JP2007301630A - Method for manufacturing highly clean steel - Google Patents

Method for manufacturing highly clean steel Download PDF

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JP2007301630A
JP2007301630A JP2006135501A JP2006135501A JP2007301630A JP 2007301630 A JP2007301630 A JP 2007301630A JP 2006135501 A JP2006135501 A JP 2006135501A JP 2006135501 A JP2006135501 A JP 2006135501A JP 2007301630 A JP2007301630 A JP 2007301630A
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magnetic field
mold
field generator
molten steel
inclusions
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JP4846441B2 (en
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Masamitsu Wakao
昌光 若生
Takahiro Sato
貴洋 佐藤
Kiyoshi Shigematsu
清 重松
Shigenori Yakura
重範 矢倉
Shuji Nakamura
州児 中村
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Nippon Steel Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To solve such a problem that inclusions in a cast slab may increase according to casting conditions and conditions for applying an electromagnetic force when both of a movable magnetic field generating device arranged in the upper portion of a casting mold and a stationary magnetic field generating device arranged in the lower portion of the casting mold are used simultaneously aiming at improving the cleanliness of the cast slab. <P>SOLUTION: When a DC magnetic field is applied in the direction of the thickness of the cast slab in the casting mold by means of a DC magnetic field generating device arranged in the continuous casting mold and a continuous flow of molten steel is formed in front of the solidified shell in the surface position of the molten steel by means of the movable magnetic field generating device arranged in the neighborhood of the position of the surface of the molten steel in the casting mold, a relational expression is controlled so as to satisfy a certain range, wherein relational expression is composed of a thrust force in the movable magnetic field generating device, the density of the magnetic flux in the DC magnetic field generating device, a casting speed, the width of the casting mold, and the flow rate of Ar gas to be injected into the casting mold via an injection nozzle. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

本発明は、連続鋳造鋳型に設置された電磁気力場発生装置を用いて、鋳片表層および内部の介在物が少ない高清浄な鋳片を連続鋳造により製造する方法に係わるものである。   The present invention relates to a method for producing a highly clean slab by continuous casting with a slab surface layer and few internal inclusions using an electromagnetic force field generator installed in a continuous casting mold.

従来の技術として、連続鋳造鋳型の上部に電磁気力場を発生する装置を組み込み、溶鋼表面位置での凝固シェル前面に連続的な溶鋼流、すなわち水平断面内を旋回するような溶鋼流を生成させ、鋳片表面近傍の介在物を少なくする連続鋳造方法が、古くから広く知られている。また、鋳型内に設置した電磁気力場を発生する装置を用いて、溶鋼流れを制動することにより、介在物が鋳片内部に多くなることを防止する連続鋳造方法も広く知られている。   As a conventional technique, a device for generating an electromagnetic force field is installed at the top of a continuous casting mold to generate a continuous molten steel flow on the front surface of the solidified shell at the molten steel surface position, that is, a molten steel flow swirling in a horizontal section. A continuous casting method for reducing inclusions in the vicinity of the slab surface has been widely known for a long time. A continuous casting method is also widely known in which a molten steel flow is braked by using a device that generates an electromagnetic force field installed in a mold, thereby preventing inclusions from increasing in the slab.

その後、鉄鋼材料ユーザーの品質厳格化要求により、鋳片表面と内部の両方において介在物が少ない鋳片のニーズが高まり、これを実現するために、鋳型下部もしくは鋳型直下に電磁石を配置して溶鋼下降流に静磁場を作用させて制動させ、かつ鋳型上部に移動磁場形成磁石を組み込み、溶鋼流れを促進する技術（例えば、特許文献１および特許文献２参照)が発明された。
しかしながら、静磁場および移動磁場に関する条件については、それらの文献の実施例にわずかな記載があるのみで、鋳造速度や鋳片幅等の操業条件が変化した時に対する最適な電磁力の付与条件に関しては不明である。 Later, due to the stricter quality requirements of steel material users, the need for slabs with few inclusions on both the slab surface and inside increased, and in order to achieve this, an electromagnet was placed under the mold or directly under the mold to create molten steel. A technique (for example, refer to Patent Document 1 and Patent Document 2) that promotes the flow of molten steel by applying a static magnetic field to the downward flow to brake and incorporating a moving magnetic field forming magnet in the upper part of the mold has been invented.
However, regarding the conditions regarding the static magnetic field and the moving magnetic field, there are only a few descriptions in the examples of those documents, and regarding the optimal electromagnetic force application conditions when the operating conditions such as casting speed and slab width change. Is unknown.

