JPH09165615A - Denitrifying method for molten metal - Google Patents
Denitrifying method for molten metalInfo
- Publication number
- JPH09165615A JPH09165615A JP7325735A JP32573595A JPH09165615A JP H09165615 A JPH09165615 A JP H09165615A JP 7325735 A JP7325735 A JP 7325735A JP 32573595 A JP32573595 A JP 32573595A JP H09165615 A JPH09165615 A JP H09165615A
- Authority
- JP
- Japan
- Prior art keywords
- molten steel
- slag
- denitrification
- flux
- blown
- 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
- Treatment Of Steel In Its Molten State (AREA)
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】この発明は、溶融金属の脱窒
方法およびその方法に使用する脱窒用フラックスに関し
て、特に極低窒素域までの脱窒を実現しようとするもの
である。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for denitrifying molten metal and a denitrifying flux used in the method, and is particularly intended to realize denitrification up to an extremely low nitrogen range.
【０００２】[0002]
【従来の技術】一般に、ステンレス鋼に代表されるCr含
有鋼の精錬は、その溶鋼中窒素の活量が溶鋼中のCr濃度
に反比例して低下するため、窒素濃度を低下することが
困難な鋼種であるが、例えば30wt％Cr含有鋼において
は、VOD 法を用いて、溶鋼中の炭素濃度〔Ｃ〕≦30ppm
および溶鋼中の窒素濃度〔Ｎ〕≦40ppm の極低炭素域か
つ極低窒素域までの精錬が工業的に行われている。2. Description of the Related Art Generally, in refining Cr-containing steel represented by stainless steel, it is difficult to lower the nitrogen concentration because the activity of nitrogen in the molten steel decreases in inverse proportion to the Cr concentration in the molten steel. Although it is a steel type, for example, in the case of steel containing 30 wt% Cr, the carbon concentration in molten steel [C] ≤ 30 ppm is determined by the VOD method.
Further, refining to the extremely low carbon region and the extremely low nitrogen region of nitrogen concentration [N] ≤ 40 ppm in molten steel is industrially performed.
【０００３】すなわち、特開昭53−94212 号公報には、
VOD 法による精錬開始時点のＣを0.8 wt％以上としてCO
ガス発生量を増大し、かつ底吹きArガス流量を増して強
攪拌とした上で、減圧下で脱窒を行うことが提案されて
いる。しかしながら、脱炭工程の時間延長およびそれに
伴う生産性の低下、さらには耐火物コストなど製鋼コス
トの上昇が避けられず、工業的規模の生産において、Ｎ
のより一層の低減は事実上困難であった。That is, Japanese Patent Laid-Open No. 53-94212 discloses that
CO at 0.8 wt% or more at the start of refining by VOD method
It has been proposed to increase the amount of gas generated and increase the flow rate of bottom-blown Ar gas to perform strong stirring, and then perform denitrification under reduced pressure. However, it is inevitable that the time for decarburization process will be extended and the productivity will be reduced accordingly, and the cost of refractories will increase steelmaking costs.
It was practically difficult to further reduce.
【０００４】一方、スラグによって脱窒を行うことにつ
いては、「鉄と鋼 第78年 (1992)第４号」の第564 〜5
71 頁に報告されている。この報告によると、スラグ−
溶鋼間の窒素の平衡関係はOn the other hand, regarding denitrification with slag, "Iron and Steel No. 78 (1992) No. 4" No. 564-5.
Reported on page 71. According to this report,
The equilibrium relationship of nitrogen between molten steel is
【数１】 の反応式により示される。そして、スラグ中の窒素濃度
（Ｎ）と〔Ｎ〕との比である窒素分配比の平衡値（以
下、平衡窒素分配比と示す）ＬN はスラグ組成と温度に
依存するほか、溶鋼中のアルミニウム濃度が高いほど、
また溶鋼中のアルミニウムおよび窒素の活性量係数が大
きいほど、平衡窒素分配比ＬN が高くなって、溶鋼から
スラグへの窒素の移動が促進される。[Equation 1] It is shown by the reaction formula of. The equilibrium value of the nitrogen distribution ratio (hereinafter referred to as the equilibrium nitrogen distribution ratio) L N, which is the ratio between the nitrogen concentration (N) and [N] in the slag, depends on the slag composition and temperature, and The higher the aluminum concentration,
Further, the larger the activity coefficient of aluminum and nitrogen in the molten steel, the higher the equilibrium nitrogen distribution ratio L N becomes, and the transfer of nitrogen from the molten steel to the slag is promoted.
【０００５】しかしながら、16％Cr鋼における平衡窒素
分配比ＬN は、アルミニウム濃度が１wt％の溶鋼に対し
て比較的脱窒に有利とされる組成のスラグを用いた場合
でも、２〜８程度にすぎず、従って効果的に脱窒素を進
めるには、アルミニウム濃度を１wt％以上に高めて脱窒
処理を行う必要がある。However, the equilibrium nitrogen distribution ratio L N in 16% Cr steel is about 2 to 8 even when slag having a composition relatively advantageous for denitrification is used for molten steel having an aluminum concentration of 1 wt%. Therefore, in order to effectively promote denitrification, it is necessary to increase the aluminum concentration to 1 wt% or more and perform denitrification treatment.
