WO2018123808A1 - Medium-carbon or low-carbon ferromanganese production method and medium-carbon or low-carbon ferromanganese - Google Patents

Medium-carbon or low-carbon ferromanganese production method and medium-carbon or low-carbon ferromanganese Download PDF

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WO2018123808A1
WO2018123808A1 PCT/JP2017/045933 JP2017045933W WO2018123808A1 WO 2018123808 A1 WO2018123808 A1 WO 2018123808A1 JP 2017045933 W JP2017045933 W JP 2017045933W WO 2018123808 A1 WO2018123808 A1 WO 2018123808A1
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medium
carbon ferromanganese
ferromanganese
low carbon
low
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PCT/JP2017/045933
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French (fr)
Japanese (ja)
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慶喜 筒井
匡伸 増川
敏生 塩田
達月 鈴木
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水島合金鉄株式会社
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Priority to JP2018559121A priority Critical patent/JP6962934B2/en
Priority to MYPI2019003264A priority patent/MY190117A/en
Publication of WO2018123808A1 publication Critical patent/WO2018123808A1/en
Priority to ZA2019/04059A priority patent/ZA201904059B/en

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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
    • C21C5/00—Manufacture of carbon-steel, e.g. plain mild steel, medium carbon steel or cast steel or stainless steel
    • C21C5/28—Manufacture of steel in the converter
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C33/00—Making ferrous alloys
    • C22C33/04—Making ferrous alloys by melting

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  • the present invention relates to a method for producing medium-low carbon ferromanganese having a low nitrogen concentration and medium-low carbon ferromanganese.
  • This method is a method in which a silicon manganese melt having a target carbon content is first prepared in an electric furnace or the like, and then a manganese oxide such as manganese ore is added to the melt to oxidize and remove silicon in the silicon manganese melt. is there.
  • This method has a problem in that the power cost increases because an electric furnace is used.
  • Patent Document 1 uses a converter type reaction vessel to blow an oxygen gas from an upper blowing lance while blowing an inert gas from the furnace bottom tuyere and stirring the molten metal.
  • a method for producing medium-low carbon ferromanganese by oxidizing and removing carbon in molten high-carbon ferromanganese is disclosed.
  • Medium-low carbon ferromanganese is used as a manganese source in the steelmaking process in the ironmaking process. Since nitrogen becomes an impurity with respect to steel, it is preferable that the nitrogen concentration of the medium-low carbon ferromanganese is low. However, the lower limit of the nitrogen concentration of the medium-low carbon ferromanganese produced by the production method disclosed in Patent Document 1 is about 400 ppm.
  • nitrogen concentration can be reduced if silicon is contained in medium-low carbon ferromanganese.
  • the nitrogen concentration of the medium / low carbon ferromanganese can be reduced to 300 ppm or less by setting the silicon concentration of the medium / low carbon ferromanganese to about 1% by mass.
  • silicon concentration is low.
  • the present invention has been made in view of the above problems, and the object of the present invention is to provide a method for producing medium and low carbon ferromanganese capable of producing medium and low carbon ferromanganese having a low silicon concentration and a nitrogen concentration of 300 ppm or less, and nitrogen. It is to provide a medium and low carbon ferromanganese having a low concentration and a low silicon concentration.
  • a reaction vessel equipped with a top blowing lance and a bottom blowing tuyere is charged with molten high carbon ferromanganese, and an oxygen-containing gas is blown from the top blowing lance, and an inert gas is fed from the bottom blowing tuyere.
  • the silicon-containing alloy raw material is used as the high-carbon ferromanganese molten metal or the medium-low carbon ferromanganese molten metal so that the silicon concentration of the medium-low carbon ferromanganese is 0.01% by mass or more and 0.5% by mass or less.
  • (3) The silicon-containing alloy raw material is used as the high-carbon ferromanganese molten metal and the medium-low carbon ferromanganese molten metal so that the silicon concentration of the medium-low carbon ferromanganese is 0.01% by mass or more and 0.5% by mass or less.
  • the method for producing medium-low carbon ferromanganese according to (1) which is added.
  • the method for producing medium-low carbon ferromanganese according to (2) wherein the silicon-containing alloy raw material is added to the molten medium-low carbon ferromanganese after completion of decarburization refining.
  • medium-low carbon ferromanganese By implementing the method for producing medium-low carbon ferromanganese according to the present invention, it is possible to produce medium-low carbon ferromanganese having a silicon concentration of 0.5% by mass or less and a low nitrogen concentration.
  • FIG. 1 is a schematic cross-sectional view showing a state where a high carbon ferromanganese molten metal is decarburized and refined using a converter-type reaction vessel.
  • FIG. 2 is a cross-sectional view showing a state in which a molten medium-low carbon ferromanganese melt is used as a mold.
  • FIG. 3 is a graph showing the relationship between the elapsed time from the end of decarburization refining and the maximum temperature of the ferromanganese surface.
  • the present inventors have found that the following three points are important for lowering the nitrogen concentration of medium-low carbon ferromanganese. 1. To reduce the amount of nitrogen absorbed when tapping the medium and low carbon ferromanganese melt. 2. 2. Argon gas is blown from the bottom blowing tuyere to lower the nitrogen partial pressure of the medium and low carbon ferromanganese melt. Use raw materials with low nitrogen content in the production of medium and low carbon ferromanganese.
  • the present inventors have shown that the nitrogen concentration of the medium-low carbon ferromanganese can be stably reduced by adding silicon within a range where the silicon concentration of the medium-low carbon ferromanganese satisfies 0.5% by mass or less. As a result, the present invention was completed.
  • the present invention will be described through embodiments of the present invention.
  • the high carbon ferromanganese is ferromanganese having a carbon concentration exceeding 2.0 mass%.
  • Medium carbon ferromanganese is ferromanganese having a carbon concentration exceeding 1.0 mass% and not more than 2.0 mass%, and low carbon ferromanganese is ferromanganese having a carbon concentration of 1.0 mass% or less. .
  • FIG. 1 is a schematic cross-sectional view showing a state in which a high-carbon ferromanganese molten metal is decarburized and refined using a converter-type reaction vessel.
  • the reaction vessel 10 is a converter-type reaction vessel, and includes a vessel main body 12 that accommodates the molten high carbon ferromanganese 20 and an upper blowing lance 16 that blows the oxygen-containing gas 24 onto the molten high carbon ferromanganese 20. .
  • a tap 14 for pouring the molten medium and low carbon ferromanganese after refining treatment, and a bottom blowing tuyere 18 for blowing argon gas 26 into the high carbon ferromanganese melt 20 at the bottom.
  • a plurality are provided.
  • the high carbon ferromanganese melt 20 reduced and smelted in the vertical smelting furnace is charged into the container body 12.
  • the high carbon ferromanganese molten metal 20 is blown with argon gas 26 from the bottom blowing tuyere 18 and stirred, and an oxygen-containing gas 24 is blown from the top blowing lance 16 to oxidize and remove carbon.
  • the oxygen-containing gas 24 blown from the upper blowing lance 16 is, for example, a mixed gas of oxygen and a non-oxidizing gas that lowers the oxygen partial pressure, such as a rare gas, or an oxygen gas containing only oxygen.
  • the argon gas 26 blown from the bottom blowing tuyere 18 is an example of an inert gas.
  • the slag 22 may be formed by adding a faux material in advance to the container body 12.
  • the molten high carbon ferromanganese 20 may be produced by reduction smelting in an electric furnace.
  • the high carbon ferromanganese molten metal 20 it is preferable to stir the high carbon ferromanganese molten metal 20 by setting the flow rate of the argon gas 26 blown into the high carbon ferromanganese molten metal 20 from the bottom blowing tuyere 18 to 0.01 Nm 3 / t ⁇ min or more. Blowing the argon gas 26 from the bottom blowing tuyere 18 lowers the nitrogen partial pressure of the high carbon ferromanganese melt 20, so the nitrogen concentration of the high carbon ferromanganese melt 20 also decreases.
  • the flow rate of the argon gas 26 blown from the bottom blowing tuyere 18 is more than 0.20 Nm 3 / t ⁇ min, the argon gas 26 is blown through as it is without contributing to the stirring of the molten high carbon ferromanganese 20. For this reason, it is preferable that the flow rate of the argon gas 26 blown into the high carbon ferromanganese molten metal 20 from the bottom blowing tuyere 18 is 0.20 Nm 3 / t ⁇ min or less.
