Abstract
An electromagnetic brake that variably influences the flow of molten steel in two width regions (B1, B2) of a mold (1) of a slab continuous casting assembly by variably adjusting the magnetic flux density in the two width regions with two magnetic circuits, each magnetic circuit having a first pole (4a), a second pole (4b), and a yoke (2) for magnetically connecting the first and the second pole (4a, 4b). The first and the second poles (4a, 4b) lie substantially opposite each other in the direction of thickness (d) of the mold (1), and the first pole (4a) extends in the direction of the second pole (4b) in the direction of thickness (d) and vice versa. At least one pole (4a, 4b) of either magnetic circuit can be moved relative to the yoke (2) in the direction of thickness (d) of the mold (1).
Claims
1-13 (canceled)
14. An electromagnetic brake for variably influencing the flow of a molten steel in a first width region and a second width region of a mold of a slab continuous casting assembly, said electromagnetic brake comprising: a first magnetic circuit for influencing the flow in the first width region of the mold; a second magnetic circuit for influencing the flow in the second width region of the mold, wherein the second width region is offset from the first width region in the width direction of the mold; and at least one coil for introducing a magnetic flux into the first magnetic circuit and the second magnetic circuit, wherein the first and second magnetic circuits each comprises, a first pole, a second pole, and a yoke for magnetic connection of the first pole and the second pole, wherein the first and the second poles are opposite in the thickness direction of the mold, and the first pole extends in the thickness direction toward the second pole, and vice versa, wherein at least one pole of the first magnetic circuit or the second magnetic circuit is displaceable relative to the yoke of the same magnetic circuit in the thickness direction of the mold, wherein an actuator for displacing a pole in the thickness direction of the mold during operation is provided, and wherein at least one pole of the first magnetic circuit or the second magnetic circuit has a pole head, which is detachably connected to the pole.
15. The electromagnetic brake as claimed in claim 14, wherein the first and the second magnetic circuits comprise at least one energizable coil.
16. The electromagnetic brake as claimed in claim 15, wherein the first and the second magnetic circuits comprise two separately energizable coils.
17. The electromagnetic brake as claimed in claim 14, wherein the pole head extends in some sections in the width direction and/or the height direction of the mold to a different extent in the thickness direction of the mold.
18. The electromagnetic brake as claimed in claim 14, wherein a longitudinal extension in the thickness direction of the mold of a pole head of the first magnetic circuit is different from a longitudinal extension of a pole head of the second magnetic circuit.
19. The electromagnetic brake as claimed in one of claims 14, wherein the pole head is formed from one or more discrete elements, and wherein the discrete elements are mechanically connected to the pole.
20. The electromagnetic brake as claimed in claim 14, wherein the yoke is arranged in the thickness direction of the mold.
21. The electromagnetic brake as claimed in claim 14, comprising at least two coils for introducing a magnetic flux into the first magnetic circuit and the second magnetic circuit.
22. The electromagnetic brake as claimed in claim 14, wherein at least one pole of the first magnetic circuit and the second magnetic circuit is displaceable relative to the yoke of the same magnetic circuit in the thickness direction of the mold.
23. The electromagnetic brake as claimed in claim 14, wherein at least one pole of the first magnetic circuit and the second magnetic circuit has a pole head, which is detachably connected to the pole.
24. A mold comprising: a first electromagnetic brake as claimed in claim 14, and a second magnetic brake which has a height offset from the first magnetic brake.
25. A method for variably influencing the flow of a molten steel in a first width region and a second width region of a mold during operation of a slab continuous casting assembly by means of an electromagnetic brake as claimed in claim 14, wherein the first and the second magnetic circuit each comprise at least one separately energizable coil, the method comprising: introducing a first magnetic flux into the first magnetic circuit by energizing a first coil with a first current, thereby influencing the flow in the first width region, and introducing a second magnetic flux into the second magnetic circuit by energizing a second coil with a second current, thereby influencing the flow in the second width region, wherein the first current is of a different strength than the second current, wherein at least one pole of the first or second magnetic circuit is displaceable relative to the mold in the thickness direction thereof, and wherein an air gap between a pole or a pole head and the mold in the first magnetic circuit is set to be of a different size than an air gap between a pole or a pole head and the mold in the second magnetic circuit.
