JP2018149602A - Method for continuously casting steel - Google Patents

Method for continuously casting steel Download PDF

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JP2018149602A
JP2018149602A JP2018099606A JP2018099606A JP2018149602A JP 2018149602 A JP2018149602 A JP 2018149602A JP 2018099606 A JP2018099606 A JP 2018099606A JP 2018099606 A JP2018099606 A JP 2018099606A JP 2018149602 A JP2018149602 A JP 2018149602A
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mold
dissimilar metal
metal filling
slab
continuous casting
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直道 岩田
Naomichi Iwata
直道 岩田
堤 康一
Koichi Tsutsumi
康一 堤
鍋島 誠司
Seiji Nabeshima
誠司 鍋島
三木 祐司
Yuji Miki
祐司 三木
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JFE Steel Corp
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JFE Steel Corp
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Abstract

PROBLEM TO BE SOLVED: To provide a method for continuously casting a steel, when the molten steel of a medium carbon steel or the like in which surface cracks are easy to be generated is continuously cast, suppressing surface cracks caused by an oscillation mark formed at a slab.SOLUTION: A molten steel 11 injected into a mold for continuous casting while vibrating the mold into a casting direction is drawn out to produce a slab. The mold, at the inner wall face of the long side 1, respectively independently includes a plurality of dissimilar metal filling parts 3 formed in such a manner that a metal having a thermal conductivity different from that of the mold is filled into circular recessed grooves provided at the inner wall face. The filling thickness H(mm) of the dissimilar filling parts 3 and the diameter d(mm) of the dissimilar metal filling parts 3 satisfy the relation in the following inequality (2). The amplitude S(mm) of the vibration, frequency f(time/min) and the distance PH (mm) between the centers in the casting direction of the dissimilar metal filling parts 3 satisfy the relation in the following inequality (3): 0.5≤H≤d(2) and S/2×≤PH≤1000×Vc/f(3).SELECTED DRAWING: Figure 6

Description

本発明は、連続鋳造用鋳型での凝固シェルの不均一冷却に起因する鋳片表面割れを防止するとともに、鋳片に形成されるオシレーションマークに起因する鋳片表面割れも防止する鋼の連続鋳造方法に関する。   The present invention prevents continuous slab surface cracking due to non-uniform cooling of the solidified shell in a continuous casting mold and also prevents slab surface cracking due to oscillation marks formed on the slab. The present invention relates to a casting method.

鋼の連続鋳造においては、鋳型内に注入された溶鋼は水冷式鋳型によって冷却され、鋳型との接触面で溶鋼が凝固して凝固層(「凝固シェル」という)が生成される。凝固シェルが、鋳型下流側に設置した水スプレーや気水スプレーによって冷却されながら、内部の未凝固層とともに鋳型下方に連続的に引き抜かれ、水スプレーや気水スプレーによる冷却によって中心部まで凝固して鋳片が製造されている。   In continuous casting of steel, molten steel injected into a mold is cooled by a water-cooled mold, and the molten steel is solidified at a contact surface with the mold to generate a solidified layer (referred to as “solidified shell”). While the solidified shell is cooled by the water spray or air-water spray installed on the downstream side of the mold, it is continuously drawn down along with the unsolidified layer inside the mold, and solidifies to the center by cooling with the water spray or air-water spray. The slab is manufactured.

鋳型内における冷却が不均一になると、凝固シェルの厚みが鋳片の鋳造方向及び鋳片幅方向で不均一となる。凝固シェルには、凝固シェルの収縮や変形に起因する応力が作用する。凝固初期においては、この応力が凝固シェルの薄肉部に集中し、この応力によって凝固シェルの表面に割れが発生する。この割れは、その後の熱応力や連続鋳造機のロールによる曲げ応力及び矯正応力などの外力により拡大し、大きな表面割れとなる。表面割れは、次工程の圧延工程において鋼製品の表面欠陥となる。従って、鋼製品の表面欠陥の発生を防止するためには、鋳片表面を溶削するまたは研削して、鋳片段階でその表面割れを除去することが必要となる。   If the cooling in the mold becomes non-uniform, the thickness of the solidified shell becomes non-uniform in the casting direction of the slab and in the slab width direction. The solidified shell is subjected to stress resulting from the shrinkage and deformation of the solidified shell. In the initial stage of solidification, this stress is concentrated on the thin portion of the solidified shell, and the stress causes cracks on the surface of the solidified shell. This crack expands due to subsequent external stresses such as thermal stress, bending stress due to the roll of a continuous casting machine, and straightening stress, resulting in a large surface crack. The surface crack becomes a surface defect of the steel product in the subsequent rolling process. Therefore, in order to prevent the occurrence of surface defects in the steel product, it is necessary to remove or break the surface cracks at the slab stage by grinding or grinding the slab surface.

鋳型内の不均一凝固は、特に、炭素含有量が0.08〜0.17質量%の鋼(「中炭素鋼」という)で発生しやすい。中炭素鋼では、凝固時に包晶反応が起こる。鋳型内の不均一凝固は、この包晶反応によるδ鉄(フェライト)からγ鉄(オーステナイト)への変態時の体積収縮による変態応力に起因すると考えられている。つまり、この変態応力に起因する歪みによって凝固シェルが変形し、この変形により凝固シェルが鋳型内壁面から離れる。鋳型内壁面から離れた部位は鋳型による冷却が低下し、この鋳型内壁面から離れた部位(この鋳型内壁面から離れた部位を「デプレッション」という)の凝固シェル厚みが薄くなる。凝固シェル厚みが薄くなることで、この部分に上記応力が集中し、表面割れが発生すると考えられている。   Inhomogeneous solidification in the mold is likely to occur particularly in a steel having a carbon content of 0.08 to 0.17% by mass (referred to as “medium carbon steel”). In medium carbon steel, a peritectic reaction occurs during solidification. It is believed that the inhomogeneous solidification in the mold is caused by transformation stress due to volume shrinkage during transformation from δ iron (ferrite) to γ iron (austenite) by this peritectic reaction. That is, the solidified shell is deformed by the strain caused by the transformation stress, and the solidified shell is separated from the inner wall surface of the mold by this deformation. The portion separated from the inner wall surface of the mold is cooled by the mold, and the thickness of the solidified shell at the portion away from the inner wall surface of the mold (the portion away from the inner wall surface of the mold is referred to as “depression”) is reduced. It is considered that the stress is concentrated on this portion and the surface cracks are generated by reducing the thickness of the solidified shell.

特に、鋳片引き抜き速度を増加した場合には、凝固シェルから鋳型冷却水への平均熱流束が増加する(凝固シェルが急速冷却される)のみならず、熱流束の分布が不規則で且つ不均一になることから、鋳片表面割れの発生が増加傾向となる。具体的には、鋳片厚みが200mm以上のスラブ連続鋳造機においては、鋳片引き抜き速度が1.5m/min以上になると表面割れが発生しやすくなる。   In particular, when the slab drawing speed is increased, the average heat flux from the solidified shell to the mold cooling water increases (the solidified shell is rapidly cooled), and the heat flux distribution is irregular and irregular. Since it becomes uniform, the occurrence of slab surface cracks tends to increase. Specifically, in a slab continuous casting machine having a slab thickness of 200 mm or more, surface cracks are likely to occur when the slab drawing speed is 1.5 m / min or more.

従来、上記中炭素鋼のような包晶反応を伴う鋼種の鋳片表面割れを防止する目的で、結晶化しやすい組成のモールドパウダーを使用することが試みられている(例えば、特許文献1を参照)。結晶化しやすい組成のモールドパウダーを用いると、モールドパウダー層の熱抵抗が増大し、凝固シェルが緩冷却されることになる。緩冷却によって凝固シェルに作用する応力が低下し、表面割れが少なくなるからである。しかし、モールドパウダーによる緩冷却効果のみでは、十分な不均一凝固の改善は得られず、変態量が大きい鋼種では割れの発生を防止することはできない。   Conventionally, it has been attempted to use a mold powder having a composition that is easily crystallized for the purpose of preventing cracking of the slab surface of a steel type with a peritectic reaction such as the above-mentioned medium carbon steel (see, for example, Patent Document 1). ). When a mold powder having a composition that is easily crystallized is used, the thermal resistance of the mold powder layer increases and the solidified shell is slowly cooled. This is because the stress acting on the solidified shell is lowered by slow cooling, and surface cracks are reduced. However, only the slow cooling effect by the mold powder does not provide sufficient improvement in non-uniform solidification, and it is not possible to prevent the occurrence of cracks in steel types having a large transformation amount.

そこで、包晶反応を伴う鋼種の鋳片表面割れを防止する目的として、特許文献2には、連続鋳造用鋳型の内壁面に、銅よりも熱伝導率が低い複数個の部位がそれぞれ独立して形成された連続鋳造用鋳型を用いることで、凝固初期の凝固シェルの不均一冷却よる表面割れ及び包晶反応を伴う中炭素鋼でのδ鉄からγ鉄への変態に起因する凝固シェル厚みの不均一による表面割れを効果的に防止できる旨が記載されている。   Therefore, in order to prevent slab surface cracking of a steel type accompanied by a peritectic reaction, Patent Document 2 discloses that a plurality of parts having lower thermal conductivity than copper are independent on the inner wall surface of a continuous casting mold. The thickness of the solidified shell caused by the transformation from δ iron to γ iron in medium carbon steel with surface cracking and peritectic reaction due to non-uniform cooling of the solidified shell at the initial stage of solidification It is described that surface cracks due to non-uniformity can be effectively prevented.

