JPH024911A - Method for refining ultra low carbon steel - Google Patents
Method for refining ultra low carbon steelInfo
- Publication number
- JPH024911A JPH024911A JP15345488A JP15345488A JPH024911A JP H024911 A JPH024911 A JP H024911A JP 15345488 A JP15345488 A JP 15345488A JP 15345488 A JP15345488 A JP 15345488A JP H024911 A JPH024911 A JP H024911A
- Authority
- JP
- Japan
- Prior art keywords
- molten steel
- gas
- steel
- carbon
- ladle
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000000034 method Methods 0.000 title claims abstract description 23
- 229910001209 Low-carbon steel Inorganic materials 0.000 title abstract description 17
- 238000007670 refining Methods 0.000 title description 2
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 112
- 239000010959 steel Substances 0.000 claims abstract description 112
- 239000007789 gas Substances 0.000 claims abstract description 42
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 33
- 239000002893 slag Substances 0.000 claims abstract description 28
- 230000036961 partial effect Effects 0.000 claims abstract description 20
- 230000001590 oxidative effect Effects 0.000 claims abstract description 14
- 238000007664 blowing Methods 0.000 claims abstract description 11
- 230000003647 oxidation Effects 0.000 claims abstract description 7
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 7
- 239000011261 inert gas Substances 0.000 claims abstract description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 32
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 30
- 239000001301 oxygen Substances 0.000 claims description 30
- 229910052760 oxygen Inorganic materials 0.000 claims description 30
- 238000002844 melting Methods 0.000 claims description 4
- 230000008018 melting Effects 0.000 claims description 4
- 238000005516 engineering process Methods 0.000 claims 1
- 238000005261 decarburization Methods 0.000 abstract description 22
- 230000002829 reductive effect Effects 0.000 abstract description 4
- 230000001105 regulatory effect Effects 0.000 abstract 1
- 230000000452 restraining effect Effects 0.000 abstract 1
- 238000007654 immersion Methods 0.000 description 17
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 16
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 description 11
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 10
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 9
- 229910052748 manganese Inorganic materials 0.000 description 9
- 239000011572 manganese Substances 0.000 description 9
- 229910052786 argon Inorganic materials 0.000 description 8
- 229910001882 dioxygen Inorganic materials 0.000 description 8
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 7
- 229910002091 carbon monoxide Inorganic materials 0.000 description 6
- 238000006243 chemical reaction Methods 0.000 description 6
- 229910052742 iron Inorganic materials 0.000 description 5
- 229910052751 metal Inorganic materials 0.000 description 5
- 239000002184 metal Substances 0.000 description 5
- 238000009849 vacuum degassing Methods 0.000 description 5
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000010079 rubber tapping Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 230000002411 adverse Effects 0.000 description 2
- 229910002090 carbon oxide Inorganic materials 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- AMWRITDGCCNYAT-UHFFFAOYSA-L hydroxy(oxo)manganese;manganese Chemical compound [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000005507 spraying Methods 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 1
