JP3589075B2

JP3589075B2 - Ladle for molten metal and method for refining molten metal

Info

Publication number: JP3589075B2
Application number: JP05989699A
Authority: JP
Inventors: 望田村; 智明田玉; 滋小倉
Original assignee: JFE Steel Corp
Current assignee: JFE Steel Corp
Priority date: 1999-03-08
Filing date: 1999-03-08
Publication date: 2004-11-17
Anticipated expiration: 2019-03-08
Also published as: JP2000256728A

Description

【０００１】
【発明の属する技術分野】
本発明は、溶融金属用取鍋及び溶融金属の精錬方法に係わり、詳しくは、溶銑、溶鋼等の溶融金属をトラブルなく安定して機械攪拌する技術である。
【０００２】
【従来の技術】
溶銑、溶鋼を取鍋（以下、鍋という）に装入し、機械式撹拌機で撹拌しつつ精錬剤を投入して脱硫等の処理を行うことは、従来より知られている。例えば、特公昭４２−１２３４３号公報は、攪拌手段にインペラを用いる技術を開示している。この技術は、鍋内に溶銑を入れ、該鍋の内径に対して１／１０〜１／３の長さに相当る代表径を有するインペラを、１５０〜３００ｒ．ｐ．ｍで回転させて、溶銑の脱硫を行うものである。
【０００３】
このような機械式撹拌技術は古くから知られていたが、その後、ガス吹き込みによる溶融金属の撹拌挙動の研究が盛んに行われるようになり、溶融金属の撹拌処理は、専らガス吹き込み撹拌が主流となった。その理由は、機械式撹拌では、溶融金属に浸漬するインペラをライニングしている耐火物の寿命が短く、処理コストが高くなり過ぎるからである。また、ガス吹き込み撹拌には、吹き込む撹拌ガスをキャリア・ガスとして粉体状の精練剤や合金剤を溶融金属中に直接吹き込め、しかも、それらの添加歩留や除去すべき不純物元素との反応効率が高い利点があった。
【０００４】
しかしながら、溶融金属の品質要求が格段に厳しくなってきた昨今、ガス吹き込み撹拌では、溶融金属に与える攪拌力に限界があり、そのような要求に十分応えられない場合が生じている。そのため、不純物を極限に近くまで低減したい精錬処理には、インペラを用いた機械式の攪拌処理が見直されつつある。ところが、旧来の機械式攪拌処理の技術を、現行の精錬処理にそのまま適用しようとしたところ、以下のような問題に遭遇した。
【０００５】
【発明が解決しようとする課題】
特公昭４２−０１２３４３号公報記載の溶銑脱硫では、インペラの回転数が大きくなるに従い、鍋内の溶銑面は、図４に示すように、攪拌軸１１上の一点を頂点とした三角錐を逆さにした形状を呈する。そして、溶銑５の鍋内静止浴面７（以下、静止浴面という）とこの形状の浴面１０とを比較すると、回転数が大きくなるほど、該浴面１０の最高点は前記静止浴面７に比べ高く盛りあがる。特公昭４２−０１２３４３号公報によれば、３００ｒ．ｐ．ｍ．では、溶銑５の浴面１０は、静止浴面７より４００ｍｍ上昇している。
【０００６】
一方、鍋６は耐火物８で内張りされ、通常、溶融金属５を収容する内部空間の平断面は円形（内径３．０〜４．５ｍ）で、且つ深さは、３．５〜４．０ｍである。近年、精錬能率の向上の見地より、該鍋６の１回あたりの精錬処理量を増加させる傾向がある。そのため、浴面と鍋６の側壁上端との間隔は非常に小さくなっており、３００ｍｍ程度しかない。このような状態で従来の機械式撹拌技術を実施すると、溶銑浴面の上昇によって溶銑５が溢れ出ることが多い。この対策としては、鍋６の受銑量を低下させるか、あるいは鍋６の側壁高さを嵩上げして、浴面に対し非常に高くしなければならない。
【０００７】
しかしながら、受銑量の低下は、大幅な搬送能率の低下を招くことが明らかである。また、側壁の嵩上げは、鍋６を搬送するクレーンに不都合が生じる。つまり、チェーンの巻上量の増加で対応できずに、建屋の改造まで必要とする。さらに、次工程で該鍋６を設置する際には、設置高さの変更を含めた設備改造に多大な費用が必要となる。加えて、鍋６自体も耐火物８の施工高さが増え、耐火物使用量の増加が余儀なくなる。
