Stopper rod and system for continuous casting

Abstract

The utility model relates to a stopper rod (1) and a system for continuous casting, the system for continuous casting comprises the stopper rod (1), and the stopper rod comprises a ridge part (12) contacted with slag in a tundish (60). Each ridge (12) has a radial extension (21) that is less than half of the radius (20) of the stopper (1) measured at said ridge (12). The ridge (12) reduces vortex generation of the stopper (1) and thus prolongs the life of the stopper. The ridges (12) are arranged in a quincunx along the lateral walls (10).

Description

Technical Field

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

[0002] Stoppers are generally used to control the flow of liquid metal flowing out of 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.

[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 contacts a slag layer floating at the interface between the liquid metal and the air. The slag flowing down along the stopper in the form of eddies chemically and mechanically erodes the stopper, thereby locally reducing the diameter of the stopper and shortening its service life. In addition, when the liquid metal level is low, the slag may be driven down by the eddies into the outlet hole.

[0004] In order to suppress eddies, Document CN 110788314 A discloses a stopper having a large stop and rib plates.

[0005] In order to extend the service life of the stopper, Document KR 20140140429 A discloses a stopper made of an elongated body and a removable protection member located at the height of the slag. It is expected that the slag will erode the removable protection member, so the removable protection member can be removed and replaced with a new one.

[0006] CN 106735153 A describes a stopper with a ring, aiming to promote the floating of inclusions to improve the cleanliness of molten steel.

[0007] The problem with these known stoppers is that they include thick protrusions, thus greatly increasing the local diameter of the stopper and consequently increasing its movement resistance in the liquid metal. Therefore, the up and down movement of the stopper cannot be finely controlled. Summary of the Utility Model

[0008] The object of the utility model is to provide a stopper that reduces eddies along its side wall.

[0009] The utility model relates to a stopper for controlling the flow of liquid metal out of a tundish, which extends axially between an upper end and a lower end and is radially defined by a side wall including a plurality of ridges, wherein the ridges extend at least partially along the circumferential direction on the side wall, wherein each ridge has a radial extension less than half of the radius obtained by the stopper at the ridge and at least 0.01 times the radius obtained by the stopper at the ridge, the ridge has an angular extension less than 180°, and the ridges are arranged in a plum blossom shape along the side wall.

[0010] The inventors have shown by simulation that the ridges break up large eddies, which cause slag entrainment along the side walls and thus strong erosion. In addition, they have shown that the average wall shear stress on the stopper rod is reduced compared to a stopper rod without ridges.

[0011] The stopper rod according to the present invention does not include any thick protrusions, since all the ridges are radially limited by half of the radius of the stopper rod at the height of the ridges in terms of size. This absence of thick protrusions provides low movement resistance and thus good control response. In the stopper rod of KR 20140140429 A, there is no such upper limit for the radial dimension of each ridge of the claimed stopper rod, where the removable protective member with reference numeral 200 has extremely large ridges. In this prior art document, the "threads" with reference numeral 110 are not intended to be used without the removable protective member or to be in contact with the slag, and form a single ridge rather than multiple ridges.

[0012] When the liquid level in the tundish is low, the slag may be driven by the eddies into the outlet holes of the tundish, flow into the mold or casting tool in the downstream process. This impairs the quality of the molded parts and causes operational and safety problems, namely demolding. When the liquid level in the tundish is low, the ridges in contact with the slag reduce the driving effect of the eddies on the slag. Therefore, the ridges reduce the problem of slag flowing into the outlet holes.

[0013] Since the ridges are arranged in a plum blossom shape along the side walls, the vertically adjacent ridges are at least partially circumferentially offset. The inventors have shown that this offset between the ridges has a strong effect on the entrainment of the slag along the stopper rod, because the slag has to move left and right when moving down along the stopper rod.

[0014] The ridges adjacent along the axial direction are not completely axially aligned. The stopper rod is preferably a single piece. The stopper rod is preferably molded as a single piece. The ridges are preferably integral with the stopper rod, and in particular with the upper end and the lower end. At least some of the ridges are closer to the lower end than the upper end.

[0015] The stopper rod does not include any such protrusion having a radial extension greater than half of the radius obtained by the stopper rod at the protrusion. The stopper rod does not include any removable protective member around the side wall. The ridges are preferably not spiral.

[0016] The side wall is the outer surface. The ridges are preferably designed to contact the slag at the top surface of the liquid metal.

[0017] In an embodiment, the ridges extend partially along the circumferential direction and partially along the axial direction on the side wall. In another embodiment, the ridges only extend along the circumferential direction.