特開2005−297001号公報JP 2005-297001 A 国際公開第2014/002409号公報International Publication No. 2014/002409

鋼の連続鋳造では、上下方向の振動を鋳型に与えつつ溶鋼を鋳型に注入し、鋳型内の溶鋼表面にモールドパウダーを投入しており、該モールドパウダーが溶融して形成される溶融スラグを凝固シェルと鋳型内壁との間に流入させ、振動と溶融スラグとによって凝固シェルが鋳型に焼き付くことを防止している。振動によって、先端部が変形を受けることになる凝固シェルを鋳型から引き抜いて得られる鋳片の表面には、オシレーションマークと呼ばれる周期的な凹凸面が形成される(図6(B)及び(C)における凝固シェル11a参照)。   In continuous casting of steel, molten steel is poured into the mold while applying vertical vibrations to the mold, and mold powder is injected into the molten steel surface in the mold, and the molten slag formed by melting the mold powder is solidified. It flows between the shell and the inner wall of the mold, and the solidified shell is prevented from being baked on the mold by vibration and molten slag. Periodic uneven surfaces called oscillation marks are formed on the surface of the slab obtained by pulling out from the mold the solidified shell whose tip portion will be deformed by vibration (see FIGS. 6B and 6B). See solidified shell 11a in C)).

オシレーションマークの凹凸面の頂部と谷部との差が大きくなると、鋳型の出口に向かうにつれて、鋳型内壁と凝固シェルとの間隔が局所的に増加または減少し、鋳造方向において凝固シェルの凝固が不均一となり、凹凸面の隣接する頂部(または谷部)間の縦割れが発生し易くなる。また。凹部の谷部は、その他の部分よりも鋳片の幅が小さくなり、連続鋳造時の矯正帯において応力が集中して掛かりやすく、鋳片の横割れの起点となり、凹部の谷部には横割れが発生し易くなる。特許文献2には、オシレーションマークに起因する問題は考慮されておらず、特許文献2の連続鋳造用鋳型を用い、特許文献1に記載されているようにモールドパウダーの組成を適宜変更したとしても、特に、中炭素鋼の溶鋼を連続鋳造するに際し、前述のオシレーションマークに起因した鋳片の表面割れを効果的に抑制する技術が確立されていないというのが実情である。   When the difference between the top and valley of the concavo-convex surface of the oscillation mark increases, the distance between the inner wall of the mold and the solidified shell locally increases or decreases toward the mold exit, and solidification of the solidified shell in the casting direction occurs. It becomes non-uniform | heterogenous and it becomes easy to generate | occur | produce the vertical crack between the top parts (or trough parts) which an uneven surface adjoins. Also. The valley of the recess has a smaller slab width than the other parts, and stress tends to concentrate on the straightening zone during continuous casting, which is the starting point for transverse cracking of the slab. Cracks are likely to occur. Patent Document 2 does not consider the problem caused by the oscillation mark, and uses the continuous casting mold of Patent Document 2 and appropriately changes the composition of the mold powder as described in Patent Document 1. However, in particular, in the continuous casting of molten steel of medium carbon steel, the actual situation is that a technique for effectively suppressing the surface crack of the slab caused by the aforementioned oscillation mark has not been established.

本発明は上記実情に鑑みてなされたもので、その目的とするところは、特に、中炭素鋼などの表面割れの発生し易い鋼種の溶鋼を連続鋳造するに際し、鋳片に形成されるオシレーションマークに起因する表面割れを抑制する鋼の連続鋳造方法を提供することである。   The present invention has been made in view of the above circumstances, and the object of the present invention is, in particular, an oscillation formed in a slab when continuously casting a molten steel of a steel type that is susceptible to surface cracking, such as medium carbon steel. It is to provide a continuous casting method of steel that suppresses surface cracks caused by marks.

上記課題を解決するための本発明の要旨は以下の通りである。
[1]連続鋳造用鋳型内に溶鋼を注入しつつ、前記連続鋳造用鋳型を鋳造方向に振動させながら前記溶鋼を引き抜いて、鋳片を製造する鋼の連続鋳造方法であって、前記連続鋳造用鋳型は、メニスカスよりも上方の任意の位置から、前記メニスカスよりも、鋳片引き抜き速度Vc(m/分)から下記の(1)式で求まる長さR(mm)以上下方の位置までの、水冷式銅鋳型の内壁面の範囲に、鋳型の熱伝導率に対して熱伝導率が80%以下あるいは125%以上である金属が、前記内壁面に設けられた円形凹溝または擬似円形凹溝に充填されて形成された、直径2〜20mmまたは円相当径2〜20mmの複数個の異種金属充填部をそれぞれ独立して有し、前記異種金属充填部の充填厚みH(mm)と前記異種金属充填部の直径または円相当径d(mm)とは下記の(2)式の関係を満たすものであり、前記連続鋳造用鋳型の振動の振幅S(mm)及び周波数f(回/分)と前記異種金属充填部の鋳造方向における中心間の距離PH(mm)とは下記の(3)式の関係を満たすことを特徴とする鋼の連続鋳造方法。
R=2×Vc×1000/60 (1)
0.5≦H≦d (2)
S/2≦PH≦1000×Vc/f (3)
[2]前記異種金属充填部の間隔P(mm)と前記異種金属充填部の直径または円相当径dとは下記の(4)式の関係を満たすことを特徴とする[1]に記載の鋼の連続鋳造方法。
P≧0.2×d (4)
[3]前記溶鋼は、炭素含有量が0.08〜0.17質量%である中炭素鋼であることを特徴とする[1]または[2]に記載の鋼の連続鋳造方法。
The gist of the present invention for solving the above problems is as follows.
[1] A continuous casting method for steel in which molten steel is poured into a continuous casting mold and the molten steel is drawn while vibrating the continuous casting mold in a casting direction to produce a slab. The casting mold is from an arbitrary position above the meniscus to a position below the meniscus by a length R (mm) or more below the slab drawing speed Vc (m / min) determined by the following equation (1). In the range of the inner wall surface of the water-cooled copper mold, a metal having a thermal conductivity of 80% or less or 125% or more with respect to the thermal conductivity of the mold is formed into a circular groove or pseudo-circular groove provided on the inner wall surface. A plurality of different metal filling portions each having a diameter of 2 to 20 mm or an equivalent circle diameter of 2 to 20 mm, which are formed by filling the grooves, are independently provided, and the filling thickness H (mm) of the different metal filling portion and the above Equivalent diameter or circle of different metal filling part d (mm) satisfies the relationship of the following equation (2), and the casting amplitude of the vibration casting S of the mold for continuous casting, S (mm) and frequency f (times / min), and the dissimilar metal filling portion. The distance between centers in PH (mm) satisfies the relationship of the following formula (3).
R = 2 × Vc × 1000/60 (1)
0.5 ≦ H ≦ d (2)
S / 2 ≦ PH ≦ 1000 × Vc / f (3)
[2] The interval P (mm) between the dissimilar metal filling portions and the diameter or equivalent circle diameter d of the dissimilar metal filling portions satisfy the relationship of the following expression (4): Steel continuous casting method.
P ≧ 0.2 × d (4)
[3] The continuous casting method of steel according to [1] or [2], wherein the molten steel is a medium carbon steel having a carbon content of 0.08 to 0.17% by mass.

本発明によれば、鋳型内壁に形成された複数の凹溝に、鋳型とは異なる熱伝導率を有する異種金属が充填された鋳型を用いて、鋳型中の異種金属充填部の中心間の距離に応じて、振動条件を適正化することで、オシレーションマークの凹凸面の頂部と谷部との差を低減し、隣接する頂部間の縦割れや凹部の谷部での横割れのない鋳片を製造することができる。   According to the present invention, a distance between centers of different metal filling portions in a mold is obtained by using a mold in which a plurality of concave grooves formed on the inner wall of the mold is filled with a different metal having a thermal conductivity different from that of the mold. Therefore, by optimizing the vibration conditions, the difference between the top and bottom of the concavo-convex surface of the oscillation mark is reduced, and there is no vertical crack between adjacent tops or horizontal cracks at the bottom of the recess. Pieces can be manufactured.

連続鋳造用鋳型の一部を構成する鋳型長辺を内壁面側から視た図である。It is the figure which looked at the mold long side which constitutes a part of mold for continuous casting from the inner wall surface side. 図1に示す異種金属充填部が形成された鋳型長辺の部位を示す図である。It is a figure which shows the site | part of the mold long side in which the dissimilar metal filling part shown in FIG. 1 was formed. 図1に示す鋳型長辺の三つの断面における熱抵抗の変化を概念的に示す図である。It is a figure which shows notionally the change of the thermal resistance in three cross sections of the casting_mold | template long side shown in FIG. 図1とは別の形態の異種金属充填部が形成された鋳型長辺の部位を示す説明図である。It is explanatory drawing which shows the site | part of the casting_mold | template long side in which the dissimilar metal filling part of the form different from FIG. 1 was formed. 熱伝導比と鋳片表面割れ長さ(mm/m)との関係を示すグラフである。It is a graph which shows the relationship between heat conduction ratio and slab surface crack length (mm / m). 図1に示す鋳型長辺の内壁近傍に形成される凝固シェルを示す図である。It is a figure which shows the solidification shell formed in the inner wall vicinity of the casting_mold | template long side shown in FIG.

