JP2003342631A - Method for desulfurizing molten steel in decompressed state - Google Patents
Method for desulfurizing molten steel in decompressed stateInfo
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- JP2003342631A JP2003342631A JP2002157916A JP2002157916A JP2003342631A JP 2003342631 A JP2003342631 A JP 2003342631A JP 2002157916 A JP2002157916 A JP 2002157916A JP 2002157916 A JP2002157916 A JP 2002157916A JP 2003342631 A JP2003342631 A JP 2003342631A
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- cao
- flux
- ratio
- desulfurization
- molten steel
- Prior art date
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Classifications
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- 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
Abstract
Description
【０００１】[0001]
【発明の属する技術分野】本発明は、例えばＲＨ真空脱
ガス装置のように浸漬管と真空槽とからなる真空脱ガス
装置内の減圧下溶鋼表面にフラックスを吹き付けて、あ
るいはフラックスを吹き込んで脱硫を行う溶鋼の減圧下
脱硫方法に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to desulfurization by spraying flux onto the surface of molten steel under reduced pressure in a vacuum degassing apparatus consisting of a dip tube and a vacuum tank such as an RH vacuum degassing apparatus, or by blowing flux. And a method for desulfurizing molten steel under reduced pressure.
【０００２】[0002]
【従来技術およびその問題点】近年の要求鋼材特性の高
まりにより、応力腐食割れや溶接不良の原因となる鋼中
Ｓ濃度のさらなる低減が求められている。鋼中Ｓ濃度の
低減は主として、転炉出鋼後の溶鋼脱硫処理で行われる
が、そのときの溶鋼脱硫はガス吹き込み攪拌や大気圧下
での脱硫フラックス吹き込みによって行われてきた。し
かし、これらの方法では溶鋼処理工程が煩雑化し、処理
時間の延長や各種コストの悪化を招いていた。2. Description of the Related Art Due to the recent increase in required steel properties, further reduction of the S concentration in steel, which causes stress corrosion cracking and welding defects, is required. The reduction of S concentration in steel is mainly performed by molten steel desulfurization treatment after tapping of a converter, and the molten steel desulfurization at that time has been performed by gas blowing stirring or desulfurization flux blowing under atmospheric pressure. However, in these methods, the molten steel treatment process becomes complicated, resulting in extension of treatment time and deterioration of various costs.
【０００３】そこで、これらの脱硫処理を真空脱ガス処
理に統合する処理方法が開発され、減圧下溶鋼表面にフ
ラックスを吹き付け、あるいは吹き込むことにより脱硫
を促進する技術が提案されてきた。Therefore, a treatment method for integrating these desulfurization treatments into a vacuum degassing treatment has been developed, and a technique has been proposed for promoting desulfurization by spraying or blowing a flux onto the surface of molten steel under reduced pressure.
【０００４】例えば、特開５−171253号公報には、ＲＨ
真空脱ガス槽内溶鋼にCaO を主成分としたCaF2を含むフ
ラックスをＲＨ真空脱ガス槽内溶鋼表面に吹き付ける技
術が開示されている。これらの技術ではフラックスと溶
鋼間の反応に着目し、より高い脱硫力を有するフラック
スやその使用方法が提示されている。For example, Japanese Patent Laid-Open No. 5-171253 discloses RH.
A technique is disclosed in which a flux containing CaF 2 containing CaO as a main component is sprayed on the molten steel in the vacuum degassing tank onto the surface of the molten steel in the RH vacuum degassing tank. These technologies focus on the reaction between the flux and molten steel, and have proposed a flux having a higher desulfurization power and a method of using the flux.
【０００５】従って、従来技術では、より脱硫力を高め
るためにフラックス中にCaF2を含有させることが必須で
あった。そのため、このCaF2により、フラックスコスト
の増加、耐火物損耗などの問題があった。Therefore, in the prior art, it was essential to include CaF 2 in the flux in order to further increase the desulfurization power. Therefore, CaF 2 causes problems such as an increase in flux cost and wear of refractory materials.
【０００６】さらに、これらの従来技術では取鍋スラグ
の作用が考慮されていないために、ＲＨ真空脱ガス装置
で脱硫処理を実施した際に脱硫効果にばらつきが生じや
すいという問題があった。Further, in these conventional techniques, since the action of the ladle slag is not taken into consideration, there is a problem that the desulfurization effect tends to vary when the desulfurization treatment is carried out by the RH vacuum degassing device.
【０００７】そこで、スラグの作用を考慮した技術も提
示された。例えば、特開平５−345910号公報には、取鍋
スラグのCaO/(Al2O3+2.5×SiO2) を0.9 以上としてCaO
を主成分とするフラックスを吹き付ける方法が示されて
いる。この技術ではスラグ中CaO 濃度を増加させること
で、スラグ中CaO 濃度が低い場合に生じる脱硫力低下を
回避するのである。しかし、この技術ではスラグ中の高
いCaO 濃度を前提とするため、CaO の多量添加が必須で
あり、その結果、CaO 原単位増加、スラグ量増加といっ
た問題を生じる。また、かかる技術では脱硫促進には、
CaO を増加させる以外に手法がないため、任意のCaO 濃
度での脱硫促進も不可能である。このため、常時CaO 濃
度を高めなければならず、製品コストの増加を招いてい
た。Therefore, a technique considering the action of slag has also been proposed. For example, in Japanese Unexamined Patent Publication (Kokai) No. 5-345910, CaO / (Al 2 O 3 + 2.5 × SiO 2 ) of ladle slag is set to 0.9 or more and CaO
A method of spraying a flux containing as a main component is shown. By increasing the CaO concentration in the slag, this technology avoids the decrease in desulfurization power that occurs when the CaO concentration in the slag is low. However, since this technology presupposes a high CaO concentration in the slag, it is essential to add a large amount of CaO, resulting in problems such as an increase in the CaO basic unit and an increase in the amount of slag. In addition, with such technology, to promote desulfurization,
Since there is no method other than increasing CaO, it is not possible to accelerate desulfurization at any CaO concentration. For this reason, the CaO concentration must be constantly increased, leading to an increase in product cost.
