JP5182322B2 - Hot phosphorus dephosphorization method - Google Patents
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Description
本発明は、上底吹き転炉で蛍石を用いずに高速で低燐銑を溶製する方法に関する。 The present invention relates to a method for melting low phosphorous iron at high speed without using fluorite in an upper-bottom blowing converter.
近年、鋼材に対する需要が高度化し、低燐鋼に対する需要が増加している。現在、溶銑の脱燐処理は、熱力学的に有利な溶銑段階の低温条件において処理する方法によって、広く一般に行われている。 In recent years, the demand for steel materials has increased, and the demand for low-phosphorus steel has increased. At present, hot metal dephosphorization is widely performed by a method in which the hot metal is processed under low temperature conditions in a hot metal stage which is thermodynamically advantageous.
溶銑脱燐装置としては上底吹き転炉が適している。それは、脱燐に必要な酸化剤として、固体酸化剤に比べて熱ロスの少ない気体酸素を、上吹きランスから高速で溶銑に吹き付けることが可能なためである。 A top-bottom blowing converter is suitable as the hot metal dephosphorization apparatus. This is because, as an oxidant necessary for dephosphorization, gaseous oxygen with less heat loss than a solid oxidant can be sprayed from the top blowing lance to the hot metal at a high speed.
溶銑脱燐は溶銑段階の低温条件において行われるため、脱燐剤として使用されるＣａＯの滓化を促進させることが重要である。ＣａＯの滓化には蛍石（ＣａＦ２）の使用が効果的である。 Since hot metal dephosphorization is performed under low temperature conditions in the hot metal stage, it is important to promote the hatching of CaO used as a dephosphorizing agent. The use of fluorite (CaF 2 ) is effective for the hatching of CaO.
しかし、蛍石を使用した場合にはＣａＯの滓化により発生したスラグがフッ素（Ｆ）を含有するため、スラグの再利用先が大幅に制限されるなどの弊害が大きい。
そのため、蛍石を用いないＣａＯ滓化促進方法が開発されてきた。
However, when fluorite is used, since the slag generated by the hatching of CaO contains fluorine (F), there is a great problem that the reuse destination of the slag is greatly limited.
Therefore, CaO hatching promotion methods that do not use fluorite have been developed.
その方法としては、例えば、上吹きランスからＣａＯ粉体を気体酸素と共に溶銑浴面へ吹き付けることでＣａＯの滓化を促進する方法が挙げられる（特許文献１）。
その方法では、上吹きランスから吹き付ける酸化カルシウム粉を塊状生石灰源と酸化カルシウム粉との総量の４０％以上として、溶銑１ｔｏｎ当たり０．０５〜０．４０Ｎｍ３／ｍｉｎの底吹きガスで撹拌しつつ、溶銑１ｔｏｎ当たり０．５〜２．０Ｎｍ３／ｍｉｎの上吹き酸素流量とともに溶銑に吹き付ける。それにより、吹錬時間１０分以下（７〜１０分間）で、スラグ中ＣａＯとＳｉＯ２の質量比が１．５〜２．５として脱燐率が８０％以上、かつ、脱燐処理後のスラグ中に未反応ＣａＯが殆ど含まれないという結果を得ている。
As the method, for example, a method of promoting the hatching of CaO by spraying CaO powder together with gaseous oxygen from the top blowing lance to the hot metal bath surface (Patent Document 1).
In that method, the calcium oxide powder sprayed from the top blowing lance is set to 40% or more of the total amount of the lump calcined lime source and the calcium oxide powder while stirring with a bottom blowing gas of 0.05 to 0.40 Nm 3 / min per 1 ton of hot metal. Then, the hot metal is sprayed together with an upper oxygen flow rate of 0.5 to 2.0 Nm 3 / min per 1 ton of hot metal. Thereby, the dephosphorization rate is 80% or more when the mass ratio of CaO and SiO 2 in the slag is 1.5 to 2.5 and the dephosphorization time is 10 minutes or less (7 to 10 minutes). As a result, almost no unreacted CaO is contained in the slag.
しかし、近年、脱燐銑を１０分以下の短時間で脱炭吹錬して生産量を増加させるようになってきたため、その予備処理としての溶銑脱燐処理も一層高速化しなければならなくなった。 However, in recent years, dephosphorization has been performed by decarburization blown in a short time of 10 minutes or less to increase the production amount, so the hot metal dephosphorization treatment as a preliminary treatment has to be further accelerated. .
特許文献１の方法では、上吹き酸素流量が０．５〜２．０Ｎｍ３／ｍｉｎ／溶銑ｔであったが、上吹き酸素流量をより大きくしなければ、近年の高速化要請に十分応えられなくなってきたのである。 In the method of Patent Document 1, the upper blown oxygen flow rate was 0.5 to 2.0 Nm 3 / min / molten iron t. However, if the upper blown oxygen flow rate is not increased further, it can sufficiently meet recent demands for speeding up. It has disappeared.
溶銑脱燐処理を高速化するためには、まず、上吹き酸素流量を増加しなければならない。
なぜなら、溶銑脱燐に最低限必要な酸素量はある程度決まっており、また熱源確保の観点から、その大部分を酸素ガスで供給しなければならないからである。
In order to speed up the hot metal dephosphorization process, first, the top blowing oxygen flow rate must be increased.
This is because the minimum amount of oxygen required for hot metal dephosphorization is determined to some extent, and from the viewpoint of securing a heat source, most of it must be supplied with oxygen gas.
なお、酸素源として酸素ガスの代わりに酸化鉄を多量に用いても、脱燐に必要な酸素量は確保できるが、酸化鉄がスラグへ溶解してＣａＯ含有スラグ中（%ＦｅＯ）を高めて脱燐反応を促進するまでには時間がかかる。 Even if a large amount of iron oxide is used instead of oxygen gas as an oxygen source, the amount of oxygen necessary for dephosphorization can be ensured, but the iron oxide dissolves in the slag and raises the CaO-containing slag (% FeO). It takes time to promote the dephosphorization reaction.
すなわち、高速溶銑脱燐では、多量の酸化鉄を投入しても吹錬時間内で脱燐反応に寄与しきれない酸化鉄の量が増えて、不経済となってしまう。
更には、酸化鉄の一部（表層部）が早期に溶解しても、吹錬初期は浴表面に溶融スラグがあまり生成していないためＣａＯ含有スラグ中へ取り込まれる前に、溶銑中［％Ｃ］と反応してしまい、脱燐に寄与できない割合が高い。
That is, in the high-speed hot metal dephosphorization, even if a large amount of iron oxide is added, the amount of iron oxide that cannot be fully contributed to the dephosphorization reaction within the blowing time increases, which is uneconomical.
Furthermore, even if a part (surface layer part) of iron oxide is dissolved early, molten slag is not generated much on the bath surface at the initial stage of blowing, so that it is in the hot metal before being taken into the CaO-containing slag [% C] is high and the ratio which cannot contribute to dephosphorization is high.
脱燐反応は、次の式で表される。
3(CaO)+5(FeO)＋2[P]＝(3CaO・P2O5)+5[Fe]
すなわち、（ＦｅＯ）単独では脱燐反応に寄与することができないのである。
The dephosphorization reaction is represented by the following formula.
3 (CaO) +5 (FeO) +2 [P] = (3CaO · P 2 O 5 ) +5 [Fe]
That is, (FeO) alone cannot contribute to the dephosphorization reaction.
そのことも、高速で溶銑脱燐処理する場合に、投入した酸化鉄を効率よく脱燐反応に寄与させるための酸化鉄添加量に上限があった理由の一つである。
また、高速脱燐処理では、従来と同量のＣａＯ粉体をより短時間で上吹きすることになるので、ＣａＯ粉体上吹き速度（単位：ｋｇ／ｍｉｎ／溶銑ｔ）を高めなければならない。
This is also one of the reasons why there is an upper limit to the amount of iron oxide added to efficiently contribute the added iron oxide to the dephosphorization reaction when hot metal dephosphorization is performed at high speed.
Further, in the high-speed dephosphorization treatment, the same amount of CaO powder as before is blown up in a shorter time, so the CaO powder top blowing speed (unit: kg / min / molten iron t) must be increased. .
さもなくば、処理後スラグの塩基度を従来並にするのに塊生石灰を多量に添加せねばならないが、短時間の高速脱燐吹錬では少なくとも一部の塊生石灰が滓化しきれずに処理後スラグ中に残留して、スラグを路盤材化するのが困難になる。 Otherwise, a large amount of bulk lime must be added to keep the basicity of the slag after treatment at the same level as before, but at least a part of the bulk lime is not hatched by high-speed dephosphorization blowing in a short time. It remains in the rear slag, making it difficult to turn the slag into roadbed material.
