JP3611664B2 - Hot metal pretreatment method - Google Patents
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Description
【０００１】
【産業上の利用分野】
本発明は、高炉又は電気炉で製造された溶銑を予備処理する方法に関する。
【０００２】
【従来の技術】
高炉で製造された溶銑を転炉で製錬して溶鋼を製造する際、溶銑の転炉装入前に溶銑予備処理設備で溶銑内に予備処理剤をインジェクションし、予め脱Ｓｉ，脱Ｓ及び脱Ｐする溶銑予備処理法が採用されている。この方法は、極低Ｓ鋼，極低Ｐ鋼等の製造に大きな効果を発揮する。
極低Ｓ鋼や極低Ｐ鋼用の溶銑予備処理では、Ｐ濃度及びＳ濃度の規格上限の情報を使用し、それぞれの規格を満足するために必要な溶銑予備処理後の溶銑成分を決定している。次いで、高炉出銑時又は溶銑予備処理前の溶銑温度，Ｓｉ濃度，Ｓ濃度及びＰ濃度の情報を使用して、処理後の溶銑成分を得るのに必要な処理剤の投入量及び気体酸素の使用量を決定している。
【０００３】
【発明が解決しようとする課題】
従来法で極低Ｓ鋼及び極低Ｐ鋼を製造する場合、特に処理前の溶銑温度が低くＰ規格又はＳ規格が厳しい条件下では、決定された処理剤の量をインジェクションすると、溶銑温度や溶銑炭素濃度が大きく低下し過ぎる。そのため、溶銑温度が液相線温度を下回り、湯面や鍋壁に近い部分で溶銑が凝固することがある。
溶銑が凝固すると、鍋壁に付着した地金を除去する作業が必要となるばかりでなく、地金付着に起因した鍋耐火物費用が上昇し、混銑炉歩留りが低下する。また、転炉に挿入される溶銑量が変動し、転炉の終点制御が困難になる。
【０００４】
特に、多量の合金成分を溶解して高Ｎｉ鋼等の高合金鋼を転炉で溶製する場合、溶銑量が少し変動しても、合金成分含有量に比較的大きな変化が発生する。このような鋼種の溶製では、溶銑段階で地金付着が発生すると、転炉への溶銑装入量変化に応じて合金成分が大きく変化する。その結果、合金成分の的中が極めて困難になる。
本発明は、このような問題を解消すべく案出されたものであり、溶銑予備処理後の溶銑を液相線温度に比較して一定の余裕をもった温度域に保持することにより、溶銑段階での地金付着を防止し、作業負荷の軽減，溶銑原単位の低減，合金成分的中精度の向上を図ることを目的とする。
【０００５】
【課題を解決するための手段】
本発明の溶銑予備処理方法は、その目的を達成するため、予備処理前溶銑のＳｉ濃度，Ｓ濃度，Ｐ濃度から予備処理後溶銑の目標Ｓ濃度，目標Ｐ濃度を得るために必要な脱Ｐ剤投入量及び脱Ｓ剤投入量を決定し、決定した脱Ｐ剤投入量及び脱Ｓ剤投入量と予備処理前溶銑のＳｉ濃度，溶銑温度とから予備処理後の溶銑温度Ｔf 及びＣ濃度を推定し、推定Ｃ濃度の関数として求められる予備処理後溶銑の液相線温度Ｔliq.と推定溶銑温度Ｔf との差ΔＴ＝（Ｔf −Ｔliq.）を余裕温度とし、該余裕温度ΔＴが一定値以上になるように脱Ｐ剤投入量及び脱Ｓ剤投入量等の操業条件を制御することを特徴とする。
この溶銑予備処理方法は、特にＰ濃度の規格が０．０１重量％以下，Ｓ濃度の規格が０．００５重量％以下，合金成分が１０重量％以上，なかでもＮｉ含有量が３０重量％以上の鋼種を溶製するときに有効である。
【０００６】
【実施の形態】
本発明では、通常の高炉溶銑を出発溶銑として使用するが、場合によっては電気炉で溶解した溶銑を使用することもできる。この溶銑を溶銑予備処理設備で脱Ｓｉ，脱Ｓ，脱Ｐする。たとえば、ＪＩＳ Ｇ２２０１に規定されている製鋼用溶銑を溶銑予備処理設備に移し、ソーダ灰，石灰，焼結鉱，鉄鉱石，それらを混合した脱Ｐ剤等の造滓剤を溶銑中にインジェクションすると共に、必要に応じて酸素を送り込むことにより脱Ｓｉ，脱Ｓ，脱Ｐ製錬する。脱Ｓｉに関しては、溶銑予備処理工程に先立って溶銑樋や溶銑鍋に溶銑を受ける高炉出銑工程の途中で溶銑を脱Ｓｉすることもできる。
