Tandish stopper with protrusions

Abstract

The present invention relates to a stopper (1) including projections (12) that contact the slag in a tundish (60). Each projection (12) has a radial length (21) which is less than half the radius (20) of the stopper (1) of the projection (12). The projections (12) rise and fall around the stopper (1). The projections (12) reduce the generation of vortices by the stopper (1) and thus extend its lifespan.

Description

Technical Field

[0001] The present invention relates to a stopper for controlling the flow of molten metal towards a mold or casting tool through an outlet hole of a tundish.

Background Art

[0002] Stoppers are typically used to control the flow of liquid metal flowing from a tundish towards a mold or casting tool. The stopper includes an elongated body having a lower end designed to close an outlet hole at the bottom of the tundish. The stopper moves up and down to close or open the outlet hole.

[0003] The lower end of the stopper is immersed in the liquid metal. The upper end of the stopper is in the air. The middle part of the stopper is in contact with a slag layer floating on the liquid metal at the interface with the air. When the slag swirls and flows down along the stopper, it chemically and mechanically erodes the stopper, locally reducing its diameter and shortening its lifespan. Further, when the level of the liquid metal is low, the slag can be pushed into the outlet hole by the vortex.

[0004] To suppress the vortex, document CN110788314A discloses a stopper having a large blocking table and rib plates.

[0005] To extend the lifespan of the stopper, document KR20140140429A discloses a stopper made from an elongated body and a removable protective piece at the height of the slag. It is expected that the slag will erode the removable protective piece, in which case it can be removed and replaced with a new one.

[0006] CN106735153A describes a stopper provided with a ring aimed at promoting the floating of inclusions in order to improve the cleanliness of molten steel.

[0007] The problem with these known stoppers is that they have thick reliefs that locally increase the diameter of the stopper significantly, and therefore increase the resistance to motion in liquid metal. Consequently, it is impossible to fine-tune the vertical movement of the stopper. [Overview of the project]

[0008] The object of the present invention is to provide a stopper that reduces vortices along the side wall.

[0009] The objective of the present invention is to provide a stopper with a particularly long lifespan.

[0010] The present invention relates to a stopper for controlling the flow of liquid metal out of a tundish, wherein the stopper extends axially between an upper end and a lower end and is radially defined by a side wall having a plurality of projections, the projections extending at least partially along the circumference on the side wall, at least two of the projections separated by a gap along the circumference, each projection having a radial length of at least 0.01 times the radius of the stopper at the projection, each projection having an axial length of at least 0.01 times the diameter of the stopper at the uppermost projection, each projection having a radial length of less than half the radius of the stopper at the projection, at least a portion of at least one of the projections rises circumferentially, at least a portion of at least the other projection falls circumferentially, and each projection extends between one or more upper points closest to the upper end and one or more corresponding lower points closest to the lower end.

[0011] Through simulations, the inventors demonstrated that such multiple vertically extending protrusions disrupt large vortices that cause slag entrapment along the sidewalls, leading to severe erosion. Furthermore, the inventors showed that the mean wall shear stress on the stopper is reduced compared to a stopper without such protrusions. The inventors also demonstrated that this vibrational shape of the multiple protrusions prevents the separation of stable, large vortices in the wake passing through the stopper, increasing the risk of slag entrapment.

[0012] The stopper according to the present invention does not have thick relief, as all projections are radially defined in size by half the radius of the stopper at their height. This absence of thick relief reduces resistance to motion and therefore improves response to control. This upper limit in the radial dimension of all projections of the claimed stopper is not present in the stopper of KR20140140429A, where the removable protective piece (reference no. 200) provides extremely large projections. In this prior art document, the “thread” of reference no. 110 is not intended for use without the removable protective piece or in contact with slug, and forms a single projection rather than multiple projections.

[0013] In this invention, the projections extend at least partially along the circumferential direction and thus form the upper and lower sides of the gap, not only axially. The inside of the gap is the side wall between the projections, and the outside of the gap is open. The gaps contain the volume of liquid metal and / or slag that tends to remain there during the vertical movement of the stopper, thereby reducing erosion at the stopper. The radial length of a projection is measured relative to the deepest point of all gaps adjacent to the projection.

