JP2019218609A - Dephosphorization method for molten iron - Google Patents

Dephosphorization method for molten iron Download PDF

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JP2019218609A
JP2019218609A JP2018117273A JP2018117273A JP2019218609A JP 2019218609 A JP2019218609 A JP 2019218609A JP 2018117273 A JP2018117273 A JP 2018117273A JP 2018117273 A JP2018117273 A JP 2018117273A JP 2019218609 A JP2019218609 A JP 2019218609A
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hot metal
dephosphorizing
dephosphorization
blowing
dephosphorizing agent
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JP7361458B2 (en
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遼 北野
Ryo Kitano
遼 北野
木下　聡
Satoshi Kinoshita
聡 木下
千裕 浅見
Chihiro Asami
千裕 浅見
昌平 柿本
Shohei Kakimoto
昌平 柿本
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Nippon Steel Corp
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Abstract

To provide a dephosphorization method for molten iron which is excellent in dephosphorization efficiency of molten iron and can suppress decarburization which is incidentally generated in dephosphorization blowing.SOLUTION: The dephosphorization method for molten iron according to one embodiment of the present invention includes a step of charging a first dephosphorization agent into molten iron, and a step of dephosphorization of the molten iron by blowing oxygen into the molten iron. In the step of dephosphorization by blowing, a second dephosphorization agent is further charged into the molten iron, so as to cause an amount of oxygen blown in a period between finishing of the charging the second dephosphorization agent and finishing of the blowing of oxygen to be 20% or less of a total blowing amount of oxygen in the dephosphorization by blowing.SELECTED DRAWING: Figure 1

Description

本発明は溶銑の脱りん方法に関する。   The present invention relates to a method for dephosphorizing hot metal.

溶銑に含まれるＰ（りん）は、強度、靭性、及び伸び等の鋼材の諸特性に悪影響を及ぼすので、鋼材の精錬段階でこれを可能な限り取り除く必要がある。   Since P (phosphorus) contained in the hot metal adversely affects various properties of the steel material such as strength, toughness, and elongation, it must be removed as much as possible during the refining stage of the steel material.

溶銑からＰを取り除く工程は脱りん精錬と称され、この脱りん精錬ではＣａＯ（又はＣａＣＯ３）を主成分とする化合物である脱りん剤が用いられる。脱りん剤は、脱りん精錬において脱りん能を有するスラグを生成することにより、脱りんに寄与する。脱りん剤の使用量が多いほど、スラグの塩基度が上昇し、スラグの脱りん能が向上する。しかしながら、脱りん剤の使用量が多いとスラグ量も増大する。スラグは環境負荷が高く、これの処理は精錬コストを増大させる。従って、脱りん工程を効率化することにより、脱りん剤の使用量を低減することが望まれる。 The step of removing P from the hot metal is called dephosphorization refining, and in this dephosphorization refining, a dephosphorizing agent that is a compound containing CaO (or CaCO 3 ) as a main component is used. The dephosphorizing agent contributes to dephosphorization by generating slag having a dephosphorizing ability in dephosphorization refining. As the amount of the dephosphorizing agent used increases, the basicity of the slag increases, and the dephosphorizing ability of the slag improves. However, when the amount of the dephosphorizing agent used is large, the amount of slag also increases. Slag has a high environmental load, and its treatment increases refining costs. Therefore, it is desired to reduce the amount of the dephosphorizing agent by increasing the efficiency of the dephosphorizing step.

特許文献１には、スピッティング量を低減して、かつ溶銑中の［Ｐ］濃度を０．０２０％以下とすることができる溶銑の脱りん方法が開示されている。この脱りん方法においては、第一脱りん剤であるＣａＯ含有物が上置き添加された溶銑をガス攪拌し、かつ、酸素含有ガスを上吹きし、カバースラグを生成して溶銑の予備脱りんを行った後、さらに、溶銑に第二脱りん剤であるＣａＯ含有脱りん剤を、酸素含有ガスをキャリアガスとして吹き付けることとされる。しかしながら特許文献１においては、スラグ量を減少させること、及び脱りん効率を向上させることが課題とされておらず、また、その方法の開示もない。例えば後述されるような、本発明者らが検討した脱りん剤の投入のタイミングについて、何ら示唆されていない。   Patent Document 1 discloses a method for dephosphorizing hot metal in which the amount of spitting can be reduced and the [P] concentration in the hot metal can be made 0.020% or less. In this dephosphorization method, the hot metal to which the CaO-containing material as the first dephosphorizing agent is placed above is gas-stirred, and the oxygen-containing gas is blown upward to generate cover slag, thereby preliminarily dephosphorizing the hot metal. After that, a CaO-containing dephosphorizing agent, which is a second dephosphorizing agent, is blown onto the hot metal with an oxygen-containing gas as a carrier gas. However, Patent Literature 1 does not discuss reducing the amount of slag and improving the dephosphorization efficiency, and does not disclose a method therefor. For example, there is no suggestion about the timing of the introduction of the dephosphorizing agent studied by the present inventors as described later.

特許文献２には、同一の転炉で脱りん精錬と脱炭精錬を行うことによるメリットを享受しつつ、Ｐ規格の特に厳しい極低りん鋼についても安定的に溶製することのできる転炉精錬方法が開示されている。この転炉精錬方法では、最初の脱りん精錬とその後のスラグ除去を行った後、脱炭精錬を行う前に、フラックスを追加して第２の脱りん精錬を行い、その後にスラグ除去を行い、さらにその後に脱炭精錬を行うことにより、脱炭精錬終了後の溶鋼中Ｐ濃度を十分に極低Ｐ鋼レベルまで低減することができるとされる。しかしながら特許文献２においては、それぞれの脱りん精錬において脱りん効率を向上させることについて検討されておらず、また、その方法の開示もない。   Patent Literature 2 discloses a converter capable of stably smelting extremely low-phosphorus steel having a particularly strict P standard while enjoying the advantages of performing dephosphorization refining and decarburization refining in the same converter. A refining method is disclosed. In this converter refining method, after performing the first dephosphorization refining and subsequent slag removal, before performing decarburization refining, a flux is added to perform a second dephosphorization refining, and then slag removal is performed. Further, by performing decarburization refining thereafter, the P concentration in the molten steel after the end of decarburization refining can be sufficiently reduced to an extremely low P steel level. However, Patent Document 2 does not discuss improving the dephosphorization efficiency in each of the dephosphorization refining, and does not disclose a method thereof.

また、脱りん精錬においては、脱りん吹錬（脱りんのために酸素を溶銑に吹き込むこと）によって付随的に生ずる脱炭反応を抑制することが好ましい。脱炭精錬において溶銑中のＣは熱源となるので、脱炭精錬の前の脱りん精錬において溶銑の炭素量が低下すると、脱炭精錬において昇熱材投入量が増大する。しかし、先行技術においてこの問題はあまり重要視されておらず、解決策も検討されていない。   Further, in the dephosphorization refining, it is preferable to suppress the decarburization reaction accompanying the dephosphorization blowing (by blowing oxygen into the hot metal for dephosphorization). Since C in the hot metal is a heat source in the decarburization refining, if the carbon content of the hot metal decreases in the dephosphorization refining before the decarburization refining, the amount of the heating material input increases in the decarburization refining. However, in the prior art, this problem is not given much importance, and no solution is considered.

特開２００１−６４７１３号公報JP 2001-64713 A 特開２０１１−１４４４１５号公報JP 2011-144415 A

本発明は、脱りん剤使用量及びスラグ発生量を増大させることなく十分に溶銑を脱りんするために、溶銑の脱りん効率に優れた溶銑の脱りん方法を提供することを課題とする。また、本発明は、脱りん吹錬の際に付随的に生ずる脱炭を抑制し、続く脱炭吹錬における昇熱材投入量を削減することを課題とする。   An object of the present invention is to provide a method for dephosphorizing hot metal with excellent hot metal dephosphorizing efficiency in order to sufficiently dephosphorize hot metal without increasing the amount of dephosphorizer used and the amount of slag generated. Further, another object of the present invention is to suppress decarburization that occurs incidentally during dephosphorization blowing, and to reduce the amount of heat-raising material input during subsequent decarburization blowing.

