【発明の詳細な説明】
［産業上の利用分野］
この発明は連続鋳造において、中心偏析を減少する鋼
の連続鋳造法に関する。
［従来の技術］
連続鋳片の中心偏析の発生機構は、凝固末期の濃化溶
鋼がロール間バルジングや凝固収縮によって変化する液
相体積を補償するために流動して集積することによって
発生する。
中心偏析を減少する方法には、凝固末期の濃化溶鋼
の流動を抑える方法、もしくは、凝固末期の濃化溶鋼
の集積場所を細かく分散させる方法がある。前者の技術
としては未凝固軽圧下法がある。後者については凝固末
期の電磁撹拌法がある。未凝固軽圧下法は凝固末期のロ
ール間隔を凝固収縮量に合わせるように設定し、鋳片を
軽圧下しながら凝固完了させることにより凝固末期の溶
鋼流動を防止し中心偏析を改善しようとするものであ
る。凝固末期の電磁撹拌法は連鋳機内の凝固完了前に、
電磁撹拌を印加することにより等軸晶を増やし、連鋳鋳
片の厚み中心付近の凝固組織を等軸晶に変えて偏析が厚
み中心に集中しないように分散させる効果がある。特
に、凝固末期の電磁撹拌は等軸晶の充填の度合いを変え
るのに効果がある。
［発明が解決しようとする問題点］
しかしながら凝固末期の濃化溶鋼の流動を抑える方法
はロール間バルジングに基づく溶鋼流動を完全に防止で
きない。実際のロール間隔の設定において、凝固収縮量
プラスアルファーの余剰の軽圧下量を加えないと偏析の
改善ができない。即ちプラスアルファーの余剰の軽圧下
量はバルジングに起因しているものであり、実際の制御
はかなり難しい。従って軽圧下量が不足すると、濃化溶
鋼の吸引が起こり偏析を形成する。一方、過剰の圧下を
すると濃化溶鋼を絞り出し、偏析となる。もうひとつの
問題点は凝固末期の鋳片内未凝固相の厚さを鋳片幅方向
に亙って均一にすることは極めて困難である。多くの場
合鋳片内未凝固相の厚みは短辺面から150〜300mm離れた
部位が厚い。このような鋳片を圧下すると未凝固相の厚
い部分は第６図に示すように未凝固相12が取り残される
ことになる。
第６図は凝固末期の鋳片断面を示した模式図である。
通常短辺面から150〜300mm範囲の未凝固相12が厚い。こ
の結果、凝固の進行に伴い凝固収縮に起因して周囲の濃
化溶鋼は、この取り残された未凝固部分に向かって流動
するため、未凝固相12に大きな偏析が生じる。
第７図は鋼片幅中央からの距離と偏析度の関係を示す
図である。図中偏析度は、鋳片厚み:220mm、鋳片幅2000
mmにおいて、鋳片厚み中心位置を鋳片幅の中央から50mm
ピッチで、3mmΦのドリルで分析試料を採取し、炭素濃
度の分析結果をレードルの粗鋼炭素濃度で割った値であ
る炭素の偏析度C/C0（C0:レードルの粗鋼の〔Ｃ〕の分
析値、C:鋳片厚み中心部の〔Ｃ〕の分析値）で示してい
る。鋳造条件は引抜速度0.75m/min,軽圧下量（引抜き方
向のロール間隔の減少量）は1.20mm/mであった。鋳片の
短辺面から150〜300mm範囲のC/C0の値は大きく、この範
囲の偏析が非常に悪いことが判る。このように軽圧下法
では適当な軽圧下を選べば、鋳片の短辺面から150〜300
mmを除いた幅中央側の偏析の改善が可能である。
電磁撹拌法では鋳片中心部に等軸晶が生成され、通常
等軸晶の凝固が起こると、等軸晶間には粒状の偏析が数
多く存在する。場合によっては粒状の偏析がＶ状につな
がりいわゆる“Ｖ偏析”が形成され易くなる。凝固末期
の電磁撹拌法はこのようなＶ偏析の形成を軽減できるが
完全に無くすることは難しい。この発明は係る事情に鑑
みてなされたものであって鋳片連続鋳造において、鋳片
の厚さ中心エッジ部の偏析を減少する鋼の連続鋳造法を
提供する。
［問題点が解決するための手段及び作用］
この発明にかかわる鋼の連続鋳造法は、鋳片厚み方向
に圧下を付与し、鋳片短辺から150〜300mmの範囲で鋳片
厚み中心位置の固相率が0.3〜0.7の範囲に、鋳片厚み方
向に静磁場を印加することを特徴とする。ここで固相率
とは単位体積中の固相部分の割合を示す。
電気伝導性の良好な液体が静磁場中の磁束に垂直に流
動すると、液体中には誘導電流が発生し、この誘導電流
と印加磁場の相互作用により流動方向と逆向きに電磁力
が流体に働き、流動を抑制する。第５図は鋳片と直流電
磁石の位置関係を示す図である。すなわち、未凝固鋳片
１の上下に直流電磁石４の磁場を設置し、鋳片厚み方向
に磁場を印加する。この場合次の電磁力が発生する。
直流磁場の磁束方向を良電動体の流体に垂直に印加
し、流体内に直流磁場内を電気伝導性の良好な溶鋼６
の溶鋼流動10が発生し、速度で運動すると、（１）式
に基づく起電力が発生する。
Ｅ＝×＝Vy・Bz （１）
この起電力Ｅにより、流体内には渦電流が流れ、渦
電流と直流磁場との相互作用により流体の運動方向
と逆方向に（２）式で示す体積力11が働く。
＝−×＝−σVy・Bz2 （２）
（ここでＩ＝1/σ・Ｅ、σ：比電気抵抗;m/Ω、y:鋳型
の幅方向、z:鋳型の厚み方向）
（２）式により体積力F11の大きさは溶鋼の流速と直
流磁場の大きさに比例する。
このような電磁力を凝固末期の溶鋼に与えて、流動を
小さく抑えて凝固させることにより偏析を軽減させる。
本願発明者等は凝固末期の中心偏析について鋭意研究を
重ねた結果、鋳片厚み中心部の固相率0.3以上の溶鋼
に電磁力を付与した理由はセミマクロ偏析（鋳片厚み中
心に見られるような粒状の正偏析）の濃度の測定結果か
ら考えると、偏析部の初期濃度（偏析部分の固相率が０
の時の濃度）はレードルの粗鋼の［Ｃ］の濃度に比し
て、固相率0.3の時の液相濃度と同じ程度まで濃化して
いることが判った。このことは、セミマクロ偏析を形成
した溶鋼は固相率0.3の溶鋼が流動して最終的に凝固し
たと考えることができる。従って固相率0.3以上の濃化
溶鋼の流動を抑制すれば良い。一方、鋳片厚み中心部の