[0014] At least two of the projections separated along the axial direction are preferably aligned in the axial direction, but do not necessarily have to be perfectly aligned in the axial direction. The stopper is preferably a single piece. The stopper is preferably integrally molded. The projections are preferably integrated with the stopper, particularly at the upper and lower ends.

[0015] The stopper does not include any projections having a radial length exceeding half the radius of the stopper. The stopper does not include any removable protective pieces around the side wall. Preferably, the projections are not helical.

[0016] The sidewall is the external surface. The projection is preferably designed to contact the slag on the upper surface of the liquid metal. The projection extends partially circumferentially and partially axially along the sidewall.

[0017] Multiple projections create a vibrating shape along the side wall. The projections extend in a vibrating shape between one or more upper points and one or more lower points. The projections extend as a wave (or at least part of a wave) between one or more upper points and one or more lower points.

[0018] In one embodiment, the side wall has a first diameter at the uppermost projection and a second diameter at the lowermost projection, with the first diameter being larger than the second. In other words, the side wall narrows as the height of the projection decreases. This narrowing of the stopper reduces the diameter of the intermediate region and therefore reduces the weight of the stopper.

[0019] In one embodiment, the side wall includes two elongated passages circumferentially partitioned by at least half of the projection. The stopper may include three or more elongated passages. The elongated passages are located along the circumference of the side wall where the liquid is not disturbed as much by the vertical motion of the projection. In other words, the elongated passages are passages that allow the liquid to remain in a more stable state around the stopper. Thus, the elongated passages reduce the wave-creating effect caused by this vertical motion.

[0020] In one embodiment, the projection is completely housed within a recess on the side wall.

[0021] The protrusions do not extend radially beyond the recesses. This shape is particularly interesting for avoiding waves.

[0022] The stopper has at least two protrusions closer to the upper end than the lower end. They are arranged perpendicular to the position of the liquid level in the steady-state casting of slag in the tundish.

[0023] The present invention also relates to a system for continuous casting, the system comprising: · a tundish having an outlet hole; · liquid metal having an upper surface in the tundish; · the stopper described herein, configured to close the outlet hole and arranged such that the upper surface of the liquid metal contacts at least some of the protrusions; · a support for holding the stopper.

[0024] In one embodiment, the system further comprises: · a mold or casting tool below the tundish configured to receive liquid metal flowing through the outlet hole; · a sensor for sensing the liquid metal in the mold or casting tool; · a data processing system connected to the sensor and the support and configured to control the support according to the information received from the sensor.

[0025] In such a system, the vertical movement of the stopper and, as a result, the flow of metal in the outlet hole are controlled based on measurements in the mold or casting tool.

[0026] The present invention also relates to a method for controlling the stopper described herein in the system described herein, the support preferably moving the stopper vertically at a frequency of 0.1 Hz to 100 Hz.

[0027] In the stopper according to the present invention, the vertical movement of the stopper is not impaired by any thick protrusions. This is particularly advantageous for rapid vibration.

[0028] In one embodiment, · the sensor transmits information to the data processing system, The data processing system controls the support in such a way that the support moves the stopper vertically, based on the information.

[0029] These and further embodiments of the present invention will be described in more detail, by reference to the accompanying drawings, for example. [Brief explanation of the drawing]

[0030] [Figure 1] This is a vertical cross-section of the tundish. [Figure 2] This is a vertical cross-section of a part of the stopper. [Figure 3] Figure 2 shows a horizontal cross-sectional view of a portion of the stopper along the plane indicated by III-III. [Figure 4] This is a 3D view of a part of the stopper. [Figure 5] This is a 3D view of a part of the stopper. [Figure 6a] This is a 3D view of a part of the stopper. [Figure 6b] This is a 3D view of a part of the stopper. [Figure 6c] This is a 3D view of a part of the stopper. [Figure 7a] This is a partial top view of a tundish equipped with a stopper, based on prior art. [Figure 7b] This is a partial top view of a tundish equipped with a stopper. [Figure 8a] This is a vertical cross-sectional view of a portion of a tundish equipped with a stopper, based on prior art. [Figure 8b] This is a vertical cross-section of a portion of a tumbler dish equipped with a stopper. [Figure 9a] This is a vertical cross-sectional view of a portion of a tundish equipped with a stopper, based on prior art. [Figure 9b] This is a vertical cross-section of a portion of a tumbler dish equipped with a stopper. [Figure 10] This plot shows a simulation of the volume of high-energy vortices over time. [Figure 11a]This is a partial top view of a tundish equipped with a stopper, based on prior art. [Figure 11b] This is a partial top view of a tundish equipped with a stopper. [Figure 12] This plot shows the simulated area of ​​high-energy vortices on the liquid surface over time. [Figure 13a] The side wall of a conventional stopper is shown, illustrating the shear stress of the wall. [Figure 13b] This shows the side wall of the stopper, where the shear stress of the wall is represented. [Figure 14] This plot shows the simulation of the shear stress in the wall over time. [Modes for carrying out the invention]