26. The method as claimed in claim 25, further comprising: detecting flow velocities of the molten steel in the first and second width regions of the mold; if the flow velocity in the first width region is higher than in the second width region: increasing the magnetic flux density in the magnetic circuit associated with the first width region, or reducing the magnetic flux density in the magnetic circuit associated with the second width region, or increasing the magnetic flux density in the magnetic circuit associated with the first width region, and reducing the magnetic flux density in the magnetic circuit associated with the second width region.
27. The method as claimed in claim 25, wherein at least one pole of the first magnetic circuit and the second magnetic circuit is displaceable relative to the mold in the thickness direction thereof.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0051] Further advantages and features of the present invention will become apparent from the following description of non-limiting exemplary embodiments, wherein the following figures show:
[0052] FIG. 1 a section through a mold filled with molten steel and having an active or inactive electromagnetic brake according to the prior art,
[0053] FIG. 2 a plan view of a mold having a first electromagnetic brake according to the prior art,
[0054] FIG. 3 a plan view of a mold having a second electromagnetic brake according to the prior art,
[0055] FIG. 4 a plan view of a mold having an electromagnetic brake not according to the invention,
[0056] FIG. 5 a plan view of a mold having a first electromagnetic brake according to the invention,
[0057] FIG. 6 a plan view of a mold having a second electromagnetic brake according to the invention,
[0058] FIG. 7 a plan view of a mold having a third electromagnetic brake according to the invention,
[0059] FIG. 8 a plan view of a mold having a fourth electromagnetic brake according to the invention,
[0060] FIG. 9 a plan view of a mold having a fifth electromagnetic brake according to the invention,
[0061] FIGS. 10a to 10d each a perspective view of a pole head,
[0062] FIG. 11 a front view and a plan view of a mold having an electromagnetic brake according to the invention,
[0063] FIG. 12 a front view of a variant of the electromagnetic brake according to FIG. 11.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0064] In the figures, the same reference signs are assigned to the same component parts or groups.
[0065] FIG. 4 shows a schematic diagram of a design, not according to the invention, of an electromagnetic brake for a slab mold, in particular a thin-slab mold, of a continuous casting assembly. In a central region between the first and second width regions B.sub.1, B.sub.2 of the mold 1, molten steel is fed into the mold 1 through a submerged entry nozzle, not shown here. Further details regarding the introduction of molten steel and regarding the fluid-mechanical phenomena can be found, for example, in Chapter 10.3 Electromagnetic Equipment for Slabs from the reference book [0066] The Making, Shaping and Treating of Steel, The AISE Steel Foundation, 11.sup.th edition, 2003.
[0067] According to FIG. 4, in a first width region B.sub.1 of the mold 1, a magnetic flux (represented by the magnetic field line F.sub.1) is introduced into the mold 1 by two coils 3a, 3c and two poles 4a, 4b. The magnetic flux F.sub.1 influences the melt in the first width region, generally slowing it down. In an analogous manner, another magnetic flux (represented by the magnetic field line F.sub.2) is introduced into a second width region B.sub.2 of the mold 1 by two further coils 3b, 3d and two further poles 4a, 4b. The magnetic flux F.sub.2 can influence the melt in the second width region. The (electro)magnetic flux density in the first width region B.sub.1 is set by the energization of the coils 3a, 3c; the magnetic flux density in the second width region B.sub.2 is set by the energization of the coils 3b, 3d. Thus, the magnetic flux F.sub.1, F.sub.2 in the respective width regions B.sub.1, B.sub.2 of the mold 1 can be set via the current supplied to the coils 3a. . . 3d and/or the number of turns of the coils. Theoretically, it is possible that instead of two coils 3a, 3c or 3b, 3d per magnetic circuit, there is also only one coil provided (e.g., 3a or 3d). Likewise, in the embodiment according to FIG. 4, it is possible to set the directions of the magnetic fluxes in the two width regions B.sub.1, B.sub.2 differently, so that, for example, the field line F.sub.1 penetrates the mold 1 in the first width region B.sub.1 from top to bottom and the field line F.sub.2 penetrates the mold 1 in the second width region B.sub.2 from bottom to top.
