Apparatus and method for continuous casting of metal products

Abstract

Apparatus (10) for the continuous casting of metal products, comprising an ingot mold (11) and a nozzle (12) for feeding molten metal (I), said nozzle (12) being provided with at least one primary outlet (13) configured to substantially direct the molten metal (I) towards a lower portion of the ingot mold (11), and a plurality of secondary outlets (14) configured to substantially direct the molten metal (I) towards a side wall (15) of the ingot mold (11).

Description

Technical Field

[0001] The present invention relates to an apparatus and a method for the continuous casting of metal products, in particular slabs, or products having a rectangular cross-section and a width much greater than thickness. Background Art

[0002] Continuous casting apparatuses are known which comprise an ingot mould configured to cast a metal product, in particular a slab.

[0003] The molten metal is introduced into the ingot mold, where it gradually solidifies and forms a solid skin.

[0004] When leaving the ingot mold, the casting has a solidified shell which has 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, gradually advances until it is completely solidified downstream of the ingot mold. The solidified product can then be sent for rolling, for example in an endless process, or cut into segments to be rolled in a coil-to-coil or semi-endless process, or even removed from the casting line to be rolled in a subsequent process.

[0005] The ingot mould can be supplied with molten metal from the tundish by means of at least one outlet nozzle of the SEN type (Submerged Entry Nozzle), ie the outlet for the metal is arranged below the level of the liquid metal meniscus.

[0006] The nozzle may be provided with a substantially axial primary outlet or a plurality of secondary outlets configured to direct molten metal primarily toward a lower portion of the ingot mould, and a plurality of secondary outlets configured to direct molten metal primarily toward a side wall of the ingot mould.

[0007] Using this type of nozzle (but not limited to this), inside the ingot mold, it is difficult to control and regulate the speed and direction of the flow of metal flowing out of the outlet to make the flow uniform so that the casting process is as efficient and productive as possible.

[0008] These problems of uneven and unstable flow of the molten metal occur particularly in the meniscus region, ie the upper surface of the metal in the ingot mould.

[0009] Current continuous casting apparatus provided with an ingot mould and a SEN cannot effectively control the uniformity of metal flow in the ingot mould, and cannot adjust their speed and / or direction from the central outlet and the lateral outlets of the SEN.

[0010] Furthermore, due to limitations of known apparatuses, it is difficult to achieve continuous casting at high speeds in order to obtain the desired high productivity of the apparatus. Summary of the invention

[0011] Therefore, there is a need to perfect an apparatus for continuous casting of metal products which overcomes the drawbacks of the prior art and meets all the requirements for controlling these metal flow conditions.

[0012] In particular, an object of the invention is to provide an apparatus for continuous casting of multifunctional metal products, the productivity of which is even increased by 30-40% compared to known apparatuses, thanks to the ability to regulate the flow of metal material in the ingot mould, for example in terms of speed and direction.

[0013] Another object of the present invention is to provide an apparatus for continuous casting of metal products which allows efficient and productive continuous casting even at high speeds.

[0014] Another object of the present invention is to provide an apparatus for continuous casting of metal products which also allows effective control of the liquid metal at low and medium casting speeds.

[0015] Another object of the present invention is to provide an apparatus for continuous casting of metal products which transforms and maintains the metal flow in the mould into a stable and optimal flow pattern, even in the meniscus region, to ensure optimal quality of the product.

[0016] It is therefore another object of the present invention to provide an apparatus for continuous casting of metal products which substantially allows controlling the flow of metal from the outlet of the SEN.

[0017] Another object of the invention is to perfect an efficient and simple method for the continuous casting of metal products.

[0018] 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.

[0019] The invention is set forth and characterized in the independent claims. The dependent claims describe other characteristics of the invention or variants to the main inventive idea.

[0020] In accordance with the above objects, an apparatus for continuous casting of metal products according to the present invention comprises an ingot mould and a submerged (SEN) nozzle for supplying molten metal, wherein the ingot mould has a substantially rectangular cross section provided with narrow and wide side walls.

