JP2795513B2 - Decarburization refining method of chromium-containing molten steel - Google Patents
Decarburization refining method of chromium-containing molten steelInfo
- Publication number
- JP2795513B2 JP2795513B2 JP2046050A JP4605090A JP2795513B2 JP 2795513 B2 JP2795513 B2 JP 2795513B2 JP 2046050 A JP2046050 A JP 2046050A JP 4605090 A JP4605090 A JP 4605090A JP 2795513 B2 JP2795513 B2 JP 2795513B2
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- Prior art keywords
- decarburization
- slag
- molten steel
- chromium
- concentration
- Prior art date
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- Carbon Steel Or Casting Steel Manufacturing (AREA)
Description
【発明の詳細な説明】 ［産業上の利用分野］ 本発明は、溶鋼中のクロムの酸化を抑え、スラグ中の
クロム酸化物の濃度の上昇を防止することにより、効率
よく脱炭を行う含クロム溶鋼の脱炭精錬法に関するもの
である。[Detailed Description of the Invention] [Industrial application field] The present invention includes a method for efficiently decarburizing by suppressing the oxidation of chromium in molten steel and preventing an increase in the concentration of chromium oxide in slag. The present invention relates to a method for decarburizing and refining chromium molten steel.
［従来の技術］ ステンレス鋼のごとき11％以上のクロムを含むような
含クロム溶鋼の脱炭法として、脱炭中期以降（例えば
［Ｃ］;0.7％以下）を減圧下で行う真空脱炭法、および
稀釈ガスを吹込み、雰囲気中のCO分圧を下げて行う稀釈
脱炭法が広く用いられている。前者は一般にVOD、後者
はAOD、および上底吹き転炉を用いて脱炭が行われてい
る。これらの方法はいずれも脱炭中期以降において溶鋼
中［Cr］の酸化損失を抑えながら効果的に脱炭を進行さ
せようとするものである。従来これらの方法での脱炭を
効率よく進めるための手段として、真空脱炭法では酸素
供給量の調整或いは真空度の調整を行う方法、また、稀
釈脱炭法では稀釈ガスと酸素供給量の調整を行う方法が
主体であり、共存するスラグを調整する方法は殆んど取
り入られていない。[Prior art] As a method of decarburizing a chromium-containing molten steel containing 11% or more chromium such as stainless steel, a vacuum decarburization method in which decarburization is performed under reduced pressure after the middle stage of decarburization (for example, [C]; 0.7% or less). And a dilution decarburization method in which a dilution gas is blown and the CO partial pressure in the atmosphere is lowered. The former is generally VOD, the latter is AOD, and decarburization is performed using a top-bottom blow converter. All of these methods are intended to effectively promote decarburization while suppressing oxidation loss of [Cr] in molten steel after the middle stage of decarburization. Conventionally, as a means for efficiently proceeding decarburization by these methods, a method of adjusting an oxygen supply amount or a degree of vacuum in a vacuum decarburization method, and a method of adjusting a dilution gas and an oxygen supply amount in a dilution decarburization method. Adjustment is mainly performed, and adjustment of coexisting slag is hardly adopted.
スラグを調整して脱炭を行う方法としては、例えば 特開昭53−45616号公報に記載されたように、脱炭
期にスラグ中MgO濃度を調整することにより、マグネシ
ア炉壁を有する転炉炉壁の保護方法 鉄と鋼、78（1986）S175に記載されたように、スラ
グ中MgO濃度を極力抑えることにより、脱炭期の溶鋼中
クロムの酸化を防止する方法 が知られている。As a method of performing decarburization by adjusting slag, for example, as described in JP-A-53-45616, a converter having a magnesia furnace wall by adjusting the MgO concentration in slag during the decarburization period Method of protecting furnace wall As described in Iron and Steel, 78 (1986) S175, there is known a method for preventing the oxidation of chromium in molten steel during the decarburization stage by minimizing the MgO concentration in slag.
