JP4180972B2 - Method of adding Bi to molten steel - Google Patents
Method of adding Bi to molten steel Download PDFInfo
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- JP4180972B2 JP4180972B2 JP2003142571A JP2003142571A JP4180972B2 JP 4180972 B2 JP4180972 B2 JP 4180972B2 JP 2003142571 A JP2003142571 A JP 2003142571A JP 2003142571 A JP2003142571 A JP 2003142571A JP 4180972 B2 JP4180972 B2 JP 4180972B2
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- 229910000831 Steel Inorganic materials 0.000 title claims description 51
- 239000010959 steel Substances 0.000 title claims description 51
- 238000000034 method Methods 0.000 title claims description 16
- 239000000843 powder Substances 0.000 claims description 66
- 229910045601 alloy Inorganic materials 0.000 claims description 33
- 239000000956 alloy Substances 0.000 claims description 33
- 229910002551 Fe-Mn Inorganic materials 0.000 claims description 30
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 16
- 229910052742 iron Inorganic materials 0.000 claims description 8
- 239000011812 mixed powder Substances 0.000 claims description 6
- 229910015902 Bi 2 O 3 Inorganic materials 0.000 description 11
- 239000002184 metal Substances 0.000 description 11
- 229910052751 metal Inorganic materials 0.000 description 11
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 7
- 230000005484 gravity Effects 0.000 description 5
- 238000002844 melting Methods 0.000 description 5
- 230000008018 melting Effects 0.000 description 5
- 239000002245 particle Substances 0.000 description 5
- 239000008188 pellet Substances 0.000 description 5
- 229910052799 carbon Inorganic materials 0.000 description 3
- 238000001704 evaporation Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000002156 mixing Methods 0.000 description 3
- 150000003568 thioethers Chemical class 0.000 description 3
- 229910000915 Free machining steel Inorganic materials 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 2
- 229910052797 bismuth Inorganic materials 0.000 description 2