[0021] The feed nozzle is provided with at least one substantially axial primary outlet configured to direct molten metal primarily toward a lower portion of the ingot mould, and a plurality of secondary outlets configured to direct molten metal primarily toward narrow side walls of the ingot mould.

[0022] According to a characteristic aspect of the invention, the apparatus comprises at least a first electromagnetic system associated at least with the opposite wide side walls of the ingot mould and configured to primarily regulate the flow of molten metal exiting from the primary outlet and at least a second, different electromagnetic system associated at least with the opposite wide side walls and configured to primarily regulate the flow of molten metal exiting from the secondary outlet.

[0023] With the aid of an electromagnetic system associated with the ingot mould, it is possible to advantageously regulate the flow of metal material from the nozzle outlet (for example in terms of speed and direction), obtaining better uniformity of the metal bath, even in the position corresponding to the meniscus of the ingot mould, increasing the productivity of the device, even by 30-40% compared with known devices, and making it possible to continuously cast slabs at high speed.

[0024] According to another aspect of the invention, the first electromagnetic system is positioned at a height below the main outlet of the nozzle.

[0025] According to another aspect of the invention, the first electromagnetic system is a static system having two or three magnets around which corresponding electrical coils are wound.

[0026] According to another aspect of the invention, the first electromagnetic system is configured to at least slow down the flow of molten metal exiting from the primary outlet and possibly stabilize the flow exiting from the secondary outlet.

[0027] According to another aspect of the invention, the second electromagnetic system is positioned substantially at the level of the lateral outlet of the SEN.

[0028] According to another aspect of the invention, the second electromagnetic system includes a plurality of electromagnetic stirrers positioned on opposite walls of the ingot mold.

[0029] According to another aspect of the invention, the second electromagnetic system comprises four electromagnetic stirrers positioned in pairs on the wall.

[0030] According to another aspect of the invention, each electromagnetic stirrer comprises a magnet on which is mounted a series of excitation electrical coils.

[0031] According to another aspect of the invention, the second electromagnetic system is configured to slow down or speed up the flow of molten metal exiting from the secondary outlet.

[0032] According to another aspect of the invention, the second electromagnetic system is configured to rotate the flow of molten metal exiting from the secondary outlet.

[0033] According to another aspect of the invention, the second electromagnetic system is positioned above the first electromagnetic system.

[0034] The invention also relates to a method for continuous casting of a metal product, in particular a slab, comprising supplying molten metal to an ingot mould by means of a submerged (SEN) nozzle, said nozzle being provided with at least one substantially axial main outlet configured to direct the molten metal mainly towards the lower part of the ingot mould, and a plurality of secondary outlets configured to direct the molten metal mainly towards the side walls of the ingot mould. The flow of the molten metal exiting from the main outlet is regulated by means of at least a first electromagnetic system located at least on opposite walls of the ingot mould, and the flow of the molten metal exiting from the secondary outlets is regulated by means of at least a second different electromagnetic system. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] These and other aspects, features and advantages of the invention will become apparent from the following description of some embodiments given as non-limiting examples with reference to the accompanying drawings, in which:

[0036] - Figure 1 is a three-dimensional view of an apparatus for continuous casting of metal products according to the present invention;

[0037] - Figure 2 yes Figure 1 A front view of the device;

[0038] - Figure 3 yes Figure 1 and Figure 2 A side view of the device;

[0039] - Figure 4 is a cross-sectional elevation view of the upper portion of the ingot mold;

[0040] - Figure 5 The first electromagnetic system was applied Figure 4 Another front view of the upper portion of the ingot mold;

[0041] - Figures 6a to 6d is a front view of an upper portion of an ingot mold to which the first and second electromagnetic systems are applied in some operating examples;

[0042] - Figure 7a and Figure 7b A front view of a portion of an ingot mold, in which each lateral outlet generates a flow that rotates upward and downward, and a top view of how the second electromagnetic system operates to make this flow uniform;

[0043] - Figure 8a and Figure 8b Respectively, a front view of a portion of an ingot mould, in which each lateral outlet generates a downwardly rotating flow, and a top view of how the second electromagnetic system operates to make this flow uniform.

