JP2006122995A - Method for continuously casting steel - Google Patents

Method for continuously casting steel Download PDF

Info

Publication number
JP2006122995A
JP2006122995A JP2004318277A JP2004318277A JP2006122995A JP 2006122995 A JP2006122995 A JP 2006122995A JP 2004318277 A JP2004318277 A JP 2004318277A JP 2004318277 A JP2004318277 A JP 2004318277A JP 2006122995 A JP2006122995 A JP 2006122995A
Authority
JP
Japan
Prior art keywords
mold
molten steel
side copper
copper plate
long side
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
JP2004318277A
Other languages
Japanese (ja)
Other versions
JP4303670B2 (en
Inventor
Kazuhisa Tanaka
和久 田中
Shinichi Fukunaga
新一 福永
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nippon Steel Corp
Original Assignee
Nippon Steel Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nippon Steel Corp filed Critical Nippon Steel Corp
Priority to JP2004318277A priority Critical patent/JP4303670B2/en
Publication of JP2006122995A publication Critical patent/JP2006122995A/en
Application granted granted Critical
Publication of JP4303670B2 publication Critical patent/JP4303670B2/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for continuously casting steel by which a mold is suppressed from being damaged at its inside surface so as to extend the service life of the mold, improve productivity, reduce production cost and improve the surface quality of a slab. <P>SOLUTION: In the continuous casting method, by which molten steel is successively poured into a mold 10 having mold copper plates 11 to 14 in which a plating layer 16 essentially consisting of either or both of nickel and cobalt is formed at the inside via an immersion nozzle 24, and, as the molten metal surface of the molten steel in the mold 10 is always covered with mold flux 25, the molten steel is solidified in the mold 10, the content of zinc incorporated into the mold flux 25 is controlled to ≤200 ppm, the inclination angle of the central axis in a molten steel discharge hole 28 formed at the immersion nozzle 24 is set to the range of ≤5° in the upward direction and to ≤45° in the downward direction, and further, casting velocity is controlled in accordance with a thermal load applied to the mold copper plates 11 to 14. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

本発明は、連続鋳造用の鋳型内面における損傷発生を抑制した鋼の連続鋳造方法に関する。 The present invention relates to a method for continuously casting steel in which the occurrence of damage on the inner surface of a mold for continuous casting is suppressed.

従来、ニッケル又はコバルトのマトリックス中に金属炭化物や金属窒化物を分散させた複合メッキ層でモールド銅板の溶鋼との接触面側を被覆することにより、高温における硬度、耐久性、及び耐摩耗性を向上させた連続鋳造用の鋳型が提案されている(例えば、特許文献1及び2参照)。
また、モールド銅板の溶鋼との接触面側に電気ニッケルメッキ層を形成し、更に、その上にクロムメッキ層を設けることにより、鋳込み初期に発生する焼付きを防止して、連続鋳造用の鋳型の使用回数を増加させる(長寿命化させる)ことが提案されている(例えば、特許文献3参照)。
Conventionally, hardness, durability, and wear resistance at high temperatures are achieved by coating the contact surface side of molten copper with a composite plating layer in which metal carbide or metal nitride is dispersed in a nickel or cobalt matrix. An improved casting mold for continuous casting has been proposed (see, for example, Patent Documents 1 and 2).
In addition, by forming an electric nickel plating layer on the contact surface side of the mold copper plate with the molten steel, and further providing a chrome plating layer thereon, seizure that occurs at the beginning of casting is prevented, and a mold for continuous casting. It has been proposed to increase the number of uses (to extend the life) (see, for example, Patent Document 3).

特開昭54−4236号公報Japanese Patent Laid-Open No. 54-4236 特開昭54−4237号公報Japanese Patent Laid-Open No. 54-4237 特開昭52−54622号公報JP 52-54622 A

しかしながら、特許文献1及び2に記載された発明では、複合メッキ層の主成分であるニッケル又はコバルトが連続鋳造時に使用するモールドフラックス中に不可避的に含有される亜鉛と反応して複合メッキ層の表層部に低融点合金を生成し、使用中の鋳型内に発生している温度勾配により、この低融点合金を起点として複合メッキ層及びモールド銅板にヒートクラックが発生するという問題が生じる。また、特許文献3で提案された鋳型では、上層のクロムメッキ層には、使用前から亀甲状の割れが存在するという問題がある。このため、この鋳型を使用すると、亀甲状の割れに沿ってモールドフラックス中の亜鉛が浸潤し下層のニッケルメッキ層まで到達してニッケルとの間で低融点合金を生成し、この低融点合金を起点としてニッケルメッキ層及びモールド銅板にヒートクラックが発生することが容易に考えられる。
また、鋳造条件によって、例えば、浸漬ノズルから吐出する溶鋼の流れが上向きになると、あるいは、鋳造速度が速くなり浸漬ノズルから吐出する溶鋼流が増大し鋳型に激しく衝突するようになると、モールド銅板に加わる熱負荷が増大するためヒートクラックが発生し易くなると共に、発生したヒートクラックが伸展し易くなって鋳型寿命が大きく縮まるという問題がある。
However, in the inventions described in Patent Documents 1 and 2, nickel or cobalt, which is the main component of the composite plating layer, reacts with zinc inevitably contained in the mold flux used during continuous casting, and the composite plating layer A low melting point alloy is generated in the surface layer portion, and a problem that heat cracks occur in the composite plating layer and the molded copper plate starts from the low melting point alloy due to the temperature gradient generated in the mold in use. Moreover, in the casting_mold | template proposed by patent document 3, there exists a problem that a tortoiseshell-like crack exists in the upper chromium plating layer before use. For this reason, when this mold is used, zinc in the mold flux infiltrates along the tortoiseshell cracks and reaches the lower nickel plating layer to form a low melting point alloy with nickel. As a starting point, it is considered that heat cracks are easily generated in the nickel plating layer and the molded copper plate.
Also, depending on the casting conditions, for example, when the flow of molten steel discharged from the immersion nozzle becomes upward, or when the casting speed increases and the molten steel flow discharged from the immersion nozzle increases and collides violently with the mold, Since the applied heat load increases, heat cracks are likely to occur, and the generated heat cracks are easily extended, resulting in a problem that the mold life is greatly shortened.

本発明はかかる事情に鑑みてなされたもので、鋳型内面における損傷発生を抑制して鋳型寿命の延長、生産性の向上、製造コストの削減、及び鋳片の表面品質向上を可能にする鋼の連続鋳造方法を提供することを目的とする。 The present invention has been made in view of such circumstances, and suppresses the occurrence of damage on the inner surface of the mold to extend the mold life, improve the productivity, reduce the manufacturing cost, and improve the surface quality of the slab. An object is to provide a continuous casting method.

本発明に係る鋼の連続鋳造方法は、内側にニッケル及びコバルトのいずれか一方又は双方を主体とするメッキ層が形成されたモールド銅板を有する鋳型内に、浸漬ノズルを介して溶鋼を順次注湯して、前記鋳型内の溶鋼の湯面をモールドフラックスで常時覆いながら該鋳型内で溶鋼を凝固させる連続鋳造方法において、
前記モールドフラックスに含有される亜鉛量を200ppm以下にし、前記浸漬ノズルに形成された溶鋼吐出孔の中心軸の傾斜角度を水平方向に対して上向き5°以下で下向き45°以下の範囲に設定すると共に、前記モールド銅板に加わる熱負荷に応じて鋳造速度を調整する。
In the continuous casting method of steel according to the present invention, molten steel is sequentially poured through an immersion nozzle into a mold having a molded copper plate in which a plating layer mainly composed of one or both of nickel and cobalt is formed. In the continuous casting method of solidifying the molten steel in the mold while always covering the molten steel surface of the molten steel in the mold with a mold flux,
The amount of zinc contained in the mold flux is set to 200 ppm or less, and the inclination angle of the central axis of the molten steel discharge hole formed in the immersion nozzle is set to a range of 5 ° or less upward and 45 ° or less downward with respect to the horizontal direction. At the same time, the casting speed is adjusted according to the thermal load applied to the mold copper plate.

