JPH10121123A - Production of molten low nitrogen steel with arc furnace - Google Patents
Production of molten low nitrogen steel with arc furnaceInfo
- Publication number
- JPH10121123A JPH10121123A JP27933696A JP27933696A JPH10121123A JP H10121123 A JPH10121123 A JP H10121123A JP 27933696 A JP27933696 A JP 27933696A JP 27933696 A JP27933696 A JP 27933696A JP H10121123 A JPH10121123 A JP H10121123A
- Authority
- JP
- Japan
- Prior art keywords
- molten steel
- carbon
- time
- refining
- molten
- 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.)
- Pending
Links
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
Landscapes
- Refinement Of Pig-Iron, Manufacture Of Cast Iron, And Steel Manufacture Other Than In Revolving Furnaces (AREA)
Abstract
Description
【0001】[0001]
【発明の属する技術分野】この発明は、スクラップ、還
元鉄および銑鉄等の鉄源原料をアーク炉で溶解し鋼を製
造する方法に関し、特に高純度酸素ガスを用いることお
よび溶湯中C含有率を適正値に維持しつつCOボイリン
グを一定時間継続させ、この間十分なスラグフォーミン
グを維持することにより低窒素溶鋼を得るためのアーク
炉の操業方法に関するものである。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing steel by melting an iron source material such as scrap, reduced iron and pig iron in an arc furnace, and more particularly to using high-purity oxygen gas and reducing the C content in the molten metal. The present invention relates to an operation method of an arc furnace for obtaining low nitrogen molten steel by maintaining CO slag for a certain period of time while maintaining an appropriate value and maintaining sufficient slag forming during this period.
【0002】[0002]
【従来の技術】従来、アーク炉でスクラップを溶解し精
錬した溶鋼から、冷延鋼板や表面処理鋼板等の薄鋼板を
製造することは、スクラップ中に多量に含まれるCuや
Sn等の不純物元素が材質に及ぼす影響の問題から不可
能であった。しかしながら、近年、スクラップ以外に還
元鉄や溶銑の配合比率を高めることにより装入原料中の
CuやSn等の不純物元素の混入量を低減させることが
可能となったので、アーク炉製鋼法によっても従来の高
炉−転炉製鋼法によってしか製造できなかった深絞り用
冷延鋼板を製造しようとする動きがある。2. Description of the Related Art Conventionally, the production of thin steel sheets, such as cold-rolled steel sheets and surface-treated steel sheets, from molten steel obtained by melting and refining scraps in an electric arc furnace is based on impurities such as Cu and Sn contained in a large amount in the scraps. Was not possible due to the problem of the effect of the material on the material. However, in recent years, by increasing the mixing ratio of reduced iron and hot metal other than scrap, it has become possible to reduce the amount of impurity elements such as Cu and Sn in the charged raw material, so that the arc furnace steelmaking method can also be used. There is a movement to manufacture cold-rolled steel sheets for deep drawing that could only be manufactured by the conventional blast furnace-converter steelmaking method.
【0003】一方、深絞り用冷延鋼板は鋼中窒素に起因
する時効現象を抑制するために、窒素含有率を通常40
ppm以下に低減することが要求される。上記状況に対
して、従来のアーク炉製鋼法による低窒素鋼製造技術と
して、例えば、「最近のアーク炉製鋼法の進歩」(平成
5年10月7日、日本鉄鋼協会発行、第121頁)や
「普通鋼電気炉操業のストラテジー」(平成6年11月
14日、日本鉄鋼協会発行、第112頁)(以上2件を
「先行技術1」という)は、アーク炉での溶落ち時の溶
湯C含有率を高めにし、精錬期の脱炭反応に伴なうCO
ボイリングを活発に行なわせたり、Arガス等による溶
鋼のガス撹拌により脱窒(脱N)を促進する方法を開示
しているが、現状では溶鋼のN含有率を50〜60pp
mまで減少させるのが限界である。また、装入鉄源原料
の75wt.%以上を直接還元鉄とする高還元鉄配合操業に
より窒素含有率が40ppm以下の溶鋼が得られるとの
記載が「5th European Electric
Steel Congress発表論文集」(199
5年6月19日開催、French Steel Fe
deration主催、Les Editions d
ela Revue de Metallurgie発
行、p.41)(「先行技術2」という)にあるが、こ
れには詳細な製造方法は記載されていない。[0003] On the other hand, a cold-rolled steel sheet for deep drawing usually has a nitrogen content of 40 to suppress the aging phenomenon caused by nitrogen in the steel.
It is required to reduce to below ppm. In response to the above situation, as a conventional low-nitrogen steel manufacturing technique using an arc furnace steelmaking method, for example, “Recent progress in arc furnace steelmaking method” (October 7, 1993, Japan Iron and Steel Association, p. 121) And "Strategy for the operation of ordinary steel electric furnaces" (published by the Iron and Steel Institute of Japan on November 14, 1994, p. 112) (the above two cases are referred to as "prior art 1") Increasing the C content in the molten metal and reducing the CO associated with the decarburization reaction during the refining period
A method is disclosed in which boiling is actively performed and denitrification (de-N) is promoted by gas stirring of molten steel with Ar gas or the like.
m is the limit. In addition, it is described that a molten steel having a nitrogen content of 40 ppm or less can be obtained by a high-reduced iron compounding operation in which 75% by weight or more of the charged iron source material is directly reduced iron.
