JP7180367B2 - Hot metal dephosphorization method - Google Patents

Hot metal dephosphorization method Download PDF

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JP7180367B2
JP7180367B2 JP2018242309A JP2018242309A JP7180367B2 JP 7180367 B2 JP7180367 B2 JP 7180367B2 JP 2018242309 A JP2018242309 A JP 2018242309A JP 2018242309 A JP2018242309 A JP 2018242309A JP 7180367 B2 JP7180367 B2 JP 7180367B2
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dephosphorization
hot metal
blowing
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converter
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JP2020105540A (en
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聡 木下
昌平 柿本
遼 北野
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Nippon Steel Corp
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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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.

高炉で生産される溶銑は主要な不純物として、りん（以下、「Ｐ」という場合がある。）や炭素（以下、「Ｃ」という場合がある。）等を含んでいる。これら不純物は、強度や靱性、伸び等の鋼材の諸特性に悪影響を及ぼすため、転炉中の溶銑の不純物を取り除く、例えばＬＤ－ＯＲＰ（ＬＤ ｃｏｎｖｅｒｔｅｒ－Ｏｐｔｉｍｉｚｅｄ Ｒｅｆｉｎｉｎｇ Ｐｒｏｃｅｓｓ）法などの精錬処理としての転炉溶銑予備処理が行われている。 Molten iron produced in a blast furnace contains phosphorus (hereinafter sometimes referred to as "P"), carbon (hereinafter sometimes referred to as "C") and the like as main impurities. These impurities adversely affect various properties of steel materials such as strength, toughness, and elongation. Converter hot metal pretreatment is being carried out.

転炉溶銑予備処理においては、低温（例えば１３００℃程度）で進行する脱りん吹錬と、当該脱りん吹錬の後に行われ、高温（例えば１７００℃程度）で進行する脱炭吹錬とがそれぞれ連続的に行われる。しかしながら、脱りん吹錬の末期においては、当該脱りん吹錬における溶銑の温度上昇に伴い、脱りん反応と同時に脱炭反応が進行してしまう場合がある。 In converter hot metal pretreatment, dephosphorization blowing proceeds at a low temperature (for example, about 1300°C) and decarburization blowing is performed after the dephosphorization blowing and proceeds at a high temperature (for example, about 1700°C). Each is performed consecutively. However, in the final stage of the dephosphorization blowing, the dephosphorization reaction and the decarburization reaction may progress simultaneously with the temperature rise of the hot metal during the dephosphorization blowing.

溶銑中の炭素は熱源として寄与する。上述のように脱りん吹錬中に脱炭反応が進行して炭素が消費され、溶銑中の炭素量が減ってしまうと、後続の脱炭吹錬において投入される昇熱材の使用量が増大し、精錬コストを増大させる一因となる。従って、脱りん吹錬の末期における脱炭反応の進行を抑制し、脱炭吹錬において投入される昇熱材の量を減少させることが望まれる。 Carbon in hot metal contributes as a heat source. As described above, if the decarburization reaction progresses during dephosphorization blowing and carbon is consumed, and the amount of carbon in the hot metal decreases, the amount of heating material used in the subsequent decarburization blowing will decrease. increases, which contributes to an increase in refining costs. Therefore, it is desirable to suppress the progress of the decarburization reaction in the final stage of the dephosphorization blowing and to reduce the amount of heating material introduced in the decarburization blowing.

特許文献１には、転炉内に保持した溶銑に、少なくとも精錬剤としての石灰石の一部を粉体として気体酸素と共に吹き付ける脱りん方法が開示されている。特許文献１に開示の脱りん方法によれば、精錬材としての石灰石の一部を粉体として吹き付けることにより、石灰石を塊で投入する場合と比べて熱ロスを低減させることができる。 Patent Literature 1 discloses a dephosphorization method in which at least a part of limestone as a refining agent is sprayed in powder form together with gaseous oxygen onto molten iron held in a converter. According to the dephosphorization method disclosed in Patent Document 1, heat loss can be reduced by spraying a part of the limestone as a refining material in the form of powder, as compared with the case of charging the limestone in lumps.

特開２０１５－２０６０９１号公報JP 2015-206091 A

上述のように、特許文献１に開示の脱りん方法によれば、石灰石の投入方法を工夫することにより熱ロスを低減することができる。しかしながら、特許文献１には、脱りん吹錬の末期における脱炭反応を抑制することにより、後続の脱炭吹錬における昇熱材の投入量を減少させるという思想は開示も示唆もない。 As described above, according to the dephosphorization method disclosed in Patent Document 1, the heat loss can be reduced by devising the method of adding limestone. However, Patent Literature 1 does not disclose or suggest the concept of reducing the amount of heating material input in the subsequent decarburization blow by suppressing the decarburization reaction at the end of the dephosphorization blow.

