Immersion nozzle for continuous casting

Abstract

To provide an immersion nozzle capable of suppressing unstable fluctuation or deviation to right or left of a discharge flow amount by devising of an internal structure of the immersion nozzle, the immersion nozzle achieving both expansion of a discharge hole effective cross-sectional area and an increase in a discharge angle suitable for high-speed casting and stabilization of a molten steel flowing.SOLUTION: A cross-sectional shape of an immersion nozzle for continuous casting is bilateral symmetry with respect to a central axis. The immersion nozzle for continuous casting includes: a body part; a discharge hole part provided in a lower end of the body part and having a pair of upper discharge holes and a pair of lower discharge holes; and an intermediate block. A part of the intermediate block projects to the inside of the immersion nozzle for continuous casting to form an internal barrier wall having a horizontal surface shape. The total sum of projection areas of right and left internal barrier walls is 30 to 70% of a cross-sectional area of a lower end of a flow path of the body part, and a projection area of the flow path sandwiched by the right and left internal barrier walls is 35 to 65% of the cross-sectional area of the lower end of the flow path of the body part. An upper end surface of a bottom part block is a horizontal surface or a recessed surface shape.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an immersion nozzle for continuous casting (hereinafter, also simply referred to as an "immersion nozzle"). In this specification, the length direction of the immersion nozzle means the direction in which the central axis of the main body of the immersion nozzle extends (the up-down direction in Figures 1 to 12(a)), the thickness direction of the immersion nozzle means the direction perpendicular to the central axis of the flow channel of the immersion nozzle and parallel to the side surface of the immersion nozzle (the direction perpendicular to the paper surface in Figures 1 to 12(a)), and the width direction means the direction perpendicular to both the length direction and the thickness direction of the immersion nozzle (the left-right direction in Figures 1 to 12(a)). [Background technology]

[0002] When continuously casting thin slabs by supplying molten steel from a tundish to a mold, high-speed casting conditions are sometimes used, with casting speeds exceeding 3 m / min and reaching 5–8 m / min. When such high-speed casting conditions are applied, the molten steel must be poured into the mold at a large downward angle to prevent disturbance of the molten steel surface inside the mold. Additionally, to dissipate the kinetic energy of the discharge flow within the mold, the discharge hole area must be increased by enlarging or increasing the number of holes.

[0003] In response to these requirements, various shapes of submerged entry nozzles have been proposed. For example, as disclosed in Patent Documents 1 to 5, a multi-hole discharge nozzle with four or more discharge holes arranged at the bottom of the submerged entry nozzle has been proposed. Alternatively, as disclosed in Patent Documents 6 to 8, there are known methods for reducing the flow rate of the downward flow inside the submerged entry nozzle by providing a barrier inside the nozzle or for smoothly distributing the downward flow to multiple discharge holes. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2004-514562 [Patent Document 2] Japanese Patent Application Publication No. 8-39208 [Patent Document 3] Patent No. 3186068 [Patent Document 4] Patent No. 4580135 [Patent Document 5] Patent No. 4542631 [Patent Document 6] Patent No. 3408884 [Patent Document 7] Patent No. 5047854 [Patent Document 8] Patent No. 6666908 Summary of the Invention [Problem to be solved by the invention]

[0005] The present inventors have carried out research mainly using water model experiments, and as a result have found that the conventional techniques have the following problems.

[0006] The downward flow of molten steel in the SEN is constantly biased or unstable due to the influence of flow restriction mechanisms such as stoppers or sliding gates that control the amount of molten steel supplied from the tundish to the SEN. The bias or fluctuation of the downward flow of molten steel in the SEN then changes the flow rate distribution to the multiple discharge holes. As a result, the flow of molten steel in the mold becomes constantly biased or unstable. This causes the solidification state of the resulting slab to be non-uniform, resulting in quality defects.

[0007] In order to stabilize the flow rate distribution to the multiple discharge holes, it is possible to reduce the opening area of ​​the discharge holes and increase the internal pressure of the submerged entry nozzle, but this would impair the effect of reducing the discharge flow rate, which is the original purpose of making the nozzle multiple. Thus, the difficulty of achieving both flow rate distribution to the multiple discharge holes and a reduction in the discharge flow rate has been a problem in the prior art. The present invention has been made in view of the above problems, and an object of the present invention is to provide an immersion nozzle which, by devising an internal structure thereof, is capable of suppressing unstable fluctuations and left / right deviations in the discharge flow rate, and which achieves both an enlarged effective cross-sectional area of ​​the discharge hole and an increased discharge angle suitable for high-speed casting, and stabilization of the flow of molten steel. [Means for solving the problem]

[0008] The gist of the present invention is as follows. (1) A submerged entry nozzle for continuous casting of steel, comprising: A long, cylindrical main body; a discharge hole portion provided at a lower end of the main body portion and having a pair of upper discharge holes and a pair of lower discharge holes; an intermediate block disposed between the upper discharge hole and the lower discharge hole; and when the continuous casting submerged entry nozzle is divided by a plane perpendicular to the thickness direction of the continuous casting submerged entry nozzle, the cross-sectional shape of the continuous casting submerged entry nozzle is bilaterally symmetrical with respect to a plane passing through the central axis of the main body and parallel to the thickness direction, a portion of the intermediate block protruding toward the inside of the continuous casting immersion nozzle to form a horizontally shaped internal barrier; When the lower end of the flow path of the main body portion and the left and right internal barriers are projected onto a horizontal plane, the sum of the projected areas of the left and right internal barriers is 30 to 70% of the cross-sectional area of ​​the lower end of the flow path of the main body portion, and the projected area of ​​the flow path sandwiched between the left and right internal barriers is 35 to 65% of the cross-sectional area of ​​the lower end of the flow path of the main body portion, a bottom block disposed at the lower end of the continuous casting submerged nozzle and sandwiched between the left and right lower discharge holes, the upper end surface of which is horizontal or concave. (2) The continuous casting submerged entry nozzle according to (1), characterized in that, under conditions where the average downward flow velocity of molten steel at the lower end of the flow path in the main body is 1.5 to 4.0 m / s, when the upper discharge flow rate from the left and right upper discharge holes is biased toward one of the left and right upper discharge holes due to left and right bias of the downward flow in the main body, the lower discharge flow rate from the lower discharge hole on the side where the upper discharge flow rate was lower becomes larger. (3) The submerged entry nozzle for continuous casting according to (1) or (2), wherein the average angle of the upper and lower walls of the lower discharge hole is equal to or greater than the average angle of the upper and lower walls of the upper discharge hole, and the difference between the average angle of the upper and lower walls of the upper discharge hole and the average angle of the lower discharge hole is 15° or less. [Effects of the Invention]

[0009] According to the present invention, by devising an internal structure of the submerged entry nozzle, it is possible to suppress unstable fluctuations and left / right deviations in the discharge flow rate, and it is possible to provide a submerged entry nozzle that achieves both an enlarged effective cross-sectional area of ​​the discharge hole and an increased discharge angle suitable for high-speed casting, and stabilization of the flow of molten steel. [Brief explanation of the drawings]