【０００８】
本発明は、かかる事情に鑑み、既存取鍋の内張耐火物の施工状態を変更するだけで、溶融金属の機械式撹拌を安定して実施可能にする溶融金属用取鍋及び該鍋を使用する溶融金属の精錬方法を提供することを目的としている。
【０００９】
【課題を解決するための手段】
発明者は、上記の目的を達成するため、取鍋の内部構造と湯面盛上りとの関係について多くの試験を重ね、その成果を本発明に具現化した。
【００１０】
すなわち、本発明は、耐火物で内張りされ、溶融金属を収容する溶融金属用取鍋において、少なくとも収容する溶融金属の静止浴面高さ近傍の平断面を、楕円形とし、その短径／長径の比を０．７５〜０．９５の範囲とすることを特徴とする溶融金属用取鍋である。
【００１１】
また、本発明は、耐火物で内張りされ、溶融金属を収容する溶融金属用取鍋において、少なくとも収容する溶融金属の静止浴面高さ近傍の平断面を、非円形状とし、前記静止浴面高さ近傍を、該静止浴面の上下に少なくとも２００ｍｍの範囲とすることを特徴とする溶融金属用取鍋である。
【００１２】
さらに、本発明は、耐火物で内張りされ、溶融金属を収容する溶融金属用取鍋において、少なくとも収容する溶融金属の静止浴面の上下に少なくとも２００ｍｍの範囲の平断面を、楕円形とし、その短径／長径の比を０．７５〜０．９５の範囲とすることを特徴とする溶融金属用取鍋である。
【００１３】
加えて、本発明は、上記の溶融金属用取鍋に溶融金属を収容し、該溶融金属に精錬剤及び／又は合金剤を添加すると共に、前記機械式撹拌手段で該溶融金属を撹拌し、精錬することを特徴とする溶融金属の精錬方法でもある。
【００１４】
本発明では、取鍋の内部構造を、溶融金属の湯面盛り上がりが抑制されるようにしたので、精錬中に該取鍋から溶融金属が溢れ出ることがなくなる。また、製錬が安定して円滑に行えるようになり、精錬の成績が向上するようになる。
【００１５】
【発明の実施の形態】
以下、図面を参照して本発明の実施の形態を説明する。
【００１６】
まず、本発明に係る鍋は、外形を新しくしても良いが、現在溶融金属を収容するのに使用している既存鍋と同じ鉄皮、外形ないし少なくとも鍋のハンドリング用吊具外形であることが好ましい。その理由は、通常の取鍋と同じ鉄皮外形形状であれば、この鍋を用いて精錬等の処理を行う諸設備、鍋をハンドリングするクレーンや台車等の移送設備、補修用の耐火物スタンド等に何ら変更を加える必要がないからである。
【００１７】
そして、本発明では、鍋の内部構造に着眼して多くの試験を行い、収容する溶融金属の静止浴面７近傍での平断面を非円形とすることで、溶融金属の撹拌時に生じる鍋内壁面近くでの浴面１０の盛り上がりを低減するようにしたのである。
【００１８】
その試験は、溶融金属を溶銑として、図２に示す装置を用いて行なわれた。該装置は、耐火物８で内張された溶銑５を収容する鍋６と、撹拌手段をその位置に移行する移動装置１と、機械式撹拌手段のインペラ３と、インペラ３の回転用モータ２と、翼が浴中に浸漬するまでインペラ３を降下する昇降手段９とで形成されている。また、この装置は、実際に精錬剤４を溶銑５中に添加し、脱硫も行なわれた。
【００１９】
また、この試験は、種々の内部構造を有する鍋６で行なわれたが、静止浴面７近傍の平断面が円形状の場合に最も浴面が高くなることがわかったので、非円形であることを本発明の第一の要件とした。さらに、引き続き試験を続行し、その中でも図１に示すような平断面が楕円形状であるのが好ましいこともわかった。なお、図１に示した楕円形状は、長径と短径の比が１００対９５のものである。この場合、図１には示していないインペラの撹拌で溶銑５を攪拌すると、溶銑５にはインペラに吸い込まれる方向に上下の流れ（記号ａ）が発生する。この流れ（ａ）は、インペラの回転数が大きいほど強く、その結果、浴面は、円錐を逆さにしたような形状に凹み、鍋の側壁近傍で浴面が上昇する。なお、この浴面の上昇は、鍋６が軸対象の容器であるため、軸対象の形状に形成される。また、流れ（ａ）により誘起される浴面は、短径上の側壁近傍で最大となるように発達する。しかしながら、長径上の側壁側に短径側との差分だけ流れが逃げることのできる空間が存在するため、流れ（ａ）は、分流して流れ（記号ｂ）を生じる。この流れ（ｂ）は、浴面の楕円周方向への流れであるので、浴面の上昇は、流れ（ｂ）方向に崩れ、浴面の上昇は、従来の円形断面の場合（図４参照）に比べて抑制される。実際の流れは、撹拌による平断面方向の流れも伴うので、非常に複雑であり、多くの試験が必要であった。この図１の例では、浴面の上昇は、従来（円形の場合）に比べて１／２以下となり、３００ｒ．ｐ．ｍ．のインペラ回転数でも、たかだか１５０ｍｍであった。つまり、鍋６に装入する溶融金属量の減量や、鍋６側壁の嵩上げを行わなくても良い量まで十分に低減できた。