上記事情に鑑み、本発明の目的は、精錬処理の脱りん吹錬の末期における脱炭反応の進行を抑制し、後続の脱炭吹錬における熱源としての炭素を溶銑中に残存させることを目的とする。 In view of the above circumstances, an object of the present invention is to suppress the progress of the decarburization reaction in the final stage of dephosphorization blowing in the refining process, and to allow carbon to remain in the hot metal as a heat source in the subsequent decarburization blowing. and

上記課題を解決するため、本発明は、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付けることにより前記溶銑を脱りん吹錬する工程と、を備え、少なくとも、前記脱りん吹錬する工程中において脱炭反応が進行する期間である当該工程の末期において、さらに第二脱りん剤を前記溶銑に投入し、前記第二脱りん剤は、酸化鉄と融体を形成し、酸化鉄よりも炭素に対する反応性を低位化させる粉体状の脱りん剤であり、前記第二脱りん剤は、ＣａＯ、ＭｇＯ、ＭｎＯ、Ａｌ ２ Ｏ ３ 、及び転炉スラグ若しくは二次精錬スラグから選択される一種以上を含むものであり、ＣａＯ、ＭｇＯ、ＭｎＯ及びＡｌ ２ Ｏ ３ を含むものであることを特徴としている。
In order to solve the above problems, the present invention provides a method for dephosphorizing hot metal, comprising the steps of: adding a first dephosphorizing agent to the hot metal; At least at the end of the process, which is a period in which the decarburization reaction proceeds during the dephosphorization blowing process, a second dephosphorization agent is further added to the hot metal, and the first The second dephosphorizing agent is a powdery dephosphorizing agent that forms a melt with iron oxide and makes the reactivity to carbon lower than that of iron oxide. It contains one or more selected from MnO, Al 2 O 3 , and converter slag or secondary refining slag, and is characterized by containing CaO, MgO, MnO and Al 2 O 3 .

本発明によれば、酸化鉄と融体を形成し、酸化鉄よりも炭素に対する反応性を低位化させる粉体状の脱りん剤を溶銑中に投入することにより、脱りん吹錬の末期における脱炭反応を抑制して熱源としての炭素を残存させることができる。その結果後続の脱炭吹錬において投入される昇熱材の量を減少させることができる。 According to the present invention, a powdery dephosphorizing agent that forms a melt with iron oxide and has a lower reactivity to carbon than iron oxide is added to the hot metal, so that at the end of dephosphorization blowing, It is possible to suppress the decarburization reaction and leave carbon as a heat source. As a result, it is possible to reduce the amount of heating material introduced in the subsequent decarburization blowing.

前記第二脱りん剤は、前記溶銑に供給される脱りん剤の総重量に対し、４０％～７０％の重量比で投入されることが望ましい。なお、脱りん剤の総重量とは、第一脱りん剤の重量と第二脱りん剤と重量の和になる。 It is preferable that the second dephosphorizing agent is added at a weight ratio of 40% to 70% with respect to the total weight of the dephosphorizing agent supplied to the hot metal. The total weight of the dephosphorizing agents is the sum of the weight of the first dephosphorizing agent and the weight of the second dephosphorizing agent.

本発明の脱りん方法によれば、精錬処理の脱りん吹錬の末期における脱炭反応の進行を抑制し、後続の脱炭吹錬における熱源としての炭素を溶銑中に残存させることができる。 According to the dephosphorization method of the present invention, it is possible to suppress the progress of the decarburization reaction in the final stage of the dephosphorization blowing of the refining process, and to allow carbon to remain in the hot metal as a heat source in the subsequent decarburization blowing.

本実施形態にかかる転炉設備の構成の概略を模式的に示す説明図である。BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing which shows typically the outline of a structure of the converter equipment concerning this embodiment. 本実施形態にかかる脱りん吹錬における粉体重量比と炭素減少量との関係を示すプロット図である。FIG. 4 is a plot diagram showing the relationship between the powder weight ratio and the amount of carbon reduction in dephosphorization blowing according to the present embodiment. 脱りん吹錬における第二脱りん剤の供給期間を模式的に示す説明図である。FIG. 4 is an explanatory diagram schematically showing a supply period of the second dephosphorization agent in dephosphorization blowing;

以下、本発明の実施形態について図面を参照して説明する。なお、本明細書および図面において、実質的に同一の機能構成を有する構成要素については、同一の符号を付することにより重複説明を省略する。 BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present specification and drawings, constituent elements having substantially the same functional configuration are denoted by the same reference numerals, thereby omitting redundant description.