そのような鋳型部に移動磁界と静磁場の両方を付与させる連続鋳造技術に関しては、他にもいくつかの発明が為されている（例えば、特許文献３、特許文献４、特許文献５、特許文献６参照）。
しかしながら、特許文献３では、鋳型内への注入ノズル孔位置の上方および下方に別々の静磁場を付与する必要があり、機構的に複雑となる問題がある。特許文献４では、鋳型内への注入ノズルの形状を下向きに限定しているため、操業の自由度が制約される。また、特許文献５では、これまで述べた方法とは逆に静磁場を鋳型上部に、移動磁場を鋳型下部に付与する技術を提示しているが、この場合には、溶鋼上面に温度の高い溶鋼が供給されにくくなるため、溶鋼表面が薄く凝固する問題がある。更に、特許文献６では、鋳型内への注入ノズル吐出孔の位置を電磁力装置が発生する磁束密度がある値以下になる位置に設置するという発明が示されているが、この場合には、電磁力の効果を十分に発揮できない恐れがある。 Several other inventions have been made regarding continuous casting technology that applies both a moving magnetic field and a static magnetic field to such a mold part (for example, Patent Document 3, Patent Document 4, Patent Document 5, Patent). Reference 6).
However, in Patent Document 3, it is necessary to apply separate static magnetic fields above and below the position of the injection nozzle hole into the mold, and there is a problem that the mechanism becomes complicated. In Patent Document 4, since the shape of the injection nozzle into the mold is limited downward, the degree of freedom of operation is restricted. In addition, Patent Document 5 presents a technique for applying a static magnetic field to the upper part of the mold and a moving magnetic field to the lower part of the mold, contrary to the method described so far. In this case, the temperature is high on the upper surface of the molten steel. Since it becomes difficult to supply molten steel, there exists a problem which the molten steel surface solidifies thinly. Furthermore, Patent Document 6 discloses an invention in which the position of the injection nozzle discharge hole in the mold is set at a position where the magnetic flux density generated by the electromagnetic force device is a certain value or less. In this case, There is a possibility that the effect of electromagnetic force cannot be fully exhibited.

以上、移動磁場と静磁場を組み合わせて用いる鋳型内電磁力の適用方法について、従来の技術を述べたが、どの発明にも共通する問題は、鋳造速度や鋳型幅が変わった場合でも鋳片表層および内部介在物を低減出来るような、電磁力条件に関する規定が無いことである。   As described above, the conventional technique has been described regarding the method of applying the electromagnetic force in the mold using a combination of the moving magnetic field and the static magnetic field. However, the problem common to all the inventions is that the slab surface layer even when the casting speed or the mold width changes. In addition, there is no provision for electromagnetic force conditions that can reduce internal inclusions.

特開昭６１−１４０３５５号公報Japanese Unexamined Patent Publication No. 61-140355 特開平０５−１７７３１７号公報JP 05-177317 A 特開平０５−１５４６２０号公報JP 05-154620 A 特開平０７−１１２２４６号公報Japanese Patent Laid-Open No. 07-112246 特開昭６２−７２４５８号公報JP-A-62-72458 特開２０００−４７１９５号公報JP 2000-47195 A

鋳型上部に設置された移動磁場発生装置と鋳型下部に設置された静磁場発生装置の双方を同時に用いる場合、鋳型上部の移動磁場により、鋳型上部の溶鋼流れは水平断面内を旋回する流れとなるが、この流れを強くすると鋳型短辺側の凝固シェルに流れが衝突し、一部の流れが短辺凝固シェル前面に沿って下方に向かい、鋳型下部の静磁場による制動が十分に効かない領域、すなわち凝固シェル前面を通過して溶鋼内部に到達する。この現象は、鋳型上部移動磁場を単独で用いた場合にも生じるが、鋳型下部の静磁場を併用した場合のほうが、影響が大きい。すなわち、鋳型下部の静磁場を併用した場合には、ノズル吐出流が静磁場によって制動され溶鋼表面に上昇してくることにより介在物の浮上が促進されるが、溶鋼表面に浮上した介在物が、前述した鋳型上部の水平溶鋼流に乗って鋳型短辺側に運ばれ、短辺に衝突した後、下降流によって鋳片内部に運ばれるため、鋳片内部の介在物が逆に悪化するという問題を生じる。   When both the moving magnetic field generator installed at the upper part of the mold and the static magnetic field generator installed at the lower part of the mold are used at the same time, the molten steel flow at the upper part of the mold is swirled in the horizontal section by the moving magnetic field at the upper part of the mold. However, when this flow is strengthened, the flow collides with the solidified shell on the short side of the mold, part of the flow goes downward along the front surface of the short solidified shell, and braking by the static magnetic field at the bottom of the mold is not sufficiently effective. That is, it passes through the front surface of the solidified shell and reaches the inside of the molten steel. This phenomenon also occurs when the upper mold moving magnetic field is used alone, but the effect is greater when the static magnetic field under the mold is used in combination. That is, when the static magnetic field at the bottom of the mold is used together, the nozzle discharge flow is braked by the static magnetic field and rises to the surface of the molten steel, which promotes the floating of inclusions. In the above-mentioned horizontal molten steel flow at the upper part of the mold, it is carried to the mold short side, and after colliding with the short side, it is carried into the slab by the downward flow, so that the inclusions inside the slab deteriorates conversely Cause problems.

この問題による悪影響の大きさは、操業条件によって異なる。すなわち、鋳型幅や鋳造速度によって影響が異なってくる。また、従来の発明では殆ど触れられていないが、注入ノズル詰まりを防止するために注入ノズル内に吹き込まれるＡｒガスの流量も大きく影響する。更に、電磁力の条件もこの問題に大きく影響する。   The magnitude of adverse effects due to this problem depends on operating conditions. That is, the influence varies depending on the mold width and casting speed. Further, although hardly mentioned in the conventional invention, the flow rate of Ar gas blown into the injection nozzle to prevent clogging of the injection nozzle also greatly affects. In addition, electromagnetic force conditions also have a significant effect on this problem.