【００２０】
なお、鍋側壁の形状があまりに複雑であったり、凹凸が激しいと、溶融金属５やその上に存在するスラグによって、内張り耐火物８の損耗が大きくなるので、耐火物８の表面ができるだけ滑らかな形状であるのが好ましい。また、耐火物８の施工上も、単純形状であることが好ましいので、実用上では、楕円形状が最も良いと考えられる。この場合、短径／長径の比は、好ましくは０．７５〜０．９５の範囲とするのが良い。短径／長径の比を小さくするほど、鍋の側壁近傍での浴面の盛上りを抑制できるが、０．７５未満では、その効果がほぼ飽和することと、溶融金属やスラグの流動によって湯面近傍の側壁耐火物の溶損が大きくなる傾向があるからである。一方、短径／長径比が０．９５を超えると、鍋内側の平断面形状が円形に近くなり、鍋の側壁近傍での湯面の盛上りが大きくなって、溶融金属の鍋外への溢出が生じる可能性が高いからである。
【００２１】
また、本発明では、鍋６の深さ方向全体にわたって、平断面が楕円状であっても良いが、浴面上昇が抑制できさえすれば良いので、一部の深さでも良い。その方が、耐火物８や中子のコストが少なくてすみ、鍋重量が少ないので、クレーン等での搬送負担が小さい。本発明では、鍋の深さ方向の一部を楕円形とする場合には、鍋の側壁近傍での湯面の盛上りを減少する効果を発揮させるため、少なくとも上下に２００ｍｍ程度の範囲をそのような形状にするのが好ましい。
【００２２】
さらに、上記した鍋６の非円形な内部構造は、耐火物８の内張り施工によって容易に形成できる。内張耐火物に煉瓦を用いる場合には、煉瓦の形状や積み方でいかような形状にも実現できるからである。また、不定形耐火物で流し込み施工する場合には、中子の形状を上記の内部形状に対応する形状として施工すれば良い。
【００２３】
次に、溶融金属５の撹拌手段を検討した。その結果、耐火物製の回転体を溶融金属５に浸漬し、モータ等の動力によって機械的に回転するのが最も良いことがわかった。撹拌手段としては、例えば特開昭６２−２３８３２１号公報に開示されるように、鍋６の外部から移動磁場を印加する電磁撹拌も知られているが、このような電磁撹拌の場合には、溶融金属５の回転力が取鍋内壁に近いほど大きくなるので、内張り耐火物８の損耗が激しい。特に、本発明のように、浴面近くの取鍋内平断面形状を非円形とした場合には、溶融金属側に突き出した（または張り出した）耐火物が溶融金属５の流動によって選択的に損耗されてしまう。しかし、発明者は、上記した多くの試験結果より、溶融金属中に回転体を浸漬し、これを機械的に撹拌する場合には、鍋内壁に近づくほど溶融金属の流速は減衰する傾向があり、上述した電磁撹拌におけるような損耗問題が生じ難いことを新たに発見した。そして、本発明では、溶融金属５の撹拌は、機械式回転体を用いて行うことにした。
【００２４】
さらに、発明者は、以上述べた本発明に係る鍋６に溶融金属５を収容し、該溶融金属５に精錬剤及び／又は合金剤を添加すると共に、該溶融金属中に回転体を浸漬して撹拌する溶融金属の処理も試みた。具体的には、溶融鉄合金の脱硫処理、脱燐処理、脱酸処理、接種処理、介在物形態制御のためのＣａやＲＥＭなどの添加処理等である。特に、脱硫処理の場合には、Ｍｇ、ＣａあるいはＲＥＭなどの金属及びそれらの合金、あるいはこれら金属ないし合金と石灰などのフラックスとの併用処理を行った。その結果、非常に良い試験成績を得たので、かかる取鍋を用いる精錬方法も本発明とした。この場合、上記機械式撹拌と併せて、回転体自体や鍋底を介して、ガス吹き込みによる攪拌を併用しても良い。
【００２５】
【実施例】
本発明に係る溶融金属用取鍋及び従来の取鍋を用いて、溶銑の脱硫精錬処理を実施した。その際、脱硫剤の投入は、処理前に一括の投げ込み投入とした。鍋６は、公称内容積６０トンであり、耐火物８で内張り施工して、その内部に平断面が直径２４００ｍｍの円状で、深さ４２００ｍｍの円筒状空間を形成した。そして、この取鍋を従来タイプとした。一方、本発明に係る溶融金属用取鍋６は、上記従来タイプ取鍋の溶銑静止浴面７を基準にして上下３００ｍｍにわたる領域に対しては（一部のものについては、鍋の全高さにわたって楕円形に構成した）、平断面が楕円となるように、側壁耐火物を施工することで構成した。この場合、楕円の（短径／長径）比は、表１のように定めた。溶銑５の撹拌には、機械式撹拌手段、具体的には、インペラ３を採用した。該インペラ３は、翼幅１００ｍｍ、代表径５００ｍｍで、図２に示すように、その回転軸を鍋６の中心軸に一致させて配置した。