[0018] The present utility model also relates to a system for continuous casting, the system comprising:

[0019] · A tundish, the tundish including an outlet hole;

[0020] · Liquid metal in the tundish, the liquid metal having a top surface;

[0021] · A stopper rod as described herein, the stopper rod being configured to close the outlet hole and being arranged such that the top surface of the liquid metal contacts at least some of the ridges; and

[0022] · A support member that holds the stopper rod.

[0023] Preferably, the system further comprises:

[0024] · A mold or casting tool below the tundish, the mold or casting tool being configured to receive the liquid metal flowing through the outlet hole;

[0025] · A sensor for sensing the liquid metal in the mold or casting tool; and

[0026] · A data processing unit connected to the sensor and the support member and being configured to control the support member based on information received from the sensor.

[0027] With such a system, the vertical movement of the stopper rod is controlled based on measurements in the mold or casting tool, and thus the metal flow into the outlet hole is controlled.

[0028] The present utility model also relates to a method for controlling a stopper rod as described herein in a system as described herein, wherein the support member vertically moves the stopper rod, preferably vertically moving the stopper rod at a frequency between 0.1 Hz and 100 Hz.

[0029] With the stopper rod according to the present utility model, the vertical movement of the stopper rod is not weakened by any thick protrusions, which is particularly advantageous for rapid oscillation. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] These and other aspects of the present utility model will be explained in more detail by way of example and with reference to the drawings, in which:

[0031] Figure 1 is a vertical cross-sectional view of the tundish,

[0032] Figure 2 is a vertical cross-sectional view of a part of the stopper rod,

[0033] Figure 3 is a part of the stopper rod along Figure 2Horizontal sectional view of the plane shown in III-III,

[0034] Figure 4 is a vertical sectional view of a part of a tundish having a stopper rod,

[0035] Figure 5 is Figure 4 an enlarged view of the stopper rod,

[0036] Figure 6 is Figure 4 a 3D view of a part of the stopper rod,

[0037] Figure 7 is a 3D view of a part of the stopper rod,

[0038] Figure 8a is a vertical sectional view of a part of a tundish having a stopper rod according to the prior art,

[0039] Figure 8b is a vertical sectional view of a part of a tundish having a stopper rod,

[0040] Figure 9a is a vertical sectional view of a part of a tundish having a stopper rod according to the prior art, and

[0041] Figure 9b is a vertical sectional view of a part of a tundish having a stopper rod. Detailed Description of the Invention

[0042] The present invention will be described with reference to specific embodiments and certain drawings, but the present invention is not limited thereto. The described drawings are illustrative and not restrictive. In the drawings, for illustrative purposes, the dimensions of some elements may be exaggerated and not drawn to scale.

[0043] In addition, the first, second, third, and similar terms in the description and claims are used to distinguish similar elements and not necessarily to describe a sequential or chronological order. These terms are interchangeable where appropriate, and the embodiments of the present invention may be operated in an order different from that described or shown herein.

[0044] In addition, although various embodiments are referred to as "preferred", they should be construed as exemplary ways of implementing the present invention rather than as limiting the scope of the present invention.

[0045] The term "comprising" as used in the claims should not be construed as being limited to the elements or steps listed thereafter; the term does not exclude other elements or steps. The term is to be interpreted as specifying the presence of the stated features, integers, steps or components but does not exclude the presence or addition of one or more other features, integers, steps or components or groups thereof. Thus, the scope of the expression "a device comprising A and B" should not be limited to a device consisting only of components A and B, but in the context of the present utility model, only components A and B of the device are listed, and further claims should be construed as including equivalents of these components.

[0046] Figure 1 Reference numeral 60 denotes the tundish. In the tundish 60, liquid metal 65 flows from the ladle long nozzle 62 to the outlet hole 61. The top surface 66 of the liquid metal is a slag layer. The stopper rod 1 controls the flow of metal through the outlet hole 61.

[0047] The stopper rod 1 comprises refractory material. The stopper rod 1 has an upper end 91 (which may be referred to as the first end) and a lower end 92 (which may be referred to as the second end), the upper end being connected to a support 69 that moves the stopper rod 1 vertically, and the lower end being capable of closing the outlet hole 61. The stopper rod 1 may include a slag line 93, which is preferably located closer to the upper end 91 than to the lower end 92 and is made of a material more corrosion-resistant than other parts of the stopper rod 1. The stopper rod 1 includes a through-hole 94 for injecting gas. The outlet hole 61 is connected to the tundish upper nozzle 71 and the submerged entry nozzle 70, thereby guiding the liquid metal to the mold 64 or the casting tool.