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000002436 steel type Substances 0.000 description 2
- 229910052717 sulfur Inorganic materials 0.000 description 2
- 239000011593 sulfur Substances 0.000 description 2
- 229910017082 Fe-Si Inorganic materials 0.000 description 1
- 229910017133 Fe—Si Inorganic materials 0.000 description 1
- -1 and in particular Inorganic materials 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 150000002505 iron Chemical class 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 239000002893 slag Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 239000000725 suspension Substances 0.000 description 1
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- Treatment Of Steel In Its Molten State (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、溶鋼へのＢｉ添加方法に関するものであり、添加したＢｉの歩留りを向上させて、溶鋼中のＢｉ濃度を効率良く高めることのできる有用なＢｉ添加方法に関するものである。
【０００２】
【従来の技術】
Ｂｉ（ビスマス）を溶鋼中に添加して得られるＢｉ含有鋼は、近年、環境問題の高まりから敬遠されているＰｂ添加鋼（快削鋼）の代替品として有用であることが一般に知られている。しかしＢｉは低融点元素であり、単体金属の状態で溶鋼中に添加しても蒸発・揮散しやすいため、溶鋼中のＢｉ濃度を効率良く高めることは困難である。
【０００３】
これまでにも、Ｂｉを溶鋼中に添加する方法として次の様な技術が提案されている。例えば特許文献１には、Ｂｉ等の低融点材料から成る金属成分の粉末を鉄または他の合金成分粉末と混合して、ペレット状に成形したものを溶鋼中に投入することが提案されている。
【０００４】
しかしこの方法では、単体金属のＢｉを使用するため、ペレットが溶融してＢｉがその他の合金粉末と分離した時点で蒸発しやすく、結果としてＢｉ歩留りの低下を招くと考えられる。またペレットサイズが小さい場合には、ペレットを炉上部から投入したときに、溶鋼表面を覆うスラグ層中に留まり溶融しないことも考えられるため、溶鋼中のＢｉ濃度を直ぐに高めることができず生産性が低下するおそれがある。
【０００５】
特許文献２には、鉛やビスマスを含有する機械切削性に優れた快削鋼を製造するに際し、鉄より比重の大きいこれらの低融点金属を、硫化物や酸化物として添加したり、該硫化物や酸化物と低融点金属を混合物として添加することで、見掛け比重を鉄と同等レベルにして溶鋼中に懸濁し易くすることが示されている。この様に硫化物や酸化物として溶鋼中に投入することで、Ｂｉの蒸発を防止することは可能となるが、これらの硫化物や酸化物のみを溶鋼中に投入しても、Ｂｉへの還元速度が遅いので、効率良く溶鋼中のＢｉ濃度を高めることは難しい。
【０００６】
また特許文献３には、比重の大きいＢｉ等の低融点金属を溶鋼中に高歩留かつ均一に分散させるため、該低融点金属または該低融点金属の酸化物のうち１種又は２種と、嵩比重の小さい炭素物質（コークス粉等）とを混合して低融点金属の見掛け比重を小さくすることが提案されている。
【０００７】
しかし、コークス粉を使用する場合には鋼中の炭素濃度や硫黄濃度が上昇しやすい。従って、Ｃ濃度の許容範囲が狭い鋼種を製造する場合には、コークス粉の添加量が制限されるといった問題が生じる。またＳ（硫黄）を除去する必要も生じる。
【０００８】
【特許文献１】
特開昭６０−６７６１４号公報
【特許文献２】
特公平２−５６４０５号公報
【特許文献３】
特公平２−９６４４号公報
【０００９】
【発明が解決しようとする課題】
