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FIELD OF THE INVENTION

The present invention concerns an apparatus and a method for casting ingots. In particular, the apparatus and method according to the present invention can be applied in the field of vertical semi-continuous casting of ingots, mainly but not exclusively large-size.

BACKGROUND OF THE INVENTION

Apparatuses are known for the semi-continuous casting of ingots, described for example in WO-A-2015/101553, which comprise a mold, also called ingot mold, into which the molten metal is introduced, for example coming from a melting plant.

The mold is suitably cooled by known cooling devices and lubricating materials are distributed in a known manner above the level of the liquid metal, also called meniscus, contained in the mold.

The first solidification of the molten metal takes place in the mold, with the formation of a solidified layer or skin of the ingot, with a self-supporting function. In this way it is possible to extract the ingot from the mold even if its core is still liquid.

The known casting apparatus also comprises a support board installed downstream of the mold and configured to receive the partly solidified ingot. The support board can be moved in a controlled manner along a vertical casting axis to allow the ingot to be removed as it gradually forms in the mold.

The speed of movement of the support board substantially corresponds to the casting speed of the ingot which, merely by way of example, can vary between 0.1 m/min and 0.5 m/min, depending on the sizes of the product. In particular, the bigger the sizes of the cast product, the lower the casting speed will be.

It is also known to install heating devices on the mold, in correspondence with the meniscus, for example burners or induction heaters, to supply heat to the liquid metal and to prevent the meniscus from starting to solidify, also called freezing. This starting solidification causes serious problems in the casting process and drastically reduces the quality of the cast product.

It is for this reason that it is important to keep the thermal condition of the meniscus carefully controlled.

It is also known to associate electromagnetic stirrers with the casting apparatus, which are configured to induce electromagnetic forces into the cast product which move, stir and mix the liquid metal contained in the mold and/or in the skin of the solidified product.

The stirring motion generated allows to homogenize the internal temperature of the liquid metal and the solidification structure and to increase the quality of the product obtained.

Casting apparatuses are known, which comprise an electromagnetic stirrer installed in a fixed position on the mold, also called mold electromagnetic stirrer (M-EMS). The metallurgical function of the M-EMS is to produce an equiaxed solidification structure by stopping the solidification in form of dendrites, generating a sink down of the smal crystals and a fill up of the liquid pool, due to the less density of liquid.

Casting apparatuses are also known, which also comprise a line or strand electromagnetic stirrer (S-EMS), which is installed downstream of the mold in correspondence with the exit of the metal product from the mold, and a final or end electromagnetic stirrer (F-EMS) which is positioned in the final solidification zone of the cast product and which may be mobile to follow its solidification.

In particular, the final stirrer F-EMS is positioned in the so-called mushy zone where there is a mixture of liquid steel and small solidified crystals. The mushy zone has still a not too high viscosity such that it can be mixed by the stirrer.

The function of the F-EMS is to mix the mushy zone to avoid the formation of small center porosities and of so-called v-type segregation. V-type segregation builds up in the final solidification zone when segregated liquid steel (segregated means having higher concentration of al oying elements) flows down between the no more moving down crystals because of the final volume contraction before complete solidification.

Once casting is concluded, the strand electromagnetic stirrer and/or the end electromagnetic stirrer can be moved along the cast product to follow the solidification profile and reduce segregation and central porosity of the product.

During the movement of the electromagnetic stirrers, it is known to provide a continuous heating of the meniscus, to prevent it from freezing and hence the upper closing of the ingot while the core is still liquid. Upper closing prevent the impurities from resurfacing, which naturally tend to rise toward the meniscus, and it would cause porosity inside the cast product and hence a considerable deterioration in the quality of the cast product. In this circumstance, about a third o the cast product has to be discarded and melted again.

WO-A-2015/101553 cited above provides to heat the liquid metal of the ingot with a graphite electrode that is put at the top of the cast ingot, while this is still in the mold, and which guarantees that a liquid condition is maintained.

However, this solution has the drawback that the graphite electrodes, as they are used up, modify the final composition of the cast product, which will therefore have a non-uniform composition along its length.

Furthermore, this solution is not very efficient because, once casting is concluded, the cast product on the one hand is constantly cooled by the mold, and on the other hand is heated to prevent the meniscus from solidifying.

