JPH05105936A - Method of decarburizing molten steel containing ultra low carbon chromium - Google Patents
Method of decarburizing molten steel containing ultra low carbon chromiumInfo
- Publication number
- JPH05105936A JPH05105936A JP26505391A JP26505391A JPH05105936A JP H05105936 A JPH05105936 A JP H05105936A JP 26505391 A JP26505391 A JP 26505391A JP 26505391 A JP26505391 A JP 26505391A JP H05105936 A JPH05105936 A JP H05105936A
- Authority
- JP
- Japan
- Prior art keywords
- molten steel
- chromium
- ladle
- low carbon
- oxygen
- 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
- 229910000831 Steel Inorganic materials 0.000 title claims abstract description 53
- 239000010959 steel Substances 0.000 title claims abstract description 53
- 238000000034 method Methods 0.000 title claims abstract description 21
- FXNGWBDIVIGISM-UHFFFAOYSA-N methylidynechromium Chemical compound [Cr]#[C] FXNGWBDIVIGISM-UHFFFAOYSA-N 0.000 title claims abstract description 7
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 claims abstract description 36
- 238000005261 decarburization Methods 0.000 claims abstract description 31
- WGLPBDUCMAPZCE-UHFFFAOYSA-N Trioxochromium Chemical compound O=[Cr](=O)=O WGLPBDUCMAPZCE-UHFFFAOYSA-N 0.000 claims abstract description 29
- 229910000423 chromium oxide Inorganic materials 0.000 claims abstract description 29
- 239000011651 chromium Substances 0.000 claims abstract description 26
- 229910001882 dioxygen Inorganic materials 0.000 claims abstract description 25
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical group [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 20
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 20
- 239000007789 gas Substances 0.000 claims abstract description 19
- 238000003756 stirring Methods 0.000 claims abstract description 19
- 238000007598 dipping method Methods 0.000 claims abstract description 17
- 238000007670 refining Methods 0.000 claims abstract description 15
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 8
- 239000000956 alloy Substances 0.000 claims abstract description 8
- 238000007664 blowing Methods 0.000 claims description 17
- 229910052760 oxygen Inorganic materials 0.000 claims description 12
- 239000001301 oxygen Substances 0.000 claims description 12
- 239000002253 acid Substances 0.000 claims description 7
- 239000011261 inert gas Substances 0.000 claims description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims 2
- UOUJSJZBMCDAEU-UHFFFAOYSA-N chromium(3+);oxygen(2-) Chemical class [O-2].[O-2].[O-2].[Cr+3].[Cr+3] UOUJSJZBMCDAEU-UHFFFAOYSA-N 0.000 claims 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 abstract description 20
- 229910052804 chromium Inorganic materials 0.000 abstract description 20
- 238000007254 oxidation reaction Methods 0.000 abstract description 10
- 230000003647 oxidation Effects 0.000 abstract description 8
- 238000007654 immersion Methods 0.000 abstract description 5
- 239000002893 slag Substances 0.000 description 10
- 238000005507 spraying Methods 0.000 description 9
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 8
- 229910001209 Low-carbon steel Inorganic materials 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 229910052742 iron Inorganic materials 0.000 description 4
- 238000002844 melting Methods 0.000 description 4
- 230000008018 melting Effects 0.000 description 4
- 238000002347 injection Methods 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- 238000004581 coalescence Methods 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 238000005187 foaming Methods 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- QSHDDOUJBYECFT-UHFFFAOYSA-N mercury Chemical compound [Hg] QSHDDOUJBYECFT-UHFFFAOYSA-N 0.000 description 1
- 229910052753 mercury Inorganic materials 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 238000009489 vacuum treatment Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Landscapes
- Treatment Of Steel In Its Molten State (AREA)
Abstract
(57)【要約】
【目的】 本発明は、極低炭素クロム含有鋼の溶製に際
し、極低炭素領域まで少ないクロム酸化量での効率的な
精錬が行える減圧処理方法を提供する。
【構成】 取鍋内溶鋼に浸漬管を浸漬し、該浸漬管内を
減圧するとともに、取鍋低部より攪拌用ガスを供給する
真空精錬において、Ｃｒ濃度が５％以上の溶鋼に対して
炭素濃度が１〜０．０２％の範囲で酸素ガスを気泡活性
面当り０．０４〜０．４０Ｎｍ3 ／（Ｈｒ・ｃｍ2 ）の
速度で上方より吹付け、かつ気泡活性面を全溶鋼表面積
の１０％以上、かつ酸素吹付け面の１００％以上とする
条件で攪拌することにより、極低炭素領域までクロム酸
化を抑制した脱炭が可能となる。さらに、その後復圧し
て浸漬管を溶鋼面より上方に引上げ、還元用合金を投入
することにより、脱炭中に生成したクロム酸化物を効率
よく回収することが可能となる。
(57) [Summary] [Object] The present invention provides a reduced pressure treatment method capable of efficiently refining an extremely low carbon chromium-containing steel to a very low carbon region with a small amount of chromium oxidation. [Constitution] In a vacuum refining in which a dipping pipe is immersed in molten steel in a ladle, the pressure in the dipping pipe is reduced, and a stirring gas is supplied from the lower part of the ladle, in a molten steel having a Cr concentration of 5% or more, the carbon concentration is Of 1 to 0.02%, oxygen gas is sprayed from above at a rate of 0.04 to 0.40 Nm 3 / (Hr · cm 2 ) per bubble activated surface, and the bubble activated surface is covered by 10% of the total molten steel surface area. % Or more and 100% or more of the oxygen-sprayed surface, it is possible to decarburize while suppressing chromium oxidation even in an extremely low carbon region. Further, after that, the pressure is restored and the immersion pipe is pulled up above the molten steel surface, and the reducing alloy is charged, whereby the chromium oxide generated during decarburization can be efficiently recovered.
