JP2010274321A - Tundish for continuous casting - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase the separation-removal function of inclusions in a molten steel while improving the yield of the steel. <P>SOLUTION: On the bottom face 13 of a tundish 1, a flat part 30 forming a flat shape at least in the lower part of an injection nozzle 20 is formed. The corner parts between the flat part 30 and the long-side walls 10, 10 have curved parts 31, 31 curved so as to be projected to the external side. The flat part 30 and the curved part 31 are formed along the long-side walls 10 of the tundish 1, and the minimum curvature radius R(m) of the curved part 31 satisfies inequality: 0.1≤R≤(W-D)/2 [wherein W denotes a distance (m) between the intersections P, P between the tangent L<SB>1</SB>of the long-side wall 10 in the position of the maximum molten metal surface M<SB>1</SB>within the tundish 1 and the extension L<SB>2</SB>of the flat part 30; and D denotes the inside diameter (m) of the injection nozzle 20]. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a tundish for continuous casting used when supplying molten steel from a ladle to a mold.

  In continuous casting of steel, molten steel whose components and temperature are adjusted in the refining process is stored in a ladle and transported to a continuous casting machine that performs the continuous casting process. The transported molten steel is injected into the mold of the continuous casting machine. However, when the molten steel is directly injected into the mold from the ladle, it is difficult to control the flow rate of the molten steel. On the other hand, it is necessary to continuously carry out casting by supplying molten steel continuously to the mold while changing the ladle. For this reason, generally, the molten steel in the ladle is once injected into an intermediate container called a tundish through an injection nozzle and the like, and after the flow rate is adjusted in the tundish, it is supplied into the mold.

  There are various types of tundish as described above. For example, a boat-shaped one whose bottom surface has a planar shape is used (Patent Document 1). According to such a tundish, the molten steel is supplied from the injection nozzle to the center of the tundish, and the molten steel passes through the refractory nozzles to the molds of the two continuous casting machines from the outlets at both ends corresponding to the tip of the boat. Leaked. For example, a rod-shaped stopper that moves up and down to adjust the opening area of the outlet is provided at the outlets at both ends of the tundish, and the flow rate control of the molten steel in the tundish is performed by this stopper. .

  Tundish not only has the function of supplying molten steel to the mold while controlling the flow rate as described above, but also slag, which is an oxide inevitably mixed during steel refining, and aluminum added for deoxidation. The non-metallic inclusions such as alumina produced from the above are floated and separated in the tundish using the fact that the specific gravity is smaller than the specific gravity of steel. As a result, non-metallic inclusions in the molten steel are prevented from being fed into the mold as they are, and are not mixed into the slab, thereby suppressing defects during rolling caused by non-metallic inclusions. .

  However, when the tundish of Patent Document 1 described above is used, as shown in FIG. 12, the bottom surface 101 of the tundish 100 has a planar shape, and the corner portion between the bottom surface 101 and the long side wall 102 is Since it is formed at an acute angle without being curved, a flow of the molten steel M along the bottom surface 101, that is, a so-called direct feed flow F, is formed without sufficiently rising in the tundish 100. With this direct feed flow F, a part of the molten steel M supplied from the injection nozzle 110 flows directly to the outlet 111. In this case, since the inclusions in the molten steel M also flow directly to the outlet 111, the inclusions cannot be sufficiently separated and removed in the tundish 100. If it does so, the molten steel M containing an inclusion will flow into a mold as it is, and the quality of the steel finally manufactured will fall.

  Therefore, in order to enhance the floating separation function of inclusions in the tundish, a dam has been provided in the tundish. For example, a plurality of flat bottom weirs are arranged in a tundish along a molten steel flow path (Patent Document 2). By these lower weirs, the flow of molten steel can be adjusted to form an upward flow of molten steel in the tundish. In this way, inclusions are made to float easily, and the inclusions are separated from the molten steel.

JP-A-9-103854 JP-A-1-157748

  However, when the tundish of Patent Document 2 is used, inclusions in the molten steel can be separated and removed during the steady operation, but when the operation is stopped, the molten steel upstream of the lower weir dams into the lower weir. It stops and does not flow downstream and remains in the tundish. Since the residual molten steel remaining on the upstream side of the lower weir is discarded after that, the yield of steel is reduced. Further, since the lower weir is provided in the tundish, an extra refractory is required, and the tundish manufacturing cost is increased.

