JP6443192B2 - Slag reforming method using FeSi alloy grains - Google Patents
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Description
本発明は、転炉等の精錬炉から取鍋への溶鋼の出鋼完了後にＦｅＳｉ合金粒を投入してスラグを改質する方法に関する。 The present invention relates to a method of reforming slag by introducing FeSi alloy grains after completion of molten steel from a refining furnace such as a converter to a ladle.
転炉においては、転炉に溶鉄を装入し、転炉精錬によって主に脱りん脱炭精錬を行う。精錬完了後に溶鋼を取鍋に出鋼し、その後、転炉炉内のスラグをスラグ鍋に排滓し、次の精錬のために溶銑を装入するという操業サイクルを繰り返している。
精錬後に転炉から出鋼した取鍋内の溶鋼表面にはスラグが浮遊しており、このスラグ中にはＭｎＯ、ＦｅＯ、Ｆｅ２Ｏ３、等の比較的還元されやすい酸化物を含有している。これらの酸化物は溶鋼中のＡｌなどと反応し、Ａｌ２Ｏ３などの非金属介在物を生成し、溶鋼清浄性を悪化させ、製品欠陥の原因となるおそれがある。
In the converter, molten iron is charged into the converter and dephosphorization and decarburization refining is performed mainly by converter refining. After the refining is completed, the molten steel is taken out into the ladle, and then the operation cycle is repeated in which the slag in the converter furnace is discharged into the slag pan and the molten iron is charged for the next refining.
Slag floats on the surface of the molten steel in the ladle that has been removed from the converter after refining, and this slag contains oxides that are relatively easily reduced , such as MnO, FeO, and Fe 2 O 3. Yes. These oxides react with Al or the like in the molten steel to generate non-metallic inclusions such as Al 2 O 3 , thereby deteriorating the cleanliness of the molten steel and causing product defects.
このため、スラグ中の酸素源となるＦｅＯなどを極力還元し、スラグ中の酸素ポテンシャルを下げ、また、生成した非金属介在物を吸着し易いスラグ組成とする必要がある。スラグ中の酸素ポテンシャルが高いままだと後工程の連続鋳造工程まで非金属介在物の生成が継続し、鋼の清浄度をより悪化させる。
その対応として、スラグ中の酸素量を低減することと非金属介在物等を吸着し易いスラグ組成に改善することが重要で、従来、転炉から取鍋への出鋼中にＣａＯ粉体を投入するとともに、出鋼完了後にスラグ表面に還元剤としてアルミニウム材を投入することがなされている。
For this reason, it is necessary to reduce FeO as an oxygen source in the slag as much as possible, lower the oxygen potential in the slag, and make the slag composition easy to adsorb the generated nonmetallic inclusions. If the oxygen potential in the slag remains high, the production of nonmetallic inclusions continues until the subsequent continuous casting process, which further deteriorates the cleanliness of the steel.
As a countermeasure, it is important to reduce the amount of oxygen in the slag and to improve the slag composition to easily adsorb non-metallic inclusions. In addition to charging, an aluminum material is added as a reducing agent to the slag surface after the completion of steel output.
例えば、スラグの還元を十分に行い、溶鋼の再酸化を抑制し、また生成したＡｌ２Ｏ３などの脱酸生成物を効率良く吸収することができる組成のスラグを得るための技術として、従来、生石灰に加えてホタル石を混合したフラックスをスラグに添加し、出鋼後さらに酸化性スラグを改質するためにアルミ灰などのスラグ還元剤を添加してスラグ組成を調整する技術が知られている（特許文献１参照）。
また、高品質の極低炭素鋼を製造する方法において、精錬炉内のスラグを改質するために、転炉より鋼の脱酸出鋼時にＣａＯとアルミニウム材を投入し、ＣａＯ−Ａｌ２Ｏ３系の低融点改質スラグを２ｋｇ／ｔ・ｓ以上存在させ、出鋼完了時に転炉スラグと改質スラグとの混合スラグを低融点とし、出鋼末期にＡｌとＣａＯを投入することにより出鋼完了後の酸素ポテンシャルを低減させる技術が知られている（特許文献２参照）。
For example, as a technique for obtaining slag having a composition capable of sufficiently reducing slag, suppressing reoxidation of molten steel, and efficiently absorbing deoxidation products such as generated Al 2 O 3 , A technology that adjusts the slag composition by adding a flux containing fluorite in addition to quick lime to the slag, and adding a slag reducing agent such as aluminum ash to further improve the oxidizing slag after steelmaking. (See Patent Document 1).
Moreover, in the method for producing a high quality ultra-low carbon steel, in order to modify the slag in the smelting furnace, CaO and aluminum material are introduced at the time of deoxidation of the steel from the converter, and CaO—Al 2 O By making 3 series low melting point slag more than 2kg / t · s, making the mixed slag of converter slag and reformed slag have low melting point at the completion of steel production, and adding Al and CaO at the end of steel production A technique for reducing the oxygen potential after completion of steel production is known (see Patent Document 2).
ところが、前述の出鋼中にＣａＯ粉体を投入後、スラグ表面にアルミニウム材を投入した場合、アルミニウムの反応によって白煙が多量発生する問題があった。例えば、取鍋をクレーンで吊り上げる際、未反応のアルミニウムが振動によって反応し、急激な発煙を引き起こし、クレーン作業に支障をきたす恐れがあった。
その場合、取鍋を転炉の下に移動し、転炉の集塵機により白煙を吸引していた。しかし、その時間、転炉から炉内スラグを排出する排滓作業ができず、転炉のサイクルタイムが伸び、生産性を著しく低下させ、また、物流も乱していた。
このため、スラグ改質のための還元剤をスラグ表面に投入した場合であっても、発煙を生じさせることのない技術の登場が望まれていた。
However, when the aluminum material is introduced into the slag surface after the CaO powder is introduced into the above-described steel, there is a problem that a large amount of white smoke is generated due to the reaction of aluminum. For example, when a ladle is lifted by a crane, unreacted aluminum reacts by vibration, causing a sudden smoking, which may hinder crane operation.
In that case, the ladle was moved under the converter and white smoke was sucked by the dust collector of the converter. However, during that time, it was impossible to discharge the slag in the furnace from the converter, and the cycle time of the converter was increased, the productivity was remarkably lowered, and the physical distribution was also disturbed.
For this reason, even if it is a case where the reducing agent for slag modification | reformation is thrown into the slag surface, the appearance of the technique which does not produce smoke was desired.
