JP2001032009A - Method for refining molten steel containing chromium - Google Patents
Method for refining molten steel containing chromiumInfo
- Publication number
- JP2001032009A JP2001032009A JP11205145A JP20514599A JP2001032009A JP 2001032009 A JP2001032009 A JP 2001032009A JP 11205145 A JP11205145 A JP 11205145A JP 20514599 A JP20514599 A JP 20514599A JP 2001032009 A JP2001032009 A JP 2001032009A
- Authority
- JP
- Japan
- Prior art keywords
- refining
- chromium
- molten steel
- acid
- molten iron
- 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.)
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- Treatment Of Steel In Its Molten State (AREA)
- Carbon Steel Or Casting Steel Manufacturing (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、クロムを含有する
溶鉄の脱炭精錬の際に、生成した脱炭スラグ中のクロム
を溶鉄に還元回収するクロムを含有する溶鋼の精錬方法
に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for refining chromium-containing molten steel for reducing and recovering chromium in the generated decarburized slag to molten iron during decarburization and refining of molten iron containing chromium.
【０００２】[0002]
【従来の技術】ステンレス溶鋼の精錬は、転炉、電気炉
等の精錬炉に炭素を２重量％以上含有する溶鉄とフェロ
クロム等の合金鉄を装入し、ランスから酸素を吹き込む
（吹酸）ことにより、炭素濃度を０．３〜０．８重量％
程度とする溶鋼（粗溶鋼）を溶製し、この粗溶鋼をＲＨ
−ＯＢ、ＶＯＤ、一本の大径の浸漬管からなる減圧精錬
装置等の二次精錬炉を用いて、減圧下で吹酸し、クロム
の酸化を抑制しながら脱炭精錬を行う方法が広く行われ
ている。しかし、精錬炉を用いた吹酸による脱炭精錬の
場合は、溶鋼中の炭素濃度の低下に伴って脱炭スラグ中
にクロム酸（Ｃｒ2 Ｏ3 ）が増加するため、フェロシリ
コンを添加してクロム酸の還元を行って、溶鋼中に回収
することが必要であり、還元用の合金鉄のコストが高く
なったり、脱炭スラグの増加や耐火物の損耗等の問題が
あった。この対策として、例えば、特開昭５３−１１９
２１０号公報には、精錬炉を用いて吹酸による脱炭精錬
を行った際に、生成した脱炭スラグを冷却固化するか、
あるいはこれを粉砕してから、次の精錬に添加すること
により、溶鉄中の炭素やシリコン（Ｓｉ）によって還元
し、溶鋼中に回収する方法が記載されている。更に、特
開平８−８５８１４号公報では、溶鉄のＳｉ濃度を０．
３０〜０．５０重量％程度に調整し、含有する炭素と併
用し、且つ溶鉄の温度を１４００℃以上にし、不活性ガ
スを吹き込んで攪拌することにより、脱炭スラグ中のク
ロム酸の還元速度を高位に維持して還元効率を高めてい
る。また、特開平９−３１５１５号公報には、吹酸によ
る脱炭精錬を行っている際に、吹酸火点の発光スペクト
ル分析により溶鋼中のクロム値（Ｃｒ％）を求め、送酸
速度と溶鋼中のクロム値の比を所定の範囲になるよう
に、送酸速度を調整して、高価な還元剤の節減と耐火物
の損耗を抑制することが提案されている。2. Description of the Related Art Refining of molten stainless steel is performed by charging molten iron containing 2% by weight or more of carbon and alloyed iron such as ferrochrome into a refining furnace such as a converter or an electric furnace, and blowing oxygen from a lance (blowing acid). As a result, the carbon concentration becomes 0.3 to 0.8% by weight.
Molten steel (coarse molten steel) having a degree of
-The method of performing decarburization refining while blowing acid under reduced pressure using a secondary refining furnace such as a decompression refining device consisting of OB, VOD, and one large-diameter dip tube while suppressing chromium oxidation is widely used. Is being done. However, in the case of decarburization refining by blowing acid using a refining furnace, chromic acid (Cr 2 O 3 ) increases in the decarburized slag as the carbon concentration in the molten steel decreases. It is necessary to reduce chromic acid and recover it in the molten steel, which causes problems such as an increase in the cost of ferroalloys for reduction, an increase in decarburized slag, and wear of refractories. As a countermeasure against this, for example, JP-A-53-119
No. 210 discloses that when decarburization by blowing acid using a refining furnace, the decarburized slag generated is cooled and solidified,
Alternatively, a method is described in which this is pulverized and then added to the next refining to be reduced by carbon or silicon (Si) in molten iron and recovered in molten steel. Further, in Japanese Patent Application Laid-Open No. 8-85814, the Si concentration of molten iron is set to 0.1.
The rate of reduction of chromic acid in decarburized slag is adjusted to about 30 to 0.50% by weight, combined with the contained carbon, and the temperature of the molten iron is set to 1400 ° C. or higher, and an inert gas is blown into the slag for stirring. Is maintained at a high level to increase the reduction efficiency. Also, Japanese Patent Application Laid-Open No. 9-31515 discloses that, during decarburization refining with blowing acid, the chromium value (Cr%) in molten steel is determined by emission spectrum analysis of the blowing acid fire point, and It has been proposed to adjust the acid feed rate so that the ratio of the chromium value in the molten steel falls within a predetermined range, thereby saving expensive reducing agents and suppressing refractory wear.
