WO2025201630A1

WO2025201630A1 - Mold flow control device for continuous casting mold

Info

Publication number: WO2025201630A1
Application number: PCT/EP2024/058106
Authority: WO
Inventors: Hongliang Yang; Bengt Rydholm; Nils Peter JACOBSON; Niklas VALLMAN; Frank Lensing; Yasin Akmese; Wilfried Klos; Jörn HOFFMEISTER
Original assignee: ABB Schweiz AG; SMS Group GmbH
Current assignee: ABB Schweiz AG; SMS Group GmbH
Priority date: 2024-03-26
Filing date: 2024-03-26
Publication date: 2025-10-02
Anticipated expiration: 2026-09-26

Abstract

A mold flow control device (1) for a casting mold (3) of a continuous casting machine comprises a manipulator (10) and an electric power supply system (60) for upper and lower coil assemblies (20, 40). The electric power supply system has an upper coil power supply (62) for supplying any of AC power, DC power, and superimposed AC and DC power to the upper coil assembly (20); a lower coil power supply (64) for supplying at least DC power to the lower coil assembly (40); and a power supply controller (66). The power supply controller (66) configured for operating the upper and lower coil power supplies (62, 64) independently of each other and in any combination with each other, and has a plurality of selectable flow control operation modes.

Description

MOLD FLOW CONTROL DEVICE FOR CONTINUOUS CASTING MOLD

Field of the Invention

The present disclosure relates generally to the field of metallurgical engineering and particularly steelmaking, more specifically, to devices used in continuous casting machines. The invention concerns improvements in mold flow control devices for continuous casting machines. Specifically, aspects of the invention relate to a mold flow control device for a casting mold of a continuous casting machine, in particular a mold flow control device being adapted for stirring and/or braking by applying AC and/or DC voltages. Further aspects relate to a casting mold with such a mold flow control device.

Technical background

Continuous casting is a critical process in the metallurgy industry, enabling the efficient, high- volume production of metal sections (slabs). In this process, molten metal is solidified into a slab for subsequent rolling in the finishing mills. A key component in this process is the casting mold, which significantly influences the quality and efficiency of the metal casting. Traditional casting molds come in various designs, such as parallel and funnel-type molds, each presenting unique challenges in controlling the flow of molten metal.

Existing technologies provide various solutions for controlling the flow within these molds. These include electromagnetic stirring systems, braking devices, and flow-modifying inserts. However, these solutions usually cater to a generic set of requirements but do not address the specific needs of different mold types or casting conditions effectively. This lack of specificity can lead to suboptimal casting outcomes, such as uneven solidification, defects in the cast product, and inefficiencies in operation. Alternatively, a mold control device may be tightly integrated with a mold and optimized for a particular mold design, but not easily applicable to other mold designs. An example for such a mold flow device is given in WO 2024/008804 Al.

An additional issue is the mold changeover time in case of change or maintenance of the mold. Current systems often require significant downtime for mold changes, which directly impacts production efficiency and operational cost. WO 2024/046708 Al describes a continuous-casting apparatus using a continuous-casting mold. The continuous-casting apparatus comprises a device with at least one electromagnetic coil unit for applying magnetic fields to the melt in the continuous-casting mold. This device is arranged laterally in relation to the continuous-casting mold. Further, the device with the electromagnetic coil unit is movable translationally and horizontally in the direction of the continuous-casting mold or away from it.

Despite advancements in continuous casting technologies, there remains a significant challenge in providing a versatile mold flow control solution that allows for optimal performance and adaptability to various molds and casting conditions in continuous casting operations, leading to excellent product quality at reduced cost.

Summary of the invention

In view of the above, a mold flow control device according to claims 1 and a casting mold according to claim 12 are provided. Further aspects are also directed to methods of continuous casting using the mold and the mold flow control device, and to the use of the mold and the mold flow control device for continuous casting.

An advantage of embodiments is that the mold flow control device, and in particular the control of its electromagnetic components, can be easily and flexibly adapted to different mold types and casting conditions, including high-throughput casting. Moreover, embodiments allow for rapid mold changes. Moreover, embodiments allow for on-site fine tuning. Thereby, it becomes possible to provide a versatile mold flow control solution that allows for optimal performance and adaptability in a large number of different continuous casting operations, and thus for high quality and efficiency of the casting process.

Further advantages, features, aspects and details that can be combined with embodiments described herein are evident from the dependent claims, the description and the drawings.