本発明の要旨とするところは以下の通りである。
（１）本発明の一態様に係る溶銑の脱りん方法は、前記溶銑に第一脱りん剤を投入する工程と、前記溶銑に酸素を吹き込むことにより前記溶銑を脱りん吹錬する工程と、を備え、前記脱りん吹錬する工程中に、さらに第二脱りん剤を前記溶銑に投入し、前記第二脱りん剤の投入終了時期と、前記酸素の吹込み終了時期との間に吹き込まれる酸素の量を、前記脱りん吹錬における前記酸素の全吹込み量の２０％以下とする。
（２）上記（１）に記載の溶銑の脱りん方法では、前記第二脱りん剤の投入終了時期と、前記酸素の吹込み終了時期との間に吹き込まれる酸素の量を、前記脱りん吹錬における前記酸素の全吹込み量の１０％以下としてもよい。
（３）上記（１）又は（２）に記載の溶銑の脱りん方法では、前記溶銑の脱りん方法が、前記溶銑に前記第一脱りん剤を投入する前に、前記溶銑の初期成分におけるＳｉ含有量を測定する工程をさらに備え、前記第一脱りん剤のＣａＯ等量と、前記溶銑の前記初期成分における前記Ｓｉ含有量のＳｉＯ２等量との比を０．８０〜１．２０としてもよい。
（４）上記（１）〜（３）のいずれか一項に記載の溶銑の脱りん方法では、前記第二脱りん剤の投入量を、前記溶銑を前記脱りん精錬する工程の終了時のスラグの装入塩基度が１．３〜４．０となるように制御してもよい。
（５）上記（１）〜（４）のいずれか一項に記載の溶銑の脱りん方法では、前記第一脱りん剤及び前記第二脱りん剤の一方又は両方を、生石灰、石灰石、カルシウムフェライト、ドロマイト系石灰、並びに転炉スラグ又は二次精錬スラグであってＣａＯを含有するものから選択される一種以上を含むものであって、ＣａＯ、ＣａＣＯ３、及びＣａＦ２のＣａＯ等量での合計含有量が３０〜１００質量％であるものとしてもよい。
（６）上記（１）〜（５）のいずれか一項に記載の溶銑の脱りん方法では、前記第一脱りん剤を、塊状の脱りん剤としてもよい。
（７）上記（１）〜（６）のいずれか一項に記載の溶銑の脱りん方法では、前記第二脱りん剤を、粉状の脱りん剤としてもよい。
（８）上記（７）に記載の溶銑の脱りん方法では、前記第二脱りん剤を、Ａｒ、Ｎ２、ＣＯ２、及びＯ２からなる群から選択される一種以上であるキャリアガスを用いて前記溶銑に吹き込んでもよい。 The gist of the present invention is as follows.
(1) A method for dephosphorizing hot metal according to one embodiment of the present invention includes a step of charging a first dephosphorizing agent to the hot metal, and a step of dephosphorizing and blowing the hot metal by blowing oxygen into the hot metal. During the dephosphorizing and blowing step, a second dephosphorizing agent is further charged into the hot metal, and the second dephosphorizing agent is blown between the completion of the supply of the second dephosphorizer and the completion of the oxygen blowing. The amount of oxygen to be supplied is set to 20% or less of the total amount of oxygen blown in the dephosphorization blowing.
(2) In the method for dephosphorizing hot metal according to the above (1), the amount of oxygen blown between the end of charging of the second dephosphorizing agent and the end of blowing of oxygen is determined by the dephosphorization. It may be 10% or less of the total amount of oxygen blown in the blowing.
(3) In the method for dephosphorizing hot metal according to the above (1) or (2), the method for dephosphorizing hot metal is characterized in that before the first dephosphorizing agent is added to the hot metal, further comprising the step of measuring the Si content, the CaO equivalent amount of the first dephosphorization agents, the ratio of the SiO 2 equivalent amount of the Si content in the initial composition of the molten iron 0.80 to 1.20 It may be.
(4) In the method for dephosphorizing hot metal according to any one of the above (1) to (3), the input amount of the second dephosphorizing agent may be adjusted at the end of the step of dephosphorizing and refining the hot metal. Control may be performed so that the basicity of charging slag is 1.3 to 4.0.
(5) In the method for dephosphorizing hot metal according to any one of the above (1) to (4), one or both of the first dephosphorizing agent and the second dephosphorizing agent may be lime, limestone, calcium, Ferrite, dolomite-based lime, and converter slag or secondary smelting slag containing one or more selected from CaO-containing slag, wherein CaO, CaCO 3 , and CaF 2 in the same amount of CaO The total content may be 30 to 100% by mass.
(6) In the method for dephosphorizing hot metal according to any one of the above (1) to (5), the first dephosphorizing agent may be a massive dephosphorizing agent.
(7) In the method for dephosphorizing hot metal according to any one of the above (1) to (6), the second dephosphorizing agent may be a powdery dephosphorizing agent.
(8) In the method for dephosphorizing hot metal according to (7), the second dephosphorizing agent is a carrier gas that is at least one selected from the group consisting of Ar, N 2 , CO 2 , and O 2. The hot metal may be blown into the hot metal.

本発明の脱りん方法によれば、脱りん吹錬時の溶銑の脱りん効率に優れるので、例えばこれに続く脱炭吹錬におけるスラグ量の抑制などが可能となる。さらに本発明の脱りん方法によれば、脱りん吹錬時の脱炭反応を抑制できるので、続く脱炭精錬における昇熱材投入量の削減が可能となる。   ADVANTAGE OF THE INVENTION According to the dephosphorization method of this invention, since the dephosphorization efficiency of the hot metal at the time of dephosphorization blowing is excellent, it becomes possible to control the amount of slag in the subsequent decarburization blowing, for example. Furthermore, according to the dephosphorization method of the present invention, since the decarburization reaction during dephosphorization blowing can be suppressed, it is possible to reduce the amount of heat-up material input in the subsequent decarburization refining.

第二脱りん剤の投入箇所の一例を示す図である。It is a figure which shows an example of the injection point of a 2nd dephosphorizing agent. 水準１〜４における実績Ｌｐの平均値（平均実績Ｌｐ）を示すグラフである。It is a graph which shows the average value (average result Lp) of the result Lp in the levels 1-4. 横軸を最低到達塩基度とし、縦軸を実績Ｌｐとした、実施例及び比較例の散布図である。It is a scatter diagram of an Example and a comparative example which made the horizontal axis the minimum attained basicity and the vertical axis made the actual result Lp. 横軸を装入塩基度とし、縦軸を実績Ｌｐとした、実施例及び比較例の散布図である。It is a scatter diagram of an Example and a comparative example which set the horizontal axis to the loading basicity and the vertical axis to the actual result Lp. 水準１〜４における脱りん吹錬中の脱炭量を示すグラフである。It is a graph which shows the decarburization amount during dephosphorization blowing at the levels 1-4.

本発明者らは、スラグ量を増大させることなく脱りん精錬の脱りん能力を向上させること（即ち、脱りん精錬の脱りん効率を高めること）について検討を重ねた。そして本発明者らは、脱りん精錬における脱りん吹錬（脱りんのために酸素を溶銑に吹き込むこと）の際に脱りん剤を投入し、且つ、その投入を脱りん吹錬の末期まで継続することで、脱りん吹錬後の溶銑に残存するりん量を減少させられることを知見した。   The present inventors have repeatedly studied to improve the dephosphorization capacity of the dephosphorization refining without increasing the amount of slag (that is, to increase the dephosphorization efficiency of the dephosphorization refining). Then, the present inventors supply a dephosphorizing agent at the time of dephosphorization blowing (injecting oxygen into hot metal for dephosphorization) in the dephosphorization refining, and supply the dephosphorizing agent until the end of the dephosphorization blowing. It was found that by continuing, the amount of phosphorus remaining in the hot metal after dephosphorization blowing could be reduced.

