FIELD OF THE INVENTION

The present invention concerns an apparatus and a method for the continuous casting of metal products, in particular slabs, or products with a rectangular section with a width much greater than the thickness.

BACKGROUND OF THE INVENTION

Continuous casting apparatuses which comprise an ingot mold configured to cast metal products, in particular slabs, are known.

The molten metal is introduced into the ingot mold to be progressively solidified with the formation of a solid skin.

Upon exiting the ingot mold, the cast product has a solidified external shell having the function of containing the liquid metal still present inside it. The ingot mold also defines a casting line along which the metal product in the process of solidification progressively advances, until it solidifies completely downstream of the ingot mold. The solidified product can then be sent to rolling, for example with an endless process, or be cut into sections to be rolled in a coil-to-coil or semi-endless process, or even taken from the line to be rolled in a subsequent process.

The ingot mold can be fed with molten metal from the tundish by means of at least one outlet nozzle of the SEN type (Submerged Entry Nozzle), that is, with the outlet of the metal disposed below the level of the liquid metal meniscus.

The nozzle can be provided with a main outlet, substantially axial, or a plurality of secondary outlets configured to direct the molten metal mainly toward the lower part of the ingot mold, and a plurality of secondary outlets configured to direct the molten metal mainly toward the lateral walls of the mold.

With this type of nozzles, but not only, inside the ingot mold it is difficult to control and regulate the speed and direction of the flows of metal that develop from the outlets, in order to make said flows uniform and therefore make the casting process as efficient and productive as possible.

Such problems of uneven and unstable flows of molten metal arise in particular in the meniscus zone, that is, at the upper level of the metal in the ingot mold.

Current continuous casting apparatuses provided with ingot mold and SEN are unable to effectively control the uniformity of the flows of metal in the mold, and are also unable to regulate their speed and/or direction, both from the central outlet as well as from the lateral outlets of the SEN.

Furthermore, due to the limitations of known apparatuses, it is difficult to achieve a continuous casting at high-speed in order to obtain a desired, high productivity of the apparatuses.

There is therefore the need to perfect an apparatus for the continuous casting of metal products that can overcome the disadvantages of the state of the art and bring all the requirements of control of such metal flow conditions.

In particular, one purpose of the present invention is to provide an apparatus for the continuous casting of multifunction metal products which, thanks to the possibility of regulating the flows of metal material in the ingot mold, for example in terms of speed and direction, increases the productivity of the apparatus even by 30-40% compared to known apparatuses.

Another purpose of the present invention is to provide an apparatus for the continuous casting of metal products that allows an effective and productive continuous casting even at high speed. Another purpose of the present invention is to provide an apparatus for the continuous casting of metal products that allows also an effective control of the liquid metal at low and intermediate casting speed.

Another purpose of the present invention is to provide an apparatus for the continuous casting of metal products that transforms and maintains the metal flow in the mould into a stable and optimal flow pattern, even in the meniscus zone, to ensure the best quality of the product.

Another purpose of the invention is therefore to provide an apparatus for the continuous casting of metal products that substantially allows to control the flows of metal from the outlets of the SEN. Another purpose of the present invention is to perfect an effective and simple method for the continuous casting of metal products.

The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independent claims. The dependent claims describe other characteristics of the present invention or variants to the main inventive idea.

In accordance with the above purposes, an apparatus for the continuous casting of metal products, according to the present invention, comprises an ingot mold and a nozzle for feeding molten metal of the submerged type (SEN), wherein the ingot mold has a substantially rectangular section provided with narrow lateral walls and wide lateral walls.

The feed nozzle is provided with at least one substantially axial main outlet, configured to direct the molten metal mainly toward the lower part of the ingot mold, and a plurality of secondary outlets, configured to direct the molten metal mainly toward the narrow lateral walls of the ingot mold.

According to a characteristic aspect of the invention, the apparatus comprises at least a first electromagnetic system associated with at least the opposite wide lateral walls of the ingot mold and configured to mainly regulate the flow of molten metal exiting from the main outlet, and at least a second distinct electromagnetic system associated at least with the opposite wide lateral walls and configured to mainly regulate the flows of molten metal exiting from the secondary outlets.