【０００６】さらに、１wt％程度の高Al濃度は実用鋼に
適していないから、特開平５−320733号公報に示される
ように、脱窒後に溶鋼中のAlを燃焼によって除去する工
程を新たに設ける必要が生じる。この方法では、酸素ガ
スによりAlを燃焼して除去する際の発熱により、100 ℃
以上の大幅な温度上昇を招くことになり、後工程の鋳造
工程との整合をはかるために、大幅な工程ロスおよび生
産性の低下は避けられない不利が伴う。また、Al濃度の
低下に伴う、スラグからメタルへの復窒も問題となる。Further, since a high Al concentration of about 1 wt% is not suitable for practical steel, a new process for removing Al in molten steel by combustion after denitrification is newly added as disclosed in Japanese Patent Laid-Open No. 5-320733. It will be necessary to provide it. In this method, 100 ° C is generated due to the heat generated when Al is burned and removed by oxygen gas.
The above-mentioned large temperature rise is caused, and in order to achieve consistency with the casting process of the subsequent process, a large process loss and a decrease in productivity are inevitable disadvantages. In addition, nitriding from slag to metal is also a problem as the Al concentration decreases.
【０００７】[0007]
【発明が解決しようとする課題】そこで、この発明の目
的は、上述したVOD 法による真空処理やスラグによる脱
窒では望めない、極低窒素域までの脱窒を、工業的に実
現し得る、新たな方途を与えるところにある。Therefore, an object of the present invention is to industrially realize denitrification to an extremely low nitrogen range, which cannot be expected by vacuum treatment by the VOD method or denitrification by slag described above. It is about giving new directions.
【０００８】[0008]
【課題を解決するための手段】この発明は、精錬容器に
装入した溶融金属の表面をスラグで覆ったのち、この被
覆スラグ面に対して酸化性ガスを該ガスが溶融金属と直
接接触しない程度に吹き付けるとともに、CaO 、Al2O3
およびCaC2を含む粉状の脱窒用フラックスを、溶融金属
中に吹き込むことを特徴とする溶融金属の脱窒方法であ
る。According to the present invention, after the surface of molten metal charged in a refining vessel is covered with slag, oxidizing gas does not come into direct contact with the molten metal with respect to the coated slag surface. Sprayed to a degree, CaO, Al 2 O 3
A method for denitrifying molten metal, characterized in that a powdery denitrifying flux containing CaC 2 is blown into the molten metal.
【０００９】また、この発明は、精錬容器に装入した溶
融金属の表面をスラグで覆ったのち、CaO 、Al2O3 およ
びCaC2を含む粉状の脱窒用フラックスを溶融金属中に吹
き込み、その後被覆スラグ面に対して酸化性ガスを該ガ
スが溶融金属と直接接触しない程度に吹き付けることを
特徴とする溶融金属の脱窒方法である。ここで、脱窒用
フラックスに２〜20wt％の金属アルミニウム粉を混合し
て溶融金属中に吹き込むことが、脱窒をより促進する上
で有利である。Further, according to the present invention, the surface of the molten metal charged into the refining vessel is covered with slag, and then a powdery denitrifying flux containing CaO, Al 2 O 3 and CaC 2 is blown into the molten metal. Then, the method for denitrifying molten metal is characterized by spraying an oxidizing gas onto the surface of the coated slag to such an extent that the gas does not come into direct contact with the molten metal. Here, it is advantageous to mix 2 to 20 wt% of metal aluminum powder with the denitrification flux and blow it into the molten metal in order to further accelerate the denitrification.
【００１０】また、上記の脱窒方法には、CaO : 30〜70
wt％、Al2O3 : 30〜70wt％およびCaC2 : 1〜25wt％を含
有する組成に成る脱窒用フラックスが有利に適合する。
この脱窒用フラックスには、さらにMgO を20wt％以下で
含有することが可能である。In addition, in the above denitrification method, CaO: 30-70
A denitrifying flux having a composition containing wt%, Al 2 O 3 : 30 to 70 wt% and CaC 2 : 1 to 25 wt% is advantageously suitable.
This denitrifying flux can further contain MgO at 20 wt% or less.
【００１１】[0011]
【発明の実施の形態】さて、在来のガスの吹き込みによ
る脱窒処理は、例えば溶鋼を対象とする場合、次の(2)
式に従うガス−溶鋼反応にて進行する。BEST MODE FOR CARRYING OUT THE INVENTION The conventional denitrification treatment by blowing gas is, for example, in the case of molten steel as follows (2)
The gas-molten steel reaction proceeds according to the formula.
【数２】 上記(2) 式に従う反応は、溶鋼中のＮ濃度に関する２次
の反応であり、Ｎ濃度が低下すると、単位時間および単
位界面積当たりの脱窒量は、Ｎ濃度の２乗に比例して著
しく低下する。例えば、VOD 炉において30wt％Cr含有鋼
をガス−溶鋼反応のみで脱窒する場合、〔Ｎ〕＜50ppm
になると脱窒速度は極端に低下し、さらにＮ濃度を低下
することが困難であった。(Equation 2) The reaction according to the above equation (2) is a second-order reaction related to the N concentration in molten steel. When the N concentration decreases, the denitrification amount per unit time and unit interfacial area is proportional to the square of the N concentration. Markedly reduced. For example, when denitrifying 30 wt% Cr-containing steel in the VOD furnace only by gas-molten steel reaction, [N] <50 ppm
Then, the denitrification rate was extremely reduced, and it was difficult to further reduce the N concentration.