本発明は、前記従来の問題点に鑑みなされたものであって、転炉などの精錬炉から取鍋に出鋼した溶鋼の上に存在するスラグの改質を行う場合に、発煙を生じさせることなくスラグの改質ができる技術の提供を目的とする。 The present invention has been made in view of the above-described conventional problems, and generates smoke when reforming slag existing on molten steel that has been discharged from a refining furnace such as a converter to a ladle. It aims at providing the technique which can modify | reform slag without this.
本発明の特徴は以下の通りである。
本発明では、まず出鋼中にＣａＯを投入し、出鋼完了後に取鍋内スラグにＦｅＳｉ粒を投入する。
ＣａＯを投入するのは、取鍋内スラグ中の酸素ポテンシャルを低減すると同時に、スラグを非金属介在物を吸着し易い組成に改善するためである。
ＣａＯは単体では融点が高いので早期に溶解するように出鋼中から投入する。
次に出鋼完了後、取鍋内スラグの表面にＦｅＳi合金粒を投入する。
The features of the present invention are as follows.
In the present invention, first, CaO is introduced into the outgoing steel, and FeSi particles are introduced into the slag in the ladle after completion of the outgoing steel.
The reason for introducing CaO is to reduce the oxygen potential in the slag in the ladle and at the same time improve the slag to a composition that easily adsorbs non-metallic inclusions.
Since CaO has a high melting point as a simple substance, it is introduced from the steel to be dissolved early.
Next, after the completion of steeling, FeSi alloy grains are put on the surface of the slag in the ladle.
従来用いていたアルミニウム材の添加に代えてＦｅＳｉ合金粒をスラグに投入することで、発煙することなくスラグの還元ができる。出鋼後の発煙が無いため、出鋼完了後、直ちに転炉炉下から取鍋を移動することができ、発煙によるロスタイムを生じないため、転炉の稼動サイクルを短縮することができる。また、白煙による炉下での待機時間のばらつきもなくなるため物流も安定する。 By introducing FeSi alloy grains into the slag instead of the conventionally used aluminum material, the slag can be reduced without generating smoke. Since there is no smoke after the steel is output, the ladle can be moved from the bottom of the converter immediately after the completion of the steel generation, and no loss time due to the smoke is generated, so the operation cycle of the converter can be shortened. In addition, the dispersion of waiting time in the furnace caused by white smoke is eliminated, so that the logistics are stable.
以上を本発明の基本とするが、ＦｅＳi合金粒は、粒径が１０ｍｍ以上、３０ｍｍ以下のものを９０質量％以上含むことが望ましい。
粒径１０ｍｍ未満のＦｅＳｉ合金粒が大量に含まれていると、ＦｅＳｉ合金粒の投入量のばらつきが大きくなるおそれがある。粒径の小さいＦｅＳｉ合金粒は秤量機に切り出す際に流れ込みがあり、それが投入量のばらつき要因となっている。また、粒径の小さいＦｅＳｉ合金はスラグの上で焼結して未溶解のまま溶け残るおそれもある。溶け残ったＦｅＳｉ合金を有したまま二次精錬を行うと、未溶解のＦｅＳｉ合金と溶鋼とが反応し、例えば、溶鋼中の必要な酸素までも低減してしまうおそれがある。
一方、３０ｍｍを超えるＦｅＳｉ合金粒では、スラグ表面に投入すると、ＦｅＳｉ合金粒が溶鋼まで到達し、溶鋼中のＳｉが増加する結果となり、あるいは、Ｃ≦０．０１％である極低炭素鋼のような、脱炭のために必要な溶鋼中酸素までも低減してしまい、脱炭処理に支障をきたしてしまうおそれがあった。
このように、１０〜３０ｍｍの適度な粒径のＦｅＳｉ合金粒であるならば、溶鋼まで到達することを抑制し、溶鋼に悪影響を与えることなく、効率よくスラグの改質を行うことができる。
Although the above is the basis of the present invention, it is desirable that the FeSi alloy particles contain 90% by mass or more of particles having a particle size of 10 mm or more and 30 mm or less.
When a large amount of FeSi alloy grains having a particle size of less than 10 mm is contained, there is a possibility that the variation in the amount of FeSi alloy grains to be introduced becomes large. FeSi alloy grains having a small particle size flow into the weighing machine, which causes a variation in the amount charged. Further, the FeSi alloy having a small particle size may be sintered on the slag and remain undissolved. If secondary refining is performed with the FeSi alloy remaining undissolved, the undissolved FeSi alloy reacts with the molten steel, and for example, there is a risk that even the necessary oxygen in the molten steel is reduced.
On the other hand, when FeSi alloy grains exceeding 30 mm are added to the slag surface, the FeSi alloy grains reach the molten steel, resulting in an increase in Si in the molten steel, or C ≦ 0.01% of ultra-low carbon steel. As a result, the amount of oxygen in the molten steel necessary for decarburization is also reduced, which may hinder the decarburization process.
Thus, if it is a FeSi alloy grain with a moderate particle diameter of 10 to 30 mm, reaching to the molten steel can be suppressed, and the slag can be modified efficiently without adversely affecting the molten steel.
本発明は、溶鋼の出鋼時にＣａＯを投入し、出鋼完了後にスラグの表面にＦｅＳｉ合金粒を投入するので、発煙することなくスラグの改質ができる。出鋼後の発煙が無いため、出鋼後直ちに取鍋の移動ができ、発煙によるロスタイムを生じないため、転炉の稼動サイクルを短縮することができる。
取鍋をクレーンで吊り上げる際、従来は未反応のアルミニウムが振動によって反応し、発煙することがあり、取鍋の周囲が発煙で見えなくなり、で問題があったが、発煙を無くすることで取鍋上方の視野が良好となり、取鍋の移動や吊り上げのための作業を問題なくできる。
In the present invention, CaO is introduced at the time of molten steel, and FeSi alloy grains are introduced on the surface of the slag after completion of the steel production, so that the slag can be modified without generating smoke. Since there is no smoke after the steel is extracted, the ladle can be moved immediately after the steel is output, and no loss time due to the smoke is generated, so that the operation cycle of the converter can be shortened.
When lifting a ladle with a crane, unreacted aluminum may react and generate smoke due to vibration, and the surrounding area of the ladle disappeared due to smoke. The field of view above the pan becomes good, and the work for moving and lifting the ladle can be performed without problems.
以下、第１実施形態に係るスラグの改質方法について図面に基づいて説明する。
図１は精錬炉として転炉１を用いた精錬工程の概要を示す。図１（Ａ）に示すように転炉１に溶銑２を収容するとともに、転炉１の炉頂から転炉１内に挿入したランス３によって溶銑２に酸素ガスを吹き込んで脱炭するとともに、リンなどの不純物の除去を行う。
Hereinafter, the slag reforming method according to the first embodiment will be described with reference to the drawings.