[0010] [Figure 1] 1A and 1B are explanatory diagrams showing the configuration of Example 1 of this embodiment, in which (a) is a cross-sectional view obtained by dividing the submerged entry nozzle 1a along a plane perpendicular to the thickness direction of the submerged entry nozzle 1a, and (b) is a side view of the submerged entry nozzle 1a. [Figure 2] 1A and 1B are explanatory diagrams showing the configuration of Example 2 of this embodiment, in which (a) is a cross-sectional view obtained by dividing the submerged entry nozzle 1b along a plane perpendicular to the thickness direction of the submerged entry nozzle 1b, and (b) is a side view of the submerged entry nozzle 1b. [Figure 3] 1A and 1B are explanatory views showing the configuration of Example 3 of this embodiment, in which (a) is a cross-sectional view obtained by dividing the submerged entry nozzle 1c along a plane perpendicular to the thickness direction of the submerged entry nozzle 1c, and (b) is a side view of the submerged entry nozzle 1c. [Figure 4]10A and 10B are explanatory diagrams showing the configuration of Example 4 of this embodiment, in which (a) is a cross-sectional view obtained by dividing the submerged entry nozzle 1d along a plane perpendicular to the thickness direction of the submerged entry nozzle 1d, and (b) is a side view of the submerged entry nozzle 1d. [Figure 5] 10A and 10B are explanatory diagrams showing the configuration of Example 5 of this embodiment, in which (a) is a cross-sectional view obtained by dividing the submerged entry nozzle 1e along a plane perpendicular to the thickness direction of the submerged entry nozzle 1e, and (b) is a side view of the submerged entry nozzle 1e. [Figure 6] 10A and 10B are explanatory diagrams showing the configuration of Example 6 of the present embodiment, in which (a) is a cross-sectional view obtained by dividing the submerged nozzle 1f along a plane perpendicular to the thickness direction of the submerged nozzle 1f, and (b) is a side view of the submerged nozzle 1f. [Figure 7] 1A and 1B are explanatory views showing the configuration of Comparative Example 1 of the present embodiment, in which (a) is a cross-sectional view obtained by dividing the submerged entry nozzle 1g along a plane perpendicular to the thickness direction of the submerged entry nozzle 1g, and (b) is a side view of the submerged entry nozzle 1g. [Figure 8] 1A and 1B are explanatory views showing the configuration of Comparative Example 2 of the present embodiment, in which (a) is a cross-sectional view obtained by dividing the submerged entry nozzle 1h along a plane perpendicular to the thickness direction of the submerged entry nozzle 1h, and (b) is a side view of the submerged entry nozzle 1h. [Figure 9] 1A and 1B are explanatory views showing the configuration of Comparative Example 3 of the present embodiment, in which (a) is a cross-sectional view obtained by dividing the submerged entry nozzle 1i along a plane perpendicular to the thickness direction of the submerged entry nozzle 1i, and (b) is a side view of the submerged entry nozzle 1i. [Figure 10] 1A and 1B are explanatory views showing the configuration of Comparative Example 4 of the present embodiment, in which (a) is a cross-sectional view obtained by dividing the submerged entry nozzle 1j along a plane perpendicular to the thickness direction of the submerged entry nozzle 1j, and (b) is a side view of the submerged entry nozzle 1j. [Figure 11] 10A and 10B are explanatory views showing the configuration of Comparative Example 5 of the present embodiment, in which (a) is a cross-sectional view obtained by dividing the submerged nozzle 1k along a plane perpendicular to the thickness direction of the submerged nozzle 1k, and (b) is a side view of the submerged nozzle 1k. [Figure 12]1A and 1B are explanatory views showing the configuration of Comparative Example 6 of the present embodiment, in which (a) is a cross-sectional view obtained by dividing the submerged nozzle 1l along a plane perpendicular to the thickness direction of the submerged nozzle 1l, and (b) is a side view of the submerged nozzle 1l. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant description will be omitted. In this embodiment, the left-right direction refers to the left-right direction when the submerged nozzle is viewed in a direction parallel to the thickness direction (viewed from the front), i.e., the width direction. In Figures 1 to 12, (a) is a cross-sectional view of the submerged nozzle viewed from the front, and (b) is a side view of the submerged nozzle viewed from a direction perpendicular to the thickness direction (viewed from the side). As will be described in detail later, in this embodiment, multiple discharge holes are provided on the left and right sides of the submerged nozzle. Furthermore, the numerical values ​​in the figures are dimensions (unit: mm). However, the numerical values ​​of the discharge holes are the cross-sectional area of ​​the discharge hole (cross-sectional area perpendicular to the length direction of the discharge hole, unit: mm 2 ) Of course, the dimensions are merely examples. Unless otherwise specified, the cross-sectional area of ​​each part in this embodiment refers to the cross-sectional area perpendicular to the length direction of the part.

[0012] First, the shape of the submerged entry nozzle according to this embodiment will be described using the submerged entry nozzle 1a shown in Fig. 1 as an example. The submerged entry nozzle 1a corresponds to Example 1 of this embodiment. The submerged entry nozzle 1a is a nozzle for continuous casting of steel, and has a shape that is symmetrical with respect to a plane that passes through the central axis 1a-1 of the main body 10 and is parallel to the thickness direction. This is because, since the mold has a symmetrical shape, it is preferable to supply molten steel evenly to the left and right.

[0013] 1. First Embodiment The submerged nozzle 1a has a long, cylindrical main body 10 and a discharge hole portion 20 provided at the lower end of the main body 10 and having a pair of upper discharge holes 21a, 21b and a pair of lower discharge holes 22a, 22b formed therein.

[0014] Molten steel stored in the tundish is supplied to the SEN 1a at a flow rate corresponding to the horizontal cross-sectional size of the mold and the casting speed through a flow rate control mechanism such as a stopper or slide plate. The molten steel supplied to the SEN 1a first passes through the main body 10 of the SEN 1a. The main body 10 has a long, tubular shape. The main body 10 is generally cylindrical or rectangular with a substantially constant flow path cross-sectional area, but it may also have a shape in which the upper cylindrical portion and the lower rectangular tubular portion are smoothly connected. The main body 10 of the SEN 1a is rectangular, with a flow path width of 110 mm, a thickness of 27 mm at the top end, and a thickness of 25 mm at the bottom end. In other words, the flow path is slightly tapered.

[0015] The lower end of the main body 10 is provided with a discharge port section 20, which is formed with a pair of upper discharge ports 21a, 21b and a pair of lower discharge ports 22a, 22b. In other words, the discharge port section 20 has a total of four discharge ports. These discharge ports open to the side surfaces of the submerged entry nozzle 1a. While conventional submerged entry nozzles typically have a pair of discharge ports, one on each side, this embodiment has two pairs of discharge ports arranged vertically, for a total of four discharge ports. This configuration provides the submerged entry nozzle 1a with the unique effects of enlarging the effective cross-sectional area of ​​the discharge ports and correcting the imbalance in the discharge flow rate between the left and right ports. Here, the effective cross-sectional area of ​​the discharge ports refers to the cross-sectional area of ​​the portion of the discharge port through which molten steel flows. The submerged entry nozzle 1a according to this embodiment functions when the number of discharge ports is an even number. The number of discharge holes is not set to more than four, for example, six, because if the number of discharge holes is increased too much, the vertical dimension of the discharge hole section 20 becomes too large.

[0016] In this embodiment, portions (tips) of the intermediate blocks 23a and 23b, which are disposed between the upper discharge holes 21a and 21b and the lower discharge holes 22a and 22b, protrude toward the interior of the submerged entry nozzle 1a, forming horizontal internal barrier walls 24a and 24b. The intermediate blocks 23a and 23b serve as the lower walls of the upper discharge holes 21a and 21b and the upper walls of the lower discharge holes 22a and 22b. The internal barrier walls 24a and 24b protrude in a direction that narrows the cross-sectional area of ​​the flow path connecting the lower end of the main body 10 to the lower discharge holes 22a and 22b. While many prior art inventions have provided barriers within the flow path, in this embodiment, the internal barriers 24a and 24b are formed by protruding portions of the intermediate blocks 23a and 23b, simplifying the structure of the submerged entry nozzle 1a and facilitating its manufacture.

[0017] It is also important that the upper surfaces of the internal barrier walls 24a, 24b are horizontal. A horizontal surface means a horizontal surface or a surface with an inclination from the horizontal surface of within ±10° (upward is positive), or a surface on which unevenness in the upward or downward direction is provided that is within 15% of the horizontal dimension of the flat surface (for example, a gently bulging spherical surface). In the submerged nozzle 1a, the horizontal dimension of the internal barrier walls 24a, 24b is 30 mm, so unevenness with a height of 30 × 0.15 = 4.5 mm may be formed on the upper surfaces of the internal barrier walls 24a, 24b.

[0018] The reason for making the internal barriers 24a, 24b horizontal is as follows. That is, when the flow of molten steel flowing down the main body 10 is biased to the left or right, the molten steel flow strongly collides with the horizontal internal barriers 24a, 24b on the side where the molten steel flow is stronger. At this time, the molten steel flow strongly bounces back, increasing the local dynamic pressure. That is, because of the strong repulsive force of the molten steel flow, the molten steel flow is more likely to move from the side where the molten steel flow is stronger to the opposite side. This suppresses bias in the molten steel flow. This effect provides a self-stabilizing function against temporal fluctuations in the downward flow within the main body 10 and bias to the left or right.

[0019] Here, when the lower end 10a of the flow path of the main body 10 and the left and right internal barrier walls 24a, 24b are projected onto a horizontal plane, the sum of the projected areas of the left and right internal barrier walls 24a, 24b is 30 to 70% of the cross-sectional area of ​​the lower end 10a of the flow path of the main body 10 (hereinafter also referred to as the "cross-sectional area of ​​the flow path at the bottom of the main body"). If the sum of the projected areas of the left and right internal barrier walls 24a, 24b is less than 30% of the cross-sectional area of ​​the flow path at the bottom of the main body, the effect of suppressing deviation of the molten steel flow becomes insufficient, and excessively large internal barrier walls 24a, 24b whose sum of the projected areas of the left and right internal barrier walls 24a, 24b exceeds 70% of the cross-sectional area of ​​the flow path at the bottom of the main body are unnecessary. In the submerged nozzle 1a, the sum of the projected areas of the left and right internal barrier walls 24a, 24b is 60 × 25 mm 2 The cross-sectional area of ​​the flow path at the bottom of the main body is 110 x 25 mm 2 Therefore, the sum of the projected areas of the left and right internal barriers 24a, 24b is 60 / 110=54.5% of the flow path cross-sectional area at the bottom of the main body, which satisfies this requirement.

