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) reduce vortex generation by the stopper (1) and thus extend its lifespan. The projections (12) are arranged in a five-point configuration along the side wall (10).

Description

Technical Field

[0001] The present invention relates to a stopper for controlling the flow of molten metal towards a mold or a 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 a 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. [[ID=十四]]

[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. Furthermore, 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 a rib plate. [[ID=廿一]]

[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. The slag is expected to 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 Initiative]

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

[0009] The present invention relates to a stopper for controlling the flow of liquid metal out of a tundish, wherein the stopper is radially defined by a side wall extending axially between an upper and lower end and having a plurality of projections, the projections extending at least partially along the circumferential direction on the side wall, each projection having a radial extension that is less than half the radius of the stopper of the projection and at least 0.01 times the radius of the stopper of the projection, the projections having extensions at angles less than 180°, and the projections are arranged in a five-point configuration along the side wall.

[0010] Through simulations, the inventors demonstrated that the protrusions disrupt large vortices that cause slag to become trapped along the sidewalls, leading to severe erosion. Furthermore, the inventors showed that the average wall shear stress on the stopper is reduced compared to a stopper without protrusions.

[0011] 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.

[0012] When the height of the tundish is low, slag can be driven by vortices into the tundish outlet hole, towards the mold or casting tool in the downstream process. This impairs the quality of the molded part and causes operational and safety problems, namely breakouts. Protrusions that come into contact with the slag when the height of the tundish is low reduce the vortex-driving effect on the slag. Therefore, they reduce the problem of slag flowing into the outlet hole.

[0013] Since the protrusions are arranged in a five-point configuration along the side wall, vertically adjacent protrusions are at least partially offset in the circumferential direction. The inventors have shown that this shift between protrusions strongly affects the slag entrapment along the stopper because the slag needs to move from side to side as it descends along the stopper.

[0014] Adjacent projections along the axial direction are not 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. At least some of the projections are closer to the lower end than to the upper end.

[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 side walls are the external surfaces. The protrusions are preferably designed to contact the slag on the upper surface of the liquid metal.

[0017] In one embodiment, the projection extends partially along the circumferential direction and partially along the axial direction on the side wall. In another embodiment, the projection is circumferential only.

[0018] The present invention also relates to a system for continuous casting, the system is · A tundish having an outlet hole, · Liquid metal having an upper surface within the tundish, · A stopper as 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.

[0019] Preferably, the system further comprises, · A mold or casting tool below the tundish, configured to receive the liquid metal flowing through the outlet hole, · A sensor for sensing the liquid metal within the mold or casting tool, · A data processing unit connected to the sensor and the support, configured to control the support according to the information received from the sensor.

[0020] In such a system, the vertical movement of the stopper, and as a result the flow of metal within the outlet hole, is controlled based on measurements within the mold or casting tool.

[0021] The invention also relates to a method for controlling a stopper as described herein in a system as described herein, the support preferably vertically moving the stopper at a frequency of 0.1 Hz to 100 Hz.

[0022] In the stopper according to the invention, the vertical movement of the stopper is not impaired by any thick protrusions. This is particularly advantageous for rapid vibrations.

[0023] [[ID=三十二]]These and further aspects of the invention will be described in more detail, by way of example, with reference to the accompanying drawings.

Brief Description of the Drawings

[0024] [Figure 1] It is a vertical cross-sectional view of the tundish. [Figure 2] It is a vertical cross-sectional view of a part of the stopper. [Figure 3] It is a horizontal cross-sectional view of a part of the stopper along the plane shown by III-III in FIG. 2. [Figure 4] It is a partial vertical cross-sectional view of a tundish equipped with a stopper. [Figure 5] It is an enlarged view of the stopper in FIG. 4. [Figure 6] It is a 3D view of a part of the stopper in FIG. 4. [Figure 7] It is a 3D view of a part of the stopper. [Figure 8a] It is a partial vertical cross-sectional view of a tundish equipped with a stopper according to the prior art. [Figure 8b] It is a partial vertical cross-sectional view of a tundish equipped with a stopper. <​​​​​​​​​​​​​​​​​​​​​​

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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, e.g., 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.

[0032] 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).

[0033] 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 protrusions 12 have an upper surface 51, a tip 52, and a bottom surface 53.