［発明が解決しようとする課題］ しかし、このような方法はスラグ中のMgOのみに着目
しているだけで、スラグ量およびスラグ中の他の成分の
脱炭精錬に及ぼす影響が明確にされていないために、効
率よく含クロム溶鋼を脱炭するまでに至っていない。[Problems to be Solved by the Invention] However, such a method focuses only on MgO in the slag, and the effect of the slag amount and other components in the slag on the decarburization refining is clarified. As a result, chromium-containing molten steel has not been efficiently decarburized.
本発明は、含クロム溶鋼の脱炭精錬において、スラグ
量およびスラグ組成の調整を行って、溶鋼中のクロム酸
化を極力抑え、効率よく脱炭を行うことを目的とする。An object of the present invention is to control the amount of slag and the slag composition in the decarburization refining of chromium-containing molten steel, to minimize chromium oxidation in the molten steel, and to efficiently decarburize.
［課題を解決するための手段］ 本発明は、溶解工程の後、脱炭炉に溶鋼を装入して脱
炭精錬を行う含クロム溶鋼の脱炭精錬において、脱炭開
始時のスラグ量を溶鋼トン当り10kg以下とし、かつ該ス
ラグ中のMgO濃度を10％以下、Al2O3濃度を10％以下、Ca
O/SiO2を1.5〜3.0に調整することを特徴とする含クロム
溶鋼の脱炭精錬法である。[Means for Solving the Problems] In the present invention, after the melting step, in the decarburization refining of chromium-containing molten steel in which molten steel is charged into a decarburization furnace to perform decarburization refining, the amount of slag at the start of decarburization is reduced. 10kg or less per ton of molten steel, MgO concentration in the slag is 10% or less, Al 2 O 3 concentration is 10% or less, Ca
This is a method for decarburizing and refining chromium-containing molten steel, wherein O / SiO 2 is adjusted to 1.5 to 3.0.
一般に含クロム溶鋼の脱炭前のスラグ量は溶鋼トン当
り20〜50kg存在する。スラグ量を調整する方法として
は、脱炭炉に装入する前に除去する方法或いは脱炭炉に
装入後炉を倒して除去する方法によって可能である。Generally, the amount of slag of chromium-containing molten steel before decarburization is 20 to 50 kg per ton of molten steel. As a method of adjusting the amount of slag, a method of removing the slag before charging it into the decarburization furnace or a method of removing the slag by loading the decarburization furnace and then turning the furnace down is possible.
また、スラグ組成の調整は前工程でのスラグ組成変化
を見込んでCaOを添加する方法、或いは、採取したスラ
グの分析結果を基に、CaOを添加する方法によって行う
ことができる。また、前工程の炉壁耐火物を種々変える
ことにより、Al2O3およびMgO濃度を調整することが可能
である。Further, the slag composition can be adjusted by a method of adding CaO in anticipation of a change in the slag composition in the previous step, or a method of adding CaO based on the analysis result of the collected slag. Further, it is possible to adjust the Al 2 O 3 and MgO concentrations by variously changing the furnace wall refractory in the preceding step.
次にスラグ量、組成の限定理由について述べる。 Next, reasons for limiting the amount of slag and the composition will be described.
第１図は脱炭開始前18％Crの含クロム溶鋼の２％Ｃか
ら0.05％ＣまでのAODでの脱炭工程において、脱炭終了
時の溶鋼中クロム濃度とスラグ量の関係を示す。図にお
いて、スラグ量を溶鋼トン当り10kg以下とすることによ
り、16.5％以上のCr濃度となりCrの酸化を1.5％以下に
抑えられる。FIG. 1 shows the relationship between the chromium concentration in molten steel and the amount of slag at the end of decarburization in the decarburization step of AOD from 2% C to 0.05% C in chromium-containing molten steel of 18% Cr before the start of decarburization. In the figure, by setting the slag amount to 10 kg or less per ton of molten steel, the Cr concentration becomes 16.5% or more, and the oxidation of Cr can be suppressed to 1.5% or less.
