JP3505077B2 - Continuous casting method of slab with few inclusions - Google Patents
Continuous casting method of slab with few inclusionsInfo
- Publication number
- JP3505077B2 JP3505077B2 JP03851298A JP3851298A JP3505077B2 JP 3505077 B2 JP3505077 B2 JP 3505077B2 JP 03851298 A JP03851298 A JP 03851298A JP 3851298 A JP3851298 A JP 3851298A JP 3505077 B2 JP3505077 B2 JP 3505077B2
- Authority
- JP
- Japan
- Prior art keywords
- molten steel
- magnetic field
- inclusions
- slab
- mold
- 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.)
- Expired - Lifetime
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- Continuous Casting (AREA)
Description
【発明の詳細な説明】
【０００１】
【発明の属する技術分野】本発明方法は、介在物の少な
い鋳片の連続鋳造方法に関するものである。
【０００２】
【従来の技術】溶鋼の連続鋳造に際し、タンディシュか
ら浸漬ノズルを介して鋳型内へ注入する溶鋼流へ鋳型両
長辺外部から静磁場を付与する電磁ブレーキ作用によっ
て、鋳型内の溶鋼流動を減衰させ鋳片内部への介在物の
捕捉を減少させることが特開平２−２８４７５０号公報
に開示されている。また、電磁ブレーキと電磁攪拌を併
用して、鋳片内部への介在物の捕捉を減少させることが
特開昭６３−１１９９５９号公報及び特開昭６１−２５
５７４９号公報に開示されている。
【０００３】
【発明が解決しようとする課題】上記のごとく、電磁ブ
レーキによって鋳型内へ浸漬ノズルから吐出される溶鋼
流動を減衰させると、溶鋼流動によっては、電磁ブレー
キによって連続鋳造機の深部へ侵入する溶鋼流動を減衰
させて介在物の侵入を抑制しているにもかかわらず、鋳
片内に介在物が多く捕捉されることがあり、鋼製品の品
質を著しく低下させることがある。このような介在物の
捕捉を減少させるために、電磁ブレーキより下方の鋳型
直下に電磁攪拌装置を設置し、溶鋼に上向きの流動を与
えることが特開昭６１−２５５７４９号公報に開示され
ているが、このような方法では、設備費がかかるうえに
攪拌する際の電力がかかりコストを上昇させることにな
る等の課題がある。本発明方法は、このような課題を有
利に解決するためになされたものであり、確実に鋳型内
注入溶鋼の吐出流れを適正な状態に抑制することによっ
て、介在物の鋳片内部への捕捉を抑制することのできる
静磁場を付与する方法を提供することを目的とするもの
である。
【０００４】
【課題を解決するための手段】本発明方法の特徴とする
ところは、タンディシュから浸漬ノズルを介して鋳型内
へ溶鋼を注入し、連続鋳造するに際して、浸漬ノズルか
ら吐出する溶鋼流へ、下記数式を満足する静磁場を付与
しつつ、鋳造することを特徴とする介在物の少ない鋳片
の連続鋳造方法である。
【数２】
但し Ｎ：スチュワート数、σ：電気伝導度、Ｂ：磁場
強度、Ｌ：鋳片厚、ρ：密度、Ｖ：速度（磁場帯上端で
の溶鋼流速）。
【０００５】
【発明の実施の形態】鋳型内へ注入する溶鋼流動による
鋳片内への溶鋼中介在物の捕捉抑制は、鋳型内の溶鋼吐
出流れを完全に均一化することによって、介在物の捕捉
を抑制できるものと考えられていたが、本発明者等の種
々実験結果から、ある程度の流速を保持しつつ、注入す
るように磁場強度を制御することによって、介在物の捕
捉を確実に抑制できることが明らかになった。即ち、鋳
型内の注入溶鋼の下降流速が小さくなると、図１に示す
ごとく（鋳片厚１７０ｍｍ、鋳片巾８００ｍｍ、注入溶
鋼量０．７ｔ／分、鋳造速度０．７〜１．０ｍ／分、磁
場付与位置鋳型内溶鋼表面下６００ｍｍ）介在物が集積
する。図示のように磁場０．５Ｔ、下向き４５°の溶鋼
吐出流の場合には、鋳片表面より２０〜３０ｍｍの磁場
コイルの直下に相当する位置の介在物の集積が認められ
るが、溶鋼吐出流が均一化されていないときは、磁場直
下に相当する位置の介在物集積はほとんど無くなる。
【０００６】このことは、ある程度の溶鋼下降流が存在
していることにより、下降流が鋳型巾方向中央部で上昇
流を形成して、介在物を浮上させることができるものと
推定できる。磁場が強くなると、この溶鋼下降流は、減
少する。また、鋳造速度が遅くなると溶鋼下降流は減少
することが明らかになった。
【０００７】このようなことからローレンツ力と溶鋼流
の慣性力の相似則であるスチュワート数＝ローレンツ力
／慣性力＝σＢ２Ｌ／ρＶ〔Ｎ：スチュワート数、σ：
電気伝導度（Ω-1・ｍ-1）、Ｂ：磁場強度（Ｔ）、Ｌ：
鋳片厚（ｍ）、ρ：密度（kg・ｍ-3）、Ｖ：速度（ｍ・
ｓ-1）（磁場帯上端での溶鋼流速）〕を用いて、鋳造速
度、浸漬ノズル形状、吐出口角度、鋳片サイズ等によっ
て決まる溶鋼流速に応じて、スチュワート数が０.３〜
５の範囲を満足する磁場強度に保持しつつ、溶鋼を鋳型
内へ注入することによって、鋳片内への介在物捕捉を著
しく抑制することを開発したものである。
【０００８】上記スチュワート数が０.３未満である
と、吐出流の減衰が不充分となり電磁ブレーキより下方
の鋳型深部へ持ち込まれる介在物の量が増加するため
に、鋳片内に捕捉される介在物が増加する。また、スチ
ュワート数が５超になると、電磁ブレーキより下方の溶
鋼下降流が減少して、鋳型巾方向中央部での上昇流の形
成による介在物浮上効果が減少するとともに、下降流速
と介在物の浮上速度が同程度となり、介在物が滞留して
鋳片内に捕捉されることとなって好ましくない。
【０００９】磁場帯上端での溶鋼流速は、例えば鋳型内
に埋め込まれた電磁式流速計で直接測定した値を用いる
ことができる。また、数値計算によって鋳型内の溶鋼流
動をシュミレーションして求めた値を用いることができ
る。更に、既に知られている水力学的な検討から得られ
た式（鉄と鋼、第７８号（１９９２）第３号、４４１頁
に記載）により求めた値を用いることができる。これら
の方法によって求められる鋳造中の溶鋼流速の鋳造速度
や巾やノズル閉塞等によって生ずる偏流等による変化に