【０００３】[0003]
【発明が解決しようとする課題】しかしながら、特開昭
５３−１１９２１０号公報では、脱炭スラグを冷却固化
したもの、あるいはこれを粉砕したものを用いるため、
脱炭スラグが保有する熱を有効に活用できない。しか
も、脱炭スラグを再度溶解する必要があり、溶鉄中の炭
素やＳｉ等により還元を行うのに要する時間が長くなり
精錬時間が延長する。更に、特開平８−８５８１４号公
報では、溶鉄のＳｉ濃度を高めることで、脱炭スラグ中
のクロム酸の還元効率をある程度良くできるが、Ｓｉの
酸化等により最終的な脱炭スラグ量が増加し、脱炭スラ
グに含まれる全クロム酸の量が増加し、結果としてクロ
ムの損失を招く。しかも、不活性ガスにより溶鉄と脱炭
スラグを攪拌するため、精錬の経過と共に炉内の温度が
低下し、還元精錬を行った後の脱炭スラグの排滓作業に
支障をきたす等の問題がある。また、特開平９−３１５
１５号公報では、溶鉄中のクロム値に応じて送酸速度を
調整するため、還元精錬の初期の溶鉄中のクロム値が低
い状態におけるクロム酸の還元速度が低下し、精錬時間
の延長や耐火物の損耗を招く等の問題がある。このよう
に、脱炭スラグに含まれるクロム酸を溶鉄中に回収する
従来の方法では、脱炭スラグの保有熱を有効に活用でき
ないか、あるいは還元の精錬時間の延長やクロムの酸化
損失、耐火物の損耗等が生じ、脱炭スラグを安定して活
用する方法が確立されていなかった。However, in Japanese Unexamined Patent Publication No. Sho 53-119210, since decarburized slag is used by cooling and solidifying it or by crushing it,
The heat held by the decarburized slag cannot be used effectively. In addition, the decarburized slag needs to be dissolved again, and the time required for reduction by carbon, Si, or the like in the molten iron becomes longer, and the refining time becomes longer. Further, in Japanese Patent Application Laid-Open No. 8-85814, the efficiency of reduction of chromic acid in decarburized slag can be improved to some extent by increasing the Si concentration of molten iron, but the final decarburized slag amount increases due to oxidation of Si and the like. However, the amount of total chromic acid contained in the decarburized slag increases, resulting in loss of chromium. In addition, since the molten iron and the decarburized slag are agitated by the inert gas, the temperature in the furnace decreases with the progress of refining, and there is a problem in that the decarburized slag is discharged after reduction and refining. is there. Also, Japanese Patent Application Laid-Open No. 9-315
In JP-A No. 15 (KOKAI), the rate of acid supply is adjusted according to the chromium value in the molten iron, so that the reduction rate of chromic acid in a state where the chromium value in the molten iron is low in the initial stage of refining and refining is reduced, so that the refining time is extended and the refractory There is a problem that the object is worn. As described above, in the conventional method of recovering chromic acid contained in decarburized slag into molten iron, the heat retained in the decarburized slag cannot be effectively utilized, or the refining time for reduction, the chromium oxidation loss, Materials were worn and the like, and a method for stably utilizing the decarburized slag was not established.
【０００４】本発明はかかる事情に鑑みてなされたもの
で、脱炭スラグに含まれるクロム酸を短時間に還元し、
クロムの酸化損失を少なくし、精錬炉の耐火物の損耗を
抑制できるクロムを含有する溶鋼の精錬方法を提供する
ことを目的とする。The present invention has been made in view of such circumstances, and reduces chromic acid contained in decarburized slag in a short time.
An object of the present invention is to provide a method for refining molten steel containing chromium, which can reduce oxidation loss of chromium and suppress wear of refractories in a smelting furnace.
【０００５】[0005]
【課題を解決するための手段】前記目的に沿う本発明の
クロムを含有する溶鋼の精錬方法は、精錬炉により溶鉄
Ａの脱炭精錬を行った際に生成した脱炭スラグを前記精
錬炉内に残留させて溶鋼を排出し、該精錬炉内に溶鉄Ｂ
を装入し、吹酸を行って前記脱炭スラグに含まれるクロ
ムを前記溶鉄Ｂ中に回収してからスラグのみを排滓し
て、引き続き前記溶鉄Ｂを脱炭精錬する溶鋼の精錬方法
において、全吹酸量の６０〜８０％を吹酸した後に、送
酸速度を低下させている。この方法により、脱炭スラグ
中のクロム（クロム酸）の還元速度が速い精錬の初期
に、十分に酸素を供給して迅速に還元し、還元精錬の後
期に残留するクロムを少なくするので、短時間の内にク
ロムを溶鉄中に回収することができる。しかも、還元精
錬中の未還元のクロムを少なくし、精錬時間を短かくで
きるので精錬炉の耐火物を損耗を抑制することができ
る。According to the present invention, there is provided a method for refining molten steel containing chromium, which comprises the steps of: And the molten steel is discharged into the smelting furnace.