[0020] Furthermore, the projected area of ​​the flow path sandwiched between the left and right internal barrier walls 24a, 24b is 35 to 65% of the cross-sectional area of ​​the flow path at the bottom of the main body. This is to make the proportions of the discharge flow rates from the upper discharge holes 21a, 21b and the lower discharge holes 22a, 22b closer to equal. In this embodiment, to maximize the effect of maximizing the effective cross-sectional area of ​​the discharge holes and suppressing drift, it is preferable that the areas of the upper and lower discharge holes 21a to 22b are the same and that the proportions of the discharge flow rates from the upper and lower discharge holes 21a to 22b are equal. 35 to 65% means 50%±15%. A more preferable range within this range is 40 to 60%. In the submerged nozzle 1a, the projected area of ​​the flow path sandwiched between the left and right internal barrier walls 24a, 24b is 50 × 25 mm 2 The cross-sectional area of ​​the flow path at the bottom of the main body is 110 x 25 mm 2 Therefore, the projected area of ​​the flow path sandwiched between the left and right internal barriers 24a, 24b is 50 / 110=45.5% of the flow path cross-sectional area at the bottom of the main body, which satisfies this requirement.

[0021] In the normal design of this embodiment, the internal barrier walls 24a, 24b protrude most inward into the submerged nozzle 1a, and therefore the internal barrier walls 24a, 24b narrow the cross-sectional area of ​​the flow path connecting the lower end 10a of the flow path in the main body 10 to the lower discharge holes 22a, 22b. However, a design variation is also possible in which parts of the intermediate blocks 23a, 23b other than the internal barrier walls 24a, 24b protrude more inward into the submerged nozzle 1a than the internal barrier walls 24a, 24b. In this case, it is preferable that the projected area of ​​the flow path sandwiched between these other parts is 35 to 65% of the cross-sectional area of ​​the flow path at the bottom of the main body.

[0022] Furthermore, since the intermediate blocks 23a and 23b are formed between the upper discharge holes 21a and 21b and the lower discharge holes 22a and 22b, the intermediate blocks 23a and 23b are also formed over the entire thickness of the flow channel. Similarly, the internal barriers 24a and 24b are also formed over the entire thickness of the flow channel.

[0023] The left and right internal barriers 24a, 24b are usually independent, but they may be partially connected to narrow the cross-sectional area of ​​the flow path in part of the thickness of the flow path. In such a case, it is preferable that the projected area of ​​the narrowest flow path is 35 to 65% of the cross-sectional area of ​​the flow path at the bottom of the main body.

[0024] The bottom block 25 is disposed at the lower end of the submerged nozzle 1a and is sandwiched between the left and right lower discharge holes 22a and 22b. The upper end surface 25a of the bottom block 25 is horizontal or concave. The bottom block 25 constitutes the bottom (lower end) of the submerged nozzle 1a. The side surfaces of the bottom block 25 form the lower walls of the lower discharge holes 22a and 22b.

[0025] By making the upper end surface 25a of the bottom block 25 horizontal or concave, the following effects can be expected. Specifically, if the molten steel flow down the main body 10 is biased to either the left or right, the discharge rate from the upper discharge holes 21a, 21b will be biased to either the left or right. For example, if the molten steel flow down the main body 10 is biased to the right, the discharge rate from the upper discharge hole 21a on the right side will increase. Furthermore, the molten steel flow that passes through the internal barriers 24a, 24b and reaches the bottom block 25 will also remain biased to the right. However, if the upper end surface 25a of the bottom block 25 is horizontal or concave, when the molten steel flow hits the upper end surface 25a, the molten steel flow will bounce back strongly, increasing local dynamic pressure. In other words, due to the strong repulsive force of the molten steel flow, the molten steel flow will tend to move from the side where the molten steel flow is stronger (i.e., the right side) to the opposite side (i.e., the left side). That is, the discharge flow from the lower discharge holes 22a, 22b is greater on the left side where the discharge flow rate from the upper discharge holes 21a, 21b is smaller. In this way, in this embodiment, a self-stabilizing effect is produced for the left and right flows.

[0026] If the upper end surface 25a of the bottom block 25 is small and limited to only the vicinity of the widthwise center or the thicknesswise center of the submerged nozzle 1a, the effect may be impaired. For this reason, the projected area of ​​the upper end surface 25a of the bottom block 25 projected onto a horizontal plane is preferably 80% or more of the projected area of ​​the flow path sandwiched between the internal barrier walls 24a, 24b. An excessively large upper end surface 25a does not increase the effect and unnecessarily increases the size of the submerged nozzle 1a. Therefore, the projected area of ​​the upper end surface 25a of the bottom block 25 projected onto a horizontal plane is preferably 120% or less of the projected area of ​​the flow path sandwiched between the internal barrier walls 24a, 24b.

[0027] The term "horizontal" used herein means that the upper end surface 25a is a horizontal surface, or a horizontal surface having upward or downward irregularities of up to 30% of its horizontal dimension (for example, a gently bulging spherical surface). In the submerged nozzle 1a, the upper end surface 25a of the bottom block 25 is concave. If this is assumed to be horizontal, the horizontal dimension is 60 mm, so that irregularities with a height of 60 x 0.30 = 18 mm may be formed on the upper end surface 25a.

[0028] The concave shape of the upper end surface 25a means that the widthwise center of the upper end surface 25a is recessed toward the left and right ends. In the submerged nozzle 1a, the upper end surface 25a of the bottom block 25 is concave. The bottom of the recess may be flat, spherical, or a curved surface with a continuously changing curvature. The maximum depth of the recess is preferably 10 to 20 mm, and preferably 30 mm or less at most. It is preferable to avoid a maximum depth of the recess exceeding 30 mm, as this would result in an unnecessarily large submerged nozzle 1a.

[0029] The submerged nozzle according to this embodiment is preferably applied to continuous casting in which the average downward flow velocity of molten steel at the lower end 10a of the flow path in the main body 10 is 1.5 to 4.0 m / s. Here, the average downward flow velocity is determined by dividing the flow rate per unit time by the cross-sectional area of ​​the flow path.

[0030] If the average downward flow velocity of the molten steel is less than 1.5 m / s, the flow of molten steel is likely to become uneven in the region from the main body 10 to the discharge port 20, and the effects of this embodiment may not be fully achieved. On the other hand, if the average downward flow velocity of the molten steel exceeds 4.0 m / s, the fluid pressure inside the submerged entry nozzle 1a increases, and the discharge flow may become stable even without this embodiment.

[0031] Therefore, in this embodiment, in continuous casting in which the average downward flow velocity of molten steel at the lower end 10a of the flow path of the main body 10 is 1.5 to 4.0 m / s, when the discharge rate from the upper discharge holes 21a, 21b is biased to either the left or right due to a left-right bias of the molten steel flow in the main body 10, the discharge rate from the lower discharge holes 22a, 22b becomes larger on the side with a smaller discharge rate from the upper discharge holes 21a, 21b. In other words, even if the discharge flows from the upper discharge holes 21a, 21b become uneven on the left and right, this is corrected by the discharge flows from the lower discharge holes 22a, 22b. This correction is achieved by the discharge flows from the upper discharge holes 21a, 21b and the lower discharge holes 22a, 22b joining together inside the mold.

[0032] In summary, the first embodiment is an invention that satisfies the following requirements. When the submerged entry nozzle is divided by a plane perpendicular to the thickness direction, the cross-sectional shape of the submerged entry nozzle is symmetrical with respect to a plane that passes through the central axis of the main body and is parallel to the thickness direction. The nozzle has a long, cylindrical main body and a discharge hole portion provided at the lower end of the main body and having a pair of upper discharge holes and a pair of lower discharge holes. A part of the intermediate block located between the upper and lower discharge holes protrudes into the inside of the submerged entry nozzle, forming a horizontal internal barrier. When the lower end of the flow path in the main body and the left and right internal barriers are projected onto a horizontal plane, the sum of the projected areas of the left and right internal barriers is 30 to 70% of the cross-sectional area of ​​the lower end of the flow path in the main body, and the projected area of ​​the flow path sandwiched between the left and right internal barriers is 35 to 65% of the cross-sectional area of ​​the lower end of the flow path in the main body. The bottom block is located at the bottom end of the submerged nozzle and is sandwiched between the left and right lower discharge holes. The top surface of the bottom block is horizontal or concave.

[0033] 2. Second Embodiment The shapes of the upper discharge holes 21a, 21b and the lower discharge holes 22a, 22b are not particularly limited. For example, the shapes of the upper and lower walls may be flat or curved. In the submerged nozzle 1a, the upper walls of the upper discharge holes 21a, 21b are curved with a curvature radius of 63.5 mm, and the lower walls are flat. The upper and lower walls of the lower discharge holes 22a, 22b are flat. However, it is preferable that the average angle of the upper and lower walls of the lower discharge holes 22a, 22b is equal to or greater than the average angle of the upper and lower walls of the upper discharge holes 21a, 21b, and that the difference between the average angle of the upper and lower walls of the upper discharge holes 21a, 21b and the average angle of the lower discharge holes 22a, 22b is 15° or less. Here, the average angle is determined by the following method. First, the angle of the upper and lower walls is positive when pointing downward and negative when pointing upward. If the upper and lower walls are flat, the angle of the upper and lower walls is the angle between the plane and the horizontal plane. If the upper and lower walls are curved, the angle between the tangent at the open end and the horizontal plane is taken as the angle of the upper and lower walls. When this condition is met, the confluence of the discharge flows from the upper discharge holes 21a and 21b and the lower discharge holes 22a and 22b within the mold is promoted, and the effect of suppressing drift can be stably demonstrated.