脱りん剤とは、ＣａＯ（又はＣａＣＯ３等）を主成分とする化合物である。脱りん剤中に含まれるＣａＣＯ３は、溶銑の熱によって短時間のうちに分解されてＣａＯ及びＣＯ２となる。脱りん剤の一例として、生石灰、石灰石、及びドロマイト系材料等の副材、転炉スラグ及び二次精錬スラグ等であってＣａＯを含有するもの、並びにそれらの混合物等がある。脱りん剤に含まれるＣａによって、脱りん吹錬中に以下の化学反応が生じる。
２［Ｐ］＋５（ＦｅＯ）→（Ｐ２Ｏ５）＋５［Ｆｅ］：式Ａ
（Ｐ２Ｏ５）＋３（ＣａＯ）→（３ＣａＯ・Ｐ２Ｏ５）：式Ｂ
式Ａ及びＢに記載された、角括弧で囲まれた化学式は溶銑中の成分の化学式であり、丸括弧で囲まれた化学式はスラグ中に溶融した成分の化学式である。脱りん吹錬においては、まず式Ａに示されるように、［Ｐ］、即ち溶銑中のＰが、（ＦｅＯ）、即ちスラグ中のＦｅＯによって酸化されてＰ２Ｏ５となる。次に式Ｂに示されるように、このＰ２Ｏ５が（ＣａＯ）、即ちスラグ中の溶融ＣａＯに固定されて、安定化された化合物である（３ＣａＯ・Ｐ２Ｏ５）が生成される。 The dephosphorizing agent is a compound containing CaO (or CaCO 3 or the like) as a main component. CaCO 3 contained in the dephosphorizing agent is decomposed in a short time by the heat of the hot metal into CaO and CO 2 . Examples of the dephosphorizing agent include auxiliary materials such as quicklime, limestone, and dolomite-based materials, converter slag, secondary refining slag, and the like containing CaO, and mixtures thereof. The following chemical reaction occurs during dephosphorization blowing by Ca contained in the dephosphorizer.
2 [P] +5 (FeO) → (P 2 O 5 ) +5 [Fe]: Formula A
(P 2 O 5 ) +3 (CaO) → (3CaO · P 2 O 5 ): Formula B
The chemical formulas enclosed in square brackets described in Formulas A and B are the chemical formulas of the components in the hot metal, and the chemical formulas enclosed in parentheses are the chemical formulas of the components melted in the slag. In dephosphorization blowing, first, as shown in Formula A, [P], i.e. P in the hot metal becomes a (FeO), i.e. P 2 O 5 is oxidized by FeO in the slag. Next, as shown in Formula B, the P 2 O 5 is fixed to (CaO), that is, the molten CaO in the slag, to produce a stabilized compound (3CaO · P 2 O 5 ). .

式Ａ及び式Ｂに示されるように、（ＣａＯ）が脱りんのために非常に重要である。従って従来技術によれば、脱りん吹錬における上述の式Ｂの反応を促進させるために、（ＣａＯ）の供給源である脱りん剤は脱りん吹錬の初期段階及び中期段階で溶銑に投入されるべきであると考えられてきた。また、脱りん剤を脱りん吹錬末期に溶銑に投入したとしても、その効果は極めて限定的なものであると考えられてきた。脱りん吹錬の末期まで脱りん剤の投入を継続すべきであるという本発明者らの知見は、従来技術と全く相違するものであった。   As shown in formulas A and B, (CaO) is very important for dephosphorization. Therefore, according to the prior art, in order to promote the reaction of the above formula B in the dephosphorization blowing, the dephosphorizing agent which is a source of (CaO) is added to the hot metal in the initial stage and the middle stage of the dephosphorization blowing. It has been thought that it should be. Even if the dephosphorizing agent is added to the hot metal at the end of dephosphorization blowing, the effect has been considered to be extremely limited. The present inventors' knowledge that the dephosphorizing agent should be continuously fed until the end of dephosphorization blowing was completely different from the prior art.

脱りん吹錬の末期における脱りん剤の投入が溶銑の脱りんに貢献する理由は、以下の通りであると推定された。式Ａに示されるように、溶銑中のＰをＰ２Ｏ５に変化させるためには、スラグ中のＦｅＯが必要とされる。しかしスラグ中のＦｅＯの量は、脱りん吹錬末期に生じる脱炭反応によって減少すると考えられる。即ち、脱りん吹錬末期には、下記式Ｃに示される脱炭反応によるＦｅＯ量の減少により、式Ａの反応の進行が抑制されると考えられる。
（ＦｅＯ）＋［Ｃ］→［Ｆｅ］＋ＣＯ↑：式Ｃ
式Ｃに記載された「ＣＯ↑」とは、ガスとなって溶銑及びスラグから放出されるＣＯである。 It is estimated that the reason why the dephosphorization at the end of dephosphorization blowing contributes to the dephosphorization of hot metal is as follows. As shown in Formula A, FeO in slag is required to change P in the hot metal to P 2 O 5 . However, it is considered that the amount of FeO in the slag is reduced by the decarburization reaction occurring at the end of dephosphorization blowing. That is, at the end of the dephosphorization blowing, it is considered that the progress of the reaction of the formula A is suppressed by the decrease in the amount of FeO due to the decarburization reaction represented by the following formula C.
(FeO) + [C] → [Fe] + CO ↑: Formula C
“CO ↑” described in Formula C is CO released as gas from hot metal and slag.

一方、脱りん吹錬末期にＣａＯが溶銑に投入された場合、以下の式Ｄによって示される、ＣａＯ及びＦｅＯの複合体（ＣａＯ−ＦｅＯ）が生成する反応が生じると考えられる。
（ＣａＯ）＋［Ｆｅ］＋１／２Ｏ２→（ＣａＯ−ＦｅＯ）：式Ｄ
このＣａＯ−ＦｅＯが、式Ａにおける（ＦｅＯ）として働き、式Ａの反応を促進するものと考えられる。即ち、脱りん吹錬末期に溶銑に投入されるＣａＯは、脱りん吹錬中に不足するスラグ中のＦｅＯを補充することにより、脱りんに寄与していると考えられる。 On the other hand, when CaO is introduced into the hot metal at the end of dephosphorization blowing, it is considered that a reaction represented by the following formula D to produce a complex of CaO and FeO (CaO-FeO) occurs.
(CaO) + [Fe] + ／ O 2 → (CaO—FeO): Formula D
It is considered that this CaO—FeO functions as (FeO) in the formula A and promotes the reaction of the formula A. That is, it is considered that CaO introduced into the hot metal at the end of dephosphorization blowing contributes to dephosphorization by replenishing FeO in slag which is insufficient during dephosphorization blowing.

また、脱りん吹錬末期までＣａＯが溶銑に投入された場合、上記式Ｄの反応が促進されることに加え、以下の式Ｅの反応が抑制されると考えられる。
［Ｃ］＋１／２Ｏ２→ＣＯ↑：式Ｅ
式Ｅの反応が抑制されることは、脱りん吹錬における脱炭が抑制されることを意味する。脱りん吹錬における脱炭が抑制され、脱りん吹錬後の溶銑にＣが多く残されると、このＣが続く脱炭吹錬において熱源として働くので、脱炭吹錬における昇熱材投入量の削減が可能となる。脱りん吹錬の末期まで脱りん剤を投入することは、このような観点からも顕著な効果を奏すると考えられる。 Further, when CaO is charged into the hot metal until the end of dephosphorization blowing, it is considered that the reaction of the following formula E is suppressed in addition to the reaction of the above formula D being promoted.
[C] + 1 / 2O 2 → CO ↑: Formula E
Suppression of the reaction of the formula E means that decarburization in dephosphorization blowing is suppressed. If decarburization during dephosphorization blowing is suppressed and a large amount of C is left in the hot metal after dephosphorization blowing, this C acts as a heat source in the subsequent decarburization blowing, so the heating material input amount during decarburization blowing Can be reduced. It is considered that the introduction of the dephosphorizing agent until the end of the dephosphorization blowing has a remarkable effect also from this viewpoint.

以上述べた技術思想に基づく本実施形態に係る溶銑の脱りん方法は、溶銑に第一脱りん剤を投入する工程と、溶銑に酸素を吹き込むことにより溶銑を脱りん吹錬する工程と、を備え、脱りん吹錬する工程において、さらに第二脱りん剤が溶銑に投入され、第二脱りん剤の投入終了時期と、酸素の吹込み終了時期との間に吹き込まれる酸素の量が、脱りん吹錬における酸素の全吹込み量の２０％以下とされる。以下に、本実施形態に係る溶銑の脱りん方法について詳細に述べる。   The method for dephosphorizing hot metal according to the present embodiment based on the technical idea described above includes a step of charging the hot metal with a first dephosphorizing agent and a step of dephosphorizing and blowing the hot metal by blowing oxygen into the hot metal. In the step of dephosphorization and blowing, the second dephosphorizing agent is further charged into the hot metal, and the amount of oxygen blown between the end of charging the second dephosphorizing agent and the end of blowing oxygen, It is 20% or less of the total amount of oxygen blown in the dephosphorization blowing. Hereinafter, the method for dephosphorizing hot metal according to the present embodiment will be described in detail.