[0048] When the outlet hole is not completely blocked by the stopper rod 1, the mold 64 or the casting tool below the tundish 60 receives the liquid metal flowing through the outlet hole 61. A sensor 67 detects at least one characteristic of the liquid metal 72 in the mold 64 or the casting tool, such as the metal level. The sensor 67 sends information to a data processing unit 68 that controls the support 69. Thus, the information is used to move the stopper rod 1 vertically. The vertical position of the stopper rod controls the flow rate into the outlet hole 61. In addition to its vertical movement for regulating the flow rate through the outlet hole 61, the stopper rod 1 may also oscillate vertically (which may be referred to as "dithering"). The frequency of the oscillation is preferably in the range from 0.1 Hz to 100 Hz, more preferably in the range from 0.2 Hz to 10 Hz, and its amplitude is in the range from 0.2 to 10 mm.

[0049] Figure 2 and Figure 3 Reference numeral 1 shows the stopper rod 1 in an embodiment of the present utility model. The stopper rod 1 has an axis 100. The stopper rod 1 is described herein with reference to an axial direction 101 (which is vertical in use), a radial direction 102 (which is horizontal in use and extends away from the axis 100 of the stopper rod) and a circumferential direction 103 (which is horizontal and perpendicular to the radial direction 102).

[0050] The stopper rod 1 has a lateral wall 10 formed by radially protruding ridges 12. The lateral wall 10 circumferentially surrounds the stopper rod 1. The ridge 12 has a top side 51, an end 52, and a bottom side 53.

[0051] For any one of the ridges 12, its radial extension 21 can be determined, and the radius 20 of the stopper rod 1 at the considered ridge 12 can also be determined. In the present utility model, the radius 20 of the stopper rod 1 at any considered ridge 12 is greater than twice the radial extension 21 of the considered ridge 12, preferably greater than three times the radial extension 21 of the considered ridge 12, more preferably greater than four times the radial extension 21 of the considered ridge 12. As Figure 2 can be seen, the radius 20 of the stopper rod 1 measured at the ridge 12 can be equal to the sum of the radial extension 21 of the ridge 12 and the radius up to the ridge 12.

[0052] The stopper rod 1 includes a group 16 of ridges 12, the group including at least two adjacent ridges 12, the at least two adjacent ridges being separated by a gap 19 along the axial direction 101. The two ridges 12 are not completely axially aligned. The radial extension 21 of the ridge 12 is preferably measured with respect to the deepest point of all the gaps 19 adjacent to the ridge 12. Preferably, the stopper rod 1 includes at most 100 ridges. The ridges 12 are not completely along the axial direction 101: any one of the ridges 12 is only circumferential, or is partially circumferential and partially axial. At least some of the ridges 12 can be in the slag line 93.

[0053] In this text, for the sake of simplicity, the diameter 22 of the stopper rod 1 at the uppermost ridge 121 is herein identified as DU. Preferably, the ridge 12 has an axial extension 41 between 0.01DU and 0.4DU, preferably between 0.03DU and 0.24DU, more preferably between 0.05DU and 0.16DU. The axial extension 41 is preferably measured as close as possible to the axis 100, that is, at the start of the ridge 12. Preferably, the gap 19 has an axial extension 42 between 0.02DU and 0.3DU, preferably between 0.04DU and 0.3DU, more preferably between 0.05DU and 0.1DU.

[0054] In this text, for the sake of simplicity, the radius 20 of the stopper rod 1 at the ridge 12 is herein identified as RS. Preferably, each ridge 12 has a radial extension 21 between 0.01RS and 0.4RS, preferably between 0.05RS and 0.3RS, more preferably between 0.1RS and 0.2RS.

[0055] The stopper 1 can be cylindrical or can have a conical vertical cross-section. The conical vertical cross-section can result in an angle α between 1° and 30° between the lateral wall 10 and the axial direction 101. The ridge 12 has an angular extension β in a plane perpendicular to the axis 100, where β is less than 180°, preferably less than 90°, 60° or 45°.

[0056] Figure 4 The stopper 1 is shown, with its lower end 92 closing 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-sticking coating 95.

[0057] Figure 5 is Figure 4 An enlarged view of the stopper 1, showing the radial extension 21 of the ridge 12 and the radius 20 of the stopper 1 at this ridge 12. The radial extension 21 of the ridge 12 is measured from the line 190, which is axial and passes through the deepest point of the gap 19 adjacent to the ridge 12.