本発明に係る鋼の連続鋳造方法においては、モールドフラックスに含有される亜鉛量を200ppm以下にするので、連続鋳造中にメッキ層中のニッケル及びコバルトのいずれか一方又は双方と亜鉛との反応によりメッキ層の表層部に生成する低融点合金量を低下させることができ、更に、浸漬ノズルから吐出する溶鋼の流れ方向と鋳造速度を調整するのでモールド銅板に加わる熱負荷を低下させることができ、生成した低融点合金を起点としてメッキ層及びモールド銅板にヒートクラックが発生するのを抑制すると共にヒートクラックの成長を抑制することが可能になる。その結果、鋳型の寿命延長が可能になる。また、鋳型寿命の延長に伴い鋳型の交換頻度が減少して、鋳片の生産性の向上、製造コストの削減を行うことが可能になる。更に、ヒートクラックの発生と成長が抑制されることで鋳型表面の平滑性が保たれ、鋳片に発生する表面欠陥を低減すると共に軽微にすることができ、圧延前の鋳片の無手入れ化が達成できる。 In the continuous casting method of steel according to the present invention, the amount of zinc contained in the mold flux is set to 200 ppm or less. Therefore, during continuous casting, one or both of nickel and cobalt in the plating layer react with zinc. The amount of low melting point alloy generated in the surface layer portion of the plating layer can be reduced, and furthermore, the flow direction of the molten steel discharged from the immersion nozzle and the casting speed can be adjusted, so the thermal load applied to the molded copper plate can be reduced, With the generated low melting point alloy as a starting point, it is possible to suppress the occurrence of heat cracks in the plating layer and the molded copper plate and to suppress the growth of heat cracks. As a result, the mold life can be extended. In addition, the mold replacement frequency decreases with the extension of the mold life, and it becomes possible to improve the slab productivity and reduce the manufacturing cost. Furthermore, by suppressing the occurrence and growth of heat cracks, the smoothness of the mold surface is maintained, surface defects occurring on the slab can be reduced and reduced, and the slab before rolling can be kept clean. Can be achieved.

特に、電磁力を鋳型内の溶鋼に付与して鋳型内で溶鋼を旋回させながら鋳造する場合は、鋳型内面に形成された凝固殻の内面側にトラップされた気泡や介在物を溶鋼の旋回流で洗浄して清浄化することができ、鋳片から表面品質に優れた薄板を製造することが可能になる。
また、電磁力で鋳型内の溶鋼を旋回させるときに溶鋼の旋回方向を所定数のキャスト毎に逆転する場合は、旋回流が鋳型内面に衝突する位置を変えることができ、鋳型内の特定部位に熱負荷が集中するのを防止できる。このため、ヒートクラックが発生するのを抑制すると共にヒートクラックの成長を抑制することが容易にでき、電磁撹拌を行う際の鋳型の寿命を更に延長することが可能になる。
In particular, when casting is performed while applying electromagnetic force to the molten steel in the mold and rotating the molten steel in the mold, bubbles or inclusions trapped on the inner surface side of the solidified shell formed on the inner surface of the mold are swirled by the molten steel. It is possible to produce a thin plate with excellent surface quality from the cast slab.
Also, when the swirling direction of the molten steel is reversed every predetermined number of casts when the molten steel in the mold is swirled by electromagnetic force, the position where the swirling flow collides with the inner surface of the mold can be changed. It is possible to prevent the heat load from concentrating on. For this reason, it is possible to easily suppress the occurrence of heat cracks and to suppress the growth of heat cracks, and it is possible to further extend the life of the mold when performing electromagnetic stirring.

続いて、添付した図面を参照しつつ、本発明を具体化した実施の形態につき説明し、本発明の理解に供する。
ここで、図1は本発明の一実施の形態に係る鋼の連続鋳造方法に適用した鋳型の一部省略正断面図、図2は同鋼の連続鋳造方法に適用した鋳型の一部省略側断面図、図3は同鋼の連続鋳造方法に適用した鋳型の平面図、図4(A)、(B)は鋳型内の溶鋼の旋回方向の説明図、図5は同鋼の連続鋳造方法に適用した鋳型に発生する損傷位置の説明図、図6は同鋼の連続鋳造方法に適用した鋳型の長辺側銅板の内側面における熱流束の変化を示す説明図である。
Next, embodiments of the present invention will be described with reference to the accompanying drawings for understanding of the present invention.
Here, FIG. 1 is a partially omitted front sectional view of a mold applied to a steel continuous casting method according to an embodiment of the present invention, and FIG. 2 is a partially omitted side of a mold applied to the steel continuous casting method. Sectional view, FIG. 3 is a plan view of a mold applied to the continuous casting method of the steel, FIGS. 4A and 4B are explanatory views of the swirling direction of the molten steel in the mold, and FIG. 5 is a continuous casting method of the steel FIG. 6 is an explanatory view showing a change in heat flux on the inner surface of the long side copper plate of the mold applied to the continuous casting method of the steel.

図1〜図3に示すように、本発明の一実施の形態に係る鋼の連続鋳造方法に適用した鋳型10は、隙間Tを設けて平行に対向配置されたモールド銅板の一例である長辺側銅板11、12と、隙間Tと実質的に同一の幅で長辺側銅板11、12と実質的に同一の長さを備え長辺側銅板11、12の間に隙間Tよりも大きな間隔を設けて平行に対向配置されるモールド銅板の一例である短辺側銅板13、14を備えている。ここで、長辺側銅板11、12及び短辺側銅板13、14の表面には、例えば、ニッケルを主体とするメッキ層16が形成されている。更に、長辺側銅板11、12及び短辺側銅板13、14には、それぞれ図示しない水冷部が設けられている。このような構成とすることにより、図3に示すように、長辺側銅板11、12及び短辺側銅板13、14により周囲を取り囲まれた、平面視して矩形状の空間部17が形成される。 As shown in FIGS. 1 to 3, the mold 10 applied to the steel continuous casting method according to one embodiment of the present invention is a long side which is an example of a molded copper plate provided with a gap T so as to face each other in parallel. The side copper plates 11 and 12 have substantially the same width as the gap T and the same length as the long side copper plates 11 and 12, and the gap between the long side copper plates 11 and 12 is larger than the gap T. The short side copper plates 13 and 14 which are examples of the mold copper plate arranged oppositely in parallel are provided. Here, for example, a plating layer 16 mainly composed of nickel is formed on the surfaces of the long side copper plates 11 and 12 and the short side copper plates 13 and 14. Furthermore, the long side copper plates 11 and 12 and the short side copper plates 13 and 14 are provided with water cooling portions (not shown), respectively. With such a configuration, as shown in FIG. 3, a rectangular space portion 17 is formed in a plan view and surrounded by the long side copper plates 11 and 12 and the short side copper plates 13 and 14. Is done.

また、図3に示すように、長辺側銅板11、12において、各短辺側銅板13、14により挟まれる領域の背面側には、電磁撹拌装置を構成する対となるコイル部18、19がそれぞれ設けられている。ここで、コイル部18は長辺側銅板11の背面側で長辺側銅板11の幅方向に並べて配置された分割コイル20、21を有し、コイル部19は長辺側銅板12の背面側で長辺側銅板12の幅方向に並べて配置された分割コイル22、23をそれぞれ有している。 Moreover, as shown in FIG. 3, in the long side copper plates 11 and 12, on the back side of the region sandwiched between the short side copper plates 13 and 14, the coil portions 18 and 19 forming a pair constituting the electromagnetic stirrer are provided. Are provided. Here, the coil portion 18 has split coils 20 and 21 arranged side by side in the width direction of the long side copper plate 11 on the back side of the long side copper plate 11, and the coil portion 19 is the back side of the long side copper plate 12. And the divided coils 22 and 23 arranged side by side in the width direction of the long side copper plate 12.

このような構成とすることにより、長辺側銅板11、12及び短辺側銅板13、14の水冷部に水を流通させながら空間部17内に浸漬ノズル24を介して溶鋼を注湯することができる。更に、コイル部18、19に流れる電流方向が逆になるように各コイル部18、19に電圧を負荷することにより、空間部17内に注湯された溶鋼で長辺側銅板11近傍に存在する溶鋼を長辺側銅板11の一端側から他端側に向けて移動させることができ、長辺側銅板12近傍に存在する溶鋼を長辺側銅板12の他端側から一端側に向けて移動させることができる。このため、注湯された溶鋼内に、例えば、右まわりの旋回流を発生させることができる。 By setting it as such a structure, pouring molten steel in the space part 17 via the immersion nozzle 24, distribute | circulating water to the water cooling part of the long side copper plates 11 and 12 and the short side copper plates 13 and 14. Can do. Furthermore, by applying a voltage to each of the coil portions 18 and 19 so that the direction of the current flowing through the coil portions 18 and 19 is reversed, the molten steel poured into the space portion 17 is present in the vicinity of the long side copper plate 11. The molten steel can be moved from one end side of the long side copper plate 11 toward the other end side, and the molten steel existing in the vicinity of the long side copper plate 12 is directed from the other end side of the long side copper plate 12 to one end side. Can be moved. For this reason, for example, a clockwise swirl flow can be generated in the molten steel poured.