Description
【０００１】[0001]
【産業上の利用分野】本発明は極低炭素領域まで少ない
クロム酸化量での効率的な精錬を可能とすることを特徴
とする極低炭素クロム含有溶鋼の脱炭方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for decarburizing molten steel containing extremely low carbon chromium, which enables efficient refining to a very low carbon region with a small amount of chromium oxidation.
【０００２】[0002]
【従来の技術】ステンレス鋼に代表されるクロム含有溶
鉄は、炭素濃度が低下した領域では脱炭反応に比べてク
ロムの酸化反応の方が起こりやすくなるため、クロムの
酸化損失を抑制して製品規格から要求される炭素濃度ま
で脱炭する方法が、種々、提案されている。中でもＡＯ
ＤとＶＯＤは広く用いられている。このうちＡＯＤはＡ
ｒで希釈した酸素ガスを浴内に吹込む方法であり、ＶＯ
Ｄは真空下で酸素を上吹きする方法であるが、いずれの
場合も脱炭反応により生成するＣＯガスの分圧を低下さ
せ、クロムの酸化反応よりも脱炭反応を優先させること
を特徴としている。このうち、炭素濃度が２００ppm 以
下といった極低炭素鋼を溶製するためには、減圧精錬が
不可欠となるため、一般的にはＶＯＤが用いられてい
る。2. Description of the Related Art Molten iron containing chromium, typified by stainless steel, is more likely to undergo an oxidation reaction of chromium than a decarburization reaction in a region where the carbon concentration is low. Various methods of decarburizing to the carbon concentration required from the standard have been proposed. Above all, AO
D and VOD are widely used. Of these, AOD is A
It is a method of blowing oxygen gas diluted with r into the bath.
D is a method in which oxygen is blown upward in a vacuum, but in any case, it is characterized by lowering the partial pressure of CO gas generated by the decarburization reaction and giving priority to the decarburization reaction over the oxidation reaction of chromium. There is. Of these, VOD is generally used because depressurization refining is indispensable for melting ultra-low carbon steel having a carbon concentration of 200 ppm or less.
【０００３】しかし、ＶＯＤは取鍋全体を真空容器内に
入れる方法、もしくは取鍋上部に蓋をして取鍋全体を真
空にする方法であるため、上部空間が狭く、酸素上吹き
時に発生するスプラッシュにより操業が阻害されるとい
う問題がある上、クロム酸化を抑制した脱炭を進行させ
るために攪拌用のガス量を増大した場合にも、鋼浴の揺
動や底吹きガスによるスプラッシュが増加し、操業に支
障が生じ、さらにはクロム歩留り、鉄分歩留りの低下を
招くという問題があった。However, since the VOD is a method of putting the entire ladle in a vacuum container or a method of putting a lid on the upper part of the ladle to make the entire ladle a vacuum, the upper space is narrow and is generated when oxygen is blown over. There is a problem that operation is hindered by splash, and even when the amount of gas for stirring is increased to promote decarburization that suppresses chromium oxidation, rocking of the steel bath and splash due to bottom blowing gas increase. However, there is a problem in that the operation is hindered, and the yield of chromium and the yield of iron are reduced.
【０００４】これに対して、特開昭６１−３７９１２号
公報においては、取鍋内の溶鋼を大径浸漬管を介して真
空槽内に吸い上げ、低部から攪拌用ガスを供給する方法
が開示されている。さらに、特開平１−１５６４１６号
公報においては、浸漬管中心に対して底吹き用ノズル位
置を適切な範囲に偏心させるとともに、上吹き酸素を底
吹きガスの浮上領域である、後述するところの気泡活性
面に衝突させる方法が開示されている。これらの方法に
より、ＶＯＤが有する上部空間が狭いという問題は解決
されたものの、極低炭素鋼の溶製に関する記述はなく、
この方法のみでは浸漬管内にクロム酸化物が多量に生成
するため、安定して極低炭素鋼を溶製することはできな
かった。On the other hand, Japanese Patent Laid-Open No. 61-37912 discloses a method of sucking molten steel in a ladle into a vacuum tank through a large-diameter dip pipe and supplying a stirring gas from a lower portion. Has been done. Further, in Japanese Patent Application Laid-Open No. 1-156416, the bottom blowing nozzle position is eccentric with respect to the center of the immersion pipe in an appropriate range, and the top blowing oxygen is a floating region of the bottom blowing gas. A method of striking an active surface is disclosed. By these methods, the problem that the upper space of VOD is narrow was solved, but there is no description about melting of ultra-low carbon steel,
Since only a large amount of chromium oxide is produced in the dip tube by this method alone, it was not possible to stably produce an ultra low carbon steel.