この溶銑予備処理に際し、Ｓ濃度及びＰ濃度の製品規格上限から溶銑予備処理後のＳ濃度及びＰ濃度の目標値を求める。次いで、予備処理前のＳｉ濃度［Ｓｉ］ｉ ％，Ｓ濃度［Ｓ］ｉ ％及びＰ濃度［Ｐ］ｉ ％から、予備処理後の目標Ｓ濃度［Ｓ］ｆ ％及び目標Ｐ濃度［Ｐ］ｆ ％を得るために必要な予備処理剤の投入量を決定する。
【０００７】
たとえば、石灰系の脱Ｐ剤（原単位Ｘ１ ｋｇ／トン）及びソーダ灰（原単位Ｘ２ ｋｇ／トン）を使用する場合、予備処理剤の投入量は次式に従って求められる。式中、ａ１ 〜ａ６ は、ａ１ ＝１２．２，ａ２ ＝０，ａ３ ＝６２．５，ａ４ ＝２５．３，ａ５ ＝２．０，ａ６ ＝０である。ただし、Ｘ２ の最小値は、予め規定しておく。
Ｘ２ ＝ａ１ （ｌｎ［Ｓ］ｉ −ｌｎ［Ｓ］ｆ ）＋ａ２
Ｘ１ ＝ａ３ ［Ｓｉ］ｉ ＋ａ４ （ｌｎ［Ｐ］ｉ −ｌｎ［Ｐ］ｆ ）−ａ５ Ｘ２ ＋ａ６ この式の右辺は、処理前の溶銑温度Ｔｉ を変数として取り込むこともできる。また、気体酸素を併用する処理条件下では、気体酸素の供給量を決定するための式を追加することもよい。
次いで、たとえば次式に従って処理後の溶銑温度Ｔｆ 及びＣ濃度Ｃｆ を推定する。式中、ｂ１ 〜ｂ８ は、ｂ１ ＝０．３５８，ｂ２ ＝４．１０５，ｂ３ ＝９４．２，ｂ４ ＝４２，ｂ５ ＝０．０１１５３，ｂ６ ＝０．０，ｂ７ ＝０．４２８６，ｂ８ ＝０．０である。
Ｔｆ ＝Ｔｉ −ｂ１ Ｘ１ −ｂ２ Ｘ２ ＋ｂ３ ［Ｓｉ］ｉ −ｂ４
［Ｃ］ｆ ＝［Ｃ］ｉ −ｂ５ Ｘ１ −ｂ６ Ｘ２ ＋ｂ７ ［Ｓｉ］ｉ −ｂ８
【０００８】
溶銑のＣ濃度の分析精度に問題がある場合、予備処理前の溶銑がＣ飽和状態にあると仮定し、溶銑温度から予備処理前のＣ濃度を推定し、この推定Ｃ濃度を前掲した式中の［Ｃ］ｉ に替えることもできる。たとえば、［Ｃ］ｉ ＝０．００２５Ｔｉ ＋１．３７を使用することもできる。
予備処理後の溶銑の液相線温度Ｔｌｉｑ．は、炭素濃度［Ｃ］ｆ の関数として次式に従って求める。
Ｔｌｉｑ．＝Ｆ（［Ｃ］ｆ ）
処理後の溶銑における液相線温度Ｔｌｉｑ．からの余裕温度ΔＴは、次式によって与えられる。液相線温度Ｔｌｉｑ．としては、たとえばＴｌｉｑ．＝−１１５［Ｃ］ｆ ＋１６４２を使用することもできる。
ΔＴ＝Ｔｆ −Ｔｌｉｑ．
このようにして与えられた余裕温度ΔＴが予め定められている値、たとえば１０℃より小さい場合、ΔＴ＝１０℃となるように脱Ｐ剤の投入量Ｘ１ を減少させる。このとき、脱Ｐ剤投入量Ｘ１ の減少量は、前掲した式の逆算で求められる。脱Ｐ剤の減少に伴って、溶銑温度Ｔｆ は上昇するが、処理後の溶銑のＰ濃度も上昇する。
【０００９】
Ｐ濃度の上昇傾向は、転炉において石灰等の造滓剤を増量し、或いは転炉吹止め時におけるＣ濃度の目標値を低下させることにより相殺される。しかし、実操業では、特に極低Ｐ鋼を溶製するとき転炉での脱Ｐに限界があることから、たとえばＰ規格が０．００５重量％以下の場合には脱燐剤減少量の限度を１０ｋｇ／トンとすることが好ましい。
以上のように、溶銑予備処理で使用する処理剤の投入量を決定する。気体酸素を併用するときには、気体酸素の供給量も同様に決定する。また、以上の各式を組み合わせることにより、処理剤の原単位から溶銑の余裕温度ΔＴを直接計算してもよく、或いは処理前の溶銑温度，溶銑成分及び目標成分から余裕温度ΔＴを直接計算しても良い。
【００１０】
余裕温度ΔＴの算出は、複数の高炉又は電気炉から出銑される溶銑のうち、余裕温度ΔＴの大きい溶銑を優先使用することにも利用される。すなわち、余裕温度ΔＴの大きな溶銑を極低Ｓ鋼又は極低Ｐ鋼用の溶銑として供給すれば、その極低Ｓ鋼又は極低Ｐ鋼用の溶銑を予備処理した後、十分な余裕温度ΔＴが確保され、溶銑段階での地金付着が防止される。その結果、地金除去の作業負荷が軽減され、溶銑原単位の低減及び合金成分的中精度の向上が図られる。
【００１１】
【実施例】