【００１２】これに対して、(1) 式のスラグ−溶鋼反応
による脱窒は、Ｎ濃度に関して１次の反応であり、Ｎ濃
度が低下しても、上記した(2) 式の反応に比べて、脱窒
速度の低下は穏やかである。また、脱硫反応などから類
推すれば、スラグ・溶鋼界面の酸素ポテンシャルさえ十
分に低く保つことができれば、Ｎ＜20ppm といった極低
窒素濃度域においても十分に大きな脱窒速度を有するも
のと考えられる。On the other hand, the denitrification by the slag-molten steel reaction of the formula (1) is a first-order reaction with respect to the N concentration, and even if the N concentration decreases, compared with the reaction of the above formula (2). Therefore, the decrease in denitrification rate is moderate. Also, by analogy with the desulfurization reaction, etc., if even the oxygen potential at the slag / molten steel interface can be kept sufficiently low, it is considered that it has a sufficiently high denitrification rate even in an extremely low nitrogen concentration region such as N <20 ppm.
【００１３】しかし、上記(1) 式の反応において、スラ
グ・溶鋼界面の酸素ポテンシャルを十分に低下するため
には、溶鋼中のアルミニウム濃度を１wt％以上に増加す
る必要があり、大幅なコスト上昇と生産性の低下を招く
ことになる。However, in the reaction of the above formula (1), in order to sufficiently reduce the oxygen potential at the slag / molten steel interface, it is necessary to increase the aluminum concentration in the molten steel to 1 wt% or more, resulting in a significant cost increase. This leads to a decrease in productivity.
【００１４】そこで、発明者らは、比較的低いアルミニ
ウム濃度の溶鋼においても、スラグ・溶鋼界面の酸素ポ
テンシャルを低下させて、高い平衡窒素分配比を得る方
法について鋭意研究を行ったところ、次の結果を得るに
到った。すなわち、CaC2を含有するフラックスを用いる
ことにより、スラグ・溶鋼界面において、次の(3) 式に
従う反応が引き起こされ、スラグ・溶鋼界面の酸素ポテ
ンシャルが低下するため、脱窒が可能になるのである。Therefore, the inventors of the present invention conducted extensive studies on a method of obtaining a high equilibrium nitrogen distribution ratio by lowering the oxygen potential at the slag / molten steel interface even in molten steel having a relatively low aluminum concentration. I came to the result. That is, by using a flux containing CaC 2 , a reaction according to the following equation (3) is induced at the slag / molten steel interface, and the oxygen potential at the slag / molten steel interface decreases, so denitrification becomes possible. is there.
【数３】 (Equation 3)
【００１５】ここで、フラックス中のCaC2含有量が脱窒
に及ぼす影響を検討するために、小型誘導溶解炉におい
て、CaO およびAl2O3 を重量比で１：１にて含む基本組
成にCaC2を混合したフラックスを用いて、そのフラック
ス中のCaC2含有量と平衡窒素分配比ＬN との関係を調査
した。すなわち、Ｃ：0.1 wt％およびAl：0.1 wt％を含
む溶鋼に、上記フラックスを50kg/tにて添加した場合の
調査結果を、図１に示す。CaC2を１wt％で含むフラック
スを用いるとＬN は約10となり、従ってCaC2を１wt％以
上で含有するフラックスを用いると、高効率の脱窒を達
成できることがわかる。しかし、フラックスのCaC2含有
量が25wt％をこえると、平衡窒素分配比ＬN を増大する
効果は小さくなる。これは、スラグ中でCaC2が飽和する
か、あるいは溶鋼中のＣ濃度が上昇してしまうことによ
り、酸素ポテンシャルが逆に上昇するためと考えられ
る。Here, in order to study the effect of the CaC 2 content in the flux on denitrification, a basic composition containing CaO and Al 2 O 3 in a weight ratio of 1: 1 was used in a small induction melting furnace. Using a flux mixed with CaC 2 , the relationship between the CaC 2 content in the flux and the equilibrium nitrogen distribution ratio L N was investigated. That is, Fig. 1 shows the results of an investigation when the above flux was added at 50 kg / t to molten steel containing C: 0.1 wt% and Al: 0.1 wt%. With a flux containing CaC 2 with 1 wt% L N is about 10, and the thus the use of a flux containing CaC 2 with 1 wt% or more, it can be seen that achieve denitrification efficiency. However, when the CaC 2 content of the flux exceeds 25 wt%, the effect of increasing the equilibrium nitrogen distribution ratio L N becomes small. It is considered that this is because CaC 2 is saturated in the slag or the C concentration in the molten steel is increased, so that the oxygen potential is increased.
【００１６】なお、フラックスは、液相率および脱窒能
の高いCaO : 30〜70wt％およびAl2O 3 : 30〜70wt％のCa
O −Al2O3 系を主成分とした組成が適しており、また耐
火物の溶損量を減少するためにMgO を20wt％程度を上限
に混合してもよい。このフラックスを用いる実際の操業
においては、反応速度の観点からフラックスと溶鋼間の
反応界面積を増大するために、粉状のフラックスを溶鋼
中に吹き込むことが望ましい。The flux has a liquid phase ratio and denitrification ability.
High CaO: 30-70wt% and AlTwoO Three: 30 ~ 70wt% Ca
O-AlTwoOThreeA composition whose main component is a system is suitable and
About 20wt% of MgO is the upper limit to reduce the melting loss of fire
May be mixed. Actual operation using this flux
In terms of reaction rate,
Molten steel powder is used to increase the reaction interfacial area.
It is desirable to blow it inside.
【００１７】ここでは、CaC2を含むフラックスを溶鋼中
に吹き込むことによって、スラグ・フラックス界面の酸
素ポテンシャルを低下させるために、次に示す(4) 式の
脱酸反応を利用している。この反応は溶鋼中のＣ濃度の
影響を受けるものである。Here, in order to reduce the oxygen potential at the slag / flux interface by blowing a flux containing CaC 2 into the molten steel, the deoxidation reaction of the following formula (4) is utilized. This reaction is affected by the C concentration in the molten steel.
