Submerged entry nozzle

Abstract

Disclosed is technology that is capable of reducing imbalances in flow rate distribution to a pair of discharge holes in a submerged entry nozzle which has a flat part. A submerged entry nozzle according to the present disclosure has a baffle in a flat flow path and has a pair of discharge holes that communicate the flat flow path and the outside. The flat flow path has a width W1 and a thickness T1, and the baffle has a width W2 and a thickness T2. The baffle is present at the center in the width direction of the flat flow path. The pair of discharge holes are present on both end sides in the width direction of the baffle. The upper end of the baffle is present above the lower ends of the pair of discharge holes. The width W2 is 50% or more of the width W1, and the thickness T2 is at least 40% but less than 80% of the thickness T1. In a cross section crossing the baffle and along the width direction and the vertical direction (left side cross section in fig. 1), the upper surface of the baffle has a recessed surface that has such a shape as to be line-symmetric with an axis of symmetry which is a straight line X passing through the center in the width direction and that is recessed downward at the center in the width direction.

Description

Submerged Entry Nozzle

[0001] The present application discloses an immersion nozzle for continuous casting, which is used, for example, to supply molten metal from a tundish, which is an intermediate vessel, to a continuous casting mold.

[0002] In so-called thin slab continuous casting, submerged entry nozzles (SENs) for supplying molten metal into a thin mold typically have a flat portion at least at the lower portion of the nozzle. Examples of SENs with flat portions include those disclosed in Patent Documents 1 to 3. The internal flow passages of these SENs with flat portions are provided with protrusions or barriers for the purpose of properly distributing and streamlining the molten metal flow. Specifically, these include members 178 and 180 shown in FIG. 35 of Patent Document 1, members 20 and 28 shown in FIG. 3 of Patent Document 2, and members 1a and 1b shown in FIG. 2 of Patent Document 3. Furthermore, although not necessarily requiring the presence of a flat portion, member 3 shown in FIG. 3 of Patent Document 4 and member 3 shown in FIG. 1 of Patent Document 5 are also believed to be provided for the same purpose.

[0003] Special Table of Contents No. 2001-501132 Publication of Special Publication No. 2004-514562 Publication of Japanese Patent Application Publication No. 2017-087264 Publication of Japanese Patent Application Publication No. 58-000361 Publication of Japanese Patent Application Publication No. Hei 8-267200

[0004] Conventional submerged entry nozzles with flattened sections are designed on the premise of an ideal state in which the downward flow from the upper part of the nozzle flows downward without bias. However, the downward flow from the upper part of the nozzle is prone to constant or periodic bias due to bias in the flow path in the flow rate adjustment mechanism located further upstream, or flow fluctuations caused by the cross-sectional area of ​​the flow path at the upper part of the nozzle being excessively large compared to the fluid flow rate. Therefore, conventional submerged entry nozzles have the problem that the flow rate distribution to the pair of discharge holes at the flattened section is prone to bias.

[0005] The present inventors conducted experimental research into the self-stabilizing function of a submerged entry nozzle having a flattened portion (this refers to the function of suppressing bias in the distribution of flow rate to a pair of discharge holes even when the downward flow from the top of the nozzle is biased; the same applies hereinafter). As a result, they found that the self-stabilizing function is not fully exhibited with projections or barriers that have a shape that follows the streamline, i.e., a shape that attempts to smoothly flow the fluid, as disclosed in the past. The present inventors further investigated the shape of the projections and barriers provided in the flow path and found a shape that is likely to exhibit the self-stabilizing function.

[0006] The present application discloses the following multiple embodiments as means for solving the above problems. <Embodiment 1> An immersion nozzle having a flat portion, wherein the flat portion has a flat flow path, the flat portion has a baffle in the flat flow path, the flat portion has a pair of discharge holes connecting the flat flow path to the outside, the flat flow path has a width W1 and a thickness T1, the baffle has a width W2 and a thickness T2, the baffle is located at the center of the flat flow path in the width direction, one of the pair of discharge holes is located at one end of the flat flow path in the width direction, the other of the pair of discharge holes is located at the other end of the flat flow path in the width direction, the upper end of the baffle is located above the lower ends of the pair of discharge holes, the width W2 is 50% or more of the width W1, and the thickness T2 is 40% or more but less than 80% of the thickness T1, An immersion nozzle wherein, in a cross section across the baffle that is taken along the width direction and the up-down direction, the upper surface of the baffle has a shape that is line-symmetrical with respect to a line passing through the center in the width direction as an axis of symmetry, and has a first concave surface that is concave downward at the center in the width direction. <Aspect 2> The immersion nozzle of Aspect 1, wherein the lower end of the baffle is located above the lower ends of the pair of discharge holes. <Aspect 3> The immersion nozzle of Aspect 1 or 2, wherein the lower end of the baffle is located below the upper ends of the pair of discharge holes. <Aspect 4> The immersion nozzle of Claim 1 or 2, wherein the upper end of the baffle is located below a position that is 30 mm above the upper ends of the pair of discharge holes. <Aspect 5> The immersion nozzle of any of Aspects 1 to 4, wherein the flattened section has an inner bottom surface facing the flattened flow path, and the inner bottom surface has a shape that is symmetrical with respect to a line passing through the center in the width direction as an axis of symmetry, and has a second concave surface that is concave downward at the center in the width direction, or has a flat surface that extends along the width direction at the center in the width direction. <Aspect 6> The immersion nozzle of Aspect 5, wherein the second concave surface has a curved surface.<Aspect 7> The immersion nozzle of Aspect 5 or 6, wherein the second concave surface has a thickness T3, and the thickness T3 is 70% or more and 100% or less of the thickness T1. <Aspect 8> The immersion nozzle of any of Aspects 5 to 7, wherein the second concave surface has a width W3, and the width W3 is 50% or more of the width W1. <Aspect 9> The immersion nozzle of any of Aspects 5 to 8, wherein the second concave surface has a depth Dp, and the depth Dp is 5 mm or more and 50 mm or less. <Aspect 10> The immersion nozzle of any of Aspects 1 to 9, wherein the flattened portion has, as outer surfaces, a wide surface, a narrow surface, and an outer bottom surface, and the pair of discharge holes are provided so as to penetrate only the narrow surface. <Aspect 11> The submerged entry nozzle of any one of Aspects 1 to 9, wherein the flat portion has, as its outer surfaces, a broad surface, a narrow surface, and an outer bottom surface, and the pair of discharge holes are provided so as to penetrate the narrow surface and the bottom surface. Aspect 12 is the immersion nozzle of any one of Aspects 1 to 9, wherein the flat section has a first baffle as the baffle in the flat flow path, the flat section has a pair of upper discharge holes and a pair of lower discharge holes that communicate the flat flow path with the outside, one of the pair of upper discharge holes is located at one widthwise end of the flat flow path, the other of the pair of upper discharge holes is located at the other widthwise end of the flat flow path, one of the pair of lower discharge holes is located at one widthwise end of the flat flow path, the other of the pair of lower discharge holes is located at the other widthwise end of the flat flow path, an upper end of the first baffle is located above lower ends of the pair of upper discharge holes, and an upper end of the first baffle is located below a position 30 mm above the upper ends of the pair of upper discharge holes. <Aspect 13> The submerged nozzle according to aspect 12, wherein a lower end of the first baffle is located above upper ends of the pair of lower discharge holes.<Aspect 14> The immersion nozzle of Aspect 12 or 13, wherein the flattened section has the first baffle and a second baffle in the flattened flow path, and the second baffle is located below the first baffle. <Aspect 15> The immersion nozzle of any of Aspects 12 to 14, wherein the inlets of the pair of lower discharge holes are located more inward in the width direction than the inlets of the pair of upper discharge holes. <Aspect 16> The immersion nozzle of any of Aspects 12 to 15, wherein the length from the lower end of the first baffle to the lower end of the flattened flow path is 90 mm or less. <Aspect 17> The immersion nozzle of any of Aspects 12 to 16, wherein the flattened section has, as outer surfaces, a wide face, a narrow face, and an outer bottom face, and the pair of upper discharge holes are provided so as to penetrate only the narrow faces. <Aspect 18> The immersion nozzle of any of Aspects 12 to 17, wherein the flat portion has, as its outer surfaces, a wide surface, a narrow surface, and an outer bottom surface, and the pair of lower discharge holes are provided between the narrow surface and the bottom surface. <Aspect 19> The immersion nozzle of any of Aspects 12 to 18, wherein the flat portion has, as its outer surfaces, a wide surface, a narrow surface, and an outer bottom surface, and the wide surface has a maximum width W. ＭＡＸ and the representative diameter D1 of the pair of upper discharge holes and the representative diameter D2 of the pair of lower discharge holes satisfy the following relationship: W ＭＡＸ An immersion nozzle satisfying the following condition: ≦3×(D1+D2) Aspect 20 The immersion nozzle of any one of Aspects 1 to 19, wherein the first concave surface is a V-shaped surface or a curved surface.

[0007] According to the immersion nozzle of the present disclosure, a predetermined baffle provided in the flat flow path facilitates the self-stabilizing function, which means that even if a bias occurs in the downward flow from the upper part of the nozzle, the immersion nozzle of the present disclosure can reduce the bias in the flow rate distribution to the pair of discharge holes.