普通鋼，特殊鋼等の製造用の溶銑予備処理設備，転炉，ＲＨ真空脱ガス設備を使用し、３０重量％以上のＮｉを含む低Ｐ，低Ｓ鋼の溶鋼を３チャージ行った。この際、本発明に従って溶銑予備処理を行った。以下に、その詳細を説明する。
先ず、ここで使用する変数の意味は以下の通りである。
ΔＴmin ：液相線からの余裕温度の最小値の目標（℃） (given)
ΔＸ1max：石灰系脱Ｐ剤原単位減少の上限（ｋｇ／トン）
（プラス値とする） (given)
Ｘ2min：ソーダ灰原単位最小値（ｋｇ／トン）（［Ｓ］f の関数） (given)
Ｔi ：処理前溶銑温度（℃） (given)
［Ｓ］i ：処理前［Ｓ］（％） (given)
［Ｓ］f ：処理後目標［Ｓ］（％） (given)
［Ｐ］i ：処理前［Ｐ］（％） (given)
［Ｐ］f ：処理後目標［Ｐ］（％） (given)
［Ｓｉ］i ：処理前［Ｓｉ］（％） (given)
［Ｃ］i ：処理前［Ｃ］（％） (given又はＴi より換算)
Ｘ1 ：石灰系脱Ｐ剤原単位（ｋｇ／トン）
Ｘ2 ：ソーダ灰原単位（ｋｇ／トン）
Ｔf ：処理後溶銑温度（℃）
［Ｃ］f ：処理後［Ｃ］（％）
Ｔliq.：処理後溶銑［Ｃ］に対応する液相線温度（℃）
ΔＴ：液相線からの余裕温度（℃）
ΔＸ1 ：石灰系脱Ｐ剤原単位の減少（ｋｇ／トン）
（減少のみ。減少をプラスとする）
【００１２】
先ず、操業前に予め決めておくべき数値を決めておく。ΔＴmin ＝５０（℃），ΔＸ1max＝１０（ｋｇ／トン），Ｘ2min＝１８．９（ｋｇ／トン），［Ｓ］f ＝０．００３（％），［Ｐ］f ＝０．００４％としている。
この３チャージにおける計算の経緯を表１に示す。Ｎo.１の実施例につき、表１の数値を説明していく。先ず、溶銑予備処理条件であるが、高炉の出銑温度及び出銑成分をそれぞれ処理前の温度及び成分としたが、その値はＴi ＝１３４０（℃），［Ｓ］i ＝０．０１１（％），［Ｐ］i ＝０．１１０（％），［Ｓｉ］i ＝０．５７（％），［Ｃ］i ＝４．５４（％）であった。先ず、次のようにソーダ灰原単位Ｘ2 及び石灰系脱Ｐ剤原単位Ｘ1を求めた。
Ｘ2 ＝ｍａｘ｛１２．２（ln［Ｓ］i −ln［Ｓ］f ，Ｘ2min｝
＝１８．９（ｋｇ／トン） ・・・・（１）
Ｘ1 ＝６２．５［Ｓｉ］i ＋２５．３（ln［Ｐ］i −ln［Ｐ］f ）
−２．０Ｘ2 ＝８１．７（ｋｇ／トン） ・・・・（２）
【００１３】
次に、ソーダ灰を前記計算通りＸ２ ＝１８．９ｋｇ／トン，脱Ｐ剤を前記計算通りＸ１ ＝８１．７ｋｇ／トンとした場合の予備処理後の溶銑の温度と［Ｃ］濃度を次のように推定した。
Ｔｌｉｑ．＝−１１５［Ｃ］ｆ ＋１６４２＝１２００（℃） ・・・・（５）
これにより、処理後溶銑における液相線温度から余裕温度ΔＴは、次式により与えられる。
ΔＴ＝Ｔｆ −Ｔｌｉｑ．＝１２４５−１２００＝４５（℃） ・・・・（６）
【００１４】
ところで、予め設定した液相線からの余裕温度の最小値の目標は、
ΔＴｍｉｎ ＝５０（℃）
であり、前記で計算した余裕温度ΔＴはこの最小値の目標より５℃低い。すなわち、
ΔＴ−ΔＴｍｉｎ ＝−５（℃）＜０ ・・・・（７）
である。したがって、このままでは余裕温度が少ないために、溶銑段階での鍋への地金付きが発生する虞れがある。そこで、石灰系脱Ｐ剤の量を減少する。ソーダ灰を減少する方法も考えられるが、次工程である転炉では脱Ｓよりも脱Ｐの方が容易であるため、脱Ｐ剤の方を減少することとしている。
ここで、脱Ｐ剤を減少する際の減少代の計算式を導く。（６）式に（３），（５）式を代入し、更に（４）式を代入すると、
（８）式のＸ１ の係数が−１．６８４であるので、余裕温度を目標とするためには、不足する余裕温度をこの係数の絶対値１．６８４で割った値だけ脱Ｐ剤を減少すればよい。ただし、脱Ｐ剤の減少の上限は、ΔＸ１ｍａｘに抑える。したがって、脱Ｐ剤の減少代ΔＸ１ は、次式で与えられる。
【００１６】