＜転炉設備の構成＞
先ず、本発明の実施形態でも用いられる一般的な転炉の設備について説明する。図１は、転炉設備の構成の概略を模式的に示す説明図である。 <Configuration of converter equipment>
First, general equipment of a converter that is also used in the embodiments of the present invention will be described. FIG. 1 is an explanatory diagram schematically showing the outline of the configuration of a converter facility.

転炉設備は、上底吹き型の転炉１を有している。転炉１には上部が開口した炉口２と、炉底を貫通する底吹き口３とが形成されている。また炉口２にはランス４が設けられている。ランス４は、その先端から転炉１内に貯留された溶銑５の火点６に向けて、酸素ガスや後述の粉体状の第二脱りん剤を吹き付けて投入することができる。 The converter facility has a top-bottom blowing type converter 1 . A converter 1 has a throat 2 with an open top and a bottom blowing throat 3 penetrating through the bottom of the furnace. A lance 4 is provided in the furnace throat 2 . The lance 4 can blow oxygen gas or a powdery second dephosphorizing agent described later toward the hot point 6 of the hot metal 5 stored in the converter 1 from its tip.

また、溶銑５の上面には、後述の塊状の第一脱りん剤が投入されることにより溶銑５中の不純物（例えばＰ）が酸化されて成るスラグ７が形成されている。 Also, on the upper surface of the hot metal 5, a slag 7 is formed by oxidizing impurities (for example, P) in the hot metal 5 by charging a lump-like first dephosphorizing agent, which will be described later.

＜転炉設備における従来の作用＞
以上のように構成された転炉設備では、溶銑５の精錬処理として、例えば脱りん吹錬と脱炭吹錬とが連続して行われる。そこで次に、転炉１で行われる従来の精錬処理の一例について説明する。 <Conventional actions in converter equipment>
In the converter equipment configured as described above, dephosphorization blowing and decarburization blowing, for example, are continuously performed as the refining process of the molten iron 5 . Therefore, an example of a conventional refining process performed in the converter 1 will now be described.

先ず、高炉で生成された不純物を含む溶銑５が、転炉１の内部に供給される。溶銑５が転炉１の内部に貯留されると、底吹き口３を介して転炉１の内部に不活性ガス、及び、酸素ガスが吹き込まれる。また、これと同時にランス４から転炉１内の溶銑５に酸素ガスが吹き付けられることにより、低温下（例えば１３００℃程度）で脱りん処理が行われる（脱りん吹錬）。 First, molten iron 5 containing impurities produced in a blast furnace is supplied into the converter 1 . When the hot metal 5 is stored inside the converter 1 , inert gas and oxygen gas are blown into the converter 1 through the bottom blowing port 3 . At the same time, oxygen gas is blown from the lance 4 to the hot metal 5 in the converter 1, so that dephosphorization treatment is performed at a low temperature (for example, about 1300° C.) (dephosphorization blowing).

脱りん吹錬が終了すると、続いて、転炉１の内部の溶銑５を出湯により転炉１の外部に設けられた取鍋（図示せず）内へ退避させる。その後、転炉１の内部の脱りん吹錬で生成されたスラグ７を転炉１から完全に排出した後、取鍋に退避させた溶銑５を転炉１の内部に再供給する。その後、転炉１内に新たに例えば石灰を添加し、底吹き口３を介して転炉１の内部に不活性ガス、及び、酸素ガスが吹き込まれる。これと同時に、ランス４から転炉１内の溶銑５に酸素ガスが吹き付けられることにより、高温下（例えば１７００℃程度）で脱炭処理が行われる（脱炭吹錬）。すなわち、酸素ガスが吹き付けられる溶銑５の火点６において脱炭反応が進行する。 After the dephosphorization blowing is completed, the hot metal 5 inside the converter 1 is subsequently withdrawn into a ladle (not shown) provided outside the converter 1 by tapping. After that, after the slag 7 generated by the dephosphorization blowing inside the converter 1 is completely discharged from the converter 1 , the molten iron 5 withdrawn to the ladle is resupplied to the inside of the converter 1 . Thereafter, lime, for example, is newly added into the converter 1 , and inert gas and oxygen gas are blown into the converter 1 through the bottom blowing port 3 . At the same time, oxygen gas is blown from the lance 4 to the hot metal 5 in the converter 1, so that decarburization is performed at a high temperature (for example, about 1700° C.) (decarburization blowing). That is, the decarburization reaction proceeds at the hot point 6 of the hot metal 5 to which the oxygen gas is blown.

以上の一連の手順により、従来、転炉設備における溶銑５の精錬処理が行われている。 Conventionally, the refining treatment of the molten iron 5 in the converter facility is performed by the series of procedures described above.