"Steel Congress Presentations" (199
Held on June 19, 5th, French Steel Fe
sponsored by duration, Les Editions d
ela Revue de Metallurgie, p. 41) (referred to as “prior art 2”), but does not describe a detailed manufacturing method.
【0004】このように現在のところ、アーク炉による
低窒素鋼の溶製、例えば、窒素含有率40ppm以下の
低窒素鋼の溶製方法については明確な方法は提案されて
いない。As described above, at present, no specific method has been proposed for melting low-nitrogen steel using an arc furnace, for example, for melting low-nitrogen steel having a nitrogen content of 40 ppm or less.
【0005】[0005]
【発明が解決しようとする課題】上述した先行技術1の
ように、アーク炉操業方法の改善により、N含有率50
〜60ppmレベルの低窒素鋼材を製造することは可能
であり、熱延鋼板レベルの加工性を有する薄鋼板を製造
することはできるが、N含有率40ppm以下が要求さ
れる深絞り用の冷延鋼板や表面処理鋼板を、特別に設備
を付加したり原料供給体制を付加せずにアーク炉操業方
法の改善により製造する技術は確立されていない。As described in Prior Art 1 described above, an improvement in the operation method of the arc furnace has resulted in an N content of 50%.
It is possible to produce low-nitrogen steel materials at levels of up to 60 ppm, and to produce thin steel sheets having workability at the level of hot-rolled steel sheets, but cold-rolling for deep drawing requires an N content of 40 ppm or less. The technology to manufacture steel sheets and surface-treated steel sheets by improving the arc furnace operation method without adding special equipment or adding a raw material supply system has not been established.
【0006】一方、上述した先行技術2によれば、アー
ク炉を用いてN含有率が40ppm以下の溶鋼を得るこ
とができる。この方法は、直接還元鉄の供給が十分にな
され得る条件下においては低窒素鋼の製造に有効であ
る。しかしながら、配合率75wt.%以上という大量の直
接還元鉄を安定して供給する条件を備えなければならな
いという問題がある。On the other hand, according to the prior art 2 described above, molten steel having an N content of 40 ppm or less can be obtained using an arc furnace. This method is effective for producing low-nitrogen steel under conditions where the supply of direct reduced iron can be sufficiently provided. However, there is a problem that a condition for stably supplying a large amount of directly reduced iron having a blending ratio of 75 wt.% Or more must be provided.
【0007】従って、この発明の目的は、大量の直接還
元鉄を用いることなく、また真空脱ガス精錬プロセスを
付加することなく、アーク炉操業方法の改善のみにより
窒素含有率40ppm以下の溶鋼を得るためのアーク炉
による低窒素溶鋼の製造方法を提供することにある。Accordingly, an object of the present invention is to obtain molten steel having a nitrogen content of 40 ppm or less only by improving the operation method of an arc furnace without using a large amount of direct reduced iron and without adding a vacuum degassing refining process. To provide a method for producing low-nitrogen molten steel using an arc furnace.
【0008】[0008]
【課題を解決するための手段】本発明者等は、上記観点
からアーク炉操業方法を改善すべく鋭意研究を重ねた。
アーク炉精錬終了時における溶鋼の窒素含有率〔N〕を
きめる要因は、炉内に装入されたスクラップの溶解を終
了した時点、所謂溶落ち時における〔N〕、および、溶
落ち時以後の精錬期に炉内に吹き込まれた酸素ガスと溶
鋼中Cとの反応により生成したCO気泡へ溶鋼中Nが離
脱する量(脱N量)と、その期間中に炉内へ侵入した空
気中の窒素がスラグを通して溶鋼に吸収される量(吸N
量)とのバランスである。従って、例えば溶落ち時の
〔N〕が与えられたときは、精錬終了時の〔N〕を低減
させるためには、溶鋼脱炭時にCO気泡を大量に発生さ
せて脱Nを促進させること、および、溶鋼表面を被覆す
るスラグをフォーミングさせることにより溶鋼への侵入
空気を遮断して吸Nを抑制することが必要である。Means for Solving the Problems The present inventors have made intensive studies to improve the operation method of the arc furnace from the above viewpoint.
The factors that determine the nitrogen content [N] of molten steel at the end of arc furnace refining are the time when melting of scrap loaded in the furnace is completed, the so-called [N] at the time of burn-through, and In the refining period, the amount of N released from the molten steel into CO bubbles generated by the reaction between oxygen gas blown into the furnace and C in the molten steel (the amount of de-N), and the amount of N in the air that entered the furnace during that period The amount of nitrogen absorbed by molten steel through slag (absorption N
Amount). Therefore, for example, when [N] at the time of burn-down is given, in order to reduce [N] at the end of refining, a large amount of CO bubbles are generated at the time of decarburization of molten steel to promote de-N. In addition, it is necessary to form a slag covering the surface of the molten steel to shut off air entering the molten steel and suppress N absorption.