塊生石灰が滓化しきれなければ、スラグの塩基度が低下して、処理後の溶銑中［％Ｐ］が増加、つまり脱燐率が低下してしまう。
特許文献２には、上底吹き転炉を用いて、上吹き酸素流量１．８〜２．１Ｎｍ３／ｍｉｎ／ｔ、底吹きＮ２流量約０．４Ｎｍ３／ｍｉｎ／ｔとして溶銑脱燐するに際し、装入塩基度が１．５となるまでは生石灰粉を上吹きし、その後は生石灰粉体を上吹きせず酸素のみを上吹きしつつ、塩基度をそれ以上に高めるためにカルシウムフェライトを添加する方法が開示されている。
If the lump lime is not fully hatched, the basicity of the slag is lowered, and [% P] in the molten iron after the treatment is increased, that is, the dephosphorization rate is lowered.
Patent Document 2 discloses hot metal dephosphorization using an upper bottom blown converter with an upper blown oxygen flow rate of 1.8 to 2.1 Nm 3 / min / t and a bottom blown N 2 flow rate of about 0.4 Nm 3 / min / t. In order to increase the basicity further, calcium lime powder is blown up until the charging basicity reaches 1.5, and then only oxygen is blown up without blowing lime powder. A method of adding ferrite is disclosed.
この方法によると、生石灰粉を上吹きする方法よりもスラグ塩基度を高めることができ、その結果処理後［Ｐ］を０．００７質量％まで低減されている。
ところが、溶銑脱燐処理時間を短縮するために、上吹き酸素流量を２〜５Ｎｍ３／ｍｉｎ／ｔへ増加すると、生石灰粉体上吹きを停止して酸素のみを上吹きしつつカルシウムフェライトを添加した期間（吹錬の後半）に、スロッピングが発生するという問題が発生した。
According to this method, the slag basicity can be increased as compared with the method in which quick lime powder is blown up, and as a result, [P] after the treatment is reduced to 0.007% by mass.
However, in order to shorten the hot metal dephosphorization time, when the top blown oxygen flow rate is increased to 2 to 5 Nm 3 / min / t, the calcium lime powder is added while the top blow of quick lime powder is stopped and only oxygen is blown up. During this period (second half of blowing), there was a problem that slopping occurred.
本発明は、ＣａＯ含有粉体を上吹きして溶銑を脱燐する方法において、上吹き酸素流量を２．０〜５．０Ｎｍ３／ｍｉｎ／溶銑ｔに増加して、上吹き酸素の供給時間が５〜８分間という短時間に高速で溶銑脱燐処理する場合に、以下を実現することを目的とする。
（１）上吹きしたＣａＯ含有粉体に含まれるＣａＯの飛散ロスを０．５ｋｇ／溶銑ｔ以下に抑制、
（２）処理後溶銑中［％Ｐ］を０．０１５質量％以下にまで低減、かつ
（３）処理後スラグ中遊離ＣａＯ（以下、「ｆ．ＣａＯ」ともいう。）を１質量％以下に低減。
According to the present invention, in the method of dephosphorizing the hot metal by blowing the CaO-containing powder, the upper blown oxygen flow rate is increased to 2.0 to 5.0 Nm 3 / min / hot metal t and the supply time of the upper blown oxygen is increased. Is intended to achieve the following when hot metal dephosphorization is performed at high speed in a short time of 5 to 8 minutes.
(1) The scattering loss of CaO contained in the top-blown CaO-containing powder is suppressed to 0.5 kg / molten iron or less,
(2) [% P] in the hot metal after treatment is reduced to 0.015 mass% or less, and (3) free CaO in the slag after treatment (hereinafter also referred to as “f. CaO”) is 1 mass% or less. Reduction.
特許文献１に記載された発明では、上吹きランスから吹き付ける酸化カルシウム粉を塊状生石灰源と酸化カルシウム粉との総量の４０質量％以上として、溶銑１ｔｏｎ当たり０．５〜２．０Ｎｍ３/ｍｉｎの上吹き酸素流量とともに溶銑に吹き付け、吹錬時間１０分以下（７〜１０分間）で、スラグ中ＣａＯとＳｉＯ２の質量比が１．５〜２．５として脱燐率が８０％以上、かつ、脱燐処理後のスラグ中に未反応ＣａＯが殆ど含まれないという結果を得ている。 In the invention described in Patent Document 1, the calcium oxide powder sprayed from the top blowing lance is 40% by mass or more of the total amount of the bulk quicklime source and the calcium oxide powder, and 0.5 to 2.0 Nm 3 / min per 1 ton of hot metal. Blowing the hot metal together with the flow rate of top blowing oxygen, blowing time of 10 minutes or less (7 to 10 minutes), the mass ratio of CaO and SiO 2 in the slag is 1.5 to 2.5, and the dephosphorization rate is 80% or more, and As a result, almost no unreacted CaO is contained in the slag after the dephosphorization treatment.
しかしながら、脱燐銑を１０分以下の短時間で脱炭吹錬して生産量を増加させるという、近年の操業形態の変化に合わせるために、脱燐処理における上吹き酸素供給時間を従来の７〜１０分間から５〜８分間に着実に短縮し、かつ、処理後溶銑中［％Ｐ］を０．０１５質量％以下にまで低減（脱燐率で８５％以上）して対応しなければならない場合が生じてきた。そのためには、上吹き酸素流量を従来の０．５〜２．０Ｎｍ３／ｍｉｎ／溶銑ｔから２．０〜５．０Ｎｍ３／ｍｉｎ／溶銑ｔに増加しても問題の無い吹錬技術を確立しておかなければならなくなった。 However, in order to keep up with the recent change in the operation mode, in which dephosphorization is decarburized and blown in a short time of 10 minutes or less to increase production, the upper blowing oxygen supply time in the dephosphorization treatment is set to the conventional 7 hours. It must be steadily shortened from 10 minutes to 5 to 8 minutes, and [% P] in the molten iron after treatment should be reduced to 0.015% by mass or less (85% or more in terms of dephosphorization). A case has arisen. For this purpose, a free blowing technologies be increased top-blown oxygen flow rate from conventional 0.5~2.0Nm 3 / min / hot metal t to 2.0~5.0Nm 3 / min / hot metal t problem I had to establish it.
ところが、上吹き酸素流量を２．０〜５．０Ｎｍ３／ｍｉｎ／溶銑ｔに増加させるとスロッピングが発生し、問題となることが分かった。
また、上吹き酸素流量を従来の０．５〜２．０Ｎｍ３／ｍｉｎ／溶銑ｔから２．０〜５．０Ｎｍ３／ｍｉｎ／溶銑ｔに増加して高速脱燐する場合、脱燐に必要なＣａＯ含有粉体量を短時間で添加しなければならない。このため、ＣａＯ含有粉体の上吹き速度（ｋｇ／ｍｉｎ／溶銑ｔ）をも高めなければならない。
However, it has been found that when the flow rate of the top blown oxygen is increased to 2.0 to 5.0 Nm 3 / min / molten iron t, slopping occurs and becomes a problem.
Further, when increasing the top-blown oxygen flow rate from conventional 0.5~2.0Nm 3 / min / hot metal t to 2.0~5.0Nm 3 / min / hot metal t speed dephosphorization, required dephosphorization The amount of CaO-containing powder must be added in a short time. For this reason, it is necessary to increase the top blowing speed (kg / min / molten iron t) of the CaO-containing powder.
ところが、ＣａＯ含有粉体の上吹き速度を高めると、スピッティングが激しくなった。しかもＣａＯ含有粉体の系外への飛散ロス量が増大したため、ＣａＯ含有粉体中のＣａＯのスラグへの歩留まりが低下して処理後スラグの塩基度が低下し、脱燐率が低下してしまった。 However, when the top blowing speed of the CaO-containing powder was increased, spitting became intense. Moreover, since the amount of scattering loss of CaO-containing powder to the outside of the system has increased, the yield of CaO in the CaO-containing powder decreases to the slag, the basicity of the slag after processing decreases, and the dephosphorization rate decreases. Oops.
なお、ＣａＯ含有粉体中のＣａＯの上吹き速度とは、当該吹錬におけるＣａＯ含有粉体に含まれるＣａＯの上吹き速度の平均値（ＣａＯ含有粉体に含まれるＣａＯの上吹き量（ｋｇ）／ＣａＯ含有粉体を上吹きしていた時間（分））である。 The top blowing rate of CaO in the CaO-containing powder is the average value of top blowing rate of CaO contained in the CaO-containing powder in the blowing (the amount of top-blowing CaO contained in the CaO-containing powder (kg ) / Time when the CaO-containing powder was blown up (minutes)).
そこで、本発明では、前記した特許文献１に記載された発明の知見に基づき、それをさらに改良することによって、前記した本発明の目的の達成を目指すことにした。
具体的には、上底吹き転炉で、塊状ＣａＯ含有物質と粉状ＣａＯ含有物質のそれぞれに含まれているＣａＯ質量の合計に対し、その合計の４０質量％以上の質量のＣａＯを粉状ＣａＯ含有物質として、先ず上吹き酸素流量を２．０〜５．０Ｎｍ３／ｍｉｎ／溶銑ｔに増加させる。この場合、その上吹き酸素流量の増加に合わせて、底吹きガス流量も後述するように０．２〜０．６Ｎｍ３／ｍｉｎ／溶銑ｔに増加させ、かつ、脱燐迅速化のために処理後スラグ中ＣａＯとＳｉＯ２の質量比を２．０〜３．０に高める。但し、その条件で、そのスラグ中の遊離ＣａＯを１％以下としなければならない。
Therefore, in the present invention, based on the knowledge of the invention described in Patent Document 1 described above, the present invention aims to achieve the object of the present invention by further improving it.