【０００８】以上のように、従来の減圧下フラックス上
吹き溶鋼脱硫法では、CaF2を使用すること、スラグ
中CaO 濃度を増加させなければならないこと、の問題が
あり、各種コストの上昇を招いていた。[0008] As described above, the conventional methods of desulfurization of molten steel on which flux is blown under reduced pressure have the problems of using CaF 2 and having to increase the CaO concentration in the slag, leading to an increase in various costs. Was there.
【０００９】[0009]
【発明が解決しようとする課題】従って、本発明の課題
は、CaF2使用量を低減し、スラグ中CaO 濃度が低濃度で
も脱硫可能とし、さらに任意のCaO 濃度での脱硫促進を
可能とする脱硫方法を提供することである。Therefore, the object of the present invention is to reduce the amount of CaF 2 used, enable desulfurization even at low CaO concentration in slag, and further promote desulfurization at any CaO concentration. It is to provide a desulfurization method.
【００１０】[0010]
【課題を解決するための手段】一般に、脱硫反応では、
スラグ中CaO/Al2O3 比が高い方が脱硫はより進行するこ
とが知られている。これは、従来の研究報告を基にした
熱力学的検討から、CaO/Al2O3 比が高い方がスラグのサ
ルファイドキャパシティが高く、加えてCaO/Al 2O3 比が
高い方がAl2O3 活量が低くなるため、Al脱酸溶鋼では酸
素活量が低くなるためと説明される。[Means for Solving the Problems] Generally, in the desulfurization reaction,
CaO / Al in slag2O3The higher the ratio, the more the desulfurization proceeds.
Is known. This is based on previous research reports
From thermodynamic studies, CaO / Al2O3The higher the ratio, the better the slag
High Rfide capacity, plus CaO / Al 2O3Ratio is
Higher is Al2O3Since the activity becomes low, acidification is difficult in Al deoxidized molten steel.
It is explained that the activity level becomes low.
【００１１】一方、CaO/Al2O3 比が一定の条件で、脱硫
反応を促進させるには、溶鋼の酸素活量を低減するしか
ない。酸素活量低減には、脱酸元素であるAl濃度を高め
れば良いが、Al濃度は製品特性の都合で上限規格が存在
するため、限界がある。On the other hand, in order to accelerate the desulfurization reaction under the condition that the CaO / Al 2 O 3 ratio is constant, there is no choice but to reduce the oxygen activity of the molten steel. The oxygen activity can be reduced by increasing the Al concentration as a deoxidizing element, but the Al concentration has a limit because there is an upper limit specification for the convenience of product characteristics.
【００１２】また、Al濃度を増加させて酸素活量を低減
するにはAl濃度を0.2 〜１％と著しく高める必要があ
り、Alコスト的にも限界がある。Al以外で酸素活量を大
幅に低減するには、10ppm 以下でもAl以上の脱酸力 (酸
素活量低減能力）を有するCaを活用すればよい。しか
し、減圧下上吹きでCaを用いると、Caの蒸発反応により
Ca濃度が上昇せず、酸素活量低減が図れないという課題
があった。Further, in order to increase the Al concentration and reduce the oxygen activity, it is necessary to remarkably increase the Al concentration to 0.2 to 1%, and there is a limit in the Al cost. In order to significantly reduce the oxygen activity other than Al, it is sufficient to utilize Ca having a deoxidizing power (oxygen activity reducing ability) equal to or higher than Al even at 10 ppm or less. However, when Ca is blown up under reduced pressure, the Ca evaporation reaction causes
There was a problem that the Ca concentration did not rise and the oxygen activity could not be reduced.
【００１３】この課題を解決するために、CaとCaO を混
合して上吹きすることで、Ca活量を安定させ、酸素活量
を低減することが可能と考えた。さらに、配合比は数％
と微量でよい。In order to solve this problem, it was considered possible to stabilize Ca activity and reduce oxygen activity by mixing and blowing Ca and CaO. Furthermore, the compounding ratio is several%
And a small amount is enough.
【００１４】このような考え方に基づき、CaとCaO を混
合したCa配合CaO フラックスを用いることで減圧下粉体
上吹きによる脱硫能力を著しく高めることに成功し、す
でに特許出願を行った (特願平11-102672 号、特願平11
-370516 号）。すなわち、一定のCaO/Al2O3 比の条件下
であればこの技術で対応できる。しかし、スラグ中CaO/
Al2O3 比が変化する場合、この技術では対応できない。Based on such an idea, by using a Ca-containing CaO flux that is a mixture of Ca and CaO, we succeeded in significantly increasing the desulfurization ability by powder upper blowing under reduced pressure, and have already filed a patent application (Japanese Patent Application Hei 11-102672, Japanese Patent Application No. 11
-370516). That is, this technique can be used under the condition of a constant CaO / Al 2 O 3 ratio. However, CaO / in the slag
If the Al 2 O 3 ratio changes, this technology cannot handle it.