- JZUFKLXOESDKRF-UHFFFAOYSA-N Chlorothiazide Chemical compound C1=C(Cl)C(S(=O)(=O)N)=CC2=C1NCNS2(=O)=O JZUFKLXOESDKRF-UHFFFAOYSA-N 0.000 description 1
- 239000004480 active ingredient Substances 0.000 description 1
- 239000003570 air Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910002092 carbon dioxide Inorganic materials 0.000 description 1
- 239000001569 carbon dioxide Substances 0.000 description 1
- -1 carbon oxide Chemical compound 0.000 description 1
- 238000007872 degassing Methods 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000007865 diluting Methods 0.000 description 1
- 229910001873 dinitrogen Inorganic materials 0.000 description 1
- 230000003628 erosive effect Effects 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000007935 neutral effect Effects 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 239000011819 refractory material Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 230000003068 static effect Effects 0.000 description 1
Landscapes
- Treatment Of Steel In Its Molten State (AREA)
Abstract
Description
（産業上の利用分野）
本発明は極低炭素鋼の溶製方法に関するものである。
（従来の技術）
従来、極低炭素鋼を溶製するためには、転炉等で精練し
た溶鋼を未脱酸状態で取鍋に受鋼し、ＲＩ］真空脱ガス
装置等で溶鋼を真空下に配置し、溶鋼中の炭素と酸素と
を反応させる方法で脱炭処理した後、最終目標の溶鋼成
分になるように、合金を添加する溶製方法か広く行われ
ている。
その際、脱炭速度をより短縮するため、真空脱ガス装置
において酸素、あるいは−酸化炭素等のガスまたは酸化
鉄等の粉末を添加する方法（たとえば特開昭４９−３４
４１４、特開昭５１−１５１２１１゜特開昭５１−１５
１２１２ ）、反応界面積を増大するため大量のガスを
吹き込む方法（特開昭５２５６４１）等が開発されてい
る。
（発明が解決しようとする課題）
一般に、溶鋼を脱炭する際、（１）式で示すように溶鋼
中の炭素と溶鋼中の酸素との反応によりＣＯガスを生成
させ、ＣＯガスを気相側に除去する方法か採用されてい
る。
Ｃ十 〇−Ｇｏ ・ ・ ・ ・
・ （１）脱炭を容騙にするためには、溶鋼中に酸素
か必要であり、溶鋼中の酸素を増加させる方法として、
−・般に純酸素」二次転炉方式が採用されている。
しかし、この方法では溶鋼中の炭素含有量が０．０２％
以下になると脱炭が進行しなくなり、目的の極低炭素鋼
が溶製できないばかりか、寧ろ、鉄の酸化が生じ、溶鋼
歩留の低下、および有効な成分であるマンガン含有量の
低下を招く等の問題があった。
そこで、鉄の酸化よりも、溶鋼中の炭素の酸化を優先さ
せるため、気体酸素あるいは固体酸素を溶鋼中に供給し
、溶鋼中の酸素を増加させると同時に、処理溶鋼を真空
下に置き、気体側の一酸化炭素の分圧を低下させること
により、（１）式の反応を右側に進行させる方法が採用
されている。
つまり、（２）式でＰｃｏを小さくすれば、同じ(Industrial Application Field) The present invention relates to a method for producing ultra-low carbon steel. (Prior art) Conventionally, in order to melt ultra-low carbon steel, molten steel refined in a converter, etc. is received in a ladle in an undeoxidized state, and then the molten steel is vacuumed using a vacuum degassing device (RI), etc. A widely used method is to decarburize the molten steel by placing it at the bottom and reacting the carbon and oxygen in the molten steel, and then adding an alloy to achieve the final target molten steel composition. At that time, in order to further shorten the decarburization rate, a method of adding oxygen, gas such as carbon oxide, or powder such as iron oxide in a vacuum degassing device (for example, JP-A No. 49-34
414, JP 51-151211° JP 51-15
1212), a method of blowing a large amount of gas in order to increase the reaction interface area (Japanese Patent Application Laid-Open No. 525641), etc. have been developed. (Problems to be Solved by the Invention) Generally, when decarburizing molten steel, CO gas is generated by a reaction between carbon in the molten steel and oxygen in the molten steel, and the CO gas is released into the gas phase. The side removal method is adopted. C10-Go ・ ・ ・ ・
・ (1) Oxygen is necessary in molten steel to make decarburization a reality, and as a method to increase oxygen in molten steel,
- Generally, a "pure oxygen" secondary converter method is adopted. However, with this method, the carbon content in molten steel is 0.02%.