[0008] FIG. 1 shows a schematic diagram of an example of a cross-sectional shape of an immersion nozzle according to an embodiment. It corresponds to the immersion nozzle according to Example 1-1. It shows a schematic diagram of an example of a cross-sectional shape of an immersion nozzle according to an embodiment. It corresponds to the immersion nozzle according to Example 2-1. It shows a schematic diagram of an example of a cross-sectional shape of an immersion nozzle according to an embodiment. It corresponds to the immersion nozzle according to Example 3-1. It shows a schematic diagram of an example of a cross-sectional shape of an immersion nozzle according to an embodiment. It corresponds to the immersion nozzle according to Example 4-1. It shows a schematic diagram of an example of a cross-sectional shape of an immersion nozzle according to an embodiment. It corresponds to the immersion nozzle according to Example 5-1. It shows a schematic diagram of an example of a cross-sectional shape of an immersion nozzle according to an embodiment. It corresponds to the immersion nozzle according to Example 6-1. It shows a schematic diagram of an example of a cross-sectional shape of an immersion nozzle according to an embodiment. It shows a schematic diagram of an example of a cross-sectional shape of an immersion nozzle according to an embodiment. It is a schematic diagram for explaining the length L2 from the lower end of the first baffle to the lower end (inner bottom surface) of the flat flow path. It is a schematic diagram for explaining the representative diameter D1 of the upper discharge hole. 1 shows a schematic diagram of the cross-sectional shape of the submerged entry nozzle according to Comparative Example 1-1. 1 shows a schematic diagram of the cross-sectional shape of the submerged entry nozzle according to Comparative Example 1-2. 1 shows a schematic diagram of the cross-sectional shape of the submerged entry nozzle according to Comparative Example 1-3. 1 shows a schematic diagram of the cross-sectional shape of the submerged entry nozzle according to Comparative Example 2-1. 1 shows a schematic diagram of the cross-sectional shape of the submerged entry nozzle according to Comparative Example 3-1. 1 shows a schematic diagram of the cross-sectional shape of the submerged entry nozzle according to Comparative Example 4-1. 1 shows a schematic diagram of the cross-sectional shape of the submerged entry nozzle according to Comparative Example 4-2. 1 shows a schematic diagram of the cross-sectional shape of the submerged entry nozzle according to Comparative Example 5-1. 1 shows a schematic diagram of the cross-sectional shape of the submerged entry nozzle according to Comparative Example 5-2. 1 shows a schematic diagram of the cross-sectional shape of the submerged entry nozzle according to Comparative Example 6-1. 1 shows a schematic diagram of the cross-sectional shape of the submerged entry nozzle according to Comparative Example 6-2. 1 shows the dimensions of the submerged entry nozzle and baffle according to Example 1-1. 1 shows the dimensions of the submerged entry nozzle and baffle according to Comparative Example 1-3. 1 shows the dimensions of the submerged entry nozzle and baffle according to Example 2-1. Dimensions of the submerged entry nozzle and baffle according to Example 3-1 are shown. Dimensions of the submerged entry nozzle and baffle according to Example 4-1 are shown. Dimensions of the submerged entry nozzle and baffle according to Example 5-1 are shown.Dimensions of the submerged entry nozzle and baffle according to Example 6-1 are shown. The configuration of the device used to evaluate the flow distribution rate is shown schematically. The shape and dimensions of the submerged entry nozzle according to Example A are shown. The shape and dimensions of the submerged entry nozzle according to Example B are shown. The shape and dimensions of the submerged entry nozzle according to Example C are shown. The shape and dimensions of the submerged entry nozzle according to Example D are shown. The shape and dimensions of the submerged entry nozzle according to Example E are shown. The shape and dimensions of the submerged entry nozzle according to Comparative Example F are shown. The shape and dimensions of the submerged entry nozzle according to Comparative Example G are shown. The shape and dimensions of the submerged entry nozzle according to Comparative Example H are shown. The shape and dimensions of the submerged entry nozzle according to Comparative Example I are shown. The shape and dimensions of the submerged entry nozzle according to Comparative Example J are shown. The evaluation results for Example A are shown. The evaluation results for Example B are shown. The evaluation results for Example C are shown. The evaluation results for Example D are shown. The evaluation results for Example E are shown. The evaluation results for Comparative Example G are shown. The evaluation results for Comparative Example I are shown. The evaluation results for Comparative Example J are shown.

[0009] An embodiment of the submerged entry nozzle of the present disclosure will be described below. However, the submerged entry nozzle of the present disclosure is not limited to the following embodiment. In this application, the flow path inlet side (upstream side of the flow path) of the submerged entry nozzle is defined as the "upper side," and the discharge hole side (downstream side of the flow path) is defined as the "lower side."

[0010] The inventors focused on protrusions that narrow the flow path thickness as a component that imparts a self-stabilizing function to the submerged entry nozzle. While providing a barrier across the entire thickness of the flow path is one method for enabling distribution and rectification of the molten metal flow, protrusions that leave a flow path in the thickness direction have the advantage of allowing the submerged entry nozzle to be designed more compactly. For example, if a barrier exists across the entire thickness of the flow path at the center of the flow path width of the submerged entry nozzle, the downward flow must bypass the barrier in order to flow below the barrier, and the submerged entry nozzle must be widened in the width direction to ensure that flow path. In contrast, protrusions that leave a flow path in the thickness direction allow the downward flow to flow down the remaining flow path in the thickness direction without bypassing it, thereby reducing the width dimension of the submerged entry nozzle.

[0011] In this application, protrusions provided inside the flow path are referred to as "baffles." The inventors experimentally discovered that the self-stabilizing function is clearly enhanced by placing a specific baffle in the center of the width direction of the flow path and forming a concave surface (first concave surface) in the center of the width direction on the upper surface of the baffle. In other words, by adopting a shape for the upper surface of the baffle that disturbs the flow and complicates the streamlines, rather than rectifying the flow, it is possible to mitigate the effects of biased downward flow from the top of the submerged entry nozzle and equalize the discharge flow rate in the width direction.

[0012] FIG. 1 shows a cross-sectional shape of an immersion nozzle 100 according to one embodiment. As shown in FIG. 1, the immersion nozzle 100 has a flat portion 10. The flat portion 10 has a flat flow path 11. The flat portion 10 has a baffle 12 in the flat flow path 11. The flat portion 10 has a pair of discharge holes 13a, 13b that communicate the flat flow path 11 with the outside. The flat flow path 11 has a width W1 and a thickness T1. The baffle 12 has a width W2 and a thickness T2. The baffle 12 is located at the center of the flat flow path 11 in the width direction. One of the pair of discharge holes 13a, 13b is located at one end of the flat flow path 11 in the width direction, and the other of the pair of discharge holes 13a, 13b is located at the other end of the flat flow path 11 in the width direction. The upper end 12ax of the baffle 12 is located above the lower ends 13ay and 13by of the pair of discharge holes 13a and 13b. It is important that, in the submerged nozzle 100, the width W2 is 50% or more of the width W1, and the thickness T2 is 40% or more and less than 80% of the thickness T1. It is also important that, in a cross section across the baffle 12 and along the width direction and the up-down direction (the cross section shown on the left side in FIG. 1 ), the upper surface 12a of the baffle 12 has a shape that is line-symmetrical with respect to a line X passing through the center in the width direction as the axis of symmetry, and that the baffle 12 has a first concave surface 12az that is concave downward at the center in the width direction.

[0013] 1. Flat Section The submerged entry nozzle 100 is used, for example, in the continuous casting of thin slabs. At least the lower portion of the submerged entry nozzle 100 has a flat cross-sectional shape so that it can be inserted into a mold with a small thickness. In the present application, this portion having a flat cross-sectional shape is referred to as the "flat section." As shown in FIG. 1 , the flat section 10 may extend from a position P1 between the upper and lower ends of the submerged entry nozzle 100 to the lower end of the submerged entry nozzle 100. The flat section 10 has, for example, a broad surface 10a along the width direction (left-right direction), a narrow surface 10b along the thickness direction, and an outer bottom surface 10c at the lower end. The width W of the broad surface 10a and the thickness T of the narrow surface 10b may be determined appropriately depending on the application of the submerged entry nozzle 100. The width W of the broad surface 10a of the flat portion 10 may be, for example, 140 mm or more and 350 mm or less, and the thickness T of the narrow surface 10b of the flat portion 10 may be, for example, 30 mm or more and 130 mm or less. This allows the submerged entry nozzle 100 to be used, for example, as a continuous casting submerged entry nozzle for supplying molten metal from a tundish, which is an intermediate vessel, to a thin mold in so-called thin slab continuous casting. The flat portion 10 may also have a length L from position P1 to its lower end. The length L may be determined appropriately depending on the application of the submerged entry nozzle 100. The length L may be, for example, 800 mm or more and 1500 mm or less. The width W of the broad surface 10a and the thickness T of the narrow surface 10b of the flat portion 10 may vary depending on the vertical position, or may be constant regardless of the vertical position. That is, the wide surface 10a may extend vertically with a constant width W, or the width W may vary (e.g., increase) from top to bottom. The narrow surface 10b may extend vertically with a constant thickness T, or the thickness T may vary (e.g., decrease) from top to bottom.

[0014] 1.1 Flat Flow Passage The flat portion 10 has a flat flow passage 11 therein. The flat flow passage 11 has a flat flow passage cross-sectional shape corresponding to the flat cross-sectional shape of the flat portion 10. That is, the flat flow passage 11 has a width W1 and a thickness T1. The width W1 is greater than the thickness T1. The width W1 and the thickness T1 are determined appropriately depending on the width W and thickness T of the flat portion 10 and the thickness of the refractory material constituting the flat portion 10. The width W1 of the flat flow passage 11 may be, for example, 100 mm or more and 300 mm or less, and the thickness T1 of the flat flow passage 11 may be, for example, 20 mm or more and 45 mm or less. The flat flow passage 11 may also have a length L1 from the position P1 to the upper ends 13ax and 13bx of the discharge holes 13a and 13b. The length L1 may be determined appropriately depending on the application of the submerged nozzle 100. The length L1 may be, for example, 600 mm or more and 1000 mm or less. The width W1 and thickness T1 of the flat flow path 11 may vary depending on the vertical position, or may be constant regardless of the vertical position. That is, the flat flow path 11 may extend vertically with a constant width W1, or the width W1 may vary (e.g., decrease) from top to bottom. The flat flow path 11 may also extend vertically with a constant thickness T1, or the thickness T1 may vary (e.g., decrease) from top to bottom.

