JPWO2018135344A1 - Method for desulfurizing molten steel and desulfurizing agent - Google Patents

Method for desulfurizing molten steel and desulfurizing agent Download PDF

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JPWO2018135344A1
JPWO2018135344A1 JP2018563279A JP2018563279A JPWO2018135344A1 JP WO2018135344 A1 JPWO2018135344 A1 JP WO2018135344A1 JP 2018563279 A JP2018563279 A JP 2018563279A JP 2018563279 A JP2018563279 A JP 2018563279A JP WO2018135344 A1 JPWO2018135344 A1 JP WO2018135344A1
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molten steel
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勇輔 藤井
勇輔 藤井
中井　由枝
由枝 中井
秀弥 正木
秀弥 正木
菊池　直樹
直樹 菊池
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/0075—Treating in a ladle furnace, e.g. up-/reheating of molten steel within the ladle
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/064—Dephosphorising; Desulfurising
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/072—Treatment with gases
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21C—PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS
    • C21C7/00—Treating molten ferrous alloys, e.g. steel, not covered by groups C21C1/00 - C21C5/00
    • C21C7/04—Removing impurities by adding a treating agent
    • C21C7/076—Use of slags or fluxes as treating agents

Abstract

本発明に係る溶鋼の脱硫処理方法は、溶鋼を収容する取鍋内に生石灰を含む脱硫剤を添加し、取鍋内で溶鋼を攪拌することによって、溶鋼中の硫黄濃度を低減する溶鋼の脱硫処理方法であって、脱硫剤として、細孔直径が０．５〜１０μｍ以下の範囲内にある細孔の容積の和が０．１ｍＬ／ｇ以上である生石灰を含む脱硫剤を用いることを特徴とする。これにより、ＣａＦ2やプリメルトフラックスを使用しなくても効率良く脱硫処理を行うことができる。The method for desulfurizing molten steel according to the present invention comprises desulfurizing a molten steel by adding a desulfurizing agent containing quick lime into a ladle containing the molten steel and stirring the molten steel in the ladle to reduce the concentration of sulfur in the molten steel. It is a processing method, and it is characterized by using a desulfurization agent containing quicklime whose sum of volume of pores whose pore diameter is in the range of 0.5 to 10 μm or less is 0.1 mL / g or more as the desulfurization agent. I assume. Thereby, desulfurization can be performed efficiently without using CaF 2 or a premelt flux.

Description

本発明は、溶鋼の脱硫処理方法及び脱硫剤に関する。   The present invention relates to a method for desulfurizing molten steel and a desulfurizing agent.

近年、鋼の高付加価値化や鉄鋼材料の使用用途拡大等に伴う材料特性向上のために、高純度鋼製造に対する要求が高まっており、特に鉄鋼材料の靭性を低下させる元素である硫黄の含有量が少ない極低硫鋼に対する要求が高くなっている。鉄鋼材料の溶製過程においては、溶銑段階での脱硫処理と溶鋼段階での脱硫処理とがあり、通常、鉄鋼材料は溶銑段階での脱硫処理のみで溶製されている。ところが、高級電磁鋼板やラインパイプ用鋼材等の極低硫鋼の溶製過程では、溶銑段階での脱硫処理のみでは十分でなく、溶銑段階での脱硫処理に加えてさらに溶鋼段階での脱硫処理が必要となる。   In recent years, there has been an increasing demand for high purity steel production in order to improve the material properties accompanying the increase in value added of steel and the usage of steel materials, etc. In particular, the inclusion of sulfur which is an element to reduce the toughness of steel materials There is an increasing demand for low-volume ultra low sulfur steel. In the process of melting steel materials, there are desulfurization processes in the hot metal stage and desulfurization processes in the molten steel stage, and normally, the steel materials are melted only by the desulfurization process in the hot metal stage. However, in the melting process of ultra-low-sulfur steel such as high-grade electrical steel sheet and steel for line pipes, desulfurization treatment at the hot metal stage is not sufficient, and in addition to desulfurization at the hot metal stage, desulfurization at the molten steel stage Is required.

一般に、溶鋼段階での脱硫処理は、溶鋼のアーク加熱手段や攪拌手段、さらには溶鋼へのフラックス又は合金粉等の粉体吹き込み手段を有する、ＡＳＥＡ−ＳＫＦ法、ＶＡＤ法、ＬＦ法等の取鍋精錬法によって行われている。取鍋精錬法は、転炉での脱炭精錬によって溶製された溶鋼を収容する取鍋内に脱硫剤を添加し、溶鋼と脱硫剤とを攪拌・混合する又はアーク加熱することによって脱硫剤を滓化させ、脱硫剤の滓化により形成されたスラグと溶鋼との間でスラグ−メタル間反応を起こさせて溶鋼中の硫黄成分をスラグ中に移行させるという流れで行われる。   Generally, the desulfurization treatment at the molten steel stage has an arc heating means and stirring means for molten steel, and further, powder blowing means such as flux or alloy powder to molten steel, such as ASEA-SKF method, VAD method, LF method, etc. It is done by the pot refining method. In the ladle refining method, a desulfurizing agent is added to a ladle containing molten steel produced by decarburizing and refining in a converter, and the molten steel and the desulfurizing agent are stirred and mixed or arc-heated to desulfurize the desulfurizing agent. Is carried out in a flow of causing the slag-metal reaction to occur between the slag formed by the desulfurization agent, and the molten steel to transfer the sulfur component in the molten steel into the slag.

ここで、脱硫剤としては、ＣａＯ（生石灰）を主成分とし、これに脱硫剤の融点降下を目的とするＡｌ2Ｏ3（アルミナ）、ＣａＦ2（蛍石）等を加えた脱硫剤が使用されている。取鍋精錬法による脱硫処理方法で効率的な脱硫反応を起こさせるためには、添加した脱硫剤を早急に滓化させること、及び、攪拌強度を高めて脱硫剤の滓化によって形成されるスラグとメタルとの接触面積を増大させることが重要となる。脱硫剤は取鍋内の溶鋼上に上置き添加されることが一般的であり、添加後にアーク加熱によって脱硫剤を滓化するにしても、また、添加後に溶鋼との攪拌・混合で脱硫剤を滓化するにしても、滓化に長時間を要する。Here, as a desulfurization agent, a desulfurization agent is used that is mainly composed of CaO (fresh lime) and added with Al 2 O 3 (alumina), CaF 2 (fluorite), etc. for the purpose of lowering the melting point of the desulfurization agent. It is done. In order to cause an efficient desulfurization reaction by the desulfurization treatment method by the ladle refining method, the added desulfurization agent is quickly solidified, and the stirring strength is increased to form slag which is formed by the deterioration of the desulfurization agent. It is important to increase the contact area between the metal and the metal. The desulfurizing agent is generally added on top of the molten steel in the ladle, and even if the desulfurizing agent is solidified by arc heating after the addition, the desulfurizing agent is stirred and mixed with the molten steel after the addition. Even if you hatch, it takes a long time to hatch.

そこで、脱硫剤の滓化促進のために、特許文献１には、生石灰、アルミナ、及び蛍石との混合品であるフラックスを添加し、その後バブリング処理を行い、脱硫処理後のスラグ組成をＣａＯ／Ａｌ2Ｏ3≧１．５、ＣａＦ2≧５質量％として溶鋼を脱硫する方法が開示されている。また、特許文献２には、脱硫剤の滓化促進のために、ＣａＯ−Ａｌ2Ｏ3のプリメルトフラックス（事前に混合、均一溶解したもの）又はＣａＯ−Ａｌ2Ｏ3−ＣａＦ2のプリメルトフラックスを脱硫剤として使用する方法が開示されている。一方、溶鋼攪拌の強化については、攪拌用ガス流量を高めることなく攪拌強度を高める手段として、特許文献３，４，５には、フラックスを攪拌用ガスに混入して吹き込む方法が開示されている。Therefore, in order to promote the degradation of the desulfurization agent, Patent Document 1 adds a flux which is a mixture of quicklime, alumina, and fluorite, and then performs bubbling treatment, and the slag composition after desulfurization treatment is CaO A method of desulfurizing molten steel is disclosed as / Al 2 O 3 1.51.5 and CaF 2 55% by mass. Further, Patent Document 2 discloses that a premelt flux of CaO-Al 2 O 3 (premixed and homogeneously dissolved) or a CaO-Al 2 O 3 -CaF 2 precursor is used to promote the degradation of the desulfurizing agent. A method is disclosed for using melt flux as a desulfurizing agent. On the other hand, with regard to the reinforcement of molten steel agitation, Patent Documents 3, 4 and 5 disclose a method of mixing a flux into a gas for agitation and blowing it as a means for enhancing the agitation strength without increasing the gas flow rate for agitation. .