  This invention is made | formed in view of this point, and it aims at improving the isolation | separation removal function of the inclusion in molten steel, improving the yield of steel in the tundish for continuous casting.

In order to achieve the above object, the present invention is a tundish for continuous casting of steel having a pair of long side walls and a pair of short side walls, and an outlet for flowing molten steel from the tundish to a mold is provided. The pouring nozzle for flowing the molten steel from the ladle into the tundish is arranged along the long side wall in the same straight line in a plan view, and the inner bottom surface of the tundish is at least below the pouring nozzle. A planar portion having a planar shape is formed at the corner portion between the planar portion and the long side wall, and a curved portion that is curved outwardly is formed, and the curved portion is formed on the long side wall. A minimum radius of curvature R (m) of the curved portion is formed so as to satisfy the following formula (1).
0.1 ≦ R ≦ (WD) / 2 (1)
However, W: distance (m) between the intersections of the tangent of the inner side surface of the long side wall of the cross section perpendicular to the long side direction at the position of the maximum molten steel surface in the tundish and the extension line of the plane portion, D: Inner diameter of injection nozzle (m)

  According to the present invention, since the tundish has the flat portion and the curved portion, the molten steel supplied into the tundish from the injection nozzle once flows through the flat portion and then rises along the curved portion. If it does so, the upward flow of molten steel can be formed in a tundish, and the inclusion in molten steel can be levitated by this upward flow. And the inventors derived | led-out said Formula (1) by experiment etc. as conditions of the curved part for fully exhibiting the floating effect of this inclusion. That is, when a curved portion satisfying the above formula (1) is provided, inclusions can be levitated and sufficiently separated and removed from the molten steel. And according to this invention, in order to form the upward flow of molten steel, it is not necessary to provide a lower dam in a tundish conventionally. Then, when the lower weir is provided, when the operation is stopped, the residual molten steel remaining on the upstream side of the lower weir can be suppressed to a very small amount, and the yield of the steel can be improved. Furthermore, since the lower weir itself is unnecessary, the manufacturing cost of the tundish can be suppressed.

  In addition, as described later, the inventors have also attempted to configure the bottom surface of the tundish only with a curved portion (no flat portion is formed). However, in such a case, not only the upward flow of the molten steel by the curved portion but also a direct flow toward the outlet in the substantially horizontal direction along the curved portion is formed in the tundish, and the flow of the molten steel in the tundish is polarized. I found out that That is, some molten steel supplied from the injection nozzle rises along the curved portion, but the remaining molten steel flows directly to the outlet along the bottom surface. If it does so, the inclusion in molten steel cannot fully be removed. Therefore, it has been found that it is effective for the tundish to have a flat portion and a curved portion as in the present invention in order to sufficiently exhibit the floating effect of inclusions.

  A convex portion having a convex shape on the inner side of the tundish may be formed on the flat portion directly under the injection nozzle.

  The long side wall at the maximum molten steel surface position may be provided with a notch that communicates from the inside to the outside of the long side wall.

  The curved portion is an intersection of the tangent to the inner side surface of the long side wall of the cross section perpendicular to the long side direction at the position of the maximum molten steel surface in the tundish centered on the pouring nozzle position and the extension line of the flat portion. It may be formed along the long side wall more than the distance between them.

  The curved portion may be formed along the long side wall from the injection nozzle to the end of the outflow port on the injection nozzle side.

  ADVANTAGE OF THE INVENTION According to this invention, the isolation | separation removal function of the inclusion in molten steel can be improved, improving the yield of steel.

It is explanatory drawing of the longitudinal cross-section which shows the outline of a structure of the tundish concerning this Embodiment. It is explanatory drawing of the cross section which shows the outline of a structure of the tundish concerning this Embodiment. It is explanatory drawing of the longitudinal cross-section which shows the outline of a structure of the tundish concerning this Embodiment. It is explanatory drawing which shows the mode of the flow of the molten steel in a tundish. It is explanatory drawing which shows the flow of the molten steel at the time of comprising the bottom face of a tundish only with a curved part. It is explanatory drawing of the longitudinal cross-section which shows the outline of a structure of the tundish concerning other embodiment. It is explanatory drawing of the cross section which shows the outline of a structure of the tundish concerning other embodiment. It is explanatory drawing of the cross section which shows the outline of a structure of the tundish concerning other embodiment. It is explanatory drawing of the cross section which shows the outline of a structure of the tundish concerning other embodiment. It is explanatory drawing of the longitudinal cross-section which shows the outline of a structure of the tundish concerning other embodiment. It is explanatory drawing of the cross section which shows the outline of a structure of the tundish concerning other embodiment. It is explanatory drawing which shows the mode of the flow of the molten steel in the conventional tundish whose bottom face is planar shape.