[0034] In the submerged nozzle 1a, the upper wall angle of the upper discharge hole 21a is 45° downward. The lower wall angle of the upper discharge hole flow path is 45° downward. The upper and lower wall angles of the lower discharge hole flow path are both 55° downward. That is, the average upper and lower wall angle of the upper discharge holes 21a, 21b is 45°, and the average upper and lower wall angle of the lower discharge hole is 55°, so the difference between these is 10°, which satisfies the requirements of the second embodiment.

[0035] As described above, this embodiment of the SEN 1a suppresses unstable fluctuations and lateral deviations in the discharge flow rate by devising an internal structure for the SEN 1a. This provides an SEN 1a that achieves both an increased effective cross-sectional area and discharge angle suitable for high-speed casting, and stabilizes the flow of molten steel. More specifically, this embodiment provides horizontal internal barriers 24a, 24b formed by portions of the intermediate blocks 23a, 23b extending toward the interior of the SEN 1a, thereby providing a self-stabilizing function against unstable fluctuations and lateral deviations in the downward flow within the main body 10 of the SEN 1a. Furthermore, by providing the top end surface 25a of the bottom block 25 with a horizontal or concave surface, a self-stabilizing function against lateral deviations in the flow discharged from the upper discharge holes 21a, 21b can be achieved by the flow discharged from the lower discharge holes 22a, 22b. Thus, this simple structure provides excellent flow stabilization within the mold.

[0036] To obtain the effects of this embodiment, it is necessary to satisfy at least the requirements of the first embodiment. To obtain even greater effects, it is preferable to satisfy the effects of the second embodiment. [Example]

[0037] The configuration and effects of the present invention will be specifically described below with reference to examples. Table 1 and Figures 1 to 12 show examples of this embodiment and comparative examples.

[0038] [Table 1]

[0039] In Table 1, the discharge flow distribution (%) is a value calculated by the following method. Specifically, the submerged entry nozzles 1a to 1l were prepared by extending the submerged entry nozzles 1a to 1l upward by 400 mm while maintaining the horizontal cross-sectional shape of the upper end of the submerged entry nozzles 1a to 1l shown in Figures 1 to 12. Next, the inlet region was limited to only the left half of the upper end of each of the submerged entry nozzles 1a to 1l, and the discharge flow distribution was calculated by the following method. 3Water was flowed into the submerged entry nozzles 1a to 1l at a rate of 0.1 / hr (corresponding to an average downward flow velocity of approximately 3.0 m / s in a 110 mm x 25 mm cross section), filling the submerged entry nozzles 1a to 1l with water, and the discharge holes were opened to the atmosphere. The water temperature was set to 30°C. In this state, the discharge flow rate from each discharge hole was measured, and from the results, the distribution ratio to each discharge hole was calculated as a percentage. The closer the total value of the discharge flow distribution on one side is to 50.0%, the more effectively the uneven flow is suppressed.

[0040] In Table 1, the flow stability index (%) refers to the percentage obtained by subtracting the total discharge flow distribution (%) of the upper and lower left-hand nozzles from the total discharge flow distribution (%) of the upper and lower right-hand nozzles, and dividing this value by the sum of the total discharge flow distribution (%) of the upper and lower left-hand nozzles and the total discharge flow distribution (%) of the upper and lower right-hand nozzles. The absolute value indicates the degree of deviation in the discharge flow distribution to the left or right, with a negative sign indicating a deviation to the right and a positive sign indicating a deviation to the left. Based on the inventor's experience, an absolute value of deviation of 2% or less is considered acceptable. Furthermore, a deviation of 3% or more can cause operational and quality problems, while a deviation of 5% or more clearly poses operational and quality problems.

[0041] Furthermore, in Table 1, the flow stability index σ / Ave. is an index that indicates the stability of the surface flow velocity when a water model experiment was conducted in which each of the submerged entry nozzles 1a to 1l was submerged in a mold. Specifically, the flow stability index σ / Ave. was a value measured by the following method. That is, a mold vessel having a thickness of 100 mm, a width of 1500 mm, and a length of 3000 mm was filled with water to a height of 100 mm below the top end, and a perforated plate was installed at the bottom end of the mold vessel to prepare a water model experiment device designed to form a uniform downward flow across the entire cross section. Next, the submerged entry nozzle was installed in the center of the thickness and width of the mold vessel so that its bottom end was located 300 mm below the water surface, and the water was then passed through a hole in the hole in the mold vessel. 3Water was flowed into the mold at a rate of σ / hr (corresponding to an average downward flow velocity of approximately 3.3 m / min in a 100 mm × 1500 mm cross section). Next, a flow simulating that occurring in a continuous casting strand (more specifically, a typical double-roll flow pattern) was created within the mold vessel from the continuous casting mold. The horizontal flow velocity was measured using a propeller current meter at a position 50 mm below the water surface, 1 / 4 width and 1 / 2 thickness from the left and right sides. The standard deviation of the flow velocity values ​​measured once every 0.2 seconds was then divided by the mean value for a total of 6,000 data points collected over a 10-minute period. The resulting value was defined as σ / Ave. The detailed conditions for supplying water into the SEN in this experiment were the same as those used to determine the discharge flow distribution (%). When the flow within the mold is stable both temporally and spatially, the index becomes small. Based on the inventor's experience, a σ / Ave. value of 0.3% or less is considered acceptable. However, a value of 0.4% or more may cause operational and quality problems.

[0042] <1. Example 1> Figure 1 shows the structure of the submerged nozzle 1a according to Example 1. As described above, the submerged nozzle 1a satisfies the requirements of the first and second embodiments. In Example 1, (a) the cross-sectional area of ​​the flow path at the bottom of the main body is 2750 mm (flow path width 110 mm × flow path thickness 25 mm). 2 (b) The total projected area of ​​the internal barriers 24a and 24b projected on the horizontal plane is 30 mm wide x 25 mm thick x 2 pieces on the left and right = 1500 mm 2 (c) The projected area of ​​the flow path sandwiched between the left and right internal barriers 24a and 24b is: flow path width 50 mm × flow path thickness 25 mm = 1250 mm 2 is.

[0043] Focusing on the discharge flow distribution in Example 1, the discharge flow distribution from the left upper discharge hole 21b is greater than the discharge flow distribution from the right upper discharge hole 21a, while the discharge flow distribution from the right lower discharge hole 22a is greater than the discharge flow rate from the left lower discharge hole 22b. Therefore, the leftward / rightward discharge flow deviation caused by the upper discharge holes 21a and 21b is corrected by the discharge flow rate from the lower discharge holes 22a and 22b being greater on the right and smaller on the left, when the upper and lower values ​​are combined.

[0044] In Example 1, the upper wall angle of the upper discharge holes 21a, 21b is 45° downward. The lower wall angle of the upper discharge hole flow path is also 45° downward. Therefore, the average upper and lower wall angle is 45°. On the other hand, the upper and lower wall angles of the lower discharge holes are both 55° downward, so the average upper and lower wall angle is 55°. That is, the average upper and lower wall angle of the lower discharge holes 22a, 22b is equal to or greater than the average upper and lower wall angle of the upper discharge holes 21a, 21b. Furthermore, the difference between the average upper and lower wall angle of the upper discharge holes 21a, 21b and the average upper and lower wall angle of the lower discharge holes 22a, 22b is small at 10°, which satisfies the second embodiment. Therefore, the discharge flows from the upper discharge holes 21a, 21b and the lower discharge holes 22a, 22b smoothly merge within the mold, and the above-mentioned effect of correcting left and right drift is easily achieved.

[0045] In addition to the above-mentioned effects, Example 1 also exhibits the effect of stabilizing the discharge flow rate due to the internal barriers 24a and 24b, and therefore satisfies the first and second embodiments, and showed good results in both the flow stability indexes of the degree of unevenness (%) and σ / Ave.