Brief description of the Figures:

The details will be described in the following with reference to the figures, wherein Figs. la,b are cross-sectional side views of a mold flow control device according to an embodiment;

Fig. 2 is a perspective view of the upper coil assembly of the mold flow control device of Figs, la, lb;

Fig. 3 is a perspective view of the lower coil assembly of the mold flow control device of Figs, la, lb;

Figs. 4a, b are perspective views of a mold flow control devices according to embodiments;

Figs. 5a-d are schematic side views of casting molds with mold flow control devices according to embodiments of the invention;

Figs. 6a-c are schematic illustrations of stirring modes carried out by an upper coil assembly of a mold flow control device according to an embodiment of the invention;

Figs. 7a, b are flow patterns for high throughput casting (a) without operation of a mold flow control device, and (b) with a mold flow control device according to an embodiment of the invention operating in braking mode; and

Figs. 8a, b are flow patterns for high throughput casting (a) without operation of a mold flow control device, and (b) with a mold flow control device according to an embodiment of the invention operating in combined mode with inward stirring.

Detailed description of the Figures and of embodiments:

Reference will now be made in detail to the various embodiments, one or more examples of which are illustrated in each figure. Each example is provided by way of explanation and is not meant as a limitation.

Within the following description of the drawings, the same reference numbers refer to the same or to similar components. Generally, only the differences with respect to the individual embodiments are described. Unless specified otherwise, the description of a part or aspect in one embodiment can be applied to a corresponding part or aspect in another embodiment as well. Further, any features illustrated or described as part of any one of these embodiments or aspects are optional unless included in claim 1, and can be used in conjunction with any other embodiment or aspect to yield yet a further embodiment or aspect. It is intended that the present disclosure includes such modifications and variations.

Figs, la is a cross-sectional view of a casting mold 3 with mold flow control device 1 according to an embodiment of the invention.

The mold 3 belongs to a continuous caster and is designed to cast slabs. For this purpose, the mold 3 has lateral walls 7 parallel to each other and delimiting an inner mold space (coquille)

2 for receiving the molten metal. In Fig. la, only one of the lateral walls 7 is shown, and the inner space 2 is delimited from the other side by another lateral wall.

The inner mold space 2 is further delimited by a pair of narrow lateral walls, parallel to the image plane of Fig. la.

The mold wall 7 is formed by a solid metal body delimiting the inner mold space 2. The mold

3 can be any mold for continuous slab casting, and may have other typical elements of such a mold, such as refractory lining of the nozzle walls and a cooling system.

The mold 3 further has a nozzle (not shown) for directing the molten metal into the inner mold space 2. The mold is configured to be fed by the nozzle with molten metal from a top side, and for general downward flow of the metal through the inner mold space 2 and for downward discharge of a strand of the metal. The nozzle may be a submerged nozzle having its outlet into the inner mold space arranged below the level of the liquid metal meniscus (below a surface of the bath of molten metal during operation).

The mold flow control device 1 further has upper and lower coil assemblies 20, 40 inserted within respective lateral recesses of the mold 3, and specifically of the side wall 7 of the mold 3. These lateral recesses are delimited from each other by a protruding portion 7a of the side wall 7.

Fig. 2 shows a perspective view of the upper coil assembly 20. The upper coil assembly has a main body housing a plurality of magnetic cores, on which respective coils are wound. These cores with coils are surrounded by a housing. On a distal side (far side in Fig. 2), protruding core portions 22 of the cores can be seen to protrude from the housing. The cores extend along a coil axis, and the coils are wound about the coil axis. In the upper coil assembly 20 of Fig. 2, the coil axis extends from the proximal end (towards the viewer in Fig. 2) to the distal end (away from the viewer and having the protruding core portions 22). The upper coil assembly includes a plurality of the iron cores, their axes being parallel to each other, as can be seen by the protruding portions 22 of the cores.

The protruding core portions (distal ends) 22 are inserted like fingers into respective concave portions in the mold 3.

The cross-section of Fig. la is taken through one of these protruding core portions 22. It can be seen how in Fig. la protruding core portions 22 are inserted like fingers into respective concave portions in the mold 3 (specifically into concave portions in the recess within the mold’s lateral wall 7. In contrast, Fig. lb shows a cross-section in a plane without core portion 22. By inserting the protruding core portions 22 into concave portions in the mold’s lateral wall 7, a particularly advantageous magnetic coupling can be achieved. Generally, the mold’s lateral wall 7 has respective upper coil assembly contacting portions formed as recesses, and these upper coil assembly contacting portions preferably have concave cavities for insertion of the respective protruding core portions 22.

When inserted in the mold as shown in Figs, la, lb, the coil axis of the upper coil assembly 20 extends perpendicular to a lateral wall surface of the mold 3, i.e., is directed towards the mold, the iron cores are located at a vertically overlapping position with a meniscus area of the mold; the iron cores have a proximal coil-winding portion on which a coil is wound, and a distal protruding portion, the protruding portion being directed towards the mold; the protruding portions protruding from a coil assembly housing of the upper coil assembly; the protruding portions being insertable into corresponding outer recesses of a lateral mold wall portion (7) of the mold.