Another solution is also known, described in KR- A-201 1 .0074153, in which the mold electromagnetic stirrer can be moved in the casting direction in order to position it in correspondence with the mold or below the mold.

When casting is interrupted, the product is removed from the mold and the electromagnetic stirrer, which is located in correspondence with the mold, is moved on the upper part of the cast product to stir and heat the molten metal present in this zone.

Cooling nozzles are provided below the mold, in correspondence with the support board, and can be moved along the length of the product until this latter has solidified.

This casting apparatus is not very efficient either, in that it is particularly complex to accurately control the thermal conditions of the liquid metal during casting.

In fact, the electromagnetic stirrer is usually powered electrically with very low-frequency electric energy, typically less than 1 OHz.

The magnetic field generated by the electromagnetic stirrer in the liquid metal induces induced currents in it, and the combination of the induced currents and the magnetic field generates electromagnetic forces inside the liquid metal which move the liquid metal. Although the induced currents produce heat inside the liquid metal, this heat is too limited to guarantee a real heating effect due to the extremely low-power frequency of the electromagnetic stirrer.

It is for this reason that an electromagnetic stirrer cannot be used as an induction heating device.

This means that low-quality cast products are obtained, and that a long length of the cast product is discarded.

One purpose of the present invention is to obtain a casting apparatus and to perfect a casting method that allow to obtain a high quality of the products that are cast.

Another purpose of the present invention is to obtain a casting apparatus that is extremely efficient and that allows to control precisely the solidification of the cast product.

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, while the dependent claims describe other characteristics of the invention or variants to the main inventive idea.

In accordance with the above purposes, an apparatus for continuous casting according to the present invention comprises:

- a mold configured to at least partly solidify liquid metal and obtain an ingot;

- a support board located downstream of the mold and configured to support a first end of the ingot and to guide the extraction of the ingot from the mold; and - at least one electromagnetic stirrer configured to induce stirring in the liquid metal.

According to one aspect of the present invention, the casting apparatus comprises an operating zone located downstream of the mold and in which a second end, opposite the first end of the ingot, can be positioned.

The electromagnetic stirrer configured to stir the liquid metal still present in correspondence with the second end, and an induction heating device, distinct and separate from the electromagnetic stirrer and configured to heat the second end of the ingot are positionable, or positioned, in the operating zone. In this way, once the casting of the liquid metal is concluded, the ingot that is formed in the mold can be extracted from it. In this step, the second end of the ingot has a peripheral skin, solidified and self-supporting, while the portion inside the skin is still liquid.

The heating device and the electromagnetic stirrer respectively provide to heat and stir the liquid metal present in correspondence with the second end until the solidification profile reaches said end too.

This allows the non metallic inclusions and gas bubbles to float up to the surface spontaneously, and therefore prevents the occurrence of inclusions and porosity inside the ingot and thus obtains a high-quality cast ingot.

The casting apparatus is also particularly effective and efficient.

BRIEF DESCRIPTION OF THE DRAWINGS

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:

- fig. 1 is a schematic section view of a casting apparatus according to the present invention;

- figs. I a- 1 h show one operating sequence of the casting apparatus in fig. 1 ;

- fig. 2 is a schematic view of a first variant of fig. 1 ;

- figs. 2a-2h show a possible operating sequence of the casting apparatus in fig.

2;

- figs. 3a-3h show a possible operating sequence of the casting apparatus in fig. 2 according to a variant of figs. 2a-2h;

- fig. 4 is a schematic view of a second variant of fig. 1 ;

- figs. 4a-4h show a possible operating sequence of the casting apparatus in fig.

2;

- fig. 5 is a schematic view of a third variant of fig. 1 ;

- figs. 5a-5g show a possible operating sequence of the casting apparatus in fig. 5.

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 form of embodiment can conveniently be incorporated into other forms of embodiment without further clarifications. DETA1LED DESCRIPTION OF SOME EMBODIMENTS

With reference to the attached drawings, an apparatus for casting ingots P is indicated in its entirety by the reference number 10 and comprises a mold 1 1 into which liquid metal is introduced to be at least partly solidified.