ここで、脱りん吹錬における脱りん反応が進行すると、当該脱りん吹錬による溶銑５の温度上昇に伴って、脱りん反応と並行して、下記式（１）に示す脱炭反応が進行する場合がある。
（ＦｅＯ）＋［Ｃ］→［Ｆｅ］＋ＣＯ↑ ： 式（１） Here, when the dephosphorization reaction in the dephosphorization blowing progresses, the decarburization reaction shown in the following formula (1) progresses in parallel with the dephosphorization reaction as the temperature of the molten iron 5 rises due to the dephosphorization blowing. sometimes.
(FeO) + [C] → [Fe] + CO↑: Formula (1)

なお、式（１）に記載された、丸括弧で囲まれた化学式はスラグ７中に溶融した成分の化学式であり、角括弧で囲まれた化学式は溶銑５中の成分の化学式である。また、式（１）に記載された上矢印は、当該上矢印で示した化学式がガスとなって溶銑５及びスラグ７から放出されることを示している。 The chemical formulas enclosed in parentheses in formula (1) are the chemical formulas of the components melted in the slag 7, and the chemical formulas enclosed in square brackets are the chemical formulas of the components in the hot metal 5. Also, the up arrow in formula (1) indicates that the chemical formula indicated by the up arrow becomes gas and is released from the hot metal 5 and the slag 7 .

溶銑５中の炭素は、後続の脱炭吹錬における熱源として寄与する。このため、式（１）に示すように、脱りん吹錬中において脱炭反応が進行して溶銑５中の炭素量が減少すると、上述のように、後続の脱炭吹錬において炉内を昇温するための昇熱材の投入量が増大し、精錬コストが増大する。 Carbon in the hot metal 5 contributes as a heat source in subsequent decarburization blowing. Therefore, as shown in formula (1), when the decarburization reaction progresses during dephosphorization blowing and the amount of carbon in the hot metal 5 decreases, as described above, in the subsequent decarburization blowing, the inside of the furnace The input amount of heating material for raising the temperature increases, and the refining cost increases.

＜本実施形態にかかる転炉設備の作用＞
そこで次に、脱りん吹錬の進行に伴って反応を開始する前記式（１）に示す脱炭反応を抑制し、後続の脱炭吹錬における熱源として寄与する炭素を残存させるための、本実施形態にかかる脱りん方法について説明する。なお、以下の説明において、脱りん吹錬中において前記式（１）に示す脱炭反応が進行する期間のことを「脱りん吹錬末期」という場合がある。 <Action of converter equipment according to the present embodiment>
Therefore, next, in order to suppress the decarburization reaction shown in the above formula (1) that starts the reaction as the dephosphorization blow progresses, and to leave the carbon that contributes as a heat source in the subsequent decarburization blow, A dephosphorization method according to an embodiment will be described. In the following description, the period in which the decarburization reaction represented by the above formula (1) proceeds during dephosphorization blowing may be referred to as the "final stage of dephosphorization blowing".

本実施形態にかかる溶銑５の脱りん吹錬では、先ず、転炉１内の溶銑５に第一脱りん剤を投入する。第一脱りん剤としては、例えば塊状のＣａＯ、すなわち塊状の生石灰や石灰石、又は、例えばリサイクルスラグ等が使用される。 In the dephosphorization blowing of the hot metal 5 according to the present embodiment, first, a first dephosphorization agent is introduced into the hot metal 5 in the converter 1 . As the first dephosphorization agent, for example, massive CaO, ie, massive quicklime or limestone, or recycled slag, for example, is used.

なお、第一脱りん剤の投入量は、第一脱りん剤のＣａＯ等量と溶銑５の初期成分におけるＳｉから計算されるＳｉＯ２等量との比（以下、「塩基度」という。）が、およそ１．０となるように決定される。かかる塩基度が高くなると、すなわち第一脱りん剤の投入量が増えると、脱りん吹錬における脱りん性能を向上させることができる反面、第一脱りん剤の投入量が増えるため、精錬コストが増大する。また、塩基度が過剰に高くなると、すなわち第一脱りん剤の投入量が過剰に増えると、ＣａＯの滓化が悪くなり、一定以上の脱りんの良化は望めない。一方、塩基度が低くなると、すなわち第一脱りん剤の投入量が減ると、脱りん精錬における脱りん性能が悪化する。これら脱りん性能及び精錬コストとのバランスにより、第一脱りん剤の投入量は、上述の通り塩基度がおよそ１．０となるように制御されることが好ましい。 The amount of the first dephosphorizing agent to be added is the ratio of the CaO equivalent of the first dephosphorizing agent to the SiO2 equivalent calculated from Si in the initial component of the hot metal 5 (hereinafter referred to as "basicity"). is determined to be approximately 1.0. When the basicity increases, that is, when the input amount of the first dephosphorization agent increases, the dephosphorization performance in dephosphorization blowing can be improved, but on the other hand, the input amount of the first dephosphorization agent increases, so the refining cost increases. increases. On the other hand, if the basicity is excessively high, that is, if the input amount of the first dephosphorizing agent is excessively increased, the slag formation of CaO is deteriorated, and a certain level of improvement in dephosphorization cannot be expected. On the other hand, when the basicity decreases, that is, when the input amount of the first dephosphorizing agent decreases, the dephosphorization performance in the dephosphorization refining deteriorates. Based on the balance between the dephosphorization performance and the refining cost, the amount of the first dephosphorization agent added is preferably controlled so that the basicity is approximately 1.0 as described above.

