプルを用いて同一条件下で転炉内の溶鋼温度、凝固温度およびスラグ起電力を測定した。本サンプルで用いた上記固体電解質５としてはZrO₂を用い、この固体電解質５に内装した標準電極としてはCr／Cr₂O₃を用いた。その測定結果の一例を図８のグラフに示す。グラフの横軸は、経過時間（秒；sec）を示している。また、このグラフに基づき、上記した数式を用いてスラグ中の酸素分圧（Po₂）の対数値（log(Po₂)）を算出した。その結果を以下の表１に示す。図８は、表１中のサンプル番号４に対応するグラフである。尚、上記した数式中、Ｔ：溶鋼温度、Ｅ：スラグ起電力（EMF）、Po₂(ref)＝10^{(8.938-39420/T)}、Ｒ（気体定数）とＦ（ファラディ定数）は既知の物理定数である。
【００２３】
表１中、「鋼番」は溶鋼を吹錬した番号を示している。また、各鋼番に対応した吹錬過程において、溶鋼が脱炭される途中の「中間」時、および溶鋼が脱炭された後に酸素吹込みを停止した「吹止」時の各測定タイミングで、一本の複合プローブを用いてスラグ起電力を測定し、上記酸素分圧測定プローブの測温センサにより溶鋼温度を測定し、上記カーボンセンサの熱電対により凝固温度を測定した。図８に示した例（サンプル番号４）では、表１中の「溶鋼温度」は、およそ２〜６秒、「凝固温度」は、およそ９〜１４秒における温度である。また表１中の「EMF（スラグ起電力）」は、図８のグラフに例示されるようにスラグ起電力曲線のうち最初の平衡状態にある領域（図中の領域Ａ）でサンプリングされた値である。
【００２４】
【表１】