[0068] FIG. 5 schematically shows a first design, according to the invention, of an electromagnetic brake for a slab mold of a continuous casting assembly. In contrast to FIG. 4, at least one pole 4a, 4b is designed to be displaceable relative to the associated yoke 2. As shown, both poles 4a, 4b associated with the left width region B.sub.1 are each designed to be displaceable relative to the left yoke 2. In addition, both poles 4a, 4b associated with the right-hand width region B.sub.2 are also each designed to be displaceable relative to the right-hand yoke 2. Due to the displaceability of at least one pole 4a, 4b, the air gap between the pole 4a, 4b and the mold 1 can be varied, so that the magnetic flux density F.sub.1 in the left width region B.sub.1 can be set to be stronger or weaker than the magnetic flux density F.sub.2 in the right width region B.sub.2. To enable trimming of the magnetic flux densities during operation, an actuator is associated with at least one pole and can displace the pole. The displacement direction of the poles 4a, 4b is indicated by arrows in FIGS. 5 to 9 and 11. Thus, in the embodiment of FIG. 5, the magnetic flux densities F.sub.1, F.sub.2 can be adjusted by displacing at least one pole 4a, 4b. If necessary, the coils 3a, 3c or 3b, 3d can additionally be energized differently.
[0069] FIG. 6 shows a simplified embodiment of the electromagnetic brake of FIG. 5. In contrast to FIG. 5, the simplified embodiment has only a single coil 3a above the mold 1 and only a single coil 3b below the mold 1. Accordingly, in this embodiment, the magnetic flux densities F.sub.1, F.sub.2 can be adjusted only by moving at least one pole 4a, 4b.
[0070] The embodiments of FIGS. 7 and 8 correspond to the embodiments of FIGS. 5 and 6, except that pole heads 6 are arranged between the poles 4a, 4b of a magnetic circuit F.sub.1, F.sub.2 and the mold 1. In addition, the field lines F.sub.1, F.sub.2 in FIG. 8 run in opposite directions to the field lines F.sub.1, F.sub.2 of FIG. 6. By means of the pole head 6, the magnetic flux density inside the mold 1 can be selectively changed, wherein a larger distance between the pole head 6 and the molten steel reduces the magnetic flux density and a smaller distance between the pole head 6 and the molten steel increases the magnetic flux density. The pole head 6 is detachably connected to the pole 4, e.g., via a screw, plug-in or clamp connection.
[0071] In FIGS. 4-8, the central regions 5 are magnetically optional, i.e., it makes no difference to the magnetic field whether they are present or not. Nevertheless, the central regions 5 may be preferred for mechanical reasons or to guide the yokes.
[0072] FIG. 9 shows a fifth embodiment of the electromagnetic brake according to the invention. In this embodiment, three magnetic circuits, represented by the field lines F.sub.1, F.sub.2 and F.sub.3, are impressed so that the molten steel emerging from a submerged entry nozzle 7 is braked to a different extent in a central region B.sub.2 than in the lateral regions B.sub.1, B.sub.3, which are arranged to the left or right of the central region B.sub.2. The magnetic field lines F.sub.1 . . . F.sub.3 are impressed only by two coils 3a, 3b. Three poles 4a, 4b, 4c are arranged in each of the coils 3a, 3b shown above and below. The middle poles 4b are designed to be non-displaceable; the poles 4a, 4c arranged to the left and right of them are displaceable by actuators 9. Of course, the middle pole 4b or the middle poles can also be designed to be displaceable. As shown, the middle poles 4b are wider than the side poles 4a, 4c. It is possible that all poles 4a. . . 4c are of equal width or that the lateral poles 4a, 4c are wider than the middle poles 4b.