Fig. 3 shows a perspective view of the lower coil assembly 40. Like the upper coil assembly of Fig. 2, also the lower coil assembly of Fig. 3 has a main body housing a plurality of magnetic cores, on which respective coils are wound. These cores with coils are surrounded by a housing. On a distal side (far side in Fig. 3), distal ends 42 of the cores can be seen to protrude from the housing. These distal ends 42 are again inserted like fingers into respective concave portions in the mold 3. The cross-section of Fig. la is taken through one of these protruding core portions 42. It can be seen how in Fig. la distal ends 42 are inserted like fingers into respective concave portions in the mold 3 (specifically into concave portions in the recess within the mold’s lateral wall 7). In contrast, Fig. lb shows a cross-section in a plane without core portion 42. Generally, the mold’s lateral wall 7 has respective lower coil assembly contacting portions formed as recesses, and these lower coil assembly contacting portions preferably have concave cavities for insertion of the respective protruding core portions 42.

The above description of further details of the upper coil assembly 20 given herein applies likewise also to the lower coil assembly 40.

The protruding core portions 42 of the lower coil assembly 40 are larger (in vertical height and/or cross-sectional area) and/or protrude more into the mold than the protruding portions 22 of the upper coil assembly (have larger horizontal protruding length). Thereby, the protruding core portions 22 and 42 are respectively optimized for coupling of AC and DC magnetic fields.

As can also be seen from Figs, la and lb, the mold wall 7 has, between the upper and lower coil assembly contacting portions, a protruding wall portion 7a that separates the upper and lower coil assembly contacting portions from each other.

Fig. 4a shows a perspective view of the mold flow control device 1 of an embodiment. The above description of Figs. 1 to 3 is applicable to the mold flow control device 1, too. In addition, Fig. 4a shows a manipulator 10. The manipulator 10 has an upper coil receiver 12 in which the upper coil assembly 20 is mounted, and a lower coil receiver 14 in which the lower coil assembly 40 is mounted.

The manipulator 10 allows horizontal movement of the upper and lower coil receivers 12, 14 and thereby of the upper and lower coil assemblies 20, 40. Thereby, the upper and lower coil assemblies 20, 40 can be brought into a mold-coupled position, in which the upper and lower coil assemblies 20, 40 are magnetically coupled to lateral mold wall portion (7) of the mold as shown in Fig. la and lb. By horizontal movement away from the mold, the upper and lower coil assemblies 20, 40 can be brought into a retracted position at a distance from the mold.

The manipulator 10 may advantageously also allow vertical movement of the upper and lower coil receivers 12, 14. Further, the upper and lower coil receivers 12, 14 may be moved together or independently from each other, in the vertical and/or horizontal direction. The horizontal movement allows fast and easy access to the mold, e.g., in case of a mold change or mold maintenance. The vertical movement allows flexible positioning of the of the upper and/or lower coil receivers 12, 14, and thereby contributes to the adaptability to different mold types and flow conditions.

Fig. 4b is a view of the mold flow control device 1 of Fig. 4a with empty upper and lower coil receivers 12, 14 (i.e., without upper and lower coil assemblies 20, 40).

The upper and lower coil receivers 12, 14 can be individually and selectively equipped with respective upper and lower coil assemblies 20, 40 as needed, in order to accommodate for a large variety of mold types and casting conditions. Some possible configurations are shown schematically in Figs. 5a-d, discussed further below.

Next, some further possible aspects relating to the manipulator are described.

According to an aspect, the mold flow control device 1 includes the upper coil 20 mounted in the upper coil receiver 12. According to a further aspect, the mold flow control device 1 further includes the lower coil 40 mounted in the lower coil receiver 14. Alternatively, either one of the manipulator’s upper coil receiver 12 or lower coil receiver 14 may be empty.

According to a further aspect, the manipulator is movable, as a single unit, between a mold- coupled position, in which any upper and lower coil assemblies 20, 40 mounted on the manipulator’s respective upper and lower coil receivers 12, 14 are magnetically coupled to one of the lateral walls 5, 7 of the mold 1, and a retracted position at a distance from the mold 1. According to a further aspect, the mold flow control device comprises a guiding system for guiding the manipulator between the mold-coupled position and the retracted position. Thereby, the manipulator can be retracted to the stand-by position during mold change, and inserted to the mold frame during operation.

The manipulator may be a single body and movable as a single body. Alternatively, the manipulator may allow for individual relative motion of the upper and lower coil receivers 12, 14.

Next, further possible aspects relating to the upper and lower coil assemblies are described.