以下、添付図面を参照して本発明の実施形態の一例を説明する。連続鋳造用鋳型は、スラブ鋳片を鋳造するための連続鋳造用鋳型の例であり、一対の鋳型長辺と一対の鋳型短辺とを組み合わせて構成される。図1は、そのうちの鋳型長辺を内壁面側から見た図である。鋳型長辺1における定常鋳造時のメニスカスの位置よりも距離Q(距離Qは任意の値)離れた上方の位置から、メニスカスよりも距離R離れた下方の位置までの内壁面の範囲には円形凹溝が複数設けられ、該円形凹溝には、鋳型の熱伝導率よりも低いあるいは高い熱伝導率となる金属(以下、「異種金属」と記す)が充填され、異種金属充填部3が複数形成されている。なお、「メニスカス」とは「鋳型内溶鋼湯面」を意味する。   Hereinafter, an example of an embodiment of the present invention will be described with reference to the accompanying drawings. The continuous casting mold is an example of a continuous casting mold for casting a slab cast piece, and is configured by combining a pair of mold long sides and a pair of mold short sides. FIG. 1 is a view of the long side of the mold as viewed from the inner wall surface side. The range of the inner wall surface from the upper position away from the meniscus position in the long casting mold 1 by a distance Q (the distance Q is an arbitrary value) to the lower position away from the meniscus by a distance R is circular. A plurality of concave grooves are provided, and the circular concave grooves are filled with a metal having a thermal conductivity lower or higher than the thermal conductivity of the mold (hereinafter referred to as “foreign metal”). A plurality are formed. “Menicus” means “molten steel surface in mold”.

図示を省略してある鋳型短辺にも、鋳型長辺と同様に、その内壁面側に異種金属充填部が形成されるものとして、以降、鋳型短辺についての説明は省略する。但し、スラブ鋳片においては、その形状に起因して長辺面側の凝固シェルに応力集中が起こりやすく、長辺面側で表面割れが発生しやすい。よって、スラブ鋳片用の連続鋳造用鋳型の鋳型長辺には、異種金属充填部を設置することが必要となるが、鋳型短辺には、必ずしも、異種金属充填部を設置する必要はない。   Similarly to the long side of the mold, the short metal side not shown is formed with a different metal filling portion on the inner wall surface side, and the description of the short side of the mold will be omitted. However, in a slab slab, stress concentration is likely to occur in the solidified shell on the long side surface due to its shape, and surface cracks are likely to occur on the long side surface side. Therefore, it is necessary to install a dissimilar metal filling part on the long side of the continuous casting mold for slab cast, but it is not always necessary to install a dissimilar metal filling part on the short side of the mold. .

図2は、図1に示す鋳型長辺の異種金属充填部が形成された部位の拡大図で、(A)は内壁面側から見た部位の図であり、(B)は、(A)のBB線断面図である。異種金属充填部3は、鋳型長辺1の内壁面側にそれぞれ独立して加工された、直径dが2〜20mmの円形凹溝2の内部に、鍍金手段や溶射手段などによって、鋳型の熱伝導率に対して熱伝導率が80%以下あるいは125%以上である異種金属が、厚みHを有するべく充填されて形成されたものである。符号5は冷却水流路、符号6はバックプレートである。全ての異種金属充填部3同士の間隔Pは特に同じである必要はないが、後述する熱抵抗の変動を確実に周期的なものとするべく、全ての異種金属充填部3同士の間隔Pは同じとすることが望ましい。なお、以下、異種金属の熱伝導率が鋳型の熱伝導率に対して80%以下である場合を説明している。   FIG. 2 is an enlarged view of a portion where the dissimilar metal filling portion of the long side of the mold shown in FIG. 1 is formed, (A) is a view of the portion viewed from the inner wall surface side, and (B) is (A) FIG. The dissimilar metal filling portion 3 is formed on the inner wall surface side of the mold long side 1 independently of the heat of the mold by a plating means, a spraying means or the like inside a circular groove 2 having a diameter d of 2 to 20 mm. A dissimilar metal having a thermal conductivity of 80% or less or 125% or more with respect to the conductivity is filled and formed to have a thickness H. Reference numeral 5 denotes a cooling water flow path, and reference numeral 6 denotes a back plate. The intervals P between all the different metal filling portions 3 do not have to be the same in particular, but the intervals P between all the different metal filling portions 3 are ensured to ensure periodic fluctuations in the thermal resistance described later. It is desirable to be the same. In the following, a case where the thermal conductivity of the dissimilar metal is 80% or less with respect to the thermal conductivity of the mold is described.

図1及び図2では、異種金属充填部3の鋳型長辺1の内壁面における形状が円形であるが、円形とする必要はない。例えば楕円形のような、所謂「角」を有していない、円形に近い形状である限り、どのような形状であっても構わない。但し、円形に近い形状の場合でも、後述する通り、この円形に近い形状の異種金属充填部3の面積から求められる円相当径は2〜20mmの範囲内とする。   1 and 2, the shape of the inner wall surface of the mold long side 1 of the dissimilar metal filling portion 3 is circular, but it is not necessary to be circular. For example, any shape may be used as long as it has a so-called “corner” -like shape, such as an ellipse, and is close to a circle. However, even in the case of a shape close to a circle, as described later, the equivalent circle diameter determined from the area of the dissimilar metal filling portion 3 having a shape close to a circle is in the range of 2 to 20 mm.

図3は、鋳型長辺の三箇所の位置における熱抵抗の変化を概念的に示す図である。熱抵抗が鋳型よりも大きい異種金属充填部3を、メニスカスの位置を含むメニスカス近傍の連続鋳造用鋳型の幅方向及び鋳造方向に複数設置することにより、メニスカス近傍の鋳型幅方向及び鋳造方向における連続鋳造用鋳型の熱抵抗が規則的且つ周期的に増減する。これによって、メニスカス近傍、つまり、凝固初期での凝固シェルから連続鋳造用鋳型への熱流束が規則的且つ周期的に増減する。この熱流束の規則的且つ周期的な増減により、δ鉄からγ鉄への変態によって発生する応力や熱応力が低減し、これらの応力によって生じる凝固シェルの変形が小さくなる。凝固シェルの変形が小さくなることで、凝固シェルの変形に起因する不均一な熱流束分布が均一化され、且つ、発生する応力が分散されて個々の歪量が小さくなる。その結果、凝固シェル表面における表面割れの発生が防止される。なお、熱抵抗が鋳型長辺1よりも低くなる異種金属充填部3を設置しても、連続鋳造用鋳型の熱抵抗を規則的且つ周期的に増減させ得る。   FIG. 3 is a diagram conceptually showing changes in thermal resistance at three positions on the long side of the mold. By disposing a plurality of different metal filling portions 3 having a thermal resistance larger than that of the mold in the width direction and the casting direction of the continuous casting mold in the vicinity of the meniscus including the position of the meniscus, continuous in the mold width direction and the casting direction in the vicinity of the meniscus. The thermal resistance of the casting mold increases and decreases regularly and periodically. As a result, the heat flux from the solidified shell in the vicinity of the meniscus, that is, in the initial stage of solidification, to the continuous casting mold increases and decreases regularly and periodically. This regular and periodic increase / decrease in the heat flux reduces the stress and thermal stress generated by the transformation from δ iron to γ iron, and reduces the deformation of the solidified shell caused by these stresses. By reducing the deformation of the solidified shell, the non-uniform heat flux distribution resulting from the deformation of the solidified shell is made uniform, and the generated stress is dispersed to reduce the amount of individual strain. As a result, occurrence of surface cracks on the surface of the solidified shell is prevented. In addition, even if the dissimilar metal filling part 3 in which the thermal resistance is lower than the mold long side 1 is installed, the thermal resistance of the continuous casting mold can be regularly increased and decreased.

初期凝固への影響を勘案すれば、異種金属充填部3を、メニスカスから、定常鋳造時の鋳片引き抜き速度Vc(m/分)に応じて、下記の(1)式から算出される距離R(mm)以上メニスカスよりも下方の位置まで設置することとする。   Considering the influence on the initial solidification, the dissimilar metal filling portion 3 is separated from the meniscus by the distance R calculated from the following equation (1) according to the slab drawing speed Vc (m / min) during steady casting. (Mm) It shall be installed to the position below the meniscus.

R=2×Vc×1000/60 (1)
すなわち、距離Rは、凝固開始した後の鋳片(凝固シェル)が異種金属充填部3の設置された範囲を通過する時間に関係しており、凝固開始後から少なくとも2秒間、鋳片は、異種金属充填部3の設置された範囲内に滞在することが好ましい。鋳片が凝固開始後から少なくとも2秒間、異種金属充填部3の設置された範囲に存在するためには、メニスカスよりも(1)式で求まる距離R以上下方に異種金属充填部3が設置されている必要がある。
R = 2 × Vc × 1000/60 (1)
That is, the distance R is related to the time required for the slab (solidified shell) after starting solidification to pass through the range in which the dissimilar metal filling portion 3 is installed, and for at least 2 seconds after the start of solidification, It is preferable to stay within the range where the dissimilar metal filling part 3 is installed. In order for the slab to exist in the range where the dissimilar metal filling part 3 is installed for at least 2 seconds after the start of solidification, the dissimilar metal filling part 3 is installed below the meniscus by a distance R or more determined by the equation (1). Need to be.

凝固開始した後の鋳片が異種金属充填部3の設置された範囲内に滞在する時間を2秒以上確保することで、異種金属充填部3による熱流束の周期的な変動の効果が十分に得られ、表面割れの発生しやすい高速鋳造時や中炭素鋼の鋳造時でも、鋳片表面割れの防止効果が得られる。異種金属充填部3による熱流束の周期的な変動の効果を安定して得る上では、鋳片が異種金属充填部3の設置された範囲を通過する時間として4秒以上を確保することがより好ましい。   By securing the time for the cast slab after the start of solidification to stay in the range where the dissimilar metal filling part 3 is installed for 2 seconds or more, the effect of the periodic fluctuation of the heat flux by the dissimilar metal filling part 3 is sufficient. As a result, the effect of preventing cracks on the slab surface can be obtained even during high-speed casting where a surface crack is likely to occur or during the casting of medium carbon steel. In order to stably obtain the effect of the periodic fluctuation of the heat flux by the dissimilar metal filling part 3, it is more preferable to secure 4 seconds or more as the time for the slab to pass through the range where the dissimilar metal filling part 3 is installed. preferable.