【０００５】[0005]
【発明が解決しようとする課題】本発明は、ＶＯＤが有
している上部空間が狭いため溶鋼の揺動やスプラッシュ
により操業に支障が生じるという問題や、特開昭６１−
３７９１２号公報や、特開平１−１５６４１６号公報に
示された方法が有する、安定して極低炭素鋼を溶製する
ことができないという問題を生じることなく、極低炭素
領域まで少ないクロム酸化量での効率的な精錬を可能と
する脱炭方法を提供するものである。SUMMARY OF THE INVENTION According to the present invention, since the upper space of the VOD is narrow, the swing and splash of molten steel may hinder the operation.
The amount of chromium oxidation is small even in the extremely low carbon region without causing the problem that the method shown in Japanese Patent No. 37912 or JP-A-1-156416 has the inability to stably produce an extremely low carbon steel. A decarburization method that enables efficient refining in
【０００６】[0006]
【課題を解決するための手段】本発明は、取鍋内のＣｒ
濃度が５％以上の溶鋼に対して浸漬管を浸漬し、該浸漬
管内を減圧するとともに、取鍋低部より攪拌用ガスを供
給する真空精錬法に関するものであり、以下の技術要素
から成り立つ。第一に炭素濃度が１〜０．０２％の範囲
で、酸素ガスを気泡活性面積当り０．０４〜０．４０Nm
3 ／（Hr・cm2 ）の速度で吹付けることであり、第二
に、引き続いて、気泡活性面積を全溶鋼表面積の１０％
以上、かつ酸素吹付け面の１００％以上とする条件で攪
拌し、炭素濃度０．０２％以下から吹酸を停止し、５To
rr以下の高真空下で攪拌することにより脱炭処理を行う
ことにあり、第三に、さらに引き続いて、複圧して浸漬
管を溶鋼面より上方に引き上げ、還元用合金を投入し、
脱炭中に生成したクロム酸化物を還元することにある。The present invention relates to Cr in a ladle.
The present invention relates to a vacuum refining method of immersing a dip pipe in molten steel having a concentration of 5% or more, reducing the pressure in the dip pipe, and supplying a stirring gas from a lower portion of a ladle, and it comprises the following technical elements. First, in the carbon concentration range of 1 to 0.02%, oxygen gas is added in an amount of 0.04 to 0.40 Nm per bubble active area.
It is spraying at a speed of 3 / (Hr · cm 2 ). Secondly, subsequently, the bubble active area is 10% of the total molten steel surface area.
Above, and stirring under the conditions of 100% or more of the oxygen sprayed surface, stop the spraying acid from the carbon concentration of 0.02% or less, 5To
The purpose is to perform decarburization treatment by stirring under a high vacuum of rr or less. Thirdly, further successively, the dipping pipe is pulled up above the molten steel surface by double pressure, and the reducing alloy is charged,
It is to reduce the chromium oxide generated during decarburization.
【０００７】[0007]
【作用】図１は本発明に係わる真空精錬装置の断面図で
あり、クロム含有溶鋼４は取鍋１に収容され、また浸漬
管２は取鍋１内のクロム含有溶鋼４中に浸漬静止され
る。浸漬管２は排気管（図示せず）と連通し、浸漬管２
内の真空度に応じて、浸漬管２内にクロム含有溶鋼４が
吸い上げられる。そして、浸漬管２内の下部断面が垂直
下方に当たる取鍋１の低部に設置されたポーラスプラグ
３より不活性ガス５が溶鋼中に吹込まれ、浸漬管２の上
方に設置された上吹きランス６より酸素ガス７が供給さ
れる。1 is a sectional view of a vacuum refining apparatus according to the present invention, in which a molten steel 4 containing chromium is contained in a ladle 1, and a dip tube 2 is dipped in the molten steel 4 containing chromium in the ladle 1 and stationary. It The immersion pipe 2 communicates with an exhaust pipe (not shown),
The molten steel 4 containing chromium is sucked up into the dip tube 2 according to the degree of vacuum inside. Then, the inert gas 5 is blown into the molten steel from the porous plug 3 installed at the lower portion of the ladle 1 whose lower cross section in the dip pipe 2 hits vertically downward, and the upper blowing lance installed above the dip pipe 2 is blown. Oxygen gas 7 is supplied from 6.
【０００８】クロム含有溶鋼を極低炭素化するために
は、炭素濃度が０．０２％以上までは酸素ガスを吹付け
て脱炭し、その後は酸素ガスの供給を停止し、高真空下
で攪拌することが必要であるが、特に重要な点は、高真
空下で攪拌する際の脱炭を効率的に実施することであ
る。本発明者は詳細な試験の結果、この際の脱炭を効率
的に実施するためには、スラグが存在しない真空にさら
される溶鋼自由表面積を大きくし、かつ自由表面におけ
る気泡活性面積を増大させることが重要であることを見
出した。これは、炭素を溶鋼中に含まれる酸素と結合さ
せて除去しようとするものであり、クロム酸化物を含む
スラグを溶融状態にして、スラグ中のクロム酸化物によ
り脱炭するという従来の思想とは大きく異なるものであ
る。In order to make the molten steel containing chromium extremely low carbon, oxygen gas is sprayed to decarburize it until the carbon concentration is 0.02% or more, after which the supply of oxygen gas is stopped and it is kept under high vacuum. Stirring is necessary, but a particularly important point is to efficiently carry out decarburization when stirring under high vacuum. As a result of detailed tests, the present inventors have found that in order to efficiently carry out decarburization at this time, the free surface area of molten steel exposed to a vacuum without slag is increased and the bubble active area on the free surface is increased. Found that is important. This is to combine carbon with oxygen contained in molten steel to remove it, and put the slag containing chromium oxide into a molten state, and decarburize with the chromium oxide in the slag. Is very different.