According to an aspect, the upper and/or lower coil assembly includes a plurality of iron cores for the upper/lower coils. Axes of the iron cores may be parallel to each other and directed toward the mold when the manipulator is in the mold-coupled position. The iron cores may be located at a vertically overlapping position with a meniscus area of the mold. The iron cores may have a proximal coil-winding portion on which a coil is wound, and a distal protruding portion. The distal protruding portion may end in an open end towards the mold.

Next, aspects relating to the position of the upper and lower coil assemblies relative to the casting mold are described. According to an aspect, the lateral wall 7 of the mold 3 has an upper coil assembly contacting portion for contacting the upper coil assembly 20, a lower coil assembly contacting portion for contacting the lower coil assembly 40, and a protruding portion 7a arranged between the upper and lower coil assembly contacting portions for separating the upper and lower coil assembly contacting portions from each other. According to a further aspect, the mold flow control device is compatible with at least parallel and funnel-type molds.

According to a further aspect, the upper and/or lower coil receiver is adapted for mounting an upper/lower coil assembly therein so that a coil axis is perpendicular to the lateral side wall of the mold (is directed towards the mold).

According to a further aspect, the upper coil receiver is located at a vertically overlapping position with a meniscus area of the mold.

Further details regarding the mechanical structure and actuation of the mold flow control device’s manipulator are described in WO 2024/046708 Al (see in particular Figs. 6 and 7 and their description), which is incorporated by reference in its entirety herein.

Fig. 4a, 4b also contain a schematic view of an electric power supply system 60 of the mold flow control device 1. The electric power supply system 60 is configured to provide electric power to the upper and lower coil assemblies 20, 40. The electric power supply system 60 has an upper coil power supply 62, a lower coil power supply 64, and a power supply controller 66 configured for operating the upper and lower coil power supplies 62, 64.

The upper coil power supply 62 is configured for supplying any of AC power, DC power, and superimposed AC and DC power to the upper coil assembly 20. For this purpose, the upper coil power supply 62 may have an AC power source, a DC power source, and a superimposing circuit for superimposing the outputs from the AC and DC power sources. The output circuit may further comprise a switch circuitry for selectably outputting either the AC power from the AC power source or the DC power from the DC power source or the superimposed AC and DC power from the superimposing circuit to the upper coil assembly. Alternatively, the upper coil power supply 62 may comprise a variable inverter with semiconductor switches operable in a DC mode for generating DC current, an AC mode for generating AC current, and a combined mode for outputting a current having a combination of DC and AC components.

The lower coil power supply 64 is configured for supplying at least DC power to the lower coil assembly 40; but it may also be configured analogously for supplying any of AC power, DC power, and superimposed AC and DC power to the lower coil assembly 40, as described above for the upper coil power supply 62.

Herein, the mentioning of just DC power herein means preferably that no AC power is superimposed on the DC power, and vice versa the mentioning of just AC power herein means preferably that no DC power is superimposed on the AC power.

While the above Figures only show one side of the mold, it is understood that the mold flow control device 1 may comprise a pair of (first and second) manipulators 10, each being as described above, and each being arranged on a respective (first and second) lateral side of the mold. Although there may be two separate (first and second) electric power supply systems for the respective (first and second) upper and lower coil assemblies, it is more preferable to provide a single electric power supply system 60 for the first and second upper and lower coil assemblies. The electric power supply system 60 may comprise an upper coil power supply 62 for supplying power to the first and second upper coil assemblies, and a lower coil power supply 64 for supplying power to the first and second lower coil assemblies. Herein, it is typically assumed that the power supplied to the first upper / lower coil assembly is the same as the power supplied to the second upper / lower coil assembly, respectively, unless stated otherwise (such as for example in Fig. 6c discussed below).

The electric power supply system 60 further has a power supply controller 66 configured for operating the upper and lower coil power supplies 62, 64 independently of each other and in any combination with each other. The power supply controller 66 has a plurality of selectable flow control operation modes, i.e., instructions for causing the upper and/or lower coil power supplies 62, 64 to supply power to the upper and/or lower coil assemblies 20, 40 in a prescribed manner for achieving a desired flow control. The flow control operation modes can be selected by issuing a corresponding command to the power supply controller 66, and the power supply controller 66 and is configured for operating the upper and lower coil power supplies 62, 64 according to any selected one of these flow control operation modes.

These multiple selectable operation modes allow for a flexible operation of the mold flow control device in a large number of mold types and flow conditions, with minimal configuration effort.

A number of these multiple operation modes are now described in further detail in the following.

Combined mode:

In the combined mode, the upper coil power supply 62 supplies superimposed AC and DC power to the upper coil assembly 20, and the lower coil power 64 supplies DC power to the lower coil assembly 40. The supplying of superimposed AC and DC power to the upper coil assembly 20 may, in particular, induce simultaneous stirring and braking in the mold.