特開平８−２６００２５号公報Japanese Patent Application Laid-Open No. 8-260025 特開平９−２１７１１０号公報Japanese Patent Application Laid-Open No. 9-217110 特開昭６１−９１３１８号公報Japanese Patent Application Laid-Open No. 61-91318 特開昭６１−２８１８０９号公報Japanese Patent Application Laid-Open No. 61-281809 特開２０００−２３４１１９号公報JP 2000-234119 A

しかしながら、特許文献１記載の方法によれば、ＣａＦ2を含有する脱硫剤を使用した場合、生成されるスラグ中のＣａＦ2によって取鍋を形成する耐火物が激しく溶損され、取鍋の寿命が大幅に短くなるという問題がある。また、特許文献２記載の方法によれば、プリメルトフラックスが非常に高価であり、処理コストが上昇するという問題がある。また、ＣａＦ2を含有する脱硫剤では前述した問題が同様に発生する。However, according to the method described in Patent Document 1, when a desulfurizing agent containing CaF 2 is used, the refractory forming the ladle is violently dissolved by the CaF 2 in the produced slag, and the lifetime of the ladle There is a problem that is greatly shortened. Further, according to the method described in Patent Document 2, there is a problem that the premelt flux is very expensive and the processing cost is increased. Further, in the desulfurizing agent containing CaF 2 , the above-mentioned problems occur similarly.

一方、特許文献３，４，５記載の方法では、吹き込みガス流量に対してフラックス吹き込み量に限界があり（固気比は５〜３０ｋｇ／ｋｇが限界）、増加可能な攪拌力には限界がある。また、攪拌用ガス流量を増加した場合には、取鍋内の溶鋼湯面の乱れ（揺動）が激しくなり、スプラッシュが発生して地金が蓋に付着する、又は、電極と溶鋼との間で短絡する等してアークが安定せず、アーク加熱が困難になるという問題等が発生する。   On the other hand, in the methods described in Patent Documents 3, 4 and 5, there is a limit to the amount of blown flux with respect to the flow rate of blown gas (solid-gas ratio is limited to 5 to 30 kg / kg), and there is a limit to the stirring power that can be increased. is there. In addition, when the gas flow rate for stirring is increased, turbulence (rocking) of the surface of the molten steel in the ladle becomes severe, splash occurs, and the metal adheres to the lid, or the electrode and the molten steel Shorting between the two leads to problems such as unstable arcs and difficulty in arc heating.

本発明は、上記課題に鑑みてなされたものであって、その目的は、ＣａＦ2やプリメルトフラックスを使用しなくても効率良く脱硫処理を行うことが可能な溶鋼の脱硫処理方法及び脱硫剤を提供することにある。This invention is made in view of the said subject, Comprising: The objective is the desulfurization processing method and desulfurization agent of molten steel which can perform desulfurization processing efficiently, without using CaF 2 or a premelt flux. To provide.

本発明に係る溶鋼の脱硫処理方法は、溶鋼を収容する取鍋内に生石灰を含む脱硫剤を添加し、取鍋内で溶鋼を攪拌することによって、溶鋼中の硫黄濃度を低減する溶鋼の脱硫処理方法であって、前記脱硫剤として、細孔直径が０．５〜１０μｍ以下の範囲内にある細孔の容積の和が０．１ｍＬ／ｇ以上である生石灰を含む脱硫剤を用いることを特徴とする。   The method for desulfurizing molten steel according to the present invention comprises desulfurizing a molten steel by adding a desulfurizing agent containing quick lime into a ladle containing the molten steel and stirring the molten steel in the ladle to reduce the concentration of sulfur in the molten steel. It is a processing method, Comprising: Using the desulfurization agent containing the quick lime whose sum of the volume of the pore whose pore diameter is in the range of 0.5-10 micrometers or less is 0.1 mL / g or more as said desulfurization agent It features.

本発明に係る溶鋼の脱硫処理方法は、上記発明において、前記生石灰が、粒径が１〜３０ｍｍ以下の範囲内にある粒子を９０％以上含むことを特徴とする。   The desulfurization treatment method for molten steel according to the present invention is characterized in that, in the above-mentioned invention, the above-mentioned quicklime contains 90% or more of particles whose particle diameter is in the range of 1 to 30 mm or less.

本発明に係る脱硫剤は、細孔直径が０．５〜１０μｍ以下の範囲内にある細孔の容積の和が０．１ｍＬ／ｇ以上である生石灰を含み、前記生石灰が、粒径が１〜３０ｍｍ以下の範囲内にある粒子を９０％以上含むことを特徴とする。   The desulfurization agent according to the present invention comprises quicklime having a pore diameter in the range of 0.5 to 10 μm or less and the sum of the volume of pores is 0.1 mL / g or more, and the quicklime has a particle diameter of 1 90% or more of particles in the range of not more than 30 mm.

本発明に係る溶鋼の脱硫処理方法は、上記発明において、下記数式（１）で示される撹拌動力密度の条件が満足されるように前記溶鋼を攪拌することを特徴とする。なお、本明細書中において、「Ｎｍ３」とは、気圧１０１３２５Ｐａ、温度２７３．１５Ｋの標準状態での気体の体積のことを意味する。The desulfurization treatment method for molten steel according to the present invention is characterized in that, in the above-mentioned invention, the molten steel is agitated such that the condition of the agitation power density represented by the following formula (1) is satisfied. Note that in this specification, "Nm 3" means that the volume of gas at standard conditions of pressure 101325 Pa, temperature 273.15 K.

Figure 2018135344
Figure 2018135344

本発明に係る溶鋼の脱硫処理方法は、上記発明において、前記溶鋼が転炉から出鋼されてから脱硫処理開始後１０分以内に溶鋼に投入されるアルミニウムの量が下記数式（２）を満足することを特徴とする。   In the desulfurization treatment method for molten steel according to the present invention, in the above-mentioned invention, the amount of aluminum introduced into the molten steel within 10 minutes after the start of the desulfurization treatment after the molten steel is removed from the converter satisfies the following formula (2). It is characterized by

Figure 2018135344
Figure 2018135344

本発明に係る溶鋼の脱硫処理方法は、上記発明において、前記取鍋内における酸素濃度が１５％以下となるように前記取鍋内にＡｒガスを吹き込むことを特徴とする。   The desulfurization treatment method for molten steel according to the present invention is characterized in that, in the above-mentioned invention, Ar gas is blown into the ladle so that the oxygen concentration in the ladle becomes 15% or less.

本発明に係る溶鋼の脱硫処理方法及び脱硫剤によれば、ＣａＦ2やプリメルトフラックスを使用しなくても効率良く脱硫処理を行うことができる。According to the method for desulfurizing the molten steel and the desulfurizing agent according to the present invention, the desulfurization can be efficiently performed without using CaF 2 or a premelt flux.

図１は、本発明を実施する際に用いたＬＦ設備の側面概略図である。FIG. 1 is a schematic side view of the LF equipment used in practicing the present invention. 図２は、本発明例及び比較例の滓化率を示す図である。FIG. 2 is a figure which shows the hatching rate of this invention example and a comparative example.

本発明の発明者らは、上記課題を解決するべく、石灰の粒度及び細孔径や溶鋼成分に着目して鋭意検討を重ねた。より具体的には、本発明の発明者らは、硫黄濃度が０．００３０質量％以下である低硫鋼を、ＣａＯ含有物質を脱硫剤の主たる構成物質として使用して取鍋精錬法による脱硫処理で溶製するにあたり、ＣａＦ2を脱硫剤の一部として使用しなくても、また、脱硫剤がプリメルトフラックスでなくても、脱硫剤として添加したフラックスを迅速に滓化させ、効率良く脱硫処理を行うことを目的とし、種々試験・研究を重ねた。The inventors of the present invention have intensively studied focusing on the particle size and pore diameter of lime and the molten steel component in order to solve the above-mentioned problems. More specifically, the inventors of the present invention use a low-sulfur steel having a sulfur concentration of 0.0030% by mass or less as a main constituent material of a desulfurizing agent using a CaO-containing material as a desulfurization agent-based desulfurization method. Even if CaF 2 is not used as a part of the desulfurizing agent and the desulfurizing agent is not a premelt flux, the flux added as a desulfurizing agent is rapidly aged, and it is efficient Various tests and researches were repeated for the purpose of desulfurizing treatment.