固相率を0.7以下にした理由は鋳片厚み中心部の固相率
が0.7以上の液相は殆ど流動しないということが判った
ためである。又前述したように、鋳片の幅方向の偏析を
調べると、偏析は鋳片短辺面から150〜300mmの範囲が非
常に悪い。鋳片の凝固厚みは幅方向で異なり、凝固末期
に鋲打法で鋳片幅中央と鋳片短辺面から200mmの位置の
凝固厚みを測定した例では、幅中央が108.0mm,鋳片短辺
面から200mmの位置は104.5mmであった。鋳片短辺面から
150〜300mmの範囲の偏析が悪い理由は、幅方向に未凝固
厚みが異なる鋳片を軽圧下すると、幅中央が完全凝固後
には鋳片短辺面から150〜300mmの範囲の未凝固部では軽
圧下の効果を発揮できにくいためである。そのためこの
範囲に電磁力を付与し、溶鋼の流動を抑えるのである。
［実施例］
以下に添付図面を参照してこの発明の一実施例を詳細
に説明する。
第１図はこの一実施例に用いられる連続鋳造機の中の
直流磁石の設置位置を示す図である。第２図はこの一実
施例に用いられる連続鋳造機の中の鋳片幅方向の直流磁
石の設置位置を示す図である。１は鋳片、２は鋳型、３
はピンチロール、４は直流電磁石、５はサポートロー
ル、６は溶鋼、７は軽圧下ロール、８は鋳片厚み中心、
９は鋳片短辺面である。鋳型２下端から10〜14m範囲の
軽圧下ロール７間に直流電磁石４を設置した。鋳型２下
端から10〜14m範囲は引抜速度0.7〜0.9m/minの時、鋳片
厚み中心８の固相率が0.3〜0.7の間に入る位置に相当し
ている。直流電磁石４は鋳片短辺面９から150〜300mmの
間の範囲（未凝固相12）をカバーできるようにした。直
流電磁石４の磁極の断面寸法は150×40mm（横×縦）で
ある。
タンデイッシュの溶鋼は浸漬ノズルを経由して鋳型２
内に注入される。鋳型２は水冷されているので外側より
冷却され凝固シェルが形成される。サポートロール５の
部分もスプレーノズルで粉霧冷却されているので凝固シ
ェルはさらに厚くなる。そしてピンチロール３帯を通過
して、更に軽圧下ロール７帯に入る。軽圧下ロール７帯
は鋳型２下端から10〜14m範囲の間にあり、この範囲内
の軽圧下ロール７間に直流電磁石４を配置した。磁場
は、鋳片の厚み方向に印加した。
軽圧下帯にはロールが10対あり、直流電磁石４はロー
ル１本おきに５対設置されており、その時の直流電磁石
４の強さは各直流電磁石４とも０〜6000ガウスの間で変
化させた。軽圧下ロール７の径は350mmΦで、軽圧下ロ
ール７のピッチは420mmに配置されている。
（実施例１）
鋳片厚み:220mm、鋳片幅:2000mm、引抜速度0.75m/min
の時、鋳型２下端から10〜14m間の軽圧下ロール７間に
直流電磁石４を配置した。磁極間距離は300mmである。
磁束密度を5000gaussにセットして鋳造試験を行った。
静磁場印加範囲（鋳型２下端から10〜14m間の範囲）に
おける鋳片表面温度は900度以上に保持するように、二
次冷却条件（ピンチロール３部）をコントロールした。
また、静磁場印加範囲の軽圧下部のロール間隔は基準
に対して引抜き方向に1m当たり1.2mmだけ狭くなるよう
に設定した。得られた鋳片の厚み中心のＣ濃度を、鋳片
の厚み方向に50mmピッチで段削試料を採取し、Ｃ分析を
行い調査した。第３図は幅方向と偏析度C/C0（C0:レー
ドルの［Ｃ］分析値,C:鋳片中心部の［Ｃ］の分析値）
の関係を示すグラフ図である。この図で●印は従来法
で、○印は本実施例である。この図から明らかなように
従来法と比較して本実施例では鋳片短辺から150〜300mm
範囲の偏析度が大幅に改善される。この実施例に基づい
て製造した鋳片を圧延し、鋼板でのHIC（水素誘起割れ:
NACE条件）テストを実施した。その結果を第１表に示
す。API規格X65クラスにおいてもHIC割れ長さ比率は皆
無であった。
（実施例２）
第４図は実施例１と同じ鋳造条件で磁束密度と偏析度
（C/C0）の関係を示すグラフ図である。この図から明ら
かなように磁束密度が2000gauss以上になると偏析度（C
/C0）は1.1となり安定する。
［発明の効果］
以上のように、この発明によれば鋳片厚み方向に圧下
を付与し、鋳片短辺から150〜300mmの鋳片厚み方向の固
相率が0.3〜0.7の範囲に、鋳片厚み方向に静磁場を印加
するので、鋳片短辺から150〜300mmの偏析度（C/C0）が
改善されたのでAPI規格×65の鋼材で水素誘気割れが全
く発生しないなどの優れた効果を有する。Description: TECHNICAL FIELD The present invention relates to a continuous casting method of steel for reducing center segregation in continuous casting. [Prior Art] A center segregation generation mechanism of a continuous cast product occurs when concentrated molten steel in the final stage of solidification flows and accumulates to compensate for a liquid phase volume that changes due to bulging between rolls and solidification contraction. As a method of reducing the center segregation, there is a method of suppressing the flow of the concentrated