[0058] The ridges 12 are arranged on the lateral 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 includes only two rows 25, 26: a first row 25 and a second row 26, with the first row 25 closer to the upper end 91 than the second row 26. The ridges 12 of the lowest row among all the rows 25, 26 can be configured to contact the upper nozzle 71 of the tundish. The diamond-shaped arrangement of the ridges 12 means there is a circumferential offset between the ridges 12 of adjacent rows 25, 26. Each row 25, 26 can include three to twelve ridges 12. The number of ridges 12 in the rows 25, 26 is preferably the same. Within each row 25, 26, the ridges 12 preferably have the same shape. The ridges 12 of different rows 25, 26 can have the same or different shapes. For example, in Figure 4 and Figure 5 the stopper 1, the ridges 12 within each row 25, 26 are the same, but are different between the rows 25, 26. The ridges 12 of the second row 26 preferably at least partially surround the narrowing 96 of the through-hole 94 of the stopper 1.

[0059] The top side 51 of the ridge 12 forms an angle θ1 with the axis 100, measured downward. The bottom side 53 of the ridge 12 forms an angle θ3 with the axis 100, measured upward. The angles θ1 and θ3 are preferably such that the top side 51 and the bottom side 53 extend towards each other as they extend radially away. In other words, such top and bottom sides get closer as they extend away from the axis 100. The angles θ1 and θ3 can be between 20° and 60°. As Figure 4 and Figure 5As shown, for the first row 25, θ1 can be less than θ3, and for the second row 26, θ1 can be greater than θ3. The end 52 of the ridge 12 can be parallel to the axis 100.

[0060] The stopper 1 preferably includes: a higher portion 55, a ridged portion 56 including the ridge 12, and a bottom portion 57 including the lower end 92. The higher portion 55 can include the upper end 91. The ridged portion 56 is directly between the higher portion 55 and the bottom portion 57. In a preferred embodiment of the present invention, the diameter obtained at the ridged portion 56 where there is no ridge 12 (this diameter is the difference between the diameter 22 of the stopper 1 at the uppermost ridge 121 and twice the radial extension 21 of the uppermost ridge 121) is greater than either the diameter 58 of the higher portion 55 or the diameter 59 of the bottom portion 57, regardless of where the diameter 58 of the higher portion 55 is measured or where the diameter 59 of the bottom portion 57 is measured. In other words, the ridge 12 is located in the thickest section of the stopper 1.

[0061] Figure 6 and Figure 7 Shows two stoppers 1 according to the present invention, where the ridge 12 is closer to the lower end 92 than to the upper end 91. In Figure 6 the embodiment, the angles θ1 and θ3 are less than 90°, while in Figure 7 the embodiment, the angle θ1 is greater than 90° and the angle θ3 is less than 90°. The end 52 of the ridge 12 can be flat, sharp, or rounded.

[0062] Figures 8a to 9b A computational fluid dynamics (CFD) simulation of a stopper 2 without any ridges (hereinafter referred to as a standard stopper) and a stopper 1 with a ridge 12 as shown in Figure 6 was compared. In these figures, the reference numeral 111 is the flow direction, the reference numeral 112 is the slag, and the reference numeral 113 is the steel.

[0063] Figure 8a (for the standard stopper 2) and Figure 8b (for the ridged stopper 1) shows the flow direction 111. It can be seen from the figure that under the same conditions, for the standard stopper 2, the steel 113 / slag 112 interface bends downward, while for the ridged stopper 1, this interface is generally flat.

[0064] Figure 9a (for the standard stopper 2) and Figure 9b (for the ridged stopper 1) shows the slag entrainment. It can be seen from the figure that under the same conditions, for the standard stopper 2, the slag 112 is entrained into the tundish nozzle 71, while for the ridged stopper 1, the slag 112 is not entrained into the tundish nozzle 71.

[0065] Although the present utility model has been described above with respect to specific embodiments, it will be readily understood that other embodiments are also possible. In addition, any feature of the stopper rod described or shown herein is considered to be combinable with any other feature of any other stopper rod.

Claims

1. A stopper rod (1) for controlling the outflow of liquid metal (65) from a tundish (60), the stopper rod extending in an axial direction (101) between an upper end (91) and a lower end (92) and being radially defined by a lateral wall (10) including a plurality of ridges (12), Among them, the ridges (12) extending at least partially along a circumferential direction (103) on the lateral wall (10), wherein each ridge (12) has a radial extension (21) that is at least 0.01 times the radius (20) of the stopper rod (1) at the ridge (12), characterized in that, each ridge (12) has a radial extension (21) less than half of the radius (20) of the stopper rod (1) at the ridge (12), the ridge (12) has an angular extension (β) of less than 180° in a plane perpendicular to the axial direction (101), the ridges (12) are arranged in a plum blossom pattern along the lateral wall (10).