その結果、本発明の発明者らは、脱硫剤として添加したフラックスの滓化促進のためには、フラックスを添加するときの溶鋼の温度、ｓｏｌ．Ａｌ濃度、石灰の粒度、及び石灰の細孔径が重要であることを知見した。但し、溶鋼の温度は、転炉からの出鋼時の溶鋼の温度によって決まり、むやみに出鋼時の溶鋼の温度を高くすることは、転炉耐火物の溶損を増大させ、処理コストの増加を招き得策ではない。   As a result, the inventors of the present invention, in order to accelerate the aging of the flux added as a desulfurizing agent, the temperature of the molten steel when adding the flux, sol. It was found that the Al concentration, the particle size of lime, and the pore diameter of lime are important. However, the temperature of the molten steel is determined by the temperature of the molten steel at the time of tapping steel from the converter, and raising the temperature of the molten steel at the time of tapping steel unavoidably increases the erosion of the converter refractories, which leads to the processing cost It is not a good idea to cause an increase.

そこで、本発明の発明者らは、石灰が有する細孔のうち、細孔直径が０．５〜１０μｍの範囲内にある細孔の容積の和が０．１ｍＬ／ｇ以上である生石灰を主成分とする粉状脱硫剤を用いることにより、高効率で脱硫処理を行うことができることを見出し、本発明を想到するに至った。なお、生石灰の細孔径分布は、以下に示す方法で測定した。   Therefore, the inventors of the present invention have mainly taken advantage of quick lime in which the total volume of pores having a pore diameter in the range of 0.5 to 10 μm among the pores possessed by lime is 0.1 mL / g or more. By using the powdery desulfurizing agent as a component, it has been found that desulfurization can be performed with high efficiency, and the present invention has been conceived. In addition, the pore size distribution of quick lime was measured by the method shown below.

まず、前処理として、生石灰を１２０℃で４時間、恒温乾燥した。次いで、Ｍｉｃｒｏｍｅｒｉｔｉｅｓ社製のオートポアＩＶ９５２０を用いて、水銀圧入法により、乾燥させた生石灰の細孔直径が約０．００３６〜２００μｍの範囲内にある細孔分布を求め、累積細孔容積曲線を算出した。さらに、算出された累積細孔容積曲線から細孔直径が０．５〜１０μｍの範囲内にある細孔の容積の和を求めた。   First, as a pretreatment, quick lime was isothermally dried at 120 ° C. for 4 hours. Then, using an Autopore IV9520 manufactured by Micromerities, the pore distribution of dried quick lime in the range of about 0.0036 to 200 μm is determined by mercury intrusion method, and the cumulative pore volume curve is calculated. did. Furthermore, the sum of the volume of pores having a pore diameter in the range of 0.5 to 10 μm was determined from the calculated cumulative pore volume curve.

細孔直径は、以下の数式（３）に示すＷａｓｈｂｕｒｎの式を用いて算出した。なお、数式（３）において、Ｐは圧力、Ｄは細孔直径、σは水銀の表面張力（＝４８０ｄｙｎｅｓ／ｃｍ）、θは水銀と試料との接触角（＝１４０ｄｅｇｒｅｅｓ）をそれぞれ示す。   The pore diameter was calculated using the Washburn equation shown in the following equation (3). In Equation (3), P represents pressure, D represents pore diameter, σ represents surface tension of mercury (= 480 dynes / cm), and θ represents contact angle between mercury and a sample (= 140 degrees).

Figure 2018135344
Figure 2018135344

高炉から出銑された溶銑は、溶銑鍋やトピードカー等の溶銑搬送用容器で受銑され、次工程の脱炭精錬を行う転炉に搬送される。通常、この搬送途中で溶銑に対して脱硫処理や脱燐処理等の溶銑予備処理が施されており、本発明は、低硫鋼を製造する技術であることから脱硫処理を実施する。また、低硫鋼の成分規格上からは脱燐処理が必要でない場合であっても、転炉出鋼後の脱硫処理における転炉スラグからの復燐を防止するために、脱燐処理を実施する。   The hot metal discharged from the blast furnace is received by a hot metal transfer container such as a hot metal pot or toped car, and is transferred to a converter for decarburizing and refining in the next step. Usually, hot metal pretreatment such as desulfurization treatment and dephosphorization treatment is applied to the hot metal in the middle of the transportation, and the present invention is a technology for producing low-sulfur steel, so the desulfurization treatment is performed. In addition, even if dephosphorization is not necessary because of the component specifications of low-sulfur steel, dephosphorization is performed to prevent reversion from converter slag in the desulfurization after converter steel removal. Do.

次に、脱硫処理及び脱燐処理の施された溶銑に対して転炉で脱炭精錬を実施し、得られた溶鋼を取鍋に出鋼する。転炉での脱炭精錬は、溶銑には既に脱硫処理及び脱燐処理が施されているので、少量の生石灰（ＣａＯ）及び少量のドロマイト（ＭｇＣＯ3−ＣａＣＯ3）又は焼成ドロマイト（ＭｇＯ−ＣａＯ）をフラックスとして使用し、炉内にスラグ（以下、「転炉スラグ」と呼ぶ）を形成させる。この転炉スラグは、溶銑の脱燐反応を促進させる役割を担うが、溶銑が既に脱燐処理されていることから、主たる役割は、吹錬中の鉄スプラッシュの発生防止及び転炉内張り耐火物の溶損抑制である。Next, decarburizing and refining is performed on the desulfurized and dephosphorized hot metal in a converter, and the obtained molten steel is discharged to a ladle. In decarburizing and refining in the converter, the molten metal has already been desulfurized and dephosphorized, so a small amount of quick lime (CaO) and a small amount of dolomite (MgCO 3 -CaCO 3 ) or calcined dolomite (MgO-CaO) ) Is used as flux to form slag (hereinafter referred to as "converter slag") in the furnace. This converter slag plays a role of promoting the dephosphorization reaction of the hot metal, but since the hot metal is already dephosphorized, the main role is to prevent the generation of iron splash during blowing and the converter lining refractory Suppression of

出鋼の末期、溶鋼に混入して転炉スラグが取鍋内に流出するので、これを防止するために、通常実施されるスラグ流出防止対策を実施する。スラグ流出防止対策を実施しても、転炉スラグの完全な流出防止は困難であり、取鍋にはある程度の量の転炉スラグが溶鋼に混入して流出する。出鋼後、溶鋼に混入して流入した転炉スラグを取鍋から除去してもよいが、転炉スラグ中のＳｉＯ2成分が、脱硫剤としてその後に添加されるＣａＯ含有物質の滓化に寄与することから除去しなくてもよい。At the end of tapping, since the converter slag mixes into the molten steel and flows out into the ladle, in order to prevent this, the slag outflow prevention measures that are usually implemented are implemented. Even if the slag outflow prevention measures are taken, it is difficult to completely prevent the converter slag from flowing out, and a certain amount of converter slag mixes with the molten steel and flows out to the ladle. After steel removal, converter slag mixed into the molten steel and flowing in may be removed from the ladle, but the SiO 2 component in the converter slag may be added to the CaO-containing material to be subsequently added as a desulfurization agent. It is not necessary to remove from contribution.