本実施形態に係る溶銑の脱りん方法では、まず、溶銑に第一脱りん剤を投入する。第一脱りん剤は、溶銑の表面にカバースラグを形成し、スピッティングを抑制することなどを目的として投入される。第一脱りん剤の形態及び投入量は特に限定されず、溶銑の成分、及び鋼材成分の目標値等に応じて適宜設定することができる。投入ロスを防止する観点から、第一脱りん剤の形態は塊状であることが好ましい。   In the method for dephosphorizing hot metal according to the present embodiment, first, a first dephosphorizing agent is introduced into hot metal. The first dephosphorizing agent is added for the purpose of forming cover slag on the surface of the hot metal and suppressing spitting. The form and amount of the first dephosphorizing agent are not particularly limited, and can be appropriately set according to the components of the hot metal, the target values of the steel material components, and the like. From the viewpoint of preventing a charging loss, the form of the first dephosphorizing agent is preferably a lump.

また、第一脱りん剤の投入量は、第一脱りん剤のＣａＯ等量と溶銑の初期成分におけるＳｉ含有量のＳｉ等量との比（即ち、第一脱りん剤のＣａＯ等量／溶銑の初期成分のＳｉ含有量のＳｉＯ２等量）が０．８０〜１．２０になるように制御されることが好ましい。脱りん剤のＣａＯ等量とは、脱りん剤中のＣａが全てＣａＯを形成していると仮定した場合の、脱りん剤のＣａＯ含有量である。溶銑の初期成分におけるＳｉ含有量のＳｉＯ２等量とは、溶銑のＳｉが全てＳｉＯ２になったと仮定した場合のＳｉＯ２量である。上述の条件を満たして第一脱りん剤を投入した場合、脱りん吹錬の進行によって溶銑中のＳｉが実質的に全てＳｉＯ２となった時点でのスラグの塩基度がおおむね０．８０〜１．２０となる。 The amount of the first dephosphorizing agent is determined by the ratio of the CaO equivalent of the first dephosphorizing agent to the Si equivalent of the Si content in the initial component of the hot metal (that is, the CaO equivalent of the first dephosphorizing agent / It is preferable that the initial content of the hot metal is controlled so that the Si content of the initial component (equivalent to SiO 2 ) is 0.80 to 1.20. The CaO equivalent of the dephosphorizing agent is the CaO content of the dephosphorizing agent on the assumption that all Ca in the dephosphorizing agent forms CaO. The SiO 2 eq of Si content in the initial composition of the molten iron, a SiO 2 amount when Si hot metal all assumed to become SiO 2. If you put the first dephosphorization agent satisfies the conditions described above, the basicity of the slag at the time when Si in the molten iron becomes substantially all SiO 2 with the progress of the dephosphorization blowing is generally 0.80 1.20.

第一脱りん剤のＣａＯ等量と溶銑の初期成分におけるＳｉ含有量のＳｉＯ２等量との比を０．８０以上とすることにより、脱りんを高い水準で実施することができる。これは、スラグ中に溶融ＣａＯを十分に供給し、スラグの脱りん能を向上させられるからであると考えられる。一方、第一脱りん剤のＣａＯ等量と溶銑の初期成分におけるＳｉ含有量のＳｉＯ２等量との比を１．２０以下とすることにより、ＣａＯの滓化率を高く保ち、脱りん効率を一層高く保つことができる。第一脱りん剤のＣａＯ等量と溶銑の初期成分におけるＳｉ含有量のＳｉＯ２等量との比は、さらに好ましくは０．８５以上、又は０．９０以上である。第一脱りん剤のＣａＯ等量と溶銑の初期成分におけるＳｉ含有量のＳｉＯ２等量との比は、さらに好ましくは１．１５以下、又は１．１０以下である。 The ratio of the SiO 2 equivalent amount of the Si content in the initial component of CaO equal amounts and the hot metal of the first dephosphorization agents by 0.80 or more, it is possible to implement the dephosphorization at a high level. This is considered to be because the molten CaO is sufficiently supplied into the slag to improve the dephosphorization ability of the slag. On the other hand, by the ratio of the SiO 2 equivalent amount of the Si content in the initial component of CaO equal amounts and the hot metal of the first dephosphorization agents and 1.20 or less for maintaining a large slag ratio of CaO, dephosphorization efficiency Can be kept higher. The ratio between the CaO equivalent of the first dephosphorizing agent and the SiO 2 equivalent of the Si content in the initial component of the hot metal is more preferably 0.85 or more, or 0.90 or more. The ratio of the SiO 2 equivalent amount of the Si content in the initial component of CaO equal amounts and the hot metal of the first dephosphorization agent is more preferably 1.15 or less, or 1.10 or less.

上述のように第一脱りん剤の投入量を制御するために、本実施形態に係る溶銑の脱りん方法では、第一脱りん剤の投入の前に溶銑の初期成分のＳｉ含有量を測定してもよい。また、後述する脱りん吹錬終了時のスラグの塩基度の推定のために、溶銑の初期成分におけるＳｉ以外の元素の含有量を合わせて測定してもよい。なお、溶銑の初期成分とは、脱りん吹錬前の溶銑の成分を意味する。溶銑のＳｉ含有量等の測定は、溶銑を炉に装入してから実施しても、その前に実施してもよい。また、溶銑が凝固した状態にある際（即ち銑鉄の形態である際）に上述の測定を実施することも当然妨げられない。   In order to control the input amount of the first dephosphorizing agent as described above, in the method for dephosphorizing hot metal according to the present embodiment, the Si content of the initial component of the hot metal is measured before the first dephosphorizing agent is input. May be. In addition, in order to estimate the basicity of slag at the end of dephosphorization blowing, which will be described later, the content of elements other than Si in the initial components of the hot metal may be measured together. The initial component of the hot metal means the component of the hot metal before dephosphorization blowing. The measurement of the Si content or the like of the hot metal may be performed after charging the hot metal into the furnace, or may be performed before that. In addition, when the molten iron is in a solidified state (that is, when the molten iron is in the form of pig iron), the above-described measurement is naturally not hindered.

なお、脱りん吹錬の開始前に溶銑に別途Ｓｉを添加する場合、及び第一脱りん剤にＳｉが含まれる場合等、スラグのＳｉＯ２源が溶銑に限られない場合、溶銑以外に由来するＳｉも第一脱りん剤の投入量の決定する際に考慮されるべきである。例えば、脱りん剤使用量の削減のために、脱りん精錬によって生じるスラグを別の脱りん精錬においてリサイクル使用する場合、溶銑以外に由来するＳｉＯ２源が生じることとなる。この場合、溶銑以外に由来するＳｉも「溶銑の初期成分におけるＳｉ含有量のＳｉＯ２等量」に含めればよい。即ち、脱りん吹錬におけるＳｉ酸化反応の終了時におけるスラグの、装入量に基づく塩基度の推定値が０．８０〜１．２０になるように、第一脱りん剤及びその他の添加物の装入量が制御されればよい。 In the case of adding an additional Si in molten iron before the start of the dephosphorization blowing and the like if Si is contained in the first dephosphorization agents, if SiO 2 source slag is not limited to molten pig iron, from a non-hot metal Should be taken into account when determining the amount of the first dephosphorizing agent. For example, when slag generated by dephosphorization refining is recycled and used in another dephosphorization refining in order to reduce the amount of dephosphorizer used, an SiO 2 source other than hot metal is generated. In this case, Si derived from sources other than the hot metal may be included in the “equivalent Si 2 content of the Si content in the initial components of the hot metal”. That is, the first dephosphorizing agent and other additives so that the estimated basicity based on the charged amount of slag at the end of the Si oxidation reaction in dephosphorization blowing is 0.80 to 1.20. What is necessary is just to control the charging amount.