以上がＮｏ．１チャージ目での操業内容であるが、Ｎｏ．２，Ｎｏ．３チャージ目でも全く同様に計算し、計算した量の剤をインジェクションした。その結果、鍋への地金付きは全く発生せず、転炉装入溶銑量も表２に示すように目標の６３．５トン±０．５トン以内に精度良く制御可能であった。また、転炉装入量が精度良く制御できたため、製品［Ｎｉ］も目標の３６重量％に対し±０．５重量％以内と精度良く制御することが可能になった。
【００１７】
【発明の効果】
以上に説明したように、本発明においては、予備処理前の溶銑成分，溶銑温度，処理剤投入量，処理後の溶銑目標成分等から処理後の溶銑温度を推定し、炭素濃度の関数として求められる処理後溶銑の液相線温度と比較して一定の余裕温度をもつように溶銑予備処理条件を制御している。これにより、溶銑温度が液相線温度より高位に保持され、鍋壁に対する地金付着や転炉への装入溶銑量の変動等が抑制され、安定した条件下の転炉製錬が可能になる。[0001]
[Industrial application fields]
The present invention relates to a method for pretreating hot metal produced in a blast furnace or an electric furnace.
[0002]
[Prior art]
When producing molten steel by smelting the hot metal produced in the blast furnace in the converter, the pretreatment agent is injected into the hot metal in the hot metal pretreatment facility before charging the hot metal into the converter, and de-Si, S and S A hot metal pretreatment method for removing P is employed. This method exerts a great effect on the production of extremely low S steel, extremely low P steel and the like.
In the hot metal pretreatment for ultra-low S steel and ultra-low P steel, information on the upper limits of the specifications of P concentration and S concentration is used to determine the hot metal components after hot metal pretreatment necessary to satisfy each standard. ing. Next, using the information on the hot metal temperature, Si concentration, S concentration and P concentration at the time of blast furnace discharge or before hot metal pretreatment, the amount of treatment agent input and the amount of gaseous oxygen necessary to obtain the hot metal components after treatment are used. The usage is determined.
[0003]
[Problems to be solved by the invention]