[0031] The present invention will be described with reference to specific embodiments and specific drawings, but the invention is not limited thereto. The drawings used for description are schematic and non-limiting. In the drawings, the sizes of some elements are exaggerated and may not be drawn to a consistent scale for illustrative purposes.

[0032] Furthermore, terms such as "first," "second," and "third" in this description and claims are used to distinguish similar elements and are not necessarily used to describe a sequential or chronological order. These terms are interchangeable under appropriate circumstances, and embodiments of the present invention may operate in an order other than those described or illustrated herein.

[0033] Furthermore, while various embodiments are referred to as "preferred," they should not be interpreted as limiting the scope of the present invention, but rather as exemplary methods by which the present invention can be carried out.

[0034] The term “comprising” as used in the claims should not be construed as limiting to the elements or steps listed thereafter. It does not exclude other elements or steps. It should be interpreted as identifying the presence of the features, components, steps, or components mentioned, but not as excluding the presence or addition of one or more features, components, steps, or components or groups thereof. Accordingly, the scope of the expression “device comprising A and B” should not be limited to a device consisting solely of components A and B; rather, with respect to the present invention, the listed components of a device should be interpreted as being only A and B, and further, the claims should be interpreted as including equivalents of those components.

[0035] Figure 1 shows the tundish 60. Inside the tundish 60, the liquid metal 65 flows from the ladle shroud 62 to the outlet hole 61. The upper surface 66 of the liquid metal is a layer of slag. The stopper 1 controls the flow of metal through the outlet hole 61.

[0036] The stopper 1 contains a flame-retardant material. The stopper 1 has an upper end 91 (which may be called the first end) connected to a support 69 that moves the stopper 1 vertically, and a lower end 92 (which may be called the second end) that can close the outlet hole 61. The stopper 1 may include a sleeve 93, which is preferably located closer to the upper end 91 than to the lower end 92 and is made of a material that is more resistant to erosion than the rest of the stopper 1. The stopper 1 includes a through hole 94 for gas injection. The outlet hole 61 is connected to a tundish upper nozzle 71 and an immersion nozzle 70 that guides the liquid metal into the mold 64 or casting tool.

[0037] The mold 64 or casting tool beneath the tundish 60 receives the liquid metal flowing through the outlet hole 61 when not completely obstructed by the stopper 1. The sensor 67 detects at least one characteristic of the liquid metal 72 in the mold 64 or casting tool, for example, the metal level. The sensor 67 transmits information to a data processing unit 68 that controls the support 69. This information is then used to move the stopper 1 vertically. The vertical position of the stopper controls the flow to the outlet hole 61. In addition to its vertical movement that regulates the flow rate through the outlet hole 61, the stopper 1 may vibrate vertically (this may be called "dithering"). The frequency of the vibration is preferably in the range of 0.1 Hz to 100 Hz, more preferably in the range of 0.2 Hz to 10 Hz, and its amplitude is in the range of 0.2 to 10 mm.

[0038] Figures 2 and 3 show a stopper 1 in an embodiment of the present invention. The stopper 1 has an axis 100. In this specification, the stopper 1 is described with reference to the axial direction 101 (perpendicular in use), the radial direction 102 (horizontal in use and extending away from the stopper axis 100), and the circumferential direction 103 (perpendicular to the horizontal and radial directions 102).