, The chromium contained in the decarburized slag is collected in the molten iron B by blowing acid, and then only the slag is discharged, and the molten iron B is subsequently decarburized and refined. After 60-80% of the total acid amount is blown, the acid feed rate is reduced. By this method, sufficient oxygen is supplied at the initial stage of refining in which the reduction rate of chromium (chromic acid) in the decarburized slag is high, and rapid reduction is performed. Chromium can be recovered in the molten iron in time. In addition, since unreduced chromium during the refining and refining can be reduced and the refining time can be shortened, the refractory of the refining furnace can be prevented from being worn.
【０００６】ここで、前記送酸速度を段階的に低下させ
てもよい。これにより、還元精錬の末期の溶鋼温度の上
昇とクロムの再酸化を抑制し、精錬炉の耐火物の損耗を
防止することができる。Here, the acid feeding rate may be reduced stepwise. As a result, it is possible to suppress a rise in the temperature of the molten steel and a reoxidation of chromium at the end of the refining and refining, thereby preventing wear of refractories of the refining furnace.
【０００７】更に、前記送酸速度を連続して低下させる
こともできる。送酸速度を連続して低下させることによ
り、還元精錬の末期の溶鋼温度の上昇とクロムの再酸化
を抑制し、精錬炉の耐火物の損耗等をより確実に防止す
ることができる。[0007] Further, the acid feeding rate can be continuously reduced. By continuously lowering the acid feeding rate, it is possible to suppress the increase in the temperature of molten steel and the reoxidation of chromium at the end of the refining and refining, and it is possible to more reliably prevent wear of refractories in the refining furnace.
【０００８】また、前記送酸速度の低下により減少する
酸素量と同量の不活性ガスを供給することもできる。こ
れにより、攪拌を十分に行って溶鋼と脱炭スラグを積極
的に接触させて、還元精錬の後期の還元速度を高位に維
持することができ、未還元のクロムを抑制することがで
きる。Further, it is possible to supply the same amount of inert gas as the amount of oxygen which decreases due to the decrease in the acid supply rate. Thereby, sufficient stirring can be performed to make the molten steel and the decarburized slag come into contact positively, so that the reduction rate in the latter half of the reduction smelting can be maintained at a high level, and unreduced chromium can be suppressed.
【０００９】[0009]
【発明の実施の形態】続いて、添付した図面を参照しつ
つ、本発明を具体化した実施の形態につき説明し、本発
明の理解に供する。図１は本発明の一実施の形態に係る
クロムを含有する溶鋼の精錬方法に適用されるクロム含
有溶鋼の精錬装置の全体図、図２は同クロム含有溶鋼の
精錬装置を用いた精錬工程の説明図、図３は溶鉄の吹酸
量とクロムの還元速度の関係を表すグラフ、図４は吹酸
量と溶鉄の温度の関係を表すグラフ、図５は溶鉄の吹酸
量とクロムの還元速度の関係を表すグラフである。図１
に示すように、本発明の一実施の形態に係るクロムを含
有する溶鋼の精錬方法に適用されるクロム含有溶鋼の精
錬装置１３は、精錬炉の一例である上底吹き転炉１と、
上底吹き転炉１内の溶鉄に上方から吹酸するランス２
と、上底吹き転炉１内にフェロクロム合金、フラック
ス、炭材等を添加するシュート４と、底部から不活性ガ
スを吹き込むノズル３を有している。このノズル３は、
外側の管に冷却流体を流して保護するように二重管構造
にしている。また、上底吹き転炉１の側壁部には、精錬
を終了した溶鋼を出鋼するための出鋼口５を備えてい
る。DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. FIG. 1 is an overall view of a chromium-containing molten steel refining apparatus applied to a chromium-containing molten steel refining method according to an embodiment of the present invention, and FIG. 2 is a refining process using the chromium-containing molten steel refining apparatus. FIG. 3 is a graph showing the relationship between the amount of blowing acid of molten iron and the reduction rate of chromium, FIG. 4 is a graph showing the relationship between the amount of blowing acid and the temperature of molten iron, and FIG. It is a graph showing the relationship of speed. FIG.
As shown in FIG. 1, a chromium-containing molten steel refining apparatus 13 applied to a method for refining chromium-containing molten steel according to an embodiment of the present invention includes an upper-bottom blow converter 1 which is an example of a refining furnace,
Lance 2 for blowing acid from above into molten iron in top and bottom blown converter 1
And a chute 4 for adding a ferrochrome alloy, a flux, a carbonaceous material and the like into the top-bottom blow converter 1, and a nozzle 3 for blowing an inert gas from the bottom. This nozzle 3
It has a double pipe structure so that the cooling fluid flows through the outer pipe to protect it. Further, a tapping port 5 for tapping molten steel that has been refined is provided on a side wall portion of the upper and bottom blown converter 1.