このとき、分割コイル20、23に流す電流値と分割コイル21、22に流す電流値に差を設けることにより、各長辺側銅板11、12に沿って形成する溶鋼の駆動力に変化を付けることができる。
更に、空間部17内に注湯された溶鋼の湯面上にモールドフラックス25を供給することにより、溶鋼の湯面をモールドフラックス25で常時覆い、しかも、注湯された溶鋼を旋回させた状態で徐々に凝固させることができる。
At this time, by providing a difference between the current value flowing through the split coils 20 and 23 and the current value flowing through the split coils 21 and 22, the driving force of the molten steel formed along the long side copper plates 11 and 12 is changed. be able to.
Furthermore, by supplying the mold flux 25 onto the molten steel surface poured into the space 17, the molten steel surface is always covered with the mold flux 25 and the molten molten steel is swirled. Can be gradually solidified.

続いて、鋳型10を使用した本発明の一実施の形態に係る鋼の連続鋳造方法について説明する。
先ず、長辺側銅板11、12及び短辺側銅板13、14の各水冷部に水を流通させて鋳型10を冷却し、電磁撹拌装置のコイル部18、19に電流を流す。このとき、分割コイル20、23に流す電流値を分割コイル21、22に流す電流値より大きく設定する。そして、鋳型10の空間部17の下流側を閉じて、溶鋼を貯留している図示しないタンディッシュから浸漬ノズル24を介して空間部17に溶鋼の注湯を開始する。空間部17内に注湯された溶鋼の湯面が所定高さに到達した時点でモールドフラックス25を鋳型10内の溶鋼の上方から供給して、溶鋼の湯面をモールドフラックス25で覆う。
Then, the continuous casting method of steel which uses the casting_mold | template 10 based on one embodiment of this invention is demonstrated.
First, the mold 10 is cooled by flowing water through the water-cooling portions of the long-side copper plates 11 and 12 and the short-side copper plates 13 and 14, and a current is passed through the coil portions 18 and 19 of the electromagnetic stirring device. At this time, the current value flowing through the split coils 20 and 23 is set larger than the current value flowing through the split coils 21 and 22. And the downstream side of the space part 17 of the casting_mold | template 10 is closed, and the pouring of molten steel is started to the space part 17 via the immersion nozzle 24 from the tundish which is not shown which has stored the molten steel. When the molten steel surface poured into the space 17 reaches a predetermined height, the mold flux 25 is supplied from above the molten steel in the mold 10 to cover the molten steel surface with the mold flux 25.

このとき、湯面と接触する側のモールドフラックス25は湯面からの熱を受けて溶融する。このため、図1、図2に示すように、鋳型10内の溶鋼の湯面上には溶融層26が形成され、更にその上部に未溶融のモールドフラックス25が存在する状態になる。また、長辺側銅板11、12及び短辺側銅板13、14の近傍の溶鋼は徐々に冷却されるので、長辺側銅板11、12及び短辺側銅板13、14の表面上には徐々に凝固殻27が形成される。
ここで、注湯された溶鋼には電磁撹拌装置のコイル部18、19によって電磁力が付加されるので、例えば図4(A)に示すように、鋳型10内の溶鋼には水平面内で右まわりに旋回する旋回流が形成される。このため、凝固殻27の内表面にトラップされた気泡や介在物は溶鋼の旋回流で洗浄されて離脱し、大気中に放散もしくはモールドフラックス25に吸収され、凝固殻27の清浄化が行われる。
At this time, the mold flux 25 on the side in contact with the molten metal surface is melted by receiving heat from the molten metal surface. Therefore, as shown in FIGS. 1 and 2, a molten layer 26 is formed on the molten steel surface of the molten steel in the mold 10, and an unmelted mold flux 25 exists further on the molten layer 26. In addition, since the molten steel in the vicinity of the long side copper plates 11 and 12 and the short side copper plates 13 and 14 is gradually cooled, gradually on the surfaces of the long side copper plates 11 and 12 and the short side copper plates 13 and 14. The solidified shell 27 is formed.
Here, since the electromagnetic force is applied to the poured molten steel by the coil portions 18 and 19 of the electromagnetic stirrer, for example, as shown in FIG. 4 (A), the molten steel in the mold 10 is moved to the right in the horizontal plane. A swirling flow swirling around is formed. For this reason, bubbles and inclusions trapped on the inner surface of the solidified shell 27 are washed away by the swirling flow of molten steel, dissipated into the atmosphere or absorbed by the mold flux 25, and the solidified shell 27 is cleaned. .

そして、鋳型10内に一定量の溶鋼が貯留され、鋳型10内の湯鋼の下流側で所定厚さの凝固殻27が形成された時点で、下流側の凝固殻27を鋳型10内から一定の鋳造速度で引き出すと共に、鋳型10内の溶鋼レベルが一定に保たれるように、浸漬ノズル24を介してタンディッシュから溶鋼を随時鋳型10内に注湯する。更に、凝固殻27を鋳型10内から引き出す際に、溶鋼の湯面上に存在している溶融層26は、凝固殻27と長辺側銅板11、12及び短辺側銅板13、14の隙間に巻き込まれて、凝固殻27が鋳型10から引き出される際の抵抗を低下させるように作用する。
凝固殻27の引き出しと共に溶融層26は徐々に鋳型10内から排出されるので、モールドフラックス25を溶鋼の上方から供給して、溶鋼の湯面がモールドフラックス25で常時覆われるようにする。そのため、連続鋳造中では、溶鋼の湯面上には供給されたモールドフラックス25が溶融した溶融層26が常時存在し、この溶融層26は長辺側銅板11、12及び短辺側銅板13、14と常に接触した状態になっている。このため、長辺側銅板11、12及び短辺側銅板13、14の内側面で溶鋼のメニスカス位置に対応する部位の近傍には、溶融層26から亜鉛が常時供給される状態になっている。
When a certain amount of molten steel is stored in the mold 10 and the solidified shell 27 having a predetermined thickness is formed on the downstream side of the hot water in the mold 10, the downstream solidified shell 27 is fixed from the mold 10. The molten steel is poured into the mold 10 from the tundish as needed through the immersion nozzle 24 so that the molten steel level in the mold 10 is kept constant. Further, when the solidified shell 27 is pulled out from the mold 10, the molten layer 26 existing on the molten steel surface is a gap between the solidified shell 27 and the long side copper plates 11 and 12 and the short side copper plates 13 and 14. It acts to reduce the resistance when the solidified shell 27 is pulled out of the mold 10.
The molten layer 26 is gradually discharged from the mold 10 as the solidified shell 27 is pulled out, so that the mold flux 25 is supplied from above the molten steel so that the molten steel surface is always covered with the mold flux 25. Therefore, during continuous casting, a molten layer 26 in which the supplied mold flux 25 is melted is always present on the molten steel surface, and the molten layer 26 includes the long side copper plates 11 and 12 and the short side copper plate 13, 14 is always in contact. For this reason, zinc is always supplied from the molten layer 26 in the vicinity of the portion corresponding to the meniscus position of the molten steel on the inner surfaces of the long side copper plates 11 and 12 and the short side copper plates 13 and 14. .

ここで、本実施の形態の鋼の連続鋳造方法においては、モールドフラックス25に含有される亜鉛量を200ppm以下にしている。このため、長辺側銅板11、12及び短辺側銅板13、14の表面に設けられたメッキ層16と反応して生成するニッケル−亜鉛系の低融点合金の生成量が少なく、ヒートクラックの起点として作用し難くなる。これによって、長辺側銅板11、12及び短辺側銅板13、14の表面に設けられたメッキ層16と、その下部の長辺側銅板11、12及び短辺側銅板13、14にヒートクラックが発生するのを抑制できる。更に、ニッケル−亜鉛系の低融点合金の生成量が少ないため、溶鋼中にメッキ層16から溶出する低融点合金量も少なくなって、メッキ層16の表層に形成される窪み(肌荒れ)も軽微になる。なお、モールドフラックス中の亜鉛含有量が200ppmを超えると、ニッケル−亜鉛系の低融点合金の生成量が多くなって、ヒートクラックの起点として作用すると共に、溶鋼中に溶出する低融点合金量も多くなって、メッキ層16の表層に形成される窪み深さが大きくなるので好ましくない。 Here, in the continuous casting method of steel of the present embodiment, the amount of zinc contained in the mold flux 25 is set to 200 ppm or less. For this reason, the amount of nickel-zinc low melting point alloy produced by reacting with the plating layer 16 provided on the surfaces of the long side copper plates 11 and 12 and the short side copper plates 13 and 14 is small, and heat cracks are generated. It becomes difficult to act as a starting point. As a result, heat cracks occur in the plating layer 16 provided on the surfaces of the long-side copper plates 11 and 12 and the short-side copper plates 13 and 14, and the long-side copper plates 11 and 12 and the short-side copper plates 13 and 14 below the plating layer 16. Can be prevented from occurring. Furthermore, since the amount of the nickel-zinc based low melting point alloy is small, the amount of the low melting point alloy eluted from the plating layer 16 in the molten steel is also small, and the dents (skin roughness) formed on the surface layer of the plating layer 16 are slight. become. If the zinc content in the mold flux exceeds 200 ppm, the amount of nickel-zinc based low melting point alloy increases, which acts as a starting point for heat cracks and also the amount of low melting point alloy eluted into the molten steel. This is not preferable because the depth of the depression formed on the surface layer of the plating layer 16 increases and the depth of the depression increases.