[0034] The radial length 21 of any of the projections 12 can be determined by considering one of them, and the radius 20 of the stopper 1 at the considered projection 12 can also be determined. In the present invention, the radius 20 of the stopper 1 at any considered projection 12 is greater than twice the radial length 21 of the considered projection 12, preferably greater than three times the radial length 21 of the considered projection 12, and more preferably greater than four times the radial length 21 of the considered projection 12. As can be seen in Figure 2, the radius 20 of the stopper 1 measured at the projection 12 can be equal to the sum of the radial length 21 of the projection 12 and the radius up to the projection 12.

[0035] 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. These two projections 12 are not perfectly aligned axially. The radial length 21 of a projection 12 is preferably measured relative to the deepest point of all gaps 19 adjacent to the projection 12. Preferably, the stopper 1 comprises up to 100 projections. The projections 12 are not perfectly aligned along the axial direction 101, and each projection 12 is circumferential only, or partially circumferential and partially axial. At least some of the projections 12 may be located within the sleeve 93.

[0036] 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.

[0037] 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.

[0038] The stopper 1 may be cylindrical or have a conical vertical cross-section. The conical vertical cross-section may have an angle α between 1° and 30° between the outer wall 10 and the axial direction 101. The projection 12 has a central angle less than 180° in a plane perpendicular to the axis 100, preferably less than 90°, 60°, or 45°.

[0039] Figure 4 shows a stopper 1 whose lower end 92 closes the outlet hole 61 of the tundish 60. The outlet hole 61 is connected to the upper nozzle 71 of the tundish. The lower end 92 is covered with an anti-stick coating 95.

[0040] Figure 5 is an enlarged view of the stopper 1 in Figure 4, showing the radial length 21 of the projection 12 and the radius 20 of the stopper 1 at the projection 12. The radial length 21 of the projection 12 is measured axially from a line 190 passing through the deepest point of the gap 19 adjacent to the projection 12.

[0041] The projections 12 are arranged on the side wall 10 in a plurality of circumferential rows 25, 26. Each row horizontally surrounds the stopper 1. The plurality of circumferential rows 25, 26 preferably include only two rows 25, 26, a first row 25 and a second row 26, with the first row 25 being closer to the upper end 91 than the second row 26. The projection 12 at the lowest position of all rows 25, 26 may be configured to contact the tundish upper nozzle 71. The five-point arrangement of the projections 12 means a circumferential offset between the projections 12 in adjacent rows 25, 26. Each row 25, 26 may contain 3 to 12 projections 12. The number of projections 12 in rows 25, 26 is preferably the same. Within each row 25, 26, the projections 12 preferably have the same shape. The projections 12 in different rows 25 and 26 may have the same or different shapes. For example, in the stopper 1 of Figures 4 and 5, the projections 12 are the same within each row 25 and 26, but different between rows 25 and 26. The projections 12 in the second row 26 are preferably located at least partially around the constricted portion 96 of the through hole 94 of the stopper 1.

[0042] The upper surface 51 of the projection 12 forms an angle θ1 with the axis 100, where θ1 is measured downward. The upper surface 53 of the projection 12 forms an angle θ3 with the axis 100, where θ3 is measured upward. The angles θ1 and θ3 are preferably such that the upper surface 51 and the lower surface 53 extend radially apart from each other. In other words, such upper and lower surfaces approach each other as they extend away from the axis 100. The angles θ1 and θ3 can be between 20° and 60°. As shown in Figures 4 and 5, θ1 may be less than θ3 for the first row 25 and greater than θ3 for the second row 26. The tip 52 of the projection 12 may be parallel to the axis 100.

[0043] The stopper 1 preferably includes an upper portion 55, a projection portion 56 including the projection 12, and a bottom portion 57 including a lower end 92. The upper portion 55 may include an upper end 91. The projection portion 56 is directly between the upper portion 55 and the bottom portion 57. In a preferred embodiment of the present invention, the projection portion 56 has a diameter without the projection 12 (this is the difference between the diameter 22 of the stopper 1 at the uppermost projection 121 and twice the radial length 21 of the uppermost projection 121), which is greater than either the diameter 58 of the upper portion 55 or the diameter 59 of the bottom portion 57, regardless of where the diameter 58 of the upper portion 55 or the diameter 59 of the bottom portion 57 is measured. In other words, the projection 12 is located at the thickest part of the stopper 1.