【００１５】そこでスラグ中CaO/Al2O3 比が変化する場
合、CaO/Al2O3 に応じたCa配合比とすることで、最小の
Ca配合比あるいは最低のCaO/Al2O3 比での脱硫が可能と
なると考えた。また、この最適バランスにより、CaF2も
全く使用しない脱硫も可能になると考えた。Therefore, when the CaO / Al 2 O 3 ratio in the slag changes, the Ca blending ratio according to CaO / Al 2 O 3 is used to minimize the
It was thought that desulfurization would be possible at a Ca compounding ratio or at the lowest CaO / Al 2 O 3 ratio. We also thought that this optimal balance would enable desulfurization without using CaF 2 .
【００１６】つまり、CaO/Al2O3 比が低下するに従い、
その分だけ酸素活量をより低減しなければならない。逆
にCaO/Al2O3 比が高ければ過剰に酸素活量を低減する必
要はない。また、CaF2についてもCaO/Al2O3 比の場合と
同様の考え方となり、CaF2が低ければ酸素活量を低減す
る必要がある。That is, as the CaO / Al 2 O 3 ratio decreases,
The oxygen activity must be reduced accordingly. On the contrary, if the CaO / Al 2 O 3 ratio is high, it is not necessary to reduce the oxygen activity excessively. In addition, CaF 2 has the same concept as in the case of the CaO / Al 2 O 3 ratio, and if CaF 2 is low, it is necessary to reduce the oxygen activity.
【００１７】従って、減圧下で行う溶鋼のフラックス脱
硫において、酸素活量増減に作用するCaとCaO/Al2O3 比
の増減の関係を明らかにすれば、スラグ中CaO/Al2O3 比
に応じた脱硫促進可能な最適Ca配合比が明確化されると
の着想を得た。Therefore, in flux desulfurization of molten steel under reduced pressure, if the relationship between Ca and CaO / Al 2 O 3 ratio, which acts to increase or decrease oxygen activity, is clarified, the CaO / Al 2 O 3 ratio in slag is clarified. The idea was to clarify the optimum Ca blending ratio that can accelerate desulfurization according to the above.
【００１８】以上のように、定性的に推測することは可
能であるが、Caが蒸発物質であること、真空槽内で
上吹またはインジェクションされるフラックスと大気圧
下取鍋スラグとの脱硫に対する定量的影響が不明確であ
ること、等の理由により予め理論的にこれらを定量的に
予測することは困難である。As described above, it is possible to qualitatively estimate that Ca is an evaporative substance, and that desulfurization between the flux blown up or injected in the vacuum chamber and the atmospheric pressure ladle slag It is difficult to theoretically predict these quantitatively beforehand because of the fact that the quantitative influence is unclear.
【００１９】そこで、250t溶鋼の脱硫処理を行う浸漬管
および真空槽から成るＲＨ真空脱ガス装置を使って上記
調査を行った。溶鋼量は250tとし、スラグはSiO2濃度20
％以下、MgO 濃度10％以下のCaO-Al2O3 系スラグとし
た。なお、ＲＨ真空脱ガス処理前のスラグ量は10〜15kg
/tであった。溶鋼中のAl濃度は0.03〜0.08％、Ｓ濃度は
15〜20ppm であった。Therefore, the above investigation was carried out using an RH vacuum degassing apparatus consisting of a dip tube and a vacuum tank for desulfurizing 250t molten steel. The amount of molten steel is 250t and the slag has a SiO 2 concentration of 20.
% Or less, and a MgO concentration of 10% or less was used as the CaO-Al 2 O 3 based slag. The amount of slag before RH vacuum degassing is 10-15kg.
It was / t. Al concentration in molten steel is 0.03-0.08%, S concentration is
It was 15 to 20 ppm.
【００２０】転炉から取鍋へ溶鋼を出鋼し、取鍋をＲＨ
真空脱ガス装置へ移動した。浸漬管を取鍋溶鋼内に浸漬
して行うＲＨ真空脱ガス処理開始直後から、真空槽内溶
鋼表面に上吹きランスから60％CaO-40％CaF2フラック
ス、または１〜５％のCaを混合したCaO フラックスをAr
ガスと共に吹き付けた。Molten steel is tapped from the converter to the ladle, and the ladle is RH.
Transferred to vacuum degasser. Immediately after starting the RH vacuum degassing process by immersing the dipping tube in the ladle molten steel, mix 60% CaO-40% CaF 2 flux or 1 to 5% Ca from the top blowing lance on the surface of the molten steel in the vacuum tank. The CaO flux
Sprayed with gas.
【００２１】フラックス量は３〜５kg/t、吹き付け速度
は0.7kg/(t・min)とした。吹き付け処理前後の溶鋼中Ｓ
濃度から、フラックス１kg/t当たりの脱硫率Ｒを(1) 式
で定義し、脱硫能力を評価した。The amount of flux was 3 to 5 kg / t, and the spraying rate was 0.7 kg / (t · min). S in molten steel before and after spraying
From the concentration, the desulfurization rate R per 1 kg / t of flux was defined by the equation (1), and the desulfurization ability was evaluated.