第２図および第３図は脱炭開始前18％Crの含クロム溶
鋼の２％Ｃから0.05％ＣまでのAODの脱炭工程において
スラグ量を溶鋼トン当り10kg以下とした場合の脱炭終了
時の溶鋼中Cr濃度とスラグ中MgOおよびAl2O3濃度の関係
を示す。なお、この場合CaO/SiO2＝２である。第２図お
よび第３図において、スラグ中MgOおよびAl2O3濃度を10
％以下にすることにより、16.5％以上のCr濃度となり、
Crの酸化が抑えられる。Fig. 2 and Fig. 3 show the decarburization process when the amount of slag is 10kg or less per ton of molten steel in the decarburization process of AOD from 2% C to 0.05% C of 18% Cr chromium-containing molten steel before the start of decarburization. The relationship between the Cr concentration in molten steel and the MgO and Al 2 O 3 concentrations in slag is shown. In this case, CaO / SiO 2 = 2. 2 and 3, the MgO and Al 2 O 3 concentrations in the slag were adjusted to 10
%, The Cr concentration becomes 16.5% or more.
Cr oxidation is suppressed.
第４図は脱炭開始前18％Crの含クロム溶鋼の２％Ｃか
ら0.05％ＣまでのAODでの脱炭工程において、スラグ量
を溶鋼トン当り、10kg以下とし、かつ、スラグ中MgO濃
度10％以下、Al2O3濃度10％以下とした場合の脱炭終了
時の溶鋼中Cr濃度とスラグ中CaO/SiO2の関係を示す。図
において、スラグ中CaO/SiO2＝1.5〜3.0の範囲で16.5％
以上のCr濃度となり、Crの酸化が抑えられる。Figure 4 shows that in the decarburization process of 18% Cr chromium-containing molten steel before the start of decarburization with AOD from 2% C to 0.05% C, the amount of slag is set to 10kg or less per ton of molten steel, and the MgO concentration in the slag. The relationship between the Cr concentration in molten steel and the CaO / SiO 2 in slag at the end of decarburization when the Al 2 O 3 concentration is 10% or less and the Al 2 O 3 concentration is 10% or less is shown. In the figure, 16.5% in the range of CaO / SiO 2 = 1.5-3.0 in slag
With the above Cr concentration, the oxidation of Cr is suppressed.
以上のように脱炭時の溶鋼中のCrの酸化を極力抑え、
効率よく脱炭を行うためには、スラグ量を溶鋼トン当り
10kg以下とし、かつ該スラグ中のMgO濃度を10％以下、A
l2O3濃度を10％以下、CaO/SiO2＝1.5〜３に調整する必
要がある。As described above, oxidation of Cr in molten steel during decarburization is suppressed as much as possible,
For efficient decarburization, the amount of slag must be
10 kg or less, and the MgO concentration in the slag is 10% or less, A
It is necessary to adjust the l 2 O 3 concentration to 10% or less and CaO / SiO 2 = 1.5-3.
［作用］ 含クロム溶鋼を脱炭する場合の脱炭反応は（１）式で
示され、反応平衡定数KCは（２）式で示される。[Operation] The decarburization reaction in the case of decarburizing molten chromium-containing steel is expressed by equation (1), and the reaction equilibrium constant K C is expressed by equation (2).
［Ｃ］＋［Ｏ］→CO（ｇ） …（１） KC＝PCO/aC・aO …（２） ここで、PCOは雰囲気中のCO分圧、aCおよびaOは溶鋼
中の［Ｃ］および［Ｏ］の活量を示す。[C] + [O] → CO (g) ... (1) K C = P CO / a C · a O ... (2) where, P CO is the partial pressure of CO in the atmosphere, a C and a O is The activity of [C] and [O] in molten steel is shown.
低炭域まで脱炭が進行し、aCが低下するとPCOを低下
させないと脱炭が進行しにくくなる。含クロム溶鋼の脱
炭では（１）の脱炭反応とともに（３）式に示す溶鋼中
Crの酸化反応が進行する。（３）式の反応平衡定数KCr
は（４）式で示される。To a low carbon range progresses decarburization, a C is less likely to progress decarburization and not to reduce the P CO when lowered. In the decarburization of molten steel containing chromium, the decarburization reaction of (1) and the
The oxidation reaction of Cr proceeds. Reaction equilibrium constant K Cr of equation (3)
Is represented by the equation (4).