【００１０】次に、前記クロム含有溶鋼の精錬装置１３
を適用した本発明の一実施の形態に係るクロムを含有す
る溶鋼の精錬方法について、図２に示す精錬工程に従っ
て説明する。まず、第１工程は、上底吹き転炉１を用い
た脱炭工程であり、溶鉄（溶銑）６にフェロクロム合金
及びフラックス等をシュート４から添加し、ランス２か
ら吹酸し、底部のノズル３から不活性ガスを吹き込み、
吹酸による溶鉄６の脱炭精錬を行う。そして、溶鉄６
は、脱炭精錬により炭素が０．３〜０．８重量％程度に
脱炭されて溶鋼７が溶製される。この脱炭精錬の開始と
共に、クロム酸（Ｃｒ2 Ｏ3 ）が生成され、終了時に
は、クロム酸を多量に含有した脱炭スラグ８が形成され
る。第２工程では、上底吹き転炉１を傾転し、前記脱炭
スラグ８を炉内に残留させて、溶鋼７を出鋼口５から取
鍋９に出鋼し、上底吹き転炉１をもとに戻す。第３工程
では、上底吹き転炉１の炉内に脱炭スラグ８を残留させ
た状態で、溶銑鍋１０から溶鉄（溶銑）１１を装入す
る。更に、第４工程は、脱炭スラグ８の還元精錬を行う
工程であり、脱炭スラグ８に含有されたクロム酸を溶鉄
１１中に還元して回収する。この還元精錬は、上底吹き
転炉１の炉内にシュート４から炭材等を添加し、ランス
２から吹酸して昇熱し、底部のノズル３から不活性ガス
の吹き込みを行い、脱炭スラグ８中のクロム酸を還元す
る。第５工程は、スラグ排滓工程であり、還元精錬でク
ロムの回収を完了した脱炭スラグ８を排滓鍋１２に排滓
する。そして、引き続き、溶鉄１１は、脱炭精錬され
る。すなわち、第１から第５までの工程が、矢印（図２
中実線）で示すように連続して繰り返されることにな
る。Next, the chromium-containing molten steel refining apparatus 13
A method for refining chromium-containing molten steel according to an embodiment of the present invention to which is applied will be described in accordance with the refining process shown in FIG. First, the first step is a decarburization step using the top-bottom blowing converter 1, in which a ferrochrome alloy and a flux are added to the molten iron (hot metal) 6 from the chute 4 and the acid is blown from the lance 2 to form a nozzle at the bottom. Inert inert gas from 3
The decarburization and refining of the molten iron 6 by the blowing acid is performed. And molten iron 6
The carbon is decarbonized to about 0.3 to 0.8% by weight by decarburization refining, and molten steel 7 is smelted. At the start of the decarburization refining, chromic acid (Cr 2 O 3 ) is generated, and at the end, a decarburized slag 8 containing a large amount of chromic acid is formed. In the second step, the top and bottom blown converter 1 is tilted, the decarburized slag 8 is left in the furnace, and the molten steel 7 is discharged from the tapping hole 5 to the ladle 9, and the top and bottom blown converter is discharged. Undo 1 In the third step, molten iron (hot metal) 11 is charged from a hot metal ladle 10 with the decarburized slag 8 remaining in the furnace of the top and bottom blown converter 1. Further, the fourth step is a step for performing refining and refining of the decarburized slag 8, and reduces and recovers the chromic acid contained in the decarburized slag 8 in the molten iron 11. In this reduction smelting, a carbon material or the like is added from the chute 4 into the furnace of the top-bottom blow converter 1, the acid is blown up from the lance 2, the temperature is raised, and inert gas is blown from the nozzle 3 at the bottom to remove carbon. The chromic acid in the slag 8 is reduced. The fifth step is a slag discharge step, in which the decarburized slag 8 from which chromium has been recovered by reduction smelting is discharged into the discharge pan 12. Then, the molten iron 11 is continuously decarburized and refined. That is, the first to fifth steps are indicated by arrows (FIG. 2).
It is repeated continuously as shown by a solid line).