【００２２】
フラックス１kg/t当たりの脱硫率Ｒ[%/(kg/t)]＝
[処理前Ｓ濃度(%) −処理後Ｓ濃度(%)]／ [処理前Ｓ濃度(%) ×フラックス
量(kg/t)] ×100 ・・・（１）
図１に、吹き付け処理前のスラグ中CaO/Al2O3 比と(1)
式で算出したＲとの関係をグラフで示す。Desulfurization rate R per 1 kg / t of flux R [% / (kg / t)] = [S concentration before treatment (%)-S concentration after treatment (%)] / [S concentration before treatment (%) x flux Amount (kg / t)] × 100 (1) Figure 1 shows the CaO / Al 2 O 3 ratio in the slag before spraying and (1)
The relationship with R calculated by the formula is shown in a graph.
【００２３】図１の結果から分かるように、スラグ中Ca
O/Al2O3 比によらず、Caを1.5 〜５％配合することによ
り、CaF2＝０のフラックスでも同一CaO/Al2O3 比であれ
ば CaO−CaF2フラックスよりも高い脱硫力が得られる。
一方、フラックスの種類によらず、スラグ中CaO/Al2O3
比の低下に伴い、各フラックスの脱硫力は低下する。こ
の現象は前述した機構に基づくものである。As can be seen from the results of FIG. 1, Ca in slag
O / Al 2 regardless of the O 3 ratio, by incorporating Ca 1.5 to 5%, high desulfurization force than CaO-CaF 2 flux if the same CaO / Al 2 O 3 ratio in the flux of CaF 2 = 0 Is obtained.
On the other hand, regardless of the type of flux, CaO / Al 2 O 3 in the slag
As the ratio decreases, the desulfurizing power of each flux decreases. This phenomenon is based on the mechanism described above.
【００２４】ところで、従来から用いられているCaO-Ca
F2フラックスでは、CaO/Al2O3=1.5(CaO 飽和) で得られ
る脱硫率Ｒは7.7 [%/(kg/t)]である。つまり、CaO-CaF2
ではCaO を最大に添加して得られる最大脱硫力はＲ＝7.
7 [%/(kg/t)]である。By the way, conventionally used CaO-Ca
With F 2 flux, the desulfurization rate R obtained at CaO / Al 2 O 3 = 1.5 (CaO saturation) is 7.7 [% / (kg / t)]. That is, CaO-CaF 2
Then, the maximum desulfurization power obtained by adding CaO to the maximum is R = 7.
It is 7 [% / (kg / t)].
【００２５】一方、Caを１％混合した試験では、CaO/Al
2O3=1.48でＲ＝10[%/(kg/t)]、Caを５％配合した試験で
は CaO/Al2O3＝1.39でＲ＝17[%/(kg/t)]と高い脱硫力が
得られる。On the other hand, in the test in which Ca was mixed at 1%, CaO / Al
2 O 3 = 1.48, R = 10 [% / (kg / t)], 5% Ca in the test CaO / Al 2 O 3 = 1.39, R = 17 [% / (kg / t)] Desulfurization power can be obtained.
【００２６】しかし、Ca配合比１％の場合、CaO/Al2O3
が0.8 程度まで低下してしまうとＲは、CaO/Al2O3 ＝1.
5でのCaO-CaF2フラックス上吹きでのＲよりも低くなっ
てしまう。However, when the Ca compounding ratio is 1%, CaO / Al 2 O 3
When R decreases to about 0.8, R is CaO / Al 2 O 3 = 1.
It becomes lower than R in CaO-CaF 2 flux top blowing at 5.
【００２７】同一CaO/Al2O3 比ではCaを配合したフラッ
クスの方が、CaO-CaF2よりも高い脱硫力を発揮するが、
低CaO/Al2O3 では脱硫力が低下するため、Caを配合した
CaOフラックスでも取鍋スラグ中CaO を高める必要があ
る。すなわち、Ca配合比を１％と固定した場合には、Ca
O 投入により、取鍋スラグ中CaO/Al2O3 比を高める必要
がある。At the same CaO / Al 2 O 3 ratio, the flux containing Ca exhibits a higher desulfurization power than CaO-CaF 2 ,
Desulfurization power decreases with low CaO / Al 2 O 3 , so Ca was added.
Even with CaO flux, it is necessary to increase CaO in the ladle slag. That is, when the Ca blending ratio is fixed at 1%,
It is necessary to increase the CaO / Al 2 O 3 ratio in the ladle slag by adding O 2 .
【００２８】ところで、図１はCaO/Al2O3 比が低下して
もCa配合比を増加すると、一定の脱硫力が得られること
を同時に示している。従って、CaO を大量投入すること
なしに、CaO-CaF2よりも常に脱硫力を高めるにはスラグ
中CaO/Al2O3 比に応じてCa配合比を変化させれば良いこ
とが解る。そこで、CaO-CaF2で得られる最大Ｒ＝7.7[%/
(kg/t)]に対し、各CaO/Al2O3 でＲ＞10[%/(kg/t)]を確
保できる最低Ca配合比の関係を図１より求めた。結果を
図２に示す。By the way, FIG. 1 also shows that even if the CaO / Al 2 O 3 ratio decreases, a constant desulfurization power can be obtained by increasing the Ca blending ratio. Therefore, it is understood that the Ca blending ratio may be changed according to the CaO / Al 2 O 3 ratio in the slag in order to always increase the desulfurization power higher than that of CaO-CaF 2 without adding a large amount of CaO. Therefore, the maximum R obtained with CaO-CaF 2 is 7.7 [% /
(kg / t)], the relationship of the minimum Ca blending ratio that can secure R> 10 [% / (kg / t)] for each CaO / Al 2 O 3 was obtained from FIG. The results are shown in Figure 2.