When producing ultra-low S steel and ultra-low P steel by the conventional method, especially when the hot metal temperature before processing is low and the P standard or S standard is severe, The hot metal carbon concentration is too low. For this reason, the hot metal temperature may be lower than the liquidus temperature, and the hot metal may solidify near the hot water surface or pan wall.
When the hot metal solidifies, not only is the work of removing the metal sticking to the pot wall necessary, but the cost of the pot refractory due to the metal sticking increases, and the yield of the kneading furnace decreases. In addition, the amount of hot metal inserted into the converter varies, making it difficult to control the end point of the converter.
[0004]
In particular, when a large amount of alloy components are melted and high alloy steel such as high Ni steel is melted in a converter, even if the amount of hot metal fluctuates slightly, a relatively large change occurs in the alloy component content. In the melting of such a steel type, when metal ingot occurs in the hot metal stage, the alloy composition greatly changes according to the change in the amount of hot metal charged into the converter. As a result, it becomes extremely difficult to hit the alloy components.
The present invention has been devised to solve such problems, and by maintaining the hot metal after the hot metal pretreatment in a temperature range having a certain margin compared to the liquidus temperature, The purpose is to prevent the adhesion of metal at the stage, to reduce the work load, to reduce the hot metal unit, and to improve the medium accuracy of the alloy composition.