molten steel at the end of solidification or a method of finely dispersing the accumulation locations of the concentrated molten steel at the end of solidification. The former technique is the uncoagulated light reduction method. For the latter, there is an electromagnetic stirring method in the final stage of coagulation. In the unsolidified light reduction method, the roll interval at the end of solidification is set to match the amount of solidification shrinkage, and solidification is completed while lightly reducing the slab to prevent molten steel flow at the end of solidification and improve center segregation. Is. Before the completion of solidification in the continuous casting machine, the electromagnetic stirring method at the end of solidification
By applying electromagnetic stirring, there is an effect of increasing equiaxed crystals and changing the solidification structure in the vicinity of the thickness center of the continuous cast slab into equiaxed crystals to disperse segregation so as not to concentrate in the thickness center. In particular, electromagnetic stirring at the end of solidification is effective in changing the degree of packing of equiaxed crystals. [Problems to be Solved by the Invention] However, a method of suppressing the flow of concentrated molten steel at the end of solidification cannot completely prevent molten steel flow due to bulging between rolls. In the actual setting of the roll interval, the segregation cannot be improved unless the solidification shrinkage plus the extra light reduction of alpha is added. That is, the surplus light reduction amount of plus alpha is caused by bulging, and actual control is quite difficult. Therefore, if the amount of light reduction is insufficient, the concentrated molten steel is sucked and segregation is formed. On the other hand, if excessive reduction is performed, the concentrated molten steel will be squeezed out and segregation will occur. Another problem is that it is extremely difficult to make the thickness of the unsolidified phase in the slab at the final stage of solidification uniform throughout the slab width direction. In many cases, the thickness of the unsolidified phase in the cast slab is thicker in the part 150 to 300 mm away from the short side surface. When such a slab is pressed down, the thick portion of the unsolidified phase leaves the unsolidified phase 12 as shown in FIG. FIG. 6 is a schematic view showing a cross section of a cast piece at the final stage of solidification.