【００１１】特に、第４工程の脱炭スラグ８の還元精錬
においては、ランス２から吹き込まれる吹酸量（送酸速
度）や上底吹き転炉１内の攪拌状態によって、クロム酸
の還元の効率が大きく影響を受ける。即ち、還元精錬の
初期には、溶鉄１１及び脱炭スラグ８に、十分に熱を付
与し、反応を活発にすることにより還元速度を高位に維
持する。これは、初期が熱供給律速域であるので、送酸
速度を速くして吹酸することにより達成できる。しか
し、還元精錬の後期では、脱炭スラグ８のクロム酸が還
元されて溶鉄１１中へ移動する移動律速域になる。この
場合、送酸速度を速くした吹酸を行うと、還元された溶
鉄１１中のクロムの再酸化、鉄の酸化や熱の供給過剰に
なり、還元剤原単位の増加や鋼浴温度の上昇による耐火
物の溶損等の支障を招く。従って、還元精錬の初期で
は、脱炭スラグ８のクロム酸を還元するのに必要な全酸
素量の６０〜８０％を一定の送酸速度で吹酸し、後期に
は、段階的あるいは連続的に送酸速度を減速させながら
吹酸を行う。図３に示すように、吹酸量が全酸素量の６
０％に達する前に送酸速度を減ずると、点線（比較例）
のように、熱供給律速域からクロムのスラグへの移動律
速域に遷移する前の範囲において、吹酸量を低下させる
ことになり、クロムの還元速度が早い時点から落ち過ぎ
て精錬時間が大幅に延長したり耐火物の損耗を生じる。Particularly, in the refining and refining of the decarburized slag 8 in the fourth step, the reduction of chromic acid depends on the amount of blowing acid (acid feeding speed) blown from the lance 2 and the stirring state in the top and bottom blowing converter 1. Efficiency is greatly affected. That is, in the initial stage of the reduction smelting, sufficient heat is applied to the molten iron 11 and the decarburized slag 8 to activate the reaction, thereby maintaining a high reduction rate. This can be achieved by increasing the acid feed rate and blowing acid since the initial stage is the heat supply rate-controlling region. However, in the latter stage of the refining refining, the chromic acid in the decarburized slag 8 is reduced and moves to the molten iron 11 in a movement-controlling region. In this case, if blowing acid is performed at an increased acid supply rate, chromium in the reduced molten iron 11 is reoxidized, iron is oxidized, and heat is excessively supplied, so that the unit consumption of the reducing agent increases and the temperature of the steel bath increases. This causes troubles such as melting of refractory. Therefore, in the initial stage of the refining and refining, 60-80% of the total amount of oxygen necessary for reducing the chromic acid in the decarburized slag 8 is blown at a constant acid supply rate, and in the latter stage, it is stepwise or continuously. The blowing acid is performed while reducing the acid feeding speed. As shown in FIG. 3, the blowing acid amount is 6 times the total oxygen amount.
If the acid feed rate is reduced before reaching 0%, the dotted line (comparative example)
In the range before the transition from the heat supply control region to the chrome slag transfer control region, the amount of blowing acid is reduced, and the chromium reduction rate drops too fast from the early point, so the refining time Or the wear of refractories.
【００１２】一方、図４に示すように、吹酸量が全酸素
量の８０％を超えて送酸速度を減ずると、点線（比較
例）に示すように、スラグへのクロムの移動律速域に遷
移した後にも高速で精錬することになり、必要以上の熱
の供給が起こり、溶鋼の温度が過剰に上昇し、精錬炉の
耐火物の損耗を招く。また、還元精錬の後期では、送酸
速度を段階的あるいは連続的に減少しながら吹酸を行う
が、この送酸速度が減少した量（吹酸量）に見合う量の
不活性ガスの一例であるアルゴンガスをランス２から供
給し、酸素とアルゴンガスの混合ガスによって、吹き込
み速度（見掛け送酸速度）が低下するのを防止する。不
活性ガスを補充する量が送酸速度の減少した量より少な
いと、脱炭スラグ８の攪拌が不足するため、脱炭スラグ
８中のクロムの移動が阻害され、還元速度が低下し、還
元精錬の時間が延長する。更に、不活性ガスを補充する
量が送酸速度の減少した量より多いと、ランス２からの
混合ガスの吹き込み速度（見掛け送酸速度）が過剰にな
り、スピッティングの発生に伴う歩留りの低下や飛散し
た地金の処理等による作業性の悪化等を生じる。On the other hand, as shown in FIG. 4, when the amount of the acid to be blown is reduced to more than 80% of the total amount of oxygen and the acid supply rate is reduced, as shown by a dotted line (comparative example), the chromium transfer to the slag is limited. After the transition to, refining is performed at a high speed, heat is supplied more than necessary, the temperature of the molten steel rises excessively, and the refractory of the refining furnace is worn. In the latter half of the refining and refining, blowing acid is carried out while decreasing the acid sending rate stepwise or continuously. However, an example of the amount of the inert gas corresponding to the reduced amount of the acid sending (blow acid amount) is used. A certain argon gas is supplied from the lance 2 to prevent the blowing speed (apparent acid feeding speed) from being lowered by the mixed gas of oxygen and argon gas. If the replenishing amount of the inert gas is smaller than the reduced amount of the acid supply rate, the stirring of the decarburized slag 8 is insufficient, so that the movement of chromium in the decarburized slag 8 is inhibited, the reduction rate is reduced, and the reduction is reduced. Refining time is extended. Further, if the amount of replenishing the inert gas is larger than the reduced amount of the acid supply rate, the blowing rate of the mixed gas from the lance 2 (apparent acid supply rate) becomes excessive, and the yield decreases due to the occurrence of spitting. In addition, the workability is deteriorated due to the treatment of the scattered metal and the like.