[0044] Figures 6 and 7 show two stoppers 1 according to the present invention, where the projection 12 is closer to the lower end 92 than to the upper end 91. In the embodiment of Figure 6, angles θ1 and θ3 are less than 90°, while in the embodiment of Figure 7, θ1 is greater than 90° and θ3 is less than 90°. The tip 52 of the projection 12 may be flat, sharp, or rounded.

[0045] Figures 8a to 9b compare computational fluid dynamics (CFD) simulations of stopper 2 without protrusions (hereinafter referred to as the standard stopper) and stopper 1 with protrusions 12 shown in Figure 6c (hereinafter referred to as the stopper with protrusions). In these figures, reference numeral 111 indicates the direction of flow, reference numeral 112 indicates slag, and reference numeral 113 indicates steel.

[0046] Figures 8a (for standard stopper 2) and 8b (for stopper 1 with projection) show the direction of flow 111. Under the same conditions, the steel 113 / slag 112 interface curved downwards with respect to standard stopper 2, but this interface appears to be generally flat with respect to stopper 1 with projection.

[0047] Figures 9a (for standard stopper 2) and 9b (for stopper 1 with projection) show slag entrapment. Under the same conditions, slag 112 is drawn into the tundish upper nozzle 71 of standard stopper 2, but it appears that slag 112 is not drawn into the tundish upper nozzle 71 of stopper 1 with projection.

[0048] 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), 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 a radial length (21) that is less than half the radius (20) of the stopper (1), The projection (12) has a central angle (β) less than 180° in a plane perpendicular to the axial direction (101), The stopper is characterized in that the projections (12) are arranged in a five-point shape along the side wall (10).

2. The stopper according to claim 1, wherein the central angle (β) is less than 90°, preferably less than 60°, and more preferably less than 45°.

3. The stopper according to any one of the prior claims, wherein the projection (12) has an upper surface (51) and a lower surface (53), and at least one of the upper surface (51) and the lower surface (53) is angled with respect to the axial direction (101) such that the upper surface (51) and the lower surface (53) move closer together as they extend radially away from the axis (100) of the stopper (1).

4. The stopper according to any one of the prior claims, wherein the projections (12) are arranged as a plurality of circumferential rows (25, 26) including a first row (25) and a second row (26), and at least one of the projections (12) in the rows (25, 26) has an upper surface (51) angled between 20° and 60° with respect to the axial direction (101) by an angle (θ1) and / or a lower surface (53) angled between 20° and 60° with respect to the axial direction (101) by an angle (θ3).

5. The stopper according to claim 3 or 4, wherein the projection (12) has a tip portion (52) parallel to the axial direction (101).

6. A stopper according to any one of the prior claims, comprising an upper portion (55), a portion with a projection (56) including the projection (12), and a bottom portion (57) including the lower end (92), wherein the portion with a projection (56) is located between the upper portion (55) and the bottom portion (57), the portion with a projection (56) is adjacent to the upper portion (55) and the bottom portion (57), and the difference between the diameter (22) of the stopper (1) at the uppermost projection (121) and the radial length (21) which is twice the uppermost projection (121) is greater than any diameter (58) of the stopper (1) at the upper portion (55) and greater than any diameter (59) of the stopper (1) at the bottom portion (57).

7. The stopper according to any one of the prior claims, wherein some of the projections (12) are at least partially arranged around the constricted portion (96) of the through hole (94) of the stopper (1).

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

9. At least two of the projections (12) are separated along the axial direction (101) by a gap (19), the gap (19) having an axial length (42) which is preferably 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), the stopper according to any one of the prior claims.

10. 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.

11. 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) for holding the stopper (1).

12. - A mold (64) or casting tool located below the tundish (60) is configured to receive the liquid metal flowing through the outlet hole (61), - A sensor (67) for sensing the liquid metal in the mold (64) or the casting tool, The system according to any one of the prior claims, further comprising: a data processing unit (68) connected to the sensor (67) and the support (69), and configured to control the support (69) in accordance with information received from the sensor (67).

13. A method for controlling a stopper according to any one of claims 1 to 10 in the system according to claim 11 or 12, wherein the support (69) moves the stopper (1) in a vertical direction.

14. The method according to claim 13, wherein the support (69) moves the stopper (1) vertically at a frequency of 0.1 Hz to 100 Hz.

15. The system is the system according to claim 12, wherein the sensor (67) transmits information to the data processing unit (68), and the data processing unit (68) controls the support (69) based on the information in such a manner that the support (69) moves the stopper (1) vertically, according to the method of claim 13 or 14.

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