取鍋内に所定の組成のＣａＯ−ＭｇＯ−Ａｌ2Ｏ3−ＳｉＯ2系の脱硫用スラグを形成するべく、フラックスとしてＣａＯ含有物質、ＭｇＯ含有物質、Ａｌ2Ｏ3含有物質、及びＳｉＯ2含有物質を取鍋内に添加する。但し、前述したように、ＭｇＯはＣａＯに比較して脱硫能が低いので、ＭｇＯ含有物質は添加しなくても構わない。また、溶鋼の脱酸及びスラグの還元（スラグ中のＦｅ酸化物及びＭｎ酸化物の還元）のために、取鍋内に金属Ａｌを添加する。A CaO-containing substance, a MgO-containing substance, an Al 2 O 3 -containing substance, and an SiO 2 -containing substance as a flux to form a CaO-MgO-Al 2 O 3 -SiO 2 -based desulfurization slag in a ladle in a predetermined composition Add the substance into the ladle. However, as described above, since MgO has a lower desulfurizing ability than CaO, the MgO-containing substance may not be added. In addition, metal Al is added to the ladle for deoxidation of molten steel and reduction of slag (reduction of Fe oxide and Mn oxide in slag).

これらの物質は、ＡＳＥＡ−ＳＫＦ法、ＶＡＤ法、及びＬＦ法のうちのいずれかの方法により脱硫処理を実施する後工程の設備で添加してもよいが、ＣａＯの滓化を促進させる観点から、転炉から取鍋への出鋼時又は出鋼直後に取鍋内に添加することが好ましい。出鋼直後に添加する生石灰は、生石灰が有する細孔のうち、細孔直径が０．５〜１０μｍの範囲内にある細孔の容積の和が０．１ｍＬ／ｇ以上であり、且つ、粒径が１〜３０ｍｍの範囲内にある粒子を９０％以上含有することが好ましい。   These substances may be added in the post-process equipment that carries out the desulfurization treatment by any of the ASEA-SKF method, the VAD method, and the LF method, but from the viewpoint of promoting the hatching of CaO It is preferable to add to the ladle at the time of tapping the steel from the converter to the ladle or immediately after tapping. Among the pores possessed by quicklime, the quicklime added immediately after tapping is the sum of the volume of the pores whose pore diameter is in the range of 0.5 to 10 μm, and the particle size is not less than 0.1mL / g. It is preferable to contain 90% or more of particles having a diameter in the range of 1 to 30 mm.

ＣａＯ含有物質、ＭｇＯ含有物質、金属Ａｌ、Ａｌ2Ｏ3含有物質、及びＳｉＯ2含有物質の添加量は、取鍋内に流出した転炉スラグの質量及び成分組成を加味し、この転炉スラグを含めて添加されるフラックスが滓化した後に取鍋内に生成されるスラグの組成が、ＳｉＯ2含有量＝５〜１５質量％の範囲内で、且つ、［（質量％ＣａＯ）＋（質量％ＭｇＯ）］／（質量％Ａｌ2Ｏ3）＝１．５〜３．０の範囲内となるように、好ましくは［（質量％ＣａＯ）＋（質量％ＭｇＯ）］／（質量％Ａｌ2Ｏ3）＝１．８〜２．５の範囲内となるように、ＣａＯ含有物質、ＭｇＯ含有物質、金属Ａｌ、Ａｌ2Ｏ3含有物質、及びＳｉＯ2含有物質のそれぞれの添加量を定める。The addition amounts of the CaO-containing substance, the MgO-containing substance, the metal Al, the Al 2 O 3 -containing substance, and the SiO 2 -containing substance take into account the mass and component composition of the converter slag that has flowed into the ladle. The composition of the slag generated in the ladle after the flux added including H2O is in the range of 5 to 15 mass% of SiO 2 content, and [(mass% CaO) + (mass % MgO)] / (mass% Al 2 O 3 ) = 1.5 to 3.0, preferably [(mass% CaO) + (mass% MgO)] / (mass% Al 2) The addition amounts of the CaO-containing substance, the MgO-containing substance, the metal Al, the Al 2 O 3 -containing substance, and the SiO 2 -containing substance are determined so that O 3 ) = 1.8 to 2.5.

この場合、生成されるスラグの（質量％ＭｇＯ）／（質量％ＣａＯ）が０．１０以下になるようにそれぞれの添加量を定めることがより好ましい。そして、これらの物質を、定めた添加量だけ取鍋内に添加する。金属Ａｌは添加した全量がＡｌ2Ｏ3になるわけではなく、溶鋼中にも溶解して残る。従って、予め試験によって溶鋼に溶解する溶解Ａｌ分とスラグ中のＡｌ2Ｏ3になる分との比率を求めておき、それに基づき金属Ａｌの添加量を設定する。ＣａＦ2は添加しない。In this case, it is more preferable to set each addition amount so that (mass% MgO) / (mass% CaO) of the slag produced | generated will be 0.10 or less. Then, these substances are added to the ladle by a predetermined addition amount. The total amount of metal Al added is not necessarily Al 2 O 3 and remains dissolved in molten steel. Therefore, the ratio of the dissolved Al content to be dissolved in the molten steel to the content to be Al 2 O 3 in the slag is determined in advance by a test, and the addition amount of metal Al is set based on that. CaF 2 is not added.

なお、本発明において、「脱硫処理後の取鍋内スラグの組成を、ＣａＦ2を実質的に含有しない組成に調整する」とは、ＣａＦ2等のフッ素化合物をＣａＯの滓化促進剤として使用しないで脱硫処理後のスラグ組成を調整することを意味し、使用するＣａＯ含有物質やＡｌ2Ｏ3含有物質等に不可避的に混入して持ち来たされるフッ素が脱硫処理後のスラグに存在しても、ＣａＦ2を実質的に含有しないスラグと定義する。Incidentally, used in the present invention, "the composition of the ladle slag after the desulfurization treatment is adjusted to a composition containing no CaF 2 substantially" and the fluorine compound such as CaF 2 as a slag formation accelerators CaO It means that the slag composition after desulfurization treatment is adjusted, and the fluorine carried by unavoidable inclusion in the CaO-containing material and the Al 2 O 3 -containing material to be used is present in the slag after desulfurization treatment Even if, it is defined as slag which does not contain CaF 2 substantially.

添加するＣａＯ含有物質としては、生石灰（ＣａＯ）、石灰石（ＣａＣＯ3）、消石灰（Ｃａ(ＯＨ)2）、ドロマイト（ＭｇＣＯ3−ＣａＣＯ3）、焼成ドロマイト（ＭｇＯ−ＣａＯ）等を使用し、ＭｇＯ含有物質としては、マグネシアクリンカー（ＭｇＯ）、ドロマイト（ＭｇＣＯ3−ＣａＣＯ3）、焼成ドロマイト（ＭｇＯ−ＣａＯ）等を使用する。Examples of CaO-containing substances to be added include quick lime (CaO), limestone (CaCO 3 ), slaked lime (Ca (OH) 2 ), dolomite (MgCO 3 -CaCO 3 ), calcined dolomite (MgO-CaO), etc. As the material to be contained, magnesia clinker (MgO), dolomite (MgCO 3 -CaCO 3 ), calcined dolomite (MgO-CaO) or the like is used.

石灰の粒度は、反応効率及び添加歩留の観点から平均粒径が１〜３０ｍｍの範囲内にあることが好ましい。排気系に吸引される量を少なくする観点からは微粉分は少ない方が望ましく、平均粒径３０ｍｍ以上の石灰は少ないことが好ましい。平均粒径の測定方法は以下の通りである。脱硫剤を１ｋｇ採取し、５００μｍ以下、５００μｍ〜１ｍｍ、１〜５ｍｍ、５〜1０ｍｍ、１０〜１５ｍｍ、１５〜２０ｍｍ、２０〜２５ｍｍ、２５〜３０ｍｍ、３０ｍｍ以上の９段階に篩い分けし、平均粒径を重量比率で計算することとし、以下に示す数式（４）により求めた。   The particle size of lime is preferably in the range of 1 to 30 mm in average particle size from the viewpoint of reaction efficiency and addition yield. From the viewpoint of reducing the amount sucked into the exhaust system, it is desirable that the amount of fine powder be small, and it is preferable that the amount of lime having an average particle diameter of 30 mm or more be small. The measuring method of average particle diameter is as follows. 1 kg of the desulfurizing agent is collected and sieved in 9 steps of 500 μm or less, 500 μm to 1 mm, 1 to 5 mm, 5 to 10 mm, 10 to 15 mm, 15 to 20 mm, 20 to 25 mm, 25 to 30 mm, 30 mm or more The diameter was calculated using a weight ratio, and was obtained by the following equation (4).