また、本実施の形態の鋼の連続鋳造方法においては、図2に示すように、浸漬ノズル24に形成された溶鋼吐出孔28の中心軸の傾斜角度を水平方向に対して上向き5°以下で下向き45°以下の範囲に設定する。
溶鋼吐出孔28の中心軸の傾斜角度が水平方向に対して上向き5°を超えると、浸漬ノズル24の溶鋼吐出孔28から吐出された溶鋼が鋳型10内の湯面に衝突し、長辺側銅板11、12及び短辺側銅板13、14の内側面で溶鋼のメニスカス位置に対応する部位の近傍では湯面位置が変動し、メニスカス位置に対応する部位の近傍での溶鋼から長辺側銅板11、12及び短辺側銅板13、14への熱伝達係数が上昇する。このため、溶鋼から長辺側銅板11、12及び短辺側銅板13、14へ移動する熱量が増加し、長辺側銅板11、12及び短辺側銅板13、14に加わる熱負荷が増加して好ましくない。更に、溶鋼が湯面に衝突した際に溶融層26及びモールドフラックス25を溶鋼中に巻き込んで、溶鋼を汚染するという問題も生じる。このため、溶鋼吐出孔28の中心軸の傾斜角度を水平方向に対して上向き5°以下とした。
In the steel continuous casting method of the present embodiment, as shown in FIG. 2, the inclination angle of the central axis of the molten steel discharge hole 28 formed in the immersion nozzle 24 is 5 ° or less upward with respect to the horizontal direction. Set the range to 45 ° or less downward.
When the inclination angle of the central axis of the molten steel discharge hole 28 exceeds 5 ° upward with respect to the horizontal direction, the molten steel discharged from the molten steel discharge hole 28 of the immersion nozzle 24 collides with the molten metal surface in the mold 10 and the long side The molten metal surface position fluctuates in the vicinity of the portion corresponding to the meniscus position of the molten steel on the inner surfaces of the copper plates 11 and 12 and the short side copper plates 13 and 14, and the long side copper plate changes from the molten steel in the vicinity of the portion corresponding to the meniscus position. 11 and 12 and the heat transfer coefficient to the short side copper plates 13 and 14 increase. For this reason, the amount of heat transferred from the molten steel to the long side copper plates 11 and 12 and the short side copper plates 13 and 14 increases, and the heat load applied to the long side copper plates 11 and 12 and the short side copper plates 13 and 14 increases. It is not preferable. Further, when the molten steel collides with the molten metal surface, the molten layer 26 and the mold flux 25 are wound into the molten steel, and the molten steel is contaminated. For this reason, the inclination angle of the central axis of the molten steel discharge hole 28 is set to 5 ° or less upward with respect to the horizontal direction.

このように、長辺側銅板11、12及び短辺側銅板13、14に加わる熱負荷を低下することにより、ニッケル−亜鉛系の低融点合金を起点としてヒートクラックが発生しても、ヒートクラックの成長を抑制することができる。
なお、溶鋼吐出孔28の中心軸の傾斜角度を水平方向に対して下向きに設定することは、メニスカス位置に対応する部位の近傍での熱負荷の低減、溶融層26及びモールドフラックス25の溶鋼中への巻き込み防止の点から好ましいが、溶鋼吐出孔28の中心軸の傾斜角度を水平方向に対して下向き45°を超えて設定すると、浸漬ノズル24から吐出された溶鋼中に混入しているガスや介在物が鋳型10の深部に達して凝固殻27にトラップされるため好ましくない。このため、溶鋼吐出孔28の中心軸の傾斜角度を水平方向に対して下向き45°以下の範囲に設定した。
Thus, even if a heat crack occurs starting from a nickel-zinc based low melting point alloy by reducing the thermal load applied to the long side copper plates 11 and 12 and the short side copper plates 13 and 14, Growth can be suppressed.
Note that setting the inclination angle of the central axis of the molten steel discharge hole 28 downward with respect to the horizontal direction reduces the thermal load in the vicinity of the portion corresponding to the meniscus position, during the molten steel of the molten layer 26 and the mold flux 25. However, if the inclination angle of the central axis of the molten steel discharge hole 28 is set to exceed 45 ° downward with respect to the horizontal direction, the gas mixed in the molten steel discharged from the immersion nozzle 24 is preferable. And inclusions reach the deep part of the mold 10 and are trapped in the solidified shell 27, which is not preferable. For this reason, the inclination angle of the central axis of the molten steel discharge hole 28 is set in a range of 45 ° or less downward with respect to the horizontal direction.

ここで、鋳型10内の溶鋼には電磁撹拌装置のコイル部18、19から電磁力が付加されて水平面内で右まわりに旋回する溶鋼の旋回流が形成されているが、このとき、分割コイル20、23に流す電流値を分割コイル21、22に流す電流値より大きく設定しているので、注湯された溶鋼で長辺側銅板11近傍に存在する溶鋼を長辺側銅板11の一端側から他端側に向けて、また、長辺側銅板12近傍に存在する溶鋼は長辺側銅板12の他端側から一端側に向けて、それぞれ前半は大きな駆動力で、後半は小さな駆動力で移動させることができる。このため、鋳型10内に均一な溶鋼の旋回流を形成することができる。 Here, the molten steel in the mold 10 is applied with electromagnetic force from the coil portions 18 and 19 of the electromagnetic stirrer to form a swirling flow of the molten steel swirling clockwise in the horizontal plane. Since the current value flowing through the divided coils 21 and 22 is set larger than the current value flowing through the split coils 21 and 22, the molten steel existing in the vicinity of the long side copper plate 11 is poured into one end side of the long side copper plate 11. From the other side of the long side copper plate 12 to the one end side, the molten steel existing in the vicinity of the long side copper plate 12 has a large driving force in the first half and a small driving force in the second half. It can be moved with. For this reason, a uniform swirling flow of molten steel can be formed in the mold 10.

しかしながら、長辺側銅板11、12に沿って移動する溶鋼の駆動力に変化を付けることにより、長辺側銅板11では空間部17を形成する面の一端側に、長辺側銅板12では空間部17を形成する面の他端側に溶鋼流が強く衝突する部位が発生する。そして、溶鋼流が強く衝突する部位の近傍では、溶鋼から各長辺側銅板11、12への熱伝達係数が上昇して、溶鋼から長辺側銅板11、12へ流入する熱量が増加し、長辺側銅板11、12に加わる熱負荷が増加する。
その結果、図5に示すように、長辺側銅板11(12)の一端側(他端側)で熱負荷が大きくなり、溶鋼のメニスカス位置に対応し溶融層26から亜鉛が常時供給される部位においてはニッケル−亜鉛系の低融点合金の生成が促進されてヒートクラックの発生及び成長と、生成した低融点合金の溶鋼中への溶出に伴うメッキ層の肌荒れが複合された損傷の発生が顕著となる。
However, by changing the driving force of the molten steel moving along the long side copper plates 11, 12, the long side copper plate 11 has a space on one end side of the surface forming the space 17, and the long side copper plate 12 has a space. A portion where the molten steel flow strongly collides is generated on the other end side of the surface forming the portion 17. And in the vicinity of the portion where the molten steel flow strongly collides, the heat transfer coefficient from the molten steel to each of the long side copper plates 11, 12 increases, and the amount of heat flowing from the molten steel to the long side copper plates 11, 12 increases. The heat load applied to the long side copper plates 11 and 12 increases.
As a result, as shown in FIG. 5, the thermal load increases on one end side (the other end side) of the long side copper plate 11 (12), and zinc is constantly supplied from the molten layer 26 corresponding to the meniscus position of the molten steel. The formation of nickel-zinc-based low melting point alloy is promoted at the site, and the generation and growth of heat cracks and the occurrence of damage that combines the rough surface of the plating layer due to the dissolution of the generated low melting point alloy into the molten steel Become prominent.