Specifically, in the top-bottom blow converter, the total amount of CaO contained in each of the massive CaO-containing material and the powdered CaO-containing material is 40% by mass or more of the total amount of CaO. As the CaO-containing substance, first, the top blowing oxygen flow rate is increased to 2.0 to 5.0 Nm 3 / min / molten iron t. In this case, the bottom blown gas flow rate is increased to 0.2 to 0.6 Nm 3 / min / molten iron t as will be described later in accordance with the increase in the top blown oxygen flow rate, and the treatment is performed to speed up the dephosphorization. The mass ratio of CaO and SiO 2 in the rear slag is increased to 2.0 to 3.0. However, the free CaO in the slag must be 1% or less under the conditions.
そのために、考察と推論に基づいて粉状ＣａＯ源に含まれるＣａＯ質量の供給速度を調整し、さらにＣａＯ・ＦｅｔＯ・ＳｉＯ２・Ａｌ２Ｏ３を含有するプリメルトフラックスを利用する。 Therefore, by adjusting the feed rate of the CaO mass contained powdered CaO source based on considerations and reasoning, further utilize a pre-melt flux containing CaO · Fe t O · SiO 2 · Al 2 O 3.
酸素ガス（本発明ではＯ２純分が８０％以上のものを使用する。)をキャリアーとしてＣａＯ含有粉体（本発明の説明において粉状ＣａＯ含有物質と同義であり、ＣａＯ純分が８０%以上の脱燐用副原料を意味する。生石灰粉単体や、生石灰粉と石灰石粉の混合物であって、最大粒径が０．１ｍｍ以下のものが例示される。）を上吹きする溶銑脱燐方法においては、火点でＣａＯ−ＦｅＯ化合物（以下、「ＣａＯ−ＦｅＯ」とも表記する。）が生成する。 CaO-containing powder (which is synonymous with powdered CaO-containing substance in the description of the present invention, with a pure CaO content of 80%) using oxygen gas (in the present invention, pure O 2 is 80% or more) as a carrier. The above-mentioned dephosphorization auxiliary raw material, which includes hot lime powder alone or a mixture of quick lime powder and limestone powder with a maximum particle size of 0.1 mm or less. In the method, a CaO—FeO compound (hereinafter also referred to as “CaO—FeO”) is generated at the fire point.
ＣａＯ含有粉体中のＣａＯの上吹き速度を制御して、このＣａＯ−ＦｅＯの組成に依存する融点（ある程度までは（％ＦｅＯ）が高いほど融点は低下する。）を制御することにより、ＣａＯ含有粉体中のＣａＯの脱燐利用効率が向上して処理後の溶銑中［％Ｐ］を低減できた。 By controlling the top blowing rate of CaO in the CaO-containing powder and controlling the melting point (the melting point decreases as (% FeO) increases to a certain extent) depending on the CaO—FeO composition. The dephosphorization utilization efficiency of CaO in the contained powder was improved, and [% P] in the hot metal after the treatment could be reduced.
ところが、ＣａＯ含有粉体中のＣａＯの上吹き速度を６ｋｇ／ｍｉｎ／溶銑ｔ超に高めると、ＣａＯ含有粉体中のＣａＯのスラグへの歩留まりが低下（すなわち、ＣａＯ含有粉体中のＣａＯの系外への飛散ロス量が増大）して処理後スラグの塩基度が低下し、脱燐率が低下してしまった。 However, when the top blowing rate of CaO in the CaO-containing powder is increased to more than 6 kg / min / molten iron t, the yield of CaO in the CaO-containing powder to the slag is reduced (that is, the CaO in the CaO-containing powder is reduced). After the treatment, the basicity of the slag was lowered and the dephosphorization rate was lowered.
ＣａＯ含有粉体中のＣａＯの上吹き速度を過度に増大すると、上吹き酸素によってＦｅＯが生成されている火点へのＣａＯ含有粉体の供給速度が多すぎて、火点でＣａＯ−ＦｅＯ化合物を生成できないＣａＯ含有粉体が発生したと考えられる。それらＣａＯ含有粉体はスラグ中に補足されず、系外へ飛散ロスしたのである。 If the top blowing speed of CaO in the CaO containing powder is excessively increased, the supply speed of the CaO containing powder to the fire point where FeO is generated by the top blowing oxygen is too high, and the CaO-FeO compound at the fire point. It is considered that CaO-containing powder that cannot generate sucrose was generated. These CaO-containing powders were not supplemented in the slag and were scattered outside the system.
以上から、ＣａＯ含有粉体中のＣａＯの上吹き速度を６ｋｇ／ｍｉｎ／溶銑ｔ以下にしなければならないことがわかった。
さらに、溶銑［%Ｓｉ］が高く、しかも処理後スラグ中塩基度を２．０〜３．０に高めなければならない場合は、吹錬前または吹錬初期に塊状生石灰などの塊状ＣａＯ含有物質をある程度添加しなければならない。
From the above, it was found that the top blowing rate of CaO in the CaO-containing powder must be 6 kg / min / molten iron or less.
Furthermore, when the hot metal [% Si] is high and the basicity in the slag after treatment must be increased to 2.0 to 3.0, a massive CaO-containing substance such as massive quicklime is added before or at the beginning of blowing. It must be added to some extent.
この塊状ＣａＯ含有物質として添加されるＣａＯの添加量が多い場合には、添加された塊状ＣａＯ含有物質の滓化を促進しなければ処理後スラグ中の遊離ＣａＯ（ｆ．ＣａＯ）が増加して、スラグを路盤材として有効利用し難くなってしまう。 When the amount of CaO added as the massive CaO-containing substance is large, free CaO (f. CaO) in the slag after treatment increases unless the hatching of the added massive CaO-containing substance is promoted. This makes it difficult to effectively use slag as a roadbed material.
スラグ中（%ＦｅＯ）を高めると塊状ＣａＯ含有物質として添加されるＣａＯのスラグへの溶解（すなわち滓化）が促進されることはわかっているが、上述したごとく短時間の溶銑脱燐処理において単に酸化鉄を多量添加しても、未利用の酸化鉄が増えるだけで、塊状ＣａＯ含有物質として添加されるＣａＯの滓化および脱燐反応は促進されない。 Although it is known that increasing the content of slag (% FeO) promotes dissolution (that is, hatching) of CaO added as a bulk CaO-containing material into the slag, as described above, Even if a large amount of iron oxide is simply added, the amount of unused iron oxide increases, and the hatching and dephosphorization reaction of CaO added as a massive CaO-containing substance is not promoted.
そこで、短時間の溶銑脱燐処理中にスラグ中（％ＦｅＯ）を高めて、塊状ＣａＯ含有物質として添加されるＣａＯのスラグへの溶解（滓化）を促進してスラグの塩基度を高めることで、処理後溶銑中［％Ｐ］を低下させる（すなわち脱燐率を向上させる）方法を鋭意検討した。その結果、ＣａＯ：３０〜５０質量%、ＦｅｔＯ（ＦｅＯ＋Ｆｅ３Ｏ４＋Ｆｅ２Ｏ３の総和）：４０〜６５質量％、ＳｉＯ２：１〜１０質量％、Ａｌ２Ｏ３：１〜２０質量％、且つそれら４成分の合計が９０質量％以上を満たす組成の低融点プリメルトフラックス４〜１０ｋｇ／溶銑ｔを吹錬中に添加し、且つ処理後のスラグ塩基度を２．０〜３．０にすれば良いことを発見した。 Therefore, the basicity of slag is increased by increasing the content of slag (% FeO) during hot metal dephosphorization for a short period of time, and promoting dissolution (hatching) of CaO added as a bulk CaO-containing material into slag. Then, the method of lowering [% P] in the hot metal after the treatment (that is, improving the dephosphorization rate) was intensively studied. As a result, CaO: 30 to 50% by mass, Fe t O (total of FeO + Fe 3 O 4 + Fe 2 O 3 ): 40 to 65% by mass, SiO 2 : 1 to 10% by mass, Al 2 O 3 : 1 to 20 Low melting point pre-melt flux 4-10 kg / molten iron t having a composition satisfying 90% by mass and the total of these four components is added during blowing and the slag basicity after treatment is 2.0-3. I found that it should be 0.0.