ここで、 はスラグ中の（Cr2O3）の活量、aCrは溶鋼中［Cr］の活
量を示す。 here, Indicates the activity of (Cr 2 O 3 ) in the slag, and a Cr indicates the activity of [Cr] in the molten steel.
（３）式の反応が進行すると吹込む酸素が脱炭に有効
に作用しなくなるとともに脱炭後スラグ中Cr2O3を還元
し、有価金属を回収するための還元剤の投入量も増大
し、精錬費用が増大する。When the reaction of the formula (3) proceeds, the injected oxygen does not work effectively for decarburization, and after decarburization, the amount of the reducing agent for reducing Cr 2 O 3 in the slag and recovering valuable metals increases. , Refining costs increase.
（３）式のCrの酸化反応を抑えるには、 を大きくする必要がある。In order to suppress the oxidation reaction of Cr in equation (3), Need to be larger.
はスラグ中の（Cr2O3）の活量係数と濃度の関係で表わ
され、（５）式で示される。 Is represented by the relationship between the activity coefficient of (Cr 2 O 3 ) in the slag and the concentration, and is expressed by equation (5).
ここで、 はスラグ中の（Cr2O3）の活量係数、 はスラグ中の（Cr2O3）の濃度を示す。 here, Is the activity coefficient of (Cr 2 O 3 ) in the slag, Indicates the concentration of (Cr 2 O 3 ) in the slag.
（５）式より、 が大きくなり、Crの酸化は抑えられる。スラグ量が少な
くなれば、溶鋼中Crの酸化に対して、スラグ中Cr2O3濃
度の増大の割合が大きくなるために、第１図に示すよう
にスラグ量を溶鋼トン当り10kg以下とする。From equation (5), And the oxidation of Cr is suppressed. If the amount of slag decreases, the rate of increase in the concentration of Cr 2 O 3 in the slag increases relative to the oxidation of Cr in the molten steel. Therefore, the amount of slag is set to 10 kg or less per ton of molten steel as shown in FIG. .
はスラグ組成に影響される。スラグ中にMgO或いはAl2O3
が高濃度に存在した場合、MgO・Cr2O3或いはMgO・Cr2O3
・Al2O3といった安定で、しかも難還元性のスピネルを
生成するために が小さくなり、［Cr］の酸化が起り易くなる。［Cr］の
酸化を抑えるために、第２図に示すようにスラグ中MgO
濃度10％以下、Al2O3濃度10％以下が必要である。 Is affected by the slag composition. MgO or Al 2 O 3 in slag
Is present in a high concentration, MgO · Cr 2 O 3 or MgO · Cr 2 O 3
・ To produce stable and non-reducible spinel such as Al 2 O 3 And [Cr] is easily oxidized. In order to suppress the oxidation of [Cr], as shown in Fig.
A concentration of 10% or less and an Al 2 O 3 concentration of 10% or less are required.
はスラグ中CaO/SiO2にも依存する。CaO/SiO2＝1.5〜３
では、 が大きくなり、［Cr］の酸化が抑えられるために、第４
図の関係が示される。 Also depends on CaO / SiO 2 in slag. CaO / SiO 2 = 1.5-3
Then Is increased, and oxidation of [Cr] is suppressed.
The relationship of the figures is shown.
［実 施 例］ 本発明をステンレス鋼の脱炭精錬に適用した場合の実
施例について説明する。第１表にAODでのステンレス鋼
の脱炭開始前の溶鋼組成およびスラグ量、スラグ組成を
示す。なお、溶鋼組成、スラグ組成は脱炭に影響を与え
る成分についてのみ挙げている。本発明例では、前工程
の溶解完了後のスラグ組成よりCaOの添加によりスラグ
組成を調整した。また、スラグ量はAODに装入する前に
排滓して調整した。[Example] An example in which the present invention is applied to decarburization and refining of stainless steel will be described. Table 1 shows the molten steel composition, the amount of slag, and the slag composition before the start of decarburization of stainless steel by AOD. In addition, the molten steel composition and the slag composition are listed only for components that affect decarburization. In the present invention, the slag composition was adjusted by adding CaO from the slag composition after the completion of the dissolution in the previous step. The amount of slag was adjusted by discharging the waste before charging the AOD.