[0015] 1.2 Baffle In the flat section 10, the baffle 12 is located at the widthwise center of the flat flow channel 11. "The baffle 12 is located at the widthwise center of the flat flow channel 11" means that the widthwise center of the baffle 12 and the widthwise center of the flat flow channel 11 essentially coincide. However, the widthwise center of the baffle 12 and the widthwise center of the flat flow channel 11 do not necessarily have to coincide perfectly; a certain degree of misalignment is acceptable as long as the self-stabilizing function is exhibited. Specifically, when the widthwise center of the baffle 12 is within a 10 mm range of the widthwise center of the flat flow channel 11, it is considered that "the baffle 12 is located at the widthwise center of the flat flow channel 11." The same applies to the "widthwise center" of the first concave surface 12az and the second concave surface 14a, which will be described later.

[0016] The baffle 12 has a width W2, for example, and extends continuously and uninterruptedly from one end to the other end in the width direction. The baffle 12 having the width W2 is likely to be more effective in suppressing drift in the width direction (left and right direction). If the baffle is divided at the center in the width direction, the baffle-free area in the center of the width direction cannot suppress drift of the downward flow. However, in this embodiment, the baffle 12 having the width W2 may be installed, and then a baffle divided in the width direction may be installed as an auxiliary baffle.

[0017] In this embodiment, it is important that the width W2 of the baffle 12 is 50% or more of the width W1 of the flat flow path 11. In other words, the baffle 12 occupies 50% or more of the width of the flat flow path 11. When the width W2 of the baffle 12 is 50% or more of the width W1 of the flat flow path 11, the baffle 12 appropriately disturbs the downward flow, making it easier to suppress drift. The width W2 of the baffle 12 may be 50% or more, 55% or more, 60% or more, 70% or more, 75% or more, 80% or more, or 85% or more of the width W1 of the flat flow path 11. In this application, the "width W2 of the baffle" refers to the maximum width of the baffle 12. Furthermore, in this application, when specifying the relationship between the width W1 of the flat flow channel 11 and the width W2 of the baffle, the "width W1 of the flat flow channel 11" refers to the narrowest width of the flat flow channel 11 within a range of 1.5 × W2 above the upper end 12ax of the baffle 12. When multiple baffles are provided vertically, the most upstream baffle is used in defining the "width W1 of the flat flow channel 11." In this case, the "width W1 of the flat flow channel 11" refers to the distance between the inner walls of the nozzle at both ends in the width direction above the discharge holes 13a and 13b (described below), and refers to the distance between the outlets of a pair of discharge holes 13a and 13b at both ends in the width direction below the discharge holes 13a and 13b. In this application, the width W2 of the baffle 12 is defined based on the width W1 of the flat flow channel 11, not the width W of the flat portion 10. In this way, by defining the width W2 of the baffle 12 based on the width W1 of the flat flow path 11, the baffle 12 can appropriately receive the fluid flowing through the flat flow path 11, thereby achieving a significant effect of suppressing drift. The width W2 of the baffle 12 may be larger or smaller than the width W1 of the flat flow path 11, or may be the same as the width W. However, in this embodiment, it is not anticipated that the baffle 12 will protrude outward in the width direction beyond the discharge holes 13a, 13b. The width W2 of the baffle 12 may be 110% or less, 115% or less, 100% or less, 95% or less, 90% or less, 85% or less, or 80% or less of the width W1 of the flat flow path 11.

[0018] The baffles 12 protrude from the broad inner walls that define the flat flow path 11. The baffles 12 have a thickness T2. The thickness T2 of the baffles 12 refers to the total thickness of the baffles in the thickness direction. For example, as shown in FIG. 1 , if the baffles 12 have baffle A protruding from one broad inner wall that defines the flat flow path 11 toward the other broad inner wall and baffle B protruding from the other broad inner wall that defines the flat flow path 11 toward the first broad inner wall, and if a gap G exists between baffle A and baffle B, the thickness T2 of the baffle 12, which is the total thickness of baffles A and B, is the distance I between one broad inner wall and the other broad inner wall minus the gap G (T2 = I - G). When there is only one baffle (when only one of baffle A and baffle B is present), the thickness of that single baffle is thickness T2. The thickness T2 of the baffle 12 is defined as the largest value between the upper surface 12a and the lower surface of the baffle 12. If the representative thickness T2 of the baffle 12 varies across the width, the average of the representative thicknesses of the baffle 12 is considered to be the "baffle thickness T2." The thickness T2 may be greater or less than the width W2. However, a greater width W2 than the thickness T2 tends to provide a more excellent self-stabilizing function. In this embodiment, it is important that the thickness T2 of the baffle 12 be 40% or more and less than 80% of the thickness T1 of the flat flow path 11. In other words, the baffle 12 accounts for 40% or more and less than 80% of the thickness of the flat flow path 11. When the thickness T2 of the baffle 12 is 40% or more of the thickness T1 of the flat flow path 11, the baffle 12 appropriately disrupts the downward flow, and the effect of suppressing drift is easily achieved. On the other hand, if the thickness T2 of the baffle 12 is less than 80% of the thickness T1 of the flat flow path 11, the thickness of the remaining flow path without the baffle 12 is ensured, flow resistance can be reduced, and the flow rate of the downward flow can be easily ensured. If the thickness T2 is too thick, the downward flow becomes a high-speed jet in the narrow remaining flow path, which may cause refractory melting or flow disturbance. The thickness T2 of the baffle 12 may be 45% or more, 50% or more, or 75% or less, 70% or less, 65% or less, 60% or less, or 55% or less of the thickness T1 of the flat flow path.

[0019] In this embodiment, it is important that, in a cross section across the baffle 12 that is along the width direction and the up-down direction (the cross section shown on the left side in FIG. 1 ), the upper surface 12a of the baffle 12 has a shape that is line-symmetrical about the line X passing through the center in the width direction as the axis of symmetry, and that the baffle 12 has a first concave surface 12az that is concave downward at the center in the width direction. As a result, even if a downward flow from above is biased toward either the width direction (left-right direction), the downward flow collides with the first concave surface 12az of the baffle 12, thereby redistributing the downward flow to the side with a slower flow velocity, thereby suppressing bias in the discharge flow from the discharge holes 13a, 13b. As described above, the shape of the upper surface 12a of the baffle 12 and the shape of the first concave surface 12az provided at the center in the width direction of the upper surface 12a may be any shape that is line-symmetrical about the line X passing through the center in the width direction as the axis of symmetry. The width Wz of the first concave surface 12az may be, for example, 60% to 100% of the width W2 of the baffle 12. If the width Wz of the first concave surface 12az is too small, the baffle 12's effect of suppressing drift tends to be reduced. Furthermore, the depth Dz of the first concave surface 12az (the height from the top of the concave surface to the deepest part of the concave surface) may be, for example, 8% to 90% or 10% to 60% of the width W2 of the baffle 12. If the depth Dz of the first concave surface 12az is too small or too large relative to the width W2 of the baffle 12, the baffle 12's effect of suppressing drift tends to be reduced. Furthermore, if the depth Dz of the first concave surface 12az is too large, the height of the baffle 12 becomes unnecessarily large. As shown in FIG. 1 , the first concave surface 12az may have a substantially uniform shape and extend in the thickness direction.

[0020] Although Fig. 1 illustrates an example of the first concave surface 12az having a V-shaped surface, the shape of the first concave surface 12az is not limited thereto. The first concave surface 12az may have a curved surface (e.g., a U-shaped surface) as shown in Fig. 2, a dish-shaped surface with a horizontal bottom surface as shown in Fig. 3, or any other concave surface. As far as the inventors have confirmed, a more excellent self-stabilizing function is likely to be exhibited when the first concave surface 12az has a V-shaped surface as shown in Fig. 1 or a curved surface as shown in Fig. 2.

[0021] In this embodiment, the shape of the lower surface 12b of the baffle 12 is not particularly limited. The lower surface 12b of the baffle 12 may have a convex surface, a concave surface, or a flat surface. In this embodiment, at least one baffle 12 is required. That is, the number of baffles 12 may be one or more. As described above, auxiliary baffles different from the baffle 12 (e.g., a baffle divided in the width direction as described above, or a baffle that does not satisfy the width W2, thickness T2, or upper surface shape described above) may be provided in addition to the baffle 12. In this embodiment, it is sufficient that at least one baffle 12 having the specific shape described above is provided, and that at least one combination of the baffle 12 and a pair of discharge holes 13a, 13b (described below) that satisfies a predetermined positional relationship is present somewhere in the flat portion. In this embodiment, in addition to the combination of the baffle 12 having the specific shape and the pair of discharge holes 13a, 13b, another baffle or discharge holes may be present.

[0022] 1.3 Discharge Holes The flat portion 10 has a pair of discharge holes 13a, 13b that communicate the flat flow path 11 with the outside. One of the pair of discharge holes 13a, 13b is located at one widthwise end of the baffle 12, and the other of the pair of discharge holes 13a, 13b is located at the other widthwise end of the baffle 12. For example, if the flat portion 10 has an outer surface including a broad surface 10a, a narrow surface 10b, and an outer bottom surface 10c, the pair of discharge holes 13a, 13b may be provided so as to penetrate only the narrow surface 10b, as shown in Figures 1 to 3. Alternatively, the pair of discharge holes 13a, 13b may be provided so as to penetrate both the narrow surface 10b and the bottom surface 10c, as shown in Figure 4. That is, the pair of discharge holes 13a, 13b may be provided from the narrow surface 10b to the bottom surface 10c.

