Method for Containing a Slab During Continuous Casting

Abstract

A method for containing a slab during continuous casting, including casting a slab along a casting axis, said slab having a predefined width, wherein the method provides a containment of the slab with a plurality of rolls, said rolls being disposed in pairs facing to each other, and defining a passage along the casting axis for the cast slab, wherein the plurality of rolls includes electromagnetic rolls provided with an electromagnetic stirrer which stirs the liquid contained in the slab.

Claims

1. Method A method for containing a slab during continuous casting, which provides to cast a slab along a casting axis, said slab having a predefined width, wherein the method provides a containment of the slab with a plurality of rolls, said rolls being disposed in pairs facing to each other, and defining a passage along the casting axis for the cast slab, wherein the plurality of rolls comprises electromagnetic rolls provided with an electromagnetic stirrer which stirs the liquid contained in the slab, and containing rolls configured to exert only a containing action on said slab during continuous casting, wherein, during casting, the electromagnetic rolls have a length less than the width of the slab so that the slab protrudes with respect to at least one end of said electromagnetic rolls, with at least one protruding portion, wherein said containing rolls have a length substantially equal to said width of the slab.

2. The method for containing a slab during continuous casting as in claim 1, wherein the slab is protruding, with respect to one end of the electromagnetic roll, by an unsupported width up to 300 mm, preferably up to 250 mm, and said protruding portion is not supported by rolls.

3. The method for containing a slab during continuous casting as in claim 2, wherein the ratio between the unsupported width of the slab and the width of the slab is comprised between 2% and 20%, preferably between 2.5% and 16%.

4. The method for containing a slab during a continuous casting as in claim 1, wherein each of the electromagnetic rolls is associated with a respective auxiliary containing roll, aligned to and in axis with the respective electromagnetic roll, said auxiliary containing roll supporting said protruding portion.

5. The method for containing a slab as in claim 1, wherein said rolls comprises a first electromagnetic roll and a second electromagnetic roll distanced to each other along the casting axis.

6. The method for containing a slab as in claim 5, wherein between the first electromagnetic roll and the second electromagnetic roll, a plurality of containing rolls is provided in order to contain and support the slab.

7. The method for containing a slab as in claim 5, 6, wherein the first electromagnetic roll is disposed so that a first edge of the slab protrudes with respect to the first electromagnetic roll, while a second edge, opposite with respect to the first edge, protrudes with respect to the second electromagnetic roll.

8. Continuous casting equipment, comprising: a mold configured to cast a slab, and a plurality of rolls disposed in pairs facing to each other, and along the casting axis in order to define a passage for the cast slab, wherein the plurality of rolls comprises electromagnetic rolls provided with an electromagnetic stirrer configured to stir the liquid contained in the slab and containing rolls configured to exert only a containing action on said slab during continuous casting, wherein the electromagnetic rolls and therefore said passage are configured to have a length less than the width of the slab so that the slab protrudes with respect to one end of said electromagnetic rolls and said containing rolls are configured to have a length substantially equal to said width of the slab.

9. The continuous casting equipment as in claim 8, wherein each of the electromagnetic rolls is associated with a respective auxiliary containing roll, aligned to and in axis with the respective electromagnetic roll.

10. The continuous casting equipment as in claim 8, wherein said rolls comprises a first electromagnetic roll and a second electromagnetic roll distanced to each other along the casting axis.

11. The continuous casting equipment as in claim 9, and 10, wherein the auxiliary containing roll associated with the first electromagnetic roll is located on a first side with respect to the casting axis, and in that the auxiliary containing roll associated with the second electromagnetic roll is located on a second side, opposite the first side, with respect to the casting axis.