【0009】本発明者等は上記着想により、脱Nを促進
させるためのCO発生条件、およびスラグフォーミング
を十分確保するための条件について、60tonから2
00ton規模のアーク炉を用いて種々の試験を行な
い、その試験結果を解析した。その結果、アーク炉精錬
終了時に窒素含有率が40ppm以下の低窒素溶鋼を得
るためには下記〜の条件を同時に満たす必要がある
との結論を得た。[0009] Based on the above idea, the present inventors have set the conditions for generating CO for promoting denitrification and the conditions for ensuring sufficient slag forming from 60 tons to 2 tons.
Various tests were performed using a 00 ton-scale arc furnace, and the test results were analyzed. As a result, it was concluded that the following conditions (1) to (4) must be simultaneously satisfied in order to obtain a low nitrogen molten steel having a nitrogen content of 40 ppm or less at the end of arc furnace refining.
【0010】精錬期における炉内への送酸速度Qo2が
下記(1)式、望ましくは(1’)式: Qo2≧0.55 Nm3 /min/ton ----------(1) Qo2≧0.67 Nm3 /min/ton ----------(1') を満たす条件下で所定の送酸時間(t* min)吹錬す
ることが必要である。かかる送酸速度Qo2に対して溶鋼
から十分なCOガスを発生させるのに必要なC含有率
〔C〕* (wt.%)を溶鋼中に確保する。かくして、溶鋼
の脱N反応:2N=N2 (g)を促進させると同時に、
十分なスラグフォーミングを確保し吸N反応を抑制する
ことができるので、溶鋼の脱Nが進行する。In the refining period, the acid supply rate Qo 2 into the furnace is expressed by the following equation (1), preferably, equation (1 ′): Qo 2 ≧ 0.55 Nm 3 / min / ton -(1) Qo 2 ≧ 0.67 Nm 3 / min / ton ----- Blowing for a specified acid supply time (t * min) under the condition of (1 ') is required. The C content [C] * (wt.%) Necessary for generating sufficient CO gas from the molten steel for such an acid feed rate Qo 2 is ensured in the molten steel. Thus, the de-N reaction of molten steel: 2 N = N 2 (g) is promoted,
Since sufficient slag forming can be ensured and the N absorption reaction can be suppressed, the N removal of molten steel proceeds.
【0011】ここで、上記送酸時間t* minは、下
記(2)式: t* ≧−7.2Qo2+15 ----------(2) を満たすことが必要であり、且つ、 精錬期間に溶鋼が含有する炭素の総量T.Cはこの期
間に送酸される全酸素が溶鋼中炭素と反応してCOを生
成すると仮定した場合の炭素当量C* 以上に存在するこ
と、が上記溶鋼中C含有率〔C〕* を確保するために必
要である。即ち、下記(3a)式: T.C≧C* ------------(3a) を満たすことが必要である。ここで、T.CおよびC*
はそれぞれ下記(4)および(5)式: T.C=CMD+Cadd ------------(4) C* =(12/11.2)Qo2t* W ------------(5) 但し、 CMD:溶落ち時の溶鋼に含まれるC重量(kg) Cadd :吹錬中に溶鋼に添加すべき炭素重量(kg) W :溶落ち時の溶鋼重量(ton) で表わされる。(3a)式と(4)および(5)式とから
下記(3b)式: CMD+Cadd ≧(12/11.2)Qo2t* W ------------(3b) が得られ、これより下記(3)式: Cadd ≧(12/11.2)Qo2t* W−CMD ------------(3) が得られる。Here, the above-mentioned acid feeding time t * min needs to satisfy the following equation (2): t * ≧ −7.2 Qo 2 +15 (2) And the total amount of carbon contained in the molten steel during the refining period. C is present at a carbon equivalent C * or more assuming that all the oxygen fed during this period reacts with carbon in the molten steel to form CO, thereby ensuring the C content [C] * in the molten steel. Needed to do so. That is, the following equation (3a): It is necessary to satisfy C ≧ C * -------- (3a). Here, T. C and C *
Is the following formulas (4) and (5), respectively: C = C MD + C add ------------ (4) C * = (12 / 11.2) Qo 2 t * W ------------ (5 ) Where C MD : weight of carbon contained in molten steel at the time of meltdown (kg) C add : weight of carbon to be added to molten steel during blowing (kg) W: weight of molten steel at the time of meltdown (ton) . From the equations (3a) and (4) and (5), the following equation (3b): C MD + C add ≧ (12 / 11.2) Qo 2 t * W ------------ (3b) is obtained, from which the following formula (3) is obtained: C add ≧ (12 / 11.2) Qo 2 t * W-C MD ------------ (3) Can be
【0012】ここで、上記(3)式で算出される炭素添
加量Cadd が正の値のときは当該重量の炭素を添加しつ
つ精錬しなければならないが、炭素添加量Cadd が負の
値または零のときは炭素を添加せずに精錬してもよい。Here, when the carbon addition amount C add calculated by the above equation (3) is a positive value, refining must be performed while adding the carbon of the relevant weight, but the carbon addition amount C add is negative. When the value is zero or zero, refining may be performed without adding carbon.