[0023] The positional relationship between the pair of discharge holes 13a, 13b and the baffle 12 may be any positional relationship that ensures the self-stabilizing function of the baffle 12. In other words, by having the upper end 12ax of the baffle 12 located above the lower ends 13ay, 13by of the pair of discharge holes 13a, 13b, at least a portion of the downward flow collides with the baffle 12 and is then discharged to the outside from the discharge holes 13a, 13b, thereby providing a self-stabilizing effect to suppress drift of at least a portion of the downward flow. In particular, a more excellent self-stabilizing function is likely to be achieved when the lower end 12ay of the baffle 12 is located above the lower ends 13ay, 13by of the pair of discharge holes 13a, 13b. In addition, a more excellent self-stabilizing function is likely to be exhibited when the lower end 12ay of the baffle 12 is located below the upper ends 13ax, 13bx of the pair of discharge holes 13a, 13b, when the upper end 12ax of the baffle 12 is located below a position 30 mm above the upper ends 13ax, 13bx of the pair of discharge holes 13a, 13b, or when the upper end 12ax of the baffle 12 is located below the upper ends 13ax, 13bx of the pair of discharge holes 13a, 13b.

[0024] The opening shape of the pair of discharge holes 13a, 13b may be determined appropriately depending on the positions at which the discharge holes 13a, 13b are provided. For example, as shown in Figures 1 to 3, the opening shape of the pair of discharge holes 13a, 13b may be a rectangle having long and short sides. In this case, the long sides of the discharge holes 13a, 13b may be 80 mm or more and 170 mm or less, and the short sides of the discharge holes 13a, 13b may be 20 mm or more and 55 mm or less.

[0025] In this embodiment, the pair of discharge holes 13a, 13b are located at substantially the same height in the flat portion 10 and are opposed to each other. Only one pair of discharge holes may be provided, or two or more pairs may be provided. That is, the submerged nozzle 100 may have two discharge holes or four or more discharge holes. In particular, when only one pair of discharge holes is provided (when the submerged nozzle 100 is a dual-hole nozzle), manufacturing costs can be reduced compared to when two or more pairs of discharge holes are provided. When two or more pairs of discharge holes are provided, it is sufficient that the upper end 12ax of a given baffle 12 is located above the lower ends 13ay, 13by of any pair of discharge holes 13a, 13b among the two or more pairs of discharge holes. Furthermore, when two or more pairs of discharge holes are provided, the lower end 12ay of one baffle 12 may be located higher than the lower ends 13ay, 13by of any pair of discharge holes 13a, 13b of the two or more pairs of discharge holes, the lower end 12ay of one baffle 12 may be located higher than the upper ends 13ax, 13bx of any pair of discharge holes 13a, 13b of the two or more pairs of discharge holes, or the upper end 12ax of one baffle 12 may be located lower than the upper ends 13ax, 13bx of any pair of discharge holes 13a, 13b of the two or more pairs of discharge holes. For example, when two or more pairs of discharge holes are provided, the upper end 12ax of one baffle 12 may be arranged to be higher than the lower ends 13ay, 13by of the pair of discharge holes 13a, 13b on the most upstream (top) side, or the lower end 12ay of one baffle 12 may be arranged to be higher than the lower ends 13ay, 13by of the pair of discharge holes 13a, 13b on the most upstream (top) side, or the lower end 12ay of one baffle 12 may be arranged to be lower than the upper ends 13ax, 13bx of the pair of discharge holes 13a, 13b on the most upstream (top) side, or the upper end 12ax of one baffle 12 may be arranged to be lower than the upper ends 13ax, 13bx of the pair of discharge holes 13a, 13b on the most upstream (top) side. Alternatively, the baffles 12 may be provided at each height position corresponding to each of two or more pairs of discharge holes.For example, the number of pairs of discharge holes and the number of baffles may be equal, and with respect to the positional relationship between the n-th pair of discharge holes 13a, 13b (n: natural number) from the most upstream side and the n-th baffle 12 from the most upstream side, the upper end 12ax of the n-th baffle 12 may be higher than the lower ends 13ay, 13by of the n-th pair of discharge holes 13a, 13b, or the lower end 12ay of the n-th baffle 12 may be higher than the lower ends 13ay, 13by of the n-th pair of discharge holes 13a, 13b, or the lower end 12ay of the n-th baffle 12 may be lower than the upper ends 13ax, 13bx of the n-th pair of discharge holes 13a, 13b, or the upper end 12ax of the n-th baffle 12 may be lower than the upper ends 13ax, 13bx of the n-th pair of discharge holes 13a, 13b.

[0026] 1.4 Inner Bottom Surface The flat portion 10 may have an inner bottom surface 14 facing the flat flow path 11. The inner bottom surface 14 corresponds to the end of the flat flow path 11. The inner bottom surface 14 may have a shape that is line-symmetrical about a line X passing through the center in the width direction as the axis of symmetry, and may have a second concave surface 14a that is concave downward at the center in the width direction. Alternatively, the inner bottom surface 14 may have a shape that is line-symmetrical about a line X passing through the center in the width direction as the axis of symmetry, and may have a flat surface 14b extending along the width direction at the center in the width direction. Alternatively, the inner bottom surface 14 may have a shape that is line-symmetrical about a line X passing through the center in the width direction as the axis of symmetry, and may have a convex surface 14c that is convex upward at the center in the width direction. For example, as shown in FIGS. 1 to 3, a downwardly concave portion may exist between the lower ends of the discharge holes 13a, 13b and the center in the width direction of the inner bottom surface 14, thereby forming the second concave surface 14a. Alternatively, as shown in Figures 4 and 5, there may be no downwardly concave portion between the lower ends of the discharge holes 13a, 13b and the widthwise center of the inner bottom surface 14, and a flat surface 14b may be present along the width direction. Alternatively, as shown in Figure 6, there may be an upwardly convex portion between the lower ends of the discharge holes 13a, 13b and the widthwise center of the inner bottom surface 14, thereby forming a convex surface 14c. In particular, when a second concave surface 14a or a flat surface 14b is formed in the widthwise center of the inner bottom surface 14 as shown in Figures 1 to 3 and 4 and 5, compared to when a convex surface 14c is formed as shown in Figure 6, even if a downward flow from above is biased in either the width direction (left or right direction), the downward flow collides with the second concave surface 14a or the flat surface 14b, thereby redistributing the downward flow to the side with a slower flow velocity, thereby further suppressing bias in the discharge flow from the discharge holes 13a, 13b.

[0027] As shown in FIG. 1 , the second concave surface 14a may have a width W3, which may be, for example, 50% or more or 60% or more of the width W1 of the flat flow path 11. Note that the "width W1 of the flat flow path 11" in this case is the same as described above, meaning the narrowest width of the flat flow path 11 within a range of 1.5 × W2 above the upper end 12ax of the baffle 12. If the width W3 of the second concave surface 14a is too small, the effect of the second concave surface 14a in suppressing drift tends to be reduced. The width W3 may be 110% or less, 105% or less, 100% or less, 95% or less, 90% or less, 85% or less, or 80% or less of the width W1. The width W3 of the second concave surface 14a may be greater than, smaller than, or the same as the width W2 of the baffle 12. For example, the width W3 of the second concave surface 14a may be 75% or more and 200% or less, or 80% or more and 190% or less, of the width W2 of the baffle 12.

[0028] As shown in FIG. 1 , the second concave surface 14a may have a depth Dp (height from the top of the concave surface to the deepest part of the concave surface), which may be, for example, 5 mm to 50 mm, or 10 mm to 30 mm. Alternatively, the depth Dp of the second concave surface 14a may be 1% to 70% or 3% to 40% of the width W3 of the second concave surface 14a. If the depth Dp of the second concave surface 14a is too small, the effect of the second concave surface 14a in suppressing drift tends to be reduced. If the depth Dp of the second concave surface 14a is too large, the cost of nozzle manufacturing increases and the space below the discharge holes 13a and 13b becomes unnecessarily large. The depth Dp of the second concave surface 14a may be 20% to 100% or 30% to 90% of the depth Dz of the first concave surface 12az of the baffle 12.

[0029] As shown in FIG. 1 , the second concave surface 14 a may have a substantially uniform shape and extend in the thickness direction. The second concave surface 14 a may have a thickness T3, which may be, for example, 70% to 100%, 80% to 100%, or 90% to 100% of the thickness T1 of the flat flow path 11. Furthermore, the thickness T3 of the second concave surface 14 a may be the same as the thickness of the inner bottom surface 14 as shown in FIG. 1 , or may be smaller than the thickness of the inner bottom surface 14. Note that the "thickness T1 of the flat flow path" here refers to the thickness T1 at the portion where the baffle 12 is located. That is, in this embodiment, the thickness T2 of the baffle 12 may be 40% to less than 80% of the thickness T1 of the flat flow path 11, and the thickness T3 of the second concave surface 14 a may be 70% to 100% of the thickness T1 of the flat flow path 11.

[0030] 1 to 3 illustrate an example of the second concave surface 14a having a flat surface at its center and curved surfaces at both widthwise ends (with rounded corners), but the shape of the second concave surface 14a is not limited to this. The second concave surface 14a may have a V-shaped surface, a U-shaped surface, a basin-shaped surface, or any other concave surface. As far as the inventors have confirmed, when the second concave surface 14a has a curved surface, and particularly when it has curved surfaces at least at both widthwise ends (with rounded corners) as shown in FIG. 1, a more excellent self-stabilizing function is likely to be exhibited.

[0031] 2. Other Parts The submerged entry nozzle 100 may have the same configuration as a conventional nozzle, except for the flat section 10. For example, the submerged entry nozzle 100 may have a non-flat section 20 upstream of the flat section 10. The cross-sectional shape of the flow path in the non-flat section 20 may be, for example, circular. The submerged entry nozzle 100 may also have a flow rate adjustment mechanism (not shown) upstream of it. Examples of the flow rate adjustment mechanism include a stopper and a slide plate (sliding gate). The upper end of the submerged entry nozzle 100 may be connected to a tundish, which is an intermediate vessel. The lower end of the submerged entry nozzle 100 may be immersed in the molten metal in the mold. The submerged entry nozzle 100 may also have a member other than the baffle 12 in addition to the baffle 12, thereby exhibiting a further self-stabilizing function.