This combined mode is particularly effective if the upper coil assembly 20 is overlapping with a meniscus portion. The supplying of superimposed AC and DC power to the upper coil assembly 20 may, in particular, include simultaneous stirring and braking in the meniscus portion.

In the combined mode, the upper part coil is fed with a combination of DC and AC current. The upper coil can thereby create several patterns of stirring force in the meniscus area such as inward stirring, outward stirring and rotational stirring.

The lower part coil is preferably fed with DC current. The lower DC magnetic field may thereby be used to reduce the penetration flow and stabilize the flow pattern in the mold.

Braking mode:

In the braking mode, the upper and/or lower coil power supply 62, 64 supplies DC power to the upper and/or lower coil assembly 20, 40, respectively. The supplying of DC power to the upper and/or lower coil assembly 20, 40 may, in particular, include braking in a meniscus portion and/or of a Submerged Entry Nozzle jet flow within the mold.

Preferably, in the braking mode, if the upper coil assembly is mounted, the upper coil power supply 62 supplies DC power to the upper coil assembly 20, and the lower coil power supply 64 supplies DC power to the lower coil assembly 40. For example, the upper part coil and lower part coil are installed into the mold and fed with DC current. Alternatively, only the lower part coil may be installed in the mold and fed with DC current.

This operation mode is particularly effective for high throughput casting and most steel grades.

Stirring mode:

In the stirring mode, the upper coil power supply 62 supplies AC power (either alone or as a combination of superimposed AC and DC power) to the upper coil assembly 20. The lower coil power supply 64 may be disabled.

This stirring mode is particularly effective if the upper coil assembly 20 is overlapping with a meniscus portion. The supplying of AC power to the upper coil assembly (20) includes stirring in a meniscus portion.

In the stirring and the combined mode, the supplying of AC power may include stirring. The AC power may be supplied for various types of stirring forces, such as inward stirring force, outward stirring force, or rotational stirring force, as discussed further below with respect to Figs. 6a-6c.

Next, further general aspects relating to the selectable flow control operation modes are described.

According to an aspect, in the braking mode or combi mode, braking includes braking of SEN jet flow and/or braking in a meniscus portion within the mold. According to an aspect, in the stirring mode or combi mode, stirring includes stirring at the meniscus portion. According to an aspect, in combi mode, stirring of meniscus, and braking of the SEN jet flow and/or braking in the meniscus portion are performed simultaneously.

The flow control operation modes may include yet further variations. For example, powering of one of the coils may be disabled if the respective upper / lower coil 20, 40 is not mounted (not connected to the respective upper / lower power supply 62, 64). For example, if the upper coil assembly is not mounted, the upper coil power supply 62 may be disabled in the braking mode, so that only the lower coil power supply 64 supplies DC power to the lower coil assembly 40. Also, the power supplied to a first one of the upper and/or lower coils 20, 40 may be the same as or the inverse of the supplied to a second one of these coils. Next, some further possible aspects relating to power supply controller and its operation are described.

According to an aspect, the power supply controller 66 is configured for operating the upper and lower coil power supplies 62, 64 independently of each other and in any combination with each other. Further, the upper and lower coil assemblies 20, 40 may be subdivided in coil subunits (e.g., a respective left and right coil sub-unit for each of the upper and lower coil assemblies 20, 40), and powered by respective power supply sub-units of the upper and lower coil power supplies 62, 64. The power supply controller 66 may be configured for operating these power supply sub-units independently of each other and in any combination with each other.

According to a further aspect, the power supply controller 66 is configured for operating the upper and/or lower coil power supplies 62, 64 (e.g., in stirring and/or combined mode) for creating stirring patterns of stirring force in a meniscus portion of the mold, the stirring pattern including at least one of inward stirring, outward stirring and rotational stirring. In particular, the power supply controller 66 may be configured for operating the upper coil power supply 62 for supplying an inward-stirring AC power to the upper coil assembly 20 for inducing an inward-directed acceleration towards a meniscus.

According to a further aspect, the power supply controller 66 is configured for operating the upper and/or lower coil power supplies 62, 64 for braking of submerged nozzle (SEN) jet flow to reduce the flow momentum in case of high throughput, and/or for braking in the meniscus area to reduce the meniscus speed and fluctuation in case of high throughput.

According to a further aspect, the power supply controller 66 is configured for operating the upper and/or lower coil power supplies 62, 64 for stirring of meniscus speed to homogenize the meniscus temperature and improve subsurface quality for surface defect sensitive steel grades like automotive exposed steel grades.

According to a further aspect, the power supply controller 66 is configured for operating the upper and/or lower coil power supplies 62, 64 for stirring of meniscus and braking of SEN jet flow simultaneously in case of moderate throughput.