【００１３】図５には、還元精錬の初期では、脱炭スラ
グのクロム酸を還元するのに必要な全酸素量の６０〜８
０％を一定の送酸速度で吹酸し、後期を段階的あるいは
連続的に減速して吹酸し、送酸速度が減少した量（吹酸
量）に見合う量の不活性ガスを補充してランスからの混
合ガスの吹き込み速度を低下させない場合を実線で示し
てあり、還元精錬の初期の還元速度を高位に安定して維
持でき、後期の還元速度の低下期間を少なくし、精錬時
間を大幅に短縮することができる。しかし、全酸素量の
６０〜８０％を一定の送酸速度で吹酸し、後期には、連
続的に減速して吹酸し、送酸速度が減少した量（吹酸
量）に見合う量の不活性ガスを補充しない比較例（点線
で示す）の場合は、還元速度が大幅に低下し、吹錬時間
が大幅に延長する。また、還元精錬の後期においては、
ランス２に不活性ガスを混合して供給することにより、
脱炭スラグ８の攪拌の保証、熱の過剰供給による異常な
温度の上昇、耐火物の損耗等の抑制に加え、雰囲気中の
ＣＯ分圧（Ｐｃｏ）を低下して、溶鉄１１中のクロムの
還元効率をより向上することができる。FIG. 5 shows that in the initial stage of the refining and refining, the total amount of oxygen required to reduce the chromic acid of the decarburized slag is 60 to 8%.
Oxygen is blown at 0% at a constant acid feed rate, and the latter period is gradually or stepwise decelerated to blow acid, and replenish the amount of inert gas corresponding to the reduced acid feed rate (blow acid amount). The solid line shows the case where the blowing speed of the mixed gas from the lance is not reduced, and the initial reduction speed of the refining and refining can be stably maintained at a high level, the reduction period of the latter reduction speed is reduced, and the refining time is reduced. It can be greatly reduced. However, an amount of 60-80% of the total oxygen is blown at a constant acid supply rate, and in the latter period, the acid is continuously decelerated and blown to an amount corresponding to the reduced amount of the acid transfer (blow acid amount). In the case of the comparative example (indicated by a dotted line) in which the inert gas is not replenished, the reduction rate is greatly reduced and the blowing time is greatly extended. In the latter half of refining refining,
By mixing and supplying an inert gas to the lance 2,
In addition to guaranteeing the stirring of the decarburized slag 8, suppressing an abnormal increase in temperature due to excessive supply of heat, and reducing the wear of refractories, the CO partial pressure (Pco) in the atmosphere is reduced to reduce the chromium in the molten iron 11. The reduction efficiency can be further improved.
【００１４】[0014]
【実施例】上底吹き転炉を用いて、炭素を３重量％以上
含む１５０トンの溶鉄にフェロクロムを装入して、ラン
スから酸素流量を２８０００Ｎｍ3 ／ｈｒで吹酸し、脱
炭精錬を行って、炭素が０．７重量％以下のクロム含有
溶鋼を溶製した。この脱炭精錬によって酸化クロムを含
有した脱炭スラグが形成され、クロムを含有した溶鋼を
出鋼し、この脱炭スラグを炉内に残留させた。そして、
炉内に新たに溶鉄を装入し、炭材を添加しながらランス
から吹酸しながら還元精錬を開始し、表１に示す還元精
錬の初期の送酸速度変更点（対全酸素量％）から送酸速
度を減少し、送酸速度の減少と共にアルゴンガス補充率
（対送酸速度低下量％）を調整して還元精錬を終了し
た。そして、溶鉄の還元終了時の温度上昇（℃）、耐火
物溶損状況、クロム還元歩留り、地金付着状況、生産性
等を調査した。表１に示すように、実施例１〜４は、吹
酸する全酸素量の６０〜８０％の範囲から送酸速度を変
更し、送酸速度低下量の同量のアルゴンガスを補充した
場合であり、前記の還元終了時の温度上昇、耐火物溶損
状況等いずれの項目についても良好であり、生産性が大
であり、総合評価として良好（○）であった。EXAMPLE Using a top-bottom blowing converter, ferrochrome was charged into 150 tons of molten iron containing at least 3% by weight of carbon, and the oxygen was blown from a lance at an oxygen flow rate of 28,000 Nm 3 / hr to carry out decarburization refining. Then, chromium-containing molten steel having 0.7% by weight or less of carbon was smelted. By this decarburization refining, decarburized slag containing chromium oxide was formed, molten steel containing chromium was tapped, and the decarburized slag was left in the furnace. And
The molten iron is newly charged into the furnace, and the refining is started while adding carbonaceous material and blowing acid from the lance, and the initial acid-feeding rate change point of the reducing refining shown in Table 1 (relative to the total oxygen content%) Then, the acid feeding rate was decreased, and the refining and refining was completed by adjusting the argon gas replenishment rate (relative to the acid feeding rate%) with the decrease in the acid feeding rate. Then, the temperature rise (° C.) at the end of the reduction of the molten iron, the state of erosion of refractories, the chromium reduction yield, the state of metal ingot, the productivity, and the like were investigated. As shown in Table 1, in Examples 1 to 4, the acid supply rate was changed from the range of 60 to 80% of the total amount of oxygen to be blown, and the same amount of argon gas as the acid supply rate was reduced. All of the items, such as the temperature rise at the end of the reduction and the state of refractory erosion, were good, the productivity was high, and the overall evaluation was good (○).