  • “Nm 3 / t ⁇ min” means the blowing amount of argon gas per minute in the high carbon ferromanganese molten metal 1t.
  • the blowing of the oxygen-containing gas 24 and the blowing of the argon gas 26 are continued until the carbon concentration of the high carbon ferromanganese melt 20 is lowered to a predetermined concentration.
  • decarburization is performed until the carbon concentration of the molten high carbon ferromanganese 20 becomes 2.0 mass% or less.
  • decarburization is performed until the carbon concentration of the molten high carbon ferromanganese 20 becomes 1.0 mass% or less.
  • the carbon concentration of the high carbon ferromanganese molten metal 20 during the decarburization treatment is determined by the measured value of the carbon concentration of the high carbon ferromanganese molten metal 20 discharged from the vertical smelting furnace and the oxygen-containing gas 24 blown from the top blowing lance 16. It can be estimated from the supply amount and the decarbonation efficiency of the molten ferromanganese obtained empirically. For this reason, the supply amount of oxygen calculated from the measured value of the carbon concentration of the high carbon ferromanganese melt 20, the decarbonation efficiency, and the target carbon concentration is supplied, so that the high carbon ferromanganese melt It is determined that 20 carbons have been reduced to the carbon concentration described above.
  • the high carbon ferromanganese molten metal 20 may be collected to measure the carbon concentration, and it may be confirmed whether there is a difference between the estimated value of the carbon concentration of the high carbon ferromanganese molten metal 20 and the measured value.
  • the blowing of the oxygen-containing gas 24 from the top blowing lance 16 is stopped and the decarburization refining is finished.
  • the silicon-containing alloy raw material is added to the molten medium-low carbon ferromanganese so that the silicon concentration of the medium-low carbon ferromanganese after cooling is 0.01% by mass or more and 0.5% by mass or less.
  • ferrosilicon or silicomanganese may be used as the silicon-containing alloy material.
  • the amount of the silicon-containing alloy raw material added to the medium-low carbon ferromanganese molten metal is determined by considering the oxidation rate of silicon in the molten metal, and the silicon concentration of the medium-low carbon ferromanganese after cooling is 0.01 mass% or more and 0.5 mass. It may be determined empirically to be less than or equal to%.
  • the silicon-containing alloy raw material so that the silicon concentration of ferromanganese is less than 0.01% by mass because the effect of reducing the nitrogen concentration of molten manganese is reduced. Since silicon becomes an impurity in steel, when the silicon-containing alloy raw material is added in an amount where the silicon concentration of ferromanganese exceeds 0.5% by mass, the silicon concentration as an impurity in the steel increases and the medium-low carbon ferromanganese This is not preferable because the value of is lowered.
  • FIG. 2 is a cross-sectional view showing a state in which the molten medium and low carbon ferromanganese is discharged from a mold.
  • the medium-low carbon ferromanganese molten metal 21 decarburized and added with the silicon-containing alloy raw material is discharged from the outlet 14 into the mold 30 through the jar 28 with the container body 12 tilted. .
  • the medium-low carbon ferromanganese melt 21 is sprinkled and air cooled in the mold 30.
  • the medium and low carbon ferromanganese molten metal 21 is 15 from the time when the blowing of the oxygen-containing gas 24 from the top blowing lance 16 is stopped and the decarburization refining is completed.
  • the maximum temperature of the ferromanganese surface exposed from the mold 30 is cooled to 800 ° C. or lower.
  • Ferromanganese has been nitrogen-absorbed even after solidifying in the mold, and the nitrogen-absorption rate is fast until the temperature reaches about 800 ° C. For this reason, the time until the surface temperature of the ferromanganese becomes 800 ° C.
  • the nitrogen absorption amount of ferromanganese decreases, and the nitrogen concentration of medium-low carbon ferromanganese can be reduced to 300 ppm or less.
  • the above-described rapid cooling of the medium-low carbon ferromanganese molten metal 21 can be performed by water spray cooling.
  • the surface temperature of ferromanganese can be measured using a radiation thermometer.
  • FIG. 3 is a graph showing the relationship between the elapsed time from the end of decarburization refining and the maximum temperature of the ferromanganese surface.
  • the horizontal axis is the elapsed time (min) from the end of decarburization refining
  • the vertical axis is the maximum temperature (° C.) of the ferromanganese surface.
  • the solid line in FIG. 3 is the surface temperature profile when water spray cooling is performed so that the maximum temperature of the ferromanganese surface is 800 ° C. or less within 15 minutes from the end of decarburization refining. It is a surface temperature profile at the time of cooling the maximum temperature of a manganese surface to near 800 degreeC.
  • the nitrogen concentration of ferromanganese cooled with the surface temperature profile shown by the solid line in FIG. 3 was lower than the nitrogen concentration of ferromanganese cooled with the surface temperature profile shown by the broken line.
  • high-temperature molten manganese and solidified manganese at 800 ° C. or higher have a high nitrogen absorption rate.
  • at least the maximum temperature of the ferromanganese surface exposed from the mold 30 that can come into contact with air is cooled to 800 ° C. or less within 15 minutes from the end of decarburization refining. Thereby, the amount of nitrogen absorbed by manganese is reduced, and the nitrogen concentration of medium-low carbon ferromanganese can be reduced to 300 ppm or less.
  • the amount of cooling water in the case of sprinkling cooling may be determined by conducting a cooling experiment on the medium-low carbon ferromanganese melt discharged from the mold 30 in advance.
  • medium / low carbon ferromanganese having a low nitrogen concentration can be produced from high carbon ferromanganese by carrying out the method for producing medium / low carbon ferromanganese according to the present embodiment.
  • silicon of medium-low carbon ferromanganese is added by adding a silicon-containing alloy raw material to the medium-low carbon ferromanganese molten metal 21 so that the silicon concentration of ferromanganese is 0.01% by mass or more and 0.5% by mass or less.
  • the nitrogen concentration of the medium-low carbon ferromanganese can be stably reduced while maintaining the concentration at 0.5% by mass or less.
  • a ferromanganese cold material may be added.
  • the temperature of the medium-low carbon ferromanganese molten metal 21 can be rapidly reduced.
  • Example 1 The high-carbon ferromanganese molten metal 26t reduced and smelted in the vertical smelting furnace was charged into the same reaction vessel as the reaction vessel 10 shown in FIG.
  • the components of the high carbon ferromanganese charged into the reaction vessel were: Mn: 73.5% by mass, Fe: 19.0% by mass, Si: 0.4% by mass, C: 7.0% by mass, P: 0 0.013 mass%, and the temperature after charging the reaction vessel was 1350 ° C.
  • argon gas was blown into the ferromanganese melt at a feed rate of 0.07 Nm 3 / t ⁇ min from the bottom blowing tuyere, and oxygen gas was fed from the top blow lance at an oxygen feed rate of 1.5 Nm 3 / t ⁇ min.
  • Decarburization refining was performed by spraying on molten ferromanganese. When the oxygen supply amount reached 80 Nm 3 per metal ton, the blowing of oxygen gas from the top blowing lance was stopped and the decarburization refining was completed.
  • the components are Mn: 75.3% by mass, Fe: 23.2% by mass, Si: 0.3% by mass, C: 1.0% by mass, P: 0.014% by mass, N : 310 ppm of ferromanganese cold material was added so that the molten metal temperature after melting was about 1550 ° C. Thereafter, the molten ferromanganese was poured out into a mold, and the molten ferromanganese was sprinkled and cooled in accordance with the surface temperature profile shown by the solid line in FIG. As a result, the maximum temperature of the ferromanganese surface exposed from the mold became 800 ° C. or less after 9 minutes from the end of decarburization refining.
  • the components of the low carbon ferromanganese produced in this way are: Mn: 75.3% by mass, Fe: 23.1% by mass, Si: 0.3% by mass, C: 1.0% by mass, P: 0 .014% by mass and N: 220 ppm.
  • Example 2 Decarburization refining was performed under the same conditions as in Example 1, and after completion of decarburization refining, the components were Mn: 75.3 mass%, Fe: 23.2 mass%, Si: 0.3 mass%, C: 1.0 A ferromanganese cold material having a mass%, P: 0.014 mass%, N: 310 ppm, and Si: 75.0 mass%, Fe: 24.5 mass% ferrosilicon were added to the molten ferromanganese. .