第一脱りん剤が溶銑５に投入されると、ランス４から転炉１内の溶銑５に酸素ガスが吹き付けられる。これにより転炉１内では、以下の式（２）及び式（３）で示すような脱りん吹錬が進行する。
２［Ｐ］＋５（ＦｅＯ）→（Ｐ２Ｏ５）＋５［Ｆｅ］ ： 式（２）
（Ｐ２Ｏ５）＋３（ＣａＯ）→（３ＣａＯ・Ｐ２Ｏ５） ： 式（３） When the first dephosphorizing agent is charged into the hot metal 5 , oxygen gas is blown from the lance 4 onto the hot metal 5 in the converter 1 . As a result, dephosphorization blowing progresses in the converter 1 as shown by the following equations (2) and (3).
2[P]+5(FeO)→(P 2 O 5 )+5[Fe]: Formula (2)
(P 2 O 5 )+3(CaO)→(3CaO·P 2 O 5 ): Formula (3)

このように、溶銑５中のＰがスラグ７中のＦｅＯによって酸化されてＰ２Ｏ５となる。そして、このＰ２Ｏ５がスラグ中の溶融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。 Thus, P in the hot metal 5 is oxidized by FeO in the slag 7 to become P 2 O 5 . Then, this P 2 O 5 is fixed to the molten CaO in the slag to produce a stabilized compound (3CaO.P 2 O 5 ).

脱りん吹錬末期に差し掛かると、すなわち、脱りん吹錬にかかる反応の進行により転炉１内の温度が上昇すると、かかる温度上昇に伴って前記式（１）に示す脱炭反応の進行がする。 When the end of the dephosphorization blowing is approaching, that is, when the temperature in the converter 1 rises due to the progress of the reaction related to the dephosphorization blowing, the decarburization reaction shown in the above formula (1) proceeds with the temperature rise. does

そこで本実施形態においては、かかる脱炭反応の進行を抑制するため、脱りん吹錬する工程において、第二脱りん剤を溶銑５に供給する。第二脱りん剤としては、例えば粉体状のＣａＯが使用され、脱りん吹錬における酸素ガスの吹き付けと同時に、ランス４から溶銑５に対して吹き付けられる。 Therefore, in the present embodiment, in order to suppress the progress of the decarburization reaction, the second dephosphorization agent is supplied to the hot metal 5 in the dephosphorization blowing step. Powdered CaO, for example, is used as the second dephosphorization agent, and is blown against the hot metal 5 from the lance 4 at the same time as the oxygen gas is blown in the dephosphorization blowing.

転炉１内に第二脱りん剤が供給されると、ランス４直下の火点６において以下の式（４）に示す反応が促進されることにより、以下の式（５）に示す脱炭反応が抑制される。
（ＣａＯ）＋［Ｆｅ］＋１／２Ｏ２→（ＣａＯ－ＦｅＯ） ： 式（４）
ＦｅＯ＋Ｃ→Ｆｅ＋ＣＯ ： 式（５） When the second dephosphorization agent is supplied into the converter 1, the reaction represented by the following formula (4) is promoted at the fire point 6 directly below the lance 4, thereby decarburizing represented by the following formula (5). reaction is suppressed.
(CaO) + [Fe] + 1/2O 2 → (CaO-FeO): Formula (4)
FeO+C→Fe+CO: Formula (5)

このように、本実施形態によれば、脱りん吹錬中の転炉１内に第二脱りん剤を供給することにより、当該脱りん吹錬末期における脱炭反応の進行を抑制し、後続の脱炭吹錬において熱源として寄与する炭素を溶銑５内に残存させることができる。 Thus, according to the present embodiment, by supplying the second dephosphorization agent into the converter 1 during dephosphorization blowing, the progress of the decarburization reaction at the final stage of the dephosphorization blow is suppressed, and the following Carbon that contributes as a heat source in decarburization blowing can remain in the hot metal 5 .