一方、異種金属充填部3の上端部の位置はメニスカスよりも上方である限りどこの位置であっても構わず、従って、距離Qはゼロを超えた任意の値で構わない。但し、鋳造中にメニスカスは上下方向に変動するので、異種金属充填部3の上端部が常にメニスカスよりも上方位置となるように、メニスカスよりも10mm程度上方位置まで、望ましくは20mm程度上方位置まで、異種金属充填部3を設置することが好ましい。なお、メニスカスの位置は、鋳型長辺銅板1の上端から60〜150mm下方位置とするのが一般的であり、これに応じて異種金属充填部3の設置範囲を決めればよい。   On the other hand, the position of the upper end portion of the dissimilar metal filling portion 3 may be anywhere as long as it is above the meniscus, and therefore the distance Q may be any value exceeding zero. However, since the meniscus fluctuates in the vertical direction during casting, the upper end portion of the dissimilar metal filling portion 3 is always located above the meniscus to a position about 10 mm above the meniscus, preferably about 20 mm above. The dissimilar metal filling part 3 is preferably installed. In general, the meniscus is positioned 60 to 150 mm below the upper end of the long copper plate 1, and the installation range of the dissimilar metal filling portion 3 may be determined accordingly.

異種金属充填部3の形状は、円形または円形に近いものとする。以下、円形に近いものを「擬似円形」と称す。異種金属充填部3の形状が擬似円形の場合には、異種金属充填部3を形成させるために鋳型長辺1の内壁面に加工される溝を「擬似円形溝」と称す。擬似円形とは、例えば楕円形や、角部にRが形成された長方形など、角部を有していない形状であり、更には、花びら模様のような形状であっても構わない。鋳型銅板表面に縦溝或いは格子溝を施し、この溝に異種金属を充填した場合には、異種金属と銅との境界面及び格子部の直交部において、異種金属と銅との熱歪差による応力が集中し、鋳型銅板表面に割れが発生するという問題が起こる。これに対して、本発明のように、異種金属充填部3の形状を円形または擬似円形とすることで、異種金属と銅との境界面は曲面状となることから、境界面で応力が集中しにくく、鋳型銅板表面に割れが発生しにくいという利点が発現する。   The shape of the dissimilar metal filling portion 3 is assumed to be circular or nearly circular. Hereinafter, a shape close to a circle is referred to as a “pseudo circle”. When the shape of the dissimilar metal filling portion 3 is a pseudo circle, a groove processed on the inner wall surface of the mold long side 1 to form the dissimilar metal filling portion 3 is referred to as a “pseudo circular groove”. The pseudo circle is a shape that does not have a corner, such as an ellipse or a rectangle with R formed at the corner, and may be a shape like a petal pattern. When a vertical groove or a lattice groove is provided on the surface of the mold copper plate, and this groove is filled with a different metal, the difference between the different metal and copper is caused by a difference in thermal strain at the boundary surface between the different metal and copper and at an orthogonal portion of the lattice portion. There is a problem that stress concentrates and cracks occur on the surface of the mold copper plate. On the other hand, since the boundary surface between the dissimilar metal and copper becomes a curved surface by making the shape of the dissimilar metal filling portion 3 circular or pseudo-circular as in the present invention, stress is concentrated on the boundary surface. The advantage that it is hard to crack and a crack does not generate | occur | produce on the casting_mold | template copper plate surface expresses.

異種金属充填部3の直径または円相当径は2〜20mmであることが必要である。2mm以上とすることで、異種金属充填部3における熱流束の低下が十分となり、上記効果を得ることができる。また、2mm以上とすることで、異種金属を鍍金手段や溶射手段によって円形凹溝2や擬似円形凹溝(図示せず)の内部に充填することが容易となる。一方、異種金属充填部3の直径または円相当径を20mm以下とすることで、異種金属充填部3における熱流束の低下が抑制され、つまり、異種金属充填部3によって、凝固遅れが抑制されて、その位置での凝固シェルへの応力集中が防止され、鋳片の表面割れ発生を防止することができる。即ち、直径または円相当径が20mmを超えると表面割れが発生することから、異種金属充填部3の直径または円相当径は20mm以下にすることが必要である。なお、異種金属充填部3の形状が擬似円形の場合は、この擬似円形の円相当径dは下記の(5)式で算出される。
円相当径d=(4×C/π)1/2 (5)
(5)式において、Cは異種金属充填部3の面積(mm)である。
The diameter or equivalent circle diameter of the dissimilar metal filling portion 3 needs to be 2 to 20 mm. By setting it as 2 mm or more, the heat flux in the dissimilar metal filling portion 3 is sufficiently lowered, and the above-described effect can be obtained. Moreover, by setting it as 2 mm or more, it becomes easy to fill a different type metal into the inside of the circular ditch | groove 2 or a pseudo | simulated circular ditch | groove (not shown) by a plating means or a spraying means. On the other hand, by setting the diameter of the dissimilar metal filling portion 3 or the equivalent circle diameter to 20 mm or less, a decrease in heat flux in the dissimilar metal filling portion 3 is suppressed, that is, the solidification delay is suppressed by the dissimilar metal filling portion 3. The stress concentration on the solidified shell at that position is prevented, and the occurrence of surface cracks in the slab can be prevented. That is, when the diameter or equivalent circle diameter exceeds 20 mm, surface cracks occur, so the diameter or equivalent circle diameter of the dissimilar metal filling portion 3 needs to be 20 mm or less. When the shape of the dissimilar metal filling portion 3 is a pseudo circle, the equivalent circle diameter d of the pseudo circle is calculated by the following equation (5).
Equivalent circle diameter d = (4 × C / π) 1/2 (5)
In the formula (5), C is the area (mm 2 ) of the dissimilar metal filling portion 3.

図1では、鋳造方向または鋳型幅方向に同一形状の異種金属充填部3を設置しているが、本発明では、必ずしも、同一形状の異種金属充填部3を設置する必要はない。また、異種金属充填部3の直径または円相当径が2〜20mmの範囲内であれば、直径の異なる異種金属充填部3を鋳造方向または鋳型幅方向に設置しても構わない。この場合も、鋳型内での凝固シェルの不均一冷却に起因する鋳片表面割れを防止することが可能となる。   In FIG. 1, the dissimilar metal filling part 3 having the same shape is installed in the casting direction or the mold width direction. However, in the present invention, it is not always necessary to install the dissimilar metal filling part 3 having the same shape. Moreover, as long as the diameter or equivalent circle diameter of the dissimilar metal filling part 3 is in the range of 2 to 20 mm, the dissimilar metal filling part 3 having a different diameter may be installed in the casting direction or the mold width direction. In this case as well, it is possible to prevent slab surface cracking due to non-uniform cooling of the solidified shell in the mold.

異種金属充填部3の充填厚みHは0.5mm以上とする必要がある。充填厚みHを0.5mm以上とすることで、異種金属充填部3における熱流束の低下が十分となり、熱流束の周期的な変動の効果を得ることができる。また、充填厚みHは異種金属充填部3の直径または円相当径d(mm)以下にする必要がある。充填厚みを異種金属充填部3の直径または円相当径と同等、またはそれらよりも小さくするので、鍍金手段や溶射手段による円形凹溝及び擬似円形凹溝への異種金属の充填が容易となり、且つ、充填した異種金属と鋳型銅板との間に隙間や割れが生じることもない。異種金属と鋳型銅板との間に隙間や割れが生じた場合には、充填した異種金属の亀裂や剥離が生じ、鋳型寿命の低下、鋳片の割れ、更には拘束性ブレークアウトの原因となる。すなわち、異種金属充填部3の充填厚みHは、下記の(2)式を満足することが必要である。   The filling thickness H of the dissimilar metal filling part 3 needs to be 0.5 mm or more. By setting the filling thickness H to 0.5 mm or more, the heat flux in the dissimilar metal filling portion 3 is sufficiently lowered, and the effect of periodic fluctuations in the heat flux can be obtained. Further, the filling thickness H needs to be equal to or less than the diameter of the dissimilar metal filling portion 3 or the equivalent circle diameter d (mm). Since the filling thickness is equal to or smaller than the diameter of the dissimilar metal filling portion 3 or the equivalent circle diameter, filling of the dissimilar metal into the circular concave groove and the pseudo circular concave groove by the plating means or the spraying means becomes easy, and No gaps or cracks occur between the filled dissimilar metal and the mold copper plate. If a gap or crack occurs between a dissimilar metal and the mold copper plate, the filled dissimilar metal will crack or peel off, leading to a reduction in mold life, cracking of the slab, and even a restrictive breakout. . That is, the filling thickness H of the dissimilar metal filling portion 3 needs to satisfy the following formula (2).

0.5≦H≦d (2)
この場合、異種金属の充填厚みHは円形凹溝或いは擬似円形凹溝の深さ以下となる。充填厚みHの上限値は、円形凹溝の直径dで決まる。但し、充填厚みHが10.0mmを超えると上記効果は飽和するので、充填厚みHは、円形凹溝の直径d以下で且つ10.0mm以下とすることが好ましい。
0.5 ≦ H ≦ d (2)
In this case, the filling thickness H of the dissimilar metal is equal to or less than the depth of the circular concave groove or the pseudo circular concave groove. The upper limit value of the filling thickness H is determined by the diameter d of the circular groove. However, since the above effect is saturated when the filling thickness H exceeds 10.0 mm, the filling thickness H is preferably not more than the diameter d of the circular groove and not more than 10.0 mm.