  • the amount of ferrosilicon added to the molten ferromanganese is such that the silicon concentration of the low-carbon ferromanganese is 0.5% by mass, and the amount of ferromanganese cold material added is after the ferromanganese cold material is dissolved.
  • the amount of the molten metal is about 1550 ° C.
  • the added ferromanganese cold material and ferrosilicon were dissolved, and the molten ferromanganese having a molten metal temperature of about 1550 ° C. was poured out into the mold, and the molten ferromanganese was cooled according to the surface temperature profile of the solid line shown in FIG. As a result, the maximum temperature of the ferromanganese surface exposed from the mold became 800 ° C. or less after 9 minutes from the end of decarburization refining.
  • the components of the low carbon ferromanganese produced in this way are: Mn: 75.3% by mass, Fe: 23.1% by mass, Si: 0.5% by mass, C: 1.0% by mass, P: 0 .014% by mass and N: 200 ppm.
  • Decarburization refining was performed under the same conditions except that the amount of argon gas blown from the bottom blowing tuyere was 0.06 Nm 3 / t ⁇ min.
  • the components were Mn: 75.3 mass%, Fe : 23.3 mass%, Si: 0.3 mass%, C: 1.0 mass%, P: 0.014 mass%, N: 310 ppm ferromanganese cold material was added, but no ferrosilicon was added .
  • the added ferromanganese cold material was melted, and the molten ferromanganese having a molten metal temperature of about 1550 ° C. was poured out into the mold, and the molten ferromanganese was cooled according to the surface temperature profile indicated by the broken line shown in FIG. As a result, the maximum temperature of the ferromanganese surface exposed from the mold decreased to 800 ° C. or less in 23 minutes from the end of decarburization refining.
  • the components of the low carbon ferromanganese produced in this way are: Mn: 75.3% by mass, Fe: 23.3% by mass, Si: 0.3% by mass, C: 1.0% by mass, P: 0 .014% by mass and N: 310 ppm.
  • the low carbon ferromaggan by the method for producing medium to low carbon ferromanganese according to the present embodiment, the medium to low carbon ferro having a low nitrogen concentration of 300 ppm or less and a silicon concentration of 0.5 mass% or less. It can be seen that manganese can be produced.
  • the silicon concentration is 0.01 mass% or more and 0.5 mass% or less, and the nitrogen concentration is 300 ppm or less. It was confirmed that carbon ferromanganese could be produced.

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Abstract

Provided are: a medium-carbon or low-carbon ferromanganese production method with which it is possible to produce a medium-carbon or low-carbon ferromanganese having a low nitrogen concentration and a low silicon concentration; and a medium-carbon or low-carbon ferromanganese having a low nitrogen concentration and a low silicon concentration. Molten high-carbon ferromanganese is charged into a reaction vessel equipped with a top-blowing lance and a bottom-blowing tuyere, and while an oxygen-containing gas is being blown in from the top-blowing lance, an inert gas is blown in from the bottom-blowing tuyere to decarbonize and refine the molten high-carbon ferromanganese so as to be turned into a molten medium-carbon or low-carbon ferromanganese, and a medium-carbon or low-carbon ferromanganese is produced by tapping the molten medium-carbon or low-carbon ferromanganese into a casting mold and cooling same, wherein the cooling is performed such that the medium-carbon or low-carbon ferromanganese exposed from the casting mold would have a surface temperature of not more than 800°C within 15 minutes of completion of the decarbonizing and refining.

Description

中低炭素フェロマンガンの製造方法および中低炭素フェロマンガンMethod for producing medium-low carbon ferromanganese and medium-low carbon ferromanganese
　本発明は、窒素濃度の低い中低炭素フェロマンガンの製造方法および中低炭素フェロマンガンに関する。 The present invention relates to a method for producing medium-low carbon ferromanganese having a low nitrogen concentration and medium-low carbon ferromanganese.
　中低炭素フェロマンガンを製造する従来の技術の中には、いわゆる脱珪法と呼ばれる方法がある。この方法は、まず、電気炉等において目標炭素含有量のシリコマンガン溶湯を準備し、その後、この溶湯にマンガン鉱石等のマンガン酸化物を添加してシリコマンガン溶湯中のシリコンを酸化除去する方法である。この方法は、電気炉を使用するために電力コストが嵩むという問題点がある。 Among the conventional techniques for producing medium-low carbon ferromanganese, there is a so-called desiliconization method. This method is a method in which a silicon manganese melt having a target carbon content is first prepared in an electric furnace or the like, and then a manganese oxide such as manganese ore is added to the melt to oxidize and remove silicon in the silicon manganese melt. is there. This method has a problem in that the power cost increases because an electric furnace is used.
　このような問題点に対し、特許文献１では、転炉型の反応容器を用いて、炉底羽口から不活性ガスを吹き込んで溶湯を撹拌しつつ、上吹きランスから酸素ガスを吹きつけることで、高炭素フェロマンガン溶湯中の炭素を酸化除去して中低炭素フェロマンガンを製造する方法が開示されている。 With respect to such problems, Patent Document 1 uses a converter type reaction vessel to blow an oxygen gas from an upper blowing lance while blowing an inert gas from the furnace bottom tuyere and stirring the molten metal. A method for producing medium-low carbon ferromanganese by oxidizing and removing carbon in molten high-carbon ferromanganese is disclosed.
特公平６－１７５３７号公報Japanese Patent Publication No. 6-17537
　中低炭素フェロマンガンは、製鉄プロセスにおける製鋼工程でマンガン源として使用される。窒素は、鋼に対して不純物になるので、中低炭素フェロマンガンの窒素濃度は低いことが好ましい。しかしながら、特許文献１に開示されている製造方法で製造される中低炭素フェロマンガンの窒素濃度の下限は４００ｐｐｍ程度である。 中 Medium-low carbon ferromanganese is used as a manganese source in the steelmaking process in the ironmaking process. Since nitrogen becomes an impurity with respect to steel, it is preferable that the nitrogen concentration of the medium-low carbon ferromanganese is low. However, the lower limit of the nitrogen concentration of the medium-low carbon ferromanganese produced by the production method disclosed in Patent Document 1 is about 400 ppm.
　中低炭素フェロマンガンに珪素を含有させれば窒素濃度を低減できることが知られている。例えば、中低炭素フェロマンガンの珪素濃度を１質量％程度にすることで、中低炭素フェロマンガンの窒素濃度を３００ｐｐｍ以下にできる。しかしながら、珪素も鋼の不純物になるので珪素濃度も低いことが好ましい。 It is known that nitrogen concentration can be reduced if silicon is contained in medium-low carbon ferromanganese. For example, the nitrogen concentration of the medium / low carbon ferromanganese can be reduced to 300 ppm or less by setting the silicon concentration of the medium / low carbon ferromanganese to about 1% by mass. However, since silicon also becomes an impurity of steel, it is preferable that the silicon concentration is low.
　本発明は、上記課題を鑑みてなされたもので、その目的とするところは、珪素濃度が低く、窒素濃度が３００ｐｐｍ以下の中低炭素フェロマンガンを製造できる中低炭素フェロマンガンの製造方法ならびに窒素濃度および珪素濃度の低い中低炭素フェロマンガンを提供することにある。 The present invention has been made in view of the above problems, and the object of the present invention is to provide a method for producing medium and low carbon ferromanganese capable of producing medium and low carbon ferromanganese having a low silicon concentration and a nitrogen concentration of 300 ppm or less, and nitrogen. It is to provide a medium and low carbon ferromanganese having a low concentration and a low silicon concentration.