Figure 2018135344
Figure 2018135344

Ａｌ2Ｏ3含有物質としては、アルミドロス（金属Ａｌを２０〜７０質量％含有、残部の主成分はＡｌ2Ｏ3）、ボーキサイト（Ａｌ2Ｏ3・２Ｈ2Ｏ）、仮焼アルミナ（Ａｌ2Ｏ3）等を使用する。アルミドロスは金属Ａｌの代替にもなる。ＳｉＯ2含有物質としては、珪砂（ＳｉＯ2）、珪灰石（ＣａＯ−ＳｉＯ2）等を使用する。この場合、取鍋内に流出した転炉スラグの質量が多い場合には、ＳｉＯ2含有物質の添加を必要としないことも起こり得る。また、ＭｇＯ含有物質は、ＭｇＯ含有物質を添加しなくても、スラグ組成が［（質量％ＣａＯ）＋（質量％ＭｇＯ）］／（質量％Ａｌ2Ｏ3）＝１．５〜３．０の範囲内、好ましくは１．８〜２．５の範囲内となるならば添加しなくてもよい。As an Al 2 O 3 containing material, aluminum dross (containing 20 to 70% by mass of metal Al, the main component of the remainder is Al 2 O 3 ), bauxite (Al 2 O 3 · 2H 2 O), calcined alumina (Al) 2 Use O 3 ) etc. Aluminum dross is also an alternative to metal Al. As the SiO 2 -containing substance, silica sand (SiO 2 ), wollastonite (CaO-SiO 2 ) or the like is used. In this case, if the mass of the converter slag flowing out into the ladle is large, it may happen that the addition of the SiO 2 -containing material is not necessary. In addition, even if the MgO-containing substance does not contain the MgO-containing substance, the slag composition is [(mass% CaO) + (mass% MgO)] / (mass% Al 2 O 3 ) = 1.5 to 3.0. If it is within the range of, preferably within the range of 1.8 to 2.5, it may not be added.

次いで、溶鋼を収容した取鍋をＡＳＥＡ−ＳＫＦ法、ＶＡＤ法、及びＬＦ法のうちのいずれかの方法によって脱硫処理を実施する設備に搬送し、溶鋼の脱硫処理を実施する。本発明では、脱硫処理をＬＦ設備で実施する場合を例として説明する。図１は、本発明を実施する際に用いたＬＦ設備の側面概略図である。図１において、符号１はＬＦ設備、符号２は取鍋、符号３は昇降式の蓋、符号４はアーク加熱用の電極、符号５，６は浸漬ランス、符号７，８は底吹きポーラス煉瓦、符号９は溶鋼、符号１０はスラグ、符号１１は原材料投入シュート、符号１２はＡｒガス導入管を示す。   Next, the ladle containing the molten steel is transported to a facility for performing the desulfurization treatment by any of the ASEA-SKF method, the VAD method, and the LF method, and the molten steel is desulfurized. In the present invention, the case where the desulfurization treatment is performed by the LF equipment will be described as an example. FIG. 1 is a schematic side view of the LF equipment used in practicing the present invention. In FIG. 1, reference numeral 1 is LF equipment, 2 is a ladle, 3 is a lift lid, 4 is an electrode for arc heating, 5 and 6 is an immersion lance, and 7 and 8 are bottom-blown porous bricks The reference numeral 9 denotes molten steel, the reference numeral 10 denotes a slag, the reference numeral 11 denotes a raw material introduction chute, and the reference numeral 12 denotes an Ar gas introduction pipe.

このＬＦ設備１では、走行台車（図示せず）に積載された、溶鋼９を収容する取鍋２を蓋３の直下の所定位置に配置し、蓋３を下降させて取鍋２の上端部に密着させ、その状態でＡｒガス導入管１２からＡｒガスを供給して取鍋２と蓋３とで囲まれる空間をＡｒガス雰囲気とする。取鍋２内の酸素濃度が１５％以下となるように炉蓋の周囲に取り付けた配管からＡｒガスを吹き込むことが好ましい。取鍋２内の酸素濃度を低減させることにより、ＬＦ処理中に空気中の酸素と反応してロスするＡｌ量を減らすことができる。取鍋２から吹き込むＡｒガスの流量は、πＬ2／４Ｑの値が５０〜１５０（ｍ／ｍｉｎ）の範囲内となる流量とすることが好ましく、より好ましくは、７０〜１００（ｍ／ｍｉｎ）の範囲内となる流量である。ここで、Ｌは取鍋の直径（ｍ）、ＱはＡｒガス流量(Ｎｍ3／ｍｉｎ)である。Ａｒガスの流量が少ないと十分に酸素濃度が低下せず、逆にＡｒガスの流量が多すぎると溶鋼温度が低下する原因となる。In the LF equipment 1, the ladle 2 containing the molten steel 9 loaded on a traveling carriage (not shown) is disposed at a predetermined position immediately below the lid 3, and the lid 3 is lowered to move the upper end of the ladle 2. In this state, the Ar gas is supplied from the Ar gas introduction pipe 12 to make the space surrounded by the ladle 2 and the lid 3 an Ar gas atmosphere. It is preferable to blow Ar gas from piping attached around the furnace lid so that the oxygen concentration in the ladle 2 is 15% or less. By reducing the oxygen concentration in the ladle 2, it is possible to reduce the amount of Al which is lost by reacting with oxygen in air during LF processing. The flow rate of Ar gas blown from the ladle 2 is preferably such that the value of πL 2 / 4Q falls within the range of 50 to 150 (m / min), more preferably 70 to 100 (m / min) The flow rate is within the range of Here, L is the diameter of the ladle (m), and Q is the Ar gas flow rate (Nm 3 / min). If the flow rate of Ar gas is low, the oxygen concentration does not decrease sufficiently, and conversely, if the flow rate of Ar gas is too high, the temperature of the molten steel decreases.

取鍋２内にＣａＯ含有物質、ＭｇＯ含有物質、金属Ａｌ、Ａｌ2Ｏ3含有物質、及びＳｉＯ2含有物質が予め添加されていない場合、及び、これらの物質の添加量が不足する場合には、この状態で原材料投入シュート１１を介して取鍋２内にこれらの物質のフラックス及び金属Ａｌを投入する。金属Ａｌは開始１０分以内に以下に示す数式（５）を満たすように添加することが好ましい。すなわち、転炉出鋼後のＡｌ濃度に応じて金属Ａｌを添加し、溶鋼中のＡｌ濃度を高めることが脱硫処理を促進させる上で好ましい。When the CaO-containing substance, the MgO-containing substance, the metal Al, the Al 2 O 3 -containing substance, and the SiO 2 -containing substance are not added in advance in the ladle 2, and when the addition amount of these substances is insufficient In this state, the flux of these substances and metal Al are introduced into the ladle 2 through the raw material input chute 11. It is preferable to add metal Al so as to satisfy the following formula (5) within 10 minutes of the start. That is, it is preferable to add metal Al in accordance with the Al concentration after converter steel removal to increase the Al concentration in the molten steel in order to accelerate the desulfurization treatment.

Figure 2018135344
Figure 2018135344

次いで、必要に応じて電極４に通電してアークを発生させ、溶鋼９を加熱すると共に添加したフラックスを滓化させた後、溶鋼９に浸漬ランス５又は浸漬ランス６を浸漬させ、浸漬ランス５、浸漬ランス６、又は、底吹きポーラス煉瓦７，８のうちの少なくとも一箇所から溶鋼９に攪拌用ガスとしてのＡｒガスを吹き込み、溶鋼９を攪拌する。溶鋼９を攪拌することによってフラックスが溶鋼９と混合され、フラックスの滓化が進行してスラグ１０が生成される。   Next, if necessary, the electrode 4 is energized to generate an arc to heat the molten steel 9 and heat the added flux, and then the immersion lance 5 or 6 is immersed in the molten steel 9 to immerse the immersion lance 5 Ar gas as a stirring gas is blown into the molten steel 9 from at least one of the immersion lance 6 or the bottom-blown porous bricks 7 and 8 to stir the molten steel 9. By stirring the molten steel 9, the flux is mixed with the molten steel 9, and the hardening of the flux proceeds to generate the slag 10.