また、異種金属充填部3同士の間隔Pは、異種金属充填部3の直径または円相当径dの0.2倍以上であることが好ましい。つまり、間隔Pは異種金属充填部3の直径または円相当径に対して下記の(4)式の関係を満足することが好ましい。   Moreover, it is preferable that the space | interval P between the different metal filling parts 3 is 0.2 times or more of the diameter of the different metal filling part 3, or the equivalent circle diameter d. That is, it is preferable that the distance P satisfies the relationship of the following expression (4) with respect to the diameter or equivalent circle diameter of the dissimilar metal filling portion 3.

P≧0.2×d (4)
間隔Pが十分に大きく、異種金属充填部3における熱流束と鋳型内壁部(異種金属充填部3が形成されていない部位)の熱流束との差が大きくなり、上記効果を得ることができる。間隔Pの上限値は特に規定しないが、この間隔が大き過ぎると、異種金属充填部3の面積率が低下するので「2.0×d」以下にすることが好ましい。
P ≧ 0.2 × d (4)
The interval P is sufficiently large, and the difference between the heat flux in the dissimilar metal filling part 3 and the heat flux of the inner wall part of the mold (the part where the dissimilar metal filling part 3 is not formed) becomes large, and the above effect can be obtained. The upper limit value of the interval P is not particularly defined, but if the interval is too large, the area ratio of the dissimilar metal filling portion 3 is lowered, so that it is preferably set to “2.0 × d” or less.

銅鋳型内壁面に銅鋳型表面の保護のための鍍金層を設けた例を図4に示す。異種金属充填部3を形成させた銅鋳型内壁面に、凝固シェルによる磨耗や熱履歴による鋳型表面の割れを防止することを目的として、鍍金層4を設けることが好ましい。鍍金層4は一般的に用いられるニッケル系合金、例えばニッケル−コバルト合金(Ni−Co合金)などを鍍金することで十分である。鍍金層4の厚みhは2.0mm以下にすることが好ましい。鍍金層4の厚みhを2.0mm以下にすることで、熱流束に及ぼす鍍金層4の影響を少なくすることができ、異種金属充填部3による熱流束の周期的な変動の効果を十分に得ることができる。   FIG. 4 shows an example in which a plating layer for protecting the copper mold surface is provided on the inner wall surface of the copper mold. It is preferable to provide a plating layer 4 on the inner wall surface of the copper mold on which the dissimilar metal filling portion 3 is formed in order to prevent wear of the solidified shell and cracking of the mold surface due to thermal history. The plating layer 4 is sufficient by plating a commonly used nickel-based alloy such as a nickel-cobalt alloy (Ni-Co alloy). The thickness h of the plating layer 4 is preferably 2.0 mm or less. By setting the thickness h of the plating layer 4 to 2.0 mm or less, the influence of the plating layer 4 on the heat flux can be reduced, and the effect of periodic fluctuation of the heat flux by the dissimilar metal filling portion 3 can be sufficiently obtained. Can be obtained.

特許文献2に記載されているように、鋳型内壁面に、複数個の異種金属充填部がそれぞれ独立して形成された鋳型を用いれば、熱流束の周期的な変動が生じ、鋳片表面割れの発生しやすい高速鋳造時や中炭素鋼の鋳造時においても、鋳片表面割れの防止効果が得られる。この熱流束の周期的な変動を生じさせるためには、異種金属の熱伝導率λは、鋳型(銅)の熱伝導率λcに対して80%以下あるいは125%以上である必要がある。熱伝導率λが、熱伝導率λcに対して80%よりも大きいあるいは125%より小さいと、異種金属充填部3による熱流束の周期的な変動の効果が不十分であるために、鋳片表面割れの発生しやすい高速鋳造時や中炭素鋼の鋳造時において、鋳片表面割れの防止効果が不十分になる。   As described in Patent Document 2, if a mold in which a plurality of different metal filling portions are independently formed on the inner wall surface of the mold is used, periodic fluctuations in the heat flux occur, and the slab surface cracks occur. The effect of preventing cracks on the slab surface can be obtained even during high-speed casting, where medium-carbon steel is likely to occur. In order to cause the periodic fluctuation of the heat flux, the thermal conductivity λ of the dissimilar metal needs to be 80% or less or 125% or more with respect to the thermal conductivity λc of the mold (copper). If the thermal conductivity λ is larger than 80% or smaller than 125% with respect to the thermal conductivity λc, the effect of the periodic fluctuation of the heat flux by the dissimilar metal filling portion 3 is insufficient, so that the slab The effect of preventing slab surface cracking is insufficient at the time of high-speed casting in which surface cracks are likely to occur or during casting of medium carbon steel.

異種金属としては、鍍金や溶射のしやすいNi(熱伝導率:約90W/(m・K))及びNi合金(熱伝導率:約40〜90W/(m・K))を用いることができるし、銅合金(熱伝導率:約100〜398W/(m・K))を用いることができる。また、Ni合金や銅合金以外の金属を使用することもできる。鋳型として、純銅(熱伝導率が398W/(m・K)程度)や前述の銅合金を採用してもよい。特に、鋳型内電磁攪拌を行う場合には、コイルからの溶鋼中への磁場強度を減衰させないために、銅以外の成分が数%加えられ、導電率が低くなった銅合金からなる鋳型を使用することとなり、銅合金の熱伝導率も純銅に比べて低下する。異種金属及び/または鋳型の金属を適宜選択することによって、異種金属の熱伝導率を鋳型(銅)の熱伝導率に対して80%以下あるいは125%以上に調整する。   As the dissimilar metal, it is possible to use Ni (thermal conductivity: about 90 W / (m · K)) and Ni alloy (thermal conductivity: about 40 to 90 W / (m · K)) that are easily plated and sprayed. Copper alloy (thermal conductivity: about 100 to 398 W / (m · K)) can be used. Moreover, metals other than Ni alloy and copper alloy can also be used. As the mold, pure copper (having a thermal conductivity of about 398 W / (m · K)) or the above-described copper alloy may be employed. In particular, when performing electromagnetic stirring in the mold, in order not to attenuate the magnetic field strength from the coil into the molten steel, use a mold made of a copper alloy with a few percent of components other than copper added to reduce the conductivity. Therefore, the thermal conductivity of the copper alloy is also lower than that of pure copper. By appropriately selecting the different metal and / or the metal of the mold, the thermal conductivity of the different metal is adjusted to 80% or lower or 125% or higher with respect to the thermal conductivity of the mold (copper).

<実験>
銅板に充填する円形凹溝に充填した異種金属の熱伝導率λと鋳型(銅)の熱伝導率λcと、連続鋳造で製造されたスラブの表面割れと、の関係を調査するべく鋼の連続鋳造を複数回行う実験を行った。実験の鋼の連続鋳造では、長辺長さ2.1m、短辺長さ0.25mの内面空間サイズを有し、異種金属充填部3が形成された水冷銅鋳型を用いている。水冷銅鋳型の上端から下端までの長さ(=鋳型長)は900mmであり、実験の鋼の連続鋳造では、メニスカスを鋳型上端より80mm下方の位置とし、メニスカスより30mm上方から、メニスカスよりも190mm下方の位置までの範囲(範囲長さ:(Q+R)=220mm)の鋳型内壁面に異種金属充填部3を形成している。
<Experiment>
In order to investigate the relationship between the thermal conductivity λ of dissimilar metals filled in circular grooves filled in copper plates, the thermal conductivity λc of molds (copper), and the surface cracks of slabs produced by continuous casting, continuous steel An experiment was conducted in which casting was performed multiple times. In the continuous casting of steel in the experiment, a water-cooled copper mold having an inner space size of a long side length of 2.1 m and a short side length of 0.25 m and having a dissimilar metal filling portion 3 formed thereon is used. The length from the upper end to the lower end of the water-cooled copper mold (= mold length) is 900 mm. In the continuous casting of the experimental steel, the meniscus is positioned 80 mm below the upper end of the mold, from 30 mm above the meniscus, and 190 mm from the meniscus. The dissimilar metal filling portion 3 is formed on the inner wall surface of the mold in the range up to the lower position (range length: (Q + R) = 220 mm).

連続鋳造の各々では、鋳型の銅として銅合金を、異種金属としてNi合金を採用し、異種金属の熱伝導率λと銅合金の熱伝導率λcとが適宜変更された連続鋳造用鋳型を用いて、銅合金に対する異種金属の熱伝導率の比λ/λcを変更している。実験の全ての連続鋳造では、直径dが2〜20mmであり、前述の(1)及び(2)式を満たしているが、異種金属の熱伝導率が、銅合金に対して80%以下であることを満たす場合とそうでない場合とがある。   In each of the continuous castings, a copper alloy is used as the mold copper, a Ni alloy is used as the dissimilar metal, and a continuous casting mold in which the heat conductivity λ of the dissimilar metal and the heat conductivity λc of the copper alloy are appropriately changed is used. Thus, the ratio λ / λc of the thermal conductivity of the dissimilar metal to the copper alloy is changed. In all the continuous castings in the experiment, the diameter d is 2 to 20 mm and satisfies the above-mentioned formulas (1) and (2), but the thermal conductivity of different metals is 80% or less with respect to the copper alloy. There are cases where some are satisfied and cases where it is not.