[0044] It must be clarified that the words and terms used in this description, as well as the figures also described in the accompanying drawings, 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.

[0045] To facilitate understanding, the same reference numerals have been used where possible to identify the same common elements in the drawings. It will be appreciated that elements and features of one embodiment may be conveniently combined or incorporated into other embodiments without further clarification. DETAILED DESCRIPTION

[0046] We will now refer in detail to possible embodiments of the invention, one or more examples of which are shown in the accompanying drawings by way of non-limiting illustration. The phraseology and terminology used herein is also for the purpose of providing non-limiting examples.

[0047] Refer to the attached drawings, see in particular Figures 1 to 4 , an apparatus 10 for continuous casting of a metal product includes an ingot mold 11 and a nozzle 12 for supplying molten metal.

[0048] The ingot mold 11 is designed to cast a slab, wherein the width of the slab is much greater than the thickness. For this purpose, the ingot mold 11 has a first narrow side wall 15 and a second wide side wall 17. The narrow side wall 15 can be moved to change the width of the ingot.

[0049] The nozzle 12 is submerged 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 side walls 15 of the ingot mold 11. The nozzle 12 is in particular a SEN (submerged inlet nozzle).

[0050] The main outlet 13 is directed substantially along the longitudinal axis L of the nozzle 12. The nozzle 12 is positioned substantially in the center of the ingot mold 11 during use. The secondary outlets 14 are directed substantially radially and are inclined downwards. For example, two diametrically opposed secondary outlets 14 or even a different number of secondary outlets 14 can be provided.

[0051] The device 10 includes: at least a first electromagnetic system 16 associated with the opposite wide side wall 17 of the ingot mold 11 and configured to mainly regulate the first flow F1 of the molten metal I leaving from the main outlet 13, and at least a second different electromagnetic system 18 associated with the opposite wide side wall 17 and configured to mainly regulate the second flow F2 of the molten metal I leaving from the secondary outlet 14.

[0052] For example, the first flow F1 can be braked and the second flow F2 can be slowed down or accelerated, so that the strength of the flows F1 and F2 can be adjusted. As we will see below, at least the second flow F2 can also be at least partially rotated.

[0053] The first electromagnetic system 16 is positioned at a certain height below the main outlet 13. In essence, the first electromagnetic system 16 is divided into two equal parts 16a and 16b, each part being positioned on one of the wide side walls 17 of the ingot mould 11 in this particular case.

[0054] The first electromagnetic system 16 is a static system with two or three magnets 19a, 19b, 19c. In the figures, as an example, a three-pole electromagnetic system 16 is shown. Respective electrical coils 20a, 20b, 20c are wound around the magnets 19a, 19b, 19c.

[0055] The first electromagnetic system 16 is configured to slow down at least the first flow F1 of molten metal exiting from the primary outlet 13 and possibly stabilize it (F1) as well as the second flow F2 exiting from the secondary outlet 14. Compare e.g. Figure 4 and Figure 5 .

[0056] Essentially, in order to regulate the first flow F1 directed generally downwards and generally with a strong thrust, the first electromagnetic system 16 generates a static magnetic field in the region below the nozzle 12, which covers the entire width of the ingot mold 11. The electric coils 20a, 20b, 20c are supplied with direct current and magnetize the magnets 19a, 19b, 19c.