【００２９】その結果、最低Ca配合比は、下記式で記述
されることが分かった。
最低Ca配合比＝−6.4 ×(CaO/Al2O3比）＋10
これは、CaO/Al2O3 比の低減に伴って低下するスラグの
サルファイドキャパシティの悪化を、酸素活量低減で補
う際にCaをより多量に必要とするという前述の機構によ
り説明される。As a result, it was found that the minimum Ca compounding ratio is described by the following formula. From Ca compounding ratio = -6.4 × (CaO / Al 2 O 3 ratio) +10 This is a deterioration of the sulfide capacity slag decreases with decrease of CaO / Al 2 O 3 ratio, supplemented by oxygen activity reduced This is explained by the mechanism described above, which requires a larger amount of Ca.
【００３０】従って、安定した脱硫力を確保するには、
0.75≦CaO/Al2O3 ≦1.55：−6.4 ×(CaO/Al2O3）＋10≦
Ｗ
CaO/Al2O3：取鍋スラグ中CaO とAl2O3 の質量比
Ｗ：フラックス中Ca純分配合比 (質量％)
とする。ここに、フラックス中Ca純分配合比Ｗはフラッ
クスに金属CaまたはCa合金として添加される全Ca分のフ
ラックス全量に対する割合である。CaF2が添加されると
きはCaF2のCa分は考えない。Therefore, in order to secure a stable desulfurization power, 0.75 ≦ CaO / Al 2 O 3 ≦ 1.55: −6.4 × (CaO / Al 2 O 3 ) + 10 ≦
W CaO / Al 2 O 3 : Mass ratio of CaO and Al 2 O 3 in ladle slag W: Mixing ratio of pure Ca in flux (mass%) Here, the pure Ca content ratio W in the flux is the ratio of the total Ca content added to the flux as metallic Ca or Ca alloy to the total amount of the flux. When CaF 2 is added, the Ca content of CaF 2 is not considered.
【００３１】また、CaO/Al2O3 ＞1.55はCaO 飽和領域で
あり、スラグ液相部の組成はCaO 飽和濃度となる。従っ
て、CaO/Al2O3 ＞1.55では、上記不等式のCaO/Al2O3 ＝
1.55のときの値0.08以上であればよい。同様に CaO/Al2
O3＜0.75の領域はアルミナ飽和となるので、上記不等式
での CaO/Al2O3＝0.75の代入値以上であればよい。よっ
て、
CaO/Al2O3 ＜0.75：Ｗ＞5.2 ％
CaO/Al2O3 ＞1.55：Ｗ＞0.08％
となる。Further, CaO / Al 2 O 3 > 1.55 is in the CaO saturation region, and the composition of the liquid phase portion of the slag becomes the CaO saturation concentration. Therefore, for CaO / Al 2 O 3 > 1.55, CaO / Al 2 O 3 =
The value at 1.55 should be 0.08 or more. Similarly CaO / Al 2
Since the region where O 3 <0.75 is saturated with alumina, it is sufficient if it is at least the substituted value of CaO / Al 2 O 3 = 0.75 in the above inequality. Therefore, CaO / Al 2 O 3 <0.75: W> 5.2% CaO / Al 2 O 3 > 1.55: W> 0.08%.
【００３２】また、Ca純分配合比Ｗが10％を超えて高い
と効果が飽和したり、清浄度が悪化する場合もあるの
で、Ｗの上限は10％とする。以上から、真空槽内減圧下
溶鋼にフラックスを吹き付けて脱硫を行う処理におい
て、フラックスが低CaF2混合比でまたはCaF2無添加で、
かつ取鍋スラグが低CaO/Al2O3 比でも脱硫を促進させる
には、フラックスをCaO と金属CaまたはCa合金の混合物
とし、フラックス中Ca純分配合比Ｗが処理開始前取鍋ス
ラグ中CaO/Al2O 3 比を用いた次式を満足することが重要
である。Further, the Ca pure content ratio W is high, exceeding 10%.
The effect may be saturated or the cleanliness may be deteriorated.
Therefore, the upper limit of W is 10%. From the above, under reduced pressure in the vacuum tank
In the process of desulfurization by spraying flux on molten steel
And low flux CaF2In mixing ratio or CaF2Without additives,
And low ladle slag CaO / Al2O3Promotes desulfurization even in ratio
The flux is a mixture of CaO and metallic Ca or Ca alloy
And the Ca content of W in the flux is W before the start of processing.
CaO / Al in rug2O 3It is important to satisfy the following equation using the ratio
Is.