If the temperature is below, decarburization will not proceed and the desired ultra-low carbon steel will not be produced, but the iron will oxidize, leading to a decrease in the yield of molten steel and a decrease in the manganese content, which is an effective component. There were other problems. Therefore, in order to give priority to the oxidation of carbon in the molten steel over the oxidation of iron, gaseous oxygen or solid oxygen is supplied into the molten steel to increase the oxygen in the molten steel, and at the same time, the treated molten steel is placed under a vacuum to A method has been adopted in which the reaction of equation (1) proceeds to the right by lowering the partial pressure of carbon monoxide on the side. In other words, if Pco is reduced using equation (2), the same
〔０〕
であっても〔Ｃ〕を小さくすることが可能となる。
Ｐｃｏ ガス側の一酸化炭素カスの分圧〔Ｃ〕 溶鋼
中の炭素濃度[0]
Even if it is, [C] can be made small. Pco Partial pressure of carbon monoxide residue on gas side [C] Carbon concentration in molten steel
〔０〕 溶鋼中の酸素濃度
Ｋ 平衡定数
１−記方法によれば、溶鋼中の炭素含有量は０．０２％
以下に低下させることが可能であり、且つ、鉄の酸化も
抑制できる等の観点で有利であるため、工業的にはＲ１
１真空脱ガス装置等による極低炭素ｆｉｉ？１の溶製方
法が広く採用されている。
しかし、この方法は、高価な真空脱カス装置が必“冴な
ばかりでなく、耐火物等の溶損のため、処理費用が高く
なる等の問題があった。
本発明は、に記のような問題点を解決し、安価な設備で
、従来行われている高価な真空脱カス装置で溶製すると
同等の極低炭素鋼の溶製方法を提供するために開発され
たものである。
（課題を解決するだめの手段）
本発明は、取鍋固溶鋼表面上酸化性スラグの占める面積
を、溶鋼表面積の２０％以下に減少且しめた炭素含有量
０．０４〜０．０２％の溶鋼表面上に、酸素分圧０５〜
０．０１気圧に調整した酸化性ガスと不活性ガスとの混
合ガスを吹きつけ、溶鋼の酸化を抑制しつつ、溶鋼を脱
炭し、炭素含有量０．０２％以下の溶鋼を溶製する極低
炭素鋼の溶製方法である。
（作 用）
本発明者らは、種々の実験を重ねてきた結果、極低炭素
鋼を溶製する場合、必ずしも溶鋼表面を高価な真空脱ガ
ス設備を用いて、高真空下に保つ必要はなく、溶鋼中の
炭素と溶鋼中の酸素が反応する気相側界面の一酸化炭素
ガスの分圧を低下させれば良いことを見出した。
つまり、溶鋼中の炭素と溶鋼中の酸素が反応する界面の
気相側の一酸化炭素ガス濃度を他のガスで希釈すれば極
低炭素鋼の溶製が可能であることを見出した。
然らば、純酸素１−吹転炉法による脱炭反応の場合、多
量の純酸素ガスを溶鋼表面上に供給しているので、気相
側の一酸化炭素ガスの分圧は低いと考えられるのに、何
故、溶鋼中の炭素含有量が０．０２％以上になると脱炭
が進行しなくなり、目的の極低炭素鋼が溶製できないば
かりか、寧ろ、鉄の酸化が生じ、溶鋼歩留の低下、およ
び有効な成分であるマンガン含有量の低下を招くかにつ
いて、再度種々の実験を重ねてきた。
その結果、純酸素上吹転炉法では一般に、脱炭と同時に
脱珪、脱燐、脱硫等のため、溶鋼表面上に精錬用スラグ
を置き精錬処理を行っていること、及び純酸素ガスを溶
鋼に供給していることが脱炭停滞の原因であることが分
かった。
つまり、このように溶鋼表面」−にスラグが存在する場
合、溶鋼中の炭素と酸素が反応して、−酸化炭素ガスの
気泡を生成させるには、生成する一酸化炭素ガスの分圧
は大気圧とスラグの静圧との和より大きくなる必要があ
る。従って、転炉法では通常、ガス側の一酸化炭素ガス
の分圧は小さいにも関わらず、溶鋼中炭素含有量が０．
０２％以下になると脱炭が進行しなくな一〕でいると考
えられる１゜
又、通常、転炉では炭素含有量４％程度の溶銑から精錬
しており、処理時間を短くリーるため、純酸素ガスを供
給しているが、極低炭素鋼を溶製するような場合は、炭
素含有量に見合って、酸素供給速度は小さくて良いこと
が分かった。寧ろ、酸素供給速度が大き過ぎると鉄およ
び溶鋼中の有効成分であるマンガンが酸化し、その酸化
鉄および酸化マンガンが」−述したスラグと同様の理由
により、悪影響を生じさせること、および過剰酸素に上
り脱炭反応ザイドの減少を招くことがわかった。
以上のごとき検討結果から、取鍋内情鋼表面−Ｊ−酸化
性スラグの占める面積を溶鋼表面積の２０％以下に減少
せしめた炭素含有量０．０４〜０．０２％の溶鋼表面上
に、酸素分圧０．５〜０．ＯＩ気圧に調整した酸化性ガ
スと４活性ガスとの混合ガスを吹きつけ、溶鋼の酸化を
抑制しつつ、溶鋼を脱炭すれば、炭素含有ｆｆ１０．０
２％以下の極低炭素鋼の溶製か可能であることを見出し
た。
本発明の要件である取鍋内温鋼表面Ｉ−酸化性スラグの
占める面積を、溶鋼表面積の２０％以下に減少せしめる
理由は、２０％以−１−の面積比では酸化性スラグによ
る溶鋼への酸素供給のため、吹きつけガスの酸素分圧だ
けでは溶鋼の酸素が抑制できなくなるためである、。