[0032] 1 to 6 illustrate an embodiment in which only one pair of discharge holes is provided, but as described above, two or more pairs of discharge holes may be provided in this embodiment. The inventors have discovered that when comparing an immersion nozzle having one pair (two) of discharge holes to an embodiment in which two pairs (four) of discharge holes are provided, the latter is more likely to suppress bias in the discharge flow. In other words, even if bias occurs in the discharge flow rate of the upper pair of discharge holes among two pairs of discharge holes, the discharge flow rate of the lower pair of discharge holes can be biased in the opposite direction to the upper pair of discharge holes, and the bias in the flow rate occurring in the upper discharge holes can be compensated for by the lower discharge holes. Below, an embodiment in which two pairs of discharge holes are provided is illustrated.

[0033] 7 , in an immersion nozzle 100 according to one embodiment, the flat portion 10 may have a first baffle as the baffle 12 in the flat flow path 11, and the flat portion 10 may have a pair of upper discharge holes 13 a, 13 b and a pair of lower discharge holes 15 a, 15 b that communicate the flat flow path 11 with the outside. In this case, one of the pair of upper discharge holes 13 a, 13 b may be located at one widthwise end of the flat flow path 11, the other of the pair of upper discharge holes 13 a, 13 b may be located at the other widthwise end of the flat flow path 11, and one of the pair of lower discharge holes 15 a, 15 b may be located at one widthwise end of the flat flow path 11, and the other of the pair of lower discharge holes 15 a, 15 b may be located at the other widthwise end of the flat flow path. In this case, the upper end 12ax of the first baffle 12 may be located above the lower ends 13ay and 13by of the pair of upper discharge holes 13a and 13b, and the upper end 12ax of the first baffle 12 may be located below a position 30 mm above the upper ends of the pair of upper discharge holes 13a and 13b.

[0034] 3.1 Flat Section, Flat Flow Channel, First Baffle, and Pair of Upper Discharge Holes The overall shapes of the flat section 10 and the flat flow channel 11 are as described above. For example, the shape of the lower portion of the broad surface 10a of the flat section 10 may be straight as shown in FIG. 7 or may be tapered as shown in FIG. 8. The first baffle may be similar to the baffle 12 described above. The pair of upper discharge holes may be similar to the pair of discharge holes 13a, 13b described above. As described above, when the flat section 10 has the broad surface 10a, narrow surface 10b, and outer bottom surface 10c as its outer surfaces, the pair of upper discharge holes 13a, 13b may be provided so as to penetrate only the narrow surface 10b.

[0035] 3.2 Pair of Lower Discharge Holes In this embodiment, a pair of lower discharge holes 15a, 15b is located below the pair of upper discharge holes 13a, 13b. In this embodiment, regardless of the positions of the lower discharge holes 15a, 15b, the self-stabilizing function of the first baffle 12 can suppress uneven flow at the upper discharge holes 13a, 13b. Furthermore, in this embodiment, the presence of the lower discharge holes 15a, 15b below the upper discharge holes 13a, 13b further enhances the uneven flow suppression effect. In other words, even if an uneven flow rate occurs in the pair of upper discharge holes 13a, 13b, the uneven flow rate in the pair of lower discharge holes 15a, 15b can be biased in the opposite direction to the upper discharge holes, and the uneven flow rate occurring in the upper discharge holes 13a, 13b can be compensated for by the lower discharge holes 15a, 15b. In the present embodiment, there are no particular limitations on the positional relationship between the pair of lower discharge holes 15 a, 15 b and the first baffle 12. For example, the lower end 12 ay of the first baffle 12 may be located above the upper ends 15 ax, 15 bx of the pair of lower discharge holes 15 a, 15 b.

[0036] The opening shape of the pair of lower discharge holes 15a, 15b may be determined appropriately depending on the positions at which the lower discharge holes 15a, 15b are provided. For example, as shown in Fig. 6, the opening shape of the pair of lower discharge holes 15a, 15b may be a rectangle having long and short sides. In this case, the long sides of the lower discharge holes 15a, 15b may be 30 mm or more and 100 mm or less, and the short sides of the lower discharge holes 15a, 15b may be 15 mm or more and 50 mm or less.

[0037] The height positions of the pair of lower discharge holes 15 a, 15 b are not particularly limited. For example, if the flat portion 10 has, as its outer surfaces, a wide surface 10 a, a narrow surface 10 b, and an outer bottom surface 10 c, the pair of lower discharge holes 15 a, 15 b may be provided between the narrow surface 10 b and the bottom surface 10 c.

[0038] 3.3 Positional Relationship Between Upper and Lower Discharge Holes in the Width Direction The pair of upper discharge holes 13a, 13b may be located directly above the pair of lower discharge holes 15a, 15b, or may be located diagonally above them. For example, as shown in FIG. 7 , the inlets of the pair of lower discharge holes 15a, 15b may be located more inward in the width direction than the inlets of the pair of upper discharge holes 13a, 13b. In other words, the inlets of the pair of lower discharge holes 15a, 15b may be located between the inlets of the pair of upper discharge holes 13a, 13b and the nozzle center axis X. In other words, the distance between the inlets of the pair of lower discharge holes 15a, 15b may be shorter than the distance between the inlets of the pair of upper discharge holes 13a, 13b. In this way, by arranging the lower discharge holes 15a, 15b more inward in the width direction than the upper discharge holes 13a, 13b, the space below the first baffle 12 can be made smaller, and stagnation of the fluid below the first baffle 12 can be more easily suppressed. As a result, the discharge state is more likely to be stabilized.

[0039] 3.4 Other Baffles As shown in FIG. 9 , in the submerged nozzle 100 according to one embodiment, the flat section 10 may include the first baffle 12 and the second baffle 16 in the flat flow path 11. In this case, the second baffle 16 may be located below the first baffle 12. In other words, in one embodiment, the flat flow path 11 may include the first baffle 12 on the upper side and the second baffle 16 on the lower side. The shape of the second baffle 16 is not particularly limited. For example, the second baffle 16 may have a width W4 and a thickness T4. The second baffle 16 may be located at the center of the flat flow path 11 in the width direction. The width W4 of the second baffle 16 may be 50% or more of the width W1. The thickness T4 of the second baffle 16 may be 40% or more and less than 80% of the thickness T1. Furthermore, in a cross section across the second baffle 16 and along the width and up-down directions, the upper surface of the second baffle 16 may have a shape that is line-symmetrical with respect to a line passing through the center in the width direction as the axis of symmetry, and may have a third concave surface that is concave downward at the center in the width direction. As described above, the shape of the second baffle 16 may satisfy the requirements for the shape of the first baffle 12. By providing such a second baffle 16 below the first baffle 12 in the flat flow path 11, a higher self-stabilizing function can be achieved.

[0040] 3.5 Supplementary Note As described above, in this embodiment, by reducing the space below the first baffle 12, stagnation of the fluid below the first baffle 12 is more easily suppressed. In this regard, as shown in FIG. 10 , it is preferable that the length L2 from the lower end 12ay of the first baffle 12 to the lower end 11x (inner bottom surface) of the flat flow path 11 be short. For example, the length L2 may be 90 mm or less, 65 mm or less, or 40 mm or less. The lower limit of the length L2 is not particularly limited, and may be, for example, greater than 10 mm, 25 mm or more, or 40 mm or more. Furthermore, as shown in FIGS. 7 to 10 , the flat flow path 11 may taper downward below the first baffle 12. In other words, below the first baffle 12, the width of the flat flow path 11 may be relatively wide at the top and narrowest at the bottom. This is believed to provide a more effective suppression of drift.

[0041] In this embodiment, the width W of the broad surface 10a at the lower part of the flattened portion 10 may be larger than the width W of the broad surface 10a at the upper part. However, in consideration of the manufacturability and handling of the submerged nozzle 100, the maximum width W of the broad surface 10a is set to be 1 / 2. ＭＡＸ For example, when the flat portion 10 has a wide surface 10a, a narrow surface 10b, and a bottom surface 10c as its outer surfaces, the maximum width W of the wide surface 10a is ＭＡＸ and the representative diameter D1 of the pair of upper discharge holes 13a, 13b and the representative diameter D2 of the pair of lower discharge holes 15a, 15b satisfy the following relationship: W ＭＡＸ ≦3×(D1+D2) may be satisfied. Here, the "representative diameter" of the discharge hole is defined as follows. In the following, the upper discharge hole 13a will be described as an example, but the representative diameters of the other discharge holes are determined in a similar manner. As shown in FIG. 11 , the shape of the upper discharge hole 13a is specified in a cross section along the width direction and the up-down direction of the submerged nozzle 100, which cross section passes through the centroid of the outlet opening of the upper discharge hole 13a. In this cross-sectional shape, the length of the line segment connecting the upper end 13ax of the outlet opening of the upper discharge hole 13a and the lower end 13ay of the outlet opening of the upper discharge hole 13a is specified. The length of this line segment is regarded as the representative diameter D1 of the upper discharge hole 13a.

[0042] 4. Applications As described above, the submerged entry nozzle 100 is used, for example, as a submerged entry nozzle for continuous casting of molten metal. More specifically, it is used as a submerged entry nozzle for supplying molten metal from a tundish, which is an intermediate vessel, to a mold during continuous casting of molten metal. Preferably, it is used as a submerged entry nozzle for continuous casting of so-called thin slabs. There are no particular limitations on the type of molten metal to be continuously cast; for example, molten steel may be used. The technology of the present disclosure also has an aspect as a method for continuous casting of molten metal. That is, a method for continuous casting of molten metal according to one embodiment includes supplying molten metal from a tundish to a mold through a submerged entry nozzle, and is characterized in that the submerged entry nozzle 100 of the present disclosure is used as the submerged entry nozzle. In the method for continuous casting of molten metal, the configuration other than that of the submerged entry nozzle may be the same as that of a conventional method.