12. The continuous casting equipment as in claim 10, wherein between the first electromagnetic roll and the second electromagnetic roll, a plurality of containing rolls are provided in order to contain and support the slab.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] These and other characteristics of the present invention will become apparent from the following description of some embodiments, given as a non-restrictive example with reference to the attached drawings wherein:

[0036] FIG. 1 is a schematic view of a continuous casting machine according to the present invention;

[0037] FIG. 2 is a section view along section line II-II of FIG. 1;

[0038] FIG. 3 is a section view along section line III-III of FIG. 2;

[0039] FIG. 4 is a lateral view of the FIG. 1;

[0040] FIG. 5 is variant of FIG. 2;

[0041] FIG. 6 is a variant of FIG. 3;

[0042] FIG. 7 is a lateral view of FIGS. 5 and 6;

[0043] FIG. 8 is a prospective view of one embodiment of the present invention.

[0044] To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one embodiment can conveniently be incorporated into other embodiments without further clarifications.

DETAILED DESCRIPTION OF SOME EMBODIMENTS

[0045] Reference will now be made in detail to the various embodiments of the invention, one or more examples of which are illustrated in the figures. Generally, only the differences with respect to individual embodiments are described. Each example is provided by way of explanation of the invention and is not meant as a limitation of the invention. For example, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield yet a further embodiment. It is intended that the present invention includes such modifications and variations.

[0046] Embodiments described here with reference to FIGS. 1-8 concern to a method for containing a slab during continuous casting.

[0047] The method provides to cast a slab S along a casting axis C of a casting equipment 10.

[0048] According to one embodiment of the present invention, the slab S is cast in a mold 15.

[0049] At the exit of the mold 15 the slab S has a solidified external skin and its inner portion, or core, which is still liquid.

[0050] The slab S has a predefined width W1. The width W1 of the slab S can be comprised between 1500 mm and 3000 mm, preferably between 1800 mm and 2500 mm.

[0051] The method provides a containment of the slab S with a plurality of rolls 11, 12.

[0052] The rolls 11, 12 are disposed in pairs facing to each other, and along the casting axis C.

[0053] The rolls 11, 12 define a passage for the cast slab S.

[0054] The rolls 11, 12 are free to rotate around respective axes of rotation that are perpendicular with respect to the casting axis C.

[0055] According to one embodiment, said plurality of rolls comprises containing rolls 11 configured to exert only a containing action on the slab S during continuous casting. The containing rolls 11 do not have the function of electromagnetic stirring, that is, they do not have a magnetic stirrer as described below.

[0056] The containing rolls 11 can be disposed faced, in pairs, to each other with respect to the casting axis C, or the slab S.

[0057] The containing rolls 11 can be of a length substantially equal to the width W1 of the cast slab S.

[0058] According to embodiments, not showed in the drawings, the containing rolls 11 can be composed by two, or more components. For example, the containing rolls 11 can be defined by two or more cylindrical bodies axially aligned with each other and supported at their respective ends by support elements. This solution allows to increase the resistance to flexion of the containing rolls 11, guaranteeing that the ferrostatic pressure of the slab S is contained.

[0059] Moreover, the plurality of rolls comprises a plurality of electromagnetic rolls 12.

[0060] According to an embodiment, the electromagnetic rolls 12 can be disposed faced, in pairs, to each other with respect to the casting axis C, or the slab S.

[0061] According to another embodiment, the electromagnetic rolls 12, or at least one of them, can be disposed faced to one of said containing rolls 11.

[0062] According to other embodiments of the present invention, the electromagnetic rolls 12 can be disposed only on one side with respect to the slab S.

[0063] The electromagnetic rolls 12 are disposed along the casting axis C faced to the liquid core of the slab S, in order to stir the liquid.

[0064] The electromagnetic rolls 12 are provided with an electromagnetic stirrer 13, which stirs the liquid contained in the slab S.

[0065] According to one solution, the electromagnetic stirrer 13 is contained inside the electromagnetic rolls 12.

[0066] In other embodiments (FIG. 1), the electromagnetic rolls 12 are also disposed in opposite pairs with respect to the slab S and along the casting axis C to exert, as well as the action of containing the slab S, also the action of stirring the liquid still present in the latter.