[0005]
[Means for Solving the Problems]
In order to achieve the object of the hot metal pretreatment method of the present invention, de-P required for obtaining the target S concentration and target P concentration of the hot metal after pretreatment from the Si concentration, S concentration, and P concentration of the hot metal before pretreatment. Hot metal temperature T f and C concentration after pretreatment are determined based on the determined dephosphorization agent charge amount and desulfurization agent charge amount, and the Si concentration and hot metal temperature of the hot metal before pretreatment. The difference ΔT = (T f −T liq .) Between the liquidus temperature T liq of the pre-treated hot metal obtained as a function of the estimated C concentration and the estimated hot metal temperature T f is defined as the margin temperature, and the margin It is characterized by controlling the operating conditions such as the amount of desorbed P agent and the amount of desorbed S agent so that the temperature ΔT becomes a certain value or more.
This hot metal pretreatment method has a P concentration standard of 0.01% by weight or less, an S concentration standard of 0.005% by weight or less, an alloy component of 10% by weight or more, and especially a Ni content of 30% by weight or more. It is effective when melting steel types.
[0006]
Embodiment
In the present invention, normal blast furnace hot metal is used as the starting hot metal, but in some cases, hot metal melted in an electric furnace can also be used. This hot metal is de-Si, de-S, and de-P in the hot metal pretreatment facility. For example, the hot metal for steelmaking specified in JIS G2201 is transferred to a hot metal pretreatment facility, and a solubilizing agent such as soda ash, lime, sintered ore, iron ore, or a de-P agent mixed with these is injected into the hot metal. At the same time, oxygen removal is performed as necessary to remove Si, S, and P. With regard to de-Si, the hot metal can be de-Si in the middle of the blast furnace leaving process in which the hot metal or hot metal ladle receives the hot metal prior to the hot metal pretreatment process.
In this hot metal pretreatment, target values of S concentration and P concentration after hot metal pretreatment are determined from the product specification upper limits of S concentration and P concentration. Next, from the Si concentration [Si] i %, the S concentration [S] i %, and the P concentration [P] i % before the pretreatment, the target S concentration [S] f % and the target P concentration [P] after the pretreatment are obtained. Determine the amount of pretreatment agent required to obtain f %.
[0007]
For example, when using a lime-based dephosphorizing agent (basic unit X 1 kg / ton) and soda ash (basic unit X 2 kg / ton), the input amount of the pretreatment agent is obtained according to the following equation. In the formula, a 1 to a 6 are a 1 = 12.2, a 2 = 0, a 3 = 62.5, a 4 = 25.3, a 5 = 2.0, and a 6 = 0. However, the minimum value of X 2 are previously defined in advance.
X 2 = a 1 (ln [ S] i -ln [S] f) + a 2
X 1 = a 3 [Si] i + a 4 (ln [P] i −ln [P] f ) −a 5 X 2 + a 6 The right side of this equation may take in the hot metal temperature T i before processing as a variable. it can. In addition, an expression for determining the supply amount of gaseous oxygen may be added under processing conditions in which gaseous oxygen is used in combination.
Next, for example, the hot metal temperature T f and the C concentration C f after the processing are estimated according to the following equation. In the formula, b 1 to b 8 are b 1 = 0.358, b 2 = 4.105, b 3 = 94.2, b 4 = 42, b 5 = 0.01153, b 6 = 0.0, b 7 = 0.4286, b 8 = 0.0.
T f = T i -b 1 X 1 -b 2 X 2 + b 3 [Si] i -b 4
[C] f = [C] i -b 5 X 1 -b 6 X 2 + b 7 [Si] i -b 8
[0008]
If there is a problem with the analysis accuracy of the hot metal C concentration, it is assumed that the hot metal before the pretreatment is in a C saturated state, the C concentration before the pretreatment is estimated from the hot metal temperature, and this estimated C concentration is [C] i can also be replaced. For example, [C] i = 0.0025T i +1.37 may be used.
Liquidus temperature T liq . Of hot metal after pretreatment. Is determined according to the following equation as a function of carbon concentration [C] f .
T liq . = F ([C] f )
The liquidus temperature T liq . Is given by the following equation. Liquidus temperature T liq . For example, T liq . = −115 [C] f +1642 can also be used.
ΔT = T f −T liq .