【0013】このように、(1)式望ましくは(1’)
式の送酸速度Qo2で酸素ガスを炉内へ供給し、且つ、
(3)式および(2)式が同時に満たされるように溶鋼
中にC add の炭素を添加しつつ時間t* の間送酸を継続
することにより、溶鋼の脱Nを所定時間継続させること
ができ、精錬終了時には溶鋼中の窒素含有率を40pp
m以下に低減させることができる。Thus, equation (1), preferably (1 ')
Formula acid transfer rate QoTwoTo supply oxygen gas into the furnace, and
Molten steel so that equations (3) and (2) are simultaneously satisfied
C inside addTime t while adding carbon*Continue acid transfer during
To continue the de-N of molten steel for a predetermined time
At the end of refining, the nitrogen content in molten steel was reduced to 40 pp.
m or less.
【0014】但し、炉内へ送酸する酸素ガスは、純度9
9.0vol.% 以上の酸素ガスであることが必要である。
通常、純酸素ガスは空気から製造するので主な不純物ガ
スとして窒素を含む。送酸すべき酸素ガス中に窒素が
1.0vol.% 以上含有されると精錬終了時に溶鋼中窒素
含有率が安定して40ppm以下にならないからであ
る。However, the oxygen gas sent into the furnace has a purity of 9%.
It is necessary that the oxygen gas is 9.0 vol.% Or more.
Normally, pure oxygen gas is produced from air, and thus contains nitrogen as a main impurity gas. This is because if the oxygen gas to be acidified contains 1.0 vol.% Or more of nitrogen, the nitrogen content in the molten steel does not stably become 40 ppm or less at the end of refining.
【0015】更に、精錬期における送酸速度Qo2は大き
いほどCOボイリングは活発になり、溶鋼の脱Nには有
利となり低窒素溶鋼を得るには有利であるが、一方CO
ガス発生速度が大きくなるにつれてスプラッシュの発生
量も多くなり溶鋼歩留の低下、およびスプラッシュ地金
の堆積による操業上の問題が生じる。上記問題の発生を
防ぐためにこの発明においては送酸速度Qo2を1.35
Nm3 /min/ton以下に限定する。Further, as the acid feeding rate Qo 2 in the refining period increases, CO boiling becomes more active, which is advantageous for denitrification of molten steel and advantageous for obtaining low nitrogen molten steel.
As the gas generation rate increases, the amount of splash generated also increases, causing a reduction in molten steel yield and an operational problem due to the accumulation of splash metal. In order to prevent the above problem from occurring, in the present invention, the acid supply rate Qo 2 is set to 1.35.
Nm 3 / min / ton or less.
【0016】なお、図3に、この発明において送酸速度
Qo2および送酸時間t* が満たすべき範囲を図示した。
以上より、この発明のアーク炉による低窒素溶鋼の製造
方法は、アーク炉でスクラップ、還元鉄および銑鉄等の
鉄源原料の内少なくとも一種を溶解し、原料の溶解を終
了後、炉内に酸素ガスを供給し、炉内に形成された溶鉄
を精錬するに際し、酸素ガスの純度を99.0vol.% 以
上とし、送酸速度Qo2および送酸時間t * がそれぞれ下
記(1)および(2)式: Qo2=0.55〜1.35(Nm3 /min/ton)の範囲内 ------------(1) t* ≧−7.2Qo2+15(min) ------------(2) を満たし、且つ、下記(3)式: Cadd ≧(12/11.2)Qo2t* W−CMD(kg)--------- (3) 但し、 W :原料溶解終了時の溶鉄量(ton) CMD:原料溶解終了時の溶鉄に含まれる炭素重量(k
g) で炭素添加量Cadd を算出し、前記炭素添加量Cadd が
正の値のときは当該重量の炭素を添加しつつ精錬するこ
とに特徴を有するものである。FIG. 3 shows the acid feeding rate in the present invention.
QoTwoAnd acid supply time t*The range which should be satisfied is illustrated.
As described above, production of low nitrogen molten steel by the arc furnace of the present invention
The method uses scrap, reduced iron and pig iron in an arc furnace.
Dissolve at least one of the iron source materials and finish dissolving the materials.
After that, supply oxygen gas into the furnace,
In refining, the purity of oxygen gas should be 99.0 vol.% Or less.
Above and acid transfer rate QoTwoAnd acid supply time t *Is below
Expressions (1) and (2): QoTwo= 0.55 to 1.35 (NmThree/ Min / ton) ------------ (1) t*≧ -7.2QoTwo+15 (min) ------------ Satisfies (2) and the following equation (3): Cadd≧ (12 / 11.2) QoTwot*WCMD(Kg) --------- (3) Where, W: amount of molten iron at the end of raw material melting (ton) CMD: Weight of carbon contained in molten iron at the end of melting of raw material (k
g) and the carbon addition amount CaddIs calculated, and the carbon addition amount C is calculated.addBut
If the value is positive, refining while adding the carbon
And features.