【００２５】
以上、上述の本発明に係る酸素分圧測定装置は、実操業における転炉内のスラグ中の酸素分圧測定に用いるのに好適なものではあるが、実験炉や電気炉などにも用いることができる。
【００２６】
【発明の効果】
本発明に係る酸素分圧測定装置は、筒状本体部先端面に形成した凹所内に棒状の固体電解質を立設し、この固体電解質を囲む位置にスラグ付着性の良好な材質の対照電極を設けて構成した酸素センサと、その感温部を前記酸素センサよりも先端側に位置付けた測温センサとからなる酸素分圧測定プローブを備えると共に、溶鋼温度をスラグ温度とみなしてスラグ中の酸素分圧を算出する演算部とを備えることにより、酸素分圧測定プローブをスラグを通過させる際に、凹所にスラグが保持され且つ対照電極にスラグが付着して、固体電解質全表面が確実にスラグで覆われるので、このような酸素分圧測定プローブを溶鋼中に浸漬しても、固体電解質の表面の一部が溶鋼に露出することなく、標準電極の酸素分圧とそのスラグ中の酸素分圧との差に対応した起電力を安定して得ることが可能となり、また、測温センサの感温部を酸素センサよりも先端側に位置付けているので、凹部に保持したスラグが感温部に付着せずに、正確な溶鋼温度を測定することができる。従って、前記演算部を用いてスラグ中の酸素分圧を正確に算出し測定することが可能となる。
【図面の簡単な説明】
【図１】本発明に係る酸素分圧測定装置の酸素分圧測定プローブの鉄製カバー部材の一部を切り欠いた要部説明図である。
【図２】本発明に係る酸素センサを示す概略断面図である。
【図３】本発明に係る酸素分圧測定プローブを転炉内の溶鋼に浸漬した状態を示す概略断面図である。
【図４】（ａ）は本発明に係る複合プローブを示す全体側面図であり、（ｂ）は（ａ）に示す複合プローブの正面図であり、（ｃ）は（ａ）に示す複合プローブの背面図である。
【図５】他の実施形態の複合プローブの正面図である。
【図６】本発明に係る複合プローブを示す要部断面図である。
【図７】本発明に係る酸素分圧測定プローブの酸素センサにスラグを保持し、熱電対測温センサが溶鋼中に露出した状態を示す概略断面図である。
【図８】複合プローブを用いて測定した結果を示すグラフである。
【図９】従来の溶鋼の酸素分圧測定用プローブの一部を切り欠いた状態を示す概略図である。
【符号の説明】
１酸素分圧測定プローブ
２筒状本体部
３環状内壁
４凹所
５固体電解質
６環状電極（対照電極）
７カバー部材
８測温センサ
８ａ保護管
８ｂ熱電対
９感温部
１０環状内壁
１１固体電解質
１２凹所
１３環状電極
１４環状内壁
１５固体電解質
１６凹所
１７環状電極
２０転炉
２０ａ，２０ｂ，２０ｃ羽口
２１溶鋼層
２２スラグ層
２４サブランス
２５メインランス
２６酸素
２７ガス
２８スラグ
３０中軸管
３１サブスリーブ
３２酸素センサ
３３カバー部材
３４筒状本体部
４０外管
４１溶鋼流入口
４２脱酸室
４２ａ脱酸室入口部
４３キル材
４４溶鋼採取室
４５サポーター
４６熱電対
４７コネクタ
５０酸素分圧測定プローブ
５１鉄製カバー部材
５２測温センサ
５２ａ熱電対
５２ｂ保護管
５４固体電解質
５５環状電極（対照電極）[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an oxygen partial pressure measuring apparatus and a measuring method for measuring an oxygen partial pressure of a slag layer formed near the surface of a molten steel in a blowing step of blowing oxygen to the molten steel in a converter.
[0002]
[Prior art]
In the steelmaking process, converters are widely used in refining processes for removing impurities such as carbon, phosphorus, silicon and manganese contained in pig iron from the blast furnace. In this converter, scrap or lime is put together with molten pig iron, and when oxygen is blown at high speed, the impurities in the molten steel combine with oxygen to generate heat and burn and are removed from the molten steel. Is done. This process is called blowing process. In the blowing process, a slag layer containing an oxide such as SiO ₂ , CaO, Al ₂ O ₃ , FeO, MnO, or MgO is formed on the molten steel. This slag layer prevents the molten steel from coming into direct contact with air and plays an important role. Further, since the oxygen partial pressure in the slag layer affects the composition of oxides in the slag layer or impurities in the molten steel, its adjustment is extremely important. Then, by appropriately controlling the oxygen partial pressure, various elements can be transferred to the molten steel phase, slag phase, or gas phase to produce a steel material having a predetermined composition. There is a need for an accurate means of measuring pressure.
[0003]
[Problems to be solved by the invention]
However, conventionally, oxygen partial pressure measurement of molten steel in a converter in actual operation has been performed, but it was difficult to measure oxygen partial pressure of a slag layer. This is due to the following reason. FIG. 9 is a schematic view showing a state in which a part of the iron cover member 51 of the oxygen partial pressure measurement probe 50 used for measuring the oxygen partial pressure of molten steel is cut out. The oxygen partial pressure measuring probe 50 has oxygen ion conductivity at the front end thereof, which includes a temperature measuring sensor 52 including a protective tube 52b in which a thermocouple 52a is disposed, and a standard electrode (not shown). A solid electrolyte 54, an annular electrode (reference electrode) 55 that surrounds the outer periphery of the tip, and an iron cover member 51 that covers the tip are provided. When such an oxygen partial pressure measuring probe 50 is immersed in molten steel through the slag layer in the converter, the cover member 51 is melted and the solid electrolyte 54 and the temperature sensor 52 are exposed in the molten steel. The cover member 51 prevents the protective tube 52b from reacting with and eroding the slag. Next, an electromotive force corresponding to the difference between the oxygen partial pressure of the standard electrode and the oxygen partial pressure in the molten steel in contact with the solid electrolyte 54 is measured between the annular electrode 55 and the standard electrode. Is measured, and the oxygen partial pressure of the molten steel is calculated based on the electromotive force and the molten steel temperature.
[0004]
However, such an oxygen partial pressure measuring probe 50 cannot be directly used for measuring the oxygen partial pressure of the slag layer even if the cover member 51 is removed. This is because (1) the protective tube 52b reacts with and erodes the slag, so the slag temperature cannot be measured directly, and (2) the slag temperature and the oxygen partial pressure are handled using the two sensors. This is because it takes several seconds to accurately measure the electromotive force generated, but it is difficult to position the sensor in a thin slag layer for several seconds. In particular, since a refining method (slagless method) for thinning the slag layer is being adopted in recent years, it is becoming increasingly difficult to position the sensor in the thin slag layer.
[0005]
Therefore, 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, so that The oxygen partial pressure in the slag was measured, and the oxygen partial pressure in actual operation was estimated from this measured value. However, since the actual operating environment and the laboratory environment are different, the estimation was limited.
[0006]
