SUBMERGED NOZZLE WITH ROTATABLE INSERT

Abstract

Submerged nozzle (1) through which molten steel can be poured from a tundish into a mould, said nozzle comprising: a substantially tubular body (2), extending from a first end (3) to a second end (4); a passageway (5), extending through the tubular body (2) along a longitudinal axis (A) from the first end (3) towards the second end (4); at least one inlet port (6), opening into the passageway (5) at said first end (3); a plurality of outlet ports (8), opening into the passageway (5) in a region (7) adjacent to the second end (4); and at least one rotatable insert (10); whereas the submerged nozzle (1) with the at least one rotatable insert (10) is configured that a molten metal entering the submerged nozzle (1) at the at least one inlet port (6) flows through the passageway (5) and around the rotatable insert (10) and exits the submerged entry nozzle (1) via the plurality of outlet ports (8), such that a rotation of the rotatable insert (10) is driven by the stream of molten metal.

Claims

1. Submerged nozzle (1) through which molten steel can be poured from a tundish into a mould, said nozzle comprising: 1.1 a substantially tubular body (2), extending from a first end (3) to a second end (4); 1.2 a passageway (5), extending through the tubular body (2) along a longitudinal axis (A) from the first end (3) towards the second end (4); 1.3 at least one inlet port (6), opening into the passageway (5) at said the first end (3); 1.4 a plurality of outlet ports (8), opening into the passageway (5) in a region (7) adjacent to the second end (4); and 1.5 at least one rotatable insert (10); 1.6 wherein the submerged nozzle (1) with the at least one rotatable insert (10) is configured such that a molten metal entering the submerged nozzle (1) at the at least one inlet port (6) flows through the passageway (5) and around the rotatable insert (10) and exits the submerged entry nozzle (1) via the plurality of outlet ports (8), such that a rotation of the rotatable insert (10) is driven by the molten metal.

2. Submerged nozzle (1) according to claim 1, wherein the at least one rotatable insert (10) is positioned inside the passageway (5).

3. Submerged nozzle (1) according to claim 1, wherein the at least one rotatable insert (10) rotates with respect to the substantial tubular body (2) when a fluid flows through the passageway (5).

4. Submerged nozzle (1) according to claim 1, wherein the submerged nozzle (1) is a submerged entry nozzle (SEN) (1a) or a monotube (1b) or a submerged entry shroud (SES) (1c).

5. Submerged nozzle (1) according to claim 1, wherein the rotatable insert (10) defines an axis of rotation (13) and comprises blades (11) with an angle between at least one surface normal (14) of the blades (11) and the axis of rotation (13) in the range of 10° to 85°.

6. Submerged nozzle (1) according to claim 1, wherein the rotatable insert (10) is in the form of a propeller with a minimum of 2 blades.

7. Submerged nozzle (1) according to claim 1, wherein the rotatable insert (10) is in the form of a propeller with a maximum of 15 blades.

8. Submerged nozzle (1) according to claim 1, wherein the rotatable insert (10) is in the form of a propeller having a propeller pitch of at least 50 mm.

9. Submerged nozzle (1) according to claim 1, wherein the rotatable insert (10) is in the form of a propeller having a propeller pitch of less than 2000 mm.

10. Submerged nozzle (1) according to claim 1, wherein the rotatable insert (10) is made from a refractory material.

11. Submerged nozzle (1) according to claim 1, wherein the rotatable insert (10) is made from a refractory material with a maximum grain size of less than 2 mm.

12. Submerged nozzle (1) according to claim 1, wherein the substantially tubular body (2) comprises a wear liner section (15) inside of the passageway (5), and wherein the rotatable insert (10) is positioned inside the passageway (5) in the region (7) of the wear liner section (15).

13. Submerged nozzle (1) according to claim 1, wherein the submerged nozzle (1) is produced by isostatic pressing.

14. A method for continuous casting of molten steel, using the submerged nozzle (1) according to claim 1.

15. Use of a submerged nozzle (1) according to claim 1 for continuous casting of molten steel.

16. Submerged nozzle (1) according to claim 2, wherein the at least one rotatable insert (10) is positioned inside the passageway in a region (7) adjacent to the second end.

17. Submerged nozzle (1) according to claim 5, wherein the angle between the at least one surface normal (14) of the blades (11) and the axis of rotation (13) is in the range of 20° to 80°.

18. Submerged nozzle (1) according to claim 8, wherein the propeller pitch is at least 200 mm.

19. Submerged nozzle (1) according to claim 10, where in refractory material is boron nitride.

20. Submerged nozzle (1) according to claim 11, wherein the maximum grain size is less than 0.7 mm.

Description

[0037] FIG. 1 shows a schematic cross-section of a schematic submerged entry nozzle (SEN) with a rotatable insert.