【００３３】CaO/Al2O3 ＜0.75：10＞Ｗ＞５％
CaO/Al2O3 ＞1.55：10＞Ｗ＞0.1 ％
0.75≦CaO/Al2O3 ≦1.55：−6.4 ×(CaO/Al2O3）＋10≦
Ｗ≦10
CaO/Al2O3：処理開始前取鍋スラグ中CaO とAl2O3 の質
量比
Ｗ：フラックス中Ca純分配合比 (質量％)CaO / Al 2 O 3 <0.75: 10>W> 5% CaO / Al 2 O 3 > 1.55: 10>W> 0.1% 0.75 ≦ CaO / Al 2 O 3 ≦ 1.55: −6.4 × (CaO / Al 2 O 3 ) ＋ 10 ≦
W ≦ 10 CaO / Al 2 O 3 : Mass ratio of CaO and Al 2 O 3 in ladle slag before starting treatment W: Mixing ratio of Ca in flux (mass%)
【００３４】[0034]
【発明の実施の形態】本発明を、転炉、ＲＨ真空脱ガス
装置、連続鋳造機を用いて脱硫鋼を製造する場合を例に
説明する。BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described by taking as an example the case of producing desulfurized steel using a converter, an RH vacuum degassing device and a continuous casting machine.
【００３５】転炉から取鍋内へ溶鋼を出鋼した後、取鍋
をＲＨ真空脱ガス装置へ移動する。この出鋼の際、取鍋
スラグ中CaO/Al2O3 比を増加させるためのCaO 投入は特
に必要ない。所定のAl濃度に調整するためのAlを添加
し、スラグ液相率が高くなる程度のCaO を添加すればよ
い。このとき、Al濃度狙い、転炉終了時の酸素濃度によ
ってAl添加量と生成Al2O3 量が判定できるが、総スラグ
量の目標値と液相率を確保するためのCaO 量だけを添加
すればよい。After the molten steel is tapped from the converter into the ladle, the ladle is moved to the RH vacuum degassing device. At the time of this tapping, CaO is not particularly required to increase the CaO / Al 2 O 3 ratio in the ladle slag. Al for adjusting the Al concentration to a predetermined value may be added, and CaO 2 may be added to such an extent that the slag liquid phase ratio becomes high. At this time, the amount of Al added and the amount of Al 2 O 3 produced can be determined by aiming at the Al concentration and the oxygen concentration at the end of the converter, but only the target value of the total slag amount and the CaO amount for securing the liquid phase ratio are added. do it.
【００３６】スラグ量を最小とし、液相率を最大とする
には、CaO/Al2O3 比が0.9 程度となるようにアルミナ生
成量に対しCaO を添加すればよい。また、スラグの溶鋼
表面被覆効果を高めたい場合は、CaO 投入量を増加させ
ればよい。この操作で、スラグ中のCaO/Al2O3 比が把握
できる。In order to minimize the amount of slag and maximize the liquid phase ratio, CaO should be added to the amount of alumina produced so that the CaO / Al 2 O 3 ratio should be about 0.9. Further, when it is desired to enhance the molten steel surface coating effect of slag, the amount of CaO added may be increased. By this operation, the CaO / Al 2 O 3 ratio in the slag can be grasped.
【００３７】ＲＨ真空脱ガス処理では、処理開始直後か
ら、フラックス上吹きを行い脱硫処理を開始してもよ
い。また、溶鋼昇温処理あるいは脱ガス、成分調整等の
処理を行ってから脱硫処理を行ってもよい。ただし、ス
ラグ中CaO/Al2O3 比とフラックス中Ca配合比は本発明の
範囲を満足させることが重要である。In the RH vacuum degassing process, the desulfurization process may be started by immediately blowing up the flux immediately after the start of the process. Further, the desulfurization treatment may be performed after the molten steel temperature rising treatment or the treatment such as degassing and component adjustment. However, it is important that the CaO / Al 2 O 3 ratio in the slag and the Ca mixing ratio in the flux satisfy the range of the present invention.
【００３８】フラックス上吹き量は、図１と処理前Ｓ濃
度、目標処理後Ｓ濃度から求まるが、２kg/t以上８kg/t
以下が望ましい。２kg/t未満であると脱硫量が少なく、
８kg/tを超えて多いと、総スラグ量が増加してしまう。The amount of blown flux is obtained from FIG. 1, the S concentration before treatment, and the S concentration after target treatment, and is 2 kg / t or more and 8 kg / t or more.
The following is desirable. If it is less than 2 kg / t, the desulfurization amount is small,
If it exceeds 8 kg / t, the total amount of slag will increase.
【００３９】フラックス上吹き速度は0.05kg/t/min以
上、２kg/t/min以下が望ましい。0.05kg/t/min未満であ
ると総処理時間が長くなりすぎ、２kg/t/minを越えて高
いとCaO によるスプラッシュが激しくなる。The flux top blowing rate is preferably 0.05 kg / t / min or more and 2 kg / t / min or less. If it is less than 0.05 kg / t / min, the total treatment time becomes too long, and if it exceeds 2 kg / t / min, the splash due to CaO becomes severe.
【００４０】上吹きに用いるランスは、ラバール、スト
レートなどいかなるタイプでも構わないが、ランス高さ
は1.5m以上、４m 以下が望ましい。ランス高さが1.5m未
満であると地金付着が激しく、４m を越えて高いとフラ
ックスの一部が排気されてしまう場合がある。The lance used for top blowing may be any type such as Laval or straight, but the lance height is preferably 1.5 m or more and 4 m or less. If the height of the lance is less than 1.5 m, the adhesion of metal is severe, and if it exceeds 4 m, a part of the flux may be exhausted.