  Embodiments of the present invention will be described below. FIG. 1 is an explanatory view of a longitudinal section showing an outline of the configuration of the tundish 1 according to the present embodiment. FIG. 2 is an explanatory diagram of a cross section showing an outline of the configuration of the tundish 1.

As shown in FIGS. 1 and 2, the tundish 1 includes a pair of long side walls 10 and 10 and a pair of short side walls 11 and 11, and the planar shape is formed in a quadrangular shape. Further, the tundish 1 includes a ceiling surface 12 and a bottom surface 13 and can store the molten steel M therein. In the vicinity of the ceiling surface 12 of the long side wall 10 of the tundish 1, as shown in FIG. 3, a notch portion 14 is formed that communicates from the inside to the outside of the long side wall 10. In the tundish 1, the molten steel M can be stored up to the lower end of the notch 14, and the lower end position of the notch 14 is the position of the maximum molten metal surface M ₁ of the molten steel M.

  As shown in FIG. 1, an injection nozzle 20 is inserted downward on the ceiling surface 12 near the center of the tundish 1. The injection nozzle 20 allows the molten steel M to flow from the upper ladle 21 into the tundish 1. Outflow ports 22 and 22 are formed at two locations on the bottom surface 13 near the short side walls 11 and 11 of the tundish 1. Each outlet 22 is connected to a nozzle 23 communicating with a mold of a continuous casting machine (not shown). With the outlet 22 and the nozzle 23, the molten steel M in the tundish 1 can be supplied to the mold. The injection nozzle 20 and the outlets 22 and 22 are arranged along the same straight line along the long side wall 11 of the tundish 1 in plan view.

  A flow rate adjusting rod 24 is provided above the outlet 22. The flow rate adjusting rod 24 can move up and down to change the opening area of the outlet 22 and adjust the flow rate of the molten steel M in the tundish 1.

  On the bottom surface 13 inside the tundish 1, as shown in FIG. 3, a planar portion 30 having a planar shape is formed at least below the injection nozzle 20. At the corner portion between the flat portion 30 and the long side walls 10 and 10 of the tundish 1, curved portions 31 and 31 that are curved outwardly are formed.

Each bending part 31 is formed so that the minimum curvature radius R (m) satisfies the following formula (1). Incidentally, the minimum curvature radius R (m) is assumed to be the case where the curvature of the bending portion 31 is not constant. In such a case, the bending portion 31 has the tightest bending, that is, the curvature radius is the same. The reason is that the minimum portion is the portion where the upward flow F ₁ of the molten steel M is hardly generated.
This formula (1) generates an upward flow F ₁ of the molten steel M along the curved portion 31 in the tundish ₁ so that inclusions in the molten steel M are sufficiently levitated by the upward flow F _1. Therefore, the inventors derived it through experiments and the like. Specifically, the behavior of the molten steel M at the normal operation of the molten steel supply (5 tons / min / strand) through the injection nozzle at the center of the tundish width (about 0.5 m to 1.5 m) that is normally used. As a result of conducting a water model experiment, it was found that when the radius of curvature is less than 0.1 m, the bending becomes too tight and the upward flow F ₁ of the molten steel M does not occur. Therefore, the lower limit value 0.1 m of the minimum curvature radius R is set to the minimum curvature radius necessary for smoothly raising the molten steel M. Incidentally, from the viewpoint of easier to more generate upward flow F ₁ of the molten steel M, preferred lower limit of the minimum radius of curvature R is 0.2 m, more preferred lower limit value is 0.3 m. On the other hand, the larger the radius of curvature, since it upward flow F ₁ of the molten steel M was also confirmed that tends to occur, the upper limit value of the minimum radius of curvature R, which is a value that can be geometrically maximum curvature When the radius is a constant value, the upper limit is reached. Accordingly, the upper limit value of the minimum radius of curvature R is such that the portion directly below the inner diameter of the injection nozzle 20 forms a flat portion 30, so the length D of this portion is excluded and the curvature of the curved portion 31 is constant. In this case, (WD) / 2 was set.
0.1 ≦ R ≦ (WD) / 2 (1)
However, W: distance between intersections P and P between the tangent line L ₁ of the inner side surface of the long side wall 10 and the extension line L ₂ of the flat portion 30 at the position of the maximum molten steel surface M _{1 in} the tundish ₁ (hereinafter, (It may be simply referred to as “lower end width”.) (M), D: Inner diameter (m) of injection nozzle 20