When the margin temperature ΔT given in this way is smaller than a predetermined value, for example, 10 ° C., the depleting agent introduction amount X 1 is decreased so that ΔT = 10 ° C. In this case, decrease of de P agent dosages X 1 is obtained by back calculation supra expression. The hot metal temperature Tf rises with the decrease of the P removal agent, but the P concentration of the hot metal after the treatment also rises.
[0009]
The increasing tendency of the P concentration is offset by increasing the amount of lime-forming agent such as lime in the converter or decreasing the target value of the C concentration at the time of converter blowing. However, in actual operation, there is a limit to de-P in the converter especially when melting extremely low P steel. For example, when the P standard is 0.005% by weight or less, the dephosphorization amount is limited. Is preferably 10 kg / ton.
As described above, the amount of treatment agent used in the hot metal preliminary treatment is determined. When gaseous oxygen is used in combination, the supply amount of gaseous oxygen is similarly determined. Further, by combining the above formulas, the margin temperature ΔT of the hot metal may be directly calculated from the basic unit of the processing agent, or the margin temperature ΔT is directly calculated from the hot metal temperature before the treatment, the hot metal component and the target component. May be.
[0010]
The calculation of the margin temperature ΔT is also used to preferentially use the hot metal having a larger margin temperature ΔT among the hot metal discharged from a plurality of blast furnaces or electric furnaces. That is, if a hot metal having a large margin temperature ΔT is supplied as a hot metal for an extremely low S steel or an extremely low P steel, a sufficient margin temperature ΔT is obtained after the hot metal for the extremely low S steel or the extremely low P steel is pretreated. Is secured, and adhesion of the metal at the hot metal stage is prevented. As a result, the work load for removing the bullion is reduced, and the reduction of the hot metal unit and the improvement of the medium accuracy of the alloy components are achieved.
[0011]
【Example】
Using hot metal pretreatment equipment, converters, and RH vacuum degassing equipment for production of ordinary steel, special steel, etc., 3 charges of low P, low S steel containing 30 wt% or more of Ni were performed. At this time, the hot metal preliminary treatment was performed according to the present invention. The details will be described below.
First, the meanings of the variables used here are as follows.
ΔT min : Target of minimum value of margin temperature from liquidus (℃) (given)
ΔX 1max : Upper limit of lime-based dephosphorization agent basic unit decrease (kg / ton)
(Given value) (given)
X 2min : Soda ash unit minimum value (kg / ton) (function of [S] f ) (given)
T i : Hot metal temperature before processing (℃) (given)
[S] i : Before processing [S] (%) (given)
[S] f : Target after processing [S] (%) (given)
[P] i : Before processing [P] (%) (given)
[P] f : Target after processing [P] (%) (given)
[Si] i : [Si] before treatment (%) (given)
[C] i: Pretreatment [C] (%) (converted from the given or T i)
X 1 : Lime-based dephosphorization agent basic unit (kg / ton)
X 2 : Soda ash unit (kg / ton)
T f : Hot metal temperature after treatment (° C)
[C] f : [C] after processing (%)
T liq .: Liquidus temperature (° C) corresponding to hot metal after treatment [C]
ΔT: Allowable temperature from liquidus (℃)
ΔX 1 : Decrease in lime-based dephosphorization agent basic unit (kg / ton)
(Decrease only. Decrease is a plus)
[0012]
First, a numerical value to be determined in advance before operation is determined. ΔT min = 50 (° C.), ΔX 1max = 10 (kg / ton), X 2min = 18.9 (kg / ton), [S] f = 0.003 (%), [P] f = 0.004 %.
Table 1 shows the calculation process for these three charges. The numerical values in Table 1 will be described for the No. 1 embodiment. First, as the hot metal pretreatment conditions, the temperature and component of the blast furnace were set as the temperature and component before the treatment, and the values thereof were T i = 1340 (° C.) and [S] i = 0.011. (%), [P] i = 0.110 (%), [Si] i = 0.57 (%), and [C] i = 4.54 (%). First, the soda ash basic unit X 2 and the lime-based de-P agent basic unit X 1 were determined as follows.