In view of the above circumstances, the present invention intends to solve the problem that the oxygen partial pressure of the slag layer in the converter in the actual operation is accurately measured.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the oxygen partial pressure measuring device of the present invention has a rod-shaped solid electrolyte having oxygen ion conductivity and having a standard electrode installed in a recess formed in the distal end surface of a cylindrical main body. An oxygen sensor comprising a reference electrode made of a material having good slag adhesion at a position surrounding the solid electrolyte, and the oxygen sensor adjacent to the oxygen sensor and having a temperature sensing portion in the axial direction of the cylindrical main body. A temperature measuring sensor for measuring the molten steel temperature positioned on the more distal end side, and an oxygen partial pressure measuring probe comprising an oxygen partial pressure in the slag generated between the standard electrode and the reference electrode of the oxygen sensor. Based on the electric power and the molten steel temperature corresponding to the thermoelectromotive force output from the temperature measuring sensor, the molten steel temperature is regarded as the slag temperature, and an arithmetic unit for calculating the oxygen partial pressure in the slag is provided. What A.
[0008]
Here, in order to prevent the temperature sensor from reacting with the slag and being eroded, the temperature sensor is preferably covered with a cover member.
[0009]
In addition, a method for measuring the partial pressure of oxygen in the slag using such an apparatus is a method in which a rod-shaped solid electrolyte having oxygen ion conductivity and having a standard electrode is provided in a recess formed in the tip surface of the cylindrical main body. And an oxygen sensor constructed by providing a reference electrode made of a material having good slag adhesion at a position surrounding the solid electrolyte, and adjacent to the oxygen sensor, the temperature sensing portion is arranged in the axial direction of the cylindrical main body portion. Using an oxygen partial pressure measurement probe consisting of a temperature sensor for measuring the molten steel temperature positioned on the tip side of the oxygen sensor, this oxygen partial pressure measurement probe passes through the slag layer at the tip of the oxygen partial pressure measurement probe and flows into the recess during this passage. While holding the slag, the temperature sensing part of the temperature sensor reaches the predetermined depth position of the molten steel layer and stops, and in the stop position, between the standard electrode and the reference electrode of the oxygen sensor via the slag in the recess Occur Both measuring the electromotive force, in which the temperature measuring using the sensor to measure the temperature of molten steel, comprising the molten steel temperature is regarded as slag temperature measuring oxygen partial pressure in the slag.
[0010]
Here, in order to prevent the temperature sensor from reacting and eroding with the slag, the temperature sensor covered with a cover member for preventing reaction with the slag is passed through the slag layer, immersed in molten steel, It is preferable that the molten steel temperature is measured by a temperature sensor that has melted and exposed the cover member.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of an oxygen partial pressure measuring apparatus according to the present invention will be described below with reference to the drawings.
[0012]
FIG. 1 is an explanatory view of a main part in which a part of an iron cover member of an oxygen partial pressure measuring probe of an oxygen partial pressure measuring apparatus according to the present invention is cut out. The oxygen partial pressure measuring probe 1 of this embodiment is formed in a rod-like shape, which is formed on the distal end surface of the cylindrical main body 2, is erected in a recess 4 having an annular inner wall 3, and includes a standard electrode (not shown). An oxygen sensor comprising a solid electrolyte 5 and an annular electrode (reference electrode) 6 made of iron having good slag adhesion disposed around the solid electrolyte 5 as an axis, and adjacent to the oxygen sensor on the tip surface And an arch-shaped temperature measuring sensor 8 covered with an iron cover member 7. This temperature measuring sensor 8 has a thermocouple 8b disposed inside a tubular protective tube 8a made of quartz or the like, and includes a temperature sensing portion 9 having a temperature measuring contact of the thermocouple 8b in the vicinity of the apex thereof. ing. Note that the temperature sensing portion 9 of the temperature sensor 8 is disposed so as to be located on the tip side of the top of the oxygen sensor for reasons described later. The solid electrolyte 5 is an oxygen ion conductor, and is generally composed mainly of zirconium oxide (zirconia) or thorium oxide, and a predetermined amount (several quantities) of silicon dioxide, alumina, titanium oxide, iron oxide, or the like, if necessary. Although it is a sintered body that is partially stabilized by solid solution, particularly partially stabilized zirconia is preferable because it has excellent thermal shock resistance and a high response speed to oxygen concentration. For the standard electrode built in such a solid electrolyte 5, a mixture of chromium and chromium oxide, molybdenum and molybdenum oxide, nickel and nickel oxide, or the like is used.
[0013]
More specifically, examples of the oxygen sensor include those shown in FIGS. 2 (a) and 2 (b). The same figure (a), (b) is a schematic sectional drawing of an oxygen sensor. The oxygen sensor shown in FIG. 6A is such that the tip of the solid electrolyte 11 disposed at the axial center of the annular inner wall 10 slightly protrudes from the recess 12, and the oxygen sensor shown in FIG. The annular inner wall 14 is retracted and the tip of the solid electrolyte 15 disposed in the axial center thereof is located in the recess 16.
[0014]
Such an oxygen partial pressure measurement probe is used in the form shown in FIG. FIG. 3 is a schematic diagram showing a state in which the oxygen partial pressure of the slag layer in the converter is measured using the oxygen partial pressure measuring probe 1. In the figure, reference numeral 20 is a converter, 21 is a molten steel layer in the converter, 22 is a slag layer, 24 is a sublance provided with the oxygen partial pressure measuring probe 1 according to the present invention at its tip, and 25 is downward from the tip. The main lance that blows oxygen into the molten steel is shown. The sublance 24 is held by an elevating device (not shown), and the bottom of the converter 20 is provided with