Usually, the unsolidified phase 12 in the range of 150 to 300 mm from the short side surface is thick. As a result, as the solidification shrinks with the progress of solidification, the surrounding concentrated molten steel flows toward the unsolidified portion left behind, so that a large segregation occurs in the unsolidified phase 12. FIG. 7 is a diagram showing the relationship between the distance from the center of the width of the billet and the degree of segregation. In the figure, the segregation degree is as follows: slab thickness: 220 mm, slab width 2000
mm, the slab thickness center position is 50 mm from the center of the slab width.
At the pitch, an analysis sample was taken with a 3 mmΦ drill, and the carbon concentration analysis result was divided by the crude steel carbon concentration of the ladle C / C 0 (C 0 : of the ladle crude steel [C] Analytical value, C: analytical value of [C] at the center of the thickness of the slab). The casting conditions were a drawing speed of 0.75 m / min and a light reduction (reduction of roll spacing in the drawing direction) of 1.20 mm / m. The value of C / C 0 in the range of 150 to 300 mm from the short side surface of the slab is large, and it can be seen that the segregation in this range is very bad. In this way, in the light reduction method, if an appropriate light reduction is selected, 150 to 300
It is possible to improve segregation on the width center side excluding mm. In the electromagnetic stirring method, equiaxed crystals are generated at the center of the slab, and when solidification of the equiaxed crystals usually occurs, many granular segregation exist between the equiaxed crystals. In some cases, granular segregation is connected in a V shape, and so-called "V segregation" is easily formed. The electromagnetic stirring method at the final stage of solidification can reduce the formation of such V segregation, but it is difficult to completely eliminate it. The present invention has been made in view of the above circumstances, and provides a continuous casting method of steel in continuous casting of a slab, which reduces segregation of the center edge portion of the thickness of the slab. [Means and Actions for Solving Problems] The continuous casting method for steel according to the present invention applies a reduction in the thickness direction of the slab and adjusts the center position of the slab thickness in the range of 150 to 300 mm from the short side of the slab. It is characterized in that a static magnetic field is applied in the thickness direction of the slab in the range of the solid fraction of 0.3 to 0.7. Here, the solid phase ratio indicates a ratio of a solid phase portion in a unit volume. When a liquid with good electrical conductivity flows perpendicular to the magnetic flux in a static magnetic field, an induced current is generated in the liquid, and the interaction between this induced current and the applied magnetic field causes electromagnetic force to act on the fluid in the direction opposite to the flow direction. Works and suppresses flow. FIG. 5 is a diagram showing the positional relationship between the cast slab and the DC electromagnet. That is, the magnetic fields of the DC electromagnets 4 are installed above and below the unsolidified slab 1, and the magnetic field is applied in the thickness direction of the slab. In this case, the following electromagnetic force is generated. The magnetic flux direction of the DC magnetic field is applied perpendicularly to the fluid of the good electric motor, and the molten steel 6 has good electrical conductivity in the DC magnetic field in the fluid.