【００２６】
また、溶銑の脱硫剤４は、ソーダ灰であり、溶銑撹拌を開始する直前にその全量を添加した。この他、本実施例では、石灰を脱硫剤４とした精錬も行った。なお、脱硫処理時間は、いずれの場合も１０分とした。また、鍋６に装入した溶銑重量は、いずれの場合も６０±１トンに調整した。操業中に鍋６から溢れた溶銑５は、鍋６の下方に鉄板を敷き全量回収したが、この回収量に鍋６に付着した量も加えて評価した。その付着量は、溶銑５を受ける前の空鍋重量と溶銑を払い出して後の空鍋重量の差で算出した。溢れた溶銑５の比率は、溢れた溶銑量を処理前溶銑重量（６０トンとした）で除して表示する。さらに、溶銑５の脱硫率は、処理後の溶銑中硫黄濃度を処理前の溶銑中硫黄濃度で除し、１から引くことで表示した。
【００２７】
かかる溶銑脱硫の操業成績を、一括して表１に示す。
【００２８】
【表１】

【００２９】
表１によれば、脱硫率は、本発明に係る取鍋を使用した場合と従来の取鍋を使用した場合とでほとんど差がない。ただし、従来の取鍋を用いた場合には、溢れた溶銑が多量にあるので、その分だけ鍋内で脱硫剤の正味使用量が多くなっていることを考えれば、本発明の取鍋の方が脱硫率は良いと言える。これは、楕円形状により浴面上昇が崩れる時に、脱硫剤４を溶銑５に巻き込み、脱硫反応が促進されたためである。所要動力は、鍋６の形状にほとんど依存せず、同一回転数において、いずれの場合も同じであった。また、この精錬中に生じた浴面の上昇結果をインペラの回転数との関係で整理し、図３に示す。図３より、本発明に係る鍋６を使用すると、浴面上昇が従来より著しく低減できることが明らかである。
【００３０】
一方、操業成績で大きく異なったのは、撹拌時の溶銑の溢れ率であり、従来の取鍋では、装入量の１０重量％を超える率であり、これでは、その鍋６は操業に適さない。インペラ３の回転数が２５０ｒ．ｐ．ｍ．の場合には、装入溶銑の２５重量％にあたる１５トンもが溢れ、鍋６が溶銑５に埋もれるといったトラブルまで併発した。一方、本発明に係る鍋６では、短径／長径の比を０．９５〜０．７５まで変化させたが、いずれも溢れる溶銑５は極めてわずかであった。
【００３１】
なお、上記実施例は、溶融金属５として溶銑を用いたが、特にこれに限定されるものではなく、本発明に係る溶融金属用取鍋６は、各種の溶鋼、溶融合金、非鉄金属等の処理にも使用できる。
【００３２】
【発明の効果】
以上述べたように、本発明により、溶融金属を収容し、その中で、該溶融金属が含有する不純物元素の除去処理を行う取鍋が、適切な形状に改造された。その結果、機械撹拌を行っても、溶銑浴面の上昇が大幅に抑制でき、溶銑を溢れ出させることがない、また大幅な搬送能率の低下を招くことがない溶融金属用取鍋を提供できた。さらに、設備の改造などに多大な費用をかけることなく、効率の良い不純物処理が可能となった。
【図面の簡単な説明】
【図１】本発明に係る取鍋の内部構造の一例を示す図であり、（ａ）は平面、（ｂ）は縦断面である。
【図２】取鍋に機械式撹拌手段を配置した状況を示す縦断面図である。
【図３】溶融金属の回転数と浴面上昇高さとの関係を示す図である。
【図４】従来の取鍋の内部構造を示す図である。
【符号の説明】
１撹拌手段の移動装置
２インペラの回転用モータ
３インペラ
４精錬剤（脱硫剤）
５熔融金属（溶銑）
６取鍋（鍋）
７静止浴面
８耐火物
９昇降手段
１０浴面
１１攪拌軸[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a ladle for molten metal and a method for refining molten metal, and more specifically, to a technique for stably mechanically stirring molten metal such as hot metal and molten steel without any trouble.