[0038] FIG. 2 shows a schematic cross-section of a schematic monotube with a rotatable insert.

[0039] FIG. 3 shows a schematic perspective view of a first rotatable insert embodiment.

[0040] FIG. 4 shows a schematic perspective view of a second rotatable insert embodiment.

[0041] FIG. 5a shows schematically the flow pattern of a double roll.

[0042] FIG. 5b shows schematically the flow pattern of a single roll.

[0043] FIG. 5c shows schematically the flow pattern of a meniscus roll.

[0044] FIG. 6 shows a schematic cross-section of a schematic submerged entry nozzle (SEN) with a rotatable insert and a wear liner section.

[0045] FIG. 1 shows a cross-section through a submerged nozzle (1), which is a submerged entry nozzle (1a) in its use position. The submerged nozzle (1) comprises a substantially tubular body (2) extending from a first end (3) (upper end) to a second end (4) (lower end), the substantially tubular body (2) is made of a carbon bonded refractory material. The submerged entry nozzle (1) further comprises a passageway (5), which extends through the tubular body (2), along a longitudinal axis (A) from the first end (3) to the second end (4). The passageway (5) defines a rotationally symmetrical opening, here in the form of a circular cylinder, with its axis coinciding with the longitudinal axis (A) of the submerged nozzle (2). At the first end (3) the inlet port (6) opens into the passageway (5). In a region (7) adjacent to the second end (4) two outlet ports (8) open into the passageway (5). The outlet ports (8) are circular openings in the wall of the tubular body (2). The submerged entry nozzle (1) further comprises a rotatable insert (10). The rotatable insert (10) is positioned inside the passageway (5), in a region (7) adjacent to the second end (4). The submerged entry nozzle (1) with the at least one rotatable insert (10) is configured that a molten metal entering the submerged entry nozzle (1) at the at least one inlet port (6) flows through the passageway (5) and around the rotatable insert (10) and exits the submerged entry nozzle (1) via the plurality of outlet ports (8), such that a rotation of the rotatable insert (10) is driven by the stream of molten metal. The at least one rotatable insert (10) rotates with respect to the substantial tubular body (2) when a fluid, such as a molten metal, flows through the passageway (5).

[0046] FIG. 2 shows a cross-section through a submerged nozzle (1), which is a monotube (1b) in its use position. The difference to the submerged entry nozzle (1a) as shown in FIG. 1 is the geometry of the monotube (1b) at its first end (3). Here the monotube (1b) shows a connection portion for connection to a slide gate plate attachment (not shown). Apart from this different attachment geometry at its first end (3), the other parts of the monotube (1b) are functionally similar to the respective parts described in connection with the submerged entry nozzle (1a) of FIG. 1.

[0047] FIG. 3 shows a schematic perspective view of a first rotatable insert (10) embodiment, the at least one rotatable insert (10) defines an axis of rotation (13). Here, the at least one rotatable insert (10) is in the form of a propeller with a shaft (12) and with 4 blades (11), the blades (11) featuring a design in that the angle between the respective surface normal (14) of the blade (11) and the axis of rotation (13) is constant over the height of the insert (10). In this example, the at least one rotatable insert (10) is in the form of a propeller having a propeller pitch of 400 mm, in an alternative setup of 560 mm. The at least one rotatable insert (10) is made from a fine-grained refractory material, here the at least one rotatable insert (10) is made from boron nitride, with a maximum grain size of 0.3 mm.

[0048] FIG. 4 shows a schematic perspective view of a second rotatable insert (10) embodiment, the at least one rotatable insert (10) defines an axis of rotation (13). Here, the at least one rotatable insert (10) is in the form of a shaft-less propeller with 10 blades (11) (this design can be called Francis Turbine). In this example, the at least one rotatable insert (10) is in the form of a propeller having a propeller pitch of 450 mm. The at least one rotatable insert (10) is made from a fine-grained refractory material, here the at least one rotatable insert (10) is made from boron nitride, with a maximum grain size of 0.3 mm. The rotatable insert (10) of FIG. 4 can be used in the embodiments according to FIGS. 1 and 2.

[0049] The mould flow pattern of a submerged nozzle according to the invention was compared to a submerged nozzle with an empty casting channel. By measuring the velocity flow in a water model, the following basic flow patterns in the mould (here the mould is of rectangular shape) could be observed:

[0050] The first flow pattern (see FIG. 5a) observed is the preferred flow pattern, the so-called double-roll. Here the flow of the fluid exiting the outlet ports of the submerged nozzle are in the form of two rolling flow patterns for each of the outlet ports, one rolling flow pattern directed basically above the outlet ports and the other one into the opposite direction and basically below the outlet port. This flow configuration is preferred because it minimizes non-metallic inclusions in steel.