従って、上記の問題を解決するためには、鋳造速度や鋳型幅、Ａｒガス流量が変化した場合にでも、最適な効果を得るための電磁力条件を求める必要があり、本発明はその条件を定める方法を提供することを課題とするものである。   Therefore, in order to solve the above problems, it is necessary to obtain electromagnetic force conditions for obtaining an optimum effect even when the casting speed, mold width, and Ar gas flow rate are changed. It is an object to provide a method for determining.

上記課題を達成するために、本発明は以下の構成を特徴とする。
注入ノズル内にＡｒを吹き込みながら連続鋳造鋳型に溶鋼を注入し、該鋳型に設置された直流磁場発生装置で、鋳型の鋳片厚み方向に直流磁場を印加し、かつ直流磁場発生装置の上方で、鋳型内の溶鋼表面が存在する位置の近傍に設置された移動磁場発生装置により溶鋼表面位置での凝固シェル前面に連続的な溶鋼流を形成させて高清浄鋼を連続鋳造する際に、以下（１）〜（３）の条件を満たすように移動磁場発生装置の推力Ｆ、鋳造速度Ｖ、鋳型幅Ｗ、注入ノズルを介して鋳型内に吹き込むＡｒガス流量Ｑ、直流磁場発生装置の磁束密度Ｍの条件を設定して鋳造することを特徴とする高清浄鋼の製造方法。
７≦Ｆ0.5×Ｖ0.5／（Ｗ×Ｑ0.7×Ｍ0.3）≦１６ （１）
１３００≦Ｆ≦７３００ （２）
０．３≦Ｍ （３）
ここで、Ｆ：移動磁場発生装置の推力 （Ｎ／ｍ2）
Ｖ：鋳造速度（ｍ／ｍｉｎ）
Ｗ：鋳型幅（ｍ）
Ｑ：注入ノズルを介して鋳型内に吹き込むＡｒガス流量（Ｎｌ／ｍｉｎ）
Ｍ：直流磁場発生装置の磁束密度（Ｔ：磁束密度分布の最大値） In order to achieve the above object, the present invention is characterized by the following configurations.
While blowing Ar into the injection nozzle, molten steel is injected into the continuous casting mold, and a DC magnetic field generator installed in the mold applies a DC magnetic field in the mold slab thickness direction, and above the DC magnetic field generator. When continuously casting high-clean steel by forming a continuous molten steel flow on the front surface of the solidified shell at the molten steel surface position by a moving magnetic field generator installed in the vicinity of the position where the molten steel surface exists in the mold, In order to satisfy the conditions (1) to (3), the thrust F of the moving magnetic field generator, the casting speed V, the mold width W, the Ar gas flow rate Q blown into the mold through the injection nozzle, and the magnetic flux density of the DC magnetic field generator. A method for producing highly clean steel, characterized by casting under the condition of M.
7 ≦ F 0.5 × V 0.5 / (W × Q 0.7 × M 0.3 ) ≦ 16 (1)
1300 ≦ F ≦ 7300 (2)
0.3 ≦ M (3)
Here, F: the thrust of the moving magnetic field generating device (N / m 2)
V: Casting speed (m / min)
W: Mold width (m)
Q: Ar gas flow rate (Nl / min) blown into the mold through the injection nozzle
M: Magnetic flux density of DC magnetic field generator (T: Maximum value of magnetic flux density distribution)

本発明は、鋳片内部の介在物を悪化させることなく、鋳片表面の介在物量を低減する方法を提供するものである。これにより、鋳片厚み方向全域にわたって介在物量が少ない鋳片を得ることが出来、製品加工においても欠陥が非常に発生しにくい鋼素材の提供が可能となる。   The present invention provides a method for reducing the amount of inclusions on the surface of a slab without deteriorating the inclusions inside the slab. Thereby, it is possible to obtain a slab with a small amount of inclusions throughout the slab thickness direction, and it is possible to provide a steel material in which defects are very unlikely to occur in product processing.

本発明者らは、鋳型上部に設置された移動磁場発生装置と鋳型下部に設置された静磁場発生装置の双方を同時に用いて、鋳型幅や鋳造速度、Ａｒガス流量を変更した種々の条件で、電磁力条件（ここでは、鋳型上部移動磁場発生装置で生成する磁場によって生じる推力と鋳型下部の静磁場で発生する磁束密度をいう）を変化させ、鋳片表層と内部の介在物を調査した。その結果の詳細解析により、鋳造速度、鋳型幅、注入ノズルを介して鋳型内に吹き込むＡｒガス流量と移動磁場発生装置の推力、直流磁場発生装置の磁束密度の関係が、ある条件を満たす場合に、介在物の個数が少なくなることを見出した。   The inventors of the present invention simultaneously use both the moving magnetic field generator installed at the upper part of the mold and the static magnetic field generator installed at the lower part of the mold, under various conditions in which the mold width, casting speed, and Ar gas flow rate are changed. The electromagnetic force conditions (here, the thrust generated by the magnetic field generated by the moving magnetic field generator at the upper part of the mold and the magnetic flux density generated by the static magnetic field at the lower part of the mold) were changed, and the slab surface layer and the inclusions inside were investigated. . Based on the detailed analysis of the results, the relationship between the casting speed, mold width, Ar gas flow rate blown into the mold through the injection nozzle, thrust of the moving magnetic field generator, and the magnetic flux density of the DC magnetic field generator satisfies certain conditions. The present inventors have found that the number of inclusions is reduced.