[0002]
[Prior art]
2. Description of the Related Art It has been conventionally known that hot metal and molten steel are charged into a ladle (hereinafter, referred to as a pan), and a refining agent is charged while stirring with a mechanical stirrer to perform a process such as desulfurization. For example, Japanese Patent Publication No. 42-12343 discloses a technique using an impeller as a stirring means. In this technique, hot metal is put into a pot, and an impeller having a representative diameter corresponding to a length of 1/10 to 1/3 of an inner diameter of the pot is supplied to the impeller at 150 to 300 rpm. p. m to rotate the hot metal to desulfurize the hot metal.
[0003]
Although such mechanical stirring technology has been known for a long time, research on the stirring behavior of molten metal by gas injection has been actively conducted, and gas injection stirring has been mainly used for the molten metal stirring process. It became. The reason for this is that, with mechanical stirring, the life of the refractory lining the impeller immersed in the molten metal is short, and the processing cost becomes too high. In addition, in the gas injection stirring, a powdered scouring agent or alloying agent is directly injected into the molten metal using the injected stirring gas as a carrier gas, and the addition yield and the reaction efficiency with the impurity element to be removed are also increased. There was a high advantage.
[0004]
However, in recent years when the quality requirements of molten metal have become much more severe, gas blowing agitation has a limit on the agitation force applied to the molten metal, and in some cases such requirements cannot be sufficiently satisfied. Therefore, a mechanical stirring process using an impeller is being reviewed for a refining process in which impurities are to be reduced to a minimum. However, when the conventional mechanical stirring technology was applied to the existing refining process as it was, the following problems were encountered.
[0005]
[Problems to be solved by the invention]
In hot metal desulfurization described in Japanese Patent Publication No. 42-012343, as the rotation speed of the impeller increases, the hot metal surface in the pan is inverted with a triangular pyramid having one point on the stirring shaft 11 as a vertex, as shown in FIG. It takes on the shape of And, when comparing the stationary bath surface 7 in the pot of the hot metal 5 (hereinafter referred to as a stationary bath surface) with the bath surface 10 of this shape, the higher the number of rotations, the higher the highest point of the bath surface 10 becomes. It rises higher than. According to Japanese Patent Publication No. 42-012343, 300r. p. m. Then, the bath surface 10 of the hot metal 5 is raised by 400 mm from the stationary bath surface 7.
[0006]
On the other hand, the pot 6 is lined with a refractory material 8, and the plane cross section of the internal space for accommodating the molten metal 5 is usually circular (inner diameter 3.0 to 4.5 m) and depth 3.5 to 4.5. 0 m. In recent years, from the viewpoint of improving the refining efficiency, there is a tendency that the refining processing amount per one time of the pot 6 is increased. Therefore, the distance between the bath surface and the upper end of the side wall of the pot 6 is very small, and is only about 300 mm. When the conventional mechanical stirring technique is performed in such a state, the hot metal 5 often overflows due to the rise of the hot metal bath surface. As a countermeasure for this, it is necessary to reduce the amount of received iron in the pan 6 or to raise the height of the side wall of the pan 6 to make it extremely high with respect to the bath surface.
[0007]
However, it is clear that a decrease in the amount of received iron leads to a significant decrease in the transport efficiency. In addition, raising the side wall causes inconvenience for the crane that transports the pot 6. In other words, it is not possible to cope with an increase in the hoisting amount of the chain, and it is necessary to modify the building. Furthermore, when the pan 6 is installed in the next process, a great deal of expense is required for equipment remodeling including a change in the installation height. In addition, the construction height of the refractory 8 also increases in the pot 6 itself, and the amount of refractory used must be increased.
[0008]
In view of such circumstances, the present invention uses a ladle for molten metal and a ladle for molten metal that can stably perform mechanical stirring of molten metal simply by changing the construction state of a refractory lining of an existing ladle. It is an object of the present invention to provide a method for refining molten metal.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, the inventor repeated many tests on the relationship between the internal structure of the ladle and the rise of the molten metal surface, and realized the results in the present invention.
[0010]
That is, the present invention provides a molten metal ladle that is lined with a refractory and contains a molten metal, wherein at least the flat section near the height of the stationary bath surface of the contained molten metal is made elliptical, and its minor axis / major axis is Is in the range of 0.75 to 0.95 .
[0011]
Further, the present invention provides a ladle for molten metal which is lined with a refractory material and accommodates molten metal, wherein at least a flat cross section near the height of the stationary bath surface of the molten metal to be accommodated has a non-circular shape, the height near a molten metal ladle, characterized in that the range of at least 200mm above and below the stationary bath surface.