[0073] It is also possible to equip individual, several or also all poles with pole heads in the embodiment according to FIG. 9. The (local) field strength can again be set via a pole head or the pole heads.
[0074] FIGS. 10a to 10d each show a pole head 6; the pole heads of FIGS. 10b and 10c are detachably connected to a pole 4 by screw connections.
[0075] FIG. 10a shows a pole head 6 formed by two elements 12. The elements 12 are detachably connected to the pole 4 by screw connections. By way of example, the upper element 12 extends less far in the thickness direction d of the mold than the lower element 12. It is not necessary that the elements 12 completely cover the end face 10 of the pole 4. The elements 12 have the effect that the local magnetic flux density, for example, is higher in the region of the lower element than in the region of the upper element, because the air gap between the upper element and the mold is larger than between the lower element and the mold. Since local differences in the magnetic flux density also locally influence the flow in the mold, pole heads are a good means to be able to locally influence flows in the mold. The elements 12 are made of low-carbon steel.
[0076] FIG. 10b shows an arc-shaped pole head 6. The shape of the pole head 6 can be used to adjust the local flux density.
[0077] FIG. 10c shows a pole head 6 in which two elements 12 are arranged one above the other and are connected to the pole 4.
[0078] FIG. 10d shows a pole head 6 formed from a plurality of rod-shaped, discrete elements 12. The elements 12 can be mechanically connected to the end face 10 of the pole 4 so that the pole head 6 can form different shapes (compare the plugging of Lego bricks onto a base plate). Specifically, the elements 12 can be inserted into slots 11 and secured.
[0079] Depending on the application, it is possible to place no pole head or one or more elements 6 of the same or different length on a pole 4. In addition, it is possible to arrange pole heads on the end face 10 of the pole 4 and/or at the right or left or the upper or lower peripheral edge of the pole. This allows the distribution of the magnetic field in the mold or the flux density acting on the molten steel to be adapted to existing requirements.
[0080] FIG. 11 shows a front view and a plan view of a mold 1 with two electromagnetic brakes arranged one above the other in the height direction h. As already described further above, molten steel is fed into the mold 1 via a submerged entry nozzle 7. As melt is fed to the mold 1 via the submerged entry nozzle 7 and at the same time the partially solidified strand formed in the mold 1 is withdrawn from the mold, a generally constant casting level 8 is formed. In the first width region B.sub.1, a magnetic field F.sub.1 is introduced by the coils 3a, 3c and the poles 4a, 4b associated with the coils. The magnetic field is closed via the left yoke 2. The magnetic flux density F.sub.1 can be set on the one hand by the current applied and the number of turns in the coils 3a, 3c and on the other hand by displacing the pole 4a by the actuator 9. The same applies for the second width region B.sub.2 and the magnetic flux density F.sub.2. Accordingly, the braking effect on the flow of the melt emerging from the submerged entry nozzle 7 can be set separately for both width regions B.sub.1, B.sub.2 of the mold 1.
[0081] By arranging a plurality of electromagnetic brakes one above the other, the flow of the molten steel can be variably influenced at different heights below the casting level.
[0082] FIG. 12 shows an alternative arrangement to the front view of FIG. 11, wherein an acute angle α, here an angle α=10°, is set between the yokes 2 and the casting level 8. This allows the electromagnetic brake to be accommodated in the machine head of the continuous caster in an even more space-saving manner.
LIST OF REFERENCE SIGNS
[0083] 1 mold
[0084] 2 yoke
[0085] 3a. . . 3d coil
[0086] 4, 4a, 4b, 4c pole
[0087] 5 central region
[0088] 6 pole head
[0089] 7 submerged entry nozzle
[0090] 8 casting level
[0091] 9 actuator
[0092] 10 end face
[0093] 11 hole
[0094] 12 element
[0095] b width direction of the mold
[0096] B.sub.1, B.sub.2, B.sub.3 width region of the mold
[0097] d thickness direction of the mold
[0098] F, F.sub.1, F.sub.2, F.sub.3 magnetic field line
[0099] h height direction of the mold
[0100] α angle of inclination