The mold 1 1 is provided with a through casting cavity 14 and with a first end edge 12 through which the liquid metal is introduced and a second end edge 13 through which the formed ingot P is discharged.

The mold 1 1 defines a casting axis X, disposed substantially vertical and along which the ingot P is moved to be discharged.

Oscillation devices and/or cooling devices, not shown in the drawings, can be associated with the mold 1 1 in a known manner, and are provided respectively to prevent the liquid metal from sticking on the casting cavity 14 and to preserve the mechanical resistance properties of the mold 1 1 .

The liquid metal can be fed to the mold 1 1 from a container, for example a tundish 1 5.

The casting apparatus 10 according to the present invention comprises a support board 16 positioned downstream of the mold 1 1 and configured to support a first end 17 of the ingot P and to guide the extraction of the ingot P from the mold 1 1.

The first end 1 7 of the ingot P substantially corresponds to the first portion of liquid metal that is solidified and discharged from the mold 1 1.

An already solidified ingot, also called dummy bar, can be associated with the support board 16, with the function of occluding the second end 1 3 of the mold 1 1 at start of casting.

The support board 16 can be moved along the casting axis X to move toward/away from the mold 1 1. The movement of the support board 16 away from the mold 1 1 defines the speed of extraction of the ingot P from the mold 1 1 and hence the casting speed.

To this purpose, movement devices, not shown in the drawings, can be associated with the support board 16, and are provided to move the support board 16 along the casting axis X.

According to one aspect of the present invention, the casting apparatus 10 comprises an operating zone 19, located downstream of the mold 1 1 , in which, at the end of the casting step, a second end 18 of the ingot P can be positioned, opposite the first end 17.

In fact, once the casting process is concluded, the method according to the present invention provides to dispose the second end 18 outside the mold 1 1 to complete the solidification as described below.

The positioning of the second end 18 outside the mold 1 1 allows to prevent the meniscus of liquid present in the ingot P from freezing, and allows to stop the cooling function of the mold 1 1 , increasing the efficiency of the apparatus 10.

According to one possible solution, the second end 18 of the ingot P is positioned in the operating zone 19 by moving the ingot P using the support board 16.

According to a variant, described hereafter, it can be provided that the second end 1 8 of the ingot P is positioned in the operating zone 19 by moving the mold 1 1.

According to another variant, a movement can be provided both of the mold 1 1 and also of the support board 16, to position the second end 1 8 in correspondence with the operating zone 19.

According to a preferential embodiment of the present invention, the operating zone 19 is located aligned with the casting axis X, and downstream of the mold 1 1 , for example under the second end edge 13 of the mold 1 1.

According to the embodiment shown in fig. 1 , the casting apparatus 10 comprises an electromagnetic stirrer 20 configured to induce electromagnetic forces in the cast liquid metal able to perform a mixing action on the cast liquid metal. The mixing action homogenizes the solidification of the liquid metal, prevents impurities and gas bubbles from being entrapped in the solidification front and promotes the up- floating of impurities or bubbles to the meniscus.

According to the embodiment shown in fig. 1 , the electromagnetic stirrer 20 is associated with the mold 1 1 and mixes at least part of the liquid metal contained therein.

According to the embodiment shown in fig. 1 , the electromagnetic stirrer 20 is disposed outside the mold 1 1 so as to surround it peripherally. In this condition, the electromagnetic stirrer 20 substantially functions as a mold electromagnetic stirrer, or M-EMS. The electromagnetic stirrer 20 is provided with one or more coils 21 wound so as to surround the mold 1 1 with its spirals. Each coil 21 is powered electrically to induce the electromagnetic forces on the liquid metal in transit.

According to a possible solution, the electromagnetic stirrer 20 is the rotational type, i.e. it generates rotational electromagnetic forces around an axis that corresponds to the casting axis. The electromagnetic stirrer 20 can be powered electrically with two-phase or three-phase alternate electric energy, with a very low frequency, typically less than 1 OHz.

The magnetic field generated by the electromagnetic stirrer 20 in the liquid metal induces induced currents in it, and the combination of the induced currents and the magnetic field generates electromagnetic forces inside the liquid metal that move the liquid metal.