X 2 = max {12.2 (ln [S] i -ln [S] f, X 2min}
= 18.9 (kg / ton) (1)
X 1 = 62.5 [Si] i +25.3 (ln [P] i -ln [P] f)
-2.0X 2 = 81.7 (kg / ton) (2)
[0013]
Next, the temperature and [C] concentration of the hot metal after pretreatment when soda ash is X 2 = 18.9 kg / ton as described above and the de-P agent is X 1 = 81.7 kg / ton as calculated above are as follows. The estimation was as follows.
T liq . = −115 [C] f + 1642 = 1200 (° C.) (5)
Thereby, margin temperature (DELTA) T is given by following Formula from the liquidus temperature in a hot metal after a process.
ΔT = T f −T liq . = 1245-1200 = 45 (° C.) (6)
[0014]
By the way, the target of the minimum value of the margin temperature from the preset liquidus is
ΔT min = 50 (° C)
The marginal temperature ΔT calculated above is 5 ° C. lower than the minimum target. That is,
ΔT−ΔT min = −5 (° C.) <0 (7)
It is. Therefore, since the marginal temperature is low as it is, there is a possibility that the metal bar is attached to the pan at the hot metal stage. Therefore, the amount of lime-based dephosphorizing agent is reduced. Although a method for reducing soda ash is also conceivable, since the P converter, which is the next step, is easier to remove P than to remove S, the amount of dephosphorizing agent is reduced.
Here, a calculation formula of a reduction allowance when reducing the de-P agent is derived. Substituting Equations (3) and (5) into Equation (6) and further substituting Equation (4),
Since (8) coefficient of X 1 in formula is -1.684, to a margin temperature target is a value only de P agent divided by the absolute value 1.684 of the coefficients a margin temperature Missing It may be reduced. However, the upper limit of the reduction of the de-P agent is suppressed to ΔX 1max . Therefore, the reduction allowance ΔX 1 of the de-P agent is given by the following equation.
[0016]
The above is No. The details of the operation at the first charge. 2, no. The same calculation was made for the third charge, and the calculated amount of the agent was injected. As a result, no metal in the pan was generated, and the amount of molten iron charged in the converter could be accurately controlled within the target 63.5 tons ± 0.5 tons as shown in Table 2. Moreover, since the amount of converter charge could be controlled with high accuracy, the product [Ni] could be controlled with accuracy within ± 0.5% by weight relative to the target of 36% by weight.
[0017]
【The invention's effect】
As described above, in the present invention, the hot metal temperature after the treatment is estimated from the hot metal component before the pretreatment, the hot metal temperature, the amount of the treatment agent introduced, the hot metal target component after the treatment, etc., and obtained as a function of the carbon concentration. The hot metal pretreatment conditions are controlled so as to have a certain marginal temperature as compared with the liquidus temperature of the hot metal after treatment. This keeps the hot metal temperature higher than the liquidus temperature, suppresses the adhesion of metal to the pan wall, fluctuations in the amount of molten iron charged to the converter, etc., and enables converter smelting under stable conditions. Become.
Claims (1)
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP08593296A JP3611664B2 (en) | 1996-03-14 | 1996-03-14 | Hot metal pretreatment method |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP08593296A JP3611664B2 (en) | 1996-03-14 | 1996-03-14 | Hot metal pretreatment method |
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| Publication Number | Publication Date |
|---|---|
| JPH09249909A JPH09249909A (en) | 1997-09-22 |
| JP3611664B2 true JP3611664B2 (en) | 2005-01-19 |
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| JP08593296A Expired - Fee Related JP3611664B2 (en) | 1996-03-14 | 1996-03-14 | Hot metal pretreatment method |
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