As shown in FIG. 2, the flat portion 30 and the curved portion 31 are formed in the shape described above up to the pair of short side walls 11, 11 along the long side wall 10 of the tundish 1.
By the way, for the minimum radius of curvature R (m) of the curved portion 31, for example, a method for calculating the radius of curvature of a general curve (Shinichi Ichimatsu, Introduction to Analytical Science, Volume 1) (18th edition) It can be determined using a well-known method such as pp265-272).

Next, the effect | action of the tundish 1 comprised as mentioned above is demonstrated based on FIGS. Incidentally, FIG. 4, for explaining the flow of molten steel M in the tundish 1 is shown a portion of the tundish 1 to the position of the melt surface M ₂ of the molten steel M at the time of steady operation.

First, molten steel M is supplied into the tundish 1 from the ladle 21 through the injection nozzle 20. And in a steady state operation, the position of the molten metal surface M ₂ of the molten steel M is stabilized at a predetermined height. The molten steel M supplied from the injection nozzle 20 collides with the bottom surface 13 of the tundish 1 and flows through the flat portion 30. At this time, the molten steel M diffuses in the horizontal direction from below the injection nozzle 20. Thereafter, the molten steel M is increased along the curved portion 31, upward flow F ₁ toward the molten metal surface M ₂ is formed. Due to the upward flow F ₁ , inclusions in the molten steel M also float up and are separated and removed before reaching the outlet 22.

Incidentally, in the tundish 1, increased sufficiently so the flow of the molten steel M toward the outlet 22 along the bottom surface 13 without a so-called direct flow F ₂ is also formed, the direct flow F ₂ upflow F Very small compared to ₁ . For this reason, the inclusions in the molten steel M flowing to the outlet 22 by the direct flow F ₂ are very small, and the inclusions are sufficiently removed in the tundish 1.

  The molten steel M from which the inclusions have been sufficiently removed flows out from the outlet 22 and is supplied to the mold of the continuous casting machine through the nozzle 23.

According to the above embodiment, since the tundish 1 has the flat part 30 and the curved part 31, the molten steel M supplied into the tundish 1 from the injection nozzle 20 flows through the flat part 30 once. Thereafter, it rises along the curved portion 31. Then, it is possible to form the upward flow F ₁ of the molten steel M in the tundish 1, this upward flow F ₁ can be floated inclusions in the molten steel M. Moreover, since the minimum radius of curvature R of the curved portion 31 satisfies the above formula (1), the inclusion floating effect in the molten steel M can be sufficiently exerted, and the inclusion is sufficiently separated from the molten steel M. Can be removed. Therefore, inclusions can be prevented from entering the mold, and high quality steel can be produced.

Further, according to the present embodiment, the inclusions are separated and removed by the upward flow F ₁ of the molten steel M, so that it is not necessary to provide a lower weir for separation and removal in the tundish 1 as in the prior art. Therefore, when the lower weir is provided, the remaining molten steel remaining on the upstream side of the lower weir can be suppressed to a very small amount when the operation is stopped, so that the molten steel M supplied into the tundish 1 is effective. It is possible to improve the yield of steel. Furthermore, since the lower weir itself is unnecessary, the manufacturing cost of the tundish can be suppressed.

By the way, the inventors also attempted to configure the bottom surface of the tundish 1 only with a curved portion (without forming a flat surface portion and with a curved portion that is convex outside the tundish 1). However, in such a case, as shown in FIG. 5, not only the upward flow F ₁ due to the curved portion but also the direct flow F ₂ toward the outlet 22 in the substantially horizontal direction along the curved portion is formed in the tundish 1. It was found that the flow of the molten steel M in the dish 1 is bipolar. That is, some molten steel M supplied from the injection nozzle 20 rises in the height direction of the long side wall 10 along the curved portion, but the remaining molten steel M flows directly to the outlet 22 along the bottom surface. End up. If it does so, the inclusion in the molten steel M cannot fully be removed. Therefore, it was found that the tundish 1 having the flat portion 30 and the curved portion 31 as in the present embodiment is effective in order to sufficiently exhibit the inclusion floating effect.