以下に本発明の詳細を記す。
まず、最適な電磁力条件を表す指標について検討した。鋳型上部の移動磁場発生装置と鋳型下部の静磁場発生装置の双方を同時に用いた場合に、鋳造条件によっては鋳片内部の介在物が悪化することがあるが、その機構は以下の通りである。すなわち、ノズル吐出流が静磁場によって制動され溶鋼表面に上昇してくることにより介在物の浮上が促進されるが、溶鋼表面に浮上した介在物が、移動磁場により生成した流れに乗り、鋳型短辺側の凝固シェルに衝突して短辺凝固シェル前面に沿って下方に向かい、鋳型下部の静磁場による制動が十分に効かない領域、すなわち凝固シェル前面を通過して溶鋼内部に到達する。 Details of the present invention will be described below.
First, an index representing the optimum electromagnetic force condition was examined. When both the moving magnetic field generator at the upper part of the mold and the static magnetic field generator at the lower part of the mold are used at the same time, the inclusions inside the slab may deteriorate depending on the casting conditions. The mechanism is as follows. . In other words, the rise of the inclusions is promoted by the nozzle discharge flow being braked by the static magnetic field and rising to the surface of the molten steel, but the inclusions floating on the surface of the molten steel ride on the flow generated by the moving magnetic field and become short of the mold. It collides with the solidified shell on the side and heads downward along the front surface of the short side solidified shell, and passes through the area where braking by the static magnetic field under the mold is not sufficiently effective, that is, passes through the front surface of the solidified shell and reaches the inside of the molten steel.

このことから、介在物が鋳型上部の溶鋼表面に上昇してくる位置が重要になる。すなわち、介在物の上昇位置が鋳型短辺に近いと、前記移動磁場により生成した流れに乗り溶鋼内部に入りやすくなり、逆に鋳型短辺から遠いと溶鋼内部に入りにくくなる。
そこで指標として、介在物が溶鋼表面に上昇する位置を注入ノズルからの鋳型幅方向の距離で表し、この距離を鋳型幅の１／２、すなわち注入ノズル位置と鋳型短辺間の距離で割って規格化したものを用いた。さらに理論解析より、この指標には、鋳型幅、注入ノズルを介して鋳型内に吹き込むＡｒガス流量、直流磁場発生装置の磁束密度がマイナス側で影響し、移動磁場の推力と鋳造速度がプラスで作用することが判った。 For this reason, the position where the inclusion rises to the molten steel surface above the mold becomes important. That is, when the rising position of the inclusion is close to the mold short side, the inclusion is likely to enter the molten steel on the flow generated by the moving magnetic field, and conversely, if the inclusion is far from the mold short side, it is difficult to enter the molten steel.
Therefore, as an index, the position where the inclusions rise to the molten steel surface is represented by the distance in the mold width direction from the injection nozzle, and this distance is divided by half the mold width, that is, the distance between the injection nozzle position and the mold short side. A standardized version was used. Furthermore, theoretical analysis shows that this index is affected by the negative side of the mold width, the flow rate of Ar gas blown into the mold through the injection nozzle, and the magnetic flux density of the DC magnetic field generator, and the thrust of the moving magnetic field and the casting speed are positive. It was found to work.

以上のことより、指標：Ｆm×Ｖn／（Ｗ×Ｑr×Ｍs）を設定した。ここで、Ｆは移動磁場発生装置の推力（Ｎ／ｍ2）、Ｖは鋳造速度（ｍ／ｍｉｎ）、Ｗは鋳型幅（ｍ）、Ｑは注入ノズルを介して鋳型内に吹き込むＡｒガス流量（Ｎｌ／ｍｉｎ）、Ｍは直流磁場発生装置の磁束密度（Ｔ：磁束密度分布におけるピーク値）である。また、ｍ、ｎ、ｒ、ｓは累乗であり、Ｗの累乗を１として基準にした場合の数値である。この数値は、以下に示す多数の実機試験により求めた。 From the above, the index: F m × V n / (W × Q r × M s ) was set. Here, F is the thrust of the moving magnetic field generator (N / m 2 ), V is the casting speed (m / min), W is the mold width (m), Q is the flow rate of Ar gas blown into the mold via the injection nozzle (Nl / min), M is the magnetic flux density (T: peak value in the magnetic flux density distribution) of the DC magnetic field generator. M, n, r, and s are powers, and are numerical values when the power of W is set to 1. This value was obtained by a number of actual machine tests shown below.

本発明者らは次に実機での試験を行ない、解析した。すなわち、鋳型上部に設置された移動磁場発生装置と鋳型下部に設置された静磁場発生装置の双方を同時に用いて、鋳型幅や鋳造速度、Ａｒガス流量、そして電磁力条件を変化させ、鋳片表層と内部の介在物を調査した。試験に用いた鋼の成分を表１に示す。また、試験条件を表２に示す。   Next, the inventors conducted tests with actual machines and analyzed them. That is, using both the moving magnetic field generator installed at the upper part of the mold and the static magnetic field generator installed at the lower part of the mold, the mold width, casting speed, Ar gas flow rate, and electromagnetic force conditions are changed, The surface and internal inclusions were investigated. Table 1 shows the components of the steel used in the test. The test conditions are shown in Table 2.