生成したスラグ１０は、溶鋼９の攪拌によって溶鋼９と攪拌・混合され、溶鋼９とスラグ１０との間でスラグ−メタル間反応が発生し、溶鋼９中の硫黄成分がスラグ中に移行する脱硫反応が発生する。この場合、脱硫反応を促進させる観点から、前述したように、浸漬ランス５，６からＡｒガスと共に、Ｃａ合金粉、金属Ｍｇ粉、及びＭｇ合金粉のうちのいずれか１種又は２種以上を溶鋼９中に吹き込むこと、或いは、脱硫処理の少なくとも一時期において、浸漬ランス５，６からの攪拌用ガスの吹き込みと底吹きポーラス煉瓦７，８からの攪拌用ガスの吹き込みとを同時に行うことが好ましい。   The formed slag 10 is stirred and mixed with the molten steel 9 by the stirring of the molten steel 9, a slag-metal reaction occurs between the molten steel 9 and the slag 10, and the sulfur component in the molten steel 9 is transferred into the slag A reaction occurs. In this case, from the viewpoint of promoting the desulfurization reaction, as described above, any one or more of Ca alloy powder, metal Mg powder, and Mg alloy powder may be used together with Ar gas from immersion lances 5 and 6. It is preferable to simultaneously blow the stirring gas from the immersion lances 5 and 6 and the blowing of the stirring gas from the bottom-blown porous bricks 7 and 8 at least at one time of desulfurization treatment, or blowing into the molten steel 9 at the same time. .

Ｃａ合金粉としては、Ｃａ−Ｓｉ合金粉やＣａ−Ａｌ合金粉等を使用し、Ｍｇ合金粉としては、Ｍｇ−Ａｌ−Ｚｎ合金粉やＭｇ−Ｓｉ−Ｆｅ合金粉等を使用する。これら金属粉の粒径は、吹き込み添加が可能である限り特定する必要はないが、反応界面積を確保する観点から最大粒径を１ｍｍ以下とすることが好ましい。溶鋼９の硫黄濃度が０．００１０質量％以下になったなら、溶鋼９へのＡｒガスの吹き込みを停止して脱硫処理を終了する。脱硫処理が終了した時点で溶鋼９の温度が目標温度よりも低い場合、アーク加熱を実施し、また、溶鋼９の成分が目標範囲内にない場合には、原材料投入シュート１１を介して成分調整用の合金鉄や金属を投入する。脱硫処理終了後は、必要に応じてＲＨ真空脱ガス装置等で脱ガス精錬を実施した後、連続鋳造機でスラブ鋳片に鋳造する。   As the Ca alloy powder, a Ca-Si alloy powder, a Ca-Al alloy powder or the like is used, and as the Mg alloy powder, a Mg-Al-Zn alloy powder, a Mg-Si-Fe alloy powder or the like is used. Although it is not necessary to specify the particle size of these metal powders as long as blowing addition is possible, it is preferable to set the maximum particle size to 1 mm or less from the viewpoint of securing the reaction interface area. When the sulfur concentration of the molten steel 9 becomes 0.0010 mass% or less, the blowing of Ar gas into the molten steel 9 is stopped to complete the desulfurization treatment. If the temperature of the molten steel 9 is lower than the target temperature at the end of the desulfurization processing, arc heating is performed, and if the component of the molten steel 9 is not within the target range, component adjustment via the raw material input chute 11 Add alloy irons and metals for After completion of the desulfurization treatment, if necessary, degassing refining is carried out with an RH vacuum degassing apparatus or the like, and then cast into slab slabs with a continuous casting machine.

以上説明したように、本発明によれば、ＣａＯ含有物質を脱硫剤の主たる構成物質として用いた取鍋精錬法による溶鋼９の脱硫処理において、脱硫処理後のスラグ組成を、ＳｉＯ2の含有量が５〜１５質量％の範囲内になるように調整するので、ＳｉＯ2がＣａＯの滓化促進剤として機能してＣａＯの滓化が促進され、また、脱硫処理後のスラグ組成を、［（質量％ＣａＯ）＋（質量％ＭｇＯ）］／（質量％Ａｌ2Ｏ3）が１．５〜３．０の範囲内になるように調整するので、スラグ１０には高い脱硫能力が確保され、その結果、ＣａＦ2を脱硫剤の一部として使用しなくても、また、脱硫剤がプリメルトフラックスでなくても、効率的に溶鋼９の脱硫処理を行うことが実現される。なお、上記説明はＬＦ設備で本発明を実施した例であるが、ＡＳＥＡ−ＳＫＦ設備及びＶＡＤ設備においても、上記に準じて本発明を適用することができる。As described above, according to the present invention, in the desulfurization treatment of the molten steel 9 by the ladle refining method using the CaO-containing material as the main constituent material of the desulfurization agent, the slag composition after the desulfurization treatment is the content of SiO 2 Is adjusted to be in the range of 5 to 15% by mass, so that SiO 2 functions as an anchorage accelerator for CaO to promote the anchorage of CaO, and the slag composition after desulfurization treatment is [( Since mass% CaO) + (mass% MgO)] / (mass% Al 2 O 3 ) is adjusted to be in the range of 1.5 to 3.0, the slag 10 has a high desulfurization ability, As a result, even if CaF 2 is not used as a part of the desulfurizing agent, and even if the desulfurizing agent is not a premelt flux, it is realized that the molten steel 9 is desulfurized efficiently. The above description is an example in which the present invention is carried out with an LF equipment, but the present invention can be applied according to the above also with an ASEA-SKF equipment and a VAD equipment.

［実施例１］
高炉から出銑された溶銑に対して脱珪処理、脱硫処理、及び脱燐処理を行った後、この溶銑を転炉に装入して脱炭精錬を実施し、炭素濃度が０．０５〜０．０９質量％の範囲内、硫黄濃度が０．００４１〜０．００４３質量％の範囲内、燐濃度が０．００４〜０．０１０質量％の範囲内にある約２５０トンの溶鋼を得た。出鋼後、取鍋へ流出した転炉スラグを徐滓せず、金属Ａｌ、生石灰、軽焼ドロマイト、及びアルミドロスが添加された取鍋を図１に示すＬＦ設備に搬送した。電極をスラグに浸漬させてアーク加熱を行いながら、浸漬ランスから２０００ＮＬ／ｍｉｎのＡｒガスを溶鋼中に吹き込んで溶鋼を攪拌し、約３０分間脱硫処理を行い、硫黄濃度を０．００２４％以下とすることを目標に脱硫処理を実施した。Example 1
The hot metal discharged from the blast furnace is subjected to desiliconization treatment, desulfurization treatment and dephosphorization treatment, and then the hot metal is charged into a converter to carry out decarburizing and refining, and the carbon concentration is 0.05 to 0.05. About 250 tons of molten steel was obtained in the range of 0.09 mass%, the sulfur concentration in the range of 0.0041 to 0.0043 mass%, and the phosphorus concentration in the range of 0.004 to 0.010 mass%. . After steel tapping, the converter slag that had flowed into the ladle was not vacuum-sintered, and the ladle to which metal Al, quick lime, light-burning dolomite, and aluminum dross were added was transported to the LF equipment shown in FIG. While the electrode is immersed in slag and arc heating is performed, Ar gas of 2000 NL / min is blown into the molten steel from the immersion lance to stir the molten steel, desulfurization is performed for about 30 minutes, and the sulfur concentration is 0.0024% or less The desulfurization treatment was carried out with the goal of

以下に示す表１に各脱硫試験における脱硫処理前後の溶鋼中硫黄濃度（化学分析値）及び脱硫率を示す。また、表１の備考欄には、本発明の範囲内の試験は「本発明例」、それ以外は「比較例」として表示した。なお、脱硫率は、脱硫処理前後の溶鋼中硫黄濃度の差分を脱硫処理前の溶鋼中硫黄濃度に対して百分率で表示した値である。また、脱硫評価が「○」とは、脱硫処理後の溶鋼中硫黄濃度が０．００２４％以下であったことを示し、脱硫評価が「×」とは、脱硫処理後の溶鋼中硫黄濃度が０．００２４％超であったことを示している。   Table 1 below shows the sulfur concentration (chemical analysis value) in the molten steel and the desulfurization ratio before and after the desulfurization treatment in each desulfurization test. Moreover, in the remarks column of Table 1, the test within the scope of the present invention was indicated as "example of the present invention", and the others were displayed as "comparative examples." In addition, the desulfurization rate is the value which displayed the difference of the sulfur concentration in molten steel before and behind a desulfurization processing as a percentage with respect to the sulfur concentration in molten steel before a desulfurization processing. Moreover, the desulfurization evaluation indicates that “o” indicates that the sulfur concentration in the molten steel after the desulfurization treatment is 0.0024% or less, and “x” indicates that the sulfur concentration in the molten steel after the desulfurization treatment is It shows that it was over 0.0024%.