[0039] The stopper 1 has a side wall 10 formed by radially projecting protrusions 12. The side wall 10 surrounds the stopper 1 in a circumferential direction. The radial length 21 of any of the protrusions 12 can be determined, and the radius 20 of the stopper 1 at the considered protrusion 12 can also be determined. In the present invention, the radius 20 of the stopper 1 at any considered protrusion 12 is greater than twice the radial length 21 of the considered protrusion 12, preferably greater than three times the radial length 21 of the considered protrusion 12, and more preferably greater than four times the radial length 21 of the considered protrusion 12. As shown in Figure 2, the radius 20 of the stopper 1 measured at the protrusion 12 can be equal to the sum of the radial length 21 of the protrusion 12 and the radius to the protrusion 12.

[0040] The stopper 1 comprises at least two projections 12. The stopper 1 may comprise two, three, four, or five projections 12. The stopper 1 comprises a group 16 of projections 12, each having at least two adjacent projections 12 separated along the axial direction 101 by a gap 19. Preferably, the stopper 1 comprises fewer than 100 projections. The projections 12 are not perfectly aligned along the axial direction 101, and each projection 12 is partially circumferential and partially axial. At least some of the projections 12 may be located within the sleeve 93.

[0041] For the sake of brevity in this specification, the diameter 22 of the stopper 1 at the uppermost projection 121 is denoted as DU. Preferably, the projection 12 has an axial length 41 of 0.01DU to 0.4DU, preferably 0.03DU to 0.24DU, and more preferably 0.05DU to 0.16DU. The axial length 41 is preferably measured as close as possible to the axis 100, i.e., at the beginning of the projection 12. Preferably, the gap 19 has an axial length 42 of 0.02DU to 0.3DU, preferably 0.04DU to 0.3DU, and more preferably 0.05DU to 0.1DU.

[0042] For the sake of brevity in this specification, the radius 20 of the stopper 1 at the projection 12 is denoted as RS. Preferably, each projection 12 has an axial length 21 of 0.01RS to 0.4RS, preferably 0.05RS to 0.3RS, and more preferably 0.1RS to 0.2RS.

[0043] The stopper 1 may be cylindrical or have a conical vertical portion at least to the height of the projection 12, such that the diameter 22 of the uppermost projection 121 is greater than the diameter 23 of the lowermost projection 122. The conical vertical portion may have an angle α between the side wall 10 and the axial direction 101 between 1° and 30°.

[0044] In some embodiments of the present invention, the projection 12 has an angular extension of β less than 350°, possibly less than 180°, in a plane perpendicular to the axis 100. Thus, the projection 12 terminates in the circumferential direction at the circumferential end 15. Examples of such embodiments are shown in Figures 3 and 4. In other embodiments of the present invention, the projection 12 has an angular extension equal to 360° in a plane perpendicular to the axis 100, β, as shown in Figures 5-6c.

[0045] Figure 4 shows projections 12 that are partially circumferential and partially axial. They demarcate the elongated passage 13 in the circumferential direction. The elongated passage 13 preferably has an angular extension greater than 2° and less than 30° in a plane perpendicular to the axis 100. The elongated passage 13 is demarcated in the circumferential direction by some of the projections 12, for example by at least half of the projections 12. In other words, the elongated passage 13 is located between some of the projections 12, for example, the circumferential ends 15 of half of the projections 12. The elongated passage 13 is preferably parallel to the axis 100. In Figure 4, each projection 12 extends between one upper point 31 and one lower point 32, with part of the projection 12 rising in the circumferential direction 103 and part of the projection 12 descending in the circumferential direction 103.

[0046] Figures 5 and 6a to 6c show projections 12 having a shape that oscillates between two upper points 31 (where "up" means closest to the upper end 91) and two lower points 32 (where "down" means closest to the lower end 92). These projections 12 have two parts that rise in the circumferential direction 103 and two parts that fall in the circumferential direction 103. Within the scope of the present invention, each projection 12 may oscillate, for example, between one upper point and one lower point, between two upper points and two lower points, or generally between N upper points and N lower points, where N is an integer from 1 to 10.