[0057] In the configuration with three magnets 19a, 19b, 19c shown by way of example in the figures, two magnets 19a and 19c are positioned on either side of the nozzle 12, one on the left and the other on the right, for each of the two parts 16a or 16b of the first electromagnetic system 16. These magnets 19a and 19c are supplied in the same way, i.e. with magnetic fields of the same direction. The central magnet 19b is positioned on the corresponding wide side wall 17 so that, according to the front view, Figure 5 , which is substantially aligned with the main outlet 13 and therefore with the lower end of the nozzle 12. The magnet 19b is supplied with a magnetic field opposite to that of the two side magnets 19a and 19c and ensures the overall closure of the magnetic field. The magnetic field then passes through the ingot mold 11 and the liquid metal and will have an "8" or "double 0" shape in a cross section or top view relative to the ingot mold 11.

[0058] In a configuration with two magnets (not shown), the magnets will be only on either side 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 returns through the magnets, forming a closed loop in the shape of "0".

[0059] The second electromagnetic system 18 is positioned substantially at the level of the secondary outlet 14 .

[0060] The second electromagnetic system 18 comprises a plurality of electromagnetic stirrers 21a, 21b, 21c, 21d positioned on the opposite wide side 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, 21d may be positioned relative to each other, for example, see Figure 1 The electromagnetic stirrers 21a and 21c, or the electromagnetic stirrers 21b and 21d, in each pair may be connected or coupled to each other.

[0061] Each electromagnetic stirrer 21a, 21b, 21c, 21d comprises a magnet 22 on which a series of excitation electrical coils 23 are mounted.

[0062] The second electromagnetic system 18 is configured to slow down or speed up the second flow F2 of molten metal exiting from the secondary outlet 14. See in particular Figure 4 The second flow F2 schematically comprises an upper branch F21 representing a molten metal flow close to the surface S of the molten metal bath and close to the meniscus M. The flow F2 also schematically comprises a lower branch F22 directed downwards, ie towards the outlet of the ingot mould 11 .

[0063] The second electromagnetic system 18 is configured to rotate the second flow F2 , as we will see below, in particular to rotate at least the upper branch F21 .

[0064] Furthermore, the second electromagnetic system 18 is positioned above the first electromagnetic system 16 and is thus located closer to the upper portion of the ingot mold 11 from which the molten metal is introduced by means of the nozzle 12 .

[0065] Essentially, in order to regulate the second flow F2 exiting from the secondary outlet 14, a magnetic field with a variable direction and / or strength is generated by means of electromagnetic stirrers 21a, 21b, 21c, 21d.

[0066] The electromagnetic stirrers 21a, 21b, 21c, 21d are excited in an alternating current, which is therefore variable in time and phase. Depending on the configuration chosen, the phase shift between the currents can be 90°, which is a typical two-phase device, or 120°, so as to create the well-known three-phase configuration. These configurations allow the generation of a magnetic field that varies in space and time, i.e. a "sliding magnetic field". Depending on the control of the phase of the current in the electrical coil 23, a magnetic field can be generated that travels in the desired direction; therefore, from left to right, or in the opposite direction, from right to left.

[0067] By combining the possible directions of travel of the electromagnetic stirrers 21a, 21b, 21c, 21d with the magnetic field overlapping the second lateral flow F2, different flow regulation functions can be generated, and therefore different operating modes for regulating the second flow F2. These modes can be set by means of a control system of the device 10 connected to the second electromagnetic system 18 (and therefore to each electromagnetic stirrer 21a, 21b, 21c, 21d). The control system can also be connected to the first electromagnetic system 16.

[0068] refer to Figure 6a In a first operating mode of the second electromagnetic system 18, magnetic fields A1 and A2 are created by means of electromagnetic stirrers 21a, 21b, 21c, 21d, where electromagnetic stirrers 21a, 21b can be seen in the figure, which are directed from the nozzle 12 to the side wall 15 of the ingot mold 11. This function allows to accelerate the lateral flow F2 of the liquid metal, thereby increasing the speed at which the molten metal moves from the secondary outlet 14 to the meniscus M.