本発明は、この様な事情に鑑みてなされたものであって、その目的は、低融点元素であるＢｉを、高歩留りで溶鋼に添加することのできる有用なＢｉ添加方法を提供することにある。
【００１０】
【課題を解決するための手段】
本発明に係る溶鋼へのＢｉ添加方法とは、Ｂｉ酸化物粉末とＦｅ−Ｍｎ系合金粉末の混合粉末を封入した鉄皮被覆ワイヤを、溶鋼中に投入するところに特徴を有するものである。
【００１１】
前記Ｂｉ酸化物粉末とＦｅ−Ｍｎ系合金粉末の質量比が、好ましくは(５０：５０)〜(９０：１０)、より好ましくは(７０：３０)〜(８５：１５)の範囲内となるよう調整することで確実にＢｉ歩留りを高めることができる。また本発明では、前記ワイヤを１．０ kg-Bi／(min・t）以上の速度で投入することによっても、Ｂｉ歩留りを高めることができる。
【００１２】
尚、前記ワイヤの投入速度は、溶鋼１ｔ（トン）について１分間あたりに投入されるワイヤ中のＢｉ量（kg-Bi）で規定している（以下、同じ）。また、前記Ｂｉ歩留り（以下、単に「歩留り」ということがある）とは、下記式（３）で示される値をいうものとする（以下、同じ）。
Ｂｉ歩留り（％）＝（［連続鋳造タンディッシュ内の溶鋼中のＢｉ量］／
［溶鋼への投入Ｂｉ量］）×１００ …（３）
【００１３】
【発明の実施の形態】
本発明者らは、前述した様な状況の下で、Ｂｉを高歩留りで溶鋼中に添加することのできる有用な方法を確立すべく様々な角度から検討を行った。その結果、Ｂｉ酸化物とＦｅ−Ｍｎ系合金粉末の混合粉末を鉄皮被覆ワイヤの形態で溶鋼中に投入すれば、高い歩留りでＢｉを添加できることを見出した。
【００１４】
また、Ｂｉ歩留りを確実に高めるには、前記Ｂｉ酸化物粉末とＦｅ−Ｍｎ系合金粉末の質量比や前記ワイヤの投入速度を最適範囲とすればよいことも見出し、上記本発明に想到した。以下、本発明でＢｉの添加方法を上記の通り規定した理由について詳述する。
【００１５】
まず本発明では、溶鋼中に投入する粉末材料として、Ｂｉ酸化物粉末とＦｅ−Ｍｎ系合金粉末を組み合わせて用いることとした。Ｂｉ単体金属ではなくＢｉ酸化物として投入することで、従来法の様に溶鋼中に投入したときに直ちにＢｉが蒸発するのを防止できるからである。また、Ｂｉ酸化物粉末とともにＦｅ−Ｍｎ系合金粉末を投入することで、Ｂｉ酸化物とＦｅ−Ｍｎ系合金中のＭｎを溶鋼中で反応させてＢｉ酸化物をＢｉに還元させ、確実にＢｉを溶鋼中に歩留らせることができる。
【００１６】
該Ｆｅ−Ｍｎ系合金粉末は、この様に還元剤として有効に作用するだけでなく、その他の還元性材料（コークス粉やＦｅ−Ｓｉ系合金粉末等）よりも、Ｂｉ酸化物粉末との配合率を調整しやすくかつワイヤに成形し易いので、Ｂｉ酸化物粉末と混合させる粉末として最適である。またＭｎ濃度の許容範囲は、いずれの鋼種においても比較的広いので、Ｆｅ−Ｍｎ系合金粉末の添加による溶鋼中のＭｎ濃度の上昇に細心の注意を払う必要がなく、投入量を調整しやすいといった利点もある。尚、前記Ｂｉ酸化物粉末としては、Ｂｉ2Ｏ3粉末を使用することができる。
【００１７】
Ｂｉ酸化物粉末とＦｅ−Ｍｎ系合金粉末を組み合わせて使用するに際し、これらの粉末の質量比を調整することで、確実にＢｉ歩留りを高めることができる。具体的には、Ｂｉ酸化物粉末とＦｅ−Ｍｎ系合金粉末を質量比で（５０：５０）〜（９０：１０）とすれば、Ｂｉ歩留りを４０％以上とすることができる。
【００１８】
Ｂｉ歩留りを５０％以上とより高めるには、Ｂｉ酸化物粉末とＦｅ−Ｍｎ系合金粉末を質量比で（７０：３０）〜（８５：１５）とするのがよい。最も好ましくは、Ｂｉ酸化物粉末とＦｅ−Ｍｎ系合金粉末を質量比で８０：２０とすることで、６０％近い高歩留りを達成することが可能となる。
【００１９】
Ｂｉ酸化物およびＦｅ−Ｍｎ系合金粉末は、どちらも最大粒径が５ｍｍ以下で、かつ粒度分布における平均粒径が１〜３ｍｍであるものを使用すれば、飛散することなく均一に混合できるので好ましい。
【００２０】
本発明では、上記混合粉末をワイヤの形態で溶鋼中へ投入する。この様にワイヤとして投入することで、ペレット状にして投入したり粉末状のまま吹き込む場合より、上記Ｂｉ酸化物粉末とＦｅ−Ｍｎ系合金粉末を確実に溶鋼中に投入してＢｉ歩留りを向上させることができる。
【００２１】
前記ワイヤは、１．０ kg-Bi／(min・t）以上の速度で投入することによって、Ｂｉ歩留りを高めることができる。ワイヤの投入速度を１．１ kg-Bi／(min・t）以上とすることでＢｉ歩留りをより向上させることができるので望ましい。しかしワイヤの投入速度が速すぎると、投入箇所でのＢｉ濃度が一時的に上昇してＢｉが蒸発し易くなるので、投入速度は１．３ kg-Bi／(min・t）以下に抑えることが好ましい。