【数４】 (Equation 4)
【００１８】一方、フラックス・溶鋼界面では、次に示
す(5) 式の反応も同時に起こり酸素ポテンシャルを上昇
するから、溶鋼中のAl濃度も脱窒反応に影響を及ぼすこ
とになる。従って、この発明方法で用いる溶鋼のＣ濃度
およびAl濃度の適正値は、従来の脱窒処理に関する実験
結果から推定することは難しい。On the other hand, at the flux / molten steel interface, the reaction of the following formula (5) also occurs simultaneously and the oxygen potential rises, so that the Al concentration in the molten steel also affects the denitrification reaction. Therefore, it is difficult to estimate the proper values of the C concentration and the Al concentration of the molten steel used in the method of the present invention from the experimental results regarding the conventional denitrification treatment.
【数５】 (Equation 5)
【００１９】そこで、小型誘導溶解炉において、溶鋼中
のＣおよびAl濃度を種々に変更して、CaO およびAl2O3
を重量比で１：１にて含む基本組成にCaC2を混合したフ
ラックスを用いて、フラックス粉を吹き込む実験を行っ
たところ、Al濃度0.03wt％未満あるいはＣ濃度1.5 wt％
超では顕著な脱窒促進効果が得られなかった。従って、
溶鋼組成は、Ｃ濃度を1.5 wt％以下およびAl濃度を0.03
wt％以上に規制することが好ましい。Therefore, in a small induction melting furnace, the concentrations of C and Al in the molten steel are changed variously, and CaO and Al 2 O 3 are changed.
An experiment was conducted in which flux powder was blown using a flux in which CaC 2 was mixed in a basic composition containing 1: 1 by weight ratio, and the Al concentration was less than 0.03 wt% or the C concentration was 1.5 wt%.
If it is over, no remarkable denitrification promoting effect was obtained. Therefore,
The molten steel composition has a C concentration of 1.5 wt% or less and an Al concentration of 0.03%.
It is preferable to regulate to wt% or more.
【００２０】また、脱窒処理において、脱窒用フラック
ス中にさらに金属Alを混合して吹き込むことが、フラッ
クス・溶鋼界面の酸素ポテンシャルを低下させるのに有
効である。そこで、脱窒用フラックス中の金属Al粉混合
量が脱窒に及ぼす影響を、５t 規模の溶解炉で調査し
た。すなわち、Ｃ：0.1 wt％およびAl：0.1 wt％を含有
する溶鋼中に、金属Al粉が混合された脱窒用フラックス
30kg/tを吹き込んだときの、金属Al粉混合率と脱窒率
（脱窒量／初期窒素濃度）の関係を、図２に示す。CaO
およびAl2O3 を重量比で１：１にて含むフラックスに金
属Al粉を混合した場合には、Al粉を混合することによ
る、脱窒率の増大はわずかであり、20wt％程度まで金属
Al粉を混合しても脱窒率は最大20％程度である。Further, in the denitrification treatment, it is effective to further mix and blow metallic Al into the denitrification flux to reduce the oxygen potential at the interface between the flux and the molten steel. Therefore, the effect of the mixed amount of metallic Al powder in the denitrification flux on denitrification was investigated in a 5t scale melting furnace. That is, a flux for denitrification in which metallic Al powder is mixed in molten steel containing C: 0.1 wt% and Al: 0.1 wt%
FIG. 2 shows the relationship between the metal Al powder mixing ratio and the denitrification ratio (denitrification amount / initial nitrogen concentration) when 30 kg / t was blown. CaO
When a metal Al powder is mixed with a flux containing Al 2 O 3 and Al 2 O 3 in a weight ratio of 1: 1, the denitrification rate is slightly increased by mixing the Al powder.
Even if Al powder is mixed, the maximum denitrification rate is about 20%.
【００２１】これに対して、CaO ：Al2O3 ：CaC2を45：
45：10の重量比で含有する組成のフラックスに金属Al粉
を混合した場合には、２wt％程度の少量の金属Al粉の混
合でも脱窒率は増大し、金属Alの混合率が10wt％で脱窒
率は約80％となり、Alを混合しない場合に比べて倍増し
た。しかし、10wt％をこえる金属Alを混合しても、脱窒
率向上の効果は飽和し、またこの方法は溶鋼中のAl濃度
の上昇を必然的に招くため、フラックス中の金属Al量が
過大となると、従来のAl濃度を上昇させていたフラック
スによる脱窒方法と同様に、脱窒後にAl濃度を調節しな
くてはならない不利をまねく。従って、脱窒用フラック
スに金属Al粉を併用する場合は、その混合率を２〜20wt
％の範囲とすることが好ましい。On the other hand, CaO: Al 2 O 3 : CaC 2 is 45:
When the metal Al powder is mixed with the flux containing 45:10 by weight, the denitrification rate increases even if a small amount of metal Al powder of about 2 wt% is mixed, and the metal Al mixing rate is 10 wt%. The denitrification rate was about 80% and doubled compared to the case where Al was not mixed. However, even if metallic Al exceeding 10 wt% is mixed, the effect of improving the denitrification rate saturates, and since this method inevitably increases the Al concentration in the molten steel, the amount of metallic Al in the flux is excessive. In that case, similar to the conventional denitrification method using flux that has increased Al concentration, there is a disadvantage in that the Al concentration must be adjusted after denitrification. Therefore, when metal Al powder is used in combination with the denitrification flux, the mixing ratio should be 2 to 20 wt.