When the molten steel flow 10 of No. 2 occurs and moves at a speed, an electromotive force based on the equation (1) is generated. E = × = V y · B z (1) Due to this electromotive force E, an eddy current flows in the fluid, and the interaction between the eddy current and the DC magnetic field causes the eddy current to flow in the direction opposite to the direction of motion of the fluid according to equation (2). The indicated volume force 11 works. = − × = −σVy · Bz 2 (2) (where I = 1 / σ · E, σ: specific electric resistance; m / Ω, y: width direction of mold, z: thickness direction of mold) (2) According to the equation, the volume force F11 is proportional to the flow velocity of molten steel and the magnitude of DC magnetic field. By applying such an electromagnetic force to the molten steel at the final stage of solidification to suppress the flow and solidify the molten steel, segregation is reduced.
The inventors of the present application have conducted extensive studies on center segregation in the final stage of solidification, and the reason for applying electromagnetic force to molten steel with a solid fraction of 0.3 or more at the center of the thickness of the cast piece is semi-macro segregation (as seen in the center of the cast piece thickness. Considering from the measurement results of the concentration of the fine granular positive segregation, the initial concentration of the segregation portion (the solid fraction of the segregation portion is 0
It was found that the concentration (at the time of) was higher than the concentration of [C] of the crude steel of Ladle, to the same extent as the liquid phase concentration at the solid phase ratio of 0.3. From this, it can be considered that the molten steel with semi-macro segregation flows and finally solidifies with the solid phase ratio of 0.3. Therefore, it is sufficient to suppress the flow of concentrated molten steel having a solid fraction of 0.3 or more. On the other hand, the reason why the solid fraction in the central portion of the thickness of the slab is set to 0.7 or less is that the liquid phase having the solid fraction of 0.7 or more in the central portion of the slab hardly flows. Further, as described above, when the segregation of the slab in the width direction is examined, the segregation is extremely poor in the range of 150 to 300 mm from the short side surface of the slab. The solidification thickness of the slab differs in the width direction, and in the example of measuring the solidification thickness at the center of the width of the slab and the position of 200 mm from the short side surface of the slab by the staking method at the final stage of solidification, the width center is 108.0 mm, the slab is short. The position 200 mm from the side surface was 104.5 mm. From the short side of the slab
The reason why the segregation in the range of 150 to 300 mm is bad is that if the slabs with different unsolidified thickness in the width direction are lightly pressed, after the center of the width is completely solidified, in the unsolidified part in the range of 150 to 300 mm from the short side surface of the slab. This is because it is difficult to exert the effect of light pressure reduction. Therefore, electromagnetic force is applied to this range to suppress the flow of molten steel. [Embodiment] An embodiment of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a diagram showing the installation position of a DC magnet in the continuous casting machine used in this embodiment. FIG. 2 is a diagram showing the installation positions of the DC magnets in the width direction of the cast piece in the continuous casting machine used in this embodiment. 1 is a slab, 2 is a mold, 3
Is a pinch roll, 4 is a DC electromagnet, 5 is a support roll, 6 is molten steel, 7 is a light reduction roll, 8 is the thickness center of the slab,
9 is a short side surface of the cast slab. The DC electromagnet 4 was installed between the light rolling rolls 7 in the range of 10 to 14 m from the lower end of the mold 2. The range of 10 to 14 m from the lower end of the mold 2 corresponds to the position where the solid fraction of the slab thickness center 8 falls between 0.3 and 0.7 when the drawing speed is 0.7 to 0.9 m / min. The DC electromagnet 4 was made to be able to cover the range (unsolidified phase 12) between 150 and 300 mm from the short side surface 9 of the cast slab. The cross-sectional dimensions of the magnetic poles of the DC electromagnet 4 are 150 × 40 mm (horizontal × vertical). Tundish's molten steel is cast into a mold 2 via an immersion nozzle.
Injected into. Since the mold 2 is water-cooled, it is cooled from the outside to form a solidified shell. Since the portion of the support roll 5 is also atomized and cooled by the spray nozzle, the solidified shell becomes thicker. Then, after passing through the pinch roll 3 zone, it further enters the light reduction roll 7 zone. The light reduction roll 7 zone is located within the range of 10 to 14 m from the lower end of the mold 2, and the DC electromagnet 4 is arranged between the light reduction rolls 7 within this range. The magnetic field was applied in the thickness direction of the slab. There are 10 pairs of rolls in the light compression zone, and 5 pairs of DC electromagnets 4 are installed every other roll. The strength of the DC electromagnets 4 at that time is varied between 0 and 6000 gauss for each DC electromagnet 4. It was The diameter of the light reduction roll 7 is 350 mmΦ, and the pitch of the light reduction roll 7 is arranged at 420 mm. (Example 1) Cast piece thickness: 220 mm, cast piece width: 2000 mm, drawing speed 0.75 m / min
At that time, the DC electromagnet 4 was placed between the light pressure rolls 7 for 10 to 14 m from the lower end of the mold 2. The distance between the magnetic poles is 300 mm.
