Apparatus and method to control continuous casting, using electromagnetic brake

Abstract

Apparatus to control continuous casting, including a mold provided with at least one entrance end through which liquid metal is introduced. Furthermore, the apparatus to control continuous casting includes at least one electromagnetic brake associated with the mold, configured to induce in the liquid metal recirculation flows, and a control and command unit connected at least to the electromagnetic brake and configured to manage the functioning thereof.

Claims

1. Apparatus to control continuous casting, said apparatus comprising a mold provided with at least one entrance end through which liquid metal is introduced, at least one electromagnetic brake associated with the mold and configured to induce in said liquid metal recirculation flows, and a control and command unit connected at least to said electromagnetic brake and configured to manage functioning thereof, wherein the apparatus comprises detection means located, at least in a condition of use, above the at least one entrance end and each configured to detect at least a reciprocal distance with respect to a level of said liquid metal, wherein said control and command unit is also connected to said detection means to acquire data of each distance from each detection mean, wherein said control and command unit is configured to process the data of each distance from each detection mean in relation to positioning of said detection means, determine characteristic parameters of a development of a surface profile of said liquid metal based upon each distance, and command a drive at least of said electromagnetic brake based on said characteristic parameters of the development of said surface profile in order to determine predefined recirculation flows of the liquid metal, and wherein the characteristic parameters of the development of said surface profile of said liquid metal comprise an evolution speed of the surface profile and instant deviations from a temporal average for each detection mean.

2. Apparatus to control continuous casting as in claim 1, wherein the characteristic parameters of the development of the surface profile of said liquid metal further comprise a spatial gradient of the surface profile, a spatial average of the distances detected in different positions, and instant deviations from a spatial average for each detection mean.

3. Apparatus to control continuous casting as in claim 1, wherein said control and command unit is configured to command the drive at least of said electromagnetic brake so as to maintain said development of the surface profile uniform.

4. Apparatus to control continuous casting as in claim 1, wherein said detection means comprise a plurality of sensors located above a surface of the liquid metal, wherein each sensor is configured to detect a reciprocal distance with respect to the level of the liquid metal.

5. Apparatus to control continuous casting as in claim 4, wherein said sensors comprise induced current sensors and/or a group of sensors selected from thermal, optical, laser, radar or capacitive sensors.

6. Apparatus to control continuous casting as in claim 1, wherein said mold has a slab shape, and comprises walls defined by substantially flat plates located in opposite pairs and wherein a first pair of plates has bigger surface sizes than surface sizes of a second pair of plates, wherein the sensors are disposed aligned along an axis orthogonal to a casting axis, and wherein said axis is positioned substantially parallel to the first pair of plates.

7. Apparatus to control continuous casting as in claim 1, wherein said detection means comprise a detector configured to detect a distance with respect to the liquid metal, and a movement device configured to move the detector above the level of liquid metal.

8. Apparatus to control continuous casting as in claim 7, wherein said mold has a slab shape, and comprises walls defined by substantially flat plates located in opposite pairs and wherein a first pair of plates have a first surface size and a second pair of plates have a second surface size, wherein the first surface size is larger than the second surface size, wherein the movement device is configured to move the detector along a longitudinal axis orthogonal to a casting axis, wherein said longitudinal axis is positioned substantially parallel to a first pair of walls.

9. Apparatus to control continuous casting as in claim 7, wherein said detector is configured as a sensor selected in a group from induced current, thermal, optical, laser, radar or capacitive sensors.

10. Apparatus to control continuous casting as in claim 1, wherein the apparatus comprises a nozzle configured to discharge the liquid metal into the mold, wherein said nozzle is connected to the control and command unit which is configured to manage functioning of the nozzle, in relation to said characteristic parameters of the development of the surface profile detected.

11. Apparatus to control continuous casting as in claim 10, wherein displacement devices are associated with the nozzle in order to move the nozzle in a direction parallel to a casting axis and to modify positioning of its exit end in the mold, and wherein said displacement devices are connected to the control and command unit which is configured to determine a movement of the displacement devices in relation to said characteristic parameters of the development of the surface profile detected.

12. Apparatus as in claim 10, wherein delivery devices are associated with the nozzle, configured to deliver auxiliary stirring gases of the liquid metal into the nozzle, and wherein at least the delivery devices are connected to the control and command unit which is configured to determine a drive of the delivery devices in relation to said characteristic parameters of the development of the surface profile detected.