[0012]
Further, the present invention, in a ladle for molten metal that is lined with refractory and contains molten metal, at least 200 mm above and below the stationary bath surface of the molten metal to be accommodated, a flat cross section in the range of 200 mm, the elliptical, a molten metal ladle you, characterized in that the ratio of minor axis / major axis in the range of 0.75 to 0.95.
[0013]
In addition, the present invention contains the molten metal in the molten metal ladle described above, while adding a refining agent and / or alloying agent to the molten metal, agitating the molten metal by the mechanical stirring means, It is also a method for refining molten metal, which is characterized by refining.
[0014]
In the present invention, the internal structure of the ladle, the molten metal surface protrusion of the molten metal is to be suppressed, thereby preventing the overflow is said mounting Pan et molten metal during smelting. In addition, smelting can be performed stably and smoothly, and the results of smelting can be improved.
[0015]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0016]
First, the pot according to the present invention may have a new outer shape, but it should have the same steel skin and outer shape as the existing pan currently used to accommodate the molten metal, or at least the outer shape of the hanging tool for handling the pan. Is preferred. The reason is that if the outer shape of the steel is the same as that of a normal ladle, various equipment for processing such as refining using this pan, transfer equipment such as cranes and bogies for handling the pan, and refractory stands for repair This is because there is no need to make any changes to the above.
[0017]
In the present invention, many tests are conducted with a focus on the internal structure of the pot, and the molten metal to be accommodated is made non-circular in cross section in the vicinity of the stationary bath surface 7 so that the molten metal generated during stirring of the molten metal can be formed. The swelling of the bath surface 10 near the wall was reduced.
[0018]
The test was carried out using molten metal as hot metal and using the apparatus shown in FIG. The apparatus includes a pan 6 for accommodating the molten iron 5 which is lined with refractory 8, the mobile device 1 to shift the stirring means to the position of that, an impeller 3 of a mechanical stirring means, rotating motor of the impeller 3 2 and lifting means 9 for lowering the impeller 3 until the wings are immersed in the bath. In this apparatus, the refining agent 4 was actually added to the hot metal 5 and desulfurization was also performed.
[0019]
In addition, this test was performed with a pot 6 having various internal structures, but it was found that the bath surface was highest when the flat cross section near the stationary bath surface 7 was circular, so that it was non-circular. This is the first requirement of the present invention. Further, the test was continued, and it was found that it was preferable that the flat cross section as shown in FIG. 1 was elliptical. The elliptical shape shown in FIG. 1 has a ratio of the major axis to the minor axis of 100 to 95. In this case, when the hot metal 5 is stirred by the impeller not shown in FIG. 1, a vertical flow (symbol a) occurs in the hot metal 5 in the direction of being sucked into the impeller. This flow (a) becomes stronger as the number of revolutions of the impeller becomes larger. As a result, the bath surface is recessed in a shape like an inverted cone, and the bath surface rises near the side wall of the pan. This rise in the bath surface is formed in a symmetrical shape because the pan 6 is a symmetrical container. Further, the bath surface induced by the flow (a) is developed such that the maximum near the side wall on the short diameter. However, since there is a space capable of escaping the flow by the difference between the minor side side wall on the long diameter, it flows (a) results in a flow (symbol b) diverted. Since the flow (b) is a flow in the elliptical circumferential direction of the bath surface, the rise of the bath surface collapses in the flow (b) direction, and the rise of the bath surface is a conventional circular cross section (see FIG. 4). ) Is suppressed. The actual flow is very complicated because it involves the flow in the plane section direction due to stirring, and many tests were required. In the example of FIG. 1, the rise of the bath surface is となり or less as compared with the conventional case (in the case of a circle), and 300 r. p. m. The impeller rotation speed was at most 150 mm. In other words, the amount of the molten metal charged into the pan 6 could be reduced to a sufficient amount without raising the side wall of the pan 6 and the amount could be sufficiently reduced.
[0020]
In addition, if the shape of the side wall of the pot is too complicated or the unevenness is severe, the wear of the refractory lining 8 increases due to the molten metal 5 and the slag existing thereon, so that the surface of the refractory 8 is as smooth as possible. Preferably, it is shaped. In addition, since it is preferable that the refractory 8 has a simple shape in construction, an elliptical shape is considered to be the best in practical use. In this case, the ratio of the minor axis / major axis is preferably in the range of 0.75 to 0.95. The smaller the ratio of the minor axis / major axis, can be suppressed excitement of the bath surface in the vicinity of the side wall of the pot, is less than 0.75, and that the effect is substantially saturated, by the flow of molten metal and slag This is because the erosion of the side wall refractory near the molten metal surface tends to increase. On the other hand, when the minor axis / major axis ratio exceeds 0.95, the flat cross-sectional shape of the pot inner becomes close to a circle, the molten metal surface in the vicinity of the side wall of the pot Sheng and uplink increases, the pan out of the molten metal This is because there is a high possibility that spills will occur.