【００２２】
本発明の方法は、対象とするＢｉ鋼の成分組成まで規定するものでなく、Ｂｉ濃度が０．０１質量％と極少量のＢｉ含有鋼から、０．３質量％と多量に添加したものまで幅広く適用することができる。また本発明のＢｉ添加方法は、溶鋼中のＢｉ以外の成分の影響を受けるものではない。例えばＢｉ以外に、Ｃ（炭素）：０．０１〜１質量％、Ｍｎ：０．０５〜２質量％、Ｓｉ：０．２質量％以下（０質量％含む）を満たすＢｉ含有鋼の製造に適用することができる。
【００２３】
【実施例】
以下、実施例を挙げて本発明をより具体的に説明するが、本発明はもとより下記実施例によって制限を受けるものではなく、前・後記の趣旨に適合し得る範囲で適当に変更を加えて実施することも可能であり、それらはいずれも本発明の技術的範囲に含まれる。
【００２４】
Ｂｉ2Ｏ3粉末（平均粒径：２ｍｍ）とＦｅ−Ｍｎ系合金粉末（平均粒径：２ｍｍ）を用い、これらＢｉ2Ｏ3粉末とＦｅ−Ｍｎ系合金粉末の質量比を（４０：６０）〜（９５：５）の間で変化させて混合した。
【００２５】
得られた混合粉末を鉄皮で被覆してワイヤ（断面：１１ｍｍ×５．３ｍｍの角型）を製造し、該ワイヤを取鍋内の溶鋼処理後の溶鋼（９０トン，Ｃ：０．３５質量％、Ｍｎ：０．７２質量％、Ｓｉ：０．１８質量％を含む）中に投入した。このときワイヤの投入速度を０．９〜１．３ kg-Bi／(min・t）の間で変化させてＢｉ含有鋼を製造した。
【００２６】
使用したＢｉ2Ｏ3粉末は１３４ｋｇ／溶鋼９０トン，Ｆｅ−Ｍｎ系合金粉末は３２ｋｇ／溶鋼９０トンであった。また上記鉄皮被覆ワイヤは、Ｂｉ2Ｏ3粉末とＦｅ−Ｍｎ系合金粉末をドラムミキサーで攪拌・混合し、得られた混合粉末をワイヤ鉄皮内に充填させながらワイヤ成形して得た。
【００２７】
この様にしてＢｉ含有鋼を溶製したときのＢｉ歩留りを上記式（３）から求めた。その結果を図１に示す。図１は、ワイヤ中のＦｅ−Ｍｎ系合金粉末の質量比とＢｉ歩留りとの関係をワイヤの投入速度別に示したグラフであり、この図１から次のように考察することができる。
【００２８】
Ｂｉ2Ｏ3粉末とＦｅ−Ｍｎ系合金粉末の混合粉末を封入したワイヤを溶鋼中に投入することで、Ｂｉ歩留りを高めることができ、特にＢｉ2Ｏ3粉末とＦｅ−Ｍｎ系合金粉末の質量比を本発明で規定する範囲内とすることで、Ｂｉ歩留りを確実に向上できる。図１に示す通り、Ｂｉ歩留りを４０％以上とするには、ワイヤの投入速度により多少の変動はあるが、Ｂｉ2Ｏ3粉末とＦｅ−Ｍｎ系合金粉末を概ね（５０：５０）〜（９０：１０）の質量比で混合するのがよく、Ｂｉ歩留りを５０％以上と更に高めるには、前記質量比を概ね（７０：３０）〜（８５：１５）とするのがよい。
【００２９】
ワイヤの投入速度については、図１から、Ｂｉ2Ｏ3粉末とＦｅ−Ｍｎ系合金粉末の質量比が同一のワイヤを使用する場合でも、ワイヤの投入速度が大きいほど歩留りが高くなる傾向がみられ、１．０ kg-Bi／(min・t）以上とすることで高歩留りを達成できることがわかる。しかし、前記ワイヤの投入速度が１．３ kg-Bi／(min・t）と高すぎると、却って歩留りが低下するので、その上限は１．２ kg-Bi／(min・t）以下に留めておくのが好ましい。
【００３０】
また図１から明らかなように、Ｂｉ歩留りを最高値まで高めるには、Ｂｉ2Ｏ3粉末とＦｅ−Ｍｎ系合金粉末の配合率を８０：２０とし、前記ワイヤの投入速度を１．２ kg-Bi／(min・t）とするのが最も好ましい。
【００３１】
尚、Ｂｉ金属粉末を単独で添加した場合にはＢｉ歩留りが０％であった。またＢｉ2Ｏ3粉末を単独で添加した場合には、Ｂｉ歩留りが５％以下であった。
【００３２】
【発明の効果】
本発明は上記のように構成されており、低融点元素であるＢｉを蒸発させることなく高歩留りで溶鋼に添加することができるので、溶鋼中のＢｉを所望の濃度まで効率良く高めることができる。
【図面の簡単な説明】
【図１】ワイヤ中のＦｅ−Ｍｎ系合金粉末の質量比とＢｉ歩留りとの関係を、ワイヤの投入速度別に示したグラフである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a Bi addition method to molten steel, and relates to a useful Bi addition method capable of improving the yield of added Bi and efficiently increasing the Bi concentration in the molten steel.