[0046] <2. Example 2> 2 shows the structure of a submerged nozzle 1b according to Example 2. The submerged nozzle 1b also satisfies the requirements of the first and second embodiments. Specifically, the requirements are as follows. When the submerged entry nozzle 1b is divided by a plane perpendicular to the thickness direction, the cross-sectional shape of the submerged entry nozzle 1b is symmetrical with respect to a plane that passes through the central axis 1b-1 of the main body 10 and is parallel to the thickness direction. The device has a long, rectangular cylindrical main body 10 and a discharge hole portion 20 provided at the lower end of the main body 10 and having a pair of upper discharge holes 21a, 21b and a pair of lower discharge holes 22a, 22b formed therein. The intermediate blocks 23a, 23b arranged between the upper discharge holes 21a, 21b and the lower discharge holes 22a, 22b partially protrude into the interior of the submerged entry nozzle 1b, forming horizontal internal barrier walls 24a, 24b. Here, the inner barriers 24a and 24b are not perfectly horizontal, but are planes inclined downward at 10 degrees from the horizontal, and therefore satisfy this requirement. When the lower end 10a of the flow path of the main body 10 and the left and right internal barriers 24a, 24b are projected onto a horizontal plane, the sum of the projected areas of the left and right internal barriers 24a, 24b is 30 to 70% of the cross-sectional area of ​​the lower end 10a of the flow path of the main body 10 (cross-sectional area of ​​the flow path at the bottom of the main body), and the projected area of ​​the flow path sandwiched between the left and right internal barriers 24a, 24b is 35 to 65% of the cross-sectional area of ​​the flow path at the bottom of the main body. The total projected area of ​​the left and right internal barriers 24a and 24b is 25 x 25 x 2 = 1250 mm 2 The cross-sectional area of ​​the flow path at the bottom of the main body is 110 x 25 = 2750 mm 2 Therefore, the sum of the projected areas of the left and right internal barriers 24a, 24b is 45.5% of the cross-sectional area of ​​the lower end 10a of the flow path of the main body 10 (cross-sectional area of ​​the flow path at the bottom of the main body). The projected area of ​​the flow path sandwiched between the left and right internal barriers 24a and 24b is 60 × 25 = 1500 mm 2 Therefore, the projected area of ​​the flow path sandwiched between the left and right internal barriers 24a, 24b is 54.5% of the cross-sectional area of ​​the flow path at the bottom of the main body. Therefore, this requirement is met. The bottom block 25, which is disposed at the lower end of the submerged nozzle 1b and is sandwiched between the left and right lower discharge holes 22a, 22b, has a concave upper end surface 25a. Therefore, the submerged nozzle 1b satisfies the requirements of the first embodiment. Furthermore, the average upper and lower wall angles of the upper discharge holes 21a, 21b are 45° and the average upper and lower wall angles of the lower discharge holes 22a, 22b are 55°, so the average upper and lower wall angles of the lower discharge holes 22a, 22b are equal to or greater than the average upper and lower wall angles of the upper discharge holes 21a, 21b. Furthermore, the difference between the average upper and lower wall angles of the upper discharge holes 21a, 21b and the average upper and lower wall angles of the lower discharge holes 22a, 22b is small at 10°, which satisfies the requirements of the second embodiment.

[0047] Like the submerged entry nozzle 1a, the submerged entry nozzle 1b of Example 2 also satisfied the first and second embodiments, and therefore showed good results in both the flow stability indexes of uneven flow (%) and σ / Ave. In Example 2, the internal barrier walls 24a, 24b were not horizontal but inclined at 10°, but the effect was comparable to that of Example 1, in which the internal barrier walls 24a, 24b were horizontal.

[0048] 3. Example 3 3 shows the structure of a submerged nozzle 1c according to Example 3. The submerged nozzle 1c also satisfies the requirements of the first and second embodiments. Specifically, the requirements are as follows. When the submerged entry nozzle 1c is divided by a plane perpendicular to the thickness direction, the cross-sectional shape of the submerged entry nozzle 1c is symmetrical with respect to a plane that passes through the central axis 1c-1 of the main body 10 and is parallel to the thickness direction. The device has a long, rectangular cylindrical main body 10 and a discharge hole portion 20 provided at the lower end of the main body 10 and having a pair of upper discharge holes 21a, 21b and a pair of lower discharge holes 22a, 22b formed therein. The intermediate blocks 23a, 23b arranged between the upper discharge holes 21a, 21b and the lower discharge holes 22a, 22b partially protrude into the interior of the submerged entry nozzle 1c, forming horizontal internal barrier walls 24a, 24b. When the lower end 10a of the flow path of the main body 10 and the left and right internal barriers 24a, 24b are projected onto a horizontal plane, the sum of the projected areas of the left and right internal barriers 24a, 24b is 30 to 70% of the cross-sectional area of ​​the lower end 10a of the flow path of the main body 10 (cross-sectional area of ​​the flow path at the bottom of the main body), and the projected area of ​​the flow path sandwiched between the left and right internal barriers 24a, 24b is 35 to 65% of the cross-sectional area of ​​the flow path at the bottom of the main body. The total projected area of ​​the left and right internal barriers 24a and 24b is 30 x 25 x 2 = 1500 mm 2 The cross-sectional area of ​​the flow path at the bottom of the main body is 110 x 25 = 2750 mm 2 Therefore, the sum of the projected areas of the left and right internal barriers 24a, 24b is 54.5% of the cross-sectional area of ​​the lower end 10a of the flow path of the main body 10 (cross-sectional area of ​​the flow path at the bottom of the main body). The projected area of ​​the flow path sandwiched between the left and right internal barriers 24a and 24b is 50 × 25 = 1250 mm2 Therefore, the projected area of ​​the flow path sandwiched between the left and right internal barriers 24a, 24b is 45.5% of the cross-sectional area of ​​the flow path at the bottom of the main body. Therefore, this requirement is met. The bottom block 25, which is disposed at the lower end of the submerged nozzle 1c and is sandwiched between the left and right lower discharge holes 22a, 22b, has a concave upper end surface 25a. Therefore, the submerged nozzle 1c satisfies the requirements of the first embodiment. Furthermore, the average angle of the upper and lower walls of the upper discharge holes 21a, 21b is 50°, and the average angle of the upper and lower walls of the lower discharge holes 22a, 22b is 55°, so the average angle of the upper and lower walls of the lower discharge holes 22a, 22b is equal to or greater than the average angle of the upper and lower walls of the upper discharge holes 21a, 21b. Furthermore, the difference between the average angle of the upper and lower walls of the upper discharge holes 21a, 21b and the average angle of the lower discharge holes 22a, 22b is small at 5°, satisfying the requirements of the second embodiment. The radius of curvature of the outer peripheral surface of the upper wall of the upper discharge holes 21a, 21b is 87 mm, and the radius of curvature of the inner peripheral surface is 107 mm.

[0049] Like the submerged entry nozzle 1a, the submerged entry nozzle 1c of Example 3 also satisfied the first and second embodiments, and therefore showed good results in both the flow stability indexes of uneven flow (%) and σ / Ave. In Example 3, the internal shapes of the internal barriers 24a, 24b, etc. were similar to those of Examples 1 and 4, and the effects were also excellent, equivalent to those of Examples 1 and 4.

[0050] <4. Example 4> 4 shows the structure of a submerged nozzle 1d according to Example 4. The submerged nozzle 1d also satisfies the requirements of the first and second embodiments. Specifically, the requirements are as follows. When the submerged entry nozzle 1d is divided by a plane perpendicular to the thickness direction, the cross-sectional shape of the submerged entry nozzle 1d is symmetrical with respect to a plane that passes through the central axis 1d-1 of the main body 10 and is parallel to the thickness direction. The device has a long, cylindrical main body 10 and a discharge hole portion 20 provided at the lower end of the main body 10 and having a pair of upper discharge holes 21a, 21b and a pair of lower discharge holes 22a, 22b formed therein. In Example 4, the upper part of the main body is cylindrical and the lower part is rectangular. The part from the top end to 260 mm in Fig. 4 is cylindrical, and the part below that is rectangular. The intermediate blocks 23a, 23b arranged between the upper discharge holes 21a, 21b and the lower discharge holes 22a, 22b partially protrude into the interior of the submerged entry nozzle 1d, forming horizontal internal barrier walls 24a, 24b. When the lower end 10a of the flow path of the main body 10 and the left and right internal barriers 24a, 24b are projected onto a horizontal plane, the sum of the projected areas of the left and right internal barriers 24a, 24b is 30 to 70% of the cross-sectional area of ​​the lower end 10a of the flow path of the main body 10 (cross-sectional area of ​​the flow path at the bottom of the main body), and the projected area of ​​the flow path sandwiched between the left and right internal barriers 24a, 24b is 35 to 65% of the cross-sectional area of ​​the flow path at the bottom of the main body. The total projected area of ​​the left and right internal barriers 24a and 24b is 30 x 25 x 2 = 1500 mm 2 The cross-sectional area of ​​the flow path at the bottom of the main body is 110 x 25 = 2750 mm 2 Therefore, the sum of the projected areas of the left and right internal barriers 24a, 24b is 54.5% of the cross-sectional area of ​​the lower end 10a of the flow path of the main body 10 (cross-sectional area of ​​the flow path at the bottom of the main body). The projected area of ​​the flow path sandwiched between the left and right internal barriers 24a and 24b is 50 × 25 = 1250 mm 2 Therefore, the projected area of ​​the flow path sandwiched between the left and right internal barriers 24a, 24b is 45.5% of the cross-sectional area of ​​the flow path at the bottom of the main body. Therefore, this requirement is met. The bottom block 25, which is disposed at the lower end of the submerged nozzle 1d and is sandwiched between the left and right lower discharge holes 22a, 22b, has a concave upper end surface 25a. Therefore, the submerged nozzle 1d satisfies the requirements of the first embodiment. Furthermore, the average upper and lower wall angles of the upper discharge holes 21a, 21b are 50° and the average upper and lower wall angles of the lower discharge holes 22a, 22b are 55°, so the average upper and lower wall angles of the lower discharge holes 22a, 22b are equal to or greater than the average upper and lower wall angles of the upper discharge holes 21a, 21b. Furthermore, the difference between the average upper and lower wall angles of the upper discharge holes 21a, 21b and the average upper and lower wall angles of the lower discharge holes 22a, 22b is small at 5°, which satisfies the requirements of the second embodiment. The radius of curvature of the outer peripheral surface of the upper wall of the upper discharge holes 21a, 21b is 220 mm, and the radius of curvature of the inner peripheral surface is 240 mm.