tuyere

20a, 20b, 20c for blowing a gas 27 containing oxygen or the like into the molten steel.
[0015]
The measurement of the oxygen partial pressure of the slag layer 22 is performed as follows. First, the oxygen partial pressure measuring probe 1 is moved downward by the driving device, penetrates the slag layer 22, is immersed in the molten steel layer 21, and is stopped at a predetermined depth position of the molten steel layer. At this time, as shown in FIG. 7, the cover member 7 is dissolved in the molten steel to expose the temperature sensor 8, and the molten slag 28 is held in the recess 4 of the oxygen sensor, so that the solid electrolyte 5 It adheres to the entire surface and the annular electrode 6. In this way, the entire surface of the solid electrolyte 5 is reliably covered with the slag 28 by adhering the slag 28 to the annular electrode 6 having good slag adhesion while allowing the slag 28 to flow in and hold in the recess 4. Even if the oxygen partial pressure measurement probe 1 is immersed in the molten steel, part of the surface of the solid electrolyte 5 is not exposed in the molten steel. In addition, as shown in FIG.2 (b), when the solid electrolyte 15 is arrange | positioned inside the recess 16, it can prevent more reliably that a part of surface of a solid electrolyte is exposed to molten steel. . Further, since the temperature sensing part 9 of the temperature sensor 8 is positioned on the tip side of the oxygen sensor, the slag 28 is prevented from adhering to the temperature sensing part 9 and obstructing the molten steel temperature measurement.
[0016]
Next, the oxygen partial pressure measurement probe 1 is maintained in a stopped state for several seconds until the oxygen partial pressure measurement of the slag 28 is completed. At this time, since the molten slag 28 has electrical conductivity, the solid electrolyte 5 and the annular electrode 6 are electrically connected, and the standard between the standard electrode built in the solid electrolyte 5 and the annular electrode 6 is the standard. An electromotive force corresponding to the difference between the oxygen partial pressure of the electrode and the oxygen partial pressure in the slag adhering to the surface of the solid electrolyte 5 is generated, and the thermoelectromotive force corresponding to the molten steel temperature by the temperature sensing portion 9 of the temperature sensor 8. Occurs. These electromotive force and thermoelectromotive force are detected by a measuring instrument located at the rear connected through an electrical contact provided in the holder 26. The stop state must be maintained for several seconds until the change in electromotive force corresponding to the oxygen partial pressure shifts to the equilibrium state.
[0017]
Next, in the measuring instrument, the molten steel temperature is calculated based on the value of the thermoelectromotive force by the temperature sensor 8, the molten steel temperature is regarded as the slag temperature, and the partial pressure of oxygen in the slag ( Po ₂ ) is calculated.
[0018]
[Expression 1]