2. The stopper rod according to claim 1, wherein The angular extension (β) is less than 90°.

3. The stopper rod according to claim 2, wherein, The angular extension (β) is less than 60°.

4. The stopper according to claim 3, wherein, The angular extension (β) is less than 45°.

5. The stopper according to any one of the preceding claims 1-4, wherein, The ridge (12) has a top side (51) and a bottom side (53), and at least one of the top side (51) and the bottom side (53) is angled relative to the axial direction (101) such that the top side (51) and the bottom side (53) come closer as they extend radially away from the axis (100) of the stopper rod (1).

6. The stopper rod according to claim 1, wherein, The ridges (12) are arranged in a plurality of circumferential rows (25, 26), the plurality of circumferential rows including a first row (25) and a second row (26), and the top side (51) of the ridges (12) in at least one of the plurality of circumferential rows (25, 26) is angled between 20° and 60° relative to the axial direction (101) and / or its bottom side (53) is angled between 20° and 60° relative to the axial direction (101).

7. The stopper according to claim 1, wherein, The ridge (12) has a tip (52) parallel to the axial direction (101).

8. The stopper according to claim 1, wherein, The stopper rod includes: a higher part (55), a ridged part (56) including the ridges (12), and a bottom part (57) including the lower end (92), the ridged part (56) being between the higher part (55) and the bottom part (57), the ridged part (56) adjoining the higher part (55) and the bottom part (57), wherein the difference between the diameter (22) of the stopper rod (1) at the uppermost ridge (121) and twice the radial extension (21) of the uppermost ridge (121) is greater than any diameter (58) of the stopper rod (1) in the higher part (55) and greater than any diameter (59) of the stopper rod (1) in the bottom part (57).

9. The stopper according to claim 1, wherein Some of the ridges (12) are at least partially located around a narrowing (96) of a through hole (94) of the stopper rod (1).

10. The stopper rod according to claim 1, wherein, Each ridge (12) has an axial extension (41) that is at least 0.01 times the diameter (22) of the stopper (1) at the uppermost ridge (121).

11. The stopper rod according to claim 10, wherein, Each ridge (12) has an axial extension (41) between 0.01 times and 0.4 times the diameter (22) of the stopper (1) at the uppermost ridge (121).

12. The stopper rod according to claim 11, wherein, Each ridge (12) has an axial extension (41) between 0.03 times and 0.24 times the diameter (22) of the stopper (1) at the uppermost ridge (121).

13. The stopper according to claim 12, wherein, Each ridge (12) has an axial extension (41) between 0.05 times and 0.16 times the diameter (22) of the stopper (1) at the uppermost ridge (121).

14. The stopper according to claim 1, wherein, At least two of the ridges (12) are separated by a gap (19) along the axial direction (101).

15. The stopper rod according to claim 14, wherein, The gap (19) has an axial extension (42) between 0.02 times and 0.3 times the diameter (22) of the stopper (1) at the uppermost ridge (121).

16. The stopper according to claim 15, wherein, The gap (19) has an axial extension (42) between 0.04 times and 0.2 times the diameter (22) of the stopper (1) at the uppermost ridge (121).

17. The stopper according to claim 16, wherein, The gap (19) has an axial extension (42) between 0.05 times and 0.1 times the diameter (22) of the stopper (1) at the uppermost ridge (121).

18. The stopper according to claim 1, wherein, Each ridge (12) has a radial extension (21) between 0.01 times and 0.4 times the radius (20) of the stopper (1) taken at the ridge (12).

19. The stopper rod according to claim 18, wherein, Each ridge (12) has a radial extension (21) between 0.05 times and 0.3 times the radius (20) of the stopper (1) taken at the ridge (12).

20. The stopper according to claim 19, wherein, Each ridge (12) has a radial extension (21) between 0.1 times and 0.2 times the radius (20) of the stopper (1) taken at the ridge (12).

21. A system for continuous casting, characterized in that, The system includes: · A tundish (60) that includes an outlet hole (61); · Liquid metal (65) in the tundish (60) that has a top surface (66); · A stopper (1) according to any one of the preceding claims 1 - 20, the stopper being configured to close the outlet hole (61) and arranged such that the top surface (66) of the liquid metal (65) contacts at least some of the ridges (12); and · A support (69) that holds the stopper (1).

22. The system according to claim 21, wherein, The system further includes: · A mold (64) or casting tool below the tundish (60), the mold or casting tool being configured to receive liquid metal flowing through the outlet hole (61); · A sensor (67) for sensing the liquid metal in the mold (64) or casting tool; and · A data processing unit (68), which is connected to the sensor (67) and the support member (69), and is configured to control the support member (69) according to the information received from the sensor (67).

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