According to the embodiment shown in fig. 1 , a movement member 22 is associated with the electromagnetic stirrer 20, and is configured to take the electromagnetic stirrer 20 to a first operating position in which it surrounds the mold 1 1 , and a second operating position in which it is disposed in correspondence with the operating zone 19.

In this way, during casting, the electromagnetic stirrer 20 stirs the liquid metal contained in the mold 11 continuously, and when the ingot P is discharged from the mold 11, it mixes the liquid metal that is present in correspondence with the second end 18 of the ingot P.

The movement member 22 can comprise guides, drive members, linear actuators, kinematic mechanisms, articulated mechanisms or similar or comparable members suitable for the purpose.

According to another aspect of the present invention, the casting apparatus 10 comprises an induction heating device 23, distinct and separate from the electromagnetic stirrer 20 and configured to heat the second end 18 of the ingot P, when the latter is outside the mold 1 1 .

The induction heating device 23 can be positioned, or is positioned, in correspondence with the operating zone 19 so as to surround the second end 18 of the ingot P.

The induction heating device 23 can comprise one or more spirals 24 disposed during use to surround the second end 18 of the ingot P and powered electrically to generate the desired heat energy.

According to a possible solution, the induction heating device 23 is powered with electric energy having a frequency comprised between about 100 Hertz and a few thousand Hertz, for example a frequency comprised between about 100Hz and about 10,000Hz.

The induction heating device 23 induces induced currents in the liquid metal which circulate on the same plane as the spirals 24 but in the opposite direction.

The induced currents are concentrated outside the product and do not penetrate inside the product, due to the high frequency. The induced currents generate a heating effect with an efficiency comprised between about 50% and 70%. The magnetic field generated by the induction heating device 23 produces a pulsing radial force on the liquid metal which therefore has no stirring function on the latter.

According to a possible solution, the induction heating device 23 can be associated with a positioning device 25 configured to position the induction heating device 23 in an operating condition in which it is in the operating zone 19, to heat the second end 18 of the ingot P, and a non-operating condition in which it is disposed in a position of non-interference with the ingot P that is extracted from the mold 1 1.

In said operating condition the induction heating device 23 surrounds the ingot P.

In the non-operating condition, the induction heating device 23 is disposed outside the operating zone 19 so as not to interfere with the movements of the ingot P and to prevent possible damage due to the high thermal flow that the ingot P itself can transmit to the induction heating device 23.

The positioning device 25 can be configured to position the induction heating device 23 above the electromagnetic stirrer 20. In this way it ensures that the liquid metal present in correspondence with the second end 1 8 does not solidify, closing the shrinkage cone.

With reference to figs, l a l h, a possible operating sequence of the casting apparatus 10 is described with reference to fig. 1.

Figs, la and l b show the functioning of the casting apparatus 10 during the casting step in which the liquid metal is discharged from the tundish 15 into the mold 11. During this step, the support board 16 is moved away from the mold 11 to promote the extraction of the ingot P, and the electromagnetic stirrer 20 is driven to stir the liquid metal present in the mold 1 1. In this condition the electromagnetic stirrer 20 is in its first operating condition in which it surrounds the mold 1 1 while the induction heating device 23 is in its non-operating condition between the ingot P and the mold 1 1.

Once the casting step is concluded (fig. 1 c), the support board 16 is moved to extract the ingot P from the mold 11 and to dispose the second end 1 8 of the ingot P in correspondence with the operating zone 19. The operating zone 19 can be distanced from the mold 1 1 by a distance sufficient to allow the passage without interference of the induction heating device 23.

In this operating condition (figs. I d and l e), both the electromagnetic stirrer 20 and the induction heating device 23 are positioned in the operating zone 19 so as to surround the second end 18 of the ingot P.

In particular, first the electromagnetic stirrer 20 and then the induction heating device 23 are inserted through the second end 18 of the ingot P, so that they are located in succession to each other along the casting axis X so as to affect a portion o the length of the ingot located in correspondence with the second end 18.

Subsequently, the solidification of the ingot P is completed (figs. If, lg and lh), keeping the electromagnetic stirrer 20 and the induction heating device 23 in the operating zone 19 until the solidification profile reaches the proximity of the second end 18 of the ingot P (fig. lh).