FIG. 1 shows an outline of a refining process using a converter 1 as a refining furnace. As shown in FIG. 1 (A), the molten metal 2 is accommodated in the converter 1 and decarburized by blowing oxygen gas into the molten metal 2 with a lance 3 inserted into the converter 1 from the top of the converter 1. Remove impurities such as phosphorus.
転炉１による精錬が終了したならば、図１（Ｂ）のように転炉１を傾動し、炉壁上側部に形成されている出鋼孔から転炉１の下方に配置されている取鍋５に溶鋼６を出鋼する。取鍋５に溶鋼６を出鋼する際、本発明ではＣａＯ（生石灰）を投入する。例えば、３００ｔ規模の転炉１から出鋼する場合、５０トン程度出鋼してからＣａＯの添加を開始することが好ましい。
取鍋５に溶鋼６を出鋼する際、転炉炉内の溶鋼６の上に存在しているＦｅＯなどの酸化性スラグ７の一部も取鍋５に流出する。ＣａＯの投入量は、３００トン規模の転炉１から溶鋼６を出鋼している場合、０．９ｋｇ／ｔ.ｓ.〜１．０ｋｇ／ｔ.ｓ.（ton-steel：１tonの溶鋼当たり）の範囲とすることができる。なお、上述のＣａＯ投入量は操業上の一例であり、上述の範囲に限るものではない。転炉からの流出スラグ量等に応じて適宜増減すれば良い。
出鋼が終了した時点において、図２（Ａ）に示すように取鍋５には溶鋼６が収容され、その上にスラグ７ａが浮遊している。本実施形態では、このスラグ７ａに対し以下に説明するようにＦｅＳｉ合金粒を極力均一に散布して、スラグの改質を行う。
取鍋５に流出されるスラグ７ａは転炉内のスラグ７の一部であるが、図２（Ａ）に示すように取鍋５溶鋼６の上に３０〜５０ｍｍ程度の厚さのスラグ７ａが形成され、その上、あるいは中に投入したＦｅＳｉが存在する。
When the refining by the converter 1 is completed, the converter 1 is tilted as shown in FIG. 1 (B), and the take-up arranged below the converter 1 from the outlet hole formed in the upper portion of the furnace wall. The molten steel 6 is put out into the pan 5. When the molten steel 6 is removed from the ladle 5, CaO (quick lime) is introduced in the present invention. For example, when steel is output from the 300-ton scale converter 1, it is preferable to start adding CaO after about 50 tons.
When the molten steel 6 is discharged from the ladle 5, part of the oxidizing slag 7 such as FeO existing on the molten steel 6 in the converter furnace also flows out to the ladle 5. The input amount of CaO is 0.9 kg / ts. To 1.0 kg / ts. (Ton-steel: 1 ton of molten steel when the molten steel 6 is discharged from the converter 1 having a scale of 300 tons. ). In addition, the above-mentioned CaO input amount is an example in operation, and is not limited to the above-described range. What is necessary is just to increase / decrease suitably according to the amount of outflow slag, etc. from a converter.
As shown in FIG. 2A, molten steel 6 is accommodated in the ladle 5 and the slag 7a is floating on it. In the present embodiment, the FeSi alloy particles are uniformly dispersed as much as possible on the slag 7a as described below, thereby modifying the slag.
Although the slag 7a which flows out into the ladle 5 is a part of the slag 7 in the converter, as shown in FIG. 2 (A), the slag 7a having a thickness of about 30 to 50 mm is formed on the ladle 5 molten steel 6. Is formed, and there is FeSi charged in or on the inside.
ＦｅＳｉ合金粒８の投入量（散布量）は、３００トン規模の転炉１から溶鋼６を出鋼した場合、０．３ｋｇ／ｔ.ｓ.〜０．４ｋｇ／ｔ.ｓ.の範囲を選択できる。
スラグ７ａに投入するＦｅＳｉ合金粒８は、市販のものは、ＦｅＳｉ合金を粉砕して得た種々の粒径のＦｅＳｉ合金粒の集合体であるが、本実施形態では１０ｍｍ〜３０ｍｍの粒径のＦｅＳｉ合金粒を９０質量％以上含むＦｅＳｉ合金粒８を用いる。より好ましくは９５質量％以上含むＦｅＳｉ合金粒８を用いる。
図３に１０ｍｍ〜３０ｍｍの粒径のＦｅＳｉ合金粒８の一例を示す。
ＦｅＳｉ合金粒８において、１０ｍｍ未満の粒径のＦｅＳｉ合金粒を１０質量％未満含有していても良い。より好ましくは５質量％未満とする。
また、更に好ましくは３０ｍｍを超える粒径のＦｅＳｉ合金粒を含有する場合、１質量％以下とする。更に好ましくは全くなくする方が良い。
ＦｅＳｉ合金粒８をスラグ７ａに投入する場合、スラグ７の表面にできるだけ均一に散布することが好ましい。
The input amount (dispersion amount) of the FeSi alloy grains 8 is selected in the range of 0.3 kg / ts. To 0.4 kg / ts when the molten steel 6 is discharged from the converter 1 having a scale of 300 tons. it can.
The commercially available FeSi alloy particles 8 to be put into the slag 7a are aggregates of FeSi alloy particles having various particle diameters obtained by pulverizing the FeSi alloy. In this embodiment, the particle diameters are 10 mm to 30 mm. FeSi alloy grains 8 containing 90 mass% or more of FeSi alloy grains are used. More preferably, FeSi alloy grains 8 containing 95% by mass or more are used.
FIG. 3 shows an example of FeSi alloy particles 8 having a particle diameter of 10 mm to 30 mm.
FeSi alloy grain 8 may contain less than 10% by mass of FeSi alloy grains having a particle size of less than 10 mm. More preferably, the content is less than 5% by mass.
More preferably, when FeSi alloy grains having a particle diameter exceeding 30 mm are contained, the content is 1% by mass or less. More preferably, it is better to eliminate it at all.
When the FeSi alloy particles 8 are charged into the slag 7a, it is preferable that the FeSi alloy particles 8 be dispersed as uniformly as possible on the surface of the slag 7.