% Is preferable.
【００２２】なお、脱窒用フラックスを溶鋼中に吹き込
むと、フラックスの浮上中にフラックスへの脱窒が進行
するが、溶鋼表面を覆うスラグの酸素ポテンシャルが高
い場合には、フラックスの浮上後に溶鋼への復窒が生じ
る。従って、フラックスの吹き込み処理前に、スラグに
還元材を添加する等の手段にて、スラグ中の酸化鉄濃度
を低下させておく必要があり、発明者らの実験結果によ
ればスラグ中の（Ｔ，Fe）を、１wt％以下まで低減して
おくことが望ましい。When the denitrifying flux is blown into the molten steel, the denitrification of the flux progresses during the floating of the flux. However, when the oxygen potential of the slag covering the surface of the molten steel is high, the molten steel is floated after the floating of the flux. Reconciliation occurs. Therefore, it is necessary to reduce the iron oxide concentration in the slag by means such as adding a reducing agent to the slag before the flux blowing treatment. It is desirable to reduce T, Fe) to 1 wt% or less.
【００２３】また、上記脱窒処理後に長時間にわたって
攪拌を継続すると、次の(6) 式のスラグ・溶鋼反応が右
側に進行して次第にスラグ中のCaC2およびAl2O3 濃度が
低下し、溶鋼中ＣおよびAl濃度が上昇することになる。
すると、スラグ中のCaC2によって上記 (4)式の反応で低
い値に維持されていたスラグ・メタル界面の酸素ポテン
シャルが、CaC2濃度の低下に従って上昇する。その結果
上記 (1)式の反応が、平衡状態に近づくよう左側に進行
し、スラグから溶鋼への復窒を引き起こすため、溶鋼表
面を覆うスラグ中の窒素を除去する必要がある。When stirring is continued for a long time after the denitrification treatment, the slag / molten steel reaction of the following formula (6) proceeds to the right and the CaC 2 and Al 2 O 3 concentrations in the slag gradually decrease. , The concentration of C and Al in the molten steel will increase.
Then, the oxygen potential at the slag-metal interface, which was maintained at a low value by the reaction of the above formula (4) by CaC 2 in the slag, increases as the CaC 2 concentration decreases. As a result, the reaction of equation (1) proceeds to the left to approach the equilibrium state and causes nitriding from the slag to the molten steel, so it is necessary to remove nitrogen in the slag covering the molten steel surface.
【数６】 (Equation 6)
【００２４】さらに、脱窒後にVOD 処理などで真空脱炭
する場合に、強攪拌下で大量の酸素を吹き付けると、酸
素ガスジェットが直接溶鋼と接する状況となり、スラグ
・溶鋼界面の酸素ポテンシャルが上昇してしまうため
に、スラグ中の窒素イオンの一部が溶鋼に復窒すること
があり、これを防止するためにも脱炭工程の前にスラグ
中の窒素を除去することは重要である。Furthermore, in the case of vacuum decarburization such as VOD treatment after denitrification, if a large amount of oxygen is blown under strong stirring, the oxygen gas jet comes into direct contact with the molten steel, increasing the oxygen potential at the slag / molten steel interface. Therefore, a part of the nitrogen ions in the slag may be converted into nitrogen in the molten steel, and in order to prevent this, it is important to remove the nitrogen in the slag before the decarburization step.
【００２５】そこで、発明者らは、スラグ上に酸化性ガ
スを吹き付けて、次の(7) 式に示すガス・スラグ反応に
よってスラグ中の窒素を除去できないかを検討した結
果、O2, H2O, CO2などを含む酸化性ガスを、スラグ面上
にガスジェットが直接溶鋼に接しない程度に吹き付ける
ことにより、溶鋼に復窒することなく、スラグ中の窒素
濃度を10ppm 以下まで速やかに低減できることがわかっ
た。[0025] Therefore, the inventors blowing an oxidizing gas onto the slag, the result of examining whether or not eliminate the nitrogen in the slag by the gas slug reaction shown in the following equation (7), O 2, H By blowing an oxidizing gas containing 2 O, CO 2, etc. onto the slag surface to such an extent that the gas jet does not directly contact the molten steel, the nitrogen concentration in the slag can be promptly reduced to 10 ppm or less without nitriding into the molten steel. It turned out that it can be reduced.
【数７】 (Equation 7)
【００２６】ここで、適当なスラグ層で溶鋼表面を覆っ
て、かつスラグの酸化脱窒に十分なガスの吹き付けを実
現するには、スラグ量、底吹きガス流量、上吹きガスの
組成せやその流量、ランス高さおよび雰囲気圧力などを
適当な範囲に制御すればよい。特に、溶鋼表面をスラグ
層で覆うためには、溶鋼１t 当たり15kg以上のスラグが
必要であり、脱窒素速度を増すために強い攪拌を溶鋼に
与える場合には、さらにスラグ量を増加することが望ま
しい。Here, in order to cover the surface of the molten steel with an appropriate slag layer and realize sufficient gas spraying for oxidative denitrification of the slag, the composition of the slag amount, the bottom blown gas flow rate, and the top blown gas should be adjusted. The flow rate, lance height, atmospheric pressure, etc. may be controlled within an appropriate range. In particular, in order to cover the surface of molten steel with a slag layer, 15 kg or more of slag is required per 1 ton of molten steel, and if strong stirring is applied to molten steel to increase the denitrification rate, the amount of slag can be further increased. desirable.