【０００９】ここで、気泡活性面積は、水モデルや水銀
モデル、あるいは実機での観察結果より、垂直方向に吹
込まれたガスに対する気泡活性面積（Ａｎ）は（１）式
で、水平方向に吹込まれたガスに対する気泡活性面積
（Ａｕ）は（２）式で与えられる。 Ａｎ＝３．１４×（０．２１２×Ｈ）2 ・・・・・（１） Ａｕ＝３．１４×（７×Ｑ0.87）／２ ・・・・・（２） ここで、Ｈは吹込み位置から浴面までの距離（ｍ）であ
り、Ｑはノズル１個当りのガス吹込み量（Nm3 ／ｓ）で
ある。[0009] Here, the bubble active area (An) for the gas blown in the vertical direction is the equation (1) according to the observation result in the water model, the mercury model, or the actual machine. The bubble active area (Au) for the trapped gas is given by equation (2). An = 3.14 × (0.212 × H) 2 (1) Au = 3.14 × (7 × Q 0.87 ) / 2 (2) where H is It is the distance (m) from the injection position to the bath surface, and Q is the gas injection amount (Nm 3 / s) per nozzle.
【００１０】この気泡活性面による自由表面脱炭を効率
的に実施するためには、次の２点が重要となる。 酸素ガス吹付け中のクロム酸化物生成量を少なくする
とともに、生成したクロム酸化物を粗大化させずに微細
分散させる。 酸素ガス吹付け停止後の攪拌により、酸素ガス供給中
に生成したクロム酸化物を鋼浴内へ巻き込ませ、浸漬管
外へ流出させる。The following two points are important in order to efficiently carry out free surface decarburization by means of this bubble activated surface. The amount of chromium oxide produced during the blowing of oxygen gas is reduced, and the produced chromium oxide is finely dispersed without coarsening. By stirring after the oxygen gas spraying is stopped, the chromium oxide generated during the oxygen gas supply is caught in the steel bath and allowed to flow out of the dipping pipe.
【００１１】ここでについては気泡活性面上に酸素ガ
スを吹付けることにより、生成したクロム酸化物を微細
化し、吹酸火点でのクロム酸化物の還元を促進させるこ
とにある。クロム酸化物は生成と同時に固体状態となる
ために還元が非常に困難である。よって還元を促進する
ためにはクロム酸化物を微細化し、溶鋼中〔Ｃ〕との接
触面積を増大させる必要がある。In this case, the oxygen oxide is blown onto the bubble active surface to make the produced chromium oxide finer and accelerate the reduction of the chromium oxide at the blowing acid hot spot. Chromium oxide is in a solid state at the same time as it is formed, so reduction is very difficult. Therefore, in order to promote the reduction, it is necessary to make the chromium oxide finer and increase the contact area with the molten steel [C].
【００１２】また、に示した点は、溶鋼中に浸漬管を
浸漬し、該浸漬管内を減圧するとともに、取鍋低部より
攪拌用ガスを供給する真空精錬に特有の現象であり、浸
漬管内で生成した酸化物が、取鍋低部より供給される攪
拌ガスにより形成される大きな下降流に乗り浴内に巻き
込まれ、浸漬管下端部を通過して管の外部に流出するも
のである。従って、適宜時間攪拌を行うことにより、浸
漬管内に存在していたクロム酸化物はほとんどすべて浸
漬管外へ流出し、真空下にさらされる浸漬管内溶鋼表面
はスラグの存在しない状態が生み出される。この効果を
効率的に実施するには、浸漬管内の溶鋼高さ（ｈ）に対
して０．５ｈよりも深い位置から０．６Nl／(min・ton)
以上とすることが望ましい。The point indicated by is a phenomenon peculiar to vacuum refining in which a dipping pipe is immersed in molten steel, the pressure in the dipping pipe is reduced, and a stirring gas is supplied from the bottom of the ladle. The oxide produced in (1) is entrained in the riding bath by a large downward flow formed by the stirring gas supplied from the lower part of the ladle, passes through the lower end of the immersion pipe, and flows out of the pipe. Therefore, by stirring for an appropriate period of time, almost all of the chromium oxide existing in the dip tube flows out of the dip tube, and the molten steel surface in the dip tube exposed under vacuum is in a state where no slag exists. In order to carry out this effect efficiently, from the position deeper than 0.5h to the molten steel height (h) in the immersion pipe, 0.6Nl / (min ・ ton)
It is desirable to set it as above.