図２は、本実施形態にかかる第二脱りん剤の、第一脱りん剤の重量に対する重量比（以下、粉体重量比という。）と、従来の脱りん吹錬における炭素の消費量に対する、本実施形態にかかる脱りん吹錬の炭素消費量の比率（ΔＣ）との関係を表したプロット図である。 FIG. 2 shows the weight ratio of the second dephosphorizing agent according to the present embodiment to the weight of the first dephosphorizing agent (hereinafter referred to as the powder weight ratio) and the amount of carbon consumed in the conventional dephosphorization blowing. , and a ratio (ΔC) of carbon consumption in dephosphorization blowing according to the present embodiment. FIG.

なお、炭素消費量の比率ΔＣは、下記式（６）により求められる。式（６）において溶銑Ｃ１（％）は転炉１内の溶銑５に含まれる炭素の割合、溶銑率（％）は転炉１内の溶銑５の割合、脱りん後Ｃ２（％）は脱りん精錬終了後における溶銑５中に含まれる炭素の割合を表している。
ΔＣ＝溶銑Ｃ１（％）×溶銑率（％）－脱りん後Ｃ２（％） ： 式（６） Note that the ratio ΔC of the carbon consumption amount is obtained by the following formula (6). In equation (6), hot metal C1 (%) is the ratio of carbon contained in hot metal 5 in converter 1, hot metal ratio (%) is the ratio of hot metal 5 in converter 1, and C2 (%) after dephosphorization is dephosphorization. It represents the ratio of carbon contained in the hot metal 5 after the completion of phosphorus refining.
ΔC = Hot metal C1 (%) × Hot metal rate (%) - C2 (%) after dephosphorization: Formula (6)

また、図２縦軸のΔＣ＝１．０は、従来の脱りん吹錬における炭素消費量を基準としたものであり、すなわち、縦軸１．０よりも小さな値であるほど、溶銑５中の炭素の消費が抑えられ、溶銑５中の炭素の残存量が多いことを示している。 In addition, ΔC = 1.0 on the vertical axis of Fig. 2 is based on the carbon consumption amount in conventional dephosphorization blowing. This indicates that the consumption of carbon in the hot metal 5 is suppressed, and the residual amount of carbon in the hot metal 5 is large.

図２に示すように、溶銑５中の炭素の消費量は、粉体重量比がおよそ４０％を境に従来に比べて減少をはじめ、粉体重量比が高くなるほど低くなっていることがわかる。 As shown in Fig. 2, the amount of carbon consumed in the hot metal 5 begins to decrease when the powder weight ratio reaches about 40%, and decreases as the powder weight ratio increases. .

これは、前記所定の供給速度で第二脱りん剤を転炉１内に供給する場合、粉体重量比が大きくなることにより転炉１内に供給する第２脱りん剤の総量が増え、第二脱りん剤の供給期間が長くなることに起因する。すなわち、図３に示すように第二脱りん剤の供給開始のタイミングＳを一定（本実施形態においては脱りん吹錬の開始直後）とした場合、およそ４０％を境として第二脱りん剤の供給期間Ｔが脱りん吹錬末期の期間と重複するようになる。そして、粉体重量比が大きくなるほど脱りん吹錬末期の期間と重複する第二脱りん剤の供給期間が長くなり、すなわち長期間にわたって脱炭反応を抑制することができる。 This is because when the second dephosphorizing agent is supplied into the converter 1 at the predetermined supply rate, the total amount of the second dephosphorizing agent supplied into the converter 1 increases due to the increase in the powder weight ratio. It originates in the supply period of a 2nd dephosphorization agent becoming long. That is, as shown in FIG. 3, when the supply start timing S of the second dephosphorization agent is constant (immediately after the start of dephosphorization blowing in this embodiment), the second dephosphorization agent supply period T overlaps with the period of the final stage of dephosphorization blowing. As the powder weight ratio increases, the supply period of the second dephosphorizing agent that overlaps with the period of the final stage of dephosphorization blowing becomes longer, that is, the decarburization reaction can be suppressed over a long period of time.