【００４１】フラックスに混合するCaは、金属Ca、Ca合
金などいかなるものでもよい。また、上吹き時の真空槽
内圧力は100Torr 以下が望ましく、さらには10Torr以下
が望ましい。真空槽内圧力が100Torr よりも高い場合、
ランスから吐出したフラックスの速度が遅く、溶鋼に十
分侵入できない。また、10Torr以下となると脱ガスが進
行するため、総処理時間の短縮が図れる。The Ca mixed with the flux may be any metal such as Ca or Ca alloy. The pressure in the vacuum chamber at the time of top blowing is preferably 100 Torr or less, more preferably 10 Torr or less. If the pressure in the vacuum chamber is higher than 100 Torr,
The flux discharged from the lance is too slow to penetrate the molten steel. Further, when the pressure is 10 Torr or less, degassing proceeds, so that the total processing time can be shortened.
【００４２】本発明ではフラックス中にCaF2を必要とし
ないが、さらなる脱硫力向上、あるいはスラグ流動性確
保を図るために、フラックス中にCaF2、MgO 、Al2O3 な
どを混合してもよい。ただし、CaF2、Al2O3 の質量配合
比はそれぞれ30％以下、MgOは15％以下であることが望
ましい。CaF2、Al2O3 がそれぞれ30％を超えて多くなる
と、CaO 量が少なくなりすぎ、一方、MgO が15％を越え
て高くなると逆に流動性が低下する場合がある。In the present invention, CaF 2 is not required in the flux, but CaF 2 , MgO, Al 2 O 3 or the like may be mixed in the flux in order to further improve desulfurization power or secure slag fluidity. Good. However, it is desirable that the mass mixing ratio of CaF 2 and Al 2 O 3 be 30% or less and MgO be 15% or less. When CaF 2 and Al 2 O 3 each exceed 30% and increase, the amount of CaO becomes too small, while when MgO exceeds 15% and increase, fluidity may decrease.
【００４３】以上のように、本発明において用いるフラ
ックスは上吹きで高い性能を発揮するが、真空処理中の
溶鋼への吹き込みでもよい。この場合も、真空槽内圧
力、フラックス形態などは前述と同様である。As described above, the flux used in the present invention exerts a high performance in the upper blowing, but it may be blown into the molten steel during the vacuum treatment. Also in this case, the pressure in the vacuum chamber and the form of the flux are the same as described above.
【００４４】以上の説明はＲＨ真空脱ガス装置を使った
場合について行ったが、すでにこれまでの説明から当業
者には自明のようにＤＨ真空脱ガス装置、タンク脱ガス
装置等を使用する場合のように減圧溶鋼一般に本発明は
適用可能である。Although the above description has been made on the case of using the RH vacuum degassing apparatus, it is already apparent to those skilled in the art from the above description that the DH vacuum degassing apparatus, the tank degassing apparatus, etc. are used. As described above, the present invention is generally applicable to reduced pressure molten steel.
【００４５】[0045]
【実施例】本例では、転炉で脱炭脱硫した溶鋼250tを取
鍋内に出鋼し、この取鍋を浸漬管および真空槽を備えた
ＲＨ真空脱ガス装置に移動して浸漬管を取鍋溶鋼に浸漬
して行う真空脱ガス処理に際して溶鋼脱硫を行った。Example In this example, 250 ton of molten steel decarburized and desulfurized in a converter was tapped into a ladle, and the ladle was moved to an RH vacuum degassing apparatus equipped with a dip tube and a vacuum tank to remove the dip tube. Molten steel desulfurization was performed during the vacuum degassing process performed by immersing the steel in a ladle.
【００４６】まず、出鋼時にAlを添加し、溶鋼中Al濃度
を0.07〜0.09％に調整した。CaO の添加量を変化させ、
CaO/Al2O3 比を0.8 〜1.5 の範囲で変化させた。ＲＨ真
空脱ガス処理では処理開始後、真空槽内圧力が５Torr以
下に安定したのを確認したのち、上吹きランスからフラ
ックスを真空槽内溶鋼表面に６kg/t吹き付けた。吹き付
け速度は１kg/t/minとし、キャリアーガスArの流量は40
00Nl/minとした。ランス高さは３m であった。First, Al was added at the time of tapping to adjust the Al concentration in the molten steel to 0.07 to 0.09%. By changing the amount of CaO added,
The CaO / Al 2 O 3 ratio was changed in the range of 0.8 to 1.5. In the RH vacuum degassing process, after starting the process, after confirming that the pressure in the vacuum tank was stabilized at 5 Torr or less, a flux of 6 kg / t was sprayed from the top blowing lance onto the molten steel surface in the vacuum tank. Spraying speed is 1kg / t / min, carrier gas Ar flow rate is 40
It was set to 00 Nl / min. The lance height was 3 m.
【００４７】表１に、フラックス吹き付け前後のＳ濃
度、脱硫率、フラックス吹き付け前のCaO/Al2O3 を示
す。フラックスはCaSi配合CaO であり、表１にはCa純分
配合比 (Ca配合比と表記) もあわせて示す。また、CaO-
40％CaF2を用いた場合は、Ca純分配合比欄に０と記し
た。Table 1 shows the S concentration before and after flux spraying, the desulfurization rate, and CaO / Al 2 O 3 before flux spraying. The flux is CaSi mixed CaO, and Table 1 also shows the Ca pure content mixing ratio (expressed as Ca mixing ratio). Also, CaO-
When 40% CaF 2 was used, 0 was written in the Ca pure content ratio column.