かかる知見に基づき導かれる本発明は次のとおりである。
（１）上底吹き転炉に、塊状ＣａＯ含有物質を投入するとともに粉状ＣａＯ含有物質を上吹き酸素と共に溶銑に上吹きする溶銑の脱燐方法において、塊状ＣａＯ含有物質および粉状ＣａＯ含有物質に含有されるＣａＯの合計量に対し、４０質量％以上のＣａＯを粉状ＣａＯ含有物質として、２．０Ｎｍ３／ｍｉｎ／溶銑ｔ以上５．０Ｎｍ３／ｍｉｎ／溶銑ｔ以下の上吹き酸素と共に溶銑へ上吹きし、かつ、０．２Ｎｍ３／ｍｉｎ／溶銑ｔ以上０．６Ｎｍ３／ｍｉｎ／溶銑ｔ以下の底吹きガス流量で該溶銑を撹拌しつつ、脱燐処理後のスラグ塩基度が２．０〜３．０になるよう調整して溶銑脱燐する方法であって、前記粉状ＣａＯ含有物質に含まれているＣａＯが１．０ｋｇ／ｍｉｎ／溶銑ｔ以上６．０ｋｇ／ｍｉｎ／溶銑ｔ以下の速度で上吹きされ、かつ、ＣａＯ：３０質量％以上５０質量％以下、ＦｅｔＯ（ＦｅＯ＋Ｆｅ３Ｏ４＋Ｆｅ２Ｏ３の総和）：４０質量％以上６５質量％以下、ＳｉＯ２：１質量％以上１０質量％以下、Ａｌ２Ｏ３：１質量％以上２０質量％以下、且つそれら４成分の合計が９０質量％以上の化学組成を有するプリメルトフラックス４〜１０ｋｇ／溶銑ｔを吹錬直前および／または吹錬中に添加することを特徴とする溶銑の脱燐方法。
The present invention derived from such knowledge is as follows.
(1) In a dephosphorization method for hot metal in which a massive CaO-containing material is introduced into an upper-bottom blowing converter and the powdered CaO-containing material is blown over molten iron together with top-blown oxygen, the massive CaO-containing material and the powdered CaO-containing material in the total amount of CaO contained, 40 wt% or more of CaO as powdery CaO-containing substance, 2.0 Nm 3 / min / hot metal t than 5.0Nm 3 / min / hot metal t with the following on-blown oxygen The slag basicity after the dephosphorization treatment was stirred while the hot metal was stirred at a bottom blowing gas flow rate of 0.2 Nm 3 / min / molten iron t to 0.6 Nm 3 / min / molten iron t. It is a method of adjusting hot metal dephosphorization to 2.0 to 3.0, wherein CaO contained in the powdered CaO-containing material is 1.0 kg / min / molten iron or more and 6.0 kg / min. / Velocity below hot metal t Is blown above and, CaO: 30 wt% to 50 wt%, (the sum of FeO + Fe 3 O 4 + Fe 2 O 3) Fe t O: 40 wt% or more 65 wt% or less, SiO 2: 1 wt% or more 10 Less than mass%, Al 2 O 3 : 1 mass% or more and 20 mass% or less, and pre-melt flux 4-10 kg / molten iron t having a chemical composition in which the total of these four components is 90 mass% or more and / or A method for dephosphorizing hot metal, which is added during blowing.
（２）吹錬開始前または開始直後に、取鍋スラグを添加することを特徴とする上記（１）記載の脱燐方法。 (2) The dephosphorization method according to (1), wherein ladle slag is added before or immediately after the start of blowing.
本発明によれば、上吹き酸素流量２．０〜５．０Ｎｍ３／ｍｉｎ／溶銑ｔという大流量でＣａＯ含有粉体を上吹きして高速に溶銑脱燐しても、以下を実現できる。
（１）上吹きしたＣａＯ含有粉体に含まれるＣａＯの飛散ロスを０．５ｋｇ／溶銑ｔ以下に抑制、
（２）処理後溶銑中［Ｐ］濃度を０．０１５質量％以下にまで低減、かつ
（３）処理後スラグ中（ｆ．ＣａＯ）を１質量％以下に低減。
According to the present invention, the following can be realized even when the CaO-containing powder is blown up at a high flow rate of 2.0 to 5.0 Nm 3 / min / molten iron t and the molten iron is dephosphorized at high speed.
(1) The scattering loss of CaO contained in the top-blown CaO-containing powder is suppressed to 0.5 kg / molten iron or less,
(2) The [P] concentration in the hot metal after treatment is reduced to 0.015 mass% or less, and (3) (f.CaO) in the slag after treatment is reduced to 1 mass% or less.
まず、上底吹き転炉であって、ＣａＯ含有粉体を上吹き酸素と共に溶銑へ上吹きして溶銑脱燐する機能を有する転炉に、［Ｃ］４．３〜４．５質量％、［Ｓｉ］０.１６〜０．４５質量％、［Ｍｎ］０．２０〜０．３０質量％、［Ｐ］０．０９５〜０．１２０質量％程度の組成を有する通常の溶銑を、適量のスクラップと共に装入する。 First, in a converter having a function of defoaming hot metal by blowing up CaO-containing powder onto hot metal together with top blown oxygen, [C] 4.3 to 4.5% by mass, [Si] 0.16-0.45% by mass, [Mn] 0.20-0.30% by mass, [P] 0.095-0.120% by mass Charge with scrap.
続いて、上吹き酸素流量を２．０〜５．０Ｎｍ３／ｍｉｎ／溶銑ｔ、底吹きガス流量を０．２〜０．６Ｎｍ３／ｍｉｎ／溶銑ｔとし、上吹き酸素の供給開始と同時に、またはその供給開始から２分間が経過するまでの時点から、上吹き酸素と共に粉状ＣａＯ含有物質を溶銑表面へ吹き付けて、溶銑の脱燐処理を開始する。 Subsequently, the top blowing oxygen flow rate is set to 2.0 to 5.0 Nm 3 / min / molten iron t, the bottom blowing gas flow rate is set to 0.2 to 0.6 Nm 3 / min / molten iron t, and simultaneously with the start of supply of the top blowing oxygen. Alternatively, from the point of time until 2 minutes have passed since the start of the supply, the powdered CaO-containing material is sprayed onto the hot metal surface together with the top-blown oxygen, and the hot metal dephosphorization process is started.
上吹き酸素流量が２．０Ｎｍ３／ｍｉｎ／溶銑ｔよりも少なくなると、脱燐に要する時間が長くなり、８分以内の脱燐処理を確実に終了させることが困難となる。一方、上吹き酸素流量が５．０Ｎｍ３／ｍｉｎ／溶銑ｔよりも多くなると、スロッピングが多くなり、上吹きしたＣａＯ含有粉体が炉外へと飛散し、脱燐率が低下する。 If the top blowing oxygen flow rate is less than 2.0 Nm 3 / min / molten iron t, the time required for dephosphorization becomes longer, and it becomes difficult to reliably end the dephosphorization process within 8 minutes. On the other hand, when the flow rate of the top blown oxygen is higher than 5.0 Nm 3 / min / molten iron t, the slopping increases, and the top blown CaO-containing powder is scattered outside the furnace, so that the dephosphorization rate decreases.
底吹きガスは、Ｎ２、Ａｒ、ＣＯ、ＣＯ２のいずれか一種またはそれらの内の二種以上を混合したガスを用いる。底吹きガス流量を０．２〜０．６Ｎｍ３／ｍｉｎ／溶銑ｔとするが、ＣＯ２を用いる場合はその流量を２倍にして換算する。ＣＯ２は溶銑中へ吹き込まれると溶銑中の［Ｃ］と反応してＣＯとなり、流量が供給されたＣＯ２の２倍になるためである。 As the bottom blowing gas, a gas in which any one of N 2 , Ar, CO, CO 2 or a mixture of two or more thereof is used. The bottom blowing gas flow rate is 0.2 to 0.6 Nm 3 / min / molten iron t. When CO 2 is used, the flow rate is doubled for conversion. This is because when CO 2 is blown into the hot metal, it reacts with [C] in the hot metal to become CO, and the flow rate is twice that of the supplied CO 2 .
底吹きガス流量が０．２Ｎｍ３／ｍｉｎ／溶銑ｔ未満であって底吹きガス流量による攪拌力が小さすぎると、底吹き攪拌によるスラグ中（ＦｅＯ）と溶銑中［Ｃ］との反応速度が低下して、吹錬中にスラグ中（％ＦｅＯ）が増加していき、吹錬後半に大規模なスロッピングが発生する。その結果、上吹き添加したＣａＯ含有粉体の一部がスラグと共に系外へ飛散ロスしてしまうため、処理後スラグの塩基度が低下する。 If the bottom blowing gas flow rate is less than 0.2 Nm 3 / min / molten iron t and the stirring force by the bottom blowing gas flow rate is too small, the reaction rate between slag (FeO) and molten iron [C] by the bottom blowing stirring is It decreases, and the amount of slag (% FeO) increases during blowing and large-scale slopping occurs in the latter half of blowing. As a result, a part of the CaO-containing powder added by spraying is lost to the outside of the system together with the slag, so that the basicity of the treated slag is lowered.
逆に、底吹きガス流量が０．６Ｎｍ３／ｍｉｎ／溶銑ｔ超であって底吹きガスによる攪拌力が強すぎると、火点で生成した（ＦｅＯ）や酸化鉄が溶融して生成した（ＦｅＯ）が溶銑中［Ｃ］と速やかに反応してしまう。このためスラグ中（％ＦｅＯ）が常に低い値となって、脱燐不良になってしまう。 Conversely, if the bottom blowing gas flow rate is more than 0.6 Nm 3 / min / molten iron t and the stirring force by the bottom blowing gas is too strong, (FeO) or iron oxide produced at the hot spot is melted and produced ( FeO) reacts quickly with [C] in the hot metal. For this reason, the slag (% FeO) always has a low value, resulting in poor dephosphorization.