By means of the electromagnetic systems associated with the ingot mold, it is advantageously possible to regulate the flows of metal material from the outlets of the nozzle, for example in terms of speed and direction, obtaining a better uniformity of the metal bath, even in correspondence with the meniscus of the ingot mold, an increase in the productivity of the apparatus, even of 30-40% compared to known apparatuses, and possibly also a continuous casting at high speed of slabs.

According to another aspect of the invention, the first electromagnetic system is positioned at a certain height below the main outlet of the nozzle.

According to another aspect of the invention, the first electromagnetic system is a static system with two or three magnetic bodies around which corresponding electric coils are wound. According to another aspect of the invention, the first electromagnetic system is configured at least to slow down the flow of molten metal exiting from the main outlet and possibly stabilize the flows exiting from the secondary outlets.

According to another aspect of the invention, the second electromagnetic system is positioned substantially at the height of the lateral outlets of the SEN.

According to another aspect of the invention, the second electromagnetic system comprises a plurality of electromagnetic stirrers positioned on the opposite walls of the ingot mold.

According to another aspect of the invention, the second electromagnetic system comprises four electromagnetic stirrers positioned on the walls in pairs.

According to another aspect of the invention, each of the electromagnetic stirrers comprises a magnetic body on which a series of excitation electric coils is mounted.

According to another aspect of the invention, the second electromagnetic system is configured to slow down or accelerate the flows of molten metal exiting from the secondary outlets.

According to another aspect of the invention, the second electromagnetic system is configured to rotate the flows of molten metal exiting from the secondary outlets. According to another aspect of the invention, the second electromagnetic system is positioned above the first electromagnetic system.

The invention also concerns a method for the continuous casting of metal products, in particular slabs, comprising feeding molten metal to an ingot mold by means of a nozzle of the submerged type (SEN) provided with at least one main outlet, substantially axial, configured to direct the molten metal mainly toward the lower part of the ingot mold, and a plurality of secondary outlets, configured to direct the molten metal mainly toward the lateral walls of the ingot mold. The flow of molten metal exiting from the main outlet is regulated by means of at least a first electromagnetic system positioned at least on opposite walls of the ingot mold, and the flows of molten metal exiting from the secondary outlets are regulated by means of at least a second distinct electromagnetic system.

BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects, characteristics and advantages 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: - fig. 1 is a three-dimensional view of an apparatus for the continuous casting of metal products according to the present invention;

- fig. 2 is a front view of the apparatus of fig. 1;

- fig. 3 is a lateral view of the apparatus of figs. 1 and 2;

- fig. 4 is a section front view of an upper part of an ingot mold; - fig. 5 is another front view of the upper part of the ingot mold of fig. 4 to which a first electromagnetic system is applied;

- figs. 6a-6d are front views of the upper part of the ingot mold to which said first electromagnetic system and a second electromagnetic system are applied in some examples of operation; - figs. 7a and 7b are respectively a front view of part of the ingot mold in which a flow with upward and downward rotation is generated by each of the lateral outlets, and a top view of how the second electromagnetic system operates in order to uniform such flow;

- figs. 8a and 8b are respectively a front view of part of the ingot mold in which a flow with downward rotation is generated by each of the lateral outlets, and a top view of how the second electromagnetic system operates in order to uniform such flow.

We must clarify that in the present description the phraseology and terminology used, as well as the figures in the attached drawings also as described, have the sole function of better illustrating and explaining the present invention, their function being to provide a non-limiting example of the invention itself, since the scope of protection is defined by the claims.

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 be conveniently combined or incorporated into other embodiments without further clarifications.

DETAILED DESCRIPTION OF SOME EMBODIMENTS We will now refer in detail to the possible embodiments of the invention, of which one or more examples are shown in the attached drawings, by way of a non-limiting illustration. The phraseology and terminology used here is also for the purposes of providing non-limiting examples. With reference to the attached drawings, please see in particular figs. 1-4, an apparatus 10 for the continuous casting of metal products comprises an ingot mold 11 and a nozzle 12 for feeding molten metal.