Figure 2007301630
Figure 2007301630

Figure 2007301630
Figure 2007301630

鋳型上部に設置された移動磁場発生装置と鋳型下部に設置された静磁場発生装置の同時使用に先立ち、まず移動磁場発生装置を単独で用いた場合の適正条件の検討を行った。評価に当たっては鋳片表層から１０ｍｍ位置までに介在物個数を実測して行なった。
その結果を図１に示す。ここでは、介在物個数の基準を１０００個／ｋｇとしたが、図より鋳片表層の介在物個数は移動磁場発生装置の推力が１３００〜７３００Ｎ／ｍ2の場合に介在物個数が基準値より下まわり良好な結果が得られることが判った。 Prior to the simultaneous use of the moving magnetic field generator installed at the upper part of the mold and the static magnetic field generator installed at the lower part of the mold, the appropriate conditions when using the moving magnetic field generator alone were examined. In the evaluation, the number of inclusions was measured from the slab surface layer to a position of 10 mm.
The result is shown in FIG. Here, the standard of the number of inclusions is 1000 / kg, but the figure indicates that the number of inclusions on the slab surface layer is higher than the standard value when the thrust of the moving magnetic field generator is 1300-7300 N / m 2. It has been found that good results can be obtained at the bottom.

次に、直流磁場発生装置を単独で用いた場合の適正条件範囲を求めた。評価は鋳片内部、すなわち鋳片表層より２０ｍｍ位置までの中心部までの介在物個数で行なった。
結果を図２に示す。同様に介在物個数基準を１０００個／ｋｇとしたが、図２より鋳片内部の介在物個数は直流磁場発生装置の磁束密度が０．３Ｔ以上の場合に基準値より下まわり良好な結果が得られることが判った。 Next, an appropriate condition range was obtained when the DC magnetic field generator was used alone. The evaluation was performed by the number of inclusions in the slab, that is, from the surface of the slab to the center part up to a position of 20 mm.
The results are shown in FIG. Similarly, the inclusion standard is 1000 / kg, but the number of inclusions in the slab is lower than the standard value when the magnetic flux density of the DC magnetic field generator is 0.3 T or more as shown in FIG. It turns out that it is obtained.

上記で得られた各々の適正条件範囲内で、次に鋳型上部に設置された移動磁場発生装置と鋳型下部に設置された静磁場発生装置の同時使用の試験を行なった。前述の通り、指標：Ｆm×Ｖn／（Ｗ×Ｑr×Ｍs）は、介在物が溶鋼表面に上昇する位置と注入ノズルとの距離を注入ノズル位置と鋳型短辺間の距離で割って規格化したものである。この指標の累乗ｍ、ｎ、ｒ、ｓを求めるため、実機試験で試験条件を変化させ、以下の３つの関係を測定した。すなわち、介在物浮上位置と比例関係にある鋳型内溶鋼流速と磁場推力との関係、鋳造速度と鋳型内溶鋼流速との関係、そして鋳型内溶鋼表面を詳細に観察することにより測定したArガスの浮上位置(実際の介在物は目視できないので介在物と類似挙動するＡｒガスで評価した)と注入ノズルとの距離を注入ノズル位置と鋳型短辺間の距離で割って規格化した値と指標との関係である。 Within each appropriate condition range obtained above, next, a test of simultaneous use of the moving magnetic field generator installed on the upper part of the mold and the static magnetic field generator installed on the lower part of the mold was performed. As described above, the index: F m × V n / (W × Q r × M s ) is the distance between the injection nozzle position and the mold short side, the distance between the position where the inclusion rises on the molten steel surface and the injection nozzle. Divided and standardized. In order to obtain the powers m, n, r, and s of this index, the test conditions were changed in an actual machine test, and the following three relationships were measured. That is, the relationship between the molten steel flow velocity in the mold and the magnetic field thrust proportional to the inclusion floating position, the relationship between the casting speed and the molten steel flow velocity in the mold, and the Ar gas measured by observing the molten steel surface in the mold in detail. Standardized values and indices by dividing the distance between the floating position (the actual inclusions are not visible and evaluated by Ar gas which behaves like inclusions) and the injection nozzle by the distance between the injection nozzle position and the mold short side It is a relationship.

まず、移動磁場発生装置の推力：Ｆの累乗は理論的には１となるが、介在物浮上位置と比例関係にある鋳型内溶鋼流速について推力との関係を測定した結果、０．５が適当であることが判ったので、ｍ＝０．５に固定した。同様に、鋳造速度：Ｖに関しても、直流磁場がない場合にはＶの累乗は１となるが、直流磁場がある場合には鋳造速度の影響代が小さくなる。これも実際に鋳造速度と鋳型内溶鋼流速との関係を測定した結果、０．５が妥当であることが判った。   First, the thrust of the moving magnetic field generator: The power of F is theoretically 1. However, as a result of measuring the relationship with the thrust for the molten steel flow velocity in the mold that is proportional to the inclusion floating position, 0.5 is appropriate. Therefore, m = 0.5 was fixed. Similarly, regarding the casting speed: V, the power of V is 1 when there is no DC magnetic field, but the influence of the casting speed is small when there is a DC magnetic field. As a result of actually measuring the relationship between the casting speed and the molten steel flow velocity in the mold, 0.5 was found to be appropriate.