スラグ７ａの上に散布した１０〜３０ｍｍの粒径のＦｅＳｉ合金粒８は、スラグ７ａの熱により溶融し、スラグ７ａ中に拡散してスラグ７ａの還元を行う。ここで、３０ｍｍ超の粒径のＦｅＳｉ合金粒を用いるとスラグ７ａで溶融しきれなかったＦｅＳｉ合金粒の一部が沈降して溶鋼６まで到達するので、溶鋼中のＳｉが所望以上に増加してしまう。あるいは、未脱酸溶鋼の場合、溶鋼６中の酸素と反応し、鋼中酸素量を低下させてしまう。
特に溶鋼６が極低炭素鋼（Ｃ≦０．０１％）のような二次精錬で脱炭処理が必要な鋼種の場合、脱炭を促進するために所定量の溶鋼中酸素が必要である。前記のように溶鋼中酸素が低減されると脱炭効率が低下する。
また、ＦｅＳｉ合金の融点が約１０００℃で、従来のＡｌの融点が６６０℃と高く、ＦｅＳｉ合金粒８をスラグ７ａに投入した際に、ＦｅＳｉ合金粒８の一部が図２（Ｂ）に示すように未溶解合金１２として残留するおそれがあるので、ＦｅＳｉ合金粒８の粒径はより小さくすることが望ましい。
逆に、１０ｍｍ未満の粒径でも、スラグ上で焼結してしまう場合があり、有効にスラグ還元に供されない。また、図２（Ｂ）のように二次精錬で浸漬管を溶鋼に浸漬するなどの際に、焼結したＦｅＳｉを未溶解合金１２として溶鋼中に押し込んでしまい、上記と同様に溶鋼中のＳｉが所望以上に増加したり、あるいは未脱酸溶鋼の場合、鋼中酸素量を低下させてしまう。
The FeSi alloy particles 8 having a particle size of 10 to 30 mm dispersed on the slag 7a are melted by the heat of the slag 7a, diffused in the slag 7a, and reduce the slag 7a. Here, when FeSi alloy particles having a particle diameter of more than 30 mm are used, part of the FeSi alloy particles that could not be melted by the slag 7a settles and reaches the molten steel 6, so that Si in the molten steel increases more than desired. End up. Or in the case of non-deoxidized molten steel, it reacts with oxygen in the molten steel 6 and reduces the amount of oxygen in the steel.
In particular, in the case where the molten steel 6 is a steel type that requires decarburization treatment by secondary refining such as extremely low carbon steel (C ≦ 0.01%), a predetermined amount of oxygen in the molten steel is required to promote decarburization. . As described above, the decarburization efficiency decreases when oxygen in the molten steel is reduced.
Further, the melting point of the FeSi alloy is about 1000 ° C., and the melting point of the conventional Al is as high as 660 ° C. When the FeSi alloy particles 8 are put into the slag 7a, a part of the FeSi alloy particles 8 is shown in FIG. As shown, since it may remain as an undissolved alloy 12, it is desirable to make the particle size of the FeSi alloy particles 8 smaller.
Conversely, even a particle size of less than 10 mm may sinter on slag and is not effectively subjected to slag reduction. In addition, when the dip tube is immersed in the molten steel by secondary refining as shown in FIG. 2 (B), the sintered FeSi is pushed into the molten steel as the unmelted alloy 12, and the molten steel in the same manner as above. When Si increases more than desired or in the case of non-deoxidized molten steel, the amount of oxygen in the steel is reduced.
このようにスラグ７ａに対し改質のために添加する還元剤として、従来投入していたアルミニウム材に替えてＦｅＳｉ合金粒８とするならば、発煙を生じない。そのため、従来、発煙が終了するまで取鍋５が転炉炉下に待機する必要がなく、取鍋５の移動を従来よりも早く開始できるので、転炉１の操業サイクルタイムを短縮することができる。 In this way, if the FeSi alloy grain 8 is used instead of the conventionally introduced aluminum material as a reducing agent added to the slag 7a for reforming, no smoke is generated. Therefore, conventionally, the ladle 5 does not have to wait under the converter furnace until smoke generation is completed, and the movement of the ladle 5 can be started earlier than before, so that the operation cycle time of the converter 1 can be shortened. it can.
例えば、３００トン転炉から取鍋に出鋼し、出鋼完了から、取鍋の溶鋼上のスラグにアルミニウム塊を投入し、発煙した場合、発煙終了まで待機する時間は、８０秒程度あり、この間、取鍋を移動できない。それに対して、ＦｅＳｉ合金粒８をスラグに投入することで、発煙が無くなるので、取鍋移動開始までの時間を８０秒程度短縮できる。この８０秒程度の時間は、従来の３００トン転炉の操業において、出鋼完了からアルミニウム材の投入、待機、サンプル回収位置までの取鍋移動時間の合計時間に対し、約７０％を占めるので、転炉サイクル時間に対し極めて大きなサイクルタイムの短縮となる。また、一般的な転炉サイクルタイムが３０〜４０分と考えても数％に相当し、短縮の効果は大きい。 For example, when steel is discharged from a 300-ton converter to the ladle, and after completion of the steel extraction, aluminum lump is put into the slag on the molten steel in the ladle and smoke is generated, the time to wait until the end of smoke is about 80 seconds, During this time, the ladle cannot be moved. On the other hand, by introducing the FeSi alloy particles 8 into the slag, smoke generation is eliminated, so that the time to start the ladle movement can be shortened by about 80 seconds. This time of about 80 seconds occupies about 70% of the total time of the ladle movement from the completion of steel output to the introduction of aluminum material, standby, and the sample collection position in the operation of the conventional 300-ton converter. The cycle time is extremely shortened with respect to the converter cycle time. Moreover, even if it considers that a general converter cycle time is 30 to 40 minutes, it corresponds to several%, and the effect of shortening is large.
鋼中酸素量を減少させることなく二次精錬ができるならば、極低炭素鋼などの高品位鋼を効率よく製造でき、且つ、好適な溶鋼６が得られる。
前述の二次精錬は、真空脱ガス装置（ＲＨ(Ruhrstahl-Heraeus）による二次精錬について例示したが、二次精錬については、ＤＨ (Dortmund-Horde)、ＬＦ(Ladle Furnace)あるいは、ＡＯＤ(Argon Oxygen Decarburization)炉、ＶＯＤ(Vacuum Oxygen Decarburization)炉などを用いた二次精錬を適用しても良いのは勿論である。
ここで用いるＦｅＳｉ合金粒８は、Ｓｉを７０質量％以上含むものが好ましい。
また、ＦｅＳｉ合金粒８は、Ｃ含有量の低いものを用いることが好ましい。一例として、Ｃ含有量１．０質量％以下のＦｅＳｉ合金粒８を用いることが好ましい。ＦｅＳｉ合金粒８において、Ｃ含有量の多いもの、例えば、Ｃ含有量３質量％以上のＦｅＳｉ合金粒８を用いると、Ｃが酸化してＣＯガスを発生し、スラグ７ａにふくれを発生する。スラグ７ａは粘度が高いため、内部でガスが発生するとスラグ７ａがふくれることとなり、結果的に取鍋５からスラグ７ａが溢れるおそれがある。スラグ７ａのふくれを無くするためにＣ含有量はできるだけ低いことが望ましく、１．０質量％以下であっても、０．５質量％以下が好ましく、０．２質量％以下がより好ましい。
If secondary refining can be performed without reducing the amount of oxygen in the steel, high-grade steel such as ultra-low carbon steel can be produced efficiently and a suitable molten steel 6 can be obtained.