[0051] The second flow pattern (see FIG. 5b) observed is acceptable, but not preferred, it is the so-called single-roll. Here the flow of the fluid exiting the outlet ports of the submerged nozzle is in the form of one (single) rolling flow pattern for each outlet port, with an initial flow going upwards (towards the meniscus; the meniscus is understood as the surface of the liquid) and then rolling down. This flow configuration is acceptable, but not preferred, because the risk for non-metallic inclusions in steel is present.

[0052] The third flow pattern (see FIG. 5c) observed should be avoided, it is the so-called meniscus roll. Here the flow of the fluid exiting the outlet ports of the submerged nozzle is in the form of two rolling flow patterns for one of the outlet ports, while for a second outlet port the flow pattern is in the form of one (single) rolling flow pattern, thus a mixture of single roll and double roll is present. This flow configuration should be avoided or reduced, because the risk for non-metallic inclusions in steel is increased.

[0053] The results of observed flow patterns for different geometries is shown below in Table I. All experiments were conducted over 30 minutes in a water model (scaled down 1:3) with an equivalent steel throughput for 3.16 tons/minute.

[0054] In the first experiment the first rotatable insert as shown in FIG. 3 was used inside the submerged nozzle (according to FIG. 1). During the experimental sequence, 99.8% of the time the observed flow pattern showed a double roll situation (according to FIG. 5a). No single roll (FIG. 5b) and a very low rate (0.2%) of meniscus roll (FIG. 5c) situation was observed at all.

[0055] In the second experiment the second rotatable insert as shown in FIG. 4 was used inside the submerged nozzle (according to FIG. 1). During the experimental sequence, 100% of the time the observed flow pattern showed a double roll situation (according to FIG. 5a). No single roll (FIG. 5b) or meniscus roll (FIG. 5c) situation was observed at all.

[0056] In the third experiment no insert was used inside the submerged nozzle (comparative example). During the experimental sequence, 83.8% of the time the observed flow pattern showed a double roll situation (according to FIG. 5a). Single roll situation (FIG. 5b) was present at 0.5% of the time, and meniscus roll situation (FIG. 5c) was observed at 15.8% of the time.

[0057] In conclusion the experiments show the reduction of the (unwanted) meniscus roll situation (FIG. 5c) by using a rotatable insert in a submerged nozzle compared to an empty passageway. Thereby the rotatable insert in a submerged nozzle improves the flow stability, as with the insert a highly stable double roll flow characteristics is achieved.

[0058] FIG. 6 shows a cross-section through a submerged nozzle (1) similar to that of FIG. 1, with the difference, that the substantially tubular body (2) comprises a wear liner section (15) inside of the passageway (5), and wherein the rotatable insert (10) is positioned inside the passageway (5) in the region (7) of the wear liner section (15). The wear liner section (15) extends to the second end (4) of the passageway (5). The wear liner section (15) was separately formed before the production of the whole submerged nozzle (1), in this example it was formed as a cage/sleeve. It showed that the production process in the case the submerged nozzle (1) is produced by isostatic pressing is simplified and that the cage/sleeve forming the wear liner section (15) could achieve an enhanced dimensional precision and thus showed an improved and more constant rotation of the rotatable insert (10).

TABLE-US-00001 TABLE I Comparison of the flow pattern (double roll, single roll or meniscus roll in percentage of the overall time) observed using the first rotatable insert (FIG. 3), the second rotatable insert/Francis turbine insert (FIG. 4) or an empty casting channel: First rotatable Second rotatable No rotatable insert insert insert (comp. example.) Double roll 99.8% 100%  83.8% Single row   0% 0% 0.5% Meniscus roll  0.2% 0% 15.8%

LIST OF REFERENCE NUMERALS AND FACTORS

[0059] 1 Submerged nozzle [0060] 1a Submerged entry nozzle (SEN) [0061] 1b Monotube [0062] 1c Submerged entry shroud (SES) [0063] 2 Tubular body [0064] 2a Slag band [0065] 3 First end [0066] 4 Second end [0067] 5 Passageway [0068] 6 Inlet port [0069] 7 Region adjacent to second end (4) [0070] 8 Outlet port [0071] 10 Rotatable insert [0072] 11 Blades [0073] 12 Shaft [0074] 13 Axis of rotation [0075] 14 Surface normal of blades (11) [0076] 15 Wear liner section/cage for rotatable insert [0077] A Longitudinal axis of tubular body (2)