【0017】[0017]
【発明の実施の形態】次に、この発明の実施形態の望ま
しい例を説明する。所定の製鋼用直流アーク炉に溶解原
料として鋼スクラップと冷銑とを装入し、更に初装入コ
ークスおよび造滓材を装入し、酸素ガスを付加しながら
原料を溶解すると共に溶湯表面に溶融スラグを形成させ
る。溶落ち後、溶鋼の測温および炭素含有率の分析をす
る。次いで、精錬期において送酸速度Qo2、送酸時間t
* で吹錬し、この間固体炭素源として粉コークスを炭素
換算量でCadd だけ吹込みながら精錬した。ここで、送
酸速度Qo2、送酸時間t* および炭素添加量Cadd は、
それぞれ上記(1’)、(2)および(3)式を満たす
ように調整する。精錬終了後、溶鋼の測温、所定の成分
組成分析をし、取鍋への出鋼時に所定量の合金鉄を添加
し成分組成を調整する。Next, a preferred example of an embodiment of the present invention will be described. A predetermined steelmaking DC arc furnace is charged with steel scrap and cold pig as raw materials for melting, further charged with initially charged coke and slag-making material, melts the raw materials while adding oxygen gas, and also on the surface of the molten metal. Form molten slag. After the burn-through, the temperature of the molten steel is measured and the carbon content is analyzed. Next, in the refining period, the acid supply rate Qo 2 and the acid supply time t
* During this time, refining was performed while blowing coke fine as a solid carbon source by C add in terms of carbon. Here, the acid supply rate Qo 2 , the acid supply time t *, and the carbon addition amount C add are:
Adjustments are made so as to satisfy the above equations (1 ′), (2) and (3), respectively. After the refining, the temperature of the molten steel is measured and a predetermined component composition is analyzed. At the time of tapping into a ladle, a predetermined amount of iron alloy is added to adjust the component composition.
【0018】上述したように、精錬期において
(1’)、(2)および(3)式が同時に満足されなけ
ればならないとの知見は、溶鋼の脱Nに及ぼすCOボイ
リング気泡中のN分圧、脱N反応速度と吸N反応速度と
のバランスにより定まる脱N速度、および、脱N所要時
間の影響に着眼し、実炉による試験結果を解析して得ら
れたものである。この場合、送酸により溶鋼中炭素と反
応して発生するCOガス気泡中に溶鋼中の窒素が拡散し
て捕捉され、溶鋼表面の溶融スラグ層を経て鋼浴から抜
け出る。同時にこのとき、溶融スラグはこのCO気泡に
よりフォーミング状態になり、鋼浴を炉内への侵入空気
から遮断する働きをする。また、この発明では、純度9
9.0vol.% 以上の酸素ガスを使用するので、酸素ガス
中の窒素含有率は1.0vol.% 未満となるから、フォー
ミングスラグ中のガスの窒素分圧は0.005atm以
下が期待される。従って、例えば、1600℃における
上記ガスと溶鋼との間の平衡窒素濃度は31.8ppm
と算出され、フォーミングスラグ層からの吸N現象が起
きることはない。また、純度99.5vol.% の酸素ガス
を使用する場合には上記窒素分圧は0.0025atm
以下が期待され、上記平衡窒素濃度は22.5ppmと
算出され一層望ましい。上記理由により、溶鋼の脱Nが
進行し精錬終了時には40ppm以下の低窒素溶鋼が得
られる。As mentioned above, the finding that the expressions (1 '), (2) and (3) must be satisfied simultaneously in the refining period is based on the effect of the N partial pressure in the CO boil bubbles on the de-N of molten steel. The results were obtained by analyzing the test results using an actual furnace, focusing on the effects of the N removal rate determined by the balance between the N removal rate and the N absorption rate, and the time required for the N removal. In this case, nitrogen in the molten steel is diffused and captured in CO gas bubbles generated by reacting with carbon in the molten steel due to acid supply, and escapes from the steel bath through a molten slag layer on the surface of the molten steel. At the same time, the molten slag is brought into a forming state by the CO bubbles, and serves to shut off the steel bath from air entering the furnace. Further, according to the present invention, a purity of 9
Since the oxygen gas of 9.0 vol.% Or more is used, the nitrogen content in the oxygen gas is less than 1.0 vol.%. Therefore, the nitrogen partial pressure of the gas in the forming slag is expected to be 0.005 atm or less. . Thus, for example, the equilibrium nitrogen concentration between the gas and molten steel at 1600 ° C. is 31.8 ppm
And the phenomenon of N absorption from the forming slag layer does not occur. When oxygen gas having a purity of 99.5 vol.% Is used, the nitrogen partial pressure is 0.0025 atm.
The following is expected, and the above-mentioned equilibrium nitrogen concentration is calculated to be 22.5 ppm, which is more preferable. For the above-mentioned reasons, the denitrification of the molten steel proceeds, and at the end of the refining, a low nitrogen molten steel of 40 ppm or less is obtained.
【0019】[0019]
【実施例】次に、この発明の低窒素溶鋼の製造方法を、
実施例によって更に詳細に説明する。本発明の範囲内の
実施例を上述した実施形態の例に準じて試験し、適宜、
本発明の範囲外の比較例も試験した。実施例の態様は2
グループに大別される。Next, a method for producing a low nitrogen molten steel of the present invention will be described.
This will be described in more detail with reference to examples. Examples within the scope of the present invention were tested according to the examples of the embodiments described above, and
Comparative examples outside the scope of the present invention were also tested. The mode of the embodiment is 2
They are roughly divided into groups.