【００２７】また、酸化性ガスの吹き付けは、脱窒用フ
ラックスを吹き込む脱窒処理の後でもよいが、脱窒用フ
ラックスの吹き込み中に酸化性ガスの吹き付けを併用し
ても同様の効果が得られる。The oxidizing gas may be blown after the denitrification treatment by blowing the denitrifying flux, but the same effect can be obtained by using the oxidizing gas while the denitrifying flux is being blown. To be
【００２８】なお、CaC2として工業的に広く利用されて
いるものは、0.2 wt％程度の窒素を含んでいるのが一般
的であるが、溶鋼中窒素濃度の目標値が20ppm 程度の脱
窒処理には利用可能である。さらに低窒素濃度域までの
脱窒を行うには、原料とするコークスの代わりに低窒素
濃度の黒鉛を用いて、Arガスで雰囲気制御を行った電気
炉にて溶製した、低窒素濃度のCaC2を用いることが望ま
しい。It should be noted that, although CaC 2 which is widely used industrially generally contains about 0.2 wt% of nitrogen, the target value of nitrogen concentration in molten steel is about 20 ppm. It is available for processing. To further denitrify to a low nitrogen concentration range, graphite with a low nitrogen concentration was used instead of coke as a raw material, and a low nitrogen concentration of low nitrogen concentration, which was melted in an electric furnace whose atmosphere was controlled by Ar gas, was used. It is desirable to use CaC 2 .
【００２９】[0029]
【実施例】図３に示すフラックスインジェクション機能
を有するVOD 炉を用いて、30wt％Cr含有鋼の精錬を行っ
た。ここで、図３において、符号１は減圧槽２内に配置
された取鍋、３は上吹きランス、４はフラックス吹き込
み用のインジェクションランス、５はインジェクション
ランスを介して粉状フラックスを溶鋼中に吹き込むフラ
ックス供給装置、６は底吹き用の羽口、７は副原料投入
口、そして８は排気口である。Example A 30 wt% Cr-containing steel was refined using a VOD furnace having a flux injection function shown in FIG. Here, in FIG. 3, reference numeral 1 is a ladle arranged in the decompression tank 2, 3 is an upper blowing lance, 4 is an injection lance for flux injection, and 5 is a powdery flux in molten steel through the injection lance. A flux supply device for blowing in, 6 is a tuyere for bottom blowing, 7 is an auxiliary material charging port, and 8 is an exhaust port.
【００３０】精錬は、まず、上底吹き転炉を用いて一次
脱炭した、Ｃ：0.4 wt％およびCr：30wt％を含む溶鋼60
t を取鍋へ出鋼後、この取鍋を減圧槽内に配置してから
取鍋内に、Al：450kg 、CaO ：600kg および軽焼ドロマ
イト：200kg を添加した。その後、減圧槽内を10torrま
で減圧し、Arガス0.6Nm3／min を底吹きしつつ、上吹き
ランスからO2ガスを25Nm3 ／min で上吹きし、Alを燃焼
して昇温そして造滓を行った。なお、メタル中のAlは0.
1 wt％であり、また、スラグ中のFeO, Cr2O3等は溶鋼中
のAlによって還元され、スラグ中の（Ｔ，Fe）は１wt％
以下であった。In refining, first, molten steel 60 containing C: 0.4 wt% and Cr: 30 wt% was first decarburized using an upper-bottom blowing converter.
After tapping t into the ladle, this ladle was placed in a decompression tank, and then Al: 450 kg, CaO: 600 kg and light burned dolomite: 200 kg were added to the ladle. After that, the pressure in the decompression tank was reduced to 10 torr, and while blowing Ar gas at 0.6 Nm 3 / min at the bottom, O 2 gas was blown at 25 Nm 3 / min from the top blowing lance to burn Al and raise the temperature. I went to the slag. Al in the metal is 0.
1 wt% and FeO, Cr 2 O 3, etc. in the slag are reduced by Al in the molten steel, and (T, Fe) in the slag is 1 wt%
It was below.
【００３１】次に、減圧槽内を大気圧まで戻して、イン
ジェクションランスを溶鋼浴面から約１ｍの深さまで浸
漬し、CaO ：50wt％、Al2O3 ：40wt％およびCaC2：10wt
％の組成のフラックスを120 kg／min の吹き込み速度で
15分間吹き込み、脱窒処理を行った。その後、Arガス0.
3Nm3／min を底吹きしつつ上吹きランスよりO2ガス５Nm
3／min をスラグ面上に10分間吹き付けて、スラグから
の窒素の除去を行った。次に、減圧槽内を再び減圧する
と共に酸素を上吹きしてＣ濃度が30ppm 以下になるまで
脱炭した後、Alを投入して還元精錬を行って成分を調整
した（実施例１）。Next, the inside of the decompression tank is returned to atmospheric pressure, the injection lance is immersed to a depth of about 1 m from the molten steel bath surface, and CaO: 50 wt%, Al 2 O 3 : 40 wt% and CaC 2 : 10 wt.
% Composition flux at a blowing rate of 120 kg / min
It was blown for 15 minutes to perform denitrification treatment. Then Ar gas 0.
3 nm 3 / min base-blown and while the top lance than O 2 gas 5Nm
The nitrogen was removed from the slag by spraying 3 / min on the slag surface for 10 minutes. Next, the inside of the decompression tank was decompressed again and oxygen was blown upward to decarburize until the C concentration became 30 ppm or less, and then Al was introduced to carry out reduction refining to adjust the components (Example 1).