[0069] Reference Figure 6b In another operating mode of the second electromagnetic system 18, magnetic fields B1 and B2 are created by means of electromagnetic stirrers 21a, 21b, 21c, 21d, which are directed by the side wall 15 towards the nozzle 12. This function allows slowing down the lateral flow F2 of the liquid metal and thus reducing the speed of the metal moving from the secondary outlet 14 to the meniscus M.

[0070] In any case, both modes described aim to obtain a quantity of molten metal in motion capable of guaranteeing stability and uniformity of the casting step following the ingot mould 11 .

[0071] refer to Figure 6c and Figure 6d , Figure 7a , Figure 7b , Figure 8a , Figure 8b In another operating mode of the second electromagnetic system 18, magnetic fields R1, R2, R3, R4 are generated, which allow to rotate the flow F2 of the molten metal, especially near the meniscus M, so as to make the molten metal bath uniform. The magnetic fields R1, R2 have the same direction and can be generated by electromagnetic stirrers 21a, 21b located on the wide side wall 17 of the ingot mold 11, while the magnetic fields R3, R4 have the same direction and can be generated by electromagnetic stirrers 21c, 21d located on the opposite wide side wall 17. The direction of the magnetic fields R1, R2 is opposite to the direction of the magnetic fields R3, R4.

[0072] Therefore, the operating mode aimed at rotating the molten metal, especially near the meniscus M, is achieved with the help of electromagnetic stirrers 21a, 21b, 21c, 21d located near the opposite wide side walls 17 with a larger surface than the ingot mold 11. This allows a more uniform metal temperature at the meniscus M and cleans the solidification front.

[0073] The strength of the magnetic field generated on the same wall 17 of the ingot mold 11 can be the same, see Figure 6c The magnetic fields R1 and R2 in, or different, see Figure 6d The magnetic fields R1 and R2 in the same wall are larger than those in the same wall. The magnetic fields generated on the same wall have the same direction. Please refer to Figure 6c and Figure 6d The magnetic fields in R1 and R2.

[0074] Figure 6d The situation is also shown in Figure 7a and Figure 7b , which respectively relate to a front view of a portion of the ingot mold 11 (wherein the second flow F2 generated by the lateral outlet schematically has two components, one component upward and the other component downward), and a top view, which shows how the second electromagnetic system 18 operates to make the second flow F2 uniform. It can be observed that the intensity of the magnetic field R3 generated by the electromagnetic stirrer 21c is less than the intensity of the magnetic field R4 generated by the electromagnetic stirrer 21d. It can be assumed that the magnetic fields R1 and R4 have the same intensity but opposite directions. It can also be assumed that the magnetic fields R2 and R3 have the same intensity and opposite directions.

[0075] Figure 7b The direction of rotation D1 of the molten metal in the ingot mould 11 due to the second electromagnetic system 18 is also schematically shown.

[0076] Figure 8a and Figure 8b A front view of a portion of the ingot mold 11 in which the second flow F2 having a downward rotation component is generated, and a top view of how the second electromagnetic system 18 operates to make the second flow F2 uniform are respectively shown.

[0077] In this case, the intensity of the magnetic field R1 is less 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 point in opposite directions relative to the magnetic fields R3 and R4 generated by the electromagnetic stirrers 21c, 21d. It can be assumed that the magnetic fields R1 and R4 have the same intensity but opposite directions. It can also be assumed that the magnetic fields R2 and R3 have the same intensity and opposite directions.

[0078] Figure 8bThe direction of rotation D1 of the molten metal in the ingot mould 11 due to the second electromagnetic system 18 is also schematically shown.

[0079] Thus, the method for continuous casting of a metal product according to the invention comprises supplying molten metal I to an ingot mold 11 by means of a nozzle 12. A first flow F1 of the molten metal I exiting from a primary outlet 13 of the nozzle 12 is regulated by means of at least a first electromagnetic system 16, and a second flow F2 of the molten metal exiting from a secondary outlet 14 of the nozzle 12 is regulated by means of a second electromagnetic system 18.