次に、注入ノズルを介して鋳型内に吹き込むＡｒガス流量：Ｑと直流磁場発生装置の磁束密度：Ｍの累乗であるｒおよびｓに関しては、ｍ＝０．５とｎ＝０．５を代入した指標の式でｒとｓを変化させ、実機試験で測定したArガスの浮上位置と注入ノズルとの距離を注入ノズル位置と鋳型短辺間の距離で割って規格化した値と対比させた。その結果、ｓ＝０．７、ｒ＝０．３の場合に両者の傾向が最も合う条件であることを見出した。   Next, with respect to r and s, which are powers of Ar gas flow rate: Q and DC magnetic field generator: M, which are blown into the mold through the injection nozzle, m = 0.5 and n = 0.5 are substituted. By changing r and s in the above index formula, the distance between the Ar gas floating position measured in the actual machine test and the injection nozzle was divided by the distance between the injection nozzle position and the mold short side and compared with the normalized value. . As a result, it was found that when s = 0.7 and r = 0.3, both tendencies are the best conditions.

結果を図３に示す。縦軸には、鋳片内の直径５３μｍ以上の介在物個数を示す。横軸は、これらの累乗の数値を入れた指標とした。図３より、鋳片内介在物個数、すなわち鋳片表層介在物と内部介在物を合計した個数が少なくなる指標の条件は、７から１６の範囲である。   The results are shown in FIG. The vertical axis represents the number of inclusions having a diameter of 53 μm or more in the slab. The horizontal axis is an index including these power values. From FIG. 3, the condition of the index for reducing the number of inclusions in the slab, that is, the total number of inclusions in the slab surface layer and the inclusions in the slab is in the range of 7 to 16.

次に、発明の条件を規定した理由とこの発明の具体的な適用法について説明する。
対象となるプロセスは連続鋳造であり、目的は鋳型上部に設置された移動磁場発生装置と鋳型下部に設置された静磁場発生装置の双方を用いて鋳片内介在物個数を低減することである。
指標は、以下の（１）に示す式で表わされ、その範囲は（１）の範囲である。
７≦Ｆ0.5×Ｖ0.5／（Ｗ×Ｑ0.7×Ｍ0.3）≦１６ （１）
ここで、Ｆ：移動磁場発生装置の推力（Ｎ／ｍ2）、Ｖ：鋳造速度（ｍ／ｍｉｎ）、Ｗ：鋳型幅（ｍ）、Ｑ：注入ノズルを介して鋳型内に吹き込むＡｒガス流量（Ｎｌ／ｍｉｎ）、Ｍ：直流磁場発生装置の磁束密度（Ｔ：磁束密度分布におけるピーク値）である。 Next, the reason for defining the conditions of the invention and the specific application method of the invention will be described.
The target process is continuous casting, and the objective is to reduce the number of inclusions in the slab using both the moving magnetic field generator installed at the upper part of the mold and the static magnetic field generator installed at the lower part of the mold. .
The index is expressed by the following formula (1), and the range is the range of (1).
7 ≦ F 0.5 × V 0.5 / (W × Q 0.7 × M 0.3 ) ≦ 16 (1)
Here, F: thrust of moving magnetic field generator (N / m 2 ), V: casting speed (m / min), W: mold width (m), Q: flow rate of Ar gas blown into mold through injection nozzle (Nl / min), M: magnetic flux density of the DC magnetic field generator (T: peak value in the magnetic flux density distribution).

この指標の式は、前述した実機試験の解析結果より得られたものである。指標の範囲の７から１６は、鋳片内介在物個数を少なくすることが出来る条件で、同じく実機試験の解析結果、図３より得られたものである。   This index formula is obtained from the analysis result of the actual machine test described above. Index ranges 7 to 16 are obtained under the condition that the number of inclusions in the slab can be reduced and obtained from FIG.

次に、移動磁場発生装置の推力Ｆ（Ｎ／ｍ2）は、以下の（２）の範囲である。
１３００≦Ｆ≦７３００ （２）
移動磁場発生装置の推力Ｆを１３００〜７３００（Ｎ／ｍ2）に規定したのは、前記図１に見られるように、移動磁場発生装置単独使用でも鋳片表層介在物個数が基準値以下となる条件を選んだ。 Then, the thrust F of the moving magnetic field generating device (N / m 2) is the scope of the following (2).
1300 ≦ F ≦ 7300 (2)
The reason why the thrust F of the moving magnetic field generator is defined to be 1300 to 7300 (N / m 2 ) is that, as shown in FIG. I chose the following conditions.

一方、直流磁場発生装置の磁束密度Ｍ（Ｔ）は、以下の（３）の範囲である。
０．３≦Ｍ （但し、Ｍは磁束密度分布の最大値である） （３）
直流磁場発生装置の磁束密度を０．３Ｔ以上としたのは、前記図２において直流磁場発生装置単独使用でも鋳片内部の介在物個数基準値以下となる条件を選んだ。 On the other hand, the magnetic flux density M (T) of the DC magnetic field generator is in the following range (3).
0.3 ≦ M (where M is the maximum value of the magnetic flux density distribution) (3)
The condition that the magnetic flux density of the DC magnetic field generator is set to 0.3 T or more is selected in FIG. 2 under the condition that the DC magnetic field generator alone is less than the reference number of inclusions in the slab.