【００１３】さらに、これらの効果を実現するために
は、酸素ガス供給中に生成されるクロム酸化物の量と形
態が重要となる。つまり、酸化物の巻き込みを容易にす
るためには、少なくとも１cm程度より小さい、微細な状
態を維持することが重要であり、例えば大量のクロム酸
化物を生成した場合には合体成長し、さらに一部は浸漬
管壁面に付着し、溶鋼内への巻き込みがほとんど生じな
い場合すらある。クロム酸化物の生成量を少なくし、か
つ微細化するためには、酸素ガスを供給する炭素濃度範
囲と、気泡活性面当りの酸素ガス吹付け流量が重要とな
る。特に、気泡活性面当りの酸素ガス吹付け流量は、全
く新しい概念である。これは、吹付けられた酸素ガスが
クロムの酸化を引き起こさずに脱炭に消費されるために
は溶鋼全体の攪拌ではなく、酸素ガスが接触する溶鋼表
面の局部的な攪拌が重要であるということを示してお
り、それを表す指標はガス流量ではなく気泡活性面積で
あることを意味している。つまり低部より供給された気
泡が表面まで浮上し破裂する際に、大きなエネルギーの
開放があり、それにより鋼浴表面に微細な液滴が多数生
成される。これが、有効な反応表面として作用し、クロ
ムの酸化に優先した脱炭を生じさせると同時に、生成す
るクロム酸化物を微細な粒子として形成させ、より微細
に分裂させる役割を果している。Further, in order to realize these effects, the amount and form of chromium oxide produced during the supply of oxygen gas are important. In other words, in order to facilitate the inclusion of oxides, it is important to maintain a fine state, which is smaller than at least about 1 cm. For example, when a large amount of chromium oxide is generated, coalescence growth occurs and The part adheres to the wall surface of the dipping pipe, and even when it is hardly caught in the molten steel. In order to reduce the amount of chromium oxide produced and to make it finer, the carbon concentration range for supplying oxygen gas and the oxygen gas spraying flow rate per bubble active surface are important. In particular, the flow rate of oxygen gas sprayed per bubble active surface is a completely new concept. This is because it is important not to stir the entire molten steel but to locally stir the surface of the molten steel in contact with oxygen gas in order that the sprayed oxygen gas is consumed for decarburization without causing oxidation of chromium. This means that the index indicating that is not the gas flow rate but the bubble active area. In other words, when the bubbles supplied from the lower part float up to the surface and burst, there is a large release of energy, and as a result, many fine droplets are generated on the steel bath surface. This acts as an effective reaction surface and causes decarburization prior to the oxidation of chromium, and at the same time, forms the formed chromium oxide as fine particles and plays a role of finer division.
【００１４】具体的には、炭素濃度が１〜０．０２％の
範囲で、酸素ガスを気泡活性面積当り０．０４〜０．４
０Nm3 ／（Hr・cm2 ）の速度で上方より吹付け、引き続
いて、気泡活性面積を全溶鋼表面積の１０％以上、かつ
酸素吹付け面の１００％以上とする条件で攪拌すること
にある。この内、図２に示すように酸素ガスの気泡活性
面当りの吹付け速度が０．０４Nm3 ／（Hr・cm2 ）未満
の場合には酸素供給速度が遅いため処理時間が長くなり
生産性を著しく阻害するという問題があり、０．４０Nm
3 ／（Hr・cm2 ）超の場合には酸素供給速度が過剰なた
めクロム酸化物の生成量が増大し、次工程以降での真空
表面脱炭や還元が困難になるという問題が生じる。また
図３に示すように気泡活性面積が全溶鋼表面積の１０％
より小さい場合には酸素ガス供給中に生成したクロム酸
化物が微細に分裂せず、下降流により浴内に巻き込まれ
ず浸漬管外へ流出しにくいため、真空表面の大きな面積
部分を強固なクロム酸化物皮膜で被覆されるため表面脱
炭が生じにくいという問題がある。さらに、炭素濃度が
１％以上の領域から真空処理をした場合には処理時間が
極めて長くなるために生産性を著しく阻害するという問
題があり、逆に０．０２％以下まで酸素ガスを供給した
場合には、クロム酸化物の生成量が加速度的に増加し、
次工程以降での真空表面脱炭や還元が困難になるという
問題が生じる。さらに、気泡活性面積が酸素吹付け面積
の１００％未満であるとクロム酸化物の生成サイトが気
泡活性面外となる領域が生じ、生成したクロム酸化物は
微細化せず合体成長し、吹酸火点での還元効率が悪化す
る。さらに、クロム酸化物が粗大化することにより、浸
漬管外への流出が困難となり、その結果として吹酸停止
後の表面脱炭が阻害されるという結果となる。Specifically, oxygen gas is added in an amount of 0.04 to 0.4 per bubble active area in a carbon concentration range of 1 to 0.02%.
Spraying from the top at a speed of 0 Nm 3 / (Hr · cm 2 ), and subsequently stirring under the condition that the bubble active area is 10% or more of the total molten steel surface area and 100% or more of the oxygen spraying surface. .. Of these, as shown in FIG. 2, when the spraying rate of oxygen gas per bubble active surface is less than 0.04 Nm 3 / (Hr · cm 2 ), the oxygen supply rate is slow and the processing time becomes long, resulting in productivity. There is a problem that it significantly inhibits 0.40 Nm
If it exceeds 3 / (Hr · cm 2 ), the oxygen supply rate is excessive and the amount of chromium oxide produced increases, causing a problem that vacuum surface decarburization and reduction in the subsequent steps become difficult. Moreover, as shown in FIG. 3, the bubble active area is 10% of the total molten steel surface area.