尚、面積比とは溶鋼表面を目視観察した場合、裸湯とな
っている溶鋼表面積と酸化性スラグで被覆されている溶
鋼表面積の合計溶鋼表面積に対して、酸化性スラグで被
覆されている溶鋼表面積の百分率である。
又、酸素分圧を０５〜０．０１気圧に調整した混合ガス
を用いる理由は０５気圧以上では鉄お上び溶鋼中のマン
ガンを酸化させ、酸化性スラグと同様の理由により、悪
影響を生じることおよび、過剰酸素に上り脱炭反応サイ
ドの減少を招くためであり、０．０１気圧以下では脱炭
に必要な酸素が不足するため、本発明では酸素分圧を０
．５〜０．０１気圧とした。
取鍋的溶鋼表面上酸化性スラグの占める面積を溶鋼表面
積の２０％以下に減少せしめる方法は溶鋼内に浸漬管を
浸漬し、浸漬管内の転炉スラグを浸漬管の外に排出する
ものであるが、」−記方法以外に、浸漬管内の転炉スラ
グを減少せしめる方法としては、出鋼時にスラグボール
、スラグストッパー等により取鍋内へのスラグ流失を抑
えるか、あるいは出鋼した後、取鍋内からスラグドラッ
ガー等を用い取鍋の外に排出しても良い。
（実施例）
以下実施例を第一図を用いて詳細に説明する。
実施例Ｉに用いた処理部溶鋼ｌは、２５０Ｌ転炉で溶銑
から炭素０．０４％、マンガン０．２５％に溶製し７た
溶鋼を取鍋２に未脱酸状態で出鋼したちのであり、取鍋
内溶鋼温度は１６３５℃であった１、その後、取鍋下部
に配置したポーラスプラグ４からアルゴンガスを２５
Ｎｍ３／ｈｒ吹き込みつつ、溶鋼内に浸漬管３を浸漬し
、浸漬管内の転炉スラグ５を浸漬管の外側に排出した。
これにより、浸１１１１管内の溶鋼表面は、面積比で８
０％か裸湯となった。
つぎに、溶鋼表面から１ｍの位置に配置した上吹きラン
ス６を用い、酸素分圧を０．１気圧に調整した酸素ガス
とアルゴンの混合ガスを、流量２５０００ Ｎｍ３／ｈ
ｒで溶鋼表面に吹きつけ、脱炭処理を２０分間行った。
なお上記以外に、酸素分圧を調整したガスとしては、酸
化性ガスとして酸素ガス以外に二酸化炭素ガス、空気あ
るいは水蒸気を用いても良い。また、中性ガスとしては
、アルゴンガス以外に窒素ガスを用いても良い。
脱炭処理後の溶鋼の炭素含有量は０．００５％、マンガ
ンは０．２１％、溶鋼温度１６０５℃であった。
実施例２に用いた処理面溶鋼ｌは、２５０を転炉で溶銑
から炭素０．０４％、マンガン０，２５％に溶製した溶
鋼を取鍋２に未脱酸状態で出鋼したものであり、取鍋内
溶鋼温度は１６３５℃であった。その後、取鍋下部に配
置したポーラスプラグ４からアルゴンガスを２５ Ｎｍ
’／ｈｒ吹き込みつつ、溶鋼内に浸漬管３を浸漬し、浸
漬管内の転炉スラグ５を浸漬管の外側に排出した。これ
により、浸漬管内の溶鋼表面は、面積比で８０％が裸湯
となった。
つぎに、溶鋼表面から１ｍの位置に配置した」二吹きラ
ンス６を用い、酸素分圧を０．０２気圧に調整した酸素
ガスとアルゴンの混合ガスを、流ｒｌｔ２５０００ Ｎ
ｍ３／ｈｒで溶鋼表面に吹きつけ、脱炭処理を３０分間
行った。
脱炭処理後の溶鋼の炭素含有量は０．００３％、マンガ
ンは０．２３％、溶鋼温度１６００℃であった。
比較例Ｉに用いた処理面溶鋼１は、２５０を転炉で溶銑
から炭素０．０４％、マンガン０．２５％に溶製した溶
鋼を取鍋２に未脱酸状態で出鋼したものであり、取鍋内
溶鋼温度は１６３５℃であった。その後、取鍋下部に配
置したポーラスプラグ４からアルゴンガスを２５ Ｎｍ
’／ｈｒ吹き込みつつ、溶鋼内に浸漬管３を浸漬し、浸
漬管内の転炉スラグ５を浸漬管の外側に排出した。これ
により、浸漬管内の溶鋼表面は、面積比で８０％が裸湯
となった。
つぎに、溶鋼表面から１ｍの位置に配置した−に吹きラ
ンス６を用い、酸素分圧を０．６気圧に調整した酸素ガ
スとアルゴンの混合ガスを、流量２５０００ Ｎｍ３／
ｈｒで溶鋼表面に吹きつけ、脱炭処理を２０分間行った
。
脱炭処理後の溶鋼の炭素含有量は０．０２１％、マンガ
ンは０．１７％、溶鋼温度１６１Ｏ℃であった。
比較例２に用いた処理面溶鋼ｌは、２５０Ｌ転炉で溶銑
から炭素０．０４％、マンガン０．２５％に溶製した溶
鋼を取鍋２に未脱酸状態で出鋼したものであり、取鍋内
溶鋼温度は１６３５℃であった。
つぎに、取鍋内に３０ｍｍ厚の転炉スラグを残留させた
まま、溶鋼表面から１ｍの位置に配置したト吹きランス
６を用い、酸素分圧を０．１気圧に調整した酸素ガスと
アルゴンの混合ガスを、流量２５０００ Ｎｍ３／ｈｒ
で溶鋼表面に吹きつけ、脱炭処理を２０分間行った。
脱炭処理後の溶鋼の炭素含有量は０．０２２％、マンガ
ンは０，１８％、溶鋼温度１６０５℃であった。
以上の如く、本発明方法を溶鋼脱炭処理に適用すること
により、安価に且つ容易に極低炭素鋼の溶製が可能にな
った。
（発明の効果）
本発明によれば、従来の極低炭素鋼の溶製法と比較して
、高価な脱ガス設備等の改造及び新設はほとんどなく、
弔に溶鋼表面のスラグを減少せしめること、吹きつけ混
合ガスの酸素分圧を調整することにより、３０分間以内
で、通常のＲＨ真空脱ガス装置を用いた場合と同様に炭
素含有量５０ｐｐｍという極低炭素鋼の溶製も可能とな
った。このように本発明によれば、従来法と比較して容
易かつ、確実に溶鋼の脱炭ができる。また、工業的規模
で正確な脱炭ができる等の優れた効果が得られ第一図は
本発明の実施方法の一例を示す説明図である。
１・・・・・溶鋼
２ ・ ・ ・ ・
３・・争・
５ ・ ・ ・ ・
６ ・ ・ ・ ・
出 願
升 理
・取鍋
・浸漬管
・転炉スラグ
・上吹ランス
人
新日本製鐵株式会社
士
第１図[0] Oxygen concentration K in molten steel According to the equilibrium constant 1-notation method, the carbon content in molten steel is 0.02%
Industrially, it is possible to reduce R1 to