The ingot mold 11 is designed to cast slabs, wherein the width of the slab is much greater than the thickness. For this purpose, the ingot mold 11 has first narrow lateral walls 15 and second wide lateral walls 17. The narrow lateral walls 15 can be mobile in order to vary the width of the cast slab.

The nozzle 12 is of the submerged type and is provided with at least one main outlet 13, configured to direct the molten metal I mainly toward the lower part of the ingot mold 11, and a plurality of secondary outlets 14 configured to direct the molten metal mainly toward the narrow lateral walls 15 of the ingot mold 11. The nozzle 12 is in particular a SEN (Submerged Entry Nozzle).

The main outlet 13 is substantially directed along a longitudinal axis L of the nozzle 12. The nozzle 12 is positioned, during use, substantially in the center of the ingot mold 11. The secondary outlets 14 are directed in a substantially radial direction and inclined downward. It is possible to provide, for example, two diametrically opposite secondary outlets 14, or even a different number of secondary outlets 14.

The apparatus 10 comprises at least a first electromagnetic system 16 associated with the opposite wide lateral walls 17 of the ingot mold 11 and configured to mainly regulate a first flow Fl of molten metal I exiting from the main outlet 13, and at least a second distinct electromagnetic system 18 associated with the opposite wide lateral walls 17 and configured to mainly regulate second flows F2 of molten metal I exiting from the secondary outlets 14.

The first flow Fl can be braked and the second flows F2 can, for example, be either slowed down or accelerated, therefore the intensity of the flows F 1 andF2 can be regulated. At least the second flows F2 can also at least partly be rotated, as we will see below.

The first electromagnetic system 16 is positioned at a certain height below the main outlet 13. Substantially, the first electromagnetic system 16 is divided into two equal parts 16a and 16b, each, in this specific case, positioned on one of the wide lateral walls 17 of the ingot mold 11.

The first electromagnetic system 16 is a static system with two or three magnetic bodies 19a, 19b, 19c. In the drawings, by way of example, a three-pole electromagnetic system 16 has been shown. Respective electric coils 20a, 20b, 20c are wound around the magnetic bodies 19a, 19b, 19c.

The first electromagnetic system 16 is configured at least to slow down the first flow Fl of molten metal exiting from the main outlet 13, and possibly stabilize it (Fl) and as well as the second flows F2 exiting from the secondary outlets 14. Please compare for example figs. 4 and 5.

Substantially, in order to regulate the first flow F 1 , which is generally directed downward and normally has a strong thrust, the first electromagnetic system 16 generates a static magnetic field in an area under the nozzle 12 and which covers the entire width of the ingot mold 11. The electric coils 20a, 20b, 20c are fed with direct current and magnetize the magnetic bodies 19a, 19b, 19c.

In the configuration with three magnetic bodies 19a, 19b, 19c shown by way of example in the attached drawings, for each of the two parts 16a or 16b of the first electromagnetic system 16, two magnetic bodies 19a and 19c are positioned on both sides of the nozzle 12, one on the left and the other on the right. These magnetic bodies 19a and 19c are fed in the same way, that is, with magnetic fields in the same direction. A central magnetic body 19b is positioned on the corresponding wide lateral wall 17 so that, according to a front view, fig. 5, it is substantially aligned with the main outlet 13 and therefore with the lower end of the nozzle 12. The magnetic body 19b is fed with a magnetic field opposite to that of the two lateral magnetic bodies 19a and 19c, and guarantees the overall closure of the field magnetic. The magnetic field then passes through the ingot mold 11 and the liquid metal and will have an “8” or “double 0” shape with respect to a cross-section or top view of the ingot mold 11.

In the configuration with two magnetic bodies, not shown, the magnetic bodies will only be on both sides of the nozzle 12, one on the left and the other on the right. The magnetic flux passes through the ingot mold 11 and the liquid metal, and goes back through the magnetic bodies, forming a closed ring in the shape of a “0”.