【００３２】また、酸素の上吹きを、上記フラックスイ
ンジェクションによる脱窒処理中に、５ Nm3／min で行
う以外は、上記と同様の操業（実施例２）およびCaO 、
Al2O 3 、CaC2を重量比で50：40：10で含むフラックスに
金属Al粉：５wt％を混合したものを用いて脱窒する際、
初期の昇熱用のAl量を90kg減らすとともに昇熱用酸素量
も減らし、脱窒処理開始時のAl濃度を0.1 wt％とした以
外は、上記と同様の操業（実施例３）も行った。なお、
実施例３は、脱炭開始時のAl濃度が0.27wt％に上昇した
が、脱窒開始時の温度が実施例１よりも約35°低いた
め、その後の脱炭処理時にAlが燃焼した後の溶鋼温度は
実施例１の場合とほぼ同等であった。In addition, the oxygen is blown onto the above flux.
5 Nm during denitrification by injectionThreeLine at / min
The same operation as above (Example 2) and CaO 2, except
AlTwoO Three, CaCTwoTo a flux containing 50:40:10 by weight ratio
When denitrifying with a mixture of metal Al powder: 5 wt%,
Reduce the initial Al heating amount by 90 kg and increase the heating oxygen amount.
The Al concentration at the start of denitrification treatment to 0.1 wt%
Outside, the same operation as described above (Example 3) was also performed. In addition,
In Example 3, the Al concentration at the start of decarburization increased to 0.27 wt%
However, the temperature at the start of denitrification was about 35 ° lower than that in Example 1.
Therefore, the molten steel temperature after Al combustion during the subsequent decarburization treatment is
It was almost the same as the case of Example 1.
【００３３】さらに、比較例１として、フラックスイン
ジェクションによる脱窒を行なわない他は、上記の操業
と同様の条件に従う精錬、そして比較例２として、フラ
ックスインジェクション中または、その後にスラグに対
する酸素ガスの吹き付けを行わない他は、上記の操業と
同様の条件に従う精錬も行った。但し、比較例１におけ
る、VOD 処理前のＣ濃度は、在来の処理と同様に初期の
Ｃ濃度を1.0 wt％として、脱窒量を確保した。Further, as Comparative Example 1, refining was carried out under the same conditions as in the above operation except that denitrification by flux injection was not carried out, and as Comparative Example 2, oxygen gas was sprayed onto the slag during or after the flux injection. Smelting was also performed according to the same conditions as the above operation except that the above was not performed. However, the C concentration before VOD treatment in Comparative Example 1 was set to 1.0 wt% as the initial C concentration as in the conventional treatment to secure the denitrification amount.
【００３４】上記各操業の各段階における、主な溶鋼成
分の推移を表１に示すように、フラックスインジェクシ
ョンの実施によって、従来は得られなかった極低窒素濃
度域までの脱窒が達成された。さらに、脱窒処理にて得
られた極低窒素濃度は、スラグへの酸素ガスの吹き付け
によって、脱炭処理後においても維持できた。As shown in Table 1 for the transition of the main molten steel components at each stage of the above-mentioned operations, by performing the flux injection, denitrification up to the extremely low nitrogen concentration range, which was not obtained conventionally, was achieved. . Furthermore, the extremely low nitrogen concentration obtained by the denitrification treatment could be maintained even after the decarburization treatment by blowing oxygen gas onto the slag.
【００３５】[0035]
【表１】 [Table 1]
【００３６】[0036]
【発明の効果】この発明によれば、従来の大量生産技術
では溶製できなかった極低窒素濃度レベルまでの脱窒が
可能であり、高品質の製品を提供し得る。According to the present invention, it is possible to denitrify to an extremely low nitrogen concentration level which cannot be melted by the conventional mass production technology, and it is possible to provide a high quality product.
【図１】スラグ中のCaC2濃度と窒素分配比との関係を示
す図である。FIG. 1 is a diagram showing the relationship between the CaC 2 concentration in slag and the nitrogen distribution ratio.
【図２】フラックス中の金属Al混合率と脱窒率との関係
を示す図である。FIG. 2 is a diagram showing a relationship between a metal Al mixing ratio in a flux and a denitrification ratio.
【図３】この発明の実施に用いたVOD 炉を示す図であ
る。FIG. 3 is a diagram showing a VOD furnace used for carrying out the present invention.
１ 取鍋 ２ 減圧槽 ３ 上吹きランス ４ インジェクションランス ５ フラックス供給装置 ６ 羽口 ７ 副原料投入口 ８ 排気口 1 Ladle 2 Decompression Tank 3 Top Blowing Lance 4 Injection Lance 5 Flux Supply Device 6 Tuyere 7 Secondary Material Input Port 8 Exhaust Port
───────────────────────────────────────────────────── フロントページの続き (72)発明者 水渡 英昭 宮城県仙台市太白区八木山本町１丁目25の １ ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideaki Mizuwata 1-25-1 Yagiyamahonmachi, Taihaku-ku, Sendai City, Miyagi Prefecture
Claims (3)
ラグで覆ったのち、この被覆スラグ面に対して酸化性ガ
スを該ガスが溶融金属と直接接触しない程度に吹き付け
るとともに、CaO 、Al2O3 およびCaC2を含む粉状の脱窒
用フラックスを、溶融金属中に吹き込むことを特徴とす
る溶融金属の脱窒方法。1. The surface of molten metal charged in a refining vessel is covered with slag, and then an oxidizing gas is sprayed onto the coated slag surface to such an extent that the gas does not come into direct contact with the molten metal. A method for denitrifying molten metal, which comprises blowing a powdery denitrifying flux containing 2 O 3 and CaC 2 into the molten metal.