The above-mentioned secondary refining has been exemplified for the secondary refining by a vacuum degassing apparatus (RH (Ruhrstahl-Heraeus)). It goes without saying that secondary refining using an Oxygen Decarburization (Oxygen Decarburization) furnace, a VOD (Vacuum Oxygen Decarburization) furnace, or the like may be applied.
The FeSi alloy grains 8 used here preferably contain 70% by mass or more of Si.
Moreover, it is preferable to use the FeSi alloy grain 8 having a low C content. As an example, it is preferable to use FeSi alloy grains 8 having a C content of 1.0 mass% or less. When FeSi alloy grains 8 having a high C content, for example, FeSi alloy grains 8 having a C content of 3% by mass or more are used, C is oxidized to generate CO gas and blisters are generated in slag 7a. Since the slag 7a has a high viscosity, when gas is generated inside, the slag 7a is swollen, and as a result, the slag 7a may overflow from the ladle 5. In order to eliminate blistering of the slag 7a, the C content is desirably as low as possible. Even if it is 1.0% by mass or less, 0.5% by mass or less is preferable, and 0.2% by mass or less is more preferable.
ところで、上述のＦｅＳｉ合金粒８を投入する際、ＦｅＳｉ合金粒８の投入量に対し、発煙が問題にならない程度少ないようであれば、アルミニウム塊を一部添加しても良い。
取鍋５の内径を４ｍと仮定し、１回の投入時にＣａＯ投入量３００ｋｇ、溶鋼６の上にスラグ７ａが層厚として３０〜５０ｍｍ流出していると仮定することができ、スラグ比重を３．０〜４．０と仮定すると、スラグボリュームは、１．０〜２．５トンとなる。
この条件に対し、１０〜３０ｍｍの粒径のＦｅＳｉ合金粒８ならば８０ｋｇを投入し、更に加えてアルミニウム塊を３０ｋｇ程度投入することができる。この割合では、スラグ７ａのスラグに対し、ＦｅＳｉ合金粒：０．０３２〜０．０８ｋｇ／ｋｇの割合で投入し、アルミニウム塊：０．０１２〜０．０３ｋｇ／ｋｇの割合で投入したこととなる。
スラグにアルミニウム塊を投入する場合、スラグボリューム１．０トンに対し、１０〜２０ｋｇの範囲で投入することが好ましい。ただし、操業の規模に応じてスラグ量が多いからといってアルミニウム塊を１００ｋｇも投入すると当然発煙が多量に発生するので、上述の３０ｋｇ程度を上限とすることが好ましい。
By the way, when the above-described FeSi alloy grains 8 are charged, a part of the aluminum lump may be added as long as the amount of smoke generation does not become a problem with respect to the amount of FeSi alloy grains 8 charged.
Assuming that the inner diameter of the ladle 5 is 4 m, it is possible to assume that the slag 7a flows out as a layer thickness of 30 to 50 mm on the molten steel 6 when the input amount of CaO is 300 kg and the slag specific gravity is 3 Assuming 0.0 to 4.0, the slag volume is 1.0 to 2.5 tons.
With respect to this condition, if FeSi alloy particles 8 having a particle diameter of 10 to 30 mm, 80 kg can be added, and in addition, about 30 kg of aluminum lump can be added. At this ratio, the FeSi alloy grains: 0.032 to 0.08 kg / kg and the aluminum lump: 0.012 to 0.03 kg / kg were added to the slag of the slag 7a. .
When the aluminum lump is thrown into the slag, it is preferably thrown in the range of 10 to 20 kg with respect to 1.0 ton of slag volume. However, if the amount of slag is large depending on the scale of operation, if 100 kg of aluminum lump is added, naturally a large amount of smoke is generated. Therefore, the above upper limit of about 30 kg is preferable.
前述のようにＣａＯとＦｅＳｉ合金８に加え、アルミニウム材を投入する場合、スラグ７ａの酸化性の改質のために、投入した結果においてスラグ７ａの中にＣａＯとＡｌ２Ｏ３の比率において、ＣａＯ／Ａｌ２Ｏ３の比で０．７以上、１．７以下の範囲で含まれていることが好ましく、０．９〜１．３５の範囲がより好ましい。
ＣａＯ／Ａｌ２Ｏ３の比を上述のように設定することが好ましい理由は、図５に示すＣａＯ−ＳｉＯ２−Ａｌ２Ｏ３の三元系状態図に太い実線で示す１６００℃の等温線に示すように、この１６００℃等温線の内側であればすべて液相領域となる。溶鋼清浄性の向上、つまり、溶鋼中の介在物を減少させるには、溶鋼表面に浮上してきた介在物をスラグでいかに捕らえて吸着するかが肝心となる。この点、スラグメタルが強攪拌されないＲＨ処理では、特に液相率が重視される。また、スラグメタルが強攪拌される工程ではＣａＯ／Ａｌ２Ｏ３の値が１．６と高い方が望ましいといえる。上述の０．９〜１．３５の範囲は上述の液相領域に完全に含まれる範囲にあり、スラグが液相であると介在物吸着能が高いと考えられるため、上述の範囲が好ましい。
As described above, when an aluminum material is added in addition to CaO and FeSi alloy 8, in order to improve the oxidizing property of the slag 7a, in the ratio of CaO and Al 2 O 3 in the slag 7a, The CaO / Al 2 O 3 ratio is preferably within the range of 0.7 or more and 1.7 or less, and more preferably within the range of 0.9 to 1.35.
The reason why it is preferable to set the ratio of CaO / Al 2 O 3 as described above is that the isotherm of 1600 ° C. indicated by a thick solid line in the ternary phase diagram of CaO—SiO 2 —Al 2 O 3 shown in FIG. As shown in FIG. 2, the liquid phase region is entirely inside the 1600 ° C. isotherm. In order to improve the cleanliness of the molten steel, that is, to reduce the inclusions in the molten steel, it is important how the inclusions floating on the surface of the molten steel are captured and adsorbed by the slag. In this regard, in the RH process in which the slag metal is not strongly stirred, the liquid phase ratio is particularly important. Further, in the process of slag metal is strongly stirred it can be said that people the value of CaO / Al 2 O 3 is high, 1.6 is desirable. The above range of 0.9 to 1.35 is in the range completely contained in the above liquid phase region, and the above range is preferable because the inclusion adsorbing ability is considered to be high when the slag is in the liquid phase.