According to a further aspect, the upper and lower coil receivers 12, 14 can be individually and selectively equipped with respective upper and lower coil assemblies 20, 40 as needed, in order to accommodate for a large variety of mold types and casting conditions. Further, the upper and lower coil receivers 12, 14 allow for individually adjustable vertical positions, and thus for variable vertical distance, between the upper and lower coil assemblies 20, 40. Further, and crucially, these various possible coil configurations and positions can be further combined with various ones of the plurality of stirring modes available from the electric power supply system. Thereby, a large variety of stirring patterns and conditions can be created in order to accommodate a large number of mold types and casting conditions with one single kind of mold flow control device.

Some possible configurations are shown schematically in Figs. 5a-d:

In Fig. 5a, only a lower coil assembly 40 is mounted. The lower coil assembly is, for example, operated in DC (braking) mode. This operation may be appropriate for, e.g., a funnel -type mold with non-parallel and approaching side walls 7 as illustrated in Fig. 5a.

In Fig. 5b, both lower and upper coil assemblies 40, 20 are mounted. Both the lower and upper coil assemblies 40, 20 may, for example, be operated in DC (braking) mode. This operation may be appropriate for, e.g., a parallel mold with parallel side walls 7 as illustrated in Fig. 5b.

In Fig. 5c, both lower and upper coil assemblies 40, 20 are mounted. The lower and upper coil assemblies 40, 20 may, for example, be operated in combined mode, with combined AC -DC current is applied to the upper coil assembly 20, and pure DC current (i.e., with AC power being at most 5% of total power) applied to the lower coil assembly 40. This operation may again be appropriate for, e.g., a parallel mold with parallel side walls 7 as illustrated in Fig. 5b.

In Fig. 5d, only the upper coil assembly 20 is mounted. The upper coil assembly 20 may, for example, be operated in combined mode, with combined AC-DC current, as discussed above for Fig. 5c. This operation may again be appropriate for, e.g., a parallel mold with parallel side walls 7 as illustrated in Fig. 5b.

Also, the AC power supply can be further varied in a number of ways and according to different stirring modes, as illustrated in Figs. 6a-6c. The top portions of these Figures show a top view of the inner space (coquille) 2 of the mold, and the lower portions of these Figures show a side view of the inner space 2. In these Figures, stirring forces are applied to the molten metal in the mold’s inner space 2 from first and second upper coil assemblies arranged at both lateral sides of the mold. These stirring forces are exemplified by arrows. In the following, only one (e.g., first) of the upper coil assemblies is described, and unless mentioned otherwise, it is understood that the first and second upper coil assembly is powered in the same manner.

Fig. 6a shows an inward stirring mode. Therein, the upper coil power supply supplies an inward-stirring AC power to the upper coil assembly 20 for inducing an inward-directed acceleration. Thereby, in the inward stirring mode, the AC power applied to the upper coil assembly exerts an inward-directed stirring force (e.g., towards the nozzle 4) onto the molten metal in the inner space 2.

Inward stirring may have the advantageous effect that the stirring force acts in a direction from the narrow face to the SEN on both sides of the broad faces to increase the meniscus speed.

Fig. 6b shows an outward stirring mode. Therein, the upper coil power supply supplies an outward-stirring AC power to the upper coil assembly 20 for inducing an outward-directed acceleration. Thereby, in the outward stirring mode, the AC power applied to the upper coil assembly exerts an outward-directed stirring force (e.g., away from the nozzle 4) onto the molten metal in the inner space 2.

Outward stirring may have the advantageous effect that the stirring force acts in a direction from the nozzle (SEN) towards the narrow face on both sides of the broad faces to decrease the meniscus speed.

Fig. 6c shows a rotational stirring mode. Therein, the upper coil power supply supplies mutually oppositely directed stirring AC powers to the first and second upper coil assemblies for inducing accelerations in mutually opposite directions (e.g., both to the left or both to the right when viewed from the respective opposite sides of the mold). Thereby, in the rotational stirring mode, the AC power applied to the first and second upper coil assemblies exerts a rotational stirring force (e.g., around the nozzle 4) onto the molten metal in the inner space 2.

Rotational stirring may have the advantageous effect that the stirring force acts in a direction from one narrow face towards another narrow face on one side of broad face and acts in one opposite direction on another side of broad face.

Also, yet further stirring modes, not shown, are possible, such as a stirring mode in which inward stirring by the first upper coil assembly and outward stirring by the second upper coil assembly are combined for producing two rotational vertices. It is advantageous if the upper coil assembly 20 is positioned in a meniscus portion of the mold, so that its induced field overlaps with the meniscus 6 of the molten metal in the mold’s inner space 2, as illustrated in Figs. 6a-6c. To this purpose, the upper coil receiver is advantageously located at a vertically overlapping position with a meniscus area of the mold. Thereby, a particularly effective stirring becomes possible. Further, it is advantageous if the upper coil assembly 20 is positioned in a nozzle portion of the mold, so that its induced field overlaps vertically with the nozzle 4, as also illustrated in Figs. 6a-6c. To this purpose, the upper coil receiver is advantageously located at a vertically overlapping position with the nozzle 4 of the mold.