脱燐剤としての副原料には、塊状のＣａＯ含有物質、粉状のＣａＯ含有物質に加えて、塊状の低融点プリメルトフラックスを４〜１０ｋｇ／溶銑ｔを使用する。
塊状ＣａＯ含有物質の投入時期は上吹き酸素の供給開始と前後して行えばよい。塊状ＣａＯ含有物質のほか、酸化鉄１０ｋｇ／溶銑ｔ以下を転炉内に投入しても良い。
In addition to the bulk CaO-containing material and the powdered CaO-containing material, 4 to 10 kg / mol t of the bulk low melting point pre-melt flux is used as an auxiliary material as a dephosphorizing agent.
What is necessary is just to perform the injection | throwing-in timing of a block CaO containing substance before and after the supply start of top blowing oxygen. In addition to the massive CaO-containing material, 10 kg of iron oxide / molten iron or less may be charged into the converter.
塊状ＣａＯ含有物質および粉状ＣａＯ含有物質に含有されるＣａＯの合計量に対し、４０質量％以上のＣａＯを粉状ＣａＯ含有物質とすることにより、ＣａＯ−ＦｅＯ系化合物を効率的に形成することが実現される。この比率の上限は設定されず、全量が粉状で供給されてもよい。 Forming a CaO-FeO-based compound efficiently by using 40 mass% or more of CaO as a powdered CaO-containing material with respect to the total amount of CaO contained in the massive CaO-containing material and the powdered CaO-containing material. Is realized. The upper limit of this ratio is not set, and the whole amount may be supplied in powder form.
粉状ＣａＯ含有物質に含まれているＣａＯの上吹き速度は１．０〜６．０ｋｇ／ｍｉｎ／溶銑ｔとする。粉状ＣａＯ含有物質に含まれているＣａＯの上吹き速度が１ｋｇ／ｍｉｎ／溶銑ｔより少ない場合には、５〜８分間という短い酸素供給時間中に必要ＣａＯ質量を供給し切れないという恐れが生じる。一方、粉状ＣａＯ含有物質の上吹き速度が６ｋｇ／ｍｉｎ／溶銑ｔより多い場合には、ＣａＯ−ＦｅＯ系化合物を形成することなく炉外にＣａＯが飛散する量が多くなる。 The top blowing rate of CaO contained in the powdered CaO-containing material is 1.0 to 6.0 kg / min / molten iron t. When the top blowing rate of CaO contained in the powdered CaO-containing material is less than 1 kg / min / molten iron t, there is a risk that the necessary CaO mass cannot be supplied during a short oxygen supply time of 5 to 8 minutes. Arise. On the other hand, when the top blowing speed of the powdered CaO-containing material is more than 6 kg / min / molten iron t, the amount of CaO scattered outside the furnace increases without forming a CaO—FeO-based compound.
塊状の低融点プリメルトフラックスの化学組成は、ＣａＯ：３０〜５０質量％、ＦｅｔＯ（ＦｅＯ、Ｆｅ３Ｏ４およびＦｅ２Ｏ３の総和）：４０〜６５質量％、ＳｉＯ２：１〜１０質量％、Ａｌ２Ｏ３：１〜２０質量％、且つそれら４成分の合計含有量が９０質量％以上である。 Chemical composition of the low-melting premelt flux massive, CaO: 30 to 50 wt%, Fe t O (FeO, the sum of Fe 3 O 4 and Fe 2 O 3): 40~65 wt%, SiO 2: 1~ 10 wt%, Al 2 O 3: 1~20 wt%, and the total content thereof 4 component is 90 mass% or more.
このプリメルトフラックスの融点は低いので、吹錬中に周囲に溶融スラグが存在しなくとも自ら滓化する。そして、プリメルトフラックスにはＣａＯ分が含まれているため、滓化すると直ちに脱燐反応に寄与できる。 Since the melting point of this pre-melt flux is low, even if there is no molten slag in the surrounding area during blowing, it will hatch itself. And since the pre-melt flux contains CaO, it can contribute to the dephosphorization reaction immediately after hatching.
更には、非常に高（％ＦｅＯ）なＣａＯ−ＦｅＯ系融体となるため、周囲にある未滓化の塊ＣａＯを取り込んで滓化を促進させることができる。
この塊状の低融点プリメルトフラックスの転炉内への投入時期は、吹錬直前および／または吹錬中に添加する。具体的には、塊状ＣａＯ含有物質と同様に上吹き酸素の供給開始と前後して投入しても良いし、上吹き酸素の供給開始後からその供給終了時点までの間に投入しても良い。
Furthermore, since it becomes a very high (% FeO) CaO—FeO-based melt, it is possible to promote hatching by taking in the surrounding non-hatched CaO.
The lump-like low melting point pre-melt flux is added into the converter immediately before and / or during blowing. Specifically, like the massive CaO-containing material, it may be added before or after the start of the supply of the top-blown oxygen, or may be introduced between the start of the supply of the top-blown oxygen and the end of the supply. .
これらの脱燐剤としての副原料の投入量は、塊状の低融点プリメルトフラックスを４〜１０ｋｇ／溶銑ｔを先ず確保し、その他の塊状ＣａＯ含有物質と粉状ＣａＯ含有物質を、それぞれの副原料に含まれているＣａＯ質量の合計に対し、粉状ＣａＯ含有物質により供給されるＣａＯ質量の比率が４０％以上として、スラグ塩基度（脱燐処理終了後のスラグを分析して得られるＣａＯとＳｉＯ２との質量濃度比（％ＣａＯ／％ＳｉＯ２））が２．０〜３．０となるように調整して投入する。 The amount of the auxiliary raw material used as the dephosphorizing agent is 4-10 kg / molten iron t of the bulk low melting point pre-melt flux, and the other bulk CaO-containing material and powdered CaO-containing material are added to the respective sub-materials. The ratio of the CaO mass supplied by the powdered CaO-containing material to the total CaO mass contained in the raw material is 40% or more, and the slag basicity (CaO obtained by analyzing the slag after completion of the dephosphorization treatment) a mass concentration ratio of SiO 2 (% CaO /% SiO 2)) is turned adjusted to be 2.0 to 3.0.
さらに、吹錬開始前もしくは開始直後、具体的には酸素供給開始後１分間が経過する前に、取鍋スラグを添加すると好ましい。取鍋スラグの組成は、概略ＣａＯ：４４％、ＳｉＯ２：９％、Ａｌ２Ｏ３：１９％、ＦｅｔＯ ：１３％、ＭｎＯ：８％である。 Furthermore, it is preferable to add ladle slag before or immediately after the start of blowing, specifically before one minute has elapsed after the start of oxygen supply. The composition of the ladle slag, schematic CaO: 44%, SiO 2: 9%, Al 2 O 3: 19%, Fe t O: 13%, MnO: 8%.
取鍋スラグを併用すると、それに含有されるＣａＯの量だけ塊状ＣａＯ含有物質により供給されるＣａＯの添加量を減らすことができる。しかも、取鍋スラグに含まれているＡｌ２Ｏ３に由来して、スラグ中（％Ａｌ２Ｏ３）が増えるので塊状ＣａＯ含有物質のスラグへの溶解速度が向上する。 When the ladle slag is used in combination, the amount of CaO supplied by the massive CaO-containing material can be reduced by the amount of CaO contained therein. Moreover, it derived from Al 2 O 3 contained in the ladle slag, the slag (% Al 2 O 3) is rate of dissolution in the slag bulk CaO-containing material is improved because increases.
なお、脱燐処理後の温度は１３５１〜１３８５℃とし、処理後溶銑中［Ｃ］は３．３〜３．６質量％とする。 The temperature after the dephosphorization treatment is 1351 to 1385 ° C., and [C] in the molten iron after treatment is 3.3 to 3.6 mass%.
溶銑（組成：［Ｃ］約４．５質量％、［Ｓｉ］約０．１６〜０．４５質量％、［Ｐ］０．０９７〜０．１１０質量％）２．５ｔを試験転炉へ装入し、その直後に酸化鉄０〜５ｋｇ／溶銑ｔ、塊生石灰０〜１４ｋｇ／溶銑ｔ、取鍋スラグ０〜１０ｋｇ／溶銑ｔ、および低融点プリメルトフラックス２〜１２ｋｇ／溶銑ｔを添加した。 2.5t of hot metal (composition: [C] about 4.5 mass%, [Si] about 0.16-0.45 mass%, [P] 0.097-0.110 mass%) is loaded into the test converter Immediately thereafter, iron oxide 0-5 kg / molten iron t, lump lime 0-14 kg / molten metal t, ladle slag 0-10 kg / molten metal t, and low melting point premelt flux 2-12 kg / molten metal t were added.