[0002]
[Prior art]
It is generally known that Bi-containing steel obtained by adding Bi (bismuth) to molten steel is useful as a substitute for Pb-added steel (free-cutting steel), which has been avoided in recent years due to increasing environmental problems. Yes. However, since Bi is a low melting point element and easily evaporates and volatilizes even when added to the molten steel in the form of a single metal, it is difficult to efficiently increase the Bi concentration in the molten steel.
[0003]
So far, the following techniques have been proposed as a method of adding Bi to molten steel. For example, Patent Document 1 proposes that a metal component powder made of a low-melting-point material such as Bi is mixed with iron or other alloy component powder and then formed into a pellet and put into molten steel. .
[0004]
However, in this method, since single metal Bi is used, it is considered that the pellet is easily evaporated when Bi is separated from other alloy powder, and as a result, the Bi yield is considered to decrease. In addition, when the pellet size is small, it is considered that when the pellet is introduced from the top of the furnace, it remains in the slag layer covering the surface of the molten steel and does not melt, so the Bi concentration in the molten steel cannot be increased immediately and productivity May decrease.
[0005]
In Patent Document 2, when producing free-cutting steel containing lead and bismuth and excellent in machine machinability, these low-melting-point metals having a specific gravity larger than iron are added as sulfides or oxides. It has been shown that by adding a product or oxide and a low-melting-point metal as a mixture, the apparent specific gravity is set to the same level as that of iron to facilitate suspension in molten steel. In this way, it is possible to prevent the evaporation of Bi by introducing it into the molten steel as sulfides and oxides, but even if only these sulfides and oxides are introduced into the molten steel, Since the reduction rate is slow, it is difficult to efficiently increase the Bi concentration in the molten steel.
[0006]
In Patent Document 3, in order to disperse a low melting point metal such as Bi having a large specific gravity in molten steel with high yield and uniformity, one or two kinds of the low melting point metal or the oxide of the low melting point metal and It has been proposed to reduce the apparent specific gravity of a low-melting-point metal by mixing with a carbon substance (coke powder or the like) having a low bulk specific gravity.
[0007]
However, when coke powder is used, the carbon concentration and sulfur concentration in the steel tend to increase. Therefore, when manufacturing a steel type with a narrow allowable range of C concentration, there arises a problem that the amount of coke powder added is limited. In addition, it is necessary to remove S (sulfur).
[0008]
[Patent Document 1]
JP 60-67614 A [Patent Document 2]
Japanese Patent Publication No. 2-56405 [Patent Document 3]
Japanese Examined Patent Publication No. 2-9644 [0009]
[Problems to be solved by the invention]
This invention is made | formed in view of such a situation, The objective is to provide the useful Bi addition method which can add Bi which is a low melting-point element to molten steel with a high yield. is there.
[0010]
[Means for Solving the Problems]
The method for adding Bi to molten steel according to the present invention is characterized in that an iron-coated wire encapsulating a mixed powder of Bi oxide powder and Fe—Mn alloy powder is put into molten steel.
[0011]
The mass ratio of the Bi oxide powder to the Fe—Mn alloy powder is preferably in the range of (50:50) to (90:10), more preferably (70:30) to (85:15). By adjusting so, the Bi yield can be surely increased. In the present invention, Bi yield can also be increased by throwing the wire at a speed of 1.0 kg-Bi / (min · t) or more.
[0012]
The wire feeding speed is defined by the Bi amount (kg-Bi) in the wire to be poured per minute for 1 t (ton) of molten steel (hereinafter the same). Further, the Bi yield (hereinafter sometimes simply referred to as “yield”) refers to a value represented by the following formula (3) (hereinafter the same).
Bi yield (%) = ([Bi amount in molten steel in continuous casting tundish] /
[Amount of Bi input to molten steel]) × 100 (3)
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Under the circumstances as described above, the present inventors have studied from various angles to establish a useful method in which Bi can be added to molten steel at a high yield. As a result, it was found that Bi can be added at a high yield if a mixed powder of Bi oxide and Fe—Mn alloy powder is put into molten steel in the form of an iron-coated wire.