  Incidentally, the plane portion 30 immediately below the injection nozzle 20 is easily melted when the molten steel M is injected from the injection nozzle 20. The water model experiment also confirms that the flow of the molten steel M exhibits the same behavior as that in the case where the portion is a plane even if a convex portion forming a convex shape is formed inside the tundish 1. is doing. Therefore, according to another embodiment of the present invention, as shown in FIG. 6 and FIG. 7, for example, on the flat portion 30 immediately below the injection nozzle 20, a convex made of a refractory that has a convex shape inside the tundish 1. The part 50 may be formed. Here, the height of the convex portion 50 having a convex shape is not particularly specified, but is about 0.1 m or less, for example, from the viewpoint of countermeasures against melting damage. By this convex portion 50, it is possible to suppress melting damage of the flat portion 30 immediately below the injection nozzle 20.

In the above embodiment, the curved portion 31 of the tundish 1 is formed from the injection nozzle 20 to the outlet 22 as shown in FIG. It may be formed up to the end on the nozzle 20 side. Even in such a case, it has been experimentally found that the upward flow F ₁ of the molten steel M can be formed in the tundish 1 by the curved portion 31 and the inclusions in the molten steel M can be sufficiently separated and removed.

  In addition, when inventors investigated, along with the long side wall 10 of the curved part 31 for fully exhibiting the above-mentioned inclusion removal effect corresponding to the case where the request | requirement of the cleanliness of the molten steel M is severer. As shown in FIG. 9, it was experimentally found that a preferable range in the direction is the range of the lower end width W of the tundish 1 around the injection nozzle 20.

  In the tundish 1 of the above embodiment, as shown in FIG.10 and FIG.11, you may further provide the lower weir 40 of the low height comprised with the plate-like refractory. The lower weir 40 is provided at one location with respect to the one outlet 22, and the lower weirs 40, 40 are respectively provided on the outlet 22 side from the middle point C between the center of the injection nozzle 20 and the center of the outlet 22. It has been. The lower weir 40 is formed upward from the bottom surface 13 of the tundish 1 and has a height of, for example, 0.05 m to 0.1 m. The lower weir 40 is provided so as to extend along the short side wall 11 of the tundish 1.

In such a case, the direct feed flow F _{2 of the} molten steel M directed toward the outlet 22 along the above-described bottom surface 13 is directed upward by the lower weir 40. Therefore, inclusions in the molten steel M of the direct flow F ₂ can also be raised toward the molten metal surface M ₂ , and inclusions can be more reliably removed from the molten steel M. Therefore, the present embodiment having the configuration of the flat portion 30, the curved portion 31, and the lower weir 40 is particularly effective for manufacturing steel with high quality requirements that hardly allow inclusions to remain.

In the present embodiment, since direct flow F ₂ of the molten steel M is very small, the lower weir 40 it is sufficient provided by at least one position relative to one outlet 22, also the height also for example 0 below weir 40 It is sufficient that the thickness is as low as .05 m to 0.1 m, and thereby sufficient inclusion removal effect is exhibited. Further, since the lower weir 40 need only have a low height, the amount of molten steel M remaining on the upstream side of the lower weir 40 when operation is stopped becomes very small, and the yield of the steel is hardly lowered.

Hereinafter, the inclusion removal effect when the tundish of the present invention is used will be described. In this example, the tundish 1 previously shown in FIGS. 1 to 3 was used, and the number of non-metallic inclusions in the molten steel M that passed through the tundish 1 and flowed into the mold was investigated under the following conditions. An experiment was conducted. In this embodiment, the length S of the long side wall 10 of the tundish 1 is 7 m (see FIG. 2), the upper end width T is 1.6 m, the lower end width W is 1.0 m, and the depth H ₁ is 1. 5 m (see FIG. 3). Further, the distance H ₂ from the upper end of the ceiling surface 12 to the lower end of the notch 14 is 0.2 m, the distance H ₃ from the lower end of the notch 14 to the hot water M ₂ during steady operation is 0.3 m, and the hot water M ₂ the height _{H 4} of a 1 m. The inner diameter D of the injection nozzle 20 is 0.2 m.