The second electromagnetic system 18 is positioned substantially at the height of the secondary outlets 14.

The second electromagnetic system 18 comprises a plurality of electromagnetic stirrers 21a, 21b, 21c, 21 d positioned on the opposite wide lateral walls 17 of the ingot mold 11. Preferably, four electromagnetic stirrers 21a, 21b, 21c, 21d are provided, positioned in pairs on two of the opposite walls 17. The electromagnetic stirrers 21a, 21b, 21c, 21 d can be positioned opposite each other, see for example the electromagnetic stirrers 21a and 21c in fig. 1, or the electromagnetic stirrers 21b and 2 Id. The electromagnetic stirrers 2 la-2 lb or 21c-21d of each pair can be reciprocally connected or coupled.

Each of the electromagnetic stirrers 21a, 21b, 21c, 21 d comprises a magnetic body 22 on which a series of excitation electric coils 23 are mounted.

The second electromagnetic system 18 is configured to slow down or accelerate the second flows F2 of molten metal exiting from the secondary outlets 14. The second flow F2, see in particular fig. 4, schematically comprises an upper branch F21 which represents the flow of molten metal in proximity to the surface S of the bath of molten metal and in proximity to the meniscus M. The flow F2 also schematically comprises a lower branch F22 directed downward, that is, toward the outlet of the ingot mold 11.

The second electromagnetic system 18 is configured to rotate the second flows F2, as we will see below, in particular at least the upper branch F21.

Furthermore, the second electromagnetic system 18 is positioned above the first electromagnetic system 16, therefore in a position closer to the upper part of the ingot mold 11 , from which the molten metal is introduced by means of the nozzle 12.

Substantially, in order to regulate the second flows F2 exiting from the secondary outlets 14, magnetic fields with variable directions and/or intensities are generated by means of the electromagnetic stirrers 21 a, 21b, 21c, 2 Id. The electromagnetic stirrers 21a, 21b, 21c, 21d are excited in alternating current, which therefore is variable in time and as a phase. As a function of the configuration chosen, the phase displacement between the currents can be of 90°, typical of two-phase devices, or 120° in order to create the well-known three- phase configuration. These configurations allow to generate a magnetic field that varies in space and time, that is, a “sliding magnetic field”. As a function of the control of the phasing of the currents in the electric coils 23, it is possible to generate magnetic fields that travel in the desired direction; therefore either from left to right, or in the opposite direction, from right to left.

By combining the electromagnetic stirrers 21a, 21b, 21c, 21 d with the possible directions of travel of the magnetic field that overlap with the second lateral flows F2, it is thus possible to generate different flow regulation functions, therefore different operating modes for regulating the second flows F2. These modes can be set by means of a control system of the apparatus 10 connected to the second electromagnetic system 18, therefore to each of the electromagnetic stirrers 21a, 21b, 21c, 2 Id. The control system can also be connected to the first electromagnetic system 16.

With reference to fig. 6a, in a first operating mode of the second electromagnetic system 18, magnetic fields Al and A2 are created by means of the electromagnetic stirrers 21a, 21b, 21c, 2 Id, of which in the drawing the electromagnetic stirrers 21a, 21b are visible, said magnetic fields Al and A2 being directed by the nozzle 12 toward the lateral walls 15 of the ingot mold 11. This function allows to accelerate the lateral flows F2 of liquid metal and therefore to increase the speed of molten metal moving from the secondary outlets 14 to the meniscus M.

With reference to fig. 6b, in another operating mode of the second electromagnetic system 18, magnetic fields Bl and B2 are created by means of the electromagnetic stirrers 21a, 21b, 21c, 2 Id, said magnetic fields Bl and B2 being directed by the lateral walls 15 toward the nozzle 12. This function allows to slow down the lateral flows F2 of liquid metal and thus reduce the speed of the metal moving from the secondary outlets 14 to the meniscus M.

In any case, both of the modes described are aimed at obtaining quantities of molten metal in motion able to guarantee stability and uniformity for the casting steps that follow the ingot mold 11.