1 Ultra-low carbon fii using vacuum degassing equipment, etc.? The melting method No. 1 is widely used. However, this method not only requires expensive vacuum descaling equipment, but also has problems such as high processing costs due to erosion of refractories. It was developed to solve these problems and to provide a method for producing ultra-low carbon steel using inexpensive equipment that is equivalent to the conventional method of producing ultra-low carbon steel using expensive vacuum descaling equipment. Means for Solving the Problems) The present invention provides molten steel with a carbon content of 0.04 to 0.02%, which reduces the area occupied by oxidizing slag on the surface of the solid-molten steel in a ladle to 20% or less of the surface area of the molten steel. On the surface, oxygen partial pressure 05 ~
A mixed gas of oxidizing gas and inert gas adjusted to 0.01 atm is blown to decarburize the molten steel while suppressing oxidation of the molten steel, producing molten steel with a carbon content of 0.02% or less. This is a method for producing ultra-low carbon steel. (Function) As a result of various experiments, the present inventors have found that when producing ultra-low carbon steel, it is not necessarily necessary to keep the surface of the molten steel under high vacuum using expensive vacuum degassing equipment. Instead, they discovered that it is sufficient to reduce the partial pressure of carbon monoxide gas at the gas-phase interface where carbon in molten steel and oxygen in molten steel react. In other words, we have found that it is possible to produce ultra-low carbon steel by diluting the carbon monoxide gas concentration on the gas phase side of the interface where carbon in molten steel and oxygen in molten steel react with another gas. Therefore, in the case of the decarburization reaction using the pure oxygen 1-blown converter method, a large amount of pure oxygen gas is supplied onto the surface of the molten steel, so the partial pressure of carbon monoxide gas on the gas phase side is considered to be low. However, when the carbon content in molten steel exceeds 0.02%, decarburization does not proceed, and not only the desired ultra-low carbon steel cannot be produced, but oxidation of the iron occurs, and the progress of molten steel slows down. We have conducted various experiments again to determine whether this would lead to a decrease in the retention and the content of manganese, which is an effective component. As a result, in the pure oxygen top-blowing converter process, refining slag is generally placed on the surface of the molten steel for desiliconization, dephosphorization, desulfurization, etc. at the same time as decarburization, and pure oxygen gas is It was found that the supply to molten steel was the cause of stagnation in decarburization. In other words, when slag is present