【0020】第1グループの実施例 第1グループは、120ton直流アーク溶解炉(電気
容量:72MVA)で、鋼スクラップ:90wt.%、冷
銑:10wt.%および初装入コークス:12kg/装入t
on、並びに造滓材:27kg/装入tonを装入し、
酸素ガスを付加しながらアーク熱および炭素の燃焼熱で
加熱・溶解した。溶落ち後、粉コークス(C純度:85
wt.%)を鋼浴に吹き込みながら所定条件で、純度99.
5vol.% の純酸素ガス(製法:深冷法)を送酸し精錬す
ると共に脱Nし、低窒素溶鋼を製造した。Example of First Group The first group is a 120-ton DC arc melting furnace (electric capacity: 72 MVA), steel scrap: 90 wt.%, Cold pig: 10 wt.%, And initially charged coke: 12 kg / charged. t
on, as well as slag-making material: 27 kg / charged ton,
It was heated and melted by arc heat and carbon combustion heat while adding oxygen gas. After burn through, coke breeze (C purity: 85
wt.%) into a steel bath while purifying at a predetermined condition.
5 vol.% Pure oxygen gas (manufacturing method: cryogenic method) was fed, refined and denitrated to produce a low nitrogen molten steel.
【0021】第2グループの実施例 第2グループは、100ton直流アーク溶解炉(電気
容量:65MVA)で、鋼スクラップ:60wt.%に対し
て、溶銑:40wt.%を装入し、初装入コークスを投入せ
ず、造滓材:28kg/装入tonを装入した。そし
て、溶銑の顕熱とアーク熱で加熱・溶解した。溶落ち時
の溶鋼C含有率は1.35wt.%と高いので、上記(3)
式の所要炭素添加量:Cadd ≧(12/11.2)Qo2
t* W−C MD(kg)の右辺は、負の値となるので送酸
中のコークスは添加しなかった。Embodiment of the Second Group The second group is a 100 ton DC arc melting furnace (electric
Capacity: 65MVA) and steel scrap: 60wt.%
And then add hot metal: 40 wt.% And charge coke for the first time
Slag-making material: 28 kg / charged ton was charged. Soshi
It was heated and melted by the sensible heat and arc heat of the hot metal. When burnt down
The content of molten steel C is as high as 1.35 wt.%.
Required amount of added carbon in the formula: Cadd≧ (12 / 11.2) QoTwo
t*WC MDSince the right side of (kg) is a negative value,
No coke was added.
【0022】表1に、第1グループの実施例および比較
例(実施例No.1、2および比較例No.1)、並びに、
第2グループの実施例および比較例(実施例No.3およ
び比較例No.3)の試験条件を示す。同表には更に、送
酸速度Qo2により定まる所要送酸時間t* 、並びに、所
要送酸時間t* および溶落ち時の溶鋼中C重量CMDによ
り定まる所要炭素添加量Cadd (コークス中のC換算
値)を示した。Table 1 shows Examples and Comparative Examples (Examples Nos. 1 and 2 and Comparative Example No. 1) of the first group, and
The test conditions of the second group of Examples and Comparative Examples (Example No. 3 and Comparative Example No. 3) are shown. Furthermore in the table, the required oxygen-flow time determined by the oxygen-flow-rate Qo 2 t *, and the required oxygen-flow time t * and burn through time of the molten steel in C wt C MD by determined required carbon amount C the add (coke C conversion value).
【0023】[0023]
【表1】 [Table 1]
【0024】第1グループの試験結果 試験結果を図1に示し、精錬終了時の溶鋼の窒素含有率
を表1に併記した。図1は、溶落ち後の送酸時間に対す
る溶鋼の窒素含有率の変化を示すグラフである。Test Results of the First Group The test results are shown in FIG. 1, and the nitrogen content of the molten steel at the end of the refining is also shown in Table 1. FIG. 1 is a graph showing a change in the nitrogen content of molten steel with respect to an acid feeding time after burn-down.
【0025】比較例No.1の試験条件は、実施例No.1
と比較し、精錬中の炭素添加量が本発明の範囲外に低い
(所要炭素添加量:833kg以上に対してこれよりも
少ない612kgの炭素が添加された)点だけが相違す
る。送酸時間12min後(精錬終了時)の溶鋼の窒素
含有率は45ppmまでしか低下していない。これは、
送酸中の溶鋼の炭素含有率の不足により精錬期後半のス
ラグフォーミングが不足したため吸Nを十分に抑制する
ことができなかったものと考えられる。The test conditions of Comparative Example No. 1 are the same as those of Example No. 1.
The only difference is that the amount of carbon added during refining is low outside the range of the present invention (the required amount of carbon added: 833 kg or more, and a smaller amount of 612 kg of carbon was added). The nitrogen content of the molten steel after the acid supply time of 12 min (at the end of the refining) has decreased only to 45 ppm. this is,
It is considered that slag forming in the latter half of the refining period was insufficient due to the insufficient carbon content of the molten steel during the acid supply, so that N absorption could not be sufficiently suppressed.