続いて、上吹き酸素（２．０〜５．５Ｎｍ３／ｍｉｎ／溶銑ｔ）と共に、ＣａＯ含有粉体としてＣａＯを９４％含有し、最大粒径が０．１ｍｍ以下である粉生石灰をＣａＯの供給速度に換算して０．８〜７ｋｇ／ｍｉｎ／溶銑ｔの速度で溶銑浴面へ吹き付けて脱燐処理した。 Subsequently, together with top-blown oxygen (2.0 to 5.5 Nm 3 / min / molten iron t), 94% CaO is contained as CaO-containing powder, and powdered lime having a maximum particle size of 0.1 mm or less is CaO. Converted to the feed rate, the phosphorus removal treatment was performed by spraying on the hot metal bath surface at a rate of 0.8 to 7 kg / min / hot metal t.
装入塩基度は１．８〜３．５とし、処理後のスラグ塩基度との関係を調査した。なお、装入塩基度とは、｛添加したフラックス中のＣａＯ分の合計量／（溶銑中［Ｓｉ］が酸化して生成したＳｉＯ２量と添加したフラックス中のＳｉＯ２分の合計量）｝である。 The charge basicity was 1.8 to 3.5, and the relationship with the slag basicity after the treatment was investigated. Note that the charging basicity, {the added total amount of CaO component in the flux / (molten iron [Si] is the total amount of SiO 2 minutes in the flux was added with SiO 2 amount produced by oxidizing)} It is.
脱燐処理中、底吹き羽口からはＮ２を０．１〜０．７Ｎｍ３／ｍｉｎ／溶銑ｔで溶銑中へ吹き込んで攪拌した。
脱燐処理後の温度は１３５１〜１３８５℃であり、処理後溶銑中［Ｃ］は３．３〜３．６質量％であった。
During the dephosphorization treatment, N 2 was blown into the molten iron at 0.1 to 0.7 Nm 3 / min / molten iron from the bottom blowing tuyere and stirred.
The temperature after dephosphorization treatment was 1351-1385 ° C., and [C] in the molten iron after treatment was 3.3-3.6 mass%.
ｉ）プリメルトフラックスの組成等
プリメルトフラックスの組成は、ＣａＯ：３０〜５０質量％、ＦｅｔＯ：４０〜６５質量％、ＳｉＯ２：１〜１０質量％、Ａｌ２Ｏ３：１〜２０質量％、且つそれら４成分の合計が９０質量％以上を満足している場合には、プリメルトフラックスの融点が十分に低く、吹錬中に速やかに滓化して脱燐反応に寄与し易いことを別途確認している。
i) the composition of the composition and the like pre-melt flux of the pre-melt flux, CaO: 30 to 50 wt%, Fe t O: 40~65 wt%, SiO 2: 1~10 wt%, Al 2 O 3: 1~20 When the mass% and the total of these four components satisfy 90 mass% or more, the melting point of the premelt flux is sufficiently low, and it is easy to contribute to the dephosphorization reaction by rapidly hatching during blowing. Is confirmed separately.
したがって、本発明に用いるプリメルトフラックスの組成を、ＣａＯ：３０〜５０質量％、ＦｅｔＯ：４０〜６５質量％、ＳｉＯ２：１〜１０質量％、Ａｌ２Ｏ３：１〜２０質量％、且つそれら４成分の合計が９０質量％以上のものとした。 Therefore, the composition of the pre-melt flux for use in the present invention, CaO: 30 to 50 wt%, Fe t O: 40 to 65 wt%, SiO 2: 1 to 10 wt%, Al 2 O 3: 1~20 wt% The total of these four components was 90% by mass or more.
上吹き酸素流量を３．０Ｎｍ３／ｍｉｎ／溶銑ｔ、底吹き窒素流量を０．５Ｎｍ３／ｍｉｎ／溶銑ｔで固定し、プリメルトフラックス以外に供給する脱燐剤としての副原料を全量生石灰とし、装入塩基度を２．５とする一定条件において、粉状ＣａＯの供給速度が３．２〜４．１ｋｇ／ｍｉｎ／ｔの範囲で、代表的な組成を有するフラックス（ＣａＯ：３５質量％、ＦｅｔＯ：５０質量％、ＳｉＯ２：５質量％、Ａｌ２Ｏ３：６質量％）を８ｋｇ／ｔ用い、プリメルトフラックス以外に供給する脱燐剤としての粉状および塊状ＣａＯの比率を４０〜１００質量％とした条件では、前記した本発明の目的（１）〜（３）を全て達成できていた。 The top blown oxygen flow rate is fixed at 3.0 Nm 3 / min / molten iron t, the bottom blown nitrogen flow rate is fixed at 0.5 Nm 3 / min / molten iron t, and all the auxiliary raw material as a dephosphorizing agent supplied in addition to the premelt flux is quicklime. And a flux having a typical composition (CaO: 35 mass) when the feed rate of powdered CaO is in the range of 3.2 to 4.1 kg / min / t under a constant condition where the charging basicity is 2.5. %, Fe t O: 50% by mass, SiO 2 : 5% by mass, Al 2 O 3 : 6% by mass) are used at 8 kg / t. Under the conditions where the ratio was 40 to 100% by mass, all of the above objects (1) to (3) of the present invention could be achieved.
本発明に係る必要要件の調査結果の内、プリメルトフラックスの組成を上記代表的な組成に固定して、その他の要件に関して調査した結果を表１に纏めて示す。 Table 1 summarizes the results of investigations on other requirements with the composition of the premelt flux fixed to the above representative composition among the investigation results of necessary requirements according to the present invention.
本発明の目的が（１）〜（３）であるため、これらの目的を全て達成できた場合に総合評価を○または◎とし、どれか一つでも満足しなかった場合は×とした。
（１）上吹きしたＣａＯ含有粉体に含まれるＣａＯの飛散ロス量が０．５ｋｇ／溶銑ｔ以下。
Since the objectives of the present invention are (1) to (3), the overall evaluation was evaluated as ◯ or ◎ when all of these objectives could be achieved, and × when not satisfied with any one.
(1) The scattering loss amount of CaO contained in the CaO-containing powder blown above is 0.5 kg / molten iron or less.
（２）処理後溶銑中［Ｐ］濃度が０．０１５質量％以下、なお、［Ｐ］濃度が０．００５質量％以下で他の目標を達成した場合は◎とした。
（３）処理後スラグ中（ｆ．ＣａＯ）が１質量％以下。
(2) When the other target was achieved when the [P] concentration in the molten iron after the treatment was 0.015% by mass or less and the [P] concentration was 0.005% by mass or less, it was marked as ◎.
(3) The slag after treatment (f.CaO) is 1% by mass or less.
表１に記載した本発明例１は、粉状で供給したＣａＯの質量比率を５８％にした例である。
ｉｉ)上吹き酸素流量と底吹き窒素流量の適用可能範囲
上記の結果に基づいて、代表的な組成を有するフラックス（ＣａＯ：３５質量％、ＦｅｔＯ：５０質量％、ＳｉＯ２：５質量％、Ａｌ２Ｏ３：６質量％）を８ｋｇ／ｔ用い、上吹き酸素流量と底吹き窒素流量の適用可能範囲を確認した。
Invention Example 1 described in Table 1 is an example in which the mass ratio of CaO supplied in powder form is 58%.
ii) Applicable range of top blown oxygen flow rate and bottom blown nitrogen flow rate Based on the above results, a flux having a typical composition (CaO: 35% by mass, Fe t O: 50% by mass, SiO 2 : 5% by mass) , Al 2 O 3 : 6 mass%) was used at 8 kg / t, and the applicable range of the top blown oxygen flow rate and the bottom blown nitrogen flow rate was confirmed.
表１の本発明例２〜３および比較例１について述べる。
上吹き酸素流量が２〜５Ｎｍ３／ｍｉｎ／溶銑ｔにおいては、短時間の吹錬にも関わらず全ての目標を達成できた。ところが、上吹き酸素流量が５Ｎｍ３／ｍｉｎ／溶銑ｔを超えると、スロッピングが発生して上吹き添加したＣａＯ粉体の一部がスラグと共に系外へ飛散ロスしてしまった。そのため、処理後スラグの塩基度が低下して、しかもスラグ量も少なくなってしまったため、処理後［％Ｐ］が目標値を達成できなかった。
Invention Examples 2-3 in Table 1 and Comparative Example 1 will be described.
When the top blowing oxygen flow rate was 2 to 5 Nm 3 / min / molten iron t, all targets could be achieved despite short-time blowing. However, when the flow rate of the top blowing oxygen exceeds 5 Nm 3 / min / molten iron t, slopping occurred and a part of the CaO powder added by top blowing was scattered to the outside along with the slag. For this reason, the basicity of the slag after treatment has decreased and the amount of slag has also decreased, so that [% P] after treatment has not achieved the target value.
表１の本発明例４〜５、比較例２〜３について述べる。
底吹きＮ２流量が０．２〜０．６Ｎｍ３／ｍｉｎ／溶銑ｔであれば、短時間の吹錬にも関わらず全ての目標を達成できた。
Invention Examples 4 to 5 and Comparative Examples 2 to 3 in Table 1 will be described.
When the bottom blowing N 2 flow rate was 0.2 to 0.6 Nm 3 / min / molten iron t, all targets could be achieved despite short-time blowing.