[0067] Each electromagnetic stirrer 13 can comprise at least one electromagnetic inductor disposed inside a respective electromagnetic roll 12. In particular, the electromagnetic stirrers 13 generate magnetic fields, and respective electromagnetic forces 17.

[0068] The electromagnetic forces 17 generate a plurality of recirculation loops 16 inside the liquid contained in the slab S, namely inside the skin.

[0069] According to possible embodiments, the electromagnetic rolls 12 have a length L above 1400 mm, and preferably below 2500 mm.

[0070] The electromagnetic rolls 12 are supported at their ends with respective support elements 26 conformed so as not to interfere with the surface of the slab S.

[0071] During casting, the electromagnetic rolls 12 have a length L lower than the width W1 of the slab S so that the slab S protrudes with respect to one end of said electromagnetic rolls 12.

[0072] Therefore, during casting the slab S has a protruding portion 20, which is not in contact with the electromagnetic rolls 12.

[0073] Moreover, the protruding portion 20 protrudes, with respect to the electromagnetic rolls 12, in a direction parallel to the rotation axis of the latters.

[0074] In particular, it is provided that the electromagnetic rolls 12 have a containing surface, configured to contain during use the slab S which is cast, and which has said length L. The slab S therefore protrudes with respect to a lateral edge of said containing surface of the electromagnetic rolls 12.

[0075] The containing surface is the one which, during use, is in direct contact with the slab S which is cast. The protruding portion 20 is therefore not in contact with the containing surface. The containing surface has a cylindrical shape.

[0076] In this way, despite having the protruding portion 20, the slab S is supported in a stable manner, preventing excessive flexions and guaranteeing the necessary electromagnetic force of the electromagnetic stirrer 13.

[0077] According to one embodiment (FIGS. 2-4), the slab S is protruding, with respect to one end of the electromagnetic roll 12, by an unsupported width W2 up to 300 mm, preferably up to 250 mm.

[0078] Therefore only a small portion of the slab S is not supported by the electromagnetic rolls 12. The steel in the edge of the slab S is almost completely solidified at this location down the casting machine and this unsupported zone is not a drawback for the quality issue.

[0079] According to another embodiment of the invention the ratio between the unsupported width W2 of the slab S which protrudes externally, that is, laterally to the electromagnetic rolls 12, and the width W1 of the slab S is comprised between 2% and 20%, preferably between 2.5% and 16%.

[0080] According to one embodiment of the present invention (FIGS. 4, 7 and 8), said electromagnetic rolls comprise a first electromagnetic roll 12 and at least a second electromagnetic roll 12, distanced to each other along the casting axis C.

[0081] While in the following reference is made to a first and second electromagnetic rolls, it is not excluded that the same teachings can be applied for more than two electromagnetic rolls.

[0082] According to embodiments, the first electromagnetic roll 12 can be faced to another first electromagnetic roll 12 in order to define a first pair 18 of electromagnetic rolls 12.

[0083] According to further embodiments, the second electromagnetic roll 12 can be faced to another second electromagnetic roll 12 in order to define a second pair 19 of electromagnetic rolls 12.

[0084] Between the first electromagnetic roll 12 and the second electromagnetic roll 12, a plurality of said containing rolls 11 can be provided in order to contain and support the slab S.

[0085] According to an embodiment, the first electromagnetic roll 12 and the second electromagnetic roll 12 are disposed so that a first edge 21 of the slab S protrudes with respect to the first electromagnetic roll 12, while a second edge 22, opposite with respect to the first edge 21, protrudes with respect to the second electromagnetic roll 12.

[0086] This disposition of the electromagnetic rolls 12 allows to maximize and homogenize as much as possible the liquid steel recirculation loop 16, as shown in FIGS. 4 and 7.