[0047] Figures 6a and 6c show lines 200 tangent to the upper and lower side walls 10 of the projection 12. Considering all tangent lines, a tangent cone or cylinder can be drawn. In Figures 6a and 6b, the side wall 10 includes a recess 14. The recess 14 is due to the concave surface of the side wall 10. That is, the recess 14 is a recess relative to the tangent cone or cylinder. In Figures 6a and 6b, the projection 12 is completely contained within the recess 14. In other words, the projection 12 does not protrude from the tangent cone or cylinder. In Figure 6a, the projection 12 is radially inward relative to the tangent cone or cylinder. In Figure 6b, the projection 12 is radially tangent to the tangent cone or cylinder. In Figure 6c, the projection 12 protrudes from the tangent cone or cylinder.

[0048] Figure 6c shows the axial distance 18 between the upper point 31 and the lower point 32 of one of the projections 12. Preferably, for each projection 12, the axial distance 18 between any upper point 31 and any lower point 32 is 0.01 to 0.4 times the diameter 22 of the stopper 1 at the uppermost projection 121, preferably 0.03 to 0.24 times the diameter 22 of the stopper 1 at the uppermost projection 121, and more preferably 0.05 to 0.16 times the diameter 22 of the stopper 1 at the uppermost projection 121.

[0049] Within the scope of the present invention, as shown in Figures 5 to 6c, each projection 12 is preferably parallel to one or two adjacent projections 12 in the axial direction, and more preferably identical.

[0050] Figures 7 to 14 compare computational fluid dynamics (CFD) simulations of stopper 2 without a protrusion (hereinafter referred to as the standard stopper) and stopper 1 with a protrusion 12 as shown in Figure 6c (hereinafter referred to as the stopper with a protrusion). The ladle shroud is on the right side of these figures, and therefore the flow comes from right to left.

[0051] Figures 7a (for a standard stopper) and 7b (for a stopper with a projection) show the top surface 66. Figures 8a (for a standard stopper) and 8b (for a stopper with a projection) show the central portion of the tundish. These show velocity contour diagrams in m / s and arrows indicating the direction of flow. In both cases, vortices appear in the wake behind the stopper.

[0052] Figures 9a (for a standard stopper) and 9b (for a stopper with a projection) show the central portion of the tundish with high-energy vortices in black. The projection 12 appears to reduce the generation of large vortices that pose a risk of slag entrapment. Figure 10 shows the volume of high-energy vortices over time. Table I provides the average and maximum volumes estimated from the plots in Figure 10. [Table 1]

[0053] Figures 11a (for a standard stopper) and 11b (for a stopper with a projection) show the central portion of the tundish with high-energy vortices in black, with arrows indicating the direction of flow. The projection 12 appears to reduce the generation of high-energy vortices on the upper surface in the wake after passing stopper 1. Table II shows the enstrophy ξ > 2s in these figures. -2 It provides the domain. [Table 2]

[0054] Figure 12 shows the area of ​​high-energy vortices on the upper surface 66 over time. Table III provides the average and maximum areas estimated from the plot in Figure 12. [Table 3]

[0055] In general, Figures 7 to 12 show that the rising and falling protrusions 12 have a significant influence on the generation of vortices, particularly on the generation of large vortices that make a significant contribution to the erosion of the stopper.

[0056] Figures 13a (for a standard stopper) and 13b (for a stopper with a projection) show the sidewalls of the stopper along with streamlines indicating the direction of flow, contours [Pa] of the wall shear stress, and black areas indicating the shear stress region of the high wall. The shear stress appears to be well distributed on the surface in the standard stopper 2, and concentrated on the projection (but not higher) in the stopper with a projection 1. Table IV shows the average wall shear stress in these figures. [Table 4]

[0057] Figure 14 shows the shear stress of the wall over time. Table V shows the average wall shear stress and the maximum wall shear stress estimated from the plots in Figure 14. [Table 5]

[0058] Since the shear stress on the wall is lower with the stopper 1 with protrusions than with the standard stopper 2, mechanical erosion is also expected to be lower.

[0059] Although the present invention has been described above in relation to specific embodiments, it will be readily apparent that other embodiments are also possible. Furthermore, any stopper feature(s) described or illustrated herein can be combined with any other stopper(s) feature(s) as described herein.