[0021]
Further, in the present invention, the flat section may be elliptical over the entire depth direction of the pot 6, but may be a part of the depth as long as the rise of the bath surface can be suppressed. In that case, the cost of the refractory 8 and the core can be reduced, and the weight of the pot is small, so that the transportation load by a crane or the like is small. In the present invention, when a part of the pot in the depth direction is formed into an elliptical shape, at least a range of about 200 mm is required in order to reduce the rise of the molten metal near the side wall of the pot. It is preferable to have such a shape.
[0022]
Further, the non-circular internal structure of the pot 6 can be easily formed by lining the refractory 8. This is because when a brick is used for the refractory lining, it can be realized in any shape depending on the shape and stacking method of the brick. In addition, in the case of casting with an irregular-shaped refractory, the core may be formed in a shape corresponding to the above-mentioned internal shape.
[0023]
Next, a means for stirring the molten metal 5 was examined. As a result, it was found that it is best to immerse the refractory rotator in the molten metal 5 and mechanically rotate the rotator by the power of a motor or the like. The agitation means, for example as disclosed in JP-A-62-238321 discloses, also known magnetic stirring for applying an externally et moving magnetic field of the pot 6, in the case of such an electromagnetic stirring Since the rotational force of the molten metal 5 increases as it approaches the inner wall of the ladle, the refractory lining 8 is greatly worn. In particular, when the flat cross section inside the ladle near the bath surface is made non-circular as in the present invention, the refractory that protrudes (or protrudes) toward the molten metal is selectively formed by the flow of the molten metal 5. It will be worn out. However, the inventor has found that, according to the results of many tests described above, when the rotating body is immersed in the molten metal and mechanically stirred, the flow velocity of the molten metal tends to decrease as it approaches the inner wall of the pot. It was newly discovered that the wear problem as in the electromagnetic stirring described above hardly occurred. In the present invention, the stirring of the molten metal 5 is performed using a mechanical rotating body.
[0024]
Furthermore, the inventor puts the molten metal 5 in the pan 6 according to the present invention described above, adds a refining agent and / or an alloying agent to the molten metal 5, and immerses the rotating body in the molten metal. The treatment of molten metal with stirring was also attempted. Specific examples include desulfurization treatment, dephosphorization treatment, deoxidation treatment, inoculation treatment, and addition treatment of Ca and REM for controlling the inclusion morphology of the molten iron alloy. In particular, in the case of desulfurization treatment, metals such as Mg, Ca or REM and alloys thereof, or a combination treatment of these metals or alloys with flux such as lime was performed. As a result, very good test results were obtained, and the refining method using such a ladle was also considered as the present invention. In this case, in addition to the mechanical stirring described above, stirring by gas blowing may be used through the rotating body itself or the bottom of the pot.
[0025]
【Example】
Using the ladle for molten metal according to the present invention and a conventional ladle, desulfurization and refining of hot metal was performed. At that time, the desulfurizing agent was charged at one time before the treatment. The pot 6 had a nominal inner volume of 60 tons, was lined with a refractory material 8, and formed therein a circular space having a circular cross section having a diameter of 2400 mm and a depth of 4200 mm. And this ladle was made into the conventional type. On the other hand, the molten metal ladle 6 according to the present invention is applied to a region extending 300 mm up and down with respect to the hot metal stationary bath surface 7 of the conventional type ladle (for some, over the entire height of the pan). It was constructed by applying a refractory material on the side wall so that the flat cross section became an ellipse. In this case, the (minor axis / major axis) ratio of the ellipse was determined as shown in Table 1. For stirring the hot metal 5, a mechanical stirring means, specifically, the impeller 3 was employed. The impeller 3 has a blade width of 100 mm and a representative diameter of 500 mm, and its rotation axis is arranged to coincide with the center axis of the pan 6 as shown in FIG.
[0026]
The desulfurizing agent 4 for hot metal was soda ash, and the entire amount was added immediately before starting hot metal stirring. In addition, in this example, refining was also performed using lime as desulfurizing agent 4. The desulfurization time was 10 minutes in each case. The weight of the hot metal charged into the pan 6 was adjusted to 60 ± 1 ton in each case. The hot metal 5 overflowing from the pan 6 during the operation was collected by laying an iron plate below the pan 6, and the amount of the hot metal 5 attached to the pan 6 was evaluated in addition to the recovered amount. The adhesion amount was calculated by the difference between the weight of the empty pot before receiving the hot metal 5 and the weight of the empty pot after dispensing the hot metal. The ratio of the overflowing hot metal 5 is indicated by dividing the overflowing hot metal amount by the weight of the hot metal before treatment (assumed to be 60 tons). Further, the desulfurization rate of the hot metal 5 was indicated by dividing the sulfur concentration in the hot metal after the treatment by the sulfur concentration in the hot metal before the treatment and subtracting 1 from the value.