【００４８】表１のNo.1〜17とNo.18 〜21、 24を比較す
るとCa配合によりCaO-CaF2以上の脱硫が得られることが
解る。さらに、No.1〜12とNo.13 〜17、22、23を比較す
ると、本発明に従いCa純分配合比を制御した方が、CaO/
Al2O3 によらず安定して高い脱硫率が得られることが解
る。Comparing Nos. 1 to 17 and Nos. 18 to 21 and 24 in Table 1, it is understood that desulfurization of CaO-CaF 2 or more can be obtained by mixing Ca. Furthermore, when comparing No. 1 to 12 and No. 13 to 17, 22, 23, it is better to control the Ca pure content ratio according to the present invention, CaO /
It can be seen that a high desulfurization rate can be stably obtained regardless of Al 2 O 3 .
【００４９】[0049]
【表１】 [Table 1]
【００５０】[0050]
【発明の効果】以上説明したように、本発明にあって
は、CaF2使用量を低減し、安定して高い脱硫率で溶鋼の
処理ができ、その実際上の意義が大きいことが分かる。As described above, according to the present invention, it is understood that the amount of CaF 2 used can be reduced, the molten steel can be stably treated with a high desulfurization rate, and its practical significance is great.
【図面の簡単な説明】[Brief description of drawings]
【図１】スラグ中のCaO/Al2O3 比とフラックス１kg/t当
たりの脱硫率の関係を示すグラフである。FIG. 1 is a graph showing the relationship between the CaO / Al 2 O 3 ratio in slag and the desulfurization rate per 1 kg / t of flux.
【図２】スラグ中のCaO/Al2O3 比とフラックス中最低Ca
配合比の関係を示すグラフである。[Fig. 2] CaO / Al 2 O 3 ratio in slag and minimum Ca in flux
It is a graph which shows the relationship of a compounding ratio.
Claims (2)
を用い、真空槽内減圧下溶鋼にフラックスを吹き付けま
たは吹き込んで脱硫を行う処理において、フラックスを
CaO と金属CaまたはCa合金との混合物とし、該フラック
ス中Ca純分の質量配合比Ｗが、処理開始前取鍋スラグ中
CaO/Al2O3 比を用いた次式を満足することを特徴とする
溶鋼の脱硫方法。 CaO/Al2O3 ＜0.75：10＞Ｗ＞5.2 ％ CaO/Al2O3 ＞1.55：10＞Ｗ＞0.08％ 0.75≦CaO/Al2O3 ≦1.55：−6.4 ×(CaO/Al2O3）＋10≦
Ｗ≦10 CaO/Al2O3 ：処理開始前取鍋スラグ中CaO とAl2O3 の質
量比 Ｗ：フラックス中Ca純分配合比 (質量％)1. In a process of desulfurizing by spraying or blowing a flux onto molten steel under reduced pressure in a vacuum tank using a vacuum degassing device comprising an immersion pipe and a vacuum tank, the flux is removed.
It is a mixture of CaO and metallic Ca or Ca alloy, and the mass ratio W of Ca in the flux is in the ladle slag before the start of treatment.
A method for desulfurizing molten steel, characterized by satisfying the following equation using a CaO / Al 2 O 3 ratio. CaO / Al 2 O 3 <0.75: 10>W> 5.2% CaO / Al 2 O 3 > 1.55: 10>W> 0.08% 0.75 ≦ CaO / Al 2 O 3 ≦ 1.55: −6.4 × (CaO / Al 2 O 3 ) + 10≤
W ≦ 10 CaO / Al 2 O 3 : Mass ratio of CaO and Al 2 O 3 in ladle slag before starting treatment W: Mixing ratio of Ca in flux (mass%)
ラックスであって、Ca純分配合比が質量比で0.08％以上
10％以下であることを特徴とする、溶鉄の脱硫剤。2. A flux comprising metallic Ca or a Ca alloy and CaO, wherein the Ca pure content is 0.08% or more by mass.
Desulfurizing agent for molten iron, characterized by being 10% or less.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10287644B2 (en) | 2011-08-12 | 2019-05-14 | Jfe Steel Corporation | Molten steel desulfurization method, molten steel secondary refining method, and molten steel manufacturing method |
| CN111471829A (en) * | 2020-04-09 | 2020-07-31 | 肖卫学 | Preparation method of high-calcium aluminum alloy and high-calcium aluminum alloy |
-
2002
- 2002-05-30 JP JP2002157916A patent/JP4096632B2/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10287644B2 (en) | 2011-08-12 | 2019-05-14 | Jfe Steel Corporation | Molten steel desulfurization method, molten steel secondary refining method, and molten steel manufacturing method |
| US11035014B2 (en) | 2011-08-12 | 2021-06-15 | Jfe Steel Corporation | Molten steel desulfurization method, molten steel secondary refining method, and molten steel manufacturing method |
| CN111471829A (en) * | 2020-04-09 | 2020-07-31 | 肖卫学 | Preparation method of high-calcium aluminum alloy and high-calcium aluminum alloy |
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