次に、溶銑を脱りん吹錬する。脱りん吹錬は、溶銑への酸素の吹込みによって実施される。この脱りん吹錬において、第二脱りん剤が溶銑に投入される。この脱りん吹錬において、第二脱りん剤の投入開始のタイミングは特に限定されず、操業状況に鑑みて適宜設定することができる。一方、脱りん吹錬において、第二脱りん剤の投入終了時期が、第二脱りん剤の投入終了時期と酸素の吹込み終了時期との間に吹き込まれる酸素の量が、脱りん吹錬における酸素の全吹込み量の２０％以下となるように制御される。なお、通常の高炉法によって得られる銑鉄に適用される脱りん吹錬において、吹き込まれる酸素の総量は約１２Ｎｍ３／ｔとされることが通常である。例えばこのような操業条件においては、約９．６Ｎｍ３／ｔの酸素を吹込み終えるまで、第二脱りん剤の投入を中止してはならない。 Next, the hot metal is dephosphorized and blown. Dephosphorization blowing is performed by blowing oxygen into the hot metal. In this dephosphorization blowing, a second dephosphorizing agent is charged into the hot metal. In this dephosphorization blowing, the timing of the start of the introduction of the second dephosphorizing agent is not particularly limited, and can be appropriately set in view of the operation situation. On the other hand, in dephosphorization blowing, the end time of the second dephosphorizing agent injection is determined by the amount of oxygen blown between the end time of the second dephosphorizing agent injection end and the oxygen blowing end time. Is controlled so as to be 20% or less of the total amount of oxygen blown. In addition, in the dephosphorization blowing applied to pig iron obtained by a normal blast furnace method, the total amount of oxygen blown is usually about 12 Nm 3 / t. For example, under such operating conditions, the introduction of the second dephosphorizing agent should not be stopped until about 9.6 Nm 3 / t of oxygen is completely blown.

第二脱りん剤の投入終了時期が早く、第二脱りん剤の投入終了時期と酸素の吹込み終了時期との間に吹き込まれる酸素の量が、脱りん吹錬における酸素の全吹込み量の２０％超となった場合、溶銑の脱りん量を向上させることができない。これは、脱りん吹錬の末期に生じる脱炭反応によるスラグ中のＦｅＯ量の減少を、第二脱りん剤の投入によって補うことができないからであると推定される。一方、第二脱りん剤の投入終了時期は遅ければ遅いほど好ましいと考えられる。従って、第二脱りん剤の投入終了時期と酸素の吹込み終了時期との間に吹き込まれる酸素の量を、脱りん吹錬における酸素の全吹込み量の１０％以下と規定してもよい。また、第二脱りん剤の投入終了時期と脱りん吹錬の終了時期とを一致させてもよい。即ち、第二脱りん剤の投入終了時期と酸素の吹込み終了時期との間に吹き込まれる酸素の量が０Ｎｍ３／ｔであってもよい。 The end time of charging the second dephosphorizing agent is early, and the amount of oxygen blown between the end time of charging the second dephosphorizing agent and the end time of blowing oxygen is the total amount of oxygen blown in the dephosphorization blowing. If it exceeds 20%, the amount of dephosphorization of the hot metal cannot be improved. This is presumed to be because the decrease in the amount of FeO in the slag due to the decarburization reaction occurring at the end of the dephosphorization blowing cannot be compensated by the introduction of the second dephosphorizer. On the other hand, it is considered that the later the completion of the addition of the second dephosphorizing agent, the better. Therefore, the amount of oxygen blown between the end of the addition of the second dephosphorizing agent and the end of the oxygen blowing may be specified as 10% or less of the total amount of oxygen blown in the dephosphorization blowing. . Further, the end time of charging the second dephosphorizing agent and the end time of dephosphorization blowing may be matched. That is, the amount of oxygen blown between the end of the supply of the second dephosphorizing agent and the end of the blowing of oxygen may be 0 Nm 3 / t.

なお、第二脱りん剤の投入速度は一定であってもよく、第二脱りん剤の投入終了に至るまでに第二脱りん剤の投入速度を徐々に減少させてもよい。ただし第二脱りん剤の投入速度を徐々に減少させる場合、第二脱りん剤の投入速度が０となった時点を第二脱りん剤の投入終了時期とみなすことは、脱りん吹錬の末期における第二脱りん剤の投入量の不足を招くこととなりかねず、好ましくない。第二脱りん剤の投入速度を徐々に減少させる場合、脱りん吹錬における第二脱りん剤の平均投入速度（第二脱りん剤の投入量を、第二脱りん剤の投入時間で割った値）の９０％まで第二脱りん剤の投入速度が減少した時点を、第二脱りん剤の投入終了時期とみなすことがよい。   In addition, the charging speed of the second dephosphorizing agent may be constant, or the charging speed of the second dephosphorizing agent may be gradually reduced until the charging of the second dephosphorizing agent is completed. However, when the charging rate of the second dephosphorizing agent is gradually reduced, the point in time when the charging speed of the second dephosphorizing agent becomes 0 is regarded as the end time of the charging of the second dephosphorizing agent. This may lead to a shortage of the input amount of the second dephosphorizing agent in the final stage, which is not preferable. In the case of gradually decreasing the charging rate of the second dephosphorizing agent, the average charging rate of the second dephosphorizing agent in the dephosphorization blowing (the charging amount of the second dephosphorizing agent is divided by the charging time of the second dephosphorizing agent). The time at which the charging rate of the second dephosphorizing agent is reduced to 90% of the value obtained by the second dephosphorizing agent may be regarded as the end time of the charging of the second dephosphorizing agent.

第二脱りん剤の形態及び投入量は特に限定されず、溶銑の成分、及び鋼材成分の目標値等に応じて適宜設定することができる。第二脱りん剤の形態は、その滓化率を向上させるために粉状とすることが好ましい。この場合、粉状の第二脱りん剤はキャリアガスを用いて溶銑に吹き込まれることが好ましい。なお、滓化率とは、脱りん後塩基度（脱りん吹錬終了後に採取されたスラグの塩基度を測定して得られた値）を、装入塩基度（溶銑及び添加物のＳｉが全てＳｉＯ２になり、投入された脱りん剤のＣａが全て溶融ＣａＯになったと仮定した場合のスラグの塩基度）で割った値として定義される値である。即ち、本実施形態において「装入塩基度」とは、投入された材料の成分から得られる計算値である。一方「実装入塩基度」とは、スラグの成分を測定して得られる値、即ち実績値である。滓化率は、脱りん剤中のＣａＯ及び／又はＣａＣＯ３の溶融の度合い（即ち、滓化の度合い）を示す指標である。スラグの塩基度とは、スラグ中の溶融ＣａＯ量と溶融ＳｉＯ２量との比であり、下記式Ｆによって算出される。
スラグの塩基度＝スラグ中の溶融ＣａＯ量／スラグ中の溶融ＳｉＯ２量：式Ｆ The form and amount of the second dephosphorizing agent are not particularly limited, and can be appropriately set according to the components of the hot metal, the target values of the steel material components, and the like. The form of the second dephosphorizing agent is preferably in the form of a powder in order to improve the slagging rate. In this case, the powdery second dephosphorizing agent is preferably blown into the hot metal using a carrier gas. The slagging rate is defined as the basicity after dephosphorization (a value obtained by measuring the basicity of slag collected after the completion of dephosphorization blowing), and the basicity of charge (salt of hot metal and additive Si). This is a value defined as a value obtained by dividing by SiO 2 and basicity of the slag (assuming that all of the Ca of the dephosphorizing agent charged into molten CaO). That is, in the present embodiment, the “basic charge” is a calculated value obtained from the components of the input materials. On the other hand, the “mounting basicity” is a value obtained by measuring a slag component, that is, an actual value. The slagging ratio is an index indicating the degree of melting of CaO and / or CaCO 3 in the dephosphorizing agent (that is, the degree of slagging). The basicity of the slag, the ratio of the molten CaO amount and melting SiO 2 content in the slag, is calculated by the following equation F.
Slag basicity = Amount of molten CaO in slag / Amount of molten SiO 2 in slag: Formula F