ここで、電磁撹拌を行いながら鋳造速度を1m/分及び1.3m/分として連続鋳造を行った場合における長辺側銅板11(溶鋼に接触する部分の幅が900mm)に加わる熱負荷として、溶鋼から長辺側銅板11のメニスカス位置に流入する熱流束を測定した。そして、例えば、長辺側銅板11と短辺側銅板13(溶鋼に接触する部分の幅が250mm)との当接部を起点(0)として、長辺側銅板11の一端側から他端側に向かうメニスカス位置上での各部位における熱流束の値を図6に示す。なお、図6には、電磁撹拌を行わないで鋳造速度を1.3m/分として連続鋳造を行った場合に溶鋼から長辺側銅板のメニスカス位置に流入する熱流束も示している。 Here, as a thermal load applied to the long side copper plate 11 (the width of the portion in contact with the molten steel is 900 mm) when continuous casting is performed at a casting speed of 1 m / min and 1.3 m / min while performing electromagnetic stirring, The heat flux flowing into the meniscus position of the long side copper plate 11 from the molten steel was measured. And, for example, starting from a contact portion between the long side copper plate 11 and the short side copper plate 13 (the width of the portion contacting the molten steel is 250 mm) from the one end side to the other end side of the long side copper plate 11 FIG. 6 shows the value of the heat flux at each part on the meniscus position toward the center. FIG. 6 also shows the heat flux flowing from the molten steel to the meniscus position of the long side copper plate when continuous casting is performed at a casting speed of 1.3 m / min without electromagnetic stirring.

図6に示すように、電磁撹拌を行わない場合、鋳型10内の溶鋼に旋回流が形成されないため、溶鋼から長辺側銅板11への熱伝達係数は長辺側銅板11の幅方向に対して一定となる。このため、長辺側銅板11の一端側から他端側に向かうメニスカス位置上での各部位における熱流束は一定(約205kcal/m2 /hr)となる。
一方、電磁撹拌を行いながら鋳造速度を1.3m/分として連続鋳造を行った場合、鋳型10内の溶鋼に旋回流が形成され、長辺側銅板11の内側面の特定部位に旋回流が衝突するようになる。このため、特定部位においては溶鋼から長辺側銅板11への熱伝達係数が増加し、溶鋼から長辺側銅板11のメニスカス位置の特定部位に流入する熱流束は増加している。図6から推定される熱流束の最大値は約247kcal/m2 /hrで、長辺側銅板11のメニスカス位置上で短辺側銅板13から約274mmの位置となる。なお、短辺側銅板13との当接部から約274mmの位置は旋回流が強く衝突する長辺側銅板11の内側面上の特定部位にほぼ一致する。また、長辺側銅板11と短辺側銅板13、14との各当接部近傍では顕著な旋回流が形成されないため、熱流束は電磁撹拌を行わない場合の熱流束の値に近づく。
As shown in FIG. 6, when electromagnetic stirring is not performed, a swirl flow is not formed in the molten steel in the mold 10, so the heat transfer coefficient from the molten steel to the long side copper plate 11 is in the width direction of the long side copper plate 11. Constant. For this reason, the heat flux at each part on the meniscus position from the one end side to the other end side of the long side copper plate 11 is constant (about 205 kcal / m 2 / hr).
On the other hand, when continuous casting is performed at a casting speed of 1.3 m / min while performing electromagnetic stirring, a swirl flow is formed in the molten steel in the mold 10, and a swirl flow is generated at a specific portion on the inner surface of the long side copper plate 11. It becomes a collision. For this reason, in a specific part, the heat transfer coefficient from molten steel to the long side copper plate 11 increases, and the heat flux flowing from the molten steel into the specific part at the meniscus position of the long side copper plate 11 increases. The maximum value of the heat flux estimated from FIG. 6 is about 247 kcal / m 2 / hr, which is a position about 274 mm from the short side copper plate 13 on the meniscus position of the long side copper plate 11. In addition, the position of about 274 mm from the contact portion with the short side copper plate 13 substantially coincides with a specific part on the inner side surface of the long side copper plate 11 where the swirl flow strongly collides. Moreover, since a remarkable swirl flow is not formed in the vicinity of each contact portion between the long side copper plate 11 and the short side copper plates 13 and 14, the heat flux approaches the value of the heat flux when electromagnetic stirring is not performed.

また、電磁撹拌を行いながら鋳造速度を1m/分として連続鋳造を行った場合、鋳型10内の溶鋼には鋳造速度が1.3m/分の場合と同等の速さの溶鋼の旋回流が形成されるが、鋳造速度が遅いため鋳型10内に注湯される単位時間当たりの溶鋼量が少なく、鋳型10内に供給される単位時間当たりの総熱量も低下する。
このため、図6に示すように、長辺側銅板11の内側面上の特定部位に旋回流が衝突して熱伝達係数が増加しても、溶鋼から長辺側銅板11のメニスカス位置の特定部位に流入する熱流束は大きく増加しない。従って、溶鋼から長辺側銅板に流入する熱流束が大きくなるような鋳造条件の場合では、鋳造速度を遅くすることで、長辺側銅板に流入する熱流束の増加を抑制できることが確認できた。
なお、鋳造速度を1m/分とすることで、図6から推定される熱流束の最大値は約223kcal/m2 /hrとなり、熱流束を鋳造速度を1.3m/分の場合に比較して約10%低減できた。また、熱流束が最大になる部位は、長辺側銅板11のメニスカス位置上で短辺側銅板13から約317mmの位置となる。この部位は旋回流が強く衝突する長辺側銅板11の内側面上の特定部位にほぼ一致する。
In addition, when continuous casting is performed at a casting speed of 1 m / min with electromagnetic stirring, a molten steel swirling flow is formed in the molten steel in the mold 10 at the same speed as when the casting speed is 1.3 m / min. However, since the casting speed is low, the amount of molten steel poured into the mold 10 is small, and the total heat amount per unit time supplied into the mold 10 also decreases.
For this reason, as shown in FIG. 6, even if a swirl flow collides with a specific part on the inner side surface of the long side copper plate 11 and the heat transfer coefficient increases, the meniscus position of the long side copper plate 11 is specified from the molten steel. The heat flux flowing into the site does not increase greatly. Therefore, in the case of casting conditions in which the heat flux flowing from the molten steel into the long side copper plate becomes large, it was confirmed that the increase in the heat flux flowing into the long side copper plate can be suppressed by slowing the casting speed. .
By setting the casting speed to 1 m / min, the maximum value of the heat flux estimated from FIG. 6 is about 223 kcal / m 2 / hr, and the heat flux is compared with the case where the casting speed is 1.3 m / min. About 10%. Further, the portion where the heat flux is maximized is a position of about 317 mm from the short side copper plate 13 on the meniscus position of the long side copper plate 11. This part substantially coincides with a specific part on the inner surface of the long side copper plate 11 where the swirl flow strongly collides.

以上のことから、電磁撹拌により長辺側銅板11、12に加わる熱負荷が増大するような場合では、鋳造速度を調整することにより鋳型10内に供給される溶鋼量を調整し、鋳型10内に供給される総熱量を制限することで、長辺側銅板11、12に加わる熱負荷が上昇するのを防止する。その結果、ニッケル−亜鉛系の低融点合金を起点としてヒートクラックが発生しても、ヒートクラックの成長を抑制することができる。
ここで、鋳造速度は0.6m/分以上で2.5m/分以下、好ましくは0.6m/分以上で2.1m/分以下にするのがよい。鋳造速度が0.6m/分未満では長辺側銅板に加わる熱負荷が低下する点では好ましいが、生産性が大きく低下するので好ましくない。また、鋳造速度が2.5m/分を超えると、長辺側銅板に加わる熱負荷が大きく増加するので好ましくない。
From the above, in the case where the thermal load applied to the long side copper plates 11 and 12 is increased by electromagnetic stirring, the amount of molten steel supplied into the mold 10 is adjusted by adjusting the casting speed, By restricting the total amount of heat supplied to, the heat load applied to the long side copper plates 11 and 12 is prevented from increasing. As a result, even if a heat crack occurs starting from a nickel-zinc based low melting point alloy, the growth of the heat crack can be suppressed.
Here, the casting speed is 0.6 m / min or more and 2.5 m / min or less, preferably 0.6 m / min or more and 2.1 m / min or less. If the casting speed is less than 0.6 m / min, it is preferable in that the thermal load applied to the long side copper plate is reduced, but it is not preferable because the productivity is greatly reduced. On the other hand, when the casting speed exceeds 2.5 m / min, the heat load applied to the long side copper plate is greatly increased, which is not preferable.