第１表の状態の溶鋼をAODにおいて同一の条件にて脱
炭精錬を行った結果を第２表に示す。なお、本例では脱
炭精錬中フラックスの添加は行なわず、Arおよび酸素ガ
ス比のみコントロールして脱炭を行った。 Table 2 shows the results of decarburizing and refining the molten steel in the state shown in Table 1 under the same conditions in AOD. In this example, flux was not added during the decarburization refining, and decarburization was performed by controlling only the Ar and oxygen gas ratios.
比較例では溶鋼中［Cr］が酸化され易いために、［C
r］は低濃度まで低下している。このため、脱炭後のス
ラグ中（Cr2O3）の還元剤が多量に必要となる。なお、
還元剤の必要量は比較例Ａを100とした場合の指数で示
している。また、脱炭酸素効率が低くなっている。これ
に対し、本発明例では溶鋼中［Cr］の酸化が抑えられる
ために、還元剤の量が低下し、脱炭酸素効率も安定して
高くなっている。 In the comparative example, [Cr] in the molten steel was easily oxidized,
r] has been reduced to low concentrations. For this reason, a large amount of the reducing agent in the slag (Cr 2 O 3 ) after decarburization is required. In addition,
The required amount of the reducing agent is indicated by an index when Comparative Example A is set to 100. In addition, the decarbonation efficiency is low. On the other hand, in the example of the present invention, since the oxidation of [Cr] in the molten steel is suppressed, the amount of the reducing agent is reduced, and the decarbonation efficiency is stably increased.
なお、脱炭酸素効率は脱炭時に吹込まれた酸素の中
で、溶鋼中の［Si］の酸化に使用された量を除いて、溶
鋼中の［Ｃ］の酸化に使用された割合を示す量である。The decarboxylation efficiency indicates the ratio of oxygen used in the oxidation of [C] in the molten steel, excluding the amount used in the oxidation of [Si] in the molten steel, in the oxygen injected during decarburization. Quantity.
［発明の効果］ 以上述べたように本発明によって、含クロム溶鋼の脱
炭精錬において、脱炭開始時のスラグ量の調整およびス
ラグ組成の調整、つまりスラグ中の（MgO）濃度、（Al2
O3）濃度およびCaO/SiO2を調整することによって、溶鋼
中クロムの酸化を抑え、脱炭反応を効率よく進行させる
ことができる。この効率的な脱炭精錬法により、スラグ
中（Cr2O3）を還元するための還元剤の量を抑えること
ができ、安価に精錬を行うことが可能となる。さらに、
少量のスラグを有効に活用することが出来るために、フ
ラックスの添加量の低減および精錬後スラグ量の低減も
はかられる。[Effects of the Invention] As described above, according to the present invention, in the decarburization and refining of chromium-containing molten steel, adjustment of the slag amount and slag composition at the start of decarburization, that is, the (MgO) concentration in the slag, (Al 2
By adjusting the O 3 ) concentration and CaO / SiO 2 , the oxidation of chromium in the molten steel can be suppressed, and the decarburization reaction can proceed efficiently. By this efficient decarburization refining method, the amount of reducing agent for reducing slag (Cr 2 O 3 ) can be reduced, and refining can be performed at low cost. further,
Since a small amount of slag can be effectively used, the amount of added flux and the amount of slag after refining can be reduced.