The solidification of the ingot P can occur naturally, keeping it outside the mold 1 1 , or forcedly, for example using cooling devices.

According to a possible embodiment, shown in fig. 2, and combinable with the embodiment described in fig. 1 , it can be provided that the casting apparatus 10 comprises an auxiliary electromagnetic stirrer 26, associated near the support board 16 and having the function of stirring at least the liquid metal present in correspondence with, or close to, the first end 17 of the cast ingot P.

The auxiliary electromagnetic stirrer 26 is substantially like the electromagnetic stirrer 20 described above, and can be equated to the final electromagnetic stirrer F-EMS described above. In particular, the auxiliary electromagnetic stirrer 26 can be positioned in the above called mushy zone.

According to a possible solution, the auxiliary electromagnetic stirrer 26 can be associated with movement members 27, schematically shown by dotted lines in figs. 2d, 2e and 2f, and provided to move the auxiliary electromagnetic stirrer 26 along the longitudinal extension of the ingot P.

As shown in figs. 2a-2h, the casting process differs from the description regarding figs. 1 a- 1 h in that, once casting is concluded, or possibly also during casting, the auxiliary electromagnetic stirrer 26 is driven to stir the liquid metal present in correspondence with the first end 17 (figs. 2b, 2d and 2e) of the ingot and is moved upwards along the longitudinal extension of the ingot P (figs. 2f, 2g and 2h) to follow the solidification profile of the liquid metal present in the latter, and to move below, in direct proximity to the electromagnetic stirrer 20. This solution prevents the formation inside the solidifying ingot P of closed sacs of still liquid material that can cause porosity and prevents the v-type segregation. With reference to figs. 3a-3h, a possible variant is shown of the embodiment shown in fig. 2, in which the electromagnetic stirrer is indicated by the reference number 320 and instead of being associated with the mold 1 1 is associated with the support board 16. In this case, during the casting step, the electromagnetic stirrer 320 functions as a final electromagnetic stirrer F-EMS.

According to the embodiment in figs. 3a-3h, the auxiliary electromagnetic stirrer is indicated by the reference number 326 and is associated with the mold 1 1.

In particular, with reference to figs. 3b-3h, the electromagnetic stirrer 320 is associated with a respective movement member 322 configured to move the electromagnetic stirrer 320 along the longitudinal extension of the ingot P and to take it at least into correspondence with the operating zone 19 at least when the casting step is interrupted.

This variant is preferred if for mechanical reasons of the caster design the auxiliary electromagnetic stirrer 326 remains fixed around the mold 1 1 or is incorporated into the mold 1 1 and therefore cannot be movable.

According to the embodiment shown in figs. 3a-3h, the auxiliary electromagnetic stirrer 326 is associated with the mold 1 1 and remains in this position during the whole casting process, and also afterward. The auxiliary electromagnetic stirrer 326 therefore functions as mold electromagnetic stirrer M- EMS.

Once the casting step is conc l uded (fig. 3 c), the second end 18 o f the ingot P is positioned in the operating zone 19. This positioning in the operating zone 19 can occur by moving the mold 11 and/or by extracting the ingot P from the mold 1 1.

In this condition the electromagnetic stirrer 320 is moved to take it to the operating zone 19 and the induction heating device 23 is taken from its non- operating condition to its operating condition to heat the second end 18 of the ingot P. According to the solution shown in figs. 3e-3h, the induction heating device 23 is positioned above the electromagnetic stirrer 320.

During the solidification of the ingot P, both the induction heating device 23 and the electromagnetic stirrer 320 are kept in the operating zone 19.

With reference to fig. 4, another embodiment of the present invention is described in which the electromagnetic stirrer is indicated by the reference number 420.

According to this embodiment, at least during casting, the electromagnetic stirrer 420 functions as a strand electromagnetic stirrer or S-EMS.

The electromagnetic stirrer 420 is associated with a movement member 422 configured to take the electromagnetic stirrer 420 at least to the operating zone 19. In particular it can be provided that the movement member 422 is movable along the longitudinal extension of the ingot P. For example, it can be provided that, at start of casting (fig. 4a), the electromagnetic stirrer 420 is positioned near the support board 16 to stir the liquid metal present in the first end 17 of the ingot P.