更に、所定数のキャスト毎、例えば、取鍋からタンディッシュに溶鋼が供給される毎に、磁撹拌装置のコイル部18、19に流す電流の方向を逆にすると共に、分割コイル21、22に流す電流値を分割コイル20、23に流す電流値より大きく設定する。これによって、図4(B)に示すように、鋳型10内の水平面内で左まわりの溶鋼の旋回流を形成できる。
このとき、分割コイル21、22に流す電流値を分割コイル20、23に流す電流値より大きく設定しているので、長辺側銅板11では他端側から一端側に向けて、長辺側銅板12は一端側から他端側に向けて、前半は大きな駆動力で溶鋼を移動させ後半は小さな駆動力で溶鋼を移動させることができる。このため、鋳型10内に左まわりの均一な溶鋼の旋回流を形成することができる。このとき、長辺側銅板11では他端側に、長辺側銅板12では一端側に溶鋼流を強く衝突するようにすることができる。その結果、右まわり及び左まわりの各旋回流を形成した際に、熱負荷の高い部位の発生する位置を変えることができ、長辺側銅板11、12内の特定部位に熱負荷が集中するのを防止できる。このため、ヒートクラックの発生を抑制できると共に、ヒートクラックが発生しても、ヒートクラックの成長を抑制することができる。
Furthermore, every time a predetermined number of casts, for example, every time molten steel is supplied from the ladle to the tundish, the direction of the current flowing through the coil portions 18 and 19 of the magnetic stirrer is reversed, and The current value to be passed is set to be larger than the current value to be passed through the split coils 20 and 23. As a result, as shown in FIG. 4B, a swirling flow of the counterclockwise molten steel can be formed in the horizontal plane in the mold 10.
At this time, since the current value flowing through the split coils 21 and 22 is set larger than the current value flowing through the split coils 20 and 23, the long side copper plate 11 extends from the other end side to the one end side in the long side copper plate 11. 12, the first half can move the molten steel with a large driving force, and the second half can move the molten steel with a small driving force from one end side to the other end side. For this reason, it is possible to form a uniform swirling flow of the left-handed molten steel in the mold 10. At this time, the molten steel flow can strongly collide with the other end side in the long side copper plate 11 and the one end side with the long side copper plate 12. As a result, when the clockwise and counterclockwise swirl flows are formed, the position where the high heat load is generated can be changed, and the heat load is concentrated on a specific part in the long side copper plates 11 and 12. Can be prevented. For this reason, generation | occurrence | production of a heat crack can be suppressed, and even if a heat crack generate | occur | produces, the growth of a heat crack can be suppressed.

次に、本発明の作用効果を確認するために行った実施例について説明する。
ここで、図7はモールドフラックス中の亜鉛含有量と長辺側銅板の寿命指数及び鋳片表面疵発生指数との関係を示す説明図、図8はモールドフラックス中の亜鉛含有量及び鋳造条件と長辺側銅板の寿命指数との関係を示す説明図、図9はモールドフラックス中の亜鉛含有量及び鋳造条件と鋳片表面疵発生指数との関係を示す説明図、図10はチャージ数で示した鋳型の使用回数と鋳型内面に発生した損傷程度の関係を示す説明図である。
Next, examples carried out for confirming the effects of the present invention will be described.
Here, FIG. 7 is an explanatory view showing the relationship between the zinc content in the mold flux, the life index of the long side copper plate, and the slab surface flaw occurrence index, and FIG. 8 shows the zinc content in the mold flux and the casting conditions. FIG. 9 is an explanatory diagram showing the relationship between the life index of the long side copper plate, FIG. 9 is an explanatory diagram showing the relationship between the zinc content in the mold flux and casting conditions, and the slab surface flaw occurrence index, and FIG. 10 is the number of charges. It is explanatory drawing which shows the relationship between the frequency | count of the usage of the mold used, and the extent of the damage which generate | occur | produced on the mold inner surface.

[試験例1]
浸漬ノズルの溶鋼吐出孔の傾斜角度を水平方向に対して下向き15°に設定して鋳型に溶鋼を供給し、電磁撹拌を行いながら鋳造速度1.2m/分の鋳造条件下で、亜鉛の含有量が50〜300ppmのモールドフラックスを使用して連続鋳造を行ない、長辺側銅板の寿命及び得られた鋳片の表面疵発生割合を調査した。その結果を図7に示す。なお、図7では、長辺側銅板の寿命及び得られた鋳片の表面疵発生割合を、亜鉛の含有量が250ppmのモールドフラックスを使用した際に得られた長辺側銅板の寿命及び表面疵発生割合を基準にした指数で表示している。
[Test Example 1]
Incorporation of zinc under casting conditions of 1.2 m / min while supplying molten steel to the mold with the tilt angle of the molten steel discharge hole of the immersion nozzle set to 15 ° downward with respect to the horizontal direction and electromagnetic stirring Continuous casting was performed using a mold flux having an amount of 50 to 300 ppm, and the life of the long side copper plate and the surface flaw generation rate of the obtained slab were investigated. The result is shown in FIG. In FIG. 7, the life of the long side copper plate and the surface flaw occurrence ratio of the obtained slab are shown as the life and surface of the long side copper plate obtained when using a mold flux with a zinc content of 250 ppm. It is displayed as an index based on the percentage of wrinkles.

図7に示すように、モールドフラックスの亜鉛含有量を200ppm以下にすることで、ニッケル−亜鉛系の低融点合金の生成量が少なくなり、低融点合金を起点とするヒートクラックの発生が抑制されて、長辺側銅板の寿命が大幅に延長されることが確認できた。また、低融点合金の生成量が少なくなるため、低融点合金の溶鋼中への溶出量が低下しメッキ層の肌荒れが少なくなる。その結果、ヒートクラックの発生とメッキ層の肌荒れを有する損傷が軽微となり、鋳片の表面における疵発生割合も大幅に低下し鋳片の表面品質向上が確認できた。 As shown in FIG. 7, when the zinc content of the mold flux is 200 ppm or less, the amount of nickel-zinc based low melting point alloy is reduced, and the occurrence of heat cracks starting from the low melting point alloy is suppressed. As a result, it was confirmed that the life of the long side copper plate was greatly extended. Moreover, since the production amount of the low melting point alloy is reduced, the elution amount of the low melting point alloy into the molten steel is reduced, and the roughness of the plating layer is reduced. As a result, the occurrence of heat cracks and damage with rough skin of the plating layer became minor, the rate of occurrence of flaws on the surface of the slab was significantly reduced, and it was confirmed that the surface quality of the slab was improved.

[試験例2]
亜鉛の含有量が50〜250ppmのモールドフラックスを使用し、浸漬ノズルの溶鋼吐出孔の傾斜角度を水平方向に対して上向き5°から下向き45°の範囲に設定して、電磁撹拌を行いながら鋳造速度0.8〜1.2m/分の鋳造条件下で連続鋳造を行った。そのとき得られた長辺側銅板の寿命及び鋳片の表面疵発生割合と、モールドフラックス中の亜鉛含有量及び鋳造条件の関係を図8及び図9に示す。
なお、図8及び図9では、長辺側銅板の寿命及び得られた鋳片の表面疵発生割合を、亜鉛の含有量が250ppmのモールドフラックスを使用し、溶鋼吐出孔の傾斜角度を水平方向に対して下向き15°、鋳造速度1.2m/分の鋳造条件の際に得られた長辺側銅板の寿命及び表面疵発生割合を基準にした指数で表示している。
[Test Example 2]
Casting with electromagnetic stirring while using mold flux with zinc content of 50-250ppm and setting the tilt angle of molten steel discharge hole of immersion nozzle in the range of 5 ° upward to 45 ° downward with respect to the horizontal direction Continuous casting was performed under casting conditions at a speed of 0.8 to 1.2 m / min. FIG. 8 and FIG. 9 show the relationship between the life of the long side copper plate obtained at that time and the surface flaw generation ratio of the slab, the zinc content in the mold flux, and the casting conditions.
In FIGS. 8 and 9, the life of the long side copper plate and the surface flaw occurrence ratio of the obtained slab are measured using a mold flux having a zinc content of 250 ppm, and the inclination angle of the molten steel discharge hole is set in the horizontal direction. The index is based on the life of the copper plate on the long side obtained under casting conditions of 15 ° downward and casting speed of 1.2 m / min and the rate of occurrence of surface defects.