[0014]
Further, in order to reliably increase the Bi yield, it has been found that the mass ratio of the Bi oxide powder to the Fe—Mn alloy powder and the charging speed of the wire may be within the optimum range, and the present invention has been conceived. The reason why the Bi addition method is defined as described above in the present invention will be described in detail below.
[0015]
First, in the present invention, a Bi oxide powder and a Fe—Mn alloy powder are used in combination as a powder material to be introduced into molten steel. This is because by adding Bi oxide instead of Bi single metal, Bi can be prevented from immediately evaporating when introduced into molten steel as in the conventional method. In addition, by introducing Fe—Mn alloy powder together with Bi oxide powder, Bi oxide and Mn in Fe—Mn alloy are reacted in molten steel to reduce Bi oxide to Bi, and reliably Bi. Can be made to yield in the molten steel.
[0016]
The Fe—Mn alloy powder not only effectively acts as a reducing agent in this way, but also contains Bi oxide powder rather than other reducing materials (coke powder, Fe—Si alloy powder, etc.). Since the rate is easy to adjust and it is easy to form into a wire, it is optimal as a powder to be mixed with Bi oxide powder. In addition, since the allowable range of Mn concentration is relatively wide in any steel type, it is not necessary to pay close attention to the increase in Mn concentration in molten steel due to the addition of Fe-Mn alloy powder, and it is easy to adjust the input amount. There are also advantages. As the Bi oxide powder, Bi 2 O 3 powder can be used.
[0017]
When the Bi oxide powder and the Fe—Mn alloy powder are used in combination, the Bi yield can be reliably increased by adjusting the mass ratio of these powders. Specifically, if the Bi oxide powder and the Fe—Mn alloy powder are in a mass ratio of (50:50) to (90:10), the Bi yield can be 40% or more.
[0018]
In order to further increase the Bi yield to 50% or more, it is preferable that the Bi oxide powder and the Fe—Mn alloy powder have a mass ratio of (70:30) to (85:15). Most preferably, a high yield of nearly 60% can be achieved by setting the mass ratio of Bi oxide powder and Fe—Mn alloy powder to 80:20.
[0019]
Bi oxides and Fe-Mn alloy powders can be mixed uniformly without scattering if both have a maximum particle size of 5 mm or less and an average particle size in the particle size distribution of 1 to 3 mm. preferable.
[0020]
In the present invention, the mixed powder is introduced into the molten steel in the form of a wire. In this way, the Bi oxide powder and the Fe-Mn alloy powder are surely introduced into the molten steel to improve the Bi yield, compared to the case where it is introduced in the form of pellets or blown in powder form. Can be made.
[0021]
By introducing the wire at a speed of 1.0 kg-Bi / (min · t) or more, the Bi yield can be increased. It is desirable to set the wire feeding speed to 1.1 kg-Bi / (min · t) or more because the Bi yield can be further improved. However, if the charging speed of the wire is too fast, the Bi concentration at the charging position will rise temporarily and Bi will easily evaporate, so the charging speed should be kept below 1.3 kg-Bi / (min · t). Is preferred.
[0022]
The method of the present invention does not prescribe the component composition of the target Bi steel. From the Bi-containing steel having a Bi concentration of 0.01% by mass and a very small amount of Bi to 0.3% by mass. Can be widely applied. Moreover, the Bi addition method of this invention is not influenced by components other than Bi in molten steel. For example, in addition to Bi, for production of Bi-containing steel satisfying C (carbon): 0.01 to 1% by mass, Mn: 0.05 to 2% by mass, Si: 0.2% by mass or less (including 0% by mass) Can be applied.
[0023]
【Example】
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. It is also possible to implement, and they are all included in the technical scope of the present invention.
[0024]
Bi 2 O 3 powder (average particle size: 2 mm) and Fe—Mn alloy powder (average particle size: 2 mm) were used, and the mass ratio of these Bi 2 O 3 powder and Fe—Mn alloy powder was (40:60). ) To (95: 5).