Where E is the electromotive force in the equilibrium state of the oxygen concentration cell, R is the gas constant (gas constant), F is the Faraday constant, Pe is the electron conduction parameter of the solid electrolyte, and Po ₂ (ref) is the reference electrode oxygen partial pressure, Po ₂ is oxygen partial pressure in the slag.
[0019]
And after calculating the oxygen partial pressure in slag in a measuring device, the holder 26 is raised using the drive device 27 and the oxygen partial pressure measuring probe 1 is made to escape from the converter 20. In addition, a microprocessor is built in the measuring instrument, and the oxygen activity in the slag is calculated using the oxygen partial pressure and the slag temperature calculated and measured in this way, or created in advance. It is also possible to provide a function (software or the like) for estimating and calculating the amount of carbon in the slag using a calibration curve. In addition, it is possible to easily display the calculated value on a digital display or a CRT, or to use the value for abnormality detection.
[0020]
Next, an embodiment of a composite probe in which the oxygen partial pressure measurement probe 1 is provided at the tip thereof will be briefly described with reference to FIGS. 4 (a) is an overall side view of the composite probe provided with the oxygen partial pressure measurement probe 1 according to the present invention at the tip, and FIG. 4 (b) is a front view of the composite probe as viewed from the left side. FIG. 3C is a rear view of the composite probe as viewed from the right side. Such a composite probe has an oxygen partial pressure measuring probe 1 having the oxygen sensor and the temperature sensor on the distal end surface of the cylindrical main body 2 having a total length of 1,500 to 2,000 mm and an outer diameter of 75 to 100 mm. And an inner shaft tube 30 having an overall length of 420 to 450 mm and an outer diameter of 54 to 65 mm, and a rear holder (not shown) that is externally bonded to the intermediate shaft tube 30 and fitted to the oxygen partial pressure measuring probe 1. And a sub sleeve 31 having a total length of 200 to 400 mm and an outer diameter of 75 to 90 mm. In FIG. 4 (a), the oxygen sensor and the temperature sensor are arranged side by side with the axis of the cylindrical main body 2 interposed therebetween, but the present invention is not limited to this, and as shown in FIG. In addition, the oxygen sensor 32 and the temperature sensor covered with the cover member 33 may be juxtaposed in a state of being more eccentric with respect to the axis of the cylindrical main body 34.
[0021]
FIG. 6 is a cross-sectional view of a principal part showing a schematic configuration of the composite probe. An oxygen sensor provided with the solid electrolyte 5, a temperature sensor covered with a cover member 7, and a carbon sensor are provided inside a paper outer tube 40 that is a constituent member of the cylindrical main body 2. The configurations of the oxygen sensor and the temperature sensor are substantially the same as those described above. The carbon sensor also includes an iron deoxidation chamber 42 having a molten steel inlet 41, a kill material 43 made of aluminum or the like disposed in the deoxidation chamber 42, and an iron molten steel collection chamber 44. The tip of a rod-shaped thermocouple 46 fixed by a supporter 45 in the deoxidation chamber 42 is disposed in the molten steel collection chamber 44. As described above, when the oxygen partial pressure measurement probe 1 is immersed in the molten steel, the molten steel that has flowed from the molten steel inlet 41 through the deoxidation chamber inlet 42a is deoxidized by the kill material 43, and then in the molten steel collection chamber 44. Here, the solidification temperature is measured by the thermocouple 46, and the carbon concentration in the molten steel is calculated by a measuring instrument located behind. Further, a connector 47 for connecting to the electrical contact of the holder is provided inside the middle shaft tube 30 and connected to lead