なお、図２及び図３に示すように粉体重量比が大きくなることにより脱炭反応を抑制できる期間を長くすることができる。しかしながら、例えば生成スラグの塩基度の上限などにおいて制限があり、第二脱りん剤の投入量、すなわち粉体重量比は、６０％～７０％を上限値とすることが望まれる。なお、上限の７０％は、上述したように塩基度が過剰に高くなると（例えば塩基度が３．５以上）、ＣａＯの滓化が悪くなり、一定以上の脱りんの良化は望めない。そこで、塩基度が３．５となる場合の第二脱りん剤の粉体重量比７０％を、上限とするのが望ましい。 As shown in FIGS. 2 and 3, the period during which the decarburization reaction can be suppressed can be lengthened by increasing the powder weight ratio. However, there are restrictions on the upper limit of the basicity of the produced slag, etc., and it is desired that the upper limit of the amount of the second dephosphorizing agent added, ie, the powder weight ratio, is 60% to 70%. As for the upper limit of 70%, if the basicity is excessively high (for example, the basicity is 3.5 or more) as described above, the slag formation of CaO deteriorates, and a certain level of improvement in dephosphorization cannot be expected. Therefore, it is desirable to set the upper limit to 70% of the powder weight ratio of the second dephosphorizing agent when the basicity is 3.5.

以上により、第二脱りん剤の投入量は前記粉体重量比が、４０％～７０％、好ましくは４０％～６０％となるように決定されることが望ましい。 From the above, it is desirable that the amount of the second dephosphorizing agent added is determined so that the powder weight ratio is 40% to 70%, preferably 40% to 60%.

なお、上記実施形態においては第二脱りん剤として粉体状のＣａＯを使用したが、上述のように前記式（１）に示す脱炭反応の進行を抑制し、酸化鉄とスラグ７を形成するものであれば、第二脱りん剤の材料はこれに限定されない。すなわち、酸化鉄と融体を形成し、酸化鉄よりも炭素に対する反応性を低位化させるものであれば、第二脱りん剤の材料は任意に選択することができ、例えばＭｇＯやＭｎＯ、Ａｌ２Ｏ３等を選択することができる。または、転炉スラグや二次精錬スラグであって、これらＣａＯ、ＭｇＯ、ＭｎＯ、若しくは、Ａｌ２Ｏ３成分を含むものであってもよい。また更に、これらから選択される一種以上を含むものであれば複数の材料が混合された第二脱りん剤を使用してもよい。 In the above embodiment, powdery CaO was used as the second dephosphorization agent, but as described above, CaO suppresses the progress of the decarburization reaction shown in the above formula (1) and forms iron oxide and slag 7. The material of the second dephosphorization agent is not limited to this, as long as it does. That is, the material of the second dephosphorization agent can be arbitrarily selected as long as it forms a melt with iron oxide and lowers the reactivity to carbon than iron oxide. 2 O 3 and the like can be selected. Alternatively, it may be converter slag or secondary refining slag containing these CaO, MgO, MnO, or Al 2 O 3 components. Furthermore, the second dephosphorization agent may be a mixture of a plurality of materials as long as it contains one or more selected from these materials.

以上より選択される第二脱りん剤として、例えば転炉スラグや二次精錬スラグを使用した場合、精錬処理における環境負荷の低減、及び、製鋼におけるコストの低減を図ることができる。 When converter slag or secondary refining slag, for example, is used as the second dephosphorizing agent selected from the above, it is possible to reduce the environmental load in refining treatment and reduce the cost in steelmaking.

なお、第二脱りん剤の溶銑５への供給は、前記式（１）に示す脱炭反応を抑制し、前記式（４）に示すＦｅ成分との反応を進行させることができれば、任意のタイミングで適宜開始することができる。すなわち、少なくとも脱りん精錬末期に第二脱りん剤を溶銑５に供給することができれば、脱炭反応の抑制を抑制し、後続の脱炭吹錬における熱源としての炭素を残存させることができる。 The supply of the second dephosphorizing agent to the hot metal 5 can suppress the decarburization reaction shown in the above formula (1), and can proceed with the reaction with the Fe component shown in the above formula (4). It can be started at any time. That is, if the second dephosphorization agent can be supplied to the hot metal 5 at least in the final stage of dephosphorization refining, suppression of the decarburization reaction can be suppressed, and carbon can remain as a heat source for subsequent decarburization blowing.

ただし、例えば第二脱りん剤の供給開始のタイミングを遅くした場合、脱りん吹錬における脱りん反応が悪化してしまうことが考えられる。これにより第二脱りん剤は、脱りん精錬の開始後に遅滞なく供給を開始し、溶銑５の塩基度を１．０以上にで維持できるように制御することが最も好ましい。 However, for example, if the timing of starting the supply of the second dephosphorization agent is delayed, the dephosphorization reaction in the dephosphorization blowing may deteriorate. Accordingly, it is most preferable to start supplying the second dephosphorizing agent without delay after the start of dephosphorization refining and to control the basicity of the hot metal 5 to be maintained at 1.0 or more.