【００１５】[0015]
【表１】 [Table 1]
【００１６】これに対し、比較例５、６は、吹酸する全
酸素量％の６０〜８０％の範囲から外れて送酸速度を変
更し、送酸速度低下量と同量の不活性ガスをを補充した
場合であり、比較例５では、還元速度が悪くなり生産性
が低下した。比較例６では、還元終了時の温度が上昇
し、耐火物溶損が大きくなり、いずれも総合評価として
悪い（×）結果となった。On the other hand, in Comparative Examples 5 and 6, the acid supply rate was changed out of the range of 60 to 80% of the total oxygen amount% to be blown, and the same amount of inert gas as the decrease in the acid supply rate was used. In Comparative Example 5, the reduction rate was reduced and the productivity was reduced. In Comparative Example 6, the temperature at the end of the reduction was increased, and the refractory erosion was increased. In each case, the overall evaluation was poor (x).
【００１７】以上、本発明の実施の形態を説明したが、
本発明はこれらの実施の形態に限定されるものではな
く、要旨を逸脱しない条件の変更等は全て本発明の適用
範囲である。例えば、底部のノズルからの不活性ガスの
一部を酸素に置換して吹き込んでも良い。更に、脱炭ス
ラグ中のクロムの還元を行う際に、アルミ合金、アルミ
ドロス等の還元剤を用いることもできる。また、精錬炉
としては、上底吹き転炉にかえて、上吹き転炉、電気
炉、ＡＯＤ（Ａｒｇｏｎ−Ｏｘｙｇｅｎ−Ｄｅｃａｒｂ
ｕｒｉｚａｔｉｏｎ）等を用いることもできる。The embodiment of the present invention has been described above.
The present invention is not limited to these embodiments, and all changes in conditions without departing from the gist are within the scope of the present invention. For example, part of the inert gas from the nozzle at the bottom may be replaced with oxygen and blown. Further, when reducing chromium in the decarburized slag, a reducing agent such as an aluminum alloy or aluminum dross can be used. Further, as the refining furnace, a top-blowing converter, an electric furnace, and an AOD (Argon-Oxygen-Decarb) are used instead of the top-bottom-blowing converter.
urization) can be used.
【００１８】[0018]
【発明の効果】請求項１〜４記載のクロムを含有する溶
鋼の精錬方法は、全吹酸量の６０〜８０％を吹酸した後
に、吹酸の送酸速度を低下させるので、クロム酸の還元
速度を速くして精錬時間を短縮し、クロムを溶鉄中に効
率良く回収でき、精錬炉の耐火物の損耗を抑制すること
ができる。According to the method for refining molten steel containing chromium according to any one of claims 1 to 4, the acid supply rate of the acid is reduced after the acid is blown to 60 to 80% of the total amount of the acid to be blown. The smelting time can be shortened by increasing the reduction rate of chromium, chromium can be efficiently recovered in the molten iron, and the wear of refractories in the smelting furnace can be suppressed.
【００１９】特に、請求項２記載のクロムを含有する溶
鋼の精錬方法は、送酸速度を段階的に低下させるので、
溶鋼温度の上昇の防止とクロムの再酸化を抑制し、精錬
炉の耐火物の損耗を防止することができる。In particular, the method for refining molten steel containing chromium according to the second aspect of the present invention reduces the rate of acid supply step by step.
It is possible to prevent the temperature of the molten steel from rising and to suppress the reoxidation of chromium, thereby preventing the refractory of the smelting furnace from being worn.
【００２０】請求項３記載のクロムを含有する溶鋼の精
錬方法は、送酸速度を連続して低下させるので、還元精
錬の末期の溶鋼温度の上昇とクロムの再酸化を抑制し、
精錬炉の耐火物の損耗等をより確実に防止することがで
きる。In the method for refining chromium-containing molten steel according to claim 3, since the acid supply rate is continuously reduced, the increase in the temperature of molten steel and the reoxidation of chromium at the end of reduction refining are suppressed,
Wear and the like of the refractory of the refining furnace can be more reliably prevented.
【００２１】請求項４記載のクロムを含有する溶鋼の精
錬方法は、送酸速度の低下により減少する酸素量と同量
の不活性ガスを供給するので、溶鉄と脱炭スラグを積極
的に接触させて、還元精錬の後期の還元速度を高位に維
持することができ、未還元のクロム酸を抑制してクロム
の歩留りを安定して向上することができる。In the method for refining molten steel containing chromium according to the present invention, since the same amount of inert gas as the amount of oxygen reduced by the reduction of the acid supply rate is supplied, the molten iron and the decarburized slag are positively contacted. As a result, the reduction rate in the latter half of the refining and refining can be maintained at a high level, and the unreduced chromic acid can be suppressed to stably improve the yield of chromium.
【図１】本発明の一実施の形態に係るクロムを含有する
溶鋼の精錬方法に適用されるクロム含有溶鋼の精錬装置
の全体図である。FIG. 1 is an overall view of a chromium-containing molten steel refining apparatus applied to a method for refining chromium-containing molten steel according to an embodiment of the present invention.
【図２】同クロム含有溶鋼の精錬装置を用いた精錬工程
の説明図である。FIG. 2 is an explanatory diagram of a refining process using the chromium-containing molten steel refining apparatus.