wires

48a, 48b, and 48c derived from the oxygen sensor, the temperature sensor, and the carbon sensor. Yes.
[0022]
Eighteen samples of such composite probes were prepared, and the molten steel temperature, solidification temperature, and slag electromotive force in the converter were measured under the same conditions using these samples. ZrO ₂ was used as the solid electrolyte 5 used in this sample, and Cr / Cr ₂ O ₃ was used as a standard electrode built in the solid electrolyte 5. An example of the measurement result is shown in the graph of FIG. The horizontal axis of the graph indicates elapsed time (seconds; sec). Further, based on this graph, the logarithmic value (log (Po ₂ )) of the oxygen partial pressure (Po ₂ ) in the slag was calculated using the above-described mathematical formula. The results are shown in Table 1 below. FIG. 8 is a graph corresponding to sample number 4 in Table 1. In the above formula, T: molten steel temperature, E: slag electromotive force (EMF), Po ₂ (ref) = 10 ^{(8.938-39420 / T)} , R (gas constant) and F (Faraday constant) are known. It is a physical constant.
[0023]
In Table 1, “steel number” indicates a number obtained by blowing molten steel. In addition, in the blowing process corresponding to each steel number, at each measurement timing of “intermediate” while the molten steel is being decarburized and “blowing” when the oxygen blowing is stopped after the molten steel is decarburized. The slag electromotive force was measured using one composite probe, the molten steel temperature was measured with the temperature sensor of the oxygen partial pressure measurement probe, and the solidification temperature was measured with the thermocouple of the carbon sensor. In the example shown in FIG. 8 (sample number 4), “molten steel temperature” in Table 1 is a temperature at about 2 to 6 seconds, and “solidification temperature” is a temperature at about 9 to 14 seconds. In addition, “EMF (slag electromotive force)” in Table 1 is a value sampled in a region (region A in the figure) in the first equilibrium state of the slag electromotive force curve as illustrated in the graph of FIG. It is.
[0024]
[Table 1]

[0025]
As described above, the oxygen partial pressure measuring apparatus according to the present invention is suitable for use in measuring oxygen partial pressure in slag in a converter in actual operation, but it is also used in an experimental furnace or an electric furnace. Can do.
[0026]
【The invention's effect】
In the oxygen partial pressure measuring device according to the present invention, a rod-shaped solid electrolyte is erected in a recess formed in the front end surface of the cylindrical main body, and a reference electrode made of a material having good slag adhesion is provided at a position surrounding the solid electrolyte. An oxygen partial pressure measuring probe comprising an oxygen sensor provided and a temperature measuring sensor having a temperature sensing portion positioned on the tip side of the oxygen sensor is provided, and the molten steel temperature is regarded as the slag temperature and oxygen in the slag When the slag is passed through the oxygen partial pressure measurement probe, the slag is held in the recess and the slag adheres to the reference electrode, so that the entire surface of the solid electrolyte is surely provided. Because it is covered with slag, even if such an oxygen partial pressure measurement probe is immersed in molten steel, the oxygen partial pressure of the standard electrode and the oxygen in the slag are not exposed to the molten steel even if a part of the surface of the solid electrolyte is exposed to the molten steel. With partial pressure In addition, since the temperature sensing part of the temperature sensor is positioned on the tip side of the oxygen sensor, the slag held in the recess does not adhere to the temperature sensing part. In addition, an accurate molten steel temperature can be measured. Therefore, it is possible to accurately calculate and measure the oxygen partial pressure in the slag using the calculation unit.
[Brief description of the drawings]
FIG. 1 is an explanatory view of a main part in which a part of an iron cover member of an oxygen partial pressure measuring probe of an oxygen partial pressure measuring apparatus according to the present invention is cut away.
FIG. 2 is a schematic sectional view showing an oxygen sensor according to the present invention.
FIG. 3 is a schematic cross-sectional view showing a state in which an oxygen partial pressure measurement probe according to the present invention is immersed in molten steel in a converter.
4A is an overall side view showing a composite probe according to the present invention, FIG. 4B is a front view of the composite probe shown in FIG. 4A, and FIG. 4C is a composite probe shown in FIG. FIG.
FIG. 5 is a front view of a composite probe according to another embodiment.
FIG. 6 is a cross-sectional view of a main part showing a composite probe according to the present invention.
FIG. 7 is a schematic cross-sectional view showing a state in which a slag is held in an oxygen sensor of an oxygen partial pressure measurement probe according to the present invention and a thermocouple temperature sensor is exposed in molten steel.
FIG. 8 is a graph showing the results of measurement using a composite probe.
FIG. 9 is a schematic view showing a state where a part of a conventional probe for measuring oxygen partial pressure of molten steel is cut away.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Oxygen partial pressure measurement probe 2 Cylindrical main-body part 3 Annular inner wall 4 Recessed part 5 Solid electrolyte 6 Annular electrode (control electrode)
7 Cover member 8 Temperature sensor 8a Protective tube 8b Thermocouple 9 Temperature sensing part 10 Annular inner wall 11 Solid electrolyte 12 Recess 13 Annular electrode 14 Annular inner wall 15 Solid electrolyte 16 Recess 17 Annular electrode 20