なお、前記移動磁場発生装置の推力は、鋳造中に実測することは出来ないので、予め非鋳造中に測定して移動磁場発生装置に付与する電流値と推力の関係を求めておき、鋳造中にその関係から電流値を基に推力の制御することが可能となる。また、静磁場の磁束密度に関しても同様に、予め非鋳造中に測定して静磁場発生装置の電流値と磁束密度の関係から、鋳造中に電流値で磁束密度を制御することが可能となる。なお、磁束密度の大きさは鉛直方向に分布を持っているが、ここでは分布の最大値の値を直流磁場発生装置の磁束密度Ｍとして用いた。   In addition, since the thrust of the moving magnetic field generator cannot be actually measured during casting, the relationship between the current value applied to the moving magnetic field generator and the thrust measured in advance during non-casting and the thrust is obtained. From this relationship, the thrust can be controlled based on the current value. Similarly, the magnetic flux density of the static magnetic field can be measured in advance during non-casting, and the magnetic flux density can be controlled by the current value during casting from the relationship between the current value of the static magnetic field generator and the magnetic flux density. . Although the magnitude of the magnetic flux density has a distribution in the vertical direction, the maximum value of the distribution is used here as the magnetic flux density M of the DC magnetic field generator.

具体的な適用方法としては、鋳造する鋼種や操業条件によって、鋳型幅と目標鋳造速度、および注入ノズルからのＡｒガス流量の各規制範囲が予め決められているので、これらの範囲の中から、前記（１）〜（３）の数値が適正範囲内に入るように、推力と磁束密度の組み合わせを決定し、それぞれの磁場発生装置の電流値を制御すれば良い。移動磁場発生装置の推力Ｆと直流磁場発生装置の磁束密度Ｍの組み合わせは複数種類存在するが、どの組み合わせでも、指標が前記式の適正範囲に入っていれば問題ない。適正範囲内であれば、鋼種によって要求される品質特性が鋳片表層部の介在物個数低減を重視する場合には移動磁場の推力を強めにし、また、要求される品質特性が鋳片内部の介在物個数低減を重視する場合には静磁場の磁束密度を強めにする等の設定をしても構わない。   As a specific application method, depending on the steel type to be cast and the operating conditions, the mold width and the target casting speed, and the respective regulation ranges of the Ar gas flow rate from the injection nozzle are determined in advance. From these ranges, What is necessary is just to determine the combination of thrust and magnetic flux density so that the numerical value of said (1)-(3) may enter in an appropriate range, and to control the electric current value of each magnetic field generator. There are a plurality of combinations of the thrust F of the moving magnetic field generator and the magnetic flux density M of the DC magnetic field generator, but any combination is acceptable as long as the index is within the appropriate range of the above equation. If it is within the appropriate range, if the quality characteristics required by the steel grade place importance on reducing the number of inclusions in the slab surface layer, the thrust of the moving magnetic field will be strengthened, and the required quality characteristics will be within the slab. When importance is attached to the reduction of the number of inclusions, settings such as increasing the magnetic flux density of the static magnetic field may be made.

以下、本発明の実施例を説明するが、実施例で採用した条件は、本発明の実施可能性及び効果を確認するための一条件例であり、本発明は、この一条件例に限定されるものではなく、本発明を逸脱せず、本発明の目的を達成する限りにおいて、種々の条件を採用し得るものである。   Examples of the present invention will be described below, but the conditions adopted in the examples are one example of conditions for confirming the feasibility and effects of the present invention, and the present invention is limited to this one example of conditions. However, various conditions can be adopted as long as the object of the present invention is achieved without departing from the present invention.

連続鋳造機を用いて鋳片を製造した。鋳片に用いた鋼の成分を表３に示す。また共通の実施条件および評価方法を表４に示し、個別の実施条件を表５に示す。   Slabs were produced using a continuous casting machine. Table 3 shows the components of the steel used for the slab. Common execution conditions and evaluation methods are shown in Table 4, and individual execution conditions are shown in Table 5.

Figure 2007301630
Figure 2007301630

Figure 2007301630
Figure 2007301630

Figure 2007301630
Figure 2007301630

実施結果を同じく表５に示すが、表より本発明の条件を満たす場合には、鋳片内の介在物個数、すなわち鋳片表層介在物と内部介在物を合計した個数が少なく、良好な清浄性の鋳片を製造することが出来た。   The implementation results are also shown in Table 5, but when the conditions of the present invention are satisfied from the table, the number of inclusions in the slab, that is, the total number of slab surface layer inclusions and internal inclusions is small, and good cleaning is achieved. Slabs could be manufactured.