ところが、底吹きＮ２流量が０．２Ｎｍ３／ｍｉｎ／溶銑ｔ未満だと、底吹き攪拌によるスラグ中（ＦｅＯ）と溶銑中［Ｃ］との反応速度が低下して、吹錬中にスラグ中（％ＦｅＯ）が増加していき、吹錬後半に大スロッピングが発生した。その結果、上吹き添加したＣａＯ粉体の一部がスラグと共に系外へ飛散ロスしてしまったために処理後スラグの塩基度が低下した。しかもスラグ量が少なくなってしまったために、処理後［％Ｐ］が目標値を達成できなかった。 However, if the bottom blowing N 2 flow rate is less than 0.2 Nm 3 / min / molten iron t, the reaction rate between slag (FeO) and molten iron [C] by bottom blowing stirring decreases, and slag is generated during blowing. Medium (% FeO) increased, and large slopping occurred in the latter half of blowing. As a result, the basicity of the slag after the treatment was lowered because a part of the CaO powder added by spraying was lost to the outside of the system together with the slag. In addition, since the amount of slag has decreased, [% P] after processing cannot achieve the target value.
一方、底吹きＮ２流量が０．６Ｎｍ３／ｍｉｎ／溶銑ｔを超えると、底吹き攪拌によるスラグ中（ＦｅＯ）と溶銑中［Ｃ］との反応速度が過度に促進されて、吹錬の早期にスラグ中（％ＦｅＯ）が低下してしまい、処理後溶銑中［％Ｐ］が目標値を達成できなかった。 On the other hand, when the bottom blowing N 2 flow rate exceeds 0.6 Nm 3 / min / molten iron t, the reaction rate of slag (FeO) and molten iron [C] by the bottom blowing stirring is excessively promoted, The amount of slag (% FeO) was lowered early, and [% P] in the hot metal after treatment could not achieve the target value.
ｉｉｉ）脱燐処理後のスラグ塩基度
さらに、前記した代表的な組成を有するフラックス（ＣａＯ：３５質量％、ＦｅｔＯ：５０質量％、ＳｉＯ２：５質量％、Ａｌ２Ｏ３：６質量％）を８ｋｇ／ｔ用い、底吹き窒素流量を０．５Ｎｍ３／ｍｉｎ／溶銑ｔで固定し、プリメルトフラックス以外に供給する脱燐剤としての副原料を全量粉状生石灰として、処理後のスラグ塩基度の適正範囲をも確認した。
iii) dephosphorization after slag basicity Furthermore, the flux having a typical composition described above (CaO: 35 wt%, Fe t O: 50 wt%, SiO 2: 5 wt%, Al 2 O 3: 6 wt %) Is 8 kg / t, the bottom blown nitrogen flow rate is fixed at 0.5 Nm 3 / min / molten iron t, and the secondary raw material as a dephosphorizing agent supplied in addition to the premelt flux is powdered quicklime, The proper range of slag basicity was also confirmed.
表１の本発明例６〜７および比較例４〜５について述べる。
処理後のスラグ塩基度を２．０〜３．０にすることで、スラグの脱燐能を高く維持して、全ての目標値を達成できた。
Invention Examples 6 to 7 and Comparative Examples 4 to 5 in Table 1 will be described.
By setting the slag basicity after the treatment to 2.0 to 3.0, the dephosphorization ability of the slag was maintained high, and all target values could be achieved.
ところが、装入塩基度を２．０未満にすると、吹錬前半のスラグ塩基度が低いためにスラグ中（％ＦｅＯ）が過度に増加して大スロッピングが発生し、上吹き添加したＣａＯ粉体の一部がスラグと共に系外へ飛散ロスしてしまったために処理後スラグの塩基度が低下した。しかもスラグ量が少なくなってしまったために、処理後［％Ｐ］が目標値を達成できなかった。 However, when the charging basicity is less than 2.0, since the slag basicity in the first half of blowing is low, the amount of (% FeO) in the slag is excessively increased and large slopping occurs, and CaO powder added by top blowing is added. Since a part of the body was lost to the outside of the system together with the slag, the basicity of the slag decreased after the treatment. In addition, since the amount of slag has decreased, [% P] after processing cannot achieve the target value.
一方、装入塩基度を３．０超にすると、スラグの融点が急激に上昇してスラグの流動性が悪化するため、火点で生成したＦｅＯ−ＣａＯ融体がスラグに取り込まれず、系外へ飛散ロスする量が急増し、目標を達成できなかった。 On the other hand, when the charging basicity is more than 3.0, the melting point of the slag rapidly increases and the fluidity of the slag deteriorates, so that the FeO—CaO melt generated at the fire point is not taken into the slag, and is outside the system. The amount of flying loss increased rapidly, and the target could not be achieved.
ｉｖ）プリメルトフラックスの添加量
プリメルトフラックスの組成を調査した条件に同じく、上吹き酸素流量を３．０Ｎｍ３／ｍｉｎ／溶銑ｔ、底吹き窒素流量を０．５Ｎｍ３／ｍｉｎ／溶銑ｔで固定し、プリメルトフラックス以外に供給する脱燐剤としての副原料を全量粉状生石灰とし、装入塩基度を２．５とする一定条件において、粉状ＣａＯの供給速度が３．９〜４．４ｋｇ／ｍｉｎ／ｔの範囲で、前記した代表的な組成を有するフラックス（ＣａＯ：３５質量％、ＦｅｔＯ：５０質量％、ＳｉＯ２：５質量％、Ａｌ２Ｏ３：６質量％）を２〜１２ｋｇ／ｔ添加し、その適正な添加量の範囲を調査した。
iv) Addition amount of pre-melt flux As with the conditions under which the pre-melt flux composition was investigated, the top blown oxygen flow rate was 3.0 Nm 3 / min / molten iron t, and the bottom blown nitrogen flow rate was 0.5 Nm 3 / min / molten iron t. The feed rate of the powdered CaO is 3.9 to 4 under a fixed condition where the auxiliary raw material as a dephosphorizing agent to be fixed and supplied in addition to the premelt flux is powdered quicklime and the charging basicity is 2.5. In the range of 4 kg / min / t, a flux having the above-described typical composition (CaO: 35 mass%, Fe t O: 50 mass%, SiO 2 : 5 mass%, Al 2 O 3 : 6 mass%) Was added in an amount of 2 to 12 kg / t, and the range of appropriate addition amount was investigated.
表１の本発明例８〜９および比較例６〜７について述べる。
プリメルトフラックス添加量が４〜１０ｋｇ／溶銑ｔにおいては、プリメルトフラックス自身による脱燐反応およびスラグ中（％ＦｅＯ）増加によるスラグ流動性（反応性）確保によるスラグ全体による脱燐反応促進効果が発揮されて、処理後溶銑中［％Ｐ］が目標値を達成した。
Invention Examples 8 to 9 and Comparative Examples 6 to 7 in Table 1 will be described.
When the pre-melt flux addition amount is 4 to 10 kg / molten iron t, the de-phosphorus reaction by the pre-melt flux itself and the de-phosphorization reaction promoting effect by the whole slag by ensuring the slag fluidity (reactivity) by increasing the slag (% FeO) As a result, [% P] in the hot metal after processing achieved the target value.
ところが、プリメルトフラックス添加量が４ｋｇ／溶銑ｔ未満だと、プリメルトフラックス自身による脱燐反応量が低下し、更にはスラグ中（％ＦｅＯ）を十分に高められないことによりスラグの流動性が上がらず、スラグ全体による脱燐反応促進効果が発揮されず、処理後溶銑中［％Ｐ］が目標に達しなかった。なお、比較例６ではプリメルトフラックスの一部量の代替として鉄鉱石を５ｋｇ／溶銑ｔ添加したが、プリメルトフラックスのような効果は発揮できなかた。 However, if the amount of pre-melt flux added is less than 4 kg / molten iron t, the amount of dephosphorization reaction by the pre-melt flux itself is reduced, and furthermore, the slag fluidity cannot be sufficiently increased (% FeO), so that the slag fluidity is reduced. The effect of promoting the dephosphorization reaction by the whole slag was not exhibited, and [% P] in the hot metal after the treatment did not reach the target. In Comparative Example 6, 5 kg of iron ore / molten iron t was added as an alternative to a part of the premelt flux, but the effect of the premelt flux could not be exhibited.
一方、プリメルトフラックス添加量が１０ｋｇ／溶銑ｔを超えると、スラグ中（％ＦｅＯ）が過剰に増加して溶銑中［Ｃ］との反応が激しくなり、スロッピングが発生した。そのため、上吹き添加したＣａＯ粉体の一部がスラグと共に系外へ飛散ロスしてしまったために処理後スラグの塩基度が低下した。しかもスラグ量が少なくなってしまったために、処理後［％Ｐ］が目標値を達成できなかった。 On the other hand, when the amount of pre-melt flux added exceeded 10 kg / molten iron t, the amount of slag (% FeO) increased excessively and the reaction with [C] in the molten iron became intense, and slapping occurred. Therefore, since a part of the CaO powder added by top blowing was scattered and lost to the outside of the system together with the slag, the basicity of the treated slag was lowered. In addition, since the amount of slag has decreased, [% P] after processing cannot achieve the target value.