Converter

20a, 20b, 20c Feather Port 21 Molten steel layer 22 Slag layer 24 Sub lance 25 Main lance 26 Oxygen 27 Gas 28 Slag 30 Middle shaft pipe 31 Sub sleeve 32 Oxygen sensor 33 Cover member 34 Tubular main body 40 Outer pipe 41 Molten steel inlet 42 Deoxidation chamber 42a Deoxidation chamber Inlet portion 43 Kill material 44 Molten steel collection chamber 45 Supporter 46 Thermocouple 47 Connector 50 Oxygen partial pressure measurement probe 51 Iron cover member 52 Temperature sensor 52a Thermocouple 52b Protective tube 54 Solid electrolyte 55 Annular electrode (reference electrode)

Claims

A rod-shaped solid electrolyte with oxygen ion conductivity is installed in a recess formed in the tip of the cylindrical main body, and a material with good slag adhesion is placed around the solid electrolyte. An oxygen sensor configured by providing an electrode, and a temperature measurement sensor for measuring a molten steel temperature adjacent to the oxygen sensor and having a temperature sensing portion positioned on the tip side of the oxygen sensor in the axial direction of the cylindrical main body. And an electromotive force corresponding to the oxygen partial pressure in the slag generated between the standard electrode and the reference electrode of the oxygen sensor, and a thermoelectromotive force output from the temperature sensor. An oxygen partial pressure measuring apparatus comprising: an arithmetic unit that calculates a partial pressure of oxygen in a slag by regarding the molten steel temperature as a slag temperature based on the molten steel temperature.

The oxygen partial pressure measuring device according to claim 1, wherein the temperature sensor is covered with a cover member for preventing reaction with slag.

A rod-shaped solid electrolyte with oxygen ion conductivity is installed in a recess formed in the tip of the cylindrical main body, and a material with good slag adhesion is placed around the solid electrolyte. An oxygen sensor configured by providing an electrode, and a temperature measuring sensor for measuring a molten steel temperature adjacent to the oxygen sensor and having a temperature sensing portion positioned on the tip side of the oxygen sensor in the axial direction of the cylindrical main body. Using the oxygen partial pressure measurement probe, the tip of the oxygen partial pressure measurement probe is passed through the slag layer, and the slag that has flowed into the recess is retained while passing through the slag layer. In this stop position, the electromotive force generated between the standard electrode and the reference electrode of the oxygen sensor is measured via the slag in the recess, and the molten steel temperature is measured using the temperature sensor. Oxygen partial pressure measuring method of the molten steel temperature in the slag formed by measuring the oxygen partial pressure is regarded as slag temperature in the slag.

The temperature sensor covered with a cover member for preventing reaction with slag is passed through a slag layer and immersed in molten steel, the cover member is melted, and the molten steel temperature is measured by the exposed temperature sensor. The oxygen partial pressure measurement method in slag as described.