応じて、磁場強度を随時変化させることによってＮの値
を本発明方法の範囲内に制御しつつ、鋳造することが望
ましいが、各鋳造の代表的な条件を用いて求めた溶鋼流
速により磁場強度を決定することができる。
【００１０】
【実施例】次に、本発明方法の実施例を比較例とともに
挙げる。
【表１】【００１１】
【表２】（表１のつづき）【００１２】注１：鋳型への注入溶鋼は、Ｃ：０．０３
〜０．０４％、Ｓｉ：０．０１〜０．０３％、Ｍｎ：
０．１５〜０．３０％、Ｐ：０．００８〜０．０１２
％、Ｓ：０．００９〜０．０１３％、Ａｌ：０．０３〜
０．０６％、残りＦｅ及び不回避不純物。
注２：溶鋼注入位置は、鋳型内溶鋼表面下の距離。
注３：溶鋼注入角度は、下向きで、鋳型中央部から両巾
方向へ浸漬ノズルを介して注入した。
注４：静磁場付与位置は、鋳型内溶鋼表面下の距離で、
鋳型長辺両側から付与した。
注５：介在物個数は、鋳片からサンプルを切り出し、ス
ライム抽出法によって測定し、比較例６を１としたとき
の介在物個数を表示した。
注６：連続鋳造は、彎曲型鋳造装置で実施。
【００１３】
【発明の効果】本発明方法によれば、鋳造鋳片内への介
在物の捕捉を著しく抑制して鋼製品の品質を向上するこ
とができる。また、静磁場の制御によって介在物の捕捉
を抑制するため、既存の設備で正確にでき、工業的に安
価で、かつ確実に鋳片の介在物を減少することができる
等の優れた効果が得られる。Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for continuously casting a slab having few inclusions. 2. Description of the Related Art In continuous casting of molten steel, the flow of molten steel in the mold is controlled by an electromagnetic braking action that applies a static magnetic field from outside both long sides of the mold to the molten steel flow injected into the mold from a tundish through an immersion nozzle. Japanese Unexamined Patent Publication No. 2-284750 discloses a method for reducing the amount of inclusions in a slab by reducing the amount of inclusions. Also, it is disclosed in Japanese Patent Application Laid-Open Nos. 63-119959 and 61-25 by using electromagnetic brakes and electromagnetic stirring in combination to reduce inclusion of inclusions in the slab.
No. 5749. [0003] As described above, when the flow of molten steel discharged from the immersion nozzle into the mold is attenuated by the electromagnetic brake as described above, depending on the flow of molten steel, the molten steel flows into the deep portion of the continuous casting machine by the electromagnetic brake. Despite the fact that the flow of molten steel is attenuated and the intrusion of inclusions is suppressed, a large amount of inclusions may be trapped in the slab, and the quality of the steel product may be significantly reduced. Japanese Unexamined Patent Publication (Kokai) No. 61-255749 discloses that an electromagnetic stirrer is provided directly below a mold below an electromagnetic brake to give an upward flow to molten steel in order to reduce such inclusions. However, in such a method, there is a problem that the equipment cost is increased, the electric power at the time of stirring is increased, and the cost is increased. The method of the present invention has been made in order to advantageously solve such a problem, and by reliably suppressing the discharge flow of molten steel injected into a mold to an appropriate state, trapping of inclusions in a slab. It is an object of the present invention to provide a method of applying a static magnetic field capable of suppressing the occurrence of a static magnetic field. [0004] A feature of the method of the present invention is that molten steel is injected from a tundish into a mold through an immersion nozzle, and