13. A method to control continuous casting of a liquid metal, comprising: introducing the liquid metal through an entrance end of a mold, managing, by a control and command unit, functioning of an electromagnetic brake associated with the mold, to induce in liquid metal recirculation flows, detecting data of at least a reciprocal distance with respect to a level of the liquid metal by means of detection means located, at least in a condition of use, above the entrance end, processing said data of at least a distance in relation to position of said detection means, determining characteristic parameters of a development of a surface profile, wherein the characteristic parameters comprise an evolution speed of the surface profile and instant deviations from a temporal average for each detection mean, driving at least of said electromagnetic brake based on said characteristic parameters of the development of said surface profile in order to determine predefined recirculation flows of the liquid metal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other characteristics of the present invention will become apparent from the following description of some embodiments, given as a non-restrictive example with reference to the attached drawings wherein:

(2) FIG. 1 is a schematic drawing of an apparatus to control continuous casting according to the present invention;

(3) FIG. 2 is a view from above of FIG. 1;

(4) FIG. 3 shows a variant of FIG. 1;

(5) FIG. 4 shows a further variant of FIG. 1;

(6) FIG. 5 schematically shows the fluid-dynamic motions in a mold.

(7) To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one embodiment can conveniently be incorporated into other embodiments without further clarifications.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

(8) With reference to the attached drawings, an apparatus 10 to control continuous casting, according to the present invention, is indicated as a whole with the reference number 10.

(9) The control apparatus 10, according to the present invention, comprises a mold 11 provided with an entrance end 12 through which the liquid metal 13 is introduced to be subsequently solidified.

(10) Preferential, although non-limiting, embodiments of the present invention provide that the mold 11 is configured to cast slabs.

(11) In particular, the invention can be applied to all types of continuously castable slabs, for example having thicknesses comprised between 22 mm and 500 mm and widths between 500 mm and 4500 mm.

(12) The mold 11 is provided with walls 14 suitably cooled by means of cooling devices, not shown.

(13) In particular, if the mold 11 is of the type for slabs, the walls 14 are defined by substantially flat plates located in opposite pairs and wherein a first pair 14a of plates has much bigger surface sizes than the surface sizes of a second pair 14b of plates.

(14) The solidification of the liquid metal 13 occurs in the mold 11 with the consequent formation of a solidified containing skin 15.

(15) The mold 11 extends along a substantially vertical or arched casting axis X.

(16) According to one aspect of the invention, the control apparatus 10 comprises at least one electromagnetic brake 16 associated with the mold 11 and configured to induce recirculation flows 17 in the liquid metal 13 (FIG. 5).

(17) The electromagnetic brake 16 can be attached to the mold 11, for example on the external surface of its walls 14.

(18) According to a possible solution (FIGS. 1-3), the control apparatus 10 comprises a plurality of electromagnetic brakes 16 which are associated on the surfaces which, during use, are external of the first pair 14a of walls of the mold 11.

(19) According to possible embodiments, the control apparatus 10 can comprise a plurality of electromagnetic brakes 16, for example at least one per wall 14 of the mold 11.

(20) According to a possible solution, the plates of the first pair 14a can each comprise a respective electromagnetic brake 16 which extends for the entire width of the plate.

(21) According to variant embodiments, the plates of the first pair 14a can each comprise a plurality of electromagnetic brakes 16 located adjacent and in a symmetrical position with respect to the center line of the mold 11.

(22) In particular (FIG. 4), it can be provided that for each plate of the first pair 14a there is at least one first electromagnetic brake 16, in this case two, distanced along the casting axis, located on one side with respect to the median axis of the mold 11, and at least one second electromagnetic brake 16, in this case two, distanced along the casting axis X, located on a second side, opposite the first with respect to the median axis of the mold 11. Furthermore, in a central position, that is, aligned with the median axis, for each plate of the first pair 14a another electromagnetic brake 16 can be provided interposed between the first and the second electromagnetic brake 16.

(23) The electromagnetic brake 16 can comprise a plurality of coils, possibly cooled, and suitably electrically powered to generate predetermined recirculation flows 17 in the mold 11.

(24) According to a further aspect of the present invention, the control apparatus 10 comprises a control and command unit 18 connected to the at least one electromagnetic brake 16 and configured to manage its functioning.

(25) By way of example only, the control and command unit 18 can be configured to control at least one electric parameter of the electric energy supplied to the electromagnetic brakes 16, such as the voltage and/or the electric current. By way of example only, it can be provided that the control and command unit 18 is configured to control at least one of either the intensity or frequency of the electric parameter above.

(26) According to further embodiments of the invention, the control apparatus 10 comprises detection means 19 located, at least in a condition of use, above the entrance end 12 of the mold 11 and each configured to detect at least a reciprocal distance 22 with respect to the level of the liquid metal 13.

(27) The control and command unit 18 can be configured to acquire the data of each distance 22 from each detection mean 19 and process them in relation to the positioning of the detection means 19, determining characteristic parameters of the development of the surface profile 20 of the liquid metal 13.