　上記課題を解決するための本発明の特徴は、以下の通りである。
（１）上吹きランスと底吹き羽口とを備えた反応容器に高炭素フェロマンガン溶湯を装入し、前記上吹きランスから酸素含有ガスを吹きつけるとともに、前記底吹き羽口から不活性ガスを吹き込むことで前記高炭素フェロマンガン溶湯を脱炭精錬して中低炭素フェロマンガン溶湯にし、前記中低炭素フェロマンガン溶湯を鋳型に出湯し、冷却することで中低炭素フェロマンガンを製造し、前記脱炭精錬が終了してから１５分以内に前記鋳型から露出した前記中低炭素フェロマンガンの表面温度が８００℃以下になるように冷却する、中低炭素フェロマンガンの製造方法。
（２）前記中低炭素フェロマンガンの珪素濃度が０．０１質量％以上０．５質量％以下になるように、珪素含有合金原料を前記高炭素フェロマンガン溶湯または前記中低炭素フェロマンガン溶湯に添加する、（１）に記載の中低炭素フェロマンガンの製造方法。
（３）前記中低炭素フェロマンガンの珪素濃度が０．０１質量％以上０．５質量％以下になるように、珪素含有合金原料を前記高炭素フェロマンガン溶湯および前記中低炭素フェロマンガン溶湯に添加する、（１）に記載の中低炭素フェロマンガンの製造方法。
（４）前記珪素含有合金原料を脱炭精錬終了後の前記中低炭素フェロマンガン溶湯に添加する、（２）に記載の中低炭素フェロマンガンの製造方法。
（５）珪素濃度が０．０１質量％以上０．５質量％以下であって、窒素濃度が３００ｐｐｍ以下である、中低炭素フェロマンガン。 The features of the present invention for solving the above-described problems are as follows.
(1) A reaction vessel equipped with a top blowing lance and a bottom blowing tuyere is charged with molten high carbon ferromanganese, and an oxygen-containing gas is blown from the top blowing lance, and an inert gas is fed from the bottom blowing tuyere. Decarburizing and refining the high carbon ferromanganese melt to a medium and low carbon ferromanganese melt, discharging the medium and low carbon ferromanganese melt into a mold and cooling to produce a medium and low carbon ferromanganese, A method for producing medium to low carbon ferromanganese, wherein the surface temperature of the medium to low carbon ferromanganese exposed from the mold is cooled to 800 ° C. or less within 15 minutes after completion of the decarburization refining.
(2) The silicon-containing alloy raw material is used as the high-carbon ferromanganese molten metal or the medium-low carbon ferromanganese molten metal so that the silicon concentration of the medium-low carbon ferromanganese is 0.01% by mass or more and 0.5% by mass or less. The method for producing medium-low carbon ferromanganese according to (1), which is added.
(3) The silicon-containing alloy raw material is used as the high-carbon ferromanganese molten metal and the medium-low carbon ferromanganese molten metal so that the silicon concentration of the medium-low carbon ferromanganese is 0.01% by mass or more and 0.5% by mass or less. The method for producing medium-low carbon ferromanganese according to (1), which is added.
(4) The method for producing medium-low carbon ferromanganese according to (2), wherein the silicon-containing alloy raw material is added to the molten medium-low carbon ferromanganese after completion of decarburization refining.
(5) Medium-low carbon ferromanganese having a silicon concentration of 0.01% by mass to 0.5% by mass and a nitrogen concentration of 300 ppm or less.
　本発明に係る中低炭素フェロマンガンの製造方法を実施することで、珪素濃度０．５質量％以下であって、窒素濃度の低い中低炭素フェロマンガンを製造できる。 By implementing the method for producing medium-low carbon ferromanganese according to the present invention, it is possible to produce medium-low carbon ferromanganese having a silicon concentration of 0.5% by mass or less and a low nitrogen concentration.
図１は、転炉型の反応容器を用いて高炭素フェロマンガン溶湯を脱炭精錬する状態を示す断面模式図である。FIG. 1 is a schematic cross-sectional view showing a state where a high carbon ferromanganese molten metal is decarburized and refined using a converter-type reaction vessel. 図２は、中低炭素フェロマンガン溶湯を鋳型に出湯する状態を示す断面図である。FIG. 2 is a cross-sectional view showing a state in which a molten medium-low carbon ferromanganese melt is used as a mold. 図３は、脱炭精錬終了からの経過時間と、フェロマンガン表面の最高温度との関係を示すグラフである。FIG. 3 is a graph showing the relationship between the elapsed time from the end of decarburization refining and the maximum temperature of the ferromanganese surface.
　本発明者らは、中低炭素フェロマンガンの窒素濃度を下げるには、以下の３点が重要であることを見出した。
１．中低炭素フェロマンガン溶湯の出湯時の吸窒量を低減させること。
２．底吹き羽口からアルゴンガスを吹込んで中低炭素フェロマンガン溶湯の窒素分圧を下げること
３．中低炭素フェロマンガンの製造に窒素含有量の少ない原料を用いること。 The present inventors have found that the following three points are important for lowering the nitrogen concentration of medium-low carbon ferromanganese.
1. To reduce the amount of nitrogen absorbed when tapping the medium and low carbon ferromanganese melt.
2. 2. Argon gas is blown from the bottom blowing tuyere to lower the nitrogen partial pressure of the medium and low carbon ferromanganese melt. Use raw materials with low nitrogen content in the production of medium and low carbon ferromanganese.
　さらに、本発明者らは、中低炭素フェロマンガンの珪素濃度が０．５質量％以下を満足する範囲で珪素を添加することで、安定的に中低炭素フェロマンガンの窒素濃度を低下できることを見出して本発明を完成させた。以下、本発明の実施形態を通じて本発明を説明する。本実施形態において、高炭素フェロマンガンとは、炭素濃度が２．０質量％超えのフェロマンガンである。中炭素フェロマンガンとは、炭素濃度が１．０質量％超えで２．０質量％以下のフェロマンガンであり、低炭素フェロマンガンとは、炭素濃度が１．０質量％以下のフェロマンガンである。 Furthermore, the present inventors have shown that the nitrogen concentration of the medium-low carbon ferromanganese can be stably reduced by adding silicon within a range where the silicon concentration of the medium-low carbon ferromanganese satisfies 0.5% by mass or less. As a result, the present invention was completed. Hereinafter, the present invention will be described through embodiments of the present invention. In the present embodiment, the high carbon ferromanganese is ferromanganese having a carbon concentration exceeding 2.0 mass%. Medium carbon ferromanganese is ferromanganese having a carbon concentration exceeding 1.0 mass% and not more than 2.0 mass%, and low carbon ferromanganese is ferromanganese having a carbon concentration of 1.0 mass% or less. .
　図１は、転炉型の反応容器を用いて高炭素フェロマンガン溶湯を脱炭精錬する状態を示す断面模式図である。反応容器１０は、転炉型の反応容器であって、高炭素フェロマンガン溶湯２０を収容する容器本体１２と、高炭素フェロマンガン溶湯２０に酸素含有ガス２４を吹きつける上吹きランス１６とを備える。容器本体１２の側面には、精錬処理後の中低炭素フェロマンガン溶湯を出湯する出湯口１４が設けられ、底部には、アルゴンガス２６を高炭素フェロマンガン溶湯２０に吹き込む底吹き羽口１８が複数設けられている。 FIG. 1 is a schematic cross-sectional view showing a state in which a high-carbon ferromanganese molten metal is decarburized and refined using a converter-type reaction vessel. The reaction vessel 10 is a converter-type reaction vessel, and includes a vessel main body 12 that accommodates the molten high carbon ferromanganese 20 and an upper blowing lance 16 that blows the oxygen-containing gas 24 onto the molten high carbon ferromanganese 20. . On the side surface of the container body 12, there is provided a tap 14 for pouring the molten medium and low carbon ferromanganese after refining treatment, and a bottom blowing tuyere 18 for blowing argon gas 26 into the high carbon ferromanganese melt 20 at the bottom. A plurality are provided.