on the molten steel surface, the partial pressure of the carbon monoxide gas produced must be large enough for the carbon and oxygen in the molten steel to react and produce carbon oxide gas bubbles. It needs to be greater than the sum of the atmospheric pressure and the static pressure of the slag. Therefore, in the converter method, although the partial pressure of carbon monoxide gas on the gas side is small, the carbon content in the molten steel is usually 0.
It is thought that decarburization will not proceed if the carbon content is less than 0.02%.In addition, normally converters are refined from hot metal with a carbon content of about 4%, and in order to shorten the processing time, Although pure oxygen gas is supplied, it has been found that when producing ultra-low carbon steel, the oxygen supply rate can be kept low, commensurate with the carbon content. On the contrary, if the oxygen supply rate is too high, manganese, which is an active ingredient in iron and molten steel, will oxidize, and the iron oxide and manganese oxide will cause adverse effects for the same reason as the slag mentioned above, and excessive oxygen It was found that the decarburization reaction led to a decrease in zide. From the above study results, it was found that oxygen Partial pressure 0.5~0. If molten steel is decarburized by blowing a mixed gas of oxidizing gas and 4 active gases adjusted to OI pressure and suppressing oxidation of molten steel, carbon content ff10.0
We have discovered that it is possible to produce ultra-low carbon steel with a carbon content of 2% or less. The reason for reducing the area occupied by oxidizing slag to 20% or less of the surface area of molten steel, which is a requirement of the present invention, is that if the area ratio is 20% or more, oxidizing slag will cause molten steel to This is because oxygen in the molten steel cannot be suppressed by the oxygen partial pressure of the blown gas alone. The area ratio refers to the area ratio of the molten steel covered with oxidizing slag to the total molten steel surface area of the bare molten steel surface area and the molten steel surface area covered with oxidizing slag. It is a percentage of the surface area. Also, the reason for using a mixed gas with an oxygen partial pressure adjusted to 0.5 - 0.01 atm is that above 0.5 atm, the manganese in the iron and molten steel will oxidize, causing an adverse effect for the same reason as oxidizing slag. This is because excess oxygen builds up and causes a decrease in the decarburization reaction side.If the pressure is below 0.01 atm, the oxygen necessary for decarburization is insufficient, so in the present invention, the oxygen partial pressure is reduced to 0.