[0051] Like the submerged entry nozzle 1a, the submerged entry nozzle 1d of Example 4 also satisfied the first and second embodiments, and therefore showed good results in both the flow stability indexes of uneven flow (%) and σ / Ave. In Example 4, the internal shapes of the internal barriers 24a, 24b, etc. were similar to those of Examples 1 and 3, and the effects were also excellent, equivalent to those of Examples 1 and 3.

[0052] <5. Example 5> 5 shows the structure of a submerged nozzle 1e according to Example 5. The submerged nozzle 1e also satisfies the requirements of the first and second embodiments. Specifically, the requirements are as follows. When the submerged entry nozzle 1e is divided by a plane perpendicular to the thickness direction, the cross-sectional shape of the submerged entry nozzle 1e is symmetrical with respect to a plane that passes through the central axis 1e-1 of the main body 10 and is parallel to the thickness direction. The device has a long, rectangular cylindrical main body 10 and a discharge hole portion 20 provided at the lower end of the main body 10 and having a pair of upper discharge holes 21a, 21b and a pair of lower discharge holes 22a, 22b formed therein. The intermediate blocks 23a, 23b arranged between the upper discharge holes 21a, 21b and the lower discharge holes 22a, 22b partially protrude into the interior of the submerged entry nozzle 1e, forming horizontal internal barrier walls 24a, 24b. When the lower end 10a of the flow path of the main body 10 and the left and right internal barriers 24a, 24b are projected onto a horizontal plane, the sum of the projected areas of the left and right internal barriers 24a, 24b is 30 to 70% of the cross-sectional area of ​​the lower end 10a of the flow path of the main body 10 (cross-sectional area of ​​the flow path at the bottom of the main body), and the projected area of ​​the flow path sandwiched between the left and right internal barriers 24a, 24b is 35 to 65% of the cross-sectional area of ​​the flow path at the bottom of the main body. The total projected area of ​​the left and right internal barriers 24a and 24b is 30 x 25 x 2 = 1500 mm 2 The cross-sectional area of ​​the flow path at the bottom of the main body is 110 x 25 = 2750 mm 2Therefore, the sum of the projected areas of the left and right internal barriers 24a, 24b is 54.5% of the cross-sectional area of ​​the lower end 10a of the flow path of the main body 10 (cross-sectional area of ​​the flow path at the bottom of the main body). The projected area of ​​the flow path sandwiched between the left and right internal barriers 24a and 24b is 50 × 25 = 1250 mm 2 Therefore, the projected area of ​​the flow path sandwiched between the left and right internal barriers 24a, 24b is 45.5% of the cross-sectional area of ​​the flow path at the bottom of the main body. Therefore, this requirement is met. The bottom block 25 is disposed at the lower end of the submerged nozzle 1e and is sandwiched between the left and right lower discharge holes 22a, 22b, and has an upper end surface 25a that is horizontal. Therefore, the submerged nozzle 1e satisfies the requirements of the first embodiment. Furthermore, the average upper and lower wall angles of the upper discharge holes 21a, 21b are 45° and the average upper and lower wall angles of the lower discharge holes 22a, 22b are 55°, so the average upper and lower wall angles of the lower discharge holes 22a, 22b are equal to or greater than the average upper and lower wall angles of the upper discharge holes 21a, 21b. Furthermore, the difference between the average upper and lower wall angles of the upper discharge holes 21a, 21b and the average upper and lower wall angles of the lower discharge holes 22a, 22b is small at 10°, which satisfies the requirements of the second embodiment. The radius of curvature of the inner peripheral surface of the upper wall of the upper discharge holes 21a, 21b is 63.5 mm.

[0053] Like the submerged nozzle 1a, the submerged nozzle 1e according to Example 5 also satisfies the first and second embodiments, but the upper end surface 25a of the bottom block 25 is horizontal. Example 5 also showed good results in both the flow stability indexes, the degree of flow unevenness (%) and σ / Ave., but due to differences in the upper end surface 25a of the bottom block 25, the results were slightly inferior to Example 1, especially in the degree of flow unevenness (%).

[0054] 6. Example 6 6 shows the structure of a submerged nozzle 1f according to Example 6. The submerged nozzle 1f satisfies the requirements of the first embodiment, but does not satisfy the requirements of the second embodiment. Specifically, the following applies. When the submerged entry nozzle 1f is divided by a plane perpendicular to the thickness direction, the cross-sectional shape of the submerged entry nozzle 1f is symmetrical with respect to a plane passing through the central axis 1f-1 of the main body 10 and parallel to the thickness direction. The device has a long, rectangular cylindrical main body 10 and a discharge hole portion 20 provided at the lower end of the main body 10 and having a pair of upper discharge holes 21a, 21b and a pair of lower discharge holes 22a, 22b formed therein. The intermediate blocks 23a, 23b arranged between the upper discharge holes 21a, 21b and the lower discharge holes 22a, 22b partially protrude into the interior of the submerged nozzle 1f, forming horizontal internal barrier walls 24a, 24b. When the lower end 10a of the flow path of the main body 10 and the left and right internal barriers 24a, 24b are projected onto a horizontal plane, the sum of the projected areas of the left and right internal barriers 24a, 24b is 30 to 70% of the cross-sectional area of ​​the lower end 10a of the flow path of the main body 10 (cross-sectional area of ​​the flow path at the bottom of the main body), and the projected area of ​​the flow path sandwiched between the left and right internal barriers 24a, 24b is 35 to 65% of the cross-sectional area of ​​the flow path at the bottom of the main body. The total projected area of ​​the left and right internal barriers 24a and 24b is 25 x 25 x 2 = 1250 mm 2 The cross-sectional area of ​​the flow path at the bottom of the main body is 110 x 25 = 2750 mm 2 Therefore, the sum of the projected areas of the left and right internal barriers 24a, 24b is 45.5% of the cross-sectional area of ​​the lower end 10a of the flow path of the main body 10 (cross-sectional area of ​​the flow path at the bottom of the main body). The projected area of ​​the flow path sandwiched between the left and right internal barriers 24a and 24b is 60 × 25 = 1500 mm 2 Therefore, the projected area of ​​the flow path sandwiched between the left and right internal barriers 24a, 24b is 54.5% of the cross-sectional area of ​​the flow path at the bottom of the main body. Therefore, this requirement is met. The bottom block 25, which is disposed at the lower end of the submerged nozzle 1f and is sandwiched between the left and right lower discharge holes 22a, 22b, has a concave upper end surface 25a. Therefore, the submerged nozzle 1f satisfies the requirements of the first embodiment. However, since the average angle of the upper and lower walls of the upper discharge holes 21a, 21b is 30° and the average angle of the upper and lower walls of the lower discharge holes 22a, 22b is 50°, the average angle of the upper and lower walls of the lower discharge holes 22a, 22b is equal to or greater than the average angle of the upper and lower walls of the upper discharge holes 21a, 21b. However, the difference between the average angle of the upper and lower walls of the upper discharge holes 21a, 21b and the average angle of the lower discharge holes 22a, 22b is large at 20°, which does not satisfy the requirements of the second embodiment.

[0055] The submerged nozzle 1f of Example 6 satisfies the first embodiment but does not satisfy the second embodiment. Therefore, there is some difficulty in merging the discharge flows from the upper discharge holes 21a, 21b and the lower discharge holes 22a, 22b. As a result, when the discharge flows from the upper discharge holes 21a, 21b become uneven on the left and right, the discharge flows from the lower discharge holes 22a, 22b are less likely to correct this. Therefore, Example 6 was slightly inferior to the other Examples in both the degree of uneven flow (%) and σ / Ave., which are flow stability indices.

[0056] <7. Comparative Example 1> 7 shows the structure of a submerged nozzle 1g according to Comparative Example 1. The submerged nozzle 1g does not satisfy the requirements of the first embodiment. Specifically, this is as follows. When the submerged entry nozzle 1g is divided by a plane perpendicular to the thickness direction, the cross-sectional shape of the submerged entry nozzle 1g is symmetrical with respect to a plane passing through the central axis 1g-1 of the main body 10 and parallel to the thickness direction. The device has a long, rectangular tubular main body 10 and a discharge hole portion 20 provided at the bottom end of the main body 10 and having a pair of discharge holes 21a, 21b formed therein. Therefore, the submerged entry nozzle 1g is a normal two-hole submerged entry nozzle and does not satisfy the requirements of the first embodiment. The bottom block 25, which is disposed at the lower end of the submerged nozzle 1g and is sandwiched between the left and right discharge holes 21a and 21b, has a concave upper end surface 25a.

[0057] Comparative Example 1 is a normal two-hole submerged entry nozzle and does not satisfy the requirements of the first embodiment. Comparative Example 1 does not exhibit the effects of the present invention at all, and therefore was inferior to the examples of the present invention in both the degree of uneven flow (%) and σ / Ave., which are flow stability indices.