　竪型製錬炉で還元製錬された高炭素フェロマンガン溶湯２０は、容器本体１２に装入される。高炭素フェロマンガン溶湯２０は、底吹き羽口１８からアルゴンガス２６が吹き込まれて撹拌されるとともに、上吹きランス１６から酸素含有ガス２４が吹きつけられて、炭素が酸化除去される。上吹きランス１６から吹きつける酸素含有ガス２４は、例えば、酸素と希ガスなどの酸素分圧を下げる非酸化性ガスとの混合ガス、または、酸素のみを含む酸素ガスである。底吹き羽口１８から吹き込むアルゴンガス２６は、不活性ガスの一例である。上吹きランス１６から酸素含有ガス２４を吹きつけると、マンガンが酸化されて高炭素フェロマンガン溶湯２０の溶湯面を覆うスラグ２２が形成される。容器本体１２に造滓材を予め添加してスラグ２２を形成させてもよい。高炭素フェロマンガン溶湯２０は、電気炉で還元製錬され製造されてもよい。 The high carbon ferromanganese melt 20 reduced and smelted in the vertical smelting furnace is charged into the container body 12. The high carbon ferromanganese molten metal 20 is blown with argon gas 26 from the bottom blowing tuyere 18 and stirred, and an oxygen-containing gas 24 is blown from the top blowing lance 16 to oxidize and remove carbon. The oxygen-containing gas 24 blown from the upper blowing lance 16 is, for example, a mixed gas of oxygen and a non-oxidizing gas that lowers the oxygen partial pressure, such as a rare gas, or an oxygen gas containing only oxygen. The argon gas 26 blown from the bottom blowing tuyere 18 is an example of an inert gas. When the oxygen-containing gas 24 is blown from the top blowing lance 16, manganese is oxidized and a slag 22 that covers the molten metal surface of the high carbon ferromanganese molten metal 20 is formed. The slag 22 may be formed by adding a faux material in advance to the container body 12. The molten high carbon ferromanganese 20 may be produced by reduction smelting in an electric furnace.
　脱炭精錬では、底吹き羽口１８から高炭素フェロマンガン溶湯２０に吹き込むアルゴンガス２６の流量を０．０１Ｎｍ３／ｔ・ｍｉｎ以上にして、高炭素フェロマンガン溶湯２０を撹拌することが好ましい。底吹き羽口１８からアルゴンガス２６を吹きこむことで、高炭素フェロマンガン溶湯２０の窒素分圧が低下するので、高炭素フェロマンガン溶湯２０の窒素濃度も低下する。一方、底吹き羽口１８から吹き込むアルゴンガス２６の流量を０．２０Ｎｍ３／ｔ・ｍｉｎより多くすると、高炭素フェロマンガン溶湯２０の撹拌に寄与せず、アルゴンガス２６がそのまま吹き抜ける。このため、底吹き羽口１８から高炭素フェロマンガン溶湯２０に吹き込むアルゴンガス２６の流量を０．２０Ｎｍ３／ｔ・ｍｉｎ以下にすることが好ましい。本実施形態において、「Ｎｍ３／ｔ・ｍｉｎ」は、高炭素フェロマンガン溶湯１ｔにおける１分当たりのアルゴンガスの吹込み量を意味する。 In decarburization refining, it is preferable to stir the high carbon ferromanganese molten metal 20 by setting the flow rate of the argon gas 26 blown into the high carbon ferromanganese molten metal 20 from the bottom blowing tuyere 18 to 0.01 Nm 3 / t · min or more. Blowing the argon gas 26 from the bottom blowing tuyere 18 lowers the nitrogen partial pressure of the high carbon ferromanganese melt 20, so the nitrogen concentration of the high carbon ferromanganese melt 20 also decreases. On the other hand, when the flow rate of the argon gas 26 blown from the bottom blowing tuyere 18 is more than 0.20 Nm 3 / t · min, the argon gas 26 is blown through as it is without contributing to the stirring of the molten high carbon ferromanganese 20. For this reason, it is preferable that the flow rate of the argon gas 26 blown into the high carbon ferromanganese molten metal 20 from the bottom blowing tuyere 18 is 0.20 Nm 3 / t · min or less. In the present embodiment, “Nm 3 / t · min” means the blowing amount of argon gas per minute in the high carbon ferromanganese molten metal 1t.
　高炭素フェロマンガン溶湯２０の炭素濃度が、所定の濃度に低下するまで酸素含有ガス２４の吹きつけ、および、アルゴンガス２６の吹き込みを継続する。中炭素フェロマンガンを製造する場合には、高炭素フェロマンガン溶湯２０の炭素濃度が２．０質量％以下になるまで脱炭する。低炭素フェロマンガンを製造する場合には、高炭素フェロマンガン溶湯２０の炭素濃度が１．０質量％以下になるまで脱炭する。 The blowing of the oxygen-containing gas 24 and the blowing of the argon gas 26 are continued until the carbon concentration of the high carbon ferromanganese melt 20 is lowered to a predetermined concentration. When producing medium carbon ferromanganese, decarburization is performed until the carbon concentration of the molten high carbon ferromanganese 20 becomes 2.0 mass% or less. When producing low carbon ferromanganese, decarburization is performed until the carbon concentration of the molten high carbon ferromanganese 20 becomes 1.0 mass% or less.
　脱炭処理中の高炭素フェロマンガン溶湯２０の炭素濃度は、竪型製錬炉から出湯した高炭素フェロマンガン溶湯２０の炭素濃度の測定値と、上吹きランス１６から吹きつける酸素含有ガス２４の供給量と、経験的に得られているフェロマンガン溶湯の脱炭酸素効率とから推定できる。このため、高炭素フェロマンガン溶湯２０の炭素濃度の測定値と、脱炭酸素効率と、目標とする炭素濃度と、から算出された供給量の酸素が供給されたことで、高炭素フェロマンガン溶湯２０の炭素が上述した炭素濃度まで低下したと判断する。脱炭精錬中に高炭素フェロマンガン溶湯２０を採取して炭素濃度を実測し、高炭素フェロマンガン溶湯２０の炭素濃度の推定値と実測値とに差がないか確認してもよい。 The carbon concentration of the high carbon ferromanganese molten metal 20 during the decarburization treatment is determined by the measured value of the carbon concentration of the high carbon ferromanganese molten metal 20 discharged from the vertical smelting furnace and the oxygen-containing gas 24 blown from the top blowing lance 16. It can be estimated from the supply amount and the decarbonation efficiency of the molten ferromanganese obtained empirically. For this reason, the supply amount of oxygen calculated from the measured value of the carbon concentration of the high carbon ferromanganese melt 20, the decarbonation efficiency, and the target carbon concentration is supplied, so that the high carbon ferromanganese melt It is determined that 20 carbons have been reduced to the carbon concentration described above. During the decarburization refining, the high carbon ferromanganese molten metal 20 may be collected to measure the carbon concentration, and it may be confirmed whether there is a difference between the estimated value of the carbon concentration of the high carbon ferromanganese molten metal 20 and the measured value.
　高炭素フェロマンガン溶湯２０が上述した炭素濃度まで低下したら、上吹きランス１６からの酸素含有ガス２４の吹きつけを停止して脱炭精錬を終了する。次いで、冷却後の中低炭素フェロマンガンの珪素濃度が０．０１質量％以上０．５質量％以下になるように、珪素含有合金原料を中低炭素フェロマンガン溶湯に添加する。珪素含有合金原料としては、例えば、フェロシリコンやシリコマンガンを用いてよい。中低炭素フェロマンガン溶湯への珪素含有合金原料の添加量は、溶湯中における珪素の酸化速度を考慮し、冷却後の中低炭素フェロマンガンの珪素濃度が０．０１質量％以上０．５質量％以下になるように経験的に定めてよい。 When the high carbon ferromanganese molten metal 20 is reduced to the above-described carbon concentration, the blowing of the oxygen-containing gas 24 from the top blowing lance 16 is stopped and the decarburization refining is finished. Next, the silicon-containing alloy raw material is added to the molten medium-low carbon ferromanganese so that the silicon concentration of the medium-low carbon ferromanganese after cooling is 0.01% by mass or more and 0.5% by mass or less. For example, ferrosilicon or silicomanganese may be used as the silicon-containing alloy material. The amount of the silicon-containing alloy raw material added to the medium-low carbon ferromanganese molten metal is determined by considering the oxidation rate of silicon in the molten metal, and the silicon concentration of the medium-low carbon ferromanganese after cooling is 0.01 mass% or more and 0.5 mass. It may be determined empirically to be less than or equal to%.
　珪素含有合金原料の添加量をフェロマンガンの珪素濃度が０．０１質量％未満となる量にすると、溶融マンガンの窒素濃度低減効果が小さくなるので好ましくない。珪素は鋼の不純物になるので、珪素含有合金原料の添加量をフェロマンガンの珪素濃度が０．５質量％を超える量にすると、鋼の不純物となる珪素濃度が高くなり、中低炭素フェロマンガンの価値が下がるので好ましくない。 It is not preferable to add the silicon-containing alloy raw material so that the silicon concentration of ferromanganese is less than 0.01% by mass because the effect of reducing the nitrogen concentration of molten manganese is reduced. Since silicon becomes an impurity in steel, when the silicon-containing alloy raw material is added in an amount where the silicon concentration of ferromanganese exceeds 0.5% by mass, the silicon concentration as an impurity in the steel increases and the medium-low carbon ferromanganese This is not preferable because the value of is lowered.