(28) Advantageously, the processing of the distance 22 in relation to the positioning of the detection means 19 allows to determine the shape of the whole surface profile 20 of the liquid metal 13 along the whole cross-section of the mold 11, and not only on localized and circumscribed portions as in some known solutions.

(29) Furthermore, the control and command unit 18 can process the data of each distance 22 determining, as characteristic parameters, the spatial average of the distances 22 detected in different positions, and the instant deviations therefrom for each detection mean 19.

(30) In some embodiments, other possible characteristic parameters can be the spatial gradient or also higher order derivatives of the surface profile 20, which allow to monitor the extent of the spatial variations in the development of the surface profile 20.

(31) The detection means 19 can be configured to detect the reciprocal distance 22 at predetermined time instants, for example in relation to specific operating steps of the casting process. According to variant embodiments, the detection means 19 can be configured to substantially detect the reciprocal distance 22 continuously.

(32) In these embodiments, the control and command unit 18 can process the data of each distance 22 determining, as characteristic parameters, the temporal average of the distance 22 on predetermined time intervals, and the instant deviations from it for each detection mean 19.

(33) In some embodiments, other possible characteristic parameters can be the evolution speed of the development of the surface profile 20, calculated starting from the time derivatives.

(34) The characteristic parameters associated with instant, temporal and spatial averages and deviations, allow to obtain an accurate determination of the development of the surface profile, since, for example, there is a reduction in the background noise effects linked to the type of sensors used and random errors in the detections due to the formation of bubbles or splashes of liquid metal 13. Furthermore, it is possible to immediately identify possible malfunctions in one or more detection means 19, for example if it/they sends/send data that are significantly and systematically far from the averages.

(35) The control and command unit 18 can also determine the action at least on the at least one electromagnetic brake 16 on the basis of the characteristic parameters of the development of the surface profile 20, in order to determine predefined recirculation flows 17 of the liquid metal 13.

(36) The control and command unit 18 can be configured to manage the functioning of the components above and command the drive of at least the electromagnetic brake 16, so as to maintain the development of the surface profile 20 uniform.

(37) Advantageously, the characteristic parameters associated with the spatial gradient and the evolution speed of the surface profile 20 allow to drive the electromagnetic brake 16, respectively, with suitable drive speed and intensity to efficiently regulate the recirculation flows 17.

(38) This characteristic therefore allows to obtain recirculation flows that are constant and regular in space and time, improving the quality of the cast product.

(39) According to one possible embodiment of the invention, the detection means 19 can comprise a plurality of sensors 21 located above the surface of the liquid metal 13.

(40) According to possible solutions, each sensor 21 is configured to detect a reciprocal distance 22 with respect to the level of the liquid metal 13.

(41) In particular, each sensor 21 is connected to the control and command unit 18 which is configured to acquire the data of each distance 22, process them in relation to the positioning of the sensors 21, and determine the surface profile 20.

(42) In particular, the control and command unit 18 can store at least the reciprocal position of each sensor 21 with respect to the other sensors, as well as with respect to the upper end 12 of the mold 11.

(43) The presence of a plurality of sensors 21 distributed above the level of the liquid metal allows to use sensors with a reduced detection field, that is, sensors of small sizes and not very invasive for the upper end 12 of the mold 11.

(44) According to possible solutions, the sensors 21 can comprise induced current sensors, that is, Eddy Current sensors. The use of this type of sensor allows to have rapid response times. Furthermore, this type of sensor allows to also reuse the latter on other molds and for different applications.

(45) According to possible variant embodiments, the sensors 21 can be selected from a group comprising thermal, optical, laser, radar or capacitive sensors.

(46) According to a possible solution of the invention, the sensors 21 can be disposed aligned along an axis Y orthogonal to the casting axis X.

(47) In the embodiment in which the mold 11 is of the type for slabs, the Y axis is positioned substantially parallel to the pair of walls with bigger sizes.

(48) For example, the plurality of sensors 21 can be distributed in a symmetrical manner, on one side and on the other, with respect to the casting axis X, as well as in scattered order.

(49) Furthermore, the sensors 21 can be equally distanced from each other to be able to detect the surface profile 20 in a uniform manner.

(50) Variations of the embodiments, provide that the plurality of sensors 21 is distributed only on one side, that is, only on a part of the surface of the liquid metal 13 with respect to the casting axis X.

(51) In these cases, it is assumed that the development of the surface profile 20 is symmetrical with respect to the casting axis X. These embodiments can be used on molds 11 with small sizes, where the surface profile 20 is almost symmetrical along the casting axis X.