第二脱りん剤の投入量は、溶銑を脱りん精錬する工程の終了時のスラグの装入塩基度が１．３〜４．０となるように制御されることが好ましい。脱りん精錬する工程の終了時のスラグの装入塩基度が１．３以上となるように第二脱りん剤の投入量を制御した場合、スラグの脱りん能を一層向上させ、溶銑の脱りんを高い水準で実施することができる。脱りん精錬する工程の終了時のスラグの装入塩基度が１．５以上、２．０以上、２．４以上、又は２．５以上となるように第二脱りん剤の投入量が制御されてもよい。一方、脱りん精錬する工程の終了時のスラグの装入塩基度が４．０以下となるように第二脱りん剤の投入量を制御した場合、スラグ量の増大を抑制し、脱りん効率を一層高く保ち、脱りん工程の環境負荷を一層低減することができる。脱りん精錬する工程の終了時のスラグの装入塩基度が３．５以下、３．４以下、３．０以下、又は２．８以下となるように第二脱りん剤の投入量が制御されてもよい。なお、溶銑を脱りん精錬する工程の終了時のスラグの装入塩基度が１．３〜４．０となる第二脱りん剤の投入量は、通常の方法により、溶銑の初期成分、第二脱りん剤の成分、第一脱りん剤等の添加物の成分及び投入量、及び溶銑への酸素の吹込み量等から推定することができる。   It is preferable that the amount of the second dephosphorizing agent is controlled so that the basicity of slag at the end of the step of dephosphorizing and refining the hot metal is 1.3 to 4.0. When the input amount of the second dephosphorizing agent is controlled so that the basicity of the slag at the end of the dephosphorizing refining process is 1.3 or more, the dephosphorizing ability of the slag is further improved, and the hot metal is removed. Phosphorus can be implemented at a high level. The input amount of the second dephosphorizing agent is controlled so that the basicity of slag at the end of the dephosphorizing refining process is 1.5 or more, 2.0 or more, 2.4 or more, or 2.5 or more. May be done. On the other hand, when the input amount of the second dephosphorizing agent is controlled so that the basicity of slag at the end of the dephosphorizing and refining process is 4.0 or less, the increase in slag amount is suppressed, and the dephosphorization efficiency And the environmental load of the dephosphorization step can be further reduced. The input amount of the second dephosphorizing agent is controlled so that the basicity of the slag at the end of the dephosphorizing and refining process is 3.5 or less, 3.4 or less, 3.0 or less, or 2.8 or less. May be done. In addition, the input amount of the second dephosphorizing agent at which the basicity of slag is 1.3 to 4.0 at the end of the step of dephosphorizing and refining the hot metal is determined by a usual method using the initial components of the hot metal, It can be estimated from the components of the second dephosphorizing agent, the components and the amounts of additives such as the first dephosphorizing agent, and the amount of oxygen injected into the hot metal.

第一脱りん剤及び第二脱りん剤の種類は、スラグの塩基度を上述のように制御できる限り、特に限定されない。例えば生石灰、石灰石、カルシウムフェライト、ドロマイト系石灰、並びに転炉スラグ又は二次精錬スラグであってＣａＯを含有するものから選択される一種以上を含むものであって、ＣａＯ、ＣａＣＯ３、及びＣａＦ２のＣａＯ等量での合計含有量が３０〜１００質量％であるものを、第一脱りん剤及び第二脱りん剤の一方又は両方として使用可能である。 The types of the first dephosphorizing agent and the second dephosphorizing agent are not particularly limited as long as the basicity of the slag can be controlled as described above. For example, quick lime, limestone, calcium ferrite, dolomite-based lime, and converter slag or secondary smelting slag containing one or more selected from CaO-containing slags, including CaO, CaCO 3 , and CaF 2 Having a total content of 30 to 100% by mass in terms of CaO equivalent can be used as one or both of the first dephosphorizing agent and the second dephosphorizing agent.

上述の要件が満たされる限り、本実施形態に係る溶銑の脱りん方法は追加の工程を備えてもよい。例えば、脱りん後の溶銑をさらに脱炭精錬に供しても良く、この脱炭精錬は脱りん精錬を実施した炉において連続的に実施しても、脱りん精錬を実施した炉とは別の炉で実施してもよい。   As long as the above requirements are satisfied, the method for dephosphorizing hot metal according to the present embodiment may include an additional step. For example, the hot metal after dephosphorization may be further subjected to decarburization refining, and this decarburization refining may be performed continuously in a furnace in which dephosphorization refining is performed, or may be performed separately from a furnace in which dephosphorization refining is performed. It may be performed in a furnace.

また、本実施形態に係る溶銑の脱りん方法を実施するための装置も特に限定されない。本発明者らが知見したところでは、例えば図１に例示される、キャリアガスを用いて粉状の第二脱りん剤５を吹き込むためのランスを有する上底吹き転炉１が、本実施形態に係る溶銑の脱りん方法を実施するために好ましい。上底吹き転炉１を用いて溶銑の脱りん精錬を行う場合、第二脱りん剤５は、溶銑に上吹き酸素６を吹き込むランス４の直下及びその近傍に投入することが好ましい。ランス４の直下及びその近傍は、溶銑中のＳｉ及びＣ等の酸化熱によって非常に高温になっている領域、即ち火点７である。この領域に第二脱りん剤５を投入することにより、第二脱りん剤５を一層効率的に溶融させることができる。なお、図１においては上吹き酸素６を吹き込むランス４を用いて第二脱りん剤５を吹き込む実施形態が図示されているが、第二脱りん剤５を吹き込むための別のランスを上底吹き転炉１に設けてもよい。また、上底吹き転炉を用い、且つ同一の転炉で脱りん精錬、スラグ除去、及び脱炭精錬を行う転炉精錬により、全体の精錬時間を短縮し、脱りん剤の使用量を一層低減し、さらに精錬での熱ロスを低減することが可能となる。一方、脱りん精錬、及び脱炭精錬それぞれを専用の炉で実施することにより、精錬効率を一層高めることもできる。   The apparatus for performing the hot metal dephosphorization method according to the present embodiment is not particularly limited. The present inventors have found that an upper-bottom blow converter 1 having a lance for blowing a powdery second dephosphorizer 5 using a carrier gas, as illustrated in FIG. It is preferable to carry out the hot metal dephosphorization method according to the above. When performing dephosphorization and refining of hot metal using the top and bottom blown converter 1, it is preferable to introduce the second dephosphorizing agent 5 directly below the lance 4 for blowing the top blow oxygen 6 into the hot metal and in the vicinity thereof. Immediately below and near the lance 4 is a region where the temperature is extremely high due to the heat of oxidation of Si and C in the hot metal, that is, a fire point 7. By introducing the second dephosphorizing agent 5 into this region, the second dephosphorizing agent 5 can be more efficiently melted. Although FIG. 1 shows an embodiment in which the second dephosphorizing agent 5 is blown using the lance 4 for blowing the top blown oxygen 6, another lance for blowing the second dephosphorizing agent 5 is provided on the upper base. It may be provided in the blowing converter 1. In addition, by using a top-bottom blower converter and converter refining in which dephosphorization refining, slag removal, and decarburization refining are performed in the same converter, the overall refining time is reduced and the amount of dephosphorizer used is further increased. It is possible to reduce the heat loss in refining. On the other hand, by performing each of the dephosphorizing refining and the decarburizing refining in a dedicated furnace, the refining efficiency can be further improved.

粉状の第二脱りん剤を溶銑に吹き込む際に用いられるキャリアガスの種類も特に限定されず、例えばＡｒ、Ｎ２、ＣＯ２、及びＯ２からなる群から選択される一種以上のガスを、キャリアガスとして使用可能である。費用、及び設備の安定性等を考慮すると、Ｎ２ガスを用いた第二脱りん剤の吹込みが好ましいと考えられる。脱りん吹錬の段階の溶銑では、溶銑のＮ取り込みを妨げる働きを有するＣの含有量が高いので、Ｎ２を用いた第二脱りん剤の吹込みを溶銑に行ったとしても、溶銑中に取り込まれるＮの量は無視できる程度に小さいと考えられる。 The type of the carrier gas used when blowing the powdery second dephosphorizing agent into the hot metal is not particularly limited. For example, at least one gas selected from the group consisting of Ar, N 2 , CO 2 , and O 2 is used. , Can be used as a carrier gas. Considering the cost and the stability of the equipment, it is considered preferable to blow the second dephosphorizing agent using N 2 gas. In the hot metal at the stage of dephosphorization blowing, the content of C having a function of hindering the incorporation of N into the hot metal is high. Therefore, even if the hot metal is injected with the second dephosphorizing agent using N 2 , Is considered to be negligibly small.