If it is smaller, the chromium oxide generated during oxygen gas supply does not finely divide, is not caught in the bath due to the downward flow, and does not easily flow out of the dip tube. There is a problem that surface decarburization is unlikely to occur because it is covered with a material film. Further, when the vacuum treatment is performed from the region where the carbon concentration is 1% or more, the treatment time becomes extremely long, so that there is a problem that productivity is significantly impaired. Conversely, oxygen gas is supplied to 0.02% or less. In this case, the amount of chromium oxide produced increases at an accelerated rate,
There arises a problem that vacuum surface decarburization and reduction become difficult in the subsequent steps. Further, when the bubble active area is less than 100% of the oxygen spraying area, a region where the generation site of chromium oxide is out of the bubble active surface is generated, and the generated chromium oxide does not become finer but coalesces and grows. The reduction efficiency at the flash point deteriorates. Further, the coarsening of the chromium oxide makes it difficult to flow out of the dipping pipe, and as a result, the surface decarburization after stopping the blowing acid is hindered.
【００１５】一方、このようにして、極低炭素鋼を溶製
した状態では酸素ガス吹付け中に生成したクロム酸化物
が浸漬管外に堆積しており、このままでの状態で、還元
用合金であるＳｉやＡｌを添加しても、浸漬管外部の溶
鋼はほとんど攪拌されないため、クロム酸化物の還元は
行われない。従って、さらに引き続いて、複圧して浸漬
管を溶鋼面より上方に引き上げた後に還元用合金を投入
し、脱炭中に生成したクロム酸化物を還元する工程が必
須となる。この場合、脱炭中に生成したクロム酸化物は
微細化しているので還元も非常に効率的に行うことが可
能である。On the other hand, in this way, in the state in which the ultra-low carbon steel is melted, the chromium oxide generated during the oxygen gas spraying is deposited outside the dip tube, and in this state as it is, the reducing alloy is used. Even if Si or Al is added, the molten steel outside the dip tube is hardly stirred, so that the chromium oxide is not reduced. Therefore, subsequently, a step of reducing the chromium oxide generated during decarburization by injecting a reducing alloy after applying a double pressure to pull up the dipping tube above the molten steel surface is essential. In this case, since the chromium oxide generated during decarburization is finely divided, reduction can be performed very efficiently.
【００１６】ここで、処理中に取鍋および浸漬管の淵に
スラグが付着する場合があるが、複圧により取鍋内の湯
面が上昇するため、この付着スラグは溶鋼熱により半溶
融状態となって取鍋内溶鋼面上に再浮上する。従って、
スラグはすべて効率よく還元することが可能である。ま
た、現状のＶＯＤでは脱炭速度が遅く、特に極低炭素ク
ロム含有鋼の溶製に際しては転炉工程での脱炭精錬の過
負荷やＶＯＤでの処理時間延長による耐火物原単位の増
大およびクロム歩留り、鉄分歩留りの低下を招いてい
る。これはＶＯＤではフリーボード制約による底吹きガ
ス量が上げられないこと、また転炉出鋼時のスラグが全
量ＶＯＤに持ち込まれるため、表面脱炭の効果が小さい
ことに起因している。[0016] Here, slag may adhere to the ladle and the edge of the dipping pipe during processing, but since the molten metal surface inside the ladle rises due to the double pressure, this adhered slag is in a semi-molten state due to the heat of molten steel. Then, it resurfaces on the surface of molten steel in the ladle. Therefore,
All slag can be efficiently reduced. Further, the current VOD has a slow decarburization rate, and especially when melting ultra-low carbon chromium-containing steel, the overload of decarburization and refining in the converter process and the increase of the refractory unit unit due to the extension of the VOD treatment time This leads to a decrease in chromium yield and iron yield. This is due to the fact that the bottom blown gas amount cannot be increased in VOD due to the freeboard restriction, and that the amount of slag when the converter steel is tapped is brought to VOD, so that the effect of surface decarburization is small.
【００１７】本発明では、フリーボード制約がないた
め、底吹きガス量の増加による攪拌力の増大が可能であ
り、かつ浸漬管内のスラグはほぼ完全に排出されるため
吹酸時の火点においてもスラグの影響がなく、脱炭反応
の促進に有利であり、また自由表面積が大きいため、吹
酸停止後の表面脱炭の効果が極めて大きく、従来法に比
べて非常に大きな脱炭速度を得ることができるため、転
炉工程での負荷が大幅に軽減され、その結果としてトー
タルのクロム歩留り、鉄分歩留りが向上する。In the present invention, since there is no freeboard restriction, the stirring force can be increased by increasing the amount of gas blown from the bottom, and since the slag in the dip pipe is almost completely discharged, at the fire point during blowing acid. Also has no effect of slag, is advantageous in promoting the decarburization reaction, and has a large free surface area, so the effect of surface decarburization after stopping the blowing acid is extremely large, and a much higher decarburization rate than the conventional method. Since it can be obtained, the load in the converter process is significantly reduced, and as a result, the total chromium yield and iron yield are improved.