[0027]
The operating results of such hot metal desulfurization are collectively shown in Table 1.
[0028]
[Table 1]

[0029]
According to Table 1, there is almost no difference in desulfurization rate between the case using the ladle according to the present invention and the case using the conventional ladle. However, when a conventional ladle is used, the molten iron overflows in a large amount, so considering that the net use amount of the desulfurizing agent in the ladle is increased by that much, the ladle of the present invention is considered. It can be said that the desulfurization rate is better. This is because the desulfurizing agent 4 was rolled into the hot metal 5 when the rising of the bath surface collapsed due to the elliptical shape, and the desulfurization reaction was promoted. The required power hardly depended on the shape of the pot 6, and was the same in each case at the same rotation speed. FIG. 3 shows the results of the rise of the bath surface generated during the refining in relation to the rotation speed of the impeller. It is clear from FIG. 3 that the use of the pot 6 according to the present invention can significantly reduce the rise in the bath surface as compared with the conventional art.
[0030]
On the other hand, what greatly differs in the operation results is the overflow rate of the hot metal at the time of stirring, and in the conventional ladle, the rate exceeds 10% by weight of the charged amount. In this case, the pan 6 is not suitable for the operation. Absent. When the rotation speed of the impeller 3 is 250 r. p. m. In the case of (1), as much as 15 tons, which is 25% by weight of the hot metal charged, overflowed, and a trouble such as the pot 6 being buried in the hot metal 5 occurred simultaneously. On the other hand, in the pot 6 according to the present invention, the ratio of the minor axis / major axis was changed from 0.95 to 0.75, but the molten metal 5 overflowing in each case was extremely small.
[0031]
In addition, although the said Example used the molten iron as the molten metal 5, it is not specifically limited, The ladle 6 for molten metals which concerns on this invention is various types of molten steel, a molten alloy, Can also be used for processing.
[0032]
【The invention's effect】
As described above, according to the present invention, a ladle for accommodating a molten metal and performing a removal treatment of an impurity element contained in the molten metal therein has been modified into an appropriate shape. As a result, even if mechanical stirring is performed, it is possible to provide a molten metal ladle that can significantly suppress the rise of the hot metal bath surface, does not overflow hot metal, and does not cause a significant decrease in transport efficiency. Was. Further, it is possible to efficiently treat impurities without spending a great deal of cost for remodeling the equipment.
[Brief description of the drawings]
FIG. 1 is a view showing an example of the internal structure of a ladle according to the present invention, wherein (a) is a plane and (b) is a longitudinal section.
FIG. 2 is a longitudinal sectional view showing a state in which a mechanical stirring means is arranged on a ladle.
FIG. 3 is a diagram showing a relationship between a rotation speed of a molten metal and a rising height of a bath surface.
FIG. 4 is a view showing the internal structure of a conventional ladle.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Moving device of stirring means 2 Motor for rotating impeller 3 Impeller 4 Refining agent (desulfurizing agent)
5 Molten metal (hot metal)
6 Ladle (pan)
7 stationary bath surface 8 refractory 9 elevating means 10 bath surface 11 stirring shaft

Claims

In a ladle for molten metal that is lined with refractory and contains molten metal,
A ladle for molten metal, characterized in that at least the flat section near the height of the stationary bath surface of the molten metal to be accommodated is elliptical, and the ratio of the minor axis / major axis is in the range of 0.75 to 0.95. .

In a ladle for molten metal that is lined with refractory and contains molten metal, at least a flat cross section near the height of the stationary metal surface of the molten metal to be accommodated is non-circular, and the vicinity of the height of the stationary metal surface is molten metal ladle, characterized in that the range of at least 200mm above and below the static bath surface.

In a ladle for molten metal which is lined with refractory and contains molten metal, at least a plane section of at least 200 mm above and below the stationary bath surface of the contained molten metal is made elliptical, and the ratio of the minor axis to the major axis the you, characterized in that the range of 0.75 to 0.95 molten metal ladle.

The ladle for molten metal according to any one of claims 1 to 3, wherein a mechanical stirring means is provided inside the molten metal.

A method for storing a molten metal in the molten metal ladle according to claim 4, adding a refining agent and / or an alloying agent to the molten metal, and stirring and refining the molten metal by the mechanical stirring means. Characterized method of refining molten metal.