[0043] The present invention will be further described below with reference to examples, but the present invention is not limited to the following examples. The present invention allows various conditions to be adopted as long as the object is achieved without departing from the gist of the present invention.

[0044] 1. Consideration of the case where the number of discharge holes in the immersion nozzle is two (one pair) 1.1 Fabrication of the immersion nozzle Figure 1 shows a schematic diagram of the shape of the immersion nozzle of Example 1-1. Figure 2 shows a schematic diagram of the shape of the immersion nozzle of Example 2-1. Figure 3 shows a schematic diagram of the shape of the immersion nozzle of Example 3-1. Figure 4 shows a schematic diagram of the shape of the immersion nozzle of Example 4-1. Figure 5 shows a schematic diagram of the shape of the immersion nozzle of Example 5-1. Figure 6 shows a schematic diagram of the shape of the immersion nozzle of Example 6-1. Figure 12 shows a schematic diagram of the shape of the immersion nozzle of Comparative Example 1-1. Figure 13 shows a schematic diagram of the shape of the immersion nozzle of Comparative Example 1-2. Figure 14 shows a schematic diagram of the shape of the immersion nozzle of Comparative Example 1-3. Figure 15 shows a schematic diagram of the shape of the immersion nozzle of Comparative Example 2-1. Figure 16 shows a schematic diagram of the shape of the immersion nozzle of Comparative Example 3-1. Figure 17 schematically shows the shape of the immersion nozzle according to Comparative Example 4-1. Figure 18 schematically shows the shape of the immersion nozzle according to Comparative Example 4-2. Figure 19 schematically shows the shape of the immersion nozzle according to Comparative Example 5-1. Figure 20 schematically shows the shape of the immersion nozzle according to Comparative Example 5-2. Figure 21 schematically shows the shape of the immersion nozzle according to Comparative Example 6-1. Figure 22 schematically shows the shape of the immersion nozzle according to Comparative Example 6-2.

[0045] 1.1.1 Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-5 The dimensions of the baffle used in Example 1-1 (FIG. 1) are shown in FIG. 23. In this example, for ease of explanation, the baffle shape shown in FIG. 23 is referred to as a V-shape. Examples 1-2 and 1-3 are the same as Example 1-1, except that the dimensions of the baffle are changed. Comparative Example 1-1 (FIG. 12) is the same as Example 1-1, except that a baffle is not provided. Comparative Example 1-2 (FIG. 13) is the same as Example 1-1, but installed upside down (convex upward; referred to as an inverted V-shape). The dimensions of the baffle used in Comparative Example 1-3 (FIG. 14) are shown in FIG. 24. Comparative Example 1-4 is the same as Example 1-1, except that the thickness of the V-shaped baffle is reduced. Comparative Example 1-5 is the same as Example 1-1, except that the thickness of the V-shaped baffle is increased. In Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-5, a basin-shaped recess is provided in the center of the width direction of the inner bottom surface.

[0046] 1.1.2 Examples 2-1 to 2-3 and Comparative Examples 2-1 to 2-4 The dimensions of the baffle used in Example 2-1 (FIG. 2) are shown in FIG. 25. For ease of explanation, the shape of the baffle shown in FIG. 25 is referred to as a U-shape in this example. Examples 2-2 and 2-3 and Comparative Examples 2-2 to 2-4 have the same baffle dimensions as in Example 2-1, but changed. Comparative Example 2-1 (FIG. 15) has the same baffle as in Example 2-1, but installed upside down (with an upward convexity; referred to as an inverted U-shape). Examples 1-1 to 1-3 and Comparative Examples 1-1 to 1-5 have a basin-shaped recess in the center of the width direction of the inner bottom surface.

[0047] 1.1.3 Examples 3-1 to 3-3 and Comparative Examples 3-1 to 3-4 The dimensions of the baffle used in Example 3-1 (FIG. 3) are shown in FIG. 26. For ease of explanation, in this example, the shape of the baffle shown in FIG. 26 is referred to as a dish shape. In Examples 3-2 and 3-3 and Comparative Examples 3-2 to 3-4, the dimensions of the baffle in Example 3-1 were changed. In Comparative Example 3-1 (FIG. 16), the same baffle as in Example 3-1 was installed upside down (convex upward; referred to as an inverted dish shape).

[0048] 1.1.4 Examples 4-1 to 4-3 and Comparative Examples 4-1 to 4-5 The dimensions of the baffle used in Example 4-1 (FIG. 4) are shown in FIG. 27. Example 4-1 is an example in which the width of the flattened flow path is increased compared to Example 1-1, and the width and thickness of the V-shaped baffle are increased and slightly reduced compared to Example 1-1. Examples 4-2 and 4-3 and Comparative Examples 4-3 to 4-5 are examples in which the dimensions of the baffle in Example 4-1 are changed. Comparative Example 4-1 (FIG. 17) is an example in which a baffle is not provided in Example 4-1. Comparative Example 4-2 (FIG. 18) is an example in which the same baffle as Example 4-1 is installed upside down (convex upward; referred to as an inverted V-shape).

[0049] 1.1.5 Examples 5-1 to 5-3 and Comparative Examples 5-1 to 5-5 The dimensions of the baffle used in Example 5-1 (FIG. 5) are shown in FIG. 28. In Example 5-1, the inner bottom surface of the submerged nozzle was not provided with a concave surface at the center in the width direction, but was instead flat. In Examples 5-2 and 5-3 and Comparative Examples 5-3 to 5-5, the dimensions of the baffle in Example 5-1 were changed. In Comparative Example 5-1 (FIG. 19), no baffle was provided. In Comparative Example 5-2 (FIG. 20), the same baffle as in Example 5-1 was installed upside down (convex upward; referred to as an inverted V-shape).

[0050] 1.1.6 Examples 6-1 to 6-3 and Comparative Examples 6-1 to 6-5 The dimensions of the baffle used in Example 6-1 (FIG. 6) are shown in FIG. 29. In Example 6-1, a convex surface (a mountain-shaped surface) was provided at the center of the width direction of the inner bottom surface of the submerged nozzle. In Examples 6-2 and 6-3 and Comparative Examples 6-3 to 6-5, the dimensions of the baffle in Example 6-1 were changed. In Comparative Example 6-1 (FIG. 21), no baffle was provided. In Comparative Example 6-2 (FIG. 22), the same baffle as in Example 6-1 was installed upside down (convex upward; referred to as an inverted V-shape).

[0051] 1.2 Evaluation method The "drift rate" in this example is the rate at which the flow is diverged by 30 m under the condition that the discharge hole of the immersion nozzle is not immersed in water. In a full-scale water model experiment, the water temperature is kept at 20 to 30°C, and the bath depth is adjusted to 700 to 900 mm. The immersion nozzle is attached to the bottom of the tundish via a three-layer slide plate (see Figure 30; slides in the mold width direction) which is a flow rate adjustment mechanism. ３ / hr of water was flowed, and the discharge flow rates from the left and right discharge holes were measured. The results were used to calculate the percentage difference in the left and right discharge flow rates relative to the average left and right discharge flow rate. The slide plate directly above the submerged entry nozzle was throttled to adjust the flow rate, resulting in a left-right bias in the downward flow above the main body of the submerged entry nozzle. The slide plate was throttled so that the middle plate of the three-layer slide plate was slid 30 mm from the fully open position to throttle the flow path, with a flow path diameter of 75 mm.

[0052] 1.3 Evaluation Results Tables 1 to 6 below show the dimensions of the submerged entry nozzle and the evaluation results of the submerged entry nozzle's flow deviation rate for each of the examples and comparative examples. In Tables 1 to 6, the "baffle width ratio" refers to the ratio (%) of the baffle width W2 to the flat flow channel width W1. The "baffle thickness ratio" refers to the ratio (%) of the baffle thickness T2 to the flat flow channel thickness T1. In the examples and comparative examples, the baffle thickness is constant, and the baffle protrudes from both long side surfaces of the rectangular flow channel by the same thickness. The baffle thickness ratio is defined as the total thickness of the two baffles relative to the thickness of the rectangular flow channel. The measurement locations and methods for the widths W1 and W2 and the thicknesses T1 and T2 are as described in the embodiments of the present application. In these examples, a flow deviation rate of 25% or less was judged to be "pass," and a flow deviation rate of more than 25% was judged to be "fail."

[0053]

[0054]

[0055]

[0056]

[0057]

[0058]

[0059] Examples 1-1 to 1-3, 2-1 to 2-3, and 3-1 to 3-3 are examples in which a predetermined baffle was attached to an immersion nozzle having a rectangular tube with a pair of discharge holes drilled in the short side wall. Examples 1-1 to 1-3 had a V-shaped baffle, Examples 2-1 to 2-3 had a U-shaped baffle, and Examples 3-1 to 3-3 had a dish-shaped baffle. Examples 1-1 to 1-3, Examples 2-1 to 2-3, and Examples 3-1 to 3-3 had a lower flow deviation rate than Comparative Examples 1-1, 2-1, and 3-1, which had no baffle, and Comparative Examples 1-2, 2-2, and 3-2, in which the respective baffles were installed upside down. In other words, a baffle with a concave upper surface can be said to be more effective in suppressing flow deviation in the discharge flow rate and in-mold flow velocity than a baffle without a baffle or a baffle with a convex upper surface, even when the downward flow supplied from the top of the immersion nozzle is biased in the width direction (left-right direction). In addition, Comparative Examples 1-3, 2-2, and 3-2 had small baffle widths, and Comparative Examples 1-4, 2-3, and 3-3 had small baffle thicknesses, so that a sufficient baffle effect was not obtained. These Comparative Examples had results equivalent to those of Comparative Example 1-1, which had no baffles, in terms of the drift rate evaluated in a full-scale water model experiment.