モールドフラックス中の亜鉛含有量が低減するのに加えて、浸漬ノズルの溶鋼吐出孔の傾斜角度が水平方向に対して下向きになる程、更に、鋳造速度が遅くなる程、長辺側銅板の寿命が大幅に延長され、鋳片の表面における疵発生割合も大幅に低下することが確認できた。
従って、溶鋼吐出孔の中心軸の傾斜角度を水平方向に対して下向きに設定して溶鋼湯面の変動を抑制し長辺側銅板におけるメニスカス位置の近傍での熱負荷の低減を図ると共に、鋳造速度を調整することにより供給される溶鋼量を調整して鋳型内に供給される総熱量を制限することで長辺側銅板に加わる熱負荷の上昇を防止できることが判明した。
In addition to reducing the zinc content in the mold flux, the longer the copper angle of the molten steel discharge hole of the immersion nozzle is downward with respect to the horizontal direction, and the slower the casting speed is, the longer the copper plate life is. As a result, it was confirmed that the ratio of flaws on the surface of the slab was greatly reduced.
Therefore, the inclination angle of the central axis of the molten steel discharge hole is set downward with respect to the horizontal direction to suppress the fluctuation of the molten steel surface, thereby reducing the thermal load in the vicinity of the meniscus position on the long side copper plate and casting. It has been found that an increase in the heat load applied to the long side copper plate can be prevented by adjusting the amount of molten steel supplied by adjusting the speed and limiting the total amount of heat supplied into the mold.

[試験例3]
ニッケルとコバルトの複合メッキ層が形成されたモールド銅板を使用した鋳型を用いて、亜鉛の含有量が150ppmのモールドフラックスを使用し、浸漬ノズルの溶鋼吐出孔の傾斜角度を水平方向に対して下向き15°に設定して、電磁撹拌を行って右まわりの旋回流を形成しながら鋳造速度1.2m/分の鋳造条件下で連続鋳造を繰り返し行った。そのとき、長辺側銅板において、溶鋼のメニスカス位置の近傍で、溶鋼の旋回流が強く衝突する部位に発生した損傷を、ヒートクラックの長さとメッキ層の肌荒れの窪み深さの総和で評価した。その結果を図10において○印で示す。なお、図10では、連続鋳造の回数を取鍋から溶鋼がタンディッシュに供給される回数(チャージ数)で示している。チャージ数の増加に伴って、ヒートクラックの長さと窪み深さの総和は増加し、500チャージで3〜5mm、650チャージで4.6〜6mmとなっている。
また、同一の鋳型、モールドフラックス、及び浸漬ノズルを使用し、電磁撹拌で形成する旋回流の方向を1チャージ毎に逆転しながら鋳造速度1.2m/分の鋳造条件下で600チャージ数の連続鋳造を繰り返し行って、ヒートクラックの長さ及び窪み深さの総和とチャージ数の関係を求めた。その結果を図10において●印で示す。
[Test Example 3]
Using a mold using a mold copper plate with a composite plating layer of nickel and cobalt, using a mold flux with a zinc content of 150 ppm, the tilt angle of the molten steel discharge hole of the immersion nozzle is downward with respect to the horizontal direction. Continuous casting was repeatedly performed under casting conditions of 1.2 m / min while setting the angle to 15 ° and forming a clockwise swirling flow by electromagnetic stirring. At that time, in the long side copper plate, in the vicinity of the meniscus position of the molten steel, the damage that occurred at the site where the swirling flow of the molten steel collides strongly was evaluated by the sum of the length of the heat crack and the depth of the rough surface of the plating layer. . The result is indicated by a circle in FIG. In addition, in FIG. 10, the frequency | count of continuous casting is shown by the frequency | count (charge number) by which molten steel is supplied to a tundish from a ladle. As the number of charges increases, the sum of the length of heat cracks and the depth of the dent increases, and is 3 to 5 mm for 500 charges and 4.6 to 6 mm for 650 charges.
In addition, using the same mold, mold flux, and immersion nozzle, the number of continuous charges of 600 charges under a casting condition of 1.2 m / min is performed while reversing the direction of the swirl flow formed by electromagnetic stirring for each charge. The casting was repeated, and the relationship between the total number of heat cracks and the depth of the depression and the number of charges was determined. The result is indicated by the mark ● in FIG.

図10に示すように、電磁撹拌で形成する旋回流の方向を1チャージ毎に逆転した場合、ヒートクラックの長さと窪み深さの総和は、600チャージで平均1.7mmであるのに対して、電磁撹拌で形成する旋回流の方向を変えない場合、600チャージで4.5mm程度と推定され、電磁撹拌で形成する旋回流の方向を逆転することで、長辺側銅板に発生する損傷を小さくすることが確認できた。
従って、旋回流が長辺側銅板に衝突する位置を変えることで、長辺側銅板の特定部位に熱負荷が集中するのを防止でき、ヒートクラック及び肌荒れの成長を抑制できることが判明した。なお、鋳造速度を0.6m/分及び2.1m/分にした場合についても鋳造を行ったが、前記と同様の傾向が得られた。
As shown in FIG. 10, when the direction of the swirl flow formed by electromagnetic stirring is reversed for each charge, the total length of heat cracks and the depth of the depression is 1.7 mm on average for 600 charges. When the direction of the swirl flow formed by electromagnetic stirring is not changed, it is estimated that the charge is about 4.5 mm at 600 charges. By reversing the direction of the swirl flow formed by electromagnetic stirring, the long side copper plate is damaged. It was confirmed to make it smaller.
Therefore, it has been found that by changing the position where the swirling flow collides with the long side copper plate, it is possible to prevent the heat load from being concentrated on a specific part of the long side copper plate and to suppress the growth of heat cracks and rough skin. In addition, although it cast also about the case where casting speed was 0.6 m / min and 2.1 m / min, the same tendency as the above was acquired.

以上、本発明の実施の形態を説明したが、本発明は、この実施の形態に限定されるものではなく、発明の要旨を変更しない範囲での変更は可能であり、前記したそれぞれの実施の形態や変形例の一部又は全部を組み合わせて本発明の鋼の連続鋳造方法を構成する場合も本発明の権利範囲に含まれる。
例えば、本実施の形態では鋳型の内側にニッケルを主体とするメッキ層が形成されたモールド銅板を有する鋳型について説明したが、鋳型の内側にコバルトを主体とするメッキ層、あるいはニッケルとコバルトの複合メッキ層が形成されたモールド銅板を有する鋳型を使用することもできる。
また、本実施の形態では電磁力により鋳型内の溶鋼を撹拌する場合について説明したが、鋳型内の溶鋼を電磁撹拌しない場合についても発生するヒートクラックや肌荒れを抑制することができ、モールド銅板の寿命向上及び鋳片表面における疵発生頻度の低下を図ることができる。
更に、電磁撹拌で鋳型内に形成する旋回流の方向を1チャージの溶鋼量のキャストが終了する毎に逆転させたが、2チャージ以上の溶鋼量のキャストが終了する毎に鋳型内の旋回流の方向を逆転させるようにしてもよい。
As mentioned above, although embodiment of this invention was described, this invention is not limited to this embodiment, The change in the range which does not change the summary of invention is possible, Each above-mentioned embodiment is possible. The case where the method for continuous casting of steel of the present invention is configured by combining some or all of the forms and modifications is also included in the scope of the present invention.
For example, in the present embodiment, a mold having a mold copper plate in which a plating layer mainly composed of nickel is formed inside the mold has been described. However, a plating layer mainly composed of cobalt or a composite of nickel and cobalt is disposed inside the mold. A mold having a molded copper plate on which a plated layer is formed can also be used.
In the present embodiment, the case where the molten steel in the mold is agitated by electromagnetic force has been described, but heat cracks and rough skin that occur even when the molten steel in the mold is not electromagnetically agitated can be suppressed. It is possible to improve the life and reduce the frequency of occurrence of flaws on the surface of the slab.
Further, the direction of the swirling flow formed in the mold by electromagnetic stirring was reversed every time the casting of the molten steel amount of one charge was completed, but the swirling flow in the mold was finished every time the casting of the molten steel amount of two charges or more was completed. The direction may be reversed.

本発明の一実施の形態に係る鋼の連続鋳造方法に適用した鋳型の一部省略正断面図である。It is a partial omission front sectional view of the casting_mold | template applied to the continuous casting method of steel which concerns on one embodiment of this invention. 同鋼の連続鋳造方法に適用した鋳型の一部省略側断面図である。It is a partial omission side sectional view of a mold applied to the continuous casting method of the steel. 同鋼の連続鋳造方法に適用した鋳型の平面図である。It is a top view of the casting_mold | template applied to the continuous casting method of the steel. (A)、(B)は鋳型内の溶鋼の旋回方向を逆転した際の説明図である。(A), (B) is explanatory drawing at the time of reversing the turning direction of the molten steel in a casting_mold | template. 同鋼の連続鋳造方法に適用した鋳型に発生する損傷位置の説明図である。It is explanatory drawing of the damage position which generate | occur | produces in the casting_mold | template applied to the continuous casting method of the steel. 同鋼の連続鋳造方法に適用した鋳型の長辺側銅板の内側面における熱流束の変化を示す説明図である。It is explanatory drawing which shows the change of the heat flux in the inner surface of the long side copper plate of the casting_mold | template applied to the continuous casting method of the steel. モールドフラックス中の亜鉛含有量と長辺側銅板の寿命指数及び鋳片表面疵発生指数との関係を示す説明図である。It is explanatory drawing which shows the relationship between the zinc content in a mold flux, the life index of a long side copper plate, and a slab surface flaw occurrence index. モールドフラックス中の亜鉛含有量及び鋳造条件と長辺側銅板の寿命指数との関係を示す説明図である。It is explanatory drawing which shows the relationship between the zinc content in a mold flux, casting conditions, and the life index of a long side copper plate. モールドフラックス中の亜鉛含有量及び鋳造条件と鋳片表面疵発生指数との変化を示す説明図である。It is explanatory drawing which shows the change of zinc content and casting conditions in a mold flux, and a slab surface flaw generation index. チャージ数で示した鋳型の使用回数と鋳型内面に発生した損傷程度の関係を示す説明図である。It is explanatory drawing which shows the relationship between the frequency | count of use of the casting_mold | template shown with the number of charges, and the damage grade which generate | occur | produced in the casting_mold | template inner surface.