Figure 2018135344
Figure 2018135344

試験水準と結果を合わせて表１に示す。細孔直径が０．５〜１０μｍの範囲内にある細孔の容積の和が適正でない比較例（試験番号１〜３）では、本発明例（試験番号４〜１５）と比較して脱硫率が低位であった。また、本発明例において、生石灰の平均粒径が１〜３０ｍｍの範囲内にある水準では、滓化が促進され溶鋼の脱硫率も高位であった。   The test levels and the results are shown in Table 1 together. In the comparative example (test numbers 1 to 3) in which the sum of the volume of pores whose pore diameter is in the range of 0.5 to 10 μm is not appropriate, the desulfurization rate is compared with the invention examples (test numbers 4 to 15) Was low. Moreover, in the example of this invention, when the average particle diameter of quick lime is in the range of 1 to 30 mm, the hardening is promoted and the desulfurization rate of the molten steel is also high.

［実施例２］
高炉から出銑された溶銑に対して脱珪処理、脱硫処理、及び脱燐処理を行った後、この溶銑を転炉に装入して脱炭精錬を実施し、炭素濃度が０．０５〜０．０９質量％の範囲内、硫黄濃度が０．００４１〜０．００４３質量％の範囲内、燐濃度が０．００４〜０．０１０質量％の範囲内にある約２５０ｔの溶鋼を得た。出鋼後、取鍋へ流出した転炉スラグを徐滓せず、金属Ａｌ、生石灰、軽焼ドロマイト、及びアルミドロスの添加された取鍋を図１に示すＬＦ設備に搬送した。電極をスラグに浸漬させてアーク加熱を行いながら、浸漬ランスから５００〜２０００ＮＬ／ｍｉｎのＡｒガスを溶鋼中に吹き込んで溶鋼を攪拌し、約３０分間脱硫処理を行い、硫黄濃度を０．００２４％以下とすることを目標に脱硫処理を実施した。Example 2
The hot metal discharged from the blast furnace is subjected to desiliconization treatment, desulfurization treatment and dephosphorization treatment, and then the hot metal is charged into a converter to carry out decarburizing and refining, and the carbon concentration is 0.05 to 0.05. About 250 t of molten steel having a sulfur concentration of 0.0041 to 0.0043 mass% and a phosphorus concentration of 0.004 to 0.010 mass% in the range of 0.09 mass% was obtained. After steel tapping, the converter slag that had flowed into the ladle was not vacuum-sintered, and the ladle to which metal Al, quick lime, light-burning dolomite, and aluminum dross were added was conveyed to the LF equipment shown in FIG. While the electrode is immersed in slag and arc heating is performed, Ar gas of 500 to 2000 NL / min is blown into the molten steel from the immersion lance to stir the molten steel, desulfurization is performed for about 30 minutes, and the sulfur concentration is 0.0024% The desulfurization treatment was carried out with the goal of making the following.

以下に示す表２に各脱硫試験における脱硫処理前後の溶鋼中硫黄濃度（化学分析値）及び脱硫率を示す。なお、脱硫評価が「○」とは、脱硫処理後の溶鋼中硫黄濃度が０．００２４％以下であったことを示している。   The sulfur concentration (chemical analysis value) in the molten steel and the desulfurization rate before and after the desulfurization treatment in each desulfurization test are shown in Table 2 shown below. In addition, desulfurization evaluation has shown that the sulfur concentration in the molten steel after a desulfurization process was 0.0024% or less with "(circle)".

Figure 2018135344
Figure 2018135344

試験水準と結果を合わせて表２に示す。撹拌動力の増加に伴いＬＦ処理開始５分後の滓化率及び脱硫率が向上することが確認された。また、攪拌動力密度が以下に示す数式（６）を満足することにより、高い滓化率及び脱硫率が得られることが確認された。   The test levels and the results are shown in Table 2. It was confirmed that the hatching rate and the desulfurization rate improved 5 minutes after the start of the LF treatment with the increase of the stirring power. Moreover, it was confirmed that the high hatching rate and the desulfurization rate are obtained when a stirring power density satisfies Numerical formula (6) shown below.

Figure 2018135344
Figure 2018135344

［実施例３］
図２は、本発明例及び比較例の滓化率を示す図である。細孔直径が０．５〜１０μｍの範囲内にある細孔の容積の和が０．２ｍＬ／ｇ、粒径が２０ｍｍ以下である生石灰を本発明例、細孔直径が０．５〜１０μｍの範囲内にある細孔の容積の和が０．０３ｍＬ／ｇ、粒径が２０ｍｍ以下である生石灰を比較例とした。図２に示すように、本発明例では比較例に比べて同一の撹拌動力密度（１３５Ｗ／ｔ）であっても滓化が促進されることが確認された。[Example 3]
FIG. 2 is a figure which shows the hatching rate of this invention example and a comparative example. The present invention example of quick lime having a total pore volume of 0.2 to 10 μm and a particle diameter of 20 mm or less, and the pore diameter of 0.5 to 10 μm The comparative example was made of quick lime having a total volume of pores in the range of 0.03 mL / g and a particle size of 20 mm or less. As shown in FIG. 2, it was confirmed that in the inventive example, the hatching is promoted even with the same stirring power density (135 W / t) as compared with the comparative example.

［実施例４］
高炉から出銑された溶銑に対して脱珪処理、脱硫処理、及び脱燐処理を行った後、この溶銑を転炉に装入して脱炭精錬を実施し、炭素濃度が０．０５〜０．０９質量％の範囲内、硫黄濃度が０．００４１〜０．００４４質量％の範囲内、燐濃度が０．００４〜０．０１０質量％の範囲内にある約２５０ｔの溶鋼を得た。出鋼後、取鍋へ流出した転炉スラグを徐滓せず、金属Ａｌ、生石灰、軽焼ドロマイト、及びアルミドロスの添加された取鍋を図１に示すＬＦ設備に搬送した。ＬＦ処理では、細孔直径が０．５〜１０μｍの範囲内にある細孔の容積の和が０．２ｍＬ／ｇ、粒径が２０ｍｍ以下である生石灰を用いた。Example 4
The hot metal discharged from the blast furnace is subjected to desiliconization treatment, desulfurization treatment and dephosphorization treatment, and then the hot metal is charged into a converter to carry out decarburizing and refining, and the carbon concentration is 0.05 to 0.05. About 250 t of molten steel having a sulfur concentration of 0.0041 to 0.0044 mass% and a phosphorus concentration of 0.004 to 0.010 mass% in the range of 0.09 mass% was obtained. After steel tapping, the converter slag that had flowed into the ladle was not vacuum-sintered, and the ladle to which metal Al, quick lime, light-burning dolomite, and aluminum dross were added was conveyed to the LF equipment shown in FIG. In the LF treatment, quick lime with a total pore volume of 0.2 mL / g and a particle size of 20 mm or less was used.

以下に示す表３に各脱硫試験における脱硫処理前後の溶鋼中硫黄濃度（化学分析値）及び脱硫率を示す。ここで、[ｓｏｌ.Ａｌ]1が溶製対象鋼種のＡｌ濃度規格上限値（質量％）、[ｓｏｌ.Ａｌ]2が転炉出鋼後の溶鋼中Ａｌ濃度（質量％）である。なお、脱硫評価が「○」とは、脱硫処理後の溶鋼中硫黄濃度が０．００２４％以下であったことを示している。Table 3 below shows the sulfur concentration (chemical analysis value) in the molten steel and the desulfurization ratio before and after the desulfurization treatment in each desulfurization test. Here, [sol. Al] 1 is the upper limit of Al concentration specification (mass%) of the target steel type to be melted and [sol. Al] 2 is the Al concentration (mass%) in the molten steel after the converter is discharged. In addition, desulfurization evaluation has shown that the sulfur concentration in the molten steel after a desulfurization process was 0.0024% or less with "(circle)".