into a molten steel stream discharged from the immersion nozzle during continuous casting. A method for continuously casting a slab with few inclusions, characterized in that casting is performed while applying a static magnetic field satisfying the following formula. (Equation 2) Where N: Stewart number, σ: electric conductivity, B: magnetic field strength, L: slab thickness, ρ: density, V: velocity (fluid steel flow velocity at the upper end of the magnetic field band). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The suppression of the inclusion of inclusions in molten steel in a slab by the flow of molten steel injected into a mold is achieved by completely homogenizing the flow of molten steel in the mold. Although it was thought that the trapping could be suppressed, the results of various experiments by the present inventors have shown that by controlling the magnetic field intensity so as to inject while maintaining a certain flow rate, the trapping of inclusions is reliably suppressed. It became clear what we could do. That is, when the descending flow rate of the poured molten steel in the mold decreases, as shown in FIG. 1 (slab thickness 170 mm, slab width 800 mm, injected molten steel amount 0.7 t / min, casting speed 0.7 to 1.0 m / min. The magnetic field is applied at a position 600 mm below the surface of the molten steel in the mold. As shown in the figure, in the case of a molten steel discharge flow with a magnetic field of 0.5 T and a downward angle of 45 °, accumulation of inclusions corresponding to a position directly below the magnetic field coil of 20 to 30 mm from the slab surface is observed. Is not uniform, there is almost no inclusion accumulation at a position corresponding to immediately below the magnetic field. This is presumed to be due to the existence of a certain amount of downflow of molten steel, whereby the downflow forms an upflow at the center in the width direction of the mold, and the inclusions can float. When the magnetic field increases, the downflow of the molten steel decreases. It was also found that the lower the casting speed, the lower the downflow of molten steel. From the above, Stewart number = Lorentz force / inertial force = σB 2 L / ρV [N: Stewart number, σ: which is a similar rule between Lorentz force and inertia force of molten steel flow]
Electric conductivity (Ω -1 · m -1 ), B: magnetic field strength (T), L:
Slab thickness (m), ρ: density (kg · m -3 ), V: speed (m ·
s -1 ) (molten steel flow rate at the upper end of the magnetic field band)], the Stewart number is 0.3 to