実験では、鋳片表面割れを評価した。実験での熱伝導率比λ/λc(−)と鋳片表面割れ長さ(mm/m)の関係を図5に示す。鋳片に表面割れが発生する場合、表面割れは縦割れが多く、該縦割れの長さを測定している。カラーチェックによる目視で縦割れを確認し、鋳片長さに対する縦割れの長さで、鋳片表面割れを評価してある。図5のグラフから、熱伝導率比λ/λcが0.8(百分率で80%に相当)以下では、凝固シェル表面での表面割れの発生が抑えられていることがわかる。また、熱伝導率比λ/λcが1.25(百分率で125%)以上であれば、熱伝導率比λ/λcが0.8以下である場合と同様に、熱抵抗の周期的な変動が鋳型内壁に生じ、鋳片の表面割れの発生が抑えられる効果が期待できる。   In the experiment, slab surface cracks were evaluated. FIG. 5 shows the relationship between the thermal conductivity ratio λ / λc (−) and the slab surface crack length (mm / m) in the experiment. When surface cracks occur in the slab, the surface cracks are often vertical cracks, and the length of the vertical cracks is measured. The vertical crack was confirmed visually by color check, and the slab surface crack was evaluated by the length of the vertical crack relative to the slab length. From the graph of FIG. 5, it can be seen that when the thermal conductivity ratio λ / λc is 0.8 (corresponding to a percentage of 80%) or less, the occurrence of surface cracks on the surface of the solidified shell is suppressed. In addition, if the thermal conductivity ratio λ / λc is 1.25 (125% in percentage) or more, the thermal resistance is periodically changed similarly to the case where the thermal conductivity ratio λ / λc is 0.8 or less. Is produced on the inner wall of the mold, and the effect of suppressing the occurrence of surface cracks in the slab can be expected.

本発明者らは、上記の連続鋳造用鋳型を用いる場合で、オシレーションマークに起因する鋳片の表面割れを効果的に抑制するべくオシレーションマークが形成される機構について鋭意検討した結果、異種金属充填部の中心間の距離に応じて、連続鋳造用鋳型に加える振動を調整することにより、オシレーションマークとなる凹凸面の頂部または谷部を、熱流束が周期的に変動する鋳型内壁部分に確実に接触させ、これにより、前記凝固シェル部分の頂部と谷部との差を低減し得ると考えた。   As a result of earnestly examining the mechanism by which the oscillation mark is formed in order to effectively suppress the surface crack of the slab caused by the oscillation mark in the case of using the above-described continuous casting mold, By adjusting the vibration applied to the casting mold for continuous casting according to the distance between the centers of the metal filling part, the mold inner wall part where the heat flux periodically fluctuates at the top or valley of the uneven surface that becomes the oscillation mark It was thought that this could reduce the difference between the top and valley of the solidified shell portion.

オシレーションマークの形成機構について説明する。鋳型長辺1の内壁近傍に形成される凝固シェル11aを図6に示す。鋼の連続鋳造方法では、冷却している鋳型に溶鋼11を注入し、鋳型の内壁近傍に凝固シェル11aを形成し、鋳型に上下方向に振動を加えつつ鋳型から未凝固の溶鋼11を有する凝固シェル11aを引き抜いて、鋼の鋳片を製造する。図6において、鋳型長辺1に振動が加えられていない初期状態の凝固シェル11aを(A)に示してあり、振動によって先端部が変形を受けた凝固シェル11aを(B)に、振動が続き、周期的な凹凸面が形成された凝固シェル11aを(C)に、示してある。   The formation mechanism of the oscillation mark will be described. A solidified shell 11a formed in the vicinity of the inner wall of the mold long side 1 is shown in FIG. In the continuous casting method of steel, molten steel 11 is poured into a cooling mold, a solidified shell 11a is formed in the vicinity of the inner wall of the mold, and solidified having unsolidified molten steel 11 from the mold while vibrating the mold in the vertical direction. The shell 11a is pulled out to produce a steel slab. In FIG. 6, the solidified shell 11a in the initial state where no vibration is applied to the mold long side 1 is shown in (A), and the solidified shell 11a whose tip is deformed by vibration is shown in (B). Subsequently, (C) shows a solidified shell 11a on which a periodic uneven surface is formed.

出口がダミーバーで閉じられた状態の鋳型に溶鋼11が注入され、図6(A)に示すように、冷却されている鋳型長辺1の内壁近傍で溶鋼11が凝固して凝固シェル11aが形成される。図示は省略してあるが、鋳型長辺1の内壁には、ナタネ油などの焼き付き防止剤がスプレーにより塗覆され、凝固シェル11aの内壁への焼き付きが防止されている。また、溶鋼11の表面にモールドパウダー21を投入することで、溶鋼11の表面には、モールドパウダーが溶融して溶融スラグ24の層が形成され、次いで、該溶融スラグ24の層の上には、半固体状(半溶融状)となる半溶融パウダー23の層が形成され、該半溶融パウダー23の層の上には、固体パウダー22の層が形成される。   Molten steel 11 is poured into a mold whose outlet is closed by a dummy bar, and as shown in FIG. 6A, the molten steel 11 is solidified near the inner wall of the cooled mold long side 1 to form a solidified shell 11a. Is done. Although illustration is omitted, the inner wall of the mold long side 1 is coated with an anti-seizing agent such as rapeseed oil by spraying to prevent the inner wall of the solidified shell 11a from being seized. Further, by introducing mold powder 21 onto the surface of molten steel 11, mold powder is melted on the surface of molten steel 11 to form a layer of molten slag 24, and then on the layer of molten slag 24. A layer of semi-molten powder 23 that is semi-solid (semi-molten) is formed, and a layer of solid powder 22 is formed on the layer of semi-molten powder 23.

図6(A)に示す状態で凝固シェル11aを鋳型から、鋳片引き抜き速度Vc(m/分)で引き抜くとともに、鋳型を振動させると、図6(B)に示すように、凝固シェル11aと鋳型長辺1の内壁との間に隙間が形成され、該隙間に溶融スラグ24が流入していくことになる。鋳型の振動によって、鋳型が下方へ向かう際の速度が、凝固シェル11aの引き抜き速度Vcよりも大きい場合が生じる。その際、溶融スラグ24のうち、高粘性部分が凝固シェル11aの先端部を押し曲げることになる。   In the state shown in FIG. 6A, when the solidified shell 11a is drawn from the mold at the slab drawing speed Vc (m / min) and the mold is vibrated, as shown in FIG. A gap is formed between the inner wall of the mold long side 1 and the molten slag 24 flows into the gap. Due to the vibration of the mold, the speed at which the mold moves downward may be larger than the drawing speed Vc of the solidified shell 11a. At that time, the highly viscous portion of the molten slag 24 pushes and bends the tip of the solidified shell 11a.

先端部が押し曲げられた後、凝固シェル11aが鋳型から引き抜かれることになるが、鋳型を上下方向に動かす振動が繰り返され、再び先端部が押し曲げられ、図6(C)に示すように、凝固シェル11aに周期的な凹凸面が形成され、鋳片にオシレーションマークが形成されることになる。凹凸面において隣接する谷部(または頂部)の間隔sd(mm)は、振動の1周期T(分)の間に、凝固シェル11aが進行する長さ(mm)であり、引き抜き速度Vc(m/分)と周期T[=1/周波数f(回/分)](分)とを用いて、次の式で表される。   After the tip is pushed and bent, the solidified shell 11a is pulled out from the mold, but the vibration for moving the mold in the vertical direction is repeated, and the tip is pushed and bent again, as shown in FIG. A periodic uneven surface is formed on the solidified shell 11a, and an oscillation mark is formed on the slab. An interval sd (mm) between adjacent valley portions (or top portions) on the concavo-convex surface is a length (mm) that the solidified shell 11a travels during one period T (minute) of vibration, and a drawing speed Vc (m / Min) and period T [= 1 / frequency f (times / min)] (min), it is expressed by the following equation.

sd=1000×Vc/f (6)
凝固シェル11aの谷部または頂部が間隔sd(mm)下方に進む間に、異種金属充填部及び鋳型銅板の両方に接すれば、谷部または頂部の凝固シェル11aの部位が抜熱される際に、周期的な熱流束変動を受けるので、その部位での不均一凝固が改善され、凹凸面の頂部と谷部との差が低減され、延いては鋳片でのオシレーションマークに起因する表面割れの発生が抑えられる。異種金属充填部3の鋳造方向における中心間の距離PH[mm]が間隔sd[mm]以下となれば、振動の1周期T(分)の間に、谷部または頂部の凝固シェル11aの部位が異種金属充填部及び鋳型銅板の両方に確実に接することになる。PH≦sdの不等式の右辺に(6)式の右辺を代入すると、次の式が導かれる。
sd = 1000 × Vc / f (6)
When the valley portion or the top portion of the solidified shell 11a moves downward in the interval sd (mm), if it contacts both the dissimilar metal filling portion and the mold copper plate, when the portion of the solidified shell 11a in the valley portion or the top portion is removed, Due to periodic heat flux fluctuations, non-uniform solidification at the site is improved, the difference between the top and valley of the uneven surface is reduced, and eventually surface cracks caused by oscillation marks in the slab Occurrence is suppressed. If the distance PH [mm] between the centers in the casting direction of the dissimilar metal filling portion 3 is equal to or less than the interval sd [mm], the portion of the solidified shell 11a at the valley or top during one period T (minute) of vibration. Reliably contacts both the dissimilar metal filling part and the mold copper plate. Substituting the right side of equation (6) for the right side of the inequality PH ≦ sd, the following equation is derived.

PH≦1000×Vc/f (7)
また、距離PHが振幅Sの半分よりも小さくなると、オシレーションの1周期の間で、凝固シェルが常に低熱伝導金属部または鋳型銅板部に接する結果、オシレーションマーク間の凸部の抜熱が周期的な熱流束変動を受けず、オシレーションマーク深さの低減効果が得られない。その結果、凝固シェルは、周期的な熱流束の変動を受けくい状態で冷却されることになるので、凹凸面の頂部と谷部との差を低減する効果が生じにくくなる。よって、距離PHは、振幅Sの半分以上となる必要があり、次の式が導かれる。
PH ≦ 1000 × Vc / f (7)
When the distance PH is smaller than half of the amplitude S, the solidified shell is always in contact with the low thermal conductive metal part or the mold copper plate part during one oscillation period, so that the heat removal of the convex part between the oscillation marks is eliminated. It is not subject to periodic heat flux fluctuations, and the effect of reducing the oscillation mark depth cannot be obtained. As a result, the solidified shell is cooled in a state where it is difficult to receive periodic fluctuations in the heat flux, and therefore, the effect of reducing the difference between the top and valley of the uneven surface is less likely to occur. Therefore, the distance PH needs to be more than half of the amplitude S, and the following equation is derived.