第１図は脱炭開始時のスラグ量と脱炭終了後の溶鋼中
［Cr］濃度の関係を示す図、第２図は脱炭開始時のスラ
グ中（MgO）濃度と脱炭終了後の溶鋼中［Cr］濃度の関
係を示す図、第３図は脱炭開始時のスラグ中（Al2O3）
濃度と脱炭終了後の溶鋼中［Cr］濃度の関係を示す図、
第４図は脱炭開始時のスラグ中（CaO）／（SiO2）と脱
炭終了後の溶鋼中［Cr］濃度の関係を示す図である。Fig. 1 shows the relationship between the amount of slag at the start of decarburization and the [Cr] concentration in molten steel after decarburization, and Fig. 2 shows the concentration of (MgO) in slag at the start of decarburization and the concentration after decarburization. Fig. 3 shows the relationship between [Cr] concentration in molten steel, and Fig. 3 shows slag (Al 2 O 3 ) at the start of decarburization.
Diagram showing the relationship between the concentration and the [Cr] concentration in molten steel after the end of decarburization,
FIG. 4 is a diagram showing the relationship between (CaO) / (SiO 2 ) in slag at the start of decarburization and [Cr] concentration in molten steel after the end of decarburization.
───────────────────────────────────────────────────── フロントページの続き (56)参考文献 特開 平１−172505（ＪＰ，Ａ) 特開 昭59−50113（ＪＰ，Ａ) 特公 昭62−1444（ＪＰ，Ｂ２) 鉄と鋼、74〔４〕 （1988） ＰＰ. 632−639 (58)調査した分野(Int.Cl.6，ＤＢ名) C21C 7/068 C21C 7/10 C21C 5/36──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-172505 (JP, A) JP-A-59-50113 (JP, A) JP-B-62-1444 (JP, B2) Iron and steel, 74 [4] (1988) PP. 632-639 (58) Fields investigated (Int. Cl. 6 , DB name) C21C 7/068 C21C 7/10 C21C 5/36
Claims (1)
炭精錬を行う含クロム溶鋼の脱炭精錬において、脱炭開
始時のスラグ量を溶鋼トン当り10kg以下とし、かつ、該
スラグ中のMgO濃度を10％以下、Al2O3濃度を10％以下、
CaO/SiO2を1.5〜3.0に調整することを特徴とする含クロ
ム溶鋼の脱炭精錬法。In the decarburizing and refining of chromium-containing molten steel in which molten steel is charged into a decarburizing furnace after the melting step to perform decarburizing refining, the amount of slag at the start of decarburizing is set to 10 kg or less per ton of molten steel, and , The MgO concentration in the slag is 10% or less, the Al 2 O 3 concentration is 10% or less,
Decarburization refining method of chromium-containing molten steel, characterized by adjusting the CaO / SiO 2 to 1.5 to 3.0.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2046050A JP2795513B2 (en) | 1990-02-27 | 1990-02-27 | Decarburization refining method of chromium-containing molten steel |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2046050A JP2795513B2 (en) | 1990-02-27 | 1990-02-27 | Decarburization refining method of chromium-containing molten steel |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH03249116A JPH03249116A (en) | 1991-11-07 |
| JP2795513B2 true JP2795513B2 (en) | 1998-09-10 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2046050A Expired - Fee Related JP2795513B2 (en) | 1990-02-27 | 1990-02-27 | Decarburization refining method of chromium-containing molten steel |
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| Country | Link |
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| JP (1) | JP2795513B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100349135B1 (en) * | 1995-12-21 | 2002-12-18 | 주식회사 포스코 | Refining method of molten steel during continuous casting of billet for cold forging |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5950113A (en) * | 1982-09-14 | 1984-03-23 | Nippon Steel Corp | Refining method of chromium steel |
| JPS621444A (en) * | 1985-06-27 | 1987-01-07 | Snow Brand Milk Prod Co Ltd | High pressure type homogenizer |
| JP2615728B2 (en) * | 1987-12-26 | 1997-06-04 | 日本鋼管株式会社 | Decarburization method for Cr-containing pig iron |
-
1990
- 1990-02-27 JP JP2046050A patent/JP2795513B2/en not_active Expired - Fee Related
Non-Patent Citations (1)
| Title |
|---|
| 鉄と鋼、７４〔４〕 （１９８８） ＰＰ．６３２−６３９ |
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| Publication number | Publication date |
|---|---|
| JPH03249116A (en) | 1991-11-07 |
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