The present invention has been developed to remarkably suppress inclusion inclusions in the slab by injecting molten steel into the mold while maintaining the magnetic field strength satisfying the range of 5 . [0008] If the Stewart number is less than 0.3 , the discharge flow is insufficiently attenuated, and the amount of inclusions brought into the deep part of the mold below the electromagnetic brake increases. Inclusions increase. When the Stewart number exceeds 5, the descending flow of molten steel below the electromagnetic brake is reduced, the effect of forming an upward flow at the center of the mold width direction is reduced, and the effect of floating the inclusions is reduced. Undesirably, the floating speed becomes almost the same, and the inclusions stay and are trapped in the slab. For the flow rate of molten steel at the upper end of the magnetic field zone, for example, a value directly measured by an electromagnetic current meter embedded in a mold can be used. Further, a value obtained by simulating the flow of molten steel in a mold by numerical calculation can be used. Furthermore, a value obtained by a formula (described in Iron and Steel, No. 78 (1992) No. 3, p. 441) obtained from a known hydrodynamic study can be used. The value of N is controlled within the scope of the method of the present invention by changing the magnetic field intensity as needed in accordance with the change in the flow velocity of the molten steel during casting determined by these methods due to the drift speed caused by the casting speed, width, nozzle blockage, etc. While it is desirable to perform casting, the strength of the magnetic field can be determined by the molten steel flow rate obtained using typical conditions of each casting. Next, examples of the method of the present invention will be described together with comparative examples. [Table 1] [Table 2] (Continued from Table 1) Note 1: The molten steel injected into the mold is C: 0.03
-0.04%, Si: 0.01-0.03%, Mn:
0.15 to 0.30%, P: 0.008 to 0.012
%, S: 0.009 to 0.013%, Al: 0.03 to
0.06%, remaining Fe and unavoidable impurities. Note 2: The molten steel injection position is the distance below the surface of the molten steel in the mold. Note 3: The molten steel injection angle was downward, and injection was performed from the center of the mold in both width directions through the immersion nozzle. Note 4: The static magnetic field application position is the distance below the surface of the molten steel in the mold.
It was applied from both sides of the long side of the mold. Note 5: The number of inclusions was measured by a slime extraction method by cutting out a sample from a slab and displaying the number of inclusions when Comparative Example 6 was set to 1. Note 6: Continuous casting is performed with a curved casting device. According to the method of the present invention, the quality of steel products can be improved by remarkably suppressing inclusions in cast slabs. In addition, since the trapping of inclusions is suppressed by controlling the static magnetic field, excellent effects can be achieved, such as being able to accurately reduce the inclusions in the cast slab by using existing equipment accurately, industrially inexpensively, and reliably. can get.