３００トン転炉を用い、転炉から内径４ｍの取鍋に溶鋼を出鋼している最中にＣａＯ粒体を３００ｋｇ投入した。この出鋼時、取鍋内の溶鋼の上に厚さ３０〜５０ｍｍのスラグが生成される。スラグの比重は約３．０〜４．０であり、取鍋内のスラグボリュームは１．０〜２．５トンとなる。
取鍋に対する出鋼完了後に行うスラグ改質試験のために、粒径１０〜５０ｍｍのＦｅＳｉ合金粒と粒径１０〜３０ｍｍのＦｅＳｉ合金粒を用意した。
用いたＦｅＳｉ合金粒を構成するＦｅＳｉ合金は、Ｓｉ：７５．４５質量％、Ｃ：０．１１質量％、Ｐ：０．０１３質量％、Ｓ＜０．００５質量％、Ａｌ：１．０５質量％、残部Ｆｅの組成である。
A 300-ton converter was used, and 300 kg of CaO particles were put into the ladle from the converter into a ladle having an inner diameter of 4 m. At the time of steeling, a slag having a thickness of 30 to 50 mm is generated on the molten steel in the ladle. The specific gravity of the slag is about 3.0 to 4.0, and the slag volume in the ladle is 1.0 to 2.5 tons.
For the slag modification test performed after the completion of steeling for the ladle, FeSi alloy particles having a particle size of 10 to 50 mm and FeSi alloy particles having a particle size of 10 to 30 mm were prepared.
The FeSi alloy constituting the FeSi alloy grains used is as follows: Si: 75.45 mass%, C: 0.11 mass%, P: 0.013 mass%, S <0.005 mass%, Al: 1.05 mass %, The composition of the balance Fe.
粒径１０〜５０ｍｍのＦｅＳｉ合金粒とは、粒度選別を行っていない原料合金粒に対し、１０ｍｍの目開きの篩にかけて残留した合金粒を再度５０ｍｍの篩にかけて篩を通過したＦｅＳｉ合金粒の集合体である。
粒径１０〜３０ｍｍのＦｅＳｉ合金粒とは、粒度選別を行っていない原料合金粒に対し、１０ｍｍの目開きの篩にかけて残留した合金粒を再度３０ｍｍの篩にかけて篩を通過したＦｅＳｉ合金粒の集合体である。
篩にかける前の原料合金粒は、１０ｍｍ以下のＦｅＳｉ合金粒が１０％、１０〜２０ｍｍのＦｅＳｉ合金粒が１５％、２０〜３０ｍｍのＦｅＳｉ合金粒が１５％、３０ｍｍ以上のＦｅＳｉ合金粒が６０％含まれていると表記されている市販品の原料合金粒である。
FeSi alloy particles having a particle size of 10 to 50 mm are aggregates of FeSi alloy particles that have passed through a sieve of 50 mm and the remaining alloy particles after passing through a sieve of 10 mm with respect to the raw material alloy particles that have not been subjected to particle size selection. Is the body.
The FeSi alloy particles having a particle size of 10 to 30 mm are aggregates of FeSi alloy particles that have passed through a sieve with a 30 mm sieve after the remaining alloy particles are passed through a sieve with an opening of 10 mm with respect to raw material alloy particles that have not been subjected to particle size selection. Is the body.
The raw material alloy grains before sieving are 10% of FeSi alloy grains of 10 mm or less, 15% of FeSi alloy grains of 10-20 mm, 15% of FeSi alloy grains of 20-30 mm, and 60 FeSi alloy grains of 30 mm or more. % Is a commercially available raw material alloy grain described as being contained.
粒径１０〜５０ｍｍのＦｅＳｉ合金粒の一例を図４（Ａ）の写真に示し、粒径１０〜３０ｍｍのＦｅＳｉ合金粒の一例を図４（Ｂ）の写真に示す。図４（Ａ）の写真から判るように、目開き５０ｍｍの篩を通過する粒で側面視略楕円形状の粒は、５０ｍｍより若干長い粒が通過するので、図４（Ａ）に示す粒の中には５０ｍｍを若干超える長さの略楕円形状の粒等が含まれている。同様に図４（Ｂ）の写真から判るように、目開き３０ｍｍの篩を通過した粒の中には３０ｍｍを若干超える長さの粒が含まれ、目開き１０ｍｍの篩で選別された粒の中には１０ｍｍ未満の粒も一部含まれている。
粒径１０〜３０ｍｍのＦｅＳｉ合金粒を得る場合に、表１に示すように各重量の合金粒を粒度選別して得たＦｅＳｉ合金粒の粒度分布測定結果を以下の表１に示す。
An example of FeSi alloy grains having a particle size of 10 to 50 mm is shown in the photograph of FIG. 4A, and an example of FeSi alloy grains having a particle diameter of 10 to 30 mm is shown in the photograph of FIG. As can be seen from the photograph in FIG. 4 (A), the particles passing through the sieve having an opening of 50 mm and having a substantially elliptical shape when viewed from the side pass slightly longer than 50 mm. Some of them have a substantially elliptical shape with a length slightly exceeding 50 mm. Similarly, as can be seen from the photograph in FIG. 4 (B), the grains that have passed through the sieve having a mesh size of 30 mm include grains having a length slightly exceeding 30 mm. Some grains less than 10 mm are also included.
When obtaining FeSi alloy grains having a particle size of 10 to 30 mm, Table 1 shows the particle size distribution measurement results of FeSi alloy grains obtained by selecting the grain sizes of the alloy grains as shown in Table 1.
ＦｅＳｉ合金粒の粒度については、１０−３０ｍｍ粒径のＦｅＳｉ合金粒１０００ｋｇをタンクに投入し、該タンクからコンテナバックに５回に分けて排出した際、排出開始（０ｋｇ）〜２０ｋｇ、２００〜２２０ｋｇ、４００〜４２０ｋｇ、６００〜６２０ｋｇ、８００〜８２０ｋｇの各回で排出した２０ｋｇを篩にかけて粒度分布を測定した。
その結果が以下の表２であり、この実績を％に換算した値が表１の％に相当する。
Regarding the grain size of the FeSi alloy grains, when 1000 kg of FeSi alloy grains having a particle size of 10-30 mm are put into a tank and discharged into the container bag in five times, the discharge starts (0 kg) to 20 kg, 200 to 220 kg. , 400 to 420 kg, 600 to 620 kg, 800 to 820 kg, and 20 kg discharged each time were sieved to measure the particle size distribution.