．． The pressure was 5 to 0.01 atm. A method for reducing the area occupied by oxidizing slag on the surface of molten steel in a ladle to less than 20% of the surface area of molten steel is to immerse an immersion tube in the molten steel and discharge the converter slag inside the immersion tube to the outside of the immersion tube. However, in addition to the method mentioned above, there are two ways to reduce converter slag in the immersion tube: use a slag ball, slag stopper, etc. to prevent slag from flowing into the ladle during tapping, or remove the slag after tapping. It is also possible to discharge the slag from inside the ladle to the outside of the ladle using a slag dragger or the like. (Example) Hereinafter, an example will be described in detail using FIG. The molten steel in the treatment section used in Example I was prepared by melting hot metal into 0.04% carbon and 0.25% manganese in a 250L converter and tapping it into a ladle 2 in an undeoxidized state. The temperature of the molten steel in the ladle was 1635°C1, and then argon gas was pumped in at 25°C from the porous plug 4 placed at the bottom of the ladle.
The immersion tube 3 was immersed in the molten steel while blowing Nm3/hr into the molten steel, and the converter slag 5 in the immersion tube was discharged to the outside of the immersion tube. As a result, the molten steel surface inside the immersion pipe 1111 has an area ratio of 8
It was 0% naked bath. Next, using a top blowing lance 6 placed 1 m from the molten steel surface, a mixed gas of oxygen gas and argon whose oxygen partial pressure was adjusted to 0.1 atm was supplied at a flow rate of 25000 Nm3/h.
The decarburization treatment was carried out for 20 minutes by spraying the molten steel onto the surface of the molten steel. In addition to the above, as the gas whose oxygen partial pressure is adjusted, carbon dioxide gas, air, or water vapor may be used as the oxidizing gas other than oxygen gas. Further, as the neutral gas, nitrogen gas may be used instead of argon gas. The carbon content of the molten steel after decarburization treatment was 0.005%, the manganese content was 0.21%, and the molten steel temperature was 1605°C. The treated molten steel l used in Example 2 was molten steel 250, which was melted from hot metal in a converter to 0.04% carbon and 0.25% manganese, and tapped into a ladle 2 in an undeoxidized state. The temperature of the molten steel in the ladle was 1635°C. After that, 25 Nm of argon gas was supplied from the porous plug 4 placed at the bottom of the ladle.
The immersion tube 3 was immersed in the molten steel while blowing the molten steel into the molten steel, and the converter slag 5 in the immersion tube was discharged to the outside of the immersion tube. As a result, 80% of the surface area of the molten steel in the immersion tube was bare water. Next, using a two-blow lance 6 placed 1 m from the surface of the molten steel, a mixed gas of oxygen gas and argon with an oxygen partial pressure adjusted to 0.02 atm was flowed at a flow rate of 25,000 N.
It was sprayed onto the surface of the molten steel at a rate of m3/hr to perform decarburization treatment for 30 minutes. The carbon content of the molten steel after decarburization treatment was 0.003%, the manganese content was 0.23%, and the molten steel temperature was 1600°C. Treated surface molten steel 1 used in Comparative Example I is molten steel molten steel 250 made from hot metal in a converter to 0.04% carbon and 0.25% manganese and tapped into ladle 2 in an undeoxidized state. The temperature of the molten steel in the ladle was 1635°C. After that, 25 Nm of argon gas was supplied from the porous plug 4 placed at the bottom of the ladle.