【0026】比較例No.2の試験条件は、実施例No.1
と比較し、精錬中酸素ガスの純度が本発明の範囲外に低
い(純度:94.0vol.% (PSA酸素であり、窒素含
有率:3.5vol.% で、不純物として残部に窒素を多量
に含む))点だけが相違する。送酸時間12min後
(精錬終了時)の溶鋼の窒素含有率は80ppmまでし
か低下していない。これは、フォーミングスラグ中のガ
スの窒素分圧が高かったために溶鋼の平衡窒素含有率が
高く、脱N反応が十分に進行しなかったためと考えられ
る。The test conditions of Comparative Example No. 2 are the same as those of Example No. 1.
The purity of oxygen gas during refining is lower than that of the present invention (purity: 94.0 vol.% (PSA oxygen, nitrogen content: 3.5 vol.%), And a large amount of nitrogen as impurities )). The nitrogen content of the molten steel after the acid supply time of 12 min (at the end of refining) has decreased only to 80 ppm. This is probably because the equilibrium nitrogen content of the molten steel was high due to the high nitrogen partial pressure of the gas in the forming slag, and the deN reaction did not sufficiently proceed.
【0027】これに対して、実施例No.1および2では
いずれも精錬終了時の窒素含有率は40ppm以下に低
下している。図1によれば、実施例No.1では窒素含有
率は所要送酸時間:9.6min以上でほぼ40ppm
以下に低下し、送酸時間12min後(精錬終了時)に
は27ppmまで低下している。実施例No.2では窒素
含有率は所要送酸時間:10.7min以上でほぼ40
ppm以下に低下し、送酸時間12min後(精錬終了
時)には33ppmまで低下している。On the other hand, in Examples Nos. 1 and 2, the nitrogen content at the end of refining was reduced to 40 ppm or less. According to FIG. 1, in Example No. 1, the nitrogen content was about 40 ppm in the required acid supply time: 9.6 min or more.
It decreases to below 27 ppm after 12 minutes of acid supply time (at the end of refining). In Example No. 2, the nitrogen content was approximately 40 at the required acid supply time of 10.7 min or more.
ppm and lower to 33 ppm after 12 minutes of acid supply time (at the end of refining).
【0028】第2グループの試験結果 試験結果を図2に示し、精錬終了時の溶鋼の窒素含有率
を表1に併記した。図2は、溶落ち後の送酸時間に対す
る溶鋼の窒素含有率の変化を示すグラフである。FIG. 2 shows the test results of the second group. Table 1 also shows the nitrogen content of the molten steel at the end of refining. FIG. 2 is a graph showing the change in the nitrogen content of molten steel with respect to the acid feeding time after burn-down.
【0029】比較例No.3は、精錬中の送酸速度が本発
明の範囲外に小さい場合である。仮りに比較例No.3が
本発明であるとして(2)式により算出される所要送酸
時間:11.0min以上よりも長時間の21min間
送酸しても、溶鋼の窒素含有率は49ppmまでしか低
下していず、図2からもわかるように脱N速度は小さ
い。この例においては、上記(3)式により算出される
所要炭素添加量は負の値となるので、精錬中に炭素を添
加しなくても溶鋼中炭素含有率は十分であったと判断さ
れる。従って、送酸速度が小さかったために、COボイ
リングが不十分であり、CO気泡への溶鋼中窒素の脱N
速度が小さかったためと考えられる。Comparative Example No. 3 is a case where the acid feed rate during refining is small outside the scope of the present invention. Assuming that Comparative Example No. 3 is the present invention, even if the required acid supply time calculated by the formula (2) is 21 minutes longer than 11.0 min or more, the nitrogen content of the molten steel is 49 ppm. 2 and the de-N-rate is small as can be seen from FIG. In this example, since the required amount of added carbon calculated by the above equation (3) is a negative value, it is determined that the carbon content in the molten steel was sufficient without adding carbon during refining. Therefore, the CO boiling was insufficient due to the low acid feed rate, and the removal of nitrogen from molten steel into CO bubbles
This is probably because the speed was low.
【0030】これに対して、実施例No.3では、窒素含
有率は所要送酸時間:9.0min以上においてほぼ4
0ppm以下に低下し、送酸時間15min後(精錬終
了時)には32ppmまで低下している。On the other hand, in Example No. 3, the nitrogen content was almost 4 at the required acid supply time of 9.0 min or more.
It has decreased to 0 ppm or less, and has decreased to 32 ppm after 15 minutes of acid supply time (at the end of refining).
【0031】上述した実施例にみられるように、この発
明によればアーク炉により窒素含有率が40ppm以下
の低窒素溶鋼を、安定して製造することができる。As can be seen from the above-described embodiment, according to the present invention, a low-nitrogen molten steel having a nitrogen content of 40 ppm or less can be stably manufactured by an arc furnace.