以下の条件での脱りん精錬を実施した。
・第一脱りん剤の形態：塊状（生石灰および石灰石から１種以上を選択）
・第一脱りん剤のＣａＯ等量と、溶銑の初期成分におけるＳｉ含有量のＳｉＯ２等量との比：０．９〜２．４
・第二脱りん剤の形態：粉状（生石灰）
・キャリアガス種類：Ｎ２
・第二脱りん剤の吹込み開始時点：溶銑のＳｉ含有量を脱りん吹錬によって０．１０質量％以下にした時点の後、且つ、前記時点以降の前記溶銑への前記酸素の吹込み量を３．０Ｎｍ３／ｔとする前
・第二脱りん剤の吹込み終了時点：以下の３水準
（水準１）粉体吹込終了時送酸割合が７０％未満
（水準２）粉体吹込終了時送酸割合が７０〜７９％
（水準３）粉体吹込終了時送酸割合が８０〜８９％
（水準４）粉体吹込終了時送酸割合が９０〜１００％
・脱りん吹錬終了時のスラグの装入塩基度：全水準において２．４〜３．４の範囲内
なお「粉体吹込開始時送酸割合」とは、第二脱りん剤の粉体の吹込みを開始した時点までに脱りん吹錬のために溶銑中に吹き込まれた酸素の量が、脱りん吹錬の完了時までに脱りん吹錬のために溶銑中に吹き込まれた全酸素量に占める割合を示す。「粉体吹込終了時送酸割合」とは、第二脱りん剤の粉体の吹込みを終了した時点までに脱りんのために溶銑中に吹き込まれた酸素の量が、脱りん吹錬の完了時までに脱りん吹錬のために溶銑中に吹き込まれた全酸素量に占める割合を示す。例えば「（水準３）粉体吹込終了時送酸割合が８０〜８９％」においては、脱りん吹錬において、第二脱りん剤の投入終了時期が、第二脱りん剤の投入終了時期と酸素の吹込み終了時期との間に吹き込まれる酸素の量が、脱りん吹錬における酸素の全吹込み量の１１％〜２０％となるように制御された。 Dephosphorization refining was performed under the following conditions.
・ Primary dephosphorizer form: Lumpy (select one or more from quicklime and limestone)
- a CaO equivalent amount of primary dephosphorization agent, the ratio of the SiO 2 equivalent amount of the Si content in the initial composition of the molten iron: 0.9 to 2.4
・ Form of secondary dephosphorizer: powdery (quicklime)
・ Carrier gas type: N 2
-Start of blowing of the second dephosphorizing agent: after the time when the Si content of the hot metal is reduced to 0.10% by mass or less by dephosphorization blowing, and after the time, the oxygen is blown into the hot metal. Before setting the amount to 3.0 Nm 3 / t and at the end of blowing the second dephosphorizing agent: the following three levels (level 1): At the end of powder blowing, the acid supply ratio is less than 70% (level 2). 70-79% of acid supply rate at the end
(Level 3) The rate of acid supply at the end of powder blowing is 80-89%
(Level 4) The acid supply ratio at the end of powder blowing is 90 to 100%
・ Basic basicity of slag at the end of dephosphorization blowing: within the range of 2.4 to 3.4 at all levels. The amount of oxygen blown into the hot metal for dephosphorization blowing by the time when the blowing of Shows the ratio to the amount of oxygen. The term "oxygen transfer rate at the end of powder blowing" refers to the amount of oxygen blown into the hot metal for dephosphorization by the time the powder blowing of the second dephosphorizing agent is completed, The percentage of the total amount of oxygen blown into the hot metal for dephosphorization and blowing by the time of completion. For example, in “(level 3) the acid supply ratio at the end of powder blowing is 80 to 89%”, in the dephosphorization blowing, the end time of charging the second dephosphorizing agent is the same as the finishing time of charging the second dephosphorizing agent. The amount of oxygen blown before the end of oxygen blowing was controlled to be 11% to 20% of the total amount of oxygen blown in the dephosphorization blowing.

各水準における効果測定は、りん分配量Ｌｐの実績値（実績Ｌｐ）を用いて行った。実績Ｌｐとは、スラグ中の単位質量％でのりん濃度（％Ｐ）の測定値と溶銑中の単位質量％でのりん濃度［％Ｐ］の測定値との比の常用対数、即ち以下の式Ｇで表される値である。実績Ｌｐが大きい場合、スラグに分配されたりんの量が多いので、高効率で脱りんが達成されていることになる。
Ｌｐ＝ｌｏｇ１０｛（％Ｐ）／［％Ｐ］｝：式Ｇ The effect measurement at each level was performed using the actual value of the phosphorus distribution amount Lp (actual Lp). The actual result Lp is the common logarithm of the ratio of the measured value of the phosphorus concentration (% P) in unit mass% of slag to the measured value of phosphorus concentration [% P] in unit mass% of hot metal, that is, This is a value represented by Expression G. When the performance Lp is large, the amount of phosphorus distributed to the slag is large, so that dephosphorization is achieved with high efficiency.
Lp = log 10 {(% P) / [% P]}: Formula G

実験結果を図２〜図４に示す。図２は、水準１〜水準４における実績Ｌｐの平均値（平均実績Ｌｐ）を示すグラフである。水準１（粉体吹込終了時送酸割合が７０％未満）及び水準２（粉体吹込終了時送酸割合が７０〜７９％）と、水準３（粉体吹込終了時送酸割合が８０〜８９％）及び水準４（粉体吹込終了時送酸割合が９０〜１００％）とを比較すると、脱りん精錬後の実績Ｌｐが、第二脱りん剤の投入を脱りん吹錬の末期まで実施することによって顕著に高められていることがわかる。   The experimental results are shown in FIGS. FIG. 2 is a graph showing the average value (average actual result Lp) of the actual results Lp at the levels 1 to 4. Level 1 (acid supply ratio at the end of powder blowing is less than 70%) and level 2 (acid supply ratio at the end of powder blowing is 70-79%) and Level 3 (acid supply ratio at the end of powder blowing is 80- 89%) and level 4 (90% to 100% of the acid supply rate at the end of powder blowing), the actual Lp after dephosphorization refining shows that the second dephosphorizing agent is charged until the end of dephosphorization blowing. It can be seen that the performance is significantly increased by the implementation.

図３は、横軸を最低到達塩基度とし、縦軸を実績Ｌｐとした、上記実験結果の散布図である。最低到達塩基度とは、第一脱りん剤のＣａＯ等量と、溶銑の初期成分におけるＳｉ含有量のＳｉＯ２等量との比である。最低到達塩基度にかかわらず、水準３及び水準４における実績Ｌｐが、その他水準における実績Ｌｐを上回っていることが確認された。 FIG. 3 is a scatter diagram of the above experimental results, in which the horizontal axis represents the lowest attained basicity and the vertical axis represents the actual result Lp. The minimum attained basicity, CaO in an equal volume of the first dephosphorization agents, the ratio of the SiO 2 equivalent amount of the Si content in the initial component of the hot metal. Regardless of the lowest attained basicity, it was confirmed that the actual Lp at level 3 and level 4 exceeded the actual Lp at other levels.

図４は、横軸を装入塩基度とし、縦軸を実績Ｌｐとした、上記実験結果の散布図である。図４における装入塩基度とは、溶銑を脱りん精錬する工程の終了時のスラグの装入塩基度（溶銑及び添加物のＳｉが全てＳｉＯ２になり、投入された脱りん剤のＣａが全て溶融ＣａＯになったと仮定した場合のスラグの塩基度）である。装入塩基度にかかわらず、水準３及び水準４における実績Ｌｐが、その他水準における実績Ｌｐを上回っていることが確認された。 FIG. 4 is a scatter diagram of the above experimental results, in which the horizontal axis is the charged basicity and the vertical axis is the actual Lp. The basicity of charge in FIG. 4 refers to the basicity of charge of slag at the end of the step of dephosphorizing and refining hot metal (the hot metal and the additive Si all become SiO 2 , and the Ca of the dephosphorizing agent charged is (Basicity of slag) assuming that all became molten CaO). Regardless of the charged basicity, it was confirmed that the actual Lp at Level 3 and Level 4 exceeded the actual Lp at other levels.