符号の説明Explanation of symbols

10:鋳型、11、12:長辺側銅板、13、14:短辺側銅板、16:メッキ層、17:空間部、18、19:コイル部、20、21、22、23:分割コイル、24:浸漬ノズル、25:モールドフラックス、26:溶融層、27:凝固殻、28:溶鋼吐出孔 10: mold, 11, 12: long side copper plate, 13, 14: short side copper plate, 16: plating layer, 17: space portion, 18, 19: coil portion, 20, 21, 22, 23: split coil 24: immersion nozzle, 25: mold flux, 26: molten layer, 27: solidified shell, 28: molten steel discharge hole

Claims (3)

内側にニッケル及びコバルトのいずれか一方又は双方を主体とするメッキ層が形成されたモールド銅板を有する鋳型内に、浸漬ノズルを介して溶鋼を順次注湯して、前記鋳型内の溶鋼の湯面をモールドフラックスで常時覆いながら該鋳型内で溶鋼を凝固させる連続鋳造方法において、
前記モールドフラックスに含有される亜鉛量を200ppm以下にし、前記浸漬ノズルに形成された溶鋼吐出孔の中心軸の傾斜角度を水平方向に対して上向き5°以下で下向き45°以下の範囲に設定すると共に、前記モールド銅板に加わる熱負荷に応じて鋳造速度を調整することを特徴とする鋼の連続鋳造方法。
Molten steel is sequentially poured through a dipping nozzle into a mold having a mold copper plate on which an inner plating layer mainly composed of one or both of nickel and cobalt is formed, and a molten metal surface of the molten steel in the mold. In a continuous casting method in which molten steel is solidified in the mold while always covering with mold flux,
The amount of zinc contained in the mold flux is set to 200 ppm or less, and the inclination angle of the central axis of the molten steel discharge hole formed in the immersion nozzle is set to a range of 5 ° or less upward and 45 ° or less downward with respect to the horizontal direction. In addition, a continuous casting method of steel, wherein a casting speed is adjusted according to a thermal load applied to the molded copper plate.
請求項1記載の鋼の連続鋳造方法において、前記鋳型内の溶鋼に電磁力を付与して該鋳型内で溶鋼を旋回させることを特徴とする鋼の連続鋳造方法。 2. The steel continuous casting method according to claim 1, wherein an electromagnetic force is applied to the molten steel in the mold to turn the molten steel in the mold. 請求項2記載の鋼の連続鋳造方法において、前記鋳型内の溶鋼の旋回方向を所定数のキャスト毎に逆転することを特徴とする鋼の連続鋳造方法。 3. The steel continuous casting method according to claim 2, wherein the swirling direction of the molten steel in the mold is reversed every predetermined number of casts.
JP2004318277A 2004-11-01 2004-11-01 Steel continuous casting method Active JP4303670B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP2004318277A JP4303670B2 (en) 2004-11-01 2004-11-01 Steel continuous casting method

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2004318277A JP4303670B2 (en) 2004-11-01 2004-11-01 Steel continuous casting method

Publications (2)

Publication Number Publication Date
JP2006122995A true JP2006122995A (en) 2006-05-18
JP4303670B2 JP4303670B2 (en) 2009-07-29

Family

ID=36718218

Family Applications (1)

Application Number Title Priority Date Filing Date
JP2004318277A Active JP4303670B2 (en) 2004-11-01 2004-11-01 Steel continuous casting method

Country Status (1)

Country Link
JP (1) JP4303670B2 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008183601A (en) * 2007-01-31 2008-08-14 Jfe Steel Kk Continuous casting method of steel, and method for manufacturing hot-dipping galvanized steel sheet

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2008183601A (en) * 2007-01-31 2008-08-14 Jfe Steel Kk Continuous casting method of steel, and method for manufacturing hot-dipping galvanized steel sheet

Also Published As

Publication number Publication date
JP4303670B2 (en) 2009-07-29

Similar Documents

Publication Publication Date Title
JP5692451B2 (en) Continuous casting mold and steel continuous casting method
JP4337565B2 (en) Steel slab continuous casting method
RU2677560C2 (en) Mold for continuous casting machine and continuous casting method for steel
JP6003850B2 (en) Manufacturing method of continuous casting mold and continuous casting method of steel
JP6044614B2 (en) Steel continuous casting method
JP5962733B2 (en) Steel continuous casting method
JP6003851B2 (en) Continuous casting mold and steel continuous casting method
JP6365604B2 (en) Steel continuous casting method
KR102245010B1 (en) Method for continuous casting of steel
JP4303670B2 (en) Steel continuous casting method
JP2011189356A (en) Method and apparatus for twin-roll casting
CN109689247B (en) Method for continuously casting steel
JP2018149602A (en) Method for continuously casting steel
JP6428721B2 (en) Continuous casting mold and steel continuous casting method
JP6801378B2 (en) Molding device for continuous casting of steel and manufacturing method of surface modified slab using it
JP2010207820A (en) Method for continuously casting slab
JP6787359B2 (en) Continuous steel casting method
JPH1058093A (en) Method for continuously casting steel
JP2016168610A (en) Steel continuous casting method
JP3610871B2 (en) Continuous casting method of steel
EP0780176A2 (en) Apparatus for and process of continuous casting
JP2011251291A (en) Secondary cooling and secondary cooling equipment in continuous casting
JP2021079418A (en) Twin-roll-type continuous casting apparatus, and twin-roll-type continuous casting method
JP2002126854A (en) Mold for continuous casting
JP2005238318A (en) Apparatus and method for continuously casting steel

Legal Events

Date Code Title Description
A621 Written request for application examination

Free format text: JAPANESE INTERMEDIATE CODE: A621

Effective date: 20060905

A977 Report on retrieval

Free format text: JAPANESE INTERMEDIATE CODE: A971007

Effective date: 20080129

A131 Notification of reasons for refusal

Free format text: JAPANESE INTERMEDIATE CODE: A131

Effective date: 20080205

A521 Written amendment

Free format text: JAPANESE INTERMEDIATE CODE: A523

Effective date: 20080401

TRDD Decision of grant or rejection written
A01 Written decision to grant a patent or to grant a registration (utility model)

Free format text: JAPANESE INTERMEDIATE CODE: A01

Effective date: 20090414

A01 Written decision to grant a patent or to grant a registration (utility model)

Free format text: JAPANESE INTERMEDIATE CODE: A01

A61 First payment of annual fees (during grant procedure)

Free format text: JAPANESE INTERMEDIATE CODE: A61

Effective date: 20090424

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20120501

Year of fee payment: 3

R151 Written notification of patent or utility model registration

Ref document number: 4303670

Country of ref document: JP

Free format text: JAPANESE INTERMEDIATE CODE: R151

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20120501

Year of fee payment: 3

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20130501

Year of fee payment: 4

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20130501

Year of fee payment: 4

S531 Written request for registration of change of domicile

Free format text: JAPANESE INTERMEDIATE CODE: R313531

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20130501

Year of fee payment: 4

R350 Written notification of registration of transfer

Free format text: JAPANESE INTERMEDIATE CODE: R350

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20130501

Year of fee payment: 4

S533 Written request for registration of change of name

Free format text: JAPANESE INTERMEDIATE CODE: R313533

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20130501

Year of fee payment: 4

R350 Written notification of registration of transfer

Free format text: JAPANESE INTERMEDIATE CODE: R350

FPAY Renewal fee payment (event date is renewal date of database)

Free format text: PAYMENT UNTIL: 20140501

Year of fee payment: 5

S533 Written request for registration of change of name

Free format text: JAPANESE INTERMEDIATE CODE: R313533

R350 Written notification of registration of transfer

Free format text: JAPANESE INTERMEDIATE CODE: R350