【0032】[0032]
【発明の効果】以上述べたように、この発明によれば、
溶解原料として高配合率の還元鉄を使用する等の特別な
原料供給体制を準備する必要がなく、常法のアーク炉操
業における鉄源原料の供給体制があれば、アーク炉操業
方法の改善により窒素含有率が40ppm以下の溶鋼を
安定して製造することができる。従って、N含有率40
ppm以下が要求される深絞り用の冷延鋼板や表面処理
鋼板の製造も可能となる等、アーク炉による低窒素溶鋼
の製造方法を提供することができ、工業上有用な効果が
もたらされる。As described above, according to the present invention,
There is no need to prepare a special raw material supply system, such as using a high blended ratio of reduced iron as a melting raw material.If there is a supply system for iron source raw materials in an ordinary arc furnace operation, improvement of the arc furnace operation method It is possible to stably produce molten steel having a nitrogen content of 40 ppm or less. Therefore, N content 40
It is also possible to provide a method for producing low-nitrogen molten steel by an arc furnace, for example, which enables the production of cold-rolled steel sheets and surface-treated steel sheets for deep drawing requiring less than 1 ppm, and has an industrially useful effect.
【図1】実施例および比較例における、溶落ち後の送酸
時間に対する溶鋼の窒素含有率の変化を示すグラフであ
る。FIG. 1 is a graph showing a change in nitrogen content of molten steel with respect to an acid feeding time after burn-down in Examples and Comparative Examples.
【図2】他の実施例および比較例における、溶落ち後の
送酸時間に対する溶鋼の窒素含有率の変化を示すグラフ
である。FIG. 2 is a graph showing a change in nitrogen content of molten steel with respect to an acid feeding time after burn-down in other examples and comparative examples.
【図3】この発明において送酸速度Qo2および送酸時間
t* が満たすべき範囲を示すグラフである。FIG. 3 is a graph showing a range to be satisfied by an acid supply rate Qo 2 and an acid supply time t * in the present invention.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 鈴木 広志 和歌山県和歌山市湊1850番地 キョウエイ 製鐵株式会社内 (72)発明者 岡田 泰和 和歌山県和歌山市湊1850番地 キョウエイ 製鐵株式会社内 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Hiroshi Suzuki 1850 Minato, Wakayama-shi, Wakayama Prefecture Inside Kyoei Steel Corporation (72) Inventor Yasukazu Okada 1850 Minato, Wakayama-shi, Wakayama Prefecture Inside Kyoei Steel Corporation
Claims (1)
鉄等の鉄源原料の内少なくとも一種を溶解し、前記原料
の溶解を終了後、炉内に酸素ガスを供給し、前記炉内に
形成された溶鉄を精錬するに際し、前記酸素ガスの純度
を99.0vol.% 以上とし、送酸速度Qo2および送酸時
間t* がそれぞれ下記(1)および(2)式: Qo2=0.55〜1.35(Nm3 /min/ton)の範囲内 ------------(1) t* ≧−7.2Qo2+15(min) ------------(2) を満たし、且つ、下記(3)式: Cadd ≧(12/11.2)Qo2t* W−CMD(kg)--------- (3) 但し、 W :原料溶解終了時の溶鉄量(ton) CMD:原料溶解終了時の溶鉄に含まれる炭素重量(k
g) で炭素添加量Cadd を算出し、前記炭素添加量Cadd が
正の値のときは当該重量の炭素を添加しつつ精錬するこ
とを特徴とする、アーク炉による低窒素溶鋼の製造方
法。At least one of an iron source material such as scrap, reduced iron and pig iron is melted in an arc furnace, and after the melting of the raw material is completed, oxygen gas is supplied into the furnace to form an iron gas. When refining molten iron, the purity of the oxygen gas is set to 99.0 vol.% Or more, and the acid supply rate Qo 2 and the acid supply time t * are expressed by the following formulas (1) and (2): Qo 2 = 0.55 Within the range of ~ 1.35 (Nm 3 / min / ton) -------- (1) t * ≥-7.2 Qo 2 +15 (min) -------- ---- Satisfies (2) and the following equation (3): C add ≧ (12 / 11.2) Qo 2 t * W-C MD (kg) --------- (3 ) However, W: molten iron amount at raw material dissolved ends (ton) C MD: carbon weight (k contained in the raw material dissolution at the end of the molten iron
g) calculating the carbon addition amount C add and, when the carbon addition amount C add is a positive value, refining while adding the carbon of the corresponding weight, the method for producing low nitrogen molten steel by an arc furnace. .
Priority Applications (1)
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---|---|---|---|
JP27933696A JPH10121123A (en) | 1996-10-22 | 1996-10-22 | Production of molten low nitrogen steel with arc furnace |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP27933696A JPH10121123A (en) | 1996-10-22 | 1996-10-22 | Production of molten low nitrogen steel with arc furnace |
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Publication Number | Publication Date |
---|---|
JPH10121123A true JPH10121123A (en) | 1998-05-12 |
Family
ID=17609768
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Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1999054512A1 (en) * | 1997-02-19 | 1999-10-28 | Kawasaki Steel Corporation | Method of judging slag forming state in electric furnace steel production and method of operating electric furnace |
-
1996
- 1996-10-22 JP JP27933696A patent/JPH10121123A/en active Pending
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1999054512A1 (en) * | 1997-02-19 | 1999-10-28 | Kawasaki Steel Corporation | Method of judging slag forming state in electric furnace steel production and method of operating electric furnace |
US6375701B1 (en) * | 1998-04-21 | 2002-04-23 | Kawasaki Steel Corporation | Method of judging slag forming state in electric furnace steel production and method of operating electric furnace |
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