一方、比較１，比較２，比較３，比較４，比較５，比較６，比較７，比較８のいずれの比較例においても、鋳片内の介在物個数は多い結果となった。すなわち、比較１では指標が３８．７、比較２では２１．３、比較３では２５．４と適正範囲より大きな数値となったため、鋳片内の介在物個数が多かった。また、比較４では指標が６．５、比較５では３．１と適正範囲より小さな数値となったため鋳片内の介在物個数が多い結果となった。なお、比較３は磁束密度の適正範囲も外れており、また比較４および比較５は推力の適正範囲も外れている。更に、指標は適正条件内に入っていても、比較６では推力が適正範囲より小さすぎたために、比較７では推力が適正範囲より大きすぎたために、また比較８では磁束密度が適正は範囲より小さすぎたために、鋳片内介在物個数が多くなった。   On the other hand, in any of the comparative examples of comparison 1, comparison 2, comparison 3, comparison 4, comparison 5, comparison 6, comparison 7, and comparison 8, the number of inclusions in the slab was large. That is, the index was 38.7 in comparison 1, 21.3 in comparison 2, 25.4 in comparison 3, and 25.4, which was larger than the appropriate range, so the number of inclusions in the slab was large. In Comparative 4, the index was 6.5, and in Comparative 5, 3.1, which was a numerical value smaller than the appropriate range, resulting in a large number of inclusions in the slab. In comparison 3, the proper range of magnetic flux density is also outside, and in comparisons 4 and 5, the proper range of thrust is also outside. Furthermore, even if the index is within the proper condition, the thrust was too small in the comparison 6 in the comparison 6, the thrust was too large in the comparison 7, and the magnetic flux density in the comparison 8 was more than the proper range. Since it was too small, the number of inclusions in the slab increased.

移動磁場発生装置の推力と鋳片表層介在物個数の関係を表した図である。It is a figure showing the relationship between the thrust of a moving magnetic field generator and the number of slab surface layer inclusions. 静磁場発生装置の磁束密度と鋳片内部介在物個数の関係を表した図である。It is a figure showing the relationship between the magnetic flux density of a static magnetic field generator, and the number of slab internal inclusions. 指標と鋳片内介在物個数の関係を表した図である。It is a figure showing the relationship between a parameter | index and the number of inclusions in a slab.

Claims (1)

注入ノズル内にＡｒを吹き込みながら連続鋳造鋳型に溶鋼を注入し、該鋳型に設置された直流磁場発生装置で、鋳型の鋳片厚み方向に直流磁場を印加し、かつ直流磁場発生装置の上方で、鋳型内の溶鋼表面が存在する位置の近傍に設置された移動磁場発生装置により溶鋼表面位置での凝固シェル前面に連続的な溶鋼流を形成させて高清浄鋼を連続鋳造する際に、以下（１）〜（３）の条件を満たすように移動磁場発生装置の推力Ｆ、鋳造速度Ｖ、鋳型幅Ｗ、注入ノズルを介して鋳型内に吹き込むＡｒガス流量Ｑ、直流磁場発生装置の磁束密度Ｍの条件を設定して鋳造することを特徴とする高清浄鋼の製造方法。
７≦Ｆ0.5×Ｖ0.5／（Ｗ×Ｑ0.7×Ｍ0.3）≦１６ （１）
１３００≦Ｆ≦７３００ （２）
０．３≦Ｍ （３）
ここで、Ｆ：移動磁場発生装置の推力 （Ｎ／ｍ2）
Ｖ：鋳造速度（ｍ／ｍｉｎ）
Ｗ：鋳型幅（ｍ）
Ｑ：注入ノズルを介して鋳型内に吹き込むＡｒガス流量（Ｎｌ／ｍｉｎ）
Ｍ：直流磁場発生装置の磁束密度（Ｔ：磁束密度分布の最大値） While blowing Ar into the injection nozzle, molten steel is injected into the continuous casting mold, and a DC magnetic field generator installed in the mold applies a DC magnetic field in the mold slab thickness direction, and above the DC magnetic field generator. When continuously casting high-clean steel by forming a continuous molten steel flow on the front surface of the solidified shell at the molten steel surface position by a moving magnetic field generator installed in the vicinity of the position where the molten steel surface exists in the mold, In order to satisfy the conditions (1) to (3), the thrust F of the moving magnetic field generator, the casting speed V, the mold width W, the Ar gas flow rate Q blown into the mold through the injection nozzle, and the magnetic flux density of the DC magnetic field generator. A method for producing highly clean steel, characterized by casting under the condition of M.
7 ≦ F 0.5 × V 0.5 / (W × Q 0.7 × M 0.3) ≦ 16 (1)
1300 ≦ F ≦ 7300 (2)
0.3 ≦ M (3)
Where F: thrust of the moving magnetic field generator (N / m 2 )
V: Casting speed (m / min)
W: Mold width (m)
Q: Ar gas flow rate (Nl / min) blown into the mold through the injection nozzle
M: Magnetic flux density of DC magnetic field generator (T: Maximum value of magnetic flux density distribution)
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JPH11285795A (en) * 1998-03-31 1999-10-19 Nippon Steel Corp Production of continuously casting slab having high cleanliness
JP2000271710A (en) * 1999-03-24 2000-10-03 Nippon Steel Corp Method for continuously casting steel
JP2001001115A (en) * 1999-04-20 2001-01-09 Nippon Steel Corp Continuous casting method of steel
JP2003117636A (en) * 2001-10-10 2003-04-23 Nippon Steel Corp Method for controlling fluidity of molten steel in mold and device for forming electromagnetic field for this purpose

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