　上記例では、珪素含有合金原料を脱炭精錬後の中低炭素フェロマンガン溶湯に添加する例を示したが、中低炭素フェロマンガン溶湯に添加することに代えて、または、中低炭素フェロマンガン溶湯に添加するとともに珪素含有合金原料を脱炭精錬中の高炭素フェロマンガン溶湯２０に添加してもよい。しかしながら、脱炭精錬中の高炭素フェロマンガンに珪素含有合金原料を添加すると、珪素が上吹きランス１６から吹きつけられる酸素含有気体によって酸化されて二酸化珪素になり、塩基度の低いスラグが増加してスロッピングが発生するおそれが生じる。このため、珪素含有合金原料は、脱炭精錬後の中低炭素フェロマンガン溶湯に添加することがより好ましい。 In the above example, an example in which the silicon-containing alloy raw material is added to the medium-low carbon ferromanganese molten metal after decarburization / refining, but instead of adding to the medium-low carbon ferromanganese molten metal, While adding to a molten metal, you may add a silicon containing alloy raw material to the high carbon ferromanganese molten metal 20 in decarburization refining. However, when a silicon-containing alloy raw material is added to high-carbon ferromanganese during decarburization refining, silicon is oxidized by the oxygen-containing gas blown from the top blowing lance 16 into silicon dioxide, and slag with low basicity increases. This may cause slapping. For this reason, it is more preferable to add the silicon-containing alloy raw material to the medium-low carbon ferromanganese melt after decarburization refining.
　図２は、中低炭素フェロマンガン溶湯を鋳型に出湯する状態を示す断面図である。図２に示すように、脱炭され珪素含有合金原料が添加された中低炭素フェロマンガン溶湯２１は、容器本体１２が傾動されて、出湯口１４から樋２８を介して鋳型３０へ出湯される。中低炭素フェロマンガン溶湯２１は、鋳型３０内で散水冷却および空気冷却される。 FIG. 2 is a cross-sectional view showing a state in which the molten medium and low carbon ferromanganese is discharged from a mold. As shown in FIG. 2, the medium-low carbon ferromanganese molten metal 21 decarburized and added with the silicon-containing alloy raw material is discharged from the outlet 14 into the mold 30 through the jar 28 with the container body 12 tilted. . The medium-low carbon ferromanganese melt 21 is sprinkled and air cooled in the mold 30.
　本実施形態に係る中低炭素フェロマンガンの製造方法では、中低炭素フェロマンガン溶湯２１は、上吹きランス１６からの酸素含有ガス２４の吹きつけを停止して脱炭精錬を終了した時点から１５分以内に、鋳型３０から露出しているフェロマンガン表面の最高温度が８００℃以下になるように冷却される。フェロマンガンは、鋳型内で凝固した後も吸窒しており、その温度が８００℃程度までは吸窒速度が速い。このため、出湯後の中低炭素フェロマンガン溶湯２１を急冷してフェロマンガンの表面温度が８００℃以下になるまでの時間を短くする。これにより、フェロマンガンの吸窒量は少なくなり、中低炭素フェロマンガンの窒素濃度を３００ｐｐｍ以下に低減できる。上述した中低炭素フェロマンガン溶湯２１の急冷は、散水冷却することで実施できる。フェロマンガンの表面温度は、放射温度計を用いて測定できる。 In the method for producing medium and low carbon ferromanganese according to the present embodiment, the medium and low carbon ferromanganese molten metal 21 is 15 from the time when the blowing of the oxygen-containing gas 24 from the top blowing lance 16 is stopped and the decarburization refining is completed. Within minutes, the maximum temperature of the ferromanganese surface exposed from the mold 30 is cooled to 800 ° C. or lower. Ferromanganese has been nitrogen-absorbed even after solidifying in the mold, and the nitrogen-absorption rate is fast until the temperature reaches about 800 ° C. For this reason, the time until the surface temperature of the ferromanganese becomes 800 ° C. or less by rapidly cooling the medium-low carbon ferromanganese molten metal 21 after tapping is shortened. Thereby, the nitrogen absorption amount of ferromanganese decreases, and the nitrogen concentration of medium-low carbon ferromanganese can be reduced to 300 ppm or less. The above-described rapid cooling of the medium-low carbon ferromanganese molten metal 21 can be performed by water spray cooling. The surface temperature of ferromanganese can be measured using a radiation thermometer.
　図３は、脱炭精錬終了からの経過時間と、フェロマンガン表面の最高温度との関係を示すグラフである。図３において、横軸は、脱炭精錬終了からの経過時間（ｍｉｎ）であり、縦軸は、フェロマンガン表面の最高温度（℃）である。図３の実線は、脱炭精錬を終了した時点から１５分以内にフェロマンガン表面の最高温度が８００℃以下になるように散水冷却した場合の表面温度プロファイルであり、破線は、空気冷却によってフェロマンガン表面の最高温度を８００℃近くまで冷却した場合の表面温度プロファイルである。 FIG. 3 is a graph showing the relationship between the elapsed time from the end of decarburization refining and the maximum temperature of the ferromanganese surface. In FIG. 3, the horizontal axis is the elapsed time (min) from the end of decarburization refining, and the vertical axis is the maximum temperature (° C.) of the ferromanganese surface. The solid line in FIG. 3 is the surface temperature profile when water spray cooling is performed so that the maximum temperature of the ferromanganese surface is 800 ° C. or less within 15 minutes from the end of decarburization refining. It is a surface temperature profile at the time of cooling the maximum temperature of a manganese surface to near 800 degreeC.
　図３の実線で示した表面温度プロファイルで冷却したフェロマンガンの窒素濃度は、破線で示した表面温度プロファイルで空気冷却したフェロマンガンの窒素濃度よりも低かった。上述したように、高温の溶融マンガンおよび８００℃以上の凝固したマンガンは、窒素の吸収速度が速い。このため、少なくとも、空気と接触し得る鋳型３０から露出したフェロマンガン表面の最高温度を、脱炭精錬が終了した時点から１５分以内に８００℃以下になるように冷却する。これにより、マンガンが吸収する窒素量は少なくなり、中低炭素フェロマンガンの窒素濃度を３００ｐｐｍ以下に低減できる。散水冷却する場合の冷却水量は、鋳型３０に出湯された中低炭素フェロマンガン溶湯の冷却実験を予め行うことで定めてよい。フェロマンガンの窒素濃度を低減させるには、脱炭精錬が終了した時点からフェロマンガン表面の最高温度が８００℃以下になるまでの時間を短くすることが好ましい。このため、空気と接触し得る鋳型３０から露出したフェロマンガン表面の最高温度を脱炭精錬が終了した時点から１０分以内に８００℃以下にすることがより好ましい。 The nitrogen concentration of ferromanganese cooled with the surface temperature profile shown by the solid line in FIG. 3 was lower than the nitrogen concentration of ferromanganese cooled with the surface temperature profile shown by the broken line. As described above, high-temperature molten manganese and solidified manganese at 800 ° C. or higher have a high nitrogen absorption rate. For this reason, at least the maximum temperature of the ferromanganese surface exposed from the mold 30 that can come into contact with air is cooled to 800 ° C. or less within 15 minutes from the end of decarburization refining. Thereby, the amount of nitrogen absorbed by manganese is reduced, and the nitrogen concentration of medium-low carbon ferromanganese can be reduced to 300 ppm or less. The amount of cooling water in the case of sprinkling cooling may be determined by conducting a cooling experiment on the medium-low carbon ferromanganese melt discharged from the mold 30 in advance. In order to reduce the nitrogen concentration of ferromanganese, it is preferable to shorten the time from the end of decarburization refining until the maximum temperature of the ferromanganese surface reaches 800 ° C. or less. For this reason, it is more preferable that the maximum temperature of the ferromanganese surface exposed from the mold 30 that can come into contact with air be 800 ° C. or less within 10 minutes from the time when the decarburization refining is completed.