なお、例えば上述のように第二脱りん剤の供給開始のタイミングを遅くする場合、第二脱りん剤の供給期間を脱りん吹錬末期の期間により長く重複させることができるため、脱炭反応の抑制効果をより適切に享受することができる。 In addition, for example, when the timing of starting the supply of the second dephosphorization agent is delayed as described above, the supply period of the second dephosphorization agent can be overlapped longer than the period of the final stage of dephosphorization blowing, so that the decarburization reaction can more appropriately enjoy the suppressing effect of

以上、本発明の実施形態について説明したが、本発明はかかる例に限定されない。当業者であれば、特許請求の範囲に記載された技術的思想の範疇内において、各種の変更例または修正例に想到しうることは明らかであり、それらについても当然に本発明の技術的範囲に属するものと了解される。 Although the embodiments of the present invention have been described above, the present invention is not limited to such examples. It is obvious that a person skilled in the art can conceive various modifications or modifications within the scope of the technical idea described in the claims, and these are also within the technical scope of the present invention. be understood to belong to

例えば、以上の実施形態によれば、脱りん吹錬が上底吹き型の転炉において行われる場合を例に説明したが、本発明にかかる脱りん吹錬が行われる転炉設備の構成は上底吹き型の転炉に限定されない。例えば本発明にかかる脱りん吹錬は、上吹き型転炉などにおいて行われてもよい。 For example, according to the above embodiment, the case where the dephosphorization blowing is performed in a top-bottom blowing type converter has been described as an example, but the configuration of the converter equipment in which the dephosphorization blowing according to the present invention is performed is It is not limited to a top and bottom blowing type converter. For example, dephosphorization blowing according to the present invention may be performed in a top-blown converter or the like.

本発明は、転炉における脱りん吹錬を行う際に有用である。 INDUSTRIAL APPLICABILITY The present invention is useful when performing dephosphorization blowing in a converter.

１ 転炉
２ 炉口
３ 底吹き口
４ ランス
５ 溶銑
６ 火点
７ スラグ 1 Converter 2 Furnace Mouth 3 Bottom Blowing Mouth 4 Lance 5 Hot Metal 6 Fire Point 7 Slag

Claims (2)

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付けることにより前記溶銑を脱りん吹錬する工程と、
を備え、
少なくとも、前記脱りん吹錬する工程中において脱炭反応が進行する期間である当該工程の末期において、さらに第二脱りん剤を前記溶銑に投入し、
前記第二脱りん剤は、酸化鉄と融体を形成し、酸化鉄よりも炭素に対する反応性を低位化させる粉体状の脱りん剤であり、
前記第二脱りん剤は、ＣａＯ、ＭｇＯ、ＭｎＯ、Ａｌ ２ Ｏ ３ 、及び転炉スラグ若しくは二次精錬スラグから選択される一種以上を含むものであり、ＣａＯ、ＭｇＯ、ＭｎＯ及びＡｌ ２ Ｏ ３ を含むものであることを特徴とする、溶銑の脱りん方法。 A method for dephosphorizing hot metal,
a step of adding a first dephosphorizing agent to the molten pig iron;
a step of dephosphorizing and blowing the molten iron by blowing oxygen onto the molten iron;
with
At least, in the final stage of the dephosphorization process, which is the period during which the decarburization reaction progresses during the dephosphorization blowing process , a second dephosphorization agent is further added to the hot metal,
The second dephosphorizing agent is a powdery dephosphorizing agent that forms a melt with iron oxide and has a lower reactivity to carbon than iron oxide,
The second dephosphorization agent contains one or more selected from CaO, MgO, MnO, Al 2 O 3 , and converter slag or secondary refining slag, and includes CaO, MgO, MnO and Al 2 O 3 A method for dephosphorizing hot metal, characterized in that it contains 前記第二脱りん剤は、前記溶銑に供給される脱りん剤の総重量に対し、４０％～７０％の重量比で投入され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。
2. The dephosphorization of hot metal according to claim 1, wherein the second dephosphorization agent is added at a weight ratio of 40% to 70% with respect to the total weight of the dephosphorization agent supplied to the hot metal. Phosphorus method.
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JP2011225925A (en) 2010-04-19 2011-11-10 Sumitomo Metal Ind Ltd Dephosphorization method for molten iron
JP2011246773A (en) 2010-05-27 2011-12-08 Sumitomo Metal Ind Ltd Method of dephosphorizing molten iron

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JP2001064713A (en) 1999-08-26 2001-03-13 Sumitomo Metal Ind Ltd Method for dephosphorizing molten iron
JP2001131623A (en) 1999-11-04 2001-05-15 Nippon Steel Corp Dephosphorizing method of molten iron
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