[0025]
The obtained mixed powder is coated with an iron skin to produce a wire (cross section: 11 mm × 5.3 mm square), and the molten steel after the molten steel treatment in the ladle (90 tons, C: 0.35) Mass%, Mn: 0.72 mass%, Si: 0.18 mass% included). At this time, Bi-containing steel was manufactured by changing the wire charging speed between 0.9 and 1.3 kg-Bi / (min · t).
[0026]
The Bi 2 O 3 powder used was 134 kg / 90 tons of molten steel, and the Fe—Mn alloy powder was 32 kg / 90 tons of molten steel. The iron-coated wire was obtained by stirring and mixing Bi 2 O 3 powder and Fe—Mn-based alloy powder with a drum mixer, and forming the wire while filling the resulting iron powder into the wire core.
[0027]
In this way, the Bi yield when the Bi-containing steel was melted was determined from the above formula (3). The result is shown in FIG. FIG. 1 is a graph showing the relationship between the mass ratio of the Fe—Mn alloy powder in the wire and the Bi yield according to the charging speed of the wire. From FIG. 1, it can be considered as follows.
[0028]
Bi yield can be increased by introducing a wire enclosing a mixed powder of Bi 2 O 3 powder and Fe—Mn alloy powder into molten steel, and in particular, Bi 2 O 3 powder and Fe—Mn alloy powder Bi yield can be reliably improved by making mass ratio into the range prescribed | regulated by this invention. As shown in FIG. 1, in order to increase the Bi yield to 40% or more, there are some fluctuations depending on the wire feeding speed, but the Bi 2 O 3 powder and the Fe—Mn alloy powder are roughly (50:50) to ( 90:10) is preferable. In order to further increase the Bi yield to 50% or more, the mass ratio is preferably about (70:30) to (85:15).
[0029]
As for the wire feeding speed, it can be seen from FIG. 1 that even when a wire having the same mass ratio of Bi 2 O 3 powder and Fe—Mn alloy powder is used, the yield tends to increase as the wire feeding speed increases. Thus, it can be seen that a high yield can be achieved by setting it to 1.0 kg-Bi / (min · t) or more. However, if the wire feeding speed is too high at 1.3 kg-Bi / (min · t), the yield will be lowered, so the upper limit is kept at 1.2 kg-Bi / (min · t) or less. It is preferable to keep it.
[0030]
As can be seen from FIG. 1, in order to increase the Bi yield to the maximum value, the mixing ratio of Bi 2 O 3 powder and Fe—Mn alloy powder is set to 80:20, and the charging speed of the wire is set to 1.2 kg. -Bi / (min · t) is most preferable.
[0031]
In addition, when Bi metal powder was added independently, Bi yield was 0%. When Bi 2 O 3 powder was added alone, the Bi yield was 5% or less.
[0032]
【The invention's effect】
The present invention is configured as described above, and Bi, which is a low melting point element, can be added to molten steel at a high yield without evaporating. Therefore, Bi in the molten steel can be efficiently increased to a desired concentration. .
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the mass ratio of Fe—Mn-based alloy powder in a wire and Bi yield according to the input rate of the wire.
Claims (4)
Ｂｉ酸化物粉末：Ｆｅ−Ｍｎ系合金粉末＝(５０：５０)〜(９０：１０) …(１)The Bi addition method to molten steel of Claim 1 which mixes the said Bi oxide powder and Fe-Mn type alloy powder by the mass ratio shown to following (1).
Bi oxide powder: Fe—Mn alloy powder = (50:50) to (90:10) (1)
Ｂｉ酸化物粉末：Ｆｅ−Ｍｎ系合金粉末＝(７０：３０)〜(８５：１５) …(２)The method for adding Bi to molten steel according to claim 2, wherein the mass ratio is in a range shown in (2) below.
Bi oxide powder: Fe—Mn alloy powder = (70:30) to (85:15) (2)
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| CN111500822A (en) * | 2020-06-03 | 2020-08-07 | 马鞍山市兴达冶金新材料有限公司 | Bismuth-iron core-spun yarn and production process thereof |
| CN114350891A (en) * | 2021-12-14 | 2022-04-15 | 鞍钢集团北京研究院有限公司 | A bismuth-manganese-ferroalloy cored wire for preparing bismuth-containing free-cutting steel |
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