[0080] It is obvious that modifications and / or additions of components may be made to the plant and method for continuous casting of metal products, in particular slabs, described thus far, without departing from the field and scope of the invention as defined in the claims.

[0081] It is also clear that, although the invention has been described with reference to some specific examples, a person skilled in the art will certainly be able to realize many other equivalent forms of apparatus for continuous casting of metal products, which have the characteristics set out in the claims and therefore fall within the scope of protection defined thereby.

[0082] In the following claims, the sole purpose of references in parentheses is to facilitate reading and they shall not be construed as limiting factors as to the scope of protection defined by the claims.

Claims

1. An apparatus (10) for continuous casting of metal products, comprising an ingot mold (11) and a submerged nozzle (12) for supplying molten metal (I), wherein the ingot mold (11) has a substantially rectangular cross-section and is provided with a narrow side wall (15) and a wide side wall (17), wherein the nozzle (12) is provided with at least one axial 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 (I) mainly toward the narrow side wall (15) of the ingot mold (11), characterized in that: The device comprises at least a first electromagnetic system (16) and at least a second different electromagnetic system (18), wherein the at least first electromagnetic system (16) is associated with at least the opposite wide side wall (17) of the ingot mold (11) and is configured to mainly regulate a first flow (F1) of molten metal (I) exiting from the main outlet (13), and the at least second different electromagnetic system (18) is associated with the opposite wide side wall (17) and is configured to mainly regulate a second flow (F2) of molten metal (I) exiting from the secondary outlet (14).

2. The device (10) according to claim 1, characterized in that The first electromagnetic system (16) is positioned at a height below the main outlet (13).

3. The device (10) according to claim 1 or 2, characterized in that The first electromagnetic system (16) is a static system having two or three magnets (19a, 19b, 19c) around which corresponding electric coils (20a, 20b, 20c) are wound.

4. The device (10) according to any of the preceding claims, characterized in that The first electromagnetic system (16) is configured to slow down at least the first flow (F1) of molten metal (I) exiting from the primary outlet (13) and possibly stabilize it (F1) and the second flow (F2) exiting from the secondary outlet (14).

5. The device (10) according to any of the preceding claims, characterized in that The second electromagnetic system (18) is positioned substantially at the level of the lateral outlet (14).

6. The device (10) according to any of the preceding claims, characterized in that The second electromagnetic system (18) includes a plurality of electromagnetic stirrers (21a, 21b, 21c, 21d) positioned on the opposite wide side walls (17) of the ingot mold (11).

7. The device (10) according to claim 6, characterized in that The second electromagnetic system (18) comprises four electromagnetic stirrers (21a, 21b, 21c, 21d) positioned in pairs on the wide side wall (17).

8. The device (10) according to any of the preceding claims, characterized in that Each of the electromagnetic stirrers (21a, 21b, 21c, 21d) comprises a magnet (22) on which a series of excitation electric coils (23) are mounted.

9. The device (10) according to any of the preceding claims, characterized in that The second electromagnetic system (18) is configured to slow down or speed up the second flow (F2) of molten metal exiting from the secondary outlet (14).

10. The device (10) according to any of the preceding claims, characterized in that The second electromagnetic system (18) is configured to rotate the second flow (F2) of molten metal exiting from the secondary outlet (14).

11. The device (10) according to any one of the preceding claims, characterized in that The second electromagnetic system (18) is positioned above the first electromagnetic system (16).

12. A method for continuous casting of a metal product, comprising supplying molten metal (I) to an ingot mold (11) by means of a nozzle (12), wherein the nozzle (12) 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 (I) mainly toward the narrow side walls (15) of the ingot mold (11), characterized in that: A first flow (F1) of molten metal (I) exiting from the primary outlet (13) is regulated by means of at least a first electromagnetic system (16) associated with opposite wide side walls (17) of the ingot mould (11), and a second flow (F2) of molten metal exiting from the secondary outlet (14) is regulated by means of at least a second different electromagnetic system (18) associated with opposite wide side walls (17) of the ingot mould (11).

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