  In the present embodiment, the minimum curvature radius R of the bending portion 31 is 8 conditions of 0 m, 0.05 m, 0.1 m, 0.2 m, 0.3 m, 0.4 m, 0.45 m, and 0.5 m. The experiment was conducted. The minimum curvature radius R of 0 m indicates that the tundish 1 has no curved portion. Further, the minimum radius of curvature R of 0.5 m indicates that the bottom surface of the tundish 1 is composed only of a curved portion.

  And in the investigation of the number of non-metallic inclusions, 100 g of molten steel sample in the mold was extracted only by non-metallic inclusions by electrolytic extraction, and the number of non-metallic inclusions having a diameter of 50 μm to 100 μm was measured. In this example, since it was confirmed in a normal operation that non-inclusions having a diameter of 50 μm to 100 μm adversely affect the quality of the steel, the number of non-inclusions having such a diameter was measured.

  Table 1 shows the results of experiments conducted under the above conditions. In Table 1, “◯” is shown if the condition of the minimum radius of curvature R of the curved portion 31 satisfies the above formula (1), and “x” is shown if the condition does not satisfy the formula (1). The inclusion number index in Table 1 indicates the ratio of the number of nonmetallic inclusions under each condition, where the number of nonmetallic inclusions is 1 when the minimum radius of curvature R of the curved portion 31 is 0 m. . If the inclusion number index is 0.5 or less, it indicates that the inclusion is sufficiently removed.

  Referring to Table 1, when the minimum curvature radius R of the curved portion 31 is 0 m, 0.5 m, 0.45 m, or 0.5 m that does not satisfy the formula (1), the inclusion number index is 0.8 or more, Things cannot be removed sufficiently. On the other hand, when the minimum radius of curvature R of the curved portion 31 is 0.1 m, 0.2 m, 0.3 m, or 0.4 m satisfying the formula (1), the inclusion number index is 0.4 or less, and the inclusion is It was found that can be removed sufficiently. That is, when the tundish of this invention was used, it turned out that an inclusion can fully be removed.

  The present invention is useful when supplying molten steel from a ladle to a mold using a tundish for continuous casting.

DESCRIPTION OF SYMBOLS 1 Tundish 10 Long side wall 11 Short side wall 12 Ceiling surface 13 Bottom surface 14 Notch part 20 Injection nozzle 21 Ladle 22 Outlet 23 Nozzle 24 Flow control rod 30 Plane part 31 Curved part 40 Lower weir 50 Convex part M Molten steel

Claims (5)

A tundish for continuous casting of steel with a pair of long side walls and a pair of short side walls,
The outflow port for flowing the molten steel from the tundish to the mold is arranged side by side on the same straight line along the long side wall in a plan view with respect to the injection nozzle for flowing the molten steel from the ladle to the tundish.
On the inner bottom surface of the tundish, at least a plane portion having a planar shape is formed below the injection nozzle,
In the corner portion between the flat portion and the long side wall, a curved portion that is curved outward is formed,
The curved portion is formed along the long side wall,
A tundish for continuous casting, wherein a minimum curvature radius R (m) of the curved portion satisfies the following formula (1).
0.1 ≦ R ≦ (WD) / 2 (1)
However, W: distance (m) between the intersections of the tangent of the inner side surface of the long side wall of the cross section perpendicular to the long side direction at the position of the maximum molten steel surface in the tundish and the extension line of the plane portion, D: Inner diameter of injection nozzle (m) 2. The tundish for continuous casting according to claim 1, wherein a convex portion having a convex shape is formed on the inner side of the tundish on the flat portion directly below the injection nozzle. The tundish for continuous casting according to claim 1 or 2, wherein the long side wall at the position of the maximum molten steel surface is provided with a notch portion extending from the inside to the outside of the long side wall. . The curved portion is an intersection of the tangent to the inner side surface of the long side wall of the cross section perpendicular to the long side direction at the position of the maximum molten steel surface in the tundish centered on the pouring nozzle position and the extension line of the flat portion. The tundish for continuous casting according to any one of claims 1 to 3, wherein the tundish is formed along the long side wall at least a distance between them. 5. The tundish for continuous casting according to claim 4, wherein the curved portion is formed along the long side wall from the injection nozzle to an end of the outflow port on the injection nozzle side.

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