The result is shown in Table 2 below, and a value obtained by converting this result into% corresponds to% in Table 1.
いずれの量の粒径１０〜３０ｍｍのＦｅＳｉ合金粒であっても、粒径１０〜３０ｍｍのＦｅＳｉ合金粒が９５〜９８％含まれており、試験目的に合致するＦｅＳｉ合金粒であると判断できる。 Any amount of FeSi alloy particles having a particle size of 10 to 30 mm contains 95 to 98% of FeSi alloy particles having a particle size of 10 to 30 mm, and can be judged to be FeSi alloy particles that meet the test purpose. .
従来から、３００ｔ転炉から内径４ｍの取鍋に出鋼した溶鋼に対し、アルミニウム材（アルミニウム滓）を８０〜１６０ｋｇ添加してスラグ改質を行っている。この場合、大量の白煙が発生し、転炉設備に常備されている集塵装置により白煙を処理し、発煙が終了するまで、８０秒程度要している。
上述のアルミニウム材に替えて、粒径１０〜５０ｍｍのＦｅＳｉ合金粒を、必要量に応じて１６０ｋｇ、１２０ｋｇ、８０ｋｇ投入するケースに分けて実施してみた。
その結果、いずれの場合も、脱Ｃモデルにより推定した脱炭後Ｃ値と実績Ｃ値との乖離が大きく、脱Ｃが推定よりも進行しないケースが多い結果となった。これは、脱Ｃ処理中に脱Ｃ反応以外の反応（２Ａｌ＋３Ｏ→Ａｌ２Ｏ３あるいはＳｉ＋２Ｏ→ＳｉＯ２の反応）により鋼中酸素濃度が低くなって脱炭速度が低下したためと思われる。
Conventionally, slag reforming is performed by adding 80 to 160 kg of aluminum material (aluminum iron) to the molten steel that has been discharged from a 300 t converter into a ladle having an inner diameter of 4 m. In this case, a large amount of white smoke is generated, and it takes about 80 seconds for the white smoke to be processed by the dust collector that is always installed in the converter facility and the smoke generation is completed.
Instead of the above-mentioned aluminum material, FeSi alloy particles having a particle size of 10 to 50 mm were divided into cases where 160 kg, 120 kg, and 80 kg were charged according to the required amount.
As a result, in any case, the difference between the post-decarburization C value estimated by the de-C model and the actual C value was large, and de-C did not progress more than the estimation in many cases. This is presumably because during the de-C treatment, the oxygen concentration in the steel was lowered due to a reaction other than the de-C reaction (reaction of 2Al + 3O → Al 2 O 3 or Si + 2O → SiO 2 ) and the decarburization rate decreased.
次に、上述のアルミニウム材に替えて、粒径１０〜３０ｍｍのＦｅＳｉ合金粒を必要量に応じて、１６０ｋｇ、１２０ｋｇ、８０ｋｇ投入するケースに分けて実施してみたが、いずれの場合も、粒径１０〜５０ｍｍのＦｅＳｉ合金粒を使用した場合よりも脱炭モデルで推定したＣ値と実績Ｃ値との乖離は小さかった。 Next, instead of the above-described aluminum material, FeSi alloy particles having a particle size of 10 to 30 mm were divided into cases where 160 kg, 120 kg, and 80 kg were charged according to the required amount. The difference between the C value estimated by the decarburization model and the actual C value was smaller than when FeSi alloy grains having a diameter of 10 to 50 mm were used.
前記転炉を用いた試験において脱炭モデルから脱炭後Ｃ値と実績Ｃ値とが乖離した原因について考察した。
図６は、取鍋に出鋼した溶鋼のスラグに対し、粒径１０〜５０ｍｍのＦｅＳｉ合金粒を投入してスラグ改質を行った場合に得られた鋼中酸素濃度と、粒径１０〜３０ｍｍのＦｅＳｉ合金粒を投入してスラグ改質を行った場合に得られた鋼中酸素濃度を対比して示すグラフである。
３００トン転炉を用いて取鍋に溶鋼を出鋼し、溶鋼の上に積層しているスラグに対し、粒径１０〜５０ｍｍのＦｅＳｉ合金粒を１６０ｋｇ投入する試験と、１２０ｋｇ投入する試験と、８０ｋｇ投入する試験を転炉精錬操業に合わせて出鋼の度に２２２回繰り返し、投入量に応じて得られた鋼中酸素濃度の出現頻度を図６に示す。
また、３００トン転炉を用いて取鍋に溶鋼を出鋼し、溶鋼の上に生成しているスラグに対し、粒径１０〜３０ｍｍのＦｅＳｉ合金粒を１６０ｋｇ投入する試験と、１１０〜１２０ｋｇ投入する試験を転炉精錬操業に合わせて取鍋に出鋼する度に２０３回繰り返し、投入量に応じて得られた鋼中酸素濃度の出現頻度を図６に示す。
The reason why the C value after decarburization and the actual C value deviated from the decarburization model in the test using the converter was considered.
FIG. 6 shows the oxygen concentration in steel obtained when FeSi alloy grains having a particle size of 10 to 50 mm are added to the slag of molten steel that has been put out in the ladle, and the particle size of 10 to 10 is obtained. It is a graph which compares and shows the oxygen concentration in steel obtained when throwing 30 mm FeSi alloy grain | grain and performing slag modification | reformation.
Using a 300-ton converter, the molten steel is taken out from the ladle, and a test in which 160 kg of FeSi alloy grains having a particle size of 10 to 50 mm are added to a slag laminated on the molten steel, a test in which 120 kg is added, FIG. 6 shows the frequency of appearance of the oxygen concentration in the steel obtained according to the amount of charging, and the test of charging 80 kg was repeated 222 times each time the steel was extracted in accordance with the converter refining operation.
In addition, a test in which 160 kg of FeSi alloy grains having a particle size of 10 to 30 mm is added to the slag produced on the ladle using a 300-ton converter, and 110 to 120 kg is added. FIG. 6 shows the frequency of occurrence of the oxygen concentration in the steel, which was repeated 203 times each time the test was performed in the ladle according to the converter refining operation, and was obtained according to the input amount.