A casting test was conducted with the magnetic flux density set to 5000 gauss.
The secondary cooling conditions (3 parts of pinch rolls) were controlled so that the surface temperature of the slab in the static magnetic field application range (range between 10 to 14 m from the lower end of the mold 2) was maintained at 900 degrees or higher. In addition, the roll spacing under the light pressure in the static magnetic field application range was set to be 1.2 mm narrower per meter in the drawing direction than the standard. The C concentration in the thickness center of the obtained slab was investigated by performing step analysis samples at 50 mm pitch in the thickness direction of the slab and performing C analysis. Fig. 3 shows the width direction and segregation C / C 0 (C 0 : Ladle [C] analysis value, C: [C] analysis value at the center of the slab)
It is a graph which shows the relationship of. In this figure, ● indicates the conventional method, and ○ indicates the present embodiment. As is clear from this figure, compared with the conventional method, in the present embodiment, 150 to 300 mm from the short side of the slab.
The segregation degree of the range is greatly improved. A slab produced according to this example was rolled to obtain HIC (hydrogen-induced cracking:
NACE condition) Test was conducted. Table 1 shows the results. Even in the API standard X65 class, there was no HIC crack length ratio. (Example 2) FIG. 4 is a graph showing the relationship between the magnetic flux density and the degree of segregation (C / C 0 ) under the same casting conditions as in Example 1. As is clear from this figure, the segregation degree (C
/ C 0 ) becomes 1.1 and is stable. [Effects of the Invention] As described above, according to the present invention, reduction is applied in the thickness direction of the cast piece, and the solid fraction in the cast piece thickness direction of 150 to 300 mm from the short side of the cast piece is in the range of 0.3 to 0.7, Since a static magnetic field is applied in the thickness direction of the slab, the segregation degree (C / C 0 ) of 150 to 300 mm from the short side of the slab has been improved, so hydrogen induction cracking does not occur at all in API standard × 65 steel materials. Has excellent effect.
【図面の簡単な説明】
第１図はこの一実施例に用いられる連続鋳造機の中の直
流磁石の設置位置を示す図、第２図はこの一実施例に用
いられる連続鋳造機の中の鋳片幅方向の直流磁石の設置
位置を示す図、第３図は幅方向と偏析度の関係を示すグ
ラフ図、第４図はこの一実施例の鋳造条件で磁束密度と
偏析度の関係を示すグラフ図、第５図は鋳片と電磁石の
位置関係を示す図、第６図は凝固末期の鋳片断面を示し
た模式図、第７図は鋼片中央からの距離と偏析度の関係
を示す図である。
１……鋳片、２……鋳型、３……ピンチロール、４……
直流電磁石、５……サポートロール、６……溶鋼、７…
…軽圧下ロール、８……鋳片厚み中心、９……鋳片短辺
面。BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing the installation position of a DC magnet in a continuous casting machine used in this embodiment, and FIG. 2 is a diagram showing a continuous casting machine used in this embodiment. The figure which shows the installation position of the DC magnet in the width direction of the slab, FIG. 3 is a graph showing the relationship between the width direction and the segregation degree, and FIG. 4 shows the relationship between the magnetic flux density and the segregation degree under the casting conditions of this embodiment. Fig. 5 is a graph showing the positional relationship between the slab and the electromagnet, Fig. 6 is a schematic diagram showing the cross section of the slab at the final stage of solidification, and Fig. 7 is the relationship between the distance from the center of the slab and the degree of segregation. FIG. 1 ... Slab, 2 ... Mold, 3 ... Pinch roll, 4 ...
DC electromagnet, 5 ... Support roll, 6 ... Molten steel, 7 ...
… Light reduction roll, 8 …… Slab thickness center, 9 …… Slab short side surface.
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(56)参考文献 特開 昭62−158555（ＪＰ，Ａ)
特開 昭59−76649（ＪＰ，Ａ)
特公 昭59−41829（ＪＰ，Ｂ２)
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(56) References JP-A-62-158555 (JP, A)
JP 59-76649 (JP, A)
Japanese Patent Sho 59-41829 (JP, B2)