S/2×≦PH≦1000×Vc/f (3)
なお、距離PHを、間隔sdの0.6倍以下とすることがより好ましい。これにより、表面割れが発生し易い鋼種・鋳造条件においても、表面割れの無い鋳片を製造することが可能となる。
S / 2 × ≦ PH ≦ 1000 × Vc / f (3)
The distance PH is more preferably 0.6 times or less of the interval sd. This makes it possible to produce a slab free of surface cracks even in steel types and casting conditions where surface cracks are likely to occur.

振動によって、図6(B)で示したように、溶融スラグ14が、凝固シェル11aと鋳型内壁との隙間へ流入するように、モールドパウダーからなる層に力が加わる。モールドパウダー(溶融スラグ)の物性(粘性など)や振動の条件(周波数fなど)によっては、溶融スラグが前記隙間に流入しなくなる虞がある。よって、実操業上は、実績のあるモールドパウダーや振動条件に合せて、(3)式で計算される中心間の距離PHとなる異種金属充填部3が複数形成されている鋳型を作製し、該鋳型を用いて鋼の連続鋳造を行うことが望ましい。距離PHが(3)式を満足すれば、間隔Pが(4)式を満たすか否かに拘わらず、凹凸面の頂部と谷部との差の低減効果が生じる。振動が、正弦波や非正弦波に基づくものであっても、凹凸面の頂部と谷部との差の低減効果は変わらない。   As shown in FIG. 6 (B), the vibration applies a force to the layer made of the mold powder so that the molten slag 14 flows into the gap between the solidified shell 11a and the inner wall of the mold. Depending on the physical properties (such as viscosity) of the mold powder (molten slag) and vibration conditions (such as frequency f), the molten slag may not flow into the gap. Therefore, in actual operation, a mold in which a plurality of dissimilar metal filling portions 3 having a center-to-center distance PH calculated by the equation (3) is formed in accordance with a proven mold powder and vibration conditions, It is desirable to perform continuous casting of steel using the mold. If the distance PH satisfies the expression (3), an effect of reducing the difference between the top part and the trough part of the concavo-convex surface occurs regardless of whether or not the distance P satisfies the expression (4). Even if the vibration is based on a sine wave or a non-sine wave, the effect of reducing the difference between the top and valley of the uneven surface is not changed.

炭素量が0.08〜0.17質量%の亜包晶鋼の鋳片は、凝固時の包晶反応による変態収縮量が大きく、オシレーションマークの凹凸面に変態収縮に起因した応力が作用することで、凹凸面の頂部と谷部との差が大きくなりやすい。本発明に従った寸法の異種金属充填部が形成された連続鋳造用鋳型を、本発明に従い振動させて鋼の連続鋳造を行うことで、凹凸面の隣接する頂部(または谷部)の距離以下の間隔で、前記応力が分散され、凹凸面の頂部と谷部との差が低減される。よって、本発明は特に亜包晶領域の溶鋼の表面割れを低減するのに好適である。   The slab of hypoperitectic steel with a carbon content of 0.08 to 0.17% by mass has a large amount of transformation shrinkage due to the peritectic reaction during solidification, and stress caused by transformation shrinkage acts on the uneven surface of the oscillation mark. By doing so, the difference between the top part and the trough part of the uneven surface tends to increase. The continuous casting mold in which the dissimilar metal filling portion having the dimensions according to the present invention is formed is vibrated according to the present invention to perform continuous casting of steel, so that the distance between the adjacent top portions (or valley portions) of the uneven surface is less than the distance. At the intervals, the stress is dispersed, and the difference between the top and valley of the uneven surface is reduced. Therefore, the present invention is particularly suitable for reducing the surface cracking of molten steel in the subperitectic region.

本発明によれば、鋳型内壁に形成された凹溝に、鋳型とは異なる熱伝導率を有する異種金属が充填された鋳型を用いて、振動条件を適正化することで、オシレーションマークの凹凸面の頂部と谷部との差を低減し、隣接する頂部間の縦割れや鋳片の幅方向に沿って形成される谷部での横割れのない鋳片を製造することができる。   According to the present invention, the unevenness of the oscillation mark can be obtained by optimizing the vibration conditions by using a mold in which a groove formed on the inner wall of the mold is filled with a different metal having a thermal conductivity different from that of the mold. The difference between the top part of a surface and a trough part can be reduced, and the cast piece without the vertical crack between adjacent top parts and the transverse crack in the trough part formed along the width direction of a cast piece can be manufactured.

図1に示すように、内壁面に、円形状の異種金属充填部が複数形成された水冷銅鋳型を準備し、中炭素鋼(化学成分、C:0.05〜0.20質量%、Si:0.10〜0.30質量%、Mn:0.50〜1.20質量%、P:0.010〜0.030質量%、S:0.002〜0.010質量%、Al:0.020〜0.050質量%、残部Fe及びその他不可避的不純物)を、準備した水冷銅鋳型で鋳造し、鋳造後の鋳片の表面割れを調査する試験を行った。水冷銅鋳型は、長辺長さが2.1m、短辺長さが0.22mの内面空間サイズを有する。   As shown in FIG. 1, a water-cooled copper mold in which a plurality of circular dissimilar metal filling portions are formed on an inner wall surface is prepared, and a medium carbon steel (chemical component, C: 0.05 to 0.20 mass%, Si : 0.10 to 0.30 mass%, Mn: 0.50 to 1.20 mass%, P: 0.010 to 0.030 mass%, S: 0.002 to 0.010 mass%, Al: 0 0.020 to 0.050 mass%, the remaining Fe and other inevitable impurities) were cast with the prepared water-cooled copper mold, and a test was conducted to investigate the surface cracks of the cast slab after casting. The water-cooled copper mold has an inner space size with a long side length of 2.1 m and a short side length of 0.22 m.

使用した水冷銅鋳型の上端から下端までの長さ(=鋳型長)は950mmであり、定常鋳造時のメニスカス(鋳型内溶鋼湯面)の位置を、鋳型上端から100mm下方位置に設定した。先ず、鋳型上端より60mm下方の位置から鋳型上端より300mm下方の位置までの範囲(Q=20mmとし、Rを適宜変更)に、鋳型内壁面に円形凹溝の加工を施してある。次いで、この円形凹溝の内部に鍍金手段を用いて、異種金属として、ニッケル合金(熱伝導率:80(W/(m・K)))を充填し、異種金属充填部を形成することとした。   The length from the upper end to the lower end of the water-cooled copper mold used (= mold length) was 950 mm, and the position of the meniscus (molten steel surface in the mold) during steady casting was set at a position 100 mm below the upper end of the mold. First, in the range from a position 60 mm below the upper end of the mold to a position 300 mm below the upper end of the mold (Q = 20 mm, R is appropriately changed), a circular groove is processed on the inner wall surface of the mold. Next, using a plating means in the inside of the circular concave groove, nickel alloy (thermal conductivity: 80 (W / (m · K))) is filled as a dissimilar metal to form a dissimilar metal filling portion. did.

鋳型の材料としては、熱伝導率が約380(W/(m・K))となる銅とし、異種金属充填部3の直径d(mm)や、異種金属充填部3の充填厚みH、鋳造方向における中心間の距離PHなどを変更した水冷銅鋳型を用い、更には、鋳片引き抜き速度Vc(m/分)、鋳型に与える振動の振幅Sや周波数fを変更して、鋼の連続鋳造を複数回行った(No.1〜33)。モールドパウダーとしては、塩基度(質量%CaO)/(質量%SiO)が1.25、1300℃での粘度が1.3poiseのものを使用した。 The mold material is copper having a thermal conductivity of about 380 (W / (m · K)), the diameter d (mm) of the dissimilar metal filling portion 3, the filling thickness H of the dissimilar metal filling portion 3, and the casting. Continuous casting of steel by using a water-cooled copper mold with different center-to-center distance PH in the direction, and further changing the slab drawing speed Vc (m / min) and the amplitude S and frequency f of vibration applied to the mold Was performed a plurality of times (Nos. 1-33). As the mold powder, one having a basicity (mass% CaO) / (mass% SiO 2 ) of 1.25 and a viscosity at 1300 ° C. of 1.3 poise was used.

No.1〜33において、製造されたスラブの表面割れを測定した。表面割れは、カラーチェックによる目視で確認し、鋳造方向に沿った縦割れ、鋳片幅方向に沿った横割れ、の両方の長さを測定し、合計長さ(mm)を、鋳造方向におけるスラブの長さ(m)で除算して、スラブの表面割れ長さ[mm/m]算出し、表面割れの尺度として求めた。また、スラブの幅方向において端と中央とで、スラブの厚みを測定し、両者の差が5mm以上ある場合には、バルジングが発生したと判断して、バルジングの発生有無を評価した。更には、レーザー距離計を用いて測定したスラブ表面の凹凸から頂部と谷部との差を測定した。   No. 1-3, the surface crack of the manufactured slab was measured. Surface cracks are confirmed visually by color check, and the lengths of both vertical cracks along the casting direction and transverse cracks along the slab width direction are measured, and the total length (mm) in the casting direction is measured. By dividing by the length (m) of the slab, the surface crack length [mm / m] of the slab was calculated and obtained as a measure of the surface crack. Further, the thickness of the slab was measured at the end and the center in the width direction of the slab, and when the difference between the two was 5 mm or more, it was determined that bulging occurred, and the presence or absence of bulging was evaluated. Furthermore, the difference between the top and valley was measured from the irregularities on the slab surface measured using a laser distance meter.