Analogous stirring modes as described above in conjunction with Fig. 6a-6c can also be applied by the lower coil power supply to the lower coil assembly. The lower coil assembly is arranged further below (e.g., below the nozzle 4 in Figs. 6a-6c).

Figs 7a and 7b illustrate advantageous flow patterns enabled by the selectable flow control operation modes according to aspects of the present invention. Fig. 7a shows a simulated flow pattern for high throughput casting without a flow control device. Fig. 7b shows a simulated flow pattern for the same casting conditions as in Fig. 7a, but with flow control device operating in braking mode. Herein, the dotted boxes illustrate the positions of the upper and lower coil assemblies 20, 40. As can be seen, the upper coil assembly 20 is arranged to vertically overlap with a meniscus 6 of the molten metal. Compared to Fig. 7a, the flow pattern of Fig. 7b produces a more even output at the bottom of the mold.

Fig. 8a shows a simulated flow pattern for low throughput casting without a flow control device. Fig. 8b shows a simulated flow pattern for the same casting conditions as in Fig. 8a, but with flow control device operating in combined mode. Herein, the dotted boxes illustrate the positions of the upper and lower coil assemblies 20, 40. As can be seen, the upper coil assembly 20 is arranged to vertically overlap with a meniscus 6 of the molten metal. Again, compared to Fig. 8a, the flow pattern of Fig. 8b produces additional stirring as well as a more even output at the bottom of the mold.

This illustrates a general advantageous aspect of the invention: Preferably, the upper coil is located at the meniscus area (with vertical overlap with the meniscus). Further, preferably, the upper boundary of upper coil is in the same level as meniscus (e.g., within up to 30% of the upper coil height). Further, the vertical center of the upper coil assembly is preferably above the upper edge of nozzle outlet. Thereby, a particular advantageous stirring pattern can be established, in particular in combination with inward stirring by the upper coil assembly.

According to aspects of the invention, the casting mold and the mold flow control device can be used in conjunction with a broad range of casting conditions for continuous casting. Some particularly advantageous casting conditions are described by means of example in the following.

According to an aspect, the casting mold is a thin-medium slab casting mold for slab thickness (at mold exit) of at least 50 mm, preferably at least 70 mm, and/or of at most 180 mm. Thin and/or medium thick slab casting provides the possibility of a wide variety of steel grades, low CO2 emission, high quality, high throughput, high productivity, and high flexibility.

Other possible aspects include thin slab casting (at cast the slab thickness between 50 and 160 mm, for example), and conventional slab casting (usually with cast slab thickness from 150 mm and above).

According to a further aspect, the casting mold is adapted for a throughput between 1.5 ton/min and 10 ton/min. Other casting conditions may include a slab width (at mold exit) of 900- 2600 mm, casting speed of 1.5 m/min- 6 m/min.

The casting mold and the mold flow control device can be used in conjunction with a broad range of steel grades. Possible steel grades include ultra-low carbon, low carbon, medium carbon, peritectic, high carbon and silicon steel grades.

According to a further aspect, the casting mold can be of any mold type, such as funnel mold or parallel mold.

In conclusion, according to aspects of the invention, two level of magnetic coils (upper and lower) are provided to control the mold flow independently. In the combined mode, the lower part coils may be fed with DC current to generate a DC magnetic field to brake the jet flow from the nozzle. Lower part coils of first and second lower coil assemblies in both sides of the broad face may form a closed magnetic loop.

The upper coil assembly can be fed with both AC and DC current simultaneously. With AC current, a traveling magnetic field can be created in the meniscus area to stir the meniscus, homogenize the meniscus temperature, and increase the meniscus temperature. With DC current, a DC magnetic field is created in the meniscus area to reduce the meniscus speed and meniscus fluctuation.

The fact that the electric power supply system has integrated the control for multiple flow control operation modes offers great advantages. In particular, it becomes possible to obtain a large coverage of many casting conditions and steel grades. Further, flexible operation modes are made available which combine braking and stirring functions in various ways. In particular relating to stirring, flexible patterns of stirring force which include inward stirring, outward stirring and rotational stirring become available. These advantages are particularly useful due to the upper and lower coil assemblies being mounted on a retractable manipulator that allows flexible positioning of the upper and lower coil assemblies, and fast retraction for quick mold change or other adjustments. Especially useful is a combination with the manipulator being vertically and horizontally movable. Thereby, a flexible operation of the mold flow control device in a large number of mold types and flow conditions becomes possible. While the foregoing is directed to embodiments, other and further embodiments may be devised without departing from the basic scope determined by the claims.