[0087] In fact (FIG. 4), this particular disposition of the first electromagnetic roll 12 and the second electromagnetic roll 12 allows to obtain a distribution of the recirculation loops 16 uniformly distributed in the zone between the first electromagnetic roll 12 and the second electromagnetic roll 12.

[0088] In particular, to generate these recirculation loops 16, the electromagnetic force 17 generated in the first electromagnetic roll 12 is directed in a first direction, opposite to a second direction along which the electromagnetic force 17 generated in the second electromagnetic roll 12 is directed.

[0089] Preferably, the unsupported width W2 of the protruding portion 20 which protrudes outside the first electromagnetic roll 12 is equal to the unsupported width W2 of the protruding portion 20 which protrudes outside the second electromagnetic roll 12.

[0090] According to a possible solution of the invention, one of said electromagnetic rolls 12 is positioned directly below the mold 15.

[0091] According to another embodiment (FIGS. 5-8), if the unsupported width W2 of the slab S is too long, each of the electromagnetic rolls 12 is associated with a respective auxiliary containing roll 14, aligned to, and in axis with, the respective electromagnetic roll 12.

[0092] Thus, the electromagnetic rolls 12 mostly support the slab S, and the auxiliary containing rolls 14 support the remaining part of the slab S, namely the protruding portion 20.

[0093] The auxiliary containing rolls 14 have not an active electromagnetic inductor inside but have only a support function.

[0094] The auxiliary containing rolls 14 have a length K which can be equal to or greater than said unsupported width W2.

[0095] Preferably, it is provided to use the auxiliary containing rolls 14 when the ratio between the unsupported width W2 and the width W1 of the slab S is comprised between 10% and 40%.

[0096] According to a possible embodiment, the auxiliary containing rolls 14 have a length K, which is comprised between 10% and 40% of the length L of the respective electromagnetic roll 12.

[0097] According to a possible solution of the present invention (FIGS. 5-8), each electromagnetic roll 12, and the respective auxiliary containing roll 14 associated therewith, are supported by said support element 26. In particular, the support element 26 is configured to support one of the electromagnetic rolls 12 and the respective auxiliary containing roll 14 in axis, one after the other, and directly next to each other.

[0098] In accordance with a possible embodiment (FIGS. 7 and 8), the first electromagnetic roll 12 comprises a respective auxiliary containing roll 14 disposed aligned with the first electromagnetic roll 12, and the second electromagnetic roll 12 comprises a respective auxiliary containing roll 14 disposed aligned with the second electromagnetic roll 12.

[0099] The auxiliary containing roll 14 associated with the first electromagnetic roll 12 is located in an opposite position with respect to the auxiliary containing roll 14 associated with the second electromagnetic roll 12.

[0100] In other words, the auxiliary containing roll 14 associated with the first electromagnetic roll 12 is located on a first side with respect to the casting axis C, while the auxiliary containing roll 14 associated with the second electromagnetic roll 12 is located on a second side, opposite the first side, with respect to the casting axis C.

[0101] As can also be seen in FIG. 8, in this variant of the casting equipment 10 too, the electromagnetic force 17 generated in the first electromagnetic roll 12 is directed in a first direction, opposite a second direction along which the electromagnetic force 17 generated in the second electromagnetic roll 12 is directed.

[0102] Embodiments of the present invention are also directed to a casting equipment 10 comprising said mold 15 configured to cast a slab S, and said plurality of rolls 11, 12 disposed in pairs facing to each other, and along the casting axis C in order to define a passage for the cast slab S.

[0103] According to the present invention, the electromagnetic forces 17 generated by the travelling magnetic field are more homogeneous along the slab width W1 because the shortening of the electromagnetic rolls 12 compared to the slab width W1 smooth the electromagnetic edge effect while maintaining sufficient stirring effect.

[0104] It is 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 the present method for contain a slab during continuous casting, having the characteristics as set forth in the claims and hence all coming within the scope of protection defined thereby.