During casting (figs. 4b and 4c), the electromagnetic stirrer 420 can be moved along the longitudinal extension of the ingot P to be positioned in an intermediate position along the length of it, and to keep the liquid metal present therein stirred.

At end of casting (fig. 4d), the electromagnetic stirrer 420 is moved to dispose it in the operating zone 19. In this operating condition, the induction heating device 23 too is positioned in the operating zone 19 in substantially the same way as described for the embodiments above.

According to the solution shown in fig. 4, the casting apparatus 10 comprises a first auxiliary electromagnetic stirrer 426 associated to the mold 11 and a second auxiliary electromagnetic stirrer 428 positionable at least in correspondence with the support board 16.

The first auxiliary electromagnetic stirrer 426 is installed integral with the mold 1 1 and provides to stir the liquid metal during casting as shown in figs. 4a- 4c, functioning as a mold electromagnetic stirrer M-EMS.

The second auxiliary electromagnetic stirrer 428 is associated with a movement member, in this case the same movement member 422 of the electromagnetic stirrer 420, configured to move the second auxiliary electromagnetic stirrer 428 along the longitudinal extension of the ingot P. In this way, also following the interruption of casting, the second auxiliary electromagnetic stirrer 428 can follow the solidification profile of the liquid metal still contained in the ingot P to move under the electromagnetic stirrer 420 described above.

In this embodiment too, the induction heating device 23 can be moved from the non-operating condition to the operating condition by the positioning device

25.

With reference to figs. 5, 5a-5g, the casting apparatus 10 comprises the electromagnetic stirrer 420, the first auxiliary electromagnetic stirrer 426 and the second auxiliary electromagnetic stirrer 428 in substantially the same way as was described with reference to figs. 4a-4h.

According to this embodiment, the induction heating device 23 is installed aligned with the casting axis and is kept in this position during the whole casting process. Therefore, it is not required to be positioned in the operating zone 19 once casting is concluded, since it is already disposed in this zone.

According to the embodiment shown in figs. 5a-5g, during casting, the induction heating device 23 is kept inactive while the electromagnetic stirrer 420 is moved by the movement members 422 along the longitudinal extension of the ingot P to stir the liquid metal present in an intermediate position of the ingot P.

The first auxiliary electromagnetic stirrer 426 and the second auxiliary electromagnetic stirrer 428 are activated to stir the liquid metal present respectively in correspondence with the mold 1 1 and in correspondence with the first end 17 of the ingot P.

The second auxiliary electromagnetic stirrer 428 can also be moved, for example by the same movement members 422, along the longitudinal extension of the ingot P to follow the solidification profile.

When casting is concluded, the second end 1 8 of the ingot P is disposed outside the mold 1 1 , by moving the mold 1 1 and/or the ingot P itself with the support board 16.

In this condition, the second end 18 finds itself in correspondence with the operating zone 19 where the induction heating device 23 is already present.

The electromagnetic stirrer 420 is moved, by the movement members 422, to take it to the operating zone 19 where therefore we have a combined action of stirring and heating the liquid metal (figs. 5d-5f).

The second auxiliary electromagnetic stirrer 428 is moved along the longitudinal extension of the ingot P until it is positioned in proximity to the operating zone 19 when the solidification profile is about to reach the second end 18 of the ingot P.

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

For example, it can be provided that the casting apparatus 10 according to the present invention also comprises a heat insulation device, not shown, positionable in the operating zone 19 when the ingot P has been extracted from the mold 1 1. The heat insulation device is configured to prevent any heat dispersion of the heat generated by the liquid metal still present in the ingot P when it is extracted from the mold 1 1 . The heat insulation device can be positioned to cover the second end 18 of the ingot P, at least at the top, and is therefore disposed above the induction heating device 23 and above the electromagnetic stirrer 20, 320, 420.

The heat insulation device therefore allows to increase the efficiency of the induction heating device 23.

As an alternative to, and/or in combination with, the heat insulation device, it can be provided that, once casting is concluded and the ingot P has been extracted from the mold 1 1 , the second end 18 of the ingot P is covered with covering powders with an insulating function, or with exothermic covering powders, in order to retain the heat of the liquid metal present in this zone. 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 10 and method for casting ingots, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.