【００１８】[0018]
【実施例】表１に１７５ton 規模の真空精錬装置を用い
た実施例を示す。この場合、底吹きＡｒガス流量として
は１０５〜１０００Nl／minにて行った。まず、転炉精
錬によりＣｒ濃度が１０〜１９％でＣが適宜濃度
（Ｃ1 ）の粗溶鋼を溶製した後、図１に示した精錬容器
へ供給し、まず炭素濃度がＣB まで約２００Torrの真空
雰囲気下で酸素ガスを上吹きしつつ脱炭精錬を行い、引
き続いて酸素ガスを供給せずに５〜１５分間、約５Torr
以下の真空雰囲気下で攪拌した。その後、本発明に従っ
て、複圧して浸漬管を溶鋼面より上方に引き上げた後に
還元用合金を投入した。このときの底吹きガス流量は一
律２００Nl／min で行った。また、比較例においては複
圧せずに浸漬管を入れた状態で還元用合金を投入した例
も実施した。EXAMPLE Table 1 shows an example using a 175 ton scale vacuum refining apparatus. In this case, the flow rate of the bottom blown Ar gas was 105 to 1000 Nl / min. First, approximately after C in Cr concentration from 10 to 19% were smelted crude molten steel suitable concentration (C 1) by converter refining, and supplies to the refining vessel as shown in FIG. 1, first, the carbon concentration to C B Perform decarburization refining while blowing oxygen gas upwards in a vacuum atmosphere of 200 Torr, and then continuously supply about 5 Torr for 5 to 15 minutes without supplying oxygen gas.
The mixture was stirred under the following vacuum atmosphere. Then, in accordance with the present invention, the dipping pipe was pulled up above the molten steel surface by double pressure, and then the reducing alloy was charged. The flow rate of the bottom blowing gas at this time was uniformly 200 Nl / min. In addition, in the comparative example, an example in which the reducing alloy was put in the dip tube without double pressure was also carried out.
【００１９】表１から明らかなように本発明が処理時
間、クロム歩留り、到達〔Ｃ〕ともに優れていることが
わかる。As is clear from Table 1, the present invention is excellent in processing time, chromium yield, and arrival [C].
【００２０】[0020]
【表１】 [Table 1]
【００２１】[0021]
【発明の効果】以上述べた如く、本発明によればクロム
酸化を抑制しつつ効率的に脱炭を行うことが可能である
から、極低炭素クロム含有溶鋼の溶製に関して本発明は
極めて有効な方法である。As described above, according to the present invention, it is possible to efficiently decarburize while suppressing the oxidation of chromium. Therefore, the present invention is extremely effective for the melting of ultra-low carbon chromium-containing molten steel. That's the method.
【図１】本発明による含クロム溶鋼の減圧脱炭法の実施
の態様の一例を示す図である。FIG. 1 is a diagram showing an example of an embodiment of a vacuum decarburization method for molten chromium-containing steel according to the present invention.
【図２】気泡活性面当りの酸素吹付け速度と処理時間・
クロム酸化物生成量の関係を示す図である。[Fig. 2] Oxygen blowing rate and treatment time per active surface of bubbles
It is a figure which shows the relationship of a chromium oxide production amount.
【図３】吹酸停止後（〔Ｃ〕≦２００ppm ）での（気泡
活性面積／全溶鋼表面積）比率と脱炭速度の関係を示す
図である。FIG. 3 is a graph showing the relationship between the (foaming active area / total molten steel surface area) ratio and the decarburization rate after stopping the blowing acid ([C] ≦ 200 ppm).
１ 取鍋 ２ 浸漬管 ３ ポーラスプラグ ４ 含クロム粗溶鋼 ５ 不活性ガス ６ 上吹きランス ７ 酸素ガス 1 Ladle 2 Dipping pipe 3 Porous plug 4 Cr-containing crude molten steel 5 Inert gas 6 Top blowing lance 7 Oxygen gas
Claims (2)
内を減圧するとともに、取鍋低部より攪拌用ガスを供給
する真空精錬において、Ｃｒ濃度が５％以上の溶鋼に対
して炭素濃度が１〜０．０２％の範囲で、酸素ガスを気
泡活性面積当り０．０４〜０．４０Nm3 ／（Hr・cm2 ）
の速度で上方より吹付け、かつ気泡活性面積を全溶鋼表
面積の１０％以上、かつ酸素吹付け面の１００％以上と
する条件で攪拌し、次いで複圧して浸漬管を溶鋼面より
上方に引き上げ、還元用合金を投入し、脱炭中に生成し
たクロム酸化物を還元することを特徴とする極低炭素ク
ロム含有溶鋼の脱炭方法。1. A molten steel having a Cr concentration of 5% or more in vacuum refining in which a dipping pipe is immersed in molten steel in a ladle, the pressure in the dipping pipe is reduced, and a stirring gas is supplied from a lower portion of the ladle. Oxygen gas per bubble active area of 0.04 to 0.40 Nm 3 / (Hr · cm 2 ) in the carbon concentration range of 1 to 0.02%
At a speed of 1, and stirred under the conditions that the bubble active area is 10% or more of the total molten steel surface area and 100% or more of the oxygen sprayed surface, and then double pressure is applied to pull the dipping pipe upward from the molten steel surface. A method for decarburizing molten steel containing ultra-low carbon chromium, which comprises charging a reducing alloy and reducing chromium oxides generated during decarburization.