ｖ）粉状ＣａＯ源として上吹き酸素と共に吹き付けるＣａＯの供給速度
前記した代表的な組成を有するフラックス（ＣａＯ：３５質量％、ＦｅｔＯ：５０質量％、ＳｉＯ２：５質量％、Ａｌ２Ｏ３：６質量％）を８ｋｇ／ｔ用い、底吹き窒素流量を０．５Ｎｍ３／ｍｉｎ／溶銑ｔで固定し、プリメルトフラックス以外に供給する脱燐剤としての副原料を全量粉状生石灰として、粉状ＣａＯ源として上吹き酸素と共に吹き付けるＣａＯの供給速度の適正範囲を確認した。
v) Feed rate of CaO sprayed with top-blown oxygen as a powdery CaO source Flux having the above-described typical composition (CaO: 35% by mass, Fe t O: 50% by mass, SiO 2 : 5% by mass, Al 2 O 3 : 6 mass%) is used at 8 kg / t, the bottom blown nitrogen flow rate is fixed at 0.5 Nm 3 / min / molten iron t, and the auxiliary raw material as a dephosphorizing agent supplied in addition to the premelt flux is used as powdery quicklime As a powdery CaO source, the appropriate range of the supply rate of CaO sprayed with top-blown oxygen was confirmed.
表１の本発明例１０〜１１および比較例８〜９について述べる。
ＣａＯ粉体上吹き速度が１．０〜６．０ｋｇ／ｍｉｎ／溶銑ｔにおいては、ＣａＯ粉体はスラグ中に補足されて脱燐反応に寄与したため、処理後溶銑中［％Ｐ］が目標値を達成した。
Invention Examples 10 to 11 and Comparative Examples 8 to 9 in Table 1 will be described.
When the spraying speed on the CaO powder was 1.0 to 6.0 kg / min / molten iron t, the CaO powder was captured in the slag and contributed to the dephosphorization reaction. Achieved.
ところが、ＣａＯ粉体上吹き速度が１．０ｋｇ／ｍｉｎ／溶銑ｔ未満だと、吹錬中にスロッピングが発生して、上吹き添加したＣａＯ粉体の一部がスラグと共に系外へ飛散ロスしてしまったために処理後スラグの塩基度が低下した。詳細な機構は不明だが、ＣａＯ粉体上吹き速度を高めると、スロッピングを抑制できることがわかった。しかもスラグ量が少なくなってしまったために、処理後［％Ｐ］が目標値を達成できなかった。 However, if the CaO powder top blowing speed is less than 1.0 kg / min / molten iron t, slopping occurs during blowing, and a part of the CaO powder added by top blowing is scattered to the outside along with the slag. As a result, the basicity of the slag decreased after the treatment. Although the detailed mechanism is unknown, it has been found that slopping can be suppressed by increasing the spraying speed on the CaO powder. In addition, since the amount of slag has decreased, [% P] after processing cannot achieve the target value.
一方、ＣａＯ粉体上吹き速度が６．０ｋｇ／ｍｉｎ／溶銑ｔを超えると、火点でＦｅＯ反応して低融点のＦｅＯ−ＣａＯ系化合物を生成できず系外へ飛散ロスしてしまうＣａＯ粉体が急増して目標を達成できなかった。火点で生成するＦｅＯ量に対して火点へ上吹きしたＣａＯ粉体量が増加すると、火点で生成するＦｅＯ−ＣａＯ系融体中の（％ＣａＯ）が増加して融体の融点が上昇し、融体中の（％ＣａＯ）がある値を超えて融体の流動性（ＣａＯ粉体との反応性）が急激に低下したために、融体と反応できないＣａＯ粉体が急増してしまったのである。 On the other hand, when the spraying speed on the CaO powder exceeds 6.0 kg / min / molten iron t, the CaO powder that does not produce a low melting point FeO-CaO-based compound due to FeO reaction at the fire point and is scattered outside the system. My body suddenly increased and I couldn't achieve my goal. When the amount of CaO powder blown up to the fire point increases with respect to the amount of FeO produced at the fire point, (% CaO) in the FeO-CaO melt produced at the fire point increases, and the melting point of the melt decreases. As the flow rate of the melt (reactivity with the CaO powder) suddenly decreases when the (% CaO) in the melt exceeds a certain value, the CaO powder that cannot react with the melt rapidly increases. It's gone.
ｖｉ）取鍋スラグの使用
組成が、ＣａＯ：４４質量％、ＳｉＯ２：９質量％、Ａｌ２Ｏ３：１９質量％、ＦｅｔＯ ：１３質量％、ＭｎＯ：８質量％であり、最大粒径が２５ｍｍ以下の取鍋スラグを、上吹き酸素の供給開始と同時に転炉内に投入した例を、表１の本発明例１２〜１３に示す。
vi) Using the composition of the ladle slag, CaO: 44 wt%, SiO 2: 9 wt%, Al 2 O 3: 19 wt%, FetO: 13 wt%, MnO: 8 is the mass%, a maximum particle size Examples of inventions 12 to 13 in Table 1 show examples in which a ladle slag of 25 mm or less is introduced into the converter at the same time as the supply of top-blown oxygen is started.
取鍋スラグを添加したところ、スラグの流動性が非常に高まって脱燐反応が促進され、処理後［％Ｐ］が０．００４質量％以下にまで低下した。これは、取鍋スラグ自身の融点が低いために吹錬の早い段階で滓化して溶融スラグを早期に形成して脱燐反応を促進したことと、取鍋スラグ中（Ａｌ２Ｏ３）により周囲の塊ＣａＯの滓化が促進されたため、取鍋スラグを添加しなかった場合より早期に高塩基度の溶融スラグが形成されて脱燐速度が向上したことによる。 When the ladle slag was added, the fluidity of the slag was greatly increased and the dephosphorization reaction was promoted, and after the treatment, [% P] decreased to 0.004% by mass or less. This is because the ladle slag itself has a low melting point, which hatched early in the blowing process to form molten slag at an early stage and promoted the dephosphorization reaction, and in the ladle slag (Al 2 O 3 ) This is because the hatching of the surrounding lump CaO was promoted, so that high basicity molten slag was formed earlier than when ladle slag was not added, and the dephosphorization rate was improved.
Claims (2)
塊状ＣａＯ含有物質および粉状ＣａＯ含有物質に含有されるＣａＯの合計量に対し、４０質量％以上のＣａＯを粉状ＣａＯ含有物質として、
２．０Ｎｍ３／ｍｉｎ／溶銑ｔ以上５．０Ｎｍ３／ｍｉｎ／溶銑ｔ以下の上吹き酸素と共に溶銑へ上吹きし、
かつ、０．２Ｎｍ３／ｍｉｎ／溶銑ｔ以上０．６Ｎｍ３／ｍｉｎ／溶銑ｔ以下の底吹きガス流量で該溶銑を撹拌しつつ、
脱燐処理後のスラグ塩基度が２．０〜３．０になるよう調整して溶銑脱燐する方法であって、
前記粉状ＣａＯ含有物質に含まれているＣａＯが１．０ｋｇ／ｍｉｎ／溶銑ｔ以上６．０ｋｇ／ｍｉｎ／溶銑ｔ以下の速度で上吹きされ、
かつ、ＣａＯ：３０質量％以上５０質量％以下、ＦｅｔＯ（ＦｅＯ＋Ｆｅ３Ｏ４＋Ｆｅ２Ｏ３の総和）：４０質量％以上６５質量％以下、ＳｉＯ２：１質量％以上１０質量％以下、Ａｌ２Ｏ３：１質量％以上２０質量％以下、且つそれら４成分の合計が９０質量％以上の化学組成を有するプリメルトフラックス４〜１０ｋｇ／溶銑ｔを吹錬直前および／または吹錬中に添加することを特徴とする溶銑の脱燐方法。 In the dephosphorization method for hot metal, the bulk CaO-containing material is charged into the top-bottom blown converter and the powdered CaO-containing material is blown over the hot metal together with top-blown oxygen .
With respect to the total amount of CaO contained in the massive CaO-containing substance and the powdered CaO-containing substance, 40% by mass or more of CaO as the powdery CaO-containing substance,
2.0Nm 3 / min / molten iron t to 5.0Nm 3 / min / molten iron t
And while stirring the hot metal at a bottom blowing gas flow rate of 0.2 Nm 3 / min / molten metal t to 0.6 Nm 3 / min / molten metal t,
A method of adjusting the slag basicity after dephosphorization to 2.0 to 3.0 and dephosphorating the hot metal,
Ca O contained in the powder-like CaO-containing material is blown over at a rate 1.0 kg / min / hot metal t or 6.0 kg / min / hot metal t,
And CaO: 30% by mass or more and 50% by mass or less, Fe t O (total of FeO + Fe 3 O 4 + Fe 2 O 3 ): 40% by mass or more and 65% by mass or less, SiO 2 : 1% by mass or more and 10% by mass or less, Al 2 O 3 : Pre-melt flux of 4 to 10 kg / molten iron t having a chemical composition of not less than 1% by mass and not more than 20% by mass and the total of these four components being not less than 90% by mass during and / or during blowing A hot metal dephosphorization method characterized by adding the hot metal.
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