【図面の簡単な説明】
【図１】鋳型内注入溶鋼降下流速と鋳片内の介在物捕捉
数との関係を示す図表である。BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a table showing the relationship between the flow velocity of molten steel poured into a mold and the number of trapped inclusions in a slab.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 石井 孝宣 愛知県東海市東海町５−３ 新日本製鐵 株式会社名古屋製鐵所内 (56)参考文献 特開 平６−79424（ＪＰ，Ａ) 特開 平８−52545（ＪＰ，Ａ) 特開 平６−182510（ＪＰ，Ａ) 特開 平２−284750（ＪＰ，Ａ) 特開 昭61−255749（ＪＰ，Ａ) 日本機械学会，機械工学便覧 基礎編 ，日本，1986年，Ａ５ 流体工学，Ａ ５−65頁 表19 野村安正 訳，噴流，日本，森北出 版，1981年，206−214頁 (58)調査した分野(Int.Cl.7，ＤＢ名) B22D 11/11 B22D 11/04 311 B22D 11/115 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takanori Ishii 5-3 Tokai-cho, Tokai-shi, Aichi Prefecture Nippon Steel Corporation Nagoya Works (56) References JP-A-6-79424 (JP, A) JP-A-8-52545 (JP, A) JP-A-6-182510 (JP, A) JP-A-2-284750 (JP, A) JP-A-61-255749 (JP, A) Japan Society of Mechanical Engineers, Mechanical Engineering Handbook Fundamentals, Japan, 1986, A5 Fluid Engineering, A5-page 65 Table 19 Translated by Nomura Yasumasa, Jet, Japan, Morikita Edition, 1981, 206-214 (58) Fields investigated (Int. Cl. 7 , DB name) B22D 11/11 B22D 11/04 311 B22D 11/115
Claims (1)
型内へ溶鋼を注入し、連続鋳造するに際して、浸漬ノズ
ルから吐出する溶鋼流へ、下記数式を満足する静磁場を
付与しつつ、鋳造することを特徴とする介在物の少ない
鋳片の連続鋳造方法。 【数１】 但し Ｎ：スチュワート数、σ：電気伝導度、Ｂ：磁場
強度、Ｌ：鋳片厚、ρ：密度、Ｖ：速度（磁場帯上端で
の溶鋼流速）。(57) [Claims 1] A static magnetic field that satisfies the following equation when a molten steel is injected from a tundish into a mold via an immersion nozzle and is continuously cast into the molten steel flow discharged from the immersion nozzle. A continuous casting method of a cast piece with few inclusions, characterized in that casting is carried out while imparting slag. (Equation 1) Where N: Stewart number, σ: electric conductivity, B: magnetic field strength, L: slab thickness, ρ: density, V: velocity (fluid steel flow velocity at the upper end of the magnetic field band).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP03851298A JP3505077B2 (en) | 1998-02-20 | 1998-02-20 | Continuous casting method of slab with few inclusions |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP03851298A JP3505077B2 (en) | 1998-02-20 | 1998-02-20 | Continuous casting method of slab with few inclusions |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH11226711A JPH11226711A (en) | 1999-08-24 |
| JP3505077B2 true JP3505077B2 (en) | 2004-03-08 |
Family
ID=12527335
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP03851298A Expired - Lifetime JP3505077B2 (en) | 1998-02-20 | 1998-02-20 | Continuous casting method of slab with few inclusions |
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| Country | Link |
|---|---|
| JP (1) | JP3505077B2 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104233153A (en) * | 2013-06-24 | 2014-12-24 | 张家港市奥神科技有限公司 | Electromagnetic zinc-plating method for hot galvanizing of steel wire or steel pipe |
-
1998
- 1998-02-20 JP JP03851298A patent/JP3505077B2/en not_active Expired - Lifetime
Non-Patent Citations (2)
| Title |
|---|
| 日本機械学会，機械工学便覧 基礎編 ，日本，１９８６年，Ａ５ 流体工学，Ａ５−６５頁 表１９ |
| 野村安正 訳，噴流，日本，森北出版，１９８１年，２０６−２１４頁 |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH11226711A (en) | 1999-08-24 |
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