内を減圧するとともに、取鍋低部より攪拌用ガスを供給
する真空精錬において、Ｃｒ濃度が５％以上の溶鋼に対
して炭素濃度が１〜０．０２％の範囲で、酸素ガスを気
泡活性面積当り０．０４〜０．４０Nm3 ／（Hr・cm2 ）
の速度で上方より吹付け、かつ気泡活性面積を全溶鋼表
面積の１０％以上、かつ酸素吹付け面の１００％以上と
する条件で攪拌し、炭素濃度０．０２％以下から吹酸を
停止し、５Torr以下の高真空下で取鍋低部からの不活性
ガスのみの供給で攪拌することにより脱炭処理を行い、
次いで複圧して浸漬管を溶鋼面より上方に引き上げ、還
元用合金を投入し、脱炭中に生成したクロム酸化物を還
元することを特徴とする極低炭素クロム含有溶鋼の脱炭
方法。2. A molten steel having a Cr concentration of 5% or more in vacuum refining in which a dipping pipe is immersed in molten steel in a ladle, the pressure in the dipping pipe is reduced, and a stirring gas is supplied from a lower portion of the ladle. Oxygen gas per bubble active area of 0.04 to 0.40 Nm 3 / (Hr · cm 2 ) in the carbon concentration range of 1 to 0.02%
At the speed of 10% or more, and stirred under the condition that the bubble active area is 10% or more of the total molten steel surface area and 100% or more of the oxygen sprayed surface, and the blowing acid is stopped from the carbon concentration of 0.02% or less. Decarburization is performed by stirring under a high vacuum of 5 Torr or less by supplying only an inert gas from the bottom of the ladle,
Next, a decarburizing method for ultra-low carbon chromium-containing molten steel, which comprises subjecting the dip tube to a pressure higher than the molten steel surface by applying multiple pressures, introducing a reducing alloy, and reducing the chromium oxide generated during decarburization.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3265053A JP2819440B2 (en) | 1991-10-14 | 1991-10-14 | Method for decarburizing molten steel containing extremely low carbon chromium |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP3265053A JP2819440B2 (en) | 1991-10-14 | 1991-10-14 | Method for decarburizing molten steel containing extremely low carbon chromium |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH05105936A true JPH05105936A (en) | 1993-04-27 |
| JP2819440B2 JP2819440B2 (en) | 1998-10-30 |
Family
ID=17411931
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP3265053A Expired - Lifetime JP2819440B2 (en) | 1991-10-14 | 1991-10-14 | Method for decarburizing molten steel containing extremely low carbon chromium |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2819440B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5902374A (en) * | 1995-08-01 | 1999-05-11 | Nippon Steel Corporation | Vacuum refining method for molten steel |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01156416A (en) * | 1987-12-11 | 1989-06-20 | Nippon Steel Corp | Vacuum decarburization method for high chromium steel with excellent decarburization properties |
-
1991
- 1991-10-14 JP JP3265053A patent/JP2819440B2/en not_active Expired - Lifetime
Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01156416A (en) * | 1987-12-11 | 1989-06-20 | Nippon Steel Corp | Vacuum decarburization method for high chromium steel with excellent decarburization properties |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5902374A (en) * | 1995-08-01 | 1999-05-11 | Nippon Steel Corporation | Vacuum refining method for molten steel |
Also Published As
| Publication number | Publication date |
|---|---|
| JP2819440B2 (en) | 1998-10-30 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| KR100214927B1 (en) | Vacuum refining method of molten steel | |
| JP2009263783A (en) | Method for refining molten steel in rh vacuum degassing apparatus | |
| JPH05105936A (en) | Method of decarburizing molten steel containing ultra low carbon chromium | |
| JPH05239534A (en) | Method for melting non-oriented electric steel sheet | |
| JP2767674B2 (en) | Refining method of high purity stainless steel | |
| JP3308084B2 (en) | Ultra low oxygen steel smelting method | |
| JP2582316B2 (en) | Melting method of low carbon steel using vacuum refining furnace | |
| JP2808197B2 (en) | Vacuum refining of molten steel using large diameter immersion tube | |
| JP3377325B2 (en) | Melting method of high cleanness ultra low carbon steel | |
| JP2724030B2 (en) | Melting method of ultra low carbon steel | |
| JP2773883B2 (en) | Melting method of ultra low carbon steel by vacuum degassing | |
| JP2648769B2 (en) | Vacuum refining method for molten steel | |
| JP3706451B2 (en) | Vacuum decarburization method for high chromium steel | |
| JP3785257B2 (en) | Method for degassing stainless steel | |
| JP2915631B2 (en) | Vacuum refining of molten steel in ladle | |
| JP3300014B2 (en) | Refining method of molten steel by vacuum degassing | |
| JPH07224317A (en) | Production of high cleanliness steel | |
| JP2001172715A (en) | Manufacturing method of ultra-low carbon stainless steel molten steel | |
| JP3025042B2 (en) | Manufacturing method of ultra-low carbon steel | |
| JP3153983B2 (en) | Melting method for high purity stainless steel | |
| JPH02197515A (en) | Smelting method for dead soft steel having high cleanness | |
| JPH0565528A (en) | Melting production of high cleanliness steel | |
| JPH08104914A (en) | High-efficiency manufacturing method of high-purity molten stainless steel | |
| JPH03134115A (en) | Method and apparatus for producing highly clean and extremely low carbon steel | |
| JPH0681024A (en) | Method for melting dead-soft steel of high cleanness and apparatus therefor |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A01 | Written decision to grant a patent or to grant a registration (utility model) |
Free format text: JAPANESE INTERMEDIATE CODE: A01 Effective date: 19980630 |