図５は、水準１〜水準４における脱りん吹錬中の脱炭量を示すグラフである。図５における「脱りん吹錬中の脱炭量」は、脱りん吹錬前の溶銑中［Ｃ］濃度の測定値と脱りん吹錬後の溶銑中［Ｃ］濃度の測定値との差を、水準２の数値を用いて規格化（正規化）した値である。この定義から、水準２（粉体吹込終了時送酸割合が７０〜７９％）の脱りん吹錬中の脱炭量は１．００となっている。一方、水準３（粉体吹込終了時送酸割合が８０〜８９％）及び水準４（粉体吹込終了時送酸割合が９０〜１００％）においては、脱りん吹錬中の脱炭量が約５％削減された。この場合、脱炭吹錬において昇熱材投入量を減少させることが可能となる。   FIG. 5 is a graph showing the amount of decarburization during dephosphorization blowing at level 1 to level 4. The “decarbonization amount during dephosphorization blowing” in FIG. 5 is the difference between the measured value of [C] concentration in hot metal before dephosphorization blowing and the measured value of [C] concentration in hot metal after dephosphorization blowing. Is normalized (normalized) using the numerical value of level 2. From this definition, the amount of decarburization during dephosphorization blowing at level 2 (the acid supply ratio at the end of powder blowing is 70 to 79%) is 1.00. On the other hand, at level 3 (acid supply ratio at the end of powder blowing is 80 to 89%) and at level 4 (acid supply ratio at the end of powder blowing is 90 to 100%), the decarburization amount during dephosphorization blowing is small. It has been reduced by about 5%. In this case, it is possible to reduce the heating material input amount in the decarburization blowing.

本発明に係る溶銑の脱りん方法は、溶銑の脱りん効率に優れる。従って本発明に係る溶銑の脱りん方法は、スラグ量を増大させることなく十分に溶銑を脱りんすることができるので、Ｐ量が低い高品位の鋼材を低い環境負荷で製造することができる。さらに本発明の脱りん方法によれば、脱りん吹錬時の脱炭反応を抑制できるので、続く脱炭精錬における昇熱材投入量の削減が可能となる。以上述べた理由により、本発明は極めて高い産業上の利用可能性を有する。   The hot metal dephosphorizing method according to the present invention is excellent in hot metal dephosphorizing efficiency. Therefore, the method for dephosphorizing hot metal according to the present invention can sufficiently dephosphorize hot metal without increasing the amount of slag, so that a high-grade steel material having a low P content can be manufactured with a low environmental load. Further, according to the dephosphorization method of the present invention, since the decarburization reaction during dephosphorization blowing can be suppressed, it is possible to reduce the amount of heat-up material input in the subsequent decarburization refining. For the reasons mentioned above, the invention has a very high industrial applicability.

１ 転炉
２ 溶銑
３ スラグ
４ ランス
５ 第二脱りん剤
６ 上吹き酸素
７ 火点 DESCRIPTION OF SYMBOLS 1 Converter 2 Hot metal 3 Slag 4 Lance 5 Second dephosphorizer 6 Top-blown oxygen 7 Fire point

Claims (8)

溶銑の脱りん方法であって
前記溶銑に第一脱りん剤を投入する工程と、
前記溶銑に酸素を吹き込むことにより前記溶銑を脱りん吹錬する工程と、
を備え、
前記脱りん吹錬する工程中に、さらに第二脱りん剤を前記溶銑に投入し、
前記第二脱りん剤の投入終了時期と、前記酸素の吹込み終了時期との間に吹き込まれる酸素の量を、前記脱りん吹錬における前記酸素の全吹込み量の２０％以下とする
ことを特徴とする溶銑の脱りん方法。 A method of dephosphorizing hot metal, wherein a step of charging a first dephosphorizing agent to the hot metal,
A step of dephosphorizing and blowing the hot metal by blowing oxygen into the hot metal,
With
During the dephosphorization blowing step, a second dephosphorizing agent is further charged into the hot metal,
The amount of oxygen blown between the end of the supply of the second dephosphorizing agent and the end of the oxygen blowing is 20% or less of the total amount of oxygen blown in the dephosphorization blowing. A method for dephosphorizing hot metal, comprising: 前記第二脱りん剤の投入終了時期と、前記酸素の吹込み終了時期との間に吹き込まれる酸素の量を、前記脱りん吹錬における前記酸素の全吹込み量の１０％以下とすることを特徴とする請求項１に記載の溶銑の脱りん方法。   The amount of oxygen blown between the end of the supply of the second dephosphorizing agent and the end of the oxygen blowing is 10% or less of the total amount of oxygen blown in the dephosphorization blowing. The method for dephosphorizing hot metal according to claim 1, wherein: 前記溶銑の脱りん方法が、前記溶銑に前記第一脱りん剤を投入する前に、前記溶銑の初期成分におけるＳｉ含有量を測定する工程をさらに備え、
前記第一脱りん剤のＣａＯ等量と、前記溶銑の前記初期成分における前記Ｓｉ含有量のＳｉＯ２等量との比を０．８０〜１．２０とすることを特徴とする請求項１又は２に記載の溶銑の脱りん方法。 Before the hot metal dephosphorization method, before adding the first dephosphorizing agent to the hot metal, further comprising a step of measuring the Si content in the initial component of the hot metal,
And CaO equivalent amount of the first dephosphorization agents, claim 1, characterized in that a 0.80 to 1.20 the ratio of SiO 2 equivalent amount of the Si content in the initial composition of the molten iron or 3. The method for dephosphorizing hot metal according to item 2. 前記第二脱りん剤の投入量を、前記溶銑を前記脱りん精錬する工程の終了時のスラグの装入塩基度が１．３〜４．０となるように制御することを特徴とする請求項１〜３のいずれか一項に記載の溶銑の脱りん方法。   The input amount of the second dephosphorizing agent is controlled so that the basicity of slag charged at the end of the step of dephosphorizing the hot metal is 1.3 to 4.0. Item 5. The method for dephosphorizing hot metal according to any one of Items 1 to 3. 前記第一脱りん剤及び前記第二脱りん剤の一方又は両方を、
生石灰、石灰石、カルシウムフェライト、ドロマイト系石灰、並びに転炉スラグ又は二次精錬スラグであってＣａＯを含有するものから選択される一種以上を含むものであって、ＣａＯ、ＣａＣＯ３、及びＣａＦ２のＣａＯ等量での合計含有量が３０〜１００質量％であるもの
とすることを特徴とする請求項１〜４のいずれか一項に記載の溶銑の脱りん方法。 One or both of the first dephosphorizing agent and the second dephosphorizing agent,
Quick lime, limestone, calcium ferrite, dolomite-based lime, and converter slag or secondary smelting slag containing one or more selected from CaO-containing slag, and containing CaO, CaCO 3 , and CaF 2 The method for dephosphorizing hot metal according to any one of claims 1 to 4, wherein a total content of CaO equivalents is 30 to 100% by mass. 前記第一脱りん剤を、塊状の脱りん剤とすることを特徴とする請求項１〜５のいずれか一項に記載の溶銑の脱りん方法。   The method for dephosphorizing hot metal according to any one of claims 1 to 5, wherein the first dephosphorizing agent is a massive dephosphorizing agent. 前記第二脱りん剤を、粉状の脱りん剤とすることを特徴とする請求項１〜６のいずれか一項に記載の溶銑の脱りん方法。   The method for dephosphorizing hot metal according to any one of claims 1 to 6, wherein the second dephosphorizing agent is a powdery dephosphorizing agent. 前記第二脱りん剤を、Ａｒ、Ｎ２、ＣＯ２、及びＯ２からなる群から選択される一種以上であるキャリアガスを用いて前記溶銑に吹き込むことを特徴とする請求項７に記載の溶銑の脱りん方法。 Said second dephosphorization agent, Ar, N 2, CO 2 , and using a carrier gas is one or more selected from the group consisting of O 2 according to claim 7, characterized in that blown into the molten iron Hot metal dephosphorization method.
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001064713A (en) * 1999-08-26 2001-03-13 Sumitomo Metal Ind Ltd Method for dephosphorizing molten iron
JP2006009146A (en) * 2004-05-24 2006-01-12 Sumitomo Metal Ind Ltd Method for refining molten iron
JP2011006758A (en) * 2009-06-29 2011-01-13 Sumitomo Metal Ind Ltd Method for dephosphorizing molten iron

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001064713A (en) * 1999-08-26 2001-03-13 Sumitomo Metal Ind Ltd Method for dephosphorizing molten iron
JP2006009146A (en) * 2004-05-24 2006-01-12 Sumitomo Metal Ind Ltd Method for refining molten iron
JP2011006758A (en) * 2009-06-29 2011-01-13 Sumitomo Metal Ind Ltd Method for dephosphorizing molten iron

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