[0060] Examples 4-1 to 4-3 are examples in which a V-shaped baffle was attached to a submerged entry nozzle (SIN) with a pair of discharge holes drilled from the short side wall of a rectangular tube to the bottom (Figure 17; Comparative Example 4-1 without a baffle). Examples 4-1 to 4-3 exhibited lower flow deviation rates than Comparative Example 4-1 without a baffle or Comparative Example 4-2, in which the baffle used in Example 4-1 was installed upside down. In other words, a baffle with a concave upper surface is more effective at suppressing flow deviation in the discharge flow rate and in-mold flow velocity, even when the downward flow supplied from the top of the SIN is biased in the width direction (left-right direction), compared to a baffle without a baffle or a baffle with a convex upper surface. Furthermore, Comparative Example 4-3 had a small baffle width, and Comparative Example 4-4 had a small baffle thickness, so neither achieved sufficient baffle effect. These comparative examples showed similar results to Comparative Example 4-1 without a baffle in terms of flow deviation rates evaluated in a full-scale water model experiment.

[0061] In Examples 5-1 to 5-3, the inner bottom surface of the flattened flow channel was not provided with a basin-shaped concave surface in the width direction center, but was instead flat along the width direction, with a V-shaped baffle attached. Examples 5-1 to 5-3 had a lower flow deviation rate than Comparative Example 5-1, which had no baffle, or Comparative Example 5-2, in which the baffle used in Example 5-1 was installed upside down. In other words, a baffle with a concave upper surface can be said to be more effective in suppressing flow deviation in the discharge flow rate and in-mold flow velocity, even when the downward flow supplied from the top of the submerged entry nozzle is biased in the width direction (left-right direction), compared to a baffle without a baffle or a baffle with a convex upper surface. Furthermore, Comparative Example 5-3 had a small baffle width, and Comparative Example 5-4 had a small baffle thickness, and neither achieved sufficient baffle effect. These comparative examples showed similar results to Comparative Example 5-1, which had no baffle, in terms of flow deviation rate evaluated in a full-scale water model experiment.

[0062] Examples 6-1 to 6-3 are examples in which a basin-shaped concave surface was not provided in the widthwise center of the inner bottom surface of the flat flow channel, but a mountain-shaped convex surface was provided, and a V-shaped baffle was attached. Examples 6-1 to 6-3 had a lower flow deviation rate than Comparative Example 6-1, which had no baffle, or Comparative Example 6-2, in which the baffle used in Example 6-1 was installed upside down. In other words, a baffle with a concave upper surface can be said to be more effective in suppressing flow deviation in the discharge flow rate and in-mold flow velocity, even when the downward flow supplied from the top of the submerged entry nozzle is biased in the width direction (left-right direction), compared to a baffle without a baffle or a baffle with a convex upper surface. Furthermore, Comparative Example 6-3 had a small baffle width, and Comparative Example 6-4 had a small baffle thickness, so neither achieved sufficient baffle effect. These comparative examples showed similar results to Comparative Example 5-1, which had no baffle, in terms of flow deviation rate evaluated in a full-scale water model experiment.

[0063] Comparative Examples 1-5, 2-4, 3-4, 4-5, 5-5, and 6-5 are examples in which the baffle thickness was increased compared to Examples 1-1, 2-1, 3-1, 4-1, 5-1, and 6-1. In these comparative examples, the baffle thickness was excessive, increasing flow resistance, and therefore water could not be supplied at the specified flow rate under the above water supply conditions. This means that molten metal cannot be supplied at the required flow rate even in an actual machine. It is estimated that the flow deviation rate for Comparative Example 4-5 would be approximately 10% if the slide plate restriction was relaxed and the specified flow rate was supplied. The reason for the improvement over Example 4-1 is that the increased baffle thickness not only increased the baffle effect, but also relaxed the slide plate restriction, reducing the deviation of the downward flow from the top of the submerged entry nozzle.

[0064] 2. Study on the case where the number of discharge holes in the submerged entry nozzle is four (two pairs) 2.1 Fabrication of the submerged entry nozzle Figures 31A to 31I show the shapes and dimensions of the submerged entry nozzles of Examples A to E and Comparative Examples F to I.

[0065] 2.1.1 Example A Example A has the cross-sectional shape and dimensions shown in Figure 31A. In Example A, the immersion nozzle has a flow path width of 110 mm directly above the discharge hole and a flow path thickness of 25 mm from directly above the discharge hole to the bottom end of the flow path. V-shaped baffles with a width of 90 mm and a thickness of 8.5 mm protrude from both long side walls of the flow path, forming a first baffle. The immersion nozzle of Example A also has two pairs of discharge holes (four holes), one above the other.

[0066] 2.1.2 Example B Example B has the cross-sectional shape and dimensions shown in Figure 31B. In Example B, the immersion nozzle has a flow path width of 110 mm directly above the discharge hole and a flow path thickness of 25 mm from directly above the discharge hole to the bottom end of the flow path. Dish-shaped baffles with a width of 90 mm and a thickness of 6.5 mm protrude from both long side walls of the flow path, forming a first baffle. The immersion nozzle of Example B also has two pairs of discharge holes (four holes) on the top and bottom.

[0067] 2.1.3 Example C Example C has the cross-sectional shape and dimensions shown in Figure 31C. In Example C, the immersion nozzle has a flow path width of 110 mm directly above the discharge hole and a flow path thickness of 25 mm from directly above the discharge hole to the bottom end of the flow path. U-shaped baffles with a width of 110 mm and a thickness of 6.5 mm protrude from both long side walls of the flow path, forming a first baffle. The immersion nozzle of Example C also has two pairs of discharge holes (four holes), one above the other.

[0068] 2.1.4 Example D Example D has the cross-sectional shape and dimensions shown in Figure 31D. In Example D, the flow path width directly above the discharge hole is 110 mm, and the flow path thickness from directly above the discharge hole to the bottom end of the flow path is 25 mm. Dish-shaped baffles having a width of 110 mm and a thickness of 6.5 mm protrude from both long side walls of the flow path, forming a first baffle. Furthermore, below the first baffle, V-shaped baffles having a width of 110 mm and a thickness of 6.5 mm protrude from both long side walls of the flow path, forming a second baffle. The immersion nozzle of Example D also has two pairs of discharge holes (four holes), one above the other.

[0069] 2.1.5 Example E Example E has the cross-sectional shape and dimensions shown in Figure 31E. In Example E, the flow path width directly above the discharge hole is 110 mm, and the flow path thickness from directly above the discharge hole to the bottom end of the flow path is 25 mm. Dish-shaped baffles having a width of 110 mm and a thickness of 6.5 mm protrude from both long side walls of the flow path, forming a first baffle. Furthermore, below the first baffle, V-shaped baffles having a width of 110 mm and a thickness of 6.5 mm protrude from both long side walls of the flow path, forming a second baffle. The immersion nozzle of Example E also has two pairs of discharge holes (four), one above the other.

[0070] 2.1.6 Comparative Example F Comparative Example F has the cross-sectional shape and dimensions shown in Fig. 31F. Comparative Example F is the same as Example A except that the thickness of the baffle is increased to 10 mm.

[0071] 2.1.7 Comparative Example G Comparative Example G has the cross-sectional shape and dimensions shown in Fig. 31G. In Comparative Example G, the thickness of the baffle in Example A was reduced to 3.8 mm.

[0072] 2.1.8 Comparative Example H Comparative Example H has the cross-sectional shape and dimensions shown in Fig. 31H. Comparative Example H is the same as Example B except that the width of the baffle is increased to 118 mm.

[0073] 2.1.9 Comparative Example I Comparative Example I has the cross-sectional shape and dimensions shown in Figure 31I. Comparative Example I is the same as Example B except that the width of the baffle is reduced to 55 mm.

[0074] 2.1.10 Comparative Example J Comparative Example J has the cross-sectional shape and dimensions shown in Figure 31J. Comparative Example J is the same as Example A except that the baffle is omitted.

[0075] 2.2 Evaluation 1 As shown in Figure 30, the submerged nozzle was connected to a water supply system consisting of a tundish and a slide gate, which is a flow rate adjusting mechanism. The intermediate plate of the slide gate was slid 29 mm ± 1 mm to the right relative to its inner diameter of 75 mm, and the nozzle was moved approximately 30 m. ３ A full-scale water model experiment was conducted with the flow rate set to 1 / hr. In the water model experiment, the bath depth in the tundish was adjusted to 800 mm±100 mm, and the water temperature was adjusted to 25°C±5°C. The discharge flow rate from each discharge hole was measured under non-immersion conditions in which all discharge holes of the submerged entry nozzle were open to the atmosphere.

[0076] 2.2.1 Evaluation Results for Example A Figure 32 shows the evaluation results for Example A. As shown in Figure 32, the discharge flow rate from the upper discharge holes was higher at the right-side discharge holes, while the discharge flow rate from the lower discharge holes was higher at the left-side discharge holes. This indicates that the flow rate bias occurring at the upper discharge holes was compensated for at the lower discharge holes. Note that Figure 32 shows the discharge flow rate bias ratio, which is calculated as a percentage of the difference in left and right discharge flow rates relative to the average left and right discharge flow rate using the sum of the discharge flow rates from the upper and lower discharge holes. Figure 33 and subsequent figures also show the same calculated discharge flow rate bias ratio. In the description of the bias ratio, "West" refers to a bias toward the left, and "East" refers to a bias toward the right. Also, in Figure 32, "Q port" on the vertical axis indicates the discharge flow rate from each discharge hole. However, because there is an error between the flow rate setting value and the actual flow rate, the sum of the discharge flow rates does not necessarily equal the setting value. The same applies to Figure 33 and subsequent figures. In Fig. 32, WU, WL, EL, and EU on the horizontal axis refer to the upper and left-hand outlet holes, the lower and left-hand outlet holes, the lower and right-hand outlet holes, and the upper and right-hand outlet holes, respectively, as viewed in the drawing. The same applies to Fig. 33 and subsequent figures.