Claims

Claims:

1. A mold flow control device (1) for a casting mold (3) of a continuous casting machine, the mold flow control device (1) comprising: a manipulator (10) having an upper coil receiver (12) for mounting an upper coil assembly (20) therein, and a lower coil receiver (14) for mounting a lower coil assembly (40) therein, and being configured for magnetically coupling any upper and lower coil assemblies (20, 40) mounted on the manipulator’s respective upper and lower coil receivers (12, 14) to the mold (1), and an electric power supply system (60) for the upper and lower coil assemblies (20, 40), the electric power supply system having o an upper coil power supply (62) for supplying any of AC power, DC power, and superimposed AC and DC power to the upper coil assembly (20); o a lower coil power supply (64) for supplying at least DC power to the lower coil assembly (40); o a power supply controller (66) configured for operating the upper and lower coil power supplies (62, 64) independently of each other and in any combination with each other, wherein the power supply controller (66) has a plurality of selectable flow control operation modes and is configured for operating the upper and lower coil power supplies (62, 64) according to any one of the flow control operation modes, and wherein the flow control operation modes comprise a combined mode, the combined mode comprising instructions for causing the upper coil power supply (62) to supply superimposed AC and DC power to the upper coil assembly (20).

2. The mold flow control device according to claim 1, wherein the combined mode further comprises instructions for causing the lower coil power (64) to supply DC power to the lower coil assembly (40).

3. The mold flow control device according to any one of the preceding claims, wherein, in the combined mode, the supplying of superimposed AC and DC power to the upper coil assembly (20) includes simultaneous stirring and braking in a meniscus portion and/or of a Submerged Entry Nozzle jet flow within the mold.

4. The mold flow control device according to any one of the preceding claims, wherein the flow control operation modes further comprise at least one of the following a) and b): a) A braking mode comprising instructions for causing, if the upper coil assembly is mounted, the upper coil power supply (62) to supply DC power to the upper coil assembly (20), and causing the lower coil power supply (64) to supply DC power to the lower coil assembly (40); and b) A stirring mode comprising instructions for causing the upper coil power supply (62) to supply AC power to the upper coil assembly (20), and preferably for disabling the lower coil power supply (64).

5. The mold flow control device according to the preceding claim, wherein at least one of the following a) and b): a) In the braking mode, the supplying of DC power to the upper and/or lower coil assembly (20, 30) includes braking in a meniscus portion and/or of a Submerged Entry Nozzle jet flow within the mold; b) In the stirring mode, the supplying of AC power to the upper coil assembly (20) includes stirring in a meniscus portion and/or of a Submerged Entry Nozzle jet flow within the mold;

6. The mold flow control device according to any one of the preceding claims, wherein the power supply controller (66) is configured for operating the upper coil power supply (62) for supplying an inward-stirring AC power to the upper coil assembly (20) for inducing an inward-directed acceleration in a meniscus portion of the mold.

7. The mold flow control device according to any one of the preceding claims, wherein the lower coil power supply (62) is adapted for supplying any of AC power, DC power, and superimposed AC and DC power to the lower coil assembly (20).

8. The mold flow control device according to any one of the preceding claims, wherein the upper coil assembly includes a plurality of iron cores for the upper coils, wherein axes of the iron cores are parallel to each other and directed toward the mold when the manipulator is in the mold-coupled position.

9. The mold flow control device according to any one of the preceding claims, wherein the upper coil receiver is adapted for mounting an upper coil assembly therein so that a coil axis of the upper coil assembly is perpendicular to a lateral wall surface of the mold.

10. The mold flow control device according to any one of the preceding claims, wherein the upper coil receiver is located at a vertically overlapping position with a meniscus area of the mold.

11. The mold flow control device according to any one of the preceding claims, wherein the manipulator (10) is movable, as a single unit, between o a mold-coupled position, in which any upper and lower coil assemblies (20, 40) mounted on the manipulator’s respective upper and lower coil receivers (12, 14) are magnetically coupled to lateral mold wall portion (7) of the mold, and o a retracted position at a distance from the mold (1).

12. A casting mold having the mold flow control device according to any one of the preceding claims.

13. The casting mold according to claim 12, wherein a lateral mold wall portion (7) of the mold (3) has an upper coil assembly contacting portion for contacting the upper coil assembly (20), a lower coil assembly contacting portion for contacting the lower coil assembly (40), and a protruding wall portion (7a) arranged between the upper and lower coil assembly contacting portions for separating the upper and lower coil assembly contacting portions from each other.