(52) In variants of the present invention, the detection means 19 can comprise a detector 23, which can be for example a sensor of the type indicated above, configured to detect a distance 22 with respect to the liquid metal 13, and a movement device 24 configured to move the detector 23 above the level of liquid metal 13, that is, above the upper end 12.

(53) According to one possible solution, the movement device 24 is configured to move the detector 23 along a longitudinal axis Z orthogonal to the casting axis X.

(54) In the embodiment in which the mold 11 is of the type for slabs, the longitudinal axis Z is positioned substantially parallel to the pair of walls with bigger sizes.

(55) The movement device 24 can be provided with at least a guide element 25 on which the detector 23 is installed slidable along the longitudinal axis Z.

(56) The guide element 25 can be associated with the entrance end 12 of the mold 11.

(57) The guide element 25 can extend for the entire width of the mold 11.

(58) The detector 23 is connected to the control and command unit 18 which is configured to receive the distance data 22 detected instantly by the detector 23 during its movement, in this way performing a scanning of the surface of the liquid metal. The control and command unit 18, by processing this distance data 22, determines the characteristic parameters of the development of the surface profile 20.

(59) In some embodiments of the present invention, the control apparatus 10 according to the present invention comprises a nozzle 26 configured to discharge the liquid metal 13 into the mold.

(60) The nozzle 26 is connected to the control and command unit 18 which is configured to manage the functioning of the nozzle 26, in relation to the characteristic parameters of the development of the surface profile 20 detected.

(61) The nozzle 26 is positioned, through the upper end 12, in the mold 11, and is partly immersed in the liquid metal 13.

(62) According to possible solutions, the nozzle 26 can be associated with displacement devices 27 (FIG. 1) configured to move the nozzle 26 in a direction parallel to the casting axis X and modify the positioning of the exit end of the nozzle 26 in the mold 11.

(63) According to possible solutions, delivery devices 28 can also be associated with the nozzle 26, which are configured to deliver in the nozzle 26 auxiliary stirring gases of the liquid metal 13 in the mold 11.

(64) Auxiliary gases can comprise inert gases, such as argon.

(65) According to possible solutions, at least one, or both, of either the displacement devices 27 or the delivery devices 28 can be connected to the control and command unit 18 which is configured to determine a movement of the displacement devices 27 and/or the drive of the delivery devices 28 in relation to the characteristic parameters of the development of the surface profile 20 detected and to determine a control of the fluid-dynamic flows of the liquid metal 13 in the mold 11.

(66) According to some embodiments of the invention, the control and command unit 18 is configured to manage the functioning at least of the electromagnetic brake 16, and possibly of the displacement devices 27 and the delivery devices 28, so as to obtain desired recirculation flows 17 such as to allow to obtain a high quality cast product.

(67) Specifically, it is provided that the control and command unit 18, as a function of the development of the surface profile 20 detected, allows to generate double recirculation flows of the liquid metal 13, as shown in FIG. 5.

(68) In particular, this flow configuration allows to generate a first recirculation 17a which develops from the discharge end of the nozzle 26 toward the surface of the liquid metal 13, and a second recirculation 17b which develops from the discharge end of the nozzle 26 toward the inside of the mold 11.

(69) The first recirculation 17a allows to avoid a stagnation of the liquid metal 13 in the upper part of the mold, which determines the so-called freezing of the meniscus, that is, an unwanted cooling of the portion of liquid metal 13 present on the surface.

(70) By means of the detection of the surface profile 20 with the detection means 19, it is possible to determine the modes, that is, the development, of the recirculation flows 17 that are established inside the mold 11. The surface profile 20, that is, the shape of the meniscus, is closely connected to the speed of the flow of the liquid metal 13 in the first recirculation 17a. The amplitude of the waves and their positioning, that is, the type of development of the surface profile 20, allow to reliably determine the energy, the speed, and therefore the flow rate of the first recirculation 17a.

(71) Based on the flow rate of the first recirculation 17a, the control unit 18 is able to act on the functioning of the electromagnetic brakes 16, in order to optimize the motion of the recirculation flows 17 contained in the liquid metal 13.

(72) In particular, it is possible to obtain the correct flow distribution between the first recirculation 17a and the second recirculation 17b in any operating casting condition.

(73) It is clear that modifications and/or additions of parts may be made to the apparatus 10 as described heretofore, without departing from the field and scope of the present invention.

(74) For example, in one possible solution, the detection means 19 can be able to detect, in addition to the development of the surface profile, also the level of the meniscus of the mold 11.

(75) It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of control apparatus 10, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

(76) In the following claims, the sole purpose of the references in brackets is to facilitate reading: they must not be considered as restrictive factors with regard to the field of protection claimed in the specific claims.