Figure 2018135344
Figure 2018135344

表３に示すように、ＬＦ処理開始１０分以内に投入したＡｌ量が上記数式（５）の範囲内にある水準では、ＬＦ処理終了時点の[ｓｏｌ.Ａｌ]3値が規格の範囲内であり、脱硫率も高位であった。一方、ＬＦ処理開始１０分以内に投入したＡｌ量が上記数式（５）に示す範囲よりも多かった水準では、ＬＦ処理終了時点の[ｓｏｌ.Ａｌ] 3値が規格上限値を上回っており、次工程のＲＨでの脱Ａｌ処理の必要が生じてしまい、ＲＨの処理時間が延長した。As shown in Table 3, at the level where the amount of Al introduced within 10 minutes of the LF processing start is within the range of the above equation (5), the [sol.Al] 3 value at the end of the LF processing is within the standard range. And the desulfurization rate was also high. On the other hand, at the level where the amount of Al injected within 10 minutes after the start of LF processing was larger than the range shown in the above equation (5), the [sol.Al] 3 value at the end of LF processing exceeds the standard upper limit value, The need for de-Al treatment in the next step RH occurred, and the treatment time of RH was extended.

［実施例５］
高炉から出銑された溶銑に対して脱珪処理、脱硫処理、及び脱燐処理を行った後、溶銑を転炉に装入して脱炭精錬を実施し、炭素濃度が０．０５〜０．０９質量％の範囲内、硫黄濃度が０．００４１〜０．００４４質量％の範囲内、燐濃度が０．００４〜０．０１０質量％の範囲内の約２５０ｔの溶鋼を得た。出鋼後、取鍋へ流出した転炉スラグを徐滓せず、金属Ａｌ、生石灰、軽焼ドロマイト、及びアルミドロスの添加された取鍋を図１に示すＬＦ設備に搬送した。ＬＦ処理では、細孔直径が０．５〜１０μｍの範囲内にある細孔の容積の和が０．２ｍＬ／ｇ、粒径が２０ｍｍ以下である生石灰を用い、ＬＦ処理開始から１０分以内に上記数式（５）を満たすように、金属Ａｌを添加した。[Example 5]
After desiliconizing treatment, desulfurizing treatment and dephosphorizing treatment to the hot metal discharged from the blast furnace, the hot metal is charged into the converter to carry out decarburizing and refining, and the carbon concentration is 0.05 to 0. About 250t of molten steel was obtained in the range of .09 mass%, the sulfur concentration in the range of 0.0041 to 0.0044 mass%, and the phosphorus concentration in the range of 0.004 to 0.010 mass%. After steel tapping, the converter slag that had flowed into the ladle was not vacuum-sintered, and the ladle to which metal Al, quick lime, light-burning dolomite, and aluminum dross were added was conveyed to the LF equipment shown in FIG. In the LF process, using the quick lime with the sum of the volume of pores with a pore diameter in the range of 0.5 to 10 μm of 0.2 mL / g and the particle size of 20 mm or less, within 10 minutes from the start of the LF process Metal Al was added to satisfy the above formula (5).

以下に示す表４に各脱硫試験における脱硫処理前後の溶鋼中硫黄濃度（化学分析値）及び脱硫率を示す。なお、脱硫評価が「○」とは、脱硫処理後の溶鋼中硫黄濃度が０．００２４％以下であったことを示している。   The sulfur concentration (chemical analysis value) in the molten steel and the desulfurization ratio before and after the desulfurization treatment in each desulfurization test are shown in Table 4 shown below. In addition, desulfurization evaluation has shown that the sulfur concentration in the molten steel after a desulfurization process was 0.0024% or less with "(circle)".

Figure 2018135344
Figure 2018135344

表４に示すように、取鍋内酸素濃度が１５％以下である水準（試験番号３７〜３９）では処理中Ａｌロスが減少することが確認された。なお、処理中Ａｌロス（エア巻き込み）は以下に示す数式（７）を用いて求めた。   As shown in Table 4, it was confirmed that Al loss during treatment decreased at a level (test numbers 37 to 39) in which the oxygen concentration in the ladle was 15% or less. In addition, Al loss (air entrainment) was calculated | required using Numerical formula (7) shown below during processing.

Figure 2018135344
Figure 2018135344

本発明によれば、ＣａＦ2やプリメルトフラックスを使用しなくても効率良く脱硫処理を行うことが可能な溶鋼の脱硫処理方法及び脱硫剤を提供することができる。ADVANTAGE OF THE INVENTION According to this invention, the desulfurization processing method and desulfurization agent of molten steel which can perform desulfurization processing efficiently even if it does not use CaF 2 or a premelt flux can be provided.

１ ＬＦ設備
２ 取鍋
３ 蓋
４ 電極
５，６ 浸漬ランス
７，８ 底吹きポーラス煉瓦
９ 溶鋼
１０ スラグ
１１ 原材料投入シュート
１２ Ａｒガス導入管1 LF equipment 2 ladle 3 lid 4 electrode 5, 6 immersion lance 7, 8 bottom blow porous brick 9 molten steel 10 slag 11 raw material feed chute 12 Ar gas introduction pipe

Claims (6)

溶鋼を収容する取鍋内に生石灰を含む脱硫剤を添加し、取鍋内で溶鋼を攪拌することによって、溶鋼中の硫黄濃度を低減する溶鋼の脱硫処理方法であって、
前記脱硫剤として、細孔直径が０．５〜１０μｍ以下の範囲内にある細孔の容積の和が０．１ｍＬ／ｇ以上である生石灰を含む脱硫剤を用いることを特徴とする溶鋼の脱硫処理方法。A desulfurization method for molten steel, which reduces sulfur concentration in molten steel by adding a desulfurizing agent containing quick lime into a ladle containing molten steel and stirring the molten steel in the ladle.
A desulfurization agent for molten steel characterized by using, as the desulfurization agent, a desulfurization agent containing quicklime having a pore diameter in the range of 0.5 to 10 μm or less and a sum of pore volumes of 0.1 mL / g or more. Processing method. 前記生石灰が、粒径が１〜３０ｍｍ以下の範囲内にある粒子を９０％以上含むことを特徴とする請求項１に記載の溶鋼の脱硫処理方法。   The desulfurization treatment method for molten steel according to claim 1, wherein the quick lime contains 90% or more of particles having a particle diameter in the range of 1 to 30 mm or less. 細孔直径が０．５〜１０μｍ以下の範囲内にある細孔の容積の和が０．１ｍＬ／ｇ以上である生石灰を含み、前記生石灰が、粒径が１〜３０ｍｍ以下の範囲内にある粒子を９０％以上含むことを特徴とする脱硫剤。   It contains quick lime whose sum of volume of pores whose pore diameter is in the range of 0.5 to 10 μm or less is 0.1 mL / g or more, and the quick lime has a particle diameter in the range of 1 to 30 mm or less A desulfurization agent characterized by containing 90% or more of particles. 下記数式（１）で示される撹拌動力密度の条件が満足されるように前記溶鋼を攪拌することを特徴とする請求項１又は２に記載の溶鋼の脱硫処理方法。
Figure 2018135344
 The method of desulfurizing treatment of molten steel according to claim 1 or 2, wherein the molten steel is stirred so as to satisfy a condition of a stirring power density represented by the following formula (1).
Figure 2018135344
 前記溶鋼が転炉から出鋼されてから脱硫処理開始後１０分以内に溶鋼に投入されるアルミニウムの量が下記数式（２）を満足することを特徴とする請求項１、２、４のうち、いずれか１項に記載の溶鋼の脱硫処理方法。
Figure 2018135344
 The amount of aluminum introduced into the molten steel within 10 minutes after the start of the desulfurization treatment after the molten steel is pulled out of the converter satisfies the following formula (2): The desulfurization treatment method of molten steel according to any one of the above.
Figure 2018135344
 前記取鍋内における酸素濃度が１５％以下となるように前記取鍋内にＡｒガスを吹き込むことを特徴とする請求項１、２、４、５のうち、いずれか１項に記載の溶鋼の脱硫処理方法。   The molten steel according to any one of claims 1, 2, 4, and 5, characterized in that Ar gas is blown into the ladle so that the oxygen concentration in the ladle is 15% or less. Desulfurization treatment method.
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