　以上、説明したように、本実施形態に係る中低炭素フェロマンガンの製造方法を実施することで、高炭素フェロマンガンから窒素濃度の低い中低炭素フェロマンガンを製造できる。さらに、フェロマンガンの珪素濃度が０．０１質量％以上０．５質量％以下になるように、珪素含有合金原料を中低炭素フェロマンガン溶湯２１に添加することで、中低炭素フェロマンガンの珪素濃度を０．５質量％以下に維持しつつ、さらに中低炭素フェロマンガンの窒素濃度を安定して低減できる。 As described above, medium / low carbon ferromanganese having a low nitrogen concentration can be produced from high carbon ferromanganese by carrying out the method for producing medium / low carbon ferromanganese according to the present embodiment. Furthermore, silicon of medium-low carbon ferromanganese is added by adding a silicon-containing alloy raw material to the medium-low carbon ferromanganese molten metal 21 so that the silicon concentration of ferromanganese is 0.01% by mass or more and 0.5% by mass or less. Further, the nitrogen concentration of the medium-low carbon ferromanganese can be stably reduced while maintaining the concentration at 0.5% by mass or less.
　本実施形態の説明において、脱炭精錬後の中低炭素フェロマンガン溶湯２１に、珪素含有合金原料を添加する例を示したが、これに加えて、フェロマンガン冷材を投入してもよい。これにより、中低炭素フェロマンガン溶湯２１の温度を急速に低下させることができる。さらに、投入するフェロマンガン冷材として窒素濃度の低いフェロマンガン冷材を用いることが好ましい。これにより、当該冷材によって持ち込まれる窒素が少なくなり、中低炭素フェロマンガンの窒素濃度の増加を抑制できる。 In the description of the present embodiment, an example in which the silicon-containing alloy raw material is added to the medium-low carbon ferromanganese molten metal 21 after decarburization refining is shown, but in addition to this, a ferromanganese cold material may be added. Thereby, the temperature of the medium-low carbon ferromanganese molten metal 21 can be rapidly reduced. Further, it is preferable to use a ferromanganese cold material having a low nitrogen concentration as the ferromanganese cold material to be charged. Thereby, the nitrogen brought in by the said cold material decreases and it can suppress the increase in the nitrogen concentration of medium-low carbon ferromanganese.
（実施例１）
　竪型製錬炉で還元製錬された高炭素フェロマンガン溶湯２６ｔを、図１に示した反応容器１０と同じ反応容器へ装入して脱炭精錬を実施した。反応容器へ装入された高炭素フェロマンガンの成分は、Ｍｎ：７３．５質量％、Ｆｅ：１９．０質量％、Ｓｉ：０．４質量％、Ｃ：７．０質量％、Ｐ：０．０１３質量％であり、反応容器へ装入した後の温度は１３５０℃であった。 Example 1
The high-carbon ferromanganese molten metal 26t reduced and smelted in the vertical smelting furnace was charged into the same reaction vessel as the reaction vessel 10 shown in FIG. The components of the high carbon ferromanganese charged into the reaction vessel were: Mn: 73.5% by mass, Fe: 19.0% by mass, Si: 0.4% by mass, C: 7.0% by mass, P: 0 0.013 mass%, and the temperature after charging the reaction vessel was 1350 ° C.
　反応容器において、底吹き羽口から０．０７Ｎｍ３／ｔ・ｍｉｎの供給量でアルゴンガスをフェロマンガン溶湯に吹き込み、上吹きランスから酸素ガスを１．５Ｎｍ３／ｔ・ｍｉｎの酸素供給速度でフェロマンガン溶湯に吹きつけて脱炭精錬を実施した。酸素供給量がメタルトン当たり８０Ｎｍ３になった時点で、上吹きランスからの酸素ガスの吹きつけを停止して脱炭精錬を終了した。 In the reaction vessel, argon gas was blown into the ferromanganese melt at a feed rate of 0.07 Nm 3 / t · min from the bottom blowing tuyere, and oxygen gas was fed from the top blow lance at an oxygen feed rate of 1.5 Nm 3 / t · min. Decarburization refining was performed by spraying on molten ferromanganese. When the oxygen supply amount reached 80 Nm 3 per metal ton, the blowing of oxygen gas from the top blowing lance was stopped and the decarburization refining was completed.
　脱炭精錬終了後、成分が、Ｍｎ：７５．３質量％、Ｆｅ：２３．２質量％、Ｓｉ：０．３質量％、Ｃ：１．０質量％、Ｐ：０．０１４質量％、Ｎ：３１０ｐｐｍのフェロマンガン冷材を、溶解後の溶湯温度が約１５５０℃になるように添加した。その後、フェロマンガン溶湯を鋳型に出湯し、図３に示した実線の表面温度プロファイルに従ってフェロマンガン溶湯を散水冷却した。これにより、鋳型から露出しているフェロマンガン表面の最高温度は、脱炭精錬終了から９分で８００℃以下になった。このようにして製造された低炭素フェロマンガンの成分は、Ｍｎ：７５．３質量％、Ｆｅ：２３．１質量％、Ｓｉ：０．３質量％、Ｃ：１．０質量％、Ｐ：０．０１４質量％、Ｎ：２２０ｐｐｍであった。
（実施例２）
　実施例１と同じ条件で脱炭精錬を行い、脱炭精錬終了後に成分が、Ｍｎ：７５．３質量％、Ｆｅ：２３．２質量％、Ｓｉ：０．３質量％、Ｃ：１．０質量％、Ｐ：０．０１４質量％、Ｎ：３１０ｐｐｍのフェロマンガン冷材と、成分がＳｉ：７５．０質量％、Ｆｅ：２４．５質量％のフェロシリコンと、をフェロマンガン溶湯に添加した。フェロマンガン溶湯に添加したフェロシリコンの添加量は、低炭素フェロマンガンの珪素濃度が０．５質量％となる量であり、フェロマンガン冷材の添加量は、フェロマンガン冷材を溶解した後の溶湯温度が約１５５０℃になる量である。 After decarburization refining, the components are Mn: 75.3% by mass, Fe: 23.2% by mass, Si: 0.3% by mass, C: 1.0% by mass, P: 0.014% by mass, N : 310 ppm of ferromanganese cold material was added so that the molten metal temperature after melting was about 1550 ° C. Thereafter, the molten ferromanganese was poured out into a mold, and the molten ferromanganese was sprinkled and cooled in accordance with the surface temperature profile shown by the solid line in FIG. As a result, the maximum temperature of the ferromanganese surface exposed from the mold became 800 ° C. or less after 9 minutes from the end of decarburization refining. The components of the low carbon ferromanganese produced in this way are: Mn: 75.3% by mass, Fe: 23.1% by mass, Si: 0.3% by mass, C: 1.0% by mass, P: 0 .014% by mass and N: 220 ppm.
(Example 2)
Decarburization refining was performed under the same conditions as in Example 1, and after completion of decarburization refining, the components were Mn: 75.3 mass%, Fe: 23.2 mass%, Si: 0.3 mass%, C: 1.0 A ferromanganese cold material having a mass%, P: 0.014 mass%, N: 310 ppm, and Si: 75.0 mass%, Fe: 24.5 mass% ferrosilicon were added to the molten ferromanganese. . The amount of ferrosilicon added to the molten ferromanganese is such that the silicon concentration of the low-carbon ferromanganese is 0.5% by mass, and the amount of ferromanganese cold material added is after the ferromanganese cold material is dissolved. The amount of the molten metal is about 1550 ° C.