With reference to figs. 6c and 6d, 7a, 7b, 8a, 8b, in another operating mode of the second electromagnetic system 18, magnetic fields Rl, R2, R3, R4 are generated, which allow to rotate the flows F2 of molten metal, in particular in proximity to the meniscus M, in order to uniform the bath of molten metal. The magnetic fields Rl, R2 have the same direction and can be produced by the electromagnetic stirrers 21a, 21b located on a wide lateral wall 17 of the ingot mold 11, while the magnetic fields R3, R4 have the same direction and can be produced by the electromagnetic stirrers 21c, 21d on the opposite wide lateral wall 17. The direction of the magnetic fields Rl, R2 is opposite to the direction of the magnetic fields R3, R4.

The operating mode aimed at the rotation of the molten metal, in particular in proximity to the meniscus M, therefore occurs by means of the electromagnetic stirrers 21a, 21b, 21c, 21 d located in proximity to the opposite wide lateral walls

17 with a greater surface than the ingot mold 11. This allows a better homogeneity of the temperature of the metal at the meniscus M and washing of the solidification front.

The intensities of the magnetic fields produced on a same wall 17 of the ingot mold 11 can be the same, please see the magnetic fields Rl and R2 in fig. 6c, or different, please see the magnetic fields Rl and R2 in fig. 6d, where the magnetic field Rl has greater intensity than the magnetic field R2. The magnetic fields generated on a same wall have the same direction, please see again the magnetic fields Rl and R2 in figs. 6c and 6d. The situation of fig. 6d is also shown in figs. 7a and 7b, which respectively concern a front view of part of the ingot mold 11 , in which a second flow F2 is generated by the lateral outlets which schematically has two components, one component upward and the other downward, and a top view which shows how the second electromagnetic system 18 operates in order to uniform the second flow F2. As can be observed, the intensity of the magnetic field R3 generated by the electromagnetic stirrer 21c is smaller than the intensity of the magnetic field R4 generated by the electromagnetic stirrer 2 Id. It is possible to hypothesize that the magnetic fields Rl and R4 have the same intensity but opposite direction. It is also possible to hypothesize that the magnetic fields R2 and R3 have the same intensity and opposite direction.

Fig. 7b also schematically shows the direction DI of rotation of the molten metal in the ingot mold 11, generated thanks to the second electromagnetic system 18. Figs. 8a and 8b respectively show a front view of part of the ingot mold 11 in which a second flow F2 is generated with a downward rotation component, and a top view of how the second electromagnetic system 18 can operate in order to uniform the second flow F2. In this case, the intensity of the magnetic field R1 is smaller than the intensity of the magnetic field R2 and the intensity of the magnetic field R3 is greater than the intensity of the magnetic field R4. The magnetic fields R1 and R2 generated by the electromagnetic stirrers 21a, 21b are directed in the opposite direction with respect to the magnetic fields R3 and R4 generated by the electromagnetic stirrers 21c, 2 Id. It is possible to hypothesize that the magnetic fields R1 and R4 have the same intensity but opposite direction. It is also possible to hypothesize that the magnetic fields R2 and R3 have the same intensity and opposite direction.

Fig. 8b also schematically shows the direction DI of rotation of the molten metal in the ingot mold 11, generated thanks to the second electromagnetic system 18.

A method for the continuous casting of metal products according to the present invention therefore comprises feeding molten metal I to the ingot mold 11 by means of the nozzle 12. The first flow Fl of molten metal I exiting from the main outlet 13 of the nozzle 12 is regulated by means of at least the first electromagnetic system 16, and the second flows F2 of molten metal exiting from the secondary outlets 14 of the nozzle 12 are regulated by means of the second electromagnetic system 18.

It is clear that modifications and/or additions of parts may be made to the apparatus and method for the continuous casting of metal products, in particular slabs, as described heretofore, without departing from the field and scope of the present invention as defined by the claims.

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 apparatus for the continuous casting of metal products, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.

In the following claims, the sole purpose of the references in brackets is to facilitate reading and they must not be considered as restrictive factors with regard to the field of protection defined by the claims.