[0058] <8. Comparative Example 2> 8 shows the structure of a submerged nozzle 1h according to Comparative Example 2. The submerged nozzle 1h does not satisfy the requirements of the first embodiment. Specifically, this is as follows. When the submerged entry nozzle 1h is divided by a plane perpendicular to the thickness direction, the cross-sectional shape of the submerged entry nozzle 1h is symmetrical with respect to a plane that passes through the central axis 1h-1 of the main body 10 and is parallel to the thickness direction. The device has a long, rectangular cylindrical main body 10 and a discharge hole portion 20 provided at the lower end of the main body 10 and having a pair of upper discharge holes 21a, 21b and a pair of lower discharge holes 22a, 22b formed therein. The intermediate blocks 23a and 23b arranged between the upper discharge holes 21a and 21b and the lower discharge holes 22a and 22b partially protrude into the inside of the submerged entry nozzle 1h to form internal barriers 24a and 24b. However, since the internal barrier walls 24a, 24b are inclined at an angle of 30° from the horizontal plane, the internal barrier walls 24a, 24b are not horizontal. Therefore, the immersion nozzle 1h does not satisfy the requirements of the first embodiment. In other words, the immersion nozzle 1h is a normal four-hole immersion nozzle that does not have the horizontal internal barrier walls specified in the present invention. The bottom block 25, which is disposed at the lower end of the submerged nozzle 1h and is sandwiched between the left and right lower discharge holes 22a, 22b, has a concave upper end surface 25a.

[0059] Comparative Example 2 is a conventional four-hole submerged entry nozzle, which does not satisfy the requirements of the first embodiment. Comparative Example 2 does not exhibit the effects of the present invention at all, and therefore was inferior to the examples of the present invention in both the flow stability indexes of uneven flow (%) and σ / Ave.

[0060] <9. Comparative Example 3> 9 shows the structure of a submerged nozzle 1i according to Comparative Example 3. The submerged nozzle 1i does not satisfy the requirements of the first embodiment. Specifically, this is as follows. When the submerged entry nozzle 1i is divided by a plane perpendicular to the thickness direction, the cross-sectional shape of the submerged entry nozzle 1i is symmetrical with respect to a plane that passes through the central axis 1i-1 of the main body 10 and is parallel to the thickness direction. The device has a long, rectangular cylindrical main body 10 and a discharge hole portion 20 provided at the lower end of the main body 10 and having a pair of upper discharge holes 21a, 21b and a pair of lower discharge holes 22a, 22b formed therein. The intermediate blocks 23a, 23b arranged between the upper discharge holes 21a, 21b and the lower discharge holes 22a, 22b partially protrude into the interior of the submerged nozzle 1f, forming horizontal internal barrier walls 24a, 24b. When the lower end 10a of the flow path in the main body 10 and the left and right internal barrier walls 24a, 24b are projected onto a horizontal plane, the sum of the projected areas of the left and right internal barrier walls 24a, 24b is less than 30% of the cross-sectional area of ​​the lower end 10a of the flow path in the main body 10 (the cross-sectional area of ​​the flow path at the bottom of the main body), and the projected area of ​​the flow path sandwiched between the left and right internal barrier walls 24a, 24b is more than 65% of the cross-sectional area of ​​the flow path at the bottom of the main body. Therefore, in this respect, the submerged nozzle 1i does not satisfy the requirements of the first embodiment. The total projected area of ​​the left and right internal barriers 24a and 24b is 15 x 25 x 2 = 750 mm 2 The cross-sectional area of ​​the flow path at the bottom of the main body is 110 x 25 = 2750 mm 2 Therefore, the sum of the projected areas of the left and right internal barriers 24a, 24b is 27.3% of the cross-sectional area of ​​the lower end 10a of the flow path of the main body 10 (cross-sectional area of ​​the flow path at the bottom of the main body). The projected area of ​​the flow path sandwiched between the left and right internal barriers 24a and 24b is 80 × 25 = 2000 mm 2 Therefore, the projected area of ​​the flow path sandwiched between the left and right internal barriers 24a, 24b is 72.7% of the cross-sectional area of ​​the flow path at the bottom of the main body. The bottom block 25, which is disposed at the lower end of the submerged nozzle 1i and is sandwiched between the left and right lower discharge holes 22a, 22b, has a concave upper end surface 25a. Therefore, the submerged nozzle 1i does not meet the requirements of the first embodiment.

[0061] The submerged nozzle 1i according to Comparative Example 3 is a comparative example in which the horizontal internal barrier walls 24a, 24b are small and do not satisfy the specified area of ​​the present invention. Since Comparative Example 3 does not exhibit the effects of the present invention, the results were inferior to those of the examples of the present invention in both the degree of unevenness (%) and σ / Ave., which are flow stability indices.

[0062] In addition, in comparison example 3, the projected area of ​​the flow path sandwiched between the internal barriers 24a and 24b extending from the left and right is large, so the discharge flow rate is biased toward the lower discharge holes 22a and 22b, which is undesirable from the perspective of ensuring the effective cross-sectional area of ​​the discharge holes and reducing the discharge flow rate.

[0063] <10. Comparative Example 4> 10 shows the structure of a submerged nozzle 1j according to Comparative Example 4. The submerged nozzle 1j does not satisfy the requirements of the first embodiment. Specifically, this is as follows. When the submerged entry nozzle 1j is divided by a plane perpendicular to the thickness direction, the cross-sectional shape of the submerged entry nozzle 1j is symmetrical with respect to a plane that passes through the central axis 1j-1 of the main body 10 and is parallel to the thickness direction. The device has a long, rectangular cylindrical main body 10 and a discharge hole portion 20 provided at the lower end of the main body 10 and having a pair of upper discharge holes 21a, 21b and a pair of lower discharge holes 22a, 22b formed therein. The intermediate blocks 23a, 23b arranged between the upper discharge holes 21a, 21b and the lower discharge holes 22a, 22b partially protrude into the interior of the submerged nozzle 1j, forming horizontal internal barrier walls 24a, 24b. When the lower end 10a of the flow path in the main body 10 and the left and right internal barrier walls 24a, 24b are projected onto a horizontal plane, the sum of the projected areas of the left and right internal barrier walls 24a, 24b is more than 70% of the cross-sectional area of ​​the lower end 10a of the flow path in the main body 10 (the cross-sectional area of ​​the flow path at the bottom of the main body). Therefore, in this respect, the submerged nozzle 1j does not satisfy the requirements of the first embodiment. The projected area of ​​the flow path sandwiched between the left and right internal barrier walls 24a, 24b is 35 to 65% of the cross-sectional area of ​​the flow path at the bottom of the main body. The total projected area of ​​the left and right internal barriers 24a and 24b is 40 x 25 x 2 = 2000 mm 2The cross-sectional area of ​​the flow path at the bottom of the main body is 110 x 25 = 2750 mm 2 Therefore, the sum of the projected areas of the left and right internal barriers 24a, 24b is 72.7% of the cross-sectional area of ​​the lower end 10a of the flow path of the main body 10 (cross-sectional area of ​​the flow path at the bottom of the main body). The projected area of ​​the flow path sandwiched between the left and right internal barriers 24a and 24b is 50 × 25 = 1250 mm 2 Therefore, the projected area of ​​the flow path sandwiched between the left and right internal barriers 24a, 24b is 45.5% of the cross-sectional area of ​​the flow path at the bottom of the main body. The bottom block 25, which is disposed at the lower end of the submerged nozzle 1j and is sandwiched between the left and right lower discharge holes 22a, 22b, has a concave upper end surface 25a. Therefore, the submerged nozzle 1j does not meet the requirements of the first embodiment.

[0064] The submerged nozzle 1j according to Comparative Example 4 is a comparative example in which the internal barrier walls 24a, 24b are excessively large and exceed the specified area range of the present invention. Comparative Example 4 does not exhibit the effects of the present invention, and therefore the flow stability index σ / Ave. is inferior to the examples of the present invention. Specifically, even though the internal barrier walls 24a, 24b are excessively large, the internal barrier walls 24a, 24b protrude toward the lower wall of the upper discharge holes 21a, 21b to ensure the projected area of ​​the flow path sandwiched between the internal barrier walls 24a, 24b protruding from the left and right sides. The lower wall of the upper discharge holes 21a, 21b, which determines the discharge angle, is shorter than in all examples of the present invention. As a result, the angle of the discharge flow from the upper discharge holes 21a, 21b is unstable, resulting in disruption of the flow within the mold.