【図３】溶鉄の吹酸量とクロムの還元速度の関係を表す
グラフである。FIG. 3 is a graph showing the relationship between the amount of blowing acid of molten iron and the reduction rate of chromium.
【図４】吹酸量と溶鉄の温度の関係を表すグラフであ
る。FIG. 4 is a graph showing the relationship between the amount of blowing acid and the temperature of molten iron.
【図５】溶鉄の吹酸量とクロムの還元速度の関係を表す
グラフである。FIG. 5 is a graph showing the relationship between the amount of blowing acid of molten iron and the reduction rate of chromium.
１：上底吹き転炉、２：ランス、３：ノズル、４：シュ
ート、５：出鋼口、６：溶鉄、７：溶鋼、８：脱炭スラ
グ、９：取鍋、１０：溶銑鍋、１１：溶鉄、１２：排滓
鍋、１３：クロム含有溶鋼の精錬装置1: Top and bottom blown converter, 2: Lance, 3: Nozzle, 4: Chute, 5: Tapping port, 6: Molten iron, 7: Molten steel, 8: Decarburized slag, 9: Ladle, 10: Hot metal pot, 11: molten iron, 12: waste pan, 13: chromium-containing molten steel refining equipment
Claims (4)
際に生成した脱炭スラグを前記精錬炉内に残留させて溶
鋼を排出し、該精錬炉内に溶鉄Ｂを装入し、吹酸を行っ
て前記脱炭スラグに含まれるクロムを前記溶鉄Ｂ中に回
収してから前記脱炭スラグのみを排滓して、引き続き前
記溶鉄Ｂを脱炭精錬する溶鋼の精錬方法において、全吹
酸量の６０〜８０％を吹酸した後に、送酸速度を低下さ
せることを特徴するクロムを含有する溶鋼の脱炭精錬方
法。Claims: 1. Decarburized slag generated when decarbonizing and refining molten iron A by a refining furnace is left in the refining furnace to discharge molten steel, and molten iron B is charged into the refining furnace. In a method for refining molten steel, the chromium contained in the decarburized slag is recovered in the molten iron B by performing acid blowing, then only the decarburized slag is discharged, and the molten iron B is subsequently decarburized and refined. A method for decarburizing and refining molten steel containing chromium, characterized in that the acid supply rate is reduced after 60-80% of the amount of the acid is blown.
精錬方法において、前記送酸速度を段階的に低下させる
クロムを含有する溶鋼の精錬方法。2. The method for refining chromium-containing molten steel according to claim 1, wherein the chromium-containing molten steel is reduced in a stepwise manner.
精錬方法において、前記送酸速度を連続して低下させる
クロムを含有する溶鋼の精錬方法。3. The method for refining chromium-containing molten steel according to claim 1, wherein said chromium-containing molten steel is continuously reduced in acid supply rate.
ロムを含有する溶鋼の精錬方法において、前記送酸速度
の低下により減少する酸素量と同量の不活性ガスを供給
するクロムを含有する溶鋼の精錬方法。4. The method for refining chromium-containing molten steel according to claim 1, wherein the same amount of inert gas as the amount of oxygen reduced by the reduction in the acid supply rate is supplied. A method for refining molten steel.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11205145A JP2001032009A (en) | 1999-07-19 | 1999-07-19 | Method for refining molten steel containing chromium |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP11205145A JP2001032009A (en) | 1999-07-19 | 1999-07-19 | Method for refining molten steel containing chromium |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JP2001032009A true JP2001032009A (en) | 2001-02-06 |
Family
ID=16502176
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP11205145A Withdrawn JP2001032009A (en) | 1999-07-19 | 1999-07-19 | Method for refining molten steel containing chromium |
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| Country | Link |
|---|---|
| JP (1) | JP2001032009A (en) |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007266632A (en) * | 2002-01-11 | 2007-10-11 | Ngk Insulators Ltd | Piezoelectric/electrostrictive device |
| JP2012216858A (en) * | 2012-06-15 | 2012-11-08 | Renesas Electronics Corp | Semiconductor device manufacturing method and semiconductor device |
| KR20200049076A (en) * | 2018-10-31 | 2020-05-08 | 주식회사 포스코 | Method for processing molten material and stainless steel manufactured using the same |
-
1999
- 1999-07-19 JP JP11205145A patent/JP2001032009A/en not_active Withdrawn
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2007266632A (en) * | 2002-01-11 | 2007-10-11 | Ngk Insulators Ltd | Piezoelectric/electrostrictive device |
| JP4562756B2 (en) * | 2002-01-11 | 2010-10-13 | 日本碍子株式会社 | Piezoelectric / electrostrictive device |
| JP2012216858A (en) * | 2012-06-15 | 2012-11-08 | Renesas Electronics Corp | Semiconductor device manufacturing method and semiconductor device |
| KR20200049076A (en) * | 2018-10-31 | 2020-05-08 | 주식회사 포스코 | Method for processing molten material and stainless steel manufactured using the same |
| KR102171769B1 (en) * | 2018-10-31 | 2020-10-29 | 주식회사 포스코 | Method for processing molten material and stainless steel manufactured using the same |
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