各連続鋳造で用いた鋳型や振動の条件、表面割れ指数、バルジングの発生有無及びオシレーションの頂部と谷部との差の結果を表1に示す。   Table 1 shows the results of the mold used in each continuous casting, the vibration conditions, the surface cracking index, the occurrence of bulging, and the difference between the top and valley of the oscillation.

メニスカスから、メニスカスよりも(1)式で求まる長さ以上下方の位置までの範囲に、鋳型の熱伝導率に対して熱伝導率が80%以下の異種金属充填部金属が形成され、且つ、(2)式を満たし、異種金属充填部の直径dが2〜20mmである鋳型を用い、(3)式を満たしているNo.の連続鋳造の場合に、表1の「本発明例/比較例」の欄で、「本発明例」と記載し、いずれかを満たさない連続鋳造の場合には「比較例」と記載してある。なお、前述の実験によって、鋳型の熱伝導率に対して熱伝導率が80%以下の異種金属が充填された異種金属充填部3が形成された水冷銅鋳型は、鋳片の表面割れの発生を抑える効果を奏することがわかっており、本発明例で用いた鋳型は、異種金属充填部3の金属の熱伝導率が、鋳型の熱伝導率に対して80%以下である。   A dissimilar metal filling portion metal having a thermal conductivity of 80% or less with respect to the thermal conductivity of the mold is formed in the range from the meniscus to the position below the meniscus by a length determined by the formula (1) and below, and Using a mold that satisfies the formula (2) and the diameter d of the dissimilar metal filling portion is 2 to 20 mm, No. 1 that satisfies the formula (3) is satisfied. In the case of continuous casting, in the column of “Invention Example / Comparative Example” in Table 1, “Invention Example” is described, and in the case of continuous casting that does not satisfy any of these, “Comparative Example” is described. is there. In the water-cooled copper mold in which the dissimilar metal filling portion 3 filled with the dissimilar metal having a heat conductivity of 80% or less with respect to the heat conductivity of the mold is formed by the above-described experiment, the surface crack of the slab is generated. In the mold used in the example of the present invention, the metal thermal conductivity of the dissimilar metal filling portion 3 is 80% or less with respect to the thermal conductivity of the mold.

No.1〜9について、No.2〜8では、異種金属充填部の直径dが2〜20mmの範囲内となり、オシレーションマークの凹凸面の頂部と谷部との差が0.5mm以下となっている。一方で、No.1及び9では、直径dがその範囲外となっており、頂部と谷部との差が0.6mm以上となっている。   No. For Nos. 1-9, no. In Nos. 2 to 8, the diameter d of the dissimilar metal filling portion is in the range of 2 to 20 mm, and the difference between the top and valley of the uneven surface of the oscillation mark is 0.5 mm or less. On the other hand, no. In 1 and 9, the diameter d is out of the range, and the difference between the top and the valley is 0.6 mm or more.

No.10及び11について、メニスカスから、メニスカスよりも(1)式で求まる長さR下方の位置までの範囲に形成されているNo.10では、頂部と谷部との差が0.45mmであるが、そうでないNo.11では、0.59mmとなり、0.6mmに近い値となっている。   No. For Nos. 10 and 11, No. 10 formed in the range from the meniscus to a position below the meniscus by the length R determined by the expression (1). 10, the difference between the top and the valley is 0.45 mm. 11 is 0.59 mm, which is close to 0.6 mm.

No.12〜18について、No.13〜17では(2)式を満たし、頂部と谷部との差が0.5mm未満となっているが、そうでないNo.12及び18では、0.6mmを超えている。   No. For Nos. 12-18, no. 13 to 17, the formula (2) is satisfied, and the difference between the top and the valley is less than 0.5 mm. In 12 and 18, it exceeds 0.6 mm.

No.19〜33について、No.21〜31では(3)式を満たし、頂部と谷部との差が0.5mm未満となっているが、そうでないNo.19、20及び32、33では、0.5mmを超えている。   No. For Nos. 19 to 33, no. Nos. 21 to 31 satisfy the formula (3) and the difference between the top and the valley is less than 0.5 mm. 19, 20 and 32, 33 are over 0.5 mm.

本発明によって、鋳型内壁に形成された凹溝に、鋳型とは異なる熱伝導率を有する異種金属が充填された鋳型を用いて、振動条件を適正化することで、オシレーションマークの凹凸面の頂部と谷部との差を低減し、隣接する頂部間の縦割れや鋳片の幅方向に沿って形成される谷部での横割れのない鋳片を製造できることがわかった。   According to the present invention, by using a mold in which a concave groove formed on the inner wall of the mold is filled with a dissimilar metal having a thermal conductivity different from that of the mold, by optimizing the vibration conditions, the uneven surface of the oscillation mark It was found that the difference between the top portion and the trough portion can be reduced, and a slab without vertical cracks between adjacent top portions and transverse cracks at the trough portions formed along the width direction of the slab can be produced.

1 鋳型長辺
2 円形凹溝
3 異種金属充填部
4 鍍金層
5 冷却水流路
6 バックプレート
11 溶鋼
11a 凝固シェル
21 モールドパウダー
22 固体パウダー
23 半溶融パウダー
24 溶融スラグ
DESCRIPTION OF SYMBOLS 1 Mold long side 2 Circular groove 3 Dissimilar metal filling part 4 Plating layer 5 Cooling water flow path 6 Back plate 11 Molten steel 11a Solidified shell 21 Mold powder 22 Solid powder 23 Semi-molten powder 24 Molten slag

Claims (4)

連続鋳造用鋳型内に溶鋼を注入しつつ、前記連続鋳造用鋳型を鋳造方向に振動させながら前記溶鋼を引き抜いて、鋳片を製造する鋼の連続鋳造方法であって、
前記連続鋳造用鋳型は、メニスカスよりも上方の任意の位置から、前記メニスカスよりも、鋳片引き抜き速度Vc(m/分)から下記の(1)式で求まる長さR(mm)以上下方の位置までの、水冷式銅鋳型の内壁面の範囲に、鋳型の熱伝導率に対して熱伝導率が80%以下あるいは125%以上である金属が、前記内壁面に周期的に設けられた凹溝に充填されて形成された異種金属充填部をそれぞれ独立して有し、
前記連続鋳造用鋳型の振動の振幅S(mm)及び周波数f(回/分)と前記異種金属充填部の鋳造方向における中心間の距離PH(mm)とは下記の(3)式の関係を満たすことを特徴とする鋼の連続鋳造方法。
R=2×Vc×1000/60 (1)
S/2≦PH≦1000×Vc/f (3)
Injecting molten steel into a continuous casting mold, pulling out the molten steel while vibrating the continuous casting mold in the casting direction, and producing a slab, a steel continuous casting method,
The continuous casting mold is lower than the meniscus by a length R (mm) or more below the meniscus from the slab drawing speed Vc (m / min) determined by the following equation (1). In the range of the inner wall surface of the water-cooled copper mold up to the position, a metal having a thermal conductivity of 80% or less or 125% or more with respect to the thermal conductivity of the mold is periodically provided on the inner wall surface. Each has a different metal filling portion formed by filling the groove,
The amplitude S (mm) and frequency f (times / minute) of the vibration of the continuous casting mold and the distance PH (mm) between the centers in the casting direction of the dissimilar metal filling portion are expressed by the following equation (3). A continuous casting method of steel characterized by satisfying.
R = 2 × Vc × 1000/60 (1)
S / 2 ≦ PH ≦ 1000 × Vc / f (3)
前記凹溝は、直径dが2〜20mmの円形凹溝または円相当径dが2〜20mmの擬似円形凹溝であり、前記異種金属充填部の充填厚みH(mm)と前記異種金属充填部の直径dまたは円相当径d(mm)とは下記の(2)式の関係を満たすことを特徴とする請求項1に記載の鋼の連続鋳造方法。
0.5≦H≦d (2)
The concave groove is a circular concave groove having a diameter d of 2 to 20 mm or a pseudo circular concave groove having an equivalent circle diameter d of 2 to 20 mm, and a filling thickness H (mm) of the dissimilar metal filling portion and the dissimilar metal filling portion. 2. The steel continuous casting method according to claim 1, wherein the diameter d or the equivalent circle diameter d (mm) satisfies the relationship of the following expression (2).
0.5 ≦ H ≦ d (2)
前記異種金属充填部の間隔P(mm)と前記異種金属充填部の直径dまたは円相当径dとは下記の(4)式の関係を満たすことを特徴とする請求項2に記載の鋼の連続鋳造方法。
P≧0.2×d (4)
The distance P (mm) between the dissimilar metal filling portions and the diameter d or equivalent circle diameter d of the dissimilar metal filling portions satisfy the relationship of the following expression (4). Continuous casting method.
P ≧ 0.2 × d (4)
前記溶鋼は、炭素含有量が0.08〜0.17質量%である中炭素鋼であることを特徴とする請求項1から請求項3のいずれか1項に記載の鋼の連続鋳造方法。   The said molten steel is a medium carbon steel whose carbon content is 0.08-0.17 mass%, The continuous casting method of the steel of any one of Claim 1 to 3 characterized by the above-mentioned.
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EP3878572A4 (en) * 2018-11-09 2021-09-15 JFE Steel Corporation Mold for continuous steel casting and continuous steel casting method

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JPH09253801A (en) * 1996-03-26 1997-09-30 Sumitomo Metal Ind Ltd Mold for continuous casting
JP2003170259A (en) * 2001-12-04 2003-06-17 Kawasaki Steel Corp High speed casting method for medium carbon steel slab
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