　添加したフェロマンガン冷材とフェロシリコンとを溶解させて、溶湯温度を約１５５０℃としたフェロマンガン溶湯を鋳型に出湯し、図３に示した実線の表面温度プロファイルに従ってフェロマンガン溶湯を冷却した。これにより、鋳型から露出しているフェロマンガン表面の最高温度は、脱炭精錬終了から９分で８００℃以下になった。このようにして製造された低炭素フェロマンガンの成分は、Ｍｎ：７５．３質量％、Ｆｅ：２３．１質量％、Ｓｉ：０．５質量％、Ｃ：１．０質量％、Ｐ：０．０１４質量％、Ｎ：２００ｐｐｍであった。
（比較例１）
　底吹き羽口からのアルゴンガスの吹き込み量を０．０６Ｎｍ３／ｔ・ｍｉｎとしたこと以外は同じ条件で脱炭精錬を行ない、脱炭精錬終了後に成分がＭｎ：７５．３質量％、Ｆｅ：２３．３質量％、Ｓｉ：０．３質量％、Ｃ：１．０質量％、Ｐ：０．０１４質量％、Ｎ：３１０ｐｐｍのフェロマンガン冷材を添加し、フェロシリコンは添加しなかった。 The added ferromanganese cold material and ferrosilicon were dissolved, and the molten ferromanganese having a molten metal temperature of about 1550 ° C. was poured out into the mold, and the molten ferromanganese was cooled according to the surface temperature profile of the solid line shown in FIG. As a result, the maximum temperature of the ferromanganese surface exposed from the mold became 800 ° C. or less after 9 minutes from the end of decarburization refining. The components of the low carbon ferromanganese produced in this way are: Mn: 75.3% by mass, Fe: 23.1% by mass, Si: 0.5% by mass, C: 1.0% by mass, P: 0 .014% by mass and N: 200 ppm.
(Comparative Example 1)
Decarburization refining was performed under the same conditions except that the amount of argon gas blown from the bottom blowing tuyere was 0.06 Nm 3 / t · min. After completion of decarburization refining, the components were Mn: 75.3 mass%, Fe : 23.3 mass%, Si: 0.3 mass%, C: 1.0 mass%, P: 0.014 mass%, N: 310 ppm ferromanganese cold material was added, but no ferrosilicon was added .
　添加したフェロマンガン冷材を溶解させて、溶湯温度を約１５５０℃としたフェロマンガン溶湯を鋳型に出湯し、図３に示した破線の表面温度プロファイルに従って、フェロマンガン溶湯を冷却した。これにより、鋳型から露出しているフェロマンガン表面の最高温度は、脱炭精錬終了から２３分で８００℃以下に低下した。このようにして製造された低炭素フェロマンガンの成分は、Ｍｎ：７５．３質量％、Ｆｅ：２３．３質量％、Ｓｉ：０．３質量％、Ｃ：１．０質量％、Ｐ：０．０１４質量％、Ｎ：３１０ｐｐｍであった。 The added ferromanganese cold material was melted, and the molten ferromanganese having a molten metal temperature of about 1550 ° C. was poured out into the mold, and the molten ferromanganese was cooled according to the surface temperature profile indicated by the broken line shown in FIG. As a result, the maximum temperature of the ferromanganese surface exposed from the mold decreased to 800 ° C. or less in 23 minutes from the end of decarburization refining. The components of the low carbon ferromanganese produced in this way are: Mn: 75.3% by mass, Fe: 23.3% by mass, Si: 0.3% by mass, C: 1.0% by mass, P: 0 .014% by mass and N: 310 ppm.
　このように、本実施形態に係る中低炭素フェロマンガンの製造方法で低炭素フェロマガンを製造することで、珪素濃度０．５質量％以下であって、３００ｐｐｍ以下の窒素濃度の低い中低炭素フェロマンガンを製造できることがわかる。 Thus, by producing the low carbon ferromaggan by the method for producing medium to low carbon ferromanganese according to the present embodiment, the medium to low carbon ferro having a low nitrogen concentration of 300 ppm or less and a silicon concentration of 0.5 mass% or less. It can be seen that manganese can be produced.
　本実施例においては、炭素濃度が１．０質量％の低炭素フェロマンガンの製造例を示したが、中炭素フェロマンガンも低炭素フェロマンガンと同様に製造できる。このように、本実施形態に係る中低炭素フェロマンガンの製造方法を実施することで、珪素濃度が０．０１質量％以上０．５質量％以下であって、窒素濃度が３００ｐｐｍ以下の中低炭素フェロマンガンが製造できることが確認できた。 In the present example, a production example of low carbon ferromanganese having a carbon concentration of 1.0% by mass was shown, but medium carbon ferromanganese can be produced in the same manner as low carbon ferromanganese. Thus, by carrying out the method for producing medium to low carbon ferromanganese according to the present embodiment, the silicon concentration is 0.01 mass% or more and 0.5 mass% or less, and the nitrogen concentration is 300 ppm or less. It was confirmed that carbon ferromanganese could be produced.
　１０　反応容器
　１２　容器本体
　１４　出湯口
　１６　上吹きランス
　１８　底吹き羽口
　２０　高炭素フェロマンガン溶湯
　２１　中低炭素フェロマンガン溶湯
　２２　スラグ
　２４　酸素含有ガス
　２６　アルゴンガス
　２８　樋
　３０　鋳型 DESCRIPTION OF SYMBOLS 10 Reaction container 12 Container body 14 Outlet 16 Top blowing lance 18 Bottom blowing tuyere 20 High carbon ferromanganese molten metal 21 Medium low carbon ferromanganese molten 22 Slag 24 Oxygen-containing gas 26 Argon gas 28 ３０ 30 Mold

Claims (5)

  1. 　上吹きランスと底吹き羽口とを備えた反応容器に高炭素フェロマンガン溶湯を装入し、
    　前記上吹きランスから酸素含有ガスを吹きつけるとともに、前記底吹き羽口から不活性ガスを吹き込むことで前記高炭素フェロマンガン溶湯を脱炭精錬して中低炭素フェロマンガン溶湯にし、
    　前記中低炭素フェロマンガン溶湯を鋳型に出湯し、冷却することで中低炭素フェロマンガンを製造し、
    　前記脱炭精錬が終了してから１５分以内に前記鋳型から露出した前記中低炭素フェロマンガンの表面温度が８００℃以下になるように冷却する、中低炭素フェロマンガンの製造方法。     A reaction vessel equipped with a top blowing lance and bottom blowing tuyere was charged with molten high carbon ferromanganese,
    Blowing the oxygen-containing gas from the top blowing lance, and decarburizing and refining the high carbon ferromanganese melt by blowing an inert gas from the bottom blowing tuyere to a medium to low carbon ferromanganese melt,
    The medium and low carbon ferromanganese molten metal is poured into a mold and cooled to produce a medium and low carbon ferromanganese,
    A method for producing medium to low carbon ferromanganese, wherein the surface temperature of the medium to low carbon ferromanganese exposed from the mold is cooled to 800 ° C. or less within 15 minutes after completion of the decarburization refining.
  2. 　前記中低炭素フェロマンガンの珪素濃度が０．０１質量％以上０．５質量％以下になるように、珪素含有合金原料を前記高炭素フェロマンガン溶湯または前記中低炭素フェロマンガン溶湯に添加する、請求項１に記載の中低炭素フェロマンガンの製造方法。 Adding a silicon-containing alloy raw material to the high-carbon ferromanganese molten metal or the medium-low carbon ferromanganese molten metal so that the silicon concentration of the medium-low carbon ferromanganese is 0.01% by mass or more and 0.5% by mass or less, The method for producing medium-low carbon ferromanganese according to claim 1.
  3. 　前記中低炭素フェロマンガンの珪素濃度が０．０１質量％以上０．５質量％以下になるように、珪素含有合金原料を前記高炭素フェロマンガン溶湯および前記中低炭素フェロマンガン溶湯に添加する、請求項１に記載の中低炭素フェロマンガンの製造方法。 Adding a silicon-containing alloy raw material to the high-carbon ferromanganese molten metal and the medium-low carbon ferromanganese molten metal so that the silicon concentration of the medium-low carbon ferromanganese is 0.01% by mass or more and 0.5% by mass or less, The method for producing medium-low carbon ferromanganese according to claim 1.
  4. 　前記珪素含有合金原料を脱炭精錬終了後の前記中低炭素フェロマンガン溶湯に添加する、請求項２に記載の中低炭素フェロマンガンの製造方法。 The method for producing medium-low carbon ferromanganese according to claim 2, wherein the silicon-containing alloy raw material is added to the molten medium-low carbon ferromanganese after completion of decarburization refining.
  5. 　珪素濃度が０．０１質量％以上０．５質量％以下であって、窒素濃度が３００ｐｐｍ以下である、中低炭素フェロマンガン。 Medium-low carbon ferromanganese having a silicon concentration of 0.01% by mass to 0.5% by mass and a nitrogen concentration of 300 ppm or less.
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