[0077] 2.2.2 Evaluation Results for Example B Figure 33 shows the evaluation results for Example B. As shown in Figure 33, the discharge flow rate from the upper discharge holes was higher at the discharge holes on the right side, whereas the discharge flow rate from the lower discharge holes was higher at the discharge holes on the left side, and the flow rate imbalance that occurred at the upper discharge holes could be compensated for at the lower discharge holes.

[0078] 2.2.3 Evaluation results for Example C Figure 34 shows the evaluation results for Example C. As shown in Figure 34, the discharge flow rate from the upper discharge holes was higher at the discharge holes on the right side, whereas the discharge flow rate from the lower discharge holes was higher at the discharge holes on the left side, and the flow rate imbalance that occurred at the upper discharge holes could be compensated for at the lower discharge holes.

[0079] 2.2.4 Evaluation Results for Example D Figure 35 shows the evaluation results for Example D. As shown in Figure 35, the discharge flow rate from the upper discharge holes was higher at the right-hand discharge holes, while the discharge flow rate from the lower discharge holes was higher at the left-hand discharge holes. This means that the flow rate imbalance that occurred at the upper discharge holes could be compensated for by the lower discharge holes. In addition, the degree of left-right flow imbalance, which is the sum of the discharge flow rates from the upper and lower discharge holes, was better than in Examples A to C.

[0080] 2.2.5 Evaluation Results for Example E The evaluation results for Example E, which was obtained by changing only the height position of the baffle compared to Example D, were equivalent to those for Example D, as shown in FIG.

[0081] 2.2.6 Evaluation Results for Comparative Example F In Comparative Example F, the flow resistance of the baffle was large, and even when the slide gate was fully opened, the specified flow rate could not be achieved.

[0082] 2.2.7 Evaluation results for Comparative Example G Figure 37 shows the evaluation results for Comparative Example G. As shown in Figure 37, the discharge flow rate from the upper discharge holes was higher at the right discharge holes, and the discharge flow rate from the lower discharge holes was higher at the left discharge holes, but the discharge flow rate deviation rate was higher than in Examples A to D, and a sufficient effect of suppressing deviation was not achieved.

[0083] 2.2.8 Evaluation Results for Comparative Example H In Comparative Example H, the flow resistance of the baffle was large, and even when the slide gate was fully opened, the specified flow rate could not be achieved.

[0084] 2.2.9 Evaluation Results for Comparative Example I Figure 38 shows the evaluation results for Comparative Example I. As shown in Figure 38, the discharge flow rate from the upper discharge holes was higher at the right discharge holes, and the discharge flow rate from the lower discharge holes was higher at the left discharge holes, but the discharge flow rate deviation rate was higher than in Examples A to D, and a sufficient effect of suppressing deviation was not achieved.

[0085] 2.2.10 Evaluation Results for Comparative Example J Figure 39 shows the evaluation results for Comparative Example J. As shown in Figure 39, the discharge flow rate from the upper discharge holes was higher at the right discharge holes, and the discharge flow rate from the lower discharge holes was also higher at the right discharge holes. This meant that the discharge flow rates on the left and right of the lower discharge holes were biased in the opposite direction to the upper side, and the effect of compensating for the bias in the upper discharge flow rate was not achieved. The discharge flow rate bias rate also had the largest value among all the examples and comparative examples.

[0086] 3. Supplementary Note: In this embodiment, an example was shown in which the baffles protruded by equal thickness from both long side surfaces of the rectangular flow channel cross section, but the protruding thickness of the baffles may be unequal, and the effects of the present invention will not be lost even if the baffles protrude only from one of the long side surfaces.

[0087] 4. Summary As is clear from the comparison of the above Examples and Comparative Examples, conventional baffles, which are installed so as not to disturb the downward flow within the submerged entry nozzle by following its streamline, are not sufficiently effective in suppressing drift. In contrast, a baffle with a concave upper surface and meeting specified dimensions actively disturbs the downward flow within the submerged entry nozzle, thereby enhancing the baffle's effect of improving discharge flow distribution and demonstrating a significant effect in suppressing drift.

[0088] 100 Submerged nozzle 10 Flat portion W Width of flat portion T Thickness of flat portion L Length (height) of flat portion 11 Flat flow path W1 Width of flat flow path T1 Thickness of flat flow path L1 Length of flat flow path 12 Baffle (first baffle) W2 Width of baffle T2 Thickness of baffle 12a Upper surface of baffle 12ax Upper end of baffle 12ay Lower end of baffle 12az First concave surface Dz Depth of concave surface Wz Width of concave surface 13a, 13b Discharge hole (upper discharge hole) 13ax, 13bx Upper end of discharge hole 13ay, 13by Lower end of discharge hole 14 Inner bottom surface 14a Second concave surface T3 Thickness of second concave surface W3 Width of second concave surface Dp Depth of second concave surface 15a, 15b Discharge hole (lower discharge hole) 20 Non-flat part

Claims

1. An immersion nozzle having a flat portion, wherein the flat portion has a flat flow path, the flat portion has a baffle in the flat flow path, the flat portion has a pair of discharge holes connecting the flat flow path to the outside, the flat flow path has a width W1 and a thickness T1, the baffle has a width W2 and a thickness T2, the baffle is located at the center of the flat flow path in the width direction, one of the pair of discharge holes is located at one end of the flat flow path in the width direction, the other of the pair of discharge holes is located at the other end of the flat flow path in the width direction, the upper end of the baffle is located above the lower ends of the pair of discharge holes, the width W2 is 50% or more of the width W1, and the thickness T2 is 40% or more but less than 80% of the thickness T1, an upper surface of the baffle has a shape that is line-symmetrical with respect to a line passing through the center in the width direction as an axis of symmetry in a cross section that is transverse to the baffle and is taken along the width direction and the up-down direction, and has a first concave surface that is concave downward at the center in the width direction.

2. The submerged nozzle according to claim 1, wherein the lower end of the baffle is located above the lower ends of the pair of discharge holes.

3. An immersion nozzle according to claim 1 or 2, wherein the lower end of the baffle is located below the upper ends of the pair of discharge holes.

4. An immersion nozzle according to claim 1 or 2, wherein the upper end of the baffle is located below a position 30 mm above the upper ends of the pair of discharge holes.

5. An immersion nozzle according to any one of claims 1 to 4, wherein the flat section has an inner bottom surface facing the flat flow path, and the inner bottom surface has a shape that is symmetrical with respect to a line passing through the center in the width direction as an axis of symmetry, and has a second concave surface that is concave downward at the center in the width direction, or has a flat surface that is aligned with the width direction at the center in the width direction.

6. The submerged entry nozzle according to claim 5, wherein the second concave surface has a curved surface.

7. An immersion nozzle according to claim 5 or 6, wherein the second concave surface has a thickness T3, and the thickness T3 is 70% or more and 100% or less of the thickness T1.

8. An immersion nozzle according to any one of claims 5 to 7, wherein the second concave surface has a width W3, and the width W3 is 50% or more of the width W1.

9. The submerged entry nozzle according to any one of claims 5 to 8, wherein the second concave surface has a depth Dp, and the depth Dp is 5 mm or more and 50 mm or less.

10. The submerged entry nozzle according to any one of claims 1 to 9, wherein the flat section has, as its outer surfaces, a wide surface, a narrow surface, and an outer bottom surface, and the pair of discharge holes are provided so as to penetrate only the narrow surface.

11. The submerged entry nozzle according to any one of claims 1 to 9, wherein the flat section has, as its outer surfaces, a wide surface, a narrow surface, and an outer bottom surface, and the pair of discharge holes are provided so as to penetrate the narrow surface and the bottom surface.

12. An immersion nozzle according to any one of claims 1 to 9, wherein the flat section has a first baffle as the baffle in the flat flow path, the flat section having a pair of upper discharge holes and a pair of lower discharge holes connecting the flat flow path to the outside, one of the pair of upper discharge holes being located at one widthwise end of the flat flow path, the other of the pair of upper discharge holes being located at the other widthwise end of the flat flow path, one of the pair of lower discharge holes being located at one widthwise end of the flat flow path, the other of the pair of lower discharge holes being located at the other widthwise end of the flat flow path, the upper end of the first baffle being located above the lower ends of the pair of upper discharge holes, and the upper end of the first baffle being located below a position 30 mm above the upper ends of the pair of upper discharge holes.

13. The submerged nozzle according to claim 12, wherein the lower end of the first baffle is located above the upper ends of the pair of lower discharge holes.

14. An immersion nozzle according to claim 12 or 13, wherein the flat section has the first baffle and a second baffle in the flat flow path, and the second baffle is located below the first baffle.

15. The submerged nozzle according to any one of claims 12 to 14, wherein the inlets of the pair of lower discharge holes are located more inward in the width direction than the inlets of the pair of upper discharge holes.

16. The submerged nozzle according to any one of claims 12 to 15, wherein the length from the lower end of the first baffle to the lower end of the flat flow path is 90 mm or less.

17. An immersion nozzle according to any one of claims 12 to 16, wherein the flat portion has, as its outer surfaces, a wide surface, a narrow surface, and an outer bottom surface, and the pair of upper discharge holes are provided so as to penetrate only the narrow surface.

18. An immersion nozzle according to any one of claims 12 to 17, wherein the flat portion has, as its outer surfaces, a wide surface, a narrow surface, and an outer bottom surface, and the pair of lower discharge holes are provided between the narrow surface and the bottom surface.

19. The submerged nozzle according to any one of claims 12 to 18, wherein the flat portion has a wide surface, a narrow surface, and an outer bottom surface as its outer surfaces, and the maximum width W of the wide surface is ＭＡＸ and the representative diameter D1 of the pair of upper discharge holes and the representative diameter D2 of the pair of lower discharge holes satisfy the following relationship: W ＭＡＸ ≦3×(D1+D2).

20. The submerged entry nozzle according to any one of claims 1 to 19, wherein the first concave surface has a V-shaped surface or a curved surface.

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