ラグで覆ったのち、CaO 、Al2O3 およびCaC2を含む粉状
の脱窒用フラックスを溶融金属中に吹き込み、その後被
覆スラグ面に対して酸化性ガスを該ガスが溶融金属と直
接接触しない程度に吹き付けることを特徴とする溶融金
属の脱窒方法。2. The surface of the molten metal charged into the refining vessel is covered with slag, and then a powdery denitrifying flux containing CaO, Al 2 O 3 and CaC 2 is blown into the molten metal, and then the coated slag is coated. A method for denitrifying a molten metal, comprising spraying an oxidizing gas onto a surface to such an extent that the gas does not come into direct contact with the molten metal.
ルミニウム粉を混合して溶融金属中に吹き込むことを特
徴とする請求項１または２に記載の溶融金属の脱窒方
法。3. The method for denitrifying molten metal according to claim 1, wherein the denitrifying flux is mixed with 2 to 20 wt% of metallic aluminum powder and blown into the molten metal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7325735A JPH09165615A (en) | 1995-12-14 | 1995-12-14 | Denitrifying method for molten metal |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP7325735A JPH09165615A (en) | 1995-12-14 | 1995-12-14 | Denitrifying method for molten metal |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH09165615A true JPH09165615A (en) | 1997-06-24 |
Family
ID=18180087
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP7325735A Pending JPH09165615A (en) | 1995-12-14 | 1995-12-14 | Denitrifying method for molten metal |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH09165615A (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0884395A1 (en) * | 1997-06-12 | 1998-12-16 | ALMAMET GmbH | Agent for fluoride-free treatment of steel melts in the casting ladle, process for its manufacture and its use |
| WO2000037688A1 (en) * | 1998-12-18 | 2000-06-29 | Usinor | Method for denitriding molten steel during its production |
| WO2007091700A1 (en) | 2006-02-09 | 2007-08-16 | Jfe Steel Corporation | Method of denitrifying molten steel |
| WO2008081763A1 (en) | 2006-12-22 | 2008-07-10 | Yoshizawa Lime Industry Co., Ltd. | Flux for obtaining steel reduced in nitrogen, oxygen, and sulfur contents through smelting |
| CN104313250A (en) * | 2014-09-24 | 2015-01-28 | 江苏共昌轧辊股份有限公司 | Roller high-speed steel molten steel tapping denitrification method |
| WO2022259807A1 (en) * | 2021-06-11 | 2022-12-15 | Ｊｆｅスチール株式会社 | Molten steel secondary refining method and steel production method |
| WO2022259808A1 (en) * | 2021-06-11 | 2022-12-15 | Ｊｆｅスチール株式会社 | Molten steel denitrification method, simultaneous denitrification and desulfurization treatment method, and steel production method |
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-
1995
- 1995-12-14 JP JP7325735A patent/JPH09165615A/en active Pending
Cited By (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0884395A1 (en) * | 1997-06-12 | 1998-12-16 | ALMAMET GmbH | Agent for fluoride-free treatment of steel melts in the casting ladle, process for its manufacture and its use |
| WO2000037688A1 (en) * | 1998-12-18 | 2000-06-29 | Usinor | Method for denitriding molten steel during its production |
| EA003345B1 (en) * | 1998-12-18 | 2003-04-24 | Усинор | Method for denitriding molten steel during its production |
| WO2007091700A1 (en) | 2006-02-09 | 2007-08-16 | Jfe Steel Corporation | Method of denitrifying molten steel |
| US7901482B2 (en) | 2006-02-09 | 2011-03-08 | Jfe Steel Corporation | Removal method of nitrogen in molten steel |
| WO2008081763A1 (en) | 2006-12-22 | 2008-07-10 | Yoshizawa Lime Industry Co., Ltd. | Flux for obtaining steel reduced in nitrogen, oxygen, and sulfur contents through smelting |
| CN104313250A (en) * | 2014-09-24 | 2015-01-28 | 江苏共昌轧辊股份有限公司 | Roller high-speed steel molten steel tapping denitrification method |
| WO2022259807A1 (en) * | 2021-06-11 | 2022-12-15 | Ｊｆｅスチール株式会社 | Molten steel secondary refining method and steel production method |
| WO2022259808A1 (en) * | 2021-06-11 | 2022-12-15 | Ｊｆｅスチール株式会社 | Molten steel denitrification method, simultaneous denitrification and desulfurization treatment method, and steel production method |
| WO2022259805A1 (en) * | 2021-06-11 | 2022-12-15 | Ｊｆｅスチール株式会社 | Molten steel denitrification method and steel production method |
| JP2022189505A (en) * | 2021-06-11 | 2022-12-22 | Ｊｆｅスチール株式会社 | Molten steel denitrification method and steel production method |
| JP2022189527A (en) * | 2021-06-11 | 2022-12-22 | Ｊｆｅスチール株式会社 | Molten steel denitrification method, simultaneous denitrification and desulfurization treatment method and steel production method |
| JP2022189519A (en) * | 2021-06-11 | 2022-12-22 | Ｊｆｅスチール株式会社 | Molten steel secondary refining method and seel production method |
| TWI824548B (en) * | 2021-06-11 | 2023-12-01 | 日商杰富意鋼鐵股份有限公司 | Secondary refining method of molten steel and manufacturing method of steel |
| TWI824546B (en) * | 2021-06-11 | 2023-12-01 | 日商杰富意鋼鐵股份有限公司 | Method for denitrification of molten steel and method for manufacturing steel |
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