[0065] <11. Comparative Example 5> 11 shows the structure of a submerged nozzle 1k according to Comparative Example 5. The submerged nozzle 1k does not satisfy the requirements of the first embodiment. Specifically, this is as follows. When the submerged entry nozzle 1k is divided by a plane perpendicular to the thickness direction, the cross-sectional shape of the submerged entry nozzle 1k is symmetrical with respect to a plane that passes through the central axis 1k-1 of the main body 10 and is parallel to the thickness direction. The device has a long, rectangular cylindrical main body 10 and a discharge hole portion 20 provided at the lower end of the main body 10 and having a pair of upper discharge holes 21a, 21b and a pair of lower discharge holes 22a, 22b formed therein. The intermediate blocks 23a, 23b arranged between the upper discharge holes 21a, 21b and the lower discharge holes 22a, 22b partially protrude into the interior of the submerged entry nozzle 1k, forming horizontal internal barrier walls 24a, 24b. When the lower end 10a of the flow path in the main body 10 and the left and right internal barrier walls 24a, 24b are projected onto a horizontal plane, the sum of the projected areas of the left and right internal barrier walls 24a, 24b is more than 70% of the cross-sectional area of ​​the lower end 10a of the flow path in the main body 10 (the cross-sectional area of ​​the flow path at the bottom of the main body), and the projected area of ​​the flow path sandwiched between the left and right internal barrier walls 24a, 24b is less than 35% of the cross-sectional area of ​​the flow path at the bottom of the main body. Therefore, in this respect, the submerged nozzle 1k does not satisfy the requirements of the first embodiment. The total projected area of ​​the left and right internal barriers 24a and 24b is 40 x 25 x 2 = 2000 mm 2 The cross-sectional area of ​​the flow path at the bottom of the main body is 110 x 25 = 2750 mm 2 Therefore, the sum of the projected areas of the left and right internal barriers 24a, 24b is 72.7% of the cross-sectional area of ​​the lower end 10a of the flow path of the main body 10 (cross-sectional area of ​​the flow path at the bottom of the main body). The projected area of ​​the flow path sandwiched between the left and right internal barriers 24a and 24b is 30 × 25 = 750 mm 2 Therefore, the projected area of ​​the flow path sandwiched between the left and right internal barriers 24a, 24b is 27.3% of the cross-sectional area of ​​the flow path at the bottom of the main body. The bottom block 25, which is disposed at the lower end of the submerged nozzle 1k and is sandwiched between the left and right lower discharge holes 22a, 22b, has a concave upper end surface 25a. Therefore, the submerged nozzle 1k does not meet the requirements of the first embodiment.

[0066] The submerged nozzle 1j according to Comparative Example 5 is a comparative example that does not satisfy the requirements of the present invention, because the internal barrier walls 24a, 24b are excessively large and the projected area of ​​the flow path sandwiched between the internal barrier walls 24a, 24b extending from the left and right is too small. Since Comparative Example 5 does not exhibit the effects of the present invention, the results were inferior to those of the examples of the present invention in both the degree of unevenness (%) and σ / Ave., which are flow stability indices.

[0067] Specifically, because the internal barriers 24a, 24b were excessively large, the projected area of ​​the flow path sandwiched between the internal barriers 24a, 24b extending from the left and right became too small. As a result, when the discharge flows from the upper discharge holes 21a, 21b became uneven on the left and right, the effect of correcting this by the discharge flows from the lower discharge holes 22a, 22b was weakened, and the degree of uneven flow (%) worsened, and accordingly, σ / Ave. also worsened.

[0068] In addition, in comparison example 5, the projected area of ​​the flow path sandwiched between the internal barriers 24a and 24b extending from the left and right is small, so the discharge flow rate is biased toward the upper discharge holes 21a and 21b, which is undesirable from the perspective of ensuring the effective cross-sectional area of ​​the discharge holes and reducing the discharge flow rate.

[0069] <12. Comparative Example 6> 12 shows the structure of a submerged nozzle 1l according to Comparative Example 6. The submerged nozzle 1l does not satisfy the requirements of the first embodiment. Specifically, this is as follows. When the submerged entry nozzle 1l is divided by a plane perpendicular to the thickness direction, the cross-sectional shape of the submerged entry nozzle 1l is symmetrical with respect to a plane passing through the central axis 1l-1 of the main body 10 and parallel to the thickness direction. The device has a long, rectangular cylindrical main body 10 and a discharge hole portion 20 provided at the lower end of the main body 10 and having a pair of upper discharge holes 21a, 21b and a pair of lower discharge holes 22a, 22b formed therein. The intermediate blocks 23a, 23b arranged between the upper discharge holes 21a, 21b and the lower discharge holes 22a, 22b partially protrude into the interior of the submerged entry nozzle 1l, forming horizontal internal barrier walls 24a, 24b. When the lower end 10a of the flow path of the main body 10 and the left and right internal barriers 24a, 24b are projected onto a horizontal plane, the sum of the projected areas of the left and right internal barriers 24a, 24b is 30 to 70% of the cross-sectional area of ​​the lower end 10a of the flow path of the main body 10 (cross-sectional area of ​​the flow path at the bottom of the main body), and the projected area of ​​the flow path sandwiched between the left and right internal barriers 24a, 24b is 35 to 65% of the cross-sectional area of ​​the flow path at the bottom of the main body. The total projected area of ​​the left and right internal barriers 24a and 24b is 30 x 25 x 2 = 1500 mm 2 The cross-sectional area of ​​the flow path at the bottom of the main body is 110 x 25 = 2750 mm 2 Therefore, the sum of the projected areas of the left and right internal barriers 24a, 24b is 54.5% of the cross-sectional area of ​​the lower end 10a of the flow path of the main body 10 (cross-sectional area of ​​the flow path at the bottom of the main body). The projected area of ​​the flow path sandwiched between the left and right internal barriers 24a and 24b is 50 × 25 = 1250 mm 2 Therefore, the projected area of ​​the flow path sandwiched between the left and right internal barriers 24a, 24b is 45.5% of the cross-sectional area of ​​the flow path at the bottom of the main body. Therefore, this requirement is met. The bottom block 25, which is located at the lower end of the submerged nozzle 1l and is sandwiched between the left and right lower discharge holes 22a, 22b, has an upper end surface 25a that is convex upward. Therefore, the submerged nozzle 1l does not satisfy the requirements of the first embodiment in this respect.

[0070] In Comparative Example 6, the upper end surface 25a of the bottom block 25 is convex in shape, which does not satisfy the requirements of the present invention. Because Comparative Example 6 does not exhibit the effects of the present invention, the flow stability indexes of uneven flow (%) and σ / Ave. were inferior to those of the Examples of the present invention. Specifically, because the upper end surface 25a of the bottom block 25 is convex in shape, when the discharge flows from the upper discharge holes 21a and 21b become uneven on the left and right sides, the discharge flows from the lower discharge holes 22a and 22b are unable to correct this, resulting in a deterioration in the uneven flow (%). Consequently, the σ / Ave. also deteriorated. The fact that the upper end surface 25a of the bottom block 25 is convex in shape increases the fluctuation in the discharge flow rate from the lower discharge holes 22a and 22b, which is thought to be one of the reasons for the deterioration in σ / Ave.

[0071] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention. [Explanation of symbols]

[0072] 1a~1l Immersion nozzle 10 Main body 20 Discharge hole 21a, 21b Upper discharge hole 22a, 22b Lower discharge hole 23a, 23b Intermediate block 24a, 24b Internal barrier 25 Bottom Block 25a Top surface of bottom block

Claims

1. A submerged entry nozzle for continuous casting of steel, comprising: A long, cylindrical main body; a discharge hole portion provided at a lower end of the main body portion and having a pair of upper discharge holes and a pair of lower discharge holes; an intermediate block disposed between the upper discharge hole and the lower discharge hole; and when the continuous casting submerged entry nozzle is divided by a plane perpendicular to the thickness direction of the continuous casting submerged entry nozzle, the cross-sectional shape of the continuous casting submerged entry nozzle is bilaterally symmetrical with respect to a plane passing through the central axis of the main body and parallel to the thickness direction, a portion of the intermediate block protruding toward the inside of the continuous casting immersion nozzle to form a horizontally shaped internal barrier; When the lower end of the flow path of the main body portion and the left and right internal barriers are projected onto a horizontal plane, the sum of the projected areas of the left and right internal barriers is 30 to 70% of the cross-sectional area of ​​the lower end of the flow path of the main body portion, and the projected area of ​​the flow path sandwiched between the left and right internal barriers is 35 to 65% of the cross-sectional area of ​​the lower end of the flow path of the main body portion, a bottom block disposed at the lower end of the continuous casting submerged nozzle and sandwiched between the left and right lower discharge holes, the upper end surface of which is horizontal or concave.

2. 2. The continuous casting submerged entry nozzle according to claim 1, wherein, under conditions where an average downward flow velocity of molten steel at a lower end of the flow path in the main body portion is 1.5 to 4.0 m / s, when the upper discharge flow rate from the left and right upper discharge holes is biased toward one of the left and right upper discharge holes due to left and right bias of the downward flow in the main body portion, the lower discharge flow rate from the lower discharge hole on the side where the upper discharge flow rate was lower becomes larger.

3. 3. The submerged entry nozzle for continuous casting according to claim 1, wherein an average angle of the upper and lower walls of the lower discharge hole is equal to or greater than an average angle of the upper and lower walls of the upper discharge hole, and a difference between the average angle of the upper and lower walls of the upper discharge hole and the average angle of the lower discharge hole is 15° or less.

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