Claims

1. A stopper (1) for controlling the flow of liquid metal (65) from a tundish (60), wherein the stopper is defined radially by a side wall (10) that extends axially (101) between an upper end (91) and a lower end (92) and has a plurality of projections (12), The projection (12) extends at least partially along the circumferential direction (103) on the side wall (10), At least two of the projections (12) are separated along the axial direction (101) by a gap (19), Each of the aforementioned projections (12) has a radial length (21) that is at least 0.01 times the radius (20) of the stopper (1) of the projection (12), Each of the aforementioned projections (12) has an axial length (41) that is at least 0.01 times the diameter (22) of the stopper (1) at the uppermost projection (121), Each of the aforementioned projections (12) has a radial length (21) that is less than half the radius (20) of the stopper (1), At least one portion of the projection (12) rises in the circumferential direction (103), and at least a portion of at least the other projection (12) slopes downward in the circumferential direction (103). The stopper (1) is characterized in that each projection (12) extends between one or more upper points (31) located closest to the upper end (91) and a corresponding number of one or more lower points (32) located closest to the lower end (92).

2. The stopper according to claim 1, wherein the side wall (10) has a first diameter (22) at the uppermost projection (121) and a second diameter (23) at the lowermost projection (122), and the first diameter (22) is larger than the second diameter (23).

3. The stopper according to any one of the prior claims, wherein the projection (12) is completely housed in a recess (14) on the side wall (10).

4. The stopper according to any one of the prior claims, wherein the axial distance (18) between each upper point (31) and each lower point (32) (multiple) of the same projection (12) is 0.01 to 0.4 times the diameter (22) of the stopper (1) at the uppermost projection (121), preferably 0.03 to 0.24 times the diameter (22) of the uppermost projection (121), and more preferably 0.05 to 0.16 times the diameter (22) of the stopper (1) at the uppermost projection (121).

5. The stopper according to any of the prior claims, wherein the projection (12) has an angular expansion (β) less than 180° in a plane perpendicular to the axial direction (101).

6. The stopper according to the prior claim, wherein each of the projections (12) terminates circumferentially at two circumferential ends (15), and the side wall (10) includes two elongated passages (13) between some of the circumferential ends (15) of the projections (12).

7. The stopper according to the prior claim, wherein the elongated passage (13) is parallel to the axial direction (101).

8. The stopper according to any one of the prior claims, wherein each of the projections (12) is parallel to one or two of the projections (12) adjacent in the axial direction.

9. The stopper according to any one of the prior claims, wherein each of the aforementioned projections (12) is identical to one or two of the aforementioned projections (12) adjacent in the axial direction.

10. Each of the aforementioned projections (12) has an axial length (41) which is 0.01 to 0.4 times the diameter (22) of the stopper (1) at the uppermost projection (121), preferably 0.03 to 0.24 times the diameter (22) of the stopper (1) at the uppermost projection (121), and more preferably 0.05 to 0.16 times the diameter (22) of the stopper (1) at the uppermost projection (121), according to any one of the prior claims.

11. The stopper according to any one of the prior claims, wherein each of the gaps (19) has an axial length (42) which is 0.02 to 0.3 times the diameter (22) of the stopper (1) at the uppermost projection (121), preferably 0.04 to 0.2 times the diameter (22) of the stopper (1) at the uppermost projection (121), and more preferably 0.05 to 0.1 times the diameter (22) of the stopper (1) at the uppermost projection (121).

12. Each of the projections (12) has a radial length (21) that is 0.01 to 0.4 times the radius (20) of the stopper (1) at the projection (12), preferably 0.05 to 0.3 times the radius (20) of the stopper (1) at the projection (12), and more preferably 0.1 to 0.2 times the radius (20) of the stopper (1) at the projection (12), according to any one of the prior claims.

13. A system for continuous casting, - A tundish (60) equipped with an outlet hole (61), - A liquid metal (65) having an upper surface (66) is placed inside the tundish (60), - A stopper (1) according to any one of the prior claims, configured to close the outlet hole (61) and positioned such that the upper surface (66) of the liquid metal (65) is in contact with at least some of the projections (12), The continuous casting system comprises a support (69) that holds the stopper (1).

14. A method for controlling a stopper according to any one of claims 1 to 12 in the system according to claim 13, wherein the support (69) moves the stopper (1) in a vertical direction.

15. The method according to claim 14, wherein the support (69) moves the stopper (1) vertically at a frequency of 0.1 Hz to 100 Hz.

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