鋼中酸素濃度（ｐｐｍ）は粒径１０〜５０ｍｍのＦｅＳｉ合金粒の場合、平均４５９ｐｐｍ、偏差９１であり、粒径１０〜３０ｍｍのＦｅＳｉ合金粒の場合、平均５０７ｐｐｍ、偏差８６である。
図６に示す結果から、粒径１０〜５０ｍｍのＦｅＳｉ合金粒の場合、鋼中酸素濃度が２８０〜４２０ｐｐｍの比較的低濃度領域において頻度が高くなった。これは、粒径１０〜５０ｍｍのＦｅＳｉ合金粒を用いてスラグ改質を行った場合、鋼中酸素濃度が低くなる確率が高く、粒径１０〜３０ｍｍのＦｅＳｉ合金粒を用いてスラグ改質を行った場合、鋼中酸素濃度が低位とならず、高位のまま保持可能であることを意味する。
In the case of FeSi alloy grains having a particle size of 10 to 50 mm, the oxygen concentration (ppm) in the steel has an average of 459 ppm and deviation 91, and in the case of FeSi alloy grains having a particle diameter of 10 to 30 mm, the average is 507 ppm and deviation 86.
From the results shown in FIG. 6, in the case of FeSi alloy grains having a particle size of 10 to 50 mm, the frequency increased in a relatively low concentration region where the oxygen concentration in the steel was 280 to 420 ppm. This is because, when slag reforming is performed using FeSi alloy grains having a particle size of 10 to 50 mm, there is a high probability that the oxygen concentration in the steel will be low, and slag reforming is performed using FeSi alloy grains having a particle size of 10 to 30 mm. If done, it means that the oxygen concentration in the steel is not low and can be kept high.
図６に示す結果から、スラグの改質を行う場合、粒径１０〜３０ｍｍのＦｅＳｉ合金粒を用いてスラグ改質を行う方が、粒径１０〜５０ｍｍのＦｅＳｉ合金粒を用いてスラグ改質を行う場合よりも鋼中酸素濃度を低下させないという利点があることがわかる。
鋼中酸素濃度を低下させないということは、特に脱炭を要する極低炭素鋼などのように二次精錬処理がなされる鋼種を製造する場合に有利となる。
即ち、ＦｅＳｉ合金粒の粒径差で処理前の溶鋼中酸素濃度の差があるため、二次精錬処理中もＦｅＳｉ合金粒の粒径が大きいと溶鋼中酸素濃度が消費され易くなるので、脱Ｃモデルと実績に乖離が生じ易くなる。このため、ＦｅＳｉ合金粒は前述の如く粒径の小さいものが好ましい。
また、上述のアルミニウム材に替えて、Ｃを４質量％含むＦｅＳｉ合金粒を１４０ｋｇ投入したところスラグにふくれを生じた。このため、Ｃを多く含むＦｅＳｉ合金粒を添加することはスラグ膨れにつながるので適用できないことがわかった。
From the results shown in FIG. 6, when slag modification is performed, slag modification using FeSi alloy particles having a particle size of 10 to 30 mm is performed using FeSi alloy particles having a particle size of 10 to 50 mm. It can be seen that there is an advantage that the oxygen concentration in the steel is not lowered as compared with the case of performing the above.
The fact that the oxygen concentration in the steel is not reduced is particularly advantageous when producing a steel type that is subjected to secondary refining treatment, such as extremely low carbon steel that requires decarburization.
That is, since there is a difference in the oxygen concentration in the molten steel before the treatment due to the difference in the particle size of the FeSi alloy particles, if the particle size of the FeSi alloy particles is large even during the secondary refining treatment, the oxygen concentration in the molten steel is easily consumed. Deviation tends to occur between the C model and results. For this reason, it is preferable that the FeSi alloy grains have a small particle diameter as described above.
In addition, when 140 kg of FeSi alloy grains containing 4% by mass of C was added instead of the above-described aluminum material, the slag was blistered. For this reason, it has been found that adding FeSi alloy grains containing a large amount of C leads to slag swelling and cannot be applied.
上述の粒径１０〜３０ｍｍのＦｅＳｉ合金粒を８０ｋｇ投入するケースに加え、アルミニウム塊３０ｋｇを付加して投入する試験を行った。対スラグ原単位はＦｅＳｉ：０．０３２〜０．０８ｋｇ／ｋｇの割合であり、アルミニウム塊：０．０１２〜０．０３ｋｇ／ｋｇの割合である。スラグ改質材としての合計の対スラグ原単位は、０．０４４〜０．１１ｋｇ／ｋｇとなる。
アルミニウム塊をＦｅＳｉ合金粒に対し追加して投入する場合、３０ｋｇが転炉サイクルタイムを延長させない程度の発煙（発煙がほとんど無く集塵の必要がない程度の発煙）を前提とした上限であり、アルミニウム塊をこれ以上投入すると発煙することを確認している。
上述の割合でＦｅＳｉ合金粒に対しアルミニウム塊を添加してスラグに投入した場合、発煙を生じることが無く、鋼中酸素濃度が目標の脱炭モデルから乖離しなかったので、良好な結果が得られた。
In addition to the case where 80 kg of the FeSi alloy particles having a particle diameter of 10 to 30 mm were added, a test was performed in which 30 kg of aluminum lump was added and added. The basic unit of slag is FeSi: 0.032 to 0.08 kg / kg, and the aluminum lump: 0.012 to 0.03 kg / kg. The total slag basic unit as the slag modifier is 0.044 to 0.11 kg / kg.
When adding an aluminum lump to FeSi alloy grains and adding it, it is the upper limit based on the premise of 30 kg of fuming to the extent that the converter cycle time is not extended (fuming to the extent that there is almost no fuming and no dust collection is necessary) It has been confirmed that smoking occurs when more aluminum lump is added.
When the aluminum lump is added to the FeSi alloy grains at the above-mentioned ratio and put into the slag, no smoke is generated, and the oxygen concentration in the steel does not deviate from the target decarburization model, so a good result is obtained. It was.
１…転炉（精錬炉）、２…溶銑、３…ランス、５…取鍋、６…溶鋼、７…スラグ、７ａ…スラグ、８…ＦｅＳｉ合金粒、１０…浸漬管、１１…真空槽、１２…未溶解合金。 DESCRIPTION OF SYMBOLS 1 ... Converter (smelting furnace), 2 ... Hot metal, 3 ... Lance, 5 ... Ladle, 6 ... Molten steel, 7 ... Slag, 7a ... Slag, 8 ... FeSi alloy grain, 10 ... Dip tube, 11 ... Vacuum tank, 12: Undissolved alloy.
Claims (5)
なお、ＣａＯ、Ａｌ２Ｏ３は、それぞれスラグ中のＣａＯ、Ａｌ２Ｏ３含有量（質量％）とする。 FeSi alloy grains and aluminum lump are put on the surface of the slag in the ladle, and the ratio of CaO / Al 2 O 3 in the slag is 0.70 or more and 1.70 or less. A slag reforming method using the FeSi alloy grain according to any one of claims 1 to 4.
Incidentally, CaO, Al 2 O 3 is, CaO respectively in the slag, and content of Al 2 O 3 (wt%).
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