The immersion tube 3 was immersed in the molten steel while blowing the molten steel into the molten steel, and the converter slag 5 in the immersion tube was discharged to the outside of the immersion tube. As a result, 80% of the surface area of the molten steel in the immersion tube was bare water. Next, using a blowing lance 6 placed 1 m from the surface of the molten steel, a mixed gas of oxygen gas and argon with an oxygen partial pressure adjusted to 0.6 atm was introduced at a flow rate of 25000 Nm3/
The decarburization treatment was carried out for 20 minutes by spraying the molten steel onto the surface of the molten steel. The carbon content of the molten steel after decarburization treatment was 0.021%, the manganese content was 0.17%, and the molten steel temperature was 1610°C. The treated surface molten steel l used in Comparative Example 2 was molten steel melted into 0.04% carbon and 0.25% manganese from hot metal in a 250L converter and tapped into ladle 2 in an undeoxidized state. The temperature of the molten steel in the ladle was 1635°C. Next, while leaving the 30 mm thick converter slag in the ladle, using a blow lance 6 placed 1 m from the molten steel surface, oxygen gas and argon gas whose oxygen partial pressure was adjusted to 0.1 atm. mixed gas at a flow rate of 25000 Nm3/hr
was sprayed onto the surface of the molten steel to perform decarburization treatment for 20 minutes. The carbon content of the molten steel after decarburization treatment was 0.022%, the manganese content was 0.18%, and the molten steel temperature was 1605°C. As described above, by applying the method of the present invention to the decarburization treatment of molten steel, it has become possible to easily and inexpensively produce ultra-low carbon steel. (Effects of the Invention) According to the present invention, compared to the conventional melting method for ultra-low carbon steel, there is almost no need for modification or new installation of expensive degassing equipment, etc.
By reducing the slag on the surface of the molten steel and adjusting the oxygen partial pressure of the blown mixed gas, the carbon content can be reduced to 50 ppm within 30 minutes, the same as when using a normal RH vacuum degassing device. It has also become possible to produce low carbon steel. As described above, according to the present invention, molten steel can be decarburized more easily and reliably than conventional methods. In addition, excellent effects such as accurate decarburization on an industrial scale can be obtained. FIG. 1 is an explanatory diagram showing an example of the method of implementing the present invention. 1... Molten steel 2 ・ ・ ・ ・ 3.・ Conflict ・ 5 ・ ・ ・ ・ 6 ・ ・ ・ ・ Application process, ladle, immersion tube, converter slag, top-blown lance person Nippon Steel Shi Co., Ltd. Figure 1
Claims (1)
面積の２０％以下に減少せしめた炭素含有量０．０４〜
０．０２％の溶鋼表面上に、酸素分圧０．５〜０．０１
気圧に調整した酸化性ガスと不活性ガスとの混合ガスを
吹きつけ、溶鋼の酸化を抑制しつつ、溶鋼を脱炭し、炭
素含有量０．０２％以下の溶鋼を溶製する極低炭素鋼の
溶製方法。A carbon content of 0.04 to 0.04 that reduces the area occupied by oxidizing slag on the surface of the molten steel in the ladle to 20% or less of the surface area of the molten steel.
Oxygen partial pressure 0.5-0.01 on the surface of 0.02% molten steel
Ultra-low carbon technology that decarburizes molten steel by blowing a mixed gas of oxidizing gas and inert gas adjusted to atmospheric pressure to suppress oxidation of molten steel and produce molten steel with a carbon content of 0.02% or less. Steel melting method.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15345488A JPH024911A (en) | 1988-06-23 | 1988-06-23 | Method for refining ultra low carbon steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15345488A JPH024911A (en) | 1988-06-23 | 1988-06-23 | Method for refining ultra low carbon steel |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH024911A true JPH024911A (en) | 1990-01-09 |
| JPH0512410B2 JPH0512410B2 (en) | 1993-02-18 |
Family
ID=15562909
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP15345488A Granted JPH024911A (en) | 1988-06-23 | 1988-06-23 | Method for refining ultra low carbon steel |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH024911A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH04362115A (en) * | 1991-06-06 | 1992-12-15 | Nippon Steel Corp | Decarburizing method for molten steel |
| US7389061B2 (en) | 2004-02-27 | 2008-06-17 | Konica Minolta Business Technologies, Inc. | Cleaning device and image forming apparatus having a cleaning brush and a collection roller that move in the same direction at a contact area therebetween |
-
1988
- 1988-06-23 JP JP15345488A patent/JPH024911A/en active Granted
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH04362115A (en) * | 1991-06-06 | 1992-12-15 | Nippon Steel Corp | Decarburizing method for molten steel |
| US7389061B2 (en) | 2004-02-27 | 2008-06-17 | Konica Minolta Business Technologies, Inc. | Cleaning device and image forming apparatus having a cleaning brush and a collection roller that move in the same direction at a contact area therebetween |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0512410B2 (en) | 1993-02-18 |
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